JPWO2016093272A1 - Liquid crystal display element, liquid crystal display device, and liquid crystal display element design method - Google Patents

Abstract

Provided is a liquid crystal display element capable of improving the scratch resistance on the back surface of the liquid crystal display element, making interference fringes invisible, and suppressing luminance unevenness. According to one aspect of the present invention, the first polarizing plate 40, the second polarizing plate 50, the liquid crystal cell 60 disposed between the first polarizing plate 40 and the second polarizing plate 50, A first optical film 41 having a first concavo-convex surface 41 </ b> A that forms a surface 30 </ b> A of the liquid crystal display element 30, and the first optical film 41. A second optical film 51 including a first polarizer 42 disposed on the liquid crystal cell 60 side, and a second polarizing plate 50 having a second uneven surface 51A forming the back surface 30B of the liquid crystal display element 30; The second polarizer 52 disposed on the liquid crystal cell 60 side of the second optical film 51, the first uneven surface 41A and the second uneven surface 51A have the same shape, and the first uneven surface The unevenness constituting 41A and the unevenness constituting the second uneven surface 51A The first concavo-convex surface 51A has an average inclination angle of θa [°], the average interval between the local peaks of the second concavo-convex surface 51A is S [μm], and the second concavo-convex surface 51A. The following formula (1) is satisfied, where N is the refractive index of the concavo-convex structure and the average distance between the first concavo-convex surface 41A and the second concavo-convex surface 51A is D [μm]. A liquid crystal display element 30 is provided. D ≦ S / (2 × tan (θa−sin−1 ((sin θa) / N))) (1)

Description

  The present invention relates to a liquid crystal display element, a liquid crystal display device, and a method for designing a liquid crystal display element.

  A liquid crystal display element used in a liquid crystal display device mainly includes a polarizing plate located on the viewer side, a polarizing plate located on the surface light source device side, and a liquid crystal cell disposed between these polarizing plates. .

  An optical film may be provided on the surface of the liquid crystal display element (the surface on the observer side) for the purpose of suppressing reflection of the observer and the background of the observer or for the purpose of improving scratch resistance (patent) Reference 1). Usually, this optical film is arrange | positioned on the surface of the polarizing plate located in the observer side.

  On the other hand, since the polarizing plate located on the surface light source device side of the liquid crystal display element may be rubbed in contact with the surface light source device, in recent years, not only the surface on the observer side of the liquid crystal display element but also the scratch resistance. In order to improve the above, it has been studied to dispose an optical film on the back surface of the liquid crystal display element (surface on the surface light source device side).

JP 2011-215515 A

In the case where optical films are arranged on both the front and back surfaces of the liquid crystal display element, it is preferable to use the same optical film from the viewpoint of reducing costs. Here, when an optical film having a concavo-convex surface is used as the optical film, the image light can be diffused. Therefore, even when the interference fringes due to the surface light source device are generated, the interference fringes are reduced. Can be invisible.
For this reason, disposing an optical film having an uneven surface on both the front surface and the back surface of the liquid crystal display element has been studied.

  However, when an optical film having an uneven surface with the same shape is arranged on both the front surface and the back surface of the liquid crystal display element, the position of the unevenness is such that the centers of the protrusions on the uneven surface coincide with each other in the thickness direction of the liquid crystal display element. It is difficult to match. That is, there is a high possibility that the position of the center of the convex portion on the concave and convex surface of the optical film on the back surface side of the liquid crystal display element is shifted from the center of the convex portion on the concave and convex surface of the optical film on the front surface side of the liquid crystal display element.

  Here, when an optical film having an uneven surface with the same shape is arranged on both the front and back surfaces of the liquid crystal display element, the light diffusion characteristics are as follows: the unevenness on the uneven surface of the optical film on the surface side of the liquid crystal display element and the liquid crystal display It changes depending on the positional relationship with the unevenness on the uneven surface of the optical film on the back side of the element. For this reason, depending on this positional relationship, continuous diffusion characteristics cannot be obtained, and luminance unevenness may occur.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a liquid crystal display element and a liquid crystal display device that can improve the scratch resistance on the back surface of the liquid crystal display element, can make interference fringes invisible, and can suppress uneven brightness. Moreover, it aims at providing the design method of the liquid crystal display element which can obtain such a liquid crystal display element.

According to one aspect of the present invention, a liquid crystal comprising a first polarizing plate, a second polarizing plate, and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate. A display element, wherein the first polarizing plate is disposed closer to a liquid crystal cell than a first optical film having a first uneven surface forming a surface of the liquid crystal display element. A second optical film having a second concavo-convex surface forming a back surface of the liquid crystal display element, and a liquid crystal cell side from the second optical film. A second polarizer disposed, and the first concavo-convex surface and the second concavo-convex surface have the same shape, and the concavo-convex constituting the first concavo-convex surface and the second concavo-convex surface are configured. The concave and convex portions having the same refractive index, the average inclination angle of the second concave and convex surface being θa [°], and the second The average distance between the local peaks of the convex surface is S [μm], the refractive index of the unevenness constituting the second uneven surface is N, and the average separation distance between the first uneven surface and the second uneven surface When D is [μm], a liquid crystal display element satisfying the following formula (1) is provided.
D ≦ S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (1)

The liquid crystal display element preferably further satisfies the following formula (2) when the maximum inclination angle of the second uneven surface is θmax [°].
D ≦ S / (2 × tan (θmax−sin ⁻¹ ((sin θa) / N))) (2)

  According to another aspect of the present invention, there is provided a surface light source device and the liquid crystal display element disposed on the viewer side with respect to the surface light source device, and the surface of the liquid crystal display device is positioned on the viewer side. In addition, a liquid crystal display device is provided in which the back surface of the liquid crystal display element is positioned on the surface light source device side.

