JP2015016558A - Optical laminate, polarizing plate, manufacturing method of polarizing plate, image display unit, manufacturing method of image display unit and visibility improvement method of image display unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visibility improvement method of an image display unit capable of obtaining an image display unit having excellent antireflection performance and contrast in a bright place even in using an optical laminate equipped with a light permeable substrate having in-plane birefringence such as a polyester film.SOLUTION: A visibility improvement method of an image display unit is equipped with an optical laminate using a light permeable substrate having in-plane birefringence such as a polyester film. An absorption axis of a polarizer of the image display unit is in a horizontal direction with respect to a display screen of the image display unit. The optical laminate is arranged such that a slow axis being a direction with a larger refractive index of the light permeable substrate and a display screen of the image display unit vertical direction become parallel.

Description

The present invention relates to an optical laminate, a polarizing plate, a method for manufacturing a polarizing plate, an image display device, a method for manufacturing an image display device, and a method for improving the visibility of an image display device.

Since liquid crystal display devices have features such as power saving, light weight, and thinness, they have rapidly spread in recent years in place of conventional CRT displays.
In such a liquid crystal display device, a polarizing element is disposed on the image display surface side of the liquid crystal cell, and it is usually required to give hardness so that the polarizing element is not damaged during handling. As a plate protective film, it is a general practice to impart hardness to the image display surface by using a hard coat film in which a hard coat layer is provided on a light transmissive substrate.

Conventionally, a film made of a cellulose ester typified by triacetyl cellulose has been used as a light-transmitting substrate of such a hard coat film. This is because cellulose ester is excellent in transparency and optical isotropy, and has almost no retardation in the plane (low retardation value). Because it has little influence on the display quality of the device and has a suitable water permeability, moisture remaining in the polarizer when the polarizing plate using the optical laminate is produced can be dried through the optical laminate. It is based on advantages such as being able to.
However, the cellulose ester film has insufficient moisture resistance and heat resistance, and there is a drawback that the polarizing function such as the polarizing function and the hue is deteriorated when the hard coat film is used as a polarizing plate protective film in a high temperature and high humidity environment. It was. In addition, cellulose ester is a material that is disadvantageous in terms of cost.

From the problems of such cellulose ester film, it is excellent in transparency, heat resistance and mechanical strength, and is cheaper than cellulose ester film and easily available in the market, or can be produced by a simple method. It is desired to use a versatile film as a light-transmitting substrate of an optical laminate. For example, an attempt has been made to use a polyester film such as polyethylene terephthalate as a cellulose ester substitute film (for example, Patent Document 1). To 3).

However, the polyester film has an aromatic ring with a high polarizability in the molecular chain, so the intrinsic birefringence is extremely large, and the molecular chain is oriented by stretching to give excellent transparency, heat resistance, and mechanical strength. Along with this, birefringence is easily developed. When an optical laminate using a light-transmitting substrate having a birefringence in the surface such as a polyester film is installed on the surface of an image display device, the antireflection performance on the surface of the optical laminate is remarkably high. In some cases, the photopic contrast may be lowered.

JP 2004-205773 A JP 2009-157343 A JP 2010-244059 A

In view of the above situation, the present invention provides an image display device excellent in antireflection performance and bright contrast even when a light-transmitting base material having a birefringence index in a plane such as a polyester film is used. Optical laminate and polarizing plate, method for producing the polarizing plate, image display device provided with the optical laminate or polarizing plate, method for producing the image display device, and bright place contrast were improved An object of the present invention is to provide a method for improving the visibility of an image display device.
In the present invention, the “state in which the bright place contrast is improved” means a state in which the antireflection performance and the bright place contrast are excellent.

The present invention is an optical laminate having a light-transmitting base material having a birefringence index in the plane and used on the surface of an image display device, wherein the light-transmitting base material has a high refractive index. The slow axis that is the direction is arranged in parallel with the vertical direction of the display screen of the image display device, and the absorption axis of the polarizer of the image display device is the horizontal direction with respect to the display screen. It is an optical laminate.
The optical layered body of the present invention preferably has an optical functional layer on one surface of the light transmissive substrate.
The light-transmitting substrate has a refractive index (nx) in the slow axis direction, which is a direction in which the refractive index is large, and a refractive index (ny) in the fast axis direction, which is a direction orthogonal to the slow axis direction. The difference (nx−ny) is preferably 0.01 or more.
When the refractive index in the slow axis direction of the light-transmitting substrate is (nx) and the refractive index in the fast axis direction that is a direction orthogonal to the slow axis direction is (ny), the optical functional layer Is preferably less than (nx + ny) / 2.
The light-transmitting substrate is preferably a substrate made of polyester, and the polyester is preferably polyethylene terephthalate or polyethylene naphthalate.
The optical layered body of the present invention has a primer layer between the light transmissive substrate and the optical functional layer, and the refractive index (np) of the primer layer is the slow phase of the light transmissive substrate. When the refractive index (nx) in the axial direction is larger than the refractive index (nf) of the optical functional layer (np> nx, nf), or the refractive index (np) of the primer layer is the light-transmitting substrate When the refractive index (ny) in the fast axis direction is smaller than the refractive index (nf) of the optical functional layer (np <ny, nf), the thickness of the primer layer is preferably 3 to 30 nm.
The optical layered body of the present invention has a primer layer between the light transmissive substrate and the optical functional layer, and the refractive index (np) of the primer layer is the slow phase of the light transmissive substrate. When the refractive index (nx) is larger than the refractive index (nx) in the axial direction and smaller than the refractive index (nf) of the optical functional layer (nx <np <nf), or the refractive index (np) of the primer layer is When the refractive index in the fast axis direction of the conductive substrate is smaller than the refractive index (ny) and larger than the refractive index (nf) of the optical functional layer (nf <np <ny), the primer layer has a thickness of 65 to 125 nm. Preferably there is.
The optical layered body of the present invention has a primer layer between the light transmissive substrate and the optical functional layer, and the refractive index (np) of the primer layer is a phase advance of the light transmissive substrate. It preferably exists between the refractive index (ny) in the axial direction and the refractive index (nx) in the slow axis direction of the light-transmitting substrate (ny <np <nx).

Further, the present invention is a polarizing plate in which an optical laminate having a light-transmitting base material having a birefringence index in a plane is provided on a polarizing element and used on a surface of an image display device, The absorption axis of the polarizing element is a left-right direction with respect to the display screen of the image display device, and the optical laminate and the polarizing element are slow phases in which the refractive index of the light-transmitting substrate is large. The slow axis, which is the direction in which the refractive index of the light transmissive substrate is large, is parallel to the vertical direction of the display screen of the image display device. It is also the polarizing plate characterized by being arrange | positioned.
The polarizing plate of the present invention preferably has an optical functional layer on one surface of the light transmissive substrate.
In the polarizing plate of the present invention, the light-transmitting substrate having a birefringence in the plane has a refractive index (nx) in the slow axis direction that is a direction in which the refractive index is large, and the slow axis direction. The difference (nx−ny) from the refractive index (ny) in the fast axis direction, which is the orthogonal direction, is preferably 0.01 or more.
In the polarizing plate of the present invention, the refractive index in the slow axis direction of the light transmissive substrate is (nx), and the refractive index in the fast axis direction which is a direction orthogonal to the slow axis direction is (ny). The refractive index of the optical functional layer is preferably less than (nx + ny) / 2.
The polarizing plate of the present invention has a primer layer between the light transmissive substrate and the optical functional layer, and the refractive index (np) of the primer layer is the slow axis of the light transmissive substrate. When the refractive index (nx) in the direction is larger than the refractive index (nf) of the optical functional layer (np> nx, nf), or the refractive index (np) of the primer layer is When the refractive index in the fast axis direction (ny) is smaller than the refractive index (nf) of the optical function layer (np <ny, nf), the primer layer preferably has a thickness of 3 to 30 nm.
The polarizing plate of the present invention has a primer layer between the light transmissive substrate and the optical functional layer, and the refractive index (np) of the primer layer is the slow axis of the light transmissive substrate. When the refractive index (nx) is larger than the refractive index (nx) in the direction and smaller than the refractive index (nf) of the optical functional layer (nx <np <nf), or the refractive index (np) of the primer layer is the light transmitting property. When the refractive index (ny) in the fast axis direction of the substrate is smaller than the refractive index (nf) of the optical function layer (nf <np <ny), the primer layer has a thickness of 65 to 125 nm. It is preferable.
The polarizing plate of the present invention has a primer layer between the light transmissive substrate and the optical functional layer, and the refractive index (np) of the primer layer is the fast axis of the light transmissive substrate. It is preferable to exist between the refractive index (ny) in the direction and the refractive index (nx) in the slow axis direction of the light transmissive substrate (ny <np <nx).

The present invention is also an image display device comprising the optical laminate of the present invention or the polarizing plate of the present invention.
The image display device of the present invention is preferably a VA mode or IPS mode liquid crystal display device.
The present invention is also a method for manufacturing an image display device including an optical laminate having a light-transmitting substrate having a birefringence index in the plane, wherein the absorption axis of the polarizer of the image display device is the image. The slow axis that is the left-right direction with respect to the display screen of the display device and the direction in which the refractive index of the light-transmitting substrate is large, and the vertical direction of the display screen of the image display device are parallel to each other. It is also a method for manufacturing an image display device, comprising a step of arranging the optical laminate.
The present invention is also a method for improving the visibility of an image display device comprising an optical laminate having a light-transmitting substrate having a birefringence index in the plane, wherein the absorption axis of the polarizer of the image display device is The slow axis, which is the left-right direction with respect to the display screen of the image display device and the direction in which the refractive index of the light-transmitting substrate is large, and the vertical direction of the display screen of the image display device are parallel to each other. In addition, this is a method for improving the visibility of an image display device, wherein the optical layered body is disposed.
The present invention is described in detail below.
In the present invention, unless otherwise specified, curable resin precursors such as monomers, oligomers, and prepolymers are also referred to as “resins”.

As a result of intensive studies, the present inventors have found that in an optical laminate or polarizing plate using a light-transmitting substrate having a birefringence in the surface, the optical laminate or polarizing plate is installed in an image display device. In addition, the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, is set to a specific direction with respect to the absorption axis of the polarizing element or the display screen of the image display device, thereby preventing reflection. In addition, the present inventors have found that an image display device with excellent bright place contrast can be obtained, and have completed the present invention. In addition, the film which consists of a cellulose ester represented by the triacetyl cellulose conventionally used as an optical laminated body as mentioned above is excellent in optical isotropy, and has almost no phase difference in a surface. For this reason, in the case of the optical laminated body or polarizing plate which used the film which consists of this cellulose ester as a light transmissive base material, it was not necessary to consider the installation direction of this light transmissive base material. That is, the above-described problems of antireflection performance and bright contrast are caused by using a light-transmitting substrate having a birefringence in the plane as the light-transmitting substrate of the optical laminate.
Here, when the liquid crystal display device is observed through polarized sunglasses, there is a problem that the visibility is lowered depending on the angle formed by the absorption axis of the polarizer on the liquid crystal display device side and the absorption axis of the polarized sunglasses. As a method for improving the visibility, a light-transmitting base material having a birefringence in-plane, such as a λ / 4 retardation film, is provided on the observer side further than the polarizer on the observer side of the liquid crystal display device. It is known. This is because the transmitted light intensity observed under crossed nicols is expressed by the following equation, where θ is the angle formed between the absorption axis of the polarizer and the slow axis of the light-transmitting substrate having a birefringence in-plane. This is a method for controlling the value represented by.
I = I0 · sin ² (2θ) · sin ² (π · Re / λ)
In the above formula, I is the intensity of light transmitted through crossed Nicols, I0 is the intensity of light incident on a light-transmitting substrate having a birefringence in-plane, λ is the wavelength of light, and Re is retardation.
Although sin ² (2θ) takes a value of 0 to 1 depending on the value of θ, in the case of the visibility improving method when observed through polarized sunglasses, the intensity of transmitted light is set to a large value. , Sin ² (2θ) = 1 so that θ is 45 ° in many cases.
However, as described above, the optical layered body of the present invention is an invention made on the basis of a technical idea completely different from that for the conventional polarized sunglasses according to the above formula.

