JP2018028053A - Method for producing transparent polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a transparent polyimide film useful as a heat-resistant transparent resin substrate material that has excellent dimensional stability, transparency, and heat resistance, and is easily peeled from a support base material to give a thin polyimide film.SOLUTION: A method for producing a transparent polyimide film is characterized in that: a polyimide precursor is obtained by the reaction between a diamine containing one or two selected from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 2,2'-dimethyl-4,4'-diaminobiphenyl, and an acid dianhydride containing 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride; and the polyimide film has a thermal expansion coefficient of 45 ppm/K or less, and a light transmittance of 5% or less on a light beam at 308 nm, and 70% or more on a light beam at 400 nm.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a transparent polyimide film, and more particularly to a method for producing a transparent polyimide film useful as a resin substrate material having high transparency, low thermal expansion coefficient, high heat resistance, and laser lift-off characteristics.

  High performance of electronic equipment is rapidly progressing, and there is a tendency for lighter and thinner products. With this trend, parts used in electronic equipment and substrates for mounting them are also required to support high performance. Is growing. For thin displays and touch panel applications, glass substrates are used as the base material for display panels. However, they are thinner, lighter, more flexible, and reduce processing costs through roll-to-roll processes. In order to achieve this, resin substrate materials have been developed. However, since resin is generally inferior in dimensional stability, transparency, heat resistance and the like as compared with glass, various studies have been made.

  Display applications include large displays such as televisions and small displays such as mobile phones, personal computers and smartphones. For example, glass substrates are used as support substrates for mounting various elements such as thin film transistors (TFTs) in organic EL devices. Is used. Similarly, in the touch panel application, there is a strong demand for a resin substrate material that can replace the glass substrate, and in that case, a low coefficient of thermal expansion (CTE) is also required, for example, 45 ppm / K or less. It is desired from the viewpoint of preventing the occurrence of the above.

  As such a resin substrate material, polyimide is one of promising materials because of its excellent heat resistance and dimensional stability.

  In recent years, in order to obtain a thin polyimide substrate, a glass substrate is used as a supporting substrate, a polyimide film is once formed on the supporting substrate, and then an electronic component is mounted, and then the polyimide film is peeled off from the glass substrate as a supporting substrate. It has also been proposed to do. For example, Patent Document 1 is a polyimide precursor resin composition for forming a flexible device substrate that is manufactured by peeling from a carrier substrate, and has a glass transition temperature of 300 ° C. or more and a thermal expansion coefficient of 20 ppm / K or less. Is disclosed. However, no consideration has been given to transparency. Patent Document 2 is a laminate comprising a polyimide film obtained by casting a polyimide precursor solution having a specific structure on an inorganic substrate, dried and imidized, and an inorganic substrate, and has a high light transmittance and an outgas. Disclose a few. However, since the thermal expansion coefficient (CTE) of polyimide exceeds 45 ppm / K, the difference from the thermal expansion coefficient of 10 ppm / K or less of the glass substrate is large and the shape stability is poor.

Patent Document 3 discloses that the transmittance of diamine and tetracarboxylic dianhydride used as raw materials is strictly controlled in order to reduce coloring of polyimide. Patent Document 4 specifies a diamine-derived structure and a tetracarboxylic dianhydride-derived structure, and is derived from a specific alicyclic tetracarboxylic dianhydride, in order to produce a colorless and transparent, low CTE polyimide film. Disclosed are a polyimide precursor and a resin composition having an amide bond imidization ratio of 10 to 100%. In addition, Patent Document 5 reacts a diamine compound and a compound containing three or more amino groups with tetracarboxylic dianhydride, and Patent Document 6 discloses a polymer solution in which fine particles are contained in a polyimide-based precursor. It is proposed to form a fine particle-containing layer.
However, it is still expected that a method for producing a transparent polyimide film useful as a practical heat-resistant transparent resin substrate material that can be replaced with a glass substrate and satisfies required characteristics such as dimensional stability will continue to be developed. It is.

JP 2010-202729 A JP2012-40836A JP 2013-23583 A International Publication No. 2015/122032 JP 2014-210896 A JP2013-209498A

  Under such background, the present invention is excellent in dimensional stability, transparency, and heat resistance, and can be easily peeled from a supporting substrate to produce a thin polyimide film, which is useful as a heat-resistant transparent resin substrate material. It aims to provide a method.

