JP2003266622A - Optical laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical polyester film having an excellent transparency, an easy slidableness, a hue and a film uniformity. <P>SOLUTION: A biaxially oriented polyester film is used as a substrate. A laminated film is provided by forming an easily slidable layer containing a globulet on at least one side of the substrate. A fine grain caused by a catalyst exists in the substrate film. A fine grain density to be measured when the substrate film is observed by a dark field microscopic method, is 200 to 20000 grain/mm<SP>2</SP>in 1 μm to 10 μm of grain size and ≤10 grain/mm<SP>2</SP>in >10 μm of grain size. A thickness of the laminated film spots is 0.5 to 7.0%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical polyester film. In particular, it relates to a polyester film excellent in film thickness uniformity, transparency, slipperiness, and color tone, and more specifically, LCD, CRT, PDP,
The present invention relates to a film for a base material such as an antireflection film, a touch screen, and a diffusion plate in a display device such as EL.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are used as various optical films because of their excellent strength, dimensional stability and chemical resistance. Especially in recent years, LCD, C
The field of display devices such as RT, PDP, and EL is a field in which the characteristics of biaxial polyester can be utilized, and is preferably used. However, in recent years, the precision and colorization of images in display materials have advanced, and the optical polyester film has excellent film thickness uniformity, improved transparency and slipperiness, and excellent color tone colorlessness. Things are desired.

[0003]

The biaxial polyester film is insufficient in slipperiness as it is, and the handling property is poor and deteriorates.
Generally, a method of improving lubricity by containing inorganic particles such as silica, calcium carbonate, kaolin, etc., organic particles such as silicone, cross-linked polystyrene, etc., and forming fine projections on the surface is carried out. ing. However, in this method, in the polyester film, it is generally necessary to contain several hundred ppm or more of inorganic particles, organic particles, and the like, and the presence of these particles causes light to scatter, resulting in a polyester. There are problems such that the transparency of the film is deteriorated and the polyester is promoted to be decomposed by these particles, so that the polyester film is easily colored yellow.

On the other hand, in order to maintain the transparency of the polyester, the polyester film does not contain the above-mentioned inorganic particles and organic particles, and a slipping layer is formed on the surface of the polyester film to improve transparency. A method of balancing slipperiness has been considered. However, if there are no particles in the polyester, or if there are too few particles, the uniformity of stretching tends to be poor during the production of a biaxially stretched film, and the uniformity of thickness, orientation, etc. tends to deteriorate. There are challenges.

An object of the present invention is to solve the above problems and to obtain an optical polyester film having excellent film uniformity, transparency, slipperiness and color tone.

[0006]

The laminated polyester film for optics of the present invention is a laminated film in which a biaxially oriented polyester film is used as a base material, and an easy sliding layer containing spherical particles is formed on at least one surface of the base material. Therefore, there are fine particles due to the catalyst metal or the additive metal in the base film, and the fine particle density measured when observing the base film by the dark field microscopy is from 1 μm to 10 μm.
Of fine particles of 200 to 20,000 particles / mm ² ,
Fine particles with a particle size of more than 10 μm are 10 particles / mm ² or less,
Further, the thickness unevenness of the laminated film is 0.5 to 7.0%.

The biaxially oriented polyester film, which is the base material of the laminated polyester film of the present invention, is made of polyethylene terephthalate, polyethylene-2,6-naphthalate, or a copolymer mainly composed of the constituent components of these resins. To be

When the above-mentioned polyester copolymer is used as the polyester for forming the biaxially oriented polyester film, the dicarboxylic acid component thereof is an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, terephthalic acid, isophthalic acid, Aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid and polyfunctional carboxylic acids such as trimetic acid are used. As the glycol component, aliphatic glycols such as diethylene glycol, triethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol and alicyclic glycols such as 1,4-cyclohexanedimethanol are used. The preferred copolymerization components and amounts are not limited as long as they can form and maintain the orientation as a biaxially oriented polyester film. The biaxially oriented polyester film may contain an antistatic agent, an antioxidant, etc. within a range that does not impair the effects of the present patent.

