KR20150038080A - Transparent polyimide laminate and manufacturing method therefor - Google Patents

Abstract

It is an object of the present invention to provide a transparent polyimide laminate having a high transparency, a small in-plane retardation, and a transparent polyimide layer which is easily peelable from a supporting substrate. In order to solve the above problems, there is provided a process for producing a transparent polyimide laminate comprising a support substrate and a transparent polyimide layer laminated on the support substrate, comprising the steps of: a) preparing a polyimide film comprising a reaction product of a tetracarboxylic acid component and a diamine component A step of applying a polyimide precursor-containing solution containing a precursor and a solvent on the supporting substrate; and b) a step of applying a polyimide precursor film comprising a coating film of the polyimide precursor-containing solution to a glass transition temperature of the transparent polyimide layer Wherein the transparent polyimide layer has a glass transition temperature of 260 占 폚 or more, a total light transmittance of 80% or more, a haze of 5% or less, an absolute value of b value in the L * a * Of not more than 5 and an in-plane retardation of 10 nm or less, and a peel strength when the transparent polyimide layer is peeled off from the support substrate is 0.005 to 0.20 kN / m. < / RTI >

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent polyimide laminate, and a transparent polyimide laminate,

The present invention relates to a transparent polyimide laminate and a process for producing the same.

BACKGROUND ART Polyimide resins have excellent heat resistance and mechanical properties, and polyimide films have been applied to substrates of various flexible printed wiring boards. Casting is one of the methods for producing polyimide films. The casting method comprises the steps of (i) applying a polyimide precursor on a supporting substrate, (ii) imidizing the polyimide precursor by a heat treatment, (iii) peeling the polyimide film from the supporting substrate, . Although the support substrate is generally a glass substrate, it has also been proposed to use a metal substrate or a non-thermoplastic resin as the support substrate (Patent Documents 1 to 3).

Conventionally, in displays such as a liquid crystal display element and an organic EL display element, inorganic glass as a transparent material is used as a panel substrate or the like. However, the inorganic glass has a high specific gravity (weight) and low flexibility and impact resistance. Therefore, films made of PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) are widely used as substrates for liquid crystal display elements and organic EL display elements requiring flexibility. However, these films are low in heat resistance, and the temperature at the time of forming various devices is limited. Therefore, a substrate having higher heat resistance is required.

On the other hand, application of a polyimide film excellent in lightweight property, impact resistance, workability, and flexibility to a panel substrate of a flexible device is also under investigation. However, the polyimide films obtained by the techniques of the above-mentioned Patent Documents 1 to 3 have low light transmittance, and it is difficult to apply them to a panel substrate of a flexible display. On the other hand, a polyimide film obtained by reacting bis (trifluoromethyl) benzidine with a tetracarboxylic acid component has been proposed as a film having high transparency and heat resistance (Patent Document 4).

Japanese Patent Application Laid-Open No. S56-52525 Japanese Patent Application Laid-Open No. 2004-322441 Japanese Patent Laid-Open No. 11-10664 Japanese Patent Application Laid-Open No. 2012-40836

However, in the polyimide film produced by the casting method, it is difficult to separate the polyimide film from the supporting substrate (glass substrate). In order to peel the polyimide film, the supporting substrate and the polyimide film are immersed in water, And irradiating the interface of the polyimide film with a laser beam.

The present invention has been made in view of such circumstances. An object of the present invention is to provide a transparent polyimide laminate having a high light transmittance, a small in-plane retardation, and a transparent polyimide layer which can be easily peeled off from a supporting substrate, and further to a process for producing the same.

A first aspect of the present invention relates to a method for producing a transparent polyimide laminate as described below.

[1] A process for producing a transparent polyimide laminate comprising a support substrate and a transparent polyimide layer laminated on the support substrate, comprising the steps of: a) mixing a polyimide precursor obtained by reacting a tetracarboxylic acid component and a diamine component with a solvent A step of applying a polyimide precursor-containing solution containing a polyimide precursor-containing solution containing a polyimide precursor-containing solution onto the support substrate; and b) a step of heating the polyimide precursor film comprising the polyimide precursor-containing solution coating film to a temperature not lower than the glass transition temperature of the transparent polyimide layer Wherein the transparent polyimide layer has a glass transition temperature of 260 占 폚 or higher, a total light transmittance of 80% or higher, a haze of 5% or lower, an absolute value of b in an L * a * A transparent polyimide layer having an in-plane retardation of 10 nm or less and a peel strength of 0.005 to 0.20 kN / m when the transparent polyimide layer is peeled off from the supporting substrate; Gt; < / RTI >

[2] The method for producing a transparent polyimide laminate according to [1], wherein the supporting substrate is a flexible substrate.

[3] The process for producing a transparent polyimide laminate according to [1] or [2], wherein the polyimide precursor-containing solution further comprises a releasing agent.

[4] The method for producing a transparent polyimide laminate according to any one of [1] to [3], wherein the oxygen concentration in the atmosphere is 5% by volume or less in a temperature region exceeding 200 ° C in the step b).

[5] The method for producing a transparent polyimide laminate according to any one of [1] to [3], wherein the atmosphere is reduced in a temperature region exceeding 200 캜 in the step b).

[6] The step b) is a step of heating the polyimide precursor film while raising the temperature from 150 ° C or lower to higher than 200 ° C, and the average temperature raising rate in the temperature range of 150-200 ° C in the step b) is 0.25 To 50 占 폚 / min. The method for producing a transparent polyimide laminate according to any one of [1] to [5]

[7] The polyimide precursor according to any one of [1] to [3], wherein the polyimide precursor is at least one compound selected from the group consisting of a tetracarboxylic acid component (A) comprising at least one tetracarboxylic acid dianhydride represented by the following formula The transparent polyimide laminate according to any one of [1] to [6], which is a compound obtained by reacting a diamine component (B) containing at least one selected diamine.

(A)

(In the formula (a), R ¹ represents a quadrivalent group having 4 to 27 carbon atoms, and further represents an aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aliphatic group, a monocyclic aromatic group or a condensed polycyclic aromatic group, Or a non-condensed polycyclic aliphatic group linked together by a bridging source, or a non-condensed polycyclic aromatic group in which the aromatic group is linked directly or by a bridging source)

[Formula b-1]

[Formula b-2]

[Formula b-3]

[8] The polyimide precursor has a repeating unit represented by the following formula (I), wherein the 1,4-bismethylene cyclohexane skeleton (X) in the formula (I) Wherein the ratio of the trans-cis structure to the trans-cis structure is 100%, and the ratio of the trans-cis structure to the trans-isomer is 100% Wherein the transparent polyimide laminate is a transparent polyimide laminate.

(I)

(X)

(X1)

(X2)

(Wherein R ¹⁰ represents a tetravalent group having 4 to 27 carbon atoms and further represents an aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aliphatic group, a monocyclic aromatic group or a condensed polycyclic aromatic group, Or a non-condensed polycyclic aliphatic group linked together by a bridging source, or a non-condensed polycyclic aromatic group in which the aromatic group is linked directly or by a bridging source)

[9] The polyimide precursor according to any one of [1] to [8], wherein the polyimide precursor is a block polyamide acid imide having a polyimide block composed of a repeating structural unit represented by the following formula (G) The transparent polyimide laminate according to any one of [1] to [6]

[Formula G]

[Formula H] <

(In the formulas (G) and (H), R ⁶ and R ⁸ each independently represent a quaternary group having 4 to 27 carbon atoms, and may be an aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aliphatic group, a monocyclic aromatic group, or a condensed polycyclic aromatic Or a non-condensed polycyclic aliphatic group in which the cyclic aliphatic group is linked directly or by a bridging source, or a non-condensed polycyclic aromatic group in which the aromatic group is linked directly or by a bridging group;

In formula (H), R ⁷ is a divalent group having 4 to 51 carbon atoms, and is an aliphatic group, a monocyclic aliphatic group (except for 1,4-cyclohexylene group), a condensed polycyclic aliphatic group, A condensed polycyclic aromatic group or a non-condensed polycyclic aliphatic group in which a cyclic aliphatic group is directly or indirectly linked to each other by a crosslinking source or a condensed polycyclic aromatic group in which an aromatic group is linked directly or by a crosslinking source,

The step a) is a step of applying the solution containing the polyimide precursor onto the support substrate fed out from the roll, and the step b) is a step of heating the polyimide precursor film after heating the polyimide precursor film, The method for producing a transparent polyimide laminate according to any one of [1] to [9], which comprises a step of winding a transparent polyimide laminate on a roll.

A second aspect of the present invention relates to the following transparent polyimide laminate or optical film.

[11] A transparent polyimide laminate obtained from the production method according to any one of [1] to [9] above.

[12] An optical film obtained by peeling a transparent polyimide layer from a support substrate of the transparent polyimide laminate according to [11].

A third aspect of the present invention relates to a method of manufacturing a transparent polyimide film, a method of manufacturing a flexible device, and various display devices.

[13] A process for producing a transparent polyimide film, which comprises a step of peeling a transparent polyimide layer from a support substrate of the transparent polyimide laminate according to [11] to obtain a transparent polyimide film.

[14] A method for manufacturing a transparent polyimide laminate, comprising the steps of: forming an element on the transparent polyimide layer of the transparent polyimide laminate described in [11]; and peeling the transparent polyimide layer after the element is formed from the support substrate Of the flexible device.

[15] A method for manufacturing a flexible device, comprising the step of forming an element on a transparent polyimide film obtained by the method according to [11].

[16] A touch panel display obtained by the flexible device manufacturing method described in [14] or [15] above.

[17] A liquid crystal display obtained by the method for manufacturing a flexible device according to the above [14] or [15].

[18] An organic EL display obtained by the method for manufacturing a flexible device according to the above [14] or [15].

According to the present invention, a transparent polyimide laminate having a transparent polyimide layer which is easily peelable from a supporting substrate, has high light transmittance and a small in-plane retardation is obtained.

1 is a side view showing an example of a production apparatus for producing a long transparent polyimide laminate by the production method of the present invention.
2 is a schematic cross-sectional view showing an example of a manufacturing method of a flexible device using the transparent polyimide laminate of the present invention.
3 is a schematic cross-sectional view showing another example of a manufacturing method of a flexible device using the transparent polyimide laminate of the present invention.
4 is a schematic cross-sectional view showing another example of a manufacturing method of a flexible device using the transparent polyimide laminate of the present invention.

