KR20180069790A - Polyimide laminate and manufacturing method thereof - Google Patents

Abstract

The present invention provides a polyimide laminate capable of suppressing warpage and facilitating separation of a resin substrate easily and a method for producing the same.
And a plurality of polyimide layers in the order of a first polyimide layer and a second polyimide layer on a support having a thermal expansion coefficient of 1-10 ppm / K, wherein a thickness of the first polyimide layer The second polyimide layer has a thickness of 5 to 30 占 퐉, and the thermal expansion coefficient of the first polyimide layer is in the range of 5 to 30 ppm / K, the glass transition temperature is not less than 300 占 폚, Wherein the first polyimide layer and the second polyimide layer are peelable at the interface, and the resin solution of the polyimide or polyimide precursor is sequentially Coating, drying, and heat treatment to form each of the above-mentioned polyimide layers.

Description

Polyimide laminate and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 of manufacturing the same, To a display device having a display portion on a resin base material (resin base material) having flexibility and a method of manufacturing the polyimide laminate.

Display devices such as liquid crystal display devices and organic EL display devices are widely used from a large display such as a television to a small display such as a cellular phone, a PC, and a smart phone. For example, in an organic EL display device, a thin film transistor (TFT) is formed on a glass substrate, an electrode, a light emitting layer, an electrode and the like are sequentially formed, and finally, a separate glass substrate, It is made by sealing.

Here, the type of the display device is not particularly limited, but includes components of a display device such as a liquid crystal display device, an organic EL display device, a display device including an electronic paper, and a color filter. In addition, it is possible to use various kinds of display devices, such as an organic EL lighting device, a touch panel device, a conductive film in which ITO or the like is laminated, a gas barrier film for preventing penetration of moisture or oxygen, Functional devices are also included. That is, the flexible device according to the present invention can be applied not only to 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 an organic EL display device, A film, a thin film transistor (TFT), a wiring layer of a liquid crystal display device, a transparent conductive layer, or the like, or a combination of two or more thereof.

By replacing the glass substrate with a resin substrate, it is possible to realize a thinner, lighter, and more flexible display device, and the use of the display device can be further widened. However, there is a problem that the resin is inferior in dimensional stability, transparency, heat resistance, moisture resistance, gas barrier properties and the like as compared with glass.

For example, Patent Document 1 discloses a polyimide useful as a plastic substrate for a flexible display and an invention related to the precursor thereof, and is a tetra (tetra Discloses that polyimides obtained by reacting various diamines with carboxylic acids are excellent in transparency. In addition, attempts have been made to reduce the weight by using a flexible resin base material instead of a glass substrate. For example, in Non-Patent Documents 1 and 2, an organic EL display device using polyimide with high transparency has been proposed .

As described above, it is known that a resin film such as polyimide is useful for a supporting substrate for a flexible display. However, since a manufacturing process of a display device is already performed using a glass substrate, most of the production facilities use a glass substrate It is designed as a premise. Therefore, it is desirable to be able to produce a display device while effectively utilizing existing production facilities.

As one example of the examination, there is a method of manufacturing a display device having a display portion on a substrate of a resin by completing a manufacturing process of a predetermined display device in the state that a resin is laminated on a glass substrate and then removing the glass substrate (See Patent Documents 2 to 3 and Non-Patent Documents 3 to 4). In the case of such a method, it becomes important to separate the resin substrate from the glass without damaging the display portion formed on the resin substrate.

That is, in Patent Document 3 and Non-Patent Document 3, after a predetermined display portion is formed on a resin substrate coated and fixed on a glass substrate, a predetermined laser beam is emitted from the glass side by a method called EPLaR (Electronics on Plastic by Laser Release) To forcefully separate the resin base material having the display portion from the glass substrate. In Patent Document 2 and Non-Patent Document 4, after a release layer is formed on a glass substrate, a polyimide layer is formed by applying a polyimide resin larger than the release layer, and a cutting line reaching the release layer is inserted The smaller polyimide film is peeled from the peeling layer.

