JP2000239618A - Self-adhesive layer protecting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide protecting film that is able to keep an extinction state under conditions where a release film is attached to, is easy for inspection of foreign matters or the like being incorporated, and has a reduced degree of lowering in adhesiveness to a self-adhesive in the course of inspection of a polarizing plate, a phase polarizing plate or a phase plate accompanying an optical evaluation between two polarizing plates in a crossed Nicol state. SOLUTION: This protecting film is a release film for protecting a self-adhesive surface applied onto a polarizing plate and a phase plate of a liquid crystal display board, and is made of a laminate film wherein a release layer is formed on one surface of a uniaxially oriented polyester film. The residual adhesion rate of the laminate film is not less than 80%. The release layer should preferably be made primarily of a cured silicone resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for an adhesive layer, and more particularly, to bonding an adhesive applied to the surface of a polarizing plate or a retardation plate to a substrate such as a liquid crystal cell. In the meantime, it relates to a release film used for protection.

[0002]

2. Description of the Related Art Generally, a liquid crystal display panel is manufactured by laminating a polarizing plate or a retardation plate on both sides of a liquid crystal cell in which liquid crystal is sealed between two substrates. When a polarizing plate or a retardation plate is laminated on a liquid crystal cell, it is mainly laminated via an adhesive. The pressure-sensitive adhesive is usually laminated on the surface of a polarizing plate or a retardation plate, and is protected by a release film until it is adhered to a substrate such as a liquid crystal cell. This is because it is essential that the display capability of the liquid crystal display panel does not decrease due to the incorporation of foreign matter or the attachment of foreign matter to the polarizing plate or retardation plate and the adhesive. Therefore, it is preferable that the inspection of the polarizing plate, the phase difference polarizing plate, or the phase difference plate involving the optical evaluation between the two polarizing plates in the crossed Nicols state is also performed with the release film adhered.

Hitherto, a release film having a biaxially oriented polyester film as a base film has been widely used as the above protective film because of its excellent mechanical and thermal properties. For example, Japanese Patent Application Laid-Open No. 7-101026 discloses a method in which a release film having a biaxially oriented aromatic polyester film as a base film is used, a direction of an orientation main axis of the biaxially oriented polyester film, a polarizing plate, and a retardation polarizing plate. Alternatively, there is described a laminate and a release film for the same, wherein the directions of the orientation axes of the retardation plates are substantially the same or substantially 90 degrees.

However, the direction of the main axis of orientation of the biaxially oriented polyester film and the direction of the axis of orientation of the polarizing plate, retardation polarizing plate or retardation plate are substantially the same, or substantially 90 degrees. In such a position, the orientation main axis of the biaxially oriented polyester film is checked, and the direction thereof is substantially the same as the direction of the orientation axis of the polarizing plate, retardation polarizing plate or retardation plate, or substantially. It is necessary to cut out at 90 degrees, which is extremely difficult in terms of productivity. When only the portion where the main orientation axis of the biaxially oriented polyester film exists in the width direction (the direction perpendicular to the machine direction) is used, there is no need to confirm the orientation main axis as described above. The part where the main orientation axis of the polyester film exists in the width direction (the direction perpendicular to the machine direction) is a part of the central part of the formed biaxially oriented polyester film, and the other parts are similarly I can not use it.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a problem to be solved is a polarizing plate having an optical evaluation between two polarizing plates in a crossed Nicols state.
In the inspection of the retardation polarizing plate or the retardation plate, the quenching state is maintained even if the release film is stuck, the inspection for inclusion of foreign matter is easy, and the adhesion with the adhesive is reduced. To provide a protective film having low characteristics.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned circumstances, and as a result, a protective film having excellent characteristics has been obtained by using a specific film as a base film and a specific residual adhesion rate. The inventors have found that the present invention can be obtained, and have completed the present invention. That is, the gist of the present invention is a release film for protecting a pressure-sensitive adhesive surface applied to a polarizing plate and a retardation plate of a liquid crystal display plate, and a release layer is provided on one surface of the uniaxially oriented polyester film. The present invention resides in a pressure-sensitive adhesive layer protective film comprising a laminated film provided, wherein the residual adhesive ratio of the laminated film is 80% or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The pressure-sensitive adhesive layer protective film of the present invention is a release film used for protecting a pressure-sensitive adhesive or the like laminated on the surface of a polarizing plate or a retardation plate, and is released on one surface of a uniaxially oriented polyester film. It consists of a laminated film provided with layers. In the present invention, a uniaxially oriented polyester film (hereinafter, abbreviated as a uniaxial film) means that the main orientation axis (γ axis) of the uniaxial film is substantially vertical (film longitudinal direction) or lateral direction (film width direction). Wherein the absolute value of the refractive index difference in the two directions is usually 0.02 or more, preferably 0.05 or more, and more preferably 0.08 or more. The uniaxial film is a film in which a sheet melt-extruded from an extrusion die is stretched and oriented by a so-called extrusion method, and preferably, a film in which the sheet is stretched and stretched in a longitudinal or transverse uniaxial direction. It is. In addition, the fluctuation of the axis angle with respect to the vertical direction or the horizontal direction of the main orientation axis (γ axis) is usually within ± 15 degrees,
It is preferably within ± 10 degrees, more preferably within ± 5 degrees.

