JP2004191463A - Substrate for display and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate to be used for a thin display having thickness reduction/weight reduction/impact resistivity/flexibility/low thermal expanding property/insulating property/heat resistivity/smoothness, and also to provide a method for manufacturing the substrate for display. <P>SOLUTION: This substrate for display is configured by forming a resin layer whose surface roughness Ra is 0.2μm or less, and Rz is 2μm or less, and whose glass transfer temperature is 150°C or more on the surface of a metallic thin plate whose thermal expansion coefficient ranging from 20°C to 300°C is 11×10<SP>-6</SP>/°C or less. It is desired that an iron/nickel system alloy thin plate is used for the metallic thin plate. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet display (also called electronic paper, flexible display), a field emission display (hereinafter abbreviated as FED), an organic EL, a liquid crystal display (hereinafter abbreviated as LCD), a plasma display (hereinafter abbreviated as PDP), and the like. The present invention relates to a substrate used for a thin display that does not use a so-called cathode ray tube and a method for manufacturing the same.
[0002]
[Prior art]
In thin displays such as LCDs and organic ELs, glass plates are used for front and back plates. However, further reductions in thickness, weight, impact resistance, and flexibility are required in the future, and studies are being made on strengthening the material when using a glass substrate. Also, studies have been made to use a substrate other than a glass substrate.
For example, it has been proposed to use PET (polyethylene terephthalate) or borosilicate glass as a substrate for electronic paper (for example, see Patent Document 1). When PET is used, it is excellent in impact resistance and flexibility, and when borosilicate glass is used, it is effective in reducing the thickness and weight.
In addition, a substrate in which a transparent gas barrier layer is provided on the surface of a transparent resin substrate has been proposed as a flexible display substrate (for example, see Patent Document 2). Further, as an electrophoretic display substrate, a method in which a transistor is deposited on a flexible substrate such as a metal foil is disclosed (for example, see Patent Document 3). These methods also have extremely excellent impact resistance and flexibility.
[0003]
[Patent Document 1]
JP-A-2002-169190 (page 5)
[Patent Document 2]
JP 2000-338901 A (page 2)
[Patent Document 3]
JP 2002-504696A (page 35)
[0004]
[Problems to be solved by the invention]
However, among the above-mentioned prior arts, those using a glass substrate have a problem that the characteristics of thinning, lightening, impact resistance, and flexibility cannot be sufficiently satisfied. Further, when a glass substrate is not used, it is insufficient to secure low thermal expansion characteristics, insulating properties, heat resistance, and smoothness like a glass substrate.
Specifically, in the method disclosed in Patent Document 1, for example, PET has a low glass transition temperature, and thus has a problem in that it is extremely softened in a heating process for forming electrodes, transistors, and the like that constitute a display element. . Further, when the thickness is reduced by using borosilicate glass, there is also a disadvantage that it is easily broken by bending deformation in daily use.
[0005]
In addition, in addition to the problem of heat resistance, a resin substrate alone needs to form, for example, a metal oxide in a vacuum as a gas barrier layer as in the method disclosed in Patent Document 2, which is not a method excellent in mass productivity.
Further, when a transistor is directly deposited on the surface of a metal substrate as in the method disclosed in Patent Document 3, large surface roughness caused by rolling flaws, crystal grain boundaries, inclusions, and the like causes fine electrodes of a display element and It becomes a barrier in forming the wiring, and also has a problem of thermal expansion matching with other members constituting the display.
An object of the present invention is to provide a substrate used for thin display applications, which has thinness, light weight, impact resistance, flexibility, low thermal expansion characteristics, insulation, heat resistance, and smoothness, and a method of manufacturing the same. It is to be.
[0006]
[Means for Solving the Problems]
The present inventor conducted various studies to satisfy all the characteristics required for a substrate. As a result, a resin layer was formed on the surface (one side or both sides) of a metal sheet having a specific coefficient of thermal expansion. As a result, the present inventors have found that this problem can be solved and arrived at the present invention.
That is, according to the present invention, a resin layer having a surface roughness of Ra: 0.2 μm or less, Rz: 2 μm or less, and a glass transition temperature of 150 ° C. or more has a thermal expansion coefficient of 11 × from 20 ° C. to 300 ° C. It is a display substrate formed on the surface of a thin metal plate having a temperature of 10 ⁻⁶ / ° C. or less.
[0007]
Preferably, the metal sheet is a display substrate which is an iron-nickel alloy sheet.
More preferably, the resin layer is a display substrate made of either a polyimide resin or a polyamideimide resin.