  The present invention includes a step of applying a polyimide precursor or a resin solution thereof on the surface of a support, and a step of heating and imidizing the polyimide precursor or a resin solution thereof to form a polyimide layer on the surface of the support. And a step of peeling the polyimide layer from the support to obtain a polyimide film, wherein the polyimide precursor is 2,2′-bis (trifluoromethyl)- From 4,4'-diaminobiphenyl (also known as 2,2'-bis (trifluoromethyl) benzidine) and 2,2'-dimethyl-4,4'-diaminobiphenyl (also known as 2,2'-dimethylbenzidine) The polyimide film is obtained by reacting a diamine containing one or two selected diamines with an acid dianhydride containing 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and , Thermal expansion Coefficient is not more than 45 ppm / K, in light of light transmittance 308nm is 5% or less, in the light of 400nm is a manufacturing method of a transparent polyimide film, wherein the 70% or more.

As for the manufacturing method of the transparent polyimide film of this invention, it is desirable to satisfy any one or more of the following.
1) A diamine selected from 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl and 2,2'-dimethyl-4,4'-diaminobiphenyl is contained in an amount of 50 mol% or more of the total diamines, In addition, 70% by mole or more of 1,2,3,4-cyclobutanetetracarboxylic dianhydride with respect to the total acid dianhydride.
2) Whether diamine other than 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl or 2,2'-dimethyl-4,4'-diaminobiphenyl is contained in 1 to 50 mol% of the total diamine Or 1 to 30 mol% of acid dianhydrides other than 1,2,3,4-cyclobutanetetracarboxylic dianhydride in the total acid dianhydrides.
3) The yellowness of the resulting polyimide film is 6 or less.
4) Laser light is irradiated to the interface between the polyimide layer and the support, and the polyimide layer is peeled off from the support substrate.

Another aspect of the present invention is a method for producing a transparent polyimide film, comprising: forming a functional layer on the polyimide layer, and then peeling the polyimide layer with the functional layer from the support. It is a manufacturing method of a transparent polyimide film with a layer.
In this case, the functional layer includes a transparent conductive layer, a wiring layer, a conductive layer, a gas barrier layer, a thin film transistor, an electrode layer, a light emitting layer, an adhesive layer, an adhesive layer, a transparent resin layer, a color filter resist, and a hard coat layer. It is preferable that it is any 1 type, or 2 or more types of layers selected from these.

  According to the production method of the present invention, a thin transparent polyimide film excellent in dimensional stability, transparency and heat resistance and excellent in film peelability (laser lift-off characteristics) from a supporting substrate can be easily obtained. The transparent polyimide film obtained by the present invention can be used as a practical flexible heat-resistant transparent resin substrate material that satisfies the required characteristics such as dimensional stability, and can be substituted for a glass substrate for display and touch panel applications by utilizing these characteristics. Available.

  In the method for producing a transparent polyimide film of the present invention, a polyimide precursor is applied on a support (support substrate), imidized to form a polyimide layer, and then the polyimide layer is peeled off from the support substrate. It is suitable for producing a polyimide film used as a transparent resin substrate material having a thickness of 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

As is well known, the polyimide precursor can be represented by the following general formula (1).
[-OCX (COOH) ₂ CO-HN-Y-NH-] (1)
Moreover, the polyimide formed by imidizing a polyimide precursor can be represented by the following general formula (2).
[-N (OC) ₂ X (CO) ₂ NY-] (2)
In the formulas (1) and (2), X is a tetravalent residue formed by removing two acid anhydride groups from an acid dianhydride, and Y is generated by removing two amino groups from a diamine. It is a valence residue.

In the synthesis of the polyimide precursor (polyamic acid), diamine and tetracarboxylic dianhydride are used. In the production method of the present invention, 2,2′-bis represented by the following formula (3a) is used as the diamine. From (trifluoromethyl) -4,4′-diaminobiphenyl (abbreviation: TFMB) or 2,2′-dimethyl-4,4′-diaminobiphenyl (abbreviation: m-TB) represented by the following formula (3b) A diamine containing one or two selected species is used.

