TW201514561A - Light guide plate, planar light source device, and transmissive image display device - Google Patents

Abstract

A light guide plate (24) according to one embodiment is provided with: a light guide plate substrate (30) for allowing light entering from an edge surface (30c) to be propagated therein; and a plurality of light-scattering dots (32) for scattering a portion of the light propagated through the light guide plate substrate, the plurality of light-scattering dots (32) being formed on a main surface (30a) of the light guide plate substrate. The percentage of light-scattering dots in which P12 is (D1/2 + D2/2) or less is 10% or less of the total number of light-scattering dots present in the group of light-scattering dots, where, among two adjacent light-scattering dots in a group of light-scattering dots formed in a prescribed region (34a) of the main surface, a first light-scattering dot (321) has a maximum width of (D1), a second light-scattering dot (322) has a maximum width of (D2), and the distance between centers of the first and second light-scattering dots is (P12). The prescribed region is a region, among a plurality of regions (34) formed by making imaginary divisions in the main surface, where the coverage rate by the group of light-scattering dots is 30% or less.

Description

Light guide plate, surface light source device and transmissive image display device

The present invention relates to a light guide plate, a surface light source device, and a transmissive image display device.

As a transmissive image display device such as a liquid crystal display device, a device including a surface light source device (backlight device) that supplies planar light by a light guide plate is known (see Patent Document 1). The surface light source device is provided with a light source along an end surface of the light guide plate. Such a surface light source device is called an edge illumination type surface light source device.

In the edge illumination type surface light source device, light incident from the end surface of the light guide plate is transmitted inside the light guide plate, and is propagated while repeating total reflection. During the propagation, a portion of the light is scattered by a plurality of light scattering points disposed on one side of the light guide plate. Light incident on the exit surface at an angle equal to or greater than the critical angle generated by the scattering is emitted from the light guide plate. A portion of the light propagating through the light guide plate is emitted from the exit surface, and the surface light is emitted from the light guide plate.

In order to make the brightness of the light exit surface of the light guide plate uniform, a plurality of light scattering points are generally formed in an arrangement pattern in which the coverage of the light scattering point is higher as the distance from the light source is higher.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2005-38768

In recent years, with the further thinning of the image display device, a thin light guide plate is required. Such a thin light guide plate tends to have a low coverage of light scattering dots. For example, compared with the conventional light guide plate, the thin light guide plate tends to have a coverage area of 40% or less. Further, the thin light guide plate has a case where an image display device having a relatively small screen size and high resolution is incorporated. An example of an image display device having a relatively small screen size and high resolution is used for an image display device of a smart phone or a tablet. Such an image display device is often used in such a manner that the user gazes at the display image from a relatively close distance (for example, about 0.3 m from the display screen).

The present inventors have found that a thin light guide plate tends to be visually recognized because the light-scattering points are easily connected to each other. In particular, the present inventors have found that if a thin type of light guide plate is incorporated into an image display device using a method of using a user to view a picture from a close position, the light scattering points are easily connected to each other and become uneven. The tendency to see.

A main object of the present invention is to provide a light guide plate, a surface light source device, and a transmissive image display device in which the connection of light scattering dots is not easily uneven.

A light guide plate according to an aspect of the present invention includes: a light guide plate substrate that causes light incident from the end face to propagate inside; and a plurality of light scattering dots formed on a main surface of the light guide plate substrate and intersecting the end face The main surface and partially scatters light propagating within the substrate of the light guide. When the diameter of the first light scattering point among the light scattering points adjacent to the light scattering point group formed in the specific area of the main surface is D ₁ , the diameter of the second light scattering point is D ₂ , and the first When the distance between the centers of the second light scattering points is P ₁₂ , the ratio of the light scattering points satisfying the formula (1) to all the light scattering points of the light scattering point group is 10% or less. The specific area is a region in which the coverage of the light scattering point group in a plurality of regions obtained by imaginarily dividing the main surface is 30% or less.

