JP6824935B2 - Manufacturing method of image display device - Google Patents

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 become widespread in recent years in place of conventional CRT displays.
In such a liquid crystal display device, a polarizing plate is arranged on the image display surface side of the liquid crystal cell, and it is usually required to impart hardness so that the polarizing element of the polarizing plate is not scratched during handling. Therefore, it is common practice 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 transmissive substrate as the polarizing plate protective film.

Conventionally, a film made of a cellulose ester typified by triacetyl cellulose has been used as a light-transmitting base material of such a hard coat film. This is because cellulose ester has excellent transparency and optical isotropic properties, and has almost no in-plane phase difference (low retardation value), so it rarely changes the vibration direction of incident linearly polarized light, and the liquid crystal display. Since it has little effect on the display quality of the device and has appropriate water permeability, it is possible to dry the water remaining in the polarizing element through the optical laminate when the polarizing plate made of the optical laminate is manufactured. It is based on advantages such as being able to do it.
However, the cellulose ester film has insufficient moisture resistance and heat resistance, and when the hard coat film is used as a polarizing plate protective film in a high temperature and high humidity environment, it has a drawback that the polarizing plate function such as polarization function and hue is deteriorated. It was. Cellulose ester was also a material disadvantageous in terms of cost.

Due to such problems of the polyethylene ester film, it is excellent in transparency, heat resistance and mechanical strength, and can be manufactured by a method that is cheaper than the cellulose ester film, easily available on the market, or a simple method. It is desired to use a general-purpose film as a light-transmitting base material for an optical laminate. For example, attempts have been made to use a polyester film such as polyethylene terephthalate (PET) as a cellulose ester substitute film (for example,). See Patent Documents 1 to 3).
Since the polyester film has an aromatic ring with a large polarizability in the molecular chain, the intrinsic birefringence is extremely large, and the molecular chain is oriented by stretching treatment to impart excellent transparency, heat resistance, and mechanical strength. It has the property that birefringence is likely to occur.

However, according to the research by the present inventors, when an optical laminate using a polyester film such as polyethylene terephthalate (PET) as a substitute film for a cellulose ester film is arranged on a polarizing element, in-plane double refraction of the polyester film is performed. Due to the tendency to develop, unevenness of different colors (hereinafter, also referred to as “nijimura”) occurs in the liquid crystal display device, especially when the display screen is observed from an angle, and the display quality of the liquid crystal display device is impaired. It turned out that there was a problem.

As an attempt to use a polyester film as a material for a light-transmitting base material instead of a cellulose ester film, for example, in Patent Document 4, a polyethylene terephthalate film which is stretched 2.5 to 6 times and has sufficient transparency is transparent. The antiglare film used as the base material is described. In this anti-glare film, if the retardation is 1000 or more, the coloring in the front becomes inconspicuous, but the color unevenness (nijimura) in the diagonal direction cannot be eliminated, so that the entire haze is 8 times the transparent sharpness. By making it above, Nijimura is eliminated. However, if the transmission sharpness is low, the visibility is lowered. Therefore, the antiglare film described in Patent Document 4 requires a haze of 5.5 to 55%. Further, in order to satisfy the relationship between the transmission sharpness and the haze, the period of the surface uneven shape is increased to make the specular reflectance of the antiglare layer a very low value of 0.05 to 2%. Since there is almost no flat surface on the surface of the glare layer, even if the Nijimura can be eliminated, there will be a problem that the image quality including blurring and contrast is inferior.

Further, in Patent Document 5, a white light emitting diode is used as a light source, and the angle between the absorption axis of the polarizing plate and the slow axis of the polymer film of the polymer film having a retardation of 3000 to 30000 nm is 45 degrees. 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, polyester and polycarbonate films, which are preferable polymer films in Patent Document 5, are soft and do not have scratch resistance, and therefore cannot be put into 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 and the image quality deteriorates.

Here, the interference fringes are that when white light hits a transparent thin film, the light reflected from the surface of the thin film and the light once entered into the thin film and reflected from the interface having a refractive index difference existing inside the thin film cause interference. This is a phenomenon in which partial iris-like colors are observed, and is a phenomenon that occurs because the intensifying wavelengths change depending on the viewing direction. This phenomenon is not only hard to see for the user but also gives an unpleasant impression, and improvement is strongly required. 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 on a polyester film. When Np is 1.64 to 1.68 and Nh is 1.50 to 1.53, as in the case of laminating the above, interference of reflected light occurs at the interface between the polymer film and the hard coat layer. The larger the difference in refractive index, the more remarkable the interference fringes.

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 making the refractive indexes of the polymer film (refractive index: Np) and the hard coat layer (refractive index: Nh) as uniform as possible (hereinafter, also referred to as interference fringe elimination method 1). .. Further, 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 set to the refractive index of the polymer film. A technique for suppressing interference fringes by setting the refractive index between (Np) and the refractive index (Nh) of the hard coat layer (hereinafter, also referred to as interference fringe elimination method 2) is known (for example, patent). References 6 and 7 etc.). The 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 mathematical formula.

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

Japanese Unexamined Patent Publication No. 2004-205773 JP-A-2009-157343 JP-A-2010-244059 JP-A-2009-156938 Japanese Unexamined Patent Publication No. 2011-107198 Japanese Unexamined Patent Publication No. 2003-177209 Japanese Unexamined Patent Publication No. 2004-345333

However, in Patent Document 5, in order to give the polymer film a high retardation value, the refractive indexes in the vertical direction and the horizontal direction of the polymer film are inevitably (hereinafter, also referred to as Nx and Ny, respectively. Here, Np- (Nx = Ny−Np) will be significantly different. Therefore, 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 set to the average value of Nx and Ny, | Nh− in the vertical and horizontal directions, respectively. Since there is a difference in refractive index between Nx | and | Nh-Ny |, 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 has the best refractive index, it is always possible. 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. In recent years, hard coat films and the like are required to be thinned, so it is not preferable to increase the film thickness of the polymer film. Therefore, if the film thickness of the polymer film cannot be increased, the above-mentioned difference in refractive index between the vertical and horizontal directions must be increased in order to increase the retardation value of the polymer film. That is, the larger the retardation value of the polymer film, the greater the problem of interference fringes. Therefore, in Patent Document 5, the problem of image quality deterioration due to the occurrence of interference fringes cannot be avoided.

As a result of further study on the problem when such a polyester film is used, a conventional polyester film is formed by using a polyester film having a certain high retardation value as a light-transmitting base material of an optical laminate. It has been found that the problem of Nijimura can be improved as compared with the case of using an optical laminate provided with a light-transmitting substrate.
However, when a polyester film having such a high retardation value is used as a light-transmitting base material, an undercoat layer is indispensable in order to ensure adhesion to the hardcoat layer. Such a hardcoat layer It has been found that the occurrence of interference fringes becomes a problem in the optical laminate having the structure of the undercoat layer and the display quality of the image display device is significantly impaired.

In view of the above situation, the present invention highly suppresses the occurrence of interference fringes even in a configuration in which a hard coat layer is laminated on a light transmissive substrate having a birefringence in the plane such as a polyester film. An object of the present invention is to provide 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.

In the present invention, at least a light transmissive substrate having a double refractive index, an undercoat layer, a hardcoat layer and an antireflection layer are laminated in this order in this order and arranged on a polarizing plate on the display screen side of an image display device. A method for manufacturing an image display device including an optical laminate used in the above, wherein the refractive index of a light-transmitting substrate having a double refractive index in the plane at a wavelength of 550 nm in the phase-advancing axis direction is nF, and the undercoat is described above. When the refractive index of the layer at a wavelength of 550 nm is nUC, the thickness of the undercoat layer is d (nm), and the refractive index of the hardcoat layer at a wavelength of 550 nm is nHC, the following equations (1) and (2) are used. The undercoat layer is filled with at least one resin selected from the group consisting of a thermosetting or thermoplastic polyester resin, urethane resin, acrylic resin, and modified products thereof, and a refractive index higher than that of the resin. The reflection hue value of the optical laminate is 3 or more in the absolute value of the hue a ^* , or the absolute value of the hue b ^* is 3 or more, and the reflection prevention Optics in which a light-transmitting substrate having a double refractive index, an undercoat layer, a hardcoat layer, and an antireflection layer are laminated in this order in which the visual sensitivity reflectance Y of the layer surface is 0.3% or less. The process of manufacturing the laminate , the phase-advancing axis in which the refractive index of the light-transmitting base material having a double refractive index in the plane is small, and the phase-advancing axis of the light-transmitting base material having the double refractive index in the plane. A method for manufacturing an image display device , which comprises a step of arranging the optical laminate so as to be parallel to the left-right direction of the display screen of the image display device.

In the optical laminate of the present invention, the phase-advancing axis of the light-transmitting substrate having a birefringence in the plane and the absorption axis of the polarizing element of the polarizing plate on the display screen side of the image display device are parallel to each other. It is preferable that they are arranged in such a manner .
Further, it is preferable that the film thickness d (nm) of the undercoat layer satisfies the following formula (3) when the refractive index of the undercoat layer at a wavelength of 650 nm is nUC650 .

