TW202035520A - Polyimide precursor composition, polyimide film and flexible device produced therefrom, and method for producing polyimide film excellent in heat resistance and transparency, and causing no problem such as coloration at high temperature - Google Patents

Abstract

Disclosed are a polyimide film and a polyimide precursor composition used for obtaining the polyimide film. The polyimide film comprises nanosilica particles, and is excellent in heat resistance and transparency; moreover, it causes no problem such as coloration at high temperature. The disclosed provides a polyimide precursor composition and a polyimide film obtained by imidizing the polyimide precursor composition, wherein the polyimide precursor composition comprises a polyimide precursor having a structural unit derived from diamine and a structural unit derived from acid dianhydride, and nanosilica particles having an average particle diameter of 1-70 nm; the polyimide precursor composition is characterized by containing 10-60 parts by mass of the nanosilica particles with respect to 100 parts by mass of the polyimide precursor, and when the polyimide precursor composition is converted into a polyimide film, it satisfies the following (1) to (5): (1) yellowness at room temperature of 10 or less, (2) yellowness after having been heated at 400DEG C for 1 hour and further heated at 450DEG C for 1 hour of 20 or less, (3) total light transmittance of 85% or more, (4) haze of less than 1, and (5) 1% heat weight reduction temperature (Td1) of 500DEG C or higher.

Description

Polyimide precursor composition, polyimide film produced therefrom, flexible device, and manufacturing method of polyimide film

The present invention relates to a polyimide film that has both high transparency and high heat resistance, and is useful as a support substrate for forming a display device, and a polyimide precursor composition for obtaining the polyimide film .

Display devices such as liquid crystal display devices, organic electroluminescence (EL) devices, or touch panels are used as various types such as large displays such as televisions, or small displays such as mobile phones, personal computers, and smartphones. The components of the display. For example, organic EL devices usually form thin film transistors (Thin Film Transistor, TFT) on a glass substrate as a supporting substrate, and then sequentially form electrodes, light-emitting layers, and electrodes on the glass substrate. Sealed and made. In addition, the touch panel has a structure in which a first glass substrate on which a first electrode is formed and a second glass substrate on which a second electrode is formed are joined via an insulating layer (dielectric layer).

That is, these structural members are laminated bodies in which various functional layers such as TFTs, electrodes, and light-emitting layers are formed on a glass substrate. By replacing the glass substrate with a resin substrate, it is possible to reduce the thickness, weight, and flexibility of constituent members using the existing glass substrate. It is expected to use it to obtain flexible devices such as flexible displays. On the other hand, the dimensional stability, transparency, heat resistance, moisture resistance, film strength, etc. of resin are inferior to glass, and various studies are being conducted.

As such a resin substrate material, polyimide is one of the promising materials due to its excellent heat resistance and dimensional stability. In particular, polyimine having a fluorine atom in the polyimide structure (fluorine-containing polyimide) or polyimide having an alicyclic structure (alicyclic polyimide) has excellent transparency and is expected to be used Flexible devices that require transparency, such as organic EL device substrates, touch panel substrates, and color filter substrates.

For example, Non-Patent Document 1 and Non-Patent Document 2 propose an organic EL display device in which a polyimide with high transparency is applied to a support substrate.

In this way, it is known that resin base materials such as polyimide are useful for flexible substrates for flexible displays. However, the dimensional stability, strength, surface hardness, etc. of the resin substrate are still inferior to glass, so further improvement is needed.

As an example of the improvement method, the addition of a filler to the resin substrate can be cited. For example, Patent Document 1 discloses a polyimide film obtained by dispersing colloidal silica in a polyamide acid solution obtained by reacting fluorine-containing tetracarboxylic dianhydride and fluorine-containing diamine, and heat-treating it. By including colloidal silica in polyimide with high transparency, a polyimide film with excellent transparency, especially low coefficient of thermal expansion (CTE) at high temperature can be obtained. However, in the aforementioned Patent Document 1, there is a problem that the light transmittance decreases as the added amount of colloidal silica increases. The foregoing indicates that, in applications requiring higher heat resistance, there are limits to the method of meeting the requirements only by including colloidal silica in the polyimide precursor.

In addition, Patent Document 2 discloses a polymer of an alicyclic tetracarboxylic dianhydride and an aromatic diamine having a carboxyl group, that is, polyamide acid containing nanosilica containing nanosilica. And a polyimide film containing nanosilica formed by imidizing the polyamide containing nanosilica. In the polyimide film containing nanosilica, even if the content of nanosilica increases, optical properties such as light transmittance and haze are almost unchanged. However, the polyimide having an alicyclic structure described in Patent Document 2 has insufficient heat resistance, and it is used in TFT substrates for transparent organic light emitting diodes (Organic Light Emitting Diode, OLED) and for transmissive displays. In applications such as TFT substrates that particularly require high-temperature heat treatment, there are problems such as coloring by heat treatment.

