CN107405909A - Mold release film - Google Patents

Abstract

The present invention provides the mold release film that a kind of visibility having after particularly heating is excellent, foreign matter generates few effect.The mold release film is the mold release film for having the first priming coat, the second priming coat and release layer containing curing type silicone resin in the base material including biaxially oriented polyester film successively lamination, and the surface resistivity values for being stripped layer surface are less than 1 × 10¹²Ω。

Description

Release film

technical field

The present invention relates to a release film, and particularly relates to a release film having an effect of excellent visibility after heat treatment and less generation of foreign matter.

Background technique

Biaxially stretched polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc. The release film of the release layer of the component is used in many fields.

However, a release film in which a release layer mainly composed of a silicone resin is provided on a biaxially stretched polyester film has a characteristic that static electricity is easily generated and charged. For example, when peeling off from an adherend such as an adhesive, peeling electrification may occur. As a result, at the processing site, not only problems caused by adhesion or entanglement of foreign matter, etc., but also problems caused by static electricity may sometimes occur. Interference will cause damage to nearby electronic components and cause serious problems such as product failure. Therefore, it is not always sufficient to rely solely on antistatic measures by equipment correspondence in the manufacturing process, and the antistatic treatment of the release film itself is strongly required under the current situation.

In order to suppress such electrification, various release films have been proposed. For example, Patent Document 1 proposes an antistatic release agent. However, the release film coated with such a release material is not sufficient because of heavy peeling from the adhesive.

In addition, Patent Document 2 proposes to provide an antistatic layer on the surface of the base film opposite to the mold release layer. However, the release film provided with an antistatic layer on the back has a certain effect on charging when the release film wound into a roll is unwound, but since the release surface has no antistatic properties, Still, the problem remains that the effect is not sufficient, or that there is no inhibitory effect on peeling electrification when the release film is peeled off from the adherend.

On the other hand, as a release film, it is often exposed to high temperature. For example, the step of applying heat to the release layer and heating the adhesive composition when drying, or heating the adherend in the state where the release film is attached.

In the application and drying process of the adhesive, heat of about 100°C to 180°C may be applied. However, as a problem of polyester films, when exposed to such high-temperature treatment, oligomers (low molecular weight components of polyester, especially cyclic trimers) contained in the films are precipitated from the inside of the films. Such precipitated oligomer penetrates the mold release layer and crystallizes inside the adhesive layer to become a foreign substance, thereby causing a problem of hindering the appearance inspection.

Therefore, depending on the application, the release film based on the biaxially stretched polyester film may not have sufficient characteristics to withstand use.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-226838

Patent Document 2: Japanese Unexamined Patent Publication No. 2002-67019

Contents of the invention

The technical problem to be solved by the invention

The present invention was made in view of the above-mentioned circumstances, and the technical problem to be solved is to provide a release film having an effect of excellent visibility after heat treatment and less generation of foreign matter. Methods used to solve technical problems

The inventors of the present invention repeatedly conducted in-depth studies on the above-mentioned technical problems, and found that the above-mentioned technical problems can be solved by setting a polyester film base material, a specific primer layer, and a mold release layer in this order, thereby completing the present invention. invention.

That is, the gist of the present invention is a release film characterized in that: a substrate comprising a biaxially stretched polyester film is sequentially laminated with a first primer layer, a second primer layer, and For the release film of the release layer of the silicone resin, the surface resistivity value of the release layer surface is less than 1×10 ¹² Ω.

The effect of the invention

According to the laminated polyester film of the present invention, even if it is treated at a high temperature for a long time, the precipitation of oligomers from the film can be suppressed, so it is possible to obtain a product with an excellent appearance that does not generate foreign matter on the surface of the release layer, and its industrial significance The use value is high.

detailed description

The base film of the release film of this invention contains polyester. The above-mentioned polyesters are phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, sebacic acid, 4,4'-diphenyl dicarboxylic acid, 1,4-cyclohexyl dicarboxylic acid, Dicarboxylic acid such as carboxylic acid or its ester with ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexyl Polyester produced by melt polycondensation of diols such as alkanedimethanol. The polyester which consists of these acid components and a diol component can be manufactured using the method normally carried out arbitrarily.

For example, the method of transesterifying a lower alcohol ester of an aromatic dicarboxylic acid with a diol, or directly esterifying an aromatic dicarboxylic acid and a diol to substantially form an aromatic dicarboxylic acid The diglycol ester, or its oligomer, is then heated under reduced pressure to make it polycondensate. Depending on the purpose, aliphatic dicarboxylic acids may also be copolymerized.

Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene 2,6-naphthalate, and polyethylene terephthalate 1,4-cyclohexanedimethanol Esters and the like may be polyesters obtained by copolymerizing the above-mentioned acid components and diol components, and may contain other components and additives as necessary.

The polyester film of the present invention has a single-layer or multi-layer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both surface layers or each layer can be made of different polyesters according to purposes.

In addition, when adding an additive to a film, it may be added to a single-layer film, or may be added to only a part of layers of a multilayer film. For example, if the film has a three-layer structure, no particles are added to the inner layer, and particles are added to one or two outer layers, thereby further achieving both slipperiness and transparency.

