JP2007294170A - Transmittance adjusting body unit, flat lighting system and liquid crystal display device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmittance adjustor unit capable of reducing occurrence of uneven luminance without deteriorating average luminance, and suppressing occurrence of uneven colors. <P>SOLUTION: This transmittance adjustor unit 24 is composed of a first transmittance adjusting member 28 and a second transmittance adjusting member 30. The first transmittance adjusting member 28 has a transparent film 29 having light transmissibility, and a large number of first transmittance adjustors 26 disposed on the surface of the transparent film 29 in a prescribed density distribution. In the second transmittance adjusting member 30, a large number of the second transmittance adjustors 32 are disposed on the surface of a transparent film 34 in a distribution density different from the prescribed density distribution or in fixed density on the surface of the transparent film 34. The second transmittance adjustor 32 is formed by a material having a practically different color from that of the first transmittance adjustor 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmittance adjusting unit that converts light emitted from a light exit surface of a light guide plate into more uniform output light, a planar illumination device that emits uniform light from the light exit surface, and a liquid crystal display device using the same. .

A liquid crystal display device uses a backlight unit that irradiates light from the back side of a liquid crystal panel (LCD) to illuminate the liquid crystal panel. The backlight unit uses a light source for illumination, a light guide plate that diffuses light emitted from the light source and irradiates the liquid crystal panel, and a component such as a prism sheet and a diffusion sheet that uniformizes the light emitted from the light guide plate. Composed.
As such a backlight unit, for example, a backlight unit disclosed in Patent Document 1 is known.

FIG. 21 is a schematic cross-sectional view of the surface light source device disclosed in Patent Document 1.
In the surface light source device (backlight unit) shown in the figure, after the fluorescent lamp 102 is embedded in the light guide plate 100, the reflection sheet 104 is disposed on the back surface of the light guide plate 100, and the transmitted light amount correction sheet is provided on the exit surface of the light guide plate 100. 106, a light diffusion plate 108, and a prism sheet 110 are laminated.
The light guide plate 100 has a substantially rectangular shape and is formed using a resin in which fine particles that diffuse illumination light are dispersed and mixed. In addition, the upper surface of the light guide plate 100 is flat and assigned to the exit surface. Further, a groove 100a having a U-shaped cross-section for embedding the fluorescent lamp 102 is formed on the back surface (surface opposite to the emission surface) of the light guide plate 100, and the emission surface of the light guide plate 100 is directly above the fluorescent lamp 102. Avoiding this, a light amount correction surface 100b that prompts emission of illumination light is formed.

  As described above, in Patent Document 1, the light guide plate 100 is formed by mixing fine particles, and the illumination light is corrected by the light amount correction surface 100b formed on a part or all of the emission surface except directly above the fluorescent lamp 102. It is described that by promoting the emission, the entire thickness can be reduced and unnatural luminance unevenness of the emitted light can be reduced.

Patent Document 2 discloses a backlight of a liquid crystal display device that can realize a reduction in size and weight of the liquid crystal display device and reduction in cost and power consumption without reducing the amount of backlight irradiation. For this purpose, a rectangular irradiation surface, a rectangular cross section grooved in parallel with the long side at the center of the short side, and a groove with a rectangular cross-section for inserting the light source, facing both sides of the long side across this groove A light guide plate having a back surface formed so that the plate thickness is gradually reduced is disclosed.
Further, in Patent Document 3, the frame of the liquid crystal display device can be narrowed and the thickness can be reduced, and in order to obtain a bright backlight unit with good light utilization efficiency, the width direction of the concave portion for arranging the light source is described. A light guide (light guide plate) is disclosed in which the parallel cross-sectional shape is a parabolic shape with the depth direction as the main axis.

  In a backlight unit using such a light guide plate, luminance distributions such as bright lines and dark lines are generated, and various methods for improving the luminance distribution have been proposed (for example, Patent Documents 4 to 6).

  In Patent Document 4, a printing portion on a dod that prevents light transmission is formed on the surface of a diffusion plate. Further, the density of the printed portion is made dense in the region where the cold cathode fluorescent lamp is located directly below, and as it goes away from the region, the amount of light emitted to the diffuser plate side reaches the entire surface of the diffuser plate. Are described as uniform.

  Moreover, in patent document 5, the light-scattering layer is formed in the light-guide plate so that an area ratio may become large as it distances from a linear light source at the lower surface of a plate body. It is described that the light scattering layer is used for extracting light inside the plate of the light guide plate from the upper surface in accordance with a change in luminance from the line light source.

Further, in Patent Document 6, the transmission adjusting means is printed with a highly reflective ink in a band shape along the longitudinal direction of the transparent substrate so as to suppress the increase in luminance due to direct irradiation by being inversely proportional to the light source amount of the linear light source. In this case, the dot density modulation pattern is obtained by decreasing the dot area or the number of dots in the in-plane direction from the edge of the protruding edge.
As a result, the light source light of the linear light source reaches the transmission adjusting means formed on the light emitting surface of the surface through each protruding edge, and the transmission amount and the transmission preventing amount are changed by the density modulation to the edge side of the protruding edge. Is adjusted so as to gradually increase in the in-plane direction, and the increase in the luminance of the portion where the linear light source is arranged due to the direct light source light is suppressed, and the uniformity of the illumination luminance of the light guide by the light guide means is ensured. ing.

In Patent Document 7, luminance is formed by reversing the gradation of data obtained by measuring at least the luminance distribution of the light exit surface of the backlight unit on a light diffusion sheet that is an optical member used in the backlight unit of the liquid crystal display device. A distribution inversion image is printed.
This luminance distribution inversion image has a highly accurate gradation pattern that reflects the luminance distribution of the light exit surface of the backlight unit, so that the light emitted from the light guide plate has little luminance unevenness after passing through the light diffusion sheet. It is described that the occurrence of bright lines is prevented.

Japanese Patent Laid-Open No. 9-304623 JP-A-8-62426 JP 10-1333027 A JP-A-5-127156 JP-A-6-235825 JP 2001-42327 A JP 2004-170698 A

  By the way, in the Japanese Patent Application No. 2004-258340 (International Publication No. 2006/028080 pamphlet), the present inventor has a transmittance adjusting body with a predetermined pattern density on a transparent film in order to suppress generation of bright lines of a linear light source. Disclosed is a transmittance adjusting body unit configured by arranging the above. By using such a transmittance adjusting body unit, the light emitted from the light exit surface of the light guide plate can be made more uniform and emitted light with reduced luminance unevenness.

  However, when a transmittance adjusting body unit is configured by arranging a single color transmittance adjusting body on a transparent film at a predetermined pattern density, color unevenness may occur depending on the pattern of the transmittance adjusting body. all right.

A first object of the present invention is to provide a transmittance adjuster unit that can reduce the occurrence of luminance unevenness without reducing the average luminance and can also suppress the occurrence of color unevenness.
A second object of the present invention is to provide a planar illumination device that can emit illumination light that is uniform and has less luminance unevenness and color unevenness, and that can be applied to a liquid crystal display device such as a wall-mounted television. There is to do.
A third object of the present invention is to provide a liquid crystal display device that is uniform, has less luminance unevenness and color unevenness, and has good image quality.

  In order to solve the first problem, a first aspect of the present invention is a transmittance adjusting body unit for diffusing and emitting incident light, and is a sheet-like optical member having light transmittance. And a plurality of first transmittance adjusting bodies arranged in a predetermined density distribution on at least one surface of the optical member, and a material having a color substantially different from that of the first transmittance adjusting body, Provided is a transmittance adjusting unit unit including a plurality of second transmittance adjusting bodies arranged at a position closer to the light incident side than the first transmittance adjusting body at a density distribution different from a predetermined density distribution or at a constant density. To do.

In the transmittance adjusting body unit according to the first aspect of the present invention, the optical member is a flat first transparent film having light permeability, and a second transparent located on the light incident side of the first transparent film. It is preferable that the first transmittance adjusting body is formed on the first transparent film, and the second transmittance adjusting body is formed on the second transparent film.
Alternatively, it is also preferable that the first transmittance adjusting body is disposed on the light emitting side surface of the optical member, and the second transmittance adjusting body is disposed on the light incident side surface of the optical member.
Or it is also preferable that the said 2nd transmittance | permeability adjustment body and the said 1st transmittance | permeability adjustment body are arrange | positioned in this order on the surface by the side of the light emission of the said optical member.
Alternatively, it is also preferable that the first transmittance adjusting body and the second transmittance adjusting body are arranged in this order on the light incident side surface of the optical member.

Further, in the transmittance adjuster unit according to the first aspect of the present invention, the plurality of second transmittance adjusters are arranged in close contact with each other without a gap to form a layer having a constant thickness. preferable.
Moreover, it is preferable that the color difference between the first transmittance adjusting body and the second transmittance adjusting body is 0.2 or more and less than 3.0.
Further, the transmittance adjusting body unit when the pattern density at a predetermined position (x, y) of the first transmittance adjusting body is ρ (x, y) and the first and second transmittance adjusting bodies are not provided. The maximum luminance F _max of the light emitted from the light emitting surface is set to 1, and the relative luminance with respect to the maximum luminance F _max of the light emitted from the predetermined position (x, y) of the emitting surface is F (x, y). And when
The relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) is expressed by the following equation:
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min )
It is preferable that c satisfies 0.5 ≦ c ≦ 1 and F _min is the minimum luminance of the relative luminance F (x, y).

  In order to solve the second problem described above, a second aspect of the present invention includes a light source, a flat light guide plate that emits light incident from the light source from a light exit surface, and a sheet shape having light transmittance. Optical member, a large number of first transmittance adjusting bodies arranged in a predetermined density distribution on at least one surface of the optical member, and a material substantially different in color from the first transmittance adjusting body. A plurality of second transmittance adjusting bodies arranged at a position closer to the light incident side than the first transmittance adjusting body at a density distribution different from the predetermined density distribution or at a constant density, Provided is a planar illumination device having a transmittance adjusting body unit disposed on a light exit surface side.

