JP2008191250A - Retardation film and manufacturing method of retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film which is excellent in adhesion between a base material and a retardation layer with respect to the retardation film using no alignment layer, and is excellent in aging stability of optical characteristics even in a high-temperature and high-humidity environment. <P>SOLUTION: The retardation film comprises the base material made of cycloolefin based resin and at least has a property as an optically negative C-plate and the retardation layer which is directly formed on the base material and contains a rod-shape compound, and satisfies, among nx, ny and nz, the following relation: nx≥ny>nz, wherein the nx, ny denote refractive indexes in arbitrary X, Y-directions which are orthogonal to each other in the in-plane direction, the nz denotes the refractive index in the thickness direction and an urethane acrylate polymer is contained in the retardation layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retardation film used in a liquid crystal display device and the like, and a method for producing the retardation film. More specifically, the present invention uses a substrate made of a cycloolefin resin and does not have an alignment layer. The present invention relates to a retardation film.

  The liquid crystal display device has features such as power saving, light weight, thinness, and the like, and has rapidly spread in recent years in place of the conventional CRT display. As a general liquid crystal display device, as shown in FIG. 3, a liquid crystal display device having an incident side polarizing plate 102 </ b> A, an outgoing side polarizing plate 102 </ b> B, and a liquid crystal cell 101 can be exemplified. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light having a vibration surface in a predetermined vibration direction, and crossed Nicols so that the vibration directions are perpendicular to each other. It is arranged to face each other. The liquid crystal cell 101 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  As such a liquid crystal display device, those using various driving methods are known depending on the arrangement form of the liquid crystal material used in the liquid crystal cell. The main ones of liquid crystal display devices that are popular today are classified into TN, STN, MVA, IPS, OCB, and the like. In particular, today, those having the MVA and IPS driving methods have come into widespread use.

  On the other hand, the liquid crystal display device has a problem of viewing angle dependency due to the refractive index anisotropy of the liquid crystal cell and the polarizing plate as a particular problem. This problem of viewing angle dependency is a problem that the color and contrast of an image that is visually recognized change when the liquid crystal display device is viewed from the front and when viewed from an oblique direction. Such a problem of viewing angle characteristics has become more serious with the recent increase in the screen size of liquid crystal display devices.

  Various techniques have been developed so far to improve the viewing angle dependency problem. As a typical method, there is a method using a retardation film. In the method using such a retardation film, a retardation film 103 having predetermined optical characteristics is disposed between the liquid crystal cell 101 and the polarizing plates 102A and 102B as shown in FIG. It is a way to improve sex problems. Since this method can improve the above-described viewing angle dependency only by incorporating the retardation film 103 into the liquid crystal display device, it is widely used as a method for easily obtaining a liquid crystal display device having excellent viewing angle characteristics. Has come to be.

  Conventionally, as the retardation film, as shown in FIG. 5, an alignment layer 22 is provided on an arbitrary transparent substrate 21, and a retardation layer 23 containing liquid crystal molecules is further formed on the alignment layer 22, In general, the liquid crystal molecules are aligned by the alignment regulating force of the alignment film so as to exhibit a desired refractive index anisotropy. As such a retardation film, for example, Patent Document 1 or Patent Document 2 discloses a retardation layer having a cholesteric regular molecular structure (a retardation layer exhibiting birefringence) on a substrate having an alignment layer. A retardation film formed in the above is disclosed. Patent Document 3 discloses a retardation film in which a retardation layer composed of a discotic compound (a retardation layer exhibiting birefringence) is formed on a substrate having an alignment layer.

  The method of improving the viewing angle dependency using the above retardation film is a liquid crystal display by appropriately designing the refractive index anisotropy of the retardation layer so as to cancel the retardation generated in the liquid crystal cell of the liquid crystal display device. This is useful in that the problem of dependency on the viewing angle of the apparatus can be greatly improved. However, as described above, the conventional retardation film has an indispensable configuration of the alignment layer for aligning the liquid crystal molecules, and thus there is a problem in the adhesion between the alignment layer and the retardation.

  In order to solve this problem, the present inventors have provided a retardation film having a configuration in which a retardation layer is directly formed on a substrate without using the alignment layer (Patent Document 4). A retardation film that does not use such an alignment layer can be formed by a simple process, and further has an advantage that it can contribute to thinning of a liquid crystal display device manufactured using the retardation film. It has attracted attention as a retardation film with excellent properties.

JP-A-3-67219 JP-A-4-322223 Japanese Patent Laid-Open No. 10-312166 International Publication No. 2006/028217 Pamphlet

  By the way, the base material which consists of triacetylcellulose has been used for the retardation film conventionally used for the liquid crystal display device. This is because the triacetyl cellulose is excellent in optical isotropy, and the use of such a substrate facilitates the design of the optical characteristics of the retardation film. However, since triacetyl cellulose has a relatively high water absorption, it has a problem that it absorbs and expands in a high-temperature and high-humidity atmosphere and changes the optical properties of the retardation film.

  In order to solve such a problem, it is also conceivable to use a base material made of a cycloolefin-based resin that has recently attracted attention as a substitute for the triacetyl cellulose instead of the base material made of the triacetyl cellulose. However, since the cycloolefin resin has a lower water absorption than the triacetyl cellulose, the problem of the hygroscopic expansion can be solved, but on the other hand, the adhesion to the retardation layer formed on the substrate is low. There was concern about the problem of a drop.

  Therefore, in the retardation film that does not use the alignment layer, the film has excellent adhesion between the retardation layer and the substrate, and excellent in temporal stability of optical characteristics even in a high-temperature and high-humidity atmosphere. It was difficult to get.

  The present invention has been made in view of such problems, and is a retardation film that does not use an alignment layer, has excellent adhesion between the substrate and the retardation layer, and is in a high-temperature, high-humidity atmosphere. The main object of the present invention is to provide a retardation film having excellent optical characteristics over time.

  In order to solve the above-mentioned problems, the present invention comprises a base material comprising a cycloolefin resin and having at least an optically negative C-plate property, and a rod-shaped compound formed directly on the base material. Nx, ny, and nz between nx, ny, and nz when the refractive index in any X, Y direction orthogonal to each other in the in-plane direction is nx, ny, and the refractive index in the thickness direction is nz. Provided is a retardation film satisfying a relationship of ≧ ny> nz, wherein the retardation layer contains a polymer of urethane acrylate.

