KR101719869B1 - Substrate film - Google Patents

Abstract

The present application relates to a method for producing a base film, a laminate or a polarizing film. A base film capable of effectively producing a polarizing film excellent in functions such as polarization performance while having a thickness of about 10 m or less, about 8 m or less, about 7 m or less, about 6 m or less, or about 5 m or less, Or a manufacturing method thereof is provided. According to the above, it is possible to easily produce a polarizing film by stretching a polarizing functional material such as a PVA resin while preventing the occurrence of tearing or curling in the stretching process.

Description

SUBSTRATE FILM

The present application relates to a base film, a laminate, and a process for producing a polarizing film.

A method for producing a polarizing film in which a dichromatic material is adsorbed and oriented on a polyvinyl alcohol-based resin (hereinafter referred to as "PVA resin") layer is well known. A typical application in which a polarizing film is used is a display device such as a liquid crystal display (LCD). For example, a PVA resin-based polarizing film having a thickness of usually about 60 μm to 80 μm is attached to both sides of a liquid crystal panel of a liquid crystal display.

The PVA resin is hydrophilic and therefore the polarizing film is sensitive to changes in temperature and humidity, and is easy to stretch and shrink, and defects such as curl easily occur. Therefore, in order to suppress the expansion and contraction and the influence of temperature and humidity, However, when the thickness of the polarizing film is thick, it is difficult to restrain expansion and contraction, and stress is generated when the polarizing film is adhered to a liquid crystal panel or the like, thereby causing unevenness on the screen . In addition, as the demand for thin-type devices and devices with low energy consumption has increased recently, the demand for thinner polarizing films is also increasing.

For example, Patent Document 1 discloses a process for producing a thin polarizing film.

Patent Document 1: Korean Patent No. 1175700

The present application provides a method for producing a base film, a laminate and a polarizing film.

The present application is directed to a substrate film. An exemplary base film may be, for example, a film used in a process of stretching a material capable of exhibiting a polarization function such as a PVA resin (hereinafter referred to as a stretched film or a stretched substrate film) . As shown in Fig. 1, for example, the stretching process may be performed by stretching a material (hereinafter, referred to as a polarizing function material) capable of exhibiting a polarizing function by stretching on one side or both sides of the base film 101 (Hereinafter may be referred to as a polarizing function material layer), and then stretching the laminate in a state in which the laminate 101 is produced. A pressure-sensitive adhesive layer may be formed on the surface of the lead-free film, for example, in a region where the polarizing function material layer is formed. The pressure-sensitive adhesive of the pressure-sensitive adhesive layer may be formed on the entire surface of the surface, or may be formed in a predetermined pattern on only a part of the surface. In this specification, a region where the pressure-sensitive adhesive is present on the surface is referred to as a tacky region, and a region where the tacky agent is not present may be referred to as a non-tacky region.

The properties of the base film can be determined in consideration of the characteristics of the polarizing functional material layer which is stretched together to perform the stretching process more efficiently and to obtain a high function and thin polarizing film.

The properties of the base film may include various physical properties that can be measured, for example, by a tensile test. The tensile curve identified in the tensile test is a load-versus-elongation curve expressed in terms of the degree of elongation (mm) with respect to the applied load; And a stress-versus-strain curve expressed as a relation of engineering strain to engineering stress. The characteristics specified in this specification are not particularly limited unless otherwise specified. Versus-strain curve, expressed in terms of the latter, i. E. The engineering strain to engineering stress.

In the present application, the tensile curve is shown in the following manner. First, prepare the specimen to measure the tensile curve so that the length is 15 mm and the length is 70 mm. The width and length of the specimen are the length except for the portion to be fixed to the tensile tester for tensile. After the specimens were fixed on the tensile tester, the specimens were pulled until the specimens were cut at a tensile rate of about 300 mm / min at room temperature in the longitudinal direction, and then the load (measured according to the distance until the specimen was cut force (X axis: distance, Y axis: force). Thereafter, the graph is converted into a graph of elongation and tensile strength (X-axis: elongation, Y-axis) by applying the width and thickness of the specimen, and from the converted graph, Tensile properties can be measured. As used herein, the term ambient temperature may mean a temperature of about 10 ° C to 30 ° C, about 25 ° C or about 23 ° C, which is a natural temperature that is neither warmed nor warmed. Unless otherwise specified otherwise in the specification, the physical properties correspond to physical properties measured at room temperature.

For example, the base film may be required to satisfy the following expression (1) from the standpoint of prevention of defects due to shrinkage after stretching of the polarizing functional material layer as described later.

[Equation 1]

E / R > = 5,

In the formula (1), E is the elongation (unit:%) of the stretching base film measured at room temperature, and R is the recovery rate (unit:%). In the above, the elongation can be obtained from the tensile curve obtained by performing the tensile test as described above at the measurement temperature.