  In the production method of the present invention, TFMB or m-TB is used as an essential component as a diamine. By using TFMB or m-TB in an amount of 50 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more of the total diamine, a structural unit derived from TFMB or m-TB is converted into a structure derived from all diamines. In the unit, it will be included at the corresponding ratio. If TFMB or m-TB is used within the above range, it is preferable because polyimide has excellent visible light transmittance and the transparency of the flexible substrate is improved.

In the production method of the present invention, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (abbreviation: CBDA) represented by the following formula (4) is used as an essential component as a tetracarboxylic dianhydride. .

  If CBDA is used in an amount of 70 mol% or more, preferably 80 mol% or more of the total acid dianhydride, the structural unit derived from CBDA is included in the corresponding unit in the structural unit derived from total acid dianhydride. Become. If CBDA is used within the above range, the resulting polyimide will have a low CTE. This improves the dimensional stability of the flexible substrate using polyimide, and enables the warp of the flexible device to be suppressed.

  In the production method of the present invention, the polyimide precursor can be obtained by reacting a diamine containing one or two selected from TFMB or m-TB with a tetracarboxylic dianhydride containing CBDA. TFMB or m-TB is preferably contained in the total diamine in an amount of 50 mol% or more. The total acid dianhydride preferably contains 70 mol% or more of CBDA.

  However, not only TFMB or m-TB and CBDA, but as an acid dianhydride component, a tetracarboxylic dianhydride component other than CBDA is included in the range of 1 to 30 mol%, and / or as a diamine component. 1 to 50 mol%, preferably 1 to 40 mol%, more preferably 1 to 30 mol%, and preferably contains a diamine component other than TFMB or m-TB. If it is this range, since the light transmittance of 308 nm of the polyimide obtained by imidating a polyimide precursor falls and peelability (laser lift-off characteristic) improves, it is preferable. When a diamine component other than TFMB or m-TB is included, a polyimide obtained by imidizing the polyimide precursor by simultaneously including a tetracarboxylic dianhydride component other than CBDA has a low light transmittance of 308 nm, 400 nm This is more preferable because the light transmittance is high and the CTE is low.

As a result, a polyimide precursor having a structural unit composed of a structure derived from TFMB or m-TB and a structure derived from CBDA, and then imidized with a polyimide having a structural unit represented by the following formula (6) Can be obtained. In the formulas (5) and (6), the diamine-derived structure shows the case where TFMB is used as a raw material. When m-TB is used as a raw material, the trifluoromethyl group (CF ₃ ) Becomes a methyl group (CH ₃ ), and when two are used in combination, they have a structure coexisting according to the amount used.

  The polyimide precursor used in the production method of the present invention preferably contains 50 to 97 mol%, more preferably 70 to 97 mol% of the structural unit represented by the formula (5) in the polyimide precursor. . Similarly, the polyimide used in the production method of the present invention obtained by imidizing this polyimide precursor also has a structural unit represented by the formula (6) in the polyimide, preferably 50 to 97 mol%, more preferably It is good to contain 70-97 mol%.

  In addition to TFMB or m-TB, diamines used for copolymerization include, for example, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,4-diaminomesitylene, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2, 6-xylidine, 4,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3'-diamino Diphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy ) Phenyl] propane 4,4'-diaminodiphenyl sulfide, 3,3'- Aminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,3-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4 , 4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis (p- β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl) -5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-a Tert-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6 -Diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine and the like.

  Among these diamines, 5-amino-2- (4-aminophenyl) benzimidazole (AAPBZI) or 5-amino-2- (4-aminophenyl) benzoxazole (AAPBZO) is preferable.

  When these diamine components other than TFMB or m-TB are used in combination, the use ratio is preferably 1 to 50 mol%, more preferably 1 to 30 mol%, based on the total diamine.

