Patent Application
20110299013
The present invention relates to a planar illumination device and a display device incorporating such a planar illumination device. More particularly, the present invention relates to a planar illumination device including a light guide member and to a display device incorporating such a planar illumination device.
Conventionally, there is known a display device that incorporates a planar illumination device including a light guide member.
The planar illumination device 2020 is an edge light type illumination device. The planar illumination device 2020 includes: a plurality of LEDs (light-emitting diodes) 2021 that are aligned in a predetermined direction (a direction perpendicular to the plane of the figure); a light guide plate 2022 that guides light from the LEDs 2021; a plurality of optical sheets 2023 that are arranged on the side of the light emitting surface 2022a of the light guide plate 2022; and a reflective sheet 2024 that is arranged on the side of the back surface 2020b of the light guide plate 2022.
The light guide plate 2022 has the function of guiding the light from the LEDs 2021 to the entire light guide plate 2022.
The optical sheets 2023 are formed with three or four sheet members composed of a diffusion plate, a light collecting lens and the like; the optical sheets 2023 have the function of making uniform the brightness of the display panel 2010. The optical sheets 2023 also have the function of collecting light from the light guide plate 2022 in an area in front thereof (on the side of the display panel 2010) and thereby increasing the brightness.
In the display device 2001 that is one conventional example, as described above, the optical sheets 2023 are arranged between the display panel 2010 and the light guide plate 2022. In general, the optical sheets 2023 each, such as the diffusion plate and the light collecting lens, have a thickness of about 40 μm to about 80 μm. Thus, it is disadvantageously difficult not only to reduce the thickness of the planar illumination device 2020 and the display device 2001 but also to reduce the manufacturing cost.
In the display device 2001 that is one conventional example, since light emitted from the light guide plate 2022 passes through the optical sheets 2023, the loss of the light when the light passes through the optical sheets 2023 is increased. Hence, the efficiency of use of light is also disadvantageously reduced.
In order to overcome these disadvantages, there is proposed a display device incorporating a planar illumination device that uses a light guide plate to collect light in an area in front thereof (on the side of the display panel) without provision of optical sheets.
The planar illumination device 2120 includes: a plurality of LEDs 2121 that are aligned in an A-direction (see
As shown in
These prisms 2122b are arranged such that, as the prisms 2122b are closer to the LEDs 2121, the distance between the adjacent prisms 2122b is increased. Since the amount of light (a beam of light) from the LEDs 2121 is increased as the prisms 2122b are closer to the LEDs 2121, as described above, the prisms 2122b are arranged such that, as the prisms 2122b are closer to the LEDs 2121, the distance between the adjacent prisms 2122b is increased, and thus it is possible to make substantially uniform the brightness of the display panel 2110.
The prisms 2122b also have the function of collecting the light from the LEDs 2121 in an area in front thereof (on the side of the display panel 2110). Specifically, the prisms 2122b have the function of suppressing the spread of the light in a B-direction (in the direction of a normal to the light entering surface 2122c of the light guide plate 2122) and then the emission of the light from the light guide plate 2122. In other words, the prisms 2122b can enhance the property of collecting light in the B-direction.
Conventionally, there is proposed a display device incorporating a planar illumination device that uses a light guide plate to collect light in an area in front thereof (on the side of the display panel) without provision of optical sheets (see, for example, patent document 1).
Patent document 1 discloses a liquid crystal display device that incorporates an LCD panel (display panel) and a backlight device (planar illumination device) arranged on the side of the back surface of the LCD panel.
In this liquid crystal display device, the backlight device includes a light source and a light guide plate that guides light from the light source. The light guide plate is formed with: a light guide body that the light from the light source enters; a first light transmission layer that is provided on the bottom surface (back surface) of the light guide body; a second light transmission layer that is provided on the bottom surface of the first light transmission layer; and a metallic mirror that is provided on the bottom surface of the second light transmission layer. The light guide body, the first light transmission layer, the second light transmission layer and the mirror are integrally formed without the intervention of an air layer.
The light guide body is formed such that the thickness of the light guide member is decreased as it extends away from the light source. In other words, the light guide body is formed in the shape of a wedge such that the bottom surface is inclined only at a predetermined angle with respect to the top surface (front surface).
The first light transmission layer has a lower refractive index than the light guide body; the second light transmission layer has a refractive index substantially equal to that of the light guide body. In the bottom surface of the second light transmission layer, a plurality of concave portions (prisms) having inclined surfaces are formed; the mirror is provided on the bottom surface of the second light transmission layer so as to embed the concave portions.
In this liquid crystal display device, within the light guide body, the light from the light source is guided while being repeatedly reflected between the top surface and the bottom surface. Here, the light guide angle (an angle of incidence with respect to the bottom surface of the light guide body) of the light is gradually changed, and the angle of incidence with respect to the bottom surface of the light guide body is gradually reduced. Then, the guided light enters the first light transmission layer. Thereafter, the light that has entered the first light transmission layer enters the second light transmission layer, and then the light is reflected forwardly (toward the liquid crystal display panel) by the mirror.
In the planar illumination device 2120 shown in
In the planar illumination device 2120, as described above, it is possible to suppress the spread of the light emitted from the light guide plate 2122 in the B-direction whereas, as shown in
When, as with the planar illumination device 2120, a diffusion plate and the like are not used and light-emitting elements such as the LEDs 2121 are used as the light source, since the light is prevented from being diffused in the A-direction within the light guide plate 2122, as shown in, for example,
On the other hand, in the liquid crystal display device disclosed in patent document 1 described above, the light is reflected forwardly (toward the liquid crystal display panel) by the metallic mirror. When the light is reflected by the metallic mirror as described above, since the light is absorbed by the mirror, the efficiency of use of light is disadvantageously reduced.
When, as in patent document 1 described above, the metallic mirror is formed in the bottom surface of the second light transmission layer, it is difficult to reduce the manufacturing time of the light guide plate, and the manufacturing cost is increased.
When, as in patent document 1 described above, the bottom surface of the light guide body is inclined with respect to the top surface (front surface), as compared with a case where the top surface and the bottom surface of the light guide body are formed substantially parallel to each other, it is difficult to form the first light transmission layer and the second light transmission layer on the bottom surface of the light guide body.
The present invention is made to solve the foregoing problems. An object of the present invention is to provide: a planar illumination device that enhances the efficiency of use of light and its brightness while suppressing uneven brightness, that reduces an increase in the manufacturing cost and that can reduce the thickness of the planar illumination device; and a display device incorporating such a planar illumination device.
To achieve the above object, according to the first aspect of the present invention, there is provided a planar illumination device which includes: a light source; and a light guide member that guides light from the light source, in which the light guide member includes: a light guide body that the light from the light source enters; and a low refractive index layer that is provided on a back surface of the light guide body without intervention of an air layer and that has a lower refractive index than the light guide body, in a side of a front surface of the light guide body or in the back surface of the light guide body, a plurality of first reflective portions are provided that gradually reduce an angle of incidence of the light from the light source with respect to the back surface of the light guide body, and in a light emitting region of the light guide member, a plurality of second reflective portions that have a function of totally and forwardly reflecting the light from the light source in an interface between a back surface of the light guide member and an air layer are formed over substantially the entire back surface of the light guide member.
In the planar illumination device according to the first aspect of the present invention, as described above, in the side of the front surface of the light guide body or in the back surface of the light guide body, a plurality of first reflective portions are provided that gradually reduce the angle of incidence of the light from the light source with respect to the back surface of the light guide body, and, in the back surface of the light guide member, a plurality of second reflective portions that forwardly reflects the light from the light source in the interface between the back surface of the light guide member and an air layer. Thus, the light from the light source is guided while being reflected repeatedly between the front surface and the back surface of the light guide body, with the result that the angle of incidence of the light with respect to the back surface of the light guide body is gradually reduced. Then, when the angle of incidence of the light with respect to the back surface of the light guide body becomes lower than the critical angle between the light guide body and the low refractive index layer, the light from the light source enters the low refractive index layer. Hence, the angle of spread of the light that enters the low refractive index layer is reduced, and the angle of spread of the light that is reflected off the interface between the back surface of the light guide member and the air layer is also reduced. In other words, it is possible not only to enhance the light collecting property but also to enhance the brightness of the liquid crystal display panel. Consequently, since it is unnecessary to provide a plurality of optical sheets such as a diffusion plate and a light collecting lens on the light guide member, it is possible not only to reduce the thickness of the planar illumination device but also to reduce an increase in the manufacturing cost.
Moreover, since it is unnecessary to provide a plurality of optical sheets, no loss of light is produced when the light passes through the optical sheets. Thus, it is possible to enhance the efficiency of use of light.
A plurality of first reflective portions that gradually reduce the angle of incidence of the light from the light source with respect to the back surface of the light guide body are provided, and thus the light from the light source is guided while being reflected repeatedly between the side of the front surface and the back surface of the light guide body, with the result that, as the light travels away from the light source, the angle of incidence with respect to the back surface of the light guide body is reduced and the light is more likely to enter the low refractive index layer. In this way, both in a part which is close to the light source and in which a large amount of light (luminous flux) is present and in a part which is distant from the light source and in which a small amount of light (luminous flux) is present, it is possible to make uniform the amount of light entering the low refractive index layer. Consequently, since light can be uniformly emitted from the entire light emitting region of the light guide member, it is possible to make uniform the brightness of the display panel.
As described above, in the planar illumination device of the first aspect, a plurality of second reflective portions that reflect forwardly the light from the light source are formed in substantially the entire back surface of the light guide member over the light emitting region of the light guide plate, and thus the light can be uniformly reflected by the second reflective portions over substantially the entire light emitting region of the light guide plate. In this way, since it is possible to more uniformly emit light from substantially the entire light emitting region of the light guide member, it is possible not only to reduce the production of dot unevenness but also to make more uniform the brightness of the display panel.
As described above, in the planar illumination device of the first aspect, a plurality of second reflective portions have the function of totally reflecting the light from the light source, and thus it is possible to suppress the emission of light that has entered the low refractive index layer through the light guide body from the back surface of the light guide member, with the result that the loss of the light can be reduced. In this way, it is possible to further enhance the efficiency of use of light.
Since the second reflective portions have the function of totally reflecting the light from the light source, unlike the case where the metallic mirror is provided on the back surface of the light guide member and the light is reflected by the metallic mirror, the light is not absorbed by the metallic mirror when the light is reflected. Thus, it is possible to further enhance the efficiency of use of light.
Since it is unnecessary to provide the metallic mirror on the back surface of the light guide member, as compared with the case where the metallic mirror is provided on the back surface of the light guide member, it is possible not only to prevent the manufacturing time of the light guide member from being elongated but also to reduce an increase in the manufacturing cost.
