Optical film and method for producing the same, polarizing plate and display device

Abstract

An optical film containing a cycloolefin resin and a compound having a structure represented by general formula (1). (Y represents an aromatic heterocycle having 5-20 members, X1 and X2 represent a substituted or unsubstituted aromatic ring group that forms a single bond with atoms constituting Y, and R represents a hydrogen atom, a cyano group, a hydroxy group, or a C1-10 alkyl group, or, when there are two, O=. n is the valence of Y and is an integer equal to or greater than 2. An angle formed by a straight line L 1 connecting the center of Y and the center of the ring located farthest from Y among the rings constituting X 1 and a straight line L2 connecting the center of Y and the center of the ring located farthest from Y among the rings constituting X2 is 110-145°.)

Description

[Technical field]

[0001] The present invention relates to an optical film and a manufacturing method thereof, a polarizing plate, and a display device. More specifically, the present invention relates to an optical film that is sufficiently thin and has a desired optical compensation value (retardation) and has good adhesion to a polarizer, a manufacturing method thereof, and a polarizing plate and a display device including the optical film. [Background technology]

[0002] In recent years, there has been a demand for thinner display devices, and accordingly, there has been a demand for thinner resin protective films used in polarizing plates provided in display devices. In polarizing plates, protective films are arranged on both sides of a polarizer by adhesion or the like. As protective films, optical films with controlled retardation are generally used to compensate for changes in retardation due to viewing angles. The optical films are usually resin films that have been processed by uniaxial or biaxial stretching or the like, and the magnitude relationship of three-dimensional refractive indexes (index ellipsoid) is controlled according to the conditions of use.

[0003] Conventionally, cellulose-based resin films have been used as protective films for such polarizing plates, but cellulose-based resins have high moisture permeability and are vulnerable to environmental changes, and in recent years, cycloolefin resins have been attracting attention.

[0004] Here, a casting method is widely used as a method for producing an optical film using a cycloolefin resin. In the casting method, means for thinning a cycloolefin resin film include reducing the film thickness at the initial stage of casting, or increasing the stretch ratio of the film.

[0005] However, when an optical film made of a cycloolefin resin is produced by a method in which the initial thickness of the film is thinned, the stretching ratio is low, and it is difficult to obtain a desired optical compensation value. In addition, there is room for improvement in the adhesion between the optical film and the polarizer, possibly due to the stretching ratio.

[0006] In such optical films, attempts have been made to increase the retardation of the obtained optical film by adding a retardation increasing agent to the resin that is the main component of the optical film (see, for example, Patent Document 1). However, when the retardation increasing agent disclosed in Patent Document 1 was used to investigate the problem that occurs when an optical film made of a cycloolefin resin is produced by the method of reducing the film thickness at the initial casting stage, the problem could not be solved. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2007-249180 A Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide an optical film, particularly an optical film mainly made of a cycloolefin resin, which has a sufficiently thin film thickness and a desired optical compensation value (retardation), and has good adhesion to a polarizer, and a manufacturing method thereof. Also, the present invention is to provide a polarizing plate and a display device which are made thin while maintaining their performance by using the optical film. [Means for solving the problem]

[0009] In the course of investigating the causes of the above problems in order to solve the above problems, the present inventors discovered that by combining a cycloolefin resin with a compound having a specific structure to form an optical film, it is possible to obtain an optical film that is thin and has a high retardation, and that also has good adhesion to a polarizer, and thus arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0010] 1. Cycloolefin resin and the following structure Formula (1) ~(5) Represented by Chemical and an optical film comprising the compound. [ka]

[0014] 2 The cycloolefin resin is a first polymer having a polar group. In the section The optical film described herein.

[0015] 3 .Section 1 or No. In item 2 A method for producing the optical film according to the present invention, structure Formula (1) ~(5) Represented by Chemical a dope containing the mixture, the cycloolefin resin, and a solvent, the dope being cast onto a support to obtain an unstretched film, and the unstretched film being stretched.

[0016] 4 A polarizer and a first element disposed on at least one surface of the polarizer. or No. In item 2 and a polarizing plate comprising the optical film according to the present invention.

[0017] 5 .Section 1 or No. In item 2 A display device comprising the optical film described above. Effect of the Invention

[0018] According to the above-mentioned means of the present invention, it is possible to provide an optical film having a sufficiently thin film thickness, a desired optical compensation value (retardation), and good adhesion to a polarizer, particularly an optical film mainly made of a cycloolefin resin, and a manufacturing method thereof. Furthermore, by using the optical film, it is possible to provide a polarizing plate and a display device that are thinned while maintaining the performance. Although the mechanism by which the effects of the present invention are expressed or the mechanism by which the effects of the present invention are acted upon has not been clarified, it is speculated as follows.

[0019] The optical film of the present invention is characterized by containing a cycloolefin resin and a compound having a structure represented by the above general formula (1) (hereinafter also referred to as compound (1)).

[0020] Compound (1) is easily polarized and oriented because ring Y located at the center of compound (1) is an aromatic heterocycle. Compound (1) is also easily polarized and oriented because ring Y ... 1 and X 2 The center of Y and X 1 A straight line L1 connecting the center of the ring that is farthest from Y among the rings that make up the ring, and a straight line L2 connecting the center of Y and X 2 The rings are bonded such that the angle formed by a straight line L2 connecting the center of the ring that is located farthest from Y among the rings that constitute the rings is within a range of 110° to 145°.

[0021] The optical film of the present invention containing a cycloolefin resin and compound (1) is usually obtained by stretching a composition containing a cycloolefin resin and compound (1). When compound (1) has the above-mentioned structure, compound (1) can physically interact with the cycloolefin resin when the cycloolefin resin is stretched. As a result, the cycloolefin resin is sufficiently oriented in the stretching direction in the obtained optical film, and the retardation of the optical film can be improved. In addition, compound (1) follows the cycloolefin resin and is uniformly oriented in the stretching direction, which is presumed to improve adhesion to other members, specifically polarizers. [Brief description of the drawings]

[0022] [Figure 1A] FIG. 1 is an xy coordinate diagram used to determine the center of ring Y (pyridine ring) in compound 1-1. [Figure 1B] FIG. 2 is an xy coordinate diagram used to determine the center of the ring (benzimidazole ring) located farthest from Y in X1 of compound 1-1. [Figure 1C]FIG. 1 is a diagram showing the angle θ between X1 and X2 with respect to the ring Y in compound 1-1. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of the configuration of the polarizing plate of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The optical film of the present invention is characterized by containing a cycloolefin resin and a compound having a structure represented by the above general formula (1). This feature is a technical feature common to each of the following embodiments.

[0024] In an embodiment of the present invention, from the viewpoint of further improving the retardation of the optical film, 1 and X 2 In addition, in an embodiment of the present invention, from the viewpoint of exerting the effects of the present invention, it is preferable that at least one of the X 1 and X 2 It is preferable that at least one of the groups contains an aromatic fused ring.

[0025] In an embodiment of the present invention, from the viewpoint of further improving the retardation of the optical film, the Y is a monocyclic ring having 6 members and one heteroatom, and the X 1 and X 2 are preferably bonded to carbon atoms on either side of the heteroatom.

[0026] In an embodiment of the present invention, from the viewpoint of adhesion to other members, specifically to a polarizer, in the optical film, the cycloolefin resin preferably has a polar group.

[0027] As a manufacturing method for producing the optical film of the present invention, from the viewpoint of expressing the effects of the present invention, it is preferable that the manufacturing method includes preparing a dope containing a compound having a structure represented by the general formula (1), the cycloolefin resin, and a solvent, casting the dope on a support to obtain an unstretched film, and stretching the unstretched film obtained.

[0028] The polarizing plate of the present invention is characterized by comprising a polarizer and the optical film of the present invention arranged on at least one surface of the polarizer. The display device of the present invention is characterized by comprising the optical film of the present invention. This allows the polarizing plate and the display device to be made thinner while maintaining their performance.

[0029] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as the lower limit and upper limit.

[0030] [Outline of the Optical Film of the Present Invention] The optical film of the present invention is characterized by containing a cycloolefin resin and a compound (1). In the optical film of the present invention, the compound (1) acts as a retardation increasing agent. The optical film of the present invention may contain a retardation increasing agent other than the compound (1). Furthermore, the optical film of the present invention may contain various additives other than the retardation increasing agent within a range that does not impair the effects of the present invention.

[0031] The components of the present invention will now be described in detail.

[0032] (Compound (1)) Compound (1) is a compound having a structure represented by the following general formula (1). In this specification, a compound having a structure represented by general formula (1) is also referred to as compound (1). Similarly, a compound having a structure represented by formula (X 1 ) is a group having a structure represented by the group (X 1 The same applies to other compounds and groups. The ring represented by Y is also sometimes called ring Y.

[0033] [ka]

[0034] In the general formula (1), Y represents an aromatic heterocycle having 5 to 20 members. 1 and X2 Each independently represents a substituted or unsubstituted aromatic ring group which forms a single bond with an atom constituting Y. Each independently represents a hydrogen atom, a cyano group, a hydroxyl group, or an alkyl group having 1 to 10 carbon atoms. When two or more R are present, two R may be present as oxo groups (=O) instead of these groups. n is the valence of Y and is an integer of 2 or more. The distance between the center of Y and X 1 A straight line L1 connecting the center of the ring that is farthest from Y among the rings that make up the ring, and a straight line L2 connecting the center of Y and X 2 The angle formed by a straight line L2 connecting the center of the ring that is located farthest from Y among the rings constituting the ring is within a range of 110° to 145°.

[0035] Below, the center of Y and X 1 A straight line L1 connecting the center of the ring that is farthest from Y among the rings that make up the ring, and a straight line L2 connecting the center of Y and X 2 The angle between the center of the ring that is farthest from Y and the line L2 that connects the center of the ring that constitutes the ring, X, is defined as the angle between the center of the ring and the ring Y. 1 and X 2 This angle is also called the angle θ.

[0036] As described below, Y is, for example, a monocyclic ring or a fused ring. In this specification, the "center of Y" is defined as follows for a monocyclic ring and a fused ring. In the case of a monocyclic ring, the "center of Y" is the geometric center. Here, the geometric center is synonymous with the geometric center in mathematics, and is, for example, the position of the xy coordinates obtained by arithmetically averaging the xy coordinates of all vertices belonging to a figure in a two-dimensional Euclidean space determined by two components x and y, for example, a hexagonal figure of a six-membered ring. In the case of Y being a fused ring, the point equidistant from the geometric center of each ring constituting the fused ring is the "center of Y".

