JP7560286B2 - Light Diffusion Materials - Google Patents

Description

The present invention relates to a light diffusing member, a backlight unit, an image display device, and an illumination device.

Image display devices such as liquid crystal display devices include a display panel and a backlight unit arranged on the back side of the display panel. Backlight units come in various types, such as edge-light type (side-light type) and direct type. Of these, direct type backlight units include a light source and a light diffusion plate arranged on the light output side of the light source. Direct type backlight units tend to achieve high brightness because light from the light source is emitted directly toward the display panel.

On the other hand, direct-type backlight units tend to have locally high brightness in the area near the light source when viewed in a plan view, which can easily result in uneven brightness. For this reason, a light diffusion plate has traditionally been given the ability to reflect light rays in order to make the brightness uniform across the entire backlight unit (see JP 2005-284283 A).

JP 2005-284283 A

The above publication describes how brightness can be made uniform by providing multiple micro-reflective dots on the surface of the diffuser plate and reflecting a portion of the light that reaches the diffuser plate by the micro-reflective dots.

However, today, it is sometimes difficult to fully eliminate uneven brightness with the configuration described in the above publication. One way to solve this problem is to increase the reflectance of each reflective dot, but it is not easy to improve the reflectance of reflective dots, and the current reflectance of reflective dots is less than 90%.

The present invention was made in consideration of these circumstances, and aims to provide a light diffusing member that can sufficiently suppress the occurrence of brightness unevenness.

The light diffusing member according to one aspect of the present invention has a plurality of reflective dot patterns arranged via a resin layer in the light transmission direction, each of the plurality of reflective dot patterns including a reflective dot, and the plurality of reflective dot patterns are arranged in an overlapping region in a planar view.

The light diffusing member according to one aspect of the present invention can sufficiently suppress the occurrence of uneven brightness.

FIG. 1 is a schematic cross-sectional view showing an image display device according to one embodiment of the present invention. FIG. 2 is a schematic plan view showing an example of a reflective dot pattern of a light diffusing member used in the image display device of FIG. FIG. 3 is a schematic plan view showing a reflective dot pattern different from the reflective dot pattern in FIG. FIG. 4 is a schematic plan view showing a reflective dot pattern different from the reflective dot patterns shown in FIGS. FIG. 5 is a schematic plan view showing a reflective dot pattern different from the reflective dot patterns shown in FIGS. FIG. 6 is a schematic plan view showing a reflective dot pattern different from the reflective dot patterns shown in FIGS. FIG. 7 is a schematic plan view showing a reflective dot pattern different from the reflective dot patterns shown in FIGS. FIG. 8 is a schematic cross-sectional view showing an image display device according to an embodiment different from the image display device in FIG. FIG. 9 is a plan view showing a reflective dot pattern formed on the light incident surface of the resin layer in the light diffusing member of the example. FIG. 10 is a plan view showing a reflective dot pattern formed on the light exit surface of the resin layer in the light diffusing member of the example. FIG. 11 is a plan view showing a reflective dot pattern formed on the light incident surface of the resin layer in the light diffusing member of the comparative example.

[Description of the embodiments of the present invention]
First, the embodiments of the present invention will be listed and described.

The light diffusing member according to one aspect of the present invention has a plurality of reflective dot patterns arranged via a resin layer in the light transmission direction, each of the plurality of reflective dot patterns including a reflective dot, and the plurality of reflective dot patterns are arranged in an overlapping region in a planar view.

The light diffusing member is arranged in an area where the multiple reflective dot patterns overlap in a planar view via the resin layer in the light transmission direction, so that the light emitted from the light source can be reflected in multiple stages in the light transmission direction. Therefore, the light diffusing member can sufficiently suppress the occurrence of uneven brightness.

It is preferable that the total area ratio of the multiple reflective dot patterns in the overlapping area in a planar view exceeds 100%. The light diffusing member can easily make the total area ratio of the multiple reflective dot patterns in the overlapping area in a planar view exceed 100%. This makes it possible to easily and reliably suppress the occurrence of uneven brightness.

It is preferable that a pair of the reflective dot patterns is formed on the light entrance surface and the light exit surface of one of the resin layers. In this way, by forming a pair of the reflective dot patterns on the light entrance surface and the light exit surface of one of the resin layers, it is easy to suppress an increase in the thickness of the light diffusion member. As a result, it is possible to promote the thinning of the device in which the light diffusion member is disposed.

