JP2003089178A - Uniaxially stretched polyester film and mold release film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a uniaxially stretched polyester film which can be used by adhering to a constituting member or the like of a large-sized liquid crystal display unit, which has a good inspectability and excellent wear resistance without necessity of releasing at the checking time and which is useful as the base of the mold release film. SOLUTION: The uniaxially stretched polyester film is obtained by laminating two or three polyester layers by co-extruding. The polyester film has a value of specific contrast (C), a three-dimensional mean surface roughness (SRa) on one surface of 0.015 to 0.040 μm, the maximum distortion of a stretching main axis measured by a microwave transmission type molecular orientation meter of 7 deg. or less, and a content of a foreign matter having a major axis of 100 μm or more or less than one per 1 m<2> of an area.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a uniaxially oriented polyester film useful as a base material for a release film provided on the surface of an adhesive layer formed on a synthetic resin plate or the like. In particular, a uniaxially oriented polyester film suitably used as a base material for a release film provided on the surface of a pressure-sensitive adhesive layer formed on the surface of a polarizing plate or a retardation plate which is a constituent member of a liquid crystal display device, and the film Regarding the release film used.

[0002]

2. Description of the Related Art A liquid crystal display device is typically manufactured by sequentially laminating a polarizing plate, a liquid crystal cell and a polarizing plate from the backlight side. Further, various compensating plates such as a phase difference plate are inserted between them for improving the display mode and viewing angle. The lamination of the polarizing plate and the retardation plate is usually performed by bonding the polarizing plate with the pressure-sensitive adhesive layer or the retardation plate with the pressure-sensitive adhesive layer to the object.

The above-mentioned polarizing plate has a structure in which a polarizing film is sandwiched between triacetyl cellulose films, and a pressure-sensitive adhesive layer for laminating is usually provided on one side of the polarizing plate, and the adhesive layer is provided. The surface is usually provided with a release film. Since triacetyl cellulose is inferior in scratch resistance and moisture resistance, a pressure-sensitive adhesive layer is not formed on the polarizing plate for the purpose of protecting it and preventing damage and dust adhesion during handling and during the manufacturing process of liquid crystal display devices. A surface protection film is provided on the surface side.

Similar to the above-mentioned polarizing plate, a pressure-sensitive adhesive layer for bonding is provided on one surface of various compensating plates such as the above retardation film, and a release film is provided. Further, a surface protective film is similarly provided on the side on which the pressure-sensitive adhesive layer is not formed. When the polarizing plate, the retardation film, etc. are actually attached to the liquid crystal cell, the release film and the surface protection film are peeled and removed.

Among the above-mentioned release films, conventionally, a film in which a release agent such as silicone is applied to at least one surface of a biaxially stretched film such as polyester or polypropylene is used.

It is customary to inspect the various components of the produced liquid crystal display device in a timely manner in order to evaluate the display capability, hue, contrast, etc., or inspect for foreign matters and scratches. Examples of the inspection method include an inspection performed by forming crossed Nicols with a polarizing plate having a protective film to be inspected using an analyzer. In such an inspection, scratches, foreign matters, and the like on the polarizing plate are detected as bright spots because light passes through the portions. Conventionally, a thin and durable biaxially stretched film has been used as a base material of a release film. However, in such a biaxially stretched film, the direction of the main orientation varies due to the bowing phenomenon that occurs in the stretching and heat treatment steps, so that the contrast and brightness vary during inspection using crossed Nicols, or Coloring due to interference due to the retardation of the film was observed, and it was difficult to confirm foreign substances. As a method for improving this, JP-A-6-148431 proposes a release film using a non-oriented film substrate made of polyester, polypropylene or the like. However, such a film is formed by a casting method, and since it is a film in a state of being almost not oriented and almost amorphous, it cannot be said that it is sufficient in terms of chemical resistance, scratch resistance, etc. In addition, since the base film itself is expensive, it is rarely used.

JP-A-08-294988 and JP-A-09-314782 disclose biaxially stretched films having improved optical anisotropy. However, such a biaxially stretched film also has a widthwise direction due to further enlargement of polarizing plates and retardation plates in the recent TFT system and STN system, and further widening of a processing raw material accompanying productivity improvement. It is not completely satisfactory in terms of stability of optical characteristics. In particular, when inspecting a large composite polarizing plate, the peripheral portion of the composite polarizing plate is viewed obliquely when looking at the whole. Therefore, such a peripheral portion is observed in a colored state, and there is a problem that it is not easy to confirm the foreign matter in this portion.

[0008]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and its purpose is to apply it to the surface of a pressure-sensitive adhesive layer provided on the surface of a constituent member of a large-sized liquid crystal display device. Another object of the present invention is to provide a uniaxially oriented polyester film useful as a base material for a release film that does not require peeling at the time of inspection and has good inspection properties. Another object of the present invention is a film having the above-mentioned properties, in the production process and the processing process, there is no contamination due to the falling of the contained inorganic particles, and a coating liquid for release when used as a release film. Another object of the present invention is to provide a uniaxially oriented polyester film which is excellent in abrasion resistance and which is not repelled and uneven. Still another object of the present invention is to provide a release film using such a uniaxially oriented polyester film.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies in view of the above circumstances, the present inventors have found that a release film having a surface suitable for forming a release layer and having a controlled contrast is obtained. The present invention has been completed by developing a uniaxially oriented polyester film useful as a base material.

The uniaxially oriented polyester film of the present invention is a uniaxially oriented polyester film in which two or three polyester layers are laminated by coextrusion,
The value of contrast (C) represented by the following formula (I) is 70 or more and 2000 or less: C = Y1 / Y2 (I) [where Y1 makes the optical axes of the two polarizers parallel to each other,
The amount of transmitted light when the polyester film is inserted between the two polarizers, Y2 is the transmission when the polyester film is inserted between the two polarizers, with the optical axes of the two polarizers being perpendicular to each other. The amount of light is shown]; the three-dimensional average surface roughness (SRa) of one surface is 0.015 to 0.040.
μm, the maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter is within 7 degrees, and the content of foreign matter having a major axis of 100 μm or more is less than 1 per 1 m ^{2 of} area.

In a preferred embodiment, the three-dimensional average surface roughness (SRa) of the surface opposite to the one surface is
Is 0.015 to 0.060 μm.

[0012] In a preferred embodiment, the uniaxially oriented polyester film contains inorganic or organic particles in at least one layer.

The release film of the present invention has a base material made of the above uniaxially oriented polyester film and a release layer.

In a preferred embodiment, the release layer is formed on the surface of the uniaxially oriented polyester film having a three-dimensional average surface roughness (SRa) of 0.015 to 0.040 μm.

In a preferred embodiment, the release film is attached to the surface of the pressure-sensitive adhesive layer of the polarizing plate or retardation plate of the liquid crystal display device.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The uniaxially oriented polyester film of the present invention is a laminated film composed of two or three polyester layers as shown below. This laminated film has a specific contrast value and a specific three-dimensional average surface roughness (SRa) for forming a release layer when the film is used as a release film.

In the uniaxially oriented polyester film of the present invention, the value of contrast (C) represented by the following formula (I) is 70 or more and 2000 or less: C = Y1 / Y2 (I) where Y1 is 2 When the optical axes of two polarizers are in parallel and the polyester film is inserted between the two polarizers, the amount of transmitted light is Y2, the optical axes of the two polarizers are perpendicular to each other, and the polyester film is The amount of transmitted light when inserted between two polarizers is shown. The value of contrast (C) is preferably 100 or more and 1500 or less, and more preferably 300 or more and 1200 or less.

When the contrast value is less than 70,
In the crossed Nicols inspection, the darkness cannot be maintained, and it is difficult to find the foreign matter in the target sample. Further, when the contrast value is greater than 2000, the crossed Nicols inspection results in a completely black state, and foreign matter and scratches in the release film are excessively detected as light spots. Inspection efficiency decreases.

