JP6963504B2 - Polyimide laminate and its manufacturing method - Google Patents

Description

The present invention relates to a polyimide laminate in which a first polyimide layer and a second polyimide layer are laminated on a support and a method for producing the same. Specifically, the present invention relates to a flexible resin composed of a second polyimide layer. The present invention relates to a polyimide laminate suitable for obtaining a display device or the like having a display portion on a base material, and a method for producing the same.

Display devices such as liquid crystal displays and organic EL display devices are widely used from large displays such as televisions to small displays such as mobile phones, personal computers, and smartphones. For example, in an organic EL display device, a thin film transistor (TFT) is formed on a glass substrate, electrodes, light emitting layers, electrodes and the like are sequentially formed, and finally, the glass substrate and a multilayer thin film are separately airtightly sealed.

Here, the type of display device is not particularly limited, but includes components of a liquid crystal display device, an organic EL display device, a display device such as electronic paper, and a display device such as a color filter. In addition, the display device includes an organic EL lighting device, a touch panel device, a conductive film on which ITO and the like are laminated, a gas barrier film that prevents permeation of moisture, oxygen, and the like, and components of a flexible circuit board. Various functional devices used are also included. That is, the flexible device referred to in the present invention includes not only components such as a liquid crystal display device, an organic EL display device, and a color filter, but also an organic EL lighting device, a touch panel device, an electrode layer or a light emitting layer of the organic EL display device, and the like. It also includes one type or a combination of two or more types such as a gas barrier film, an adhesive film, a thin film transistor (TFT), a wiring layer of a liquid crystal display device, or a transparent conductive layer.

By replacing the glass substrate with a resin base material, it is possible to realize thinning, weight reduction, and flexibility, and it becomes possible to further expand the use of the display device. However, resin has a problem that it is inferior in dimensional stability, transparency, heat resistance, moisture resistance, gas barrier property, etc. as compared with glass.

For example, Patent Document 1 relates to a polyimide useful as a plastic substrate for a flexible display and an invention relating to a precursor thereof, using tetracarboxylic acids containing an alicyclic structure such as cyclohexylphenyltetracarboxylic acid. , Discloses that the polyimide reacted with various diamines has excellent transparency. In addition to this, attempts have been made to reduce the weight by using a flexible resin base material instead of the glass substrate. For example, in Non-Patent Documents 1 and 2, an organic EL display device using highly transparent polyimide is used. Has been proposed.

As described above, it is known that a resin film such as polyimide is useful as a supporting base material for a flexible display, but the manufacturing process of a display device has already been performed using a glass substrate, and the production equipment thereof. Most of them are designed on the assumption that a glass substrate is used. Therefore, it is desirable to be able to produce display devices while effectively utilizing existing production equipment.

As one of the study examples, a display unit is provided on the resin base material by completing the manufacturing process of a predetermined display device in a state where the resin is laminated on the glass substrate and then removing the glass substrate. There is a method of manufacturing a display device (see Patent Documents 2 to 3 and Non-Patent Documents 3 to 4). In the case of such a method, it is important to separate the resin base material and the glass without damaging the display portion formed on the resin base material.

That is, in Patent Document 3 and Non-Patent Document 3, after forming a predetermined display portion on the resin base material coated and fixed on the glass substrate, a method called EPLaR (Electronics on Plastic by Laser Release) process is used. A laser is irradiated from the glass side to forcibly separate the resin base material provided with the display unit from the glass substrate. Further, in Patent Document 2 and Non-Patent Document 4, after forming a release layer on a glass substrate, a polyimide resin is applied one size larger than the release layer to form a polyimide layer, and a cutting line reaching the release layer is inserted. Therefore, a slightly smaller polyimide film is peeled off from the peeling layer.

On the other hand, when the resin is laminated on the glass substrate, warpage becomes a big problem. That is, while the coefficient of thermal expansion of a glass substrate is several ppm / K, resin generally has a coefficient of thermal expansion of several tens of ppm / K or more. Therefore, for example, a resin solution is applied onto a glass substrate and heated. When it is cured by a treatment or the like to form a resin layer and allowed to cool to room temperature, warpage occurs. If such warpage cannot be suppressed, the subsequent formation of the display portion and the like will be adversely affected.

