KR100895569B1 - Diffusing board and surface light source device - Google Patents

Abstract

The diffusion plate of the present invention can suppress moire streaks, color flickering and screen brightness deterioration of the screen of the liquid crystal display device, and the configuration is as follows. On the surface of the transparent board | substrate 83, the pattern which roughly rectangular shape was arrange | positioned at lattice form using the composite pattern 86 is formed. The composite pattern 86 is produced by synthesizing a plurality of first uneven patterns 84 having a long linear shape in one direction and a plurality of second uneven patterns 85 having a randomly arranged concave lens shape. .

Diffuser Plate, Surface Light Source Device

Description

DIFFUSING BOARD AND SURFACE LIGHT SOURCE DEVICE

The present invention relates to a diffusion plate and a surface light source device. In particular, it relates to a surface light source device used as a backlight for illuminating a liquid crystal display panel, and a diffusion plate for diffusing light emitted from the surface light source device.

1 is an exploded perspective view showing a backlight type surface light source device 11 according to a first conventional example, and FIG. 2 is a schematic cross-sectional view thereof. The surface light source device 11 includes a light guide plate 12 for confining light, a light emitting portion 13, and a reflecting plate 14. The light guide plate 12 is formed of a transparent and high refractive index resin such as polycarbonate resin or polymethyl methacrylate, and the bottom surface of the light guide plate 12 has irregular semi-circular cross-sectional shape and dots of diffuse reflection ink. The pattern 15 is formed by printing or the like. The light emitting part 13 mounts so-called point light sources 17 such as a plurality of light emitting diodes (LEDs) on the circuit board 16, and faces the side surface (light incident surface 18) of the light guide plate 12. Doing. The reflecting plate 14 is formed of, for example, a white resin sheet having a high reflectance, and both sides are attached to the lower surface of the light guide plate 12 by a double-sided tape 19.

Thus, as shown in FIG. 2, the light emitted from the light emitting portion 13 and guided into the light guide plate 12 from the light incident surface 18 (in the drawing, the light is indicated by an arrow) is a light guide plate. The inside of the light guide plate 12 is guided by repeating total reflection between the light exit surface 20 of 12 and the surface on the opposite side thereof. The light guiding the inside of the light guide plate 12 is diffusely reflected by touching the pattern 15, and the light reflected so as to be an incident angle smaller than the critical angle of total reflection with respect to the light exit surface 20 is the light exit surface 20. It is taken out from the outside. In addition, since light leaked to the outside through the portion where the pattern 15 on the lower surface of the light guide plate 12 does not exist is reflected by the reflection plate 14 and returns to the inside of the light guide plate 12 again, the lower surface of the light guide plate 12 Loss of light in the

In this way, the light emitted from the light exit surface 20 of the light guide plate 12 is emitted in a direction substantially parallel to the light exit surface 20 of the light guide plate 12, as it is shown in FIG. The luminance in the direction perpendicular to the light exit surface 20 (hereinafter may be referred to as a front face) is lowered and becomes very dark when viewed from the front. For this reason, the diffusion sheet 21 having a random pattern is disposed to face the light exit surface 20 of the light guide plate 12. Light emitted almost in parallel with the light exit surface 20 is scattered by the diffusion sheet 21, so that the amount of emitted light in a direction perpendicular to the light exit surface 20 increases. However, in the surface light source device 11 of this type, since the light is diffused randomly by the diffusion sheet 21, the directivity of the light transmitted through the diffusion sheet 21 is extremely wide and close to Lambert light. The front brightness | luminance of the light source device 11 was low.

Therefore, various inventions for improving the front luminance of the surface light source device have been proposed. 3 is an exploded perspective view showing the backlight type surface light source device 31 according to the second conventional example, and FIG. 4 is a schematic cross-sectional view thereof. In this surface light source device 31, a plurality of fine deflection pattern elements 35 having a triangular cross-sectional shape are provided on the lower surface of the light guide plate 32. In order to uniformize the luminance distribution, the deflection pattern element 35 has a small pattern density in the vicinity of the light emitting portion 33, and gradually increases as the distance from the light emitting portion 33 increases. Moreover, the mirror surface reflective sheet 34 is arrange | positioned facing the lower surface of the light guide plate 32. As shown in FIG. At a position facing the light incident surface 38 of the light guide plate 32, a rod-shaped light emitting portion 33 made of a cold cathode ray tube is disposed. The prism sheet 42 is arrange | positioned in the position which opposes the light output surface 40 of the light guide plate 32, and the uneven diffuser plate 41 is put on it. In the prism sheet 42, cross-sectional triangular prisms 42a extending linearly in a direction parallel to the longitudinal direction of the light emitting portion 33 are arranged in parallel with each other and at a constant pitch.

In this surface light source device 31, as shown in FIG. 4, the light of the light emitting part 33 guided in the light guide plate 32 is between the light output surface 40 of the light guide plate 32, and the surface on the opposite side. The light guide plate 32 is guided by repeating total reflection at. When the light guiding the light guide plate 32 reaches the deflection pattern element 35, the light guiding angle a becomes large and is reflected so as to be an incident angle smaller than the critical angle of total reflection with respect to the light exit surface 40. It exits from the surface 40 to the outside. Therefore, also in this surface light source device 31, the light radiate | emitted from the light exit surface 40 is radiate | emitted in the direction substantially parallel to the light exit surface 40. FIG. Light emitted from the light guide plate 32 toward a direction substantially parallel to the light exit surface 40 is bent in a direction substantially perpendicular to the light exit surface 40 by passing through the prism sheet 42.

As shown in FIG. 3, the y-axis direction is determined in a direction perpendicular to the light incident surface 38 of the light guide plate 32, parallel to the light incident surface 38, and also parallel to the light exit surface 40. It is assumed that the x-axis direction is taken in one direction, and the z-axis direction is taken in a direction perpendicular to the light exit surface 40. In addition, phi x shall represent the azimuth angle measured from the z-axis direction in the zx plane, and phi y shall represent the azimuth angle measured from the z-axis direction in the yz plane.

Since light directing the light guide plate 32 and exiting from the light exit surface 40 does not control the directivity of light in the x-axis direction, light spreads in the light guide plate 32 in the x-axis direction is large, and the prism sheet The directivity in the φx direction of the light transmitted through 42 is as wide as Δφx in FIG. 5. On the other hand, since light is emitted from the light exit surface 40 toward a narrow range substantially parallel to the light exit surface 40, the directivity in the φy direction of the light transmitted through the prism sheet 42 is Δφy in FIG. 5. Narrow as

If the directivity is too wide, the front luminance is lowered. On the contrary, even if the directivity is too narrow, the image becomes invisible even if the observer slightly shifts the position of the face, resulting in poor visibility. Therefore, in this surface light source device 31, as shown in FIG. 4, the uneven diffuser 41 is arrange | positioned on the prism sheet 42, and in the yz plane of the light which permeate | transmitted the prism sheet 42 was carried out. The directivity in the phi y direction is widened by β = 20 ° with the uneven diffuser 41. As a result, according to this surface light source device 31, the front brightness higher than the surface light source device 11 by a 1st prior art example is obtained, and also the fall of the visibility in a liquid crystal display device can be prevented. .

FIG. 6A is a plan view showing the arrangement of the diffusion pattern 43 in the uneven diffuser 41, and FIG. 6B is the uneven diffuser 41 in the cross section parallel to the zx plane. Fig. 6 (c) is a diagram showing a cross-sectional shape of the uneven diffuser plate 41 in the cross section parallel to the yz plane. The diffusion pattern 43 is configured to diffuse the light passing through the uneven diffuser plate 41 greatly in the yz plane, but not so much in the zx plane. That is, the diffusion pattern 43 formed on the surface of the uneven diffusion plate 41 extends linearly in the direction parallel to the x-axis, and the unevenness curved in a wave shape in the cross section parallel to the yz plane. It is a pattern. In addition, in the cross section parallel to the zx plane, the diffusion pattern 43 is formed in a flat straight shape, but a joint 44 dent concave is formed between the diffusion patterns 43 due to the sag during molding.

