JP2018062079A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film which causes little production and adhesion of a foreign substance in a production process when various products and members are produced, and to provide a product which suppresses occurrence of defects by a foreign matter from the viewpoint of charging and oligomer precipitation for various products and members using the release film and has excellent appearance.SOLUTION: A release film is formed by layering a base material formed of a biaxially stretched polyester film, a first undercoat layer, a second undercoat layer and a release layer in this order, where the second undercoat layer contains hydrolyzable alkoxy silicate and/or its polycondensate, and the release layer contains a curable silicone resin.SELECTED DRAWING: None

Description

  The present invention relates to a release film, and more particularly to a release film with less foreign matter generation and foreign matter adhesion in the manufacturing process.

The biaxially stretched polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc., and is a release layer that uses this as a base material and is provided with a release layer mainly composed of silicone resin. Mold films are used in many fields.
However, a release film based on a biaxially stretched polyester film has a problem that it is easily charged due to its properties, and a low molecular weight component of polyester (an oligomer such as a cyclic trimer) contained in the substrate itself upon heating. There is a problem that precipitates, which may cause problems in industrial use.

For example, the release film is generally used after being bonded to another member via an adhesive layer and then peeled off. However, since the release film is easily charged, the release film is peeled off at the time of peeling. Occurs. The peeling electrification at this time may damage a member that is an adherend or cause a defect by attracting surrounding dust.
More specifically, in a coreless pressure-sensitive adhesive having a structure in which a pressure-sensitive adhesive layer is sandwiched between two release films, one release film is peeled off and bonded to another member. If dust adheres to the adhesive surface by peeling electrification at this time and is bonded to another member, the dust is trapped between the adhesive surface and the member, and re-peeling cannot be performed, resulting in a defective product.

On the other hand, it is often exposed to high temperature as an application in which a release film is used. For example, a transparent conductive film provided with an ITO sputtering layer used in a touch panel or the like is heated at about 150 ° C. for 1 hour or more in the ITO crystallization process. Such a pressure-sensitive adhesive layer and a release film for laminating the transparent conductive film may be laminated on the transparent conductive film before crystallization of ITO, and both may be subjected to a crystallization step. However, as a problem of the polyester film, when it is exposed to such a high temperature, the oligomer contained in the film is precipitated from the inside of the film. The oligomer thus precipitated migrates to the adhesive layer and crystallizes inside the adhesive layer to become a foreign substance, resulting in a product having defects.
For this reason, a release film based on a biaxially stretched polyester film did not have sufficient characteristics to withstand use depending on the application.

JP 2007-45953 A JP 2007-200823 A JP 2012-150779 A

This invention is made | formed in view of the said situation, The subject is providing the release film with few foreign material generation | occurrence | production and foreign material adhesion in a manufacturing process at the time of manufacturing various products and members.
Another object of the present invention is to obtain a product having an excellent appearance by suppressing the occurrence of defects due to foreign matters from the viewpoints of both charging and oligomer precipitation for various products and members using a release film. To do.

  As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by providing a polyester film substrate, a specific undercoat layer and a release layer. The invention has been completed.

That is, the gist of the present invention resides in the following [1] to [5].
[1] A base material composed of a biaxially stretched polyester film, a first undercoat layer, a second undercoat layer, and a release layer are laminated in this order, and the second undercoat layer comprises a hydrolyzable alkoxysilicate and A release film containing / or a polycondensate thereof, wherein the release layer contains a curable silicone resin.
[2] The release film according to [1], wherein the first undercoat layer contains the following component (A).
(A): Electronically conductive compound [3] The release film according to [1] or [2], wherein the first undercoat layer contains the following component (B).
(B): One or more compounds selected from the group of polyalkylene oxide (b1), glycerin (b2), polyglycerin (b3), and alkylene oxide adduct (b4) of glycerin or polyglycerin or derivatives thereof [4 The biaxially stretched polyester film has a multilayer structure, and the layer in contact with the first undercoat layer is a layer having a thickness of 2 μm or more containing 80% by weight or more of polyester having an oligomer content of 0.7% by weight or less [1. ] The release film according to any one of [3].
[5] A pressure-sensitive adhesive with a release film comprising the release film according to any one of [1] to [4] and a pressure-sensitive adhesive layer.

According to the release film of the present invention, problems due to charging in the manufacturing process are suppressed. Moreover, according to the release film of the present invention, oligomer precipitation from the film can be suppressed even when a high temperature treatment is performed.
For this reason, it is possible to suppress the occurrence of defects due to foreign matters from the viewpoints of both charging and oligomer precipitation, and to obtain a product having an excellent appearance with respect to a product using a release film. The utility value is high.

