KR102080965B1 - Polyimide precursor solution and polyimide film prepared therefrom - Google Patents

Abstract

The polyimide according to the present invention may provide a polyimide film having a more relaxed relaxation behavior due to temperature change by introducing a polyimide repeating structure including a structure showing thermal expansion behavior in a polyimide structure showing thermal shrinkage behavior in a plane direction. And a polyimide precursor solution according to the present invention, which is a flexible device involving high temperature processes, in particular of organic light emitting diode (OLED) devices using oxide TFT and low temperature polysilane (LTPS) processes. It can be used advantageously in the process.

Description

Polyimide precursor solution and polyimide film made therefrom {POLYIMIDE PRECURSOR SOLUTION AND POLYIMIDE FILM PREPARED THEREFROM}

The present invention provides a polyimide precursor solution for producing a polyimide film having improved heat shrinkage characteristics.

Polyimide (PI) is a polymer with relatively low crystallinity or mostly amorphous structure. It is easy to synthesize, can make thin film, and does not need a crosslinker for curing. It is a polymer material with excellent heat resistance, chemical resistance, excellent mechanical properties, electrical properties and dimensional stability. It is widely used in electric and electronic materials such as automotive, aerospace, flexible circuit boards, liquid crystal alignment films for LCDs, adhesives and coating agents. have.

However, although polyimide is a high-performance polymer material with high thermal stability, mechanical properties, chemical resistance, and electrical properties, it does not satisfy the colorless and transparent property, which is a basic requirement for the display field, and also requires a lower coefficient of thermal expansion. There is a problem to do. For example, Kapton's coefficient of thermal expansion, sold by DuPont, has a low coefficient of thermal expansion of about 30 ppm / ° C, but this also does not meet the requirements of plastic substrates. Therefore, many studies have been conducted to minimize changes in optical properties and thermal history while maintaining basic properties of polyimide.

In general, aromatic polyimides have a unique color of dark brown, because the π electrons of benzene in the imide main chain are generated by the bonds between chains. The theory can be explained by the reason that σ electrons, π electrons, and nonbonding non-covalent electron pairs exist in the imide structure, thereby enabling electron excitation.

In the case of a general polyimide absorbs light in the visible range of wavelengths from 400 nm or less to 500 nm, the color becomes yellow-red. Therefore, in order to lower CT-complex, which is a disadvantage of aromatic polyimide, an electronegative element such as trifluoromethyl (-CF ₃ ), sulfone (-SO ₂ ), and ether (-O-) is used in this main chain. There is a method of reducing the resonance effect by limiting the transfer of π electrons by introducing, and also by introducing an olefin-based cycloolefin structure instead of benzene to reduce the density of π electrons in the main chain to form a colorless and transparent polyimide film. It can manufacture.

On the other hand, polyamide-imide has been widely used as an industrial material in the fields of electricity, electronics, machinery, aviation, etc. because of its excellent heat resistance, mechanical strength, electrical properties, and the like. In addition, since the structure itself is different from the general polyimide, polyamideimide is known to be soluble in an organic solvent, and is also used for applications in which solution molding such as enamel varnish, coating for electrical insulation, and paint is essential.

However, there is still a need for the development of polymers for flexible displays with lower coefficient of thermal expansion, high solubility, transparency and thermal stability for use in the display field.

The problem to be solved by the present invention is to provide a polyimide precursor solution for producing a polyimide film with improved heat resistance and optical properties.

Another object of the present invention is to provide a polyimide film prepared from the polyimide precursor solution.

Another object of the present invention is to provide a method for producing a polyimide film using the polyimide precursor solution.

The present invention to solve the above technical problem,

The present invention provides a polyimide precursor solution comprising a polyamic acid and an organic solvent prepared by polymerizing a polymerization component including tetracarboxylic dianhydride of Formula 1 and Formula 2 and diamine of Formula 3 below.

[Formula 1]

[Formula 2]

[Formula 3]

In Chemical Formula 3,

R ₁ and R ₂ are each independently a halogen atom consisting of -F, -Cl, -Br and -I, a hydroxyl group (-OH), a thiol group (-SH), a nitro group (-NO ₂ ), and a cyan A substituent selected from a furnace group, an alkyl group having 1 to 10 carbon atoms, a halogenoalkoxy group having 1 to 4 carbon atoms, a halogenoalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 20 carbon atoms,

Q ₁ is a single bond, -O-, -CR ₁₈ R _19- , -C (= O)-, -C (= O) O-, -C (= O) NH-, -S-, -SO ₂ -A phenylene group and combinations thereof, wherein R ₁₈ and R ₁₉ are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms and a fluoroalkyl group having 1 to 10 carbon atoms It will be.

According to an embodiment, the compound of Formula 2 may be included in an amount of 10 to 35 mol% based on the total content of the tetracarboxylic dianhydride.

