JP7757795B2 - Electronic display device and manufacturing method thereof - Google Patents

Description

The present invention relates to a narrow-frame electronic display device and a manufacturing method thereof, and in particular to an electronic display device of the type that mounts a driver IC on the back surface of the display panel. Hereinafter, the electronic display device may also be referred to simply as the display device.

The screen sizes of LCDs, self-emissive displays such as OLEDs and microLEDs, and reflective displays such as electrophoretic displays are constantly increasing. However, manufacturing these displays requires large-area microfabrication technology and highly clean environments, and building manufacturing plants is extremely expensive. Even a single defective pixel can be fatal to a product, so the larger the screen size of a display device, the lower the yield. Even if the frequency of defective pixels is one pixel per square meter, for an electronic display device with a screen size of one square meter, most products will likely be defective. On the other hand, if the product size is 10 cm square, or 100 cm square, then there will likely only be one defective product out of 100, resulting in 99 acceptable products.

Given this background, attempts are being made to realize large-area electronic display devices by tiling small and medium-sized electronic display devices. The width of the frame of each electronic display device is important in tiling. If the frame is too wide, the tiling joints become noticeable, which diminishes the appeal of the large display area. The width of the frame depends on the layout of peripheral devices and components, such as the driver circuits, mounted on the electronic display device.
Typically, the drive circuit elements of a display device (driver ICs, hereinafter also referred to as driver ICs or driver elements) are attached to the periphery of the display device using TAB, COF, or the like. One proposed configuration involves folding TAB or COF, which uses a bendable film substrate, at the edge of the electronic display device, and arranging the drive circuitry on the side or back of the electronic display device (Patent Documents 1 and 2). More recently, another proposed configuration involves forming the electronic display device on a polymer film, folding it at the edge, and arranging the peripheral circuitry on the back of the electronic display device, thereby making the electronic display device more compact (Patent Documents 3 and 4).

Patent No. 2987903 Japanese Patent Application Publication No. 10-148839 US Patent Application Publication No. 2018/0090702 International Publication No. 2020/065910

In driver mounting using TAB or COF, it is common to use an ACF (anisotropic conductive film) to connect electrodes formed on the display device to the terminals of the TAB or COF for electrical connection with the electronic display device. In other words, since it is necessary to arrange electrodes for connection with the TAB or COF around the periphery of the display section of the electronic display device, the frame width cannot be narrower than the electrode width.
On the other hand, in a method in which the display unit of an electronic display device is fabricated on a film substrate and the edges are folded over to the back, after the driver elements are mounted, processing that deforms the entire electronic display device is required, which may result in damage to the driver elements or damage to the connection between the driver elements and the electronic display device, etc. Furthermore, in order to mount the driver IC after processing that deforms the electronic display device on the film substrate, pressure, heat, ultrasonic vibrations, etc., that occur during driver element mounting are transmitted through the film substrate to the backplane side of the electronic display device, which may destroy the TFTs of the electronic display device, which are particularly delicate parts.

The inventors conducted extensive research to solve these problems, and as a result, they discovered an electronic display device structure and manufacturing method that can be manufactured using existing electronic display device manufacturing equipment, has a narrow frame, and can achieve a high yield rate in terms of driver circuit implementation, thereby arriving at the present invention.

That is, the present invention has the following configuration.
[1] a substrate,
a polymer film folded so as to sandwich the substrate and adhered to both the first surface and the second surface of the substrate;
an electronic display device formed on the surface of the polymer film attached to the first surface of the substrate;
a driving circuit element for an electronic display device mounted on the surface of the polymer film attached to the second surface of the substrate;
Wiring formed on the surface of the polymer film to electrically connect the electronic display device and a driving circuit element;
Including,
An electronic display device, wherein the outer dimension Lo of the electronic display device and the outer dimension Ld of the display unit of the electronic display device satisfy the following relationship:
Lo<(1/2)×(Ld+5×Lpx)
Here,
Lo: outer dimensions of the electronic display device; Ld: outer dimensions of the display section of the electronic display device; Lpx: pixel size of the electronic display device.
[2] a substrate,
a polymer film having a softening temperature of 150°C or higher and 380°C or lower, which is folded so as to sandwich the substrate and is adhered to both the first surface and the second surface of the substrate;
a wiring formed on a surface of the polymer film opposite to the surface bonded to the substrate, the wiring extending from the first surface side to the second surface side of the substrate;
an electronic display device formed on the surface of the polymer film opposite to the surface bonded to the substrate;
1. An electronic display device comprising:
[3] The electronic display device according to [1] or [2], wherein the polymer film has an elastic modulus of 3 GPa or more and an elongation at break of 3% or more.
[4] The electronic display device according to any one of [1] to [3], wherein the polymer film is a polyimide film having a thickness of 3 μm or more and 75 μm or less.
[5] The electronic display device according to any one of [1] to [4], wherein the polymer film is a polyimide film having a total light transmittance of 85% or more and a yellow index of 5 or less.
[6] The electronic display device according to any one of [1] to [5], wherein the polymer film and the first surface of the substrate are bonded via a silane coupling agent condensate layer.
[7] The electronic display device according to any one of [1] to [6], wherein the polymer film and the second surface of the substrate are bonded via a silane coupling agent condensate layer.
[8] The electronic display device according to any one of [1] to [7], wherein the polymer film and the side surface of the substrate are bonded via a silane coupling agent condensate layer.
[9] The electronic display device according to any one of [1] to [8], wherein a part or all of the part of the polymer film facing the side surface of the substrate is thinned.
[10] The electronic display device according to any one of [1] to [9], wherein a part of the polymer film facing the side surface of the substrate is removed.
[11] The electronic display device according to any one of [1] to [10], wherein a driving IC for the electronic display device is mounted on the second surface side of the substrate.
[12] (a) preparing a laminate having a substrate and a polymer film adhered to at least one surface of the substrate;
(b) forming an electronic display device and wiring on the polymer film;
(c) removing the substrate outside the area where the electronic display device is formed, and dividing the area into a display area bonded to the substrate and a wiring area from which the substrate has been removed;
(d) heating the vicinity of the boundary between the display area and the wiring area to a temperature equal to or higher than the softening point of the polymer film, and bending the wiring area along the side surface of the substrate;
(e) The method for manufacturing an electronic display device according to any one of [1] to [11], further comprising at least a step of bending the wiring region from the side surface of the substrate toward the rear surface (second surface).
[13] The method for manufacturing an electronic display device according to [12], wherein the heating means is light irradiation.
[14] The method for manufacturing an electronic display device according to [12], wherein the heating means is direct contact of a heated object.
[15] The method for manufacturing an electronic display device according to [12], wherein the heating means is electromagnetic induction heating.

The present invention preferably further includes the following configuration.
[16] The electronic display device according to any one of [1] to [11], wherein the radius of curvature of the corner where the polymer film is bent from the first surface of the substrate toward the side surface is three times or less the sum of the thickness of the polymer film and the thickness of the wiring.
[17] The electronic display device according to any one of [1] to [11], wherein the length Lp of the polymer film parallel to the side surface of the substrate is 30% or more of the thickness Ts of the substrate.

The present invention preferably further includes the following configuration.
[18] The electronic display device according to any one of [1] to [11], wherein the thickness of the wiring is 3 μm or less.
[19] The electronic display device according to any one of [1] to [11], wherein the wiring is a sintered body of nanometal particles.
[20] The electronic display device according to any one of [1] to [11], wherein the wiring contains metal particles and a thermoplastic resin binder.
[21] The method for manufacturing an electronic display device according to any one of [12] to [15], wherein the laminate is a laminate in which a polymer film and a substrate are bonded via a silane coupling agent condensate layer.
[22] The method for manufacturing an electronic display device according to any one of [12] to [15], wherein the laminate is a laminate in which a polymer film and a substrate are bonded with an adhesive.
[23] The method for manufacturing an electronic display device according to any one of [12] to [15], wherein the laminate is obtained by applying a polymer solution to a substrate and drying the applied solution.
[24] The method for manufacturing an electronic display device according to any one of [12] to [15], wherein the laminate is obtained by applying a polymer precursor solution to a substrate, drying it, and undergoing a chemical reaction.
[25] The method for manufacturing an electronic display device according to any one of [12] to [15], wherein the laminate is obtained by thermocompression bonding a polymer film to a substrate.

According to a first embodiment of the present invention, in an electronic display device, an electronic display device serving as a display unit is formed on a polymer film that is folded so as to sandwich a substrate and is adhered to both a first surface and a second surface of the substrate, the polymer film being adhered to the substrate, and the outer shape of the display portion of the electronic display device is approximately the same as the outer shape of the substrate. Wiring for transmitting drive signals for the electronic display device is formed on the polymer film, and the wiring together with the polymer film is folded along the side of the substrate and adhered to the back side (second surface) of the substrate, and a drive circuit element (hereinafter also referred to as a driver IC) for driving the electronic display device is connected to the wiring on the back side of the substrate.
This type of display device structure has long been known for the purpose of narrowing the frame width of a display device, but in conventional display devices, the film that is folded from the front side (first surface) of the substrate to the back side (second surface) is a TAB or COF base film, which is separate from the substrate of the electronic display device itself.
In this invention, the display area of the electronic display device and the lead-out wiring around the electronic display device are formed on a common polymer film substrate. Therefore, there are no terminals required for connection, as in TAB or COF. Therefore, the lead-out wiring can be bent near the base where it leaves the display area, making it possible to narrow the frame of the electronic display device.
Furthermore, in the present invention, by using a polymer film with a predetermined physical property, it is possible to fold the film at an angle close to an acute angle without damaging the wiring and the electronic display device. As a result, the length Lov (1/2 × "external dimension of electronic display Lo" - "external dimension of substrate Ld") of the overhanging portion of the polymer film extending outward from the edge of the substrate can be reduced, thereby enabling an even narrower frame.

According to the second embodiment of the present invention, the structure of the electronic display device of the present invention does not require an electrode region for connecting the TAB or COF to the electronic display device, allowing wiring to be routed from very close to the display device. Furthermore, because the polymer film supporting the wiring softens upon heating, even when the routed wiring is directly bent close to the display device or almost to the side of the display device, the softened polymer film absorbs the strain caused by deformation, minimizing damage to the wiring and allowing the wiring to be made very thin, preferably 3 μm or less. Furthermore, since stress on the wiring can be reduced, metal films that are relatively resistant to deformation can be used as wiring. For example, wiring can be applied using printed electronics technologies such as inkjet printing, reverse printing, and microcontact printing using nano-sized metal particles. These printed electronics technologies produce wiring as low-temperature sintered bodies of metal particles, which tend to be more fragile than wiring composed of bulk metal layers and are therefore unsuitable for applications involving bending. However, by combining the present invention with these new wiring formation technologies, these technologies can be combined.
In addition, the present invention can use wiring obtained by printing a conductive paste containing metal particles and a thermoplastic resin binder. Wiring using a conductive paste with such a composition can be thermally deformed together with the polymer film having a softening temperature of the present invention because the binder resin has thermoplasticity. During use, the wiring is firmly fixed in an environment below the softening temperature, preventing damage to the wiring due to vibration, etc.
As a result, the frame width of the electronic display device can be narrowed to the thickness of the wiring and polymer film, and the driver IC can be mounted on the back side of the substrate, further reducing space.