Hereinafter, the present invention will be described in more detail, but the present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
In the following, “mass%” and “wt%” and “part by mass” and “part by weight” have the same meaning.
The release film of the present invention comprises a substrate, a first undercoat layer, a second undercoat layer, and a release layer laminated in this order, and has any other layer as long as it has this configuration. May be. Below, each layer is demonstrated.

[Base material]
The base material in the release film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. Polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method.

  For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester used for the base material include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a copolymerized polyester and may contain other components and additives as necessary.

The polyester film in the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on the purpose.
Moreover, when adding an additive in a film, it can also add to a single layer film or only to the one part layer of a multilayer film. For example, the film has a three-layer structure, and particles are not added to the inner layer, but particles are added to one or both of the outer layers, thereby making it possible to achieve better compatibility between slipperiness and transparency.

  Moreover, it is preferable to use polyester with little oligomer content for the polyester film in this invention. The amount of the polyester having a low oligomer content is preferably 80% by weight or more of the total polyester when the film has a single layer structure, and the undercoat layer when the film has a multilayer structure. It is suitable that it is 80% by weight or more of the surface layer in contact. The polyester having a low oligomer content specifically refers to a polyester having a cyclic trimer content of 0.7% by weight or less. Particularly preferably, the content of the cyclic trimer is 0.5% by weight or less. When the polyester film is heated at a high temperature, a good effect can be obtained when the content of the cyclic trimer is 0.7% by weight or less in order to suppress oligomer precipitation on the film surface. . Also, simply reducing the oligomer content does not reduce the amount of precipitation from the polyester film accordingly, especially when heating with the adhesive layer on the film surface, etc. When the content is 0.5% by weight or less, the amount of precipitation can be significantly reduced.

  When the surface layer of the polyester film having a multilayer structure is a polyester having a low oligomer content, the thickness of the surface layer is preferably 2 μm or more, more preferably 5 μm or more. The thicker the thickness is, the more the oligomer precipitation is suppressed. However, when the thickness is smaller than the above range, the sufficient oligomer precipitation suppression effect may not be obtained.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles during the polyester production process can be used.

  The particle size and content of the particles used are selected according to the application and purpose of the film, but the average particle size (d50) is preferably 0.01 to 3 μm, more preferably 0.02 to 2.5 μm, and even more preferably. Is in the range of 0.03 to 2 μm. When the average particle diameter of the particles exceeds 3 μm, the surface roughness of the film becomes too rough, or the particles are likely to fall off from the film surface. If the average particle size is less than 0.01 μm, the surface roughness is too small, and sufficient slipperiness and scratch resistance may not be obtained.

  Although content of particle | grains is not limited, It is 0.0003 to 1.0 weight% normally with respect to the polyester layer containing particle | grains, Preferably it is 0.0005 to 0.5 weight%. When the particle content is less than 0.0003% by weight, the slipperiness and scratch resistance of the film may be insufficient. On the other hand, when the content exceeds 1.0% by weight, the film In some cases, the transparency of the film is insufficient. In addition, when it is particularly desired to ensure transparency and smoothness of the film, the film may be substantially free of particles. Further, various stabilizers, lubricants, antistatic agents and the like can be appropriately added to the film.

Although the thickness of the polyester film which is a base material in this invention is not limited, Usually, 5-500 micrometers, Preferably it is 10-300 micrometers, More preferably, it is 20-200 micrometers. When the thickness of the polyester film exceeds the above upper limit, the flexibility of the film is low, the processing suitability may be deteriorated, and the work for peeling the release film may be troubled. If the thickness of the polyester film is less than the lower limit, it is difficult to laminate the undercoat layer or the release layer, and wrinkles may occur when the polyester film is bonded to the pressure-sensitive adhesive layer.
The haze of the polyester film as the substrate in the present invention is preferably 15% or less, more preferably 5% or less, and still more preferably 3% or less. If the haze of the polyester film is larger than this range, it may be difficult to use in appearance in optical applications. In addition, the suitable numerical range of said haze is not only the haze value of the polyester film which is a base material alone, but also a laminated body provided with the first undercoat layer on the base material, and further provided with a second undercoat layer. The same numerical range is suitable for any haze of the laminated body and the laminated body (release film of the present invention) provided with a release layer.

  The polyester film used for the substrate in the present invention needs to be biaxially stretched. If the polyester film used as the base material is not biaxially stretched, the mechanical strength and dimensional stability are insufficient, causing problems in the manufacturing process using the release film.

