JP4750679B2 - Surface illumination device and liquid crystal display device - Google Patents

Description

  The present invention relates to a planar illumination device for emitting uniform planar light from a light emitting 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. 20 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, when manufacturing a large planar illumination device used for a large-screen liquid crystal television or a liquid crystal monitor, it is necessary to manufacture a large-sized light guide plate. However, the size of the light guide plate that can be produced is limited due to the limitation of the size of the mold for producing the light guide plate. Therefore, a method is adopted in which a plurality of light guide plate blocks manufactured from one mold are connected to produce a large light guide plate, and a planar illumination device is configured using the large light guide plate. . However, when a planar illumination device is configured using a light guide plate in which a plurality of light guide plate blocks are connected, the luminance of the connection portion of the light guide plate block is different from other portions, and the connection portion is visually recognized as a bright line or a dark line. There was a thing.

  In the Japanese Patent Application No. 2004-258340, the present inventor has a transmittance adjusting body configured by arranging a transmittance adjusting body at a predetermined pattern density on a transparent film in order to suppress generation of bright lines of a linear light source. Disclosed unit. 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.

The present invention has been made in view of such circumstances, and a first object of the present invention is to provide bright lines or dark lines in a region corresponding to a connection portion of adjacent light guide plate units when a plurality of light guide plate units are connected. Is to provide a planar illumination device capable of illuminating a wide range with illumination light having no luminance unevenness.
A second object of the present invention is to provide a liquid crystal display device that can display an image with good image quality evenly even with a large size with little uneven brightness.

  In order to solve the first problem, a first aspect of the present invention is a light source of a rod-shaped light source, a back surface in which a groove for accommodating the rod-shaped light source is formed, and a surface opposite to the back surface. A light guide plate formed by arranging a plurality of light guide plate blocks formed integrally with at least two flat light guide plate units each having a light output surface for emitting light; and A light-emitting surface of the light guide plate, comprising: a sheet-like optical member that is disposed on the light-emitting surface side and has light transmittance; and a large number of transmittance adjusting bodies that are disposed on at least one surface of the optical member. A transmittance adjusting body unit that diffuses and emits light emitted from the light guide plate block, a density distribution of the transmittance adjusting body of the transmittance adjusting body unit at a position corresponding to a joint portion of the light guide plate block, and Paired with the connection part of the light guide plate unit And density distribution of the transmittance adjusters of the transmittance adjusting member unit in the position is to provide a planar lighting device that different from each other.

In the planar lighting device according to the first aspect of the present invention, the density of the transmittance adjusting body of the transmittance adjusting body unit at a position corresponding to the joint portion of the light guide plate block is integrated between the light guide plate units. It is preferable that the density of the transmittance adjusting body of the transmittance adjusting body unit at the corresponding position is higher than the density.
In the planar illumination device according to the first aspect of the present invention, the pattern density of the transmittance adjusting body of the transmittance adjusting body unit at a predetermined position (x, y) in the region corresponding to the light guide plate block is ρ. (X, y), the maximum luminance F _max of illumination light obtained when the transmittance adjusting unit unit is not provided, and the maximum luminance F of illumination light emitted from the predetermined position (x, y). _When the relative luminance with respect to _max is F (x, y),
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))
Or
ρ (x, y) = c {F (x, y) −F _min } / (F _max −F _min ) + ρ _b
(Where c is 0.5 ≦ c ≦ 1, ρ _b satisfies 0 <ρ _b ≦ 1.5, and F _min is the minimum luminance of the relative luminance F (x, y))
Is preferably satisfied.

  In order to solve the first problem, the second aspect of the present invention is a light source of a rod-shaped light source, a rear surface on which a groove for accommodating the rod-shaped light source is formed, and a surface opposite to the rear surface. A light guide plate formed by arranging a plurality of light guide plate blocks formed integrally with at least two flat light guide plate units each having a light output surface for emitting light; and A first transmission member that is disposed on the light exit surface side and has a light-transmitting sheet-like first optical member, and a plurality of first transmittance adjusting bodies disposed on at least one surface of the first optical member. A number of second adjustment members disposed at positions corresponding to joint portions of the light guide plate block on at least one surface of the first optical member and a sheet-shaped second optical member having light transmittance; Second transmittance having two transmittance adjusters A transmittance adjusting body unit including a regulating member, and a density distribution of the second transmittance adjusting body and a density distribution of the first transmittance adjusting body at a position corresponding to a connection portion of the light guide plate unit. The planar illumination device is characterized by being different from each other.

In the planar illumination device according to the second aspect of the present invention, the pattern density at a predetermined position (x1, y1) of the first transmittance adjusting body is ρ1 (x1, y1), and the transmittance adjusting body unit is not provided. In this case, when the maximum luminance F1 _max of the illumination light is 1, and the relative luminance with respect to the maximum luminance F1 _max of the illumination light emitted from the predetermined position (x1, y1) is F1 (x1, y1), the relative The relationship between the brightness F1 (x1, y1) and the pattern density ρ1 (x1, y1) is the following formula:
ρ1 (x1, y1) = c ₁ {F1 (x1, y1) −F1 _min } / (F1 _max −F1 _min )
(Wherein, _{c 1} satisfies _{0.5 ≦ c 1 ≦ 1, F1} min is the minimum luminance of the relative brightness F1 (x1, y1))
Or
ρ1 (x1, y1) = c ₁ {F1 (x1, y1) −F1 _min } / (F1 _max −F1 _min ) + ρ _b
(Wherein, _{c 1 is, 0.5 ≦ c 1 ≦ 1,} ρ b satisfies _{0 <ρ b ≦ 1.5, F1} min is the minimum luminance of the relative brightness F1 (x1, y1))
Is preferably satisfied.

Further, when the pattern density at a predetermined position (x2, y2) of the second transmittance adjusting body is ρ2 (x2, y2), and the second transmittance adjusting member is not provided, the light emission of the transmittance adjusting body unit. When the maximum luminance F2 _max of the illumination light emitted from the surface is 1, and the relative luminance with respect to the maximum luminance F2 _max of the illumination light emitted from the predetermined position (x2, y2) is F2 (x2, y2) , The relationship between the relative luminance F2 (x2, y2) and the pattern density ρ2 (x2, y2) is
ρ2 (x2, y2) = c ₂ {F2 (x2, y2) −F2 _min } / (F2 _max −F2 _min )
(Wherein, _{c 2} satisfies _{0.5 ≦ c 2 ≦ 1, F2} min is the minimum luminance of the relative brightness F2 (x2, y2))
Is preferably satisfied.

  In order to solve the second problem, a third aspect of the present invention is a planar illumination device according to the first or second 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.