[0037] Compound (1) is easily polarized and oriented because ring Y located at the center of compound (1) is an aromatic heterocycle. Compound (1) is also easily polarized and oriented because ring Y ... 1 and X 2By bonding these together so that the angle θ falls within the above-mentioned specific range, the orientation of the cycloolefin resin in the stretching direction can be promoted. The effect of the present invention can be obtained by the action of the compound (1).

[0038] Ring Y is an aromatic heterocycle having 5 to 20 members, and may be a monocycle or a condensed ring. The number of members of ring Y is preferably 5 to 10, and more preferably 5 or 6.

[0039] The heteroatom of the ring Y includes a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, a bromine atom, etc., and is preferably a nitrogen atom, an oxygen atom, or a sulfur atom, and is particularly preferably a nitrogen atom from the viewpoint of the adhesiveness of the obtained optical film. The number of heteroatoms of the ring Y is preferably 1 to 6, and more preferably 1 to 3. Specific examples of the ring Y include the following aromatic heterocycles.

[0040] Specific examples of the 5-membered monocyclic aromatic heterocycle include a furan ring, a pyrrole ring, an imidazole ring, a thiophene ring, a pyrazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, and an isothiazole ring.

[0041] Specific examples of the 6-membered monocyclic aromatic heterocycle include a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, a triazine ring, a pyran ring, a thiopyran ring, an oxazine ring, and a thiazine ring.

[0042] Specific examples of the 7-membered monocyclic aromatic heterocycle include an azepine ring, an oxepine ring, and a thiopine ring. Specific examples of the 8-membered monocyclic aromatic heterocycle include an azocine ring, an oxocine ring, and a thiepine ring. Specific examples of the 9-membered monocyclic aromatic heterocycle include an azonine ring, an oxonine ring, and a thionine ring.

[0043] Examples of the two fused rings include a fused ring of a five-membered ring and a five-membered ring, such as a dihydropyrrolopyrrole ring, a furopyrrole ring, and a thienopyrrole ring.

[0044] Examples of condensed rings of 5-membered and 6-membered rings include a benzofuran ring, an isobenzofuran ring, an indole ring, an isoindole ring, a benzothiophene ring, a benzimidazole ring, an azaindole ring, a pyrazolopyridine ring, a pyrazolopyrimidine ring, a purine ring, an indazole ring, a benzoxazole ring, a benzisoxazole ring, a benzothiazole ring, a benzisothiazole ring, and a benzotriazole ring.

[0045] Examples of the condensed ring of a 6-membered ring include a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, a cinnoline ring, a chromene ring, an isochromene ring, a benzoxazine ring, a pyridopyrimidine ring, and a pyridopyrazine ring.

[0046] Examples of the three-ring condensed ring include a carbazole ring, a dibenzofuran ring, an acridine ring, a phenazine ring, a phenoxazine ring, a phenothiazine ring, and a phenoxathiin ring.

[0047] Y is preferably a 6-membered monocyclic aromatic heterocycle, preferably containing one heteroatom, and particularly preferably a pyridine ring.

[0048] In the general formula (1), n ​​represents the valence of the ring Y. n depends on the type of the ring Y shown above. For example, when the ring Y is a pyridine ring, n is 5, and when the ring Y is a triazine ring, n is 3. 1 and X 2 In order to bond to via a single bond, n is an integer of 2 or more.

[0049] In the general formula (1), R is X bonded to the ring Y. 1 and X 2 The number of R is a number obtained by subtracting 2 from the valence n of the ring Y, that is, n-2. Each R is independently a hydrogen atom, a cyano group, a hydroxyl group, or an alkyl group having 1 to 10 carbon atoms. When two or more R are present, two R may be present as an oxo group (=O) instead of these groups.

[0050] When there are multiple R's, the multiple R's may be the same or different. When R's is an alkyl group, the alkyl group may be linear, branched or cyclic, or may be a combination of these. When R's is an alkyl group, it is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms. From the viewpoint of availability, it is preferable that all of n-2 R's are hydrogen atoms.

[0051] X 1 and X 2 X is a substituted or unsubstituted monovalent aromatic ring group. 1 and X 2 It is preferable that at least one of X has an aromatic heterocycle. 1 and X 2 It is preferable that at least one of X has an aromatic condensed ring. 1 and X 2 It is preferable that at least one of X is an aromatic condensed ring containing a heteroatom. 1 and X 2 may be the same or different, and are preferably the same from the viewpoint of optical compensation or ease of production.

[0052] X 1 and X 2 The bonding positions of the rings Y and X are 1 A straight line L1 connecting the center of the ring that is farthest from Y among the rings that make up the ring, and a straight line L2 connecting the center of the ring Y and X 2 The angle between the center of the ring that is farthest from Y and the line L2 that connects the center of the ring that constitutes X and the ring Y. 1 and X 2 This is the position where the angle θ between the compound and the cycloolefin resin becomes 110° or more and 145° or less. The angle θ is preferably 110 to 130°, and more preferably 110 to 125°. Compounds with angle θ outside the above range cannot contribute to the orientation of the cycloolefin resin in the optical film, and the compound itself is not sufficiently oriented during stretching.

[0053] X 1 and X 2 The ring constituting X may be a single ring or a condensed ring.1 and X 2 If the ring bonded to the ring Y is an aromatic ring, an alicyclic ring may be bonded to the ring Y. 1 and X 2 It is preferable that all of the rings constituting X are aromatic rings. 1 The ring that is the furthest from Y among the rings that constitute the ring X will be referred to as "ring X". 1L In this specification, X 1 The ring X is the ring that is the furthest from Y among the rings that make up 1L The "center of ring X" is defined as follows for a single ring and a fused ring. 1L If is a monocyclic ring, its center is the geometric center. 1L If is a condensed ring, the points equidistant from the geometric centers of the rings that compose the condensed ring are ring X. 1L is the center of

[0054] Similarly, X 2 The ring that is located farthest from Y among the rings constituting the rings is hereinafter referred to as "ring X". 2L In this specification, X 2 The ring X is the ring that is the furthest from Y among the rings that make up 2L The "center of ring X" is defined as follows for a single ring and a fused ring. 2L If is a monocyclic ring, its center is the geometric center. 2L If is a condensed ring, the points equidistant from the geometric centers of the rings that compose the condensed ring are ring X. 2L is the center of

[0055] The angle θ is the angle X in the ring Y 1 and X 2 In addition to the bonding position of X 1 and X 2 Therefore, the following X 1 and X 2 By adjusting the bonding position in ring Y taking into consideration the structure of the above, the angle θ is adjusted to fall within the above range.

[0056] For example, if ring Y is a six-membered ring, X 1 and X 2Depending on the structure, in order to adjust the angle θ to the above range, X 1 and X 2 is preferably bonded to the meta position, and more preferably to carbon atoms on both sides of the heteroatom from the viewpoint of adhesiveness of the resulting optical film.

[0057] Below, X 1 The following will be explained in detail. 2 This also applies to. X 1 is a substituted or unsubstituted monovalent aromatic ring group. 1 X has a structure in which at least an aromatic ring is bonded to Y through a single bond, and a hydrogen atom bonded to the aromatic ring may be substituted with a substituent. 1 For example, X binds to Y. 11 and X 11 X 12 and further substituted with an aromatic ring group or an alicyclic group represented by X 12 X 13 In the structure in which a plurality of ring structures are bonded together by a single bond, X may be substituted with an aromatic ring group or an alicyclic group represented by the following formula: 1 can be expressed, for example, by the following formula (X).

[0058] Formula (X) -X 11 -X 12 -……-X 1L-1 -X 1L In formula (X), X 11 is a divalent aromatic ring group bonded to ring Y, and X 12 and X 1L-1 is a divalent aromatic or alicyclic group, X 1L is a monovalent aromatic or alicyclic group. L represents the number of rings contained in the group represented by formula (X). X 1L is the terminal ring and is the ring furthest from Y.

[0059] X 1 The number of rings including an aromatic ring contained in the formula (X), for example, L in the formula (X) may be 1 or 2 or more. 1The number of rings that Y and X have in compound (1) is preferably 1 to 3, and more preferably 1 to 2. 1 , X 2 The division of X 1 , X 2 The number of rings in is equal, or X 1 and X 2 The rings are cut so that the difference in the number of rings between them is 1. That is, in compound (1), ring Y is a ring located approximately in the center of the rings constituting compound (1).

[0060] As described above, from the viewpoint of optical compensation, X 1 For example, X in formula (X) 11 ~X 1L are preferably all aromatic rings. In that case, X 1 The one or more aromatic rings contained in may be a single ring or a condensed ring. From the viewpoint of optical compensation, it is preferable that at least one of the aromatic rings is a condensed ring.

[0061] X 1 In the above formula, the aromatic ring may contain a heteroatom, and preferably contains a heteroatom. Examples of the heteroatom include a nitrogen atom, an oxygen atom, and a sulfur atom, and from the viewpoint of optical compensation, a nitrogen atom is particularly preferable.

[0062] X 1 In the formula, the number of heteroatoms per aromatic ring is preferably 1 to 5, and more preferably 1 to 2. 1 When the compound (1) has a heteroatom, the compound (1) itself is easily oriented in the optical film when the compound (1) is formed into an optical film, which is preferable.

[0063] X 1 The case where all of the rings in X are aromatic rings will be explained using a group having a structure represented by formula (X). 11 ~X 1L is a single ring or a condensed ring, and it is preferable that any one of them is a condensed ring; X 11 It is particularly preferred that X is a condensed ring. 11 ~X 1LEach of X preferably contains 1 to 5, more preferably 1 to 2 heteroatoms. 11 It is preferred that X has a heteroatom adjacent to the carbon atom bonded to Y. Alternatively, X 11 In the present invention, a structure in which a heteroatom is bonded to Y is also preferred.

[0064] X 1 In the above, the hydrogen atom bonded to the aromatic ring may be substituted with a substituent. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cyano group, and an amino group. The alkyl group contained in the alkyl group and alkoxy group may be linear or branched, or may have a structure in which these are combined. When the substituent is an alkyl group or an alkoxy group, the number of carbon atoms is more preferably 1 to 5. X 1 From the viewpoint of heat resistance, it is preferable that the group has no substituent.

[0065] X 1 Examples of the aromatic ring contained in the aryl group include a monocyclic aromatic ring not containing a heteroatom such as a benzene ring, and examples of the aromatic condensed ring include a naphthalene ring and an anthracene ring.

[0066] Examples of the aromatic ring containing a heteroatom include the aromatic heterocycles exemplified above as Y. X 1 When X has an aromatic ring containing a heteroatom, 1 It is preferred that X has a heteroatom adjacent to the carbon atom that bonds to ring Y. Alternatively, X 1 In the present invention, a structure in which a heteroatom is bonded to Y is also preferred.

