JP2008009328A - Retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film in which a transparent substrate comprising a cycloolefin-based resin is used, and which has properties as a positive C plate and excels in adhesion between a retardation layer and the transparent substrate. <P>SOLUTION: The retardation film comprises the transparent substrate comprising the cycloolefin-based resin, an adhesive alignment layer formed on the transparent substrate, containing a polymer of a polymerizable monomer and having alignment control power to perform homeotropic alignment of a liquid crystal material, and the retardation layer formed on the adhesive alignment layer, containing a liquid crystal material and satisfying the relationship of nx=ny<zy among refractive indexes nx and ny in an arbitrary x direction and y direction perpendicular to each other in an in-plane direction and a refractive index nz in a thickness direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retardation film used for a liquid crystal display device and the like, and more particularly to a retardation film using a transparent substrate made of a cycloolefin resin.

  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 100 having an incident side polarizing plate 102 </ b> A, an output side polarizing plate 102 </ b> B, and a liquid crystal cell 104 can be exemplified. The polarizing plates 102A and 102B are configured to selectively transmit only linearly polarized light (schematically illustrated by arrows in the figure) having a vibration surface in a predetermined vibration direction. They are arranged to face each other in a crossed Nicol state so as to have a right angle relationship with each other. The liquid crystal cell 104 includes a large number of cells corresponding to the pixels, and is disposed between the polarizing plates 102A and 102B.

  Such a liquid crystal display device is known to use various driving methods depending on the arrangement form of the liquid crystal material used in the liquid crystal cell. The main liquid crystal display devices that are widely used today are TN, It is classified into STN, MVA, IPS and OCB. In particular, today, those having the MVA and IPS drive systems 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 as a specific problem. This problem of viewing angle dependency is a problem in which the color and contrast of a visually recognized image change between 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 as the liquid crystal display device has recently been enlarged.

In order to improve such a problem of viewing angle dependency, various techniques have been developed so far, and a representative method is a method using a retardation film. In the method using such a retardation film, the retardation film 30 having predetermined optical characteristics is disposed between the liquid crystal cell 104 and the polarizing plate 102B as shown in FIG. It is a way to improve the problem. Since this method can improve the viewing angle dependency only by incorporating the retardation film 30 in 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.
Here, as the retardation film, for example, a film having a structure in which a retardation layer containing a regularly arranged liquid crystal material is formed on a transparent substrate or a film made of a stretched film is generally known. It has been.
Among them, in an IPS (In-Plane Switching) type liquid crystal display device, a retardation film having a retardation layer having properties as a positive C plate is obtained by homeotropic alignment of a liquid crystal material. .

  Conventionally, a film made of cellulose triacetate has been widely used as a transparent substrate constituting such a retardation film. Cellulose triacetate is a material with low birefringence and excellent optical isotropy, so it is easy to design optical properties, and because it uses cellulose, which is a natural material, as a raw material, it is industrially inexpensive. The main reason is that it is highly useful in that it is available in However, the retardation film used in the liquid crystal display device as described above is required to have a desired birefringence according to the display method of various liquid crystal display devices, and the cellulose triacetate has heat resistance. There is a problem that it is low and has high water absorption, so that it is easily deformed by heat and moisture. There is also a problem that the birefringence variation due to moisture absorption is large.

  In order to solve such a problem, Patent Document 1 and Patent Document 2 disclose a retardation film using a cycloolefin resin instead of the cellulose triacetate. The cycloolefin-based resin has an advantage that the glass transition point and the moisture absorption rate can be controlled within a preferable range by molecular design, and good heat resistance and appropriate water absorption can be realized. Therefore, by using a cycloolefin resin, it is possible to obtain a retardation film with little optical property change and dimensional change due to water absorption.

Taking advantage of such a cycloolefin resin, Patent Document 3 discloses that a retardation layer in which a liquid crystal material is homeotropically aligned is formed on a substrate made of a cycloolefin resin, and is suitable for an IPS liquid crystal display device. A retardation film having properties as a positive C plate used in the above is disclosed. Such a retardation film has an advantage that, by using a transparent substrate made of a cycloolefin-based resin, moisture absorption deformation or the like that has been a problem when a film made of triacetyl cellulose has been conventionally used can be improved. .
However, since the cycloolefin-based resin generally has low adhesion to the liquid crystal material used for the retardation layer, the retardation film described in Patent Document 3 includes a retardation layer and a transparent substrate. There was a problem that the adhesion of the material was low and the practicality was poor.
In this regard, Patent Document 4 discloses the idea of using a pressure-sensitive adhesive made of an acrylic resin or the like to bond a homeotropically aligned retardation layer and a transparent substrate made of a cycloolefin-based resin, Even when such a pressure-sensitive adhesive is used, it has been difficult to achieve sufficient adhesion between the retardation layer and the transparent substrate.

  For these reasons, a retardation film using a cycloolefin-based resin has the above-described advantages, but has a problem of lack of practicality.

Japanese Patent Laying-Open No. 2005-8698 Japanese Patent Application Laid-Open No. 2004-309979 JP 2002-174725 A JP 2003-121853 A

  The present invention has been made in view of such problems, and is a retardation film having a property as a positive C plate using a transparent substrate made of a cycloolefin-based resin, including a retardation layer and The main purpose is to provide a retardation film having excellent adhesion to a transparent substrate.

  In order to solve the above problems, the present invention provides a transparent substrate made of a cycloolefin resin, a polymer formed of a polymerizable monomer formed so as to be in contact with the transparent substrate, and further homeotropic alignment of a liquid crystal material. An alignment layer having an alignment regulating force to be formed, and a refractive index nx and ny in any x direction and y direction that are formed on the adhesion alignment layer and contain a liquid crystal material and are orthogonal to each other in the in-plane direction. A retardation film having a relationship of nx = ny <nz with a refractive index nz in the thickness direction, wherein the polymerizable monomer has the following formulas (I), (II ), (III), (IV), and (V) having at least one polymerizable functional group selected from the group consisting of the polymerizable monomer, Heavy A phase difference characterized by having a value (N / M) divided by the number M of elements other than carbon and hydrogen constituting the functional monomer (hereinafter sometimes simply referred to as “carbon content ratio”) of 3 or more. Provide film.

Here, in the above formula, R ¹ , R ² and R ³ represent a methyl group or hydrogen. R ⁴ represents hydrogen, a methyl group or an ethyl group.

According to the present invention, at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V) is added to the adhesive alignment layer. And having a carbon content ratio of 3 or more, and containing a polymer of a polymerizable monomer, the adhesive alignment layer, the transparent substrate made of the cycloolefin resin, and a retardation layer containing a liquid crystal material Adhesion with can be improved. For this reason, according to the present invention, a retardation film using a transparent substrate made of a cycloolefin resin can be obtained, and a retardation film excellent in adhesion between the retardation layer and the transparent substrate can be obtained. .
In addition, a relationship of nx = ny <nz is established between the refractive indexes nx and ny in any x direction and y direction in which the retardation layer is orthogonal to each other in the in-plane direction, and the refractive index nz in the thickness direction. By being a thing, the property as a positive C plate can be provided to the retardation film of this invention.
Therefore, according to the present invention, there is provided a retardation film having properties as a positive C plate using a transparent substrate made of a cycloolefin resin, and the adhesion between the retardation layer and the transparent substrate. An excellent retardation film can be obtained.

  In the present invention, it is preferable that a surfactant is contained in the adhesive alignment layer. This is because it is possible to impart an alignment regulating force for homeotropic alignment of the liquid crystal material to the adhesive alignment layer without using a separate vertical alignment layer.