The method for producing the biaxially oriented polyester film is not particularly limited. For example, the molten polyester resin is extruded into a sheet shape on a rotating cooling drum by a method such as an electrostatic printing method or an air knife method to obtain an unstretched sheet having no unevenness in thickness as much as possible. Subsequently, the obtained unstretched sheet is heated to 80 to 120 ° C. and stretched 2.8 to 4.5 times in the longitudinal direction (longitudinal direction), and then 80 to
In the zone heated to 180 ° C., the film is stretched 2.8 to 4.5 times in the transverse direction (width direction). Further, heat treatment is performed in a heat treatment zone of 160 to 240 ° C. In this heat treatment step, relaxation treatment may be performed in the longitudinal direction and / or the lateral direction, if necessary. Regarding the stretching step, in addition to the above-described sequential stretching in the longitudinal and transverse directions, a multi-stage sequential stretching method of vertical and horizontal, vertical and horizontal, vertical and horizontal and vertical or a simultaneous vertical and horizontal biaxial stretching method may be used.

The substrate of the biaxially oriented polyester film of the present invention contains an appropriate amount of fine particles derived from the catalyst metal or additive metal added during the polyester synthesis. As a method of containing such particles, for example, a metal compound such as manganese, magnesium, calcium, lithium, sodium, and potassium during a transesterification reaction,
Phosphorus compound, also, during the polycondensation reaction, antimony, germanium, such as titanium metal compound is added, during the polyester synthesis, dicarboxylic acid component which is a polyester constituent component, or by reacting with a glycol component, the metal component alone, Alternatively, there may be mentioned a method of forming and containing particles bound to an organic component in a composite state. When such particles are associated with a dicarboxylic acid component or a glycol component, which are polyester constituent components, the refractive index is relatively close to that of the polyester film. Further, these particles are characterized in that the size and amount of the particles can be controlled by appropriately selecting the kind, amount and combination of the above metal compounds, or the temperature and reaction rate during polyester synthesis.

The base material of the biaxially oriented polyester film of the present invention may contain a very small amount of 3 to 3, if necessary.
If the amount is 50 ppm by weight, in addition to the particles derived from the above-mentioned catalyst metal and additive metal, inorganic inert particles such as silica, kaolin, alumina and calcium phosphate having an average particle size of 2 μm or less, spherical crosslinked polyacryl It may also contain organic particles such as spherical crosslinked polystyrene and spherical silicone. In addition, a film obtained by laminating an easy-sliding layer containing spherical particles is melted, and the recovered polymer that is made into chips can also be used as a mixture with a novel polymer obtained by polyester synthesis, in a biaxially oriented polyester film substrate. A small amount of particles are mixed, but this is possible because it is also a very small amount.

The amount of fine particles due to the catalyst metal and the additive metal is determined by the amount observed when measured by dark field microscopy (details will be described later). Further, as described above, a very small amount of inorganic inactive particles and organic inactive particles are simultaneously observed by a dark field microscope, but they may be regarded as particles due to the catalyst metal and the additive metal and may be measured. The amount of particles is 10
The number of particles having a size of μm or more is 10 particles / mm ² or less, and the number of particles having a particle size of 1 μm to 10 μm is 200 to 20000 particles / mm ² . Preferably, 30 particles having a particle size of 1 μm to 10 μm are used.
It is 0 to 15000 pieces / mm ² , and more preferably 500 to 10000 pieces / mm ² .

10 particles having a particle size exceeding 10 μm
When it is present in an amount of more than the number of pieces / mm ² , it is conspicuous as a foreign matter-like defect on the screen when used in an optical film. On the other hand, particle size 1
When the amount of particles from μm to 10 μm is less than 200 particles / mm ² , the tendency of poor uniformity of stretching due to insufficient effect of preventing stress concentration by particles during production of biaxially stretched film. Therefore, unevenness in thickness and orientation is likely to occur. On the other hand, when the amount of particles exceeds 20,000 particles / mm ² , the amount of particles in the film is too large, so that the transparency of the film is deteriorated due to light scattering by particles and the screen is blurred when used for an optical film. Issues such as occur.

The thickness unevenness of the laminated polyester film of the present invention is 0.5 to 7.0%, preferably 0.7 to 5%, more preferably 1 to 4%. Thickness unevenness is 0.
When it is less than 5%, even if it contains the above particles,
It is necessary to extremely slow down the film forming speed, etc., resulting in poor productivity and difficulty in commercial production. On the other hand, if it exceeds 7.0%, the film thickness is insufficiently uniform, and therefore, when it is used as a film for a base material such as an antireflection film, a touch screen, a diffusing plate, an image is distorted or color spots are generated. The problem occurs.