According to another aspect of the present invention, a liquid crystal comprising a first polarizing plate, a second polarizing plate, and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate. A method for designing a display element, wherein the first polarizing plate has a first optical film having a first concavo-convex surface forming a surface of the liquid crystal display element, and is closer to the liquid crystal cell than the first optical film. A second optical film having a second concavo-convex surface that forms the back surface of the liquid crystal display element, and a liquid crystal that is more liquid crystal than the second optical film. A second polarizer disposed on the cell side, the unevenness constituting the first uneven surface and the unevenness forming the second uneven surface have the same refractive index, and the first unevenness The surface and the second uneven surface have the same shape, and the average inclination angle of the second uneven surface is θa [°], The average interval between the local peaks of the second irregular surface is S [μm], the refractive index of the irregularities constituting the second irregular surface is N, and the first irregular surface and the second irregular surface. A design method of a liquid crystal display element is provided, wherein the liquid crystal display element is designed so that the average separation distance D satisfies the following formula (1) where the average separation distance is D [μm]: The
D ≦ S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (1)

In the design method of the liquid crystal display element, it is preferable that the average separation distance D further satisfies the following formula (2) when the maximum inclination angle of the second uneven surface is θmax [°].
D ≦ S / (2 × tan (θmax−sin ⁻¹ ((sin θa) / N))) (2)

  According to the liquid crystal display element of one embodiment of the present invention and the liquid crystal display device of another embodiment, since the liquid crystal display element satisfies the above formula (1), the scratch resistance on the back surface of the liquid crystal display element is improved. Interference fringes can be made invisible and luminance unevenness can be suppressed. In addition, according to the method for designing a liquid crystal display element according to another aspect of the present invention, the liquid crystal display element is designed so that the average separation distance D satisfies the above formula (1). Thus, a liquid crystal display element can be obtained in which interference fringes can be made invisible and luminance unevenness can be suppressed.

1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment. It is a schematic diagram for demonstrating the calculation method of the condensing distance in an uneven surface. It is a ray tracing figure in case the average separation distance between uneven | corrugated surfaces is shorter than a condensing distance. It is a ray tracing figure in case the average separation distance between uneven | corrugated surfaces is longer than a condensing distance. It is a graph which shows the diffusion characteristic of the optical film which concerns on Examples 1-4. It is a graph which shows the diffusion characteristic of the optical film which concerns on Comparative Examples 1-3.

  Hereinafter, a liquid crystal display element according to an embodiment and a design method of the liquid crystal display element will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to the present embodiment, FIG. 2 is a schematic diagram for explaining a method of calculating a light collection distance on an uneven surface, and FIG. 3 is an average separation distance between the uneven surfaces. FIG. 4 is a ray tracing diagram in the case where the average separation distance between the concave and convex surfaces is longer than the condensing distance. In the present specification, terms such as “film”, “sheet”, and “plate” are not distinguished from each other only based on the difference in names. Therefore, for example, “film” is a concept including a member that can also be called a sheet or a plate. As a specific example, the “optical film” includes members called “optical sheet”, “optical plate”, and the like. In the present specification, the “weight average molecular weight” is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting to polystyrene by a conventionally known gel permeation chromatography (GPC) method.

[Liquid Crystal Display]
As shown in FIG. 1, the liquid crystal display device 10 according to the present embodiment includes a surface light source device 20 and a liquid crystal display element 30 disposed closer to the viewer than the surface light source device 20.

<<< Surface light source device >>>
The surface light source device 20 illuminates the liquid crystal display element 30 in a planar shape from the back side. The surface light source device 20 includes, for example, a light source 21 and a light guide plate 22 disposed on the side of the light source 21. As the light source 21. A fluorescent lamp such as a linear cold cathode tube, a point light emitting diode (LED), an incandescent lamp, or the like can be used.

  The light guide plate 22 includes a light incident surface 22A located on the light source 21 side and a light outgoing surface 22B located on the liquid crystal display element 30 side. The light emitted from the light source 21 enters from the light incident surface 22A of the light guide plate 22 and is emitted from the light output surface 22B of the light guide plate 22. The surface light source device 20 includes, in addition to the light source 21 and the light guide plate 22, a prism lens sheet disposed on the viewer side from the light guide plate 22, a reflection plate disposed on the side opposite to the light output side of the light guide plate 22, and the like. May be.

<<< Liquid Crystal Display Element >>>
As shown in FIG. 1, the liquid crystal display element 30 is disposed between the first polarizing plate 40, the second polarizing plate 50, and the first polarizing plate 40 and the second polarizing plate 50. A liquid crystal cell 60; an adhesive layer 71 disposed between the first polarizing plate 40 and the liquid crystal cell 60; and an adhesive layer 72 disposed between the second polarizing plate 50 and the liquid crystal cell 60. ing. The first polarizing plate 40 is located closer to the viewer than the liquid crystal cell 60, and the second polarizing plate 50 is located closer to the surface light source device 20 than the liquid crystal cell 60. In the present embodiment, the adhesive layers 71 and 72 are provided, but the adhesive layers 72 and 73 may not be provided.

<< Liquid Crystal Cell >>
A known liquid crystal cell can be used as the liquid crystal cell 60. The liquid crystal cell 60 is composed of, for example, a liquid crystal layer, an alignment film, an electrode layer, a color filter and the like between two glass substrates, and the liquid crystal molecules in the liquid crystal layer are determined depending on whether or not voltage is applied to the electrode layer. The orientation direction changes. Thus, for example, when the first polarizing plate 40 and the second polarizing plate 50 are arranged in crossed Nicols, the linearly polarized light component in a specific direction transmitted through the second polarizing plate 50 is applied with voltage. When passing through the liquid crystal cell 60 made, the polarization direction is rotated by 90 °, so that the first polarizing plate 40 is transmitted, but when passing through the liquid crystal cell 60 to which no voltage is applied, the polarization direction is changed. Therefore, the first polarizing plate 40 is not transmitted.

<< first polarizing plate and second polarizing plate >>
As shown in FIG. 1, the first polarizing plate 40 includes a first optical film 41, a first polarizer 42 disposed closer to the liquid crystal cell 60 than the first optical film 41, and a first polarized light. And a protective film 43 that is disposed closer to the liquid crystal cell 60 than the polarizer 42 and protects the first polarizer 42. As shown in FIG. 1, the second polarizing plate 50 includes a second optical film 51, a second polarizer 52 disposed on the liquid crystal cell 60 side from the second optical film 51, and a second polarizer 52. The protective film 53 is disposed on the liquid crystal cell 60 side of the polarizer 52 and protects the second polarizer 52. The protective films 43 and 53 may be retardation films. In the present embodiment, the first polarizing plate 40 includes the protective film 43 and the second polarizing plate 50 includes the protective film 53, but the protective films 43 and 53 may not be provided.