A. Manufacturing Method of Transparent Polyimide Laminate

In the production method of the present invention, as the transparent polyimide laminate comprising the supporting substrate and the transparent polyimide layer, the peel strength when the transparent polyimide layer is peeled off from the supporting substrate is 0.005 to 0.20 kN / m, Is in the range of 0.01 to 0.15 kN / m, more preferably 0.05 to 0.10 kN / m. The peel strength is a value measured in accordance with JIS C-6471 (peeling angle of 90 DEG).

As described above, when a polyimide film is formed on a supporting substrate by a general casting method, it is difficult to separate the obtained polyimide film from the supporting substrate, so that the polyimide film and the supporting substrate are immersed in water or the supporting substrate and the polyimide film It is necessary to irradiate the interface with the laser beam to peel off. Further, after the device is formed on the polyimide film, if the film is peeled off from the supporting substrate, stress may be applied to the device, or water may adhere to the device, thereby damaging the device.

On the other hand, in the transparent polyimide laminate produced by the production method of the present invention, the peel strength of the transparent polyimide layer and the support substrate is small. Therefore, even after the element is formed on the transparent polyimide layer, the transparent polyimide layer can be easily peeled from the support substrate.

The manufacturing method of the present invention includes the following two processes.

a) a step of applying a polyimide precursor-containing solution containing a polyimide precursor and a solvent obtained by reacting a tetracarboxylic acid component and a diamine component onto a support substrate

b) heating the polyimide precursor film comprising the coating film of the polyimide precursor-containing solution at a temperature not lower than the glass transition temperature of the transparent polyimide layer

The transparent polyimide laminate of the present invention can be produced, for example, as a long transparent polyimide laminate 30 by the apparatus shown in Fig. 1 comprises a polyimide precursor applying device 20, an endless belt 21 and a plurality of heating furnaces 10 arranged along the moving direction of the endless belt 21 Respectively. A polyimide precursor is applied to the supporting substrate 11, which is unwound from a roll, by a coating device 20 to form a coating film 1 of a polyimide precursor. The coating film 1 of the polyimide precursor is imidized by the heating furnace 10 to obtain a transparent polyimide laminate in which the supporting substrate 11 and the transparent polyimide layer 1 'are laminated. Thereafter, the elongated transparent polyimide laminate is taken up to form a roll 30.

1. For process a)

A polyimide precursor-containing solution containing a polyimide precursor and a solvent obtained by reacting a tetracarboxylic acid component and a diamine component is prepared. The kind of the polyimide precursor contained in the polyimide precursor-containing solution is not particularly limited, but from the viewpoint of increasing the total light transmittance of the obtained transparent polyimide layer, it is preferable that the polyimide precursor contains an alicyclic group in the main chain of the polyimide precursor. The polyimide precursor-containing solution containing such a polyimide precursor will be described in detail later.

The prepared polyimide precursor-containing solution is applied on a supporting substrate. The supporting substrate is not particularly limited as long as it has solvent resistance and heat resistance. The supporting substrate preferably has good releasability from the obtained transparent polyimide layer, and is preferably a flexible substrate made of a metal or a heat resistant polymer film. Examples of the flexible substrate made of a metal include copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium, gold, cobalt, titanium, tantalum, zinc, lead, tin, Indium, or a metal foil made of an alloy thereof. The releasing agent may be coated on the surface of the metal foil.

Examples of the flexible substrate made of the heat resistant polymer film include a polyimide film, an aramid film, a polyetheretherketone film, and a polyether sulfone film. The flexible substrate made of the heat resistant polymer film may contain a releasing agent or an antistatic agent, or may be coated with a releasing agent or an antistatic agent on the surface. It is preferable that the supporting substrate is a polyimide film because the releasability from the obtained transparent polyimide layer is good and the heat resistance and the solvent resistance are high.

The ten-point average roughness (Rz) of the surface of the support substrate is preferably less than 0.4 mu m, more preferably not more than 0.2 mu m, and further preferably not more than 0.1 mu m. When the 10-point average roughness of the surface of the supporting substrate is small, the haze of the transparent polyimide layer formed on the supporting substrate tends to be small. The ten-point average roughness (Rz) of the surface of the supporting substrate is a value measured in accordance with JIS B-0601, and is a value measured toward the width direction of the supporting substrate.

It is preferable that the surface of the supporting substrate has no defects such as adhesion of foreign matter or scratches of stripe shape. Even if the 10-point average roughness (Rz) is low, haze of the obtained transparent polyimide layer tends to increase when these defects are present in the supporting substrate. Defects on the surface of the supporting substrate can be evaluated as " number of defects per unit area ". Defects are confirmed by visual observation. The number of defects included in the support substrate 210 mm x 297 mm (A4 size) is preferably 10 or less, more preferably 5 or less, and still more preferably 1 or less.

The shape of the supporting substrate is appropriately selected in accordance with the shape of the transparent polyimide laminate to be produced, and may be a mono-sheet form or a long form. The thickness of the supporting substrate is preferably 5 to 150 mu m, more preferably 10 to 70 mu m. If the thickness of the supporting substrate is less than 5 占 퐉, wrinkles may be generated in the supporting substrate during the application of the solution containing the polyimide precursor, or the supporting substrate may be torn.

The application of the solution containing the polyimide precursor to the support substrate is not particularly limited as long as the solution containing the polyimide precursor can be applied with a constant film thickness. Examples of the application device include a die coater, a comma coater, a roll coater, a gravure coater, a curtain coater, a spray coater, a lip coater and the like.

The thickness (coating film thickness) of the coating film of the polyimide precursor-containing solution is appropriately selected according to the thickness of the desired transparent polyimide layer and the concentration of the polyimide precursor in the solution containing the polyimide precursor.

2. For process b)

In the step b), a coating film of the polyimide precursor-containing solution formed on the supporting substrate in the above-mentioned step a); The polyimide precursor film is heated. Concretely, i) heating the polyimide precursor film while raising the temperature from a temperature lower than or equal to 150 캜 to a temperature lower than or equal to 200 캜, and further ii) subjecting the resulting polyimide precursor film to a constant It is preferable that the step is a step of heating for a time.

i) The temperature at which a general polyimide precursor is imidized is from 150 to 200 캜. Therefore, when the temperature of the polyimide precursor film is rapidly raised to 200 ° C or higher, the polyimide precursor on the surface of the coating film is imidized before the solvent is volatilized from the polyimide precursor film. When the solvent in the coating film is foamed or the solvent is discharged to the outside, unevenness may occur on the surface of the coating film. Therefore, it is preferable to gradually increase the temperature of the polyimide precursor film in the temperature range of 150 to 200 캜. Concretely, the rate of temperature rise in the temperature range of 150 to 200 캜 is preferably 0.25 to 50 캜 / min, more preferably 1 to 40 캜 / min, and still more preferably 2 to 30 캜 / min .

The temperature rise may be continuous or stepwise (continuous), but it is preferable to keep the temperature continuously in view of suppressing appearance defects of the obtained transparent polyimide layer. Further, in the above-mentioned whole temperature range, the heating rate may be constant or may be varied on the way.

An example of a method of heating the monocylate polyimide precursor film while raising the temperature is a method of raising the temperature in the oven for heating the polyimide precursor film. In this case, the heating rate is adjusted by setting the oven. 1, the heating furnace 10 for heating the polyimide precursor film 1 is heated by heating the polyimide precursor film in the conveying direction of the supporting substrate 11 Movement) direction; The temperature of the heating furnace 10 is changed for each heating furnace 10. For example, the temperature of each heating furnace 10 may be increased along the moving direction of the supporting substrate 11. [ In this case, the temperature raising rate is adjusted by the conveying speed of the supporting substrate 11.

ii) The polyimide precursor film is heated while raising the temperature, and then heated for a certain time at a temperature (constant temperature) equal to or higher than the glass transition temperature of the transparent polyimide layer obtained. The temperature at this time is not particularly limited as long as it is not lower than the glass transition temperature of the obtained transparent polyimide layer, but is more preferably 5 to 30 ° C higher than the glass transition temperature of the obtained transparent polyimide layer, Lt; RTI ID = 0.0 > 20 C < / RTI > higher than the glass transition temperature of the mid layer. The polyimide precursor can be sufficiently imidized by heating at a temperature not lower than the glass transition temperature of the obtained transparent polyimide layer for a certain period of time. Further, since the transparent polyimide layer is heated at a temperature higher than the glass transition temperature of the obtained transparent polyimide layer for a certain period of time, the transparent polyimide layer is softened and the solvent in the transparent polyimide layer is sufficiently volatilized. The heating time at a temperature higher than the glass transition temperature is appropriately selected according to the heating temperature, the thickness of the polyimide precursor film, the amount of the solvent contained in the polyimide precursor-containing solution, and the like. It is usually about 0.5 to 2 hours.

The heating method when the polyimide precursor film is heated at a predetermined temperature is not particularly limited, and for example, it is heated in an oven adjusted to a predetermined temperature. The long polyimide precursor film is heated by a heating furnace maintained at a constant temperature.

Polyimides are liable to be oxidized when heated at a temperature exceeding 200 캜. When the polyimide is oxidized, the obtained transparent polyimide layer is yellowed, and the total light transmittance of the transparent polyimide layer is lowered. Therefore, it is preferable that (i) the oxygen concentration in the heating atmosphere be 5 vol% or less, or (ii) the heating atmosphere is reduced in the temperature range exceeding 200 deg.

(i) When the oxygen concentration in the heating atmosphere is 5 vol% or less, the oxidation reaction of the polyimide is suppressed. The oxygen concentration in the temperature range exceeding 200 DEG C is more preferably 3 vol% or less, and more preferably 1 vol% or less. The method of lowering the oxygen concentration is not particularly limited, but a method of introducing an inert gas into a heating atmosphere and the like can be used. The oxygen concentration in the atmosphere is measured by a commercially available oxygen concentration meter (e.g., a zirconia-type oxygen concentration meter).

(ii) Further, even when the heating atmosphere is reduced, the oxidation reaction of the polyimide is suppressed. When the heating atmosphere is reduced, the pressure in the atmosphere is preferably 5 kPa or less, more preferably 1 kPa or less. When the heating atmosphere is reduced, the polyimide precursor film is heated by a vacuum oven or the like.

Process (b) The imidization ratio of the transparent polyimide layer at the end of heating is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more. If the imidization ratio is less than 90%, imidization proceeds at the time of use of the transparent polyimide layer, and moisture may be released from the transparent polyimide layer. The imidization ratio can be calculated from the measured value of the IR absorption spectrum of the transparent polyimide layer. Specifically, it is calculated by the following method.

