WO2018235532A1

WO2018235532A1 - Raw material film, stretched optical film manufacturing method, and stretched optical film

Info

Publication number: WO2018235532A1
Application number: PCT/JP2018/020386
Authority: WO
Inventors: 絵美川崎; 雅洋川崎; 亘大橋; 敦稲富; 孝徳磯崎; 久保　敬次
Original assignee: 株式会社クラレ
Priority date: 2017-06-21
Filing date: 2018-05-28
Publication date: 2018-12-27
Also published as: JPWO2018235532A1; TWI682957B; CN110809725B; KR102565518B1; CN110809725A; KR20200016897A; TW201906915A; JP7093349B2

Abstract

The present invention provides a raw material film with which a stretched optical film that is thin and not easily torn can be relatively easily obtained, the stretched optical film that is thin and not easily torn, and a stretched optical film manufacturing method by which this stretched optical film can be relatively easily obtained. The present invention is a raw material film for manufacturing a stretched optical film, the raw material film having an average thickness of 45 μm or less, and containing a vinyl alcohol-based polymer as a main component, and resin particles with a glass transition temperature of 30°C or lower, wherein the content of the resin particles relative to 100 parts by mass of the vinyl alcohol-based polymer is 1-50 parts by mass inclusive.

Description

Original film, method of producing stretched optical film, and stretched optical film

The present invention relates to a raw film, a method for producing a stretched optical film, and a stretched optical film.

A polarizing plate having a light transmitting and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal that changes the polarization state of light. Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is laminated on the surface of a polarizing film. As a polarizing film constituting a polarizing plate, an iodine-based stretched film obtained by uniaxially stretching a vinyl alcohol polymer film (hereinafter sometimes referred to as "vinyl alcohol polymer" may be abbreviated as "PVA") is oriented Those in which dichroic dyes such as dyes (I ₃ ^- and I ₅ ^- etc.) and dichroic organic dyes are adsorbed are in the mainstream. Such a polarizing film uniaxially stretches a PVA film containing a dichroic dye in advance, adsorbs a dichroic dye simultaneously with uniaxial stretching of the PVA film, or uniaxially stretches a PVA film Manufactured by, for example, adsorbing a dye.

LCDs are now used in a wide range of small devices such as calculators and watches, smartphones, notebook computers, LCD monitors, LCD color projectors, LCD TVs, car navigation systems, mobile phones, measuring instruments used indoors and outdoors ing. In recent years, with the development of mobile applications such as small notebook computers and mobile phones in particular, there has been an increasing demand for thinner polarizing plates. In addition, since the use place is widely used by portability, the improvement of the durability is also required at the same time.

As one of the methods for thinning the polarizing plate, thinning of the polarizing film and the protective film can be mentioned. For this purpose, it is necessary to reduce the thickness of a raw film (PVA film) as a raw material of a polarizing film. However, a thin original film is likely to be torn in the stretching direction in the drying step of producing a polarizing film, the step of laminating the obtained polarizing film and a protective film, and the like. In addition, when the polarizing film is thin, the polarizing film may tear in the stretching direction or may be finely cracked at the end face of the polarizing film during handling such as punching or cutting the polarizing film or the polarizing plate. For this reason, when a thin raw film is used, the productivity and yield of the polarizing plate and the LCD are reduced, which tends to lead to high cost. As described above, the reduction in thickness of the raw film and the polarizing film tends to lower the productivity and yield, leading to an increase in cost. Moreover, although thickness reduction is anticipated also in extending | stretching optical films other than a polarizing film, such as retardation film, it has a disadvantage that it becomes easy to produce a tear etc. similarly.

As a technique for producing a thin polarizing film with a high yield, a method is known in which a thin PVA film is formed on a plastic film by a coating method, and the laminate is stretched and dried (see Patent Documents 1 and 2). In addition, in order to improve the handleability such as punching properties of the obtained polarizing film, a polarizing film is produced under specific conditions, and then a polarizing plate in which a urethane resin layer is laminated on at least one side of this polarizing film (Patent Document 3 A composition (see Patent Document 4) capable of forming a cured resin layer excellent in flexibility and flexibility is also proposed.

Patent No. 4804588 Patent No. 4815544 Patent No. 3315914 gazette JP 2014-115538 A

However, the methods described in

Patent Documents

1 and 2 have the following disadvantages.
(1) Coating operation and subsequent drying operation are complicated.
(2) Since the heat treatment for the insolubilizing treatment of the PVA film needs to be performed in the state of a laminate, the plastic film to be used is limited to one which can be stretched even after the heat treatment, resulting in an increase in cost.
(3) In a laminate formed by forming a PVA film on a plastic film by a coating method, the adhesive strength between the plastic film and the PVA film is relatively high. For this reason, when such a laminate having high adhesive strength is stretched, appropriate neck-in of the PVA film is hindered, and it is difficult to obtain a polarizing film having excellent polarization performance.

Further, the methods described in Patent Documents 3 and 4 also have disadvantages such as an increase in cost due to an increase in the number of steps at the time of manufacturing a polarizing plate, a decrease in yield, and the like.

The present invention has been made based on the above circumstances, and the object of the present invention is to provide a raw film, a thin, tear-resistant stretched optical film, and a thin, tear-resistant drawn optical film that can be obtained relatively easily. And it is providing the manufacturing method of the stretched optical film which can obtain such a stretched optical film comparatively easily.

As a result of intensive studies to achieve the above object, the present inventors have added resin particles having a relatively low glass transition temperature to the film, even when the thickness of the film is reduced. Thus, the inventors have found that a stretched optical film which is not easily torn can be obtained, and further studies have been made based on these findings to complete the present invention.

That is, the present invention made to solve the above problems is as follows.
[1] The resin particle having an average thickness of 45 μm or less and containing a vinyl alcohol polymer as a main component and a resin particle having a glass transition temperature of 30 ° C. or less, relative to 100 parts by mass of the vinyl alcohol polymer A raw film film for producing a stretched optical film, which has a content of 1 part by mass or more and 50 parts by mass or less.
[2] The raw film film of [1], wherein the average particle diameter of the resin particles is 1 nm or more and 300 nm or less.
The manufacturing method of the extending | stretching optical film provided with the process of extending | stretching the original film of [3] [1] or [2].
[4] The resin particles having an average thickness of 20 μm or less and containing a vinyl alcohol polymer as a main component and a resin particle having a glass transition temperature of 30 ° C. or less, relative to 100 parts by mass of the vinyl alcohol polymer A stretched optical film having a content of 1 parts by mass or more and 50 parts by mass or less.
[5] The drawing of [4], wherein the length of the resin particle in the drawing direction observed in a transmission electron microscope image in a cut surface parallel to the drawing direction is longer than the length in the direction perpendicular to the drawing direction Optical film.

According to the present invention, a raw film capable of relatively easily obtaining a thin, tear-resistant stretched optical film, a thin, tear-resistant stretched optical film, and such a stretched optical film can be obtained relatively easily. The manufacturing method of a stretched optical film can be provided.

It is a schematic diagram which shows the cut surface parallel to the extending | stretching direction in the extending | stretching optical film which concerns on one Embodiment of this invention.

<Raw film>
The raw film film which concerns on one Embodiment of this invention is a film used for manufacture of a stretched optical film. That is, the said raw film is a film used as the material of extending | stretching optical films, such as a polarizing film and retardation film. A stretched optical film is obtained by stretching the raw film.

The raw film may be a single layer film or a multilayer film (laminate). As a form of a multilayer film, the film etc. which have the PVA layer formed by the coating method etc. on the thermoplastic resin film can be mentioned, for example. The raw film is preferably a single layer film from the viewpoint that the effects of the present invention are more remarkably exhibited, the complexity of laminating (coating etc.) operation, the cost of the thermoplastic resin film, and the like.