  In order to solve the above problems, the present invention provides a transparent substrate made of a cycloolefin resin, an adhesion functional layer formed on and in contact with the transparent substrate, and containing a polymer of a polymerizable monomer, and the adhesion A liquid crystal material that is formed on the functional layer and has a homeotropic alignment, and further includes a refractive index nx and ny in any x direction and y direction orthogonal to each other in the in-plane direction, and a refractive index nz in the thickness direction. A retardation film having a relationship of nx = ny <nz, wherein the polymerizable monomer is represented by the following formulas (I), (II), (III), (IV): And at least one polymerizable functional group selected from the group consisting of (V), and the number N of carbon atoms constituting the polymerizable monomer is the same as the carbon number constituting the polymerizable monomer and To provide a phase difference film, wherein the value obtained by dividing the number of elements M other than hydrogen (N / M) is 3 or more.

Here, in the above formula, R ¹ , R ² and R ³ represent a methyl group or hydrogen. R ⁴ represents hydrogen, a methyl group, or an ethyl group.

According to the present invention, the adhesion functional layer has at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V). In addition, by including a polymer of a polymerizable monomer having a carbon content ratio of 3 or more, it is possible to improve the adhesion between the adhesion functional layer and the transparent substrate made of the cycloolefin resin. For this reason, according to the present invention, a retardation film using a transparent substrate made of a cycloolefin resin can be obtained, and a retardation film excellent in adhesion between the retardation layer and the transparent substrate can be obtained. .
In addition, a relationship of nx = ny <nz is established between the refractive indexes nx and ny in any x direction and y direction in which the retardation layer is orthogonal to each other in the in-plane direction, and the refractive index nz in the thickness direction. By being a thing, the property as a positive C plate can be provided to the retardation film of this invention.
Therefore, according to the present invention, there is provided a retardation film having properties as a positive C plate using a transparent substrate made of a cycloolefin resin, and the adhesion between the retardation layer and the transparent substrate. An excellent retardation film can be obtained.

  The present invention is a retardation film having a property as a positive C plate using a transparent substrate made of a cycloolefin resin, and a retardation film excellent in adhesion between the retardation layer and the transparent substrate. There is an effect that it can be obtained.

  Hereinafter, the retardation film of the present invention will be described. In addition, the retardation film of this invention can be classified into two aspects by the difference in the structure. Therefore, hereinafter, the retardation film of the present invention will be described separately for each embodiment.

A. First, the retardation film of the first aspect of the present invention will be described. The retardation film of this embodiment is formed so as to be in contact with a transparent substrate made of a cycloolefin-based resin and the transparent substrate, contains a polymer of a polymerizable monomer, and further aligns the liquid crystal material in a homeotropic alignment. An adhesive alignment layer having a refractive index nx and ny in any x direction and y direction that are formed on the adhesive alignment layer and contain a liquid crystal material and are orthogonal to each other in the in-plane direction; A retardation layer satisfying a relationship of nx = ny <nz with the refractive index nz, wherein the polymerizable monomer has the formula (I), (II), (III), It has at least one polymerizable functional group selected from the group consisting of (IV) and (V), and has a carbon content ratio of 3 or more.

Such a retardation film of this embodiment will be described with reference to the drawings. FIG. 1 is a schematic view showing an example of the retardation film of this embodiment. As illustrated in FIG. 1, a retardation film 10 of this embodiment includes a transparent substrate 1 made of a cycloolefin-based resin, and an adhesive property that is formed on the transparent substrate 1 and has an alignment regulating force for homeotropic alignment of a liquid crystal material. It has an alignment layer 2 and a retardation layer 3 formed on the adhesive alignment layer 2 and containing a liquid crystal material.
In such an example, the retardation film 10 of this embodiment is selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V) for the adhesive orientation layer 2. And a polymer of a polymerizable monomer having at least one polymerizable functional group and having a carbon content ratio of 3 or more, and the retardation layers 3 are mutually in the in-plane direction. A relationship of nx = ny <nz is established between the refractive indexes nx and ny in arbitrary x and y directions orthogonal to each other and the refractive index nz in the thickness direction.
In addition, in the retardation film 10 of this embodiment, since the adhesive alignment layer 2 has an alignment regulating force for homeotropic alignment of the liquid crystal material, the phase difference is caused by the action of the adhesive alignment layer 2. The liquid crystal material contained in the layer 3 usually has homeotropic alignment.

According to this aspect, at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V) is added to the adhesive alignment layer. And having a carbon content ratio of 3 or more to improve the adhesion between the adhesive orientation layer and the transparent substrate made of the cycloolefin resin. it can. For this reason, according to this aspect, it is a retardation film using a transparent substrate made of a cycloolefin resin, and a retardation film having excellent adhesion between the retardation layer and the transparent substrate can be obtained. .
Here, the adhesive property between the transparent substrate and the adhesive alignment layer can be improved by containing a polymer of the polymerizable monomer having the structure in the adhesive alignment layer for the following reason. It is considered based.
In other words, cycloolefin resins have a problem of poor adhesion to liquid crystal materials generally used for retardation films and the like, but this is widely used for transparent substrates for retardation films. It is thought that the main cause was that the molecular polarity was lower than that of cellulose triacetate.
In this respect, in the retardation film of this embodiment, the polymerizable monomer constituting the polymer of the polymerizable monomer contained in the adhesive alignment layer has the above formulas (I), (II), (III), (IV And at least one polymerizable functional group selected from the group consisting of (V) and having a carbon content of 3 or more, the polarity of the polymerizable monomer is The polarity of the cycloolefin resin can be approximated. For this reason, since the polymer of the polymerizable monomer used in this embodiment has excellent adhesion to the cycloolefin resin, it improves the adhesion between the adhesion alignment layer and the transparent substrate. It is thought that you can.

In addition, a relationship of nx = ny <nz is established between the refractive indexes nx and ny in any x direction and y direction in which the retardation layer is orthogonal to each other in the in-plane direction, and the refractive index nz in the thickness direction. By being a thing, the property as a positive C plate can be provided to the retardation film of this aspect.
In this aspect, since the adhesive alignment layer has an alignment regulating force for homeotropic alignment of the liquid crystal material, the liquid crystal material contained in the retardation layer is usually the adhesive alignment layer. Thus, homeotropic alignment is formed. For this reason, in this embodiment, the above retardation layer is naturally established in the above relationship between nx, ny, and nz by the contribution of the birefringence of the liquid crystal material having such homeotropic alignment. Can do.
Therefore, according to the present embodiment, the retardation film having properties as a positive C plate using a transparent substrate made of a cycloolefin resin, the adhesion between the retardation layer and the transparent substrate. An excellent retardation film can be obtained.

The retardation film of this embodiment has at least a transparent substrate, an adhesive alignment layer, and a retardation layer.
Hereinafter, each structure used for the retardation film of this aspect is demonstrated in order.

1. Adhesive alignment layer First, the adhesive alignment layer used in this embodiment will be described. The adhesive alignment layer used in this embodiment has at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V). In addition, it contains a polymer of a polymerizable monomer having a carbon content ratio of 3 or more, and further has an alignment regulating force for homeotropic alignment of the liquid crystal material. The adhesive alignment layer used in this embodiment has a function of homeotropically aligning a liquid crystal material contained in a retardation layer described later to impart a property as a positive C plate to the retardation layer, and a transparency described later. It has a function of bonding the substrate and the retardation layer.
Hereinafter, such an adhesive alignment layer will be described in detail.

(1) Polymerizable monomer First, the polymerizable monomer used in this embodiment will be described. The polymerizable monomer used in this embodiment has at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V). And the said carbon content ratio is 3 or more. In this aspect, since the carbon content ratio of the polymerizable monomer is in the above range, the polarity of the polymerizable monomer can be approximated to the polarity of the cycloolefin resin constituting the transparent substrate described later. It is possible to improve the adhesion between the conductive alignment layer and the transparent substrate described later.

