JP2015219508A - Optical laminate, method for manufacturing optical laminate, image display device and method for improving interference fringe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical laminate capable of highly suppressing the occurrence of an interference fringe even when a hard coat layer is laminated on an optically transparent base material having a birefringence in the in-plane, such as a polyester film.SOLUTION: The optical laminate has at least, an optically transparent base material having a birefringence in the in-plane, an undercoat layer, a hard coat layer and an antireflection layer laminated in this order and is arranged and used on a polarizer on the display screen side of an image display device. The optically transparent base material having a birefringence in the in-plane is arranged so that a fast axis direction small in the refractive index of the optically transparent base material having a birefringence in the in-plane is parallel to the horizontal direction of the display screen of the image display. When the refractive index of the optically transparent base material having a birefringence in the in-plane at a wavelength of 550 nm in the direction of the fast axis is set to nF; the refractive index of the undercoat layer at a wavelength of 550 nm is set to nUC; the film thickness of the undercoat layer is set to d; and the refractive index of the hard coat layer at a wavelength of 550 nm is set to nHC, the following formulae (1) and (2) are satisfied.

Description

The present invention relates to an optical laminate, a method for manufacturing the optical laminate, an image display device, and a method for improving interference fringes of the 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 plate is disposed on the image display surface side of the liquid crystal cell, and it is usually required to impart hardness so that the polarizer of the polarizing plate is not damaged during handling. Therefore, it is common to impart hardness to the image display surface by using a hard coat film in which a hard coat layer or the like is provided on a light-transmitting substrate as a polarizing plate protective film.

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 to use a polyester film such as polyethylene terephthalate (PET) as a cellulose ester substitute film has been made (for example, Patent Literatures 1 to 3).
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.

However, according to the study by the present inventors, when an optical laminate using a polyester film such as polyethylene terephthalate (PET) as a cellulose ester film substitute film is disposed on a polarizing element, in-plane birefringence of the polyester film. Due to the property of being easily developed, unevenness of different colors (hereinafter also referred to as “Nizimura”) occurs in the liquid crystal display device, particularly when the display screen is observed obliquely, and the display quality of the liquid crystal display device is impaired. It became clear that there was a problem.

As an attempt to use a polyester film as a material for a light-transmitting substrate instead of a cellulose ester film, for example, in Patent Document 4, a polyethylene terephthalate film having sufficient transparency by stretching 2.5 to 6 times is transparent. An antiglare film used as a substrate is described. In this anti-glare film, if the retardation is 1000 or more, the coloration at the front becomes inconspicuous, but the color unevenness in the oblique direction cannot be eliminated, so the total haze is 8 times the transmitted sharpness. Nijimura has been eliminated by making the above. However, since visibility will fall if a permeation | transmission clarity is low, the anti-glare film of patent document 4 needs 5.5 to 55% as a haze. Furthermore, in order to satisfy the relationship between the transmission definition and haze, the period of the surface irregularity is increased, and the regular reflectance of the antiglare layer is set to a very low value of 0.05 to 2%. Since there is almost no flat surface on the surface of the glare layer, there is a problem that the image quality including white blurring and contrast is inferior even if the wiggle can be eliminated.

Further, in Patent Document 5, a white light emitting diode is used as a light source, and an angle between an absorption axis of a polarizing plate and a slow axis of the polymer film is 45 degrees in a polymer film having a retardation of 3000 to 30000 nm. It is described that when the screen is observed through a polarizing plate such as sunglasses, good visibility can be ensured regardless of the observation angle. However, polyesters and polycarbonate films, which are preferable polymer films in Patent Document 5, are soft and have no scratch resistance, and thus cannot be put to practical use unless a hard coat layer is provided on the surface of the polymer film. However, when a hard coat layer is provided on the surface of the polymer film, if the difference in refractive index between the two becomes large, interference fringes due to the difference in refractive index occur, resulting in image quality degradation.

Here, the interference fringe means that when white light hits a transparent thin film, the light reflected from the surface of the thin film and the light reflected from the interface having a difference in refractive index once entering the thin film cause interference. This is a phenomenon in which a partial iris-like color is seen, and is a phenomenon that occurs because the wavelength that strengthens changes depending on the viewing direction. This phenomenon is not only difficult to see for the user but may give an unpleasant impression, and improvement is strongly demanded. When a hard coat layer (refractive index: Nh) is provided on a polymer film (refractive index: Np), when there is a difference (refractive index difference) between Np and Nh, for example, a general-purpose hard coat layer for a polyester film In the case where Np is 1.64 to 1.68 and Nh is 1.50 to 1.53, as in the case of laminating films, interference of reflected light occurs at the interface between the polymer film and the hard coat layer. The larger the refractive index difference is, the more conspicuous the interference fringes are.

すなわち、特許文献５に記載の発明においても、干渉縞を防止するには、上記干渉縞解消法１に基づいてハードコート層を設けたり、上記干渉縞解消法２に基づいて中間層を設けたりする必要があった。 On the other hand, it is known that interference fringes can be eliminated by aligning the refractive indices of the polymer film (refractive index: Np) and hard coat layer (refractive index: Nh) as much as possible (hereinafter also referred to as interference fringe elimination method 1). . Furthermore, an intermediate layer (for example, a primer layer for improving adhesion) may be provided between the polymer film and the hard coat layer. At that time, the refractive index of the intermediate layer is changed to the refractive index of the polymer film. There is also known a technique for suppressing interference fringes by using an intermediate refractive index between (Np) and the refractive index (Nh) of the hard coat layer (hereinafter also referred to as interference fringe elimination method 2) (for example, patents). References 6 and 7). The intermediate refractive index (Nph) between the refractive index (Np) of the polymer film and the refractive index (Nh) of the hard coat layer is theoretically calculated by the following formula.

That is, also in the invention described in Patent Document 5, in order to prevent interference fringes, a hard coat layer is provided based on the interference fringe elimination method 1, or an intermediate layer is provided based on the interference fringe elimination method 2. There was a need to do.

JP 2004-205773 A JP 2009-157343 A JP 2010-244059 A JP 2009-156938 A JP2011-107198A Japanese Patent Laid-Open No. 2003-177209 JP 2004-345333 A

However, in Patent Document 5, in order to give a high retardation value to the polymer film, the refractive index in the longitudinal direction and the lateral direction of the polymer film (hereinafter also referred to as Nx and Ny, respectively, where Np- Nx = Ny−Np). For this reason, the refractive index Nh of the hard coat layer cannot be determined based on the interference fringe elimination method 1, and even if Nh is an average value of Nx and Ny, | Nh− Since the refractive index difference of Nx | and | Nh−Ny | exists, the interference fringes cannot be eliminated. Similarly, since the refractive indexes in the vertical direction and the horizontal direction are different, the refractive index of the intermediate layer cannot be determined based on the interference fringe elimination method 2, and even if the intermediate layer is set to the optimum refractive index, Interference fringes will occur. The retardation is a value obtained by multiplying the difference in refractive index between the vertical and horizontal directions of the polymer film by the film thickness of the polymer film. Recently, since a hard coat film or the like is required to be thin, it is not preferable to increase the film thickness of the polymer film. For this reason, if the film thickness of the polymer film cannot be increased, in order to increase the retardation value of the polymer film, the above-described difference between the vertical and horizontal refractive indexes must be increased. That is, as the retardation value of the polymer film is increased, interference fringes become a larger problem. Therefore, in Patent Document 5, the problem of image quality degradation due to the occurrence of interference fringes cannot be avoided.

As a result of further investigation on the problem in the case of using such a polyester film, a polyester film having a somewhat high retardation value is used as the light-transmitting substrate of the optical layered body, and thus a conventional polyester film is used. It has been found that the problem of Nizimura can be improved as compared with the case where an optical layered body provided with a light-transmitting substrate is used.
However, when such a polyester film having a somewhat high retardation value is used as a light-transmitting substrate, an undercoat layer is essential to ensure adhesion with the hard coat layer. In addition, it has been found that in the optical laminate having the structure having the undercoat layer, the generation of interference fringes becomes a problem and the display quality of the image display device is significantly impaired.

In view of the above situation, the present invention highly suppresses the generation of interference fringes even when a hard coat layer is laminated on a light-transmitting substrate having a birefringence in a plane such as a polyester film. It is an object of the present invention to provide an optical laminate, a method for producing the optical laminate, an image display device, and a method for improving interference fringes of the image display device.

