JP2006274130A - Polyimide film and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyimide film that has not only improved dimensional stability and processability but also actualizes improvement in yield and productivity even in the case of having ≥1,000 mm width. <P>SOLUTION: The polyimide film has ≥1,000 mm width, ≤±3% dispersion of L value in the width direction (TD direction) and heat shrinkage percentages at 200°C both in the length direction (MD direction) and in the width direction (TD direction) of ≤0.07%. Consequently, since dispersion of anisotropy in the width direction is reduced, not only dimensional stability and processability but also yield and productivity of a polyimide film are improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wide polyimide film having a width of 1000 mm or more and its typical use, in particular, stabilizing the quality in the width direction, further improving the yield and productivity, and various The present invention relates to a polyimide film that can be suitably used for the production of a flexible wiring board and its use.

  In recent years, the demand for various printed circuit boards has increased with the reduction in weight, size and density of electronic products. Among these printed boards, the demand for flexible wiring boards is growing. The flexible wiring board is also referred to as a flexible printed wiring board (FPC). The flexible wiring board has a structure in which a circuit made of a metal layer is formed on an insulating film.

  The above-mentioned flexible wiring board is generally formed of various insulating materials, a flexible insulating film is used as a substrate, and a metal foil is bonded to the surface of the substrate by heating and pressure bonding via various adhesive materials. Manufactured by. A polyimide film or the like is preferably used as the insulating film, and an epoxy or acrylic thermosetting adhesive is generally used as the adhesive material. A flexible wiring board using such a thermosetting adhesive has a three-layer structure of substrate / adhesive material / metal foil, and is hereinafter referred to as “three-layer FPC” for convenience of explanation.

  Moreover, as a flexible wiring board, the flexible wiring board which provided the metal layer directly on the insulating film, and the thing using a thermoplastic polyimide for the contact bonding layer are proposed. Since these flexible wiring boards are in a state in which a metal layer is directly formed on an insulating substrate, they are hereinafter referred to as “two-layer FPC” for convenience of explanation. This two-layer FPC is suitably used for applications that require higher heat resistance, flexibility, electrical reliability, and the like compared to a three-layer FPC.

  Since the two-layer FPC and the three-layer FPC have advantages according to their uses, the demand for any flexible wiring board has grown in recent years. For this reason, polyimide films used as substrates / base materials for the above-mentioned various flexible wiring boards are increasingly required to improve physical properties and workability, and are used as flexible wiring boards. In some cases, it is also important to reduce the manufacturing cost by improving the yield and productivity of the polyimide film. In addition, a yield here refers to the rate of the polyimide film which can be used as a use of a flexible wiring board among the total production.

  For example, in terms of improvement in physical properties, dimensional stability is particularly required for flexible wiring boards, and it is widely known to those skilled in the art that polyimide film as a substrate / base material is required to have a low heat shrinkage rate. Various techniques for improving the heat shrinkage rate are known (see, for example, Patent Documents 1 and 2). In these technologies, the heat shrinkage rate at a specific temperature is specified below a specific upper limit, and the L value, tensile strength, tensile elastic modulus, linear expansion coefficient, Young's modulus, water absorption rate, It is defined by combining multiple physical properties such as expansion coefficient.

  In terms of improvement in workability, a technique for specifying the L value among the above-mentioned physical properties is also known in order to improve workability in a polyimide film (see Patent Document 3). In this technique, by specifying a preferable range of the L value according to the thickness, for example, the punchability is improved.

Furthermore, in terms of yield and productivity improvement, as a technology for improving productivity by improving quality, in order to make flatness excellent in flexible printed wiring boards, a heat-resistant plastic film (preferably a substrate) In order to improve the wrinkle and meandering that occurs during processing (refer to cited document 4), or to regulate the amount of slack in the polyimide film) and the lengthwise unilateral elongation to a specified value or less, or a thickness of 1000 mm or more For a polyimide film having a thickness of 29 μm or less, a technique (see cited reference 5) or the like for defining a maximum tarmi value at a specific load and for defining an upper limit of the amount of heat shrinkage has been proposed.
Japanese Patent Laid-Open No. 10-77353 (published March 24, 1998) JP 2003-335874 A (published November 28, 2003) JP 2004-107659 A (Released on December 9, 2004) Japanese Patent Laid-Open No. 5-327147 (published on December 10, 1993) JP 2004-346210 A (published April 8, 2004)

  However, at the present time, it has not been progressing slowly to consider improvement in yield and productivity as well as improvement in dimensional stability and workability.

  Specifically, in the conventional techniques (Patent Documents 1 to 3) for improving the dimensional stability and workability described above, for example, Patent Document 1 shows that quality stabilization and film thinning can be realized. However, substantially improving the yield and productivity of the polyimide film is substantially not considered. Further, among the techniques related to the improvement of productivity due to the quality improvement, the technique disclosed in Patent Document 4 discloses that the flatness is excellent, but no disclosure is made about the improvement of dimensional stability. There is no suggestion.

  Furthermore, in the technique disclosed in Patent Document 5, since productivity is improved by performing a stretching operation, there is a problem that a large variation occurs in anisotropy in the width direction. Yes. Recently, in the production of flexible wiring boards, in order to further improve the yield and productivity during processing, it is desired to widen the polyimide film as a raw material. Although the technique disclosed in Patent Document 5 proposes a technique for producing a wide polyimide film having a width of 1000 mm or more, there is a problem of variation in anisotropy at each position in the width direction as described above. As a result, it cannot be effectively resolved, and as a result, the yield and productivity have not been sufficiently improved.