Moreover, it is preferable to use the polyester with few oligomer content for the polyester film of this invention. As the amount of polyester with a small oligomer content, it is preferably 50% by weight or more of the total polyester when the film has a single-layer structure, and it is preferably in contact with the primer layer when the film has a multi-layer structure. 50% by weight in the skin layer. The polyester with a small oligomer content means, for example, a polyester with a cyclic trimer content of 0.7% by weight or less. It is particularly preferable that the cyclic trimer is 0.5% by weight or less. In order to suppress the precipitation of an oligomer on the surface of a film when heating a polyester film at high temperature, a good effect can be acquired by making it 0.7 weight% or less. In addition, it is known that simply reducing the oligomer content does not result in a corresponding decrease in the amount of precipitation. In particular, when heating with an adhesive layer or the like on the surface of the film, the oligomer content is 0.5 wt. % is the limit, and the amount of precipitation can be significantly reduced.

In addition, when the surface layer of the film having a multilayer structure is made of polyester with a low oligomer content in this way, the thickness of the surface layer is usually 2 μm or more, preferably 3 μm or more. The thicker the thickness, the more the precipitation of oligomers is suppressed. According to the results of tests under various conditions in which the release film was subjected to a heating process, it is known that when the thickness of the surface layer is thinner than the above range, a sufficient low temperature cannot be obtained. Polymer precipitation inhibition effect.

In the polyester film of the present invention, particles can be contained for the purpose of ensuring the slipperiness of the film, preventing the occurrence of scratches, and the like. As such particles, for example, silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, alumina, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, Inorganic particles, such as inorganic particles, cross-linked polymer particles, organic particles such as calcium oxalate, precipitated particles during the polyester production process, and the like can also be used.

The particle size and content of the particles used are selected according to the use and purpose of the film, and the average particle size (d50) is usually 0.01 to 3 μm, preferably 0.02 to 2.5 μm, more preferably 0.03 to 2 μm. When the average particle diameter exceeds 3.0 μm, the surface roughness of the film may become excessively rough, and the particles may be easily detached from the film surface. When the average particle diameter is less than 0.01 μm, the surface roughness may be too small, and sufficient slipperiness may not be obtained.

The particle content is usually in the range of 0.0003 to 1.0% by weight, preferably 0.0005 to 0.5% by weight, based on the particle-containing polyester layer. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when it is added in excess of 1.0% by weight, the transparency of the film may be insufficient. In addition, when it is desired to particularly ensure the transparency, smoothness, etc. of the film, it is also possible to have a configuration that does not substantially contain particles. In addition, various stabilizers, lubricants, antistatic agents, and the like can be appropriately added to the film.

As a film forming method of the film of the present invention, generally known film forming methods can be employed. For example, first, the sheet obtained by melt extrusion is stretched to 2 to 6 times at 70 to 145°C by a roll stretching method to obtain a uniaxially stretched polyester film, and then, in a tenter, The stretching direction perpendicular to the stretching direction is stretched to 2 to 6 times at 80 to 160° C., and then heat-treated at 150 to 250° C. for 1 to 600 seconds to obtain a film. In addition, at this time, it is preferable to perform a method of performing 0.1 to 20% relaxation in the longitudinal and/or transverse directions in the heat treatment zone and/or the cooling zone at the exit of the heat treatment.

The first undercoat layer of the present invention can be formed by any method of so-called off-line coating, in which a coating layer is subsequently provided on a film obtained by film formation, and in-line coating, in which a coating layer is provided during film production. However, it is preferably provided by an in-line coating, especially a coating stretching method in which stretching is performed after coating.

In-line coating is a method of coating in the process of producing a polyester film. Specifically, it is a method of coating at any step from melt extrusion of polyester to biaxial stretching, thermal fixation, and winding. . In general, in a substantially amorphous unstretched sheet obtained by melting and quenching, a uniaxially stretched film obtained by stretching in the longitudinal direction (longitudinal direction), and a biaxially stretched film before heat setting Any one of them can be applied. In particular, as a coating stretching method, a method of stretching in the transverse direction after coating a uniaxially stretched film is excellent. According to the above method, since film formation and coating layer coating can be performed at the same time, there is an advantage in manufacturing cost. Since the film is stretched after coating, uniform coating is achieved on the film, so the characteristics of the coating layer are stable. . In addition, the polyester film before biaxial stretching is first covered with a resin layer constituting the coating layer, and then the film and the coating layer are simultaneously stretched, whereby the base film and the coating layer are firmly adhered to each other. . In addition, regarding the biaxial stretching of the polyester film, stretching in the transverse direction while holding the ends of the film with tenter clips, the film is constrained in the length/width direction, and heat fixation can be performed without causing High temperature is applied while maintaining planarity without wrinkles, etc. Thereby, since the heat treatment performed after coating can be made into high temperature which cannot be achieved by other methods, the film-forming property of a coating layer improves, and a coating layer and a polyester film adhere firmly. As a polyester film provided with a coating layer, the uniformity of a coating layer, the improvement of film-forming property, and the adhesion|attachment of a coating layer and a film often exhibit preferable characteristics.

In the case of the coating and stretching method, for reasons of operation, working environment, and safety, the coating liquid used is desirably an aqueous solution or an aqueous dispersion, as long as water is used as the main medium and does not exceed the scope of the present invention. The scope of the gist may also contain organic solvents.

The first undercoat layer of the present invention is preferably obtained by applying a coating solution having a crosslinking agent ratio of 70% by weight or more relative to the total non-volatile components, followed by drying. In addition, other components may be contained in the coating liquid.