In the present invention, at least a light-transmitting substrate having a birefringence in the plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, and disposed on a polarizing plate on the display screen side of the image display device. The light-transmitting substrate having a birefringence in the plane is an optical laminate used in the above-described manner, and the light-transmitting substrate having a birefringence in the plane is in a direction in which the refractive index is small. The refractive index at a wavelength of 550 nm in the fast axis direction of a light-transmitting substrate that is arranged so that the phase axis and the horizontal direction of the display screen of the image display are parallel and has a birefringence in the plane is expressed as nF. When the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, the thickness of the undercoat layer is d, and the refractive index of the hard coat layer at a wavelength of 550 nm is nHC, the following formulas (1) and (2) Features that meet An optical laminate that.

また、本発明の光学積層体は、反射色相値が、色相ａ^＊の絶対値が３以上であるか、又は、色相ｂ^＊の絶対値が３以上であることが好ましい。 In the optical layered body of the present invention, the fast axis of the light-transmitting substrate having a birefringence in the plane is parallel to the absorption axis of the polarizer of the polarizing plate on the display screen side of the image display device. It is preferable that they are arranged as described above.
In the optical layered body of the present invention, the visibility reflectance Y on the surface of the antireflection layer is preferably 0.3% or less.
Moreover, it is preferable that the film thickness d of the undercoat layer satisfies the following formula (3) when the refractive index at a wavelength of 650 nm of the undercoat layer is nUC650.

In the optical layered body of the present invention, it is preferable that the reflected hue value has an absolute value of hue a ^* of 3 or more, or an absolute value of hue b ^* of 3 or more.

In the present invention, at least a light-transmitting base material having an in-plane birefringence, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order on the polarizing plate on the display screen side of the image display device. A method for producing an optical layered body used by arranging a light-transmitting base material having a birefringence index in the plane and a light-transmitting base material having a birefringence index in the plane. A phase advance axis of a light-transmitting substrate having a birefringence in the plane, the phase advance axis being a small direction, and a step of arranging the phase display axis so that the horizontal direction of the display screen of the image display is parallel When the refractive index at a wavelength of 550 nm in the direction is nF, the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, the thickness of the undercoat layer is d, and the refractive index of the hard coat layer at a wavelength of 550 nm is nHC, Formula (1) and (2) it is also a method for producing an optical laminate and satisfies the.

Moreover, this invention is also an image display apparatus provided with the optical laminated body of the said invention.
The image display device of the present invention is preferably a VA mode or IPS mode liquid crystal display device including a white light emitting diode as a backlight light source.

In the present invention, at least a light-transmitting base material having an in-plane birefringence, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order on the polarizing plate on the display screen side of the image display device. A method for improving interference fringes of an image display device using an optical layered body disposed on a substrate, wherein a light-transmitting substrate having a birefringence in the plane is provided, and light having a birefringence in the plane is provided. A light-transmitting substrate having a birefringence in the plane in which the fast axis, which is the direction in which the refractive index of the transparent substrate is small, and the horizontal direction of the display screen of the image display are parallel to each other The refractive index at a wavelength of 550 nm in the fast axis direction is nF, the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, the thickness of the undercoat layer is d, and the refractive index of the hard coat layer at a wavelength of 550 nm is nHC. When the bottom Is also the interference fringe method for improving an image display device characterized by satisfying the formula (1) and (2).

以下に、本発明を詳細に説明する。
なお、本発明では、特別な記載がない限り、モノマー、オリゴマー、プレポリマー等の硬化性樹脂前駆体も“樹脂”と記載する。

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 on the optical laminate having a structure in which a light-transmitting base material having a birefringence in-plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, When the optical laminate is installed in the image display device, the fast axis, which is the direction in which the refractive index of the light-transmitting substrate is small, is set to a specific direction with respect to the display screen of the image display device. The inventors have found that the occurrence of interference fringes can be suppressed to a high degree by making the refractive indexes of the respective layers constituting the optical laminated body have a specific relationship, and the present invention has been completed.
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 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-mentioned problem of interference fringes is caused by using a light-transmitting substrate having a birefringence in the surface as the light-transmitting substrate of the optical laminate.
Here, conventionally, it is known that an interference fringe can be improved by providing a concavo-convex shape on the surface of the optical laminate, but an optical laminate having such a concavo-convex shape on the surface, There is a problem that white turbidity occurs, and there is a problem that a clear display image cannot be obtained when it is installed on the surface of an image display device.
On the other hand, according to the optical layered body of the present invention, the above-mentioned problem of interference fringes can be solved without using the conventional method of improving the interference fringes due to the uneven shape on the surface of the optical layered body. This is the case when it is used for a touch panel with an air gap structure because it does not occur, and it can see clear and highly realistic moving images and still images and has no uneven surface on the optical laminate surface. However, a clear image can be obtained without causing problems such as glare.

In the present invention, at least a light-transmitting substrate having a birefringence in the plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, and disposed on a polarizing plate on the display screen side of the image display device. It is an optical layered body used.
In the optical layered body of the present invention, the fast axis, which is the direction in which the refractive index of the light-transmitting substrate is small, is arranged in parallel with the left-right direction of the display screen of the image display device.
Here, since the image display device is normally used in a state where it is installed and fixed indoors (in a bright place), light reflected by the wall surface or floor surface is incident on the display screen of the image display device. The The inventors focused on the fact that most of the light reflected on the wall surface or floor surface and incident on the display screen of the image display device vibrates in the left-right direction of the display screen.
On the other hand, in an optical laminate in which a light-transmitting substrate having an in-plane birefringence index, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, due to optical interference at the upper and lower interfaces of the undercoat layer In the case of reducing interference fringes, a design in which interference fringes are further suppressed is possible when the difference between the refractive index of the light-transmitting substrate having a birefringence in the surface and the refractive index of the hard coat layer is small. The refractive index of a light-transmitting substrate having a birefringence in the plane is often higher than the refractive index of a resin material generally used for the hard coat layer, and therefore the birefringence is increased in the plane. The fast axis, which is the direction in which the refractive index of the light-transmitting substrate is small, is close to the refractive index of the hard coat layer.
For these reasons, a light-transmitting substrate having a birefringence in the surface can be easily designed with reduced interference fringes when optically designed in accordance with the fast axis.
From the relationship between the external light incident on the display screen of the image display device in these rooms and the optical laminate having the above-described configuration, the optical laminate of the present invention is arranged in a direction in which the refractive index of the light-transmitting substrate is small. A certain fast axis and the horizontal direction of the display screen of the image display device are arranged in parallel.
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 fast axis, which is the direction in which the angle is small, is in a state in which it is directed in a direction parallel to the vibration direction of the light reflected from the wall surface or floor surface. As described above, in the image display device, the optical layered body is formed by installing the optical layered body so that the direction of the fast axis, which is the direction in which the refractive index of the light-transmitting base material is small, becomes a specific direction. The generation of interference fringes can be highly suppressed.
The above-mentioned “the fast axis that is the direction in which the refractive index of the light-transmitting substrate is small is arranged in parallel with the horizontal direction of the display screen of the image display device” means that the fast axis is the above It means a state in which the optical laminated body is arranged on the image display device in a range of 0 ° ± 15 ° with respect to the left and right direction of the display screen. Further, the “left-right direction of the display screen of the image display device” means a direction perpendicular to the vertical direction of the display screen when the image display device is installed so that the display screen is perpendicular to the floor surface. That is, it means a direction horizontal to the floor on which the image display device is installed.
The angle formed between the fast axis, which is the direction in which the refractive index of the light-transmitting substrate is small, and the horizontal direction of the display screen of the image display device is preferably 0 ° ± 5 °, and preferably 0 ° ± 2 °. Is more preferable, and it is still more preferable that it is 0 degree.

The optical layered body of the present invention has a refractive index at a wavelength of 550 nm in the fast axis direction of a light-transmitting substrate having a birefringence in the plane, nF, and a refractive index at a wavelength of 550 nm of the undercoat layer as nUC. When the film thickness of the undercoat layer is d and the refractive index at a wavelength of 550 nm of the hard coat layer is nHC, the following expressions (1) and (2) are satisfied.

By satisfy | filling said Formula (1), the improvement effect of the interference fringe by the optical laminated body of this invention will be excellent. This is because the reflectance R of the reflection that occurs at the interface between the layers when light is incident on a laminate formed by laminating a plurality of layers is represented by the following formula (A): a hard coat layer and an undercoat layer When the reflection based on the following formula (A) occurs at the interface between the undercoat layer and the light-transmitting substrate, and the reflected lights are superposed with the same intensity in a state where the phases are different from each other by π. This is because the interference fringe intensity is weakest. In addition, the relational expression of the refractive index and thickness at this time becomes following formula (B) and (C).
R = (n1-n2) ² / (n1 + n2) ² (A)
n2 = (n1 × n3) ^1/2 (B)
d = (1/4) × (λ / n2) (C)
In the above formulas (A) to (C), n1 represents the refractive index of the first layer, n2 represents the refractive index of the second layer, n3 represents the refractive index of the third layer, and d represents the thickness of the second layer. .

