TW201906915A - Blank film, method for producing stretched optical film, and stretched optical film - Google Patents

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 [mu]m or less, and containing a vinyl alcohol-based polymer as a main component, and resin particles with a glass transition temperature of 30 DEG 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

   Raw material film, manufacturing method of stretched optical film, and stretched optical film   

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

The polarizing plate with the function of transmitting and shielding light, and the liquid crystal that changes the polarization state of light are the basic components of a liquid crystal display (LCD). Many polarizing plates have a structure in which a protective film such as a cellulose triacetate (TAC) film is bonded to the surface of a polarizing film. As a polarizing film constituting a polarizing plate, a vinyl alcohol-based polymer film (hereinafter, "vinyl alcohol-based polymer" may be abbreviated as "PVA") is uniaxially stretched to attract a oriented stretched film. Those who have a dichroic pigment such as an iodine-based pigment (I ₃ ⁻ , I ₅ ^−, etc.) or a dichroic organic dye have become the mainstream. Such a polarizing film is obtained by uniaxially stretching a PVA film containing a dichroic dye in advance, or adsorbing a dichroic dye while uniaxially stretching the PVA film, or uniaxially stretching the PVA film. It is manufactured by adsorbing a dichroic dye and the like.

LCDs are gradually used in small devices such as computers and watches, smartphones, notebook computers, LCD monitors, LCD color projectors, LCD TVs, car navigation systems, mobile phones, and indoor and outdoor measurement equipment. In range. In recent years, especially with the progress of portable applications such as small notebook computers and mobile phones, the demand for thinning of polarizing plates has become stronger. In addition, because of the wide range of usage sites due to the mobilization, durability improvement is also required at the same time.

One of the methods for reducing the thickness of a polarizing plate includes reducing the thickness of a polarizing film and a protective film. For this reason, it is necessary to reduce the thickness of the raw material film (PVA film) which is a raw material of a polarizing film. However, the thin raw material film is easily torn in the stretching direction in a drying step when manufacturing a polarizing film, a step of bonding the obtained polarizing film and a protective film, and the like. In addition, when the polarizing film is thin, when performing operations such as punching or cutting the polarizing film or polarizing plate, the polarizing film is likely to tear in the stretching direction, or fine edges are easily generated on the end face of the polarizing film. crack. Therefore, when a thin material film is used, the productivity or yield of the polarizing plate or LCD is reduced, which tends to cause high costs. In this way, the productivity and yield of the thinned thin film or polarizing film are reduced, which tends to cause high costs. In addition, it is also expected to reduce the thickness of stretched optical films other than polarizing films such as retardation films, but there are also disadvantages such that tearing easily occurs.

As a technique for producing a thin polarizing film with good yield, a method of forming a thin PVA film on a plastic film by a coating method, and stretching and drying the laminated body is known (see Patent Documents 1 and 2). In addition, in order to improve the operability such as the punchability of the obtained polarizing film, it is also proposed that after the polarizing film is manufactured under specific conditions, the polarizing film has at least a single-area layer of urethane resin layer polarized light. Plate (see Patent Document 3); and a composition capable of forming a cured resin layer having excellent flexibility (see Patent Document 4).

Prior art literature Patent literature

Patent Document 1 Japanese Patent No. 4804588

Patent Document 2 Japanese Patent No. 4815544

Patent Document 3 Japanese Patent No. 3315914

Patent Document 4 Japanese Patent Application Publication No. 2014-115538

However, the methods described in Patent Documents 1 and 2 have the following disadvantages.

(1) The coating operation or subsequent drying operations are complicated.

(2) The heat treatment for the insolubilization treatment of the PVA film needs to be performed in the state of the laminate, so the plastic film used is limited to those that can be stretched after the heat treatment, and the cost becomes high.

(3) In a laminated body formed by forming a PVA film on a plastic film by a coating method, the bonding strength between the plastic film and the PVA film is high. Therefore, if such a laminated body with high adhesive strength is stretched, it will prevent moderate neck-in of the PVA film, and it will be difficult to obtain a polarizing film with excellent polarizing performance.

In addition, the methods described in Patent Documents 3 and 4 also cause disadvantages such as an increase in cost and a decrease in yield due to an increase in the number of steps in the production of a polarizing plate.

The present invention is based on the above-mentioned things, and its object is to provide: a blank film that can obtain a thin and easy-to-tear stretch optical film relatively easily; a thin and easy-to-tear stretch optical film; and can compare The manufacturing method of the stretched optical film which can obtain such a stretched optical film easily.

The present inventors repeatedly conducted an intensive review in order to achieve the above-mentioned object, and found that even when the thickness of the film is reduced, it is possible to add resin particles having a low glass transition temperature to the film. A non-tearing stretched optical film was obtained, and based on these knowledge and insights, the review was further repeated to complete the present invention.

That is, the present invention completed to solve the above-mentioned problems is as follows.

[1] A raw material film for the production of a stretched optical film, having an average thickness of 45 μm or less, a vinyl alcohol-based polymer containing main components, and resin particles having a glass transition temperature of 30 ° C. or lower, compared to the vinyl alcohol-based The content of the resin particles in 100 parts by mass of the polymer is 1 part by mass or more and 50 parts by mass or less.

[2] The blank film according to [1], wherein the average particle diameter of the resin particles is 1 nm to 300 nm.

[3] A method for producing a stretched optical film, comprising the step of stretching a base material film such as [1] or [2].

[4] A stretched optical film having an average thickness of 20 μm or less, a vinyl alcohol polymer containing main components, and resin particles having a glass transition temperature of 30 ° C. or less, based on 100 parts by mass of the vinyl alcohol polymer. The content of the resin particles is 1 part by mass or more and 50 parts by mass or less.

[5] The stretched optical film according to [4], wherein the length of the stretched direction of the resin particles observed in a transmission electron microscope image in a cut surface parallel to the stretched direction is a ratio that is the same as that of the stretched The length is long in the vertical direction.

According to the present invention, it is possible to provide: a blank film capable of relatively easily obtaining a thin and easily tearable stretched optical film; a thin and easily tearable optical film; and relatively easily obtaining such a stretch Manufacturing method of stretched optical film of optical film.

1‧‧‧ stretched optical film

2‧‧‧ resin particles

X‧‧‧ Stretching direction

A‧‧‧length in the stretching direction

B‧‧‧ Length in a direction perpendicular to the stretching direction

FIG. 1 is a schematic view showing a cut surface parallel to a stretching direction of a stretched optical film according to an embodiment of the present invention.

A form for implementing the invention     <Blank film>    

A raw material film according to an embodiment of the present invention is a film for producing a stretched optical film. That is, the raw material film is a film that is a material of a stretched optical film such as a polarizing film or a retardation film. By stretching this raw material film, a stretched optical film can be obtained.

The blank film may be a single-layer film or a multilayer film (laminate). Examples of the form of the multilayer film include a film having a PVA layer formed on a thermoplastic resin film by a coating method or the like. From the viewpoints that the effects of the present invention are more significantly exhibited, the complexity of lamination (coating, etc.) operations, the cost of a thermoplastic resin film, and the like, the base material film is preferably a single-layer film.

    (The average thickness)    

The upper limit of the average thickness of the blank film is 45 μm, preferably 40 μm, more preferably 35 μm, and even more preferably 30 μm. When the average thickness of the raw material film is equal to or less than the above upper limit, a thin stretched optical film can be obtained. On the other hand, as the lower limit of this average thickness, 1 μm is preferred, 3 μm is more preferred, 10 μm is even more preferred, and 20 μm is even more preferred. When the average thickness of the raw material film is at least the above lower limit, the tear resistance of the obtained stretched optical film can be further improved.