In the present invention, a portion or all of the polymer film is preferably adhered to the substrate via a silane coupling agent condensate. The presence of the silane coupling agent condensate layer is the result of silane coupling agent treatment. The thickness of this silane coupling agent condensate layer is extremely thin, practically negligible compared to the thickness of the substrate and polymer film. As a result, the flatness of the polymer film layer is almost entirely controlled by the substrate, resulting in an extremely smooth surface. This is an essential characteristic for the formation of electronic display devices, which require large-area, high-precision processing. When a polymer film is used without a support (substrate) or is adhered to a substrate with a common adhesive or pressure-sensitive adhesive several micrometers to several tens of micrometers thick, undulations occur on the polymer film surface when the polymer film is folded. This undulation can be fatal in microfabrication, which requires extremely precise exposure operations.

The heat resistance of the silane coupling agent condensate layer is higher than that of typical organic adhesives, and it can withstand high temperatures during various processes for forming electronic display devices, specifically processes for forming amorphous silicon thin films, polysilicon thin films, oxide semiconductor thin films, and compound semiconductor films. Furthermore, it can withstand chemicals, solvents, and plasma processing used in processing processes such as exposure, development, etching, and resist stripping. Therefore, the electronic display device of the present invention can be processed directly on the polymer film of the laminate obtained by laminating a polymer film on a substrate via a silane coupling agent condensate layer. This processing method can be performed using conventional electronic display device manufacturing equipment, treating the flexible film as if it were a single substrate.
The present invention can also be applied to a process in which a solution of a polymer precursor (a typical example is polyamic acid, a precursor of polyimide) is applied to a substrate, and then dried and cured to form a polymer film on the substrate, provided that precise thickness control is performed.

Furthermore, in this invention, the polymer film, which serves as the substrate for the electronic display device, is supported by an inorganic substrate, preferably glass, thereby maintaining the flatness of the electronic display device. Furthermore, the lead-out wiring portion, which is folded from the periphery of the electronic display device and routed to the back of the substrate, can be adhered to the back of the substrate along with the base polymer film. Because the polymer film is supported by a rigid substrate, the driver IC can be directly bonded to the terminals on the polymer film after adhesion. Bonding accuracy often decreases when the polymer film does not have a support (substrate) or when the support has low rigidity. On the other hand, the electronic display device of this invention can achieve high bonding accuracy. Of course, this effect is not limited to inorganic substrates, as long as a substrate with flatness comparable to that of glass and a high compressive modulus is used.

Fig. 1A is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 1A, polymer films are bonded to both the first and second surfaces of a substrate via silane coupling agent layers. Fig. 1(B) is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 1(B), polymer films are bonded to both the first surface and the second surface of the substrate via a silane coupling agent layer. Fig. 2(A) is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 2(A), the first surface of the substrate and the polymer film are bonded via a silane coupling agent layer, and the second surface of the substrate and the polymer film are bonded with an adhesive. Fig. 2(B) is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 2(B), the first surface of the substrate and the polymer film are bonded via a silane coupling agent layer, and the second surface of the substrate and the polymer film are bonded with an adhesive. Fig. 3(A) is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 3(A), the first surface of the substrate and the polymer film are bonded with an adhesive, and the second surface of the substrate and the polymer film are bonded via a silane coupling agent condensate layer. Fig. 3(B) is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 3(B), the first surface of the substrate and the polymer film are bonded with an adhesive, and the second surface of the substrate and the polymer film are bonded via a silane coupling agent condensate layer. Fig. 4 is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 4, the first and second surfaces of the substrate, and further the side surfaces of the substrate and the polymer film are bonded via a silane coupling agent condensate layer. Fig. 5 is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention. In the embodiment of Fig. 5, polymer films are bonded to both the first and second surfaces of the substrate via silane coupling agent layers. The polymer films at the side surfaces of the substrate are thinned. 6 is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention, in which the display portion of the electronic display device is larger than the substrate size. 7 is a schematic diagram showing the cross-sectional structure of one embodiment of the electronic display device of the present invention, in which a gap exists on the side surface of the substrate. FIG. 8 is a diagram illustrating the first half of an example of the manufacturing process of the electronic display device of the present invention when a film lamination method is used. FIG. 9A is a diagram illustrating the latter half of an example of the manufacturing process of the electronic display device of the present invention when a film lamination method is used. FIG. 9B is a diagram illustrating the latter half of an example of the manufacturing process of the electronic display device of the present invention when a film lamination method is used. FIG. 10 is a diagram illustrating the first half of an example of the manufacturing process of the electronic display device of the present invention when the varnish method is used. FIG. 11A is a diagram illustrating the latter half of an example of the manufacturing process of the electronic display device of the present invention when the varnish method is used. FIG. 11B is a diagram illustrating the latter half of an example of the manufacturing process of the electronic display device of the present invention when the varnish method is used. FIG. 12 is a schematic diagram showing a case where a driver IC is mounted using a conventional TAB. 13A is a schematic diagram showing the details of the side surface of the electronic display device of the present invention, with the silane coupling agent layer, adhesive layer, and driver IC omitted. 13B is a schematic diagram showing the details of the side surface of the electronic display device of the present invention, with the silane coupling agent layer, adhesive layer, and driver IC omitted. FIG. 14 is a schematic diagram showing the details of the side surface of the electronic display device of the present invention, showing the state when the gap portion is filled with resin. FIG. 15 is a schematic diagram showing details of the side surface of the electronic display device of the present invention, showing the state in which there is substantially no gap. FIG. 16 is a schematic diagram showing the details of the side portion of the electronic display device of the present invention, in which there is essentially no gap, and furthermore, the polymer film on the side of the substrate has been removed, and the wiring has been made into flying leads. FIG. 17 is a schematic diagram showing the details of the side portion of the electronic display device of the present invention, in which there is essentially no gap, the polymer film on the side of the substrate is removed, the wiring is made into flying leads, and the dimensions of the display portion of the electronic display device are larger than the dimensions of the substrate. FIG. 18 is a schematic diagram showing a case where a driver IC is mounted using a conventional TAB. FIG. 19 is a schematic diagram showing the configuration of a side portion of an example of a conventionally proposed electronic display device. Fig. 20 is a schematic diagram showing the shape of the side portion of an example of a conventionally proposed electronic display device. A large gap exists between the side surface of the substrate and the polymer film, which hinders narrowing of the frame width. FIG. 21 is a layout diagram of a simulated display device used in an embodiment of the present invention.

The present invention will be described in detail below with reference to the drawings. Figures 1(A) and 1(B) are schematic diagrams showing the cross-sectional structure of a representative embodiment of an electronic display device of the present invention.
The substrate 15 is an important element that supports the entire electronic display device of the present invention.
Examples of substrates that can be used include organic substrates such as polymer plates and polymer sheets, composite material substrates such as glass fiber reinforced resin substrates, inorganic filler reinforced resin substrates, and carbon fiber reinforced resin substrates, and inorganic substrates such as glass substrates, metal substrates, metal foils, silicon wafers, and other semiconductor wafers. For practical purposes, flat substrates can be used. Flexible glass having a thickness of approximately several tens of micrometers can also be used as the substrate. The preferred thickness of the inorganic substrate 15 is 20 μm or more, more preferably 45 μm or more, and even more preferably 300 μm or more. It is also preferably 5 mm or less, more preferably 1.2 mm or less, and even more preferably 0.7 mm or less. By maintaining the thickness of the inorganic substrate within the above range, durability and handleability are improved.
Examples of glass substrates include quartz glass, high silicate glass (96% silica), soda-lime glass, lead glass, aluminoborosilicate glass, borosilicate glass (Pyrex (registered trademark)), borosilicate glass (alkali-free), borosilicate glass (microsheet), aluminosilicate glass, etc. Among these, those with a linear expansion coefficient of 5 ppm/°C or less are desirable, and commercially available products such as liquid crystal glass "Corning (registered trademark) 7059,""Corning (registered trademark) 1737," and "EAGLE" manufactured by Corning Incorporated, "AN100" manufactured by Asahi Glass Co., Ltd., "OA10" manufactured by Nippon Electric Glass Co., Ltd., and "AF32" manufactured by Schott GmbH are desirable.
Furthermore, these inorganic substrates, preferably substrates having a thin film formed on the surface thereof, of metals such as chromium, nickel, nichrome, molybdenum, and tungsten, or metal oxides, metal nitrides, silicon nitride, aluminum nitride, and silicon carbide, may also be used.
Alternatively, a metal substrate or metal foil having an anodized film formed on the surface, or an inorganic substrate coated with a fluororesin or silicone resin may be used.
Examples of resins that can be used for organic substrates and composite material substrates include epoxy resins, polyimide resins, phenolic resins, melamine resins, cross-linked polyester resins, polyether ether ketone resins, bismaleimide triazine resins, and cross-linked acrylic resins.

<Polymer film>
The polymer film 30 can be made of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, wholly aromatic polyester, other copolymer polyester, polymethyl methacrylate, other copolymer acrylate, polycarbonate, polyamide, polysulfone, polyether sulfone, polyether ketone, polyamide imide, polyether imide, aromatic polyimide, alicyclic polyimide, fluorinated polyimide, cellulose acetate, cellulose nitrate, aromatic polyamide, polyvinyl chloride, polyphenol, polyarylate, polyphenylene sulfide, polyphenylene oxide, polystyrene, liquid crystal polymer, or the like.

The softening temperature of the polymer film of the present invention is preferably 150° C. or higher and 380° C. or lower. Here, the softening temperature is the glass transition temperature obtained by measuring the thermal viscoelasticity.
The softening temperature (glass transition temperature) of the polymer film of the present invention is preferably 165°C or higher, more preferably 180°C or higher. The upper limit of the softening temperature (glass transition temperature) is preferably 360°C, more preferably 345°C. Since the present invention involves a process of softening and bending the polymer film by heating, the polymer film is required to have a softening temperature in a range that allows thermal deformation. On the other hand, since the formation of an electronic display device also requires a process that requires high temperatures, a certain level of heat resistance is required.
Among these polymer films, polymer films obtained by condensation polymerization reactions (condensation polymer films) are preferred in the present invention. Particularly effective and useful in the present invention are polymers with heat resistance of 100°C or higher, preferably 150°C or higher, i.e., so-called engineering plastic films. Heat resistance here refers to the property of a glass transition temperature or heat distortion temperature of 100°C or higher (preferably 150°C or higher). Condensation polymerization polymer films (condensation polymer films) preferably used in the present invention include polyester, polyamide, polyamideimide, polyimide, polybenzazole, polyimidebenzazole, polyethylene naphthalate film, and liquid crystal polymer film, and more preferably polyimide film, polyethylene naphthalate film, or liquid crystal polymer film.