Preferably, in the planar illumination device of the first aspect, the front surface and the back surface of the light guide body are formed to be substantially parallel to each other. With this configuration, it is possible to easily form the low refractive index layer on the back surface of the light guide body as compared with, for example, the case where the wedge-shaped light guide body in which the back surface is inclined with respect to the front surface is used.
Preferably, in the planar illumination device of the first aspect, each of the first reflective portions includes a first inclination surface that is inclined with respect to the front surface or the back surface of the light guide body. With this configuration, it is possible to easily and gradually reduce the angle of incidence of the light from the light source with respect to the back surface of the light guide body.
Preferably, in the planar illumination device of the first aspect, the first inclination surface is inclined at an angle that is equal to or more than 0.1° but equal to or less than 5° with respect to the front surface or the back surface of the light guide body. With this configuration, the angle of incidence of the light with respect to the back surface of the light guide body is reduced by 0.2° or more but 10° or less each time the light is reflected by the first reflective portion. In this way, it is possible to more easily and gradually reduce the angle of incidence of the light with respect to the back surface of the light guide body.
In the planar illumination device of the first aspect, in a surface where the first reflective portions are provided, a first flat surface portion that is substantially parallel to the front surface or the back surface of the light guide body may be formed between the first reflective portions adjacent to each other in the direction of a normal to the light entering surface of the light guide body.
Preferably, in the planar illumination device of the first aspect, each of the second reflective portions includes a second inclination surface that is inclined with respect to the back surface of the light guide member. With this configuration, it is possible to easily and forwardly reflect light which enters the low refractive index layer and has a small angle of spread while the small angle of spread is being kept.
Preferably, in the planar illumination device in which the second reflective portion has the second inclination surface, the second inclination surface is inclined at an angle that is equal to or more than 40° but equal to or less than 50° with respect to the back surface of the light guide member. With this configuration, it is possible to totally and forwardly reflect the light from the light source with ease.
Preferably, in the planar illumination device in which the second reflective portion has the second inclination surface, the second inclination surface is curved. With this configuration, as compared with the case where the second inclination surface is flat, it is possible to prevent the angle of spread of the light that is reflected totally and forwardly from being lowered too much. By controlling the inclination angle of the second inclination surface, it is possible to control the angle of spread of the light.
Preferably, in the planar illumination device of the first aspect, the second reflective portions are continuously formed without any space therebetween in the direction of the normal to the light entering surface of the light guide body. With this configuration, the second reflective portions allow the light to be more uniformly reflected, and thus the light can be uniformly emitted from substantially the entire light emitting region of the light guide member. In this way, it is possible to make uniform the brightness of the display panel.
Preferably, in the planar illumination device of the first aspect, the second reflective portions are formed to have substantially the same shape and substantially the same size. With this configuration, the second reflective portions allow the light to be more uniformly reflected, and thus the light can be uniformly emitted from substantially the entire light emitting region of the light guide member. In this way, it is possible to make uniform the brightness of the display panel.
Preferably, in the planar illumination device of the first aspect, in the side of the front surface of the light guide body or in the back surface of the light guide body, a plurality of third reflective portions are formed that diffuse the light from the light source in a first direction in which the light entering surface of the light guide body extends. With this configuration, the light can be diffused in the first direction within the light guide body, it is possible to make uniform the brightness of a part of the display panel opposite the front of the light source and the brightness of parts of the display panel other than the part opposite the front of the light source. In other words, it is possible to make more uniform the brightness of the display panel.
A plurality of third reflective portions that diffuse the light from the light source in the first direction in which the light entering surface of the light guide body extends are formed, and thus, light incident at a large angle of incidence with respect to the back surface of the light guide body, as seen from the side of the light entering surface of the light guide body, is reflected by the third reflective portions, with the result that it is possible to reduce the angle of incidence with respect to the back surface of the light guide body. In this way, since it is possible to suppress the spread of the light entering the low refractive index layer in the first direction, it is possible to suppress the spread of the light emitted from the light guide member in the first direction. Consequently, it is possible not only to enhance the property of collecting the light in the first direction but also to further enhance the brightness of the display panel.
Preferably, in the planar illumination device in which the third reflective portions are formed in the side of the front surface of the light guide body or in the back surface of the light guide body, each of the third reflective portions includes a pair of inclination surfaces that is inclined with respect to the front surface or the back surface of the light guide body. With this configuration, the light from the light source can be diffused toward both sides of the first direction by the pair of inclination surfaces, it is possible to further enhance the brightness of the display panel.
In the planar illumination device in which each of the third reflective portions includes the pair of inclination surfaces, an angle formed by the pair of inclination surfaces may be equal to or more than 120° but equal to or less than 140°.
Preferably, in the planar illumination device in which the third reflective portions are formed in the side of the front surface of the light guide body or in the back surface of the light guide body, in a surface where the third reflective portions are provided, a second flat surface portion that is substantially parallel to the front surface or the back surface of the light guide body is formed between the third reflective portions adjacent to each other in the first direction, and a width of the second flat surface portion in the first direction is equal to or more than a width of the third reflective portion in the first direction. With this configuration, it is not only possible to suppress the spread of the light entering the low refractive index layer in the first direction but also to enhance the property of collecting the light in the first direction.
Preferably, in the planar illumination device in which the third reflective portions are formed in the side of the front surface of the light guide body or in the back surface of the light guide body, the light source includes a light-emitting element. When, as described above, the light-emitting element are used as the light source, since it is more likely that the brightness of the part of the display panel opposite the front of the light source differs from the brightness of the parts of the display panel other than the part opposite the front of the light source, it is especially effective to provide a plurality of third reflective portions that diffuse the light from the light source in the first direction.
Preferably, in the planar illumination device of the first aspect, the light guide member further includes a first reflective portion formation layer that is provided on a back surface of the low refractive index layer without intervention of an air layer and that has a higher refractive index than the low refractive index layer, and the second reflective portions are formed in the back surface of the first reflective portion formation layer. With this configuration, it is unnecessary to provide the second reflective portions in the low refractive index layer, and thus it is possible to reduce the thickness of the low refractive index layer. Since a transparent material that is used for the low refractive index layer and that has a relatively low refractive index is expensive, when the first reflective portion formation layer is provided and the thickness of the low refractive index layer is reduced, it is possible to reduce an increase in the manufacturing cost of the light guide member.
Preferably, in the planar illumination device of the first aspect, a light shielding member is arranged above a part of the front surface of the light guide body on the side of the light source through a layer that has a lower refractive index than the low refractive index layer. In a part of the light guide member near the light source, light is more likely to be emitted from the light guide member without the intervention of the low refractive index layer, and thus the brightness of a part of the display panel near the light source is more likely to be increased. Hence, when the light shielding member is arranged above the part of the light guide member near the light source, it is possible to shield the part of the light guide member near the light source from light, with the result that it is possible to suppress the uneven brightness of the display panel.
The light shielding member is arranged above the part of the front surface of the light guide member on the side of the light source through the layer (For example, an air layer) having a lower refractive index than the low refractive index layer, and thus, as compared with a case where the light shielding member is arranged above the part of the front surface of the light guide member on the side of the light source without the intervention of the air layer, the light is easily reflected by the front surface of the light guide member. In other words, it is possible to suppress the emission of the light from the front surface of the light guide member and then the absorption of the light by the light shielding member. In this way, it is possible to further reduce a decrease in the efficiency of use of light.
Preferably, the planar illumination device of the first aspect further includes a reflective member that reflects, toward the light guide member, light emitted from the back surface of the light guide member. With this configuration, it is possible to reflect the light emitted from the back surface of the light guide member toward the light guide member, with the result that it is possible to further enhance the efficiency of use of light.
Preferably, in the planar illumination device of the first aspect, in a first region, of the surface where the first reflective portions are provided, that extends a first distance from the light entering surface of the light guide body, a third inclination surface is formed, and an angle formed by the third inclination surface and the light entering surface is more than 90°. With this configuration, it is possible to increase the angle of incidence, with respect to the third inclination surface, of the light that travels from the light entering surface or the back surface of the light guide body to the front surface of the light guide body. Thus, the light can easily be totally reflected by the third inclination surface toward the back surface of the light guide body. In other words, it is possible to suppress the emission of light from the first region. Consequently, it is possible to enhance the efficiency of use of light.
Preferably, in the planar illumination device in which the third inclination surface is formed in the first region, the second reflective portions are not formed in a second region that extends a second distance from the light entering surface of the light guide body within the back surface of the light guide member but the second reflective portions are formed in a region other than the second region. With this configuration, in the second region of the light guide member, the light is not reflected forwardly by the second reflective portions. In this way, it is possible to suppress the emission of the light from the portion of the light guide member near the light source, and thus it is possible to further enhance the efficiency of use of light.
Preferably, in the planar illumination device in which the second reflective portions are not formed in the second region, the first distance is equal to or more than the second distance. With this configuration, the light that has been reflected forwardly by the second reflective portions can easily be totally reflected by the first reflective portions toward the back surface of the light guide member.
Preferably, in the planar illumination device of the first aspect, the surface of the second reflective portion includes a light diffusing surface. With this configuration, it is possible to somewhat increase the angle of spread of the light when the light is transmitted or totally reflected by the second reflective portions. In other words, it is possible to prevent the angle of spread of the light that is reflected totally and forwardly from being lowered too much.
In the planar illumination device of the first aspect, the first reflective portions may be formed with a constant pitch in the direction of the normal to the light entering surface of the light guide body, and the second reflective portions may be formed with a constant pitch in the direction of the normal to the light entering surface of the light guide body. When the first reflective portions are formed with a constant pitch, and the second reflective portions are formed with a constant pitch, the first reflective portions and the second reflective portions are slightly inclined relative to each other as seen from the side of the front surface of the light guide member, moiré fringes are produced. In this case, one of the pitches of the first reflective portions and the second reflective portions is appropriately set for the other of the first reflective portions and the second reflective portions, and thus it is possible not only to reduce the pitch of the moiré fringes but also to suppress the production of the moiré fringes in visual terms.
Preferably, in the planar illumination device in which the first reflective portions are formed with a constant pitch and the second reflective portions are formed with a constant pitch, the first reflective portions are formed at a predetermined angle with respect to the second reflective portions when viewed from the side of the front surface of the light guide member. With this configuration, as in the case where one of the pitches of the first reflective portions and the second reflective portions is appropriately set for the other of the first reflective portions and the second reflective portions, it is possible not only to reduce the pitch of the moiré fringes but also to suppress the production of the moiré fringes in visual terms.