    (PVA)    

This material film contains PVA (vinyl alcohol-based polymer) as a main component. In addition, the main component refers to a component having the largest content on a mass basis (the same applies hereinafter). PVA is a polymer having a vinyl alcohol unit (-CH ₂ -CH (OH)-) as a structural unit. The PVA may have a vinyl ester unit and other units in addition to the vinyl alcohol unit.

As the PVA, vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, trimethyl vinyl acetate, vinyl kochate, vinyl laurate, vinyl stearate can be used. Polyvinyl ester obtained by polymerizing one or two or more vinyl esters such as vinyl benzoate and isopropenyl acetate is obtained by saponification. Among the above-mentioned vinyl esters, from the viewpoint of ease of production, availability, and cost of PVA, a compound having a vinyloxycarbonyl group (H ₂ C = CH-O-CO-) in the molecule is more preferable, and more Preferred is vinyl acetate.

The polyvinyl ester is preferably obtained by using only one or more vinyl esters as a monomer, and more preferably obtained by using only one vinyl ester as a monomer. Within the scope of the effect, it may be a copolymer of one or more vinyl esters and other monomers copolymerizable therewith.

Examples of other monomers copolymerizable with the vinyl ester include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutylene; (meth) acrylic acid or a salt thereof; Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate (Meth) acrylates such as esters, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, etc. ; (Meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (Meth) acrylamidoamine, (meth) acrylamidopropylsulfonic acid or a salt thereof, (meth) acrylamidopropyldimethylamine or a salt thereof, N-methylol (methyl) (Meth) acrylamide derivatives such as acrylamide or derivatives thereof; N-vinylfluorenamines such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone; Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl ethyl Vinyl ethers such as methyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tertiary butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; (meth) acrylonitrile Ethylene cyanide; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; allyl compounds such as allyl acetate, chloropropylene; maleic acid, or its salts, esters or anhydrides; clothing Conic acid, or its salt, ester, or anhydride; vinyl silyl compounds such as vinyltrimethoxysilane; unsaturated sulfonic acid or its salt.

The polyvinyl ester can have one or two or more structural units derived from the monomer.

Based on the molar numbers of all the structural units constituting the polyvinyl ester, the upper limit of the proportion of the structural units derived from other monomers in the polyvinyl ester is preferably 15 mol%, and more preferably 10 mol%. , More preferably 5 mol%, even more preferably 1 mol%.

As the PVA, an ungraft copolymer can be preferably used. However, as long as the effect of the present invention is not significantly impaired, PVA may be modified by one or two or more types of graft copolymerizable monomers. The graft copolymerization can be performed on at least one of a polyvinyl ester and a PVA obtained by saponifying it. Examples of the above-mentioned graft copolymerizable monomer include an unsaturated carboxylic acid or a derivative thereof; an unsaturated sulfonic acid or a derivative thereof; an α-olefin having 2 to 30 carbon atoms; and the like. The proportion of the structural units derived from the graft copolymerizable monomer in the polyvinyl ester or PVA is preferably 5 mol% or less based on the molar number of all the structural units constituting the polyvinyl ester or PVA.

The PVA may be partially crosslinked or uncrosslinked. The PVA may have a part of its hydroxyl groups reacted with aldehyde compounds such as acetaldehyde and butyraldehyde to form an acetal structure, or may not react with these compounds without forming an acetal structure.

The lower limit of the polymerization degree of the PVA is preferably 1,000, more preferably 1,500, and even more preferably 2,000. When the degree of polymerization of PVA is at least the above lower limit, the optical properties of the obtained stretched optical film can be improved. On the other hand, the upper limit of the polymerization degree is preferably 10,000, more preferably 8,000, and even more preferably 5,000. By setting the polymerization degree of PVA to be equal to or less than the above-mentioned upper limit, it is possible to suppress an increase in the manufacturing cost of PVA and the occurrence of defects during film formation. The degree of polymerization of PVA means an average degree of polymerization measured in accordance with the description of JIS K6726-1994.

The lower limit of the degree of saponification of PVA is preferably 95 mol%, more preferably 98 mol%, and even more preferably 99 mol% because the moisture and heat resistance of the obtained stretched optical film becomes good. It is preferably 99.5 mol%. On the other hand, the upper limit of the degree of saponification may be substantially 100 mol%. In addition, the degree of saponification of PVA refers to the ratio of the molar number of vinyl alcohol units to the total molar number of vinyl alcohol units in a structural unit (typically a vinyl ester unit) that can be converted into a vinyl alcohol unit by saponification. (Mole%). The degree of saponification can be measured in accordance with the description of JIS K6726-1994.

The lower limit of the content of PVA in the green film is preferably 60% by mass, more preferably 70% by mass, and even more preferably 75% by mass. By setting the content of PVA to be at least the above lower limit, the obtained stretched optical film exhibits optical characteristics such as polarization performance more favorably. On the other hand, the upper limit of this content is preferably 95% by mass, more preferably 90% by mass, and even more preferably 85% by mass. By setting the content of PVA to be equal to or less than the above-mentioned upper limit, the obtained stretched optical film becomes more difficult to tear.

    (Resin particles)    

This raw material film contains resin particles having a glass transition temperature of 30 ° C or lower. By containing such a resin particle, this raw material film can obtain a stretched optical film which is thin and not easily torn. The reason for this effect is not clear, but as a result of observing the cross-section of the tear portion of the stretched optical film produced from the base film, the cross-section becomes rough, so it is presumed that the resin particles dispersed in the film suppress the tear Spread without becoming easy to tear. In particular, when the glass transition temperature of the resin particles is 30 ° C. or lower, that is, below the general stretching treatment temperature when a stretched optical film is manufactured using a blank film, the resin particles can also be lowered during the stretching step. Deformation in the stretching direction. Thereby, PVA can be fully aligned while maintaining the adhesion between the PVA and the resin particles. Therefore, it is estimated that the stretched optical film obtained from the raw material film is less likely to tear, and by adjusting the content of the resin particles and the average particle diameter, optical characteristics such as polarization performance can also be improved.

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 of substantially only resin.

The upper limit of the glass transition temperature (Tg) of the resin particles (the Tg of the polymer of the main component of the resin particles) is 30 ° C, preferably 25 ° C, more preferably 20 ° C, still more preferably 15 ° C, and even more preferably 10 ° C. With this, the glass transition temperature is equal to or lower than the above upper limit, and a stretched optical film that is not easily torn can be obtained. In addition, by setting the glass transition temperature to be equal to or lower than the above-mentioned upper limit and adjusting the content of the resin particles and the average particle diameter, optical characteristics such as polarization performance can also be improved.

The lower limit of the glass transition temperature of the resin particles is not particularly limited. For example, it is preferably -100 ° C, more preferably -80 ° C, and even more preferably -60 ° C. By setting the glass transition temperature to the above lower limit or more, the aggregation of the resin particles at the time of heating in the film forming step for producing a thin film is suppressed, and the obtained green film and the stretched optical film can be suppressed. Cloudy. Moreover, the optical characteristics of the obtained stretched optical film can be improved.

The glass transition temperature of the resin particles is a measurement value using DSC (Differential Scanning Calorimetry) performed on the resin film obtained by forming the resin particles with the film. When the resin particles include a plurality of different types of resins, the glass transition temperature of the resin having the lowest glass transition temperature is set as the glass transition temperature of the resin particles.

The lower limit of the content of the resin particles in the material 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 setting the content of the resin particles to be at least the above-mentioned lower limit, it is possible to make the obtained stretched optical film difficult to tear, and improve workability and the like. On the other hand, the upper limit of this content is 50 parts by mass, preferably 30 parts by mass, more preferably 20 parts by mass, and even more preferably 15 parts by mass. By setting the content of the resin particles to be equal to or less than the above-mentioned upper limit, it is possible to improve the light transmittance of the obtained stretched optical film, and to improve optical characteristics such as polarization performance.