The light diffusing member may include a plurality of the resin layers arranged at intervals in the transmission direction, and the reflective dot pattern may be formed on at least one of the light entrance surface and the light exit surface of each of the resin layers. In this way, the light diffusing member may include a plurality of the resin layers arranged at intervals in the transmission direction, and the reflective dot pattern may be formed on at least one of the light entrance surface and the light exit surface of each of the resin layers, thereby increasing the degree of freedom in designing the entire plurality of reflective dot patterns. As a result, the occurrence of uneven brightness may be easily and reliably suppressed.

It is preferable that at least two of the plurality of reflective dot patterns have different occupancy rates. In this way, by making the occupancy rates of at least two of the plurality of reflective dot patterns different, it is easy to adjust the reflectance of light rays in the entire plurality of reflective dot patterns. As a result, it is easy to suppress the occurrence of uneven brightness.

The area ratio of the plurality of reflective dot patterns may be gradually decreased or increased in the transmission direction. With this light diffusing member, the brightness unevenness is gradually eliminated in the transmission direction of the light beam. In this case, the area ratio of the plurality of reflective dot patterns is gradually decreased or increased in the transmission direction, so that the desired reflection function can be easily imparted to each reflective dot pattern at each stage.

It is preferable that the occupancy rate of the multiple reflective dot patterns is equal. In this way, by making the occupancy rate of the multiple reflective dot patterns equal, it is possible to easily suppress the occurrence of uneven brightness while facilitating the design of the multiple reflective dot patterns.

It is preferable that the occupancy rate of at least one of the reflective dot patterns is 100%. In this way, by having the occupancy rate of at least one of the reflective dot patterns be 100%, the total occupancy rate of the multiple reflective dot patterns in the overlapping area in a planar view can be made sufficiently large. As a result, the occurrence of brightness unevenness can be easily and reliably suppressed.

The arrangement of the reflective dots in the reflective dot pattern may be multiple rings, radial, rectangular or random. In this way, by having the arrangement of the reflective dots in the reflective dot pattern be multiple rings, radial, rectangular or random, the occurrence of brightness unevenness can be easily suppressed.

A backlight unit according to another aspect of the present invention includes the light diffusing member.

The backlight unit is equipped with a diffusion material, which can adequately suppress the occurrence of uneven brightness.

An image display device according to another aspect of the present invention includes the backlight unit.

Since the image display device is equipped with the backlight unit, it is possible to sufficiently suppress the occurrence of uneven brightness.

An illumination device according to another aspect of the present invention includes the backlight unit.

Since the lighting device is equipped with the backlight unit, it is possible to sufficiently suppress the occurrence of uneven brightness.

In the present invention, the "area ratio of the reflective dot pattern" refers to the area ratio of the multiple reflective dots in the surface area (unit area) on the resin layer where the reflective dot pattern is provided.

[Details of the embodiment of the present invention]
The present invention will now be described in detail with reference to the drawings.

[First embodiment]
<Image display device>
FIG. 1 shows an image display device 10 including a light diffusion member 1 according to one embodiment of the present invention. The image display device 10 includes a backlight unit 20 and a display panel 30 arranged on the front side (viewer side) of the backlight unit 20. The image display device 10 also includes a casing (not shown) that houses the backlight unit 20. The image display device 10 and the backlight unit 20 are themselves one embodiment of the present invention. The backlight unit 20 is a direct type backlight unit. The backlight unit 20 includes the light diffusion member 1, one or more light sources 2 (three light sources are illustrated in FIG. 1) arranged on the back side (opposite the viewer side) of the light diffusion member 1, a reflective sheet 3 arranged on the back side of the one or more light sources 2, and a prism sheet (first prism sheet 4 and second prism sheet 5) arranged on the front side of the light diffusion member 1. In this embodiment, the image display device 10 is a liquid crystal display device. That is, the display panel 30 is a liquid crystal panel. The image display device 10 may be a portable display device such as a smartphone or tablet terminal, or may be a relatively large display device such as a television or personal computer. It is preferable that the prism ridges of the first prism sheet 4 and the prism ridges of the second prism sheet 5 are perpendicular to each other in a plan view. The light source 2 may be, for example, an LED light source. The image display device 10 may include other optical sheets in addition to the light diffusion member 1, the first prism sheet 4, and the second prism sheet 5. The image display device 10 may also be configured to not include one or both of the first prism sheet 4 and the second prism sheet 5.