In the planar illumination devices according to the first and second aspects of the present invention, even if the emission area of illumination light is increased by using a light guide plate in which a plurality of light guide plate blocks are connected, the connection portion between adjacent light guide plate blocks is used. Since the generated bright line or dark line is not visually recognized, it is possible to illuminate a wide area with the planar illumination light having no luminance unevenness.
Further, since the liquid crystal display device of the third aspect of the present invention uses the planar illumination device of the first or second aspect, even if the display area is made larger than the conventional one, the luminance unevenness is small and good. An image can be displayed with high image quality.

Hereinafter, a planar illumination device of the present invention and a liquid crystal display device using the same will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 10 according to a second aspect of the present invention using the planar illumination device 2 (hereinafter also referred to as a backlight unit) according to the first aspect of the present invention. 2A shows a schematic cross-sectional view of one light guide plate block 17 of the backlight unit 2 shown in FIG. 1, and FIG. 2B shows one of the backlight units 2 shown in FIG. The schematic sectional drawing of the light-guide plate unit 18 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, a prism sheet 16, a light guide plate 19, a reflector 20, a reflection sheet 22, and a transmittance adjusting body. And a unit 24. As shown in FIG. 1, the light guide plate 19 used in the backlight unit 2 of the present embodiment is composed of a plurality of light guide plate blocks 17 formed by integrating three light guide plate units. In the present invention, a light guide member having a flat rectangular light emission surface for emitting light and a back surface on which one groove for accommodating a linear light source is formed on the opposite surface of the light emission surface Is referred to as a light guide plate unit, and at least two light guide plate units integrally molded are referred to as a light guide plate block. A large-sized light guide member configured by connecting a plurality of light guide plate blocks is referred to as a light guide plate. Hereinafter, each component of the backlight unit 2 will be described.

(light source)
The light source (rod-shaped 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, an external electrode tube, a normal fluorescent tube, an LED (light emitting diode), or the like can also be used.
For example, an LED light source in which a columnar or prismatic transparent light guide having a length equivalent to a parallel groove 18f of a light guide plate unit 18 described later is used and LEDs are arranged on the top and bottom surfaces of the light guide is used as a light source. It may be used instead of 12. 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)
As described above, the light guide plate 19 constituting the backlight unit is configured by connecting a plurality of light guide plate blocks 17 formed by integrating three light guide plate units 18 in parallel. FIG. 2A shows a schematic sectional view of a light guide plate block (triple type light guide plate unit) 17 formed by integrating three light guide plate units 18A, 18B and 18C. ) Shows a schematic sectional view of the light guide plate unit 18. As shown in FIGS. 2A and 2B, the light guide plate unit 18 includes a rectangular light emitting surface 18a, a thick portion 18b parallel to one side thereof, and both sides of the thick portion 18b. A thin end portion 18c formed parallel to the one side, and an inclined back surface that forms an inclined back surface 18d, with the thickness decreasing toward the thin end portions 18c on both sides in a direction perpendicular to the one side from the thick portion 18b. A portion 18e and a parallel groove 18f for accommodating the light source 12 are formed in the thick portion 18b in parallel with the one side. 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.
As shown in FIG. 2B, the inclined back surface 18 d is partially formed with a curved surface, and is smoothly connected to the inclined back 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 entire inclined back surface 18d with a curved surface.

Further, as shown in FIG. 2B, the light guide plate unit 18 has a symmetrical shape with respect to a center line M passing through the center of the parallel groove 18f and perpendicular to the light exit surface 18a of the light guide plate unit 18. ing. 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.
As shown in FIG. 2 (A), the light guide plate block 17 is configured by integrally connecting light guide plate units having the structure shown in FIG. 2 (B). In other words, as shown in FIG. 2 (A), the light guide plate block 17 has a flat rectangular light exit surface 17a and three linear parallel lights for accommodating a rod-shaped light source on the opposite side. A plate-like transparent member having a back surface on which grooves are formed. The back parallel grooves 18f are formed on the back surface at equal intervals in parallel to each other. The back surface sandwiched between the parallel grooves 18f is inclined with respect to the light exit surface so that the thickness gradually decreases as the distance from the parallel grooves 18f increases. In addition, the rear surface of the part from the parallel grooves 18f located on both outer sides toward the end surface of the light guide plate block 17 is also inclined with respect to the light exit surface so that the plate thickness gradually decreases in the same manner. The light guide plate block 17 having such a structure is individually manufactured.
In the illustrated example, three parallel grooves are formed on the back surface of the light guide plate block 17. However, the present invention is not limited to this, and at least the parallel grooves for accommodating the light source 12 on the back surface of the light guide plate block 17 are provided. Two may be formed.

  In the light guide plate block 17 having the structure shown in FIG. 2A, of the light radiated from the light source 12 arranged in the parallel groove 18f of each light guide plate unit 18, the side wall (incoming light) forming the parallel groove 18f is formed. Light incident on the inside of the light guide plate unit 18 from the light surface is reflected by the inclined back surface 18d of each 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 each light guide plate unit 18, but the leaked light is formed on the inclined back surface 18 d side of the light guide plate unit 18 to be described later (see FIG. 1). And is again incident on the inside of the light guide plate 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 block 17 composed of the three light guide plate units 18 is, for example, a method of molding a heated raw material resin by extrusion molding or injection molding, or a casting polymerization method of molding by polymerizing monomers, oligomers, etc. in a mold. Etc. can be manufactured integrally. As a material of the light guide plate block 17, 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 can be used. The transparent resin may be mixed with fine particles for scattering light, whereby the light emission efficiency from the light emission surface can be further increased.

In the present embodiment, the parallel groove 18f of each light guide plate unit 18 of the light guide plate block 17 has a triangular cross-sectional shape perpendicular to the length direction of the parallel groove 18f (hereinafter simply referred to as the cross-sectional shape of the parallel groove). It is formed as follows. The shape of the parallel groove 18f will be described later.
In the example of FIG. 2A, the light guide plate block 17 is configured by integrally molding the three light guide plate units 18, but the light guide plate block is configured by integrally molding the two light guide plate units. Alternatively, the light guide plate block may be configured by integrally forming four or more light guide plate units.

(Prism sheet)
The prism sheet 16 is a transparent sheet formed by arranging a plurality of prisms in parallel. The prism sheet 16 increases the light collecting property of the light emitted from the light emitting surface 18a of the light guide plate unit 18 of the light guide plate 19 to increase the luminance. Can be improved. The prism sheet 16 is arranged so that the extending direction of the prism row is parallel to the parallel groove 18 f of the light guide plate unit 18 of the light guide plate 19. 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.
Although one prism sheet is used here, a prism sheet can be further added. In the case of using a plurality of prism sheets, the arrangement order thereof is not particularly limited. For example, in FIG. 1, a first prism sheet having a prism extending in a direction parallel to the parallel groove of each light guide plate unit 18 constituting the light guide plate 19 is disposed immediately above the light guide plate 19. A second prism sheet having a prism extending in a direction perpendicular to the parallel groove 18f of each light guide plate unit 18 constituting the light guide plate 19 may be disposed on the prism sheet, or vice versa. good.

