JP5285557B2 - Aromatic polyimide film and method for producing the same - Google Patents

Description

  The present invention relates to a polyimide film and a method for producing the same. More specifically, the present invention relates to a polyimide film having a low friction coefficient, excellent handling properties, and a small number of protrusions, and a method for producing the same.

  Polyimide films are known to have excellent properties in heat resistance, cold resistance, chemical resistance, electrical insulation, mechanical strength, etc., and electrical insulation materials for wires, heat insulating materials, flexible printed circuit boards (FPC) It is widely used as a base film of IC, a carrier tape film for IC tape automated bonding (TAB), a tape for fixing IC lead frames, and the like. Among these, in particular, in applications such as FPC, TAB carrier tape, and lead fixing tape, a polyimide film and a copper foil are usually bonded and used via various adhesives.

  An important practical characteristic when a polyimide film is used in these applications is the slipperiness (slidability) of the film. In various film processing steps, the slidability between the film support (for example, roll) and the film and the slidability between the films are ensured, thereby improving the operability and handling in each step. This is because the occurrence of defects such as wrinkles on the film can be avoided.

  Moreover, in the flexible printed wiring board use which is the main use of the polyimide film, the copper foil and the film are usually bonded through various adhesives. The polyimide film has a chemical structure and chemical resistance (solvent). Since adhesion to copper foil is often insufficient due to stability, the polyimide film is subjected to surface treatment such as alkali treatment, corona treatment, plasma treatment, sandblast treatment, etc., and then bonded to the copper foil. .

  On the other hand, in COF applications, a two-layer copper-clad laminate that directly forms a conductive layer on a film without using an adhesive is used. Two-layer copper-clad laminates are suitable for fine pitch because there is no adhesive, and the demand for them is increasing in recent years. Conventionally, since there was an adhesive layer on the film, the unevenness of the film was rarely reflected directly on the conductive layer.

  However, since the adhesive layer disappears, the unevenness of the film directly affects the unevenness of the conductive layer. For this reason, there is an increasing demand for foreign matter and the surface of the film. Among them, an automatic optical inspection system (AOI) was introduced as a foreign matter inspection method.

  Also, in recent finer pitches of electronic components, especially COF inspection, inspection of line width, foreign matter, etc. by visual inspection has conventionally been the mainstream, but since AOI has been introduced, inorganic powder The heat-resistant film manufactured with the conventional formulation that mixes with the body has been sufficiently satisfactory in terms of running performance, but in AOI, since inorganic powder is too large, the recent narrow pitch of COF, etc. As a result, inorganic particles may be judged as foreign substances, which is a major obstacle to automatic inspection systems.

  As a conventional smoothing technology for polyimide films, an inert inorganic compound (for example, alkaline earth metal orthophosphate, dibasic calcium phosphate anhydride, calcium pyrophosphate, silica, talc) is added to polyamic acid (for example, Further, a method of performing plasma treatment after forming fine protrusions on the film surface with fine particles (see, for example, Patent Document 2) is known. However, these inorganic particles have a problem that they are not suitable for automatic optical inspection systems due to their large particle size.

In addition, inorganic particles having an average particle diameter of 0.01 to 100 μm are held on the polyimide surface layer by embedding a part of each particle, and a plurality of protrusions made of the exposed inorganic particles are formed on the surface of the film. A method (for example, see Patent Document 3) in which 1 × 10 to 5 × 10 ⁸ pieces / mm ² exists in a layer is known. This method is characterized in that the slippery effect is effectively obtained by actively exposing the inorganic particles on the surface and reducing the friction coefficient of the film surface, but the inorganic particles are partially exposed. For this reason, there is a problem that scratches occur on the other film surface that comes into contact with the film, resulting in poor appearance.

JP-A-62-68852 JP 2000-191810 A Japanese Patent Laid-Open No. 5-25295

  An object of the present invention is to provide a polyimide film having a low coefficient of friction, excellent handling properties and a small number of protrusions, and a method for producing the same.

  In view of such circumstances, as a result of intensive research, the present inventor has provided a fine protrusion using predetermined inorganic particles on the surface of the film, thereby providing a low friction coefficient, excellent handling properties, and a small number of protrusions. The inventors have found that a film can be obtained, and have further studied to complete the present invention.