[Number 1] P ₁₂ ≦(D ₁ /2+D ₂ /2)...(1)

In the above configuration, in the specific region where the coverage of the light scattering point group is 30% or less, the ratio of the light scattering point satisfying the formula (1) is 10% or less, so that it is difficult to visually recognize that the light scattering point is not connected. All.

The total area of all of the above specific areas may also be 90% or more with respect to the effective area of the main surface.

In this case, the ratio of the light scattering points satisfying the formula (1) is 10% or less in a specific region of 90% or more of the effective area of the main surface, so that it is less likely to recognize unevenness due to the connection of the light scattering points. .

The maximum width of the light scattering points included in the light scattering point group may be in the range of 30 μm to 100 μm. In this case, even if the maximum width of the light scattering point is in the range of 30 μm to 100 μm, the ratio of the light scattering point satisfying the formula (1) is in a specific region where the coverage of the light scattering point group is 30% or less. Below 10%, it is not easy to recognize the unevenness caused by the connection of light scattering points.

The thickness of the light guide plate substrate may be less than 1 mm.

Even if the thickness of the light guide substrate is less than 1 mm, it is difficult to recognize that the ratio of the light scattering point of the formula (1) is 10% or less in a specific region where the coverage of the light scattering point group is 30% or less. Uneven due to the connection of light scattering points.

The light guide plate substrate may have a rectangular shape in plan view. In this case, the length of the short side of the planar shape of the light guide plate substrate may be 250 mm or less.

A light guide plate including a light guide plate substrate having a rectangular shape and a short side of 250 mm in length, for example, can be easily incorporated into a smart phone, a flat plate, or the like. There is a tendency for users such as smart phones and tablets to view the display screen from a close distance. In this case, since the ratio of the light scattering point of the formula (1) is 10% or less in a specific region where the coverage of the light scattering point group is 30% or less, it is difficult to visually recognize the light scattering point. The connection caused unevenness.

A surface light source device according to another aspect of the present invention includes: a light guide plate according to an aspect of the present invention; and a light source that supplies light to an end surface of the light guide plate substrate included in the light guide plate.

A transmissive image display device according to still another aspect of the present invention includes: a light guide plate according to an aspect of the present invention; a light source that supplies light to an end surface of the light guide plate substrate included in the light guide plate; and a transmissive image display portion. It is illuminated by light emitted from the light guide plate to display an image.

Since the above-described surface light source device and transmissive image display device include the light guide plate of one aspect of the present invention, it is difficult to recognize the unevenness due to the connection of the light scattering points.

According to the present invention, it is possible to provide a light guide plate, a surface light source device, and a transmissive image display device in which the connection of light scattering dots is not easily uneven.

10‧‧‧Transmissive image display device

12‧‧‧Transmission type image display unit

14‧‧‧ surface light source device

16‧‧‧Optical components

18‧‧‧Liquid Crystal Unit

20‧‧‧Polar plate

22‧‧‧Polar plate

24‧‧‧Light guide

26‧‧‧Light source department

26a‧‧‧ Point light source

28‧‧‧reflector

30‧‧‧Light guide plate substrate

30a‧‧‧ point forming surface (main surface)

30b‧‧‧Outlet

30c‧‧‧ end face

30d‧‧‧ end face

30e‧‧‧ end face

30f‧‧‧ end face

32‧‧‧Light scattering points

32 ₁ ‧‧‧1st light scattering point

32 ₂ ‧‧‧2nd light scattering point

34‧‧‧Imaginary area

34a‧‧‧Specific areas

D ₁ ‧‧‧Diameter of the first light scattering point

D ₂ ‧‧‧Diameter of the second light scattering point

L1‧‧‧1st imaginary line

L2‧‧‧2nd imaginary line

P ₁₂ ‧‧‧ The distance between the centers of the first and second light scattering points

X‧‧‧ axis

Y‧‧‧ axis

Z‧‧‧ axis

Fig. 1 is a schematic view showing a schematic configuration of a transmissive image display device according to an embodiment.