[0067] As compound (1), compounds 1-1 to 1-6 having structures represented by the following formulas 1-1 to 1-6 are preferred.

[0068] [ka]

[0069] In such compounds 1-1 to 1-6, the Y center and X 1A straight line L1 connecting the center of the ring that is farthest from Y among the rings that make up the ring, and a straight line L2 connecting the center of Y and X 2 The angle between the center of the ring that is farthest from Y and the line L2 that connects the center of the ring that constitutes X and the ring Y. 1 and X 2 The angle θ will be explained below.

[0070] In the above compound 1-1, ring Y is a pyridine ring. In compound 1-1, the aromatic ring group located to the left of the pyridine ring is X. 1 The aromatic ring group on the right side is X 2 Then, X 1 and X 2 are aromatic ring groups with the 2-position of the benzimidazole bonded. And X 1 and X 2 Each of the rings constituting the ring is X 1 and X 2 It is the ring that is located furthest from Y among the rings that constitute the ring.

[0071] Hereinafter, a method for determining the center of ring Y (pyridine ring) in compound 1-1 will be described with reference to FIGS. 1A to 1C. 1 and X 2 A method for determining the center of the ring (benzimidazole ring) located farthest from Y in compound 1-1, and a method for determining the center of X relative to ring Y in compound 1-1. 1 and X 2 A method for determining the angle θ will be described below.

[0072] FIG. 1A shows an xy coordinate diagram used to determine the center of ring Y (pyridine ring) in compound 1-1. The center Yc of the pyridine ring is the geometric center of the hexagonal pyridine ring, and is the position of the xy coordinate obtained by arithmetically averaging the xy coordinates of all vertices belonging to the hexagon, i.e., (x1, y1), (x2, y2), (x3, y3), (x4, y4), (x5, y5), and (x6, y6). Specifically, the x coordinate of the center Yc of the pyridine ring is represented by (x1+x2+x3+x4+x5+x6) / 6, and the y coordinate is represented by (y1+y2+y3+y4+y5+y6) / 6.

[0073] FIG. 1B shows X in compound 1-1. 1 The xy coordinate diagram used to determine the center of the ring (benzimidazole ring) located farthest from Y in the above formula is shown below. The coordinates of each vertex belonging to the benzimidazole ring are indicated as (x1, y1), (x2, y2), (x3, y3), (x4, y4), (x5, y5), (x6, y6), (x7, y7), (x8, y8), and (x9, y9).

[0074] Center X of the benzimidazole ring 1 To find c, first determine the geometric center X of the benzene ring. 1b c and the geometric center X of the imidazole ring 1a c is calculated in the same manner as above. Specifically, the geometric center X of the benzene ring is 1b The x coordinate in c is expressed as (x4+x5+x6+x7+x8+x9) / 6, and the y coordinate is expressed as (y4+y5+y6+y7+y8+y9) / 6. The geometric center X of the imidazole ring 1a The x coordinate in c is expressed as (x1+x2+x3+x4+x5) / 5, and the y coordinate is expressed as (y1+y2+y3+y4+y5 / 5. Next, the geometric center X of the benzene ring 1b c and the geometric center X of the imidazole ring 1a Draw a line connecting c and the point that bisects the line is the center X of the benzimidazole ring. 1 c.

[0075] X in compound 1-1 2 The center X of the ring (benzimidazole ring) located farthest from Y in 2 c is also the above X 1 As in the case of X 2 Geometric center X of the benzene ring in 2b c and the geometric center X of the imidazole ring 2a Find c, draw a line connecting these two points, and divide the line into two equal parts by X. 2 Center X of the benzimidazole ring in 2 Let's call it c.

[0076] In compound 1-1, X to ring Y 1 and X 2As shown in Figure 1C, the angle θ between the center Yc of the pyridine ring and the center X of the benzimidazole ring located to the left of it is 1 The straight line L1 connecting Yc and Yc, the center of the pyridine ring, and the center X of the benzimidazole ring to the right of Yc 2 The angle θ in compound 1-1 thus determined is 112°.

[0077] In compound 1-2, ring Y is a pyridine ring, and the aromatic ring group on the left side of the pyridine ring is X. 1 The aromatic ring group on the right side is X 2 Let X 1 consists of two benzimidazole rings, and X 2 is composed of two benzene rings. In compound 1-2, X to ring Y 1 and X 2 The angle θ between the center of the pyridine ring and the X 1 A straight line L1 connecting the center of the benzimidazole ring that is located farthest from the pyridine ring among the two benzimidazole rings that constitute the compound, and a straight line L2 connecting the center of the pyridine ring and X 2 The angle θ in compound 1-2 is 123°.

[0078] In compound 1-3, ring Y is a fused ring. Ring Y in compound 1-3 is a pyrazolo[1,5-a]pyrimidine ring, and the aromatic ring group located on the left side (5th position) of the pyrazolo[1,5-a]pyrimidine ring is X. 1 The aromatic ring group on the right side (position 2) is X 2 In compound 1-3, the pyrazolo[1,5-a]pyrimidine ring is X 1 , X 2 The substituents (R) other than X are -CH3 and =O. 1 is a 2-pyridyl group, and X 2 is a phenyl group. In compound 1-3, X to ring Y is 1 and X 2The angle θ is the angle between a straight line L1 connecting the center of the pyrazolo[1,5-a]pyrimidine ring and the center of the pyridine ring located to the left of it, and a straight line L2 connecting the center of the pyrazolo[1,5-a]pyrimidine ring and the center of the benzene ring located to the right of it. The angle θ in compound 1-3 thus determined is 144°.

[0079] The angle θ determined for compounds 1-4 to 1-6 in the same manner as above was 120° for compound 1-4, 115° for compound 1-5, and 123° for compound 1-6.

[0080] Among the above compounds 1-1 to 1-6, the compound having a high retardation value, for example, a retardation value Ro, is preferably a compound having a pyridine ring, and X 1 and X 2 Compounds 1-1, 1-2 and 1-4 are preferred in that at least one of them contains a condensed ring. 1 and X 2 are bonded, and at least one of them contains a condensed ring. Furthermore, from the viewpoint of better adhesiveness, compound 1-2 is particularly preferred.

[0081] In the optical film of the present invention, the compound (1) may be used alone or in combination of two or more. From the viewpoint of preventing bleed-out and precipitation while exerting the above-mentioned effects of the present invention, the compound (1) is added in a ratio of, for example, 0.5 to 10 mass%, preferably 2 to 6 mass%, relative to the cycloolefin resin (100 mass%), which is the main raw material of the optical film.

[0082] In the optical film of the present invention, the compound (1) acts as a retardation enhancer as described above. In the optical film of the present invention, the compound (1) may be used in combination with other retardation enhancers other than the compound (1) within a range that does not impair the effects of the present invention. Examples of other retardation enhancers include discotic or rod-shaped compounds. As the discotic or rod-shaped compound, a compound having at least two aromatic rings can be preferably used as a retardation enhancer.

[0083] The retardation increasing agent preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

[0084] (Cycloolefin resin) The optical film of the present invention contains a cycloolefin resin as a resin that mainly constitutes the optical film. The optical film of the present invention may contain a resin other than the cycloolefin resin as long as the effect of the present invention is not impaired as described below, but the resin is preferably composed of only the cycloolefin resin. The cycloolefin resin used in the present invention includes a (co)polymer having a structure represented by the following general formula (4).

[0085] [ka]

[0086] [In the formula, R 1 ~R 4 are each independently a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, a silyl group, or a hydrocarbon group substituted with a polar group (i.e., a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, or a silyl group). 1 ~R 4 Two or more of R may be bonded to each other to form an unsaturated bond, a monocyclic ring, or a polycyclic ring, and the monocyclic ring or polycyclic ring may have a double bond or form an aromatic ring. 1 and R2 With or R 3 and R 4 and m may form an alkylidene group. p and m are integers of 0 or more.

[0087] The cycloolefin resin according to the present invention preferably has a polar group. As the (co)polymer having the structure represented by the above general formula (4), in the general formula (4), R 1 and R 3 is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 to 2 carbon atoms; R 2 and R 4 is a hydrogen atom or a monovalent organic group, and R 2 and R 4 At least one of the above represents a polar group having polarity other than a hydrogen atom or a hydrocarbon group, m is an integer of 0 to 3, and p is an integer of 0 to 3, more preferably m+p=0 to 4, further preferably 0 to 2, and particularly preferably m=1 and p=0. The specific monomer where m=1 and p=0 is preferred in that the resulting cycloolefin resin has a high glass transition temperature and excellent mechanical strength.

[0088] Examples of the polar group of the specific monomer include a carboxy group, a hydroxy group, an alkoxycarbonyl group, an allyloxycarbonyl group, an amino group, an amide group, and a cyano group, and these polar groups may be bonded via a linking group such as a methylene group. Examples of the polar group include a hydrocarbon group to which a polar divalent organic group such as a carbonyl group, an ether group, a silyl ether group, a thioether group, and an imino group is bonded as a linking group. Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group, or an allyloxycarbonyl group is preferred, and an alkoxycarbonyl group or an allyloxycarbonyl group is particularly preferred.

[0089] In addition, R 2 and R 4 At least one of the formula -(CH2) n COOR 10The monomer having a polar group represented by the formula (I) is preferred in that the resulting cycloolefin resin has a high glass transition temperature, low moisture absorption, and excellent adhesion to various materials. 10 is a hydrocarbon group, preferably an alkyl group, having 1 to 12 carbon atoms, more preferably 1 to 4, and particularly preferably 1 or 2. n is an integer of 0 to 5, and preferably 0 to 2.

[0090] Specific examples of the copolymerizable monomer include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, and dicyclopentadiene.

[0091] The cycloolefin preferably has 4 to 20 carbon atoms, and more preferably has 5 to 12 carbon atoms.

[0092] In the present invention, the cycloolefin resins can be used alone or in combination of two or more kinds.

[0093] The preferred molecular weight of the cycloolefin resin according to the present invention is, in terms of intrinsic viscosity [η]inh, 0.2 to 5 dL / g, more preferably 0.3 to 3 dL / g, and particularly preferably 0.4 to 1.5 dL / g; the polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 8,000 to 100,000, more preferably 10,000 to 80,000, and particularly preferably 12,000 to 50,000; and the weight average molecular weight (Mw) is in the range of 20,000 to 300,000, more preferably 30,000 to 250,000, and particularly preferably 40,000 to 200,000.