That is, in order to manufacture such a flexible device requiring extremely high heat resistance, it is difficult in the prior art to apply a transparent polyimide substrate. [Prior Art Literature] [Patent Literature]

[Patent Document 1] WO2013/161970 Publication [Patent Document 2] WO2017/098936 Publication [Non-Patent Literature]

[Non-Patent Document 1] S.An et al. (S.An et.al.), "A 2.8-inch wide quarter video graphics array (Wide Quarter Video Graphics Array) using high-performance low-temperature polycrystalline TFTs on a plastic substrate , WQVGA) Flexible Active Matrix Organic Light Emitting Diode (AMOLED) (2.8-inch WQVGA Flexible AMOLED Using High Performance Low Temperature Polysilicon TFT on Plastic Substrates)", Society For Information Display (Society For Information Display) , SID) 2010 Abstract (DIGEST), p706 (2010) [Non-Patent Document 2] Oishi et.al., "Transparent PI for flexible display (Transparent PI for flexible display)", International Display Workshops (IDW) '11 FLX2/FMC4-1

[Problems to be Solved by Invention] The inventors of the present invention conducted intensive studies and found that a polyimide precursor composition obtained by adding nano-silica particles to a specific fluorine-containing polyimide precursor The polyimide film formed by the imidization of the imide precursor composition is unexpectedly transparent and colored even when it contains high nano-silica particles and is heat-treated at a high temperature. The above-mentioned problems can be solved without causing problems, and the present invention has been completed. [Technical means to solve the problem]

That is, the present invention is a polyimine precursor composition containing a polyimine precursor and nanosilica particles, the polyimine precursor having structural units derived from diamine and acid-derived The structural unit of dianhydride, and the polyimide precursor composition is characterized by: The average particle diameter of the nano-silica particles is 1 nm～70 nm, With respect to 100 parts by mass of the polyimide precursor, it contains 10 parts by mass to 60 parts by mass of nanosilica particles, When making the polyimide precursor composition into a polyimide film, the following (1) to (5) are satisfied. (1) The yellowness at room temperature is 10 or less. (2) The yellowness after heating at 400°C for 1 hour and further heating at 450°C for 1 hour is 20 or less. (3) The total light transmittance is over 85%. (4) The haze is less than 1. (5) The 1% thermal weight reduction temperature (Td1) is above 500℃.

[式（1）中，X為O、C=O或SO₂ ]The polyimide precursor composition desirably satisfies any one or more of the following [1] to [3]. [1] The coefficient of thermal expansion (CTE) of the polyimide film is 65 ppm/K or less. [2] The light transmittance of the polyimide film at 308 nm is 5% or less, and the light transmittance at 430 nm is 70% or more. [3] The polyimide precursor contains 50 mol% or more, preferably 90 mol% or more of the structural units derived from the fluorine atom-containing diamine of all the structural units derived from the diamine, and contains the diamine-derived 50 mol% or more, preferably 90 mol% or more of all the structural units of the anhydride are derived from the aromatic acid dianhydride represented by the following formula (1). [化1]

[In formula (1), X is O, C=O or SO ₂ ]

In addition, another aspect of the present invention or an invention related to the present invention is shown in [4] and [5] below. [4] A polyimide film obtained by imidizing the polyimide precursor composition. [5] A flexible device formed by laminating a functional layer on the polyimide film.

In addition, the present invention is a method for producing a polyimide film, characterized in that a polyimide film that satisfies the following (1) to (5) is manufactured by sequentially performing the following steps. (1) The yellowness at room temperature is 10 or less. (2) The yellowness after heating at 400°C for 1 hour and further heating at 450°C for 1 hour is 20 or less. (3) The total light transmittance is over 85%. (4) The haze is less than 1. (5) The 1% thermal weight reduction temperature (Td1) is above 500℃. The steps include: The step of preparing a polyimine precursor composition, the polyimine precursor composition containing a polyimine precursor and nanosilica particles with an average particle diameter of 1 nm to 70 nm, the polyimide precursor composition The imine precursor has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and contains 10 parts by mass to 60 parts by mass of the nanodioxide relative to 100 parts by mass of the polyimide precursor Silicon particles The step of coating the polyimide precursor composition on a carrier substrate and performing heat treatment to form a polyimide film on the carrier substrate; and The step of peeling the formed polyimide film from the carrier substrate. [Effects of the invention]

The polyimide precursor composition of the present invention and the polyimide film obtained by the imidization of the polyimide precursor composition contain predetermined nano-silica particles, so it has high heat resistance [Low Coefficient of Thermal Expansion (CTE)] Excellent, even in the case of high content of nano-silica particles, excellent transparency, will not cause coloration problems during heat treatment at high temperature, but yellowness, haze and other spectral characteristics It is excellent, so it is particularly applicable to flexible devices that require high-temperature heat treatment, such as TFT substrates for transparent OLEDs and TFT substrates for transmissive displays.

First, the polyimide precursor composition of the present invention contains at least a polyimide precursor and nanosilica particles with an average particle size of 1 nm to 70 nm, and has the following characteristics: 100 parts by mass of the precursor, the nanosilica particles contain 10 parts by mass to 60 parts by mass, preferably 20 parts by mass to 50 parts by mass, and then the polyimide precursor composition is amideified When it becomes a polyimide film, the following (1) to (5) are satisfied. (1) The yellowness at room temperature is 10 or less. (2) The yellowness after heating at 400°C for 1 hour and further heating at 450°C for 1 hour is 20 or less. (3) The total light transmittance is over 85%. (4) The haze is less than 1. (5) The 1% thermal weight reduction temperature (Td1) is above 500℃.

[式（1）中，X為O、C=O或SO₂ ]<Polyimine precursor> Here, as long as the polyimine precursor is a polyimine precursor having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, it becomes a polyimide precursor. In the case of an imine film, polyimide precursors that all satisfy the characteristics of the yellowness (YI) and the like are not limited respectively, and it is preferable to use an aromatic diamine containing a fluorine atom as the structural unit of the diamine. An amine is preferable, and as the acid dianhydride, a fluorine atom-free substance is mentioned, and it is preferable to use an aromatic acid dianhydride represented by the following formula (1). [化2]

[In formula (1), X is O, C=O or SO ₂ ]

