Patent Application
20090059122
The present application claims priority to Japanese Patent Application No. 2007-217528 filed in the Japanese Patent Office on Aug. 23, 2007 and Japanese Patent Application No. 2008-183784 filed in the Japanese Patent Office on Jul. 15, 2008 the entire content of which are being incorporated herein by reference.
A liquid crystal display device having a backlight (surface emitting device) has been used as a display device such as, word processor, laptop personal computer, and the like. Since reduction in weight and thickness of the surface emitting device of liquid crystal display device is required, an edge light-type backlight having a linear light source, such as a fluorescent tube, disposed on the side of a transparent plate (light guide plate) and having a liquid crystal display panel disposed on the light guide plate, has been a mainstream.
However, recently, as liquid crystal display devices, such as those for television use, are increased in size, luminance tends to be insufficient by use of the edge light-type backlight, and therefore, a direct-below type backlight having a linear light source disposed directly below a liquid crystal display panel has come to be widely used.
With respect to the light sources (linear light sources) 2, 2, . . . , for example, cold cathode fluorescent tubes (CCFLs), et al are used, and the light sources are formed in a cylindrical shape extending in a predetermined direction.
The reflection plate 3 is disposed for reusing the light reflected from the diffusion plate 4 or the like, or the light emitted from the light sources 2, 2, . . . but not reached the diffusion plate 4.
The diffusion plate 4 is an optical element having a thickness at least 1 mm or more, and diffusing properties and dispersing properties of the diffusion plate are improved by causing a transparent substrate to randomly contain a resin having a refractive index different from that of the transparent substrate. It is used as an optical element for suppressing variations of the front luminance distribution.
In the backlight device 1, the reflection plate 3 and the diffusion plate 4 are disposed opposite to each other by sandwiching the light sources 2, 2, . . . .
In the backlight device 1, the light emitted from the light sources 2, 2, . . . is outputted from the diffusion plate 4, but, when the distance between the light sources 2, 2, . . . and the diffusion plate 4 is reduced or the distance between the light sources 2, 2, . . . is increased, the luminance of irradiation light fluxes of the backlight device 1 are, as shown in
In order to suppress such luminance variations, as shown in
The optical element (prism sheet) 5 typically used as a luminance improvement sheet includes a plurality of linear protrusions (prisms) having triangle shapes and continuously formed on the front surface or back surface of the optical element at a regular pitch. These linear protrusions function as a luminance distribution-forming layer 5a for suppressing the luminance variations in the optical axis direction of the light outputted from the light sources 2, 2, . . . .
The optical element 5 is disposed such that the direction of the ridge line of the linear protrusions functioning as a luminance distribution-forming layer 5a coincides with the longitudinal direction of the light sources 2, 2, . . . . By using the optical element 5, as shown in
With respect to the surface emitting device 1 shown in
For solution of the uneven oblique-luminance distribution, for example, there is a method in which a plurality of diffuser sheets are stacked on one another and disposed on a prism sheet, but in this method, since a plurality of diffuser sheets are stacked, there is an issue of a great loss of the luminance of the light from the light sources, or the like.
Further, for solution of the uneven oblique luminance distribution, there is a method in which, for example, as shown in
Accordingly, it is desirable to provide a surface emitting device and a liquid crystal display device which can solve the issues and suppress uneven luminance as viewed from the all directions.
The present disclosure relates to a surface emitting device and a liquid crystal display device. More particularly, the present disclosure relates to the front luminance in a predetermined position between light sources is caused to have a minimum value in a predetermined range, thereby suppressing uneven luminance in a state viewed from the all directions.
According to an embodiment, the surface emitting device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light emitted from a plurality of light sources, a reflective surface for reflecting the light emitted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light emitted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light emitted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 1.8 to 2.3, the front luminance φ under x=L/2 takes a minimum value φ0, and the minimum value φ0 satisfies the following formula: 0.65·φmax≦φ0≦0.85·φmax.
According to an embodiment, another surface emitting device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 2.8 to 4.2, the front luminance φ under x=L/2 takes a minimum value φ0, the front luminance φ under x=0 takes a minimum value φ1), and the following formulas are both satisfied: 0.65·φmax≦φ0≦0.85·φmax, and φ0<φ1.
According to an embodiment, a liquid crystal display device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light emitted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element, and a liquid crystal panel displaying an image and irradiated by light outputted from the plurality of light sources. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 1.8 to 2.3, the front luminance φ under x=L/2 takes a minimum value φ0, and the minimum value φ0 satisfies the following formula:
0.65·φmax≦φ0≦0.85·φmax.
According to an embodiment, another liquid crystal display device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element, and a liquid crystal panel displaying an image and irradiated by light outputted from the plurality of light sources. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 2.8 to 4.2, the front luminance φ under x=L/2 takes a minimum value φ0, the front luminance φ under x=0 takes a minimum value φ1 and the following formulas are satisfied: 0.65·φmax≦φ0≦0.85·φmax and φ0<φ1.
Therefore, in the surface emitting device and liquid crystal display device, a maximum value of the luminance as viewed from oblique side and a minimum value of the front luminance are present at substantially the same position in respect of a moving distance from the light sources.
