JP2020021037A - Anisotropic diffusion plate, backlight unit, liquid crystal display, and electronic apparatus - Google Patents

Abstract

To provide an anisotropic diffusion plate that achieves both light diffusion properties with excellent anisotropy and excellent light transmissivity, a backlight unit that achieves both light diffusion properties with excellent anisotropy and excellent light transmissivity, and a liquid crystal display and an electronic apparatus that include such a backlight unit and are excellent in reliability.SOLUTION: When an anisotropic diffusion plate 10 of the present invention emits incident light made incident from an incident surface 40 from an emission surface 50 as diffused emission light, the light diffusing power in the transverse direction and the light diffusing power in the fore-and-aft direction are different from each other. When the incident light with a size of 3 mmΦ is made incident perpendicularly to the incident surface 40 from a light source, a half power angle in a luminous intensity distribution in the fore-and-aft direction of the emission light and a half power angle in a luminous intensity distribution in the transverse direction of the emission light have an area in which the difference between the half power angles indicates an anisotropy of 3° or more and less than 15°, and the total light transmittance of the emission light to the incident light with a size of 3 mmΦ is 70% or more and 99% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an anisotropic diffusion plate, a backlight unit, a liquid crystal display, and an electronic device.

  2. Description of the Related Art As a liquid crystal display device, a liquid crystal display device including a liquid crystal panel as an image display unit and a surface light source as a backlight disposed on the back side of the liquid crystal panel is known.

  In this liquid crystal display device, the surface emitting light source includes a lamp box (housing) and a plurality of light emitting elements as point light sources arranged in a grid (matrix) in the lamp box. Further includes a light diffusing plate (anisotropic diffusing plate) disposed on the front side of the surface emitting light source, that is, between the surface emitting light source and the liquid crystal panel (for example, see Patent Document 1).

  In the liquid crystal display device having such a configuration, in recent years, it has been proposed to use a light emitting diode (LED) as a light emitting element (point light source) from the viewpoints of energy saving and light emitting element size reduction of the liquid crystal display device.

  However, an LED is a light-emitting element having an extremely high directivity for emitting light in a concentrated manner toward the front as compared with a white light bulb or a fluorescent lamp. Furthermore, from the viewpoint of miniaturization of the liquid crystal display device, it is required that the LED be disposed at a position where the distance from the light diffusion plate is small.

  Therefore, when an LED is used as a light emitting element included in the surface emitting light source, the light diffusing plate does not have sufficient light diffusing properties, so that the light emitting element (LED) that can be seen through the LED is dotted. As a result, there is a problem that display unevenness occurs in an image displayed by the liquid crystal display device. Further, for the purpose of suppressing the interstitiality of the LED, it is conceivable to reduce the light transmittance of the light diffusion plate, that is, to increase the content of the diffusion material used for the light diffusion plate. A sufficient amount of light from the surface emitting light source via the light diffusion plate cannot be obtained, which causes a problem that the display characteristics of an image in the liquid crystal display device are deteriorated.

  In general, a liquid crystal display device has a rectangular liquid crystal panel. Therefore, if the light emitted from the LED, which is a point light source having high directivity, is isotropically diffused by the light diffusion plate, the diffused light is located outside the display area of the liquid crystal panel in the lateral direction of the liquid crystal panel. Will be spread. For this reason, since part of the diffused light wastes, it is required that the emitted light be anisotropically diffused by the light diffusion plate.

JP 2009-63998 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an anisotropic diffusion plate that achieves both excellent light anisotropy and excellent light transmittance, and excellent anisotropic light diffusion and excellent light. It is an object of the present invention to provide a backlight unit that achieves both transparency and a liquid crystal display device and an electronic device that include the backlight unit and have excellent reliability.

Such an object is achieved by the present invention described in the following (1) to (14).
(1) An anisotropic diffusion plate in which the light diffusing ability in the left-right direction and the light diffusing ability in the front-rear direction are different when emitting incident light incident from the incident surface as emission light diffused from the emission surface. ,
When the incident light having a size of 3 mmΦ is perpendicularly incident on the incident surface from the light source, a half-value angle in the front-back luminous intensity distribution of the outgoing light and a half-value angle in the left-right luminous intensity distribution of the outgoing light Has a region exhibiting anisotropy whose half-value angle difference is 3 ° or more and less than 15 °, and
An anisotropic diffusion plate, wherein a total light transmittance of the outgoing light with respect to the incident light having a size of 3 mmΦ is 70% or more and 99% or less.

  (2) The exit surface has, in plan view, a convex shape formed by overlapping a plurality of spindles having a spindle shape, which are arranged in a close-packed manner, between adjacent ones. The anisotropic diffusion plate according to the above (1), which has a concave shape.

(3) The anisotropic diffusion plate is made of a transparent resin having a refractive index of n,
When the incident light is perpendicularly incident on the incident surface, at an arbitrary position of the spindle, the angle θ between the normal to the arbitrary position and the incident light is 0 ≦ θ <Sin ^{− 1} The anisotropic diffusion plate according to the above (2), which satisfies the relationship of (1 / n).

  (4) The anisotropic diffusion plate according to (3), wherein the transparent resin is mainly composed of a polycarbonate-based resin.

  (5) In the area of 1 cm × 1 cm in a plan view, 1% of the area satisfies the relationship of incident angle = 0 when the incident light is incident perpendicularly to the incident plane. The anisotropic diffusion plate according to any one of (1) to (4) below.

  (6) When the incident light is incident perpendicularly to the incident surface in a region of 1 cm long × 1 cm wide in plan view, the exit surface has 18 regions satisfying a relation of incident angle> critical angle. % Or less, the anisotropic diffusion plate according to any one of the above (1) to (5).

  (7) When the incident light is perpendicularly incident on the incident surface in an area of 1 cm long × 1 cm wide in plan view, the exit surface has an incident angle distribution in the front-rear direction of the incident light, The anisotropic diffusion plate according to any one of (1) to (6) above, wherein the incident light has a different incident angle distribution in the left-right direction.

  (8) The anisotropic diffusion plate according to any one of (1) to (7), wherein the emission surface has a surface roughness Ra of 0.1 μm or less.

  (9) The anisotropic diffusion plate according to any one of (1) to (8), wherein a low refractive index layer having a lower refractive index than the refractive index of the anisotropic diffusion plate is formed on the incident surface.

