JPH08164581A - Heat resistant optical plastic laminated sheet and manufacture of the same - Google Patents

Abstract

PURPOSE: To provide a sheet with impact resistance, regidity, and good optical characteristics CONSTITUTION: At least one first layer composed of a polysulfone resin which has aromatic groups and sulfone groups linking with the aromatic groups in the main chain and the second layer which has a lower glass transition temperature than the first layer and is composed of a polysulfone resin having aromatic sulfone groups in the main chain are laminated to make a sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically transparent and heat resistant optical plastic laminated sheet, a method for producing the same, and a heat resistant transparent substrate using the laminated sheet.

[0002]

2. Description of the Related Art With the rapid progress of electronics technology, attention has been paid to optoelectronic elements represented by liquid crystal display elements, which are used for various purposes by forming the elements on a glass substrate having a transparent conductive layer. ing. In particular, when incorporated in a portable device, the weight of the device is increased due to the large specific gravity of glass, which has led to a trend toward thinner glass substrates, making it possible to use substrates of about 0.4 mm. However, there is a problem with the mechanical strength of glass, especially brittleness, and the durability of the element is reduced.Therefore, it is necessary to use a substrate that has undergone a special treatment such as tempered glass, and to protect the element from impact, a metal frame or Measures such as using a plastic sheet for surface protection have been implemented. But,
There is a problem that the yield is reduced due to cracking during the manufacturing process of the device.

As described above, there is a strong demand for a substrate that is light and resistant to cracking, and there are great expectations for a display device using a plastic substrate from the viewpoints of lightness and impact resistance.
Several attempts have been tried for plastic substrates having a thickness on the order of mm.

A solvent casting method is known as a typical method for obtaining a plastic substrate material having high heat resistance and good surface smoothness. However, when a film is thickened to have rigidity, foaming is performed. In addition to defects such as easily occur, productivity is greatly reduced, so industrial implementation is difficult,
The limit is about 200 μm. Further, when the film is thickened by the melt extrusion method, the optical isotropy is impaired, and the surface smoothness and appearance by the die line at the time of molding are poor, and it is difficult to use it as a liquid crystal display substrate.

Therefore, plastics which are essentially low birefringence materials such as polymethylmethacrylate and modified olefins, and curable plastics such as crosslinked acrylic and epoxy as disclosed in JP-A-6-194501 are formed into sheets. Although it has been studied to use it after molding, the former has problems such as lack of heat resistance required in the glass process, and the latter has poor productivity and lack of practical mass production. It is also possible to laminate the heat-resistant optical film into a sheet, but there is no adhesive having excellent heat resistance and reliability, and when laminating by heating, a high processing temperature is required, and the resin is modified. -Undesired deterioration of properties such as coloring occurs. Therefore, it has rigidity and heat resistance that can maintain compatibility with the glass process, has excellent impact resistance, and
No industrially usable material has yet been found that satisfies optical properties such as transparency and low retardation.

[0006]

In view of the above situation, the present invention is expected to be compatible with the glass process, has excellent heat resistance and optical characteristics, and has mass productivity, and a heat-resistant optical plastic laminated sheet and the same. The present invention provides a manufacturing method and a heat-resistant transparent substrate using the laminated sheet.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have a laminated structure of a layer having high heat resistance and a layer having physical properties at room temperature. The inventors have found that an optical plastic sheet having rigidity, optical characteristics, and heat resistance can be obtained, and arrived at the present invention.

That is, the first aspect of the present invention is to provide at least one first layer made of a polysulfone resin having an aromatic group in its main chain and a sulfone group as its bonding group, and an optical layer having a glass transition temperature lower than that of the first layer. An optical plastic laminate sheet excellent in heat resistance and transparency, which is obtained by laminating a second layer made of a transparent material, and a second aspect of the present invention is that the main chain has an aromatic group and a sulfone group as its bonding group. Heat resistance and transparency, characterized in that at least one first layer made of a polysulfone-based resin and a second layer made of an optically transparent material having a glass transition temperature lower than that of the layer are directly laminated by heating. In the third aspect of the present invention, a heat-resistant transparent substrate for an optoelectronic element using the above optical plastic laminated sheet is contained.

Examples of the polysulfone resin having an aromatic group and a sulfone group as a bonding group in the main chain constituting the first layer include the following, which may be used alone or in combination with 2
Used in combination of two or more species.

[0010]

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The polysulfone resin (1) is produced by the Friedel-Crafts reaction of diphenyl ether chlorosulfone as shown in the following formula.