Further, in the present invention, at least a light transmissive base material having a double refractive index, an undercoat layer, a hard coat layer and an antireflection layer are laminated in this order on a polarizing plate on the display screen side of the image display device. It is a method of manufacturing an optical laminate used by arranging in the above-mentioned plane, in which a light-transmitting base material having a double refractive index in the plane has a refractive index of a light-transmitting base material having a double refractive index in the plane. The phase-advancing axis of a light-transmitting substrate having a double refractive index in the plane, which comprises a step of arranging the phase-advancing axis in a small direction so as to be parallel to the left-right direction of the display screen of the image display. 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 film thickness of the undercoat layer is d, and the refractive index of the hardcoat layer at a wavelength of 550 nm is nHC, the following It is also a method for producing an optical laminate, which is characterized by satisfying the formulas (1) and (2).

The present invention is also an image display device characterized by including the above-mentioned optical laminate of the present invention.
The image display device of the present invention is preferably a VA mode or IPS mode liquid crystal display device provided with a white light emitting diode as a backlight source.

Further, in the present invention, at least a light transmissive base material having a double refractive index, an undercoat layer, a hardcoat layer and an antireflection layer are laminated in this order on a polarizing plate on the display screen side of an image display device. This is a method for improving interference fringes of an image display device using an optical laminate used in the above-mentioned plane, in which a light-transmitting base material having a double refractive index in the plane is used. A light-transmitting base material having a double refractive index in the plane is arranged so that the phase-advancing axis, which is the direction in which the refractive index of the transparent base material is small, is parallel to the left-right direction of the display screen of the image display. The refractive index at a wavelength of 550 nm in the phase-advancing axis direction is nF, the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, the film thickness of the undercoat layer is d, and the refractive index of the hardcoat layer at a wavelength of 550 nm is nHC. It is also a method for improving interference fringes of an image display device, which satisfies the following equations (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 will be 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 diligent studies on an optical laminate having a structure in which a light-transmitting base material having a double refractive index, an undercoat layer, a hardcoat layer and an antireflection layer are laminated in this order, the present inventors have described the above. When the optical laminate is installed in the image display device, the phase advance axis, which is the direction in which the refractive index of the light transmissive substrate is small, is set to a specific direction with respect to the display screen of the image display device. The present invention has been completed by finding that the occurrence of interference fringes can be highly suppressed by setting the refractive index of each layer constituting the optical laminate to have a specific relationship.
As described above, the film made of cellulose ester represented by triacetyl cellulose, which has been conventionally used as an optical laminate, has excellent optical isotropic properties and has almost no in-plane phase difference. Therefore, in the case of an optical laminate using the film made of the cellulose ester as the light-transmitting base material, it is not necessary to consider the installation direction of the light-transmitting base material. That is, the above-mentioned problem of interference fringes is caused by using a light-transmitting base material having a birefringence in the plane as the light-transmitting base material of the optical laminate.
Here, conventionally, it is known that the interference fringes can be improved by providing an uneven shape on the surface of the optical laminate. However, an optical laminate having a structure having an uneven shape on the surface has been used. There is a problem that a cloudy feeling occurs, and there is a problem that a clear display image cannot be obtained when the image is installed on the surface of an image display device.
On the other hand, according to the optical laminate of the present invention, the above-mentioned problem of interference fringes can be solved without using the conventional method for improving interference fringes due to the uneven shape of the surface of the optical laminate, so that a feeling of cloudiness is caused by external light. This is a case where it is used for a touch panel or the like having an air gap structure because it does not occur, a clear and highly realistic moving image or a still image can be viewed, and the surface of the optical laminate does not have an uneven shape. However, a clear image can be obtained without causing problems such as glare.

In the present invention, at least a light transmissive substrate having a birefringence, an undercoat layer, a hardcoat layer and an antireflection layer are laminated in this order and arranged on a polarizing plate on the display screen side of an image display device. It is an optical laminate used in the above.
In the optical laminate of the present invention, the phase advance axis, which is the direction in which the refractive index of the light transmissive substrate is small, is arranged parallel to the left-right direction of the display screen of the image display device.
Here, since the image display device is usually installed in a room (bright place) and used in a fixed state, the light reflected by the wall surface or the floor surface is incident on the display screen of the image display device. To. The present inventors have focused on the fact that most of the light reflected by the wall surface or the floor surface and incident on the display screen of the image display device is in a state of vibrating in the left-right direction of the display screen.
On the other hand, in an optical laminate in which a light-transmitting substrate having a double refractive index, an undercoat layer, a hardcoat layer, and an antireflection layer are laminated in this order in the plane, due to optical interference at the upper and lower interfaces of the undercoat layer. In order to reduce the interference fringes, the smaller the difference between the refractive index of the light-transmitting base material having the double refractive index in the plane and the refractive index of the hard coat layer, the more the design can suppress the interference fringes. In many cases, the refractive index of the light-transmitting substrate having a birefringence in the plane is higher than the refractive index of the resin material generally used for the hard coat layer. Therefore, the birefringence is set in the plane. The phase-advancing 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 this reason, it is easy to design a light-transmitting substrate having an in-plane birefringence with reduced interference fringes when the optical design is made in line with the phase-advancing 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 configuration, the optical laminate of the present invention is used in the direction in which the refractive index of the light transmissive substrate is small. It is assumed that a certain phase-advancing axis is arranged so that the left-right direction of the display screen of the image display device is parallel to each other.
That is, the optical laminate of the present invention is limited to those installed on the surface of the image display device, and the image display device on which the optical laminate of the present invention is installed has the refractive index of the light transmissive substrate. The phase-advancing axis, which is in a small direction, faces a direction parallel to the vibration direction of the light reflected on the wall surface or the floor surface. As described above, in the image display device, the optical laminate is installed so that the direction of the phase advance axis, which is the direction in which the refractive index of the light transmissive substrate is small, is a specific direction. , The occurrence of interference fringes can be highly suppressed.
The phrase "the phase-advancing axis in the direction in which the refractive index of the light-transmitting substrate is small is arranged parallel to the left-right direction of the display screen of the image display device" means that the phase-advancing axis is described above. It means a state in which the optical laminate is arranged on the image display device within a range of 0 ° ± 15 ° with respect to the left-right direction of the display screen. Further, the "horizontal direction of the display screen of the image display device" is 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 surface on which the image display device is installed.
The angle formed by the phase-advancing axis, which is the direction in which the refractive index of the light-transmitting substrate is small, and the left-right direction of the display screen of the image display device is preferably 0 ° ± 5 °, and is 0 ° ± 2 °. Is more preferable, and 0 ° is even more preferable.

Further, in the optical laminate of the present invention, the refractive index of the light transmissive substrate having a birefringence in the plane at a wavelength of 550 nm in the phase-advancing axis direction is nF, and the refractive index of the undercoat layer at a wavelength of 550 nm is nUC. When the thickness of the undercoat layer is d and the refractive index of the hardcoat layer at a wavelength of 550 nm is nHC, the following formulas (1) and (2) are satisfied.

By satisfying the above formula (1), the effect of improving the interference fringes by the optical laminate of the present invention becomes excellent. This is because the reflectance R of the reflection that occurs at the interface between each layer when light is incident on the laminated body formed by laminating a plurality of layers is represented by the following formula (A), and the hard coat layer and the undercoat layer. When reflections based on the following formula (A) occur at the interface with and the interface between the undercoat layer and the light transmissive substrate, and these reflected lights are superposed with equal intensity in a state where the phases are π different from each other. This is because the interference fringe strength is the weakest. The relational expression between the refractive index and the thickness at this time is the following equations (B) and (C).
R = (n1-n2) ² / (n1 + n2) ² (A)
n2 = (n1 × n3) ^1/2 (B)
d = (1/4) × (λ / n2) (C)
However, 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 base material is not particularly limited as long as it has an in-plane birefringence, and examples thereof include a base material made of polycarbonate, acrylic, polyester, etc. Among them, cost and mechanical. It is preferable that the polyester base material is advantageous in terms of strength. In the following description, a light-transmitting base material having an in-plane birefringence will be described as a polyester base material.
In the optical laminate of the present invention, even if the light-transmitting base material is a light-transmitting base material made of cellulose ester or the like, which has been conventionally used as an optically isotropic material, it has a birefringence. It can be used by having.

In the optical laminate of the present invention, the refractive index (nx) in the direction in which the refractive index is large in the plane of the polyester base material (slow phase axis direction) and the direction orthogonal to the slow phase axis direction (phase advance axis direction). The difference nx-ny (hereinafter, also referred to as Δn) from the refractive index (ny) of is preferably 0.01 or more. If the Δn is less than 0.01, the effect of improving the transmittance may be reduced. On the other hand, the above 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 liable to be torn or torn, and its practicality as an industrial material may be significantly reduced.
From the above viewpoint, the more preferable lower limit of Δn is 0.05, and the more preferable upper limit is 0.27. If Δn exceeds 0.27, the durability of the polyester base material in the moisture resistance test may be inferior. A more preferable upper limit of Δn is 0.25 because the durability in the moisture resistance test is excellent. By satisfying such Δn, it is possible to improve the suitable light transmittance.