[0094] By having the intrinsic viscosity [η]inh, number average molecular weight and weight average molecular weight within the above ranges, the heat resistance, water resistance, chemical resistance and mechanical properties of the cycloolefin resin, as well as the moldability as the optical film of the present invention, are improved.

[0095] The glass transition temperature (Tg) of the cycloolefin resin according to the present invention is usually 110° C. or higher, preferably 110 to 350° C., more preferably 120 to 250° C., and particularly preferably 120 to 220° C. If the Tg is less than 110° C., it is not preferable because it may be deformed when used under high temperature conditions or by secondary processing such as coating or printing. On the other hand, if the Tg exceeds 350° C., molding becomes difficult and the resin is more likely to deteriorate due to heat during molding.

[0096] The cycloolefin resin may be blended with specific hydrocarbon resins, for example, those described in JP-A-9-221577 and JP-A-10-287732, or known thermoplastic resins, thermoplastic elastomers, rubbery polymers, organic fine particles, inorganic fine particles, etc., within the scope not impairing the effects of the present invention, and may also contain additives such as specific wavelength dispersion agents, sugar ester compounds, rubber particles, etc.

[0097] As the cycloolefin resin described above, commercially available products can be preferably used. Examples of commercially available products include those sold by JSR Corporation under the trade names ARTON G, ARTON F, ARTON R, and ARTON RX, and those sold by Zeon Corporation under the trade names ZEONOR ZF14, ZF16, ZEONEX 250, and ZEONEX 280. These can be used.

[0098] (Additives) The optical film of the present invention may contain a conventionally known retardation enhancer other than the compound (1) within a range that does not impair the effects of the present invention. The optical film of the present invention may further contain various additives other than the retardation enhancer. The additives include a plasticizer, an ultraviolet absorber, an antioxidant, an antistatic agent, etc.

[0099] [Plasticizer] In the optical film of the present invention, a plasticizer can be used to improve the fluidity of the composition during production and the flexibility of the optical film. Examples of the plasticizer include phthalate esters, fatty acid esters, trimellitates, phosphate esters, polyesters, and epoxy types.

[0100] Among these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance to phthalate plasticizers such as dioctyl phthalate, but are somewhat inferior in plasticizing effect and compatibility.

[0101] Therefore, by selecting or combining these plasticizers depending on the application, the composition can be used in a wide range of applications.

[0102] Polyester plasticizers are the reaction products of mono- to tetra-carboxylic acids and mono- to hexa-valent alcohols, but the most commonly used are those obtained by reacting dicarboxylic acids with glycols. Representative dicarboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, and sebacic acid.

[0103] In particular, the use of adipic acid, phthalic acid, etc., provides a product with excellent plasticizing properties. Examples of glycols include ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, dipropylene, etc. These divalent carboxylic acids and glycols may be used alone or in combination.

[0104] The ester-based plasticizer may be any of ester, oligoester, and polyester types, and the molecular weight is preferably in the range of 100 to 10,000, and more preferably in the range of 600 to 3,000. If the molecular weight is in this range, the plasticizing effect is large. The molecular weight of the polyester is the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0105] In addition, the viscosity of the plasticizer is correlated with the molecular structure and molecular weight, but in the case of adipic acid plasticizers, the range of 200 to 5000 mPa·s (25°C) is preferable due to compatibility and plasticization efficiency. Furthermore, several polyester plasticizers may be used in combination.

[0106] The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass per 100 parts by mass of the cycloolefin resin, which is the main raw material of the optical film of the present invention. If the amount of the plasticizer added exceeds 30 parts by mass, the surface becomes sticky, which is not practically preferable.

[0107] [Ultraviolet absorber] The optical film of the present invention preferably contains an ultraviolet absorbing agent, and examples of the ultraviolet absorbing agent used include benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based agents. For example, triazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone can be exemplified.

[0108] Among the ultraviolet absorbents, those with a molecular weight of 400 or more are less likely to volatilize due to their high boiling point and are less likely to scatter during high-temperature molding, and therefore can effectively improve weather resistance with the addition of a relatively small amount.

[0109] Examples of ultraviolet absorbers with a molecular weight of 400 or more include benzotriazoles such as 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2-benzotriazole and 2,2-methylenebis[4-(1,1,3,3-tetrabutyl)-6-(2H-benzotriazol-2-yl)phenol], hindered amines such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, and further 2-(3,5-di-t-butyl-4-hiperidinyl). Examples of the hybrid compounds include bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-n-butylmalonate, 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, and the like, which have both hindered phenol and hindered amine structures in the molecule, and these can be used alone or in combination of two or more. Among these, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2-benzotriazole and 2,2-methylenebis[4-(1,1,3,3-tetrabutyl)-6-(2H-benzotriazol-2-yl)phenol] are particularly preferred.

[0110] The ultraviolet absorber is added to the cycloolefin resin, which is the main raw material of the optical film, in an amount of, for example, 0.1 to 5.0 mass %, preferably 0.5 to 5.0 mass %, from the viewpoint of preventing bleed-out and precipitation while exerting the effect as an ultraviolet absorber.

[0111] [Antioxidants] In the present invention, as the antioxidant, a commonly known one can be used in the optical film. In particular, lactone-based, sulfur-based, phenol-based, double bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used. For example, those commercially available under the trade names IrgafosXP40 and IrgafosXP60 from BASF Japan Ltd. are preferred.

[0112] The phenol-based compound is preferably one having a 2,6-dialkylphenol structure, and examples of the commercially available compounds include those sold under the trade names Irganox 1076 and Irganox 1010 by BASF Japan Ltd. and Adeka STAB AO-50 by ADEKA Corporation.

[0113] The phosphorus-based compound is preferably commercially available under the trade names, for example, Sumilizer GP from Sumitomo Chemical Co., Ltd., ADK STAB PEP-24G, ADK STAB PEP-36, and ADK STAB 3010 from ADEKA Corporation, IRGAFOS P-EPQ from BASF Japan Ltd., and GSY-P101 from Sakai Chemical Industry Co., Ltd.

[0114] The above hindered amine compounds are preferably commercially available under the trade names of Tinuvin 144 and Tinuvin 770 from BASF Japan Ltd. and ADK STAB LA-52 from ADEKA Corporation.

[0115] The sulfur-based compounds are preferably, for example, those commercially available from Sumitomo Chemical Co., Ltd. under the trade names Sumilizer TPL-R and Sumilizer TP-D.

[0116] The double bond compound is preferably one commercially available from Sumitomo Chemical Co., Ltd. under the trade names Sumilizer GM and Sumilizer GS.

[0117] Furthermore, it is also possible to incorporate a compound having an epoxy group as an acid scavenger, as described in US Pat. No. 4,137,201.

[0118] The amount of these antioxidants, etc. to be added is determined appropriately depending on the process for recycling, but they are added in the range of, for example, 0.05 to 20 mass %, preferably 0.1 to 1 mass %, relative to the cycloolefin resin which is the main raw material of the optical film.

[0119] A synergistic effect can be obtained by using several different types of antioxidants in combination rather than using only one type. For example, a lactone-based, phosphorus-based, phenol-based and double bond-based compound is preferably used in combination.

[0120] The optical film may be composed of one layer (single layer) or multiple layers, but is preferably composed of a single layer because it reduces display unevenness and can be made thinner.

[0121] (Optical film properties) Regarding the physical properties of the optical film of the present invention, the thickness is preferably 30 μm or less from the viewpoint of thinning, and more preferably 5 to 30 μm from the viewpoints of strength, uniformity and productivity.

[0122] (phase difference value) The optical film of the present invention preferably has an in-plane retardation value Ro (nm) defined by the following formula (i) of 30 nm or more, and a thickness direction retardation value Rt (nm) defined by the following formula (ii) of 100 nm or more.

[0123] Formula (i) Ro = (n x -n y )×d Formula (ii) Rt = {(n x +n y ) / 2-n z}×d (n x is the refractive index of the optical film in the slow axis direction in the film plane, n y is the refractive index of the optical film in a direction perpendicular to the slow axis in the film plane (the fast axis direction), n z is the refractive index in the thickness direction of the optical film, d is the film thickness of the optical film (nm). The refractive index was measured at a wavelength of 550 nm under an environment of 23° C. and 55% RH.

[0124] The in-plane retardation value Ro and the thickness direction retardation value Rt of the optical film can be measured by the following method.

[0125] 1) The optical film is conditioned for 24 hours in an environment of 23°C and 55% RH. The average refractive index of the obtained optical film is measured with an Abbe refractometer. The thickness d of the optical film is also measured with a commercially available micrometer. 2) The retardation value Ro and retardation value Rt of the optical film after humidity conditioning are measured at a measurement wavelength of 550 nm using an automatic birefringence meter Axoscan (manufactured by Axometrics) in an environment of 23°C and 55% RH. Specifically, the measurements are performed by the following methods i) to iii).

[0126] i) The phase difference value Ro is measured using an Axoscan when light with a measurement wavelength of 550 nm is incident parallel to the normal direction of the surface of the sample piece. ii) Furthermore, the retardation value R(θ) is measured by Axoscan when light with a measurement wavelength of 550 nm is incident at an angle of θ (incident angle (θ)) with respect to the normal to the surface of the sample piece, with the in-plane slow axis of the sample piece as the tilt axis (axis of rotation). The retardation value R(θ) is measured at six points every 10° in the range of θ from 0° to 50°. The in-plane slow axis of the sample piece can be confirmed by Axoscan. iii) From the measured phase difference value Ro and phase difference value R(θ) and the average refractive index and thickness described above, the Axoscan x , n y and n z is calculated, and the phase difference value Rt at a measurement wavelength of 550 nm is calculated based on the above formula (ii).

[0127] The optical film of the present invention can obtain a high optical compensation value (retardation) even when the film thickness is thinned in response to the thinning of display devices. For example, in the optical film of the present invention, the retardation value Ro when the film thickness is 20 μm is preferably 80 nm or more, more preferably 145 nm or more.

[0128] (Hayes) The optical film of the present invention is preferably highly transparent. The haze of the optical film is preferably 4.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less. The haze can be measured by a haze meter (HGM-2DP, Suga Test Instruments) at 25°C and 60% RH for a sample of 40 mm x 80 mm according to JIS K-6714.

[0129] [Method of manufacturing optical film] The optical film of the present invention can be formed by a known forming method including a stretching step, such as melt casting, solution casting, calendar molding, etc. The melt casting and solution casting are preferably used, and the solution casting is particularly preferred.

