Patent Application
20080259248
The present application claims priority from Japanese Patent Application Nos. 2007-110818 and 2008-89480, filed on Apr. 19, 2007, and Mar. 31, 2008, respectively, the disclosure of which is incorporated herein by reference in its entirety.
1 Field of the Invention
The present invention relates to a multilens member which controls the directivity of the incident light, the multilens member having an overhang shape. The present invention also relates to an illumination apparatus and a liquid crystal display apparatus based on the use of the same.
2. Description of the Related Art
Conventionally, various types of illumination apparatuses, such as backlight units for liquid crystal displays, are provided with any mechanism for adjusting the brightness and the broadening of the light beam emitted from the light source. In most of the illumination apparatuses, an optical member such as an optical sheet, which controls the directivity of the light, is installed in an optical path thereof or an light-exit port of a light source housing. The optical member has the light transmissivity, and it has such a function that the traveling direction of the incident light is aligned or uniformized in the predetermined direction and/or the incident light is diffused or diverged.
A representative example of the optical member, which is provided to uniformize the traveling direction of the incident light in the predetermined direction, i.e., to control the directivity of the incident light, is a prism sheet (see, for example, Japanese Patent Application Laid-open No. 10-506500 (PCT)). The prism sheet generally has the following structure. That is, a plurality of prism-shaped optical structural members (hereinafter referred to as “prism-shaped structural members” as well) or a lenticular lens-shaped optical structural members (hereinafter referred to as “lens-shaped structural members” as well) are continuously aligned or arranged on a sheet-shaped base member. The prism-shaped structural members extend in a predetermined direction and each of them has a triangular cross section in a direction perpendicular to the extending direction. The lens-shaped structural members extend in a predetermined direction and each of them has a semicircular (semielliptic) cross section in a direction perpendicular to the extending direction. In the case of the prism sheet, the traveling direction of the light beam (directivity of the light) is controlled in accordance with the prism effect or the lens effect by the optical structural members formed on the base member.
Conventionally, in the backlight unit for the liquid crystal display apparatus, for example, two prism sheets, each of which has a plurality of prism-shaped structural members provided on a base member as described above, are used. The respective prism sheets are arranged so that the extending directions of the prism-shaped structural members thereof are perpendicular to one another (see, for example, Japanese Patent Application Laid-open No. 10-506500 (PCT)).
The prism sheet group 207 is composed of two prism sheets 207a, 207b. As shown in
In the case of the backlight unit 201 based on the side light system as shown in
The following methods have been hitherto used as the method for forming the optical structural members such as those having, for example, the prism-shaped form or the lenticular lens-shaped form on the sheet-shaped base member in the optical member such as the prism sheet as described above. The methods include, for example, the thermal transfer (heat transfer) system and the photo-polymer method. In the thermal transfer method, a mold, which has recesses, on a surface thereof, corresponding to the shapes of the optical structural members such as those having, for example, the prism-shaped form or the lenticular lens-shaped form (as obtained by inverting the shapes of the optical structural members), is manufactured; the mold is heated; and the base member is pressed thereagainst to transfer the recesses of the surface of the mold onto the base member. In the photo-polymer method, the space between the mold and the base member is filled with an ultraviolet-curable resin, and then the resin is cured by being irradiated with the ultraviolet light to form the optical structural members.
An optical sheet, in which optical structural members are formed on both surfaces of a sheet-shaped base member, has been hitherto suggested as an optical sheet for controlling the directivity of the light-(see, for example, Japanese Patent No. 3455884).
As described above, in the conventional liquid crystal display apparatus and/or the illumination apparatus called “backlight unit” to be installed on the back surface of the display device such as the liquid crystal panel, a plurality of optical sheets ( for example, two prism sheets) are stacked. When the number of sheets is increased, the scattering and the absorption of the transmitted light are increased, and the optical performance is deteriorated. Further, when the number of sheets is increased, problems arise, for example, such that the thicknesses of the illumination apparatus and the liquid crystal display apparatus are increased, and the cost is raised.
The present invention has been made in order to solve the problems as described above, an object of which is to provide an optical member as well as an illumination apparatus and a liquid crystal display apparatus provided with the same, wherein it is possible to improve the optical performance of the illumination apparatus and the liquid crystal display apparatus and it is possible to realize the thin sizes (small sizes) and the low cost of the illumination apparatus and the liquid crystal display apparatus.
According to a first aspect of the present invention, there is provided a multilens member including a base member which has light transmissivity; a plurality of first lenses which are formed on the base member; and a plurality of second lenses each of which has a first surface facing the base member, and each of which is joined onto one of the first lenses at the first surface, wherein: the first surface of each of the second lenses has a junction which is joined to one of the first lenses and an overhang which overhangs outwardly from the junction.
The multilens member of the present invention resides in the optical member to provide the optical function including, for example, the prism function and the lens function with respect to the incident light, wherein the first lens group composed of the plurality of first lenses formed on the base member and the second lens group composed of the plurality of second lenses are joined to one another. That is, the optical member includes the optical structural member which is provided on the base member and which is composed of the first lens group and the second lens group. The phrase “first lenses and second lenses are joined” referred to in this specification has the meaning including not only the case in which the first lenses and the second lenses are directly jointed to one another by means of, for example, the fusion or welding but also the case in which the first lenses and the second lenses are indirectly joined to one another by using, for example, the adhesive (by the aid of any adhesive layer). When the surface of the first lens opposed to the base member is a curved surface, and the base member and the first lens make point-to-point contact with each other, then the surface of the first lens, which is disposed in the tangential direction of the portion allowed to make contact with the base member, is the surface of the first lens opposed to the base member.