  The carbon content ratio of the polymerizable monomer used in this embodiment is not particularly limited as long as it is within the range specified in this embodiment, and is arbitrary depending on the type of cycloolefin resin constituting the transparent substrate described later. Can be determined. Among these, the polymerizable monomer used in this embodiment preferably has a carbon content in the range of 3 to 10, particularly preferably in the range of 3 to 7, and more preferably in the range of 3 to 5. Some are preferred. The carbon content ratio indicates that the larger the value, the smaller the polarity of the polymerizable monomer. Therefore, when the carbon content ratio is smaller than the above range, the polarity of the polymerizable monomer becomes too large, and the transparency described later This is because the difference between the polarity of the cycloolefin-based resin constituting the substrate widens, and as a result, the adhesion between the transparent substrate and the adhesive alignment layer described later may be insufficient. Moreover, when it is larger than the above range, the ratio of the polymerizable functional group contained in the polymerizable monomer becomes too small, and the solvent resistance of the adhesive alignment layer may be impaired.

Here, as described above, the carbon content ratio is a value (N / M) obtained by dividing the carbon number N constituting the polymerizable monomer by the number M of elements other than carbon and hydrogen constituting the polymerizable monomer. However, “the number N of carbon atoms constituting the polymerizable monomer” means the number of carbons indicated when the polymerizable monomer is represented by a molecular formula. The “number of elements M other than carbon and hydrogen constituting the polymerizable monomer” means the sum of the numbers of elements other than carbon and hydrogen expressed when the polymerizable monomer is expressed by a molecular formula. Is. Therefore, for example, in the case of 1,6-hexanediol diacrylate having a molecular formula of C ₁₂ H ₁₈ O ₄ , the number of carbon atoms N constituting the polymerizable monomer is 12, other than carbon and hydrogen constituting the polymerizable monomer. Since the number of elements M is 4, the above N / M is 3. In the case of acryloylmorpholine having a molecular formula of C ₇ H ₁₁ NO ₂ , the number N of carbon atoms constituting the polymerizable monomer is 7, and the number M of elements other than carbon and hydrogen constituting the polymerizable monomer is 3 (nitrogen). + / Oxygen), the N / M is 2.3.

  The polymerizable monomer used in this embodiment may contain one of the polymerizable functional groups in the molecule, or may contain a plurality of polymerizable functional groups. In particular, in this embodiment, it is preferable to use a polymerizable monomer containing a plurality of polymerizable functional groups. Thereby, since the crosslink density of the polymer of the polymerizable monomer in the adhesive alignment layer can be increased, an adhesive alignment layer having excellent solvent resistance can be obtained.

  In addition, when the polymerizable monomer used in this embodiment is formed by bonding a plurality of the polymerizable functional groups, all of the polymerizable functional groups may be the same or different from each other.

  Moreover, it is preferable that the polymerizable monomer used for this aspect has an aliphatic hydrocarbon. By having an aliphatic hydrocarbon, the carbon content ratio is within the range specified in this embodiment, and the polarity of the polymerizable monomer used in this embodiment is close to the polarity of the cycloolefin resin used in the transparent substrate described later It is because it becomes easy to do.

  The aliphatic hydrocarbon used in the present embodiment may be a linear one, a branched one, or a cyclic one. Linear or cyclic ones are preferred. Since the hydrocarbon chain is linear or cyclic, the molecular structure of the polymerizable monomer can be approximated by the molecular structure of a cycloolefin resin used for a transparent substrate described later. This is because, as a result of making it possible to make the polarities closer, it is possible to obtain a retardation film having more excellent adhesion between the transparent substrate and the adhesive alignment layer.

In addition, the polymerizable monomer used in this embodiment preferably has a hydroxyl value of 150 mgKOH / g or less, more preferably 50 mgKOH / g or less, and particularly preferably 5 mgKOH / g or less. The polymerizable monomer used in this embodiment preferably has an acid value of 150 mgKOH / g or less, more preferably 50 mgKOH / g or less, and particularly preferably 5 mgKOH / g or less.
When the polymerizable monomer used in this embodiment has a highly polar hydroxyl group and acidic group (carboxylic acid, phosphoric acid, sulfonic acid, etc.), and either the hydroxyl value or acid value is higher than 150 mgKOH / g, the carbon content ratio Even within the range specified in this embodiment, it becomes difficult to approximate the polarity of the polymerizable monomer to that of the cycloolefin resin described later, and the adhesion between the adhesive alignment layer and the transparent substrate is lowered. This is because cases are also assumed.
Here, the hydroxyl value can be measured by a method based on JIS K0070. Moreover, the said acid value can be measured by the method based on JISK2501.

  Specific examples of the polymerizable monomer used in this embodiment include, for example, polymerizable monomers represented by the following formulas (VI) and (VII).

In the above formula, X ¹ , X ² , and X ³ are each independently a polymerizable functional group of any one of the above formulas (I), (II), (III), (IV), and (V). To express. Y ¹ is a linear or branched hydrocarbon represented by —C _m H _{2m + 1} (m is an integer of 4 to 17), a cyclohexyl group, an isobornyl group, an unsubstituted group or an alkyl group. Represents a phenyl group or a biphenyl group. r ¹ , r ² , r ³ and r ⁴ are each independently 0 or 1;
Further, Y ² represents a linear or branched hydrocarbon represented by —C _n H _2n — (n is an integer of 1 to 34), a cyclohexyl group, a tricyclodecanedimethyl group, a phenyl group, Or represents a biphenyl group.

  In the present embodiment, among the polymerizable monomers represented by the above formulas (VI) and (VII), the following polymerizable monomers can be preferably used (hereinafter, the numerical values in <> represent the respective compounds). The carbon content ratio is shown.

A polymerizable monomer having a polymerizable functional group represented by the above formula (I); cyclohexyl acrylate <4.5>, isobornyl acrylate <6.5>, 1,6-hexanediol diacrylate <3>, 1 , 9-nonanediol diacrylate <3.75>, 2-methyl-1,8-octanediol diacrylate <3.75>, 2-butyl-2-ethyl-1,4-propanediol diacrylate <3. 75>, 1,10-decanediol diacrylate <3.75>, tricyclodecane dimethanol diacrylate <4.5>.
Polymerizable monomer having a polymerizable functional group represented by the above formula (II): 1,6-hexanediol divinyl ether <5>, cyclohexanediol divinyl ether <5>, cyclohexanedimethanol divinyl ether <6>, nonanediol Divinyl ether <6.5>, trimethylpropane trivinyl ether <4>.
A polymerizable monomer having a polymerizable functional group represented by the above formula (III); ethylhexyl glycidyl ether <5.5>.
A polymerizable monomer having a polymerizable functional group represented by the above formulas (III) and (IV); dipentene dioxide <5>.
A polymerizable monomer having a polymerizable functional group represented by the above formula (V); 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane <7>, di [1-ethyl (3-oxetanyl)] methyl Ether <4>.
A polymerizable monomer having a polymerizable functional group represented by the above formulas (I) and (V); 3-ethyl-3-oxetanylmethyl acrylate <3>.

  In addition, it can be clarified, for example, by NMR analysis that the polymerized product of the polymerizable monomer is contained in the adhesive alignment layer in this embodiment.

(2) Polymerized monomer monomer Next, the polymerizable monomer polymer used in this embodiment will be described. A polymerized polymerizable monomer used in this embodiment is obtained by polymerizing the polymerizable monomer described above.

  The polymer of the polymerizable monomer used in this embodiment is not particularly limited as long as it is obtained by polymerizing the polymerizable monomer described above. Examples of such a polymerized product of polymerizable monomers include an embodiment in which only the same polymerizable monomer is polymerized and an embodiment in which two or more kinds of polymerizable monomers are polymerized. In this embodiment, any polymer of polymerizable monomers of any embodiment can be used preferably. Among them, a polymer of polymerizable monomers of an embodiment in which only the same polymerizable monomer is polymerized is used. It is preferable.

