KR20170038175A - Method for producing polyimide film - Google Patents

Abstract

Provided is a method for producing a polyimide film which contributes to improve productivity and reduce costs by reducing time of a heating process. A polyimide precursor or a polyimide resin solution is coated on a coating base material to have a polyimide film thickness of 50 m or less, and a polyimide film which does not have a defective outer appearance caused by bubbles or bubble stains is produced on the coating base material by completing heating. The polyimide film can be peeled from the coating base material, and the polyimide film includes one or more polyimide layers. Polyimide constituting a major polyimide layer has a structure unit of 70 mole% represented by formula (1), and the heating time is 10 minutes or less.

Description

METHOD FOR PRODUCING POLYIMIDE FILM [0002]

The present invention relates to a process for producing a polyimide film, and more particularly to a process for producing a polyimide film which can be preferably used for a flexible device such as a liquid crystal display device, an organic EL display device, and a touch panel.

Organic EL devices used for various displays including a large display such as a television and a small display such as a cellular phone, a personal computer, and a smart phone generally have a thin film transistor (hereinafter referred to as TFT) formed on a glass substrate as a supporting substrate , And an electrode, a light emitting layer, and an electrode are sequentially formed and hermetically sealed with a separate glass substrate or multilayer thin film at the end. In the structure of the organic EL device, there are a bottom emission structure that draws light from the glass substrate side, which is the supporting substrate, and a top emission structure, which draws light from the reverse side of the glass substrate that is the supporting substrate. In addition, a transparent structure in which an electronic device such as a TFT is seen from the outside is also proposed since a structure in which external light passes through the structure can be taken. All of which can be realized by selecting an electrode or a substrate material having transparency.

In addition, by replacing the supporting substrate of such an organic EL device with a resin from a conventional glass substrate, it is possible to make it ultra thin, lightweight, and flexible, and widen the use of the organic EL device. However, various investigations have been made in view of deterioration of dimensional stability, transparency, heat resistance, moisture resistance, gas barrier properties, and the like compared with general glass.

For example, Patent Document 1 discloses that a fluorine-containing polyimide composition in which an acid anhydride and a fluorinated alkyl group are introduced into a diamine has a low dielectric constant, a low water absorption rate, and a low thermal expansion property and is applicable to a material for a printed board or an optical waveguide.

For example, Patent Document 2 relates to a polyimide useful as a plastic substrate for a flexible display and a precursor thereof, and relates to a polyimide and its precursor which are obtained by reacting various diamines with tetracarboxylic acids containing an alicyclic structure such as cyclohexylphenyltetracarboxylic acid And polyimide has excellent transparency.

In Patent Documents 1 and 2, a stable polyimide precursor solution is obtained from a tetracarboxylic acid dianhydride and a diamine, and the solution is coated on a substrate such as glass and subjected to heat treatment to obtain a polyimide film. However, in order to obtain a fully imidized polyimide film, it is necessary to gradually raise the temperature and conduct a plurality of heating processes over several hours. When the heat treatment is completed in a short time, bubbles are contained in the polyimide film, or bubble marks are formed to deteriorate characteristics such as appearance and mechanical strength.

Patent Document 3 discloses a polyimide layer in which a base film is imidated by applying a polyamic acid solution as a support material, and after forming a functional layer on the polyimide layer side, the interface between the polyimide layer and the support material is used And separating and removing the support material, thereby making the base film thinner. However, in Patent Document 3, it is also necessary to conduct heat treatment at a heating rate of about 4 ° C / min to 20 ° C / min from 160 ° C to 360 ° C after heating and drying at 130 ° C.

In addition to the above, attempts have been made to reduce the weight of the supporting substrate by using a flexible resin. For example, in Non-Patent Documents 1 and 2, an organic EL device in which polyimide having high transparency is applied to a supporting substrate has been proposed. However, the polyimide films described in these documents also require a curing reaction by heat treatment for several hours.

Japanese Patent Laid-Open No. 251564/1991 Japanese Patent Application Laid-Open No. 2008-231327 Japanese Patent Application Laid-Open No. 2014-166722

 S. An et al., "2.8-inch WQVGA Flexible AMOLED Using Low Temperature Polysilicon TFT on Plastic Substrates ", SID 10 D1GEST, p706 (2010)  Oishi et al., "Transparent PI for flexible display ", IDW '11 FLX2surasshuFMC4-1

It is strongly desired to shorten the time of the heat treatment process for obtaining the polyimide film significantly because it contributes greatly to improvement of productivity and cost reduction. However, if a resin solution of a polyimide precursor or polyimide containing a solvent is to be dried in a short period of time, foaming due to rapid evaporation of volatile components occurs, and there is a problem that bubbles or bubbles are generated due to breakage of bubbles. Further, when imidization is carried out, there is a problem that water vapor generated in the dehydration reaction in the imidization step is abruptly generated, so that foaming or bubble shatter may occur in the same way to cause appearance defects, and the curing reaction by imidization becomes insufficient.