<First optical film and second optical film>
The first optical film 41 includes a first uneven surface 41 </ b> A that forms the surface 30 </ b> A of the liquid crystal display element 30. The second optical film 51 includes a second uneven surface 51 </ b> A that forms the back surface 30 </ b> B of the liquid crystal display element 30. In the liquid crystal display device 10, the front surface 30 </ b> A of the liquid crystal display element 30 is a surface on the viewer side of the liquid crystal display element 30, and the back surface 30 </ b> B of the liquid crystal display element 30 is in the liquid crystal display device 10. It is a surface on the surface light source device 20 side.

The first uneven surface 41A of the first optical film 41 and the second uneven surface 51A of the second optical film 51 have the same shape. In the present specification, “the first uneven surface of the first optical film and the second uneven surface of the second optical film have the same shape” means that at least the average inclination angle of the first uneven surface is θa. ₁ [°], and the average inclination angle of the second uneven surface is θa ₂ [°], | θa ₂ −θa ₁ | / θa ₂ is in the range of 0 to 0.1 and When the average interval between the local peaks of the first uneven surface is S ₁ [μm] and the average interval between the local peaks of the second uneven surface is S ₂ [μm], | S ₂ −S ₁ | / S ₂ is When the arithmetic average roughness of the first uneven surface is Ra ₁ [μm] and the arithmetic average roughness of the second uneven surface is Ra ₂ [μm] It means that | Ra ₂ −Ra ₁ | / Ra ₂ is in the range of 0 or more and 0.1 or less.

The definition of the average inclination angle θa (θa ₁ , θa ₂ ) shall be in accordance with the surface roughness measuring instrument: SE-3400 / Kosaka Laboratory Co., Ltd. instruction manual (revised 1995.07.20). Specifically, θa is represented by the following formula.
θa = tan ⁻¹ Δa
In the formula, Δa represents the slope as an aspect ratio, and is a value obtained by dividing the total sum of the differences between the minimum and maximum portions of each unevenness (corresponding to the height of each convex portion) by the reference length.

The definitions of the average interval S (S ₁ , S ₂ ) of the local summit and the arithmetic average roughness Ra (Ra ₁ , Ra ₂ ) shall conform to JIS B0601-1994.

The average inclination angle θa, the average distance S between the local peaks, and the arithmetic average roughness Ra are average values when measured 20 times. The average inclination angle θa, the average interval S between the local peaks, and the arithmetic average roughness Ra are measured using the surface roughness measuring instrument (model number: SE-3400 / manufactured by Kosaka Laboratory) under the following measurement conditions. Measurements can be made.
1) Stylus of surface roughness detector (trade name SE2555N (2μ standard) manufactured by Kosaka Laboratory Ltd.)
・ Tip radius of curvature 2μm, apex angle 90 degrees, material diamond 2) Measurement conditions of surface roughness measuring instrument ・ Reference length (cutoff value λc of roughness curve): 0.8 mm
Evaluation length (reference length (cutoff value λc) × 5): 4.0 mm
・ Feeding speed of stylus: 0.5mm / s
・ Preliminary length: (cutoff value λc) × 2
・ Vertical magnification: 2000 times ・ Horizontal magnification: 10 times

  The average inclination angle θa of the first concavo-convex surface 41A and the second concavo-convex surface 51A is preferably 0.1 ° or more and 5.0 ° or less from the viewpoint of suppressing reflection while suppressing reflection. Moreover, it is preferable that the average space | interval S of the local peak of the 1st uneven surface 41A and the 2nd uneven surface 51A is 10 micrometers or more and 200 micrometers or less from a viewpoint of suppressing a brightness nonuniformity more. The arithmetic average roughness Ra of the first uneven surface 41A and the second uneven surface 51A is preferably 0.02 μm or more and 0.5 μm or less from the viewpoint of making the interference fringes more invisible.

  The unevenness that forms the first uneven surface 41A and the unevenness that forms the second uneven surface 51A have the same refractive index. In the present specification, “the unevenness constituting the first uneven surface and the unevenness forming the second uneven surface have the same refractive index” means that the refractive index of the unevenness constituting the first uneven surface and the second It means that the absolute value of the difference from the refractive index of the unevenness constituting the uneven surface is in the range of 0 or more and 0.02 or less.

  The refractive index of the concavo-convex constituting the first concavo-convex surface 41A and the concavo-convex constituting the second concavo-convex surface 51A is the same as that of the first concavo-convex layer 45 or the second concavo-convex surface 51A having the first concavo-convex surface 41A described later. After forming the 2nd uneven | corrugated layer 55 which has, it can measure with an Abbe refractometer (NAR-4T by Atago Co., Ltd.) and an ellipsometer.

  The refractive index of the unevenness constituting the first uneven surface 41A and the second uneven surface 51A is preferably 1.40 or more and 1.60 or less from the viewpoint of making interference fringes less likely to occur.

Since the first optical film 41 and the second optical film 51 are disposed via the liquid crystal cell 60 or the like, they are separated from each other. The average inclination angle of the second uneven surface 51A is θa [°], the average interval between the local peaks of the second uneven surface 51A is S [μm], and the refractive index of the unevenness constituting the second uneven surface 51A is N, and when the average distance between the first uneven surface 41A of the first optical film 41 and the second uneven surface 51A of the second optical film 51 is D [μm], the liquid crystal display element 30 is The following formula (1) is satisfied.
D ≦ S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (1)

  Since the second uneven surface 51A acts as a lens, the light emitted from the light guide plate 22 of the surface light source device 20 and incident on the second optical film 51 is refracted by the second uneven surface 51A, and at a certain point Focus and then diffuse. In the above formula (1), the average distance D between the first uneven surface 41 </ b> A of the first optical film 41 and the second uneven surface 51 </ b> A of the second optical film 51 is the second of the second optical film 51. It is below the condensing distance in the uneven surface 51A. In this specification, “the average separation distance between the first uneven surface of the first optical film and the second uneven surface of the second optical film” means the first unevenness in the thickness direction of the liquid crystal display element. It means the average of the distance from the bottom of the concave / convex concave portion constituting the surface to the bottom of the concave / convex concave portion constituting the second concave / convex surface.