[0130] To produce the optical film of the present invention by a solution casting method, specifically, a production method including the following steps (1) to (3) is used. (1) A step of preparing a dope containing a compound having a structure represented by the above general formula (1), a cycloolefin resin, and a solvent (hereinafter referred to as a "dope preparation step"). (2) A process of casting the dope obtained in (1) onto a support to obtain an unstretched film (hereinafter referred to as the "casting process"). (3) A step of stretching the unstretched film obtained in (2) (hereinafter referred to as the "stretching step").

[0131] In the above-mentioned production method, the stretching step (3) usually includes a step of drying the solvent from the unstretched film obtained in (2) (hereinafter referred to as "drying step"). The optical film obtained in the stretching step is usually wound up into a roll shape. This step is hereinafter referred to as "winding step". Each step will be described below.

[0132] (1) Dope preparation process A process of preparing a dope by dissolving the cycloolefin resin and the compound (1) according to the present invention, and optionally other resins or additives in an organic solvent mainly consisting of a good solvent for the cycloolefin resin according to the present invention in a dissolving vessel while stirring the cycloolefin resin, or a process of mixing a solution containing the compound (1) and optionally other additives into the cycloolefin resin solution (which may optionally contain other resins) to prepare a dope which is a main solution.

[0133] When the optical film of the present invention is produced by a solution casting method, the organic solvent useful for forming the dope can be any organic solvent that can dissolve the cycloolefin resin of the present invention, the compound (1) of the present invention, and other compounds at the same time.

[0134] Examples of the organic solvent to be used include chlorine-based solvents such as chloroform and dichloromethane, aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof, alcohol-based solvents such as methanol, ethanol, isopropanol, n-butanol, and 2-butanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, etc. Only one of these solvents may be used, or two or more of them may be used in combination.

[0135] The organic solvent used in the present invention is preferably a mixed solvent of a good solvent and a poor solvent. Examples of the good solvent include a chlorine-based organic solvent such as dichloromethane, and a non-chlorine-based organic solvent such as methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, Examples of the good solvent include 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, etc., and among these, dichloromethane is preferable. The good solvent is preferably used in an amount of 55% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the solvent.

[0136] The poor solvent is preferably an alcohol-based solvent, and the alcohol-based solvent is preferably selected from methanol, ethanol, and butanol, from the viewpoint of improving peelability and enabling high-speed casting. Among them, it is preferable to use methanol or ethanol. When the ratio of alcohol in the dope is high, the web (the dope film formed by casting the dope on the casting support is called the web) gels and becomes easy to peel from the metal support, and when the ratio of alcohol is low, it also plays a role in promoting dissolution of the cycloolefin resin and other compounds in the non-chlorine organic solvent system. In the production of the optical film of the present invention, it is preferable to use a dope having an alcohol concentration in the range of 0.5 to 15.0 mass % in order to improve the flatness of the obtained optical film.

[0137] For dissolving the cycloolefin resin according to the present invention, the compound (1) according to the present invention, and other compounds, various dissolution methods can be used, such as a method carried out at normal pressure, a method carried out at a pressure equal to or lower than the boiling point of the main solvent, a method carried out under pressure equal to or higher than the boiling point of the main solvent, a cooling dissolution method as described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, and a high-pressure method as described in JP-A-11-21379. In particular, a method carried out under pressure equal to or higher than the boiling point of the main solvent is preferred.

[0138] The concentration of the cycloolefin resin according to the present invention in the dope is preferably in the range of 10 to 40 mass %. Compound (1) and other additives are added to the dope during or after dissolution, for example, in the amount shown above relative to the cycloolefin resin, and then dissolved and dispersed, filtered with a filter medium, degassed, and sent to the next process by a liquid delivery pump.

[0139] The dope is preferably filtered using a main filter having a leaf disc filter, for example, a filter medium having a 90% collection particle size 10 to 100 times the average particle size of the fine particles.

[0140] In the present invention, it is preferable that the filter medium used for filtration has a small absolute filtration accuracy. However, if the absolute filtration accuracy is too small, the filter medium is likely to become clogged, and the filter medium must be replaced frequently, which reduces productivity.

[0141] Therefore, in the present invention, the filter medium used in the dope containing the cycloolefin resin and the compound (1) has an absolute filtration precision of preferably 0.008 mm or less, more preferably 0.001 to 0.008 mm, and even more preferably 0.003 to 0.006 mm.

[0142] There are no particular limitations on the material of the filter medium, and any ordinary filter medium can be used, but filter medium made of plastic fibers such as polypropylene or Teflon (registered trademark), or metal filter medium such as stainless steel fiber, are preferred as they do not easily lose fibers.

[0143] In the present invention, the flow rate of the dope during filtration is 10 to 80 kg / (h m 2 ), preferably 20 to 60 kg / (h m 2 ) is preferable. Here, the flow rate of the dope during filtration is preferably 10 kg / (h m 2 ) or more, efficient productivity is achieved, and the flow rate of the dope during filtration is 80 kg / (h m 2 ) is preferable because the pressure applied to the filter medium is appropriate and the filter medium is not damaged.

[0144] The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

[0145] In many cases, the main dope may contain about 10 to 50 mass % of recycled materials. The recycled materials are, for example, the optical film of the present invention that has been finely pulverized, and include the cut-off portions of both sides of the film that are generated during the film formation of the optical film, and the original optical film that has scratches or the like that exceed the specified value of the film.

[0146] As the raw material of the resin used for preparing the dope, the cycloolefin resin according to the present invention which has been previously pelletized can also be preferably used.

[0147] (2) Casting process (2-1) Dope distribution In this process, the dope is sent to a pressure die through a liquid sending pump (e.g., a pressure type constant volume gear pump) and cast from the pressure die slit onto a casting position on an endless support that moves indefinitely, such as a stainless steel belt or a metal support such as a rotating metal drum.

[0148] The metal support in the casting process is preferably one with a mirror-finished surface, and a stainless steel belt or a cast metal drum with a plated surface is preferably used as the metal support. The width of the cast can be in the range of 1 to 4 m, preferably in the range of 1.3 to 3 m, and more preferably in the range of 1.5 to 2.8 m. The surface temperature of the metal support in the casting process is set to -50°C to a temperature at which the solvent does not boil and foam, more preferably in the range of -30 to 0°C. A higher temperature is preferable because the drying speed of the web can be increased, but if the temperature is too high, the web may foam or the flatness may deteriorate. The preferred support temperature is appropriately determined in the range of 0 to 100°C, and more preferably in the range of 5 to 30°C. Alternatively, it is also a preferred method to gel the web by cooling it and peel it off from the drum in a state containing a large amount of residual solvent.

[0149] The method for controlling the temperature of the metal support is not particularly limited, but includes a method of blowing hot or cold air or a method of bringing hot water into contact with the back side of the metal support. Using hot water is preferable because heat is transferred more efficiently, and the time until the temperature of the metal support becomes constant is shorter. When using hot air, hot air above the boiling point of the solvent may be used in consideration of the temperature drop of the web due to the latent heat of evaporation of the solvent, and air at a temperature higher than the target temperature may be used while preventing foaming. In particular, it is preferable to change the temperature of the support and the temperature of the drying air between casting and peeling to perform efficient drying.

[0150] The die is preferably a pressure die, which can adjust the slit shape of the die nozzle and can easily make the film thickness uniform. Pressure dies include coat hanger dies and T-dies, and either one is preferably used. The surface of the metal support is a mirror finish. In order to increase the film formation speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked.

[0151] (2-2) Solvent evaporation process This is a step in which the web is heated on the support for casting to evaporate the solvent, and this is a step in which the amount of residual solvent at the time of peeling, which will be described later, is controlled.

[0152] The solvent can be evaporated by blowing air from the web side, by transferring heat from the back side of the support using a liquid, or by transferring heat from the front and back sides using radiant heat, but the back side liquid heat transfer method is preferred because of its high drying efficiency. A combination of these methods is also preferably used. It is preferable to dry the web on the support after casting in an atmosphere of 30 to 100°C on the support. To maintain the atmosphere at 30 to 100°C, it is preferable to apply hot air at this temperature to the top surface of the web or heat it by means of infrared rays or the like.

[0153] From the viewpoints of surface quality, moisture permeability, and releasability, it is preferable to peel the web from the support within 30 to 180 seconds.

[0154] (2-3) Peeling process In this process, the web from which the solvent has evaporated on the metal support is peeled off at the peeling position. The peeled off web is sent to the next process as an unstretched film.

[0155] The temperature at the peeling position on the metal support is preferably in the range of 10 to 40°C, and more preferably in the range of 11 to 30°C.

[0156] In the present invention, the solvent in the web is evaporated in the solvent evaporation step, and the amount of the residual solvent in the web on the metal support at the time of peeling is preferably within a range of 15 to 100 mass %. The amount of the residual solvent is preferably controlled by the drying temperature and drying time in the solvent evaporation step.

[0157] When the residual solvent amount is 15% by mass or more, the drying time during the drying process on the support is not long, and the productivity is improved. Also, when the residual solvent amount is 100% by mass or less, the unstretched film has self-supporting properties, peeling failure of the unstretched film can be avoided, and the mechanical strength of the unstretched film can be maintained, so that the flatness during peeling is improved and the occurrence of wrinkles and vertical streaks due to peeling tension can be suppressed.

[0158] The residual solvent amount in the web or unstretched film is defined by the following formula (Z).

[0159] Formula (Z): Residual solvent amount (%)=(mass of web or unstretched film before heat treatment−mass of web or unstretched film after heat treatment) / (mass of web or unstretched film after heat treatment)×100 The heat treatment for measuring the amount of residual solvent refers to a heat treatment at 115° C. for 1 hour.

[0160] The peel tension when peeling the web from the metal support to obtain an unstretched film is usually within the range of 196 to 245 N / m, but if wrinkles are likely to occur during peeling, it is preferable to peel the web at a tension of 190 N / m or less.

[0161] In the present invention, the temperature at the peeling position on the metal support is preferably within the range of -50 to 40°C, more preferably within the range of 10 to 40°C, and most preferably within the range of 15 to 30°C.

[0162] (3) Drying and stretching process The drying process can also be divided into a preliminary drying process (first drying process) and a main drying process (second drying process).

[0163] (3-1) Pre-drying process The unstretched film obtained by peeling the web from the metal support is pre-dried in a first drying device. The pre-drying of the film may be performed by drying the film while transporting it between multiple rollers arranged above and below, or by fixing both ends of the film with clips and drying the film while transporting it, as in a tenter dryer.

[0164] The means for drying the unstretched film is not particularly limited, and generally can be hot air, infrared rays, a heated roller, microwaves, etc., but from the viewpoint of simplicity, it is preferable to dry the film with hot air.

