TWI861481B - Stretched film, method for manufacturing stretched film, polarizing plate and liquid crystal display device - Google Patents

Abstract

The stretched film of the present invention is a stretched film containing a cycloolefin resin having a polar group, and the half-value width of the diffraction peak when the surface of the stretched film is irradiated with X-rays at an angle of 0.1 degree is in the range of 4.6 to 5.4 degrees, and the residual solvent content is in the range of 5 to 500 mass ppm.

Description

Stretched film, method for manufacturing stretched film, polarizing plate and liquid crystal display device

The present invention relates to a stretched film, a method for manufacturing the stretched film, a polarizing plate and a liquid crystal display device, and more particularly to a stretched film having a low-alignment surface, moderate moisture permeability and excellent adhesion.

Cycloolefin resin has excellent transparency, optical properties and durability. Optical films using cycloolefin resin to adjust the phase difference can be applied to VA type liquid crystal display devices. Conventionally, as a method for manufacturing optical films using cycloolefin resin, melt casting film forming method and solution casting film forming method are known.

The production of retardation film for VA type liquid crystal display device (hereinafter referred to as "VA") requires stretching in order to show the desired phase difference. When stretching is performed using a cycloolefin resin to show the phase difference for VA by a well-known method, the resin molecular chain is extremely highly oriented and the density increases, especially on the outermost surface, which hinders the diffusion of the ultraviolet curing adhesive (hereinafter also referred to as UV paste) during the production of polarizing plates, and there is a problem of poor adhesion. Recently, as a retardation film for VA, a thin film is required, but in particular, in the case of a thin film, a high-magnification stretching is required to show the phase difference, so there is a problem that the adhesion is greatly deteriorated when using UV paste.

Therefore, as a retardation film with excellent adhesion to other films, there is a technique disclosed that selectively heats only the surface of the retardation film to reduce the orientation of the resin molecular chain on the surface of the retardation film and improves the adhesion (for example, refer to patent document 1). In addition, there is also a technique disclosed that a coating liquid containing a good solvent is applied to the surface of the retardation film to reduce the orientation of the resin molecular chain on the surface of the film (for example, refer to patent document 2).

However, when the film disclosed in the aforementioned patent documents 1 and 2 is laminated to a polarizer layer (also referred to as "polarizer film", "polarizing film" and "polarizer film"), from the perspective of drying, the film needs to have a moderate moisture permeability in order to allow moisture from the polarizer layer to escape. That is, from the perspective of bonding between the film and the paste interface, the surface is preferably low-oriented, and from the perspective of bonding including the drying step after bonding with the polarizer layer, it must have a moderate moisture permeability. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Publication No. 2012-159665 [Patent Document 2] Japanese Patent Publication No. 2019-028109

[The problem that the invention is trying to solve]

The present invention is made in view of the above problems and conditions, and solves the problem by providing a stretched film with a low-aligned surface and moderate moisture permeability and excellent adhesion, and a method for manufacturing the stretched film. In addition, a polarizing plate and a liquid crystal display device using the stretched film are provided. [Means for solving the problem]

In order to solve the above-mentioned problem, the inventors of the present invention have found in the process of examining the causes of the above-mentioned problem that by setting the half-value width of the diffraction peak of the surface of the stretched film containing the cycloolefin resin having a polar group to a specific range when irradiated with X-rays at an angle of 0.1 degrees and by controlling the amount of residual solvent, a stretched film with a low surface orientation and excellent adhesion having moderate moisture permeability can be provided, thereby achieving the present invention. That is, the above-mentioned problem of the present invention is solved by the following means.

1. A stretched film containing a cycloolefin resin having a polar group, characterized in that: The half-value width of the diffraction peak when the surface of the stretched film is irradiated with X-rays at an angle of 0.1 degrees is in the range of 4.6 to 5.4 degrees, and The residual solvent content is in the range of 5 to 500 mass ppm.

2. The oxygen permeability of the stretched film described in Item 1 is within the range of 3000 to 5000 mL/( ^m2・24hr・atm) at a temperature of 23°C and a humidity of 0%RH.

3. The stretched film as described in item 1 or 2, wherein the half-value width is in the range of 4.8 to 5.2 degrees.

4. The stretched film as described in any one of Items 1 to 3, which contains fine particles.

5. A method for producing a stretched film, which is a method for producing a stretched film as described in any one of items 1 to 4, characterized in that the stretched film is produced by a solution casting method.

6. A method for producing a stretched film as described in item 5, wherein a dope containing the aforementioned cycloolefin resin having a polar group is cast on a support to form a web, and then a stretching treatment is applied at a stretching ratio in the stretching step expressed as an area ratio in the range of 1.2 to 3.0 times.

7. A method for producing a stretched film as described in item 5 or 6, wherein after a slurry containing the aforementioned cycloolefin hydrocarbon resin having a polar group is cast on a support to form a mesh, the amount of residual solvent at the beginning of the stretching step is set to a range of 700 to 30,000 mass ppm.

8. A polarizing plate characterized by comprising a stretched film as described in any one of items 1 to 4.

9. A liquid crystal display device characterized by having a polarizing plate as described in item 8. [Effect of the invention]

By means of the above-mentioned means of the present invention, a stretched film having a low-alignment surface and a moderate moisture permeability and excellent adhesion and a method for manufacturing the stretched film can be provided. In addition, a polarizing plate and a liquid crystal display device using the stretched film can be provided. Although the mechanism for the effect of the present invention is not clear, it can be inferred as follows. By setting the half-value width of the diffraction peak when the surface of the stretched film containing a cycloolefin resin having a polar group is irradiated with X-rays at an angle of 0.1 degree to a range of 4.6 to 5.4 degrees, the resin molecular chain on the surface becomes low-alignment, and the adhesion of the ultraviolet curing adhesive during the production of the polarizing plate is excellent. Furthermore, by setting the residual solvent amount of the stretched film to the range of 5 to 500 mass ppm, the orientation of the resin molecular chain on the surface is difficult to become uniform, and becomes a low orientation, which also has excellent adhesion. Furthermore, as mentioned above, by setting the resin molecular chain on the surface of the stretched film to a low orientation, appropriate moisture permeability can be ensured, resulting in excellent adhesion.

Moreover, in the present invention, the so-called "alignment" refers to the arrangement of the molecular chains in the resin in a certain direction. For example, the state in which the molecular chain arrangement in the resin is high in the direction perpendicular to the film thickness is called "high alignment". Therefore, in a resin with small interactions between resins, a high alignment region can be formed on the surface by stretching. The high alignment region adopts a structure with relatively regular main chain spacing (high crystallinity). In the present invention, by setting the surface to low alignment, a structure with irregular main chain spacing and less regularity is adopted, thereby improving adhesion.

[Form of implementing the invention]

The stretched film of the present invention is a stretched film containing a cycloolefin resin having a polar group, and is characterized in that the half-value width of the diffraction peak when the surface of the stretched film is irradiated with X-rays at an angle of 0.1 degrees is in the range of 4.6 to 5.4 degrees, and the residual solvent amount is in the range of 5 to 500 mass ppm. This feature is a common or corresponding technical feature of each of the following embodiments.

As an embodiment of the present invention, the oxygen permeability is preferably within the range of 3000 to 5000 mL/(m ²・24hr・atm) at a temperature of 23°C and a humidity of 0%RH, which is preferred in terms of being able to properly release the moisture of the adhesive and becoming a film that is not prone to long-term adhesive deterioration. In addition, the half-value width is preferably within the range of 4.8 to 5.2 degrees, which is preferred in terms of being able to achieve a low surface orientation and having appropriate moisture permeability. Furthermore, the stretched film of the present invention containing microparticles is preferred in terms of being able to prevent the surface from becoming highly oriented.

The method for producing a stretched film of the present invention is characterized in that the stretched film is produced by a solution casting method, whereby the stretching conditions can be controlled in a wide range by adjusting the amount of residual solvent, especially the stretching conditions in a low temperature region (below Tg+30°C).

In addition, the method for producing the stretched film of the present invention is to cast the slurry containing the aforementioned cycloolefin resin having a polar group on a support to form a mesh sheet, and then perform stretching treatment in the stretching step at a stretching ratio expressed as an area ratio in the range of 1.2 to 3.0 times, which is preferably in order to make the aforementioned half-value width within the aforementioned range, and to achieve a low-orientation surface and moderate moisture permeability. Furthermore, after the slurry containing the aforementioned cycloolefin hydrocarbon resin having a polar group is cast on a support to form a mesh, the residual solvent amount at the beginning of the extension step is set to within the range of 700 to 30,000 mass ppm, which is also preferable in that the aforementioned half-value width can be within the aforementioned range, and the surface can be low-oriented and have moderate moisture permeability.

The stretched film of the present invention can be applied to a polarizing plate. Furthermore, the polarizing plate can be used in a liquid crystal display device.

Hereinafter, the present invention and its constituent elements and forms and aspects for implementing the present invention will be described. In addition, "to" in the present invention is used to mean that the numerical values described before and after it are included as lower limits and upper limits.

[Overview of the stretched film of the present invention] The stretched film of the present invention is a stretched film containing a cycloolefin resin having a polar group, and is characterized in that the half-value width of the diffraction peak when the surface of the stretched film is irradiated with X-rays at an angle of 0.1 degrees is in the range of 4.6 to 5.4 degrees, and the residual solvent amount is in the range of 5 to 500 mass ppm.