According to this invention, the adhesiveness of the said phase difference layer and the said base material can be improved by the polymer of urethane acrylate being contained in the said phase difference layer. For this reason, according to this invention, the phase difference film excellent in the adhesiveness of the said phase difference layer and the said base material can be obtained.
In addition, according to the present invention, since the base material made of cycloolefin resin is used, the base material can be prevented from hygroscopic expansion in a high temperature and high humidity atmosphere. Therefore, according to the present invention, it is possible to obtain a retardation film excellent in temporal stability of optical characteristics even in a high temperature and high humidity atmosphere.
For this reason, according to the present invention, the retardation film does not use an alignment layer, has excellent adhesion between the substrate and the retardation layer, and the optical characteristics over time even in a high-temperature and high-humidity atmosphere. A retardation film having excellent stability can be obtained.

  In the present invention, the urethane acrylate preferably has a weight average molecular weight (Mw) in the range of 1000 to 40000. This is because when the weight average molecular weight (Mw) of the urethane acrylate is within such a range, the retardation layer can be made excellent in optical property development.

  Moreover, in this invention, it is preferable that content of the polymer of the said urethane acrylate in the said phase difference layer exists in the range of 5 mass%-40 mass%. It is because the adhesiveness of the said retardation layer and the said base material in the retardation film of this invention can be made more excellent because the said content is in such a range.

  In order to solve the above problems, the present invention uses a base material having a property as an optically negative C plate, which is made of a cycloolefin-based resin, and the rod-shaped compound and urethane acrylate are dissolved in a solvent. By coating the retardation layer forming coating liquid directly on the substrate, the retardation layer forming layer forming step for forming the retardation layer forming layer and the retardation layer forming layer forming step are performed. A heat retaining step for keeping the formed retardation layer forming layer at a temperature of 35 ° C. or lower, and a urethane polymerization step for polymerizing the urethane acrylate contained in the retardation layer forming layer kept warm in the heat retaining step; A method for producing a retardation film comprising a retardation layer forming step including a drying step of drying the retardation layer forming layer.

According to the present invention, when the retardation layer forming coating liquid contains urethane acrylate, the retardation layer formed on the substrate by the retardation layer forming step and the adhesion between the substrate and the substrate. Can be improved. For this reason, according to this invention, the phase difference film excellent in the adhesiveness of the said base material and the said phase difference layer can be manufactured.
In addition, according to the present invention, since the base material made of cycloolefin resin is used, the base material can be prevented from hygroscopic expansion in a high temperature and high humidity atmosphere. For this reason, according to the present invention, it is possible to produce a retardation film excellent in temporal stability of optical characteristics even in a high temperature and high humidity atmosphere.
For this reason, according to the present invention, the retardation film does not use an alignment layer, has excellent adhesion between the substrate and the retardation layer, and the optical characteristics over time even in a high-temperature and high-humidity atmosphere. A retardation film excellent in stability can be produced.

  The present invention is a retardation film that does not use an alignment layer, and has excellent adhesion between a base material and a retardation layer, and also has excellent temporal stability of optical characteristics even in a high-temperature and high-humidity atmosphere. There is an effect that can be obtained.

The present invention relates to a retardation film and a method for producing a retardation film.
Hereinafter, the retardation film of the present invention and the method for producing the retardation film will be described in order.

A. Retardation Film First, the retardation film of the present invention will be described. The retardation film of the present invention is composed of a cycloolefin-based resin and has at least a substrate having properties as a negative C plate, and a retardation layer formed directly on the substrate and containing a rod-shaped compound, In the in-plane direction, when the refractive indexes in arbitrary X and Y directions orthogonal to each other are nx and ny, and the refractive index in the thickness direction is nz, there is a relationship of nx ≧ ny> nz between nx, ny and nz. In other words, the retardation layer contains a polymer of urethane acrylate.

Such a retardation film of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of the retardation film of the present invention. As illustrated in FIG. 1, the retardation film 10 of the present invention is made of a cycloolefin-based resin, and is formed directly on the substrate 1 having at least an optically negative C plate property and the substrate 1. The retardation film 2 as a whole has a relationship of nx ≧ ny> nz between the above nx, ny and nz.
In such an example, the retardation film 10 of the present invention is characterized in that the retardation layer 2 contains a rod-shaped compound and a polymer of urethane acrylate.

According to this invention, the adhesiveness of the said phase difference layer and the said base material can be improved by the polymer of urethane acrylate being contained in the said phase difference layer. For this reason, according to this invention, the phase difference film excellent in the adhesiveness of the said phase difference layer and the said base material can be obtained.
In addition, according to the present invention, since the base material made of cycloolefin resin is used, the base material can be prevented from hygroscopic expansion in a high temperature and high humidity atmosphere. Therefore, according to the present invention, it is possible to obtain a retardation film excellent in temporal stability of optical characteristics even in a high temperature and high humidity atmosphere.
For this reason, according to the present invention, the retardation film does not use an alignment layer, has excellent adhesion between the substrate and the retardation layer, and the optical characteristics over time even in a high-temperature and high-humidity atmosphere. A retardation film having excellent stability can be obtained.

Here, the reason why the adhesiveness between the retardation layer and the substrate can be improved by including the urethane acrylate polymer in the retardation layer is not clear, but the following reason It is thought that it is based on.
That is, as described above, the substrate used in the present invention is made of a cycloolefin resin, but the urethane acrylate is compatible with the cycloolefin resin constituting the substrate. For this reason, in the present invention, the urethane acrylate polymer is contained in the retardation layer, whereby the urethane acrylate polymer is located near the boundary between the retardation layer and the substrate in the retardation film of the present invention. It is considered that a state in which the cycloolefin-based resin and the cycloolefin-based resin are compatible is formed, thereby improving the adhesion between the retardation layer and the substrate.
However, the above reason is only an estimate, and even if the adhesion between the base material and the retardation layer is improved by a mechanism different from the above reason, the configuration is substantially the same as the present invention. The inventions possessed belong to the technical scope of the present invention.

The retardation film of the present invention has at least the substrate and the retardation layer.
Hereafter, each structure used for the retardation film of this invention is demonstrated in order.

1. Retardation Layer First, the retardation layer used in the present invention will be described. The retardation layer used in the present invention is directly formed on a base material to be described later, and contains a rod-like compound and a polymer of urethane acrylate.
In the present invention, by containing the urethane acrylate polymer in the retardation layer, a retardation layer having excellent adhesion between the retardation layer and a substrate described later can be obtained.

  In the present invention, the term “directly formed” means that the retardation layer is in direct contact with the surface of the substrate without interposing another layer between the substrate and the retardation layer described later. It means that it is formed.

  Hereinafter, such a retardation layer will be described in detail.

(1) Polymer of urethane acrylate First, a polymer of urethane acrylate contained in the retardation layer will be described. The urethane acrylate polymer used in the present invention is obtained by polymerizing a urethane acrylate having a urethane bond portion (—O—CO—N <) and a (meth) acrylate group.