Preferably, in the planar illumination device of the first aspect, the light guide member further includes a second reflective portion formation layer that is arranged on the front surface of the light guide body without intervention of an air layer or is arranged between the light guide body and the low refractive index layer, the first reflective portions are formed in the second reflective portion formation layer, and the second reflective portion formation layer has a higher refractive index than the low refractive index layer. With this configuration, since it is unnecessary to form the first reflective portions in the front surface and the back surface of the light guide body, it is possible to make flat the front surface and the back surface of the light guide body. In this way, it is possible to easily form the light guide body with a flat-plate glass or a thermosetting resin or the like.
Preferably, in the planar illumination device including the second reflective portion formation layer, the second reflective portion formation layer has a refractive index equal to or higher than the light guide body. With this configuration, it is possible to prevent the suppression of the entry of the light from the light source into the second reflective portion formation layer.
Preferably, in the planar illumination device of the first aspect, when the refractive index of the light guide body is n1, and the refractive index of the low refractive index layer is n2, a relationship “n1/n2>1.18” holds true. In this case, as the light guide body, a polycarbonate or the like may be used, and, as the low refractive index layer, a resin or the like including hollow particles such as a fluorine acrylate or an inorganic filler may be used.
According to the second aspect of the present invention, there is provided a display device including the planar illumination device configured as described above and a display panel that is illuminated by the planar illumination device. With this configuration, it is possible to obtain a display device that enhances the efficiency of use of light and its brightness while suppressing uneven brightness, that reduces an increase in the manufacturing cost and that can reduce the thickness of the display device.
As described above, according to the present invention, it is possible to easily obtain: a planar illumination device that enhances the efficiency of use of light and its brightness while suppressing uneven brightness, that reduces an increase in the manufacturing cost and that can reduce the thickness of the planar illumination device; and a display device incorporating such a planar illumination device.
Embodiments of the present invention will be described below with reference to accompanying drawings.
The structure of a liquid crystal display device 1 incorporating a backlight device 20 according to a first embodiment of the present invention will first be described with reference to
As shown in
The liquid crystal display panel 10 includes: an AM substrate (active matrix substrate) 11; an opposite substrate 12 that is arranged opposite the AM substrate 11; and a liquid crystal layer (not shown) that is arranged between the AM substrate 11 and the opposite substrate 12.
As shown in
In the first embodiment, as shown in
In the first embodiment, the light guide plate 22 is formed with: a light guide body 23 that has a light entering surface 23a which light from the LEDs 21 enters; and a low refractive index layer 24 that has a lower refractive index than the light guide body 23. The refractive index (n1) of the light guide body 23 is equal to or more than about 1.42; the refractive index preferably falls within a range from about 1.59 to about 1.65. The refractive index (n2) of the low refractive index layer 24 is less than about 1.42; the refractive index preferably falls within a range from about 1.10 to about 1.35. The relationship “n1/n2>1.18 (=1.59/1.35)” preferably holds true between the refractive index (n1) of the light guide body 23 and the refractive index (n2) of the low refractive index layer 24.
When the light guide body 23 is formed of an acrylic resin or the like, it is possible to acquire a refractive index of about 1.49 as the refractive index of the light guide body 23; when the light guide body 23 is formed of polycarbonate or the like, it is possible to acquire a refractive index of about 1.59 as the refractive index of the light guide body 23. When the light guide body 23 is formed of the acrylic resin, as compared with a case where the light guide body 23 is formed of polycarbonate, it is possible to further enhance translucency. When the low refractive index layer 24 is formed of fluorine acrylate or the like, it is possible to acquire a refractive index of about 1.35 as the refractive index of the low refractive index layer 24. When the low refractive index layer 24 is formed of resin or the like that contains hollow particles such as a nano-sized inorganic filler, it is possible to acquire a refractive index of about 1.30 or less as the refractive index of the low refractive index layer 24.
The light guide body 23 is formed substantially in the shape of a rectangular parallelepiped. Specifically, the light guide body 23 is formed such that the light emitting surface 23b and the back surface 23c of the light guide body 23 are substantially parallel to each other. The light emitting surface 23b is one example of a “front surface of a light guide body”, a “surface where a first reflective portion is provided” and a “front surface of a light guide member” according to the present invention. The back surface 23c is one example of a “surface where a third reflective portion is provided” according to the present invention.
The light entering surface 23a of the light guide body 23 is arranged substantially parallel to the light emitting surface of the LEDs 21.
In the first embodiment, as shown in
The flat surface portions 23d are formed within the same surface as the light emitting surface 23b, and are formed substantially parallel to the back surface 23c. As shown in
The concave prism 23e is formed with an inclination surface 23f that is inclined with respect to the flat surface portion 23d (the light emitting surface 23b) and a vertical surface 23g that is substantially vertical with respect to the flat surface portion 23d (the light emitting surface 23b). The inclination surface 23f is one example of a “first inclination surface” according to the present invention.
As shown in
As shown in
The inclination surface 23f (the prism 23e) is formed to have a predetermined width W2 in the B-direction. The width W2 of the inclination surface 23f (the prism 23e) in the B-direction is equal to or less than about 0.25 mm; the width W2 preferably falls within a range from about 0.01 mm to about 0.10 mm. The inclination surfaces 23f (the prisms 23e) are arranged in the B-direction with a predetermined pitch P1 (=W1+W2).
The width W1 of the flat surface portion 23d in the B-direction, the inclination angle α1 of the inclination surface 23f, the width W2 of the inclination surface 23f (the prism 23e) in the B-direction and the pitch P1 of the inclination surfaces 23f (the prisms 23e) in the B-direction may be constant regardless of the distance from the LEDs 21.
In the first embodiment, as shown in
The flat surface portions 23h are formed within the same surface as the back surface 23c. The flat surface portion 23h is formed to have a predetermined width W3 in the A-direction.
The concave prism 23i is formed with a pair of inclination surfaces 23j that is inclined with respect to the flat surface portion 23h (the back surface 23c). The angle (the vertex angle of the prism 23i) α2 formed by the pair of inclination surfaces 23j preferably falls within a range from about 120° to about 140°.
The pair of inclination surfaces 23j (the prism 23i) is formed to have a predetermined width W4 in the A-direction. The width W4 of the pair of inclination surfaces 23j (the prism 23i) in the A-direction is equal to or less than about 0.1 mm; the width W4 preferably falls within a range from about 0.010 mm to about 0.030 mm.
The pitch P2 (=W3+W4) of the prisms 23i in the A-direction preferably satisfies a formula “P2≧W4×2.” In other words, the width W3 of the flat surface portion 23h in the A-direction is preferably equal to or more than the width W4 of the pair of inclination surfaces 23j in the A-direction.
The prisms 23i are preferably formed to have the same shape, the same size and the same pitch regardless of the position where the prism 23i is formed within the surface of the light guide body 23. In other words, the width W3 of the flat surface portion 23h in the A-direction, the angle (the vertex angle of the prism 23i) α2 formed by the pair of inclination surfaces 23j, the width W4 of the pair of inclination surfaces 23j (the prism 23j) in the A-direction and the pitch P2 of the pairs of inclination surfaces 23j (the prism 23j) in the A-direction are preferably set constant on an individual basis.
As shown in
In the back surface 24a (the back surface of the light guide plate 22) of the low refractive index layer 24, a plurality of concave prisms 24b are formed. The prisms 24b are formed in at least the entire light emitting region 22a (see
As shown in
In the first embodiment, the inclination surface 24c is formed to be not curved but flat. The inclination surface 24c is formed such that, as the inclination surface 24c extends away from the LEDs 21, the inclination surface 24c extends closer to the light guide body 23. An inclination angle α3 at which the inclination surface 24c is inclined with respect to the back surface 24a preferably falls within a range from about 40° to about 50°. In other words, the angle formed by the inclination surface 24c and the vertical surface 24d preferably falls within a range from about 50° to about 40°.
The inclination surface 24c (the prism 24b) is formed to have a predetermined width W5 in the B-direction. The width W5 of the inclination surface 24c (the prism 24b) in the B-direction is equal to or less than about 0.1 mm; the width W5 preferably falls within a range from about 0.010 mm to about 0.025 mm.
The inclination surfaces 24c (the prisms 24b) are arranged in the B-direction with a pitch P3 equal to the width W5. In other words, a plurality of prisms 24b are formed in the B-direction without any space; no flat surface portion is provided between the prism 24b and the prism 24b.
Regardless of the position where the prism 24b is formed within the surface of the low refractive index layer 24, in substantially the entire back surface 24a of the low refractive index layer 24, the prisms 24b may be formed to have the same shape, the same size and the same pitch. The prisms 24b are formed to have the same shape, the same size and the same pitch in this way, and thus it is possible to reduce a change in the light collecting property within the surface of the low refractive index layer 24. It is therefore possible to make uniform the brightness of the liquid crystal display panel 10.
The optical path of light emitted from the LEDs 21 of the backlight device 20 according to the first embodiment will now be described with reference to
The light emitted from the LEDs 21 has high intensity in the forward direction (the B-direction) of the LEDs 21, and spreads at an angle of ±90° with respect to the forward direction (the B-direction) both in the A-direction and in the C-direction. As shown in
Of the light that has entered the light entering surface 23a of the light guide body 23, light Q1 that travels toward the light emitting surface 23b of the light guide body 23 travels toward the inclination surface 23f of the prism 23e at an angle of incidence that is equal to or more than θ2 (=90°−θ1−α1), and much of the light is totally reflected by the prism 23e (the interface between the light emitting surface 23b of the light guide body 23 and the air layer) of the light guide body 23 toward the back surface 23c.
Then, light Q2 that has been totally reflected by the prism 23e travels toward the back surface 23c (the low refractive index layer 24) at an angle of incidence that is equal to or more than θ3 (=90°−θ1−α1×2). Here, of the light Q2 that travels toward the back surface 23c, only light incident at an angle of incidence that is less than a critical angle between the light guide body 23 and the low refractive index layer 24 enters the low refractive index layer 24. On the other hand, of the light Q2 that travels toward the back surface 23c, light incident at an angle of incidence that is equal to or more than the critical angle between the light guide body 23 and the low refractive index layer 24 is totally reflected toward the light emitting surface 23b by the back surface 23c (the interface between the light guide body 23 and the low refractive index layer 24) of the light guide body 23.
Light Q3 that has been totally reflected by the back surface 23c travels toward the inclination surface 23f of the prism 23e at an angle of incidence that is equal to or more than θ4 (=90°−θ1−α1×3), and is totally reflected by the prism 23e of the light guide body 23 toward the back surface 23c.
