JP2019143043A - Polyimide film for forming display device, polyimide laminate, and display device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film for forming a display device in which warpage is suppressed and there is no anisotropy of thermal expansion coefficient in the longitudinal direction and the width direction. SOLUTION: It consists of a single layer or a plurality of polyimide layers, (a) the thickness is in the range of 3 μm to 50 μm, (b) the thermal expansion coefficient is 10 ppm / K or less, (c) 23 Keep the convex surface at the center of the polyimide film of 50 mm square after humidity conditioning for 20 hours under the condition of ℃ and humidity of 50%, and keep it in contact with the flat surface. When the average warpage amount is 10 mm or less, (d) the difference between the thermal expansion coefficient (CTE-MD) in the longitudinal (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is A polyimide film for forming a display device that satisfies ± 3 ppm / K or less. [Selection figure] None

Description

  The present invention relates to a polyimide film for forming a display device and a polyimide laminate useful as a resin substrate or the like for forming the display device, a display device using these, and a method for manufacturing the same.

  Display devices such as liquid crystal display devices and organic EL display devices are used for various display applications such as large displays such as televisions and small displays such as mobile phones, personal computers, and smartphones. As a typical display device, there is an organic EL display device. For example, in this organic EL display device, a thin film transistor (hereinafter referred to as TFT) is formed on a glass substrate which is a supporting base, and an electrode, a light emitting layer, and an electrode Are sequentially formed and finally hermetically sealed with a glass substrate or a multilayer thin film.

  These constituent members are laminates in which various functional layers are formed on a glass substrate. By replacing this glass substrate with a resin substrate, it is possible to make a component using a conventional glass substrate thinner, lighter, curved, and flexible. Using this, it is expected to obtain a flexible device such as a flexible display. On the other hand, since the resin is inferior in dimensional stability, transparency, heat resistance, moisture resistance, film strength and the like as compared with glass, various studies have been made.

  In patent document 1, after forming an EL element on the 2nd polyimide layer of the laminated body formed by laminating | stacking a 1st polyimide layer and a 2nd polyimide layer on a glass base material, separating a 1st polyimide layer. Has proposed a display device having an EL element on a polyimide substrate made of a second polyimide layer. However, the warp in the polyimide base material after being separated from the first polyimide layer is not taken into consideration, and measures for suppressing the warp have not been studied.

  On the other hand, although it is a technique regarding circuit board materials, such as a flexible circuit board, in patent document 2, the polyimide by which the film curl after high temperature processing was reduced by using the polyimide which has diamino diphenyl ethers and phenylenediamine in a principal chain is used. Films have been proposed, but the dimensional accuracy is not sufficient.

  Similarly, regarding a circuit board material, Patent Document 3 proposes a polyimide film in which a dimensional change is reduced during high-temperature processing by controlling in-plane retardation of the polyimide film.

International Publication WO2014 / 050933 Pamphlet International Publication WO2006 / 114901 Pamphlet JP 2017-200799 A

  An object of the present invention is to provide a polyimide film for forming a display device, in which warpage is suppressed and there is no anisotropy of the thermal expansion coefficient in the longitudinal direction and the width direction. Another object of the present invention is to provide a polyimide laminate in which the occurrence of warpage is suppressed and the resin substrate can be easily and easily separated.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by controlling the thickness and thermal expansion coefficient of the polyimide film, and have completed the present invention.

That is, the polyimide film for forming a display device of the present invention comprises a single layer or a plurality of polyimide layers. And the polyimide film for display apparatus formation of this invention has the following conditions (a)-(d);
(A) The thickness is in the range of 3 μm or more and 50 μm or less;
(B) the coefficient of thermal expansion is 10 ppm / K or less;
(C) Standing at a temperature of 23 ° C. and a humidity of 50% so that the convex surface at the center of the polyimide film of 50 mm square after humidity conditioning for 20 hours is in contact with the flat surface, and calculating the average value of the four corners When the average warpage amount is used, the average warpage amount is 10 mm or less;
(D) The difference between the thermal expansion coefficient (CTE-MD) in the longitudinal (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is ± 3 ppm / K or less;
It is characterized by satisfying.

In addition to the above conditions (a) to (d), the polyimide film for forming a display device of the present invention,
(E) The value of in-plane retardation (RO) is in the range of 1 nm to 50 nm;
It may satisfy.

In the polyimide film for forming a display device of the present invention, the polyimide layer is a single-layer first polyimide layer having the lowest thermal expansion coefficient and a single-layer or multiple-layer second layer laminated on one side of the polyimide layer. It may consist of a polyimide layer. The thermal expansion coefficient (CTE1) of the first polyimide layer and the thermal expansion coefficient (CTE2) of the second polyimide layer are expressed by the following formula (1);
1 ppm / K <(CTE2-CTE1) ≦ 10 ppm / K (1)
It may satisfy.

  In the polyimide film for forming a display device of the present invention, the second polyimide layer may be a single layer.

The polyimide laminate of the present invention is a polyimide laminate comprising a release polyimide film and a polyimide film directly laminated on the release polyimide film. And as for the polyimide laminated body of this invention, the said polyimide film has the following conditions (a)-(d);
(A) The thickness is in the range of 3 μm or more and 50 μm or less;
(B) the coefficient of thermal expansion is 10 ppm / K or less;
(C) Standing at a temperature of 23 ° C. and a humidity of 50% so that the convex surface at the center of the polyimide film of 50 mm square after humidity conditioning for 20 hours is in contact with the flat surface, and calculating the average value of the four corners When the average warpage amount is used, the average warpage amount is 10 mm or less;
(D) The difference between the thermal expansion coefficient (CTE-MD) in the longitudinal (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is ± 3 ppm / K or less;
It is characterized by satisfying.

In the polyimide laminate of the present invention, the polyimide film is in addition to the conditions (a) to (d),
(E) The value of in-plane retardation (RO) is in the range of 1 nm to 50 nm;
It may satisfy.

The polyimide laminate of the present invention comprises a single-layer first polyimide layer and a single layer or a plurality of second polyimide layers laminated on one side of the first polyimide layer, and The first polyimide layer may be in a position in contact with the release polyimide film. The polyimide laminate of the present invention has a thermal expansion coefficient (CTE1) of the first polyimide layer and a thermal expansion coefficient (CTE2) of the second polyimide layer of the following formula (1);
1 ppm / K <(CTE2-CTE1) ≦ 10 ppm / K (1)
It may satisfy.

  In the polyimide laminate of the present invention, the second polyimide layer may be a single layer.

The manufacturing method of the display apparatus of this invention is a manufacturing method of the display apparatus provided with the display part on the polyimide base material. And the manufacturing method of the display apparatus of this invention laminated | stacks the polyimide laminated body in any one of the said, and a support body so that the surface by the side of the said release polyimide film and one surface of the said support body may contact | connect. And a process of
Forming a predetermined display part on the polyimide film in the polyimide laminate,
Separating the release polyimide film and the polyimide film at their boundary surfaces, and obtaining a display device including the display unit on the polyimide film as the polyimide substrate;
It is characterized by including.