Therefore, the present inventors have completed the present invention by paying attention to the type and structure of the polyimide precursor and polyimide used, the thickness to be applied, and the heat treatment time to be used as a reason for the inadequate foaming or curing process.

That is, the gist of the present invention is as follows.

(1) A polyimide precursor or a polyimide resin solution is coated on the coated substrate so that the thickness of the polyimide film is 50 탆 or less, and the heat treatment is completed, whereby no appearance defect due to air bubbles or air bubbles A method of forming a polyimide film, wherein the polyimide film is separable from the coated substrate, the polyimide film is composed of a single layer or a plurality of polyimide layers, and the polyimide constituting the main polyimide layer is represented by the general formula (1) Is 70 mol% or more, and the heat treatment time is 10 minutes or less.

[Wherein Ar ₁ represents a tetravalent organic group having an aromatic ring, and Ar ₂ represents a divalent organic group represented by the following general formula (2) or (3).

Wherein R ₁ to R ₈ independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a fluorine-substituted hydrocarbon group having 1 to 5 carbon atoms.

(2) In the above (1)

Wherein the resin solution is a polyimide precursor solution and the heat treatment comprises a preheating step at 180 to 220 占 폚 and a curing step at a maximum temperature exceeding 220 占 폚 of 320 占 폚 or more.

(3) In the above (2)

Wherein the holding time at 320 占 폚 in the curing step is at least 1 minute.

(4) In the above (1) or (2)

 Wherein the holding time in the preheating step of 180 to 220 占 폚 is 0.5 minutes or more, and the total of the preheating step and the curing step is 3 minutes or more.

(5) In any one of the above-mentioned (1) to (4)

Wherein the polyimide film has a water vapor transmission rate of 10 to 70 g / m < 2 > / day.

(6) In any one of the above-mentioned (1) to (5)

Wherein at least one of R ₁ to R _{4 in} the general formula (2) or R ₁ to R ₈ in the general formula (3) is a fluorine atom or a fluorine-substituted hydrocarbon group.

(7) A polyimide precursor or a resin solution of polyimide is coated on a coated substrate so that the thickness of the polyimide film is 50 탆 or less, and when the heat treatment is completed, defective appearance due to air bubbles or air bubbles And forming a functional layer on the polyimide film and forming a functional layer-attached polyimide film, wherein the polyimide film is separable from the coated substrate, and the polyimide film is a single layer or a plurality of , And the polyimide constituting the main polyimide layer has 70 mol% or more of the structural unit represented by the general formula (1), and the heat treatment time is within 10 min A method for producing a polyimide film with a functional layer.

According to the present invention, since the time required for the heat treatment process in obtaining a polyimide film in the production of a flexible device such as a liquid crystal display device, an organic EL display device, and a touch panel can be remarkably shortened by using the polyimide film, And it can contribute greatly to reduction of manufacturing cost.

1 is a schematic view of an apparatus for forming a functional layer on a coated polyimide film comprising a coated substrate and a polyimide layer.
2 is a schematic cross-sectional view showing a step of peeling off a coated substrate from a polyimide film with a functional layer after forming a functional layer.

In the method for producing a polyimide film of the present invention, a polyimide precursor or a resin solution of polyimide is coated on the coated substrate so that the thickness of the polyimide film is 50 탆 or less, and the heat treatment is completed, Thereby forming a polyimide film having no apparent defective appearance.

In the polyimide precursor or polyimide used in the present invention, the diamine and the acid dianhydride, which are monomers as raw materials, may be composed of a single species or a plurality of monomers.

The polyimide film of the present invention preferably comprises a polyimide having a structural unit represented by the general formula (1). Or a copolymer using plural kinds of monomers having a structural unit represented by the general formula (1), more preferably a structural unit represented by the general formula (1) in an amount of 70 mol% or more, preferably 90 to 100 Mol% of the polyimide resin.

In the case where the polyimide film is composed of a plurality of polyimide layers, the main polyimide layer should satisfy the above requirements, but it is preferable that the total polyimide layer contains 70 mol% or more of structural units represented by the general formula (1), preferably 90 to 100 Mol%. Here, the main polyimide layer is preferably a layer occupying 50% or more of the total thickness of the polyimide layer.

In the general formula (1), Ar ₂ is a divalent organic group represented by the general formula (2) or (3).

In the general formula (2) or (3), R ₁ to R ₈ independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, A fluorine-substituted hydrocarbon group. Examples of the alkyl group having 1 to 5 carbon atoms and the alkoxy group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a methoxy group and an ethoxy group. The fluorine-substituted hydrocarbon group having 1 to 5 carbon atoms is preferably a fluorine-substituted alkyl group having 1 to 5 carbon atoms.