The transparent polyimide layer is peeled off from the support substrate, and its IR absorption spectrum is measured. The ratio A of the absorption peak height at 1370 cm ^-1 (CN stretching vibration of the imide ring) to the absorption peak height of 1500 cm ^-1 (peak (reference) by C = C stretching vibration of the benzene ring) is calculated. On the other hand, a polyimide precursor film comprising a polyimide precursor-containing solution having the same composition was prepared and heated at 270 캜 for 2 hours or more to completely imidize it. By measuring, IR absorption spectrum even for this film, similarly to the absorption peak height of the ^1500cm-1 (the benzene ring C = C peak (standard) according to the stretching vibration) 1370cm ^-1 absorption peak height (imide ring of the new CN Vibration "). Then, the value of the ratio A to the ratio B (ratio A / ratio B) × 100 (%) is obtained, and this is regarded as the imidization rate.

On the other hand, at the end of the step b), the amount of the solvent remaining in the transparent polyimide layer (mass of the remaining solvent x 100 / mass of the transparent polyimide layer) is preferably 1.0% by mass or less, more preferably 0.8% By mass or less, more preferably 0.5% by mass or less. If the residual amount of the solvent exceeds 1.0% by mass, the solvent may be released from the transparent polyimide layer during use of the transparent polyimide layer. The remaining amount of the solvent is determined by separating the transparent polyimide layer from the supporting substrate, pyrolyzing the transparent polyimide layer with an electric furnace pyrolysis furnace, etc., and analyzing the pyrolyzed component with a gas chromatographic mass spectrometer.

When the obtained transparent polyimide laminate is long after the completion of the heating, the step of winding the transparent polyimide laminate into a roll can be performed as described above.

3. Solution containing polyimide precursor

The polyimide precursor-containing solution to be applied in the step a) includes a polyimide precursor and a solvent, and if necessary, a release agent is included. When the releasing agent is contained in the solution containing the polyimide precursor, the releasability of the transparent polyimide layer and the supporting substrate in the transparent polyimide laminate is enhanced. The polyimide precursor-containing solution may contain various additives as required.

3-1. Polyimide precursor

The polyimide precursor is obtained by reacting the tetracarboxylic acid component (A) and the diamine component (B). The concentration of the polyimide precursor contained in the polyimide precursor-containing solution is preferably 5 to 50 mass%, and more preferably 10 to 40 mass%. If the concentration of the polyimide precursor is more than 50% by mass, the viscosity of the polyimide precursor-containing solution becomes excessively high, which may make it difficult to coat the substrate. On the other hand, if it is less than 5% by mass, the viscosity of the solution containing the polyimide precursor becomes excessively low, and the polyimide precursor film may not be coated with a desired thickness in some cases. Further, it takes time to dry the solvent, and the production efficiency of the polyimide film deteriorates.

3-1-1. The tetracarboxylic acid component (A)

The tetracarboxylic acid component (A) constituting the polyimide precursor includes a tetracarboxylic acid dianhydride represented by the following formula (a). In the tetracarboxylic acid component (A), the tetracarboxylic acid dianhydride represented by the formula (a) may be contained singly or two or more kinds thereof may be contained.

(A)

In formula (a), R ¹ represents a tetravalent organic group having 4 to 27 carbon atoms. R ¹ is an aliphatic group; Monocyclic aliphatic group; Condensed polycyclic aliphatic groups; A monocyclic aromatic group; A condensed polycyclic aromatic group; A non-condensed polycyclic aliphatic group in which the cyclic aliphatic group is linked directly or by a bridge source; The aromatic group may be a direct or a non-condensed polycyclic aromatic group linked together by a bridging source.

The tetracarboxylic acid dianhydride represented by the formula (a) is preferably an aromatic tetracarboxylic acid dianhydride or an alicyclic tetracarboxylic dianhydride.

Examples of the aromatic tetracarboxylic acid dianhydride represented by the formula (a) include pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic acid (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2- (3,4-dicarboxyphenoxy) benzene dianhydride, 1,3-bis (3,4-dicarboxyphenoxy) benzene dianhydride, 1,3- Water, 4,4'-bis (3,4-dicarboxyphenoxy) biphenyl dianhydride, 2,2-bis [(3,4-dicarboxyphenoxy) phenyl] propane dianhydride, 6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,2 ', 3,3'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, Bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenoxy) benzene dianhydride, 1,4-bis (2,3-dicarboxyphenoxy) benzene dianhydride, bis Bis (2,3-dicarboxyphenoxy) benzene dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,3-bis (3,4-dicarboxybenzoyl) benzene dianhydride, 1,4 Benzene dianhydride, 1,3-bis (2,3-dicarboxybenzoyl) benzene dianhydride, 1,4-bis (2,3-dicarboxybenzoyl) benzene dianhydride , 4,4'-isophthaloyldiphthalic anhydride diazodiphenylmethane-3,3 ', 4,4'-tetracarboxylic acid dianhydride , Diazodiphenylmethane-2,2 ', 3,3'-tetracarboxylic acid dianhydride, 2,3,6,7-thioxanthontetracarboxylic acid dianhydride, 2,3,6,7-anthraquinone tetra Carboxylic acid dianhydride, 2,3,6,7-zinthontetracarboxylic acid dianhydride, and the like.

Examples of alicyclic tetracarboxylic acid dianhydrides represented by formula (a) include cyclic butyetetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetra Carboxylic acid dianhydride, bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid Dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentyl acetic acid dianhydride, bicyclo [2.2.1] heptane- 3-ethylcyclohex-1-en-3- (1,2), 5,6-tetracarboxylic acid dianhydride, decahydro-1 , 4,5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) - dicarboxylic acid dianhydride, 3,3 ', 4,4'-dicyclohexyl Tetracarboxylic dianhydride and the like is water.

When the tetracarboxylic acid dianhydride represented by the general formula (a) contains an aromatic ring such as a benzene ring, a part or all of the hydrogen atoms on the aromatic ring may be replaced by a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, Or the like may be substituted. When an aromatic ring such as a benzene ring is contained in the tetracarboxylic acid dianhydride represented by the general formula (a), an ethynyl group, a benzocyclobutene-4'-yl group, a vinyl group, an allyl group, A crosslinking point group selected from a cyanate group, a nitryl group, and an isopropenyl group may be included in the structure of the tetracarboxylic acid. Particularly, the tetracarboxylic acid dianhydride represented by the general formula (a) preferably contains a group which is a crosslinking point such as a vinylene group, a vinylidene group, and an ethynylidene group in the main chain skeleton within a range that does not impair molding processability .

The tetracarboxylic acid component (A) may contain, in addition to the tetracarboxylic acid dianhydride represented by the above formula (a), hexacarboxylic acid methylmercury and octacarboxylic acid maleic anhydride. When these anhydrous products are included, branching chains are introduced into the obtained polyimide. These anhydrous products may be contained in only one kind, or two or more kinds may be included.

3-1-2. The diamine component (B)

The diamine component (B) constituting the polyimide precursor includes the diamines represented by the following formulas (b-1) to (b-3). The diamine component (B) may include only one diamine represented by the following formulas (b-1) to (b-3), or two or more diamines. The diamine component (B) may contain diamines (b-4) other than the diamines represented by the general formulas (b-1) to (b-3).

[Formula b-1]

[Formula b-2]

[Formula b-3]

In the cyclohexane skeleton of cyclohexadian represented by the formula (b-1), there are the following two kinds of geometric isomers (cis / trans). The trans sieve is represented by the following formula (Z-1), and the cysteine is represented by the following formula (Z-2).

[Z-1]

[Z-2]

The cis / trans ratio of the cyclohexane skeleton in the formula (Z-1) is preferably 50/50 to 0/100, more preferably 30/70 to 0/100. When the ratio of the trans-isomer increases, the molecular weight of the polyimide precursor is likely to increase. Therefore, the strength of the film tends to increase.

The cis / trans ratio of the unit derived from cyclohexane contained in the polyimide precursor is measured by nuclear magnetic resonance spectroscopy.

The position of the aminomethyl group of the norbornane diamine represented by the formula (b-2) is not particularly limited. For example, the norbornane diamine represented by the general formula (b-2) may include structural isomers having different positions of aminomethyl groups, optical isomers including S, R forms, and the like. They may be included in any proportion.

There are two kinds of geometric isomers (cis / trans) in the 1,4-bismethylene cyclohexane skeleton (X) of 1,4-bis (aminomethyl) cyclohexane represented by the formula b-3. The trans sieve is represented by the following formula (X1), and the cis structure is represented by the following formula (X2).

(X)

(X1)

(X2)

The ratio of the cis / trans ratio of the 1,4-bis (aminomethyl) cyclohexane-derived unit is preferably 40/60 to 1/100, more preferably 20/80 to 0/100. The glass transition temperature of the polyimide contained in the constituent component of the diamine represented by the formula (b-3) is controlled by the sheath / trans ratio and the glass transition temperature of the polyimide is .

The cis / trans ratio of the 1,4-bis (aminomethyl) cyclohexane-derived unit contained in the polyimide precursor is measured by nuclear magnetic resonance spectroscopy.

The diamine component (B) may contain a diamine (b-4) represented by the following formula other than the diamines represented by the above-mentioned formulas (b-1) to (b-3).

[Formula b-4]

In the formula (b-4), R 'is a divalent group having 4 to 51 carbon atoms. R 'is an aliphatic group; A monocyclic aliphatic group (except 1,4-cyclohexylene group, group represented by the following formula X and group represented by the following formula Y); Condensed polycyclic aliphatic groups; A monocyclic aromatic group; A condensed polycyclic aromatic group; A non-condensed polycyclic aliphatic group in which the cyclic aliphatic group is linked directly or by a bridge source; The aromatic group may be a direct or a non-condensed polycyclic aromatic group linked together by a bridging source.

(X)

[Formula Y]

Examples of the diamine represented by the above formula (b-4) include diamines having a benzene ring, diamines having an aromatic substituent, diamines having a spirobifluorine ring, siloxane diamines, ethylene glycol diamines, Amines, alicyclic diamines, and the like.