On the other hand, when a resin is laminated on a glass substrate, warpage becomes a serious problem. In other words, since the coefficient of thermal expansion of the glass substrate is several ppm / K, the resin generally has a thermal expansion coefficient of tens of ppm / K or more. For example, the resin solution is coated on a glass substrate, A resin layer is formed, and when it is cooled to room temperature (cooling), warpage is generated. If such warping can not be suppressed, adversely affecting the formation of the display portion thereafter.

(IGZO) or a low-temperature polysilicon (LTPS) method is used for the flexible display TFT substrate process in the process using the polyimide laminate or the polyimide laminate. At this time, since the coefficient of thermal expansion of the glass substrate is several ppm / K, the resin usually has a thermal expansion coefficient of tens of ppm / K or more, so that the laminate is warped and the display portion can not be made finer have.

With respect to this point, Patent Document 3 discloses that a resin layer (b) having a thermal expansion coefficient between the support substrate and the resin film (a) is formed between the support substrate and the resin film (a) The effect of suppressing warping is not sufficient.

Patent Document 1: JP-A-2008-231327 Patent Document 2: Japanese Patent Publication No. 4834758 Patent Document 3: Japanese Patent Publication No. 5408848

Non-Patent Document 1: S. An et. " 2.8-inch WQVGA Flexible AMOLED Using Low Temperature Polysilicon TFT on Plastic Substrates ", SID2010 DIGEST, p.706 (2010) Non-Patent Document 2: Oishi et. quot; Transparent PI for flexible display ", IDW '11 FLX2 / FMC4-1 Non-Patent Document 3: E. I. Haskal et. al., " Flexible OLED Displays Made with the EPLaR Process ", Proc. Eurodisplay '07, pp.36-39 (2007) Non-Patent Document 4: Cheng-Chung Lee et. " A Novel Approach to Make Flexible Active Matrix Displays ", SID2010 DIGEST, pp.810-813 (2010)

If a predetermined display portion is formed with the resin substrate laminated on the glass substrate as described above and then the glass substrate is removed to obtain a display device, the conventional glass substrate is used as a part of the display device, The use of the display device can be further expanded by the viewpoint of thinning, lightening, and flexibility. In order to do so, it becomes important to facilitate the separation of the support body and the resin substrate represented by the glass substrate, and to solve the problem of warping in the state where the glass substrate and the resin substrate are laminated.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a polyimide laminate capable of suppressing warpage and easily separating a resin substrate. Another object of the present invention is to provide a method for producing a polyimide laminate, in which occurrence of warpage is suppressed, and separation of the resin base material is easy and simple.

Therefore, the present inventors have conducted extensive studies in order to solve these problems. As a result, the present inventors have previously proposed the invention of Japanese Patent Application No. 2014-062776, but as a result of repeated examination, it has been surprisingly found that a support having a thermal expansion coefficient Forming a first polyimide layer having a specific composition in a range of 5 to 30 ppm / K and forming a second polyimide layer having a specific composition having a thermal expansion coefficient higher than that of the first polyimide layer on the first polyimide layer, And the resin base material can be easily separated. Thus, the present invention has been accomplished.

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

(1) A laminate comprising a plurality of polyimide layers in the order of a first polyimide layer and a second polyimide layer on a support having a thermal expansion coefficient of 1 to 10 ppm / K,

The first polyimide layer has a film thickness of 1 to 50 占 퐉, a thermal expansion coefficient of the support is not less than a thermal expansion coefficient of 5 to 30 ppm / K, a glass transition temperature is not less than 300 占 폚,

The film thickness of the second polyimide layer is 5 to 30 占 퐉, the coefficient of thermal expansion is not less than the coefficient of thermal expansion of the first polyimide layer,

Wherein the first polyimide layer and the second polyimide layer are peelable at the interface thereof.