The display device of the present invention, a polyimide base material comprising the polyimide film for forming a display device according to any one of the above,
A display unit formed on the polyimide substrate;
It has.

  Since the polyimide film for forming a display device of the present invention is a film that is suppressed in warpage and has no anisotropy using a low thermal expansion polyimide, it is high in a display device using this as a resin substrate (polyimide substrate). Dimensional stability accuracy can be realized. Moreover, since the polyimide film for forming a display device of the present invention is excellent in handling properties and can reduce dimensional changes during processing, it can be suitably used as a resin substrate for forming a display device. .

It is sectional drawing which shows the structure of the polyimide laminated body which concerns on one embodiment of this invention. It is explanatory drawing which shows the main processes in the manufacturing method of the display apparatus which concerns on one embodiment of this invention.

  Next, an embodiment of the present invention will be described.

[Polyimide film for display device formation]
The polyimide film for forming a display device according to an embodiment of the present invention is a polyimide film composed of a single layer or a plurality of polyimide layers, and satisfies the following conditions (a) to (d). In the present specification, “polyimide film” is simply referred to as “polyimide film for display device formation” and “polyimide film” (polyimide film 200) in a polyimide laminate to be described later.

(A) The thickness is in the range of 3 to 50 μm.
In order to control the thermal expansion coefficient, the thickness of the polyimide film of the present embodiment is in the range of 3 to 50 μm, preferably in the range of 10 to 30 μm, more preferably in the range of 15 to 25 μm. If the thickness of the polyimide film of the present embodiment is less than 3 μm, it may be difficult to handle the manufacturing process due to a decrease in electrical insulation and handling, and if it exceeds 50 μm, it becomes difficult to control warpage. The thermal expansion coefficient tends to increase.

(B) The coefficient of thermal expansion is 10 ppm / K or less.
The thermal expansion coefficient of the polyimide film of the present embodiment is in the range of 10 ppm / K or less, preferably in the range of 7 ppm / K or less in order to reduce the dimensional change. When the thermal expansion coefficient exceeds 10 ppm / K, a dimensional change is not reduced and a problem such as misalignment of the display element may occur when a display device based on the polyimide film of the present invention is manufactured.

(C) Convex surface of the central portion of a 50 mm square polyimide film after conditioning for 20 hours at 23 ° C. and a humidity of 50% (here, “convex surface” is a generally gently bent polyimide film fragment, (Meaning the surface on the outer peripheral side of the bend) is placed so as to be in contact with a flat surface, and the average value of the four corners is taken as the average amount of warpage, the average amount of warpage is 10 mm or less.
The average amount of warpage of the polyimide film of the present embodiment is the improvement in handling properties when manufacturing a display device using the polyimide film of the present embodiment as a base material, and the displacement of the display element due to floating during processing In order to prevent this, a range of 10 mm or less, preferably a range of 5 mm or less is good.

(D) The difference between the thermal expansion coefficient (CTE-MD) in the longitudinal (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is ± 3 ppm / K or less.
The polyimide film of this embodiment is a difference between CTE-MD and CTE-TD in order to reduce dimensional change during processing when manufacturing a display device using the polyimide film of this embodiment as a base material. Is in the range of ± 3 ppm / K or less, preferably in the range of ± 1 ppm / K or less.

  Moreover, the polyimide film according to an embodiment of the present invention preferably satisfies the following condition (e) in addition to the above conditions (a) to (d).

(E) The value of in-plane retardation (RO) is in the range of 1 nm to 50 nm.
The polyimide film of this embodiment has an in-plane retardation (RO) value in the range of 1 nm to 50 nm, preferably in the range of 1 nm to 20 nm, more preferably in the range of 1 nm to 15 nm.

  In addition, the polyimide film according to an embodiment of the present invention is preferably a polyimide film composed of a plurality of polyimide layers.

When the polyimide film according to an embodiment of the present invention includes a plurality of polyimide layers, the polyimide layer is laminated on one side of the first polyimide layer having the lowest thermal expansion coefficient and the first polyimide layer. A single polyimide layer or a plurality of second polyimide layers,
The thermal expansion coefficient (CTE1) of the first polyimide layer and the thermal expansion coefficient (CTE2) of the second polyimide layer are expressed by the following formula (1):
1 ppm / K <(CTE2-CTE1) ≦ 10 ppm / K (1)
Within the range is good. By changing the thermal expansion coefficient in the thickness direction of the polyimide film, it is possible to prevent the retardation (ROL) in the thickness direction from decreasing and to reduce the average warpage. The difference between CTE1 and CTE2 (CTE2-CTE1) is preferably in the range of 2 ppm / K to 10 ppm / K, and more preferably in the range of 2 ppm / K to 7 ppm / K.

<Form of polyimide film>
The polyimide film of the present embodiment is not particularly limited as long as it satisfies the conditions (a) to (d) as described above, and may be a film (sheet) made of an insulating resin. It may be a film of an insulating resin laminated on a substrate such as a resin sheet such as a foil, a glass plate, a polyimide film, a polyamide film, or a polyester film.

<Filler>
The polyimide film of this Embodiment may contain an inorganic filler as needed. Specific examples include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride. These may be used alone or in combination of two or more.

<Polyimide>
The polyimide film of the present embodiment has a polyimide layer made of polyimide and consists of a single layer or a plurality of layers. Here, when the polyimide layer is composed of a plurality of layers, a single first polyimide layer having the lowest thermal expansion coefficient and a second layer composed of a single layer or a plurality of layers laminated on one side of the first polyimide layer. The polyimide layer may be included. In this specification, when the “first polyimide layer” and the “second polyimide layer” are not distinguished, they are simply referred to as “polyimide layer”.

  The polyimide which comprises a polyimide layer is obtained by imidating the polyamic acid obtained by making tetracarboxylic dianhydride and diamine react. Therefore, in the polyimide film of the present embodiment, the polyimide constituting the polyimide layer contains a tetracarboxylic acid residue derived from tetracarboxylic dianhydride and a diamine residue derived from diamine. In the present invention, the tetracarboxylic acid residue means a tetravalent group derived from tetracarboxylic dianhydride, and the diamine residue means a divalent group derived from a diamine compound. Represents that.

  Hereinafter, specific examples of polyimide used in the present embodiment will be understood by describing acid anhydrides and diamines.

