JP2025024098A - Flexible Liquid Crystal Display - Google Patents

Abstract

To provide a flexible liquid crystal display device including a substrate formed of polyimide and capable of reducing process cost without using laser exfoliation, improving the mechanical strength of the liquid crystal display device and achieving a display having bending resistance.SOLUTION: A flexible liquid crystal display device (1) comprising a thin film transistor (TFT) wiring layer (300), a liquid crystal layer (500), a color filter layer (800), transparent polyimide layers (200 and 900) and glass substrates (100 and 1000) has a laminated structure obtained by laminating the TFT wiring layer (300), the color filter layer (800), the transparent polyimide layers (200 and 900) and the glass substrates (100 and 1000) in this order. The thicknesses of the glass substrates (100 and 1000) are 10-70 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a display device, and more specifically to a flexible liquid crystal display device.

Conventional display devices were not flexible and were rigid. In recent years, flexible display devices have been developed, including those that use organic light-emitting elements (OLED) and those that use liquid crystal elements (LCD).

In order to achieve flexibility, it has been proposed to use resin instead of glass as the substrate for the display device. Here, in order to form the substrate only from resin, it has been considered to form a polyimide layer on a glass substrate, and then after going through a display formation process, peel the polyimide layer from the glass substrate by irradiating it with a laser from the glass substrate side (Patent Document 1). However, in this case, there is a problem that the display device is destroyed when peeled off because the mechanical strength of the polyimide layer is insufficient, and that the display device is destroyed when repeatedly wound up and unwound.

On the other hand, in rigid-type display devices, the glass substrate has been etched to make it thinner, but as mentioned above, this display device has no flexibility (Patent Document 2).

Special Publication No. 2007-512568 JP 2018-16518 A

When laser peeling as described in Patent Document 1 is used, very expensive process costs are required. Furthermore, the manufacturing process for organic light-emitting display devices is generally more expensive than the manufacturing process for liquid crystal display devices. Therefore, there is a demand for utilizing the conventional manufacturing process for liquid crystal display devices while keeping costs down.

In view of the above requirements, the present invention aims to realize a flexible liquid crystal display device having a substrate on which polyimide is formed, which reduces process costs without using laser peeling, improves the mechanical strength of the liquid crystal display device, and has bending resistance.

The present inventors have found that the above-mentioned problems can be solved by maintaining and thinning the glass substrate for the TFT wiring layer or the color filter layer in a flexible liquid crystal display device, and have completed the present invention. One embodiment of the present invention is exemplified below.
[1]
A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
The flexible liquid crystal display device has a laminated structure in which the TFT wiring layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the glass substrate has a thickness of 10 to 70 μm.
[2]
2. The flexible liquid crystal display device according to item 1, wherein the glass substrate has a thickness of 10 to 50 μm.
[3]
3. The flexible liquid crystal display device according to item 1 or 2, wherein the glass substrate has a thickness of 10 to 24 μm.
[4]
A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
the flexible liquid crystal display device has a laminated structure in which the TFT wiring layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the thickness of the glass substrate after chemical etching is 10 to 70 μm.
[5]
5. The flexible liquid crystal display device according to any one of claims 1 to 4, wherein the transparent polyimide layer and the glass substrate are supports for the TFT wiring layer.
[6]
A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
The flexible liquid crystal display device has a laminated structure in which the color filter layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the glass substrate has a thickness of 10 to 70 μm.
[7]
7. The flexible liquid crystal display device according to item 6, wherein the glass substrate has a thickness of 10 to 50 μm.
[8]
8. The flexible liquid crystal display device according to item 6 or 7, wherein the glass substrate has a thickness of 10 to 24 μm.
[9]
A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
The flexible liquid crystal display device has a laminated structure in which the color filter layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the thickness of the glass substrate after chemical etching is 10 to 70 μm.
[10]
A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
the flexible liquid crystal display device has a layered structure I in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the flexible liquid crystal display device has a layered structure II in which the color filter layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the glass substrate has a thickness of 10 to 70 μm.
[11]
Item 11. The flexible liquid crystal display device according to item 10, wherein the glass substrate has a thickness of 10 to 50 μm.
[12]
Item 12. The flexible liquid crystal display device according to item 10 or 11, wherein the glass substrate has a thickness of 10 to 24 μm.
[13]
A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
the flexible liquid crystal display device has a layered structure I in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the flexible liquid crystal display device has a layered structure II in which the color filter layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the glass substrate has a thickness of 10 to 70 μm after chemical etching.
[14]
Item 14. The flexible liquid crystal display device according to any one of items 6 to 13, wherein the transparent polyimide layer and the glass substrate are supports for the color filter layer.
[15]
The polyimide contained in the transparent polyimide layer has a constitutional unit derived from a diamine, and the diamine is selected from the group consisting of diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-bis(4-aminophenoxy)phenyl 15. The flexible liquid crystal display device according to any one of items 1 to 14, wherein the bis(4-aminophenyl)phenyl is at least one selected from the group consisting of 1,4-bis(3-aminophenoxy)biphenyl, 4,4-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(3-aminopropyldimethylsilyl)benzene, and 9,9-bis(4-aminophenyl)fluorene (BAFL).
[16]
The polyimide contained in the transparent polyimide layer has a structural unit derived from an acid anhydride, and the acid anhydride is selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic dianhydride (ODPA), norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (CpODA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2-di Carboxylic acid anhydrides, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, p-phenylenebis(trimellitate anhydride), thio-4,4'-diphthalic dianhydride dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 16. The flexible liquid crystal display device according to any one of items 1 to 15, wherein the dianhydride is at least one selected from the group consisting of bis(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and bicyclohexyl-3,3',9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).
[17]
Item 17. The flexible liquid crystal display device according to any one of items 1 to 16, wherein the liquid crystal layer is between the TFT wiring layer and the color filter layer.
[18]
A method for manufacturing a flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer and a glass substrate, comprising the steps of:
a lamination step of forming a laminated structure in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
and etching the glass substrate so that the thickness of the glass substrate in the laminated structure falls within a range of 10 to 70 μm.
[19]
Item 19. The method for manufacturing a flexible liquid crystal display device according to item 18, wherein in the etching step, the thickness of the glass substrate is adjusted to within a range of 10 to 50 μm.
[20]
20. The method for manufacturing a flexible liquid crystal display device according to item 18 or 19, wherein in the etching step, the TFT wiring layer and the transparent polyimide layer are masked.
[21]
A method for manufacturing a flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer and a glass substrate, comprising the steps of:
forming a laminated structure in which the color filter layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
and etching the glass substrate so that the thickness of the glass substrate in the laminated structure falls within a range of 10 to 70 μm.
[22]
22. The method for manufacturing a flexible liquid crystal display device according to item 21, wherein in the etching step, the thickness of the glass substrate is adjusted to within a range of 10 to 50 μm.
[23]
23. The method for manufacturing a flexible liquid crystal display device according to item 21 or 22, wherein in the etching step, the color filter layer and the transparent polyimide layer are masked.
[24]
A method for manufacturing a flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer and a glass substrate, comprising the steps of:
a lamination step of forming a laminate structure I in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
a lamination step of forming a laminate structure II in which the color filter layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
a step of bonding the TFT wiring layer and the color filter layer via a sealant;
and an etching step of etching the glass substrate in the laminated structures I and II so that the thickness of the glass substrate falls within a range of 10 to 70 μm.
[25]
25. The method for manufacturing a flexible liquid crystal display device according to item 24, wherein in the etching step, the thickness of the glass substrate is adjusted to within a range of 10 to 50 μm.