The optical layered body of the present invention has a light-transmitting base material having a birefringence index in the plane and is used by being disposed on the surface of an image display device. The light-transmitting base material has a refractive index of A slow axis that is a large direction is arranged in parallel with the vertical direction of the display screen of the image display device.
Here, since the image display device is normally installed and used indoors, reflection of light reflected from the wall surface or floor surface on the display screen (the surface of the optical laminate) of the image display device is prevented. By doing so, the antireflection performance can be made excellent.
FIG. 1 is an image diagram of light reflected from a wall surface or a floor surface entering a display screen of an image display device. As shown in FIG. 1, the present inventors reflect random light emitted from a light source 10 such as a fluorescent lamp on the wall surface or floor surface, enter the display screen 11 of the image display device, and brighten the light. The reflected light that lowers the contrast and causes a reduction in visibility is mostly light that vibrates in the left-right direction of the display screen 11 (light with a more remarkable Brewster angle, S-polarized light). Since the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, is arranged in parallel with the vertical direction of the display screen of the image display device, the optical layered body of the present invention is arranged. is there. That is, the optical layered body of the present invention is limited to those for use on the surface of the image display device, and the image display device provided with the optical layered body of the present invention has the refractive index of the light-transmitting substrate. The slow axis, which is the direction in which the current is large, is in a state in which it is oriented in a direction perpendicular to the vibration direction of the many lights reflected on the wall surface and floor surface. Thus, the image display device in which the optical layered body is installed so that the direction of the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, becomes a specific direction, has antireflection performance and bright place contrast. It will be excellent.
This is because, in the image display device having the configuration in which the optical layered body of the present invention is arranged in the specific state described above, the light transmission with respect to light (S-polarized light) that vibrates in the left-right direction with a large proportion of incidence on the display screen. This is because the direction of the fast axis, which is the direction in which the refractive index of the conductive substrate is small, becomes parallel, and external light reflection at the outermost surface can be reduced.
The reason for this is that the reflectance R of the substrate surface having a refractive index of N is:
R (%) = (N−1) ² / (N + 1) ²
In the base material having refractive index anisotropy such as the light-transmitting base material in the optical layered body of the present invention, the refractive index N is set as follows in the image display device. This is because the rate at which the refractive index of the fast axis with a small refractive index is applied increases.
In addition, for the above reasons, the optical layered body is installed without considering the arrangement direction to the image display device, despite the optical layered body using the light-transmitting base material having the in-plane retardation. As in the present invention, when the optical laminate is installed so that the direction of the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, is a specific direction, the reflectance in the latter case is It is lower than the former reflectance. The “state with excellent antireflection performance” in the present invention refers to such a state.
The contrast of the image display device is divided into a dark place contrast and a bright place contrast. The dark place contrast is calculated as (brightness of white display / brightness of black display), and the bright place contrast is {(white display brightness). Luminance + external light reflection) / (black display luminance + external light reflection)}. In any case of contrast, the influence of the denominator becomes larger and the contrast is lowered. That is, if the external light reflection at the outermost surface can be reduced, the bright place contrast is improved as a result.
The above-mentioned "the slow axis that is the direction in which the refractive index of the light transmissive substrate is large is arranged in parallel with the vertical direction of the display screen of the image display device" means that the slow axis is the above It means a state in which the optical laminated body is arranged on the image display device in the range of 0 ° ± 40 ° with respect to the vertical direction of the display screen.
In the optical layered body of the present invention, the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is preferably 0 ° ± 30 °, and is 0 ° ± 10 °. More preferably, 0 ° ± 5 ° is even more preferable. In the optical laminate of the present invention, the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is 0 ° ± 40 °, so that the contrast of the bright place by the optical laminate of the present invention is increased. Improvements can be made.
In the optical layered body of the present invention, the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is most preferably 0 ° from the viewpoint of improving the bright place contrast. For this reason, the angle between the slow axis of the light transmissive substrate and the vertical direction of the display screen is preferably 0 ° ± 30 °, more preferably 0 °, rather than 0 ° ± 40 °. ° ± 10 °. Furthermore, when the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is 0 ° ± 5 °, the bright contrast can be improved to the same level as when the angle is 0 °. This is more preferable.
In this specification, regarding the angle formed by the two axes, the angle formed clockwise with respect to the reference angle is plus (+) as viewed from the observer side, and is counterclockwise with respect to the reference angle. The angle formed is minus (−). When an angle is indicated without particular notation, it means a case where the angle is clockwise with respect to a reference angle (that is, a case where the angle is positive).

Moreover, in the optical laminated body of this invention, the absorption axis of the polarizer of the said image display apparatus is a left-right direction with respect to the said display screen.
As described above, it is possible to reduce reflection in the optical laminate of the present invention of light (S-polarized light) that vibrates in the left-right direction with a large proportion of incidence on the display screen of the image display device. S polarized light will be transmitted. Usually, the transmitted S-polarized light is absorbed inside the image display apparatus, but there is very little light returning to the observer side. However, in the optical layered body of the present invention, since the absorption axis of the polarizer is in the horizontal direction with respect to the display screen, S-polarized light transmitted through the optical layered body of the present invention can be absorbed, and more observation is performed. The light returning to the person side can be reduced, and as a result, the display image can be made more excellent.
Note that “the absorption axis of the polarizer of the image display device is in the horizontal direction with respect to the display screen” means that the absorption axis is in the range of 0 ° ± 40 ° with respect to the horizontal direction of the display screen. Means that the polarizer is disposed in the image display device.
In the optical layered body of the present invention, the angle between the absorption axis of the polarizer and the horizontal direction of the display screen is preferably 0 ° ± 30 °, and more preferably 0 ° ± 10 °. 0 ° ± 5 ° is more preferable. In the optical layered body of the present invention, the above-described effects can be obtained when the angle between the absorption axis of the polarizer and the left-right direction of the display screen is 0 ° ± 40 °.

The light-transmitting substrate having a birefringence in the plane is not particularly limited, and examples thereof include a substrate made of polycarbonate, acrylic, polyester, etc. Among them, polyester that is advantageous in cost and mechanical strength. A substrate is preferred. In the following description, a light-transmitting substrate having a birefringence in the plane will be described as a polyester substrate.

It is preferable that the polyester base material has a retardation of 3000 nm or more because it can prevent the occurrence of azimuth and the visibility is extremely improved. When it is less than 3000 nm, when the optical layered body of the present invention is used in a liquid crystal display device (LCD), a rainbow-colored stripe-like pattern may be visually recognized and display quality may deteriorate. On the other hand, the upper limit of the retardation of the polyester base material is not particularly limited, but is preferably about 30,000 nm. If it exceeds 30,000 nm, the film thickness becomes considerably large, which is not preferable.
It is preferable that the retardation of the said polyester base material is 5000-25000 nm from a viewpoint of thin film formation. A more preferable range is 7000 to 20,000 nm. When the range is within this range, the optical laminate of the present invention is applied to the image display device, and the slow axis of the polyester substrate is relative to the vertical direction of the display screen. When arranged in the range of 0 ° ± 30 ° -40 °, that is, the slow axis of the polyester base material is arranged with an angle slightly shifted from the completely parallel to the vertical direction of the display screen. Even if it is done, it is possible to further improve the anti-Nizimura property. The optical layered body of the present invention has a retardation of 3000 nm or more even when the slow axis of the polyester base material is ± 30 ° to 40 ° from the complete parallel to the vertical direction of the display screen. If it is, it has Nizimura prevention property and there is no problem in practical use. However, as described above, the angle between the slow axis of the polyester base and the vertical direction of the display screen is most preferably 0 °. The angle with the direction is more preferably 0 ° ± 10 °, and further preferably 0 ° ± 5 °.

The retardation is the refractive index (nx) in the direction having the highest refractive index (slow axis direction) in the plane of the polyester substrate, and the refraction in the direction orthogonal to the slow axis direction (fast axis direction). It is represented by the following formula by the rate (ny) and the thickness (d) of the polyester base material.
Retardation (Re) = (nx−ny) × d
The retardation can be measured, for example, by KOBRA-WR manufactured by Oji Scientific Instruments (measurement angle 0 °, measurement wavelength 589.3 nm).
Further, using two polarizing plates, the orientation axis direction (principal axis direction) of the polyester substrate is obtained, and the refractive indexes (nx, ny) of two axes orthogonal to the orientation axis direction are Abbe's refractive indices. It calculates | requires by the total (NAGO-4T by Atago Co., Ltd.). Here, an axis showing a larger refractive index is defined as a slow axis. The polyester base material thickness d (nm) is measured using an electric micrometer (manufactured by Anritsu), and the unit is converted to nm. Retardation can also be calculated from the product of the refractive index difference (nx−ny) and the thickness d (nm) of the film.
In addition, a refractive index can also be measured using an Abbe refractometer and an ellipsometer, and the optical laminated body of this invention is mentioned later using a spectrophotometer (Shimadzu UV-3100PC). When having an optical functional layer, the average reflectance (R) of the optical functional layer at a wavelength of 380 to 780 nm is measured, and from the obtained average reflectance (R), the refractive index (n) A value may be obtained.
The average reflectance (R) of the optical functional layer is a surface (back surface) on which 50 μm PET without easy adhesion treatment is coated with each raw material composition to form a cured film having a thickness of 1 to 3 μm, and PET is not applied. In order to prevent back surface reflection, the average reflectance of each cured film was measured after applying a black vinyl tape (for example, Yamato vinyl tape No 200-38-21 38 mm width) having a width larger than the measurement spot area. The refractive index of the polyester base material was measured after black vinyl tape was similarly applied to the surface opposite to the measurement surface.
R (%) = (1-n) ² / (1 + n) ²
Further, as a method for measuring the refractive index of the optical functional layer after becoming an optical layered product, a cured film of each layer is scraped off with a cutter or the like to prepare a powder sample, and JIS K7142 (2008) B method (powder) Alternatively, the Becke method according to (for granular transparent materials) can be used. In the Becke method, a Cargill reagent having a known refractive index is used, the powder sample is placed on a glass slide, the reagent is dropped on the sample, and the sample is immersed in the reagent. This is observed by using a microscope, and this is a method in which the refractive index of the sample is the refractive index of the reagent in which the bright line generated in the sample outline due to the difference in refractive index between the sample and the reagent;
In the case of a polyester base material, the refractive index (nx, ny) varies depending on the direction. Therefore, instead of the Becke method, the above-mentioned black vinyl tape is applied to the treated surface of the optical functional layer, so that a spectrophotometer (V7100 type, Automatic absolute reflectance measurement unit VAR-7010 (manufactured by JASCO Corporation), polarization measurement: S-polarized light, the slow axis of the light-transmitting substrate is installed in parallel, and the fast axis is installed in parallel In this case, the reflectivity (nx, ny) of the slow axis and the fast axis can be calculated from the above formula.

In the present invention, when the polyester base material is a PET base material made of polyethylene terephthalate (PET) described later, the nx-ny (hereinafter also referred to as Δn) is 0.05 or more. Is preferred. If Δn is less than 0.05, the fast axis refractive index is large, and thus the above-described image display apparatus may not be improved in bright place contrast. Further, the film thickness necessary for obtaining the retardation value described above may be increased. On the other hand, the Δn is preferably 0.25 or less. If it exceeds 0.25, it becomes necessary to stretch the PET base material excessively, so that the PET base material is likely to be torn and torn, and the practicality as an industrial material may be significantly reduced.
From the above viewpoint, the more preferable lower limit of Δn in the case of the PET substrate is 0.07, and the more preferable upper limit is 0.20. In addition, when said (DELTA) n exceeds 0.20, the durability of the PET base material in a heat-and-moisture resistance test may be inferior. Since the durability in the wet heat resistance test is excellent, the more preferable upper limit of Δn in the case of the PET base material is 0.15.
In addition, as (nx) in the case of the said PET base material, it is preferable that it is 1.66-1.78, a more preferable minimum is 1.68, and a more preferable upper limit is 1.73. Moreover, as (ny) in the case of the said PET base material, it is preferable that it is 1.55-1.65, a more preferable minimum is 1.57 and a more preferable upper limit is 1.62.
When nx and ny are in the above-described range and satisfy the above-described relationship of Δn, it is possible to improve suitable antireflection performance and bright place contrast.
Moreover, when the said polyester base material is a PEN base material which uses the polyethylene naphthalate (PEN) mentioned later as a raw material, as for said (DELTA) n, a preferable minimum is 0.05 and a preferable upper limit is 0.30. If Δn is less than 0.05, the film thickness necessary to obtain the retardation value described above is increased, which is not preferable. On the other hand, if the above Δn exceeds 0.30, the PEN substrate tends to be torn and torn, and the practicality as an industrial material may be significantly reduced. The more preferable lower limit of Δn in the case of the PEN substrate is 0.07, and the more preferable upper limit is 0.27. This is because if Δn is smaller than 0.07, it is difficult to obtain the sufficient effect of suppressing the above-mentioned azimuth and color change. In addition, when said (DELTA) n exceeds 0.27, durability of the PEN base material in a heat-and-moisture resistance test may be inferior. Moreover, since the durability in a heat-and-moisture resistance test is excellent, a more preferable upper limit of Δn in the case of the PEN substrate is 0.25.
In addition, as (nx) in the case of the said PEN base material, it is preferable that it is 1.70-1.90, a more preferable minimum is 1.72 and a more preferable upper limit is 1.88. Moreover, as (ny) in the case of the said PEN base material, it is preferable that it is 1.55-1.75, a more preferable minimum is 1.57 and a more preferable upper limit is 1.73.