According to an embodiment, another surface emitting device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for suppressing luminance variations of light outputted from the plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of light sources by sandwiching the optical element. Based on assumption that the luminance distribution-forming layer of the optical element is constituted of a plurality of structure portions protruding in the optical axis direction of the light outputted from the light sources and lined with the array direction of the plurality of light sources, light source distance L represents a distance between the centers of the light sources adjacent to each other, optical-axial distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, and ψ represents a tangent angle formed between a tangent line tangent to the outer surface of a structure portion and a plane perpendicular to the optical axis, in a cross-section at the direction lined with the structure portions of the luminance distribution-forming layer, when L/H is in the range of from 2.8 to less than 3.5, with respect to the outer surfaces of the cross-sections of the structure portions in direction lined with the structure portions, the ratio Q of a portion having a tangent line angle ψ, in which ratio of array direction component of a cross-section of the structure portion of outer surface portion of cross-section of the structure portion at a direction lined with the structure portion becomes 39° or above and 59° or less with respect to array direction component of a cross-section of the structure portion of outer surface of a cross-section of the structure portion, satisfies the following formula: 0.37≦Q≦0.70.
According to an embodiment, another liquid crystal display device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for suppressing luminance variations of light outputted from the plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of light sources by sandwiching the optical element, and a liquid crystal panel displaying an image and irradiated by light outputted from the plurality of light sources. Based on assumption that the luminance distribution-forming layer of the optical element is constituted of a plurality of structure portions protruding in the optical axis direction of the light outputted from the light sources and lined with the array direction of the plurality of light sources, light source distance L represents a distance between the centers of the light sources adjacent to each other, optical-axial distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, and y represents a tangent angle formed between a tangent line tangent to the outer surface of a structure portion and a plane perpendicular to the optical axis, in a cross-section at the direction lined with the structure portions of the luminance distribution-forming layer, when L/H is in the range of from 2.8 to less than 3.5, with respect to the outer surfaces of the cross-sections of the structure portions in direction lined with the structure portions, the ratio Q of a portion having a tangent line angle ψ, in which ratio of array direction component of a cross-section of the structure portion of outer surface portion of cross-section of the structure portion at a direction lined with the structure portion becomes 39° or above and 59° or less with respect to array direction component of a cross-section of the structure portion of outer surface of a cross-section of the structure portion, satisfies the following formula: 0.37≦Q≦0.70.
Therefore, in another surface emitting device and another liquid crystal display device, a maximum value of the luminance as viewed from oblique side and a minimum value of the front luminance are present at substantially the same position in respect of a moving distance from the light sources.
According to an embodiment, a surface emitting device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 1.8 to 2.3, the front luminance φ under x=L/2 takes a minimum value φ0, and the following formula is satisfied: 0.65·φmax≦φ0≦0.85·φmax.
Accordingly, luminance distribution as viewed from all angles becomes almost constant, and whereby unevenness of luminance as viewed from all directions may be suppressed.
According to an embodiment, another surface emitting device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 2.8 to 4.2, the front luminance φ under x=L/2 takes a minimum value φ0, the front luminance φ under x=0 takes a minimum value φ1 and the following formulas are satisfied: 0.65·φmax≦φ0≦0.85·φmax and φ0<φ1.
Accordingly, luminance distributions become almost constant when viewed from all angles, and whereby unevenness of luminance as viewed from all directions may be suppressed.
According to an embodiment, a liquid crystal display device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element, and a liquid crystal panel displaying an image and irradiated by light outputted from the plurality of light sources. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 1.8 to 2.3, the front luminance φ under x=L/2 takes a minimum value φ0, and the following formula is satisfied: 0.65·φmax≦φ0≦0.85·φmax.
Accordingly, luminance distribution as viewed from all angles become almost constant, and unevenness of luminance as viewed from all directions may be suppressed.
According to an embodiment, another liquid crystal display device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for
suppressing luminance variations of the light outputted from a plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of the light sources by sandwiching the optical element, and a liquid crystal panel displaying an image and irradiated by light outputted from the plurality of light sources. Based on assumption that light source distance L represents a distance between the centers of each light sources adjacent to each other, optical-axial direction distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, φ represents front luminance on the optical element of light outputted from the light source and passing the optical element, and φmax represents the maximum value of the front luminance φ on the optical element, when L/H is in the range from 2.8 to 4.2, the front luminance φ under x=L/2 takes a minimum value φ0, the front luminance φ under x=0 takes a minimum value φ1 and the following formulas are satisfied: 0.65·φmax≦φ0≦0.85·φmax and φ0<φ1.
Accordingly, luminance distribution as viewed from all angles become almost constant, and unevenness of luminance as viewed from all directions may be suppressed.
According to an embodiment, another surface emitting device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for suppressing luminance variations of light outputted from the plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, and a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of light sources by sandwiching the optical element. Based on assumption that the luminance distribution-forming layer of the optical element is constituted of a plurality of structure portions protruding in the optical axis direction of the light outputted from the light sources and lined with the array direction of the plurality of light sources, light source distance L represents a distance between the centers of the light sources adjacent to each other, optical-axial distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, and ψ represents a tangent angle formed between a tangent line tangent to the outer surface of a structure portion and a plane perpendicular to the optical axis, in a cross-section at the direction lined with the structure portions of the luminance distribution-forming layer, when L/H is in the range of from 2.8 to less than 3.5, with respect to the outer surfaces of the cross-sections of the structure portions in direction lined with the structure portions, the ratio Q of a portion having a tangent line angle ψ, in which ratio of array direction component of a cross-section of the structure portion of outer surface portion of cross-section of the structure portion at a direction lined with the structure portion becomes 39° or above and 59° or less with respect to array direction component of a cross-section of the structure portion of outer surface of a cross-section of the structure portion, satisfies the following formula: 0.37≦Q≦0.70.