(2) The polyimide laminate of (1) above, wherein the second polyimide layer has a light transmittance (light transmittance) at a wavelength of 500 nm of 80% or more.

(3) The polyimide laminate according to (1) or (2), wherein the elastic modulus of the first polyimide layer is 3 to 11 GPa and the elastic modulus of the second polyimide layer is 3 to 5 GPa.

(4) The polyimide laminate according to any one of (1) to (3), wherein the second polyimide layer has a thermal expansion coefficient of 10 to 80 ppm / K.

(5) The polyimide laminate according to any one of (1) to (4), wherein the first polyimide layer and the second polyimide layer have a peeling strength of 1 to 100 N / m.

(6) The polyimide laminate according to any one of (1) to (5), wherein the first polyimide layer contains a polyimide having a structural unit represented by the following general formula (1).

[Chemical Formula 1]

Wherein X is an aromatic (aromatic) or alicyclic (alicyclic) divalent organic group (organic group), and R is a substituent (substituent) having 1 to 6 carbon atoms)

(7) The polyimide laminate according to any one of (1) to (6), wherein the second polyimide layer comprises a polyimide having a structural unit represented by the following general formula (2).

(2)

(Wherein Y is an aromatic or alicyclic divalent organic group)

(8) The polyimide laminate according to any one of (1) to (7) above, wherein the second polyimide layer has a light transmittance at a wavelength of 500 nm of 80% or more and retardation in the thickness direction of 200 nm or less. sieve.

(9) After a predetermined display portion is formed on the second polyimide layer, it is separated from the interface between the first polyimide layer and the second polyimide layer to form a resin base material (resin base material) layer made of the second polyimide layer The polyimide laminate according to any one of (1) to (8), wherein the polyimide laminate is used for obtaining a display device having a display portion.

(10) A method for producing a polyimide precursor, comprising the steps of applying a resin solution of polyimide or polyimide precursor onto a support having a thermal expansion coefficient of 1 to 10 ppm / K, A resin solution of a polyimide or polyimide precursor other than the resin solution is applied and dried and heat treated to form a first polyimide layer having a thermal expansion coefficient equal to or higher than the thermal expansion coefficient of the first polyimide layer To form a second polyimide layer on the second polyimide layer.

According to the present invention, it is possible to obtain a polyimide laminate in which the occurrence of warpage is suppressed and in which the second polyimide layer can be separated from the first and second polyimide layers laminated on the support. Therefore, for example, a display device provided with a display portion on a resin substrate made of a second polyimide layer can be obtained, and a predetermined display portion can be formed on the second polyimide layer with high accuracy and reliability, , It is possible to realize a thin, lightweight, and flexible display device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a state in which the first and second polyimide layers are separated from the support at the interface between the support and the first polyimide layer. FIG.
2 is a simulation view showing a state in which a warp occurs in the polyimide laminate.

First, the polyimide laminate according to the present invention comprises a support having a thermal expansion coefficient of 1-10 ppm / K. Such a support is made of an inorganic material, for example, a glass substrate having a thermal expansion coefficient of 1 to 10 ppm / K, a silicon wafer having a thermal expansion coefficient of 1 to 6 ppm / K, a silicon wafer having a thermal expansion coefficient of 1 to 10 ppm / K, silicon carbide having a coefficient of thermal expansion of 1 to 10 ppm / K, and the like. Among them, a glass substrate or a silicon wafer is suitable.

On the support, a first polyimide layer having a thermal expansion coefficient of 5 to 30 ppm / K or more and a glass transition temperature of 300 캜 or more is laminated on the support. By inserting such a first polyimide layer between the support and the second polyimide layer described later, it is possible to reliably suppress the occurrence of the warping phenomenon. Especially, even when a relatively large laminate corresponding to the fourth generation (680 x 880 mm to 730 x 920 mm) 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 to be described later. The glass transition temperature of the first polyimide layer may be 300 ° C or higher, but it is preferably 320 ° C or higher because the application range of the display device is wide.