  As a method for forming a polyester film used in the present invention, a generally known method for forming a film can be employed, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A biaxially stretched film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

[First subbing layer]
In this invention, the 1st undercoat layer is laminated | stacked with respect to the said base material. Although the 1st undercoat layer in this invention is not limited, It is preferable to contain the following (A) component.
(A): Electronically conductive compound

(A) Although an electronically conductive compound is not limited, Specifically, an electronically conductive organic compound, for example, polyacetylene, polyphenylene, polyaniline, polypyrrole, polyisothianaphthene, polythiophene, etc. are mentioned. Among these, polythiophene, that is, a polymer obtained by singly or copolymerizing thiophene or a thiophene derivative is preferable.
In particular, (A) as an electron conductive compound, a compound composed of thiophene or a thiophene derivative is doped with another anionic compound, or a compound (polymer) having an anionic group and self-doped However, it exhibits excellent conductivity and is suitable. More specifically, examples of the polythiophene include those obtained by polymerizing a compound represented by the following general formula (1) or (2) in the presence of a polyanion. Moreover, these copolymers may be sufficient and a mixture may be sufficient.

（上記式（１）中、Ｒ^１およびＲ^２は、それぞれ独立して、水素または炭素数が１〜２０の脂肪族炭化水素基、脂環族炭化水素基、芳香族炭化水素基を表す。）

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

（上記式（２）中、ｎは１〜４の整数を表す。）

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

Examples of the polyanion used at the time of polymerization include organic acids such as poly (meth) acrylic acid, polymaleic acid, and polystyrene sulfonic acid. These organic acids may be partially or completely neutralized. As a method for producing such a polymer, for example, a method as disclosed in JP-A-7-90060 can be employed.
In the present embodiment, a particularly preferred embodiment is one in which n is 2 in the compound of the above formula (2) and polystyrene sulfonic acid is used as a polyanion.

In the first undercoat layer, as the component (B), from the group of polyalkylene oxide (b1), glycerin (b2), polyglycerin (b3), and alkylene oxide adduct (b4) to glycerin or polyglycerin. It is more preferable to contain one or more selected compounds or derivatives thereof. Moreover, you may use arbitrary mixtures of (b1)-(b4) as (B) component. Component (B) is a compound that has almost no antistatic performance itself, but when used in combination with component (A), it tends to improve the appearance of the first subbing and the effect of suppressing deterioration of antistatic performance over time. There is.
When the first undercoat layer is provided by a coating and stretching method, the component (A) usually has a rigid property, and thus the coating film structure may be broken by stretching and the antistatic performance may be lost. However, combining the component (A) with the component (B) produces an effect that the antistatic performance is not lost even after stretching. For this reason, when providing a 1st undercoat layer by in-line coating (after-mentioned), it is especially suitable.

A preferable example of the polyalkylene oxide (b1) or a derivative thereof includes a structure containing an ethylene oxide or propylene oxide skeleton. If the alkyl chain in the alkylene oxide structure becomes too long, the hydrophobicity becomes strong, the uniform dispersibility in the coating solution deteriorates, and the antistatic property and transparency of the first undercoat layer tend to deteriorate. . Particularly preferred is ethylene oxide.
Examples of glycerin (b2) and polyglycerin (b3) include compounds represented by the following general formula (3).

  In the above formula (3), the compound in which n is 1 is glycerin (b2), and the compound in which n is 2 or more is polyglycerin (b3). In the present embodiment, n in the formula is preferably in the range of 1-20, more preferably in the range of 2-20. Moreover, the mixture of the polyglycerol from which n differs may be sufficient. When glycerin (b2) is used, since the transparency of the obtained first undercoat layer may be slightly inferior, polyglycerin (b3) is preferred.

  The alkylene oxide adduct (b4) to glycerin or polyglycerin has a structure obtained by addition polymerization of alkylene oxide or a derivative thereof to the hydroxyl group of the compound represented by the general formula (3). Here, the structure of the alkylene oxide added or its derivative may differ for every hydroxyl group of glycerol or polyglycerol skeleton. Moreover, it is sufficient that it is added to at least one hydroxyl group in the molecule, and it is not necessary that alkylene oxide or a derivative thereof is added to all hydroxyl groups.

  Moreover, what is preferable as an alkylene oxide or its derivative added to glycerol or polyglycerol is a structure containing ethylene oxide or a propylene oxide skeleton. When the alkyl chain unit constituting the alkylene oxide structure becomes too long, the hydrophobicity becomes strong, the uniform dispersibility in the coating liquid deteriorates, and the antistatic property and transparency of the first undercoat layer tend to deteriorate. is there. Particularly preferred is ethylene oxide.