[0008] The polyester constituting the uniaxial film refers to a polyester obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. A typical polyester is polyethylene terephthalate (P
ET), polyethylene-2,6-naphthalenedicarboxylate (PEN) and the like.

The above-mentioned polyester may be a copolymer containing a third component. Examples of the dicarboxylic acid component of the copolymerized polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid,
Adipic acid, sebacic acid, oxycarboxylic acid (for example,
P-oxybenzoic acid and the like), and as the glycol component, ethylene glycol, diethylene glycol,
Propylene glycol, butanediol, 1,4-cyclohexane dimethanol, neopentyl glycol and the like can be mentioned. Two or more of these dicarboxylic acid components and glycol components may be used in combination.

In the present invention, in consideration of the handling property, it is preferable that the film contains particles under conditions that do not impair the transparency. Examples of the particles include silicon dioxide, calcium carbonate, aluminum oxide, titanium dioxide, kaolin, talc, zeolite, lithium fluoride, barium sulfate, carbon black, and JP-B-59-5.
No. 216, heat-resistant polymer fine powder and the like. These particles may be used in combination of two or more kinds. The average particle size of the particles is usually 0.02 to 2 μm.
m, preferably 0.05 to 1.5 μm, more preferably 0.05 to 1 μm. The content of the particles is usually 0.1.
It is from 0.01 to 2% by weight, preferably from 0.02 to 1% by weight.

As a method for incorporating particles into the film, a known method can be adopted. For example, particles can be added at any stage of the polyester production process. In particular, at the stage of esterification or the stage after the end of the transesterification reaction and before the start of the polycondensation reaction, it is preferable to add as a slurry dispersed in ethylene glycol or the like to advance the polycondensation reaction. Also, using a kneading extruder with a vent,
A method of blending a slurry in which particles are dispersed in ethylene glycol or water with a polyester raw material, a method of blending dried particles with a polyester raw material using a kneading extruder, and the like can also be adopted.

In order to obtain the film of the present invention, first,
The polyester is melt-extruded from an extrusion die and cooled and solidified by a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. In the present invention, both may be used in combination as needed. In stretching a uniaxial film, first, the unstretched sheet is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C, preferably 80 to 11 ° C.
0 ° C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, stretching is performed in a direction orthogonal to the stretching direction of the first stage. The stretching temperature is usually 70 to 12
0 ° C., preferably 80 to 115 ° C .;
It is usually 3.0 to 7 times, preferably 3.5 to 6 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or relaxation within 30% to obtain a stretched film.

In the above-mentioned stretching, stretching in one direction is performed by 2
It is also possible to adopt a method of performing the above steps. In that case, it is preferable that the stretching is performed in such a manner that the stretch ratio in the two directions finally falls within the above range. If necessary, the film may be stretched in the vertical and / or horizontal directions again before or after the heat treatment. In the present invention, it is necessary to provide a release layer on one surface of the uniaxial film. The release layer is preferably formed by coating a coating liquid containing a curable silicone resin as a main component, followed by drying and curing. In the release layer, optional additives in a range that does not impair the properties, for example, various resins, dyes, coloring agents such as pigments, infrared reflectors, infrared absorbers, ultraviolet absorbers, heat stabilizers,
An anti-blocking agent, an antioxidant and the like may be contained.

The above-mentioned curable silicone resin is not particularly limited. For example, any of a condensation reaction type, an addition reaction type, an ultraviolet curing type, and an electron beam curing type can be used.

In the present invention, the coating solution can be coated by a known method such as a rod coating method, a reverse roll coating method, a gravure roll coating method, or an air knife coating method.
After application, for example, in the case of a thermosetting type such as a condensation reaction type or an addition reaction type, usually 50 ° C to 150 ° C, preferably 80 ° C
Temperature within the range of ~ 130 ° C, usually within 2 minutes, preferably 1 minute.
By performing the heat treatment within a period of time within minutes, a cured film can be formed. The coating amount of the curable silicone resin is 1 to 25 g / m ² , and more preferably ^{2 to 20} g / m ^2.
The thickness of the silicone resin coating film after curing is preferably 0.01 to 1 μm, more preferably 0.05 to 0.5 μm.
Is preferable. When the thickness of the coating film is less than 0.01 μm, the mold release performance tends to decrease. When the thickness of the coating film exceeds 1 μm, curing of the coating film tends to be insufficient, and the release performance may change with time.