Specifically, the coefficient of thermal expansion of the first polyimide layer is larger than that of the support, preferably 5 to 30 ppm / K, and more preferably 5 to 15 ppm / K. If the coefficient of thermal expansion is less than 5 ppm / K, the first polyimide layer itself may be retracted, which may easily peel off the glass. Also, if the coefficient of thermal expansion is larger than 30 ppm / K, the warp inhibiting effect is weakened. The first polyimide layer preferably has a modulus of elasticity of 3 to 11 GPa, preferably 5 to 10 GPa. By the combination of the first polyimide layer and the second polyimide layer, it is possible to effectively suppress the warpage of the laminate .

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

(3)

In the general formula (1), X represents an aromatic group (aromatic group) or an alicyclic group (alicyclic group) having at least one aromatic ring (aromatic ring) or alicyclic ring (Organic group), and R is a substituent (substituent) having 1 to 6 carbon atoms. Specific examples of suitable raw materials for forming the group (X) include pyromellitic acid dianhydride (PMDA), naphthalene-2,3,6,7-tetracarboxylic acid dianhydride (NTCDA) 3 ', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, etc. . Specific examples of suitable R include, for example, -CH ₃ and -CF ₃ .

Among them, when R is -CF ₃ , the peeling property at the interface between the first polyimide layer and the second polyimide layer can be enhanced, and these can be easily separated.

In addition to the structural units shown in the above general formula (1), those which can be incorporated, suitably at most 50 mol%, include structural units using general acid anhydrides and diamines. Among them, pyromellitic dianhydride (PMDA), naphthalene-2,3,6,7-tetracarboxylic acid dianhydride (NTCDA), 3,3 ', 4,4'-biphenyltetra Examples of the carboxylic acid anhydride (BPDA), cyclohexanetetracarboxylic acid dianhydride, phenylenebis (trimellitic acid monoester anhydride), 4,4'-oxydiphthalic acid dianhydride, benzophenone-3,4,3 ' Tetracarboxylic acid dianhydride, tetracarboxylic acid dianhydride, diphenylsulfone-3,4,3 ', 4'-tetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,4' - (2,2'- Fluoroisopropylidene) diphthalic acid dianhydride and the like. Examples of the diamine include m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminodiphenyl ether, 1,3-bis , 4'-diaminodiphenylsulfone, 2,2-bis (4-aminobenzyloxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 9,9-bis (4-aminophenyl) fluorene, and the like.

In the present invention, a second polyimide layer having a thermal expansion coefficient equal to or higher than the thermal expansion coefficient 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, more preferably 10 to 70 ppm / K. If the coefficient of thermal expansion is less than 10 ppm / K, the second polyimide layer alone tends to be excessively hard and is likely to be cut, which may cause deterioration in workability. Conversely, if the coefficient of thermal expansion is larger than 80 ppm / K, There is a possibility to do it. Further, from the viewpoint of more effectively suppressing the warping when the laminate is formed, the elastic modulus of the second polyimide layer is preferably 3 GPa to 5 GPa.

Generally, when the thermal expansion coefficient of polyimide is reduced, the transparency is lowered and the retardation in the thickness direction (phase difference due to difference in birefringence) is increased. Therefore, the second polyimide layer separated from the first polyimide layer may be used as a resin base material (resin base material) of a display device, a gas barrier film, or a touch panel substrate And the like. In contrast, in the present invention, the use of the second polyimide layer having a relatively large thermal expansion coefficient as described above is allowed. This is because the warpage as a laminate is suppressed by the presence of the first polyimide layer described above.

