JPH0557857A - Manufacture of optical laminated sheet - Google Patents

Abstract

PURPOSE:To provide a method of industrially advantageously manufacturing optically laminated sheets having an extraordinarily excellent surface smoothness, and more particularly optically laminated sheets suitable for an electrode substrate of manufacturing liquid crystal displaying panels. CONSTITUTION:After spreading resin solution for forming a bridgeable resin cured layer onto a biaxially oriented polyethylene terephthalate film of 0.004mum in its surface roughness, drying is effected until the quantity of a residual solvent in the seal-dried skin film reaches 5-100wt.% of the weight of a absolutely dried skin film. Subsequently, by press-bonding the side of the seal-dried skin film of the laminated body onto the resin layer for a lower layer in superimposed relation, the semi-dried skin film is transferred to the resin layer for a lower layer, and thereafter the biaxially oriented polyethylene terephthalate film is separation-removed, and further dry-curing is performed thereto for forming a resin layer. The surface smoothness of a free surface of the resin layer becomes 0.1mum or less at the measurement by means of a surface roughness meter utilizing optical interference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for industrially producing an optical laminated sheet having an extremely excellent surface smoothness, particularly an optical laminated sheet suitable for an electrode substrate for producing a liquid crystal display panel. Is.

[0002]

2. Description of the Related Art Conventionally, glass has been used as a substrate for liquid crystal display transparent electrodes, but it cannot be made thin.
Due to problems such as inferior impact resistance and difficulty in mass production, plastic substrates have recently been used more frequently, and the applicant has also filed several applications as described below. There is.

For example, in Japanese Patent Laid-Open No. 63-71829, an aqueous anchor coat layer is provided on at least one surface of a base material layer made of a sheet of polycarbonate resin or the like and having a retardation value of 30 nm or less. There is shown an electrode substrate for a liquid crystal display panel, in which a single-layer or multi-layer protective layer made of a cured product of an air-permeable resin and / or a crosslinkable resin is provided thereon.

In JP-A-64-50021, a laminate of a gas-permeable synthetic resin film layer and a cured crosslinkable resin layer is adhered to each other with their gas-permeable synthetic resin film layer surfaces facing each other. An electrode substrate for a liquid crystal display panel is shown which has a structure in which it is laminated and integrated via an agent layer.

In JP-A-64-50022, a cross-linking agent capable of reacting with the gas-permeable synthetic resin film layer is used on both sides of the gas-permeable synthetic resin film layer formed by a casting method. There is disclosed a method for producing an electrode substrate for a liquid crystal display panel, in which the cured crosslinkable resin layer is directly formed by a casting method.

Japanese Patent Laid-Open No. 2-137922 discloses a retardation value of 30 having a resin layer having no solvent resistance.
For the production of liquid crystal display panels in which an alcohol-soluble UV-curable adhesive layer or a water-based thermosetting adhesive layer is laminated on the resin layer side of a substrate sheet having a thickness of nm or less, and a release sheet is further laminated on the adhesive layer. Is shown as an example of a base sheet, and a sheet having a layer structure of a resin sheet such as polycarbonate / anchor coating layer / air-permeable synthetic resin layer / phenoxyether-based crosslinked polymer layer is shown as an example of the base sheet. I have been given.

In Japanese Patent Application Laid-Open No. 2-149819, the electrode support film side of an electrode support film with a transparent electrode having a structure in which a transparent electrode is provided on one surface of an electrode support film that can be wound into a roll is referred to as a retardation value. Shows a liquid crystal cell substrate with a transparent electrode laminated and integrated on a base material having a light transmittance of 80 nm or less and a light transmittance of 60% or more. As an example of an electrode supporting film, a resin film layer / anchor coating layer / crosslinking is shown. Cured resin layer, resin film layer / anchor coating layer / air permeable synthetic resin film layer / crosslinkable resin cured product layer, crosslinkable resin cured product layer / air permeable synthetic resin film layer / anchor coating layer / resin film Layer / anchor coating layer / air-permeable synthetic resin film layer / crosslinkable resin cured material layer, crosslinkable resin cured material layer / air-permeable synthetic resin layer Film having a layer structure such as a film layer / adhesive layer / penetration resistance temper synthetic resin film layer / crosslinkable resin cured material layer is raised.