  The present invention has been made in view of the above problems, and its purpose is not only to improve dimensional stability and workability, but also to improve yield and productivity even when it has a width of 1000 mm or more. It is in providing the polyimide film which can implement | achieve, and its typical utilization technique.

  As a result of intensive investigations in view of the above problems, the present inventors, in particular, when having a width of 1000 mm or more, by controlling the heat shrinkage rate and L value of the polyimide film in the width direction that has been a problem in the past. The inventors have uniquely found that stable anisotropy can be realized, and have completed the present invention.

  That is, the polyimide film according to the present invention has a width of 1000 mm or more in order to solve the above problems, and the variation in L value in the width direction is ± 3% or less, and at 200 ° C. The heat shrinkage ratio is 0.07% or less in both the length direction and the width direction.

  In the said polyimide film, it is preferable that the tear strength retention before and behind a pressure cooker test is 60% or more. Furthermore, in the said polyimide fill, it is preferable that average thickness is 5-25 micrometers. Further, if the polyimide film contains at least a polyamic acid that is a polyimide precursor and an organic solvent, and is obtained by firing a gel film having self-supporting property, then the final firing of the gel film It is preferable that the heat treatment is performed at a temperature range of 400 to 550 ° C. for 5 to 400 seconds.

  Although the utilization technique of this invention is not specifically limited, For example, the laminated body manufactured using the said polyimide film is contained in this invention. As this laminated body, the thing of the structure formed by laminating | stacking a metal layer on the surface of a polyimide film can be mentioned, for example, Of course, it is not limited to this.

  Moreover, the flexible wiring board formed using the said polyimide film or the said laminated body is also contained in this invention.

  In the present invention, as described above, in a polyimide film having a width of 1000 mm or more, the variation in the L value in the width direction is controlled to ± 3% or less, and the heat shrinkage rate at 200 ° C. is the length direction (MD). The width direction (TD) is controlled to 0.07% or less. Thereby, since variation in the anisotropy in the width direction in the polyimide film can be sufficiently reduced, not only the dimensional stability and workability can be improved, but the entire film can be obtained even if it has a width of 1000 mm or more. It can be used. Therefore, the yield improvement accompanying productivity improvement can be aimed at.

  Moreover, in laminates and flexible wiring boards obtained using this polyimide film, it is possible to improve the dimensional stability and variations of the polyimide film used as the substrate, so that, for example, flexible wiring boards are used in harsh environments. Even in such a case, reliability that can withstand this can be obtained.

  Therefore, the present invention has an effect that it is possible to achieve improvement in dimensional stability, reliability, and yield of the two-layer FPC and the three-layer FPC that have been increasingly demanded in recent years.

  An embodiment of the present invention will be described as follows. However, the present invention is not limited to this, and can be implemented in various modifications within the scope described.

(I) The polyimide film concerning this invention The polyimide film concerning this invention is a wide polyimide film which has a width | variety of 1000 mm or more, Comprising: L value in the width direction, and the heat shrinkage rate in a length direction and the width direction, Is controlled.

  In addition, it is very preferable that the polyimide film according to the present invention is continuously manufactured. In this case, the continuous manufacturing (production) direction becomes the length direction (longitudinal direction), and this length direction The direction orthogonal to the width direction is the width direction. As widely used in the technical field to which the present invention belongs, the length direction is appropriately referred to as MD (Machine Direction) direction, and the width direction is appropriately referred to as TD (Transverse Direction) direction.

  The control of the L value in the polyimide film according to the present invention is defined by the variation of the L value in the width direction (TD direction). Specifically, the L value variation in the TD direction may be at least ± 3% or less. When the variation of the L value exceeds the above upper limit, not only the dimensional stability and workability of the resulting polyimide film are impaired, but also the variation in the anisotropy in the width direction is likely to occur.

  The variation of the L value is evaluated based on whether or not L values measured at a plurality of locations in the width direction of the polyimide film are within a range of ± 3% based on the average value of the measured values. At this time, the number of L values actually measured is preferably at least 10 points. If it is 10 points or more, sufficient reliability can be secured for the parameter of variation in the L value. Of course, the actual measurement value may exceed 10 points. Moreover, although it is preferable that the space | interval of the position which measures L value is equal, it may be uneven.

  The L value is an index representing the color tone defined in the color difference display method of JIS Z 8730, which is disclosed in the above-mentioned Patent Document 3, and specifically, a Lab color based on Hunter color difference. The L value is calculated by the following equations (1) to (3) from the tristimulus values X, Y, Z defined in JIS Z 8722. However, a and b in each of the following formulas represent the chromaticness index in Hunter's color difference formula, and X, Y, and Z represent tristimulus values in the XYZ system.

L value = 10Y ^(1/2) (1)
a = 17.5 (1.02X−Y) / Y ^(1/2) (2)
b = 7.0 (Y-0.847Z) / Y ^(1/2) (3)
In this invention, as shown in the Example mentioned later, using a commercially available color difference meter, the measurement area of 10 mmφ is measured, and the L value is measured at 10 cm intervals in the width direction of the polyimide film, and the average value is calculated. Variation is evaluated as a standard.