Accordingly, luminance distribution as viewed from all angles become almost constant, and unevenness of luminance as viewed from all directions may be suppressed.
According to an embodiment, another liquid crystal display device includes a plurality of light sources disposed on the identical plane, an optical element having light transmission properties and having formed thereon a luminance distribution-forming layer for suppressing luminance variations of light outputted from the plurality of light sources, a reflective surface for reflecting the light outputted from the plurality of light sources, the reflective surface being disposed opposite to the optical element by sandwiching the plurality of light sources with an air layer in between the reflective surface and the optical element, a diffuser means for diffusing the light outputted from the plurality of light sources, the diffuser means being disposed opposite to the plurality of light sources by sandwiching the optical element, and a liquid crystal panel displaying an image and irradiated by light outputted from the plurality of light sources. Based on assumption that the luminance distribution-forming layer of the optical element is constituted of a plurality of structure portions protruding in the optical axis direction of the light outputted from the light sources and lined with the array direction of the plurality of light sources, light source distance L represents a distance between the centers of the light sources adjacent to each other, optical-axial distance H represents a distance from the center of the light source to the optical element in the optical axis direction, moving distance x represents a distance in the direction from the light source to the adjacent light source, and ψ represents a tangent angle formed between a tangent line tangent to the outer surface of a structure portion and a plane perpendicular to the optical axis, in a cross-section at the direction lined with the structure portions of the luminance distribution-forming layer, when L/H is in the range of from 2.8 to less than 3.5, with respect to the outer surfaces of the cross-sections of the structure portions in direction lined with the structure portions, the ratio Q of a portion having a tangent line angle ψ in which ratio of array direction component of a cross-section of the structure portion of outer surface portion of cross-section of the structure portion at a direction lined with the structure portion becomes 39° or above and 59° or less with respect to array direction component of a cross-section of the structure portion of outer surface of a cross-section of the structure portion, satisfies the following formula: 0.37≦Q≦0.70.
Accordingly, luminance distribution as viewed from all angles become almost constant, and unevenness of luminance as viewed from all directions may be suppressed.
Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures.
Below, embodiments for using the surface emitting device and liquid crystal display device will be described with reference to the accompanying drawings.
In an embodiment, the surface emitting device is applied to a backlight device for liquid crystal display device. The application range of the surface emitting device is not limited to the backlight device of liquid crystal display device, and the surface emitting device can be widely applied to lighting devices for use in other image display devices.
A surface emitting device 10 is used as a direct below-type backlight device in, for example, a liquid crystal display device 50 (see
The surface emitting device 10 has a configuration in which required parts are respectively disposed in a housing 11, and includes a plurality of light sources (linear light sources) 12, 12, . . . , a reflection plate 13, a diffuser means 14, an optical element (optical plate) 15, and an optical element group 16.
With respect to the light sources 12, 12, . . . , fluorescent tubes, such as cold cathode fluorescent tubes or hot cathode fluorescent tubes, are used. The light sources 12, 12, . . . individually have a cylindrical form and are disposed on the reflection plate 13 so that it extends in the Y direction shown in
In the surface emitting device 10, a plurality of light sources 12, 12, . . . are disposed at regular intervals on the reflection plate 13 and uniformity of the arrangement of the light sources is kept. Therefore, the light from the light sources 12, 12, . . . , which have reached the below-described liquid crystal display panel, are unlikely to exhibit partially uneven luminance, which is caused due to the arrangement of the light sources 12, 12, . . . .
A reflective surface 13a is a surface facing the light sources 12, 12, . . . of the reflection plate 13. Part of the light from the light sources 12, 12, . . . are reflected on the reflective surface 13a and directed toward the optical element 15. For the reflection plate 13, any material having an ability to reflect light can be used, for example, a reflection plate formed of aluminum, polyethylene terephthalate (PET), or polycarbonate can be used.
The diffuser means 14 is disposed opposite to the light sources 12, 12, . . . by sandwiching the optical element 15. The diffuser means 14 has a function to diffuse the incident light which has passed through the optical element 15 to render the luminance distribution of the irradiation light fluxes even.
With respect to the diffuser means 14, any materials, such as a diffusion plate or a diffuser sheet in the form of a film are usable as long as light transmission properties and light diffusion functions are provided. The diffuser means 14 formed of, for example, polystyrene, a cycloolefin polymer, acryl, or polycarbonate is used. With respect to the diffuser sheet, materials for supporting diffusion of light, such as filler particles, applied on, e.g., a PET substrate is used. With respect to the diffuser means 14, at least any one of the diffusion plate and diffuser sheet is used, but both of them can be used in a stacked form.
Liquid crystal display panel (not shown) is disposed on the light output side of the diffuser means 14.
The optical element 15 is disposed between the light sources 12, 12, . . . and the diffuser means 14. The optical element 15 is, for example, a prism sheet or lenticular lens sheet having light transmission properties, and has a configuration in which a luminance distribution-forming layer 18 is integrally formed at a light output side of a substrate 17.
The substrate 17 is formed of a plate material made of a transparent synthetic resin, such as an acrylic resin, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, a styrene resin, or a styrene-methyl methacrylate copolymer resin. The substrate 17 can be made in the form of a sheet or film, but it is preferred that the substrate is made of a plate material having high rigidity because the plate material disposed in the housing 11 is unlikely to suffer deflection, warpage, thermal deformation, and the like and a distance from the light sources 12 in the Z direction is unlikely to change. With respect to the thickness of the substrate 17, there is no particular limitation, and the thickness of the substrate may be as small as the thickness of a sheet or film as long as predetermined rigidity can be secured.