Furthermore, regarding the aromatic diamine containing fluorine atoms, it is preferable to use a diamine derived from the viewpoint of transparency, heat resistance, and adaptability to the laser lift-off process. 50 mol% or more of all the structural units of, more preferably 60 mol% or more, and still more preferably 90 mol% or more. As the aromatic diamine having a fluorine atom, for example, 2,2'-bis(trifluoromethyl)benzidine, 2,2'-bis(trifluoromethyl)-4,4'-di Amino diphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 4,4'-diaminooctafluorobiphenyl, 4,4'-bis(2- (Trifluoromethyl)-4-aminophenoxy)biphenyl, 2-trifluoromethyl-4,4'-diaminodiphenyl ether, 2,2-bis(4-(2-(trifluoromethyl) (Methyl)-4-aminophenoxy)phenyl)hexafluoropropane, 4,4'-bis(3-(trifluoromethyl)-4-aminophenoxy)biphenyl, 2,5-diamino Dibenzotrifluoride and p-bis(2-(trifluoromethyl)-4-aminophenoxy)benzene are 2,2'-bis, from the viewpoints of transparency, heat resistance, and laser peeling. (Trifluoromethyl)benzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether.

In addition, as the structural unit derived from diamine, other diamines other than those described above can be used, and it is preferable to use less than 50 mol% of all structural units derived from diamine. As other diamines, diamines having one or more aromatic rings can be preferably used. Examples include: 2,2'-dimethyl-4,4'-diaminobiphenyl (alias: 2,2'-dimethyl-benzidine), 3,3'-dimethyl-4,4 '-Diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl Phenyl-p-phenylenediamine, 2,4-diamino mesitylene, 4,4'-methylene bis-o-toluidine, 4,4'-methylene bis-2,6-xylidine, 4 ,4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3 '-Diaminodiphenylpropane, 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'-diaminodi Phenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl Ether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4' -Diamino-p-terphenyl, 3,3'-diamino-p-terphenyl, bis(p-amino-tert-butylphenyl) ether, bis(p-methyl-δ-aminopentyl)benzene , P-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diamino Naphthalene, 2,4-bis(β-amino-tert-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-benzene Dimethylamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 5-amino- 2-(4-Aminophenyl)benzimidazole and the like. From the viewpoint of fast reaction and high transparency, 4,4'-diaminodiphenyl ether, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-benzene are preferred Diamine, 2,4-diamino mesitylene, 2,4-toluenediamine, m-phenylenediamine, 2,2'-dimethyl-4,4'-diaminobiphenyl, 5-amino-2 -(4-Aminophenyl)benzimidazole or p-phenylenediamine.

On the other hand, with regard to the aromatic acid dianhydride represented by the formula (1), particularly from the viewpoints of transparency, heat resistance, and adaptability to the laser lift-off process, it is preferable to use an acid derived from two The anhydride is preferably 50 mol% or more in all structural units, more preferably 60 mol% or more, and still more preferably 90 mol% or more. Among them, 4,4'-oxodiphthalic dianhydride is particularly preferred from the viewpoint of transparency, heat resistance, and yellowness at high temperatures.

Moreover, as a structural unit derived from an acid dianhydride, other acid dianhydrides other than the above can be used, and it is preferable to use less than 50 mol% of all structural units derived from an acid dianhydride. As other acid dianhydrides, well-known acid dianhydrides can be preferably used. Examples include: 4,4'-(2,2'-hexafluoroisopropylidene) diphthalic dianhydride, 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 acid Dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone 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-hexa Hydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 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 dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane Anhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2 ,3-Dicarboxyphenyl)sulfuric acid dianhydride, bis(3,4-dicarboxyphenyl)sulfuric acid 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, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine- 2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 2,2 -Bis{(4-(3,4-dicarboxyphenoxy)phenyl)}hexafluoropropane dianhydride, etc. In addition, these acid dianhydrides may be used alone, or two or more of them may be used in combination. It is preferably pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, which can impart strength and flexibility to the polyimide film, and is preferably excellent in heat resistance and transparency and 1,2,3,4-cyclobutane tetracarboxylic dianhydride capable of controlling CTE in an appropriate range.

The polyimide precursor in the present invention can be produced by a known method, and the known method is preferably used at a molar ratio (acid dianhydride/diamine) of 0.960 to 1.040, more preferably 0.980 to 1.020 The acid dianhydride and diamine are polymerized in an organic polar solvent. For example, it can be obtained by dissolving diamine in an aprotic amide solvent such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone under a nitrogen stream, and then adding acid diamine. The anhydride reacts at room temperature for about 3 hours to 20 hours. For rapid reaction, heating may be performed at a temperature of 40°C to 80°C for 15 minutes to 5 hours. At this time, the molecular end may be sealed with aromatic monoamine or aromatic monocarboxylic dianhydride. As the solvent, in addition to the above, dimethylformamide, 2-butanone, diglyme, xylene, γ-butyrolactone, etc. may be used. One type or two or more types may be used in combination. . In order to improve solubility, xylene, hexane, etc. can also be added.

＜Nano silicon dioxide particles＞ Next, the nano-silica particles used in the polyimide precursor composition of the present invention represent nano-sized silica particles, and from the viewpoint of imparting transparency and heat resistance, the average particle size is used. It is 1 nm～70 nm silica particles. The preferred lower limit is 5 nm, and the more preferred lower limit is 8 nm. In addition, a preferable upper limit is 60 nm, a more preferable upper limit is 50 nm, and an even more preferable upper limit is 25 nm. The average particle size can be expressed as the weight (number) average particle size measured by the dynamic light scattering method. Regarding the nano-silica particles, well-known nano-silica particles can be preferably used, and a colloidal solution prepared by dispersing colloidal silica in an organic solvent can be suitably used, and it can be combined with the obtained poly The solution of the imine precursor and the like are mixed to form the composition of the present invention. If the average particle size is less than 1 nm, it may cause aggregation when mixed with a polyimide precursor solution or the like, and if it exceeds 70 nm, the transparency and heat resistance of the film may deteriorate.

