JP2002240143A - Method for manufacturing polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyester film of which the defect such as a scratch, a stickiness stain, a crater-shaped spot or the like to be generated in a stretching process is eliminated. SOLUTION: The polyester film is manufactured by using a ceramic roll of which the surface roughness is 0.03-0.04 μm as center line average roughness, the maximum depth is 1.0 μm or less, the number (roughness density) of recessed parts with a depth of 0.5 μm or more is 15 or less per 1 inch, and the hardness is 1,100 HV or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester film, and more particularly, to a method for producing a polyester film by a longitudinal stretching method using a ceramic roll.

[0002]

2. Description of the Related Art Conventionally, 0.01 to 0.01
A preheating method in which a ceramic layer is coated with a thickness of 5 mm, a drawing method using a drawing roll (Japanese Patent Publication No. 48-46666), or a heating and drawing method using a polymer resin roll having a surface roughness Rmax of 1.5 μm or more. Performing method (Japanese Patent Publication No. 47-7982)
No. 7) has been proposed. However, the former method is simply a roll in which a ceramic layer is coated on a metal roll surface.
An anti-adhesion effect cannot always be obtained. As in the latter case, if the surface roughness Rmax is increased and the degree of surface roughening is increased, adhesion unevenness is reduced, but scratches are more likely to occur and the pattern on the ceramic roll surface is transferred to the film. There is a problem that drawbacks such as being performed occur.

A method of controlling Rmax and the number of concave portions has also been proposed (Japanese Patent Application Laid-Open No. 62-116127). However, the regulation of Rmax alone is not enough to prevent the occurrence of adhesion and surface damage. Was not.

[0004]

SUMMARY OF THE INVENTION In view of the background of the prior art, the present invention provides a method for producing a polyester film in which defects such as scratches, adhesive stains and crater-like spots generated in a stretching step are eliminated. It is something you want to do.

[0005]

The present invention employs the following means in order to solve the above-mentioned problems. That is, in the method for producing a polyester film of the present invention, the center line average roughness of the surface roughness is 0.03 to 0.0
4 μm, the maximum depth is 1.0 μm or less, the number of recesses with 0.5 μm or more (roughness density) is 15 or less per inch,
It is characterized by using a ceramic roll having a hardness of 1100 HV or more.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to a method for producing a polyester film in which the above problems, that is, defects such as scratches, adhesive stains and crater-like spots generated in the stretching step, have been eliminated, and specific studies have been made. When a ceramic roll was used in a stretching process, it was found that such a problem could be solved at once.

That is, a specific ceramic roll, that is, a ceramic roll in which the surface roughness and the center line average roughness are controlled in a specific range, specifically, the center line average roughness of the surface roughness, a specific maximum Number of recesses with depth (roughness density)
Such a problem can be solved by using a ceramic roll whose hardness is controlled.

The ceramic roll used in the present invention has a center line average roughness of surface roughness of 0.03 to 0.04.
It is important that the thickness is μm, preferably 0.01 to 0.2 μm. If the value exceeds this value, scratches occur, and if the value is less than this value, the adhesion tends to become strong.

Further, the maximum depth of the surface roughness must be 1.0 μm or less. When the thickness exceeds 1.0 μm, the thermal conductivity is reduced, and thermal conductivity unevenness is generated, and local crater-like spots are easily formed, thereby providing an inferior appearance. Further, in such a concave portion, the number of concave portions whose maximum depth is 0.5 μm or more is from 0 to 15, preferably from 0 to 15, per inch.
It is important that there are five. Beyond this range,
The film slips on the roll, and scratches are likely to occur.

[0010] In order to obtain a ceramic roll constituting a very mirror-like surface, a chromia ceramic material is preferably used as the ceramic material.