As the lower limit of the average particle diameter of the resin particles in the blank film, it is preferably 1 nm, more preferably 5 nm, still more preferably 10 nm, even more preferably 20 nm, and even more preferably 30 nm. By setting the average particle diameter of the resin particles to be equal to or more than the above lower limit, the obtained stretched optical film is less likely to tear, and operability and the like are improved. On the other hand, the upper limit of the average particle diameter may be, for example, 500 nm, preferably 300 nm, more preferably 200 nm, and even more preferably 100 nm. By setting the average particle diameter of the resin particles to be equal to or less than the above-mentioned upper limit, particularly 300 nm or less, it is possible to improve the light transmittance of the obtained stretched optical film, and to improve optical characteristics such as polarization performance.

The average particle diameter of the resin particles in the raw material film is a measured value based on a TEM (transmission electron microscope) image of the film cut surface. The presence or absence and the dispersed state of the resin particles can be observed in the form of a sea-island structure by measuring the TEM of the cut surface that is perpendicular to the in-plane direction of the material film. The island structure refers to a structure in which a discontinuous portion (island portion) is mixed in a continuous portion (sea portion) in a mixture containing two kinds of physical properties. Due to the different dyeability of resin particles and PVA, the color of the part that looks continuous becomes darker and the color of the part that looks discontinuous becomes lighter, or the color of the part that looks continuous The color becomes darker. In this TEM image, resin particles are observed as island portions. For the TEM image of the film cut surface, resin particles were mechanically selected using image analysis software, and the average value of the diameters of these resin particles was calculated. The calculated value is taken as the average particle diameter of the resin particles. A specific method for measuring the average particle diameter of the resin particles is the method described in the examples.

The resin particles contain a polymer. The polymer is not particularly limited as long as the glass transition temperature is 30 ° C. or lower, and examples thereof include polyolefins, polyurethanes, acrylic resins, and the like, and acrylic resins are preferred. Acrylic resin means a polymer containing a structural unit derived from a (meth) acrylate.

Examples of the (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and hexane (meth) acrylate. (Meth) acrylates such as dodecyl (meth) acrylate, stearyl (meth) acrylate, etc .; dicyclopentyl (meth) acrylate, isoamyl (meth) acrylate, etc. have (Meth) acrylic acid esters of alicyclic group; aryl (meth) acrylates such as phenyl (meth) acrylate and the like.

Among the acrylic resins, the resin particles preferably include an acrylic resin including a structural unit (alkyl (meth) acrylate unit) derived from an alkyl (meth) acrylate. The lower limit of the number of carbon atoms of the alkyl group possessed by the alkyl (meth) acrylate is 1, preferably 2, more preferably 3, and even more preferably 4. On the other hand, the upper limit of the carbon number of this alkyl group is, for example, 10, preferably 8, more preferably 6, and even more preferably 4. Moreover, an alkyl acrylate unit is also preferable. That is, among the alkyl (meth) acrylate units, a butyl acrylate unit is most preferable. The resin particle-based glass using an acrylic resin containing such an (meth) acrylic acid alkylate unit has a low glass transition point and can further improve the difficulty of tearing and optical characteristics. The reason is not clear, but it is estimated that the flexibility of the resin particles is improved, and the resin particles are liable to be deformed in the stretching direction during the stretching treatment.

Further, as the acrylic resin, an acrylic resin containing (meth) acrylic units (-CH ₂ -CHCOOH- and -CH ₂ -C (CH ₃ ) COOH-) can 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, a block copolymer of a (meth) acrylic unit and an alkyl (meth) acrylate unit is preferred. When the acrylic resin is a block copolymer, it may be any of a diblock copolymer and a triblock copolymer.

As the resin particles, particles made of a single polymer may be used, or particles with a so-called core-shell structure in which materials on the inside and outside are different may be used. When using a core-shell type particle | grain, it is preferable that the material of a core contains the acrylic resin containing a (meth) acrylic-acid unit. When a core-shell type particle is used, the material of the shell is preferably an acrylic resin containing a (meth) acrylate unit containing an alicyclic group or a (meth) acrylic unit.

The resin particles can be produced by a known method. As the resin particles, a commercially available product can be used. Moreover, the method of making this raw material film contain a resin particle is also not specifically limited. For example, resin particles may be added to a PVA chip, or resin particles may be added to a film-forming dope used during film formation.

    (Plasticizer)    

The blank film can further include a plasticizer. By including a plasticizer, this raw material film can improve workability, stretchability, and the like. Examples of preferred plasticizers include polyhydric alcohols. Specific examples include ethylene glycol, glycerol, propylene glycol, diethylene glycol, diglycerol, triethylene glycol, tetraethylene glycol, and trihydroxy alcohol. Methylpropane and the like. These plasticizers can be used alone or in combination of two or more. Among these, glycerin is preferred from the viewpoint of the effect of improving stretchability.

The lower limit of the content of the plasticizer in the blank film is preferably 2 parts by mass, more preferably 3 parts by mass, still more preferably 4 parts by mass, and even more preferably 6 parts by mass relative to 100 parts by mass of PVA. Serving. When the content of the plasticizer is set to the above lower limit or higher, the stretchability is further improved. On the other hand, the upper limit of this content is preferably 20 parts by mass, more preferably 17 parts by mass, and even more preferably 14 parts by mass. By setting the content of the plasticizer to be equal to or less than the above-mentioned upper limit, it is possible to prevent the raw material film from becoming too soft or the plasticizer from oozing out of the surface, thereby reducing the workability.

    (Other additives, etc.)    

In addition to PVA, resin particles, and plasticizers, the raw material film can be further suitably blended according to needs: fillers, processing stabilizers such as copper compounds, weather resistance stabilizers, colorants, ultraviolet absorbers, Light stabilizers, antioxidants, antistatic agents, flame retardants, other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, release agents, release agents, reinforcing agents, cross-linking agents , Antifungal agents, preservatives, crystallization rate delaying agents and other additives.

However, as the upper limit of the content of the additives other than PVA, resin particles, and plasticizer in the material film, the upper limit is preferably 1% by mass, and even more preferably 0.2% by mass. When the content of other additives exceeds the above-mentioned upper limit, the tear strength or optical characteristics of the obtained stretched optical film may be affected.

As the lower limit of the swelling degree of the raw material film, it is preferably 160%, more preferably 170%, and still more preferably 180%. When the degree of swelling is equal to or more than the above-mentioned lower limit, excessive crystallization can be suppressed, and it is possible to stably stretch to a high magnification. On the other hand, as the upper limit of the swelling degree, 240% is preferred, 230% is more preferred, and 220% is even more preferred. When the degree of swelling is equal to or less than the above upper limit, dissolution during stretching is suppressed, and stretching can be performed even at a higher temperature. In addition, the degree of swelling of the raw material film means: the mass when the raw material film is immersed in distilled water at 30 ° C for 15 minutes divided by the raw material which is dipped in distilled water at 30 ° C for 15 minutes, and dried at 105 ° C for 16 hours. The percentage of the value obtained by the quality of the film.

The shape of the blank film is not particularly limited, and it is preferably a long film because it can continuously produce a stretched optical film with good productivity. There is no particular limitation on the length of the long blank film, and it can be appropriately set according to the application of the stretched optical film to be manufactured, and for example, it can be set in a range of 5 m to 20,000 m. The width of the blank film is not particularly limited. For example, the lower limit can be set to 50 cm. In recent years, a wide-width polarizing film has been required. The lower limit is preferably 1 m, more preferably 2 m, and even more preferably 4 m. The upper limit of the width of the material film is not particularly limited, and can be set to 7 m, for example. When the width is too wide, when a stretched optical film is manufactured with a practical device, it tends to become difficult to stretch uniformly.