In the planar illumination device according to the second aspect of the present invention, the optical member is a flat first transparent film having light transmissivity, and a second transparent film located on the light incident side with respect to the first transparent film. It is preferable that the first transmittance adjusting body is formed on the first transparent film, and the second transmittance adjusting body is formed on the second transparent film.
Alternatively, it is also preferable that the first transmittance adjusting body is disposed on the light emitting side surface of the optical member, and the second transmittance adjusting body is disposed on the light incident side surface of the optical member.
Or it is also preferable that the said 2nd transmittance | permeability adjustment body and the said 1st transmittance | permeability adjustment body are arrange | positioned in this order on the surface by the side of the light emission of the said optical member.
Alternatively, it is also preferable that the first transmittance adjusting body and the second transmittance adjusting body are arranged in this order on the light incident side surface of the optical member.

  In order to solve the second problem, the third aspect of the present invention has a light source, a flat light guide plate that emits light incident from the light source from a light exit surface, and light transmittance. A sheet-shaped optical member, and a transmittance adjusting body unit for diffusing and emitting incident light, and having a large number of first transmittance adjusting bodies disposed on at least one surface of the optical member And a planar illumination device in which a second transmittance adjusting body formed of a material having a color substantially different from that of the first transmittance adjusting body is arranged at a predetermined density on a light exit surface of the light guide plate. I will provide a.

  In order to solve the third problem, a fourth aspect of the present invention is a planar illumination device according to the second or third aspect of the present invention and a light emission surface side of the planar illumination device. There is provided a liquid crystal display device having a liquid crystal display panel and a drive unit for driving the liquid crystal display panel.

  The first aspect of the present invention reduces luminance unevenness without lowering the average luminance by arranging a large number of first transmittance adjusting bodies arranged with a predetermined density distribution on at least one surface of the optical member. Furthermore, the first transmittance adjusting body is formed of a material substantially different in color from the first transmittance adjusting body, and has a density distribution different from the density distribution of the first transmittance adjusting body or a constant density. The occurrence of color unevenness can be prevented or reduced by arranging the second transmittance adjusting body at a position closer to the light incident side.

  In addition, according to the planar illumination device of the second or third aspect of the present invention, luminance unevenness is suppressed while maintaining high luminance without lowering average luminance, and occurrence of color unevenness is prevented or suppressed. The generated planar illumination light can be generated.

  Further, since the liquid crystal display device of the fourth aspect of the present invention uses the planar illumination device of the second or third aspect, it is uniform and has little luminance unevenness and color unevenness, and can display an image with good image quality. Can be displayed.

Hereinafter, the transmittance adjusting body unit, the planar illumination device, and the liquid crystal display device using the same according to the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.
FIG. 1 shows a schematic cross-sectional view of a planar illumination device 2 (hereinafter also referred to as a backlight unit) according to a second aspect of the present invention having the transmittance adjusting body unit 24 according to the first aspect of the present invention. Such a planar illumination device 2 is used as a backlight unit of the liquid crystal display device according to the third aspect of the present invention. 2A and 2B are a schematic partial perspective view of one light guide plate unit 18 of the backlight unit 2 shown in FIG. 1 and a liquid crystal display device 10 using the backlight unit 2. A schematic partial sectional view is shown. As shown in FIGS. 1, 2A, and 2B, a liquid crystal display device 10 basically includes a backlight unit 2 and a liquid crystal display panel 4 disposed on the light emission surface side of the backlight unit 2. And a drive unit 6 for driving them (connection portion to the backlight unit 2 is not shown).

The liquid crystal display panel 4 applies a partial electric field to liquid crystal molecules arranged in a specific direction in advance to change the arrangement of the molecules, and uses the change in the refractive index generated in the liquid crystal cell to make a liquid crystal display. Characters, figures, images, etc. can be displayed on the surface of the display panel 4.
The liquid crystal display panel 4 includes, for example, GH, PC, TN, STN, ECB, PDLC, IPS (In-Plane Switching), VA (Vertical Aligned) type (MVA, PVA, EVA), OCB, ferroelectric A liquid crystal display panel according to a liquid crystal display mode such as liquid crystal or antiferroelectric liquid crystal can be used. The driving method of the liquid crystal display panel 4 is not particularly limited, and a known driving method such as a simple matrix method or an active matrix method can be used.
Further, the drive unit 6 can control the transmittance of light transmitted through the liquid crystal display panel 4 by applying a voltage to a transparent electrode (not shown) in the liquid crystal display panel 4 to change the direction of the liquid crystal molecules. .

  The backlight unit 2 is a planar illumination device for irradiating the entire surface of the liquid crystal display panel 4 with uniform light from behind the liquid crystal display panel 4, and emits light substantially the same as the image display surface of the liquid crystal display panel 4. It has a surface (light emitting surface). As shown in FIG. 1, the backlight unit 2 basically includes a light source 12, a diffusion film 14, two prism sheets 16 and 17, a light guide plate 19, a reflector 20, and a reflection sheet 22. , And a transmittance adjusting unit unit 24. As shown in FIG. 1, the light guide plate 19 used in the backlight unit 2 of the present embodiment includes a plurality of light guide plate units 18. Hereinafter, each component of the backlight unit 2 will be described.

(light source)
The light source 12 is a rod-shaped cold cathode tube having a small diameter, and is used for illuminating the liquid crystal display panel 4. The light source 12 is disposed in a parallel groove 18f formed in the light guide plate unit 18, and is connected to the drive unit 6 (not shown). Here, a cold cathode tube is used as the light source 12, but the present invention is not limited to this, and any rod-shaped light source may be used. As the light source 12, for example, a normal fluorescent tube, an LED (light emitting diode), or the like can also be used.
For example, an LED light source having a columnar or prismatic transparent light guide having a length equivalent to the parallel groove 18 f of the light guide plate unit 18 and LEDs arranged on the top and bottom surfaces of the light guide 12 is used as the light source 12. It may be used instead. Such an LED light source can emit LED light from the side surface of the light guide by entering LED light from the top and bottom surfaces of the light guide.

(Light guide plate)
The light guide plate 19 is configured by connecting a plurality of light guide plate units 18 in parallel. The light guide plate unit 18 includes a rectangular light emitting surface 18a, a thick portion 18b parallel to one side thereof, thin end portions 18c formed in parallel to the one side on both sides of the thick portion 18b, In the direction perpendicular to the one side from the portion 18b, the thickness is reduced toward the thin end portions 18c on both sides, and the inclined back surface portion 18e forming the inclined back surface 18d and the thick portion 18b are formed in parallel to the one side. And a parallel groove 18f for accommodating the light source 12. That is, the light guide plate unit 18 is a flat plate having a rectangular outer shape on the surface, and is formed of a transparent resin. The light guide plate unit 18 has one surface that is flat, and the other surface is inclined with respect to one surface so that the plate thickness becomes thinner toward one side.
As shown in FIG. 2, the inclined rear surface 18 d is formed with a partially curved surface so as to be smoothly connected to the inclined rear surface of the adjacent light guide plate unit 18. Here, the end of the inclined back surface 18d is partially formed as a curved surface, but may be a flat surface. It is also possible to form the inclined back surface 18d with a curved surface.

  As shown in FIG. 1, the light guide plate unit 18 has a symmetrical shape with respect to a center line perpendicular to the light exit surface 18a of the light guide plate unit 18 through the center of the parallel groove 18f. The light guide plate 19 is formed by connecting a plurality of light guide plate units 18 with the thin-walled portion as a joint.

  On the opposite side of the light-emitting surface 18a of the thick portion 18b of the light guide plate unit 18, a parallel groove 18f for accommodating the light source 12 is formed extending in the longitudinal direction. The depth of the parallel groove 18f is preferably determined so that a part of the light source 12 does not protrude from the lower surface of the light guide plate unit 18. The depth of the light source 12, the mechanical strength of the light guide plate unit 18, and the change over time are preferably determined. It is preferable to determine in consideration. Further, the thickness of the thick portion 18 b and the thin end portion 18 c of the light guide plate unit 18 can be arbitrarily changed according to the dimensions of the light source 12. Here, although the parallel groove 18f of the light guide plate unit 18 may be formed in a direction perpendicular to the longitudinal direction of the light guide plate unit 18, the light use efficiency from the light source 12 accommodated in the parallel groove 18f is increased. Therefore, it is preferable to form in the longitudinal direction.

  In the light guide plate unit 18 having the structure shown in FIGS. 2 (A) and 2 (B), the light guide plate from the side wall forming the parallel groove 18f out of the light emitted from the light source 12 arranged in the parallel groove 18f. The light incident on the inside of the unit 18 is reflected by the inclined back surface 18d of the light guide plate unit 18 and then exits from the light exit surface 18a. At this time, a part of the light leaks from the lower surface of the light guide plate unit 18, but the leaked light is reflected by a later-described reflection sheet 22 formed on the inclined back surface 18 d side of the light guide plate unit 18 and again the light guide plate. The light enters the unit 18 and exits from the light exit surface 18a. In this way, uniform light is emitted from the light exit surface 18a of the light guide plate unit 18.

  The light guide plate unit 18 can be manufactured using, for example, a method in which a heated raw material resin is molded by extrusion molding or injection molding, a casting polymerization method in which a monomer, an oligomer, or the like is molded in a mold. As the material of the light guide plate 19, for example, a transparent resin such as MS resin, acrylic resin, or COP (cycloolefin polymer) can be used, and more specifically, PC (polycarbonate), PMMA (polymethyl methacrylate). ), PET (polyethylene terephthalate), PP (polypropylene), benzyl methacrylate, and the like. The transparent resin may be mixed with fine particles for scattering light, whereby the light emission efficiency from the light emission surface 18a can be further increased.

  In the present embodiment, the parallel grooves 18f of the light guide plate unit 18 are formed such that a cross-sectional shape perpendicular to the length direction of the parallel grooves 18f (hereinafter simply referred to as a cross-sectional shape of the parallel grooves) is a triangular shape. . The shape of the parallel groove 18f will be described later.