  (10) The anisotropic diffusion plate according to any one of (1) to (8), wherein a dielectric multilayer film is formed on the incident surface.

  (11) The anisotropic diffusion plate according to any one of the above (1) to (10), wherein the anisotropic diffusion plate has an optical retardation of 200 nm or less.

(12) An anisotropic diffusion plate according to any one of the above (1) to (11), and a light-emitting substrate arranged to face the anisotropic diffusion plate,
The backlight unit according to claim 1, wherein the light-emitting substrate includes a base substrate and a plurality of light-emitting diodes arranged in a grid on a surface of the base substrate facing the anisotropic diffusion plate.

(13) A liquid crystal display device comprising: the backlight unit according to (12); and a liquid crystal panel disposed to face the anisotropic diffusion plate of the backlight unit.
(14) An electronic apparatus comprising the liquid crystal display device according to (13).

  According to the present invention, when the incident light incident from the incident surface is emitted as the outgoing light diffused from the exit surface, the anisotropic diffusion plate in which the light diffusing ability in the left-right direction and the light diffusing ability in the front-back direction are different. When the incident light having a size of 3 mmΦ is perpendicularly incident on the incident surface from the light source, the half-value angle in the front-back luminous intensity distribution of the outgoing light, and the left-right luminous intensity distribution of the outgoing light A half-value angle difference from the half-value angle has a region exhibiting anisotropy of 3 ° or more and less than 15 °, and the total light transmittance of the outgoing light with respect to the incident light having the size of 3 mmΦ is 70% or more and 99% or more. % Or less. Therefore, it can be said that this anisotropic diffusion plate achieves both light diffusion with excellent anisotropy and excellent light transmittance. Therefore, in a liquid crystal display device including such an anisotropic diffusion plate, even if an LED is used as an optical element, it is possible to accurately suppress or prevent the spotting of the LED through the anisotropic diffusion plate. Further, it is possible to appropriately suppress or prevent the wasted diffused light from being wasted, and to display an image with excellent display characteristics. As a result, an electronic device including the liquid crystal display device has excellent reliability.

It is a longitudinal section showing an embodiment of a liquid crystal display of the present invention. FIG. 2 is a plan view for describing a configuration of an emission surface in an anisotropic diffusion plate included in the liquid crystal display device illustrated in FIG. 1. FIG. 2 is a partially enlarged plan view in which a projection provided on an emission surface is enlarged for explaining a configuration of an emission surface of an anisotropic diffusion plate included in the liquid crystal display device illustrated in FIG. 1 is a side view illustrating an embodiment of a display panel of an automobile having a liquid crystal display device of the present invention as a display unit.

  Hereinafter, an anisotropic diffusion plate, a backlight unit, a liquid crystal display device, and an electronic apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  The anisotropic diffusion plate of the present invention has a structure in which the light diffusing ability in the left-right direction and the light diffusing ability in the front-rear direction are different when the incident light incident from the incident surface is emitted as the emission light diffused from the emission surface. When the incident light having a size of 3 mmΦ is perpendicularly incident on the incident surface from a light source, a half-value angle in a front-back luminous intensity distribution of the outgoing light, and a left-right luminous intensity distribution of the outgoing light The half-value angle in has a region where the half-value angle difference shows anisotropy of 3 ° or more and less than 15 °, and the total light transmittance of the outgoing light with respect to the incident light having the size of 3 mmΦ is: 70% or more and 99% or less.

  As described above, according to the present invention, the anisotropic diffusion plate has a half-value in the luminous intensity distribution in the front-rear direction of the emitted light when the incident light having a size of 3 mmΦ is incident from the light source perpendicularly to the incident surface. A half-value angle difference between the angle and the half-value angle in the luminous intensity distribution of the emitted light in the left-right direction has an anisotropy region of 3 ° or more and less than 15 °. Therefore, it can be said that this anisotropic diffusion plate has excellent light anisotropy with excellent anisotropy. Further, the total light transmittance of the outgoing light with respect to the incident light having the size of 3 mmΦ is 70% or more and 99% or less. Therefore, it can be said that this anisotropic diffusion plate has excellent light transmittance. Therefore, in the liquid crystal display device having the anisotropic diffusion plate having such a configuration, even when the LED is used as the optical element, the dotiness in which the LED can be seen through the anisotropic diffusion plate is accurately suppressed. Alternatively, it is possible to accurately prevent or prevent the diffused light from being wasted, and to display an image with excellent display characteristics. As a result, an electronic device including the liquid crystal display device has excellent reliability.

  Hereinafter, first, a liquid crystal display device including the anisotropic diffusion plate of the present invention, that is, a liquid crystal display device of the present invention will be described.

<Liquid crystal display device>
FIG. 1 is a longitudinal sectional view showing an embodiment of the liquid crystal display device of the present invention, FIG. 2 is a plan view for explaining a configuration of an emission surface in an anisotropic diffusion plate provided in the liquid crystal display device shown in FIG. FIG. 3 is a partially enlarged plan view in which a projection provided on the emission surface is enlarged to explain the configuration of the emission surface of the anisotropic diffusion plate included in the liquid crystal display device shown in FIG. In the following description, the upper side in FIG. 1 is referred to as “upper”, and the lower side is referred to as “lower”. The X direction in FIGS. 2 and 3 is referred to as a “lateral direction”, the Y direction is referred to as a “back and forth direction”, and the Z direction is referred to as a “vertical direction”. Further, the drawings used (including FIGS. 1 to 3 and the drawings shown below) are appropriately enlarged or reduced so that the portions to be described can be recognized.

  As shown in FIG. 1, the liquid crystal display device 100 includes a liquid crystal panel 20 forming an image display unit, and a surface emitting light source 30 as a backlight, which is disposed on the opposite side (back side) of the display surface of the liquid crystal panel 20. And a direct liquid crystal display device (direct liquid crystal display) having an anisotropic diffusion plate 10 disposed between the liquid crystal panel 20 and the surface light source 30.

  The liquid crystal panel 20 constitutes a transmissive image display unit having a liquid crystal cell 21 and two polarizing plates 22 arranged on the front surface (upper surface) and the rear surface (lower surface) of the liquid crystal cell 21. I have. Here, the liquid crystal cell 21 has, for example, a configuration having a pair of transparent electrodes and an enclosure including a liquid crystal compound sealed between the transparent electrodes, and further arranged corresponding to the transparent electrodes on the front side. A color image can be displayed by having the color filter set.