Fig. 2 is a plan view showing a state in which a light guide plate of an embodiment is viewed from the side of the dot formation surface.

Fig. 3 is a view showing an example of the arrangement of light scattering points.

Fig. 4 is a view showing another example of the arrangement of light scattering points.

Fig. 5 is a view showing the relationship between the size and position of the first and second light scattering points.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Label the same elements with the same symbols. The description of the repetition is omitted. The size ratio of the schema does not have to be consistent with the specifier. In the description, words indicating "upper" and "lower" are words based on the convenience of the state shown in the drawing.

Fig. 1 is a schematic view showing a schematic configuration of an embodiment of a transmissive image display device. Fig. 2 is a plan view showing a state in which a light guide plate is viewed from a side of a light guide plate on which a light scattering point is formed. The configuration of the transmissive image display device 10 is shown in an exploded manner in FIG. The transmissive image display device 10 can be preferably used for smart phones, tablets, and notebook computers for mobile use. The application object of the transmissive image display device 10 is not limited to the illustrated smart type. Mobile phones and tablets. The transmissive image display device 10 can also be used for notebook computers and television devices other than mobile phones.

The transmissive image display device 10 shown in FIG. 1 mainly includes a transmissive image display unit 12 and a surface light source device 14 that outputs surface light for supply to the transmissive image display unit 12. The optical member 16 may be disposed between the transmissive image display unit 12 and the surface light source device 14. Examples of the optical member include an optical sheet such as a reflective polarization separation sheet, a light diffusion sheet, a microlens sheet, a lenticular lens sheet, and a ruthenium sheet. The exemplified optical sheets may be configured singly or in combination as long as they do not depart from the gist of the present invention.

Hereinafter, for convenience of explanation, as shown in FIG. 1 , the direction in which the transmissive image display unit 12 and the optical member 16 are arranged with respect to the surface light source device 14 is referred to as a Z-axis direction. The two directions orthogonal to the Z-axis direction are referred to as an X-axis direction and a Y-axis direction. The X-axis direction and the Y-axis direction are orthogonal to each other.

The transmissive image display unit 12 displays an image by illuminating the surface light emitted from the surface light source device 14. In the example of the transmissive image display unit 12, a liquid crystal display panel as a polarizing plate bonding body of the polarizing plates 20 and 22 is disposed on both surfaces of the liquid crystal cell 18. In this case, the transmissive image display device 10 is a liquid crystal display device (or a liquid crystal television). As the liquid crystal cell 18 and the polarizing plates 20 and 22, a liquid crystal cell and a polarizing plate used in a transmissive image display device such as a liquid crystal display device of the prior art can be used. An example of the liquid crystal cell 18 is a TFT (Thin Film Transistor) type liquid crystal cell. Other examples of the liquid crystal cell 18 include an STN (Super Twisted Nematic) type, a TN (Twisted Nematic) type, an IPS (In Plane Switching) type, and a VA (Vertical). Alignment, vertical alignment type liquid crystal cell, etc.

The surface light source device 14 shown in FIG. 1 is an edge illumination type surface light source device that supplies light to the transmissive image display unit 12. The surface light source device 14 includes a light guide plate 24 and a light source unit 26 disposed on the side of the light guide plate 24.

The light source unit 26 includes a plurality of points arranged in a line shape (arranged in the Y-axis direction in FIG. 1) Shape light source 26a. An example of the point light source 26a is a light emitting diode. The light source unit 26 may be provided above or below the light source unit 26 on the side opposite to the light guide plate 24 side, and a reflector for reflecting the light from the light source unit 26 and guiding the light guide plate 24 as a reflection portion may be provided. The light is efficiently incident on the light guide plate 24. Here, the light source unit 26 including a plurality of point light sources 26a is exemplified. However, the light source unit 26 may be a linear light source such as a Cold Cathode Fluorescent Lamp (CCFL).

