KR102543034B1 - Liquid crystal display element, liquid crystal display device, and method for designing liquid crystal display element - Google Patents

Abstract

A liquid crystal display element capable of improving 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, a first polarizing plate 40, a second polarizing plate 50, and a liquid crystal cell 60 disposed between the first polarizing plate 40 and the second polarizing plate 50, It is a liquid crystal display element 30, and the 1st optical film 41 in which the 1st polarizing plate 40 has the 1st uneven surface 41A which forms the surface 30A of the liquid crystal display element 30, and the 1st optical film A second uneven surface 51A having a first polarizer 42 arranged on the side of the liquid crystal cell 60 rather than (41), and the second polarizing plate 50 forming the back surface 30B of the liquid crystal display element 30 2nd optical film 51 having , and the 2nd polarizer 52 arrange|positioned on the liquid crystal cell 60 side rather than the 2nd optical film 51, and the 1st uneven surface 41A and the 2nd uneven surface 51A has the same shape, the concavities and convexities constituting the first concave-convex surface 41A and the concavities and convexities constituting the second concave-convex surface 51A have the same refractive index, and the average inclination angle of the second concave-convex surface 51A is θa [ °], the average spacing of local mountain tops of the second uneven surface 51A is S [μm], the refractive index of the irregularities constituting the second uneven surface 51A is N, and the first uneven surface ( 41A) and the second concavo-convex surface 51A, when D [μm] is the average separation distance, the liquid crystal display device 30 characterized in that the following formula (1) is satisfied.
D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1)

Description

Liquid crystal display element, liquid crystal display device, and design method of liquid crystal display element

The present invention relates to a liquid crystal display element, a liquid crystal display device, and a design method of the liquid crystal display element.

A liquid crystal display element used in a liquid crystal display device mainly includes a polarizing plate positioned on the observer side, a polarizing plate positioned 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 (surface on the side of the observer) for the purpose of suppressing reflection of the observer and the observer's background or the like, or for the purpose of enhancing scratch resistance (see Patent Document 1). Usually, this optical film is placed on the surface of a polarizing plate positioned on the viewer's side.

On the other hand, since the polarizing plate located on the surface light source device side of the liquid crystal display element comes into contact with the surface light source device and there is a risk of being rubbed, in recent years, not only the surface of the liquid crystal display element on the viewer side but also the scratch resistance has been improved. Arrangement of an optical film also on the back surface (surface on the surface light source device side) of the liquid crystal display element has been studied.

Japanese Unexamined Patent Publication No. 2011-215515

When arranging an optical film on both the front and back surfaces of a liquid crystal display element, it is preferable to use the same optical film from a viewpoint of reducing cost. Here, when an optical film having a concavo-convex surface is used as the optical film, since video light can be diffused, even when interference fringes caused by the surface light source device are generated, the interference fringes can be made invisible.

For this reason, arrange|positioning the optical film which has a concavo-convex surface on both the front surface and back surface of a liquid crystal display element is examined.

However, when an optical film having concavo-convex surfaces of the same shape is disposed on both the front and rear surfaces of the liquid crystal display element, the alignment of the concavo-convex portions is performed so that the centers of convex portions of the concavo-convex surfaces coincide with each other in the thickness direction of the liquid crystal display element. It is difficult to do. That is, there is a high possibility that the center of the convex portion on the concave-convex surface of the optical film on the rear side of the liquid crystal display element is shifted from the center of the convex portion on the concave-convex surface of the optical film on the surface side of the liquid crystal display element.

Here, the diffusion characteristics of light in the case where optical films having concavo-convex surfaces of the same shape are disposed on both the front and rear surfaces of the liquid crystal display element are It changes according to the positional relationship with the unevenness in the uneven surface of the optical film on the rear side of the liquid crystal display element. For this reason, depending on this positional relationship, continuous diffusion characteristics cannot be obtained, and there is a possibility that luminance non-uniformity may occur.

The present invention has been made to solve the above problems. That is, it is an object 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 non-uniformity. 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 display device including a first polarizing plate, a second polarizing plate, and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate, wherein the first polarizing plate comprises the liquid crystal A first optical film having a first concavo-convex surface constituting a surface of a display element, and a first polarizer disposed closer to a liquid crystal cell than the first optical film, wherein the second polarizing plate constitutes a back surface of the liquid crystal display element. A second optical film having a second convex-convex surface and a second polarizer arranged closer to a liquid crystal cell than the second optical film, wherein the first concave-convex surface and the second concave-convex surface have the same shape, and the first concavo-convex surface is provided. The unevenness constituting the 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 [°], and the average spacing of local peaks of the second uneven surface is When S [μm], the refractive index of the concavo-convex constituting the second concave-convex surface is N, and the average separation distance between the first concave-convex surface and the second concave-convex surface is D [μm], the following formula A liquid crystal display element characterized by satisfying (1) is provided.

D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1)

The liquid crystal display element preferably further satisfies the following formula (2) when the maximum inclination angle of the second concavo-convex surface is θmax [°].

D≤S/(2×tan(θmax-sin ^-1 ((sinθmax)/N))) (2)

According to another aspect of the present invention, a surface light source device and the liquid crystal display element arranged on an observer side relative to the surface light source device are provided, the surface of the liquid crystal display element is located on the observer side, and the liquid crystal display element A liquid crystal display device is provided, characterized in that the rear surface is located on the surface light source device side.