That is, the present invention
[1] Projections on the film surface are formed from inorganic particles having an average particle size of 0.01 to 1 μm and a number particle size distribution range of average particle size × 0.7 to average particle size × 1.3, A polyimide film characterized in that the number of protrusions is 1 × 10 ² to 1 × 10 ⁶ pieces / mm ² ,
[2] The polyimide film as described in [1] above, wherein the aggregation rate of particles forming the surface of the film is 30% or less,
[3] The polyimide film as described in [1] or [2], wherein the powder mainly composed of inorganic particles is contained in a proportion of 0.05 to 0.9% by weight based on the weight of the film resin.
[4] One or more aromatic diamine components selected from the group consisting of paraphenylenediamine and 4,4′-diaminodiphenyl ether, a pyromellitic dianhydride, and 3,3 ′, 4,4′- The polyimide film according to any one of [1] to [3], wherein the polyimide film is produced from one or more acid anhydride components selected from the group consisting of biphenyltetracarboxylic dianhydride,
[5] The polyimide film comprises an aromatic diamine component having a molar ratio of 4,4′-diaminodiphenyl ether and paraphenylenediamine of 69/31 to 90/10, pyromellitic dianhydride, 3,3 ′, [4] In the above [4], it is produced from a polyamic acid comprising an acid anhydride component having a molar ratio with 4,4′-biphenyltetracarboxylic dianhydride of 80/20 to 60/40. A polyimide film, and [6] (1) one or more aromatic diamine components selected from the group consisting of paraphenylenediamine and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 3,3 ′, 4, One or more acid anhydride components selected from the group consisting of 4′-biphenyltetracarboxylic dianhydride are polymerized in an organic solvent to obtain a polyamic acid solution. Step (2) Inorganic particles having an average particle diameter of 0.01 to 1 μm and a number particle size distribution in the range of average particle diameter × 0.7 to average particle diameter × 1.3 are the same organic as the organic solvent. A slurry dispersed in a solvent is prepared, and the slurry is added in any of the steps (1). (3) The polyamic acid solution obtained in the step (2) is subjected to a cyclization reaction to form a gel. A method for producing a polyimide film including a step of obtaining a film;
About.

  The polyimide film of the present invention has a low coefficient of friction, excellent handling properties, and a small number of protrusions. Therefore, particularly for a fine pitch circuit substrate, particularly for COF (Chip on Film) wiring with a narrow pitch on the TD of the film. Useful.

Hereinafter, the present invention will be specifically described. In the polyimide film of the present invention, the film surface protrusion is an inorganic particle having an average particle diameter of 0.01 to 1 μm and a number particle size distribution range of average particle diameter × 0.7 to average particle diameter × 1.3. The number of protrusions is 1 × 10 ² to 1 × 10 ⁶ pieces / mm ² . In the present invention, the use of inorganic particles is superior in dispersibility and heat resistance compared to the case where organic particles are used. In addition, heat resistance is difficult with organic particles, and polyimide with a high production temperature may be decomposed. The inorganic particles in the present invention may be contained in the polyimide film, and fine protrusions are formed on the surface of the polyimide film with the inorganic particles in the vicinity of the film surface as a nucleus.

  The average particle size of the inorganic particles used in the present invention is not particularly limited as long as it is in the range of 0.01 μm to 1 μm, but is preferably 0.05 μm to 0.7 μm, and preferably 0.1 μm to 0.6 μm. More preferred. This is because if the average particle size is 0.1 μm or more and 0.6 μm or less, the balance between the slipperiness and the unevenness of the film surface is particularly good. If the average particle size is less than 0.01 μm, the film's slidability effect decreases, which is not preferable, and if it exceeds 1.0 μm, it is not preferable because the particles are locally large. The average particle diameter in the present invention is determined by randomly selecting particles from an SEM image observed at a magnification of 10,000 to 100,000 using a scanning electron microscope (SEM), and obtaining the diameter (particle diameter). The length average of the individual was calculated and taken as the average particle diameter (length average diameter). In addition, when the number of protrusions was less than 30 in one field of view SEM image, the number was set to 30 or more in multiple fields of view. Although it does not specifically limit as said scanning electron microscope used for the measurement of the average particle diameter of this invention, S5000 (brand name; Hitachi, Ltd. make) etc. are mentioned.

本発明の無機粒子は、粒度分布が非常に狭いため、粗大な粒子、または非常に細かい粒子が含まれない。粗大な粒子は、そのまま凸突起を形成する場合があり、非常に細かい粒子は凝集しやすく、結果として粗大な粒子を形成し凸突起を形成する場合があるが、本発明の無機粒子は、このようなおそれがない。 The inorganic particles used in the present invention are not particularly limited as long as the number particle size distribution is in the range of average particle size × 0.7 to average particle size × 1.3, but there are variations in the size and height of the film surface protrusions. The number particle size distribution is more preferably in the range of average particle size × 0.75 to average particle size × 1.25 in that it can be suppressed. Since the inorganic particles in the present invention are uniform in size, the coefficient of variation (CV value) is monodisperse of 15% or less, and the number particle size distribution indicating the distribution of the existence ratio for each particle diameter is: It will be sharp. The CV value was calculated from the following formula.