The uniaxially oriented polyester film of the present invention has a three-dimensional average surface roughness (SRa) on one surface of 0.015 to 0.040 μm, preferably 0.020 to
It is in the range of 0.035 μm. When this uniaxially oriented polyester film is used as a base material for a release film, a release layer is formed on the surface. SRa is 0.015
When the thickness is less than μm, the slipperiness is poor, fine scratches are generated on the film surface during processing, and workability is deteriorated. If SRa exceeds 0.040 μm, repellency is likely to occur particularly in the release layer.

The three-dimensional average surface roughness (SRa) of the surface of the film opposite to the above surface is not particularly limited,
The range is preferably 0.015 to 0.060 μm, and more preferably 0.020 to 0.055 μm.
When the three-dimensional average surface roughness is in such a range, workability when handling the film becomes good.

In the uniaxially oriented polyester film of the present invention, the maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter is 7 degrees or less, preferably 5 degrees or less, more preferably 4 degrees or less. When the strain of the orientation main axis is larger than 7 degrees, in the inspection of a polarizing plate or the like using the film, when a crossed Nicol is formed with a protective polarizing plate to be inspected using an analyzer, a difference in lightness and darkness becomes large, and the inspection is performed. Interfere with.

The uniaxially oriented polyester film of the present invention is a laminated polyester film having two or three layers as described above. This laminated film usually has the above-mentioned specific three-dimensional average surface roughness (SRa) of 0.015 to 0.04.
A layer (A layer) having 0 μm on the surface is the outermost layer, and a layer mainly for controlling contrast (this is referred to as B layer) is provided. When the layers other than the A layer and the B layer are C layers, the layer structure of the uniaxially oriented polyester film of the present invention may be A / B, A / B / A, A / B / C and the like.

The uniaxially oriented polyester film of the present invention preferably contains at least one layer of inorganic or organic particles (particularly the above-mentioned layer B) in order to adjust the contrast or improve the surface condition (described later). ). The major axis 100 due to the aggregation of the inorganic or organic particles
The number of foreign matters having a size of μm or more is less than 1 per 1 m ² of the area of the polyester film. The number of foreign matters is measured by visual inspection using, for example, the crossed Nicols method. If the number of foreign substances is 1 or more, it is determined as a defective product in the above inspection, and the yield is reduced.

Further, in the uniaxially oriented polyester film of the present invention, the difference between the maximum value and the minimum value of the refractive index Ny in the main orientation direction is preferably 0.007 or less, more preferably 0.005 or less, and more preferably. The range is 0.004 or less. When the difference between the maximum value and the minimum value of the refractive index Ny in the main orientation direction is larger than 0.007, in the inspection such as a polarizing plate having a release film using the film as a base material, the brightness in the film width direction The difference between the two may become large and may interfere with the inspection.

The haze of the uniaxially oriented polyester film of the present invention is preferably in the range of 10.0 to 20.0%, more preferably in the range of 11.0 to 18.0%, and further preferably in the range of 12.0 to 16.0. % Range. Haze is 1
If it is less than 0.0%, the contrast at the time of inspection using crossed nicols becomes high, resulting in a completely black state. Therefore, minute foreign matters, scratches and the like in the film are detected as light spots, which may result in deterioration of inspection efficiency. On the other hand, when the haze value is larger than 20.0%, the transparency is poor and the accuracy of the inspection by transmitted light tends to be poor.

When the uniaxially oriented polyester film of the present invention is held at 105 ° C. for 30 minutes, the heat shrinkage rate in the stretching direction and the vertical direction is preferably 3.0% or less, more preferably 2.0% or less. When the value of the heat shrinkage ratio is more than 3.0%, the film is greatly shrunk by heating during the processing for providing the release layer or the adhesive layer. Therefore, the flatness is deteriorated and wrinkles and curls are likely to occur.

The thickness of the laminated polyester film of the present invention is not particularly limited as long as it can be formed into a film. Usually, the total film thickness of the laminated two or three layers is in the range of 9 to 300 μm, more preferably 12 to 250 μm.

As described above, when the uniaxially oriented polyester film of the present invention is composed of the A layer, the B layer and, if necessary, the C layer, the thickness of the B layer with respect to the entire layer. Is preferably in the range of 0.70 to 0.90, more preferably 0.75 to 0.85. If the above value is 0.
When it exceeds 90, the B layer becomes relatively thick. Since the B layer often contains a relatively large amount of particles, the surface roughness of the A layer may be rough due to the influence of the particles. When it is less than 0.70, the particle concentration in the B and C layers is often extremely high in order to adjust the contrast. Therefore, the formation of coarse protrusions due to the aggregation of particles increases. As a result, a coarse protrusion may be detected in the crossed Nicols inspection, resulting in an excessive inspection.

The polyester used as a raw material for the uniaxially oriented polyester film of the present invention is a crystalline polyester which can be obtained by polycondensing an aromatic dicarboxylic acid or its ester and a diol. Typical examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid and naphthalene-2,6-dicarboxylic acid, and examples of the diol include ethylene glycol, diethylene glycol, tetramethylene glycol and neopentyl glycol. Can be mentioned.

The above polyester is obtained by directly polycondensing an aromatic dicarboxylic acid and a diol. Other,
The aromatic dicarboxylic acid dialkyl ester and the diol are transesterified and then polycondensed, or the diglycol ester of the aromatic dicarboxylic acid is polycondensed.

Specific examples of such polyesters include polyethylene terephthalate, polyethylene-2,
Examples thereof include 6-naphthalate, polytetramethylene terephthalate, and polytetramethylene-2,6-naphthalate. The above polyester may be a copolymer containing the third component. Examples of the dicarboxylic acid component of the copolymer polyester include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, sebacic acid, adipic acid and terephthalic acid, and examples of the glycol component include ethylene glycol, diethylene glycol and propylene. Glycol, butanediol, 1,4-
Examples thereof include cyclohexanedimethanol and neopentyl glycol. Two or more kinds of these dicarboxylic acid components and glycol components may be used in combination.

Among the polyester materials that can be used as a raw material for the polyester film of the present invention as described above, polyethylene terephthalate is particularly low in impurities and has transparency, mechanical properties, surface smoothness, solvent resistance, and scratch resistance. It is most preferably used because of its comprehensive performance such as moisture permeability and cost.

Various additives may be incorporated into the polyester film of the present invention within the range where the effects of the present invention are not impaired. For example, antioxidants, heat resistance stabilizers, weather resistance stabilizers, ultraviolet absorbers, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents and the like are used.

The organic or inorganic fine particles are used for adjusting the contrast as described above. That is,
The polyester material containing the fine particles is used as a film, and the minute alignment unevenness around the fine particles generated by stretching the film is used to adjust the contrast in the crossed Nicols state. These fine particles are
It is blended to give the polyester film slipperiness.

Typical inorganic particles to be added include silica, colloidal silica, alumina, aluminum sol, kaolin, talc, mica, calcium carbonate and calcium phosphate. As the organic particles, acrylic particles, styrene particles, olefin particles, imide particles and the like can be used. The average particle size of the added particles is preferably 0.01 μm or more and 10 μm or less, more preferably 0.05 μm or more and 8 μm or less, and most preferably 0.1 μm or more and 3 μm or less.

These particles are contained mainly in the layer (B layer) for controlling contrast, but may be contained in other layers. When these particles are contained in the B layer, the content of the particles in the layer is preferably 0.05% by weight or more and 0.50% by weight or less, more preferably 0.08% by weight or more, It is 0.30% by weight or less. When these particles are contained in the A layer or the C layer, the content of the particles in the layer (when the particles are contained in the A layer and the C layer, the total weight of the A layer and the C layer is Content) is preferably 0.01% by weight or more and 0.20% by weight or less, more preferably 0.05% by weight or more, 0.1
It is 5% by weight or less. The particle size and content of these particles are appropriately determined in consideration of the degree of contrast required, the layer thickness of the film, and the like.

The uniaxially oriented polyester film of the present invention is preferably produced by a coextrusion method. In this co-extrusion method, the polyester material and, if necessary, the above additives are charged into two or three extruders, which are laminated using a multi-manifold of two or three layers or a feed block, and Extruded as a molten sheet. Next, the molten sheet extruded from the die is 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 use the electrostatic application adhesion method or the liquid application adhesion method in order to improve the adhesion between the sheet and the rotary cooling drum.