When the period in the x-axis direction of the diffusion pattern 43 is Λx and the period in the y-axis direction is Λy, the period Λy in the plane in which light is to be diffused is larger than the other period Λx. It is small (that is, Λx >> Λy). The period Λ x of the diffusion pattern 43 is preferably 50 to 200 μm, and the period Λ y is preferably 5 to 20 μm. This is because when the periods Λx and Λy of the diffusion pattern 43 exceed the respective upper limit values, the diffusion pattern 43 can be visually recognized and the display quality in the liquid crystal display device is degraded. In addition, when the periods Λx and Λy of the diffusion pattern 43 fall below the respective lower limits, fabrication of the pattern becomes difficult, so that a manufacturing error of the diffusion pattern 43 becomes larger than that of the pattern shape, and the light utilization efficiency is increased. This is because it is lowered or the diffracted light becomes dominant, causing problems such as color unevenness.

FIG. 7 is a view for explaining the action of the diffusion pattern 43 on the yz plane, and FIG. 8 is a view for explaining the action of the diffusion pattern 43 on the zx plane. In the cross section parallel to the yz plane, the diffusion pattern 43 has a waveform. When the tangential angle of the light emission point is γ, the diffusion angle (deflection angle) of the light exiting the diffusion pattern 43 (φy) )silver,

φy = γ / (n-1)

Is displayed. Here, n is the refractive index of the resin constituting the uneven diffusion plate 41, and the refractive index of air is 1.

On the other hand, since the diffusion pattern 43 is flat in the zx plane, as shown in FIG. 8, light passing through the diffusion pattern 43 is not diffused. In the joint 44 between the diffusion patterns 43, diffusion occurs in the zx plane, but since the period Λx in the x-axis direction is considerably larger than the period Λy in the y-axis direction, The amount of light diffused in the zx plane by the seam 44 is only a small amount of light compared to the amount of light diffused in the yz plane by the diffusion pattern 43. Therefore, the uneven diffuser plate 41 mostly produces only diffusion in the yz plane.

10 is a diagram showing the diffusion characteristics of the uneven diffusion plate 41. As shown in this characteristic diagram, the uneven diffusion plate 41 almost diffuses light in the zx plane in the φx direction and generates diffusion with a spread of about 20 ° in the yy direction in the yz plane. . As shown in FIG. 9, the directivity characteristic of the light radiate | emitted from the prism sheet 42 is wide in phi x direction, and narrow in phi y direction. When the uneven diffusion plate 41 having the diffusion characteristic as shown in FIG. 10 is provided on the prism sheet 42 having such a directivity characteristic, the directivity characteristic of the light emitted from the surface light source device 31 is as shown in FIG. That is, in the φ x direction, the directivity of the light emitted from the uneven diffuser plate 41 is almost the same as the directivity of the light passed through the prism sheet 42, but in the φy direction, the directivity of the light emitted from the uneven diffuser plate 41 is obtained. It is larger than the directivity of the light which has passed through the prism sheet 42, and spreads about 20 degrees from both sides about the z-axis in the (phi) x direction and the (phi) y direction, and has a viewing angle sufficient for using for a liquid crystal display device.

12 is a perspective view showing a backlight type surface light source device 51 according to a third conventional example, and FIG. 13 is a schematic cross-sectional view thereof. In this surface light source device 51, the light emitting part 53 which consists of point light sources, such as LED, is arrange | positioned near the corner part of the light guide plate 52. As shown in FIG. On the lower surface of the light guide plate 52, deflection pattern elements 55 having a triangular cross-sectional shape are arranged in a concentric shape with the light emitting portion 53 as the center. The deflection pattern element 55 has a small pattern density in the vicinity of the light emitting portion 53, and has a large pattern density as it moves away from the light emitting portion 53. The mirror surface reflective sheet 54 is arrange | positioned in the position which opposes the lower surface of the light guide plate 52. The prism sheet 62 is arrange | positioned in the position which opposes the light output surface 60 of the light guide plate 52, and the uneven diffused plate 61 is put on it. The prism sheet 62 is formed with a cross-sectional triangular prism extending in an arc shape around the light emitting portion 53.

The position or direction in this surface light source device 51 is shown using cylindrical coordinates. As shown in FIG. 14, the z-axis direction is determined in a direction perpendicular to the light exit surface 60 of the light guide plate 52, and the radial direction centering on the light emitting part 53 is defined as the r-axis direction. The angle measured from one side surface of (52) is θ, and the directions perpendicular to the r-axis direction and the z-axis direction are the θ-axis direction. In addition, the azimuth angle measured from the z axis in a plane parallel to the r axis direction and the z axis direction is φ r, and the azimuth angle measured from the z axis in a plane perpendicular to the r axis direction and parallel to the z axis direction is φ θ. do.

In this surface light source device 51, as shown in FIG. 13, the light which entered the light guide plate 52 from the light emitting part 53 (point light source) spreads radially centering on the light emitting part 53. As shown in FIG. In addition, in the planar view seen from the z-axis direction, since each deflection pattern element 55 is disposed so that its longitudinal direction is orthogonal to the direction (r-axis direction) subsequent to the light emitting portion 53, the light guide plate The light guiding inside 52 does not scatter in the θ direction even when reflected by the deflection pattern element 55, and proceeds almost immediately along the r-axis direction. Therefore, the directivity of the light reflected by the deflection pattern element 55 and exiting from the light exit surface 60 of the light guide plate 52 and bent in a substantially vertical direction by the prism sheet 62 is as shown in FIG. 14. . Although the directivity of the light transmitted through the prism sheet 62 is narrow in the directivity (Δφr) in the φr direction and in the directivity (Δφθ) in the φθ direction, the direction of light guiding the light guide plate 52 is almost r. Since they are gathered in the axial direction, the directivity in the φθ direction (Δφθ) is particularly narrow.

Therefore, in the third conventional example, the uneven diffuser plate 61 needs to widen the light transmitted through the prism sheet 62 in the φθ direction. Therefore, as shown in Fig. 15A, in this uneven diffusion plate 61, the diffusion pattern 63 extending in the r-axis direction is concentric or radially centered on the light emitting portion 53. Posted in. The diffusion pattern 63 has a flat pattern as shown in FIG. 15B in the cross section shown by P1-P1 in FIG. 15A, and a joint 64 is formed between the diffusion patterns 63. Occurs. In addition, in the cross section shown by P2-P2 in FIG.15 (a), the diffusion pattern 63 becomes a wavy pattern as shown in FIG.15 (c).

The operation of the diffusion pattern 63 is also the same as that of the diffusion pattern 43 in the second conventional example (see FIGS. 7 and 8), but the direction in which light is diffused is different, and r in the third conventional example is used. The axial direction corresponds to the x-axis direction in the second conventional example, and the θ-axis direction in the third conventional example corresponds to the y-axis direction in the second conventional example. Therefore, when the period in the r-axis direction of the diffusion pattern 63 is Λr and the period in the θ-axis direction is Λθ, the period Λr in the r-axis direction is larger than the period Λθ in the θ direction. (Ie Λr >> Λθ). The period Λ r of the diffusion pattern 63 is preferably 50 to 200 μm, and the period θ is preferably 5 to 20 μm.