When either one or both of Ar ₁ and Ar ₂ in the general formula (1) has a fluorine atom or a fluorine-substituted hydrocarbon group, transparency of the obtained polyimide film is improved. In a preferable embodiment, at least one of R ₁ to R ₄ in the general formula (2) is a fluorine atom or a fluorine-substituted hydrocarbon group. In the general formula (3), at least one of R ₁ to R ₈ is fluorine Atom or a fluorine-substituted hydrocarbon group.

Specific preferred examples of R ₁ to R _{8 in} the general formula (2) or the general formula (3) include -H, -CH ₃ , -OCH ₃ , -F, -CF ₃ and the like, It is preferable that at least one of R ₁ to R ₈ is any one of -F and -CF ₃ .

In the general formula (1), Ar ₁ represents a tetravalent organic group having an aromatic ring. Specific examples of Ar ₁ include, for example, the following tetravalent acid anhydride residues.

Specific examples of Ar ₂ include the following diamine residues.

Particularly preferred Ar ₂ is represented by the following formula.

Although the polyimide film is obtained from the resin solution of the polyimide precursor or polyimide used in the present invention, the polyimide film constituting the polyimide film is determined by the polyimide precursor or polyimide contained in the resin solution, A polyimide precursor or a polyimide used as a raw material can be understood by explaining the polyimide constituting the polyimide.

Therefore, the polyimide constituting the polyimide film will be described. The preferred polyimide is a polyimide including the structural units represented by the following formulas (4) and (5). The ratio of the formula (4) to the formula (5) is preferably in the range of (4) :( 5) = 50: 50 to 100: 0, 5, and more preferably (4) :( 5) = 85: 15 to 95: 5. And these are contained in the polyimide in an amount of 90 to 100 mol%.

Here, the structural unit of the general formula (4) mainly improves properties such as low thermal expansion and high heat resistance, and the structural unit of the general formula (5) is effective for improving high transparency. The polyimide of this preferred embodiment does not exclude those containing structural units other than the structural units represented by the general formulas (4) and (5) (hereinafter, referred to as structural units a and b, respectively). However, the structural units other than the structural units a and b are preferably contained in a molar ratio of less than 10%, and most preferably a polyimide film composed only of the structural units a and b.

The polyimide film formed on the coated substrate may be composed of not only a single layer but also a plurality of polyimide layers. For example, the polyimide layer on the coated substrate side may be a layer having a composition that is easy to peel off from the coated substrate, May be a layer having a composition which is easy to be fused with the functional layer. In this case, the main polyimide layer is preferably a polyimide layer on the functional layer side.

The polyimide including the structural unit represented by the general formula (1) may contain other structural units. Such a structural unit is preferably less than 30 mol% of the total structural units. On the other hand, other polyimides not containing the structural unit represented by the general formula (1) may be present. It is preferable that such polyimide has a structural unit other than the above in terms of the total structural units of less than 30 mol%.

Other polyimide resins not containing the structural unit represented by the general formula (1) can be selected from general acid anhydrides and diamines, but acid anhydrides and diamines having a thermal expansion coefficient of not more than 15 ppm / K are selected, It is preferable that the thickness is adjusted or multi-layered, and it is less than 30 mol%, preferably less than 10 mol%.

Examples of the acid anhydrides preferably used in the present invention include pyromellitic acid dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride, 1,4-cyclohexanedicarboxylic acid, 1,2 , 3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane 2-anhydride and the like.

Examples of the diamine include 4,4'-diaminodiphenylsulfone, trans-1,4-diaminocyclohexane, 4,4'-diaminocyclohexylmethane, 2,2'-bis (4-aminocyclohexyl) -Hexafluoropropane, 2,2'-bis (trifluoromethyl) -4,4'-diaminobicyclohexane, and the like.

The same groups as those described above are also preferable for the acid anhydrides and diamines to which other structural units in the case where the polyimide including the structural unit represented by the general formula (1) include other structural units are included.

The polyimide precursor or polyimide used in the present invention can be prepared by polymerizing a diamine and an acid anhydride in the presence of a solvent to form a polyimide precursor resin or by imidizing the resulting precursor resin by heat treatment, can do. The molecular weight of the polyimide precursor or polyimide can be controlled mainly by changing the molar ratio of the diamine and the acid anhydride of the starting material, but usually the molar ratio is equimolar (1: 1).

As a method for producing the resin solution of the polyimide precursor or polyimide, for example, a diamine is dissolved in an organic solvent, and then an acid dianhydride is added to the solution to prepare a polyamic acid which is a polyimide precursor. Examples of the organic solvent include dimethylacetamide, dimethylformamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene, etc. These solvents may be used alone or in combination. If necessary, imidization is carried out, and this is dissolved in a solvent to obtain a resin solution of polyimide. The imidization process can be performed using thermal imidization by heat dehydration.