The cross-linking agent used here refers to a cross-linking resin that reacts especially with heat, and examples thereof include amino resin-based, isocyanate-based, oxazoline-based, and epoxy-based resins. Also included are other polymeric crosslinking reactive compounds having reactive groups on the polymer backbone.

In the present invention, when an oxazoline-based crosslinking agent is used, it is preferable because both the suppression of oligomer precipitation from the polyester film and the appearance of the undercoat layer are satisfactory.

Moreover, since the effect of suppressing the oligomer which precipitates from a polyester film at the time of heating becomes high especially when using together 2 or more types of crosslinking agents, it is preferable. This is presumed to be because there are crosslinking agents having different reaction rates when forming the undercoat layer, thereby filling the voids of the undercoat layer more effectively, thereby serving as a layer that suppresses precipitation of oligomers.

As a result of examining various combinations, particularly high effects were obtained when an oxazoline system, an epoxy system, or an amino resin system, an oxazoline system, and an epoxy system were used in combination.

The oxazoline-based crosslinking agent is preferably a polymer containing an oxazoline group in the molecule, and can be produced by homopolymerizing an addition polymerizable oxazoline group-containing monomer or polymerizing with other monomers. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl- 2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazole phenoline etc., and these 1 type or the mixture of 2 or more types can be used. Among these, 2-isopropenyl-2-oxazoline is preferable because it is easy to obtain industrially, and other monomers may be any monomers that can be copolymerized with addition polymerizable oxazoline group-containing monomers.

Moreover, in the oxazoline type crosslinking agent of this invention, content of an oxazoline group is 0.5-10 mmol/g normally, Preferably it is 3-9 mmol/g, More preferably, it is the range of 5-8 mmol/g. In particular, when two or more crosslinking agents are used in combination, a high effect can be obtained by selecting an oxazoline-based crosslinking agent in the above-mentioned range.

The epoxy-based crosslinking agent is a compound having an epoxy group in the molecule, for example, epichlorohydrin and hydroxy or amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerol, bisphenol A, etc. Condensates of polyepoxides, diepoxides, monoepoxides, glycidylamine compounds, etc.

Examples of polyepoxides include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglyceryl polyglycidyl ether, triglycidyl tris(2-hydroxyethyl)isocyanate , glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether; as diepoxy compounds, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, m-benzene Diphenol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether; as Monoepoxides, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether; as glycidyl amine compounds, N, N, N', N'-tetra Glycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylamino)cyclohexane, etc.

Among amino resin-based cross-linking agents, the cross-linking agent obtained by methylolating the amino group of melamine resin and then methylating a part of its methylol group is water-soluble, easy to handle, and has low reactivity. High, and the release film excellent in the adhesiveness of an undercoat layer and a base film, and the durability of an undercoat layer can be obtained.

Moreover, when the said crosslinking component is contained, the component for promoting crosslinking, for example, a crosslinking catalyst etc. can be used together.

The coating liquid for forming the first undercoat layer may contain substances other than the above-mentioned components as necessary. For example, surfactants, other binders, granules, defoamers, applicability improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments, and the like. These additives may be used alone or in combination of two or more as necessary.

Moreover, the thickness of a 1st primer layer is finally the range of 0.003-1 micrometer, Preferably it is 0.005-0.5 micrometer, More preferably, it is 0.01-0.2 micrometer as a film thickness on the biaxially stretched polyester film. When the thickness is thinner than this range, the amount of oligomers precipitated from the film may not be sufficiently reduced. Moreover, when it is thicker than this range, problems, such as deterioration of the appearance of a 1st primer layer and easy blocking, may arise.

In addition, the thickness of the first undercoat layer can be confirmed by dyeing the coating film with a heavy metal such as a ruthenium compound or an osmium compound, adjusting the cross section of the coating film by ultrathin sectioning, and then examining the coating film with a transmission electron microscope. The coating layer of the cross-section of the cloth film was observed at multiple locations, and the measured values were averaged.

As a method of coating a coating liquid on a polyester film, for example, a coating technique as described in "Coating Method" ("Coating Method") written by Yuji Harasaki, Maki Shoten, 1979, can be used. Specifically, air knife coater, blade coater (blade coater), bar coater, knife coater (knife coater), extrusion coater, dip coater, reverse roll coater, etc. Machine, transfer roll coater, gravure coater, roll coater, cast coater, spray coater, curtain coater, calender coater, extrusion coater and other technologies.

In addition, in order to improve the applicability and adhesiveness of the coating agent to the film, the film may be subjected to chemical treatment, corona discharge treatment, plasma treatment, etc. before coating.

In addition, the second undercoat layer of the present invention is obtained by applying a coating liquid containing a thiophene-based conductive compound and drying it. The thiophene-based conductive polymer mentioned here preferably refers to a polymer obtained by doping a compound containing thiophene or a thiophene derivative with another anionic compound, or a compound containing thiophene or a thiophene derivative. Anionic-based self-doping polymers. These substances are suitable because they exhibit excellent electrical conductivity.

As the compound (A), for example, a compound obtained by polymerizing a compound of the following formula (1) or (2) in the presence of a polyanion can be exemplified.

In the above formula (1), R ¹ and R ² independently represent hydrogen or an aliphatic hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group, etc. having 1 to 20 carbon atoms.