Alternatively, in the process of using the polyimide laminate, the flexible display TFT substrate process usually uses the In-Ga-Zn-O semiconductor (IGZO) or low temperature polysilicon (LTPS) method, and heats up to 350 ° C. or higher. multiply. At that time, the coefficient of thermal expansion of the glass substrate is several ppm / K, whereas the resin generally has a coefficient of thermal expansion of several tens of ppm / K or more, so that the laminated body is warped and the display unit is displayed. There is a risk that it will not be possible to miniaturize.

Regarding this point, in Patent Document 3, a resin layer (b) is provided between the support substrate and the resin film (a) so that the coefficient of thermal expansion is between the support substrate and the resin film (a). Although disclosed, the effect of suppressing warpage is not sufficient.

Japanese Unexamined Patent Publication No. 2008-231327 Japanese Patent No. 4834758 Japanese Patent No. 5408884

S. An et. al., "2.8-inch WQVGA Flexible AMOLED Using High Performance Low Temperature Polysilicon TFT on Plastic Substrates", SID2010 DIGEST, p706 (2010) Oishi et. al., "Transparent PI for flexible display", IDW'11 FLX2 / FMC4-1 E.I. Haskal et. Al. "Flexible OLED Displays Made with the EPLaR Process", Proc.Eurodisplay '07, pp.36-39 (2007) Cheng-Chung Lee et. Al. "A Novel Approach to Make Flexible Active Matrix Displays", SID10 Digest, pp.810-813 (2010)

As described above, if a predetermined display unit is provided in a state where a resin base material is laminated on a glass substrate and then the glass substrate can be removed to obtain a display device, a conventional glass substrate can be used as a part of the display device. The application of the display device can be further expanded from the viewpoint of thinning, weight reduction, flexibility, and the like. For that purpose, the support typified by the glass substrate and the resin base material can be easily separated, and the problem of warpage when the glass substrate and the resin base material are laminated is solved. It becomes important to do.

Therefore, an object of the present invention is to provide a polyimide laminate in which warpage is suppressed and the resin base material can be easily and easily separated. Another object of the present invention is to provide a method for producing a polyimide laminate in which the occurrence of warpage is suppressed and the resin base material can be easily and easily separated.

Therefore, as a result of diligent studies to solve these problems, the present inventors have previously proposed the invention according to Japanese Patent Application No. 2014-062776, but as a result of further studies, it is surprising. A first polyimide layer having a specific composition, which has a larger coefficient of thermal expansion and is in the range of 5 to 30 ppm / K, is provided on a support such as a glass substrate, and the coefficient of thermal expansion is first on the first polyimide layer. It has been found that by providing a second polyimide layer having a specific composition equal to or higher than the polyimide layer, a laminate in which the occurrence of warpage is suppressed can be obtained, and the resin base material can be easily separated. , The present invention has been completed.

That is, the gist of the present invention is as follows.
(1) A laminate having a plurality of polyimide layers in the order of a first polyimide layer and a second polyimide layer on a support having a coefficient of thermal expansion of 1 to 10 ppm / K.
The thickness of the first polyimide layer is 1 to 50 μm, the coefficient of thermal expansion is equal to or higher than the coefficient of thermal expansion of the support, 5 to 30 ppm / k, and the glass transition temperature is 300 ° C. or higher.
The thickness of the second polyimide layer is 5 to 30 μm, the coefficient of thermal expansion is equal to or greater than the coefficient of thermal expansion of the first polyimide layer, and the first polyimide layer and the second polyimide layer are at the interface thereof. A polyimide laminate characterized by being peelable.

（式中、Ｘは芳香族又は脂環式の４価の有機基であり、Ｒは炭素数１〜６の置換基である。）
（７）第２のポリイミド層が、下記一般式（２）で表される構造単位を有するポリイミドを含む上記（１）〜（６）のいずれかのポリイミド積層体。

（式中、Ｙは芳香族又は脂環式の４価の有機基である。）
（８）第２のポリイミド層が、波長５００ｎｍにおける光透過率が８０％以上であり、かつ、厚さ方向のリタデーションが２００ｎｍ以下である上記（１）〜（７）のいずれかのポリイミド積層体。
（９）第２のポリイミド層上に所定の表示部を形成した後、第１のポリイミド層と第２のポリイミド層との界面で分離して、第２のポリイミド層からなる樹脂基材上に表示部を備えた表示装置を得るのに用いられる上記（１）〜（８）のいずれかのポリイミド積層体。(2) The second polyimide layer is the polyimide laminate according to (1) above, which has a light transmittance of 80% or more at a wavelength of 500 nm.
(3) The polyimide laminate according to (1) or (2) above, wherein the first polyimide layer has an elastic modulus of 3 to 11 GPa, and the second polyimide layer has an elastic modulus of 3 to 5 GPa.
(4) The polyimide laminate according to any one of (1) to (3) above, wherein the coefficient of thermal expansion of the second polyimide layer is 10 to 80 ppm / K.
(5) The polyimide laminate according to any one of (1) to (4) above, wherein the peel strength between the first polyimide layer and the second polyimide layer is 1 to 100 N / m.
(6) The polyimide laminate according to any one of (1) to (5) above, wherein the first polyimide layer contains a polyimide having a structural unit represented by the following general formula (1).