  Examples of tetracarboxylic acid residues contained in polyimide include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride. Preferred examples include tetracarboxylic acid residues derived from products. Among these, a tetracarboxylic acid residue derived from BPDA (hereinafter also referred to as BPDA residue) tends to form an ordered structure, and the amount of change in in-plane retardation (RO) under a high temperature environment is small. This is particularly preferable. Moreover, although the BPDA residue can provide the self-supporting property of the gel film as the polyamic acid of the polyimide precursor, it tends to increase CTE after imidization. From such a viewpoint, the BPDA residue is preferably in the range of 3 to 70 mol%, more preferably in the range of 5 to 60 mol%, with respect to all tetracarboxylic acid residues contained in the polyimide.

  Preferred examples of the tetracarboxylic acid residue other than the BPDA residue contained in the polyimide include a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue). . The PMDA residue is preferably in the range of 30 to 97 mol%, more preferably in the range of 40 to 95 mol%, based on all tetracarboxylic acid residues contained in the polyimide. Although PMDA residue is arbitrary, it is a residue which plays a role of control of a thermal expansion coefficient and control of a glass transition temperature.

  Other tetracarboxylic acid residues include, for example, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 2,3 ′, 3,4 ′ -Biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-, 2,3,3', 4'- or 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2, , 3 ′, 3,4′-diphenyl ether tetracarboxylic dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, 3,3 ″, 4,4 ″-, 2,3,3 '', 4 ''-or 2,2 '', 3,3 ''-p-terphenyltetracarboxylic dianhydride, 2,2-bis (2,3- or 3,4-dicarboxyphenyl) -Propane dianhydride, bis (2,3- or 3.4-dicarboxyphenyl) methane dianhydride, bis (2,3- or 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1- Bis (2,3- or 3,4-dicarbo Xylphenyl) ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7- Anthracene tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6- Naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2, 3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid Dianhydride 2,3,6,7- (or 1,4,5,8-) tetrachloronaphthalene-1,4,5,8- (or 2,3,6,7-) tetracarboxylic acid Nothing 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1 , 2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene- Tetracarboxylics derived from aromatic tetracarboxylic dianhydrides such as 2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis (2,3-dicarboxyphenoxy) diphenylmethane dianhydride An acid residue is mentioned.

  In tetracarboxylic acid residues contained in polyimide, 2,3 ′, 3,4′-diphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 4, Tetracarboxylic acid residues derived from tetracarboxylic dianhydride of 4'-oxydiphthalic anhydride and 2,3 ', 3,4'-diphenyltetracarboxylic dianhydride are included in non-thermoplastic polyimides Preferably it is 20 mol parts or less with respect to 100 mol parts of all the tetracarboxylic acid residues, More preferably, 15 mol parts or less are good. When these tetracarboxylic acid residues exceed 20 mole parts with respect to all tetracarboxylic acid residues contained in the non-thermoplastic polyimide, the orientation of the molecule is lowered, and it is difficult to control in-plane retardation (RO). Become.

  In the polyimide film of the present embodiment, the diamine residue contained in the polyimide is, for example, a diamine residue derived from a diamine compound represented by the following general formula (A1) (hereinafter referred to as “A1 residue”). Are preferred).

  In the above formula (A1), Y is independently a hydrogen atom, a monovalent hydrocarbon group having 1 to 3 carbon atoms which may be substituted with a halogen atom or a phenyl group, or an alkoxy group having 1 to 3 carbon atoms, or An alkenyl group, n represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4; Here, “independently” means that in the above formula (A1), a plurality of substituents Y and integers p and q may be the same or different.

  The A1 residue is easy to form an ordered structure and promotes the orientation in the in-plane direction of the molecular chain, so that in-plane retardation can be suppressed. From such a point of view, the A1 residue is preferably 20 mol% or more, more preferably 50 mol% or more, still more preferably in the range of 70 to 99 mol% with respect to all diamine residues contained in the polyimide. Good.

  Moreover, as A1 residue, the diamine residue represented, for example by following General formula (1) is mentioned preferably.

In the general formula (1), R ₁ and R ₂ are each independently an alkyl group having 1 to 3 carbon atoms which may be substituted with a halogen atom or a phenyl group, or an alkoxy group having 1 to 3 carbon atoms, or An alkenyl group having 2 to 3 carbon atoms is shown.

  The diamine residue represented by the general formula (1) tends to form an ordered structure, and can particularly advantageously suppress the amount of change in in-plane retardation (RO) under a high temperature environment. From such a viewpoint, the diamine residue represented by the general formula (1) is preferably 20 mol% or more, more preferably 50 mol% or more, and still more preferably based on the total diamine residues contained in the polyimide. The range of 60 to 90 mol% is preferable.

  Preferable specific examples of the diamine residue represented by the general formula (1) include 2,2′-dimethyl-4,4′-diaminobiphenyl (m-TB) and 2,2′-diethyl-4,4 ′. -Diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2 2,2′-n-propyl-4,4′-diaminobiphenyl (m-NPB), 2,2′-divinyl-4,4′-diaminobiphenyl (VAB), 4,4′-diaminobiphenyl, 4,4 Examples include diamine residues derived from diamine compounds such as' -diamino-2,2'-bis (trifluoromethyl) biphenyl (TFMB). Among these, in particular, 2,2′-dimethyl-4,4′-diaminobiphenyl (m-TB) tends to form an ordered structure and reduces the amount of change in in-plane retardation (RO) in a high temperature environment. This is particularly preferable.

  Preferred examples of the diamine residue other than the diamine residue represented by the general formula (1) include diamine residues derived from p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA) and the like. More preferred is a diamine residue derived from p-PDA (hereinafter also referred to as PDA residue). The PDA residue is preferably in the range of 0 to 80 mol%, more preferably in the range of 0 to 50 mol%, based on all diamine residues contained in the polyimide. The PDA residue is optional, but is a residue that plays a role in controlling the thermal expansion coefficient and the glass transition temperature.

In the present specification, the “diamine compound” may have a hydrogen atom in two terminal amino groups substituted, for example, —NR ₃ R ₄ (where R ₃ and R ₄ are independently alkyl Meaning an arbitrary substituent such as a group).

  Moreover, in order to improve the elongation and bending resistance in the case of a polyimide film, the polyimide is at least one selected from the group consisting of diamine residues represented by the following general formulas (2) to (4). It preferably contains a diamine residue.

In the above formula (2), R ₅ and R ₆ are each independently a hydrogen atom, a halogen atom, an alkyl group that may be substituted with a halogen atom having 1 to 4 carbon atoms, or a halogen atom having 1 to 4 carbon atoms. Or an alkenyl group that may be substituted with a halogen atom having 2 to 4 carbon atoms, and X independently represents —O—, —S—, —CH ₂ —, —CH (CH ₃ )-, -C (CH ₃ ) _2- , -CO-, -COO-, -SO _2- , -NH- or -NHCO- represents a divalent group, and m and n are each independently 1 Represents an integer of ~ 4.