The light-transmitting substrate is not particularly limited as long as it has a birefringence in the plane, and examples thereof include substrates made of polycarbonate, acrylic, polyester, etc. Among them, cost and mechanical properties are particularly important. A polyester substrate that is advantageous in strength is preferred. In the following description, a light-transmitting substrate having a birefringence in the plane will be described as a polyester substrate.
In the optical layered body of the present invention, the light-transmitting substrate may be a birefringent index even if it is a light-transmitting substrate made of cellulose ester or the like that has been conventionally used as an optically isotropic material. It can be used by having

In the optical layered body of the present invention, the refractive index (nx) in the direction in which the refractive index is large (slow axis direction) in the plane of the polyester substrate, and the direction (fast axis direction) orthogonal to the slow axis direction The difference nx−ny (hereinafter also referred to as Δn) from the refractive index (ny) is preferably 0.01 or more. When Δn is less than 0.01, the effect of improving transmittance may be reduced. On the other hand, the Δn is preferably 0.30 or less. If it exceeds 0.30, it becomes necessary to stretch the polyester base material excessively, so that the polyester base material is likely to be torn and torn, and the practicality as an industrial material may be remarkably lowered.
From the above viewpoint, the more preferable lower limit of Δn is 0.05, and the more preferable upper limit is 0.27. In addition, when said (DELTA) n exceeds 0.27, durability of the polyester base material in a moist heat resistance test may be inferior. Since the durability in the heat and humidity resistance test is excellent, the more preferable upper limit of Δn is 0.25. By satisfying such Δn, a suitable improvement in light transmittance can be achieved.

In the present specification, whether or not the light-transmitting substrate has a birefringence in the plane is determined by Δn (nx−ny) ≧ 0.0005 at a refractive index of a wavelength of 550 nm. It is assumed that those having birefringence and those having Δn <0.0005 do not have 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.
In addition, 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 is generally known as an isotropic material, is determined by the above measuring method. These were 0.0000375 and 0.00005, respectively, and were judged to have no birefringence (isotropic).
In addition, as a method for measuring the birefringence, two polarizing plates are used to determine the orientation axis direction (major axis direction) of the light-transmitting substrate, and refraction of two axes perpendicular to the orientation axis direction The rate (nx, ny) can be determined by an Abbe refractometer (NAG-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 Measure the reflectivity of 5 degrees when the fast axis is parallel, and from the following formula (I) showing the relationship between the reflectivity (R) and the refractive index (n), each of the slow axis and the fast axis The refractive index (nx, ny) of the wavelength can also be calculated.
R (%) = (1-n) ² / (1 + n) ² formula (I)

The average refractive index can be measured using an Abbe refractometer or an ellipsometer, and the refractive index nz in the thickness direction of the light-transmitting film is measured by the above method, using nx and ny. And can be calculated from the following formula (II).
Average refractive index N = (nx + ny + nz) / 3 Formula (II)

Here, a calculation method of nx, ny, and nz will be described with a specific example.
Nx is the refractive index in the slow axis direction of the light transmissive substrate, ny is the refractive index in the fast axis direction of the light transmissive substrate, and nz is the refractive index in the thickness direction of the light transmissive substrate. It is.
(Calculation of three-dimensional refractive index wavelength dispersion)
First, a calculation method of three-dimensional refractive index wavelength dispersion will be specifically described by taking a cycloolefin polymer as an example.
The average refractive index wavelength dispersion of a cycloolefin polymer film having no in-plane birefringence was measured using an ellipsometer (UVISEL Horiba, Ltd.), and the results are shown in FIG. From this measurement result, the average refractive index wavelength dispersion of the cycloolefin polymer film having no in-plane birefringence was defined as the refractive index wavelength dispersion of nx, ny, and nz.
The film was uniaxially stretched at a free temperature at a stretching temperature of 155 ° C. to obtain a film having a birefringence in the plane. The film thickness was 100 μm. This free-end uniaxially stretched film was measured with a birefringence meter (KOBRA-21ADH, Oji Scientific Instruments) with four retardation values (447.6 nm, 547.0 nm, 630.6 nm) at an incident angle of 0 ° and 40 °. 743.4 nm).
Based on the average refractive index (N) and retardation value at each wavelength, the three-dimensional refractive index using the Couchy or Sellmeier equation, etc., using the three-dimensional chromatic dispersion calculation software attached to the birefringence meter. The chromatic dispersion was calculated and the result is shown in FIG. In FIG. 2, ny is shown substantially overlapping with nz. From this result, a three-dimensional refractive index wavelength dispersion of a cycloolefin polymer film having an in-plane birefringence was obtained.
(Calculation of refractive indices nx, ny and nz using a spectrophotometer)
Taking polyethylene terephthalate as an example, a method of calculating refractive indexes nx, ny, and nz using a spectrophotometer will be specifically described.
The average refractive index wavelength dispersion of polyethylene terephthalate having no in-plane birefringence was performed in the same manner as the above-described method for calculating the three-dimensional refractive index wavelength dispersion.
The refractive index wavelength dispersion (nx, ny) of polyethylene terephthalate having a birefringence in the plane was calculated using a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit VAR-7010, manufactured by JASCO Corporation). Polarization measurement: S-polarized light after a black vinyl tape (for example, Yamato vinyl tape No200-38-21 38 mm width) having a width larger than the measurement spot area is pasted on the surface opposite to the measurement surface to prevent back surface reflection. Then, the 5-degree spectral reflectance was measured when the alignment axis of the light-transmitting substrate was installed in parallel and when the axis orthogonal to the alignment axis was installed in parallel. The results are shown in FIG. The refractive index wavelength dispersion (nx, ny) was calculated from the above formula (I) showing the relationship between the reflectance (R) and the refractive index (n). A direction indicating a larger reflectance (refractive index calculated by the above formula (I)) is nx (also referred to as a slow axis), and a smaller reflectance (refractive index calculated by the above formula (I)) is indicated. The direction was ny (also called fast axis). Here, the orientation axis is a state in which a film having a birefringence in-plane is sandwiched between two polarizing plates placed in a crossed Nicol state on a light source, the film is rotated, and light leakage is minimized. In this case, the transmission axis of the polarizing plate or the same direction as the absorption axis can be used as the orientation axis of the film. The refractive index nz can be calculated from the average refractive index (N) and the above formula (II).

The material constituting the polyester base material is not particularly limited as long as it satisfies the above-described Δn, 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, a polarizing plate having excellent light transmittance can be obtained even with a highly versatile film such as PET. Furthermore, PET is excellent in transparency, heat or mechanical properties, Δn can be controlled by stretching, and has a large intrinsic birefringence, so that it can have a birefringence relatively easily.

The method for obtaining the polyester base material is not particularly limited as long as it satisfies the above-described Δn. For example, a polyester such as the above-mentioned PET, which is 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. The birefringence of the substrate may be reduced.
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.

The thickness of the polyester base material is preferably in the range of 5 to 300 μm. If it is less than 5 μm, tearing, tearing and the like are likely to occur, and the utility as an industrial material may be significantly reduced. On the other hand, if it exceeds 300 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 10 micrometers, a more preferable upper limit is 200 micrometers, and a still more preferable upper limit is 150 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.

In the optical layered body of the present invention, the fast axis of the light-transmitting substrate having a birefringence in the plane is parallel to the absorption axis of the polarizer of the polarizing plate on the display screen side of the image display device. It is preferable to arrange | position. By arranging the light-transmitting substrate and the polarizer in such a specific relationship, it becomes easy to absorb light having a polarization parallel to the fast axis transmitted through the optical laminate of the present invention. Therefore, the effect of improving interference fringes by the optical laminate of the present invention is more excellent. As described above, the outdoor light in the room has many vibration components in the horizontal direction of the display screen of the image display device, and the fast axis of the light-transmitting substrate and the absorption axis of the polarizer are used as the image display device. When installed in parallel to the left and right direction of the display screen, when the external light transmitted through the light transmissive substrate reaches the polarizer, it absorbs more external light and reduces interference fringes at the polarizer interface. This is because it can.
The above-mentioned “the fast axis of the light-transmitting base material having a birefringence in the plane and the absorption axis of the polarizer of the polarizing plate on the display screen side of the image display device are arranged in parallel. The phrase “has” means that the angle formed by the fast axis of the light-transmitting substrate and the absorption axis of the polarizer is 0 ° ± 15 °.
In the present invention, the angle formed by the fast axis, which is the direction in which the refractive index of the light-transmitting substrate is small, and the absorption axis of the polarizer is more preferably 0 ° ± 5 °, more preferably 0 ° ± 2 ° is more preferable, and 0 ° is most preferable.