The polymer films preferably used in the present invention are polyimide films, polyamide films, polyamideimide films, polybenzoxazole films, and polyimidebenzoxazole films, and aromatic polyimides, alicyclic polyimides, polyamideimides, polyetherimides, etc. can also be used. When the present invention is used particularly in the manufacture of flexible display elements, it is preferable to use colorless and transparent polyimide-based resin films, but this is not necessarily the case when forming rear elements for reflective or self-luminous displays.

In general, a polyimide film is obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting diamines with tetracarboxylic acids in a solvent to a support for producing the polyimide film, drying the solution to form a green film (also called a "precursor film" or "polyamic acid film"), and then subjecting the green film to high-temperature heat treatment on the support for producing the polyimide film or after peeling it off from the support to cause a dehydration ring-closing reaction.
Examples of polyimide films preferably used in the present invention include polyimide films obtained from polyimide resins containing the following chemical compositions.
- Polyimide resin obtained from pyromellitic acid and diaminodiphenyl ether,
- Polyimide resin obtained from biphenyltetracarboxylic acid and phenylenediamine,
- Polyimide resin obtained from pyromellitic acid and phenylenediamine,
- Polyimide resins using a diamine compound having a benzoxazole skeleton as the diamine component,
- Polyimide resins using cyclohexyltetracarboxylic acid or cyclobutanetetracarboxylic acid,
・Polyimide resin using alicyclic tetracarboxylic acid and aromatic diamine with amide bond
- Polyimide resins using fluorine-containing monomers,
Polyimide resins using ion-containing monomers: These are examples of the main components of tetracarboxylic acids or diamines, respectively, but other polyimide resins may also be used, such as polyimide resins copolymerized with a second or third component, polyimide resins made by combining polyimides of multiple compositions to form polymer blends or polymer alloys, and polyimide resins incorporating inorganic fillers or polydimethylsiloxane components. Polyimide films having a structure in which polyimide resins of different compositions are laminated in the thickness direction may also be used.

In the present invention, it is preferable to use a polyimide film having an elastic modulus of preferably 3 GPa or more, more preferably 4 GPa or more, even more preferably 5 GPa or more, and preferably 15 GPa or less, even more preferably 12 GPa or less, as the polymer film. If the elastic modulus is within this range, bending at the substrate edge is possible and damage to the wiring can be minimized. If the elastic modulus is lower than this range, the polymer film may deform significantly when bending, which may cause wiring breakage. On the other hand, if the elastic modulus is too high, bending may be difficult.
The polymer film of the present invention is preferably a polyimide film having a breaking elongation of 3% or more, preferably 5% or more, more preferably 7% or more, and even more preferably 9% or more. The breaking elongation is also a measure of foldability; if the breaking elongation is low, the film is brittle and prone to cracking, and may crack when bent, but if the breaking elongation is 5% or more, the film can be bent.
Furthermore, the polymer film of the present invention is preferably a polyimide film having a thickness of 3 μm or more and 75 μm or less. The film thickness is preferably 6 μm or more, and more preferably 12 μm or more. The upper limit is preferably 60 μm, and more preferably 45 μm or less. The film thickness is related to the bendability, and if the film thickness is within a certain range, bending becomes relatively easy.
Furthermore, the linear expansion coefficient of the polymer film of the present invention is 35 ppm/K or less, preferably 18 ppm/K or less, more preferably 9 ppm/K or less. The lower limit of the linear expansion coefficient is -5 ppm/K, preferably -2 ppm/K. Furthermore, it is preferable that the difference in the linear expansion coefficient between the polymer film and the substrate is 10 ppm/K or less. By keeping the linear expansion coefficient within a predetermined range, warping of the laminate is suppressed and the defective rate during production is reduced.

In the present invention, it is preferable to use a polymer film that exhibits a storage modulus at 30°C of 1.0 x ¹⁰⁹ Pa or more and a storage modulus at 300°C of less than 3.0 x ¹⁰⁸ Pa, as measured using a thermal viscoelasticity measurement method (DMA). Polymer films that fall within this range can be considered to be in the category of thermoplastic.

In the present invention, in order to fold the polymer film along the side of the substrate without stress, it is preferable to adjust the compressive strength of the polymer film to be weaker than the tensile strength of the polymer film. Specifically, for example, voids can be intentionally formed in the polymer film to make it more susceptible to buckling under compressive stress.

In the present invention, the polymer film is preferably a polyimide film having a total light transmittance of 85% or more and a yellow index of 5 or less. A total light transmittance of 88% or more is preferred, and 91% or more is even more preferred. There is no particular upper limit, but a value of 99% or more is sufficient for use in electronic display devices, and 98% or less is acceptable. The yellow index is preferably 4 or less, and even more preferably 3 or less. This means that the polyimide film is colorless and transparent. There is no particular lower limit for the yellow index, but a value of 1 or more is sufficient for use in electronic display devices. When a colorless and transparent polyimide film is used, the present invention can be applied to liquid crystal electronic display devices, which are light-transmitting display devices.

A preferred manufacturing method for producing the electronic display device of the present invention involves the process of forming a laminate in which the substrate and polymer film are bonded together. Examples of techniques for obtaining such a laminate include the film lamination method and the varnish method.

<Film lamination method>
A polymer film and a substrate are bonded together using an adhesive or pressure-sensitive adhesive to obtain a laminate. Examples of adhesives that can be used include epoxy adhesives, silicone adhesives, acrylic adhesives, and pressure-sensitive adhesives. However, when high-temperature processes are used to form electronic display devices, it is necessary to use a highly heat-resistant adhesive. Furthermore, in the present invention, a highly heat-resistant adhesive method can be used in which the substrate and polymer film are bonded via a silane coupling agent condensate. When high temperatures are required to form electronic display devices, the substrate also needs to be heat-resistant, so it is preferable to use the adhesive in combination with an inorganic substrate, preferably a glass substrate.
In the adhesion method using a silane coupling agent, the silane coupling agent is applied to the adhesive surface of either or both of the polymer film and the substrate, and then the two are superimposed and heated. The organic group of the silane coupling agent reacts with the polymer film surface, and the methoxy group and ethoxy group of the silane coupling agent react with hydroxyl groups on the inorganic substrate surface, and the silane coupling groups self-condense to form a condensate layer, thereby achieving adhesion. In this method, by combining it with the technology disclosed in, for example, Japanese Patent Publication No. 5224011, it is possible to control the adhesive strength and form patterns of strong and weak adhesive areas, which can be applied in situations where the substrate and polymer film are partially peeled off.

<Varnish method>
This method involves applying a resin solution or a polymer precursor solution that will form the polymer film to a substrate, drying it on the substrate, and optionally conducting a chemical reaction to obtain a polymer film. A typical example is the use of a polyimide resin solution or a solution of a polyamic acid, which is a polyimide precursor, to obtain a polyimide film.
In the varnish method, for example, by using the technique disclosed in Japanese Patent No. 5,862,866, it is possible to control the adhesive strength between the substrate and the polymer film and form a pattern of areas with strong and weak adhesive strength.

The properties of the polymer film specified in the present invention were determined by the following methods.
<Substrate thickness, polymer film thickness>
The thickness of the polymer film was measured using a micrometer (Militron 1245D manufactured by Fine Leaf Co., Ltd.) and the average value of 10 points was calculated.

<Tensile Modulus, Tensile Breaking Strength, and Tensile Breaking Elongation of Polymer Film>
From the polymer film to be measured, strip-shaped test pieces measuring 100 mm x 10 mm in each of the machine direction (MD) and width direction (TD) were cut out, and the tensile modulus, tensile strength at break, and tensile elongation at break were measured in each of the MD and TD directions using a tensile tester (Shimadzu Corporation, "Autograph (registered trademark); model name AG-5000A") at a tensile speed of 50 mm/min and a chuck distance of 40 mm, and the average values of all the measured values in the MD and TD directions were obtained.

<Glass transition temperature of polymer film measured by thermal viscoelasticity method>
The glass transition temperature was measured by measuring a polymer film (e.g., a polyimide film) having a size of 5 mm × 20 mm using a dynamic viscoelasticity measuring device (DMA: manufactured by UBM, product name: E4000F) from 30°C to 400°C at a heating rate of 4°C/min and a frequency of 1 Hz, and the temperature at which the change in elastic modulus (mechanical tan δ) was maximized was defined as the glass transition temperature.

<Coefficient of Linear Expansion (CTE) of Polymer Film>
The expansion/contraction rate was measured under the following conditions in the machine direction (MD direction) and width direction (TD direction) of the polymer film to be measured, and the expansion/contraction rate/temperature was measured at intervals of 15°C (30°C to 45°C, 45°C to 60°C, ...). This measurement was carried out up to 300°C, and the average value of all the measured values measured in the MD direction and TD direction was calculated as the coefficient of linear expansion (CTE).
Device name: MAC Science "TMA4000S"
Sample length: 20 mm
Sample width: 2 mm
Heating start temperature: 25°C
Heating end temperature: 400°C
Temperature rise rate: 5°C/min. Atmosphere: Argon Initial load: 34.5g/ ^mm2

<Total light transmittance>
The total light transmittance (TT) of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. The same measurement was performed three times, and the arithmetic average value was used.

<Yellow index>
The tristimulus values X, Y, and Z of the film were measured using a color meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source in accordance with ASTM D1925, and the yellowness index (YI) was calculated using the following formula: The same measurement was performed three times, and the arithmetic mean value was used.
YI=100×(1.28X-1.06Z)/Y

<Silane Coupling Agent Condensate Layer>
The silane coupling agent condensate layer 20 is literally a layer made of a condensate of a silane coupling agent. The silane coupling agent layer functions to bond the substrate and the polymer film. Part or all of the adhesive surfaces of the polymer film and the substrate are bonded via the silane coupling agent condensate layer. The silane coupling agent condensate layer is preferably present on the first surface and/or the second surface of the substrate, and more preferably on the first surface and the second surface of the substrate. It is further preferable that the silane coupling agent condensate layer is present on the entire first surface and the entire second surface of the substrate. It is also preferable that the polymer film and the side surface of the substrate are bonded via the silane coupling agent condensate layer.
Silane coupling agents are a general term for compounds that organically modify the surface of inorganic materials through a dealcoholization condensation reaction between hydroxyl groups present mainly on the surface of inorganic materials and methoxy groups, ethoxy groups, etc. contained in the silane coupling agent molecule. Such dealcoholization reactions also occur between silane coupling agents, resulting in a condensation product in which the silane coupling agents are linked by siloxane bonds.

In the present invention, the silane coupling agent is preferably a compound containing 10% by mass or more of silicon (Si). Furthermore, it is preferable that the silane coupling agent has an alkoxy group in its structure. Specific examples of silane coupling agents that can be preferably used in the present invention include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, aminophenyltrimethoxysilane, aminophenethyltrimethoxysilane, and aminophenylaminomethylphenethyltrimethoxysilane.

Among the above silane coupling agents, silane coupling agents containing one silicon atom per molecule are particularly preferred. Examples include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, aminophenyltrimethoxysilane, aminophenethyltrimethoxysilane, and aminophenylaminomethylphenethyltrimethoxysilane. When particularly high heat resistance is required in the process, those in which the silicon and amino groups are connected by an aromatic group are desirable. In addition to the above, 11-amino-1-undecenethiol can also be used as the coupling agent.