Since the inorganic particle of the present invention has a very narrow particle size distribution, it does not include coarse particles or very fine particles. Coarse particles may form convex protrusions as they are, and very fine particles are likely to aggregate, and as a result, coarse particles may be formed to form convex protrusions. There is no fear.

  The number particle size distribution of the inorganic particles of the present invention is in the range of average particle size × 0.7 to average particle size × 1.3. For example, when the average particle size is 0.2 μm, the number particle size distribution is in the range of 0.14 μm to 0.26 μm. If the particle diameter is in the range of less than average particle diameter × 0.7 or exceeding average particle diameter × 1.3, it is not preferable because the projection group having the intended size cannot be formed. The number particle size distribution of the present invention is obtained by measuring the particle diameter by the method described above using a scanning electron microscope (SEM) and counting the number of particles for each particle diameter.

The material of the inorganic particles used in the present invention is not particularly limited, but silica (SiO ₂ ) or a hydrate thereof, alumina, titanium oxide, calcium phosphate, zirconium oxide, and the like are preferably used.

The number of protrusions on the film surface of the polyimide film of the present invention is not particularly limited as long as it is 1 × 10 ² to 1 × 10 ⁶ pieces / mm ² , but is 5 × 10 ² to 1 × 10 ⁵ pieces / mm ^2. preferable. If the number of protrusions is 5 × 10 ² to 1 × 10 ⁵ pieces / mm ² , the balance between film transportability and surface smoothness is excellent. When the number of protrusions is less than 1 × 10 ² pieces / mm ² , it is not preferable in terms of film transportability, and when it exceeds 1 × 10 ⁶ pieces / mm ² , it is not preferable in terms of poor surface smoothness. The number of protrusions on the film surface of the present invention is the number of surface protrusions obtained by observing the film surface with an SEM (scanning electron microscope) and counting all the protrusions that can be clearly seen in one field of view of the SEM, converted to 1 mm ^2. It was. In addition, when the number of protrusions was less than 30, it was set to 30 or more in a plurality of visual fields. This is because if the number of protrusions is less than 30, the error in the aggregation rate becomes large and the evaluation becomes inaccurate. Although it does not specifically limit as said scanning electron microscope used for the measurement of the number of surface protrusions, S5000 (brand name; Hitachi, Ltd. make) etc. are mentioned. The height of the protrusion on the film surface is not particularly limited, but is usually 5 nm or more and less than 2 μm, and preferably 5 nm or more and 1 μm or less. If it is 2 μm or more, problems such as disconnection occur when wiring is formed, and if it is less than 5 nm, it is not preferable in that the surface smoothness is inferior. The height of the protrusion is “SURFACE 1” using a scanning laser microscope (trade name: 1LM15W, manufactured by Lasertec Corporation) using a 100 × lens (CF Plan 100 × / 0.95∞ / 0 EPI, manufactured by Nikon). It was measured by photographing and analyzing the film surface in the mode.

本発明のポリイミドフィルムの凝集率は、３０％以下が好ましい。凝集率を下げる方法としては、（ｉ）無機粒子そのもの（つまり、粉状）ではなく、スラリーとしてあらかじめ分散させてから加える方法、（ｉｉ）スラリーとポリアミド酸溶液の粘度差を小さくする方法（具体的には、スラリーにポリアミド酸を加え粘度を上げる、あるいは重合完了前の粘度の低い状態のポリアミド酸溶液にスラリーを添加する等）、（ｉｉｉ）充分に攪拌しながら無機粒子を加える方法等が挙げられる。 Further, in the present invention, the protrusion means one formed from one particle or a plurality of particles, and one composed of a plurality of particles is regarded as agglomeration, and the number of particles involved in this agglomeration formation is The ratio was expressed by the following formula, and this was defined as the aggregation rate.

The aggregation rate of the polyimide film of the present invention is preferably 30% or less. As a method of reducing the aggregation rate, (i) a method of adding after dispersing in advance as a slurry instead of the inorganic particles themselves (that is, powdery), and (ii) a method of reducing the viscosity difference between the slurry and the polyamic acid solution (specifically (E.g., adding a polyamic acid to the slurry to increase the viscosity, or adding the slurry to a low-viscosity polyamic acid solution before the completion of polymerization), (iii) a method of adding inorganic particles while stirring sufficiently, etc. Can be mentioned.