In addition, in the above, the polyvinyl alcohol film having the same width and length and having a thickness of 30 탆 was attached to one side of the base film cut so that the length of the side was 50 mm and the length was 100 mm The polyvinyl alcohol film was taken out from water after being stretched five times in the longitudinal direction at a water temperature (60 DEG C), and the polyvinyl alcohol film was peeled off. After the film was held at room temperature for 1 hour, 100 占 (TA) / A ", and A in the above formula is the longitudinal length of the substrate film before stretching.

When the ratio (E / R) according to Equation 1 is adjusted to fall within the above range, a polarizing film having a very thin shape and excellent polarizing function or transmittance can be obtained through effective drawing in a drawing process described later. The ratio E / R may be 10 or more, 15 or more, 20 or more, 25 or more, or 30 or more in another example. In another example, the ratio E / R may be less than 600, less than 500, less than 400, less than 300, less than 200, less than 100, less than 70, less than 65, less than 60, less than 55, less than 50, less than 45, have.

The base film may have the above elongation within a range of about 200% to 1500% while satisfying the above-mentioned formula (1). The elongation may be about 250% or more and about 300% or more in other examples. In other examples, the elongation may be about 1400%, 1300%, 1200%, 1100%, 1000%, 900%, 800%, 700%, 600%, or 550%.

The restoration rate of the base film may also be less than 30%, less than 25%, or less than about 20%. The restoration rate may also be about 5% or more, 10% or more, or 15% or more.

The base film has a tensile curve (elongation and tensile strength of elongation and tensile strength, measured while being stretched until the specimen is cut) measured in the above-mentioned manner, ) May be in the range of 2000 Nmm to 10,000 Nmm. In another example, the integrated value may be 2500 Nmm or more, 3000 Nmm or more, 3500 Nmm or more, or 4000 Nmm or more. The integrated value may also be less than or equal to 9000 Nmm, less than or equal to 8000 Nmm, or less than or equal to 7600 Nmm in other examples. Such a range can be advantageous for forming a very thin and highly functional polarizing film in a drawing process described later.

The tensile strength of the base film may be, for example, in the range of 45 MPa to 200 MPa. The tensile strength may be 50 MPa or more in another example. The tensile strength may also be 150 MPa or 100 MPa or less in other examples. Such a range can be advantageous for forming a very thin and highly functional polarizing film in a drawing process described later.

The yield point of the base film may be, for example, in the range of 10 MPa to 150 MPa. The yield point may be 15 MPa or more in another example. The yield point may also be 100 MPa or less in other examples. Such a range can be advantageous for forming a very thin and highly functional polarizing film in a drawing process described later.

The elastic limit of the base film may be, for example, in the range of 200 MPa to 1,000 MPa. The elastic limit may be 250 MPa or more, 300 MPa or more, or 350 MPa or more in another example. The elastic limit may also be 900 MPa or less, 850 MPa or less, or 800 MPa or less in other examples. Such a range can be advantageous for forming a very thin and highly functional polarizing film in a drawing process described later.

If the base film is selected in relation to the polarizing functional material layer so as to satisfy at least one of the physical properties mentioned above, the base film is very thin, for example, about 10 mu m or less, about 8 mu m or less , A polarizing film having a thickness of about 7 占 퐉 or less, about 6 占 퐉 or less, or about 5 占 퐉 or less while exhibiting a high performance can be effectively produced, and the tearing of polarizing films and the occurrence of curling can be effectively prevented have.

For example, the base film may have an absolute value of a difference (AB) between the integral value (A) of the tensile curve and the integral value (B) of the polarizing function material layer measured in the same manner is in the range of 1,500 Nmm to 10,000 Nmm May be selected to fall within the range. In another example, the absolute value of the difference may be at least 2,000 Nmm, at least 2,500 Nmm, at least 3,000 Nmm, at least 3,500 Nmm, or at least about 4,000 Nmm. In addition, the absolute value of the difference may be less than or equal to about 9,000 Nm, less than or equal to 8,000 Nm, less than or equal to 7,000 Nm, or less than or equal to 6,500 Nmm in other examples.

For example, the base film may be selected so that the absolute value of the difference between the tensile strength thereof and the tensile strength of the polarizing function material layer falls within a range of about 0.5 MPa to 40 MPa. In the above, the tensile strength refers to a value obtained by dividing the maximum tensile load from the tensile test to the fracture of the specimen by the cross-sectional area of the specimen before the tensile test.

The base film can be selected so that, for example, the absolute value of the difference between the elongation percentage and the elongation percentage of the polarizing function material layer falls within a range of 15% to 500%. The absolute value of the difference may be 20% or more in another example. Further, the absolute value of the difference may be 400% or less, 300% or less, 200% or 160% or less in other examples.