The polarizer 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 laminating the polarizer and the light transmissive substrate, it is preferable to saponify the light transmissive substrate. Adhesion is improved by the saponification treatment.

The undercoat layer is a layer that functions as an adhesive layer provided for the purpose of improving the adhesion between the light-transmitting substrate and a hard coat layer described later.
The material for the undercoat layer is not particularly limited as long as it satisfies the above-described refractive index conditions. Conventionally known materials can be appropriately selected and used. And thermoplastic polyester resins, urethane resins, acrylic resins, and modified products thereof.
Moreover, in order to adjust the refractive index of the said undercoat layer, high refractive index fine particles, high refractive index resin, a chelate compound, etc. can be added.

As said polyester resin, the polyester obtained from the following polybasic acid component and a diol component can be used, for example.
Examples of the polybasic acid component include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyro Examples include merit acid, dimer acid, and 5-sodium sulfoisophthalic acid.

Examples of the diol component include ethylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, and dimethylolpropane. Examples thereof include poly (ethylene oxide) glycol and poly (tetramethylene oxide) glycol.

Moreover, as said acrylic resin, what is obtained by copolymerizing the monomer illustrated below is mentioned, for example.
Examples of the monomer include alkyl acrylate and alkyl methacrylate (the alkyl group includes methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, Cyclohexyl groups, etc.); hydroxy-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate; epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether; Acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt) ) Monomers having a carboxy group or a salt thereof; acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate (the alkyl group includes a methyl group, Ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N-di Alkoxyacrylamide, N, N-dialkoxymethacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), acryloylmorpholine, N-methylolacrylamide, N-methylolmethacrylamide, -Monomers having amide groups such as phenylacrylamide and N-phenylmethacrylamide; monomers of acid anhydrides such as maleic anhydride and itaconic anhydride; 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2- Such as oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, etc. Oxazoline group-containing monomer: methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, vinyl isocyanate, allyl isocyanate, styrene, α-methyl styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkylmer Ynoic acid monoesters, alkyl fumaric acid monoesters, alkyl itaconic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene and the like.

Examples of the urethane resin include those composed of polyol, polyisocyanate, chain extender, crosslinking agent and the like.
Examples of the polyol include a dehydration reaction between a dicarboxylic acid and a glycol containing a polyether such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polycaprolactone, and the like. Examples include polyesters to be produced, polycarbonates having carbonate bonds, acrylic polyols, and castor oil.

Examples of the polyisocyanate include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

Examples of the chain extender or crosslinking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, 4,4′-diaminodiphenylmethane, 4,4′-. Examples include diaminodicyclohexylmethane and water.

As the high refractive index fine particles, for example, metal oxide fine particles having a refractive index of 1.60 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), niobium pentoxide (Nb ₂ O ₅ , refractive index: 2.33), tantalum oxide _(Ta 2 _{O 5:} refractive index 2.16) and unloading Mont zinc (ZnSb ₂ O _6, refractive index: 1.90 to 2.00), and the like.
The high refractive index fine particles preferably have an average primary particle diameter of 5 to 100 nm. When the average primary particle diameter exceeds 100 nm, optical scattering occurs in the undercoat layer, resulting in poor transparency. When the average primary particle diameter is less than 5 nm, aggregation of fine particles increases and the secondary particle diameter increases. Optical scattering may occur, and the transparency of the undercoat layer may deteriorate.
The refractive index of these high refractive index fine particles is, for example, mixed with a thermoplastic resin whose refractive index is known and a metal oxide whose mass is measured, and then molded into a transparent pellet having an appropriate thickness, The refractive index of the pellet can be measured, and the refractive index of the high refractive index fine particles can be calculated from the blending ratio with the resin having the known refractive index. The refractive index measurement can be obtained by, for example, an Abbe refractometer by the Becke method according to JIS K7142 (2008) A method, and for example, DR-M4 manufactured by Atago Co., Ltd. can be used. The wavelength for measuring the refractive index is 589 nm.
The average primary particle diameter can be obtained as an average value of particle diameters for 20 particles by image analysis by observation with a transmission electron microscope such as TEM or STEM.
The content of the high refractive index fine particles is not particularly limited. For example, the refractive index of the undercoat layer to be formed is a weighted average with the value of the refractive index measured in advance of the cured resin component added to the undercoat layer. What is necessary is just to adjust suitably with the relationship with another component so that a rate may satisfy | fill the relationship mentioned later.

Further, the high refractive index resin is not particularly limited as long as it is a resin having a higher refractive index than the above-described resin and the material of the undercoat layer. For example, epoxy resin, acrylic resin, polyester resin, amino resin, polyurethane Conventionally known resins such as resins can be mentioned.
Specific examples of such a high refractive index resin include, for example, Oxol EA-0200, Oxol EA-F5003, Oxol EA-F5503, and Oxol EA-F5510 (all of which are Osaka Gas Chemical Co., Ltd.), which are resins having a fluorene skeleton. Manufactured), A-BPEF (9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene) (manufactured by Shin-Nakamura Chemical Co., Ltd.), adamantate M-104, adamantate X, which is a resin having an adamantane skeleton -A-101, adamantate X-A-201, adamantate MM, adamantate EM, adamantate HM, adamantate HA, adamantate MA, adamantate EA (all manufactured by Idemitsu Kosan Co., Ltd.), a resin having a biphenyl skeleton New Frontier OPPE Nylphenol acrylate) (Daiichi Kogyo Seiyaku Co., Ltd.), bisphenol A EO adduct di (meth) acrylate which is a resin having a bisphenol A skeleton, bisphenol A PO adduct di (meth) acrylate, bisphenol A epoxy acrylate, Light acrylate POB-A (m-phenoxybenzyl acrylate) (made by Kyoeisha Chemical Co., Ltd.), which is a resin having a diphenyl oxide skeleton, and 4,4′-bis (β- (meth) acryloyloxy, which is a resin having a diphenyl sulfone skeleton Ethoxy) diphenylsulfone, 4,4′-di (β- (meth) acryloyloxyethoxy) diphenyl sulfide, which is a resin having a diphenyl sulfide skeleton, and the like. These may be used independently and 2 or more types may be used together.

Examples of the chelate compound include a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, and a water-soluble zirconium compound.
Examples of the water-soluble titanium chelate compound include diisopropoxybis (acetylacetonato) titanium, isopropoxy (2-ethyl-1,3-hexanediolato) titanium, diisopropoxybis (triethanolaminato). Examples thereof include titanium, di-n-butoxybis (triethanolaminato) titanium, hydroxybis (lactato) titanium, ammonium salt of hydroxybis (lactato) titanium, ammonium beloxocitrate ammonium salt, and the like.
Examples of the water-soluble titanium acylate compound include oxotitanium bis (monoammonium oxalate).
Examples of the water-soluble zirconium compound include zirconium tetraacetylacetonate and zirconium acetate.

In the optical layered body of the present invention, the film thickness d of the undercoat layer preferably satisfies the following formula (3).

