JP6724790B2 - Liquid crystal display device, liquid crystal display device, and method for designing liquid crystal display device - Google Patents

Description

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

A liquid crystal display element used in a liquid crystal display device mainly includes a polarizing plate located on the observer side, a polarizing plate located on the surface light source device side, and a liquid crystal cell arranged 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 glare of the observer and the background of the observer, enhancing scratch resistance, etc. Reference 1). Usually, this optical film is arranged on the surface of a polarizing plate located on the viewer side.

On the other hand, since the polarizing plate positioned on the surface light source device side of the liquid crystal display element may come into contact with the surface light source device and be rubbed, not only the surface of the liquid crystal display element on the viewer side but also scratch resistance In order to improve the above, it is considered to dispose an optical film also on the back surface (surface on the surface light source device side) of the liquid crystal display element.

JP, 2011-215515, A

When arranging the optical films on both the front surface and the back surface of the liquid crystal display element, it is preferable to use the same optical film from the viewpoint of cost reduction. Here, when an optical film having a concavo-convex surface is used as the optical film, the image light can be diffused, so that even if interference fringes caused by the surface light source device are generated, the interference fringes Can be made invisible.
Therefore, it is considered to dispose an optical film having an uneven surface on both the front surface and the back surface of the liquid crystal display element.

However, when the optical film having the uneven surface of the same shape is arranged on both the front surface and the back surface of the liquid crystal display element, in the thickness direction of the liquid crystal display element, the position of the unevenness is adjusted so that the centers of the convex portions of the uneven surface coincide with each other. Matching is difficult. That is, it is highly possible that the center of the convex portion on the concave-convex surface of the optical film on the back surface of the liquid crystal display element is displaced from the center of the convex portion on the concave-convex surface of the optical film on the front surface side of the liquid crystal display element.

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

The present invention has been made to solve the above problems. That is, it is an object of the present invention to provide a liquid crystal display element and a liquid crystal display device capable of improving scratch resistance on the back surface of the liquid crystal display element, making interference fringes invisible, and suppressing luminance unevenness. 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 including a first polarizing plate, a second polarizing plate, and a liquid crystal cell arranged between the first polarizing plate and the second polarizing plate. A display element, wherein the first polarizing plate is arranged on a liquid crystal cell side of the first optical film having a first uneven surface forming a surface of the liquid crystal display element and the first optical film. A second optical film having a first polarizer, wherein the second polarizing plate has a second concave-convex surface serving as a back surface of the liquid crystal display element, and a liquid crystal cell side closer than the second optical film. And a second polarizer arranged, wherein the first uneven surface and the second uneven surface have the same shape, and the uneven surface and the second uneven surface which form the first uneven surface are formed. The concaves and convexes to be formed have the same refractive index, the average inclination angle of the second concave and convex surface is θa [°], and the average interval between the local peaks of the second concave and convex surface is S [μm]. Satisfying the following formula (1), where N is the refractive index of the unevenness forming the uneven surface and D is an average distance between the first uneven surface and the second uneven surface is D [μm]. A liquid crystal display device is provided.
D≦S/(2×tan(θa-sin ⁻¹ ((sin θa)/N))) (1)

It is preferable that the liquid crystal display element further satisfy the following expression (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, a surface light source device and the above-mentioned liquid crystal display element arranged on the observer side of the surface light source device are provided, and the surface of the liquid crystal display element is located on the observer side. A liquid crystal display device is also provided, wherein the back surface of the liquid crystal display element is located on the surface light source device side.

According to another aspect of the present invention, a liquid crystal including a first polarizing plate, a second polarizing plate, and a liquid crystal cell arranged between the first polarizing plate and the second polarizing plate. A method of designing a display device, wherein the first polarizing plate has a first optical film having a first concave-convex surface forming a surface of the liquid crystal display device, and a liquid crystal cell side of the first optical film. A second optical film having a first polarizer arranged, wherein the second polarizing plate has a second concave-convex surface serving as a back surface of the liquid crystal display element; and a liquid crystal formed from the second optical film. A second polarizer arranged on the cell side, wherein the unevenness forming the first uneven surface and the unevenness forming the second uneven surface have the same refractive index, and the first unevenness is provided. The surface and the second uneven surface have the same shape, the average inclination angle of the second uneven surface is θa [°], and the average interval between the local peaks of the second uneven surface is S [μm], When the refractive index of the irregularities forming the second irregular surface is N and the average distance between the first irregular surface and the second irregular surface is D [μm], the average distance D is Provided is a method for designing a liquid crystal display device, which comprises designing the liquid crystal display device so as to satisfy the following formula (1).
D≦S/(2×tan(θa-sin ⁻¹ ((sin θa)/N))) (1)

In the method of designing the liquid crystal display element, it is preferable that the average separation distance D further satisfies the following expression (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 aspect of the present invention and the liquid crystal display device of another aspect, since the liquid crystal display element satisfies the above formula (1), it is possible to improve scratch resistance on the back surface of the liquid crystal display element. Therefore, the interference fringes can be made invisible, and the uneven brightness can be suppressed. Further, according to the method for designing a liquid crystal display element of another aspect of the present invention, the liquid crystal display element is designed so that the average distance D satisfies the above expression (1). It is possible to obtain a liquid crystal display element that can improve the brightness, can make the interference fringes invisible, and can suppress the uneven brightness.