FIG. 17 is a diagram showing diffusion characteristics of the uneven diffuser plate 61. As shown in this characteristic diagram, the uneven diffusion plate 61 hardly diffuses light in the zr plane in the φr direction, but causes diffusion with a spread of about 20 ° in the zθ plane in the φθ direction. As shown in FIG. 16, the directivity characteristic of the light emitted from the prism sheet 62 is wide in the φr direction and narrow in the φθ direction. If the uneven diffusion plate 61 having the diffusion characteristic as shown in FIG. 17 is provided on the prism sheet 62 having such a directivity characteristic, the directivity characteristic of the light emitted from the surface light source device 51 is as shown in FIG. . That is, in the φr direction, the directivity of the light emitted from the uneven diffuser plate 61 is almost the same as the directivity of the light passed through the prism sheet 62, but in the φθ direction, the directivity of the light emitted from the uneven diffuser plate 61 is obtained. It is larger than the directivity of the light passing through the prism sheet 62, and spreads in the φr direction or the φθ direction about 20 degrees around both sides of the z axis, and has a viewing angle sufficient for use in the liquid crystal display device.

However, in the surface light source devices 31 and 51 using the uneven diffuser plates 41 and 61 as used in the second and third conventional examples, as shown in FIG. 19, the liquid crystal display panel ( When the liquid crystal display device is formed by stacking the liquid crystal display device 65, the moire fringes M of several mm cycles are generated on the surface of the liquid crystal display panel 65, thereby degrading the display quality of the liquid crystal display device. FIG. 20 illustrates an embodiment in which moire fringes actually occur. FIG. 21 shows a liquid crystal display panel 65 in which one pixel is formed by the red pixel R, the green pixel G, and the blue pixel B, and the opening period of the pixel is Λc = 120 μm. Is part of. The liquid crystal display as shown in FIG. 21 on the surface light source device 31 of the second conventional example using the uneven diffuser plate 41 in which the period in the x-axis direction is Λx = 200 µm and the period in the y-axis direction is Λy = 20 µm. When the panel 65 is overlapped, the moire fringes as shown in FIG. 20 appear in a period of several mm on the liquid crystal display panel 65 to reduce the image of the liquid crystal display device. In the case of the surface light source device as in the third conventional example, although not shown, radial moire stripes are generated.

Here, in the case of using the uneven diffuser plate in which the linear diffusion pattern is arranged, the cause of moire fringes on the surface of the liquid crystal display panel is considered as follows. FIG. 22: shows the aspect which observed the uneven diffuser plate 41 which carried out the light from the back side under the microscope (FIG. 50 shows this microscope photograph). In the joint 44 between the diffusion patterns 43, the light becomes bright as much as the diffusion pattern 43 does not diffuse in the φy direction, and the uneven diffuser plate 41 has a luminance peak along the joint 44. . Since the period between these joints 44 is about 100 micrometers, the luminance peak of the uneven diffuser 41 is also repeated in this period and will generate | occur | produce. Since the period of the luminance peak and the period Λc of the recovery of the liquid crystal display panel 65 have a close value, it is considered that the moire fringe M is generated due to both interference.

In addition, when the uneven diffuser plates 41 and 61 used in the second and third conventional examples are used, color blurring as shown in FIG. 23 occurs on the surface of the liquid crystal display panel 65. There is a problem. This cause is considered as follows. For example, the period of the y-axis direction of the diffusion pattern 43 provided in the uneven diffuser plate 41 is set to Λy = 10 μm, and the apertures of the red, green, and blue pixels of the liquid crystal display panel 65 are opened. The width is said to be W = 35 mu m. When such a surface light source device and a liquid crystal display panel overlap, as shown in FIG. 24, the diffusion pattern 43 which passes each pixel may be two cases and three cases. For example, in the case of FIG. 24, although three diffusion patterns 43 pass through the opening of the red pixel R and the opening of the blue pixel B, two diffusion patterns 43 pass through the opening of the green pixel G. Only the diffusion patterns 43 pass through. Therefore, there is a difference in emission intensity of up to 1.5 times between each pixel. In this way, a difference in emission intensity is generated between the pixels of each emission color, and in addition, since the emission intensity of the pixel of which emission color is strong varies depending on the location, the color is changed to different colors depending on the location, and this is seen as a color tingling. I think.

In addition, as the uneven diffusion plate used in the second conventional example or the third conventional example, a randomly formed granular uneven pattern may be used. 25 (a), 25 (b), 26 (a) and 26 (b) are explanatory views for explaining the structure of the uneven diffusion plate 71 having another pattern. As shown in Fig. 25A, the uneven diffuser plate 71 is arranged so that the repeating pattern 72 is periodically arranged from side to side without any gap. As shown in Fig. 10B, the repeating pattern 72 is a random arrangement of the recesses 73 with almost no gaps. The widths H and D in the longitudinal and lateral directions of one repeating pattern 41 are larger than the size of the pixels of the liquid crystal display panel in order to prevent moire fringes, and any of them is preferably 100 µm or more and 1 mm. It is as follows. Moreover, the dimension of the recessed part 73 which comprises the repeating pattern 72 is uneven, It is preferable that outer diameter G is 5 micrometers or more and 30 micrometers or less (preferably about 10 micrometers is preferable). Further, the concave portion 73 has a concave lens shape as shown in Figs. 26A and 26B.

Since the uneven diffusion plate 71 has a special diffusion characteristic, the uneven shape of the pattern must be precisely controlled. In this case, if one uneven pattern is arranged periodically, all of the uneven patterns become the same shape, and thus all uneven patterns can be produced in the same manner and an accurate uneven shape can be obtained. However, in such a method, moire streaks are generated on the screen of the liquid crystal display device, or pixels are prominent. On the contrary, when trying to arrange the uneven pattern randomly, the shape and size of the uneven pattern must be changed one by one, and it becomes difficult to produce an accurate shape. Moreover, there exists a possibility that the characteristic of an uneven | corrugated diffuser board may change with a location. Therefore, in this uneven diffuser plate 71, the concave portion 73 having a random shape or dimension is randomly arranged to form a repeating pattern 72, and the repeating pattern 72 is periodically arranged, The pattern production of the uneven diffuser plate 71 is facilitated while suppressing occurrence of moire fringes and the like.

27 (a) and 27 (b) are diagrams illustrating the action of the uneven diffuser plate 71. Since the concave-convex diffuser plate 71 has a large number of concave portions 73 arranged at random, and each of the concave portions 73 has a concave lens shape, as shown in FIG. When light is incident on the incident light, the incident light is diffused around the optical axis by the action of the concave lens. Therefore, this uneven diffuser 71 exhibits diffusion characteristics as shown in FIG. 27B, sets the refractive index of the uneven diffuser 71 to n, and provides the center and the edges (vertical points) of the recess 73. If the inclination of the line segment connecting () is set to ε, in this diffusion characteristic, a peak also occurs at a position of φx = φy = ± ε / (n-1) on both sides of the peak having a high center. In addition, this diffusion characteristic becomes rotationally symmetrical about the z-axis when the recessed part 73 is circular.

FIG. 28 is a diagram showing actual diffusion characteristics of the uneven diffusion plate 71, and the diffusion characteristics in the φx direction and the diffusion characteristics in the φy direction coincide with each other. When the uneven diffuser plate 71 having such characteristics is replaced with the uneven diffuser plate 41 of the second conventional example, the directivity characteristic of FIG. 9 after passing through the prism sheet 42 is the uneven diffuser plate 71. After passing through, it is converted as shown in FIG. As a result, in the phi x direction and the phi y direction, the directivity is spread around 20 degrees, and a viewing angle sufficient for use in the liquid crystal display device is obtained.

According to such an uneven diffuser plate 71, since the recesses 73 are randomly arranged, moire fringes do not occur. However, since the recesses 73 are randomly arranged, local deviations occur, a difference in emission intensity is generated between the pixels of the liquid crystal display panel, and the color flickers as in the case of the uneven diffuser 41. There is a problem with this. The problem of this color mating is the same even when used for the third conventional example.