The base film may be selected so that, for example, the absolute value of the difference between the yield point and the yield point of the polarizing function material layer falls within the range of 1 MPa to 50 MPa. The absolute value of the difference may be 3 MPa or more or 5 MPa or more in another example. Further, the absolute value of the difference may be 45 MPa or less, 40 MPa or less, or 35 MPa or less in other examples.

The base film can be selected so as to fall within a range in which the absolute value of the difference between the elastic limit of the base film and the elastic limit of the polarizing function material layer is 1,000 MPa or less. In other examples, the absolute value of the difference may be at least 50 MPa, at least 100 MPa, at least 150 MPa, at least 200 MPa, or at least 230 MPa. In addition, the absolute value of the difference may be 900 MPa or less, 800 MPa or less, 700 MPa or less, or 660 MPa or less in another example.

The kind of the base film is not particularly limited as long as it is selected so as to satisfy at least one of the above properties. Examples of the base film include a cellulose-based film such as TAC (triacetyl cellulose); Polyethersulfone-based films; An ethylene-vinyl acetate copolymer film, an ethylene-alkyl (meth) acrylate copolymer (in which the alkyl may be an alkyl group having 1 to 4 carbon atoms) film, an ethylene-alpha Polyolefins such as olefin copolymer films or propylene-alpha-olefin copolymer films; Polyvinyl chloride; Elastomer film; Acrylic film; Or a base material film made of a polymer such as urethane type. However, for example, a film such as an amorphous PET (poly (ethylene terephthalate)) film or a polymethylpentene film exhibits a tensile behavior different from that of a general PVA resin layer as a polarizing functional material layer I do not.

An example that can be used as the base film is a thermoplastic polyurethane film (hereinafter referred to as TPU (thermoplastic polyurethane) film). As used herein, the TPU film may be a single layer film containing a TPU film as a main component or a multi-layered film including at least a TPU film. Such a TPU film may be a non-oriented film, or a uniaxial, biaxial or multiaxial oriented film. As the TPU film, a polyester TPU film, a polyether TPU film, or a polycaprolactone TPU film is known. Among these known materials, an appropriate type can be selected in consideration of the above characteristics. For example, a polyester TPU film can be used as the base film. As the TPU film, an aromatic or aliphatic TPU film may be used.

The TPU film is usually prepared by reacting a polyol component, a polyisocyanate component, and a chain extender component, and the TPU thus prepared has a soft segment and a hard segment. Usually, the soft segment is a main component of the polyol component, and the hard segment includes a urethane bond or a urea bond produced by the reaction of the polyisocyanate and the chain extender, and an unreacted portion of these components. Therefore, in the TPU film, the ratio of the soft and hard segments can be controlled through the control of the raw material component, so that the above-mentioned tensile properties can be easily controlled. The TPU film used as the substrate film may thus be a reactant of a mixture comprising a polyol, a polyisocyanate and a chain extender.

The kind of the polyol contained in the mixture is not particularly limited. For example, one or more components selected from the group consisting of aliphatic or aromatic polyether glycols, aliphatic or aromatic polyester glycols and polycaprolactone glycols, which are conventionally used for the formation of soft segments, can be used as the polyol. For example, the polyester polyol may be selected from the group consisting of adipic acid, sebasic acid, isophthalic acid, dimethyl terephthalate, terephthalic acid, dimethyl phthalate ), Phthalic acid, dimethyl isophthalic acid, dimethyl naphthalene 2,6-dicarboxylic acid, oxalic acid, malonic acid, succinic acid, can be produced by reacting a glycol with a dibasic acid such as succinic acid, glutaric acid, azelaic acid, nona acid, or dodeca-deca acid . In view of the above-described ease of securing each property or ease of control, the polyol having a weight average molecular weight within a range of about 500 to 5,000 can be used.

The kind of the chain extender contained in the mixture is not particularly limited, and a component commonly used for forming the hard segment can be used. Such components include, for example, ethylene glycol, 1,6-hexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-pentanediol, neopentyl glycol or 1,4- An aliphatic diol having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, or 1 to 8 carbon atoms may be exemplified.

The kind of the polyvalent isocyanate compound contained in the mixture is not particularly limited, and a component commonly used for forming a hard segment can be used. Examples of such components include aliphatic or aromatic diisocyanates such as toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoboron diisocyanate, tetramethyl xylene diisocyanate, methylene diphenyl diisocyanate, and naphthalene diisocyanate. Isocyanates can be exemplified, but are not limited thereto.

The mixture may further comprise various components known to be applicable to the manufacture of TPU films in addition to the components described above.