  The surface-emitting light source 30 (light-emitting substrate) has a flat base material (base substrate) and a wall standing upright from an edge of the base material, so that an opening that opens to the front side (top side). And a light emitting element 32 as a plurality of point light sources arranged in the lamp box 31 by being arranged in a grid on the front surface (upper surface) side of the base material. It has.

  In this surface emitting light source 30, the light emitting element 32 is formed of a light emitting diode (LED) having an extremely high directivity of emitting light intensively forward as compared to a white light bulb or a fluorescent lamp.

  The anisotropic diffusion plate 10 is fixed to the lamp box 31 so as to cover the opening. Thus, the anisotropic diffusion plate 10 is disposed between the lamp box 31 and the liquid crystal panel 20. That is, the anisotropic diffusion plate 10 is disposed on the lower surface side to face the lamp box 31, and light (incident light) emitted by the liquid crystal panel 20 on the upper surface side passes (transmits) through the anisotropic diffusion plate 10. Then, when emitted as the diffused emitted light, the light diffusing ability in the left-right direction and the light diffusing ability in the front-back direction are diffused with different anisotropy. Then, the light (emitted light) diffused with anisotropy is applied to the liquid crystal panel 20.

  In addition, at least one isotropic diffusion plate that isotropically diffuses the light emitted by the light emitting element 32 may be disposed between the surface light source 30 and the anisotropic diffusion plate 10. Further, between the anisotropic diffusion plate 10 and the liquid crystal panel 20, at least one prism sheet for dispersing and refracting light diffused from the anisotropic diffusion plate 10 toward the liquid crystal panel 20 is provided. Is also good.

  Further, in such a liquid crystal display device 100, the anisotropic diffusion plate 10 and the surface light source 30 constitute a backlight unit (the backlight unit of the present invention).

  In the liquid crystal display device 100 configured as described above, the anisotropic diffusion plate 10 is configured by the anisotropic diffusion plate of the present invention. Therefore, the anisotropic diffusion plate 10 is configured to emit the incident light from the incident surface 40 on the surface emitting light source 30 side as the diffused light from the exit surface 50 on the liquid crystal panel 20 side. The light diffusing ability and the light diffusing ability in the front-back direction can be diffused with different anisotropy. That is, when the incident light having a size of 3 mmΦ is perpendicularly incident on the incident surface 40 from the light source, the half-value angle in the luminous intensity distribution in the front-back direction of the outgoing light and the luminous intensity distribution in the left-right direction of the outgoing light The half-value angle has a region where the half-value angle difference indicates anisotropy of 3 ° or more and less than 15 °. The total light transmittance of the outgoing light with respect to the incident light having the size of 3 mmΦ is 70% or more and 99% or less. Therefore, it can be said that the anisotropic diffusion plate 10 achieves both light diffusion with excellent anisotropy and excellent light transmittance.

  Therefore, in the liquid crystal display device 100, an LED is used as the light emitting element 32, and the separation distance between the base (base substrate) of the lamp box 31 and the anisotropic diffusion plate 10 is, for example, 0.5 mm or more. Even if the distance is set close to 10.0 mm or less in order to reduce the size (thickness) of the liquid crystal display device 100, the light emitting element 32 (LED) can be seen through the anisotropic diffusion plate 10. The dotiness can be suppressed or prevented accurately. Therefore, the liquid crystal display device 100 can display an image with excellent display characteristics.

  Further, when the length in the left-right direction in the display area of the liquid crystal panel 20 is A, and the length in the front-rear direction is B, the aspect ratio A / B is 1.2 or more and 3.0 or less, preferably 1 or more. Even if the display area of the liquid crystal panel 20 has a rectangular shape as described above, the light (emitted light) diffused in the front-rear direction, which is the short direction of the liquid crystal panel 20, is a liquid crystal. Diffusion outside the display area of panel 20 can be accurately suppressed or prevented. That is, it is possible to appropriately suppress or prevent the waste of the diffused light (emitted light). As a result, the power consumed by the liquid crystal display device 100 is reduced.

  In the present embodiment, like the liquid crystal panel 20 and the surface light source 30, such an anisotropic diffusion plate 10 forms a rectangular flat plate in a plan view, and the incident surface 40 on the surface light source 30 side and the liquid crystal panel The exit surface 50 on the 20 side is formed of a flat surface and a convex surface, respectively, and contains a transparent resin as a main material.

  In the anisotropic diffusion plate 10 having such a shape, the half-value angle difference has a region exhibiting anisotropy of 3 ° or more and less than 15 °, and the total light transmittance in the region is 70% or more and 99% or less. This is because the emission surface 50 on the liquid crystal panel 20 side is formed as a convex surface. A detailed description of the convex shape of the emission surface 50 will be given later. Hereinafter, constituent materials such as a transparent resin constituting the above will be described.

  The transparent resin (base resin) is included in the anisotropic diffusion plate 10 as a main material, and is used to mold the anisotropic diffusion plate 10 into a flat plate shape (substrate shape).

  The transparent resin is not particularly limited as long as it has transparency. For example, acrylic resin, polystyrene resin, polyethylene resin, polypropylene resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) And the like, such as polyester-based resins, polycarbonate-based resins, cycloolefin-based resins, vinyl chloride-based resins, and polyacetal-based resins, which can be used alone or in combination of two or more. . Among these, a polycarbonate resin is particularly preferable. Polycarbonate resin has high mechanical strength such as transparency (light transmission) and rigidity, and also has high heat resistance. Therefore, by using polycarbonate resin as the transparent resin, the transparency of the anisotropic diffusion plate 10 can be improved. The impact resistance and heat resistance of the anisotropic diffusion plate 10 can be improved. Further, since the polycarbonate resin has a specific gravity of about 1.2 and is classified as light among the resin materials, the use of the polycarbonate resin as the transparent resin makes it possible to reduce the weight of the anisotropic diffusion plate 10. Can be achieved.

  Various polycarbonate resins can be used, and among them, aromatic polycarbonate resins are preferable. The aromatic polycarbonate-based resin has an aromatic ring in its main chain, whereby the strength of the anisotropic diffusion plate 10 can be further improved.