In the present embodiment, particularly preferred embodiments of the compound (B) include polyglycerin (b3), and glycerin or an alkylene oxide adduct (b4) to polyglycerin. When polyalkylene oxide (b1) or glycerin (b2) is used, the appearance of the resulting layer may be slightly inferior.
As the polyglycerin (b3), those having n of 2 to 20 in the compound of the above formula (3) are particularly preferred. Further, as the alkylene oxide adduct (b4) to glycerin or polyglycerin, a compound in which ethylene oxide or polyethylene oxide is added to the compound of the above formula (3) where n is 2 is particularly preferable. The number of additions is particularly preferably in the range of 300 to 2000 in terms of the weight average molecular weight as the final compound (b4).

  In addition, in the alkylene oxide adduct (b4) to glycerin or polyglycerin, the copolymerization ratio of the alkylene oxide or the derivative thereof to the glycerin or polyglycerin skeleton is not particularly limited. The alkylene oxide moiety is preferably 20 or less, more preferably 10 or less. When the ratio of alkylene oxide or its derivative to glycerin or polyglycerin skeleton is larger than this range, it becomes close to the characteristics when ordinary polyalkylene oxide is used. May be inferior.

The content of the (A) electronic conductive compound in the first undercoat layer is not limited, but the upper limit is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 60% by mass or less. (A) When content of an electronically conductive compound is higher than the said upper limit, transparency of a coating film may become inadequate or antistatic performance may become inadequate.
Moreover, the lower limit of the content of the (A) electronic conductive compound in the first undercoat layer is preferably 1% by mass or more, and more preferably 2% by mass or more. (A) When content of an electronically conductive compound is lower than the said minimum, antistatic performance will become inadequate or the coating film for having sufficient antistatic performance will become very thick. When the coating film is thick, the appearance and transparency are deteriorated and the film tends to be blocked.

  Although content of the component (B) which occupies in a 1st undercoat layer is not limited, Preferably an upper limit becomes like this. Preferably it is 90 mass% or less, More preferably, it is 85 mass% or less, More preferably, it is 80 mass% or less. When content of a component (B) is higher than the said upper limit, the antistatic performance with time in a 1st undercoat layer may fall. The lower limit is preferably 5% by mass or more, more preferably 20% by mass or more, and further preferably 40% by mass or more. When content of a component (B) is lower than the said minimum, there exists a possibility that an external appearance and transparency may deteriorate.

In providing the first undercoat layer, a surfactant can be included in the coating solution in order to improve the coating property to the film (base material). That is, a surfactant can be included in the first undercoat layer. As this surfactant, it is particularly preferable to use a surfactant containing (poly) alkylene oxide, (poly) glycerin, or a derivative thereof in the structure without inhibiting the antistatic property of the resulting layer.
In the coating liquid for providing the first undercoat layer, components other than those described above can be contained as necessary. That is, the first undercoat layer can contain components other than those described above. For example, surfactants, other binders, particles, antifoaming agents, coatability 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, although the thickness of a 1st undercoat layer is not limited, Preferably it is 0.005-1.5 micrometers as a film thickness on the biaxially stretched polyester film which is a base material, More preferably, it is 0.008-1. It is 0 μm, more preferably 0.01 to 0.5 μm. When the thickness of the first undercoat layer is thinner than the lower limit, sufficient antistatic performance may not be obtained, while when the thickness of the first undercoat layer exceeds the upper limit, There is a possibility that the appearance / transparency deteriorates, the film is blocked, and the strength of the second undercoat layer is reduced.
The thickness of the first undercoat layer is determined by dyeing the film provided with the first undercoat layer with a heavy metal such as a ruthenium compound or an osmium compound, adjusting the cross section of the coated film by an ultrathin section method, and then transmitting the film. This can be confirmed by observing a plurality of coating layers on the coated film cross section with a scanning electron microscope and averaging the measured values.

As a method of providing the first undercoat layer on the substrate, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, 1979, can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And a technique such as an extrusion coater.
In addition, in order to improve the applicability | paintability to the base material of the coating agent which forms a 1st undercoat layer, and adhesiveness, you may perform a chemical process, a corona discharge process, a plasma process, etc. to a base material before application | coating.

  The first undercoat layer in the present invention is a so-called off-line coating in which a coating layer (first undercoat layer) is provided later on the film (base material) formed, and the coating layer during film formation of the film (base material). Any of so-called in-line coatings provided with a (first undercoat layer) can be employed. Especially, it is preferable to provide by the coating extending | stretching method which extends | stretches after in-line coating, especially application | coating.

  In-line coating is a method of coating within the process of manufacturing a polyester film. Specifically, it is a method of coating at any stage from melt extrusion of polyester to biaxial stretching and then heat setting and winding. is there. Normally, it is coated on either a substantially amorphous unstretched sheet obtained by melting and quenching, then a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do.