The proportions of the components in the mixture are not particularly limited and may be selected so that the soft and hard segments are present in appropriate proportion in the TPU film to exhibit the properties described above. In one example, the total weight of the polyisocyanate component and chain extender in the mixture may range from about 1 to 90 parts by weight relative to 100 parts by weight of the polyol component. Unless otherwise specified, unit weight parts in the present specification means the weight ratio between the components. For example, the mixture may comprise from 1 part by weight to 50 parts by weight or from 5 parts by weight to 45 parts by weight, relative to 100 parts by weight of the polyol component, of a polyisocyanate compound and from about 0.1 to about 30 parts by weight, And 0.5 to 20 parts by weight of a chain extender. Within this range, soft and hard segments in the TPU can be present in the appropriate proportions as contemplated herein.

The method of producing TPU by reacting the mixture and the method of producing the film using TPU are not particularly limited, and the known methods for the production of TPU and the production of film can be employed without limitation.

The thickness of the base film is not particularly limited and may be selected within a range that exhibits the above-described characteristics, and may be within a range of, for example, about 50 탆 to 300 탆 or about 100 탆 to 200 탆, no.

A pressure-sensitive adhesive layer may be formed on the surface of the base film as described above. Such a pressure-sensitive adhesive layer can be used for adhering a polarizing functional material layer and a base film in a stretching step described later.

As the adhesive, various kinds can be used without particular limitation. For example, an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, a silicone pressure-sensitive adhesive or a rubber pressure-sensitive adhesive may be used as the pressure-sensitive adhesive.

In one example, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer, and may include, for example, an acrylic polymer crosslinked by a polyfunctional crosslinking agent.

The acrylic polymer is, for example, weight-average molecular weight may be used (M _w Weight Average Molecular Weight) of not less than 400,000. The weight average molecular weight is a value converted to standard polystyrene measured by GPC (Gel Permeation Chromatograph). Unless otherwise specifically stated herein, the term "molecular weight" means weight average molecular weight. The upper limit of the molecular weight of the acrylic polymer is not particularly limited, and can be controlled within a range of, for example, 2.5 million or less.

The acrylic polymer may include, for example, a polymerizable monomer having a (meth) acrylic acid ester monomer and a crosslinkable functional group. The weight ratio of each monomer in the above is not particularly limited, and can be designed, for example, in consideration of the desired peeling force.

As the (meth) acrylic acid ester monomer contained in the polymer, for example, alkyl (meth) acrylate can be used. In consideration of the cohesive force of the pressure-sensitive adhesive, the glass transition temperature, (Meth) acrylate. Examples of the monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (Meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl But are not limited to, one or more of octyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate.

The copolymerizable monomer having a crosslinkable functional group can be copolymerized with the other monomer contained in the (meth) acrylic acid ester monomer or the polymer and provides a crosslinking point capable of reacting with the multifunctional crosslinking agent in the main chain of the polymer after copolymerization It is a monomer that can be. The crosslinkable functional group may be a hydroxyl group, a carboxyl group, an isocyanate group, a glycidyl group or an amide group, and in some cases, it may be a photo-crosslinkable functional group such as an acryloyl group or a methacryloyl group. In the case of a photocrosslinkable functional group, a compound having a photocrosslinkable functional group may be reacted with the crosslinkable functional group provided by the copolymerizable monomer. In the production of pressure-sensitive adhesives, various copolymerizable monomers that can be used in accordance with desired functional groups are known. Examples of such monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl Monomers having a hydroxyl group such as 8-hydroxyoctyl (meth) acrylate, 2-hydroxyethyleneglycol (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate; (Meth) acryloyloxypropionic acid, 4- (meth) acryloyloxybutyric acid, acrylic acid dimer, itaconic acid, maleic acid, and Monomers having a carboxyl group such as maleic anhydride and the like; But are not limited to, glycidyl (meth) acrylate, (meth) acrylamide, N-vinylpyrrolidone or N-vinylcaprolactam. One or more of such monomers may be contained in the polymer.

The acrylic polymer can be prepared, for example, by solution polymerization, photo polymerization, bulk polymerization, suspension polymerization, or emulsion polymerization.

The kind of the polyfunctional crosslinking agent for crosslinking the acrylic polymer in the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include those which are present in the polymer in a known crosslinking agent such as an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, A suitable crosslinking agent may be selected depending on the kind of the crosslinkable functional group. Examples of the isocyanate crosslinking agent include diisocyanates such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoboron diisocyanate, tetramethylxylene diisocyanate, and naphthalene diisocyanate, and diisocyanates such as diisocyanate And a reaction product of a polyol and the like. As the polyol, trimethylol propane or the like may be used. Examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N ', N'-tetraglycidylethylenediamine, glycerin diglycidyl ether, Aziridine crosslinking agents such as N, N'-toluene-2,4-bis (1-aziridine carboxamide), N, N'-diphenylmethane- (2-methyl aziridine) or tri-1-aziridinyl phosphine oxide, and examples of the metal chelate crosslinking agent include acetyl (meth) acrylate Examples of the polyvalent metal include aluminum, iron, zinc, tin, titanium, antimony, magnesium or vanadium, and the like. Examples of the polyvalent metal include compounds in which a polyvalent metal is coordinated with a compound such as acetone or ethyl acetoacetate. A polyfunctional acrylate or the like can be used. In consideration of the kind of the crosslinkable functional group contained in the polymer, one or more crosslinking agents may be used.