  This aromatic polycarbonate resin is synthesized by, for example, an interfacial polycondensation reaction between bisphenol and phosgene, a transesterification reaction between bisphenol and diphenyl carbonate, and the like.

  Examples of the bisphenol include bisphenol A and bisphenol (modified bisphenol) which is a source of the repeating unit of the polycarbonate represented by the following formula (1).

（式（１）中、Ｘは、炭素数１〜１８のアルキル基、芳香族基または環状脂肪族基であり、ＲａおよびＲｂは、それぞれ独立して、炭素数１〜１２のアルキル基であり、ｍおよびｎは、それぞれ０〜４の整数であり、ｐは、繰り返し単位の数である。）

(In the formula (1), X is an alkyl group having 1 to 18 carbon atoms, an aromatic group or a cycloaliphatic group, and Ra and Rb are each independently an alkyl group having 1 to 12 carbon atoms. , M and n are each an integer of 0 to 4, and p is the number of repeating units.)

  As the bisphenol that is the source of the repeating unit of the polycarbonate represented by the formula (1), specifically, for example, 4,4 ′-(pentane-2,2-diyl) diphenol, 4,4 ′-( Pentane-3,3-diyl) diphenol, 4,4 ′-(butane-2,2-diyl) diphenol, 1,1 ′-(cyclohexanediyl) diphenol, 2-cyclohexyl-1,4-bis ( 4-hydroxyphenyl) benzene, 2,3-biscyclohexyl-1,4-bis (4-hydroxyphenyl) benzene, 1,1′-bis (4-hydroxy-3-methylphenyl) cyclohexane, 2,2′- Bis (4-hydroxy-3-methylphenyl) propane and the like can be mentioned, and one or more of these can be used in combination.

  In particular, it is preferable that the polycarbonate-based resin is mainly composed of a bisphenol-type polycarbonate-based resin having a skeleton derived from bisphenol. By using such a bisphenol-type polycarbonate-based resin, the anisotropic diffusion plate 10 exhibits further excellent strength.

  Further, the anisotropic diffusion plate 10 may further include a fluorescent whitening agent. When the anisotropic diffusion plate 10 is configured to include a fluorescent whitening agent, the anisotropic diffusion plate 10 allows the incident light from the surface light source 30 to be emitted to the liquid crystal panel 20 as emission light. White light (emitted light) can be emitted more reliably.

  Specifically, since the anisotropic diffusion plate 10 contains a fluorescent whitening agent, the surface emitting light source provided with the anisotropic diffusion plate 10 has a xy chromaticity diagram of 0.28 ≦ x ≦ It preferably emits light satisfying a relationship of 0.40 and 0.28 ≦ y ≦ 0.40, and 0.30 ≦ x ≦ 0.36 and 0.30 ≦ y ≦ 0 It is more preferable to emit light that satisfies the relationship of .36. Thus, it can be said that the anisotropic diffusion plate 10 emits white light toward the liquid crystal panel 20 from the surface light source 30.

  Examples of the fluorescent whitening agent include, but are not particularly limited to, benzophenone type, benzotriazole type, hydroxyphenyltriazine type and benzooxazolylthiophene type. Can be used in combination, and among them, a benzooxazolylthiophene type is preferable. Thereby, in the xy chromaticity diagram, x and y can relatively easily satisfy the above relation.

  Further, the content of the fluorescent whitening agent in the anisotropic diffusion plate 10 is preferably set to 0.001 wt% or more and 0.07 wt% or less, more preferably 0.003 wt% or more and 0.01 wt% or less. Thus, in the xy chromaticity diagram, x and y can easily satisfy the above relationship.

  The anisotropic diffusion plate 10 may further include an antioxidant, a filler, a plasticizer, a light stabilizer, a UV absorber, a heat ray absorber, as necessary, in addition to the transparent resin and the fluorescent whitening agent described above. Various additives such as a flame retardant may be included.

  As described above, in the anisotropic diffusion plate 10, in the present embodiment, the entrance surface 40 on the surface light source 30 side and the exit surface 50 on the liquid crystal panel 20 side are formed of a flat surface and a convex surface, respectively. In such an anisotropic diffusion plate 10, the half-value angle difference has a region exhibiting anisotropy of 3 ° or more and less than 15 °, and the total light transmittance in the region is 70% or more and 99% or less. However, such a configuration is possible because, of the incident surface 40 on the surface emitting light source 30 side and the exit surface 50 on the liquid crystal panel 20 side, the exit surface 50 on the liquid crystal panel 20 side is constituted by a convex surface. Hereinafter, the emission surface 50 constituted by this convex surface will be described.

  In the present embodiment, in the plan view, the exit surface 50 is formed by adjoining a plurality of spindles 56 having a spindle shape arranged in a close-packed manner on a plane 55 as shown in FIG. 2B. A convex surface is formed by arranging a plurality of convex portions 51 having a convex shape formed by overlapping edges of each other (see FIG. 2A).

  In such an emission surface 50, the convex portion 51 (convex body) functions as light diffusion means for anisotropically diffusing light (emitted light). As described above, the convex portion 51 is derived from the spindle 56 having a shape (vertical spindle shape) in which the spindle shape is vertically divided (half-split) by a plane passing through the center axis (see FIG. 2B). That is, the convex portion 51 is formed by overlapping the spindles 56 of the closest-packed arrangement with each other between adjacent ones. , In a plan view.

  The convex portion 51 having such a configuration is arranged such that its long axis (center axis) is parallel to the Y direction (front-back direction) and its short axis is parallel to the X direction (left-right direction). Therefore, the convex portion 51 has a semi-elliptical cross section in the Y direction and a semi-elliptical cross section in the X direction having a larger curvature than the semi-ellipse. By arranging the convex portions 51 in such an arrangement, the anisotropic diffusion plate 10 has a light diffusing ability in both the X direction and the Y direction, and has a light diffusing ability in the X direction (lateral direction). It exhibits a diffusivity with anisotropy greater than the light diffusivity in the Y direction (front-back direction).