The thickness of the ceramic layer of such a ceramic roll is preferably 0.01 to 3 mm, more preferably 0.1 to 0.3 mm.
It is good to be 1-0.5 mm. When the thickness of the ceramic layer is less than 0.01 mm, the void ratio in the layer is low, so that the anti-adhesion effect tends to decrease. When the thickness is more than 3 mm, the thermal conductivity of the roll deteriorates, and uneven heating may occur. It tends to occur easily.

The surface of the ceramic roll is preferably free of scratches (scratches) and pinholes generated during polishing, and more preferably has a friction coefficient of 0.2.
Those having a range of 4 to 0.36 μs are used.

In order to prevent the surface of the ceramic roll from being damaged, a ceramic roll having a surface hardness of 1100 HV or more is preferably used.

Next, FIG. 2 shows an example of a roughness curve obtained by measuring the surface of the ceramic roll used in the present invention with a surface roughness measuring instrument. In the figure, curve 7 is a roughness curve. The broken line 8 indicates the center line of the roughness curve. Straight line 9 is 0.5 μm from center line
The following levels are indicated. In the roughness curve 7,
The roughness density can be represented by the number of depressions per inch below the level of the straight line 9. In the present invention, the number of such concave portions is 15 or less.

Next, a method for producing the polyester film of the present invention will be described.

FIG. 1 shows an example of an apparatus for a longitudinal stretching step used in carrying out the method for producing a polyester film of the present invention. In this example of the apparatus, both the preheating roll and the stretching roll use the ceramic roll of the present invention. The polyester film 1 is preheated by a preheated ceramic roll 2, passed through a stretched ceramic roll 3 provided below a radiation heater 4, stretched in a vertical direction, and once cooled by a cooling roll 5. ,
The film is stretched in the transverse direction by the tenter 6.

Such a ceramic roll can be used in any of forced drive, induction drive, and a combination of both. Further, the heating method depends on the heating of the roll body, but it is also possible to use both radiation heating and heater irradiation to the extent that sticking does not occur.

The proper temperature range of the ceramic roll is preferably from 75 to 135 ° C. from the viewpoint of preventing surface flaws and adhesion of the polyester film.

As the polyester film 1 to be preheated and stretched, an unstretched polyester film or a uniaxially stretched polyester film is used.

The polyester constituting the polyester film is selected from the group consisting of polyethylene terephthalate, homopolyesters and copolyesters having ethylene terephthalate units as main repeating structural units, and polymer blends containing such polyesters as a main component. A polymer made from a polymer can be used.

The polyester film thus obtained has low surface roughness, excellent smoothness, and excellent optical properties.
Particularly, it is suitably used for optical applications.

[0022]

The present invention will be described below in more detail with reference to examples.

The flaws, spots, and adhesive stains referred to in the examples are based on the following definitions.

Scratch: When the film slides on the roll, scratches occur. This is expressed as a pickpocket.

Crater-like spots: The roughening of the surface roughness of the roll deteriorates the adhesion between the roll and the film, and causes oligomers and monomers adhering to the concave portions of the roll to adhere to form crater-like spots. Say.

Adhesive dirt: A step-like dirt that is generated when the releasability is deteriorated due to the adhesion between the roll and the film.

Product acceptance criteria: In the examples, a film having a center line average roughness of 0.01 μm, a maximum roughness of 0.5 μm, a film thickness of 0.2 ± 0.01 mm, and no scratches or stains on the surface was accepted. did.

Next, the method of measuring the characteristic value in the embodiment is as follows. (1) Centerline average roughness and maximum depth Measured based on JIS B-0601. (2) Number of recesses of 0.5 μm or more (roughness density) Set to PPI-3 using Kosaka roughness meter (Surfcoder SE400) based on JIS B-0601, A count level is provided at 0.5 μm or less, and every two points where the count level intersects the roughness curve are counted as one concave portion, and the number is determined by counting the number between the reference lengths.

Example 1 Using an unstretched polyester film as a raw material, a film for optical use was manufactured using a longitudinal stretching apparatus as shown in FIG.