The laminated polyester film of the present invention has 2
An axially oriented polyester film is used as a base material, and an easily slipping layer that also serves to improve adhesiveness is formed on at least one surface of the base material. The method for forming the easy-slip layer is not particularly limited, but preferably an unstretched sheet, or one side of a uniaxially stretched film,
Alternatively, it is formed by an in-line coating method in which a resin for forming an easy-slip layer and a mixed dispersion of spherical particles are applied to both surfaces, and then stretched and heat-treated.

The resin for forming the easy-slip layer is not particularly limited, but it is preferable to use a copolyester resin as a main component. As the copolyester resin,
Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, and sodium 5-sulfoisophthalate, and the glycol component includes copolymerized polyesters such as ethylene glycol, tetramethylene glycol, and neopentyl glycol. In particular, the glass transition point is 4
A polyester resin in the range of 0 to 100 ° C is preferable. Also, as a component to coexist with the polyester resin,
For example, in order to improve the adhesiveness with the acrylic resin which is the main component of the hard coat for which the laminated polyester film for optics is preferably used, and to improve the scratch resistance of the easy-sliding layer, alkyl acrylate, alkyl acrylate, etc. Acrylic resin whose main component is
Those containing an epoxy or oxazoline crosslinking agent can also be preferably used.

The easy-slip layer contains spherical particles in order to impart a slip property to the film. Examples of the particles include inorganic particles such as spherical silica and spherical alumina, and organic particles such as spherical crosslinked polyacryl, spherical crosslinked polystyrene and spherical silicone. Since these spherical particles generally have a uniform particle size and a small content of coarse particles, it is possible to provide uniform, smooth and fine projections to the easy-slipping layer. As spherical particles, the inorganic particles are excellent in imparting slipperiness even in a small amount, and the organic particles have soft characteristics in addition to the above characteristics, so that the film is hard to be damaged when it is dropped from the slippery layer. Have. In addition, it is also preferable that inorganic particles and organic particles are mixed and contained as the spherical particles. On the other hand, as particles, calcium carbonate, calcium phosphate, ordinary silica, kaolin and the like, the shape is not uniform such as lumpy, plate-like, and the particle size is not uniform,
It is difficult to give uniform fine protrusions to the easy-slip layer,
It is difficult to balance slipperiness and film haze.

The average particle size of the spherical particles contained in the easy-slip layer is preferably 200 nm or less, more preferably 150 nm or less, and further preferably 100 nm or less. When the average particle diameter of the spherical particles exceeds 200 nm, light is likely to be scattered, and the film haze tends to increase and yellowish coloring tends to occur. Two or more kinds of particles having an average particle diameter of 100 nm or less may be mixed and contained.
The content of the spherical particles contained in the easy-slip layer is 40%.
The following is preferable, and 30% or less is more preferable. When the content exceeds 40%, the film haze tends to increase and the particles tend to fall off from the easy-slip layer.

The thickness of the laminated polyester film of the present invention is preferably 50 μm, more preferably 100 to 250 μm. The haze value of the laminated polyester film is 0.
It is preferably 3 to 1.5%. When the film haze exceeds 1.5%, the sharpness of an image on a display device or the like decreases, which is not preferable.

The color b * value of the laminated polyester film of the present invention measured by transmitted light is preferably -0.5 to 1.5. If the color b * value is less than −0.5, the bluishness of an image on a display device tends to be too strong.
Further, if the color b * value exceeds 1.5, the image of a display device or the like tends to have a yellowish color tone, which is not preferable.

In the laminated polyester film of the present invention, in order to adjust the color tone, a blue-based, green-based, red-based dye, pigment or the like is added to these resin base materials in the base polyester film or in the easy-slip layer. It is also possible. Among these, blue dyes and pigments are preferable in terms of complementing the yellow tint of the film. The blue dyes and pigments are not particularly limited, but Color Index Solvent Blue 45 (Color Index Solvent Bl)
blue dyes such as ue45), or
A phthalocyanine-based blue pigment having a maximum absorption in the vicinity of 600 to 700 nm is preferable, and a color index solvent blue 45-based dye is particularly preferable in terms of heat resistance and solubility in polyester. The content of these dyes may be set in consideration of the fact that the color b * value of the laminated polyester film measured by transmitted light is preferably −0.5 to 1.5. For example, when adding a blue dye in the base polyester film,
0.2 to 5 ppm by weight is preferable, and when it is contained in the easily slipping layer, it is 200 to 5 in consideration of the thickness of the easily slipping layer.
000 ppm by weight is preferred.