[0165] The drying temperature in the pre-drying step of the unstretched film is preferably the glass transition point of the unstretched film minus 5° C. or lower, and it is effective to perform heat treatment for 1 minute to 30 minutes at a temperature of 30° C. or higher. The drying temperature is within the range of 40 to 150° C., and more preferably within the range of 50 to 100° C.

[0166] In the present invention, it is preferable to adjust the amount of residual solvent in the unstretched film at the time of stretching in the drying step, which will be described later, but the adjustment of the amount of residual solvent may be performed at the early stage of the stretching step. The control of the amount of residual solvent is preferably performed by adjusting the drying temperature and drying time in the pre-drying step.

[0167] (3-2) Stretching process In the method for producing the optical film of the present invention, the unstretched film having a specific residual solvent content is stretched at a low stretch ratio in a stretching device, thereby suppressing the occurrence of minute crazes near the film surface. Furthermore, during the stretching, the compound (1) itself is oriented, and the compound (1) acts as described above to control the orientation of the cycloolefin resin in the film, thereby making it possible to obtain the target retardation value Ro and retardation value Rt even at a low stretch ratio.

[0168] In the method for producing an optical film of the present invention, in the step of stretching the unstretched film, the amount of residual solvent at the start of stretching is preferably 1% by mass or more and less than 15% by mass, more preferably within the range of 2 to 10% by mass.

[0169] If the amount of residual solvent at the start of stretching is less than 1% by mass, excessive stress will be applied during stretching, making it easier for microscopic crazes to occur near the film surface and deteriorating the adhesiveness of UV paste.

[0170] On the other hand, if the amount of residual solvent is 15% by mass or more, it becomes difficult to apply stress during stretching, and therefore it becomes difficult to sufficiently orient compound (1) and the cycloolefin resin in the film.

[0171] The optical film of the present invention is produced by stretching the unstretched film in the longitudinal direction (also referred to as MD direction or casting direction) and / or the width direction (also referred to as TD direction), and is preferably produced by stretching at least in the width direction using a stretching device.

[0172] The stretching operation may be divided into multiple stages. When biaxial stretching is performed, simultaneous biaxial stretching may be performed, or it may be performed stepwise. In this case, stepwise means, for example, that stretching in different stretching directions can be performed sequentially, or that stretching in the same direction can be divided into multiple stages and stretching in a different direction can be added to any of the stages.

[0173] That is, for example, the following stretching step is also possible: Stretch in the longitudinal direction → Stretch in the transverse direction → Stretch in the longitudinal direction → Stretch in the longitudinal direction Stretch in the width direction → Stretch in the width direction → Stretch in the length direction → Stretch in the length direction Simultaneous biaxial stretching also includes a case where the film is stretched in one direction and contracted by relaxing the tension in the other direction.

[0174] The optical film of the present invention is preferably stretched by stretching an unstretched film in the longitudinal direction and / or width direction, preferably in the width direction, at a temperature range of (Tg+5) to (Tg+50)°C, where Tg is the glass transition temperature of the film, so that the film thickness after stretching is in the desired range. Stretching in the above temperature range makes it easy to adjust the retardation and reduces the stretching stress, thereby reducing the haze. In addition, an optical film is obtained that is suppressed from breaking and has excellent flatness and colorability of the film itself. The stretching temperature is preferably in the range of (Tg+10) to (Tg+40)°C.

[0175] The glass transition temperature Tg referred to here is the midpoint glass transition temperature (Tmg) measured at a heating rate of 20° C. / min using a commercially available differential scanning calorimeter and determined in accordance with JIS K7121 (1987). A specific method for measuring the glass transition temperature Tg of the optical film is to measure using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. in accordance with JIS K7121 (1987).

[0176] The optical film of the present invention is preferably prepared by stretching the unstretched film at least in the width direction at a stretch ratio within the range of 10 to 100% of the original width, and more preferably in the longitudinal and lateral directions of the film at a stretch ratio within the range of 5 to 60%. Within the above ranges, the generation of minute crazes near the film due to high-magnification stretching is suppressed, and in particular, by containing compound (1), not only can the desired retardation values ​​Ro and Rt be obtained, but the optical film can also be made thinner. The stretch ratio in the present invention is the longitudinal or lateral length d of the unstretched film before stretching. 11 The length d of the longitudinal or transverse direction of the optical film after stretching 12 Length d 11 This refers to the percentage change from

[0177] There is no particular limitation on the method of stretching in the longitudinal direction. For example, there is a method in which a plurality of rolls are provided with different peripheral speeds, and the difference in the roll peripheral speeds is used to stretch the film in the longitudinal direction, a method in which both ends of an unstretched film are fixed with clips or pins, and the distance between the clips or pins is increased in the direction of travel to stretch the film in the longitudinal direction, or a method in which the film is simultaneously stretched in both the longitudinal and transverse directions to stretch the film in both the longitudinal and transverse directions. Of course, these methods may be used in combination.

[0178] To stretch in the width direction, for example, a method as disclosed in JP-A-62-46625 in which the entire drying process or part of the drying process is carried out while holding both width ends of the web in the width direction with clips or pins (called the tenter method), of which the tenter method using clips and the pin tenter method using pins are preferably used.

[0179] When stretching in the width direction, it is preferable to stretch the film in the width direction at a stretching speed of 250 to 500% / min from the viewpoint of improving the flatness of the optical film.

[0180] A stretching speed of 250% / min or more is preferable from the viewpoint of productivity, since the flatness is improved and the film can be processed at high speed, and a stretching speed of 500% / min or less is preferable, since the film can be processed without breaking.

[0181] A preferred stretching speed is within the range of 300 to 400% / min, which is effective when stretching at a low ratio. The stretching speed is defined by the following formula 1.

[0182] Formula 1 Stretching speed (% / min)=[(d1 / d2)-1]×100(%) / t (In formula 1, d1 is the width dimension in the stretching direction of the optical film of the present invention after stretching, d2 is the width dimension in the stretching direction of the unstretched film before stretching, and t is the time (min) required for stretching.)

[0183] In the stretching step, usually, holding and relaxation are performed after stretching. That is, this step is preferably performed in the order of a stretching step in which an unstretched film is stretched, a holding step in which the obtained stretched film is held in a stretched state, and a relaxation step in which the stretched film is relaxed in the stretched direction. In the holding step, the stretching at the stretch ratio achieved in the stretching step is held at the stretching temperature in the stretching step. In the relaxation step, the stretching in the stretching step is held in the holding step, and then the tension for stretching is released, thereby relaxing the stretching. The relaxation step may be performed at a temperature equal to or lower than the stretching temperature in the stretching step.

[0184] (3-3) Main drying process In the method for producing an optical film of the present invention, in the main drying step, the stretched film after stretching is heated and dried by a second drying device. When the stretched film is heated by hot air or the like, a means for preventing the mixing of used hot air by installing a nozzle capable of exhausting used hot air (air containing a solvent or wet air) is preferably used. The hot air temperature is more preferably in the range of 40 to 350°C. The drying time is preferably about 5 seconds to 60 minutes, more preferably 10 seconds to 30 minutes.

[0185] The heating and drying means is not limited to hot air, and may be, for example, infrared rays, a heating roller, microwaves, etc. From the viewpoint of simplicity, it is preferable to dry the film with hot air or the like while transporting the film with transport rollers arranged in a staggered pattern. The drying temperature is more preferably in the range of 40 to 350°C, taking into consideration the amount of residual solvent, the expansion and contraction rate during transport, etc.

[0186] In the drying step, the stretched film is preferably dried until the amount of residual solvent becomes 0.5% by mass or less, thereby obtaining the optical film of the present invention.

[0187] (4) Winding process (4-1) Knurling After a predetermined heat treatment or cooling treatment, the optical film is preferably cut off at its ends using a slitter before being wound up in order to obtain a good rolled appearance. Furthermore, it is preferable to perform knurling on both widthwise ends.

[0188] The knurling process can be performed by pressing a heated embossing roller against the widthwise end of the optical film. The embossing roller has fine projections and recesses formed thereon, and pressing the roller against the optical film forms projections and recesses on the optical film, thereby making the end bulkier.

[0189] The height of the knurling at both widthwise ends of the optical film of the present invention is preferably 4 to 20 μm and the width is preferably 5 to 20 mm.

[0190] In the present invention, the knurling is preferably performed after drying and before winding in the film production process.

[0191] (4-2) Winding process This is the step of winding up the film as an optical film after the residual solvent content in the film has reached 2% by mass or less. By keeping the residual solvent content preferably to 0.4% by mass or less, an optical film with good dimensional stability can be obtained.

[0192] The winding method may be any commonly used method, such as a constant torque method, a constant tension method, a taper tension method, or a program tension control method with constant internal stress, and any of these may be used appropriately.

[0193] [Polarizing plate] The polarizing plate of the present invention is characterized by comprising a polarizer and the optical film of the present invention arranged on at least one surface of the polarizer. The polarizing plate has, for example, a polarizer and two protective films arranged on both surfaces of the polarizer, at least one of the two protective films being the optical film of the present invention.

[0194] Fig. 2 is a cross-sectional view showing an example of the configuration of a polarizing plate of the present invention. As shown in Fig. 2, a polarizing plate 10 has a polarizer 1 and protective films 2 and 3 arranged on both surfaces of the polarizer 1. At least one of the protective films 2 and 3 is the optical film of the present invention. The polarizer 1 and the protective films 2 and 3 are bonded together via an optional adhesive layer (not shown).

[0195] <Polarizer> Any suitable polarizer can be used as the polarizer. For example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film is uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye, or a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochlorinated polyvinyl chloride. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine to a polyvinyl alcohol film and uniaxially stretching the film is particularly preferred because it has a high polarization dichroic ratio.

[0196] A polarizer obtained by uniaxially stretching a polyvinyl alcohol-based film after adsorbing iodine can be produced, for example, by dyeing the polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. If necessary, the polyvinyl alcohol-based film may contain boric acid, zinc sulfate, zinc chloride, or the like, or may be immersed in an aqueous solution of potassium iodide or the like. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing.