(Average thickness)
The upper limit of the average thickness of the raw film is 45 μm, preferably 40 μm, more preferably 35 μm, and still more preferably 30 μm. A thin stretched optical film can be obtained because the average thickness of the raw film is equal to or less than the above upper limit. On the other hand, the lower limit of the average thickness is preferably 1 μm, more preferably 3 μm, still more preferably 10 μm, and still more preferably 20 μm. The tear resistance of the stretched optical film obtained can be improved more because the average thickness of the said original film is more than the said minimum.

(PVA)
The raw film contains PVA (vinyl alcohol polymer) as a main component. In addition, a main component means the component with the largest content on a mass basis (following, the same). PVA is a polymer having a vinyl alcohol unit (—CH ₂ —CH (OH) —) as a structural unit. PVA may have vinyl ester units and other units in addition to vinyl alcohol units.

As PVA, one or two kinds of vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate and the like What is obtained by saponifying a polyvinyl ester obtained by polymerizing species or more can be used. Among the above vinyl esters, compounds having a vinyloxycarbonyl group (H ₂ C = CH—O—CO—) in the molecule are preferable in terms of easiness of production of PVA, easiness of availability, cost and the like, Vinyl acetate is more preferred.

The polyvinyl ester is preferably one obtained using only one or two or more vinyl esters as a monomer, and more preferably one obtained using only one vinyl ester as a monomer. As long as the effects of the present invention are not significantly impaired, it may be a copolymer of one or more vinyl esters and other monomers copolymerizable therewith.

Examples of the other monomer copolymerizable with the above vinyl ester include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene;
(Meth) acrylic acid or a salt thereof;
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate;
(Meth) acrylamide;
N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N- dimethyl (meth) acrylamide, diacetone (meth) acrylamide, (meth) acrylamidopropane sulfonic acid or a salt thereof, (meth) acrylamido propyl dimethyl amine Or (meth) acrylamide derivatives such as salts thereof, N-methylol (meth) acrylamide or derivatives thereof;
N-vinylamides such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone and the like;
Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether and the like;
Vinyl cyanides such as (meth) acrylonitrile;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride;
Maleic acid, or a salt, ester or acid anhydride thereof;
Itaconic acid, or a salt, ester or acid anhydride thereof;
Vinyl silyl compounds such as vinyl trimethoxysilane;
Unsaturated sulfonic acid or its salt etc. can be mentioned.

The polyvinyl ester can have a structural unit derived from one or more of the above monomers.

The upper limit of the proportion of the structural unit derived from the other monomer in the polyvinyl ester is preferably 15 mol%, more preferably 10 mol%, based on the number of moles of all structural units constituting the polyvinyl ester. 5 mol% is more preferable, and 1 mol% is still more preferable.

As PVA, those which have not been graft copolymerized can be preferably used. However, as long as the effects of the present invention are not significantly impaired, PVA may be modified with one or more graft copolymerizable monomers. The graft copolymerization can be performed on at least one of a polyvinyl ester and PVA obtained by saponifying it. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; and α-olefins having 2 to 30 carbon atoms. It is preferable that the ratio of the structural unit derived from the monomer which can be graft-copolymerized in polyvinyl ester or PVA is 5 mol% or less based on the number-of-moles of all the structural units which comprise polyvinyl ester or PVA.

In the above PVA, part of its hydroxy groups may be crosslinked or may not be crosslinked. In the above PVA, a part of the hydroxy group may be reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or not reacted with these compounds to form an acetal structure May be

The lower limit of the polymerization degree of PVA is preferably 1,000, more preferably 1,500, and still more preferably 2,000. By the polymerization degree of PVA being more than the said lower limit, the optical characteristic of the stretched optical film obtained can be improved. On the other hand, the upper limit of the degree of polymerization is preferably 10,000, more preferably 8,000, and still more preferably 5,000. By making the polymerization degree of PVA below the said upper limit, the raise of the manufacturing cost of PVA and the defect generation | occurrence | production at the time of film forming can be suppressed. The degree of polymerization of PVA means an average degree of polymerization measured according to the description of JIS K 6726-1994.

The lower limit of the degree of saponification of PVA is preferably 95 mol%, more preferably 98 mol%, still more preferably 99 mol%, particularly preferably 99.5 mol%, since the wet heat resistance of the stretched optical film obtained becomes good. preferable. On the other hand, the upper limit of the degree of saponification may be substantially 100 mol%. The degree of saponification of PVA is the ratio of the number of moles of vinyl alcohol units to the total number of moles of structural units (typically vinyl ester units) that can be converted to vinyl alcohol units by saponification and vinyl alcohol units (mol% Say). The degree of saponification can be measured according to the description of JIS K6726-1994.

As a minimum of content of PVA in the original film concerned, 60 mass% is preferred, 70 mass% is more preferred, and 75 mass% is still more preferred. By making content of PVA more than the said lower limit, in the stretched optical film obtained, optical characteristics, such as polarization performance, are expressed more favorably. On the other hand, 95 mass% is preferable as an upper limit of this content, 90 mass% may be more preferable, and 85 mass% may be further preferable. By making content of PVA below the said upper limit, the obtained stretched optical film becomes more difficult to tear.

(Resin particles)
The raw film contains resin particles having a glass transition temperature of 30 ° C. or less. By containing such resin particles, the raw film can obtain a stretched optical film which is thin and hardly tears. The reason why such effects occur is not clear, but when the cross section of the stretched optical film produced from the raw film was observed when the cross section was observed, it was dispersed in the film because the cross section became rough. It is presumed that the resin particles are less likely to be torn by suppressing the propagation of tears. In particular, when the glass transition temperature of the resin particles is 30 ° C. or less, that is, the general stretching treatment temperature at the time of producing a stretched optical film using a raw film, the resin particles are also stretched in the stretching step. Can be transformed into Thereby, the PVA can be sufficiently oriented while maintaining the adhesion between the PVA and the resin particles. For this reason, it is assumed that the stretched optical film obtained from the raw film does not easily tear, and that optical properties such as polarization performance can be enhanced by adjusting the content of resin particles and the average particle diameter. Ru.

The resin particles are particles whose main component is a polymer (resin). The lower limit of the content of the polymer in the resin particles is, for example, 50% by mass, preferably 80% by mass, and more preferably 95% by mass. The resin particles may be formed substantially only of resin.

The upper limit of the glass transition temperature (Tg) of the resin particles (Tg of the polymer which is the main component of the resin particles) is 30 ° C., preferably 25 ° C., more preferably 20 ° C., still more preferably 15 ° C. C. is even more preferred. When the glass transition temperature is less than or equal to the above upper limit, a stretched optical film that is difficult to tear can be obtained. Moreover, optical characteristics, such as polarization performance, can also be improved by making this glass transition temperature below the said upper limit, and adjusting content of resin particles, and an average particle diameter.

Although the lower limit of the glass transition temperature of the resin particles is not particularly limited, for example, -100 ° C. is preferable, -80 ° C. is more preferable, and -60 ° C. is more preferable. By making this glass transition temperature more than the said minimum, aggregation of the resin particle at the time of the heating in the film forming process which produces an original film is suppressed, and the white turbidity of the obtained original film and a stretched optical film is suppressed. be able to. Moreover, the optical characteristic of the stretched optical film obtained can be improved.

In addition, the glass transition temperature of a resin particle is formed into a film using a resin particle, and is taken as a measured value by DSC (differential scanning calorimetry) performed on the obtained resin film. When resin particles contain a plurality of different resins, the glass transition temperature of the resin having the lowest glass transition temperature is taken as the glass transition temperature of the resin particles.

The lower limit of the content of resin particles in the raw film is 1 part by mass, preferably 3 parts by mass, more preferably 5 parts by mass, and even more preferably 7 parts by mass with respect to 100 parts by mass of PVA. By making content of a resin particle more than the said lower limit, the obtained stretched optical film can be made hard to tear and handling property etc. improve. On the other hand, the upper limit of the content is 50 parts by mass, preferably 30 parts by mass, more preferably 20 parts by mass, and still more preferably 15 parts by mass. By making content of a resin particle below into the said upper limit, the light transmittance of the stretched optical film obtained can be made into a favorable state, and optical characteristics, such as polarization performance, can be improved.