The above formula (1) is derived as follows.
FIG. 2 is a schematic diagram schematically showing the concavo-convex shape in order to make it easy to explain the method of calculating the light collection distance on the concavo-convex surface. First, assume uneven portions 81 and 82 having uneven surfaces 81A and 82A spaced apart from each other as shown in FIG. The concave and convex portions 81 and 82 are arranged such that the concave and convex surfaces 81A and 82A are outside each other. The average inclination angle of the concavo-convex surface 82A located on the light incident side is θa, the average interval between the local peaks of the concavo-convex surface 82A is S, the light is incident on the concavo-convex surface 82A, and the refraction angle of the light when refracted is ψ , N is the refractive index of the concavo-convex portion 82, F is the condensing distance, and D is the average separation distance between the concavo-convex surfaces. The average interval S between the local peaks of the concavo-convex surface 82A can be regarded as the average width of the convex portions.
In FIG. 2, it seems that the light L is incident on the valley where the uneven portion 82 does not exist, but this is for easy illustration of the behavior of the light L condensing. The incident position is slightly shifted from the valley.

First, the following formula (3) is established from Snell's law. When the following formula (3) is modified, the following formula (4) is obtained.
sinθa / sinψ = N (3)
ψ = sin ⁻¹ ((sin θa) / N) (4)
On the other hand, in FIG. 2, the following formula (5) is established.
φ = θa−ψ (5)
Therefore, when the above equation (4) is substituted into ψ in the above equation (5), the following equation (6) is obtained.
φ = θa−sin ⁻¹ ((sin θa) / N) (6)

On the other hand, the condensing distance F is represented by the following formula (7) from FIG.
F = S / (2 × tanφ) (7)
Substituting the above equation (6) into φ in the above (7), the following equation (8) is obtained.
F = S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (8)
Therefore, when the average separation distance D between the concavo-convex surfaces 81A and 82A is equal to or smaller than the condensing distance F, the above equation (1) is obtained.

  The average separation distance D between the first concavo-convex surface 41A and the second concavo-convex surface 51A is preferably 200 μm or more and 10,000 μm or less from the viewpoint of reducing the weight and thickness of the liquid crystal display device and manufacturing yield.

The inventor surprisingly found that the first uneven surface and the second uneven surface have the same shape, and the unevenness constituting the first uneven surface and the unevenness constituting the second uneven surface are the same refraction. The first optical film having the first uneven surface and the second unevenness so that the average separation distance D between the first uneven surface and the second uneven surface satisfies the above formula (1). When the second optical film having a surface is disposed, continuous diffusion characteristics can be obtained regardless of the positional relationship between the unevenness on the first uneven surface and the unevenness on the second uneven surface. I found out.

  Specifically, when the two concavo-convex surfaces have the same shape and the concavo-convex portions constituting the concavo-convex surface have the same refractive index, the average separation distance between the concavo-convex surfaces is equal to or less than the light collection distance, When the diffusion state of the light emitted from the concavo-convex surface on the emission side was simulated when exceeding the optical distance, the average separation distance D between the concavo-convex surface 91 and the concavo-convex surface 92 is the condensing distance as shown in FIG. When F exceeds F, that is, when the above formula (1) is not satisfied, depending on the positional relationship between the unevenness on the uneven surface 91 and the unevenness on the uneven surface 92, light may be emitted separately from the uneven surface 91. is there. It is considered that due to the separately emitted light, continuous diffusion characteristics cannot be obtained and luminance unevenness occurs. On the other hand, as shown in FIGS. 3A and 3B, when the average separation distance D between the uneven surface 91 and the uneven surface 92 is equal to or less than the light collection distance F, the unevenness and the unevenness on the uneven surface 91 are obtained. Regardless of the positional relationship between the unevenness on the surface 92, the light emitted from the uneven surface 91 is emitted without being divided. Therefore, when the average separation distance between the first uneven surface and the second uneven surface is equal to or smaller than the light collection distance, that is, when the above formula (1) is satisfied, the unevenness and the second unevenness on the first uneven surface. Regardless of the positional relationship between the projections and depressions on the surface, the light is not separated and emitted from the first projections and depressions of the first optical film, so that it is considered that continuous diffusion characteristics can be obtained.

When the maximum inclination angle of the second uneven surface 51A is θmax [°], the liquid crystal display element 30 preferably further satisfies the following formula (2).
D ≦ S / (2 × tan (θmax−sin ⁻¹ ((sin θa) / N))) (2)

  Since the average inclination angle θa is the average inclination angle of the uneven surface, there are unevenness having an inclination angle smaller than θa and unevenness having an inclination angle larger than θa in the uneven surface. In the unevenness having an inclination angle larger than θa, the condensing distance is shorter than the condensing distance when the inclination angle is θa. For this reason, when the average inclination angle θa is used, most of the unevenness has a condensing distance that is equal to or greater than the average separation distance between the first uneven surface and the second uneven surface. It is also assumed that there is one having a light collection distance shorter than the average separation distance between the uneven surface and the second uneven surface. On the other hand, since θmax is the maximum inclination angle of the uneven surface, the condensing distance is the shortest. Therefore, by satisfying the above formula (2), the condensing distance of all the unevenness on the second uneven surface 51 </ b> A is such that the first uneven surface 41 </ b> A of the first optical film 41 and the second unevenness of the second optical film 51. There is no possibility of becoming shorter than the average distance D from the two uneven surfaces 51A. Therefore, luminance unevenness can be further suppressed.

  θmax is obtained, for example, by measuring the surface shape of the uneven surface and analyzing the data obtained there. Examples of the apparatus for measuring the surface shape include a contact-type surface roughness meter and a non-contact-type surface roughness meter (for example, an interference microscope, a confocal microscope, an atomic force microscope, etc.). Among these, an interference microscope is preferable from the viewpoint of simplicity of measurement. Examples of such an interference microscope include “NewView” series manufactured by Zygo.

  The maximum inclination angle θmax of the first concavo-convex surface 41A and the second concavo-convex surface 51A is preferably 0.5 ° or more and 15 ° or less from the viewpoint of suppressing reflection while suppressing reflection.

  The total haze value of the first optical film 41 and the second optical film 51 is preferably 0% or more and 40% or less. Further, the internal haze value of the first optical film 41 and the second optical film 51 is preferably 0% or more and 30% or less. The total haze value and the internal haze value are values when measured as the entire first optical film or the entire second optical film. For example, in the present embodiment, since no functional layer such as a low refractive index layer is provided on the uneven layers 45 and 55 as described later, the total haze value and the internal haze value of the first optical film 41 are It is a value measured using the first optical film 41 composed of the light transmissive substrate 44 and the uneven layer 45. Further, for example, when a functional layer such as a low refractive index layer is provided on the concavo-convex layer, the total haze value and internal haze value of the optical film are determined from the light-transmitting substrate, the concavo-convex layer, and the functional layer. It is the value measured using the optical film.