This raw material film can relatively easily produce a stretched optical film that is not easily torn during manufacture and operation. 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 material film can be easily used to produce a polarizing film having good polarizing performance, and is therefore particularly preferably used as a raw material film for producing a polarizing film.

    (Manufacturing method of blank film)    

The manufacturing method of the raw material film of the present invention is not particularly limited, and a manufacturing method in which the thickness and width of the raw material film after film formation becomes more uniform can be preferably used. For example, it is possible to use one or two or more of the above-mentioned PVA and resin particles in which a constituent material film is dissolved in a liquid medium, and further plasticizers, other additives, and surfactants to be described later. The film-forming stock solution is obtained by film-forming. Moreover, according to need, it can also manufacture using the film-forming stock solution in which PVA was melted. In the film-forming dope, the resin particles are preferably uniformly mixed. When the film-forming dope contains at least one of a plasticizer, other additives, and a surfactant, it is preferred that the components are uniformly mixed.

Examples of the liquid medium include water, dimethylmethylene, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerol, propylene glycol, and diamine. Ethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and the like. These liquid media can be used in one kind or two or more kinds. Among these, water is preferable from the viewpoint of small environmental burden and recyclability.

The volatile content of the film-forming solution (the content of the volatile components in the liquid-forming solution that is removed by evaporation or evaporation during film formation) 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 even more preferably 60% by mass. Since the volatile content of the film-forming dope is above the lower limit described above, the viscosity of the film-forming dope will not become too high, and the filtering and defoaming system during the preparation of the film-forming dope will proceed smoothly. Manufacturing becomes easy. On the other hand, as the upper limit of the volatile content, 95% by mass is preferred, 90% by mass is more preferred, and 85% by mass is even more preferred. Since the volatile content of the film-forming dope is equal to or less than the above-mentioned upper limit, the concentration of the film-forming dope does not become too low, and it is easy to manufacture an industrial blank film.

The film-forming dope preferably contains a surfactant. By including a surfactant, the film forming property is improved and the occurrence of uneven thickness of the thin film is suppressed, and the film becomes easy to peel off the metal roller or tape used for the self-made film. When a raw material film is produced from a film-forming dope containing a surfactant, the raw material film may contain a surfactant. The type of the surfactant is not particularly limited, and from the standpoint of releasability from a metal roll or a belt, an anionic surfactant and a nonionic surfactant are preferred.

As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate; a sulfate type such as polyoxyethyl lauryl ether sulfate and octyl sulfate; and a sulfonic acid such as dodecylbenzenesulfonate Type and so on.

As the nonionic surfactant, for example, an alkyl ether type such as polyoxyethyl oleyl ether; an alkylphenyl ether type such as polyoxyethyl octylphenyl ether; polyoxyethylene Types of alkyl esters such as laurate; Types of alkylamines such as polyoxyethyl laurylamine ether; Types of alkylamines such as polyoxyethyl laurate amine; Polyoxyethyl ethoxylate Polypropylene glycol ethers such as alkyl ethers; alkanolamines such as diethanolamine laurate and diethanolamine oleate; allylphenyl ethers such as polyoxyalkylene allylphenyl ether and the like.

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

In the case where the film-forming dope or the obtained raw material film contains a surfactant, the lower limit of the content thereof is relative to 100 parts by mass of PVA contained in the film-forming dope or the material film, preferably 0.01 part by mass, more It is preferably 0.02 parts by mass. When the content of the surfactant is at least the above-mentioned lower limit, the film-forming property and the peeling property are further improved. On the other hand, the upper limit of this content is preferably 0.5 parts by mass, more preferably 0.3 parts by mass, and still more preferably 0.1 parts by mass. When the content of the surfactant is equal to or less than the above-mentioned upper limit, the surfactant can be prevented from oozing out of the surface of the material film, blocking can occur, and operability is reduced.

Examples of the film forming method in the case of producing a thin film using the above-mentioned film forming stock solution include a cast film forming method, an extrusion film forming method, a wet film forming method, and a gel film forming method. These film forming methods may be used alone or in combination of two or more. Among these film-forming methods, the casting film-forming method and the extrusion film-forming method can obtain a blank film having a uniform thickness and width and good physical properties, and are therefore preferred. The produced thin film can be dried and heat-treated as required.

The heat treatment temperature is not particularly limited as long as it is appropriately adjusted. If the heat treatment temperature is too high, discoloration or deterioration of the material film can be seen. Therefore, the upper limit of the heat treatment temperature is preferably 210 ° C, more preferably 180 ° C, and even more preferably 150 ° C. On the other hand, the lower limit of the heat treatment temperature is, for example, 60 ° C, and preferably 90 ° C.

The heat treatment time is not particularly limited as long as it is appropriately adjusted. From the viewpoint of efficiently producing a thin film, the upper limit is preferably 30 minutes, and more preferably 15 minutes. On the other hand, as this lower limit, for example, 1 minute is preferable, and 3 minutes is more preferable.

    <Stretched Optical Film>    

The stretched optical film according to an embodiment of the present invention is an optical film including a 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, preferably uniaxially stretched. The uniaxially stretched stretched optical film can be suitably used as a polarizing film or the like. The stretched optical film may be a single-layer film or a multilayer film, and is preferably a single-layer film.

    (The 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 even more preferably 14 μm. When the average thickness of the stretched optical film is equal to or less than the above upper limit, sufficient thickness reduction can be achieved. On the other hand, as the lower limit of this average thickness, 5 μm is preferred, 8 μm is more preferred, and 10 μm is even more preferred. Since the average thickness of the stretched optical film is equal to or more than the above-mentioned lower limit, it is more difficult to tear, and operability and the like can be improved.

    (Ingredients, etc.)    

This stretched optical film contains PVA and resin particles as main components.

The upper limit of the glass transition temperature (Tg) of the resin particles contained in the stretched optical film (the Tg of the polymer of the main component of the resin particles) is 30 ° C, preferably 25 ° C, more preferably 20 ° C, and even more It is preferably 15 ° C, and even more preferably 10 ° C. As a result, the glass transition temperature is equal to or lower than the above-mentioned upper limit, and the stretched optical film is difficult to tear, and is excellent in workability and the like. In addition, by setting the glass transition temperature to be equal to or lower than the above-mentioned upper limit and adjusting the content of the resin particles and the average particle diameter, optical characteristics such as polarization performance can be improved. The lower limit of the glass transition temperature of the resin particles is not particularly limited. For example, it is preferably -100 ° C, more preferably -80 ° C, and even more preferably -60 ° C. By setting the glass transition temperature to the above lower limit or more, aggregation of the resin particles is suppressed, and white turbidity of the stretched optical film can be suppressed. Moreover, the optical characteristics of the stretched optical film can be improved.

The glass transition temperature of the resin particles contained in the stretched optical film is the same as the resin particles contained in the raw material film, and it is set to a DSC (resin film formed by using the resin particles to form a resin film) Measured by calorimetric scanning calorimetry).

The lower limit of the content of the resin particles in the stretched optical 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 setting the content of the resin particles to be at least the above lower limit, it is possible to make the stretched optical film less prone to tearing and improve the operability and the like. On the other hand, the upper limit of this content is 50 parts by mass, preferably 30 parts by mass, more preferably 20 parts by mass, and even more preferably 15 parts by mass. By setting the content of the resin particles to be equal to or less than the above-mentioned upper limit, the optical transmittance of the stretched optical film can be made good, and optical characteristics such as polarization performance can be improved.