In the multilens member of the present invention, for example, when both of the first lenses and the second lenses are formed with the prism-shaped structural members (structural members which extend in the predetermined direction and each of which has the triangular cross section in the direction perpendicular to the extending direction) as described above, and when the first lens group and the second lens group are joined to one another so that the extending directions of the prism-shaped structural members of the first lenses and the second lenses are perpendicular to one another, then the function, which is the same as or equivalent to that of the conventional prism sheet group composed of two prism sheets as described above, is obtained with one optical member. In this arrangement, in the case of the multilens member of the present invention, it is possible to reduce the thickness by an amount corresponding to one sheet of the base member of the prism sheet as compared with the conventional prism sheet group. Therefore, it is possible to realize the thin size and the low cost of the optical member. In the case of the multilens member of the present invention, it is possible to reduce the thickness by the amount corresponding to one sheet of the base member of the prism sheet as compared with the conventional prism sheet group. Therefore, it is possible to reduce the scattering and the absorption of the transmitted light, and it is possible to improve the optical performance.
In the case of the multilens member of the present invention, when the first lenses and the second lenses, which have different functions with respect to the incident light, are used, it is possible to allow one optical member to possess a plurality of optical functions. Therefore, it is also possible to widen the degree of freedom of the design of the optical member. It is possible to provide the optical member which is applicable to a variety of ways of use.
In the multilens member of the present invention, the surface (first surface) of the second lens, which is opposed to the base member, has the junction which is to be joined to the first lens and the overhang which is allowed to overhang outwardly from the junction. In other words, the surface (first surface) of the second lens, which is opposed to the base member, is larger than the junction between the first lens and the second lens. In this arrangement, the overhang structure (roof structure) is formed at the part of the optical structural member composed of the first lens and the second lens. Therefore, it is possible to increase the light which is allowed to outgo to the outside from the first lens and which is thereafter allowed to income into the second lens again. Therefore, it is possible to enhance the effect including, for example, the prism function and the lens function of the multilens member.
In the multilens member of the present invention, an angle, which is formed by the overhang of each of the second lenses and the base member, may not be less than 180 degrees. In this arrangement, it is possible to increase the areal size of the overhang of the second lens as viewed from the side surface of the first lens (surface other than the surface opposed to the second lens and the base member). It is possible to increase the light (an amount of the light) which is allowed to outgo to the outside from the first lens described above and which is thereafter allowed to come into the second lens again. Most of the light outgoing from the side surface of the first lenses travels upwardly (in a direction from the base member to the second lenses). When a light traveling upwardly (upward-outgoing light, upward emission light) among the light outgoing from the side surface of the first lenses, can be entered efficiently into the second lenses, the upward emission light can be further subjected to the optical function (prism function, lens function etc.) by the second lenses. Therefore, it is possible to enhance the effect including, for example, the prism function and the lens function of whole of the multilens member. Here, when the angle, which is formed between the overhang and the base member, is not less than 180 degrees, the upward emission light never travel parallel to the overhang. Therefore, a missing-light amount of the upward emission light can be decreased, because a light which travels in parallel to the overhang to go away without entering the second lenses can be decreased. That is, when the angle, which is formed between the overhang and the base member, is not less than 180 degrees, the light, which is allowed to outgo from the side surface of the first lens and which is directed toward the second lens, is successfully allowed to come into the second lens from the overhang. Therefore, it is possible to enhance the effect including, for example, the prism function and the lens function of whole of the multilens member.
In the multilens member of the present invention, hollow spaces may be defined by the first lenses and the second lenses.
In the optical structural member composed of the first lens group and the second lens group of the multilens member of the present invention, it is possible to form the structure in which the overhang of the second lens (outer wall surface of the second lens adjacent to the junction between the first lens and the second lens) protrudes from the junction to the outside (structure in which the projection allowed to protrude to the outside is formed on the side surface of the optical structural member composed of the first lens and the second lens). That is, it is possible to form the overhang structure at the part of the side surface of the optical structural member composed of the first lens and the second lens. In particular, when the structure, in which the upper surface of the plurality of first lenses are bridged by the second lenses, is provided, the hollow spaces, which are defined by the first lenses and the second lenses, are formed at the inside of the multilens member. When the multilens member has the hollow spaces or the overhang structure of the optical structural member therein as described above, the light beam, which is allowed to come into the multilens member, can pass through the interfaces between the optical structural member and the air a plurality of times. It is possible to increase the amount of refraction of the incident light.
In the case of the optical sheet described in Japanese Patent No. 3455884 described above, the incident light can be also allowed to pass through the interfaces between the optical structural member and the air a plurality of times (refracted a plurality of times). However, generally, the incident light can be refracted only twice at the light-incoming point and the light-outgoing point of the optical sheet, except for the incident light component having an extremely shallow angle of incidence with respect to the sheet surface (angle of incidence approximately in parallel to the sheet surface). On the contrary, when the multilens member has the hollow spaces at the inside or the overhang structure of the optical structural member as in the multilens member of the present invention, the light beam can be refracted by allowing the light beam to pass through the interfaces between the optical structural member and the air three times or more, depending on the optical path of the light beam. Therefore, in the case of the multilens member of the present invention, it is possible to increase the amount of refraction of the incident light, and it is possible to improve the light-collecting performance, as compared with the optical sheet described in Japanese Patent No. 3455884 as well.
In the multilens member of the present invention, each of the second lenses may have a tapered shape which is tapered in a direction directed from the base member toward the second lens. In this arrangement, the areal size of the surface of the second lens opposed to the base member is increased. Therefore, it is possible to increase the amount of the light which is included in the light directed from the first lens toward the air and which is allowed to come into the second lens again. It is possible to enhance the light-collecting performance of the optical sheet.