The material constituting the polyester base material is not particularly limited as long as it satisfies the retardation described above, but is synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Examples include linear saturated polyester. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene naphthalate (polyethylene-2,6-naphthalate, polyethylene-1,4-naphthalate). , Polyethylene-1,5-naphthalate, polyethylene-2,7-naphthalate, polyethylene-2,3-naphthalate) and the like. The polyester used for the polyester substrate may be a copolymer of these polyesters. The polyester is mainly used (for example, a component of 80 mol% or more), and a small proportion (for example, 20 mol% or less). It may be blended with these types of resins. Polyethylene terephthalate or polyethylene naphthalate is particularly preferable as the polyester because of good balance between mechanical properties and optical properties. In particular, it is preferably made of polyethylene terephthalate (PET). This is because polyethylene terephthalate is highly versatile and easily available. In the present invention, an optical laminate that can produce a liquid crystal display device with high display quality can be obtained even with a highly versatile film such as PET. Furthermore, PET is excellent in transparency, heat or mechanical properties, can control the retardation by stretching, has a large intrinsic birefringence, and can obtain a large retardation relatively easily even when the film thickness is small.

The method for obtaining the polyester base material is not particularly limited as long as the above-described retardation is satisfied. For example, the polyester, such as PET, as a material is melted and extruded into a sheet to form glass. The method of heat-processing after transverse stretching using a tenter etc. at the temperature more than transition temperature is mentioned.
The transverse stretching temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C. Further, the transverse draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. When the transverse draw ratio exceeds 6.0 times, the transparency of the resulting polyester base material tends to be lowered, and when the transverse draw ratio is less than 2.5 times, the draw tension becomes small. In some cases, the birefringence of the substrate becomes small, and the retardation cannot be increased to 3000 nm or more.
In the present invention, the unstretched polyester is subjected to transverse stretching under the above conditions using a biaxial stretching test apparatus, and then stretched in the flow direction with respect to the transverse stretching (hereinafter also referred to as longitudinal stretching). Also good. In this case, the longitudinal stretching preferably has a stretching ratio of 2 times or less. When the draw ratio of the above-mentioned longitudinal stretching exceeds twice, the value of Δn may not be within the preferred range described above.
The treatment temperature during the heat treatment is preferably 100 to 250 ° C, more preferably 180 to 245 ° C.
Here, the conventional polyester base material has been obtained by stretching an unstretched polyester base material in the longitudinal direction and then stretching the unstretched polyester base material in the width direction at the same degree as the longitudinal direction. However, the polyester base material obtained by such a stretching method has a problem that the bowing phenomenon easily occurs. On the other hand, the polyester base material having the retardation value in the present invention is obtained by stretching a roll-shaped unstretched light-transmitting film only in the width direction or slightly stretching in the longitudinal direction and then stretching in the width direction. Can be obtained. The polyester base material obtained in this way can suppress the occurrence of the bowing phenomenon, and its slow axis exists along the width direction.
Although the optical layered body of the present invention can be provided on a polarizing element to be a polarizing plate as will be described later, the roll-shaped polarizing element has an absorption axis along the longitudinal direction. Therefore, when the light transmissive substrate and the polarizing element are bonded together by a roll-to-roll method, the angle between the absorption axis of the polarizing element and the slow axis of the light transmissive substrate is vertical. Can be formed. The angle formed between the slow axis of the light-transmitting substrate and the absorption axis of the polarizing element will be described in detail later.

Examples of the method for controlling the retardation of the polyester substrate produced by the above-described method to 3000 nm or more include a method of appropriately setting the draw ratio, the drawing temperature, and the film thickness of the produced polyester substrate. Specifically, for example, the higher the stretching ratio, the lower the stretching temperature, and the thicker the film, the easier it is to obtain high retardation. The lower the stretching ratio, the higher the stretching temperature, and the film thickness. The thinner, the easier it is to obtain low retardation.

The thickness of the polyester substrate is preferably in the range of 40 to 500 μm. When the thickness is less than 40 μm, the retardation of the polyester base material cannot be increased to 3000 nm or more, the anisotropy of mechanical properties becomes remarkable, and tearing, tearing, and the like easily occur, and the practicality as an industrial material is remarkably reduced. Sometimes. On the other hand, if it exceeds 500 μm, the polyester base material is very rigid, the flexibility specific to the polymer film is lowered, and the practicality as an industrial material is also lowered, which is not preferable. The minimum with more preferable thickness of the said polyester base material is 50 micrometers, a more preferable upper limit is 400 micrometers, and a still more preferable upper limit is 300 micrometers.

The polyester base material preferably has a transmittance in the visible light region of 80% or more, more preferably 84% or more. In addition, the said transmittance | permeability can be measured by JISK7361-1 (The test method of the total light transmittance of a plastic-transparent material).

In the present invention, the polyester substrate may be subjected to surface treatment such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, and flame treatment without departing from the spirit of the present invention. Good.

The optical layered body of the present invention preferably has an optical functional layer on one surface of the light transmissive substrate, and the refractive index in the slow axis direction of the light transmissive substrate is (nx), When the refractive index in the fast axis direction, which is a direction orthogonal to the phase axis direction, is (ny), the refractive index of the optical functional layer is preferably less than (nx + ny) / 2. When the refractive index of the optical functional layer is (nx + ny) / 2 or more, the difference between the refractive index of the optical functional layer and the refractive index in the slow axis direction of the light transmissive substrate is the light transmissive group. Since it is smaller than the difference between the refractive index in the fast axis direction of the material, in order to obtain the effect of excellent antireflection performance and bright place contrast, the refractive index of the light-transmitting base material is the direction in which it is large. It is preferable to arrange the slow axis so as not to be parallel to the vertical direction of the display screen of the image display device but to be parallel to the horizontal direction of the display screen. In addition, a material having a refractive index of (nx + ny) / 2 or higher is generally more expensive than a material having a refractive index of less than (nx + ny) / 2, and the hardness of the optical functional layer, etc. There are also inferior characteristics.

The optical functional layer is preferably a hard coat layer having a hard coat performance, and the hard coat layer has a hardness of a pencil hardness test according to JIS K5600-5-4 (1999) (load 4.9 N). Is preferably H or more, more preferably 2H or more.
The hard coat layer is a layer that ensures the hard coat properties of the surface of the optical laminate of the present invention, and includes, for example, a hard coat containing an ionizing radiation curable resin that is a resin curable by ultraviolet rays and a photopolymerization initiator. It is preferable that it is formed using the layer composition.

In the optical layered body of the present invention, examples of the ionizing radiation curable resin include compounds having one or more unsaturated bonds, such as a compound having an acrylate functional group. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like, and ethylene oxide ( A polyfunctional compound modified with EEO), or a reaction product of the polyfunctional compound and (meth) acrylate (for example, poly (meth) acrylate ester of polyhydric alcohol). It is possible. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate.

In addition to the above compounds, polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyds having a relatively low molecular weight (number average molecular weight of 300 to 80,000, preferably 400 to 5000) having an unsaturated double bond. Resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, and the like can also be used as the ionizing radiation curable resin. The resin in this case includes all dimers, oligomers, and polymers other than monomers.
Preferred compounds in the present invention include compounds having 3 or more unsaturated bonds. When such a compound is used, the crosslink density of the hard coat layer to be formed can be increased, and the coating hardness can be improved.
Specifically, in the present invention, pentaerythritol triacrylate, pentaerythritol tetraacrylate, polyester polyfunctional acrylate oligomer (3 to 15 functional), urethane polyfunctional acrylate oligomer (3 to 15 functional) and the like are used in appropriate combination. Is preferred.

The ionizing radiation curable resin can be used in combination with a solvent-drying resin. By using the solvent-drying resin in combination, film defects on the coated surface can be effectively prevented. In addition, the said solvent dry type resin means resin which becomes a film only by drying the solvent added in order to adjust solid content at the time of coating, such as a thermoplastic resin.
The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and a thermoplastic resin can be generally used.
The thermoplastic resin is not particularly limited. For example, a styrene resin, a (meth) acrylic resin, a vinyl acetate resin, a vinyl ether resin, a halogen-containing resin, an alicyclic olefin resin, a polycarbonate resin, or a polyester resin. Examples thereof include resins, polyamide-based resins, cellulose derivatives, silicone-based resins, rubbers, and elastomers. The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoint of film forming properties, transparency, and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

Moreover, the said composition for hard-coat layers may contain the thermosetting resin.
The thermosetting resin is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea cocondensation Examples thereof include resins, silicon resins, polysiloxane resins, and the like.

The photopolymerization initiator is not particularly limited, and known ones can be used. For example, specific examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoylbenzoate, α-amylo. Examples include oxime esters, thioxanthones, propiophenones, benzyls, benzoins, and acylphosphine oxides. In addition, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine, and the like.

As the photopolymerization initiator, when the ionizing radiation curable resin is a resin system having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, etc. may be used alone or in combination. It is preferable to use it. When the ionizing radiation curable resin is a resin system having a cationic polymerizable functional group, the photopolymerization initiator may be an aromatic diazonium salt, aromatic sulfonium salt, aromatic iodonium salt, metallocene compound, benzoin sulfone. It is preferable to use acid esters alone or as a mixture.
As the initiator used in the present invention, in the case of an ionizing radiation curable resin having a radically polymerizable unsaturated group, 1-hydroxy-cyclohexyl-phenyl-ketone is compatible with the ionizing radiation curable resin, and yellow This is preferable because of little change.

The content of the photopolymerization initiator in the hard coat layer composition is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable resin. When the amount is less than 1 part by mass, the hardness of the hard coat layer in the optical laminate of the first invention may not be within the above-described range. This is because the ionizing radiation does not reach and internal curing is not promoted, and there is a risk that the pencil hardness of 3H or higher on the surface of the target hard coat layer may not be obtained.
The minimum with more preferable content of the said photoinitiator is 2 mass parts, and a more preferable upper limit is 8 mass parts. When the content of the photopolymerization initiator is in this range, a hardness distribution does not occur in the film thickness direction, and uniform hardness is likely to occur.

The hard coat layer composition may contain a solvent.
As said solvent, it can select and use according to the kind and solubility of the resin component to be used, for example, ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol etc.), ethers ( Dioxane, tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.), Halogenated carbons (dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), water, alcohols (ethanol, isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cello) Lube, ethyl cellosolve), cellosolve acetates, sulfoxides (dimethyl sulfoxide), amides (dimethylformamide, dimethylacetamide, etc.) and the like can be exemplified, it may be a mixed solvent thereof.
In particular, in the present invention, it is preferable that at least one of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or a mixture thereof is included in the ketone solvent because of excellent compatibility with the resin and coating properties.

Although it does not specifically limit as a content rate (solid content) of the raw material in the said composition for hard-coat layers, Usually, it is preferable to set it as 5-70 mass%, especially 25-60 mass%.

The hard coat layer composition increases the hardness of the hard coat layer, suppresses curing shrinkage, prevents blocking, controls the refractive index, imparts antiglare properties, and properties of particles and the surface of the hard coat layer Depending on the purpose such as changing the color, conventionally known organic, inorganic fine particles, dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, anti-coloring agents, coloring agents (pigments, dyes), A foaming agent, a leveling agent, a flame retardant, an ultraviolet absorber, an adhesion-imparting agent, a polymerization inhibitor, an antioxidant, a surface modifier, and the like may be added.
In addition, it is preferable that the organic and inorganic particles added for the purpose of imparting the antiglare property include fine particles capable of maintaining the polarization state of light incident on the optical laminate of the present invention. By using such fine particles, the light (S-polarized light) that passes through the optical laminate of the present invention and vibrates in the left-right direction with a high ratio of incidence on the display screen of the image display device is displayed on the display screen of the image display device. On the other hand, it can absorb with the polarizer in which the absorption axis was installed in the left-right direction.

Moreover, the said composition for hard-coat layers may mix and use a photosensitizer, As a specific example, n-butylamine, a triethylamine, poly-n-butylphosphine etc. are mentioned, for example.