More preferably, the metal sheet is a display substrate having a thickness of 20 to 500 μm.
More preferably, the thickness of the resin layer is 2 to 50 μm.
[0008]
The present invention also provides a varnish obtained by dissolving a resin in an organic solvent, after immersing a metal sheet having a coefficient of thermal expansion of 11 × 10 ⁻⁶ / ° C. or less from 20 ° C. to 300 ° C., pulling up the metal sheet, This is a method for manufacturing a display substrate in which heat treatment is performed at 100 to 400 ° C.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
An important feature of the present invention is that by forming a resin layer having high heat resistance and high surface smoothness on the surface of a thin metal plate having low thermal expansion characteristics, the thin, lightweight, and low resistance required for a thin display substrate is obtained. It combines impact, flexibility, low thermal expansion, insulation, heat resistance, and smoothness.
Hereinafter, the present invention will be described in detail.
[0010]
As a thin display substrate, in addition to the characteristics (1) low thermal expansion characteristics, 2) insulation, 3) heat resistance, 4) smoothness of the current glass plate, 5) thinning, (6) Light weight, (7) Impact resistance, and (8) Flexibility are required. The use of a thin metal plate can easily satisfy the above requirements (5) to (8), but it is necessary to improve the low thermal expansion characteristics, insulation, heat resistance, and smoothness of the glass plate.
[0011]
First, regarding a low thermal expansion characteristic, in order to replace a glass substrate used as a conventional thin display substrate, it is necessary to use a metal material having a low thermal expansion characteristic equivalent to that of a glass substrate.
Although the thermal expansion characteristics (particularly the thermal expansion coefficient) slightly vary depending on the type of glass used, the thermal expansion coefficient of glass generally used as a substrate is 4 to 9 × 11 ⁻⁶ / ° C. Since the substrate is heated to 150 to 300 ° C. in the manufacturing process of the display, when a substrate having a large thermal expansion is used, misalignment of electrodes, transistors, wirings, and the like for a display element becomes large. It will be difficult. Therefore, a glass substrate having a low thermal expansion characteristic has been used so far. However, in the present invention, since a low thermal expansion characteristic is required for the same reason, the coefficient of thermal expansion from 20 ° C. to 300 ° C. is 11 × 10 ^−6. / ° C or less.
Materials having a thermal expansion coefficient in this range include, for example, metals such as tungsten, molybdenum, tantalum, and iron-nickel alloys. However, in view of easy weight reduction and availability, inexpensive iron- It is preferable to use a nickel-based alloy.
[0012]
The thermal expansion coefficient of the iron-nickel alloy can be adjusted by the nickel content. In order to easily obtain the above thermal expansion coefficient, the nickel content is 27 to 52% by mass, and the balance is substantially the same. It is preferable to use iron or replace nickel with 20% by mass or less of cobalt.
The iron-nickel alloy referred to in the present invention refers to iron-nickel-alloy such as the iron-nickel-cobalt alloy described above and an iron-nickel-chromium alloy containing 7% by mass or less of chromium. Refers to an alloy as the main component.
[0013]
More specific examples of the above-mentioned iron-nickel alloy include an iron-36 mass% nickel alloy, an iron-42 mass% nickel alloy, an iron-47 mass% nickel alloy, and an iron-50 mass% nickel alloy.
Further, iron-nickel-chromium alloys such as iron-42 mass% nickel-6 mass% chromium alloy, iron-31 mass% nickel-5 mass% cobalt alloy, iron-29 mass% nickel-17 mass% cobalt alloy, etc. Iron-nickel-cobalt alloy.
Further, an alloy obtained by appropriately adding an element for improving the strength to these alloys may be used as a material of the metal sheet.
Since these iron-nickel alloys can be easily thinned by cold rolling, they can be thinned, and since the hardness can be easily adjusted by softening annealing and the rolling ratio, they have impact resistance and flexibility. It is suitable as a thin metal plate.
[0014]
Next, in order to form electrodes and wiring of the display element on the display substrate, it is necessary to impart insulation to the surface of the conductive metal thin plate.
In order to impart insulation, a method of coating a resin is simple. However, as described above, the resin is heated to 150 to 300 ° C. in the manufacturing process of the display, so that a resin having a glass transition temperature of 150 ° C. or more is used. You need to choose.
In the case of a resin lower than this, extremely softened during heating, the desired thickness and shape cannot be maintained, or the resin is melted and flows out or decomposed. In general, the higher the glass transition temperature, the higher the melting point or the thermal decomposition temperature of the resin, and it can be used even in a high-temperature process. More preferably, the glass transition temperature is 180 ° C. or higher.