In addition, with regard to the nanosilica particles, as long as the polyimide precursor composition of the present invention can satisfy the above (1) to (5) when the polyimide precursor composition of the present invention is made into a polyimide film, the surface can be used. Well-known surface treatment and functional group modification such as a treatment agent may not be performed. For example, from the viewpoint of miscibility or dispersibility with the polyimide precursor, a silane coupling agent, a functional group such as an amino group or a carboxylic acid can also be used. On the other hand, from the viewpoint of suppressing coloration during high-temperature heat treatment, it is preferable to use silicon dioxide particles that have not been surface-treated. Furthermore, when using a colloidal solution of nanosilica particles, a dispersant may be added to the colloidal solution. Examples of dispersants include anionic surfactants, cationic surfactants, nonionic surfactants, zwitterionic surfactants, wetting oligomers, sodium polyacrylates, and modified sodium polyacrylates. , Water-soluble cellulose grafted amphiphilic copolymer, block copolymer series, fatty acid amide series, sulfate ester series anionic active agent series, polycarbonate polyester series, containing phosphoric acid group and/or sulfonic acid group polyether A well-known organic dispersant such as a carbonate mesh type polymer system and a phosphate derivative of a polyoxyalkylene group. On the other hand, from the viewpoint of suppressing coloration during high-temperature heat treatment, silica particles that do not use such a dispersant are preferable. Furthermore, the polyimide precursor composition of the present invention may also contain fillers other than the aforementioned nanosilica particles.

Furthermore, as described above, with respect to 100 parts by mass of the polyimide precursor, the nanosilica particles used in the present invention contain 10 parts by mass to 60 parts by mass, preferably 20 parts by mass to 50 parts by mass Appropriate. If the nanosilica particles are less than 10 parts by mass relative to 100 parts by mass of the polyimide precursor, the heat resistance is insufficient and the CTE may increase. On the other hand, if it exceeds 60 parts by mass, the film will become The self-supporting property is insufficient, and the film may be broken when peeled from the substrate.

＜Production of polyimide film＞ The polyimide film of the present invention is obtained by the imidization of the polyimide precursor composition of the present invention. The imidization can be performed by a thermal imidization method or a chemical imidization method. Thermal imidization is performed by the following method: use an applicator to coat the polyimide precursor composition on any supporting substrate such as glass, metal, resin, etc., and pre-dry it at a temperature of 150°C or less for 2 minutes After ~60 minutes, heat treatment is usually performed at a temperature of about room temperature to about 360°C for about 10 minutes to about 20 hours for solvent removal and imidization. When the desired polyimide film is available, the heat treatment temperature can reach 280°C. The heat treatment temperature can also be changed between 280°C and 360°C according to the necessary mechanical characteristics. Chemical imidization is to add a dehydrating agent and a catalyst to a solution of a polyimine precursor composition (also called polyamide acid), and perform chemical dehydration at 30°C to 60°C. As a representative dehydrating agent, acetic anhydride is exemplified, and as a catalyst, pyridine is exemplified. In thermal imidization, if a combination of the type of acid dianhydride or diamine and the type of solvent is selected, the imidization can be completed in a short time, so that it can be performed within 60 minutes including preheating. Heat treatment. It can be applied as a polyimide precursor composition solution dissolved in a solvent.

Furthermore, regarding the preferred degree of polymerization of the polyimide precursor of the present invention, the viscosity of the polyimide precursor solution using an E-type viscometer is 1,000 cP to 300,000 cP, preferably 3,000 cP to 300,000 The range of cP. The molecular weight of the polyimide precursor can be determined by the Gel Permeation Chromatography (GPC) method. The preferred molecular weight range (in terms of polystyrene) of the polyimide precursor is desirably a number average molecular weight of 15,000-250,000 and a weight average molecular weight of 30,000-800,000, but these are standards and sometimes outside the stated range Can also be tolerated. The preferable molecular weight of polyimide is also in the range equivalent to the molecular weight of its precursor.

The polyimide film obtained by imidizing the polyimide precursor composition of the present invention is used as a reference thickness, for example, in the state of a polyimide film having a thickness of 3 μm to 50 μm, In addition, it is preferable to exhibit the following physical properties in a state of 10 μm.

The yellowness (YI) at room temperature is 10 or less. It is preferably 5 or less, more preferably 4 or less, and still more preferably 3 or less. If the yellowness (YI) is 10 or less, it can be suitably used for substrates requiring high transparency and low coloration, such as TFT substrates for organic EL devices, touch panel substrates, and color filter substrates.

Furthermore, the yellowness (YI) when heated at 400°C for 1 hour and at 450°C for 1 hour is preferably 20 or less, preferably 19 or less, and more preferably 18 or less. It is also suitable for applications requiring high-temperature heat treatment, such as TFT substrates for transparent OLEDs or TFT substrates for transmissive displays.

In addition, from the viewpoint of transparency, the total light transmittance in the visible region is preferably 85% or more. Preferably it is 90% or more. The light transmittance at 430 nm is preferably 70% or more, and preferably 80% or more. In addition, the light transmittance at 308 nm is preferably 3% or less. Preferably it is less than 1%, more preferably less than 0.5%. If it is in these ranges, light in the near ultraviolet region is absorbed, and the transmittance of light in the visible light region is high. It can absorb 308 nm laser light generated by excimer lasers while maintaining the transparency of the visible light region. As a result, in the manufacture of flexible devices such as organic EL device substrates, touch panel substrates, and color filter substrates, laser irradiation on the flexible substrate can prevent damage to the display device on the polyimide film. Peel off the glass support material. The laser lift-off technique can be preferably applied. Furthermore, the so-called laser lift-off method is, for example, a technique in which a polyimide layer is formed on glass as a supporting substrate, various functional layers are formed on the polyimide layer to form a laminate, and the glass is passed through The support material is irradiated with a laser on the bottom surface of the polyimide layer, thereby peeling the glass support material from the polyimide layer to produce a polyimide film with a functional layer.