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

Further, the method for applying the hard coat layer composition onto the light-transmitting substrate is not particularly limited, and examples thereof include a gravure coating method, a spin coating method, a dip method, a spray method, a die coating method, and a bar coating method. And publicly known methods such as a roll coater method, a meniscus coater method, a flexographic printing method, a screen printing method, and a pead coater method.

The coating film formed by applying the hard coat layer composition on the light-transmitting substrate is preferably heated and / or dried as necessary and cured by irradiation with active energy rays or the like.

Examples of the active energy ray irradiation include irradiation with ultraviolet rays or electron beams. Specific examples of the ultraviolet light source include light sources such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light fluorescent lamp, and a metal halide lamp. Moreover, as a wavelength of an ultraviolet-ray, the wavelength range of 190-380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type.

In addition, since the preferable film thickness (at the time of hardening) of the said hard-coat layer is 0.5-100 micrometers, More preferably, it is 0.8-20 micrometers, Since curl prevention property and crack prevention property are especially excellent, Most preferably, it is the range of 2-10 micrometers. It is. The film thickness of the hard coat layer is an average value (μm) obtained by observing a cross section with an electron microscope (SEM, TEM, STEM) and measuring any 10 points. As for the film thickness of the hard coat layer, as an alternative method, any 10 points may be measured using a Digimatic Indicator IDF-130 manufactured by Mitutoyo Corporation to obtain an average value.

By containing an antistatic agent in the hard coat layer composition, antistatic performance can be imparted to the hard coat layer.
As the antistatic agent, conventionally known ones can be used. For example, a cationic antistatic agent such as a quaternary ammonium salt, fine particles such as tin-doped indium oxide (ITO), a conductive polymer, or the like can be used. Can do.
When using the said antistatic agent, it is preferable that the content is 1-30 mass% with respect to the total mass of all the solid content.

The optical layered body of the present invention preferably further has a low refractive index layer on the hard coat layer.
The low refractive index layer is preferably 1) a resin containing inorganic fine particles of low refractive index such as silica or magnesium fluoride, 2) a fluorine-based resin which is a low refractive index resin, 3) silica or magnesium fluoride Fluorine resin containing low-refractive-index inorganic fine particles, 4) Any of low-refractive-index inorganic thin films such as silica or magnesium fluoride. For resins other than fluorine-based resins, the same resins as the binder resins described above can be used.
Moreover, it is preferable that the silica mentioned above is a hollow silica fine particle, and such a hollow silica fine particle can be produced by, for example, a production method described in Examples of JP-A-2005-099778.
These low refractive index layers preferably have a refractive index of 1.47 or less, particularly 1.42 or less.
In addition, the thickness of the low refractive index layer is not limited, but it may be set appropriately from the range of about 10 nm to 1 μm.

As the fluororesin, a polymerizable compound containing a fluorine atom in at least a molecule or a polymer thereof can be used. Although it does not specifically limit as a polymeric compound, For example, what has hardening reactive groups, such as a functional group hardened | cured by ionizing radiation, and a polar group thermally cured, is preferable. Moreover, the compound which has these reactive groups simultaneously may be sufficient. In contrast to this polymerizable compound, a polymer has no reactive groups as described above.

As the polymerizable compound having a functional group that is cured by ionizing radiation, fluorine-containing monomers having an ethylenically unsaturated bond can be widely used. More specifically, to illustrate fluoroolefins (eg, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluorobutadiene, perfluoro-2,2-dimethyl-1,3-dioxole, etc.) Can do. As those having a (meth) acryloyloxy group, 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, 2- (perfluorobutyl) ) Ethyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) acrylate, 2- (perfluorodecyl) ethyl (meth) acrylate, α-trifluoro (Meth) acrylate compounds having a fluorine atom in the molecule, such as methyl methacrylate and α-trifluoroethyl methacrylate; a C 1-14 fluoroalkyl group having at least 3 fluorine atoms in the molecule, fluoro A cycloalkyl group or a fluoroalkylene group and at least two (medium There are also fluorine-containing polyfunctional (meth) acrylic acid ester compounds having an acryloyloxy group.

Preferable examples of the thermosetting polar group include hydrogen bond forming groups such as a hydroxyl group, a carboxyl group, an amino group, and an epoxy group. These are excellent not only in adhesion to the coating film but also in affinity with inorganic ultrafine particles such as silica. Examples of the polymerizable compound having a thermosetting polar group include 4-fluoroethylene-perfluoroalkyl vinyl ether copolymer; fluoroethylene-hydrocarbon vinyl ether copolymer; epoxy, polyurethane, cellulose, phenol, polyimide, and the like. Examples include fluorine-modified products of each resin.
Examples of the polymerizable compound having both a functional group curable by ionizing radiation and a polar group curable by heat include acrylic or methacrylic acid moieties and fully fluorinated alkyl, alkenyl, aryl esters, fully or partially fluorinated vinyl ethers, fully Alternatively, partially fluorinated vinyl esters, fully or partially fluorinated vinyl ketones and the like can be exemplified.

Moreover, as a fluorine resin, the following can be mentioned, for example.
Polymer of monomer or monomer mixture containing at least one fluorine-containing (meth) acrylate compound of a polymerizable compound having an ionizing radiation curable group; at least one fluorine-containing (meth) acrylate compound; and methyl (meth) Copolymers with (meth) acrylate compounds that do not contain fluorine atoms in the molecule such as acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; fluoroethylene , Fluorine-containing compounds such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 3,3,3-trifluoropropylene, 1,1,2-trichloro-3,3,3-trifluoropropylene, hexafluoropropylene Monomer homopolymer or Copolymer such as. Silicone-containing vinylidene fluoride copolymers obtained by adding a silicone component to these copolymers can also be used. The silicone components in this case include (poly) dimethylsiloxane, (poly) diethylsiloxane, (poly) diphenylsiloxane, (poly) methylphenylsiloxane, alkyl-modified (poly) dimethylsiloxane, azo group-containing (poly) dimethylsiloxane, Dimethyl silicone, phenylmethyl silicone, alkyl aralkyl modified silicone, fluorosilicone, polyether modified silicone, fatty acid ester modified silicone, methyl hydrogen silicone, silanol group containing silicone, alkoxy group containing silicone, phenol group containing silicone, methacryl modified silicone, acrylic Modified silicone, amino modified silicone, carboxylic acid modified silicone, carbinol modified silicone, epoxy modified silicone, mercapto modified silicone Over emissions, fluorine-modified silicones, polyether-modified silicone and the like. Of these, those having a dimethylsiloxane structure are preferred.

Furthermore, non-polymers or polymers composed of the following compounds can also be used as the fluororesin. That is, a fluorine-containing compound having at least one isocyanato group in the molecule is reacted with a compound having at least one functional group in the molecule that reacts with an isocyanato group such as an amino group, a hydroxyl group, or a carboxyl group. Compound obtained: a compound obtained by reacting a fluorine-containing polyol such as fluorine-containing polyether polyol, fluorine-containing alkyl polyol, fluorine-containing polyester polyol, fluorine-containing ε-caprolactone modified polyol with a compound having an isocyanato group Can be used.

Moreover, each binder resin as described above can be mixed and used together with the above-described polymerizable compound or polymer having a fluorine atom. Furthermore, various additives and solvents can be used as appropriate in order to improve the curing agent for curing reactive groups and the like, to improve the coating property, and to impart antifouling properties.

In the formation of the low refractive index layer, 0.5 to 5 mPa · s (25 ° C.) at which preferable coating properties can be obtained for the viscosity of the composition for a low refractive index layer obtained by adding a low refractive index agent and a resin, It is preferable to set it as the range of 0.7-3 mPa * s (25 degreeC) preferably. An antireflection layer excellent in visible light can be realized, a uniform thin film with no coating unevenness can be formed, and a low refractive index layer particularly excellent in adhesion can be formed.

The resin curing means may be the same as the curing means in the hard coat layer described later. When a heating means is used for the curing treatment, it is preferable to add a thermal polymerization initiator that generates, for example, a radical by heating to start polymerization of the polymerizable compound, to the fluororesin composition.

As a method for producing the optical layered body of the present invention, for example, a hard coat layer coating film is formed on a polyester substrate prepared by the above-described method, and dried as necessary. The film is cured to form a hard coat layer. And the optical laminated body of this invention can be manufactured by forming the said low-refractive-index layer on the said hard-coat layer by a well-known method as needed.
Moreover, it is although it does not specifically limit as a drying method of the said coating film for hard-coat layers, Generally, it is good to dry for 3 to 120 second at 30-120 degreeC.

What is necessary is just to select a well-known method suitably as a method of hardening the said coating film for hard-coat layers according to a structural component. For example, if the binder resin component to be contained is of an ultraviolet curable type, it may be cured by irradiating the coating film with ultraviolet rays.
When irradiating the ultraviolet light is preferably ultraviolet irradiation amount is 80 mJ / cm ² or more, more preferably 100 mJ / cm ² or more, more preferably 130 mJ / cm ² or more.

The optical layered body of the present invention preferably has a primer layer between the light transmissive substrate and the optical functional layer.
The primer layer is a layer provided for the first purpose to improve the adhesion between the polyester base material and the hard coat layer described above. The preferred thickness of the primer layer is an interference fringe resulting from the provision of the primer layer. From the viewpoint of preventing the occurrence of the above, the relationship between the refractive index (nx, ny) of the light-transmitting substrate, the refractive index (nh) of the optical functional layer, and the refractive index (np) of the primer layer is as follows: It is selected appropriately.
(1) When the refractive index (np) of the primer layer is larger than the refractive index (nx) in the slow axis direction of the light-transmitting substrate and the refractive index (nf) of the optical functional layer (np> nx, nf), or when the refractive index (np) of the primer layer is smaller than the refractive index (ny) in the fast axis direction of the light-transmitting substrate and the refractive index (nf) of the optical functional layer (np) <Ny, nf) The thickness of the primer layer is preferably 3 to 30 nm.
(2) When the refractive index (np) of the primer layer is larger than the refractive index (nx) in the slow axis direction of the light transmissive substrate and smaller than the refractive index (nf) of the optical functional layer ( nx <np <nf), or the refractive index (np) of the primer layer is smaller than the refractive index (ny) in the fast axis direction of the light-transmitting substrate, and the refractive index (nf) of the optical functional layer ) (Nf <np <ny), the primer layer preferably has a thickness of 65 to 125 nm. (3) The refractive index (np) of the primer layer includes a refractive index (ny) in the fast axis direction of the light transmissive substrate and a refractive index (nx) in the slow axis direction of the light transmissive substrate. In the case (ny <np <nx), the thickness of the primer layer is not particularly limited from the viewpoint of preventing interference fringes. From the viewpoint of reducing the amount of reflection at the interface between the primer layer and the light-transmitting substrate and weakening the interference fringes, the refractive index (np) of the primer layer is closer to (nx + ny) / 2. preferable.

In (1) and (2) described above, the reason why the thickness of the primer layer is preferable is that in (1), the interface between the primer layer and the optical functional layer (interface A), the light-transmitting substrate and the primer layer When the interface (interface B) is compared, the change in the refractive index with respect to the incidence of external light is opposite in the interface A and interface B. Therefore, when external light is reflected at the interface, if one of the interfaces A and B is free-end reflection, the other is fixed-end reflection, and the phase is reversed. This is because the light interferes and the intensity decreases.
On the other hand, in (2), since the change in refractive index is the same between the interface A and the interface B, the phase of the reflected light at the interface A and the interface B is the same. This is because when the wavelength is 1/4 of the light wavelength, the reflected light at both interfaces interferes and the intensity decreases. Here, the range of the thickness of the primer layer in (2) is that the refractive index of the primer layer is usually about 1.47 to 1.63 as will be described later. Is a value calculated with a light wavelength of 380 to 780 nm.
In addition, when the difference in refractive index between the primer layer, the light-transmitting substrate and the optical functional layer is equal, the reflectance at both interfaces is also equal, and the effect of interference in the above (1) and (2) is most exhibited. Is done.

In the case of the above (1), the primer layer preferably has a thickness of 3 to 30 nm. When the thickness is less than 3 nm, the adhesion between the polyester base material and the hard coat layer may be insufficient. When the thickness exceeds 30 nm, the interference fringe prevention property of the optical laminate of the present invention may be insufficient. is there. The more preferable lower limit of the thickness of the primer layer in the case of (1) is 10 nm, and the more preferable upper limit is 20 nm.
In the case of (2), the primer layer preferably has a thickness of 65 to 125 nm. Outside this range, the interference fringe preventing property of the optical layered body of the present invention may be insufficient. The more preferable lower limit of the thickness of the primer layer in the case of (2) is 70 nm, and the more preferable upper limit is 110 nm.
Moreover, in the case of said (3), although the thickness is not specifically limited and the said primer layer should just set arbitrarily, A preferable minimum is 3 nm and a preferable upper limit is 125 nm.
In addition, the thickness of the said primer layer is the average value (nm) obtained by measuring arbitrary 10 points | pieces, for example by observing the cross section of the said primer layer with an electron microscope (SEM, TEM, STEM). is there. In the case of a very thin thickness, a high-magnification observation is recorded as a photograph and further magnified for measurement. When enlarged, a layer interface line that is very thin enough to be clearly recognized as a boundary line becomes a thick line. In that case, the center portion obtained by dividing the thick line width into two is measured as a boundary line.