  The control of the heat shrinkage rate in the polyimide film according to the present invention is evaluated based on whether the heat shrinkage rate at 200 ° C. is 0.07% or less in both the MD direction and the TD direction. The heat shrinkage rate is preferably calculated according to IPC-TM-650 2.2.4 Method A, based on dimensional changes before and after heat treatment of the polyimide film at 200 ° C. for 2 hours. If the heat shrinkage can be evaluated with sufficient reliability, another known method may be used as long as the temperature condition of 200 ° C. is adopted.

  The upper limit of the heat shrinkage rate in the present invention may be 0.07% or less as described above, but is preferably 0.04% or less. When the heat shrinkage rate exceeds the above upper limit, the dimensional stability of the resulting polyimide film is lowered, and thus the yield of the flexible wiring board tends to be lowered.

Here, in the polyimide film concerning this invention, the dispersion | variation in the anisotropy of TD direction can be reduced by prescribing | regulating the dispersion | distribution of the L value of the said TD direction, and the heat shrinkage rate of MD and TD direction. However, the method for evaluating the anisotropy in the TD direction is not particularly limited, and a known method may be used. In this invention, as shown in the Example mentioned later, the film surface (surface) of the said test piece is made into xy plane using the test piece of the polyimide film cut out to the predetermined size by the predetermined interval in the width direction (TD direction). The birefringence index Δn _xy when the thickness direction is the z-axis is used as a reference. If the birefringence Δn _xy = 0, there is virtually no anisotropy.

In the polyimide film according to the present invention, the birefringence Δn _xy at each position in the TD direction is 0.01 or less, and the difference between the maximum value and the minimum value of the birefringence index Δn _xy at each position is 0. .01 or less is preferable. In other words, when the birefringence index Δn _xy exceeds the upper limit, there is a tendency that variation in dimensional stability increases in the polyimide film obtained.

  In the polyimide film according to the present invention, as described above, both the variation in the L value in the TD direction and the heat shrinkage rate in the MD and TD directions may be equal to or less than the appropriate upper limit values. More preferably, the tear strength retention before and after the pressure cooker test (PCT test) is 60% or more. The specific method of the PCT test and the tear strength retention rate is not particularly limited, and the tear strength retention rate may be measured by a known method before and after performing a known PCT treatment. As shown in the examples described later, PCT treatment is performed according to ASTM D-1938, and the tear strength retention is measured before and after that.

  In the present invention, the tear strength retention before and after the PCT test may be 60% or more, but more preferably 70% or more. If the tear strength retention is less than the above lower limit, the reliability, particularly flexibility, of the polyimide film under high temperature and high humidity and the laminate or flexible wiring board produced thereby tends to be impaired.

  In the polyimide film according to the present invention, other physical property values and shapes are not particularly limited. For example, about the thickness (film thickness), what is necessary is just to set appropriate thickness according to a use. However, the film thickness is particularly preferably in the range of 5 to 25 μm from the viewpoint of improving flexibility when used for flexible wiring board applications. In other words, in the polyimide film concerning this invention, it becomes possible to manufacture suitably the thin polyimide film in the range of 5-25 micrometers by satisfying the various conditions mentioned above.

(II) Manufacturing method of polyimide film The manufacturing method of the polyimide film concerning this invention is not specifically limited, A well-known manufacturing method can be used. Moreover, the kind of polyimide resin to be used is not particularly limited, and it can be produced using a known monomer raw material, but non-thermoplastic polyimide is preferably used in consideration of flexible wiring board applications.

  In the following description, a representative example of the kind of polyimide resin preferably used as the polyimide film according to the present invention and an example of a preferable production method using this polyimide resin will be described and the details will be described.

  As a typical example of the method for producing a polyimide film according to the present invention, at least (a) a step of polymerizing polyamic acid (polyamic acid) which is a precursor of a polyimide resin (polyamic acid polymerization step), (b) obtained The obtained polyamic acid is cast as an organic solvent solution on a support to form a liquid film (liquid film forming process), (c) a process of converting the liquid film into a gel film (gel film forming process), ( d) A method including a step (firing step) of heating and imidizing (firing) the gel film can be mentioned.

<Polyamide acid polymerization step>
In the polyamic acid polymerization step, any known polyamic acid polymerization (synthesis) method can be used and is not particularly limited. Usually, the acid dianhydride component and the diamine component are dissolved in an organic solvent that is a polymerization solvent so as to have substantially equimolar amounts, respectively, and the acid dianhydride and the diamine are controlled under controlled temperature conditions. By stirring until the polymerization of is complete. The polyamic acid obtained by this production method is an organic solvent solution (hereinafter referred to as a polyamic acid solution for convenience), and the concentration of the polyamic acid is usually in the range of 5 to 35% by weight, preferably 10 to 30% by weight. It is within the range. A concentration within this range provides a molecular weight and solution viscosity suitable for the present invention.

  As a method for polymerizing the polyamic acid, any known method and a combination thereof can be used. The characteristic of the polyamic acid polymerization method is the order of addition of the monomer components. Therefore, various physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomer components. Therefore, in the present invention, the addition order of the monomer components may be appropriately determined according to various physical properties required for the non-thermoplastic polyimide to be finally obtained. A monomer component may be added.