  In the example shown in FIG. 1, 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, the 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. Is preferably provided. 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.

3A and 3B, the prism sheet 23 is disposed between the reflection sheet 22 and the inclined back surface 18d of the light guide plate unit 18, but an optical element having the same effect as the prism sheet may be disposed. In addition, a sheet in which optical elements having a lens effect, for example, optical elements such as a lenticular lens, a concave lens, a convex lens, and a pyramid type are regularly arranged may be provided.
3A and 3B, as a preferred embodiment, the backlight unit is configured using the prism sheet 23, but the luminance on the light exit surface 18a by the parallel grooves 18f of the light guide plate unit 18 is made more uniform. In such a case, such a prism sheet 23 is of course unnecessary and the prism sheet 16 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 reflects light leaking from the back surface (lower surface in the drawing) of each light guide plate block 17 of the light guide plate 19 and makes it incident on each light guide plate block 17 again. Can be improved. The reflection sheet 22 is formed so as to cover the lower surface (inclined back surface) of each light guide plate block 17, that is, the inclined back surface 18 d 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 respective light guide plate units 18 of the respective light guide plate blocks 17. The reflector 20 can reflect light from the lower surface of the light source 12 and allow light to enter from the side wall surface of the parallel groove 18 f of each light guide plate unit 18. In the present embodiment, the reflective film 22 and the reflector 20 are provided separately, but the reflective film 22 and the reflector 20 may be integrated into a single plate-like member.

  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 figure) of each light guide plate block 17, for example, PET or PP (polypropylene). ), Etc., a resin sheet in which a void is formed by stretching after being kneaded and stretched, a sheet having a mirror surface formed by aluminum deposition or the like on the surface of a transparent or white resin sheet as described above, or a metal such as aluminum It can be formed of a foil or a resin sheet carrying a metal foil, or a thin metal plate having sufficient reflectivity on the surface.

(Diffusion film)
The diffusion film 14 is a single film for diffusing and uniformizing the light emitted from the light exit surface of the light guide plate 19, such as 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 shaped 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.

(Transmittance adjustment unit)
Next, the transmittance adjusting unit 24 will be described. The transmittance adjusting body unit 24 includes a first transmittance adjusting member 28 and a second transmittance adjusting member 30. In the illustrated example, the first transmittance adjusting member 28 is disposed closer to the light incident side than the second transmittance adjusting member 30. However, in the present invention, there is no limitation in the arrangement order of the first transmittance adjusting member 28 and the second transmittance adjusting member 30. Moreover, the 1st transmittance | permeability adjustment member 28 and the 2nd transmittance | permeability adjustment member 30 may be arrange | positioned closely mutually, and may be arrange | positioned at predetermined intervals.

The first transmittance adjusting member 28 mainly has a function of reducing luminance unevenness of planar illumination light emitted from the light emitting surface of the light guide plate block 17. The second transmittance adjusting member 30 has a function of preventing or reducing the generation of bright lines or dark lines at the boundary portions of the light guide plate blocks 17 adjacent to each other when a large light guide plate 19 is configured by combining a plurality of light guide plate blocks 17. have. Thus, by using the transmittance adjusting body unit 24 configured by combining the first transmittance adjusting member 28 and the second transmittance adjusting member 30, planar illumination light from the light exit surface of the light guide plate block. Brightness unevenness and brightness unevenness at the boundary between adjacent light guide plate blocks can be reduced at the same time, and uniform illumination light with reduced brightness unevenness can be obtained from the light guide plate 19.
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) can be made of the same material.

Hereinafter, the first transmittance adjusting member 28 and the second transmittance adjusting member 30 will be described in detail.
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 uneven brightness of the light emitted from the light exit surface 17a of the light guide plate block 17, and includes the transparent film 29 and the transparent film. 29 and a large number of first transmittance adjusting bodies 26 arranged on the surface.
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. 4A is an arrangement pattern of the first transmittance adjusting body 26 formed on the transparent film 29, and is arranged in a region corresponding to the light exit surface of one light guide plate block 17. FIG. FIG. 4B is a schematic diagram showing an example of an arrangement pattern of the first transmittance adjusting body 26, and FIG. 4B shows a single light guide plate unit 18 of the arrangement pattern of the first transmittance adjusting body 26 in FIG. It is an expansion schematic diagram which expands and shows the corresponding part. 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 M.
The arrangement pattern of the first transmittance adjusting body 26 of the first transmittance adjusting member 28 is not provided with the first transmittance adjusting member 28 and the backlight unit 17 using the light guide plate block 17 as will be described in detail later. Is designed based on the luminance distribution of the illumination light. Accordingly, when a large light guide plate is configured by combining a plurality of light guide plate blocks 17 and a backlight unit is configured using the large light guide plate, the first transmittance adjustment shown in FIG. The arrangement pattern of the bodies 26 is repeatedly formed so as to correspond to the respective light guide plate blocks, whereby one first transmittance adjusting member is produced.