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. FIG. 9 is a ray tracing diagram when the average separation distance between the uneven surfaces is shorter than the converging distance. FIG. 9 is a ray tracing diagram when the average separation distance between the uneven surfaces is longer than the converging 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 and a method for designing a liquid crystal display element according to embodiments 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 focusing distance on an uneven surface, and FIG. 3 is an average separation distance between the uneven surfaces. Is a ray tracing diagram when the distance is shorter than the focusing distance, and FIG. 4 is a ray tracing diagram when the average distance between the uneven surfaces is longer than the focusing distance. In the present specification, terms such as “film”, “sheet”, “plate” and the like are not distinguished from each other based only on the difference in designation. Therefore, for example, the “film” is a concept including members that can also be called sheets or plates. As one specific example, the "optical film" also includes members called "optical sheet" and "optical plate". Further, in the present specification, the “weight average molecular weight” is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting it into 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 arranged on the viewer side of 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 manner from the back side. The surface light source device 20 includes, for example, a light source 21 and a light guide plate 22 arranged 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 entrance surface 22A located on the light source 21 side and a light exit surface 22B located on the liquid crystal display element 30 side. The light emitted from the light source 21 enters from the light entrance surface 22A of the light guide plate 22 and exits from the light exit 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 arranged on the viewer side of the light guide plate 22 and a reflection plate arranged on the opposite side of the light exit side of the light guide plate 22. May be.

<<< Liquid crystal display element>>>
As shown in FIG. 1, the liquid crystal display element 30 is arranged 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 arranged between the first polarizing plate 40 and the liquid crystal cell 60, and an adhesive layer 72 arranged 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. Although the adhesive layers 71 and 72 are provided in the present embodiment, the adhesive layers 72 and 73 may not be provided.

<< liquid crystal cell >>
As the liquid crystal cell 60, a known liquid crystal cell can be used. 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 separated depending on whether or not a voltage is applied to the electrode layer. The orientation direction changes. Thereby, for example, when the first polarizing plate 40 and the second polarizing plate 50 are arranged in crossed Nicols, the voltage applied to the linearly polarized component in the specific direction transmitted through the second polarizing plate 50 is not applied. Since the polarization direction of the liquid crystal cell 60 is rotated by 90° when passing through the liquid crystal cell 60, the light is transmitted through the first polarizing plate 40, but the polarization direction is changed when passing through the liquid crystal cell 60 to which no voltage is applied. Since it is maintained, it does not pass through the first polarizing plate 40.

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

<First Optical Film and Second Optical Film>
The first optical film 41 has a first concave-convex surface 41A forming the surface 30A of the liquid crystal display element 30. The second optical film 51 includes a second concave-convex surface 51A that forms the back surface 30B of the liquid crystal display element 30. The front surface 30A of the liquid crystal display element 30 is the viewer-side surface of the liquid crystal display element 30 in the liquid crystal display device 10, and the back surface 30B of the liquid crystal display element 30 is the surface of the liquid crystal display element 30 in the liquid crystal display device 10. This is the 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 or more and 0.1 or less, and When the average spacing of the local peaks of the first uneven surface is S ₁ [μm] and the average spacing of the local peaks of the second uneven surface is S ₂ [μm], |S ₂ −S ₁ |/S ₂ When the arithmetic mean roughness of the first uneven surface is Ra ₁ [μm] and the arithmetic mean roughness of the second uneven surface is Ra ₂ [μm], the value is in the range of 0 or more and 0.1 or less. 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 ) is in accordance with the surface roughness measuring instrument: SE-3400/manufactured by Kosaka Laboratory Ltd. (instruction manual, 1995.07.20 revised). Specifically, θa is represented by the following formula.
θa=tan ⁻¹ Δa
In the formula, Δa represents the inclination by an aspect ratio, and is a value obtained by dividing the sum of the differences (corresponding to the height of each convex portion) between the minimum and maximum portions of each unevenness by the reference length.