  The expression “(meth) acrylate group” includes an acrylate group and a methacrylate group.

  As said urethane acrylate, it has a urethane coupling | bond part (-O-CO-N <) and a (meth) acrylate group, and if it does not impair the arrangement | sequence of the rod-shaped compound mentioned later, it will be specifically limited. is not. Accordingly, the urethane acrylate used in the present invention may be one having a single (meth) acrylate group (monofunctional) or one having a plurality of (meth) acrylate groups (multifunctional). May be. The urethane acrylate used in the present invention may have a single urethane bond or may have a plurality of urethane bonds.

As the weight average molecular weight (Mw) of the urethane acrylate used in the present invention, the retardation layer used in the retardation film of the present invention can be provided with desired optical properties, and can be adhered to a substrate described later. The property is not particularly limited as long as the property can be in a desired range. Among these, the urethane acrylate used in the present invention preferably has a weight average molecular weight (Mw) in the range of 1000 to 40000, particularly preferably in the range of 1000 to 30000, and more preferably in the range of 1500 to 20000. It is preferable to be within. This is because, when the weight average molecular weight (Mw) is within the above range, the retardation layer used in the present invention can be made excellent in optical property development.
In addition, when a weight average molecular weight (Mw) is smaller than the said range, the addition amount for making the adhesiveness of the phase difference layer used for this invention and the base material mentioned later into a desired range increases, for example. On the other hand, if the weight average molecular weight (Mw) is larger than the above range, it may be difficult to impart desired optical properties to the retardation layer.

  Specific examples of the urethane acrylate used in the present invention include UV7610B manufactured by Nippon Synthetic Chemical Industry Co., Ltd. and UV7640B manufactured by the same company.

  The polymer of urethane acrylate used in the present invention is not particularly limited as long as the urethane acrylate described above is polymerized. Therefore, the urethane acrylate polymer used in the present invention may be one obtained by polymerizing one type of urethane acrylate, or may be one obtained by polymerizing a plurality of urethane acrylates.

  Moreover, the urethane acrylate polymer used in the present invention may be only one kind or two or more kinds.

  In the present invention, the amount of the urethane acrylate polymer contained in the retardation layer is an amount that allows the adhesion between the retardation layer used in the present invention and the substrate described later to be within a desired range. There is no particular limitation as long as it is present. In particular, in the present invention, the content of the urethane acrylate polymer in the retardation layer is preferably in the range of 5% by mass to 40% by mass, and particularly in the range of 5% by mass to 30% by mass. It is preferable to be within a range of 5% by mass to 20% by mass. It is because the adhesiveness of the said retardation layer and the said base material in the retardation film of this invention can be made more excellent because the said content is in such a range.

(2) Rod-shaped compound Next, the rod-shaped compound contained in the retardation layer in the present invention will be described. The rod-shaped compound used in the present invention is contained in the retardation layer, and the relationship of nx ≧ ny> nz is established among the nx, ny and nz in the retardation film of the present invention. It has a function of imparting optical characteristics.
Here, the “rod-shaped compound” in the present invention refers to a compound in which the main skeleton of the molecular structure is rod-shaped.
Hereinafter, such a rod-like compound will be described.

  The rod-shaped compound used for this invention will not be specifically limited if a desired optical characteristic can be provided to the phase difference layer in this invention. Especially, it is preferable that the rod-shaped compound used for this invention is a liquid crystalline material which shows liquid crystallinity. This is because by using a liquid crystalline material as the rod-shaped compound, the retardation layer used in the present invention can be made excellent in the development of optical characteristics per unit thickness.

  The rod-like compound used in the present invention is preferably a liquid crystalline material exhibiting a nematic phase among the above liquid crystalline materials. This is because a liquid crystalline material exhibiting a nematic phase is easier to arrange in a predetermined form than liquid crystal materials exhibiting other liquid crystal phases.

  Furthermore, the rod-shaped compound used in the present invention preferably has a structure having spacers at both ends of the mesogen among the liquid crystalline materials exhibiting the nematic phase. This is because the liquid crystalline material having such a structure is excellent in flexibility and can effectively prevent the retardation layer in the present invention from becoming clouded.

  As the rod-like compound used in the present invention, those having a polymerizable functional group in the molecule are suitably used, and those having a polymerizable functional group capable of three-dimensional crosslinking are particularly preferable. Since the rod-shaped compound has a polymerizable functional group, the rod-shaped compound can be polymerized and fixed. By fixing the rod-shaped compound in an oriented state, the alignment stability is excellent. This is because it is possible to obtain a retardation film that hardly changes in optical characteristics. In the present invention, the rod-shaped compound having the polymerizable functional group and the rod-shaped compound having no polymerizable functional group may be mixed and used.

The “three-dimensional crosslinking” means that liquid crystal molecules are polymerized three-dimensionally to form a network (network) structure.

  The polymerizable functional group is not particularly limited, and various polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat can be used. Typical examples of such polymerizable functional groups include radical polymerizable functional groups and cationic polymerizable functional groups.

Representative examples of the radical polymerizable functional group include a functional group having at least one addition-polymerizable ethylenically unsaturated double bond. More specifically, a vinyl group having or without a substituent, an acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) can be given.
On the other hand, specific examples of the cationic polymerizable functional group include an epoxy group.
As the polymerizable functional group, in addition to the radical polymerizable functional group and the cationic polymerizable functional group, for example, polymerizable functional groups such as isocyanate groups and unsaturated triple bonds can be used. However, in the present invention, a functional group having an ethylenically unsaturated double bond is preferably used from the viewpoint of the process.

  The rod-like compound in the present invention is a liquid crystalline material exhibiting liquid crystallinity and particularly preferably has a polymerizable functional group at the terminal. For example, if nematic liquid crystalline materials having polymerizable functional groups at both ends are used, they can be polymerized three-dimensionally to form a network structure, have alignment stability, and have optical properties. A retardation layer having excellent expression can be obtained. Moreover, even if it has a polymerizable functional group at one end, it can be cross-linked with other molecules to stabilize the sequence. Examples of such a liquid crystalline material include compounds represented by the following formulas (1) to (6).

  Here, the liquid crystalline materials represented by the chemical formulas (1), (2), (5) and (6) are disclosed in DJ Broer et al., Makromol. Chem. 190, 3201-3215 (1989), or DJ Broer et al., Makromol. Chem. 190, 2250 (1989), or by methods analogous thereto. The preparation of liquid crystalline materials represented by the chemical formulas (3) and (4) is disclosed in DE 195,04,224.

Specific examples of the nematic liquid crystalline material having an acrylate group at the terminal include those represented by the following chemical formulas (7) to (17).