Here, an example of the design method of the arrangement pattern of the first transmittance adjusting body 26 of the first transmittance adjusting member 28 will be described. First, the pattern density at an arbitrary position (x1, y1) of the first transmittance adjusting member 28 is set to ρ1 (x1, y1). When the backlight unit is configured using the light guide plate block 17 without including the first transmittance adjusting member 28, any light emitting surface (surface on the liquid crystal display panel 4 side) of the backlight unit 2 is arbitrary. The relative luminance of the light emitted from the position (x1, y1) is F1 (x1, y1). At this time, the pattern density ρ1 (x1) so that the relationship between the pattern density ρ1 (x1, y1) of the first transmittance adjusting member 28 and the relative luminance F1 (x1, y1) satisfies the following formula 1 or formula 2. , Y1) is designed.
ρ1 (x1, y1) = c ₁ {F1 (x1, y1) −F _min } / (F _max −F _min ) Equation 1
Or
ρ1 (x1, y1) = c ₁ {F1 (x1, y1) −F _min } / (F _max −F _min ) + ρ _b Equation 2
In Formula 1 and Formula 2, 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 Minimum brightness. The relative luminance F1 (x1, y1) uses the maximum luminance F _max as a reference point (F _max = 1).
In Formula 1 and Formula 2, c ₁ is the maximum density, and it is preferable to satisfy 0.5 ≦ c ₁ ≦ 1.
Here, the pattern density ρ1 (x1, y1) is an occupation rate per unit area (1 mm ² ) of the transmittance adjusting body 26 existing at an arbitrary position (x1, y1), and ρ1 (x1, y1) When = 1, the transmittance adjusting body 26 is disposed on the entire surface within the unit area, and when ρ1 (x1, y1) = 0, it is not disposed at all within the unit area.
Moreover, when the density design of the arrangement of the transmittance adjusting bodies is performed according to the above formula 1, luminance unevenness may be visually recognized depending on the angle observed from other than the front direction. In order to improve this, it is preferable to further add a “uniform density distribution (bias density ρb)” to the calculated density distribution, as shown in Equation 2 above. Thereby, luminance unevenness can be reduced and the angle dependency of the luminance unevenness can be eliminated or reduced.
Here, the bias density ρ _b is preferably 0 to 1.50 (0 to 150%), that is, 0 <ρ _b ≦ 1.5, and 0.01 ≦ ρ _b ≦ 1.5. More preferred. In addition, when the arrangement density exceeds 1 (100%), the transmittance adjusting body is arranged twice. That is, the transmittance adjusting body having the arrangement density of (ρ _b −1) is arranged on the entire surface of the transmittance adjusting body. Here, the transmittance adjusting body has a uniform thickness, and the thickness of the transmittance adjusting body is doubled in the portion where the transmittance adjusting body is arranged in a double layer.

By arranging the first transmittance adjusting body 26 of the first transmittance adjusting body member 28 so as to satisfy the pattern density ρ1 (x1, y1) of the above formula 1, it corresponds to the light guide plate block 17 of the backlight unit 2. It is possible to suppress a decrease in average luminance of the illumination light emitted from the light emitting surface of the region and reduce luminance unevenness. In this way, by using the first transmittance adjusting member 28 to reduce the luminance unevenness in the region corresponding to the light guide plate block, 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 ₁ is preferably 0.5 ≦ c ₁ ≦ 1. Maximum density c ₁ a by 0.5 or more, it is possible to suppress the reduction of the average luminance can be emitted uniform light with high luminance.
The first transmittance adjusting body 26 preferably has a pattern density ρ1 (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 26 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.
In addition, as in the present embodiment, when a backlight unit is configured using a linear light source and a plurality of uniaxially extending light guide plate units, the shape of the first transmittance adjusting body is changed to that of the linear light source. It is good also as an elongate strip shape parallel to an axis | shaft.

Next, the second transmittance adjusting member 30 will be described.
As shown in FIG. 1, the second transmittance adjusting member 30 is disposed on the light emission side of the first transmittance adjusting member 28. The second transmittance adjusting member 30 disposed on the light emitting side of the first transmittance adjusting member 28 is for preventing generation of bright lines or dark lines in a region corresponding to the joint portion of the adjacent light guide plate blocks 17. Is provided. The second transmittance adjusting member 30 is configured by forming a second transmittance adjusting body 32 in a predetermined pattern on a transparent film 34, and the second transmittance adjusting body 32 is a first transmittance adjusting body. 26 is made of the same material. 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 body 32 is arranged with a predetermined density distribution on the transparent film 34 in a region corresponding to the joint portion of the adjacent light guide plate blocks 17.

  As described above, the arrangement pattern of the first transmittance adjusting member 28 is a luminance distribution of illumination light when the backlight unit is configured using one light guide plate block without including the first transmittance adjusting member 28. Designed based on. Therefore, as shown in FIG. 1, a plurality of light guide plate blocks 17 are connected to form a large light guide plate 19, and one first transmittance adjusting member is provided on the light exit surface side of the large light guide plate 19. When the backlight unit is configured by arranging 28, when the luminance distribution of the illumination light of the backlight unit is observed, the bright line in the region corresponding to the joint portion (connection portion) of each light guide plate block 17 Or dark lines may occur. Therefore, in the backlight unit of the present embodiment, the second transmittance adjusting member 30 is provided to correct the luminance unevenness at the joint portion of each light guide plate block 17. The arrangement pattern of the second transmittance adjusting body 28 of the second transmittance adjusting member 30 is such that the first transmittance adjusting member is arranged on the light exit surface side of a large light guide plate configured by combining a plurality of light guide plate blocks. When the backlight unit is configured, the backlight unit is designed based on the luminance distribution of illumination light from the joint portion of the light guide plate blocks of the backlight unit. As a method for designing the arrangement pattern of the second transmittance adjusting body based on such luminance distribution, the same method as the method for designing the arrangement pattern of the first transmittance adjusting body 28 described above can be used. This will be specifically described below.

First, the pattern density at an arbitrary position (x2, y2) of the second transmittance adjusting member is set to ρ2 (x1, y1). And, when the backlight unit is configured using the light guide plate 19 including the plurality of light guide plate blocks 17 without including the second transmittance adjustment member 30, the first transmittance adjustment member 28 is provided. The relative luminance of light emitted from an arbitrary position (x2, y2) on the light emission surface (surface on the liquid crystal display panel 4 side) of the backlight unit is defined as F2 (x2, y2). At this time, the pattern density ρ2 (x2, y2) is set so that the relationship between the pattern density ρ2 (x2, y2) of the second transmittance adjusting body 32 and the relative luminance F2 (x2, y2) satisfies the following formula 2. Is designed.
ρ2 (x2, y2) = c ₂ {F2 (x2, y2) −F2 _min } / (F2 _max −F2 _min ) Equation 3
In Formula 3, F2 _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 second transmittance adjusting member 30 is not provided, and F2 _min is the minimum luminance. is there. In the relative luminance F2 (x2, y2), the maximum luminance F2 _max is set as a reference point (F2 _max = 1).
In Equation 3, _{c 2} is the maximum density, preferably in the 0.5 ≦ _{c 2} ≦ 1.
Here, the pattern density ρ2 (x2, y2) is an occupation rate per unit area (1 mm ² ) of the transmittance adjusting body 26 existing at an arbitrary position (x2, y2), and ρ2 (x2, y2) When = 1, the second transmittance adjusting body 32 is arranged on the entire surface within the unit area, and when ρ2 (x2, y2) = 0, it is not arranged at all within the unit area.