The resin solution of the polyimide precursor or polyimide is applied on the coated substrate so that the thickness of the polyimide film is 50 탆 or less. The application is carried out by applying the above resin solution onto a coated substrate such as a metal roll and then heating and drying it on the coated substrate to obtain a gel film having self-supporting property. Thereafter, the coated film is peeled from the coated substrate and further heated at a high temperature while being held in a tenter, The method of obtaining a mid film is excellent in productivity and is widely practiced industrially.

As another method, for example, the resin solution is applied on an arbitrary coated substrate such as a glass plate or a copper foil by using an applicator, preliminarily dried, further heat-treated for solvent removal and imidization, A method of removing the coated base material by peeling or etching is preferable. When the resin solution is applied to the coated substrate in a pourable manner, the viscosity of the resin solution is preferably in the range of 500 to 70,000 cps. The surface of the coated substrate to be the coating surface of the resin solution may be appropriately subjected to the surface treatment, and then the coating may be performed. When a coated substrate such as a glass plate or a copper foil is used, the thickness thereof can be arbitrarily set. For example, a thickness of 100 to 700 mu m can be exemplified in view of the role as a coated substrate, winding property, and the like, but there is no particular limitation. However, it is preferable that the polyimide layer is thinner than the coated substrate. A polyimide film may also be used as the coating material.

The method of applying the resin solution such as the polyimide precursor to the coated base material is not particularly limited and a known method such as a spin coater, a spray coater, a bar coater, or a method of extruding from a slit-shaped nozzle can be used Can be applied. In general, when applying a solution of a highly oriented resin having a rigid molecular chain, it is known that retardation occurs due to shear stress generated at the time of coating. Surprisingly, in the present invention, The method of application does not affect the retardation. For this reason, it is possible to select an arbitrary coating method compatible with the thickness precision and productivity of the polyimide film.

The thinner the film thickness of the polyimide film, the thinner it is, the easier it is for the solvent and the water vapor to easily escape. The film thickness of the polyimide film should be such that the strength as the polyimide film is maintained. In order to complete the heat treatment process in a short time in the present invention, it is required to be 50 mu m or less. However, in consideration of maintaining the minimum strength as the polyimide film, the film thickness is preferably 5 mu m or more. More preferably 10 to 30 占 퐉. The film thickness after the heat treatment of the polyimide film can be arbitrarily set by adjusting the coating film thickness in consideration of the solid content concentration of the resin solution and the film reduction (film thickness reduction) due to curing shrinkage.

The degree of polymerization of the polyimide precursor and the polyimide used for forming the polyimide film from the viewpoint of uniformly controlling the film thickness of the film when the coating is performed is preferably in the range of from 500 to 200,000 cP , And more preferably in the range of 1000 to 100,000 cP.

A resin solution of a polyimide precursor or polyimide is coated on a coated substrate, followed by drying and heat treatment.

Most of the drying is preferably carried out at less than 180 ° C, and the heat treatment is carried out at 180 ° C or more. In the heat treatment at 180 占 폚 or more, removal of the residual solvent and imidization are caused. However, since there is generation of air bubbles when the solvent removal or imidization is concentrated at the same time, the preliminary heating step is performed at 180 to 220 占 폚, It is preferable to apply the main heating process at a temperature exceeding 220 캜 at which imidization or polyimide heat treatment is dominant. The main heating process is also referred to as a curing process.

When the polyimide precursor resin solution is subjected to heat treatment in the present invention, the heat treatment for heat drying, preliminary drying and solvent removal is referred to as a preliminary heating process, and the heat treatment at a high temperature for imidization is referred to as a main heating process. In the present invention, these preheating step and main heating step are collectively referred to as a heat treatment step, but the total time of these heat treatment steps (hereinafter also referred to as a heat treatment time) is within 10 minutes. By reducing the heat treatment time to 10 minutes or less, it is possible to suppress the decrease of the CTE in addition to contributing to the improvement of the productivity and suppressing the total cost. When imidization is to be completely terminated while suppressing the maximum foaming, the heat treatment time is preferably 2 minutes or more, more preferably 3 minutes or more. In the preliminary heating step, it has been confirmed that the solvent can be almost completely removed by keeping at 180 to 220 ° C for 0.5 minutes or less, and there is no foaming. In the main heating step, when maintained in a temperature region of 320 ° C or more for 1 minute, It is confirmed that it is completed. In addition, it is preferable to carry out heat treatment at 180 to 220 deg. C in the preliminary heating step to suppress foaming, but it is also possible to provide a step of raising the temperature from a low temperature of less than 180 deg. It is preferable that the preheating step is 5 minutes or less from the viewpoint of the productivity of the polyimide film.

When the polyimide resin solution is subjected to a heat treatment, imidization is not required, but there is a possibility that the solvent will remain only by the preliminary heating. In the flexible device to which the polyimide film of the present invention is applied, the solvent is required to be reduced to ppm order The main heating process by high temperature heating is required as in the case of heating the polyimide precursor resin solution.