In particular, as a coating stretching method, a method of stretching in the transverse direction after coating on a uniaxially stretched film is excellent. According to such a method, since the film formation of the base material and the coating layer coating can be performed simultaneously, there is an advantage in manufacturing cost. Moreover, the polyester film before biaxial stretching is first covered with a resin layer constituting the coating layer, and then the base film and the coating layer are firmly adhered by stretching the film and the coating layer simultaneously. become. On the other hand, since the coating layer is stretched together with the base film, the coating layer may be finely broken. Depending on the purpose of the coating layer, the desired performance may not be obtained due to the fine cracks. Therefore, an optimum method may be selected from the above production methods depending on the combination of materials used.
In the case of the coating stretching method, the coating solution to be used is preferably an aqueous solution or an aqueous dispersion for safety reasons in terms of handling, working environment, and water within the range not exceeding the gist of the present invention. In addition, an organic solvent may be contained.

[Second subbing layer]
The second undercoat layer in the present invention contains a hydrolyzable alkoxysilicate and / or a polycondensate thereof. Examples of the hydrolyzable alkoxysilicate include a structure represented by the general formula Si (OR ₁ ) ₄ .
Here, R ₁ represents a hydrocarbon group having 1 to 10 carbon atoms. More specifically, R ₁ includes an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and the like. The ethoxy silicate in which R ₁ is an ethyl group is preferable because of easy hydrolysis and subsequent condensation reaction. Note that it is not necessary that all tetrafunctional R _{1 s} are the same.

Moreover, as a 2nd undercoat layer, after hydrolyzing the structure of general formula Si (OR < ₁ >) ₄ , the structure which carried out the polycondensation of two or more is also suitable. This polycondensation can also proceed to some extent in the state of the coating solution. In other words, the polycondensation proceeds in advance in the state of the coating solution to obtain a quantity body, and the quantity body is further reacted with the heat after coating to increase the coating speed or to achieve desired characteristics even in a short drying furnace. There are effects such as being able to obtain.

Furthermore, for the purpose of improving adhesion and slipperiness of the second undercoat layer, inorganic particles may be contained in the second undercoat layer. Specific examples of the inorganic particles include silica, alumina, kaolin, calcium carbonate. , Titanium oxide, barium salt and the like.
Also, if necessary, in the second undercoat layer, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, organic polymer particles, an antioxidant, an ultraviolet absorber foaming agent, a dye, etc. May be contained.

In the range not exceeding the gist of the present invention, for the purpose of improving dispersibility, improving film forming property, etc., the organic solvent used in the coating solution for providing the second undercoat layer may be only one type, and suitably two or more types. May be used.
The coating amount of the second undercoat layer in the present invention is usually in the range of 0.005 to 1 μm, preferably 0.005 to 0.5 μm, as the thickness of the coating after drying. When the coating amount is less than the above lower limit, the uniformity of coating thickness may be insufficient, and the amount of oligomer precipitated from the surface of the coating layer after heat treatment may increase. On the other hand, when the coating exceeds the upper limit, problems such as slippage deterioration may occur.

  The thickness of the second undercoat layer is determined by dyeing the film provided with the second undercoat layer with a heavy metal such as a ruthenium compound or an osmium compound, adjusting the cross section of the coated film by an ultrathin section method, and then transmitting This can be confirmed by observing a plurality of coating layers on the coated film cross section with a scanning electron microscope and averaging the measured values.

  In the present invention, as a method of providing the second undercoat layer, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And a technique such as an extrusion coater.

The second undercoat layer in the release film of the present invention does not usually continue to exist as a hydrolyzable alkoxysilicate, but exists as a cured layer by curing (polycondensation).
In the present invention, the curing conditions for forming the second undercoat layer on the first undercoat layer are not limited, but usually a heat treatment of 100 ° C. or higher is preferably given, preferably 120 to 200 ° C. for 3 to 40 seconds. More preferably, the heat treatment is performed at 120 to 160 ° C. for 3 to 40 seconds as a guide. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. When the heat treatment is not performed at 100 ° C. or higher, the amount of oligomers deposited is increased, or the coating layer is not sufficiently cured, and the variation in the peeling force of the release layer tends to be unfavorable.

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

As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet ray curable type, an electron beam curable type, and a solventless type can be used.
Specific examples include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461 manufactured by Shin-Etsu Chemical Co., Ltd .; -Corning Asia Co., Ltd. DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210; Toshiba Silicone Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721; Toray Dow Corning Co., Ltd. SD7220, SD7226, SD7229, etc. are mentioned. Further, a release control agent may be used in combination to adjust the release property of the release layer.

