JPH0696265B2 - Method for producing polyester film - Google Patents

Description

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 drawing using a heating drawing roll in which the surface of a metal roll is covered with a ceramic layer with a thickness of 0.01 to 5 mm (Japanese Patent Publication No. 48-44666) (2) Rmax of surface roughness is 1.5 μm or more Method of heating and drawing with polymer resin roll (Japanese Patent Publication No. 47-49827) (3) Rmax is 1.0 μm or more and 6 μm or less on the heating roll, there are 10 recesses / mm or more, and the center of the section curve There is known a method (Japanese Patent Laid-Open No. 62-116127) in which a roll whose surface is finished so as not to have protrusions higher than the line by 1.5 μm or more is used.

[Problems to be Solved by the Invention]

However, the method disclosed in JP-B-48-44666 is
It is a roll in which the surface of a metal roll is coated with a ceramic layer, and the effect of preventing sticking is not always recognized with a simple ceramic material.

Further, as shown in JP-B-47-79827, increasing Rmax of the surface roughness and increasing the degree of roughening reduces adhesive non-uniformity, but easily causes scratches and spots. It is easy to get dirt, so the upper limit is required. Moreover, the regulation of Rmax alone is not sufficient to prevent the occurrence of adhesion and surface scratches.

Further, in the method disclosed in Japanese Patent Laid-Open No. 62-116127, it is still insufficient to control only Rmax and the number of recesses, and it is necessary to control the center line average roughness. Also, 10
When there are many protrusions up to 1.5 μm from the center line when stretched at a rate of more than 1 piece / mm, sticking tends to occur due to more flat surfaces due to finishing. It is not preferable because stains easily occur due to adhesion of monomers.

[Means for Solving the Problems]

The present invention has a center line average roughness of surface roughness of 0.02 to 0.2 μm.
In the method for producing a polyester film having a maximum roughness of 0.2 to 2.0 μm, the center line average roughness of the surface roughness is 0.7 to 2.0 μm as the preheating roll when the film is stretched in the longitudinal direction (longitudinal direction) of the film. Depth less than 15μm, 0.5μm
Using a ceramic roll having the number of recesses (roughness density) of 17 to 28 per 1 mm length as a stretching roll, the centerline average roughness of surface roughness is 0.5 to 1.5 μm, and the maximum depth is 10.0.
A method for producing a polyester film, which comprises using a ceramic roll having a number of recesses (roughness density) of not more than 0.5 μm and not less than 0.5 μm per mm length of 12 to 22.

The center line average roughness of the preheating roll used in the present invention is 0.7 to 2.0.
μm, preferably 1.0 to 1.7 μm. When it is lower than the above range, the film tends to stick to the film, and when it exceeds the above range, the film may cause slipping scratches on the roll.

The maximum depth is 15 μm or less, preferably 12 μm or less. When it exceeds the above range, the thermal conductivity is lowered and uneven thermal conductivity is caused to locally form crater-like spots, resulting in poor appearance.

The number of recesses of 0.5 μm or more is 17 to 28, preferably 20 to 25 per 1 mm length. When it is lower than the above range, the film tends to stick to the film, and when it exceeds the above range, the film may cause slipping scratches on the roll.

The center line average roughness of the stretching roll used in the present invention is 0.5 to 1.5.
μm, preferably 0.7 to 1.3 μm. When it is lower than the above range, the film tends to stick to the film, and when it exceeds the above range, the film may cause slipping scratches on the roll.

The maximum depth is 10.0 μm or less, preferably 7.0 μm or less. When it exceeds the above range, the thermal conductivity is lowered and uneven thermal conductivity is caused to locally form crater-like spots, resulting in poor appearance.

The number of recesses of 0.5 μm or more is 12 to 22, preferably 14 to 20, per 1 mm length. When it is lower than the above range, the film tends to stick to the film, and when it exceeds the above range, the film may cause slipping scratches on the roll.

The ceramic roll used in the present invention is processed on the surface of the metal roll by pulverizing and spraying the ceramic onto the surface of the metal roll by a sintering rod type or powder type flame spraying method.

Alumina, zirconia, zircon and the like can be used as the ceramic raw material, and more specifically, for example, aluminum oxide (Al ₂ O ₃ : 90% or more), silicon oxide (SiO ₂ : 0.
3% or more), sodium oxide (Na ₂ O: 0.1% or more), calcium oxide (CaO: 0.1% or more), iron oxide (Fe ₂ O ₃ : 0.05%)
Above), titanium oxide (TiO ₂ : 0.01% or more), etc.