The definitions of the average spacing S (S ₁ , S ₂ ) of the local peaks and the arithmetic average roughness Ra (Ra ₁ , Ra ₂ ) are in accordance with JIS B0601-1994.

The average inclination angle θa, the average interval S between the local peaks, and the arithmetic average roughness Ra are average values after 20 measurements. The average inclination angle θa, the average spacing S of the local peaks and the arithmetic average roughness Ra are determined by the following measurement conditions using, for example, a surface roughness measuring instrument (model number: SE-3400/manufactured by Kosaka Laboratory Ltd.). A measurement can be made.
1) Stylus for the surface roughness detection unit (trade name SE2555N (2μ standard) manufactured by Kosaka Laboratory Ltd.)
・Tip radius of curvature 2 μm, vertical angle 90°, material diamond 2) Measuring conditions of surface roughness measuring instrument ・Reference length (cutoff value λc of roughness curve): 0.8 mm
-Evaluation length (reference length (cut-off value λc) x 5): 4.0 mm
・Feeding speed of stylus: 0.5 mm/s
・Spare length: (cutoff value λc) x 2
・Vertical magnification: 2000 times ・Horizontal magnification: 10 times

The average inclination angle θa of the first uneven surface 41A and the second uneven surface 51A is preferably 0.1° or more and 5.0° or less from the viewpoint of suppressing glare and suppressing whitening. The average distance S between the local peaks of the first uneven surface 41A and the second uneven surface 51A is preferably 10 μm or more and 200 μm or less from the viewpoint of further suppressing uneven brightness. 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 forming the first uneven surface 41A and the unevenness forming the second uneven surface 51A have the same refractive index. In the present specification, "the unevenness forming 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 forming 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 within the range of 0 or more and 0.02 or less.

The refractive indices of the unevenness forming the first uneven surface 41A and the unevenness forming the second uneven surface 51A are the same as those of the first uneven layer 45 having the first uneven surface 41A and the second uneven surface 51A described later. After forming the 2nd uneven|corrugated layer 55 which it has, it can measure with an Abbe refractometer (NAR-4T by the Atago company) or an ellipsometer.

The refractive index of the unevenness forming 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 that interference fringes are less likely to occur.

Since the first optical film 41 and the second optical film 51 are arranged via the liquid crystal cell 60 and the like, they are separated from each other. The average inclination angle of the second uneven surface 51A is θa[°], the average interval of the local peaks of the second uneven surface 51A is S[μm], and the refractive index of the unevenness forming the second uneven surface 51A is Assuming that N is N and 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. Focuses and then diffuses. In the above formula (1), the average separation distance D 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 the second distance of the second optical film 51. It means that the distance is less than or equal to the light collecting distance on the uneven surface 51A. In the present specification, "the average 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 distances from the bottoms of the concave and convex portions forming the surface to the bottoms of the concave and convex portions forming the second concave and convex surface.

The above formula (1) is derived as follows.
FIG. 2 is a schematic diagram in which the concavo-convex shape is schematically illustrated in order to facilitate the description of the method of calculating the light collecting distance on the concavo-convex surface. First, it is assumed that the uneven portions 81 and 82 have the uneven surfaces 81A and 82A that are separated from each other as shown in FIG. The uneven portions 81 and 82 are arranged such that the uneven surfaces 81A and 82A are on the outside. The average inclination angle of the uneven surface 82A located on the light incident side is θa, the average interval of the local peaks of the uneven surface 82A is S, and the refraction angle of light when incident on the uneven surface 82A and refracted is ψ. The refractive index of the uneven portion 82 is N, the light collecting distance is F, and the average distance between the uneven surfaces is D. The average interval S of the local peaks of the uneven surface 82A can be regarded as the average width of the convex portions.
In FIG. 2, the light L appears to be incident on the valley where the uneven portion 82 does not exist, but this is for facilitating the illustration of the behavior of focusing the light L. The incident position is a position slightly displaced from the valley.

First, from Snell's law, the following equation (3) is established. Then, by modifying the following expression (3), the following expression (4) is obtained.
sin θa/sin ψ=N (3)
ψ=sin ⁻¹ ((sin θa)/N) (4)
On the other hand, in FIG. 2, the following equation (5) is established.
φ=θa−ψ (5)
Therefore, by substituting the above equation (4) into ψ of the above equation (5), the following equation (6) is obtained.
φ=θa−sin ⁻¹ ((sin θa)/N) (6)

On the other hand, from FIG. 2, the focusing distance F is represented by the following formula (7).
F=S/(2×tanφ) (7)
By substituting the above equation (6) for 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 uneven surfaces 81A and 82A is equal to or less than the light collecting distance F, the above formula (1) is obtained.