(Prism sheet)
The prism sheets 16 and 17 are transparent sheets formed by arranging a plurality of prisms in parallel. The prism sheets 16 and 17 improve the light collecting property of the light emitted from the light emitting surface 18a of the light guide plate unit 18 to improve the luminance. be able to. One of the prism sheets 16 and 17 is disposed so that the extending direction of the prism row is parallel to the parallel groove 18 f of the light guide plate unit 18, and the other is disposed vertically. That is, the prism sheets 16 and 17 are arranged so that the extending directions of the prism rows are perpendicular to each other. The prism sheet 16 is arranged such that the apex angle of the prism does not face the light exit surface 18 a of the light guide plate unit 18. Here, the order of arrangement of the prism sheets 16 and 17 is that a prism sheet 16 having a prism extending in a direction parallel to the parallel groove of the light guide plate is arranged immediately above the light guide plate, and on the prism sheet 16, A prism sheet having prisms extending in a direction perpendicular to the parallel grooves 18f of the light guide plate unit 18 may be disposed, or vice versa.

  In the illustrated example, a prism sheet is used, but a sheet in which optical elements similar to prisms are regularly arranged may be used instead of the prism sheet. In addition, a sheet that regularly includes an optical element such as a lens effect, for example, a lenticular lens, a concave lens, a convex lens, or a pyramid type can be used instead of the prism sheet.

  In the present invention, as shown in FIGS. 3A and 3B, a prism sheet 23 is also provided between the reflection sheet 22 and the inclined back surface 18d opposite to the light exit surface 18a of the light guide plate unit 18. It is preferable to provide it. 3A is a schematic cross-sectional view showing a state in which the prism sheet 23 is disposed between the reflection sheet 22 and the inclined back surface 18d of the light guide plate unit 18, and FIG. FIG. 6 is a schematic plan view and a schematic cross-sectional view of the prism sheet 23 disposed between the light guide plate unit 18 and the inclined back surface 18d of the light guide plate unit 18 as viewed from the light guide plate side. The prism sheet 23 provided between the reflection sheet 22 and the inclined back surface 18d of the light guide plate unit 18 is arranged so that the extending direction of the prism 23a is perpendicular to the parallel grooves 18f of the light guide plate unit 18, and It is preferable to arrange the prism 23 a so that the apex angle of the prism 23 a faces the inclined back surface 18 d of the light guide plate unit 18.

Although a prism sheet is used here, an optical element having the same effect as the prism sheet may be used, and an optical element having a lens effect, for example, an optical element such as a lenticular lens, a concave lens, a convex lens, or a pyramid type is regular. You may provide the sheet | seat arrange | positioned.
In the illustrated example, the prism sheets 16 and 17 and more preferably the prism sheet 23 are used. However, when the luminance on the light exit surface 18a by the parallel grooves 18f of the light guide plate unit 18 is made more uniform. Of course, the prism sheet 23 is unnecessary, and either one or both of the prism sheets 16 and 17 may not be used. The cost of the apparatus can be reduced by reducing the number of expensive prism sheets used or by stopping the use of prism sheets.

(Reflective sheet and reflector)
The reflection sheet 22 is for reflecting the light leaking from the back surface (the lower surface in the figure) of the light guide plate unit 18 so as to enter the light guide plate unit 18 again, and can improve the light use efficiency. . The reflection sheet 22 is formed so as to cover the lower surface (inclined back surface) of the light guide plate unit 18. The reflector 20 is provided behind the light source 12 so as to close the parallel grooves 18 f of the light guide plate unit 18. The reflector 20 can reflect light from the lower surface of the light source 12 and make the light incident from the side wall surface of the parallel groove 18 f of the light guide plate unit 18.

  The reflection sheet 22 may be formed of any material as long as it can reflect light leaking from the back surface (the lower surface in the drawing) of the light guide plate unit 18, for example, PET or PP (polypropylene). Resin sheet with increased reflectivity by forming voids by kneading and stretching filler, etc., transparent or white resin sheet surface as described above, with mirror surface formed by aluminum vapor deposition, etc., metal foil such as aluminum Or it can form with the resin sheet which carry | supported metal foil, or the metal thin plate which has sufficient reflectivity on the surface.

(Diffusion film)
The diffusion film 14 is for diffusing and uniformizing the light emitted from the light exit surface 18a of the light guide plate unit 18, and is, for example, MS resin, acrylic resin, or COP (cycloolefin polymer). Optically transparent resin, more specifically, a film made of optically transparent resin such as PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, etc. It is formed by imparting light diffusibility to the member. The method is not particularly limited. For example, the surface of the flat plate member is subjected to surface roughening by fine unevenness processing or polishing (hereinafter, the surface on which these are applied is referred to as “sand-rubbed surface”) to impart diffusibility. Or pigments such as silica, titanium oxide, and zinc oxide that scatter light on the surface, or beads such as resin, glass, zirconia, etc., together with a binder, or the above-mentioned pigments and beads that scatter light into the above resin It is formed by kneading a kind. In the present invention, the diffusion film 14 may be a mat type or coating type diffusion film.
In the present invention, as the diffusion film 14, it is preferable to use a film-like member having a thickness of 500 μm or less that uses the above-mentioned material and imparts light diffusibility.

  The diffusion film 14 is preferably arranged at a predetermined distance from the light exit surface 18a of the light guide plate unit 18, and the distance is appropriately changed according to the light amount distribution from the light exit surface 18a of the light guide plate unit 18. obtain. Thus, by separating the diffusion film 14 from the light emitting surface 18 a of the light guide plate unit 18 by a predetermined distance, light emitted from the light emitting surface 18 a of the light guide plate unit 18 is between the light emitting surface 18 a and the diffusion film 14. And further mixing (mixing). Thereby, the brightness | luminance of the light which permeate | transmits the diffusion film 14 and illuminates the liquid crystal display panel 4 can be made further uniform. As a method of separating the diffusion film 14 from the light emitting surface 18a of the light guide plate unit 18 by a predetermined distance, for example, a method of providing a spacer between the diffusion film 14 and the light guide plate unit 18 can be used.

  In particular, when the thickness of the backlight unit 2 may be slightly increased, the luminance of the light output surface 18a of the light guide plate unit 18 corresponding to the parallel grooves 18f is increased depending on the cross-sectional shape of the parallel grooves 18f of the light guide plate unit 18. It is not necessary to sufficiently reduce the peak value, and the luminance of illumination light emitted from the diffusion film 14 is reduced by partially reducing the gap between the diffusion film 14 and the light exit surface 18a of the light guide plate unit 18. The distribution may be uniform. Further, there is a limit to the improvement of the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 (the taper of the tip of the parallel groove), and the luminance peak value on the light exit surface 18a of the light guide plate unit 18 corresponding to the parallel groove 18f. In the case where it is not possible to completely reduce or sufficiently reduce the brightness distribution of the illumination light emitted from the diffusion film 14 by providing a gap between the diffusion film 14 and the light exit surface 18a of the light guide plate unit 18. It may be uniform.

(Transmittance adjustment unit)
Next, the transmittance adjusting unit 24 will be described. The transmittance adjuster unit 24 includes a first transmittance adjusting member 28 and a second transmittance adjusting member 30, and the second transmittance adjusting member 30 is disposed on the light incident side with respect to the first transmittance adjusting member 28. The The first transmittance adjusting member 28 and the second transmittance adjusting member 30 may be disposed in close contact with each other, or may be disposed at a predetermined interval.
The first transmittance adjusting member 28 mainly functions as a luminance unevenness reducing member that reduces the luminance unevenness of the planar light from the light emitting surface of the light guide plate 19, while the second transmittance adjusting member. 30 has a function as a color unevenness reducing member that reduces the occurrence of color unevenness of illumination light.
Both the first transmittance adjusting member 28 and the second transmittance adjusting member 30 are configured by arranging a large number of transmittance adjusting bodies on a transparent film. A transmittance adjusting body (first transmittance adjusting body) 26 disposed on the transparent film 29 of the first transmittance adjusting member 28 and a transmittance adjusting body disposed on the transparent film 34 of the second transmittance adjusting member 30 ( The second transmittance adjusting body 32 is made of materials of substantially different colors.

First, the first transmittance adjusting member 28 will be described.
As described above, the first transmittance adjusting member 28 of the present embodiment is used to reduce luminance unevenness of light emitted from the light guide plate unit 18, and is disposed on the surface of the transparent film 29 and the transparent film 29. A plurality of first transmittance adjusting bodies 26.

  The transparent film 29 has a film shape and is made of PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), PMMA (polymethyl methacrylate), benzyl methacrylate, MS resin, other acrylic resin, or COP. It is formed of an optically transparent member such as (cycloolefin polymer).

The first transmittance adjusting body 26 is a dot of various sizes having a predetermined transmittance, has a shape such as a quadrangle, a circle, a hexagon, etc., and has a dot size corresponding to a predetermined pattern, for example, a position. The patterns (halftone dot patterns) with different numbers of dots are formed on the entire surface of the transparent film 29 on the light guide plate unit 18 side by printing or the like.
The first transmittance adjusting body 26 may be any diffuse reflector, for example, a material such as silica, titanium oxide, zinc oxide or other pigment that scatters light or a resin, glass, zirconia or other beads coated with a binder. Or the surface roughening pattern by fine uneven | corrugated processing or grinding | polishing on the surface may be sufficient. In addition, it is a material with high reflectance and low light absorption. For example, metals such as Ag and Al can be used.
As the first transmittance adjusting body 26, a general white ink used in screen printing, offset printing, or the like can be used. For example, an ink in which titanium oxide, zinc oxide, zinc sulfate, barium sulfate, etc. are dispersed in an acrylic binder, a polyester binder, a vinyl chloride binder, etc., or an ink in which silica is mixed with titanium oxide to impart diffusibility. Can be used.

FIG. 4 shows an example in which the first transmittance adjusting bodies 26 are arranged in a halftone dot pattern. Here, FIG. 4 (A) is a schematic diagram showing an example of an arrangement pattern of the first transmittance adjusting body 26 formed on the transparent film 29, and FIG. 4 (B) is a diagram of FIG. 4 (A). FIG. 6 is an enlarged schematic view showing a portion corresponding to one light guide plate unit 18 in an arrangement pattern of one transmittance adjusting body 26 in an enlarged manner. In FIGS. 4A and 4B, the center of the light guide plate unit 18, that is, the center of the parallel groove 18f is indicated by a one-dot chain line.
Thus, by arranging a large number of first transmittance adjusting bodies 26 in a predetermined pattern on the surface of the transparent film 29 on the light guide plate unit 18 side, the pattern of the first transmittance adjusting body 26 according to the position on the surface. Density varies.