In said formula (2), n represents the integer of 1-4.

As the polyanion mentioned here, poly(meth)acrylic acid, polymaleic acid, polystyrenesulfonic acid, polyvinylsulfonic acid, etc. can be illustrated, for example.

In addition, as a method for producing the above-mentioned polymer, for example, a method disclosed in JP-A-7-90060 can be employed.

In the present invention, an embodiment in which n=2 in the compound of the above formula (2) and polystyrenesulfonic acid is used as the polyanion is exemplified as a particularly preferable embodiment.

In addition, when these polyanions are acidic, some or all of them may be neutralized. As the base used for neutralization, ammonia, organic amines, and alkali metal hydroxides are preferable.

The coating liquid for forming the second undercoat layer may contain various components other than these.

For example, polyether resin, polyester resin, acrylic resin, polyurethane resin, vinyl resin, epoxy resin, amide resin, etc. are mentioned. These respective skeleton structures may have a composite structure substantially by copolymerization or the like. Examples of the resin having a composite structure include acrylic resin-grafted polyester, acrylic resin-grafted polyurethane, vinyl resin-grafted polyester, vinyl resin-grafted polyurethane, and the like. By containing these resins, the intensity|strength of the coating layer obtained, and the adhesiveness with a base film, another primer layer, and a mold release layer may be improved. From the standpoint of stability when mixed with thiophene-based conductive polymers, it is easy to use polyester resins obtained by copolymerizing sulfoisophthalic acid, acrylic resins using reactive emulsifiers, and non-ionic emulsifiers. acrylic resin, urethane resin in which a carboxyl group is introduced into the skeleton using dimethylolpropionic acid or dimethylolbutyric acid, etc.

Furthermore, for example, glycerol, polyglycerol, glycerol or an alkylene oxide adduct of polyglycerol, polyalkylene oxides, polysaccharides, compounds having an amino group, and the like may be contained. When these compounds are contained, the effect of improving the transparency and antistatic performance of the obtained 2nd undercoat layer may be acquired.

Further, for the purpose of improving the fixability and slipperiness of the undercoat layer, inorganic particles may be contained, and specific examples thereof include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt, and the like.

In addition, antifoaming agents, applicability improving agents, thickeners, organic lubricants, organic polymer particles, antioxidants, ultraviolet absorbers, foaming agents, dyes, and the like may be contained as necessary.

Within the range not exceeding the gist of the present invention, for the purpose of improving dispersibility, improving film-forming properties, etc., only one type of organic solvent may be used, or two or more types may be used as appropriate.

A compound solution obtained by dispersing with water can also be diluted with a water-miscible organic solvent, such as alcohols, to form a coating solution.

The coating amount of the second undercoat layer of the present invention is usually in the range of 0.01 to 1 μm, preferably 0.02 to 0.5 μm as the thickness of the film after drying. When the coating amount is less than 0.01 μm, the antistatic performance may become insufficient, or the performance may become uneven depending on the position. On the other hand, when the coating exceeds 1 μm, the strength of the coating film may be weak and fall off, or the curing of the silicone of the release layer may be hindered.

In addition, the thickness of the second undercoat layer can be confirmed by dyeing the coating film with a heavy metal such as a ruthenium compound or an osmium compound, adjusting the cross section of the coating film by an ultrathin section method, and then examining the coating film with a transmission electron microscope. The coating layer of the cross-section of the cloth film was observed at multiple locations, and the measured values were averaged.

In the present invention, the method of providing the second undercoat layer can utilize, for example, a coating technique as shown in "Coating method" ("coating method") written by Yuji Harasaki, Maki Shoten, 1979. Specifically, air knife coaters, blade coaters, bar coaters, knife coaters, squeeze coaters, dip coaters, reverse roll coaters, transfer roll coaters, Gravure coater, roller lick coater, cast coater, spray coater, curtain coater, calender coater, extrusion coater and other technologies.

In the present invention, regarding the curing conditions when forming the second undercoat layer on the polyester film, heat treatment is usually performed at 100°C or higher, preferably at 100°C to 200°C for 3 to 40 seconds, more preferably at 120°C to 160°C. The heat treatment is performed for 3 to 40 seconds as a standard. In addition, if necessary, active energy ray irradiation such as heat treatment and ultraviolet irradiation may be used in combination. When the heat treatment is not performed at 100° C. or higher, the curing of the coating layer is insufficient, so the variation in the antistatic performance and the peeling force of the release layer increases, which is not preferable.

In the present invention, a release layer containing a curable silicone resin is further provided on the first primer layer and the second primer layer on the biaxially stretched polyester film obtained as described above. It may be a type mainly composed of a curable silicone resin, or a modified silicone type obtained by graft polymerization with organic resins such as polyurethane resins, epoxy resins, and alkyd resins.

As the type of curable silicone resin, any curing reaction type such as addition type, condensation type, ultraviolet curing type, electron beam curing type, and solvent-free type can be used.

If specific examples are given, Shin-Etsu Chemical Co., Ltd. products KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, Dow Corning Asia Co., Ltd. DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, Toshiba Silicones Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, Dow Corning Toray Co., Ltd. make SD7220, SD7226, SD7229, etc. Moreover, in order to adjust the releasability of a mold release layer, etc., you may use a peeling control agent together.