According to one embodiment, the compound of Formula 1 may be included in more than 65 mol% based on the total content of the tetracarboxylic dianhydride.

According to one embodiment, the viscosity of the polyimide precursor solution may be 2,000 to 8,000cp or less.

According to an embodiment, the polymerization component may further include a compound of Formula 4a or 4b.

[Formula 4a]

[Formula 4b]

In Chemical Formulas 4a and 4b,

R ₃ and R ₄ are each independently a hydrogen atom, a halogen atom consisting of -F, -Cl, -Br and -I, a hydroxyl group (-OH), a thiol group (-SH), a nitro group (-NO ₂ ), A cyano group (-CN), an alkyl group having 1 to 10 carbon atoms, a halogenoalkoxy group having 1 to 4 carbon atoms, a halogenoalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 20 carbon atoms.

According to an embodiment, the total content of the compound of Formula 2 and the compound of Formula 4a or 4b is included in an amount of 10 to 35 mol% based on the total content of the tetracarboxylic dianhydride, and the compound of Formula 2 may be at least It may contain 1 mol% or more.

According to one embodiment, the tetracarboxylic dianhydride may be reacted in excess with respect to the diamine.

According to one embodiment, the tetracarboxylic dianhydride diamine may be a 1: 0.98 ~ 1: 0.99 molar ratio is reacted.

According to one embodiment, the organic solvent may be positive logP, N, N-diethylacetamide (N, N-diethylacetamide, DEAc), N, N-diethylformamide (N, N-diethylformamide, DEF ), N-ethylpyrrolidone (N-ethylpyrrolidone, NEP) or a mixture thereof may be selected.

In order to solve the other problem of the present invention, it provides a polyimide film prepared from the polyimide precursor solution.

According to an embodiment, the polyimide film has a coefficient of thermal expansion (CTE) of -15 to 10 ppm after n + 1 heating (n is an integer of 0 or more) and a cooling process after heating in a temperature range of 100 ° C to 450 ° C. / ° C.

According to an embodiment, the polyimide film has a coefficient of thermal expansion (CTE) of 0 to 10 ppm / ° C after a cooling process after n + 1 heating (n is an integer of 0 or more) in a range of 100 ° C to 450 ° C. Can be.

According to one embodiment, the yellowing degree (YI) of the polyimide film may be 20 or less.

According to one embodiment, the polyimide film, the average linear expansion coefficient (CTE) measured at 50 ~ 250 ℃ according to the TMA Method is 35.0ppm / ℃ or less, L value is 90 or more when measuring the color coordinates by UV spectrometer, The value a may be 5 or less, and the value b may be 10 or less.

In order to solve another problem of the present invention,

Applying the polyimide precursor solution onto a substrate;

It provides a method for producing a polyimide film comprising the step of heat-treating the applied polyimide precursor solution at a temperature of 300 ℃ to 500 ℃.

The present invention also provides a transparent polyimide substrate for Oxide TFT or LTPS made of the polyimide precursor solution.

The polyimide according to the present invention may provide a polyimide film having a more relaxed relaxation behavior due to temperature change by introducing a polyimide repeating structure including a structure showing thermal expansion behavior in a polyimide structure showing thermal shrinkage behavior in a plane direction. And a polyimide precursor solution according to the present invention is a flexible device involving a high temperature process, in particular an organic light emitting diode (OLED) device using an oxide TFT and a low temperature polycrystalline silicon (LTPS) process It can be used advantageously in the process of.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

All compounds or organic groups herein may be substituted or unsubstituted unless otherwise specified. Herein, the term "substituted" means that at least one hydrogen contained in the compound or organic group is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a hydroxy group And substituted with a substituent selected from the group consisting of an alkoxy group, a carboxylic acid group, an aldehyde group, an epoxy group, a cyano group, a nitro group, an amino group, a sulfonic acid group and derivatives thereof having 1 to 10 carbon atoms.

In addition, in the present specification, "combination of these", unless otherwise specified, a single bond, a double bond, a triple bond, an alkylene group having 1 to 10 carbon atoms (for example, methylene group (-CH _2- ), Ethylene groups (-CH ₂ CH _2- ) and the like, fluoroalkylene groups having 1 to 10 carbon atoms (e.g., fluoromethylene groups (-CF _2- ), perfluoroethylene groups (-CF ₂ CF _2- ); ), A hetero atom such as N, O, P, S, or Si or a functional group containing the same (e.g., intramolecular carbonyl group (-C = O-), ether group (-O-), ester group ( Or a heteroalkylene group including -COO-), -S-, -NH-, or -N = N-, or the like, or that two or more functional groups are condensed and connected.

Flexible devices with high temperature processes require heat resistance at high temperatures, especially for organic light emitting diode (OLED) devices using oxide TFTs and low temperature polycrystalline silicon (LTPS) processes. Also close to. At such a temperature, even polyimide having excellent heat resistance is likely to be pyrolyzed, and thermal contraction or expansion may occur. Therefore, in order to manufacture a flexible device, it is necessary to develop a polyimide that can exhibit excellent thermal stability while maintaining high transparency at high temperature with excellent mechanical properties.