  Here, the transmittance adjuster unit 24 is configured by using the two transmittance adjusting members of the first transmittance adjusting member 28 and the second transmittance adjusting member 30. However, only one transmittance adjusting member is used for the transmittance. The adjusting body unit 24 can also be configured. Thereby, the number of parts can be reduced and the cost can be reduced. Further, in this case, in one sheet of the first transmittance adjusting member that covers the entire light emission side surface of the light guide plate 19, the light guide plate unit is located at a position corresponding to a portion that is physically connected integrally. The density distribution of the first transmittance adjusting body to be arranged is the density of the first transmittance adjusting body arranged at a position corresponding to a portion (joint portion) where the light guide plate blocks are physically connected to each other. What is necessary is just to design so that it may differ from distribution. Further, when the transmittance adjusting body unit is configured with only one transmittance adjusting member in this way, for example, when the joint portion of the light guide plate block becomes a bright line, the region corresponding to the joint portion The density of the transmittance adjusting body disposed on the light guide plate unit may be increased more than the density of the transmittance adjusting body disposed in a region corresponding to a portion where the light guide plate units are integrally connected. In addition, when the region corresponding to the joint portion of the light guide plate block is a dark line, the density of the transmittance adjusting body disposed in the region corresponding to the joint portion is physically integrated with the light guide plate unit. Thus, the density may be lower than the density of the transmittance adjusting body disposed in the region corresponding to the connected portion. As described above, the density distribution of the transmittance adjusting body in the region corresponding to the joint portion of the light guide plate block is transmitted to the region corresponding to the portion where the light guide plate unit is physically integrated and connected. By making it different from the rate adjuster, it is possible to prevent or suppress luminance unevenness that occurs in a region corresponding to a joint portion of a plurality of light guide plate blocks. As a result, illumination light having a large area that is uniform and has no uneven brightness can be obtained.

In the present invention, the second transmittance adjusting body 32 may be formed on at least one surface of the diffusion film 14 shown in FIG. 1, and the first transmittance adjusting body 26 may be formed on the prism sheet 16. In this case, the second transmittance adjusting member is configured by the diffusion film 14 and the second transmittance adjusting body 32 formed on the surface thereof, and the first transmittance adjusting formed on the surface of the prism sheet 16. The body 26 constitutes the first transmittance adjusting member.
In FIG. 1, the second transmittance adjusting body may be formed on the light exit surface of the light guide plate 19, and the first transmittance adjusting body may be disposed on the surface on which the second transmittance adjusting body is formed. it can. 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. When the first transmittance adjusting member is disposed on the light exit surface side of the light guide plate 19, it is necessary to align the light guide plate 19 and the first transmittance adjusting member 28 during manufacturing. By forming the second transmittance adjusting body on the emission surface and further disposing 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. The process can be simplified.
Although the first transmittance adjusting body and the second transmittance adjusting body can be directly arranged on the light guide plate, an effect such as misalignment prevention can be obtained, but the first transmittance adjusting body 26 is used as the light guide plate 19. When forming directly on the light emission surface, it is preferable to arrange the second transmittance adjusting body 32 on the transparent film 30 or on the prism sheet. By forming the second transmittance adjusting body 32 on the sheet-like member, it is possible to more suitably suppress the luminance unevenness generated at the connection portion of the light guide plate block.

  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 16. May be.

Further, in the present embodiment, as shown in FIG. 1, the transmittance adjuster unit 24, the diffusion film 14, and the prism sheet 16 are laminated in this order on the emission surface side of the light guide plate 19. There is no particular limitation on the arrangement order of the respective members on the surface side. For example, the transmittance adjuster unit, the prism sheet, and the diffusion film may be laminated in this order on the emission surface side of the light guide plate 19.
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.

Here, when the first transmittance adjusting body 26 is disposed on the light exit surface of the light guide plate 19, that is, on the light exit surface of the light guide plate block 17, the maximum density c _{1 is set} to 0 < It is also preferable that c ₁ ≦ 0.3 and the bias density ρ _b be 0.5 ≦ ρ _b .

  By arranging the first transmittance adjusting body 26 directly on the light emitting surface of the light guide plate 19, for example, when the planar illumination device is arranged so that the light emitting surface is parallel to the vertical direction, the light emitting surface is changed. Even when arranged vertically downward, it is possible to prevent a positional shift between the light exit surface and the arrangement pattern of the transmittance adjusting body.

Further, the maximum density c ₁ of the first transmittance adjusting body 26 of the first transmittance adjusting member 28 is 0 <c ₁ ≦ 0.3, and the bias density ρ _b is 0.5 ≦ ρ _b . By arranging so as to satisfy the pattern density ρ (x, y), even when the first transmittance adjusting body 28 is arranged directly on the light emitting surface, the light emitted from the light emitting surface of the planar illumination device 10. It is possible to suppress a decrease in average luminance and to reduce luminance unevenness.

In the above equation 2, the [rho _b is 0.5 or more, the entire surface of the light exit plane of the light guide plate 19 by disposing the first transmittance adjusters 26 above a certain density, the first transmittance adjusters 26 It is possible to prevent the occurrence of non-uniformity of angle depending on the pattern density.
Here, the angle-dependent unevenness is observed when the luminance distribution changes depending on the angle at which the light exit surface is observed, for example, when viewed from a direction perpendicular to the light exit surface and when viewed from a direction inclined by 45 °. Depending on the angle, this means uneven brightness.
That is, by the [rho _b 0.5 or more, it is possible to prevent the brightness distribution of the light emitted from the light exit surface of the light guide plate (luminance unevenness), varies depending on the viewing angle the light exit surface of the light guide plate .
Further, by determining the pattern density according to the relative luminance F1 (x1, y1) using the above equation 2, it is possible to reduce luminance unevenness while maintaining high luminance.
In addition, by setting the range of c to 0.3 or less, even when the first transmittance adjusting body is directly disposed on the light exit surface, the luminance unevenness can be suitably reduced.

As described above, the maximum density c ₁ of the first transmittance adjusting body 26 of the first transmittance adjusting member 28 is 0 <c ₁ ≦ 0.3, and the bias density ρb is 0.5 ≦ ρ _b . By arranging so as to satisfy the pattern density ρ1 (x1, y1), luminance unevenness can be reduced both in a direction perpendicular to the light emission surface and in an oblique direction, and high-luminance light can be emitted.

  In this way, if the luminance unevenness is reduced by using the first transmittance adjusting member 28, it is not necessary to sufficiently diffuse the light by the diffusion film 14, so that the diffusion film 14 can be made thinner. . Further, the use of the prism sheet can be stopped, or the number of prism sheets used can be reduced, and a lighter and cheaper backlight unit can be provided.

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 screening method can be used. Of these, it is preferable to use the FM screening method. 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 30 can also be arranged using various methods such as the FM screening method and the AM screening 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.
Moreover, when printing the 1st transmittance | permeability adjuster and the 2nd transmittance | permeability adjuster on the surface of a transparent film, alignment marks are other than the area | region where these 1st transmittance | permeability adjusters and a 2nd transmittance | permeability adjuster are formed. You may form in this area | region. Thereby, when arrange | positioning a 1st transmittance | permeability adjustment member and a 2nd transmittance | permeability adjustment member on the surface of a light-guide plate, positioning becomes easy.

