WO2008050763A1 - Direct backlight device - Google Patents

Abstract

A direct backlight device having an improved luminance uniformity of the light-emitting surface. The direct backlight device has a reflector, a light source, and a light diffuser. A rough structure of a predetermined Ra (max) is fabricated on the light exit surface. A light transmission suppressing layer is provided in a region (MR) on the light entrance surface. The minimum value of the transmittance of (MR) is 5% or more smaller than the transmittance of the parts of the light diffuser and light transmission suppressing layer between the position which is the projection of the center position of the light source onto the light diffuser and the position which is the projection of the middle position between the light source and the adjacent light source onto the light diffuser. An average distance (a) between the centers of the light source and its adjacent light source and an average distance (b) between the center of the light source and the light entrance surface satisfies a predetermined relation. The region (MR) is within a distance (M) from the reference line which is the projection of the center line of the light source onto the light entrance surface of the light diffuser, and (M) and (b) satisfy a predetermined relation.

Description

 Specification

 Direct backlight unit

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a direct type backlight device, and more particularly to a direct type backlight device capable of increasing the luminance uniformity of a light emitting surface.

 Background art

 Conventionally, in a liquid crystal display device, a plurality of light sources, a reflecting plate that reflects light from these light sources, direct light from the light source and reflected light from the reflecting plate are incident from a light incident surface. A direct type backlight device including a light diffusing plate that diffuses incident light from a light emitting surface and emits the light is used. In such a direct type backlight device, there is a problem in that the portion directly above the light source tends to have higher luminance than the other portions on the light emitting surface which is the light emitting surface. For this reason, there is a need for the development of a technology that has sufficient luminance and that equalizes the luminance of the light emitting surface (suppresses luminance unevenness).

 [0003] For example, Patent Document 1 discloses a technique in which a pattern made of white ink dots is provided on a surface of a light diffusing plate that faces a linear light source so that the portion closer to the linear light source has a higher density. ing. With such a configuration, the luminance uniformity of the light emitting surface can be increased. However, in such a configuration, if the distance between the linear light sources is increased or the distance between the linear light sources and the light incident surface is decreased, the amount of light incident on the light diffusing plate is small at the intermediate position of the linear light sources and Since the light diffuses on the light diffusing plate, the luminance between the linear light sources is low, and the luminance between the linear light source and the intermediate light is not balanced, resulting in uneven luminance. .

[0004] Therefore, in Patent Document 2, in a direct type backlight device, a configuration in which a plurality of lenticular or prism-like concavo-convex structures extending along the longitudinal direction of a linear light source are provided on a light incident surface of a light diffusing plate. Is described. In this case, an embodiment is disclosed in which the distance between the linear light sources is equal to the distance between the linear light sources and the light incident surface. According to such a configuration, it is possible to increase the luminance while increasing the luminance uniformity, but if the distance between the linear light sources is increased or the distance between the linear light sources and the light incident surface is decreased, In the uneven structure, directly above the linear light source In this case, it is impossible to sufficiently suppress the light, and the brightness in the middle of the linear light source cannot be balanced, resulting in uneven brightness.

 [0005] Also, in Patent Documents 3 and 4, in a direct type backlight device, a concavo-convex structure on the light exit surface of the light diffusing plate and a light incident surface corresponding to the convex portion or a reflecting portion at a position inside the light diffusing plate The prepared structure is described. According to such a configuration, the force S can be increased by suppressing light emission in unnecessary directions, and since the reflection portion exists evenly over the entire surface of the light diffusing plate, it is located between the linear light sources. If the distance between the linear light sources is increased or the distance between the linear light sources and the light incident surface is decreased, the luminance between the linear light source and the intermediate light cannot be balanced, resulting in uneven luminance. There was a problem that would occur.

 [0006] Patent Document 1: Japanese Patent Laid-Open No. 6-273760

 Patent Document 2: Japanese Patent Laid-Open No. 2000-182418

 Patent Document 3: Japanese Unexamined Patent Publication No. 2006-318886

 Patent Document 4: Japanese Unexamined Patent Publication No. 2006-208930

 Disclosure of the invention

 Problems to be solved by the invention

Meanwhile, in recent years, there has been a demand for the development of a technology for reducing power consumption by reducing the number of linear light sources and a thinner backlight device. However, in the configurations shown in Patent Documents !! to 4, the distance between the linear light sources is made larger than the distance between the linear light source and the light incident surface, in other words, the number of linear light sources used is reduced. If the distance between the linear light source and the light incident surface is reduced, the power consumption can be reduced and the knocklight device can be made thinner. There is a problem that uneven brightness occurs only by providing a pattern of dots or by providing a plurality of lenticular or prismatic uneven structures extending along the longitudinal direction of the linear light source. For this reason, there is a demand for the development of a technology that can sufficiently increase the luminance uniformity even in a mode in which the number of linear light sources is reduced. Such a problem occurs not only in a linear light source but also in a point light source.

[0008] An object of the present invention is to provide a direct type backlight device capable of increasing the luminance uniformity of a light emitting surface. Means for solving the problem

[0009] The present inventor is not limited to the type of light source, and in a light diffusing plate having an uneven structure on at least one surface, the distance between the light sources, the refractive index of the material constituting the light diffusing plate, It was found that the above-mentioned object can be achieved by highly relating the installation conditions of the light transmission suppressing layer that suppresses the lightness and the light transmittance.

According to the present invention, the following direct type backlight device is provided.

 [1] A reflecting plate, a plurality of linear light sources arranged substantially in parallel, direct light from these linear light sources and reflected light from the reflecting plate are incident from a light incident surface and diffused to obtain a light emitting surface. A direct-type backlight device comprising: a light diffusing plate that emits light from at least one of the light emitting surface and the light incident surface; A concavo-convex structure in which Ra (max), which is the maximum value of the center line average roughness Ra measured along various directions at 3 111 to 1,000 m, is formed, and the light emitting surface and the light emitting surface At least one of the light incident surfaces has light that suppresses transmission of light in at least the range M.

 R

 A transmission suppressing layer is provided, and in the range M, the light diffusing plate and the light transmission suppressing layer are provided.

 R

 The minimum value of the transmittance of the portion including the control layer is the position where the center position of the linear light source is projected onto the light diffusion plate, and the position where the center position of the adjacent linear light source is projected onto the light diffusion plate. The average distance between the centers of the adjacent linear light sources that is 5% or more lower than the transmittance value of the portion including the light diffusing plate and the light transmission suppressing layer at an intermediate position of a (mm), The average distance between the center of the linear light source and the light incident surface is b (mm), and the relationship of 1.7≤a / b≤23.0 is satisfied, and the range M is the center line of the linear light source. Light expansion

 R

 The position projected on the incident surface of the scattering plate is the reference line, and the area within the distance M (mm) from this reference line, where M and b are 0≤ M <b X tan (2 π / 9) Direct type backlight device that satisfies the relationship.

[2] Light diffusion in which a reflecting plate, a plurality of point light sources, direct light from these point light sources and reflected light from the reflecting plate are incident from a light incident surface and diffused to be emitted from the light emitting surface And at least one of the light emitting surface and the light incident surface along at least a part of the surface along various directions within the surface. Ra (max), which is the maximum value of the average roughness Ra of the center line, measured from 3 m to 1; A concavo-convex structure of 000 m is formed, and at least one of the light emitting surface and the light incident surface is provided with a light transmission suppressing layer that suppresses light transmission at least in the range M.

 R

In the range M, the portion including the light diffusion plate and the light transmission suppressing layer

 R

The minimum transmittance is a position intermediate between a position where the center position of the point light source is projected onto the light diffusion plate and a position where the center position of the adjacent point light source is projected onto the light diffusion plate. The average distance a (mm) between the centers of the adjacent point light sources that is 5% or more lower than the transmittance value of the portion including the light diffusing plate and the light transmission suppressing layer in the point light source The average distance between the center and the light incident surface is b (mm), and satisfies the relationship of 0.5≤a / b≤15.0, and the range M is the center of the point light source as the light diffusing plate. Projected onto the incident surface

 R

Is a region within a distance M (mm) from this reference point, where M and b are direct type backlights that satisfy the relationship 0≤M <b X tan (2 7i / 9) apparatus.

[3] In the direct type backlight device, the concavo-convex structure is a linear prism having a polygonal cross section extending substantially parallel to the longitudinal direction of the linear light source, or a shape in which the cross section includes a curved portion. A certain wrench quilla S, a direct-type backlight device that has a plurality of side-by-side structures.

 [4] In the direct type backlight device, the light transmission suppressing layer is a direct type backlight device configured by a printing layer that reflects and / or absorbs incident light.

[5] The direct-type backlight device, wherein the printing layer is provided such that light transmittance increases continuously or stepwise as the distance from the light source increases.

 [6] In the direct type backlight device, in the surface on which the printing layer is formed, the center line average roughness Ra at the position where the printing layer is formed is 0.005, 1 m to 5 m. Type backlight device.

 [7] In the direct type backlight device, the concavo-convex structure is a direct type backlight device having a configuration in which a plurality of dot-like protrusions or concave structural units are arranged.

[8] In the direct type backlight device, the uneven structure is formed on the light emitting surface, and the light incident surface is a substantially flat surface having a center line average roughness Ra of less than 3 in. . [9] In the direct type backlight device, the maximum value of the arithmetic average inclination angles Θ measured along various directions within the surface on which the uneven structure is formed is Θ (max) (degrees) A direct-type backlight device satisfying the relationship sin− ¹ (R / 2nb) −siiT ¹ (1 / n)> Θmax, where n is the refractive index of the concavo-convex structure portion and R is the outer diameter of the light source.

 [10] In the direct type backlight device, the light transmission suppression layer is provided at least at a predetermined position NO on either the light emitting surface or the light incident surface, and the position NO is light power Is a position where a path exiting in the direction parallel to the thickness direction of the light diffusing plate and the light incident surface or the light emitting surface of the light diffusing plate intersect with each other. The transmittance of the portion including the light diffusing plate and the light transmission suppressing layer at the position NO is a transmittance between the position NO and a position where an intermediate position of the adjacent light source is projected onto the light diffusing plate. Direct type backlight device that is 5% lower than the maximum value of

 [11] In the direct type backlight device, transmission of a portion including the light diffusion plate and the light transmission suppressing layer in a range N within a distance R / 2 centered on the position NO

 R

The average value of the transmittance TB of the portion including the light diffusing plate and the light transmission suppressing layer between the position NO and the position where the center of the light source is projected onto the light diffusing plate is defined as the minimum value TA. In this case, a direct backlight device that satisfies TA <TB.

[12] In the direct type backlight device, the light diffusing plate is made of a resin composition containing a transparent resin, and the resin composition has a total light transmittance of 0% or more measured by normal incident light. Direct type backlight device that is less than%.

 [13] In the direct type backlight device, the light diffusion plate is formed of a resin composition containing a transparent resin, and the water absorption rate of the resin composition is 0.25% or less.

The invention's effect

According to the present invention, the average distance between the centers of the light sources (linear light source and point light source) and the average distance between the center of the light source and the light incident surface satisfy a certain relationship, and at least the light diffusion plate is provided. By forming a concavo-convex structure on at least a part of one surface and providing a predetermined light transmission suppression layer on at least one surface of the light diffusing plate, when the number of light sources used is reduced or light diffusion Even when the distance between the plate and the light source is reduced, the V effect can be obtained if the luminance uniformity of the light emitting surface can be increased.

Brief Description of Drawings

FIG. 1 is a longitudinal sectional view schematically showing a direct type backlight device according to a first embodiment of the present invention.

 FIG. 2 is a diagram for explaining Fresnel reflection on the light incident surface of the light diffusing plate.

FIG. 3 is a diagram for explaining the influence of the concavo-convex structure on the light emission direction.

FIG. 4 is a diagram for explaining a projected area of a light source onto a light incident surface of a light diffusing plate.

FIG. 5 is a graph for explaining Fresnel reflection at the light incident surface of the light diffusing plate.

FIG. 6 is a diagram for explaining the relationship between the incident angle of light from the light source to the light incident surface of the light diffusing plate and the projected area on the light incident surface of the light diffusing plate of the light source.

 FIG. 7 is a diagram illustrating how light enters the light incident surface of the light diffusing plate.

 FIG. 8 is a longitudinal sectional view schematically showing the shape of a lenticular.

 FIG. 9 is a diagram for explaining a light transmission suppressing layer provided on a light incident surface of a light diffusing plate.

 FIG. 10 is a diagram for explaining the effect of the printed layer provided on the light incident surface of the light diffusing plate.

 [FIG. 11] FIG. 11 is a diagram for explaining an effect when the print layer shown in FIG. 10 is not provided.

[FIG. 12] FIG. 12 is a diagram for explaining how light that enters a light diffusion plate from a linear light source travels.

 FIG. 13 is a diagram for explaining a light path from a light source to a concavo-convex structure.

[FIG. 14] FIG. 14 is a diagram for explaining the relationship between the critical angle and the perpendicularly incident light in the uneven structure.

[FIG. 15] FIG. 15 is a diagram for explaining an image of a linear light source observed through a light diffusion plate. [FIG. 16] FIG. 16 is for explaining a light path from the linear light source. FIG. [FIG. 17] FIG. 17 is a diagram for explaining how the light incident from the linear light source enters the printing layer provided on the light incident surface of the light diffusion plate.

 FIG. 18 is a diagram for explaining the relationship between distances M and b.

 FIG. 19 is a longitudinal sectional view schematically showing a direct type backlight device according to a second embodiment of the present invention.

 FIG. 20 is a longitudinal sectional view schematically showing a first aspect of the linear prism.

 FIG. 21 is a longitudinal sectional view schematically showing a second mode of the linear prism.

 FIG. 22 is a longitudinal sectional view schematically showing a direct type backlight device according to a third embodiment of the present invention.

 FIG. 23 is a plan view schematically showing a first mode of arrangement of point light sources.

FIG. 24 is a plan view schematically showing a second mode of arrangement of point light sources.

FIG. 25 is a plan view schematically showing a third mode of arrangement of point light sources.