The weight ratio of the polyfunctional crosslinking agent in the pressure-sensitive adhesive layer can be adjusted, for example, in consideration of the desired peeling force.

The pressure-sensitive adhesive layer can be formed, for example, by coating a coating solution containing an acrylic polymer and a polyfunctional crosslinking agent as described above, and inducing a crosslinking reaction between the polymer and the polyfunctional crosslinking agent under appropriate conditions.

The thickness of the pressure-sensitive adhesive layer is not particularly limited as it can be appropriately selected in consideration of the application to be used, for example, the desired peel force and the like.

The present application also relates to a laminate including the base film and a polarizing functional material layer formed on one side or both sides of the base film, for example, a laminating laminate. This laminate can be stretched to form a film exhibiting a polarization function (hereinafter referred to as a polarizing film).

The type of the polarizing functional material layer is not particularly limited as long as it can exhibit a function of polarizing by stretching, for example, capable of extracting only light vibrating in one direction from light incident on the light while vibrating in various directions, A layer containing a PVA resin can be exemplified. The PVA-based resin can be obtained, for example, by gelling a polyvinyl acetate-based resin. The polyvinyl acetate-based resin that can be used at this time may include not only homopolymers of vinyl acetate but also copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of the monomer copolymerizable with vinyl acetate include monomers such as unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group, or a mixture of two or more thereof. no. The degree of gelation of the PVA resin is usually 85 mol% to 100 mol% or 98 mol% or more, but is not limited thereto. The PVA resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with an aldehyde may be used. The degree of polymerization of the PVA-based resin may generally be about 1,000 to 10,000 or about 1,500 to 5,000.

The method of forming the polarizing functional material layer containing a PVA resin or the like on one surface or both surfaces of the base film is not particularly limited. For example, a coating liquid prepared by dissolving a material such as PVA resin in a solvent such as water is applied to the base film, or a film formed by forming a raw material such as a PVA resin , A polarizing functional film), for example, a PVA resin film or the like laminated on a base film. Although not particularly limited, a method of attaching the polarizing function film to the base film in the above-described manner may be used in consideration of the proper stretching process and the function of the polarizing film obtained after stretching. In this process, the polarizing function film can be performed through the above-mentioned pressure-sensitive adhesive layer.

In the laminate, a dichroic material may be dyed in the polarization-functional material layer. Any kind of dichroic substance may be used as long as it is known to exhibit appropriate dichroism and be used for the production of a polarizing film. Examples of the dichroic materials include iodide, organic dyes, and mixtures thereof. Examples of the iodide include lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, valium iodide, Calcium, tin iodide, or titanium iodide. However, the present invention is not limited thereto.

The thickness (thickness before stretching) of the polarizing functional material layer in the laminate is not particularly limited and may be selected within an appropriate range in consideration of the thickness after stretching. For example, the thickness of the polarizing functional material layer may be in the range of 15 mu m to 100 mu m. The thickness range may be in the range of 20 탆 to 90 탆, 20 탆 to 80 탆, 20 탆 to 70 탆, 20 탆 to 60 탆, 20 탆 to 50 탆, or 20 탆 to 40 탆 in another example.

The present application also relates to a method for producing a polarizing film comprising stretching a laminate comprising the laminate, that is, a base film and a polarizing functional material layer formed on one or both sides of the base film.

Prior to stretching the laminate, a dyeing process may be performed in which the layer of polar functional material is dyed with the dichroic material exemplified above. The dyeing step can be carried out, for example, by immersing the laminate in a dyeing solution. The dyeing solution can be prepared, for example, by dissolving the above-mentioned dichroic substance in a solvent. As the solvent of the dyeing solution, usually water is used. The ratio of the dichroic substance in the dyeing solution is not particularly limited. Typically the dyeing solution may comprise from about 0.1 to 4.3 parts by weight of a dichroic material relative to 100 parts by weight of the solvent. As the dichroic material, the above-mentioned materials can be used. When iodine is used as the dichroic substance, iodide can be further added to the dyeing liquid from the viewpoint of promoting dissolution of iodine and improving dyeing efficiency. The iodide may be added in an amount of about 0.02 part by weight to 20 parts by weight or 0.1 part by weight to 10 parts by weight, based on 100 parts by weight of the solvent, but is not limited thereto. Examples of the iodide include, but are not limited to, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. The immersion time in the dyeing solution is usually about 5 seconds to 5 minutes, and the temperature of the dyeing solution in this process may be usually in the range of 20 to 50 캜, but is not limited thereto.