<X-ray diffraction peak> In the present invention, in order to evaluate the orientation of the surface of the stretched film, the X-ray diffraction method is appropriate. In particular, it is preferable to reduce the incident angle θ of the incident X-ray and to shallow the information depth of the X-ray detected by diffraction, which is called the thin film method. Specifically, the incident angle θ of the incident X-ray is fixed at about 0.1 degrees, and the intensity of the X-ray is measured while changing the angle of the detector. In the present invention, as an X-ray diffraction device, an X-ray diffraction device RINT-TTRII (manufactured by Rigaku Denki Co., Ltd.) is used. The cathode (anticathode) is set to Cu, and it is operated at 50kV-300mA. The height limit slit is 10mm, the divergence slit is 2/3, and the optical system is adjusted in such a way that the half-value width of the peak of Al(200) when measuring aluminum foil is 0.35 degrees. Fix the film, fix θ at 0.1 degrees, scan 2θ at 0.02 degree steps from 5 to 35 degrees, and accumulate 1 second at each step to obtain the diffraction pattern. Perform background processing to obtain the half-value width of the diffraction peak.

The half-value width of the aforementioned diffraction peak is in the range of 4.6 to 5.4 degrees, preferably in the range of 4.8 to 5.2 degrees. The half-value width of the aforementioned diffraction peak indicates the distance between crystals. Since the lower the orientation, the more random the main chain spacing in the resin, the wider the half-value width becomes.

As a means to make the half width of such a diffraction peak within the aforementioned range, it is possible to cite the control of the residual solvent amount at the start of the stretching step, the stretching ratio during the stretching, the heating temperature during the stretching, the drying time and the drying time during the formal drying after the stretching step, etc. Specifically, the residual solvent amount at the start of the stretching is preferably set in the range of 700 to 30,000 mass ppm. The stretching ratio is preferably set in the range of 1.2 to 3.0 times expressed as an area ratio (area ratio). The heating temperature during the stretching is preferably set in the range of 100 to 200°C.

In addition, the amount of residual solvent at the start of the aforementioned extension can be controlled by the drying temperature and drying time during the preliminary drying before the extension step as described below.

<Residual solvent amount> The residual solvent amount of the stretched film of the present invention is in the range of 5 to 500 mass ppm, preferably in the range of 5 to 100 mass ppm. In the present invention, the residual solvent amount of the stretched film is defined by the following formula (Z1) as long as it is within the aforementioned range at any time within a period of 3 months from the shipment of the stretched film. Formula (Z1): Residual solvent amount (ppm) = (mass of stretched film before heat treatment - mass of stretched film after heat treatment) / (mass of stretched film after heat treatment) × 10 ⁶ Moreover, the heat treatment when measuring the residual solvent amount means heat treatment at 115°C for 1 hour.

In addition, as a means for making the residual solvent amount of the stretched film within the aforementioned range, similar to the means for controlling the half-value width of the diffraction peak mentioned above, there can be cited control of the residual solvent amount at the start of stretching in the stretching step, or the stretching ratio during stretching, the heating temperature during stretching, the drying time during formal drying after the stretching step, and the drying time, etc.

<Oxygen Permeability> The oxygen permeability of the stretched film of the present invention is preferably in the range of 3000 to 5000 mL/(m ² ·24 hr·atm) (1 atm is 1.01325×10 ⁵ Pa), and more preferably in the range of 4000 to 5000 mL/(m ² ·24 hr·atm).

In the present invention, the oxygen permeability is calculated as follows. Under the conditions of temperature 23°C and humidity 0%RH, an oxygen permeability measuring device (model name "Oxtran" (registered trademark) ("OXTRAN" 2/20), manufactured by MOCON, USA) is used to measure according to the B method (isobaric method) described in JIS K7126 (1987). In addition, the measurement is performed once for each of the two test pieces, and the average of the two measured values is regarded as the value of the oxygen permeability.

The aforementioned oxygen permeability is controlled by the orientation state of the surface of the stretched film. By limiting the half-value width of the aforementioned diffraction peak and the aforementioned residual solvent amount of the stretched film within the aforementioned range, the surface becomes low-oriented, the main chain spacing is random and a structure with less regularity is adopted, resulting in a film with low oxygen permeability.

[Stretched film composition] The stretched film of the present invention contains a cycloolefin resin having a polar group.

(1.1) Cycloolefin resin The cycloolefin resin of the present invention is preferably a polymer of a cycloolefin monomer, or a copolymer of a cycloolefin monomer and a copolymerizable monomer other than the cycloolefin monomer.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

In the general formula (A-1), at least one of ^R1 to ^R4 represents a polar group, and the others independently represent a hydrogen atom or a alkyl group having 1 to 30 carbon atoms. p represents an integer of 0 to 2. However, ^R1 and ^R2 do not simultaneously represent hydrogen atoms, and ^R3 and ^R4 do not simultaneously represent hydrogen atoms.

In the general formula (A-1), the alkyl group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ is preferably a alkyl group having 1 to 10 carbon atoms, and more preferably a alkyl group having 1 to 5 carbon atoms. The alkyl group having 1 to 30 carbon atoms may further have a linking group containing a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom. Examples of such a linking group include bivalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a sulfide ether bond. Examples of the alkyl group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

In the general formula (A-1), examples of polar groups represented by R ¹ to R ⁴ include carboxyl, hydroxyl, alkoxy, alkoxycarbonyl, aryloxycarbonyl, amino, amide and cyano. Among them, carboxyl, hydroxyl, alkoxycarbonyl and aryloxycarbonyl are preferred. From the viewpoint of ensuring solubility during film formation from a solution, alkoxycarbonyl and aryloxycarbonyl are preferred.

From the perspective of improving the heat resistance of the stretched film, p in the general formula (A-1) is preferably 1 or 2. This is because when p is 1 or 2, the resulting polymer becomes larger and the glass transition temperature is easily increased.

In the general formula (A-2), ^R5 represents a hydrogen atom, a alkyl group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. ^R6 represents a polar group, specifically, a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). p represents an integer of 0 to 2.

^R5 in the general formula (A-2) preferably represents a alkyl group having 1 to 5 carbon atoms, and more preferably represents a alkyl group having 1 to 3 carbon atoms.

^R6 in the general formula (A-2) preferably represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group, and more preferably an alkoxycarbonyl group or an aryloxycarbonyl group from the viewpoint of ensuring solubility during film formation from a solution.

From the viewpoint of improving the heat resistance of the stretched film, p in the general formula (A-2) is preferably 1 or 2. This is because when p is 1 or 2, the resulting polymer becomes larger and the glass transition temperature is easily increased.

Cycloolefin monomers having a structure represented by the general formula (A-2) are preferred from the viewpoint of improving solubility in organic solvents. Generally speaking, organic compounds reduce their crystallinity by breaking down their symmetry, and thus their solubility in organic solvents increases. Since R ⁵ and R ⁶ in the general formula (A-2) only replace the carbon atoms of the ring structure on one side with respect to the symmetry axis of the molecule, the symmetry of the molecule is low, that is, the cycloolefin monomers having a structure represented by the general formula (A-2) are highly soluble, and therefore are suitable for the case of manufacturing stretched films by solution casting.

The content ratio of the cycloolefin monomer having the structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer may be, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% relative to the total of all cycloolefin monomers constituting the cycloolefin resin. If the cycloolefin monomer having the structure represented by the general formula (A-2) is contained in a certain amount or more, the orientation of the resin increases, and thus the phase difference (hysteresis) value tends to increase.

Hereinafter, specific examples of the cycloalkene monomer having a structure represented by the general formula (A-1) are shown in Exemplary Compounds 2, 3, and 9 to 14, and specific examples of the cycloalkene monomer having a structure represented by the general formula (A-2) are shown in Exemplary Compounds 15 to 34.

Examples of the copolymerizable monomers copolymerizable with the cycloolefin monomers include copolymerizable monomers capable of ring-opening copolymerization with the cycloolefin monomers and copolymerizable monomers capable of addition copolymerization with the cycloolefin monomers.

Examples of the copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene.

Examples of the addition copolymerizable monomers include compounds containing an unsaturated double bond, vinyl cyclic hydrocarbon monomers, and (meth)acrylates.

Examples of compounds containing unsaturated double bonds include olefinic compounds having 2 to 12 carbon atoms (preferably 2 to 8 carbon atoms), and examples thereof include ethylene, propylene, and butene.

Examples of the vinyl-based cyclic hydrocarbon monomers include vinylcyclopentene-based monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene.

Examples of the (meth)acrylate include alkyl (meth)acrylates having 1 to 20 carbon atoms, such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer may be, for example, in the range of 20 to 80 mol %, preferably in the range of 30 to 70 mol %, based on the total of all monomers constituting the copolymer.

The cycloolefin resin is a polymer obtained by polymerizing or copolymerizing a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2), as described above. Examples thereof include the following polymers (1) to (7).

(1) Ring-opening polymers of cycloolefin monomers (2) Ring-opening copolymers of cycloolefin monomers and copolymerizable monomers capable of ring-opening copolymerization with the cycloolefin monomers (3) Hydrogenates of the ring-opening (co)polymers of (1) or (2) above (4) (Co)polymers obtained by cyclizing the ring-opening (co)polymers of (1) or (2) above by Friedel-Quaft reaction and then hydrogenating them (5) Saturated copolymers of cycloolefin monomers and compounds containing unsaturated double bonds (6) Addition copolymers of cycloolefin monomers and vinyl cyclic monomers and their hydrogenates (7) Alternating copolymers of cycloolefin monomers and (meth)acrylates

The polymers of (1) to (7) above can be obtained by a known method, for example, the method described in Japanese Patent Application Publication No. 2008-107534 or Japanese Patent Application Publication No. 2005-227606.

For example, the catalyst or solvent used in the ring-opening copolymerization of (2) above may be described in paragraphs 0019 to 0024 of Japanese Patent Publication No. 2008-107534. The catalyst used in the hydride of (3) and (6) above may be described in paragraphs 0025 to 0028 of Japanese Patent Publication No. 2008-107534. The acid compound used in the Friedel-Quaft reaction of (4) above may be described in paragraph 0029 of Japanese Patent Publication No. 2008-107534. The catalyst used in the addition polymerization of (5) to (7) above may be described in paragraphs 0058 to 0063 of Japanese Patent Publication No. 2005-227606. The alternating copolymerization reaction (7) mentioned above can be carried out, for example, using the method described in paragraphs 0071 and 0072 of Japanese Patent Publication No. 2005-227606.