In the present specification, whether or not the light-transmitting substrate has a birefringence in the plane is determined by the case where Δn (nx−ny) ≧ 0.0005 at the refractive index at a wavelength of 550 nm. It is assumed that the substance has birefringence, and that Δn <0.0005 does not have birefringence. The birefringence can be measured by using a KOBRA-WR manufactured by Oji Measuring Instruments Co., Ltd. by setting the measurement angle to 0 ° and the measurement wavelength to 552.1 nm. At this time, the film thickness and the average refractive index are required to calculate the birefringence. The film thickness can be measured using, for example, a micrometer (Digital Micrometer, manufactured by Mitutoyo) or an electric micrometer (manufactured by Anritsu). The average refractive index can be measured using an Abbe refractive index meter or an ellipsometer.
Δn of TD80UL-M (manufactured by Fuji Film Co., Ltd.) made of triacetyl cellulose and ZF16-100 (manufactured by Nippon Zeon Co., Ltd.) made of cycloolefin polymer, which are generally known as isotropic materials, can be determined by the above measuring method. , 0.0000375 and 0.00005, respectively, and it was judged that they did not have birefringence (isotropic).
In addition, as a method for measuring the double reflectance, the orientation axis direction (direction of the main axis) of the light transmissive substrate is obtained using two polarizing plates, and the refractive index of the two axes orthogonal to the orientation axis direction is obtained. The rate (nx, ny) can be determined by an Abbe reflectance meter (NAR-4T manufactured by Atago Co., Ltd.), or after attaching a black vinyl tape (for example, Yamato vinyl tape No. 200-38-21 38 mm width) on the back surface. Polarization measurement using a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit, VAR-7010 manufactured by Nippon Kogaku Co., Ltd.): With S polarization, when the slow axis is parallel to S polarization , The 5 degree reflectance when the phase-advancing axes are parallel is measured, and the slow-phase axis and the phase-advancing axis are obtained from the following equation (I) showing the relationship between the reflectance (R) and the refractive index (n). The reflectance of the wavelength (nx, ny) can also be calculated.
R (%) = (1-n) ² / (1 + n) ² equation (I)

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

Here, the calculation method of nx, ny, and nz will be described with reference to specific examples.
In addition, nx is the refractive index in the slow axis direction of the light transmitting base material, ny is the refractive index in the phase advance axis direction of the light transmitting base material, and nz is the refractive index in the thickness direction of the light transmitting base material. Is.
(Calculation of three-dimensional refractive index wavelength dispersion)
First, a method for calculating the 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 the cycloolefin polymer film having no birefringence in the plane was measured using an ellipsometer (UVISEL Horiba Seisakusho), and the results are shown in FIG. From this measurement result, the average refractive index wavelength dispersion of the cycloolefin polymer film having no birefringence in the plane was defined as the refractive index wavelength dispersion of nx, ny, and nz.
This film was uniaxially stretched at a free end at a stretching temperature of 155 ° C. to obtain a film having an in-plane birefringence. The film thickness was 100 μm. This free-end uniaxially stretched film was measured with a birefringence measuring instrument (KOBRA-21ADH, Oji measuring instrument) at four wavelengths (447.6 nm, 547.0 nm, 630.6 nm) at incident angles of 0 ° and 40 °. It was measured at 743.4 nm).
Based on the average refractive index (N) and retardation value at each wavelength, the three-dimensional refractive index using the three-dimensional wavelength dispersion calculation software attached to the birefringence measuring meter and the formula of Cauchy or Cellmeier. The wavelength dispersion was calculated and the result is shown in FIG. In FIG. 2, ny is shown so as to substantially overlap with nz. From this result, a three-dimensional refractive index wavelength dispersion of a cycloolefin polymer film having a birefringence in the plane was obtained.
(Calculation of refractive indexes nx, ny, nz using a spectrophotometer)
Taking polyethylene terephthalate as an example, a method for calculating the 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 in the above-mentioned three-dimensional refractive index wavelength dispersion calculation method.
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 measuring unit VAR-7010 manufactured by JASCO Corporation). A black vinyl tape (for example, Yamato Vinyl Tape No. 200-38-21 38 mm width) with a width larger than the measurement spot area is attached to the surface opposite to the measurement surface to prevent backside reflection, and then polarization measurement: S polarization. 5 degree spectral reflectance was measured when the alignment axes of the light-transmitting substrate were installed in parallel and when the axes orthogonal to the alignment axes were 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). The direction showing the larger reflectance (refractive index calculated by the above formula (I)) is defined as nx (also referred to as the slow axis), and the smaller reflectance (refractive index calculated by the above formula (I)) is shown. The direction was ny (also referred to as the phase advance axis). Here, the orientation axis is a state in which a film having a birefringence index is sandwiched between two polarizing plates installed in a cross Nicol state on a light source, and the film is rotated to minimize light leakage. At this time, the orientation axis of the film can be the same direction as the transmission axis or the absorption axis of the polarizing plate. Further, the refractive index nz can be calculated by the above 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-mentioned 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 polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), and 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 can be exemplified. Further, the polyester used for the polyester base material may be a copolymer of these polyesters, and the polyester is mainly composed of the above polyester (for example, a component of 80 mol% or more) and a small proportion (for example, 20 mol% or less). It may be blended with the type of resin. As the polyester, polyethylene terephthalate or polyethylene naphthalate is particularly preferable because it has a good balance of mechanical 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 film having extremely high versatility such as PET. Further, PET is excellent in transparency, thermal or mechanical properties, Δn can be controlled by stretching, and the natural birefringence is large, so that the birefringence can be relatively easily obtained.

The method for obtaining the polyester base material is not particularly limited as long as it satisfies the above-mentioned Δn, but for example, unstretched polyester obtained by melting the polyester such as PET as a material and extruding it into a sheet is glass. Examples thereof include a method of performing heat treatment after lateral stretching using a tenter or the like at a temperature equal to or higher than the transition temperature.
The transverse stretching temperature is preferably 80 to 130 ° C., more preferably 90 to 120 ° C. The lateral stretching ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. If the transverse stretching ratio exceeds 6.0 times, the transparency of the obtained polyester base material tends to decrease, and if the transverse stretching ratio is less than 2.5 times, the stretching tension also decreases, so that the obtained polyester can be obtained. The birefringence of the substrate may be small.
Further, in the present invention, the unstretched polyester is laterally stretched 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). May be good. In this case, the longitudinal stretching preferably has a stretching ratio of 2 times or less. If the draw ratio of the longitudinal stretching exceeds 2 times, the value of Δn may not be within the above-mentioned preferable range.
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, etc. are likely to occur, and its practicality 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 peculiar to the polymer film is lowered, and the practicality as an industrial material is also lowered, which is not preferable. The more preferable lower limit of the thickness of the polyester base material is 10 μm, the more preferable upper limit is 200 μm, and the further preferable upper limit is 150 μm.

Further, the polyester base material preferably has a transmittance of 80% or more in the visible light region, and more preferably 84% or more. The transmittance can be measured by JIS K7361-1 (a test method for the total light transmittance of a plastic-transparent material).

Further, in the present invention, the polyester base material may be subjected to surface treatment such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, and flame treatment within a range not deviating from the gist of the present invention. Good.

In the optical laminate of the present invention, the phase-advancing axis of the light-transmitting substrate having a birefringence in the plane and the absorbing axis of the polarizing element of the polarizing plate on the display screen side of the image display device are parallel to each other. It is preferably arranged in. By arranging the light-transmitting base material and the polarizer in such a specific relationship, it becomes easy to absorb light having polarization parallel to the phase-advancing axis transmitted through the optical laminate of the present invention. Therefore, the effect of improving the interference fringes by the optical laminate of the present invention becomes more excellent. This is because, as described above, the outside light in the room has a large amount of vibration components in the left-right direction of the display screen of the image display device, and the phase-advancing axis of the light-transmitting base material and the absorption axis of the polarizer are combined with the image display device. When installed parallel to the left and right directions of the display screen of, it is possible to absorb more external light when the external light transmitted through the light transmissive substrate reaches the polarizer and reduce interference fringes at the polarizer interface. Because it can be done.
It should be noted that the above-mentioned "phase-advancing axis of the light transmissive substrate having a birefringence in the plane and the absorbing axis of the polarizing plate of the polarizing plate on the display screen side of the image display device are arranged so as to be parallel to each other. "Yes" means that the angle formed by the phase-advancing axis of the light-transmitting substrate and the absorbing axis of the polarizer is 0 ° ± 15 °.
In the present invention, the angle formed by the phase-advancing axis in the direction in which the refractive index of the light-transmitting substrate is small and the absorbing axis of the polarizer is more preferably 0 ° ± 5 °, more preferably 0 ° ±. It is more preferably 2 ° and most preferably 0 °.

