JPH02111525A - Manufacture of polyester film - Google Patents

Abstract

PURPOSE:To prevent generation of a surface flaw, lateral steplike adhesive dirt and a craterlike spot of a film, by a method wherein a polyester film is preheated and stretched by making use of a ceramic roll whose surface roughness and roughness density are made appropriate. CONSTITUTION:At the time of manufacturing of a polyester film where mean surface roughness on the center line and the maximum surface roughness are respectively 0.2-1.0mum and 2.0-10.0mum, a ceramic roll whose mean roughness on the center line, maximum surface roughness and a number of recessed parts (roughness density) of at least 0.5mum are respectively 0.7-2.0mum, not exceeding 15mum and 17-28 pieces per 1mm in length is used for a preheating roll. The ceramic roll whose mean surface roughness on the center line, the maximum roughness and the roughness on the center line, the maximum roughness and the roughness density are respectively 0.1-0.5mum, not exceeding 5.0mum and 5-12 pieces per 1mm in length is used for a stretching roll. When mean roughness on the center line of the roll is finer than the above-mentioned range, the roll becomes apt to adhere to the film and when the same exceeds the above-mentioned range, it becomes the cause of generation of a scratch. When the maximum roughness exceeds the above-mentioned range the same becomes a craterlike spot locally. When the roughness density is lower than the above-mentioned range, the same becomes apt to adhere to the film and when it exceeds the above-mentioned range, this becomes the cause of the generation of the scratch.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a polyester film, and more particularly to a method for longitudinally stretching a polyester film using a ceramic roll.

[Conventional technology]

(1) A method of stretching using a heated stretching roll in which the surface of the metal roll is coated with a ceramic layer with a thickness of 0.01 to 5 mm (Japanese Patent Publication No. 48-44666) (2) The surface roughness Rmax is 1. A method of heating and stretching with a polymer resin roll of 5 μm or more (Japanese Patent Publication No. 47-49827) (3) The heating roll has an Rmax of 1.0 μm or more and 6 μm.
A method using a roll whose surface is finished so that the number of concave portions is 10 or more per mm and that there is no convex portion that is 1.5 μm or more higher than the center line of the cross-sectional curve (Japanese Patent Laid-Open No. 62-116
No. 127), etc. are known.

[Problem to be solved by the invention]

However, the method disclosed in Japanese Patent Publication No. 4B-44666 uses a metal roll whose surface is coated with a ceramic layer, and a mere ceramic material alone does not necessarily have an anti-stick effect.

Furthermore, as shown in Japanese Patent Publication No. 47-79827, if the surface roughness Rmax is increased and the degree of surface roughening is increased, adhesive unevenness will be reduced, but scratches will be more likely to occur and spots will appear. It is necessary to regulate the upper limit because dirt is likely to come out. Furthermore, regulating Rmax alone is not sufficient to prevent the occurrence of adhesion and surface scratches.

Furthermore, in the method disclosed in Japanese Patent Application Laid-Open No. 62-116127, if only Rmax and the number of recesses are managed,
This is still insufficient and the center line average roughness needs to be controlled. Also, when stretched at 10 pieces/mm or more, if there are many convex parts up to 1.5 μm from the center line, there will be many flat surfaces due to finishing and adhesion is likely to occur.On the other hand, if there are few convex parts up to 1.5 μm, This is undesirable because the area of the recesses increases and contamination due to monomer adhesion is likely to occur.

[Means to solve the problem]

In the present invention, the center line average roughness of the surface roughness is 0.2 to 1.0.
In a method for manufacturing a polyester film having a maximum roughness of 2.0 to 10.0 μm in μm, when stretching the film in the longitudinal direction (vertical direction), a preheating roll is used that has a center line average roughness of 0.0 μm. 7-2.0μm, maximum depth 1
A ceramic roll having a number of recesses (roughness density) of 5 μm or less and 0.5 μm or more per 1 mm length is used, and as a stretching roll, the center line average roughness of the surface roughness is 0.
．． 1 to 0.5 μm 1 Maximum depth is 5.0 μm or less, 0.5
The number of recesses of μm or more (roughness density) is 5 to 1 per 1 mm length.
This is a method for producing a polyester film characterized by using two ceramic rolls.

The center line average roughness of the preheating roll used in the present invention is 0.7~
It is 2.0 μm, preferably 1.0 to 1.7 μm. If it is lower than the above range, it will tend to stick to the film, whereas if it exceeds the above range, the film will slide on the roll and cause scratches.