[0197] Washing the polyvinyl alcohol-based film with water not only removes dirt and antiblocking agents from the surface of the polyvinyl alcohol-based film, but also swells the polyvinyl alcohol-based film, preventing unevenness such as uneven dyeing. The film may be stretched after dyeing with iodine, or may be stretched while dyeing. The film may also be dyed with iodine after stretching. The film may be stretched in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

[0198] The polarizer preferably satisfies 0.030≦Rpva≦0.040. Rpva is the refractive index in the direction in which the refractive index is maximum in the plane of the polarizer at a wavelength of 1000 nm. x The refractive index in the direction perpendicular to the direction in which the refractive index is maximum is n y Then, Rpva=n x -n yRpva is more preferably 0.030≦Rpva≦0.039, and particularly preferably 0.030≦Rpva≦0.035. It is presumed that such characteristics are satisfied by increasing the amount of crystals that do not contribute to the orientation in the polarizer (typically, have low orientation). A polarizer with Rpva in this range can have excellent dimensional stability and optical durability in a high-temperature and high-humidity environment. As a result, even when the polarizer is used in a polarizing plate in which an optical film is provided on only one side of the polarizer, dimensional change and deterioration of optical properties are unlikely to occur, and dimensional stability and optical durability that are practically acceptable can be realized.

[0199] The dichroic ratio DR of the polarizer is preferably 160 or more, more preferably 160 to 220, particularly preferably 170 to 210, and most preferably 175 to 185. If the dichroic ratio DR is within such a range, a liquid crystal panel and a liquid crystal display device having high front contrast can be obtained by using the polarizing plate of the present invention. Such a liquid crystal panel and a liquid crystal display device are suitable for use in, for example, televisions. The dichroic ratio DR can be calculated from the following formula. Dichroic ratio DR=log(0.919 / k2) / log(0.919 / k1) Here, k1 is the transmittance in the transmission axis direction of the polarizer, k2 is the transmittance in the absorption axis direction of the polarizer, and the constant 0.919 is the interface reflectance.

[0200] The transmittance (single transmittance) Ts of the polarizer is preferably 42% or more, more preferably 42.0% or more and 44.0% or less, and particularly preferably 42.5% or more and 43.0% or less. If the transmittance Ts is in such a range, a liquid crystal panel or liquid crystal display device with high brightness can be obtained by using the polarizing plate of the present invention. Such a liquid crystal panel and liquid crystal display device are suitable for use in, for example, televisions. The transmittance of the polarizing plate can be calculated from the following formula. Transmittance={(k1+k2) / 2}×100 [%] Here, k1 is the transmittance in the transmission axis direction of the polarizer, and k2 is the transmittance in the absorption axis direction of the polarizer.

[0201] As described above, the polarizer may be a polarizer mainly composed of a polyvinyl alcohol (PVA) resin containing iodine or a dichroic substance such as a dichroic dye. The iodine content of the polarizer is preferably 1.8% by mass or more and 5.0% by mass or less, and more preferably 2.0% by mass or more and 4.0% by mass or less. By setting the iodine content within the above range, a polarizing plate with a transmittance in a preferred range can be obtained, and a liquid crystal display device with a high contrast ratio in the front direction can be obtained.

[0202] The boric acid content of the polarizer is preferably 0.5% by mass or more and 3.0% by mass or less, more preferably 1.0% by mass or more and 2.8% by mass or less, and particularly preferably 1.5% by mass or more and 2.6% by mass or less, calculated as boron. This makes it possible to obtain a polarizer having excellent dimensional stability and optical durability in a humid environment without increasing the amount of boric acid.

[0203] The polarizer may preferably further contain potassium. The potassium content is preferably 0.2% by mass or more and 1.0% by mass or less, more preferably 0.3% by mass or more and 0.9% by mass or less, and particularly preferably 0.4% by mass or more and 0.8% by mass or less. By setting the potassium content in the above range, a polarizing plate having a transmittance in a preferred range and a high degree of polarization can be obtained.

[0204] The linear expansion coefficient of the polarizer in the transmission axis direction is not particularly limited and may be any appropriate value. For example, in the case of using a polarizer mainly composed of a polyvinyl alcohol (PVA) resin containing a dichroic material, the linear expansion coefficient of the polarizer in the transmission axis direction is 4.0×10 -5 / ℃ or more 5.0×10 -5 / ℃ or less.

[0205] The thickness of the polarizer is not particularly limited and is generally about 1 to 80 μm.

[0206] <Protective film> At least one of the two protective films is the optical film of the present invention. When one of the two protective films is the optical film of the present invention, the other may be another optical film.

[0207] Other examples of optical films include commercially available cellulose ester films (e.g., Konica Minolta TAC KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC These include 4UA, KC6UAKC, 2UAH, KC4UAH, KC6UAH, all manufactured by Konica Minolta, Inc., Fujitac T40UZ, Fujitac T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, all manufactured by Fujifilm Corporation.

[0208] The thickness of the other optical films is not particularly limited, but is preferably from 10 to 100 μm, more preferably from 10 to 60 μm, and particularly preferably from 20 to 60 μm.

[0209] The protective film may further include other layers as necessary, such as an anti-reflection layer, an antistatic layer, a retardation layer, and a brightness enhancing film layer.

[0210] <Adhesive layer> The adhesive layer may be a layer obtained by drying a completely saponified aqueous solution of polyvinyl alcohol (water paste), or may be a layer of a cured product of an active energy ray-curable adhesive.

[0211] [Display device] The optical film and polarizing plate of the present invention can be used in various display devices such as liquid crystal displays (LCDs), organic electroluminescent displays (OLEDs), and touch panels.

[0212] <Liquid crystal display device> The liquid crystal display device of the present invention includes a liquid crystal cell, a first polarizing plate arranged on one side of the liquid crystal cell (e.g., the surface on the viewing side), and a second polarizing plate arranged on the other side of the liquid crystal cell (e.g., the surface on the backlight side), one or both of the first and second polarizing plates being polarizing plates having the optical film of the present invention.

[0213] The liquid crystal cell has two electrode substrates and a liquid crystal layer disposed therebetween, and is preferably in a TN mode, a VA mode, an OCB mode, an IPS mode or an ECB mode.

[0214] In TN mode liquid crystal cells, rod-shaped liquid crystal molecules are aligned substantially horizontally when no voltage is applied, and are further aligned with a twist angle of 60 to 120°. TN mode liquid crystal cells are most commonly used as color TFT liquid crystal display devices, and are described in many publications.

[0215] In a VA mode liquid crystal cell, rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied.

[0216] VA mode liquid crystal cells include (1) narrowly defined VA mode liquid crystal cells in which rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied and substantially horizontally when voltage is applied (described in JP-A-2-176625), (2) multi-domain VA mode liquid crystal cells (described in SID97, Digest of Tech. Papers (Proceedings) 28 (1997) 845) in order to widen the viewing angle (3) n-ASM mode liquid crystal cells in which rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied and substantially horizontally when voltage is applied (described in Proceedings of the Japan Liquid Crystal Symposium 58-59 (1998)), and (4) SURVIVAIVAL mode liquid crystal cells (announced at LCD International 98).

[0217] An OCB mode liquid crystal cell is a bend alignment mode liquid crystal cell in which rod-shaped liquid crystal molecules are aligned in substantially opposite directions (symmetrically) at the top and bottom of the liquid crystal cell, and is disclosed in U.S. Pat. Nos. 4,583,825 and 5,410,422. Because the rod-shaped liquid crystal molecules are aligned symmetrically at the top and bottom of the liquid crystal cell, a bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is called an OCB (Optically Compensatory Bend) liquid crystal mode. An advantage of a bend alignment mode liquid crystal display device is its fast response speed.

[0218] The IPS mode liquid crystal cell is a type in which switching is performed by applying a transverse electric field to a nematic liquid crystal, and is described in detail in Proc. IDRC (Asia Display 1995), pp. 577-580 and pp. 707-710.

[0219] In a liquid crystal cell of the ECB mode, rod-shaped liquid crystal molecules are aligned substantially horizontally when no voltage is applied. The ECB mode is one of the liquid crystal display modes having the simplest structure, and is described in detail in, for example, JP-A-5-203946.

[0220] The first polarizing plate includes a first polarizer arranged on one side of the liquid crystal cell (e.g., the viewing side), a protective film F1 arranged on the side of the first polarizer opposite the liquid crystal cell, and a protective film F2 arranged on the side of the first polarizer facing the liquid crystal cell.

[0221] The second polarizing plate includes a second polarizer arranged on the other side of the liquid crystal cell (e.g., the side facing the backlight), a protective film F3 arranged on the side of the second polarizer facing the liquid crystal cell, and a protective film F4 arranged on the side of the second polarizer opposite the liquid crystal cell.

[0222] It is preferable that the absorption axis of the first polarizer and the absorption axis of the second polarizer are perpendicular to each other (in a crossed Nicol state).

[0223] At least one of the protective films F1, F2, F3 and F4 may be the optical film of the present invention. Among them, the optical film of the present invention is preferably used as the protective film F2 or F3. A liquid crystal display device including the optical film of the present invention as the protective film F2 or F3 is a liquid crystal display device that realizes a thin structure while maintaining high functionality.

[0224] By using the polarizing plate of the present invention, it is possible to obtain a liquid crystal display device that is thin and maintains high functionality, especially in a liquid crystal display device having a large screen of 30 inches or more.

[0225] <Organic EL display device> The optical film of the present invention can be used as a substrate (base film) or a protective film for an organic EL device, etc. The polarizing plate of the present invention can also be used as a circular polarizing plate for an organic EL display device.

[0226] The organic EL display of the present invention may comprise an organic EL element having a light-reflecting electrode, a light-emitting layer, a transparent electrode layer and a transparent plastic film substrate, and a circular polarizing plate.

[0227] The circularly polarizing plate has a polarizer (linearly polarizing film) and a λ / 4 film provided between a transparent substrate and the polarizer. The optical film of the present invention can be preferably used as a transparent plastic film substrate or a λ / 4 film.

[0228] In an organic EL display device, when a current is applied between the light-reflecting electrode and the transparent electrode layer, the light-emitting layer emits light and an image can be displayed. Furthermore, since all light incident on the organic EL display device from the outside is absorbed by the polarizer, even if it is reflected by the light-reflecting electrode of the organic EL display, it is not emitted to the outside, and deterioration of display characteristics due to reflection of the background can be suppressed.

[0229] When the optical film of the present invention is used in an organic EL display device, the contents described in each of JP-A-11-335661, JP-A-11-335368, JP-A-2001-192651, JP-A-2001-192652, JP-A-2001-192653, JP-A-2001-335776, JP-A-2001-247859, JP-A-2001-181616, JP-A-2001-181617, JP-A-2002-181816, JP-A-2002-181617, JP-A-2002-056976, and the like can be applied. It is also preferable to use it in combination with the contents described in JP-A Nos. 2001-148291, 2001-221916, and 2001-231443.

[0230] <Touch panel> The optical film of the present invention is suitable for use in a touch panel. For example, a touch panel can be produced according to the description in paragraphs

[0073] to

[0075] of JP-A-2009-176608.