The average distance D between the first uneven surface 41A and the second uneven surface 51A is preferably 200 μm or more and 10000 μm or less from the viewpoint of making the liquid crystal display device lightweight and thin and manufacturing yield.

The present inventor has surprisingly found that the first uneven surface and the second uneven surface have the same shape, and the unevenness forming the first uneven surface and the unevenness forming the second uneven surface have the same refraction. Ratio, the first optical film having the first uneven surface and the second uneven surface 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 arranged, 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 that.

Specifically, when the two uneven surfaces have the same shape and the unevenness forming the uneven surface has the same refractive index, the average separation distance between the uneven surfaces is equal to or less than the light collecting distance, When the diffusion state of the light emitted from the uneven surface on the emitting side is simulated when the light distance is exceeded, as shown in FIG. 4, the average separation distance D between the uneven surface 91 and the uneven surface 92 is the condensing distance. When F is exceeded, that is, when the above expression (1) is not satisfied, light may be emitted separately from the uneven surface 91 depending on the positional relationship between the unevenness on the uneven surface 91 and the unevenness on the uneven surface 92. is there. It is considered that due to the light emitted separately, continuous diffusion characteristics cannot be obtained, resulting in uneven brightness. 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 collecting distance F, the unevenness and the unevenness on the uneven surface 91. Regardless of the positional relationship between the irregularities on the surface 92, the light emitted from the irregular 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 less than the light collecting distance, that is, when the above expression (1) is satisfied, the unevenness on the first uneven surface and the second uneven surface Regardless of the positional relationship between the irregularities on the surface, the light is not separately emitted from the first irregular surface of the first optical film, and it is considered that continuous diffusion characteristics can be obtained.

When the maximum inclination angle of the second uneven surface 51A is θmax [°], it is preferable that the liquid crystal display element 30 further satisfy the following expression (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 a larger inclination angle than θa in the uneven surface. In the unevenness having the inclination angle larger than θa, the light collecting distance is shorter than the light collecting distance when the inclination angle is θa. Therefore, when the average inclination angle θa is used, most of the irregularities have a light collecting distance equal to or more than the average separation distance between the first irregular surface and the second irregular surface. It is also envisioned that some have a light collecting distance that is shorter than the average distance between the uneven surface and the second uneven surface. On the other hand, θmax is the maximum inclination angle of the uneven surface, and therefore the focusing distance is the shortest. Therefore, by satisfying the above equation (2), the converging distances of all the concavities and convexities on the second concavo-convex surface 51A are the same as the first concavo-convex surface 41A of the first optical film 41 and the second concavo-convex surface of the second optical film 51. There is no possibility of becoming shorter than the average separation distance D from the second uneven surface 51A. Therefore, uneven brightness can be suppressed more.

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 surface roughness meter and a non-contact surface roughness meter (for example, an interference microscope, a confocal microscope, an atomic force microscope, etc.). Among these, the interference microscope is preferable because of the ease of measurement. Examples of such an interference microscope include "NewView" series manufactured by Zygo.

The maximum inclination angle θmax of the first uneven surface 41A and the second uneven surface 51A is preferably 0.5° or more and 15° or less from the viewpoint of suppressing the glare and suppressing the white discoloration.

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. The internal haze values of the first optical film 41 and the second optical film 51 are preferably 0% or more and 30% or less. The total haze value and the internal haze value are values measured as the entire first optical film or the entire second optical film. For example, 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 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 including the light-transmissive base material 44 and the uneven layer 45. Further, for example, when a functional layer such as a low refractive index layer is provided on the uneven layer, the total haze value and the internal haze value of the optical film are from the light-transmitting substrate, the uneven 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 according to JIS K7136 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 and the second optical film is measured according to JISK7136. Further, the internal haze value is obtained as follows. On the surface of the concavo-convex layer of the first optical film, a resin having a refractive index equal to that of the resin forming the concavo-convex surface, or a resin having a refractive index difference with the resin of 0.02 or less is dried with a wire bar to have a film thickness of 8 μm. That is, it is applied so that the unevenness of the uneven surface is completely eliminated and the surface is flattened, and dried at 70° C. for 1 minute. Then, the applied resin is irradiated with ultraviolet rays of 100 mJ/cm 2 to remove the resin. Let it harden. As a result, the unevenness existing on the surface of the first optical film is crushed and a film having a flat surface is obtained. However, when the resin for coating the surface of the uneven layer is easily repelled and difficult to wet due to the inclusion of a leveling agent or the like in the composition forming the uneven layer having the uneven shape, the uneven layer is previously formed. The surface is saponified (soaked with 2 mol/L NaOH (or KOH) solution at 55° C. for 3 minutes, washed with water, completely removed of water droplets with Kimwipe (registered trademark), etc., and then left in a 50° C. oven for 1 minute. It is advisable to apply hydrophilic treatment by (drying). Then, in this state, an internal haze value is obtained by measuring the haze value according to JISK7136 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory). This internal haze does not take into account the uneven shape of the surface of the first optical film or the 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 due only to the uneven shape of the surface in the first optical film or the second optical film, and by subtracting the internal haze value from the overall haze value, the first optical film or the second optical film The surface haze value resulting only from the uneven shape of the surface of the optical film is obtained.