The lower limit of the average particle diameter of the resin particles in the raw film is preferably 1 nm, more preferably 5 nm, still more preferably 10 nm, still more preferably 20 nm, and still more preferably 30 nm. By setting the average particle diameter of the resin particles to the above lower limit or more, the stretched optical film obtained is more difficult to be torn, and the handling property and the like are improved. On the other hand, the upper limit of the average particle size may be, for example, 500 nm, preferably 300 nm, more preferably 200 nm, and still more preferably 100 nm. By setting the average particle diameter of the resin particles to the upper limit or less, particularly 300 nm or less, the light transmittance of the obtained stretched optical film can be brought into a good state, and optical characteristics such as polarization performance can be enhanced.

In addition, let the average particle diameter of the resin particle in the said raw film be a measured value based on the TEM (transmission electron microscope) image of the film cut surface. By measuring the TEM of the cut surface perpendicular to the in-plane direction of the raw film, the presence or absence of the resin particles and the dispersed state can be observed as a sea-island structure. The sea-island structure is a structure in which a discontinuous part (island part) is mixed in a part (sea part) which appears continuously in a mixture consisting of two kinds of physical properties. Because the dyeability of the resin particle and PVA is different, the color of the part that appears continuously is dark, the color of the part that appears discontinuous is light, the color of the part that appears continuously is light, and the part that appears discontinuous The color becomes darker. In the TEM image, resin particles are observed as island portions. The resin particles are mechanically extracted from the TEM image of the cut surface of the film using image analysis software, and the average value of the diameters of these resin particles is calculated. The calculated value is taken as the average particle size of the resin particles. The specific measuring method of the average particle diameter of resin particle is taken as the method as described in the Example.

The resin particles contain a polymer. The polymer is not particularly limited as long as it has a glass transition temperature of 30 ° C. or less, and polyolefin, polyurethane, acrylic resin and the like can be mentioned, but acrylic resin is preferable. An acrylic resin refers to a polymer containing a structural unit derived from (meth) acrylic acid ester.

As (meth) acrylic ester,
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, etc. (Meth) acrylic acid alkyl ester;
(Meth) acrylic esters having an alicyclic group such as dicyclopentanyl (meth) acrylate and isobornyl (meth) acrylate;
Examples include aryl (meth) acrylates such as phenyl (meth) acrylate and the like.

Among the acrylic resins, the resin particles preferably include an acrylic resin containing a structural unit ((meth) acrylic acid alkyl ester unit) derived from a (meth) acrylic acid alkyl ester. Although the minimum of carbon number of the alkyl group which the (meth) acrylic acid alkyl ester has is 1, 2 is preferable, 3 is more preferable, and 4 is even more preferable. On the other hand, the upper limit of the carbon number of this alkyl group is, for example, 10, 8 is preferable, 6 is more preferable, and 4 is more preferable. It is also preferable that it is an acrylic acid alkyl ester unit. That is, among the (meth) acrylic acid alkyl ester units, butyl acrylate units are most preferable. Resin particles using an acrylic resin containing such (meth) acrylic acid alkyl ester units have a low glass transition temperature, and can further improve the tear resistance and optical properties. The reason for this is not clear, but it is speculated that the flexibility of the resin particle is increased and the resin particle is easily deformed in the drawing direction during the drawing process.

Further, as the acrylic resin, acrylic resins containing (meth) acrylic acid units (-CH ₂ -CHCOOH- and -CH ₂ -C (CH ₃ ) COOH-) can also be suitably used. Resin particles using such a polymer can exhibit good dispersibility and the like in a PVA matrix. In this case, for example, block copolymers of (meth) acrylic acid units and (meth) acrylic acid alkyl ester units are preferable. When the acrylic resin is a block copolymer, any of a diblock copolymer, a triblock copolymer and the like may be used.

The resin particles may be particles formed of one type of polymer, or particles having a so-called core-shell type structure with different inner and outer materials may be used. When core-shell type particles are used, the material of the core preferably contains an acrylic resin containing (meth) acrylic acid alkyl ester units. When core-shell type particles are used, the material of the shell is preferably an acrylic resin containing an alicyclic group-containing (meth) acrylic acid ester unit or a (meth) acrylic acid unit.

The resin particles can be produced by a known method. Moreover, a resin particle may use a commercial item. Moreover, the method of making the said raw film film contain a resin particle is not specifically limited, either. For example, resin particles may be added to a PVA chip, or resin particles may be added to a film forming solution used for film formation.

(Plasticizer)
The raw film can further contain a plasticizer. When the said raw film film contains a plasticizer, the handling property, the improvement of a stretchability, etc. can be aimed at. Preferred plasticizers include polyhydric alcohols, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane and the like. One or more of these plasticizers can be used. Among these, glycerin is preferable from the viewpoint of the effect of improving the stretchability.

As a minimum of content of a plasticizer in the original film, 2 mass parts is preferred to 100 mass parts of PVA, 3 mass parts is more preferred, 4 mass parts is still more preferred, and 6 mass parts is still more preferred. Stretchability is further improved by setting the content of the plasticizer to the above lower limit or more. On the other hand, as an upper limit of this content, 20 mass parts is preferred, 17 mass parts is more preferred, and 14 mass parts is still more preferred. By making content of a plasticizer below the said upper limit, it can suppress that a raw film becomes too soft, a plasticizer bleeds out on the surface, and a handling property falls.

(Other additives etc.)
In addition to PVA, resin particles, and plasticizers, the raw film may further include a filler, a processing stabilizer such as a copper compound, a weather resistant stabilizer, a colorant, an ultraviolet light absorber, a light stabilizer, an antioxidant, and charging. Inhibitors, flame retardants, other thermoplastic resins, lubricants, fragrances, antifoams, deodorants, extenders, release agents, mold release agents, reinforcing agents, crosslinking agents, fungicides, preservatives, crystallization Other additives, such as a speed retarder, can be added as appropriate.

However, as an upper limit of content of additives other than PVA, a resin particle, and a plasticizer in the raw film concerned, 1 mass% may be preferred, and 0.2 mass% may be more preferred. When the content of other additives exceeds the above upper limit, the tear strength and optical properties of the resulting stretched optical film may be affected.

The lower limit of the degree of swelling of the raw film is preferably 160%, more preferably 170%, and still more preferably 180%. When the degree of swelling is at least the above lower limit, it is possible to suppress the progress of crystallization extremely, and it is possible to stably stretch to a high magnification. On the other hand, the upper limit of the degree of swelling is preferably 240%, more preferably 230%, and still more preferably 220%. When the degree of swelling is not more than the above upper limit, dissolution at the time of stretching is suppressed, and it becomes possible to stretch even under higher temperature conditions. The degree of swelling of the raw film is the mass obtained by immersing the raw film in distilled water at 30 ° C for 15 minutes, and the raw film dried at 105 ° C for 16 hours after being immersed in distilled water at 30 ° C for 15 minutes. It means the percentage of the value obtained by dividing by the mass of the film.

The shape of the raw film is not particularly limited, but is preferably a long film because a stretched optical film can be produced continuously with high productivity. The length of the long raw film is not particularly limited, and can be appropriately set depending on the application of the stretched optical film to be produced, for example, to be in the range of 5 m or more and 20,000 m or less. it can. The width of the original film is not particularly limited, and the lower limit can be, for example, 50 cm. However, since a wide polarizing film is required in recent years, the lower limit is preferably 1 m, more preferably 2 m, and further 4 m. preferable. The upper limit of the width of the raw film is not particularly limited, and may be, for example, 7 m. When the width is too wide, it tends to be difficult to uniformly stretch when producing a stretched optical film with a device that has been put into practical use.

