JP2011094042A - Polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film having good surface properties, hardly causing winding slip, and capable of securing the surface properties of the film of preventing the winding slip in a state of a roll of a long continuous length, and hardly causing problems in sputtering and plating. <P>SOLUTION: The polyimide film is the one containing inorganic particles regulated so that the shape of the contained inorganic particle may be amorphous, and the proportion thereof based on the solid component of a polyimide resin may be within the range of 0.01-0.50 wt.%. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a polyimide film that can be suitably used for electronic materials such as a flexible printed board and a base film for COF.

  2. Description of the Related Art In recent years, electronic devices have been rapidly improved in performance, function, and size, and accordingly, there is an increasing demand for downsizing and weight reduction of electronic components used in electronic devices. In response to the above request, the demand for flexible printed wiring boards (hereinafter also referred to as FPC) is growing particularly. An FPC generally has a structure in which an insulating film such as a polyimide film having flexibility is used as a substrate (base film), a metal layer is provided on the surface of the substrate, a circuit pattern is formed, and a cover layer is provided on the surface. is doing.

  Among the above FPCs, those in which a metal layer is directly formed on a polyimide film by sputtering, plating or the like can form a finer circuit, and thus can be suitably used for applications requiring high density. The Since the polyimide film used here forms a fine circuit, surface smoothness is required.

  On the other hand, when industrially producing a plastic film with a long length, it is generally performed to add inorganic particles as an anti-blocking material in order to ensure transportability and winding property, and polyimide film is no exception. . By adding an anti-blocking material, irregularities are formed on the film surface, sticking to a transport roll and blocking during winding can be prevented, and a long film can be produced stably. However, since the addition of the anti-blocking material acts in the direction of deteriorating the smoothness of the film surface, problems such as pinholes occur when the metal layer is formed by sputtering or plating as described above. Moreover, when the unevenness | corrugation formed is large, when winding up in roll shape, it will become easy to produce a winding gap. In order to solve this problem, attempts have been made to achieve both transportability and smoothness by using spherical silica having a small particle size (see, for example, Patent Documents 1 to 3).

  However, since the small particle size has small irregularities formed on the film surface, and the spherical contact area is small, the effect as an anti-blocking material is small. Therefore, there is a problem that the tension at the time of winding in a roll shape has to be weakened, and there is a problem that winding deviation easily occurs due to the feeding tension when the film is fed out again. On the other hand, attempts have been made to use amorphous inorganic particles instead of spherical particles (see, for example, Patent Document 4), but this is a manufacturing method in which a polyamide resin is melt-extruded from a die into water. A general method for producing a polyimide film is to cast and dry a precursor polyamic acid solution on a support to give it a self-supporting property, and then peel it off and fire it. Since the manufacturing method is greatly different, it is not certain whether or not the desired film surface state is obtained when amorphous particles are used.

JP 2008-88371 A JP 2008-7631 A JP 63-108038 A JP-A-9-67515

  The present invention has been made in view of the above, and an object of the present invention is to provide a polyimide film that has good surface properties and hardly causes winding deviation.

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have found that the shape of the inorganic particles used as the anti-blocking material is indefinite and the contact area is increased to prevent the film from slipping and maintain the surface property. The present invention has been completed.

  That is, the present invention is a polyimide film containing inorganic particles, wherein the shape of the inorganic particles contained is indefinite, and the ratio is in the range of 0.01 to 0.50% by weight with respect to the polyimide resin solid content. It is related with the polyimide film characterized by being.

  A preferred embodiment relates to the polyimide film, wherein the inorganic particles are silica.

  A preferred embodiment relates to the polyimide film, wherein the average particle diameter of the inorganic particles is 2 μm or less.

  The polyimide film obtained by the present invention can prevent winding deviation in a long roll state, and can secure film surface properties that do not cause problems in sputtering and plating.

  Embodiments of the present invention will be described below.

<Polyimide film>
The polyimide film used in the present invention is manufactured using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid. Usually, the polyamic acid obtained by dissolving a substantially equimolar amount of an aromatic dianhydride and an aromatic diamine in an organic solvent is obtained. The organic solvent solution is produced by stirring under controlled temperature conditions until the polymerization of the acid dianhydride and the diamine is completed.