The thickness of the ceramic layer is usually 0.01 to 3 mm, preferably 0.1 to 0.5 mm. If the thickness of the ceramic layer is less than 0.01 mm, the occurrence of sticking cannot be prevented. If the thickness of the ceramic layer is more than 3 mm, the thermal conductivity of the roll deteriorates and uniform heating cannot be performed.

In addition, it is more preferable that the surface of the ceramic roll of the present invention is further provided with unevenness at the concave portion from the surface line.

The unevenness of the surface of the ceramic roll of the present invention, the unevenness is previously formed on the surface of the metal roll by metal, and the surface is coated with ceramic by the above method, or the surface of the metal roll having no unevenness is ceramic. It is manufactured by forming irregularities of ceramic at the same time as coating and then appropriately polishing and removing the convexes within 0.5 mm.

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 meter. In the figure, curve 7 is the roughness curve. The broken line 8 shows the roughness curve of the roll surface immediately after the ceramic is sprayed on the surface of the metal roll in the process of manufacturing the ceramic roll, and the ceramic roll of the present invention is obtained by polishing the convex portion shown by the broken line 8. That is, the straight line 9 is a polishing removal line. Also,
The straight line 10 indicates the center line of the roughness curve, and the 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
A recess 12 of 0.5 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 existing per 1 mm in length.

In the present invention, the polyester is a well-known polyester, and a raw material is a polymer selected from the group consisting of polyethylene terephthalate, a copolymerized polyester having ethylene terephthalate units as main repeating constitutional units, and a polymer blend containing such polyester as a main component. And the polyester.

The present invention has a center line average roughness of surface roughness of 0.02 to 0.2 μm.
It is applied to produce a polyester film having a maximum roughness of 0.2 to 2.0 μm, and in order to obtain such surface roughness, inorganic particles are added to the above polyester, if necessary.

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

The ceramic roll may be used in any mode of forced drive, floating drive, and a combination of both. Further, although the heating method is roll heating, mild radiation heating to the extent that adhesion does not occur and heater irradiation may be used together. The suitable temperature range of the ceramic roll is usually 75 to 13 in order to prevent the occurrence of surface scratches and adhesion of the polyester film.
It is 5 ° C. When manufacturing a polyester biaxially stretched film, film surface scratches, adhesion,
Since dirt has a great influence on the commercial value, the material of the heating roll and the surface condition are often problems, but by adopting the method of the present invention, surface scratches, crater-like spots, and horizontal step-like sticky dirt. The drawbacks such as can be solved.

The surface scratches, crater-like spots, and horizontal adhesive stains are as follows.

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

(2) Crater-like spots It means that due to the roughening of the surface roughness of the roll, the adhesion between the roll and the film deteriorates, and oligomers, monomers, etc. attached to the recesses of the roll adhere to cause crater-like spots.

(3) Horizontal step-like stain This is a step-like stain that occurs when peelability deteriorates due to sticking between the roll and the film.

The method of measuring the characteristic value of the present invention is as follows.

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

(2) Number of recesses of 0.5 μm or more (roughness density) According to JIS B-0601, set to PPI-3 using a Kosaka type roughness meter (type surfcorder SE40D type) and check the roughness curve. A count level is provided at 0.5 μm or less from the center line, and a count is made as one recess at every two intersections of this count level and the roughness curve. The number of recesses is calculated within the standard length, and per 1 mm Convert to.

〔Example〕

Example 1 A smooth polyester film was formed using an apparatus as shown in FIG. As a ceramic roll for preheating, coated with a ceramic sintered rod type containing aluminum oxide 98.55%, silicon oxide 0.58%, sodium oxide 0.31%, magnesium oxide 0.23%, calcium oxide 0.19%, iron oxide 0.10%, titanium oxide 0.04%. With the rolled roll, coating thickness 0.3mm, finishing accuracy 1S, center line average roughness 1.3μm,
Roughness density of recesses with maximum depth of 8.0 μm and 0.5 μm or more is 1 mm
Using 22 ceramic rolls in length, as a ceramic roll for drawing, 94% aluminum oxide, 2.5% titanium oxide, 2.0% silicon oxide, was coated by a ceramic powder flame spraying method containing 1.0% iron oxide. Roll, coating thickness 0.3mm, finishing accuracy 1S, center line average roughness 1.0μm,
Ceramic rolls with a maximum depth of 5 μm and roughness densities of 0.5 μm or more with 17 in 1 mm are used. Polyester unstretched film, 1000 μm preheat ceramic roll for preheating to 90 ° C. Is stretched 3.0 times in the machine direction, continuously stretched 3.0 times in the transverse direction, and wound with a winder to produce a polyester film with a center line average roughness of 0.03 μm, maximum roughness and 0.30 μm. Filmed
The surface of the obtained film was free from scratches, crater-like spots, and lateral adhesive unevenness.