The raw film can relatively easily produce a stretched optical film which is difficult to tear during production and handling. Therefore, it can be suitably used as a material of a stretched optical film such as a polarizing film or a retardation film. Among them, the raw film is particularly preferably used as a raw film for producing a polarizing film because a polarizing film having good polarizing performance can be easily produced.

(Production method of raw film)
The method for producing the raw film of the present invention is not particularly limited, and a production method in which the thickness and width of the raw film after film formation can be made more uniform can be preferably employed. For example, one or more of the above-mentioned PVA and resin particles constituting the raw film, and, if necessary, a plasticizer, other additives, and a surfactant described later may be contained in the liquid medium. It can be obtained by forming a film using the dissolved film-forming solution. Moreover, it can manufacture also using the film forming undiluted | stock solution which melt | dissolved PVA as needed. In the membrane-forming solution, the resin particles are preferably uniformly mixed. Moreover, when a film forming undiluted | stock solution contains at least 1 sort (s) of a plasticizer, another additive, and surfactant, it is preferable that those components are mixed uniformly.

Examples of the liquid medium include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine and the like. It can be mentioned. These liquid media can be used alone or in combination of two or more. Among these, water is preferable from the viewpoint of small impact on the environment and recovery.

The volatilization fraction of the undiluted solution (content ratio of volatile components such as liquid medium in the undiluted solution to be removed by volatilization or evaporation during film deposition) varies depending on the film forming method, film forming conditions, etc. In general, the lower limit is preferably 50% by mass, more preferably 55% by mass, and still more preferably 60% by mass. When the volatilization fraction of the membrane-forming solution is at least the above lower limit, the viscosity of the membrane-forming solution does not become too high, and filtration and degassing are smoothly carried out at the time of preparation of the membrane-forming solution. The manufacture of the film is facilitated. On the other hand, the upper limit of the volatile fraction is preferably 95% by mass, more preferably 90% by mass, and still more preferably 85% by mass. When the volatilization fraction of the membrane-forming solution is not more than the above-mentioned upper limit, the concentration of the membrane-forming solution does not become too low, and the industrial production of the original film becomes easy.

The membrane-forming solution preferably contains a surfactant. By including the surfactant, the film forming property is improved, generation of thickness unevenness of the raw film is suppressed, and peeling of the film from a metal roll or belt used for film formation becomes easy. When a raw film is produced from a film-forming stock solution containing a surfactant, the raw film may contain a surfactant. The type of surfactant is not particularly limited, but from the viewpoint of releasability from metal rolls and belts, anionic surfactants and nonionic surfactants are preferred.

The anionic surfactant is preferably, for example, a carboxylic acid type such as potassium laurate; a sulfuric acid ester type such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and a sulfonic acid type such as dodecylbenzene sulfonate.

Examples of nonionic surfactants include alkyl ether types such as polyoxyethylene oleyl ether; alkyl phenyl ether types such as polyoxyethylene octyl phenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene lauryl amino ether Alkylamine type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as lauric acid diethanolamide, oleic acid diethanolamide; polyoxyalkylene Preferred is an allyl phenyl ether type such as allyl phenyl ether.

These surfactants can be used alone or in combination of two or more.

When the membrane-forming solution or the resulting raw film contains a surfactant, the lower limit of the content is preferably 0.01 parts by mass with respect to 100 parts by mass of PVA contained in the membrane-forming solution or the raw film, 0 .02 parts by mass is more preferable. When the content of the surfactant is the above lower limit or more, the film forming property and the releasability are further improved. On the other hand, as an upper limit of this content, 0.5 mass part is preferred, 0.3 mass part is more preferred, and 0.1 mass part is still more preferred. When content of surfactant is below the said upper limit, it can suppress that a surfactant bleeds out on the surface of a raw film, blocking arises, and a handling property falls.

As a film forming method at the time of forming an original film film using the film forming solution, for example, a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method and the like can be mentioned. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable because a raw film having uniform thickness and width and good physical properties can be obtained. Drying and heat treatment can be performed on the formed raw film as required.

There is no restriction | limiting in particular in the heat processing temperature, What is necessary is just to adjust suitably. If the heat treatment temperature is too high, discoloration or deterioration of the original film is observed. Therefore, as an upper limit of heat treatment temperature, 210 ° C is preferred, 180 ° C is more preferred, and 150 ° C is still more preferred. On the other hand, the lower limit of the heat treatment temperature is, for example, 60 ° C., preferably 90 ° C.

There is no restriction | limiting in particular in heat processing time, Although it may adjust suitably, As a viewpoint which manufactures an original film efficiently, as an upper limit, 30 minutes are preferable and 15 minutes are more preferable. On the other hand, as the lower limit, for example, one minute is preferable, and three minutes is more preferable.

<Stretch optical film>
The stretched optical film according to an embodiment of the present invention is an optical film containing PVA oriented in a predetermined direction, such as a polarizing film or a retardation film. The stretched optical film may be uniaxially stretched or biaxially stretched, but is preferably uniaxially stretched. The stretched optical film uniaxially stretched can be suitably used as a polarizing film or the like. The stretched optical film may be a monolayer film or a multilayer film, but is preferably a monolayer film.

(Average thickness)
The upper limit of the average thickness of the stretched optical film is 20 μm, preferably 18 μm, more preferably 16 μm, and still more preferably 14 μm. By the average thickness of the said stretched optical film being below the said upper limit, sufficient thickness reduction can be achieved. On the other hand, the lower limit of the average thickness is preferably 5 μm, more preferably 8 μm, and still more preferably 10 μm. When the average thickness of the stretched optical film is equal to or more than the above lower limit, it is possible to make it more difficult to tear and to improve the handling property and the like.

(Component etc)
The stretched optical film contains PVA as a main component and resin particles.

The upper limit of the glass transition temperature (Tg) of the resin particles contained in the stretched optical film (Tg of the polymer which is the main component of the resin particles) is 30 ° C., preferably 25 ° C., more preferably 20 ° C. 15 ° C. is more preferred, and 10 ° C. is even more preferred. When the glass transition temperature is less than or equal to the above upper limit, the stretched optical film is not easily torn and is excellent in handleability and the like. Moreover, optical characteristics, such as polarization performance, can also be improved by making this glass transition temperature below the said upper limit, and adjusting content of resin particles, and an average particle diameter. Although the lower limit of the glass transition temperature of the resin particles is not particularly limited, for example, -100 ° C. is preferable, -80 ° C. is more preferable, and -60 ° C. is more preferable. By making this glass transition temperature more than the said minimum, aggregation of a resin particle is suppressed and the cloudiness of a stretched optical film can be suppressed. Also, the optical properties of the stretched optical film can be enhanced.

In addition, the glass transition temperature of the resin particle contained in the said stretched optical film was film-formed using the resin particle like the resin particle contained in a raw film, and it went with respect to this obtained resin film It is a measured value of DSC (differential scanning calorimetry).

The lower limit of the content of resin particles in the stretched optical film is 1 part by mass, preferably 3 parts by mass, more preferably 5 parts by mass, and still more preferably 7 parts by mass with respect to 100 parts by mass of PVA. By making content of a resin particle more than the said lower limit, a stretched optical film can be made hard to tear and handling property etc. improve. On the other hand, the upper limit of the content is 50 parts by mass, preferably 30 parts by mass, more preferably 20 parts by mass, and still more preferably 15 parts by mass. By making content of a resin particle below the said upper limit, the light transmittance of a stretched optical film can be made into a favorable state, and optical characteristics, such as polarization performance, can be improved.