Next, the above unstretched sheet is stretched in the transverse direction by gradually widening the width of the tenter rail with a tenter type stretching machine to obtain a uniaxially oriented polyester film. A schematic diagram of an example of the tenter used is shown in FIG.
The above process is performed, for example, through the preheating zone 21, the stretching zone 22, and the heat setting zone 23 of the tenter, and finally a film having a width W is prepared. First, both ends of the unstretched sheet obtained by the above-mentioned method are gripped with clips and guided to the preheating zone 21. The preheating zone 21 is composed of one or more zones set to a predetermined preheating temperature. The temperature of the preheating zone 21 is preferably above the glass transition temperature of the polyester material used and below 130 ° C.

After preheating, the polyester film is subsequently stretched in the stretching zone 22. Drawing zone 22
Is composed of one or more zones in which the temperature and the stretching conditions are set so as to obtain a predetermined stretching ratio. According to the method of the present invention, the temperature of the stretching zone is (Tg + 70) to (Tg
+10) ° C., preferably (Tg + 65) to
It is in the range of (Tg + 25) ° C. Here, Tg is the glass transition temperature of the polyester material used. When the stretching temperature is lower than (Tg + 10) ° C., the thickness unevenness tends to increase, and as a result, a difference in contrast occurs in the width direction, which may cause a problem during crossed Nicols inspection. When the stretching temperature is higher than (Tg + 70) ° C.,
Crystallization proceeds, the resulting uniaxially stretched polyester film is likely to tear in the stretching direction, and the yield decreases.

The stretching speed of the polyester film in the stretching zone 22 is in the range of 1500 to 4000% / min, and the stretching ratio is preferably 2.0 to 6.0 times, particularly 3.
0 to 5.0 times is preferable. Angle φ formed by the running direction between the tenter rail and the center of the film in the stretching zone 22
(See FIG. 5) is preferably 10 ° <φ <25 °, more preferably 12 <φ <20 °. Angle φ
Is less than 10 °, the tenter stretching zone 22
Therefore, it is difficult to stably control the ambient temperature in the tenter and the film temperature for a long time. At the same time, in terms of energy saving, it is not preferable that the tenter stretching zone 22 is long. If the angle φ is greater than 25 °,
Since the orientation of the film in the stretching direction becomes extremely high, the film becomes very easy to tear in the stretching direction.

After stretching, the polyester film is subsequently heat set in the heat setting zone 23. Heat setting zone 23
Is composed of one or more zones in which the heat setting temperature and relaxation conditions are set so as to obtain a predetermined relaxation rate. The temperature of the heat setting zone is (Tg + 130) to (Tg + 30) ° C.
Range, preferably (Tg + 120) to (Tg +
40) C. range. If the temperature of the heat setting zone 23 is (T
When it is lower than g + 30) ° C., the heat shrinkage rate of the obtained uniaxially oriented polyester film is high, and wrinkles during processing are
It causes curling. The temperature of the heat setting zone 23 is (Tg
When the temperature is higher than +130) ° C., crystallization proceeds, the resulting film tends to tear in the stretching direction, and the yield decreases.

The amount of relaxation in the heat setting zone 23 in the stretching direction is about 1 to 10%, although it depends on the transverse stretching conditions.
The heat shrinkage rate at 105 ° C. of the film after the relaxation treatment is
It is preferable to set the relaxation amount and the heat setting temperature so as to be preferably 3% or less, more preferably 2% or less. The difference between the temperature of the heat setting zone 23 and the temperature of the stretching zone 22 is preferably 20 to 60 ° C, more preferably 25 to 50 ° C. When the difference between the temperature in the stretching zone and the temperature in the heat setting zone is smaller than 20 ° C., heat setting hardly makes sense. When the temperature difference is larger than 60 ° C., the distortion in the main orientation direction due to bowing becomes large, and as a result, the inspection and the cross nicol formation have uneven contrast and brightness, and stable inspection cannot be performed.

Further, in the method for producing a uniaxially stretched polyester film of the present invention, the stretching step and the heat setting step are carried out by different tenters, and a cooling step is provided between the stretching step and the heat setting step to obtain a glass. It is also possible to cool the film once below the transition temperature and then perform heat setting. This method is preferable because the amount of bowing can be further reduced. The length of the cooling step is preferably such that the following formula (II) is satisfied:

(L / W) ≧ 1.0 (II) Here, L is the length of the cooling step, which means that the temperature of the step is substantially lower than the temperature of the step before the cooling step (ie, the stretching step). It means the distance of the process from the point where it reaches the temperature of the next process (that is, the heat setting process) that is substantially higher than the temperature of the cooling process. W is the film width, which means the distance between the clips of the tenter at the tenter exit. In the above formula (II), the length L of the cooling step and the film width W are represented by the same unit. The tenter that performs transverse stretching and the tenter that performs heat setting may be separated. In this case, since the film is cooled by running the film in the air, the running distance in the air can be set to the length L of the cooling process. Also in this case, it is preferable that the ratio of the length of the cooling step L to the film width W satisfies the above formula (II).

The uniaxially oriented polyester film of the present invention is subjected to corona discharge treatment for treating the film surface (in air,
Treatment in nitrogen or carbon dioxide) or in-line coating can be applied. These treatments can be carried out in the usual way during the above steps. For example, as an in-line coat, a coating treatment agent such as an aqueous solution, an aqueous emulsion, or an aqueous slurry can be applied to the film before the stretching with a tenter for the purpose of improving antistatic property, slipperiness, adhesiveness and the like.

The release film of the present invention is a film obtained by forming a release layer on at least one surface of the uniaxially oriented polyester film of the present invention. The release layer is formed on the surface of the film having a three-dimensional average surface roughness (SRa) of 0.015 to 0.040 μm. The abrasion resistance is improved by forming the release layer on such a surface. Further, as will be described later, when the release layer is formed, the release coating liquid does not repel and become uneven. The release layer preferably contains at least one selected from silicone resins and fluororesins as a main component.

As the above-mentioned silicone resin, a silicone resin generally used as a release agent can be used, and it is generally used in the relevant field as described in “Silicone Material Handbook” (Toray Dow Corning, ed., 1993.8). It can be used by selecting it from the silicone resins. Generally, a thermosetting or ionizing radiation curable silicone resin (including a resin and a resin composition) is used. As the thermosetting silicone resin, for example, condensation reaction type and addition reaction type silicone resin, and as the ionizing radiation curing type silicone resin, ultraviolet ray or electron beam curing type silicone resin can be used. A release layer is formed by applying these on a film which is a base material and drying or curing.

As the condensation reaction type silicone resin, for example, polydimethylsiloxane having an OH group at the terminal and polydimethylsiloxane having a hydrogen at the terminal (hydrogensilane) are used as an organic tin catalyst (for example, an organic tin acylate catalyst). A composition capable of forming a three-dimensional crosslinked structure by a condensation reaction using

As the addition reaction type silicone resin, for example, a composition capable of forming a three-dimensional crosslinked structure by reacting a polydimethylsiloxane having a vinyl group introduced at the terminal with hydrogensilane using a platinum catalyst is known. Can be mentioned.

The ultraviolet curable or electron beam curable silicone resin is, for example, as the most basic type, a resin which is crosslinked and cured by a radical reaction in the same manner as usual silicone rubber crosslinking, and is photocured by the introduction of an acrylic group. Examples thereof include a resin, a resin composition in which an onium salt is decomposed by ultraviolet rays to generate a strong acid, and thereby an epoxy ring is cleaved to crosslink, and a resin composition in which crosslinking is performed by an addition reaction of thiol to vinylsiloxane. Since electron beams have higher energy than ultraviolet rays, radical crosslinking reaction occurs without using an initiator as in the case of ultraviolet curing.