FIG. 26 is a view for explaining a light transmission suppressing layer provided on the light incident surface of the light diffusing plate.

 FIG. 27 is a cross-sectional view schematically showing the tip of a cutting tool.

 FIG. 28 is a perspective view showing a concavo-convex structure surface formed on a stamper.

 FIG. 29 is a longitudinal sectional view for explaining the shape of a reflecting plate.

 FIG. 30 is a view for explaining a light transmission suppressing layer provided on a light incident surface of a light diffusing plate.

 FIG. 31 is a diagram for explaining a light transmission suppressing layer provided on a light incident surface of a light diffusing plate.

 FIG. 32 is a longitudinal sectional view schematically showing a diffusion plate of Comparative Example 8.

BEST MODE FOR CARRYING OUT THE INVENTION

<First embodiment>

 (Direct type backlight device)

A direct type backlight device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing a direct type backlight device 1 according to the present embodiment. As shown in FIG. 1, the direct type backlight device 1 includes a plurality of linear light sources 10 and a plurality of linear light sources 10. The reflecting plate 20 that reflects the light from the linear light source 10 and the direct light from the linear light source 10 and the reflected light from the reflecting plate 20 are incident from the light incident surface 30A. A light diffusing plate 30 that diffuses and exits from the light emitting surface 30B, and a light transmission suppression layer 50 provided on the light incident surface 30A of the light diffusing plate 30 are provided.

[0014] (Linear light source)

 The linear light source 10 uses a straight-tube cold-cathode tube (CCFU) from the viewpoint of luminance uniformity. The linear light source 10 is not limited to a cold-cathode tube. Fluorescent tubes (EEFU, hot cathode tubes, xenon lamps, mercury xenon lamps and light emitting diodes (LEDs) arranged in a straight line, or a combination of LED and light guide can also be used. In the embodiment, a straight tube is used as the linear light source, but a substantially U-shaped tube in which two substantially parallel tubes are connected by one semicircular tube, and three substantially parallel tubes. Can be listed as a substantially N-shaped tube connected by two semicircular tubes, and a substantially W-shaped tube formed by connecting four substantially parallel tubes by three semicircular tubes. .

[0015] In the present invention, a combination of LEDs arranged in a straight line or a combination of an LED and a light guide is also considered as a single linear light source. Of those connected by a semicircular tube, approximately U A letter-shaped tube is considered to be two linear light sources, an approximately N-shaped tube is considered to be three linear light sources, and an approximately W-shaped tube is considered to be four.

 [0016] The number of linear light sources used is not particularly limited. For example, when the direct type backlight device of the present invention is used in a 32-inch liquid crystal display device, the number of linear light sources is, for example, an even number such as 16, 14, 12, 8, or an odd number. The power to make a book is S.

In the present embodiment, the plurality of linear light sources 10 are arranged substantially parallel to each other. The average distance between the central axes of any adjacent linear light sources 10 is substantially constant at a (mm). Note that “substantially parallel” means within a range of ± 5 degrees from a truly parallel state. However, in the present invention, the plurality of linear light sources are not limited to this embodiment, and may be arranged in parallel. In addition, the average distance between the central axes of the adjacent linear light sources may be random, or may have regularity that increases or decreases toward a specific location. Here, the specific part is, for example, a central part including a line connecting one long side of a rectangular light diffusion plate or the central positions of opposing short sides. In the present embodiment, the relationship (A) of 1.7 ≦ a / b ≦ 23.0 is satisfied between the average distance a (mm) and the average distance b (mm). Furthermore, it is preferable to satisfy the relationship (B) of 3 · 5≤a / b≤17.0. It is further more preferable to satisfy the relationship (C) of 3 · 5≤a / b≤ll. By satisfying such a preferable relationship, the number of linear light sources used can be reduced and the power consumption of the device can be suppressed while keeping the backlight thickness appropriate. In addition, with the above structure, the thickness of the backlight device can be further reduced.

 [0019] In order to reduce the number of light sources used in the direct type backlight device or to reduce the thickness of the device, it is sufficient to increase a / b. However, in order to suppress luminance unevenness, the configuration of the device is specified. It is important to be within the range of. This will be described below.

 FIG. 2 is a view for explaining Fresnel reflection on the light incident surface, and is a longitudinal sectional view schematically showing an adjacent light source and a light diffusion plate. FIG. 5 is a graph for explaining Fresnel reflection at the light incident surface of the light diffusion plate having a refractive index of 1.53, and shows the relationship between the incident angle (degrees) and the reflectance. Here, the average value of the reflectance of s-wave and p-wave light is shown.

 As shown in FIG. 2, assuming that the position where the intermediate position between adjacent linear light sources is projected onto the light incident surface is A, the incident angle of light from the linear light source toward position A (in this application, the incident angle is the incident angle). The angle between the normal direction of the surface and the incident direction) increases, and the amount of reflected light (Fresnel reflection) at position A increases. Further, as shown in FIG. 5, it can be seen that the reflectivity increases when the incident angle exceeds 40 degrees (ie, a / b = 1.7). Therefore, in an aspect where the incident angle exceeds 40 degrees, the luminance at position A is low. Furthermore, when the incident angle exceeds 60 degrees (that is, a / b = 3.5), the reflectance value becomes nearly twice that of the incident angle of 40 degrees, and this tendency becomes remarkable. . For this reason, when the incident angle is within the above range, the luminance at the position B (FIG. 2) where the linear light source is projected is higher than the position A, and the luminance unevenness occurs on the light emitting surface. Here, “projection” specifically means that an image of a light source is projected onto a surface with a viewpoint angle perpendicular to the surface.

[0021] Therefore, by providing a light transmission suppressing layer at the position B where the linear light source is projected onto the light diffusing plate, the amount of light emitted from the light diffusing plate at the position B can be suppressed. it can. In this way, by suppressing the amount of emitted light at position B, uneven brightness on the light emitting surface can be eliminated. However, as shown by the arrow on the left side of Fig. 3, there is no uneven structure at position A. In such a case, the incident light is emitted from the light diffusion plate at the same angle as the incident angle. For this reason, a predetermined concavo-convex structure is provided at position A, and the direction of the emitted light is changed to the front direction as shown by the arrow on the right side of FIG. The luminance unevenness of the light surface can be reduced.

 FIG. 4 is a diagram for explaining the projected area of light incident on the light incident surface from the linear light source. As shown in Fig. 4, at the position C where the light from the linear light source is incident at an incident angle Θa, the light from the linear light source is lighter than at the position B where the light from the linear light source is incident at an incident angle of 0 degree. The projected area of the light incident on the incident surface is 1 / cos Θ a times. Here, since the luminance is the luminous intensity per unit area, the luminance on the light emitting surface decreases as the distance from the linear light source increases, that is, as the incident angle increases.

 FIG. 6 is a graph for explaining the relationship between the incident angle (degrees) of light from the linear light source to the light incident surface and the projected area on the light incident surface. As shown in Fig. 6, the 1 / cos Θ a is straight from Θ a starting from 80 degrees (ie a / b = ll. 3) and 85 degrees (ie a / b = 22.9). ) Will increase rapidly. In other words, when the incident angle exceeds 85 degrees, the brightness between the linear light sources decreases rapidly, making it difficult to suppress brightness unevenness.

 For this reason, in this invention, it is necessary to satisfy | fill the relationship (A) mentioned above.

[0024] The outer diameter R (mm) of the linear light source 10 is 2≤R≤30, preferably 2.5≤R≤25, more preferably 2.5≤R≤20. The average distance b (mm) between the central axis of the linear light source 10 and the light incident surface 30A of the light diffusing plate 30 is designed in consideration of the thickness and luminance uniformity of the direct type backlight device. 3. 0≤b≤32.0, preferably (3.3.0≤b≤27.0, more preferably (3.3.0≤b≤22.0. This reduces damage to the linear light source. In addition, the thickness of the direct backlight device can be made appropriate, and in this case, the average distance a (mm) between the centers of the adjacent linear light sources is further set to 20≤a≤200, preferably By setting 22≤a≤170, more preferably 23≤a≤150, the number of linear light sources used can be reduced, so that the equipment can be assembled easily and consume less power, or The thickness of the device can be reduced and the angle difference between Θ and Θc in Fig. 7 can be reduced. When the angle difference between Θ and Θc increases, light from various angles enters the light diffusing plate at one point, and the light path is controlled by the uneven structure. It becomes difficult to control the luminance unevenness.

In the present embodiment, the plurality of linear light sources 10 are of the same type having the same diameter. However, a plurality of types of linear light sources having different diameters can be used.

 In the present embodiment, the plurality of linear light sources 10 are arranged such that the average distance b (mm) to the light incident surface 30A is substantially constant for all the linear light sources. Note that “almost constant” means that the maximum value of the average distance b (mm) / the minimum value of the average distance b (mm) ≤ 1 · 3 is satisfied. However, a plurality of linear light sources may be arranged so that some linear light sources are closer to the light incident surface 30 mm than other linear light sources. For example, it may be random or may have regularity that becomes larger or smaller as it goes to a specific location. Here, the specific location is, for example, a central location including a long side of a rectangular light diffusing plate, or a central location including a line connecting the central locations of opposing short sides.

[0026] (Reflector)

 For the reflecting plate 20, a resin colored in white or silver, a metal, or the like can be used. Among these, from the viewpoint of weight reduction, a resin can be preferably used for the reflector 20. The color of the reflector 20 is preferably white from the viewpoint of improving the luminance uniformity. Also, from the viewpoint of highly balancing brightness and brightness uniformity, it is possible to use a mixture of white and silver.

[0027] In the region of the reflecting plate located between the plurality of linear light sources, a protrusion that protrudes toward the light diffusing plate and extends along the longitudinal direction of the plurality of linear light sources may be provided. Good. At this time, it is preferable that the protrusion is provided at a substantially middle position between adjacent linear light sources. Furthermore, the cross-sectional shape in the short direction of the protrusion is not particularly limited, but an isosceles triangle, an isosceles trapezoid, a shape obtained by cutting a circle, a shape obtained by cutting an ellipse with a line segment parallel to the minor axis, and an ellipse Examples include a shape cut by a line segment parallel to the long axis, a shape in which convex curves are connected so as to be line targets, and a shape in which convex curves are connected so as to be line-symmetric. The apex portions of these shapes may be pointed or rounded. From the viewpoint of luminance uniformity and ease of production, a triangular shape is preferred. In addition, the cross-sectional shape of the protrusions is preferably line symmetric with respect to a line segment perpendicular to the thickness direction of the light diffusion plate. This By adopting such a configuration, it is possible to suppress uneven brightness on the light exit surface of the light diffusing plate.

[0028] The protrusions may be formed so as to extend continuously in a bowl shape, or may be formed such that a plurality of vertical bodies are connected in the longitudinal direction without being spaced apart. However, it is preferable to be continuous in a bowl shape in that the luminance uniformity can be further improved.

[0029] As the method for installing the protrusion, a method of painting a metal frame with a protrusion in white or silver, a method of attaching a white or silver reflective sheet to a metal frame with a protrusion, white or For example, it is possible to cite a method of bending a silver flat reflective sheet and placing it on a flat metal frame, a method of forming a white or silver resin using a mold having a predetermined shape, and the like.

[0030] (Light diffusion plate)

 As a material constituting the light diffusion plate 30, glass and resin can be used. As the resin, a transparent resin, a resin composition of two or more resins that are difficult to mix, a resin composition in which a light diffusing agent is dispersed in the transparent resin, and the like can be used. Among these, the light diffusing plate 30 is made of a material that is light in weight and easy to mold, so that a resin is preferable, and a brightness improvement is easy, and a transparent resin is preferable. From the viewpoint of easy adjustment of the rate and haze, a resin composition in which a light diffusing agent is dispersed in a transparent resin is preferred.

 [0031] The transparent resin is a resin having a total light transmittance of 70% or more measured with a 2 mm-thick plate smooth on both sides based on JIS K7361-1, for example, polyethylene, propylene-ethylene copolymer , Polypropylene, polystyrene, copolymers of aromatic butyl monomers and (meth) acrylic acid alkyl esters having a lower alkyl group, polyethylene terephthalate, terephthalic acid monoethylene glycol-cyclohexane dimethanol copolymer And polycarbonate, acrylic resin, and resin having an alicyclic structure. In addition, (meth) acrylic acid is acrylic acid and methacrylic acid.

[0032] Among these, as the transparent resin, polycarbonate, polystyrene, an aromatic bule monomer containing 10% or more of an aromatic bur monomer, and a (meth) acrylic acid alkyl ester having a lower alkyl group are used. Copolymer and resin having an alicyclic structure have a water absorption of 0.25% or less. Resin strength Less deformation due to moisture absorption It is preferable in that a light diffusion plate of a mold can be obtained.

 In particular, when a / b is smaller than 1.7, the distance between the light diffusing plate and the linear light source is short, or the linear light sources are separated from each other, so that the light diffusing plate is easily heated locally. As a result, if the water absorption is greater than 0.25%, the local moisture content fluctuates greatly, resulting in a difference in expansion coefficient depending on the location, deformation is particularly likely to occur, and uneven brightness occurs. In this case, the water absorption is preferably 0.25% or less, more preferably 0.15% or less.

 [0033] Further, a resin having an alicyclic structure is more preferable in that it has good fluidity and can efficiently produce a large light diffusion plate. In addition, a resin composition in which a light diffusing agent is mixed with a resin having an alicyclic structure has both high permeability and high diffusibility necessary for a light diffusion plate, and can improve chromaticity, so that it is more preferable. Can be used.

 [0034] The resin having an alicyclic structure is a resin having an alicyclic structure in the main chain and / or side chain. From the viewpoints of mechanical strength and heat resistance, a resin containing an alicyclic structure in the main chain is particularly preferred. Examples of the alicyclic structure include a saturated cyclic hydrocarbon (cycloalkane) structure and an unsaturated cyclic hydrocarbon (cycloalkene, cycloalkyne) structure. From the viewpoint of mechanical strength, heat resistance, etc., the cycloalkane structure is more preferable as the alicyclic structure, although the cycloalkane structure and the cycloalkene structure are preferred. The number of carbon atoms constituting the alicyclic structure is usually 4 to 30, preferably 5 to 20, and more preferably 5 to 15; In this case, the mechanical strength, heat resistance, and formability of the light diffusion plate can be highly balanced, which is preferable.