(3) Adhesive Alignment Layer The adhesive alignment layer in this embodiment has an alignment regulating force (hereinafter, sometimes simply referred to as “homeotropic alignment regulating force”) that causes homeotropic alignment of the liquid crystal material. As an embodiment in which the adhesive alignment layer in this embodiment has such homeotropic alignment regulating force, a liquid crystal material contained in a retardation layer described later is homeotropically aligned to a predetermined degree, and the retardation layer is formed in the retardation layer. There is no particular limitation as long as it is an aspect capable of imparting properties as a predetermined positive C plate. As such an embodiment, the adhesive alignment layer contains an alignment control compound that expresses a homeotropic alignment regulating force, and the adhesive alignment layer is formed on the adhesive layer containing a polymer of the polymerizable monomer. And an aspect in which an alignment layer having the homeotropic alignment regulating force is laminated. In this embodiment, any of these embodiments can be suitably used, but it is preferable to use the former embodiment. This is because according to the former aspect, the homeotropic alignment regulating force can be easily imparted to the adhesive alignment layer simply by adding the alignment control compound to the adhesive alignment layer. In the latter embodiment, when forming the adhesive alignment layer in this embodiment, two steps of forming the adhesion layer and forming the alignment layer are required. According to the aspect, the adhesive alignment layer can be formed in one step, and therefore the retardation film of this aspect can be made more excellent in productivity.

  The alignment control compound is not particularly limited as long as a desired homeotropic alignment regulating force can be imparted to the adhesive alignment layer in this embodiment. Among these, as the orientation control compound used in this embodiment, a surfactant can be suitably used. In the adhesive alignment layer, the surfactant can be present at the boundary between the adhesive alignment layer and the retardation layer described later, and can be arranged with a specific direction of the molecule directed toward the retardation layer. This is because the homeotropic alignment regulating force can be easily imparted to the adhesive alignment layer in this embodiment.

  As said surfactant used for this aspect, a sulfonate surfactant can be mentioned, for example, A fluorinated sulfonate surfactant is used suitably especially.

  Specific examples of the fluorinated sulfonate surfactant include trade names FC-4430 and FC-4432 (both manufactured by 3M Company).

  The content of the alignment control compound in the adhesive alignment layer is particularly limited as long as it is within a range in which a desired homeotropic alignment regulating force can be imparted to the adhesive alignment layer depending on the type of the alignment control compound and the like. Is not to be done. Among them, the content of the orientation control compound in this embodiment is preferably in the range of 0.01% by mass to 20% by mass with respect to the polymerized polymerizable monomer contained in the adhesive alignment layer. In particular, it is preferably within a range of 0.01% by mass to 10% by mass.

  In addition, when using the thing which has the structure by which the orientation layer provided with the said homeotropic orientation control force was laminated | stacked on the adhesion layer containing the polymer of the said polymerizable monomer as an adhesive orientation layer in this aspect, the said orientation Examples of the layer include a liquid crystal vertical alignment film made of polyamic acid, polyimide, or the like. As such an alignment layer, for example, those described in JP-A-2005-115231 and the like can be used.

  The adhesive alignment layer in this embodiment contains a polymer of the polymerizable monomer. For this reason, as an aspect of the adhesive alignment layer in this aspect, there may be mentioned an aspect consisting only of a polymer of the polymerizable monomer, and an aspect including a polymer of the polymerizable monomer and another compound. it can. In this embodiment, any of these embodiments can be suitably used, but in particular, an embodiment in which other compounds are contained in addition to the polymerized monomer is preferable. By including other compounds in addition to the polymerized polymer of the polymerizable monomer, it becomes possible to impart functionality according to the use of the retardation film of this embodiment to the adhesive orientation layer in this embodiment. is there.

  As said other compound used for this aspect, if a desired functionality can be provided to the said adhesive orientation layer, it will not specifically limit. Examples of such other compounds include the alignment control compounds described above.

2. Retardation layer Next, the retardation layer used in this embodiment will be described. The retardation layer used in this embodiment contains a liquid crystal material, and nx between the refractive indices nx and ny in any x direction and y direction orthogonal to each other in the in-plane direction, and the refractive index nz in the thickness direction. = Ny <nz is established.

Here, in this embodiment, since the homeotropic alignment regulating force of the adhesive alignment layer contributes to homeotropic alignment formation of the liquid crystal material contained in the retardation layer, the liquid crystal material is usually a retardation layer. Thus, homeotropic alignment is formed. And, by such homeotropic alignment of the liquid crystal material, the retardation layer of this embodiment satisfies the relationship of nx = ny <nz.
Therefore, it can be said that the fact that the retardation layer used in this embodiment has the relationship of nx = ny <nz is equivalent to the fact that the liquid crystal material forms homeotropic alignment in the retardation layer.

  Hereinafter, the retardation layer used in this embodiment will be described.

(1) Liquid crystal material First, the liquid crystal material will be described. The liquid crystal material used in the present embodiment is not particularly limited as long as it can provide the above-described nx, ny, and nz of the retardation layer with the retardation that satisfies the above relationship. As such a liquid crystal material, a homeotropic liquid crystal material that can be homeotropically aligned is usually used.

  The homeotropic liquid crystal material used in this embodiment preferably has a polymerizable functional group. This is because by using such a liquid crystal material, it is possible to polymerize each other via a polymerizable functional group, so that the mechanical strength of the retardation layer in this embodiment can be improved. In addition, the alignment stability of the homeotropic liquid crystal material in the retardation layer can be improved.

  As the polymerizable functional group, various polymerizable functional groups that are polymerized by the action of ionizing radiation such as ultraviolet rays and electron beams, or heat are used. Representative examples of these polymerizable functional groups include radically polymerizable functional groups or cationic polymerizable functional groups. Further, representative examples of radically polymerizable functional groups include functional groups having at least one addition-polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups having or not having substituents, An acrylate group (generic name including an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group) and the like can be given. Specific examples of the cationic polymerizable functional group include an epoxy group. In addition, examples of the polymerizable functional group include an isocyanate group and an unsaturated triple bond. In this embodiment, among these polymerizable functional groups, a functional group having an ethylenically unsaturated double bond is preferably used from the viewpoint of the process.

  Note that the homeotropic liquid crystal material used in this embodiment may have a plurality of the above-described polymerizable functional groups, or may have only one.

  As such a homeotropic liquid crystal material, a material having a homeotropic alignment (first homeotropic liquid crystal material) capable of forming a homeotropic alignment without using a vertical alignment film and a homeotropic alignment by itself are formed. Although it cannot be used, a material that can form homeotropic alignment by using a vertical alignment film (second homeotropic liquid crystal material) can be given. In the retardation film of this embodiment, since the adhesive alignment layer has homeotropic alignment regulating force, not only the first homeotropic liquid crystal material but also the second homeotropic liquid crystal material. Can also be suitably used.

  The first homeotropic liquid crystal material is not particularly limited as long as homeotropic alignment can be formed without using a vertical alignment film and a desired retardation can be imparted to the retardation layer in this embodiment. Is not to be done. Such a first homeotropic liquid crystal material includes a monomer unit containing a liquid crystalline fragment side chain having a positive refractive index anisotropy and a monomer unit containing a non-liquid crystalline fragment side chain. Examples of the liquid crystal polymer include a chain type liquid crystal polymer and a side chain type liquid crystal polymer containing a monomer unit containing the liquid crystalline fragment side chain and a monomer unit containing a liquid crystalline fragment side chain having an alicyclic ring structure. be able to. Examples of such a liquid crystal polymer include compounds described in JP-A No. 2003-121853, JP-A No. 2002-174725, and JP-A No. 2005-70098.

  On the other hand, as the second homeotropic liquid crystal material, any homeotropic alignment can be formed by using a vertical alignment film, and any desired retardation can be imparted to the retardation layer in this embodiment. It is not particularly limited. Especially, in this aspect, the nematic liquid crystal material which shows a nematic phase is used suitably. This is because nematic liquid crystal materials can easily form homeotropic alignment by using a vertical alignment film.

  Specific examples of the second homeotropic liquid crystal material used in this embodiment are described in, for example, JP-A-7-258638, JP-A-10-508882, and JP-A-2003-287623. Such compounds can be mentioned. In particular, in this embodiment, a compound represented by the following chemical formula can be suitably used as the second homeotropic liquid crystal material.