Among them, the polymers of (1) to (3) and (5) are preferred, and the polymers of (3) and (5) are more preferred.

That is, in terms of being able to increase the glass transition temperature of the obtained cycloolefin resin and improving the light transmittance, the cycloolefin resin preferably contains at least one of the structural unit represented by the following general formula (B-1) and the structural unit represented by the following general formula (B-2), and more preferably contains only the structural unit represented by the general formula (B-2), or contains both the structural unit represented by the general formula (B-1) and the structural unit represented by the general formula (B-2).

The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloalkene monomer represented by the general formula (A-1), and the structural unit represented by the general formula (B-2) is a structural unit derived from the cycloalkene monomer represented by the general formula (A-2).

In the general formula (B-1), X represents -CH=CH- or -CH ₂ CH ₂ -. R ¹ to R ⁴ and p are each synonymous with R ¹ to R ⁴ and p in the general formula (A-1).

In the general formula (B-2), X represents -CH=CH- or -CH ₂ CH ₂ -. R ⁵ to R ⁶ and p are independently the same as R ⁵ to R ⁶ and p in the general formula (A-2).

The cycloolefin resin of the present invention may be a commercial product. Examples of commercial products of cycloolefin resins include Arton G (e.g., G7810, etc.), Arton F, Arton R (e.g., R4500, R4900, and R5000, etc.), and Arton RX manufactured by JSR Corporation.

The intrinsic viscosity [η]inh of the cycloolefin resin is preferably in the range of 0.2 to 5 cm ³ /g, more preferably in the range of 0.3 to 3 cm ³ /g, and particularly preferably in the range of 0.4 to 1.5 cm ³ /g, when measured at 30°C.

The number average molecular weight (Mn) of the cycloolefin resin is preferably in the range of 8,000 to 100,000, more preferably in the range of 10,000 to 80,000, and particularly preferably in the range of 12,000 to 50,000.

The weight average molecular weight (Mw) of the cycloolefin resin is preferably in the range of 20,000 to 300,000, more preferably in the range of 30,000 to 250,000, and particularly preferably in the range of 40,000 to 200,000.

The number average molecular weight or weight average molecular weight of cycloolefin resins can be measured by gel permeation chromatography (GPC) in terms of polystyrene.

(Gel Permeation Chromatography) Solvent: Dichloromethane Column: Shodex K806, K805, K803G (Showa Denko Co., Ltd., 3 columns connected for use) Column temperature: 25°C Sample concentration: 0.1 mass % Detector: RI Model 504 (GL Science Co., Ltd.) Pump: L6000 (Hitachi, Ltd.) Flow rate: 1.0 ml/min Calibration curve: Calibration curve using 13 samples of STK standard polystyrene (Tosoh Co., Ltd.) with a range of Mw=500 to 2800000. It is best to use the 13 samples at approximately equal intervals.

When the intrinsic viscosity [η]inh, the number average molecular weight and the weight average molecular weight are within the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties and film forming processability of the cycloolefin resin become good.

The glass transition temperature (Tg) of the cycloolefin resin is usually above 110°C, preferably in the range of 110 to 350°C, more preferably in the range of 120 to 250°C, and particularly preferably in the range of 120 to 220°C.

If the glass transition temperature (Tg) is 110°C or higher, deformation under high temperature conditions can be easily suppressed. On the other hand, if the glass transition temperature (Tg) is 350°C or lower, molding becomes easier and resin deterioration caused by heat during molding can be easily suppressed.

The content of the cycloolefin resin relative to the film is preferably 70% by mass or more, more preferably 80% by mass or more.

(1.2) Other additives The stretched film of the present invention may contain the following as other additives in addition to the above-mentioned cycloolefin resin.

(1.2.1) Plasticizer The stretched film of the present invention is preferably used to impart processability to a polarizing plate protective film, etc., and preferably contains at least one plasticizer. The plasticizer is preferably used alone or in combination of two or more.

Among plasticizers, at least one plasticizer selected from the group consisting of sugar esters, polyesters and styrene compounds is preferably included from the viewpoint of being able to effectively control moisture permeability and having compatibility with base resins such as cellulose esters.

The molecular weight of the plasticizer is preferably 15,000 or less, and further preferably 10,000 or less, from the viewpoint of improving moisture and heat resistance and compatibility with base resins such as cellulose ester.

When the compound with a molecular weight of 10,000 or less is a polymer, the weight average molecular weight (Mw) is preferably 10,000 or less. The preferred weight average molecular weight (Mw) ranges from 100 to 10,000, and more preferably from 400 to 8,000.

In particular, in order to obtain the effect of the present invention, the compound having a molecular weight of 1500 or less is preferably contained in a range of 6 to 40 parts by mass, and more preferably in a range of 10 to 20 parts by mass, relative to 100 parts by mass of the base resin. By containing it in the above range, it is preferable to take into account both effective control of moisture permeability and compatibility with the base resin.

〈Sugar ester〉 In the stretched film of the present invention, a sugar ester compound may be contained for the purpose of preventing hydrolysis. Specifically, as the sugar ester compound, a sugar ester having at least one of 1 to 12 pyranose structures or furanose structures, in which all or part of the OH groups of the structure are esterified, may be used.

〈Polyester〉 The stretched film of the present invention may also contain polyester.

The polyester is not particularly limited, but for example, a polymer having a hydroxyl group at the end obtained by a condensation reaction between a dicarboxylic acid or an ester-forming derivative thereof and a diol (polyester polyol), or a polymer having the hydroxyl group at the end of the polyester polyol blocked by a monocarboxylic acid (terminal-blocked polyester) can be used. The ester-forming derivative mentioned here is an ester of a dicarboxylic acid, a dicarboxylic acid chloride, or an anhydride of a dicarboxylic acid.

〈Styrene compounds〉 In the stretched film of the present invention, in addition to or in place of the above-mentioned sugar esters and polyesters, styrene compounds may also be used for the purpose of improving the water resistance of the stretched film.

The styrene compound may be a homopolymer of a styrene monomer or a copolymer of a styrene monomer and a copolymer monomer other than the styrene monomer. The content ratio of the constituent units derived from the styrene monomer in the styrene compound is preferably in the range of 30 to 100 mol %, and more preferably in the range of 50 to 100 mol %, because the molecular structure has a certain volume.

Examples of styrene monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; hydroxystyrenes such as p-hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, and 3,4-dihydroxystyrene; vinylbenzyl alcohol; alkoxy-substituted styrenes such as p-methoxystyrene, p-tert-butoxystyrene, and m-tert-butoxystyrene; 3-vinylbenzoic acid, 4-ethylbenzyl alcohol, and 4-hydroxystyrene; Vinylbenzoic acid such as alkenylbenzoic acid; 4-vinylbenzyl acetate; 4-acetyloxystyrene; 2-butylamide styrene, 4-methylamide styrene, p-sulfonamide styrene and other amide styrenes; 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline, vinylbenzyldimethylamine and other aminostyrenes; 3-nitrostyrene, 4-nitrostyrene and other nitrostyrenes; 3-cyanostyrene, 4-cyanostyrene and other cyanostyrene; vinylphenylacetonitrile; phenylstyrene and other arylstyrenes, indene and the like. The styrene monomer may be one type or a combination of two or more types.

(1.2.2) Optional components The stretched film of the present invention may contain other optional components such as antioxidants, colorants, ultraviolet absorbers, matting agents, acrylic particles, hydrogen bonding solvents and ionic surfactants. In particular, it is preferred to contain matting agents (microparticles). These components can be added in a range of 0.01 to 20 parts by mass relative to 100 parts by mass of the base resin.

<Antioxidant> The stretched film of the present invention can use commonly known antioxidants. In particular, lactone-based, sulfur-based, phenol-based, double-bond-based, hindered amine-based, and phosphorus-based compounds can be preferably used.

These antioxidants are added in the range of 0.05-20 mass % relative to the resin of the main raw material of the stretched film, preferably in the range of 0.1-1 mass %. Compared with using only one type, these antioxidants can achieve a synergistic effect by using several different types of compounds. For example, it is preferred to use lactone, phosphorus, phenol and double bond compounds together.

〈Colorant〉 The stretched film of the present invention preferably contains a colorant in order to adjust the color tone within the range that does not damage the effect of the present invention.

Coloring agent refers to dye or pigment, and in the present invention refers to the effect of making the color tone of the liquid crystal screen blue or adjusting the yellow index or reducing the haze.

As a coloring agent, various dyes and pigments can be used, and anthraquinone dyes, azo dyes, phthalocyanine pigments, etc. are effective.

〈Ultraviolet absorber〉 Since the stretched film of the present invention can also be used on the visual recognition side or backlight side of the polarizing plate, it can contain an ultraviolet absorber for the purpose of imparting ultraviolet absorption function.

The ultraviolet absorber is not particularly limited, and examples thereof include benzotriazole-based, 2-hydroxybenzophenone-based, or salicylic acid phenyl ester-based ultraviolet absorbers. 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-tert-butyl-2-hydroxyphenyl)benzotriazole, and benzophenones such as 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone can be used. The above ultraviolet absorbers can be used alone or in combination of two or more.

The amount of UV absorber used depends on the type of UV absorber, usage conditions, etc., but generally speaking, it is added in the range of 0.05-10 mass % relative to the base resin, preferably in the range of 0.1-5 mass %.

〈Matting agent〉 In the stretched film of the present invention, in order to impart irregularities to the film surface during film formation, ensure slippage, and achieve a stable roll-up shape, it is preferred that a matting agent be included. In addition, when handling the produced film, the matting agent can also play its role in preventing damage or deterioration in handling performance.

As the matting agent, there can be cited inorganic compound particles or resin particles. Examples of inorganic compound particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. The particles containing silicon are preferred in terms of lower turbidity, and silicon dioxide is particularly preferred.