The first optical film 41 includes a light-transmissive base material 44 and an uneven layer 45 provided on the viewer side of the light-transmissive base material 44 (the side opposite to the liquid crystal cell 60 side) and having an uneven surface. I have it. The second optical film 51 is provided with a light transmissive base material 54 and an uneven layer 55 provided on the surface light source device 20 side of the light transmissive base material 54 (the side opposite to the liquid crystal cell 60 side) and having an uneven surface. It has 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 41A of the first optical film 41. The uneven surface of the uneven layer 55 serves as the second uneven surface 51A of the second optical film 51.
The "functional layer" is a layer intended to exhibit some function in the optical film, and specifically exhibits a function such as antireflection property, antistatic property, or antifouling property. Layers for. The functional layer is not limited to a single layer and may be a laminate of two or more layers.

((Transparent substrate))
The light transmissive substrates 44 and 54 are not particularly limited as long as they have light transmissivity, and examples thereof include a cellulose acylate substrate, a cycloolefin polymer substrate, a polycarbonate substrate, an acrylate polymer substrate, and a polyester substrate. , Or a glass substrate.

Examples of the cellulose acylate base material include a cellulose triacetate base material and a cellulose diacetate base material. Examples of the cycloolefin polymer base material include base materials made of polymers such as norbornene-based monomers and monocyclic cycloolefin monomers.

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.

As the acrylate-based polymer base material, for example, a poly(meth)acrylate base material, a poly(meth)acrylate base material, a methyl(meth)acrylate-butyl(meth)acrylate copolymer base material, etc. may be used. Can be mentioned.

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

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 to the polarizer, and among the cellulose acylate base materials, a triacetyl cellulose base material (TAC base material) is preferable. The triacetyl cellulose substrate is a light transmissive substrate capable of having an average light transmittance of 50% or more in the visible light range of 380 to 780 nm. The average light transmittance of the triacetylcellulose base material is preferably 70% or more, more preferably 85% or more.

Incidentally, as the triacetyl cellulose base material, in addition to pure triacetyl cellulose, it is possible to use a component other than acetic acid as a fatty acid which forms an ester with cellulose such as cellulose acetate propionate and cellulose acetate butyrate. Good. In addition, other cellulose lower fatty acid ester such as diacetyl cellulose, or various additives such as a plasticizer, an ultraviolet absorber and a slippery lubricant may be added to these triacetyl cellulose, if necessary.

A cycloolefin polymer base material is preferable from the viewpoint of excellent retardation and heat resistance, and a polyester base material is preferable from the viewpoint of mechanical properties and heat resistance.

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

((Rough layer))
The uneven layers 45 and 55 are layers having an uneven surface. The concavo-convex layer 45 is a layer exhibiting an antiglare property and a light diffusing property, and the concavo-convex layer 55 is a layer exhibiting a light diffusing property, 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 is a layer that exhibits antiglare properties and light diffusion properties, and also 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 a light diffusion property and, for example, a function such as a hard coat property, an antireflection property, an antistatic property, or an antifouling property.

When the concavo-convex layers 45 and 55 are layers that exhibit hard coat properties in addition to the antiglare property, the concavo-convex layers 45 and 55 have a pencil hardness test (4. 4.) defined in JIS K5600-5-4 (1999). It has a hardness of "H" or more under a load of 9N.

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) can be formed, for example, by (A) a transfer method using a mold. A method of forming an uneven surface using a composition for an uneven layer containing (B) 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. And the like, or (D) a method of forming an uneven surface by giving unevenness to the surface of the 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).

(Cured product of curable resin precursor)
In the present specification, the “curable resin precursor” means a resin precursor having a resin precursor having an ionizing radiation curability and a thermosetting property and becoming a resin by the ionizing radiation curing or the heat curing. The resin may include a solvent-drying resin as well as a cured product of a 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 (meth)acryloyl group, vinyl group and allyl group. In addition, in this specification, "(meth)acryloyl group" is meant to include both "acryloyl group" and "methacryloyl group". Further, the ionizing radiation irradiated when curing the ionizing radiation-curable resin precursor means, among electromagnetic waves or charged particle beams, those having an energy quantum capable of polymerizing or cross-linking molecules, and usually ultraviolet rays ( UV) or electron beam (EB) is used, but in addition, electromagnetic waves such as X-ray and γ-ray, and charged particle beam such as α-ray and ion ray can be used. The thermosetting resin precursor having thermosetting property has at least one thermopolymerizable functional group.