In the present invention, as a method for providing a release layer on the second undercoat layer, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, or the like can be used.
The coating amount of the release layer in 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 and coating area of the coating material and the usage amount of the coating material. If the coating amount is less than this, it may be difficult to obtain uniform releasability, and if it is more than this, problems such as blocking may occur.
In addition, the thickness of a mold release layer can also be calculated | required by confirming from a cross section with a transmission electron microscope as mentioned above, and dividing by specific gravity. Generally, the specific gravity of the curable silicone is often about 0.9 to 1.2. 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 .

In addition, although formation of a 2nd undercoat layer and a mold release layer can employ | adopt both off-line coating and in-line coating, it is usually off-line coating.
In addition, after the application of the second undercoat layer and the release layer, the polycondensation reaction in the second undercoat layer and the curing reaction in the release layer can be performed simultaneously.

  Although the aspect which uses the release film of this invention is not limited at all, It is preferable to use as a pressure-sensitive adhesive with a release film (pressure-sensitive adhesive sheet) by forming a laminate with a pressure-sensitive adhesive layer. one of. It is also preferable to provide release films on both sides of the pressure-sensitive adhesive layer. There are no restrictions on the material and thickness of the pressure-sensitive adhesive layer used here, and a known pressure-sensitive adhesive can be appropriately selected and used.

  The pressure-sensitive adhesive with a release film (pressure-sensitive adhesive sheet) using the release film of the present invention can suppress the occurrence of defects due to foreign matters from the viewpoints of both charging and oligomer precipitation. It can be suitably used for parts, OA equipment, automobile members, image display devices, precision parts, and the like.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In addition, the evaluation method in an Example and a comparative example is as follows.

(1) Measuring method of intrinsic viscosity of polyester 1 g of polyester was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and the measurement was performed at 30 ° C.

(2) Method for measuring content of ester cyclic trimer contained in polyester raw material Approximately 200 mg of polyester raw material is weighed and dissolved in 2 ml of a mixed solvent of chloroform / HFIP (hexafluoro-2-isopropanol) ratio 3: 2. It was. After dissolution, 20 ml of chloroform was added, and 10 ml of methanol was added little by little. The precipitate is removed by filtration, and the precipitate is washed with a mixed solvent of chloroform / methanol ratio 2: 1. The filtrate / washing solution is collected, concentrated by an evaporator, and then dried. After the dried product was dissolved in 25 ml of DMF (dimethylformamide), this solution was supplied to liquid chromatography (“LC-7A” manufactured by Shimadzu Corporation) to determine the amount of oligomer in DMF, and this value was calculated as the amount of polyester raw material. The amount of oligomer contained (% by weight) was divided. The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method).

The standard sample was prepared by accurately weighing an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml.
The conditions for the liquid chromatograph were as follows.
Mobile phase A: acetonitrile Mobile phase B: 2% by weight acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(3) Measuring method of average particle size (d50: μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(4) Coating layer thickness A film was fixed with an embedding resin, a cross section was cut with a microtome, and a sample was prepared 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 points on the film were measured, and the average of 9 points excluding 3 points from the larger value and 3 points from the smaller value was defined as the coating layer thickness.

(5) Appearance of release film The obtained release film was visually evaluated using a halogen light in a dark room, and judged according to the following criteria.
5: When there are no defects in appearance and excellent 4: When uneven appearance defects are slightly observed, but when appearance is good 3: When uneven appearance defects are observed, and appearance is normal 2: Uneven appearance If the appearance defect is slightly high and the appearance is slightly bad 1: Many uneven appearance defects are recognized and the appearance is bad

(6) Love-off test After leaving the release film in a room at 23 ° C./50% RH for 30 days, the release surface is rubbed several times with a fingertip, and the condition of the release surface is judged according to the following evaluation criteria, It was used as a measure of adhesion.
○: Good with no change on the film surface ×: Traces rubbed with fingers on the film surface are observed, and the peel force is also changed

(7) Surface resistivity (Ω)
Using a low resistivity meter (Loresta GP MCP-T600 manufactured by Mitsubishi Chemical Corporation), measure the surface resistivity of the release layer surface after conditioning the release film sample for 30 minutes in a measurement atmosphere of 23 ° C and 50% RH. did.
If the sample has a high resistance value and cannot be measured by the above method, use a high resistance measuring instrument (HP4339B and measuring electrode: HP16008B manufactured by Hewlett-Packard Japan), and measure the atmosphere at 23 ° C. and 50% RH. After adjusting the humidity of the release film sample for 30 minutes, the surface resistivity of the release layer surface was measured.
If the surface resistivity is less than 1.0 × 10 ¹⁰ Ω, the antistatic property is good.
If the surface resistivity is less than 1.0 × 10 ⁸ Ω, the antistatic property is extremely excellent.