[0008]

When the above-mentioned sheet-like substrate is used as an electrode substrate for manufacturing a liquid crystal display panel, a transparent electrode such as ITO is formed on the cured crosslinkable resin layer, and further thereon. After the alignment film is provided on, the liquid crystal cell is assembled. In this case, the liquid crystal that can be contained between the substrates is TN.
In the case of (twisted nematic) liquid crystal, some irregularities on the substrate surface on the transparent electrode formation side have almost no effect on product quality. This is because a liquid crystal display panel assembled from a liquid crystal cell using TN liquid crystal has an achromatic color, and if the light and shade are clear, the panel is acceptable.

However, when the liquid crystal contained between the substrates is STN (super twisted nematic) liquid crystal, the STN liquid crystal twists about 270 ° although the gap between the substrates is only about 5 to 6 μm. Therefore, even if there is a slight unevenness on the substrate surface on the transparent electrode forming side, the display is colored purple, green, etc. and the screen becomes very difficult to see. It was the biggest weakness of LCD panels. The electrode substrate according to the applicant's application cited above has not sufficiently solved this problem.

Under such a background, the present invention industrially advantageously manufactures an optical laminated sheet having extremely excellent surface smoothness, particularly an optical laminated sheet suitable for an electrode substrate for producing a liquid crystal display panel. It is intended to provide a method.

[0011]

Means for Solving the Problems The method for producing an optical laminated sheet of the present invention comprises a resin solution for forming a resin layer (2) on a biaxially stretched plastic sheet (3) having a surface roughness of 0.15 μm or less. After casting, it is dried until the amount of residual solvent in the semi-dry coating (2a) becomes 5 to 100% by weight of the absolute dry coating weight, and then the semi-dry coating (2a) side of this laminate is used as the lower layer resin. After transferring the semi-dry film (2a) to the lower resin layer (1) by stacking and pressing on the layer (1), the biaxially stretched plastic sheet (3) is peeled and removed. Alternatively, it is characterized in that the semi-dry coating (2a) thus transferred is dried and cured to form a resin layer (2).

The present invention will be described in detail below.

As the resin constituting the resin layer (2), various resins can be used as long as they can be dissolved in a solvent to form a film, but the purpose is to make an electrode substrate for manufacturing a liquid crystal display panel. In this case, heat resistance, solvent resistance, transparent electrode forming property and the like are required, and therefore it is particularly desirable to use a resin composition in which a crosslinking agent is mixed with a crosslinking agent.

Examples of such crosslinkable resins include phenoxyether type crosslinkable resins, epoxy resins, acrylic resins, acrylic epoxy resins, melamine resins, phenol resins or urethane resins. Of these, as typical examples, a phenoxyether type crosslinkable resin and an acrylic resin will be described in detail.

Among the crosslinkable resins, a particularly preferable resin is a phenoxy ether type polymer represented by the following chemical formula 1.

[0016]

[Chemical 1]

(Wherein R ^{1 to} R ⁶ are each hydrogen, a lower alkyl group having 1 to 3 carbon atoms or Br, R ⁷ is a lower alkylene group having 2 to 4 carbon atoms, m is an integer of 0 to 3, n is 2
It means an integer of 0 to 300, respectively. )

A phenoxyether-type crosslinked polymer is obtained by subjecting the hydrogen portion of the hydroxyl group of this polymer to a crosslinking reaction with a polyfunctional compound as a crosslinking agent. As the cross-linking agent (polyfunctional compound) to be reacted to obtain a cross-linked polymer, a group having a high reaction activity with a hydroxyl group, for example, an isocyanate group,
A compound having two or more carboxyl groups, a reactive group in the carboxyl group (for example, a halide, an active amide, an active ester, an acid anhydride group, etc.), mercapto or the like is used, and polyisocyanate is particularly important. ..