The present invention makes it possible to reduce process costs without using laser peeling, while at the same time improving the mechanical strength of the liquid crystal display device and providing a flexible liquid crystal display device with bending resistance.

1 is a schematic cross-sectional view of a flexible liquid crystal display device according to one embodiment of the present invention; 1 is a schematic cross-sectional view of a laminated structure including a TFT wiring layer, a transparent polyimide layer, and a glass substrate (thickness: more than 300 μm) in this order before an etching process. 1 is a schematic cross-sectional view of a laminated structure including a TFT wiring layer, a transparent polyimide layer, and a glass substrate (thickness: 10 to 70 μm) in that order after an etching process. FIG. 2 is a schematic cross-sectional view of a laminated structure including a color filter layer, a transparent polyimide layer, and a glass substrate (thickness: more than 300 μm) in this order before an etching process. FIG. 2 is a schematic cross-sectional view of a laminated structure including a color filter layer, a transparent polyimide layer, and a glass substrate (thickness: 10 to 70 μm) in that order after an etching process. 11 is a schematic flow diagram of a manufacturing method for a flexible liquid crystal display device according to a third embodiment. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments.
The flexible liquid crystal display device according to the present invention includes a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate having a thickness of 10 to 70 μm, and has the following laminate structure I and/or laminate structure II:
I. A laminated structure in which a TFT wiring layer, a transparent polyimide layer, and a glass substrate are laminated in this order;
II. A laminated structure in which a color filter layer, a transparent polyimide layer, and a glass substrate are laminated in this order;
The flexible liquid crystal display device according to the present invention can achieve both reduced process costs and bending resistance.

Surprisingly, the present invention has found that flexible liquid crystal displays have significantly lower process costs than organic light-emitting displays (OLEDs), and that maintaining a thin glass substrate can contribute to both reduced process costs and bending resistance. From this perspective, the thickness of the glass substrate is 10 to 70 μm, preferably 10 to 50 μm, more preferably 10 to 24 μm, and even more preferably 10 to 20 μm. From the same perspective, the transparent polyimide layer and the glass substrate preferably constitute a TFT wiring layer substrate as a support for the TFT wiring layer, and/or preferably constitute a color filter layer substrate as a support for the color filter layer.
Here, the term "flexible" in flexible liquid crystal display device means that the liquid crystal display device can be bent to a radius of curvature of 150 mm or less without breaking, preferably to a radius of curvature of 3 mm, and also means that the device has flexibility and is therefore unlikely to break even if dropped. This is a feature not found in conventional rigid liquid crystal display devices that use only glass as a substrate.
In addition, in the present invention, the glass substrate in the laminate of the transparent polyimide layer and the glass substrate can be etched to thin it during the manufacturing process of the display. Therefore, since the display is manufactured using a thick glass substrate in the process before etching, stable manufacturing is possible, and there is also an advantage in that the yield is improved.