The luminance distribution-forming layer 18 has a function of suppressing luminance variations of the light from the light sources 12. The luminance distribution-forming layer 18 is constituted of a plurality of structure portions 18a, 18a, . . . each having an edge extending in the Y direction shown in
The array pitch of the structure portions 18a, 18a, . . . is not relevant to the array pitch of the light sources 12, 12, . . . , and the structure portions 18a, 18a, . . . are arrayed at a very small pitch.
The optical element 15 may have a configuration in which the luminance distribution-forming layer 18 is integrally molded on the substrate 17, but also has configurations in which the luminance distribution-forming layer 18 made of an ultraviolet curing resin is transferred to the substrate 17, or in which the luminance distribution-forming layer 18 is bonded on the substrate 17 by press molding.
The optical element group 16 is constituted of a single or a plurality of various optical elements, such as a diffuser sheet, a prism sheet, or a reflective polarizer. When the optical element group 16 is constituted of a plurality of optical elements, the plurality of optical elements are arranged in a stacked manner. The optical element group 16 is disposed opposite to the optical element 15 by sandwiching the diffuser means 14.
In the surface emitting device 10 having the above-described configuration, a space between the reflection plate 13 and the optical element 15 is formed as an air layer 19.
In the surface emitting device 10, the light emitted from the light sources 12, 12, . . . successively pass through the optical element 15, diffuser means 14, and optical element group 16 and irradiates the liquid crystal display panel. In this instance, part of the emitted light are reflected on the reflective surface 13a of the reflection plate 13 and directed toward the optical element 15.
The light incident on the optical element 15 is refracted at the incident plane of the optical element 15, and further refracted and directed toward the diffuser means 14 when emitted from the optical element 15. The light incident on the diffuser means 14 is diffused and emitted, and reaches the liquid crystal display panel through the optical element group 16.
In
In
As shown in
By using the factors (parameters), the surface emitting device 10 satisfies the following formulae (1) to (3).
n0·sin ψ=n·sin(ψ−θ2) (1)
n0·sin θ1=n·sin θ2 (2)
x=H·tan θ1+d1·tan θ2 (3)
Using the formulae (1) to (3), an arbitrary tangent line angle ψ is applied to the formula (1) to calculate a refraction angle θ2, the calculated refraction angle θ2 is applied to the formula (2) to calculate an incident angle θ1, and the calculated incident angle θ1 and refraction angle θ2, an optical-axial distance H, and a thickness d1 of the optical element are applied to the formula (3) to calculate a moving distance x. Accordingly, the moving distance x corresponding to the tangent line angle ψ is primarily determined, and the divided image 12A of a light which reaches a contact point of the luminance distribution-forming layer 18 having the tangent line angle ψ moves in the direction of the adjacent light source 12 by distance corresponding to x.
Thus the moving distance x of the divided images 12A is primarily determined according to the tangent line angle ψ.
As shown in
In
In the surface emitting device 10, as shown in
With respect to the front luminance distribution of light from the light sources 12, the shape is not limited to the triangle, and the shape may be, for example, a shape of substantial triangle having a rounded top (see
In the surface emitting device 10, as described above, the front luminance at the centers of the spaces between the light sources 12, 12 adjacent to each other, namely, in positions of x=L/2, are minimum. Based on assumption that φ represents front luminance, a minimum value φ0 of the front luminance φ satisfies the formula below in respect of the maximum value φmax of the front luminance φ.
0.65φmax≦φ0≦0.85φmax (4)
At x=L/2, the front luminance φ takes a minimum value φ0, and the minimum value φ0 satisfies the formula (4) above, so that, when L/H is in the range of from 1.8 to 2.3, uniformity of the luminance distribution when the liquid crystal display panel is viewed from all angles is secured.
For satisfying the formula (4) above, it is desirable that the structure portions 18a, 18a, . . . in the luminance distribution-forming layer 18 of the optical element 15 is formed in a shape which satisfies the following formula when L/H is in the range of from 1.8 to 2.3.
35°+5°·L/H≦a≦50°+5°·L/H (5)
When the maximum tangent line angle a of the structure portions 18a satisfies the formula (5) above; the width of the bottom part of the luminance distribution of a light from the single light source 12 can be controlled.
For satisfying the formulae (4) and (5), it is necessary that the structure portions 18a have a shape such that the maximum tangent line angle a becomes a predetermined angle, but, when the thickness d1 of the optical element 15 and the optical-axial distance H are determined, the tangent line angle ψ of the structure portions 18a becomes a function of only the moving distance x based on the above formulae (1) to (3).
The optical-axial distance H and the thickness d1 of the optical element are given and a relationship between the tangent line angle ψ and the moving distance x is derived from the formulae (1) to (3), and the light sources distance L is given and the structure portions 18, 18a, . . . are formed in the shape which satisfies the formulae (4) and (5), and thus the luminance distribution of light is controlled by the tangent line angle ψ, so that the luminance distribution is surely even.
When a specific tangent line angle ψ occupies the majority in the structure portions 18a, a large amount of light are refracted in a moving distance x corresponding to the tangent line angle ψ. For example, when the structure portions 18a are formed in a shape of substantial triangle having a vertical angle of 90°, a tangent line angle ψ=45° occupies the majority, and a large amount of light are refracted in a moving distance x corresponding to the tangent line angle ψ=45°, and only the luminance level in that portion becomes high. Therefore, when a specific tangent line angle ψ occupies the majority in the structure portions 18a, there is a possibility that the front luminance φ becomes maximum in x=L/2 or a portion around it.