  The dynamic friction coefficient of the film of the present invention was measured based on JIS K-7125 (1999). Specifically, using a slip coefficient measuring device Slip Tester (Technology), the same surfaces of two films are overlapped with each other, a 200 g weight is placed thereon, and one end of the film is fixed. One was pulled at 100 mm / min and the coefficient of friction was measured. In the polyimide film of the present invention, the film surface is modified by the above-described inorganic particles, and for example, the friction coefficient (dynamic friction coefficient) is about 0.2 to 0.5, the sliding property is good, and the handling property is excellent.

  The inorganic particles of the present invention can be produced by a known method, and are not particularly limited. For example, JP-B-4-65,006, JP-A-9-142828, JP-A-2007-277025, It can be produced by the method described in JP 2007-153732 A. As such a method, specifically, a so-called sol-gel, in which an organosilicate is hydrolyzed in the presence of a hydrolysis catalyst such as an ammonia catalyst or an organic amine catalyst, and an inorganic component is precipitated while a dehydration polycondensation reaction proceeds. Law. Moreover, you may use a commercial item, for example, Snowtex UP, Snowtex OUP, Snowtex PS-S, Snowtex PS-S (above, the product made by Nissan Chemical Industries), PL-1, PL-3, PL Colloidal silica such as -7, PL-20, SP-03F, SP-1B (manufactured by Fuso Chemical Industry Co., Ltd.), Oscar (manufactured by JGC Catalysts & Chemicals), and the like.

  The blending ratio of the inorganic particles used in the present invention is not particularly limited, but it is preferably uniformly dispersed in the film at a ratio of 0.05% by weight to 0.9% by weight with respect to the film resin weight. From the viewpoint of the slipperiness effect, a ratio of 0.1% by weight to 0.8% by weight is more preferable. If it exceeds 0.9% by weight, mechanical strength may decrease or surface roughening may occur due to aggregation of particles, and if it is 0.05% by weight or less, sufficient slipperiness effect is not observed, which is not preferable.

  In the film surface protrusions caused by the inorganic particles, the number of protrusions having a height of 2 μm or more (also referred to as the number of protrusions) is preferably 5 or less / 20 × 100 mm, and more preferably 3 or less / 20 × 100 mm. It is preferably 1 or less / 20 × 100 mm. If it is more than this, it is not preferable since the inorganic particles are judged as foreign substances by the automatic inspection system and cause trouble.

  Next, the manufacturing method of the polyimide film of this invention is demonstrated in detail below. The production process includes, for example, (1) a process of polymerizing an aromatic diamine component and an acid anhydride component in an organic solvent to obtain a polyamic acid solution, and (2) an average particle diameter of 0.01 to 1 μm and a number A slurry in which inorganic particles having a particle size distribution range of average particle size x 0.7 to average particle size x 1.3 are dispersed in the same organic solvent as the organic solvent is prepared, and the slurry is prepared in the step (1). (3) A step of cyclizing the polyamic acid solution obtained in the step (2) to obtain a gel film can be included.

  Step (1) is a step of obtaining a polyamic acid solution by polymerizing an aromatic diamine component and an acid anhydride component in an organic solvent.

  Specific examples of the aromatic diamine are not particularly limited as long as the effects of the present invention are not hindered, but paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4′-diaminodiphenyl ether, 3,4 ′. -Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxy bench Zin, 1,4-bis (3methyl-5aminophenyl) benzene or amide-forming derivatives thereof. Among them, the amount of diamine such as paraphenylenediamine or 4,4′-diaminodiphenyl ether, which has an effect of increasing the tensile modulus of the film, is adjusted, and the finally obtained polyimide film has a tensile modulus of 4.0 GPa or more. It is preferable to make it. These aromatic diamines can be used alone or in admixture of two or more. Of these aromatic diamines, paraphenylenediamine and 4,4'-diaminodiphenyl ether are preferred. When paraphenylenediamine and 4,4′-diaminodiphenyl ether are used in combination, (i) 4,4′-diaminodiphenyl ether and (ii) paraphenylenediamine are used at 69/31 to 90/10 (molar ratio). It is more preferable to use at 70/30 to 85/15 (molar ratio).