  In the present invention, the rod-shaped compound may be only one kind or two or more kinds. For example, when the rod-shaped compound is used by mixing a liquid crystalline material having one or more polymerizable functional groups at both ends and a liquid crystalline material having one or more polymerizable functional groups at one end, The polymerization density (crosslink density) and the optical characteristics can be arbitrarily adjusted by adjusting the ratio, which is preferable.

The rod-shaped compound used in the present invention has a function of imparting predetermined optical characteristics to the retardation film of the present invention by arranging in the retardation layer. In the present invention, the rod-shaped compound is a retardation layer. As an aspect to be arranged within the above, the retardation film of the present invention is particularly limited as long as it is an aspect capable of imparting an optical characteristic in which a relationship of nx ≧ ny> nz is established between nx, ny and nz. Is not to be done.
Here, as described above, since the rod-shaped compound used in the present invention has a molecular structure in which the main skeleton is rod-shaped, it is arranged in such a manner that the major axis directions of the molecules are aligned in one direction on average. By this, it becomes easy to provide the retardation film of the present invention with optical characteristics that satisfy the relationship of nx>ny> nz. Moreover, when the rod-shaped compound forms a random homogeneous orientation, it becomes easy to impart optical characteristics satisfying the relationship of nx = ny> nz to the retardation film of the present invention.

  Here, the “random homogeneous orientation” means that the arrangement direction of the rod-shaped compounds in the retardation layer is first random, and second, the size of the domain formed by the rod-shaped compounds in the retardation layer is visible. It is intended to indicate an arrangement mode having three characteristics: smaller than the wavelength of the optical region, and thirdly, that the rod-shaped compound is in-plane oriented in the retardation layer.

(3) Other compounds The retardation layer in the present invention may contain other compounds in addition to the urethane acrylate polymer and the rod-shaped compound. As such other compounds, those capable of imparting a desired function to the retardation layer can be appropriately selected and used depending on the use of the retardation film of the present invention. As said other compound used for this invention, a photoinitiator, a polymerization inhibitor, a leveling agent, a chiral agent, a silane coupling agent etc. can be mentioned, for example.
In addition, about these other compounds used for this invention, since what is generally used for an optical film can be used, detailed description here is abbreviate | omitted.

(4) Retardation layer The thickness of the retardation layer used for this invention will not be specifically limited if it exists in the range which can provide a desired optical characteristic to a retardation layer according to the kind of said rod-shaped compound. In particular, in the present invention, the thickness of the retardation layer is preferably in the range of 0.5 μm to 20 μm, more preferably in the range of 0.5 μm to 16 μm, particularly in the range of 0.5 μm to 12 μm. It is preferable to be within.

  In addition, the configuration of the retardation layer in the present invention is not limited to a configuration composed of a single layer, and may have a configuration in which a plurality of layers are stacked.

2. Next, the substrate used in the present invention will be described. The base material used in the present invention is made of a cycloolefin resin and has at least the property as an optically negative C plate. In the present invention, since the above-mentioned retardation layer contains a polymer of urethane acrylate, even if a substrate made of a cycloolefin resin is used, the retardation having excellent adhesion between the substrate and the retardation layer. A film can be obtained. In addition, since the cycloolefin-based resin has low water absorption, the retardation film of the present invention has optical characteristics even in a high-temperature, high-humidity atmosphere by using a base material made of such a cycloolefin-based resin. There is little fluctuation and it has excellent durability.
Hereinafter, such a base material will be described.

The substrate used in the present invention has at least the property as an optically negative C plate, but here, the above “having the property as an optically negative C plate” The retardation in the thickness direction of the substrate (Rth ¹ ) means 10 nm or more. Therefore, the substrate used in the present invention is not particularly limited as long as the thickness direction retardation (Rth ¹ ) is 10 nm or more, but the thickness direction retardation (Rth ¹ ) is 10 nm. It is preferably in the range of ˜250 nm, in particular, in the range of 25 nm to 200 nm, and particularly preferably in the range of 40 nm to 150 nm.

Here, the retardation in the thickness direction (Rth ¹ ) refers to the refractive index in the slow axis direction in the plane of the substrate as nx ¹ , the refractive index in the fast axis direction in the plane as ny ¹ , and the thickness direction. Is expressed as Rth ¹ = {(nx ¹ + ny ¹ ) / 2-nz ¹ } × d ¹ where nz ^{1 is} the refractive index and d ¹ is the thickness of the substrate.
The retardation (Rth ¹ ) in the thickness direction of the substrate can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  In addition, the thing which has the property as an optical negative C plate as a base material used for this invention is used for the said phase difference layer by using the base material which has such an optical property. This is because it becomes easy to arrange the rod-like compounds in a manner capable of imparting optical characteristics satisfying the relationship of nx ≧ ny> nz to the retardation film of the present invention.

  The base material used in the present invention is made of a cycloolefin resin, but the cycloolefin resin constituting the base material used in the present invention is a resin having a monomer unit made of a cyclic olefin (cycloolefin). If it is, it will not specifically limit. Examples of such a monomer comprising a cyclic olefin include norbornene and polycyclic norbornene monomers.

  In addition, as a cycloolefin type resin used for this invention, any of a cycloolefin polymer (COP) or a cycloolefin copolymer (COC) can be used conveniently.

  The cycloolefin resin used in the present invention may be a homopolymer of a monomer composed of the above cyclic olefin or a copolymer.

In addition, the cycloolefin resin used in the present invention preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and in particular, has a range of 0.1% to 0.7% by mass. preferable. This is because by using such a cycloolefin-based resin, it is possible to make the retardation film of the present invention less susceptible to changes in optical properties and dimensions due to water absorption.
Here, the saturated water absorption is obtained by immersing in 23 ° C. water for 1 week according to ASTM D570 and measuring the increased weight.

  Furthermore, the cycloolefin resin used in the present invention preferably has a glass transition point in the range of 100 ° C to 200 ° C, particularly preferably in the range of 100 ° C to 180 ° C, and in particular, 100 ° C. What is in the range of -150 degreeC is preferable. This is because, when the glass transition point is within the above range, the retardation film of the present invention can be made more excellent in heat resistance and processability.

  The transparency of the substrate used in the present invention may be arbitrarily determined according to the transparency required for the retardation film of the present invention, but it is usually preferable that the transmittance in the visible light region is 80% or more. 90% or more is more preferable. This is because if the transmittance is low, the selection range of the rod-like compound or the like may be narrowed. Here, the transmittance | permeability of a base material can be measured by JISK7361-1 (the test method of the total light transmittance of a plastic transparent material).