In the surface emitting device 10, in order to prevent the front luminance φ from becoming maximum under x=L/2 or a portion around it, it is arranged that the ratio P of a portion having a tangent line angle ψ in which ratio of array direction component of a cross-section of the structure portion of outer surface portion of cross-section of the structure portion at a direction lined with the structure portion 18a, 18a, . . . becomes 40° or above and “a” or less, satisfies the formula (6) below.
Specifically, when array direction component of cross section of structure portion of the whole of the outer surfaces J of the cross-sections of the structure portions in a direction lined with the structure portions 18, 18a, . . . (see
0.15≦P≦0.45 (6)
As mentioned above, character a represents the maximum tangent line angle in the structure portions.
When the ratio P falls in the constant range shown in the formula (6), no maximum value of the front luminance φ is present in x=L/2 or a portion around it.
L/H=2.0 is applied to the formula (5) above to calculate the maximum tangent line angle a. As a result, the calculated maximum tangent line angle a is in the range of 45° to 60°. Therefore, in each of the shape examples 1 to 4 shown in
With respect to each of the shape examples 1 to 4, the ratio P of a tangent line angle ψ in the range of 40° to a to the total distribution of the tangent line angle ψ is determined. In each of the shape examples 1 to 4, the ratio P falls in the range of from 0.25 to 0.38, and hence satisfies the formula (6) above.
Further, in each of the shape examples 1 to 4, the minimum value φ0 falls in the range of from 0.65φmax to 0.85φmax and satisfies the formula (4) above.
On the other hand,
As similar with
L/H=2.0 is applied to the formula (5) above to calculate the maximum tangent line angle a. As a result, the calculated maximum tangent line angle a is in the range of 45° to 60°. Therefore, in each of the shape examples shown in
With respect to each of the shape examples 5 to 11, the ratio P of a tangent line angle ψ in the range of 40° to a out of the total distribution of the tangent line angle ψ is determined. In each of the shape examples 5, 6, 7, 8, 10, and 11 other than the shape example 9, the ratio P is 0 or in the range of more than 0.45, and hence does not satisfy the formula (6) above.
Further, in each of the shape examples 5 to 11, the minimum value φ0 of the front luminance φ in positions of x=L/2 is smaller than 0.65φmax, the front luminance φ has no minimum value φ0 at positions of x=L/2, or the minimum value φ0 is larger than 0.85φmax. Therefore, in each of the shape examples 5 to 11, the formula (4) above is not satisfied.
The above results have confirmed that the luminance distribution as viewed from any angle is substantially constant in the examples in which the formulae (4), (5), and (6) above are satisfied (shape examples 1 to 4).
In the surface emitting device 10, as mentioned above, when L/H is in the range of from 1.8 to 2.3, it is desirable that the formula (5) above is satisfied, but, when L/H is in the range of from 2.8 to 4.2, it is desirable that the following formula (5)′ is satisfied.
35°+5°·L/H≦a≦(Smaller angle selected from 50°+5°·L/H and 65°) (5)′
When the maximum tangent line angle a of the structure portions 18a satisfies the formula (5)′ above, the width of the bottom part of the luminance distribution of a light emitted from the single light source 12 can be controlled.
The case where L/H is in the small range of from 1.8 to 2.3 is described above, but, when L/H is in a large range, the optical-axial distance H between the light sources and the optical element becomes small or the light sources distance L between the light sources adjacent to each other becomes large, and it is likely that the luminance under x=0 (in positions immediately above the light sources) tends to be larger than the luminance under x=L/2. Therefore, when L/H is in the range of large values, it is desirable that the front luminance distribution φ has a shape shown in
The light incident perpendicularly on the lower surface of the optical element (surface facing the light sources) from the light sources is internally reflected at the luminance distribution-forming layer, but, when the maximum tangent line angle a becomes large, the above reflection angle becomes small, and the light outputted from the luminance distribution-forming layer is likely to be incident on the diffuser means without being incident on the adjacent luminance distribution-forming layer. When the light is incident on the diffuser means, the diffuser means averages the angles, whereby the amount of light under x=0 is increased. Therefore, even if a minimum value φ1 is taken under x=0, the luminance under x=0 becomes too large, and the luminance distribution as viewed from any angle is unlikely to become substantially constant. Accordingly, when L/H is in the enlarged range of i.e., 2.8 to 4.2, the upper limit of the maximum tangent line angle a in the formula (5)′ is set to be 65°, in order to avoid high angle.
When the ratio P is large, the tangent line angles ψ of the structure portions 18a tends to be large, and the luminance of the divided images at positions near to x=L/2 is increased, so that the luminance of the divided images in positions immediately above the light sources is reduced. For example, when L/H is in the range of from 2.8 to less than 3.5, it is assumed that the ratio P satisfies the following formula:
0.55≦P≦0.70 (6)′.
When L/H is in the range of from 3.5 to 4.2, it is assumed that the ratio P satisfies the following formula:
0.60≦P≦0.75 (6)″.
However, when values of the ratio P become too large, the minimum value φ1 of the front luminance distribution φ at positions immediately above the light sources becomes too small, and there is a possibility that luminance of the light which has passed through the diffuser means is lowered at positions immediately above the light sources. Therefore, in order to prevent the luminance of the light which has passed through the diffuser means from becoming too small at positions immediately above the light sources, it is necessary that the minimum value φ1 of the front luminance distribution under x=0 is larger than the minimum value φ0 of the front luminance distribution under x=L/2.