Examples of diamines having a benzene ring include,

<1> A diamine having one benzene ring such as p-phenylenediamine, m-phenylenediamine, p-xylenediamine, m-xylenediamine, and the like;

&Lt; 2 > A process for producing a compound represented by the following formula (1), wherein 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, Aminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, Diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2 (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2 (3-aminophenyl) propane, , 2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- , 1,3,3,3-hexafluoropropane, 1,1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,1- A diamine having two benzene rings such as ethane;

(3-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis Benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis Benzene, 1,4-bis (3-amino-alpha, alpha -dimethylbenzyl) benzene, -α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4- (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzonitrile, 2 , And 6-bis (3-aminophenoxy) pyridine;

(4-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) Bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) (4-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- ) Phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2- Bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- , Diamines having four benzene rings such as 1,1,3,3,3-hexafluoropropane;

Benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- Benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) Methylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -?,? - dimethylbenzyl] benzene, 1,4- -Dimethylbenzyl] benzene, and 1,4-bis [4- (4-aminophenoxy) -?,? - dimethylbenzyl] benzene;

<6> A process for preparing 4,4'-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, ] Benzophenone, 4,4'-bis [4- (4-amino- alpha, alpha -dimethylbenzyl) phenoxy] diphenylsulfone, 4,4'-bis [4- (4-aminophenoxy) Yl] diphenyl sulfone, and the like.

Examples of diamines having an aromatic substituent include 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibenoxybenzophenone, 3,3'- 3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, and the like.

Examples of spirobibodies having a phosphorus ring include 6,6'-bis (3-aminophenoxy) -3,3,3 ', 3'-tetramethyl-1,1'-spirobindaine, 6,6'-bis (4-aminophenoxy) -3,3,3 ', 3'-tetramethyl-1,1'-spirobindaine and the like.

Examples of siloxane dianamines include 1,3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, Aminopropyl) polydimethylsiloxane,?,? - bis (3-aminobutyl) polydimethylsiloxane, and the like.

Examples of ethylene glycol di-amines include bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) Bis (2-aminoethoxy) ethyl] ether, bis [2- (3-aminopropoxy) ethyl] ether, 1,2- Ethane, ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2-aminoethoxy) , Diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, and the like.

Examples of the alkylenediamine include ethylene diamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7- Diaminoheptane, 1,8-diaminooctane, 1,9-diaminonone, 1,10-diaminodecane, 1,11-diaminodecane, 1,12-diaminododecane, etc. .

Examples of alicyclic diamines include bis (aminomethyl) cyclohexene except cyclobutanediamine, cyclohexanediamine, di (aminomethyl) cyclohexane [1,4-bis (aminomethyl) cyclohexane (Including norbornene diamines such as norbornene diamine), diaminooxycycycloheptane, diaminomethylbicycloheptane (including norbornene diamine), diaminobutyric acid (Aminocyclohexyl) methane [or methylenebis (cyclohexylamine)], bis (aminocyclohexylamine), isophoronediamine, diaminotricyclo-decadecane, diaminomethyltricyclodecane, bis (Aminocyclohexyl) isopropylidene, and the like.

3-1-3. Preferred polyimide precursors

The polyimide precursor contained in the polyimide precursor-containing solution is not particularly limited as long as the polyimide precursor is obtained by reacting the tetracarboxylic acid component (A) and the diamine component (B) described above, A tetracarboxylic dianhydride represented by the general formula (a) and a tetracarboxylic acid dianhydride represented by the general formula (b) and a diamine represented by the general formula (b) (Represented by the following formula (H)) bonded to a diamine represented by any one of the following formulas.

[Formula G]

[Formula H] &lt;

In the formulas (G) and (H), R ⁶ and R ⁸ each independently represent a tetravalent group having 4 to 27 carbon atoms. R ⁶ and R ⁸ are each independently an aliphatic group; Monocyclic aliphatic group; Condensed polycyclic aliphatic groups; A monocyclic aromatic group; A condensed polycyclic aromatic group; A non-condensed polycyclic aliphatic group in which the cyclic aliphatic group is linked directly or by a bridge source; The aromatic group may be a direct or a non-condensed polycyclic aromatic group linked together by a bridging source. Specifically, it is the same as R ¹ in the tetracarboxylic acid dianhydride represented by the above-mentioned formula (a).

In formula (H), R ⁷ represents a divalent group having 4 to 51 carbon atoms. R ⁷ is an aliphatic group; Monocyclic aliphatic group (except 1,4-cyclohexylene group); Condensed polycyclic aliphatic groups; A monocyclic aromatic group; A condensed polycyclic aromatic group; A non-condensed polycyclic aliphatic group in which the cyclic aliphatic group is linked directly or by a bridge source; The aromatic group may be a direct or a non-condensed polycyclic aromatic group linked together by a bridging source. Specifically, it may be the same as R 'of the diamine represented by the above formula (b-4), or may be a group represented by the following formula (X) or (Y)

(X)

[Formula Y]

It is particularly preferable that R ⁷ in the formula (H) is a norbornane (a group represented by the above formula (Y)). That is, the polyimide block represented by the formula (H) is preferably a polyimide block containing the diamine represented by the above-mentioned formula (b-2).

M and n in the formulas (G) and (H) represent the number of repeating structural units in each block. The average value of m and the average value of n are each independently preferably 2 to 1000, more preferably 5 to 500.

It is preferable that the ratio of m and n is an average value of m: n = 9: 1 to 1: 9 and an average value of m: an average value of n = 8: 2 to 2: When the ratio of the repeating number m of the repeating structural unit represented by the formula (G) is more than a certain value, the coefficient of thermal expansion of the obtained polyimide film becomes small. When the ratio of the number of repeating m is more than a predetermined value, the visible light transmittance of the obtained polyimide film is increased. On the other hand, since the cyclohexanediamine is generally expensive, if the ratio of the number m of repeating structural units represented by the formula G is made small, the cost can be reduced.

The ratio of the total number of repeating structural units represented by the formula (G) to the total number of the repeating structural units represented by the formula (H) contained in the block polyamic acid imide which may be a polyimide precursor is (G): (H) = 9 : 1 to 1: 9, and more preferably (G) :( H) = 8: 2 to 2: 8.

3-2. solvent

The solvent contained in the polyimide precursor-containing solution is not particularly limited as long as it is a solvent capable of dissolving the tetracarboxylic acid component (A) and the diamine component (B). For example, it may be an aprotic polar solvent or a water-soluble alcohol solvent.

Examples of aprotic polar solvents include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, 3-dimethyl-2-imidazolidinone and the like; Examples of the solvent include ether-based compounds such as 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, tetrahydroperfuryl alcohol, , Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-methoxy-2-propanol, Propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, polyethylene glycol, polypropylene glycol, tetrahydrofuran, dioxane , 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and the like.

Examples of the water-soluble alcoholic solvent include aliphatic alcohols such as methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, Butene diol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2- - pentane diol, 1,2,6-hexyl lyol, diacetone alcohol and the like.

The polyimide precursor-containing solution may contain only one kind of these solvents or two or more kinds of these solvents. The solvent preferably contains N, N-dimethylacetamide, N-methyl-2-pyrrolidone or a mixture thereof.

3-3. Release agent

The polyimide precursor-containing solution may contain a release agent. The releasing agent contained in the polyimide precursor-containing solution is not particularly limited as long as it can increase the releasability between the supporting substrate and the transparent polyimide layer, and may be a known internal releasing agent. Examples of internal mold release agents include aliphatic alcohols, fatty acid esters, triglycerides, fluorine surfactants, higher fatty acid metal salts, and phosphoric acid ester type release agents. From the viewpoint that it is difficult to impair the transparency of the obtained transparent polyimide layer, it is preferable to use a phosphoric acid ester based mold release agent. Examples of the phosphoric ester type releasing agent include the compounds described in JP-A No. 2000-256377.

The amount of the releasing agent contained in the solution containing the polyimide precursor is preferably from 0.01 to 0.38 parts by mass, more preferably from 0.02 to 0.30 parts by mass, more preferably from 0.02 to 0.30 parts by mass with respect to 100 parts by mass of the polyimide precursor contained in the polyimide precursor- Is 0.04 to 0.20 parts by mass. When the amount of the releasing agent is less than 0.01 part by mass, the peel strength at the time of peeling off the transparent polyimide layer from the supporting substrate becomes large. On the other hand, when the amount of the releasing agent exceeds 0.38 parts by mass, it becomes difficult to apply the polyimide precursor-containing solution onto the supporting substrate.

3-4. Other additives

As described above, the polyimide precursor-containing solution may contain various additives in such a range that the transparency and heat resistance of the obtained transparent polyimide layer are not impaired. Examples of the various additives include antioxidants, heat stabilizers, antistatic agents, flame retardants, and ultraviolet absorbers.

3-5. Method for preparing polyimide precursor-containing solution

The polyimide precursor-containing solution is obtained by reacting the above-mentioned tetracarboxylic acid component (A) with the above-mentioned diamine component (B) in the above-mentioned solvent. Y / x is preferably 0.9 to 1.1, more preferably 0.95 to 1.05, and more preferably 0.97 to 1.05, in terms of the number of moles of the diamine component (B) in the solvent and the number of moles of the tetracarboxylic acid component (A) More preferably 1.03, and particularly preferably 0.99 to 1.01. By polymerizing the tetracarboxylic acid component (A) and the diamine component (B) at such a ratio, the molecular weight (polymerization degree) of the polyimide precursor can be appropriately adjusted.

The order of the polymerization reaction is not particularly limited. For example, first, a vessel equipped with a stirrer and a nitrogen introduction tube is prepared. A solvent to be described later is introduced into a container substituted with nitrogen, and the diamine is added so that the solid content concentration of the obtained polyimide precursor becomes 50 mass% or less, and the temperature is adjusted to stir and dissolve. To this solution, a tetracarboxylic acid component (A) is added to the diamine component (B) so that the molar ratio is 1, and the temperature is adjusted and the mixture is stirred for about 1 to 50 hours to obtain a polyimide precursor- A precursor-containing solution can be obtained.

When the polyimide precursor is a block polyamide acid imide, for example, polyamide acid imide may be produced by adding a polyimide solution at the terminal of the acid anhydride to a solution of polyamine acid at the amine end and stirring. The diamine unit of the polyamic acid preferably contains a cyclohexane-containing diamine (diamine represented by the above-described formula b-1 or b-3); The diamine unit of the polyimide preferably contains a diamine other than the cyclohexane-containing diamine (the diamine represented by the above-mentioned formula (b-2) or (b-4)). This is because the polyimide (b-1 or b-3) containing cyclohexane in the structure is difficult to dissolve in the solvent. The polyamic acid is prepared by the aforementioned method. The releasing agent is appropriately added as needed.