Then, light Q4 that has been totally reflected by the prism 23e travels toward the back surface 23c (the low refractive index layer 24) at an angle of incidence that is equal to or more than θ5 (=90°−θ1−α1×4). Here, of the light Q4 that travels toward the back surface 23c, only light incident at an angle of incidence that is less than the critical angle between the light guide body 23 and the low refractive index layer 24 enters the low refractive index layer 24. On the other hand, of the light Q4 that travels toward the back surface 23c, light incident at an angle of incidence that is equal to or more than the critical angle between the light guide body 23 and the low refractive index layer 24 is totally reflected toward the light emitting surface 23b by the back surface 23c of the light guide body 23.
As described above, the light emitted from the LEDs 21 is repeatedly reflected between the prism 23e (the light emitting surface 23b) and the back surface 23c of the light guide body 23, and thus the light is guided such that the angle of incidence with respect to the back surface 23c of the light guide body 23 is gradually reduced, and enters the low refractive index layer 24.
The light emitted from the LEDs 21 is repeatedly reflected between the prism 23e and the back surface 23c of the light guide body 23, and thus the angle of incidence with respect to the back surface 23c of the light guide body 23 is reduced by about (α1×2) at a time. Hence, the angle of spread of the light in the B-direction that has entered the low refractive index layer 24 is equal to or less than about (α1×2).
Of the light that has entered the light entering surface 23a of the light guide body 23, light Q5 that travels toward the back surface 23c of the light guide body 23 is likewise repeatedly reflected between the back surface 23c of the light guide body 23 and the prism 23e (the light emitting surface 23b), and enters the low refractive index layer 24.
Thereafter, as shown in
Since the refractive index (n1) of the light guide body 23 is equal to or more than about 1.42 (from about 1.59 to about 1.65) and the refractive index of the air layer is about 1, the critical angle between the light guide body 23 and the air layer is lower than that between the light guide body 23 and the low refractive index layer 24. Hence, almost no light is emitted from the light emitting surface 23b without passing through the prisms 24b of the low refractive index layer 24.
Since, in the first embodiment, as shown in
Here, as seen from the side of the light entering surface 23a of the light guide body 23, light incident at a large angle of incidence with respect to the back surface 23c of the light guide body 23 is reflected by the inclination surface 23j of the prism 23i, and thus the angle of incidence with respect to the back surface 23c of the light guide body 23 is reduced.
Then, the light from the LEDs 21 enters the low refractive index layer 24 as described above while being diffused in the A-direction.
The reason why the spread of the light emitted from the light guide plate 22 in the A-direction is suppressed will now be described in detail with reference to
The light emitted from the LEDs 21 spreads at an angle of ±90° with respect to the forward direction (the B-direction) of the LEDs 21 both in the A-direction and in the C-direction. The light emitted from the LEDs 21 is refracted when entering the light entering surface 23a of the light guide body 23, and spreads at an angle of ±θ1 with respect to the B-direction both in the A-direction and in the C-direction. The angle θ1 is the critical angle between the light guide body 23 and the air layer.
Here, when, within the light guide body 23, the light is present within an angle range θ with respect to the B-direction both in the A-direction and the C-direction, formula (1) below holds true:
θ≦θ1=arcsin(1/n1) (1)
When the critical angle between the light guide body 23 and the low refractive index layer 24 is assumed to be φ, only light of a region that satisfies formula (2) below may enter the low refractive index layer 24:
π/2−θ<φ=arcsin(n2/n1) (2)
When this region is shown diagrammatically, it is represented by a region T1 (hatched region) of
When a component of the light entering the light guide body 23 that spreads in the C-direction is assumed to be θC, the angle of incidence at which the light enters the low refractive index layer 24 is π/2−θC. Since the conditions under which the light enters the low refractive index layer 24 are π/2−θC<φ and φ<π/2−θC<90, formula (3) below is given:
cos(π/2−θC)=sin θC>cos φ (3)
When a component of the light entering the light guide body 23 that spreads in the A-direction is assumed to be θA, it follows from
sin2 θA=sin2 θ−sin2 θC (4)
Here, since sin θ≦sin θ1 and cos φ<sin θC≦sin θ1 are given by formulas (1) and (3) above, formula (5) below is given by formula (4) above:
0≦sin2 θA<sin2 θ1−cos2 φ (5)
For example, when n1=1.59 and n2=1.35, the permissible range of θA is expressed by 0≦θA<19.95, and thus the spread of the light in the A-direction can be suppressed. Although the effect of suppressing the spread of the light in the A-direction is slightly reduced by the prisms 23i, since the width W3 of the flat surface portion 23h in the A-direction is equal to or more than the width W4 of the prism 23i in the A-direction, much of the effect of suppressing the spread of the light in the A-direction can be maintained.
The influences of the flat surface portions 23h and the prisms 23i will be further described. With respect to the light reflected by the flat surface portions 23h of the light guide body 23, as shown in
Thus, it is possible to suppress uneven spread of the light both in the C-direction and the A-direction within the light guide body 23. In other words, since the prisms 23i change the spread of the light both in the C-direction and the A-direction within the light guide body 23 at any time, it is possible to make the components of the light in the C-direction and the A-direction equivalent to each other.
Hence, with respect to the light of the region T1 satisfying formula (2) above, the components of the light that spreads both in the C-direction and the A-direction are changed by the prisms 23i, and thus, when the light satisfies formula (3) above, the light enters the low refractive index layer 24. Consequently, it is possible to uniformly emit, from the light guide plate 22, the light in which the spread of the light in the A-direction is suppressed.
The method of manufacturing the light guide plate 22 of the backlight device 20 according to the first embodiment will now be described with reference to
The light guide body 23 is first formed with an imprint method using heat. Specifically, as shown in
Then, the film material 23k is separated from the upper mold 30 and the lower mold 31 and is cooled, and is divided into individual pieces, with the result that the light guide body 23 can be obtained as shown in
Although, instead of the imprint method, the light guide body 23 can be formed by injection molding, when the light guide body 23 is formed using the film material 23k with the imprint method, it is possible to manufacture the light guide body 23 with a roll-to-roll method. In this way, it is possible not only to reduce the manufacturing time but also to reduce the manufacturing cost.
Thereafter, with the imprint method using UV light (ultraviolet rays), the low refractive index layer 24 is formed on the back surface 23c of the light guide body 23. Specifically, as shown in
As shown in
Then, as shown in
The processes up to the formation of the low refractive index layer 24 may be performed with the roll-to-roll method, and thereafter the light guide plate 22 (the light guide body 23 and the low refractive index layer 24) may be divided into individual pieces.
In the first embodiment, as described above, in the light emitting surface 23b of the light guide body 23, a plurality of prisms 23e that gradually reduce the angle of incidence of the light from the LEDs 21 with respect to the back surface 23c of the light guide body 23 are provided, and thus the light from the LEDs 21 is guided while being reflected repeatedly between the light emitting surface 23b and the back surface 23c of the light guide body 23, with the result that the angle of incidence of the light with respect to the back surface 23c of the light guide body 23 is gradually reduced. Then, when the angle of incidence of the light with respect to the back surface 23c of the light guide body 23 becomes lower than the critical angle between the light guide body 23 and the low refractive index layer 24, the light from the LEDs 21 enters the low refractive index layer 24. Hence, the angle of spread of the light in the B-direction that enters the low refractive index layer 24 is reduced, and the angle of spread of the light in the B-direction that is reflected off the interface between the back surface 24a of the low refractive index layer 24 and the air layer is also reduced. In other words, it is possible not only to enhance the light collecting property but also to enhance the brightness of the liquid crystal display panel 10. Consequently, since it is unnecessary to provide a plurality of optical sheets such as a diffusion plate and a light collecting lens on the light guide plate 22, it is possible not only to reduce the thickness of the backlight device 20 but also to reduce an increase in the manufacturing cost.
Moreover, since it is unnecessary to provide a plurality of optical sheets, no loss of light is produced when the light passes through the optical sheets. Thus, it is possible to enhance the efficiency of use of light.
A plurality of prisms 23e that gradually reduce the angle of incidence of the light with respect to the back surface 23c of the light guide body 23 are provided, and thus the light from the LEDs 21 is guided while being reflected repeatedly between the light emitting surface 23b and the back surface 23c of the light guide body 23, with the result that, as the light travels away from the LEDs 21, the angle of incidence with respect to the back surface 23c of the light guide body 23 is reduced and the light is more likely to enter the low refractive index layer 24. In this way, both in a part which is close to the LEDs 21 and in which a large amount of light (luminous flux) is present and in a part which is distant from the LEDs 21 and in which a small amount of light (luminous flux) is present, it is possible to make uniform the amount of light entering the low refractive index layer 24. Consequently, since light can be uniformly emitted from the entire light emitting region 22a of the light guide plate 22, it is possible to make uniform the brightness of the liquid crystal display panel 10.
As described above, in the first embodiment, a plurality of prisms 24b that reflect forwardly the light from the LEDs 21 are formed in substantially the entire back surface 24a of the low refractive index layer 24 over the light emitting region 22a of the light guide plate 22, and thus the light can be uniformly reflected by the prisms 24b over substantially the entire light emitting region 22a of the light guide plate 22. In this way, since it is possible to more uniformly emit light from the entire light emitting region 22a of the light guide plate 22, it is possible not only to reduce the production of dot unevenness but also to make more uniform the brightness of the liquid crystal display panel 10.
As described above, in the first embodiment, a plurality of prisms 24b have the function of totally reflecting the light from the LEDs 21, and thus it is possible to suppress the emission of light that has entered the low refractive index layer 24 through the light guide body 23 from the back surface 24a of the low refractive index layer 24. In this way, since the loss of the light is reduced, it is possible to further enhance the efficiency of use of light.
Since the prisms 24b have the function of totally reflecting the light from the LEDs 21, unlike the case where the metallic mirror is provided on the back surface 24a of the low refractive index layer 24 and the light is reflected by the metallic mirror, the light is not absorbed by the metallic mirror when the light is reflected. Thus, it is possible to further enhance the efficiency of use of light.
Since it is unnecessary to provide the metallic mirror on the back surface 24a of the low refractive index layer 24, as compared with the case where the metallic mirror is provided on the back surface 24a of the low refractive index layer 24, it is possible not only to prevent the manufacturing time of the light guide plate 22 from being elongated but also to reduce an increase in the manufacturing cost.
In the first embodiment, as described above, the light emitting surface 23b and the back surface 23c of the light guide body 23 are formed substantially parallel to each other, and thus it is possible to easily form the low refractive index layer 24 on the back surface 23c of the light guide body 23 as compared with, for example, the case where the wedge-shaped light guide body in which the back surface is inclined with respect to the light emitting surface is used.