(8) Peeling force After affixing an adhesive tape (Nitto Denko No. 31B tape, substrate thickness 25 μm) to the surface of the release layer of the release film sample, heat it for 1 hour in a 100 ° C hot air circulating thermostat. Then, after taking out from the thermostat, the peeling force after being left at 23 ° C. for 30 minutes was measured. For the peel force, a 180 ° peel test was performed using a tensile tester (“Intesco Model 2001” manufactured by Intesco Corporation) under the condition of a tensile speed of 300 mm / min.
When the peeling force is high, when used as a release film, an error in the peeling process may occur, or the adhesive may be deformed. In this test, if the peel force was 20 mN / cm or less, it was judged to be sufficiently small.

(9) Adhesive layer optical defect inspection 1
On the release surface of the release film, an acrylic pressure-sensitive adhesive Coponil N-2233 (manufactured by Nippon Synthetic Chemical Industry) was applied to a thickness of 3 μm after drying to provide an adhesive layer. The release film was attached to a glass plate via this adhesive layer, and then heated at 160 ° C. for 2.5 hours. Thereafter, the foreign matter generated in the adhesive layer was examined under an optical microscope. In the inspection, 12 areas of 100 mm × 100 mm were selected from arbitrary positions of the sample, and the number of foreign matters having a size of 5 μm or more was counted. A total of 12 foreign substances were excluded from the total of 12 inspection ranges, and the determination was made based on the following criteria from the total number of foreign substances within the 10 inspection ranges.
○: Foreign matter is not found △: Foreign matter is 1 or more and less than 3 (slightly problematic)
×: 3 or more foreign matters (problem in practical use)

(10) Adhesive layer optical defect inspection 2
The release film is peeled off from the test piece heated at 160 ° C. for 2.5 hours by the same process as in the adhesive layer optical defect inspection 1, and further adhered to the glass plate, and the adhesive layer is sandwiched between the two glass plates. A test piece in a heated state was prepared. Next, this test piece was aged for 10 days in an environment of 60 ° C. and 95% RH. By this aging treatment, the oligomer dissolved in the pressure-sensitive adhesive layer grows and becomes more apparent as a foreign substance. The foreign matter generated in the adhesive layer of the test piece was examined under an optical microscope. In the inspection, 12 areas of 100 mm × 100 mm were selected from arbitrary positions of the sample, and the number of foreign matters having a size of 5 μm or more was counted. A total of 12 foreign substances were excluded from the total of 12 inspection ranges, and the determination was made based on the following criteria from the total number of foreign substances within the 10 inspection ranges.
○: Foreign matter is not found △: Foreign matter is 1 or more and less than 3 (slightly problematic)
×: 3 or more foreign matters (problem in practical use)

The polyesters used in the examples and comparative examples are as follows.
<Polyester 1>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part by weight of ethyl acid phosphate to this reaction mixture, 0.04 part by weight of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in 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 is pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C. to obtain a polyester having an intrinsic viscosity of 0.75 and an oligomer (cyclic trimer) content of 0.46% by weight. 2 was obtained.

<Polyester 3>
In the production method of polyester 1, after adding 0.04 part by weight of ethyl acid phosphate, 0.3 part by weight of silica particles having an average particle diameter (d50) of 1.6 μm dispersed in ethylene glycol was added. Polyester 3 was obtained using the same method as the production method of polyester 1 except that .04 parts by weight was added and the polycondensation reaction was stopped at the time corresponding to the 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.

The composition contained in the coating liquid for providing the first undercoat layer was as follows.
(A1): Poly (ethylenedioxythiophene) -poly (styrenesulfonic acid) (Baytron P AG, manufactured by HC Starck)
(B1): Polyethylene oxide adduct (average molecular weight 350) to the polyglycerol skeleton where n = 2 in the formula (3)
(B2): Polyvinyl alcohol (saponification degree 88 mol%, polymerization degree 500)
(E1): A nonionic surfactant having a structure having polyethylene oxide in the side chain, represented by the following formula (4). (M + n = 10 was used)

The composition contained in the coating liquid for providing the second undercoat layer was as follows.
(S1): Hydrolyzable alkoxysilicate (Colcoat N-103X manufactured by Colcoat)
(S2): Ethylated methylol melamine (containing acid catalyst)