Here, the light density of the backlight unit 2 when the pattern density at an arbitrary position (x, y) of the first transmittance adjusting member 28 is ρ (x, y) and the first transmittance adjusting member 28 is not provided. Let F (x, y) be the relative luminance of light emitted from an arbitrary position (x, y) on the surface (the surface on the liquid crystal display panel 4 side). At this time, the relationship between the pattern density ρ (x, y) of the first transmittance adjusting member 28 and the relative luminance F (x, y) preferably satisfies the following formula 1.
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min ) Equation 1
In Formula 1, F _max is the maximum luminance of light emitted from the light exit surface of the diffusion film 14 of the backlight unit 2 when the first transmittance adjusting member 28 is not provided, and F _min is the minimum luminance. is there. Note that the relative luminance F (x, y) uses the maximum luminance F _max as a reference point (F _max = 1).
Here, c is the maximum density, and is preferably 0.5 ≦ c ≦ 1.
Here, the pattern density ρ (x, y) is an occupation rate per unit area (1 mm ² ) of the transmittance adjusting body 26 existing at an arbitrary position (x, y), and ρ (x, y). When = 1, the transmittance adjusting body 26 is disposed on the entire surface within the unit area, and when ρ (x, y) = 0, it is not disposed at all within the unit area.

By arranging the first transmittance adjusting body 26 of the first transmittance adjusting body member 28 so as to satisfy the pattern density ρ (x, y) of the above formula 1, the light is emitted from the light emitting surface of the backlight unit 2. It is possible to suppress a decrease in average luminance of light and reduce luminance unevenness. Thus, by reducing the luminance unevenness using the transmittance adjusting unit 28, the diffusion film 14 does not need to sufficiently diffuse the light. As a result, the diffusion film 14 can be made thinner, the use of the prism sheet can be stopped, or the number of prism sheets used can be reduced, providing a lighter and cheaper backlight unit. can do.
Here, as described above, the maximum density c is preferably 0.5 ≦ c ≦ 1. By setting the maximum density c to 0.5 or more, it is possible to suppress a reduction in average luminance, and it is possible to emit uniform light with high luminance.
The first transmittance adjusting body 26 preferably has a pattern density ρ (x, y) = 1, that is, the transmittance when the first transmittance adjusting body is disposed on the entire surface is 10% or more and 50% or less. 20% or more and 40% or less is more preferable.
By setting the transmittance to 10% or more, luminance unevenness can be suitably reduced, and by setting the transmittance to 50% or less, luminance unevenness can be reduced without reducing the average luminance.
Furthermore, the said effect can be acquired more suitably by making the transmittance | permeability into 20% or more and 40% or less.

In the present embodiment, the first transmittance adjusting body is arranged in a quadrangular shape, but the present invention is not limited to this, and may be any shape such as a triangle, a hexagon, a circle, and an ellipse.
Further, when the linear light source and the uniaxially extending light guide plate unit as in the present embodiment are used for the backlight unit, the shape of the first transmittance adjusting body is parallel to the axis of the linear light source. It may be an elongated band shape.

Next, the second transmittance adjusting member 30 will be described.
As shown in FIG. 2, the second transmittance adjusting member 30 is disposed and used on the light incident side of the first transmittance adjusting member 28. The second transmittance adjusting member 30 is configured by forming a second transmittance adjusting body 32 on a transparent film 34 in a predetermined pattern or uniformly. The second transmittance adjusting body 32 is made of a material having a color substantially different from that of the first transmittance adjusting body 26.
The transparent film 34 may be configured using the same material as the transparent film 29 of the first transmittance adjusting member 28 or may be configured using a different material.

The second transmittance adjusting member 30 disposed on the light emitting side of the first transmittance adjusting member 28 can prevent the color unevenness of the illumination light emitted from the first transmittance adjusting member 28. When the first transmittance adjusting member 28 configured by arranging the first transmittance adjusting body 26 of a single color on the transparent film 29 in a predetermined pattern is arranged on the light emission side of the light guide plate 19, the first transmission It has been found that depending on the pattern of the rate adjusting body 26, color unevenness occurs between light from directly above the light source 12 of the backlight unit 2 and light from a position farthest from the light source 12. In this case, the pattern itself of the first transmittance adjusting body 26 is visually recognized in the form of uneven color, and there is a possibility that uniform illumination light cannot be obtained. Such a phenomenon is that the light reflected by the first transmittance adjusting body 26 is incident on the inside of the light guide plate 19 and is then emitted from the light guide plate 19 again and reflected by the first transmittance adjusting body 26. As a result of repeated reflection on the transmittance adjusting body 26, it is considered that the reflected light is tinted and color unevenness occurs.
In the present invention, the second transmittance adjusting member 30 including the second transmittance adjusting body 32 that is substantially different in color from the first transmittance adjusting body 26 is disposed on the light incident side of the first transmittance adjusting member 28. As a result, the occurrence of uneven color is prevented.

The second transmittance adjusting body 32 only needs to be substantially different from the color of the first transmittance adjusting body 26, and the absolute value ΔEp of the color difference between the first transmittance adjusting body 26 and the second transmittance adjusting body 32. Is preferably 0.2 or more because the effect of adjusting the color is difficult to be confirmed if it is too small, and if the color difference of the ink itself is too large, the transmittance adjuster itself is visually recognized. For this reason, it is preferably less than 3.0.
The second transmittance adjusting body 32 may be composed of a single material or may be composed of a plurality of materials. For example, when ink is used as the material of the first transmittance adjusting body, monochromatic ink may be used, or white ink and color adjusting ink may be mixed and used. In the present invention, as the second transmittance adjusting body, for example, ink that is color-corrected by intentionally mixing components of other colors with respect to the ink used for the first transmittance adjusting body can be used.
For example, when white ink is used for the first transmittance adjusting body 26, titanium oxide is generally used as the white ink. Therefore, the illumination light of the planar illumination device using such a first transmittance adjusting body is slightly yellow. It will be colored. Further, when a linear light source having a high color temperature (10000 K or more) is used, the illumination light of the planar illumination device is conspicuous in yellow. In such a case, as the material of the second transmittance adjusting body 32, a material to which blueness adjusting inks such as blue, ultramarine, and indigo are added can be used.

The second transmittance adjusting body 32 may be arranged on the transparent film 34 in a predetermined density distribution pattern, or may be arranged at a constant density. In the case where the second transmittance adjusting body 32 is uniformly formed on the surface of the transparent film 34, each second transmittance adjusting body 32 has a constant density at regular intervals on the surface of the transparent film 34. It may be arranged in such a halftone dot pattern, or may be arranged in close contact with the entire surface of the transparent film 34 without gaps to constitute a layer composed of the second transmittance adjusting body 32.
Further, when the second transmittance adjusting body 32 is arranged in a predetermined pattern, as the arrangement pattern of the second transmittance adjusting body 32, when the luminance unevenness cannot be improved only by the first transmittance adjusting body, the transmittance For the luminance distribution including the adjusting body 1, it is preferable to use the density distribution obtained by the calculation formula of Formula 1.
By arranging the second transmittance adjusting body 32 in such a pattern, the luminance unevenness can be further improved.

In the present embodiment, the transmittance adjusting unit 24 is configured by the first transmittance adjusting member 28 and the second transmittance adjusting member 30, but the present invention is not limited to this. That is, in the above example, the first transmittance adjusting body 26 and the second transmittance adjusting body 34 are formed on the separate transparent films 29 and 34, respectively, and the first transmittance adjusting member 28 and the second transmittance adjusting member 30 are formed. Although the first transmittance adjusting body 26 and the second transmittance adjusting body 34 are formed on the same transparent film, the transmittance adjusting body unit may be configured. Thereby, the number of parts can be reduced and the cost can be reduced.
In the case of such a configuration, the second transmittance adjusting body 32 is disposed so as to be positioned closer to the light incident side than the first transmittance adjusting body 26. 5A to 5C show configuration examples of the transmittance adjusting unit. 5A to 5C show an example in which the second transmittance adjusting body 34 is arranged in a layered manner without a gap. 5A to 5C, the lower side in the figure is the light incident side.
In FIG. 5A, a layer (second transmittance adjusting layer) 37 composed of the second transmittance adjusting body is formed on the light incident side surface of the transparent film 36, and the light emitting side surface is formed. This is a configuration example of a transmittance adjusting body unit 40 in which a large number of first transmittance adjusting bodies 26 are arranged.
In FIG. 5B, a large number of first transmittance adjusting bodies 26 are formed on the light incident side surface of the transparent film 36, and the second transmittance adjusting bodies 26 are arranged on the second side. It is a structural example of the transmittance adjusting body unit 41 in which the transmittance adjusting layer 37 is formed. The transmittance adjusting body unit 41 having such a structure can be easily manufactured by printing on the transparent film 36 using ink as the first transmittance adjusting body 26 and the second transmittance adjusting layer 37. That is, the first transmittance adjusting body 26 is formed in a predetermined pattern on the transparent film 36 by printing, and then the second transmittance adjusting layer 37 is formed on the same surface as the surface on which the first transmittance adjusting body 26 is printed. It is obtained by forming by printing.
FIG. 5C is a configuration example of a transmittance adjusting unit 42 in which the first transmittance adjusting body 26 and the second transmittance adjusting layer 37 are formed on the light emitting side surface of the transparent film 36. The transmittance adjusting body unit 42 having such a structure is formed on the light emitting surface of the transparent film 36 by forming the second transmittance adjusting layer 37 by printing or the like, and then on the surface on which the second transmittance adjusting layer 37 is formed. Furthermore, it can be easily manufactured by forming the first transmittance adjusting body 26 in a predetermined pattern by printing or the like.