In the multilens member of the present invention, the overhang of each of the second lenses may be parallel to the base member. In this arrangement, the angle, which is formed by the overhang of the second lens and the base member, is 180 degrees. In this arrangement, there is no fear that the upward emission light, which is allowed to outgo from the side surface of the first lens and which is directed toward the second lens, travels in parallel to the overhang to go away without entering the second lenses. Therefore, the upward emission light is successfully allowed to come into the second lens from the overhang. The shape of the second lens is not complicated, the multilens sheet can be produced with ease. Further, it is possible to increase the areal size of the overhang surface of the second lens as viewed from the side surface of the first lens. It is possible to enhance the light-collecting performance of the optical sheet.
In the multilens member of the present invention, the first lenses may include a plurality of first linear members which extend in a first direction, and the first linear members may be aligned in a direction perpendicular to the first direction.
In the multilens member of the present invention, the second lenses may include a plurality of second linear members which extend in a second direction, and the second linear members may be aligned in a direction perpendicular to the second direction.
In the multilens member of the present invention, the first direction may be perpendicular to the second direction
In the multilens member of the present invention, the first direction may be parallel to the second direction. For example, when both of the first lenses and the second lenses are formed with the prism-shaped structural members as described above, and the extending directions of the first lenses and the second lenses are identical with each other, then the overhang structure is formed at the part of the side surface of the optical structural member composed of the first lenses and the second lenses. In this arrangement, in particular, the light beam, which comes into the first lens obliquely, is successfully allowed to pass through the interfaces between the optical structural member (lens) and the air a plurality of times. It is possible to increase the amount of refraction of the oblique incident light. Therefore, in this arrangement, the optical member is obtained, which is more preferable for the way of use in which the incident light is required to be refracted more abruptly (for example, for the illumination apparatus having such a structure that the light beam, which is allowed to come at a shallow angle, is allowed to outgo while greatly changing the angle).
In the multilens member of the present invention, a cross section of each of the first lenses in a plane perpendicular to the first direction may have a trapezoidal shape. In this arrangement, the junction surface between the first lens and the second lens is increased. Therefore, it is easy to form the second lenses on the first lenses, and it is possible to increase the strength of the multilens member.
In the multilens member of the present invention, a cross section of each of the second lenses in a plane perpendicular to the second direction may have a triangular shape. In the multilens member of the present invention, the plurality of second lenses may be arranged such that adjacent second lenses among the plurality of second lenses are separated.
In the multilens member of the present invention, each of the first lenses may include a first structure which has a joining portion joined to one of the second lenses, and a second structure of which length is shorter than that of the first structure, the length being in a direction from the base member toward the second lenses. Further, a shape of the first structure may be substantially same as that of the second structure. It is noted that the light, which passes through the junction between the first lens and the second lens and which travels toward the second lens, undergoes the decrease in the light-collecting effect to be brought about by the first lens. Therefore, it is desirable that the junction between the first lens and the second lens has a small areal size. In relation thereto, in the case of the multilens member of the present invention, the first lens is joined to the second lens at the part thereof (first structural member). Therefore, it is possible to decrease the areal size of the junction between the first lens and the second lens, and it is possible to improve the optical performance of the multilens member, as compared with the case in which the first lens and the second lens are joined to one another in the entire structural member for constructing the first lens.
According to a second aspect of the present invention, there is provided an illumination apparatus including a light source; and a multilens member including: a base member which has light transmissivity; a plurality of first lenses which are formed on the base member; and a plurality of second lenses each of which has a first surface facing the base member and each of which is joined onto one of the first lenses at the first surface, wherein the first surface of each of the second lenses has a junction which is joined to one of the first lenses and an overhang which overhangs outwardly from the junction. The illumination apparatus of the present invention may further comprise an optical guide plate which guides light emitted from the light source to the multilens member.
According to a third aspect of the present invention, there is provided a liquid crystal display apparatus including: a liquid crystal display device; a light source; and a multilens member including: a base member which has light transmissivity; a plurality of first lenses which are formed on the base member; and a plurality of second lenses each of which has a first surface facing the base member and each of which is joined to the plurality of first lenses at the first surface, wherein the first surface of each of the second lenses has a junction which is joined to one of the first lenses and an overhang which overhangs outwardly from the junction. The liquid crystal display apparatus of the present-invention may further include an optical guide plate which guides light emitted from the light source to the multilens member.
In the illumination apparatus and the liquid crystal display apparatus of the present invention, the multilens member of the present invention described above is used as the optical member for adjusting the directivity of the light. Therefore, it is possible to realize the thin size (small size) and the low cost of the illumination apparatus and the liquid crystal display apparatus. Further, it is possible to provide the illumination apparatus in which the optical performance is improved as compared with the conventional illumination apparatus and the liquid crystal display apparatus.
According to the multilens member of the present invention, the optical structural member, which is formed by joining the first lenses and the second lenses, is formed on the base member. Therefore, it is possible to improve the optical performance.
According to the multilens member, the illumination apparatus, and the liquid crystal display apparatus of the present invention, the first lenses and the second lenses are joined to one another, and it is unnecessary to form the first lenses and the second lenses on distinct base members respectively. Therefore, it is possible to realize the thin size and the low cost of the multilens member, the illumination apparatus, and the liquid crystal display apparatus.
An explanation will be specifically made below with reference to the drawings about embodiments of the multilens member, the illumination apparatus, and the liquid crystal display apparatus according to the present invention. However, the present invention is not limited thereto.
In this first embodiment, an explanation will be made about a liquid crystal display apparatus as well as an illumination apparatus and a multilens member to be used therefor.