As the acrylic resin, a compound containing at least three or more acryloyloxy groups or / and methacryloyloxy groups in the molecule (hereinafter referred to as a polyfunctional (meth) acryloyloxy group-containing compound) is a main component. A composition containing a polyfunctional unsaturated monomer and / or an initial radical reaction product thereof as a main component can be mentioned. Particularly preferred is a polyfunctional unsaturated monomer containing at least 3 or more (meth) acryloyloxy groups in the molecule, in an amount of 50% by weight or more based on all unsaturated monomers,
A composition comprising an unsaturated monomer mixture or / and its initial radical reactant, which is preferably contained in an amount of 70% by weight, particularly preferably 90% by weight or more.

When the resin layer (2) is a cured crosslinkable resin layer, its thickness is usually 2 to 500 μm, preferably 3
It is often set to μm to 200 μm.

Examples of the biaxially stretched plastic sheet (3) include a biaxially stretched polyethylene terephthalate film, a biaxially stretched polybutylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a biaxially stretched polypropylene film and the like. The biaxially stretched polyethylene terephthalate film is particularly important in view of cost and cost.

The biaxially stretched plastic sheet (3) has a surface roughness of 0.15 μm or less, preferably 0.05 μm or less,
Further, it is required to be 0.01 μm or less, and when the surface roughness is larger than 0.15 μm, an optical laminated sheet having desired smoothness cannot be obtained. Among the crystalline plastics films that do not contain a filler, the surface smoothness is remarkably improved by biaxial stretching, so that the smoothness can be increased as described above.

The above biaxially stretched plastic sheet (3)
After casting the resin solution for forming the resin layer (2) on top, the amount of residual solvent in the semi-dry coating (2a) was 5-100% of the absolute dry coating weight.
Drying is carried out until the weight%, preferably 15-80% by weight. Semi-dry coating (2a) if the degree of drying is too low
The resin layer (2) with a smooth surface cannot be obtained because
Further, in the process described below, the biaxially stretched plastic sheet (3) becomes sticky and difficult to peel off, and when the drying is too much, the semi-dry coating (2a) will not be deformed, so that the resin layer (2) The surface smoothness cannot be obtained and the intended purpose cannot be achieved.

Separately from the above, a lower resin layer (1) is prepared. Examples of the lower layer resin (1) include a base material layer, an air-permeable resin layer, a crosslinkable resin cured product layer, and a laminate of these layers. Particularly, the base material layer / air-permeable resin layer, Base material layer / air permeable resin layer / crosslinkable resin cured material layer, crosslinkable resin cured material layer / air permeable resin layer / base material layer / air permeable resin layer, crosslinkable resin cured material layer / air permeable resistance Layer structure such as resin layer / base material layer / air-permeable resin layer / crosslinkable resin cured material layer, crosslinkable resin cured material layer / air-permeable resin layer / air-permeable resin layer / crosslinkable resin cured material layer is important. In the case of a laminated structure, an anchor coating layer or an adhesive layer can be provided between the layers.

Examples of the base material layer include polycarbonate, polymethylmethacrylate, polyethersulfone, polysulfone, polyarylate, amorphous polyolefin, polyparabanic acid resin, and polyamide. The base layer preferably has a heat distortion temperature of 80 ° C. or higher. The base material layer is obtained by a casting method or an extrusion method,
The thickness is often about 30 μm to 3 mm.

The air-permeable resin constituting the air-resistant resin layer includes, for example, a layer formed of a polymer containing 50 mol% or more of an acrylonitrile component, a vinyl alcohol component or a vinylidene halide component. Polymers having a hydroxyl group such as polyvinyl alcohol or copolymer modified products or graft products thereof, and ethylene-vinyl alcohol copolymer having an ethylene content of 15 to 50 mol% are important.