Therefore, the polyimide forming the second polyimide layer can be appropriately selected depending on the use of the polyimide laminate. Among them, in the case of using as a resin substrate having flexibility in a display device such as a liquid crystal display device, an organic EL display device, an electronic paper, a color filter, and a touch panel, A polyimide having a structural unit, and preferably a polyimide containing 50 mol% or more of the structural unit represented by the general formula (2). In addition to the structural units shown in the general formula (2), those which can be contained (suitably containing at most 50 mol%) are preferably provided with transparency, and those similar to those described in the general formula (1) . Examples of suitable acid anhydrides include pyromellitic acid dianhydride (PMDA), naphthalene-2,3,6,7-tetracarboxylic acid dianhydride (NTCDA), 3,3 ', 4,4'-biphenyltetracarboxylic acid (BPDA), cyclohexanetetracarboxylic acid dianhydride, phenylenebis (trimellitic acid monoester anhydride), 4,4'-oxydiphthalic acid dianhydride, benzophenone-3,4,3 ', 4'-tetra Carboxylic acid dianhydride, diphenylsulfone-3,4,3 ', 4'-tetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 4,4' - (2,2'-hexafluoro Cyclohexanedicarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride and the like, and the like. . Examples of the diamine include m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminodiphenyl ether, 1,3-bis , 4'-diaminodiphenylsulfone, 2,2-bis (4-aminobenzyloxyphenyl) propane, bis [4- (4-aminophenoxy) phenyl] sulfone, 9,9-bis (4-aminophenyl) fluorene, and the like.

[Chemical Formula 4]

(Wherein Y is an aromatic or alicyclic divalent organic group)

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

[Chemical Formula 5]

Among them, from the viewpoint of obtaining a second polyimide layer having a light transmittance at a wavelength of 500 nm of 80% or more and a retardation in the thickness direction of 200 nm or less,

[Chemical Formula 6]

Or the like.

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

(7)

The various polyimides as described above are obtained by imidizing a polyimide precursor (hereinafter also referred to as " polyamic acid "), but the resin solution of polyamic acid is a solution of diamine and acid dianhydride equimolar) in an organic solvent. Specifically, it can be obtained, for example, by dissolving a diamine in an organic polar solvent such as N, N-dimethylacetamide in a nitrogen stream, adding an anhydride of the tetracarboxylic acid and reacting at room temperature for about 5 hours. From the viewpoint of the uniformity of the 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 suitable molecular weight range of the first and second polyimide layers is also in 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 a polyimide or polyimide precursor is applied, dried, and heat-treated, respectively. That is, in order to obtain the polyimide laminate of the present invention, a resin solution of a polyimide or polyimide precursor is preferably applied, dried, and heat-treated on a support having a thermal expansion coefficient of 1 to 10 ppm / K, To 30 ppm / K, a resin solution of a polyimide or polyimide precursor is applied, dried, and heat-treated to form a second polyimide layer having a thermal expansion coefficient of 10 to 80 ppm / K . At this time, it is preferable to imidize the resin by the sufficient heat treatment in applying the resin solution to be the first polyimide layer on the support and heat treatment, because it facilitates the separation of the second polyimide layer. For example, it is preferable to perform a preliminary heat treatment at 90 to 130 캜 for 5 to 30 minutes for drying, and then a high-temperature heat treatment at 130 to 360 캜 for 10 to 240 minutes for imidization.

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 separation at these interfaces, the first or second polyimide layer It is preferable that at least one of the layers is formed of 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 suitably from 1 to 200 N / m, more preferably from 1 to 100 N / m, For example, a degree of separability that can be easily separated by hand. The separation surface (separation surface) of the second polyimide layer at the interface between the first polyimide layer and the second polyimide layer has a surface roughness (Ra) of 1 to 80 Nm) is maintained as it is, so that there is no case that adverse effects on the visibility of the display device are adversely affected.

In the polyimide laminate of the present invention, the thickness of the support is preferably from 0.01 to 1.0 mm, more preferably from 0.02 to 0.7 mm, and the thickness of the first polyimide layer is preferably from 1 to 50 m, Mu m, and the thickness of the second polyimide layer is preferably 5 to 30 mu m, and more preferably 10 to 20 mu m. The thickness of each of these layers affects the warp generated in the laminate, and therefore, it is preferable that the thickness falls within the above range. Here, in the present invention, the polyimide laminate can be optimized by calculating the deflection (deflection) on the basis of the following idea with respect to the laminate in which different materials are laminated.