In the present invention, the release force of the release film to the pressure-sensitive adhesive is not particularly limited as long as it can be peeled off, but it is usually 2 to 400 mN / cm, preferably 4 to 200 mN / cm. Preferably 8 to 10
0 mN / cm. In the present invention, the residual adhesive ratio of the release film is 80% or more, preferably 85% or more, and more preferably 90% or more. If the value is less than 80%, for example, the adhesive strength is reduced when a polarizing plate or a retardation plate is attached to a glass substrate or the like, which is not preferable.

The total light transmittance (TL) of the release film of the present invention constituted as described above is not particularly limited, but is usually 80% or more, preferably 85% or more. With a TL of about 80% or more, an inspection involving optical evaluation such as contamination can be performed with the protective film adhered to the surface of the polarizing plate or retardation plate. In the present invention, the film thickness is not particularly limited, but is usually 5 to 150 μm, preferably 10 to 100 μm.
m, more preferably 25 to 75 μm. When the thickness of the film is less than 5 μm, the protective property tends to decrease, and the handling property may be deteriorated. When the thickness of the film exceeds 150 μm, the flexibility and the total light transmittance tend to decrease. It may cause trouble.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples and comparative examples, “parts” means “parts by weight”. The measuring methods and evaluation criteria used in the present invention are as follows.

(1) Peeling force of release film A double-sided adhesive tape (“No. 502” manufactured by Nitto Denko Corporation) is applied on the release layer of the sample film, and pressed with a 2 kg rubber roller specified in JIS Z0237. , And 50 mm in width to obtain a sample for peel force measurement. After leaving for 1 hour after the pressure bonding, using an Instron type tensile tester, 180
The sample was peeled at a tensile speed of 300 mm / min in the degree direction, and the average value of the stress was taken as the peel force of the sample. This test was repeated for 10 samples, and their arithmetic mean was used as the peel force. The atmosphere used for this test was 23
C., 50% RH standard condition.

(2) Residual Adhesion Rate Double-sided adhesive tape ("No. 502" manufactured by Nitto Denko Corporation)
After sticking to a cold-rolled stainless steel plate (SUS304) specified in IS G4305, the adhesive strength to the stainless steel plate is measured, and the value is defined as (f0). On the other hand, the adhesive strength after the double-sided pressure-sensitive adhesive tape peeled off by the method described in the evaluation criteria (1) was attached to the stainless steel plate was measured, and the value was set to (f1). Rate.

[0021]

## EQU1 ## Residual adhesion rate = (f1 / f0) × 100

The measurement of the adhesive strength was carried out according to JIS Z023.
The sample was pressed with a 2 kg rubber roller specified in No. 7 to obtain samples for measuring the adhesive strength of f0 and f1, respectively, left for 1 hour after pressing, and then pulled in a 180 ° direction using an Instron type tensile tester. Peel at 300mm / min,
The stress was measured for each of 10 samples, and their average values were defined as f0 and f1, respectively.

(3) Total light transmittance (T) of the laminated film
L) According to JIS-K7105, the total light transmittance (TL) was measured with an integrating sphere turbidimeter (“NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd.). (4) Absolute value of refractive index difference Using an Abago refractometer manufactured by Atago Optical, sample films in the vertical and horizontal directions are sampled, and the refractive index of each sample in the sample sampling direction is measured, and calculated by the following equation. did.

[0024]

## EQU2 ## Absolute value of refractive index difference = | vertical refractive index-lateral refractive index |

The refractive index was measured at 23 ° C. using a sodium D line. (5) Ease of inspection (quenching state) A sample film was arranged between two polarizing plates in a crossed Nicols state, and the presence or absence of a quenching state when the whole was viewed from above was evaluated.

Production Example 1 (Polyester A) 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, methanol was distilled off, and transesterification was carried out. The temperature was raised to 230 ° C. over 4 hours from the start of the reaction, and the transesterification was substantially completed. Next, an ethylene glycol slurry containing 0.1 part of silica particles having an average particle size of 1.54 μm was added to the reaction system, and ethyl acid phosphate was added to the slurry.
After adding 04 parts and 0.01 parts of germanium oxide, 1
In 00 minutes, the temperature reached 280 ° C and the pressure reached 15 mmHg. Thereafter, the pressure was gradually reduced to finally 0.3 mmHg.
And After 4 hours, the inside of the system was returned to normal pressure to obtain polyester A. The content of the silica particles of the polyester A was 0.1% by weight.