The average particle size of the primary particles of the microparticles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm. These can be mainly contained as secondary agglomerates in the range of 0.05 to 0.3 μm, and particles in the range of 80 to 400 nm in average particle size are not agglomerated and are also preferably contained as primary particles. The content of these microparticles in the film is preferably in the range of 0.01 to 1 mass %, particularly preferably in the range of 0.05 to 0.5 mass %. In addition, in the case of a multi-layer structure by co-casting, it is preferred to contain the added amount of microparticles on the surface.

For example, the silicon dioxide particles can be commercially available under the trade names of Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (all manufactured by AEROSIL Co., Ltd., Japan). The zirconium oxide particles can be commercially available under the trade names of Aerosil R976 and R811 (all manufactured by AEROSIL Co., Ltd., Japan).

Examples of resin microparticles include silicone resins, fluororesins, and acrylic resins. Silicone resins are preferred, and those having a three-dimensional mesh structure are particularly preferred, such as those commercially available under the trade names of Tospearl 103, Tospearl 105, Tospearl 108, Tospearl 120, Tospearl 145, Tospearl 3120, and Tospearl 240 (all manufactured by Toshiba Silicone Co., Ltd.). Among these, Aerosil 200V, Aerosil R972V, and Aerosil R812 are particularly preferred because they have a great effect of reducing the friction coefficient while maintaining a low haze of the substrate film.

[Method for producing stretched film] The stretched film of the present invention is characterized in that it is produced by a solution casting method. Specifically, the method for producing stretched film of the present invention is preferably produced by the following steps: (1) a step of preparing a slurry containing the aforementioned cycloolefin resin having a polar group (slurry preparation step), (2) a step of casting the aforementioned slurry on a support to form a mesh (also called a cast film) (casting step), (3) a step of evaporating a solvent from the mesh on the support (solvent evaporation step). (4) a step of peeling the mesh sheet off the support (peeling step), (5) a step of drying the obtained film (hereinafter also referred to as "raw film") (first drying step), (6) a step of stretching the film (stretching step), (7) a step of further drying the stretched film (second drying step), and (8) a step of rolling up the obtained stretched film (rolling up step).

In particular, in the stretching step (6), the stretching treatment is performed at a stretching ratio in the range of 1.2 to 3.0 times expressed as an area ratio, which is preferred in that the half-value width of the aforementioned diffraction peak and the amount of residual solvent of the obtained stretched film can be within the range of the present invention, and the surface can be low-oriented and have appropriate moisture permeability. The stretching ratio mentioned in the present invention refers to the ratio (%) of the area of the stretched film relative to the area of the original film before stretching. That is, the total stretching ratio caused by the stretching of the original film in the longitudinal (length) direction and the transverse (width) direction is stretched in the range of 1.2 to 3.0 times expressed as an area ratio. Furthermore, in the stretching step (6), it is preferable to set the residual solvent amount of the original film at the beginning of stretching to the range of 700 to 30,000 mass ppm, which is also preferable in that the half-value width of the aforementioned diffraction peak and the residual solvent amount of the obtained stretched film can be within the range of the present invention.

The above steps are explained with reference to the drawings. FIG. 1 is a diagram schematically showing an example of the slurry preparation step, casting step, drying step and winding step of the preferred solution casting film forming method in the present invention. The microparticle dispersion in which the solvent and the matting agent are dispersed by the disperser is stored in the storage tank 62 from the feed tank 61 through the filter 64. On the other hand, the cycloolefin resin as the main slurry is dissolved in the dissolving tank 1 together with the solvent, and the matting agent stored in the storage tank 62 is appropriately added and mixed to form the main slurry. The main slurry obtained is filtered from the filter 3 and the storage tank 4 through the filter 6, the additive is added through the confluence pipe 20, mixed in the mixer 21 and sent to the pressure die 22.

On the other hand, additives (such as ultraviolet absorbers) are dissolved in the solvent, passed through the filter 12 from the additive feed tank 10, and stored in the storage tank 13. Then, they pass through the filter 15, the conduit 16, the confluence pipe 20, and the mixer 21 to be mixed with the main slurry.

The main slurry fed to the pressure die 22 is cast on a metal belt-shaped support 31 to form a mesh 32, and is peeled off at a designated peeling position 33 after drying to obtain a raw material film. The peeled mesh 32 is dried to a designated residual solvent amount while passing through a plurality of conveying rollers in the first drying device 34, and then stretched to a designated stretching ratio in the length direction or width direction by a stretching device 35, and heated to a designated residual solvent amount at the same time. After stretching, it is to be changed to a designated residual solvent amount by the second drying device 36, and is dried while passing through a conveying roller 37, and is rolled into a roll by a winding device 38. The following describes each step.

(1) Slurry preparation step In an organic solvent mainly a good solvent for the aforementioned cycloolefin resin, the cycloolefin resin, a phase difference increasing agent, a matting agent (microparticles) or other compounds as required are stirred in a dissolving vessel while dissolving to prepare a slurry, or in the cycloolefin resin solution, a phase difference increasing agent, a matting agent or other compound solution is mixed to prepare a slurry as the main dissolving liquid.

When the stretched film of the present invention is produced by solution casting, any organic solvent suitable for forming the slurry can be used without limitation as long as it can dissolve the cycloolefin resin and other compounds at the same time.

Examples of the organic solvent 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 solvent, ethyl solvent, butyl solvent, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, and diethyl ether. Only one of these solvents may be used, or two or more of them may be used in combination.

The organic solvent used in the present invention is preferably a mixed solvent of a good solvent and a weak solvent. The good solvent, for example, as a chlorine-based organic solvent, can be methylene chloride, and as a non-chlorine-based organic solvent, can be 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, 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, isopropanol, n-butanol, 2-butanol, 3-butanol, etc., preferably dichloromethane. 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 relative to the total amount of the solvent.

The weak solvent is preferably an alcohol solvent, and the alcohol solvent is selected from methanol, ethanol and butanol, which is preferred from the viewpoint of improving the releasability and enabling high-speed casting. Among them, methanol or ethanol is preferably used. If the ratio of alcohol in the slurry becomes higher, the mesh will gel and be easily peeled off from the metal support. In addition, if the proportion of alcohol is small, it also has the effect of promoting the dissolution of cycloolefin resins and other compounds in the non-chlorine organic solvent system. In the film preparation of the stretched film of the present invention, from the point of view of improving the planarity of the obtained stretched film, it is better to use a slurry with an alcohol concentration in the range of 0.5 to 15.0 mass % for film preparation.

In dissolving cycloolefin resins and other compounds, various dissolving methods can be used, such as a method under normal pressure, a method below the boiling point of the main solvent, a method under pressure above the boiling point of the main solvent, a method using a cooling dissolution method as described in Japanese Patent Application Laid-Open No. 9-95544, Japanese Patent Application Laid-Open No. 9-95557 or Japanese Patent Application Laid-Open No. 9-95538, and a method under high pressure as described in Japanese Patent Application Laid-Open No. 11-21379. However, a method under pressure above the boiling point of the main solvent is particularly preferred.

The concentration of cycloolefin resin in the slurry is preferably in the range of 10 to 40 mass %. The compound is added to the slurry during or after dissolution, dissolved and dispersed, filtered with a filter material, defoamed, and then sent to the next step with a liquid delivery pump. Regarding the filtration of the slurry, it is preferred to filter the slurry with a main filter 3 having a blade type filter, for example, with a filter material that captures 90% of the particle size within the range of 10 to 100 times the average particle size of the microparticles.

In the present invention, the filter material used for filtering is preferably one with a small absolute filtration accuracy. However, if the absolute filtration accuracy is too small, the filter material is easily clogged and the filter material must be frequently replaced, which has the problem of reducing productivity. Therefore, in the present invention, the filter material used for cycloolefin resin slurry is preferably one with an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and even more preferably in the range of 0.003 to 0.006 mm.

There is no particular restriction on the material of the filter, and common filter materials can be used. Plastic fiber filters such as polypropylene and Teflon (registered trademark) or metal filters such as stainless steel fibers are preferred because the fibers do not fall off.

In the present invention, the flow rate of the slurry during filtration is preferably 10 to 80 kg/(h·m ² ), more preferably 20 to 60 kg/(h·m ² ). Here, if the flow rate of the slurry during filtration is 10 kg/(h·m ² ) or more, efficient productivity is achieved, and if the flow rate of the slurry during filtration is within 80 kg/(h·m ² ), the pressure applied to the filter material is appropriate and the filter material is preferably not damaged.

The filter pressure is preferably below 3500 kPa, more preferably below 3000 kPa, and even more preferably below 2500 kPa. Furthermore, the filter pressure can be controlled by appropriately selecting the filter flow rate and the filter area. In most cases, the main slurry contains about 1 to 50% by mass of return material.

The so-called scraps are, for example, finely crushed cycloolefin resin films, the parts of the cycloolefin resin films that have been cut off when the cycloolefin resin films are being made, or the cycloolefin resin film raw materials that have been scratched beyond the specified value of the film.

In addition, as the raw material of the resin used for preparing the slurry, it is preferable to use cycloolefin resins and other compounds that have been granulated in advance.

(2) Casting step (2-1) Casting of slurry The slurry is fed to the pressure die 22 through a liquid feeding pump (e.g., a pressure-type metering gear pump), and the slurry is cast from the pressure die slit at a casting position on a metal support body such as an endlessly moving ring-shaped metal support body 31, such as a stainless steel belt or a rotating metal drum.

The metal support in the casting step is preferably a mirror-finished metal support. A stainless steel belt or a casting with a coated surface is preferably used as the metal support. The casting width can be set to a range of 1 to 4 m, preferably 1.3 to 3 m, and more preferably 1.5 to 2.8 m.