The above-mentioned curable silicone resin preferably has a degree of polymerization of about 500 to 200,000, especially about 1000 to 100,000 after being cured. Specific examples of these include the following resins: Shin-Etsu KS-7 made by Chemical Industry Co., Ltd.
18, KS-774, KS-775, KS-778, K
S-779H, KS-830, KS-835, KS-8
37, KS-838, KS-839, KS-841, K
S-843, KS-847, KS-847H, X-62
-2418, X-62-2422, X-62-212
5, X-62-2492, X-62-2494, X-6
2-5048, X-62-470, X-62-236
6, X-62-630, X-92-140, X-92-
128, KS-723A ・ B, KS-705F, KS-
708A, KS-883, KS-709, KS-71
9; TPR-6701, TPR manufactured by Toshiba Silicon Co., Ltd.
-6702, TPR-6703, TPR-3704, T
PR-6705, TPR-6721, TPR-672
2, TPR-6700, XSR-7029, YSR-3
022, YR-3286; D manufactured by Dow Corning Co., Ltd.
K-Q3-202, DK-Q3-203, DK-Q3-
204, DK-Q3-205, DK-Q3-210, D
K-Q3-240, DK-Q3-3003, DK-Q3
-3057, SFXF-2560; SD-7226, SD-72 manufactured by Toray Dow Corning Silicone Co., Ltd.
29, SD-7320, BY-24-900, BY-2
4-171, BY-24-312, BY-24-37
4, SRX-375, SYL-OFF23, SRX-2
44, SEX-290; SILCOLASE 425 manufactured by IC Japan Co., Ltd. and the like. further,
JP-A-47-34447, JP-B-52-4091
Silicone resins described in Japanese Patent No. 8 can also be used. These curable silicone resins may be used alone or in combination of two or more.

As the fluororesin, a fluororesin generally used as a release agent can be used. Examples of such a fluororesin include a polymer (including an oligomer) made of a fluorine-containing vinyl polymerizable monomer or a copolymer thereof, a fluorine-containing vinyl polymerizable monomer and a vinyl polymerizable monomer not containing a fluorine atom. Examples thereof include a copolymer with a monomer or a mixture thereof, and a resin having 5 to 80 mol% of fluorine atoms.

Examples of the polymer comprising the above-mentioned fluorine-containing vinyl polymerizable monomer include the following polymers: poly [2
-(Perfluorononenyloxy) ethyl methacrylate], poly [2- (perfluorononenyloxy) ethyl acrylate], poly [2- (perfluorononenyloxybenzoyloxy) ethyl methacrylate], poly [2- (per Fluorononenyloxybenzoyloxy) ethyl acrylate], poly [2,2,2-trifluoroethyl methacrylate], poly [2,2,2-trifluoroethyl acrylate], poly [2,2,3,2]
3,3-pentafluoropropyl methacrylate], poly [2,2,3,3,8-pentafluoropropyl acrylate], poly [1-methyl-2,2,3,3,4,4]
4-hexafluorobutyl methacrylate], poly [1
-Methyl-2,2,3,3,4,4-hexafluorobutyl acrylate], poly [perfluoroheptylethyl methacrylate], poly [perfluoroheptylethyl acrylate], poly [perfluoroheptyl vinyl ether], poly [α , Β, β-trifluorostyrene], polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene and the like.

The fluorine-free vinyl polymerizable monomer copolymerizable with the above-mentioned fluorine-containing vinyl polymerizable monomer includes a hydrocarbon-based vinyl polymerizable monomer and a hydrocarbon-based non-conjugated divinyl polymerizable monomer. Examples thereof include monomers and functional group-containing vinyl polymerizable monomers. Among these, hydrocarbon-based vinyl polymerizable monomers include, but are not limited to, the following compounds: methyl acrylate, propyl acrylate, butyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, acrylic. Octyl acid acrylate, octadecyl acrylate, lauryl acrylate, N, N-diethylaminoethyl acrylate, methyl methacrylate, propyl methacrylate, butyl methacrylate, isoamyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, octadecyl methacrylate, Lauryl methacrylate, N, N-diethylaminoethyl methacrylate, vinyl acetate, vinyl propionate,
Vinyl caprate, vinyl laurate, vinyl stearate, styrene, α-methylstyrene, p-methylstyrene, vinyl chloride, vinyl bromide, vinylidene chloride, allyl heptanoate, allyl acetate, allyl caprate, allyl caproate, vinyl. Methyl ketone, vinyl ethyl ketone, 1,3-butadiene, 2-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, isoprene and the like. Hydrocarbon-based non-conjugated divinyl polymerizable monomers include, but are not limited to, the following compounds: ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, diethyl glycol diester. Acrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, divinylbenzene, vinyl acrylate, dibromoneopentyl glycol dimethacrylate, etc. Functional group-containing vinyl polymerizable monomers include, but are not limited to, the following compounds: acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylol acrylamide, N-butoxymethyl acrylamide, diacetone acrylamide. , Methylol diacetone acrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate and the like.

In addition to the above silicone resin and fluororesin, the release layer may contain additives usually used in the art within a range not impairing the effects of the present invention. Examples thereof include antifoaming agents, coatability improvers, thickeners, antistatic agents, antioxidants, ultraviolet absorbers, magnetizing agents, dyes and the like.

The thickness of the release layer is not particularly limited, but is preferably in the range of 0.05 to 5 μm. If the thickness of the coating film is smaller than this range, the releasing performance may be deteriorated and satisfactory performance may not be obtained. On the contrary, if the thickness of the coating film is thicker than this range, it may take time to cure and the productivity may be lowered.

As a method for forming a release layer on the surface of the above-mentioned uniaxially oriented polyester film which is a base film,
Although not particularly limited, a coating method is preferably used. Examples of the coating method include an air doctor coating method, a knife coating method, a rod coating method, a forward rotation roll coating method, a reverse roll coating method, a gravure coating method, a kiss coating method, a bead coating method, a slit orifice coating method, and a cast coating method. Are used.

Further, the surface protective film or the release film of the present invention is preferably provided with an antistatic layer for the purpose of suppressing the generation of static electricity. The antistatic layer is formed on the surface of the substrate opposite to the release layer. Alternatively, it is also possible to form an antistatic layer on the base film and then form a release layer thereon.

The antistatic layer can be formed by applying an antistatic resin composition to a base film. The antistatic agent contained in this antistatic resin composition,
Examples include the following substances: various cationic antistatic agents having a cationic group such as quaternary ammonium salt, pyridinium salt, and aliphatic amine salt; sulfonate group, sulfate ester group, phosphate ester group. , Anionic antistatic agents having anionic groups such as phosphonate groups; amphoteric antistatic agents such as amino acids, aminosulfuric acid esters; nonionic antistatic agents such as amino alcohols, glycerin, polyethylene glycols, etc. Various surfactant type antistatic agents. Polymeric antistatic agents obtained by polymerizing the above antistatic agents can also be used. Monomers or oligomers having a tertiary amino group or a quaternary ammonium group and capable of being polymerized by ionizing radiation (for example, N, N-
Polymerizable antistatic agents such as dialkylaminoalkyl (meth) acrylate monomers) and their quaternary compounds can also be used.

In addition to the antistatic agent, the antistatic resin composition contains a binder for improving the strength of the coating film of the antistatic layer, the adhesion to the base film, the water resistance, the solvent resistance, the blocking property and the like. It is preferable to contain As the binder, a polymer compound such as a thermoplastic resin and / or a thermosetting resin is preferable. Examples of the thermoplastic resin include thermoplastic polyester resin, acrylic resin, and polyvinyl resin, and examples of the thermosetting resin include thermosetting acrylic resin, urethane resin, melamine resin, and epoxy resin. Further, it is particularly preferable that the antistatic resin composition contains at least one cross-linking agent selected from the following compounds: methylol- or alkylol-based melamine compound, urea compound, glyoxal compound. , Acrylamide compounds, epoxy compounds, polyisocyanates, etc.

The surface specific resistance value of the antistatic layer can be arbitrarily set according to the purpose of use. For example, the surface specific resistance value of the antistatic layer is preferably 1 × 10 ¹¹ Ω / □ or less. Surface resistivity is 1 × 10 ¹¹ Ω /
If it is □, dust does not usually adhere.