The polyimide laminate of the present invention can be suitably used for obtaining a display device provided with a display portion on a resin substrate made of the second polyimide layer as described above. That is, after a predetermined display portion is formed 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 the display portion is formed on the second polyimide layer side. When the handleability of the resin base material (second polyimide layer) or dimensional stability is ensured in the process of manufacturing the display portion The display device is not constituted because it is eventually removed. Also in the first polyimide layer, the display device is not finally removed to constitute the display device, and even if the transparency is low, the display device is of no concern. By using such a polyimide laminate, it is possible to obtain a display device in which a predetermined display portion can be formed on the second polyimide layer with high accuracy and reliability, and a thin, lightweight, and flexible display can be obtained have. Furthermore, the polyimide laminate of the present invention can be applied to a substrate for a deposition mask or a fan-out wafer level package (FOWLP) in addition to the display device.

The display unit constituting the display device is not particularly limited. For example, in the case of an organic EL display device, an organic EL element or the like typically including a TFT, an electrode, and a light emitting layer corresponds to a display portion. In the case of a liquid crystal display device, a TFT, a driving circuit, a color filter as required, and the like are used. In addition to these, various display devices such as an electronic paper and a MEMS display, and various functional layers formed on a conventional glass substrate, correspond to parts necessary for displaying a predetermined image (moving image or image). Among them, for example, an annealing step of about 400 DEG C is generally required for the formation of a TFT, and the polyimide laminate of the present invention has heat resistance capable of withstanding such an annealing process.

Example

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

First, the meaning of the abbreviation (abbreviation) to be used in the following and the evaluation method of physical properties in the 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:? -Butyrolactone

[Light transmittance (%)]

In the polyimide film (50 mm x 50 mm), the light transmittance at 500 nm was determined with a U4000 type spectrophotometer.

[Thermal Expansion Coefficient (CTE)]

A polyimide film having a size of 3 mm x 15 mm was heated at a constant temperature raising rate (10 DEG C / min) under a load of 5.0 g with a thermomechanical analysis (TMA) apparatus at a temperature range of 30 DEG C to 280 DEG C The tensile test was carried out and the coefficient of thermal expansion (ppm / K) was measured from the elongation of the polyimide film with respect to the temperature at the time of lowering the temperature from 250 占 폚 to 100 占 폚.

[Modulus of elasticity]

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 a rate of 50 mm / min while applying a load of 10 kg. The tensile modulus (E ' Respectively.

[Measurement of curl (flexure)] [

After a first polyimide layer and a second polyimide layer were formed on a glass substrate, a laminate of 100 cm square was produced. Then, the polyimide layer surface of the second layer was placed upright and allowed to stand at 23 DEG C and 50% RH for 24 hours. After the standing, the warpage of the laminate was judged as a spacer having a thickness of 1 mm. X " indicating that the spacer enters the lower side of the laminate and "? &Quot; indicating that the spacer does not enter the lower side of the laminate without warping.

[Calculation of Curl (Simulation)]

As a calculation method, a finite deformation method is used in which a final shell distortion is balanced with a thermal deformation and its own weight, and a finite element which performs numerical computation using a shell element, Element method (see Fig. 2).

The larger the value, the more curl (bending) is likely to occur.

[Thickness direction retardation]

Retardation (thickness direction retardation: Rth) in the thickness direction of the second polyimide layer was determined using a device M-2000V manufactured by J. A. Woollam Japan Corp.