In the first embodiment, as described above, the inclination surface 23f that is inclined with respect to the light emitting surface 23b of the light guide body 23 is provided in the prism 23e, and thus it is possible to easily and gradually reduce the angle of incidence of the light from the LEDs 21 with respect to the back surface 23c of the light guide body 23.
Since, in the first embodiment, as described above, the inclination surface 23f is inclined at an angle of 5° or less (0.1° or more but 3° or less) with respect to the light emitting surface 23b of the light guide body 23, the light is repeatedly reflected between the prisms 23e and the back surface 23c, and thus the angle of incidence of the light with respect to the back surface 23c of the light guide body 23 is reduced by 10° or less (0.2° or more but 6° or less) at a time. In this way, it is possible to more easily and gradually reduce the angle of incidence of the light with respect to the back surface 23c of the light guide body 23.
In the first embodiment, as described above, the flat surface portion 23d is formed between the prisms 23e adjacent to each other in the B-direction, and thus it is possible to suppress the dispersion of the light emitted from the light guide body 23.
Since, in the first embodiment, as described above, a plurality of prisms 24b are continuously formed in the B-direction without any space, and thus the light can be more uniformly reflected by the prisms 24b, it is possible to more uniformly emit the light from the entire light emitting region 22a of the light guide plate 22. In this way, it is possible to make more uniform the brightness of the liquid crystal display panel 10.
Since, in the first embodiment, as described above, a plurality of prisms 24b are formed to have the same shape and the same size, and thus the light can be more uniformly reflected by the prisms 24b, it is possible to more uniformly emit the light from the entire light emitting region 22a of the light guide plate 22.
Since, in the first embodiment, as described above, a plurality of prisms 23i that diffuse the light from the LEDs 21 in the A-direction are formed on the back surface 23c of the light guide body 23, and thus the light can be diffused in the A-direction within the light guide body 23, it is possible to make uniform the brightness of a part of the liquid crystal display panel 10 opposite the front of the LEDs 21 and the brightness of parts of the liquid crystal display panel 10 other than the part opposite the front of the LEDs 21. In other words, it is possible to make more uniform the brightness of the liquid crystal display panel 10.
A plurality of prisms 23i that diffuse the light from the LEDs 21 in the A-direction are formed, and thus, light incident at a large angle of incidence with respect to the back surface 23c of the light guide body 23, as seen from the side of the light entering surface 23a of the light guide body 23, is reflected by the prisms 23i, with the result that it is possible to reduce the angle of incidence with respect to the back surface 23c of the light guide body 23. In this way, since it is possible to suppress the spread of the light entering the low refractive index layer 24 in the A-direction, it is possible to suppress the spread of the light emitted from the light guide plate 22 in the A-direction. Consequently, it is possible not only to enhance the property of collecting the light in the A-direction but also to further enhance the brightness of the liquid crystal display panel 10.
Since, in the first embodiment, as described above, the prism 23i is formed by the pair of inclination surfaces 23j, and thus the light from the LEDs 21 can be diffused toward both sides of the A-direction by the pair of inclination surfaces 23j, it is possible to further enhance the brightness of the liquid crystal display panel 10.
In the first embodiment, as described above, the width W3 of the flat surface portion 23h in the A-direction is equal to or more than the width W4 of the prism 23i in the A-direction, and thus the amount of light that passes through the flat surface portions 23h and then enters the low refractive index layer 24 can be increased as compared with the amount of light that passes through the prisms 23i and then enters the low refractive index layer 24. The light that passes through the flat surface portions 23h and then enters the low refractive index layer 24 is less inclined with respect to the C-direction than the light that passes through the prisms 23i and then enters the low refractive index layer 24. Hence, the width W3 of the flat surface portion 23h in the A-direction is made equal to or more than the width W4 of the prism 23i in the A-direction, and thus it is possible not only to suppress the spread of the light entering the low refractive index layer 24 in the A-direction but also to further enhance the property of collecting the light in the A-direction.
When the LEDs 21 are used as the light source, since it is more likely that the brightness of the part of the liquid crystal display panel 10 opposite the front of the LEDs 21 differs from the brightness of the parts of the liquid crystal display panel 10 other than the part opposite the front of the LEDs 21, it is especially effective to provide, as described above, a plurality of prisms 23i that diffuse the light from the LEDs 21 in the A-direction.
In the second embodiment, with reference to
In a backlight device 120 of the second embodiment of the present invention, as shown in
The light guide body 123 of the second embodiment is formed into the shape of a light guide body that is obtained by reversing the light guide body 23 of the first embodiment with respect to the C-direction.
Specifically, in the second embodiment, in the back surface 123c of the light guide body 123, along the direction (B-direction) of the normal to the light entering surface 123a of the light guide body 123, a plurality of flat surface portions 123d and a plurality of concave prisms 123e are formed alternately. The back surface 123c is one example of a “surface where a first reflective portion is provided” according to the present invention; the flat surface portion 123d is one example of a “first flat surface portion” according to the present invention. Moreover, the prism 123e is one example of a “first reflective portion” according to the present invention.
The concave prism 123e is formed with an inclination surface 123f that is inclined with respect to the flat surface portion 123d (the back surface 123c) and a vertical surface 123g that is substantially vertical with respect to the flat surface portion 123d (the back surface 123c). The inclination surface 123f is formed such that, as the inclination surface 123f extends away from the LEDs 21, the inclination surface 123f extends closer to a light emitting surface 123b. The light emitting surface 123b is one example of a “front surface of a light guide body”, a “front surface of a light guide member” and a “surface where a third reflective portion is formed” according to the present invention; the inclination surface 123f is one example of a “first inclination surface” according to the present invention.
In the second embodiment, as shown in
The concave prism 123i is formed by a pair of inclination surfaces 123j that are inclined with respect to the flat surface portions 123h.
The other portions of the structure of the backlight device 120 according to the second embodiment are the same as in the first embodiment.
In the backlight device 120 of the second embodiment, as shown in
Then, the light from the LEDs 21 enters the low refractive index layer 124. Thereafter, substantially all the light that has entered the low refractive index layer 124 is totally reflected by prisms 124b, and is emitted forwardly from the light emitting surface 123b. The prism 124b is one example of a “second reflective portion” according to the present invention.
The method of manufacturing the light guide plate 122 of the backlight device 120 according to the second embodiment is the same as in the first embodiment.
The effects of the second embodiment are the same as the first embodiment.
In the third embodiment, with reference to
In a backlight device 220 of the third embodiment of the present invention, as shown in
In the third embodiment, as shown in
In the third embodiment, as shown in
The back surface 223c of the light guide body 223 (the interface between the light guide body 223 and the low refractive index layer 224) is formed to be flat.
The other portions of the structure of the backlight device 220 according to the third embodiment and the optical path of the light emitted from the LEDs 21 are the same as in the first and second embodiments.
The method of manufacturing the light guide plate 222 of the backlight device 220 according to the third embodiment will now be described with reference to
As shown in
Then, as shown in
Then, the film materials 23k and 224e are separated from the upper mold 230 and the lower mold 231 and are cooled, and are divided into individual pieces, with the result that the light guide plate 222 composed of the light guide body 223 and the low refractive index layer 224 can be obtained as shown in
Since, in the third embodiment, as described above, the light guide body 223 and the low refractive index layer 224 can be formed simultaneously, it is possible not only to prevent the manufacturing time of the light guide plate 222 from being elongated but also to reduce an increase in the manufacturing cost.
The other effects of the third embodiment are the same as the first and second embodiments.
In the fourth embodiment, with reference to
In a backlight device 320 of the fourth embodiment of the present invention, as shown in
In the fourth embodiment, the light emitting surface 323b of the light guide body 323 is formed to be flat. The light emitting surface 323b is one example of a “front surface of a light guide body” and a “front surface of a light guide member” according to the present invention.
In the fourth embodiment, as shown in
In the fourth embodiment, as shown in
The other portions of the structure of the backlight device 320 according to the fourth embodiment, the optical path of the light emitted from the LEDs 21, the method of manufacturing the light guide plate 322 and the effects of the fourth embodiment are the same as the first and second embodiments.
In the fifth embodiment, with reference to
In a backlight device 420 of the fifth embodiment of the present invention, as shown in
Although, in
As shown in
In the fifth embodiment, a plurality of concave prisms 425b are formed on the back surface 425a (see
As shown in
The other portions of the structure in the fifth embodiment are the same as in the first to fourth embodiments.
In the backlight device 420 of the fifth embodiment, as shown in
Since the prism layer 425 has a higher refractive index than the low refractive index layer 424, the light that has entered the low refractive index layer 424 enters the prism layer 425 without being totally reflected by the back surface 424a (the interface between the low refractive index layer 424 and the prism layer 425) of the low refractive index layer 424.
Thereafter, as shown in
The method of manufacturing the light guide plate 422 of the backlight device 420 according to the fifth embodiment is the same as in the first to fourth embodiments.
In the fifth embodiment, as described above, the prism layer 425 is formed on the back surface 424a of the low refractive index layer 424 without the intervention of an air layer, and the prisms 425b are formed on the back surface 425a of the prism layer 425. In this way, it is unnecessary to provide prisms in the low refractive index layer 424, and thus it is possible to reduce the thickness of the low refractive index layer 424. Since a transparent material that is used for the low refractive index layer 424 and that has a relatively low refractive index is expensive, when the prism layer 425 is provided and the thickness of the low refractive index layer 424 is reduced, it is possible to reduce an increase in the manufacturing cost of the light guide plate 422.
The other effects of the fifth embodiment are the same as the first to fourth embodiments.
In the sixth embodiment, with reference to
In a backlight device 520 of a liquid crystal display device 501 according to the sixth embodiment of the present invention, as shown in
Although, in
In the sixth embodiment, the light shielding member 530 is arranged between the light guide plate 522 and the liquid crystal display panel 10.
Specifically, the light shielding member 530 is arranged above a part of the light emitting surface 523b of the light guide body 523 on the side of the LEDs 21 through a layer that has a lower refractive index than the low refractive index layer 524. The light emitting surface 523b is one example of a “front surface of a light guide body”, a “surface where a first reflective portion is provided” and a “front surface of a light guide member” according to the present invention.
Although, in
The other portions of the structure of the backlight device 520 according to the sixth embodiment, the optical path of the light emitted from the LEDs 21, and the method of manufacturing the light guide plate 522 are the same as in the first to fifth embodiments.