The maximum depth is 15 μm or less, preferably 12 μm or less. If it exceeds the above range, the thermal conductivity decreases and uneven heat conduction occurs, resulting in localized crater-like spots and poor appearance.

The number of recesses of 0.5 μm or more is 17 to 28, preferably 20 to 25 per 1 mm length. If it is lower than the above range, it will tend to stick to the film, whereas if it exceeds the above range, the film will slide on the roll and cause scratches.

The center line average roughness of the stretching roll used in the present invention is 0.1 to
It is 0.5 μm, preferably 0.2 to 0.4 μm. If it is lower than the above range, it will tend to stick to the film, whereas if it exceeds the above range, the film will slide on the roll and cause scratches.

The maximum depth is 5.0 μm or less, preferably 4.0 μm or less. If it exceeds the above range, the thermal conductivity decreases and uneven heat conduction occurs, resulting in localized crater-like spots and poor appearance.

The number of recesses of 0.5 μm or more is 5 to 12, preferably 6 to 11, per 1 mm length. If it is lower than the above range, it will tend to stick to the film, whereas if it exceeds the above range, the film will slide on the roll and cause scratches.

The ceramic roll used in the present invention is processed by crushing and spraying ceramic onto the surface of the metal roll using a sintered rod method or a powder flame spraying method.

As ceramic raw materials, alumina, zirconia, zircon, etc. can be used, but more specifically, aluminum oxide (Al2O2: 90% or more), silicon oxide (
SiO2: 0.3% or more), sodium oxide (Na20
:0.1% or more), calcium oxide (CaO:0.1%
above), iron oxide (Fe203: 0.05% or more), titanium oxide (Ti02: Q, 0.1% or more), magnesium oxide (MgO: 1% or more), etc.

The thickness of the ceramic layer is usually 0.01 to 3 mm,
Preferably it is 0.1 to Q and 5 mm.

If the thickness of the ceramic layer is less than 0.01 mm, it is impossible to prevent the occurrence of adhesion. Moreover, if the thickness of the ceramic layer becomes thicker than 3 mm, the thermal conductivity of the roll will deteriorate.
Uniform heating will not be possible.

In addition, it is more preferable that the surface of the ceramic roll of the present invention has rough irregularities formed at the concave portions from the surface line.

The unevenness on the surface of the ceramic roll of the present invention can be achieved by forming unevenness on the surface of the metal roll in advance with metal and coating this surface with ceramic by the above method, or by coating the surface of the metal roll with no unevenness with ceramic. After coating and simultaneously forming ceramic irregularities, the convex part was 3.5 m long.
It is manufactured by polishing and removing as appropriate within m.

FIG. 2 shows an example of a roughness curve obtained by measuring the surface of a ceramic roll used in the present invention with a surface roughness meter. In the figure, curve 7 is the roughness curve.

A broken line 8 indicates the roughness curve of the roll surface immediately after ceramic is sprayed onto the metal roll surface in the ceramic roll manufacturing process, and the ceramic roll of the present invention has the convex portions shown by the broken line 8 polished.

That is, straight line 9 is a polishing removal line. Also, straight line 10
indicates the center line of the roughness curve, and straight line 11 indicates the count level located 0.5 μm or less from the center line. The part of the roughness curve below the count level is 0.
．． A recess 12 of 5 μm or more is shown. The roughness density referred to in the present invention is the number of recesses 12 of 0.5 μm or more that exist per 1 mm of length.

In the present invention, the polyester is a well-known polyester, and the raw material is a polymer selected from the group consisting of polyethylene terephthalate, copolyester having ethylene terephthalate units as the main repeating unit, and polymer blends in which such polyester is the main component. Made of polyester.

In the present invention, the center line average roughness of the surface roughness is 0.2 to 1.0.
A polyester film with a maximum roughness of 2.0 to 10.0 μm in μm is 'IIA! However, in order to obtain such surface roughness, inorganic particles are added to the above polyester as necessary.

In the present invention, the film to be preheated and stretched is
It is an unstretched or at least uniaxially stretched film of the above polyester.

The ceramic roll may be used in any of the following modes: forced drive, idle drive, or a combination of both.

The heating method is roll heating, but a combination of light radiation heating that does not cause adhesion and heater irradiation may be used. The appropriate temperature range for the ceramic roll is usually 75 to 135°C in order to prevent surface scratches and adhesion of the polyester film. When manufacturing polyester biaxially stretched film, the film surface scratches, adhesion, and stains that occur during the heating process have a major impact on the product value, so the material and surface condition of the heating roll often pose problems. By employing the method of the present invention, defects such as surface scratches, crater-like spots, and transverse adhesive stains can be eliminated.