In addition, since the uneven diffuser plate 71 diffuses light equally in all directions around the optical axis, the luminance of the screen of the liquid crystal display device is compared with the case where the uneven diffuser plate 41 or the uneven diffuser plate 61 is used. There is a problem that is reduced by about 15%.

As described above, as the uneven diffuser plate in which the linear pattern is formed, the moire stripes and the color blur are problematic, and in the uneven diffuser plate in which the granular patterns are randomly arranged, the color blur and the brightness Deterioration is a problem, and it is desired to solve such a fault.

In addition, Patent Document 1 describes the conventional example as described above.

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-215584

Problems to be Solved by the Invention

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problems, and an object thereof is to suppress moire streaks and color blurring of a screen of a liquid crystal display device, and also to reduce the luminance decrease of the screen. To provide a diffuser plate.

Means to solve the problem

The first diffusion plate according to the present invention diffuses incident light in one plane including the optical axis of the incident light to either surface of the substrate on which light enters from one surface and light exits from the other surface. Characterized in that a composite pattern obtained by superimposing a first concave-convex shape composed of a plurality of concave portions or convex portions and a second concave-convex portion composed of a plurality of concave portions or convex portions that diffuse incident light around the optical axis of the incident light are formed. have. In addition, the optical axis of incident light refers to the direction parallel to the light beam of the maximum luminous intensity among incident light beams.

In the first diffusion plate of the present invention, since the first uneven shape and the second uneven shape overlap, the first uneven shape is larger than the case of only the first uneven shape when the diffusion degree of the whole diffuser plate is equal. Can contribute less and reduce the occurrence of moire streaks. Further, since the light can be diffused in a direction different from the first uneven shape by the second uneven shape, moire fringes can be further reduced. In addition, when the diffusion degree of the whole diffuser plate is equal, the contribution from a 2nd uneven shape can be made smaller than the case of only a 2nd uneven shape, and the fall of brightness can be made small. In addition, according to the first diffusion plate of the present invention, since the pattern shape becomes finer as a result of the overlapping of the first uneven shape and the second uneven shape, it is possible to reduce the variation in the pixels of the emission colors of the liquid crystal display panel. Can reduce color flicker.

In one embodiment of the first diffusion plate of the present invention, the x-axis and the y-axis are determined in two orthogonal directions parallel to one of the surfaces of the substrate, and the z-axis is determined in the direction perpendicular to the one surface. The surface shape of the first unevenness,

z = f (x, y)

Represented by the shape of the surface of the second unevenness,

Z = g (x, y)

When represented by, the surface shape of the composite pattern,

0≤ξ≤1

Using phosphorus parameter (ξ)

z = (1-ξ) × f (x, y) + ξ × g (x, y)

It is characterized by that. Therefore, according to this embodiment, by changing the parameter ξ in the range of 0 to 1, the distribution plate can be designed by arbitrarily changing the distribution ratio of the first uneven shape and the second uneven shape. In particular, when z = f (x, y) and z = g (x, y) represent a first uneven shape and a second uneven shape having the same degree of diffusion, varying the degree of diffusion of the diffusion plate. The distribution ratio of the first uneven shape and the second uneven shape can be changed without.

In another embodiment of the first diffusion plate of the present invention, in the above embodiment, the parameter ξ is

0.1≤ξ≤0.3

I am doing it. By setting the parameter ξ within this range, the contrast of the image when used in the liquid crystal display device can be increased to prevent color blurring, and the luminance can be maintained high.

In still another embodiment of the first diffusion plate of the present invention, the first unevenness is configured by periodically arranging a linear recess or a convexity extending in one direction, and the second unevenness is a spherical surface. A concave or convex portion of a shape or a conical shape is arranged aperiodically. According to the shape of the concave portion or the convex portion of the first uneven shape having a long linear shape in one direction, for example, a cylindrical lens, incident light can be diffused in a plane perpendicular to the longitudinal direction. Further, according to the concave portion or convex portion of the second uneven shape having a spherical shape or a conical shape, for example, a concave lens shape, the incident light can be diffused around the optical axis. In addition, when a composite pattern is produced according to this embodiment, the composite pattern has a region substantially parallel to the surface of the substrate, and the region is a lattice in which rough rectangles are arranged when viewed from any surface side of the substrate. The shape of the shape is formed. Therefore, the effect of preventing the color blurring at the time of using for a liquid crystal display device becomes high.

In still another embodiment of the first diffuser plate of the present invention, the substrate of the recessed or convex portions constituting the second recessed and projected portions with respect to the arrangement period of the recessed or convex portions constituting the first irregularities. Since the maximum dimension seen from the direction perpendicular | vertical to is characterized by being 1/3 to 3 times, it is possible to reduce color flicker of the screen of the liquid crystal display device.

The second diffuser plate according to the present invention diffuses incident light in one plane including the optical axis of the incident light to either surface of the substrate on which light enters from one surface and light exits from the other surface. The first concave-convex shape made up of a plurality of concave portions or convex portions to be made, and the second concave-convex shape made up of a plurality of concave portions or convex portions for diffusing incident light within a plane including the optical axis of the incident light, the two planes orthogonal to each other It is arrange | positioned in the direction to say, It is characterized by the above-mentioned.

Also in the second diffusion plate according to the present invention, when combined with a liquid crystal display panel, it is possible to reduce moire fringes and to suppress a decrease in luminance, and also to reduce color blurring of the screen.

In an embodiment of the second diffusion plate of the present invention, the incident light is a light beam having a narrow directivity characteristic in one of two directions orthogonal to the optical axis and having a wide directivity in the other direction. The recessed part or convex part which comprises 1 uneven shape is arrange | positioned so that incident light may diffuse in the plane parallel to the direction where the said directivity characteristic of the said incident light is narrow, and the recessed part or convex part which comprises said 2nd uneven shape is the said incident light Is arranged to diffuse incident light in a plane parallel to the wide direction, and the diffusion degree of the first uneven shape is larger than that of the second uneven shape. Therefore, using this diffuser plate, the incident light can be diffused largely by the first uneven shape in the direction in which the directivity of incident light is narrow, and the incident light can be diffused small by the second uneven shape in the direction where the directivity of the incident light is wide. The visibility of the screen of the liquid crystal display device can be improved.

In another embodiment of the second diffuser plate of the present invention, the concave portion or the convex portion constituting the first concave-convex shape and the concave portion or the convex portion constituting the second concave-convex shape are long in one direction. It is a linear recessed part or convex part. According to the shape of the linear concave or convex portion, for example, cylindrical lens, elongated in one direction, incident light can be diffused in a plane perpendicular to the longitudinal direction. Further, the degree of diffusion of each can be adjusted by the curvature of the surface of the concave portion or the convex portion constituting the first uneven shape and the second uneven shape.

In still another embodiment of the second diffuser plate of the present invention, the period of the concave portion or the convex portion constituting the first concave-convex shape in the direction parallel to the plane in which incident light diffuses by the first concave-convex shape is given. The period of the concave portion or the convex portion constituting the second concave-convex shape in the direction parallel to the plane in which incident light diffuses by the second concave-convex shape is 1/3 to 3 times. According to this embodiment, the color blurring of the screen of a liquid crystal display device can be reduced.

In still another embodiment of the first and second diffuser plates of the present invention, the first uneven shape has a radially concave portion or a convex portion that is elongated in one direction and is disposed radially about a predetermined point. Therefore, the diffusion plate of the present invention can be applied to a surface light source device using a micro light source.

Particularly, in one of the surface light source devices according to the present invention, the light source is a point light source, and almost the entire surface on the side opposite to the light exit surface of the light guide plate has a shape having directionality in the longitudinal direction, and the length direction is the point. A deflection pattern element facing substantially perpendicular to the light source is arranged at intervals from each other, and on a surface of the prism sheet facing the light guide plate, a prism of a triangular cross-sectional outline is formed around a point corresponding to the point light source. The first concave-convex shape which is formed in a shape and forms a composite pattern of the diffusion plate has a radially concave portion or a convex portion that is elongated in one direction and is disposed radially around the point corresponding to the point light source. .