φ0<φ1 (7)
As similar with
L/H=3.0 is applied to the formula (5)′ above to calculate the maximum tangent line angle a. As a result, the maximum tangent line angle a is in a range from 50° to 65°. Therefore, in each of the shape examples 12 to 14 shown in
With respect to each of the shape examples 12 to 14, the ratio P of a tangent line angle ψ of 40° to a out of the total distribution of the tangent line angle ψ is determined. In each of the shape examples 12 to 14, the ratio P falls in the range from 0.62 to 0.68, and hence the formula (6)′ above is satisfied.
Further, with respect to each of the shape examples 12 to 14, the minimum value φ0 of the front luminance φ in positions of x=L/2 falls in the range from 0.65φmax to 0.85φmax, and the formula (4) above is satisfied.
In addition, with respect to each of the shape examples 12 to 14, φ0<φ1), that is, the formula (7) above is satisfied.
On the other hand,
As similar with
L/H=3.0 is applied to the formula (5)′ above to calculate the maximum tangent line angle a. As a result, the maximum tangent line angle a is in the range from 50° to 65°. Therefore, in each of the shape examples 16 and 17 shown in
With respect to each of the shape examples 15 to 18, the ratio P of a tangent line angle ψ of 40° to a out of the total distribution of the tangent line angle ψ is determined. As a result, although the shape examples 15 and 18 satisfy the formula (6)′ above, the shape examples 16 and 17 do not satisfy the formula (6)′ above.
Further, in each of the shape examples 16 and 17, the formula (4) above is satisfied, but, in each of the shape examples 15 and 18, the minimum value φ0 is smaller than 0.65φmax or larger than 0.85φmax, and the formula (4) above is not satisfied.
In addition, in the shape example 15, φ0<φ1, that is, the formula (7) above is satisfied, but, in each of the shape examples 16 and 18, φ0>φ1, that is, the formula (7) above is not satisfied. In the shape example 17, φ1 is not included, and hence the formula (7) above is not satisfied.
The above results have confirmed that the luminance distribution as viewed from any angle becomes substantially constant in each of the examples in which the formulae (4), (5)′, (6)′, and (7) above are satisfied (shape examples 12 to 14).
As similar with
L/H=4.0 is applied to the formula (5)′ above to calculate the maximum tangent line angle a. As a result, the maximum tangent line angle a is 55° to 65°. Therefore, in each of the shape examples 19 to 21 shown in
With respect to each of the shape examples 19 to 21, the ratio P of a tangent line angle ψ of 40° to a out of the total distribution of the tangent line angle ψ is determined. In each of the shape examples 19 to 21, the ratio P falls in the range from 0.61 to 0.73, and hence the formula (6)″ above is satisfied.
Further, in each of the shape examples 19 to 21, the minimum value φ0 of the front luminance φ in positions of x=L/2 falls in the range from 0.65φmax to 0.85φmax, and the formula (4) above is satisfied.
In addition, in each of the shape examples 19 to 21, φ0<φ1, that is, the formula (7) above is satisfied.
On the other hand,
As similar with
L/H=4.0 is applied to the formula (5)′ above to calculate the maximum tangent line angle a. As a result, the maximum tangent line angle a is in the range from 55° to 65°. Therefore, in each of the shape examples 22 and 26 shown in
With respect to each of the shape examples 22 to 26, the ratio P of a tangent line angle ψ of 40° to a out of the total distribution of the tangent line angle ψ is determined. In each of the shape examples 23 and 24, the formula (6)″ above is satisfied, but, in each of the shape examples 22, 25, and 26, the formula (6)″ above is not satisfied.
Further, in the shape example 22, the formula (4) above is satisfied, but, in each of the shape examples 23 to 26, the minimum value φ0 is smaller than 0.65φmax or larger than 0.85φmax, and hence the formula (4) above is not satisfied.
In addition, in each of the shape examples 23 to 26, φ0<φ1, that is, the formula (7) above is satisfied, but, in the shape example 22, φ0>φ1), that is, the formula (7) above is not satisfied.
The above results have confirmed that the luminance distribution as viewed from any angle becomes substantially constant in each of the examples in which the formulae (4), (5)′, (6)″, and (7) above are satisfied (shape examples 19 to 21).
In the surface emitting device 10, the diffuser means 14 has a total light transmittance T of 0.55 to 0.85. The diffuser means 14 has a function to average the angle distribution of the irradiation light fluxes emitted from the light sources 12, 12, . . . and from the optical element 15, but as the total light transmittance T becomes smaller, the above function of the diffuser means becomes more prominent. When the total light transmittance T is around 0.55, the averaging function is saturated (becomes substantially maximum), and, even if the total light transmittance T becomes smaller than 0.55, the averaging function does not change so largely, and hence the luminance loss is increased. As the total light transmittance T becomes smaller from around 0.85, the function of averaging the angle distribution becomes prominent. Therefore, when a total light transmittance T of the diffuser means 14 is in the range from 0.55 to 0.85, the function can sufficiently average the angle distribution of the diffuser means 14 while suppressing the luminance variations.
Excluding the data of solid lines, data of
In the configuration in which the optical element is disposed, light emitted from the light sources, which passes the optical element and reaches the diffuser means, are diffused by the diffuser means, excluding a part of the light, and are emitted toward the diffuser sheet and prism sheet. A part of the emitted light is reflected and returned to the diffuser means, and diffused by the diffuser means and optical element and emitted again toward the diffuser sheet and prism sheet.