(In the formula, X is an aromatic or alicyclic tetravalent organic group, and R is a substituent having 1 to 6 carbon atoms.)
(7) The polyimide laminate according to any one of (1) to (6) above, wherein the second polyimide layer contains a polyimide having a structural unit represented by the following general formula (2).

(In the formula, Y is an aromatic or alicyclic tetravalent organic group.)
(8) The polyimide laminate according to any one of (1) to (7) above, wherein the second polyimide layer has a light transmittance of 80% or more at a wavelength of 500 nm and a retardation in the thickness direction of 200 nm or less. ..
(9) After forming a predetermined display portion on the second polyimide layer, it is separated at the interface between the first polyimide layer and the second polyimide layer, and is placed on a resin base material composed of the second polyimide layer. The polyimide laminate according to any one of (1) to (8) above, which is used to obtain a display device provided with a display unit.

(10) A resin solution of polyimide or polyimide precursor is applied on a support having a coefficient of thermal expansion of 1 to 10 ppm / K, dried, and heat-treated so that the coefficient of thermal expansion is equal to or greater than the coefficient of thermal expansion of the support, 5 After forming the first polyimide layer of 30 ppm / K, a resin solution of polyimide or polyimide precursor different from the resin solution is applied, dried, and heat-treated to thermally expand the first polyimide layer having a coefficient of thermal expansion. A method for producing a polyimide laminate, which comprises forming a second polyimide layer having a coefficient or more.

According to the present invention, it is possible to obtain a polyimide laminate in which the occurrence of warpage is suppressed and the second polyimide layer can be separated from the first and second polyimide layers laminated on the support. Therefore, for example, in obtaining a display device having a display unit on a resin base material made of a second polyimide layer, a predetermined display unit can be accurately and reliably formed on the second polyimide layer. At the same time, the display device can be made thinner, lighter, and more flexible.

It is sectional drawing which shows the mode that the 1st and 2nd polyimide layers are peeled off from a support at the interface between a support and a 1st polyimide layer. It is a simulation figure which shows the state which the warp occurs in the polyimide laminated body.

First, the polyimide laminate in the present invention includes a support having a coefficient of thermal expansion of 1 to 10 ppm / K. Such a support is made of an inorganic material, and for example, a glass substrate having a coefficient of thermal expansion of 1 to 10 ppm / K, a silicon wafer having a coefficient of thermal expansion of 1 to 6 ppm / K, and a silicon wafer having a coefficient of thermal expansion of 1 to 6 ppm / K are generally used. Stainless steel having a coefficient of 1 to 10 ppm / K, silicon carbide having a coefficient of thermal expansion of 1 to 10 ppm / K, and the like can be mentioned, and among them, a glass substrate or a silicon wafer is preferable.

Further, a first polyimide layer having a coefficient of thermal expansion of 5 to 30 ppm / K or more and a glass transition temperature of 300 ° C. or more is laminated on the support. By interposing such a first polyimide layer between the support and the second polyimide layer described later, the occurrence of warpage can be reliably suppressed. In particular, even when a relatively large laminated body corresponding to the fourth generation (680 × 880 mm to 730 × 920 mm) or later of the so-called glass substrate is used, the effect of suppressing warpage can be sufficiently obtained. In addition, the presence of the first polyimide layer can increase the degree of freedom in designing the second polyimide layer, which will be described later. The glass transition temperature of the first polyimide layer may be 300 ° C. or higher, but preferably 320 ° C. or higher for the reason that the applicable range of the display device is expanded.

Specifically, the coefficient of thermal expansion of the first polyimide layer is larger than that of the support, and is preferably 5 to 30 ppm / K, preferably 5 to 15 ppm / K. If the coefficient of thermal expansion is less than 5 ppm / K, the first polyimide layer itself becomes brittle and may easily peel off from the glass. Further, when the coefficient of thermal expansion becomes larger than 30 ppm / K, the warp suppressing effect becomes weak. The elastic modulus of the first polyimide layer is preferably 3 to 11 GPa, preferably 5 to 10 GPa, and when a laminate is formed by combining such a first polyimide layer and a second polyimide layer. Warp can be effectively suppressed.