  As the polymerization method, any known method and a combination thereof can be used. The characteristic of the polymerization method in the polymerization of polyamic acid is the order of addition of the monomers, and the physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomers. Therefore, in the present invention, any method of adding monomers may be used for the polymerization of polyamic acid. The following method is mentioned as a typical polymerization method.

That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent, and this is reacted with a substantially equimolar aromatic tetracarboxylic dianhydride for polymerization.
2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, a method of polymerizing with an aromatic diamine compound so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps,
3) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding an aromatic diamine compound here, using the aromatic tetracarboxylic dianhydride so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. How to polymerize,
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar,
5) A method of polymerizing by reacting a mixture of substantially equimolar aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent,
And so on. These methods may be used singly or in combination.

  In the present invention, the polyamic acid obtained by using any of the above polymerization methods may be used, and the polymerization method is not particularly limited.

  At the time of polyamic acid polymerization, the polyamic acid solution is 5 μm or less, preferably 3 μm or less, particularly preferably 2 μm or less in the middle of the polymerization in order to prevent foreign materials derived from the raw material from entering the film and deteriorating the surface properties of the film. It is preferable to perform filtration with a filter. The viscosity of the polyamic acid solution at this time is preferably 100 poises or less, more preferably 50 poises or less, and most preferably 30 poises or less. When the filter opening is larger than the above range, the foreign matter in the raw material passes through and is finally mixed into the polyimide film, which may impair the surface smoothness of the film. When the viscosity of the polyamic acid solution is higher than the above range, the time required for filter filtration becomes longer, and the productivity may decrease.

  Regarding the concentration of the polyamic acid solution at the time of synthesis, a lower concentration is preferable because the amount of the solvent contained in the polyamic acid solution increases and the mixing property with the imidization accelerator is improved. However, if the concentration is too low, it is difficult to produce a thick film. The concentration of the polyamic acid solution is preferably 5 to 30 wt%, and more preferably 10 to 20 wt%.

  Moreover, about the viscosity of a polyamic-acid solution, since the lower one improves a miscibility with an imidation promoter, it is preferable. However, lowering the viscosity leads to lowering the molecular weight of the polyamic acid, so that the obtained fill may not exhibit desired physical properties. In consideration of ensuring both film properties and mixing properties, the viscosity of the polyamic acid solution is preferably 1000 to 3500 poise, and more preferably 1500 to 3000 poise. On the other hand, the viscosity of polyamic acid depends on the concentration. If the molecular weight is the same, the lower the concentration, the lower the viscosity. For this reason, the concentration of the polyamic acid may be adjusted to achieve a desired viscosity. However, in order to obtain a film having sufficient strength, the weight average molecular weight of the polyamic acid is preferably at least 100,000 or more.

  A conventionally well-known method can be used about the method of manufacturing a polyimide film from the said polyamic-acid solution. An example is shown below.

  The polyamic acid solution is extruded from a T-die or the like and cast on a rotating support such as a drum or endless belt. At this time, in order to promote the imidization reaction, it is preferable from the viewpoint of productivity that an imidization accelerator containing a dehydrating ring-closing agent and / or a catalyst is previously mixed with the polyamic acid solution. As the dehydrating ring-closing agent, acid anhydrides such as aliphatic acid anhydrides and aromatic acid anhydrides can be suitably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be suitably used.

  The cast polyamic acid solution is heated on the support to volatilize the solvent, and at the same time, imidization proceeds to some extent to obtain a gel film having self-supporting properties. The gel film is peeled off from the support, passed through a heating furnace with both ends in the width direction fixed, and removal of the remaining solvent and imidization are completed to obtain a polyimide film. What is necessary is just to adjust suitably about the solvent residual rate in the state of a gel film, the degree of imidation, and the temperature setting of a heating furnace in view of the kind of polyamic acid, the thickness of the polyimide film obtained, a physical property variation, etc.