なお、上記式（３）中、ｎＵＣ６５０は、アンダーコート層の波長６５０ｎｍにおける屈折率を表す。
上記アンダーコート層の膜厚ｄが上記式（３）を満たすことで、本発明の光学積層体による干渉縞の改善効果がより優れたものとなる。これは、上述したように、複数の層が積層されてなる積層体に光が入射したとき、２つの界面で反射されたそれぞれの光が位相π異なる状態で等しい強度で重ね合わせられるときに最も干渉縞強度の弱い状態となるためである。なお、これらの光の位相差は、下記式（４）及び（５）を満たすときにπとなる。
すなわち、ｎ１を第１層の屈折率、ｎ２を第２層の屈折率、ｎ３を第３層の屈折率、ｄを第２層の膜厚、λを光の波長とした場合、
ｎ１＜ｎ２＜ｎ３ 又は ｎ１＞ｎ２＞ｎ３ （４）
ｄ＝（１／４）×（λ／ｎ２） （５）
さらに、赤色領域である波長６５０ｎｍにおける干渉を特に弱めることで干渉縞の視認性を抑えることができる。
なお、上記アンダーコート層の厚みｄは、例えば、上記アンダーコート層の断面を、電子顕微鏡（ＳＥＭ、ＴＥＭ、ＳＴＥＭ）で観察することにより、任意の１０点を測定して得られた平均値（ｎｍ）である。非常に薄い厚みの場合は、高倍率観察したものを写真として記録し、更に拡大することで測定する。拡大した場合、層界面ラインが、境界線として明確に分かる程度に非常に細い線であったものが、太い線になる。その場合は、太い線幅を２等分した中心部分を境界線として測定する。

In the above formula (3), nUC650 represents the refractive index of the undercoat layer at a wavelength of 650 nm.
When the film thickness d of the undercoat layer satisfies the above formula (3), the interference fringe improving effect by the optical layered body of the present invention becomes more excellent. As described above, when light is incident on a laminated body formed by laminating a plurality of layers, the light reflected at the two interfaces is superposed with the same intensity in a state of different phase π. This is because the interference fringe intensity is weak. The phase difference between these lights becomes π when the following expressions (4) and (5) are satisfied.
That is, when n1 is the refractive index of the first layer, n2 is the refractive index of the second layer, n3 is the refractive index of the third layer, d is the thickness of the second layer, and λ is the wavelength of light,
n1 <n2 <n3 or n1>n2> n3 (4)
d = (1/4) × (λ / n2) (5)
Furthermore, the visibility of interference fringes can be suppressed by particularly weakening interference at a wavelength of 650 nm, which is a red region.
The thickness d of the undercoat layer is, for example, an average value obtained by measuring any 10 points by observing the cross section of the undercoat layer with an electron microscope (SEM, TEM, STEM) ( nm). 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.

In the optical layered body of the present invention, the undercoat layer uses a composition for an undercoat layer prepared by mixing and dispersing the above-described materials and, if necessary, a photopolymerization initiator and other components in a solvent. Can be formed.
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 undercoat layer composition preferably has a total solid content of 1 to 20%. If it is less than 1%, residual solvent may remain or whitening may occur. If it exceeds 20%, the viscosity of the composition for the undercoat layer becomes high, 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 2 to 10%.

Application of the undercoat layer composition to the polyester substrate can be carried out at any stage, but 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 orientation crystallization 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. It includes a film that has been stretched and oriented at low magnification in two directions (a biaxially stretched film that has been finally re-stretched in the machine direction or the transverse direction to complete orientation crystallization). Among them, it is preferable to apply the aqueous coating liquid of the composition for an undercoat layer to an unstretched film or a uniaxially stretched film oriented in one direction, and perform longitudinal stretching and / or lateral stretching and heat setting as it is. .
When applying the composition for an undercoat layer to a polyester substrate, physical treatment such as corona surface treatment, flame treatment, plasma treatment or the like is performed on the surface of the polyester substrate as a pretreatment for improving coatability, Or it is preferable to use this and a chemically inert surfactant together with the composition for undercoat layers.

As a coating method of the undercoat 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.
When an undercoat layer is formed on both sides of the polyester base material, the polyester base material can be easily slipped, and as a result, the optical layered body of the present invention can be suitably produced by roll-to-roll. .

The hard coat layer is formed on the undercoat layer, and the hardness is preferably H or more in a pencil hardness test (load 4.9 N) according to JIS K5600-5-4 (1999). More preferably.
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 is not particularly limited as long as it satisfies the above-described refractive index conditions. Can be used. Specifically, for example, it is preferably formed using a composition for a hard coat layer containing an ionizing radiation curable resin which is a resin curable by ultraviolet rays and a photopolymerization initiator.

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 trimethylolpropane 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 ( Or a reaction product (for example, poly (meth) acrylate ester of polyhydric alcohol) modified with the above polyfunctional compound and (meth) acrylate. It is. 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 resins, cellulose derivatives, silicone 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 viewpoints 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 present invention may not be within the above-described range. When the amount exceeds 10 parts by mass, ionizing radiation is transmitted to the deep part of the coated film. This is because the internal hardness is not promoted and the surface hardness 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, it may be a mixed solvent.
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.

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.

The method for applying the hard coat layer composition onto the undercoat layer is not particularly limited. For example, a gravure coating method, a spin coating method, a dip method, a spray method, a die coating method, a bar coating method, a roll Well-known methods, such as a coater method, a meniscus coater method, a flexographic printing method, a screen printing method, a speed coater method, can be mentioned.

The coating film formed by applying the hard coat layer composition on the undercoat layer 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.

The antireflection layer is a layer through which external light enters from the display screen of the image display device, and is preferably a low refractive index layer. When the antireflection layer is a low refractive index layer, reflection of the external light can be suitably reduced.

The low refractive index layer is preferably 1) a resin containing low refractive index particles such as silica and magnesium fluoride, 2) a fluorine-based resin which is a low refractive index resin, and 3) containing silica or magnesium fluoride. Fluorine-based resin, 4) A thin film of a low refractive index material such as silica or magnesium fluoride. For resins other than fluorine-based resins, the same resins as the binder resins described later 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 1.45 or less, particularly 1.42 or less.
Further, the thickness of the low refractive index layer is not limited, but it may be set appropriately from the range of about 30 nm to 1 μm.
In addition, although the low refractive index layer is effective in a single layer, two or more low refractive index layers and high refractive index layers are provided for the purpose of adjusting a lower minimum reflectance or a higher minimum reflectance. Is also possible as appropriate. When providing two or more layers having different refractive indexes, it is preferable to provide a difference in the refractive index and thickness of each layer.

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 Copolymers and the like. 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, a binder resin can also be mixed and used with the polymeric compound and polymer which have the above-mentioned 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.

As said binder resin, a transparent thing is preferable, for example, it is preferable that the ionizing radiation hardening type resin which is resin hardened | cured by an ultraviolet-ray or an electron beam hardens | cures by irradiation of an ultraviolet-ray or an electron beam.

Examples of the ionizing radiation curable resin include compounds having one or more unsaturated bonds such as compounds having functional groups such as acrylates. 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 trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and pentaerythritol. Tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) ) Acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate Rate, tetrapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanuric acid di (meth) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, diglycerin Polyfunctional compounds such as tetra (meth) acrylate, adamantyl di (meth) acrylate, isoboronyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate Etc. Of these, pentaerythritol tetraacrylate (PETTA) is preferably used. In the present specification, “(meth) acrylate” refers to methacrylate and acrylate. In the present invention, as the ionizing radiation curable resin, a compound obtained by modifying the above-described compound with PO, EO or the like can also be used.

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 is used in combination with a solvent-drying resin (a thermoplastic resin or the like, which is a resin that forms a film only by drying the solvent added to adjust the solid content during coating). You can also. By using the solvent-drying resin in combination, film defects on the coating surface of the coating liquid can be effectively prevented when the hard coat layer is formed.
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 transparency and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are more preferable.

Moreover, as said binder resin, you may contain a 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.

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.

In the formation of the low refractive index layer, the viscosity of the composition for low refractive index layer obtained by adding the above-mentioned material is 0.5 to 5 mPa · s (25 ° C.), preferably 0. It is preferable to set it as the thing of the range of 7-3 mPa * s (25 degreeC). 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 low refractive index layer can be formed by curing the resin in the coating film after drying the coating film formed by applying the low refractive index layer composition on the light transmissive substrate.

Examples of the resin curing means include a method of irradiating with ionizing radiation, for example, a method using a light source 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 lamp. It is done.
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.
When a heating means is used for the curing treatment, a thermal polymerization initiator that generates, for example, radicals to start polymerization of the polymerizable compound by heating may be added to the fluororesin composition. preferable.

The low refractive index layer composition preferably further contains a photopolymerization initiator.
The photopolymerization initiator is not particularly limited, and known ones can be used. Specific examples include, for example, acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester, thioxanthones, propio Examples include phenones, 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 layer thickness (nm) d _A of the low refractive index layer is expressed by the following formula (a):
d _A = mλ / (4n _A ) (a)
(In the above formula,
n _A represents the refractive index of the low refractive index layer;
m represents a positive odd number, preferably 1;
λ is a wavelength, preferably a value in the range of 480 to 580 nm)
Those satisfying these conditions are preferred.

In the present invention, the low refractive index layer is represented by the following formula (b):
120 <n _A d _A <145 (b)
It is preferable from the viewpoint of low reflectivity.