In the above formula (3), R ₅ , R ₆ and R ₇ are each independently a hydrogen atom, a halogen atom, or an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, or a carbon number having 1 to 4 Represents an alkoxy group that may be substituted with a halogen atom, or an alkenyl group that may be substituted with a halogen atom having 2 to 4 carbon atoms, and X independently represents —O—, —S—, —CH ₂ —, — A divalent group selected from CH (CH ₃ ) —, —C (CH ₃ ) ₂ —, —CO—, —COO—, —SO ₂ —, —NH— or —NHCO—; o independently represents an integer of 1 to 4.

In the above formula (4), R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom, a halogen atom, or an alkyl group which may be substituted with a C 1-4 halogen atom, or a carbon number. 1 represents an alkoxy group that may be substituted with 1 to 4 halogen atoms or an alkenyl group that may be substituted with 2 to 4 carbon atoms, and X ₁ and X ₂ each independently represent a single bond, —O— , —S—, —CH ₂ —, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —, —CO—, —COO—, —SO ₂ —, —NH— or —NHCO—. A divalent group is shown, except that both X ₁ and X ₂ are single bonds, and m, n, o and p each independently represent an integer of 1 to 4.

Note that “independently” means that in one of the above formulas (2) to (4) or (2) to (4), a plurality of linking groups X, linking groups X ₁ , X ₂ , Means that the substituents R ₅ , R ₆ , R ₇ , R ₈ , and integers m, n, o, and p may be the same or different.

  Since the diamine residue represented by the general formulas (2) to (4) has a flexible portion, flexibility can be imparted to the polyimide film. Here, since the diamine residue represented by the general formulas (3) and (4) has 3 or 4 benzene rings, the benzene residue is added to the benzene ring in order to suppress an increase in the coefficient of thermal expansion (CTE). The terminal group to be bonded is preferably in the para position. Moreover, from the viewpoint of suppressing an increase in the coefficient of thermal expansion (CTE) while imparting flexibility to the polyimide film, the diamine residues represented by the general formulas (2) to (4) are all diamine residues contained in the polyimide. Preferably it is in the range of 3 to 40 mol%, more preferably in the range of 3 to 30 mol%, based on the group. When the diamine residue represented by the general formulas (2) to (4) is less than 3 mol%, the elongation in the case of a film is lowered, and the bending resistance and the like are lowered. On the other hand, when it exceeds 40 mol%, the orientation of the molecule is lowered and it is difficult to reduce CTE.

In the general formula (2), preferred examples of the groups R ₅ and R ₆ include a hydrogen atom or an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms or a carbon atom. The alkenyl group of several 2-3 can be mentioned. In the general formula (2), preferred examples of the linking group X include —O—, —S—, —CH ₂ —, —CH (CH ₃ ) —, —SO ₂ — or —CO—. Can do. Preferable specific examples of the diamine residue represented by the general formula (2) include 4,4′-diaminodiphenyl ether (4,4′-DAPE), 3,3′-diaminodiphenyl ether, and 3,4′-diaminodiphenyl ether. 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3,4'-diaminodiphenyl Propane, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4 '-Diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, etc. It includes diamine residues derived from a diamine compound.

In the general formula (3), preferred examples of the groups R ₅ , R ₆ and R ₇ include a hydrogen atom or an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms. Group or an alkenyl group having 2 to 3 carbon atoms. In the general formula (3), preferred examples of the linking group X include —O—, —S—, —CH ₂ —, —CH (CH ₃ ) —, —SO ₂ — or —CO—. Can do. Preferable specific examples of the diamine residue represented by the general formula (3) include 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,4-bis (4-aminophenoxy) benzene ( TPE-Q), bis (4-aminophenoxy) -2,5-di-tert-butylbenzene (DTBAB), 4,4-bis (4-aminophenoxy) benzophenone (BAPK), 1,3-bis [2 Examples include diamine residues derived from diamine compounds such as-(4-aminophenyl) -2-propyl] benzene 1,4-bis [2- (4-aminophenyl) -2-propyl] benzene.

In the general formula (4), preferred examples of the groups R ₅ , R ₆ , R ₇ and R ₈ include a hydrogen atom or an alkyl group which may be substituted with a halogen atom having 1 to 4 carbon atoms, or 1 to 1 carbon atoms. 3 alkoxy groups or alkenyl groups having 2 to 3 carbon atoms. In the general formula (4), preferred examples of the linking groups X ₁ and X ₂ include a single bond, —O—, —S—, —CH ₂ —, —CH (CH ₃ ) —, —SO ₂ —. Or -CO- can be mentioned. However, from the viewpoint of providing a bent portion, the case where both of the linking groups X ₁ and X ₂ are single bonds is excluded. Preferable specific examples of the diamine residue represented by the general formula (4) include 4,4′-bis (4-aminophenoxy) biphenyl (BAPB), 2,2′-bis [4- (4-aminophenoxy). ) Phenyl] propane (BAPP), 2,2′-bis [4- (4-aminophenoxy) phenyl] ether (BAPE), bis [4- (4-aminophenoxy) phenyl] sulfone and other diamine compounds. Diamine residues.

  Examples of other diamine residues include 2,2-bis- [4- (3-aminophenoxy) phenyl] propane, bis [4- (3-aminophenoxy) phenyl] sulfone, and bis [4- (3- Aminophenoxy) biphenyl, bis [1- (3-aminophenoxy)] biphenyl, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy)] benzophenone, 9,9-bis [4- (3-aminophenoxy) phenyl] fluorene, 2,2-bis- [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2, 2-bis- [4- (3-aminophenoxy) phenyl] hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'- Methylenedi-2,6-xylidine, 4,4'-methylene-2,6 -Diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3 ''-diamino-p-terphenyl, 4,4 '-[1, 4-phenylenebis (1-methylethylidene)] bisaniline, 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisaniline, bis (p-aminocyclohexyl) methane, bis (p-β-amino -t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5- Aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5- Diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diamino Examples thereof include diamine residues derived from aromatic diamine compounds such as pyridine, 2,5-diamino-1,3,4-oxadiazole and piperazine.

  In polyimide, by selecting the types of tetracarboxylic acid residues and diamine residues, and the molar ratios when two or more tetracarboxylic acid residues or diamine residues are applied, the thermal expansion coefficient, storage The elastic modulus, tensile elastic modulus, etc. can be controlled. In addition, in a non-thermoplastic polyimide, when it has a plurality of polyimide structural units, it may exist as a block or randomly, but it is random from the viewpoint of suppressing variation in in-plane retardation (RO). It is preferable that it exists in.