In the stretched optical film, the length in the stretching direction (diameter in the stretching direction) of the resin particles observed in a transmission electron microscope (TEM) image in a cut surface parallel to the stretching direction is perpendicular to the stretching direction It is preferable that the length is longer than the length in the normal direction (diameter in the direction perpendicular to the stretching direction). That is, it is preferable that the resin particle in the said extending | stretching optical film is an ellipse which has a long axis along the extending | stretching direction. In such a case, the PVA can form a sufficiently oriented state while maintaining the adhesion between the PVA and the resin particles. For this reason, it is assumed that the stretched optical film is less likely to be torn, and that optical properties such as polarization performance can be enhanced by adjusting the content of resin particles and the average particle diameter. In addition, such an elliptical resin particle may be formed by a resin particle deform | transforming along an extending | stretching direction, when extending | stretching the raw film containing the resin particle whose glass transition temperature is 30 degrees C or less. In addition, the extending | stretching direction in a extending | stretching optical film is an orientation direction of the crystal | crystallization of PVA normally.

Specifically, as shown in FIG. 1, in the TEM image of the cut surface parallel to the stretching direction X of the stretched optical film 1, the length A of the stretching direction X of the resin particle 2 (island portion) is stretched Preferably, it is longer than the length B in the direction perpendicular to the direction X. Further, the lower limit of the ratio (A / B) of the length A of the drawing direction X to the length B of the resin particle 2 in the direction perpendicular to the drawing direction X is preferably 1.2, more preferably 1.6. , 2.0 is more preferred. The upper limit of this ratio (A / B) may be, for example, 3 or 2.6.

The lower limit of the length A in the stretching direction of the resin particles is preferably 1 nm, more preferably 10 nm, still more preferably 30 nm, still more preferably 50 nm, and still more preferably 70 nm. On the other hand, the upper limit of the length A may be, for example, 800 nm, but 300 nm is preferable, 200 nm is more preferable, and 100 nm is more preferable. The lower limit of the length B in the direction perpendicular to the stretching direction of the resin particles is preferably 1 nm, more preferably 10 nm, still more preferably 20 nm, and still more preferably 30 nm. On the other hand, the upper limit of the length B may be, for example, 500 nm, but 200 nm is preferable, 100 nm is more preferable, and 50 nm is more preferable. When the length A and the length B are in the above-mentioned ranges, it is more difficult for tearing to occur, and optical properties such as polarization performance can be enhanced by adjusting the content of resin particles and the average particle diameter.

The length A in the stretching direction of the resin particles and the length B in the direction perpendicular to the stretching direction are measured by the following method. The resin particles are mechanically extracted using image analysis software with respect to a TEM image of the film cut surface parallel to the stretching direction. The average length in the long axis direction of the extracted resin particles is taken as length A, and the average length in the short axis direction is taken as length B. From the length A and the length B, the ratio of lengths (A / B) is also determined. These specific measurement methods are the methods described in the examples.

Preferred forms of PVA and resin particles contained in the stretched optical film are the same as the PVA and resin particles contained in the above-described raw film. The other components that may be contained in the stretched optical film are the same as the above-described raw film. When the stretched optical film is a polarizing film, the stretched optical film has a dichroic dye adsorbed on the front and back surfaces. As a dichroic dye, an iodine based dye is common.

When the stretched optical film is a polarizing film, the lower limit of the degree of polarization when the transmittance is 44.0% may be, for example, 70% as the polarization performance, but it is preferably 99.0%. And 99.8% is more preferable, and 99.9% is more preferable. When the degree of polarization is less than the above lower limit, the contrast of the LCD may be lowered when used in a smartphone, a notebook computer, a liquid crystal television, a car navigation system, or the like.

When the stretched optical film is a polarizing film, this polarizing film is usually used as a polarizing plate by laminating a protective film which is optically transparent and has mechanical strength on both sides or one side thereof. As the protective film, a cellulose triacetate (TAC) film, a cellulose acetate / butyrate (CAB) film, an acrylic film, a polyester film or the like is used. Moreover, as an adhesive agent for bonding, a PVA-type adhesive agent, an ultraviolet curable adhesive agent, etc. can be mentioned, A PVA-type adhesive agent is preferable.

A retardation film, a viewing angle improvement film, a brightness enhancement film, etc. may be further bonded to the polarizing plate obtained as described above. In addition, the stretched optical film of this invention can also be used as said retardation film. The polarizing plate can be used as a component of an LCD by bonding it to a glass substrate after being coated with an acrylic or other pressure-sensitive adhesive.

<Production method of stretched optical film>
The stretched optical film according to an embodiment of the present invention can be obtained by the production method including the step of stretching the raw film described above. That is, the said stretched optical film can be manufactured by the method similar to the former except using the raw film mentioned above. That is, according to the manufacturing method, it is possible to relatively easily obtain a thin and tear-resistant stretched optical film without undergoing a special process. Hereinafter, the specific manufacturing method in case the said extending | stretching optical film is a polarizing film is demonstrated.

As a specific method for producing the polarizing film, the raw film may be subjected to swelling treatment, dyeing treatment, uniaxial stretching treatment, and if necessary, crosslinking treatment, fixing treatment, washing treatment, drying. Examples of the method include treatment and heat treatment. In this case, the order of the treatments such as swelling treatment, dyeing treatment, crosslinking treatment, uniaxial stretching, and fixation treatment is not particularly limited, and two or more treatments may be performed simultaneously. Also, one or more of each treatment may be performed twice or more.

The swelling treatment can be carried out by immersing the raw film in water. As a minimum of temperature of water at the time of immersing in water, 20 ° C is preferred, 22 ° C is more preferred, and 25 ° C is still more preferred. On the other hand, as an upper limit of this temperature, 40 ° C is preferred, 38 ° C is more preferred, and 35 ° C is still more preferred. Moreover, as a minimum of time to immerse in water, 0.1 minute is preferable, and 0.5 minute is more preferable. On the other hand, as an upper limit of this time, 5 minutes are preferable and 3 minutes are more preferable. In addition, the water at the time of immersing in water is not limited to a pure water, The aqueous solution which various components melt | dissolved may be sufficient, and the mixture of water and an aqueous medium may be sufficient.

The dyeing process can be carried out by contacting the original film with a dichroic dye. As a dichroic dye, an iodine based dye is generally used. As a time of a dyeing | staining process, you may be any stage before uniaxial stretching processing, at the time of uniaxial stretching processing, and after uniaxial stretching processing. The dyeing process is generally carried out by immersing the raw film as a dyeing bath in a solution containing iodine-potassium iodide (in particular, an aqueous solution). The concentration of iodine in the dye bath is preferably 0.01% by mass or more and 0.5% by mass or less, and the concentration of potassium iodide is preferably 0.01% by mass or more and 10% by mass or less. Moreover, 20 degreeC is preferable and, as for the minimum of the temperature of a dyeing | staining bath, 25 degreeC is more preferable. On the other hand, 50 degreeC is preferable and, as for the upper limit of this temperature, 40 degreeC is more preferable.

By subjecting the raw film to a crosslinking treatment, elution of PVA into water can be effectively prevented when wet stretching at high temperature. From this point of view, the crosslinking treatment is preferably performed before the uniaxial stretching treatment. The crosslinking treatment can be carried out by immersing the raw film in an aqueous solution containing a crosslinking agent. As said crosslinking agent, 1 type (s) or 2 or more types of boron inorganic compounds, such as boric acid, borates, such as borax, can be used. The lower limit of the concentration of the crosslinking agent in the aqueous solution containing the crosslinking agent is preferably 1% by mass, more preferably 2% by mass, and still more preferably 3% by mass. On the other hand, the upper limit of the concentration is preferably 15% by mass, more preferably 7% by mass, and still more preferably 6% by mass. When the concentration of the crosslinking agent is in the above range, sufficient stretchability can be maintained. The aqueous solution containing the crosslinking agent may contain an auxiliary such as potassium iodide. 20 degreeC is preferable and, as for the minimum of the temperature of the aqueous solution containing a crosslinking agent, 25 degreeC is more preferable. On the other hand, 50 degreeC is preferable and, as for the upper limit of this temperature, 40 degreeC is more preferable. By setting the temperature within the above range, crosslinking can be efficiently performed.