Silane coupling agents are generally liquids that are applied to a substrate or polymer film to form a layer, using a gas-phase coating method such as wet coating or vapor deposition.
As a method for wet-coating the silane coupling agent, a stock solution of the silane coupling agent or a solution diluted with a solvent such as an alcohol solution or an aqueous solution can be used, and a conventionally known solution application means (conventionally known application device) such as spin coating, curtain coating, dip coating, slit die coating, gravure coating, bar coating, comma coating, applicator method, screen printing, or spray coating can be appropriately used.
The silane coupling agent can also be applied spot-wise using a dispenser, a dropper, or by drawing with a brush.

The silane coupling agent layer can also be applied via the gas phase, as in a vapor deposition method. Specifically, the substrate or polymer film is formed by exposing it to the vapor of the silane coupling agent, i.e., the silane coupling agent in a substantially gaseous state. The vapor of the silane coupling agent can be obtained by heating the liquid silane coupling agent to a temperature between 40°C and the boiling point of the silane coupling agent. The boiling point of silane coupling agents varies depending on their chemical structure, but is generally in the range of 100-250°C. However, heating above 200°C is not recommended, as it may cause side reactions on the organic groups of the silane coupling agent. The silane coupling agent may also be applied to both sides of the substrate or polymer film.

<Wiring>
The wiring 40 of the present invention is formed on the surface of the polymer film 30 opposite the surface bonded to the substrate 15, extending from the first surface to the second surface of the substrate. It preferably electrically connects (contacts) the electronic display device with a driving element (driver IC). The wiring is actually spread throughout the electronic display device like a mesh, forming a multilayer wiring structure. However, for convenience, the diagram shows only the portion extending from the periphery of the electronic display device to its outer periphery. The wiring is generally preferably a metal layer, typically made of copper, silver, aluminum, gold, nickel, chromium, tin, or lead, which have high electrical conductivity, or molybdenum or tungsten, which have low linear expansion coefficients. Furthermore, alloys such as brass, cupronickel, bronze, invar, stainless steel, and solder may also be used as needed. Such wiring is formed using vacuum metallizing techniques such as vapor deposition and sputtering, wet metallizing techniques such as electroless plating, or plasma spraying, either singly or in combination. Furthermore, the wiring is patterned by etching or masking.
Although omitted in the drawings for simplicity, the wiring is preferably insulated and protected by resin etc. The insulating protection is preferably provided on the top, bottom and side surfaces of the wiring.

<Driver circuit element (driver IC)>
The driver circuit element (driver IC) 50 of the electronic display device is an integrated electronic circuit element that supplies image signals and power to the electronic display device. The driver IC may be a conventional semiconductor element, preferably mounted as a bare chip. The driver IC 50 is preferably mounted on the surface opposite the electronic device 60. In Figure 1, it is mounted on the surface of the polymer film attached to the second surface of the inorganic substrate. Although not shown in the figure, in face-down bonding, connection bumps or other devices are formed on the electrodes extending from the wiring. In face-up bonding, the wiring is subjected to a surface treatment suitable for wire bonding. TAB bonding of the wiring as flying leads is also possible. Gold plating, tin plating, or other surface treatments for the wiring are preferred. After mounting the driver IC, underfill, overcoat, or pod encapsulation may be applied.

<Electronic display devices>
The electronic display device 60 in the present invention refers to electronic display devices commonly referred to as FPDs (flat panel displays), such as liquid crystal displays, OLEDs (organic light-emitting diodes), micro LED arrays, and electrophoretic displays, and is the part of the electronic display device of the present invention that displays images. It does not include CRTs (cathode ray tubes). In principle, it can also be applied to FEDs, PDPs, fluorescent display tubes, and the like. The present invention is preferably combined with large-area technology using tiling, and is preferably combined with self-luminous OLEDs, micro LED arrays, or reflective display devices such as electrophoretic electronic display devices and reflective liquid crystal display devices.
The electronic display device 60 is preferably formed on the surface opposite to the driver IC 50, and in Fig. 1, it is formed on the surface opposite to the adhesive surface (non-adhesion side) of the polymer film that is adhered to the first surface of the inorganic substrate. In other words, it is preferably constructed on the surface of the polymer film.
Generally, electronic display devices are composed of a backplane and a frontplane. The following process is an example of how to form an electronic display device in the present invention. First, a gas barrier film, an anchor layer, and the like are formed as needed on the surface of the non-adhered side of a polymer film bonded to a substrate. Then, thin-film semiconductor elements and pixel drive electrodes that directly handle pixel signals are formed. Light emitters or electrophoretic elements are then arranged. After that, a frontplane equipped with opposing electrodes or, if necessary, a color filter is either built up or attached to the backplane to obtain an electronic display device.
As is well known, an electronic display device is a collection of individual pixels. In this invention, the pixel dimension (hereinafter also referred to as pixel size or pixel dimension) of an electronic display device is defined as Lpx. The pixel dimension can be calculated by dividing the dimension of the electronic display device in either the X or Y direction by the number of pixels constituting the same direction. When three RGB color pixels exist in one pixel for color display, the RGB color set is counted as one pixel. In a reflective display, for example, when four colors, YMCK, exist in one pixel, the YMCK color set is counted as one pixel.

<Adhesive layer>
In the present invention, when it is necessary to bond the polymer film and the substrate without using a silane coupling agent, an adhesive may be used to form the adhesive layer 70. It is preferable to use a relatively heat-resistant adhesive, such as an epoxy resin or silicone resin, commonly used in the electronics field. In the present invention, the adhesive preferably contains less than 10% by mass of silicon (Si). Furthermore, it is preferable that the adhesive does not contain an alkoxy group in its structure.

<Casting resin>
When a gap exists between the side surface of the substrate and the polymer film on the side of the electronic display device of the present invention, the gap is filled with the resin to fix the polymer film located on the side surface of the substrate and indirectly protect the wiring formed on the polymer film. The casting resin can be epoxy resin, acrylic resin, silicone resin, urethane resin, phenolic resin, melamine resin, etc.

The process for manufacturing the electronic display device of the present invention using the film lamination method will be described with reference to FIGS. 8, 9A, and 9B.
Step A in FIG. 8 shows the substrate 15 before processing.
8 shows the state in which a silane coupling agent condensate layer 20 has been formed on the surface of the substrate 15. However, in this state, the silane coupling agent has not yet been completely condensed. At this stage, a preliminary treatment for forming a pattern with varying adhesive strength, as described in Japanese Patent No. 5224011, can be added.
Step C in Figure 8 shows the state in which a polymer film 30 is further adhered. The adhesive surface of the polymer film is preferably chemically activated by plasma treatment or the like, i.e., it is preferable to make it a state in which highly chemically active functional groups such as carboxyl groups, hydroxyl groups, amino groups, and carbonyl groups are present. The organic portion of the silane coupling agent reacts with these functional groups, and the methoxy and ethoxy groups of one silane coupling agent undergo a dealcoholization reaction while reacting with hydroxyl groups and the like on the surface of the substrate, thereby adhering the two. The silane coupling agents also condense with each other to form a condensate layer.
Steps A to C correspond to "(a) a step of preparing a laminate having a substrate and a polymer film adhered to at least one surface of the substrate."
8, wiring is formed on the polymer film. For convenience, only the peripheral portion is shown.
The electronic display device is formed in step E of Figure 8. The wiring actually extends in a mesh-like pattern within the electronic display device.
Steps D and E correspond to "(b) step of forming an electronic display device and wiring on a polymer film."

In step F of FIG. 8 , a portion of the substrate corresponding to the wiring region is removed, dividing the laminate into a display region X1 and a wiring region X2. More precisely, the removal is preferably performed so that the dimensions of the display area of the electronic display device are the same as the dimensions of the remaining substrate, or the dimensions of the substrate are smaller by approximately the same or less than the dimensions corresponding to the substrate thickness. This results in a polymer film that forms the wiring region surrounding the electronic display device in a frame-like shape. To remove a specific portion of the substrate, the substrate can be cut mechanically or by laser irradiation, or a notch can be created and then separated. In the case of a metal substrate, the relevant portion can also be removed by etching. In theory, dissolving and removing unnecessary portions is also possible in the case of a substrate using a strong alkali or hydrofluoric acid.
This step F corresponds to "(c) a step of removing the substrate outside the area where the electronic display device is formed, and dividing the area into a display area adhered to the substrate and a wiring area from which the substrate has been removed."

First, the second half of the manufacturing process for an electronic display device using the film lamination method will be described with reference to Figure 9(A). Step G1 in Figure 9(A) shows a state in which a slit 31 is made in the polymer film surrounding the periphery of the electronic display device from the side opposite the side with the wiring. The slit can be made halfway through the polymer film or to the boundary between the polymer film and the wiring, like a half-cut. Note that for convenience, the slit is drawn at an acute angle in the figure, but if a slit with a 90-degree opening is made, it will be possible to bend the polymer film at a right angle at the slit.
9A shows the state in which thinning treatment is performed on the opposite side of the wiring of the polymer film surrounding the periphery of the electronic display device. When thinning, the thickness is preferably 90% or less of the thickness of the polymer film, more preferably 60% or less, and even more preferably 30% or less. Furthermore, the thickness is preferably 1% or more, more preferably 5% or more, and even more preferably 10% or more.
Step G1 or step G2 is performed to enable bending the polymer film at an acute angle and to minimize damage to the wiring. Either slit formation or thinning may be performed alone, or both may be used in combination as appropriate.
In addition, if the polymer film has thermoplasticity, it is also possible to bend the polymer film by heating the polymer film part, preferably locally, to a temperature above the heat distortion temperature, and the polymer film can be bent without applying stress to the wiring part even without the slits or thinning.
Step H in Figure 9(A) shows the case where the wiring has been thinned by step G2. A silane coupling agent 21 is applied in advance to the second surface (rear surface) of the substrate where the folded polymer film comes into contact. In this case, the required amount can be applied to the required area using a dispenser or the like. In a laboratory setting, application can also be done using a dropper or paintbrush.
9(A) shows a state in which the polymer film is folded and the corresponding portion of the polymer film is bonded to the second surface (rear surface) of the substrate via a silane coupling agent layer. In this case, as in steps A to C, the reaction of the silane coupling agent bonding the substrate and the polymer film and the self-condensation reaction proceed simultaneously in parallel to form a silane coupling agent layer.
J in FIG. 9A shows a state in which a driving circuit element (driver IC) of an electronic display device is mounted.