 [0035] The proportion of the repeating unit having an alicyclic structure in the resin having an alicyclic structure may be appropriately selected according to the purpose of use, but is usually 50% by weight or more, preferably 70% by weight or more. More preferably, it is 90% by weight or more. If the proportion of the repeating unit having an alicyclic structure is too small, the heat resistance is lowered, which is not preferable. The repeating unit other than the repeating unit having an alicyclic structure in the resin having an alicyclic structure is appropriately selected according to the purpose of use.

[0036] Specific examples of the resin having an alicyclic structure include (1) ring-opening polymer of norbornene monomer and the opening of norbornene monomer and other monomers capable of ring-opening copolymerization. Ring copolymers, hydrogenated products thereof, addition polymers of norbornene monomer and norborn Norbornene polymers such as addition copolymers of ene monomers and other monomers copolymerizable therewith; (2) Monocyclic cyclic olefin polymers and their hydrogenated products; (3) Cyclic Co-polymers and hydrogenated products thereof; (4) Polymers of bur cycloaliphatic hydrocarbon monomers and bully alicyclic hydrocarbon monomers and other monomers copolymerizable therewith Copolymers of these and hydrogenated products thereof, hydrogenated aromatic rings of polymers of bully aromatic monomers, and bully aromatic monomers and other monomers copolymerizable therewith. For example, it may be a buralicyclic hydrocarbon polymer such as a hydrogenated aromatic ring of a copolymer.

 [0037] Among these, a ring-opening polymer hydrogenated product of norbornene monomer preferred by norbornene polymer and vinyl alicyclic hydrocarbon polymer from the viewpoint of heat resistance, mechanical strength and the like, Hydrogenated ring-opening copolymer of norbornene monomer and other monomers capable of ring-opening copolymerization, hydrogenated aromatic ring of vinyl aromatic monomer polymer, and vinyl aromatic More preferred is a hydrogenated aromatic ring copolymer of a monomer and another monomer copolymerizable therewith.

 [0038] The light diffusing agent is a particle having a property of diffusing light, and can include an inorganic filler and an organic filler. Inorganic fillers include silica, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, and mixtures thereof. Examples of the organic filler include acrylic resin, polyurethane, polychlorinated butyl, polystyrene resin, polyacrylonitrile, polyamide, polysiloxane resin, melamine resin, and benzoguanamine resin. Among organic fillers, polystyrene resin, polysiloxane resin, and fine particles made of these cross-linked products are preferred because of their high dispersibility, high heat resistance, and no coloration (yellowing) during molding. Fine particles made of a cross-linked product of a polysiloxane resin are more preferred in that they are more excellent in heat resistance.

[0039] Examples of the shape of the light diffusing agent include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fiber shape. Among these, light diffusion is possible. A spherical shape is preferred in that the direction can be isotropic. The light diffusing agent is preferably used in a state of being uniformly dispersed in the transparent resin. [0040] In the case where the light diffusing agent is dispersed in the transparent resin, the content of the light diffusing agent can be appropriately selected according to the thickness of the light diffusing plate, the interval between the linear light sources, and the like. It is more preferable to adjust so that the total light transmittance of the resin composition in which is dispersed is 40% to 98%, and more preferably 45% to 95%. By setting the total light transmittance to the above preferable range, the luminance and the luminance uniformity can be further improved.

 [0041] The total light transmittance is based on JIS K7361-1 (this standard is measured using a single beam photometer equipped with a light source and a photo detector specified by the CIE standard). It is a value measured with a 2 mm thick plate smooth on both sides.

 [0042] The thickness of the light diffusing plate 30 is preferably 0.4 mm to 5 mm, more preferably 0.8 mm to 4 mm. By setting the thickness of the light diffusing plate 30 within the above-mentioned preferable range, it is possible to suppress stagnation due to its own weight and facilitate molding.

 As shown in FIG. 1, a concavo-convex structure 40 is formed on the light emitting surface 30B corresponding to one surface. In the present embodiment, the concavo-convex structure 40 is configured to include a plurality of lenticulars 41 having a convex arcuate cross section extending substantially in parallel along the longitudinal direction of the linear light source 10. Here, the center line average roughness Ra along the direction perpendicular to the longitudinal direction of the lenticular 41 (left-right direction in the figure) is 3 111 to 1; 1, OOO rn. In the light exit surface 30B, among the centerline average roughness Ra measured along various directions in the surface, the centerline average roughness Ra measured along the left-right direction shows the maximum value. . Note that the center line average roughness Ra of the light exit surface 30B, which is the target surface, can be obtained by reading directly using an ultra-deep shape measuring microscope based on JIS B0601. The light incident surface 30A corresponding to the other surface is a flat surface having a center line average roughness Ra of 3 m or less in an arbitrary direction within the surface. Here, “the maximum value of the centerline average roughness Ra measured along various directions” can be simply the maximum value of the centerline average roughness measured along all directions.

[0044] The curve constituting the cross section of the lenticular 41 may be an arc as described above, an elliptic arc, a parabolic arc, or the like. Further, as shown in FIG. 8, it may be a shape having two oblique sides S of a triangle and a curved portion C (for example, an arc shape) formed in a curved shape at the apex portion of the triangle. Note that the length of the curved portion C is 40% or more of the total length of the two hypotenuses S and the curved portion C. [0045] The method for forming the concavo-convex structure on the surface of the light diffusing plate is not particularly limited. For example, the method may be a method of forming the concavo-convex structure on the surface of the plate-shaped light diffusing plate. It is also possible to form the concavo-convex structure integrally with the formation of the flat plate portion (in this specification, sometimes referred to as a light diffusing plate base).

 [0046] Examples of a method for forming a concavo-convex structure on the surface of the flat light diffusing plate include, for example, a method of cutting the surface of the flat light diffusing plate, and a process having a desired shape on the flat light diffusing plate. A method of laminating or affixing a sheet having a concavo-convex structure such as a rhythm sheet, applying a photo-curing resin or a thermosetting resin to the surface of a flat light diffusing plate, and applying a desired shape to the coating film with a roll or a mold With a force S, mention may be made of a method of transferring and curing the coating film in that state, and an embossing method of pressing the surface of the flat light diffusion plate with a roll or a stamp having a desired shape.

 [0047] Further, as a method of integrally forming the concavo-convex structure simultaneously with the formation of the light diffusing plate base, a casting method using a casting mold capable of forming a desired concavo-convex structure, a mold capable of forming a desired concavo-convex structure An injection molding method using can be mentioned. As described above, the injection molding method and the casting method have a simple process because the concavo-convex structure can be formed simultaneously with the formation of the light diffusion plate base. The casting method can be performed in a mold capable of forming a plate, or can be performed continuously while pouring the raw material between two continuous belts and driving the belt. In the injection molding method, in order to increase the shape transfer rate, it is preferable that the mold temperature at the time of injecting the resin is raised and the mold is rapidly cooled during cooling. Alternatively, an injection compression molding method may be applied in which the mold is expanded when the resin is injected and then the mold is closed.

 Next, the light transmission suppressing layer provided on the light incident surface of the light diffusing plate will be described.

FIG. 9 is a diagram for explaining a light transmission suppressing layer provided on the light incident surface. As shown in FIG. 9, in the direct backlight device 1 of the present embodiment, the light incident surface 30A has a position X projected from the central axis of an arbitrary linear light source 1 OA and the linear light source 1 OA. A light transmission suppressing layer 50 that suppresses light transmission is provided in a region between the position Y projected from the central axis of the adjacent linear light source 10B. In the present embodiment, the light transmission suppressing layer 50 is provided so that the light transmittance increases as the distance from the linear light source 10A located at the closest position increases. Note that the light transmittance in the present invention is the total light transmittance of light incident from the center of the light source toward the position of interest unless otherwise specified.

 [0050] The light transmission suppressing layer 50 is composed of a printed layer that reflects and / or absorbs incident light. By using a light transmission suppression layer as a printing layer, reflected light is scattered as shown in FIG. 10, and the amount of light at an intermediate position between adjacent linear light sources can be increased, thereby suppressing uneven brightness on the light emitting surface. You can power s. When only the uneven structure of the light diffusing plate with no printed layer is used, the light that exits the linear light source and enters the light diffusing plate perpendicularly as shown in Fig. 11 has a relatively narrow angular range due to the boundary condition of total reflection. Therefore, if the distance between the linear light sources is increased or the distance between the linear light sources and the light incident surface is reduced, the reflected light will not reach the middle of the linear light sources efficiently, and brightness unevenness will be suppressed. I ca n’t.

 In addition, if the number of linear light sources is reduced or the thickness of the backlight device is reduced, the position where the linear light source is projected becomes brighter than other parts under certain conditions. It is necessary to install the layer at the projection position of the linear light source to suppress uneven brightness. The explanation is given below.

 FIG. 12 is a diagram for explaining how the light incident on the light diffusion plate from the linear light source travels. FIG. 13 is a diagram for explaining the path of light reaching the concavo-convex structure from the linear light source. FIG. 14 is a diagram for explaining the relationship between the critical angle and the light incident perpendicularly in the concavo-convex structure. As shown in FIG. 13, the slope S1 of the concavo-convex structure of the light diffusing plate has a linear shape. There is light L1 that is perpendicularly incident on the light incident surface from the center of the light source and light L2 that is incident from the end of the linear light source. The angle between the vertical direction of the main surface of the light diffusing plate and the light L2 incident on the light diffusing plate is Θ d, and the angle between the vertical direction of the main surface of the light diffusing plate and the light L2 incident on the light diffusing plate is Θ e Then, the relationship of Eq. (1) is satisfied by the law of refraction.

Θ e = sin ^{_ 1} ((l / n) sin ed) (1)

 Furthermore, if the refractive index of the concavo-convex structure is n, the outer diameter of the linear light source is R (mm), and the distance between the center of the linear light source and the light incident surface is b (mm), Equation (1) is ).

Θ e = sin ^{_ 1} (R / 2nb)… (2)

On the other hand, the critical angle Θ g of the material constituting the concavo-convex structure is expressed by Equation (3). Θ g = sin ^{_ 1} (l / n) (3)

 Therefore, the arithmetic average inclination angle of the concavo-convex structure in the cross section parallel to the light source arrangement direction (left and right direction in FIGS. 12 to 14) and perpendicular to the main surface of the light diffusion plate is Θ (max), and the light L1 and the concavo-convex structure slope The angle 6f between the line 1401 indicating the critical angle Θg direction and the light L1 is expressed by equation (4).

 Θ f = 90-0 g- θ ΐι

= 90-sin ^{_ 1} (l / n)-(90-Θ (max))

 = θ (max) — sin (1 / n

 Here, when Θ e is large, that is, when the relationship of Equation (5) is satisfied, the linear light source force, etc., is emitted from the light diffusion plate without being reflected by the slope S 1 of the concavo-convex structure. become.

 Θ e> Θ f

 Substituting Equation 2 and Equation 4

 sin (R / 2nb)> Θ (max) — sin (\ / n)

sin ^{_ 1} (R / 2nb) + sin ^{_ 1} (l / n)> Θ (max)… (5)

[0052] In order to prevent the position where the linear light source is projected on the light emitting surface which is the light emitting surface of the light diffusing plate from becoming brighter than other portions, the light from the linear light source is used as the light diffusing plate. In order to reflect light with the uneven structure of this and return the light into the backlight device, it is necessary to totally reflect on the slope S 1. However, total reflection does not occur when the relationship of equation (5) is satisfied. Therefore, as shown in Fig. 17, it is necessary to suppress the transmission of light for the projected position of the linear light source by providing a printing layer in the range that includes the position where the linear light source is projected, thereby reducing uneven brightness. Can be suppressed. This effect becomes more prominent as the outer diameter R of the light source increases or the distance b force S between the light source center and the light incident surface decreases. The arithmetic average inclination angle can be obtained based on JIS B0601-1994. In this embodiment, it can be calculated using an ultra-deep shape measuring microscope VK-9500 (manufactured by Keyence Corporation).

[0053] Further, as described above, since the area where the Fresnel reflection at the upper part of the light source is small is higher than the other parts, the light transmission is suppressed at least in the area M where the brightness is high as shown in FIG.

 R

By providing the layer, luminance unevenness can be suppressed. That is, it is necessary to provide a light transmission suppression layer at least in the range where the incident angle to the light diffusion plate is 40 ° from directly above the light source. here The range M is the reference line (when the light source is a linear light source) or the reference point (the light source is a point light source).

R

 Is a region within a distance of M (mm). When the light source is a linear light source, the reference line is the position where the center line of the linear light source is projected onto the incident surface of the light diffusion plate. When the light source is a point light source, the reference point is the position where the center point of the point light source is projected onto the incident surface of the light diffusion plate. Here, M and b must satisfy the following formula (6).

[0054] In the range Μ, transmission of a portion including the light diffusion plate and the light transmission suppressing layer

 R

 The minimum value of the rate is at a position intermediate between the position where the center position of the linear light source is projected onto the light diffusion plate and the position where the center position of the adjacent linear light source is projected onto the light diffusion plate. The transmittance is 5% or more lower than the transmittance of the portion including the light diffusion plate and the light transmission suppressing layer.

 Here, the “transmittance of the portion including the light diffusion plate and the light transmission suppressing layer” means the transmittance of light that transmits both of the light diffusion plate at a location where the transmission suppressing layer is provided. It is the transmittance of light that is transmitted through the light diffusion plate only!

In the present application, the reference to the difference in transmittance such as “5% or more lower” indicates a difference between a certain value of the transmittance expressed in percentage and other values. For example, transmission at a certain point Ρ

 A

 If the transmission rate is 50% and the transmission at another point P is 55%, the transmission at point P

 B A

 The excess rate is 5% lower than the transmittance at point P.