[0012]

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The polysulfone-based resin after (2) has a bisphenol sodium salt of 4,4 'as shown in the following formula.
-It can be obtained by aromatic nucleophilic substitution polymerization of dichlorophenyl sulfone. At this time, by selecting various bisphenol species, polysulfone-based resins as exemplified in (2) to (7) can be obtained. The bisphenols may be used alone or in combination of two or more. The polysulfone-based resin that can be used in the present invention is not limited to the resins (1) to (7) exemplified in the structural formula.

[0014]

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The first layer is laminated on one surface or both surfaces of the second layer having a glass transition temperature lower than that of the first layer, and plays a role of preventing thermal deformation of the second layer during high temperature heating.
The thickness of the first layer is determined by the thickness of the laminated sheet and the required heat-resistant shape stability.
It is 0 to 80%. When the laminated sheet is simply used as a substrate for a liquid crystal display device, the sheet is required to have a low retardation, and depending on the type of the liquid crystal display device, it is generally preferably 50 nm or less, more preferably 20 nm.
It is less than or equal to nm. Further, when imparting a retardation function to the sheet, it can be easily obtained by previously imparting a specific retardation to at least one layer to be laminated and then laminating. Generally, it is required to impart a retardation of 100 nm or more, preferably 300 nm or more. In particular, it is convenient for the thermal stability of the obtained retardation sheet to impart a specific retardation to the first layer having high heat resistance.

In order to impart a specific retardation to the first layer, it can be obtained by orienting the above-mentioned polymer material. Generally, it can be obtained by uniaxially or biaxially stretching a polymer film having little optical anisotropy. These films can be obtained by a known film forming technique, but a film formed by a solvent casting method is most preferably used in view of surface properties and optical characteristics.

The retardation is determined by the film thickness of the film and the degree of molecular orientation, and the molecular orientation is greatly influenced by the stretching conditions. Therefore, in order to precisely control the retardation, the thickness of the first layer should be relatively thin,
It is preferable to take a large control range of the stretching conditions. Therefore, the thickness of the first layer is preferably selected from 20 to 150 μm, and more preferably 40 to 100 μm.
Further, JP-A-2-160204 and JP-A-3-8551
As seen in No. 9, a special material in which the refractive index in the film thickness direction is adjusted so as to be different from any refractive index in the in-plane direction can also be suitably used. Even in this case, the first
The layer may be not only a single layer but also a multilayer having two or more layers.

The material constituting the second layer is generally made of a material having a low birefringence and easily forming a thick film,
Heat resistance lower than that of the first layer is used. When the second layer is heated to the glass transition temperature or higher in the lamination process by the heat fusion method or the like, it is possible to use a material having no low birefringence, and the optical properties required for the second layer are used. The initial characteristics are greatly eased. Although the glass transition temperature of the material forming the second layer depends on the required degree of heat resistance, it is generally 100 ° C. or higher, preferably 140 ° C. or higher. 2 than glass transition temperature
The temperature is preferably 0 ° C. or higher, more preferably 40 ° C. or lower. The heat resistance of the laminated plastic sheet of the present invention is largely contributed by the heat resistance of the first layer. The second layer is composed of a single layer or a plurality of layers of two or more layers.

The material forming the second layer is preferably a material excellent in affinity with the first layer, and it is necessary to select an optimum plastic material. The second layer plays a role of providing rigidity of the sheet at room temperature. Further, since it is protected from thermal deformation by the first layer, even when it is heated at a temperature higher than the glass transition temperature, it is protected by the first layer having a high glass transition temperature present on one side or both sides thereof. ,
It retains its shape without flowing even under stress such as pressure. The thickness of the second layer is determined by the properties required for the laminated sheet, as in the case of the thickness of the first layer, but 80 to 20% of the total thickness of the laminated sheet is selected.

In the plastic laminated sheet of the present invention, the plastic constituting each layer can be molded by the melt coextrusion method, but each layer alone is formed into a film by a solvent casting method or a melt extrusion method to a required thickness. A high-quality plastic laminated sheet can be easily obtained by laminating afterwards. It is possible to laminate using an adhesive, but it is necessary to select the adhesive so as not to impair the heat resistance of the laminated sheet. Heat lamination is preferable because of its high temperature characteristics. In this case, it is necessary to select the material in consideration of the affinity between the first layer and the second layer.