The uniaxial stretching treatment may be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, it can be carried out in an aqueous solution of boric acid or in the above-mentioned dyeing bath or in a fixed treatment bath described later. In the case of dry stretching, uniaxial stretching may be performed at room temperature, or uniaxial stretching may be performed while heating, or uniaxial stretching in air using a raw film after water absorption. You may Among these, a wet stretching method is preferable, and uniaxial stretching in a boric acid aqueous solution is more preferable. The lower limit of the boric acid concentration of the aqueous boric acid solution is preferably 0.5% by mass, more preferably 1.0% by mass, and still more preferably 1.5% by mass. On the other hand, 6.0 mass% is preferable, as for the upper limit of this boric acid concentration, 5.0 mass is more preferable, and 4.0 mass% is more preferable. The boric acid aqueous solution may contain potassium iodide, and the concentration thereof is preferably 0.01% by mass or more and 10% by mass or less.

30 degreeC is preferable, as for the minimum of the extending | stretching temperature in uniaxial stretching process, 40 degreeC is more preferable, and 50 degreeC is further more preferable. By setting the lower limit of the stretching temperature to 30 ° C. or higher, which is the upper limit of the glass transition temperature of the resin particles, the resin particles are favorably deformed so as to extend in the stretching direction at the time of stretching. This makes it possible to relatively easily obtain a stretched optical film which is difficult to be split and which is excellent in handleability.

The lower limit of the draw ratio in uniaxial stretching is preferably 5 times, more preferably 5.5 times, and still more preferably 6 times in terms of the polarization performance of the obtained polarizing film. Although the upper limit in particular of a draw ratio is not restrict | limited, For example, 10 times are preferable and 8 times may be more preferable.

In the production of the polarizing film, it is preferable to carry out a fixing treatment after the uniaxial stretching treatment in order to strengthen the adsorption of the dichroic dye (iodine-based dye etc.) to the raw film. As a fixing process bath used for a fixing process, the aqueous solution containing 1 type, or 2 or more types of boron inorganic compounds, such as a boric acid and borax, can be used. In addition, if necessary, an iodine compound or a metal compound may be added to the fixing treatment bath. 0.5 mass% is preferable and, as for the minimum of the density | concentration of the boron inorganic compound in a fixed process bath, 1 mass% is more preferable. On the other hand, 15 mass% is preferable and 10 mass% of the upper limit of this concentration is more preferable. By setting this concentration within the above range, the adsorption of the dichroic dye can be made stronger. The lower limit of the temperature of the fixed treatment bath is preferably 15 ° C. On the other hand, 60 degreeC is preferable and, as for the upper limit of this temperature, 40 degreeC is more preferable.

The washing treatment is generally performed by immersing the raw film in water or the like. At this time, it is preferable that water and the like used for the washing treatment contain an auxiliary agent such as potassium iodide from the viewpoint of improving the polarization performance. At this time, the concentration of iodide such as potassium iodide is preferably 0.5% by mass or more and 10% by mass or less. The lower limit of the temperature of water and the like used for the washing treatment is generally 5 ° C., preferably 10 ° C., and more preferably 15 ° C. On the other hand, the upper limit of this temperature is generally 50 ° C., preferably 45 ° C., and more preferably 40 ° C. It is not preferable that the temperature of water or the like is too low from the economic point of view. On the other hand, if the temperature of water or the like is too high, the polarization performance may be degraded.

Although the conditions in particular of a drying process are not restrict | limited, As a minimum of drying temperature, 30 degreeC is preferable and 50 degreeC is more preferable. On the other hand, as an upper limit of drying temperature, 150 degreeC is preferable and 130 degreeC is more preferable. By drying at a temperature within the above range, it is easy to obtain a polarizing film having excellent dimensional stability.

By performing heat treatment after the drying treatment, a polarizing film further excellent in dimensional stability can be obtained. Here, the heat treatment is a treatment to further heat the polarizing film having a moisture content of 5% or less after the drying treatment to improve the dimensional stability of the polarizing film. Although the conditions in particular of heat processing are not restrict | limited, It is preferable to heat-process within the range of 60 degreeC or more and 150 degrees C or less. When the heat treatment is performed at a temperature lower than 60 ° C., the dimensional stabilization effect by the heat treatment is insufficient. On the other hand, when the heat treatment is performed at a temperature higher than 150 ° C., yellowing may be intensely generated in the polarizing film.

<Other Embodiments>
The raw film, the stretched optical film, and the method for producing the stretched optical film of the present invention are not limited to the above embodiment. For example, although a stretched optical film and a method for producing the same have been described focusing on the case where the stretched optical film is a polarizing film, the stretched optical film is not limited to a polarizing film. For example, a stretched optical film other than a polarizing film such as a retardation film is also within the scope of the present invention, and can be produced by a production method comprising the step of stretching the raw film of the present invention. The manufacturing method of the retardation film as one Embodiment of this invention can be performed using a conventionally well-known method except extending | stretching the raw film of this invention.

The present invention is specifically described by the following examples, but the present invention is not limited by these examples. In addition, each evaluation method employ | adopted in the following Example and a comparative example is shown below.

[Glass transition temperature of resin particles]
After dissolving the raw film obtained in each of the following Examples or Comparative Examples in water, the resin particles are filtered with a filter (“MF-Millipore Membrane Filter VSWP with a pore size of 0.025 μm, available from Merck”), The collected matter (resin particles) was dried. Thereafter, the resin particles were heat-treated at 100 ° C. to collect a resin film formed only from the resin particles. The glass transition temperature of the resin film was determined using DSC (“Q2000” from TA Instruments). This was taken as the glass transition temperature of the resin particles.

[Swelling degree of original film]
About 1.5 g of raw film obtained in each of the following Examples or Comparative Examples was collected. This was cut into about 2 mm × 10 cm, wrapped in 100 mesh (“N-N0110S 115” by NBC Meshtec Inc.), and immersed in distilled water at 30 ° C. for 15 minutes. Thereafter, centrifugal dewatering was performed at 3,000 rpm for 5 minutes to remove the mesh, and then the mass (W1) of the swollen original film was determined. Subsequently, the raw film was dried by a dryer at 105 ° C. for 16 hours, and then the mass (W2) was determined. The swelling degree of the raw film was calculated by the following equation.
Swelling degree (%) = {(W1) / (W2)} × 100

[Average particle size of resin particles in raw film]
The raw film obtained in each of the following Examples or Comparative Examples is cut with an ultramicrotome ("Ultra cut S / FC-S" manufactured by Leica), and then subjected to osmium tetraoxide vapor under an atmosphere of 23 ° C. 5 It was exposed for a day to stain the hydroxyl group of PVA. After the staining process, a frozen section for observation was further cut out under an atmosphere of -100 ° C. using a diamond knife ("Ultra Cryo Dry" 2 mm 35 ° by DiATOME). Thereafter, the over-stained frozen sections for observation were washed with distilled water and dried. The cut surface was observed using a transmission electron microscope ("transmission electron microscope HT7000" manufactured by Hitachi High-Technologies Corporation) to obtain a TEM image. The acceleration voltage was set to 100 kV, the emission current was set to 10 μA, and the electron gun used a LaB6 filament.

The average particle diameter of the resin particles in the raw film was measured by the following method using the TEM image obtained by the above method. First, a TEM image is opened using an image analysis software "Image-Pro Plus 7.0J" (manufactured by Media Cybernetics), then converted to an 8-bit scale by "conversion" and flattened by "filter processing" I did the processing. Next, set the contrast value to 80 in "Contrast Enhance", select "Average Particle Size" on the measurement item setting page in "Count / Size", and then automatically extract bright colored objects. Then, the resin particles were extracted, and the average particle diameter of the resin particles in the raw film was calculated. The particle size smaller than 1/10 of the maximum diameter in the TEM image was removed as noise. Moreover, in the TEM image, when the color of the resin particle is darker than that of PVA, the dark particle is automatically extracted to calculate the average particle diameter of the resin particle in the raw film.