In the present invention, the glass transition temperature of the resin refers to a temperature at which the elastic modulus of the dried and cured resin suddenly decreases when heated. In general, the glass transition temperature can be measured using a dynamic viscoelasticity measuring device (hereinafter referred to as DMA).
[0015]
By the way, since a thin metal plate is used in the present invention, it is necessary to make the surface roughness of the thin metal plate smooth with a resin layer.
It is desired that the above-described resin is coated on the surface of a thin metal plate and thin electrodes and fine wiring for a display element can be formed on the surface with high precision. Therefore, the surface roughness is Ra: 0.2 μm or less and Rz: 2 μm or less. Within this range, formation of fine electrodes and fine wiring is facilitated. The range of Ra: 0.2 μm or less and Rz: 2 μm or less is the surface roughness of a glass plate conventionally used as a display substrate. More preferably, Ra: 0.1 μm or less, Rz: 1 μm or less.
[0016]
As a material of the resin having the above glass transition temperature, a polyimide resin or a polyamideimide resin is preferable. These indicate resins having an imide bond in the molecular chain, and have high heat resistance. A resin obtained by mixing these two types can be used, and a mixed resin of a thermosetting type obtained by mixing a polyamideimide resin and an epoxy resin can also be used.
[0017]
As the thickness of the metal thin plate, the thinner the better, the thinner and lighter the weight. However, if it is too thin, it cannot be held due to low bending strength, and it is difficult to roll, and the cost will increase due to an increase in man-hours. Therefore, a thickness of 20 μm to 500 μm is preferable. Further, the thickness of the resin layer is required to be 2 μm or more in order to ensure smoothness and insulating properties. If the thickness is too large, an increase in the amount of thermal expansion due to the resin becomes a problem.
[0018]
Next, a method for manufacturing a display substrate of the present invention will be described.
As a method for manufacturing the display substrate of the present invention, there are a method of attaching a resin film to a thin metal plate, and a method of applying a varnish obtained by dissolving a resin in an organic solvent to the thin metal plate and then heating and drying and curing the varnish.
In the method of attaching a resin film, problems such as remaining unjoined portions with a thin metal plate and entrapment of foreign matter are likely to occur. The method of applying a varnish is relatively excellent in smoothness and adhesion, is easy to smoothly adjust the surface roughness of the resin layer, and is advantageous in mass productivity and quality reliability.
[0019]
Specifically, as a method of applying a varnish to a metal thin plate, there is a method in which after the varnish is dropped on the metal thin plate, the varnish is rotated around a center point on the plane of the metal thin plate as an axis, and the varnish is spread by centrifugal force. Although it is excellent in that it can be applied thinly and uniformly, there is a disadvantage that it is inferior in mass productivity because it is processed in a single wafer.
In addition, there is a method in which a varnish dripped onto a metal sheet is spread by using a bar extending in the width direction of the metal sheet. This method has an advantage of being excellent in mass productivity because it can be applied continuously by supplying a thin metal plate in a strip state.
[0020]
Here, when a varnish is applied to only one side of the thin metal plate and dried and cured by heating to form a resin layer, shrinkage due to volatilization of the organic solvent from the varnish, and curing shrinkage of the resin, Due to the shrinkage, warpage with the resin layer inside is likely to occur. Therefore, it is preferable to provide a resin layer having substantially the same thickness on both sides of the thin metal plate. However, in the above-described method, it is necessary to apply a varnish on one side and then dry and treat each side one by one, which significantly reduces the mass production speed. There are drawbacks.
[0021]
Therefore, in the present invention, it is preferable that the metal thin plate is dipped in the varnish, and then the metal thin plate is pulled up to apply a varnish. According to this method, continuous application is possible by continuously passing a strip-shaped metal thin plate through a tank filled with varnish, and simultaneous application can be performed on both surfaces, which is very excellent in mass productivity.
Further, in this method, a rod is arranged in the width direction of the metal sheet near the place where the metal sheet is pulled up from the varnish, and the varnish passes through a gap between the metal sheet and the rod maintained at a desired value, thereby forming a varnish. It is possible to control the coating thickness.
[0022]
After the varnish is applied to the metal sheet in this manner, the varnish is heat-treated at 100 to 400 ° C., and dried and cured. Although the temperature condition depends on the resin and the solvent component used, at 100 ° C. or lower, even if the low boiling organic solvent volatilizes, moisture may remain due to moisture absorption. The higher the temperature, the shorter the drying and curing time, but the greater the shrinkage of the resin during the cooling process, the more likely it is to warp. Therefore, practical drying and curing temperatures are within the above ranges.