  Here, in the said embodiment, although the transparent film was used as an optical member by which the 1st transmittance | permeability adjusting body or the 2nd transmittance adjusting body is arrange | positioned, this invention is not limited to this, A diffusion film or a prism sheet Alternatively, the first transmittance adjusting body or the second transmittance adjusting body may be disposed. For example, in FIGS. 5A to 5C, a large number of first transmittance adjusting bodies 26 and second transmittance adjusting layers 53 are formed on the transparent film 36, but instead of the transparent film 36, FIG. The first transmittance adjusting body 26 and the second transmittance adjusting body 32 may be formed on the diffusion film 14 or the prism sheets 16 and 17 shown. As a result, the number of parts can be reduced, and the manufacturing cost can be reduced.

  In the present invention, the second transmittance adjusting body 32 is formed on at least one surface of the diffusion film 14 shown in FIG. 1, and the first transmittance adjusting body 26 is formed on at least one of the prism sheets 16 and 17. You can also. In this case, the second transmittance adjusting member is constituted by the diffusion film 14 and the second transmittance adjusting body 32 formed on the surface thereof, and is formed on at least one of the prism sheets 16 and 17 and on the surface thereof. The first transmittance adjusting member 26 constitutes a first transmittance adjusting member.

In addition, as shown in FIG. 6, a layer (second transmittance adjusting layer 37) composed of the second transmittance adjusting body can be formed on the light exit surface of the light guide plate 18. In this case, as shown in FIG. 6, the first transmittance adjusting member 28 is disposed on the light emitting surface of the light guide plate 18 on the side where the second transmittance adjusting layer 37 is formed. On 28, the diffusion film 14 and the prism sheets 16 and 17 are arranged in this order to constitute a backlight unit. Thereby, the number of parts can be reduced and the cost can be reduced. Here, the second transmittance adjusting layer 37 is formed on the light exit surface of the light guide plate, but the second transmittance adjusting body may be arranged in a predetermined pattern.
Moreover, a 2nd transmittance | permeability adjustment body can be formed on the light emission surface of a light-guide plate, and also a 1st transmittance | permeability adjustment body can be arrange | positioned on the surface in which the 2nd transmittance | permeability adjustment body was formed. In this case, since the first transmittance adjusting member 28 in the figure is not necessary, the number of parts can be further reduced, and the cost can be further reduced. Further, when the first transmittance adjusting member is disposed on the light emitting surface side of the light guide plate, it is necessary to align the light guide plate and the first transmittance adjusting member at the time of manufacture, but on the light emitting surface of the light guide plate. By forming the second transmittance adjusting body on the surface and further arranging the first transmittance adjusting body on the surface on which the second transmittance adjusting body is formed, it is not necessary to perform alignment at the time of manufacturing, and the assembly process is simplified. Can be

  In this embodiment, the transmittance adjusting unit 24 is provided between the light guide plate 19 and the diffusion film 14. However, the arrangement position is not limited to this, and the arrangement is provided between the diffusion film 14 and the prism sheet 17. May be.

Further, in the present embodiment, as shown in FIG. 1, the light transmission plate 19 has a configuration in which the transmittance adjusting unit unit 24, the diffusion film 14, and the prism sheets 17 and 16 are laminated in this order on the light exit surface side. There is no particular limitation on the order of arrangement of the respective members on the exit surface side, and for example, the transmittance adjuster unit, the prism sheet, and the diffusion film may be laminated on the exit surface side of the light guide plate 19 in this order.
Moreover, in the said embodiment, although the 1st transmittance | permeability adjustment body 26 of the 1st transmittance | permeability adjustment member 28 was arrange | positioned so that the pattern density (rho) (x, y) of the said Formula 1 might be satisfy | filled as a suitable aspect, this invention. Is not limited to this, and the first transmittance adjusting body can be arranged with various pattern densities for suppressing the occurrence of luminance unevenness. For example, the first transmittance adjusting member may be a known transmittance adjusting body unit in which the first transmittance adjusting body is arranged so as to have a density distribution in a direction perpendicular to the axis of the linear light source.

The first transmittance adjustment body 26 of the first transmittance adjustment member 28 has a pattern density distribution adjusted according to the light incident on the first transmittance adjustment member 28. The pattern density distribution may be adjusted by changing the size of the first transmittance adjusting body 26 or may be adjusted by changing the arrangement interval of the first transmittance adjusting bodies 26 having a fixed shape.
As an arrangement method of the first transmittance adjusting body 26 according to the pattern density, various methods such as an FM screening method and an AM core method can be used, and among these, the FM screening method is preferably used. By using the FM screening method, it is possible to disperse and arrange the first transmittance adjusting bodies as fine and uniform dots, and the arrangement pattern of the first transmittance adjusting body 26 from the light exit surface of the backlight unit. Can be made difficult to visually recognize. That is, the arrangement pattern of the first transmittance adjusting body 26 is projected from the light emitting surface of the backlight unit, and uneven light can be prevented from being emitted, and more uniform light can be emitted. Further, it is possible to prevent the dot size from becoming too small and the formation of the first transmittance adjusting body 26 from becoming difficult.
Further, the second transmittance adjusting body 32 of the second transmittance adjusting member 26 can also be arranged using various methods such as the FM screening method, the AM core method, and when arranged using the FM screening method. The same effect as described above can be obtained.

The first transmittance adjusting body 26 and the second transmittance adjusting body 32 have a maximum dimension of 500 μm or less. For example, in the case of a rectangular shape, the length of one side is 500 μm or less, and in the case of an elliptical shape, the major axis is 500 μm or less. It is preferable that the thickness be 200 μm or less. By setting the maximum dimensions of the first transmittance adjusting body 26 and the second transmittance adjusting body 32 to 500 μm or less, the shapes of the first transmittance adjusting body 26 and the second transmittance adjusting body 32 are not easily seen, and the maximum By making the size 200 μm or less, the shapes of the first transmittance adjusting body 26 and the second transmittance adjusting body 32 become invisible, and when actually used as a liquid crystal display device, the first transmittance adjusting body 26 and The shape of the second transmittance adjusting body 32 is not projected on the light exit surface of the backlight unit, resulting in uneven brightness, and the uneven brightness can be efficiently reduced.
Moreover, it is more preferable that the first transmittance adjusting body 26 and the second transmittance adjusting body 32 have a maximum dimension of 100 μm or less. By setting the maximum dimension to 100 μm or less, the dimension can be more surely less than the discriminating ability of the naked eye, and when actually used as a liquid crystal display device, the first transmittance adjustment body 26 and the second transmittance adjustment are performed. The shape of the body 32 is not projected on the light exit surface of the backlight unit, resulting in uneven brightness, and the uneven brightness can be reduced more reliably and efficiently.

Moreover, as a method for printing the first transmittance adjusting body and the second transmittance adjusting body on the surface of the transparent film, various printing methods such as screen printing, offset printing, gravure printing, and ink jet printing can be used. Offset printing has the advantage that it is excellent in productivity, and screen printing has the advantage that the ink thickness can be increased and the transmittance of the pattern portion can be lowered without increasing the ink density. . Inkjet printing can be printed on a three-dimensional object, and is optimal as a method for forming the first or second transmittance adjusting body on the surface of the light guide plate.
When the first transmittance adjusting body and the second transmittance adjusting body are formed on a transparent film, a diffusion film, a prism sheet, a light guide plate, etc. by such a printing method, the first transmittance adjusting body and the second transmittance adjusting body are printed. It is only necessary to perform two printings of the two transmittance adjusting body, but the number of printings may be further increased.

  The preferred embodiment of the backlight unit of the present invention has been described above in detail. Next, the backlight unit of the present invention including the transmittance adjusting body unit of the present invention will be described in more detail together with specific examples. To do.

In this example, a backlight unit having the same configuration as the backlight unit shown in FIGS. That is, the backlight unit 2 of this embodiment includes the light source 12, the diffusion film 14, the prism sheets 16 and 17, the light guide plate unit 18, the reflector 20, the reflection film 22, and the first transmittance adjusting member 28. And the second transmittance adjusting member 30.
In this embodiment, a cold cathode tube having a diameter R of 2.0 mm and a color temperature of 30000 K was used as the light source 12. Further, as shown in FIG. 7, the light guide plate unit 18 has a distance L from the center of the light guide plate unit 18 to the surface where the thickness of the light guide plate unit 18 is the thinnest, that is, the joint surface with the adjacent light guide plate unit 18. 15 mm, the thickness D of the thickest portion 18b of the light guide plate unit 18 is 4.5 mm, the distance d ₁ between the tip portion of the parallel groove 18f and the light exit surface is 1.0 mm, and the inclined back surface of the thickness d ₂ the thickness of the light guide plate unit of the thinnest surface when formed into a flat end and 1.5 mm, a width G ₁ of the end portion of the light exit surface 18a and the opposite side of the parallel groove 18f 4. 0 mm, the tip of the parallel groove 18 f is curved, the curvature radius r ₁ of the most advanced part is 0 mm, the inclined back surface of the joint with the adjacent light guide plate is planar, and the curvature radius of the extremely thin part is 0 mm The shape was as follows.
The diffusion film had a haze of 87.6% and a total light transmittance of 87.3%.
The prism sheets 16 and 17 were made of a material whose base is PET, a thickness of 400 μm, a prism with a pitch of 100 μm, and an apex angle of 90 °. The reflector 20 was integrated with a reflective film, and the reflective film 22 was a product manufactured by Mitsui Chemicals Co., Ltd. with a white Lefster thickness of 180 μm (a mixture of an inorganic filler and voids in a polypropylene base film).

Moreover, the 1st transmittance | permeability adjustment member 28 by which the 1st transmittance | permeability adjustment body 26 was arrange | positioned with the pattern density shown in FIG. 4 as the 1st transmittance | permeability adjustment member 28 was produced.
An acrylic film having a thickness of 0.18 mm was prepared as the transparent film 29, and a predetermined pattern was printed on the acrylic film with a screen printer using TiO ₂ screen ink to produce the first transmittance adjusting member 28. In pattern printing, the dot area ratio was 50%, and the dot size was 300 μ (60 lines).
Further, an appropriate amount of colored ink was prepared for the ink so as to match the color of the light source for color adjustment. As the screen ink, Jujo Ink Cure 470M high density white was used. As the color adjustment ink, an ink prepared by mixing Jujo Ink Cure Cure 4746M Indigo and Teikoku Ink UV FIL-135TC Magenta at a weight ratio of 1: 1 was used. Further, a mesh used for printing was a mesh 355 manufactured by Premax.
Here, a method for calculating the pattern density of the first transmittance adjusting body 26 of the first transmittance adjusting member 28 will be described in detail.