  In addition to CBDA, tetracarboxylic dianhydrides used for copolymerization include, for example, 4,4 ′-(2,2′-hexafluoroisopropolyden) diphthalic dianhydride (“bis (3,4) -Dicarboxyphenyl) hexafluoropropane dianhydride "or abbreviated as" 6FDA "), naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene-1,2,5,6 -Tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride 3 , 3 ', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3 ', 4'-benzophenone tetracarboxylic dianhydride Anhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4 , 5,8-Tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene -1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride Anhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3 , 6,7-Tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic dianhydride, 3,3``, 4,4 ''-p -Terphenyltetracarboxylic dianhydride, 2,2``, 3,3 ''-p-terphenyltetracarboxylic dianhydride, 2,3,3 ', 4'-p-terphenyltetracarboxylic acid Dianhydride 2,2-bis (2,3-dicarboxyphenyl) -propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3-dicarboxyphenyl) Ether dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) sulfone dianhydride, bis ( 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride Perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride Perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride Anhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic Acid dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, (Trifluoromethyl) pyromellitic dianhydride, di (trifluoromethyl) pyromellitic dianhydride, di (heptafluoropropyl) pyromellitic dianhydride, pentafluoroethylpyromellitic dianhydride, bis { 3,5-di (trifluoromethyl) phenoxy} pyromellitic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 5,5'-bis (trifluoromethyl) ) -3,3 ', 4,4'-tetracarboxybiphenyl dianhydride, 2,2', 5,5'-tetraki (Trifluoromethyl) -3,3 ', 4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis (trifluoromethyl) -3,3', 4,4'-tetracarboxydiphenyl ether dianhydride 5,5′-bis (trifluoromethyl) -3,3 ′, 4,4′-tetracarboxybenzophenone dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} benzene dianhydride, bis {( Trifluoromethyl) dicarboxyphenoxy}, trifluoromethylbenzene dianhydride, bis (dicarboxyphenoxy) trifluoromethylbenzene dianhydride, bis (dicarboxyphenoxy) bis (trifluoromethyl) benzene dianhydride, bis ( Dicarboxyphenoxy) tetrakis (trifluoromethyl) benzene dianhydride, 2,2-bis {(4- (3,4-dicarboxyphenoxy) phenyl} hexafluoro Propane dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} biphenyl dianhydride, bis {(trifluoromethyl) dicarboxyphenoxy} bis (trifluoromethyl) biphenyl dianhydride, bis {(trifluoromethyl) Dicarboxyphenoxy} diphenyl ether dianhydride, bis (dicarboxyphenoxy) bis (trifluoromethyl) biphenyl dianhydride, and the like.

  Among these tetracarboxylic dianhydrides, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic anhydride (PMDA) or 6FDA is exemplified as a preferable one. .

  When these tetracarboxylic dianhydride components other than CBDA are used in combination, the use ratio is preferably 1 to 30 mol%, preferably 1 to 28 mol%, more preferably based on the total tetracarboxylic dianhydride. Is 1 to 20 mol%, more preferably 1 to 10 mol%.

  In the production method of the present invention, a polyimide precursor (polyamic acid) is known to be polymerized in an organic polar solvent using diamine and dianhydride in a molar ratio (substantially equimolar) of 0.9 to 1.1. It can manufacture by the method of. Specifically, after dissolving diamine in an aprotic amide solvent such as N, N-dimethylacetamide and N-methyl-2-pyrrolidone under a nitrogen stream, acid dianhydride is added, and at room temperature, 3 to It can be obtained by reacting for about 20 hours. At this time, the molecular terminal may be sealed with an aromatic monoamine or an aromatic monocarboxylic anhydride. Other examples of the solvent include dimethylformamide, 2-butanone, diglyme, xylene, γ-butyllactone, etc., and these can be used alone or in combination of two or more.

  In the production method of the present invention, the polyimide precursor thus obtained is imidized by a thermal imidization method or a chemical imidization method. In thermal imidization, a polyimide precursor is applied on an arbitrary supporting substrate material such as glass, metal, resin (polyimide film, etc.) using an applicator, and preliminarily dried at a temperature of 130 ° C. or lower for 3 to 60 minutes. Thereafter, it is usually carried out by heat treatment at room temperature to about 360 ° C. for about 30 minutes to 24 hours for solvent removal and imidization. In chemical imidization, a dehydrating agent and a catalyst are added to a polyimide precursor (also referred to as “polyamic acid”) solution, and dehydration is performed chemically at 30 to 60 ° C. A typical dehydrating agent is acetic anhydride, and a catalyst is pyridine. Thermal imidation can be completed in a relatively short time by selecting a combination of acid dianhydride, diamine, and solvent, and heat treatment including preheating can be performed within 60 minutes. is there. Moreover, combined use of thermal imidization and chemical imidization is also possible. When applying the polyimide precursor, it may be applied as a polyimide precursor solution in which the polyimide precursor is dissolved in a known solvent. In addition, it is good to use the thickness of a support base material about 0.02-1.0 mm, for example. In addition, when apply | coating a polyimide precursor, you may apply | coat as a polyimide precursor solution which dissolved the polyimide precursor in the well-known solvent.