The surface temperature of the metal support in the casting step is -50℃ to the temperature below which the solvent does not boil and foam, preferably -30～100℃. The higher the temperature, the faster the drying speed of the mesh (the slurry film formed by casting the slurry on the casting support is called the mesh), but if it is too high, the mesh may foam or the flatness may deteriorate. The preferred support temperature is appropriately determined within the range of 0～100℃, preferably within the range of 5～30℃. Alternatively, it is also a better method to gel the mesh by cooling it and peel it off from the drum in a state containing more residual solvent.

There are no particular restrictions on the method of controlling the temperature of the metal support, but there are methods of spraying warm air or cold air or making warm water contact the back of the metal support. The use of warm water is more suitable because the heat is efficiently transferred, so the time until the temperature of the metal support becomes fixed is short. When using warm air, considering the temperature drop of the mesh caused by the evaporation latent heat of the solvent, while using warm air above the boiling point of the solvent, it is also possible to prevent foaming and use air at a higher temperature than the target temperature. In particular, it is better to change the temperature of the support and the temperature of the drying air from casting to peeling to perform drying efficiently.

The die head is preferably a pressure die head that can adjust the slit shape of the metal mouth part of the die head and make the film thickness easy to become uniform. Among the pressure die heads, there are hanger-type dies and T-dies, which can be used preferably. The surface of the metal support body is a mirror surface. In order to increase the film-making speed, two or more pressure dies can be set on the metal support body to divide the amount of slurry and stack them.

(2-2) Solvent evaporation step Heating the mesh on the metal support for casting to evaporate the solvent is a step for controlling the amount of residual solvent during the subsequent stripping.

In order to evaporate the solvent, there are methods such as blowing air from the side of the mesh, transferring heat from the back of the support through liquid, transferring heat from the surface to the inside through radiant heat, etc., but the back liquid heat transfer method is more suitable because of its good drying efficiency. In addition, it is also better to use a combination of these methods. It is better to dry the mesh on the support after casting in an environment of 30 to 100°C on the support. In order to maintain an environment of 30 to 100°C, it is better to blow warm air of this temperature onto the mesh or heat it by means such as infrared rays.

From the perspective of surface quality, moisture permeability, and peelability, it is preferred that the mesh be peeled off from the support within 30 to 180 seconds.

(2-3) Peeling step The mesh from which the solvent has evaporated on the metal support is peeled at the peeling position. The peeled mesh is sent to the next step as a raw material film. The temperature of 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.

In the present invention, the solvent in the mesh is evaporated in the aforementioned solvent evaporation step, but the residual solvent amount of the mesh on the metal support at the time of stripping is preferably set in the range of 15 to 100 mass %. The residual solvent amount is preferably controlled by the drying temperature and drying time in the aforementioned solvent evaporation step. If stripping is performed in a state where the residual solvent amount is large, the mesh is too soft, which is easy to damage the flatness during stripping, and wrinkles or longitudinal stripes caused by the stripping tension are easy to occur. Therefore, considering these points, the residual solvent amount during stripping is determined.

The residual solvent amount of the mesh or raw material film is defined by the following formula (Z2). Formula (Z2): Residual solvent amount (%) = (mass of the mesh or raw material film before heat treatment - mass of the mesh or raw material film after heat treatment) / (mass of the mesh or raw material film after heat treatment) × 100 In addition, the so-called heat treatment when measuring the residual solvent amount means heat treatment at 115°C for 1 hour.

The peeling tension when peeling the mesh from the metal support to the original film is usually in the range of 196 to 245 N/m. However, when wrinkles are easily introduced during peeling, it is better to peel with a tension of less than 190 N/m.

In the present invention, it is preferred to set the temperature of the peeling position on the metal support to be 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.

(3) Drying and extension steps The drying step can also be divided into a preliminary drying step (the first drying step) and a main drying step (the second drying step).

(3-1) Preliminary drying step (first drying step) The raw film obtained by peeling the mesh sheet from the metal support is preliminarily dried in the first drying device 34. The preliminarily drying of the raw film can be carried out by using a plurality of rollers arranged above and below to dry the raw film while conveying it, or by fixing the two ends of the raw film with clips as in a tenter dryer to dry the film while conveying it.

There is no particular restriction on the drying method. Generally, it can be done by hot air, infrared, heating roller, microwave, etc. However, hot air is preferred for simplicity.

The drying temperature of the preparatory drying step of the mesh sheet is preferably (Tg-5)°C or less when the glass transition temperature of the original film is taken as Tg. Heat treatment at a temperature above (Tg+30)°C for 1 to 30 minutes is effective. Specifically, the drying temperature is in the range of 40 to 150°C, more preferably in the range of 80 to 100°C.

In the present invention, it is preferred to adjust the residual solvent amount in the raw material film during the stretching described later in the drying step, but the residual solvent amount adjustment can also be performed at the initial stage of the stretching step. The control of the residual solvent amount is preferably performed by the drying temperature and drying time in the preparatory drying step.

(3-2) Stretching step The raw film after the preliminary drying step is stretched in the stretching device 35 at a specific residual solvent amount described later, at a specific stretching ratio and at a specific heating temperature.

(Residual solvent amount) Specifically, in the step of stretching the raw film, the residual solvent amount in the raw film at the start of stretching is preferably in the range of 700 to 30,000 mass ppm, more preferably in the range of 2,000 to 20,000 mass ppm. By setting such a residual solvent amount, the half-width of the diffraction peak of the surface of the stretched film of the present invention after stretching when irradiated with X-rays at an angle of 0.1 degrees can be within the aforementioned specific range, and the residual solvent amount of the stretched film is suppressed, so that a stretched film with a low surface orientation and moderate moisture permeability and excellent adhesion can be obtained. Moreover, when stretching is performed multiple times, it is preferred that the residual solvent amount in the raw film is within the aforementioned range even in at least one of the stretching operations. Here, the residual solvent amount in the aforementioned original film at the start of stretching is defined by the following formula (Z3). Formula (Z3): Residual solvent amount (ppm) = (mass of original film before heat treatment - mass of original film after heat treatment) / (mass of original film after heat treatment) × 10 ⁶ Moreover, the heat treatment when measuring the residual solvent amount means heat treatment at 115°C for 1 hour.

The raw film of the present invention is preferably stretched in the length direction (also called MD direction, casting direction) and/or the width direction (also called TD direction), and is preferably manufactured by stretching in the width direction at least by a stretching device.

The stretching operation may be divided into multiple stages and implemented. Furthermore, when performing biaxial stretching, biaxial stretching may be performed simultaneously or in stages. In this case, the so-called stages may include, for example, stretching in different directions in sequence, or stretching in the same direction may be divided into multiple stages, and stretching in different directions may be applied in any stage.

That is, for example, the stretching steps may be as follows: ・Stretching in the length direction → stretching in the width direction → stretching in the length direction → stretching in the length direction ・Stretching in the width direction → stretching in the width direction → stretching in the length direction → stretching in the length direction Moreover, in the simultaneous biaxial stretching, stretching in one direction is also included, and the tension is relaxed in the other direction to make it contract.

(Stretching temperature) In addition, the film thickness after stretching is in the desired range, and the stretching is preferably carried out in the temperature range of (Tg-30) to (Tg+50)°C in the length direction and/or width direction, preferably in the width direction, when the glass transition temperature of the original film is Tg. By stretching in the above-mentioned temperature range, the half-value width of the aforementioned diffraction peak or the aforementioned residual solvent amount of the obtained stretched film of the present invention can be controlled within the above-mentioned range, and a stretched film with a low surface orientation and excellent adhesion can be obtained. In addition, the adjustment of the phase difference is easy, and the stretching stress can be reduced to reduce the haze. In addition, the occurrence of cracks is suppressed, and a stretched film with excellent planarity and coloring properties of the film itself is obtained. It is better to carry out the stretching temperature within the range of (Tg-40) to (Tg+40)℃. Drying is carried out within the range of 100 to 200℃.

The glass transition temperature Tg mentioned here is the midpoint glass transition temperature (Tmg) obtained by measuring at a heating rate of 20°C/min using a commercially available differential scanning calorimeter in accordance with JIS K7121 (1987). The specific method for measuring the glass transition temperature Tg of the stretched film is in accordance with JIS K7121 (1987) using a differential scanning calorimeter DSC220 manufactured by SEIKO Instruments Co., Ltd.

(Stretching ratio) In the present invention, the original film is stretched at a stretching ratio in the range of 1.2 to 3.0 times as expressed by area ratio, which is preferably so that the half-value width of the diffraction peak and the amount of residual solvent of the obtained stretched film can be within the range of the present invention, and the surface can be low-oriented and have appropriate moisture permeability. Specifically, the original film can be stretched in either the width direction or the length direction, and is preferably stretched in both the width direction and the length direction, and can be stretched in the range of 1.2 to 3.0 times as expressed by area ratio.

There is no particular limitation on the method of extending in the longitudinal direction. For example, there can be cited a method of extending in the longitudinal direction by applying a difference in circumferential speed to a plurality of rollers, a method of fixing both ends of the mesh with clips or needles, and extending in the longitudinal direction by enlarging the interval between the clips or needles in the traveling direction, or a method of extending in both the longitudinal and transverse directions by simultaneously enlarging the longitudinal and transverse directions. Of course, these methods can also be used in combination.

For stretching in the width direction, for example, a method (also called a tentering method) is used in which the width of the mesh is kept at both ends in the width direction by a clip or a needle while drying the mesh in the width direction, using the whole drying step or a part of the drying step as shown in Japanese Patent Publication No. 62-46625. Among them, the tentering method using clips and the pin tentering method using needles are preferably used. When stretching in the width direction, stretching at a stretching speed of 250 to 500%/min in the width direction of the film is preferred from the perspective of improving the flatness of the film.

If the stretching speed is 250%/min or more, the flatness is improved and the film can be processed at a high speed, which is more suitable from the perspective of production adaptability. If it is within 500%/min, the film can be processed without breaking, which is more suitable.

