JP5035779B2 - Method for producing polyimide film - Google Patents

Description

This invention relates to a method of manufacturing a polyimide film arm which metal foil or metal thin film typified by copper foil is used as a support or coverlay film for a flexible printed circuit protection of the electrical wiring board is laminated. More specifically, a method of manufacturing a polyimide film arm color unevenness in the film width direction is superior less and handling.

  Polyimide film has high heat resistance and high electrical insulation, so it is used in a wide range of industrial fields as an electrical insulation material that requires heat resistance. Especially, a support for electrical wiring boards laminated with copper foil. For example, solder can be used to connect an electrical component such as an IC and a copper foil, and the electrical wiring can be reduced in size and weight.

  In connection with this, the use range of the flexible printed circuit board is widened, and improvement of productivity, quality, and quality of the polyimide film are also problems.

  In order to improve the productivity per unit time of the polyimide film, for example, it is conceivable to increase the film width of the production line, but a technique for making the film physical properties uniform in the width direction is newly required. The polyimide film is heat-treated at a high temperature after drying the solvent to improve mechanical properties and flatness, but the heat-treated polyimide film becomes darker due to the crosslinking reaction and the L value decreases, If the heat treatment is not performed uniformly in the width direction, a difference in color strength will occur especially at the center and the end of the film. However, there is no known document that devises the heat treatment conditions to improve the color unevenness of the polyimide film. Therefore, the present inventor considered adding a gradient in the width direction to the heater output of the heat treatment zone, but it was found that an excessive gradient causes a poor flatness of the film. We also considered improving the air flow by increasing the amount of air supplied to the heat treatment zone and making the temperature uniform in the zone, but this led to increased output of the heater, which not only deteriorated energy intensity but also radiant heat. The problem was that the bundle increased and the film surface was modified.

  Therefore, as a result of intensive studies to solve such problems and improve the L value unevenness in the width direction while keeping the film flatness in a good state, the heat treatment conditions of the film are not improved. The problem was solved by setting the residual solvent concentration distribution in the width direction of the film immediately before the heat treatment so as to be a certain special value or less.

  There is no known literature for improving the color unevenness of the polyimide film by devising the heat treatment condition of the polyimide.

  The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue.

Therefore, an object of the present invention is to provide a method for producing a polyimide film arm color unevenness in the film width direction is superior less and handling.

  In order to achieve the above object, according to the present invention, there is provided a polyimide film characterized in that the L value unevenness per 1 m in the film width direction is 2.0 or less.

In addition , the method for producing a polyimide film of the present invention comprises forming a polyamic acid film into a sheet-like polyamic acid film by continuously extruding or applying the polyamic acid solution from a die onto a rotating support, and then closing the ring to heat drying. In this step, the residual solvent concentration distribution in the width direction of the film immediately before the heat treatment is controlled to 18 % or less.

  According to the present invention, as described below, a polyimide film with little color unevenness in the film width direction and excellent handling can be obtained.

  The present invention will be specifically described below.

Polyimide film obtained by the production method of the polyimide film of the present invention, hereinafter L value unevenness of 2.0 per film width direction 1 m, Ri der particularly 1.5 or less, more, piece extension of the longitudinal direction of the film is 6mm Hereinafter, it is particularly preferably 4 mm or less, and by satisfying such characteristics, it is possible to obtain a polyimide film with little color unevenness in the film width direction and excellent handling.

  In addition, the L value unevenness per 1 m in the film width direction referred to in the present invention uses SM-7-CH manufactured by Suga Test Instruments Co., Ltd., and when the film thickness decreases, the sensitivity of the detector becomes dull and appropriate evaluation cannot be performed. Is a value obtained by superimposing one sheet for a film of 50 microns or more and a minimum number of films of 50 microns or more for a film of less than 50 microns.

  In addition, the film stretch in the longitudinal direction is strictly divided into four so that the film heated by an electric heater has a width of 500 mm, and 6.5 m in the longitudinal direction is sampled and uniformly spread on a flat plate. In this case, the string is stretched between both ends of the 6.5 m side, and the distance between the side of the film and the string is measured at the end and the center.

A polyimide film satisfying such characteristics is formed into a sheet-like polyamic acid film by continuously extruding or applying a polyamic acid solution from a die onto a rotating support, and in a step of ring-closing and heating and drying, it can be produced by control the width direction residual solvent concentration distribution of the heat treatment immediately before the film 18% or less.

  As a method for controlling the residual solvent concentration distribution in the film width direction to 20% or less, the conventional slit-type air blowing nozzle is affected by air having different temperatures leaking from the rooms before and after the drying zone. Even though it was difficult to dry uniformly, it was possible to reduce unevenness in drying in the width direction by dividing the slit to prevent the blown air from falling and adding improvements such as increasing the drying zone. Residual solvent concentration distribution in the film width direction can be controlled.

  The polyamic acid, which is a polyimide precursor used in the present invention, is composed of an aromatic tetracarboxylic acid and an aromatic diamine, and is composed of a repeating unit represented by the following formula 1.