A liquid crystal display panel used in the conventional liquid crystal display apparatus was used for the liquid crystal display panel 7. Specifically, although not shown, the structure of the liquid crystal display panel 7 was the following structure. That is, a polarizing plate, a glass substrate, a transparent conductive film for forming a pixel electrode, an orientation film, a liquid crystal layer, an orientation film, a transparent conductive film for forming an opposing electrode, a color filter, a glass substrate, and a polarizing plate were stacked in this order.
As shown in
The optical members other than the multilens sheet 10 were those which were the same as the optical members of the conventional backlight unit. Specifically, the optical guide plate 2 was formed of polycarbonate. A sheet, which was obtained by vapor-depositing silver on a surface of a PET film, was used for the reflecting sheet 3. A material, which was obtained by bead-coating a PET film, was used for the lower diffusion sheet 4, wherein the thickness was 70 μm and the haze was 85%. A material, which was obtained by bead-coating a PET film, was used for the upper diffusion sheet 6, wherein the thickness was 70 μm and the haze was 30%.
A polycarbonate (PC) sheet was used as the base member 50. Any arbitrary material is usable for the base member 50 of the multilens sheet 5 of the present invention, provided that the material is light transmissive. For example, acrylic resins such as polyethylene terephthalate (PET) are usable as the base member 50, other than PC. Any base member having any shape, which is not limited to only the sheet-shaped base member, is usable as the base member 50. For example, it is also allowable to use a plate-shaped base member having a thickness of about 0.5 to 100 mm, and it is also allowable to use a base member having a three-dimensional surface. When the sheet-shaped material is used as in this embodiment, it is preferable to use a sheet having a thickness of 30 to 500 μm in consideration of, for example, the easiness of the processing and the handling performance.
As shown in
In this embodiment, as described later on, the first prism-shaped structures 5a were formed such that the surface of the base member 50 was directly deformed by means of the thermal transfer method. That is, the first prism-shaped structures 5a were formed of polycarbonate. Any arbitrary material is usable as the material for forming the first prism-shaped structure 5a, provided that the material is light transmissive. It is preferable to appropriately select a resin material having a refractive index of 1.3 to 2.0 depending on, for example, the optical characteristic to be required and the way of use. For example, it is possible to use transparent plastic resins including, for example, acrylic resins, urethane resins, styrene resins, epoxy resins, and silicone resins, and transparent inorganic materials, including, for example, glass. In this embodiment, the refractive index of the first prism-shaped structure 5a was 1.59.
In this embodiment, the cross-sectional shape of the first prism-shaped structure 5a was such a shape that an apex portion of an isosceles triangle having an apex angle of 50 degrees was truncated into a planar surface so that the surface was parallel to the base, i.e., a trapezoidal shape (substantially triangular shape). The width of the upper side of the trapezoidal cross section was about 6.74 μm, the width of the lower side was about 100 μm, and the height was 100 μm. The shape and the size of the cross section of the first prism-shaped structure 5a were identical (uniform) in the extending direction (Y direction) of the first prism-shaped structure 5a. That is, the first prism-shaped structure 5a was formed with a linear member having a trapezoidal prism shape. In the first optical adjusting layer 51, the first prism-shaped structures 5a were arranged at a pitch of about 100 μm on the base member 50. The size and the pitch of the first prism-shaped structure 5a are appropriately changeable depending on, for example, the optical characteristic to be required and the way of use.
As shown in
In this embodiment, the second prism-shaped structure 5b was formed of an ultraviolet-curable resin. The refractive index of the second prism-shaped structure 5b was 1.53. Any arbitrary material is usable as the material for forming the second prism-shaped structure 5b, provided that the material is light transmissive in the same manner as the first prism-shaped structure 5a. It is preferable to appropriately select a resin material having a refractive index of 1.3 to 2.0 depending on, for example, the optical characteristic to be required and the usage (application).
In this embodiment, the cross-sectional shape of the second prism-shaped structure 5b was an isosceles triangle having an apex angle of 50 degrees, a width of the base of about 24 μm, and a height of about 12 μm. The shape and the size of the cross section of the second prism-shaped structure 5b were identical (uniform) in the extending direction (X direction) of the second prism-shaped structure 5b. That is, the second prism-shaped structure 5b was formed with a linear member having a triangular prism shape. The gap between the adjoining second prism-shaped structures 5b was about 5 μm, and the pitch of the second prism-shaped structures was about 29 μm.
In the multilens sheet 5 of this embodiment, as described later on, the second prism-shaped structures 5b were joined to the upper surfaces of the first prism-shaped structures 5a. Specifically, as shown in
As described above, in the multilens sheet 5 of this embodiment, the first prism-shaped structures 5a and the second prism-shaped structures 5b are joined to one another so that the extending direction of the first prism-shaped structures 5a is mutually perpendicular to the extending direction of the second prism-shaped structures 5b. Therefore, the function, which is the same as or equivalent to the function to be obtained by the conventional prism sheet group composed of the two prism sheets as described above, is obtained with one multilens sheet 5. In the multilens sheet 5 of this embodiment, it is possible to reduce the thickness by an amount corresponding to one sheet of the base member of the prism sheet as compared with the conventional prism sheet group. Therefore, it is possible to realize the thin size and the low cost of the optical member for the optical adjustment, the illumination apparatus including, for example, the backlight unit, and the liquid crystal display apparatus. In the multilens sheet 5 of this embodiment, it is possible to reduce the thickness by an amount corresponding to one sheet of the base member of the prism sheet as compared with the conventional prism sheet group. Therefore, it is possible to suppress the scattering and the absorption of the transmitted light, and it is possible to suppress the deterioration of the optical performance. That is, when the multilens sheet 5 of this embodiment is used, it is possible to provide the liquid crystal display apparatus and the backlight unit which are thin at the low cost, while maintaining, for example, the brightness (luminance), the field angle, and the display quality which are equivalent to or more excellent than those of the conventional technique.