In this stretched optical film, it is preferable that the length of the stretched direction (diameter of the stretched direction) of the resin particles observed in a transmission electron microscope (TEM) image on a cut surface parallel to the stretched direction is preferably It is longer than the length (diameter of the direction perpendicular | vertical to a stretching direction) of the direction perpendicular | vertical to the said stretching direction. That is, it is preferable that the resin particles in the stretched optical film have an oval shape having a long axis along the stretching direction. In such a case, the PVA can form a sufficient alignment state while maintaining the adhesion between the PVA and the resin particles. Therefore, it is presumed that this stretched optical film is less prone to tearing, and by adjusting the content of the resin particles and the average particle diameter, it is possible to improve optical characteristics such as polarization performance. In addition, such an oval-shaped resin particle can be formed by deforming the resin particle along the stretching direction when the raw material film containing the resin particle having a glass transition temperature of 30 ° C. or less is stretched. In addition, the stretching direction in the stretched optical film is usually the orientation direction of the crystals of PVA.

Specifically, as shown in FIG. 1, in the TEM image of a cut surface of the stretched optical film 1 parallel to the stretching direction X, the length A of the stretching direction X of the resin particles 2 (island portion) is preferable. The length B is longer than the length B in the direction perpendicular to the stretching direction X. The lower limit of the ratio (A / B) of the length A of the stretching direction X of the resin particles 2 to the length B in the direction perpendicular to the stretching direction X is preferably 1.2, more preferably 1.6, and More preferably, it is 2.0. 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, even more preferably 30 nm, even more preferably 50 nm, and even more preferably 70 nm. On the other hand, as the upper limit of the length A, for example, it may be 800 nm, preferably 300 nm, more preferably 200 nm, and even more preferably 100 nm. The lower limit of the length B of the resin particles in a direction perpendicular to the stretching direction is preferably 1 nm, more preferably 10 nm, still more preferably 20 nm, and even more preferably 30 nm. On the other hand, the upper limit of the length B may be, for example, 500 nm, preferably 200 nm, more preferably 100 nm, and even more preferably 50 nm. When the length A and the length B are within the above range, tearing is less likely to occur, and by adjusting the content of the resin particles and the average particle diameter, optical characteristics such as polarization performance can also be improved.

The length A of the resin particles in the stretching direction and the length B in the direction perpendicular to the stretching direction were measured by the following methods. For the TEM image of the film cut surface parallel to the stretching direction, the resin particles were mechanically selected using image analysis software. The average length in the major axis direction of the selected resin particles was calculated as the length A, and the average length in the minor axis direction was calculated as the length B. The length ratio (A / B) is also calculated from the length A and the length B. The specific measurement methods are those described in the examples.

The preferred aspect of the PVA and the resin particles contained in the stretched optical film is the same as the PVA and the resin particles contained in the above-mentioned raw material film. The other components which can be contained in this stretched optical film are also the same as those of the above-mentioned raw material film. When the stretched optical film is a polarizing film, the stretched optical film has a dichroic pigment adsorbed on the front and back surfaces. The dichroic pigment is generally an iodine-based pigment.

In the case where the stretched optical film is a polarizing film, the lower limit of the degree of polarization at a transmittance of 44.0% is used as the lower limit of the polarization performance, for example, it may be 70%, preferably 99.0%, and more preferably 99.8% , And more preferably 99.9%. In the case where the degree of polarization is less than the above-mentioned lower limit, if it is used in a smart phone, a notebook computer, an LCD TV, a car navigation system, etc., the contrast of the LCD may decrease.

When the stretched optical film is a polarizing film, the polarizing film is usually used as a polarizing plate by bonding an optically transparent and mechanically strong protective film on both sides or one side of the polarizing film. As a protective film, a cellulose triacetate (TAC) film, a cellulose acetate-butyrate (CAB) film, an acrylic film, a polyester film, etc. can be used. Examples of the adhesive used for bonding include PVA-based adhesives and UV-curable adhesives. PVA-based adhesives are preferred.

The polarizing plate obtained as described above can be further bonded with a retardation film, a viewing angle enhancement film, a brightness enhancement film, and the like. The stretched optical film of the present invention can also be used as the retardation film. The polarizing plate can be used as a part of an LCD after being coated with an adhesive such as acrylic, and then bonded to a glass substrate.

    <Manufacturing method of stretched optical film>    

The stretched optical film according to an embodiment of the present invention can be obtained by a manufacturing method including the step of stretching the above-mentioned raw material film. That is, this stretched optical film can be manufactured by the same method as the conventional one except that the above-mentioned raw material film is used. That is, according to this manufacturing method, it is possible to obtain a thin stretch optical film that is thin and not easily torn without going through a special step. Hereinafter, a specific manufacturing method when the stretched optical film is a polarizing film will be described.

Specific methods for producing the polarizing film include a swelling treatment, a dyeing treatment, a uniaxial stretching treatment, and a cross-linking treatment, a fixing treatment, a cleaning treatment, and a drying treatment as required. , Heat treatment, etc. In this case, the order of each treatment such as swelling treatment, dyeing treatment, cross-linking treatment, uniaxial stretching, and fixing treatment is not particularly limited, and two or more treatments can be performed simultaneously. In addition, one or two or more of each treatment can be performed twice or more.

The swelling treatment can be performed by immersing the raw material film in water. The lower limit of the temperature of water when immersed in water is preferably 20 ° C, more preferably 22 ° C, and even more preferably 25 ° C. On the other hand, the upper limit of this temperature is preferably 40 ° C, more preferably 38 ° C, and even more preferably 35 ° C. The lower limit of the time for immersion in water is preferably 0.1 minutes, and more preferably 0.5 minutes. On the other hand, the upper limit of this time is preferably 5 minutes, and more preferably 3 minutes. The water to be immersed in water is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or a mixture of water and an aqueous medium.

The dyeing process can be performed by making a dichroic dye contact a base material film. As a dichroic pigment, an iodine-based pigment is generally used. The period of the dyeing treatment may be any one of before the uniaxial stretching treatment, during the uniaxial stretching treatment, and after the uniaxial stretching treatment. The dyeing process is generally performed by immersing a raw material film in a solution (particularly an aqueous solution) containing iodine-potassium iodide as a dyeing bath. The concentration of iodine in the dyeing bath is preferably from 0.01% by mass to 0.5% by mass, and the concentration of potassium iodide is preferably from 0.01% by mass to 10% by mass. The lower limit of the temperature of the dyeing bath is preferably 20 ° C, and more preferably 25 ° C. On the other hand, the upper limit of this temperature is preferably 50 ° C, and more preferably 40 ° C.

By performing a cross-linking treatment on the raw material film, it is possible to effectively prevent the PVA from eluting into water when wet stretching is performed at a high temperature. From this viewpoint, the crosslinking treatment is preferably performed before the uniaxial stretching treatment. The crosslinking treatment can be performed by immersing the raw material film in an aqueous solution containing a crosslinking agent. As said crosslinking agent, 1 type, or 2 or more types of boron inorganic compounds, such as a borate such as a boric acid and a 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 even more preferably 3% by mass. On the other hand, the upper limit of this concentration is preferably 15% by mass, more preferably 7% by mass, and even more preferably 6% by mass. When the concentration of the crosslinking agent is within the above range, sufficient stretchability can be maintained. The aqueous solution containing a crosslinking agent may contain adjuvants, such as potassium iodide. The lower limit of the temperature of the aqueous solution containing a crosslinking agent is preferably 20 ° C, and more preferably 25 ° C. On the other hand, the upper limit of this temperature is preferably 50 ° C, and more preferably 40 ° C. By setting this temperature within the above range, crosslinking can be performed efficiently.