  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 FIG. 1 was produced. That is, the backlight unit 2 of this embodiment includes a light source 12, a diffusion film 14, a prism sheet 16, a light guide plate 19, a reflector 20, a reflection film 22, a first transmittance adjusting member 28, It is composed of two transmittance adjusting members 30.
In this embodiment, a cold cathode tube having a diameter R of 2.6 mm was used as the light source 12. In addition, as shown in FIG. 2A, the light guide plate unit 18 extends 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 smallest, that is, the joint surface with the adjacent light guide plate unit 18. The distance L is 14 mm, the thickness D of the thickest portion 18b of the light guide plate unit 18 is 5.5 mm, and the distance d ₁ between the tip of the parallel groove 18f and the light exit surface is 1.0 mm. , the thickness d ₂ the thickness of the light guide plate unit of the thinnest surface when the flat ends of the inclined rear planes and 1.5 mm, the width G ₁ of the end portion of the light exit surface 18a and the opposite side of the parallel groove 18f Is 5.3 mm, the tip of the parallel groove 18 f is a curved surface, the curvature radius r ₁ of the most distal portion is 0.25 mm, the inclined back surface of the joint with the adjacent light guide plate is planar, and its joint surface Curvature of minimum thickness near 18g The radius _{r 2} was the shape and 15mm.
The diffusion film had a haze of 87.6% and a total light transmittance of 87.3%.
The prism sheet 16 is made of a material whose base is PET, has a thickness of 400 μm, and 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 μm (60 lines).
As the screen ink, Jujo Ink Cure 4707M 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 order to calculate the pattern density ρ1 (x1, y1) of the first transmittance adjusting member 28 that satisfies the above formula 1, in the backlight unit shown in FIG. 1, the transmittance adjuster unit 24, that is, the first transmittance. Except for the adjustment member 28 and the second transmittance adjustment member 30 and using only one light guide plate block, a backlight unit having the same configuration and shape as in FIG. 1 is used. The relative luminance F1 (x1, y1) of the light emitted from the surface was measured.

Here, the relative luminance F1 (x1, y1) was measured as follows.
First, the backlight unit 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. Then, the luminance at the position of the light emitting surface of the backlight unit is measured by a luminance meter to obtain information on the luminance regarding the specific position of the light emitting surface of the light guide plate unit.
Thereafter, by moving the XY stage, the relationship between the position on the light exit surface of the backlight unit and the luminance is obtained, and the maximum luminance of the calculated luminance is F1 _max and the minimum luminance is F1 _min . The maximum brightness F1 _max was set to 1, and the ratio of the brightness at each position to the maximum brightness F1 _max was set as the relative brightness F1 (x1, y1) at that position (x1, y1). The measurement results thus measured are shown in FIG. Here, in the graph of FIG. 5, 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 ρ1 (x1, y1) corresponding to the relative luminance F1 (x1, y1) is calculated from the measured maximum luminance F1 _max and the minimum luminance F1 _min using the above formula 1. In the present embodiment, the maximum relative luminance F1 when density _{c 1} were as _c 1 = 0.25,0.5,0.75,1 respectively (x1, y1) and the pattern density .rho.1 (x1, y1 ) Was calculated. FIG. 6 shows the calculation result. In FIG. 6, the vertical axis represents the pattern density ρ1 (x1, y1), and the horizontal axis represents the relative luminance F1 (x1, y1).
As shown in FIG. 6, the relationship between the relative luminance F1 (x1, y1) and the pattern density ρ1 (x1, y1) is a proportional relationship, and the pattern is obtained when the relative luminance F1 (x1, y1) is the minimum luminance F1 _min. density ρ1 (x1, y1) is 0, the pattern density at the maximum brightness F1 _max ρ1 (x1, y1) is the maximum density _{c 1.}

Next, based on the relationship between the relative luminance F1 (x1, y1) and the pattern density ρ1 (x1, y1) shown in FIG. 6, the relative luminance F1 (x1) of the backlight unit of the present embodiment shown in FIG. , Y1), the distribution of the pattern density ρ1 (x1, y1) is calculated. Figure 7 shows the distribution of the calculated pattern density ρ1 (x1, y1) for the case where the maximum density _{c 1} was _c 1 = 0.25,0.5,0.75,1. In FIG. 7, the vertical axis indicates the pattern density ρ1 (x1, y1), and the horizontal axis indicates the distance from the center of the light guide plate unit (the center of the parallel groove).

Next, when the calculated maximum density c _{1 is set} to c ₁ = 0.25, 0.5, 0.75, 1, based on the distribution of the pattern density ρ1 (x1, y1) that satisfies Expression 1. A first transmittance adjusting member 28 on which the first transmittance adjusting body 26 was arranged was produced.
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. 3A), and the calculated pattern density ρ (x, y ), The first transmittance adjusting member 28 was produced by appropriately arranging the first transmittance adjusting body 26 having a width direction of 0 to 1 mm. That is, L ₁ and L ₄ of the first transmittance adjusting member shown in FIG. 4B are L ₁ = L ₄ = 1.0 mm, L ₂ and L ₃ are L ₂ = L ₃ = 0.5 mm, w1 The first transmittance adjusting body 26 was repeatedly arranged by setting ~ 4 to 0 mm <w ≦ 1 mm, and the first transmittance adjusting member 28 was produced.
Here, in this embodiment, when the first transmittance adjusting body 26 is disposed on the entire surface, that is, when the pattern density ρ1 (x1, y1) is 1, the white ink having a transmittance of 33% at a wavelength of 550 nm is used. The produced first transmittance adjusting body 26 was disposed.

  When the first transmittance adjusting member 28 produced in this way was arranged in the backlight unit, the relative luminance of the light emitted from the emission surface of the backlight unit was measured. The measurement method was the same as the measurement method for measuring the relative luminance F1 (x1, y1) described above. The measurement results are shown in FIG. Here, in 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). For comparison, the backlight unit shown in FIG. 1 except that the transmittance adjusting body unit 24 is not provided, that is, the first transmittance adjusting member 28 and the second transmittance adjusting member 30 are not provided. The vertical brightness | luminance of the light radiate | emitted from the light-projection surface of the backlight unit of the same structure is also shown collectively.

As shown in FIG. 8, by arranging the first transmittance adjusting member 28, it is possible to reduce luminance unevenness compared to the case where the first transmittance adjusting member 28 and the second transmittance adjusting member 30 are not disposed. I understand.
Furthermore, it can be seen from this result that the maximum density c ₁ should be 0.5 ≦ c ₁ ≦ 1 in order to make the luminance unevenness ± 10% or less.