The composition of the release layer was as follows.
<Release layer composition 1>
(R1): curable silicone resin (LTC303E: manufactured by Toray Dow Corning)
(R2): Curing agent (SRX212: manufactured by Toray Dow Corning)
50 parts by weight of R1, 1 part by weight of R2, and 800 parts by weight of “methyl ethyl ketone / toluene / n-heptane mixed solvent (mixing ratio is 1/2/2)”

<Releasing layer composition 2>
(R3): curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.)
(R4): Curing agent (CAT-PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.)
48 parts by weight of R3, 1 part by weight of R4, and 820 parts by weight of “methyl ethyl ketone / toluene / n-heptane mixed solvent (mixing ratio is 1/2/2)”

[Example 1]
A blend of polyester 2 and polyester 3 at a weight ratio of 93/7 was used as the raw material for layer A and polyester 1 alone as the raw material for layer B. The two layers of the A layer are divided into two layers and three layers (A layer / B layer / A layer) with the B layer as an intermediate layer (A layer / B layer / A layer). Is used to cool and solidify while adhering to a mirror surface cooling drum having a surface temperature of 40 to 50 ° C., and the thickness composition ratio becomes A layer / B layer / A layer = 2.5 / 33 / 2.5, unstretched polyethylene terephthalate A film was created. This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film.
A coating solution as shown in Table 1 was applied to one side of the obtained uniaxially oriented film. Next, the film was guided to a tenter stretching machine, and the coating liquid was dried and heat-treated using the heat, stretched 4.0 times in the width direction at 100 ° C, and further heat-treated at 230 ° C. A 2% relaxation treatment was applied in the direction. Thus, a laminated polyester film was obtained in which a first subbing layer having a thickness of 0.04 μm was provided on a biaxially oriented polyethylene terephthalate film having a thickness of 38 μm.
On the first undercoat layer of the obtained film, a coating solution as shown in Table 1 was applied, dried at 130 ° C. for 30 seconds and heat-treated, and the coating thickness after drying was as shown in Table 1. An undercoat layer was provided.
Further, the release layer composition 1 was applied on the second undercoat layer by a reverse gravure coating method so that the coating amount after drying was 0.1 g / m ^2, and then dried at 150 ° C. for 30 seconds. A release film was obtained by heat treatment. Table 1 shows the results of evaluating various properties of the obtained release film.

[Example 2]
A release film was obtained in the same manner as in Example 1 except that the release layer paint was changed to the release layer composition 2. Table 1 shows the results of evaluating various properties of the obtained release film.

[Example 3]
A release film was obtained in the same manner as in Example 1 except that polyester 1 and polyester 3 blended at a weight ratio of 90/10 were used as the raw material for the A layer. Table 1 shows the results of evaluating various properties of the obtained release film.

[Example 4]
A release film was obtained in the same manner as in Example 1 except that the composition of the first undercoat layer was changed as shown in Table 1. Table 1 shows the results of evaluating various properties of the obtained release film.

[Comparative Example 1]
A release film was obtained in the same manner as in Example 2 except that the components and thickness of the second undercoat layer were changed as shown in Table 1. Table 1 shows the results of evaluating various properties of the obtained release film.

[Comparative Example 2]
A release film was obtained in the same manner as in Example 2 except that the first undercoat layer was not provided. Table 1 shows the results of evaluating various properties of the obtained release film.

[Comparative Example 3]
A release film was obtained in the same manner as in Example 1 except that the second undercoat layer was not provided. Table 1 shows the results of evaluating various properties of the obtained release film.

  The release film of the present invention can be suitably used as a release film used in applications where it is particularly necessary to avoid defects due to foreign matter generation and foreign matter adhesion in manufacturing processes of various industrial products.

Claims (5)

  A base material composed of a biaxially stretched polyester film, a first undercoat layer, a second undercoat layer, and a release layer are laminated in this order, and the second undercoat layer is hydrolyzable alkoxysilicate and / or its A release film containing a polycondensate, wherein the release layer contains a curable silicone resin. The release film according to claim 1, wherein the first undercoat layer contains the following component (A).
(A): Electronically conductive compound The release film according to claim 1 or 2, wherein the first undercoat layer contains the following component (B).
(B): one or more compounds selected from the group consisting of polyalkylene oxide (b1), glycerin (b2), polyglycerin (b3), and glycerin or an alkylene oxide adduct of polyglycerin (b4) or a derivative thereof   2. The biaxially stretched polyester film has a multilayer structure, and the layer in contact with the first undercoat layer is a layer having a thickness of 2 μm or more containing 80% by weight or more of polyester having an oligomer content of 0.7% by weight or less. The release film in any one of -3.   The adhesive with a release film which has a release film in any one of Claims 1-4, and an adhesive layer.