In addition, the transparency of the polyimide film is represented by, for example, the haze (also referred to as "HAZE") specified in Japanese Industrial Standards (JIS) K7136. The haze is less than 1, preferably 0.8 or less is appropriate.

In addition, the coefficient of thermal expansion (CTE) is also required to be low, and is preferably 65 ppm/K or less, and more preferably 60 ppm/K or less.

Furthermore, from the viewpoint of heat resistance, the thermal decomposition temperature (1% thermal weight loss temperature, Td1) is 500° C. or higher, preferably 510° C. or higher.

Furthermore, the polyimide film preferably has an elastic modulus (E') of 4 GPa or less. Preferably it is 3.5 GPa or less. Here, the elastic modulus is the tensile elastic modulus at room temperature. If it is within the above range, when manufacturing flexible devices such as functional layer lamination in TFT substrates for organic EL devices, touch panel substrates, color filters, etc., the residual stress of the substrate is small, and the manufacturing yield of the flexible device Excellent.

The specific method for making the polyimide precursor composition into a polyimide film is not limited. When polyimide is used as a supporting substrate, it is advantageous to use a film-like or laminate containing polyimide layers In the form of body. Preferably, the polyimide laminate can be obtained by: preparing a resin solution (polyimine precursor composition) containing a polyimine precursor; after coating it on a carrier substrate, proceed Drying, heat treatment, or coating the resin solution that has completed the imidization in the liquid phase on the substrate and drying to become a polyimide film (polyimide film formation step), or a separately made polyimide film The amine film is attached to another substrate. From the viewpoint of production efficiency, it is desirable to peel off the polyimide film formed by imidization on the carrier substrate as described above (peeling step), or it may be directly combined with a separately produced polyimide film. The films together become a laminate, and they are peeled off as necessary to become a laminate film.

In addition, the polyimide film of the present invention is suitable as a polyimide film with a functional layer. The polyimide film in this case can also be made to contain a multilayer polyimide. In the case of a single layer, it is suitable to have a thickness of 3 μm to 50 μm. On the other hand, in the case of multiple layers, it is sufficient as long as the main polyimide layer has a polyimide film having the above-mentioned thickness. Here, the so-called main polyimide layer refers to the polyimide layer whose thickness occupies the largest ratio in the multilayer polyimide, and it is suitable to set the thickness to 3 μm-50 μm, and more preferably It is 4 μm～30 μm.

The polyimide film of the present invention can be formed into a laminate by forming an element layer or the like (functional layer) having various functions on the polyimide layer. Examples of functional layers include display devices represented by liquid crystal display devices, organic EL display devices, touch panels, color filters, and electronic paper, or their constituent parts. It also includes conductive films, touch panel films, gas barrier films, flexible circuit boards, and other various functional devices used with display devices. That is, the so-called functional layer includes not only constituent parts such as liquid crystal display devices, organic EL display devices, and color filters, but also organic EL lighting devices, touch panel devices, electrode layers or light-emitting layers of organic EL display devices, Gas barrier film, adhesive film, thin film transistor (TFT), wiring layer of liquid crystal display device, or transparent conductive layer, etc. are one or a combination of two or more.

When a functional layer such as a display element is formed on the polyimide film of the present invention, the formation conditions are appropriately set according to the target device. After a metal film, an inorganic film, an organic film, etc. are formed on the polyimide layer (film) by a known method, it is patterned into a predetermined shape or heat-treated as necessary. That is, the method for forming the functional layer is not particularly limited. For example, sputtering, vapor deposition, chemical vapor deposition (CVD), printing, exposure, dipping, etc. can be appropriately selected. If necessary, these processes can also be performed in a vacuum chamber or the like. The separation of the support material (glass) from the polyimide film can be carried out immediately after the formation of the functional layer through various processes, or it can be integrated with the support material within a certain period of time after the formation, and will be used for example in display devices. The form is stripped and removed before use.

Hereinafter, as an example of the flexible device of the present invention, an outline of a method of manufacturing an organic EL display device having a bottom emission structure as a functional layer will be described.

A gas barrier layer is provided on the polyimide film of the present invention to have a structure that can prevent moisture or oxygen from permeating. Secondly, a circuit constituent layer containing thin film transistors (TFT) is formed on the upper surface of the gas barrier layer. In the organic EL display device, low temperature poly-silicon (LTPS)-TFT with fast action speed is mainly selected as the thin film transistor. The circuit configuration layer is formed by forming an anode electrode in which a transparent conductive film containing, for example, indium tin oxide (ITO) is formed in each of the pixel regions arranged in a matrix on the upper surface thereof. An organic EL light-emitting layer is formed on the upper surface of the anode electrode, and a cathode electrode is formed on the upper surface of the light-emitting layer. The cathode electrode is formed in common in each pixel area. A gas barrier layer is formed again to cover the surface of the cathode electrode, and a sealing substrate is provided on the outermost surface to protect the surface. From the viewpoint of reliability, it is desirable to also laminate a gas barrier layer that prevents moisture or oxygen from passing through the surface of the sealing substrate on the cathode electrode side. The organic EL light-emitting layer is formed by a multi-layer film (anode electrode-light-emitting layer-cathode electrode) such as a hole injection layer-a hole transport layer-a light-emitting layer-an electron transport layer. The organic EL light-emitting layer is degraded by moisture or oxygen. It is formed by vacuum evaporation, and therefore, it is usually formed continuously in vacuum, including electrode formation.