The polarizer is not particularly limited, and for example, a polyvinyl alcohol film dyed and stretched with iodine or the like, a polyvinyl formal film, a polyvinyl acetal film, an ethylene-vinyl acetate copolymer saponified film or the like can be used. In the laminating treatment of the polarizer and the light transmissive base material, it is preferable to perform a saponification treatment on the light transmissive base material. 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 base material and the hardcoat layer described later.
The material of the undercoat layer is not particularly limited as long as it satisfies the above-mentioned refractive index conditions, and conventionally known materials can be appropriately selected and used. Specifically, for example, thermosetting is used. Examples thereof include sexual or thermoplastic polyester resins, urethane resins, acrylic resins, and modified products thereof.
Further, in order to adjust the refractive index of the undercoat layer, high refractive index fine particles, high refractive index resin, chelate compound and the like can be added.

As the polyester resin, for example, a polyester obtained from the following polybasic acid component and diol component can be used.
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, and pyro. Examples thereof 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, dimethylolpropane and the like. Examples thereof include poly (ethylene oxide) glycol and poly (tetramethylene oxide) glycol.

In addition, examples of the acrylic resin include those obtained by copolymerizing the monomers exemplified below.
Examples of the monomer include alkyl acrylates and alkyl methacrylates (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group and 2-ethylhexyl group. Cyclohexyl group, 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, and allyl glycidyl ether; It has a carboxy group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.) or salts thereof. Monomer: acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethalkoxylamide, N, N-dialkylacrylamide, N, N-dialkylmethacrylate (alkyl groups include 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-alkoxymethacrylate, N, N-alkoxyacrylamide, N, N-dialkoxymethacryl Amid (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), acryloylmorpholin, N-methylolacrylamide, N-methylolmethacrylate, N-phenylacrylamide, N-phenylmethacrylate and other amide groups. Monomer having: Alkoxy anhydride monomer such as maleic anhydride, itaconic anhydride; 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, Oxazoline group-containing monomers such as 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline; methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, Vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinylmethyl ether, vinyl ethyl ether, vinyltrialkoxysilane, alkylma Examples thereof include laine acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate and butadiene.

Examples of the urethane resin include those composed of polyols, polyisocyanates, chain length extenders, cross-linking agents and the like.
The polyol may be obtained by a dehydration reaction between a glycol containing, for example, a polyether such as polyoxyethylene glycol, polyoxypropylene glycol, or polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, or polycaprolactone, and a dicarboxylic acid. Examples thereof include polyester produced, polycarbonate having a carbonate bond, acrylic polyol, castor oil and the like.

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

Examples of the chain length extender or cross-linking agent include ethylene glycol, propylene glycol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, triethylenetetramine, 4,4'-diaminodiphenylmethane, 4,4'-. Examples thereof 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), and cerium oxide (CeO ₂ , refractive index). 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, refractive index: 1.95 to 2.00), phosphotin 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 zinc antimonate (ZnSb ₂ O ₆ , refractive index: 1.90 to 2.00) and the like can be mentioned.
The high refractive index fine particles preferably have an average primary particle diameter of 5 to 100 nm. If the average primary particle size exceeds 100 nm, optical scattering may occur in the undercoat layer and the transparency may deteriorate. If the average primary particle size is less than 5 nm, the fine particles agglomerate more and the secondary particle size becomes larger. As a result, optical scattering may occur and the transparency of the undercoat layer may deteriorate.
For the refractive index of these high refractive index fine particles, for example, a thermoplastic resin having a known refractive index and a metal oxide whose mass has been measured are mixed, and then molded into transparent pellets having an appropriate thickness. The refractive index of the pellets can be measured, and the refractive index of the high refractive index fine particles can be calculated from the compounding ratio with the resin having a known refractive index. The refractive index measurement can be obtained by an Abbe refraction meter by, for example, the Becke method according to the 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.
Further, the average primary particle size can be obtained as an average value of the particle sizes of 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, and for example, the refraction of the undercoat layer formed by a weighted average of the cured product of the resin component added to the undercoat layer with the value of the refractive index measured in advance. It may be appropriately adjusted in relation to other components so that the rate satisfies the relation described later.

The high refractive index resin is not particularly limited as long as it is a material for the undercoat layer and a resin having a higher refractive index than the above-mentioned resin. For example, epoxy resin, acrylic resin, polyester resin, amino resin, polyurethane. Examples thereof include conventionally known resins such as resins.
Specific examples of such a high refractive index resin include Oxol EA-0200, Oxol EA-F5003, Oxol EA-F5503, and Oxol EA-F5510, which are resins having a fluorene skeleton. , A-BPEF (9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene) (manufactured by Shin-Nakamura Chemical Co., Ltd.), Adamantate M-104, a resin having an Adamantane skeleton, Adamantate X -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.), resin having a biphenyl skeleton New Frontier OPPE (Oxophenylphenol acrylate) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), EO adduct di (meth) acrylate of bisphenol A, which is a resin having a bisphenol A skeleton, PO adduct di (meth) of bisphenol A Acrylate, bisphenol A epoxy acrylate, light acrylate POB-A (m-phenoxybenzyl acrylate) (manufactured by Kyoeisha Chemical Co., Ltd.), which is a resin having a diphenyl oxide skeleton, and 4,4'-bis (β), which is a resin having a diphenyl sulfone skeleton. Examples thereof include − (meth) acryloyloxyethoxy) diphenylsulfone, 4,4′-di (β- (meth) acryloyloxyethoxy) diphenylsulfide, which is a resin having a diphenylsulfide skeleton. These may be used alone or in combination of two or more.

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-hexanediorat) titanium, and diisopropoxybis (triethanolaminato). Examples thereof include titanium, di-n-butoxybis (triethanol aminato) titanium, hydroxybis (lactoto) titanium, hydroxybis (lactoto) titanium ammonium salt, titanium beloxocitrate ammonium salt and the like.
In addition, 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 laminate 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 effect of improving the interference fringes by the optical laminate of the present invention becomes more excellent. This is most likely when light is incident on a laminate consisting of multiple layers, as described above, when the light reflected at the two interfaces is superposed at the same intensity with different phases of π. This is because the strength of the interference fringes is weak. The phase difference of these lights becomes π when the following equations (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 film 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)
Further, the visibility of the interference fringes can be suppressed by particularly weakening the interference in the wavelength 650 nm, which is a red region.
The thickness d of the undercoat layer is an average value (1) obtained by observing the cross section of the undercoat layer with an electron microscope (SEM, TEM, STEM) and measuring any 10 points. nm). In the case of a very thin thickness, the one observed at high magnification is recorded as a photograph and measured by further enlarging it. When enlarged, the layer interface line, which was so thin that it can be clearly seen as a boundary line, becomes a thick line. In that case, the central portion obtained by dividing the thick line width into two equal parts is measured as the boundary line.

In the optical laminate of the present invention, the undercoat layer uses a composition for an undercoat layer prepared by mixing and dispersing the above-mentioned material and, if necessary, a photopolymerization initiator and other components in a solvent. Can be formed.
The mixing and dispersion may be carried out using a known device such as a paint shaker, a bead mill or a kneader.

Water is preferably used as the solvent, and it is preferable to use it in the form of an aqueous coating solution such as an aqueous solution, an aqueous dispersion or an emulsion. It may also contain some organic solvent.
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 hydrocarbons (eg, hexane, cyclohexane), halogenated hydrocarbons (eg, methylene chloride, chloroform, carbon tetrachloride), aromatic carbides Hydrogen (eg, benzene, toluene, xylene), amide (eg, dimethylformamide, dimethylacetamide, n-methylpyrrolidone), ether (eg, diethyl ether, dioxane, tetrahydrofuran), ether alcohol (eg, 1-methoxy-2- Propanol), esters (eg, methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate) and the like.

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

The composition for the undercoat layer 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 deteriorates, unevenness or streaks appear on the surface, or a desired film thickness may not be obtained. The solid content is more preferably 2 to 10%.

The coating of the composition for the undercoat layer on the polyester base material can be carried out at any stage, but it is preferably carried out in the process of manufacturing the polyester base material, and further, before the orientation crystallization is completed. It is preferable to apply it to the polyester base material of.
Here, the polyester base material before the alignment crystallization is completed is an unstretched film, a uniaxially oriented film in which the unstretched film is oriented in either the vertical direction or the horizontal direction, and further in the vertical direction and the horizontal direction. It includes a film which has been stretched and oriented at a low magnification in two directions (a biaxially stretched film which has not been finally re-stretched in the longitudinal direction or the horizontal direction to complete the orientation crystallization). Among them, it is preferable to apply the aqueous coating liquid of the composition for the undercoat layer to the unstretched film or the uniaxially stretched film oriented in one direction, and perform longitudinal stretching and / or transverse stretching and heat fixing as it is. ..
When the composition for the undercoat layer is applied to the polyester base material, the surface of the polyester base material is subjected to physical treatment such as corona surface treatment, flame treatment, and plasma treatment as a preliminary treatment for improving the coatability. Alternatively, it is preferable to use a chemically inert surfactant together with the composition for the undercoat layer.