  The preferred degree of polymerization of the polyimide precursor and the polyimide in the production method of the present invention is 1,000 to 40,000 cP, preferably 3,000 to 5,000 cP, as the viscosity of the polyimide precursor solution measured by an E-type viscometer. . The molecular weight of the polyimide precursor can be determined by the GPC method. The preferred molecular weight range (polystyrene conversion) of the polyimide precursor is preferably in the range of 15,000 to 250,000 in number average molecular weight and 30,000 to 800,000 in weight average molecular weight, preferably in the range of 50,000 to 300,000. Not all out of range polyimides can be used. The molecular weight of polyimide is also in the same range as the molecular weight of its precursor.

  In the production method of the present invention, various fillers and additives may be blended with the polyimide precursor or polyimide as necessary within a range not impairing the object of the present invention. For example, inorganic fine particles such as silica, alumina, boron nitride, and aluminum nitride may be added for the purpose of improving slipperiness and thermal conductivity.

  Next, the polyimide laminated body in which the polyimide layer was formed on the surface of a support body (support base material) peels a polyimide layer from a support body, and obtains a polyimide film. Since the suitable means for this peeling differs depending on the type of the support, a suitable means is adopted. If the support is a copper foil or the like, there are means for dissolving it with an acid. When the support is a resin (polyimide) film, a polyimide having a thickness of 25 μm or more and a heat resistance of 400 ° C. or more is suitable. When the support is made of a transparent material such as a glass substrate, a laser lift-off (LLO) method is suitable. In the LLO method, laser light is irradiated from the glass substrate side. If the laser light has a wavelength in the ultraviolet region, preferably in the near ultraviolet region near 308 μm, it is efficiently absorbed by the polyimide film obtained in the present invention to generate heat, and at the same time, between the glass substrate and the polyimide layer. A gap is formed in the substrate, and peeling is easy or possible.

  Moreover, the polyimide film obtained by the production method of the present invention may be composed of not only a single layer but also a plurality of layers of polyimide.

  By the production method of the present invention, a thin polyimide layer (film) can be formed on a supporting substrate, and a transparent polyimide film having excellent performance in transparency, dimensional stability, heat resistance, and ease of peeling from the supporting substrate is obtained. be able to. That is, for a light beam having a light transmittance of 400 nm, it is 70% or more, preferably 80% or more, and the coefficient of thermal expansion (CTE) is 45 ppm / K or less, preferably 35 ppm / K or less, more preferably 30 ppm / K or less. It can be easily removed from the supporting substrate by a known method. In particular, in the production method of the present invention, the polyimide has a light transmittance of 5% or less, preferably 3% or less in the wavelength region of the laser beam (for example, 308 nm). Since it is absorbed without passing through, it is easily peeled off at the interface with the supporting substrate (glass substrate), has excellent releasability (laser lift-off: LLO) from the supporting substrate by laser light irradiation, and has a thickness of 30 μm or less. More preferably, it is suitable for obtaining a thin transparent polyimide film of 20 μm or less, more preferably 15 μm or less.

  Here, unless otherwise specified, the thermal expansion coefficient (CTE) is a linear expansion coefficient when changed from 250 ° C. to 100 ° C., and the polyimide in the production method of the present invention has a thermal expansion coefficient (10 ppm) of glass. / K or less), the shape stability is excellent when glass is used as the supporting substrate. For example, when manufacturing a flexible device such as a functional layer lamination in a TFT substrate for organic EL devices having a bottom emission structure or a top emission structure, a touch panel substrate, a color filter, etc., the substrate warpage can be suppressed, and the manufacturing yield of the flexible device is excellent . And the light ray of an invisible light area | region can be absorbed and the transmittance | permeability of a visible light area | region can be improved. Within this range, 308 nm laser light (excimer laser) can be absorbed while maintaining transparency in the visible light region. As a result, by irradiating a flexible substrate such as an organic EL device substrate, a touch panel substrate, or a color filter substrate with a laser, the polyimide layer (film) is made of glass without damaging the display device on the transparent polyimide layer. It can be made to peel and it can manufacture suitably by the laser lift-off method. The yellowness (YI) is 6 or less, preferably 4 or less. If it is this range, it can be used conveniently for the board | substrates which are required to be transparent and colorless, such as a TFT substrate for organic EL devices, a touch panel substrate, and a color filter substrate. In addition, from the viewpoint of heat resistance, the glass transition temperature is 300 ° C or higher, preferably 350 ° C or higher, more preferably 380 ° C or higher, and the thermal decomposition temperature (Td1) is 340 ° C or higher, preferably 380 ° C or higher. is there.