[Evaluation of laminate state quality]

The laminate obtained by applying a resin to a glass was subjected to quality evaluation by visual or manual work. &Quot; x " when the film was peeled off from the glass substrate or could not be evaluated because the film was broken due to backing, and "? &Quot;

[Peelability]

The polyimide laminate was peeled off from the edge of each side of the polyimide laminate to the surface of the second polyimide layer through the first polyimide layer vertically with a cutter knife to approximately 5 After scratching four straight lines parallel to each side with a distance of mm, the first polyimide layer and the support were peeled by hand (Fig. 1) in the peeling range divided by the scratches. Subsequently, the interface between the first polyimide layer and the second polyimide layer was similarly peeled by hand. The case of being peelable by hand was defined as "? &Quot;, and the case where peeling was not possible was defined as " x ". The peel strengths are shown in Table 3 together.

A resin solution (polyamic acid solution) for forming the first and second polyimide layers related to the polyimide laminate of the examples and the like was prepared (prepared) according to the following Synthesis Examples 1 to 7. The mass composition of the monomers in each polyamic acid solution is summarized in Table 1.

Synthesis Example 1

8.49 g of TFMB was dissolved in 85 g of GBL in a nitrogen stream while stirring in a separable flask of 100 ml. Then 5.04 g of PMDA was 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. Thereafter, the solution was stirred at room temperature for 4 hours to carry out a polymerization reaction, and was maintained for a day. Then, a viscous, colorless polyamic acid solution was obtained, and it was confirmed that a polyamic acid (A) having a high degree of polymerization was produced.

Synthesis Examples 2 to 7

A polyamic acid solution was 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 acid (resin) (B to G).

Example 1

Solvent GBL was added to the polyamide acid solution (A) obtained in Synthesis Example 1 to dilute the solution so as to have a viscosity of 3000 cP. Then, on a glass substrate having a size of 150 mm x 150 mm, a thickness of 0.7 mm and a CTE of 3.5 ppm / Using a spin coater so as to have a thickness of 14 mu m after film formation (film formation). Subsequently, heat treatment was performed at 90 占 폚 for 3 minutes, then at 110 占 폚 for 10 minutes, and preliminary drying was performed. Then, the temperature was raised from 90 DEG C to 360 DEG C over 30 minutes, and a first polyimide layer (polyimide (A)) of 150 mm x 150 mm was formed on the glass substrate.

Next, on the first polyimide layer, the polyamic acid solution (B) obtained in Synthesis Example 2 was diluted with DMAc (solvent) so as to have a viscosity of 3000 cP and then applied so as to have a film thickness after heat treatment of about 10 탆. Subsequently, heat treatment was performed at 90 占 폚 for 3 minutes, then at 110 占 폚 for 10 minutes, and preliminary drying was performed. Then, the temperature was raised from 90 DEG C to 360 DEG C over 30 minutes, and a second polyimide layer (polyimide (B)) having a size of 150 mm x 150 mm was formed to obtain a polyimide laminate according to Example 1.

The obtained polyimide laminate was subjected to various evaluations such as physical properties. The results are shown in Tables 2 and 3. (CTE), light transmittance, modulus of elasticity (modulus of elasticity) of each of the first polyimide layer (polyimide (A)) and the second polyimide layer (polyimide , The glass transition temperature (Tg), and the retardation, the polyamic acid solution obtained in Synthesis Examples 1 and 2 was separately applied to the glass substrate as described above so as to have a film thickness of about 15 탆 after heat treatment , Heated at 90 占 폚 for 3 minutes, then subjected to a heat treatment at 110 占 폚 for 10 minutes, preliminarily dried, then heated at 90 占 폚 to 360 占 폚 over 30 minutes, and thereafter peeled off from the glass substrate. And the state of the film was measured.

The curvature of curvature was also calculated by simulation, and the results are shown in Table 2. The results of the simulation were matched with the results of determination of warpage by actual measurement.

Example 2

As shown in Table 2, in the same procedure as in Example 1 except that the resin (C) obtained in Synthesis Example 3 was used as the first polyimide layer and the resin (B) obtained in Synthesis Example 2 was used as the second polyimide layer (C) / resin (B) "shown in the" layered structure "in Table 2 and Table 3 as the polyimide layered product in the following Examples and Comparative Examples Also referred to as " support / first polyimide layer / second polyimide layer "). The polyimide laminate was also measured for physical properties such as warpage. The results are also shown in Tables 2 and 3.