According to another aspect of the present invention, a method for designing a liquid crystal display element including a first polarizing plate, a second polarizing plate, and a liquid crystal cell disposed between the first polarizing plate and the second polarizing plate, wherein the first polarizing plate, A first optical film having a first concavo-convex surface constituting the surface of the liquid crystal display element, and a first polarizer disposed closer to a liquid crystal cell than the first optical film, and the second polarizing plate is a back surface of the liquid crystal display element. A second optical film having a second concave-convex surface and a second polarizer arranged on a liquid crystal cell side of the second optical film, comprising the concavo-convex constituting the first concave-convex surface and the second concave-convex surface. The irregularities 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 [°], and the average of local peaks of the second uneven surface When the interval is S [μm], the refractive index of the concavo-convex constituting the second concave-convex surface is N, and the average separation distance between the first concave-convex surface and the second concave-convex surface is D [μm], A method for designing a liquid crystal display element is provided, characterized in that the liquid crystal display element is designed so that the average separation distance D satisfies the following formula (1).

D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1)

In the design method of the liquid crystal display element, when the maximum inclination angle of the second concavo-convex surface is θmax [°], it is preferable that the average separation distance D further satisfies the following formula (2).

D≤S/(2×tan(θmax-sin ^-1 ((sinθmax)/N))) (2)

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

1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment.
Fig. 2 is a schematic diagram for explaining a method for calculating the condensing distance on a concave-convex surface.
3 is a ray tracing diagram when the average separation distance between concave-convex surfaces is shorter than the condensing distance.
4 is a ray tracing diagram in the case where the average separation distance between concave-convex surfaces is longer than the condensing distance.
5 is a graph showing diffusion characteristics of optical films according to Examples 1 to 4;
6 is a graph showing diffusion characteristics of optical films according to Comparative Examples 1 to 3.

Hereinafter, the liquid crystal display element according to the embodiment and the design method of the liquid crystal display element will be described with reference to the drawings. 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 for calculating a convergence distance on an uneven surface, and FIG. It is a ray tracing diagram in the case of being short, and FIG. 4 is a ray tracing diagram in the case where the average separation distance between concave-convex surfaces is longer than the condensing distance. In this specification, terms such as "film", "sheet", and "plate" are based only on differences in names and are not distinguished from each other. Therefore, for example, a "film" is a concept that includes a member that can also be called a sheet or a plate. As a specific example, the "optical film" also includes members called "optical sheets" and "optical plates". In addition, in this specification, "weight average molecular weight" is a value obtained by dissolving in a solvent, such as tetrahydrofuran (THF), and polystyrene conversion by the conventionally well-known gel permeation chromatography (GPC) method.

[liquid crystal display device]

As shown in FIG. 1 , the liquid crystal display device 10 according to the present embodiment is composed of a surface light source device 20 and a liquid crystal display element 30 disposed on the viewer side rather than the surface light source device 20 .

<<<Flat Light Device>>>

The surface light source device 20 illuminates the liquid crystal display element 30 onto the surface from the rear 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 dotted light emitting diode (LED), or an incandescent lamp can be used.

The light guide plate 22 has a light incident surface 22A located on the light source 21 side and a light exit surface 22B located on the liquid crystal display element 30 side. Light emitted from the light source 21 enters from the light incident 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 disposed closer to the observer than the light guide plate 22, a reflector disposed on the side opposite to the light exit side of the light guide plate 22, and the like. You can do it.

<<<liquid crystal display element>>>

As shown in FIG. 1 , the liquid crystal display element 30 includes a first polarizing plate 40 , a second polarizing plate 50 , and a liquid crystal cell disposed between the first polarizing plate 40 and the second polarizing plate 50 . (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 are equipped The first polarizing plate 40 is positioned closer to the observer than the liquid crystal cell 60, and the second polarizing plate 50 is positioned closer to the surface light source device 20 than the liquid crystal cell 60. In this embodiment, although the adhesive layers 71 and 72 are provided, the adhesive layers 72 and 73 do not need to be provided.

<<liquid crystal cell>>

As the liquid crystal cell 60, a known liquid crystal cell may 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, etc. between two glass substrates, and the alignment direction of liquid crystal molecules in the liquid crystal layer depends on whether or not voltage is applied to the electrode layer. this changes Accordingly, 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 subjected to voltage application. Since the polarization direction is rotated by 90° when passing through the liquid crystal cell 60, the first polarizing plate 40 is transmitted, but the polarization direction is maintained when passing through the liquid crystal cell 60 to which voltage is not applied. It is not transmitted through the first polarizing plate 40 .

<<The first polarizing plate and the second polarizing plate>>

As shown in FIG. 1, the first polarizing plate 40 includes a first optical film 41, a first polarizer 42 disposed on the side of the liquid crystal cell 60 rather than the first optical film 41, 1 It is arrange|positioned on the liquid crystal cell 60 side rather than the polarizer 42, and is equipped with the protective film 43 which protects the 1st polarizer 42. 1, the second polarizing plate 50 includes a second optical film 51 and a second polarizer 52 disposed on the side of the liquid crystal cell 60 rather than the second optical film 51. , It is disposed on the side of the liquid crystal cell 60 rather than the second polarizer 52, and is further equipped with a protective film 53 that protects the second polarizer 52. The protective films 43 and 53 may be retardation films. In this embodiment, the first polarizing plate 40 is provided with a protective film 43, and the second polarizing plate 50 is provided with a protective film 53, but the protective films 43 and 53 are provided. You do not have to do.