The material constituting such a primer layer is not particularly limited as long as it has adhesion to a light-transmitting substrate, and materials conventionally used as a primer layer of an optical laminate can be used.
However, when considering the material of the primer layer for the conventional optical laminate, the refractive index of the primer layer is in the range of 1.47 to 1.63 when a material that also satisfies the adhesion and hardness is selected. Compared with the case where the layer thickness is not controlled, the optical laminate of the present invention is preferable because the material selection range of the primer layer is very large.
Note that the refractive index (nf) of the optical functional layer exhibits the most effective effects due to interference in the above (1) and (2), so the refractive index of the primer layer, the light-transmitting substrate and the optical functional layer. The closer the difference is, the better. In (3), the closer to the refractive index of the primer layer, the better from the viewpoint of suppressing an increase in the interface.

In the optical layered body of the present invention, the primer layer is formed using a primer layer composition prepared by mixing and dispersing the above-described materials and, if necessary, a photopolymerization initiator and other components in a solvent. can do.
The mixing and dispersing may be performed using a known apparatus such as a paint shaker, a bead mill, a kneader.

As the solvent, water is preferably used, and is preferably used in the form of an aqueous coating liquid such as an aqueous solution, an aqueous dispersion, or an emulsion. Further, some organic solvent may be included.
Examples of the organic solvent include alcohols (eg, methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol), ketones (eg, acetone, methyl ethyl ketone, methyl). Isobutyl ketone, cyclopentanone, cyclohexanone, heptanone, diisobutyl ketone, diethyl ketone), aliphatic hydrocarbon (eg, hexane, cyclohexane), halogenated hydrocarbon (eg, methylene chloride, chloroform, carbon tetrachloride), aromatic carbonization Hydrogen (eg, benzene, toluene, xylene), amide (eg, dimethylformamide, dimethylacetamide, n-methylpyrrolidone), ether (eg, diethyl ether, dioxane, tetrahydrofuran) ), Ether alcohols (e.g., 1-methoxy-2-propanol), esters (e.g., methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate) and the like.

The other components are not particularly limited. For example, a leveling agent, organic or inorganic fine particles, a photopolymerization initiator, a thermal polymerization initiator, a crosslinking agent, a curing agent, a polymerization accelerator, a viscosity modifier, an antistatic agent, an oxidation agent. Examples thereof include an inhibitor, an antifouling agent, a slip agent, a refractive index adjuster, and a dispersant.

The primer layer composition preferably has a total solid content of 3 to 20%. If it is less than 3%, residual solvent may remain or whitening may occur. If it exceeds 20%, the viscosity of the composition for the primer layer is increased, the coatability is lowered, unevenness and streaks appear on the surface, and the desired film thickness may not be obtained. The solid content is more preferably 4 to 10%.

Application of the primer layer composition to the polyester substrate can be carried out at any stage, but it is preferably carried out during the production process of the polyester substrate, and further before the orientation crystallization is completed. It is preferable to apply to a polyester substrate.
Here, the polyester base material before the crystal orientation is completed is an unstretched film, a uniaxially oriented film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction, and further in the longitudinal direction and the transverse direction. In the direction (low-stretch orientation orientation (biaxially stretched film before reorientation in the machine direction or transverse direction to complete orientation crystallization)). Especially, it is preferable to apply | coat the aqueous coating liquid of the said composition for primer layers to an unstretched film or the uniaxially stretched film orientated to one direction, and to perform longitudinal stretching and / or lateral stretching, and heat setting as it is.
When the primer layer composition is applied to a polyester substrate, physical treatment such as corona surface treatment, flame treatment, plasma treatment or the like is performed on the polyester substrate surface as a pretreatment for improving the coating property, or It is preferred to use a chemically inert surfactant together with the primer layer composition.

As a method for applying the primer layer composition, any known coating method can be applied. For example, a roll coating method, a gravure coating method, a roll brush method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method and the like can be used alone or in combination. In addition, a coating film may be formed only in the single side | surface of a polyester base material as needed, and may be formed in both surfaces.

Further, as described above, the interference fringe prevention performance of the primer layer is manifested by setting the refractive index and thickness of the primer layer in the specific range.
The primer layer or hard coat layer having such a specific refractive index is obtained by adding high refractive index fine particles or low refractive index fine particles to the hard coat layer composition or primer layer composition described above. It is preferable to form using the composition which adjusted.

As the high refractive index fine particles, for example, metal oxide fine particles having a refractive index of 1.50 to 2.80 are preferably used. Specific examples of the metal oxide fine particles include titanium oxide (TiO ₂ , refractive index: 2.71), zirconium oxide (ZrO ₂ , refractive index: 2.10), cerium oxide (CeO ₂ , refraction). rate: 2.20), tin oxide (SnO _2, refractive index: 2.00), antimony tin oxide (ATO, refractive index: 1.75 to 1.95), indium tin oxide (ITO, the refractive index: 1.95 to 2.00), phosphorus tin compound (PTO, refractive index: 1.75 to 1.85), antimony oxide (Sb ₂ O ₅ , refractive index: 2.04), aluminum zinc oxide (AZO, Refractive index: 1.90 to 2.00), gallium zinc oxide (GZO, refractive index: 1.90 to 2.00) and zinc antimonate (ZnSb ₂ O ₆ , refractive index: 1.90 to 2.00) ) And the like. Among them, tin oxide (SnO ₂ ), antimony tin oxide (ATO), indium tin oxide (ITO), phosphorus tin compound (PTO), antimony oxide (Sb ₂ O ₅ ), aluminum zinc oxide (AZO), Gallium zinc oxide (GZO) and zinc antimonate (ZnSb ₂ O ₆ ) are conductive metal oxides, and can impart antistatic properties by controlling the diffusion state of fine particles and forming conductive paths. There are advantages.
As the low refractive index fine particles, for example, those having a refractive index of 1.20 to 1.45 are preferably used. As such low refractive index fine particles, fine particles used in conventionally known low refractive index layers can be used. For example, the above-described hollow silica fine particles, LiF (refractive index 1.39), MgF ₂ ( Metal fluoride such as magnesium fluoride, refractive index 1.38), AlF ₃ (refractive index 1.38), Na ₃ AlF ₆ (cryolite, refractive index 1.33) and NaMgF ₃ (refractive index 1.36). Compound fine particles.

The content of the high refractive index fine particles and the low refractive index fine particles is not particularly limited. For example, the weighted average of the refractive index values measured in advance of the cured resin component added to the hard coat layer composition Thus, the refractive index of the hard coat layer to be formed may be appropriately adjusted in relation to other components so as to satisfy the above-described relationship.

The hard coat layer is formed by applying the hard coat layer composition on the primer layer formed by the above-described method to form a hard coat layer coating film, and drying it as necessary. It can be formed by curing a coating film for a coat layer.
When the hard coat layer composition contains an ultraviolet curable resin, the primer layer composition contains an initiator used for curing the hard coat layer coating film. The adhesion between the coat layer and the primer layer can be obtained more reliably.

The optical layered body of the present invention preferably has a hardness of HB or higher, more preferably H or higher, in a pencil hardness test (load 4.9 N) according to JIS K5600-5-4 (1999).

The optical layered body of the present invention preferably has a total light transmittance of 80% or more. If it is less than 80%, color reproducibility and visibility may be impaired when mounted on an image display device, and a desired contrast may not be obtained. The total light transmittance is more preferably 90% or more.
The total light transmittance can be measured by a method based on JIS K-7361 using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150).

The optical layered body of the present invention preferably has a haze of 1% or less. If it exceeds 1%, desired optical characteristics cannot be obtained, and the visibility when the optical laminate of the present invention is placed on the image display surface is lowered.
The haze can be measured by a method based on JIS K-7136 using a haze meter (manufactured by Murakami Color Research Laboratory, product number: HM-150).

When the optical functional layer is a hard coat layer, the optical layered body of the present invention is formed by forming a hard coat layer on the light-transmitting substrate using, for example, the above-described composition for hard coat layer. Can be manufactured. When the optical functional layer has a structure in which a low refractive index layer is laminated on the hard coat layer, the hard coat layer is formed on the light-transmitting substrate using the above-described hard coat layer composition. After that, the low refractive index layer can be produced by forming the low refractive index layer on the hard coat layer using the above-described composition for low refractive index layer.
About the formation method of the said composition for hard-coat layers and a hard-coat layer, the composition for low-refractive-index layers, and the formation method of a low-refractive-index layer, the material and method similar to having mentioned above are mentioned.

An optical laminate having a light-transmitting substrate having a birefringence index in the plane is a polarizing plate provided on the polarizing element and used on the surface of the image display device, The absorption axis is a horizontal direction with respect to the display screen of the image display device, and the light-transmitting base material and the polarizing element are a slow axis that is a direction in which the refractive index of the light-transmitting base material is large. The polarizing axis is arranged perpendicular to the absorption axis, and the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, is arranged in parallel with the vertical direction of the display screen of the image display device. A polarizing plate is also one aspect of the present invention.

As said optical laminated body in the polarizing plate of this invention, the thing similar to the optical laminated body of this invention is mentioned.
In the polarizing plate of the present invention, the light-transmitting substrate having a birefringence index in the plane preferably has a retardation of 3000 nm or more for the same reason as the optical laminate of the present invention described above, and has a refractive index. The difference (nx−ny) between the refractive index (nx) in the slow axis direction, which is the larger direction, and the refractive index (ny) in the fast axis direction, which is the direction perpendicular to the slow axis direction, is 0.01. The above is preferable.
In addition, the polarizing plate of the present invention preferably has an optical functional layer similar to the optical layered body of the present invention described above on one surface of the above light-transmitting substrate, and similarly to the optical layered body of the present invention. The optical function when the refractive index in the slow axis direction of the light transmissive substrate is (nx) and the refractive index in the fast axis direction, which is a direction orthogonal to the slow axis direction, is (ny). The refractive index of the layer is preferably less than (nx + ny) / 2.
Moreover, the polarizing plate of the present invention has a primer layer between the light transmissive substrate and the optical functional layer for the same reason as the optical laminate of the present invention described above, and the thickness of the primer layer is It is preferable to select appropriately according to the above (1) to (3).

The polarizing element is not particularly limited, and for example, a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film, etc. dyed and stretched with iodine or the like can be used. In the laminating process of the polarizing element and the optical laminate, it is preferable to saponify the light-transmitting substrate. By the saponification treatment, the adhesiveness is improved and an antistatic effect can be obtained.

In the polarizing plate of the present invention, the light transmissive substrate and the polarizing element are such that the slow axis that is the direction in which the refractive index of the light transmissive substrate is large and the absorption axis of the polarizing element are perpendicular to each other. Are arranged as follows. In the polarizing plate of the present invention, the light-transmitting substrate and the polarizing element are arranged as described above, and the slow axis that is the direction in which the refractive index of the light-transmitting substrate is large is an image display device. Since it is installed in parallel with the vertical direction of the display screen, the antireflection performance and the bright place contrast are excellent as in the above-described optical laminate of the present invention.
In the above-mentioned “the light-transmitting substrate and the polarizing element, the slow axis that is the direction in which the refractive index of the light-transmitting substrate is large and the absorption axis of the polarizing element are arranged perpendicularly. ”Means that the angle between the slow axis of the light transmissive substrate and the absorption axis of the polarizing element is in the range of 90 ° ± 40 °. Means the state of being installed.
In the polarizing plate of the present invention, the angle between the slow axis of the light transmissive substrate and the absorption axis of the polarizing element is preferably 90 ° ± 30 °, and preferably 90 ° ± 10 °. Is more preferably 90 ° ± 5 °. In the polarizing plate of the present invention, the angle between the slow axis of the light-transmitting substrate and the absorption axis of the polarizing element is 90 ° ± 40 °, thereby improving the antireflection performance and the bright place contrast described above. Can be planned. In the polarizing plate of the present invention, the angle between the slow axis of the light-transmitting substrate and the slow axis of the polarizing element is 90 °, in order to improve antireflection performance and bright place contrast. And most preferred. For this reason, the angle between the slow axis of the light-transmitting substrate and the absorption axis of the polarizing element is preferably 90 ° ± 30 °, more preferably 90 °, rather than 90 ° ± 40 °. ° ± 10 °. Furthermore, when the angle between the slow axis of the light-transmitting substrate and the absorption axis of the polarizing element is 0 ° ± 5 °, the same level of antireflection performance and lightness as when the angle is 0 °. The contrast can be improved, which is more preferable.