Suitable materials for the second layer of the present invention include polyesters having relatively low glass transition temperatures, polyarylates, polycarbonates, polysulfone resins having an aromatic group in its main chain and a sulfone group as its bonding group, and the like. These may be used alone or in combination of two or more. The polysulfone-based resin has a high affinity with the first layer and is particularly preferable as the second layer material.

Since the heat-resistant optical plastic laminate sheet of the present invention is formed by laminating the first layer and the second layer as described above, it has the advantage of the solvent casting method that a thin film having excellent optical characteristics can be easily obtained. The advantage is that the heat-resistant thick film sheet can be obtained at low cost. When a laminated sheet is obtained by a laminating method,
As the high heat-resistant layer (first layer), a film formed by a solvent casting method can be used from the viewpoint of optical characteristics and surface smoothness. Further, a material having a relatively low glass transition temperature is used because it is easy to obtain a film having good optical characteristics by a melt extrusion method with high productivity.
It is also possible to use a melt extruded film as the layer to reduce the cost of the laminated sheet.

Further, according to the heating laminating method, since the second layer is generally heated to the glass transition temperature or higher during laminating, it is subjected to the effect of thermal annealing.
The birefringence possessed by the single film is reduced and improved by the thermal annealing, and as a result, the obtained laminated sheet is characterized in that it is smaller than the total retardation of the single film. One of the preferable heating laminating methods is a heating / pressurizing laminating method using a heating roll or a belt. The required heating temperature varies depending on the material to be laminated, but is preferably higher than the glass transition temperature of the material forming the second layer and lower than the glass transition temperature of the material forming the first layer. In the thermal lamination, it is also possible to carry out heating in a plurality of stages, such as pre-compression bonding at a relatively low temperature, followed by heating to lamination temperature and main compression bonding. A vacuum laminating method can also be preferably used in order to prevent entrapment of bubbles during thermal lamination. The plastic laminated sheet of the present invention having the above-described structure preferably has a thickness of 0.2 to 1 mm, and has a thickness of 0.3 to 0.7 in order to maintain sharing or compatibility with glass in the process such as rigidity.
mm is particularly preferred. Regarding optical characteristics, the total light transmittance is preferably 80% or more.

Like the glass, the plastic laminated sheet of the present invention can be subjected to secondary processing such as transparent conductive processing as a substrate for optoelectronic elements, but the processing conditions are that the transparent conductive film is used. It is necessary to find the optimal conditions by referring to the existing conditions. Also,
Unlike glass substrates, the barrier performance against oxygen, water vapor, etc. deteriorates, so if necessary, organic gas barrier processing such as ethylene-vinyl alcohol copolymer or polyvinylidene chloride, or inorganic gas barrier consisting of silica / alumina, etc. Perform processing.

On the other hand, as described above, it is possible to give a function to at least one first layer in advance. For example,
The film constituting the first layer is preliminarily stretched to give a certain birefringence to give a retardation film, and then a laminated sheet is formed to obtain a plastic laminated sheet in which the retardation film is integrated. In this case, since the retardation film constituting the first layer has a high glass transition temperature, it has a feature that the retardation does not decrease so much even in the heating lamination, and a sheet with a highly controlled retardation is used. Obtainable.

When the first layer made of the retardation film is provided on both sides of the second layer, and the optical axes of the retardation film of the first layer are kept parallel to each other, the retardation of the obtained sheet is , The sum of each. When the first layer is arranged in this way, it is possible to prevent undesired deformation such as warpage of the obtained sheet, as compared with the case where one first layer exhibits a retardation. Further, it is also preferable that the respective retardation films constituting the first layer are arranged such that their optical axes are appropriately crossed for the purpose of improving the characteristics such as improving the contrast of the obtained liquid crystal display device. Usually ST
The N liquid crystal display device requires a plurality of retardation films in addition to the substrate. By adopting such a configuration, the substrate material has the function of a plurality of retardation films. It has an advantage that the structure can be simplified. The relative angle of the optical axis formed by the two first layers is variously determined in relation to various parameters for designing the liquid crystal display device. According to the present laminated sheet, a laminated sheet having a required relative angle can be easily obtained. Further, the present laminated sheet does not limit the provision of layers other than the first and second layers. The two first layers may have the same retardation value or different retardation values. Further, if necessary, the type of material forming these first layers may be changed.

A transparent conductive plastic laminated sheet can be obtained by using a film having a transparent conductive layer on the surface as the first layer. Furthermore, one first
A retardation / transparent conductive integrated plastic laminated sheet can also be obtained by using a retardation film as the layer film and a transparent conductive film as the first layer film.