  In the backlight unit 2 shown in FIGS. 1 to 3, in order to calculate the pattern density ρ (x, y) of the first transmittance adjusting member 28 that satisfies the above formula 1, the transmittance adjusting body unit 24, that is, the first From the light emitting surface of the backlight unit when the backlight unit having the same configuration and shape is used except that the first transmittance adjusting member 28 and the second transmittance adjusting member are not provided and the transmittance adjusting body unit 24 is not provided. The relative brightness F (x, y) of the emitted light was measured.

Here, the relative luminance F (x, y) was measured as follows.
First, the backlight unit 32 is fixed to an XY stage, and a luminance meter is fixed so as to be perpendicular to the light emission surface of the backlight unit 32. Then, the luminance at the position of the light emitting surface of the backlight unit 32 is measured by a luminance meter, and information on the luminance relating to the specific position of the light emitting surface of the light guide plate unit 18 is obtained.
Thereafter, by moving the XY stage, the relationship between the position on the light exit surface of the backlight unit 32 and the luminance is obtained, and the maximum luminance of the calculated luminance is F _max and the minimum luminance is F _min . The maximum luminance F _max was set to 1, and the ratio of the luminance at each position to the maximum luminance F _max was set as the relative luminance F (x, y) at the position (x, y). The measurement results thus measured are shown in FIG. Here, in the graph of FIG. 8, the vertical axis represents relative luminance, and the horizontal axis represents the distance from the center of the light guide plate (the center of the parallel groove).

Next, the pattern density ρ (x, y) corresponding to the relative luminance F (x, y) is calculated from the measured maximum luminance F _max and the minimum luminance F _min using the above formula 1. Here, in this embodiment, the relative luminance F (x, y) and the pattern density ρ (x, y) when the maximum density c is c = 0.25, 0.5, 0.75, and 1, respectively. The relationship was calculated. FIG. 9 shows the calculation result. In FIG. 9, the vertical axis indicates the pattern density ρ (x, y), and the horizontal axis indicates the relative luminance F (x, y).
As shown in FIG. 9, the relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) is a proportional relationship, and the pattern is obtained when the relative luminance F (x, y) is the minimum luminance F _min. When the density ρ (x, y) is 0 and the maximum luminance F _max is reached, the pattern density ρ (x, y) becomes the maximum density c.

  Next, based on the relationship between the relative brightness F (x, y) and the pattern density ρ (x, y) shown in FIG. 9, the relative brightness F (x of the backlight unit of the present embodiment shown in FIG. , Y), the distribution of the pattern density ρ (x, y) is calculated. FIG. 10 shows the distribution of the pattern density ρ (x, y) calculated when the maximum density c is c = 0.25, 0.5, 0.75, and 1. In FIG. 10, the vertical axis represents the pattern density ρ (x, y), and the horizontal axis represents the distance from the center of the light guide plate (the center of the parallel groove).

Next, when the calculated maximum density c is c = 0.25, 0.5, 0.75, and 1, the transmittance is based on the distribution of the pattern density ρ (x, y) that satisfies Equation 1. A transmittance adjusting body unit 28 in which the adjusting body 26 was arranged was prepared.
Here, in the present embodiment, the distribution of the pattern density ρ (x, y) is calculated every 0.5 mm in the width direction (lateral direction in FIG. 5A), and the calculated pattern density ρ (x, y ), The transmittance adjusting body unit 28 was created by appropriately arranging the transmittance adjusting body 26 having a size in the width direction of 0 to 1 mm. That is, L ₁ and L ₄ of the transmittance adjusting body unit shown in FIG. 4B are set to L ₁ = L ₄ = 1.0 mm, L ₂ and L ₃ are set to L ₂ = L ₃ = 0.5 mm, w1 to The transmittance adjusting body 26 was arranged with w4 being 0 mm ≦ w ≦ 1 mm, and a transmittance adjusting body unit 28 was produced.
Here, in the present embodiment, when the transmittance adjusting body is disposed on the entire surface, that is, when the pattern density ρ (x, y) is 1, the transmission created by the white ink having a transmittance of 33% at a wavelength of 550 nm. A rate adjuster 26 was placed.

  When the transmittance adjusting unit 28 thus created was arranged in the backlight unit 30, the relative luminance of the light emitted from the emission surface of the backlight unit 30 was measured. The measurement method was the same as the measurement method for measuring the relative luminance F (x, y) described above. The measurement results are shown in FIG. Here, in FIG. 11, the vertical axis represents relative luminance, and the horizontal axis represents the distance from the center of the light guide plate (the center of the parallel groove). For comparison, the vertical luminance of the light emitted from the light emitting surface of the backlight unit having the same configuration except that the transmittance adjusting unit 24 is not provided is also shown.

As shown in FIG. 11, by arranging the transmittance adjusting body unit 24, it is possible to reduce the luminance unevenness compared to the case where the transmittance adjusting body unit 24 is not arranged.
Furthermore, it can be seen from this result that the maximum density c should be 0.5 ≦ c ≦ 1 in order to make the luminance unevenness ± 10% or less.

Subsequently, the second transmittance adjusting member 30 is made of an ink having a color different from that of the ink used for the production of the first transmittance adjusting member 28. It was produced by solid printing at (60 lines). For the transparent film 34, an acrylic film having a thickness of 0.18 mm was used as in the first transmittance adjusting member 28.
In this embodiment, the color difference with respect to the printed matter (first transmittance adjusting body 26) formed on the transparent film 29 of the first transmittance adjusting member 28 is 0.0, 0.1, 0.3, 1.. Eight types of inks having values of 0, 1.5, 2.0, 2.5, and 3.2 were prepared, and eight types of second transmittance adjusting members 30 were prepared using each ink.
Then, each of the second transmittance adjusting members 30 was incorporated into the backlight unit having the structure shown in FIG. 1 to produce eight types of backlight units.
The printed matter (second transmission) formed on the transparent film 34 of the second transmittance adjusting member 30 with respect to the printed matter (first transmittance adjusting body 26) formed on the transparent film 29 of the first transmittance adjusting member 28. The color difference of the rate adjusting body 32) was obtained by measuring CIE L ^* a ^* b ^* of each printed matter on a barium sulfate plate using spectrino and determining the difference in measured values. In the CIELab color space, a ^* and b ^* were calculated using the CIE 1976 (L ^* , a ^* , b ^* ) uniform perceptual color space (“New Color Science Handbook”, University of Tokyo Press (1980). (See Chapter 4, etc.)).

  Further, in this embodiment, as the ink used for forming the second transmittance adjusting member of the second transmittance adjusting member 30, an ink having a different color from the ink used in the first transmittance adjusting member is produced. Further, the white ink and the color adjustment ink were mixed and adjusted so that the mixing ratio of the amount of the color adjustment ink to the amount of the white ink was within a range of 1% at the maximum.

Next, in-plane color measurement of the eight types of backlight units produced as described above was performed using a spectroradiometer (SR-3) manufactured by Topcon Corporation at an aperture angle of 0.1 °. The measurement locations were five directly above the light emitting portion and five farthest portions (joint portions). Then, the average values of 5 locations immediately above the light emitting portion and 5 locations of the farthest portion were respectively obtained, and the absolute value ΔEi of CIE L ^* a ^* b ^* color difference was defined as the color difference in the issuer.

  A visual test by 10 people was also conducted to deal with the actual appearance. Specifically, when viewed from a position 2 mm above the vertical line at the center of the backlight unit, if the number of people who judge that the color unevenness has been visually recognized is 6 or more, △, 2 if it is 3 or more and 5 or less. If it was less than one name, it was rated as ○. The results are shown in Table 1 below.

From the above results, by making the color of the second transmittance adjusting body substantially different from the color of the first transmittance adjusting body, there is obtained a planar light source that is uniform and free from unevenness in brightness and color unevenness without pattern recognition. I understand that
Also, by combining with a liquid crystal panel, a thin and light liquid crystal display device with good image quality could be obtained. Although the embodiment has been described in detail above, the present invention is not limited to this.
In the embodiment and the examples, the transmittance adjusting body unit is configured by using two types of transmittance adjusting body units of the first transmittance adjusting member and the second transmittance adjusting member. It is also possible to configure the transmittance adjusting body unit using the rate adjusting member. In this case, what is necessary is just to adjust the material of the transmittance | permeability adjustment body so that the color of the transmittance | permeability adjustment body of each transmittance | permeability adjustment member may mutually differ.

  Moreover, in the said embodiment and Example, although the edge part of the inclination back surface of a light-guide plate was partially formed in the curved surface, the shape of a light-guide plate is not specifically limited, For example, as shown in FIG. The end of each may also be formed in a plane. That is, a rectangular light emitting surface 48a, a thick portion 48b that is parallel to one side of the rectangular light exit surface 48b, is positioned substantially in the center of the rectangular shape, a thin end portion 48c that is formed in parallel to the thick portion 48b, and the rod-shaped light source 12 A parallel groove 48f for housing is formed in the approximate center of the thick part 48b in parallel with the one side, and includes the axis of the rod-shaped light source 12 on both sides of the parallel groove 48f and is perpendicular to the rectangular light emitting surface 48a. A shape having an inclined back surface portion 48e that forms a slanted back surface 48d, and is thinned toward the thin end portions 48c on both sides in a direction orthogonal to the one side from the thick wall portion 48b. The light guide plate 48 can also be used. Even when the light guide plate 48 having such a shape is used, the luminance unevenness of the light emitted from the light guide plate 48 is reduced, so that a backlight unit with less luminance unevenness can be provided.

  Further, in the present embodiment, the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 is triangular, but the cross-sectional shape of the parallel groove 18f is that of the light guide plate unit 18 through the deepest part or center of the parallel groove 18f. Any shape that is symmetric with respect to the center line perpendicular to the light exit surface and that narrows toward the light exit surface 18a may be used. For example, as shown in FIGS. be able to. Alternatively, the cross-sectional shape of the parallel groove 18f of the light guide plate unit 18 may be a suspended line shape.