The method for forming the antistatic layer on the surface of the substrate film is not particularly limited, but a coating method is preferably used. For example, as a coating method, an air doctor coating method, a knife coating method, a rod coating method, a forward rotation roll coating method, a reverse roll coating method, a gravure coating method, a kiss coating method, a bead coating method, a slit orifice coating method, a cast coating method, etc. Is mentioned.

When a release layer is formed on the surface of the above uniaxially oriented polyester film, for example, after applying a silicone resin or a fluororesin by the above method,
The release layer is formed by drying and curing this. The resin is cured by heating, irradiation with ionizing radiation, or the like. Drying and curing can be done individually or simultaneously. When it is carried out simultaneously, it is preferably carried out at a temperature of 80 ° C. or higher. The drying and curing conditions are preferably 80 ° C. or higher and 10 seconds or longer. If the drying temperature is less than 80 ° C. or the curing time is less than 10 seconds, the coating film is not completely cured, and the coating film tends to fall off.

Schematic diagrams showing examples of the layer structure of the release film of the present invention are shown in FIGS. 1 to 3, respectively. As shown in FIG. 1, the release film 101 of the present invention has a release layer 2 on one surface of a substrate 1 made of a uniaxially oriented polyester film. In another embodiment, as shown in FIG. 2, the release film 102 has the release layer 2 on one surface of the substrate 1 and the antistatic layer 3 on the other surface. In still another embodiment, as shown in FIG. 3, the release film 103 of the present invention is used.
Is a structure in which the antistatic layer 3 and the release layer 2 are sequentially laminated on the base material 1.

The release film of the present invention is attached to the surface of the pressure-sensitive adhesive layer formed on the surface of an optical member such as a polarizing plate or a retardation plate of a liquid crystal display device. FIG. 4 schematically shows a state in which the surface protective film and the release film of the present invention are attached to the polarizing plate 200 which is an optical member. Polarizing plate 2
00 is triacetyl cellulose (T
AC) film 12 is laminated, and further TAC film 1
The adhesive layer 13 for laminating is laminated on the second layer 2. The pressure-sensitive adhesive layer surface on one side of this polarizing plate 200 has 1
The axially oriented polyester film 1 is attached as a surface protective film, and the release film 101 of the present invention is attached on the surface of the other pressure-sensitive adhesive layer so that the release layer 2 is in contact with the pressure-sensitive adhesive layer 13 of the polarizing plate. There is.

The uniaxially oriented polyester film of the present invention is a uniaxially oriented polyester film in which two or three polyester layers are laminated by coextrusion as described above, and has a contrast (C) value and one surface. Has a three-dimensional average surface roughness (SRa) within a specific range. Furthermore, the maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter is within a predetermined range, and the amount of foreign matter is extremely small. Such a uniaxially oriented polyester film is suitably used as a base material of a release film attached to the surface of an adhesive layer formed on the surface of a base material such as a synthetic resin plate. This film has excellent abrasion resistance and can be manufactured at low cost. The release film produced using this substrate is particularly suitably applied to the pressure-sensitive adhesive layer on the surface of the polarizing plate or the retardation plate which is a constituent member of the liquid crystal display device. The polarizing plate and the retardation plate to which the release film is attached do not require peeling of the release film at the time of inspection and have good inspectability. This release film is preferably used by being attached to a constituent member of a large-sized liquid crystal display device.

[0067]

EXAMPLES Next, the present description will be further described with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof. The methods for evaluating physical properties in the following examples and comparative examples are as follows.

<Three-dimensional surface roughness (SRa)> One surface of the polyester film (the surface on which the release layer is formed)
Using a stylus type three-dimensional surface roughness meter (SE-3AK, manufactured by Kosaka Laboratory Ltd.), the radius of the needle is 2 μm, and the load is 3
Under the conditions of 0 mg and a needle speed of 0.1 mm / sec, the film is measured in the longitudinal direction of the film at a cutoff value of 0.25 mm over a measuring length of 1 mm. The measurement is performed by dividing the measurement length of 1 mm into 500 points at a pitch of 2 μm. The height of each point is imported into the three-dimensional roughness analyzer (TDA-21). Perform the same operation in the width direction of the film by 2μ
150 times continuously at m intervals, that is, 0.
Perform over 3 mm to allow the analyzer to capture the data. Based on these data, the three-dimensional average surface roughness SRa is obtained using an analyzer.

<Contrast Value> A rectangular film having a length of 500 mm and a full width in the width direction is cut out from a roll-shaped film. As shown in FIG. 6, 100 mm so as to include a part of one long side a ₀ of this rectangular film.
Cut out three or more square-shaped film samples.
However, one of the square samples includes the center point X of the long side, and two include each end of the long side a _{0 and} a part of the longitudinal side. To cut out.

Next, the optical axes of the two polarizers are set in parallel with each other, and the 100 mm square film sample is placed in a sample holder in which the bases of the two polarizers are exactly parallel to the polarization direction. Then, the amount of light transmitted through the two polarizers and the film sample is measured. Similarly, the amount of transmitted light when the optical axes of the two polarizers are perpendicular to each other is measured, and the contrast of each film sample is calculated according to the formula (I).

C = Y1 / Y2 (I) [where C is the contrast, Y1 is the optical axis of the two polarizers in a parallel state, and the film is inserted between the two polarizers. The amount of transmitted light, Y2, shows the amount of transmitted light when the optical axes of the two polarizers are made orthogonal and the film is inserted between the two polarizers]. The contrast values for each film sample thus obtained are averaged.

<Heat Shrinkage at 105 ° C.> As described below, a sample (Sample 1) for measuring the heat shrinkage in a stretching direction (transverse direction) from a long film and a direction (longitudinal direction) perpendicular thereto. A sample (Sample 2) for measuring the heat shrinkage rate of is cut out. These samples are strips having a long side of 200 mm and a short side of 10 mm. First,
As shown in FIG. 7, the central portion of the entire width (from end to end in the stretching direction) of the film is used as a reference, the long side (indicated by a in FIG. 7) is parallel to the stretching direction, and the short side (in FIG. 7 by b). A plurality of samples 1 are cut out at intervals of 200 mm (distance between short sides of samples) so that (shown) is vertical. Next, a plurality of samples 2 are cut out at intervals of 200 mm (distance from the center of the sample to the center) so that the long side is perpendicular to the stretching direction and the short side is parallel. Marks are made at two positions at intervals of 150 mm along the longitudinal direction of each of the cut out samples. A tension (5 g) is applied in the longitudinal direction of this sample film, and the interval (length) A between the marks is measured. Then, this sample 1
The sample is left unloaded for 30 minutes in an oven in an atmosphere of 05 ° C., taken out of the oven, and cooled to room temperature. Next, the tension (5 g) is applied again in the longitudinal direction, and the interval (length) B between the marks is measured. The heat shrinkage rate was calculated from the following formula, and the average value for sample 1 and sample 2
The average value of is calculated. In Table 1 showing the results of Examples and Comparative Examples, the heat shrinkage ratio in the stretching direction (Sample 1) is “heat shrinkage ratio TD”, and the heat shrinkage ratio in the perpendicular direction (Sample 2) is “heat shrinkage ratio MD”. ".

Thermal shrinkage rate (%) at 105 ° C. = [(Length A before heat treatment-length B after heat treatment) / length A before heat treatment] × 100 (%)

<Haze> According to JIS K 7136, the sample film is divided into 5 equal parts in the stretching direction, and the turbidimeter (NDH-3 manufactured by Nippon Denshoku Industries Co., Ltd.
00A) is used for sampling and measurement, and an average value is obtained.