The polyimide film obtained by the production method of the present invention is suitable as a practical flexible heat-resistant transparent resin substrate material that satisfies the required properties such as dimensional stability, replacing the glass substrate which is an existing material in thin display and touch panel applications. Available to: That is, using a polyimide film as a substrate material, functional layers such as elements having various functions can be formed on the surface. Illustrative examples include not only main display devices such as liquid crystal display devices, organic EL display devices, touch panels, and electronic paper, but also related components such as thin film transistors (TFTs), color filters, conductive films, gas barrier films, and flexible circuit boards. An adhesive film can also be formed.
In this case, the polyimide film may be made of not only a single layer but also a plurality of layers of polyimide.

  In addition, the formation method of the functional layer is appropriately set according to the target device, but in general, after forming a metal film, an inorganic film, an organic film, etc. on the polyimide film, It can be obtained by a known method such as patterning into a predetermined shape or heat treatment as required. That is, the means for forming these display elements is not particularly limited, and may be appropriately selected, for example, sputtering, vapor deposition, CVD, printing, exposure, immersion, etc. These process processes may be performed by, for example. And after forming a functional layer on a polyimide film, it may be immediately after forming a functional layer through various process treatments, or separating a support substrate and a polyimide film with a functional layer, or for a certain period of time For example, it may be integrated with the support base material, and may be separated and removed immediately before use as a display device, for example.

  In the production method of the present invention, the polyimide layer (film) formed on the support base material further forms a functional layer thereon, and then peels the polyimide film from the support base material together with the functional layer. For example, after the assembly manufacturing process of various electronic components for forming a functional layer on a polyimide film is completed, the polyimide film with a functional layer on the obtained support substrate is subjected to laser light irradiation to obtain a polyimide layer with a functional layer. (Film) is peeled from the supporting substrate. As above-mentioned, if an excimer laser (wavelength 308nm) is used and it irradiates to the interface of a support base material (glass) and a polyimide film, a polyimide film with a functional layer can be easily peeled from a support base material.

  In addition, when peeling a polyimide film with a functional layer from a support base material, if a polyimide film is extended | stretched, retardation will become large. For this reason, the method of peeling so that the stress concerning a polyimide film in the case of peeling becomes small is preferable. In order to prevent the stretching of the polyimide film, after forming a stretching prevention layer such as an adhesive on the support base material, forming a polyimide layer (film) thereon, and further forming a functional layer thereon A method is preferred in which the polyimide film is peeled together with the stretch prevention layer and the functional layer, and the stress necessary for peeling is dispersed in the other layers.

  Hereinafter, based on an Example and a comparative example, this invention is demonstrated concretely. The present invention is not limited to these examples.

Abbreviations of raw materials used in Examples and the like are shown below.
-TFMB: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl-m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl-AAPBZI: 5-amino-2- (4-aminophenyl) benzimidazole / AAPBZO: 5-amino-2- (4-aminophenyl) benzoxazole / CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride / PMDA: pyromellitic acid 2 Anhydride, BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 6FDA: 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, NMP: N -Methyl-2-pyrrolidone

The measuring method and evaluation method of each physical property in Examples etc. are shown below.
[Light transmittance and yellowness (YI)]
Light transmittance (T308, T355, T400, T430) at 308 nm, 355 nm, 400 nm, and 430 nm was determined for a polyimide film (50 mm × 50 mm, thickness: 10 to 15 μm) using a SHIMADZU UV-3600 spectrophotometer. Further, YI (yellowness) was calculated based on the following calculation formula.
YI = 100 × (1.2879X−1.0592Z) / Y
X, Y, and Z are the tristimulus values of the test piece, specified in JIS Z 8722.