In such a surface light source device, in addition to the effect of using the diffuser plate according to the present invention, the light emitted from the point light source is emitted from the light exit surface of the light guide plate as light having a narrow viewing angle, and the diffuser plate has a good viewing angle. It is possible to obtain the surface light source device having high light utilization efficiency and good visibility.

In addition, the component demonstrated above of this invention can be combined arbitrarily as possible.

1 is an exploded perspective view showing a surface light source device according to a first conventional example.

2 is a schematic sectional view of a surface light source device according to a first conventional example.

3 is an exploded perspective view showing a surface light source device according to a second conventional example.

4 is a schematic sectional view of a surface light source device according to a second conventional example.

Fig. 5 is a perspective view showing the directivity characteristic of light transmitted through the prism sheet in the above surface light source device.

6 (a) is a plan view showing the arrangement of the diffusion pattern in the uneven diffuser plate used in the second conventional example, and FIG. 6 (b) shows the cross-sectional shape of the uneven diffuser plate in the cross section parallel to the zx plane. Fig. 6 (c) is a diagram showing the cross-sectional shape of the uneven diffuser plate in the section parallel to the yz plane.

7 is a view for explaining the operation of the diffusion pattern in the yz plane.

Fig. 8 is a diagram explaining the action of the diffusion pattern in the zx plane.

9 is a diagram illustrating the directivity characteristic of light emitted from a prism sheet.

10 is a diagram illustrating diffusion characteristics of an uneven diffuser plate.

FIG. 11 is a diagram showing the directivity characteristic of light emitted from the surface light source device when using the uneven diffuser plate having the diffusion characteristics as shown in FIG. 10; FIG.

12 is an exploded perspective view showing a surface light source device according to a third conventional example.

13 is a schematic cross-sectional view of a surface light source device according to a third conventional example.

Fig. 14 is a perspective view showing the directivity characteristic of light transmitted through a prism sheet in the surface light source device as described above.

Fig. 15A is a plan view of the uneven diffuser plate used in the third conventional example, Fig. 15B is a sectional view taken along the line P1-P1 in Fig. 15A, and Fig. 15C is Fig. 15A. Sectional view along the P2-P2 line.

Fig. 16 is a diagram showing the directivity characteristic of light emitted from a prism sheet.

17 is a diagram illustrating diffusion characteristics of an uneven diffuser plate.

FIG. 18 is a diagram showing directivity characteristics of light emitted from a surface light source device when using the uneven diffuser plate having the diffusion characteristics as shown in FIG. 17; FIG.

Fig. 19 is a diagram showing moire fringes occurring on the surface of a liquid crystal display panel in the second conventional example.

20 is a diagram showing actual moire stripes.

21 is a schematic plan view showing a pixel opening of a liquid crystal display panel.

Fig. 22 is a diagram explaining why moire fringes occur.

FIG. 23 is a diagram illustrating color wobble occurring on the surface of a liquid crystal display panel. FIG.

FIG. 24A is an enlarged view of a portion F of FIG. 23, and FIG. 24B is a diagram showing the light emission intensity of each pixel of red, green, and blue.

25 (a) and 25 (b) are explanatory views for explaining the structure of an uneven diffuser plate having another pattern.

26 (a) and 26 (b) are a perspective view and a cross-sectional view showing the shape of the concave portion provided in the above uneven diffuser plate.

FIG. 27A is a diagram illustrating the action of the uneven diffuser plate, and FIG. 27B is a diagram illustrating the diffusion characteristics thereof.

FIG. 28 is a diagram showing diffusion characteristics of an uneven diffuser plate. FIG.

Fig. 29 is a diagram showing the directing characteristics of light after passing through the uneven diffuser plate as described above.

30 is an exploded perspective view showing a surface light source device using the uneven diffusion plate according to the first embodiment of the present invention.

FIG. 31A shows a first uneven pattern, FIG. 31B shows a second uneven pattern, and FIG. 31C shows a first uneven pattern shown in FIG. 31A and FIG. The pattern which shows the pattern of the uneven diffuser plate shape | molded using the synthetic pattern synthesize | combined from the 2nd uneven pattern of b).

FIG. 32A is a diagram illustrating the action of the first uneven pattern, and FIG. 32B is a diagram illustrating the action of the second uneven pattern.

33 (a), 33 (b), 33 (c), 33 (d), 33 (e) and 33 (f) show a method of synthesizing the first uneven pattern and the second uneven pattern. To explain.

Fig. 34 is a change of the inverse of the contrast between the brightness of the screen of the liquid crystal display device and the openings of the respective emission colors R, G, and B of the liquid crystal display panel when the synthesis ratio ξ is changed from 0 to 1; A diagram showing the results of a simulation.

Fig. 35 (a) shows an image of a composite pattern of an uneven diffuser plate viewed under a microscope, and Fig. 35 (b) shows a power spectrum image thereof.

Fig. 36 is a diagram showing the distance (spatial frequency) from the origin of the power spectrum image of Fig. 35 (b) on the horizontal axis and the intensity on the vertical axis;

Fig. 37 is a diagram showing an aspect of photographing the uneven diffuser plate through a microscope.

Fig. 38 is an enlarged view showing the composite pattern of the uneven diffuser plate and the luminance distribution in the x-axis direction.

39 shows luminance and directivity characteristics when the uneven diffuser plate of the present invention is used.

40 shows luminance and directivity characteristics in the case of using the uneven diffuser plate provided with only the first uneven pattern.

Fig. 41 is a diagram showing luminance and directivity characteristics in the case of using the uneven diffuser plate provided with only the second uneven pattern;

FIG. 42 is a view for explaining an aspect in which the uneven diffuser plate of Example 1 is overlapped with the liquid crystal display panel. FIG.

Fig. 43 is a view showing the change of contrast with respect to the size ratio (K / Λy) of the pattern in the uneven diffuser plate.

FIG. 44A is a diagram showing a pattern shape in the zx plane of the composite pattern, and FIG. 44B is a diagram showing the directivity characteristics in the zx plane.

45 (a) is a diagram showing a pattern shape in the yz plane of the composite pattern, and FIG. 45 (b) is a diagram showing the directivity characteristics in the yz plane.

Fig. 46 is a perspective view showing a surface light source device according to a second embodiment of the present invention.

Fig. 47 (a) is a schematic diagram showing a pattern of the diffusion plate according to the third embodiment of the present invention, and Fig. 47 (b) shows an image when the pattern of Fig. 47 (a) is viewed under a microscope.

48A is a diagram showing a cross section in a direction orthogonal to the longitudinal direction of the first uneven pattern, and FIG. 48B is a diagram showing a cross section in a direction orthogonal to the longitudinal direction of the second uneven pattern.

Fig. 49 is a schematic diagram showing a liquid crystal display device according to a fourth embodiment of the present invention.

50 is a micrograph of the uneven diffuser plate shown in FIG. 22.

FIG. 51 is a micrograph of the uneven diffuser plate shown in FIG. 38.

(Explanation of symbols for the main parts of the drawing)

32: Light guide plate 33: Light emitting part

34 mirror surface reflection sheet 35 deflection pattern element

38: light entrance plane 40: light exit plane

42: prism sheet 52: light guide plate

53: light emitting portion 54: mirror reflective sheet

55: deflection pattern element 60: light exit surface

81: surface light source device 82: uneven diffuser plate

83: transparent substrate 85: second uneven pattern

86: composite pattern 91: surface light source device

92: uneven diffuser plate

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, of course, this invention is not limited to the following example.