The air-permeable resin layer is usually formed by a casting method, and its oxygen permeability (measured according to ASTM D-1434-75) is 30 cc / 24 hr · m ² · atm or less, especially 20 cc / 24 hr · m ² ·
Atm or less, more preferably 10 cc / 24 hr · m ² · atm or less. The air-permeable resin layer has a thickness of 1 to 50 μm
In particular, it is suitable to set in the range of 2 to 20 μm. If it is less than 1 μm, the air resistance is insufficient and it is 50 μm.
If it exceeds, it will be against the trend of thinning.

As the crosslinkable resin cured product layer, first, the resin layer
The crosslinkable resin cured product layer as described in the explanation of (2) is used.

Semi-dry coating of a laminate comprising the biaxially stretched plastic sheet (3) / semi-dry coating (2a) produced above
When the (2a) side is superposed on the lower resin layer (1) and pressure-bonded, the semi-dry coating (2a) is transferred to the lower resin layer (1). After this operation, biaxially stretched plastic sheet (3)
Is removed by peeling, but heating is performed before or after the peeling, and the transferred semi-dry coating (2a) is dried and cured to form a resin layer.
(2)

In the resin layer (2) located on the surface of the obtained laminated sheet, the biaxially stretched plastic sheet (3) is used.
The surface that was in contact with is the free surface.

The surface roughness of the free surface of the resin layer (2) depends on the degree of surface smoothness of the biaxially stretched plastic sheet (3),
The biaxially stretched plastic sheet (3) has a thickness of 0.5 μm or less, preferably 0.2 μm or less, more preferably 0.1 μm or less, depending on the pressure and temperature at the time of pressure bonding. Generally, the surface roughness of a melt extruded film is 3 to 4 μm for a 100 μm thick film.
m, the surface roughness of the casting film is 100 to 100 μm, and the surface roughness of the free surface of the resin layer (2) is so small that it can be said that it is out of the ordinary.

The resin layer (2) has a retardation value of 60 nm or less, preferably 30 nm or less, and a total light transmittance of 60% or more, preferably 70% or more, considering that it is used for optical applications. Is desirable.

By the above operation, a laminated sheet having a layer structure of the lower resin layer (1) / resin layer (2) and having an extremely high surface smoothness of the free surface of the resin layer (2) can be obtained. The resin layer
A liquid crystal cell substrate can be prepared by providing a transparent electrode on (2) and further forming an alignment film on the transparent electrode.

For forming the transparent electrode, a vacuum deposition method, a sputtering method, an ion plating method, a metal spraying method, a metal plating method, a chemical vapor deposition method, a spray method, etc. are adopted.
The sputtering method is particularly important. As a material of the transparent electrode, a metal such as Sn, In, Ti, Pb, Tb or an oxide thereof is mainly used, and the layer thickness of the transparent electrode is at least 100 angstrom, and further 20
It is usually 0 angstrom or more.

The optical laminated sheet thus obtained is particularly important as an electrode substrate for manufacturing a liquid crystal display panel, but can be applied to applications such as a retardation plate, a polarizing plate, an optical disk and an optical card. it can.

[0036]

In the optical laminated sheet obtained by the method of the present invention, the surface smoothness of the free surface of the resin layer (2) located on the surface of the laminated sheet is extremely high. Even when it is used as an electrode substrate for a liquid crystal cell, the display does not become very difficult to see due to colors such as purple and green.

[0037]

EXAMPLES The present invention will be further described with reference to examples. Hereinafter, “parts” means parts by weight.