Thus, the polymerization method of the polyamic acid is not particularly limited, but examples of typical polymerization methods include the following methods. In addition, these methods may be used independently and can also be used combining partially.
1) After dissolving a diamine component in an organic polar solvent, a substantially equimolar acid dianhydride component is added to the diamine component, followed by stirring and reaction to polymerize.
2) An acid dianhydride component and a diamine component in an excessively small molar amount are dissolved in an organic polar solvent, stirred and reacted, and a prepolymer having acid anhydride groups at both ends is dissolved in an organic polar solvent. Get as. Subsequently, the diamine component is added to the prepolymer solution and stirred and polymerized so that the acid dianhydride component and the diamine component are substantially equimolar in all steps.
3) An acid dianhydride component and a diamine component in an excess molar amount are dissolved in an organic polar solvent and stirred and reacted to obtain a prepolymer having amino groups at both ends as a solution of the organic polar solvent. . Subsequently, the acid dianhydride component is added to the prepolymer solution and stirred and polymerized so that the acid dianhydride component and the diamine component are substantially equimolar in all steps.
4) After the acid dianhydride component is dissolved in an organic polar solvent, the diamine component is added so as to be substantially equimolar with the acid dianhydride component, followed by stirring and reaction.
5) A substantially equimolar mixture of an acid dianhydride component and a diamine component is dissolved in an organic polar solvent, and stirred and reacted for polymerization.

  In the above polymerization method, each monomer component (acid dianhydride component and / or diamine component) may be composed of only one type of compound or may be composed of two or more types of compounds. In addition, even when added to an organic polar solvent, these compounds may not dissolve due to the problem of solubility in the same solvent, but if they are evenly dispersed throughout the solvent, they are regarded as substantially dissolved. It's okay. Therefore, the term “dissolution” can be replaced with “dispersion” in the description of the methods 1) to 5).

  The organic polar solvent (polymerization solvent) used for polymerizing the polyamic acid is not particularly limited as long as it dissolves the polyamic acid, and any solvent can be used. Amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like can be preferably used, and N, N-dimethylformamide and N, N-dimethylacetamide are particularly preferable. It can be preferably used.

  The compound that can be used as the acid dianhydride component in the present invention is not particularly limited, but is preferably an aromatic tetracarboxylic dianhydride, specifically, for example, pyromellitic dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxy) Phenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyl) Nyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ) Ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), ethylene bis (trimellitic acid monoester) Acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), and analogs of these compounds. These compounds may be used singly or as a mixture in combination at an arbitrary ratio.

  The compound that can be used as the diamine component in the present invention is not particularly limited, but is preferably an aromatic diamine, and specifically, for example, 4,4′-oxydianiline, p-phenylenediamine. 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenylsulfone, 4,4 ′ -Diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4 ' -Diaminodiphenylsilane, 4,4'-diamy Diphenylethylphosphine oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1 , 2-diaminobenzene, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, and analogs of these compounds. These compounds may be used singly or as a mixture in combination at an arbitrary ratio.

<Liquid film formation process>
In the liquid film forming step, an organic solvent solution of polyamic acid (referred to as a polyamic acid solution for convenience) is prepared using the polyamic acid obtained in the polyamic acid polymerization step or a polyamic acid that has already been synthesized. A polyamic acid solution is cast on a support to form a liquid film.

  The polyamic acid solution formed at this time preferably contains a curing agent. Therefore, the polyamic acid solution prepared in this step may be a film-forming dope to which a curing agent is added in advance. Thus, in this invention, a chemical imidation method can be used suitably as a method of imidating a polyamic acid.

  In general, the two most widely known methods for imidizing polyamic acid are a thermal imidization method (thermal cure method) performed only by heat and a chemical imidization method (chemical cure method) using a curing agent. Yes. Any method may be employed, but it is particularly preferable to employ the chemical imidization method from the viewpoint of imparting higher productivity.

  The curing agent contains at least a chemical dehydrating agent, and more preferably contains a chemical dehydrating agent and a catalyst. The chemical dehydrating agent is not particularly limited as long as it is a dehydrating and cyclizing agent for polyamic acid, but specific examples of the main component include, for example, aliphatic acid anhydrides, aromatic acid anhydrides, N , N′-dialkylcarbodiimide, lower aliphatic halide, halogenated lower aliphatic acid anhydride, arylsulfonic acid dihalide, thionyl halide, or a mixture of two or more thereof can be preferably used. Among these compounds, aliphatic acid anhydrides and aromatic acid anhydrides can be particularly preferably used.

  The catalyst is not particularly limited as long as it is a component having an effect of promoting dehydration and ring closure of a chemical dehydrating agent on polyamic acid. Specifically, for example, an aliphatic tertiary amine, Aromatic tertiary amines and heterocyclic tertiary amines can be used. Among these compounds, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, and β-picoline can be particularly preferably used.

  The amount of the chemical dehydrating agent and the catalyst used is not particularly limited as long as it can be imidized to a desired degree, but the chemical dehydrating agent is contained in the polyamic acid solution to which the chemical dehydrating agent is added. It is preferably in the range of 0.5 to 5 mol, more preferably in the range of 1.0 to 4 mol, relative to 1 mol of the amic acid unit in the polyamic acid. The catalyst is preferably in the range of 0.05 to 3 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the polyamic acid solution to which the chemical dehydrating agent and the catalyst are added. More preferably in the range of 2 to 2 mol.

  If the amount of the chemical dehydrating agent and the catalyst used is less than the above range, chemical imidization may be insufficient, and fracture may occur during imidization (firing) or mechanical strength may decrease. Moreover, when the usage-amount of a chemical dehydrating agent and a catalyst exceeds the said range, progress of imidation will become quick too much and it may become difficult to cast into a film form.