<First optical film and second optical film>

The 1st optical film 41 is equipped with the 1st uneven surface 41A which forms the surface 30A of the liquid crystal display element 30. The 2nd optical film 51 is equipped with the 2nd uneven surface 51A which forms the back surface 30B of the liquid crystal display element 30. In the liquid crystal display device 10, the surface 30A of the liquid crystal display element 30 is the observer side surface of the liquid crystal display element 30, and the back surface 30B of the liquid crystal display element 30 is the liquid crystal display device ( In 10), it is a surface of the liquid crystal display element 30 on the surface light source device 20 side.

41 A of 1st uneven surfaces in the 1st optical film 41 and 51 A of 2nd uneven surfaces in the 2nd optical film 51 have the same shape. In this specification, "the first concave-convex surface in the first optical film and the second concave-convex surface in the second optical film have the same shape" means that at least the average inclination angle of the first concave-convex surface is θa ₁ [° ], and when the average inclination angle of the second concave-convex surface is θa ₂ [°], |θa ₂ -θa ₁ |/θa ₂ is within the range of 0 or more and 0.1 or less, and the local peak of the first concave-convex surface When the average spacing of is S ₁ [μm] and the average spacing of the peaks of local peaks of the second concave-convex surface is S ₂ [μm], |S ₂ -S ₁ |/S ₂ ranges from 0 to 0.1. , when the arithmetic mean roughness of the first uneven surface is Ra ₁ [㎛] and the arithmetic mean roughness of the second uneven surface is Ra ₂ [㎛], |Ra ₂ -Ra ₁ |/Ra ₂ is 0 It means within the range of more than 0.1 and less.

The definition of the average inclination angle θa (θa ₁ , θa ₂ ) is to be in accordance with the surface roughness measuring instrument: SE-3400/Co., Ltd. Kosaka Kenkyosho product instruction manual (revised on July 20, 1995). Specifically, (theta)a is expressed by the following formula.

θa=tan ^{- 1} Δa

In the formula, Δa represents the inclination as an aspect ratio, and is a value obtained by dividing the total sum of the difference between the smallest part and the largest part of each concavo-convex part (corresponding to the height of each convex part) by the reference length.

The definition of the average interval S (S ₁ , S ₂ ) and the arithmetic mean roughness Ra (Ra ₁ , Ra ₂ ) of the local peaks shall be in accordance with JISB0601-1994.

The average inclination angle θa, the average spacing S of local peaks, and the arithmetic mean roughness Ra are taken as average values when measured 20 times. The average inclination angle θa, the average spacing S of local peaks, and the arithmetic average roughness Ra are, for example, using a surface roughness measuring instrument (model number: SE-3400/manufactured by Kosaka Kensho Co., Ltd.) under the following measurement conditions. measurements can be made by

1) The stylus of the surface roughness detector (trade name SE2555N (2μ standard) manufactured by Kosaka Kenkyusho Co., Ltd.)

Tip curvature radius 2㎛, apex angle 90 degrees, material diamond

2) Measurement conditions of the surface roughness meter

・Standard length (cutoff value λc of the roughness curve): 0.8 mm

・Evaluation length (standard length (cutoff value λc) × 5): 4.0 mm

·Feeding speed of stylus: 0.5mm/s

Spare length: (cutoff value λc) × 2

・Vertical magnification: 2000 times

・Horizontal magnification: 10x

The average inclination angle θa of the first concave-convex surface 41A and the second concave-convex surface 51A is preferably 0.1° or more and 5.0° or less from the viewpoint of suppressing projection and suppressing color fading. In addition, the average spacing S of 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 luminance non-uniformity. The arithmetic average roughness Ra of the first concave-convex surface 41A and the second concave-convex surface 51A is preferably 0.02 μm or more and 0.5 μm or less from the viewpoint of making interference fringes more easily invisible.

The irregularities constituting the first concave-convex surface 41A and the concavo-convex constituting the second uneven surface 51A have the same refractive index. In this specification, "the irregularities constituting the first uneven surface and the irregularities constituting the second uneven surface have the same refractive index" means the refractive index of the irregularities constituting the first uneven surface and the concavities and convexities constituting the second uneven surface It means that the absolute value of the difference of the refractive index of is in the range of 0 or more and 0.02 or less.

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

The refractive index of the concavo-convex constituting the first concavo-convex surface 41A and the second concavo-convex surface 51A is preferably 1.40 or more and 1.60 or less from the viewpoint of making interference fringes more difficult to generate.

Since the 1st optical film 41 and the 2nd optical film 51 are arrange|positioned via the liquid crystal cell 60 etc., they are spaced apart from each other. The average inclination angle of the second concave-convex surface 51A is θa [°], the average spacing of the peaks of local hills of the second concave-convex surface 51A is S [μm], and the second concave-convex surface 51A is Assuming that the refractive index of the concavo-convex is N and the average distance between the first concave-convex surface 41A of the first optical film 41 and the second concave-convex surface 51A of the second optical film 51 is D [μm] At this time, the liquid crystal display element 30 satisfies the following formula (1).

D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1)

Since the second concave-convex surface 51A acts as a lens, light emitted from the light guide plate 22 of the surface light source device 20 and incident on the second optical film 51 is transmitted by the second concave-convex surface 51A. It is refracted, condensed at a certain point, and then diffused. Equation (1) above indicates that the average separation distance D between the first concave-convex surface 41A of the first optical film 41 and the second concave-convex surface 51A of the second optical film 51 is the second optical film 51 It is shown that it is equal to or less than the condensing distance in the second uneven surface 51A of . In this specification, "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 uneven surface constituting the first uneven surface in the thickness direction of the liquid crystal display element. It shall mean the average of the distances from the bottom of the concave part to the bottom of the concave part of the concavo-convex part constituting the second concave-convex surface.