Such a polarizing plate of the present invention comprises a light-transmitting substrate of the optical laminate and the polarizing element, a slow axis in which the refractive index of the light-transmitting substrate is large, and the polarizing element. The slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, is parallel to the vertical direction of the display screen of the image display device. Placed in.

In the polarizing plate of the present invention, the absorption axis of the polarizing element is in the left-right direction with respect to the display screen of the image display device.
As described with reference to FIG. 1, it is possible to reduce reflection of light (S-polarized light) oscillating in the left-right direction, which has a large ratio of incidence on the display screen of the image display device, in the above-described optical laminate of the present invention. However, as a result, a lot of S-polarized light is transmitted. Usually, the transmitted S-polarized light is absorbed inside the image display apparatus, but there is very little light returning to the observer side. However, in the polarizing plate of the present invention, since the absorption axis of the polarizing element is in the horizontal direction with respect to the display screen, it can absorb the S-polarized light transmitted through the optical laminate of the present invention, and is more observed. The light returning to the person side can be reduced, and as a result, the display image can be made more excellent.
“The absorption axis of the polarizing element is in the horizontal direction with respect to the display screen” means that the absorption axis is in the range of 0 ° ± 40 ° with respect to the horizontal direction of the display screen. It means the state of arrangement.
In the polarizing plate of the present invention, the angle between the absorption axis of the polarizing element and the left-right direction of the display screen is preferably 0 ° ± 30 °, more preferably 0 ° ± 10 °, More preferably, it is 0 ° ± 5 °. In the polarizing plate of the present invention, when the angle between the absorption axis of the polarizing element and the horizontal direction of the display screen is 0 ° ± 40 °, the above-described effect can be obtained.

The image display device provided with the optical layered body of the present invention described above or the polarizing plate of the present invention is also one aspect of the present invention.
The image display device of the present invention may be an image display device such as an LCD, PDP, FED, ELD (organic EL, inorganic EL), CRT, tablet PC, touch panel, or electronic paper.

The LCD, which is a typical example of the above, includes a transmissive display body and a light source device that irradiates the transmissive display body from the back. When the image display device of the present invention is an LCD, the optical laminate of the present invention or the polarizing plate of the present invention is formed on the surface of this transmissive display.

When the image display device of the present invention is a liquid crystal display device having the optical laminate or polarizing plate of the present invention, the light source of the light source device is irradiated from below the optical laminate of the present invention or the polarizing plate of the present invention. A retardation plate may be inserted between the liquid crystal display element and the polarizing plate of the present invention. An adhesive layer may be provided between the layers of the liquid crystal display device as necessary.

The PDP is disposed with a surface glass substrate having an electrode formed on the surface and a discharge gas sealed between the surface glass substrate, the electrode and minute grooves formed on the surface, and red in the grooves. And a rear glass substrate on which green and blue phosphor layers are formed. When the image display device of the present invention is a PDP, the surface of the surface glass substrate or its front plate (glass substrate or film substrate) is provided with the optical laminate of the present invention described above.

The image display device of the present invention is an ELD device that emits light when a voltage is applied, such as zinc sulfide or a diamine substance: a phosphor is deposited on a glass substrate, and the voltage applied to the substrate is controlled. It may be an image display device such as a CRT that generates an image visible to human eyes. In this case, the optical layered body of the present invention described above is provided on the outermost surface of each display device as described above or the surface of the front plate.

Here, when the present invention is a liquid crystal display device having the above optical laminate, the image display device of the present invention is preferably a VA mode or IPS mode liquid crystal display device.
In the VA (Vertical Alignment) mode, liquid crystal molecules are aligned so as to be perpendicular to the substrate of the liquid crystal cell when no voltage is applied, and dark display is performed. By applying voltage, the liquid crystal molecules are collapsed. This is an operation mode indicating display.
The IPS (In-Plane Switching) mode is a method in which display is performed by rotating the liquid crystal within the substrate surface by a horizontal electric field applied to a pair of comb electrodes provided on one substrate of the liquid crystal cell. is there.
The image display device using the optical laminate or polarizing plate of the present invention is preferably in the VA mode or the IPS mode for the following reason.
As described with reference to FIG. 1, the image display device of the present invention reflects the light (S-polarized light) that vibrates in the left-right direction, which has a high ratio of incidence on the display screen, on the optical laminate or polarizing plate of the present invention. As a result, a large amount of S-polarized light is transmitted. Normally, these transmitted S-polarized light is absorbed inside the display device, but there is very little light returning to the observer side. In the VA mode or the IPS mode, since the absorption axis of the polarizer installed on the observer side from the liquid crystal cell is in the horizontal direction with respect to the display screen, the S-polarized light transmitted through the optical laminate or the polarizing plate of the present invention. This is because the light returning to the observer side can be reduced.

In the image display device of the present invention, the backlight source is not particularly limited, and a known light source such as a cold cathode fluorescent tube (CCFL), a hot cathode fluorescent tube (HCFL), an LED, an organic EL, or an inorganic EL can be used. However, among these, a white light emitting diode (white LED) or a cold cathode fluorescent tube (CCFL) is preferably used.
The white LED is an element that emits white by combining a phosphor with a phosphor system, that is, a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor. In particular, white light-emitting diodes, which consist of light-emitting elements that combine blue light-emitting diodes using compound semiconductors with yttrium, aluminum, and garnet yellow phosphors, have a continuous and broad emission spectrum, so they have anti-reflection performance. In addition, it is effective for improving the contrast of a bright place and is excellent in luminous efficiency, and thus is suitable as the backlight light source in the present invention. Further, since white LEDs with low power consumption can be widely used, it is possible to achieve an energy saving effect.
The CCFL is an element that utilizes discharge and fluorescence. Gas and mercury are sealed in a glass tube, and applied to the inner wall of the glass tube by applying a voltage between electrodes installed at both ends of the glass tube. Make the phosphor glow. Since the CCFL has a property of emitting light in all directions, when used as a backlight light source, luminance unevenness is reduced as compared with a case where an LED that emits light having high directivity is used as a backlight light source. Also, CCFL has a weaker wavelength on the blue side than LED, so the display image of the image display device of the present invention is less irritating to the eyes of the observer by using CCFL as a backlight light source. .

The image display device of the present invention may be an organic EL display device in which an absorption axis of a polarizing element is installed in the left-right direction with respect to the display screen. The organic EL display device does not require a polarizing element on the principle of image display, but has a configuration in which a polarizing element, a λ / 4 phase difference plate, and an organic EL element are stacked in this order from the observer side from the viewpoint of preventing external light reflection. May be used. At this time, the polarizing element and the λ / 4 retardation plate function as a circularly polarizing plate for preventing reflection of external light. However, a normal λ / 4 retardation plate is λ / 4 only for a specific wavelength. Since it functions as a phase difference plate, it cannot prevent all incident external light reflection. For this reason, by setting the absorption axis of the polarizing element in the horizontal direction with respect to the display screen, the S-polarized light incident on the display screen is absorbed and the light incident on the image is reduced, thereby returning to the viewer side. The incoming light can be reduced.
As an image display method of the organic EL display device, a white light emitting layer is used and a color filter method for obtaining a color display by passing a color filter, a blue light emitting layer is used, and a part of the light emission is applied to a color conversion layer. Examples thereof include a color conversion method for obtaining a color display by passing through, a three-color method using red, green, and blue light-emitting layers, a method using a color filter in combination with the three-color method, and the like. The material of the light emitting layer may be a low molecule or a polymer.

In any case, the image display device of the present invention can be used for display display of a television, a computer, electronic paper, a touch panel, a tablet PC, or the like. In particular, it can be suitably used for the surface of high-definition image displays such as CRT, liquid crystal panel, PDP, ELD, FED, and touch panel.

In addition, a method for manufacturing an image display device including an optical laminate having a light-transmitting substrate having a birefringence index in the plane is also one aspect of the present invention.
That is, the method for manufacturing an image display device of the present invention is a method for manufacturing an image display device including an optical laminate having a light-transmitting base material having a birefringence in the plane, and the polarization of the image display device The absorption axis of the child is in the horizontal direction with respect to the display screen of the image display device, the slow axis being the direction in which the refractive index of the light transmissive substrate is large, and the vertical direction of the display screen of the image display device It has the process of arrange | positioning the said optical laminated body so that may become parallel.
In the method for producing an image display device of the present invention, examples of the optical layered body include the same optical layered body as described above.
Further, the above-mentioned “the absorption axis of the polarizer of the image display device is in the horizontal direction with respect to the display screen of the image display device” means that the angle formed by the absorption axis and the horizontal direction of the display screen is This means that the polarizer is arranged so as to be in the range of 0 ° ± 40 °.
Further, as described in the optical layered body of the present invention, the angle between the absorption axis of the polarizer and the horizontal direction of the display screen is preferably 0 ° ± 30 °, and preferably 0 ° ± 10 °. Is more preferably 0 ° ± 5 °.
In addition, the above-mentioned “position the optical laminate so that the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, and the vertical direction of the display screen of the image display device are parallel” Means that the optical layered body is arranged so that an angle formed by the slow axis and the vertical direction of the display screen is in a range of 0 ° ± 40 °.
Further, as described in the optical laminate of the present invention, the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is preferably 0 ° ± 30 °, and 0 ° ± 10 More preferably, the angle is 0 ° ± 5 °.

The above-described image display device of the present invention has excellent antireflection performance and bright place contrast, and improved visibility. Such a visibility improving method by the image display apparatus of the present invention is also one aspect of the present invention.
That is, the method for improving the visibility of the image display device of the present invention is a method for improving the visibility of an image display device comprising an optical laminate having a light-transmitting substrate having a birefringence index in the plane. The absorption axis of the polarizer of the display device is the left-right direction with respect to the display screen of the image display device, and the slow axis is the direction in which the refractive index of the light-transmitting substrate is large, and the display of the image display device The optical laminated body is arranged so that the vertical direction of the screen is parallel.
In the visibility improving method of the image display device of the present invention, examples of the optical laminate include the same optical laminates of the present invention described above, and the image display device of the present invention described above. The thing similar to an image display apparatus is mentioned.
Further, the above-mentioned “the absorption axis of the polarizer of the image display device is in the horizontal direction with respect to the display screen of the image display device” means that the angle formed by the absorption axis and the horizontal direction of the display screen is This means that the polarizer is arranged so as to be in the range of 0 ° ± 40 °.
Further, as described in the optical layered body of the present invention, the angle between the absorption axis of the polarizer and the horizontal direction of the display screen is preferably 0 ° ± 30 °, and preferably 0 ° ± 10 °. Is more preferably 0 ° ± 5 °.
In addition, the above-mentioned “position the optical laminate so that the slow axis, which is the direction in which the refractive index of the light-transmitting substrate is large, and the vertical direction of the display screen of the image display device are parallel” Means that the optical layered body is arranged so that an angle formed by the slow axis and the vertical direction of the display screen is in a range of 0 ° ± 40 °.
Further, as described in the optical laminate of the present invention, the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is preferably 0 ° ± 30 °, and 0 ° ± 10 More preferably, the angle is 0 ° ± 5 °.

Since the optical laminate and the polarizing plate of the present invention have the above-described configuration, even when a light-transmitting substrate having a birefringence in a plane such as a polyester film is used, antireflection is performed. An image display device excellent in performance and bright place contrast can be obtained.
For this reason, the optical laminate and the polarizing plate of the present invention include a cathode ray tube display (CRT), a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (ELD), a field emission display (FED), and electronic paper. It can be suitably applied to touch panels, tablet PCs, and the like.

It is an image figure of a mode that the light reflected on the wall surface or the floor surface injects into the display screen of an image display apparatus.

