JPH04110148A - Mat polyester film - Google Patents

Abstract

PURPOSE:To obtain a laminated polyester film having both of matting effect and tenacity by using a polyester film having certain physical properties formed by laminating at least two or more layers by co-extrusion. CONSTITUTION:In a composite film wherein two or more layers are laminated by co-extrusion, a mat polyester film wherein the glossiness Gs (60 deg.) of the single surface (A-surface) of the film is 10-90% and the thickness ratio of the layer constituting the A-surface to the whole of the film is 0.4 or less and the sum of the breaking strengths in the longitudinal and lateral. directions of the film is 36 kg/mm<2> or more is used. For example, a raw material A1 composed of polyethylene terephthalate containing 0.05wt.% of amorphous silica particles and a raw material B1 composed of polyethylene terephthalate containing 2.7wt.% of said silica particles are respectively dried and compounded as a three-layer structure wherein the raw material B1 is used as outer layers and the raw material A1 is used as an inner layer and the thickness ratio B1/A1/B1 of the layers is 1.25/22.5/1.25 using separate melting extruders to prepare an amorphous sheet which is, in turn, stretched to be thermally fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminated polyester film having an excellent matte effect and excellent toughness.

[Prior art and problems to be solved by the invention] Matte polyester films have excellent toughness, durability, heat resistance, transparency, and chemical resistance, so they are used for transfer foils, building materials, and displays. It is used for a wide range of purposes such as plates and labels.

An effective method for obtaining a matte polyester film is to add inert particles to polyester and then biaxially stretch the film. However, the lower the gloss Gs (60°) of the film, ie the greater the matting effect, the less toughness the film loses.

Therefore, matte films cannot be used in applications that require relatively high strength, such as transfer foil applications.

(Means for Solving the Problems) In view of the above problems, the inventors of the present invention have made extensive studies and found that a small amount (
It was discovered that a polyester film having certain physical properties, which is formed by laminating two or more layers by coextrusion, has both a matte effect and toughness, and the present invention was completed.

That is, the gist of the present invention is to provide a composite film in which two or more layers are laminated by coextrusion, in which the glossiness Os (60°) of one side (A side) of the film is 10 to 90%, and the layer constituting the A side is The matte polyester film has a thickness ratio of 0.4 or less to the entire film, and a sum of the breaking strength in the longitudinal direction and the transverse direction of the film is 361 g/Wz or more.

The present invention will be explained in more detail below.

The term "polyester" used in the present invention refers to a polyester obtained using terephthalic acid or its ester and ethylene glycol as main starting materials, but it may contain other third components. In this case, the dicarboxylic acid component is one or more of oxycarboxylic acid components such as isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, terephthalic acid, adipic acid, sebacic acid, and p-oxyethoxybenzoic acid. It is possible to use

As the glycol component, one or more of ethylene glycol, propylene glycol, butanediol, 1,4 cyclohexanedimetatool, neopentyl glycol, etc. can be used. In any case, the polyester of the present invention is preferably a polyester in which 80% or more of the repeating structural units have ethylene terephthalate units.

Further, the polyester may contain arbitrary additives such as a heat stabilizer, an antiblocking agent, an antioxidant, a coloring agent, an antistatic agent, and an ultraviolet absorber.

Furthermore, in addition to the above polyester, polymers other than polyester, such as polycarbonate, polyolefin,
Polyamide or the like may be added or mixed as long as it does not exceed the gist of the present invention, for example, 30 wt% or less of the total. As described above, a method of roughening the film surface by adding and mixing other kinds of polymers to impart suitable surface gloss and writability is also mentioned as one method for realizing the present invention.

In order to impart slipperiness, surface gloss, etc. to the film, it is also preferable to contain organic, inorganic, etc. fine particles, and if necessary, stabilizers, colorants, antioxidants, antifoaming agents, and antistatic agents. The film may also contain additives such as additives. Fine particles that impart slipperiness and surface gloss to the film include known inert particles such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate, lithium fluoride, and carbon black. Internal particles formed inside the polymer during polyester production due to particles, insoluble high-melting point organic compounds during melt film formation of polyester resin, crosslinked polymers, and metal compound catalysts used during polyester synthesis, such as alkali metal compounds and alkaline earth metal compounds. Examples include particles.