  The organic solvent used in the polyamic acid solution prepared in this step is not particularly limited, and without affecting the physical properties of the polyamic acid or the resulting polyimide, the formation of a liquid film and the subsequent gel film An organic solvent suitable for forming, firing, etc. may be appropriately selected and used. Specific examples include organic polar solvents as polymerization solvents exemplified in the polyamic acid polymerization step. If these organic polar solvents are used, the polyamic acid polymerization solvent solution obtained in the polyamic acid polymerization step can be used as it is as the polyamic acid solution.

  Various physical properties of the polyamic acid solution are not particularly limited. For example, the solid content concentration and viscosity of the polyamic acid in the polyamic acid solution may be appropriately set within a range suitable for liquid film formation and gel film formation.

  The support for casting the polyamic acid solution is not dissolved or altered by the polyamic acid solution and can withstand heat treatment performed to remove the organic solvent from the polyamic acid solution. There is no particular limitation as long as it has heat resistance. Specifically, for example, a self-rotating support that continuously forms and transports a gel film by rotating the surface, such as an endless belt or a drum, can be preferably used. Use of these as a support is preferable because the cast and applied polyamic acid solution can be dried well and a polyimide film can be continuously produced.

  The material and shape of the support are not particularly limited, and a flat plate such as a glass plate or an aluminum foil may be used. Further, when the above-mentioned endless belt or drum is used as the support, a preferable material is stainless steel as shown in Examples described later.

  Further, the specific method and conditions for forming a liquid film on the support are not particularly limited, and the physical properties and types of the polyamic acid solution, the thickness of the polyimide film to be obtained, the support Various known methods may be used based on the type, production efficiency, and the like. For example, in the examples described later, a liquid film is formed by casting a polyamic acid solution on a support using a T die.

<Gel film formation process>
In the gel film forming step, the liquid film formed on the support is partially cured and / or dried to form a gel-like film (gel film) having an organic solvent remaining and having self-indicating properties. Convert.

Since the solid content (resin content) contained in the gel film is in an intermediate stage until it is cured from polyamic acid to polyimide, it has self-supporting properties. The gel film contains an organic solvent used in the polyamic acid solution and a volatile component such as a curing agent or a product generated by a reaction of the curing agent. The weight of volatile matter is calculated by the following formula (4). In the following equation, W _A represents the weight of the gel film, W _B represents the weight after heating 20 minutes the gel film at 450 ° C..

(W _A -W _B ) × 100 / W _B (4)
The weight (content) of the volatile component calculated by the above formula (4) is preferably in the range of 5 to 500% by weight, more preferably in the range of 5 to 200% by weight, and 5 to 150%. It is particularly preferred that it is in the range of wt%. If a gel film having a volatile content within this range is used, it is possible to avoid the film from being broken in the subsequent baking step, and the film from being unevenly colored due to uneven drying. On the other hand, when the content of the volatile matter in the gel film is out of the above range, problems such as anisotropy and variations in characteristics may occur.

  There are no particular restrictions on the heating and / or drying conditions when converting the liquid film to a gel film, the type of polyamic acid used, the formation state of the liquid film, the thickness of the polyimide film to be obtained, and the curing agent used. Appropriate conditions are appropriately set according to various conditions such as the type of the above. Typically, the curing agent is activated by heating on the support in the temperature range of 80 to 200 ° C., preferably in the temperature range of 100 to 180 ° C., resulting in partial curing and / or drying. Can do.

<Baking process>
In the baking step, the obtained gel film is peeled off from the support and heated (baked) to completely imidize the remaining amic acid and remove volatile components to obtain a polyimide film.

  In the baking step, it is very preferable to fix the end of the gel film in the TD direction. Thereby, the shrinkage | contraction at the time of hardening can be avoided effectively. The fixing means is not particularly limited, and a known tenter pin or clip may be used.

  The firing (heating) conditions in the firing step are not particularly limited, and it is possible to remove complete imidization of amic acid and volatile matter, that is, water generated by the imidization reaction, residual organic solvent, and residual curing agent. Any condition is acceptable. In general, it is preferable to use a plurality of heating furnaces (firing furnaces) and heat them by gradually increasing the temperature. The heating time in each stage at this time is not particularly limited, and an appropriate time may be set according to the type of polyamic acid / polyimide, the thickness of the polyimide film to be obtained, the type of heating furnace, and the like. Good. Generally, it is between several tens of seconds to several minutes.

  In the stepwise firing, it is preferable to finally heat at a temperature range of 400 to 550 ° C. for 5 to 400 seconds. If it is heated (fired) under the above conditions in the final stage, the physical properties of the resulting polyimide film can be further improved. The heating temperature in the final stage is more preferably in the range of 400 to 500 ° C, and particularly preferably in the range of 400 to 480 ° C. If the heating temperature in the final stage is too low, the tear strength retention before and after PCT tends to be small, and if it is too high, the L value tends to vary.

  The heating time in the final stage may be within the above range, but is long when the heating temperature is relatively low (at a temperature closer to the lower limit in the temperature range), and the heating temperature is relatively When the temperature is high (when the temperature is closer to the upper limit in the above temperature range), it is preferable to shorten it. If the heating time is too short, the tear strength retention before and after the PCT tends to decrease, and if it is too long, the variation in L value tends to increase.