Production Example 2 (Polyester film A1) Polyester A was dried at 180 ° C for 4 hours in an inert gas atmosphere, melt-extruded at 290 ° C by a melt extruder, and the surface temperature was adjusted by using an electrostatic contact method. It was cooled and solidified on a cooling roll set at 40 ° C. to obtain an unstretched sheet. The obtained sheet was stretched 4.5 times in the transverse direction at 85 ° C. in a tenter. Then, it heat-set at 230 degreeC, and obtained the polyester film A1 of thickness 40 micrometers.

Production Example 3 (Polyester film A2) Polyester A was dried in an inert gas atmosphere at 180 ° C for 4 hours, melt-extruded at 290 ° C by a melt extruder, and the surface temperature was adjusted by using an electrostatic application adhesion method. It was cooled and solidified on a cooling roll set at 40 ° C. to obtain an unstretched sheet. The obtained sheet was stretched 4.5 times in the machine direction at 85 ° C. by a roll stretching machine. Then, it guided to the tenter and heat-set at 230 degreeC, and obtained the polyester film A2 of thickness 40 micrometers.

Production Example 4 (Polyester Film A3) Polyester A was dried at 180 ° C. for 4 hours in an inert gas atmosphere, melt-extruded at 290 ° C. by a melt extruder, and the surface temperature was adjusted by using an electrostatic contact method. It was cooled and solidified on a cooling roll set at 40 ° C. to obtain an unstretched sheet. After stretching the obtained sheet 3.5 times in the longitudinal direction at 85 ° C.,
The film was stretched 3.7 times in the transverse direction at 0 ° C., and further heat-set at 230 ° C. to obtain a polyester film A3 having a thickness of 40 μm.

Example 1 100 parts by weight of a curable silicone resin (KS-779 manufactured by Shin-Etsu Chemical Co., Ltd.) was applied on the surface of a polyester film A1.
Using a coating solution consisting of 1 part by weight of a curing agent (CAT PL-8 manufactured by Shin-Etsu Chemical Co., Ltd.) and 2200 parts by weight of a mixed solvent of methyl ethyl ketone / toluene, the coating thickness after curing was adjusted to 0.1 μm with a Meyer bar. A release film coated and formed with a cured silicone resin film was obtained.

Example 2 A release film was obtained in the same manner as in Example 1 except that the polyester film A1 was changed to the polyester film A2. Example 3 In Example 1, 100 parts by weight of a curable silicone resin (KS-723A manufactured by Shin-Etsu Chemical Co., Ltd.), 25 parts by weight (KS-723B manufactured by Shin-Etsu Chemical Co., Ltd.), and a curing agent (manufactured by Shin-Etsu Chemical Co., Ltd.) A release film was obtained in the same manner as in Example 1, except that a coating solution comprising 5 parts by weight of CAT PS-3) and 2,200 parts by weight of a mixed solvent of methyl ethyl ketone / toluene was used.

Example 4 In Example 1, 100 parts by weight of a curable silicone resin (X-62-5039A manufactured by Shin-Etsu Chemical Co., Ltd.) was used.
5 parts by weight of curing agent (X-62-5039B manufactured by Shin-Etsu Chemical Co., Ltd.), mixed solvent of methyl ethyl ketone / toluene 2200
A release film was obtained in the same manner as in Example 1 except that the coating liquid was composed of parts by weight.

Comparative Example 1 A release film was obtained in the same manner as in Example 1 except that the polyester film A1 was changed to the polyester film A3. Comparative Example 2 In Example 1, 100 parts by weight of a curable silicone resin (KS-779 manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part by weight of a curing agent (CAT PL-8 manufactured by Shin-Etsu Chemical Co., Ltd.), 2200 parts by weight of a mixed solvent of methyl ethyl ketone / toluene A release film was obtained in the same manner as in Example 1 except that 5 parts of silicone oil was added to the coating solution consisting of The results obtained above are shown in Table 1 below.

[0034]

[Table 1]

[0035]

The release film of the present invention has a residual adhesion ratio,
It is excellent in transparency and testability, is extremely useful when used as a protective film for an adhesive layer for polarizing plates and retardation plates, and has a high industrial value.

Claims (2)

[Claims] 1. A release film for protecting a surface of an adhesive applied to a polarizing plate and a retardation plate of a liquid crystal display plate, wherein a release layer is provided on one surface of a uniaxially oriented polyester film. An adhesive layer protective film comprising a laminated film, wherein the residual adhesive ratio of the laminated film is 80% or more. 2. The film according to claim 1, wherein the release layer contains a cured silicone resin as a main component.