  The total haze value and the internal haze value can be measured by a method based on JISK7136 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory). Specifically, using a haze meter, the total haze value of the first optical film or the second optical film is measured according to JISK7136. Moreover, an internal haze value is calculated | required as follows. On the surface of the concavo-convex layer of the first optical film, a resin whose refractive index is the same as that of the resin forming the concavo-convex surface or whose refractive index difference with this resin is 0.02 or less is a dry film thickness of 8 μm with a wire bar. That is, it was applied so that the uneven shape of the uneven surface was completely eliminated and the surface could be flattened, dried at 70 ° C. for 1 minute, and then irradiated with 100 mJ / cm 2 of ultraviolet light to the applied resin, Harden. Thereby, the unevenness which exists in the surface of the 1st optical film is crushed, and the film used as the flat surface is obtained. However, when the leveling agent or the like is contained in the composition for forming the uneven layer having the uneven shape, the resin applied to the surface of the uneven layer is likely to be repelled and difficult to wet. The surface was saponified (soaked in 2 mol / L NaOH (or KOH) solution at 55 ° C. for 3 minutes, washed with water, completely removed with Kimwipe (registered trademark) etc., and then in a 50 ° C. oven for 1 minute. It is preferable to perform hydrophilic treatment by drying. And in this state, an internal haze value is calculated | required by measuring a haze value according to JISK7136 using a haze meter (HM-150, Murakami Color Research Laboratory make). This internal haze does not take into account the irregular shape of the surface of the first optical film or antiglare film.

  The surface haze value of the first optical film 41 and the second optical film 51 is preferably 0% or more and 20% or less. The surface haze value is caused only by the uneven shape of the surface in the first optical film or the second optical film. By subtracting the internal haze value from the overall haze value, the first optical film or the second optical film is obtained. The surface haze value resulting from only the irregular shape of the surface in the optical film is required.

  The first optical film 41 includes a light transmissive substrate 44 and a concavo-convex layer 45 provided on the viewer side of the light transmissive substrate 44 (on the opposite side to the liquid crystal cell 60 side) and having a concavo-convex surface. I have. The second optical film 51 is provided on the light transmissive substrate 54 and the concavo-convex layer 55 provided on the surface light source device 20 side of the light transmissive substrate 54 (on the side opposite to the liquid crystal cell 60 side) and having a concavo-convex surface. And.

In the present embodiment, since the functional layer such as the low refractive index layer is not provided on the uneven layers 45 and 55, the uneven surface of the uneven layer 45 becomes the first uneven surface 41 </ b> A of the first optical film 41. The uneven surface of the uneven layer 55 is the second uneven surface 51 A of the second optical film 51.
The “functional layer” is a layer intended to exhibit some function in the optical film. Specifically, for example, it exhibits a function such as antireflection property, antistatic property, or antifouling property. A layer for. The functional layer is not limited to a single layer but may be a laminate of two or more layers.

((Light transmissive substrate))
The light-transmitting base materials 44 and 54 are not particularly limited as long as they have light-transmitting properties. For example, cellulose acylate base materials, cycloolefin polymer base materials, polycarbonate base materials, acrylate polymer base materials, polyester base materials. Or a glass substrate.

  As a cellulose acylate base material, a cellulose triacetate base material and a cellulose diacetate base material are mentioned, for example. As a cycloolefin polymer base material, the base material which consists of polymers, such as a norbornene-type monomer and a monocyclic cycloolefin monomer, is mentioned, for example.

  Examples of the polycarbonate substrate include aromatic polycarbonate substrates based on bisphenols (bisphenol A and the like), aliphatic polycarbonate substrates such as diethylene glycol bisallyl carbonate, and the like.

  Examples of the acrylate polymer base material include a poly (meth) methyl acrylate base material, a poly (meth) ethyl acrylate base material, and a (meth) methyl acrylate- (meth) butyl acrylate copolymer base material. Can be mentioned.

  Examples of the polyester base material include base materials containing at least one of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as constituent components.

  Examples of the glass substrate include glass substrates such as soda lime silica glass, borosilicate glass, and alkali-free glass.

  Among these, a cellulose acylate base material is preferable because of excellent retardation and easy adhesion with a polarizer, and among the cellulose acylate base materials, a triacetyl cellulose base material (TAC base material) is preferable. A triacetyl cellulose base material is a light-transmitting base material capable of setting an average light transmittance to 50% or more in a visible light region of 380 to 780 nm. The average light transmittance of the triacetyl cellulose base material is preferably 70% or more, and more preferably 85% or more.

  In addition, as a triacetyl cellulose base material, in addition to pure triacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like may be used in combination with components other than acetic acid as a fatty acid forming an ester with cellulose. Good. Further, these triacetylcelluloses may be added with other additives such as other cellulose lower fatty acid esters such as diacetylcellulose, or plasticizers, ultraviolet absorbers, and lubricants as necessary.

  A cycloolefin polymer substrate is preferred from the standpoint of retardation and heat resistance, and a polyester substrate is preferred from the standpoint of mechanical properties and heat resistance.

  The thickness of the light-transmitting substrates 44 and 54 is not particularly limited, but can be 5 μm or more and 1000 μm or less. The lower limit of the thickness of the light-transmitting substrates 44 and 54 is 15 μm or more from the viewpoint of handling properties. Is preferably 25 μm or more. The upper limit of the thickness of the light-transmitting substrates 44 and 54 is preferably 80 μm or less from the viewpoint of thinning.

((Uneven layer))
The uneven layers 45 and 55 are layers having an uneven surface. The concavo-convex layer 45 is a layer that exhibits antiglare properties and light diffusibility, and the concavo-convex layer 55 is a layer that exhibits light diffusibility, but the concavo-convex layers 45 and 55 exhibit other functions in addition to these functions. It may be a layer. Specifically, the concavo-convex layer 45 exhibits antiglare properties and light diffusion properties, and may be a layer that exhibits functions such as hard coat properties, antireflection properties, antistatic properties, and antifouling properties. Good. Similarly, the concavo-convex layer 55 may be a layer that exhibits light diffusing characteristics and also exhibits functions such as hard coat properties, antireflection properties, antistatic properties, and antifouling properties.

  When the concavo-convex layers 45 and 55 are layers exhibiting hard coat properties in addition to the antiglare property, the concavo-convex layers 45 and 55 are subjected to a pencil hardness test (4. JISK5600-5-4 (1999)). It has a hardness of “H” or higher at 9N load).