Example 1 On one surface of a polycarbonate sheet (thickness 110 μm, retardation value 12 nm) as an example of the base material layer (1a),
After applying a water-soluble quaternized ester urethane-based anchor coating agent and drying it to form an anchor coating layer with a thickness of 0.5 μm, from above the anchor coating layer, ethylene-vinyl acetate copolymer with ethylene content of 32 mol% is added. A resin solution having a composition of 20 parts of coalesced water, 45 parts of water, 50 parts of n-propanol and 4 parts of methylolated melamine (Sumitec M-3 manufactured by Sumitomo Chemical Co., Ltd.) was cast at a temperature of 1
It was dried by passing through a dryer at 10 ° C. As a result, the air-permeable resin layer (1b) having a thickness of 8 μm was formed.

Then, a phenoxy ether resin (manufactured by Tohto Kasei Co., Ltd.) 4 was formed on the air-permeable resin layer (1b).
An applicator of a curable resin composition solution having a composition of 0 part, 40 parts of methyl ethyl ketone, 20 parts of cellosolve acetate, and 40 parts of a 75% solution of an adduct of tolylene diisocyanate and trimethylolpropane (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) Apply using
It was dried at 80 ° C. for 4 minutes and then heated at 130 ° C. for 20 minutes to form a phenoxyether resin-based crosslinkable resin cured product layer (1c) having a thickness of 10 μm.

Next, an anchor coating layer is provided on the other surface of the polycarbonate sheet (1a) in the same manner as described above, and the air-permeable resin having a thickness of 9 μm is formed on the anchor coating layer in the same manner as described above. Layer (1b) was formed. The layer structure at this time is (1b) / (1a) / (1b) / (1c).

On the other hand, biaxially stretched plastic sheet (3)
As an example, a crosslinked resin cured product layer (1
c) A solution having the same composition as the curable resin composition solution for forming was applied using an applicator and dried at 60 ° C. for 1 minute. The amount of residual solvent in the formed semi-dry film (2a) was 30% by weight based on the weight of the absolutely dry film.

Next, the semi-dry coating (2a) side of the laminate comprising the biaxially stretched plastic sheet (3) / semi-dry coating (2a) produced above was also produced (1b) / (above). 1a) / (1b)
/ (1c) The lower resin layer (1) having a layer structure of (1c) was laminated on the (1b) side, and bonded by pressure bonding between roll groups under the conditions of a temperature of 80 ° C. and a pressing pressure of 10 kgf / cm ² . .. Then, after leaving at room temperature for 36 hours, the biaxially stretched plastic sheet (3) was peeled off from the laminated sheet (the peeling operation was smooth), and the temperature was raised to 125 ° C. Aging was performed by heating for 60 minutes or more.

By the above operation, the semi-dry coating (2a) transferred to the lower resin layer (1) is dried and cured to form a crosslinkable resin cured material layer (2), and the surface smoothness of its free surface is It was 0.1 μm or less when measured by a non-contact type surface roughness meter using the interference of.

The thus obtained laminated sheet had a retardation value of 18 nm, a visible light transmittance of 89% and an oxygen transmittance (measured according to ASTM D-1434-75) of 0.5 cc / 24.
hr · m ² · atm, surface pencil hardness is 2H on both sides,
It had no moisture permeability.

Next, a transparent electrode made of an ITO layer having a thickness of 500 angstrom was directly formed on the surface of the cured crosslinkable resin layer (2) on the side of the above laminated sheet which became the smooth surface by a sputtering method. Using this laminated sheet as an electrode substrate, an alignment film was formed and a rubbing treatment was performed, a liquid crystal cell was assembled, and a retardation plate and a polarizing plate were laminated according to a conventional method to produce a liquid crystal display panel. The obtained liquid crystal display panel showed no coloring in the display and had a performance comparable to that of a liquid crystal display panel using glass as a substrate.

Example 2 After a laminate having a layer structure of (1b) / (1a) / (1b) / (1c) was prepared in the same manner as in Example 1, the air-permeable resin layer (1b) was further formed. From above, a solution of the same composition as the curable resin composition solution for forming (1c) above is applied using an applicator, and the temperature is set to 80 ° C.
And dried for 4 minutes to form a semi-dry film (1d) having a thickness of 4 μm. The layer structure at this time is (1d) / (1b) / (1a) / (1b) / (1c).