  Specific examples of the acid anhydride component are not particularly limited as long as the effects of the present invention are not hindered, but pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3, 4'-biphenyltetracarboxylic acid, 3,3 ', 4,4'-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether , Pyridine-2,3,5,6-tetracarboxylic acid, or acid anhydrides such as amide-forming derivatives thereof, preferred are acid tetraanhydrides of aromatic tetracarboxylic acids, pyromellitic acid dianhydride And / or 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is particularly preferred. These acid anhydride components can be used alone or in admixture of two or more. Of these, it is more preferable to use pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride at 80/20 to 60/40 (molar ratio), It is particularly preferable to use at 75/25 to 65/35 (molar ratio).

  In the present invention, the organic solvent used for forming the polyamic acid solution is not particularly limited. For example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; N, N-dimethylformamide, N, N-diethylformamide and the like Formamide solvents; N, N-dimethylacetamide (DMAc), acetamide solvents such as N, N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; Examples include phenolic solvents such as o-, m-, or p-cresol, xylenol, halogenated phenol, and catechol; or aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone. Or as a mixture Better bur, further xylene, the use of aromatic hydrocarbons is also possible such as toluene.

  The polymerization method may be carried out by any known method, and is not particularly limited. For example, (i) the aromatic diamine component is first put in an organic solvent, and then the acid anhydride component is converted into the aromatic diamine component. (Ii) a method in which the total amount of the acid anhydride component is first put in a solvent, and then the aromatic diamine component is added in an amount equivalent to the acid anhydride component for polymerization. (Iii) After one aromatic diamine component is put in a solvent, after mixing for a time required for the reaction at a ratio of 95 to 105 mol% of the acid anhydride component with respect to the reaction component, the other aromatic diamine component is mixed. A method in which a diamine component is added, and then an acid anhydride component is added so that the wholly aromatic diamine component and the acid anhydride component are approximately equal in amount, and polymerization is performed, and (iv) the acid anhydride component is placed in a solvent. After that, one side of the reaction components After mixing for a time required for the reaction at a ratio of 95 to 105 mol% of the aromatic diamine component, an acid anhydride component is added, and then the other aromatic diamine component is replaced with a wholly aromatic diamine component and an acid anhydride component. (V) A method in which a polymer is added so as to be approximately equal to each other and polymerized, and (v) a polyamic acid solution (A And the other aromatic diamine component and the acid anhydride component are reacted in an excess in another solvent to prepare a polyamic acid solution (B). Next, a method of mixing the obtained polyamic acid solutions (A) and (B) to complete the polymerization. In (vi) and (v), the aromatic diamine component is excessive in preparing the polyamic acid solution (A). In the case of the polyamic acid solution (B), the acid anhydride component is excessive, and when the polyamic acid solution (A) is excessive, the aromatic acid diamine component is excessive in the polyamic acid solution (B). Examples thereof include a method in which the polyamic acid solutions (A) and (B) are mixed and prepared so that the total aromatic diamine component and acid anhydride component used in these reactions are approximately equal. The conditions for the polymerization reaction may be known conditions, and are not particularly limited. The polymerization reaction may be performed at normal temperature and normal pressure, and the polymerization reaction time may be, for example, 30 minutes to 30 hours.

  The polyamic acid solution thus obtained preferably contains 5 to 40% by weight of solid content, more preferably 10 to 30% by weight. The viscosity of the polyamic acid solution is a value measured by a rotational viscometer method using a Brookfield viscometer in accordance with JIS K6726_1994, and is not particularly limited, but is preferably 10 to 2000 Pa · s (100 to 20000 poise), The thing of 100-1000 Pa.s (1000-10000 poise) is more preferable from the point of supply of the stable liquid feeding. Moreover, the polyamic acid in the organic solvent solution may be partially imidized.

  In step (2), inorganic particles having an average particle size of 0.01 to 1 μm and a number particle size distribution in the range of average particle size × 0.7 to average particle size × 1.3 are the same as the organic solvent. In this step, a slurry dispersed in an organic solvent is prepared, and the slurry is added at any stage of the step (1). The preparation of the slurry is not particularly limited, and examples thereof include a method of dispersing the inorganic particles in the organic solvent described above (for example, a polar solvent such as N, N-dimethylacetamide (DMAc)) to form a slurry. In order to obtain the slipperiness of the film, the prepared slurry is dispersed in the organic solvent or solution at any stage of the step (1) at the blending ratio of the inorganic particles. The timing of adding the inorganic particles is not particularly limited as long as it is before the cyclization reaction, and step (2) is not necessarily performed after step (1). For example, (i) an organic solvent before polyamic acid polymerization In addition, an inorganic particle slurry dispersed in the same organic solvent (for example, a polar solvent) as the organic solvent used in the production of polyimide may be added. (Ii) To the polyamic acid solution obtained by the polymerization reaction, An inorganic particle slurry dispersed in the same organic solvent (for example, polar solvent) as the organic solvent used for the production of polyimide may be added, but it is preferable to add it to the polyamic acid solution.