  In addition, in this process, in order to relieve the internal stress remaining in the gel film, it may be under a minimum necessary tension when the gel film is conveyed during the heating (firing) treatment. This heat treatment may be performed in parallel with the baking process, but such a process may be provided separately. Although the tension | tensile_strength added at this time is not specifically limited, It is preferable to exist in the range of 1-100N, and it is preferable to exist in the range of 1-50N. If it is within this range, it is not necessary to apply excessive tension to the gel film, so that it is possible to avoid a decrease in physical properties of the resulting polyimide film.

  The heating conditions for applying the tension are appropriately set according to the characteristics of the gel film / polyimide film and the type of apparatus such as a heating furnace to be used, and are not particularly limited. The heating temperature may be 200 ° C. or higher and 500 ° C. or lower, preferably 250 ° C. or higher and 500 ° C. or lower, and more preferably 300 ° C. or higher and 450 ° C. or lower. The heating time may be in the range of 1 to 300 seconds, preferably in the range of 2 to 250 seconds, and preferably in the range of 5 to 200 seconds. The internal stress can be relaxed by the heat treatment under these conditions, and the heat shrinkage rate at 200 ° C. can be reduced.

  Further, the gel film may be stretched before and after fixing the gel film to such an extent that the anisotropy of the obtained polyimide film is not deteriorated. At this time, the volatile content of the gel film is preferably in the range of 100 to 500% by weight, and more preferably in the range of 150 to 500% by weight. If the volatile content is below this range, stretching tends to be difficult, and if it exceeds this range, the self-supporting property of the film is poor and the stretching operation itself tends to be difficult.

  The specific method for performing the stretching is not particularly limited, and any known method such as a method using a differential roll or a method of widening the fixing interval of the tenter can be used.

  In addition, in the manufacturing method of the polyimide film concerning this invention, it is not necessary for each process mentioned above to be included, and one part may be abbreviate | omitted as needed, and another process is added. Needless to say. For example, when a polymerized polyamic acid solution is used, the polyamic acid polymerization step can be omitted.

<Addition of filler>
In the polyimide film concerning this invention, components other than the said non-thermoplastic polyimide may be contained. As such other components, various resins that can be blended with non-thermoplastic polyimide and do not impair the physical properties required for polyimide films, various additives for improving various properties of polyimide films, etc. Can be mentioned. Among these, in the present invention, it is preferable to add a filler. By adding the filler, various properties such as slidability, thermal conductivity, conductivity, corona resistance, loop stiffness, and the like of the obtained adhesive film can be improved.

  Although the filler used by this invention is not specifically limited, The inorganic filler which consists of various inorganic compounds can be mentioned. More specifically, oxides such as silica, mica, titanium oxide, and alumina; inorganic nitrides such as silicon nitride and boron nitride; and phosphate compounds such as calcium hydrogen phosphate and calcium phosphate.

  The particle size of the filler is not particularly limited because it is determined by the film characteristics to be modified and the type of filler to be added, etc., but generally the average particle size is in the range of 0.05 to 100 μm. It is sufficient that it is within the range of 0.1 to 75 μm, more preferably within the range of 0.1 to 50 μm, and further preferably within the range of 0.1 to 25 μm. If the particle size is below this range, the modification effect is less likely to appear. If the particle size is above this range, the surface properties may be greatly impaired or the mechanical properties may be greatly deteriorated.

  The amount of filler added is also not particularly limited because it is determined by the film properties to be modified, the particle size of the filler, and the like, but is generally 0.01-100 parts by weight with respect to 100 parts by weight of polyimide. Within a range of 0.01 to 90 parts by weight, and more preferably within a range of 0.02 to 80 parts by weight. If the amount of filler added is less than this range, the effect of modification by the filler hardly appears, and if it exceeds this range, the mechanical properties of the film may be greatly impaired.

  Although the method for adding the filler is not particularly limited, specifically, for example, (1) added to the polymerization reaction solution before or during the polymerization of the polyamic acid, (2) after the completion of the polymerization of the polyamic acid, Examples of the method include kneading the filler using a three-roll or the like, (3) separately preparing a dispersion containing the filler, and mixing this with a polyamic acid solution.

  Among these methods, (3) a method in which a dispersion containing a filler is mixed with a polyamic acid solution is preferable. If this method is adopted, the filler can be mixed immediately before forming the gel film, so that the possibility of the filler remaining in the adhesive film production line and the accompanying filler mixing can be reduced most. .

  The method for preparing the dispersion containing the filler is not particularly limited, and it may be prepared as a dispersion by adding the filler to be used to an appropriate solvent. The solvent is the same organic polar solvent as the polyamic acid solvent. Is preferably used. Further, in order to disperse the filler satisfactorily and stabilize the dispersion state, additives such as a dispersant and a thickener may be used within a range that does not affect the film physical properties.

(III) Use of the present invention The polyimide film according to the present invention can be suitably used for the production of a laminate including a polyimide layer. That is, the present invention includes a laminate produced using the polyimide film. Although the specific structure of the said laminated body is not specifically limited, As a typical structure, the laminated body which has a structure formed by laminating | stacking a metal layer on the surface of a polyimide film can be mentioned. This metal layer may be laminated | stacked on the surface of the polyimide film through the contact bonding layer as needed.