[0022]

EXAMPLES The present invention will be described below based on examples.
In addition, "part" in an Example and a comparative example shows a weight part. Further, the present invention is not limited to these examples.

(1) Particle Measurement by Dark Field Microscopy The surface of the laminated film was treated with methyl ethyl ketone to remove the easy-sliding layer, and then a microscope (Nikon Mi) was used.
The image was taken by a transmission dark-field measuring method using a photo-FX) at a light source 10 scale and 100 times. The obtained photograph was counted with an image analyzer for the number of particles observed with a diameter of 1 to 10 μm.

(2) Film thickness unevenness An Anritsu electronic micrometer (KG601B) was used to measure the thickness of the film in the width direction and the length direction under the following conditions, and the difference between the maximum value and the minimum value was measured. The value divided by the film thickness was defined as the thickness r. Sample area: 2 m in the length direction, 3 m in the width direction Measurement interval: 30 cm intervals in the length direction Measurement speed: 5 mm / sec

(3) Haze value of film According to JIS-K7105 standard, haze value was measured using a haze meter (NDH-20 manufactured by Nippon Denshoku Industries Co., Ltd.).

(4) Color b * value measured by the transmitted light of the film According to JIS-Z8722 and 8729 standards, the color of the transmitted light of the film was measured using a color meter (SZ-Σ90 manufactured by Nippon Denshoku Industries Co., Ltd.). The b * value was measured.

[Example 1] (Synthesis of polyester for film substrate) Dimethyl terephthalate: 100 parts, ethylene glycol: 65 parts, manganese acetate tetrahydrate: 0.04 parts were charged into a reaction vessel,
The temperature was raised to 240 ° C. in 3 hours to carry out a transesterification reaction. Subsequently, orthophosphoric acid: 0.02 part and antimony trioxide 0.02 part were added, and then, under reduced pressure (to 2 mmHg), the temperature was raised to 290 ° C. in 3 hours to carry out a polycondensation reaction to obtain a unique property. Polyethylene terephthalate resin pellets having a viscosity of 0.65 dl / g were obtained.

<Preparation of coating liquid for easy sliding layer> 65% by weight of the following polyester resin (a), 20% of a crosslinking agent (b),
10% by weight of spherical particles (C) and 5% by weight of wetting agent (D)
The mixture was dispersed and mixed at a ratio of 1 to prepare an aqueous coating liquid having a total concentration of these components of 8%. (A) Polyester resin: acid component 70 mol% 2,6-naphthalenedicarboxylic acid / isophthalic acid 25 mol% / 5-sodium sulfoisophthalic acid 5 mol%, glycol component ethylene glycol 90 mol% / diethylene glycol 10 mol % Polyester resin. (B) Cross-linking agent: methyl methacrylate 25 mol%,
2-isopropenyl-2-oxazoline 30 mol%,
Consists of 10 mol% polyethylene oxide methacrylate / 35% acrylamide. (C) Spherical particles: spherical crosslinked acrylic particles (particle size 100
nm). (D) Wetting agent: polyoxyethylene lauryl ether.

<Film Forming> Polyethylene terephthalate resin pellets were dried under reduced pressure at 140 ° C. for 6 hours, then fed to an extruder, and at about 285 ° C., the molten polyester resin was electrostatically charged on a rotary cooling drum. It was extruded into a sheet by means such as a printing method and an air knife method to obtain an unstretched sheet with no unevenness in thickness. Subsequently, the obtained sheet is heated to 100 ° C., and the sheet is longitudinally (longitudinally) 3.
It was stretched 5 times to obtain a uniaxially oriented film. Then, the coating liquid was applied to both sides of the uniaxially oriented film by the reverse roller method. Further, in the zone heated to 140 ° C., after stretching 3.8 times in the transverse direction (width direction), 22
Heat treatment is performed in a heat treatment zone at 0 ° C, and the thickness is 125μ.
A biaxially oriented laminated polyester film of m was obtained. The thickness of the easy-sliding layers formed on both sides of the film is 80, respectively.
was nm.

Example 2 Except that the manganese acetate tetrahydrate in Example 1 was changed to magnesium acetate tetrahydrate,
A film was obtained in the same manner as in Example 3.