Further, it was found that, when the optical element is used and L/H is in the range shown in the diagram, by using the diffuser means having a total light transmittance T shown in the diagram, the luminance variation generation ratio is lowered. It has been found that the luminance variation generation ratio is largely reduced especially when the diffuser means having a total light transmittance T of 0.66 to 0.85 (data supplement) is used. Therefore, when the diffuser means has a total light transmittance T of 0.66 to 0.85, the diffuser means can exhibit maximum function to average the angle distribution of the diffuser means while suppressing the luminance variations.
It is presumed that, when the total light transmittance T of the diffuser means becomes high, the amount of the light returning from the diffuser sheet and prism sheet to the light source side by exceeding diffuser means becomes large, and the amount of the light diffused by the diffuser means and optical element is increased, thereby lowering the luminance variation generation ratio.
In the surface emitting device, as described above, when L/H is in the large range, for example, L/H is in the range of from 2.8 to less than 3.5, the luminance in positions of x=0, namely, in positions immediately above the light sources becomes high, and the luminance variations are likely to be caused. Therefore, it is desired that, among the light being emitted from the optical element to the diffuser means and being around positions of x=0, the light returning to the optical element is increased in amount. When, among the light being emitted from the optical element to the diffuser means and being around positions of x=0, the light returning to the optical element is increased in amount, the front luminance distribution is likely to be in a shape shown in
For example, when using an optical element formed so that the tangent line angle ψ is 65°, the luminance immediately above the light sources (x=0) is high and the luminance between the light sources is low, and the amount of the light returning from the diffuser means to the light sources is small. When using an optical element formed so that the tangent line angle ψ is, for example, 45°, the luminance immediately above the light sources (x=0) is low and the luminance between the light sources is high, and the amount of the light returning from the diffuser means to the light sources is large.
As described above, when L/H is in the large range, it is desirable that, among the light around positions of x=0, the amounts of light returning to the optical element are increased, and the data of
Therefore, when L/H is in the large range, i.e., in the range of from 2.8 to less than 3.5, by using an optical element constituted of structure portions having a tangent line angle v of 39 to 59°, the luminance variations may be suppressed.
As similar with the above-described ratio P, when array direction component of cross section of structure portion of the whole of the outer surfaces J of the cross-sections of the structure portions at a direction lined with the structure portions (see
With respect to the outer surfaces of the cross-sections of the structure portions at a direction lined with the structure portions, out of portions excluding portions having a tangent line angle ψ in which ratio of array direction component of cross section of structure portion is 39° or above and 59° or less, the ratio of a portion having a tangent line angle ψ in which ratio of array direction component of cross section of structure portion is more than 59° is taken as a ratio R. A ratio R is 0.36 in the shape example 27, 0.59 in the shape example 28, 0.90 in the shape example 29, 0.86 in the shape example 30, and 1.00 in the shape example 31.
A Ratio R is 0% in the Shape Example 32 and 100% in the Shape example 33.
Therefore, when UH is in the range from 2.8 to less than 3.5, and the ratio Q of a portion having a tangent line angle ψ, in which ratio of array direction component of a cross-section of the structure portion of outer surface portion of cross-section of the structure portion at a direction lined with the structure portion becomes 39° or above and 59° or less, satisfies the formula: 0.37≦Q≦0.70, whereby the luminance variations may be suppressed.
As shown by indications V, V, . . . in
Shape examples in which the contrast around portions immediately above the light sources can be further lowered to further suppress the luminance variations include the shape example 29 in which the ratio R is 0.90, the shape example 30 in which the ratio R is 0.86, and the shape example 33 in which the ratio R is 1.0, in addition to the shape example 31 in which the ratio R is 1.00. Therefore, when the ratio R of a portion having a tangent line angle ψ of more than 59° out of a portion excluding the portion having a tangent line angle ψ of 39 to 59° is 0.80 or more, the luminance variations may be further suppressed.
In the surface emitting device 10, by forming the luminance distribution-forming layer 18 in the optical element 15 so that the cross-section (outer surface) of the layer has a desired curved shape, the luminance can be suppressed from being uneven, but in many cases, it is difficult to form the luminance distribution-forming layer 18 into a curved shape from the processing reasons. Therefore, the luminance distribution-forming layer 18 is formed in the shape of polygon described below, which approximates to a curved shape, thus suppressing the luminance from being uneven while securing good processability.
Examples of cross-sections of the luminance distribution-forming layer 18 in the optical element 15 are described below (see
The luminance distribution-forming layer 100 is constituted of an outer surface 101 parallel to the array direction of the light sources, and outer surfaces 102, 102, 103, 103, . . . , 107, 107 individually having slope angles with respect to the array direction of the light sources, the slope angle becoming large as outer surface getting close to the light source based on the outer surface 101. The luminance distribution-forming layer 100 has a shape which is line symmetrical in the array direction of the light sources based on a middle line M crossing the point which divides the outer surface 101 into two halves.
The luminance distribution-forming layer 100 is formed from, for example, thirteen (13) outer surfaces (line segments) having different slope angles, but the number of the outer surfaces is not limited to 13, and the number of the outer surfaces can be arbitrarily determined by taking into consideration of the light sources distance L or the like.
When the luminance distribution-forming layer 100 having a cross-section in the shape of polygon which approximates to a curved shape as shown in
Further, when the outer surface 101 parallel to the array direction of the light sources is formed, the minimum value φ0 of the front luminance φ may be easily controlled.
The luminance distribution-forming layer 200 shown in
The structure portion 200a has, for example, seven outer surfaces, and includes surfaces 201, 202, 202, 203, 203, 204, 204. The structure portion 200b also has, for example, seven outer surfaces, and includes outer surfaces 205, 206, 206, 207, 207, 208, 208.