 B

 [0056] In general, it is sufficient that there is at least a printed layer at a position where the light source is projected perpendicularly to the light diffusing plate. However, such a mode is not necessarily optimal for a light diffusing plate provided with an uneven structure. This will be described below.

FIG. 15 is a diagram showing a position where an image of the linear light source is observed after passing through the light diffusing plate, and FIG. 16 is a diagram for explaining a light path from the linear light source. . As shown in FIG. 15, the light emitted from the light source is refracted by the concavo-convex structure of the light incident surface and the light exit surface of the light diffusion plate, and an image is observed at a position different from the position directly above the light source. In other words, since the brightness is highest at a position slightly shifted immediately above the light source, it is necessary to block the light of this path with the printed layer, thereby suppressing uneven brightness. Also, the transmittance of the printed layer on this path It is preferable to make it lower than the minute (specifically, 2% or more lower). The position at which the image of the light source is observed is when the emitted light in FIG. 16 is perpendicular to the light diffusing plate, in other words, when θ 1 becomes equal to Θ (max). Here, from the law of refraction, the following formulas (7) and (8) hold.

 sin Θ l = nsin Θ k---(7)

 nsin Θ j = sin θ ί (8)

 Also, Θ k and Θ j have the following relationship.

 0k = Θ (max)-Θ] (9)

 Substituting Equations (7) and (9) into Equation (8),

 Θ i = sin (nX sin Θ j)

 = sin (n X sin (Θ (max) — Θ kj j

 = sin (nXsin (0 (max) — sin (1 / nXsin Θ 1)))

 Since Θ1 = Θ (max),

 Θ i = sin (nXsin (0 (max) —sin / nXsin0 (max)))) (10) Therefore, the position where the center of the linear light source is projected onto the light incident surface and the line on the light diffusion plate The distance O from the position on the light incident surface of the optical path where the image of the light source is observed is as follows.

 O = bXtan0i --- (ll)

 Substituting equation (10) into equation (11),

 0 = bXtan (sin (nXsin (0 (max) —sin (l / nXsin0 (max))))) where the center of the linear light source is projected onto the light incident surface, a position away from the distance O. This is the position NO of the path of the light emitted from the center of the light source and emitted parallel to the thickness direction of the light diffusion plate.

 Considering the outer diameter of the linear light source, at least the distance N (from the position at which the center of the linear light source is projected onto the light incident surface is used to block the image of the linear light source on the light diffusion plate with the printed layer. It is necessary to provide a printing layer in the range N where mm) satisfies the following relationship. Range N is shown in Figure 15.

 R R

In the example shown, the area is indicated by an arrow 1501.

bX tan (sin (nXsin (Θ max) — sin (1 / nXsin Θ (max))))) — R / 2 ^ N≤bXtan (sin (nXsin (Θ (max) — sin (1 / nXsin Θ (max ))))) + R / 2 [0058] Since the position NO is the brightest position on the diffusion plate, it is important to make the light transmittance at that portion the lowest. That is, the minimum transmittance TA of the portion including the light diffusion plate and the light transmission suppressing layer at the position NO is set, and the position between the position NO and the center of the light source is projected onto the light diffusion plate. When the average value TB of the transmittance of the portion including the light diffusing plate and the light transmission suppressing layer is set to the aspect satisfying TA <TB, it is possible to further suppress the luminance unevenness. is there.

 [0059] This print layer can be formed in a dot shape with, for example, white ink. When a dot-like printed layer is used in this way, the linear transmittance is controlled so that the light transmittance increases as the distance from the nearest linear light source 10 increases. As the distance from the light source 10 increases, the formation area of the printed layer decreases. The reduction in the formation area means that the number and area of dot-like print layers per unit area are reduced. As a method for reducing the formation area of the print layer, the print layer may be continuously reduced or gradually reduced as the distance from the linear light source is increased.

 [0060] Specifically, as shown in FIG. 9, the position X projected from the central axis of the linear light source 10A, and from this position X, the central axis of the linear light source 1 OA and the central axis of the linear light source 10B Divide the area between the position Z and the half of the distance between them at equal intervals (shown in Fig. 9 when they are divided into 10 equal parts), and each of these equally divided areas from the left side of Figure 9 In order, the areas are A1 to A10. Formed to gradually reduce the print layer formation range (unit:%) per unit area from the area A1 closest to the central axis of the linear light source 10A to the area A10 farthest from the linear light source 10A It has been. The formation range of the printing layer in each region is, for example, region A1: 90%, region A2: 87%, region A3: 72%, region A4: 50%, region A5: 35%, region A6: 19%, region A7: 11%, Area A8: 7%, Area A9: 3%, Area A10: 0%. Although not shown in FIG. 9, a similar print layer that is symmetric about Z can be provided in the region from position Y to position Z.

[0061] Further, in the light incident surface 30A, the center line average roughness Ra at the position where the print layer is formed is 0.005 to 111 to 5 to 111. By setting it as such a range, the light which injected into the printing layer can be further scattered, and the brightness nonuniformity of a light emission surface can further be reduced. Ra here is the value measured along various directions in the plane, similar to Ra on the light exit surface 30B. The maximum value can be set.

 According to the present embodiment, the linear light source 10 and the light diffusing plate 30 are arranged so as to satisfy the relationship (1), and from the linear light source 10 closest to the light incident surface 30A of the light diffusing plate 30. Distance A light transmission suppression layer 50 is provided to control the light transmittance to increase as the distance from the closest linear light source 10 increases, and the light exit surface 30B has a center line average. Ra (max), which is the maximum value of roughness Ra, is 3 μm to 1,000 μm, and the uneven structure 40 having a thickness of 1,000 μm is formed. Therefore, in the region directly above the linear light source 10, the light transmission suppressing layer 50 Since the transmittance of incident light can be suppressed, the power consumption can be suppressed and the luminance uniformity of the light emitting surface can be increased.

 [0063] Further, since the light transmission suppressing layer 50 is formed of a printing layer, the light transmission suppressing layer 50 can be formed by a simple operation. At this time, since the portion where the printing layer is provided in the light diffusion plate 30 is slightly roughened, the light scattering effect can be enhanced and the luminance uniformity of the light emitting surface can be further improved. Further, by using a resin having a water absorption of 0.25% or less as the material of the light diffusing plate 30, it is possible to suppress the displacement of the printed layer provided on the light incident surface 30A of the light diffusing plate 30, The optical function can be fully demonstrated.

 <Second Embodiment>

 Next, a direct type backlight device according to a second embodiment of the present invention will be described. This embodiment is different from the first embodiment in the configuration of the concavo-convex structure. For this reason, in this embodiment, this difference will be mainly described, and the description of the same or similar components as those in the above embodiment will be omitted or simplified. FIG. 19 is a longitudinal sectional view schematically showing the direct type backlight device according to the present embodiment. The direct type backlight device 2 includes a light diffusing plate 230 having a light incident surface 230A and a light emitting surface 230B. On the light emitting surface 230B, a concavo-convex concavo-convex structure 240 in which a plurality of linear prisms 241 having a polygonal cross section are arranged substantially in parallel is formed.

[0065] The linear prism 241 can be a linear prism having a triangular cross-sectional shape (sometimes referred to as a triangular prism in this specification). It is possible to increase the apex angle of the triangle constituting the triangular prism from 40 ° to 170 °, and the distance between adjacent triangular prisms in the same plane to be 20 111 to 700 か 111. By setting the apex angle and spacing as described above, the luminance unevenness of the light emitting surface can be reduced. It can be suppressed sufficiently.

[0066] Here, as the plurality of triangular prisms constituting the concavo-convex structure, it is common to use all of the same shape (including those that can be seen), and it is also possible to use a plurality of types of force. .

 [0067] Examples of the configuration including a plurality of types of triangular prisms include the following configurations. For example, as shown in FIG. 20, the triangular prism is formed so that the angles formed by two inclined surfaces constituting the triangle and the surface perpendicular to the thickness direction of the light diffusion plate are equal to each other. Between a specific point P of the light diffuser and a point Q that is a predetermined distance away from the point P in the short direction of the triangular prism, it decreases continuously or intermittently as the distance from the points P and Q increases. You may form so that it may become. At this time, it is preferable to arrange a linear light source at a position where the points P and Q are projected. In this specification, “equal angle” means that the difference is within 1 degree.

 [0068] Further, the triangular prism has a cross-sectional shape that is axisymmetric with respect to a plane including the thickness direction of the light diffusion plate and the longitudinal direction of the triangular prism, and the concavo-convex structure includes a plurality of types of triangular prisms having different shapes. It is good also as such a structure. At this time, it is preferable that all of these types of triangular prisms are included within the range of the width of the linear light source along the direction perpendicular to the longitudinal direction of the triangular prisms.

 [0069] The linear prism may have a polygonal cross section other than a triangular cross section. Examples of polygons include pentagons and heptagons. For example, as shown in FIG. 21, the linear prism is formed in a polygonal cross section including at least four planes, and at least two of the four planes and the other two planes A cross-sectional pentagonal configuration that is inclined in opposite directions with respect to a plane including the thickness direction of the light diffusion plate and the longitudinal direction of the linear prism can be employed.

 [0070] According to the direct type backlight device of the present embodiment, the same effect as in the first embodiment can be obtained with the force S.

 <Third Embodiment>

Next, a direct type backlight device according to a third embodiment of the present invention will be described. This embodiment is different from the first embodiment in that the light source is a point light source and the structure of the concavo-convex structure. The structure of the light transmission suppressing layer is different. For this reason, in this embodiment, it demonstrates centering on these differences. FIG. 22 is a longitudinal sectional view schematically showing a direct type backlight device according to this embodiment. As shown in FIG. 22, the direct type backlight device 3 according to this embodiment includes a plurality of point light sources 310 and a light diffusion plate 330 having a light incident surface 330A and a light emitting surface 330B. Further, the light emitting surface 330B is formed with a concavo-convex structure 340 in which a plurality of structural units 341 are arranged. The light incident surface 330A is provided with a light transmission suppressing layer 350 formed of a printing layer.

[0072] (Light diffusion plate)

 As the structural unit 341 constituting the concavo-convex structure 340, a structure having a shape in which the inclined side surface including the pyramid and the truncated pyramid has three or more inclined side surfaces, a hemisphere and a hemispherical sphere are used as a dot-like protrusion or a depression. Examples thereof include hemispherical structures. Such a structural unit is preferably a protrusion or depression that narrows the light emission direction.

 [0073] As a specific shape of the structural unit 341, for example, as a structure having a shape having three or more inclined side surfaces, a pyramid shape, a truncated pyramid shape, and a lenticular stripe IJ or a linear prism shape are used. For example, the shape can be a V-shaped or U-shaped cut. Examples of the pyramid include a triangular pyramid, a quadrangular pyramid, a pentagonal pyramid, and a hexagonal pyramid. Examples of the pyramid include a triangular pyramid, a quadrangular pyramid, a pentagonal pyramid, and a hexagonal pyramid. Further, for example, the hemispherical structure may be a dome shape such as a hemisphere or a semi-elliptical sphere, or a dome shape such as a polygonal hemisphere or a semi-elliptical sphere. FIG. 22 shows a case where a plurality of hemispherical structures are arranged.

 [0074] The plurality of structural units 341 constituting the concavo-convex structure 340 may be composed of only one type, or may be composed of a combination of a plurality of types.

In the present embodiment, it is preferable to periodically and regularly arrange a group including the structural unit 341 or the plurality of structural units 341 in order to improve luminance uniformity. The period of these structural units or group is more preferably 20 m or more and 700 m or less, and even more preferably 40 m or more and 400 m or less. When the period is within the above range, it can be easily formed and the occurrence of uneven brightness can be suppressed. [0076] (Point light source)

 The point light source 310 has a point-like light emitting portion, and can raise the power of raising an LED or a laser, for example. Some LEDs emit various colors such as white, red (R), green (G), and blue (B). In this embodiment, (1) using only a white LED as a point light source, (2) a combination of RGB three primary colors, and (3) a combination of RGB three primary colors with an intermediate or white color, etc. Can be selected and used as appropriate in consideration of balance

[0077] In the combination of the three primary colors of RGB ((2) and (3)), (A) at least one red LED, green LED, and blue LED are placed close to each other, and each color is mixed and white And (B) Red LED, Green LED, and Blue LED are appropriately arranged. In the case of (A), a combination of LEDs arranged close together is regarded as one point light source.

 In this embodiment, a value obtained by measuring the dimension of the point light source in the short side direction of the light diffusing plate is set as the outer diameter R of the point light source 310. In addition, the range N represented by the formula (12) is a short length of the light diffusing plate.

 R

 In addition to having a width R in the side direction, the long side direction has the same width as the value measured in the short side direction of the light diffusing plate.

[0079] In the present embodiment, the plurality of point light sources 310 are discretely arranged. As the arrangement of the point light sources, for example, the point light sources are arranged in a straight line; as shown in FIG. 23, they are arranged at predetermined intervals along the vertical and horizontal directions of the direct type knock light device. As shown in FIG. 24, the point light sources P1 to P4 in FIG. 23 are removed, that is, the point light sources 310 are arranged at each of the four vertices of the rectangle, and the diagonal lines of the rectangle are further arranged. Such as a point light source 310 arranged at the intersection; as shown in FIG. 25, a point light source 310 arranged at each vertex of a honeycomb structure in which regular hexagons are continuously formed; That's the power S.

[0080] In this embodiment, the average distance a (mm) and the average distance b (mm) satisfy the relationship of 0.5≤a / b≤15.0, and It is preferable to satisfy 6≤a / b≤13.0. By satisfying such a relationship, the amount of point light sources used can be reduced and the power consumption of the device can be suppressed. [0081] Here, the average distance between the centers of the point light sources may be uniform at all locations or may be partially changed. The case of partial change is, for example, the case where the average distance between the centers of the point light sources is narrowed at the center of the direct type backlight device.

 Here, the adjacent point light sources are two point light sources in a state where no other point light sources exist on the line connecting the centers of the two point light sources. It is. The average distance between the centers of adjacent point light sources is a point light source L1 and a plurality of point light sources L2 to Ln (n is an integer of 4 or more) adjacent to the point light source L1. Three points are selected in order from the shortest distance between the centers of the point light source L1 and the other point light sources L2 to Ln, and these three numerical values are averaged.