Any known coating method can be applied as the coating method of the composition for the undercoat layer. For example, a roll coating method, a gravure coating method, a roll brushing 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. The coating film may be formed on only one side of the polyester base material or on both sides, if necessary.
When the undercoat layers are formed on both sides of the polyester base material, the polyester base material can be imparted with slipperiness, and as a result, the optical laminate 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), and is preferably 2H. The above is more preferable.
The hard coat layer is a layer that guarantees the hard coat property of the surface of the optical laminate of the present invention, and is not particularly limited as long as it satisfies the above-mentioned refractive index conditions, and conventionally known ones are appropriately selected. Can be used. Specifically, for example, it is preferably formed by 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 two or more unsaturated bonds, such as compounds having an acrylate-based functional group. Examples of the compound having an unsaturated bond of 1 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 trimethylpropantri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra. (Meta) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, etc., and ethylene oxide (meth). Examples thereof include a polyfunctional compound modified with EO) or the like, or a reaction product of the polyfunctional compound and (meth) acrylate or the like (for example, a poly (meth) acrylate ester of a polyhydric alcohol). In addition, in this specification, "(meth) acrylate" refers to methacrylate and acrylate.

In addition to the above compounds, relatively low molecular weight (number average molecular weight 300 to 80,000, preferably 400 to 5000) polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd having an unsaturated double bond. Resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins and the like can also be used as the ionization 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 three or more unsaturated bonds. When such a compound is used, the crosslink density of the formed hard coat layer 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 appropriately combined and used. Is preferable.

The ionizing radiation curable resin can also be used in combination with a solvent-drying resin. By using the solvent-drying resin together, it is possible to effectively prevent film defects on the coated surface. The solvent-drying resin refers to a resin such as a thermoplastic resin that forms a film simply by drying a solvent added to adjust the solid content at the time of coating.
The solvent-drying resin that can be used in combination with the ionizing radiation curable resin is not particularly limited, and in general, a thermoplastic resin can be used.
The thermoplastic resin is not particularly limited, and 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, and a polyester resin. Examples thereof include resins, polyamide resins, cellulose derivatives, silicone resins and rubbers or elastomers. The thermoplastic resin is preferably non-crystalline and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoint of film forming property, transparency and weather resistance, styrene resin, (meth) acrylic resin, alicyclic olefin resin, polyester resin, cellulose derivative (cellulose ester, etc.) and the like are preferable.

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

The photopolymerization initiator is not particularly limited, and known photopolymerization initiators can be used. For example, specific examples of the photopolymerization initiator include acetophenones, benzophenones, Michler benzoylbenzoates, and α-amilo. Examples thereof include xim esters, thioxanthones, propiophenones, benzyls, benzoins, and acylphosphine oxides. Further, it is preferable to use a photosensitizer in combination, 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 radically polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoins, benzoin methyl ethers and the like are used alone or mixed. It is preferable to use it. When the ionizing radiation curable resin is a resin system having a cationically polymerizable functional group, the photopolymerization initiator includes an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, and a benzoin sulfone. It is preferable to use an acid ester or the like 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. It is preferable because there is little change.

The content of the photopolymerization initiator in the composition for the hard coat layer is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable resin. If it 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 range, and if it exceeds 10 parts by mass, ionizing radiation is emitted to the deep part of the coated film. This is because it does not reach and internal curing is not promoted, and the target surface hardness of the hard coat layer may not be obtained.
The more preferable lower limit of the content of the photopolymerization initiator is 2 parts by mass, and the more preferable upper limit is 8 parts by mass. When the content of the photopolymerization initiator is in this range, the hardness distribution does not occur in the film thickness direction, and the hardness tends to be uniform.

The composition for the hard coat layer may contain a solvent.
The solvent can be selected and used according to the type 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.), Carbon halides (di dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), water, alcohols (ethanol, isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.) ), Cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.) and the like, and a mixed solvent thereof may be used.
In particular, in the present invention, it is preferable that the ketone solvent contains at least one of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or a mixture thereof, because it is excellent in compatibility with the resin and coatability.

The content ratio (solid content) of the raw material in the composition for the hard coat layer is not particularly limited, but is usually 5 to 70% by mass, particularly preferably 25 to 60% by mass.

The composition for the hard coat layer has properties of particles and the surface of the hard coat layer, which increase the hardness of the hard coat layer, suppress curing shrinkage, prevent blocking, control the refractive index, impart antiglare properties, and impart antiglare properties. Conventionally known organic, inorganic fine particles, dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, anticoloring agents, coloring agents (pigments, dyes), defoamers, etc., depending on the purpose such as changing 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.

Further, the composition for the hard coat layer may be used by mixing a photosensitizer, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylhosophine and the like.

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

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

The coating film formed by applying the composition for the hard coat layer 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 above-mentioned activation energy beam irradiation include irradiation with ultraviolet rays or electron beams. Specific examples of the ultraviolet source include light sources such as ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, and metal halide lamps. Further, as the wavelength of ultraviolet rays, a wavelength range of 190 to 380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as Cockcroft-Walt type, bandegraft type, resonant transformer type, insulated core transformer type, linear type, dynamistron type, and high frequency type.

The preferable film thickness (when cured) of the hard coat layer is 0.5 to 100 μm, more preferably 0.8 to 20 μm, and the curl prevention property and crack prevention property are particularly excellent, so that the range is most preferably 2 to 10 μm. 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 arbitrary 10 points. As another method, the film thickness of the hard coat layer may be measured at any 10 points using a digital indicator IDF-130 manufactured by Mitutoyo Co., Ltd., and an average value may be obtained.

The antireflection layer is a layer on which external light is incident 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, the reflection of the external light can be suitably reduced.

The low refractive index layer preferably contains 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) silica or magnesium fluoride. Fluorine-based resin, 4) Thin film of low refractive index substance such as silica and magnesium fluoride. As the resin other than the fluororesin, the same resin as the binder resin described later can be used.
Further, the above-mentioned silica is preferably hollow silica fine particles, and such hollow silica fine particles can be produced, for example, by the production method described in Examples of JP-A-2005-0997778.
It is preferable that these low refractive index layers have a refractive index of 1.45 or less, particularly 1.42 or less.
The thickness of the low refractive index layer is not limited, but usually it may be appropriately set within the range of about 30 nm to 1 μm.
Further, although the effect can be obtained with a single layer of the low refractive index layer, two or more low refractive index layers and two or more 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 the two or more layers having different refractive indexes are provided, it is preferable to provide a difference in the refractive index and the thickness of each layer.

As the fluorine-based resin, a polymerizable compound containing a fluorine atom in at least a molecule or a polymer thereof can be used. The polymerizable compound is not particularly limited, but for example, one having a curing reactive group such as a functional group that is cured by ionizing radiation and a polar group that is thermosetting is preferable. Further, a compound having these reactive groups at the same time may be used. In contrast to this polymerizable compound, the polymer does not have any of the above-mentioned reactive groups.

As the polymerizable compound having a functional group that is cured by ionizing radiation, a fluorine-containing monomer having an ethylenically unsaturated bond can be widely used. More specifically, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, perfluorobutadiene, perfluoro-2,2-dimethyl-1,3-dioxol, etc.) shall be exemplified. Can be done. Examples of those having a (meth) acryloyloxy group include 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3,3-pentafluoropropyl (meth) acrylate, and 2- (perfluorobutyl). ) Ethyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) acrylate, 2- (perfluorodecyl) ethyl (meth) acrylate, α-trifluoro (Meta) acrylate compounds having a fluorine atom in the molecule, such as methyl methacrylate and ethyl α-trifluoromethacrylate; fluoroalkyl groups having 1 to 14 carbon atoms having at least 3 fluorine atoms in the molecule, fluoro There are also fluorine-containing polyfunctional (meth) acrylic acid ester compounds having a cycloalkyl group or a fluoroalkylene group and at least two (meth) acryloyloxy groups.

The preferred thermosetting polar group is, for example, a hydrogen bond-forming group such as a hydroxyl group, a carboxyl group, an amino group, or 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-based 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 that is cured by ionization radiation and a polar group that is thermosetting include a partially fluorinated alkyl or methacrylic acid, a fully fluorinated alkyl, an alkenyl, an aryl ester, a completely or partially fluorinated vinyl ether, and a completely fluorinated vinyl ether. Alternatively, partially fluorinated vinyl esters, complete or partially fluorinated vinyl ketones and the like can be exemplified.

In addition, examples of the fluororesin include the following.
A monomer or a polymer of a monomer mixture containing at least one fluorine-containing (meth) acrylate compound of a polymerizable compound having an ionizing radiation curable group; at least one of the fluorine-containing (meth) acrylate compounds and methyl (meth). Polymers with (meth) acrylate compounds that do not contain fluorine atoms in their molecules, such as acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; fluoroethylene , Fluorine-containing, such as vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, 3,3,3-trifluoropropylene, 1,1,2-trichloro-3,3,3-trifluoropropylene, hexafluoropropylene. Examples thereof include homopolymers and copolymers of monomers. A silicone-containing vinylidene fluoride copolymer in which a silicone component is contained in these copolymers can also be used. In this case, the silicone components include (poly) dimethylsiloxane, (poly) diethylsiloxane, (poly) diphenylsiloxane, (poly) methylphenylsiloxane, alkyl-modified (poly) dimethylsiloxane, and 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 Examples thereof include modified silicone, amino-modified silicone, carboxylic acid-modified silicone, carbinol-modified silicone, epoxy-modified silicone, mercapto-modified silicone, fluorine-modified silicone, and polyether-modified silicone. Of these, those having a dimethylsiloxane structure are preferable.