  Specific examples of the second homeotropic liquid crystal material include compounds described in JP-A-10-319408. In particular, in this embodiment, a compound represented by the following chemical formula can be suitably used as the second homeotropic liquid crystal material.

In the above formula, x is 1 to 12, Z is a 1,4-phenylene group or 1,4-cyclohexylene group, R ⁵ is halogen or cyano, or has 1 to 12 carbon atoms. An alkyl group or an alkoxy group, and L is H, halogen or CN, or an alkyl group, an alkoxy group or an acyl group having 1 to 7 carbon atoms.

  When a compound having a polymerizable functional group is used as the liquid crystal material, the liquid crystal material contained in the retardation layer in this embodiment is a polymer obtained by polymerization through the polymerizable functional group.

(2) Retardation layer The liquid crystal material contained in the retardation layer in this aspect may be one type, or two or more types. When two or more kinds of liquid crystal materials are used, the first homeotropic liquid crystal material and the second homeotropic liquid crystal material may be mixed and used.

  In addition, the retardation layer in this embodiment may contain a compound other than the liquid crystal material. Such other compounds are not particularly limited as long as they do not impair the alignment state of the liquid crystal material in the retardation layer or the optical properties of the retardation layer, and the retardation film of this embodiment It can be appropriately selected and used depending on the purpose of use. Examples of such other compounds include a polymerization initiator, a polymerization inhibitor, a plasticizer, a surfactant, and a silane coupling agent. In particular, in this embodiment, when the polymerizable liquid crystal material is used as the liquid crystal material, it is preferable to use a polymerization initiator or a polymerization inhibitor as the other compound.

  Examples of the polymerization initiator include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-amino acetophenone, 4,4-dichloro. Benzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, p- tert-Butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethyl ketal, benzylmethoxyethyl acetal, benzo Methyl ether, benzoin butyl ether, anthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzsuberone, 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-benzoyl) oxy , 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, Adeka N1717, carbon tetrabromide, tri Examples include combinations of photoreducing dyes such as bromophenyl sulfone, benzoin peroxide, eosin, and methylene blue with reducing agents such as ascorbic acid and triethanolamine. In this embodiment, 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.

  Examples of the polymerization inhibitor include diphenylpicrylhydrazide, tri-p-nitrophenylmethyl, p-benzoquinone, p-tert-butylcatechol, picric acid, copper chloride, methylhydroquinone, methoquinone, tert-butylhydroquinone and the like. Although a polymerization inhibitor for the reaction can be used, a hydroquinone polymerization inhibitor is preferred from the viewpoint of storage stability, and methyl hydroquinone is particularly preferred.

  The surfactant has a function of assisting homeotropic alignment of the liquid crystal material in the retardation layer. Such a surfactant is described in “1. Adhesive alignment layer”. Since it is the same as what was demonstrated in the term, description here is abbreviate | omitted.

  Furthermore, a compound as shown below can be added to the retardation layer in this embodiment within a range that does not impair the purpose of this embodiment. 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 thickness of the retardation layer in this embodiment is not particularly limited as long as it is within a range in which desired optical characteristics can be imparted to the retardation film used in this embodiment, depending on the type of the liquid crystal material. In particular, in this embodiment, it is preferably in the range of 0.5 μm to 10 μm, particularly preferably in the range of 0.5 μm to 5 μm, and more preferably in the range of 1 μm to 3 μm.

The retardation layer in this embodiment exhibits retardation, but such retardation can be arbitrarily adjusted according to the use of the retardation film of this embodiment. In particular, the retardation layer in this embodiment preferably has a retardation (Rth) in the thickness direction in the range of −1000 nm to 0 nm, and particularly preferably in the range of −300 nm to 0 nm.
Here, the above-mentioned retardation in the thickness direction (hereinafter sometimes simply referred to as “Rth”) refers to the refractive indices in arbitrary x and y directions orthogonal to each other in the in-plane direction, nx, ny, and thickness, respectively. This is an amount represented by Rth = {(nx + ny) / 2−nz} × d, where nz is the refractive index in the direction. Moreover, the said thickness direction retardation can be measured by a parallel Nicol rotation method, for example using KOBRA-WR by Oji Scientific Instruments.

3. Transparent substrate Next, the transparent substrate used in this embodiment will be described. The transparent substrate used in the present invention is made of a cycloolefin resin.

  Here, the cycloolefin resin in this embodiment means a resin having a monomer unit composed of a cyclic olefin (cycloolefin). Moreover, as a monomer which consists of the said cyclic olefin, a norbornene, a polycyclic norbornene-type monomer, etc. can be mentioned, for example.

  The cycloolefin resin used in this embodiment may be a homopolymer of a monomer comprising the above cyclic olefin, or may be a copolymer.

The cycloolefin resin used in this embodiment is not particularly limited as long as a transparent substrate having desired transparency can be obtained. Among them, the cycloolefin resin used in this embodiment preferably has a saturated water absorption at 23 ° C. of 1% by mass or less, and particularly preferably within a range of 0.1% by mass to 0.7% by mass. . This is because the use of such a cycloolefin-based resin can make the retardation film of this embodiment 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.

  Further, the cycloolefin resin used in this embodiment 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 the retardation film of this embodiment can be made more excellent in heat resistance and workability by having the glass transition point within the above range.

  Examples of such a cycloolefin resin include those having a structural unit represented by the following formula (a) or the following formula (b).

Here, in the above formula (a), t and u each independently represent 0 or a positive integer, except when t and u are 0 at the same time. A represents an ethylene group or a vinylene group, and R ^{11 to} R ¹⁴ are each independently a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 30 carbon atoms, or — (CH ₂ ) n—COOR ( n represents 0 to 5, and R represents an alkyl group having 1 to 12 carbon atoms.
Here, R ¹¹ or R ¹² and R ¹³ or R ¹⁴ may be bonded to each other to form a carbocyclic or heterocyclic ring. Furthermore, the carbocycle or heterocycle may be a monocyclic structure or a polycyclic structure.

In the above formula (b), B represents an ethylene group or a vinylene group. R ^{15 to} R ¹⁸ each independently represent a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 30 carbon atoms. Further, R ¹⁵ and R ¹⁶ , or R ¹⁷ and R ¹⁸ may be integrated to form a divalent hydrocarbon group.

  In the transparent substrate used in this embodiment, only one kind of the cycloolefin-based resin may be used, or two or more kinds may be used.

The transparency of the transparent substrate used in this embodiment may be arbitrarily determined according to the use of the retardation film of this embodiment, etc., but it is usually preferable that the transmittance in the visible light region is 80% or more, 90 % Or more is more preferable. When the transmittance is in the above range, for example, when the retardation film of this embodiment is used for a viewing angle compensation film of a liquid crystal display device, it is possible to prevent the display luminance of the liquid crystal display device from being lowered. Because.
Here, the transmittance of the transparent substrate can be measured by JIS K7361-1 (a test method for the total light transmittance of a plastic-transparent material).

  The thickness of the transparent substrate used in this embodiment is not particularly limited as long as it is within a range in which a desired self-supporting property can be provided. In particular, in this embodiment, it is preferably in the range of 25 μm to 1000 μm, particularly preferably in the range of 30 μm to 100 μm. This is because if the thickness of the transparent substrate is smaller than the above range, the necessary self-supporting property may not be imparted to the transparent substrate of this embodiment. Further, if the thickness is thicker than the above range, for example, when cutting the retardation film of the present embodiment, the processing waste may increase or the cutting blade may be worn quickly.

  The configuration of the transparent substrate in this embodiment is not limited to a configuration consisting of a single layer, and may have a configuration in which a plurality of layers are stacked. 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.