In the sixth embodiment, as described above, the light shielding member 530 is arranged above the part of the light emitting surface 523b of the light guide body 523 on the side of the LEDs 21. In a part of the light guide plate 522 near the LEDs 21, light is more likely to be emitted from the light guide plate 522 without the intervention of the low refractive index layer 524, and thus the brightness of a part of the liquid crystal display panel 10 near the LEDs 21 is more likely to be increased. Hence, when the light shielding member 530 is arranged above the part of the light guide body 523 (the light guide plate 522) near the LEDs 21, it is possible to shield the part of the light guide plate 522 near the LEDs 21 from light, with the result that it is possible to suppress the uneven brightness of the liquid crystal display panel 10.
The light shielding member 530 is arranged above the part of the light emitting surface 523b of the light guide body 523 on the side of the LEDs 21 through the layer (air layer) having a lower refractive index than the low refractive index layer 524, and thus, as compared with a case where the light shielding member 530 is arranged above the part of the light emitting surface 523b of the light guide body 523 on the side of the LEDs 21 without the intervention of the air layer, the light is easily reflected by the light emitting surface 523b of the light guide body 523. In other words, it is possible to suppress the emission of the light from light emitting surface 523b of the light guide body 523 and then the absorption of the light by the light shielding member 530. In this way, it is possible to further reduce a decrease in the efficiency of use of light.
The other effects of the sixth embodiment are the same as the first to fifth embodiments.
In the seventh embodiment, with reference to
A backlight device 620 of a liquid crystal display device 601 according to the seventh embodiment of the present invention, as shown in
In the seventh embodiment, the reflective member 630 is not embedded within prisms 524b of the low refractive index layer 524 in the light guide plate 522. The prism 524b is one example of a “second reflective portion” according to the present invention.
The reflective member 630 is formed with, for example, a dielectric multilayer mirror, a silver-coated reflective plate or a white PET resin; the reflective member 630 has the function of reflecting forwardly (toward the light guide plate 522) light emitted from the back surface 522c of the light guide plate 522.
Since, in the backlight device 620 of the present invention, much of light is not emitted from the back surface 524a of the low refractive index layer 524, a white PET resin that has a relatively low reflectivity and is inexpensive is preferably used as the reflective member 630.
The other portions of the structure of the backlight device 620 according to the seventh embodiment and the optical path of the light emitted from the LEDs 21 are the same as in the first to sixth embodiments.
Since, in the seventh embodiment, as described above, the provision of the reflective member 630 allows the light emitted from the back surface 524a of the low refractive index layer 524 to be reflected toward the light guide plate 522, it is possible to further enhance the efficiency of use of light.
The other effects of the seventh embodiment are the same as the first to sixth embodiments.
In the eighth embodiment, with reference to
In the backlight device of the eighth embodiment of the present invention, as shown in
For example, the inclination surface 724c may be arc-shaped. When, as shown in
In the eighth embodiment, as shown in
The other portions of the structure in the eighth embodiment are the same as in the first to fourth, the sixth and the seventh embodiments.
In the eighth embodiment, as described above, the inclination surfaces 724c of the prisms 724b are curved, and thus the light can be reflected totally and forwardly by the inclination surfaces 724c (the interface between the inclination surface 724c of the prism 724b and an air layer) of the prisms 724b while the light spreads in the B-direction. In other words, for example, as compared with the case where the inclination surface 24b shown in
The other effects of the eighth embodiment are the same as the first to fourth, the sixth and the seventh embodiments.
In the ninth embodiment, with reference to
In the backlight device of the ninth embodiment of the present invention, as shown in
When, as shown in
In the ninth embodiment, as shown in
The other portions of the structure in the ninth embodiment are the same as in the eighth embodiment.
The other effects of the ninth embodiment are the same as the fifth and eighth embodiments.
A confirmatory experiment that was conducted to confirm the effects described above will now be described with reference to
In this confirmatory experiment, on Examples 1 and 2 corresponding to the ninth embodiment, Example 3 corresponding to the fifth embodiment and Comparative Example 1 corresponding to the planar illumination device shown in
In Example 1, as shown in
In Example 2, as shown in
In Example 3, as shown in
In Comparative Example 1, as shown in
On Examples 1 to 3 and Comparative Example 1, the property of collecting light both in the A-direction and in the B-direction (distribution of light) was determined The results of the simulation were shown in
Therefore, it is shown that, by controlling the inclination angle of the inclination surface 825c, it is possible to control the angle of spread of the light in the B-direction. Since, as described above, the angle of spread of the light in the B-direction can be controlled, it is possible to control the wide viewing angle according to the application of the liquid crystal display device.
It is also shown that the following effects were produced. In other words, it is shown that, in Examples 1 to 3, as compared with Comparative Example 1, the increase in the angle of spread of the light in the A-direction can be suppressed. Specifically, in Examples 1 and 2, the full width at half maximum of the light in the A-direction was about 49°, and, in Example 3, the full width at half maximum of the light in the A-direction was about 55°. On the other hand, in Comparative Example 1, the full width at half maximum of the light in the A-direction was about 76°. As described above, by this experiment, it is also possible to confirm the effect of suppressing the spread of the light emitted from the light guide plate in the A-direction, as described in the first embodiment.
In the tenth embodiment, with reference to
In a liquid crystal display device 901 incorporating a backlight device 920 according to the tenth embodiment of the present invention, as shown in
In the tenth embodiment, the inclination surface 923d is formed in a region (first region) of the light emitting surface 923b of the light guide body 923 on the side of the LEDs 21. The inclination surface 923d is formed such that, as the inclination surface 923d extends away from the LEDs 21, it extends away from a back surface 923c. In other words, the inclination surface 923d is formed such that an angle formed by the inclination surface 923d and a light entering surface 923a is greater than 90°. The light emitting surface 923b is one example of a “front surface of a light guide body”, a “surface where a first reflective portion is provided” and a “front surface of a light guide member” according to the present invention. The inclination surface 923d is one example of a “third reflective surface” according to the present invention.
The inclination surface 923d is formed such that an angle α31 formed by the inclination surface 923d and the light emitting surface 923b falls within a range of about 1° to about 8°.
As described above and shown in
As shown in
In the region of the light guide body 923 other than the region where the inclination surface 923d is formed, as in the first embodiment, a plurality of prisms 923e are formed. The prism 923e is one example of a “first reflective portion” according to the present invention.
In the tenth embodiment, in a region (second region) of the low refractive index layer 924 that extends a predetermined distance W12 from the light entering surface 923a of the light guide body 923, the flat portion 924a where prisms 924b are not formed is provided. The region that extends the predetermined distance W12 from the light entering surface 923a of the light guide body 923 is arranged to correspond to the non-display region 10a of the liquid crystal display panel 10. In the region of the low refractive index layer 924 other than the region extending the predetermined distance W12 from the light entering surface 923a of the light guide body 923, the prisms 924b are formed. The region (the region other than the region extending the predetermined distance W12 from the light entering surface 923a) where the prisms 924b are formed is arranged to correspond to the display region 10b of the liquid crystal display panel 10. The prism 924b is one example of a “second reflective portion” according to the present invention.
The region 922a of a light guide plate 922 where the prisms 924b are provided in the low refractive index layer 924 functions as a light emitting region. The light guide plate 922 is one example of a “light guide member” according to the present invention.
The other portions of the structure in the tenth embodiment are the same as in the first to fifth and the sixth to eighth embodiments.
In the tenth embodiment, as described above, the inclination surface 923d is formed in the region of the light emitting surface 923b of the light guide body 923 on the side of the LEDs 21, and thus it is possible to increase the angle of incidence, with respect to the inclination surface 923d, of the light that travels from the light entering surface 923a or the back surface 923c of the light guide body 923 to the light emitting surface 923b of the light guide body 923. Thus, the light can easily be totally reflected by the inclination surface 923d toward the back surface 923c of the light guide body 923. In other words, it is possible to suppress the emission of light from the portion of the light guide body 923 near the LEDs 21. Consequently, it is possible to enhance the efficiency of use of light.
Since light that has been reflected by the inclination surface 923d toward the back surface 923c is more likely to be totally reflected by an interface between the back surface 923c of the light guide body 923 and the low refractive index layer 924, in the portion near the LEDs 21, it is possible to suppress the entry of the light into the low refractive index layer 924.
Since, in the tenth embodiment, as described above, in the region (the flat portion 924a) of the low refractive index layer 924 that corresponds to the non-display region 10a of the liquid crystal display panel 10, the prisms 924b are not formed, in the portion of the low refractive index layer 924 near the LEDs 21, the light is not reflected forwardly by the prisms 924b. In this way, it is possible to suppress the emission of the light from the portion of the light guide body 923 near the LEDs 21, and thus it is possible to further enhance the efficiency of use of light.
Since, in the tenth embodiment, as described above, the inclination surface 923d is formed such that the length W11 of the inclination surface 923d in the B-direction is about twice as long as the length W12 of the flat portion 924a of the low refractive index layer 924 in the B-direction, the light that has been reflected forwardly by the flat portion 924a of the low refractive index layer 924 can easily be totally reflected by the inclination surface 923d toward the back surface 923c.
The other effects of the tenth embodiment are the same as the first to fourth and the sixth to eighth embodiments.
In the eleventh embodiment, with reference to
In a liquid crystal display device 1001 incorporating a backlight device 1020 according to the eleventh embodiment of the present invention, as shown in
In the eleventh embodiment, in a region (second region) of the prism layer 1025 that extends a predetermined distance W12 from the light entering surface 923a of the light guide body 923, a flat portion 1025a where prisms 1025b are not formed is provided. In the region of the prism layer 1025 other than the region extending the predetermined distance W12 from the light entering surface 923a of the light guide body 923, the prisms 1025b are formed. The region 1022a of a light guide plate 1022 where the prisms 1025b are provided in the prism layer 1025 functions as a light emitting region. The prism 1025b is one example of a “second reflective portion” according to the present invention.
The other portions of the structure and the other effects in the eleventh embodiment are the same as in the tenth embodiment.
A confirmatory experiment that was conducted to confirm the effects of the inclination surface 923d of the light guide body 923 and the flat portion 1025a of the prism layer 1025 will now be described with reference to
In this confirmatory experiment, on Example 4 corresponding to the eleventh embodiment and Example 3 corresponding to the fifth embodiment, the luminous flux of light emitted from the liquid crystal display panel 10 was determined by simulation.
In Example 4, an angle α31 formed by the inclination surface 923d and the light emitting surface 923b was set at about 4°. In Example 4, as in Example 3, the refractive index of the light guide body 923 was set at 1.59, and the refractive index of the low refractive index layer 424 was set at 1.26.