In the optical layered body of the present invention, the visibility reflectance Y of the antireflection layer surface is preferably 0.3% or less. If it exceeds 0.3%, the effect of improving the interference fringes of the optical layered body of the present invention may be inferior. Since the interference fringes are reduced as the amplitude of the surface reflection light of the optical layered body of the present invention is smaller, the upper limit of the luminous reflectance Y is more preferably 0.2%.
The visibility reflectance Y on the surface of the antireflection layer is a color matching function Y defined by the CIE (International Commission on Illumination) with respect to a spectral reflectance of 380 nm to 780 nm with respect to a C light source defined in JIS Z8701. The visibility is corrected using (λ).
Visibility corresponds to the color sensation of the human eye, that is, the sensitivity of the sensitivity of the color receptive cells of the retina.

In the optical layered body of the present invention, the reflected hue value is such that the absolute value of the hue a ^* is 3 or more (a ^* ≦ −3, 3 ≦ a ^* ), or the absolute value of the hue b ^* is 3. It is preferable that (b ^* ≦ −3, 3 ≦ b ^* ). Any one of the absolute value of the hue a ^{* and} the absolute value of the hue b ^* is 3 or more is preferable because the visibility of the interference fringes is lowered.
The reflected hue is a method for displaying an object color using tristimulus values X, Y, and Z in the XYZ color system defined in JIS Z8701, and the reflected hue value is a spectral reflectance of 380 nm to 780 nm. Of CIE 1976 (L * a * b *) defined in JIS Z8729 for a * and b *.

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).

The optical layered body of the present invention controls the refractive indexes of the light-transmitting substrate, the undercoat layer, and the hard coat layer having a birefringence in the plane so as to satisfy the relationship represented by the above-described formula (1). And it can manufacture by arrange | positioning the transparent base material which has a birefringence in the said surface in a predetermined direction. Such a method for producing an optical layered body of the present invention is also one aspect of the present invention.

That is, in the method for producing an optical layered body of the present invention, at least a light transmissive substrate having an in-plane birefringence, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order. A method for producing an optical layered body used by being disposed on a polarizing plate on the display screen side, wherein a light-transmitting substrate having a birefringence in the plane and a light transmission having a birefringence in the plane A step of arranging the fast axis, which is the direction in which the refractive index of the conductive base material is small, and the horizontal direction of the display screen of the image display to be parallel to each other, and transmitting light having a birefringence in the plane The refractive index at a wavelength of 550 nm in the fast axis direction of the base material is nF, the refractive index at a wavelength of 550 nm of the undercoat layer is nUC, the film thickness of the undercoat layer is d, and the refractive index of the hard coat layer at a wavelength of 550 nm. With nHC When in, and satisfies the following formula (1) and (2).

In the method for producing an optical layered body of the present invention, the light transmissive substrate having an in-plane birefringence, the undercoat layer, the hard coat layer, the antireflection layer, and the polarizer, The thing similar to an optical laminated body is mentioned.
Further, the “arrangement is made so that the fast axis, which is the direction in which the refractive index of the light-transmitting base material having a birefringence index in the plane is small, and the horizontal direction of the display screen of the image display” are parallel to each other. And have the same meaning as the optical layered body of the present invention described above.
Moreover, it is preferable to laminate | stack the transparent base material which has a birefringence in the said surface, and the said polarizer through the undercoat layer mentioned above.

The image display apparatus provided with the above-described optical laminate 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 is formed on the surface of the transmissive display body.

When the image display device of the present invention is a liquid crystal display device having the optical laminate of the present invention, the light source of the light source device is irradiated from the lower side of the optical laminate of the present invention. A retardation plate may be inserted between the liquid crystal display element and the polarizing plate on the light source side. 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, in the case where the present invention is a liquid crystal display device having the above optical laminate, the backlight light source in the liquid crystal display device is not particularly limited, but is preferably a white light emitting diode (white LED). The display device is preferably a VA mode or IPS mode liquid crystal display device including a white light emitting diode as a backlight light source.
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, so that it 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 VA (Vertical Alignment) mode refers to a dark display in which liquid crystal molecules are aligned so as to be perpendicular to the substrate of the liquid crystal cell when no voltage is applied, and the liquid crystal molecules are collapsed when a voltage is applied. This is an operation mode showing bright 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 layered body of the present invention is preferably in the VA mode or IPS mode including a white light emitting diode as a backlight light source for the following reason.
That is, the image display device of the present invention can reduce the reflection of the light (S-polarized light) oscillating in the left-right direction with a large ratio of incidence on the display screen on the optical laminate of the present invention. The S-polarized light will be 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, the absorption axis of the polarizer placed closer to the observer than the liquid crystal cell is in the left-right direction with respect to the display screen, and thus absorbs the S-polarized light transmitted through the optical laminate of the present invention. This is because the light returning to the observer side can be reduced.

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.

Moreover, such an image display apparatus can be manufactured by laminating | stacking the optical laminated body of this invention manufactured by the method mentioned above on the polarizing plate by the side of a display screen, for example.
That is, in the method for manufacturing an image display device of the present invention, at least a light-transmitting substrate having a birefringence in the plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order. A method for manufacturing an image display device using an optical laminate that is used by being disposed on a polarizing plate on the display screen side, wherein a light-transmitting substrate having a birefringence in the plane is formed in the plane. A step of arranging the fast axis, which is a direction in which the refractive index of the light-transmitting substrate having a refractive index is small, and the horizontal direction of the display screen of the image display in parallel, The refractive index at a wavelength of 550 nm in the fast axis direction of the light-transmitting substrate having a birefringence is nF, the refractive index at a wavelength of 550 nm of the undercoat layer is nUC, the film thickness of the undercoat layer is d, and the hard Coat layer wavelength When the refractive index at 50nm and NHC, and satisfies the following formula (1) and (2).

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.
In addition, the fast axis, which is the direction in which the refractive index of the light-transmitting base material having a birefringence in the plane is small, and the horizontal direction of the display screen of the image display are parallel to each other. “Arrangement” has the same meaning as the optical layered body of the present invention described above.
Moreover, it is preferable to laminate | stack the transparent base material which has a birefringence in the said surface, and the said polarizer through the undercoat layer mentioned above.

The image display device of the present invention uses the optical laminate of the present invention described above, and the fast axis of the light-transmitting substrate having a birefringence in the plane and the left and right of the display screen of the image display device Since the light-transmitting substrate, the undercoat layer, and the hard coat layer that constitute the optical laminate satisfy the specific refractive index relationship, the interference fringes are formed. Occurrence is improved. Such a method for improving interference fringes of an image display apparatus is also one aspect of the present invention.

That is, in the method for improving interference fringes of the image display device of the present invention, at least a light-transmitting base material having an in-plane birefringence, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, and image display is performed. An interference fringe improvement method for an image display device using an optical laminate used by being disposed on a polarizing plate on the display screen side of the device, wherein the light-transmitting substrate having a birefringence in the plane is The light-transmitting substrate having a birefringence in the plane is arranged so that the fast axis, which is the direction in which the refractive index is small, and the horizontal direction of the display screen of the image display are parallel to each other. The refractive index at a wavelength of 550 nm in the fast axis direction of the light-transmitting substrate having a refractive index is nF, the refractive index at a wavelength of 550 nm of the undercoat layer is nUC, and the refractive index at a wavelength of 550 nm of the hard coat layer is nHC. When And satisfies the serial formula (1) and (2).

In the method for improving interference fringes of an image display device of the present invention, examples of the optical laminate include the same optical laminate as described above, and the image display device includes the above-described optical laminate. The thing similar to an image display apparatus is mentioned.
Further, the above-mentioned “arrangement so that the fast axis, which is the direction in which the refractive index of the light-transmitting substrate having a birefringence index in the plane is small, and the horizontal direction of the display screen of the image display are parallel” is This means the same thing as the optical layered body of the present invention described above.

Since the optical layered body of the present invention has the above-described configuration, even if the hard coat layer is stacked on a light-transmitting substrate having a birefringence in a plane such as a polyester film, Thus, the generation of interference fringes can be highly suppressed.

It is a graph which shows the average refractive index wavelength dispersion of the cycloolefin polymer film which does not have a birefringence in a surface. It is a graph which shows the three-dimensional refractive index wavelength dispersion of the cycloolefin polymer film which has birefringence in a surface. It is a graph which shows the 5-degree reflectivity of nx and ny measured with the spectrophotometer.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

(Production of light-transmitting substrate)
(Preparation of light-transmitting substrate A having in-plane birefringence)
A polyethylene terephthalate material was melted at 290 ° C. and slowly cooled on glass to obtain a light-transmitting substrate a. Δn at a wavelength of 550 nm was 0.00035, and the average refractive index N was 1.6167.
The light transmissive substrate a was uniaxially stretched 4.0 times at 120 ° C. to produce a light transmissive substrate A having birefringence in the plane. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.701, ny = 1.0165, and nz = 1.5476.