<Manufacturing method of polyimide film>
As an aspect of the manufacturing method of the polyimide film of this embodiment, for example, [1] A method of manufacturing a polyimide film by imidizing after applying and drying a polyamic acid solution on a supporting substrate, [2] supporting group There is a method of producing a polyimide film by applying a polyamic acid solution to a material and drying it, then peeling the polyamic acid gel film from a supporting substrate and imidizing it. Moreover, when the polyimide film of this Embodiment is a polyimide film which consists of a polyimide layer of multiple layers, as an aspect of the manufacturing method, for example, [3] A polyamic acid solution is apply | coated and dried to a support base material. A method of performing imidization after repeating this several times (casting method), [4] A method of performing imidization after applying and drying polyamic acid in multiple layers simultaneously by multilayer extrusion (multilayer extrusion method) ) And the like.

The method of [1] is, for example, the following steps 1a to 1c;
(1a) applying a polyamic acid solution to a supporting substrate and drying;
(1b) forming a polyimide layer by heat-treating polyamic acid on a supporting substrate and imidizing;
(1c) a step of obtaining a polyimide film by separating the support substrate and the polyimide layer;
Can be included.

The method of [2] is, for example, the following steps 2a to 2c;
(2a) applying a polyamic acid solution to a supporting substrate and drying;
(2b) a step of separating the support substrate and the polyamic acid gel film;
(2c) a step of obtaining a polyimide film by heat-treating the polyamic acid gel film and imidizing;
Can be included.

  The method [3] is the same as the method [1] or [2] except that the step 1a or the step 2a is repeated a plurality of times to form a polyamic acid laminated structure on the support substrate. It can be carried out in the same manner as the method [1] or [2].

  The method [4] is the same as the method [1] except that in step 1a of the method [2] or step 2a of the method [2], the laminated structure of polyamic acid is simultaneously applied and dried by multilayer extrusion. It can be carried out in the same manner as the method [1] or [2].

  It is preferable that the polyimide film manufactured by this invention completes the imidation of a polyamic acid on a support base material. Since the polyamic acid resin layer is imidized in a state of being fixed to the support substrate, it is possible to suppress the expansion and contraction change of the polyimide layer in the imidization process, and to maintain the thickness and dimensional accuracy of the polyimide film.

  Further, the polyamic acid gel film on the support substrate is separated, and the polyamic acid gel film is subjected to in-plane retardation (RO) by imidization simultaneously or continuously with uniaxial stretching or biaxial stretching. You may control. At this time, in order to control RO more precisely and highly, it is preferable to appropriately adjust conditions such as the stretching operation and the heating rate during imidization, the imidation completion temperature, and the load.

<Synthesis of polyimide>
In general, a polyimide can be produced by reacting a tetracarboxylic dianhydride and a diamine compound in a solvent to form a polyamic acid and then ring-closing with heating. For example, a precursor of polyimide by dissolving a tetracarboxylic dianhydride and a diamine compound in an organic solvent in an approximately equimolar amount, and stirring and polymerizing at a temperature in the range of 0 to 100 ° C. for 30 minutes to 24 hours. A polyamic acid is obtained. In the reaction, the reaction components are dissolved so that the precursor to be produced is in the range of 5 to 30% by weight, preferably in the range of 10 to 20% by weight in the organic solvent. Examples of the organic solvent used in the polymerization reaction include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N, N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -Butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and further, aromatic hydrocarbons such as xylene and toluene can be used in combination. In addition, the amount of such organic solvent used is not particularly limited, but it should be adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. Is preferred.

  The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but can be concentrated, diluted or replaced with another organic solvent as necessary. Moreover, since polyamic acid is generally excellent in solvent solubility, it is advantageously used. The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If it is out of this range, defects such as uneven thickness and streaks are likely to occur in the film during the coating operation by a coater or the like. The method for imidizing the polyamic acid is not particularly limited, and for example, heat treatment in which heating is performed in the solvent at a temperature within the range of 80 to 400 ° C. for 1 to 24 hours is suitably employed.

[Polyimide laminate]
A polyimide laminate 300 according to an embodiment of the present invention includes a layer made of a release polyimide film 100 and a layer made of a polyimide film 200 directly laminated on the release polyimide film 100, as shown in FIG. And. The polyimide film 200 can be suitably used as, for example, a resin substrate (polyimide substrate) in an electronic device such as a display device. That is, the polyimide film 200 can be used for, for example, a resin substrate or a resin base material in an electronic device.

<Release polyimide film>
The release polyimide film 100 is preferably such that the polyimide film 200 can be easily separated from the boundary surface. Preferably, the adhesive strength at the interface between the release polyimide film 100 and the polyimide film 200 is 1 N / m or more and 500 N / m or less, more preferably 2 N / m or more and 300 N / m or less, and even more preferably 10 N / m or more. By being 200 N / m or less, it has a separability enough to be easily peeled off by human hands.

  The thermal expansion coefficient of the release polyimide film 100 is preferably 25 ppm / K or less and more preferably 10 ppm / K or less in order to suppress warpage. Moreover, from the viewpoint of the peelability and heat resistance of the polyimide film 200, the glass transition temperature (Tg) of the release polyimide film 100 is preferably 300 ° C. or higher. As a specific example, for example, polyimide having a structural unit composed of biphenyltetracarboxylic dianhydride and phenylenediamine as a main component can be cited. Examples of commercially available products include Upilex-S manufactured by Ube Industries, Kapton manufactured by Toray DuPont, and Xenomax manufactured by Toyobo.

  The thickness of the release polyimide film 100 is not particularly limited, but is preferably 10 μm or more from the viewpoint of production stability and handling properties. The upper limit of the thickness is not particularly limited, but is preferably 100 μm or less in consideration of cost and the like.

  In order to adjust the adhesive strength with the polyimide film 200, the release polyimide film 100 may be subjected to a modification treatment such as plasma treatment on the surface of the release polyimide film 100 to increase the wettability of the surface state. Alternatively, heat treatment may be performed to reduce the wettability of the surface state.

<Method for producing polyimide laminate>
As an aspect of the manufacturing method of the polyimide laminated body 300 of this Embodiment, [1] After apply | coating and drying the solution of a polyamic acid to the mold release polyimide film 100, it imidizes and forms the layer of the polyimide film 200 There is a method for producing the polyimide laminate 300, and [2] there is a method for producing the polyimide laminate 300 by pressure-bonding the polyimide film 200 to the release polyimide film 100. The production method of [1] is employed. It is preferable. In the method [1], since the expansion / contraction change of the polyimide film 200 is suppressed during the imidization process, the thickness and dimensions of the polyimide film 200 can be controlled with high accuracy. In order to improve the releasability of the release polyimide film 100 and the polyimide film 200, the relation between the glass transition temperature Tg ₂ of the glass transition temperature Tg ₁ and the polyimide film 200, for example, release the polyimide film 100, Tg _{It is} preferable that ₁ ≦ Tg ₂ ≦ Tg ₁ + 30 ° C., and the upper limit T _max of the heat treatment temperature during imidization is Tg ₁ ≦ T _max ≦ Tg ₁ + 30 ° C.