Addition-type curable silicone resins are preferable from the viewpoint that the obtained mold release layer has excellent peeling properties and does not impose an environmental load such as the use of an organotin catalyst.

Addition-type curable silicone has a technical problem that the curing reaction tends to be insufficient on a layer containing a large amount of nitrogen, such as the first undercoat layer of the present invention. Insufficient curing reaction tends to cause problems such as the silicone mold release layer being easily peeled off from the film, or the peeling property becoming unstable. However, such curing inhibition can also be suppressed by providing the second undercoat layer as in the present invention.

In the present invention, conventionally known coating methods such as reverse roll coating, gravure coating, bar coating, and doctor blade coating can be used as a method of providing a release layer on the polyester film.

The coating amount of the release layer of the present invention is usually in the range of 0.01 to 1 g/m ² as a dry film after the release layer is formed. The coating amount of the release layer can be calculated from the weight concentration of the coating material, the coating area, and the usage-amount of the coating material. When the coating amount is less than this range, it may be difficult to obtain uniform releasability, and when it is more than this range, problems such as blocking may occur.

Moreover, as mentioned above, the coating amount can also be calculated|required by confirming the thickness of a mold release layer from a cross section with a transmission electron microscope, and dividing by a specific gravity. Generally, the specific gravity of curable silicone is about 0.9 to 1.2 in many cases. When the specific gravity is 1, the coating amount of the release layer having a thickness of 0.1 μm is 0.1 g/m ² .

Regarding the biaxially oriented polyester film used in the present invention, it is preferable that the inclination of the orientation main axis is 12 degrees or less depending on the method of use. In addition, the inclination of the orientation main axis mentioned here is also called an orientation angle, and means the inclination with respect to the main axis of a film width direction or a longitudinal direction. In the method of using the mold release film, inspection may be performed by the crossed Nicol prism method of polarized transmitted light. For example, when a polarizing plate is bonded with a release film via an adhesive, when the crossed Nicol method is used as the inspection of the polarizing plate, the release film is also placed under the crossed Nicol prism at the same time. In this inspection step, when a release film using a biaxially oriented polyester film having an orientation angle of more than 12 degrees is used, light leakage is large, which hinders detection of defects such as foreign matter and flaws.

In the biaxially oriented polyester film of the present invention, the direction of the main axis of orientation can be adjusted by changing conditions such as the temperature and draw ratio of longitudinal stretching, the temperature and draw ratio of lateral stretching, and relaxation treatment.

Example

The following examples are given to illustrate the present invention in more detail, but the present invention is not limited to the following examples unless the gist is exceeded.

In addition, the evaluation methods in Examples and Comparative Examples are as follows.

(1) Determination method of intrinsic viscosity of polyester:

1 g of polyester was accurately weighed, 100 ml of a mixed solvent of phenol/tetrachloroethane=50/50 (weight ratio) was added to dissolve it, and the measurement was performed at 30°C.

(2) Determination method of ester-containing cyclic terpolymer contained in polyester raw materials:

Weigh about 200 mg of the polyester raw material and dissolve it in 2 ml of a mixed solvent with a ratio of chloroform/HFIP (hexafluoro-2-isopropane) of 3:2. After dissolution, 20 ml of chloroform was added, and then 10 ml of methanol was added little by little. The precipitate was removed by filtration, and then the precipitate was washed with a mixed solvent of chloroform/methanol ratio of 2:1, and the filtrate and washing liquid were collected, concentrated by an evaporator, and dried to solidify. After dissolving the dried solidified product in 25 ml of DMF (dimethylformamide), the solution was subjected to liquid chromatography ("LC-7A" manufactured by Shimadzu Corporation) to obtain the amount of oligomers in DMF, and the The value was divided by the amount of the polyester raw material dissolved in the chloroform/HFIP mixed solvent to obtain the oligomer-containing amount (% by weight). The amount of oligomers in DMF was obtained by the peak area ratio of the peak area of the standard sample and the peak area of the measured sample (absolute calibration curve method).

The standard sample was prepared by accurately weighing preliminarily fractionated oligomers (cyclic trimers) and dissolving them in accurately weighed DMF. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg/ml.

In addition, the conditions of liquid chromatography were set as follows.

Mobile Phase A: Acetonitrile

Mobile phase B: 2% acetic acid in water

Column: "MCI GEL ODS 1HU" manufactured by Mitsubishi Chemical Corporation

Column temperature: 40°C

Flow rate: 1ml/min

Detection wavelength: 254nm

(3) Determination method of average particle size (d50: μm):

The value of the cumulative (weight basis) 50% of the equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (SA-CP3, manufactured by Shimadzu Corporation) was defined as the average particle diameter.

(4) Determination of the direction (orientation angle) of the main axis of orientation:

The orientation of the polyester film was observed with a polarizing microscope manufactured by Carl Zeiss, and the direction of the main orientation axis in the polyester film was measured by how many degrees it was inclined relative to the width direction of the polyester film, and it was used as an orientation angle. This measurement was carried out at a total of three locations of the central part and both ends of the obtained film, and the value of the largest orientation angle among the three locations was defined as the maximum orientation angle.

(5) Coating layer thickness:

The membrane was fixed with embedding resin, the cross section was cut with a microtome, and the sample was adjusted by staining with 2% osmic acid at 60° C. for 2 hours. The obtained sample was observed with a transmission electron microscope (JEM2010 manufactured by JEOL Ltd.), and the thickness of the coating layer was measured. A total of 15 locations of the film were measured, and the average of 9 points except the 3 points with the largest numerical value and the 3 points with the smallest value was taken as the thickness of the coating layer.