The transparent substrate used in this embodiment may exhibit retardation. Such retardation is not particularly limited as long as a desired refractive index anisotropy can be imparted to the retardation film according to the use of the retardation film of the present embodiment. In particular, the transparent substrate used in this embodiment preferably has an in-plane retardation in the range of 0 nm to 1000 nm, and particularly preferably in the range of 0 nm to 300 nm.
Here, the in-plane retardation (hereinafter sometimes simply referred to as “Re”) is the refractive index in the slow axis direction in the plane of the transparent substrate is nx, and the in-plane fast axis direction is in the in-plane retardation direction. When the refractive index is ny and the thickness of the transparent substrate is d, Re = (nx−ny) × d. The Re can be measured by, for example, a parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments.

  Specific examples of the transparent substrate made of cycloolefin-based resin used in the present embodiment 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, etc. Can be mentioned.

4). Retardation Film The retardation exhibited by the retardation film of this embodiment can be appropriately determined according to the use of the retardation film of this embodiment, etc. Among them, the retardation film of this embodiment has an Nz factor of 1. Is preferably 0.0 or less, and more preferably in the range of −1.5 ≦ Nz <1.0.
Here, the Nz factor is a parameter that defines the shape of the refractive index ellipsoid. It is determined by the refractive index nx and ny in the arbitrary x direction and y direction orthogonal to each other in the in-plane direction, and the refractive index nz in the thickness direction. Is represented by the following equation.
Nz = (nx-nz) / (nx-ny)
The Nz factor can be obtained by, for example, measuring nx, ny, and nz by the parallel Nicol rotation method using KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd., and then calculating according to the above formula. it can.

  The Re wavelength dispersion of the retardation film of this embodiment may be a reverse dispersion type in which the Re value decreases as the wavelength becomes shorter, or a positive dispersion type in which the Re value increases as the wavelength becomes shorter. Alternatively, a flat type in which the Re value does not have wavelength dependency may be used.

  The form of the retardation film of this embodiment is not particularly limited. For example, the retardation film of the present embodiment may be in the form of a sheet that matches the screen size of a liquid crystal display device using the retardation film of the present embodiment, or may be long. There may be.

5. Use of Retardation Film The retardation film of this embodiment can be used as a viewing angle compensation film, an elliptically polarizing plate, a brightness enhancement film and the like used in a liquid crystal display device.

  When the retardation film of this embodiment is used as a viewing angle compensation film for a liquid crystal display device, the retardation film of this embodiment can be used alone, and the retardation film of this embodiment and other optical functions can be used. It is also possible to use it laminated with a film. Furthermore, it is also possible to directly laminate another retardation layer on the surface opposite to the side where the retardation layer is formed on the substrate used for the retardation film of this embodiment.

  As an example of laminating the retardation film of this embodiment and another optical functional film, for example, by laminating a liquid crystal layer containing cholesteric aligned liquid crystal molecules on the retardation film of this embodiment, Examples of use as a brightness enhancement film for liquid crystal display devices can be given.

  Moreover, the retardation film of this aspect can be used also for the use as a polarizing plate by bonding together with a polarizer. That is, the polarizing plate is usually composed of a polarizer and a polarizing plate protective film formed on both surfaces thereof. In this aspect, for example, as one polarizing plate protective film, the retardation of this aspect is provided. By using a film, it can be used as a polarizing plate having a viewing angle compensation function of a liquid crystal display device.

6). Production method of retardation film The production method of the retardation film of this embodiment is not particularly limited as long as it can produce the retardation film having the above-described configuration. As such a method, for example, using the transparent substrate, an adhesive alignment layer forming step of forming an adhesive alignment layer on the transparent substrate, and a retardation forming a retardation layer on the adhesive alignment layer And a method using a layer forming step.
Hereinafter, such a method will be described as an example of the method for producing the retardation film of the present embodiment.

(1) Adhesive alignment layer forming step First, the adhesive alignment layer forming step will be described. In the adhesive alignment layer forming step, as a method for forming the adhesive alignment layer on the transparent substrate, an adhesive alignment containing a polymer of a polymerizable monomer as described above and having a homeotropic alignment regulating force is included. The method is not particularly limited as long as the layer can be formed. As such a method, for example, an adhesive alignment layer forming layer is formed by applying a coating liquid for forming an adhesive alignment layer in which a polymerizable monomer and an alignment control compound are dissolved in a solvent on the transparent substrate. Examples thereof include a method using a layer forming step for forming an adhesive alignment layer and a curing treatment step for forming the adhesive alignment layer by polymerizing the polymerizable monomer. According to such a method, an adhesive alignment layer to which a homeotropic alignment regulating force is imparted by the alignment control compound can be formed.

  The coating method for coating the adhesive alignment layer forming coating liquid on the transparent substrate in the layer forming step for forming the adhesive alignment layer is not particularly limited as long as the desired planarity can be achieved. is not. Examples of such coating methods include gravure coating, reverse coating, knife coating, dip coating, spray coating, air knife coating, roll coating, printing, curtain coating, die coating, and casting. Method, bar coating method, extrusion coating method, E-type coating method and the like.

  As a method for drying the coating film of the adhesive alignment layer forming coating solution, a commonly used drying method such as a heat drying method, a vacuum 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.

  The solvent used in the adhesive alignment layer-forming coating solution is not particularly limited as long as it can dissolve the polymerizable monomer and the alignment control compound 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 addition, the solvent used in this step may be one kind or a mixed solvent of two or more kinds of solvents.

  The polymerizable monomer and the alignment control compound are the same as those described in the above section “1. Adhesive alignment layer”, and thus the description thereof is omitted here.

  In the curing treatment step, the method for polymerizing the polymerizable monomer is not particularly limited as long as it is a method capable of inducing a polymerization reaction of the polymerizable monomer contained in the adhesive alignment layer forming layer. . Such a method depends on the type of the polymerizable monomer, but in general, the method for irradiating the adhesive alignment layer forming layer with ultraviolet rays or the adhesive alignment layer forming layer is used. A heating method or the like is used.

  As the ultraviolet rays, those having a wavelength in the range of 150 nm to 500 nm, more preferably in the range of 250 nm to 450 nm are usually used.

(2) Retardation layer formation process Next, the said retardation layer formation process is demonstrated. In this step, the method for forming the retardation layer on the adhesive alignment layer is not particularly limited as long as it can form a retardation layer having a desired retardation. As such a method, for example, a method of applying the above-described homeotropic liquid crystal material homeotropically after coating the above-described homeotropic liquid crystal material-containing coating liquid on the adhesive alignment layer. Can be mentioned.

  In such a method, the method of applying the retardation layer forming coating liquid onto the adhesive alignment layer and drying it is not particularly limited, and is generally used for a retardation film. A known method can be used as a method for forming the film. As such a coating method and a drying method, for example, the coating method and the drying method of the coating liquid for forming an adhesive alignment layer described in the above section “(1) Adhesive alignment layer forming step” can be used. .

  In this step, as a method for homeotropic alignment of the homeotropic liquid crystal material, a method of heating the homeotropic liquid crystal material to a temperature higher than the transition temperature to the homeotropic liquid crystal phase is usually used.

  When a compound having a polymerizable functional group is used as the homeotropic liquid crystal material, the homeotropic liquid crystal is aligned and then subjected to polymerization treatment by ultraviolet irradiation or the like.

  The homeotropic liquid crystal material is the same as that described in the section “2. Retardation layer”, and a description thereof will be omitted here.

B. Next, the retardation film of the second aspect of this aspect will be described. The retardation film of this aspect is formed on a transparent substrate made of a cycloolefin resin, an adhesive functional layer formed to be in contact with the transparent substrate, and containing a polymer of a polymerizable monomer, and the adhesive functional layer. A liquid crystal material having homeotropic alignment, and nx = between the refractive indices nx and ny in any x direction and y direction orthogonal to each other in the in-plane direction and the refractive index nz in the thickness direction. a retardation layer that satisfies the relationship of ny <nz, wherein the polymerizable monomer is represented by the following formulas (I), (II), (III), (IV), and (V): And having at least one polymerizable functional group selected from the group consisting of, and dividing the carbon number N constituting the polymerizable monomer by the number M of elements other than carbon and hydrogen constituting the polymerizable monomer. It is characterized in that the value (N / M) is 3 or more.