[0023]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
(Example 1)
A 150 μm thick iron-42 mass% nickel-based alloy thin plate having a thermal expansion coefficient of 4.3 × 10 ⁻⁶ / ° C. was prepared, and washed with an alkaline degreasing solution and dilute hydrochloric acid.
The surface roughness of this iron-nickel alloy thin plate was measured using a laser scanning microscope according to JIS B 0601 in an area of about 150 × 150 μm, and it was found that Ra: 0.2076 μm and Rz: 2.5887 μm. Was.
Next, a polyamideimide-based varnish diluted with N-methyl-2-pyrrolidone was prepared, and the alloy thin plate was immersed in the varnish and then pulled up. Subsequently, drying and curing were performed by a heat treatment at 150 ° C. for 1 hour, to produce a display substrate of the present invention.
[0024]
When the surface roughness of the resin layer was measured by the above-described measurement method, it was Ra: 0.04788 μm and Rz: 0.8796 μm. The thickness of this resin layer was 10 μm per side, and the glass transition temperature measured using DMA was 220 ° C.
Using this display substrate, electrodes and transistors were formed in a state where the display substrate was heated to 300 ° C., and then assembled into a sheet display.
[0025]
(Example 2)
A 100 μm thick iron-50 mass% nickel-based alloy thin plate having a thermal expansion coefficient of 10.2 × 10 ⁻⁶ / ° C. is prepared, washed with an alkaline degreasing solution and dilute hydrochloric acid, and then fixed on a glass plate. did. The surface roughness of the iron-nickel alloy thin plate measured by the measurement method described in Example 1 was Ra: 0.1956 μm and Rz: 2.4701 μm.
Next, a varnish prepared by dissolving a polyimide resin and an epoxy resin in cyclohexanone was prepared and dropped on the alloy thin plate described above. Subsequently, a coating rod in which a wire having a constant diameter was densely wound around a round bar was transferred in the width direction of the alloy thin plate, and moved at a constant speed perpendicular to the width direction to spread the varnish.
Thereafter, drying at 120 ° C. and curing at 170 ° C. were performed as a heat treatment to produce a display substrate according to the present invention.
[0026]
When the surface roughness of this resin layer was measured in the same manner as in Example 1, it was Ra: 0.05166 μm and Rz: 0.8062 μm. The thickness of the resin layer was 21 μm, and the glass transition temperature measured using DMA was 240 ° C.
Using this display substrate, electrodes and transistors were formed in a state where the display substrate was heated to 300 ° C., and then assembled into a sheet display.
[0027]
(Comparative Example 1)
Conventionally, a glass plate having a thickness of 697 μm used as a display substrate was prepared, and its surface roughness was measured in the same manner as in Example 1. As a result, Ra: 0.05103 μm and Rz: 0.7901 μm.
[0028]
As described above, the display substrate of the present invention has a surface smoothness equivalent to that of a conventionally used glass plate, and can be dramatically reduced in thickness. In addition, the glass plate is easily broken by impact load or bending, but the product of the present invention is a composite material of elastically deformable metal and resin, so it has both impact resistance and flexibility, It is very useful as a display substrate.
[0029]
【The invention's effect】
By using the present invention, a thin display substrate having both thinness, light weight, impact resistance, flexibility, low thermal expansion characteristics, insulation, heat resistance, and smoothness can be obtained. This is an indispensable technology for displays that have the expected impact resistance and flexibility.

Claims (6)

A resin layer having a surface roughness Ra: 0.2 μm or less, Rz: 2 μm or less, a glass transition temperature of 150 ° C. or more, and a metal having a thermal expansion coefficient of 11 × 10 ⁻⁶ / ° C. or less from 20 ° C. to 300 ° C. A display substrate formed on a thin plate surface. The display substrate according to claim 1, wherein the metal sheet is an iron-nickel alloy sheet. The display substrate according to claim 1, wherein the resin layer is any one of a polyimide resin and a polyamideimide resin. The display substrate according to any one of claims 1 to 3, wherein the thin metal plate has a thickness of 20 to 500 µm. The display substrate according to claim 1, wherein the resin layer has a thickness of 2 to 50 μm. After immersing a metal sheet having a coefficient of thermal expansion of 11 × 10 ⁻⁶ / ° C. or less from 20 ° C. to 300 ° C. in a varnish obtained by dissolving a resin in an organic solvent, the metal sheet is pulled up and heated at 100 to 400 ° C. A method for producing a display substrate, comprising performing a heat treatment.