4. On the transparent polyimide layer

In the transparent polyimide laminate obtained by the above-described method, the total light transmittance of the transparent polyimide layer is 80% or more, more preferably 83% or more, and still more preferably 85% or more. If the total light transmittance is 80% or more, a transparent polyimide layer can be applied for applications considered to require transparency. The total light transmittance of the transparent polyimide layer is adjusted by the type of polyimide, the oxygen concentration or pressure of the atmosphere in the above-mentioned step b), and the like. Particularly, by lowering the oxygen concentration in the atmosphere in the temperature region exceeding 200 占 폚 in the step b) or lowering the pressure in the atmosphere, oxidation of the polyimide is suppressed, and the total light transmittance of the transparent polyimide layer is increased. The total light transmittance was measured with a light source D65 according to JIS-K7105 for the transparent polyimide layer by peeling off the transparent polyimide layer from the supporting substrate.

The in-plane retardation of the transparent polyimide layer in the transparent polyimide laminate is 10 nm or less, preferably 5 nm or less, more preferably 3 nm or less. When the in-plane retardation of the transparent polyimide layer is 10 nm or less, the transparent polyimide layer can be applied to a panel substrate of a flexible display device or the like. When the imidization proceeds partially or the solvent is volatilized after the above-mentioned step b), the in-plane retardation tends to become large. Therefore, in order to reduce the in-plane retardation, it is desirable to sufficiently increase the imidization rate at the end of the above-mentioned step (b) and sufficiently reduce the amount of the residual solvent at the end of the step (b). The in-plane retardation is a value measured by a photoelastic constant measuring apparatus at 25 ° C and a wavelength of 550 nm. Specifically, the transparent polyimide layer is peeled off from the supporting substrate, and the refractive index of the transparent polyimide layer is measured with a photoelastic constant measuring apparatus. The direction in which the refractive index becomes maximum is defined as X-axis, the direction perpendicular to the X- . When the refractive index in the X-axis direction is nx, the refractive index in the Y-axis direction is ny, and the thickness of the transparent polyimide layer is d, a value represented by (nx-ny) xd is defined as the in-plane retardation.

The glass transition temperature (Tg) of the transparent polyimide layer in the transparent polyimide laminate is 260 占 폚 or higher, preferably 270 占 폚 or higher, and more preferably 300 占 폚 or higher. If the glass transition temperature of the transparent polyimide layer is 260 占 폚 or higher, the transparent polyimide layer can be applied to applications requiring high heat resistance. For example, in general, the process temperature at the time of forming an electronic device is 250 DEG C, and the transparent polyimide layer obtained in the present invention is applicable to a panel substrate of an apparatus including such an electronic device. The glass transition temperature of the transparent polyimide layer is adjusted, for example, by the equivalent of an imide group contained in the polyimide, the structure of the diamine component constituting the polyimide or the structure of the tetracarboxylic acid dianhydride component. The glass transition temperature is measured with a thermomechanical analyzer (TMA).

The haze of the transparent polyimide layer in the transparent polyimide laminate is 5% or less, preferably 3% or less, and more preferably 1% or less. When the haze of the transparent polyimide layer is 5% or less, the transparent polyimide layer can be applied to various optical films. The haze of the transparent polyimide layer is adjusted by the heating conditions of the polyimide precursor-containing solution, the crystallinity of the polyimide, the surface roughness of the supporting substrate, and the like.

Furthermore, the absolute value of the b value represented by the L * a * b coloring system of the transparent polyimide layer in the transparent polyimide laminate is 5 or less, preferably 3 or less. On the other hand, the b value is preferably a positive value (0 or more). The L * a * b color system is specified in JIS Z 8729. When the b value is a positive value, it indicates that the transparent polyimide layer has a yellowish period, and when the b value is a negative value, it indicates that the transparent polyimide layer has a blue period. In general, the polyimide film has a large b value and is often yellow or brown. On the other hand, the transparent polyimide layer in the transparent polyimide laminate of the present invention has an absolute value of b value of 5 or less and little coloration. Therefore, the polyimide layer can also be applied to substrates for various displays.

The thickness of the transparent polyimide layer in the transparent polyimide laminate is not particularly limited, but is preferably 5 to 100 m, more preferably 10 to 50 m. A transparent polyimide layer having such a thickness can be used as a substrate for various flexible devices and the like.

Here, the present invention is a liquid crystal display device having a glass transition temperature of 260 占 폚 or higher, a total light transmittance of 80% or higher, a haze of 5% or lower, an absolute value of b value in the L * a * b color system of 5 or lower, Polyimide films are also provided. The polyimide film is preferably composed of a transparent polyimide layer obtained by the above-mentioned production method of the transparent polyimide laminate. Furthermore, the physical properties of the polyimide film are preferably in the same range as that of the polyimide layer described above.

B. Use of transparent polyimide laminate

The transparent polyimide film obtained by peeling the transparent polyimide layer of the above-mentioned transparent polyimide laminate from the supporting substrate can be applied to substrates and optical films of various flexible devices. Further, since the transparent polyimide film has a high total light transmittance and a very small in-plane retardation, it is particularly suitable for a substrate of a flexible display. Examples of the flexible display include a touch panel, a liquid crystal display, an organic EL display, and the like.

The touch panel is generally a panel body composed of (i) a transparent substrate having a transparent electrode (detection electrode layer), (ii) an adhesive layer, and (iii) a transparent substrate having a transparent electrode (driving electrode layer). The above-described transparent polyimide film can be applied to both the transparent substrate on the detection electrode layer side and the transparent substrate on the drive electrode layer side.

Further, the liquid crystal cell of the liquid crystal display device normally has a laminated structure in which (i) a first transparent plate, (ii) a liquid crystal material sandwiched by a transparent electrode, and (iii) to be. The above-described transparent polyimide film is applicable to both the first transparent plate and the second transparent plate. The above-described transparent polyimide film is also applicable to a substrate for a color filter in a liquid crystal display device.

The organic EL panel is usually a panel in which a transparent substrate, an anode transparent electrode layer, an organic EL layer, a cathode reflective electrode layer, and an opposing substrate are stacked in this order. The above-mentioned transparent polyimide film can be applied to any of the transparent substrate and the counter substrate.

The transparent polyimide layer (transparent polyimide film) of the above-mentioned transparent polyimide laminate is easily peeled off from the supporting substrate. Therefore, when obtaining the flexible display, the transparent polyimide layer may be peeled off and then the element may be formed on the transparent polyimide layer. After the element is formed on the transparent polyimide layer, the transparent polyimide layer is peeled off from the support substrate You can.

When the transparent polyimide layer is peeled from the supporting substrate, foreign matter may be adsorbed to the transparent polyimide layer due to peeling electrification, and damage to the device may occur. Therefore, it is preferable to take measures to prevent the transparent polyimide laminate from being charged. Specifically, (a) an antistatic agent is added to the polyimide precursor-containing solution, (b) an antistatic agent is coated on the supporting substrate, (c) a coating device for coating the solution containing the polyimide precursor, It is preferable to provide an electrostatic removing member (for example, a discharging bar, a discharging yarn, an ion blowing type static electricity removing device, etc.). These countermeasures may be performed only one kind or a plurality of countermeasures may be performed.

The method for forming the element on the transparent polyimide layer includes the following three methods. On the other hand, in any of the methods, the method of forming the element is not particularly limited and may be a known method.

(i) Method 1

The first method is to peel off the transparent polyimide film (transparent polyimide layer) 1 'from the supporting substrate 11 in the transparent polyimide laminate 12, as shown in the schematic sectional view of Fig. 2 (Fig. 2 (a)), and then the element 13 is formed on the transparent polyimide film 1 '(Fig. 2 (b)). In the first method, the element 13 may be formed on the transparent polyimide film 1 'after bonding the separated transparent polyimide film 1' to another substrate (not shown).

(ii) Method 2

3, the device 13 is formed on the transparent base polyimide layer 1 'and the laminated transparent polyimide layer 1' (FIG. 3 (a)), A transparent polyimide film (transparent polyimide layer) 1 'is peeled off from the supporting substrate 11 (Fig. 3 (b)) to obtain a transparent polyimide film 1' on which the element 13 is formed 3 (c)). In the second method, the stress applied to the transparent polyimide layer 1 'at the time of forming the element 13 is likely to be absorbed by the supporting substrate 11. Therefore, it is difficult for the transparent polyimide layer 1 'to be torn or broken when the device 13 is formed.

(iii) Third method

The third method is as follows. After the side of the supporting substrate 11 in the transparent polyimide laminate 12 is bonded to the other substrate 14 (Fig. 4 (a)), as shown in the schematic cross- , Various elements 13 are formed on the transparent polyimide layer 1 '(FIG. 4 (b)), a transparent polyimide film (transparent polyimide layer) 1' is peeled off from the supporting substrate 11 (Fig. 4 (c)), thereby obtaining the polyimide film 1 'on which the element 13 is formed (Fig. 4 (d)). In the third method, since the other substrate 14 is bonded to the transparent polyimide laminate 12, the transparent polyimide laminate 12 is not bent at the time of manufacturing the device 13. [ Therefore, the element 13 can be formed on the transparent polyimide layer 1 'by various methods. Further, also in the third method, the stress applied to the transparent polyimide layer 1 'during the formation of the element 13 is likely to be absorbed by the supporting substrate 11. [ Therefore, it is difficult for the transparent polyimide layer 1 'to be torn or broken when the device 13 is formed.

The other substrate 14 to be bonded to the transparent polyimide laminate 12 is not particularly limited as long as it is a rigid substrate, and may be a glass substrate, a metal substrate, a ceramic substrate, a resin substrate, or the like. The method of bonding the support substrate 11 of the transparent polyimide laminate 12 to the other substrate 14 is not particularly limited and may be a bonding method using an adhesive or the like.

5. Other

The above-described method for producing a polyimide laminate can also be applied to a method for producing a resin laminate having a supporting substrate and various resin layers. Specifically, it is possible to provide a method for producing a resin laminate, which comprises the steps of (a) applying a varnish containing various resins onto a supporting substrate, and (b) thermally curing the coating film of the varnish. According to the method for producing the resin laminate, a resin film which can be easily peeled off from the supporting substrate is obtained. Examples of the various resins include polyimide resins (polyimide precursors), aramid resins, polyetheretherketone resins, and polyether sulfone resins other than those described above.