[Length of resin particles in polarizing film]
A TEM image of a cut surface was obtained for the polarizing film obtained in each of the following examples or comparative examples, in the same manner as the method described in "Average particle diameter of resin particles in raw film". However, about this polarizing film, it observed from the cutting plane parallel to the extending | stretching direction.
Length A (long-axis length) of resin particles in a polarizing film in the stretching direction and length B (single-axis in a direction perpendicular to the stretching direction) by the following method using the TEM image obtained by the above method Axis length was measured. First, a TEM image is opened using an image analysis software "Image-Pro Plus 7.0J" (manufactured by Media Cybernetics), then converted to an 8-bit scale by "conversion" and flattened by "filter processing" I did the processing. Next, set the contrast value to 80 in "Contrast enhancement", select "Elliptical major axis / minor axis ratio" on the measurement item setting page in "Count / Size", and then automatically extract bright colored objects The resin particles are extracted mechanically, and the length A (length in the stretching direction) of the resin particles in the polarizing film in the major axis direction and the length B in the minor axis direction (the direction perpendicular to the stretching direction) The lengths) and their length ratios (A / B) were calculated. The particle size smaller than 1/10 of the maximum diameter in the TEM image was removed as noise. In addition, when the color of the resin particle is darker than that of PVA in the TEM image, each length of the resin particle in the polarizing film was calculated by automatically extracting a dark-colored object.

[Tear resistance evaluation: piercing property]
The polarizing film obtained in each of the following Examples or Comparative Examples was allowed to stand at a temperature of 23 ° C. and a relative humidity of 20% for 24 hours. After this, a piece of film of 40 mm × 20 mm in the width direction was cut out from the polarizing film in the length direction (stretching direction of the polarizing film), and 4 sides were fixed by sandwiching with a metal frame. Thereafter, the polarizing film is attached to a tensile test apparatus ("Autograph AGS-H" manufactured by Shimadzu Corporation), and the stretching direction of the polarizing film and the long side of a minus driver (contact area with polarizing film: 1 mm x 5 mm) A flathead screwdriver was attached to the upper chuck so that was parallel, and the flathead screwdriver was pressed against the polarizing film at a speed of 1 mm / min. Then, the maximum load when the minus driver penetrated the polarizing film was taken as the piercing strength, and the piercing property was evaluated based on the following criteria. In addition, since A and B can be used without a problem in practical use, it was determined to be good, and C was determined to be defective.
A: piercing strength 5 N or more B: piercing strength 3 N or more and less than 5 N C: piercing strength less than 3 N

[Evaluation of tear resistance: cutting ability]
The polarizing film obtained in each of the following examples or comparative examples was allowed to stand at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. After this, this polarizing film was cut using a cutter knife at a speed of 600 mm / min in the direction perpendicular to the stretching direction, and the cut cross section was observed with a stereomicroscope. The angle between the blade of the cutter knife and the stretching direction of the polarizing film was 45 °. Then, the number of cracks present per cm of the cut cross section of the polarizing film was measured, and the cutting property was evaluated based on the following criteria. In addition, since A and B can be used without a problem in practical use, it was determined to be good, and C was determined to be defective.
A: No crack B: 1 to 4 pieces / cm
C: 5 or more / cm

[Evaluation of tear resistance: punching property]
The polarizing film obtained in each of the following examples or comparative examples was allowed to stand at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. After this, the polarizing film is placed on a cutting mat (Kokuyo "mar 40 N"), the polarizing film is punched out using a circular punch 10 mm in diameter (belt punch "TPO-100" from Three Etch Co.), and circular The punched end face of the hollowed out polarizing film was observed with a stereomicroscope. Then, the number of cracks present in the polarizing film was measured, and the punching property was evaluated based on the following criteria. In addition, since A and B can be used without a problem in practical use, it was determined to be good, and C was determined to be defective.
A: No crack B: 1 to 4 per week C: 5 or more per week

[Polarization performance of polarizing film]
(Measurement of transmittance Ts)
From the center of the polarizing film, two samples of 2 cm in length were taken in the stretching direction of the polarizing film. For one sample, using a spectrophotometer with integrating sphere (“V7100” of JASCO Corporation), according to JIS Z 8722 (Method of measuring object color), C light source, visible light region of 2 ° visual field Visibility correction was performed, and the light transmittance when tilted + 45 ° with respect to the length direction and the light transmittance when tilted −45 ° was measured, and their average value Ts1 (%) was determined. . The same was applied to the other sample, and the light transmittance when tilted by + 45 ° and the light transmittance when tilted by −45 ° was measured, and their average value Ts2 (%) was determined. Ts1 and Ts2 were averaged using the following calculation formula (1) to obtain the transmittance Ts (%) of the polarizing film.
Ts = (Ts1 + Ts2) / 2 (1)
In the following examples or comparative examples, the staining processing conditions were adjusted to prepare a sample so that the transmittance Ts was 44.0%, and the following measurement of the degree of polarization V was performed.

(Measurement of polarization degree V)
With regard to the two samples used in the measurement of the transmittance Ts, the light transmittance T _⊥ (%) in the case of overlapping so that the stretching directions are orthogonal to each other and the stacking so that the stretching directions become parallel The light transmittance T _// (%) was measured. This measurement conforms to JIS Z 8722 (Method for measuring object color) using an integrating sphere-equipped spectrophotometer (“V7100” from JASCO Corporation), and a C light source, a visible light region of 2 ° visual field. The correction was carried out. The degree of polarization V (%) was determined from the measured T _// (%) and T _⊥ (%) using the following formula (2).
_{_{V = {(T // -T ⊥}} ) / (T // + T ⊥)} 1/2 × 100 ··· (2)

Production Example 1 Production of Resin Particle A In a dried 0.5 L pressure polymerization vessel, 0.20 g of potassium peroxodisulfate as a polymerization initiator, a reactive emulsifier “JS-20” manufactured by Sanyo Chemical Industries, Ltd. 36. 0 g and 300 g of ion exchange water were charged. This was deoxygenated by bubbling nitrogen gas for 30 minutes to obtain a starting emulsion. Next, the temperature of the starting emulsion was raised to 60 ° C. with stirring, and then 45.0 g of n-butyl acrylate, 0.45 g of allyl methacrylate, and 0.23 g of trimethylolpropane trimethacrylate were separately added. The mixture was added continuously at a rate of 1.0 ml / min.
Thereafter, when it is confirmed that the conversion of each monomer calculated by the method to be described later exceeds 95% by mass, 5.6 g of the decyclopentadilated dicyclopentanyl methacrylate is 1.0 ml / min. Added continuously at speed. After the addition, it is confirmed that the monomer conversion rate calculated by the above method exceeds 95% by mass, the polymerization tank is heated to 100 ° C. for polymerization, and the residual monomer is detected by gas chromatography The polymerization was carried out until the limit was reached. It cooled to 25 degreeC after superposition | polymerization, and obtained the emulsion solution (resin content 17 mass%) containing the resin particle A. The polymerization time required for cooling from the polymerization start to 25 ° C. was 8 hours. In addition, the obtained resin particles are core-shell type particles in which the core is n-butyl polyacrylate and the shell is dicyclopentanyl polymethacrylate.
(Monomer conversion rate)
The coated polymer particles or the weight are dropped by dropping the emulsion (0.100 g) sampled every hour from the polymerization start into a solution of tetrahydrofuran (10.0 g, 0.1 mass% 4-tert-butyl catechol added). A solution of coalesced particles in tetrahydrofuran was prepared. This solution was analyzed by gas chromatography (Shimadzu GC-14A, column UAWAX-20EX-1.0F), and the monomer conversion rate was determined from the detected amount of monomer and the addition amount of monomer at the time of initiation of the emulsion polymerization. (%) Was calculated.