  As a method for forming the uneven surface of the uneven layer 45 (first uneven surface 41A) and the uneven surface of the uneven layer 55 (second uneven surface 51A), for example, (A) The uneven surface is formed by a transfer method using a mold. (B) A method of forming an uneven surface using a composition for an uneven layer containing a curable resin precursor that becomes a binder resin after curing and fine particles, and (C) roughening the surface of the uneven layer by sandblasting. The method of forming an uneven surface by (D) or the method of forming an uneven surface by providing unevenness on the surface of an uneven layer with an embossing roll.

  The uneven layers 45 and 55 include, for example, a cured product of a curable resin precursor, and are formed by the method (A).

(Curing product of curable resin precursor)
The “curable resin precursor” in the present specification means a resin precursor in which the resin precursor has ionizing radiation curability and thermosetting, and becomes a resin by ionizing radiation curing or thermosetting. The resin may contain a solvent-drying resin in addition to the cured product of the curable resin precursor. The ionizing radiation curable resin precursor having ionizing radiation curability has at least one ionizing radiation polymerizable functional group.
In the present specification, the “ionizing radiation polymerizable functional group” is a functional group capable of undergoing a polymerization reaction upon irradiation with ionizing radiation. Examples of the ionizing radiation polymerizable functional group include ethylenic double bonds such as a (meth) acryloyl group, a vinyl group, and an allyl group. In the present specification, “(meth) acryloyl group” means both “acryloyl group” and “methacryloyl group”. The ionizing radiation irradiated when curing the ionizing radiation curable resin precursor means an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or cross-linking molecules. UV) or electron beam (EB) is used, but other charged particle beams such as electromagnetic waves such as X-rays and γ-rays, α-rays and ion beams can also be used. The thermosetting resin precursor having thermosetting properties has at least one thermopolymerizable functional group.

  Examples of the ionizing radiation curable resin precursor include ionizing radiation polymerizable monomers, ionizing radiation polymerizable oligomers, and ionizing radiation polymerizable prepolymers, which can be appropriately adjusted and used. As the ionizing radiation curable resin precursor, a combination of an ionizing radiation polymerizable monomer and an ionizing radiation polymerizable oligomer or an ionizing radiation polymerizable prepolymer is preferable.

-Ionizing radiation polymerizable monomer The ionizing radiation polymerizable monomer has a weight average molecular weight of less than 1000. As the ionizing radiation polymerizable monomer, a polyfunctional monomer having two or more ionizing radiation polymerizable functional groups (that is, bifunctional) is preferable.

  Examples of the bifunctional or higher monomer include trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and pentaerythritol tri (meth). Acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditri Methylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate, Lapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanuric acid di (meth) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, diglycerin tetra ( (Meth) acrylate, adamantyl di (meth) acrylate, isoboronyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and these are PO, EO And the like modified.

  Among these, from the viewpoint of obtaining a concavo-convex layer having high hardness, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA) and the like are preferable.

-Ionizing radiation polymerizable oligomer The ionizing radiation polymerizable oligomer has a weight average molecular weight of 1,000 or more and less than 10,000.
As the ionizing radiation polymerizable oligomer, a bifunctional or higher polyfunctional oligomer is preferable. Polyfunctional oligomers include polyester (meth) acrylate, urethane (meth) acrylate, polyester-urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, and isocyanurate (meth). Examples include acrylate and epoxy (meth) acrylate.

-Ionizing radiation polymerizable prepolymer The ionizing radiation polymerizable polymer has a weight average molecular weight of 10,000 or more, and the weight average molecular weight is preferably from 10,000 to 80,000, more preferably from 10,000 to 40,000. When the weight average molecular weight exceeds 80,000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained optical laminate may be deteriorated. Examples of the polyfunctional polymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

  The thermosetting resin precursor is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea Examples thereof include respective precursors such as co-condensation resins, silicon resins, and polysiloxane resins.

  The solvent-drying resin is a resin that forms a film only by drying a solvent added to adjust the solid content during coating, such as a thermoplastic resin. When the solvent-drying type resin is added, film defects on the coating surface of the coating liquid can be effectively prevented when the antiglare layer 12 is formed. It does not specifically limit as solvent dry type resin, Generally, a thermoplastic resin can be used.

  Examples of thermoplastic resins include styrene resins, (meth) acrylic resins, vinyl acetate resins, vinyl ether resins, halogen-containing resins, alicyclic olefin resins, polycarbonate resins, polyester resins, polyamide resins. , Cellulose derivatives, silicone resins and rubbers or elastomers.

  The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoint of transparency and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

  The uneven layers 45 and 55 can be formed by the following method, for example. First, the following concavo-convex layer composition is applied between the surface of the light-transmitting substrate 44 and a mold having a groove having a shape corresponding to the first concavo-convex surface 41A. Similarly, the following concavo-convex layer composition is applied between the surface of the light-transmitting substrate 54 and a mold having a groove corresponding to the second concavo-convex surface 51A.

  The concavo-convex layer composition contains at least the curable resin precursor. In addition, you may add a solvent and a polymerization initiator to the composition for uneven | corrugated layers as needed. Furthermore, the composition for the concavo-convex layer includes conventionally known dispersants, surfactants, antistatic agents, silanes depending on purposes such as increasing the hardness of the concavo-convex layer, suppressing cure shrinkage, and controlling the refractive index. Coupling agent, thickener, anti-coloring agent, coloring agent (pigment, dye), antifoaming agent, leveling agent, flame retardant, UV absorber, adhesion-imparting agent, polymerization inhibitor, antioxidant, surface modifier Further, an easy lubricant or the like may be added.

(solvent)
The solvent is used for the purpose of adjusting the viscosity for facilitating the application of the composition for the uneven layer, adjusting the evaporation rate and the dispersibility for the fine particles, and adjusting the degree of aggregation of the fine particles during the formation of the uneven layer. It can be used for the purpose of easily forming an uneven surface. Examples of the solvent include alcohols (eg, methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol), ketones (acetone, methyl ethyl ketone (MEK), cyclohexanone. , Methyl isobutyl ketone, diacetone alcohol, cycloheptanone, diethyl ketone, etc.), ethers (1,4-dioxane, dioxolane, tetrahydrofuran, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons ( Cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl lactate) ), Cellosolves (methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethylsulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.), etc., and mixtures thereof may be used. .