On the other hand, on the same biaxially stretched plastic sheet (biaxially stretched polyethylene terephthalate film) (3) as in Example 1, a curable resin composition solution for forming the above-mentioned crosslinkable resin cured product layer (1c) was prepared. A solution having the same composition as above was applied using an applicator and dried at 80 ° C. for 4 minutes. The amount of residual solvent in the formed semi-dry coating (2a) was 2 times the absolute dry coating weight.
It was 5% by weight.

Next, the semi-dry coating (2a) side of the laminate comprising the biaxially stretched plastic sheet (3) / semi-dry coating (2a) produced above was also produced (1d) / (above). 1b) / (1a)
While superimposing it on the (1d) side of the lower resin layer (1) having a layer structure of / (1b) / (1c), a temperature of 80 ° C and a pressing pressure of 10 kgf / cm.
^Under the conditions of ^2, the rolls were bonded together by pressure bonding. Then, after leaving at room temperature for 36 hours, the biaxially stretched plastic sheet (3) was peeled off from the laminated sheet (the peeling operation was smooth), and the temperature was raised to 125 ° C. Aging was performed by heating for 60 minutes.

By the above operation, the semi-dry film (2a) transferred to the lower resin layer (1) is dried and cured to form a crosslinkable resin cured product layer (2), and the surface smoothness of its free surface is It was 0.1 μm or less when measured by a non-contact type surface roughness meter using the interference of.

The thus obtained laminated sheet had a retardation value of 16 nm, a visible light transmittance of 89% and an oxygen transmittance (measured according to ASTM D-1434-75) of 0.4 cc / 24.
hr · m ² · atm, the pencil hardness of the surface was H on both sides, and it had no moisture permeability.

When a liquid crystal display panel was produced using this laminated sheet in the same manner as in Example 1, the same preferable result as in Example 1 was obtained.

[0052]

In the optical laminated sheet obtained by the method of the present invention, even when it is used as an electrode substrate of a liquid crystal cell in which STN liquid crystal is sealed, for example, purple, green or the like is displayed. It does not happen that the screen becomes very hard to see due to color.

As the liquid crystal display panel becomes larger year by year,
Although the spread of the STN liquid crystal system is remarkable, the present invention enables display characteristics to be comparable even if a plastics substrate is used instead of the glass substrate for the purpose.

In particular, as the lower resin layer (1), a laminate containing a base layer / air-permeable resin layer is used, and the resin layer (2)
When using a cross-linkable resin cured product layer as, in addition to the achromaticity of the display, so that all of the air resistance, moisture resistance, non-coloring, high surface hardness, heat resistance, organic chemical resistance should be satisfied. Become.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication C08L 73/00 LQQ 9167-4J // B44C 1/175 A 9134-3K G02F 1/1335 510 510 72- 2K

Claims (4)

[Claims] 1. A residual solvent amount in a semi-dry coating (2a) after casting a resin solution for forming a resin layer (2) on a biaxially stretched plastic sheet (3) having a surface roughness of 0.15 μm or less. Is dried to 5 to 100% by weight of the absolute dry film, and then the semi-dry film (2a) side of this laminate is superposed on the lower resin layer (1) and pressure-bonded to form a semi-dry film ( After transferring 2a) to the lower resin layer (1), biaxially stretched plastic sheet
(3) is removed by peeling, and heating is performed before or after the peeling, and the transferred semi-dry coating (2a) is dried and cured to form a resin layer.
(2) A method for producing an optical laminated sheet, which comprises: 2. The method according to claim 1, wherein the resin layer (2) is a cured crosslinkable resin layer. 3. The method according to claim 1, wherein the resin layer (2) of the obtained optical laminated sheet has a surface roughness of 0.5 μm or less. 4. The method according to claim 1, wherein the optical laminated sheet is an electrode substrate for manufacturing a liquid crystal display panel.