Note that surface scratches, crater-like spots, and horizontal adhesive stains refer to the following.

(1) Surface scratches When the film slips on the roll, scratches occur. This is called a surface scratch.

(2) Crater-shaped spots This refers to the roughening of the roll surface, which deteriorates the adhesion between the roll and the film, and oligomers, monomers, etc. that adhere to the recesses of the roll, resulting in crater-shaped spots.

(3) Horizontal step-shaped adhesive stain Refers to the step-shaped stain that occurs when the peelability deteriorates due to adhesion between the roll and the film.

Furthermore, the method for measuring characteristic values of the present invention is as follows.

(1) Center line average roughness and maximum depth According to JIS B-0601.

(2) Number of recesses of 0.5 μm or more (roughness density) JIS
According to B-0601, using a small plate roughness meter 7 (type Surf loader 5E40D type), set it to PPl-3, set the count level 0°5 μm below the center line of the roughness curve, Every two points where this count level intersects with the roughness curve are counted as one recess, and the number of recesses is determined between the reference lengths and converted to 1 mm.

〔Example〕

Example 1 A roughened polyester film was formed using a polyester containing 2.5% by weight of inorganic particles having an average particle size of 5.0 μm as a raw material using an apparatus as shown in FIG. Aluminum oxide 9 as a preheating ceramic roll
8.55%, silicon oxide 0.58%, sodium oxide 0
．． 31%, magnesium oxide 0.23%, calcium oxide 0°19%, iron oxide 0.10%, titanium oxide 0.04
% coated with ceramic using a sintered rod method, coating thickness Q: 3mm, finishing accuracy: 1S, center line average roughness: 1.3μm, maximum depth: 8.0μm, recesses of 0.5μm or more. A ceramic roll having a roughness density of 22 per 1 mm length was used, and the ceramic roll for stretching contained 90.12% of chromium oxide, 5.78% of silicon oxide, 1.60% of magnesium oxide, and 1.6% of aluminum oxide. 59
A roll coated with ceramic containing 0.20% calcium oxide, 0.47% iron oxide using a sintered rod method, coating thickness Q, 3 mm, finishing accuracy 1S, center line average roughness 0.3 μm. , Maximum depth * 2.0 μm A ceramic roll having a roughness density of 8 in 1 mm of recesses of 10.5 μm or more was used to prepare an unstretched polyester film with a thickness of 1000 μm, and the ceramic roll for preheating was set at 90°C. Then, the ceramic roll for stretching was set at 98°C, stretched 3°0 times in the longitudinal direction, continuously stretched 3.0 times in the horizontal direction, wound up with a winder, and the center line average roughness was 0.57 μm 1 maximum. A polyester film with a roughness of 5.0 μm was formed. 1
No surface scratches, crater-like spots, or horizontal step-like adhesive unevenness were observed in the tested film.

Example 2 As a preheating roll, the center line average roughness is 0.7 μm, the maximum depth is 4.0 μm, and the roughness density of recesses of 0.5 μm or more is 1 m.
A ceramic roll having 19 rolls in a length of m is used, and as a stretching roll, the center line average roughness is 0.1 μm, the maximum depth is 1.0 μm, and the roughness density of recesses of 0.5 μm or more is 1 m.
A polyester film having a center line average roughness of 0.56 μm and a maximum roughness of 5.0 μm was formed in the same manner as in Example 1 except that a ceramic roll having 6 rolls in m length was used.

No surface scratches, crater-like spots, or horizontal step-like adhesive unevenness were observed in the obtained film.

Example 3 As a preheating roll, the center line average roughness was 1.8 μm, the maximum depth was 14.0 μm, and the roughness density of the recesses of 0.5 μm or more was 1.
Using a ceramic roll with 26 pieces in mm length,
As a stretching roll, the center line average roughness is 0.5 μm, the maximum depth is 4.0 μm, and the roughness density of concave portions of 0°5 μm or more is 1.
A ceramic roll having 10 rolls in mm length was used, and the other conditions were the same as in Example 1, and the center line average roughness was 0.57 μm.
A polyester film having a maximum roughness of 5.0 μm was formed. The resulting film has surface scratches, crater-like spots,
No horizontal step-like adhesive unevenness was observed.