(6) Erase test (rub-off test):

After the sample of the polyester film was left in a room at 23°C/50%RH for 30 days, the release surface was rubbed several times with fingertips, and the state of the release surface was judged according to the following evaluation criteria as a criterion for adhesion.

A: No change is seen on the surface of the film, good

B: Traces of rubbing with fingers are seen on the surface of the film, and the peeling force also changes

(7) Optical defect inspection of adhesive layer 1:

An acrylic adhesive COPONYL N-2233 (manufactured by Nippon Gosei Chemical Co., Ltd.) was applied to the release surface of the release film so that the thickness after drying would be 2 μm, thereby providing an adhesive layer. After affixing the release film to the glass plate via this adhesive layer, it heated at 180 degreeC for 10 minutes. Thereafter, the release film was peeled off, followed by sticking to a glass plate, and aging treatment was performed for 10 days in an environment of 60° C. and 90% RH with the adhesive layer sandwiched between the two glass plates. After that, foreign matter generated in the adhesive layer was checked under an optical microscope. For the inspection, 12 areas of 100 mm x 100 mm are selected from any part of the sample, and the number of foreign objects with a size of 2 μm or more is counted. Except for the 2 with the largest number of foreign objects among all 12 inspection areas, the judgment is made according to the following criteria based on the total number of foreign objects in the 10 inspection areas.

A: No foreign matter can be seen

B: 1 or more and less than 3 foreign objects (a little practical problem)

C: There are 3 or more foreign substances (a practical problem)

(8) Optical defect inspection of adhesive layer 2:

An acrylic adhesive COPONYL N-2233 (manufactured by Nippon Gosei Chemical Co., Ltd.) was applied to the release surface of the release film so that the thickness after drying would be 2 μm, thereby providing an adhesive layer. After affixing the release film to the glass plate via this adhesive layer, it heated at 180 degreeC for 30 minutes. Thereafter, the release film was peeled off, followed by sticking to a glass plate, and aging treatment was performed for 10 days in an environment of 60° C. and 90% RH with the adhesive layer sandwiched between the two glass plates. After that, foreign matter generated in the adhesive layer was checked under an optical microscope. For the inspection, 12 areas of 100 mm x 100 mm are selected from any part of the sample, and the number of foreign objects with a size of 2 μm or more is counted. Except for the 2 with the largest number of foreign objects among all 12 inspection areas, the judgment is made according to the following criteria based on the total number of foreign objects in the 10 inspection areas.

A: No foreign matter can be seen

B: 1 or more and less than 3 foreign objects (a little practical problem)

C: There are 3 or more foreign substances (a practical problem)

(9) Surface resistivity:

Using the Mitsubishi Chemical Corporation low resistivity meter: Loresta GP MCP-T600, the sample was conditioned for 30 minutes in a measurement atmosphere of 23° C. and 50% RH, and then the surface resistivity of the release layer was measured. The lower the surface resistivity value is, the more excellent the antistatic effect is, and it is good when it is less than 1×10 ¹² Ω, and very good when it is less than 1×10 ⁸ Ω.

(10) Visual inspection under crossed Nicol prism:

The release film was brought into close contact with the polarizing plate through an adhesive so that the width direction of the release film was parallel to the orientation axis of the polarizer to prepare a sample. Overlay the inspection polarizer on the release film after adhesion so that the orientation axis is perpendicular to the film width direction, irradiate white light from the polarizer side, and visually observe through the inspection polarizer, and evaluate the perpendicularity according to the following criteria Visual inspection under Nicol prism.

A: No light interference, can be inspected

B: There is light interference, but can be inspected

C: light interference, difficult to check

The references of A and B are practically preferable levels.

The polyesters used in Examples and Comparative Examples are the following polyesters.

(polyester 1):

Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, as a catalyst, take 0.09 parts by weight of magnesium acetate tetrahydrate and place it in the reactor. At the same time, the reaction temperature was gradually increased, so that it was 230° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230°C to 280°C. On the other hand, the pressure was gradually decreased from normal pressure to finally 0.3 mmHg. After the reaction started, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The obtained polyester 1 had an intrinsic viscosity of 0.63 and an oligomer (cyclic trimer) content of 0.97% by weight.

(polyester 2):

Polyester 1 was pre-crystallized at 160° C., and then solid-phase polymerized at 220° C. under a nitrogen atmosphere to obtain polyester 2 having an intrinsic viscosity of 0.75 and an oligomer (cyclic trimer) content of 0.46% by weight.

(polyester 3):

In the manufacture method of polyester 1, after adding 0.04 part of ethyl acid phosphate, adding 1.5 parts of synthetic calcium carbonate particles and 0.04 part of antimony trioxide dispersed in ethylene glycol with an average particle diameter (d50) of 0.8 μm, Polyester 3 was obtained by the same method as the production method of polyester 1 except that the polycondensation reaction was stopped at a point corresponding to an intrinsic viscosity of 0.65. The obtained polyester 3 had an intrinsic viscosity of 0.65 and an oligomer (cyclic trimer) content of 0.91% by weight.

As the composition contained in the coating solution for forming the first undercoat layer, the following were used.