Examples of the ionizing radiation-curable resin precursor include an ionizing radiation-polymerizable monomer, an ionizing radiation-polymerizable oligomer, and an ionizing radiation-polymerizable prepolymer, which can be appropriately adjusted and used. The ionizing radiation curable resin precursor is preferably a combination of an ionizing radiation polymerizable monomer and an ionizing radiation polymerizable oligomer or an ionizing radiation polymerizable prepolymer.

Ionizing radiation-polymerizable monomer The ionizing radiation-polymerizable monomer has a weight average molecular weight of less than 1,000. 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 functional monomer include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate. 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, tetrapentaerythritol 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, isobornyl di(meth)acrylate, dicyclopentane di(meth) Examples thereof include acrylate, tricyclodecane di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and those modified with PO, EO, or the like.

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

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 polyfunctional oligomer having two or more functional groups is preferable. As the polyfunctional oligomer, polyester (meth)acrylate, urethane (meth)acrylate, polyester-urethane (meth)acrylate, polyether (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, isocyanurate (meth). Examples thereof 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 10,000 or more and 80,000 or less, more preferably 10,000 or more and 40,000 or less. When the weight average molecular weight is more than 80,000, the viscosity is high and thus the coating suitability is deteriorated, 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, and examples thereof include 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 of co-condensation resin, silicon resin, polysiloxane resin and the like.

The solvent-drying resin is a resin such as a thermoplastic resin that forms a film only by drying the solvent added to adjust the solid content during coating. When the solvent-drying resin is added, it is possible to effectively prevent film defects on the coating surface of the coating liquid when forming the antiglare layer 12. The solvent drying type resin is not particularly limited, and generally a thermoplastic resin can be used.

Examples of the thermoplastic resin include styrene resin, (meth)acrylic resin, vinyl acetate resin, vinyl ether resin, halogen-containing resin, alicyclic olefin resin, polycarbonate resin, polyester resin, polyamide resin. , 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). Particularly, from the viewpoints 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 concavo-convex layers 45 and 55 can be formed by, for example, the following method. First, the following composition for a concavo-convex layer is applied between the surface of the light transmissive substrate 44 and a mold having a groove having a shape corresponding to the first concavo-convex surface 41A. Similarly, the following composition for an uneven layer is applied between the surface of the light transmissive substrate 54 and a mold having a groove having a shape corresponding to the second uneven surface 51A.

The concavo-convex layer composition contains at least the curable resin precursor. In addition, a solvent and a polymerization initiator may be added to the composition for uneven layer, if necessary. Furthermore, the composition for a concavo-convex layer contains a conventionally known dispersant, surfactant, antistatic agent, silane according to the purpose of increasing the hardness of the concavo-convex layer, suppressing curing shrinkage, controlling the refractive index, and the like. Coupling agent, thickener, anti-coloring agent, colorant (pigment, dye), defoaming agent, leveling agent, flame retardant, ultraviolet absorber, adhesion promoter, polymerization inhibitor, antioxidant, surface modifier , A slipping agent and the like may be added.

(solvent)
The solvent has a predetermined purpose by adjusting the viscosity for facilitating application of the uneven layer composition, adjusting the evaporation rate and dispersibility with respect to fine particles, and adjusting the degree of aggregation of the fine particles during the uneven layer formation. It can be used for the purpose of making it easy to form 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 etc.), Examples thereof include cellosolves (methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.), and a mixture thereof may be used.

(Polymerization initiator)
The polymerization initiator is a component that is decomposed by light irradiation to generate radicals to initiate or proceed with the 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, and specific examples thereof include, for example, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, thioxanthones, propiophenone. And benzyls, benzoins, and acylphosphine oxides. Further, 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 composition for the uneven layer 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 setting the content of the polymerization initiator within this range, inhibition of curing can be suppressed.

The content ratio (solid content) of the raw materials in the composition for a concavo-convex layer is not particularly limited, but is usually preferably 5 mass% or more and 70 mass% or less, and more preferably 25 mass% or more and 60 mass% or less.

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

The method for preparing the composition for the uneven layer is not particularly limited as long as each component can be uniformly mixed, and for example, a known apparatus such as a paint shaker, a bead mill, a kneader, and a mixer can be used.