  The thickness of the base material used in the present invention is not particularly limited as long as it has necessary self-supporting properties depending on the use of the retardation film of the present invention. In particular, in the present invention, the range of 10 μm to 188 μm is preferable, the range of 20 μm to 125 μm is particularly preferable, and the range of 30 μm to 100 μm is particularly preferable. This is because if the thickness of the substrate is thinner than the above range, the self-supporting property required for the retardation film of the present invention may not be obtained. Further, if the thickness is thicker than the above range, for example, when cutting the retardation film of the present invention, processing waste may increase or the cutting blade may be worn quickly.

The configuration of the polarizing plate protective film in the present invention is not limited to a configuration composed of a single layer, and may have a configuration in which a plurality of layers are laminated.
Moreover, when it has the structure by which the several layer was laminated | stacked, the layer of the same composition may be laminated | stacked, and the several layer which has a different composition may be laminated | stacked.

Moreover, the base material used in the present invention may be subjected to a stretching treatment. By using a base material that has been subjected to stretching treatment, there is an advantage that the adhesion between the base material and the retardation layer can be further improved.
Here, the stretching treatment is not particularly limited, and may be arbitrarily determined according to the material constituting the substrate. Examples of such a stretching process include a uniaxial stretching process and a biaxial stretching process.
In addition, when using the substrate subjected to the above-described uniaxial stretching treatment as the base material used in the present invention, the retardation film of the present invention may be imparted with optical characteristics satisfying the relationship of nx>ny> nz. It becomes easy.

  Specific examples of the substrate used in the present invention include, for example, Topas manufactured by Ticona, Arton manufactured by JSR, ZEONOR manufactured by Nippon Zeon, ZEONEX manufactured by Nippon Zeon, Apel manufactured by Mitsui Chemicals, and these substrates. The thing etc. which performed the extending | stretching process can be mentioned.

3. Other Configurations The retardation film of the present invention may have other configurations in addition to the retardation layer and the substrate. As such another configuration, a configuration having an arbitrary function can be used according to the use of the retardation film of the present invention. Among these, examples of the other configuration preferably used in the present invention include an antireflection layer, an ultraviolet absorption layer, an infrared absorption layer and an antistatic layer.
Hereinafter, these other configurations will be described in order.

  As the antireflection layer, for example, a transparent substrate film formed with a low refractive index layer made of a material having a lower refractive index than the transparent substrate, or the transparent substrate film A high refractive index layer made of a material having a higher refractive index than that of the material and a low refractive index layer made of a material having a lower refractive index than that of the transparent substrate, which are alternately laminated in this order one or more layers. Etc. These high-refractive index layers and low-refractive index layers are evacuated so that the optical thickness represented by the product of the geometric thickness and the refractive index of the layer is 1/4 of the wavelength of light to be prevented from being reflected. It is formed by vapor deposition or coating. As the constituent material of the high refractive index layer, titanium oxide, zinc sulfide and the like are used, and as the constituent material of the low refractive index layer, magnesium fluoride, cryolite and the like are used.

  Examples of the ultraviolet absorbing layer include a film formed by adding an ultraviolet absorber made of a benzotriazole-based compound, a benzophenone-based compound, a salicylate-based compound, or the like in a film such as a polyester resin or an acrylic resin. It is done.

  Moreover, as an infrared absorption layer used for this invention, what formed the infrared absorption layer by coating etc. on film base materials, such as a polyester resin, is mentioned, for example. As the infrared absorbing layer, for example, a film formed by adding an infrared absorber made of a diimmonium compound, a phthalocyanine compound or the like into a binder resin made of an acrylic resin, a polyester resin or the like is used.

4). Retardation Film The retardation film of the present invention has optical characteristics in which a relationship of nx ≧ ny> nz is established among the nx, ny and nz. As an aspect in which the relationship of nx ≧ ny> nz is established among the nx, ny, and nz, there are an aspect in which the relationship of nx>ny> nz is established and an aspect in which the relationship of nx = ny> nz is established. However, the retardation film of the present invention may have optical characteristics of any of these aspects.

  In addition, the retardation film of the present invention has a configuration in which the retardation layer is directly formed on the base material. As an aspect in which the base material and the retardation layer are laminated, The base material and the retardation layer may be laminated as independent layers, or there is no clear interface between the base material and the retardation layer, and the rod-shaped compound is between them. It may be an aspect in which the content of is laminated so as to change continuously or intermittently.

  The thickness of the retardation film of the present invention is not particularly limited as long as it is within a range in which desired optical properties can be expressed, but is usually preferably within a range of 20 μm to 150 μm, and particularly within a range of 25 μm to 130 μm. It is preferable that it is in a range, and it is preferable to exist in the range of 30 micrometers-110 micrometers especially.

  The retardation film of the present invention preferably has a haze value measured according to JIS K7105 in the range of 0% to 2%, particularly preferably in the range of 0% to 1.5%. In particular, it is preferably in the range of 0% to 1%.

  Furthermore, the retardation (Rth) in the thickness direction of the retardation film of the present invention may be appropriately selected according to the application of the present invention, and is not particularly limited. In particular, in the present invention, the retardation in the thickness direction (Rth) is preferably in the range of 60 nm to 450 nm, particularly preferably in the range of 70 nm to 400 nm, and more preferably in the range of 80 nm to 350 nm. Since the retardation (Rth) in the thickness direction is within the above range, the retardation film of the present invention can be made suitable for improving the viewing angle characteristics of a VA (Vertical Alignment) type liquid crystal display device. is there.

Here, the retardation in the thickness direction (Rth) is represented by Rth = {(nx + ny) / 2−nz} × d by the nx, ny and nz and the thickness d of the retardation film. is there.
The retardation in the thickness direction (Rth) can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  Also, the in-plane retardation (Re) of the retardation film of the present invention may be appropriately selected according to the use of the retardation film of the present invention, and is not particularly limited. In particular, in the present invention, the in-plane retardation (Re) is preferably in the range of 20 nm to 150 nm, particularly preferably in the range of 30 nm to 130 nm, and more preferably in the range of 40 nm to 110 nm. When the in-plane retardation (Re) is within the above range, the retardation film of the present invention is used as a retardation film suitable for improving the viewing angle characteristics of a VA (Vertical Alignment) liquid crystal display device. Because it can.

  The in-plane retardation (Re) value may have wavelength dependency. For example, the long wavelength side may have a larger value than the short wavelength side, and the short wavelength side may have a larger value than the long wavelength side. This is because the viewing angle characteristics of the liquid crystal display device can be improved in the entire visible light region by having the wavelength dependency of the in-plane retardation (Re) value.