Then, on Examples 3 and 4, the distribution of the luminous flux of the light emitted from the liquid crystal display panel 10 was determined, and the luminous flux of the light emitted from the non-display region 10a of the liquid crystal display panel 10 was determined The distribution of the luminous flux of the light determined by simulation on Example 4 and the distribution of the luminous flux of the light determined by simulation on Example 3 are shown in
When the luminous flux of the light emitted from the LEDs 21 was assumed to be 100, in Example 4, the luminous flux of the light emitted from the non-display region 10a of the liquid crystal display panel 10 was about 1. On the other hand, in Example 3, the luminous flux of the light emitted from the non-display region 10a of the liquid crystal display panel 10 was about 8. In other words, it is shown that, in Example 4, as compared with Example 3, the luminous flux of the light emitted from the non-display region 10a of the liquid crystal display panel 10 can be reduced to about one-eighth
In the twelfth embodiment, with reference to
In a backlight device according to the twelfth embodiment of the present invention, as shown in
Specifically, minute projections and recesses (not shown) are formed in the inclination surface 1124c and the vertical surface 1124d, and the minute projections and recesses have the function of increasing the angle of spread of light when the light is transmitted or reflected. The projections and recesses (not shown) may be formed either in the inclination surface 1124c or in the vertical surface 1124d.
The projections and recesses in the inclination surface 1124c and the vertical surface 1124d may be formed either chemically or mechanically. The projections and recesses may be formed by forming minute projections and recesses in the surface of a mold and then performing an imprint method with this mold. In this case, it is possible to simultaneously perform the formation of the prism 1124b and the formation of the projections and recesses.
The size and shape of the projections and recesses in the inclination surface 1124c and the vertical surface 1124d are controlled, and thus it is possible to control the angle of spread of light. The size and shape of the projections and recesses in the inclination surface 1124c and the vertical surface 1124d may be set such that they have desired haze values (=a value obtained by expressing in percentage a value obtained by dividing a scattered light transmittance by a total light transmittance).
In the twelfth embodiment, light that has entered the low refractive index layer 1124 is transmitted by the inclination surfaces 1124c and the vertical surfaces 1124d of the prisms 1124b while being diffused, and thereafter the light is reflected totally and forwardly by the inclination surfaces 1124c while being diffused in the B-direction. The light that has entered the low refractive index layer 1124 is diffused, for example, three to five times (five times in
The other portions of the structure in the twelfth embodiment are the same as in the first to fourth, the sixth to eighth and the tenth embodiments.
In the twelfth embodiment, as described above, the inclination surface 1124c and the vertical surface 1124d of the prism 1124b are formed as the light diffusing surfaces in which the minute projections and recesses are formed, and thus light can be transmitted or totally reflected by the inclination surfaces 1124c and the vertical surfaces 1124d of the prisms 1124b while being diffused. In other words, it is possible to prevent the angle of spread of the light that is reflected totally and forwardly from being lowered too much. In this way, it is possible not only to prevent the angle of spread of the light that is emitted from the light guide body 23 from being lowered too much but also to prevent the wide viewing angle of the liquid crystal display panel 10 from being lowered too much. Consequently, it is possible to prevent the dim liquid crystal display panel 10 from being viewed when seen in any position other than a position (a position of the liquid crystal display panel 10 in the C-direction) directly in front of the liquid crystal display panel 10.
Since, in the twelfth embodiment, as described above, the inclination surface 1124c and the vertical surface 1124d of the prism 1124b are formed as the light diffusing surfaces in which the minute projections and recesses are formed, and thus the light that is emitted from the light guide body 23 can be diffused, the light guide body 23 can emit light that is easy on the eyes
Since the light that is emitted from the light guide body 23 can also be diffused, it is also possible to reduce moiré fringes, which will be described in a fourteenth embodiment.
The other effects in the twelfth embodiment are the same as in the first to fourth, the sixth to eighth and the tenth embodiments.
In the thirteenth embodiment, with reference to
In a backlight device according to the thirteenth embodiment of the present invention, as shown in
In the thirteenth embodiment, as in the twelfth embodiment, light that has entered the prism layer 1225 is transmitted by the inclination surfaces 1225c and the vertical surfaces 1225d of the prisms 1225b while being diffused, and thereafter the light is reflected totally and forwardly (toward the light guide body 423) by the inclination surfaces 1225c while being diffused in the B-direction.
The other portions of the structure and the other effects in the thirteenth embodiment are the same as in the twelfth embodiment.
In the fourteenth embodiment, with reference to
In the fourteenth embodiment of the present invention, as shown in
When, as described above, regular groove lines (the prisms 23e and the prisms 24b) overlap each other, moiré fringes are more likely to occur. Specifically, when, as shown in
The moiré fringes occur even when the groove lines of the prisms 24b in the low refractive index layer and the groove lines of the prisms 23e in the light guide body 23 are arranged at an angle of, for example, a few tenths of a degree. The moiré fringes occur in such a direction that the distance between the intersections O is minimized.
By reducing the pitch d of the moiré fringes, it is possible to suppress the occurrence of the moiré fringes. It is clear that the pitch d of the moiré fringes changes as the pitch P1 of the prisms 23e (groove line n) and the pitch P3 of the prisms 24b (groove line m) are changed.
Hence, in the fourteenth embodiment, the pitch P1 of the prisms 23e and the pitch P3 of the prisms 24b are set at optimum values, and thus the pitch d is reduced and the occurrence of the moiré fringes in visual terms is suppressed.
Specifically, when the distance between the intersections O is assumed to be w, and k is a natural value, the pitch P1 of the prisms 23e and the pitch P3 of the prisms 24b are set such that the pitch d expressed by formula (11) below is minimized When the pitch d is minimized, it is preferable to fix one of the pitch P1 and the pitch P3 and then determine the other of the pitch P1 and the pitch P3 when the pitch d reaches the smallest.
d=P3×cos R/sin γ (11)
Here, R satisfies formula (12) below:
tan R=1/tan γ−k×P3/(P1×sin γ) (12)
“k” is such a value that the distance w between the intersections O is minimized Here, w is given by formula (13) below:
w={P12+(P1/tan γ−k×P3/sin γ)2}1/2 (13)
Although, in the fourteenth embodiment, the bias angle γ is not set, regardless of the value of the bias angle γ, the values P1 and P3 are not changed when the pitch d of the moiré fringes is minimized, and thus it is possible to conduct the calculation.
The method of writing formulas (11) to (13) will be described in detail below with reference to
As shown in
x=P1×n (14)
The groove line of the prism 24b in the low refractive index layer 24 is expressed by formula (15) below:
y=x/tan γ−P3×m/sin γ (15)
Formulas (14) and (15) above give formula (16) below:
y=P1×n/tan γ−P3×m/sin γ (16)
Since the pitch P1 of the groove lines of the prisms 23e is greater than the pitch P3 of the groove lines of the prisms 24b, for the intersections O on the moiré fringes, the relationship “m=k×n+N” is established between m, n and N. When the pitch P1 of the groove lines of the prisms 23e is less than the pitch P3 of the groove lines of the prisms 24b, the relationship “n=k×m+N” is established.
Substitution of the relationship “m=k×n+N” into formula (16) above yields the formula of the moiré fringes that is expressed by formula (17) below:
y=(P1/tan γ−P3×k/sin γ)/n−P3×N/sin γ (17)
The moiré fringes are expressed by formula (18) below in (x, y) coordinates:
y={1/tan γ−P3×k/(P1×sin γ)}x−P3×N/sin γ (18)
Since, in formulas (14) and (17) above, the distance between n=0 and n=1 is the distance w between the intersections O, formula (13) above is given.
As shown in formula (12) above, since 1/tan γ−k×P3/(P1×sin γ) is assumed to be tan R, formula (11) that is the formula of the pitch d of the moiré fringes is given by formula (18) above.
In the fourteenth embodiment, as described above, the pitch P1 of the prisms 23e and the pitch P3 of the prisms 24b are set such that the pitch d of the moiré fringes is minimized, and thus it is possible to reduce the pitch d of the moiré fringes, with the result that the occurrence of the moiré fringes in visual terms can be suppressed.
The other effects of the fourteenth embodiment are the same as the first to thirteenth embodiments.
In the fifteenth embodiment, with reference to
In the fifteenth embodiment of the present invention, as in the fourteenth embodiment, the prisms 23e of the light guide body 23 are formed with the constant pitch P1 (see
In the fifteenth embodiment, as shown in
The groove lines of the prisms 23e in the light guide body 23 may be formed obliquely to the light entering surface 23a (see
When the groove lines of the prisms 23e in the light guide body 23 and the groove lines of the prisms 24b in the low refractive index layer 24 are formed obliquely to the light entering surface 23a of the light guide body 23, and the light is reflected or transmitted by the prisms 23e of the light guide body 23 and the prisms 24b of the low refractive index layer 24, the light is refracted in the A-direction (see
Both the groove lines of the prisms 23e in the light guide body 23 and the groove lines of the prisms 24b in the low refractive index layer 24 may be formed obliquely to the light entering surface 23a of the light guide body 23.
Since, as the bias angle γ is increased, the light is more likely to be refracted in the A-direction, the bias angle γ is preferably equal to or less than 10 degrees.
In the fifteenth embodiment, as described above, the groove lines of the prisms 23e in the light guide body 23 and the groove lines of the prisms 24b in the low refractive index layer 24 are arranged to be inclined relative to each other when seen horizontally, and thus it is possible to reduce the pitch d of the moiré fringes. In this way, it is possible to suppress the occurrence of the moiré fringes in visual terms.
The other effects in the fifteenth embodiment are the same as in the first to fourteenth embodiments.
In the sixteenth embodiment, with reference to
In a backlight device 1320 of the sixteenth embodiment of the present invention, as shown in
In the sixteenth embodiment, the front surface 1323b and the back surface 1323c of the light guide body 1323 are formed with flat surfaces, and no prism is formed therein.
The prism layer 1326 is formed integrally on the front surface 1323b of the light guide body 1323 without the intervention of an air layer.
In the sixteenth embodiment, the prism layer 1326 has a higher refractive index than the low refractive index layer 1324; the prism layer 1326 preferably has a higher refractive index than the light guide body 1323.
In the light emitting surface 1326a of the prism layer 1326, a plurality of concave prisms 1326b for reducing an angle of incidence with respect to the low refractive index layer 1324 and a plurality of prisms (for example, the prisms 23e in the first embodiment) for diffusing the light in the A-direction are formed. The light emitting surface 1326a is one example of a “surface where a first reflective portion is provided” and a “front surface of a light guide member” according to the present invention; the prism 1326b is one example of a “first reflective portion” according to the present invention.