 [0083] When the average distance between the centers of the point light sources partially changes, a direct type backlight device is configured as follows. In other words, at a certain location, the average between the centers of adjacent point light sources by selecting three point light sources from the closest distance among the point light sources and the point light sources adjacent to this point light source. Find the distance. Then, the area surrounded by these four point light sources whose average distance was measured was projected onto the light incident surface of the light diffusing plate, so that the relationship described later was satisfied based on the obtained average distance. Design the diffuser

[0084] In the case of the combination of the above three primary colors RGB (A), the center of the point light source regarded as one is identified based on the centers of the LEDs arranged close to each other, and Based on this, the distance between adjacent point light sources is obtained. In the case of the configuration (B) combining the above three primary colors of RGB, the distance between adjacent point light sources is determined according to the above definition regardless of the color.

 [0085] Next, the light transmission suppressing layer 350 will be described.

FIG. 26 is a diagram for explaining the light transmission suppressing layer 350 provided on the light incident surface 330A. As shown in FIG. 26, in the direct type backlight device 3 of the present embodiment, the light incident surface 330A is adjacent to the position S where the central axis of an arbitrary point light source 310A is projected and the point light source 310A. A light transmission suppression layer 350 is provided in a region between the point T and the position T where the central axis of the point light source 310B is projected. The light transmission suppression layer 350 is the closest point light source 310A It is provided so that the light transmittance increases as the distance of the force increases.

Specifically, for example, as shown in FIG. 26, when a plurality of point light sources 310 are arranged in a square lattice, first, along the vertical and horizontal directions of the square lattice. Point-shaped light source 3 Axis SI, S2 passing through the center of 10A and point SI, T2 passing through the center of point-shaped light source 310B laterally adjacent to point-shaped light source 310A and point-wise light source 310A Consider the axes S2 and T1 that pass through the center of the point light source 310C. Then, consider an axis TC indicating an intermediate position between the axes T1 and T2, and an axis SC indicating an intermediate position between the axes S1 and S2. For example, in the point light source 310A, the region on the right side of the point light source 310A is divided into, for example, five equal parts between the axis T1 and the axis TC, and similarly, the region below the point light source 310A. For example, the axis S 1 and the axis SC are divided into five equal parts. Further, although not shown in the figure, the left and upper regions of the point light source 310A are also divided into, for example, five equal parts. The five equally-divided lines are connected to each other, and the formed rectangular region is defined as regions A11 to A15 in order from the side closer to the point light source 310A. From the area Al l closest to the center of the point light source 310A to the area A15 farthest from the point light source 310A, the formation range (unit:%) of the printed layer per unit area is gradually reduced. . For example, the printing layer formation range in each region is, for example, region Al 1: 90%, region A12: 75%, region A13: 30%, region A14: 10%, region A15: 0% S can.

[0087] As another method, the point light source passes through the midpoint of the line connecting the center position of a point light source LSI and the center position of the point light source LS 2 adjacent to the point light source LSI. The concentric circle between the circle centered at the center of LS 1 and the center of the point light source LSI is divided into five equal parts (in this case, each of the five equal areas is closer to the center of the point light source LSI. From B1 to B15) and from B11 to B15, the print layer formation range (unit:%) per unit area should be reduced step by step. For example, the printing layer formation range in each region is, for example, region B11: 90%, region B12: 75%, region B13: 30%, region B14: 10%, region B15: 0%, force S it can.

[0088] In this way, a predetermined print layer is formed in a direction with respect to one point light source among a plurality of point light sources adjacent to a certain point light source. Then, the printed layer is formed on the other point light sources among the plurality of adjacent point light sources in the same manner as described above. As described above, the light transmission suppressing layer 350 is formed. [0089] According to the direct type backlight device of the present embodiment, it is possible to achieve the same effect S as in the first embodiment. In addition, by using an LED, which is a point light source, as a light source, it is possible to expand the color gamut compared to using a linear light source.

 [0090] <Modification>

 The present invention is not limited to the above-described embodiment, and can be modified within the scope of the claims of the present application and the equivalent scope thereof.

 For example, in the above-described embodiment, the light transmission suppression layer is provided so that the light transmittance increases as the distance from the light source increases (such an arrangement is referred to as configuration A). In particular, it does not have to be so. For example, there may be a portion that does not partially satisfy the relational configuration A. At this time, other methods for forming the print layer so as to satisfy the above-mentioned configuration A include, for example, a configuration in which the thickness of the print layer is reduced as the distance from the light source increases, and the ink concentration of the print layer is reduced! / , The ability to list things that use things. In the above-described embodiment, as the distance from the light source increases, the force configured to increase the light transmittance stepwise may be configured to increase continuously.

 In the embodiment, white ink is used as the ink constituting the printing layer. However, white pigment and white dye can be used as such white ink. A transparent pigment can also be used as the ink constituting the printing layer.

 In the embodiment, the light transmission suppressing layer is provided on the light incident surface of the light diffusing plate. However, the light transmission suppressing layer may be provided on the light emitting surface, or on both the light incident surface and the light emitting surface. Also good.

 In the embodiment, the light transmission suppressing layer is provided on the entire surface of one surface of the light diffusion plate.

 1S It is not always necessary to provide it on the entire surface, but it should be provided at least directly above the light source.

In the embodiment, the concavo-convex structure is provided on the entire surface of the light emitting surface of the light diffusing plate. However, the light emitting surface and the light incident surface are not necessarily provided on the entire surface of the light emitting surface. It may be formed at least at a part of at least one of the surfaces. Here, at least a part of the portion means that the area where the concavo-convex structure is formed is 30% or more of the area of the light emitting surface. In the direct type backlight device, in order to further improve the luminance and the luminance uniformity, for example, an optical member such as a diffusion sheet or a prism sheet can be disposed downstream of the light exit surface. Further, for the purpose of further improving the luminance of the light emitting surface, for example, a reflective polarizer shown below can be disposed downstream of the light emitting surface.

 [0096] As the reflective polarizer, a reflective polarizer that utilizes the difference in reflectance of the polarization component depending on the Brewster angle (for example, the one described in JP-A-6-508449); selection by cholesteric liquid crystal Reflective polarizer utilizing reflection characteristics; specifically, a cholesteric liquid crystal force, a laminate of a film and a quarter-wave plate (for example, those described in JP-A-3-45906); Reflective polarizer with a metal linear pattern (for example, the one described in JP-A-2-308106); at least two kinds of polymer films are laminated, and anisotropy of reflectance due to refractive index anisotropy Reflective polarizers that utilize properties (for example, those described in Japanese Patent Publication No. 9 506837); having a sea-island structure formed of at least two kinds of polymers in a polymer film, and having an anisotropic refractive index Reflective polarizer utilizing the anisotropy of reflectivity due to the nature ( For example, those described in US Pat. No. 5,825,543); a reflective polarizer in which particles are dispersed in a polymer film and the anisotropy of reflectance due to refractive index anisotropy is utilized (for example, (Refer to JP-A-11-509014); a reflective polarizer that utilizes anisotropy of reflectance based on the scattering ability difference depending on size, in which inorganic particles are dispersed in a polymer film (for example, The ones described in Kaihei 9-297204) can be used.

 Example

 Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. The present invention is not limited to these examples. Parts and% are based on weight unless otherwise specified.

 [0098] (Production Example 1: Light diffusion plate pellet P1)

99.7 parts of a resin having an alicyclic structure as a transparent resin (Nippon Zeon Co., Ltd., ZENOA 1060R, water absorption 0.01%) and a polysiloxane polymer having an average particle diameter of 2 m as a light diffusing agent 0.3 parts of fine particles made of a cross-linked product were mixed, kneaded with a twin screw extruder, extruded into a strand, and cut with a pelletizer to produce a light diffusion plate pellet P1. From this light diffusion plate pellet P1, using an injection molding machine (clamping force lOOOkN), the thickness is 2m A test plate of 100 mm × 50 mm was formed at m. The total light spring transmittance and haze of the test plate were measured using an integrating sphere color difference turbidimeter in accordance with JIS K7361-liJIS K7136. The total light transmittance was 85%, and-^ z was 99%.

 [0099] (Production Example 2: Pellet P2 for light diffusion plate)

 Mixing 99.9 parts of resin having the alicyclic structure as a transparent resin (Nippon Zeon Co., Ltd., ZENOA 1060R) and 0.1 part of fine particles of a cross-linked product of the polysiloxane polymer as a light diffusing agent Then, they were kneaded with a twin screw extruder, extruded into a strand shape, and cut with a pelletizer to produce a light diffusion plate pellet P2. From this light diffusion plate pellet P2, a 100 mm × 50 mm test plate having a smooth thickness of 2 mm on both sides was formed using the injection molding machine. When the total light transmittance and haze of this test plate were measured in the same manner as described above, the total light transmittance was 94%, and-^ z was 89%.

 [0100] (Production Example 3: Light diffusion plate pellet P3)

 97.5 parts of resin having the alicyclic structure as a transparent resin (Nippon ZEON Co., Ltd., ZENOOR 1060R) and 2.5 parts of fine particles of a cross-linked product of the polysiloxane polymer as a light diffusing agent are mixed. The mixture was then kneaded with a twin screw extruder, extruded into a strand, and cut with a pelletizer to produce a light diffusion plate pellet P3. From this light diffusion plate pellet P3, a test plate having a smooth thickness of 2 mm and a thickness of 2 mm and a thickness of 100 mm × 50 mm was formed using the injection molding machine. When the total light transmittance and haze of this test plate were measured in the same manner as described above, the total light transmittance was 55%, and-^ z was 99%.

 [0101] (Production Example 4: Light diffusion plate pellet P4)

 A biaxial extruder is prepared by mixing 99.9 parts of polystyrene (PS Japan Co., Ltd., G9504) as a transparent resin and 0.1 part of fine particles of a cross-linked product of the polysiloxane polymer as a light diffusing agent. And then extruded into a strand shape and cut with a pelletizer to produce a light diffusion plate pellet P4. From this light diffusion plate pellet P4, a 100 mm × 50 mm test plate having a smooth thickness of 2 mm on both sides was molded using the injection molding machine. When the total light transmittance and pitch of this test plate were measured in the same manner as described above, the total light transmittance was 86%, and-^ z was 99%.

[0102] (Production Example 5: Stamper S1) A nickel-phosphorus electroless plating with a thickness of 100 m is applied to the entire surface of a stainless steel SUS430 (hereinafter sometimes referred to as a “metal member”) with dimensions of 800 mm x 500 mm and a thickness of 100 mm. Using a circular diamond cutting tool, with a width of 70 m, a depth of 22.3 m, and a pitch of 70 111, parallel to the 800 mm (long) side on the nickel-phosphorus electroless plating surface A groove with a cross-sectional shape of a part of a circle with a radius of 38.6 m (a part slightly smaller than a semicircle) was formed by cutting.

 [0103] (Production Example 6: Stamper S2)

 A nickel phosphorous electroless plating with a thickness of 100 μm is applied to the entire surface of a metal member having the same dimensions as described above, and a diamond cutting tool with a vertex angle of 100 degrees and a triangular cross section is used, and the nickel phosphorous electroless plating surface is long. In parallel with the 800mm (long) side, a prism array with a sawtooth-like cross section with a width of 70 m, height of 29.4 ^ 111, pitch of 70 m, and apex angle of 100 degrees was formed by cutting. .

 [0104] (Production Example 7: Stamper S3)

 Using a focused ion beam device (manufactured by Hitachi High-Technologies Corporation) with a diamond cutting tool with an apex angle of 115 degrees, a cutting tool TX having a cross-sectional shape shown in FIG. 27 was created. Next, a nickel phosphorus electroless plating having a thickness of 100 [I m] was applied to the entire surface of the metal member having the same dimensions as described above. On the nickel phosphorus electroless plating surface, the cutting tool TX is used to extend a flat fi on the longitudinal side, width 70 mm 111, height 22.3 mm, pitch 70 mm 111, radius 38.6 mm The shape of a part of the cylinder of m (semi-cylindrical shape, but the cross section is slightly smaller than the semicircle) was formed by cutting.

 [0105] Furthermore, using the same cutting tool TX, cutting was performed in a direction perpendicular to the longitudinal direction of the shape (short direction) with a width of 70 μm, a height of 22.3 m, and a pitch of 70 μm. Went. In this manner, as shown in FIG. 28, a concavo-convex structure surface was created in which a plurality of structures whose periodic pyramid-shaped inclined side surfaces bulge outward were periodically arranged. Next, nickel is formed to a thickness of 500 μm on the nickel phosphorous electroless plating surface of the metal member on which the uneven structure surface is formed by electroplating using a nickel sulfamate aqueous solution. The stamper S3 was obtained by peeling off from the surface.

[0106] (Production Example 8: Stamper S ⁴ ) Photoresist (Nippon Zeon Co., Ltd., ZPP1700P G-30) is applied to the entire surface of a glass substrate with a diameter of 900 mm, exposed to light, and developed to form a cylindrical convex part with a radius of 31 m and a height of 30 m. They were formed so as to be arranged in a square lattice pattern. The glass substrate provided with the cylindrical protrusions was post-beta at 140 ° C. to deform the shape of the protrusions to form a substantially hemispherical protrusion having a bottom radius of 35 m and a height of 35 m. Next, electroless nickel plating was performed on the substantially hemispherical convex portions provided on the glass substrate. Next, nickel was formed to a thickness of 500 μm on the electrode by using an aqueous solution of nickel sulfamate, and the formed product was peeled off from the glass substrate provided with the projections, and the dimensions were 800 mm × 500 mm. The stamper S4 was obtained.

[0107] (Production Example 9: Stamper S5)

 A nickel phosphorus electroless plating with a thickness of 100 μm was applied to the entire surface of a metal member with dimensions of 800 mm x 500 mm and a thickness of 100 mm, and a nickel phosphorus electroless plating was performed using a diamond cutting tool with a vertex angle of 130 degrees and a triangular cross section. Cut a prism row with a sawtooth-shaped section with a width of 100 111, a height of 23.3 ^ 111, a pitch of 100 m, and an apex angle of 130 degrees in a direction parallel to the 800 mm long side. Formed by processing.