As a result of the above, an electronic display device having thinned wiring on the side surface as shown in FIG. 5 can be obtained.
If the thinning process corresponding to step G2 is not performed, the shape will be as shown in Fig. 1(A). Even if two 90-degree slits are made, the shape will be as shown in Fig. 1(A) in schematic form.
Here, we have exemplified a method in which a polymer film is adhered to an inorganic substrate, the electronic display device portion is not peeled off from the inorganic substrate, and the inorganic substrate portion used in production is incorporated into the electronic display device, but it is also possible to peel the entire polymer film off the inorganic substrate at the stage of proceeding up to step E, prepare a new substrate of the specified size, re-adhere it, and proceed to step F. From the perspective of suitability for the manufacturing process, the use of a highly heat-resistant inorganic substrate for the manufacture of electronic display devices is preferable, but if the product requires lighter weight and flexibility, one option is to use a lighter, thinner substrate such as a polymer plate, polymer sheet, or FRP plate.
Figure 2 shows the case where an adhesive is used instead of a silane coupling agent in steps H to I of Figure 9(A). When a silane coupling agent is used to bond the second surface of the inorganic substrate to the polymer film, the silane coupling agent layer is extremely thin, so the inorganic substrate, which can be considered a rigid body, effectively supports the polymer film directly. Therefore, the only elastic layer supporting the wiring is the polymer film layer, and the heat, pressure, and ultrasonic vibrations during bonding are not absorbed more than necessary, resulting in low-defect bonding.
On the other hand, when an adhesive is used, the elastic layer is a two-layer structure consisting of a polymer film and an adhesive layer, which tends to attenuate ultrasonic vibrations during bonding. However, in the case of Figure 2(A), the polymer film of the display element portion and the inorganic substrate are bonded on the first surface side of the inorganic substrate with a very thin silane coupling agent layer, which suppresses attenuation of ultrasonic vibrations throughout the device, making it possible to ensure a sufficiently high yield rate of bonding. However, when an adhesive is used, it is preferable to apply it as thinly as possible and to use an adhesive that exhibits a high elastic modulus as a cured product.

Figure 3(A) shows a case where a polymer film is bonded to an inorganic substrate using an adhesive instead of a silane coupling agent in step B. In this case, contrary to Figure 2(A), vibration absorption occurs in the display device as a whole due to the adhesive layer occupying a large area. However, because the adhesive layer directly below the bonding site is a very thin silane coupling agent layer, it is possible to ensure a sufficiently high bonding yield rate, as in the case of Figure 2(A).
Figure 4 shows a state in which the side portions of the polymer film and inorganic substrate are also bonded with a silane coupling agent condensate. When tiling electronic display devices obtained by the present invention, the side surfaces of the display devices are easily damaged, so it is a preferred embodiment to securely bond and fix the side surfaces to the inorganic substrate. The configuration shown in Figure 4 can be achieved by not performing the flying lead formation in step G of Figure 9(A), but instead applying a silane coupling agent to the side surfaces of the inorganic substrate in step H, and then bending the polymer film along the side surfaces of the inorganic substrate.

Next, the second half of the manufacturing process for an electronic display device using the film lamination method will be described with reference to Figure 9(B). In step G of Figure 9(B), a silane coupling agent or a solution 21 of the silane coupling agent is applied to part or all of the back side (second surface) of the remaining substrate. In this case, the required amount can be applied to the required area using a dispenser or the like. In a laboratory setting, application can also be performed using a dropper or paintbrush. When a solution is used, a silane coupling agent film is formed by drying.
Prior to this, a portion of the surface of the polymer film that was attached to the substrate in the wiring region can be thinned by plasma etching, sandblasting, other mechanical grinding methods, chemical etching, or the like.
9(B), the polymer film in the wiring region is heated at a location adjacent to the display region, and then the polymer film is folded along the side (cut surface) of the substrate together with the wiring, and then folded toward the back side (second surface) of the substrate. This process corresponds to "(d) a process of heating the vicinity of the boundary between the display region and the wiring region to a temperature equal to or higher than the softening point of the polymer, and folding the wiring region along the side surface of the substrate, and (e) a process of further folding the wiring region from the side surface of the substrate toward the back side (second surface)."
A silane coupling agent 21 is applied to the second surface (rear surface) of the substrate in advance, and the polymer film is adhered to the substrate as the silane coupling agent condenses and the polymer film and the silane coupling agent react with each other, and the substrate and the silane coupling agent react with each other.
The polymer film can be heated by any of a variety of methods, including irradiation with ultraviolet light, infrared light, laser light, or a strong flash lamp; direct contact with a heated object; heating by radiant heat by bringing a heated object close to the film; heating the wiring itself by electromagnetic induction; and heating using microwaves.
The heating temperature is preferably in the range of the softening temperature of the polymer film to the softening temperature + 80°C.
9(B) shows a state in which the polymer film is folded and the corresponding portion of the polymer film is bonded to the second surface (rear surface) of the substrate via a silane coupling agent layer. Note that although a silane coupling agent is used in this example, an adhesive may be used instead of the silane coupling agent.
J in FIG. 9B shows a state in which a drive circuit element (driver IC) for an electronic display device is mounted.

As a result of the above, an electronic display device having a side surface as shown in FIG. 1B in outline and in FIG. 13B in detail can be obtained.
Here, an example has been given in which the polymer film is adhered to the inorganic substrate, the electronic display device portion is not peeled off from the inorganic substrate, and the inorganic substrate portion used in production is incorporated into the electronic display device, but it is also possible to peel the entire polymer film off the inorganic substrate at the stage of proceeding up to step E, prepare a new substrate of a predetermined size, re-adhere it, and proceed to step F. From the viewpoint of suitability for the manufacturing process, it is preferable to use a highly heat-resistant inorganic substrate for the manufacture of electronic display devices, but if the product is required to be lightweight and flexible, one option is to use a lighter, thinner substrate such as a polymer board, polymer sheet, or FRP board.
FIG. 2B shows a case where an adhesive is used instead of a silane coupling agent when bonding the polymer film and the substrate to obtain a laminate in steps B and C.
FIG. 3B shows a case where the polymer film is bonded to the second surface of the inorganic substrate using an adhesive instead of a silane coupling agent in steps I to H.
FIG. 6 shows a case where the display area is larger than the substrate size.
FIG. 7 shows a case where there is a gap between the folded polymer film and the side surface of the substrate, and the gap is filled with a casting resin 90.

Next, a process for manufacturing the electronic display device of the present invention using the varnish method will be described with reference to FIGS. 10, 11A and 11B.
Step A in FIG. 10 shows the substrate before processing.
Step B in Figure 10 shows a state in which a polymer solution or polymer precursor solution 35 has been applied to the surface of the substrate. The silane coupling agent (layer) is omitted from the figure because it may or may not be used. However, when performing the patterning of adhesive strength described in Japanese Patent No. 5,862,866, a silane coupling agent may be applied to the substrate, and the polymer solution or polymer precursor solution may be applied after performing a preliminary treatment for patterning.
Step C in FIG. 10 shows a state in which a polymer film is formed on the substrate after drying and, if necessary, chemical reaction.
As with the film lamination method, steps A to C correspond to "(a) a step of preparing a laminate having a substrate and a polymer film adhered to at least one surface of the substrate" in the varnish method. The subsequent steps are generally the same as those in the film lamination method.
10, wiring is formed on the surface of the polymer film opposite to the adhesive surface (non-adhesive side). For convenience, only the peripheral portion is shown.
The electronic display device is formed in step E of Figure 10. The wiring is actually connected to a wiring layer arranged in a mesh pattern within the electronic display device.
Steps D and E correspond to "(b) step of forming an electronic display device and wiring on a polymer film" in the varnish method.
In step F of FIG. 10, a part of the substrate is removed to divide it into a display area X1 and a wiring area X2.

First, the second half of the manufacturing process for an electronic display device using the varnish method will be described with reference to Fig. 11(A). Step G1 in Fig. 11(A) shows the state in which slits 31 are made in the polymer film surrounding the periphery of the electronic display device from the side opposite to the side with wiring.
11A shows a state in which the polymer film surrounding the periphery of the electronic display device is thinned from the opposite side to the wiring side. In this case, the wiring also becomes so-called flying leads 41.
If the polymer film has thermoplastic properties, it is possible to bend the polymer film by heating the polymer film, preferably locally, to a temperature above the heat distortion temperature, as in the case of using the film lamination method, and the polymer film can be bent without applying stress to the wiring portion even without the need for the slits or thinning.
Step H in Figure 11(A) shows a case where the film is bent sideways without performing the slitting process in step G1 or the thinning process in step G2. A silane coupling agent 21 is applied in advance to the second surface (rear surface) of the substrate where the folded polymer film will come into contact. In this case, the required amount can be applied to the required locations using a dispenser or the like. In a laboratory setting, application can also be performed using a dropper or paintbrush.
11(A) shows a state in which the polymer film is folded and the corresponding portion of the polymer film is bonded to the second surface (rear surface) of the substrate via a silane coupling agent layer. In this case, as in steps A to C, the reaction of the silane coupling agent bonding the substrate and the polymer film and the self-condensation reaction proceed simultaneously in parallel to form a silane coupling agent layer.
J in FIG. 11A shows a state in which a driving circuit element (driver IC) of an electronic display device is mounted.
As a result, an electronic display device having the configuration illustrated in Figure 1A can be obtained (although there is no silane coupling agent layer between the first surface of the substrate and the polymer film layer).
In the varnish method, as in the film lamination method, one possible embodiment is to peel the entire polymer film off the inorganic substrate at the stage of step E, prepare a new substrate of a predetermined size, re-adhere the film, and proceed to step F.

In FIG. 11B, the steps from step G onwards are the same as those in the film lamination method.
In the varnish method, as in the film lamination method, one possible embodiment is to peel the entire polymer film off the inorganic substrate at the stage of step E, prepare a new substrate of a predetermined size, re-adhere the film, and proceed to step F.

In the present invention, it is preferable that the outer dimension Lo of the electronic display device and the outer dimension Ld of the display unit of the electronic display device have the following relationship:
Lo<(1/2)×(Ld+5×Lpx)
Here,
Lo: outer dimensions of the electronic display device, Ld: outer dimensions of the display portion of the electronic display device, and Lpx: pixel size of the electronic display device.
This relationship will be explained using Figures 13(A) and 13(B). Figures 13(A) and 13(B) show cross sections near the side surfaces of an electronic display device. The cutting direction of the cross section is either the X direction or the Y direction of the electronic display device. In the present invention, it is necessary to establish the above relationship in either the X direction or the Y direction of the display device, or preferably in both directions.
The dimension Lov of the area outside the display area where an image cannot be displayed (overhang portion) is half the dimension obtained by subtracting the dimension Ld of the area where an image can actually be displayed from the outer dimension Lo of the electronic display device. Lov can be understood as the minimum width of the frame. In the present invention, it is a preferred feature that this overhang width is 2.5 times or less the pixel dimension.
If the frame width is set to about 2.5 times or less the display pixel, the width of the non-display area that occurs when tiling is performed will be about 5 times or less the pixel size, making the tiling joints less noticeable, more preferably 2.4 times or less, even more preferably 2.2 times or less, and particularly preferably 2.0 times or less.