<Light Diffusion Member>
The light diffusing member 1 includes a plurality of reflective dot patterns (first reflective dot pattern 11a, second reflective dot pattern 12a, and third reflective dot pattern 13a) arranged via resin layers in the light transmission direction (Z direction in FIG. 1) (hereinafter, the first reflective dot pattern 11a, the second reflective dot pattern 12a, and the third reflective dot pattern 13a are also collectively referred to as "reflective dot patterns 11a to 13a"). The light diffusing member 1 includes a plurality of resin layers (first resin layer 11b, second resin layer 12b, and third resin layer 13b) arranged at intervals in the light transmission direction (hereinafter, the first resin layer 11b, the second resin layer 12b, and the third resin layer 13b are also collectively referred to as "resin layers 11b to 13b"). The resin layers 11b to 13b each have a surface facing the light source 2 that constitutes a light incident surface, and a surface on the opposite side constitutes a light exit surface. The first resin layer 11b, the second resin layer 12b, and the third resin layer 13b are arranged in this order in the light transmission direction. No other optical sheets are arranged between the resin layers adjacent to each other in the light transmission direction. In other words, the first resin layer 11b and the second resin layer 12b, and the second resin layer 12b and the third resin layer 13b face each other in the light transmission direction without any other optical sheets in between.

(Reflective dot pattern)
The light diffusing member 1 has reflective dot patterns 11a to 13a formed on at least one of the light incident surface and the light exit surface of each of the resin layers 11b, 12b, and 13b. The reflective dot patterns 11a to 13a protrude from the surfaces of the resin layers 11b to 13b. In this embodiment, the reflective dot patterns 11a to 13a are formed on the light incident surface of each of the resin layers 11b, 12b, and 13b. Specifically, the first reflective dot pattern 11a is formed on the light incident surface of the first resin layer 11b, the second reflective dot pattern 12a is formed on the light incident surface of the second resin layer 12b, and the third reflective dot pattern 13a is formed on the light incident surface of the third resin layer 13b. The light diffusing member 1 has the reflective dot patterns 11a to 13a formed on at least one of the light incident surface and the light exit surface of each of the resin layers 11b, 12b, and 13b, thereby increasing the degree of freedom in designing the multiple reflective dot patterns 11a to 13a. As a result, the occurrence of uneven luminance can be easily and reliably suppressed.

The multiple reflective dot patterns 11a to 13a are arranged in overlapping areas in a planar view. These reflective dot patterns 11a to 13a are arranged overlapping at intervals in the light transmission direction. In this embodiment, one reflective dot pattern 11a to 13a is arranged on the light incidence surface of each of the resin layers 11b, 12b, and 13b. The reflective dot patterns 11a to 13a are formed on substantially the entire light incidence surface of the resin layers 11b, 12b, and 13b. Since the light diffusion member 1 has one reflective dot pattern 11a to 13a formed on each of the light incidence surfaces, it is possible to easily suppress the occurrence of positional deviation of the reflective dot patterns 11a to 13a relative to the light source 2, positional deviation between the reflective dot patterns 11a to 13a, and uneven brightness due to printing accuracy, etc. The centers of the reflective dot patterns 11a to 13a may coincide in a planar view.

The multiple reflective dot patterns 11a to 13a each include multiple reflective dots. The multiple reflective dots are formed, for example, using ink containing a white pigment or a silver pigment as a binder component. The multiple reflective dots are formed by a printing method such as screen printing, inkjet printing, gravure printing, offset printing, flexographic printing, and dispenser printing. As the printing method, screen printing is preferable because it is possible to form the multiple reflective dots easily and with high precision. The shape of the reflective dots is not particularly limited, but examples include a hemispherical shape and a spherical declination shape. The average diameter of the multiple reflective dots can be, for example, 20 μm or more and 100 μm or less.

Specific examples of reflective dot patterns 11a to 13a that can be provided on resin layers 11b to 13b are described below with reference to Figures 2 to 7. Note that the first reflective dot pattern 11a formed on the first resin layer 11b, the second reflective dot pattern 12a formed on the second resin layer 12b, and the third reflective dot pattern 13a formed on the third resin layer 13b may be different from each other or may include the same ones.