The wavelength of light emitted from the light-emitting layer of an organic EL display device is mainly 440 nm to 780 nm. Therefore, as a transparent resin film substrate used in an organic EL display device, the average transmittance in the wavelength region is required to be at least 80% the above. On the other hand, with laser peeling technology, the glass support material is peeled from the resin film. In the case of peeling the glass support material from the polyimide layer by the irradiation of ultraviolet (UV) laser light, if the transmittance at the wavelength of the UV laser light is high, an additional absorption/peeling layer is required to produce Sexual decrease. Among the laser lift-off technologies, 308 nm laser devices are currently generally used. In order to perform peeling without providing an absorption/peeling layer, the polyimide itself needs to fully absorb 308 nm laser light, and it is desirable to not transmit light as much as possible in the wavelength region. [Example]

Hereinafter, the present invention will be specifically described based on examples and comparative examples. Furthermore, the present invention is not limited to these contents.

The abbreviations and evaluation methods of materials used in Examples and Comparative Examples are shown. (Acid dianhydride) ·ODPA: 4,4'-oxodiphthalic anhydride ·6FDA: 4,4'-(2,2'-hexafluoroisopropylidene) diphthalic dianhydride (Diamine) ·TFMB: 2,2'-bis(trifluoromethyl)benzidine (Solvent) ·NMP: N-methyl-2-pyrrolidone ·DMAc: N,N-Dimethylacetamide [Filler (Nanosilica Particles)] ·NMP-ST: A colloidal solution prepared by dispersing colloidal silica in N-methyl-2-pyrrolidone (manufactured by Nissan Chemical Co., Ltd., solid content of silica particles: 30 wt%; average silica Particle size: 12 nm) ·DMAC-ST: A colloidal solution made by dispersing colloidal silica in N,N-dimethylacetamide (manufactured by Nissan Chemical Co., Ltd., solid content of silica particles: 20 wt%; silica The average particle size: 12 nm) ·OP-1354A White: A colloidal solution made by dispersing colloidal silica in N-methyl-2-pyrrolidone (manufactured by Toyo Color Co., Ltd., solid content of silica particles: 20 wt%; silica-based Average particle size: 30 nm) ·DMAC-ST-ZL: a colloidal solution made by dispersing colloidal silica in N,N-dimethylacetamide (manufactured by Nissan Chemical Co., Ltd., solid content of silica particles: 20 wt%; two The average particle size of silicon oxide: 80 nm) In addition, the average particle diameter is the weight (number) average particle diameter of the harmonic particle diameter (diameter) based on the intensity of scattered light measured by the dynamic light scattering method.

(Light transmittance and YI) Use Shimadzu UV-3600 spectrophotometer to calculate the light transmittance of each wavelength from 300 nm to 700 nm on the polyimide film (50 mm×50 mm, thickness: 10 μm) . In addition, YI (yellowness) is calculated based on the following calculation formula. YI=100×(1.2879X-1.0592Z)/Y Here, X, Y, and Z are the tristimulus values of the test piece, which are specified in JIS Z 8722. In addition, the YI measured at room temperature is set to (YI ₀ ), the YI measured after heating at 400°C for 1 hour in a nitrogen environment is set to (YI ₄₀₀ ), and the heating is performed at 400°C in a nitrogen environment The YI measured after 1 hour and then heat treatment at 430°C for 1 hour in a nitrogen environment is set to (YI ₄₃₀ ), which will be heated at 400°C for 1 hour in a nitrogen environment and then at 450°C in a nitrogen environment The YI measured after the heat treatment for 1 hour is set to (YI ₄₅₀ ).

[Calculation of total light transmittance (T.T.) and haze (turbidity)] The total light transmittance (TT) and haze (turbidity) of the film are measured by the HAZE METER NDH5000 manufactured by Nippon Denshoku in accordance with JIS K 7136 on the polyimide film (50 mm×50 mm, thickness 10 μm) for measurement.

[1% thermal weight reduction temperature (Td1%)] A thermogravimetric (TG) device TG/DTA6200 manufactured by Seiko (SEIKO) was used to measure the polyimide film (thickness: 10 μm) with a weight of 5 mg to 15 mg in a nitrogen environment at a constant heating rate ( 10℃/min) The weight change when the temperature is raised from 30℃ to 550℃, based on the weight of 200℃ (0%), the temperature when the weight reduction rate is 1% is set to 1% thermal weight reduction temperature (Td1% ).

[Coefficient of Thermal Expansion (CTE)] Using a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA), a load of 5.0 g is applied to a polyimide film (thickness: 10 μm) with a size of 3 mm×15 mm on one side, and a certain The heating rate is increased from 30°C to 280°C, and then cooled at a rate of 5°C/min, to obtain the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C.

(Membrane self-supporting) When the film was peeled off from the glass, the case where a film of 100 mm×100 mm was obtained without breaking the film was regarded as ○, and the case where the film was broken was regarded as ×.

[Synthesis Example 1] Under nitrogen flow, 101.24 g of TFMB was dissolved in 500 g of NMP in a 2000 ml separable flask. Then, 98.86 g of OPDA was added to the solution. In addition, the molar ratio (a/b) of acid dianhydride (a) and diamine (b) was 1.010. The solution was heated at 40°C for 10 minutes to dissolve the contents, and then 300 g of NMP was added, and the solution was continuously stirred at room temperature for 24 hours to carry out the polymerization reaction to obtain a polyimide with a viscosity of 225,000 cP. Body A (viscous, colorless solution).

[Synthesis Example 2] Except that the solvent of Synthesis Example 1 was changed to DMAc, the polymerization reaction was performed in the same manner as Synthesis Example 1 to obtain polyimide precursor B (viscous colorless solution) with a viscosity of 232,000 cP.