(Example 1)

30 is an exploded perspective view showing the surface light source device 81 using the diffusion plate according to the first embodiment of the present invention. This surface light source device 81 is comprised by the light guide plate 32, the light emission part 33, the mirror surface reflection sheet 34, the prism sheet 42, and the uneven diffused plate 82. As shown in FIG. Among these, the structural members other than the uneven diffuser plate 82 are the same as those of the second conventional example already described, and thus their explanations are omitted, and the structure and operation of the uneven diffuser plate 82 are described below. Explain only.

The uneven diffuser plate 82 is formed by molding the first uneven shape and the second uneven shape on the upper surface of the transparent substrate 83 by a stamper method or the like. The first uneven shape and the second uneven shape are combined so that they are combined. have. 31 (a) and 31 (b) show a first uneven shape and a second uneven shape as the source of the composite pattern, respectively, and FIG. 31 (c) shows the first uneven shape and the second uneven shape. It is a figure which shows a part of the pattern formed in the surface of the uneven diffuser board 82 based on one pattern.

The 1st uneven | corrugated shape is comprised by the some 1st uneven | corrugated pattern 84 (concave part or convex part). The first concave-convex pattern 84 is formed in a wave shape, a semicircle shape, a semi-ellipse shape, a cylindrical lens shape, a triangular prism shape, a cross-sectional trapezoidal shape, or the like, and extends in a straight shape with a uniform cross section. It has a linear shape to a rod shape. Further, the first uneven patterns 84 are arranged in parallel with each other and are repeatedly arranged in periods Λx and Λy in the x direction and the y direction. As shown in Fig. 32 (a), when light is incident vertically from the lower surface side, it includes the optical axis of the incident light (rays of maximum luminous intensity) and is perpendicular to the longitudinal direction of the first uneven pattern 84. Diffusing incident light in a plane is a typical optical action of the first uneven pattern 84.

The 2nd uneven | corrugated shape is comprised by the some 2nd uneven | corrugated pattern 85 (concave part or convex part). The second uneven pattern 85 is formed in a spherical concave lens shape, a non-spherical concave lens shape, a conical shape, a cone shape, a pyramidal shape, a pyramidal shape, or the like, and is randomly arranged. The size of the second uneven pattern 85 may be random. In addition, it is preferable that the whole of the 2nd uneven | corrugated pattern 85 is comprised by repeating and periodically arrange | positioning the basic pattern arranged at random (refer to description of FIG. 25). As shown in Fig. 32 (b), when light is incident vertically from the lower surface side, incident light is diffused around a straight line parallel to the optical axis of the incident light and passing through the center of the second uneven pattern 85. Is a typical optical action of the second uneven pattern 85.

The composite pattern 86 on the surface of the surface light source device 81 includes a plurality of first uneven patterns 84 arranged as shown in FIG. 31 (a) and a plurality of second uneven lines arranged as shown in FIG. 31 (b). The pattern 85 is overlapped and synthesized. 33 (a), 33 (b), 33 (c), 33 (d), 33 (e) and 33 (f) show the first uneven pattern 84 and the second uneven pattern ( 85) describes how to synthesize. 33A and 33B are pattern shapes in the cross section parallel to the yz plane of the first uneven pattern 84 and pattern shapes in the cross section parallel to the zx plane. 33 (c) and 33 (d) are pattern shapes in the cross section parallel to the yz plane of the second uneven pattern 85 and pattern shapes in the cross section parallel to the zx plane. 33 (e) and 33 (f) are pattern shapes in the cross section parallel to the yz plane of the composite pattern 86 and pattern shapes in the cross section parallel to the zx plane.

The height of the first uneven pattern 84 shown in FIGS. 33A and 33B is z = z1, and the shape of the first uneven pattern 84 is

z = z1 = f (x, y)

It is indicated by. Similarly, the height of the 2nd uneven | corrugated pattern 85 shown in FIG.33 (c) and FIG.33 (d) is set to z = z2, and the shape of the 2nd uneven | corrugated pattern 85 is

z = z2 = g (x, y)

It is indicated by. At this time, the shape of the composite pattern 86 of FIGS. 33E and 33F is expressed as an overlap between the first uneven pattern 84 and the second uneven pattern 85. That is, when the height of the composite pattern 86 is z = z 3, the shape of the composite pattern 86 is

z = z3 = z1 + z2 = f (x, y) + g (x, y)

Is displayed. In this way, when the shape of the composite pattern 86 is determined, an Ni disk is produced by an electron beam drawing method or the like, a stamper is produced from the disk, and the UV curable resin applied on the transparent substrate 83 is applied using the stamper. It can shape | mold with a stamper, harden | cure ultraviolet-ray curable resin by ultraviolet irradiation, and the uneven diffuser board 82 can be obtained.

Moreover, the pattern shape of the 1st uneven | corrugated pattern 84: z1 = f (x, y) shows the pattern of the spreading degree made into the objective, and the pattern shape of the 2nd uneven | corrugated pattern 85: z2 = g (x and y) also represent a pattern of the degree of diffusion desired.

z = z3 = (1-ξ) × f (x, y) + ξ × g (x, y)... (One)

The composite pattern 86 of the pattern shape shown by is shown as a pattern of the degree of diffusion almost aimed again. Here, ξ is a synthesis ratio of the second uneven pattern 85, and 0 ≦ ξ ≦ 1. Therefore, when the composite pattern 86 is designed using the formula (1), the shape of the composite pattern 86 can be changed with ξ as a parameter while maintaining the desired degree of diffusion. Therefore, by determining the value of ξ that can change the ξ so that moire fringes, color blurring, brightness reduction, and the like can be made as small as possible, the shape of the optimal composite pattern 86 can be determined.

FIG. 34 shows the brightness of the screen of the liquid crystal display device when the composition ratio ξ is changed from 0 to 1, and the opening of each of the emission colors R, G, and B of the liquid crystal display panel shown in FIG. The inverse of the contrast is simulated. As shown in Fig. 34, the brightness of the screen decreases as ξ becomes larger and the ratio of the second uneven pattern 85 increases. This is because the luminance of the second uneven pattern 85 is about 15% lower than that of the first uneven pattern 84. The inverse of the contrast is large in the range of ξ = 0.2 to 0.8. However, when ξ is smaller than 0.2, the inverse of the contrast is small, and even if it exceeds 0.8, the inverse of the contrast is small.

According to Fig. 34, when the synthesis ratio ξ increases from 0 to 0.5, the inverse of the contrast is close to 1, making color blurring difficult, but the luminance gradually decreases. Therefore, the value of the synthesis ratio ξ of the second uneven pattern 85 is determined in an area in which the inverse of the contrast is 0.95 or more and the luminance does not decrease by more than 10% compared to the first uneven pattern 84. Therefore, as a value (design area) of the composition ratio of the second uneven pattern 85,

0.1≤ξ≤0.3

It is preferable to set it as this, and about 0.2 are especially preferable.

However, even if a molding die (stamper) for molding the composite pattern 86 is actually synthesized and manufactured with the first uneven pattern 84 and the second uneven pattern 85 accurately, The molded composite pattern 86 involves some deformation. That is, in the composite pattern 86 which synthesize | combined the 1st uneven | corrugated pattern 84 and the 2nd uneven | corrugated pattern 85, since a pattern becomes fine compared with the 1st and 2nd uneven | corrugated patterns 84 and 85, a composite pattern The resin of (86) is less likely to be filled in the tip portion of the pattern, or the pattern is slightly skewed. As a result, the upper surface of the first uneven pattern 84, the tip portion of the second uneven pattern 85, or the like becomes an area substantially parallel to the transparent substrate 83, and is shown in FIG. 51 shows a photomicrograph of the composite pattern 86 in FIG. 51, the region substantially parallel to the transparent substrate 83 forms a lattice shape in which rough rectangles are arranged. In particular, when the compounding ratio ξ is small, since the first uneven pattern 84 is strong, the compound pattern 86 has a lattice shape in which rough rectangles are arranged, as shown in Figs. 31 (c) and 51. It is easy to become a pattern of.