  In addition, since the convex portion 51 has the above-described configuration, the flat portion 57 formed between the plurality of spindles 56 on the plane 55 can be accurately suppressed or prevented from being formed on the emission surface 50. it can. Therefore, at the position where the convex portion 51 of the emission surface 50 is formed, an area of 1 cm × 1 cm in plan view is selected, and the incident light from the surface light source 30 is perpendicularly incident on the incident surface 40. In this case, the region satisfying the relationship of the incident angle = 0, that is, the region where the flat portion is formed is set to preferably 1% or less, more preferably 0.5% or less. Thereby, it is possible to accurately suppress or prevent the incident light from passing through the flat portion without being anisotropically diffused. Therefore, the anisotropic diffusion plate 10 can improve the anisotropic light diffusion efficiency.

  Furthermore, the convex portion 51 having the above-described configuration can reduce the occupation area of the total reflection light region 52 where the incident light is totally reflected in the convex portion 51. Therefore, at the position where the convex portion 51 of the emission surface 50 is formed, an area of 1 cm × 1 cm in plan view is selected, and the incident light from the surface light source 30 is perpendicularly incident on the incident surface 40. In this case, the region satisfying the relationship of incident angle> critical angle, that is, the total reflection light region 52 where incident light is totally reflected is preferably 18% or less, more preferably 0.3% or more and 15% or less. Is set. Thereby, it is possible to accurately suppress the incident light that has entered the convex portion 51 from being totally reflected without being emitted from the emission surface 50 side. Therefore, the total light transmittance of the anisotropic diffusion plate 10 can be improved, that is, the anisotropic diffusion plate 10 can have excellent light transmittance. Therefore, the total light transmittance of the outgoing light with respect to the incident light when the incident light having a size of 3 mmΦ is incident from the light source perpendicularly to the incident surface 40 can be set to 70% or more and 99% or less.

Here, in the convex portion 51, as described above, a region that satisfies the relationship of incident angle> critical angle constitutes a total reflection light region 52 where incident light is totally reflected. A region satisfying the relationship of incident angle ≦ critical angle constitutes a transmitted light region 53 that emits incident light to the exit surface 50 side as exit light. In the transmitted light region 53 (arbitrary position) of such a convex portion 51, assuming that the anisotropic diffusion plate 10 is formed of a transparent resin having a refractive index of n, the surface is perpendicular to the incident surface 40. Assuming that incident light is incident from the light emitting light source 30, the angle θ between the normal to the transmitted light region 53 (arbitrary position) and the incident light has a relationship of 0 ≦ θ <Sin ⁻¹ (1 / n). To be satisfied. Therefore, in the anisotropic diffusion plate 10 made of a transparent resin having a refractive index n, in the transmitted light region 53 of the convex portion 51, the incident light is more reliably reflected on the exit surface 50 side without being totally reflected. It can be emitted. Then, at a position where the convex portion 51 of the emission surface 50 is formed, an area of 1 cm × 1 cm in plan view is selected, and the incident light from the surface light source 30 is incident perpendicularly to the incident surface 40. As described above, as described above, the cross-sectional shape of the convex portion 51 in the Y direction (front-back direction) has a semi-elliptical shape, and the cross-sectional shape of the convex portion 51 in the X direction (left-right direction) has a larger curvature than the semi-ellipse. Because of the elliptical shape, the incident angle distribution of the incident light in the Y direction and the incident angle distribution of the incident light in the X direction are different in the transmitted light region 53 of the convex portion 51. The anisotropic diffusion plate 10 exhibits anisotropic diffusion ability.

Also, in plan view, the length _{L Y} in the Y direction (longitudinal direction) of the convex portion 51 is preferably 50μm or more 200μm or less, and more preferably set to 70μm or 150μm or less, X direction (lateral direction of the convex portion 51 the length _{L X} in) is preferably 25μm or more 80μm or less, and more preferably set to 40μm or 70μm or less. Furthermore, the aspect ratio _L Y / _{L X} of the length _{L Y} and length _{L X} is 1.5 to 5.0, is preferably set to 1.8 to 2.2. Thereby, the anisotropic diffusion plate 10 can exhibit the diffusion ability with more excellent anisotropy. Therefore, when incident light having a size of 3 mmΦ is incident on the incident surface 40 perpendicularly from the light source, the half-value angle in the luminous intensity distribution in the Y direction of the outgoing light and the half-value angle in the luminous intensity distribution in the X-direction of the outgoing light Can be reliably set within the range of 3 ° or more and less than 15 °.

  Further, the emission surface 50 forms a convex surface by forming a convex portion 51 on the surface, and the surface roughness Ra is preferably 0.1 μm or less, and 0.005 μm to 0.08 μm. It is more preferred that: By forming the projections 51 having such a fine surface roughness Ra on the emission surface 50, in the region where the projections 51 are formed, a more uniform anisotropy is provided in the X direction and the Y direction. The emitted light can be dispersed.

  Here, by providing the emission surface 50 with the convex portion 51 having the above-described configuration, in the region where the convex portion 51 is formed, the incident light having a size of 3 mmΦ is perpendicular to the incident surface 40. When light is incident from a light source, the half-value angle difference between the half-value angle in the luminous intensity distribution of the emitted light in the Y direction (front-back direction) and the luminous intensity distribution in the X-direction (left-right direction) of the emitted light is 3%. The anisotropy of not less than 15 ° and less than 15 ° may be shown, but the half angle difference preferably shows anisotropy of not less than 4.5 ° and not more than 13 °. Thereby, it can be said that the anisotropic diffusion plate 10 exerts the diffusing ability with more excellent anisotropy. Therefore, in the liquid crystal display device 100, it is possible to more accurately suppress or prevent the scattered point of the light emitting element 32 (LED) that is seen through the anisotropic diffusion plate 10.

  Further, in the present embodiment, since the convex portion 51 is arranged so that the central axis thereof is parallel to the Y direction (front-back direction), the light diffusing ability in the X direction (left-right direction) is in the Y direction (front-back direction). ), The half power angle in the luminous intensity distribution in the X direction of the emitted light is larger than the half power angle in the luminous intensity distribution in the Y direction. When the half-value angle difference is within the range, the half-value angle in the luminous intensity distribution of the emitted light in the X direction is preferably 5 ° or more and 30 ° or less, and 8 ° or more and 20 ° or less. Is more preferable, and it is more preferable that it is 10 degrees or more and 15 degrees or less. By setting the half-value angle difference within the above-described range and setting the half-value angle in the luminous intensity distribution of the emitted light in the X direction within the above-described range, the aspect ratio A / B in the display region is within the above-described range. When irradiating the panel 20 with diffused light (emitted light), the diffused light can be more accurately suppressed or prevented from being diffused outside the display area of the liquid crystal panel 20. . Furthermore, even if the light emitting elements 32 included in the surface emitting light source 30 are arranged in the lamp box 31 in a grid pattern at equal intervals in both the X direction and the Y direction, the half-value angle difference is within the range. By setting the half-value angle in the luminous intensity distribution of the emitted light in the X direction within the above range, the liquid crystal panel 20 has a display area having an aspect ratio A / B within the above-described range. The dispersed outgoing light can be more uniformly irradiated.