In the reflective dot patterns 21 to 24 in Figs. 2 to 5, multiple reflective dots 21a to 24a are arranged in a rectangular shape, in the reflective dot pattern 25 in Fig. 6, multiple reflective dots 25a are arranged in a multiple ring shape, and in the reflective dot pattern 26 in Fig. 7, multiple reflective dots 26a are arranged in a radial shape. In addition to these configurations, for example, the multiple reflective dots may be arranged randomly. With the light diffusing member 1, the occurrence of brightness unevenness can be easily suppressed by arranging the multiple reflective dots in the reflective dot patterns 11a to 13a in a multiple ring shape, radial shape, rectangular shape, or random shape.

The reflective dot patterns 21 to 23 in Figs. 2 to 4 have different occupancy rates of the multiple reflective dots 21a to 23a. That is, the occupancy rate of the reflective dot pattern 21 in Fig. 2 is greater than that of the reflective dot pattern 22 in Fig. 3, which is greater than that of the reflective dot pattern 23 in Fig. 4. The occupancy rate of each reflective dot pattern 21, 22, and 23 can be calculated by the ratio of the total planar area of the multiple reflective dots 21a to 23a in the unit areas R1 to R3 to the planar area of the area (unit areas R1 to R3) formed by connecting the centers of the multiple reflective dots 21a to 23a arranged on the outer edge parts of the reflective dot patterns 21, 22, and 23. The occupancy rate of the reflective dot patterns 24 to 26 in Figs. 5 to 7 can also be calculated in a similar manner.

The occupancy rate of the reflective dot pattern 24 in FIG. 5 is greater than that of the reflective dot pattern 21 in FIG. 2. More specifically, the occupancy rate of the reflective dot pattern 24 in FIG. 5 is 100%. In the reflective dot pattern 24 in FIG. 5, multiple reflective dots 24a are arranged so as to partially overlap, forming a solid pattern with an overall occupancy rate of 100%. By making the occupancy rate of at least one reflective dot pattern 11a-13a 100%, the light diffusing member 1 can sufficiently increase the total occupancy rate of the multiple reflective dot patterns 11a-13a in the overlapping region in a planar view. As a result, the occurrence of uneven brightness can be easily and reliably suppressed.

The reflective dot pattern 25 in FIG. 6 is a multiple circular ring shape. The reflective dot pattern 25 may be configured so that the density of the reflective dots 25a varies in the radial direction. For example, the reflective dot pattern 25 may be configured so that the density of the reflective dots 25a decreases in the radially outward direction. The reflective dot pattern 25 in FIG. 6 has multiple reflective dots 25a arranged in a multiple circular shape, making it easy to change the density of the reflective dots 25a in response to the amount of light incident from the light source 2. The specific shape of the reflective dot pattern 25 can be designed according to the shape and arrangement of the light source 2, and may be, for example, a multiple polygonal ring shape.

The reflective dot pattern 26 in FIG. 7 has a higher density of reflective dots 26a on the central side than on the radially outer side. By increasing the density of reflective dots 26a on the central side, the reflective dot pattern 26 in FIG. 7 can effectively reflect light from the area directly above the light source 2, etc.

In the above-mentioned reflective dot patterns 21 to 26, the arrangement of the reflective dots 21a to 26a may be fine-tuned so that the centers of the multiple reflective dots 21a to 26a are not aligned in a straight line. By fine-tuning the arrangement of the reflective dots 21a to 26a, it is possible to eliminate the regularity of the arrangement of the reflective dots 21a to 26a and to easily suppress the occurrence of moire.

Of the reflective dot patterns 11a to 13a provided on the resin layers 11b to 13b in FIG. 1, at least two of the reflective dot patterns 11a to 13a may have different occupancy rates. With this configuration, it is easy to adjust the reflectance of light rays across the multiple reflective dot patterns 11a to 13a. As a result, it is easy to suppress the occurrence of uneven brightness.

The reflective dot patterns 11a to 13a provided on the resin layers 11b to 13b may have a gradually decreasing or increasing occupied area ratio in the light transmission direction. The light diffusion member 1 can gradually eliminate brightness unevenness in the light transmission direction. In this case, the reflective dot patterns 11a to 13a have a gradually decreasing or increasing occupied area ratio in the light transmission direction, so that the desired reflection function at each stage can be easily imparted to each of the reflective dot patterns 11a, 12a, and 13a. For example, the light diffusion member 1 can reduce the occupied area ratio of the reflective dot patterns 11a to 13a in the light transmission direction in a gradual decrease in the occupied area ratio of the reflective dot patterns 11a to 13a in accordance with the stages of reduction in brightness unevenness. As a result, it is easy to suppress brightness reduction while sufficiently suppressing brightness unevenness.