The reason why heat treatment can be performed in such a short period of time is not necessarily clarified. However, the polyimide is a straight-chain polyimide which is considered to have a rigid and bulky structure, and a film having a somewhat thin shape is extremely short And that the removal of the solvent and the imidization reaction are completed.

And water vapor transmission rate as a polyimide film as a physical property index for completing the solvent removal or imidization reaction in a short time. It is expected that the ease of solvent escape is an indicator of the ease of water vapor escaping from the imidization reaction, and that foaming will not occur in any specific range. The range of the water vapor permeability estimated from the structure experimentally confirmed in the present situation is preferably 1 to 100 g / m 2 / day, more preferably 10 to 70 g / m 2 / day, particularly 20 to 60 g / m 2 / day. If it is smaller than this range, volatile components such as a solvent may solidify before imbibing from the inside of the film to cause foaming, and if it is larger than this range, gas barrier properties are low, A gas barrier film is indispensable for use as a flexible device such as a touch panel, and therefore there is a fear of lowering productivity and increasing cost due to addition of a process.

The present invention also provides a method for manufacturing a display device, which comprises applying a resin solution of a polyimide precursor or polyimide onto a coated substrate and, after the heat treatment is completed, forming a functional layer such as a device for a display device or a conductive layer for a touch panel on the polyimide film To form a functional layer-attached polyimide film. The polyimide film with a functional layer can be widely used for various flexible devices by appropriately peeling the coated substrate from the polyimide film. Thus, the coated base material and the polyimide film are formed with an adhesive strength capable of peeling. On the other hand, as described above, functional layers such as a display element and a conductive layer may be formed in the state that the polyimide film is present on the coated substrate, and it is preferable that the adhesive strength is such that the film is not peeled off during the manufacturing process. The bonding strength between the coating base material and the polyimide film in this case is in the range of 0.1 to 100 N / m, preferably 1 to 50 N / m.

As a method of peeling the polyimide film from the coated substrate, a method of physically peeling using a jig or the like may be used, but a laser lift-off method using an absorption wavelength of 300 to 400 nm of polyimide may also be used. In this case, a known laser can be used.

The polyimide film produced by the present invention may have a thermal expansion coefficient of 15 ppm / K or less, and the polyimide film may be composed of a plurality of polyimide layers. The polyimide having a structural unit represented by the above-mentioned general formula (1) preferably has sufficient magnetic support and strength for a flexible device, and it is preferable that the polyimide has a relatively rigid property with an elastic modulus of about 5 GPa to 10 GPa .

The polyimide film produced by the present invention has no appearance defects due to bubbles or bubble traces. Here, the appearance defects are those which pass the appearance inspection described in the examples.

When the polyimide film produced by the present invention is used for applications requiring transparency such as a touch panel or a bottom emission type organic EL display device, the transmittance thereof is preferably from 440 nm to 780 nm It is preferable that the film is formed of polyimide which gives a transmittance of 80% or more in a wavelength region of 440 nm to 780 nm when film is formed into a film. Such a polyimide is a polyimide having a structural unit represented by the formula (4) and the formula (5) at a certain level or more.

In order to use the polyimide film produced by the present invention with a touch panel or a bottom emission type organic EL display device, the functional layer described in detail below is formed on the polyimide film. Hereinafter, specific embodiments for further forming a functional layer on the polyimide film will be described in detail.

(Production of transparent conductive film)

A transparent conductive film can be obtained by laminating a transparent conductive layer 3 on a long roll-shaped polyimide film having a polyimide layer 2 on a coated substrate 1 as shown in Fig. That is, in this case, the transparent conductive layer corresponds to the functional layer 3. In order to obtain a transparent conductive film, for example, a polyimide film composed of a polyimide having sufficient heat resistance is used as the coated substrate 1, and a polyimide layer (polyimide film) 2 is formed thereon by the heat treatment of the present invention, And a rolled-up polyimide film with a long coat base material is prepared.

The polyimide film 10 having the coating material base is set on a roll-to-roll apparatus as shown in Fig. As shown in Fig. 1, the coated polyimide film 10 is wound around the roll-winding mechanism 14, the feeding mechanism 12, the winding mechanism 13, and the winding-side roll- And the transparent conductive layer is laminated on the surface of the polyimide layer 2 of the coated polyimide film 10 with the coating material base layer 10 stretched in the longitudinal direction by a means such as a vapor deposition method in the processing section 11. At this time, when a vacuum environment is required for the lamination of the transparent conductive layer, the entire roll-to-roll apparatus may be provided in the vacuum chamber to carry out the process. After the transparent conductive layer is formed, it can be separated and thinned by using the interface between the coated substrate and the polyimide layer (polyimide film) 2.

When ITO is used as the transparent conductive layer, the transparent conductive layer is in an amorphous state at the time of deposition on the polyimide film 10 having the coated substrate, and the resistance value thereof is high. For example, when a transparent conductive film is applied to a touch panel, lower resistance is required. Therefore, after the patterning process for the electrode pattern for the touch panel, the annealing process is performed at about 200 ° C. to 300 ° C. to lower the resistance value. However, in the same polyimide film as the present embodiment, And sufficient low resistance can be achieved by an annealing treatment.