In order to solve the problem according to the present invention,

Provided is a polyimide precursor solution comprising a polyamic acid and an organic solvent prepared by polymerizing a polymerization component including tetracarboxylic dianhydride of Formula 1 and Formula 2 and diamine of Formula 3 below.

[Formula 1]

[Formula 2]

[Formula 3]

In Chemical Formula 3,

R ₁ and R ₂ are each independently a halogen atom consisting of -F, -Cl, -Br and -I, a hydroxyl group (-OH), a thiol group (-SH), a nitro group (-NO ₂ ), and a cyan And a substituent selected from a furnace group, an alkyl group having 1 to 10 carbon atoms, a halogenoalkoxy group having 1 to 4 carbon atoms, a halogenoalkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 20 carbon atoms, and preferably a halogen atom and a halogeno group. It may be a substituent selected from an alkyl group, an alkyl group, an aryl group and a cyano group, the alkyl group may be one selected from methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, the aryl The group may be selected from a phenyl group and a naphthalenyl group. For example, the halogen atom may be fluoro (-F), the halogenoalkyl group is a fluoroalkyl group having 1 to 10 carbon atoms containing a fluoro-based atom, fluoromethyl group, perfluoroethyl group, trifluoro It may be selected from a methyl group, and more preferably may be a substituent containing a fluoro-based atom, such as a fluoro atom and a fluoroalkyl group.

Q ₁ is a single bond, -O-, -CR ₁₈ R _19- , -C (= O)-, -C (= O) O-, -C (= O) NH-, -S-, -SO ₂ -A phenylene group and combinations thereof, wherein R ₁₈ and R ₁₉ are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms and a fluoroalkyl group having 1 to 10 carbon atoms It will be.

In this case, the "fluoro-based substituent" of the present invention means not only a "fluoro atom substituent" but also a "substituent containing a fluoro atom".

According to one embodiment, the diamine of Formula 3 may be selected from compounds represented by Formulas 3a to 3d.

In Chemical Formulas 3a to 3d, Q ₁ is the same as that of Chemical Formula 3.

Compound containing the structure of Formula 2 is used in the production of polyimide together with the compound represented by the formula (1), thereby alleviating the planar shrinkage characteristics due to heat of the polyimide film, generated during the cooling step after the heating step The shrinkage phenomenon of the film can be improved.

According to an embodiment, the polymerization component may further include a compound of Formula 4a or 4b.

[Formula 4a]

[Formula 4b]

In Chemical Formulas 4a and 4b,

R ₃ and R ₄ are each independently a hydrogen atom, a halogen atom consisting of -F, -Cl, -Br and -I, a hydroxyl group (-OH), a thiol group (-SH), a nitro group (-NO ₂ ), A cyano group (-CN), an alkyl group of 1 to 10 carbon atoms, a halogenoalkoxy group of 1 to 4 carbon atoms, a halogenoalkyl group of 1 to 10 carbon atoms, an aryl group of 6 to 20 carbon atoms, preferably May be a substituent selected from a halogen atom, a halogenoalkyl group, an alkyl group, an aryl group and a cyano group, wherein the alkyl group is selected from methyl, ethyl, propyl, isopropyl, t-butyl, pentyl and hexyl groups The aryl group may be selected from a phenyl group, a naphthalenyl group. For example, the halogen atom may be fluoro (-F), the halogenoalkyl group is a fluoroalkyl group having 1 to 10 carbon atoms containing a fluoro-based atom, fluoromethyl group, perfluoroethyl group, trifluoro It may be selected from a methyl group, and more preferably may be a substituent containing a fluoro-based atom, such as a fluoro atom and a fluoroalkyl group.

According to an embodiment, in the case of the polyimide including the compound of Formula 1 and the structure of Formula 4a together, it may generate crystallinity of the polyimide, and in the structure of the copolymer, phase separation may occur due to such crystallinity. In addition to causing haze or lower glass transition temperatures, strong ordered arrangements can lead to interactions by charge-transfer resulting in higher YI. However, in the case of Chemical Formula 2, which is the structural isomer of Chemical Formula 4a, since it has an asymmetrical structure, it does not exhibit a characteristic according to a crystalline or regular array, thereby providing a colorless transparent polyimide compared to a symmetric structure of Chemical Formula 4a. have. In addition, the shrinkage characteristics according to the temperature change during the high temperature process from the above structural characteristics can be significantly improved.

According to one embodiment, Formula 1 may be included as 65 mol% or more, preferably 70 mol% or more and more preferably 75 mol% or more based on the total content of the tetracarboxylic dianhydride.