Example

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited at all by this. In Examples and Comparative Examples, the peel strength, the imidization ratio, the residual amount of the solvent, the glass transition temperature, the total light transmittance, the haze value, the b value in the L * a * b color system, The roughness was measured by the following method.

1) Peel strength

The transparent polyimide laminate produced in Examples and Comparative Examples was cut into a length of 50 mm and a width of 3.5 mm. This transparent polyimide laminate was measured for peel strength according to the method specified in JIS C-6471. Specifically, the ends of the short sides of the transparent polyimide laminate were held and peeled off from the supporting substrate at a peeling angle of 90 deg. And a peeling rate of 50 mm / min, and the stress at peeling was measured. The stress was measured by a tensile tester EZ-S manufactured by Shimadzu Corporation, and an adhesive tape peeling test apparatus.

2) Imidization rate

The transparent polyimide layer was peeled off from the transparent polyimide laminate produced in Examples and Comparative Examples, and the imidization ratio of the transparent polyimide layer was calculated as follows. On the other hand, the measurement of the IR absorption spectrum was carried out by attaching a multiple reflection type infrared spectrum measuring device (ATR PR0410-M, manufactured by Nippon Bunko K.K.) to an FT-IR spectrometer (FT / IR 300E,

The IR absorption spectra of the transparent polyimide layers prepared in Examples and Comparative Examples were measured. For each film, the ratio A (peak stretching vibration) of the absorption peak at 1370 cm ^-1 (CN stretching vibration of the imide ring) to the absorption peak height at 1500 cm ^-1 (peak (reference) by C = C stretching vibration of the benzene ring) Respectively. On the other hand, a transparent polyimide layer was prepared in the same manner as in each of the examples and the comparative examples and heated at 270 캜 for 2 hours or more to completely imidize it. For these films, respectively, by measuring the IR absorption spectrum, the absorption peak and similarly the height of 1500cm ^-1 (the benzene ring C = C peak (standard) according to the stretching vibration), absorption peaks height of about 1370cm ^-1 (imide Quot; CN stretching vibration of the ring).

 Then, the value A (ratio A / ratio B) × 100 (%) of the ratio A to the ratio B of the corresponding film was obtained and used as the imidization rate.

3) Remaining amount of solvent

The transparent polyimide layer was peeled off from the transparent polyimide laminate prepared in Examples and Comparative Examples, and the residual amount of the solvent in the transparent polyimide layer was measured. The measurement was carried out by connecting an electric furnace type pyrolysis furnace (PYR-2A manufactured by Shimadzu Corporation (pyrolysis temperature: 320 ° C)) and a gas chromatographic mass spectrometer (GC-8A (column Uniport HP 80/100 KG-02) manufactured by Shimadzu Corporation) , And the amount of the solvent contained in the film was specified. At this time, the injector and detector temperatures of the apparatus were 200 ° C and the column temperature was 170 ° C.

4) Total light transmittance

The transparent polyimide layer was peeled off from the transparent polyimide laminate prepared in Examples and Comparative Examples, and the total light transmittance of the transparent polyimide layer was measured. Specifically, it was measured by a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS-K-7105 with a light source D65.

5) Hayes

The transparent polyimide layer was peeled off from the transparent polyimide laminate prepared in Examples and Comparative Examples, and the haze of the transparent polyimide layer was measured. Specifically, it was measured by a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS-K-7105 with a light source D65.

6) b value

The transparent polyimide layer was peeled off from the transparent polyimide laminate prepared in Examples and Comparative Examples to measure the b value of the transparent polyimide layer. The b value of the transparent polyimide layer on the calibrated white plate was measured three times using a color chromatic meter (measurement head: CM-2500d, manufactured by Konica Minolta Co., Ltd.) in a C light source, 2 ° field of view, and SCI mode. The b value was taken as the average value of the three measured values.

7) In-plane retardation R0

The transparent polyimide layer was peeled off from the transparent polyimide laminate produced in Examples and Comparative Examples. The in-plane retardation of the transparent polyimide layer was measured in the X and Y modes of a photoelastic constant measuring device PEL-3A-102C manufactured by Uni-Opt. The measurement temperature was 25 占 폚 and the measurement wavelength was 550 nm. Specifically, the refractive index of the polyimide film is measured by a photoelastic constant measuring apparatus, and the refractive index nx in the X-axis direction and the Y-axis in the direction Y Refractive index ny in the axial direction is derived. Then, when the thickness of the film is d, a value expressed by (nx-ny) xd is defined as the in-plane retardation.

8) Ten point average roughness of supporting substrate

The 10-point average roughness of the supporting substrate used in Examples and Comparative Examples was measured according to JIS B 0601. At this time, 10-point average roughness in the width direction of the supporting substrate was measured with a surface roughness and contour shape measuring device (Surfcom 1400D, manufactured by Tokyo Precision) with a cutoff value of 0.25 mm and a measuring length of 2.5 mm.

The abbreviations of the compounds used in Examples and Comparative Examples are as follows.

[Diamine component]

14BAC: 1,4-bis (aminomethyl) cyclohexane

NBDA: Novoane diamine

ODA: 4,4'-diaminodiphenyl ether

CHDA: trans-1,4-cyclohexane diamine

[Component of tetracarboxylic acid]

PMDA: pyromellitic dianhydride

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

[solvent]

DMAc: N, N-dimethylacetamide

NMP: N-methyl-2-pyrrolidone

(Synthesis Example 1)

469.4 g (3.3 moles) of 14BAC and 5761 g of DMAc were added to a 300 mL five-neck separable flask equipped with a thermometer, a stirrer and a nitrogen inlet tube and stirred. To this mixture was added 970.9 g (3.3 moles) of BPDA in powder form. After the addition of BPDA, the reaction vessel was bathed in an oil bath maintained at 120 DEG C for 5 minutes. After about 3 minutes from the addition of BPDA, the salt precipitated but then dissolved rapidly. This mixed solution was further stirred at room temperature for 18 hours to obtain a polyimide precursor-containing solution.

(Synthesis Example 2)

39.7 g (0.180 mol) of PMDA and 130 g of DMAc were added to a 300 mL five-neck separable flask equipped with a thermometer, a stirrer, a nitrogen inlet tube and a dropping funnel, and stirred to obtain a PMDA slurry. On the other hand, a mixed solution of 27.8 g (0.180 mol) of NBDA and 27.8 g of DMAc was prepared. This mixed solution was dropped into the slurry over 120 minutes while maintaining the temperature constant. Thereafter, the mixed solution was stirred at 50 캜 for 5 hours to obtain a polyimide precursor-containing solution.

(Synthesis Example 3)

14.1 g (0.099 mole) of 14BAC, 1.7 g (0.011 mole) of NBDA and 189 g of DMAc were added to a 300-mL five-neck separable flask equipped with a thermometer, a stirrer and a nitrogen inlet tube and stirred. To this mixed solution, 29.1 g (0.099 mole) of BPDA in powdery form and 2.4 g (0.011 mole) of PMDA were added. After the addition of BPDA and PMDA, the reaction vessel was bathed in an oil bath maintained at 120 캜 for 5 minutes. After about 3 minutes from the addition of BPDA and PMDA, the salt precipitated, but then rapidly dissolved. This mixed solution was further stirred at room temperature for 18 hours to obtain a polyimide precursor-containing solution.

(Synthesis Example 4)

10.0 g (0.050 mol) of ODA and 119 g of DMAc were added to a 300 mL five-neck separable flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube and stirred. To this mixed solution, 10.9 g (0.050 mol) of PMDA in powder form was added while maintaining the temperature constant. Thereafter, the mixed solution was stirred at 50 캜 for 5 hours to obtain a polyimide precursor-containing solution.

(Synthesis Example 5)

Synthesis of amide acid oligomer solution

11.4 g (0.100 mol) of CHDA and 116 g of NMP as a solvent were added to a 300 mL five-neck separable flask equipped with a thermometer, a stirrer and a nitrogen inlet tube, and stirred until the solution became transparent. To this solution, 27.1 g (0.092 mol) of BPDA was charged as a powder, and the reaction vessel was kept in an oil bath maintained at 120 DEG C for 5 minutes. After the charging of BPDA, salt was deposited. Thereafter, the salt dissolved and became homogeneous, increasing the viscosity of the solution. After removing the oil bath, the mixture was further stirred at room temperature for 18 hours to obtain an amide acid oligomer solution having an amino group derived from CHDA at the terminal.

· Synthesis of imide oligomer solution

11.1 g (0.072 mol) of NBDA and 94.5 g of NMP were added to a 300-mL five-necked separable flask equipped with a thermometer, a stirrer and a nitrogen inlet tube, and stirred until the solution became transparent. 29.4 g (0.100 mol) of BPDA was charged as a powder to the solution, and the reaction vessel was kept in an oil bath maintained at 120 DEG C for 5 minutes. After charging BPDA, salt was deposited temporarily. Thereafter, it was confirmed that the solution became a homogeneous transparent solution with the increase in viscosity.

A cooling tube and a Dean Stark type thickener were attached to the separable flask, 80.0 g of xylene was added to the reaction solution, and dehydration thermal imidization reaction was carried out at 180 ° C for 4 hours while stirring. After the reaction, xylene was distilled off to obtain an imide oligomer solution having an acid anhydride structure derived from BPDA at the terminal.

Synthesis of block polyamide acid imide solution

40.0 g of the aforementioned amide acid oligomer solution and 9.99 g of the imide oligomer solution described above were mixed and stirred for 10 minutes with a high viscosity material stirring defoamer (product name: UM-118 manufactured by Japan Unix Co., Ltd.) to obtain a block polyamide acid imide Solution.

(Example 1)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was coated on a polyimide film (UPILEX 50S (50 탆) made by Ube Kosan Co., Ltd.) with a doctor blade fixed on a glass substrate with a doctor blade. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was raised from 30 DEG C to 270 DEG C over 120 minutes (temperature raising rate 2 DEG C / min), and further maintained at 270 DEG C for 2 hours, A transparent polyimide laminate was produced. The thickness of the obtained transparent polyimide layer was 30 탆.

The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.039 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 260 占 폚, a total light transmittance of 87%, an in-plane retardation (Ro) of 0.8 nm, an imidization rate of 98% and a solvent residual amount of 0.2 mass%.

(Example 2)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 1 except that the oxygen concentration in the inner oven was changed to 5.0%. The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.039 kN / m.

 The transparent polyimide film after peeling had a glass transition temperature (Tg) of 261 占 폚, a total light transmittance of 87%, an in-plane retardation (Ro) of 0.8 nm, an imidization rate of 98% and a solvent residual amount of 0.2 mass%.