Considering that a transparent conductive film is provided on a touch panel or the like, it is preferable that the thickness is as thin as possible. However, when a film having a thickness of 50 占 퐉 is applied to a roll-to-roll apparatus alone, it is difficult to handle the film and the stretching of the film in the conveying process becomes a problem. Therefore, the processing is performed without separating the coating material and the polyimide layer A transparent conductive film having a thickness of about 10 mu m or less (a thickness of the transparent conductive layer of about 100 nm) can be industrially produced with good productivity.

(Production of gas barrier film)

For example, when water or oxygen enters the organic EL light-emitting layer of the organic EL device, characteristic deterioration is caused, so that a gas barrier layer for preventing penetration of moisture or oxygen is indispensable. Thus, in the process processing section 11, an inorganic oxide film such as silicon oxide, aluminum oxide, silicon carbide, silicon oxide silicon carbide, silicon carbide nitride, silicon nitride, silicon nitride oxide, or the like is formed by a CVD method, Other than this, a gas barrier film that is thinned in the same manner as in the case of the transparent conductive film can be obtained.

However, if the difference between the CTE of the gas barrier layer made of the inorganic oxide film and the CTE of the polyimide film made of the polyimide layer 2 is increased, the curl will be generated and the dimensional stability will deteriorate. Therefore, there is a possibility that cracks are generated. Particularly, in the case of producing a large-area film, warping becomes more significant. Therefore, when the polyimide layer 2 selected from the appropriate acid anhydride and diamine is formed as described above, the CTE can be 15 ppm / K or less, and the difference from the inorganic oxide film having a CTE of 10 ppm / K or less is small So that problems such as these can be solved. The gas barrier layer may be formed of one kind of the inorganic film as described above, or two or more types of the gas barrier layer.

(Fabrication of Thin Film Transistor)

First, a thin-film transistor (TFT) is divided into an amorphous silicon TFT (a-Si TFT) and a polysilicon TFT, and in a polysilicon TFT, a low-temperature polysilicon TFT (LTPS-TFT) have. Hereinafter, a method for obtaining an a-Si TFT having a bottom gate structure in obtaining a thin film transistor (TFT) used for a backplane or the like of a liquid crystal display device will be described.

A gas barrier layer is formed on the polyimide film 10 with a coating material in advance in the same manner as the above-described method for producing a gas barrier film in order to prevent intrusion of oxygen or water vapor from the outside. Subsequently, a material for forming the gate electrode and the wiring is formed. As the film forming material, mainly an Al-based material is used and laminated by means such as sputtering. After the film formation, the gate and wiring patterns are transferred in a photolithography process, and are formed (patterned) into a predetermined shape by an etching process.

Subsequently, a gate insulating film (SiN, SiO ₂ Or the like) and the semiconductor layer (a-Si) are similarly formed by CVD or the like, and are formed into a predetermined shape. Hereinafter, a processing step such as a film forming step, a photolithographic step, and an etching step is repeated to form a drain wiring, a source electrode, an interlayer insulating film, and the like, and an a-Si TFT can be obtained. In order to obtain the a-Si TFT as described above, the polyimide film 10 with a coated substrate may be treated successively by arranging the process processing portions 11 for various process processes side by side, or alternatively, The polyimide film may be subjected again to the roll-to-roll process so as to divide the process into several steps.

(Production of organic EL display device)

For example, in order to obtain an organic EL display device having a bottom emission structure, first, a gas barrier layer is formed on the polyimide layer 2 side of the coated-material-provided polyimide film 10 in the same manner as the above- Or to prevent the permeation of oxygen. Subsequently, on the upper surface of the gas barrier layer, a circuit constituting layer including the above-described thin film transistor (TFT) is formed. In this case, an LTPS-TFT is mainly selected as a thin film transistor. The circuit layer 3 is formed by forming an anode electrode made of, for example, a transparent conductive film of ITO, on 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. This cathode electrode is formed in common to each pixel region. Then, a gas barrier layer is formed again to cover the surface of the cathode electrode, and a sealing substrate is further provided on the outermost surface for surface protection. It is preferable to laminate a gas barrier layer for preventing moisture and oxygen from permeating the surface of the sealing substrate on the cathode electrode side.

In this manner, in the organic EL display device, various thin films are generally formed on the polyimide layer 2 of the coated polyimide film 10 in the above order, and finally sealed with a sealing substrate. The organic EL light emitting layer is formed as a multilayer film (anode electrode-light emitting layer-cathode electrode) such as a hole injecting layer-hole transporting layer-light emitting layer-electron transporting layer. Particularly, since the organic EL light emitting layer is deteriorated by moisture or oxygen, And is formed continuously in a vacuum including an electrode formation.