On the other hand, the reflective dot patterns 11a to 13a provided on the resin layers 11b to 13b may have the same occupancy rate. By having the multiple reflective dot patterns 11a to 13a have the same occupancy rate, it is possible to easily suppress the occurrence of uneven brightness while simplifying the design of the multiple reflective dot patterns 11a to 13a.

The total area ratio of the multiple reflective dot patterns 11a to 13a in the overlapping areas in a planar view is preferably more than 100%. The light diffusing member 1 can easily make the total area ratio of the multiple reflective dot patterns 11a to 13a in the overlapping areas in a planar view more than 100%. This makes it possible to easily and reliably suppress the occurrence of uneven brightness. Note that "the total area ratio of the multiple reflective dot patterns in the overlapping areas in a planar view" means, for example, when there are three reflective dot patterns 11a to 13a in the light transmission direction, the total area ratio of the reflective dot patterns 11a to 13a in the areas where all three reflective dot patterns 11a to 13a overlap in a planar view.

Of the multiple reflective dot patterns 11a-13a that overlap in a planar view, the outer edges of at least two of the reflective dot patterns 11a-13a do not have to coincide in a planar view. By using reflective dot patterns 11a-13a whose outer edges do not coincide, the light diffusing member 1 makes it easy to fine-tune the light reflection function of the reflective dot patterns 11a-13a as a whole in the radial direction. Note that Figures 2-7 do not show whether the outer edges of the reflective dot patterns 21-26 coincide or not.

(Resin Layer)
The resin layers 11b to 13b are, for example, substantially rectangular parallelepipeds with a thickness smaller than the length in the planar direction. The resin layers 11b to 13b may have a light diffusing function. For example, the resin layers 11b to 13b may include a resin matrix and a light diffusing agent contained in the resin matrix.

The resin matrix must be transparent to transmit light, and therefore the main component is a transparent, particularly colorless and transparent, synthetic resin. Examples of the synthetic resin include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant polyvinyl chloride. Note that the "main component" refers to the component with the largest content by mass, for example, a component with a content of 50% by mass or more.

The light diffusing agent is not particularly limited as long as it can diffuse light, and examples thereof include inorganic fillers and organic fillers. Examples of the inorganic fillers include silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, and mixtures thereof. Examples of the organic fillers include acrylic resins, acrylonitrile resins, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamides, etc.

The average thickness of the resin layers 11b to 13b can be, for example, about 0.1 mm or more and 3.0 mm or less.

<Advantages>
In the light diffusing member 1, a plurality of reflective dot patterns 11a to 13a are arranged in an area where they overlap in a plan view via the resin layers 11b to 13b in the light transmission direction, so that the light emitted from the light source 2 can be reflected in multiple stages in the light transmission direction. Therefore, the light diffusing member 1 can sufficiently suppress the occurrence of uneven brightness.

The light diffusing member 1 can distribute the function that was previously performed by one reflective dot pattern among multiple reflective dot patterns 11a-13a. Therefore, the light diffusing member 1 can easily make the occupancy area ratio of each reflective dot pattern 11a-13a smaller than that of a conventional reflective dot pattern. By distributing the light reflection function among multiple reflective dot patterns 11a, 12a, and 13a, the light diffusing member 1 can easily fully exhibit its overall light reflection function even if the alignment of each reflective dot pattern 11a, 12a, and 13a with the light source 2 is not performed as strictly as required for conventional reflective dot patterns.

The backlight unit 20 includes the light diffusing member 1, so the occurrence of uneven brightness can be sufficiently suppressed.

The image display device 10 is equipped with the backlight unit 20, so the occurrence of uneven brightness can be sufficiently suppressed.

[Second embodiment]
<Image display device>
The image display device 40 of FIG. 8 includes a backlight unit 50 and a display panel 30 disposed on the front side of the backlight unit 50. The backlight unit 50 is a direct-type backlight unit. The backlight unit 50 includes the light diffusion member 41, one or more light sources 2 (three light sources are illustrated in FIG. 8) disposed on the back side of the light diffusion member 41, a reflecting sheet 3 disposed on the back side of the one or more light sources 2, and a prism sheet (a first prism sheet 4 and a second prism sheet 5) disposed on the front side of the light diffusion member 41. The image display device 40 can be configured similarly to the image display device 10 of FIG. 1 except that the configuration of the light diffusion member 41 is different. Therefore, only the light diffusion member 41 will be described below.