Here, the in-plane retardation (Re) is expressed by Re = (nx−ny) × d by the above nx, ny, and d.
The in-plane retardation (Re) can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

5. Use of retardation film The use of the retardation film of the present invention is not particularly limited. For example, an optical compensator (for example, a viewing angle compensator), an elliptically polarizing plate, and a brightness enhancement plate used in a liquid crystal display device. Etc. Among them, the retardation film of the present invention can be suitably used as an optical compensator for improving the viewing angle dependency of a liquid crystal display device, and most preferably used as an optical compensator for a VA liquid crystal display device. be able to.

  Moreover, the retardation film of this invention can be used also for the use as a polarizing film by bonding with a polarizing layer. A polarizing film is usually formed by forming a polarizing layer and protective layers on both surfaces thereof. In the present invention, for example, by forming the protective film on one side as the above-described retardation film, for example, a liquid crystal display. It can be set as the polarizing film which has the optical compensation function which improves the viewing angle characteristic of an apparatus.

  Although it does not specifically limit as said polarizing layer, For example, an iodine type polarizing layer, a dye type polarizing layer using a dichroic dye, a polyene type polarizing layer, etc. can be used. The iodine-based polarizing layer and the dye-based polarizing layer are generally produced using polyvinyl alcohol.

B. Next, a method for producing the retardation film of the present invention will be described. The method for producing a retardation film of the present invention comprises a retardation layer comprising a cycloolefin resin and having at least an optically negative C plate property, and a rod-like compound and urethane acrylate dissolved in a solvent. By forming the coating liquid for forming directly on the substrate, it is formed by the layer forming step for forming the phase difference layer and the layer forming step for forming the phase difference layer. A temperature maintaining step for keeping the phase difference layer forming layer at a temperature of 35 ° C. or lower, a urethane polymerization step for polymerizing the urethane acrylate contained in the phase difference layer forming layer kept warm in the temperature maintaining step, A retardation layer forming step including a drying step of drying the phase difference layer forming layer.

Such a method for producing a retardation film of the present invention will be described with reference to the drawings. FIG. 2 is a schematic view showing an example of a method for producing a retardation film of the present invention. As illustrated in FIG. 2, the method for producing a retardation film of the present invention uses a base material 1 made of a cycloolefin resin and having at least an optically negative C plate property (FIG. 2A). ), Forming a retardation layer forming layer 2 ′ on the substrate 1 by directly coating the retardation layer forming coating solution on the substrate 1. 2 (b)), a heat retaining step for keeping the retardation layer forming layer 2 ′ formed by the retardation layer forming layer forming step at a temperature of 35 ° C. or less (FIG. 2 (c)), and By irradiating ultraviolet rays to the retardation layer forming layer 2 ′ kept warm in the heat retaining step, the urethane polymerization step for polymerizing the urethane acrylate (FIG. 2 (d)), the retardation layer forming layer 2 ′ is And a retardation layer forming step including a drying step (FIG. 2E). The retardation film 10 in which the retardation layer 2 is directly formed on the substrate 1 is manufactured.
In such an example, the method for producing a retardation film of the present invention is such that the retardation layer forming coating solution used in the retardation layer forming layer forming step is obtained by dissolving a rod-shaped compound and urethane acrylate in a solvent. It is characterized by being.

According to the present invention, when the retardation layer forming coating liquid contains urethane acrylate, the retardation layer formed on the substrate by the retardation layer forming step and the adhesion between the substrate and the substrate. Can be improved. For this reason, according to this invention, the phase difference film excellent in the adhesiveness of the said base material and the said phase difference layer can be manufactured.
In addition, according to the present invention, since the base material made of cycloolefin resin is used, the base material can be prevented from hygroscopic expansion in a high temperature and high humidity atmosphere. For this reason, according to the present invention, it is possible to produce a retardation film excellent in temporal stability of optical characteristics even in a high temperature and high humidity atmosphere.
For this reason, according to the present invention, the retardation film does not use an alignment layer, has excellent adhesion between the substrate and the retardation layer, and the optical characteristics over time even in a high-temperature and high-humidity atmosphere. A retardation film excellent in stability can be produced.

The method for producing a retardation film of the present invention includes at least the retardation layer forming step.
Hereafter, each process used for this invention is demonstrated in order.

1. Retardation Layer Formation Step First, the retardation layer formation step used in the present invention will be described. This step includes at least the layer forming step for forming the retardation layer, the heat retaining step, the urethane polymerization step, and the drying step.
Hereinafter, each step included in this step will be described in detail.

(1) Retardation layer forming layer forming step First, the retardation layer forming layer forming step will be described. In this step, a retardation layer forming coating solution in which a rod-like compound and a urethane acrylate are dissolved in a solvent is formed using a base material having a property as an optically negative C plate, which is made of a cycloolefin resin. It is a retardation layer forming layer forming step of forming a retardation layer forming layer by coating directly on the substrate.
The method for producing a retardation film of the present invention includes a base material made of a cycloolefin resin by using urethane acrylate in the retardation layer forming coating liquid used in this step. A retardation film having excellent adhesion with the retardation layer can be produced. In addition, the method for producing a retardation film of the present invention is excellent in temporal stability of optical characteristics even in a high-temperature and high-humidity atmosphere by using a substrate made of cycloolefin resin as a base material used in this step. A retardation film can be produced.
Hereinafter, the layer forming process for forming the retardation layer will be described.

  In addition, about the base material used for this process, since it is the same as that of what was demonstrated in the term of the said "A. retardation film", description here is abbreviate | omitted.

The retardation layer forming coating solution used in this step is a solution in which a rod-like compound and urethane acrylate are dissolved in a solvent.
Here, the rod-like compound and the urethane acrylate used in the coating solution for forming the retardation layer are the same as those described in the section “A. Retardation film”, and thus the description thereof is omitted here. .

  The solvent used in the retardation layer forming coating solution is not particularly limited as long as it can dissolve the rod-shaped compound and the urethane acrylate at a desired concentration. Examples of such solvents include hydrocarbon solvents such as benzene and hexane, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane, chloroform, dichloromethane, and the like. Alkyl halide solvents, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, amide solvents such as N, N-dimethylformamide, sulfoxide solvents such as dimethyl sulfoxide, cyclohexane, etc. Examples thereof include alcohol solvents such as methanol solvents, ethanol, and propanol. In the present invention, among these solvents, a ketone solvent is preferably used, and cyclohexane is preferably used.

  Moreover, the solvent used for this process may be one type, or two or more types.