  Moreover, in the cross-sectional shape of a parallel groove, it can also be set as the shape where the deepest part (connection part of the side wall which forms a parallel groove) of a parallel groove becomes a cusp. That is, two curved lines or straight lines that are symmetrical with respect to a center line that passes through the center of the parallel groove and is perpendicular to the light exit surface of the light guide plate, the cross-sectional shape of the tip portion of the parallel groove having one sharp intersection that intersects each other It can form from a part of. In the present invention, even if the cross-sectional shape of the parallel groove of the light guide plate is any of the above shapes, uniform light can be emitted from the light exit surface of the light guide plate.

  In FIG. 15, the cross-sectional shape of the tip portion of the parallel groove is symmetrical with respect to a center line perpendicular to the light exit surface of the light guide plate through the center of the parallel groove 18 f having one sharp intersection that intersects each other. An example of the case of consisting of a part of two curves is shown. The light guide plate 50 shown in FIG. 15 is a case where two curves 54 a and 54 b that are symmetric with respect to the center line S passing through the center of the parallel groove and perpendicular to the light exit surface 52 of the light guide plate 50 are arcs. In this case, as shown in FIG. 15, the center position of the arc 54a corresponding to one side wall forming the parallel groove 18f is different from the center position of the arc 54b corresponding to the other side wall. As a result, the portion 56 where the arc-shaped side walls meet has a sharp shape as shown in FIG.

  Further, in FIG. 16, the cross-sectional shape of the tip portion of the parallel groove is symmetrical with respect to the center line perpendicular to the light exit surface of the light guide plate through the center of the parallel groove having one sharp intersection that intersects each other. Still another example in the case of consisting of a part of two curves is shown. The light guide plate 60 shown in FIG. 16 is a case where two curves 64a and 64b that are symmetrical with respect to the center line X passing through the center of the parallel groove 18f and perpendicular to the light exit surface of the light guide plate are parabolas. In FIG. 16, the side wall of the parallel groove 18f is formed such that the focal point of the parabola 64a corresponding to one side wall of the parallel groove 18f is different from the focal point of the parabola 64b corresponding to the other side wall 22b.

  As shown in FIG. 16, in the case where the cross-sectional shape of the tip portion of the parallel groove is formed by two curves 64a and 64b that intersect at the intersection 64, the intersection of the curves 64a corresponding to one side wall of the parallel groove 18f ( The angle θ between the tangent line at the cusp 64 and the tangent line at the intersection 64 of the curve 64b corresponding to the other side wall is preferably 90 degrees or less, and more preferably 60 degrees or less.

  1 to 16 show examples of the light guide plate in which the curved lines forming the side walls of the parallel grooves are concave toward the center of the parallel grooves in the cross-sectional shape of the parallel grooves. Another embodiment of the light plate is shown in FIGS. FIG. 17 shows an example of the light guide plate 70 in which the cross-sectional shape of the parallel groove 18f is formed by two curves 72a and 72b that protrude toward the center of the parallel groove 18f. FIG. 18 shows the cross-sectional shape of the parallel groove 18f. Is an example of the light guide plate 80 formed from a curve obtained by combining convex curves 82a and 82b and concave curves 84a and 84b toward the center of the parallel groove 18f. The light guide plates 70 and 80 having parallel grooves having a cross-sectional shape as shown in FIGS. 17 and 18 can also emit light with sufficient illuminance from the light exit surface while suppressing the generation of bright lines.

  Thus, in the cross-sectional shape of the parallel groove of the light guide plate, the portion corresponding to the parallel groove can be a convex or concave curve or straight line toward the center of the parallel groove, and a combination thereof. Also good. These curves are not limited to the arc in the illustrated example, and may be any part of a curve such as an ellipse, a parabola, or a hyperbola that is convex or concave toward the center of the parallel groove. In the present invention, if the cross-sectional shape of the tip portion of the parallel groove is tapered as will be described later, the curve constituting the parallel groove is a circle that is convex or concave toward the center of the parallel groove, It may be a part of a curve such as an ellipse, a parabola, or a hyperbola, and is preferably a curve that can be approximated by a tenth-order function.

  Also, if the cross-sectional shape of the top (deepest part) of the tip of the parallel groove is only one chamfered flat shape or rounded circular shape with one sharp intersection symmetrically with respect to the center line of the parallel groove Of course, it may be oval, parabolic, or hyperbolic. In addition to this, as described above, the peak value of the illuminance may be reduced by using a top portion (deepest portion) of the tip portion of the parallel groove as a rubbing surface.

  Furthermore, illuminance and luminance can be handled in substantially the same manner on the surface of the light guide plate. Therefore, in the shape of the light guide plate, it is considered that the luminance on the light exit surface of the light guide plate can also be made uniform by designing the light guide plate to have the shape shown above.

  Here, in the light guide plate used in the backlight unit (planar illumination device) of the present invention, the portion corresponding to the inclined back surface 18d (second portion) other than the parallel grooves 18f on the light exit surface 18a of the light guide plate unit 18 (second portion). Depending on the ratio of the peak value (illuminance peak value) of the bright line formed in the portion (first portion) corresponding to the parallel groove 18f on the light exit surface 18a of the light guide plate unit 18 to the average value of illuminance formed in Thus, the tip shape of the parallel groove 18f of the light guide plate unit 18 is tapered, that is, the degree of tapering of the tip shape of the parallel groove 18f of the light guide plate unit 18 is controlled according to the value of this ratio. preferable. In this case, this ratio is preferably 3 or less, more preferably 2 or less.

  This ratio is the thickness of the backlight unit 2 (the distance between the light emitting surface 18a of the light guide plate unit 18 and the diffusion film 14), the diffusion efficiency and the number of diffusion films 14 used in the backlight unit 2. The prism sheets 16, 17 and 23 are preferably set according to the diffusion efficiency, the number of used sheets, and the like. That is, the thickness of the backlight unit 2 (the distance between the light emitting surface 18a of the light guide plate unit 18 and the diffusion film 14) can be increased to some extent (or larger), or the diffusion film 14 used in the backlight unit 2 can be used. If the diffusion efficiency of the light guide plate unit 18 is high and the number of used sheets can be increased, or if the diffusion efficiency of the prism sheets 16, 17 and 23 is high and the number of used sheets can be increased, the illumination emitted from the light exit surface 18a of the light guide plate unit 18 Light diffusion (mixing, etc.) can be sufficiently performed, so that the cost is high, but the light emission of the light guide plate unit 18 with respect to the average value of the illuminance of the second portion of the light emission surface 18a of the light guide plate unit 18 The ratio of the peak value of the illuminance of the first portion of the surface 18a can be set large to some extent. However, if this is not the case, the cost can be reduced, but the value of this ratio needs to be set small.

On the other hand, in the light guide plate used in the planar illumination device of the present invention, the peak value of the illuminance of the first portion of the light exit surface 18a of the light guide plate unit 18 is the second portion of the light exit surface 18a of the light guide plate unit 18. The tip shape of the parallel groove 18f of the light guide plate unit 18 is tapered so that the average value of illuminance is 3 times or less, more preferably 2 times or less. Here, the peak value of the illuminance of the first portion of the light exit surface 18a of the light guide plate unit 18 is set to be not more than three times the average value of the illuminance of the second portion of the light exit surface 18a of the light guide plate unit 18. Thus, the illuminance distribution of the illumination light emitted from the light exit surface 18a of the light guide plate unit 18 is made more uniform than before.
As a result, it is not necessary to sufficiently diffuse the illumination light emitted from the light exit surface 18a of the light guide plate unit 18 (mixing or the like).
By using such a light guide plate, the planar illumination device of the present invention can use a low-cost diffusion film 14 having a low diffusion efficiency, can reduce the number of sheets used, and is expensive. The use of the prism sheets 16, 17 and 23 itself can be stopped, or the use of the low-cost prism sheets 16, 17 and 23 which are not so high in diffusion efficiency can be used, or the number of used sheets can be reduced. Thereby, a lighter and cheaper backlight unit can be provided.

  In the light guide plate used in the backlight unit of the present invention, in the cross-sectional shape of the parallel groove 18 f of the light guide plate unit 18, the tip portion for tapering the parallel groove 18 f extends from the center of the rod-shaped light source 12 to the light emitting surface 18 a. It is preferable that the angle with respect to the normal to go is a portion that is within 90 degrees on both sides, more preferably a portion that is within 60 degrees. That is, in the present invention, in order to reduce the peak value of the illuminance of the first portion corresponding to the parallel groove 18f of the light exit surface 18a of the light guide plate unit 18, the portion where the parallel groove 18f is tapered is the parallel groove 18f. However, if the peak value can be reduced, a predetermined tip portion may be used.

Further, as shown in FIG. 19, the light guide plate used in the backlight unit of the present invention has the light guide plate units 94 and 96 so that the light emitting surfaces 94a and 96a of the light guide plate units 94 and 96 all form the same plane. When a large-sized light guide plate is configured by arranging a plurality of light guide plates in parallel, the inclined back surface 94d of one light guide plate unit 94 and the inclined back surface 96d of the other light guide plate unit 96 connected thereto are not crossed, that is, The inclination angles of the inclined back surfaces 94d and 96d of the light guide plate units 94 and 96 can be adjusted so that a smooth flat surface or curved surface is formed at the connecting portion of the inclined back surfaces. In the light guide plate shown in FIG. 19, the surface formed by the inclined back surfaces 94d and 96d of the light guide plate units 94 and 96 is formed in an arch shape. FIG. 19 shows an example in which two light guide plate units are connected to each other, but even when three or more light guide plate units are arranged in parallel, a smooth plane or curved surface is formed at the connecting portion of the inclined back surface. Thus, it is preferable to adjust the inclination angle of the inclined back surface.
By using such a light guide plate having the large light emitting surfaces 94a and 96a, a backlight unit having a large light emitting surface can be obtained, so that a liquid crystal display device having a large display screen can be obtained. In particular, the present invention can be applied to a wall-mounted liquid crystal display device such as a wall-mounted television.