  In the above formula 1, R1 is a tetravalent organic group having at least one aromatic ring, the carbon number of which is 25 or less, and the two carboxyl groups bonded to R1 are amides of the aromatic ring in R1. The carbon atom to which the group is bonded is bonded to the adjacent carbon atom, and R2 is a divalent organic group having at least one aromatic ring, the carbon number of which is 25 or less And the amino group is bonded to the carbon atom of the aromatic ring in R2.

  Specific examples of the aromatic tetracarboxylic acids include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3,3 ', 4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6- Examples include tetracarboxylic acids and amino-forming derivatives thereof. In the production of polyamic acid, these acid anhydrides are preferably used.

  Specific examples of the aromatic diamines include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone. 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3′-dimethoxybenzidine, 1,4-bis (3methyl-5aminophenyl) benzene and amides thereof And forming derivatives.

  Specific examples of the organic solvent used in the present invention include organic polar amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and these organic solvents. May be used alone or in combination of two or more or in combination with a non-polar solvent such as benzene, toluene, xylene.

  The organic solvent solution of polyamic acid used in the present invention contains a solid content of 5 to 40% by weight, preferably 10 to 30% by weight, and the viscosity is 100 to 20000 poise as measured by a Brookfield viscometer. Preferably, the one having 1000 to 10000 poise is preferable for stable liquid feeding. Moreover, the polyamic acid in the organic solvent may be partially imidized, and may contain a small amount of an inorganic compound.

  In the present invention, aromatic tetracarboxylic acids and aromatic diamines are polymerized in such a proportion that their respective mole numbers are approximately equal, or one of them is in the range of 10 mol%, preferably 5 mol%. On the other hand, it may be blended excessively. The polymerization reaction is continuously carried out in the temperature range of 0 to 80 ° C. for 10 minutes to 30 hours with stirring and / or mixing in an organic solvent. If necessary, the polymerization reaction is divided or the temperature is increased or decreased. It doesn't matter. Although there is no restriction | limiting in particular in the addition order of both reactants, It is preferable to add aromatic tetracarboxylic acid in the solution of aromatic diamines. Vacuum defoaming during the polymerization reaction is an effective method for producing a high-quality polyamic acid organic solvent solution. Moreover, you may perform a polymerization reaction by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction.

  Specific examples of the ring-closing catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylenediamine, and double-ring tertiary amines such as isoquinoline, pyridine and betapicoline. It is preferred to use at least one amine selected from cyclic tertiary amines.

  Specific examples of the dehydrating agent used in the present invention include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. And / or benzoic anhydride is preferred.

  As a method for producing a polyimide film from an organic solvent of polyamic acid, an organic solvent solution of polyamic acid containing a ring-closing catalyst and a dehydrating agent is cast on a support from a base with a slit and formed into a film. The gel film has a self-supporting property by drying with heat, and then peels off from the support, and further includes a thermal ring closure method in which imidization is performed by drying / heat treatment at a high temperature, and a ring closure catalyst and a dehydrating agent are included. The polyamic acid organic solvent was cast from a slitted die onto a support, formed into a film, and partially imidized on the support to form a self-supporting gel film. A chemical cyclization method in which peeling, heat drying / imidization, and heat treatment is performed is a typical method.

  However, in the polyimide film manufacturing method of the present invention, it is an essential condition to control the residual solvent concentration distribution in the width direction of the film immediately after the heat treatment after drying to 20% or less, whereby the film flatness is in a good state. Thus, it is possible to obtain a film with improved L value unevenness in the width direction.

In the present invention, the residual solvent concentration distribution in the film width direction needs to be 18 % or less. However, the L value unevenness in the width direction can be improved by reducing the amount of heat converted into the latent heat of vaporization of the solvent as much as possible. Therefore, it is preferable to control the dry state of the film immediately before the heat treatment so that it is preferably 15% or less, more preferably 10% or less.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, ODA represents 4,4'-diaminodiphenyl ether, PMDA represents pyromellitic dianhydride, and DMAc represents N, N-dimethylacetamide.

[Example 1]
PMDA 99.3 to 100 mol% was reacted with ODA in a DMAc solution to obtain a polyamic acid solution. Β-picoline and acetic anhydride were added to this polyamic acid solution, stirred and cooled, and cast onto a drum from a die to obtain a self-supporting polyimide gel film. The gel film was peeled off from the drum, and introduced into the oven while being stretched in the longitudinal direction and the width direction with the end pinned, and dried at a temperature of 260 ° C. by blowing air.
Since the conventional slit-type air blowing nozzle is affected by the air with different temperatures leaking from the room before and after the drying zone, it was difficult to dry uniformly in the width direction. The drying unevenness in the width direction was reduced by preventing the collapse and increasing the drying zone by one zone.

  After drying, a heat treatment with a heater was not performed, and a polyimide film not subjected to heat treatment having a film width of 2200 mm and an average thickness of 50 microns was obtained.