In one embodiment, the glass substrate included in the laminate structure I and/or the laminate structure II has a thickness after chemical etching of 10 to 70 μm, preferably 10 to 50 μm, more preferably 10 to 24 μm, and even more preferably 10 to 20 μm, from the viewpoint of achieving both reduced process costs and bending resistance. The chemically etched glass substrate preferably has a surface roughness (Z) of 0.1 to 1.0 nm (measured by AFM), an amount of alkaline elution of more than 0 and 1.0 mg or less (based on JIS R3502), and preferably does not contain microscratches (foreign matter having dimensions in μm), and/or does not contain silica particles with an average particle size of 80 nm or less.

If desired, the flexible liquid crystal display device may include additional components, such as alignment films, sealants, polarizing films, planar electrodes, etc., and may define or have additional stacking structures other than stacking structures I and II.

Figure 1 is a schematic cross-sectional view of a flexible liquid crystal display device according to one embodiment of the present invention. In the flexible liquid crystal display device (1), the side of the liquid crystal layer (500) is sealed with a sealant (600) to form a liquid crystal display unit. On one side of the liquid crystal display unit, a laminate structure I in which a TFT wiring layer (300), a transparent polyimide layer (200), and a glass substrate (100) are laminated in this order is provided so as to bring the TFT wiring layer (300) into contact with the sealant (600). On the other side of the liquid crystal display unit, a laminate structure II in which a color filter layer (800), a transparent polyimide layer (900), and a glass substrate (1000) are laminated in this order is provided so as to bring the color filter layer (800) into contact with the sealant (600). Alignment films (400, 700) may be provided to contact the upper and lower parts of the liquid crystal layer (500).

A liquid crystal layer (500) is between the TFT wiring layer (300) and the color filter layer (800). A glass substrate (100) and a transparent polyimide layer (200) are used as a TFT wiring layer substrate, and a transparent polyimide layer (200) is between the glass substrate (100) and the TFT wiring layer (300). A glass substrate (1000) and a transparent polyimide layer (900) are used as a color filter layer substrate, and a transparent polyimide layer (900) is between the glass substrate (1000) and the color filter layer (800). Each component of the flexible liquid crystal display device is described below.

<Liquid crystal display unit>
The liquid crystal display unit is filled with liquid crystal. The liquid crystal layer is made of liquid crystal, and its periphery is sealed with a sealant. If desired, the upper and lower parts of the liquid crystal layer may be covered with an alignment film. The liquid crystal display unit is preferably sealed so that foreign matter such as gas or liquid does not enter the inside. The sealant and alignment film can be formed, for example, from a known ultraviolet-curing resin or a thermosetting resin, and the material can be determined depending on the sealability, bonding with the TFT wiring layer or the color filter layer, and the like.

<Glass substrate>
In one embodiment, at least a pair of glass substrates are arranged to sandwich the liquid crystal display unit. The pair of glass substrates may have the same dimensions in terms of the manufacturing process and cost of the flexible liquid crystal display device. The glass substrate material may be, for example, an alkali-free glass substrate. If desired, the glass substrate may be subjected to various treatments, such as hydrophobization, hydrophilization, smoothing, roughening, and chemical etching.

Methods for controlling the thickness of the glass substrate to within the range of 10 to 70 μm include, for example, (i) preparing a glass substrate having a thickness of 10 to 70 μm in advance and using it, and (ii) preparing a glass substrate having a thickness of more than 70 μm (for example, a thickness of more than 300 μm) and adjusting the thickness to within the range of 10 to 70 μm by chemical etching during the manufacturing process. Among these, the above (ii) is preferred from the viewpoints of the strength of the glass substrate and the bending resistance of the flexible liquid crystal display device.

<TFT Wiring Layer>
TFT (thin-film-transistor) is a display element that uses a thin-film transistor as a switching element, and is widely used in liquid crystal displays and flat-screen televisions. TFT is formed on a substrate, and in the case of conventional rigid displays, a glass substrate has been used as the substrate. In recent years, the use of heat-resistant polyimide has also been considered in conjunction with the study of foldable displays.

Conventionally, when using transparent polyimide as a TFT substrate, it has been considered to form a transparent polyimide layer on a glass substrate, then form a TFT wiring layer, and then perform laser peeling to peel the polyimide from the glass substrate. However, problems have been reported, such as the laser peeling process being very expensive, and the mechanical strength of the TFT wiring layer and polyimide after peeling being insufficient, resulting in breakage and low yields in the manufacturing process.

As a solution to these problems, the present invention uses a transparent polyimide layer and a glass substrate with a thickness of 10 to 70 μm as the substrate for the TFT wiring layer, achieving both low process costs, improved yield, and good mechanical properties. Here, the thickness of the glass substrate as the substrate for the TFT wiring layer is 10 to 70 μm, preferably 10 to 50 μm, and more preferably 20 to 50 μm.

<Color filter layer>
A color filter is a filter that produces the colors of an image or video. A pattern consisting of three color resists, red (R), green (G) and blue (B), is formed on the substrate, and the borders are divided into a grid shape by a black matrix (BM) to prevent the color resists from mixing with each other. In the case of conventional rigid displays, a glass substrate has been used as the substrate for this color filter. In recent years, bendable displays have been considered, and the use of heat-resistant polyimide has also been considered.

When using polyimide as a color filter substrate, it has been considered to form the polyimide on a glass substrate, then form a color filter, and then perform laser peeling to peel the polyimide from the glass substrate. However, problems have been reported, such as the laser peeling process being very expensive, and the mechanical strength of the color filter layer after peeling being insufficient, resulting in tears and low yields in the manufacturing process.