In addition, the compound of Formula 2 may be included in 10 to 35 mol%, preferably 10 to 30 mol%, more preferably 15 to 30 mol% relative to the total content of tetracarboxylic dianhydride. Alternatively, the compound of Formula 2 may be included together with the compound of Formula 4a or 4b, and when the compound of Formula 2 and the compound of Formula 4a or 4b are used together as described above, the compound of Formula 2 and Formula 4a Alternatively, the total content of 4b may be included in 10 to 35 mol%, preferably 10 to 30 mol%, more preferably 15 to 30 mol% with respect to the total content of tetracarboxylic dianhydride, in this case The content of 2 may be included at least 1 mol% or more, preferably 2 mol% or more.

In the polyimide film according to the present invention, by using the tetracarboxylic dianhydride represented by the general formula (2) together with the tetracarboxylic dianhydride of the general formula (1), the shrinkage characteristics of the film can be alleviated, and the structural isomer of Heat resistance and YI may be improved than a polyimide film composed of Formulas 4a or 4b and Formula 1 only.

According to one embodiment, the tetracarboxylic dianhydride may be included in excess with respect to the diamine content, preferably the diamine is 1: 0.95 to 1: 0.99 molar ratio, more preferably 1: 0.98 to 1: 0.99 It may be reacted in a molar ratio. When the tetracarboxylic dianhydride is included in an excessive amount compared to the diamine, it may be easier to adjust the viscosity and optical properties of the polyimide precursor compared to the case where the same amount or the diamine is reacted in an excessive amount.

In addition, polyimide in which diamine is polymerized in excess is advantageous in terms of viscosity and molecular weight stability, but diamine excess polyimide substrates may cause problems in high temperature heat treatment processes such as CTE shrinkage at high temperatures. However, when the dianhydride is reacted in excess, not only the stability of the molecular weight and viscosity but also the CTE shrinkage behavior in the high temperature heat treatment process may be alleviated.

The method for reacting the tetracarboxylic dianhydride with diamine can be carried out according to a conventional polyimide precursor polymerization production method such as solution polymerization. Specifically, it can be prepared by dissolving diamine in an organic solvent, followed by polymerization by adding tetracarboxylic dianhydride to the resulting mixed solution.

The reaction can be carried out under an inert gas or nitrogen stream and can be carried out in anhydrous conditions.

In addition, the polymerization temperature may be carried out at -20 ℃ to 60 ℃, preferably 0 ℃ to 45 ℃. If the reaction temperature is too high, the reactivity may be increased to increase the molecular weight, it may be disadvantageous in the process by increasing the viscosity of the precursor composition.

In addition, the organic solvent that can be used in the polymerization reaction may be a partition coefficient (LogP value) at 25 ℃ positive water and a boiling point of 180 ℃ or less, more specifically, the partition coefficient LogP value is 0.01 to 3, or 0.01 to 2, or 0.01 to 1. The distribution coefficient can be calculated using ACD / LogP module of ACD / Percepta platform of ACD / Labs, and ACD / LogP module uses QSPR (Quantitative Structure-Property Relationship) methodology based algorithm using molecular 2D structure. I use it.

When the partition coefficient value is positive, it means that the polarity of the solvent is hydrophobic. According to the researches of the present inventors, a polyimide precursor solution is prepared using a specific solvent having a positive partition coefficient value, and a polyimide precursor solution is prepared using the same. In this case, it can be seen that the curling properties of the solution are improved. In addition, the present invention can control the liquid curling of the solution without using an additive that adjusts the surface tension of the material, such as a leveling agent and the smoothness of the coating film by using a solvent having a positive logP as described above, Since additional additives such as additives are not used, it is possible to eliminate the quality and process problems such as the low molecular weight material contained in the final product, and to form a polyimide film having more uniform properties.

For example, in the process of coating a polyimide precursor solution on a glass substrate, the shrinkage of the coating solution layer during the curing process of the coating solution coated on the substrate or the conditions of leaving the coating solution coated on the substrate under humidity conditions This can cause liquid curls. The liquid phenomena of the coating solution may lead to variations in the thickness of the film, thereby causing the film to break or the edges to break when cutting due to the lack of bending resistance of the film, resulting in process workability and yield. This can cause the problem of deterioration. In addition, when a fine foreign substance having polarity is introduced onto the polyimide precursor solution coated on the substrate, in the polyimide precursor solution containing a polar solvent having a negative log P, the position of the foreign substance is determined by the polarity of the foreign substance. As a reference, sporadic coating cracks or changes in thickness may occur.However, in the case of using a hydrophobic solvent having a positive log P, the occurrence of changes in thickness due to cracking of coatings may be reduced even when a fine foreign substance having polarity is introduced. Can be suppressed.

Specifically, the polyimide precursor solution including a solvent in which Log P is a positive number may have a curl rate of 0% to 0.1% or less defined by Equation 1 below.