[Coefficient of thermal expansion (CTE)]
A polyimide film having a size of 3 mm × 15 mm was heated from 30 ° C. to 280 ° C. at a constant heating rate (10 ° C./min) while applying a 5.0 g load with a thermomechanical analysis (TMA) apparatus, and then The temperature was lowered from 250 ° C. to 100 ° C., and the thermal expansion coefficient was measured from the amount of elongation (linear expansion) of the polyimide film during the temperature drop.

[Glass transition temperature (Tg)]
The dynamic viscoelasticity of a polyimide film (5 mm × 70 mm) was measured with a dynamic thermomechanical analyzer from 23 ° C. to 500 ° C. at a rate of 5 ° C./minute, and the glass transition temperature (tan δ maximum value: ° C. )

[Pyrolysis temperature (Td1)]
Measure the change in weight of a polyimide film weighing 10 to 20 mg under a nitrogen atmosphere when the temperature is raised from 30 ° C. to 550 ° C. at a constant speed using a thermogravimetric analysis (TG) device TG / DTA6200 manufactured by SEIKO. Then, based on the weight at 200 ° C., the temperature when the weight reduction rate was 1% was defined as the thermal decomposition temperature (Td1).

[Peelability: LED]
This is the laser irradiation energy density (mJ / cm ² ) until the polyimide layer and the supporting substrate (glass substrate) can be peeled off (abbreviation: LED). The irradiation conditions are the same as “Removability: Laser Lift Off (LLO)” described in the next paragraph “0048”. The higher the energy density, the more difficult it is to peel off. Considering the lifetime of the laser irradiation apparatus, those having a low irradiation energy density are preferable. The upper limit of measurement was 300 mJ / cm ² , and “x” was given for samples that could not be peeled off at 300 mJ / cm ² or less.

[Peelability: Laser lift-off (LLO)]
Using an excimer laser processing machine (wavelength 308 nm), a laser with a beam size of 14 mm x 1.2 mm, a moving speed of 6 mm / s, and an overlap rate of 80% was irradiated from the support substrate (glass) side, and the support substrate and polyimide The state in which the layers are completely separated (determine the peeling range with a cutter, and the polyimide film naturally peels off from the glass after one cut has been made), and the whole or part of the coating substrate and polyimide layer is separated Is impossible, or the state where the polyimide layer is discolored is defined as “x”.

Synthesis example 1
In order to synthesize the polyimide precursor, 8.57 g of TFMB was dissolved in 85 g of NMP in a 100 ml separable flask under a nitrogen stream. To this solution was then added 0.67 g of AAPBZI. After stirring for 10 minutes, 5.76 g CBDA was added. The molar ratio of the diamine component to the tetracarboxylic dianhydride component was 0.99 (substantially equimolar). Thereafter, this solution was stirred at room temperature for 24 hours to carry out a polymerization reaction to obtain a polyamic acid A (viscous colorless solution) having a high degree of polymerization (Mw 80,000 or more, viscosity 5,000 cP or more).

Synthesis Examples 2-18
A polyamic acid solution was prepared in the same manner as in Synthesis Example 1 except that the diamine and tetracarboxylic dianhydride were changed to the compositions shown in Tables 1 and 2, and polyamic acids B to R were obtained.

  In Tables 1 and 2, the unit of the amount of diamine and tetracarboxylic dianhydride is g, and the numerical value in parentheses indicates mol% in the diamine component or tetracarboxylic dianhydride component.

Example 1
A solvent NMP is added to the polyimide precursor solution A obtained in Synthesis Example 1 and diluted to have a viscosity of 4000 cP, and then a glass substrate (Corning E-XG, size = 150 mm × 150 mm, thickness = 0) The thickness of the polyimide after curing was about 15 μm using a spin coater. Subsequently, heating was performed at 100 ° C. for 15 minutes. Then, the temperature is raised from room temperature to 300 ° C. (360 ° C. in Comparative Example 4) at a constant heating rate (3 ° C./min) in a nitrogen atmosphere, held at 130 ° C. for 10 min, and 150 mm × on a glass substrate. A 150 mm polyimide layer (polyimide A) was formed to obtain a polyimide laminate A.