Example 3 A film was obtained in the same manner as in Example 1, except that the antimony trioxide in Example 1 was changed to 0.005 part of tetrabutoxytitanium.

[Example 4] The film thickness was changed to 175 by changing the amount of molten polyester resin in Example 1.
A film was obtained in the same manner as in Example 1 except that the thickness was changed to μm.

Example 5 A film was obtained in the same manner as in Example 1 except that the spherical crosslinked acrylic particles in the coating solution in Example 1 were changed to spherical silica having an average particle size of 80 nm.

Example 6 In Example 1, 0.0001 part of Terrazol Blue RLS was used as a blue dye,
Example 1 except that antimony trioxide was added subsequent to the addition.
A film was obtained in the same manner as in.

[Embodiment 7] In the coating liquid used in Embodiment 1, as a blue dye, terazol blue RLS was added in an amount of 0.
A film was obtained in the same manner as in Example 1 except that 1 part was added.

[Comparative Example 1] The same as Example 1 except that the amount of antimony trioxide in Example 1 was 0.10 part and the amount of orthophosphoric acid was trimethyl phosphate, 0.01 part. A film was obtained by the method of.

Comparative Example 2 In Example 1, the amount of antimony trioxide was 0.01 part, and the amount of orthophosphoric acid was
A film was obtained in the same manner as in Example 1 except that the film thickness was 0.06.

Comparative Example 3 A film was obtained in the same manner as in Example 1 except that the spherical crosslinked acrylic particles in the coating liquid in Example 1 were changed to amorphous silica having an average particle size of 230 nm.

[Comparative Example 4] The same procedure as in Example 1 was repeated, except that 0.05 part of calcium carbonate having an average particle size of 0.6 μm was added to the polyester for the film substrate. , A film was obtained.

The film qualities of the above Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1. In each of the examples, the film thickness unevenness, haze, and color tone were excellent. On the other hand, each of the comparative examples had problems.

[0041]

[Table 1]

[0042]

According to the present invention, it is possible to obtain an optical polyester film having excellent uniformity of film thickness, improvement of transparency and slipperiness, and colorless color tone.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 9:00 B29L 9:00 (72) Inventor Kei Mizutani 3-37-19 Oyama, Sagamihara City, Kanagawa Human DuPont Films Co., Ltd. Sagamihara Research Center (72) Inventor Yoshiyuki Watanabe 3-37-19 Oyama, Sagamihara City, Kanagawa Teijin DuPont Films Co., Ltd. Sagamihara Research Center F-term (reference) 4F100 AA29 AB09B AB09C AB12B AB12C AB14B AB14C AB22B AB22C AK25 AK41A AK42 AT00A BA02 BA03 BA06 BA07 BA10B BA10C CA13B CA13C CA19B CA19C DE01B DE01C EJ38A GB41 JA13B JA13C JA20A JN01 YY00B YY00C 4F210 AA24 Q01 Q03 AH AB01 AB03 AB12 AB03 AB03 AB12 AB03 AB03 AB12

Claims (6)

[Claims] 1. A laminated film comprising a biaxially oriented polyester film as a base material, and an easy sliding layer containing spherical particles formed on at least one surface of the base material, wherein the base material film contains fine particles derived from a catalyst. The density of fine particles having particles present and measured when observing the substrate film by dark-field microscopy is 200 to 2 for fine particles having a particle size of 1 μm to 10 μm.
0000 pieces / mm ^2, fine particles of a particle diameter exceeding 10μm is 10 / mm ² or less, laminated polyester film for optical, characterized in that further a 0.5 to 7.0% the thickness unevenness of the laminated film . 2. The fine particles are manganese, magnesium,
The laminated polyester film for optics according to claim 1, which is a particle containing at least one element selected from the group consisting of calcium, lithium, sodium, potassium, antimony, germanium, titanium and phosphorus. 3. The laminated polyester film for optics according to claim 1, wherein the spherical particles contained in the easy-slip layer are inorganic particles and / or organic particles. 4. The haze value of the laminated film is 0.3 to 1.
It is 5%, The laminated polyester film for optics in any one of Claims 1-3. 5. The laminated polyester film for optics according to claim 1, wherein the laminated film has a color b * value of -0.5 to 1.5 as measured by transmitted light. 6. The laminated polyester film for optics according to claim 1, wherein a blue dye is contained in the base polyester film or the easy-slip layer.