(Preparation of light-transmitting substrate B having birefringence in the plane)
A polyethylene naphthalate material was melted at 290 ° C. and slowly cooled on glass to obtain a light-transmitting substrate b. At the wavelength of 550 nm, Δn = 0.004, and the average refractive index N = 1.6833.
The light transmissive substrate b was uniaxially stretched 4.0 times at 120 ° C. to produce a light transmissive substrate B having birefringence in the plane. The refractive index wavelength dispersion (nx, ny) was calculated using a spectrophotometer. The refractive index at a wavelength of 550 nm was nx = 1.8472, ny = 1.6466, and nz = 1.5561.

Example 1
The undercoat layer composition 1 having the following composition was applied to the surface of the light-transmitting substrate A so that the film thickness after drying (40 ° C. × 1 minute) was 0.085 μm, and an ultraviolet irradiation device (fusion) Undercoat layer (refractive index of 1.57) is cured by irradiating with UV light at an integrated light quantity of 50 mJ / cm ² under a nitrogen atmosphere (oxygen concentration of 200 ppm or less) using a UV system Japan light source H bulb. ) Was formed.
On the formed undercoat layer, the composition 1 for hard coat layer having the following composition was applied so that the film thickness after drying (60 ° C. × 1 minute) would be 10 μm, and an ultraviolet irradiation device (Fusion UV System Japan) A hard coat layer (refractive index of 1.54) is formed using a light source H bulb (made by the company) under a nitrogen atmosphere (oxygen concentration of 200 ppm or less) and cured by ultraviolet irradiation with an integrated light amount of 50 mJ / cm ^2. did.
Next, a composition 1 for a high refractive index layer having the following composition was applied on the formed hard coat layer so that the film thickness after drying (50 ° C. × 1 minute) was 0.16 μm, and an ultraviolet irradiation device A high refractive index layer (refractive index) using a UV light source H bulb manufactured by Fusion UV System Japan Co., Ltd. and cured under ultraviolet irradiation with an integrated light amount of 50 mJ / cm ² under a nitrogen atmosphere (oxygen concentration of 200 ppm or less). 1.62) was formed.
Then, on the formed high refractive index layer, the composition 1 for low refractive index layer having the following composition was applied so that the film thickness after drying (40 ° C. × 1 minute) was 0.10 μm, and then irradiated with ultraviolet rays. Using a device (Fusion UV System Japan, light source H bulb), under a nitrogen atmosphere (oxygen concentration of 200 ppm or less), UV irradiation is performed with an integrated light amount of 100 mJ / cm ² to cure and a low refractive index layer (refractive Ratio 1.33) was formed to produce an optical laminate.
The manufactured optical laminate had a surface reflectance from the low refractive index layer side of 0.45%, and the reflection hue at that time was a * of −0.56 and b * of −0.74.

(Composition 1 for undercoat layer)
OPPE (Oxophenylphenol acrylate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.5 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec)
1.5 parts by mass polymerization initiator (Irgacure 184; manufactured by BASF Japan) 0.15 parts by mass leveling agent (F554; manufactured by DIC) 0.003 parts by mass MIBK 97 parts by mass

(Composition 1 for hard coat layer)
UV-7600B (manufactured by Nippon Synthetic Chemical) 24 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel-Cytec)
24 parts by mass polymerization initiator (Irgacure 184; manufactured by BASF Japan) 2 parts by mass leveling agent (F554; manufactured by DIC) 0.05 parts by mass MIBK 50 parts by mass

(Composition 1 for high refractive index layer)
B364M (manufactured by Gokoku Color Co., Ltd.) 7.3 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel-Cytec)
1.6 parts by mass polymerization initiator (Irgacure 127; manufactured by BASF Japan) 0.08 parts by mass leveling agent (F554; manufactured by DIC) 0.03 parts by mass MIBK 48 parts by mass PGME 43 parts by mass

(Composition 1 for low refractive index layer)
Hollow silica fine particles (solid content of silica fine particles: 20% by mass, solution; methyl isobutyl ketone, average particle size: 60 nm) 9 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec)
1 part by mass polymerization initiator (Irgacure 127; manufactured by BASF Japan) 0.07 part by mass Modified silicone oil (X22164E; manufactured by Shin-Etsu Chemical Co., Ltd.) 0.08 part by mass MIBK 80 parts by mass PGMEA 10 parts by mass

(Example 2)
An optical laminate provided with a polarizer by bonding a polarizer to the back surface of the optical laminate obtained in Example 1 so that the fast axis of the light-transmitting substrate A and the absorption axis of the polarizer are parallel to each other. Got the body.

(Example 3)
An optical laminate was produced in the same manner as in Example 1 except that the low refractive index layer composition 2 (refractive index after curing 1.30) having the following composition was used instead of the low refractive index layer composition 1. .
The surface reflectance from the low refractive index layer side was 0.16%, and the reflected hue at that time was a * of 1.10 and b * of −2.15.

(Composition 2 for low refractive index layer)
Hollow silica fine particles (solid content of the silica fine particles: 20% by mass, solution; methyl isobutyl ketone, average particle size: 60 nm) 10.5 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec)
0.75 parts by mass polymerization initiator (Irgacure 127; manufactured by BASF Japan) 0.07 parts by mass modified silicone oil (X22164E; manufactured by Shin-Etsu Chemical Co., Ltd.) 0.08 parts by mass MIBK 78.6 parts by mass PGMEA 10 parts by mass

Example 4
An optical laminate was produced in the same manner as in Example 1 except that the thickness of the undercoat layer after coating was 0.100 μm.
The surface reflectance from the low refractive index layer side was 0.44%, and the reflection hue at that time was a * of −0.38 and b * of −0.22.

(Example 5)
Except that the film thickness after drying of the high refractive index layer was 0.14 μm and the film thickness after drying of the low refractive index layer was 0.09 μm, it was the same as in Example 1. An optical laminate was produced.
The surface reflectance from the low refractive index layer side was 0.51%, and the reflection hue at that time was a * 4.85 and b * -0.02.

(Example 6)
An optical laminate was produced in the same manner as in Example 1 except that the low refractive index layer was coated so that the film thickness after drying was 0.11 μm.
The surface reflectance from the low refractive index layer side was 0.56%, and the reflection hue at that time was −0.57 for a * and −6.52 for b *.

(Example 7)
The undercoat layer is coated so that the film thickness after drying is 0.100 μm, the high refractive index layer is coated so that the film thickness after drying is 0.14 μm, and the low refractive index layer is dried. An optical laminate was produced in the same manner as in Example 1 except that the coating was applied to a thickness of 0.09 μm.
The surface reflectance from the low refractive index layer side was 0.19%, and the reflection hue at that time was 5.18 for a * and -1.14 for b *.

(Example 8)
Instead of the light-transmitting substrate A having birefringence in the surface, a light-transmitting substrate B having birefringence in the surface is used. An optical laminate was produced in the same manner as in Example 1 except that the composition 2 (refractive index after curing 1.59) was used.
The surface reflectance from the low refractive index layer side was 0.44%, and the reflection hue at that time was −0.61 for a * and −0.98 for b *.

(Composition 2 for undercoat layer)
OPPE (Oxophenylphenol acrylate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.5 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel-Cytec)
0.5 parts by mass polymerization initiator (Irgacure 184; manufactured by BASF Japan) 0.15 parts by mass leveling agent (F554; manufactured by DIC) 0.003 parts by mass MIBK 97 parts by mass

Example 9
Instead of the hard coat layer composition 1, a hard coat layer composition 2 (refractive index after curing of 1.50) having the following composition was used, and instead of the undercoat layer composition 1, an undercoat layer having the following composition was used. An optical laminate was produced in the same manner as in Example 1 except that the composition 3 (refractive index after curing 1.55) was used.
The surface reflectance from the low refractive index layer side was 0.85%, and the reflection hue at that time was −0.57 for a * and 0.68 for b *.