The plastic laminated sheet of the present invention can be commonly used or compatible with glass in terms of heat resistance and optical characteristics, and is widely used as a substrate for optoelectronic devices. Further, unlike glass, it has excellent impact resistance and is lightweight, and is therefore particularly useful as a substrate material for a liquid crystal display element that is required to have a large area.

[0029]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.
The polysulfone-based resins (1) to (5) refer to the polysulfone-based resins having the above structural formula.

Example 1 As a material for the first layer, a film was formed by a solvent casting method, a glass transition temperature was 225 ° C., a retardation was 10 nm, and a 75 μm-thick A4 size polysulfone resin (1) (trade name) ICI VICTREX PE
S) film is used, and as the material for the second layer, a film having a retardation of 13 nm made of polysulfone resin (2) (trade name Amoco polysulfone) and having a thickness of 200 μm is used. The pieces were sandwiched and temporarily pressure-bonded at 180 ° C. with a vacuum laminating machine. Then, it was sandwiched between glass plates and heated to 220 ° C. and subjected to final pressure bonding to obtain a firmly fused laminated sheet of 350 μm. The softening temperature (inflection point of displacement) of the obtained laminated sheet by TMA analysis was 250 ° C., which was about the same softening temperature as the film of the polysulfone-based resin (1) alone. The produced laminated sheet maintained its shape even when pressed at 20 ° C. and 20 kg / cm ² , and had excellent retardation of 20 nm and excellent heat resistance and optical isotropy. The surface roughness was 0.028 μm on average.

Example 2 As a material for the first layer, a glass transition temperature of 28 obtained by a solvent casting method using a polysulfone resin (4).
The same second layer polysulfone resin (2) film as in Example 1 was used except that a film having a thickness of 75 μm and a retardation of 11 nm was used at 0 ° C., and the film (2) was sandwiched between two films (4). Then, temporary pressure bonding was performed at 180 ° C. with a vacuum laminating machine, then sandwiched between glass plates, heated to 230 ° C. and subjected to final pressure bonding to obtain a firmly fused laminated sheet of 350 μm. The softening temperature of the obtained laminated sheet by TMA analysis is 300 ° C, and the laminated sheet has a softening temperature of 20 kg / cm ² at 190 ° C.
It retained its morphology even when pressurized with, and had excellent heat resistance and optical isotropy with a retardation of 18 nm.

Example 3 As the material of the second layer, 15 formed by the melt extrusion method
400 μm thick film of polysulfone resin (2) having retardation of 0 nm (glass transition temperature: 19
(0 ° C.) and heat fusion with two polysulfone-based resin (1) films in the same manner as in Example 1 to obtain a laminated sheet having a thickness of 550 μm. The softening temperature of this laminated sheet is 25
After pressurizing at 20 ° C. and 20 kg / cm ² at 0 ° C., the retardation was 19 nm.

Example 4 A film of polysulfone resin (1) having a thickness of 75 μm was longitudinally uniaxially stretched by free-end uniaxial stretching to obtain a retardation film having a retardation of 420 nm. Using this retardation film and an unstretched film of polysulfone resin (1) having a thickness of 75 μm as the first layer,
As the material of the second layer, 20 formed by the melt extrusion method
Using a 200 μm thick polysulfone-based resin (2) film having a retardation of nm, heat fusion was performed in the same manner as in Example 1, and the retardation film was integrated into 350.
A laminated sheet having a thickness of μm was obtained. The resulting laminated sheet has 4
It had a retardation of 15 nm. Further, the in-plane retardation distribution was 8 nm and had good uniformity.

Example 5 Polysulfone resin (5) was used as the material for the first layer, and the retardation was 8 nm and 75 by the solvent casting method.
A film having a thickness of μm was obtained (glass transition temperature: 280
° C). As the material of the second layer, a film (glass transition temperature: 190 ° C.) of a polysulfone resin (2) having a retardation of 150 nm and a thickness of 400 μm formed by a melt extrusion method was used. 5) It was sandwiched between two sheets and temporarily pressure-bonded at 180 ° C. with a vacuum laminating machine. After that, it was sandwiched between glass plates, heated to 230 ° C., permanently pressure-bonded, and heat-fused to obtain a multilayer sheet having a thickness of 550 μm. The softening temperature of this multi-layer sheet is 300 ° C.
Retardation after pressurizing at 20 ℃ / cm ² is 1
It was 9 nm.