[Synthesis Example 3] Under nitrogen flow, 116.66 g of TFMB was dissolved in 500 g of NMP in a 2000 ml separable flask. Then, 83.34 g of 6FDA was added to the solution. In addition, the molar ratio (a/b) of acid dianhydride (a) and diamine (b) was 1.010. The solution was heated at 40°C for 10 minutes to dissolve the contents, and then 300 g of NMP was added, and the solution was continuously stirred at room temperature for 24 hours to carry out the polymerization reaction to obtain a polyimide with a viscosity of 134,000 cP. Body C (viscous, colorless solution).

[Table 1] Synthesis example 1 2 3 Anhydride name ODPA ODPA 6FDA Weight (g) 98.86 98.86 83.34 Diamine name TFMB TFMB TFMB Weight (g) 101.24 101.24 116.66 Polymerization solvent NMP DMAc NMP Acid/amine molar ratio 1.010 1.010 1.010 Resin viscosity after polymerization (cP) 225,000 232,000 134,000 Polyimide precursor A B C

<Addition of nanosilica particles and preparation of polyimide precursor composition> (Allocation example A-1) To 65 g (13 g in solid content) of the polyimide precursor solution A prepared in Synthesis Example 1, 8.50 g of NMP-ST (Nissan Chemical Co., Ltd.) was added as nanosilica particles Manufacture, the solid content concentration of silica particles: 30 wt%; the average particle size of silica: 12 nm) is diluted with 89.0 g of NMP, and stirred with a rotating and revolving mixer for 2 minutes to prepare polyimide Precursor solution (composition) A-1.

(Allocation example A-2 ~ Allocation example A-4) The types and weights of filler solutions and solvents used in the preparation of Formulation Example A-1 were changed to the types and weights shown in Tables 2 and 3, and the polyimide precursor solution was prepared by the same method as Formulation Example A-1 (Composition) A-2 to A-4.

(Allocation example B-1) To 65 g (13 g in solid content) of the polyimide precursor solution B prepared in Synthesis Example 2, 8.50 g of DMAC-ST (manufactured by Nissan Chemical Co., Ltd., silica particle solid content) was added Concentration: 20 wt%; average particle size of silica: 12 nm) and 84.6 g of DMAc were diluted, and stirred for 2 minutes with a rotating and revolving mixer to prepare polyimide precursor solution (composition) B -1.

(Allocation example B-2) The amounts of DMAC-ST and DMAc used in the preparation of Formulation Example B-1 were changed to the amounts shown in Table 2, and the polyimide precursor solution (composition) B was prepared by the same method as Formulation Example B-1 -2.

(Allocation example B-3) The filler solution used in the preparation of preparation example B-1 was set to 32.17 g of DMAC-ST-ZL (manufactured by Nissan Chemical Co., Ltd., solid content of silica particles: 20 wt%; average particle size of silica) : 80 nm), the amounts of the matrix resin and DMAc were changed to the amounts shown in Table 2, and the polyimide precursor solution (composition) B-3 was prepared by the same method as the preparation example B-1.

(Allocation example C-1) To 65 g (13 g in solid content) of the polyimide precursor solution C prepared in Synthesis Example 3, 8.50 g of NMP-ST (manufactured by Nissan Chemical Co., Ltd., silica particle solid content) was added Concentration: 30 wt%; average particle size of silicon dioxide: 12 nm) and 89.0 g of NMP were diluted, and stirred with a rotating and revolving mixer for 2 minutes to prepare a polyimide precursor solution (composition) C -1.

[Table 2] Allocation example A-1 A-2 B-1 B-2 Matrix resin species Polyimide precursor A Polyimide precursor A Polyimide precursor B Polyimide precursor B Weight (g) 65 65 65 65 Filler solution species NMP-ST NMP-ST DMAC-ST DMAC-ST Weight (g) 8.50 21.24 12.87 32.17 Dilution solvent species NMP NMP DMAc DMAc Weight (g) 89.0 76.3 84.6 65.3 Average particle size of filler 12 nm 12 nm 12 nm 12 nm Filler dispersant no no no no Filler surface treatment agent no no no no Filler concentration (wt%) (relative to PI resin) [filler solid content (g)/PI solid content (g)] 20 wt% (2.6/13.0) 50 wt% (6.5/13.0) 20 wt% (2.6/13.0) 50 wt% (6.5/13.0) Polyimide precursor solution A-1 A-2 B-1 B-2

[table 3] Allocation example A-3 A-4 C-1 B-3 Matrix resin species Polyimide precursor A Polyimide precursor A Polyimide precursor C Polyimide precursor B Weight (g) 65 65 65 150 Filler solution species NMP-ST OP-1354A white NMP-ST DMAC-ST-ZL Weight (g) 31.86 12.87 8.50 33.8 Dilution solvent species NMP NMP NMP DMAc Weight (g) 65.6 84.6 89.0 20.8 Average particle size of filler 12 nm 30 nm 12 nm 80 nm Filler dispersant no Organic Dispersant no no Filler surface treatment agent no no no no Filler concentration (wt%) (relative to PI resin) [filler solid content (g)/PI solid content (g)] 75 wt% (9.75/13.0) 20 wt% (2.6/13.0) 20 wt% (2.6/13.0) 30 wt% (6.8/22.5) Polyimide precursor solution A-3 A-4 C-1 B-3

＜Formation of polyimide film＞ (Example 1) Use a spin coater to coat the polyimide precursor solution A-1 obtained in Formulation Example A-1 on a glass substrate (E-XG manufactured by Corning, size=150 mm×150 mm, thickness=0.7 mm) so that the thickness of the cured polyimide is about 10 μm. Next, heating was performed at 120°C for 7 minutes. Then, in a nitrogen environment, the temperature is increased from room temperature to 385°C at a certain heating rate (4°C/min), and then the temperature is lowered to room temperature to form a 150 mm×150 mm polyimide film on the glass substrate to obtain The polyimide film of was peeled from the glass, thereby obtaining a polyimide film A-1. Various characteristics are shown in Table 4.