(Polymerization initiator)
The polymerization initiator is a component that is decomposed by light irradiation to generate radicals to initiate or advance polymerization (crosslinking) of the ionizing radiation polymerizable compound.

  The polymerization initiator is not particularly limited as long as it can release a substance that initiates radical polymerization by light irradiation. The polymerization initiator is not particularly limited, and known ones can be used. Specific examples include, for example, acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester, thioxanthones, propiophenone. , Benzyls, benzoins, acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

  As the polymerization initiator, when the binder resin is a resin system having a radically polymerizable unsaturated group, it is preferable to use acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether or the like alone or in combination. .

  The content of the polymerization initiator in the uneven layer composition is preferably 0.5 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the ionizing radiation polymerizable compound. By making the content of the polymerization initiator within this range, inhibition of curing can be suppressed.

  Although it does not specifically limit as a content rate (solid content) of the raw material in the composition for uneven | corrugated layers, Usually, 5 to 70 mass% is preferable, and it is more preferable to set it as 25 to 60 mass%.

(Leveling agent)
As the leveling agent, for example, silicone oil, fluorine-based surfactant and the like are preferable because the uneven layer has a Benard cell structure. When a resin composition containing a solvent is applied and dried, a surface tension difference or the like is generated between the coating film surface and the inner surface in the coating film, thereby causing many convections in the coating film. The structure generated by this convection is called a Benard cell structure, and causes a problem such as the skin and coating defects in the uneven layer to be formed.

  The method for preparing the concavo-convex layer composition is not particularly limited as long as each component can be mixed uniformly. For example, the composition can be performed using a known apparatus such as a paint shaker, a bead mill, a kneader, or a mixer.

  After coating the uneven layer composition between the light-transmitting substrates 44 and 54 and the mold, the coating-like uneven layer composition is irradiated with light such as ultraviolet rays to form a curable resin precursor. The composition for the uneven layer is cured by polymerization (crosslinking). And the uneven | corrugated layers 45 and 55 are formed by releasing the hardened | cured material of the composition for uneven | corrugated layers.

  When ultraviolet rays are used as the light for curing the uneven layer composition, ultraviolet rays emitted from ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, and the like can be used. Moreover, as a wavelength of an ultraviolet-ray, the wavelength range of 190-380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type.

<First polarizer and second polarizer>
The first polarizer 42 and the second polarizer 52 transmit only a specific linearly polarized light component. Examples of the first polarizer and the second polarizer include a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, which are dyed with iodine and stretched. . When laminating the first optical film 41 and the first polarizer 42 or when laminating the second optical film 51 and the second polarizer 52, the light-transmitting substrates 44 and 54 are saponified in advance. It is preferable to perform the treatment. By applying the saponification treatment, the adhesiveness is improved.

<< Design method of liquid crystal display element >>
As described above, the design method of the liquid crystal display element 30 according to the present embodiment includes the first polarizing plate 40, the second polarizing plate 50, the first polarizing plate 40, and the second polarizing plate 50. A first optical film 41 having a first concave and convex surface 41 </ b> A that forms a surface 30 </ b> A of the liquid crystal display element 30, and a first optical film. And a first polarizer 42 disposed closer to the liquid crystal cell 60 than 41, and the second polarizing film 50 has a second uneven surface 51A that forms the back surface 30B of the liquid crystal display element 30. 51 and the second polarizer 52 disposed on the liquid crystal cell 60 side with respect to the second optical film 51, the unevenness constituting the first uneven surface 41A and the second uneven surface 51A Having the same refractive index, The concave / convex surface 41A and the second concave / convex surface 51A have the same shape, the average inclination angle of the second concave / convex surface 51A is θa [°], and the average interval between the local peaks of the second concave / convex surface 51A is S [μm]. Where the refractive index of the unevenness constituting the second uneven surface 51A is N, and the average separation distance between the first uneven surface 41A and the second uneven surface 51A is D [μm], the average separation distance D Is a method of designing the liquid crystal display element 30 so as to satisfy the following formula (1).
D ≦ S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (1)

The liquid crystal display element 30 is preferably designed so that the average separation distance D satisfies the following formula (2) when the maximum inclination angle of the second uneven surface 51A is θmax [°].
D ≦ S / (2 × tan (θmax−sin ⁻¹ ((sin θa) / N))) (2)

  According to the present embodiment, the first uneven surface 41A and the second uneven surface 51A have the same shape, and the unevenness constituting the first uneven surface 41A and the unevenness constituting the second uneven surface 51A are the same. In the case of having a refractive index, the average distance D between the first uneven surface 41A and the second uneven surface 51A satisfies the above formula (1). Regardless of the positional relationship between the unevenness and the unevenness on the second uneven surface 51A, continuous diffusion characteristics can be obtained. Thereby, luminance unevenness can be suppressed.

  According to this embodiment, since the second optical film 51 is disposed on the back surface 30B of the liquid crystal display element 30, the scratch resistance on the back surface 30B of the liquid crystal display element 30 can be improved.

  According to the present embodiment, since the second optical film 51 having the second uneven surface 51A is arranged on the back surface 30B of the liquid crystal display element 30, the interference fringes caused by the surface light source device 20 are generated. Even if it exists, an interference fringe can be made invisible. Here, the first optical film having the first uneven surface is disposed on the surface of the liquid crystal display element, and the second optical film having the second uneven surface is not disposed on the back surface of the liquid crystal display element. However, since the image light can be diffused on the first concavo-convex surface, the interference fringes can be weakened. However, in addition to the first optical film, the second optical film should be disposed. Compared with the case of only the first optical film, the image light is diffused more. Thereby, the interference fringes can be made invisible.

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions.