FIG. 35A shows an image of the composite pattern 86 of the uneven diffuser plate 82 viewed under a microscope. As shown in FIG. 37, parallel light is irradiated to the uneven diffuser plate 82 from the lower surface side, and the composite pattern 86 is image | photographed through the microscope objective lens 87. As shown in FIG. According to Fig. 35A, the patterns of both the first uneven pattern 84 elongated in one direction and the second uneven pattern 85 randomly arranged in plural can be observed. At this time, in the second uneven pattern 85, the sides where the adjacent uneven patterns cross each other become a straight line, so that the second uneven pattern 85 actually appears to have a polygonal arrangement.

35 (b) shows a power spectrum image obtained by two-dimensional Fourier transform of the original image of FIG. 35 (a). In the power spectral image of FIG. 35B, the peak existing on the y axis and the peak spreading in all directions can be observed. The peak present on this y-axis corresponds to the period Λy in the y-axis direction of the first uneven pattern 84 elongated in one direction. The peak spreading in all directions corresponds to the external dimension K of the 2nd uneven pattern 85 arranged in multiple numbers.

FIG. 36 shows a graph (power spectral component) in which the distance (spatial frequency) from the origin of the power spectrum image of FIG. 35B is taken along the horizontal axis, and the intensity is taken along the vertical axis. Here, the peak by the component of the 1st uneven | corrugated pattern 84 and the peak by the component of the 2nd uneven | corrugated pattern 85 are shown separately.

Next, the effect of moire elimination by the uneven diffusion plate 82 of this invention is demonstrated. In the case of the second conventional example, moire fringes are generated because the luminance peak is periodically generated at the joint 44 of the diffusion pattern 43. However, in the concave-convex diffuser plate 82 used in the present invention, since the components of the first concave-convex pattern 84 corresponding to the diffusion pattern 43 are part of the composite pattern 86, the luminance peak is that much. Becomes small, and moire fringes become less likely to occur. In addition, when the second uneven pattern 85 overlaps with the first uneven pattern 84, the seam of the pattern disappears, so that a large luminance peak does not occur periodically as in the luminance distribution shown in FIG. 51 shows a photomicrograph of the uneven diffuser plate shown here). As a result, the gap between the uneven diffusion plate 82 and the opening pitch of the liquid crystal display panel is less likely to cause interference, and the moire fringes can be eliminated.

In addition, according to the uneven diffusion plate 82 according to the present invention, it is expected that luminance between the first uneven pattern 84 and the second uneven pattern 85 is obtained. 39, 40, and 41 show the case of using the uneven diffuser plate 82 of the present invention, the case of using the uneven diffuser plate having only the first uneven pattern 84, and the second uneven pattern 85, respectively. In the case of using the uneven diffuser plate provided with bay, luminance and directivity characteristics were compared. In either case, the directivity is about 20 degrees, and the viewing angle is sufficient to be used for display.

On the other hand, if the luminance in the case of using the diffusion plate of only the first uneven pattern 84 is taken as a reference, and this is 1, the luminance in the case of using the diffusion plate of only the second uneven pattern 85 is 0.85, In the case of the uneven diffuser plate 82, the value was 0.95. Therefore, in the case where the uneven diffuser plate 82 of the present invention is used, the luminance is lowered as compared with the case of using the uneven diffuser plate of only the first uneven pattern 84, but the uneven diffuser plate of only the second uneven pattern 85 is used. Compared with the case of using, the luminance is improved by 10% or more.

Next, the reason why color blurring is eliminated by using the uneven diffuser plate 82 of the present invention will be described. As can be seen from FIG. 22, by overlapping the first uneven pattern 84 and the second uneven pattern 85, the composite pattern 86 is second compared with the first uneven pattern 84. The pattern is finer than that of the uneven pattern 85 and uniformly distributed throughout the uneven diffuser plate 82. Therefore, as shown in FIG. 42, when the liquid crystal display panel 65 is superimposed on the surface light source device 81, the composite pattern 86 distributed in the red pixel 65R and the green pixel 65G are distributed. The difference in distribution amount between the composite pattern 86 and the composite pattern 86 distributed in the blue pixel 65B is not recognized. As a result, the light shines at the same brightness as the pixels of each light emission color, and color flickering is less likely to occur.

Specifically, the opening period of the liquid crystal display panel 65 is Λc = 150 μm, the opening size of each light emitting color is vertical D1 = 100 μm and width D2 = 35 μm. In addition, the 1st uneven | corrugated pattern 84 has the period X in a x direction of Λx = 100 micrometers, and the y-direction period has Λy = 10 micrometer, and the 2nd uneven | corrugated pattern 85 has the external dimension K = 11micrometer. It is. In this configuration, if the ratio of the luminance in the red pixel 65R, the green pixel 65G, and the blue pixel 65B is measured,

Luminance of the red pixel: Luminance of the green pixel: Luminance of the blue pixel = 1.03: 1.03: 1

The contrast ratio is improved to 1.03. Therefore, according to the uneven diffusion plate 82, the color blurring of the screen can be almost improved.

In addition, with respect to the ratio K / Λy of the period Λy in the y-direction of the first uneven pattern 84 and the outline dimension of the second uneven pattern 85, the contrast of the luminance in the pixel aperture is shown in FIG. 43. Changes together. The condition for not seeing the color flicker is about 1.1 in contrast. Therefore, according to the experimental result also regarding the relationship between the period (La) of the direction orthogonal to the longitudinal direction of the 1st uneven | corrugated pattern 84, and the external dimension K of the 2nd uneven | corrugated pattern 85,

1 / 3≤K / Λy≤3

Is preferred, and in particular,

1 / 2≤K / Λy≤2

This is preferred.

Fig. 44 (a) shows a cross section of the composite pattern 86 in the yz plane, and Fig. 44 (b) shows the diffusion characteristics of the composite pattern 86 in the yz plane. 45 (a) shows a cross section of the composite pattern 86 in the zx plane, and FIG. 45 (b) shows the diffusion characteristics of the composite pattern 86 in the zx plane. In the yz plane, the angle of inclination of the composite pattern 86 is obtained by adding the angle ε of the second uneven pattern 85 to the angle of inclination γ of the first uneven pattern 84. ε) determines the diffusion characteristics in the yz plane. Incidentally, the inclination angle of the composite pattern 86 in the zx plane is determined only by the inclination angle ε of the second uneven pattern 85, and its diffusion characteristic has a peak at ± ε / (n-1). . Therefore, by adjusting the angles γ and ε of the first uneven pattern 84 and the second uneven pattern 85, the diffusion characteristics in the yz plane and the diffusion characteristics in the zx plane can be optimized.

(Example 2)

Fig. 46 is a perspective view showing the surface light source device 91 of Embodiment 2 of the present invention. Also in this Example 2, since components other than the uneven diffused plate 92 have the structure similar to 3rd prior art example, the detail is abbreviate | omitted. In addition, in the uneven diffuser plate 92 used in the second embodiment, the linear first uneven pattern 93 extending radially about the light source 53 and the spherical or conical shape arranged aperiodically The composite pattern 95 is formed by overlapping the second uneven patterns 94 such as the image. Also regarding the second embodiment, if the x-axis direction and the y-axis direction in the description of the first embodiment are read in the r-axis direction and the θ-axis direction, respectively, the description of the first embodiment also applies to the second embodiment.