(Example 3)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 1, except that the heating rate was changed to 10 캜 / min. The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.032 kN / m.

 The transparent polyimide film after peeling had a glass transition temperature (Tg) of 260 占 폚, a total light transmittance of 87%, an in-plane retardation (Ro) of 0.7 nm, an imidization rate of 95% and a residual solvent amount of 0.5% by mass.

(Example 4)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 3, except that the maximum attained temperature of the internal oven was changed to 280 캜 and the rate of temperature rise was 2 캜 / min. The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.040 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 261 占 폚, a total light transmittance of 86%, an in-plane retardation (R0) of 0.7 nm, and an imidization rate of 100%.

(Example 5)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was coated on a polyimide film (UPILEX 50S) made of Ube Kosan Co., Ltd., which had been fixed to a glass substrate with a capton tape, with a doctor blade. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled at 20%, and the temperature was raised from 30 占 폚 to 180 占 폚 over 75 minutes (temperature raising rate 2 占 폚 / min) and further maintained at 180 占 폚 for 2 hours. Thereafter, the sample was transferred to a vacuum oven and the pressure was reduced to 1 kPa or less by full vacuum, and then the temperature was elevated. The decompression oven was heated from 30 占 폚 to 270 占 폚 over 60 minutes (at a heating rate of 4 占 폚 / min) and further held at 270 占 폚 for 1 hour to prepare a transparent polyimide laminate on a glass substrate.

The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.031 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 260 占 폚, a total light transmittance of 86%, an in-plane retardation (R0) of 0.5 nm, an imidization rate of 96% and a residual solvent amount of 0.7% by mass.

(Example 6)

The polyimide precursor-containing solution prepared in Synthesis Example 2 was coated on a polyimide film (UPILEX 50S) made of Ube Kosan Co., Ltd., which was fixed to a glass substrate with a capton tape, with a doctor blade. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was raised from 30 占 폚 to 300 占 폚 over 135 minutes (temperature raising rate 2 占 폚 / min), and further maintained at 300 占 폚 for 2 hours, A transparent polyimide laminate was produced.

The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.029 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 290 占 폚, a total light transmittance of 88%, an in-plane retardation (R0) of 0.3 nm, an imidization rate of 98% and a residual solvent amount of 0.6% by mass.

(Example 7)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 1 except that the polyimide precursor-containing solution to be used was changed to that prepared in Synthesis Example 3, and the rate of temperature increase was 2 ° C / min. The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.041 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 266 占 폚, a total light transmittance of 88%, an in-plane retardation (Ro) of 0.6 nm, an imidization rate of 96% and a residual solvent amount of 0.3% by mass.

(Reference Example 1)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was coated on a glass substrate with a doctor blade on an aluminum foil (50 탆) made of Tokai aluminum and fixed with a capton tape. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was raised from 30 DEG C to 270 DEG C over 120 minutes (temperature raising rate 2 DEG C / min), and further maintained at 270 DEG C for 2 hours, A transparent polyimide laminate was produced. The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.19 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 261 占 폚, a total light transmittance of 85%, an in-plane retardation (Ro) of 1.4 nm, an imidization rate of 99% and a solvent residual amount of 0.1% by mass.

(Reference Example 2)

A polyimide precursor-containing solution prepared in Synthesis Example 1 was prepared in the same manner as in Example 8 except that a polyimide precursor-containing solution containing a peeling component in an amount of 0.01 g (equivalent to 500 ppm in terms of solid content) of a duo-formaldehyde releasing agent, A transparent polyimide laminate was produced. The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.007 kN / m.

 The transparent polyimide film after peeling had a glass transition temperature (Tg) of 260 占 폚, a total light transmittance of 85%, an in-plane retardation (R0) of 1.1 nm, an imidization rate of 99% and a solvent residual amount of 0.1% by mass.

(Reference Example 3)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 9 except that the supporting substrate used was changed to SUS304 (50 m). The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.009 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 262 占 폚, a total light transmittance of 86%, an in-plane retardation (R0) of 1.2 nm, an imidization rate of 99% and a solvent residual amount of 0.2 mass%.

(Example 8)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was continuously and directly applied on a polyimide film (UPILEX 50S (50 탆) made by Ube Industries) using a die coater, and a drying furnace with an oxygen concentration of 0.0% , Heating was carried out stepwise (corresponding to a heating rate of 5 캜 / minute) and heating was carried out to a maximum temperature of 270 캜 to prepare a transparent polyimide laminate. The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.039 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 261 占 폚, a total light transmittance of 87%, an in-plane retardation (R0) of 2.0 nm, an imidization rate of 97% and a residual solvent amount of 0.8% by mass.

(Example 9)

The block polyamide acid imide solution prepared in Synthesis Example 5 was coated on a polyimide film (UPILEX 50S (50 탆, Rz = 0.03 탆)) made of UBE acid by a doctor blade with a doctor blade fixed on a glass substrate. Then, a sample consisting of a glass substrate, a support substrate, and a block polyimide acid imide film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was raised from 30 DEG C to 270 DEG C over 120 minutes (temperature raising rate 2 DEG C / min), and further maintained at 270 DEG C for 2 hours, A transparent polyimide laminate was produced. The thickness of the transparent polyimide layer of the obtained transparent polyimide laminate was 30 mu m. The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.030 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 286 占 폚, a total light transmittance of 85%, a haze of 1.0%, a b value of 1.8, an in-plane retardation (R0) of 0.9 nm and an imidization rate of 98% The residual solvent amount was 0.5% by mass.

(Comparative Example 1)

Except that the polyimide precursor-containing solution to be used was changed to the one prepared in Synthesis Example 4, and the temperature was raised from 30 占 폚 to 300 占 폚 over 135 minutes (heating rate 2 占 폚 / min) and maintained at 300 占 폚 for 2 hours. , A transparent polyimide laminate was produced on a glass substrate. The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.025 kN / m.

The glass transition temperature (Tg) of the transparent polyimide film after peeling was not detected, and the total light transmittance was 78%, the in-plane retardation (R0) was 0.9 nm, the imidization rate was 95%, and the residual solvent amount was 0.9 mass%.

(Comparative Example 2)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 1, except that the oxygen concentration in the inner oven was changed to 10.0%. The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.031 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 259 占 폚, a total light transmittance of 79%, an in-plane retardation (R0) of 0.8 nm, an imidization rate of 97% and a residual solvent amount of 0.5% by mass.

(Comparative Example 3)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 1, except that the maximum attained temperature of the internal oven was changed to 230 캜. The peel strength at the interface of the support substrate / transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.010 kN / m.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 250 占 폚, a total light transmittance of 90%, an in-plane retardation (Ro) of 0.8 nm, an imidization rate of 78% and a residual solvent amount of 3.0% by mass.

(Comparative Example 4)

A transparent polyimide laminate was produced on a glass substrate in the same manner as in Example 1 except that the supporting substrate used was changed to a copper foil (NA-DFF (12 mu m)) manufactured by Mitsui Mining Co., Attempts were made to peel off the transparent polyimide layer from the copper foil (support substrate) of the transparent polyimide laminate separated from the glass substrate, but peeling was not possible.

(Comparative Example 5)

A solution containing a polyimide precursor containing a peeling component in an amount of 0.10 g (equivalent to 5000 ppm based on solid content) of a duo-phthalate releasing agent Gerek UN was added to 100 g of the polyimide precursor-containing solution prepared in Synthesis Example 1, The aluminum foil (support substrate; 50 mu m) was coated with a doctor blade. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, and the temperature was raised from 30 ° C to 270 ° C over 120 minutes (temperature increase rate 2 ° C / min), and further maintained at 270 ° C for 2 hours. The transparent polyimide laminate taken out from the oven was found to be difficult to form because the transparent polyimide layer on the supporting substrate was partially agglomerated by "cissing ".

(Comparative Example 6)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was directly coated on a glass substrate with a doctor blade. Then, a sample made of a glass substrate and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was raised from 30 DEG C to 270 DEG C over 120 minutes (temperature raising rate 2 DEG C / min), and further maintained at 270 DEG C for 2 hours, To prepare a transparent polyimide layer. The thickness of the obtained transparent polyimide layer was 30 탆.

Attempts were made to peel the transparent polyimide layer from the glass substrate, but it was difficult to peel off the transparent polyimide layer easily. Thus, the glass substrate / transparent polyimide layer was immersed in distilled water to peel off the transparent polyimide film from the glass substrate.

The transparent polyimide film after peeling had a glass transition temperature (Tg) of 260 占 폚, a total light transmittance of 87%, an in-plane retardation (Ro) of 0.8 nm, an imidization rate of 98% and a solvent residual amount of 0.1% by mass.

(Comparative Example 7)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was coated on a polyimide film (UPILEX 50S (50 탆, Rz = 0.03 탆)) made of UBE acid by a doctor blade with a doctor blade fixed on a glass substrate. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was elevated from 30 ° C to 200 ° C over 85 minutes (heating rate 2 ° C / min), and further maintained at 200 ° C for 2 hours. The peel strength of the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.008 kN / m.

The transparent polyimide film after peeling was fixed to a metal frame made of stainless steel by using a capton tape. This was placed in an inert oven, and the oxygen concentration in the inert oven was controlled at 0.0%, and the temperature was elevated from 30 ° C to 250 ° C over 110 minutes (temperature raising rate 2 ° C / min). The film was then held at 250 DEG C for 2 hours to obtain a transparent polyimide film having a thickness of 30 mu m. The obtained transparent polyimide film had a glass transition temperature (Tg) of 258 占 폚, a total light transmittance of 87%, a haze of 3.7%, a b value of 0.9, an in-plane retardation (R0) of 80 nm and an imidization ratio of 88% The amount was 1.5% by mass.

(Comparative Example 8)

The polyimide precursor-containing solution prepared in Synthesis Example 1 was coated on a polyimide film (UPILEX 50S (50 탆, Rz = 0.03 탆)) made of UBE acid by a doctor blade with a doctor blade fixed on a glass substrate. Then, a sample consisting of a glass substrate, a support substrate, and a polyimide precursor film was placed in an inert gas oven. Thereafter, the oxygen concentration in the inner oven was controlled to 0.0%, the temperature was raised from 30 DEG C to 270 DEG C over 120 minutes (temperature raising rate 2 DEG C / min), and further maintained at 270 DEG C for 2 hours, A transparent polyimide laminate was produced. The peel strength at the interface between the support substrate and the transparent polyimide layer of the transparent polyimide laminate separated from the glass substrate was 0.039 kN / m.