The means for obtaining the first polyimide layer is not particularly limited, and one of them is to form the first polyimide layer with a polyimide having a structural unit represented by the following general formula (1). Preferably, it is a polyimide containing 50 mol% or more of the structural unit represented by the following general formula (1).

Here, X in the general formula (1) is an aromatic group or an alicyclic group, and is a tetravalent organic group having one or more aromatic rings or alicyclics, and R is a carbon number 1 to 6. Substituent of. Among these, suitable specific examples of raw materials for forming the group X include, for example, pyromellitic acid dianhydride (PMDA) and naphthalene-2,3,6,7-tetracarboxylic acid dianhydride (NTCDA). ), 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic Acid dianhydride and the like can be mentioned. Moreover, as a preferable specific example of R, for example, -CH ₃ , -CF _{3, and the} like can be mentioned.

Among them, when R is -CF ₃ , the peelability at the interface between the first polyimide layer and the second polyimide layer can be enhanced, and the separation of these can be facilitated.

A general acid anhydride and a diamine were used for those that can be contained in addition to the structural unit represented by the above general formula (1), preferably those that can contain up to 50 mol%. Structural units can be mentioned. Among them, the acid anhydrides preferably used are pyromellitic dianhydride (PMDA), naphthalene-2,3,6,7-tetracarboxylic hydride (NTCDA), 3,3', 4,4. '-Biphenyltetracarboxylic acid dianhydride (BPDA), cyclohexanetetracarboxylic acid dianhydride, phenylenebis (trimeritic acid monoester anhydride), 4,4'-oxydiphthalic acid dianhydride, benzophenone-3,4, 3', 4'-Tetracarboxylic Acid Dianhydride, Diphenylsulfone-3,4,3', 4'-Tetracarboxylic Acid Dianhydride, 2,3,6,7-Naphthalene Tetracarboxylic Acid Dianhydride, 4 , 4'-(2,2'-hexafluoroisopropyridene) diphthalate dianhydride and the like. On the other hand, as diamines, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminodiphenyl ether, 1,3-bis (4-aminophenoxy) benzene, 4,4'-diamino Diphenyl sulfone, 2,2-bis (4-aminobenzyloxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 4,4'-diaminobenzanilide, 9,9-bis (4-amino) Phenyl) Fluorene and the like.

Further, in the present invention, a second polyimide layer having a coefficient of thermal expansion equal to or higher than the coefficient of thermal expansion of the first polyimide layer is laminated on the first polyimide layer. Specifically, the coefficient of thermal expansion of the second polyimide layer is preferably 10 to 80 ppm / K, preferably 10 to 70 ppm / K. If the coefficient of thermal expansion is less than 10 ppm / K, the second polyimide layer alone is too hard and may be easily cut, resulting in poor workability. On the contrary, if it is larger than 80 ppm / K, the effect of suppressing warpage becomes small. Warpage may occur. Further, from the viewpoint of more effectively suppressing the warp when formed into a laminated body, the elastic modulus of the second polyimide layer is preferably 3 to 5 GPa.

In general, when the coefficient of thermal expansion of polyimide becomes small, the transparency decreases and the retardation in the thickness direction (phase difference due to the difference in birefringence) increases. Therefore, the second polyimide layer separated from the first polyimide layer is unsuitable when it is considered to be used as a resin base material of a display device, a gas barrier film, a touch panel substrate, or the like. On the other hand, in the present invention, as described above, the use of the second polyimide layer having a relatively large coefficient of thermal expansion is permitted. This is because the presence of the first polyimide layer described above suppresses warpage as a laminated body.