The surface light source device 14 may further include a reflection plate 28 that is located on the opposite side of the transmissive image display portion 12 with respect to the light guide plate 24. The reflecting plate 28 is for causing the light emitted from the light guide plate 24 to the side of the reflecting plate 28 to be incident on the light guiding plate 24 again. As shown in FIG. 1, the reflecting plate 28 may also be in the form of a sheet. The reflector 28 may also be a bottom surface of the housing of the surface light source device 14 that houses the light guide plate 24. The reflecting surface of the reflecting plate 28 may be a surface that reflects the mirror surface, or may be a surface that reflects the light while scattering.

The light guide plate 24 converts the light emitted from the light source unit 26 into planar light and emits it to the transmissive image display unit 12. The light guide plate 24 includes a light guide plate substrate 30 and a plurality of light scattering dots 32 provided on the light guide plate substrate 30. The light scattering dots 32 are schematically shown in FIGS. 1 and 2, and the size and number thereof do not necessarily coincide with other figures. The light guide plate 24 scatters light that is incident from the light source unit 26 and propagates through the light guide plate substrate 30 by total reflection by the light scattering point 32, thereby converting light from the light source unit 26 into planar light and emitting it. . The scattering of light by the light scattering point 32 includes diffuse reflection.

The light guide plate substrate 30 includes a dot forming surface 30a as a main surface, which forms a plurality of light scattering dots 32, and an exit surface 30b as the other main surface, which functions as a light emitting surface in the light guide plate 24. And four end faces 30c, 30d, 30e, 30f which intersect with the dot forming face 30a and the exit face 30b. Examples of the planar shape of the light guide plate substrate 30 include a substantially rectangular shape and a substantially square shape. In the following description, the light guide plate substrate 30 has a substantially rectangular shape in plan view unless otherwise specified. In one embodiment, as illustrated in FIG. 1, the end faces 30c, 30d, 30e, and 30f are substantially positive with the dot forming surface 30a and the exit surface 30b. cross. The end surface 30c may be a flat surface, or may have a surface in which a concavity and convexity are formed, such as a 稜鏡 shape or a lenticular lens shape.

The dot forming surface 30a may be a substantially flat surface. The dot forming surface 30a may also be a surface subjected to liquid dispensing treatment. The exit surface 30b is a surface opposite to the dot formation surface 30a. In the transmissive image display device 10, the exit surface 30b faces the transmissive image display portion 12 (or the optical member 16). The exit surface 30b may be a flat surface as in the present embodiment, or may have a surface having an uneven shape. As shown in FIG. 2, the end surface 30c and the end surface 30d are located on the opposite side to each other in the X-axis direction. The end surface 30c is opposed to the light source unit 26. In this case, the end surface 30c is incident on the light incident surface of the light from the light source unit 26. The end surface 30e and the end surface 30f are located on opposite sides of each other in the Y-axis direction.

The light guide plate substrate 30 is mainly formed of a light transmissive material. The light transmissive material is preferably a polyalkyl (meth) acrylate resin sheet, a polystyrene sheet, or a polycarbonate resin sheet, and among these, a polymethyl methacrylate resin sheet is preferred. (PMMA (polymethyl methacrylate) resin sheet). The light guide plate substrate 30 may also contain diffusing particles. When the light guide plate base material 30 contains a light transmissive resin, the light guide plate base material 30 is a light transmissive resin sheet.

In one embodiment, the light guide plate substrate 30 can satisfy at least one of the following (a) and (b).

(a) The thickness of the light guide plate substrate 30 is less than 1 mm.

(b) The length of the short side of the light guide plate substrate 30 is 250 mm or less.

The thickness of the light guide plate substrate 30 is usually 0.3 mm or more. The length of the short side of the light guide plate substrate 30 is usually 50 mm or more.

A plurality of light scattering points 32 will be described with reference to Figs. 2 to 4 . FIG. 3 is a diagram for explaining the arrangement of the light scattering dots 32. 4 is a diagram for explaining the relationship between two adjacent light scattering points 32.