  Moreover, as a laminated body concerning this invention, the adhesive film which laminated | stacked the thermoplastic polyimide layer on the at least one surface of the polyimide film concerning this invention may be contained. Such an adhesive film can be suitably used as a coverlay film of a flexible printed wiring board.

  Although it does not specifically limit as a metal layer laminated | stacked on the said adhesive film, When using the laminated body concerning this invention as a flexible metal-clad laminated board for an electronic device and an electrical equipment use, for example, copper Alternatively, a metal foil made of a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (including 42 alloy), aluminum, an aluminum alloy, or the like can be given. Moreover, in general flexible metal-clad laminates, copper foils such as rolled copper foil and electrolytic copper foil are frequently used, but these copper foils can also be preferably used in the present invention. In addition, the antirust layer, the heat-resistant layer, or the contact bonding layer may be apply | coated to the surface of these metal foil.

  Moreover, the flexible wiring board formed using the said polyimide film or the said laminated body is also contained in this invention. Specifically, a flexible printed wiring board (FPC) can be mentioned. Although the specific manufacturing method of the upper FPC is not particularly limited, specifically, for example, a metal foil is laminated on a polyimide film, a pattern etching process is performed, and a desired pattern circuit is formed on the metal foil. A method can be mentioned.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In the following examples and comparative examples, the heat shrinkage rate, the variation in L value, the anisotropy evaluation, the tear strength retention before and after PCT, and the workability of the polyimide film were evaluated as follows.

[Heating shrinkage]
According to IPC-TM-650 2.2.4 Method A, the heat shrinkage ratio was calculated from the dimensional change before and after the polyimide film was heated at 200 ° C. for 2 hours.

[L variation of L value]
Using a small portable color difference meter (trade name: NR-3000A) manufactured by Nippon Denshoku Industries Co., Ltd., measuring the L value at 10 points at 10 cm intervals in the width direction (TD direction) of the polyimide film with a measurement area of 10 mmφ, The variation was evaluated based on whether or not the maximum value and the minimum value of the L value were within the range of 97 to 103 (± 3%) when the average value of 10 points was 100. In addition, it calibrated by 1 point fair with the attached white fair board.

[Anisotropy evaluation]
A film piece test piece cut into 2 × 2 cm at 10 cm intervals in the width direction of the polyimide film, and the extinction angle is determined with a polarizing microscope (manufactured by Nippon Optical Co., Ltd., trade name: OPTIPHOT / POL) under crossed Nicols. The birefringence (Δn _xy : where the film surface of the test piece is the xy plane and the thickness direction is the z-axis) was determined from the refractive index in two directions in the orthogonal film surface, and was used as a measure of anisotropy. The birefringence was measured using a refractometer (manufactured by Atago Co., Ltd., 4T type) equipped with an eyepiece with a polarizing plate and using a Na lamp as a light source.

[Tear strength retention before and after PCT test]
Measurements were taken before and after PCT treatment according to ASTM D-1938. The PCT treatment was performed for 12 hours under the conditions of 150 ° C. and 100% RH.

[Evaluation of processability of polyimide film]
A hole having a diameter of 0.2 mm was drilled with a punching machine, and this hole was observed with a microscope.

[Synthesis Example 1 of Polyamic Acid Solution]
In 309 kg of N, N-dimethylformamide (DMF), 6.14 kg of paraphenylenediamine (PDA) was dissolved and cooled to 0 ° C. with a cooling jacket. 11.15 kg of pyromellitic dianhydride (PMDA) was added thereto and stirred for 1 hour. To this, 26.55 kg of 4,4′-oxydianiline (ODA) was added and dissolved, and then 28.92 kg of PMDA was added and stirred for 1 hour. During the treatment, the cooling jacket maintained 0 ° C., but the reaction solution obtained by the treatment had a temperature rise due to reaction heat, and the temperature rose to a maximum of 20 ° C.

  Separately, a PMDA solution was prepared so that the weight ratio was DMF: PMDA = 16.5: 1.24, and gradually added to the reaction solution. When the viscosity reached 2800 poise at 23 ° C., the addition of the PMDA solution was stopped. As a result, a polyamic acid solution having a solid concentration of about 18.5% and a molar ratio of PDA and ODA as the diamine component of 30:70 was obtained.

[Synthesis Example 2 of Polyamic Acid Solution]
35.42 kg ODA was dissolved in 310 kg DMF and cooled to 0 ° C. by a cooling jacket. To this, 37.42 kg of PMDA was added over 1 hour and further stirred for 1 hour. During this treatment, the cooling by the cooling jacket maintained 0 ° C., but the reaction solution obtained by the treatment had a temperature rise due to reaction heat, and the temperature rose to a maximum of 29 ° C.

  Separately, a PMDA solution was prepared so that DMF: PMDA = 15.4: 1.16 by weight, and gradually added to the reaction solution. When the viscosity reached 3000 poise at 23 ° C., the addition of the PMDA solution was stopped. As a result, a polyamic acid solution having a solid concentration of about 18.5% was obtained.

[Example 1]
A curing agent was prepared by mixing isoquinoline / acetic anhydride / DMF at a ratio of 4.81 / 11.41 / 28.77 by weight. This curing agent was added to the polyamic acid solution obtained in Synthesis Example 1. The addition amount was set so that the curing agent was in a ratio of 45 parts by weight with respect to 100 parts by weight of the polyamic acid in the polyamic acid solution. After the addition of the curing agent, the mixture was quickly stirred with a mixer, and the polyamic acid solution was extruded from a T die with a width of 1200 mm and cast onto a stainless endless belt (support) to form a liquid film. The endless belt was run at a speed of 12 m / min at a position 15 mm below the T die. The liquid film on the endless belt was dried at 120 ° C. for 100 seconds to be converted into a self-supporting gel film, and peeled off from the endless belt. The amount of residual volatile components in the obtained gel film was 45% by weight.