[0108] (Production Example 10: Stamper S6)

 A nickel phosphorus electroless plating with a thickness of 100 μm was applied to the entire surface of a metal member with dimensions of 800 mm x 500 mm and a thickness of 100 mm, and a nickel phosphorus electroless plating was performed using a diamond cutting tool with a vertex angle of 130 degrees and a triangular cross section. Cut a prism row with a sawtooth-shaped section with a width of 100 111, a height of 23.3 ^ 111, a pitch of 100 m, and an apex angle of 130 degrees in a direction parallel to the 800 mm long side. Formed by processing. Here, the prism rows were formed so that four strip-shaped regions with a width of 30 mm were formed at intervals of 90 mm, rather than being formed on the entire plating surface. In other words, the prism row was formed between the 30 mm wide regions where the prism rows were formed, and an area with a width of 60 mm was provided.

[0109] (Production Example 11: Stamper S7)

Nickel-Norelin electroless plating with a thickness of 100 μm was applied to the entire surface of a metal member with dimensions of 800 mm X 500 mm and thickness 10 mm, and nickel-phosphorus electroless was performed using a diamond cutting tool with a radius of 115 111 and a semicircular cross-section. Parallel to the length of 800mm (longitudinal) side In the direction, a groove having a width of 150 m, a depth of 50 m, a pitch of 150 111, and a part of a circle with a radius of 115 m (a portion smaller than a semicircle) was formed by cutting.

 [0110] (Production Example 12: Stamper S8)

 A nickel lurin electroless plating with a thickness of 100 μm was applied to the entire surface of a metal member with dimensions of 800 mm x 500 mm and a thickness of 100 mm, and using a diamond cutting tool with a vertex angle of 40 degrees and a triangular cross section, a nickel phosphorus electroless plating was performed. Cutting a prism row with a sawtooth-shaped cross section with a width of 100 111, a height of 68.7 ^ 111, a pitch of 50 m, and an apex angle of 40 degrees in a direction parallel to the 800 mm long side Formed by processing.

 <Example 1>

 A reflector sheet (RF188 made by Gidden Co., Ltd.) is attached to the inside of a milky white plastic case with an inner dimension width of 700 mm, depth of 400 mm, and depth of 20 mm. 12 cold-cathode tubes 3mm in diameter and 430mm in length, 5mm apart, placed so that the distance a between the centers of the cold-cathode tubes is 33mm, the vicinity of the electrodes is fixed with silicone sealant, and an inverter is installed . In the backlight of this design, the distance b between the cold cathode tube center and the light incident surface of the light diffusing plate (the surface on the cold cathode tube side) was 15 mm. For this reason, a / b was 2.20.

 [0112] Next, a mold having the stamper S 1 obtained in Production Example 5 was prepared, and using this and the light diffusion plate pellet P1 obtained in Production Example 1, an injection molding machine (clamping force) 4, 410 kN), and was molded at a cylinder temperature of 280 ° C and a mold temperature of 85 ° C. As a result, a light with a thickness of 730mm x 430mm with a thickness of 2mm is provided on one side, which has a concavo-convex structure in which a plurality of substantially semi-cylindrical lenticulars are arranged in parallel to extend in the longitudinal direction, and the other side is a flat surface. Diffusion plate D1 was obtained. The one surface on which the concavo-convex structure was formed was measured for the centerline average roughness Ra along various directions in the surface using an ultra-deep microscope. The center line average roughness Ra measured in the direction) was the maximum value, and the maximum value Ra (max) was 5. O ^ m. Further, when the centerline average roughness Ra was measured in the same manner for the other surface, which was a flat surface, the Ra was constant regardless of the direction in the surface, and was 0.6 μm. .

[0113] Next, white ink is printed on the other surface of the light diffusion plate D1 where the uneven structure is not formed. Thus, the printed layer was formed so that the formation range decreased with increasing distance from the central axis of the cold cathode tube. Specifically, as shown in FIG. 9, a position X where the central axis of the linear light source 10A is projected, and a distance between the central axis of the linear light source 10A and the central axis of the linear light source 10B from this position X. The area between the half position Z is divided into 10 at equal intervals, and these equally divided areas are designated as areas A1 to A10 in order from the left side of FIG. The printing layer formation range (unit:%) per unit area from the area A1 closest to the central axis of the linear light source 10A to the area A10 farthest from the linear light source 10A is as follows. It was formed so as to reduce it. The formation range of the printed layer in each area is as follows: Area A1: 90%, Area A2: 87%, Area A3: 72%, Area A4: 50%, Area A5: 35%, Area A6: 19%, Area A7: 11%, Area A8: 7%, Area A9: 3%, Area A10: 0%.

[0114] Such a light diffusing plate D1 was arranged on the plastic case so that the concavo-convex structure was the light emitting surface on the opposite side of the cold cathode tube. Furthermore, a diffusion sheet (manufactured by Kimoto Co., Ltd., 188GM3) is installed on top of this, and a prism sheet (manufactured by Sumitomo 3EM Co., Ltd., BEF 3) is installed thereon, and the longitudinal direction of the prism rows of the prism sheet is the cold cathode tube. It was installed so as to be on the side far from the light diffusion plate. On top of that, a direct-type backlight device was fabricated by installing a reflective polarizer (DBEF-D, manufactured by Sumitomo 3M Co., Ltd.) using birefringence.

Yes

 [0115] In the backlight before installing the optical sheet, the total light transmittance directly above the light source is 60%, the total light transmittance of light incident from the center of the light source toward the position NO is 64%, and the adjacent light source The total light transmittance of the light incident on the projected position of the intermediate position was 72%.

[0116] Next, a tube current of 5 mA was applied to the manufactured direct type backlight to light the cold cathode tube, and the two-dimensional color distribution measurement device was used to equidistantly equip the short line direction on the center line of the light diffusion plate. The luminance in the front direction at 100 points was measured, and an average luminance value La and luminance unevenness Lu were obtained according to the following formulas 1 and 2. In this example, the average luminance was 4690 cd / m ² and the luminance unevenness was 0.8%.

 Luminance average value La = (Ll + L2) / 2 (Formula 1)

 Luminance unevenness Lu = ((Ll— L2) / La) X 100 (Equation 2)

L1: Average brightness maximum value directly above the cold cathode fluorescent lamps L2: Average brightness minimum value sandwiched between brightness maximum values

 Note that the luminance unevenness is an index indicating the uniformity of luminance, and the value increases when the luminance unevenness is bad.

[0117] <Example 2>

The 16 cold cathode tubes are arranged such that the distance a between the centers of the cold cathode tubes is 23 mm, and the distance b between the center of the cold cathode tube and the light incident surface of the light diffusion plate is 8 mm. The same operation as in Example 1 was conducted except that the current was 4 mA. At this time, a / b was 2.88. In this example, the luminance average value was 5350 cd / m ² and the luminance unevenness was 0.95%.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 60%, and the total light transmittance of light incident from the center of the light source toward the position NO is 64%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 74%.

[0118] <Example 3>

Ten cold cathode tubes are arranged such that the distance a between the centers of the cold cathode tubes is 40 mm, and the distance b between the center of the cold cathode tube and the light incident surface of the light diffusion plate is 18 mm. The same operation as in Example 1 was conducted except that the current was 6 mA. At this time, a / b was 2.22. In this example, the average luminance was 4086 cd / m ² and the luminance unevenness was 0.90%.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 60%, and the total light transmittance of light incident from the center of the light source toward the position NO is 64%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 72%.

<Example 4>

Prepare a mold with the stamper S2 obtained in Production Example 6 and use the light diffusion plate pellet P1 obtained in Production Example 1 and use an injection molding machine (clamping force 4, 410 kN). Molded at a cylinder temperature of 280 degrees and a mold temperature of 85 degrees. As a result, one surface has a concavo-convex structure in which a plurality of linear prisms (triangular prisms) having a triangular cross section are arranged in parallel so as to extend in the longitudinal direction, and the other surface is a flat surface. The light diffusing plate D2 of 730mm x 430mm was obtained. When the center line average roughness Ra was measured along various directions in the surface of the one surface on which the concavo-convex structure was formed using an ultra-deep microscope, the short direction (430 mm) of the light diffusing plate D2 was measured. Centerline average roughness Ra measured in the The maximum value Ra (max) was 6.6 m. Also, when the centerline average roughness Ra was measured in the same manner for the other flat surface, Ra was constant regardless of the direction in the surface, and was 0.6 m.

[0120] Further, the eight cold cathode tubes are arranged such that the distance a between the centers of the cold cathode tubes is 50 mm, and the distance b between the center of the cold cathode tubes and the light incident surface of the light diffusion plate is 23 mm. In the same manner as in Example 1 except that the applied current was 8 mA. At this time, a / b was 2.17. In this example, the luminance average value was 4067 cd / m ² and the luminance unevenness was 0.65%. In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 60%, and the total light transmittance of light incident from the center of the light source toward the position NO is 64%. The total light transmittance of light incident on the projected position of the intermediate position of the light source was 77%.

[0121] <Example 5>

Example 4 was the same as Example 4 except that the light diffusion plate D2 was changed to the light diffusion plate D1. In this example, the luminance average value was 3864 cd / m ² and the luminance unevenness was 0.75%.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 60%, and the total light transmittance of light incident from the center of the light source toward the position NO is 64%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 72%.

[0122] <Example 6>

 Place a 0.5mm aluminum plate for heat dissipation on the bottom of a milky white plastic case with an inner width of 700mm, a depth of 400mm, and a depth of 20mm, and then apply a reflective sheet (E-60L, manufactured by Toray Industries, Inc.) on it. And made a reflector. Next, a white tip type LED (made by Nichia Corporation, NSSM025T: size: 3.0 X 3.0 X 1.8 mm), which is a point light source, is vertically and horizontally centered on the bottom of the reflector. They were both installed in a 26 mm square grid pattern (as shown in Fig. 23) and wired so that a direct current could be supplied to the electrodes. In the backlight of this design, the distance b between the LED center and the light incident surface of the light diffusing plate was 19.1 mm. For this reason, a / b was 1.36.

[0123] An injection molding machine (clamping force 4, 410 kN) was prepared by using the mold with the stamper S4 obtained in Production Example 8 and the light diffusion plate pellet P2 obtained in Production Example 2. Was used and molded at a cylinder temperature of 280 degrees and a mold temperature of 85 degrees. This will allow you to A light diffusing plate D3 having a thickness of 2 mm and a thickness of 730 mm × 430 mm having a concavo-convex structure in which a plurality of shaped structures are periodically arranged in a square lattice pattern and the other surface being a flat surface was obtained. When the average roughness Ra of the one surface on which the concavo-convex structure was formed was measured along various directions in the surface using an ultra-deep microscope, it passed through the apex portion of the structure. The centerline average roughness Ra measured in the direction was the maximum value, and the maximum value Ra (max) was 8.5 111. Further, when the centerline average roughness Ra was measured in the same manner for the other surface, which was a flat surface, Ra was constant regardless of the direction in the surface and was 0.6 m.

[0124] Next, white ink is printed on the other surface of the light diffusing plate D3 where the concavo-convex structure is not formed so that the formation range decreases as the distance from the center of the LED increases. A layer was formed. Specifically, as shown in Fig. 26, a certain rectangular LED was selected, and a total of four line segments were created by connecting the center positions of adjacent LEDs in the vertical and horizontal directions of this LED. . Next, a rectangular line connecting the middle positions of these line segments was set. The area between this rectangular line and the rectangular LED is divided into 5 equal parts along the direction away from the center of the LED, as shown in Fig. 26, and these areas are divided into areas Al 1 to A15. From the region Al l closest to the center of the LED to the region A15 farthest from the LED, the formation range (unit:%) of the printed layer per unit area was gradually reduced. Specifically, region Al 1: 90%, region A12: 75%, region A13: 30%, region A14: 10%, region A1 5: 0%.

 [0125] Such a light diffusing plate D3 was arranged on the plastic case so as to be a light emitting surface on the opposite side of the concavo-convex structural force SLED. Furthermore, a diffusion sheet (manufactured by Kimoto Co., Ltd., 1 88GM3) is installed on top of this, and a prism sheet (manufactured by Sumitomo 3EM Co., Ltd., BEF3) is installed on the diffusion sheet. It was installed so that it was parallel to the long side direction of and the side far from the light diffusion plate. On top of that, a direct-type backlight device was fabricated by installing a reflective polarizer (DBEF D, manufactured by Sumitomo 3EM Co., Ltd.) using birefringence.

[0126] Next, for the direct type backlight obtained in this way, the red chip, the green chip, and the blue chip constituting the white chip type LED are respectively 2.2V, 3.5V, and 3.6V. The LED is turned on by applying a current of The luminance in the front direction of 100 points was measured at equal intervals in the short direction on the center line of the diffusion plate, and the average luminance La and luminance unevenness Lu were obtained according to the following formulas 1 and 2. In this example, the average luminance was 1415 cd / m ² and the luminance unevenness was 0.95%.

 Luminance average value La = (Ll + L2) / 2 (Formula 1)

 Luminance unevenness Lu = ((Ll— L2) / La) X 100 (Equation 2)

 L1: Average luminance maximum just above the LED

 L2: Average brightness minimum value between two brightness maximum values

 Note that the luminance unevenness is an index indicating the uniformity of luminance, and the value increases when the luminance unevenness is bad.

 In the backlight before installing the optical sheet! /, The total light transmittance just above the light source is 43%, and the total light transmittance of light incident from the center of the light source toward the position NO is 58%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 63%.

 <Example 7>

The light diffusion plate D1 is changed to the light diffusion plate D2, and the distance a between the cold cathode tube centers is set to 24 mm, and the distance b between the cold cathode tube center and the light incident surface of the light diffusion plate is 6.5 mm. In the same manner as in Example 2 except that RF188 (manufactured by Gidden Co., Ltd.) was changed to a reflection sheet described later and white ink was printed in the manner described below. At this time, a / b was 3.69. In this example, the average luminance value was 5400 cd / m ² and the luminance unevenness was 0.73%.