(Example 2 to Example 4, Comparative Example 1 to Comparative Example 6) The polyimide precursor solution A-1 used in Example 1 was changed to the solutions shown in Tables 1 to 3, and the polyimide membranes A and A-2 to A were obtained by the same method as in Example 1. -4, B-1～B-3, C, C-1. Furthermore, in Comparative Example 4, the solution of polyimide precursor C prepared in Synthesis Example 3 was used directly, and in Comparative Example 5, the solution of polyimine precursor A prepared in Synthesis Example 1 was directly used for implementation and implementation. The same operation of Example 1 was carried out to form a polyimide film. Various characteristics are shown in Table 4 and Table 5.

[Table 4] Example 1 Example 2 Example 3 Example 4 Polyimide film A-1 A-2 B-1 B-2 YI ₀ 4.7 3.3 4.5 3.2 YI ₄₀₀ 7.5 6.2 7.3 6.1 YI ₄₃₀ 14.7 14 13.9 13.7 YI ₄₅₀ 17.2 17.6 17.5 18.1 Total light transmittance (%) 90.09 90.94 90.2 90.96 Haze 0.34 0.22 0.31 0.21 Td1 (℃) 518 506 518 506 CTE (ppm/K) 63.3 53.4 61.2 52.2 308 nm transmittance (%) 0 0 0 0 430 nm transmittance (%) 84.03 87.45 85 86.4 Membrane self-supporting ○ ○ ○ ○

[table 5] Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Polyimide film A-3 A-4 C-1 C A B-3 YI ₀ 3.1 12.51 2.69 2.01 2.7 29.0 YI ₄₀₀ 6.0 22.3 3.4 3.2 3.8 - YI ₄₃₀ 9.2 28.3 9.8 12.0 7.0 - YI ₄₅₀ 18 45.3 53.61 20.33 9.36 - Total light transmittance (%) 91.01 88.80 91.18 90.15 90.07 83.54 Haze 0.2 7.10 0.3 0.38 0.35 12.6 Td1 (℃) 498 525 493 487 536 510 CTE (ppm/K) 49.7 66.4 60.4 72 71.7 58.0 308 nm transmittance (%) 0 0 0 0 0 0 430 nm transmittance (%) 88 69.28 88.35 89 84.05 50 Membrane self-supporting X ○ ○ ○ ○ 〇

Claims (8)

A polyimine precursor composition, containing a polyimine precursor and nanosilica particles, the polyimine precursor having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride , And the polyimide precursor composition is characterized by: The average particle diameter of the nano-silica particles is 1 nm～70 nm, With respect to 100 parts by mass of the polyimide precursor, containing 10 to 60 parts by mass of the nanosilica particles, When making the polyimide precursor composition into a polyimide film, the following (1) to (5) are satisfied: (1) The yellowness at room temperature is below 10; (2) The yellowness after heating at 400°C for 1 hour and then at 450°C for 1 hour is 20 or less; (3) The total light transmittance is above 85%; (4) The haze is less than 1; (5) The 1% thermal weight reduction temperature (Td1) is above 500℃. The polyimide precursor composition according to claim 1, wherein when it becomes a polyimide film, the following (6) is further satisfied: (6) The coefficient of thermal expansion (CTE) is 65 ppm/K or less. The polyimide precursor composition according to claim 1 or 2, wherein the polyimide film has a light transmittance of 308 nm or less of 5%, and a light transmittance of 430 nm of 70% or more. The polyimine precursor composition according to any one of claims 1 to 3, wherein the polyimine precursor contains more than 50 mole% of all structural units derived from diamines derived from fluorine-containing atoms The structural unit of the diamine of which contains 50 mol% or more of the structural unit derived from the aromatic acid dianhydride represented by the following formula (1) of all structural units derived from the acid dianhydride;

In formula (1), X is O, C=O or SO ₂ . The polyimine precursor composition according to claim 4, wherein the polyimine precursor contains 90 mol% or more of structural units derived from fluorine atom-containing diamines of all structural units derived from diamines , Containing 90 mol% or more of the structural units derived from the aromatic acid dianhydride represented by the formula (1) of all the structural units derived from the acid dianhydride. A polyimide film, characterized in that it is obtained by imidizing the polyimine precursor composition according to any one of claims 1 to 5. A flexible device is formed by laminating a functional layer on the polyimide film according to claim 6. A method for manufacturing a polyimide film, characterized in that: a polyimide film satisfying the following (1) to (5) is manufactured by sequentially performing the following steps: (1) The yellowness at room temperature is below 10; (2) The yellowness after heating at 400°C for 1 hour and then at 450°C for 1 hour is 20 or less; (3) The total light transmittance is above 85%; (4) The haze is less than 1; (5) The 1% thermal weight reduction temperature (Td1) is above 500℃; The steps include: The step of preparing a polyimine precursor composition, the polyimine precursor composition containing a polyimine precursor and nanosilica particles with an average particle diameter of 1 nm to 70 nm, the polyimide precursor composition The imine precursor has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and contains 10 parts by mass to 60 parts by mass of the nanodioxide relative to 100 parts by mass of the polyimide precursor Silicon particles The step of coating the polyimide precursor composition on a carrier substrate and performing heat treatment to form a polyimide film on the carrier substrate; and The step of peeling the formed polyimide film from the carrier substrate.