[Equation 1]

Curl rate (%) = [(A-B) / A] × 100

In the formula 1,

A: Area in a state where the polyimide precursor solution is completely coated on the substrate (100 mm × 100 mm)

B: Area after this curling occurs from the edge end of the substrate coated with the polyimide precursor solution or polyimide film

The phenomenon of liquid curling of the polyimide precursor solution and the film may occur within 30 minutes after coating the polyimide precursor solution solution, and in particular, the thickness of the edge may be thickened by starting to curl from the edge.

After coating the polyimide precursor solution according to the present invention on a substrate for 10 minutes or more, for example 10 minutes or more, for example, 40 minutes or more, the curling rate of the coated resin composition solution after being left in humidity conditions is 0.1 It may be less than%, for example, at a temperature of 20 ℃ to 30 ℃, humidity conditions of 40% or more, more specifically 40%, 50%, 60%, 70 humidity conditions in the range of 40% to 80% In each humidity condition of%, 80%, for example, it may exhibit a very small curl rate of 0.1% or less even after being left for 10 to 50 minutes at a humidity condition of 50%, preferably 0.05%, more preferably Can exhibit a near-zero curl rate.

The curling rate is maintained even after curing, for example, after coating the polyimide precursor solution on a substrate for 10 minutes or more, for example, at a temperature of 20 ℃ to 30 ℃, more than 40% humidity conditions, more Specifically, in a humidity range of 40% to 80%, that is, 40%, 50%, 60%, 70%, 80% of each humidity condition, for example, 50% humidity conditions for 10 to 50 minutes The curling rate of the post-cured polyimide film may be 0.1% or less, that is, almost no curling of the film occurs in the curing process by heat treatment, specifically, at 0.05%, more preferably at almost 0%. It can indicate a near curl rate.

The polyimide precursor solution according to the present invention can obtain a polyimide film having more uniform properties by solving the liquid phenomena caused by shrinkage of the coating layer, it is possible to further improve the yield of the manufacturing process.

In addition, the density of the organic solvent according to the present invention may be less than 1g / cm ³ measured by the standard measuring method of ASTM D1475, when the density has a value of 1 or more can increase the relative viscosity can reduce the efficiency of the process have.

As a solvent that can be used in the present invention, N, N-diethylacetamide (DEAc), N, N-diethylformamide (DEF), N-ethylpy It may be one selected from the group of ralidone (N-ethylpyrrolidone, NEP) or a mixture thereof.

It is preferable that the polyimide precursor solution manufactured by the above-mentioned manufacturing method contains solid content in the quantity which makes the said composition have appropriate viscosity in consideration of processability, such as applicability | paintability in the film formation process. According to one embodiment, the content of the composition can be adjusted so that the content of the total polyimide precursor is 5 to 20% by weight, preferably 8 to 18% by weight, more preferably 8 to 12% by weight or less. have.

Alternatively, the polyimide precursor solution may be adjusted to have a viscosity of 2,000 cP or more, or 3,000 cP or more, and the viscosity of the polyimide precursor solution is 10,000 cP or less, preferably 9,000 cP or less, more preferably 8,000 cP or less. It is preferable to adjust to have a viscosity of. When the viscosity of the polyimide precursor solution exceeds 10,000 cP, the efficiency of degassing during the processing of the polyimide film may be reduced, thereby reducing the efficiency of the process. Optical and mechanical properties may be degraded.

In addition, the molecular weight of the polyimide according to the present invention may have a weight average molecular weight of 10,000 to 200,000 g / mol, or 20,000 to 100,000 g / mol, or 30,000 to 100,000 g / mol. Moreover, it is preferable that the molecular weight distribution (Mw / Mn) of the polyimide which concerns on this invention is 1.1-2.5. If the weight average molecular weight or molecular weight distribution of the polyimide is out of the above range, it may be difficult to form a film or the characteristics of the polyimide film such as permeability, heat resistance and mechanical properties may be deteriorated.

Subsequently, the polyimide precursor obtained as a result of the said polymerization reaction is imidated, and a transparent polyimide film can be manufactured. In this case, the imidization process may specifically include a chemical imidization method or a thermal imidization method.

For example, after adding a dehydrating agent and an imidization catalyst to the polymerized polyimide precursor solution, it is heated to a temperature of 50 ° C. to 100 ° C. and imidized by a chemical reaction, or the alcohol is removed while refluxing the solution. Polyimide can be obtained by the method of imidating.

In the chemical imidization method, pyridine, triethylamine, picoline, or quinoline may be used as the imidation catalyst, and in addition, N- of a substituted or unsubstituted nitrogen-containing heterocyclic compound and a nitrogen-containing heterocyclic compound Oxide compounds, substituted or unsubstituted amino acid compounds, aromatic hydrocarbon compounds having a hydroxyl group or aromatic heterocyclic compounds, and especially 1,2-dimethylimidazole, N-methylimidazole, N-benzyl-2- Lower alkylimidazoles such as methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 5-methylbenzimidazole, and N-benzyl-2-methylimidazole. Substituted pyridine such as dozol derivative, isoquinoline, 3,5-dimethylpyridine, 3,4-dimethylpyridine, 2,5-dimethylpyridine, 2,4-dimethylpyridine, 4-n-propylpyridine, p-toluenesulfonic acid and the like May be used.