Example 3

As shown in Table 2, in the same procedure as in Example 1 except that the resin (G) obtained in Synthesis Example 7 was used as the first polyimide layer and the resin (B) obtained in Synthesis Example 2 was used as the second polyimide layer To obtain a polyimide laminate. The polyimide laminate was also measured for physical properties such as warpage. Simulation of the deflection was also 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 that the three-layer structure was used using the polyimide resin shown in Table 2, and physical properties such as warpage were measured. In addition, the curl amount was compared with the calculated value by the simulation.

Comparative Example 4

DMAc was added to the polyamic acid solution (B) obtained in Synthesis Example 2 to dilute the solution so as to have a viscosity of 3000 cP. Then, a film was formed on the same glass substrate as in Example 1 using a spin coater to have a thickness of about 15 탆 after heat treatment Respectively. Then, the temperature was raised from 90 DEG C to 360 DEG C over 30 minutes, and a 100 mm x 100 mm polyimide layer was formed on the glass substrate to obtain a two-layered polyimide laminate.

1: Support
2: a first polyimide layer
3: a second polyimide layer

Claims (10)

A laminate comprising a first polyimide layer and a second polyimide layer in the order of a polyimide layer on a support having a coefficient of thermal expansion (thermal expansion coefficient) of 1-10 ppm / K,
The first polyimide layer has a film thickness of 1 to 50 占 퐉, a thermal expansion coefficient of the support is not less than a thermal expansion coefficient of 5 to 30 ppm / K, a glass transition temperature is not less than 300 占 폚,
The film thickness of the second polyimide layer is 5 to 30 占 퐉, the coefficient of thermal expansion is not less than the coefficient of thermal expansion of the first polyimide layer,
Wherein the first polyimide layer and the second polyimide layer are peelable at the interface thereof.
The method according to claim 1,
And the second polyimide layer has a light transmittance (light transmittance) at a wavelength of 500 nm of 80% or more.
3. The method according to claim 1 or 2,
Wherein the first polyimide layer has a modulus of elasticity of 3 to 11 GPa and the second polyimide layer has a modulus of elasticity of 3 to 5 GPa.
4. The method according to any one of claims 1 to 3,
And the second polyimide layer has a thermal expansion coefficient of 10 to 80 ppm / K.
5. The method according to any one of claims 1 to 4,
And the peel strength of the first polyimide layer and the second polyimide layer is 1 to 100 N / m.
6. The method according to any one of claims 1 to 5,
Wherein the first polyimide layer contains a polyimide having a structural unit represented by the following general formula (1).
[Chemical Formula 1]

Wherein X is an aromatic (aromatic) or alicyclic (alicyclic) divalent organic group (organic group), and R is a substituent (substituent) having 1 to 6 carbon atoms)
7. The method according to any one of claims 1 to 6,
Wherein the second polyimide layer comprises a polyimide having a structural unit represented by the following general formula (2).
(2)

(Wherein Y is an aromatic or alicyclic divalent organic group)
8. The method according to any one of claims 1 to 7,
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. The method according to any one of claims 1 to 8,
After a predetermined display portion is formed on the second polyimide layer, the display portion is separated from the interface between the first polyimide layer and the second polyimide layer to form a display portion on the resin base (resin base) made of the second polyimide layer A polyimide laminate used for obtaining a display device.
A resin solution of a polyimide or polyimide precursor is coated on a support having a thermal expansion coefficient of 1 to 10 ppm / K, dried, and heat treated so that the thermal expansion coefficient is 5 to 30 ppm / K A polyimide or polyimide precursor resin solution different from the resin solution is applied, dried, and heat-treated to form a second polyimide layer having a thermal expansion coefficient of not less than the thermal expansion coefficient of the first polyimide layer, To form a polyimide layer.

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