On the other hand, Lov in Figure 13(A) is the sum of the wiring thickness Lb and the side gap Lg. Here, the wiring thickness is the sum of the polymer film thickness and the wiring thickness. If the polymer film is thinned, it is the sum of the thinned polymer film thickness and the wiring thickness, and if the polymer film is completely removed at the bent portion, Lb is equal to the wiring thickness.
Both the polymer film and the wiring have a finite bending modulus. Therefore, (unless the polymer film is slit or thinned, or temporarily plasticized by heating), the polymer film is bent with a finite radius of curvature Ri. In this case, the radius of curvature corresponds to the sum of Lg and Lb, i.e., Lov.
Ri=Lg+Lb=Lov
The above is a geometric solution for the ideal case where the polymer film and wiring are bent in a perfect arc. In reality, the bent part is distorted into an elliptical arc, so it deviates from the ideal shape.
In the present invention, it is preferable to bend the cable so that the bending radius Rr is between 0.7 and 3 times Ri.
0.7×Lov ≦ Rr ≦ 3×Lov
It is more preferably 0.8 times or more and 2.5 times or less, and even more preferably 1 time or more and 2 times or less.

When the polymer film and wiring are bent with a curvature radius Lov and the substrate thickness Ts is sufficiently thick (Ts>2×Lov), a section Lp can be provided where the side surface of the substrate is parallel to the polymer film and wiring. Lp is calculated as follows: Lp=Ts-2×Lg
This is also a geometric solution in the case of ideal deformation, and in reality it deviates from the ideal form, but in the present invention it is preferable that Lp is at least 30% or more of the substrate thickness Ts. That is,
Lp ≧ 0.3 × Ts
It is more preferably 40% or more, and even more preferably 50% or more.

Also, Lov in Figure 13(B) is the sum of the flying wire thickness Tw and the side gap Lg. The thickness of the flying wire is equal to the thickness of the wire. The flying wire is bent with a finite radius of curvature Ri. In this case, the radius of curvature corresponds to the sum of Lg and Tw, i.e., is equal to Lov.
Ri=Lg+Tw=Lov
The above is a geometric solution for the ideal case where the polymer film and wiring layer are bent in a perfect arc. In reality, the bent part is distorted like an ellipse, so it deviates from the ideal shape.
In the present invention, it is preferable to bend the cable so that the bending radius Rr is between 0.7 and 3 times Ri.
0.7×Lov ≦ Rr ≦ 3×Lov
It is more preferably 0.8 times or more and 2.5 times or less, and even more preferably 1 time or more and 2 times or less.

When the flying wiring is bent with a curvature radius Lov and the substrate thickness Ts is sufficiently thick (Ts>2×Lov), a section Lp can be provided where the substrate side surface is parallel to the wiring polymer film and the wiring layer. Lp is calculated as follows: Lp=Ts-2×Lg
This is also a geometric solution in the case of ideal deformation, and in reality it deviates from the ideal form, but in the present invention it is preferable that Lp is at least 30% or more of the substrate thickness Ts. That is,
Lp ≧ 0.3 × Ts
It is more preferably 40% or more, and even more preferably 50% or more.

14 shows the state when a resin is filled into the gaps that occur on the side surfaces of the electronic display device of the present invention. By filling the gaps with resin and fixing the shape of the polymer film on the side surfaces, the side surface shape of the electronic display device of the present invention can be maintained well. By using a mold or the like during fixing, it is possible to make the side surface shape closer to the ideal shape.
Figure 15 shows the state of the electronic display device of the present invention when there is essentially no gap in the side portion. This shape can be achieved by partially heating and plasticizing the polymer film, thereby deforming the polymer film. In this case, Lov is equal to the sum of the polymer film and wiring thickness, allowing for a very narrow frame width.

16 shows the case where there is no gap and the polymer film is further thinned at the side of the substrate, in which case Lov is equal to the wiring thickness.
FIG. 17 shows a configuration in which the display area of the electronic display device has been further removed, and since the outer dimensions Lo of the electronic display device and the dimensions Ld of the display area of the electronic display device are substantially equal, it is possible to eliminate the frame.

Figure 18 shows a conventional electronic display device using TAB technology, where a silane coupling agent is used to bond the polymer film that serves as the TAB base material to the second surface of the substrate. The TAB and electronic display device are connected by an anisotropic conductive film (ACF). Because the ACF portion cannot be used for display, the width of the ACF is included in the frame, preventing the frame from becoming narrower.

Figure 19 shows a detailed cross-sectional schematic diagram of the side of a previously proposed electronic display device similar to the present invention. Because the polymer film is bent with a large curvature, the overhang is large, making it difficult to narrow the frame width. This shape occurs because the polymer film has poor flexibility, and reducing the curvature increases the likelihood of the film being damaged.

Figure 20 shows a detailed cross-sectional schematic diagram of the side of a previously proposed electronic display device similar to the present invention. Because the polymer film is bent with a large curvature, the overhang is large, making it difficult to narrow the frame width. This shape occurs because the polymer film has poor flexibility, and reducing the curvature increases the likelihood of the film being damaged.

Figure 12 shows a conventional electronic display device using TAB technology, where a silane coupling agent is used to bond the polymer film that serves as the TAB base material to the second surface of the substrate. The TAB flying wiring and the electronic display device are connected by an anisotropic conductive film (ACF). Because the ACF portion cannot be used for display, the width of the ACF is included in the frame, preventing the frame from becoming narrower.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
<Laminate Production A> (Film Lamination Method 1)
(Production of polyimide film Apf)
Colorless polyimide "Neoprene (registered trademark)" L-3430 manufactured by Mitsubishi Gas Chemical Company, Inc. was pulverized and dissolved in NMP, and Snowtex (DMAC-ST30, manufactured by Nissan Chemical Industries, Ltd.), in which colloidal silica (average particle size: 0.08 μm) was dispersed in dimethylacetamide, was added to the polyimide solution A so that the colloidal silica accounted for 1.5 mass % of the total polymer solid content, thereby obtaining a polyimide solution Asol with a solid content of 18%.
The resulting polyimide solution Asol was applied to a mirror-finished endless continuous stainless steel belt (coating width: 1240 mm) using a die coater and dried for 20 minutes at 90 to 115° C. After drying, the self-supporting polyimide film was peeled off from the support and both ends were cut to obtain a green film Agf.
The resulting green film (Agf) was conveyed through a pin tenter with a final pin sheet spacing of 1140 mm and heat-treated at 150°C for 4 minutes in the first stage, 250°C for 4 minutes in the second stage, and 300°C for 8 minutes in the third stage. It was then cooled to room temperature over 2 minutes, and the film was wound up into a roll to obtain a colorless, transparent polyimide film (Apf). The resulting polyimide film had a thickness of 35 μm, a glass transition temperature of 303°C, a total light transmittance of 92%, a yellow index of 1.2, a tensile modulus of 3.7 GPa, a tensile elongation at break of 24%, a coefficient of thermal expansion (CTE) of 58 ppm/K, a water absorption of 2.1%, and a coefficient of humidity expansion (CHE) of 63 ppm/% RH.

(Laminate production 1 by film lamination method)
One side of the polyimide film Apf was subjected to nitrogen plasma treatment using a vacuum plasma treatment device in a roll-to-roll system, and then cut into a square of 280 mm x 280 mm.
An isopropyl alcohol solution containing 1% by mass of a silane coupling agent ("KBE-903" manufactured by Shin-Etsu Chemical Co., Ltd.) was spin-coated onto a 300 mm x 300 mm, 0.5 mm thick glass substrate, which was then dried at 100°C for 1 minute. Furthermore, as a treatment to weaken the activity of the silane coupling agent in the periphery of the glass (a treatment to pattern the strength of the adhesive), a central 250 mm x 250 mm portion of the glass was masked with a light-shielding plastic sheet, and the entire surface was irradiated with ultraviolet light using a UV/ozone cleaner manufactured by LAN Technical Services.
Next, the plasma-treated surface of the film and the silane coupling agent-treated surface of the glass substrate were brought into contact with each other using a vacuum laminator, and heat-treated at 150° C. for 1 minute to obtain a laminate A.

<Laminate Production B> (Film Lamination Method 2)
(Production of polyimide film Bpf)
While introducing nitrogen gas into a reaction vessel equipped with a nitrogen inlet tube, Dean-Stark apparatus, reflux condenser, thermometer, and stirrer, 32.02 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) and 230 parts by mass of N,N-dimethylacetamide (DMAc) were added and completely dissolved, and then 44.42 parts by mass of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride (6FDA) was added in portions as a solid, followed by stirring at room temperature for 24 hours. Thereafter, a polyamic acid solution Bpaa having a solids content of 25% by mass and a reduced viscosity of 1.10 dl/g was obtained.
Next, 204 parts by weight of DMAc was added to the resulting polyamic acid solution Bpaa to dilute it to a polyamic acid concentration of 15% by weight, and then 1.3 parts by weight of isoquinoline was added as an imidization accelerator. Next, 12.25 parts by weight of acetic anhydride as an imidization agent was slowly added dropwise while stirring the polyamic acid solution. Stirring was continued for 24 hours to carry out a chemical imidization reaction, yielding a polyimide solution Bsolz.
Next, 100 parts by mass of the obtained polyimide solution Bsolz was transferred to a reaction vessel equipped with a stirring device and a stirrer, and 150 parts by mass of methanol was slowly added dropwise while stirring, whereupon precipitation of a powdery solid was confirmed.
The powder content of the reaction vessel was then dehydrated and filtered, washed with methanol, and then vacuum dried at 50° C. for 24 hours, followed by heating at 260° C. for an additional 5 hours to obtain polyimide powder Bpd. 20 parts by mass of the obtained polyimide powder Bpd was dissolved in 80 parts by mass of DMAc to obtain a polyimide solution Bsol.

In an atmosphere conditioned to 25°C and 45% RH, the polyimide solution Bsol was applied to the non-slip surface of a temporary support, polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd., hereinafter abbreviated as PET film), using an apparatus equipped with a roll-to-roll comma coater and a continuous drying oven, so that the final film thickness would be 25 μm. Next, the film was heated at 110°C for 10 minutes in a continuous dryer as primary heating, to obtain a semi-dried coating Bgf with a residual solvent content of 25% by mass, which was then wound up together with the temporary support into a roll.
The obtained roll was set again in the above-mentioned device, and Bgf was unwound together with the temporary support. Bgf was peeled off from the temporary support, passed through a pin tenter with pin sheets, and the film edges were gripped by inserting them into the pins. The pin sheet spacing was adjusted so that the film would not break and unnecessary slack would not occur, and the film was conveyed, and as a final heating, heated for 3 minutes at 200°C, 3 minutes at 250°C, and 6 minutes at 300°C. Thereafter, the film was cooled to room temperature over 2 minutes, and poorly flat portions on both ends of the film were cut off with a slitter. The film was then wound up into a roll to obtain a roll of polyimide film Bpf having a width of 530 mm and a length of 80 m.
The resulting polyimide film had a thickness of 25 μm, a glass transition temperature of 320° C., a total light transmittance of 92%, a yellow index of 0.8, a tensile modulus of 3.4 GPa, a tensile elongation at break of 18%, and a coefficient of thermal expansion (CTE) of 62 ppm/K.