The formula (1) is derived as follows.

Fig. 2 is a schematic diagram illustrating a concavo-convex shape in order to easily explain the calculation method of the convergence distance on the concavo-convex surface. First, concavo-convex parts 81 and 82 having concavo-convex surfaces 81A and 82A spaced apart from each other as shown in FIG. 2 are assumed. Further, the concavo-convex portions 81 and 82 are arranged so that the concavo-convex surfaces 81A and 82A are outward from each other. When the average angle of inclination of the concave-convex surface 82A located on the light incident side is θa, the average spacing of the peaks of local peaks of the concave-convex surface 82A is S, and light is incident on the concave-convex surface 82A and is refracted. Let ψ be the angle of refraction of light, the refractive index of the concave-convex portion 82 be N, the condensing distance F, and the average separation distance between concave-convex surfaces D. The average spacing S of the peaks of the local peaks of the concave-convex surface 82A can be regarded as the average width of the convex portions.

In Fig. 2, it appears that the light L is incident on the valley where the concavo-convex portion 82 does not exist. It is slightly out of position from

First, from Snell's law, the following formula (3) holds. And when following formula (3) is modified, following formula (4) is obtained.

sinθa/sinψ=N (3)

ψ=sin ^-1 ((sinθa)/N) (4)

On the other hand, in FIG. 2, the following formula (5) holds.

φ=θa-ψ (5)

Therefore, when the above formula (4) is substituted for ψ in the above formula (5), the following formula (6) is obtained.

φ=θa-sin ^-1 ((sinθa)/N) (6)

On the other hand, from Fig. 2, the condensing distance F is expressed by the following formula (7).

F=S/(2×tanφ) (7)

When the expression (6) is substituted for φ in the expression (7), the following expression (8) is obtained.

F=S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (8)

Therefore, when the average separation distance D between the uneven surfaces 81A and 82A is equal to or less than the condensing distance F, the above expression (1) is obtained.

The average separation distance D between the first concave-convex surface 41A and the second concave-convex surface 51A is preferably 200 μm or more and 10000 μm or less from the viewpoint of ultra-light weight and manufacturing yield of the liquid crystal display device.

Surprisingly, the present inventors found that the first uneven surface and the second uneven surface have the same shape, and the first uneven surface has the same refractive index as the uneven constituting the first uneven surface and the second uneven surface. When the first optical film having the first concave-convex surface and the second optical film having the second concave-convex surface are disposed so that the average separation distance D between the concave-convex surface and the second concave-convex surface satisfies Equation (1), the first concave-convex surface It was found that continuous diffusion characteristics were obtained regardless of the positional relationship between the concavo-convex and the concavo-convex on the second concavo-convex surface.

Specifically, in the case where the two uneven surfaces have the same shape and the uneven surfaces constituting the uneven surfaces have the same refractive index, when the average separation distance between the uneven surfaces is less than or equal to the condensing distance, and in the case of exceeding the condensing distance , As a result of simulating the diffusion state of the light emitted from the concave-convex surface on the emission side, as shown in FIG. That is, when the above expression (1) is not satisfied, light is divided and emitted from the uneven surface 91 depending on the positional relationship between the uneven surface 91 and the uneven surface 92. may be thrown away. It is considered that, because of the divided and emitted light, continuous diffusion characteristics cannot be obtained, and luminance non-uniformity occurs. In contrast, as shown in (a) and (b) of FIG. 3 , when the average separation distance D between the uneven surface 91 and the uneven surface 92 is equal to or less than the light condensing distance F, in the uneven surface 91 Even if there is any positional relationship between the concavo-convex surface and the concavo-convex surface 92, the light emitted from the concave-convex surface 91 is emitted undivided. Accordingly, when the average separation distance between the first and second uneven surfaces is equal to or less than the converging distance, that is, when the above formula (1) is satisfied, the unevenness on the first uneven surface and the unevenness on the second uneven surface Regardless of this positional relationship, since the light is not divided and emitted from the 1st concavo-convex surface of the 1st optical film, it is thought that a continuous diffusion characteristic is acquired.

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 ((sinθmax)/N))) (2)

Since the average inclination angle θa is the average inclination angle of the uneven surface, there are irregularities having an inclination angle smaller than θa or irregularities having an inclination angle greater than θa among the uneven surfaces. For irregularities having an inclination angle larger than θa, the converging distance becomes 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 irregularities have a light-converging distance equal to or longer than the average separation distance between the first uneven surface and the second uneven surface. It is also assumed that there are those having a short condensing distance. On the other hand, since θmax is the maximum inclination angle of the concave-convex surface, the condensing distance is the shortest. Therefore, by satisfying the above expression (2), the convergence distance of all the concavo-convex surfaces in the second concave-convex surface 51A is reduced between the first concave-convex surface 41A of the first optical film 41 and the second optical film 51 There is no possibility of becoming shorter than the average separation distance D of the second concavo-convex surface 51A of ). Therefore, brightness nonuniformity can be suppressed more.

θmax is obtained, for example, by measuring the surface shape of the uneven surface and analyzing the data obtained therefrom. As a device for measuring the surface shape, a contact type surface roughness meter or a non-contact type surface roughness meter (for example, an interference microscope, a confocal microscope, an atomic force microscope, etc.) is exemplified. Among these, an interference microscope is preferable from the point of simplicity of measurement. As such an interference microscope, the "NewView" series by Zygo, etc. are mentioned.