As the dehydrating agent, acid anhydrides such as acetic anhydride can be used.

Alternatively, the polyimide precursor solution may be imidized by applying a heat treatment on a substrate.

The polyimide precursor solution may be in the form of a solution dissolved in an organic solvent, and in the case of having such a form, for example, when a polyimide precursor is synthesized in an organic solvent, the solution may be the reaction solution itself obtained. The reaction solution may be diluted with another solvent. Moreover, when obtaining a polyimide precursor as a solid powder, it may be made to melt | dissolve this in the organic solvent and set it as the solution.

The present invention comprises the steps of applying the polyimide precursor solution on a substrate;

It provides a method for producing a polyimide film comprising the step of heat-treating the applied polyimide precursor solution.

The polyimide precursor solution is applied to a substrate and heat treated on an IR oven, a hot air oven or a hot plate, wherein the heat treatment temperature may be in the range of 300 ° C. to 500 ° C., preferably 320 ° C. to 480 ° C. It may also proceed with a multistage heating process within the temperature range. The heat treatment process may be performed for 20 minutes to 70 minutes, preferably 20 minutes to 60 minutes or so.

The organic solvent contained in the polyimide precursor solution of the present invention may be the same as the organic solvent used in the synthesis reaction.

As long as this invention is a range in which an effect is not impaired, you may add a silane coupling agent, a crosslinking | crosslinked compound, the imidation promoter, etc. for the purpose of advancing imidation efficiently.

The present invention provides a polyimide comprising a repeating structure represented by the following formula (5a) and (5b).

[Formula 5a]

[Formula 5b]

By introducing a polyimide repeating structure including the structure of formula (5b) to a polyimide structure having a severe heat shrinkage behavior due to cooling during the heating and cooling process of the formula (5a), by polymerizing a polyimide structure having thermal expansion characteristics at an appropriate ratio The heat resistance of the film can be optimized in the heating and cooling process.

The polyimide film according to the present invention may be excellent in heat resistance according to the temperature change, for example, the polyimide film according to the present invention is preferably 8 to 15㎛ based on the film thickness of 8 to 20㎛ As a reference, the coefficient of thermal expansion after n + 1 heating and cooling processes in a temperature range of 100 ° C. to 450 ° C. may have a value of −15 to 10 ppm / ° C. or less, more preferably −10 to 10 ppm / ° C. or less, Or it may have a value of 0 to 10ppm / ℃ or less.

Moreover, it is preferable that average linear expansion coefficient (CTE) measured at 50-250 degreeC according to TMA-Method is 35.0 ppm / degree C or less.

In addition, hazes have a haze value of 1 or less, preferably 0.9 or less, or 0.7 or less, and more preferably 0.5 or less, so that a polyimide film having improved transparency can be provided. In this case, the thickness of the polyimide film may be 8 to 15㎛, preferably 10 to 12㎛.

In addition, the transmittance of light with a wavelength of 380 to 760 nm in the film thickness range of 5 to 30 μm is 80% or more, and the yellowness (YI) is about 25 or less, preferably about 20 or less, and more preferably about 16 or less. It may be a colorless transparent polyimide film having a value of.

In the polyimide film according to the present invention, the polyimide film of the present invention has a transmittance of 88% or more at 550 nm and a transmittance at 440 nm when measuring transmittance with a UV spectrometer at 380 to 780 nm based on a film thickness of 5 to 100 μm. It is preferable that it is 70% or more.

In addition, the polyimide film of the present invention preferably has an L value of 90 or more, a value of 5 or less, and a b value of 10 or less when the color coordinate is measured by a UV spectrometer based on a film thickness of 5 to 100 μm.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

The abbreviations indicated below are as follows.

DEAc: diethylacetamide (N, N-diethylacetamide)

TFMB: 2,2'-bis (trifluoromethyl) -4,4'-biphenyl diamine (2,2'-bis (trifluoromethyl) -4,4'-biphenyl diamine)

PMDA: Pyromellitic Dianhydride

BPDA: 3,3,4,4'-biphenyltetracarboxylic dianhydride (3,3 ', 4,4' '-Biphenyltetracarboxylic dianhydride)

a-BPDA: 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride (2,3,3', 4'-Biphenyltetracarboxylic dianhydride)

Example 1 a-BPDA (0.15) PMDA (0.85) / TFMB (0.999)

After filling 90 g of the organic solvent DEAc in the stirrer through which the nitrogen stream flowed, 16.7 g of TFMB was dissolved while maintaining the temperature of the reactor at 25 ° C. 2.31 g of a-BPDA and 9.6 g of PMDA were added to the TFMB solution at the same temperature, and then dissolved and stirred for a predetermined time to prepare a polyamic acid. The organic solvent was added to prepare a polyimide precursor solution so that the solid content concentration of the polyimide precursor solution prepared from the reaction was 12-18 wt%. The viscosity of the polyimide precursor solution was 6,700 cP.