Here, in the above formula, R ¹ , R ² and R ³ represent a methyl group or hydrogen. R ⁴ represents hydrogen, a methyl group, or an ethyl group.

Such a retardation film of this embodiment will be described with reference to the drawings. FIG. 2 is a schematic view showing an example of the retardation film of this embodiment. As illustrated in FIG. 2, the retardation film 20 of this embodiment includes a transparent substrate 21 made of a cycloolefin resin, an adhesion functional layer 22 formed on the transparent substrate 21, and an adhesive functional layer 22 on the adhesion functional layer. And a retardation layer 23 containing a liquid crystal material.
In such an example, the retardation film 20 of this embodiment is selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V) for the adhesion functional layer 22. A polymer of a polymerizable monomer having at least one polymerizable functional group and a carbon content ratio of 3 or more, and the retardation layer 23 is orthogonal to each other in the in-plane direction. The relationship of nx = ny <nz is established between the refractive indices nx and ny in the arbitrary x direction and y direction and the refractive index nz in the thickness direction.
In the retardation film 20 of this embodiment, since the liquid crystal material has homeotropic alignment, the liquid crystal material contained in the retardation layer 23 has homeotropic alignment. become.

According to this aspect, the adhesion functional layer has at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V). In addition, by including a polymer of a polymerizable monomer having a carbon content ratio of 3 or more, it is possible to improve the adhesion between the adhesion functional layer and the transparent substrate made of the cycloolefin resin. For this reason, according to this aspect, it is a retardation film using a transparent substrate made of a cycloolefin resin, and a retardation film having excellent adhesion between the retardation layer and the transparent substrate can be obtained. .
In addition, a relationship of nx = ny <nz is established between the refractive indexes nx and ny in any x direction and y direction in which the retardation layer is orthogonal to each other in the in-plane direction, and the refractive index nz in the thickness direction. By being a thing, the property as a positive C plate can be provided to the retardation film of this aspect.
Therefore, according to the present embodiment, the retardation film having properties as a positive C plate using a transparent substrate made of a cycloolefin resin, the adhesion between the retardation layer and the transparent substrate. An excellent retardation film can be obtained.

  The reason why the adhesion between the transparent substrate and the adhesion functional layer can be improved by containing a polymer of a polymerizable monomer having the above structure in the adhesion functional layer is the above-mentioned “A. First Aspect”. This is the same as the reason explained in the section of “Phase difference film”, and the explanation here is omitted.

The retardation film of this embodiment has at least the transparent substrate, the adhesion functional layer, and the retardation layer, and may have other layers as necessary. Hereinafter, each structure used for the retardation film of this aspect is demonstrated in order.
In addition, about the transparent substrate used for this aspect, since it is the same as that of what was demonstrated in the above-mentioned item of "A. Retardation film of 1st aspect", description here is abbreviate | omitted.

1. First, the adhesion functional layer used in this embodiment will be described. The adhesion functional layer used in this embodiment has at least one polymerizable functional group selected from the group consisting of the above formulas (I), (II), (III), (IV), and (V). And a polymer of a polymerizable monomer having a carbon content ratio of 3 or more. And the contact | adherence functional layer used for this aspect has a function which adhere | attaches the phase difference layer and transparent substrate which are mentioned later.

  Here, except that the adhesion functional layer used in this embodiment does not have an alignment regulating force for homeotropic alignment of the liquid crystal material, the “adhesion” described in the section “A. Retardation film of the first embodiment” above. Since this is the same as the “alignment orientation layer”, the description thereof is omitted here.

2. Retardation layer Next, the retardation layer used in this embodiment will be described. The retardation layer used in this embodiment contains a liquid crystal material having homeotropic orientation, and has refractive indexes nx and ny in arbitrary x and y directions orthogonal to each other in the in-plane direction, and a refractive index nz in the thickness direction. In this case, a relationship of nx = ny <nz is established.

  Here, since the liquid crystal material used in this embodiment has homeotropic alignment, it has a property that homeotropic alignment can be formed without using a vertical alignment film. Therefore, in the retardation layer in this embodiment, the liquid crystal material usually forms homeotropic alignment. When the liquid crystal material forms homeotropic alignment in this way, the relationship of nx = ny <nz is established, so that the retardation layer used in this embodiment has the relationship of nx = ny <nz. Having it can be said that it is in agreement with the liquid crystal material forming homeotropic alignment.

  The retardation layer used in the present embodiment is the same as the above-mentioned “A. Except for the use of the“ first homeotropic liquid crystal material ”described in“ A. Retardation film of first embodiment ”. Since it is the same as that of what was demonstrated in the term of the phase difference film of the 1st mode, explanation here is omitted.

3. Retardation Film The retardation exhibited by the retardation film of this embodiment can be appropriately determined according to the use of the retardation film of this embodiment, etc. Among them, the retardation film of this embodiment has an Nz factor of 1. Is preferably 0.0 or less, and more preferably in the range of −1.5 ≦ Nz <1.0.
Here, since the definition of the Nz factor and the measurement method are the same as those described in the section “A. Retardation film of first aspect”, description thereof is omitted here.

  The Re wavelength dispersion of the retardation film of this embodiment may be a reverse dispersion type in which the Re value decreases as the wavelength becomes shorter, or a positive dispersion type in which the Re value increases as the wavelength becomes shorter. Alternatively, a flat type in which the Re value does not have wavelength dependency may be used.

  The form of the retardation film of this embodiment is not particularly limited. For example, the retardation film of the present embodiment may be in the form of a sheet that matches the screen size of a liquid crystal display device using the retardation film of the present embodiment, or may be long. There may be.

4). Use of Retardation Film The retardation film of this embodiment can be used as a viewing angle compensation film, an elliptically polarizing plate, a brightness enhancement film and the like used in a liquid crystal display device. Specific examples of such applications are the same as those described in the section “A. Retardation Film of First Aspect” above, and thus description thereof is omitted here.

5. Manufacturing method of retardation film Next, the manufacturing method of the retardation film of this aspect is demonstrated. The method for producing the retardation film of the present embodiment is not particularly limited as long as the method can produce the retardation film having the above configuration. As such a method, for example, using the transparent substrate, an adhesion functional layer forming step of forming an adhesion functional layer on the transparent substrate, and a retardation layer forming step of forming a retardation layer on the adhesion functional layer Can be mentioned.

(1) Adhesion functional layer formation process First, the said adhesion functional layer formation process is demonstrated. In the adhesion functional layer forming step, the method for forming the adhesion functional layer on the transparent substrate is not particularly limited as long as it is a method capable of forming the adhesion functional layer containing a polymer of the polymerizable monomer described above. . As such a method, for example, an adhesive functional layer forming layer is formed by applying an adhesive functional layer forming coating solution obtained by dissolving a polymerizable monomer in a solvent onto the transparent substrate. Examples thereof include a method using a forming step and a curing treatment step of forming an adhesion functional layer by polymerizing the polymerizable monomer.

  Here, the coating method for coating the adhesive alignment layer forming coating liquid on the transparent substrate in the layer forming step for forming the adhesive functional layer and the method for drying the coated film are described in “A. Since it is the same as the coating method of the adhesive orientation layer forming coating solution and the coating method drying method described in the section of “Retardation film of the first embodiment”, description thereof is omitted here.

  The solvent used in the adhesive functional layer-forming coating solution is not particularly limited as long as it can dissolve the polymerizable monomer and the orientation control compound at a desired concentration. Such a solvent is the same as the solvent used in the coating liquid for forming an adhesive alignment layer described in the above section “A. Retardation film of the first aspect”, and thus the description thereof is omitted here. To do.

  The method for polymerizing the polymerizable monomer in the curing treatment step is not particularly limited as long as it is a method capable of inducing a polymerization reaction of the polymerizable monomer. As such a method, for example, a method similar to the method described in the section of “A. Retardation film of first aspect” can be used, and thus the description thereof is omitted here.