Furthermore, a non-polymer or a polymer 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 and a carboxyl group. The obtained compound; a compound obtained by reacting a fluorine-containing polyol such as a fluorine-containing polyether polyol, a fluorine-containing alkyl polyol, a fluorine-containing polyester polyol, and a fluorine-containing ε-caprolactone-modified polyol with a compound having an isocyanato group, and the like. Can be used.

Further, the binder resin can be mixed and used together with the above-mentioned polymerizable compound or polymer having a fluorine atom. Further, a curing agent for curing the reactive group and the like, various additives and solvents can be appropriately used in order to improve the coatability and impart antifouling property.

The binder resin is preferably transparent, and for example, an ionizing radiation curable resin, which is a resin that is cured by ultraviolet rays or electron beams, is preferably cured by irradiation with ultraviolet rays or electron beams.

Examples of the ionizing radiation curable resin include compounds having one or two or more unsaturated bonds such as compounds having a functional group such as an acrylate-based resin. Examples of the compound having an unsaturated bond of 1 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, neopentylglycoldi (meth) acrylate, trimethylolpropane tri (meth) ) Acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate, tetrapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanurate di. (Meta) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, diglycerin tetra (meth) acrylate, adamantyldi (meth) acrylate, isoboroldi (meth) acrylate, dicyclopentane Examples thereof include polyfunctional compounds such as di (meth) acrylate, tricyclodecanedi (meth) acrylate, and trimethylolpropane tetra (meth) acrylate. Of these, pentaerythritol tetraacrylate (PETTA) is preferably used. In addition, in this specification, "(meth) acrylate" refers to methacrylate and acrylate. Further, in the present invention, as the ionizing radiation curable resin, the above-mentioned compound modified with PO, EO or the like can also be used.

In addition to the above compounds, relatively low molecular weight (number average molecular weight 300 to 80,000, preferably 400 to 5000) polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd having an unsaturated double bond. Resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins and the like can also be used as the ionization 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 three or more unsaturated bonds. When such a compound is used, the crosslink density of the formed hard coat layer 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 appropriately combined and used. Is preferable.

The ionizing radiation curable resin is used in combination with a solvent-drying resin (a resin such as a thermoplastic resin that forms a film simply by drying a solvent added to adjust the solid content at the time of coating). You can also do it. By using the solvent-drying resin together, it is possible to effectively prevent film defects on the coated surface of the coating liquid 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 in general, a thermoplastic resin can be used.
The thermoplastic resin is not particularly limited, and 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, and a polyester resin. Examples thereof include resins, polyamide resins, cellulose derivatives, silicone resins and rubbers or elastomers. The thermoplastic resin is preferably non-crystalline 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.

Further, the binder resin may contain a thermosetting resin.
The thermosetting resin is not particularly limited, and for example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, and melamine-urea cocondensation. Examples thereof include resins, silicon resins, and polysiloxane resins.

The solvent can be selected and used according to the type 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.), Carbon halides (di dichloromethane, dichloroethane, etc.), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), water, alcohols (ethanol, isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.) ), Cellosolve acetates, sulfoxides (dimethyl sulfoxide, etc.), amides (dimethylformamide, dimethylacetamide, etc.) and the like, and these may be mixed solvents.
In particular, in the present invention, it is preferable that the ketone solvent contains at least one of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or a mixture thereof, because it is excellent in compatibility with the resin and coatability.

In the formation of the low refractive index layer, the viscosity of the composition for the low refractive index layer obtained by adding the above-mentioned material is 0.5 to 5 mPa · s (25 ° C.), preferably 0. It is preferably in the range of 7 to 3 mPa · s (25 ° C.). It is possible to realize an antireflection layer having excellent visible light, to form a uniform thin film with no coating unevenness, and to form a low refractive index layer having particularly excellent adhesion.
A low refractive index layer can be formed by applying the low refractive index layer composition to the light transmissive substrate, drying the coating film, and then curing the resin in the coating film.

Examples of the curing means for the resin include a method of irradiating ionizing radiation, and examples thereof include a method of using a light source such as an ultra-high 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. Be done.
Further, as the wavelength of ultraviolet rays, a wavelength range of 190 to 380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as Cockcroft-Walt type, bandegraft type, resonant transformer type, insulated core transformer type, linear type, dynamistron type, and high frequency type.
Further, when a heating means is used for the curing treatment, a thermal polymerization initiator that generates radicals to initiate the polymerization of the polymerizable compound by heating may be added to the fluororesin composition. preferable.

The composition for a low refractive index layer preferably further contains a photopolymerization initiator.
The photopolymerization initiator is not particularly limited, and known ones can be used. Specific examples thereof include acetophenones, benzophenones, Michler benzoylbenzoates, α-amyloxime esters, thioxanthones, and propio. Examples thereof include phenones, benzyls, benzoins and acylphosphine oxides. Further, it is preferable to use a photosensitizer in combination, 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 radically polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoins, benzoin methyl ethers and the like are used alone or mixed. It is preferable to use it. When the ionizing radiation curable resin is a resin system having a cationically polymerizable functional group, the photopolymerization initiator includes an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, and a benzoin sulfone. It is preferable to use an acid ester or the like 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. It is preferable because there is little change.

The layer thickness (nm) d _A of the low refractive index layer is 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 the wavelength, preferably in the range of 480-580 nm)
Those satisfying are preferable.

Further, 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 to satisfy the above conditions in terms of low reflectance.

In the optical laminate of the present invention, the visible sensitivity reflectance Y on the surface of the antireflection layer is preferably 0.3% or less. If it exceeds 0.3%, the effect of improving the interference fringes of the optical laminate of the present invention may be inferior. Since the interference fringes are reduced as the amplitude of the surface reflected light of the optical laminate of the present invention is smaller, the more preferable upper limit of the visual reflectance Y is 0.2%.
The luminosity factor 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 the spectral reflectance of 380 nm to 780 nm with respect to the C light source defined in JIS Z8701. The visual sensitivity is corrected using (λ).
The luminosity factor corresponds to the color sensation of the human eye, that is, the sensitivity of the color sensory cells of the retina.

The optical laminate of the present invention, the reflective hue value, or 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 The above (b ^* ≦ -3, 3 ≦ b ^* ) is preferable. It is preferable that either the absolute value of the hue a ^{* or} the absolute value of the hue b ^* is 3 or more 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 the CIE1976 (L * a * b *) specified in JIS Z8729, a * and b *.

Further, the optical laminate of the present invention preferably has a total light transmittance of 80% or more. If it is less than 80%, the color reproducibility and visibility may be impaired when the image is attached to the 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 conforming to JIS K-7361 using a haze meter (manufactured by Murakami Color Technology Laboratory, product number; HM-150).

Further, the optical laminate of the present invention preferably has a haze of 1% or less. If it exceeds 1%, the 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 conforming to JIS K-7136 using a haze meter (manufactured by Murakami Color Technology Research Institute, product number; HM-150).

The optical laminate of the present invention controls the refractive index of the light transmissive base material, the undercoat layer and the hardcoat layer having a birefringence in the plane so as to satisfy the relationship represented by the above formula (1). However, it can be produced by arranging a light-transmitting substrate having a birefringence in the plane in a predetermined direction. Such a method for producing an optical laminate of the present invention is also one of the present inventions.

That is, in the method for producing an optical laminate of the present invention, at least a light transmissive base material having a double refractive index, an undercoat layer, a hardcoat layer and an antireflection layer are laminated in this order in an in-plane manner of an image display device. A method for manufacturing an optical laminate used by arranging it on a polarizing plate on the display screen side, wherein a light-transmitting base material having a double refractive index in the plane is used, and a light-transmitting base material having a double refractive index in the plane is transmitted. It has a step of arranging the phase-advancing axis, which is the direction in which the refractive index of the sex substrate is small, and the left-right direction of the display screen of the image display so as to be parallel to each other, and has a double refractive index in the plane. The refractive index of the sex substrate at a wavelength of 550 nm in the phase-advancing axis direction is nF, the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, the film thickness of the undercoat layer is d, and the refractive index of the hardcoat layer at a wavelength of 550 nm. When nHC, the following equations (1) and (2) are satisfied.

In the method for producing an optical laminate of the present invention, the light transmissive substrate having a birefringence in the plane, the undercoat layer, the hardcoat layer and the antireflection layer, and the polarizer of the present invention are used. The same as the optical laminate can be mentioned.
Further, the above-mentioned "arranged so that the phase-advancing axis, which is the direction in which the refractive index of the light-transmitting substrate having a birefringence in the plane is small, is parallel to the left-right direction of the display screen of the image display". Has the same meaning as the above-mentioned optical laminate of the present invention.
Further, it is preferable that the light transmissive substrate having a birefringence in the plane and the polarizer are laminated via the undercoat layer described above.