  Both ends of this gel film were fixed to a tenter pin and subjected to heating and imidization treatment. The heating conditions are 200 ° C. × 30 seconds (first furnace: hot air circulation), 250 ° C. × 30 seconds (second furnace: hot air circulation), 360 ° C. × 30 seconds (third furnace: hot air circulation), 450 ° C. × 2 Minutes (fourth furnace: far-infrared type) (see Table 1). Thereby, a polyimide film having a width of 1200 mm and a thickness of 12.5 μm was obtained.

  The obtained polyimide film was slit so as to have a width of 1028 mm, and heat-treated for 30 seconds under a tension of 3 kg / m in a heating furnace at 300 ° C. Various physical properties were measured or evaluated as described above for the polyimide film after the heat treatment. The results are shown in Table 2.

[Example 2]
A gel film was obtained in exactly the same manner as in Example 1 except that the polyamic acid solution obtained in Synthesis Example 2 was used. The amount of residual volatile components in the obtained gel film was 45% by weight. Both ends of this gel film were fixed to a tenter pin and subjected to heating and imidization treatment. The heating conditions were the same as in Example 1 (see Table 1). Thereby, a polyimide film having a width of 1200 mm and a thickness of 25 μm was obtained.

  The obtained polyimide film was slit so as to have a width of 1028 mm, and heat-treated for 30 seconds under a tension of 3 kg / m in a heating furnace at 300 ° C. Table 2 shows the physical properties of the polyimide film after the heat treatment.

Example 3
After fixing both ends of the obtained gel film to the tenter pin, the heating conditions shown in Table 1, that is, the heating conditions up to the first to third furnaces are the same, and the heating conditions in the fourth furnace are set to 420 ° C. × 5 minutes. A polyimide film according to the present invention was obtained in the same manner as in Example 1 except that was heated and imidized.

  The obtained polyimide film was slit so as to have a width of 1028 mm, and heat-treated for 30 seconds under a tension of 3 kg / m in a heating furnace at 300 ° C. Table 2 shows the physical properties of the polyimide film after the heat treatment.

Example 4
After fixing both ends of the obtained gel film to the tenter pin, the heating conditions shown in Table 1, that is, the heating conditions up to the first to third furnaces are the same, and the heating conditions in the fourth furnace are set to 500 ° C. × 20 seconds. A polyimide film according to the present invention was obtained in the same manner as in Example 1 except that was heated and imidized.

  The obtained polyimide film was slit so as to have a width of 1028 mm, and heat-treated for 30 seconds under a tension of 3 kg / m in a heating furnace at 300 ° C. Table 2 shows the physical properties of the polyimide film after the heat treatment.

[Comparative Examples 1-4]
After fixing both ends of the obtained gel film to a tenter pin, a polyimide film as a comparative example was obtained in the same manner as in Example 1 except that the gel film was heated and imidized under the heating conditions shown in Table 1, respectively.

  Each obtained polyimide film was slit so as to have a width of 1028 mm, and heat-treated for 30 seconds in a 300 ° C. heating furnace under a tension of 3 kg / m. Table 2 shows the physical properties of the polyimide film after the heat treatment.

  As is apparent from the results in Table 2, if at least the L value and the heat shrinkage rate are within the predetermined ranges in the polyimide film, the variation in the anisotropy in the width direction is small, and the workability and the like are also excellent. I understand that.

  Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments and examples respectively. Embodiments and examples obtained by appropriately combining them are also included in the technical scope of the present invention.

  As described above, in the present invention, since the L value in the width direction of the polyimide film and the heat shrinkage rate in the length direction and the width direction are set in appropriate ranges, only dimensional stability and workability are improved. In addition, the yield and productivity can be improved, and further, the reliability of the flexible wiring board obtained by using this can be improved. Therefore, the present invention can be used not only in the field of manufacturing various resin molded products typified by polyimide films and laminates, but also related to the manufacture of electronic components such as flexible wiring boards using these. It can be applied to a wide range of fields.

Claims (7)

  It has a width of 1000 mm or more, variation in the L value in the width direction is ± 3% or less, and the heat shrinkage at 200 ° C. is 0.07% or less in both the length direction and the width direction. A polyimide film characterized by that.   The polyimide film according to claim 1, wherein the tear strength retention before and after the pressure cooker test is 60% or more.   The polyimide film according to claim 1 or 2, wherein an average thickness is 5 to 25 µm. The polyimide film contains at least a polyamic acid that is a polyimide precursor and an organic solvent, and is obtained by baking a gel film having self-supporting property,
Furthermore, the polyimide film of Claim 1, 2 or 3 which was heat-processed for 5 to 400 seconds in the temperature range of 400-550 degreeC in the final step of baking of a gel film.   The laminated body manufactured using the polyimide film of any one of Claim 1 thru | or 4.   The laminated body of Claim 5 formed by laminating | stacking a metal layer on the surface of a polyimide film. The flexible wiring board formed using the polyimide film of any one of Claims 1 thru | or 4, or the laminated body of Claim 5 or 6.