Following the dyeing process or without a dyeing process, the stretching process may proceed. The manner of performing the stretching process is not particularly limited and can be performed in a known manner. The stretching of the laminate can be carried out in a solution, for example, an aqueous solution. The temperature of the solution in which the stretching process is performed is not particularly limited as long as proper stretching can be performed, and may be usually in the range of 85 占 폚 or less, 20 占 폚 to 70 占 폚, or 30 占 폚 to 65 占 폚. The stretching may be performed so that the thickness of the stretched polarizing film is in the range of about 10 mu m or less, about 8 mu m or less, about 7 mu m or less, about 6 mu m or less, or about 5 mu m or less. The lower limit of the thickness of the stretched polarizing film is not particularly limited and may be, for example, about 0.5 占 퐉 or more, 1 占 퐉 or more, 1.5 占 퐉 or more, 2 占 퐉 or more, or about 2.5 占 퐉 or more. For this purpose, the stretching can be carried out at a draw magnification of, for example, about 2 to 15 times or about 5 to 15 times. The dichroic material of the polarizing function material layer or the polarizing film can be appropriately oriented within the range of the stretching magnification described above.

If necessary, the stretching process can be carried out together with the crosslinking process. The crosslinking step can be carried out, for example, by immersing the laminate in an aqueous solution of boric acid. When the stretching step is carried out in the aqueous boric acid solution, the stretching can proceed with crosslinking. The crosslinking step is also a step of insolubilizing the PVA resin of the swollen polarizing functional material layer or the polarizing film so as not to dissolve in water.

The boric acid aqueous solution can be obtained by dissolving boric acid or borate in water as a solvent. In addition to boric acid or borate, boron compounds such as boron, glyoxal or glutaraldehyde may also be used. The boric acid concentration is not particularly limited, and is generally adjusted so that boric acid is present in a proportion of 1 part by weight to 10 parts by weight based on 100 parts by weight of water. For example, iodide can be added to the aqueous boric acid solution for the purpose of inhibiting the elution of iodine adsorbed to the PVA-based resin layer as the material of the polarization-functional layer. The concentration of the iodide may be generally from 0.05 to 15% by weight or from 0.5 to 8% by weight. As the iodide, the materials mentioned in the dyeing step can be used. The immersion time in the aqueous solution of boric acid is usually about 15 seconds to 5 minutes, and the temperature of the aqueous solution of boric acid is usually in the range of 20 占 폚 to 70 占 폚.

The above-mentioned crosslinking step may be carried out before the dyeing step. In this case, the process may proceed in the order of crosslinking, dyeing and stretching using an aqueous boric acid solution. When a thin polarizing film is intended to be produced, dissolution of the material of the polarizing functional material layer, for example, PVA resin, into the dyeing liquid during the dyeing process may occur, and therefore, Lt; / RTI > If necessary, a crosslinking step with an aqueous boric acid solution may be carried out from the viewpoint of reinforcing boric acid remaining in the dyeing step in all steps of the stretching step.

After the stretching process, the cleaning process can be performed. The cleaning step is a step of cleaning the remnants of the laminated film including the stretched polarizing film. If this treatment is insufficient, boric acid may precipitate from the thin polarizing film after drying the laminate. For example, the cleaning may be performed in a cleaning liquid containing potassium iodide so that a material such as PVA resin does not dissolve. The concentration of potassium iodide in the cleaning liquid may be generally about 0.5 to 10% by weight. The temperature of the cleaning liquid may be generally from 10 to 50 캜, and the immersion time may be usually from 1 second to 1 minute, but is not limited thereto.

The drying process can then proceed. As the drying step, it can be carried out by a known appropriate method, for example, naturally drying, blow drying or heat drying. The temperature and time of drying are not particularly limited and may be adjusted so that proper drying can be carried out.

The laminate including the stretched polarizing film may be used as it is, or may be used after peeling off the base film if necessary. If necessary, the base film may be peeled from the polarizing film through an appropriate transfer process, and transferred to another optical functional film.

A base film capable of effectively producing a polarizing film excellent in functions such as polarization performance while having a thickness of about 10 m or less, about 8 m or less, about 7 m or less, about 6 m or less, or about 5 m or less, Or a manufacturing method thereof is provided. According to the above, it is possible to easily produce a polarizing film by stretching a polarizing functional material such as a PVA resin while preventing the occurrence of tearing or curling in the stretching process.

1 is a cross-sectional view of one exemplary laminate.

Hereinafter, the present invention will be described in detail by way of examples and comparative examples, but the scope of the present invention is not limited by the following examples.