  Step (3) is a step of obtaining a gel film by cyclizing the polyamic acid solution obtained in the step (2). The method of cyclizing the polyamic acid solution is not particularly limited. Specifically, (i) a method of obtaining a gel film by casting the polyamic acid solution into a film and thermally dehydrating and cyclizing ( Thermal cyclization method), or (ii) a method in which a gel film is prepared by mixing the polyamic acid solution with a cyclization catalyst and a conversion agent to chemically decyclize, and obtaining a gel film by heating (chemical cyclization method). The latter method is preferable in that the linear thermal expansion coefficient of the resulting polyimide film can be kept low.

  The cyclization catalyst is not particularly limited, and examples thereof include aliphatic tertiary amines such as trimethylamine and triethylenediamine; aromatic tertiary amines such as dimethylaniline; and heterocycles such as isoquinoline, pyridine and β-picoline. A tertiary amine etc. are mentioned, The 1 or more heterocyclic tertiary amine chosen from the group which consists of isoquinoline, a pyridine, and (beta) -picoline is preferable. Examples of the conversion agent include, but are not limited to, aliphatic carboxylic anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride; aromatic carboxylic anhydrides such as benzoic anhydride, and the like. Preference is given to benzoic anhydride. The content of these conversion agents is not particularly limited, but is preferably about 10 to 40% by weight and more preferably about 15 to 30% by weight with respect to 100% by weight of the polyamic acid solution.

  Although the film forming method of a film is not specifically limited, For example, it can form into a film with a continuous film forming apparatus using the said polyamic acid solution. Specifically, the polyamic acid solution is formed into a film shape through a slit-shaped base, cast on a heated support, undergoes a thermal ring-closing reaction on the support, and has a self-supporting gel. It becomes a film and is peeled from the support.

  The support is not particularly limited, and examples thereof include a metal (for example, stainless steel) rotating drum, an endless belt, and the like. The temperature of the support is (i) a liquid or gas heat medium, and (ii) an electric heater. And is not particularly limited.

  The gel film is preferably heated to 30 to 200 ° C., more preferably 40 to 150 ° C. by heat received from a support, heat received from a heat source such as hot air or an electric heater, and a ring-closing reaction is performed. It becomes self-supporting by drying volatile matter, and is obtained by peeling from the support.

  An imide film can be obtained from the peeled gel film, and the method is not particularly limited, but a suitable example will be described below. The peeled gel film is usually stretched in the running direction while regulating the running speed with a rotating roll. Stretching in the running direction is performed at a magnification of 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times. The gel film stretched in the running direction is introduced into a tenter device, and both ends in the width direction are held by the tenter clip, and stretched in the width direction while running with the tenter clip. Stretching in the width direction is performed at a magnification of 1.05 to 2.3 times, preferably 1.1 to 2.0 times, and more preferably 1.1 to 1.7 times. The film is heated with hot air, an infrared heater or the like for 15 seconds to 10 minutes. Next, heat treatment is performed with hot air and / or an electric heater at a temperature of 250 to 500 for 15 seconds to 20 minutes to obtain a polyimide film.

  In the present invention, the thickness of the polyimide film is not particularly limited, but is preferably in the range of 3 μm to 250 μm, and more preferably in the range of 10 μm to 80 μm. If it is thinner or thicker than this, the film-forming property of the film is remarkably deteriorated. The width of the polyimide film of the present invention is not particularly limited.

  The polyimide film thus obtained may be annealed as necessary. Annealing treatment causes thermal relaxation of the film and can reduce the heat shrinkage rate. The annealing temperature is not particularly limited, but is preferably 200 to 500 ° C. In the manufacturing method of the polyimide film of the present invention, since the orientation of the film to TD is strong, the heat shrinkage rate at TD tends to be high, but the heat shrinkage rate at 200 ° C. is reduced by the thermal relaxation from the annealing treatment, Since both TD can be suppressed to 0.05% or less, the dimensional accuracy is further improved, which is preferable. Specifically, it is preferable to carry out the annealing treatment by running the film in a furnace at 200 to 500 ° C. under low tension. The time during which the film stays in the furnace is the processing time, but it is controlled by changing the running speed, and the processing time is preferably 30 seconds to 5 minutes. If the treatment time is shorter than this, heat is not sufficiently transferred to the film, and if the treatment time is longer, the film becomes superheated and the flatness is impaired. Moreover, 10-50 N / m is preferable and the film tension at the time of driving | running | working has more preferable 20-30 N / m. When the tension is lower than this range, the running property of the film is deteriorated, and when the tension is high, the heat shrinkage rate in the running direction of the obtained film is increased, which is not preferable.