One example of the planar shape of the light scattering dots 32 formed on the dot formation surface 30a is substantially circular. The material of the light scattering point 32 can use a light scattering ink. As the material of the light scattering point 32 For the material, for example, an ultraviolet curable ink, an aqueous ink, a solvent ink or the like can be used. The light scattering dots 32 can be formed by an inkjet printing method, a screen printing method, or the like. Light scattering dots 32 may also be formed by illumination of the laser light.

The plurality of light-scattering points 32 are formed so as to satisfy the coverage ratio set in each of the virtual regions 34 when the dot-forming surface 30a is divided into a plurality of virtual regions 34 as indicated by a one-dot chain line as shown in FIGS. 3 and 4 . It is formed on an imaginary lattice point (hereinafter referred to as a virtual lattice point) for forming the light scattering point 32. The imaginary lattice point is an intersection of the first imaginary line L1 extending in the first direction and the second imaginary line L2 extending in the second direction orthogonal to the first direction, as indicated by a broken line in FIGS. 2 to 4 . In FIGS. 2 to 4, the first direction is parallel to the direction of the short side. The plurality of first imaginary lines L1 are parallel to each other. Similarly, the plurality of second imaginary lines L2 are parallel to each other. The first imaginary line L1 and the second imaginary line L2 may not be orthogonal. The intersection angle θ between the first imaginary line L1 and the second imaginary line L2 is 30 degrees to 150 degrees, preferably 60 degrees to 120 degrees.

In Fig. 3 and Fig. 4, the dot formation surface 30a is virtually divided into 8 × 13 pieces. The number of divisions is for convenience of explanation, and the number of divisions is not limited to 8×13. The size of the virtual region 34 is not particularly limited as long as the number of the imaginary lattice points in the virtual region 34 is set to be the same.

FIG. 3 and FIG. 4 show an example in which the entire surface of the dot formation surface 30a is imaginarily divided. However, the dot formation region in which the light scattering dots 32 are formed in the dot formation surface 30a may be divided into a plurality of imaginary regions. For example, there is a case where a region where the light scattering dots 32 are not formed is provided in a fixed width near the peripheral portion of the dot forming surface 30a. In the case of such a configuration, the region of the dot forming surface 30a other than the region of the fixed width described above forms a dot formation region of the light scattering dots 32. For example, when the size of the dot forming surface 30a is 175 mm × 300 mm, the width of the light-incident surface (the end surface 30c in Fig. 2) is 3 mm, and the other three sides are 1 mm. That is, when the size of the dot formation surface 30a is 175 mm × 300 mm, one of the sizes of the dot formation regions is 171 mm × 298 mm. Usually, the area of the dot formation region is 95% or more with respect to the area of the dot formation surface 30a. In the following description, in order to simplify the explanation, The entire surface of the dot formation surface 30a will be described as a dot formation region.

The coverage set for the virtual region 34 is the ratio of the sum of the areas of the light scattering dots 32 (the area of the plan view shape) included in the virtual region 34 to the area of the virtual region 34.

The coverage is set such that the brightness of the exit surface 30b becomes uniform. Generally, the light scattering dots 32 are arranged such that the coverage is higher as the distance from the light source portion 26 is higher. In the one-side light incident type in which the light source unit 26 is disposed on one end surface (the end surface 30c in FIG. 2), the light scattering point 32 is disposed in such a manner as to face the end surface opposite to the end surface on which the light is incident from the light source unit 26 ( In the vicinity of the end face 30d) in Fig. 2, the coverage becomes higher.