1. Evaluation of tensile properties

The tensile properties of the base film or the polarizing function material layer (PVA-based resin film in Examples and Comparative Examples) were evaluated in the following manner. The specimen was prepared by cutting the base film or the polarizing functional material layer of the example or comparative example so as to have a width of 15 mm and a length of 90 mm. Then, the upper and lower 10 mm of the vertical direction were wrapped by taping, and the taped portions were fixed to the measuring device (XP plus, TA). Next, a graph of a force (X-axis: distance, Y-axis: distance) measured according to the distance until the specimen is cut while the specimen is stretched in the longitudinal direction at a tensile rate of 300 mm / The elongation and tensile strength (X-axis: elongation, Y-axis tensile strength) of the specimen are plotted using the width and thickness of the specimen, Respectively. A method of evaluating tensile properties such as tensile elastic modulus, tensile elastic modulus and elongation from a tensile curve is known.

2. Restoration rate  evaluation

The restoration rate was evaluated in the following manner. First, the base film of the embodiment or the comparative example is cut so that the length is 50 mm and the length is 100 mm. Thereafter, a polyvinyl alcohol film having a length of 30 mu m and a length of 30 mu m, which are the same as those of the base film, is adhered on one surface of the base film to produce a laminate. In the above, the adhesion between the polyvinyl alcohol film and the base film is carried out using a conventional aqueous polyvinyl alcohol-based adhesive. Thereafter, the laminate is immersed in water (temperature: 60 DEG C) and then stretched five times in the longitudinal direction. Then, the polyvinyl alcohol film is peeled off from water, held at room temperature for 1 hour, and the length (T) in the longitudinal direction of the base film is measured. Subsequently, the measured length (T) is substituted into the formula "100 × (TA) / A" to obtain the restoration rate. In the above formula, A is a longitudinal length of the base film before stretching.

3. Melt index ( MI )

The melt index was measured according to ASTM D1238 by weight of a sample passing through a 500 g load and a 215 mm diameter 2.095 mm diameter orifice for 10 minutes (unit: g / 10 min).

4. Evaluation of hardness

The hardness was measured using a 2 mm thick specimen at room temperature using a shore D hardness meter (Japan ASKER).

Manufacturing example  1. Preparation of base film TPU  Film (A)

A polyester polyol having a weight average molecular weight (Mw) of about 2,000, prepared by a known esterification reaction of adipic acid and 1,4-butane diol, A TPU film was prepared in a known manner using a mixture comprising MDI (Methylene Diphenyl Diisocyanate) and 1,4-butanediol (chain extender). Specifically, the polyester polyol and methylene diphenyl diisocyanate were added to the reactor in a weight ratio of 1: 1.46 (polyester polyol: MDI), and while stirring at 80 rpm at a rate of 200 rpm while introducing nitrogen, , To prepare an isocyanate-terminated prepolymer. Subsequently, 14 parts by weight of a chain extender (1,4-butanediol) was added to 100 parts by weight of the prepolymer, and while stirring at 200 rpm while feeding nitrogen at 80 ° C, the content of isocyanate (NCO) TPU was synthesized by the reaction. The synthesized TPU was cast to prepare a TPU film having a thickness of about 50 탆.

Manufacturing example  2. Preparation of base film TPU  Film (B))

Except that a mixture of 1,4-butanediol (BD) and neopentane glycol (NPG) in a weight ratio of 1: 0.5 (BD: NPG) was used as a chain extender, Thick TPU film.

Manufacturing example  3. Preparation of Base Film TPU  Film (C)

Except that a mixture of 1,4-butanediol (BD) and neopentane glycol (NPG) in a weight ratio of 1: 1.5 (BD: NPG) was used as a chain extender, Thick TPU film.

The properties of each of the films thus prepared are summarized in Table 1 below.

TPU film PVA system
Resin film Unmatched
PET film A B C Tensile curve integral value 4343 7317 5404 1566 728 The tensile strength 51 83 53 53 66 Elongation 378 491 413 519.8 6.8 yield point 22 83 46 53 66 Elastic limit 545 390 754 120 1404 Recovery rate 19 18.8 11.3 MI 30 30 30 Hardness 80D 75D 75D Tensile Curve Integral Value Unit: Nmm
Tensile Strength Unit: MPa
Elongation Unit:%
Yield Point Unit: MPa
Elastic limit unit: MPa
Restoration Rate Unit:%
MI (at 215 ° C and 5 Kg) Unit: g / 10 min
PVA Coating Film: A film (thickness: about 30 탆) film formed by using a known PVA tnwlfmf used for polarizing film production,
The amorphous PET film (manufactured by LG Hausys)

Example  One.

On one side of the TPU film (A) prepared in Preparation Example 1, a known pressure-sensitive adhesive layer containing an acrylic copolymer crosslinked with isocyanate was applied to form a pressure-sensitive adhesive layer. Then, the PVA resin film shown in Table 1 was laminated on the pressure-sensitive adhesive layer to produce a laminate. Subsequently, the laminate was immersed in a dyeing solution (solvent: water) containing iodine and potassium iodide at a temperature of about 30 ° C for an appropriate time to adsorb iodine on the PVA resin film. The content of iodine in the dyeing solution was about 0.1 parts by weight based on 100 parts by weight of water, and the content of potassium iodide was about 0.7 parts by weight based on 100 parts by weight of water. Subsequently, the laminate was immersed in an aqueous boric acid solution containing boric acid and potassium iodide at a temperature of about 60 DEG C, and stretched until the final PVA resin film had a thickness of about 5.8 mu m (draw ratio: about 5.6 times). The PVA resin film was peeled off from the stretched laminate and measured. As a result, it was confirmed that a polarizing film having a transmittance of about 40% or more and a polarization degree of 99% or more was produced.