<Inorganic particles>
The polyimide film according to the present invention is added with inorganic particles as an anti-blocking material in order to prevent long conveyance and blocking during winding. The shape of the inorganic particles used must be indefinite. By using amorphous inorganic particles, the contact area between the films when rolled up is increased, and it becomes easy to get caught, so it is possible to suppress winding deviation without impairing the smoothness of the film surface. is there. The “indefinite shape” as used in the present invention refers to a shape that is not a true sphere, and includes various shapes such as an ellipse and a polygon. However, even if it is elliptical or polygonal, it is not classified as indeterminate if it is composed only of particles of a single shape such as a triangular pyramid or a cube. In the present application, at least four kinds of particles having different shapes are treated as irregular particles. Conventionally known means can be used as means for producing amorphous inorganic particles. Examples thereof include a method of pulverizing an ingot and a method of forming spherical particles and then pulverizing them with a bead mill or the like to make them indefinite.

  As addition amount of an inorganic particle, it adds 0.01 to 0.50 weight% with respect to a polyimide resin solid content, Preferably it adds in 0.05 to 0.30 weight%. When the amount is less than the above range, the effect as an anti-blocking material may not be obtained. On the other hand, when the amount is larger than the above range, the surface smoothness of the resulting polyimide film may be impaired. As a method for adding the inorganic particles, a method of adding to the polyamic acid solution which is a polyimide precursor in the state of a dispersion dispersed in an organic solvent is preferable in order to uniformly disperse in the obtained polyimide film. Particularly preferred is a method of adding to a polyamic acid solution having a low viscosity after filtration during polymerization. As a method of dispersing the inorganic particles in the organic solvent, any known method such as an ordinary stirrer, ultrasonic wave, bead mill, etc. may be used. However, a dispersion means such as a bead mill has a large external force applied to the particles themselves, and the particles may be crushed during the dispersion and the shape and size may be changed. Further, in order to prevent the inorganic particles from reaggregating in the dispersion before use, a polyamic acid solution may be added to the dispersion to obtain a state of about 50 to 200 poise.

  The inorganic particles used in the present invention preferably use silica from the viewpoints of chemical stability, supply ability and the like. Examples of the method for producing amorphous silica include a method of pulverizing natural meteorite, a method of pulverizing ingot obtained by melting natural meteorite at high temperature, a method of pulverizing silica particles larger than a desired size with a bead mill, etc. However, it may be selected as appropriate.

  The average particle diameter of the inorganic particles is preferably 2 μm or less, and more preferably 1.5 μm or less. When the average particle size is larger than the above range, the surface smoothness of the resulting polyimide film may be impaired. The lower limit of the particle diameter is preferably 0.05 μm or more, and more preferably 0.1 μm or more. When the average particle diameter is smaller than the above range, it is difficult for irregularities to be formed on the film surface, and the effect as an anti-blocking material may not be exhibited. The particle size may be appropriately adjusted so as to obtain a desired size by adjusting the pulverization conditions, classification after pulverization, filtration after preparing the dispersion, and the like. In addition, amorphous inorganic particles tend to have a wide particle size distribution due to their production method. Since the surface smoothness of the resulting polyimide film is remarkably impaired when particles having a large particle diameter are mixed, it is preferable to remove the coarse particles in advance by classification or remove the coarse particles with a filter when added to the polyamic acid.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to these. In addition, the winding deviation of the polyimide film in an Example and a comparative example and the evaluation method of surface smoothness are as follows.

[Winding misalignment]
The film obtained in the example or the comparative example was slit to a width of 514 mm, and was wound up by 1500 m on a 6-inch core with a winding tension of 33N. Side plates were attached to both ends of the core of the wound roll, put into a vacuum oven, decompressed to about 0.007 atm at room temperature, and left for 1 hour.
After 1 hour, the pressure was returned to normal pressure, and the roll was taken out and set in a film feeding device. The case where the winding deviation was less than 1 mm, the case where it was 1 mm or more and less than 5 mm, and the case where the winding deviation was 5 mm or more were evaluated as x.

[Surface smoothness]
Three samples of 10 × 30 cm were cut out from arbitrary locations on the films obtained in Examples or Comparative Examples, and observed with a 400 × polarizing microscope to count inorganic particle aggregates of 5 μm or more. When the total number of aggregates was less than 2, ◯, 2 or more and less than 5 were evaluated as Δ, and 5 or more were evaluated as ×.