The light scattering dots 32 may be formed on all the imaginary lattice points as shown in FIGS. 2 and 3, or may form the light scattering dots 32 not as part of the imaginary lattice points as shown in FIG. When the light scattering dots 32 are formed on all the imaginary lattice points as shown in FIGS. 2 and 3, the distance between the centers of the adjacent light scattering dots 32 in the first and second directions is constant. On the other hand, when the light scattering dots 32 are not formed in a part of the imaginary lattice points as shown in FIG. 4, the distance between the centers of the light scattering points 32 adjacent to each other in the first and second directions is based on the The direction of each of 1 and 2 directions may be an integral multiple of the interval of the imaginary lattice points. The distance between the centers of the light-scattering points 32 corresponding to an integral multiple of the imaginary lattice point interval is appropriately selected so as to emit uniform light from the exit surface 30b. As long as the light scattering dots 32 are arranged such that the uniform light is emitted from the exit surface 30b, for example, a part of the light scattering dots 32 may be slightly deviated from the virtual lattice dots.

In the case where the light scattering dots 32 are formed on all the imaginary lattice points, the coverage is mainly determined by the size of the light scattering dots 32 formed at the imaginary lattice points. When the light scattering dots 32 are not formed in all of the imaginary lattice points in one imaginary region 34, that is, the light scattering dots 32 are elongated and spaced apart as compared with the case where all the imaginary lattice dots are formed with the light scattering dots 32. The coverage is primarily determined by the size of the light scattering spot 32 and the number of light scattering points 32 in an imaginary region 34.

In the thin light guide plate 24 of the light guide plate substrate 30 having a thickness of less than 1 mm, an imaginary area The coverage of 34 can usually be below 40%. In the thin light guide plate 24 having a thickness of the light guide plate substrate 30 of less than 1 mm, a region having an area of 90% or more of the effective area of the dot formation surface 30a may be a region having a coverage of 30% or less. The effective area of the dot formation surface 30a means the area of the dot formation region. In other words, the effective area of the dot formation surface 30a is an area formed in the region where the plurality of light scattering dots 32 are disposed on the dot formation surface 30a, and corresponds to the sum of the areas of the plurality of imaginary regions.

Hereinafter, in the virtual region 34, each of the virtual regions 34 having a coverage ratio of 30% or less is referred to as a specific region 34a. For example, in Fig. 3, the specific area 34a is an imaginary area 34 in which a portion of the hatching is marked. One of the two light scattering points 32 adjacent to the light scattering point group of the specific region 34a is referred to as a first light scattering point 32 ₁ , and the other light scattering point 32 is referred to as a second light scattering point 32 . ₂ .

Fig. 5 is a view showing the relationship between the size and position of the first and second light-scattering points 32 ₁ and 32 ₂ .

Regarding the light guide plate 24, when the diameter of the first light scattering point 32 ₁ (the maximum width when the light scattering point is viewed from the top) is D ₁ , the diameter (maximum width) of the second light scattering point 32 ₂ is D ₂ . When the distance between the centers of the first and second light-scattering points 32 ₁ and 32 ₂ is P ₁₂ , the ratio of the light-scattering points 32 in which P ₁₂ satisfies the following formula (2) is 10% or less. In one embodiment, the diameter of the light scattering spot 32 in the specific region 34a may be 30 μm to 100 μm.

[Number 2] P ₁₂ ≦(D ₁ /2+D ₂ /2)...(2)

The ratio of the light scattering point 32 in which P ₁₂ satisfies the formula (2) is 10% or less, which is a case where the number of light scattering points 32 satisfying the formula (2) is divided by the light scattering point group constituting the specific region 34a. The value obtained by the number of all light scattering points 32 is 10 or less in percentage. When the number of light scattering points 32 satisfying the formula (2) is included, for example, there is a satisfaction in different directions (for example, the first direction and the second direction) with respect to one first light scattering point 32 ₁ . In the case of the second light-scattering point 32 ₂ adjacent to the equation (2), the common first light-scattering point 32 _{1 is} counted as one. In other words, when one of the two light scattering points 32 adjacent to each other has the same light scattering point 32, the number of light scattering points 32 satisfying the equation (2) is three.