(2) Retardation layer formation process Next, the said retardation layer formation process is demonstrated. The method for forming the retardation layer on the adhesion functional layer in this step is not particularly limited as long as it is a method capable of forming a retardation layer having a desired retardation. As such a method, for example, a method similar to the method described in the section “A. Retardation film of the first aspect” can be used, and thus the description thereof is omitted here.

  In addition, this aspect is not limited to the said embodiment. The above-described embodiment is an exemplification, and this embodiment has substantially the same configuration as the technical idea described in the claims of this embodiment and exhibits any similar effect. Are included in the technical scope.

  Next, this embodiment will be described more specifically by showing examples.

(1) Example 1
Tricyclodecane dimethanol diacrylate (carbon content ratio = 4.5) was used as the polymerizable monomer, the polymerizable monomer was dissolved in MEK (methyl ethyl ketone) so as to have a solid content of 40% by mass, and an initiator was added. The coating solution for forming the adhesion functional layer was coated on a Re = 100 nm transparent substrate made of norbornene resin (trade name: Arton, manufactured by JSR), and then dried with warm air at 80 ° C. for 2 minutes, 120 mJ / The adhesion functional layer was formed by curing with UV of cm ^{2 so} as to have a thickness of 6 μm.

Next, a liquid crystal mixture of 50% by mass of the side chain polymer represented by the chemical formula A and 50% by mass of the photopolymerizable liquid crystal represented by the following formula B, a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907, photopolymerization) 5% by mass with respect to the functional compound) was dissolved in the cyclohexanone solution so as to have a solid content of 20%, and a leveling agent was further added to obtain a coating solution for forming a retardation layer. After coating the retardation layer forming coating liquid on the adhesion functional layer, the liquid crystal mixture was homeotropically aligned by drying at 100 ° C. for 1 minute and then cooling to room temperature. Further, the film was cured with UV of 100 mJ / cm ² to form a retardation layer having a thickness of 1 μm on the adhesion functional layer, thereby producing a retardation film.

(2) Example 2
A retardation film was produced in the same manner as in Example 1 except that 1,9-nonanediol diacrylate (carbon content ratio = 3.75) was used as the polymerizable monomer.

(3) Example 3
Tricyclodecane dimethanol diacrylate (carbon content ratio = 4.5) was used as a polymerizable monomer, and 0.05% by mass of an alignment control compound (trade name FC-4430: manufactured by 3M Company) was added to the polymerizable monomer. The obtained mixture was dissolved in MEK (methyl ethyl ketone) so as to have a solid content of 40% by mass, and an initiator was further added to obtain a coating solution for forming an adhesive alignment layer. Next, the coating liquid for forming an adhesive alignment layer was applied on a Re = 100 nm transparent substrate made of norbornene resin (trade name: Arton, manufactured by JSR), and then heated with hot air at 80 ° C. for 2 minutes. It dried and hardened | cured by UV of 120 mJ / cm < ² >, and the adhesive orientation layer was formed so that it might become thickness 6 micrometers.

Next, a liquid crystal mixture containing a liquid crystal material represented by the following formulas C, D, and E, a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907, 5% by mass with respect to the liquid crystal mixture), and cyclohexanone solution In order to obtain a coating solution for forming a retardation layer, the solid content was dissolved to 20% by mass, and a leveling agent was further added. Next, after coating the retardation layer forming coating solution on the adhesive alignment layer, it was dried at 60 ° C. for 2 minutes to cause homeotropic alignment. Further, the film was cured with UV of 100 mJ / cm ² to form a retardation layer having a thickness of 1 μm on the adhesive alignment layer, thereby producing a retardation film.

(4) Example 4
As the polymerizable monomer, a mixture of 30 parts by weight of tricyclodecane dimethanol diacrylate (carbon content ratio = 4.5) to 100 parts by weight of pentaerythritol triacrylate (carbon content ratio = 1.86) was used. Except for this, a retardation film was produced in the same manner as in Example 3.
Here, the pentaerythritol triacrylate was used as an alignment control compound for imparting alignment to the adhesive alignment layer.

(5) Comparative Example 1
A retardation film was produced in the same manner as in Example 1 except that pentaerythritol triacrylate (carbon content ratio = 1.86) was used as the polymerizable monomer.

(6) Comparative Example 2
A retardation film was produced in the same manner as in Example 3 except that neopentyl glycol diacrylate (carbon content ratio = 1.86) was used as the polymerizable monomer.

(7) Evaluation Liquid crystal orientation evaluation and adhesiveness evaluation were performed about the retardation film produced in the said Example and comparative example. In the liquid crystal orientation evaluation, nx, ny, and nz of the retardation film were calculated using an automatic birefringence measuring device KOBRA. If nx>nz> ny, it was determined that a positive C plate function was imparted. .
As a result, it was confirmed that the positive C plate function was imparted to any of the retardation films prepared in the above Examples and Comparative Examples.

In addition, the above-mentioned adhesion evaluation is performed by placing 1 mm square cuts in a grid pattern, and attaching an adhesive tape (product name: cello tape (registered trademark)) manufactured by Nichiban Co., Ltd. to the surface of the retardation layer, and thereafter adhesive tape Was peeled off and visually observed. At this time, the evaluation was performed based on the number of cells in the portion where the adhesion was not peeled / the number of cells in the region where the tape was attached.
The evaluation results are shown in Table 1.

  As shown in Table 1, although the retardation film produced in the said Example had favorable adhesiveness, the adhesiveness produced in the said comparative example was not what can endure practicality.

It is the schematic which shows an example of the retardation film of this invention. It is the schematic which shows the other example of the retardation film of this invention. It is the schematic which shows a part of common liquid crystal display device typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Adhesive orientation layer 3 ... Retardation layer 10, 20 ... Retardation film 21 ... Transparent substrate 22 ... Adhesion functional layer 23 ... Retardation layer

Claims (3)

A transparent substrate made of cycloolefin resin;
An adhesive alignment layer formed so as to be in contact with the transparent substrate, containing a polymer of a polymerizable monomer, and further having an alignment regulating force for homeotropic alignment of the liquid crystal material;
Between any refractive index nx and ny in the x direction, y direction, and refractive index nz in the thickness direction, which are formed on the adhesive alignment layer and contain a liquid crystal material, and are orthogonal to each other in the in-plane direction, a retardation film having a relationship of nx = ny <nz, and a retardation film,
The polymerizable monomer has at least one polymerizable functional group selected from the group consisting of the following formulas (I), (II), (III), (IV), and (V); The value obtained by dividing the number N of carbon atoms constituting the polymerizable monomer by the number M of elements other than carbon and hydrogen constituting the polymerizable monomer (N / M) is 3 or more. the film.

(In the above formula, R ¹ , R ² , and R ³ represent a methyl group or hydrogen. R ⁴ represents a hydrogen, a methyl group, or an ethyl group.)   The retardation film according to claim 1, wherein a surfactant is contained in the adhesive alignment layer. A transparent substrate made of cycloolefin resin;
An adhesion functional layer formed so as to be in contact with the transparent substrate and containing a polymer of a polymerizable monomer;
A refractive index nx and ny in any x direction and y direction orthogonal to each other in the in-plane direction, and a refractive index nz in the thickness direction are formed on the adhesion functional layer and contain a liquid crystal material having homeotropic alignment. A retardation film having a relationship of nx = ny <nz, and a retardation film,
The polymerizable monomer has at least one polymerizable functional group selected from the group consisting of the following formulas (I), (II), (III), (IV), and (V); The value obtained by dividing the number N of carbon atoms constituting the polymerizable monomer by the number M of elements other than carbon and hydrogen constituting the polymerizable monomer (N / M) is 3 or more. the film.

(In the above formula, R ¹ , R ² , and R ³ represent a methyl group or hydrogen. R ⁴ represents a hydrogen, a methyl group, or an ethyl group.)

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