(Manufacture of organic EL lighting apparatus)

In order to obtain the organic EL illumination, the bottom emission structure except for the TFT layer in the organic EL display device described above is generally used for the functional layer. Here, a transparent electrode such as ITO is generally used for the anode electrode, and the electrode resistance becomes low resistance as the high temperature treatment is performed. As described above, in the case of ITO, heat treatment is generally performed at about 200 to 300 ° C. Further, the organic EL illumination is in the direction of enlargement, and the resistance value of the ITO electrode becomes insufficient, and various alternative electrode materials are being searched. In this case, although the temperature of the annealing process is likely to be higher than 200 to 300 ° C, the polyimide film of the present invention has sufficient heat resistance and can be applied to various alternative electrode materials.

(Production of other functional layers)

In addition to the above examples, for example, various functional layers required for obtaining a deposition mask, a substrate for a fan-out wafer level package (FOWLP), etc. in addition to an electronic paper or a touch panel are formed on a polyimide film 10 with a coated substrate, And then the coated substrate is separated and removed by using the interface between the polyimide layer 2 and the coated substrate to form a thinned laminated member, the thickness and weight can be reduced as compared with the conventional case. .

(Example)

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to the scope of the following examples.

The abbreviations of the monomers and solvents in the synthesis of the polyimide, and the measuring methods and conditions for various physical properties in the examples are shown below.

TFMD: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl

PMDA: pyromellitic acid dianhydride

DMAc: N, N-dimethylacetamide

6FDA: 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride

BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic acid dianhydride

(Coefficient of thermal expansion: CTE)

A polyimide film having a size of 3 mm x 15 mm was subjected to a tensile test in a temperature range of 30 ° C to 260 ° C at a constant heating rate (20 ° C / min) while applying a load of 5.0 g in a thermomechanical analysis (TMA) , And the thermal expansion coefficient (ppm / K) was measured from the elongation of the polyimide film relative to the temperature.

(The tensile strength)

Toyo seiki seisaku-sho, ltd. The tensile strength of the sample was measured by using a Strograph R-1. The tensile strength of the sample was determined by dividing the maximum point load by the cross-sectional area.

(Tear strength)

Toyo seiki seisaku-sho, ltd. Measurement was carried out at a sample size of 63.5 × 50 (mm) and a notch length of 12.5 mm using a production light load tester.

(Imidization rate)

Fourier transform infrared spectrophotometer (commercially available product: JASCO Corporation FT production / IR620) use, and by measuring the infrared absorption spectrum of the polyimide thin film in one reflection ATR method 1780㎝ times on the basis of a benzene ring of the absorbent body near 1015㎝ ^{-1 -1} > derived from the imide group.

(Visual inspection)

The polyimide film after the heat treatment was observed with a naked eye to confirm whether or not foaming was caused. And those without foaming with a diameter of 30 탆 or more were regarded as good (acceptable).

(apply)

An applicator having an in-plane non-uniformity of its thickness adjusted to be 1 탆 or less with respect to the polyimide film after the heat treatment was used.

(Heat treatment)

Heat treatment was started one hour after reaching a predetermined temperature by using a forced convection type hot air oven equipped with a blowing fan. A polyimide film material coated with a polyimide precursor or a polyimide resin solution on a coated substrate is placed in the center of a hot air oven where the hot air is strongly aerated and placed on a table made of stainless steel wire so as not to interfere with the circulation of hot air And heat treatment was performed by a plurality of heating furnaces having different set temperatures. In this case, the time required to pass through the heating furnace was the heat treatment time, and the temperature unevenness at the position of the material for the polyimide film was 2 占 폚.

Example 1

(Polyimide A)

12.55 g of TFMB was dissolved in solvent DMAc while stirring in a 200 ml separable flask under nitrogen flow. Then, 17.45 g of 6FDA was added to this solution. Thereafter, the solution was stirred at room temperature for 5 hours to carry out the polymerization reaction, and maintained for one week or less. A viscous polyamic acid solution was obtained, and it was confirmed that a polyamic acid A with a high degree of polymerization was produced. The polyamic acid solution obtained above was applied to a glass plate having a thickness of 0.5 mm using an applicator so as to have a thickness of about 25 占 퐉 after the heat treatment and then heated at 130 占 폚 and 160 占 폚 using a nitrogen oven Heated at 180 占 폚 for 1 minute, 220 占 폚 for 1 minute, 280 占 폚 for 1 minute, 320 占 폚 for 1 minute, and 360 占 폚 for 1 minute to obtain a laminate of a glass substrate and a polyimide film . A cutter was inserted into the interface between the glass substrate and the polyimide film of this laminate, and the polyimide film was peeled from the glass substrate to obtain a polyimide film A. The obtained polyimide film A was subjected to various evaluations and the results are shown in Table 2.

