JP2009226632A - Method of manufacturing ultra-thin polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an ultra-thin polyimide film of about ≤10 μm by using a simple apparatus and a process suitable for continuous production. <P>SOLUTION: The method of manufacturing the ultra-thin polyimide film characteristically comprises: a process (I) of applying a polyimide resin precursor solution containing a releasing agent on a base material; a process (II) of drying the applied polyimide resin precursor solution, a process (III) of thermally curing a polyimide resin precursor solution layer to form the polyimide film; and a process (IV) of exfoliating the polyimide film from the base material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an extremely thin polyimide film.

  In response to the downsizing and higher density of electronic devices and peripheral devices, the demand for ultra-thin films that have high strength and high elastic modulus as well as heat resistance is rapidly increasing as materials used for parts and the like. ing. Conventionally, as a method for producing a polyimide film, a polyimide resin precursor dissolved in a solvent is applied onto a support such as a metal endless belt, dried, peeled, and stretched vertically and horizontally as necessary. A method of heat setting is known.

  For example, Patent Documents 1 and 2 disclose that an aromatic polyamic acid solution contains a specific amount of phosphoric acid ester or carboxylic acid so that the solution is cast on a substrate such as an endless belt, heated, and then self-treated from the substrate. A method is disclosed in which the support film is peeled and further heated to imidize.

  However, when an extremely thin polyimide film having a thickness of about 10 μm or less is manufactured by such a method, the polyimide precursor film is peeled off from the endless belt, the film is held by clips or pins in the subsequent stretching and heat treatment, etc. In this process, even if the film has a self-supporting property, there is a problem that the film tends to break due to its thinness.

  In Patent Document 3, it is described that in a method for producing an extremely thin heat-resistant film of 6 μm or less, the peeling tension that affects the thickness can be reduced by making the peeling point of the self-supporting film from the endless belt constant. ing.

  However, generally, the process of peeling a self-supporting film from a substrate such as an endless belt and the subsequent heat treatment process are not suitable when an extremely thin film is produced because it is difficult to handle. When going through these steps, the temperature of the self-supporting film is high, so the elastic modulus is low, so the film tends to stretch due to the tension at the time of peeling, and in order to obtain uniform quality in such an extremely thin film Requires advanced control. Further, the endless belt is expensive, and a cheaper manufacturing method is demanded.

Patent Document 4 describes a method for producing an ultrathin film having a thickness of 1 to 5 μm by dissolving and removing a support with a chemical such as acid or alkali as a method that does not involve peeling of the self-supporting film. Has been. Further, Patent Document 5 describes a method in which a varnish is applied to a substrate on which a release agent is adhered and imidized, and then a tape is attached to a polyimide film to be peeled from the substrate. These methods do not apply peeling tension and may prevent the occurrence of tearing due to peeling. However, none of these methods are suitable for continuous production, and there is a problem that the environmental load due to the use of chemicals is concerned. is there.
Japanese Examined Patent Publication No. 62-60416 Japanese Patent Publication No. 63-5421 JP-A-9-220726 JP 2000-309026 A JP 2002-361659 A

  An object of the present invention is to provide a method for producing an extremely thin polyimide film having a thickness of about 10 μm or less by a simple process suitable for continuous production.

  As a result of diligent research to solve the above-mentioned problems, the present inventors apply a polyimide resin precursor solution containing a release agent to a base material, thermally cure it, and then peel off the base material. Thus, the inventors have found that the above-mentioned problems can be solved, and have reached the present invention.

That is, the gist of the present invention is a method for producing an ultrathin polyimide film characterized by including the following steps (I) to (IV).
(I) The process of apply | coating the polyimide resin precursor solution containing a mold release agent on a base material,
(II) a step of drying the applied polyimide resin precursor solution,
(III) A step of thermosetting the polyimide resin precursor solution layer to form a polyimide film, and (IV) a step of peeling the polyimide film from the substrate.

  According to the present invention, an ultra-thin polyimide film having a thickness of 10 μm or less can be stably and continuously manufactured with a simple apparatus or process.

  By heat curing on the substrate, there is no need for stretching or heat treatment after peeling, so there is no need for a process such as stretching, which tends to cause tearing in ultra-thin polyimide film, and gripping the film with clips or pins in heat treatment Become. Moreover, by adding a release agent, the film can be easily peeled off from the substrate even after thermosetting.

  The production method of the present invention is applied to the production of an ultrathin polyimide film. In the present invention, “ultra-thin” refers to a thickness of 10 μm or less. In addition, as thickness of the polyimide film to which the manufacturing method of this invention is applied, the range of 1-5 micrometers is preferable. When the film thickness is less than 1 μm, the film handling tends to be difficult in the production method of the present invention in terms of peeling from the substrate. Further, although the film can be manufactured even when the thickness of the film exceeds 5 μm, since a known manufacturing method can be applied, the merit of applying the present invention is reduced.