  The content of the rod-shaped compound in the retardation layer forming coating liquid is as follows. According to the coating method for applying the retardation layer forming coating liquid on a substrate, etc. If it is in the range which can make the viscosity of a coating liquid into a desired value, it will not be limited especially. In particular, in the present invention, the content of the rod-shaped compound is preferably in the range of 10% by mass to 40% by mass, particularly in the range of 10% by mass to 35% by mass in the retardation layer forming coating solution. It is preferable that it is in the range of 10 mass%-30 mass% especially.

  Moreover, as content of the said urethane acrylate in the said coating liquid for phase difference layer formation, in the phase difference film formed by this invention, the adhesiveness of a phase difference layer and a base material can be in a desired range. The amount is not particularly limited. Especially in this invention, it is preferable that content of the said urethane acrylate exists in the range of 5 mass%-40 mass% in solid content of the said coating liquid for phase difference layer formation, Especially 10 mass%- It is preferably in the range of 30% by mass, and more preferably in the range of 15% by mass to 25% by mass.

  The retardation layer forming coating solution used in this step preferably contains a photopolymerization initiator. It is because it becomes easy to superpose | polymerize the said urethane acrylate in the urethane polymerization process mentioned later by including a photoinitiator in the said coating liquid for phase difference layer formation.

  Examples of the photopolymerization initiator used in this step include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino acetophenone, 4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpro Piophenone, p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethyl ketal, benzylmethoxyethyla Tar, benzoin methyl ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberon, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis ( p-azidobenzylidene) cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione 2- (o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o- Nzoyl) oxime, Michler's ketone, 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone , Naphthalene sulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, Adeca N1717, carbon tetrabromide And a combination of a photoreductive dye such as tribromophenylsulfone, benzoin peroxide, eosin, and methylene blue with a reducing agent such as ascorbic acid and triethanolamine. In this step, these photopolymerization initiators can be used alone or in combination of two or more.

  Furthermore, when using the said photoinitiator, a photoinitiator adjuvant can be used together. Examples of such photopolymerization initiation assistants include tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as ethyl 2-dimethylaminoethylbenzoate and ethyl 4-dimethylamidebenzoate. Yes, but not limited to these.

  Moreover, the compound as shown below can be added to the phase difference layer forming coating solution used in this step within a range not impairing the object of the present invention. Examples of compounds that can be added include polyester (meth) acrylate obtained by reacting (meth) acrylic acid with a polyester prepolymer obtained by condensing polyhydric alcohol and monobasic acid or polybasic acid; A polyurethane (meth) acrylate obtained by reacting a compound having two isocyanate groups with each other and then reacting the reaction product with (meth) acrylic acid; bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak Type epoxy resins, polycarboxylic acid polyglycidyl esters, polyol polyglycidyl ethers, aliphatic or cycloaliphatic epoxy resins, amino group epoxy resins, triphenolmethane type epoxy resins, dihydroxybenzene type epoxy resins and the like (meta Acu Photopolymerizable compounds such as epoxy (meth) acrylate obtained by reacting Le acid; photopolymerizable liquid crystal compound having an acryl group or methacryl group and the like. The amount of these compounds added to the retardation layer forming coating solution can be determined within a range where the object of the present invention is not impaired. By adding the above compound, the mechanical strength of the retardation layer formed by this step is improved, and the stability may be improved.

  This step is a step of forming the retardation layer forming coating solution on the substrate by directly coating the retardation layer forming coating solution on the substrate. The coating method for coating the layer forming coating liquid on the substrate is not particularly limited as long as it can form a retardation layer forming layer having a desired flatness with a uniform thickness. Absent. Specifically, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, spin coating method, roll coating method, printing method, dip pulling method, curtain coating method, die coating Method, casting method, bar coating method, extrusion coating method, E-type coating method and the like.

  The “direct coating” in the present invention means that the retardation layer forming coating solution is applied so that the retardation layer forming coating solution is in contact with the substrate. Is.

  Further, the thickness of the coating film of the retardation layer forming coating solution is not particularly limited as long as the desired flatness can be achieved, but is usually within a range of 0.1 μm to 50 μm. In particular, the range of 0.5 μm to 30 μm is preferable, and the range of 0.5 μm to 10 μm is particularly preferable. If the thickness of the coating film of the retardation layer forming coating liquid is thinner than the above range, the planarity of the retardation layer forming layer may be impaired, and if the thickness is thicker than the above range, in the drying step described later. This is because there is a possibility that the drying load of the solvent increases and the productivity decreases.

(2) Thermal insulation process Next, the said thermal insulation process is demonstrated. This step is a step of keeping the phase difference layer forming layer formed by the phase difference layer forming layer forming step at a temperature of 35 ° C. or lower.
By including this step in the retardation layer forming step, the rod-like compounds contained in the retardation layer forming layer can be randomly arranged in the plane, and therefore the method for producing a retardation film of the present invention Thus, a retardation film having a small haze and a desired retardation can be produced.

  In this step, the temperature for keeping the retardation layer forming layer is not particularly limited as long as it is 35 ° C. or lower. Especially, it is preferable that the heat retention temperature in this process is in the range of 15 ° C to 35 ° C, in particular, in the range of 25 ° C to 35 ° C, and further in the range of 30 ° C to 35 ° C. It is preferable. It is because the haze of the phase film manufactured by this invention will become large when heat retention temperature is higher than the said range.

  Further, in this step, the heat retention time for keeping the phase difference layer forming layer at the heat retention temperature is particularly limited as long as the haze of the phase difference film formed according to the present invention is within a predetermined range. It is not a thing but it determines suitably according to the said heat retention temperature etc. In particular, the heat retention time in this step is preferably in the range of 0.5 minutes to 10 minutes, particularly preferably in the range of 1 minute to 7 minutes, and more preferably in the range of 2 minutes to 4 minutes. It is preferable that

  In this step, the method for keeping the retardation layer forming layer at the temperature is not particularly limited as long as it can be kept at the desired temperature.

(3) Urethane polymerization step Next, the urethane polymerization step will be described. This step is a step of polymerizing the urethane acrylate contained in the phase difference layer forming layer that has been kept warm in the above warming step.

  In this step, the method for polymerizing the urethane acrylate is not particularly limited as long as it can induce a polymerization reaction of the (meth) acrylate group of the urethane acrylate. A method of irradiating active layer with active radiation is used.

  The actinic radiation is not particularly limited as long as it is a radiation capable of inducing a polymerization reaction of the (meth) acrylate group. However, ultraviolet light or visible light may be used from the viewpoint of easiness of the irradiation apparatus. Among them, it is preferable to use irradiation light having a wavelength of 150 nm to 500 nm, preferably 250 nm to 450 nm, and more preferably 300 nm to 400 nm.