(Photometric contrast evaluation method)
The observer side of the liquid crystal monitor (LCD2090 UXi (manufactured by NEC)) using CCFL as the backlight light source so that the relationship between the S-polarized light at the time of reflectance measurement and the fast axis of the light-transmitting substrate is the same. The optical laminate was placed on the polarizing element so that the optical functional layer was on the observer side, and the bright spot contrast of the display screen was visually evaluated at an ambient illuminance of 400 lux (light spot).
Specifically, the photopic contrast is expressed by the following equation, and since the change rate of the photopic white luminance is generally small and the photopic black luminance change rate is large, the photopic contrast is governed by the photopic black luminance. Further, since the original black luminance of the panel is small and negligible compared with the photopic black luminance, the blackness (photopic black luminance) was evaluated in the following manner to substantially evaluate the photopic contrast.
That is, for two types of liquid crystal monitors having different angles between the S-polarized light and the fast axis of the light-transmitting substrate, one is the liquid crystal monitor A, the other is the liquid crystal monitor B, and the liquid crystal monitors A and B are arranged. Subject performs a sensory evaluation (visually observe a black-displayed LCD monitor from a position 50 to 60 cm away and evaluate which one appears black), and a liquid crystal monitor with 12 or more people who answered black is excellent in bright place contrast When the number of people is less than 12, that is, when the number is 11 or less, the evaluation is inferior. In addition, the angle which installs an optical laminated body to liquid crystal monitor A and B is evaluating by swinging an angle suitably for every Example and a comparative example. In addition, when 13 or more subjects replied that they were black, they were considered particularly excellent.
Light place contrast: CR = LW / LB
Brightness white brightness (LW): Brightness when the display device displays white in a bright place with ambient light (peripheral illuminance 400 lux) Bright spot black brightness (LB): Bright place with ambient light (ambient illuminance 400) When the same evaluation was performed using a liquid crystal monitor (FLATRON IPS226V (manufactured by LG Electronics Japan)) using an LED as a backlight light source, It was confirmed that the contrast was the same as that of the liquid crystal monitor using CCFL as the backlight source.

(Reflectance measurement method)
A black vinyl tape (Yamato Vinyl Tape No200-38-21 38 mm wide was applied to the side opposite to the measurement layer, the side where the optical functional layer of the optical laminate was provided, and then the spectrophotometer (V7100, automatic absolute Reflectivity measurement unit VAR-7010 (manufactured by JASCO Corporation), polarization measurement: the case where the slow axis of the light-transmitting substrate is installed in parallel with the S-polarized light, and the fast axis is installed in parallel The 5 degree reflectivity was measured.

(Measurement of refractive index)
It measured using the ellipsometer (made by UVISEL Horiba Ltd.).

(Judgment whether or not it has birefringence in the surface)
Whether or not the light-transmitting substrate has an in-plane birefringence is that a compound having Δn (nx−ny) ≧ 0.0005 at a refractive index of a wavelength of 550 nm has a birefringence. And those having Δn <0.0005 have no birefringence.
The birefringence can be measured by setting a measurement angle of 0 ° and a measurement wavelength of 552.1 nm using KOBRA-WR manufactured by Oji Scientific Instruments. At this time, for calculating the birefringence, the film thickness and the average refractive index are required. The film thickness can be measured using, for example, a micrometer (Digital Micrometer, manufactured by Mitutoyo Corporation) or an electric micrometer (produced by Anritsu Corporation). The average refractive index can be measured using an Abbe refractometer or an ellipsometer.
Δn of TD80UL-M (manufactured by Fuji Film Co., Ltd.) made of triacetyl cellulose and ZF16-100 (made by Nippon Zeon Co., Ltd.) made of cycloolefin polymer, which are generally known as isotropic materials, , 0.00007, and 0.00005, and it was determined that they do not have birefringence (isotropic).
As another method for measuring birefringence, two polarizing plates are used to determine the orientation axis direction (principal axis direction) of the light-transmitting substrate, and the refractive indexes of two axes perpendicular to the orientation axis direction. (Nx, ny) can be obtained by an Abbe refractometer (NAGO-4T manufactured by Atago Co., Ltd.), and a black vinyl tape (for example, Yamato vinyl tape No200-38-21 38 mm width) is attached to the back surface. Using a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit, VAR-7010, manufactured by JASCO Corporation), polarization measurement: S-polarized light, with slow axis parallel to S-polarized light, The reflectivity (nx, ny) of each wavelength of the slow axis and the fast axis can be calculated from the following formula by measuring the reflectivity of 5 degrees when the fast axes are parallel.
R (%) = (1-n) ² / (1 + n) ²

(Example 1, Comparative Example 1)
The polyethylene terephthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, closely adhered onto a water-cooled and cooled rotating quenching drum, and cooled to produce an unstretched film. This unstretched film is preheated at 120 ° C. for 1 minute using a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.), and then stretched at 120 ° C. to a stretch ratio of 1.1 times. Stretching was performed at a stretching ratio of 4.0 times in the direction of 90 degrees to obtain a light-transmitting substrate having nx = 1.70, ny = 1.59, (nx−ny) = 0.11, and a film thickness of 80 μm. It was.
Next, as an optical functional layer, pentaerythritol triacrylate (PETA) is dissolved in 30% by mass in MIBK solvent, and a photopolymerization initiator (Irg184, manufactured by BASF) is added at 5% by mass with respect to the solid content. The layer composition was coated with a bar coater so that the film thickness after drying was 5 μm to form a coating film.
Next, the formed coating film is heated at 70 ° C. for 1 minute, the solvent is removed, and the coated surface is fixed by irradiating with ultraviolet rays, and has an optical functional layer having a refractive index (nf) of 1.53. Got the body. The reflectance of the optical laminate of Example 1 measured by setting the S-polarized light and the light-transmitting base material in parallel with the fast axis (the angle between the S-polarized light and the light-transmitting base material being 0 °). Is 4.40%, measured by setting the S-polarized light and the slow axis of the light-transmitting substrate in parallel (the angle between the S-polarized light and the fast axis of the light-transmitting substrate is 90 °). The reflectance of Comparative Example 1 was 4.70%, and the optical laminate of Example 1 was superior in antireflection performance.
In addition, on the polarizing element on the viewer side of the liquid crystal monitor (FLATORON IPS226V (manufactured by LG Electronics Japan)) so that the relationship between the S-polarized light at the time of reflectance measurement and the fast axis of the light-transmitting substrate is the same. In addition, the optical laminate was placed so that the optical functional layer was on the observer side, and the bright spot contrast of the display screen was visually evaluated at an ambient illuminance of 400 lux (light spot).
In the case of Example 1, the S-polarized light that vibrates in the left-right direction with respect to the display screen having a high incidence on the display screen is parallel to the fast axis of the light-transmitting substrate (the slow axis of the light-transmitting substrate) Is parallel to the vertical direction of the display screen, that is, the angle between the slow axis of the light-transmitting substrate and the vertical direction of the display screen is 0 °). The slow axis of the light-transmitting substrate was set in parallel (the slow axis of the light-transmitting substrate and the vertical angle of the display screen were 90 °) and evaluated. As a result, the liquid crystal monitor A using the optical laminate of Example 1 was particularly superior in the bright contrast of the display screen than the liquid crystal monitor B using the optical laminate of Comparative Example 1. On the other hand, the liquid crystal monitor B using the optical laminate of Comparative Example 1 was inferior in bright place contrast and inferior in antireflection performance as compared with the liquid crystal monitor A using the optical laminate of Example 1.

(Example 2, comparative example 2)
Reflection of the optical laminate of Example 2 measured using the optical laminate obtained in Example 1 so that the angle between the S-polarized light and the fast axis of the light-transmitting substrate is 5 °. The reflectance is 4.41%, and the reflectance of the optical laminated body of Comparative Example 2 measured by setting the angle between the S-polarized light and the slow axis of the light-transmitting substrate to be 5 ° is 4 The optical layered body of Example 2 was superior in antireflection performance.
Further, the liquid crystal monitor A using the optical laminate of Example 2 evaluated in the same manner as in Example 1 is particularly superior in the bright place contrast of the display screen than the liquid crystal monitor B using the optical laminate of Comparative Example 2. It was. On the other hand, the liquid crystal monitor B using the optical laminate of Comparative Example 2 was inferior in bright place contrast and in antireflection performance as compared with the liquid crystal monitor A using the optical laminate of Example 2.
In addition, the liquid crystal monitor A ′ in which the angle formed by the S-polarized light in the optical laminated body of Example 2 and the fast axis of the light-transmitting substrate is the same angle on the negative side, and the S-polarized light in the optical laminated body of Comparative Example 2 When the reflectance and the bright place contrast were evaluated for the liquid crystal monitor B ′ in which the angle formed by the slow axis of the light-transmitting substrate was the same angle on the negative side, the liquid crystal monitor using the optical laminate of Example 2 was evaluated. The results were the same as those of the liquid crystal monitor B using the optical laminate of A and Comparative Example 2.

(Example 3, Comparative Example 3)
Reflection of the optical laminate of Example 3 measured using the optical laminate obtained in Example 1 so that the angle between the S-polarized light and the fast axis of the light-transmitting substrate is 10 °. The reflectance is 4.44%, and the reflectance of the optical laminated body of Comparative Example 3 measured by setting the angle between the S-polarized light and the slow axis of the light-transmitting substrate to be 10 ° is 4 The optical laminate of Example 3 was superior in antireflection performance.
In addition, the liquid crystal monitor A using the optical laminate of Example 3 evaluated in the same manner as in Example 1 is particularly superior in the bright place contrast of the display screen than the liquid crystal monitor B using the optical laminate of Comparative Example 3. It was. On the other hand, the liquid crystal monitor B using the optical laminate of Comparative Example 3 was inferior in bright place contrast and in antireflection performance as compared with the liquid crystal monitor A using the optical laminate of Example 3.
The liquid crystal monitor A ′ in which the angle formed by the S-polarized light in the optical laminate of Example 3 and the fast axis of the light-transmitting substrate is the same angle on the negative side, The liquid crystal monitor using the optical laminate of Example 3 was evaluated for the reflectance and the bright place contrast with respect to the liquid crystal monitor B ′ in which the angle formed by the slow axis of the light-transmitting substrate was the same angle on the negative side. The results were the same as those of the liquid crystal monitor B using the optical laminate of A and Comparative Example 3.

(Example 4, comparative example 4)
Reflection of the optical laminate of Example 4 measured using the optical laminate obtained in Example 1 so that the angle formed between the S-polarized light and the fast axis of the light-transmitting substrate is 30 °. The reflectance is 4.51%, and the reflectance of the optical laminate of Comparative Example 4 measured by setting the angle between the S-polarized light and the slow axis of the light-transmitting substrate to be 30 ° is 4 The optical layered body of Example 4 was superior in antireflection performance.
In addition, the liquid crystal monitor A using the optical laminate of Example 4 evaluated in the same manner as in Example 1 has a brighter contrast on the display screen than the liquid crystal monitor B using the optical laminate of Comparative Example 4. It was. On the other hand, the liquid crystal monitor B using the optical laminate of Comparative Example 4 was inferior in bright place contrast and in antireflection performance as compared with the liquid crystal monitor A using the optical laminate of Example 4.
Note that the liquid crystal monitor A ′ in which the angle formed by the S-polarized light in the optical laminate of Example 4 and the fast axis of the light-transmitting substrate is the same angle on the minus side, and the S-polarized light in the optical laminate of Comparative Example 4 When the reflectance and the bright place contrast were evaluated for the liquid crystal monitor B ′ in which the angle formed by the slow axis of the light-transmitting substrate was the same angle on the negative side, the liquid crystal monitor using the optical laminate of Example 4 was evaluated. The results were the same as those of the liquid crystal monitor B using the optical laminate of A and Comparative Example 4.

(Example 5, Comparative Example 5)
The polyethylene terephthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, closely adhered onto a water-cooled and cooled rotating quenching drum, and cooled to produce an unstretched film. This unstretched film was preheated at 120 ° C. for 1 minute with a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.), and then stretched at 120 ° C. to a stretch ratio of 4.0 times. A primer layer resin composition comprising 28.0 parts by mass of an aqueous dispersion and 72.0 parts by mass of water was uniformly applied by a roll coater. Next, the coated film was dried at 95 ° C., and stretched at a stretching ratio of 1.8 times in the direction of 90 degrees from the previous stretching direction, nx = 1.68, ny = 1.63, (nx− ny) = 0.05 and a light-transmitting substrate having a primer layer with a refractive index (np) of 1.56 and a film thickness of 100 nm was obtained on a film with a film thickness of 40 μm.
An optical laminate having an optical functional layer with a refractive index (nf) of 1.53 was obtained in the same manner as in Example 1 except that the obtained light-transmitting substrate was used. The optical functional layer was formed on the primer layer. Using the obtained optical laminate, the reflectance was measured in the same manner as in Example 1 (the angle between the S-polarized light and the fast axis of the light-transmitting substrate was 0 °), and the contrast in the bright place was evaluated. The reflectance of the optical laminated body of Example 5 is 4.38%, and the S-polarized light and the slow axis of the light-transmitting substrate are parallel (the angle between the S-polarized light and the fast axis of the light-transmitting substrate is The reflectivity of the optical laminate of Comparative Example 5 measured at 90 ° was 4.47%, and the optical laminate of Example 5 was superior in antireflection performance.
In addition, the liquid crystal monitor A using the optical laminate of Example 5 evaluated in the same manner as in Example 1 is particularly superior in the bright place contrast of the display screen than the liquid crystal monitor B using the optical laminate of Comparative Example 5. It was. On the other hand, the display screen of the liquid crystal monitor B using the optical laminate of Comparative Example 5 was inferior to the bright place contrast as compared with the liquid crystal monitor A using the optical laminate of Example 5.