The image display device provided with the above-mentioned optical laminate of the present invention is also one of the present inventions.
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 transparent display body and a light source device that irradiates the transparent display body from the back surface. 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 transparent 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 each layer of the liquid crystal display device, if necessary.

The PDP is arranged with a surface glass substrate having electrodes formed on its surface and a discharge gas sealed between them facing the surface glass substrate, and electrodes and minute grooves are formed on the surface, and red is formed in the grooves. It is provided with a back glass substrate on which a 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 the front plate thereof (glass substrate or film substrate) is also provided with the above-mentioned optical laminate of the present invention.

The image display device of the present invention is an ELD device that emits light when a voltage is applied, a zinc sulfide substance: a light emitter is deposited on a glass substrate, and the voltage applied to the substrate is controlled for display, or an electric signal is emitted. It may be an image display device such as a CRT that converts the voltage into and generates an image visible to the human eye. In this case, the above-mentioned optical laminate of the present invention is provided on the outermost surface of each display device as described above or the surface of the front plate thereof.

Here, in the case of the liquid crystal display device having the optical laminate according to the present invention, the backlight light source in the liquid crystal display device is not particularly limited, but a white light emitting diode (white LED) is preferable, and the image of the present invention. The display device is preferably a VA mode or IPS mode liquid crystal display device provided with a white light emitting diode as a backlight source.
The white LED is a phosphor type, that is, an element that emits white by combining a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor and a phosphor. Among them, the white light emitting diode consisting of a light emitting element combining a blue light emitting diode using a compound semiconductor and an yttrium aluminum garnet yellow phosphor has antireflection performance because it has a continuous and wide light emitting spectrum. It is suitable as the backlight light source in the present invention because it is effective in improving the contrast in bright places and also has excellent luminous efficiency. In addition, since white LEDs with low power consumption can be widely used, it is possible to achieve the effect of energy saving.
In addition, the above-mentioned VA (Vertical Alignment) mode means that when no voltage is applied, the liquid crystal molecules are oriented so as to be perpendicular to the substrate of the liquid crystal cell to indicate a dark display, and the liquid crystal molecules collapse when a voltage is applied. This is the operation mode that indicates a clear display with.
The IPS (In-Plane Switching) mode is a method in which a liquid crystal is rotated in a substrate surface by a lateral electric field applied to a comb-shaped electrode pair provided on one substrate of a liquid crystal cell to display. is there.
It is preferable that the image display device using the optical laminate of the present invention is in VA mode or IPS mode provided with a white light emitting diode as a backlight source for the following reasons.
That is, the image display device of the present invention can reduce the reflection of light (S-polarized light) vibrating in the left-right direction, which is often incident on the display screen, in the optical laminate of the present invention, but as a result, many S polarized light will be transmitted. Normally, these transmitted S-polarized light are absorbed inside the display device, but there is very little light returning to the observer side. In the VA mode or the IPS mode, since the absorption axis of the polarizer installed on the observer side of the liquid crystal cell is in the left-right direction with respect to the display screen, the S-polarized light transmitted through the optical laminate of the present invention is absorbed. 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 televisions, computers, electronic papers, touch panels, tablet PCs and the like. In particular, it can be suitably used on the surface of high-definition image displays such as CRTs, liquid crystal panels, PDPs, ELDs, FEDs, and touch panels.

Further, such an image display device can be manufactured, for example, by laminating the optical laminate of the present invention produced by the above-mentioned method on a polarizing plate on the display screen side.
That is, in the method for manufacturing an image display device of the present invention, at least a light transmissive substrate having a double refractive index, an undercoat layer, a hard coat layer and an antireflection layer are laminated in this order in the plane of the image display device. It is a method of manufacturing an image display device using an optical laminate used by arranging it on a polarizing plate on the display screen side, and a light transmissive substrate having a double refractive index in the above plane is laminated in the above plane. It has a step of arranging the phase-advancing axis in which the refractive index of the light-transmitting substrate having a refractive index is small and the left-right direction of the display screen of the image display so as to be parallel to each other. The refractive index of the light transmissive substrate having a double refractive index at a wavelength of 550 nm in the phase-advancing axis direction is nF, the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, the film thickness of the undercoat layer is d, and the hard When the refractive index of the coat layer at a wavelength of 550 nm is nHC, the following formulas (1) and (2) are satisfied.

In the method for manufacturing the image display device of the present invention, examples of the optical laminate include the same optical laminate as the above-mentioned optical laminate of the present invention.
In addition, the phase-advancing axis, which is the direction in which the refractive index of the light-transmitting substrate having a birefringence in the plane is small, is parallel to the left-right direction of the display screen of the image display. "Arrange" has the same meaning as the above-mentioned optical laminate of the present invention.
Further, it is preferable that the light transmissive substrate having a birefringence in the plane and the polarizer are laminated via the undercoat layer described above.

The image display device of the present invention uses the above-mentioned optical laminate of the present invention, and has a phase-advancing axis of a light-transmitting base material having a birefringence in the plane and left and right of the display screen of the image display device. The interference fringes are arranged so as to be parallel to each other, and the light-transmitting base material, the undercoat layer, and the hardcoat layer constituting the optical laminate satisfy a specific refractive index relationship. The occurrence will be improved. A method for improving interference fringes of such an image display device is also one of the present inventions.

That is, in the method for improving interference fringes of the image display device of the present invention, at least a light transmissive substrate having a double refractive index, an undercoat layer, a hardcoat layer and an antireflection layer are laminated in this order to display an image. A method for improving interference fringes of an image display device using an optical laminate used by arranging it on a polarizing plate on the display screen side of the device, wherein a light transmissive substrate having a double refractive index in the plane is used. The phase-advancing axis, which is the direction in which the refractive index of the light-transmitting substrate having a double refractive index in the plane is small, is arranged so as to be parallel to the left-right direction of the display screen of the image display, and the double refractive index is provided in the plane. The refractive index of the light transmissive substrate having a refractive index at a wavelength of 550 nm in the phase-advancing axis direction was defined as nF, the refractive index of the undercoat layer at a wavelength of 550 nm was defined as nUC, and the refractive index of the hardcoat layer at a wavelength of 550 nm was defined as nHC. When, it is characterized in that the following equations (1) and (2) are satisfied.

In the method for improving interference fringes of the image display device of the present invention, examples of the optical laminate are the same as those of the above-mentioned optical laminate of the present invention, and the above-mentioned image display device of the present invention is described above. The same as the image display device can be mentioned.
In addition, the above-mentioned "arranged so that the phase-advancing axis in which the refractive index of the light-transmitting substrate having a birefringence in the plane is small and the left-right direction of the display screen of the image display are parallel". , Means the same as the above-mentioned optical laminate of the present invention.

Since the optical laminate of the present invention has the above-mentioned structure, even if the hard coat layer is laminated on a light-transmitting base material having an in-plane birefringence such as a polyester film. , The occurrence of interference fringes can be suppressed to a high degree.

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

(Preparation of light transmissive substrate)
(Preparation of light transmissive base material A having birefringence in the plane)
The polyethylene terephthalate material was melted at 290 ° C. and slowly cooled on glass to obtain a light-transmitting substrate a. At a wavelength of 550 nm, Δn = 0.00035 and the average refractive index N = 1.6167.
The light-transmitting base material a was uniaxially stretched at a fixed end of 4.0 times at 120 ° C. to prepare a light-transmitting base material 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 = 1.6015, and nz = 1.5476.

(Preparation of light transmissive base material B having birefringence in the plane)
The polyethylene naphthalate material was melted at 290 ° C. and slowly cooled on glass to obtain a light-transmitting substrate b. At a wavelength of 550 nm, Δn = 0.0004 and an average refractive index N = 1.6833.
The light-transmitting base material b was uniaxially stretched at a fixed end of 4.0 times at 120 ° C. to prepare a light-transmitting base material 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.

( Reference example 1)
The composition 1 for the undercoat layer having the following composition is applied to the surface of the light transmissive base material A so that the film thickness after drying (40 ° C. × 1 minute) is 0.085 μm, and an ultraviolet irradiation device (fusion) is applied. Using a light source H valve manufactured by UV System Japan Co., Ltd., the undercoat layer (refractive index 1.57) is cured by irradiating with ultraviolet rays at an integrated light intensity of 50 mJ / cm ² in a nitrogen atmosphere (oxygen concentration of 200 ppm or less). ) Was formed.
On the formed undercoat layer, the composition 1 for a hard coat layer having the following composition is applied so that the film thickness after drying (60 ° C. × 1 minute) is 10 μm, and an ultraviolet irradiation device (Fusion UV System Japan) is applied. A hard coat layer (refractive index 1.54) is formed by irradiating ultraviolet rays with an integrated light intensity of 50 mJ / cm ² and curing in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) using a light source H valve manufactured by the same company. did.
Next, the composition 1 for a high refractive index layer having the following composition is applied onto the formed hard coat layer so that the film thickness after drying (50 ° C. × 1 minute) is 0.16 μm, and an ultraviolet irradiation device is used. A high refractive index layer (refractive index) is cured by irradiating ultraviolet rays with an integrated light amount of 50 mJ / cm ² in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) using (Fusion UV System Japan, Inc., light source H valve). 1.62) was formed.
Then, the composition 1 for a low refractive index layer having the following composition is applied onto the formed high refractive index layer so that the film thickness after drying (40 ° C. × 1 minute) is 0.10 μm, and is irradiated with ultraviolet rays. A low refractive index layer (refractive index) is cured by irradiating ultraviolet rays with an integrated light amount of 100 mJ / cm ² in a nitrogen atmosphere (oxygen concentration of 200 ppm or less) using an apparatus (Fusion UV System Japan, Inc., light source H valve). A refractive index of 1.33) was formed to produce an optical laminate.
The manufactured optical laminate had a surface reflectance of 0.45% from the low refractive index layer side, and the reflected hue at that time was −0.56 for a * and −0.74 for b *.