(Example 3)

Fig. 47A is a plan view showing a pattern provided in the uneven diffusion plate 96 according to the third embodiment of the present invention. In Example 3, the linear 1st uneven | corrugated pattern 97 is arrange | positioned in parallel with each other in the period of (Lay), and the linear 2nd uneven | corrugated pattern 98 is arranged in parallel with each other in the period of (Lax). . In Example 3, the 1st uneven | corrugated pattern 97 and the 2nd uneven | corrugated pattern 98 are also shape | molded in cross-sectional wave shape, cross-sectional semicircle shape, cylindrical lens shape, cross-sectional trapezoidal shape, triangular prism shape, etc. The uneven pattern 97 and the second uneven pattern 98 are arranged such that their longitudinal directions are perpendicular to each other. Since these patterns are fine, even when viewed under a microscope, they are shown in a lattice shape as shown in Fig. 47B.

FIG. 48A is a view showing a cross section in a direction orthogonal to the longitudinal direction of the first uneven pattern 97, and FIG. 48B is a view in a direction orthogonal to the longitudinal direction of the second uneven pattern 98. It is a figure which shows a cross section. As shown in FIG. 48, the pattern height H2 of the second uneven pattern 98 is smaller than the pattern height H1 of the first uneven pattern 97, and the pattern period of the second uneven pattern 98 ( Λx is longer than the pattern period Λy of the first uneven pattern 97. Therefore, the diffusion characteristic of the second uneven pattern 98 is smaller than that of the first uneven pattern 97.

In particular, the aspect ratio H2 / Λx of the second uneven pattern 98 is made to be about 1/5 smaller than the aspect ratio H1 / Λy of the first uneven pattern 97. By the combination of the first uneven pattern 97 and the second uneven pattern 98, the diffusion characteristic in the x direction can be made smaller than the diffusion characteristic in the y direction, and the luminance can be prevented from decreasing substantially.

Therefore, the luminance peak at the joint of the first uneven pattern 97 becomes smaller by diffusing light by the second uneven pattern 98, and the luminance peak at the joint of the second uneven pattern 98 is also the first. The light is diffused by the uneven pattern 97 so as to be small. As a result, moire fringes are less likely to occur due to interference with the period of the pixel aperture of the liquid crystal display panel.

In addition, since the pattern becomes fine due to the vertical and horizontal combinations of the first uneven pattern 97 and the second uneven pattern 98, the pattern becomes difficult to be biased in each pixel opening of the liquid crystal display panel, and color blurring is also reduced. do. In particular, in order to reduce color blurring, the ratio of the period Λy of the first uneven pattern 97 and the period Λx of the second uneven pattern 98 is

1 / 3≤Λx / Λy≤3

Is preferably. More preferably,

1 / 2≤Λx / Λy≤2

It is good to do.

(Example 4)

49 is a schematic sectional view showing a liquid crystal display device 111 according to the present invention. This is, for example, provided so that the liquid crystal display panel 112 faces the surface light source device 81 of the first embodiment.

As described above, according to the diffusion plate of the present invention, moire fringes and color blurring can be suppressed while maintaining the brightness of the screen of the liquid crystal display device high.

Claims (15)

On either side of the substrate where light enters from one side and light exits from the other side, A first concave-convex shape comprising a plurality of concave portions or convex portions for diffusing the incident light in one plane including the optical axis of the incident light, and a second concave portion or convex portion for diffusing the incident light around the optical axis of the incident light The composite pattern obtained by superimposing uneven | corrugated shape is formed, The x-axis and the y-axis are determined in two orthogonal directions parallel to one surface of the substrate, and the z-axis is determined in the direction perpendicular to the one surface, so that the surface shape of the first uneven shape is z = f (x, y) Represented by the shape of the surface of the second unevenness, Z = g (x, y) When displayed as The surface shape of the composite pattern is 0≤ξ≤1 Using phosphorus parameter (ξ) z = (1-ξ) × f (x, y) + ξ × g (x, y) Diffusion plate, characterized in that represented by. delete The method of claim 1, The parameter ξ is 0.1≤ξ≤0.3 Diffusion plate characterized in that. The method of claim 1, The first concave-convex shape is configured by periodically arranging linear concave portions or convex portions extending in one direction. The said 2nd uneven | corrugated shape is comprised by arrange | positioning a spherical shape or conical recessed part or convex part aperiodically, The diffuser plate characterized by the above-mentioned. The method of claim 4, wherein The said composite pattern has the area | region substantially parallel to the surface of the said board | substrate, The said area | region forms the lattice shape which the rectangular form arranged as seen from either surface side of the said board | substrate. The method of claim 4, wherein 3 to 3 times or more the largest dimension seen from the direction perpendicular | vertical to the said board | substrate with respect to the arrangement | positioning part of the recessed part or convex part which comprises the said 1st uneven shape. Diffusion plate, characterized in that less than twice. On either side of the substrate where light enters from one side and light exits from the other side, A first concave-convex shape comprising a plurality of concave portions or convex portions for diffusing incident light in one plane including the optical axis of the incident light, and a plurality of concave portions or convex for diffusing incident light in one plane including the optical axis of the incident light The 2nd uneven | corrugated shape which consists of parts is arrange | positioned in the direction in which the said plane is orthogonal to each other, The diffuser plate characterized by the above-mentioned. The method of claim 7, wherein The incident light is a light beam having a narrow directivity in one of two directions orthogonal to the optical axis and having a wide directivity in the other direction, The concave portion or the convex portion constituting the first unevenness is arranged to diffuse the incident light in a plane parallel to the narrow direction of the directivity characteristic of the incident light, The concave portion or the convex portion constituting the second unevenness is arranged to diffuse the incident light in a plane parallel to the direction in which the directivity of the incident light is wide, The diffusion degree of a said 1st uneven shape is larger than the diffusion degree of a 2nd uneven shape, The diffuser plate characterized by the above-mentioned. The method of claim 7, wherein The concave portion or the convex portion constituting the first concave-convex shape and the concave portion or the convex portion constituting the second concave-convex shape are both linear concave portions or convex portions extending in one direction. . The method of claim 7, wherein Parallel to the plane in which incident light diffuses by the second uneven shape with respect to the period of the concave or convex portion constituting the first uneven shape in a direction parallel to the plane in which incident light diffuses by the first uneven shape. The period of the recessed part or convex part which comprises the 2nd uneven shape in one direction is 1/3 to 3 times, The diffuser plate characterized by the above-mentioned. The method of claim 1, The said 1st uneven shape is a diffuser plate in which the linear recessed part or convex part extended in one direction is arrange | positioned radially. The method of claim 7, wherein The said 1st uneven shape is a diffuser plate in which the linear recessed part or convex part extended in one direction is arrange | positioned radially. Light source, A light guide plate which spreads the light introduced from the light source into a plane shape and emits the light from the light exit surface; The surface light source device provided with the diffuser plate in any one of Claim 1 or 3-12 arrange | positioned facing the light exit surface of the said light guide plate. Light source, A light guide plate which spreads the light introduced from the light source into a plane shape and emits the light from the light exit surface; A prism sheet disposed so as to face the light exit surface of the light guide plate, and to deflect the light emitted from the light guide plate in a direction perpendicular to the light exit surface and to exit from a surface opposite to the surface opposite to the light guide plate; The surface light source device provided with the diffusion plate in any one of Claim 1 or 3-12 arrange | positioned facing the surface which the light of the said prism sheet exits. The method of claim 14, The light source is a point light source, In the whole surface of the light-emitting plate and the opposite side of the light guide plate, there is a shape having a directionality in the longitudinal direction, and the deflection pattern elements in which the longitudinal direction is perpendicular to the point light source are arranged at intervals from each other. On the surface of the prism sheet that faces the light guide plate, a prism having a triangular cross section is formed in an arc shape around the point corresponding to the point light source. The first concave-convex shape for forming the composite pattern of the diffusion plate is a surface light source, characterized in that the linear concave or convex portions extending in one direction are arranged radially with respect to the point corresponding to the point light source. Device.

Images