Example 6 As a material for the first layer, a 75 μm thick A4 size polysulfone resin (5) film having a glass transition temperature of 280 ° C. and a retardation of 10 nm was formed by a solvent casting method. Used as the material of the second layer,
A 200 μm thick film made of polysulfone resin (3) having a retardation of 15 nm was used, and the film (3) was sandwiched between two films (5) and temporarily bonded at 220 ° C. by a vacuum laminating machine. Then, sandwich it with a glass plate 2
It was heated to 60 ° C. and permanently press-bonded to obtain a strongly fused laminated sheet of 350 μm. The softening temperature of the obtained laminated sheet by TMA analysis is 300 ° C. The formed laminated sheet retains its shape even when pressed at 20 ° C. and 20 kg / cm ² , and has a retardation of 20 nm and excellent heat resistance. And had optical isotropy.

Example 7 A film of polysulfone resin (1) used as the material for the first layer in Example 1, and a gas barrier layer made of SiOx, ITO on one surface of the polysulfone resin (1) film. A transparent conductive layer film having a thickness of 75 μm and a surface resistance of 60 Ω / □ in which a transparent conductive layer consisting of is formed is used as the material of the first layer, and the layer of 20 nm formed by the melt extrusion method is used as the material of the second layer. 200μm thick polysulfone-based resin with a foundation (2)
The film (2) was sandwiched between the above two kinds of polysulfone-based resin films, and heat fusion was performed in the same manner as in Example 1 to obtain a laminated sheet having a transparent conductive layer on the surface. The obtained laminated sheet had a thickness of 350 μm and a surface resistance of 45 Ω / □.

Example 8 The polysulfone-based resin (1) retardation film described in Example 4 and the transparent conductive film described in Example 7 were each used as the first layer, and the materials for the second layer were prepared by the melt extrusion method. 20 with molded 20 nm retardation
Using a 0 μm thick film of polysulfone resin (2), heat fusion was carried out in the same manner as in Example 1 to obtain a laminated sheet having a transparent conductive layer on the surface and having a retardation. The obtained laminated sheet had a thickness of 345 μm,
It had a phase difference of nm and a surface resistance of 45Ω / □.

Example 9 Using the laminated sheet obtained in Example 1, a SiOx layer of 500 Å and an ITO layer 1000 were formed by a vacuum sputtering method.
By successively forming Å, a heat resistant transparent substrate having a barrier layer and a transparent conductive layer was prepared. The heat-resistant transparent substrate obtained is
Surface resistance is 50Ω / □, oxygen permeability is 1.0cc / m ² / da
It was less than y.

[0039]

INDUSTRIAL APPLICABILITY As described above, the present invention provides a heat-resistant transparent plastic laminated sheet having impact resistance and rigidity and excellent optical characteristics. The plastic laminated sheet is useful as an optical substrate which replaces glass in the field of optoelectronics, particularly in the field of liquid crystal display devices.

Claims (10)

[Claims] 1. A at least one first layer made of a polysulfone resin having an aromatic group in its main chain and a sulfone group as its bonding group, and a second layer made of an optically transparent material having a glass transition temperature lower than that of the layer. An optical plastic laminated sheet having excellent heat resistance and transparency, which is formed by laminating layers. 2. The optical plastic laminated sheet according to claim 1, wherein the first layer is arranged on both sides of the second layer. 3. The optical plastic laminate sheet according to claim 1, which has a retardation of 50 nm or less. 4. The optical plastic laminate sheet according to claim 1, wherein at least one first layer is made of a birefringent material having a retardation of 100 nm or more. 5. The optical plastic laminate sheet according to claim 1, wherein the first layer and the second layer are directly laminated. 6. The optical plastic laminate sheet according to claim 1, wherein the second layer comprises a polysulfone-based resin having an aromatic group in the main chain and a sulfone group as a bonding group thereof. 7. A transparent conductive layer is provided on the surface,
The optical plastic laminated sheet described. 8. At least one first layer made of a polysulfone resin having an aromatic group in its main chain and a sulfone group as its bonding group, and a second layer made of an optically transparent material having a glass transition temperature lower than that of the first layer. A method for producing an optical plastic laminated sheet having excellent heat resistance and transparency, which is characterized in that the layers are directly laminated by heating. 9. The method according to claim 8, wherein the film of the first layer to be laminated is a film obtained by a solvent casting method. 10. A heat-resistant transparent substrate for an optoelectronic element, which uses the optical plastic laminated sheet according to claim 1.