(Composition 1 for undercoat layer)
OPPE (OXOphenylphenol acrylate, manufactured by Dai-ichi 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 for hard coat layer 1)
UV-7600B (manufactured by Nippon Synthetic Chemistry) 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 for high refractive index layer 1)
B364M (manufactured by Mikuni Color Co., Ltd.) 7.3 parts by mass Pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec Co., Ltd.)
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 for low refractive index layer 1)
Hollow silica fine particles (solid content of the 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 Ltd.) 0.07 parts by mass Modified silicone oil (X22164E; manufactured by Shin-Etsu Chemical Co., Ltd.) 0.08 parts by mass MIBK 80 parts by mass PGMEA 10 parts by mass

( Reference example 2)
A polarizer is attached to the back surface of the optical laminate obtained in Reference Example 1 so that the phase-advancing axis of the light-transmitting base material A and the absorption axis of the polarizer are parallel to each other, and the optical laminate provided with the polarizer is provided. I got a body.

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

(Composition for low refractive index layer 2)
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 Ltd.) 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

( Reference example 4)
An optical laminate was produced in the same manner as in Reference Example 1 except that the undercoat layer was applied so that the film thickness after drying was 0.100 μm.
The surface reflectance from the low refractive index layer side was 0.44%, and the reflected hue at that time was −0.38 for a * and −0.22 for b *.

( Reference example 5)
The same applies to Reference Example 1 except that the high refractive index layer was applied so that the dried film thickness was 0.14 μm, and the low refractive index layer was applied so that the dried film thickness was 0.09 μm. An optical laminate was manufactured.
The surface reflectance from the low refractive index layer side was 0.51%, and the reflected hue at that time was 4.85 for a * and −0.02 for b *.

( Reference example 6)
An optical laminate was produced in the same manner as in Reference Example 1 except that the low refractive index layer was applied 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 reflected hue at that time was −0.57 for a * and −6.52 for b *.

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

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

(Composition 2 for undercoat layer)
OPPE (OXOphenylphenol acrylate, manufactured by Dai-ichi 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

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

(Composition for hard coat layer 2)
MIBK-SD (Nissan Chemical Industries, 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) 0.05 parts by mass

(Composition 3 for undercoat layer)
OPPE (OXOphenylphenol acrylate, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 0.6 parts by mass Pentaerythritol triacrylate (PETA) (manufactured by 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

( Reference example 10)
Instead of the composition 1 for the hard coat layer, the composition 3 for the hard coat layer (refractive index after curing 1.58) having the following composition is used, and instead of the composition 1 for the undercoat layer, the composition for the undercoat layer An optical laminate was produced in the same manner as in Reference 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 reflected hue at that time was 0.30 for a * and −2.54 for b *.

(Composition for hard coat layer 3)
B364M (manufactured by Mikuni 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 Ltd.) (Manufactured by) 0.05 parts by mass

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

(Composition for Undercoat Layer 4)
B364M (manufactured by Mikuni Color Co., Ltd.) 7.3 parts by mass Pentaerythritol triacrylate (PETA) (manufactured by Daicel Cytec Co., Ltd.)
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 Reference Example 1 except that the undercoat layer was applied so that the film thickness after drying was 0.300 μm.
The surface reflectance from the low refractive index layer side was 0.47%, and the reflected hue at that time was 0.89 for a * and 0.90 for b *.

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

(Interference fringes)
The surface opposite to the low refractive index layer of each of the optical laminates obtained in Examples , Reference Examples and Comparative Examples (the side surface of the light-transmitting base material, the surface of the polarizer for the optical laminate according to Reference Example 2). , It is attached to a black acrylic plate to prevent backside reflection via an undercoat layer (adhesive layer), and an optical laminate is used to assume a polarized environment in a room (bright place) with a relatively strong light source. The state of interference fringes under a three-wavelength tube (manufactured by Hitachi, Ltd., Akarin rod 20 type 18W, FL20SS-EX-N / 18-J, three-wavelength type daylight color) installed between and as a polarizing light source. Observed. At this time, the light source and each optical laminate are observed so that the phase-advancing axis of the light-transmitting base material of each optical laminate is parallel to the polarization direction of the light source and the surface of the low refractive index layer is observed from substantially the front. Visually observe so that the angle formed by the observation position is within 10 °, and further observe visually so that the angle formed by the light source, each optical laminate, and the observation position is 45 ° as an observation from an oblique position. , The presence or absence of interference fringes was evaluated according to the following criteria.
Using the optical laminate according to Reference Example 1, the optical laminate according to Reference Example 11 was observed so that the phase-advancing axis of the light-transmitting substrate was at an angle of 15 ° with the polarization direction of the light source. Evaluation was performed using the optical laminate according to Reference Example 1 and observed so that the phase-advancing axis of the light-transmitting substrate was at an angle of 30 ° with the polarization direction of the light source, and evaluated as Comparative Example 3 for reference. Using the optical laminate of Example 1 and observing the light-transmitting substrate so that the phase-advancing axis formed an angle of 90 ° with the polarization direction of the light source, it was evaluated as Comparative Example 4.
⊚ *: Interference fringes could not be visually recognized at any observation angle.
⊚: Interference fringes could not be visually recognized at any of the observation angles.
◯: Interference fringes were slightly generated at all observation angles, but there was no problem.

As shown in Table 1, the optics according to the embodiment satisfying the formulas (1) and (2) and in which the phase-advancing axis of the light-transmitting base material and the left-right direction of the image display device are arranged in parallel. The laminated body was excellent in preventing interference fringes.
On the other hand, the optical laminate according to Comparative Example 1 did not satisfy the formula (1), the optical laminate according to Comparative Example 2 did not satisfy the formula (2), and the optical laminates according to Comparative Examples 3 and 4 did not satisfy the formula (1). Since the phase-advancing axis of the light-transmitting base material and the left-right direction of the image display device were not parallel, the preventability of interference fringes was inferior.
The optical laminates obtained in Examples , Reference Examples and Comparative Examples were all subjected to a method conforming to JIS K-7361 using a haze meter (manufactured by Murakami Color Technology Research Institute, product number; HM-150). When the light transmittance was measured and the haze was measured by a method conforming to JIS K-7136, the total light transmittance was 93% or more in all the examples , reference examples and comparative examples, and the haze of the base material was determined. The deducted haze of only the coating film portion was 0.3% or less.

When the optical laminate of the present invention is used in an image display device, even if the hard coat layer is laminated on a light transmissive substrate having a birefringence in the plane such as a polyester film. The occurrence of interference fringes can be suppressed to a high degree.

Claims (1)

At least, a light transmissive substrate having a birefringence, an undercoat layer, a hardcoat layer, and an antireflection layer are laminated in this order in the plane and arranged on a polarizing plate on the display screen side of an image display device for use. A method for manufacturing an image display device including an optical laminate.
The refractive index of the light transmissive substrate having a birefringence in the plane at a wavelength of 550 nm in the phase-advancing axis direction is nF, the refractive index of the undercoat layer at a wavelength of 550 nm is nUC, and the film thickness of the undercoat layer is d. (Nm), when the refractive index of the hard coat layer at a wavelength of 550 nm is nHC, the following formulas (1) and (2) are satisfied.
The undercoat layer contains at least one resin selected from the group consisting of thermosetting or thermoplastic polyester resins, urethane resins, acrylic resins, and modified products thereof, and has a higher refractive index than the resins. Including high refractive index resin
The reflected hue value of the optical laminate has an absolute value of hue a ^* of 3 or more, or an absolute value of hue b ^* of 3 or more.
A light transmissive substrate having a double refractive index, an undercoat layer, a hardcoat layer, and an antireflection layer having a visible reflectance Y of 0.3% or less on the surface of the antireflection layer are laminated in this order. The process of manufacturing the optical laminate
The phase-advancing axis of the light-transmitting substrate having a birefringence in the plane in the direction in which the refractive index of the light-transmitting substrate having the birefringence in the plane is small, and the display screen of the image display device. A method for manufacturing an image display device , which comprises a step of arranging the optical laminate so as to be parallel to the left-right direction.

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