JP2008163266A - Release polyester film for hot press molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold release polyester film for hot press molding that can reduce stains on circuit parts and circuit surfaces during hot press molding, especially at the time of production of a flexible printed circuit board (FPC), can provide sufficient mold releasability, and is suitable for a film for processing. <P>SOLUTION: The mold release polyester film for hot press molding is produced by applying a liquid coating to a polyester film, the liquid coating comprising a fluorine-containing urethane resin and an isocyanate-based crosslinking agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a release polyester film characterized by being used at the time of hot press molding, and in particular, a hot press suitable as a process film used for manufacturing a flexible printed wiring board (hereinafter abbreviated as FPC). A release polyester film for molding is provided.

  In recent years, with the rapid progress of electronic devices, as the degree of integration of IC (Integrated Circuits) increases, printed wiring boards have been frequently used for the purpose of meeting the demands for higher accuracy, higher density, and higher reliability. ing.

  As this printed wiring board, there are a single-sided printed wiring board, a double-sided printed wiring board, a multilayer printed wiring board, and a flexible printed wiring board. The application field of the multilayer FPC is widened in that the conductor layers can be connected to each other and the lead of the electronic component to be mounted to an arbitrary conductor layer.

  In the FPC manufacturing process, a cover lay, which is a heat-resistant resin film, is bonded with an adhesive on an insulating substrate, for example, on a flexible circuit board having a predetermined circuit on the surface of a polyimide resin film, for the purpose of insulation and circuit protection. Alternatively, hot press molding such as attaching a reinforcing plate to a connector portion or the like is performed using a release film. In the hot press molding process, it has releasability with FPC, has the ability to prevent contamination of the conductor by sufficiently following the unevenness of FPC, has the ability to suppress the adhesive flow from the end face of the coverlay, It is desirable to have a performance with plating on a circuit in a later process. Therefore, a film having properties such as releasability, heat resistance, low contamination, cushioning properties, rigidity and uniform moldability has been demanded.

  In such a situation, it has been proposed that a film of poly-4-methylpentene-1 is used as a release film in the hot press molding step because of its excellent release properties and heat resistance ( Patent Documents 1, 2, and 3).

  Since this poly-4-methylpentene-1 has a high melting point of 235 ° C., it exhibits excellent releasability and heat resistance even in the process performed at about 180 ° C. It is evaluated. However, in recent years, there has been a tendency for high-quality FPC to be demanded especially for increasing the wiring speed and improving reliability, and the conditions of heating and pressurization at the time of manufacture have become severe, and poly-4-methylpentene-1 The film alone may have insufficient film rigidity.

  On the other hand, Patent Documents 4 to 9 disclose a fluorine-based film or a film provided with a release layer as a release film used for such applications.

  In recent years, due to the increasing social demand for environmental issues and safety, in addition to the functions of heat resistance to withstand heat press molding, releasability for printed wiring boards and heat press plates, these release films Ease of disposal processing has been demanded. Furthermore, it is also important not to contaminate the circuit part in order to improve the product yield at the time of hot press molding.

  However, the fluorine-based film conventionally used as a release film is excellent in heat resistance, releasability, and non-contamination, but is expensive and difficult to burn in waste incineration after use. In addition, there is a problem that toxic gas is generated. Moreover, the film provided with the release layer may cause contamination of the printed wiring board, particularly the circuit portion and the circuit surface due to the migration of components contained in the release layer on the surface, and may impair the quality.

JP-A-57-70653 Japanese Patent Publication No. 58-15959 JP 2005-307059 A Japanese Patent Laid-Open No. 5-283862 Japanese Patent Laid-Open No. 1-229045 Japanese Patent Laid-Open No. 11-105209 JP-A-11-227108 JP 2006-175637 A JP 2006-175672 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is to reduce the contamination of the circuit part and circuit surface during hot press molding, particularly during FPC manufacturing, and to provide sufficient releasability. The object is to provide a release polyester film for hot press molding.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by providing a coating layer composed of a combination of specific types of compounds, and the present invention is completed. It came.

  That is, the gist of the present invention resides in a release polyester film for hot press molding, which is obtained by applying a coating liquid containing a fluorine-based urethane resin and an isocyanate-based crosslinking agent as essential components to a polyester film. .