(C1): A polymer-type crosslinking agent having an oxazoline group grafted to an acrylic resin (EPOCROS manufactured by Nippon Catalase Co., Ltd.) The amount of oxazoline group=7.7mmol/g

(C2): A polymer-type crosslinking agent (EPOCROS manufactured by Nippon Catalase Co., Ltd.) with an oxazoline group grafted to an acrylic resin. Amount of oxazoline group = 4.5 mmol/g

(C3): Polyglycerol polyglycidyl ether with epoxy content = 5.5 (eq/kg)

(C4): Hexamethoxymethylolated melamine with imino/methylol/methoxy molar ratio of 1.5/2/2.5

(T1): 2-amino-2-methylpropanol hydrochloride

(B1): A water-soluble acrylic resin having a glass transition point of 44°C obtained by polymerization with the following composition

Methyl methacrylate/isobutyl acrylate/2-hydroxyethyl methacrylate=50/30/10

(B2): In the presence of alkoxypolyethylene glycol methacrylate as a reactive emulsifier, alkyl acrylate, alkyl methacrylate, methacrylic acid, N-methylolacrylamide An aqueous dispersion of acrylic resin obtained by copolymerization of the main component, with a glass transition point of 50°C, an acid value of 14 mgKOH, and an average particle diameter of 0.05 μm.

(F1): Silica particles with an average particle size of 0.07 μm measured by the BET method

(S1): surfactant Surfynol 465 (manufactured by Air Products)

As the composition contained in the coating solution for forming the second undercoat layer, the following were used.

(A1): The coating material SEPLEGYDA AS-Q01 (manufactured by Shin-Etsu Polymer) containing a thiophene-based conductive polymer was diluted to 10 times the concentration to prepare a second undercoat layer coating liquid.

Dilution solvent: methanol/propylene glycol monomethyl ether mixed solvent (mixing ratio 4:1)

The following substances are used as the composition of the release layer.

(R1): Curable silicone resin (LTC303E: manufactured by Dow Corning Toray)

(R2): curing agent (SRX212: manufactured by Dow Corning Toray)

＜Manufacturing example of polyester film＞

(manufacturing example 1):

The material obtained by blending polyester 1 and polyester 3 at a weight ratio of 60/40 is used as the raw material of A layer, and only the material of polyester 1 is used as the material of B layer, respectively, and supplied to two vent-type twin-screw extruders , heated to 285°C to melt it, and co-extruded with two types of three-layer (A layer/B layer/A layer) layer composition in which layer A is divided into two outermost layers (surface layers) and layer B is the middle layer Take out, use the electrostatic close contact method to make it close to the mirror surface cooling drum with a surface temperature of 40-50 ° C, and cool it to solidify, and make an undrawn product with a thickness composition ratio of A layer/B layer/A layer=3/32/3 Stretched polyethylene terephthalate film. This film was stretched 2.9 times in the longitudinal direction while passing through a set of heating rolls at 90° C. to form a uniaxially oriented film. Next, the film was introduced into a tenter stretching machine, stretched 5.1 times in the width direction at 120°C, heat-treated at 210°C, and then relaxed by 5% in the width direction to obtain a biaxially oriented polyamide film with a film thickness of 38 μm. Ethylene terephthalate film.

(Manufacturing example 2):

A material obtained by blending polyester 2 and polyester 3 at a weight ratio of 60/40 is used as a raw material for layer A, and only polyester 1 is used as a material for layer B, respectively, and supplied to two vent-type twin-screw extruders , heated to 285°C to melt it, and co-extruded with two types of three-layer (A layer/B layer/A layer) layer composition in which layer A is divided into two outermost layers (surface layers) and layer B is the middle layer Take out, use the electrostatic close contact method to make it close to the mirror surface cooling drum with a surface temperature of 40-50 ° C, and cool it to solidify, and make an undrawn product with a thickness composition ratio of A layer/B layer/A layer=3/32/3 Stretched polyethylene terephthalate film. This film was stretched 2.9 times in the longitudinal direction while passing through a set of heating rolls at 90° C. to form a uniaxially oriented film. Next, the film was introduced into a tenter stretching machine, stretched 5.1 times in the width direction at 120°C, heat-treated at 210°C, and then relaxed by 5% in the width direction to obtain a biaxially oriented polyamide film with a film thickness of 38 μm. Ethylene terephthalate film.

(manufacturing example 3):

A material obtained by blending polyester 2 and polyester 3 at a weight ratio of 60/40 is used as a raw material for layer A, and only polyester 1 is used as a material for layer B, respectively, and supplied to two vent-type twin-screw extruders , heated to 285°C to melt it, and co-extruded with two types of three-layer (A layer/B layer/A layer) layer composition in which layer A is divided into two outermost layers (surface layers) and layer B is the middle layer Take out, use the electrostatic close contact method to make it close to the mirror surface cooling drum with a surface temperature of 40-50 ° C, and cool it to solidify, and make an undrawn product with a thickness composition ratio of A layer/B layer/A layer=3/32/3 Stretched polyethylene terephthalate film. This film was stretched 3.4 times in the longitudinal direction while passing through a set of heating rolls at 90° C. to form a uniaxially oriented film. Next, the film was introduced into a tenter stretching machine, stretched 4.0 times in the width direction at 120°C, heat-treated at 230°C, and then relaxed at 4.5% in the width direction to obtain a biaxially oriented polyamide film with a film thickness of 38 μm. Ethylene terephthalate film.