The maximum inclination angle θmax of the first concave-convex surface 41A and the second concave-convex surface 51A is preferably 0.5° or more and 15° or less from the viewpoint of suppressing projection and also suppressing color fading.

As for all haze values of the 1st optical film 41 and the 2nd optical film 51, 0 % or more and 40 % or less are preferable. Moreover, as for the internal haze value of the 1st optical film 41 and the 2nd optical film 51, 0 % or more and 30 % or less are preferable. 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 this embodiment, since functional layers, such as a low refractive index layer, are not provided on the uneven layers 45 and 55 as mentioned later, the total haze value and internal haze of the 1st optical film 41 The value is a value measured using the first optical film 41 including the light-transmitting substrate 44 and the concave-convex layer 45 . In addition, 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 the optical film including the light-transmitting substrate, the concavo-convex layer, and the functional layer. It is a value measured using a 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 Shikisai Kijutsu Genkyujo). Specifically, using a haze meter, the total haze value of the 1st optical film and the 2nd optical film is measured according to JISK7136. In addition, internal haze value is calculated|required as follows. On the surface of the concavo-convex layer of the first optical film, a resin having a refractive index equivalent to that of the resin forming the concavo-convex surface or having a refractive index difference of 0.02 or less with the resin is dried by wire to have a film thickness of 8 μm, that is, a completely concavo-convex shape of the concavo-convex surface. It is applied so that the film thickness disappears and the surface becomes flat, and after drying at 70° C. for 1 minute, the applied resin is irradiated with 100 mJ/cm 2 ultraviolet rays to cure the resin. As a result, irregularities existing on the surface of the first optical film are crushed, and a film having a flat surface is obtained. However, when a leveling agent or the like is contained in the composition for forming the concavo-convex layer having the concavo-convex shape, when the resin applied to the surface of the concavo-convex layer is easily repelled and difficult to wet, the surface of the concavo-convex layer is subjected to saponification treatment (2 mol) in advance. After immersing in /L NaOH (or KOH) solution at 55 ° C for 3 minutes, washing with water, completely removing water droplets with Kimwipe (registered trademark) or the like, and then drying in an oven at 50 ° C for 1 minute) to perform hydrophilic treatment You can do it. And in this state, internal haze value is calculated|required by measuring a haze value according to JISK7136 using a haze meter (HM-150, manufactured by Murakami Shikisai Kijutsu Genkyuso). This internal haze does not take account of the concavo-convex shape of the surface of the first optical film or the anti-glare film.

As for the surface haze value of the 1st optical film 41 and the 2nd optical film 51, 0 % or more and 20 % or less are preferable. The surface haze value is derived only from the concavo-convex shape of the surface of the first optical film or the second optical film, and by subtracting the internal haze value from the total haze value, the first optical film or the second optical film The surface haze value resulting only from the concavo-convex shape of the surface is obtained.

The first optical film 41 is provided on a light transmissive substrate 44 and an observer side of the light transmissive substrate 44 (a side opposite to the liquid crystal cell 60 side), and further includes a concavo-convex layer 45 having a concavo-convex surface. ) is provided. The second optical film 51 is provided on the light transmissive substrate 54 and 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 further forms a concavo-convex surface. It is provided with the uneven layer 55 which has.

In this embodiment, since no functional layer such as a low refractive index layer is provided on the uneven layers 45 and 55, the uneven surface of the uneven layer 45 is the first uneven surface of the first optical film 41 ( 41A), and the uneven surface of the uneven layer 55 becomes the 2nd uneven surface 51A of the 2nd optical film 51.

A "functional layer" is a layer intended to exhibit a certain function in an optical film, specifically, a layer for exhibiting functions such as antireflection, antistatic, or antifouling properties is exemplified. can The functional layer may be a single layer or a laminate of two or more layers.

((light transmissive substrate))

The light-transmitting substrates 44 and 54 are not particularly limited as long as they have light-transmitting properties, and examples include cellulose acylate substrates, cycloolefin polymer substrates, polycarbonate substrates, acrylate-based polymer substrates, polyester substrates, Or a glass base material is mentioned.

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 containing 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 (such as bisphenol A) and aliphatic polycarbonate substrates such as diethylene glycol bisallyl carbonate.

Examples of the acrylate-based polymer substrate include polymethyl (meth)acrylate substrates, polyethyl (meth)acrylate substrates, and methyl (meth)acrylate-butyl (meth)acrylate copolymer substrates.

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.

As a glass base material, glass base materials, such as soda lime silica glass, borosilicate glass, and non-alkali glass, are mentioned, for example.

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

In addition to pure triacetyl cellulose, as the triacetyl cellulose base material, a component other than acetic acid may be used in combination as a fatty acid that forms an ester with cellulose, such as cellulose acetate propionate or cellulose acetate butyrate. Further, other cellulose lower fatty acid esters such as diacetyl cellulose, or various additives such as plasticizers, ultraviolet absorbers, and lubricants may be added to these triacetyl celluloses as needed.

A cycloolefin polymer substrate is preferable in terms of excellent retardation and heat resistance, and a polyester substrate is preferable in terms of mechanical properties and heat resistance.

The thickness of the light-transmitting substrates 44 and 54 is not particularly limited, but may be 5 μm or more and 1000 μm or less, and the lower limit of the thickness of the light-transmitting substrates 44 and 54 is 15 μm from the viewpoint of handling properties and the like. More than that is preferable, and 25 micrometers or more are more preferable. 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.