（式中、Ｙは芳香族又は脂環式の４価の有機基である。）Therefore, the polyimide forming the second polyimide layer can be appropriately selected depending on the use of the polyimide laminate. In particular, when it is used as a flexible resin base material in display devices such as liquid crystal displays, organic EL display devices, electronic papers, color filters, and touch panels, it is represented by the following general formula (2). A polyimide having a structural unit can be mentioned, and a polyimide containing 50 mol% or more of the structural unit represented by the general formula (2) is preferable. It should be noted that those that can be included in addition to the structural units represented by the general formula (2) (preferably those containing a maximum of 50 mol%) are preferably those having transparency, and the general formula is used. Examples thereof are the same as those described in (1). Suitable acid anhydrides include pyromellitic dianhydride (PMDA), naphthalene-2,3,6,7-tetracarboxylic hydride (NTCDA), 3,3', 4,4'-. Biphenyltetracarboxylic acid dianhydride (BPDA), cyclohexanetetracarboxylic acid dianhydride, phenylenebis (trimeritic acid monoester anhydride), 4,4'-oxydiphthalic acid dianhydride, benzophenone-3,4,3' , 4'-Tetracarboxylic dianhydride, Diphenylsulfone-3,4,3', 4'-Tetracarboxylic acid dianhydride, 2,3,6,7-Naphthalene tetracarboxylic dianhydride, 4,4 '-(2,2'-Hexafluoroisopropylidene) diphthalic acid dianhydride, 1,4-cyclohexanedicarboxylic acid, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5 -Cyclohexanetetracarboxylic acid dianhydride and the like. On the other hand, as diamines, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminodiphenyl ether, 1,3-bis (4-aminophenoxy) benzene, 4,4'-diamino Diphenyl sulfone, 2,2-bis (4-aminobenzyloxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 4,4'-diaminobenzanilide, 9,9-bis (4-amino) Phenyl) Fluorene and the like.

(In the formula, Y is an aromatic or alicyclic tetravalent organic group.)

Here, Y in the general formula (2) is preferably any one represented by the following formula (3).

のいずれかであるのがよい。Above all, from the viewpoint of obtaining a second polyimide layer having a light transmittance of 80% or more at a wavelength of 500 nm and a retardation in the thickness direction of 200 nm or less, it is preferable.

It should be one of.

Most preferably, the second polyimide layer is formed of the polyimide represented by the following formula (4).

Various polyimides as described above are obtained by imidizing a polyimide precursor (hereinafter, also referred to as "polyamic acid"), but a resin solution of polyamic acid is substantially composed of diamine and acid dianhydride which are raw materials. It can be obtained by using an equimolar amount of polyimide and reacting it in an organic solvent. Specifically, for example, it can be obtained by dissolving diamine in an organic polar solvent such as N, N-dimethylacetamide under a nitrogen stream, adding tetracarboxylic dianhydride, and reacting at room temperature for about 5 hours. can. Here, from the viewpoint of uniform film thickness at the time of coating and the mechanical strength of the obtained polyimide, the weight average molecular weight (Mw) of the polyamic acid is preferably about 10,000 to 300,000. The preferred molecular weight range of the first and second polyimide layers is also the same molecular weight range as the polyamic acid.

The first and second polyimide layers in the present invention are preferably obtained by a so-called casting method in which a resin solution of polyimide or a polyimide precursor is applied, dried, and heat-treated, respectively. .. That is, in obtaining the polyimide laminate of the present invention, preferably, a resin solution of polyimide or a polyimide precursor is applied and dried on a support having a coefficient of thermal expansion of 1 to 10 ppm / K, and heat-treated to heat the polyimide laminate. After forming the first polyimide layer having an expansion coefficient of 5 to 30 ppm / K, a resin solution of polyimide or a polyimide precursor is applied, dried, and heat-treated to treat a second polyimide layer having a coefficient of thermal expansion of 10 to 80 ppm / K. Form a polyimide layer. At that time, when the resin solution to be the first polyimide layer is applied on the support and imidized by sufficient heat treatment when heat-treating, in order to facilitate the separation of the second polyimide layer. desirable. For example, after performing a preliminary heat treatment at 90 to 130 ° C. for about 5 to 30 minutes for drying or the like, a high temperature heat treatment for about 10 to 240 minutes at 130 to 360 ° C. is further performed for imidization. Is preferable.

The polyimide laminate thus obtained can be separated at the interface between the first polyimide layer and the second polyimide layer, but in order to facilitate the separation at these interfaces, it is preferable to use the first polyimide layer. It is preferable that at least one of the first or second polyimide layer is formed from a fluorine-containing polyimide having a fluorine atom in the polyimide structure. By using such a fluorine-containing polyimide, the peel strength between the first polyimide layer and the second polyimide layer can be preferably 1 to 200 N / m, preferably 1 to 100 N / m. Therefore, for example, it has a separability that can be easily peeled off by human hands. Further, the surface roughness (generally, surface roughness Ra = about 1 to 80 nm) obtained by the casting method is maintained as it is on the separation surface of the second polyimide layer at the interface between the first polyimide layer and the second polyimide layer. Therefore, the visibility of the display device is not adversely affected.