Hereinafter, the present invention will be described in detail.
The polyester constituting the polyester film in the present invention is terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid, etc. Manufactured by melt polycondensation of dicarboxylic acid or its ester with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol Polyester. Polyesters comprising 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 of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  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 use and purpose of the film, but the average particle size is usually in the range of 0.01 to 5.0 μm. If the average particle size exceeds 5.0 μm, the surface roughness of the film becomes too rough, or the particles are likely to fall off from the film surface. When the average particle size is less than 0.01 μm, the surface roughness is too small and sufficient slipperiness may not be obtained. About particle content, it is 0.0003 to 3.0 weight% normally with respect to polyester, Preferably it is the range of 0.0005 to 2.5 weight%. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 3.0% by weight, the film frequently breaks. Productivity may be reduced. In addition, various stabilizers, lubricants, antistatic agents, and the like can be added as appropriate.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, 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 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 maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable.

  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 surface layers can be made of different polyesters depending on the purpose.

  The polyester film of the present invention has a coating layer, and the coating layer is naturally included in the concept of the present invention, whether it is provided on only one side of the film or on both sides.

  The fluorine-based urethane resin used in the present invention is a resin having two or more fluorine atoms and a urethane bond, for example, a polyfluoroalkyl group (hereinafter referred to as Rf group) and a urethane bond. A fluoroalkyl urethane compound is mentioned. The Rf group means a group in which two or more hydrogen atoms of an alkyl group are substituted with fluorine atoms. The number of carbon atoms in the Rf group is preferably 1-20, particularly 4-16. The structure of the Rf group may be linear or branched, and is preferably linear. The ratio of fluorine atoms in the Rf group is represented by [(number of fluorine atoms in the Rf group) / (number of hydrogen atoms contained in the alkyl group having the same carbon number corresponding to the Rf group)] × 100 (%). In some cases, it is preferably 60% or more, more preferably 80% or more, and particularly substantially 100%. The Rf group may contain a chlorine atom, and an etheric oxygen atom or a thioetheric sulfur atom may be inserted between carbon-carbon bonds.

The Rf group is preferably a perfluoroalkyl group in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms (hereinafter referred to as RF group), and the RF group has 1 to 20 carbon atoms, particularly 4 to 4 carbon atoms. 16 is preferred. Further, the structure of the RF group may be linear or branched, and is preferably linear. Further, the RF group is preferably a group represented by F (CF ₂ ) _p — (p is an integer of 4 to 16), and particularly preferably a group in which p is 6 to 12. Specific examples of the RF group are listed below, but are not limited thereto.

_{C 4 F 9 - [F (} CF 2) 4 - including structural isomers groups such _{-, (CF 3) 2 CFCF} 2 -, (CF 3) 3 C-, and _{CF 3 CF 2 CF (CF 3} ) _], C _{5 F 11} - [e.g. _{F (CF 2) 5 -]} , C 6 F 13 - [ e.g. _{F (CF 2) 6 -]} , C 7 F 15 - [ e.g. _{F (CF 2) 7 -]} , C ₈ F ₁₇ - [e.g. _{F (CF 2) 8 -]} , C 9 F 19 - [ e.g. _{F (CF 2) 9 -]} , C 10 F 21 - [ e.g. _{F (CF 2) 10 -]} , H ( CF _{2) s} - _(s is 2-16 integer)

  The content of the fluorinated urethane resin is usually 1 to 90% by weight, preferably 5 to 80% by weight, more preferably 10 to 70% by weight, based on the total weight of the coating film. If it is less than 1% by weight, the releasability may be insufficient, and if it exceeds 90% by weight, it may be disadvantageous for non-contamination.

  The coating liquid in the present invention also contains an isocyanate-based crosslinking agent as an essential component. The isocyanate-based crosslinking agent is not particularly limited as long as it is a compound having two or more isocyanate groups, and the isocyanate groups may be blocked. Another polymer skeleton having an isocyanate group may be used, and examples thereof include a reaction product of a polyfunctional isocyanate and a compound having two or more groups that react with the isocyanate group.

  The polyfunctional isocyanate is preferably a polyisocyanate having two or more isocyanate groups and a modified product thereof, and examples thereof include an aliphatic polyfunctional isocyanate, an alicyclic polyfunctional isocyanate, and an aromatic polyfunctional isocyanate. As a modified body, a nurate modified body, a trimethylol modified body, or a burette modified body is preferable. In the polyfunctional isocyanate, a part of the isocyanate group may be blocked.