(Laminate production 2 by film lamination method)
The polyimide film Bpf was cut to a size of 280 mm x 280 mm, and subjected to UV irradiation for 3 minutes using a UV ozone layer value manufactured by LAN Technical Services Co., Ltd. as a surface activation treatment.
A 300 mm x 300 mm, 0.5 mm thick glass substrate was exposed to a silane coupling agent ("KBE-903" manufactured by Shin-Etsu Chemical Co., Ltd.) at 40°C or higher for 5 minutes, and then held in dry nitrogen at 60°C for 5 minutes to perform a silane coupling agent treatment. Next, the UV-irradiated surface of the film Bpf and the silane coupling agent-treated surface of the glass substrate were aligned, and the two were adhered together using a vacuum laminator. Heat treatment was then performed at 150°C for 1 minute to obtain a laminate B.

<Laminate Production C> (Varnish Method 1)
The polyimide solution Asol obtained in the process of producing the polyimide film Apf was applied to a glass substrate of 300 mm × 300 mm and 0.5 mm thickness using a bar coater so that the final film thickness would be 18 μm and the effective size would be 280 mm × 280 mm. The applied film was then dried in a vacuum dryer at 250°C for 30 minutes and then heat-treated in an inert furnace substituted with nitrogen at 450°C for 5 minutes, to obtain a laminate C consisting of a polyimide film layer and a glass substrate.

<Laminate Production D> (Varnish Method 2)
The polyimide solution Bsol obtained in the process of producing the polyimide film Bpf was applied to a glass substrate of 300 mm × 300 mm and 0.5 mm thickness using a bar coater so that the final film thickness would be 15 μm and the effective size would be 280 mm × 280 mm. The applied film was then heat-treated in a vacuum dryer and a nitrogen-substituted inert furnace at 150°C for 10 minutes, 250°C for 10 minutes, and 300°C for 5 minutes to obtain a laminate D consisting of a polyimide film layer and a glass substrate.

<Manufacturing of simulated devices>
Using the resulting laminates A to D, simulated display devices were formed on each polyimide film. A layout diagram (top view) of the simulated display device is shown in Figure 21. A polyimide film 300 was laminated or coated onto a glass substrate 150. Wiring 400 was formed by metallizing the polyimide film by sputtering a nickel-chromium alloy followed by sputtering a 100 nm thick copper layer, then electroplating the copper to a thickness of 8 μm, etching the resulting wiring, and then electroless tin plating the wiring surface. After forming the wiring, the simulated display device 600 was formed by masking areas outside the specified range and forming an amorphous silicon thin film, which was then considered a display device. The process up to this point corresponds to step E in Figure 8 or step E in Figure 10.
Five mock display devices were fabricated using each of the laminates A to D, and the flying wiring was formed and molded into mock electronic display devices, as described below.

Example 1A
First, a scribe was made in the glass substrate of the laminate A from the rear surface along the edge of the simulated display device that could be observed through the glass substrate, and then the glass substrate was divided to remove the glass portion that supported the wiring portion. This corresponds to step F in Fig. 8 or step F in Fig. 10.
Next, a silane coupling agent was applied to the second surface of the substrate, which corresponds to step G in FIGS. 9(A) and 9(B) or step G in FIGS. 11(A) and 11(B).
<Forming into a simulated display device>
Next, molding processes corresponding to steps H to J in FIGS. 9(A) and 9(B) or 11(A) and 11(B) were carried out.
First, the area other than the wiring area near the display area corresponding to the bending point was masked with a light-shielding glass substrate from the second surface. The corresponding area was then heated by irradiating it with xenon lamp light using a Hitachi High-Technologies Corporation optical baking machine called "PulseForge." Immediately afterward, the wiring area of the polymer film was first bent along the side of the glass substrate and then bent along the back surface of the glass substrate. A polyimide film was then attached to the back surface (second surface) of the glass substrate in a position previously coated with a silane coupling agent, and then secured with clips and a backing plate. The polyimide film was then heated at 100°C for 5 minutes to bond the polyimide film to the back surface of the glass. This area corresponds to the location where the driver IC will be mounted. The temperature of the heated area was measured using an infrared thermometer and was found to be 370°C.
<Examples 1B, 1C, and 1D>
The same processing was carried out using laminates B to D. These are designated as Examples 1B, 1C, and 1D, respectively. In all cases, including Example 1A, no wiring damage was observed, and no particular problems occurred during the molding process.

Example 2A
The same procedure was followed as in Example 1A, except that the bent portion was heated by contacting the portion with a stainless steel metal bar heated to 400°C. The temperature of the heated portion was measured with an infrared thermometer and found to be 380°C.
<Examples 2B, 2C, and 2D>
The same processing was carried out using laminates B to D. These are designated as Examples 2B, 2C, and 2D, respectively. In all cases, including Example 2A, no damage to the flying wiring was observed, and no particular problems were found during the molding process.

(Preparation of Polyamic Acid Solution (PAA1) and Lubricated Polyamic Acid Solution (V1))
The nitrogen inlet tube, thermometer, and liquid-contacting parts of the vessel equipped with a stirring rod, as well as the infusion piping, were made of austenitic stainless steel SUS316L. After the reactor was purged with nitrogen, 223 parts by weight of 5-amino-2-(p-aminophenyl)benzoxazole (DAMBO) was added. Next, 4000 parts by weight of N-methyl-2-pyrrolidone was added and completely dissolved, and then 420 parts by weight and 217 parts by weight of pyromellitic dianhydride (PMDA) were added to the previously obtained preliminary dispersion. The mixture was stirred at 25°C for 48 hours, yielding a brown, viscous polyamic acid solution (PAA1). The reduced viscosity (ηsp/C) was 5.5 dl/g. To the obtained polyamic acid solution (PAA1), a dispersion obtained by dispersing colloidal silica in dimethylacetamide ("Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.) was added as a lubricant so that the silica (lubricant) accounted for 0.5 mass% of the total polymer solid content in the polyamic acid solution, thereby obtaining a lubricated polyamic acid solution (V1).

The reduced viscosity of the polyamic acid was measured by the following method.
<Reduced Viscosity (ηsp/C) of Polyamic Acid>
A solution of a polymer (polyamic acid) dissolved in N-methyl-2-pyrrolidone to a concentration of 0.2 g/dl was measured at 30° C. using an Ubbelohde type viscometer.

(Preparation of Polyamic Acid Solution (PAA2) and Lubricated Polyamic Acid Solution (V2))
The nitrogen inlet tube, thermometer, and liquid-contacting parts of the vessel equipped with a stirring rod, as well as the infusion tubing, were made of austenitic stainless steel SUS316L. After the reactor was purged with nitrogen, 108 parts by weight of phenylenediamine (PDA) was added. Next, 3600 parts by weight of N-methyl-2-pyrrolidone was added and completely dissolved. Then, 420 parts by weight of the previously obtained preliminary dispersion and 292.5 parts by weight of diphenyltetracarboxylic dianhydride (BPDA) were added and stirred at 25°C for 12 hours, yielding a brown, viscous polyamic acid solution (PAA2). The reduced viscosity (ηsp/C) of this solution was 4.5 dl/g. Colloidal silica was then added in the same manner as in the preparation of polyamic acid solution (V1), yielding a lubricated polyamic acid solution (V2).

(Preparation of Polyamic Acid Solution (PAA3) and Lubricated Polyamic Acid Solution (V3))
The nitrogen inlet tube, thermometer, and liquid-contacting parts of the vessel equipped with a stirring rod, as well as the infusion tubing, were made of austenitic stainless steel SUS316L. After the interior of the reaction vessel was purged with nitrogen, 200 parts by weight of diaminodiphenyl ether (ODA) was added. Next, 3,800 parts by weight of N-methyl-2-pyrrolidone was added and completely dissolved. Then, 390 parts by weight and 217 parts by weight of pyromellitic dianhydride (PMDA) were added to the previously obtained preliminary dispersion, and the mixture was stirred at 25°C for 5 hours, yielding a brown, viscous polyamic acid solution (PAA3). The reduced viscosity (ηsp/C) of this solution was 3.7 dl/g. Colloidal silica was added in the same manner to obtain a lubricated polyamic acid solution (V3).

[Preparation of Polyamic Acid Solution (PAA4) and Lubricated Polyamic Acid Solution (V4)]
After purging the atmosphere inside a reaction vessel equipped with a nitrogen inlet tube, thermometer, and stirrer with nitrogen, 1,765 parts by weight of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 310 parts by weight of 4,4'-oxydiphthalic acid (ODPA), 1,601 parts by weight of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 1,136 parts by weight of 4-amino-N-(4-aminophenyl)benzamide (DABAN), and 20,000 parts by weight of N,N-dimethylacetamide were charged into the reaction vessel under a nitrogen atmosphere and dissolved, followed by stirring at room temperature for 24 hours. The resulting solution was then diluted with an appropriate amount of N,N-dimethylacetamide to obtain a polyamic acid solution (PAA4) with a reduced viscosity of 4.50 dl/g. Colloidal silica was then added in the same manner to obtain a lubricated polyamic acid solution (V4).

[Preparation of Polyimide Solution (PI5) and Lubricated Polyimide Solution (V5)]
After replacing the atmosphere in a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer with nitrogen, 4610 parts by mass of N,N-dimethylacetamide (DMAC) and 640 parts by mass of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) were added to the reaction vessel under a nitrogen atmosphere and stirred to dissolve the TFMB in the DMAC. Next, while stirring the reaction vessel, 897.37 parts by mass of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride (6FDA) was added over a period of about 10 minutes under a nitrogen stream. The polymerization reaction was continued for 6 hours while adjusting the temperature to be in the range of 20 to 40°C, and a viscous polyamic acid solution (PAA5) was obtained.
Next, 4,100 parts by mass of DMAC was added to the obtained polyamic acid solution (PAA5) to dilute it, and then 258.3 parts by mass of isoquinoline was added as an imidization accelerator. The polyamic acid solution was kept at a temperature of 30 to 40°C while stirring, and 1,225 parts by mass of acetic anhydride was slowly added dropwise as an imidization agent over a period of about 10 minutes. Thereafter, the liquid temperature was further kept at 30 to 40°C and stirring was continued for 12 hours to carry out a chemical imidization reaction, thereby obtaining a polyimide solution (PI5a).

Next, 10,000 parts by mass of the resulting polyimide solution (PI5a) containing the imidization agent and imidization accelerator was transferred to a reaction vessel equipped with a stirrer and stirring blades. While stirring at 120 rpm, the temperature was maintained at 15-25°C, and 15,000 parts by mass of methanol was added dropwise at a rate of 10 g/min. When approximately 8,000 parts by mass of methanol had been added, the polyimide solution became cloudy, confirming the precipitation of a powdery polyimide resin. The entire 15,000 parts by mass of methanol was then added, completing the precipitation of the polyimide resin. The contents of the reaction vessel were then filtered using a suction filtration device, and washed and filtered with 10,000 parts by mass of methanol to obtain a polyimide resin powder. The resulting polyimide resin powder was dried at 50°C for 24 hours using a dryer equipped with a local exhaust system, and then further dried at 260°C for 2 hours to remove remaining volatile components, yielding a dried polyimide powder. The reduced viscosity of the resulting dry polyimide powder was 5.40 dL/g. Next, 400 parts by mass of the resulting dry polyimide powder was dissolved in 3,000 parts by mass of DMAc to obtain a polyimide solution (PI5). Colloidal silica was then added in the same manner to obtain a lubricant-containing polyimide solution (V5).
The polyamic acid solutions or polyimide solutions and solutions containing lubricants obtained are listed in Tables 1 and 2.