((Convex-convex layer))

The concavo-convex layers 45 and 55 are layers having concavo-convex surfaces. The uneven layer 45 is a layer that exhibits anti-glare properties and light-diffusing properties. The uneven layer 55 is a layer that exhibits light-diffusing properties. In addition to these functions, the uneven layers 45 and 55 perform other functions. It may be a layer that exhibits. Specifically, the concavo-convex layer 45 exhibits anti-glare properties and light diffusion properties, and may also be a layer that exhibits functions such as hard coating properties, antireflection properties, antistatic properties, or antifouling properties, for example. Similarly, the concavo-convex layer 55 may be a layer that exhibits functions such as hard coating properties, antireflection properties, antistatic properties, or antifouling properties, for example, while exhibiting light diffusing properties.

When the uneven layers 45 and 55 are layers that exhibit hard coating properties in addition to anti-glare properties, the uneven layers 45 and 55 are subjected to a pencil hardness test (load of 4.9 N) specified by JISK5600-5-4 (1999). has a hardness of "H" or higher.

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

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

(cured product of curable resin precursor)

The "curable resin precursor" in this specification means a resin precursor in which the resin precursor has ionizing radiation curability or thermosetting properties and becomes a resin by ionizing radiation curing or thermal curing. Resin may contain solvent drying type resin other than the hardened|cured material of curable resin precursor. An ionizing radiation curable resin precursor having ionizing radiation curability has at least one ionizing radiation polymerizable functional group.

The "functional group polymerizable by ionizing radiation" in the present specification is a functional group capable of undergoing a polymerization reaction by irradiation with ionizing radiation. As an ionizing radiation polymerizable functional group, ethylenic double bonds, such as a (meth)acryloyl group, a vinyl group, and an allyl group, are mentioned, for example. In addition, the "(meth)acryloyl group" in this specification is the meaning containing both a "acryloyl group" and a "methacryloyl group." In addition, as ionizing radiation irradiated when curing the ionizing radiation curable resin precursor, it means having an energy quantum capable of polymerizing or crosslinking molecules among electromagnetic waves or charged particle beams, and usually, ultraviolet rays (UV) or electron beams (EB ) is used, but in addition, electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion beams can also be used. A 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, and these can be appropriately adjusted and used. As the ionizing radiation curable resin precursor, a combination of an ionizing radiation polymerizable monomer, an ionizing radiation polymerizable oligomer or an ionizing radiation polymerizable prepolymer is preferable.

･Ionizing radiation polymerizable monomer

An 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 (ie, bifunctional) or more ionizing radiation polymerizable functional groups 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, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, neopentyl glycol di(meth)acrylate ) Acrylates, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaeryth Litoldeca(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, adamantyldi(meth)acrylate, isoboronyldi(meth)acrylate, dicyclopentanedi(meth)acrylate, tricyclodecanedi(meth) Acrylate, ditrimethylolpropane tetra(meth)acrylate, and what modified|denatured these with PO, EO, etc. are mentioned.

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

･Ionizing radiation polymerizable oligomer

The ionizing radiation polymerizable oligomer has a weight average molecular weight of 1000 or more and less than 10000.

As the ionizing radiation polymerizable oligomer, a bifunctional or higher polyfunctional oligomer 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 rate, isocyanurate (meth)acrylate, epoxy (meth)acrylate, etc. are mentioned.

･Ionizing radiation polymerizable prepolymer

The ionizing radiation polymerizable polymer has a weight average molecular weight of 10000 or more, and the weight average molecular weight is preferably 10000 or more and 80000 or less, more preferably 10000 or more and 40000 or less. When the weight average molecular weight exceeds 80000, the viscosity is high, so the coating suitability is reduced, and there is a possibility that the appearance of the obtained optical laminate is 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 resins, urea resins, diallylphthalate resins, melamine resins, guanamine resins, unsaturated polyester resins, polyurethane resins, epoxy resins, aminoalkyd resins, and melamine-urea. Respective precursors, such as a cocondensation resin, a silicon resin, and a polysiloxane resin, are mentioned.

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

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

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

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

The composition for the concave-convex layer contains at least the curable resin precursor. In addition, you may add a solvent and a polymerization initiator to the composition for uneven layers as needed. In addition, in the composition for the concave-convex layer, according to the purpose of increasing the hardness of the concavo-convex layer, suppressing curing shrinkage, or controlling the refractive index, conventionally known dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, anti-coloring agents , a colorant (pigment, dye), an antifoaming agent, a leveling agent, a flame retardant, an ultraviolet absorber, an adhesion imparting agent, a polymerization inhibitor, an antioxidant, a surface modifier, a lubricant, and the like may be added.

(solvent)

The purpose of the solvent is to adjust the viscosity of the composition for the concave-convex layer so as to facilitate application of the composition for the concave-convex layer, to adjust the evaporation rate or dispersibility to fine particles, and to adjust the degree of aggregation of the concave-convex layer during formation of the concave-convex layer to form a predetermined concave-convex surface. It can be used for the purpose of making it easy to form. As the solvent, for example, alcohol (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.), cellosolves (methyl cellosolve, ethyl cellosolve, butyl cellosolve, etc.), cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide, dimethyl acetamide etc.), etc. can be exemplified, 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 upon light irradiation. The polymerization initiator is not particularly limited, and known ones can be used, and specific examples thereof include acetophenones, benzophenones, Michler's benzoyl benzoate, α-amyloxime esters, thioxanthones, and propiope. Rice paddies, benzyls, benzoins, and acylphosphine oxides are exemplified. Moreover, it is preferable to mix and use a photosensitizer, 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 having a radically polymerizable unsaturated group, it is preferable to use acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. alone or in combination. do.