To address these problems, the present invention uses a transparent polyimide layer and a glass substrate with a thickness of 10 to 70 μm as the substrate for the color filter layer, achieving both low process costs, improved yield, and good mechanical properties. Here, the thickness of the glass substrate as the substrate for the color filter layer is 10 to 70 μm, preferably 10 to 50 μm, and more preferably 20 to 50 μm.

<Transparent polyimide layer>
The transparent polyimide layer is a layer that contains polyimide and is transparent to visible light. The transparent polyimide layer can be colorless and transparent from the viewpoint of being used in a flexible liquid crystal display device. Specifically, the transparent polyimide layer according to this embodiment can have a light transmittance of 70% or more (calculated as a 10 μm thickness) in the visible light region of 400 nm to 750 nm, which is not available in conventional brown polyimides (e.g., Kapton, etc.). The polyimide contained in the transparent polyimide layer is a resin obtained by heating a polyimide precursor obtained by reacting a diamine compound with an acid dianhydride compound, and has a high heat resistance characteristic required for the process of a liquid crystal display device.

Examples of diamine compounds include diaminodiphenyl sulfone (e.g., 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, etc.), p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, bis[4 -(4-aminophenoxy)phenyl]sulfone, 4,4-bis(4-aminophenoxy)biphenyl, 4,4-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and 1,4-bis(3-aminopropyldimethylsilyl)benzene, 9,9-bis(4-aminophenyl)fluorene (BAFL), etc.

Among the above diamine compounds, diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4 -Bis(4-aminophenoxy)biphenyl, 4,4-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(3-aminopropyldimethylsilyl)benzene, and at least one of BAFL are preferred.

｛式中、Ｒ_１は、複数ある場合にはそれぞれ独立に、炭素数１～５の１価の脂肪族炭化水素基又は炭素数６～１０の１価の芳香族基を示し、Ｒ_２は、複数ある場合にはそれぞれ独立に、炭素数１～５の１価の脂肪族炭化水素基又は炭素数６～１０の１価の芳香族基を示し、そしてｍは、１～２００の整数を示す｝
で表される構造単位を含んでよい。 The polyimide precursor and the polyimide obtained therefrom have the following general formula (1):

{In the formula, when there are multiple R1 _'s , each independently represents a monovalent aliphatic hydrocarbon group having 1 to 5 carbon atoms or a monovalent aromatic group having 6 to 10 carbon atoms, when there are multiple R2 _'s , each independently represents a monovalent aliphatic hydrocarbon group having 1 to 5 carbon atoms or a monovalent aromatic group having 6 to 10 carbon atoms, and m represents an integer of 1 to 200.}
The compound may include a structural unit represented by the following formula:

｛式中、Ｐ_５は、それぞれ独立に、二価の炭化水素基を示し、同一でも異なっていてもよく、Ｐ_３及びＰ_４は、それぞれ一般式（１）で定義されたＲ_１及びＲ_２と同じであり、かつｌは、１～２００の整数を表す。｝
で表されるジアミノ（ポリ）シロキサンが好ましい。 The polyimide precursor and the polyimide obtained therefrom may have the structural unit of general formula (1) at any position in the molecule, but from the viewpoints of the type of siloxane monomer, cost, and the molecular weight of the resulting polyimide precursor, it is preferable that the structure of general formula (1) is derived from a silicon-containing compound, for example, a silicon-containing diamine. Examples of the silicon-containing diamine include those represented by the following formula (2):

In the formula, _P5 each independently represents a divalent hydrocarbon group and may be the same or different, _P3 and _P4 are the same as _R1 and _R2 defined in general formula (1), respectively, and l represents an integer of 1 to 200.
Preferred is a diamino(poly)siloxane represented by the following formula:

Specific examples of the compound represented by general formula (2) include methylphenyl silicone oil modified at both ends with amines (manufactured by Shin-Etsu Chemical Co., Ltd.: X22-1660B-3 (number average molecular weight 4400), X22-9409 (number average molecular weight 1340)), methylphenyl silicone oil modified at both ends with acid anhydrides (manufactured by Shin-Etsu Chemical Co., Ltd.: X22-168-P5-B (number average molecular weight 4200)), and methylphenyl silicone oil modified at both ends with epoxy groups ( Examples include Shin-Etsu Chemical's X22-2000 (number average molecular weight 1240), dimethyl silicone modified with amino at both ends (Shin-Etsu Chemical's X22-161A (number average molecular weight 1600), X22-161B (number average molecular weight 3000), KF8021 (number average molecular weight 4400), Toray Dow Corning's BY16-835U (number average molecular weight 900), Chisso's Silaplane FM3311 (number average molecular weight 1000)).

Examples of acid dianhydride compounds include pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic dianhydride (ODPA), norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (CpODA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2 dicarboxylic anhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'- Benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, p-phenylene bis(trimellitate anhydride), thio-4,4'-diphthalic dianhydride, sulfonyl-4 ,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenyl)phenyl]propane dianhydride Examples of the dianhydride include bis(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, and 1,2,7,8-phenanthrenetetracarboxylic dianhydride, bicyclohexyl-3,3',9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), etc.

Among the above-mentioned acid dianhydride compounds, BPDA, ODPA, CpODA, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 6FDA, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2-dicarboxylic anhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2- Propylene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, p-phenylenebis(trimellitate anhydride), thio-4,4'-diphthalic dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl) 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane At least one of the following dianhydrides is preferred: 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and BPAF.