[0231] The touch panel can be used as an input device by being incorporated into a display device such as a liquid crystal display device, a plasma display device, an organic EL display device, a CRT display device, electronic paper, etc. By using the optical film according to the present invention, a thin touch panel can be realized while maintaining high functionality.

[0232] The touch panel may be of a resistive film type or a capacitive type, and the capacitive input device has the advantage that it is only necessary to form a transparent conductive film on one substrate, and is therefore preferably of the capacitive type. In such a capacitive input device, for example, a type in which the transparent electrode layer has electrode patterns extending in mutually intersecting directions, and when a finger or the like comes into contact with the electrode, the change in capacitance between the electrodes is detected to detect the input position, may be preferably used. For the configuration of such a touch panel, for example, the descriptions in JP2010-86684A, JP2010-152809A, JP2010-257492A, etc. may be referred to.

[0233] Regarding the configuration of an image display device having a touch panel as a component, the configurations disclosed in "Latest Touch Panel Technology" (published July 6, 2009 by Techno Times Co., Ltd.), supervised by Mitani Yuji, "Touch Panel Technology and Development", CMC Publishing (2004,12), FPD International 2009 Forum T-11 Lecture Textbook, Cypress Semiconductor Corporation Application Note AN2292, etc. can be applied.

[0234] In addition, the description in JP-A-2002-48913 and the like can also be used to understand the configuration of a liquid crystal display into which a touch panel can be incorporated. EXAMPLES

[0235] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, the terms "parts" and "%" are used, but they represent "parts by mass" or "% by mass" unless otherwise specified.

[0236] [Optical film] 1. Optical film materials (1) Cycloolefin resin Cycloolefin resin A (wherein R is CH3) consisting of units having a structure represented by the following formula (I) was used as the cycloolefin resin having a polar group. Cycloolefin resin B consisting of units having a structure in which the group represented by COOR in the following formula (I) is replaced with a hydrogen atom was used as the cycloolefin resin not having a polar group.

[0237] [ka]

[0238] (2) Additives (2-1) Compound (1) As compound (1), compounds 1-1 to 1-6 were used.

[0239] (2-2) Comparative Example Compound Compounds Cf-1 to Cf-3 having structures represented by the following formulas Cf-1 to Cf-3 were prepared for comparison. In the compounds Cf-1 to Cf-3, X to the ring Y of the compound (1) 1 and X 2 The angles corresponding to the angle θ are 128°, 150°, and 75°, respectively.

[0240] [ka]

[0241] 2. Preparation of Optical Film <Preparation of Optical Film 1> (Preparation of dope) The following components were placed in a sealed container, heated and stirred until completely dissolved, and filtered using Azumi Filter Paper No. 24 manufactured by Azumi Filter Paper Co., Ltd. to prepare a dope. Cycloolefin resin A: 228 parts by mass Compound 1-1: 12 parts by mass Dichloromethane: 659 parts by mass Ethanol: 42 parts by weight

[0242] (Film forming) The obtained dope was kept at 40°C and uniformly cast onto a stainless steel belt, which was an endless metal support kept at 40°C. The cast dope was dried until the residual solvent amount was 80% by mass, and then peeled off from the stainless steel belt to obtain a film-like material (unstretched film). The obtained film-like material was dried at 40°C until the residual solvent amount was 5% by mass, and then stretched in the width direction at a stretching ratio of 1.5 times (stretching ratio 50%). The obtained film-like material (stretched film) was further dried at 120°C while being transported by multiple rolls, to obtain an optical film 1 having a thickness of 20 μm and a width of 1.3 m.

[0243] <Preparation of Optical Films 2 to 10> Optical films 2 to 10 were obtained in the same manner as for optical film 1, except that the type of cycloolefin resin or the type of compound was changed as shown in Table I. Table I shows the type of cycloolefin resin (in Table I, "COP") used in the preparation of optical films 1 to 10, the type of compound, and the ratio of X to Y ring in the compound. 1 and X 2 and the compound content (mass % relative to 100 mass % of cycloolefin resin).

[0244] 3. Evaluation The prepared Optical Films 1 to 10 were evaluated for retardation value Ro and retardation value Rt and for adhesion to a polarizer by the following methods. 3-1. Retardation value Ro and retardation value Rt of optical film The in-plane retardation value Ro and the thickness direction retardation value Rt of each of the Optical Films 1 to 10 were measured by the following method.

[0245] 1) The optical film was conditioned for 24 hours under an environment of 23°C and 55% RH. The average refractive index of the obtained optical film was measured with an Abbe refractometer. The thickness d of the optical film was also measured with a commercially available micrometer. 2) The retardation value Ro and retardation value Rt of the optical film after humidity conditioning at a measurement wavelength of 550 nm were measured using an automatic birefringence meter Axoscan (manufactured by Axometrics) under an environment of 23°C and 55% RH. Specifically, the measurements were performed by the following methods i) to iii).

[0246] i) The phase difference value Ro was measured using an Axoscan when light with a measurement wavelength of 550 nm was incident parallel to the normal direction of the surface of the sample piece. ii) Furthermore, the retardation value R(θ) was measured by Axoscan when light with a measurement wavelength of 550 nm was incident at an angle of θ (incident angle (θ)) with respect to the normal to the surface of the sample piece, with the in-plane slow axis of the sample piece as the tilt axis (axis of rotation). The retardation value R(θ) was measured at six points every 10° in the range of θ from 0° to 50°. The in-plane slow axis of the sample piece was confirmed by Axoscan. iii) From the measured phase difference value Ro and phase difference value R(θ) and the average refractive index and thickness described above, the Axoscan x , n yand n z The retardation values ​​Ro and Rt at a measurement wavelength of 550 nm were calculated based on the following formulas (i) and (ii).

[0247] Formula (i) Ro = (n x -n y )×d Formula (ii) Rt = {(n x +n y ) / 2-n z}×d (n x is the refractive index of the optical film in the slow axis direction in the film plane, n y is the refractive index of the optical film in a direction perpendicular to the slow axis in the film plane (the fast axis direction), n z is the refractive index in the thickness direction of the optical film, d is the film thickness of the optical film (nm). The refractive index was measured at a wavelength of 550 nm under an environment of 23° C. and 55% RH.

[0248] The retardation of the optical film was evaluated using Ro, and the evaluation criteria for Ro were as follows: ◎:145nm or more ○: 120 nm or more and less than 145 nm △: 80nm or more and less than 120nm ×: Less than 80 nm If it was rated as △ or better, it was judged to be good.

[0249] (Adhesion to polarizer) (1) Preparation of polarizer A long roll polyvinyl alcohol film having a thickness of 120 μm was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 5 times in the conveying direction at 50° C. to prepare a polarizer.

[0250] (2) Preparation of peel test samples Each of the optical films 1 to 10 was cut to a width of 40 to 50 mm and a length of 120 mm, and was attached to one side of the polarizer obtained above using a water-based adhesive (a water-based adhesive containing a polyvinyl alcohol resin), and was then dried in an oven at 90° C. for 10 minutes to bond the two together. After bonding, the polarizer with the optical film was cut to a width of 25 mm and a length of 120 mm to prepare a peel test sample.

[0251] (3) Evaluation of adhesion In the peel test sample, the optical film was peeled off from the polarizer by 20 mm in the 120 mm direction, and placed on a Tensilon (manufactured by Orientec Co., Ltd.) as a gripping portion of a clip, and the peel strength (adhesion) was measured. The evaluation criteria were as follows.

[0252] (Evaluation Criteria) ◎: Peel strength is 3.0 (N / 25mm) or more ○: Peel strength is 1.0 (N / 25mm) or more and less than 3.0 (N / 25mm) △: Peel strength is 0.5 (N / 25mm) or more and less than 1.0 (N / 25mm) ×: Peel strength is 0 (N / 25mm) or more and less than 0.5 (N / 25mm) If it was rated as △ or better, it was judged to be good.

[0253] [Table 1]

[0254] As can be seen from Table I, the optical film of the present invention containing a cycloolefin resin and compound (1) has a sufficiently thin thickness, a desired optical compensation value, and good adhesion to the polarizer.

[0255] [Display device] (1) Preparation of polarizing plate A polarizing plate was produced using the optical film 2 obtained above and a polarizer as follows. One side of the optical film 2 is exposed to 810 (W·min / m 2) of irradiation. Then, after a predetermined time had elapsed since the corona treatment, the optical film 2 was attached to one surface of the polarizer via a water-based adhesive (a water-based adhesive containing a polyvinyl alcohol resin) so that the corona-treated surface faced the polarizer. In addition, the TAC film 6UA manufactured by Konica Minolta, which had been subjected to an alkali saponification treatment, was attached to the other surface of the polarizer (the surface not facing the optical film) via the same water-based adhesive as above. The obtained laminate was dried in an oven at 90°C for 10 minutes to obtain a polarizing plate.

[0256] (2) Fabrication of display device The polarizing plate obtained above was attached to a commercially available liquid crystal display device as follows. Using a VA mode liquid crystal display device, the previously attached polarizing plates on both sides were peeled off, and the above-obtained polarizing plates were each attached to the glass surface of a liquid crystal cell. The prepared polarizing plates were each attached so that the optical film 2 was on the outer side of the glass surface of the liquid crystal cell and so that the absorption axis of the polarizer was oriented in the same direction as the previously attached polarizing plate, thereby producing a liquid crystal display device.

[0257] The liquid crystal display device thus obtained had image quality as good as that before the polarizing plate was replaced, but was thinner than that before the polarizing plate was replaced. [Industrial Applicability]

[0258] In the present invention, it is possible to provide an optical film having a sufficiently thin thickness, a desired optical compensation value (retardation), and good adhesion to a polarizer, particularly an optical film mainly made of a cycloolefin resin, and a manufacturing method thereof. Furthermore, by using the optical film, it is possible to provide a polarizing plate and a display device that are thinned while maintaining their performance. [Explanation of symbols]

[0259] 10 Polarizing plate 1 Polarizer 2, 3 Protective film (one of which is the optical film of the present invention)

Claims

1. An optical film comprising a cycloolefin resin and a compound represented by any one of the following structural formulas (1) to (5): 【Chemistry 1】

2. The optical film according to claim 1 , wherein the cycloolefin resin has a polar group.

3. A method for producing the optical film according to claim 1 or 2, comprising: preparing a dope containing a compound represented by any one of structural formulas (1) to (5), the cycloolefin resin, and a solvent; casting the dope on a support to obtain an unstretched film; and stretching the unstretched film.

4. A polarizing plate comprising: a polarizer; and the optical film according to claim 1 or 2, which is disposed on at least one surface of the polarizer.

5. A display device comprising the optical film according to claim 1 or 2.

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