 [0128] As shown in Fig. 29, the reflective sheet is MCPET (manufactured by Furukawa Electric Co., Ltd.) so that the convex part 2950 is arranged in the middle of the cold cathode tube in 15 regions between the cold cathode tubes 2910. ) Was created by bending. The shape of the convex part was a triangular section with a height of 4 mm and a width of 8 mm.

 Also, print the white ink on the other surface of the light diffusing plate D2 where the uneven structure is not formed so that the formation range decreases as the distance from the central axis of the cold-cathode tube decreases. Formed. Specifically, as shown in Fig. 30, the formation range of the printed layer in the area A1 from the position X to 2.5 mm projected from the central axis of the linear light source 10A is 75%, from 2.5 mm to 7.5 mm The formation range of the printing layer in area A2 was set to 20%.

In the backlight before installing the optical sheet, the total light transmittance just above the light source is 61 %, The total light transmittance of the light incident from the center of the light source toward the position NO was 58%, and the total light transmittance of the light incident on the position where the intermediate position of the adjacent light source was projected was 76%.

<Example 8>

 A reflector sheet (RF188, manufactured by Gidden Co., Ltd.) is attached to the inner surface of a milky white plastic case with an inner width of 700mm, depth of 400mm, and depth of 25mm. Place four hot cathode tubes (made by Elevum Co., Ltd.) with a diameter of 15.5 mm and a length of 800 mm at a distance of 75 mm so that the distance a between the centers of the hot cathode tubes is 90 mm, and the area near the electrodes is silicone. It was fixed with a sealant and an inverter was attached. In the backlight of this design, the distance b between the center of the hot cathode tube and the light incident surface of the light diffusing plate was 15.25 mm. For this reason, the a / b force was .90.

[0130] Next, a mold having the stamper S2 obtained in Production Example 6 was prepared, and using this and a resin having an alicyclic structure (Nippon Zeon Co., Ltd., Zeonor 1060R), an injection molding machine ( Molding was performed at a cylinder temperature of 280 degrees and a mold temperature of 85 degrees using a clamping force of 4,410 kN. As a result, one surface has a concavo-convex structure in which a plurality of linear prisms (triangular prisms) having a triangular cross section are arranged in parallel so as to extend in the longitudinal direction, and the other surface is a flat surface. A light diffusion plate D4 of 730 mm X 430 mm at 2 mm was obtained. When the one surface on which the concavo-convex structure was formed was measured for the centerline average roughness Ra along various directions in the surface using an ultra-deep microscope, the short direction (430 mm) of the light diffusing plate D4 was measured. The centerline average roughness Ra measured in the direction of (1) was the maximum value, and the maximum value Ra (max) was 6.6 m. The centerline average roughness Ra was measured in the same manner for the other flat surface, and Ra was 0.6111.

 [0131] Next, white ink is printed on the other surface of the light diffusing plate D4 where the concavo-convex structure is not formed so that the formation range decreases as the distance from the center axis of the hot cathode tube increases. In addition, a printing layer was formed. Specifically, as shown in FIG. 30, the formation range of the printed layer in the area A1 from the position X to 10.0 mm projected from the central axis of the linear light source 10A is 50%, 10.0 mm to 20.0 mm The formation range of the printed layer in the area A2 was set to 20%.

[0132] Such a light diffusing plate D4 was arranged on the plastic case so that the concavo-convex structure was the light emitting surface on the opposite side of the hot cathode tube. Furthermore, on this, a diffusion sheet (Kimoto Co., Ltd. 188GM3) and a prism sheet (Sumitomo 3EM Co., Ltd., BEF3) on it so that the longitudinal direction of the prism row of the prism sheet is parallel to the hot cathode tube and away from the light diffusion plate installed. On top of that, a direct-type backlight device was fabricated by installing a diffusion sheet (Kimoto 188GM3).

In this example, the average luminance was 8030 cd / m ² and the luminance unevenness was 0.90%.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 55%, and the total light transmittance of light incident from the center of the light source toward the position NO is 65%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 78%.

 <Example 9>

Replacing the resin with an alicyclic structure (Nippon Zeon Co., Ltd., ZENOOR 1060R) with the light diffusion plate pellet P4 obtained in Production Example 4, and using this and the stamper S1 obtained in Production Example 5, light diffusion A plate D5 was prepared, and the same procedure as in Example 8 was performed except that the light diffusing plate D5 and RF188 (manufactured by Gidden Co., Ltd.) were changed to a reflection sheet described later. At this time, a / b was 5.90. In this example, the average luminance value was 8190 cd / m ² and the luminance unevenness was 0.70%.

 [0135] The reflection sheet was prepared by bending MCPET (Furukawa Electric Co., Ltd.) in three areas between the hot cathode tubes so that the convex part was placed between the hot cathode tubes. . The shape of the convex part was a triangular section with a height of 20 mm and a width of 40 mm.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 63%, and the total light transmittance of light incident from the center of the light source toward the position NO is 60%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 65%.

<Example 10>

 The same operation as in Example 7 was performed except that the method for forming the printing layer was changed.

White ink is printed on the other surface of the light diffusing plate D2 where the uneven structure is not formed, and a printed layer is formed so that the formation range decreases as the distance from the central axis of the cold-cathode tube decreases. did. Specifically, referring to FIG. 31, the formation range of the printed layer in the area A1 from the position X to 1.0 mm from the projection of the central axis of the linear light source 10A is 60%, 1.0 mm force, etc. 2 Up to 5mm area A2 printing layer formation range 75%, 2.5mm to 7.5mm area The formation range of the printing layer in area A3 was 20%. Note that the area A4 in FIG. 31 did not have a printing layer. At this time, a / b was 3.69. In this example, the average luminance value was 542 Ocd / m ² and the luminance unevenness was 0.52%.

 In the backlight before installing the optical sheet, the total light transmittance just above the light source is 65%, the total light transmittance of light incident from the center of the light source toward the position NO is 58%, and it is an intermediate position between adjacent light sources. The total light transmittance of the light incident on the projected position was 76%.

 [0137] <Comparative Example 1>

 The light diffusion plate pellet P1 obtained in Production Example 1 was used and molded using an injection molding machine (clamping force 4,410 kN) at a cylinder temperature of 280 degrees and a mold temperature of 85 degrees. As a result, a flat light diffusion plate D6 having a thickness of 2 mm and a thickness of 730 mm × 430 mm was obtained. For each surface of the light diffusion plate D6, the centerline average roughness Ra was measured in the same manner, and Ra was 0.6 mm.

[0138] The light diffusing plate D6 is used instead of the light diffusing plate D1, white ink is printed on the light incident surface of the light diffusing plate D6, and it is formed as it moves away from just above the central axis of the cold cathode tube. A direct type backlight device was obtained in the same manner as in Example 1 except that the same print layer as that in Example 1 with a reduced range was formed. In this example, the luminance average value was 4737 cd / m ² and the luminance unevenness was 5.3%.

 In the backlight before installing the optical sheet! /, The total light transmittance just above the light source is 40%, and the total light transmittance of light incident from the center of the light source toward the position NO is 40%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 80%.

 [0139] <Comparative Example 2>

A flat light diffusing plate D7 was prepared using the light diffusing plate pellet P3 instead of the light diffusing plate pellet P1. A crite device was obtained. In this example, the luminance average value was 3863 cd / m ² and the luminance unevenness was 2.0%.

 In the backlight before installing the optical sheet! /, The total light transmittance just above the light source is 35%, and the total light transmittance of light incident from the center of the light source toward the position NO is 35%. The total light transmittance of light incident on the projected position of the intermediate position of the light source was 45%.

[0140] <Comparative Example 3> The same as in Example 2 except that the distance a between the centers of the cold cathode tubes was set to 23. Omm and the distance b between the center of the cold cathode tubes and the light incident surface of the light diffusion plate was 15 mm. went. At this time, a / b was 1.53. In this example, the average luminance value was 5296 cd / m ² and the luminance unevenness was 1.90%.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 60%, and the total light transmittance of light incident from the center of the light source toward the position NO is 64%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 73%.

[0141] <Comparative Example 4>

The same operation as in Example 8 was performed except that printing was not performed on the light diffusion plate D4. At this time, a / b was 5.90. In this example, the average luminance was 7560 cd / m ² and the luminance unevenness was 10.1%.

[0142] <Comparative Example 5>

Instead of the light diffusing plate D4, the light diffusing plate D1 is installed, and two are arranged so that the distance a between the centers of the hot cathode tubes is 300 mm, and the center of the hot cathode tube and the light incident surface of the light diffusing plate are arranged. The same operation as in Example 8 was performed except that the distance b was 10.25 mm and printing described later was performed. At this time, a / b was 29.27. In this example, the average luminance value was 3825 cd / m ² and the luminance unevenness was 118.6%.

 [0143] On the other surface of the light diffusion plate D1 where the uneven structure is not formed, white ink is printed so that the formation range decreases as the distance from the position directly above the central axis of the hot cathode tube decreases. A layer was formed. Specifically, as shown in FIG. 31, the position X force projected from the central axis of the linear light source 10A, the formation range of the printed layer in the area A1 up to 10.0 m, 75%, 10. Omm force, The area of the printed layer in area A2 up to 25.0 mm is 60%, the area from 25. Omm to 40. Omm is 35% in the area of printed layer A3, 40. Omm force, etc. 65. Omm The formation range of the printed layer in area A4 was set to 20%.

 In the backlight before installing the optical sheet! /, The total light transmittance directly above the light source is 62%, and the total light transmittance of light incident from the center of the light source toward the position NO is 62%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 30%.

[0144] <Comparative Example 6> Prepare a mold equipped with the stamper S2 obtained in Production Example 6 and the stamper S5 obtained in Production Example 9, and use this and a resin having an alicyclic structure (Nippon Zeon Co., Ltd., ZEONOR 1060R). Using an injection molding machine (clamping force 4,410 kN), molding was performed at a cylinder temperature of 280 degrees and a mold temperature of 85 degrees. Thus, one surface has a concavo-convex structure in which a plurality of linear prisms (triangular prisms) having a triangular cross section with a vertex angle of 100 degrees are arranged in parallel to extend in the longitudinal direction, and the other surface has an apex angle of 130. A light diffusing plate D8 having a thickness of 2 mm and a thickness of 730 mm x 430 mm was obtained having a concavo-convex structure in which a plurality of linear prisms (triangular prisms) having a triangular cross section extending in the longitudinal direction in a substantially parallel manner. When the one surface on which the concavo-convex structure with an apex angle of 100 degrees was formed was measured for centerline average roughness Ra along various directions in the surface using an ultra-deep microscope, the short side of the light diffusing plate D8 was measured. The centerline average roughness Ra measured in the hand direction (430 mm direction) was the maximum value, and the maximum value Ra (max) was 6.6 m. In addition, when the other surface on which the concavo-convex structure with an apex angle of 130 degrees was formed was measured for the center line average roughness Ra along various directions in the surface using an ultradeep microscope, the light diffusing plate D8 The centerline average roughness Ra measured in the short direction (430 mm direction) was the maximum value, and the maximum value Ra (max) was 5.5 m. Except for using this light diffusing plate D8, a surface with a concavo-convex structure with an apex angle of 100 degrees was arranged on the plastic case so as to be the light emitting surface on the opposite side of the hot cathode tube, the same as in Example 8. Thus, a direct type backlight device was obtained. In this example, the average brightness was 7950 cd / m ² and the uneven brightness was 1.9%.

 In the backlight before installing the optical sheet! /, The total light transmittance just above the light source is 53%, and the total light transmittance of light incident from the center of the light source toward the position NO is 66%. The total light transmittance of light incident on the projected position of the intermediate position of the light source was 77%. <Comparative Example 7>

Prepare a mold attached with the stamper S2 obtained in Production Example 6 and the stamper S6 obtained in Production Example 10, and use this and a resin having an alicyclic structure (Zeon Corporation, Zeonor 1060R), Using an injection molding machine (clamping force 4,410 kN), molding was performed at a cylinder temperature of 280 degrees and a mold temperature of 85 degrees. Thus, one surface has a concavo-convex structure in which a plurality of linear prisms (triangular prisms) having a triangular cross section with a vertex angle of 100 degrees are arranged in parallel to extend in the longitudinal direction, and the other surface has an apex angle of 130. Width of triangular prism with 30 degree cross section (triangular prism) 30 A light diffusing plate D9 having a thickness of 2 mm and a thickness of 730 mm x 430 mm was obtained, having a concavo-convex structure in which a plurality of 4 mm strips were arranged in parallel so as to extend in the longitudinal direction. When the one surface on which the concavo-convex structure with an apex angle of 100 degrees was formed was measured for the center line average roughness Ra along various directions in the surface using an ultradeep microscope, the light diffusion plate D9 The centerline average roughness Ra measured in the short direction (430 mm direction) was the maximum value, and the maximum value Ra (max) was 6.6 m. Further, when the other surface on which the concavo-convex structure with an apex angle of 130 degrees was formed was measured for centerline average roughness Ra along various directions in the surface using an ultradeep microscope, the apex angle 130 The centerline average roughness Ra measured in the short direction (430mm direction) of the light diffuser D8 is the maximum value, and the maximum value Ra (max) is 5.5 μm Met. Using this light diffusing plate D9, the concavo-convex structure with an apex angle of 130 degrees is formed on the hot cathode tube so that the surface with the concavo-convex structure with an apex angle of 100 degrees becomes the light emitting surface on the opposite side of the hot cathode tube. A direct type backlight device was obtained in the same manner as in Example 8 except that it was arranged on the plastic case. Here, the central line force S in the width direction and the center line of each hot-cathode tube in the region of 30 mm width having an uneven structure with an apex angle of 130 degrees coincide with the line projected on the light diffusion plate.

The arrangement position of the light diffusion plate was adjusted.