Although it does not specifically limit as a heat shrinkage rate of the polyimide film of this invention, -0.02%-+ 0.02% are preferable. Heat shrinkage was measured by preparing a 20cm x 20cm film, measuring the film dimension (L1) after leaving it in a room adjusted to 25 ° C and 60% RH for 2 days, and then heating at 200 ° C for 60 minutes. The film size (L2) was measured after being left in a room adjusted to 25 ° C. and 60% RH for 2 days, and calculated by the following formula.

  In order to give adhesion to the obtained polyimide film, the film surface may be subjected to electrical treatment such as corona treatment or plasma treatment or physical treatment such as blast treatment. The pressure of the atmosphere in which the plasma treatment is performed is not particularly limited, but is usually in the range of 13.3 to 1330 kPa, preferably 13.3 to 133 kPa (100 to 1000 Torr), and preferably 80.0 to 120 kPa (600 to 900 Torr). Is more preferable.

The atmosphere in which the plasma treatment is performed contains at least 20 mol% of an inert gas, preferably contains 50 mol% or more of inert gas, more preferably contains 80 mol% or more, and contains 90 mol% or more. Most preferred is. The inert gas includes He, Ar, Kr, Xe, Ne, Rn, N ₂ and a mixture of two or more thereof. A particularly preferred inert gas is Ar. Furthermore, oxygen, air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, tetrafluoromethane (carbon tetrafluoride), trichlorofluoroethane, trifluoromethane, etc. are mixed with the inert gas. May be. Preferred mixed gas combinations used as the plasma treatment atmosphere of the present invention are argon / oxygen, argon / ammonia, argon / helium / oxygen, argon / carbon dioxide, argon / nitrogen / carbon dioxide, argon / helium / nitrogen, argon / Helium / nitrogen / carbon dioxide, argon / helium, helium / air, argon / helium / monosilane, argon / helium / disilane and the like.

Processing power density when a plasma treatment is not particularly limited, 200 W · min / ^{m 2} or more preferably, 500 W · min / ^{m 2} or more is more preferable, 1000W · min / ^{m 2} or more is most preferred. The plasma irradiation time for performing the plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of the plasma treatment can be sufficiently exhibited without accompanying film deterioration. The gas type, gas pressure, and treatment density of the plasma treatment are not limited to the above conditions, and may be performed in the atmosphere.

  The effects of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

[Synthesis Example 1]
Pyromellitic dianhydride (molecular weight 218.12) / biphenyltetracarboxylic dianhydride (molecular weight 294.22) / 4,4′-diaminodiphenyl ether (molecular weight 200.24) / paraphenylenediamine (molecular weight 108.14) Was prepared at a molar ratio of 70/30/70/30 and polymerized to a 18.5 wt% solution in DMAc to obtain a 3000 poise polyamic acid solution.

[Synthesis Example 2]
Pyromellitic dianhydride (molecular weight 218.12) / 4,4'-diaminodiphenyl ether (molecular weight 200.24 was prepared at a molar ratio of 100/100, and in DMAc (N, N-dimethylacetamide) 18. Polymerization was performed with a 5% by weight solution to obtain a 3000 poise polyamic acid solution.

[Synthesis Example 3]
Biphenyltetracarboxylic dianhydride (molecular weight 294.22) / paraphenylenediamine (molecular weight 108.14) was prepared at a molar ratio of 100/100, polymerized as a 18.5% by weight solution in DMAc, and 3000 poise. A polyamic acid solution was obtained.

[Example 1]
A slurry in which silica particles having an average particle size of 0.2 μm and a number particle size distribution range of average particle size × 0.82 to average particle size × 1.18 are dispersed in DMAc in the polyamic acid solution prepared in Synthesis Example 1. After adding 0.2% by weight per resin weight and stirring and dispersing sufficiently, the varnish-like polyamic acid solution was converted into polyimide using a continuous film-forming apparatus, and at the same time dried and solidified to form a polyimide film. Obtained. The obtained characteristics are shown in Table 1.