<Distortion of Oriented Principal Axis> A rectangular film having a length of 500 mm and a full width in the width direction is cut out from a roll-shaped film. Based on the center of the film in the width direction, the width of the film is 10 mm at intervals of 300 mm.
Cut out multiple 0 mm square films (Fig. 8
reference). The sides of the square film should be parallel to the longitudinal and width directions, respectively. Each of the molecular orientation directions (orientation main axis) of the cut sample film is measured by a microwave transmission type molecular orientation meter. When the width direction of the film is 0 °, the difference from 0 ° is calculated when the molecular orientation angle is smaller than 45 °, and the difference from 90 ° when larger than 45 ° with reference to the width direction. The molecular orientation angle with the largest absolute value is taken as the maximum value, and this is taken as the maximum strain of the orientation main axis. As the microwave transmission type molecular orientation meter, a molecular orientation meter (MOA-2001A) manufactured by Kanzaki Paper Co., Ltd. is used.

<Measurement of the number of foreign matters> A film sample is cut into a size according to the standard raw paper size A5 size of Japanese Industrial Standards. The whole area of the cut film is visually inspected by the crossed Nicols method to perform foreign matter inspection. The inspection is performed on 15 samples, and the result is used to convert the number of foreign matters per m ² . Next, the detected foreign matter in the sample film is observed with transmitted light using an optical microscope, and the maximum diameter of the portion observed as an optically abnormal range is defined as the foreign matter size (major axis). The optically abnormal range refers to a range in which light leaks and is visible when the crossed Nicols state (dark field) is set. When a cavity (void) existing around the foreign matter is observed as an optically abnormal range, the size of the foreign matter is taken to include this cavity. Whether the foreign matter is caused by the aggregation of the added particles is determined by performing elemental analysis. In this way, the number of foreign substances having a major axis of 100 μm or more due to the aggregation of the added particles is counted as the number of foreign substances.

<Refractive index in each direction of film (Nx, Ny,
Measurement of Nz)> As shown below, a plurality of strip-shaped samples having a long side of 40 mm and a short side of 20 mm are cut out from a long film. The short side is parallel to the stretching direction (horizontal direction) with the center of the entire width of the film (from the end to the end in the stretching (transverse) direction) as the reference, and the distance between samples (from the center to the center of the strip-shaped sample). A plurality of samples are cut out along the stretching direction so that the intervals (up to) are 100 mm apart (see FIG. 9). Refractive index N of this sample in the main orientation direction
y, the refractive index Nx in the direction perpendicular to the main orientation direction on the film surface, and the refractive index Nz in the film thickness direction are measured. The measurement is performed by using an Abbe refractometer 4T manufactured by Atago Co., Ltd., by attaching a polarizing plate to the eyepiece lens, and adjusting the orientation of the polarizing plate and the orientation of the film. Diiodomethane is used as the intermediate liquid. A value obtained by averaging the refractive index values in each direction of the plurality of samples is defined as an average refractive index. Further, for Ny, the difference between the maximum and minimum measured values is obtained.

<Abrasion resistance> A polyester film is slit into a tape to form a tape. The surface of the film on which the release layer is formed, and the surface opposite to the surface are rubbed in sequence to a metal guide roll, and the speed is 30 m / min.
Run m. The amount of white powder generated on the surface of the guide roll after rubbing the guide roll is evaluated and ranked in three stages as shown below. ⊚: No powder is visually observed. ◯: Some powder is recognized, but there is no problem in practical use. X: A large amount of powder adheres, and cannot be practically used.

<Processing characteristics> A UV-curable silicone resin (cured by ring opening and crosslinking of epoxy ring) was applied to the surface of the base film, heated at 80 ° C. for 30 seconds, and then U
A mold release treatment is performed by performing V irradiation (thickness of the mold release layer is 0.1 μm). The irregularity of flatness during the release treatment, the occurrence of curl, and the repelling of the release layer are evaluated according to the following criteria.

<Disorder of flatness> A sample of 2 m is cut out in the longitudinal direction from the product (long shape with a width of 1 m) within 1 day after the mold release processing, and the mold release surface is the upper side on the flatness inspection table. So put. The sample is brought into close contact with the inspection table using a rolling rod. After being left for 3 minutes, a portion having poor flatness floats up from the surface of the inspection table. Therefore, this portion is evaluated as follows.

Regarding the seaweed-like defects at both ends in the width direction of the film, ◎ is 3 or less places where the floating height is 3 mm or more, ○ is 3 or 5 places.
When there are 6 or more places, the result is x. Regarding the bulge-like permanently deformed defects (vertical wrinkles due to heat, etc.) in the whole film, if there are three or less places where the lifted height is 3 mm or more, other than the above-mentioned wakame-shaped defects, ◎ 3
A case of ~ 5 places is marked with O, and a case of 6 places or more is marked with x.

The overall evaluation of the irregularity of flatness is ◎ when both the seaweed-like defects and the bulge-like defects are ◎, and when one is ○ and the other is ○ or ◎, one or both. If the evaluation of x is x, it is x.

<Generation of Curl> A sample is cut out in a widthwise direction and a longitudinal direction at a width of 10 mm and a length of 100 mm at the central portion in the widthwise direction of the product within one day after the release processing. This sample is placed on a flat table so that the mold release surface faces upward, and the floating height of the sample end is measured. When the lifting height is less than 1 mm, it is marked with ⊚, when it is 1 to 3 mm, it is marked with ◯, and when it is larger than 3 mm, it is marked with x.

<Releasing of Release Layer> For products after release processing
Part of the release layer where cissing is observed.
Minutes (Silicone resin is repelled and not evenly applied
The number of parts). Repelling is observed in the release layer
2 pieces / m^TwoIf less than ◎, 2 to 5 pieces / m ^TwoPlace
The total is ○, 6 pieces / m^TwoThe above case is defined as x.

<Comprehensive Evaluation of Machining Properties> Evaluation of flatness irregularity, curl, and repelling of the release layer at the time of mold release processing is all ⊚, ⊙ when at least one is ×, and otherwise. The case is marked with ○.

<Inspection Property> After subjecting the base film to a release processing treatment as required, the base film is used as a surface protective film for a polarizing plate or a retardation plate or a release film, and inspected by a crossed Nicol method. The result of the inspection is evaluated in three levels according to the rate of occurrence of defective products due to errors caused by the film. Here, the occurrence of a defective product due to an error means that the product cannot be inspected due to coloring and that the product cannot be inspected due to a difference in brightness (contrast difference). The processing of the original fabric for the protective film or the release film is performed with a width of 1300 mm or more, and then cut into 15-inch size and then inspected. The inspection is performed by dividing the entire width evenly so that there is no deviation from the end and center of the original. ◎: Less than 1% ○: 1% to 2% ×: 3% or more

(Production Example 1: Production of Polyester A) When the temperature of the esterification reaction can reached 200 ° C., 86.4 parts by weight of terephthalic acid and 6 parts of ethylene glycol were added.
4.6 parts by weight were charged, and 0.017 parts by weight of antimony trioxide, 0.064 parts by weight of magnesium acetate tetrahydrate, and 0.16 parts by weight of triethylamine were charged as a catalyst while stirring. Then, the temperature was increased by pressurization, and the pressure esterification reaction was performed under the conditions of a gauge pressure of 0.34 MPa and 240 ° C. Then, the esterification reactor was returned to normal pressure, and 0.014 parts by weight of trimethyl phosphate was added. Furthermore, the temperature was raised to 260 ° C. over 15 minutes, and 0.012 parts by weight of trimethyl phosphate was added. Then, 15 minutes later, a dispersion treatment was performed with a high pressure disperser, and the average particle size was 2.50.
An ethylene glycol slurry of μm silica particles was added in an amount of 0.03 part by weight based on the particle content. The silica particles were prepared by preliminarily preparing an ethylene glycol slurry of silica containing 0.1 part by weight of sodium tripolyphosphate aqueous solution in terms of sodium atom based on 100 parts by weight of the silica particles, and centrifuging this to obtain coarse particles. The particles are obtained by cutting a part by 35% and then performing a filtration treatment with a metal filter having an opening of 5 μm. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction vessel,
Carry out polycondensation reaction at 0 ° C under reduced pressure to give an intrinsic viscosity of 0.62dl
/ G of polyethylene terephthalate resin (A) was obtained (hereinafter, may be abbreviated as PET (A)).