Next, the second transmittance adjusting member 30 was produced as follows.
First, an acrylic film having a thickness of 0.18 mm was prepared as the transparent film 34 in the same manner as the first transmittance adjusting member 28. Next, a predetermined pattern was printed on an acrylic film with a screen printer using TiO ₂ screen ink to produce the second transmittance adjusting member 30. In pattern printing, the dot area ratio was 50%, and the dot size was 300 μm (60 lines). Further, a mesh used for printing was a mesh 355 manufactured by Premax.

Here, a method for calculating the pattern density of the second transmittance adjusting body 32 of the second transmittance adjusting member 30 will be described in detail.
A backlight unit having the same configuration as the backlight unit shown in FIG. 1 except that the second transmittance adjusting member is not provided is manufactured, and the relative luminance of the illumination light emitted from the light exit surface of the backlight unit is set. It was measured. The relative luminance measurement method is the same as described above. FIG. 9 shows the luminance distribution of the region corresponding to the connecting portion of adjacent light guide plate blocks on the light exit surface of the backlight unit. In FIG. 9, the horizontal axis indicates the distance from the connecting portion of the adjacent light guide plate blocks, and the vertical axis indicates the relative luminance. As can be seen from FIG. 9, bright lines are generated at positions corresponding to connecting portions of adjacent light guide plate blocks.

  Next, based on this luminance distribution, the pattern density of the second transmittance adjusting body was obtained in the same manner as the calculation of the pattern density of the first transmittance adjusting body described above. FIG. 10 shows a pattern density distribution of the second transmittance adjusting body 32 at a position corresponding to a connecting portion of adjacent light guide plate blocks. Based on the distribution of the pattern density, the second transmittance adjusting member 30 is formed by printing the second transmittance adjusting body 32 at each position corresponding to the connecting portion of the adjacent light guide plate blocks of the acrylic film. Was made.

  Using the first transmittance adjusting member 28 and the second transmittance adjusting member 30 obtained as described above, a backlight unit having the structure shown in FIG. 1 is produced, and the light emission surface of the backlight unit is adjusted. The luminance distribution was measured. FIG. 11 shows a relative luminance distribution at a position corresponding to a connecting portion of adjacent light guide plate blocks on the light exit surface of the backlight unit using the first transmittance adjusting member 28 and the second transmittance adjusting body member 30. It was. In FIG. 11, the horizontal axis indicates the distance from the connection portion of the adjacent light guide plate blocks, and the vertical axis indicates the relative luminance. As shown in FIG. 11, the bright line is not visually recognized at the position corresponding to the connecting portion of the adjacent light guide plate blocks, and good luminance uniformity can be obtained.

  Also, by combining with a liquid crystal panel, a thin and light liquid crystal display device with good image quality could be obtained. As mentioned above, although the Example of the backlight unit of this invention was described in detail, this invention is not limited to this.

  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 storage is formed in the approximate center of the thick part 48b in parallel with the one side, and includes a shaft of the rod-shaped light source 12 on both sides of the parallel groove 48f and is perpendicular to the light emitting surface 48a. With the inclined back surface portion 48e forming the inclined back surface 48d, with the thickness becoming thinner from the thick wall portion 48b toward the thin end portions 48c on both sides in the direction orthogonal to the one side. An optical 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 so that the focal point of the curve 64a corresponding to one side wall of the parallel groove 18f is different from the focal point of the curve 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, a portion (second portion) corresponding to the inclined back surface 18d other than the parallel grooves 18f in the light exit surface 18a of each light guide plate unit 18. ) To the average value of the illuminance formed in the ratio of the peak value (illuminance peak value) of the bright line formed in the portion corresponding to the parallel groove 18f (first portion) on the light exit surface 18a of the light guide plate unit 18 Accordingly, the tip shape of the parallel groove 18f of the light guide plate unit 18 is tapered, that is, the degree of taper 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. Is preferred. In this case, this ratio is preferably 3 or less, more preferably 2 or less.

  This ratio is determined by the thickness of the backlight unit 2 (the distance between the light emitting surface 18a of the light guide plate unit 18 and the first transmittance adjusting member 28 of the transmittance adjusting body unit 24) or the backlight unit 2. It is preferable to set according to the diffusion efficiency and number of diffusion films 14 used, the diffusion efficiency and number of prism sheets 16 and 23 used, and the like. That is, when the thickness of the backlight unit 2 (the distance between the light emitting surface 18a of the light guide plate unit 18 and the first transmittance adjusting member 28 of the transmittance adjusting body unit 24) can be increased to some extent (or larger), When the diffusion efficiency of the diffusion film 14 used in the backlight unit 2 is high and the number of sheets used can be increased, or when the diffusion efficiency of the prism sheets 16 and 23 is high and the number of sheets used can be increased, the light guide plate unit 18 Although the diffusion (mixing, etc.) of the illumination light emitted from the light exit surface 18a can be sufficiently performed, the average value of the illuminance of the second portion of the light exit surface 18a of the light guide plate unit 18 is high cost. The ratio of the peak value of the illuminance of the first portion of the light exit surface 18a of the light guide plate unit 18 to the light guide plate unit 18 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 and 23 itself can be stopped, or the use of the low-cost prism sheets 16 and 23 having a very low diffusion efficiency can be used, or the number of sheets used 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, 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 parts 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. 19, the reflection plate 35 may be arranged on the side surface of the light guide plate block 17 arranged on the outermost side. By disposing such a reflection plate 35 on the side surface, light leakage from the side surface of the light guide plate block 17 can be prevented, and the light utilization efficiency can be further enhanced. The reflection plate 35 can be formed using the same material as the reflection 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 integrated light guide plates used for the planar lighting device of the present invention in parallel. (A) is a schematic sectional view of one light guide plate block of the backlight unit shown in FIG. 1, and (B) is a schematic sectional view of one light guide plate unit of the backlight unit shown in FIG. is there. (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. (A) 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, (B) is the 1st transmission of the 1st transmittance | permeability adjustment member shown to (A). It is a figure which shows a part of arrangement pattern of a rate adjustment body in detail. 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. 6 is a graph showing the relationship between the relative luminance calculated in FIG. 5 and the pattern density. Based on the relative luminance calculated in FIG. 5, the distribution of the pattern density of the transmittance adjusting body unit satisfying the present invention when the maximum density c ₁ was set to 0.25, 0.5, 0.75, and ₁ was calculated. It is a graph which shows a calculation result. 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 when the maximum density c1 calculated in FIG. 7 is 0.25, 0.5, 0.75, ₁ It is a graph which shows. It is a luminance distribution of the area | region corresponding to the connection part of the adjacent light-guide plate block of the light emission surface of a backlight unit. It is distribution of the pattern density of the 2nd transmittance | permeability adjustment body 34 in the position corresponding to the connection part of an adjacent light-guide plate block. It is a relative luminance distribution of the position corresponding to the connection part of the adjacent light-guide plate block of the light emission surface of the backlight unit using the 1st transmittance | permeability adjustment member and the 2nd transmittance | permeability adjustment body member. 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 a part of planar illumination apparatus which has arrange | positioned the reflecting plate on the side surface of the light-guide plate. 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 (planar lighting device)
4 Liquid crystal display panel 6 Drive unit 10 Liquid crystal display device 12 Light source (linear light source)
14 Diffusion film 16 Prism sheet 17 Light guide plate block 18 Light guide plate unit 18a, 48a Light exit surface 18b, 48b Thick portion 18c, 48c Thin end portion 18d, 48d Inclined back surface 18f, 48f Parallel groove 19 Light guide plate 22 Reflective sheet 23 Prism Sheet 23a Prism 24 Transmittance adjuster unit 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)
48, 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 (8)