  The polyimide resin precursor referred to in the present invention is a polyimide resin having an imide bond by heat curing and having a structural unit represented by the following structural formula (1). Any compound can be used as long as it is such a compound. For example, a polyamic acid represented by the following structural formula (2) can be used as a polyimide resin precursor. The polyamic acid can be usually produced as a polyimide resin precursor solution composed of a polyamic acid and a solvent.

  In the structural formulas (1) and (2), R represents a tetravalent organic residue, and R ′ represents a divalent organic residue.

  The polyimide resin precursor is usually produced as a solution, and examples of the solvent therefor include aprotic polar solvents, ether compounds, and water-soluble alcohol compounds.

  Examples of the aprotic polar solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide and the like.

  The ether compounds include 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol. Monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, di Propylene glycol monoethyl ether, tripropylene glycol monomethyl ether, poly Ji glycol, polypropylene glycol, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and the like.

  Examples of water-soluble alcohol compounds include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,3-butanediol. 1,4-butadiol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol And diacetone alcohol.

  These solvents can be used as a mixture of two or more. Among these solvents, particularly preferred examples include N, N-dimethylacetamide and N-methyl-2-pyrrolidone as the sole solvent, and examples of the mixed solvent include N, N-dimethylacetamide and N- Examples thereof include a combination of methyl-2-pyrrolidone, N-methyl-2-pyrrolidone and methanol, N-methyl-2-pyrrolidone and 2-methoxyethanol.

  Next, the manufacturing method of a polyimide resin precursor is demonstrated. First, a solution composed of a polyamic acid is prepared by, for example, mixing an aromatic tetracarboxylic dianhydride represented by the following structural formula (3) and an aromatic diamine represented by the following structural formula (4) with the above solvent such as aprotic polarity. It can manufacture by making it react in a solvent.

Here, R ₁ represents a tetravalent aromatic residue.

Here, R ₂ represents a divalent aromatic residue.

  In the above reaction, the ratio of the tetracarboxylic dianhydride and the diamine is preferably 1.04 to 0.96 mol of tetracarboxylic dianhydride with respect to 1 mol of diamine, more preferably 1 mol of diamine. The amount of tetracarboxylic dianhydride is 1.03 to 0.97 mol. Moreover, -20-80 degreeC is preferable and, as for reaction temperature, 50-80 degreeC is more preferable.

  In the above reaction, the mixing order of the monomer and the solvent is not particularly limited and may be any order. When a mixed solvent is used as a solvent, a solution composed of polyamic acid can also be obtained by dissolving or suspending separate monomers in each solvent, mixing them, and reacting at a predetermined temperature and time with stirring. Is obtained. Two or more kinds of polyimide resin precursor solutions may be mixed and used.

  Specific examples of the aromatic tetracarboxylic dianhydride represented by the structural formula (3) include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4. '-Benzophenone tetracarboxylic acid, 3,3', 4,4'-diphenylsulfone tetracarboxylic acid, 2,3,3 ', 4'-diphenyl ether tetracarboxylic acid, 2,3,3', 4'-benzophenone tetra Carboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ', 4,4 '-Diphenylmethanetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3, , 9,10-tetracarboxyperylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexa Fluoropropane dianhydride and the like. These aromatic tetracarboxylic dianhydrides can be used in combination of two or more.

  In the present invention, pyromellitic acid or 3,3 ′, 4,4′-biphenyltetracarboxylic acid can be used as a particularly preferred aromatic tetracarboxylic dianhydride. These can be used alone or in combination.

  Specific examples of the aromatic diamine represented by the structural formula (4) include p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4 ' -Diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis (anilino) ethane, diaminodiphenylsulfone , Diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, Diaminobenzotrifluoride, 1,4- (P-aminophenoxy) benzene, 4,4'-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4'-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) Examples include hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane. Two or more of these aromatic diamines can be mixed and used.

  In the present invention, p-phenylenediamine or 4,4′-diaminodiphenyl ether can be used as a particularly preferred aromatic diamine. These can be used alone or in combination.

  In the present invention, when a polyimide resin precursor solution is produced, an amine, diamine, dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid derivative having a polymerizable unsaturated bond is added to form a crosslinked structure during thermosetting. Can be made. As the unsaturated compound, maleic acid, nadic acid, tetrahydrophthalic acid, ethynylaniline and the like can be used.

  There is no particular problem even if a partially imidized polyimide resin precursor is present in the polyimide resin precursor due to synthesis conditions, drying conditions, and other reasons of the polyimide resin precursor.