(Composition 2 for hard coat layer)
MIBK-SD (manufactured by Nissan Chemical Co., Ltd.) 75.5 parts by mass Pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec) 22.5 parts by mass Polymerization initiator (Irgacure 184; manufactured by BASF Japan) 1.8 parts by mass Leveling agent (F554; manufactured by DIC Corporation) 0.05 parts by mass

(Composition 3 for undercoat layer)
OPPE (Oxophenylphenol acrylate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0.6 parts by mass Pentaerythritol triacrylate (PETA) (Daicel Cytec)
2.4 parts by mass polymerization initiator (Irgacure 184; manufactured by BASF Japan) 0.15 parts by mass leveling agent (F554; manufactured by DIC) 0.003 parts by mass MIBK 97 parts by mass

(Example 10)
Instead of composition 1 for hard coat layer, composition 3 for hard coat layer (refractive index after curing 1.58) having the following composition was used, and composition for undercoat layer was used instead of composition 1 for undercoat layer. An optical laminate was produced in the same manner as in Example 1 except that 2 (refractive index after curing 1.59) was used.
The surface reflectance from the low refractive index layer side was 0.62%, and the reflection hue at that time was 0.30 for a * and −2.54 for b *.

(Composition 3 for hard coat layer)
B364M (manufactured by Gokoku Color Co., Ltd.) 65 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec) 33 parts by mass polymerization initiator (Irgacure 184; manufactured by BASF Japan) 1.9 parts by mass leveling agent (F554; DIC) 0.05 parts by mass)

(Comparative Example 1)
An optical laminate was produced in the same manner as in Example 1 except that the undercoat layer composition 4 (refractive index after curing 1.62) having the following composition was used instead of the undercoat layer composition 1.
The surface reflectance from the low refractive index layer side was 0.49%, and the reflection hue at that time was 1.70 for a * and 1.44 for b *.

(Composition 4 for undercoat layer)
B364M (manufactured by Gokoku Color Co., Ltd.) 7.3 parts by mass pentaerythritol triacrylate (PETA) (manufactured by Daicel-Cytec)
1.6 parts by mass polymerization initiator (Irgacure 184; manufactured by BASF Japan) 0.08 parts by mass leveling agent (F554; manufactured by DIC) 0.03 parts by mass MIBK 48 parts by mass PGME 43 parts by mass

(Comparative Example 2)
An optical laminate was produced in the same manner as in Example 1 except that the film thickness after drying of the undercoat layer was 0.300 μm.
The surface reflectance from the low refractive index layer side was 0.47%, and the reflection hue at that time was 0.89 for a * and 0.90 for b *.

The presence or absence of occurrence of interference fringes in the optical laminates according to Examples and Comparative Examples was evaluated by the following method, and the results are shown in Table 1.

(Interference fringes)
Undercoat the surface opposite to the low refractive index layer of each optical laminate obtained in the examples and comparative examples (side surface of the light-transmitting substrate, the surface of the polarizer for the optical laminate according to Example 2). It is attached to a black acrylic plate to prevent back reflection through a layer (adhesive layer), and a polarizer is placed between the optical laminate to assume a polarizing environment in a room (light) with a relatively strong light source. The state of interference fringes was observed under a three-wavelength tube (manufactured by Hitachi, Ltd., Akarin rod 20 type 18W, FL20SS-EX-N / 18-J, 3 wavelength type daylight), which was installed in the light source. At this time, the light source and each optical laminate so that the fast axis of the light-transmitting substrate of each optical laminate is parallel to the polarization direction of the light source and the surface of the low refractive index layer is almost observed from the front. And the observation position is visually observed so that the angle formed by the observation position is within 10 °. Further, as an observation from an oblique position, the observation is performed such that the angle formed by the light source, each optical laminate, and the observation position is 45 °. The occurrence of interference fringes was evaluated according to the following criteria.
In addition, what was observed using the optical laminate according to Example 1 so that the fast axis of the light-transmitting base material forms an angle of 15 ° with the polarization direction of the light source is referred to as the optical laminate according to Example 11. Evaluated and evaluated as Comparative Example 3 using the optical laminate according to Example 1 and observing the fast axis of the light-transmitting substrate at an angle of 30 ° with the polarization direction of the light source. A comparative example 4 was evaluated by using the optical layered body of Example 1 and observing such that the fast axis of the light-transmitting substrate forms an angle of 90 ° with the polarization direction of the light source.
*: Interference fringes could not be visually recognized at any observation angle.
A: The interference fringes could not be visually recognized at any observation angle.
○: Interference fringes were slightly generated at any observation angle, but the level was satisfactory.
X: Interference fringes were generated.

As shown in Table 1, the optical system according to the example satisfying the formulas (1) and (2) and the fast axis of the light-transmitting substrate and the horizontal direction of the image display device are arranged in parallel. The laminate was excellent in preventing interference fringes.
On the other hand, the optical laminated body according to Comparative Example 1 does not satisfy the formula (1), the optical laminated body according to Comparative Example 2 does not satisfy the expression (2), and the optical laminated bodies according to Comparative Examples 3 and 4 are Since the fast axis of the light-transmitting substrate and the left-right direction of the image display device were not parallel, the interference fringe prevention property was poor.
In addition, about the optical laminated body obtained by the Example and the comparative example, using a haze meter (Murakami Color Research Laboratory make, product number; HM-150), it is a total light transmittance by the method based on JISK-7361. The haze was measured by a method in accordance with JIS K-7136, and in all Examples and Comparative Examples, the total light transmittance was 93% or more, and the coating film portion obtained by subtracting the haze of the substrate. Only the haze was 0.3% or less.

Even when the optical laminate of the present invention has a configuration in which a hard coat layer is laminated on a light-transmitting substrate having a birefringence in a plane such as a polyester film, it is used in an image display device. The occurrence of interference fringes can be highly suppressed.

Claims (9)

At least a light-transmitting substrate having a birefringence in the plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, and are used by being disposed on a polarizing plate on the display screen side of the image display device. An optical laminate,
The light-transmitting substrate having a birefringence in the plane includes a fast axis that is a direction in which the refractive index of the light-transmitting substrate having a birefringence in the surface is small, and a display screen of the image display. It is arranged so that the horizontal direction is parallel,
The refractive index at a wavelength of 550 nm in the fast axis direction of the light-transmitting substrate having a birefringence in the plane is nF, the refractive index at a wavelength of 550 nm of the undercoat layer is nUC, and the film thickness of the undercoat layer is d. An optical laminate characterized by satisfying the following formulas (1) and (2) when the refractive index at a wavelength of 550 nm of the hard coat layer is nHC.

2. The fast axis of the light-transmitting substrate having a birefringence in the plane and the absorption axis of the polarizer of the polarizing plate on the display screen side of the image display device are arranged in parallel. Optical laminate. The optical laminated body according to claim 1 or 2, wherein the visibility reflectance Y of the surface of the antireflection layer is 0.3% or less. The optical laminate according to claim 1, 2 or 3, wherein the film thickness d of the undercoat layer satisfies the following formula (3) when the refractive index at a wavelength of 650 nm of the undercoat layer is nUC650.

5. The optical laminate according to claim 1, wherein the reflected hue value has an absolute value of hue a * of 3 or more, or an absolute value of hue b * of 3 or more. At least a light-transmitting substrate having a birefringence in the plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, and are used by being disposed on a polarizing plate on the display screen side of the image display device. A method for producing an optical laminate,
A light-transmitting base material having a birefringence index in the plane, a fast axis that is a direction in which the refractive index of the light-transmitting base material having a birefringence index in the plane is small, and a display screen of the image display Having a step of arranging so that the horizontal direction is parallel,
The refractive index at a wavelength of 550 nm in the fast axis direction of the light-transmitting substrate having a birefringence in the plane is nF, the refractive index at a wavelength of 550 nm of the undercoat layer is nUC, and the film thickness of the undercoat layer is d. The method for producing an optical laminate, wherein the following formula (1) and formula (2) are satisfied when the refractive index at a wavelength of 550 nm of the hard coat layer is nHC.

An image display device comprising the optical laminate according to claim 1, 2, 3, 4 or 5. 8. The image display device according to claim 7, which is a VA mode or IPS mode liquid crystal display device including a white light emitting diode as a backlight light source. At least a light-transmitting substrate having a birefringence in the plane, an undercoat layer, a hard coat layer, and an antireflection layer are laminated in this order, and are used by being disposed on a polarizing plate on the display screen side of the image display device. An interference fringe improving method for an image display device using an optical laminate,
A light-transmitting base material having a birefringence index in the plane, a fast axis that is a direction in which the refractive index of the light-transmitting base material having a birefringence index in the plane is small, and a display screen of the image display Arrange it so that the horizontal direction is parallel,
The refractive index at a wavelength of 550 nm in the fast axis direction of the light-transmitting substrate having a birefringence in the plane is nF, the refractive index at a wavelength of 550 nm of the undercoat layer is nUC, and the film thickness of the undercoat layer is d. An interference fringe improving method for an image display device, wherein the following formulas (1) and (2) are satisfied when a refractive index at a wavelength of 550 nm of the hard coat layer is nHC.

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