(Production Example 2: Preparation of Polyester B) Polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g was prepared in the same manner as in Production Example 1 except that the amount of silica particles added was 0.20 parts by weight. (B) was obtained (hereinafter,
It may be abbreviated as PET (B)).

(Production Example 3: Preparation of Polyester C) Polyethylene terephthalate resin having an intrinsic viscosity of 0.62 dl / g was prepared in the same manner as in Production Example 1 except that the amount of silica particles added was 0.40 parts by weight. C) was obtained (hereinafter P
ET (C) may be abbreviated).

(Example 1) PET (A) and (B) were vacuum dried, and each was subjected to 2 by a separate melt extruder.
Melted at 90 ° C. The molten PET was filtered using a filter capable of removing 95% of particles of 4 μm, joined and laminated so as to form a layer having a structure of A / B / A in a feed block, and extruded from a T die. The extruded sheet was brought into close contact with a casting drum having a surface temperature of 30 ° C. by electrostatic charge to obtain an unstretched film having a thickness of about 160 μm. The layer ratio is A: in terms of the PET discharge amount converted by each extruder.
It was adjusted so that B: A = 1: 8: 1.

This unstretched film was introduced into a tenter stretching machine and preheated in a preheating zone at 95 ° C. for about 6 seconds, and then in the stretching zone at 120 ° C., a stretching ratio of 4.0 times, and a stretching speed of 3
It was stretched in the width direction at 800% / min. At this time, the angle φ formed by the running direction of the tenter rail and the center of the film is 1
It was 5.0 °. After that, the film L / W ≧ 1.0
Was cooled to 50 ° C. Next, the film is heat treated at 160 ° C. in a heat setting zone, and then 3.0 in the width direction.
% Relaxation treatment was performed. After the film temperature was cooled to Tg or lower, it was removed from the clip. After cutting the ears, wind the film as usual, and the width is about 4000m.
A long uniaxially oriented polyethylene terephthalate film having a thickness of m and a thickness of about 40 μm was obtained and wound into a roll.

The heat shrinkage ratio of the obtained film in the film longitudinal direction (MD) at 105 ° C. for 30 minutes was 1.3.
%, The heat shrinkage ratio in the film width direction (TD) is 1.0%, and the average value (Nave) of the refractive indexes Nx, Ny, and Nz in each direction of the film.
Is 1.595, (Ny-Nx) is 0.095, the maximum strain of the orientation main axis in the full width of the film is 3 °, the difference between the maximum value and the minimum value of the refractive index Ny in the main orientation direction is 0.004, and the film haze Is 15.3%, the contrast is 1100, and the three-dimensional average surface roughness (SRa) of one surface is 0.025 μ.
m, and SRa on the opposite surface was 0.023 μm. In the foreign matter inspection of this film, no aggregated foreign matter due to the added particles having a major axis of 100 μm or more was observed. The evaluation of abrasion resistance was ⊚.

On one surface (surface having SRa of 0.025 μm) of the uniaxially stretched polyethylene terephthalate film having a thickness of 40 μm obtained as described above, a mold release was conducted under the conditions described in the section of “Processing characteristics” evaluation. Layers,
A release film was obtained. The processing characteristics during release film production were ⊚. The release film was attached to one surface of the polarizing plate, and the protective film was attached to the other surface of the polarizing plate. The polarizing plate is a linear polarizing plate having a structure in which a polyvinyl alcohol (PVA) film dyed with iodine having a thickness of 20 μm is used as a polarizing film and the film is sandwiched between TAC films having a thickness of 80 μm. The uniaxially oriented polyester film, which is the base material of the release film, was attached to the absorption axis of the linear polarizing plate so that the main axis direction was perpendicular or parallel. As the protective film, the same uniaxially oriented polyester film was attached in the same direction. An acrylic adhesive is used as the adhesive for attaching the release film and the protective film,
The adhesive layer had a thickness of 30 μm. When the obtained polarizing plate to which the protective film and the release film were adhered was inspected by the crossed Nicols method, the inspectability was ⊚.
As described above, this uniaxially stretched polyester film was suitable as the base material for the release film of the polarizing plate.

(Example 2) PET (A) and PET
(B) is merged and laminated so as to form a layer of A / B in the feed block, and the layer ratio is A: B = 1: 9 in terms of PET discharge amount by each extruder. With the same method as in Example 1 except that the width is adjusted to about 400
A long uniaxially oriented polyethylene terephthalate film having a thickness of 0 mm and a thickness of about 40 μm was obtained and wound into a roll.

The heat shrinkage of the obtained film in the longitudinal direction (MD) of the film at 105 ° C. for 30 minutes was 1.4%,
The thermal shrinkage in the film width direction (TD) is 1.2%, the average value (Nave) of the refractive indices Nx, Ny, and Nz in each direction of the film is 1.589, (Ny-Nx) is 0.096, and the entire film width. , The maximum strain of the orientation main axis is 4 °, the difference between the maximum value and the minimum value of the refractive index Ny in the main orientation direction is 0.004, the film haze is 17.2%, the contrast is 920, and one surface of the film (A Three-dimensional average surface roughness (SR)
a) was 0.024 μm, and SRa on the opposite surface (B layer surface) was 0.062 μm. In the foreign matter inspection of this film, no aggregated foreign matter due to the added particles having a major axis of 100 μm or more was observed. The evaluation of abrasion resistance was ○.

Adhesive layers were provided on both sides of the polarizing plate in the same manner as in Example 1, the protective film and the release film using the above uniaxially stretched polyethylene terephthalate film were attached, and the protective film and the release film were attached. A polarizing plate was obtained. The processing property when preparing the release film was ⊚. The testability was ◎. As described above, this uniaxially stretched polyester film was suitable as the base material for the release film of the polarizing plate.

Comparative Example 1 A long uniaxially oriented polyethylene having a width of about 4000 mm and a thickness of about 40 μm was prepared in the same manner as in Example 1 except that a single-layer unstretched sheet was produced using only PET (B). A terephthalate film was obtained and wound into a roll.

The heat shrinkage of the obtained film in the film longitudinal direction (MD) at 105 ° C. for 30 minutes was 1.4%,
The heat shrinkage ratio in the film width direction (TD) is 1.0%, the average value (Nave) of the refractive indices Nx, Ny, and Nz in each direction of the film is 1.592, (Ny-Nx) is 0.093, and the full width of the film. , The maximum strain of the orientation main axis is 3 °, the difference between the maximum value and the minimum value of the refractive index Ny in the orientation main axis direction is 0.004, the film haze is 19.1%, the contrast is 820, and one surface of the film (A Three-dimensional average surface roughness (SR)
a) was 0.062 μm, and SRa on the opposite surface (B layer surface) was 0.063 μm. In the foreign matter inspection of this film, no aggregated foreign matter due to the added particles having a major axis of 100 μm or more was observed. The abrasion resistance evaluation was x.

Adhesive layers were provided on both sides of the polarizing plate in the same manner as in Example 1, the protective film and the release film using the above uniaxially stretched polyethylene terephthalate film were attached, and the protective film and the release film were attached. A polarizing plate was obtained. The processing characteristic when preparing the release film was x. The testability was ◎.

Comparative Example 2 PET (A) and PET
(B) is combined and laminated so as to form a layer of A / B in the feed block, and the layer ratio is A: B = 5: 5 in terms of PET discharge amount by each extruder. With the same method as in Example 1 except that the width is adjusted to about 400
A long uniaxially oriented polyethylene terephthalate film having a thickness of 0 mm and a thickness of about 40 μm was obtained and wound into a roll.

The heat shrinkage of the obtained film in the film longitudinal direction (MD) at 105 ° C. for 30 minutes was 1.3%,
The heat shrinkage ratio in the film width direction (TD) is 1.1%, the average value (Nave) of the refractive indexes Nx, Ny, and Nz in each direction of the film is 1.590, (Ny-Nx) is 0.095, and the film full width is The maximum strain of the orientation main axis is 4 °, the difference between the maximum value and the minimum value of the refractive index Ny in the orientation main axis direction is 0.004, the film haze is 9.0%, the contrast is 3000, and one surface of the film (A Three-dimensional average surface roughness (SR)
a) was 0.023 μm, and SRa on the opposite surface (B layer surface) was 0.062 μm. In the foreign matter inspection of this film, no aggregated foreign matter due to the added particles having a major axis of 100 μm or more was observed. The evaluation of abrasion resistance was ○.