Further, in the polyimide laminated body of the present invention, the thickness of the support is preferably 0.01 to 1.0 mm, preferably 0.02 to 0.7 mm, and the thickness of the first polyimide layer is 1 to 50 μm. The thickness of the second polyimide layer is preferably 5 to 30 μm, preferably 10 to 20 μm. Since the thickness of each of these layers also affects the warpage generated in the laminated body, it is preferable to keep the thickness within the above range. Here, in the present invention, it is possible to optimize the polyimide laminated body by calculating the warp deformation (warp amount) of the laminated board in which different materials are laminated based on the following idea. ..

Further, as described above, the polyimide laminate of the present invention can be suitably used for obtaining a display device having a display unit on a resin base material composed of a second polyimide layer. That is, after forming a predetermined display portion on the second polyimide layer in the polyimide laminate, it may be separated at the interface between the first polyimide layer and the second polyimide layer. Here, the support serves as a pedestal when forming the display portion on the second polyimide layer side, and the handleability of the resin base material (second polyimide layer) in the manufacturing process of the display portion is improved. Although dimensional stability and the like can be ensured, they are not finally removed to form a display device. Similarly, the first polyimide layer is not finally removed to form a display device, and it does not matter if the first polyimide layer is inferior in transparency. By using such a polyimide laminate, a predetermined display unit can be accurately and surely formed on the second polyimide layer, and a thin, lightweight, and flexible display device can be obtained. Can be done. Further, the polyimide laminate of the present invention can be applied to a vapor deposition mask and a substrate for a fan-out wafer level package (FOWLP) in addition to the above display device.

The display unit constituting the display device is not particularly limited. For example, in the case of an organic EL display device, a TFT, an electrode, an organic EL element including a light emitting layer, or the like typically corresponds to the display unit. Further, in the case of a liquid crystal display device, it is a TFT, a drive circuit, a color filter or the like if necessary. In addition to these, various functional layers conventionally formed on a glass substrate, including various display devices such as electronic paper and MEMS displays, are used to project a predetermined image (moving image or image). The necessary parts correspond to the display unit. Of these, for example, the formation of a TFT generally requires an annealing step of about 400 ° C., and the polyimide laminate in the present invention has heat resistance that can withstand such an annealing step.

Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples. The present invention is not limited to these contents.

First, the meanings of the abbreviations used below and the evaluation method of physical properties, etc. in Examples and the like are shown.
・ PMDA: pyromellitic acid dianhydride ・ BPDA: 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride ・ 6FDA: 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane Dianhydride ・ AAPBZ: 5-amino-2- (4-aminophenyl) benzoimidazole ・ BAPP: 2,2'-bis (4-aminophenoxyphenyl) propane ・ TFMB: 2,2'-bis (trifluoromethyl) )-4,4'-Diaminobiphenyl / DMAc: N, N-dimethylacetamide / GBL: γ-butyl lactone

[Light transmittance (%)]
The light transmittance of a polyimide film (50 mm × 50 mm) at 500 nm was determined with a U4000 type spectrophotometer.

[Coefficient of thermal expansion (CTE)]
A tensile test of a 3 mm x 15 mm size polyimide film in a temperature range of 30 ° C to 280 ° C at a constant temperature rise rate (10 ° C / min) while applying a load of 5.0 g using a thermomechanical analysis (TMA) device. The coefficient of thermal expansion (ppm / K) was measured from the amount of elongation of the polyimide film with respect to the temperature when the temperature was lowered from 250 ° C. to 100 ° C.

[Elastic modulus]
Using a tension tester, a polyimide film having a width of 12.4 mm and a length of 160 mm was subjected to a tensile test at 50 mm / min while applying a load of 10 kg, and a tensile elastic modulus (E') at 25 ° C. was determined.

[Measurement of curl (warp)]
After forming the first polyimide layer and the second polyimide layer on the glass substrate, a 100 cm square laminate was prepared. Then, the polyimide layer surface of the second layer was turned up, and the mixture was allowed to stand at 23 ° C. and 50% RH for 24 hours. After standing, the warp of the laminated body was determined by a spacer having a thickness of 1 mm. That is, the one in which the spacer enters the lower side of the laminated body is marked with "x" with warp, and the one in which the spacer does not enter the lower side of the laminated body is marked with "○" without warping.