[Manufacturing method of display device]
FIG. 2 is a schematic process diagram in the manufacturing method of the display device of the present embodiment. In the manufacturing method of the display device, a substrate provided with the polyimide laminate 300 on the support 400 in advance is used. And the predetermined | prescribed display part 500 is formed in the polyimide film 200 side of the polyimide laminated body 300, Then, it isolate | separates in the boundary surface of the mold release polyimide film 100 and the polyimide film 200, The resin substrate ( The display device 600 including the display unit 500 on the polyimide base material can be manufactured.

  More specifically, first, a support 400 serving as a base in the manufacturing process of the display unit 500 in a liquid crystal display device, an organic EL display device, an LED element, or the like is prepared. The support 400 is not particularly limited as long as it has chemical strength and mechanical strength that can withstand heat history, atmosphere, and the like in the manufacturing process of the display unit 500 that forms various display devices. Although a glass substrate and a metal substrate are illustrated, it is preferable to use a glass substrate. As the glass substrate, for example, those generally used in the production of organic EL display devices can be used. The glass substrate serves as a pedestal when the display unit 500 is formed on the polyimide base material. In the manufacturing process of the display unit 500, it is possible to ensure the handleability and dimensional stability of the polyimide base material. Even if it exists, it is finally removed and the display device 600 is not configured.

  The polyimide laminate 300 is provided on the support 400. As the method, the polyimide laminate 300 may be directly adhered to the support 400 and laminated, or an arbitrary adhesive layer may be formed. You may make it laminate. FIG. 2A shows a state in which the polyimide laminate 300 is directly laminated on the support 400. The laminate shown in FIG. 2A may be produced by a method in which a polyimide laminate 300 produced in advance and a support 400 are bonded together, or the release polyimide film 100 is formed on the support 400 by a casting method. The polyimide or its precursor resin solution that constitutes the polyimide, and the polyimide or its precursor resin solution that constitutes the polyimide film 200 may be sequentially applied and heated.

  FIG. 2B shows a state in which the display unit 500 is formed on the surface of the polyimide film 200 in the polyimide laminate 300. The display unit 500 includes, for example, a TFT element, an organic EL element, a color filter, an LED, a transistor, an electron emitting element, electronic ink, an electrophoretic element, GLV (grating light valve), and MEMS (micro electro mechanical system). Display elements used, DMD (digital micromirror device), DMS (digital micro shutter), IMOD (interferometric modulation) element, electrowetting element, piezoelectric ceramic display, display element using carbon nanotube, etc. May be included.

  In FIG. 2C, after forming the display unit 500, the polyimide film 200 is used as a base material by separating at the boundary surface between the release polyimide film 100 and the polyimide film 200, and the display unit 500 is provided thereon. The display device 600 obtained is shown. In addition, after forming the display part 500, you may remove | separate in the boundary surface of the mold release polyimide film 100 and the polyimide film 200 after removing the support body 400 first.

  As described above, the display device 600 including the display unit 500 on the resin substrate (polyimide substrate) made of the polyimide film 200 can be manufactured.

  The features of the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to the examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Measurement of coefficient of thermal expansion (CTE)]
Using a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA), a polyimide film having a size of 3 mm × 20 mm was heated from 30 ° C. to 250 ° C. at a constant heating rate while applying a load of 5.0 g. Furthermore, after maintaining at that temperature for 10 minutes, it was cooled at a rate of 5 ° C./minute, and an average thermal expansion coefficient (thermal expansion coefficient) from 250 ° C. to 100 ° C. was determined. CTE-MD is a thermal expansion coefficient in the longitudinal (MD) direction, and CTE-TD is a thermal expansion coefficient in the width (TD) direction.

[Measurement of in-plane retardation (RO)]
Using a birefringence meter (manufactured by Photonic Lattice, trade name: wide-range birefringence evaluation system WPA-100, measurement area: MD: 200 mm × TD: 150 mm), in-plane direction retardation of a predetermined sample is obtained. It was. The incident angle is 0 ° and the measurement wavelength is 543 nm.

[Measurement of retardation in thickness direction (ROL)]
A sample prepared by thin-film cutting of a polyimide film with an ultramicrotome was used to measure retardation in the thickness direction using a microscopic birefringence meter (trade name: PI-micro) manufactured by Photonic Lattice. The incident angle is 0 ° and the measurement wavelength is 520 nm.

[Measurement of warpage]
The polyimide film was warped by adjusting the polyimide film having a size of 50 mm × 50 mm at 23 ° C. and a humidity of 50% for 20 hours, and then allowing the convex surface at the center of the sample to be in contact with a flat surface. The distance of lifting from the stationary surface of the corner was measured, and the average value was taken as the average warpage.

[Evaluation of adhesive strength]
The adhesive strength was evaluated by measuring 180 ° peel strength by a T-peeling test method on a sample cut into a strip shape having a width of 25 mm using a strograph R-1 manufactured by Toyo Seiki Seisakusho.

Abbreviations used in Examples and Comparative Examples indicate the following compounds.
m-TB: 2,2′-dimethyl-4,4′-diaminobiphenyl DAPE: 4,4′-diaminodiphenyl ether PMDA: pyromellitic dianhydride BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic Acid dianhydride DMAc: N, N-dimethylacetamide

(Synthesis Example 1)
Under a nitrogen stream, in a 300 ml separable flask, 2.550 g DAPE (0.0127 mol), 15.333 g m-TB (0.0721 mol) and a solids concentration of 15 wt% and 212.5 g of DMAc was added and dissolved by stirring at room temperature. Next, 6.0847 g of BPDA (0.0207 mol) and 13.532 g of PMDA (0.0620 mol) were added, and then the polymerization reaction was continued for 3 hours at room temperature to prepare a polyamic acid solution a. did.

  Next, the polyamic acid solution a was uniformly applied onto a stainless support substrate so that the thickness after curing was about 25 μm, and then dried by heating at 130 ° C. Furthermore, stepwise heat treatment was performed from 130 ° C. to 360 ° C. to complete imidization, and a resin film 1 (CTE; 7.6 ppm / K) was prepared.

(Synthesis Example 2)
Under a nitrogen stream, 1.188 g DAPE (0.0059 mol), 16.740 g m-TB (0.0787 mol) and a solids concentration of 15 wt% in a 300 ml separable flask and 212.5 g of DMAc was added and dissolved by stirring at room temperature. Next, 6.071 g of BPDA (0.0206 mol) and 13.502 g of PMDA (0.0618 mol) were added, and then the polymerization reaction was continued for 3 hours at room temperature to prepare a polyamic acid solution b. did.

  Next, the polyamic acid solution b was uniformly applied on a stainless support substrate so that the thickness after curing was about 25 μm, and then dried at 130 ° C. by heating. Furthermore, stepwise heat treatment was performed from 130 ° C. to 360 ° C. to complete imidization, and a resin film 2 (CTE; 3.9 ppm / K) was prepared.