Example 2 a-BPDA (0.25) PMDA (0.75) / TFMB (0.999)

After filling 90 g of the organic solvent DEAc in the stirrer through which the nitrogen stream flowed, 16.7 g of TFMB was dissolved while maintaining the temperature of the reactor at 25 ° C. 3.75 g of a-BPDA and 8.56 g of PMDA were added to the TFMB solution at the same temperature to dissolve and stir for a predetermined time to prepare a polyamic acid. The organic solvent was added to prepare a polyimide precursor solution so that the solid content concentration of the polyimide precursor solution prepared from the reaction was 12-18 wt%. The viscosity of the polyimide precursor solution was 6,250 cP.

Example 3 a-BPDA (0.02) BPDA (0.28) PMDA (0.7) / TFMB (0.999)

After filling 90 g of the organic solvent DEAc in the stirrer through which the nitrogen stream flowed, 16.7 g of TFMB was dissolved while maintaining the temperature of the reactor at 25 ° C. 0.308 g of a-BPDA, 4.312 g of BPDA, and 8.0 g of PMDA were added to the TFMB solution at the same temperature to dissolve and stir for a predetermined time to prepare a polyamic acid. The organic solvent was added to prepare a polyimide precursor solution so that the solid content concentration of the polyimide precursor solution prepared from the reaction was 12-18 wt%. The viscosity of the polyimide precursor solution was 4,500 cP.

Comparative Example 1 TFMB (0.99) / PMDA (1.0)

After filling with 100g of N, N-diethylacetamide (DEAc) (distribution coefficient 0.32, density 0.9130g / cm ³ ) in the stirrer with nitrogen stream, TFMB (2,2`-bis) while maintaining the reactor temperature at 25 ℃ 10.17 g of (trifluoromethyl) -4,4′-biphenyl diamine) was dissolved. To the TFMB solution was added 7 g of PMDA (Pyromellitic Dianhydride) to dissolve for a certain time and stirred. The polyimide precursor solution was prepared by adding DEAc to the polyimide precursor solution prepared from the above reaction so that the solid content concentration was 10.0 to 10.5 wt%. The viscosity of the polyimide precursor solution was 9,500 cps.

<Production of Polyimide Film>

The polyimide precursor solution prepared in Examples 1 to 3 and Comparative Example 1 was spin coated on a glass substrate. The glass substrate coated with the polyimide precursor solution was placed in an oven and heated at a rate of 4 ° C./min, and a 450 ° C. curing process was performed. After completion of the curing process, the glass substrate was immersed in water, the film formed on the glass substrate was removed and dried at 100 ° C. in an oven to prepare a film of polyimide having a thickness of 8 to 12 μm.

Experimental Example 1 Evaluation of Heat Resistance of a Polyimide Film

Table 1 shows the CTE of the polyimide films prepared from the polyimide precursor solutions of Examples 1 to 3 and Comparative Example 1 by the following method.

After preparing a film having a thickness of 8 to 12 μm in a size of 5 × 20 mm, the sample is loaded using an accessory. The length of the film actually measured was made the same at 16 mm. After setting the film pulling force to 0.02N and proceeding the first temperature increase step at a temperature increase rate of 5 ℃ / min in the temperature range of 100 ℃ to 450 ℃, cooling at 4 ℃ / min in the temperature range of 450 ℃ to 100 ℃ The pattern of change in thermal expansion when cooled at speed was measured by TMA (Q400 from TA). At this time, the inflection point seen in the temperature increase section in the first temperature increase step was set to Tg.

A film having a thickness of 8 to 12 μm is prepared by the method of preparing the film, and the sample is loaded using an accessory after preparing a film having a size of 4 × 20 mm. The pulling force of the film was set to 0.01 N and measured at a temperature rising rate of 10 ° C./min in a temperature range of 50 ° C. to 250 ° C.

Analysis item Comparative Example 1 Example 1 Example 2 Example 3 Solid content (%) 10.0 15.2 15.8 13.3 Viscosity (cp) 9500 6700 6250 4500 thickness
(Μm) 9.5 10.3 10.0 11 CTE
100 ~ 450 ℃
(ppm / ℃) 1 ^st
cooling -20 0.98 6.8 -14 Tg (℃)
~ 450 ℃ N.D N.D N.D N.D CTE
50 ~ 250 ℃
(ppm / ℃) heating -15 0.3 3.5 -7.5

As can be seen from the results of Table 1, the polyimide films of Examples 1 to 3 according to the present invention exhibited very low negative values of CTE in the primary cooling process or values of 10 ppm / ° C. or less, which were heated And it may mean that the expansion and contraction behavior of the film according to the cooling process is significantly reduced. In addition, even if included in the same amount from the results of Example 1 and Example 3 may mean that the polyimide film containing a-BPDA can be much more improved heat resistance to temperature changes than BPDA. In addition, the polyimide precursor solution according to the present invention may exhibit a low viscosity at a high solid content, so that the coating property and uniformity of the film may be improved, and thus the manufacturing process of the film may be more efficiently performed.