In the light guide plate 24 having the above configuration, the light incident from the end surface 30c is guided inside the light guide plate base material 30, and propagates while being totally reflected. During the propagation, the light scattered by the light scattering dots 32 is incident on the exit surface 30b under conditions different from the total reflection conditions, and thus is emitted from the exit surface 30b. Since a part of the light propagating in the light guide plate base material 30 is emitted from the exit surface 30b, the planar light is emitted from the exit surface 30b.

In the specific region 34a, that is, in the region where the coverage is 30% or less, the ratio of the light-scattering points 32 satisfying the formula (2) is 10% or less, and thus the connection of the adjacent light-scattering points 32 and 32 is suppressed. Therefore, for example, even if the user gaze into the display screen of the transmissive image display device 10 having the light guide plate 24 from a close position (for example, within 0.3 m from the display screen), it is difficult to visually recognize the connection due to the light scattering point 32. Caused by unevenness.

In one embodiment, the light scattering spot 32 in the specific region 34a has a diameter of 30 μm to 100 μm. Even in such a form, since the ratio of the light-scattering points 32 satisfying the formula (2) in the specific region 34a is 10% or less, unevenness due to the connection of the light-scattering points 32 is hardly recognized.

In one embodiment, the light guide plate 24 is a thin light guide plate having a thickness of the light guide plate substrate 30 of less than 1 mm, less than 0.8 mm, or less than 0.5 mm. Even in such a form, it is difficult to recognize the unevenness caused by the connection of the light scattering dots 32.

In one embodiment, the area occupied by all the specific regions 34a (the total area of all the specific regions) is 90% or more of the effective area of the dot formation surface 30a. In such a form, in the region of 90% or more of the effective area of the dot formation surface 30a, the ratio of the light scattering point 32 satisfying the formula (2) is 10% or less, so that it is harder to visually recognize the light scattering point 32. The connection caused unevenness.

In many cases, the light guide plate 24 of a transmissive image display device such as a smart phone or a tablet has a length of a short side of 250 mm or less and further 200 mm or less. Further, wisdom Users such as mobile phones and tablets have a tendency to stare at the display screen in the vicinity. In other words, in the case where the ratio of the light-scattering points 32 satisfying the formula (2) is 10% or less in the specific region 34a, the unevenness due to the connection of the light-scattering points 32 is also reduced.

In one embodiment, the shape of the light guide plate substrate 30 satisfies at least one of the above (a) and (b), and the area occupied by all the specific regions 34a is 90% or more of the effective area of the dot formation surface 30a. In such a form, the ratio of the light scattering dots 32 satisfying the formula (2) is also 10% or less, so that unevenness due to the connection of the light scattering dots 32 is less likely to be recognized.

In one embodiment, the specific region 34a having a coverage ratio of 20% or less in the plurality of specific regions 34a exists in the dot formation surface 30a. In such a form, even if the sum of the areas of the specific regions 34a having a coverage of 20% or less is 85% of the effective area and further 90%, the ratio of the light scattering points 32 satisfying the formula (2) is 10% or less. Therefore, the unevenness caused by the connection of the light scattering points 32 is also reduced.

In one embodiment, the specific region 34a having a coverage ratio of 10% or less in the plurality of specific regions 34a exists in the dot formation surface 30a. In such a form, even if the sum of the areas of the specific regions 34a having a coverage of 10% or less is 50% of the effective area and further 60%, the ratio of the light scattering points 32 satisfying the formula (2) is 10% or less. Therefore, the unevenness caused by the connection of the light scattering points 32 is also reduced.

In other words, when at least one of the specific regions 34a having a coverage ratio of 20% or less and 10% or less in the plurality of specific regions 34a exists in the dot formation surface 30a, the light scattering of the equation (2) is satisfied in the specific region 34a. The configuration of the light guide plate 24 having a ratio of the dots 32 of 10% or less is more effective.

The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit and scope of the invention.