It is preferable that content of the polymerization initiator in the composition for uneven layers is 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. Curing inhibition can be suppressed by making content of a polymerization initiator into this range.

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

(leveling agent)

As the leveling agent, for example, silicone oil, fluorine-based surfactant, etc. are preferable from the viewpoint of avoiding the concavo-convex layer from becoming a Barnard cell structure. When a resin composition containing a solvent is applied and dried, a difference in surface tension or the like occurs between the surface and inner surface of the coating film, thereby causing a large number of convection currents in the coating film. The structure generated by this convection is called a Bernard cell structure, and causes problems such as orange peel and coating defects in the concave-convex layer formed.

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

After the composition for the concavo-convex layer is applied between the light-transmitting substrates 44 and 54 and the mold, the composition for the concavo-convex layer on the coating film is irradiated with light such as ultraviolet rays to polymerize (crosslink) the curable resin precursor, thereby curing the composition for the concavo-convex layer. And the uneven layers 45 and 55 are formed by releasing the hardened|cured material of the composition for uneven layers.

As the light for curing the composition for the concave-convex layer, when ultraviolet rays are used, ultraviolet rays emitted from an ultra-high 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. In addition, 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 Walton type, van der Graf type, resonance transformer type, insulating core transformer type, linear type, dynamite type, and 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 dyed with iodine or the like and stretched, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer-based saponified film, and the like. . 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 subjected to saponification treatment in advance. It is desirable to carry out By performing a saponification process, adhesiveness becomes favorable.

<<Design method of liquid crystal display element>>

As described above, in the design method of the liquid crystal display element 30 according to the present embodiment, 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 liquid crystal cell 60 disposed therebetween and having a first concave-convex surface 41A in which the first polarizing plate 40 forms the surface 30A of the liquid crystal display element 30; , a second polarizer 42 arranged on the side of the liquid crystal cell 60 rather than the first optical film 41, and the second polarizing plate 50 constituting the rear surface 30B of the liquid crystal display element 30. In the liquid crystal display element 30 provided with the 2nd optical film 51 which has the uneven surface 51A, and the 2nd polarizer 52 arrange|positioned rather than the 2nd optical film 51 to the liquid crystal cell 60 side , The concavo-convex constituting the first concave-convex surface 41A and the concavo-convex constituting the second concave-convex surface 51A have the same refractive index, and the first 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 [°], the average spacing of the peaks of local hills of the second concave-convex surface 51A is S [μm], and the second concave-convex surface 51A is When the refractive index of the irregularities 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 satisfies the following formula (1) Liquid crystal This is a method of designing the display element 30 .

D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1)

When the maximum inclination angle of the second uneven surface 51A is θmax[°], it is preferable to design the liquid crystal display element 30 so that the average separation distance D satisfies the following formula (2).

D≤S/(2×tan(θmax-sin ^-1 ((sinθmax)/N))) (2)

According to this embodiment, the 1st uneven surface 41A and the 2nd uneven surface 51A have the same shape, and the unevenness which comprises the 1st uneven surface 41A and the unevenness which comprises the 2nd uneven surface 51A are In the case of having the same refractive index, since the average separation distance D between the first uneven surface 41A and the second uneven surface 51A satisfies the above formula (1), from the above reason, the first uneven surface 41A ) and the unevenness of the second uneven surface 51A, no matter what positional relationship there is, continuous diffusion characteristics can be obtained. In this way, luminance non-uniformity can be suppressed.

According to this embodiment, since the 2nd optical film 51 is arrange|positioned on the back surface 30B of the liquid crystal display element 30, the scratch resistance in the back surface 30B of the liquid crystal display element 30 can be improved. there is.

According to this embodiment, since the second optical film 51 having the second uneven surface 51A is disposed on the back surface 30B of the liquid crystal display element 30, interference fringes caused by the surface light source device 20 Even when , interference fringes can be made invisible. Here, even when the first optical film having the first concavo-convex surface is disposed on the surface of the liquid crystal display element and the second optical film having the second concavo-convex surface is not disposed on the back surface of the liquid crystal display element, the first concavo-convex surface Since video light can be diffused in , it is possible to attenuate the interference fringe, but the arrangement of the second optical film in addition to the first optical film diffuses the video light more than the case of only the first optical film. let it In this way, the interference fringes can be made invisible.

Example

In order to explain this invention in detail, it demonstrates by giving an Example below, but this invention is not limited to these description.

<Example 1>

First, in order to simplify and simulate the liquid crystal display element described in the above embodiment, an optical film in which the surface was determined as the first uneven surface and the back surface became the second uneven surface was designed. Specifically, the average inclination angle θa of the first uneven surface and the second uneven surface is each set to 3°, the local average interval S between the first uneven surface and the second uneven surface is each set to 50 μm, and the first uneven surface is set to and the arithmetic mean roughness Ra of the second uneven surface were each set to 0.3 μm, and the refractive indexes of the irregularities constituting the first uneven surface and the second uneven surface were each 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, while changing the position of the second uneven surface relative to the first uneven surface. , the diffusion characteristics of the light emitted from the first uneven surface were simulated. Here, “0%” in FIGS. 5 and 6 indicates the case where the position of the concavo-convex on the second concave-convex surface with respect to the concavo-convex on the first concavo-convex surface completely coincides in the thickness direction of the optical film. As shown, "20%", "40%", "60%", and "80%" indicate the position of the unevenness on the second uneven surface relative to the unevenness on the first uneven surface in the thickness direction of the optical film. 20%, 40%, 60%, and 80% are shown, and "100%" indicates the position of the unevenness on the second uneven surface relative to the unevenness on the first uneven surface of the optical film. The case where there is a complete shift in the thickness direction (the case where the center position of the convex-convex portion of the first uneven surface coincides with the position of the valley of the uneven surface on the second uneven surface) is shown. In addition, when the condensing distance at the time of making light incident on the 2nd concave-convex surface was calculated|required from said Formula (8), it was 1.404 micrometer.