The uniaxial stretching treatment can be performed by any one of a wet stretching method and a dry stretching method. In the case of the wet stretching method, it can be carried out in a boric acid aqueous solution, or it can be carried out in the above-mentioned dyeing bath or a fixing treatment bath described later. Further, in the case of the dry stretching method, uniaxial stretching treatment may be performed while maintaining room temperature, or uniaxial stretching treatment may be performed while heating, or a water-absorbent blank film may be used in the air. Uniaxial stretching is performed. Among these, a wet stretching method is preferred, and a uniaxial stretching treatment in an aqueous boric acid solution is more preferred. The lower limit of the boric acid concentration of the boric acid aqueous solution is preferably 0.5% by mass, more preferably 1.0% by mass, and even more preferably 1.5% by mass. On the other hand, the upper limit of the boric acid concentration is preferably 6.0% by mass, more preferably 5.0% by mass, and even more preferably 4.0% by mass. The boric acid aqueous solution may contain potassium iodide, and its concentration is preferably set to 0.01% by mass or more and 10% by mass or less.

The lower limit of the stretching temperature in the uniaxial stretching treatment is preferably 30 ° C, more preferably 40 ° C, and even more preferably 50 ° C. By setting the lower limit of the stretching temperature to 30 ° C, which is the upper limit of the glass transition temperature of the resin particles, the resin particles are well deformed so as to extend in the stretching direction during stretching. This makes it relatively easy to obtain a stretched optical film that is not easily torn and is excellent in operability.

The lower limit of the stretching ratio in the uniaxial stretching treatment is preferably 5 times, more preferably 5.5 times, and still more preferably 6 times from the viewpoint of the polarization performance of the polarizing film obtained. The upper limit of the draw ratio is not particularly limited, and for example, it is preferably 10 times, and more preferably 8 times.

When manufacturing a polarizing film, in order to stabilize adsorption of a dichroic dye (iodine-type dye, etc.) to a raw material film, it is preferable to perform a fixing process after a uniaxial stretching process. As the fixed treatment bath used for the fixed treatment, an aqueous solution containing one or two or more boron inorganic compounds such as boric acid and borax can be used. If necessary, an iodine compound or a metal compound may be added to the fixed treatment bath. The lower limit of the concentration of the boron inorganic compound in the fixed treatment bath is preferably 0.5% by mass, and more preferably 1% by mass. On the other hand, the upper limit of this concentration is preferably 15% by mass, and more preferably 10% by mass. By setting the concentration within the above range, the adsorption of the dichroic dye can be made more stable. The lower limit of the temperature of the fixed treatment bath is preferably 15 ° C. On the other hand, the upper limit of this temperature is preferably 60 ° C, and more preferably 40 ° C.

The cleaning treatment is generally performed by immersing the raw material film in water or the like. In this case, from the standpoint of improvement in polarizing performance, water and the like used in the cleaning treatment are preferably auxiliaries containing potassium iodide and the like. 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 in the cleaning 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. From an economic point of view, the temperature of water and the like is too low to be good. On the other hand, if the temperature of water or the like is too high, the polarization performance may decrease.

The conditions of the drying treatment are not particularly limited, and the lower limit of the drying temperature is preferably 30 ° C, and more preferably 50 ° C. On the other hand, the upper limit of the drying temperature is preferably 150 ° C, and more preferably 130 ° C. It is easy to obtain a polarizing film excellent in dimensional stability by drying at the temperature in the said range.

By performing the heat treatment after the drying treatment, a polarizing film having excellent dimensional stability can be further obtained. Here, the heat treatment refers to a process of further heating the polarizing film having a moisture content of 5% or less after the drying treatment to improve the dimensional stability of the polarizing film. The conditions for the heat treatment are not particularly limited, and it is preferable to perform the heat treatment in a range of 60 ° C to 150 ° C. When the heat treatment is performed at a temperature lower than 60 ° C, the effect of dimensional stabilization due to the heat treatment is insufficient. On the other hand, if heat treatment is performed at a temperature higher than 150 ° C., yellowing may be severely occurred in the polarizing film.

    <Other embodiments>    

The manufacturing method of the blank film, the stretched optical film, and the stretched optical film of this invention is not limited to the said embodiment. For example, as the stretched optical film and a method for producing the same, the case where the stretched optical film is a polarizing film will be described, but 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 manufacturing method including a step of stretching the base material film of the present invention. The method for producing a retardation film according to an embodiment of the present invention can be performed by a conventionally known method in addition to stretching the base material film of the present invention.

    [Example]    

The present invention will be described more specifically by the following examples, but the present invention is not limited to these examples. In addition, each evaluation method used in the following examples and comparative examples is shown below.

    [Glass transition temperature of resin particles]    

The raw material films obtained in each of the following examples or comparative examples were dissolved in water, and then filtered with a filter capable of trapping resin particles ("MF-Millipore Membrane Filter VSWP" by Merck, pore size 0.025 µm) The collected material (resin particles) is dried. After that, the resin particles were heat-treated at 100 ° C. to obtain a resin film formed only from the resin particles. The glass transition temperature of the resin film was determined using DSC ("Q2000" by TA Instruments). Let this be the glass transition temperature of a resin particle.

    [Swelling degree of blank film]    

About 1.5 g of the material film obtained in each of the following examples or comparative examples was taken. This was cut into about 2 mm x 10 cm, and then wrapped in a 100 mesh ("N-N0110S 115" of NBC Meshtech) and immersed in distilled water at 30 ° C for 15 minutes. Thereafter, centrifugal dehydration was performed at 3,000 rpm for 5 minutes, and the mass (W1) of the swollen material film was determined after removing the sieve. Next, this raw material film was dried with a dryer at 105 ° C. for 16 hours, and then the mass (W2) was determined. The swelling degree of the raw material film was calculated by the following formula.

Swelling (%) = ((W1) / (W2)) × 100

    [Average particle diameter of resin particles in the material film]    

The raw material films obtained in each of the following examples or comparative examples were cut out with an ultra-thin microtome ("Ultracut S / FC-S" by Leica), and then a 23 ° C gas was used in the rhenium tetroxide vapor After exposure to the environment for 5 days, the hydroxyl group of PVA was dyed. After the dyeing treatment, a diamond knife ("Ultra Cryo Dry" from DiATOME Corporation 2mm, 35 °) was further used to cut out frozen sections for observation in a gas environment of -100 ° C. After that, the frozen sections for observation that have been excessively stained are washed with distilled water and dried. The cut surface was observed with a transmission electron microscope ("Transmission Electron Microscope HT7000" by Hitachi High-Technologies) to obtain a TEM image. The acceleration voltage is set to 100 kV, the emission current is set to 10 μA, and the electron gun uses a LaB6 filament.

Using the TEM image obtained by the above method, the average particle diameter of the resin particles in the material film was measured by the following method. First, using image analysis software "Image-Pro Plus 7.0J" (manufactured by Media Cybernetics), after opening the TEM image, the conversion was changed to an 8-bit level in "Conversion", and the flattening processing was performed in "Filtering". Next, set the contrast value to 80 in "Contrast Enhancement", select "Average Particle Size" on the measurement item setting page in "Count / Size", and automatically select bright-colored objects to mechanically select the resin Particles, and the average particle diameter of the resin particles in the material film was calculated. In addition, those having a particle diameter smaller than 1/10 of the maximum diameter in the TEM image are removed as noise. When the color of the resin particles in the TEM image is darker than that of the PVA, the dark particles are automatically selected to calculate the average particle diameter of the resin particles in the material film.

    [Length of resin particles in polarizing film]    

The polarizing films obtained in each of the following examples or comparative examples were performed in the same manner as described in the "average particle diameter of the resin particles in the material film" to obtain a TEM image of the cut surface. However, this polarizing film was observed from a cut surface parallel to the stretching direction.