Both ends of the obtained film were cut 100 mm each, and about 10 g of the film was cut out from a position where the film was equally divided into 8 in the width direction. The cut film was placed in a round bottom flask and weighed to 0.01 g, and then 500 ml of pure water was added. 20 ± 0.1 g of granular sodium hydroxide was weighed and placed in the round bottom flask and stirred until it was dissolved. A round bottom flask was set in a mantle heater, a condenser was attached, and an Erlenmeyer flask into which 20 ml of 0.05 molar sulfuric acid was charged was attached to a distilling receiving part. After confirming that the film was hydrolyzed by boiling the round bottom flask at total reflux for 3 hours, water flow through the cooler was stopped, and about 300 ml was distilled from the round bottom flask into the Erlenmeyer flask. Phenolphthalein was added to the Erlenmeyer flask, titrated with a 0.1 molar aqueous sodium hydroxide solution, and the residual solvent was determined by the following formula.
Residual DMAc (%) = [(Tb−T) / S] X0.8712
S: Sample weight Tb: Blank titration (ml)
T: Distillate droplet quantification (ml)

  The difference between the maximum value and the minimum value of the eight residual solvent amounts measured was 18% of the average value.

  After the obtained film was heat-treated with an electric heater and both ends were cut by 100 mm each, the film was cut from a total of five locations, 300 mm from the end of the film and from the end to the center, and the center of the film. The value was measured. The average L value was 47.8, the difference between the maximum value (both film end portions) and the minimum value (film center portion) was 1.2, and the L value unevenness per 1 m in the width direction was 1.2. Further, the film heat-treated with the electric heater was divided into four strictly so as to have a width of 500 mm, and 6.5 m in the longitudinal direction was sampled and uniformly spread on a flat plate. A string was stretched between both ends of a 6.5 m side, and the distance between the side of the film and the string was measured at the end and the center to measure the half elongation of the film. The maximum value of the single elongation of each of the four divided films was 3 mm.

  This polyimide film had little color unevenness in the film width direction and was excellent in handling.

[Comparative Example 1]
PMDA 99.3 to 100 mol% was reacted with ODA in a DMAc solution to obtain a polyamic acid solution. Β-picoline and acetic anhydride were added to this polyamic acid solution, stirred and cooled, and cast onto a drum from a die to obtain a self-supporting polyimide gel film. The gel film was peeled off from the drum and introduced into the oven and dried while being stretched in the longitudinal direction and the width direction with the end pinned. At this time, air with different temperatures, which intentionally leaks from the rooms before and after the drying zone, was blown to generate temperature unevenness on the film surface, thereby causing drying unevenness. After drying, a heat treatment with a heater was not performed, and a polyimide film not subjected to heat treatment having a film width of 2200 mm and an average thickness of 50 microns was obtained.

  Both ends of the obtained film were cut by 100 mm each, and about 10 g of the film was cut out from the position equally divided into 8 in the width direction, and the residual solvent amount was measured by the same method as in Example 1. The difference between the maximum value and the minimum value of the residual solvent amount at 8 points was 22% of the average value.

  About the film heat-processed by making the output of an electric heater the same as the comparative example 1, L value nonuniformity was measured by the same method as Example 1. FIG. The average value of the L values was 48.2, and the unevenness of the L value per 1 m in the width direction was 3.3. Further, the half elongation was measured by the same method as in Example 1. The maximum value of the half elongation of each of the four divided films was 5 mm.

  This polyimide film had many color unevenness in the film width direction and was inferior in handling.

[Comparative Example 2]
PMDA 99.3 to 100 mol% was reacted with ODA in a DMAc solution to obtain a polyamic acid solution. Β-picoline and acetic anhydride were added to this polyamic acid solution, stirred and cooled, and cast onto a drum from a die to obtain a self-supporting polyimide gel film. The gel film was peeled off from the drum and introduced into the oven and dried while being stretched in the longitudinal direction and the width direction with the end pinned. At this time, similarly to Comparative Example 1, temperature unevenness on the film surface was intentionally generated to cause drying unevenness. After drying, a heat treatment with a heater was not performed, and a polyimide film not subjected to heat treatment having a film width of 2200 mm and an average thickness of 50 microns was obtained.

  Both ends of the obtained film were cut by 100 mm each, and about 10 g of the film was cut out from the position equally divided into 8 in the width direction, and the residual solvent amount was measured by the same method as in Example 1. The difference between the maximum value and the minimum value of the residual solvent amount at 8 points was 22% of the average value. The electric heater output during the heat treatment was adjusted in the film width direction to obtain a film having an average L value of 46.7 and an L value unevenness of 1.8. When the piece elongation was measured by the same method as in Example 1, the maximum value of the piece elongation of each of the four divided films was 9 mm.

  This polyimide film had many color unevenness in the film width direction and was inferior in handling.

  Since the polyimide film of the present invention has little color unevenness in the film width direction and excellent handling, the support or flexible printing of an electric wiring board on which a metal foil or a metal thin film typified by a copper foil is laminated It can be widely used as a coverlay film for circuit protection.

Claims (1)

A sheet of polyamic acid film is formed by continuously extruding or applying the polyamic acid solution from a die onto a rotating support, and in the process of ring-closing and heat drying, the film remains in the width direction immediately before heat treatment. The manufacturing method of the polyimide film whose L value nonuniformity per 1 m of film width directions is 2.0 or less characterized by controlling solvent concentration distribution to 18 % or less.