  In the present invention, the polyimide resin precursor solution produced as described above is used by containing a release agent. The mold release agent is blended for the purpose of facilitating peeling from the substrate when the polyimide resin precursor is cured to form a polyimide film. As the release agent, known release agents can be applied, and examples thereof include higher fatty acids such as stearic acid and palmitic acid, amides and metal salts thereof, and stearic acid is preferable. It is necessary to add 0.01 to 2 parts by mass with respect to 100 parts by mass of the polyimide resin solid content, and preferably 0.01 to 1 part by mass. When the added amount is less than 0.01 parts by mass, the effect is poor, and when it is more than 2 parts by mass, the effect is not changed, but the physical properties of the film tend to be lowered.

  Other polyimide resin precursors include surfactants, organosilanes, pigments, conductive carbon black and fillers such as fine metal particles, abrasives, dielectrics, lubricants, and other polymers as required. Etc. can be added. These are usually added at the stage of the polyimide resin precursor solution.

In the present invention, an extremely thin polyimide film is produced by the following steps (I) to (IV) using the polyimide resin precursor solution.
(I) The process of apply | coating the polyimide resin precursor solution containing a mold release agent on a base material,
(II) a step of drying the applied polyimide resin precursor solution,
(III) A step of thermosetting the polyimide resin precursor solution layer to form a polyimide film, and (IV) a step of peeling the polyimide film from the substrate.

Hereinafter, the steps (I) to (IV) will be described in more detail.

<Process (I)>
This step is a step of applying a polyimide resin precursor solution containing a release agent on a base material to form a coating film of the solution on the base material. The solid content concentration and viscosity of the polyimide precursor solution used for coating are not particularly limited as long as coating is possible, but the solid content concentration is preferably 5 to 30% by mass, more preferably 5 to 20% by mass. . Moreover, as a solution viscosity, the range of 0.03-10 Pa.s / 30 degreeC is preferable, More preferably, it is the range of 0.05-8 Pa.s / 30 degreeC.

  The application of the polyimide resin precursor solution to the substrate can be performed using any coating machine, but is a die coater, lip coater, gravure coater, bar coater, doctor blade coater, comma coater, reverse roll coater, Examples include a bar reverse roll coater. In addition, it is also possible to apply multiple layers for the purpose of improving characteristics, and the polyimide resin precursor solutions in each layer may be the same or different.

  Examples of the substrate include metal foils such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or alloys thereof, and Teflon (registered trademark), polyimide film, glass fiber fabric, etc. There is no particular limitation as long as the material can withstand the curing process. Aluminum and stainless steel are preferable. The thickness of the substrate is preferably 25 to 300 μm, and more preferably 50 to 200 μm.

  It is preferable that the surface of the substrate on which the polyimide resin precursor solution is applied is smooth. For example, if the above-mentioned various metal foil base materials are as smooth as commercial products, they can be used without problems.

<Process (II)>
This step is a step of drying the polyimide resin precursor solution applied to the substrate. “Drying” as used herein refers to reducing the amount of solvent in the polyimide resin precursor solution by means such as heating. Any device can be used for drying, and a hot air dryer is preferable, but infrared heating, electromagnetic induction heating, or the like may be used or used in combination. A temperature range of 50 to 200 ° C. is suitable for drying.

  Drying is preferably performed immediately after application. In addition, a process (III) (curing) may be performed continuously with drying, and after winding once after drying, a hardening process may be performed after an appropriate time.

  When winding up once after drying, it is preferable to remove the solvent until the solid concentration in the coating film is 50% by mass or more, more preferably continuously. If the solid content concentration is less than 50% by mass, winding may not be performed satisfactorily due to stickiness of the coated surface.

<Process (III)>
This step is a step of thermosetting the polyimide resin precursor solution layer to form a polyimide film.

  The thermosetting temperature is 200 ° C. or higher, preferably 300 ° C. or higher. Moreover, an upper limit is about 450 degreeC. Heat treatment is sufficiently performed at such a high temperature. When polyimide is thermally cured, a gas such as water or a solvent is generated. Therefore, the thermal curing is preferably performed under hot air circulation.

  When performing thermosetting, the base material on which the polyimide resin precursor solution layer is formed may be cut out to an appropriate width or length. At this time, it is efficient to perform thermosetting in a state where the cut base material is wound around an appropriate core such as an aluminum core with the coating surface facing outward.

  In the present invention, the steps (I) to (III) are carried out on the same substrate without peeling off the polyimide resin precursor solution from the substrate. Thus, production efficiency improves by performing continuously from application | coating of a polyimide resin precursor solution to polyimide film formation.

<Process (IV)>
This step is a step of peeling the polyimide film from the substrate.