After coating the uneven layer composition between the light-transmissive substrates 44, 54 and the mold, the coating film-shaped 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 polymerizing (crosslinking). Then, by releasing the cured product of the uneven layer composition, the uneven layers 45 and 55 are formed.

When ultraviolet rays are used as light for curing the composition for the uneven layer, ultraviolet rays emitted from an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp or the like can be used. Further, as the wavelength of ultraviolet rays, a wavelength range of 190 to 380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as Cockcroft-Walt type, Van Degraft type, resonance transformer type, insulating core transformer type, linear type, dynamitron type, and high frequency type.

<First Polarizer and Second Polarizer>
The first polarizer 42 and the second polarizer 52 allow only a specific linearly polarized light component to pass therethrough. Examples of the first polarizer and the second polarizer include a polyvinyl alcohol film dyed with iodine or the like and stretched, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, and the like. .. When laminating the first optical film 41 and the first polarizer 42 or laminating the second optical film 51 and the second polarizer 52, the light transmitting base materials 44 and 54 are previously saponified. It is preferable to apply a treatment. Adhesion is improved by performing the saponification treatment.

<< liquid crystal display element design method >>
As described above, the method for designing 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 comprising a liquid crystal cell 60 disposed between the first optical film 41 and the first polarizing film 40 having a first uneven surface 41A forming the surface 30A of the liquid crystal display element 30, and a first optical film. A second optical film having a first polarizer 42 arranged closer to the liquid crystal cell 60 than the liquid crystal cell 41, and a second polarizing plate 50 having a second uneven surface 51A forming a back surface 30B of the liquid crystal display element 30. 51 and the second polarizer 52 arranged on the liquid crystal cell 60 side of the second optical film 51, in the liquid crystal display element 30, the unevenness forming the first uneven surface 41A and the second uneven surface 51A The first and second uneven surfaces 41A and 51A have the same shape, the average inclination angle of the second and third uneven surfaces 51A is θa [°], and The average spacing of the local peaks of the two uneven surfaces 51A is S [μm], the refractive index of the unevenness forming the second uneven surface 51A is N, and the first uneven surface 41A and the second uneven surface 51A are This is a method of designing the liquid crystal display element 30 so that the average separation distance D satisfies the following expression (1) when the average separation distance is D [μm].
D≦S/(2×tan(θa-sin ⁻¹ ((sin θa)/N))) (1)

It is preferable to design the liquid crystal display element 30 so that the average separation distance D satisfies the following expression (2), where θmax[°] is the maximum inclination angle of the second uneven surface 51A.
D≦S/(2×tan(θmax-sin ⁻¹ ((sin θa)/N))) (2)

According to this embodiment, the first uneven surface 41A and the second uneven surface 51A have the same shape, and the unevenness forming the first uneven surface 41A and the unevenness forming the second uneven surface 51A are the same. In the case of having a refractive index, since the average separation distance D between the first uneven surface 41A and the second uneven surface 51A satisfies the above expression (1), the first uneven surface 41A in the first uneven surface 41A has the above-mentioned reason. Regardless of the positional relationship between the unevenness and the unevenness on the second uneven surface 51A, continuous diffusion characteristics can be obtained. Thereby, uneven brightness can be suppressed.

According to this embodiment, since the second optical film 51 is arranged 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, when the interference fringes caused by the surface light source device 20 occur. Even if there is, interference fringes can be made invisible. Here, there is a case where the first optical film having the first uneven surface is arranged on the surface of the liquid crystal display element and the second optical film having the second uneven surface is not arranged on the back surface of the liquid crystal display element. However, since the image light can be diffused by the first uneven surface, it is possible to weaken the interference fringes, but it is better to arrange the second optical film in addition to the first optical film. , The image light is more diffused as compared with the case where only the first optical film is used. This makes it possible to make the interference fringes invisible.

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

<Example 1>
First, in order to simplify the simulation of the liquid crystal display element described in the above embodiment, an optical film having a first uneven surface and a second uneven surface was designed. Specifically, the average inclination angle θa of each of the first uneven surface and the second uneven surface is set to 3°, and the average interval S between the local portions of the first uneven surface and the second uneven surface is set to 50 μm, respectively. The arithmetic mean roughness Ra of the first uneven surface and the second uneven surface was set to 0.3 μm, and the refractive index of the unevenness forming the first uneven surface and the second uneven surface was set to 1.515. Then, the average separation distance between the first uneven surface and the second uneven surface is set to 0.29 times the condensing distance when light is incident on the second uneven surface. The diffusion characteristics of the light emitted from the first uneven surface were simulated while changing the position of the second uneven surface with respect to. Here, “0%” in FIGS. 5 and 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 aligned in the thickness direction of the optical film. "20%", "40%", "60%", "80%" means that the position of the unevenness on the second uneven surface with respect to the unevenness on the first uneven surface is in the thickness direction of the optical film. 20%, 40%, 60%, and 80%, and "100%" means that the position of the unevenness on the second uneven surface with respect to the unevenness on the first uneven surface is the thickness of the optical film. The figure shows a case where there is a complete deviation in the vertical direction (the center position of the convex portion of the concave and convex on the first concave and convex surface and the position of the concave and convex valley on the second concave and convex surface are the same). The light collecting distance when light was made incident on the second uneven surface was calculated from the above equation (8) and found to be 1.404 μm.