[Examples 2 to 6]
A polyimide film having a thickness of 38 μm was added and formed in the same manner as in Example 1 except that a silica DMAc slurry having an average particle size and number particle size distribution range shown in Table 1 was added to the polyamic acid solution prepared in the synthesis example. Got. The obtained characteristics are shown in Table 1.

[Comparative Examples 1-4]
A polyimide film having a thickness of 38 μm was added and formed in the same manner as in Example 1 except that a silica DMAc slurry having the average particle size and number particle size distribution ranges shown in Table 2 was added to the polyamic acid solution prepared in the synthesis example. Got. The obtained characteristics are shown in Table 2.

[Film surface observation]
The film was shadowed with Ag at a shadowing angle of 5 °, Pt was sputter coated, and then the surface was observed using a scanning electron microscope (SEM) S5000 (trade name; manufactured by Hitachi, Ltd.). The average particle size, deviation from the average particle size, the number of protrusions, and the aggregation rate were measured by the method described above. The results are shown in Tables 1 and 2.

[Friction coefficient (dynamic friction coefficient)]
Based on JIS K-7125 (1999), using a slip coefficient measuring device Slip Tester (manufactured by Technonez), the same surface of the film was overlapped, a 200 g weight was placed thereon, and one end of the film was fixed. The other was pulled at 100 mm / min, and the coefficient of friction was measured. The results are shown in Tables 1 and 2.

[Convex number]
Projections with a height of 2 μm or more were counted in a 20 × 100 mm range of the film. Since the number of protrusions is basically uniformly dispersed, no particular problem occurs even if the protrusions are counted within the above-described range of the film. The height of the protrusion is “SURFACE 1” using a scanning laser microscope (trade name: 1LM15W, manufactured by Lasertec Corporation) using a 100 × lens (CF Plan 100 × / 0.95∞ / 0 EPI, manufactured by Nikon). It was measured by photographing and analyzing the film surface in the mode. The results are shown in Tables 1 and 2.

  As described above, the films of Examples 1 to 6 have a low coefficient of friction, excellent handling properties, and a small number of protrusions, which are suitable for COF (Chip on Film) applications. It was confirmed that the friction coefficient was high and handling was difficult, the number of protrusions was large, and it was not suitable for COF applications.

  The polyimide film of the present invention has a low coefficient of friction, excellent handling properties, and a small number of protrusions. Therefore, it is particularly useful for fine pitch circuit substrates, particularly for COF (Chip on Film) wiring with a narrow pitch on the TD of the film. It is.

Claims (5)

The protrusions on the film surface are formed from inorganic particles having an average particle diameter of 0.01 to 1 μm and a number particle size distribution in the range of average particle diameter × 0.7 to average particle diameter × 1.3. There Ri 1 × ¹⁰ 2 ~1 × ^{10 6} cells / mm ² der, and characterized in that the powder to the inorganic particles mainly is contained in a proportion of 0.2 to 0.9 wt% per film resin weight Polyimide film.   2. The polyimide film according to claim 1, wherein the aggregation rate of particles forming the surface of the film is 30% or less. The polyimide film comprises one or more aromatic diamine components selected from the group consisting of paraphenylenediamine and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic The polyimide film according to claim 1 or 2 , wherein the polyimide film is produced from one or more acid anhydride components selected from the group consisting of acid dianhydrides. The polyimide film is composed of an aromatic diamine component having a molar ratio of 4,4′-diaminodiphenyl ether and paraphenylenediamine of 69/31 to 90/10, pyromellitic dianhydride, and 3,3 ′, 4,4. 4. The polyimide film according to claim 3 , wherein the polyimide film is produced from a polyamic acid composed of an acid anhydride component having a molar ratio with '-biphenyltetracarboxylic dianhydride of 80/20 to 60/40. 5. (1) one or more aromatic diamine components selected from the group consisting of paraphenylenediamine and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic acid A step of polymerizing one or more acid anhydride components selected from the group consisting of dianhydrides in an organic solvent to obtain a polyamic acid solution; (2) an average particle size of 0.01 to 1 μm and a number particle size distribution; A slurry in which inorganic particles having an average particle diameter of 0.7 to an average particle diameter of 1.3 is dispersed in the same organic solvent as the organic solvent is prepared. A step of adding the powder mainly composed of inorganic particles in a proportion of 0.2 to 0.9% by weight per film resin weight , (3) the polyamic acid obtained in the step (2) Anti-cyclizing solution Method for producing a polyimide film was comprising the step of obtaining a gel film is.