The preferred stretching speed is in the range of 300-400%/min, which is effective for low-ratio stretching. The stretching speed is defined by the following formula 1. Formula 1: Stretching speed (%/min) = [(d1/d2)-1] × 100 (%)/t (In formula 1, d1 is the width dimension of the stretched film of the present invention in the aforementioned stretching direction after stretching, d2 is the width dimension of the original film in the aforementioned stretching direction before stretching, and t is the time required for stretching (min)).

The stretched film of the present invention has a desired phase difference value by stretching as described above. The in-plane phase difference value Ro and the phase difference value Rt in the thickness direction can be calculated from the obtained refractive indices nx, ny, and nz by measuring the three-dimensional refractive index at a wavelength of 590nm using an automatic double refractometer Axo Scan Mueller Matrix Polarimeter (manufactured by AXO METRIX) at 23°C and 55%RH.

The stretched film of the present invention is a stretched film represented by the following formulas (i) and (ii) whose in-plane phase difference Ro is in the range of 40 to 60 nm and whose thickness phase difference Rt is in the range of 110 to 140 nm. When a VA type liquid crystal display device is provided, it is preferable from the viewpoint of improving visual recognition such as viewing angle and contrast. The stretched film can be adjusted to the above phase difference value range by adjusting the elongation rate while stretching at least in the aforementioned width direction.

Formula (i): Ro = ( _{nx -ny} ) × d (nm) Formula (ii): Rt = {( _nx + _ny )/2- _nz } × d (nm) [In formulas (i) and (ii), _nx represents the refractive index in the direction x where the refractive index is maximum in the in-plane direction of the film. _ny represents the refractive index in the direction y that is orthogonal to the aforementioned direction x in the in-plane direction of the film. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness of the film (nm)].

In the stretching step, holding and relaxing are usually performed after stretching. That is, this step is preferably performed in the order of a stretching stage for stretching the original film, a holding stage for holding the original film in a stretched state, and a relaxing stage for relaxing in the direction in which the original film is stretched. In the holding stage, the stretching of the elongation rate achieved in the stretching stage is maintained at the stretching temperature of the stretching stage. In the relaxing stage, after the stretching in the stretching stage is maintained in the holding stage, the stretching is relaxed by releasing the tension used for stretching. The relaxing stage can be performed at a temperature below the stretching temperature of the stretching stage.

(3-3) Formal drying step In the formal drying step, the stretched film is dried by heating it with the second drying device 36. By this formal drying step, the half-value width of the aforementioned diffraction peak and the aforementioned residual solvent amount of the stretched film of the present invention can also be controlled within the aforementioned range. When the film is heated by hot air, it is also preferable to use a means that is provided with a nozzle that can exhaust the used hot air (air containing solvent or humidified air) to prevent the used hot air from mixing. The hot air temperature is preferably in the range of (Tg-20) to (Tg+50)°C when the glass transition temperature of the original film is regarded as Tg, and specifically, it is preferably in the range of 40 to 250°C. In addition, the drying time is preferably about 5 seconds to 60 minutes, and more preferably 10 seconds to 30 minutes.

In addition, the heating and drying means are not limited to hot air, for example, infrared rays, heating rollers, microwaves, flash lamp annealing, etc. can be used. From the perspective of simplicity, it is better to transport the film with a staggered transport roller 37 while drying with hot air. The drying temperature is preferably in the range of 40 to 350°C, taking into account the amount of residual solvent, the elongation during transportation, etc. In addition, when using flash lamp annealing, it is better to irradiate within the range of 200 to 1000V and 100 to 5000μsec. In the drying step, it is better to dry the film until the amount of residual solvent becomes less than 100 mass ppm.

(4) Rolling step (4-1) Rolling process After the specified heat treatment or cooling treatment, it is better to set up a slitting machine to cut off the ends before rolling, because it can obtain a good winding posture. In addition, it is better to roll the ends of the width.

The embossing process can be formed by pushing a heated embossing roller to the width end of the film. The embossing roller has fine bumps and depressions, and by pushing the bumps and depressions on the film, the volume of the end can be increased.

The height of the knurling at both ends of the width of the stretched film of the present invention is preferably 4 to 20 μm, and the width is preferably 5 to 20 mm. In addition, in the present invention, the knurling process is preferably performed after drying and before winding in the film-making step of the film.

(4-2) Winding step After the residual solvent amount in the stretched film becomes less than 500 mass ppm, the stretched film is wound up. By making the residual solvent amount preferably less than 100 mass ppm, a film with good dimensional stability can be obtained.

The winding method can be used by general users, and there are fixed moment method, fixed tension method, tapered tension method, and planned tension control method with constant internal stress, etc., which can be used flexibly.

According to the method for producing a stretched film of the present invention, the stretching is performed in the stretching step at a stretching ratio expressed as an area ratio within the range of 1.2 to 3.0 times, and the residual solvent amount at the start of stretching is within the range of 700 to 30,000 mass ppm, and the half-value width of the diffraction peak when the surface of the stretched film of the present invention is irradiated with X-rays at an angle of 0.1 degrees can be within the range of 4.6 to 5.4 degrees, and the residual solvent amount of the stretched film can be controlled within the above range. As a result, the surface of the stretched film becomes low-oriented, and appropriate moisture permeability can be ensured, and excellent adhesion can be achieved.

[Physical properties of stretched film] <Moisture permeability> The moisture permeability (40°C, 95%RH) of the stretched film of the present invention is in the range of 1 to 500 g/(m ²・24h), preferably in the range of 10 to 200 g/(m ²・24h). There is no particular limitation to make the moisture permeability within the aforementioned range, but it is preferred to appropriately select the type and film thickness of the resin constituting the stretched film. In the present invention, the moisture permeability is measured based on the calcium chloride-cup method described in JIS Z 0208, and the film to be measured is placed at a temperature of 40°C and 95%RH for 24 hours.

<Stretched film length, width, thickness> The stretched film of the present invention is preferably in the form of a long strip, specifically, preferably about 100 to 10,000 m in length, and is rolled into a roll. In addition, the width of the stretched film of the present invention is preferably 1 m or more, more preferably 1.3 m or more, and particularly preferably 1.3 to 4 m.

The thickness of the film after stretching is preferably in the range of 10 to 50 μm from the viewpoint of thinning the display device and productivity. If the thickness is 10 μm or more, a certain film strength or phase difference can be exhibited. If the thickness is 50 μm or less, the desired phase difference can be obtained and it can be applied to the thinning of polarizing plates and display devices. It is preferably in the range of 20 to 40 μm.

[Application of stretched film] The stretched film of the present invention can be used as a protective film for polarizing plates, etc., and can be used in various optical measuring devices and display devices such as liquid crystal display devices or organic electroluminescent display devices.

[Polarizing plate] The polarizing plate of the present invention is characterized by having the aforementioned stretched film of the present invention. Specifically, the polarizing plate 200 of the present invention is a polarizing plate formed by laminating at least a polarizing plate protective film 300, a polarizer layer 400, a stretched film 100 of the present invention, and an adhesive sheet 500 in sequence as shown in FIG. 2 .

<Adhesive sheet> The adhesive sheet has an adhesive layer formed of an adhesive composition. Examples of adhesive sheets include: a double-sided adhesive sheet having only an adhesive layer; a double-sided adhesive sheet having a substrate and adhesive layers formed on both sides of the substrate, at least one of the adhesive layers being formed of an adhesive composition; a single-sided adhesive sheet having a substrate and the above-mentioned adhesive layer formed on one side of the substrate; and an adhesive sheet having a separator attached to the surface of the adhesive layer of the adhesive sheet that does not contact the substrate.

As the aforementioned adhesive composition, for example, it is preferably composed of an acrylic adhesive main agent, a crosslinking agent, and an antioxidant. As the aforementioned acrylic adhesive main agent, for example, 4-hydroxybutyl acrylate unit (4-HBA), butyl acrylate unit, methyl acrylate unit, etc. can be cited. As the aforementioned crosslinking agent, toluene diisocyanate compounds, xylyl diisocyanate, etc. can be cited. As the aforementioned antioxidant, there can be cited hindered phenol antioxidants such as pentaerythritol-tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) (manufactured by BASF Japan, IRGANOX1010) and phosphorus antioxidants such as tris-(2,4-di-tert-butylphenyl) phosphite (manufactured by BASF Japan, IRGAFOS168).

The adhesive composition preferably contains the acrylic adhesive main agent in an amount of 10 to 90% by mass, the crosslinking agent in an amount of 0.01 to 5.00% by mass, and the antioxidant in an amount of 0.01 to 5.00% by mass.

(Water content) The aforementioned adhesive sheet should have a low water content in order to suppress the occurrence of high humidity shock. On the other hand, if the water content is low, poor adhesion will occur. However, the adhesive sheet preferably contains a lot of water. Therefore, the water content of the adhesive sheet is preferably in the range of 3.0 to 10.0%, and particularly preferably in the range of 3.5 to 5.5%.

The moisture content of the adhesive sheet is obtained by forming an adhesive layer on a polyester film with a thickness of 50 μm, cutting it into 60 mm × 130 mm, attaching the adhesive sheet to a polycarbonate film with a thickness of 1 mm cut into 70 mm × 150 mm, and placing it in an environment of 40°C and 95% RH for 48 hours, and measuring the mass increase of the adhesive.

In order to make the moisture content of the adhesive sheet within the range of 3.0 to 10.0%, for example, the content of 4-hydroxybutyl acrylate unit (4-HBA) in the adhesive composition can be within the range of 4.0 to 25 mass %.

(Polarizer layer) The so-called "polarizer layer" refers to a component that allows only light with a polarized wavefront in a certain direction to pass through. Currently, the representative polarizing film (also called "polarizer film" and "polarizer film") that constitutes the polarizer layer is known to be a polyvinyl alcohol-based polarizing film. Among the polyvinyl alcohol-based polarizing films, there are those that dye the polyvinyl alcohol-based films with iodine and those that dye them with dichroic dyes.