The fine particles contained in the film of the present invention for imparting surface gloss are preferably those mainly composed of silicon oxide fine particles, and the inclusion of the particles efficiently imparts desired surface gloss and writability. Ru.

In the above embodiment, it is also a preferable S type to contain other fine particles, such as titanium oxide, in addition to silicon oxide fine particles.

In the film of the present invention, the average particle size of the fine particles contained in the layer imparting surface gloss is usually 0.5 to 10 μm.
m range. If the average particle size is less than 0.5 μm, it is not suitable because a film with the desired surface gloss cannot be obtained. Moreover, if the average particle diameter exceeds 10 μm, the unevenness of the film surface will be too large to be practical. The average particle size of the fine particles contained in the film is preferably 1.0 to 108 m1, more preferably 1.5 to 10 m, and particularly preferably 2.0 m to 108 m.
It is in the range of 0 to 7.0 μm.

In the film of the present invention, the amount of fine particles contained in the layer imparting surface gloss is preferably 0.2 to 10% by weight, more preferably 0.2 to 7.0% by weight, particularly preferably 0.2 to 10% by weight. It ranges from 2 to 5.0% by weight.

The intrinsic viscosity of the polyester film of the present invention is preferably 0.50 or more, more preferably 0.60 or more. If the intrinsic viscosity of the film is less than 0.50, it is not preferable because a film with sufficient mechanical strength cannot be obtained.

Glossiness Gs (60°) of one side (side A) of the film of the present invention
) must be in the range of 10 to 90%. Gs
(60°) is less than 10%, the film surface is too rough;
Not practical. On the other hand, when Qs(60') exceeds 90%, the erasing effect is insufficient. Glossiness of side A is 0s (
60°) is preferably in the range of 10 to 60%, more preferably 10 to 40%.

In the film of the present invention, the sum of the breaking strength in the longitudinal direction and the transverse direction of the film is 36 kg/ms2 or more.

The sum of the breaking strength in the longitudinal and transverse directions of the film is 36b
If it is less than /m2, the mechanical strength is insufficient and it cannot be put to practical use. The sum of the breaking strengths of the film in the longitudinal and transverse directions is preferably 40 kg/wm2 or more, more preferably 45 kg/w" or more, particularly preferably 50 kg/wm2 or more. The film of the present invention also has the following properties: The film may be highly strengthened in the vertical or horizontal direction.

The film of the present invention needs to have at least two layers laminated by coextrusion. With ordinary single-layer films, it is not possible to improve both the glossiness Gs (60') of the film surface and the mechanical strength of the film.

The thickness ratio of the layer constituting side A to the entire film is 0.
．． 4 or less. Such a thickness ratio is preferably 0.3
Below, it is more preferably 0.2 or below. Thickness ratio is 0
．． If it exceeds 4, it is not preferable because the effect of improving film strength by lamination is small.

The thickness of the film of the present invention is not particularly limited, but the thickness preferably used as a base film for transfer foils, building materials, labels, display boards, etc. is 5 to 500 μm, more preferably 5 to 200 μm. , particularly preferably 5 to 75
It is in the μm range.

Next, the method for manufacturing the film of the present invention will be specifically explained.
As long as the constituent requirements of the present invention are satisfied, the invention is not particularly limited to the following examples.

In order to impart surface gloss, a polyester raw material (al) containing inorganic particles and the like as necessary and a separately prepared polyester raw material ('b) are separately heated in a homper dryer, paddle dryer oven, etc. After drying using a commonly used dryer or vacuum dryer, etc., melt extrusion at 200 to 320 ° C. using a separate extruder,
By a coextrusion method, the raw material (Al) is composited so that the layer composed of the material becomes a surface layer on at least one side, and is cooled and solidified on a casting drum to form an amorphous sheet consisting of two or more layers. At this time, It is preferable to use a conventional electrostatic application method because it improves the thickness unevenness of the amorphous sheet.

The obtained amorphous sheet is then stretched in the longitudinal and transverse directions at an area magnification of 13 times or more to form a biaxially oriented polyester film, and further heat treated at a temperature in the range of 210 to 250°C.

In the heat treatment step, it is also a preferred embodiment of the present invention to perform relaxation of 0.1 to 30% in the transverse and/or longitudinal directions in the highest temperature zone of the heat treatment and/or in the cleaning zone at the exit of the heat treatment. be. Particularly in the transverse method, it is preferred to carry out a relaxation of 5 to 30%. Further, in the heat treatment step, a two-stage heat treatment may be performed.