Using the TEM image obtained by the above method, the length A (long-axis length) of the resin particles in the polarizing film and the length B (short-axis length) in the direction perpendicular to the direction of extension were measured by the following methods. ). First, using image analysis software "Image-Pro Plus 7.0J" (manufactured by Media Cybernetics), after opening the TEM image, the conversion was changed to an 8-bit level in "Conversion", and the flattening processing was performed in "Filtering". Next, set the contrast value to 80 in "Contrast Enhancement", and select "Long-axis / Short-axis ratio of ellipse" in the measurement item setting page in "Count / Size", and make it automatically select bright-colored objects This mechanically selects the resin particles to calculate the length A (length in the stretching direction) of the resin particles in the polarizing film, the length B (length in the direction perpendicular to the stretching direction) in the short axis direction, and These length ratios (A / B). In addition, those having a particle diameter smaller than 1/10 of the maximum diameter in the TEM image are removed as noise. When the color of the resin particles in the TEM image is darker than that of the PVA, the dark particles are automatically selected to calculate the respective lengths of the resin particles in the polarizing film.

    [Tear resistance evaluation: Puncture property]    

The polarizing films obtained in the following Examples or Comparative Examples were allowed to stand at a temperature of 23 ° C. and a relative humidity of 20% for 24 hours. Thereafter, the polarizing film was cut into a film sheet having a length direction (the direction in which the polarizing film is stretched) of 40 mm × a width direction of 20 mm, and was clamped by a metal frame to fix the four sides. Then, this polarizing film was installed in a tensile test device ("Autograph AGS-H" by Shimadzu Corporation), and a flat-blade screwdriver (contact area with the polarizing film: 1 mm × 5 mm) was used to draw the polarizing film in the stretching direction. ) The long sides are parallel. A flat screwdriver is mounted on the upper chuck, and the flat screwdriver is pressed against the polarizing film at a speed of 1mm / min. Then, the maximum load when the flat-blade screwdriver penetrates the polarizing film is set as the puncture strength, and the puncture property is evaluated by the following criteria. In addition, since A and B were practically usable without problems, they were judged to be good, and C was judged to be bad.

A: The jab strength is 5N or more

B: The jab strength is 3N or more and less than 5N

C: Jab strength is less than 3N

    [Tear resistance evaluation: Cutting property]    

The polarizing films obtained in the following Examples or Comparative Examples were allowed to stand at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. Then, this polarizing film was cut at a speed of 600 mm / min using a blade in a direction perpendicular to the stretching direction, and the cut cross section was observed with a stereo microscope. The angle between the cutting edge of the blade and the stretching direction of the polarizing film was set to 45 °. Then, the number of cracks per 1 cm of the cut cross section of the polarizing film was measured, and the cutability was evaluated by the following criteria. In addition, since A and B were practically usable without problems, they were judged to be good, and C was judged to be bad.

A: No cracks

B: 1 ~ 4 pieces / cm

C: 5 or more / cm

    [Tear resistance evaluation: punchability]    

The polarizing films obtained in the following Examples or Comparative Examples were allowed to stand at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. Then, the polarizing film was placed on a cutting pad ("MA-40N" by Kokuyo Corporation), and a circular hole punch (HHH company's "TPO-100" with a hole punch) of 10 mm in diameter was used to perform the polarization film. For punching, observe the punched end face of the polarizing film hollowed out into a circle with a stereo microscope. Then, the number of cracks existing in the polarizing film was measured, and punchability was evaluated by the following criteria. In addition, since A and B were practically usable without problems, they were judged to be good, and C was judged to be bad.

A: No cracks

B: 1 ~ 4 pieces / week

C: 5 or more per week

    [Polarization performance of polarizing film]         (Measurement of transmittance Ts)    

From the central portion of the polarizing film, two samples with a length of 2 cm were taken in the stretching direction of the polarizing film. Using a spectrophotometer with a integrating sphere ("V7100" of Japan Spectrophotometer Co., Ltd.) for one piece of sample, the visual sensitivity of the C light source and the visible light region with a 2 ° field of view was corrected in accordance with JIS Z 8722. The transmittance of light in the case of + 45 ° inclination with respect to the longitudinal direction and the transmittance of light in the case of -45 ° with respect to the longitudinal direction were measured, and these average values Ts1 (%) were obtained. The same was performed for the other sample, and the transmittance of light when the tilt was + 45 ° and the transmittance of light when the tilt was -45 ° were measured, and these average values Ts2 (%) were obtained. Using the following calculation formula (1), Ts1 and Ts2 were averaged to obtain the transmittance Ts (%) of the polarizing film.

Ts = (Ts1 + Ts2) / 2 ... (1)

In the following examples or comparative examples, samples were prepared so that the transmittance Ts became 44.0% by adjusting the dyeing treatment conditions, and the following polarization degree V was measured.

    (Measurement of Polarization V)    

For the two samples used in the measurement of the transmittance Ts described above, the transmittance T _⊥ (%) of the light in the case where the stretching directions are orthogonal to each other is measured, and the method is parallel to the stretching direction. The light transmittance T _// (%) of the overlapped case. This measurement was performed by using a spectrophotometer with an integrating sphere ("V7100" from Japan Spectroscopy Corporation) in accordance with JIS Z 8722 (method for measuring the color of an object) and correcting the visual sensitivity of the visible light region with a 2 ° field of view. Using the following calculation formula (2), the polarization degree V (%) was obtained from the measured T _// (%) and T _⊥ (%).

V = ((T _// -T _⊥ ) / (T _// + T _⊥ )) ^1/2 × 100 ... (2)

    [Production Example 1] Production of Resin Particle A    

Into the dried 0.5L pressure-resistant polymerization tank, 0.20 g of potassium peroxodisulfate as a polymerization initiator, 36.0 g of a reactive emulsifier "JS-20" of Sanyo Chemical Industry Co., Ltd., and 300 g of ion-exchanged water were charged. This was debubbled by bubbling with nitrogen for 30 minutes to obtain a starting emulsion. Next, the temperature of the starting emulsion was raised to 60 ° C while stirring, and then 45.0 g of each of n-butyl acrylate, 0.45 g of allyl methacrylate, and trihydroxy methacrylate were continuously added at a rate of 1.0 ml / minute. A mixed solution of 0.23 g of methylpropane trimethacrylate.

Thereafter, when it was confirmed that the conversion rate of each monomer calculated by the method described below exceeded 95% by mass, 5.6 g of decyclopentyl methacrylate was continuously added at a rate of 1.0 ml / minute. After the addition, it was confirmed that the monomer conversion calculated by the above method exceeded 95% by mass, the polymerization tank was heated to 100 ° C. to perform polymerization, and the polymerization was continued until the residual monomer became below the detection limit of the gas chromatography method. After the polymerization, it was cooled to 25 ° C. to obtain a latex solution containing resin particles A (resin content: 17% by mass). In addition, the polymerization time required from the start of polymerization to cooling to 25 ° C was 8 hours. The obtained resin particle-based core was a core-shell type particle of poly-n-butyl acrylate and a shell of polydicyclopentyl methacrylate.

    (Monomer conversion)    

The emulsion polymer (0.100 g) sampled every hour from the start of the polymerization was dropped into a tetrahydrofuran solution (10.0 g, 0.1% by mass of 4-tert-butylcatechol was added) to prepare coated polymer particles or polymerize Tetrahydrofuran solution of particles. This solution was analyzed by gas chromatography (Shimadzu Corporation GC-14A, column UWAAX-20EX-1.0F), and the monomer conversion was calculated from the amount of monomers detected and the amount of monomers added at the point of emulsion polymerization initiation. (%).