Comparative Example 1 As a preheating roll, the center line average roughness is 0.4 μm, the maximum depth is 5.0 μm, and the roughness density of recesses of 0.5 μm or more is 1 m.
Using a ceramic roll having 14 rolls in m length, as a stretching roll, the average roughness of the center line is 0.05 μm, the R depth is 1.0 μm, and the roughness density of the concave portion of 0°5 μm or more is 1.
A ceramic roll having one roll per mm length was used, and the rest was the same as in Example 1, with a center line average roughness of 0.55 μm,
A polyester film having a maximum roughness of 5.0 μm was formed. Although no surface scratches or crater-like spots were observed on the obtained film, transverse step-like adhesive unevenness was observed over the entire surface.

Comparative Example 2 As a preheating roll, the center line average roughness was 2.4 μm, the maximum depth was 19.0 μm, and the roughness density of recesses of 0.5 μm or more was 1
Using a ceramic roll having 31 pieces in mm length,
As a stretching roll, the center line average roughness is 0.7 μm! The bed entry depth is 6.0 μm, and the roughness density of the recesses of 0°5 μm or more is 1
A ceramic roll having 13 rolls in mm length was used, and the other conditions were the same as in Example 1, and the center line average roughness was 0.58 μm.
A polyester film having a maximum roughness of 5.1 μm was formed. In the obtained film, no horizontal step-like adhesive unevenness was observed, but surface scratches and crater-like spots were observed on the entire surface.

Comparative Example 3 As a preheating roll, the center line average roughness is 1.0 μm, the maximum depth is 5.0 μm, and the roughness density of recesses of 0.5 μm or more is 1 m.
A ceramic roll having 20 ceramic rolls in a length of m is used, and as a stretching roll, the center line average roughness is 0.05 μm, the maximum depth is 1.0 μm, and the roughness density of the recesses of 0°5 μm or more is 1.
A ceramic roll having one piece per mm length was used, and the rest was the same as in Example 1, with a center line average roughness of 0.54 μm,
A polyester film having a radius of 5.0 μm was formed. Although no surface scratches or crater-like spots were observed on the 1q film, transverse step-like adhesive unevenness was observed over the entire surface.

Comparative Example 4 As a preheating roll, the center line average roughness was 2.4 μm, the maximum depth was 19.0 μm, and the roughness density of recesses of 0.5 μm or more was 1
Using a ceramic roll having 31 pieces in mm length,
As a stretching roll, the center line average roughness is 0.5 μm, the maximum depth is 4.0 μm, and the roughness density of concave portions of 0°5 μm or more is 1.
A ceramic roll having 10 rolls in mm length was used, and the other conditions were the same as in Example 1, and the center line average roughness was 0.53 μm.
A polyester film having a maximum roughness of 5.1 μm was formed. In the obtained film, no horizontal step-like adhesive unevenness was observed, but surface scratches and crater-like spots were observed on the entire surface.

[Effects of the Invention] The present invention uses a ceramic roll with an optimized surface roughness and roughness density to preheat and stretch a polyester film, thereby eliminating surface scratches caused by the film slipping on the roll and rolling. It is possible to prevent horizontal step-like adhesive stains and crater-like spots caused by adhesion between the film and the film.

[Brief explanation of the drawing]

FIG. 1 shows an example of an apparatus for preheating and stretching steps used in carrying out the present invention. FIG. 2 shows an example of a roughness curve obtained when the surface of a ceramic roll used in the practice of the present invention is measured with a surface roughness meter. 1... Polyester film 2... Preheating ceramic roll 3... Stretched ceramic roll 4... Radiation heater 5... Cooling roll 6... Tenter 7... Roughness curve 8... Polishing removal Previous roughness curve 9...Polishing removal line 10...Center line of roughness curve 11...Count level 12...Concave portion of 0.5 μm or more Fig. 1 Fig. 2

Claims (1)

[Claims] (1) Center line average roughness of surface roughness is 0.2 to 1.0 μm
In the manufacturing method of a polyester film having a maximum roughness of 2.0 to 10.0 μm, when stretching the film in the longitudinal direction (vertical direction), the center line average roughness of the surface roughness is 0.7 as a preheating roll. ~2.0μm, maximum depth 15μm
m or less, the number of recesses (roughness density) of 0.5 μm or more is 1 m
Using ceramic rolls with 17 to 28 pieces per m length,
As a stretching roll, the center line average roughness of the surface roughness is 0.1.
~0.5μm, maximum depth 5.0μm or less, 0.5μm
A method for producing a polyester film, characterized by using a ceramic roll having the above number of recesses (roughness density) of 5 to 12 per 1 mm length.