Next, a method for manufacturing the multilens sheet of this embodiment will be explained with reference to
At first, a polycarbonate sheet having a thickness of 200 μm was prepared as the base member (Step S11 shown in
Subsequently, the second optical adjusting layer 52 (second lens group), which was composed of the plurality of second prism-shaped structures 5b, was formed as follows on the first optical adjusting layer 51 which was composed of the plurality of first prism-shaped structures 5a (Steps S13 and S14 shown in
An explanation will now be made about a production apparatus used to form the second optical adjusting layer 52 including the plurality of second prism-shaped structures 5b.
A projection-recess shape, which is obtained by inverting the projection-recess shape of the surface of the second optical adjusting layer 52, is formed on the surface of the roll mold 21. In this embodiment, the cross-sectional shape of the second prism-shaped structure 5b is triangular. Therefore, a plurality of V-shaped grooves 26, each of which corresponded to the cross-sectional shape of the second prism-shaped structure 5b, were formed on the surface of the roll mold 21.
In this embodiment, the second optical adjusting layer 52, which was composed of the plurality of second prism-shaped structures 5b, was formed as follows by using the production apparatus 20 described above. At first, the base member 50, which had the first optical adjusting layer 51 formed on the surface, was installed to the production apparatus 20, and the base member 50 was fed toward the roll mold 21 (in the direction of the arrow A as shown in
Subsequently, the ultraviolet-curable resin 27 was applied by the resin supply unit 22 to the surface of the roll mold 21 rotating in the direction of the arrow A1 as shown in
Subsequently, the ultraviolet light was radiated from the ultraviolet light radiation unit 25 onto the base member 50 in such a state that the ultraviolet-curable resin 27, which had passed through the space between the roll mold 21 and the control roll 24, was allowed to make contact with the upper surface portions of the first prism-shaped structures 5a. In this procedure, the ultraviolet-curable resin 27, which is contained in the grooves 26 of the surface of the roll mold 21, is cured to form the second prism-shaped structures 5b on the first optical adjusting layer 51. Further, the lower surfaces of the second prism-shaped structures 5b are adhered and fixed to the upper surfaces of the first prism-shaped structures 5a. The optical structure, which is composed of the first prism-shaped structures 5a and the second prism-shaped structures 5b, is formed on the base member 50 (Step S14 shown in
In order to exfoliate the second prism-shaped structures 5b from the surface of the roll mold 21 with ease, it is necessary that the adhesive force between the surface of the roll mold and the second prism-shaped structures 5b should be weaker than the adhesive force between the second prism-shaped structures 5b and the first prism-shaped structures 5a. For this purpose, it is preferable that the surface of the roll mold 21 is previously subjected to the mold release treatment. As for the mold release treatment, it is preferable to adopt a method in which the surface of the roll mold 21 is coated with a releasing agent including, for example, fluorine-based resin, DLC (diamond-like carbon), and inorganic matter such as TiN. In this embodiment, a coating agent of fluorine-based resin (KP-801M produced by Shin-Etsu Chemical Co., Ltd.) was added as the releasing agent to the surface of the roll mold 21.
In this embodiment, the multilens sheet 5 having the structure shown in
In the method for producing the multilens sheet of this embodiment, it is unnecessary to perform the filling agent-applying step and the washing step as compared with a manufacturing method of a third embodiment as described later on. Therefore, the method for producing the multilens sheet of this embodiment is easier and more convenient.
This embodiment is illustrative of the case in which only the second optical adjusting layer 52 was formed by using the production apparatus provided with the mold roll shown in
The structures of the first optical adjusting layer 51 and the second optical adjusting layer 52 of the multilens sheet 5 manufactured in this embodiment were observed by a scanning electron microscope (SEM). Obtained results are shown in
As clarified from the sectional image shown in
In the upper surface image shown in
Subsequently, the backlight unit (illumination apparatus) 10 was constructed as shown in
According to the result described above, it has been revealed that the optical characteristics (for example, the brightness, the field angle, and the display quality) can be improved as compared with the conventional technique, when the multilens sheet 5 of this embodiment is used. Further, the thickness can be reduced by the amount of one sheet of the base member in the backlight unit and the liquid crystal display apparatus based on the use of the multilens sheet 5 of this embodiment. Therefore, the optical characteristics can be not only improved as compared with the conventional technique, but the backlight unit and the liquid crystal display apparatus, which are thin at the low cost, can be also obtained.
This embodiment is illustrative of the exemplary case in which the first optical adjusting layer 51 is directly formed on the surface of the base member 50 by means of the thermal transfer method. However, the present invention is not limited thereto. For example, as in the third embodiment described later on, the first optical adjusting layer 51 (the plurality of first prism-shaped structures 5a) may be formed such that the base member is allowed to make contact with a mold having a surface formed with a projection-recess shape obtained by inverting the projection-recess shape of the first optical adjusting layer 51, and the ultraviolet-curable resin is charged and cured between the mold and the base member. Alternatively, the first optical adjusting layer 51 can be also formed, for example, by means of the well-known extrusion molding method, the press molding method, and the injection molding method in which the melted resin is injected into a mold having a template of the optical structure formed therein.
The method for joining the first prism-shaped structures 5a and the second prism-shaped structures 5b is not limited to the method described above. For example, as in the second embodiment described later on, an adhesive may be applied to at least one of the lower surface portion of the second prism-shaped structure 5b subjected to the extrusion molding and the upper surface portion of the first prism-shaped structure 5a, and the first prism-shaped structure 5a and the second prism-shaped structure 5b may be formed integrally by the aid of an adhesive layer.