The polyvinyl alcohol-based polarizing film can be a film obtained by dyeing the polyvinyl alcohol-based film with iodine or dichroic dye after uniaxial stretching (preferably a film further treated with a boron compound for durability); or a film obtained by dyeing the polyvinyl alcohol-based film with iodine or dichroic dye and then uniaxial stretching (preferably a film further treated with a boron compound for durability). The absorption axis of the polarizing film (polarizer layer) is usually parallel to the maximum stretching direction.

For example, ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol% as described in Japanese Patent Application Laid-Open No. 2003-248123 and Japanese Patent Application Laid-Open No. 2003-342322 can be used. Among them, ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73°C is preferably used.

The thickness of the polarizer layer is preferably in the range of 5 to 30 μm, and more preferably in the range of 5 to 20 μm in order to reduce the thickness of the polarizer.

When the stretched film of the present invention is used as a λ/4 film, the angle between the in-plane slow axis of the stretched film of the present invention and the absorption axis of the polarizer layer is preferably in the range of 20 to 70 degrees, more preferably 30 to 60 degrees, and particularly preferably 40 to 50 degrees. When the stretched film of the present invention is used as a phase difference film for VA, the in-plane slow axis of the stretched film of the present invention and the absorption axis of the polarizer layer may be slightly orthogonal.

Furthermore, the polarizer layer and the stretched film are preferably bonded together through an adhesive or a pressure-sensitive adhesive. The adhesive may be a water-based adhesive containing a polyvinyl alcohol resin or a urethane resin as a main component, or a photocurable adhesive containing a photocurable resin such as an epoxy resin as a main component. The pressure-sensitive adhesive may be a base polymer containing an acrylic polymer, a polysilicone polymer, a polyester, a polyurethane, and a polyether. Among them, a water-based adhesive is preferred because it has good affinity with the stretched film of the present invention and is not easily deformed by water absorption. The bonding of the polarizer layer and the stretched film of the present invention can usually be performed in a roll-to-roll manner.

(Polarizing plate protective film) A polarizing plate protective film is disposed on the surface of the polarizer layer opposite to the stretched film. Examples of polarizing plate protective films include commercially available cellulose acylate films (e.g., Konica Minolta TAC KC6UA, KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC8UY-HA, KC8UX-RHA, KC8UE, KC4UE, KC4HR-1, KC4KR-1, KC4UA, KC6UA, all manufactured by Konica Minolta Opto Co., Ltd.) and the like.

The thickness of the polarizing plate protective film is not particularly limited, but is preferably in the range of 10 to 100 μm, more preferably in the range of 10 to 60 μm, and particularly preferably in the range of 20 to 60 μm.

[Liquid crystal display device] The liquid crystal display device of the present invention is a liquid crystal display device formed by laminating the aforementioned polarizing plate to at least one side of a liquid crystal cell, and is characterized in that the aforementioned adhesive sheet is adjacent to the aforementioned liquid crystal cell.

Fig. 3 is a model diagram showing an example of the basic structure of a liquid crystal display device. As shown in Fig. 3, the liquid crystal display device 20 of the present invention includes a liquid crystal cell 30, a first polarizing plate 40 and a second polarizing plate 50 sandwiching the liquid crystal cell 30, and a backlight 60.

The display mode of the liquid crystal cell 30 can be, for example, TN (Twisted Nematic), VA (Vertical Alignment) or IPS (In Plane Switching). For liquid crystal cells for mobile devices, the IPS mode is preferred. For liquid crystal cells for medium and large applications, the VA mode is preferred.

The first polarizing plate 40 is disposed on the visual recognition side of the liquid crystal cell 30, and includes a first polarizer layer 41, a protective film 43 (F1) disposed on the surface of the first polarizer layer 41 opposite to the liquid crystal cell, and a protective film 45 (F2) disposed on the surface of the first polarizer layer 41 on the liquid crystal cell side.

The second polarizing plate 50 is disposed on the backlight side of the liquid crystal cell 30, and includes a second polarizer layer 51, a protective film 53 (F3) disposed on the surface of the second polarizer layer 51 on the liquid crystal cell side, and a protective film 55 (F4) disposed on the surface of the second polarizer layer 51 on the opposite side of the liquid crystal cell.

The absorption axis of the first polarizer layer 41 and the absorption axis of the second polarizer layer 51 are preferably orthogonal.

The protective film 45 (F2) can be used as the stretching film of the present invention. The protective film 45 (F2) and the first polarizer layer 41 are directly laminated. The in-plane slow axis of the protective film 45 (F2) and the absorption axis of the first polarizer layer 41 can be slightly orthogonal. The protective film 45 (F2) and the liquid crystal cell 30 can be connected through the adhesive sheet 48. In addition, the protective films 43 (F1), 53 (F3) and 55 (F4) can be used as the aforementioned polarizer protective films, for example.

In FIG. 2 , a protective film 45 (F2) is shown as an example of the stretch film of the present invention, but the present invention is not limited thereto, and 53 (F3) can also be used as the stretch film of the present invention. [Example]

The present invention is specifically described below with reference to the following examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, the operation is performed at room temperature (25° C.). Also, unless otherwise specified, “%” and “parts” refer to “mass %” and “mass parts”, respectively.

[Preparation of stretched film 101] <Cycloolefin hydrocarbon resin> As the cycloolefin hydrocarbon resin used in the embodiment, the following cycloolefin hydrocarbon resin was used. Cycloolefin hydrocarbon resin: ARTON G7810 (manufactured by JSR Corporation)

<Preparation of microparticle additive solution> 11.3 parts by mass of microparticles (Aerosil R972V, manufactured by Nippon AEROSIL Co., Ltd.) and 84 parts by mass of ethanol were stirred in a dissolver for 50 minutes and then dispersed with a homogenizer. 5 parts by mass of microparticle dispersion were gradually added to the well-stirred dichloromethane (100 parts by mass) in the dissolving tank. Furthermore, the microparticles were dispersed with a mill in such a way that the particle size of the secondary particles became a specified size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a microparticle additive solution.

<Preparation of main slurry> Prepare the main slurry of the following composition. First, add dichloromethane and ethanol to a pressure dissolving tank. Add cycloolefin resin and fine particle additive liquid into the pressure dissolving tank filled with dichloromethane while stirring. Heat it, dissolve the resin while stirring, and filter it using Amchi filter paper No. 244 manufactured by Amchi filter paper (Co., Ltd.) to prepare the main slurry. Cycloolefin resin (ARTON G7810 (manufactured by JSR Corporation)) 100 parts by mass Methylene chloride                                                 200 parts by mass Ethanol                                                  10 parts by mass Microparticle additive liquid                                      3 parts by mass Next, an endless belt casting device was used to uniformly cast the main slurry on a stainless steel belt support at a temperature of 31°C and a width of 1800 mm. The temperature of the stainless steel belt was controlled at 28°C. The conveying speed of the stainless steel belt was set to 20 m/min. On a stainless steel belt support, the solvent was evaporated in such a way that the residual solvent amount in the film after casting became 30.3 mass %. Then, the optical film 101 (unstretched) was peeled off from the stainless steel belt support at a peeling tension of 128 N/m. Before stretching, the optical film 101 was heated and dried at 100°C in a belt dryer, and after controlling the residual solvent amount at the beginning of stretching to 1000 mass ppm, it was heated at Tg+25°C (190) and stretched at the stretching ratio listed in Table I. After stretching, it was dried at Tg-20°C (145°C) for 30 minutes in a belt dryer. In this way, a stretched film 101 having the film thickness described in the following Table I is obtained.

[Preparation of stretched film 102] In addition to heating and drying the optical film 101 for 1 minute in a belt dryer at Tg+25°C (190°C) after stretching the stretched film 101, a stretched film 102 having the film thickness described in the following Table I was obtained in the same manner.

[Preparation of stretched film 103] In the preparation of the stretched film 101, except that the optical film 101 was heated and dried at 60°C before stretching, and the residual solvent amount at the beginning of stretching was controlled to be 5000 mass ppm, the stretched film 103 having the film thickness described in the following Table I was obtained in the same manner.

[Preparation of stretched film 104] In addition to the above-mentioned preparation of stretched film 101, the above-mentioned optical film 101 was heated and dried at 50°C in a belt dryer before stretching, and the residual solvent amount at the beginning of stretching was controlled to be 30,000 mass ppm, and then heated at Tg-30°C (135°C) and stretched at the stretching ratio listed in Table I. After stretching, it was dried at Tg-20°C (145°C) in a belt dryer. In this way, a stretched film 104 with a film thickness listed in the following Table I was obtained.

[Preparation of stretched film 105] In the preparation of the stretched film 101, after the stretching of the optical film 101, a flash annealing device (manufactured by Novacentrix, model Pulse Forge 1300) was used to irradiate at 550B and 50μsec, and a stretched film 105 having the film thickness described in the following Table I was obtained in the same manner.

[Preparation of stretched film 106] In addition to the above-mentioned preparation of stretched film 101, the above-mentioned optical film 101 was heated and dried at 80°C in a belt dryer before stretching, and the residual solvent amount at the beginning of stretching was controlled to be 2000 mass ppm, and then heated at Tg+50°C (215°C) and stretched at the stretching ratio listed in Table I. After stretching, it was dried at Tg-20°C (145°C) in a belt dryer. In this way, a stretched film 106 with a film thickness listed in the following Table I was obtained.

[Preparation of film 107] A ZB film (cycloolefin resin film without polar groups) of a phase difference film manufactured by ZEON Corporation of Japan was used as film 107. The ZB film was stretched without residual solvent and was a stretched film.

[Preparation of thin film 108] The thin film 107 was irradiated with a flash lamp annealing device (manufactured by Novacentrix, model Pulse Forge 1300) at 550V and 50μsec to obtain a thin film 108 having the film thickness described in the following Table I.