  Specific examples of the polyfunctional isocyanate include hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), tolylene diisocyanate (TDI), phenylene diisocyanate (PDI), diphenylmethane diisocyanate (MDI), hydrogenation Examples thereof include MDI and the like, and isocyanurate-modified products, trimethylol-modified products, or trisburettes or trifunctional amine derivatives.

  The group that reacts with an isocyanate group in a compound having two or more groups that react with an isocyanate group is preferably a hydroxyl group, an amino group, a carboxyl group, or the like, and particularly preferably a hydroxyl group. As the compound having two or more groups that react with an isocyanate group, a polyether-based, polyester-based, or polycarbonate-based polyol having two hydroxyl groups is preferable.

  The content of the isocyanate crosslinking agent is preferably 5 to 90% by weight, more preferably 10 to 80% by weight, based on the total weight of the coating film. If it is less than 5% by weight, it is disadvantageous in terms of non-contamination, and if it is too much, necessary releasability may not be obtained.

  In the coating liquid used in the present invention, a water-soluble or water-dispersible binder resin can be used in combination as necessary. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, and the like. In these, each skeleton structure may have a composite structure substantially by copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, and vinyl resin graft polyurethane. By containing these resins, the strength of the resulting coating layer and the adhesion to the base film can be improved.

  Further, if necessary, other cross-linking reactive compounds may be included. The cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the coating layer can be improved by a crosslinking reaction with a functional group contained in another resin or compound or by self-crosslinking. As the crosslinking reactive compound that can be used, amino resins such as melamine, benzoguanamine, and urea, carbodiimide, oxazoline, epoxy, and glyoxal are preferably used. Also included are polymer-type cross-linking reactive compounds having reactive groups in other polymer skeletons.

  Coating liquids used in the present invention are surfactants, antifoaming agents, coating property improving agents, thickeners, organic lubricants, organic particles, inorganic particles, antioxidants, ultraviolet absorbers, foaming agents, dyes, You may contain additives, such as a pigment. These additives may be used alone or in combination of two or more as necessary.

  The coating liquid in the present invention is preferably an aqueous solution or a water dispersion from the viewpoint of handling, working environment, and stability of the coating liquid composition, but water is the main medium. An organic solvent may be contained as long as it does not exceed the range.

  The coating layer according to the present invention is provided by coating, and particularly in the present invention, it is provided by in-line coating in which coating is performed during film formation.

  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 a substantially amorphous unstretched sheet obtained by melting and quenching, followed by a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. Among these, a method in which a uniaxially stretched film is coated, dried in a tenter and stretched in the transverse direction, and further heat treated together with the base film is excellent. According to such a method, since film formation and coating layer coating can be performed simultaneously, there is a merit in manufacturing cost, thin film coating is easy to perform stretching after coating, and heat treatment applied after coating is other than that. Since the high temperature is not achieved by this method, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. In particular, when the coating layer contains a cross-linking reactive compound, there is an advantage that the reaction residue hardly remains due to the high-temperature heat treatment of in-line coating. The presence of a reactive residue in the coating layer causes a reaction with the components of the overcoat layer when blocking when the film is wound into a roll or when another layer is provided on the coating layer in a later step. This is not preferable.

  As a method for applying the coating solution to the polyester film, 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 techniques such as an extrusion coater and a bar coater.

The coating amount of the coating layer, when viewed as a final coating, typically 0.003~1.5g / ^{m 2,} preferably from 0.005 to 0.5 / ^{m 2,} more preferably 0.01 to 0 .3 g / m ² . When the coating amount is less than 0.003 g / m ² , there is a possibility that sufficient releasability may not be obtained, and a coating layer exceeding 1.5 g / m ² is not preferable because it deteriorates the appearance and increases the cost. . In addition, you may provide the other coating layer and process in the opposite surface of a coating layer.

The film of the present invention relates to a release polyester film characterized by being used at the time of hot press molding, and is particularly suitable for use in the production of flexible printed wiring boards because of its excellent release properties and non-staining properties. Can be used.

  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 etc. in an Example and a comparative example are as follows.

(1) Water drop contact angle (°)
2 μL of ion-exchanged water was dropped, and the water droplet contact angle on the film surface after 1 minute was measured by a θ / 2 method using a contact angle measuring device (CA-A type manufactured by Kyowa Interface Science Co., Ltd.).