<Example 1>
First, in order to simplify and simulate the liquid crystal display element described in the above embodiment, an optical film having a surface with a first uneven surface and a back surface with a second uneven surface was designed. Specifically, the average inclination angle θa of the first concavo-convex surface and the second concavo-convex surface is 3 °, the average interval S between the local portions of the first concavo-convex surface and the second concavo-convex surface is 50 μm, The arithmetic average roughness Ra of the first uneven surface and the second uneven surface was 0.3 μm, respectively, and the refractive index of the unevenness constituting the first uneven surface and the second uneven surface was 1.515, respectively. And the average separation distance of the 1st uneven surface and the 2nd uneven surface is set to 0.29 times the condensing distance when light is incident on the 2nd uneven surface, and the 1st uneven surface While changing the position of the second concavo-convex surface with respect to the above, the diffusion characteristics of light emitted from the first concavo-convex surface were simulated. Here, “0%” in FIG. 5 and FIG. 6 represents a case where the positions of the unevenness on the second uneven surface with respect to the unevenness on the first uneven surface are completely matched in the thickness direction of the optical film. “20%”, “40%”, “60%”, and “80%” mean that the position of the unevenness on the second uneven surface relative to the unevenness on the first uneven surface is the thickness direction of the optical film. Represents 100%, and the position of the unevenness on the second uneven surface relative to the unevenness on the first uneven surface is the thickness of the optical film. This represents a case where they are completely deviated in the vertical direction (when the center position of the concavo-convex convex portion on the first concavo-convex surface coincides with the position of the concave / convex valley on the second concavo-convex surface). In addition, it was 1.404 micrometers when the condensing distance when light injects into the 2nd uneven | corrugated surface from the said Formula (8) was calculated | required.

<Example 2>
In Example 2, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average separation distance between the first uneven surface and the second uneven surface was 0.43 times the condensing distance. .

<Example 3>
In Example 3, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average separation distance between the first uneven surface and the second uneven surface was 0.71 times the condensing distance. .

<Example 4>
In Example 3, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average separation distance between the first uneven surface and the second uneven surface was set to 1.00 times the condensing distance. .

<Comparative Example 1>
In Comparative Example 1, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average separation distance between the first uneven surface and the second uneven surface was 1.29 times the condensing distance. .

<Comparative example 2>
In Comparative Example 2, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average separation distance between the first uneven surface and the second uneven surface was 1.57 times the condensing distance. .

<Comparative Example 3>
In Comparative Example 3, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average separation distance between the first uneven surface and the second uneven surface was 2.14 times the condensing distance. .

  The results will be described below. 5A to 5D are graphs showing diffusion characteristics of the optical films according to Examples 1 to 4, and FIGS. 6A to 6C are diffusion characteristics of optical films according to Comparative Examples 1 to 3. It is a graph which shows. As shown in FIGS. 6A to 6C, in Comparative Examples 1 to 3, the average separation distance between the first uneven surface and the second uneven surface causes light to enter the second uneven surface. The condensing distance is exceeded, that is, since the above (1) is not satisfied, depending on the positional relationship between the unevenness constituting the first uneven surface and the unevenness forming the second uneven surface, it is discontinuous. It was confirmed that the diffusion characteristics were observed (Diffusion characteristics at 80% and 100% in Comparative Example 1 in FIG. 4, Diffusion characteristics at 60%, 80% and 100% in Comparative Example 2, Comparative Example (See all diffusion characteristics in 3). On the other hand, as shown in FIGS. 5A to 5D, in Examples 1 to 4, the average separation distance between the first uneven surface and the second uneven surface is the second uneven surface. What is the concavo-convex constituting the first concavo-convex surface and the concavo-convex constituting the second concavo-convex surface because it is equal to or shorter than the condensing distance when light is incident, that is, the above formula (1) is satisfied It was confirmed that continuous diffusion characteristics can be obtained even with a simple positional relationship.

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display device 20 ... Surface light source device 30 ... Liquid crystal display element 30A ... Front surface 30B ... Back surface 40 ... 1st polarizing plate 41 ... 1st optical film 41A ... 1st uneven surface 42 ... 1st polarizer 50 ... 2nd polarizing plate 51 ... 2nd optical film 51A ... 2nd uneven surface 52 ... 2nd polarizer 60 ... Liquid crystal cell

Claims (5)

A liquid crystal display element comprising a first polarizing plate, a second polarizing plate, and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate,
A first optical film having a first uneven surface on which the first polarizing plate forms the surface of the liquid crystal display element; and a first polarizer disposed closer to the liquid crystal cell than the first optical film; With
A second optical film having a second uneven surface on which the second polarizing plate forms the back surface of the liquid crystal display element; and a second polarizer disposed closer to the liquid crystal cell than the second optical film; With
The first uneven surface and the second uneven surface have the same shape,
The unevenness constituting the first uneven surface and the unevenness constituting the second uneven surface have the same refractive index,
The average inclination angle of the second uneven surface is θa [°], the average interval between the local peaks of the second uneven surface is S [μm], and the refractive index of the unevenness constituting the second uneven surface A liquid crystal display element satisfying the following formula (1), where N is N and an average separation distance between the first uneven surface and the second uneven surface is D [μm].
D ≦ S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (1) 2. The liquid crystal display element according to claim 1, further satisfying the following formula (2) when a maximum inclination angle of the second uneven surface is θmax [°].
D ≦ S / (2 × tan (θmax−sin ⁻¹ ((sin θa) / N))) (2)   A liquid crystal display element according to claim 1, wherein the liquid crystal display element is disposed closer to an observer than the surface light source apparatus, the surface of the liquid crystal display element is located on the observer side, and the liquid crystal A liquid crystal display device, wherein the back surface of the display element is positioned on the surface light source device side. A method for designing a liquid crystal display device comprising a first polarizing plate, a second polarizing plate, and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate,
A first optical film having a first uneven surface on which the first polarizing plate forms the surface of the liquid crystal display element; and a first polarizer disposed closer to the liquid crystal cell than the first optical film; With
A second optical film having a second uneven surface on which the second polarizing plate forms the back surface of the liquid crystal display element; and a second polarizer disposed closer to the liquid crystal cell than the second optical film; With
The unevenness constituting the first uneven surface and the unevenness constituting the second uneven surface have the same refractive index,
The first uneven surface and the second uneven surface have the same shape,
The average inclination angle of the second uneven surface is θa [°], the average interval between the local peaks of the second uneven surface is S [μm], and the refractive index of the unevenness constituting the second uneven surface Is N, and the average separation distance between the first concavo-convex surface and the second concavo-convex surface is D [μm], the liquid crystal display element is adjusted so that the average separation distance D satisfies the following formula (1). A design method of a liquid crystal display element, characterized by designing.
D ≦ S / (2 × tan (θa−sin ⁻¹ ((sin θa) / N))) (1) The liquid crystal display element is designed so that the average separation distance D further satisfies the following formula (2) when a maximum inclination angle of the second uneven surface is θmax [°]. 5. A method for designing a liquid crystal display element according to 4.
D ≦ S / (2 × tan (θmax−sin ⁻¹ ((sin θa) / N))) (2)