(Synthesis Example 3)
Under a nitrogen stream, in a 300 ml separable flask, 0.862 g DAPE (0.0043 mol), 17.381 g m-TB (0.0817 mol) and a solid concentration of 15 wt% and 212.5 g of DMAc was added and dissolved by stirring at room temperature. Next, 3.703 g of BPDA (0.0126 mol) and 15.554 g of PMDA (0.0712 mol) were added, and then the polymerization reaction was continued for 3 hours at room temperature to prepare a polyamic acid solution c. did.

  Next, the polyamic acid solution c was uniformly coated on a stainless steel support substrate so that the thickness after curing was about 25 μm, and then heated and dried at 130 ° C. Furthermore, stepwise heat treatment was performed from 130 ° C. to 360 ° C. to complete imidization, and a resin film 3 (CTE; 1.3 ppm / K) was prepared.

[Example 1]
Synthesis Example 2 on release polyimide film 1 (registered trademark; manufactured by Toyobo Co., Ltd .; Xenomax, thickness: 38 μm, long shape, CTE-MD; 2.8 ppm / K, CTE-TD; 0.8 ppm / K) The polyamic acid solution b prepared in (1) was uniformly applied so that the thickness after curing was about 25 μm, and then dried by heating at 130 ° C. Thereafter, stepwise heat treatment was performed from 130 ° C. to 360 ° C. to complete imidization, and the polyimide laminate 1 was prepared by cooling to room temperature.

About this polyimide laminated body 1, the polyimide film 1 was prepared by peeling from the mold release polyimide film 1. FIG. The peel strength was 4 N / m.
The evaluation results of the polyimide film 1 are as follows. In addition, in the state before peeling from the support substrate (including the release polyimide film as the support substrate), the surface on the side in contact with the support substrate is the A surface of the polyimide film, and the other surface is the polyimide It is set as B side of a film.
CTE-MD; 3.8 ppm / K
CTE-TD; 4.0 ppm / K
In-plane retardation (RO); 18nm
Average warpage: 1.0mm
Retardation (ROL) at 4 μm point in the depth direction from surface A; 70 nm
Retardation (ROL) at a point of 20 μm in the depth direction from the B surface; 69 nm

[Example 2]
The polyamic acid solution c prepared in Synthesis Example 3 was uniformly applied to the release polyimide film 1 so that the thickness after curing was about 12.5 μm, and then heated and dried at 130 ° C. On top of that, the polyamic acid solution a prepared in Synthesis Example 1 is uniformly applied so that the thickness after curing is about 12.5 μm, dried at 130 ° C., and then stepwise from 130 ° C. to 360 ° C. A heat treatment was performed to complete imidization, and the mixture was cooled to room temperature to prepare a polyimide laminate 2.

About this polyimide laminated body 2, the polyimide film 2 was prepared by peeling from the mold release polyimide film 1. FIG. The peel strength was 4 N / m.
The evaluation results of the polyimide film 2 are as follows.
CTE-MD; 6.6 ppm / K
CTE-TD; 6.1 ppm / K
In-plane retardation (RO); 11 nm
Average warpage: 1.2mm
CTE difference (CTE2-CTE1) between the first polyimide layer (A surface side) and the second polyimide layer (B surface side); 6.7 ppm / K

[Example 3]
The polyamic acid solution c prepared in Synthesis Example 3 was uniformly applied to the release polyimide film 1 so that the thickness after curing was about 16 μm, and then heated and dried at 130 ° C. On top of that, the polyamic acid solution b prepared in Synthesis Example 2 is uniformly applied so that the thickness after curing is about 9 μm, dried at 130 ° C., and then stepwise heat-treated from 130 ° C. to 360 ° C. To complete imidization and cooled to room temperature to prepare a polyimide laminate 3.

About this polyimide laminated body 3, the polyimide film 3 was prepared by peeling from the mold release polyimide film 1. FIG. The peel strength was 4 N / m.
The evaluation results of the polyimide film 3 are as follows.
CTE-MD; 4.0 ppm / K
CTE-TD; 4.3 ppm / K
In-plane retardation (RO); 3.0 nm
Average warpage amount: 0.7mm
CTE difference (CTE2-CTE1) between the first polyimide layer (A surface side) and the second polyimide layer (B surface side); 2.6 ppm / K

[Example 4]
Using a multi-manifold type three-layer coextrusion three-layer die having a lip width of 200 mm, the polyamic acid solution c prepared in Synthesis Example 3 and the polyamic acid solution b prepared in Synthesis Example 2 were prepared from the side close to the release polyimide film 1. Extrusion-casting was applied to the surface of the release polyimide film 1 so as to obtain a sequential two-layer structure. Then, stepwise heat treatment was performed at a temperature of 130 ° C. to 360 ° C. to complete imidization, and the polyimide laminate 4 was prepared by cooling to room temperature.

About this polyimide laminated body 4, the polyimide film 4 was prepared by peeling from the mold release polyimide film 1. FIG. The peel strength was 4 N / m.
The evaluation results of the polyimide film 4 are as follows.
CTE-MD; 4.2 ppm / K
CTE-TD; 4.5 ppm / K
In-plane retardation (RO): 5 nm
Average warpage: 1.3mm
The first polyimide layer (A surface side, thickness; 16 μm) and the second polyimide layer (B surface side, thickness;
9 μm) CTE difference (CTE2−CTE1); 3.0 ppm / K

[Production Example 1]
In the polyimide laminate 1 prepared in Example 1, the surface of the release polyimide film 1 side was attached to a glass substrate using an adhesive, and then the micro LED element (LED) serving as a display unit on the surface of the polyimide film 1 side. Chip; about 20 μm, square, flake shape) was formed. After that, the polyimide film 1 is cut so as to surround the display portion, the interface between the release polyimide film 1 and the polyimide film 1 is peeled and separated, and the display having the micro LED element on the polyimide substrate made of the polyimide film 1 A device was prepared. At this time, the release polyimide film 1 and the polyimide film 1 can be easily separated without causing damage to the device of the display unit and by being peeled off by a person without using means such as laser peeling. done.

(Reference Example 1)
After the polyamic acid solution b prepared in Synthesis Example 2 is uniformly applied on the surface of the support substrate 1 (made of stainless steel, thickness: 16 μm) that has been cured so that the thickness after curing is about 55 μm, 130 ° C. And dried with heat. Thereafter, stepwise heat treatment was performed from 130 ° C. to 380 ° C. to complete imidization, and after cooling to room temperature, the polyimide film 5 was prepared by peeling from the support substrate 1.