Production Example 2 Production of Resin Particle B In a twin-screw extruder (manufactured by Parker Corporation), from the hopper, (meth) acrylic block copolymer, methyl methacrylate-n-butyl acrylate-methyl methacrylate triblock A copolymer (Klarity (registered trademark) LA 2140, manufactured by Kuraray Co., Ltd., 24 mass% of methyl methacrylate unit) is supplied at 0.66 kg / hour, and 72 kg / hour of N-methylcyclohexylamine ((meth 2.) An amount of 40 moles per 100 moles of methyl methacrylate unit in the acrylic polymer was supplied, and melt kneading was performed at a cylinder temperature of 220 ° C. and a screw rotation speed of 100 rpm. Thus, a methacrylic anhydride-n-butyl acrylate copolymer 1 was obtained. This was pulverized to 20 mm ³ or less and immersed in hot water at 80 ° C. for 24 hours to convert the acid anhydride to a carboxy group to obtain methacrylic acid-acrylic acid n-butyl-methacrylic acid triblock copolymer. . Thereafter, the copolymer was taken out by filtration, dried and dissolved in methanol so as to have a solid content concentration of 10% by mass. Thereafter, water of the same mass as methanol is added dropwise to obtain a dispersion solution, and the resulting solution is treated under reduced pressure at 60 ° C. to distill off methanol, and methacrylic acid-acrylic acid n-butyl-methacrylic acid triacetate An emulsion solution (resin content: 10% by mass) containing the resin particles B of the block copolymer was obtained.

Hereinafter, commercially available resin particles used in Examples and Comparative Examples are shown.
Resin particle C: "AE986B" from E-tech (particles made of acrylic resin)
Resin particle D: "UC-143" (made of acrylic resin) made by Siden Chemical Co., Ltd.
Resin particle E: "QE-1042" from Starlight PMC
Resin particle F: "KE-1062" from Starlight PMC
Resin particles G: E-Tech's "N 827 (A) -1" (particles made of acrylic resin)

Example 1
(Production of raw film)
PVA (saponified product of homopolymer of vinyl acetate, polymerization degree is 2,400, saponification degree is 99.95 mol%), glycerin (12 parts by mass with respect to 100 parts by mass of PVA) and surfactant (0.03 mass parts with respect to 100 mass parts of PVA) and water were mixed, and the PVA aqueous solution was obtained by melt | dissolving at 90 degreeC for 4 hours. Thereafter, 10 parts by mass of the resin particles A were added to 100 parts by mass of the PVA aqueous solution, and the mixture was stirred at 85 ° C. for 30 minutes. Thereafter, the PVA aqueous solution was kept at 85 ° C. for 16 hours for degassing of the PVA aqueous solution.
The PVA aqueous solution was dried on a metal roll at 80 ° C. to obtain a PVA film. Then, heat processing were performed for 10 minutes with a 110 degreeC dryer, and the original film of Example 1 with an average thickness of 30 micrometers was obtained.

(2) Production of Polarized Film From the raw film obtained in the above (1), a rectangular test piece of 9 cm in length direction x 5 cm in width direction was collected. The two ends of the test piece in the lengthwise direction are fixed to a drawing jig so that the size of the drawn part is 5cm in the length direction x 5cm in the width direction, and while immersed in water at a temperature of 30 ° C for 38 seconds It was uniaxially stretched (first-stage stretching) in the lengthwise direction to 2.2 times its original length at a drawing speed of 1 / min. Then, while immersed in an iodine / potassium iodide aqueous solution at a temperature of 30 ° C. containing iodine at 0.03% by mass and potassium iodide at a concentration of 3% by mass for 60 seconds, the original film was drawn at a stretching rate of 24 cm / min. Uniaxial stretching (second stage stretching) in the lengthwise direction up to 3.3 times the length of. Then, while immersing in a boric acid / potassium iodide aqueous solution at a temperature of 30 ° C. containing about 3% by weight of boric acid and 3% by weight of potassium iodide, at a drawing speed of 24 cm / min. The film was uniaxially stretched (third-stage stretching) in the lengthwise direction up to 3.6 times the original length. Subsequently, while immersing in a boric acid / potassium iodide aqueous solution at a temperature of 58 ° C. containing 4% by mass of boric acid and about 5% by mass of potassium iodide, the critical draw ratio at a drawing speed of 24 cm / min. Four films were attached, and the film was uniaxially stretched (four-step stretching) in the length direction until the draw ratio at which two sheets were cut was taken as the limit draw ratio). Then, the fixing treatment was performed by immersion for 10 seconds in an aqueous potassium iodide solution containing 1.5% by mass of boric acid and 3% by mass of potassium iodide. Then, it was dried for 4 minutes with a dryer at 60 ° C. to obtain a polarizing film (average thickness 13 μm) of Example 1 which is a stretched optical film.

[Examples 2 to 6, Comparative Examples 1 to 4]
Each original film and polarizing film of Examples 2 to 6 and Comparative Examples 1 to 4 in the same manner as Example 1 except that the type and amount of the resin particles added to the PVA aqueous solution are as shown in Table 1. I got In Comparative Example 1, no resin particles were added.

Comparative Example 5
A raw film and a polarizing film of Comparative Example 5 were obtained in the same manner as in Comparative Example 1 except that the average thickness of the raw film was 60 μm. The average thickness of the obtained polarizing film was 26 μm.

[Evaluation]
The glass transition temperature of the resin particles, the degree of swelling of the raw film, and the average particle size of the resin particles in the raw film were measured using the obtained raw films by the method described above. Further, using the obtained polarizing film, the length A (length in the stretching direction), the length B (length in the direction perpendicular to the stretching direction), and the length of the resin particles in the polarizing film The measurement of the power ratio (A / B) and the evaluation of the piercing property, cutting property, punching property, and polarization performance were performed. The results are shown in Table 1.

As shown in Table 1, the polarizing films obtained in Examples 1 to 6 have the evaluations of piercing property, cutting property and punching property of A or B, and although thin, they are not easily torn, and they are easy to handle and produce. It turns out that it is excellent in the nature. In addition, it is understood that Examples 1 to 6 can be carried out without complicated steps, and the polarizing film can be relatively easily manufactured. Furthermore, in the polarizing films of Examples 1 to 4, it is understood that the polarization performance is particularly good.

On the other hand, it is understood that the polarizing films obtained in Comparative Examples 1 to 4 have low evaluations of piercing property, cutting property and punching property and are easy to tear. Moreover, in the comparative example 5, although the obtained polarizing film had tear resistance, the thin polarizing film was not obtained.

1: Stretched optical film 2: Resin particles X: Stretching direction A: Stretching direction length B: Length in the direction perpendicular to the stretching direction

The raw film of the present invention can be suitably used as a material such as a polarizing film which is a constituent material of LCD. Moreover, the manufacturing method of the extending | stretching optical film of this invention, and an extending | stretching optical film can be used suitably as a polarizing film or its manufacturing method.

Claims

Average thickness is 45 μm or less,
Containing a vinyl alcohol polymer which is a main component, and resin particles having a glass transition temperature of 30 ° C. or less,
The raw film film for stretched optical film manufacture whose content of the said resin particle with respect to 100 mass parts of said vinyl alcohol polymers is 1 mass part or more and 50 mass parts or less.
The raw film film according to claim 1, wherein an average particle diameter of the resin particles is 1 nm or more and 300 nm or less.
A process for producing a stretched optical film, comprising the step of stretching the raw film according to claim 1 or 2.
The average thickness is 20 μm or less,
Containing a vinyl alcohol polymer which is a main component, and resin particles having a glass transition temperature of 30 ° C. or less,
The stretched optical film, wherein the content of the resin particle is 1 part by mass to 50 parts by mass with respect to 100 parts by mass of the vinyl alcohol polymer.
5. The stretching optical system according to claim 4, wherein a length of the resin particle in the stretching direction observed in a transmission electron microscope image in a cut surface parallel to the stretching direction is longer than a length in a direction perpendicular to the stretching direction. the film.