[Calculation of curl (warp) (simulation)]
As a calculation method, a finite element method was used in which the final warp deformation in a state where the thermal deformation and its own weight were balanced was discreteized using a laminated shell element and numerically calculated by a computer (see FIG. 2).
The larger the value, the more likely it is that curl (warp) will occur.

[Thickness direction retardation]
The retardation (thickness direction phase difference: Rth) in the thickness direction of the second polyimide layer was determined using the apparatus M-2000V manufactured by JE Woolam Japan.

[Laminated state quality evaluation]
The quality of the laminate obtained by coating the glass with resin was visually and manually evaluated. When the film was peeled off from the glass substrate or the film was too brittle to be evaluated, it was evaluated as "x", and when there was no particular problem in appearance, it was evaluated as "○".

[Peelability]
Approximately 5 mm from the end of each side of the polyimide laminate so that it penetrates the first polyimide layer with a cutter knife perpendicular to the surface of the second polyimide layer of the polyimide laminate and reaches the surface of the glass substrate. After opening and making four straight cuts parallel to each side, the first polyimide layer and the support were manually peeled for the peeling range separated by the cuts (FIG. 1). Then, the interface between the first polyimide layer and the second polyimide layer was peeled off by hand in the same manner. If it can be peeled off by hand, it is marked with "○", and if it cannot be peeled off, it is marked with "x". The peel strength is also shown in Table 3.

According to the following Synthesis Examples 1 to 7, resin solutions (polyamic acid solutions) for forming the first and second polyimide layers related to the polyimide laminates of Examples and the like were prepared. Table 1 summarizes the mass composition of the monomers in each polyamic acid solution.

Synthesis example 1
TFMB: 8.49 g was dissolved in 85 g of GBL of solvent with stirring in a 100 ml separable flask under a nitrogen stream. PMDA: 5.04 g was then added to this solution. After 10 minutes, 1.47 g of acid anhydride 6FDA was added. The molar ratio of acid anhydride to diamine was 0.998. Then, the solution was stirred at room temperature for 4 hours to carry out a polymerization reaction and kept for 24 hours. Then, it was confirmed that a viscous colorless polyamic acid solution was obtained and a polyamic acid A having a high degree of polymerization was produced.

Synthesis Examples 2-7
Polyamic acid solutions were prepared in the same manner as in Synthesis Example 1 except that the acid anhydride and diamine were changed to the mass compositions shown in Table 1, to obtain polyamic acids (resins) B to G.

Example 1
Solvent GBL is added to the polyamic acid solution A obtained in Synthesis Example 1 to dilute it so that the viscosity becomes 3000 cP, and then the size is 150 mm × 150 mm, the thickness is 0.7 mm, and the CTE is 3.5 ppm /. It was applied onto a K glass substrate using a spin coater so that the thickness after film formation was 14 μm. Subsequently, heat treatment was performed at 90 ° C. for 3 minutes and then at 110 ° C. for 10 minutes to perform pre-drying. Then, the temperature was raised from 90 ° C. to 360 ° C. over 30 minutes to form a first polyimide layer (polyimide A) having a size of 150 mm × 150 mm on the glass substrate.

Next, on the first polyimide layer, the polyamic acid solution B obtained in Synthesis Example 2 is diluted with DMAc (solvent) so that the viscosity becomes 3000 cP, and then the film thickness after heat treatment becomes about 10 μm. Was applied to. Subsequently, heat treatment was performed at 90 ° C. for 3 minutes and then at 110 ° C. for 10 minutes to perform pre-drying. Then, the temperature was raised from 90 ° C. to 360 ° C. over 30 minutes to form a second polyimide layer (polyimide B) having a size of 150 mm × 150 mm to obtain a polyimide laminate according to Example 1.

The obtained polyimide laminate was evaluated in various ways such as physical properties. The results are shown in Tables 2 and 3. Here, regarding the first polyimide layer (polyimide A) and the second polyimide layer (polyimide B) in this polyimide laminated body, the thermal expansion coefficient (CTE), light transmission rate, elasticity, and glass transition temperature (Tg), respectively. ) And the polyimide are separately applied to the same glass substrate as above so that the polyamic acid solutions obtained in Synthesis Examples 1 and 2 have a film thickness of about 15 μm after heat treatment. , 90 ° C for 3 minutes, then 110 ° C for 10 minutes, pre-drying, then raising the temperature from 90 ° C to 360 ° C over 30 minutes, and then peeling from the glass substrate. It was measured in the state of the polyimide film obtained.
A simulation calculation was also performed for the amount of warpage (curl), and the results are also shown in Table 2. The result of the simulation was consistent with the result of the warp judgment by the actual measurement.