[Film manufacturing example]
The lubricant-containing polyamic acid solution (V1) was applied to a polyethylene terephthalate film support to a final thickness of 38 μm, and then dried for 30 minutes at 110° C. The polyamic acid film, which had become self-supporting after drying, was peeled off from the support to obtain a polyamic acid film (green film).
The obtained green film was passed through a continuous heat treatment furnace and subjected to two heating stages: the first stage was at 200°C for 3 minutes, the temperature was raised at a rate of 4°C/sec, and the second stage was at 480°C for 5 minutes to allow the imidization reaction to proceed. Thereafter, the film was cooled to room temperature over 5 minutes, and both ends (edge portions) were slit to obtain a polyimide film F1 having a width of 524 mm, a length of approximately 200 m, and a thickness of 38 μm at the center only.

Similarly, lubricated polyamic acid solutions (V2), (V3), and (V4) and lubricated polyimide solution (V5) were used, and the coating thickness and heat treatment conditions were adjusted appropriately to obtain polyimide film F2 from lubricated polyamic acid solution V2, polyimide film F3 from lubricated polyamic acid solution V3, polyimide film F4 from lubricated polyamic acid solution V4, and polyimide film F5 from lubricated polyamic acid solution V5. The properties of the resulting polyimide films are listed in Table 3. The values in the table are average values in the MD and TD directions. MD is the longitudinal direction during film production, and TD is the width direction during film production.

[Polyimide film/glass substrate laminate]
<Vacuum plasma treatment of polyimide film>
The polyimide film F1 was subjected to a vacuum plasma treatment using a device for treating long films. The vacuum chamber was evacuated to a pressure of 1×10 ⁻³ Pa or less, argon gas was introduced into the vacuum chamber, and argon gas plasma treatment was performed for 20 seconds under conditions of a discharge power of 100 W and a frequency of 15 kHz.

<Silane coupling agent treatment of glass substrate>
The glass substrate [G] was a 470 mm x 370 mm, 0.7 mm thick OM10G manufactured by Nippon Electric Glass Co., Ltd. After replacing the atmosphere in a chamber equipped with a hot plate and a support stand for the inorganic substrate with clean, dry nitrogen, the UV/ozone-treated glass substrate was placed on the support stand, and a petri dish filled with a silane coupling agent (3-aminopropyltrimethoxysilane) was placed so that the liquid level was located 200 mm below the glass substrate. The petri dish was heated to 100°C on a hot plate, and the underside of the glass substrate was exposed to silane coupling agent vapor for 3 minutes. After that, the petri dish was removed from the chamber and placed in a clean bench. The glass substrate was placed on a hot plate adjusted to 120°C with the side opposite the exposed surface in contact with the hot plate, and heat-treated for 1 minute to perform the silane coupling agent treatment.

<Lamination>
The plasma-treated surface of the polyimide film was placed on the silane coupling agent-treated surface of the glass substrate, and the two were temporarily pressure-bonded using a roll laminator. The resulting polyimide film was then placed in a clean bench and placed on a hot plate adjusted to 150°C with the inorganic substrate side in contact with the hot plate, and heat-treated for 3 minutes to obtain a polyimide film/glass substrate laminate (LF1). The resulting polyimide/glass substrate laminate was stored in an environment at a temperature of 20 to 25°C and a relative humidity of 65±30%.
Similarly, a polyimide film/glass substrate laminate (LF2) was obtained from Film F2 and a glass substrate. Further, polyimide film/glass substrate laminates (LF3), (LF4), and (LF5) were obtained from Films F3, F4, and F5 and a glass substrate.

Example 3
Using the obtained polyimide film/glass substrate laminate, a simulated display panel was fabricated by the process shown in Figures 8 and 9A. For convenience, this process is referred to as the film method. The glass substrate corresponds to step A in Figure 8, the glass substrate treated with a silane coupling agent corresponds to step B, and the polyimide film/glass laminate corresponds to step C. For the wiring layer 40, a nickel-chromium alloy layer was formed by sputtering, followed by a thin copper film formed by sputtering, which was then thickened by electrolytic copper plating, and unnecessary portions were etched away using an etching resist, thereby forming patterning by a so-called subtractive method to form the wiring 40.

The electronic display device layer 60 was formed as an electrophoretic element driven by a TFT using an amorphous silicon thin film as a semiconductor, and the glass substrate was cut with a laser cutter to remove unnecessary portions. In step G2 of Figure 9A, the film was thinned to 20% of its original thickness using a laser processing machine, and the wiring 40 was folded back onto the back side of the glass substrate. A 1% by mass solution of 3-aminopropyltrimethoxysilane in methanol was used as the silane coupling agent solution 21, and it was dropped into a predetermined position using a dispenser (for convenience, the display device layer is shown facing up, but in reality, the operation is performed upside down after this step). After drying, the folded polyimide film was pressed against the back side of the glass substrate and heated to complete the adhesion, following the process for preparing a polyimide film/glass substrate laminate. Finally, a driver IC was mounted to obtain a simulated panel (PF1).
In the same way, multiple (PF1) panels were fabricated and arranged in a tiled pattern to increase the area, and image signals were sent to check the display. It was confirmed that there were no particular pixel defects between the simulated panels, and that good quality images were displayed.

<Examples 4 to 7>
Thereafter, the polyimide film glass laminates (LF2), (LF3), (LF4), and (LF5) were used to similarly obtain simulated panels (PF2), (PF3), (PF4), and (PF5), respectively. In all cases, satisfactory image display results were obtained over a large area by tiling.

Example 8
Next, an example using the varnish method is shown. Step A in Figure 10 is a glass substrate. Step B shows the state in which a polyamic acid solution (PAA1) is applied to a glass substrate to a predetermined thickness, and step C shows the state in which a polyimide layer is formed by drying and then heating in an inert oven, i.e., a polyimide layer/glass substrate laminate (LS1) is obtained. Thereafter, the same operations as in the film method were carried out, proceeding to the steps shown in Figure 11A. In step G1, a laser processing machine was used to make a half-cut cut in the film, and the wiring portion was folded back onto the film. The same operations were then carried out to produce a simulated panel (PS1). Here, too, tiling was carried out as in the film method, and the display image quality was observed, confirming that good image quality was obtained.

<Examples 9 to 11>
Similarly, simulated panels (PS2), (PS3), and (PS4) were obtained from the polyamic acid solutions (PAA2), (PAA3), and (PAA4). In all cases, good image display results were obtained by tiling.

As described above, the electronic display device of the present invention allows for a narrow frame, has a low defect rate for driver IC mounting, and is preferably applicable to self-emissive and reflective elements, resulting in a display device that is suitable for tiling applications. The present invention will make an enormous contribution to industry, particularly as a technology for economically manufacturing large-area display devices.

1: Electronic display device 10: Substrate 15: Substrate
20: Silane coupling agent condensate layer
21: Silane coupling agent (solution)
30: Polymer film
31: Slit section (half cut section)

32: Polyimide etching part
33: Heating region 35: Polymer solution or polymer precursor solution 40: Wiring
41: Thinned part
42: Flying lead portion 50: Drive circuit element (driver IC) of electronic display device
60: Electronic display device
70: Adhesive layer
80: Anisotropic conductive film (ACF)
90: Casting resin
150: Glass substrate 300: Polyimide film 310: Cutout area of polyimide film 400: Wiring 600: Simulated display device X1: Area 1 (display area)
X2: Area 2 (wiring area)
Lo: outer dimension of electronic display device Ld: outer dimension of display part of electronic display device Lg: side gap Lb: wiring thickness (polymer film thickness Tf + wiring thickness Tw)
Lp: lateral parallel part dimension Lpx: pixel dimension (pixel size) of electronic display device
Lov: Overhang dimension (Lg + Lb)
Ts: substrate thickness, Tf: polymer film thickness, Tw: wiring thickness (flying wiring layer thickness),

Claims (14)

substrate,
a polymer film having a softening temperature of 150°C or higher and 380°C or lower, which is folded so as to sandwich the substrate and is adhered to both the first surface and the second surface of the substrate;
a wiring formed on a surface of the polymer film opposite to the surface bonded to the substrate, the wiring extending from the first surface side to the second surface side of the substrate;
an electronic display device formed on the surface of the polymer film opposite to the surface bonded to the substrate;
1. An electronic display device comprising: The electronic display device described in claim 1, characterized in that the polymer film has an elastic modulus of 3 GPa or more and a breaking elongation of 3% or more. The electronic display device described in claim 1 or 2, characterized in that the polymer film is a polyimide film having a thickness of 3 μm or more and 75 μm or less. An electronic display device according to any one of claims 1 to 3, characterized in that the polymer film is a polyimide film having a total light transmittance of 85% or more and a yellow index of 5 or less. An electronic display device according to any one of claims 1 to 4, characterized in that the polymer film and the first surface of the substrate are bonded via a silane coupling agent condensate layer. An electronic display device according to any one of claims 1 to 5, characterized in that the polymer film and the second surface of the substrate are bonded via a silane coupling agent condensate layer. An electronic display device according to any one of claims 1 to 6, characterized in that the polymer film and the side surface of the substrate are bonded via a silane coupling agent condensate layer. An electronic display device according to any one of claims 1 to 7, characterized in that part or all of the portion of the polymer film facing the side surface of the substrate is thinned. An electronic display device according to any one of claims 1 to 8, characterized in that a portion of the polymer film facing the side surface of the substrate is removed. An electronic display device according to any one of claims 1 to 9, characterized in that a drive IC for the electronic display device is mounted on the second surface side of the substrate. (a) providing a laminate having a substrate and a polymer film adhered to at least one side of the substrate;
(b) forming an electronic display device and wiring on the polymer film;
(c) removing the substrate outside the area where the electronic display device is formed, and dividing the area into a display area bonded to the substrate and a wiring area from which the substrate has been removed;
(d) heating the vicinity of the boundary between the display area and the wiring area to a temperature equal to or higher than the softening point of the polymer film, and bending the wiring area along the side surface of the substrate;
11. The method for manufacturing an electronic display device according to claim 1, further comprising at least the step (e) of bending the wiring region from the side surface of the substrate toward the rear surface (second surface). 12. The method for manufacturing an electronic display device according to claim 11, wherein the heating means is light irradiation. 12. The method for manufacturing an electronic display device according to claim 11, wherein the heating means is direct contact with a heated object. 12. The method for manufacturing an electronic display device according to claim 11, wherein the heating means is electromagnetic induction heating.