<Method of Manufacturing a Flexible Liquid Crystal Display Device>
Another aspect of the present invention is a method for manufacturing a flexible liquid crystal display device, which includes a TFT wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate. Unless otherwise specified, the method for manufacturing a flexible liquid crystal display device may use the components, raw materials, and process conditions described above for the flexible liquid crystal display device, either alone or in combination.

The first embodiment of the method for producing a flexible liquid crystal display device includes the following steps:
(A-I) a lamination step of forming a laminate structure I in which a TFT wiring layer, a transparent polyimide layer, and a glass substrate are laminated in this order;
(B-I) an etching step of etching the glass substrate in the laminate structure I so that the thickness of the glass substrate is within a range of 10 to 70 μm;
Includes.

In the first embodiment, the steps (A-I) and (B-I) can reduce process costs and improve yield without using laser peeling, while ensuring bending resistance of the flexible liquid crystal display device. In addition, before or during step (A-I), a glass substrate having a thickness of more than 70 μm (for example, a thickness of more than 300 μm) is prepared for the TFT wiring layer, and in step (B-I), the thickness of the glass substrate is adjusted to within a range of 10 to 70 μm by chemical etching, thereby improving the strength of the glass substrate and the mechanical strength of the flexible liquid crystal display device. From this perspective, in step (B-I), the thickness of the glass substrate is preferably adjusted to within a range of 10 to 50 μm, more preferably within a range of 10 to 24 μm, and even more preferably within a range of 10 to 20 μm.

Steps (A-I) and (B-I) will be described with reference to FIG. 2 and FIG. 3. FIG. 2 is a schematic cross-sectional view of a laminate structure I formed using a TFT wiring layer (300), a transparent polyimide layer (200), and a glass substrate (100) having a thickness of more than 300 μm, for example, during step (A-I) before step (B-I). The transparent polyimide layer (200) on the glass substrate (100) having a thickness of more than 300 μm can be formed, for example, by applying or spraying a polyimide precursor resin composition under a nitrogen atmosphere (then heating to form a polyimide), and bonding the glass substrate (100) and the transparent polyimide layer (200). The TFT wiring layer (300) on the transparent polyimide layer (200) can be formed by metal (e.g., Al) sputtering, lithography patterning, chemical vapor deposition, etc.

Figure 3 is a schematic cross-sectional view of the laminate structure I in which the glass substrate (100) is etched to a thickness within the range of 10 to 70 μm, for example, during or after step (B-I). From the viewpoint of leaving the glass substrate (100) with a thickness of 10 μm or more, chemical etching is preferable, and etching with a hydrofluoric acid solution is more preferable. From the viewpoint of achieving both reduced process costs and bending resistance, it is preferable that the etching solution does not contain silica particles with an average particle size of 80 nm or less. In step (B-I), it is preferable to mask the TFT wiring layer (300) and transparent polyimide layer (200) of the laminate structure I with, for example, a sealant, and etch the exposed glass substrate (100).

The second embodiment of the method for producing a flexible liquid crystal display device includes the following steps:
(A-II) a lamination step of forming a laminate structure II in which a color filter layer, a transparent polyimide layer, and a glass substrate are laminated in this order;
(B-II) In the laminate structure II, an etching step of etching the glass substrate is included so that the thickness of the glass substrate falls within the range of 10 to 70 μm.

In the second embodiment, by steps (A-II) and (B-II), it is possible to reduce process costs without using laser peeling, and to ensure the bending resistance of the flexible liquid crystal display device. In addition, before or during step (A-II), a glass substrate having a thickness of more than 70 μm (for example, a thickness of more than 300 μm) is prepared for the color filter layer, and in step (B-II), the thickness of the glass substrate is adjusted to within a range of 10 to 70 μm by chemical etching, thereby improving the strength of the glass substrate and the mechanical strength of the flexible liquid crystal display device. From this perspective, in step (B-II), it is preferable to adjust the thickness of the glass substrate to within a range of 10 to 50 μm, more preferably within a range of 10 to 24 μm, and even more preferably within a range of 10 to 20 μm.

Steps (A-II) and (B-II) will be described with reference to FIG. 4 and FIG. 5. FIG. 4 is a schematic cross-sectional view of a laminate structure II formed using a color filter layer (800), a transparent polyimide layer (900), and a glass substrate (1000) having a thickness of more than 300 μm, for example, during step (A-II) prior to step (B-II). The transparent polyimide layer (900) on the glass substrate (1000) having a thickness of more than 300 μm can be formed, for example, by applying or spraying a polyimide precursor resin composition under a nitrogen atmosphere (then heating to form a polyimide), and bonding the glass substrate (1000) and the transparent polyimide layer (900). The color filter layer (800) on the transparent polyimide layer (900) can be formed according to known color filter and black matrix manufacturing methods.

Figure 5 is a schematic cross-sectional view of the laminate structure II in which the glass substrate (1000) is etched to a thickness within the range of 10 to 70 μm, for example, during or after step (B-II). From the viewpoint of leaving the glass substrate (1000) with a thickness of 10 μm or more, chemical etching is preferable, and etching with a hydrofluoric acid solution is more preferable. From the viewpoint of achieving both reduced process costs and bending resistance, it is preferable that the etching solution does not contain silica particles with an average particle size of 80 nm or less. In step (B-II), it is preferable to mask the color filter layer (800) and transparent polyimide layer (900) of the laminate structure II with, for example, a sealant, and etch the exposed glass substrate (1000).