<Light Diffusion Member>
The light diffusing member 41 includes a plurality of reflective dot patterns (first reflective dot pattern 43a and second reflective dot pattern 44a) arranged via a resin layer 42 in the light transmission direction (Z direction in FIG. 8). The surface of the resin layer 42 facing the light source 2 constitutes a light incident surface, and the opposite surface constitutes a light exit surface. The first reflective dot pattern 43a and the second reflective dot pattern 44a are formed on the light incident surface and the light exit surface of one resin layer 42. The specific configuration of the resin layer 42 may be the same as that of the resin layers 11b to 13b in FIG. 1.

(Reflective dot pattern)
Each of the reflective dot patterns 43a and 44a includes a plurality of reflective dots. The reflective dot patterns 43a and 44a are arranged in regions that overlap each other in a plan view.

The occupancy rate of each reflective dot pattern 43a, 44a and the specific arrangement of the multiple reflective dots can be the same as those of the reflective dot patterns 11a to 13a in FIG. 1. In addition, the occupancy rate of the entire multiple reflective dot patterns 43a, 44a in the overlapping region of the light diffusion member 41 in a plan view can be the same as that of the light diffusion member 1 in FIG. 1.

<Advantages>
In the light diffusion member 41, the first reflective dot pattern 43a and the second reflective dot pattern 44a are formed on the light entrance surface and the light exit surface of one resin layer 42, so that it is easy to prevent the thickness of the light diffusion member 41 from increasing. As a result, it is possible to promote the thinning of the device in which the light diffusion member 41 is disposed. In addition, with this configuration, it is easy to prevent the decrease in brightness caused by the resin layer 42.

[Other embodiments]
The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

For example, when the light diffusing member has multiple resin layers, the reflective dot pattern may be formed on both the light incident surface and the light exit surface of one or more of the resin layers. When the light diffusing member has multiple resin layers, the reflective dot pattern may be formed only on the light exit surfaces of these resin layers, or the reflective dot pattern may be formed on any of the light incident surface and the light exit surface.

The light diffusing member may have two or more reflective dot patterns formed on the light entrance surface or light exit surface of one resin layer. An example of a configuration in which two or more reflective dot patterns are formed on the light entrance surface or light exit surface of one resin layer is a configuration in which one reflective dot pattern is arranged corresponding to one or more light sources. For example, when one reflective dot pattern is arranged corresponding to one light source, the number of reflective dot patterns on the light entrance surface or light exit surface matches the number of light sources.

In the above embodiment, a configuration in which a solid pattern is formed by partially overlapping multiple reflective dots is exemplified. On the other hand, the light diffusing member can also form a solid pattern by filling one surface of the resin layer. Note that when a solid pattern is formed by filling one surface of the resin layer, the occupancy rate of this reflective dot pattern is 100%.

The specific configuration of the resin layer is not limited to the configuration described in the above embodiment. For example, the resin layer may have an uneven shape capable of diffusing light rays on one or both of the light entrance surface and the light exit surface.

The number of resin layers is not particularly limited. The number of resin layers may be, for example, two or four or more.

The specific configuration of the reflective dot pattern is not limited to the configuration described in the above embodiment. For example, the light diffusion member may have a reflective dot pattern with an extremely small occupancy rate. By using a reflective dot pattern with a small occupancy rate, the light diffusion member can increase the degree of freedom in alignment with a light source, etc. Specifically, the occupancy rate of the reflective dot pattern may be more than 0% and less than 30%, or more than 0% and less than 10%.

The total occupancy rate of the multiple reflective dot patterns in the overlapping areas in a planar view can be designed according to the characteristics required of the image display device. For example, the total occupancy rate may be 100% or less.

A backlight unit equipped with the light diffusing member may be disposed in a lighting device other than an image display device. A lighting device in which the backlight unit is disposed can sufficiently suppress the occurrence of uneven brightness.