In this second embodiment, a multilens sheet, which had the same or equivalent structure (structure shown in
At first, the first optical adjusting layer 51 (the plurality of first prism-shaped structures 5a) was formed on the base member 50 in the same manner as in the first embodiment (Steps S21 and S22 shown in
Subsequently, the second prism-shaped structures 5b (linear members (thread-like members, filiform members) each having a triangular prism shape) were molded by means of a method including, for example, the extrusion molding (Step S23 shown in
Subsequently, the second optical adjusting layer 52, which was composed of the plurality of second prism-shaped structures 5b, was formed on the first optical adjusting layer 51 as follows (Steps S24 and S25 shown in
An explanation will now be made about a production apparatus of this embodiment used to form the second optical adjusting layer 52 composed of the plurality of second prism-shaped structures 5b.
In this embodiment, as shown in
At first, the plurality of molded second prism-shaped structures 5b were wound around the holder 32. Subsequently, as shown in
Subsequently, the base member 50, on which the first optical adjusting layer 51 had been formed, was installed to the production apparatus 30, and the base member 50 was fed toward the guide roll 31 (in the direction of the arrow A4 shown in
Subsequently, as shown in
In this embodiment, the multilens sheet 5 having the structure shown in
In the backlight unit and the liquid crystal display apparatus based on the use of the multilens sheet 5 of this embodiment, the optical characteristic can be not only improved as compared with the conventional technique, but the thickness can be also reduced by the thickness corresponding to one sheet of the base member. Therefore, the backlight unit and the liquid crystal display apparatus, which are thin at the low cost, are obtained.
In this third embodiment, a multilens sheet, which had the same or equivalent structure (structure shown in
A polyethylene terephthalate (PET) sheet having a thickness of 50 μm was used as the base member 50.
The first prism-shaped structures 5a were formed of an ultraviolet-curable resin. The first prism-shaped structure 5a had a refractive index of 1.59. The cross-sectional shape of the first prism-shaped structure 5a was such a shape that an apex portion of an isosceles triangle having an apex angle of 90 degrees was truncated into a planar surface so that the surface was parallel to the base, i.e., a trapezoidal shape (substantially a triangular shape). The width of the upper side of the cross section was about 8 μm, the width of the lower side was about 40 μm, and the height was about 16 μm. The shape and the size of the cross section of the first prism-shaped structure 5a was identical (uniform) in the extending direction (Y direction) of the first prism-shaped structure 5a. That is, the first prism-shaped structure 5a was formed with a linear member having a trapezoidal prism shape. In the first optical adjusting layer 51, the first prism-shaped structures 5a were arranged at a pitch of about 40 μm on the base member 50. The size and the pitch of the first prism-shaped structure 5a are appropriately changeable depending on, for example, the optical characteristic to be required and the way of use. However, in the production method of this embodiment, it is preferable that the size of the first prism-shaped structure 5a is designed so that the pitch of the first prism-shaped structure 5a is within a range of 7 to 50 μm, in consideration of the processability (easiness of the processing) of the second prism-shaped structure 5b as described later on.
The second prism-shaped structures 5b were formed of the same or equivalent material as that of the first prism-shaped structures 5a. The second prism-shaped structure 5b had a refractive index of 1.59. The cross-sectional shape of the second prism-shaped structure 5b was an isosceles triangle having an apex angle of 90 degrees, a width of the lower side of about 30 μm, and a height of about 15 μm. The shape and the size of the cross section of the second prism-shaped structure 5b was identical (uniform) in the extending direction (X direction) of the second prism-shaped structure 5b. That is, the second prism-shaped structure 5b was formed with a linear member having a triangular prism shape. The gap between the adjoining second prism-shaped structures 5b was about 5 μm, and the pitch of the second prism-shaped structures 5b was about 35 μm.
Next, an explanation will be made with reference to
Subsequently, an aqueous solution of 10% polyvinyl alcohol (PVA, filler) was applied onto the first optical adjusting layer 51, followed by being dried and cured. After that, the surface applied with PVA was wiped with water to expose the upper surface portions of the first prism-shaped structures 5a. PVA was charged into the recesses of the first optical adjusting layer 51 as described above (Step S33 shown in
Subsequently, the second optical adjusting layer 52, which was composed of the plurality of second prism-shaped structures 5b, was formed on the first optical adjusting layer 51 (Step S34 shown in
When the upper surface portions of the first prism-shaped structures 5a are made flat as described above, the junction surfaces (adhesion surfaces or fusion surfaces) of the first prism-shaped structures 5a and the second prism-shaped structures 5b are widened. Therefore, the second prism-shaped structures 5b can be fixed onto the first prism-shaped structures 5a stably.
Subsequently, the multilens sheet 5, which was manufactured as described above, was immersed in water to apply the ultrasonic wave, and thus the filler (PVA) having been contained in the multilens sheet 5 was removed (Step S35 shown in
In this embodiment, the multilens sheet 5 was manufactured as described above. In the method for producing the multilens sheet 5 of this embodiment, it is unnecessary to form the first prism-shaped structures 5a and the second prism-shaped structures 5b on distinct base members respectively. Therefore, the multilens sheet can be manufactured easily at the low cost.
The method for forming the first optical adjusting layer 51 is not limited to the method of this embodiment described above. It is also possible to form the first optical adjusting layer 51 by deforming the base member 50 itself. For example, the thermal transfer method is also available such that a mold, which has a surface formed with a projection-recess shape obtained by inverting the projection-recess shape of the first optical adjusting layer 51, may be heated, and the mold may be pressed against the base member 50 to transfer the projection-recess shape of the mold to the base member, in the same manner as in the first embodiment. Alternatively, the first optical adjusting layer 51 can be also formed by means of the well-known extrusion molding method, the press molding method, and the injection molding method in which a melted resin is injected into a mold having a template of the optical structure formed therein.