[Preparation of film 109] For the aforementioned film 107, an organic solvent (a mixed solution of ethyl acetate and methylcyclohexane in a mass ratio of 1:1) was applied with a wireless bar, and dried with a belt dryer at 155°C for 5 minutes to obtain film 109.

[Preparation of film 110] The unstretched optical film 101 in the preparation of the stretched film 101 is dried in a belt dryer at 155°C for 30 minutes to form a film 110.

[Preparation of stretched film 111] Referring to paragraphs 0301 and 0302 of Japanese Patent Publication No. 2013-3232, the following composition is put into a mixing tank, stirred to dissolve each component, and then filtered with a filter paper with an average pore size of 34μm and a sintered metal filter with an average pore size of 10μm to prepare a cellulose ester slurry. The slurry is cast on a stainless steel belt support in the same manner as the aforementioned optical film 101, and the solvent is evaporated until the residual solvent in the cast film reaches 30.3% by mass. Then, the optical film 111 was peeled off from the stainless steel belt support at a peeling tension of 128 N/m. Then, the optical film 111 was heated and dried at 50°C in a belt dryer before stretching, and the residual solvent amount at the start of stretching was controlled to be 3000 mass ppm. Then, it was heated at Tg+20°C (90°C) and stretched at the stretching ratio listed in Table I. After stretching, it was dried at Tg-10°C (60°C) in a belt dryer. In this way, a stretched film (triacetyl cellulose film: TAC) 111 with a film thickness listed in Table I below was obtained. (Composition of main slurry) Methylene chloride                                             340 parts by mass Ethanol                                                      64 parts by mass Cellulose acetate propionate (acetyl substitution degree 1.88, propionyl substitution degree 0.58)                                                              100 parts by mass Carboxylic acid sugar ester compound (benzyl sucrose with an average substitution degree of 6.5) 9 parts by mass The following aromatic terminal polyester compound (5)           3 parts by mass

[Residual solvent content of the film] The residual solvent content of each obtained film was measured as follows. After the film was prepared as described above, the mass of the film was measured after 1 hour, and it was regarded as the mass before the heat treatment. Then, the film was heat treated at 115°C for 1 hour, and the mass of the film after the heat treatment was measured. The residual solvent content was calculated by the following formula. The results are shown in the following Table I. Formula: Residual solvent content (ppm) = (mass of the film before the heat treatment - mass of the film after the heat treatment) / (mass of the film after the heat treatment) × 10 ⁶

[Half-value width of diffraction peak] For each thin film obtained, the half-value width of diffraction peak was measured as follows. The incident angle θ of the incident X-ray was fixed at 0.1 degrees, and the intensity of the X-ray was measured while changing the angle of the detector. Specifically, as an X-ray diffraction device, an X-ray diffraction device RINT-TTRII (manufactured by Rigaku Denki Co., Ltd.) was used. The cathode (anticathode) was set to Cu and operated at 50kV-300mA. The height limit slit was 10mm, the divergence slit was 2/3, and the optical system was adjusted so that the half-value width of the peak of Al(200) when measuring aluminum foil became 0.35 degrees. Fix the film, fix θ at 0.1 degrees, scan 2θ at 0.02 degree steps from 5 to 35 degrees, accumulate 1 second at each step, and obtain the diffraction pattern. Perform background processing and calculate the half-value width of the diffraction peak. The results are shown in Table I below.

[Oxygen permeability] For each of the obtained films, the oxygen permeability was measured as follows. Under the conditions of temperature 23°C and humidity 0%RH, the oxygen permeability measuring device (model name "Oxtran" (registered trademark) ("OXTRAN" 2/20), manufactured by MOCON, USA) was used to measure according to the B method (isobaric method) described in JIS K7126 (1987). In addition, the measurement was performed once for each of the two test pieces, and the average of the two measured values was taken as the value of the oxygen permeability. The results are shown in the following Table I.

[Preparation of polarizing plate] ＜Preparation of polarizer layer＞ A polyvinyl alcohol film with a thickness of 70 μm was swelled in water at 35°C. The obtained film was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution composed of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water at 45°C. The obtained film was uniaxially stretched at a stretching temperature of 55°C and a stretching ratio of 5 times. After washing the uniaxially stretched film with water, it was dried to obtain a polarizing film (polarizer layer) with a thickness of 20 μm.

<Preparation of UV-curable adhesive liquid (UV paste)> After mixing the following components, defoaming was performed to prepare a UV-curable adhesive liquid. In addition, triarylphosphonium hexafluorophosphate was mixed as a 50% propylene carbonate solution, and the solid content of triarylphosphonium hexafluorophosphate is shown below. 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolead GT-301 (epoxy resin produced by DAICEL) 40 parts by mass 1,4-Butanediol diglycidyl ether 15 parts by mass Triarylphosphonium hexafluorophosphate 2.3 parts by mass 9,10-Dibutoxyanthracene 0.1 parts by mass 1,4-Diethoxynaphthalene 2.0 parts by mass The films 101 to 111 prepared above were prepared, and the surfaces thereof were subjected to a corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m/min. Next, the above-mentioned ultraviolet curing adhesive is applied to the corona discharge treated surface of the film by a rod coater in such a manner that the film thickness after curing becomes about 3 μm, thereby forming an adhesive layer. The above-mentioned polyvinyl alcohol-iodine polarizer layer is bonded to the obtained adhesive layer. The above-mentioned films 101 to 111 are similarly bonded to the other side of the polarizer layer to produce each polarizing plate 101 to 111. Next, ultraviolet rays are irradiated from both sides of the bonded laminate using an ultraviolet irradiation device with a conveyor belt (the lamp is a D bulb manufactured by FUSION UV SYSTEMS) in such a manner that the accumulated light amount becomes 750 mJ/ ^cm2 , thereby curing the ultraviolet curing adhesive layer.

[Evaluation] ＜Initial Adhesion＞ Using the polarizing plate obtained above, a 90-degree peel test (according to JIS Z0237:2009) was performed using a 90-degree peel test fixture (P90-200N) manufactured by IMADA Co., Ltd. in an environment of 23°C and 55%RH, and the peel strength (adhesion) at the interface between the film and the polarizer layer was measured. In addition, the evaluation was performed using the following evaluation criteria, and if it was △ or above, it was judged to be good. (Evaluation criteria) ○: Peel strength is 2.0 (N/25mm) or more △: Peel strength is 1.5 or more and less than 2.0 (N/25mm) ×: Peel strength is 1.0 or more and less than 1.5 (N/25mm) ××: Peel strength is less than 1.0 (N/25mm)

<Polarizing plate adhesion after durability> The polarizing plate obtained above was stored in an environment of 0℃・0%RH for 100 hours and subjected to a durability test. In the same way as the evaluation method of the initial adhesion, a 0-degree peel test (according to JIS Z0237:2009) was performed using a 90-degree peel test fixture (P90-200N) manufactured by IMADA Co., Ltd. The ratio of the peel strength after the durability test to the peel strength before the durability test (the peel strength of the initial adhesion) was calculated. In addition, the evaluation was performed according to the following evaluation criteria. If it is △ or above, it is judged to be good. (Evaluation criteria) ○: 95% or more △: 80% or more but less than 95% ×: 50% or more but less than 80% ××: less than 50%

As shown in the above results, it is confirmed that compared with the thin film of the comparative example, the stretched film of the present invention has a low surface orientation and is excellent in initial adhesion and post-durable adhesion.

3,6,12,15,64: Filter 4,13: Storage kettle 2,5,11,14: Liquid delivery pump 8,16: Conduit 10: Additive feed kettle 20: Confluence pipe 21: Mixer 22: Pressurized die head 31: Metal belt (metal support) 32: Mesh 33: Stripping position 34: First drying device 35: Extension device 36: Second drying device 37: Transport roller 38: Winding device 61: Feed kettle 62: Storage kettle 63: Pump 30: Liquid crystal cell 40: First polarizing plate 41: First polarizing layer 43: Protective film (F1) 45: Protective film (F2) 48: Adhesive sheet 50: Second polarizing plate 51: Second polarizing mirror layer 53: Protective film (F3) 55: Protective film (F4) 60: Backlight 100: Stretching film 200: Polarizing plate 300: Polarizing plate protective film 400: Polarizing mirror layer 500: Adhesive sheet

[FIG. 1] is a diagram showing a schematic diagram of a method for manufacturing a stretched film of the present invention. [FIG. 2] is a model diagram showing an example of the structure of a polarizing plate of the present invention. [FIG. 3] is a model diagram showing an example of the structure of a liquid crystal display device of the present invention.

Claims (8)

A stretched film comprising a cycloolefin resin having a polar group, characterized in that when the surface of the stretched film is irradiated with X-rays at an angle of 0.1 degree, the half-value width of the diffraction peak is within the range of 4.6 to 5.4 degrees, the residual solvent content is within the range of 5 to 500 mass ppm, and the oxygen permeability is within the range of 3000 to 5000 mL/(m ² ‧24hr‧atm) under the conditions of temperature 23°C and humidity 0%RH. For example, the stretched film of claim 1, wherein the half-value width is within the range of 4.8 to 5.2 degrees. The stretched film of claim 1 or 2 contains microparticles. A method for manufacturing a stretched film, which is a method for manufacturing a stretched film as in any one of claims 1 to 3, characterized in that the stretched film is manufactured by a solution casting method. A method for producing a stretched film as claimed in claim 4, wherein a dope containing the aforementioned cycloolefin resin having a polar group is cast on a support to form a web, and then a stretching treatment is performed at a stretching ratio in the stretching step expressed as an area ratio in the range of 1.2 to 3.0 times. In the method for producing a stretched film as claimed in claim 4 or 5, after a slurry containing the aforementioned cycloolefin resin having a polar group is cast on a support to form a mesh, the amount of residual solvent at the beginning of the stretching step is set within the range of 700 to 30,000 mass ppm. A polarizing plate characterized by having a stretched film as described in any one of claims 1 to 3. A liquid crystal display device characterized by having a polarizing plate as claimed in claim 7.

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