The evaluation results of the polyimide film 5 are as follows.
CTE-MD; 9.8 ppm / K
CTE-TD; 9.7 ppm / K
In-plane retardation (RO); 49nm
Average warpage: 21.3mm

(Reference Example 2)
The polyamic acid solution a obtained in Synthesis Example 1 was uniformly applied on the support substrate 1 so that the thickness after curing was about 16 μm, and then heated and dried at 130 ° C. On top of that, the polyamic acid solution b obtained in Synthesis Example 2 was uniformly applied so that the thickness after curing was about 9 μm, dried at 130 ° C., and then stepwise heat-treated from 130 ° C. to 360 ° C. The polyimide film 6 was prepared by completing imidization, cooling to room temperature, and then peeling from the support substrate 1.

The evaluation results of the polyimide film 6 are as follows.
CTE-MD; 13.5 ppm / K
CTE-TD; 14.6 ppm / K
In-plane retardation (RO); 19.4 nm
Average warpage: 13.0mm

  Examples 1 to 4 and Reference Examples 1 to 2 are polyimide films in which a polyamic acid solution is applied onto a supporting substrate, and drying and imidization are completed on the supporting substrate. In any polyimide film, CTE or the like It was confirmed that the film was excellent in dimensional stability because of good directivity and low in-plane retardation.

  Comparing Example 1 and Reference Example 1 in which the polyimide layer is a single layer, in Example 1, since the thickness of the polyimide film and the retardation (ROL) in the thickness direction are controlled with high precision, the average warpage amount is It could be suppressed to 10 mm or less. On the other hand, in Reference Example 1, since the polyimide film was not controlled to have a predetermined thickness, the average warpage amount exceeded 10 mm.

  In addition, when Examples 2 to 4 and Reference Example 2 in which the polyimide layer is a plurality of layers are compared, in Examples 2 to 4, the first polyimide layer directly laminated on the support substrate is made to have low thermal expansion, By designing the coefficient of thermal expansion (CTE) to be smaller than the CTE of the second polyimide layer within the range satisfying the formula (1), the warpage toward the A-side is suppressed, and the average warpage amount of the polyimide film is 10 mm. I was able to keep it below. On the other hand, in Reference Example 2, since the polyimide layer having a large CTE out of the two polyimide layers was arranged on the A surface side, the average warpage amount exceeded 10 mm. Until now, when forming a plurality of polyimide layers on a supporting substrate, CTE control between layers considering the retardation (ROL) in the thickness direction has not been performed, so the layers are directly laminated on the supporting substrate. The ROL on the A-side of the polyimide layer was low, and CTE tended to increase compared to the B-side, and warping toward the A-side was likely to occur as in Reference Example 2. On the other hand, as shown in Example 2 to Example 4, in consideration of ROL, the CTE of the first polyimide layer is designed to be smaller than the CTE of the second polyimide layer, thereby suppressing the occurrence of warpage. It was confirmed that the manufactured multilayer polyimide film could be produced.

As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment.

DESCRIPTION OF SYMBOLS 100 ... Release polyimide film, 200 ... Polyimide film, 300 ... Polyimide laminated body, 400 ... Support body, 500 ... Display part, 600 ... Display apparatus

Claims (10)

A polyimide film for forming a display device comprising a single layer or a plurality of polyimide layers,
The following conditions (a) to (d);
(A) The thickness is in the range of 3 μm or more and 50 μm or less;
(B) the coefficient of thermal expansion is 10 ppm / K or less;
(C) Standing at a temperature of 23 ° C. and a humidity of 50% so that the convex surface at the center of the polyimide film of 50 mm square after humidity conditioning for 20 hours is in contact with the flat surface, and calculating the average value of the four corners When the average warpage amount is used, the average warpage amount is 10 mm or less;
(D) The difference between the thermal expansion coefficient (CTE-MD) in the longitudinal (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is ± 3 ppm / K or less;
The polyimide film for display apparatus formation characterized by satisfy | filling. In addition to the conditions (a) to (d),
(E) The value of in-plane retardation (RO) is in the range of 1 nm to 50 nm;
The polyimide film for forming a display device according to claim 1, wherein: The polyimide layer is composed of a single first polyimide layer having the lowest thermal expansion coefficient and a single layer or a plurality of second polyimide layers laminated on one side of the polyimide layer,
The thermal expansion coefficient (CTE1) of the first polyimide layer and the thermal expansion coefficient (CTE2) of the second polyimide layer are expressed by the following formula (1):
1 ppm / K <(CTE2-CTE1) ≦ 10 ppm / K (1)
The polyimide film for forming a display device according to claim 1, wherein:   The display device forming polyimide film according to claim 3, wherein the second polyimide layer is a single layer. A polyimide laminate comprising a release polyimide film and a polyimide film directly laminated on the release polyimide film,
The polyimide film has the following conditions (a) to (d):
(A) The thickness is in the range of 3 μm or more and 50 μm or less;
(B) the coefficient of thermal expansion is 10 ppm / K or less;
(C) Standing at a temperature of 23 ° C. and a humidity of 50% so that the convex surface at the center of the polyimide film of 50 mm square after humidity conditioning for 20 hours is in contact with the flat surface, and calculating the average value of the four corners When the average warpage amount is used, the average warpage amount is 10 mm or less;
(D) The difference between the thermal expansion coefficient (CTE-MD) in the longitudinal (MD) direction and the thermal expansion coefficient (CTE-TD) in the width (TD) direction is ± 3 ppm / K or less;
A polyimide laminate characterized by satisfying In addition to the above conditions (a) to (d), the polyimide film is further
(E) The value of in-plane retardation (RO) is in the range of 1 nm to 50 nm;
The polyimide laminate according to claim 5, wherein: The polyimide film is composed of a single first polyimide layer and a single layer or a plurality of second polyimide layers laminated on one side of the first polyimide layer, and the first polyimide layer comprises In the position in contact with the release polyimide film,
The thermal expansion coefficient (CTE1) of the first polyimide layer and the thermal expansion coefficient (CTE2) of the second polyimide layer are expressed by the following formula (1):
1 ppm / K <(CTE2-CTE1) ≦ 10 ppm / K (1)
The polyimide laminate according to claim 5 or 6, wherein:   The polyimide laminate according to claim 7, wherein the second polyimide layer is a single layer. A manufacturing method of a display device provided with a display unit on a polyimide substrate,
Laminating the polyimide laminate according to any one of claims 5 to 8 and a support so that the surface on the release polyimide film side and one surface of the support are in contact with each other;
Forming a predetermined display part on the polyimide film in the polyimide laminate,
Separating the release polyimide film and the polyimide film at their boundary surfaces, and obtaining a display device including the display unit on the polyimide film as the polyimide substrate;
A method for manufacturing a display device, comprising: A polyimide base material comprising the polyimide film for forming a display device according to any one of claims 1 to 4,
A display unit formed on the polyimide substrate;
A display device comprising:

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