A rod-shaped light source;
At least two flat light guide plate units having a back surface in which a groove for accommodating the rod-shaped light source is formed and a light emitting surface for emitting light of the rod-shaped light source on the opposite surface of the back surface are integrated. A light guide plate formed by arranging a plurality of light guide plate blocks arranged in parallel;
A light-transmitting sheet-like optical member disposed on the light exit surface side of the light guide plate, and a plurality of transmittance adjusting bodies disposed on at least one surface of the optical member; A transmittance adjusting body unit that diffuses and emits light emitted from the light exit surface of
Density distribution of the transmittance adjusting body of the transmittance adjusting body unit at a position corresponding to the joint portion of the light guide plate block, and the transmittance adjusting body unit at a position corresponding to the connection portion of the light guide plate unit. and density distribution of the transmittance adjusters is, unlike each other, and has an area where the pattern density is 1 or more of the transmittance adjusters, the one or more regions the pattern density, the transmittance adjusters are A planar illumination device, wherein the planar illumination device is arranged in a double manner . The density of the transmittance adjusters is, the transmittance adjusters of the position corresponding to the to Ru portion integral with the light guide plate unit between the transmittance adjusters unit at a position corresponding to the joint portion of the light guide plate block The planar illumination device according to claim 1, wherein the planar illumination device has a density higher than that of the transmittance adjusting body of the unit. A pattern density of the transmittance adjusting body of the transmittance adjusting body unit at a predetermined position (x, y) in a region corresponding to the light guide plate block is ρ (x, y), and the transmittance adjusting body unit is not provided. The maximum luminance F _max of the illumination light obtained in this case is set to 1, and the relative luminance with respect to the maximum luminance F _max of the illumination light emitted from the predetermined position (x, y) is F (x, y), which is added to the whole. the bias density is uniform density distributions when the [rho _b,
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 ) + ρ _b
(Where c satisfies 0.5 ≦ c ≦ 1, ρ _b satisfies 0 <ρ _b ≦ 1.5, and F _min is the minimum luminance of the relative luminance F (x, y))
The planar illumination device according to claim 1 or 2, wherein: A rod-shaped light source;
At least two flat light guide plate units having a back surface in which a groove for accommodating the rod-shaped light source is formed and a light emitting surface for emitting light of the rod-shaped light source on the opposite surface of the back surface are integrated. A light guide plate formed by arranging a plurality of light guide plate blocks arranged in parallel;
A sheet-shaped first optical member disposed on the light exit surface side of the light guide plate and having light transmittance, and a plurality of first transmittance adjusting bodies disposed on at least one surface of the first optical member. A first transmissivity adjusting member, a sheet-like second optical member having light transmissivity, and a position corresponding to a joint portion of the light guide plate block on at least one surface of the first optical member. A transmittance adjusting body unit including a second transmittance adjusting member having a plurality of second transmittance adjusting bodies.
The first transmittance adjusting member has a region where the pattern density of the first transmittance adjusting body is 1 or more, and the transmittance adjusting body is doubled in a region where the pattern density is 1 or more. And
And the density distribution of the said 2nd transmittance | permeability adjustment body and the density distribution of the said 1st transmittance | permeability adjustment body of the position corresponding to the connection part of the said light-guide plate unit differ mutually, The planar illumination device characterized by the above-mentioned .   5. The planar illumination according to claim 4, wherein a density of the second transmittance adjusting body is higher than a density distribution of the first transmittance adjusting body at a position corresponding to a connection portion of the light guide plate unit. apparatus. The pattern density at a predetermined position (x1, y1) of the first transmittance adjuster is ρ1 (x1, y1), the maximum luminance F1 _max of illumination light when the transmittance adjuster unit is not provided is 1, the relative luminance with respect to the maximum brightness F1 _max of the illumination light emitted from the predetermined position (x1, y1) and F1 (x1, y1), when the bias density is uniform density distribution that is added to the whole was [rho _b In addition,
The relationship between the relative luminance F1 (x1, y1) and the pattern density ρ1 (x1, y1) is expressed by the following equation:
ρ1 (x1, y1) = c ₁ {F1 (x1, y1) −F1 _min } / (F1 _max −F1 _min ) + ρ _b
(Wherein, _{c 1} satisfies _{0.5 ≦ c 1 ≦ 1, ρ} b satisfies _{0 <ρ b ≦ 1.5, F1} min is the minimum luminance of the relative brightness F1 (x1, y1) is there)
The planar illumination device according to claim 4 or 5, satisfying The pattern density at a predetermined position (x2, y2) of the second transmittance adjuster is ρ2 (x2, y2), and the light transmittance surface of the transmittance adjuster unit when the second transmittance adjuster member is not provided. When the maximum brightness F2 _max of the emitted illumination light is 1, and the relative brightness of the illumination light emitted from the predetermined position (x2, y2) with respect to the maximum brightness F2 _max is F2 (x2, y2),
The relationship between the relative luminance F2 (x2, y2) and the pattern density ρ2 (x2, y2) is expressed by the following equation:
ρ2 (x2, y2) = c ₂ {F2 (x2, y2) −F2 _min } / (F2 _max −F2 _min )
(Wherein, _{c 2} satisfies _{0.5 ≦ c 2 ≦ 1, F2} min is the minimum luminance of the relative brightness F2 (x2, y2))
The planar illumination device according to any one of claims 4 to 6, which satisfies The planar illumination device according to any one of claims 1 to 7,
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.

Images