(2) Evaluation method of releasability Using a multi-stage press machine, the release polyester film, FPC, release polyester film are stacked in this order, heated and pressurized at 170 ° C. and 20 kg / cm ² for 45 minutes, and then released from FPC. The case where the moldability was easy was evaluated as ◯, and the case where there was a problem in processing suitability such as poor release properties and tearing of the film was evaluated as ×.

(3) Contamination evaluation of circuit board FPC obtained after heating and pressurization obtained by the method of (2) is visually observed for the presence or absence of electrode contamination and electrode contamination. The case where it was made was set as x.

The polyester raw materials used in Examples and Comparative Examples are as follows.
(Polyester 1): Polyethylene terephthalate chip having an intrinsic viscosity of 0.66 substantially containing no particles

(Polyester 2): Polyethylene terephthalate chip having an intrinsic viscosity of 0.66 and containing 0.2 parts by weight of amorphous silica having an average particle diameter of 2.5 μm

Moreover, the following was used as a coating composition.
(A-1): Urethane compound having a perfluoroalkyl group (Asahi Guard manufactured by Asahi Glass)
(A-2): Long chain alkyl group graft compound (Rezemu made by Chukyo Yushi)
(A-3): Acrylic compound having a perfluoroalkyl group (Dickguard manufactured by Dainippon Ink and Chemicals)
(B-1): Alicyclic polyfunctional isocyanate-based crosslinking agent (Elastotron manufactured by Daiichi Kogyo Seiyaku)
(C-1): Carbodiimide compound (Nisshinbo Carbodilite)
(C-2): Crosslinkable resin of alkylol melamine / urea copolymer (Beckamine manufactured by Dainippon Ink & Chemicals, Inc.)

(Production example of polyester film)
Polyester 1 and polyester 2 are blended at a weight ratio of 92/8, sufficiently dried, melted by heating to 280 to 300 ° C., extruded into a sheet form from a T-shaped die, and surface temperature using an electrostatic adhesion method. It cooled and solidified, making it closely_contact | adhere to a 40-50 degreeC mirror surface cooling drum, and the unstretched polyethylene terephthalate 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. This uniaxially oriented film was guided to a tenter stretching machine, stretched 4.0 times in the width direction at 100 ° C., and further heat treated at 230 ° C. to obtain a biaxially oriented polyethylene terephthalate film having a film thickness of 38 μm.

Example 1:
In the process as shown in the production example of the polyester film, a coating composition as shown below was applied to one side of the uniaxially oriented film after stretching in the longitudinal direction. Next, the film was guided to a tenter stretching machine, and the coating composition was dried using the heat. Thereafter, the same process as in the polyester film production example was performed, and 0.04 g / mm on the base film having a film thickness of 38 μm. A laminated biaxially oriented polyethylene terephthalate film in which a coating layer having an amount of m ² was laminated was obtained.
-Coating solution composition: 40 parts of (A-1) and 60 parts of (B-1). However, “part” represents a weight ratio in the resin solid content (hereinafter the same).

Examples 2-4 and Comparative Examples 1-3:
In the same manner as in Example 1, except that the composition of the coating solution was changed to the following, a coating layer having an amount of 0.04 g / m ² was laminated on a base film having a film thickness of 38 μm. An axially oriented polyethylene terephthalate film was obtained.
Example 2 Coating solution composition: 20 parts of (A-1), 40 parts of (B-1), and 40 parts of (C-1).
Example 3 Coating solution composition: (A-1) was 60 parts and (B-1) was 40 parts.
Example 4 Coating solution composition: 40 parts of (A-1), 30 parts of (B-1), and 30 parts of (C-1).
Comparative Example 1 Coating solution composition: (A-2) was 40 parts and (B-1) was 60 parts.
Comparative Example 2 Coating solution composition: (A-2) was 40 parts, (B-1) was 30 parts, and (C-1) was 30 parts.
Comparative Example 3 Coating solution composition: (A-3) was 80 parts and (C-2) was 20 parts.
The evaluation characteristics of the obtained film are as shown in Table 1 below.

  The film of the present invention can be suitably used as, for example, a release film for hot press molding.

Claims (1)

A release polyester film for hot press molding, which is obtained by applying a coating liquid containing a fluorine-based urethane resin and an isocyanate-based crosslinking agent as essential components to a polyester film.