<Example 2>

In Example 2, 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 0.43 times the condensing distance.

<Example 3>

In 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 set to 0.71 times the condensing distance.

<Example 4>

In 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 set to 1.00 times the condensing distance.

<Comparative Example 1>

In Comparative Example 1, 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 1.29 times the condensing distance.

<Comparative Example 2>

In Comparative Example 2, 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 1.57 times the condensing 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 set to 2.14 times the condensing distance.

The results are described below. Figures 5 (a) to (d) are graphs showing diffusion characteristics of the optical films of Examples 1 to 4, and Figures 6 (a) to (c) are diffusion characteristics of the optical films of Comparative Examples 1 to 3. It is a graph representing a characteristic. As shown in (a) to (c) of FIG. 6 , in Comparative Examples 1 to 3, the average separation distance between the first uneven surface and the second uneven surface is light condensing when light is incident on the second uneven surface. Since the distance was exceeded, that is, since the above (1) was not satisfied, it was confirmed that a discontinuous diffusion characteristic was observed depending on the positional relationship between the concavo-convex constituting the first concave-convex surface and the concavo-convex constituting the second concavo-convex surface. (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 all diffusion characteristics in Comparative Example 3 reference). In contrast, as shown in (a) to (d) of FIG. 5 , in Examples 1 to 4, the average separation distance between the first uneven surface and the second uneven surface is when light is incident on the second uneven surface. Since the convergence distance is equal to or less than the light condensing distance at the time, that is, since the above expression (1) is satisfied, no matter what positional relationship the concavo-convex constituting the first concave-convex surface and the concavo-convex concavity constituting the second concavo-convex surface are, continuous diffusion characteristics can be obtained. Confirmed.

10: liquid crystal display
20: surface light source device
30: liquid crystal display element
30A: surface
30B: back side
40: first polarizer
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 (6)

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,
The first polarizing plate includes a first optical film having a first uneven surface constituting a surface of the liquid crystal display element, and a first polarizer disposed on a liquid crystal cell side from the first optical film,
The second polarizing plate includes a second optical film having a second concave-convex surface forming a back surface of the liquid crystal display element, and a second polarizer disposed on a liquid crystal cell side from the second optical film,
The first concave-convex surface and the second concave-convex surface have the same shape,
The irregularities constituting the first concave-convex surface and the concavo-convex constituting the second concave-convex surface have the same refractive index,
The average inclination angle of the second concave-convex surface is θa [°], the average spacing of local peaks of the second concave-convex surface is S [μm], and the refractive index of the concavo-convex constituting the second concave-convex surface is N And, when the average separation distance between the first uneven surface and the second uneven surface is D [μm], the following formula (1) is satisfied.
D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1) The liquid crystal display device according to claim 1, wherein the following formula (2) is further satisfied when the maximum inclination angle of the second concave-convex surface is θmax[°].
D≤S/(2×tan(θmax-sin ^-1 ((sinθmax)/N))) (2) The liquid crystal display device according to claim 1 or 2, wherein S is an average spacing of local peaks of the first and second concave-convex surfaces and is 10 μm or more and 200 μm or less. A surface light source device and the liquid crystal display element according to claim 1 or 2 arranged on an observer side relative to the surface light source device, wherein the surface of the liquid crystal display element is located on the observer side, and the liquid crystal display element Characterized in that the back surface is located on the surface light source device side, the liquid crystal display device. 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,
The first polarizing plate includes a first optical film having a first uneven surface constituting a surface of the liquid crystal display element, and a first polarizer disposed on a liquid crystal cell side from the first optical film,
The second polarizing plate includes a second optical film having a second concave-convex surface forming a back surface of the liquid crystal display element, and a second polarizer disposed on a liquid crystal cell side from the second optical film,
The irregularities constituting the first concave-convex surface and the concavo-convex constituting the second concave-convex surface have the same refractive index,
The first concave-convex surface and the second concave-convex surface have the same shape,
The average inclination angle of the second concave-convex surface is θa [°], the average spacing of local peaks of the second concave-convex surface is S [μm], and the refractive index of the concavo-convex constituting the second concave-convex surface is N And, when the average separation distance between the first uneven surface and the second uneven surface is D [μm], the average separation distance D satisfies the following formula (1). Characterized in that the liquid crystal display device is designed A method for designing a liquid crystal display element.
D≤S/(2×tan(θa-sin ^-1 ((sinθa)/N))) (1) The method according to claim 5, characterized in that the liquid crystal display device is designed so that the average separation distance D also satisfies the following equation (2) when the maximum inclination angle of the second concave-convex surface is θmax[°], A design method for a liquid crystal display device.
D≤S/(2×tan(θmax-sin ^-1 ((sinθmax)/N))) (2)

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