The third embodiment of the manufacturing method for a flexible liquid crystal display device provides a liquid crystal display unit, performs all of the above-described steps (A-I), (A-II), (B-I) and (B-II), and bonds the liquid crystal display unit with stacked structures I and II via a sealant, and injects liquid crystal between the TFT wiring layer of stacked structure I and the color filter layer of stacked structure II to form a liquid crystal layer. Fig. 6 is a schematic flow diagram of the manufacturing method for a flexible liquid crystal display device according to the third embodiment.
Alternatively, the above-described steps (A-I) and (B-I) may be carried out, and the liquid crystal display unit may be joined to the laminated structures I and II via a sealant, and liquid crystal may be injected between the TFT wiring layer (300) of the laminated structure I and the color filter layer (800) of the laminated structure II to form a liquid crystal layer (500) (FIG. 6a).
(B-III) In the laminate structure I and the laminate structure II, a glass substrate (100, 1000) of the laminate structure I and the laminate structure II is etched through an etching process so that the thickness of the glass substrate falls within the range of 10 to 70 μm (FIG. 6b), thereby obtaining a flexible liquid crystal display device (1) similar to that described above.

Methods for thinning the glass substrate in steps (B-I), (B-II), and (B-III) include chemical etching and physical polishing. However, polishing can cause micro-scratches, and from the viewpoint of optical compensation, chemical etching is preferred.

The manufacturing methods according to the first, second and third embodiments can produce the flexible liquid crystal display device (1) shown in FIG. 1.

(Synthesis of transparent polyimide precursor)
<Synthesis Example 1>
In a 3L separable flask with a stirring rod, 233 g of N-methylpyrrolidone (NMP) was added while introducing nitrogen gas, 31.1 g of TFMB (2,2'-bis(trifluoromethyl)benzidine) as a diamine, 13.20 g of X-22-1660B-3 (methylphenyl silicone oil modified with amines at both ends, number average molecular weight 4400, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicon-containing compound were added while stirring, and then 22.9 g of BPAF (9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride) and 10.9 g of PMDA (pyromellitic dianhydride) were added as acid dianhydrides. Here, the molar ratio of acid dianhydride:diamine was 100:99. Next, the flask was heated to 80°C using an oil bath, and after stirring for 3 hours, the oil bath was removed and the temperature was returned to room temperature, and a transparent NMP solution of polyamic acid (hereinafter also referred to as varnish A) was obtained. The obtained varnish was stored in a freezer and was thawed before use for evaluation.

<Synthesis Example 2>
In a 3L separable flask with a stirring rod, NMP (405 g) was added while introducing nitrogen gas, and TFMB (12.6 g) and BAFL (1,4-bis(3-aminopropyldimethylsilyl)benzene, 9,9-bis(4-aminophenyl)fluorene) 20.5 g were added as diamines while stirring, followed by the addition of 38.4 g of CpODA (norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride) as an acid dianhydride. Here, the molar ratio of acid dianhydride:diamine was 100:98. Next, the flask was heated to 80°C using an oil bath, and after stirring for 3 hours, the oil bath was removed and the temperature was returned to room temperature, and a transparent NMP solution of polyamic acid (hereinafter also referred to as varnish B) was obtained. The obtained varnish was stored in a freezer, and was thawed and used when evaluating.

(Preparation of test samples)
Example 1
The polyimide precursor composition (varnish A) of Synthesis Example 1 was applied to an area 5 mm inside from the edge of an alkali-free glass substrate (hereinafter also referred to as "glass substrate" or simply "substrate") having a length of 300 mm, width of 350 mm, and thickness of 0.7 mm, so that the film thickness after imidization was 10 μm. A slit coater (LC-R300G, manufactured by SCREEN Finetech Solutions) was used for application. The solvent was removed from the obtained glass substrate with the coating film by a reduced pressure dryer (manufactured by Tokyo Ohka Kogyo Co., Ltd.) under conditions of 80° C., 100 Pa, and 30 minutes. The glass substrate having the coating film of the obtained polyimide precursor composition was heated at 400° C. for 1 hour in a nitrogen atmosphere (oxygen concentration 300 ppm or less) using an oven (INH-9N1, manufactured by Koyo Thermo Systems Co., Ltd.) to form a polyimide layer on the glass substrate, and it was visually confirmed that the polyimide layer was transparent.

Next, an aluminum film was formed to a thickness of 100 nm by sputtering over the entire glass substrate on which the polyimide layer was formed, and then patterned by photolithography to form an aluminum pattern. Next, a SiN layer was formed to a thickness of 200 nm over the entire substrate by CVD.

After that, an acrylic sealant was applied to the surface of the substrate on which the SiN layer was formed and to the sides of the substrate.

To etch the glass substrate, the substrate coated with the sealant was immersed in an etching bath of 50 wt% high-purity hydrofluoric acid (manufactured by Stella Chemifa Corporation) and etched until the glass substrate had a thickness of 70 μm, after which it was washed with ultrapure water. The thickness of the glass substrate was evaluated by cutting the substrate, embedding it in epoxy, and observing the cross section with an optical microscope.

The etched sample was then immersed in an alkaline stripper (TMAH (tetramethylammonium hydroxide)) to remove the sealant and obtain an evaluation sample.

<Examples 2 to 4, Comparative Examples 1 and 2>
Samples were prepared in the same manner as in Example 1, except that the etching conditions were adjusted to give the glass substrate a thickness as shown in Table 1.