Examples 2-11, Comparative Examples 1-7
Except having replaced the polyimide precursor A with any of the polyimide precursors B to R, the same operation as in Example 1 was performed to obtain polyimide laminates B to R. The code | symbol of a polyimide precursor and a polyimide laminated body respond | corresponds, it means that the polyimide laminated body B was obtained from the polyimide precursor B, and it is the same also about the code | symbol C or less.

  The obtained polyimide laminates A to R were measured for laser lift-off (LLO) and LED. The results are shown in Tables 3 and 4.

For the measurements other than the above, the polyimide film was peeled off from the laminate. In this case, the laminate was prepared in accordance with the above except that a 75 μm polyimide film was used as the substrate instead of the glass substrate. . Detailed preparation conditions are shown below.
After adding the solvent NMP to the polyamic acid solutions A to R obtained in Synthesis Examples 1 to 15 to dilute the viscosity to 3000 cP, on the 75 μm polyimide film (Upilex-S) substrate, Coated. Subsequently, heating was performed at 100 ° C. for 15 minutes. In a nitrogen atmosphere, the temperature was raised from room temperature to 300 ° C. (360 ° C. in Comparative Example 4) at a constant rate of temperature increase (3 ° C./min), and held at 130 ° C. for 10 minutes to obtain a polyimide laminated film. . Thereafter, the polyimide base material (Upilex-S) was peeled off, and polyimide films A to R as simple substances obtained by imidizing the polyamic acid solutions A to R were obtained. The above peeling was performed by peeling only the formed polyimide layer from the substrate with tweezers after making a round cut with a cutter to determine the peeling range. The thickness of these films is shown in the section of thickness.

  The obtained polyimide films A to R were subjected to various evaluations such as CTE, light transmittance, YI, Td1, and Tg. The results are shown in Tables 3 and 4.

Claims (7)

A step of applying a polyimide precursor or a resin solution thereof on the surface of the support; a step of heating and imidizing the polyimide precursor or the resin solution thereof to form a polyimide layer on the surface of the support; and the polyimide. A step of peeling a layer from the support to obtain a polyimide film, and a method for producing a polyimide film comprising:
The polyimide precursor includes one or two selected from 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl and 2,2′-dimethyl-4,4′-diaminobiphenyl. It is obtained by reacting a diamine with an acid dianhydride including 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and the thermal expansion coefficient of the polyimide film is 45 ppm / K or less. A method for producing a transparent polyimide film, wherein the light transmittance is 5% or less for a light beam having a wavelength of 308 nm and 70% or more for a light beam having a wavelength of 400 nm.   A diamine selected from 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl and 2,2′-dimethyl-4,4′-diaminobiphenyl is contained in an amount of 50 mol% or more of the total diamine, and The method for producing a transparent polyimide film according to claim 1, comprising 1,2,3,4-cyclobutanetetracarboxylic dianhydride in an amount of 70 mol% or more of the total acid dianhydride.   1 to 50 mol% of diamine other than 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl or 2,2′-dimethyl-4,4′-diaminobiphenyl is included in the total diamine, or The manufacturing method of the transparent polyimide film of Claim 1 which contains 1-30 mol% of acid dianhydrides other than 1,2,3,4-cyclobutane tetracarboxylic dianhydride in all the acid dianhydrides.   The method for producing a transparent polyimide film according to claim 1, wherein the yellowness is 6 or less.   The manufacturing method of the transparent polyimide film of Claim 1 which irradiates a laser beam to the interface of a polyimide layer and a support body, and peels a polyimide layer from a support body.   In the manufacturing method of the transparent polyimide film in any one of Claims 1-5, after forming a functional layer on a polyimide layer, it comprises the process of peeling the polyimide layer with a functional layer from a support body, It is characterized by the above-mentioned. A method for producing a transparent polyimide film with a functional layer.   The functional layer is selected from the group consisting of a transparent conductive layer, a wiring layer, a conductive layer, a gas barrier layer, a thin film transistor, an electrode layer, a light emitting layer, an adhesive layer, an adhesive layer, a transparent resin layer, a color filter resist, and a hard coat layer. The method for producing a transparent polyimide film with a functional layer according to claim 4, which is any one kind or two or more kinds of layers.