In the above embodiment, the light scattering dots 32 are arranged on the virtual lattice points. However, for example, at least one of the light scattering points 32 may also be formed offset from the imaginary lattice points. In addition to the light incident from the end surface 30c, the light guide plate 24 may also enter light from the end surface 30d. Or, The light guide plate 24 has three end faces or four end faces incident light. The method of injecting the light guide plate 24 can be determined, for example, according to the size of the surface light source device or the transmissive image display device to which the light guide plate 24 is applied, and the method of use thereof.

In the light guide plate 24, a light scattering point 32 may also be formed on the exit surface 30b. The arrangement of the light scattering dots 32 formed on the exit surface 30b satisfies the same conditions as the arrangement of the light scattering dots 32 formed on the dot formation surface 30a shown in FIG. The light scattering dots 32 formed on the exit surface 30b can also scatter light by, for example, diffusing the light while transmitting it. When the light scattering dots 32 are formed on the exit surface 30b, the light scattering dots 32 may not be formed on the surface opposite to the exit surface 30b.

The planar shape of the light scattering dots 32 is not limited to a circular shape, and may be an elliptical shape, a triangular shape, or a quadrangular shape. In the case where the shape of the light scattering point 32 is elliptical, the maximum width is the length of the long side, and in the case of a triangle and a quadrangle, the maximum width is the length of the longest side. The center of the light scattering point 32 may be, for example, a position of the center of gravity of the point.

Although the planar shape of the light guide plate base material 30 is mainly described as a rectangular shape, as described above, the light guide plate base material 30 may have a square shape in plan view. In this case, for example, even if the one side is 250 mm or less, since the ratio of the light scattering points 32 satisfying the formula (2) is 10% or less, it is more difficult to visually recognize the unevenness due to the connection of the light scattering points 32.

30a‧‧‧ point forming surface (main surface)

30c‧‧‧ end face

30d‧‧‧ end face

30e‧‧‧ end face

30f‧‧‧ end face

32‧‧‧Light scattering points

34‧‧‧Imaginary area

34a‧‧‧Specific areas

L1‧‧‧1st imaginary line

L2‧‧‧2nd imaginary line

Claims (7)

A light guide plate comprising: a light guide plate substrate that propagates light incident from an end surface; and a plurality of light scattering dots formed on a main surface of the light guide plate substrate and intersecting with the end surface And partially scattering one of the light propagating in the light guide substrate; and forming a first light scattering point among two adjacent light scattering points in a light scattering point group formed in a specific region of the main surface The maximum width in plan view is D ₁ , the maximum width in the plan view of the second light scattering point is D ₂ , and the distance between the centers of the first and second light scattering points is P ₁₂ , and the expression is satisfied. The ratio of the light scattering point of (1) to all the light scattering points of the light scattering point group is 10% or less, and the specific area is the light scattering point group in a plurality of regions obtained by virtually dividing the main surface The coverage is 30% or less, [1] P ₁₂ ≦ (D ₁ / 2 + D ₂ /2) ( ₁ ). The light guide plate of claim 1, wherein the total area of all of the specific areas is 90% or more with respect to the effective area of the main surface. The light guide plate of claim 1 or 2, wherein the maximum width of the light scattering points included in the light scattering point group is in the range of 30 μm to 100 μm. The light guide plate of any one of claims 1 to 3, wherein the thickness of the light guide plate substrate is less than 1 mm. The light guide plate according to any one of claims 1 to 4, wherein the light guide plate substrate has a rectangular shape in plan view, and a length of the short side of the planar shape of the light guide plate substrate is 250 mm or less. A surface light source device comprising: the light guide plate according to any one of claims 1 to 5; and a light source that supplies light to the end surface of the light guide plate substrate included in the light guide plate. A transmissive image display device comprising: the light guide plate according to any one of claims 1 to 5; a light source that supplies light to the end surface of the light guide plate substrate included in the light guide plate; and a transmissive image The display unit displays an image by being irradiated with light emitted from the light guide plate.