<Examples 5 to 7, Comparative Examples 4 and 5>
A sample was prepared in the same manner as in Example 1, except that the varnish used was changed to Varnish B and the glass substrate had a thickness as shown in Table 1.

<Comparative Example 3>
In Example 1, using a sample before etching of the glass substrate, an excimer laser (wavelength 308 nm) was irradiated from the glass substrate side of the glass substrate on which the polyimide was formed, to peel off the polyimide from the glass substrate (without the glass substrate).

<Comparative Example 6>
On a non-alkali glass substrate (hereinafter referred to as "glass substrate" or simply "substrate") having dimensions of 300 mm length x 350 mm width x 0.7 mm thickness, an aluminum film was formed by sputtering to a thickness of 100 nm, and then patterned by photolithography to form an aluminum pattern. Subsequently, a SiN layer was formed by CVD to a thickness of 200 nm on the entire substrate, to produce a substrate without a PI film.

After that, an acrylic sealant was applied to the surface of the substrate on which the SiN layer was formed and to the side of the substrate to obtain a laminate.

The glass substrate was thinned by polishing instead of etching. Specifically, the side of the laminate coated with the sealant was fixed to the polishing head of a polishing device, and the polishing was performed by rotating the polishing head and the polishing pad. Polishing was performed at a pressure of 100 g/ ^cm2 using colloidal silica with an average particle size of 80 nm or less as the polishing slurry. Thereafter, the polishing pad and slurry were replaced with a polishing pad and slurry for finishing, and finishing polishing was performed, etching was performed until the thickness of the glass substrate was 24 μm, and cleaning was performed with ultrapure water. The thickness of the glass substrate was evaluated by cutting the substrate, embedding it in epoxy, and observing the cross section of the substrate with an optical microscope.

The laminate was then immersed in an alkaline stripper (tetramethylammonium hydroxide (TMAH)) to remove the sealant and obtain an evaluation sample.

(Optical microscope observation of aluminum surface)
The aluminum surfaces of the substrates obtained in the examples and comparative examples were observed with an optical microscope (hereinafter also referred to as "OM observation"). The observation results were evaluated according to the following criteria.
A (Fair): No corrosion is observed on the aluminum surface.
B (Unacceptable): Corrosion is observed on the aluminum surface.

Corrosion was observed in samples with glass substrates that were 5 μm or less thick. This is thought to be because there were thin spots on the glass substrate, where the polyimide was first corroded by hydrofluoric acid (HF), and then the aluminum was corroded.

(Bending resistance evaluation)
The bending resistance of the substrates obtained in the examples and comparative examples was evaluated. Specifically, the minimum radius of curvature at which no cracks were generated in the substrate was evaluated. By measuring the radius of curvature, the bending resistance was evaluated according to the following criteria.
A (Excellent): Curvature radius is 30mm or less B (Good): Curvature radius is more than 30mm and less than 40mm C (Acceptable): Curvature radius is more than 40mm and less than 50mm D (Unacceptable): Curvature radius is more than 50mm

The radius of curvature was large in the samples with a glass substrate having a thickness of 10 μm or less. This is considered to be because the glass substrate was too thick and the glass broke.
Furthermore, a comparison between Example 7 and Comparative Example 6 confirmed that even when the glass substrate had the same thickness, the glass substrate alone had no bending resistance, whereas the composite material of the glass substrate and the PI film had sufficient bending resistance.

(Curl Evaluation)
The curl of the substrates obtained in the examples and comparative examples was evaluated. Specifically, the obtained samples were left to stand overnight in a thermostatic chamber at 23°C and 50% Rh. Then, the samples were left to stand for another 30 minutes on a smooth glass plate with the glass substrate side facing down. The maximum amount of the sample lifted from the glass plate was measured as the curl amount, and evaluation was performed according to the following criteria.
A (Acceptable): Curl amount is 15mm or less B (Not acceptable): Curl amount is more than 15mm or cylindrical

The samples with the largest amount of curl were those with a glass substrate thickness of 5 μm or less, or those without a glass substrate. The curling is thought to be due to differences in the elongation caused by water absorption between the polyimide and inorganic film.

The type of polyimide precursor varnish, the thickness of the glass substrate, and various evaluation results are shown in Table 1 below.

(Manufacturing of flexible liquid crystal display devices)
Using the sample of Example 7 (glass substrate thickness: 24 μm), a 100 nm Poly-Si layer was formed on the SiN film by CVD, and then annealed at 380° C. Furthermore, an alignment film was formed on the TFT wiring layer. Next, an acrylic sealant was formed on the boundary of the liquid crystal cell, and liquid crystal was dropped into the area surrounded by the sealant to produce a TFT substrate.

On the other hand, a polyimide layer was formed on another glass substrate (thickness: 700 μm) in the same manner as in the above example, and then a black matrix and a color filter were formed on the surface of the polyimide layer. An alignment film was then formed on the color filter. Next, the alignment film was etched in the same manner as in Example 7 so that the glass substrate had a thickness of 24 μm, thereby producing a color filter substrate.

The TFT substrate and color filter substrate were bonded together via a sealant to produce a flexible liquid crystal display device. This flexible liquid crystal display device includes a TFT substrate made of a 24 μm thick glass substrate and a polyimide layer, and a color filter substrate made of a 24 μm thick glass substrate and a polyimide layer, and has excellent mechanical strength, bending resistance, and curl resistance.