  Although the peeling method from a base material is not specifically limited, For example, the following mechanical means can be used. At one end of the polyimide film with a base material after thermosetting in a wound state, the film and the base material are fixed to different cores with an adhesive tape, etc. It can be peeled from the material. At this time, handling property can be improved by slitting the edge of the polyimide film after thermosetting before peeling, or by peeling from the substrate after reinforcing with a protective film, a mending tape or the like. In the present invention, as described above, since the polyimide resin precursor before curing contains a release agent, peeling from the substrate is facilitated.

  Depending on the material of the substrate, chemical etching is possible, but in the present invention, the peelability of the film from the substrate is good. A polyimide film is obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to this.

[Reference Example 1] (Synthesis example of polyimide resin precursor solution)
After adding 0.67 kg of p-phenylenediamine and 10 kg of N-methyl-2-pyrrolidone to the reaction kettle and stirring it at room temperature for 5 minutes, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 1.8 kg was added and stirred in a hot water bath at 70 ° C. for 2 hours to obtain a uniform polyimide resin precursor solution containing 20% by mass of polyamic acid as a polyimide resin precursor. This is designated as solution (I).

[Example 1]
Add 11 kg of stearic acid as a mold release agent and 7.2 kg of N-methyl-2-pyrrolidone as a diluting solvent to 11 kg of the solution (a), and mix them with a disperser for 1 hour. The filtered solution was used as a coating solution. The addition amount of stearic acid was 0.5 parts by mass with respect to 100 parts by mass of the polyimide solid content to be formed, the solid content concentration of the coating liquid was 11% by mass, and the solution viscosity was 3 Pa · s / 30 ° C. . This was continuously applied onto an aluminum foil having a width of 540 mm and a thickness of 50 μm using a comma coater so that the coating thickness after curing was 3 μm, and dried at 140 ° C. for 3 minutes. At this time, the solid content concentration of the coating film increased to 70% by mass.

  Next, the base material in a state where the coating film was in close contact was cut out to a length of 500 mm, and wound around an aluminum core having an inner diameter of 6 inches with the coating surface facing outward for one turn. Subsequently, 140 ° C to 200 ° C, 200 ° C to 250 ° C was heated for 4 minutes each, and 250 ° C to 350 ° C was heated for 16 minutes, and further heated at 350 ° C for 2 hours in a hot air inert oven. Then, a curing reaction was performed, and after cooling, the aluminum foil was peeled off to obtain an extremely thin polyimide film.

[Comparative Example 1]
A coating solution similar to Example 1 was prepared except that stearic acid was not added to the solution (i). Using this, a coating film was formed using a comma coater in the same manner as in Example 1, and dried at 140 ° C. for 3 minutes. Similarly to Example 1, the base material was cut out to 500 mm, wound around an aluminum core, and subjected to a curing reaction under the same temperature and time conditions. When the formed polyimide film was peeled from the base material, the film was broken. .

[Comparative Example 2]
Using the coating solution of Example 1, in the same manner as in Example 1, using a comma coater, the coating thickness after curing is 3 μm on an aluminum foil having a width of 540 mm and a thickness of 50 μm. And dried at 140 ° C. for 3 minutes. Although an attempt was made to peel the coating film from the substrate in this state, the coating film could not be peeled off as a film.

  Table 1 shows the production status and the evaluation results of the polyimide film in Example 1 and Comparative Examples 1 and 2.

  As shown in Table 1, in Example 1, peeling was easy and a polyimide film having a good appearance was obtained.

On the other hand, in Comparative Example 1, the adhesive force between the cured polyimide film and the base material was strong, and could not be easily peeled off, and immediately broke. Moreover, in Comparative Example 2, an attempt was made to peel the coating film from the substrate once after drying, but it was broken. It has been found that it is difficult to peel off the polyimide film before curing from the substrate with such a thickness.

Claims (4)

A method for producing an ultrathin polyimide film comprising the following steps (I) to (IV):
(I) The process of apply | coating the polyimide resin precursor solution containing a mold release agent on a base material,
(II) a step of drying the applied polyimide resin precursor solution,
(III) A step of thermosetting the polyimide resin precursor solution layer to form a polyimide film, and (IV) a step of peeling the polyimide film from the substrate. The method for producing a polyimide film according to claim 1, wherein the polyimide film has a thickness of 1 to 5 μm. The method for producing a polyimide film according to claim 1, wherein the content of the release agent is 0.01 to 2 parts by mass with respect to 100 parts by mass of the polyimide. 2. The method for producing a polyimide film according to claim 1, wherein the steps (I) to (III) are carried out on the same substrate without peeling off the polyimide resin precursor solution from the substrate.