In the above embodiment, a configuration has been described in which the image display device is a liquid crystal display device. However, the image display device may be an image display device other than a liquid crystal display device. Furthermore, even if the image display device is a liquid crystal display device, other specific configurations are not particularly limited as long as the light diffusing member is included.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Example]
A light diffusion member having the configuration of FIG. 8 in which a reflective dot pattern is formed on each of the light incident surface and the light exit surface of one resin layer was prepared. The reflective dot pattern (first reflective dot pattern) formed on the light incident surface of the resin layer is shown in FIG. 9, and the reflective dot pattern (second reflective dot pattern) formed on the light exit surface of the resin layer is shown in FIG. 10. In both the first reflective dot pattern and the second reflective dot pattern, a plurality of reflective dots are arranged in a lattice shape at equal intervals in the X-axis direction and the Y-axis direction as a whole. The occupancy rate of the first reflective dot pattern is 78.5%, and the occupancy rate of the second reflective dot pattern is 40%. In addition, the diameter of the reflective dot is 60 μm for both the first reflective dot pattern and the second reflective dot pattern. The luminance unevenness when light is incident from the back side of the light diffusion member of the example was obtained by simulation. The luminance ratio ((maximum luminance-minimum luminance)/average luminance) in the screen was used as an evaluation index of the luminance unevenness. The luminance ratio in the example was 27.3%.

[Comparative Example]
A light diffusing member having the same configuration as the example was prepared, except that it had the first reflective dot pattern of FIG. 11 instead of the first reflective dot pattern of the example, and did not have the second reflective dot pattern on the light exit surface of the resin layer. In the first reflective dot pattern of the comparative example, the reflective dots arranged in the central part of the pattern partially overlap each other. This first reflective dot pattern is designed so that the density of the reflective dots decreases from the central part of the pattern toward the radial outside. The diameter of the reflective dots of the first reflective dot pattern in the comparative example is 60 μm. The luminance ratio of the light diffusing member of the comparative example was calculated in the same manner as the example. The luminance ratio in the comparative example was 33.1%.

<Evaluation Results>
The light diffusing member of the Example has a luminance ratio 5.8% smaller than that of the light diffusing member of the Comparative Example. This shows that the light diffusing member of the Example has a more uniform luminance than the light diffusing member of the Comparative Example, and thus reduces luminance unevenness.

The above results show that arranging two reflective dot patterns in which multiple reflective dots are arranged in a lattice pattern at equal intervals in the X-axis and Y-axis directions so that they overlap in a planar view can reduce brightness unevenness more effectively than providing a single reflective dot pattern in which the density of the reflective dots is adjusted according to the amount of light. In addition to reducing brightness unevenness, the configuration of the embodiment makes it easier to prevent unintended connections between reflective dots (dot crushing) and deterioration of image quality due to misalignment of the print.

As described above, the light diffusing member according to one aspect of the present invention can easily suppress uneven brightness, and is therefore suitable for use in the backlight unit of a liquid crystal display device.

Reference Signs List 1, 41 Light diffusion member 2 Light source 3 Reflection sheet 4 First prism sheet 5 Second prism sheet 10, 40 Image display device 11a, 43a First reflective dot pattern 11b First resin layer 12a, 44a Second reflective dot pattern 12b Second resin layer 13a Third reflective dot pattern 13b Third resin layer 20, 50 Backlight unit 21, 22, 23, 24, 25, 26 Reflection dot patterns 21a, 22a, 23a, 24a, 25a, 26a Reflection dot 30 Display panel 42 Resin layers R1, R2, R3 Unit area

Claims (7)

A plurality of resin layers are provided in a light transmission direction, and each of the resin layers has a reflective dot pattern on at least one of a light incident surface and a light exit surface,
the reflective dot patterns provided on the plurality of resin layers each include a reflective dot, and are arranged in regions where the reflective dots overlap each other in a plan view;
A light diffusing member in which the reflective dots are formed in a hemispherical or semicircular shape . The light diffusing member according to claim 1, wherein the total area occupied by the multiple reflective dot patterns in the overlapping area in the plan view is greater than 100%. The light diffusing member according to claim 1 or 2, wherein a pair of the reflective dot patterns are formed on the light entrance surface and the light exit surface of at least one of the resin layers. The light diffusing member according to any one of claims 1 to 3, wherein at least two of the reflective dot patterns have different occupancy rates in a plan view. The light diffusing member according to claim 4, in which the occupancy area ratio of the plurality of reflective dot patterns gradually decreases or increases in the transmission direction. The light diffusing member according to any one of claims 1 to 3, wherein the occupancy area ratios of the multiple reflective dot patterns in a plan view are equal. 2. The light diffusion plate according to claim 1, wherein the reflective dot pattern is formed as a solid pattern in which a plurality of the reflective dots are arranged so as to partially overlap each other .

Images