The “half-value angle difference” is a parameter (characteristic value) indicating the light diffusing ability of the outgoing light emitted from the emission surface 50. Specifically, when the incident light is incident perpendicularly from the incident surface 40 side of the anisotropic diffusion plate 10, the luminous intensity distribution of the emitted light on the exit surface 50 side is large in the normal direction of the exit surface 50, It becomes smaller as it is closer to the tangential direction of the surface 50. When the luminous intensity distribution of the emitted light is plotted with the horizontal axis (X axis) as an angle θ from the normal direction and the vertical axis (Y axis) as luminous intensity I, a mountain-shaped luminous intensity distribution curve is obtained. , The angle width θ _H of the luminous intensity distribution curve corresponding to a half (I _0/2 ; half) of the maximum luminous intensity I ₀ is referred to as a half-value angle. In this embodiment, the half-value angle of the emitted light in the X-direction light intensity distribution is larger than the half-value angle of the Y-direction light intensity distribution. Therefore, a “half-value angle difference” is obtained by calculating the difference between the half-value angle of the luminous intensity distribution of the emitted light in the X direction and the half-value angle of the luminous intensity distribution of the emitted light in the Y direction. Also, the larger the “half angle difference”, the more the anisotropic diffusion plate 10 has a large anisotropy and a light diffusing ability.

  Further, in a region where the convex portion 51 is formed, when incident light having a size of 3 mmΦ is incident from the light source perpendicularly to the incident surface 40, the incident light is all rays of light emitted as emitted light. The transmittance may be 70% or more and 99% or less, but is preferably 80% or more and 99% or less. Thereby, it can be said that the anisotropic diffusion plate 10 exhibits more excellent light transmittance. Therefore, in the liquid crystal display device 100, the amount of light from the surface light source 30 can be sufficiently obtained, and the liquid crystal display device 100 has excellent image display characteristics while reducing power consumption. Can be.

  Furthermore, the anisotropic diffusion plate 10 has an average thickness of preferably about 0.1 mm or more and 2.0 mm or less, preferably about 0.5 mm or more and 1.0 mm or less. By setting the average thickness of the anisotropic diffusion plate 10 within such a range, the thickness of the anisotropic diffusion plate 10 can be reduced while the bending of the anisotropic diffusion plate 10 is appropriately suppressed or Can be prevented. Therefore, the anisotropic diffusion plate 10 can exhibit light diffusion and light transmission with more uniform anisotropy over the whole.

  The anisotropic diffusion plate 10 preferably has an optical retardation of 200 nm or less, more preferably 150 nm or less. Here, the anisotropic diffusion plate 10 can be manufactured by, for example, hot pressing using a mold having an upper mold having a concave portion corresponding to the shape of the convex portion 51 and a lower mold having a flat surface. . At this time, a flat plate containing the constituent material of the anisotropic diffusion plate 10 is prepared, and the flat plate in a molten or softened state is sandwiched between the upper die and the lower die, and the flat plate is solidified in this state. Thus, the anisotropic diffusion plate 10 is manufactured. When the anisotropic diffusion plate 10 is molded using such a mold, the optical phase difference is equal to or less than the upper limit, so that the shape of the anisotropic diffusion plate 10 with respect to the shape of the mold is good. Therefore, an optical design in which the optical phase difference is equal to or less than the upper limit value can be reproduced with high accuracy. In particular, when the phase difference of the anisotropic diffusion plate 10 is 150 nm or less, there is obtained an advantage that fluctuation in the outgoing orientation angle from the design of the orientation distribution can be suppressed.

  Further, the anisotropic diffusion plate 10 may include a low refractive index layer formed on the incident surface 40. The low refractive index layer has a refractive index lower than the refractive index of the anisotropic diffusion plate 10. The reflectance at which the incident light is reflected toward the surface light source 30 can be reduced. Therefore, the amount of light emitted from the emission surface 50 as emission light is increased.

  The low-refractive-index layer may be any one of an inorganic type, an organic type, and a composite of an organic type and an inorganic type.

  Examples of the inorganic low refractive index layer include metal fluoride fine particles. Examples of the metal fluoride fine particles include magnesium fluoride, aluminum fluoride, calcium fluoride, lithium fluoride, and the like, and one or more of these can be used in combination. In addition, in order to impart adhesion of the metal fluoride fine particles, a resin base layer made of an ultraviolet ray or an electron beam curable resin may be formed on the incident surface 40.

  Examples of the organic low refractive index layer include a fluorine-containing resin having a low refractive index because the resin contains a large amount of fluorine atoms. As the fluorinated resin, polytetrafluoroethylene and polyvinylidene fluoride are preferable. For example, the fluorinated resin can be formed by laminating a sheet made of the fluorinated resin on the incident surface 40 via an adhesive.

  Examples of the low-refractive index layer made of an organic-inorganic composite include those containing an ultraviolet or electron beam-curable resin, inorganic fine particles having voids, and metal fluoride fine particles. Examples of the inorganic fine particles having voids include those having a gas filled inside the inorganic fine particles and those having a porous structure containing a gas therein. Specific examples include hollow silica fine particles and silica fine particles having a nanoporous structure. Examples of the metal fluoride fine particles include magnesium fluoride, aluminum fluoride, calcium fluoride, and lithium fluoride. The average particle size of the inorganic fine particles and the metal fluoride fine particles is preferably 5 to 100 nm, more preferably 20 to 80 nm, and further preferably 40 to 70 nm. When the average particle diameter of the fine particles is in this range, excellent transparency can be imparted to the low refractive index layer.

  Further, the anisotropic diffusion plate 10 may include a dielectric multilayer film formed on the incident surface 40. The dielectric multilayer film can reduce the reflectance of incident light from the surface light source 30 toward the surface light source 30. Therefore, the amount of light emitted from the emission surface 50 as emission light is increased.