(Example 6, Comparative Example 6)
The polyethylene naphthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, and brought into close contact with a water-cooled cooled quenching drum to cool, thereby producing an unstretched film. This unstretched film was preheated at 120 ° C. for 1 minute using a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.), and then stretched at 120 ° C. at a stretch ratio of 4.5 times. A primer layer resin composition comprising 28.0 parts by mass of an aqueous dispersion and 72.0 parts by mass of water was uniformly applied by a roll coater. Next, this coated film was dried at 95 ° C., and stretched at a stretch ratio of 1.5 times in the direction of 90 degrees from the previous stretching direction, nx = 1.80, ny = 1.60, (nx− ny) = 0.20 On a film having a thickness of 40 μm, a light-transmitting substrate was obtained in which a primer layer having a refractive index (np) of 1.56 and a thickness of 100 nm was provided.
An optical laminate having an optical functional layer with a refractive index (nf) of 1.53 was obtained in the same manner as in Example 1 except that the obtained light-transmitting substrate was used. The optical functional layer was formed on the primer layer. Using the obtained optical layered body, the reflectance of the optical layered body of Example 6 measured so that the angle between the S-polarized light and the fast axis of the light-transmitting substrate was 0 ° was measured. The reflectance of the optical laminated body of Comparative Example 6 measured by setting the angle between the S-polarized light and the slow axis of the light-transmitting substrate to be 0 ° was 4.77%. Thus, the optical laminate of Example 6 was superior in antireflection performance.
In addition, the liquid crystal monitor A using the optical laminate of Example 6 evaluated in the same manner as in Example 1 is particularly superior in the bright place contrast of the display screen than the liquid crystal monitor B using the optical laminate of Comparative Example 6. It was. On the other hand, the display screen of the liquid crystal monitor B using the optical laminate of Comparative Example 6 was inferior to the bright place contrast as compared with the liquid crystal monitor A using the optical laminate of Example 6.

(Comparative Example 7)
The reflectance measured by using the optical laminate produced in Example 1 and setting the angle between the S-polarized light and the fast axis of the light-transmitting substrate to be 45 ° is 4.55%, S The reflectance measured by setting the polarization and the slow axis of the light-transmitting substrate to be 45 ° is also 4.55%, and there is no difference in the reflectance. It was not obtained.
A liquid crystal monitor A in which the optical laminate of Example 4 was installed, and a liquid crystal in which the optical laminate in which the angle between the S-polarized light and the fast axis of the light-transmitting substrate in Comparative Example 7 was 45 ° was installed. Using the liquid crystal monitor B as the monitor, the bright place contrast was evaluated in the same manner as in Example 1. As a result, the bright contrast of the display screen of the liquid crystal monitor A using the optical laminate of Example 4 was superior to the bright contrast of the display screen of the liquid crystal monitor B using the optical laminate of Comparative Example 7. . In the same manner, the contrast of the liquid crystal monitor B ′ in which the optical layered body in which the angle between the S-polarized light of the comparative example 7 and the slow axis of the light-transmitting substrate is 45 ° is installed is also evaluated for the liquid crystal monitor B ′ As a result, the result was the same as that of the liquid crystal monitor B.
Next, the liquid crystal monitor using the optical laminate of Examples 1, 2, and 3 was designated as liquid crystal monitor A, and the liquid crystal monitor using the optical laminate of Example 4 was designated as liquid crystal monitor B. Similarly, the bright place contrast was evaluated. However, rather than the bright contrast of the display screen of the liquid crystal monitor B using the optical laminate of Example 4, the display screen of the liquid crystal monitor A using the optical laminates of Example 1, Example 2 and Example 3 is better. The photopic contrast was excellent.

(Reference Example 1)
nx = 1.48026, ny = 1.48019, (nx−ny) = 0.00007, a film thickness of 80 μm, an in-plane retardation of 5.6 nm, and a triacetylcellulose (TD80ULM manufactured by Fuji Film) substrate An optical laminate was prepared by providing an optical functional layer having a refractive index (nf) of 1.53 on the top in the same manner as in Example 1.
Using the obtained optical laminate, measurement was performed by setting the S-polarized light and the light-transmitting base material in parallel with the fast axis (the angle between the S-polarized light and the light-transmitting base material being 0 °). The reflectivity was 4.39%, and the reflection was measured by setting the S-polarized light and the slow axis of the light-transmitting substrate in parallel (the angle between the S-polarized light and the light-transmitting substrate being 0 °). The rate was similarly 4.39%, and there was no difference in reflectance. Although there is no difference in the reflectance, there is no problem in the reflectance because triacetyl cellulose is used as the light-transmitting substrate. The liquid crystal monitor on which the optical laminated body installed so that the angle between the S-polarized light and the phase advance axis of the light-transmitting substrate is 0 ° is set as a liquid crystal monitor A, and the retardation of the S-polarized light and the light-transmitting substrate is delayed. When the liquid crystal monitor on which the optical layered body that was installed and measured so that the angle formed with the axis was 0 ° was used as the liquid crystal monitor B, the bright spot contrast was evaluated in the same manner as in Example 1. There was no difference. According to the reference example 1, when a light-transmitting base material that does not have a birefringence index in the surface that has been used in a conventional liquid crystal display device is used, there is no problem of visibility and no problem with visibility. Was confirmed.

The optical laminate and the polarizing plate of the present invention are a cathode ray tube display (CRT), a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (ELD), a field emission display (FED), a touch panel, electronic paper, It can be suitably applied to a tablet PC or the like.

10 Light source 11 Display screen

Claims (20)

An optical layered body having a light-transmitting substrate having a birefringence index in the plane and used on the surface of an image display device,
The slow axis, which is the direction in which the refractive index of the light transmissive substrate is large, is arranged in parallel with the vertical direction of the display screen of the image display device, and the absorption axis of the polarizer of the image display device is the display screen. An optical laminate characterized by being in the left-right direction. The optical laminate according to claim 1, further comprising an optical functional layer on one surface of the light-transmitting substrate. The light-transmitting substrate has a difference between the refractive index (nx) in the slow axis direction, which is a direction in which the refractive index is large, and the refractive index (ny) in the fast axis direction, which is a direction orthogonal to the slow axis direction. The optical laminate according to claim 1 or 2, wherein (nx-ny) is 0.01 or more. When the refractive index in the slow axis direction of the light-transmitting substrate is (nx) and the refractive index in the fast axis direction that is perpendicular to the slow axis direction is (ny), the refractive index of the optical functional layer The optical layered body according to claim 2 or 3, wherein the rate is less than (nx + ny) / 2. 5. The optical laminate according to claim 1, wherein the light transmissive substrate is a substrate made of polyester. The optical laminate according to claim 5, wherein the polyester is polyethylene terephthalate or polyethylene naphthalate. Having a primer layer between the light transmissive substrate and the optical functional layer;
When the refractive index (np) of the primer layer is larger than the refractive index (nx) in the slow axis direction of the light-transmitting substrate and the refractive index (nf) of the optical functional layer (np> nx, nf) Or
When the refractive index (np) of the primer layer is smaller than the refractive index (ny) in the fast axis direction of the light-transmitting substrate and the refractive index (nf) of the optical functional layer (np <ny, nf) ,
The optical layered body according to claim 2, 3, 4, 5 or 6, wherein the primer layer has a thickness of 3 to 30 nm. Having a primer layer between the light transmissive substrate and the optical functional layer;
When the refractive index (np) of the primer layer is larger than the refractive index (nx) in the slow axis direction of the light-transmitting substrate and smaller than the refractive index (nf) of the optical functional layer (nx <np <Nf) or
When the refractive index (np) of the primer layer is smaller than the refractive index (ny) in the fast axis direction of the light-transmitting substrate and larger than the refractive index (nf) of the optical functional layer (nf <np <Ny),
The optical laminate according to claim 2, 3, 4, 5, or 6, wherein the primer layer has a thickness of 65 to 125 nm. Having a primer layer between the light transmissive substrate and the optical functional layer;
The refractive index (np) of the primer layer is between the refractive index (ny) in the fast axis direction of the light transmissive substrate and the refractive index (nx) in the slow axis direction of the light transmissive substrate. The optical laminate according to claim 2, 3, 4, 5 or 6, which is present (ny <np <nx). An optical laminate having a light-transmitting substrate having a birefringence index in a plane is a polarizing plate provided on a polarizing element and used on the surface of an image display device,
The absorption axis of the polarizing element is in the horizontal direction with respect to the display screen of the image display device,
The optical laminate and the polarizing element are arranged so that a slow axis that is a direction in which the refractive index of the light-transmitting substrate is large and an absorption axis of the polarizing element are perpendicular to each other,
A polarizing plate, wherein a slow axis, which is a direction in which the refractive index of the light-transmitting substrate is large, is arranged in parallel with the vertical direction of the display screen of the image display device. The polarizing plate of Claim 10 which has an optical function layer on one surface of a light-transmissive base material. The light-transmitting substrate having a birefringence in the plane has a refractive index (nx) in the slow axis direction, which is a direction in which the refractive index is large, and a fast axis direction, which is a direction orthogonal to the slow axis direction. The polarizing plate according to claim 10 or 11, wherein a difference (nx-ny) from a refractive index (ny) is 0.01 or more. When the refractive index in the slow axis direction of the light-transmitting substrate is (nx) and the refractive index in the fast axis direction that is perpendicular to the slow axis direction is (ny), the refractive index of the optical functional layer The polarizing plate according to claim 11 or 12, wherein the rate is less than (nx + ny) / 2. Having a primer layer between the light transmissive substrate and the optical functional layer;
When the refractive index (np) of the primer layer is larger than the refractive index (nx) in the slow axis direction of the light-transmitting substrate and the refractive index (nf) of the optical functional layer (np> nx, nf) Or
When the refractive index (np) of the primer layer is smaller than the refractive index (ny) in the fast axis direction of the light-transmitting substrate and the refractive index (nf) of the optical functional layer (np <ny, nf) ,
The polarizing plate according to claim 11, wherein the primer layer has a thickness of 3 to 30 nm. Having a primer layer between the light transmissive substrate and the optical functional layer;
When the refractive index (np) of the primer layer is larger than the refractive index (nx) in the slow axis direction of the light-transmitting substrate and smaller than the refractive index (nf) of the optical functional layer (nx <np <Nf) or
When the refractive index (np) of the primer layer is smaller than the refractive index (ny) in the fast axis direction of the light-transmitting substrate and larger than the refractive index (nf) of the optical functional layer (nf <np <Ny),
The polarizing plate according to claim 11, wherein the primer layer has a thickness of 65 to 125 nm. Having a primer layer between the light transmissive substrate and the optical functional layer;
The refractive index (np) of the primer layer is between the refractive index (ny) in the fast axis direction of the light transmissive substrate and the refractive index (nx) in the slow axis direction of the light transmissive substrate. The polarizing plate according to claim 11, wherein the polarizing plate is present (ny <np <nx). The optical laminate according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, or the polarizing plate according to claim 10, 11, 12, 13, 14, 15 or 16. A characteristic image display device. The image display device according to claim 17, wherein the image display device is a VA mode or IPS mode liquid crystal display device. A method for manufacturing an image display device comprising an optical laminate having a light-transmitting substrate having a birefringence in-plane,
The absorption axis of the polarizer of the image display device is in the horizontal direction with respect to the display screen of the image display device,
The step of disposing the optical laminate so that a slow axis, which is a direction in which the refractive index of the light-transmitting substrate is large, and a vertical direction of a display screen of the image display device are parallel to each other. A method for manufacturing an image display device. A method for improving the visibility of an image display device comprising an optical laminate having a light-transmitting substrate having a birefringence in-plane,
The absorption axis of the polarizer of the image display device is in the horizontal direction with respect to the display screen of the image display device,
An image in which the optical laminate is arranged so that a slow axis, which is a direction in which the refractive index of the light-transmitting substrate is large, and a vertical direction of a display screen of the image display device are parallel to each other. A method for improving the visibility of a display device.

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