The film after peeling was fixed to the metal frame made of stainless steel by using a capton tape. The oxygen concentration in the inner oven was controlled to 0.0%, and the temperature was raised from 30 ° C to 270 ° C over 120 minutes (temperature increase rate 2 ° C / min), and further maintained at 270 ° C for 2 hours To obtain a transparent polyimide film having a thickness of 30 mu m. The obtained transparent polyimide film had a glass transition temperature (Tg) of 260 占 폚, a total light transmittance of 88%, a haze of 1.5%, a b value of 0.8, an in-plane retardation (R0) of 12 nm and an imidization rate of 100% Was not detected.

As shown in Table 1, when the polyimide precursor was heated at a temperature not lower than the glass transition temperature of the obtained transparent polyimide layer (Examples 1 to 9, Reference Examples 1 to 3, Comparative Examples 2 and 6, and Comparative Example 8 ), The residual solvent amount was 1.0% by mass or less and the imidization rate was 95% or more. On the contrary, in the case of heating at a temperature lower than the glass transition temperature of the obtained transparent polyimide layer (Comparative Example 3 and Comparative Example 7), the residual solvent amount was 3.0% by mass and the imidization rate was less than 90% The imide of the mid precursor was insufficient.

Further, in the case where a polyimide film was obtained on the supporting substrate by heating to a glass transition temperature or higher (Examples 1 to 9, Reference Examples 1 to 3, and Comparative Examples 1, 2 and 6), the in-plane retardation was 10 nm or less. On the other hand, when the polyimide film was peeled off from the supporting substrate after heating at a temperature not higher than the glass transition temperature on the supporting substrate, and the polyimide film was fixed to the metal frame and further heated (Comparative Example 7) , The polyimide film was peeled off from the supporting substrate, and the polyimide film was fixed to a metal frame, and further heated to a glass transition temperature or higher (Comparative Example 8), the in-plane retardation exceeded 10 nm. If the in-plane retardation exceeds 10 nm, the use as an optical film is limited.

In the case where the supporting substrate was a polyimide film (Examples 1 to 9 and Comparative Examples 1 to 3, 7 and 8), the peel strength when the transparent polyimide layer was peeled from the supporting substrate was 0.041 kN / m or less , And the peelability of the transparent polyimide layer was good.

On the other hand, when the supporting substrate was an aluminum substrate, the peel strength when peeling the transparent polyimide layer from the supporting substrate was relatively high (0.19 kN / m) (Reference Example 1). On the other hand, even when the support substrate was made of an aluminum substrate, the peel strength was significantly lowered when the release agent was contained in the polyimide precursor-containing solution (Reference Example 2). However, if the amount of the releasing agent was too large, the polyimide precursor-containing solution could not be uniformly applied (Comparative Example 5). Further, when the release agent was contained in the polyimide precursor-containing solution using the SUS plate as the supporting substrate, the peel strength when peeling the transparent polyimide layer from the supporting substrate was low, and the peeling property was good (Reference Example 3) .

On the other hand, in the case where the supporting substrate was made of copper foil and the releasing agent was not contained in the polyimide precursor-containing solution (Comparative Example 4), the peel strength of the supporting substrate and the transparent polyimide layer was too high to peel them apart. Further, in the case where the supporting substrate was a glass substrate (Comparative Example 6), the supporting substrate and the transparent polyimide layer had high peel strength, and the transparent polyimide layer could not be peeled off unless immersed in water.

On the other hand, if the supporting substrate is an aluminum substrate or an SUS plate, the 10-point average roughness (Rz) of the surface of the supporting substrate is rough and the haze of the transparent polyimide layer formed on the supporting substrate tends to be high (Reference Examples 1 to 3 ).

In addition, when the main chain of the polyimide contained an alicyclic group, the total light transmittance was high (Examples 1 to 9, Reference Examples 1 to 3, and Comparative Examples 3 and 6 to 8). On the contrary, the transparent aromatic polyimide film (Comparative Example 1) had a low total light transmittance. Further, even when the main chain of the polyimide contained alicyclic groups, the total light transmittance was lowered when the oxygen concentration at the time of heating the polyimide precursor-containing solution exceeded 5% by volume (Comparative Example 2). At the time of heating, the polyimide is oxidized and it is presumed that the film is yellowed.

The transparent polyimide film obtained from the transparent polyimide laminate of the present invention has a high total light transmittance and a small in-plane retardation. Therefore, it can be applied to a substrate for a touch panel, a substrate for a color filter, a substrate for a liquid crystal cell, a substrate for an organic EL display, and the like, and various panel substrates of a flexible display.

1: polyimide precursor film
1 ': transparent polyimide layer
10: heating furnace
11: Support substrate
12: transparent polyimide laminate
13: Element
14: another substrate
20: dispensing device
21: Endless belt
30:

Claims (18)

A method for producing a transparent polyimide laminate comprising a support substrate and a transparent polyimide layer laminated on the support substrate,
a) applying a polyimide precursor-containing solution containing a polyimide precursor and a solvent, which are obtained by reacting a tetracarboxylic acid component and a diamine component, onto the support substrate;
b) heating the polyimide precursor film comprising the coating film of the polyimide precursor-containing solution at a temperature not lower than the glass transition temperature of the transparent polyimide layer,
The transparent polyimide layer preferably has a glass transition temperature of 260 占 폚 or higher, a total light transmittance of 80% or more, a haze of 5% or less, an absolute value of b in the L * a * b color system of 5 or less, Or less,
And a peel strength when the transparent polyimide layer is peeled from the supporting substrate is 0.005 to 0.20 kN / m. The method according to claim 1,
Wherein the supporting substrate is a flexible substrate. The method according to claim 1,
Wherein the polyimide precursor-containing solution further comprises a releasing agent. The method according to claim 1,
Wherein the oxygen concentration in the atmosphere is set to 5% by volume or less in a temperature region exceeding 200 캜 in the step b). The method according to claim 1,
And the atmosphere is decompressed in a temperature region exceeding 200 캜 in the step b). The method according to claim 1,
The step b) is a step of heating the polyimide precursor film while raising the temperature from 150 캜 or lower to higher than 200 캜,
Wherein an average temperature raising rate in a temperature range of 150 to 200 캜 in the step b) is set to 0.25 to 50 캜 / minute. The method according to claim 1,
Wherein the polyimide precursor is a polyimide precursor,
A tetracarboxylic acid component (A) comprising at least one tetracarboxylic dianhydride represented by the following formula (a)
(B) comprising at least one diamine selected from the group consisting of compounds represented by the following formulas (b-1) to (b-3)
Wherein the transparent polyimide laminate is a compound obtained by reacting a polyimide precursor with a polyimide precursor.
(A)

(In the formula (a), R ¹ represents a quadrivalent group having 4 to 27 carbon atoms, and further represents an aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aliphatic group, a monocyclic aromatic group or a condensed polycyclic aromatic group, Or a non-condensed polycyclic aliphatic group linked together by a bridging source, or a non-condensed polycyclic aromatic group in which the aromatic group is linked directly or by a bridging source)
[Formula b-1]

[Formula b-2]

[Formula b-3]

8. The method of claim 7,
Wherein the polyimide precursor has a repeating unit represented by the following formula (I)
The 1,4-bismethylene cyclohexane skeleton (X) in the formula (I) is composed of the trans-isomer represented by the formula (X1) and the isoform represented by the formula (X2)
Wherein a content ratio of the trans-isomer and a cis structure (trans-isomer + cis isomer = 100%) is 60%? Trans-isomer? 100% and 0%?
(I)

(X)

(X1)

(X2)

(Wherein R ¹⁰ represents a tetravalent group having 4 to 27 carbon atoms and further represents an aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aliphatic group, a monocyclic aromatic group or a condensed polycyclic aromatic group, Or a non-condensed polycyclic aliphatic group linked together by a bridging source, or a non-condensed polycyclic aromatic group in which the aromatic group is linked directly or by a bridging source) The method according to claim 1,
Wherein the polyimide precursor is a polyimide precursor,
A polyamic acid block composed of a repeating structural unit represented by the following formula (G)
Is a block polyimide acid imide having a polyimide block composed of a repeating structural unit represented by the following formula (H).
[Formula G]

[Formula H] &lt;

(In the formulas (G) and (H), R ⁶ and R ⁸ each independently represent a quaternary group having 4 to 27 carbon atoms, and may be an aliphatic group, a monocyclic aliphatic group, a condensed polycyclic aliphatic group, a monocyclic aromatic group, or a condensed polycyclic aromatic Or a non-condensed polycyclic aliphatic group in which the cyclic aliphatic group is linked directly or by a bridging source, or a non-condensed polycyclic aromatic group in which the aromatic group is linked directly or by a bridging group;
In formula (H), R ⁷ is a divalent group having 4 to 51 carbon atoms, and is an aliphatic group, a monocyclic aliphatic group (except for 1,4-cyclohexylene group), a condensed polycyclic aliphatic group, A condensed polycyclic aromatic group or a non-condensed polycyclic aliphatic group in which a cyclic aliphatic group is directly or indirectly linked to each other by a crosslinking source or a condensed polycyclic aromatic group in which an aromatic group is linked directly or by a crosslinking source, The method according to claim 1,
The step a) is a step of applying the polyimide precursor-containing solution onto the supporting substrate fed from the roll,
Wherein the step b) includes a step of winding the transparent polyimide laminate on a roll after heating the polyimide precursor film. A transparent polyimide laminate obtained from the production process according to claim 1. An optical film obtained by peeling a transparent polyimide layer from a support base of the transparent polyimide laminate according to claim 11. A process for producing a transparent polyimide film, which comprises a step of peeling a transparent polyimide layer from a supporting substrate of the transparent polyimide laminate according to claim 11 to obtain a transparent polyimide film. A step of forming an element on the transparent polyimide layer of the transparent polyimide laminate according to claim 11;
And a step of peeling the transparent polyimide layer after forming the element from the supporting substrate. A manufacturing method of a flexible device, comprising the step of forming an element on a transparent polyimide film obtained by the manufacturing method according to claim 11. A touch panel display obtained by the method of manufacturing a flexible device according to claim 14 or 15. A liquid crystal display obtained by the manufacturing method of a flexible device according to claim 14 or 15. An organic EL display obtained by the manufacturing method of a flexible device according to claim 14 or 15.

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