In this example, the average brightness was 7880 cd / m ² and the brightness unevenness was 2.8%.

 In the backlight before installing the optical sheet! /, The total light transmittance just above the light source is 53%, and the total light transmittance of light incident from the center of the light source toward the position NO is 66%. The total light transmittance of the light incident on the projected position of the intermediate position of the light source was 75%. <Comparative Example 8>

On the uneven structure surface of the stamper S7 obtained in Production Example 11, 95% by weight of UV curable resin (manufactured by Shin-Nakamura Chemical Co., Ltd., NK Ester AMP-20GY) and a polymerization initiator (manufactured by Ciba Specialty Chemicals, Inc., Irgacure 184) Apply a mixture of 5% by weight, and place a 90 mm x 600 mm size substrate film (Teijin Limited, Teijin Tetron film (brand name: 03, 50 m thickness)) on top. Air bubbles were removed by pressing from the top. This was cured by irradiating with 600 mj / cm ^{2 of} ultraviolet rays from the film side. Thereafter, the film was peeled off from the stamper S7 and cut into a size of 800 mm × 500 mm to obtain a UV-curable resin layer 3205 and a base material FINEREM 3204 force, and FINEREM 1 as described above. Uneven structure surface of this film 1 White ink 3201 was printed on the surface opposite to the surface of the concavo-convex structure so as to form a strip having a width of 100 〃m and a height of 100 帯 m in a direction parallel to the concavo-convex structure. Further, an adhesive layer 3203 was applied to this surface so that the height from the surface opposite to the uneven structure of the film 1 was 150 m. This was adhered to the light diffusing plate D7 (3202) so that the concavo-convex structure was on the outside to obtain a light diffusing plate D10. Figure 32 shows the cross-sectional structure. The surface on which the concavo-convex structure was formed was measured for the centerline average roughness Ra along various directions in the surface using an ultra-deep microscope. The short direction of the light diffusing plate D10 (430 mm direction) The centerline average roughness Ra measured at the maximum was the maximum value, and the maximum value Ra (max) was 12.5 m. For the other surface, which was a flat surface, the centerline average roughness Ra was measured in the same manner, and Ra was 0.6 m. This light diffusing plate D10 was used in the same manner as in Example 8 except that the surface having the concavo-convex structure was arranged on the plastic case so as to be the light emitting surface opposite to the hot cathode tube. A mold backlight device was obtained. In this example, the average luminance was 6680 cd / m ² and the luminance unevenness was 3.5%.

 In the backlight before installing the optical sheet, the total light transmittance directly above the light source is 31%, the total light transmittance of light incident from the center of the light source in the position NO direction is 30%, and it is an intermediate position between adjacent light sources. The total light transmittance of the light incident on the projected position was 30%.

 [0147] The results of Examples 1 to 10 and Comparative Example;! To 8 are shown in Tables 1 to 4.

[0148] [Table 1]

Unit Example 1 Example 2 Example 3 Example 4 Example 5 Light source Type ― CCFL CCFL CCFL CCFL CCFL Quantity used 1 12 16 10 8 8 Optical sheet 1 ― Reflected polarized light Reflected polarized light Reflected polarized light Reflected polarized light Reflected polarized light Sheet Sheet卜 2 ― Prism Prism Prism Prism Sheet Sheet Sheet Sheet Sheet 3 ― Diffusion Diffusion Diffusion Diffusion Sheet Sheet Sheet Sheet Sheet Sheet Diffusion Plate Pattern Wrench Wrench Wrench Type Kyura Kyura Kyura Kyura Diffuser concentration wt% 0.3 0.3 0.3 0.3 0.3 Total light

 % 85 85 85 85 85 Transmittance

 % 99 99 99 99 99 Print layer / jm of print layer surface 0.15 0.15 0.15 0.15 0.15 Roughness Ra

 Center of light source mm 33 23 40 50 50 Average distance a

 Light source center

 Light incident surface mm 15 8 18 23 23 Average distance b

a / b ― 2.20 2.88 2.22 2.17 2.17 Evaluation Central luminance cd / m ^z 4690 5350 4086 4067 3864 Luminance unevenness% 0.80 0.95 0.90 0.65 0.75

Unit Example 6 Example 7 Example 8 Example I II §Example 9 Example 10 Light source type ― LED CCFL HCFL HCFL CCFL Quantity used ― 390 16 4 4 16 Optical diffusion Diffusion

 Sheet 1 ― Reflected polarized light Reflected polarized light Reflected polarized light Sheet Sheet Sheet prism Prism Prism Sheet 2 Sheet 1 Prism pre

 Sheet sheet sheet sheet sheet

-Diffusion Diffusion Diffusion Diffusion Sheet 3

 Sheet Sheet Sheet Sheet Sheet Diffusion plate Pattern 100 ° 3 100 ° 3 100 ° 3 Wrench Type Hemispherical angle prism angle prism angle prism Yuram diffuser concentration wt% 0.1 0.3 0 0.1 0.3 total light

 % 94 85 92 86 85 Transparent half

 % 89 99 0.3 99 99 Print layer Print layer surface tim 0.15 0.15 0.15 0.15 0.15 Roughness Ra

 Center of light source mm 26 24 90 90 24 Average distance a

 Light source center

 Mm of incident surface 19.1 6.5 15.25 15.25 6.5 Average distance b

a / b ― 1.36 3.69 5.90 5.90 3.69 Evaluation Central luminance cd / m '1415 5400 8030 8190 5420 Luminance unevenness% 0.95 0.73 0.90 0.70 0.52 Unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4

 Light source type ― CCFL CCFL CCFL HCFL

 Quantity used-12 12 16 4

 Optical sheet 1 ― Reflected polarized light Reflected polarized light Diffused

 Reflected polarization

 Sheet Sheet Sheet 2 ― Prism Prism Prism Prism

 Sheet Sheet Sheet Sheet Sheet 3 ― Diffusion Diffusion Diffusion Diffusion

 Sheet Sheet Sheet Sheet Diffuser pattern 100. Three

 wrench

 Type None None Square prism

 Kyuramu Diffusion agent concentration wt% 0.3 2.5 0.3 0

 Total rays

 % 85 55 85 92

 Transmittance

 Haze% 99 99 99 0.3

 Print layer Print layer surface

 urn 0.15 0.15 0.15

 Roughness Ra None Center of light source mm 33 33 23 90

 Average distance a

 Light source center

 Mm of light incident surface 15 15 15 15.25 Average distance b

 a / b ― 2.20 2.20 1.53 5.90

 Evaluation Central luminance cd / nr 4737 3863 5296 7560

 Brightness unevenness% 5.3 2.0 1.9 10.1

[0151] [Table 4] Unit Comparison Example 5 Comparison Example 6 Comparison Example 7 Comparison Example 8 Light source Type ― HCFL HCFL HCFL HCFL

 Quantity used ― 2 4 4 4

 Optical sheet 1 ― Diffusion Diffusion Diffusion Diffusion

 Sheet Cutter Sheet Sheet Sheet Sheet 2 ― Prism Prism Prism Prism

 Sheet Sheet Sheet Sheet Sheet 3 ― Diffusion Diffusion Diffusion Diffusion

 Sheet Sheet Sheet Sheet Diffuser pattern 100 °

 Wrench 100 ° Wrench + Average / 130 °

 Yuraichi Ha 30 °

 (30mm) One printing Diffuser concentration wt% 0.3 0 t% 0 t% 2.5wt

 Total rays

 % 85 92% 92% 55%

 Transparent half

 Haze% 99 0.3% 0.3% 99%

 Print layer Print layer surface jum 0.15 No print No print Uniform print

 Roughness Ra

 Center of light source mm 300 90 90 90

 Average distance a

 Light source center

 Light incident surface 10.25 15.25 15.25 15.25

 Average distance b

 a / b ― 29.27 5.90 5.90 5.90

Evaluation Central luminance cd / m ² 3825 7950 7880 6680

 Uneven brightness% 118.6 1.9% 2.8% 3.5%

[0152] Examples as shown in Tables 1 to 4; ~ 10, the average distance between the center of the light source and the light When the average distance between the center of the light source and the light incident surface satisfies a certain relationship and the reflection suppressing layer is appropriately disposed, it is possible to suppress uneven brightness on the light emitting surface. On the other hand, as shown in Comparative Examples 1 to 8, when the predetermined relationship was not satisfied, uneven brightness occurred on the light emitting surface.

Claims

The scope of the claims  [1] A reflecting plate, a plurality of linear light sources arranged substantially in parallel, and direct light from these linear light sources and reflected light from the reflecting plate are incident from a light incident surface and diffused to emit light. A direct-type backlight device comprising a light diffusing plate that exits from a surface,  At least one of the light emitting surface and the light incident surface has at least a portion of the center line average roughness Ra measured along various directions in the surface. A concavo-convex structure having a maximum value Ra (max) of 3 m to 1,000 m is formed, and at least one of the light emitting surface and the light incident surface has light in at least a range M. A light transmission suppression layer for suppressing transmission of  R  In the range M, the portion including the light diffusing plate and the light transmission suppressing layer is not transparent.  R  The minimum value of the excess rate is at a position intermediate between the position where the center position of the linear light source is projected onto the light diffusion plate and the position where the center position of the adjacent linear light source is projected onto the light diffusion plate. 5% or more lower than the transmittance value of the portion including the light diffusion plate and the light transmission suppressing layer  The average distance between the centers of the adjacent linear light sources is a (mm), and the average distance between the center of the linear light source and the light incident surface is b (mm), and 1.7≤a / b≤23 Satisfying the relationship of 0, the range M is a position where the center line of the linear light source is projected onto the incident surface of the light diffusing plate.  R  Is a region within a distance M (mm) from this reference line, where M and b satisfy the relationship 0 ≤ M <b X tan (2 π / 9)  Direct type backlight device. [2] Light diffusion in which a reflecting plate, a plurality of point light sources, direct light from these point light sources and reflected light of the reflecting plate force are incident from the light incident surface, diffused and emitted from the light emitting surface A direct-type backlight device comprising: At least one of the light emitting surface and the light incident surface has at least a portion of the center line average roughness Ra measured along various directions in the surface. A concavo-convex structure having a maximum value Ra (max) of 3 m to 1,000 m is formed, and at least one of the light emitting surface and the light incident surface has light in at least a range M. A light transmission suppression layer for suppressing transmission of In the range M, the portion including the light diffusing plate and the light transmission suppressing layer is not transparent. R  The minimum value of the excess rate is an intermediate position between a position where the center position of the point light source is projected onto the light diffusion plate and a position where the center position of the adjacent point light source is projected onto the light diffusion plate. 5% or less lower than the transmittance value of the portion including the light diffusion plate and the light transmission suppressing layer  The average distance a (mm) between the centers of the adjacent point light sources, and the average distance between the center of the point light source and the light incident surface is b (mm), and 0.5≤a / b≤15. 0 The range M is a position obtained by projecting the center point of the point light source onto the incident surface of the light diffusing plate.  R  Is a region within a distance M (mm) from this reference point, where M and b satisfy the relationship 0 ≤ M <b X tan (2 π / 9)  Direct type backlight device. [3] In the direct type backlight device according to claim 1,! /,  The concavo-convex structure is a direct type in which a plurality of linear prisms having a polygonal cross section extending substantially parallel to the longitudinal direction of the linear light source or a lenticular having a cross section including a curved portion are arranged. Backlight device. [4] In the direct type backlight device according to claim 1 or 2,  The light transmission suppressing layer is constituted by a printing layer that reflects and / or absorbs incident light! /, A direct type backlight device. [5] In the direct type backlight device according to claim 4,  The direct-type backlight device, wherein the printing layer is provided so that the light transmittance increases continuously or stepwise as the distance from the light source increases. [6] The direct type backlight device according to claim 1 or 2,  A direct type backlight device having a center line average roughness Ra of 0.005 μηι ^ δ μm at a position where the print layer is formed on the surface on which the print layer is formed. [7] The direct-type backlight device according to [1] or [2], wherein the concavo-convex structure has a configuration in which a plurality of dotted projections or concave structural units are arranged. [8] In the direct type backlight device according to claim 1 or 2, The uneven structure is formed on the light exit surface,  The light incident surface is a direct type backlight device having a substantially flat surface with a center line average roughness Ra of less than 3 m.  [9] The direct type backlight device according to claim 1 or 2, The maximum value of the arithmetic mean inclination angle Θ measured along various directions within the surface on which the concavo-convex structure is formed is Θ (max) (degrees), the refractive index of the concavo-convex structure portion is n, the outer diameter of the light source and R (mm), sin- i C / Snb) + sin_ 1 (l / n)> Θ max direct type backlights device satisfies the relationship.  [10] The direct type backlight device according to claim 9,  The light transmission suppressing layer is provided at least at a predetermined position NO on either the light emitting surface or the light incident surface,  The position NO is a path where light exits from the center of the light source, passes through the light diffusing plate and exits in a direction parallel to the thickness direction of the light diffusing plate, and the light incident surface of the light diffusing plate. Or the position where the light exit surface intersects,  The transmittance of the portion including the light diffusing plate and the light transmission suppressing layer at the position NO is the maximum of the transmittance between the position NO and a position where an intermediate position of the adjacent light source is projected onto the light diffusing plate. Direct type backlight device that is 5% lower than the value. [11] In the direct type backlight device according to claim 10,  The light diffusing plate in a range N within a distance R / 2 centered on the position NO, and  R  The minimum direct TA of the transmittance of the portion including the light transmission suppression layer,  When the average straight TB of the transmittance of the portion including the light diffusion plate and the light transmission suppressing layer between the position NO and the position where the center of the light source is projected onto the light diffusion plate,  Direct type backlight device that satisfies TA <TB. [12] In the direct type backlight device according to claim 1 or 2,  The light diffusion plate is composed of a resin composition containing a transparent resin, This resin composition is a direct type backlight device having a total light transmittance of 40% or more and 98% or less measured with normal incident light. 3. The direct type backlight device according to claim 1, wherein the light diffusing plate is composed of a resin composition containing a transparent resin, and the water absorption rate of the resin composition is 0.25% or less. Light equipment.