    [Production Example 2] Production of Resin Particle B    

To a twin-screw extruder (manufactured by Parker Corporation), a (meth) acrylic block copolymer was supplied with a methyl methacrylate-n-butyl acrylate-methyl methacrylate triblock from a hopper at 0.66 kg / hour. Segment copolymer (Kurarity (registered trademark) LA2140, manufactured by Kuraray (shares), methyl methacrylate unit 24% by mass), 72 kg / hour from a cylinder (relative to (meth) acrylic polymer The amount of methyl methacrylate unit in the sample was 100 mol and the amount was 40 mol). N-methylcyclohexylamine was supplied, and melt-kneaded 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, thereby converting an acid anhydride into a carboxyl group to prepare a methacrylic acid-n-butyl acrylate-methacrylic acid triblock copolymer. Then, this copolymer was taken out by filtration, dried, and dissolved in methanol so as to have a solid content concentration of 10% by mass. Then, the same mass of water as methanol was dropped to obtain a dispersion solution, and the obtained solution was subjected to reduced pressure treatment at 60 ° C., and the methanol was distilled off to obtain methacrylic acid-n-butyl acrylate-methacrylic acid terpolymer. Latex solution of resin particles B of the segment copolymer (resin content: 10% by mass).

Commercial resin particles used in the examples and comparative examples are shown below.

Resin particles C: "AE986B" (acrylic resin particles) from E-tec

Resin particles D: "UC-143" (acrylic resin particles) from SAIDEN CHEMICAL INDUSTRY

Resin particle E: "QE-1042" by Starlight PMC

Resin Particle F: "KE-1062" by Starlight PMC

Resin particles G: "N827 (A) -1" by E-tec (acrylic resin particles)

    [Example 1]         (1) Manufacture of thin film    

Mixed with PVA (saponified product of homopolymer of vinyl acetate, degree of polymerization of 2,400, degree of saponification of 99.95 mole%), glycerin (12 parts by mass with respect to 100 parts by mass of PVA), and surfactant (with respect to 100 parts by mass of PVA) (Parts are 0.03 parts by mass) and dissolved in water at 90 ° C for 4 hours to obtain a PVA aqueous solution. Then, 10 mass parts of resin particles A with respect to 100 mass parts of PVA was added to this PVA aqueous solution, and it stirred at 85 degreeC for 30 minutes. Thereafter, in order to defoam the PVA aqueous solution, the PVA aqueous solution was kept at 85 ° C. for 16 hours.

The PVA aqueous solution was dried on a metal roll at 80 ° C to obtain a PVA film. Then, it heat-processed in the dryer at 110 degreeC for 10 minutes, and obtained the raw material film of Example 1 with an average thickness of 30 micrometers.

    (2) Manufacturing of polarizing film    

From the raw material film obtained in the above (1), a rectangular test piece having a length of 9 cm and a width of 5 cm was taken. Both ends of the test piece in the longitudinal direction were fixed to a stretching jig so that the size of the stretched portion became 5 cm in the lengthwise direction and 5 cm in the widthwise direction. The test piece was immersed in water at a temperature of 30 ° C. for 38 seconds at 24 cm / The stretching speed of one minute is uniaxially stretched in the longitudinal direction (the first stretch) to be 2.2 times the original length. After that, it was immersed in an iodine / potassium iodide aqueous solution at a temperature of 30 ° C. containing iodine at a concentration of 0.03% by mass and potassium iodide at a concentration of 3% by mass for 60 seconds at a stretching speed of 24 cm / minute in the longitudinal direction. Uniaxial stretching (stretching in the second stage) to 3.3 times the original length. Next, while immersed in a boric acid / potassium iodide aqueous solution at a temperature of 30 ° C. containing boric acid at a concentration of 3% by mass and potassium iodide at a concentration of 3% by mass for about 20 seconds, a stretching speed of 24 cm / minute was applied in the longitudinal direction The upper uniaxial stretching (stretching in the third stage) is up to 3.6 times the original length. Next, while immersing in a boric acid / potassium iodide aqueous solution at a temperature of 58 ° C. containing boric acid at a concentration of 4% by mass and potassium iodide at a concentration of about 5% by mass, uniaxially pulling at a stretching rate of 24 cm / minute in the longitudinal direction. Stretching (stretching in the fourth step) to the limit stretch ratio (install 4 sheets of film, and use the stretch ratio of 2 pieces as the limit stretch ratio). Thereafter, it was immersed in an aqueous potassium iodide solution containing boric acid at a concentration of 1.5% by mass and potassium iodide at a concentration of 3% by mass for 10 seconds to perform a fixing treatment. Then, it dried in the dryer at 60 degreeC for 4 minutes, and obtained the polarizing film (average thickness 13 micrometers) of Example 1 which stretched an optical film.

    [Examples 2 to 6, Comparative Examples 1 to 4]    

Except that the types and amounts of the resin particles added to the PVA aqueous solution were set as shown in Table 1, the same procedures as in Example 1 were performed to obtain each of the raw material films and polarizing films of Examples 2 to 6 and Comparative Examples 1 to 4. In addition, in Comparative Example 1, no resin particles were added.

    [Comparative Example 5]    

A green sheet 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 green sheet was 60 μm. The average thickness of the obtained polarizing film was 26 μm.

    [Evaluation]    

Using each of the obtained raw material films, the glass transition temperature of the resin particles, the swelling degree of the raw material film, and the average particle diameter of the resin particles in the raw material film were measured by the methods 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) of the resin particles in the polarizing film, and the length ratio thereof were performed by the above-mentioned method. (A / B) measurement, and evaluation of puncture, cutting, punching, and polarizing performance. The results are shown in Table 1.

As shown in Table 1, it can be seen that the polarizing film obtained in Examples 1 to 6 had an evaluation of puncture, dicing, and punching properties of A or B, was thin, was not easily torn, and was excellent in operability and productivity. In addition, it can be seen that Examples 1 to 6 are performed without complicated steps, and it is relatively easy to manufacture a polarizing film. Moreover, it turns out that the polarizing films of Examples 1 to 4 are particularly excellent in polarizing performance.

On the other hand, it was found that the polarizing film systems obtained in Comparative Examples 1 to 4 had low evaluations of puncture properties, dicing properties, and punchability, and were easy to tear. In addition, although the polarizing film obtained in Comparative Example 5 had tear resistance, a thin polarizing film could not be obtained.

Industrial availability

The blank film of the present invention can be suitably used as a material such as a polarizing film as a constituent material of an LCD. Moreover, the manufacturing method of the stretched optical film of this invention, and a stretched optical film can be used suitably as a polarizing film or its manufacturing method.

Claims (5)

    A raw material film for the production of a stretched optical film, having an average thickness of 45 μm or less, containing a main component of a vinyl alcohol polymer, and resin particles having a glass transition temperature of 30 ° C. or lower. The content of the resin particles in parts by mass is 1 to 50 parts by mass.         The blank film of claim 1, wherein the average particle diameter of the resin particles is 1 nm to 300 nm.         The manufacturing method of the stretched optical film provided with the process of stretching the blank film as described in claim 1 or 2.         A stretched optical film having an average thickness of 20 μm or less, containing a vinyl alcohol polymer as a main component, and resin particles having a glass transition temperature of 30 ° C. or less, and 100 parts by mass of the resin particles of the vinyl alcohol polymer The content is 1 mass part or more and 50 mass parts or less.         The stretched optical film according to claim 4, wherein the length of the stretched direction of the resin particles in a cut surface parallel to the stretched direction as observed in a transmission electron microscope image is a ratio of a length perpendicular to the stretched direction. The length in the direction is long.