Example  2.

A polarizing membrane was prepared in the same manner as in Example 1, except that the TPU film (B) prepared in Preparation Example 2 was used. The transmittance of the prepared polarizing film was about 40% or more, and the degree of polarization was about 99% or more.

Example  3.

A polarizing membrane was prepared in the same manner as in Example 1, except that the TPU film (C) prepared in Preparation Example 3 was used. The transmittance of the prepared polarizing film was about 40% or more, and the degree of polarization was about 99% or more.

Comparative Example  One.

A polarizing membrane was prepared in the same manner as in Example 1, except that the amorphous PET film shown in Table 1 was used in place of the TPU film. However, in this case, as the stretching magnification increases, the PVA-based resin film is broken or the curl is severely generated, so that the polarizing film of appropriate performance can not be produced.

100:
101: base film
102: polarizing function material layer or polarizing film

Claims (15)

Wherein an integral value of the tensile curve is in the range of 2000 Nmm to 10,000 Nmm and an adhesive layer is formed on the surface, and the restoration ratio (R) in the following expression (1) is in the range of 5% to 30% Base film:
[Equation 1]
E / R > = 5,
In the formula (1), E is an elongation (unit:%) of the stretch base film measured at room temperature, R is a restoration ratio (unit:%), the restoration ratio is 50 mm, , A polyvinyl alcohol film having the same width and length and having a thickness of 30 mu m was adhered to the laminate, and the laminate was stretched 5 times in the longitudinal direction at a temperature of 60 DEG C in water (temperature: 60 DEG C) , The polyvinyl alcohol film is peeled off from the water, and the length (T) in the longitudinal direction of the base film measured after holding at room temperature for 1 hour is substituted into the formula "100 x (TA) / A" And A in the above formula is the longitudinal length of the substrate film before stretching. 2. The substrate film according to claim 1, wherein the elongation is in the range of 200% to 1500%. The substrate film according to claim 1, wherein the tensile strength is in the range of 20 MPa to 200 MPa. The film according to claim 1, wherein the integral value of the tensile curve is in the range of 2500 Nmm to 10,000 Nmm. The film blank according to claim 1, wherein the yield point is in the range of 10 MPa to 150 MPa. The film according to claim 1, wherein the elastic limit is in the range of 200 MPa to 1,000 MPa. The substrate film according to claim 1, wherein the base film comprises a thermoplastic polyurethane. An adhesive base film satisfying the following formula (1) and having a pressure-sensitive adhesive layer formed on its surface; And a polarizing function material layer adhered to the one surface or both surfaces of the base film by the pressure-sensitive adhesive layer, wherein an integral value (A) of a tensile curve of the base film and a tensile strength of the polarizing function material layer The absolute value of the difference (AB) of the integrated value (B) of the curve is 2000 N mm or more;
[Equation 1]
E / R > = 5,
In the formula (1), E is an elongation (unit:%) of the stretch base film measured at room temperature, R is a restoration ratio (unit:%), the restoration ratio is 50 mm, , A polyvinyl alcohol film having the same width and length and having a thickness of 30 mu m was adhered to the laminate, and the laminate was stretched 5 times in the longitudinal direction at a temperature of 60 DEG C in water (temperature: 60 DEG C) , The polyvinyl alcohol film is peeled off from the water, and the length (T) in the longitudinal direction of the base film measured after holding at room temperature for 1 hour is substituted into the formula "100 x (TA) / A" And A in the above formula is the longitudinal length of the substrate film before stretching. The laminate according to claim 8, wherein the polar functional material layer is a film or a coating layer comprising a polyvinyl alcohol-based resin. The laminate according to claim 8, wherein the thickness of the polarizing functional material layer is in the range of 15 탆 to 100 탆. A method for producing a polarizing film, which comprises stretching the laminate of claim 8. 12. The method of manufacturing a polarizing film according to claim 11, wherein the stretching is performed at a stretching magnification within a range of 2 to 15 times the original length. 12. The method of claim 11, wherein the stretching is carried out in an aqueous solution at a temperature in the range of 20 캜 to 80 캜. 14. The method of producing a polarizing film according to claim 13, wherein the aqueous solution is an aqueous solution of boric acid. 12. The polarizing film producing method according to claim 11, wherein the thickness of the polarizing function material layer after stretching is 10 m or less.

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