  This dielectric multilayer film is formed by repeating a high refractive index layer containing a high refractive index dielectric material and a low refractive index layer containing a low refractive index dielectric material. As the refractive index dielectric material, for example, a ceramic material, a glass material, a resin material, and the like can be cited. Among these materials, one or more of them can be used so that the high refractive index layer has a higher refractive index than the low refractive index layer. Two or more kinds are used in combination.

  Examples of the ceramic material include alumina, zirconia, magnesia, silica, titanium oxide, niobium pentoxide, aluminum nitride, silicon nitride, silicon carbide, barium titanate, and perovskite-type barium calcium zirconate titanate crystal particles (BCTZ type crystal particles). ), Calcium fluoride, magnesium fluoride and the like. Examples of the glass material include quartz glass and borosilicate glass. Further, examples of the resin material include polyethylene, polypropylene, polytetrafluoroethylene, polyethylene terephthalate, polyvinylidene fluoride, polyphenylene sulfide, phenol resin, melamine resin, unsaturated polyester resin, and epoxy resin.

  Note that, in the present embodiment, the case where the emission surface 50 is configured by a convex surface having a plurality of convex portions 51 has been described. However, the present invention is not limited to this case. It may be configured by a concave surface having a plurality of concave portions having a concave shape.

  Further, in the present embodiment, the convex portion 51 is arranged so that its central axis is parallel to the Y direction (front-rear direction). However, the present invention is not limited to this. For example, the liquid crystal panel 20 is long in the Y direction. In the case of a rectangular shape, the protrusions 51 can be arranged such that the central axis of the protrusions 51 is parallel to the X direction (left-right direction).

<Electronic equipment>
Next, an example in which the present invention is applied to a display panel of an automobile as an electronic device (the electronic device of the present invention) including the above-described liquid crystal display device 100 will be described.

  FIG. 4 is a side view showing an embodiment of a display panel of an automobile having the liquid crystal display device of the present invention as a display unit. In the following description, the upper side in FIG. 1 is referred to as “upper”, and the lower side is referred to as “lower”.

  As shown in FIG. 4, a display panel 150 (electronic device of the present invention) including a display section for displaying a center information display, a speedometer, a tachometer, a water temperature gauge, a fuel gauge, and the like has a display section of the liquid crystal display device 100. It is configured and used by being mounted on an automobile 200. The display panel 150 is built in the upper part of the dashboard 201 of the vehicle 200, whereby information such as the speed of the vehicle, the number of revolutions of the engine, etc. displayed by the liquid crystal display device 100 is displayed as an image on the driver H. Will be recognized.

  Note that the electronic device of the present invention may be a personal computer, a smartphone, a television, a video camera, an electronic organizer, a medical device (eg, a blood pressure monitor, a blood glucose meter, a liquid crystal display for an endoscope) in addition to the display panel of the automobile in FIG. The present invention can be applied to an electronic device including a display unit, such as a device and a device including a touch panel (for example, an automatic ticket vending machine).

  As described above, the anisotropic diffusion plate, the backlight unit, the liquid crystal display device, and the electronic apparatus of the present invention have been described, but the present invention is not limited to these.

  For example, in the above embodiment, the case where the liquid crystal display device including the anisotropic diffusion plate of the present invention is applied to a direct type liquid crystal display device has been described. However, the present invention is not limited thereto. For example, an edge light type liquid crystal display device Can also be applied.

  Further, in the above embodiment, the case where the anisotropic diffusion plate of the present invention is applied to a liquid crystal display diffusion plate provided in a liquid crystal display device has been described. , Window glass, roof members for lighting, and the like.

  Hereinafter, the present invention will be described more specifically based on examples. The present invention is not limited by these examples.

1. Production of anisotropic diffusion plate (Example 1)
[1] First, a plate-like polycarbonate substrate (“EC105”, manufactured by Sumitomo Bakelite Co., Ltd.) having a thickness of 0.5 mm is prepared, and further, convex portions 51 to be formed (L _Y = 70 μm, L _X = 40 μm, A mold having an upper mold having a concave portion corresponding to a shape having a height of 15 μm and a lower mold having a flat surface was prepared.

  [2] Next, with the polycarbonate substrate sandwiched between the upper mold and the lower mold, the anisotropic diffusion plate 10 of Example 1 was obtained by hot pressing with heating.

(Examples 2 to 7, Comparative Examples 1 to 4)
Examples 2 to 7 and Comparative Examples 1 to 7 were performed in the same manner as in Example 1 except that a mold having an upper die having a concave portion corresponding to the convex portion 51 having the size shown in Table 1 was prepared. An anisotropic diffusion plate 10 of Example 4 was obtained.

2. Evaluation The anisotropic diffusion plate 10 of each example and each comparative example was evaluated by the following method.

1) Half-value angle, half-value angle difference For the anisotropic diffusion plates 10 of each of the examples and comparative examples, each is perpendicular to the incidence surface 40 corresponding to the region where the projection 51 of the emission surface 50 is formed. , Incident light having a size of 3 mmΦ was incident from a light source. The luminous intensity distribution in the Y direction (front-back direction) of the outgoing light and the luminous intensity distribution in the X direction (left-right direction) of the outgoing light emitted from the outgoing surface 50 at this time are compared with the goniophotometer (Murakami Color Research Laboratory). ("GP-200", manufactured by the same company).

  Thereafter, based on the obtained luminous intensity distribution, a half-value angle of the luminous intensity distribution of the emitted light in the X direction (left-right direction) and a half-value angle of the luminous intensity distribution of the emitted light in the Y direction (front-rear direction) are obtained. The half value angle difference was determined from the half value angle.

2) Measurement of the incident angle distribution of the incident light in the front-rear direction and the incident angle distribution in the left-right direction For each of the anisotropic diffusion plates 10 of each of the examples and the comparative examples, the projection 51 of the emission surface 50 is formed. A laser microscope ("VK-9700", manufactured by KEYENCE, Inc.) shows the incident angle distribution of the incident light in the front-rear direction and the incident angle distribution of the incident light in the left-right direction in a region of 1 cm × 1 cm in plan view. ).

  In addition, the critical angle of the anisotropic diffusion plate 10 of each example and each comparative example was about 40 °. Therefore, in this specification, at least one of the X direction and the Y direction of the outgoing light, a region where the critical angle exceeds 40 ° is determined to be the total reflection light region 52. did.