<Example 2>
In Example 2, the diffusion characteristics were simulated under the same conditions as in Example 1 except that the average distance between the first uneven surface and the second uneven surface was 0.43 times the light collecting 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 light collecting 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 1.00 times the light collecting 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 distance between the first uneven surface and the second uneven surface was 1.29 times the light collecting 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 distance between the first uneven surface and the second uneven surface was set to 1.57 times the light collecting distance. ..

<Comparative example 3>
In Comparative Example 3, 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 light collecting distance. ..

The results will be described below. 5A to 5D are graphs showing the diffusion characteristics of the optical films according to Examples 1 to 4, and FIGS. 6A to 6C are the diffusion characteristics of the 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 allows light to be incident on the second uneven surface. Since the converging distance is exceeded, that is, the condition (1) above is not satisfied, discontinuity may occur depending on the positional relationship between the unevenness forming the first uneven surface and the unevenness forming the second uneven surface. 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, and comparative examples. See all diffusion properties 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 was equal to the second uneven surface. Since it is equal to or less than the converging distance when light is made incident, that is, the above expression (1) is satisfied, what is the unevenness forming the first uneven surface and the unevenness forming the second uneven surface? It was confirmed that continuous diffusion characteristics can be obtained even with such a positional relationship.

10... Liquid crystal display device 20... Surface light source device 30... Liquid crystal display element 30A... Front surface 30B... Back surface 40... First polarizing plate 41... First optical film 41A... First uneven surface 42... First polarizer 50 ...Second polarizing plate 51...second optical film 51A...second uneven surface 52...second polarizer 60...liquid crystal cell

Claims (5)

A liquid crystal display device comprising: a first polarizing plate, a second polarizing plate, and a liquid crystal cell arranged between the first polarizing plate and the second polarizing plate,
A first optical film in which the first polarizing plate has a first uneven surface that forms the surface of the liquid crystal display element, and a first polarizer arranged closer to the liquid crystal cell than the first optical film. Equipped with
A second optical film in which the second polarizing plate has a second concave-convex surface that forms the back surface of the liquid crystal display element, and a second polarizer arranged closer to the liquid crystal cell than the second optical film. Equipped with
The first uneven surface and the second uneven surface have the same shape,
The unevenness forming the first uneven surface and the unevenness forming 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 forming the second uneven surface is Where N is N and the average distance between the first uneven surface and the second uneven surface is D [μm], the liquid crystal display element satisfies the following formula (1).
D≦S/(2×tan(θa-sin ⁻¹ ((sin θa)/N))) (1) The liquid crystal display element according to claim 1 , wherein an average distance S between local peaks of the first and second uneven surfaces is 10 μm or more and 200 μm or less. A surface light source device, and a liquid crystal display device according to the surface light source device according to claim 1 or 2 disposed on the observer side of, said surface is positioned on the viewer side of the liquid crystal display device, and the liquid crystal A liquid crystal display device, wherein the back surface of the display element is located 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 arranged between the first polarizing plate and the second polarizing plate,
A first optical film in which the first polarizing plate has a first uneven surface that forms the surface of the liquid crystal display element, and a first polarizer arranged closer to the liquid crystal cell than the first optical film. Equipped with
A second optical film in which the second polarizing plate has a second concave-convex surface that forms the back surface of the liquid crystal display element, and a second polarizer arranged closer to the liquid crystal cell than the second optical film. Equipped with
The unevenness forming the first uneven surface and the unevenness forming 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 forming the second uneven surface is Is N and the average separation distance between the first uneven surface and the second uneven surface is D [μm], the liquid crystal display device is designed so that the average separation distance D satisfies the following formula (1). A method for designing a liquid crystal display device, characterized by designing.
D≦S/(2×tan(θa-sin ⁻¹ ((sin θa)/N))) (1) The liquid crystal display device is designed so that the average separation distance D further satisfies the following expression (2) when the maximum inclination angle of the second uneven surface is θmax [°]. 4. The method for designing a liquid crystal display element according to item 4 .
D≦S/(2×tan(θmax-sin ⁻¹ ((sin θmax)/N))) (2)