The method for joining the first prism-shaped structures 5a and the second prism-shaped structures 5b is not limited to the-method of this embodiment described above as well. For example, as in the second embodiment, the second prism-shaped structures 5b may be manufactured by means of the method including, for example, the extrusion molding, the adhesive may be applied to at least one of the upper surface portions of the first prism-shaped structures 5a and the lower surface portions of the second prism-shaped structures 5b, and the first prism-shaped structures 5a and the second prism-shaped structures 5b may be joined to one another by the aid of the adhesive.
In this embodiment, the second optical adjusting layer 52 is formed in the same manner as the first optical adjusting layer 51. However, the present invention is not limited thereto. Another method for forming the second optical adjusting layer 52 is available. That is, it is also allowable to use, for example, the thermal transfer method in which a thermoplastic resin is dissolved and applied onto the first optical adjusting layer 51 to form a resin layer beforehand, and a heated mold is pressed against the resin layer to transfer a projection-recess shape of the mold. It is also possible to form the second optical adjusting layer 52 by means of, for example, the well-known extrusion molding method and the press molding method.
This embodiment is illustrative of the exemplary case in which the multilens sheet is immersed in the solvent to perform the ultrasonic washing when the filler is removed. However, the present invention is not limited thereto. For example, it is also allowable that the ultrasonic washing is not performed. Further, it is also allowable to perform the temperature regulation, for example, such that the solvent is heated to a predetermined temperature.
Subsequently, the optical characteristic was also evaluated for the multilens sheet 5 manufactured in this embodiment in the same manner as in the first embodiment. As a result, in the backlight unit of the third embodiment, the front luminance ratio was about 1.15 times that of the backlight unit of Comparative Example explained in the first embodiment, and the field angle was about 50 degrees as well. The luminance characteristic, which was more excellent than that of Comparative Example, was obtained.
In this fourth embodiment, a multilens sheet was manufactured, in which the extending direction of first prism-shaped structures (first lenses) of a first optical adjusting layer was the same as the extending direction of second prism-shaped structures (second lenses) of a second optical adjusting layer.
The multilens sheet 40 of this embodiment was manufactured in the same manner as in the third embodiment. However, when the second optical adjusting layer 43, which was composed of the plurality of second prism-shaped structures 45, is formed on the first optical adjusting layer 42 (Step S34 shown in
As shown in
The first prism-shaped structure 44 was formed of the ultraviolet-curable resin in the same manner as in the first embodiment. The refractive index of the first prism-shaped structure 44 was 1.58. In this embodiment, the trapezoidal cross section of the first prism-shaped structure 44 had the following size or dimension. That is, both of the bottom angles were 70 degrees, the width of the upper side was about 11.8 μm, the width of the lower side was about 30 μm, and the height was about 25 μm. The shape and the size of the cross section of the-first prism-shaped structure 44 was identical (uniform) in the extending direction (Y direction) of the first prism-shaped structure 44. That is, the first prism-shaped structure 44 was formed with a linear member having a trapezoidal prism shape. In the first optical adjusting layer 42, the first prism-shaped structures 44 were aligned at a pitch of about 30 μm. When the cross section of the first prism-shaped structure 44 is trapezoidal as in this embodiment, the junction surface is increased between the first prism-shaped structure 44 and the second prism-shaped structure 45 as described later on. Therefore, the second prism-shaped structure 45 is formed with ease. Further, it is possible to increase the strength of the multilens sheet 40.
As shown in
A material for forming the second prism-shaped structure 45 was the same as or equivalent to that of the first prism-shaped structure 44. The refractive index of the second prism-shaped structure 45 was 1.58. In this embodiment, the triangular cross section of the second prism-shaped structure 45 was a regular triangle (i.e., all of the three angles including the apex angle were 60 degrees) in which the width of the lower surface was about 27 μm (height was about 23.4 μm). The shape and the size of the cross section of the second prism-shaped structure 45 were identical (uniform) in the extending direction (Y direction) of the second prism-shaped structure 45. That is, the second prism-shaped structure 45 was formed with a linear member having a triangular prism shape. The gap between the adjoining second prism-shaped structures 45 was about 30 μm.
An explanation will be made with reference to
When the overhang structure is not provided at the part of the side surface of the optical structure, the oblique incident light 47 as shown in
The optical structure having the overhang structure as described above is not limited to the multilens sheet having the first prism-shaped structures 44 and the second prism-shaped structures 45 which extend in the identical direction as in the multilens sheet 40 shown in
A method may be also conceived to increase the amount of refraction with respect to the oblique incident light, in which a plurality of optical sheets having no overhang structure are stacked and used on a part of the side surface of the optical structure as shown in
The first to third embodiments described above are illustrative of the exemplary case in which the gaps are provided between the adjoining second prism-shaped structures in the second optical adjusting layer. However, the present invention is not limited thereto. The adjoining second prism-shaped structures may make contact with each other.
The first to third embodiments described above are illustrative of the exemplary case in which the prism-shaped structure, which has the trapezoidal cross section, is used as the first optical structure for constructing the first optical adjusting layer. However, the present invention is not limited thereto. A prism-shaped structure having a triangular cross section may be used as the first optical structure.