  Further, in order to connect a plurality of light guide plate units to form a large light guide plate, it may be formed by connecting thin portions of separately formed light guide plate units, or from the viewpoint of manufacturing efficiency. A number of light guide plate units necessary to form a light guide plate corresponding to the screen size may be integrally formed.

  Further, in the backlight unit of the present invention, as shown in FIG. 20, the reflection plate 24 may be arranged on the side surface of the light guide plate unit 18 arranged on the outermost side. By disposing such a reflector 24 on the side surface, light leakage from the side surface of the light guide plate unit 18 can be prevented, and the light utilization efficiency can be further enhanced. In addition, the reflecting plate 24 can be formed using the same material as the reflecting sheet or reflector described above.

  Here, the transmittance adjusting body unit of the present invention is not limited to the above shape, and can be used for a backlight unit and a liquid crystal display device using light guide plates of various shapes such as a tandem type and a direct type.

  As mentioned above, although the diffusion film of this invention, the backlight unit provided with the same, and the liquid crystal display device were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it is various improvement. Of course, you may make changes.

It is a schematic structure sectional view at the time of arranging a plurality of light guide plates used in a planar lighting device of the present invention in parallel. (A) And (B) is the schematic perspective view and schematic sectional drawing of a liquid crystal display device which respectively used the backlight unit which has the transmittance | permeability adjustment body unit of this invention. (A) is a schematic sectional drawing which shows a mode that the prism sheet is arrange | positioned between a reflective sheet and the inclination back surface of a light-guide plate, (B) is between a reflection sheet and the inclination back surface of a light-guide plate. It is the schematic plan view and schematic cross section which looked at the arrange | positioned prism sheet from the light-guide plate side. It is a figure which shows an example of the arrangement pattern of the 1st transmittance | permeability adjustment body of a 1st transmittance | permeability adjustment member. (A)-(C) are typical sectional views of the transmittance adjusting body unit in which the first transmittance adjusting body and the second transmittance adjusting body are formed on the same transparent film, respectively. It is typical sectional drawing of the backlight unit in which the 2nd transmittance | permeability adjustment layer comprised from a 2nd transmittance | permeability adjustment body was formed on the light emission surface of a light-guide plate. It is a figure for demonstrating the dimension of the light-guide plate of the planar illuminating device of this embodiment. It is a graph of the relative brightness | luminance of the light radiate | emitted from the light-projection surface of the backlight unit which is not equipped with the transmittance | permeability adjustment body unit. It is the graph which showed the relationship between the relative brightness | luminance calculated in FIG. 8, and pattern density. A calculation for calculating the pattern density distribution of the transmittance adjusting body unit that satisfies the present invention when the maximum density c is set to 0.25, 0.5, 0.75, 1 based on the relative luminance calculated in FIG. It is a graph which shows a result. When the maximum density c calculated in FIG. 10 is 0.25, 0.5, 0.75, 1, the relative luminance of the light emitted from the light emitting surface of the planar illumination device in which the transmittance adjusting unit unit is arranged is shown. It is a graph to show. It is typical sectional drawing of the light-guide plate which made the inclined back surface flat. It is a schematic sectional drawing of the light-guide plate in case the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove is a hyperbola. It is a schematic sectional drawing of a light-guide plate in case the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove is an ellipse. The cross-sectional shape perpendicular to the length direction of the parallel grooves is formed of a part of two circular arc curves that are symmetric with respect to the center line that passes through the center of the parallel grooves and is perpendicular to the light exit surface of the light guide plate. It is a schematic sectional drawing. The portion of the light guide plate in which the cross-sectional shape perpendicular to the length direction of the parallel grooves is formed from a part of two parabolas that pass through the center of the parallel grooves and is symmetric with respect to the center line perpendicular to the light exit surface of the light guide plate It is a schematic sectional drawing. FIG. 5 is a partial schematic cross-sectional view of a light guide plate in which a cross-sectional shape perpendicular to the length direction of parallel grooves is formed from two curves protruding toward the center of the parallel grooves. It is a partial schematic sectional drawing of the light-guide plate in which the cross-sectional shape perpendicular | vertical to the length direction of a parallel groove is formed from the curve which combined the convex curve and the concave curve toward the center of a parallel groove. It is a schematic diagram which shows another example of the shape of a light-guide plate. It is the structural example which has arrange | positioned the reflecting plate in the side surface of the light guide plate, when the light guide plate of this invention is arrange | positioned in parallel. It is a disassembled perspective view of the surface light source device which has the conventional light-guide plate.

Explanation of symbols

2 Backlight unit 4 Liquid crystal display panel 6 Drive unit 10 Liquid crystal display device 12 Light source (linear light source)
DESCRIPTION OF SYMBOLS 14 Diffusion films 16, 17 Prism sheet 18 Light guide plate unit 18a Light emission surface 18b Thick part 18c Thin end part 18d Inclined back surface 18f Parallel groove 18g Protrusion part 19 Light guide plate 22 Reflective sheet 23 Prism sheet 23a Prism 24 Reflector 26 First Transmittance adjuster (transmittance adjuster)
28 First transmittance adjusting member 29, 34 Transparent film 30 Second transmittance adjusting member 32 Second transmittance adjusting body (transmittance adjusting body)
41, 42, 43 Transmittance adjuster unit 48 Light guide plate 48a Rectangular light exit surface 48b Thick portion 48c Thin end portion 48d Inclined back surface 48f Parallel grooves 50, 60, 80, 100 Light guide plate 52 Light exit surface 54a, 54b, 64a, 64b, 72a, 72b, 82a, 82b Curve 64 Intersection 94, 96 Light guide plate unit 94d, 96d Inclined back surface 100b Light quantity correction surface

Claims (15)

A transmittance adjuster unit for diffusing and emitting incident light,
A sheet-like optical member having optical transparency;
A large number of first transmittance adjusters arranged in a predetermined density distribution on at least one surface of the optical member;
The first transmittance adjusting body is formed of a material having a substantially different color, and is disposed at a position closer to the light incident side than the first transmittance adjusting body with a density distribution different from the predetermined density distribution or at a constant density. And a plurality of second transmittance adjusting bodies.   The optical member is composed of a flat first transparent film having light transmittance, and a second transparent film located on the light incident side of the first transparent film, and the first transmittance adjuster is The transmittance adjusting body unit according to claim 1, wherein the transmittance adjusting body unit is formed on the first transparent film, and the second transmittance adjusting body is formed on the second transparent film.   The said 1st transmittance | permeability adjustment body is arrange | positioned on the surface by the side of the light emission of the said optical member, The said 2nd transmittance | permeability adjustment body is arrange | positioned on the surface by the side of the light incidence of the said optical member. Transmittance adjuster unit.   2. The transmittance adjuster unit according to claim 1, wherein the second transmittance adjuster and the first transmittance adjuster are arranged in this order on a light emitting side surface of the optical member.   The transmittance adjusting body unit according to claim 1, wherein the first transmittance adjusting body and the second transmittance adjusting body are arranged in this order on a light incident side surface of the optical member.   The transmittance adjusting body unit according to any one of claims 1 to 5, wherein the plurality of second transmittance adjusting bodies are arranged in close contact with each other without a gap to form a layer having a certain thickness.   The transmittance adjustment body unit according to any one of claims 1 to 6, wherein a color difference between the first transmittance adjustment body and the second transmittance adjustment body is 0.2 or more and less than 3.0. The pattern density at a predetermined position (x, y) of the first transmittance adjuster is ρ (x, y), and the light of the transmittance adjuster unit when the first and second transmittance adjusters are not provided. The maximum luminance F _{max of} light emitted from the emission surface is 1, and the relative luminance of the light emitted from the predetermined position (x, y) on the emission surface with respect to the maximum luminance F _max is F (x, y). sometimes,
The relationship between the relative luminance F (x, y) and the pattern density ρ (x, y) is expressed by the following equation:
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min )
(Where c is 0.5 ≦ c ≦ 1 and F _min is the minimum luminance of relative luminance F (x, y))
The transmittance adjuster unit according to any one of claims 1 to 7, which satisfies the following conditions. A light source;
A flat light guide plate that emits light incident from the light source from a light exit surface;
A sheet-like optical member having optical transparency, a large number of first transmittance adjusting bodies arranged in a predetermined density distribution on at least one surface of the optical member, and substantially the same as the first transmittance adjusting body A plurality of second transmittance adjusting bodies which are formed of a material having a different color and are arranged at a position closer to the light incident side than the first transmittance adjusting body at a density distribution different from the predetermined density distribution or at a constant density. And a transmittance adjusting body unit disposed on the light exit surface side of the light guide plate.   The optical member is composed of a flat first transparent film having light transmittance, and a second transparent film located on the light incident side of the first transparent film, and the first transmittance adjuster is The planar illumination device according to claim 9, wherein the planar illumination device is formed on the first transparent film, and the second transmittance adjusting body is formed on the second transparent film.   The first transmittance adjusting body is disposed on a light emitting side surface of the optical member, and the second transmittance adjusting body is disposed on a light incident side surface of the optical member. Planar lighting device.   The planar illumination device according to claim 9, wherein the second transmittance adjusting body and the first transmittance adjusting body are arranged in this order on a light emitting side surface of the optical member.   The planar illumination device according to claim 9, wherein the first transmittance adjusting body and the second transmittance adjusting body are arranged in this order on a light incident side surface of the optical member. A light source;
A flat light guide plate that emits light incident from the light source from a light exit surface;
A sheet-shaped optical member having light transmittance, and a plurality of first transmittance adjusting bodies disposed on at least one surface of the optical member, and transmitting light for diffusing incident light to be emitted. A rate adjusting unit,
A surface on which a second transmittance adjusting body formed of a material having a color substantially different from that of the first transmittance adjusting body is arranged with a predetermined density distribution or a constant density on the light emitting surface of the light guide plate Illuminator. The surface illumination device according to any one of claims 9 to 14,
A liquid crystal display panel disposed on the light exit surface side of the planar illumination device;
A liquid crystal display device comprising: a drive unit that drives the liquid crystal display panel.

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