In FIG. 1, the center roll average roughness 0.03 μm, maximum depth 0.9 μm, 0.5 μm
A ceramic roll having a roughness density of 10 m / inch or more, a surface hardness of 1300 HV, and a friction coefficient of 0.3 μs was used.

The obtained polyester film has a center line average roughness of 0.011 μm, a maximum roughness of 0.41 μm, and a film thickness of 0.2 mm, and has no defects such as surface scratches, crater-like spots, and adhesive stains. The optical characteristics such as total light transmittance were also good.

Example 2 In the same manner as in Example 1, as a stretching roll, the surface roughness was 0.04 μm in the center line average roughness, 1.0 μm in the maximum depth, 0.1 mm in the maximum depth.
A polyester film was manufactured using a ceramic roll having a concave roughness density of 5 μm or more, a length of 12 / inch, a surface hardness of 1300 HV, and a friction coefficient of 0.32 μs.

The obtained polyester film has a center line average roughness of 0.009 μm, a maximum roughness of 0.44 μm, and a film thickness of 0.2 mm, and has no defects such as surface scratches, crater-like spots and adhesive stains. The optical characteristics such as total light transmittance were also good.

Comparative Example 1 In the same manner as in Example 1, as a stretching roll, the surface roughness was determined to be center line average roughness 0.09 μm, maximum depth 1.1 μm, and 0.1 mm.
A polyester film was manufactured using a ceramic roll having a concave density of 150 μm / inch, a surface hardness of 800 HV, and a friction coefficient of 0.32 μs.

The obtained polyester film had a center line average roughness of 0.009 μm, a maximum roughness of 0.44 μm, and a film thickness of 0.2 mm, but had many surface scratches.
Product acceptance criteria (center line average roughness 0.01 μm, maximum roughness 0.5 μm, film thickness 0.2 ± 0.01 mm, surface scratches,
(No dirt), and was a rejected product. Comparative Example 2 A polyester film was manufactured in the same manner as in Comparative Example 1, except that a hard chrome plating roll having a surface roughness of 0.2 S was used instead of the ceramic roll.

The resulting polyester film did not have any surface scratches, but did not meet the product acceptance criteria due to sticky stain due to poor peeling and was a rejected product.

[0037]

According to the present invention, it is possible to prevent scratches caused by the film slipping on the roll, adhesive stains caused by the adhesion between the roll and the film, and crater-like spots. Further, according to the present invention, since the surface hardness is high, troubles such as generation of scratches during use and damages due to accidents do not occur, and continuous use can be performed with confidence.

[Brief description of the drawings]

FIG. 1 shows an example of an apparatus in a longitudinal stretching step used for carrying out the present invention.

FIG. 2 shows an example of a roughness curve obtained when a surface of a ceramic roll used for carrying out the present invention is measured by a surface roughness meter.

[Explanation of symbols]

 1: polyester film 2: preheated ceramic roll 3: stretched ceramic roll 4: radiation heater 5: cooling roll 6: tenter 7: roughness curve 8: center line of roughness curve 9: count level 10: 0.5 μm or more Recess

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B29L 11:00 B29L 11:00 F term (Reference) 3J103 AA02 FA09 GA24 HA04 HA51 4F210 AA24 AG01 AH73 AJ06 QA03 QC02 QG01 QG18 QM05 QM07

Claims (3)

[Claims] A center line average roughness of the surface roughness is 0.03 to 0.03.
0.04μm, maximum depth 1.0μm or less, 0.5μ
A method for producing a polyester film, comprising using a ceramic roll having a number of recesses (roughness density) of not more than 15 per inch and a hardness of not less than 1100 HV per inch. 2. The method for producing a polyester film according to claim 1, wherein said ceramic roll is used as a stretching roll. 3. A method for producing a polyester film, wherein the film produced by the method according to claim 1 is used for optical purposes.