The first to third embodiments described above are illustrative of the exemplary case in which the linear member having the trapezoidal cross section is used as the first optical structure for constructing the first optical adjusting layer and the linear member having the triangular cross section is used as the second optical structure for constructing the second optical adjusting layer. However, the present invention is not limited thereto. The cross-sectional shapes of the first optical structure and the second optical structure can be appropriately changed depending on, for example, the optical characteristic to be required and the way of use. For example, one of the first optical structure and the second optical structure may be formed with a lens-shaped structure having a semicircular cross section. An example of such an arrangement is shown in
The second optical adjusting layer 82 as shown in
The multilens sheets of the first to fourth embodiments and the first to third modified embodiments described above are illustrative of the exemplary case in which both of the first optical structure and the second optical structure are formed with the linear members each of which has the predetermined cross-sectional shape and each of which extends in the predetermined direction. However, the present invention is not limited thereto. The first optical structure and/or the second optical structure may be formed with any member having, for example, a polygonal prism shape, a conical shape, and a semispherical (semielliptic) shape, other than the linear member. An example of such an arrangement is shown in
A multilens sheet 90 shown in
The multilens sheets of the first to fourth embodiments and the first to fourth modified embodiments described above are illustrative of the exemplary case wherein the overhang structure is provided at the part of the optical structure constructed by the first lenses and the second lenses. For example, as shown in
The multilens sheets of the first to fourth embodiments and the first to fourth modified embodiments described above are illustrative of the exemplary case wherein all of the first lenses have the junction portions (junction surfaces, joining portions) to be joined to the second lenses. However, the present invention is not limited thereto. The multilens sheet of the present invention may be constructed, for example, as a multilens sheet 400 shown in
In the sixth modified embodiment, both of the first members 410 and the second members 411 have the substantially identical shapes. In other words, the second member 411 has the triangular prism shape, and the first member 410 also has the substantially triangular shape having the flat joining portion 410a disposed at the upper portion. However, it is not necessarily indispensable that the first member and the second member have the substantially identical shapes. For example, the first member may have a substantially triangular prism shape, and the second member may have a semicolumnar shape. Further, a height of each of the first members of the first prism-shaped structures is the same with each other, in order to be joined to the second prism structures. However, it is not necessarily indispensable that a shape of each of the first members is the same with each other, and the shape of each of the first member can be formed arbitrary. The number and the arrangement of the first members having the junction portions may be arbitrary in the first prism-shaped structures, provided that the second lenses such as the second prism-shaped structures can be supported and/or fixed stably. Further, it is not necessarily indispensable that a shape of each of the second prism structures is the same with each other, and the shape of each of the second prism structures can be formed arbitrary. Furthermore, it is not necessarily indispensable that the directions of arrangement of the second prism-shaped structures and the first prism-shaped structures are perpendicular to one another. The directions of arrangement may be arbitrary.
The multilens sheets of the first to fourth embodiments and the first to sixth modified embodiments described above are illustrative of the exemplary case wherein the both of the first optical structures for constructing the first optical adjusting layer and the second optical structures for constructing the second optical adjusting layer are arranged periodically (at equal pitches). However, the present invention is not limited thereto. For example, the optical structures may be arranged at random pitches, or the optical structures may be arranged so that a plurality of periods exist in a mixed manner.
The multilens sheets of the first to fourth embodiments and the first to sixth modified embodiments described above are illustrative of the exemplary case wherein all of the plurality of optical structures, which constitute the respective optical adjusting layers, have the same shape and the same size. However, the present invention is not limited thereto. The respective optical adjusting layers may be constructed by combining optical structures having different shapes and different sizes.
The multilens sheets of the first to fourth embodiments and the first to sixth modified embodiments described above are illustrative of the exemplary case of the multilens sheet provided with the two optical adjusting layers. However, the present invention is not limited thereto. Three or more layers of the optical adjusting layers may be provided. Such a multilens sheet can be manufactured by repeating the method for forming the second optical adjusting layer as explained in the production methods of the first to fourth embodiments.
The multilens sheets of the first to third embodiments and the first to sixth modified embodiments described above are illustrative of the exemplary case wherein the base member is formed of the transparent material. However, the present invention is not limited thereto. The base member may be formed of a semitransparent material, i.e., a diffusion sheet. In this arrangement, it is unnecessary to distinctly provide any diffusion sheet in the backlight unit and the liquid crystal display apparatus. Therefore, it is possible to realize thinner sizes of the backlight unit and the liquid crystal display apparatus. In this arrangement, for example, one sheet of the multilens sheet plays the roles of the prism sheet and the diffusion sheet. It is possible to decrease the number of sheets for constructing the backlight unit and-the liquid crystal display apparatus. Therefore, it is possible to further suppress the scattering and the absorption of the transmitted light, and it is possible to further improve the optical performance.
The first to third embodiments described above are illustrative of the exemplary case wherein the multilens member of the present invention is applied to the illumination apparatus and the liquid crystal display apparatus based on the side light system (edge light system) in which the light source is arranged on the side of the optical guide plate. However, the present invention is not limited thereto. The multilens member of the present invention is also applicable of any illumination apparatus and any liquid crystal display apparatus of the direct type in which the light source is provided on the side of the optical guide plate opposite to the liquid crystal display panel. Also in this case, the effect, which is the same as or equivalent to the effect of the first to third embodiments described above, is obtained.
In the multilens member of the present invention, the optical structure, which is formed by joining the first lens group and the second lens group, is formed on the base member. Therefore, it is possible to improve the optical performance, and it is possible to realize the thin size and the low cost for the multilens member, the illumination apparatus, and the liquid crystal display apparatus. Therefore, the multilens member, the illumination apparatus, and the liquid crystal display apparatus of the present invention are preferred for various ways of use.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-110818 | Apr 2007 | JP | national |
| 2008-89480 | Mar 2008 | JP | national |