1 Flexible liquid crystal display device 100 Glass substrate (TFT wiring layer substrate)
200 Transparent polyimide layer (TFT wiring layer substrate)
300 TFT wiring layer 400 Orientation film 500 Liquid crystal layer 600 Sealing material 700 Orientation film 800 Color filter layer 900 Transparent polyimide layer (color filter layer substrate)
1000 Glass substrate (color filter layer substrate)

Claims (25)

A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
The flexible liquid crystal display device has a laminated structure in which the TFT wiring layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the glass substrate has a thickness of 10 to 70 μm. The flexible liquid crystal display device according to claim 1, wherein the glass substrate has a thickness of 10 to 50 μm. The flexible liquid crystal display device according to claim 1 or 2, wherein the glass substrate has a thickness of 10 to 24 μm. A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
the flexible liquid crystal display device has a laminated structure in which the TFT wiring layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the thickness of the glass substrate after chemical etching is 10 to 70 μm. The flexible liquid crystal display device according to any one of claims 1 to 4, wherein the transparent polyimide layer and the glass substrate are supports for the TFT wiring layer. A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
The flexible liquid crystal display device has a laminated structure in which the color filter layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the glass substrate has a thickness of 10 to 70 μm. The flexible liquid crystal display device according to claim 6, wherein the glass substrate has a thickness of 10 to 50 μm. The flexible liquid crystal display device according to claim 6 or 7, wherein the thickness of the glass substrate is 10 to 24 μm. A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
The flexible liquid crystal display device has a laminated structure in which the color filter layer, the transparent polyimide layer and the glass substrate are laminated in this order, and the thickness of the glass substrate after chemical etching is 10 to 70 μm. A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
the flexible liquid crystal display device has a layered structure I in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the flexible liquid crystal display device has a layered structure II in which the color filter layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the glass substrate has a thickness of 10 to 70 μm. The flexible liquid crystal display device according to claim 10, wherein the glass substrate has a thickness of 10 to 50 μm. The flexible liquid crystal display device according to claim 10 or 11, wherein the thickness of the glass substrate is 10 to 24 μm. A flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer, and a glass substrate,
the flexible liquid crystal display device has a layered structure I in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the flexible liquid crystal display device has a layered structure II in which the color filter layer, the transparent polyimide layer, and the glass substrate are layered in this order, and the glass substrate has a thickness of 10 to 70 μm after chemical etching. The flexible liquid crystal display device according to any one of claims 6 to 13, wherein the transparent polyimide layer and the glass substrate are supports for the color filter layer. The polyimide contained in the transparent polyimide layer has a structural unit derived from a diamine, and the diamine is selected from the group consisting of diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-bis(4-aminophenoxy)phenyl )biphenyl, 4,4-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(3-aminopropyldimethylsilyl)benzene, and 9,9-bis(4-aminophenyl)fluorene (BAFL), which is at least one selected from the group consisting of. The polyimide contained in the transparent polyimide layer has a structural unit derived from an acid anhydride, and the acid anhydride is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic dianhydride (ODPA), norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (CpODA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2-di Carboxylic acid anhydrides, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, p-phenylenebis(trimellitate anhydride), thio-4,4'-diphthalic dianhydride dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, The flexible liquid crystal display device according to any one of claims 1 to 15, wherein the dianhydride is at least one selected from the group consisting of bis(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and bicyclohexyl-3,3',9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). The flexible liquid crystal display device according to any one of claims 1 to 16, wherein the liquid crystal layer is between the TFT wiring layer and the color filter layer. A method for manufacturing a flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer and a glass substrate, comprising the steps of:
a lamination step of forming a laminated structure in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
and etching the glass substrate so that the thickness of the glass substrate in the laminated structure falls within a range of 10 to 70 μm. The method for manufacturing a flexible liquid crystal display device according to claim 18, wherein the thickness of the glass substrate is adjusted to within a range of 10 to 50 μm in the etching process. The method for manufacturing a flexible liquid crystal display device according to claim 18 or 19, wherein the etching step involves masking the TFT wiring layer and the transparent polyimide layer. A method for manufacturing a flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer and a glass substrate, comprising the steps of:
forming a laminated structure in which the color filter layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
and etching the glass substrate so that the thickness of the glass substrate in the laminated structure falls within a range of 10 to 70 μm. The method for manufacturing a flexible liquid crystal display device according to claim 21, wherein the thickness of the glass substrate is adjusted to within a range of 10 to 50 μm in the etching process. The method for manufacturing a flexible liquid crystal display device according to claim 21 or 22, wherein the color filter layer and the transparent polyimide layer are masked in the etching process. A method for manufacturing a flexible liquid crystal display device including a thin film transistor (TFT) wiring layer, a liquid crystal layer, a color filter layer, a transparent polyimide layer and a glass substrate, comprising the steps of:
a lamination step of forming a laminate structure I in which the TFT wiring layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
a lamination step of forming a laminate structure II in which the color filter layer, the transparent polyimide layer, and the glass substrate are laminated in this order;
a step of bonding the TFT wiring layer and the color filter layer via a sealant;
and an etching step of etching the glass substrate in the laminated structures I and II so that the thickness of the glass substrate falls within a range of 10 to 70 μm. The method for manufacturing a flexible liquid crystal display device according to claim 24, wherein the thickness of the glass substrate is adjusted to within a range of 10 to 50 μm in the etching process.

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