Example 2
As shown in Table 2, the same as in Example 1 except that the resin C obtained in Synthesis Example 3 is used as the first polyimide layer and the resin B obtained in Synthesis Example 2 is used as the second polyimide layer. A polyimide laminate was obtained by the procedure (a polyimide laminate composed of "glass / resin C / resin B" shown in "Laminate composition" in Tables 2 and 3, and the same applies to the following Examples and Comparative Examples. In this order, "support / first polyimide layer / second polyimide layer" is shown). Physical properties such as warpage were also measured for this polyimide laminate. The results are also shown in Tables 2 and 3.

Example 3
As shown in Table 2, the same as in Example 1 except that the resin G obtained in Synthesis Example 7 is used as the first polyimide layer and the resin B obtained in Synthesis Example 2 is used as the second polyimide layer. A polyimide laminate was obtained by the procedure. For this polyimide laminate, physical properties such as warpage were measured, and the amount of warpage was also simulated and evaluated. The results are also shown in Tables 2 and 3.

Comparative Examples 1 to 3
A polyimide laminate was prepared by the same procedure as in Example 1 except for the three-layer structure using the polyimide resin shown in Table 2, and the physical properties such as warpage were measured. At the same time, the amount of warpage (curl) was compared with the value calculated by the simulation.

Comparative Example 4
DMAc was added to the polyamic acid solution B obtained in Synthesis Example 2, diluted to a viscosity of 3000 cP, and then the film thickness after heat treatment was increased on the same glass substrate as in Example 1 using a spin coater. It was applied so as to be about 15 μm. Then, the temperature was raised from 90 ° C. to 360 ° C. over 30 minutes to form a polyimide layer of 100 mm × 100 mm on the glass substrate to obtain a polyimide laminate having a two-layer structure.

1 Support 2 First polyimide layer 3 Second polyimide layer

Claims (8)

A laminate having a plurality of polyimide layers in the order of a first polyimide layer and a second polyimide layer on a support having a thickness of 0.01 to 1.0 mm and a coefficient of thermal expansion of 1 to 10 ppm / K.
The thickness of the first polyimide layer is 5 to 50 μm, the coefficient of thermal expansion is equal to or higher than the coefficient of thermal expansion of the support, 5 to 30 ppm / K, the glass transition temperature is 300 ° C. or higher, and the elastic modulus is 3 to 3 to. Being 11 GPa,
The thickness of the second polyimide layer is 5 to 30 μm, the coefficient of thermal expansion is equal to or greater than the coefficient of thermal expansion of the first polyimide layer, 10 to 80 ppm / K , and the first polyimide layer and the second polyimide are used. The layer is a polyimide laminate characterized by being peelable at its interface. The polyimide laminate according to claim 1, wherein the second polyimide layer has a light transmittance of 80% or more at a wavelength of 500 nm. The polyimide laminate according to claim 1 or 2 , wherein the peel strength between the first polyimide layer and the second polyimide layer is 1 to 100 N / m. The polyimide laminate according to any one of claims 1 to 3 , wherein the first polyimide layer contains a polyimide having a structural unit represented by the following general formula (1).

(In the formula, X is an aromatic or alicyclic tetravalent organic group, and R is a substituent having 1 to 6 carbon atoms.) The polyimide laminate according to any one of claims 1 to 4 , wherein the second polyimide layer contains a polyimide having a structural unit represented by the following general formula (2).

(In the formula, Y is an aromatic or alicyclic tetravalent organic group.) The second polyimide layer has a light transmittance of 80% or more at a wavelength of 500 nm and
The polyimide laminate according to any one of claims 1 to 5 , wherein the retardation in the thickness direction is 200 nm or less. After forming a predetermined display portion on the second polyimide layer, the display portion is separated at the interface between the first polyimide layer and the second polyimide layer, and the display portion is formed on the resin base material composed of the second polyimide layer. The polyimide laminate according to any one of claims 1 to 6 , which is used to obtain a display device provided. The method for producing a polyimide laminate according to claim 1, wherein a resin solution of polyimide or a polyimide precursor is applied onto a support, dried, and heat-treated to form a first polyimide layer. the resin solution different polyimide or polyimide precursor is applied and dried to the resin solution, the production method of the polyimide laminate, and forming a second polyimide layer by heat treatment.

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