Example 1
N, N-dimethylformamide (hereinafter referred to as DMF) was added to a reactor maintained at 20 ° C. under a nitrogen atmosphere, and 4,4′-diaminodiphenyl ether (hereinafter referred to as ODA) was added and dissolved therein. Subsequently, 97 mol% of pyromellitic dianhydride (hereinafter referred to as PMDA) was added to ODA and stirred for 30 minutes to obtain a 20 poise polyamic acid solution. This polyamic acid solution was filtered through a 3 μm filter and transferred to another reactor.

On the other hand, 200 g of crushed silica (average particle size 1.1 μm) was added to 1800 g of DMF in another container, and sonication was performed for 30 minutes. After the treatment, the solution was added to the reactor containing the polyamic acid solution while passing through a 5 μm filter, and stirred for 10 minutes.
To this polyamic acid solution, a separately prepared 7 wt% DMF solution of PMDA (filtered with a 1 μm filter) was gradually added and stirring was continued. Finally, the viscosity at 20 ° C. was 2500 poise and the solid content concentration was 18 A polyamic acid solution having a filler concentration of 0.03% by weight based on the solid content of the polyimide film finally obtained was 0.5%.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.3 / 4.0) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless endless belt running 20 mm below the die. After heating this resin film at 130 ° C. for 100 seconds, the self-supporting gel film is peeled off from the endless belt (volatile content 40% by weight) and fixed to the tenter clip, 300 ° C. for 20 seconds, 400 ° C. × It was dried and imidized for 20 seconds at 450 ° C. for 20 seconds to obtain a polyimide film having a thickness of 25 μm.

(Example 2)
A polyimide film was obtained in the same manner as in Example 1 except that crushed silica having an average particle size of 1.9 μm was used.

(Example 3)
A polyimide film was obtained in the same manner as in Example 1 except that a component having an average particle diameter of 1.5 μm was extracted from the crushed silica having an average particle diameter of 4.0 μm by classification.

(Comparative Example 1)
A polyimide film was obtained in the same manner as in Example 1 except that true spherical silica having an average particle size of 0.3 μm was used.

(Comparative Example 2)
Example 1 except that true spherical silica having an average particle size of 0.3 μm is used and the amount of filler dispersion added is adjusted so that the filler concentration relative to the final polyimide film solid content is 0.01% by weight. The same operation was performed to obtain a polyimide film.

(Comparative Example 3)
Example 1 except that true spherical silica having an average particle size of 0.3 μm is used and the amount of filler dispersion added is adjusted so that the filler concentration with respect to the final polyimide film solid content is 0.08 wt%. The same operation was performed to obtain a polyimide film.

(Comparative Example 4)
A polyimide film was obtained in the same manner as in Example 1 except that true spherical silica having an average particle size of 3.5 μm was used.

(Comparative Example 5)
A polyimide film was obtained in the same manner as in Example 1 except that the addition amount of crushed silica was adjusted so that the filler concentration was 0.60% by weight.

(Comparative Example 6)
A polyimide film was obtained in the same manner as in Example 1 except that the amount of crushed silica was adjusted so that the filler concentration was 0.005% by weight.

Table 1 shows the evaluation results of the polyimide films obtained in the examples and comparative examples. The polyimide film of the example using amorphous particles resulted in a balance between winding deviation and film surface smoothness. On the other hand, the film of the comparative example using spherical particles having a small particle diameter caused winding deviation, and when the addition amount was reduced, blocking became severe and the film could not be wound into a roll. Conversely, increasing the amount added resulted in deterioration of the surface properties. Even when the particle size was increased, it was not possible to balance winding deviation and smoothness.
On the other hand, even when amorphous particles were used, if the amount added was too large, the surface properties of the film deteriorated. On the contrary, when the addition amount is too small, the anti-blocking effect is lost and the film cannot be wound into a roll.

Claims (3)

  A polyimide film containing inorganic particles, wherein the shape of the contained inorganic particles is indefinite, and the ratio is in the range of 0.01 to 0.50% by weight with respect to the polyimide resin solid content. A polyimide film.   The polyimide film according to claim 1, wherein the inorganic particles are silica.   The polyimide film according to claim 1 or 2, wherein the average particle diameter of the inorganic particles is 2 µm or less.