  Examples of light sources that can irradiate actinic radiation in the above wavelength range include low-pressure mercury lamps (sterilization lamps, fluorescent chemical lamps, black lights), high-pressure discharge lamps (high-pressure mercury lamps, metal halide lamps), short arc discharge lamps (ultra-high pressure). Examples thereof include a mercury lamp, a xenon lamp, and a mercury xenon lamp. Among these, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, and the like can be given. Irradiation intensity can be appropriately adjusted according to the content of the photopolymerization initiator.

  In addition, when using the rod-shaped compound which has a polymerizable functional group as a rod-shaped compound used for the said phase difference layer formation layer formation process, the said rod-shaped compound and the said urethane acrylate may be polymerized simultaneously in this process.

(4) Drying process Next, the drying process will be described. This step is a step of drying the retardation layer forming layer.

  In this step, the method for drying the retardation layer forming layer is not particularly limited as long as the amount of the solvent contained in the retardation layer can be within a desired range. As such a drying method, a commonly used drying method such as a heat drying method, a reduced pressure drying method, a gap drying method, or the like can be used. Further, the drying method in this step is not limited to a single method, and a plurality of drying methods may be employed, for example, by changing the drying method sequentially according to the amount of remaining solvent.

2. Other Steps The method for producing a retardation film of the present invention includes at least the retardation layer forming step, but may include other steps as necessary. The other process used in the present invention is not particularly limited as long as it can impart a desired function to the retardation film produced according to the present invention.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically by showing examples.

(1) Example 1
A photopolymerizable liquid crystal compound represented by the following formula (I) as a rod-shaped compound is dissolved in cyclohexanone by 20% by mass, and urethane acrylate (manufactured by Nippon Synthetic Chemical Co., Ltd., trade name: UV7610B, molecular weight: 14000 Mw) is used as the photopolymerizable compound. The ink added in an amount of 5% by mass was applied to a COP (cycloolefin polymer) film (manufactured by JSR Corporation, trade name: ARTON) by bar coating.

  Subsequently, after heating a coating film for 2 minutes at 23 degreeC, the said photopolymerizable liquid crystal compound was fixed by irradiating a coating surface with an ultraviolet-ray. Further, the film was heated at 80 ° C. for 4 minutes to remove the solvent, thereby producing a retardation film.

(2) Example 2
A retardation film was produced in the same manner as in Example 1 except that the amount of urethane acrylate added was 10% by mass with respect to the photopolymerizable compound.

(3) Example 3
A retardation film was produced in the same manner as in Example 1 except that the amount of urethane acrylate added was 15% by mass with respect to the photopolymerizable compound.

(4) Example 4
A retardation film was produced in the same manner as in Example 1 except that the amount of urethane acrylate added was 20% by mass with respect to the photopolymerizable compound.

(5) Example 5
A retardation film was produced in the same manner as in Example 3 except that Nippon Synthetic Chemical Co., Ltd., trade name: UV7640B (molecular weight: 1500 Mw) was used as the urethane acrylate.

(6) Example 6
A retardation film was produced in the same manner as in Example 4 except that Nippon Synthetic Chemical Co., Ltd., trade name: UV7640B (molecular weight: 1500 Mw) was used as the urethane acrylate.

(7) Comparative Example 1
A retardation film was produced in the same manner as in Example 4 except that nonanediol acrylate (trade name: NK Ester A-NOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.) was used instead of urethane acrylate.

(8) Comparative Example 2
A retardation film was produced in the same manner as in Example 4 except that pentaerythritol triacrylate (trade name: KAYARAD PET-30 manufactured by Nippon Kayaku Co., Ltd.) was used instead of urethane acrylate.

(9) Comparative Example 3
A retardation film was produced in the same manner as in Example 4 except that hexanediol diacrylate (trade name: KS-HDDA manufactured by Nippon Kayaku Co., Ltd.) was used instead of urethane acrylate.

(Evaluation)
A peel test was performed on the retardation films prepared in the above Examples and Comparative Examples. As a peeling test, a 1 mm square cut is put in a grid pattern in the prepared sample, and an adhesive tape (Nichiban Co., cello tape (registered trademark)) is applied to the retardation layer, and then the tape is peeled off and visually observed. did. And the adhesion degree was evaluated based on the following formula from the observation result. The results are shown in Table 1.
Adhesion degree (%) = (part which was not peeled / area where tape was applied) × 100

  As shown in Table 1, as the amount of urethane acrylate added to the rod-shaped compound increased, the degree of adhesion (%) increased, and it was confirmed that 100% adhesion could be achieved by adding 20% by mass. In addition, it was shown that the use of urethane acrylate having a large molecular weight (Mw) can achieve a high degree of adhesion (%) with a small addition amount. In addition, when using a polymer other than urethane acrylate, the degree of adhesion was 0% regardless of the amount added.

It is the schematic which shows an example of the retardation film of this invention. It is the schematic which shows an example of the manufacturing method of the retardation film of this invention. It is the schematic which shows an example of a common liquid crystal display device. It is the schematic which shows an example of the liquid crystal display device in which the phase difference film was used. It is the schematic which shows an example of a general retardation film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Phase difference layer 2 '... Phase difference layer formation layer 10 ... Phase difference film 21 ... Base material 22 ... Orientation layer 23 ... Phase difference layer 101 ... Liquid crystal cell 102A, 102B ... Polarizing plate 103 ... Phase difference the film

Claims (4)

A substrate made of cycloolefin resin, having at least an optically negative C plate property, and a retardation layer formed directly on the substrate and containing a rod-shaped compound, and in the in-plane direction, Retardation film in which the relationship of nx ≧ ny> nz is established between nx, ny, and nz, where nx, ny are the refractive indexes in arbitrary X and Y directions orthogonal to each other, and nz is the refractive index in the thickness direction. Because
A retardation film comprising a urethane acrylate polymer in the retardation layer.   The retardation film according to claim 1, wherein the urethane acrylate has a weight average molecular weight (Mw) in a range of 1000 to 40000.   3. The retardation film according to claim 1, wherein the content of the urethane acrylate polymer in the retardation layer is in the range of 5% by mass to 40% by mass. Using a base material made of a cycloolefin resin and having at least an optically negative C-plate property,
A retardation layer for forming a retardation layer forming layer on the substrate by directly coating a coating solution for forming a retardation layer in which a rod-shaped compound and urethane acrylate are dissolved in a solvent on the substrate. A forming layer forming step;
A heat retaining step for retaining the phase difference layer forming layer formed by the phase difference layer forming layer forming step at a temperature of 35 ° C. or less;
A urethane polymerization step for polymerizing urethane acrylate contained in the phase difference layer forming layer kept warm in the heat retention step;
A method for producing a retardation film comprising a retardation layer forming step including a drying step of causing the retardation layer forming layer to form.

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