Adhesive layers were provided on both sides of the polarizing plate in the same manner as in Example 1, the protective film and the release film using the above uniaxially stretched polyethylene terephthalate film were attached, and the protective film and the release film were attached. A polarizing plate was obtained. The processing property of the film was ⊚. As for the inspection quality, the contrast was high, and the result was an excessive inspection, which was x.
Therefore, this film was not suitable as a base material for the release film of the polarizing plate.

(Comparative Example 3) PET (A) and PET
(C) is combined and laminated so as to form a layer of A / C in the feed block, and the layer ratio is A: C = 5: 5 in terms of PET discharge amount by each extruder. With the same method as in Example 1 except that the width is adjusted to about 400
A long uniaxially oriented polyethylene terephthalate film having a thickness of 0 mm and a thickness of about 40 μm was obtained and wound into a roll.

The heat shrinkage of the obtained film in the longitudinal direction (MD) of the film at 105 ° C. for 30 minutes was 1.4%,
The heat shrinkage ratio in the film width direction (TD) is 1.1%, the average value (Nave) of the refractive indices Nx, Ny, and Nz in each direction of the film is 1.591, (Ny-Nx) is 0.093, and the entire film width. , The maximum strain of the orientation main axis is 4 °, the difference between the maximum value and the minimum value of the refractive index Ny in the orientation main axis direction is 0.004, the film haze is 18.8%, the contrast is 840, and one surface of the film (A Three-dimensional average surface roughness (SR)
a) was 0.022 μm, and SRa of the opposite surface (C layer surface) was 0.082 μm. In the foreign matter inspection of this film, the number of aggregated foreign matter due to the added particles having a major axis of 100 μm or more was 5 particles / m ² . The abrasion resistance evaluation was x.

Adhesive layers were provided on both sides of the polarizing plate in the same manner as in Example 1, a protective film and a release film using the above uniaxially stretched polyethylene terephthalate film were attached, and a protective film and a release film were attached. A polarizing plate was obtained. The processing characteristic of the film was x. As for the inspection quality, agglomerates of the added particles were detected and the result was x. Therefore, this film was not suitable as a base material for the release film of the polarizing plate.

(Comparative Example 4) After stretching the film in the stretching zone, the film was continuously cooled to 1 in the same tenter without cooling.
In the same manner as in Example 1 except that the heat treatment was performed at 85 ° C,
A long uniaxially oriented polyethylene terephthalate film having a width of about 4000 mm and a thickness of about 40 μm was obtained and wound into a roll.

The heat shrinkage of the obtained film in the longitudinal direction (MD) of the film at 105 ° C. for 30 minutes was 1.
4%, thermal shrinkage in the film width direction (TD) is 1.1%,
The maximum strain of the orientation main axis in the full width of the film is 10 °, and the difference between the maximum value and the minimum value of the refractive index Ny in the orientation main axis direction is 0.0.
04, film haze 15.0%, contrast 1
150, the three-dimensional average surface roughness (SRa) of one surface was 0.024 μm, and the SRa of the other surface was 0.024 μm. In the foreign matter inspection of this film, the major axis is 100μ
No aggregated foreign matter due to the added particles of m or more was observed.
The evaluation of abrasion resistance was ⊚.

Adhesive layers were provided on both sides of the polarizing plate in the same manner as in Example 1, a protective film and a release film using the above uniaxially stretched polyethylene terephthalate film were attached, and a protective film and a release film were attached. A polarizing plate was obtained. The processing property of the film was ⊚. Regarding the inspection property, the difference in the contrast in the width direction was large, and was ×.
Therefore, this film was not suitable as a substrate for a surface protective film of a polarizing plate and a release film.

[0109]

[Table 1]

[0110]

As described above, according to the present invention, there is provided a uniaxially oriented polyester film which can be suitably used as a base material for a release film on the surface of an adhesive layer formed on a synthetic resin plate or the like. The release film using this uniaxially oriented polyester film is particularly preferably used for the surface of the pressure-sensitive adhesive layer formed on the polarizing plate or the retardation plate which is a constituent member of the liquid crystal display device. This release film does not require peeling at the time of inspection and has good inspectability. The film has excellent abrasion resistance and low cost, and is particularly preferably used as a release film used as a constituent member of a large-sized liquid crystal display device.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a release film of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a release film of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of a release film of the present invention.

FIG. 4 is a schematic cross-sectional view showing a state in which the release film of the present invention is attached to a polarizing plate surface together with a surface protective film.

FIG. 5 is a schematic view showing a tenter used for producing the uniaxially oriented polyester film of the present invention.

FIG. 6 is a schematic view showing cutting out of a sample film from a long film in Examples and Comparative Examples.

FIG. 7 is a schematic view showing cutting out of a sample film from a long film in Examples and Comparative Examples.

FIG. 8 is a schematic diagram showing cutting of a sample film from a long film in Examples and Comparative Examples.

FIG. 9 is a schematic view showing cutting of a sample film from a long film in Examples and Comparative Examples.

[Explanation of symbols]

1 Uniaxially oriented polyester film 2 Release layer 3 Antistatic layer 11 Polarizing film 12 Triacetyl cellulose (TAC) film 13 Adhesive layer 21 preheating zone 22 Drawing zone 23 Heat setting zone 101, 102, 103 Release film 200 Polarizer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasushi Sasaki             Toyobo Co., Ltd. 10-24 Toyocho, Tsuruga City, Fukui Prefecture             Film Development Laboratory Tsuruga Film Center             In the center (72) Inventor Harunobu Kuroiwa             2-8 Dojimahama 2-chome, Kita-ku, Osaka City, Osaka Prefecture             Toyobo Co., Ltd. F term (reference) 2H049 BA02 BA06 BB54 BC09 BC22                 2H091 FA08X FA08Z FA11X FA11Z                       GA17 LA02 LA12                 4F100 AA01A AK01A AK25G AK41A                       AK41B AK41C AK42 AL05A                       AR00D BA03 BA04 BA10A                       BA10C BA12 DD07 DE01A                       EH20 EJ37A EJ37B EJ37C                       GB41 GB90 JK09 JL02 JL14D                       JN30

Claims (6)

[Claims] 1. A uniaxially oriented polyester film in which two or three polyester layers are laminated by coextrusion, and the value of contrast (C) represented by the following formula (I) is 70 or more and 2000 or less. C = Y1 / Y2 (I) [where Y1 makes the optical axes of the two polarizers parallel to each other,
The amount of transmitted light when the polyester film is inserted between the two polarizers, Y2 is the transmission when the polyester film is inserted between the two polarizers, with the optical axes of the two polarizers being perpendicular to each other. Light intensity], and the three-dimensional average surface roughness (SRa) of one surface is 0.01
5 to 0.040 μm, the maximum strain of the orientation main axis measured by a microwave transmission type molecular orientation meter is 7 degrees or less, and the content of foreign substances having a major axis of 100 μm or more is less than 1 per 1 m ^{2 of} area, uniaxial Oriented polyester film. 2. The three-dimensional average surface roughness (SRa) of the surface opposite to the one surface is 0.015 to 0.060 μm.
The uniaxially oriented polyester film according to claim 1, which is m. 3. The uniaxially oriented polyester film according to claim 1, which contains inorganic or organic particles in at least one layer. 4. A release film having a base material made of the uniaxially oriented polyester film according to claim 1 and a release layer. 5. The uniaxially oriented polyester film,
Three-dimensional average surface roughness (SRa) is 0.015-0.040
The release film according to claim 3, which has the release layer on a surface having a thickness of μm. 6. The release film according to claim 3, which is affixed to the pressure-sensitive adhesive layer surface of a polarizing plate or a retardation plate of a liquid crystal display device.