The outer surfaces 201, 205 are parallel to the array direction of the light sources. The slope angles with respect to the outer surfaces 202, 203, 204 to the array direction of the light sources are, respectively, the same as those of the outer surfaces 103, 105, 107 of the luminance distribution-forming layer 100, and the slope angles with respect to the outer surfaces 206, 207, 208 to the array direction of the light sources are, respectively, the same as those of the outer surfaces 102, 104, 106 of the luminance distribution-forming layer 100.
When using the luminance distribution-forming layer 200 formed of the structure portions 200a, 200b, 200a, 200b, . . . , which are obtained by dividing the shape of the luminance distribution-forming layer 100, the number of the outer surfaces of each of the structure portions 200a, 200b is small, whereby the processing of optical element can be made easily.
The luminance distribution-forming layer 300 shown in
The structure portion 300a has, for example, six outer surfaces, and is formed of outer surfaces 301, 301, 302, 302, 303, 303. The structure portion 300b also has, for example, six outer surfaces, and is formed of outer surfaces 304, 304, 305, 305, 306, 306.
The slope angles of the outer surfaces 301, 302, 303 with respect to the array direction of the light sources are, respectively, the same as those of the outer surfaces 103, 105, 107 of the luminance distribution-forming layer 100, and the slope angles of the outer surfaces 304, 305, 306 with respect to the array direction of the light sources are, respectively, the same as those of the outer surfaces 102, 104, 106 of the luminance distribution-forming layer 100.
Between the structure portions 300a and 300b, a parallel plane 307 which is parallel to the array direction of the light sources is formed. The parallel plane 307 corresponds to the outer surface 101 of the luminance distribution-forming layer 100.
When using the luminance distribution-forming layer 300 formed of the structure portions 300a, 300b, 300a, 300b, . . . , which are obtained by dividing the shape of the luminance distribution-forming layer 100, the number of the outer surfaces of each of the structure portions 300a, 300b is small, whereby the processing of optical element can be made easily.
When the luminance distribution-forming layer 300 is employed, an optical element is formed by injection molding using, for example, a mold 1000. As shown in
The luminance distribution-forming layers having two types of structure portions successively forming a plurality of arrays, are described above as examples, but the division number of the shape of polygon is not limited to two, but the number may be three or more. These structures are obtained by dividing the shape of polygon into a plurality of structure portions, and exhibit not a great difference in optical properties as those of the undivided luminance distribution-forming layer 100, and the structure can be arbitrarily selected by taking into consideration of processability.
Next, an optical element package and a bonded optical element having a structure in which the optical element 15 and diffuser means 14 are integrated are described (see
As described above, in the surface emitting device 10, the optical element 15, diffuser means 14, and optical element group 16 are disposed in this order from the light sources 12, 12, . . . side, and, depending on the thicknesses of the parts, it is possible that stiffness is low to cause warpage or waviness, el al, thereby contributing to cause uneven luminance.
For preventing the occurrence of warpage or waviness, the optical element 15 and diffuser means 14, or the optical element 15, diffuser means 14, and optical element group 16 may be wrapped by a packaging member 20, such as a transparent sheet or a transparent film, to form an optical element package 21 (see
Alternatively, for example, the optical element 15 and diffuser means 14 may be bonded by using an ultraviolet curing resin, a pressure-sensitive adhesive, and the like to form a bonded optical element 22 (see
When the optical element package 21 or the bonded optical element 22 is formed, the stiffness may be improved by increasing the thickness, thereby preventing the occurrence of warpage, waviness, and the like.
In the optical element package 21 or the bonded optical element 22, the optical element 15 is arranged to have a thickness d1 in the range from 0.05 mm to 0.40 mm and the diffuser means 14 is arrange d to have a thickness d2 in the range from 1.0 mm to 2.5 mm. Even when the optical element 15 having a small thickness and small stiffness is used, the diffuser means 14 having a large thickness is used to form an the optical element package 21 or the bonded optical element 22, so that the optical element 15 may be disposed near to the light sources 12, 12, . . . .
When the optical element 15 is formed by having a thickness d1 as small as in the range from 0.05 mm to 0.40 mm, and by integrating the substrate 17 with the luminance distribution-forming layer 18 by, e.g., melt extrusion, not only can the cost for materials be reduced to lower the production cost, but also the form transfer properties can be enhanced to improve the molding accuracy of the luminance distribution-forming layer 18.
Further, when the optical element 15 is formed by having a thickness d1 as small as in the range from 0.05 mm to 0.40 mm, for example, and by bonding the luminance distribution-forming layer 18 with the substrate 17 by use of an ultraviolet curing resin, the thick substrate 17, such as a biaxially drawn PET film is not required to be formed, thereby making it possible to achieve reduction in thickness and production cost.
In addition, the optical element 15 may be formed so that a part of the structure portions 18a, 18a, . . . in the luminance distribution-forming layer 18 has different size (see
Thus the contact area between the diffuser means 14 and the optical element 15 is reduced, making it possible to suppress damages caused between the structure portions 18a, 18a, . . . and the diffuser means 14.
The above-described shape can be formed by using a mold 500 for forming the optical element 15 such that, for example, as shown in
The specific shapes and structures for the individual parts described in the above embodiment are merely examples, and the technical scope of the present embodiment is not limited by the example.
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-217528 | Aug 2007 | JP | national |
| 2008-183784 | Jul 2008 | JP | national |