(Polyimide B)

17.01 g of TFMB was dissolved in solvent DMAc while stirring in a 200 ml separable flask under nitrogen flow. Then, 10.06 g of PMDA and 2.93 g of 6FDA were added to this solution. Thereafter, the solution was stirred for 5 hours at room temperature, and polymerization reaction was carried out for one week or less. A viscous polyamic acid solution was obtained and it was confirmed that a polyamic acid B with a high polymerization degree was produced. The film was formed into a film similar to the polyamic acid A to obtain a polyimide film B. The obtained polyimide film B was subjected to various evaluations and the results are shown in Table 2.

Examples 2 to 7

A polyimide acid solution A and a polyimide acid solution B used in Example 1 were coated on a glass plate having a thickness of 0.5 mm as in Example 1 and then subjected to various heat treatment conditions as shown in Table 1 to obtain a polyimide film. Various evaluation results of the obtained polyimide film are shown in Table 2

Comparative Examples 1 and 2

A polyamic acid solution A used in Example 1 was coated on a 0.5 mm-thick glass plate in the same manner as in Example 1, and a polyimide film was obtained under the heat treatment conditions shown in Table 1.

In the polyimide film obtained under the heat treatment conditions of Comparative Example 1, a large number of bubbles were observed, and a volatile component such as a solvent was foamed. In addition, the polyimide film obtained under the heat treatment conditions of Comparative Example 2 could not be peeled off from the glass substrate by the method of Example 1, and thus all of the properties could not be evaluated.

Comparative Example 3

A polyamic acid B solution was applied to a glass plate having a thickness of 0.5 mm in the same manner as in Example 1, and a polyimide film was obtained under the heat treatment conditions shown in Table 1.

In the polyimide film obtained under the heat treatment conditions of Comparative Example 3, a large number of bubbles were observed in the same manner as in Comparative Example 1, and a volatile component such as a resin was foamed.

Reference example

The polyamic acid B solution used in Example 1 was coated on a 0.5 mm thick glass plate in the same manner as in Example 1 and then gradually heated from 130 占 폚 as conventionally well known and finally heated at 360 占 폚 35 minutes) to obtain a polyimide film. For reference, various evaluation results of the obtained polyimide film are shown in Table 2 as well.

1 Coating base 2 Polyimide layer
3 Functional layer 10 Polyimide film with coating base material
11 Process processor

Claims (6)

A polyimide precursor or a resin solution of polyimide is coated on a coated substrate so that the thickness of the polyimide film is 50 탆 or less and the heat treatment is completed to form a polyimide film having no appearance defects due to air bubbles or air bubbles on the coated substrate As a method for forming a film, it is preferable that the polyimide film is peelable from the coated substrate, the polyimide film comprises a single layer or a plurality of polyimide layers, and the polyimide constituting the main polyimide layer is represented by the general formula (1) Wherein the polyimide film has 70% by mol or more of a structural unit to be lengthened, and the heat treatment time is within 10 minutes.

[Wherein Ar ₁ represents a tetravalent organic group having an aromatic ring, and Ar ₂ represents a divalent organic group represented by the following general formula (2) or (3)

Wherein R ₁ to R ₈ independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a fluorine-substituted hydrocarbon group having 1 to 5 carbon atoms. The method according to claim 1,
Wherein the resin solution is a polyimide precursor solution and the heat treatment comprises a preheating step at 180 to 220 占 폚 and a curing step at a maximum temperature exceeding 220 占 폚 of 320 占 폚 or more. 3. The method of claim 2,
Wherein the holding time at 320 占 폚 in the curing step is at least 1 minute. The method according to claim 2 or 3,
Wherein the holding time in the preheating step of 180 to 220 占 폚 is 0.5 minutes or more, and the total of the preheating step and the curing step is 3 minutes or more. 5. The method according to any one of claims 1 to 4,
Wherein at least one of R ₁ to R _{4 in} the general formula (2) or R ₁ to R ₈ in the general formula (3) is a fluorine atom or a fluorine-substituted hydrocarbon group. A polyimide precursor or a resin solution of polyimide is coated on a coated substrate so that the thickness of the polyimide film is 50 탆 or less and the heat treatment is completed to form a polyimide film having no appearance defects due to air bubbles or air bubbles on the coated substrate A method for producing a functional layer-attached polyimide film by forming a functional layer on a polyimide film after the film is formed, wherein the polyimide film is peelable from the coated substrate and the polyimide film is a single layer or a plurality of polyimide layers , Wherein the polyimide constituting the main polyimide layer has 70 mol% or more of the structural unit represented by the general formula (1), and the heat treatment time is within 10 min. ≪ / RTI >

[Wherein Ar ₁ represents a tetravalent organic group having an aromatic ring, and Ar ₂ represents a divalent organic group represented by the following general formula (2) or (3)

Wherein R ₁ to R ₈ independently represent a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a fluorine-substituted hydrocarbon group having 1 to 5 carbon atoms.

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