Example 1:

In the process of Production Example 1, the coating liquid shown in Table 1 was coated on one surface of the obtained uniaxially oriented film. Next, the film is introduced into a tenter stretching machine, and the coating liquid is dried and heat-treated by using the heat thereof, and by the same procedure as in Production Example 1, a biaxially oriented polyethylene terephthalate film having a film thickness of 38 μm is obtained. The laminated polyester film which provided the 1st primer layer of the thickness shown in Table 1 on the alcohol ester film.

The obtained film was further coated with a second undercoat layer coating liquid so that the coating thickness after drying would be 0.05 μm, followed by drying and heat treatment at 120° C. for 30 seconds.

Next, the following release layer coating was applied by the reverse gravure coating method so that the coating amount after drying was 0.1 g/m ² , and then dried and heat-treated at 150° C. for 30 seconds to obtain A release film in which a first undercoat layer, a second undercoat layer and a release layer are laminated sequentially on the film.

(R1) 100 copies

(R2) 1 copy

MEK/toluene mixed solvent (mixing ratio 1:2) 1500 parts

Embodiment 2～7, comparative example 1:

In the process of Production Example 2, the coating liquid shown in Table 1 was coated on one surface of the obtained uniaxially oriented film. Next, the film is introduced into a tenter stretching machine, and the coating liquid is dried and heat-treated by using the heat thereof, and by the same procedure as in Production Example 2, a biaxially oriented polyethylene terephthalate film having a film thickness of 38 μm is obtained. The laminated polyester film which provided the 1st primer layer of the thickness shown in Table 1 on the alcohol ester film.

The second undercoat layer coating liquid was further coated on the obtained film so as to have the coating thickness after drying shown in Table 2, and dried and heat-treated at 120° C. for 30 seconds.

Next, the following release layer coating was applied by the reverse gravure coating method so that the coating amount after drying was 0.1 g/m ² , and then dried and heat-treated at 150° C. for 30 seconds to obtain a polyester film A release film with a first primer layer, a second primer layer, and a release layer is laminated in sequence.

(R1) 100 copies

(R2) 1 copy

MEK/toluene mixed solvent (mixing ratio 1:1) 1500 parts

Embodiment 8:

In the process of Production Example 3, the coating liquid shown in Table 1 was coated on one surface of the obtained uniaxially oriented film. Next, this film is introduced into a tenter stretching machine, and the coating solution is dried and heat-treated by using its heat, and the same process as that of Production Example 3 is used to obtain a biaxially oriented polyethylene terephthalate film having a film thickness of 38 μm. The laminated polyester film which provided the 1st primer layer of the thickness shown in Table 1 on the alcohol ester film.

The obtained film was further coated with a second undercoat layer coating solution so as to have the coating thickness after drying shown in Table 2, and dried and heat-treated at 120° C. for 30 seconds.

Next, the following release layer coating was applied by the reverse gravure coating method so that the coating amount after drying was 0.1 g/m ² , and then dried and heat-treated at 150° C. for 30 seconds to obtain a polyester film A release film with a first primer layer, a second primer layer, and a release layer is laminated in sequence.

(R1) 100 copies

(R2) 1 copy

MEK/toluene mixed solvent (mixing ratio 1:1) 1500 parts

Comparative example 2:

In the same process as Examples 2-8, the release film which laminated|stacked the 2nd primer layer and the release layer sequentially on the polyester film was obtained similarly except not providing the 1st primer layer.

Comparative example 3:

In the same process as Examples 2-8, except not having provided the 2nd primer, it carried out similarly, and obtained the release film which laminated|stacked the 1st primer and the release layer sequentially on the polyester film.

[Table 1]

The weight ratios in Table 1 represent the weight ratios of the non-volatile components of the respective components in the coating liquid.

[Table 2]

Table 3 shows properties of the films obtained in Examples and Comparative Examples.

[table 3]

Industrial availability

The film of the present invention can be suitably used as a release film for use in applications where foreign matter or electrification generated on an adherend after exposure to high temperature becomes a problem. In addition, characteristics suitable for use in inspection under crossed Nicols are also imparted.

Claims (5)

1. A release film, characterized in that: It is a release film in which a first primer layer, a second primer layer, and a release layer containing a curable silicone resin are sequentially laminated on a base material including a biaxially stretched polyester film, and the surface of the release layer is The surface resistivity value is less than 1×10 ¹² Ω. 2. Release film as claimed in claim 1, is characterized in that: The first undercoat layer is a layer obtained by applying a coating solution having a crosslinking agent ratio of 70% by weight or more relative to the total non-volatile components, and drying the coating solution. 3. The release film as claimed in claim 1 or 2, characterized in that: The second undercoat layer is a layer obtained by applying a coating liquid containing a thiophene-based conductive compound and drying it. 4. The release film according to any one of claims 1 to 3, characterized in that: The polyester film layer constituting the surface in contact with the primer layer in the polyester film is a layer composed of 50% by weight or more of polyester having an oligomer content of 0.7% by weight or less, and a layer with a thickness of 2 μm or more. 5. The release film according to any one of claims 1 to 4, characterized in that: The direction of the orientation main axis of a biaxially-oriented polyester film is 12 degrees or less.