In the sixteenth embodiment, the light that has entered the light guide body 1323 is repeatedly reflected between the prisms 1326b of the prism layer 1326 and the back surface 1323c of the light guide body 1323, and thus the light is guided such that the angle of incidence with respect to the back surface 1323c of the light guide body 1323 is gradually reduced, and enters the low refractive index layer 1324. Then, the light is reflected totally and forwardly by the low refractive index layer 1324, and is emitted forwardly from the light emitting surface 1326a.
The light guide body 1323 may be formed with, for example, a glass substrate or a thermosetting resin. The low refractive index layer 1324 may be formed of, for example, a thermoplastic resin or a UV cured resin. The prism layer 1326 may be formed of, for example, a thermoplastic resin or a UV cured resin.
Although, in the sixteenth embodiment, a description is given of a case where the prism layer 1326 in which the prisms 1326b and the prisms (not shown) that diffuse light in the A-direction is formed on the front surface 1323b of the light guide body 1323, the prism layer 1326 in which the prisms 1326b and the prisms (not shown) that diffuse light in the A-direction may be formed on the back surface 1323c (between the light guide body 1323 and the low refractive index layer 1324) of the light guide body 1323. The prism layer 1326 in which the prisms 1326b are provided and the prism layer that diffuses the light in the A-direction may be separately formed on the front surface 1323b and the back surface 1323c of the light guide body 1323.
The other portions of the structure in the sixteenth embodiment are the same as in the first to fifteenth embodiments.
The method of manufacturing the light guide plate 1322 of the backlight device 1320 according to the sixteenth embodiment will now be described. With reference to
As shown in
Then, as shown in
Then, the film material 1324a, the light guide body 1323 and the film material 1326c are separated from the upper mold 1330 and the lower mold 1331 and are cooled, and are divided into individual pieces, with the result that the light guide plate 1322 can be obtained as shown in
For example, when the prism layer 1326 is formed on the back surface 1323c of the light guide body 1323 (between the light guide body 1323 and the low refractive index layer 1324), the low refractive index layer 1324 is preferably formed after the formation of the prism layer 1326.
With reference to
As shown in
As shown in
When the light guide body 1323 is formed with a transparent member such as glass, the UV light may be applied from the side of the light guide body 1323. Specifically, as shown in
Then, as shown in
As shown in
Then, the UV cured resin 1324b, the light guide body 1323 and the UV cured resin 1326d are separated from the quartz substrate 1335 and are divided into individual pieces, with the result that the light guide plate 1322 can be obtained as shown in
When the prism layer 1326 is formed on the back surface 1323c of the light guide body 1323 (between the light guide body 1323 and the low refractive index layer 1324), the low refractive index layer 1324 is preferably formed after the formation of the prism layer 1326.
Although, in the sixteenth embodiment, the prism layer 1326 is formed after the formation of the low refractive index layer 1324, the low refractive index layer 1324 may be formed after the formation of the prism layer 1326.
Although, in the sixteenth embodiment, the UV cured resin 1324b is cured and thereafter the UV cured resin 1326d is cured, for example, after application of the UV cured resin 1324b, the UV cured resin 1326d may be applied with the UV cured resin 1324b being semi-cured through a prebake. Both the UV cured resins 1324b and 1326d may be cured simultaneously by application of the UV light.
The method of manufacturing the other portions of the light guide plate 1322 in the sixteenth embodiment is the same as in the first embodiment.
Since, in the sixteenth embodiment, as described above, no prism is formed in the light guide body 1323, the front surface 1323b and the back surface 1323c of the light guide body 1323 can be formed as flat surfaces. In this way, it is possible to easily form the light guide body 1323 with a flat-plate glass or a thermosetting resin or the like.
The other effects in the sixteenth embodiment are the same as in the first to fifteenth embodiments.
In the seventeenth embodiment, with reference to
In a backlight device 1420 of the seventeenth embodiment of the present invention, as shown in
The prism layer 1425 is formed integrally on the back surface 1424a of the low refractive index layer 1424 without the intervention of an air layer.
The low refractive index layer 1424 may be formed of, for example, a thermoplastic resin or a UV cured resin. The prism layer 1425 may be formed of, for example, a thermoplastic resin or a UV cured resin.
The other portions of the structure in the seventeenth embodiment are the same as the sixteenth embodiment.
The method of manufacturing the light guide plate 1422 of the backlight device 1420 according to the seventeenth embodiment will now be described. With reference to
As shown in
Then, as shown in
Then, as shown in
Then, the film materials 1425a and 1424b, the light guide body 1323 and the film material 1326c are separated from the upper mold 1330 and the lower mold 1331 and are cooled, and are divided into individual pieces, with the result that the light guide body 1422 can be obtained as shown in
With reference to
As shown in
Then, as shown in
Then, as shown in
When the light guide body 1323 is formed with a transparent member such as glass, and the film material 1424b is formed of a transparent resin or a UV cured resin, the UV light may be applied from the side of the light guide body 1323. Specifically, as shown in
Then, as shown in
As shown in
Then, the light guide body 1323, the film material 1424b, the UV cured resin 1425b and the UV cured resin 1326d are separated from the quartz substrate 1335 and are divided into individual pieces, with the result that the light guide plate 1422 can be obtained as shown in
The method of manufacturing the other portions of the light guide plate 1422 in the seventeenth embodiment is the same as in the first embodiment.
The effects of the seventeenth embodiment are the same as the sixteenth embodiment.
It should be noted that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is indicated not by the description of the above embodiments but by the scope of claims, and further includes all modifications that are equivalent in meaning to the scope of claims and that fall within the scope of claims.
For example, although, in the above embodiments, the planar illumination device is applied to the backlight device, the present invention is not limited to this application. The planar illumination device may be applied to a planar illumination device other than the backlight device.
Although, in the above embodiments, the display panel and the display device are applied to the liquid crystal display panel and the liquid crystal display device, respectively, the present invention is not limited to this application. The display panel and the display device may be applied to a display panel and a display device other than the liquid crystal display panel and the liquid crystal display device.
Although, in the above embodiments, the LEDs are used as the light source, the present invention is not limited to this application. A light-emitting element other than the LED, such as a semiconductor laser element, may be used; a light source other than a light-emitting element may be used.
Although, in the above embodiments, the first to third reflective portions are formed with the prisms, the present invention is not limited to this configuration. The first to third reflective portions may be formed to have a structure other than prisms, such as cylinders.
Although, in the above embodiments, the prisms are formed to be concave, the present invention is not limited to this configuration. The prisms may be formed to be convex.
A layer such as an adhesive layer may be formed between the light guide body and the low refractive index layer. The refractive index of the layer, such as an adhesive layer, arranged between the light guide body and the low refractive index layer is not particularly limited. The refractive index is preferably higher than that of the low refractive index layer.
Although, in the above embodiments, the inclination angle (α1) of the first inclination surface (for example, the inclination surface 230 is formed regardless of the distance from the LEDs 21 such that the inclination angle is constant, the present invention is not limited to this configuration. As in a first variation of the present invention shown in
Although, in the above embodiments, the width (W1) of the first flat surface portion (for example, the flat surface portion 23d) in the B-direction is set regardless of the distance from the LEDs 21 such that the width is constant, the present invention is not limited to this configuration. As in a second variation of the present invention shown in
Although, in the above embodiments, the width (W2) of the first inclination surface (for example, the inclination surface 230 in the B-direction is set regardless of the distance from the LEDs 21 such that the width is constant, the present invention is not limited to this configuration. As in a third variation of the present invention shown in
Since, in the configuration of the first to third variations, light that is guided through a light guide body 1523, 1623 or 1723 is more likely to enter a low refractive index layer 1524 as the light guide body extends away from the LEDs 21, both in a part which is close to the LEDs 21 and in which a large amount of light (luminous flux) is present and in a part which is distant from the LEDs 21 and in which a small amount of light (luminous flux) is present, it is possible to make uniform the amount of light entering the low refractive index layer 1524. Consequently, it is possible to more uniformly emit light from the light guide body 1523, 1623 or 1723.
Although, in the above embodiments, the first flat surface portion (for example, the flat surface portion 23d) is formed between the first reflective portions (for example, the prisms 23e) adjacent to each other in the B-direction, the present invention is not limited to this configuration. A plurality of first reflective portions may be continuously formed in the B-direction without formation of the first flat surface portion and any space between the first reflective portions.
Although, in the above embodiments, the second reflective portions (for example, the prisms 24b) are continuously formed in the B-direction without any space therebetween, the present invention is not limited to this configuration. The flat surface portion may be formed between the second reflective portions adjacent to each other in the B-direction. In this case, the width of the flat surface portion in the B-direction is preferably minimized.
The values of the angles, the widths and the like described in the above embodiments are one example; values of the angles, the widths and the like that are different from those of the angles, the widths and the like described in the above embodiments may be employed.
Although, in the above embodiments, a layer other than the air layer is not provided on the front surface (light emitting surface) of the light guide member, the present invention is not limited to this configuration. A layer that has a lower refractive index than the low refractive index layer may be provided on the front surface of the light guide body.
Although, in the above embodiments, the second reflective portion (for example, the prism 24b) is formed with the inclination surface that is inclined with respect to the back surface of the light guide member and the vertical surface that is vertical with respect to the back surface, the present invention is not limited to this configuration. The vertical surface may be inclined, by a smaller amount than the inclination surface, with respect to the back surface of the light guide member.
Although, in the fourteenth and fifteen embodiments, the projections and recesses are formed in the inclination surfaces and the vertical surfaces of the prisms so as to diffuse the light that has entered the low refractive index layer and the prism layer, the present invention is not limited to this configuration. In order to diffuse the light that has entered the low refractive index layer and the prism layer, diffusing particles for diffusing the light may be contained in the low refractive index layer and the prism layer.
Although, in the above embodiments, when the light guide plate is formed, the prisms are formed using the flat plate-shaped mold and the quartz substrate, the present invention is not limited to this configuration. When the light guide plate is formed, the prisms may be formed using a roll-shaped mold and the quartz substrate.
Although, in the sixteenth and seventeenth embodiments, the second reflective portion formation layer (the prism layer 1326) and the first reflective portion formation layer (for example, the low refractive index layer 1324) are formed of the thermosetting resin or the UV cured resin, the present invention is not limited to this configuration. The second reflective portion formation layer (the prism layer 1326) and the first reflective portion formation layer (for example, the low refractive index layer 1324) may be formed of a thermoplastic resin.
Although, in the above embodiments, as one example of the method of forming the light guide plate, the method using the UV cured resin is employed, the present invention is not limited to this method. A light cured resin that is cured by light other than UV light may be used.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-053104 | Mar 2009 | JP | national |
| 2009-148805 | Jun 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/067465 | 10/7/2009 | WO | 00 | 8/15/2011 |