Experimental Example 2 Evaluation of Optical Properties of Polyimide Film

The yellowness and UV color coordinates of the prepared film are measured and shown in Table 2.

Yellowness Index (YI) of the prepared film was measured using a color difference meter (Color Eye 7000A).

Color coordinates of the prepared film was measured according to ASTM E 1347-06 standard using a UV spectrometer (Varian, Cary 100), the light source (Illuminant) was based on the measured value by CIE D65.

Analysis item Comparative Example 1 Example 1 Example 2 Example 3 Yellow road 21 16.0 15 15 Color coordinates L 88 95.7 95.4 95.3 a -2.31 -1.26 -1.35 -1.28 b 10.09 5.35 5.12 7.87

As shown in Table 2, it can be seen that the optical properties of the polyimide films of Examples 1 to 3 exhibit significantly superior values compared to the polyimide films of Comparative Example 1.

Accordingly, the polyimide precursor solution according to the present invention may provide a polyimide film having improved optical properties as well as heat resistance in a high temperature process.

The specific parts of the present invention have been described in detail above, and it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. Therefore, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (17)

To the polymerization component consisting of tetracarboxylic dianhydride consisting of 65 to 90 mol% of tetracarboxylic dianhydride of Formula 1 and 10 to 35 mol% of tetracarboxylic dianhydride of Formula 2 Polyimide precursor solution comprising a polyamic acid and an organic solvent prepared by polymerization:
[Formula 1]

[Formula 2]

[Formula 3]

In Chemical Formula 3,
R ₁ and R ₂ are each independently a halogen atom, a hydroxyl group (-OH), a thiol group (-SH), a nitro group (-NO ₂ ), a cyano group, an alkyl group having 1 to 10 carbon atoms, and 1 to 4 carbon atoms. Is a substituent selected from a halogenoalkoxy group, a halogenoalkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms,
Q ₁ is a single bond, -O-, -CR ₁₈ R _19- , -C (= O)-, -C (= O) O-, -C (= O) NH-, -S-, -SO ₂ -A phenylene group and combinations thereof, wherein R ₁₈ and R ₁₉ are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms and a fluoroalkyl group having 1 to 10 carbon atoms It will be. delete delete The method of claim 1,
Polyimide precursor solution having a viscosity of 2,000 to 8,000cp or less of the polyimide precursor solution. delete delete The method of claim 1,
Wherein said tetracarboxylic dianhydride is reacted in excess with respect to diamine. The method of claim 1,
The said tetracarboxylic dianhydride and diamine react in a 1: 0.98-1: 0.99 molar ratio polyimide precursor solution. The method of claim 1,
The polyimide precursor solution of which the organic solvent is a positive LogP. The method of claim 9,
N, N-diethylacetamide (DEAc), N, N-diethylformamide (DEF), N-ethylpyrrolidone (N, N-diethylacetamide, DEAc) N-ethylpyrrolidone, NEP) or a mixture thereof. A polyimide film made of the polyimide precursor solution according to any one of claims 1, 4 and 7 to 10. The method of claim 11,
The polyimide film is a polyimide film having a coefficient of thermal expansion (CTE) of -15 to 10 ppm / ° C after the cooling process after heating n + 1 times (n is an integer of 0 or more) in the range of 100 ° C to 450 ° C. The method of claim 11,
The polyimide film is a polyimide film having a coefficient of thermal expansion (CTE) of 0 to 10ppm / ℃ after the cooling process after n + 1 (n is an integer of 0 or more) in the range of 100 ℃ to 450 ℃. The method of claim 11,
The polyimide film whose yellowness degree (YI) of the said polyimide film is 20 or less. The method of claim 11,
The polyimide film has an average linear expansion coefficient (CTE) of 35.0 ppm / ° C. or less measured at 50 to 250 ° C. according to the TMA Method, an L value of 90 or more and a value of 5 or less when measured by a color spectrometer with a UV spectrometer. The polyimide film whose b value is 10 or less. Applying a polyimide precursor solution according to any one of claims 1, 4 and 7 to 10 on a substrate;
Method for producing a polyimide film comprising the step of heat-treating the applied polyimide precursor solution to 300 ℃ to 500 ℃. A transparent polyimide substrate for oxide TFT or LTPS made of the polyimide precursor solution of any one of claims 1, 4 and 7 to 10.