It is also preferable to re-stretch in the machine or transverse direction for high strength.

During or after the above stretching process, a coating layer may be formed on one or both sides of the film, or a corona discharge treatment may be applied to give the film surface gloss, adhesiveness, antistatic properties, slipperiness, mold releasability, etc. etc. may be applied. especially,
A preferred embodiment is to form a coating layer on the surface of the film in order to impart surface gloss to the film. When forming a coating layer in order to impart surface gloss to the film, it is preferable to include organic, inorganic, etc. fine particles, such as silicon oxide fine particles, in the coating layer. The content of fine particles contained in the coating layer is preferably 5.0 to 50 iv.
t%, more preferably 10-40 wt%, particularly preferably 10-30-t%, and the average particle size is
It is preferably in the range of 0.1 to 3.0 times the thickness of the coating layer, more preferably 0.5 to 2.0 times the thickness of the coating layer.

Further, the coating layer formed during or after the stretching process may have two or more functions, such as surface gloss and mold release properties, or may be a multilayer coating layer of two or more layers.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples unless it goes beyond the gist thereof.

In addition, the evaluation method of the film is shown below.

(1) Glossiness of film 0s (60°)
Degree specular gloss Gs (60') JIS Z 874
Measured according to 1. That is, the reflectance of the sample was determined based on the reflectance of a black standard plate at an incident angle and a reflection angle of 60 degrees, and was defined as the glossiness.

(2) Film thickness It was measured from a photograph of a cross section of the film.

(3) Breaking strength■ Using a tensile tester manufactured by Intesco Model 2001, a sample film with a length of 50 m and a width of 15 cm was tested in a room controlled at a temperature of 23°C and a humidity of 50% RH.
It was pulled at a speed of 200 mm/min, and the following values were determined according to the following formulas.

Tensile breaking strength σ=F/A Example 1 Polyethylene terephthalate containing 0.05% by weight of amorphous silica particles with an average particle size of 2.4 μm was used as a raw material (A,)
Polyethylene terephthalate containing 2.7% by weight of the particles was used as a raw material (B,).

After drying the raw material (A1) and raw material (B1) separately by a conventional method, the raw material (A1) and the raw material (B1) are dried separately using a separate melt extruder.
B,) is the outer layer, the raw material (AI) is the inner layer, and the thickness ratio Bl
An amorphous sheet was produced by forming a three-layer composite with /AI /Bl =1.25/22°5/1.25.

This sheet was stretched 3.6 times in the machine direction at 85°C, then 4.0 times in the transverse direction at 95°C, and heat-set at 230°C to obtain a film with an average thickness of 25 μm.

Example 2 The weight ratio of the raw material (A,) and raw material (B+) of Example 1 was 35
: Polyethylene terephthalate blended at a ratio of 65 was used as the raw material (C).

After drying raw material (C) and raw material (A1) separately by a conventional method, raw material (C) and raw material (
A,) was composited into two layers with a thickness ratio of C/AI = 5/20 to produce an amorphous sheet.

Using this sheet, stretching film formation was carried out in exactly the same manner as in Example 1 except that the longitudinal stretching ratio was changed to 3.8 times, and the average thickness was 2.
A 5 μm film was obtained.

Comparative Example 1 The raw material (A,) of Example 1 was dried in a conventional manner, then extruded in a single layer using an extruder, and rapidly solidified to obtain an amorphous sheet. The obtained sheet was stretched and film-formed in exactly the same manner as in Example 2 to obtain a film with an average thickness of 25 μl.

The results obtained above are summarized in Table 1 below.

〔Effect of the invention〕

The film of the present invention has an excellent matte effect and excellent toughness, and is suitable for applications requiring high strength, such as a base film for transfer foil, and its industrial value is expensive.

Out wish Man Diafoil Co., Ltd. teenager Reason Man

Claims (1)

[Claims] (1) A composite film in which two or more layers are laminated by coextrusion, and the glossiness of one side (side A) of the film is Gs (60°)
is 10 to 90%, the thickness ratio of the layer constituting side A to the entire film is 0.4 or less, and the sum of the breaking strength in the longitudinal and transverse directions of the film is 36 kg/mm^
A matte polyester film characterized in that the polyester film is 2 or more.