3) Total light transmittance About the anisotropic diffusion plate 10 of each example and each comparative example, using a haze meter (manufactured by Murakami Color Research Laboratory, “HR-100”), the total in the thickness direction was used. Light transmittance was measured according to ASTM D1003.

4) Front Brightness of Backlight Unit First, the anisotropic diffusion plate 10 of each of the examples and comparative examples is fixed to the lamp box 31 of the surface-emitting light source 30 so as to cover the opening. Thus, a backlight unit was manufactured.

  Next, the light emitting element 32 included in the lamp box 31 is turned on, and the front luminance in the backlight unit is measured using a luminance measuring device (“RISA-COLOR / ONE” manufactured by HI-LAND), and as follows. evaluated.

：: 2200 cd / m ² or more and 2500 cd / m ² or less.
○: less than 2000cd / ^{m 2} more than 2200cd / ^{m 2.}
×: less than 1,800 cd / ^{m 2} or more 2000 cd / ^{m 2.}

5) Unevenness of Brightness of Backlight Unit First, the anisotropic diffusion plates 10 of the examples and comparative examples are fixed to the lamp box 31 of the surface light source 30 so as to cover the opening. Thus, a backlight unit was manufactured.

  Next, the light emitting element 32 included in the lamp box 31 was turned on, and the luminance unevenness in the backlight unit was evaluated as follows.

◎: In the anisotropic diffusion plate 10, the LED was not dotted,
The emitted light is emitted uniformly.
：: In the anisotropic diffusion plate 10, the spotting of the LED slightly occurred,
It can be said that the emitted light is emitted almost uniformly.
×: In the anisotropic diffusion plate 10, the dottedness of the LED clearly occurs,
It cannot be said that the emitted light is emitted uniformly.

  Table 1 below shows the evaluation results of the anisotropic diffusion plate 10 of each of the examples and the comparative examples obtained as described above.

  As shown in Table 1, in the anisotropic diffusion plate 10 in each example, since the front luminance is high and the luminance non-uniformity does not occur, it is possible to suppress or prevent the spotting that the LED can be seen through. It has been found that the diffused light can be suppressed or prevented from being wasted.

  On the other hand, in the anisotropic diffusion plate 10 in each comparative example, the result that the front luminance improvement and the luminance unevenness suppression cannot be achieved at the same time, that is, the suppression of the dotiness that the LED can be seen through, and the diffused light The results showed that it was not compatible with the suppression of waste.

DESCRIPTION OF SYMBOLS 10 Anisotropic diffusion plate 20 Liquid crystal panel 21 Liquid crystal cell 22 Polarizing plate 30 Surface light source 31 Lamp box 32 Light emitting element 40 Incident surface 50 Output surface 51 Convex part 52 Total reflection light area 53 Transmitted light area 55 Plane 56 Spindle 57 Flat Part 100 liquid crystal display device 150 display panel 200 automobile 201 dashboard H driver

Claims (14)

When emitting the incident light incident from the incident surface as the outgoing light diffused from the outgoing surface, an anisotropic diffusion plate having a different light diffusing ability in the left-right direction and the light diffusing ability in the front-rear direction,
When the incident light having a size of 3 mmΦ is perpendicularly incident on the incident surface from the light source, a half-value angle in the front-back luminous intensity distribution of the outgoing light and a half-value angle in the left-right luminous intensity distribution of the outgoing light Has a region exhibiting anisotropy whose half-value angle difference is 3 ° or more and less than 15 °, and
An anisotropic diffusion plate, wherein a total light transmittance of the outgoing light with respect to the incident light having a size of 3 mmΦ is 70% or more and 99% or less.   The exit surface has, in plan view, a plurality of spindle-shaped close-packed spindles, each of which has a convex shape or a concave shape formed by overlapping edges of adjacent spindles. The anisotropic diffusion plate according to claim 1, wherein the diffusion plate is provided. The anisotropic diffusion plate is made of a transparent resin having a refractive index n,
When the incident light is perpendicularly incident on the incident surface, at an arbitrary position of the spindle, the angle θ between the normal to the arbitrary position and the incident light is 0 ≦ θ <Sin ⁻ 3. The anisotropic diffusion plate according to claim 2, wherein a relationship of ¹ (1 / n) is satisfied. 4.   The anisotropic diffusion plate according to claim 3, wherein the transparent resin is mainly composed of a polycarbonate resin.   When the incident light is perpendicularly incident on the incident surface in an area of 1 cm long × 1 cm wide in plan view, the area where the incident angle = 0 is satisfied is 1% or less. The anisotropic diffusion plate according to claim 1.   When the incident light is perpendicularly incident on the incident surface in a region of 1 cm long × 1 cm wide in plan view, the exit surface has a region satisfying the relationship of incident angle> critical angle of 18% or less. The anisotropic diffusion plate according to any one of claims 1 to 5.   When the incident light is perpendicularly incident on the incident surface in an area of 1 cm × 1 cm in plan view, the exit surface has an incident angle distribution in the front-rear direction of the incident light, and an incident angle distribution of the incident light. The anisotropic diffusion plate according to any one of claims 1 to 6, wherein an incident angle distribution in a left-right direction is different.   The anisotropic diffusion plate according to claim 1, wherein the emission surface has a surface roughness Ra of 0.1 μm or less.   The anisotropic diffusion plate according to any one of claims 1 to 8, wherein a low-refractive-index layer lower than the refractive index of the anisotropic diffusion plate is formed on the incident surface.   The anisotropic diffusion plate according to any one of claims 1 to 8, wherein a dielectric multilayer film is formed on the incident surface.   The anisotropic diffusion plate according to any one of claims 1 to 10, wherein the anisotropic diffusion plate has an optical retardation of 200 nm or less. An anisotropic diffusion plate according to any one of claims 1 to 11, and a light-emitting substrate disposed to face the anisotropic diffusion plate,
The backlight unit according to claim 1, wherein the light-emitting substrate includes a base substrate and a plurality of light-emitting diodes arranged in a grid on a surface of the base substrate facing the anisotropic diffusion plate.   13. A liquid crystal display device comprising: the backlight unit according to claim 12; and a liquid crystal panel facing the anisotropic diffusion plate of the backlight unit.   An electronic apparatus comprising the liquid crystal display device according to claim 13.

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