Example 2 As a preheating roll, center line average roughness 1.0 μm, maximum depth
Roughness density of recesses of 5.0μm, 0.5μm or more is 2 in 1mm length
Using a ceramic roll having 0 rolls, as a stretching roll, the center line average roughness is 0.8 μm, the maximum depth is 3.0 μm, 0.5
Using a ceramic roll having a concave density of 15 μm or more in a length of 1 mm, a polyester film having a center line average roughness of 0.19 μm and a maximum roughness of 1.95 μm was produced in the same manner as in Example 1. did. The surface of the obtained film was free from scratches, crater-like spots, and lateral adhesive unevenness.

Example 3 As a preheating roll, center line average roughness 1.7 μm, maximum depth 1
Roughness density of recesses of 2.0 μm and 0.5 μm or more is 2 in 1 mm length
Using a ceramic roll with 5 rolls, the centerline average roughness of 1.3μm, maximum depth of 7.0μm, 0.5
A polyester film having a center line average roughness of 0.19 μm and a maximum roughness of 1.95 μm was produced in the same manner as in Example 1 except that a ceramic roll having a roughness density of 20 μm or more in a recess of 1 μm or more was used in a length of 1 mm. did. The surface of the obtained film was free from scratches, crater-like spots, and lateral adhesive unevenness.

Comparative Example 1 Center line average roughness 0.4 μm, maximum depth as preheating roll
Roughness density of recesses of 5.0 μm and 0.5 μm or more is 1 in 1 mm length
Using a ceramic roll with 4 rolls, the centerline average roughness is 0.3μm, maximum depth is 3.0μm, 0.5
Using a ceramic roll having a concave density of 6 μm or more in a length of 1 mm, a polyester film having a center line average roughness of 0.19 μm and a maximum roughness of 1.95 μm was produced in the same manner as in Example 1. did. No surface scratches or crater-like spots were observed on the obtained film, but lateral adhesive unevenness was observed on the entire surface.

Comparative Example 2 As a preheating roll, centerline average roughness 2.4 μm, maximum depth 1
Roughness density of recesses of 9.0 μm and 0.5 μm or more is 3 in 1 mm length
Using a ceramic roll with one, as a drawing roll, centerline average roughness 1.8μm, maximum depth 13.0μm, 0.5
A polyester film having a center line average roughness of 0.19 μm and a maximum roughness of 1.95 μm was produced in the same manner as in Example 1 except that a ceramic roll having a roughness density of recesses of μm or more of 24 in 1 mm length was used. did. Surface scratches and crater-like spots were found on the entire surface of the obtained film.

Comparative Example 3 As a preheating roll, center line average roughness 1.0 μm, maximum depth
Roughness density of recesses of 5.0μm, 0.5μm or more is 2 in 1mm length
Using a ceramic roll having 0 rolls, as a stretching roll, the center line average roughness is 0.3 μm, the maximum depth is 3.0 μm, 0.5
Using a ceramic roll having a recess density of 6 μm or more in a length of 1 mm, a ceramic film having a center line average roughness of 0.20 μm and a maximum roughness of 2.0 μm was produced in the same manner as in Example 1. did. No surface scratches or crater-like spots were observed on the obtained film, but lateral adhesive unevenness was observed on the entire surface.

〔The invention's effect〕

The present invention uses a ceramic roll having an optimized surface roughness and roughness density, by preheating and stretching the polyester film, surface scratches caused by the film slipping on the roll, and adhesion between the roll and the film. It is possible to prevent the occurrence of horizontal step-like adhesive stains and crater-like spots.

[Brief description of drawings]

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

Continuation of the front page (56) Reference JP-A-1-304928 (JP, A) JP-A-1-141007 (JP, A) JP-A 63-265069 (JP, A) JP-A 60-143929 (JP , A)

Claims (1)

[Claims] 1. The center line average roughness of the surface roughness is 0.02 to 0.2 μ.
In the method for producing a polyester film having a maximum roughness of 0.2 to 2.0 μm in m, a center line average roughness of surface roughness of 0.7 to 2.0 μm is used as a preheating roll when stretching in the longitudinal direction (longitudinal direction) of the film. Maximum depth is 15μm or less, 0.5μ
The number of recesses (roughness density) of m or more (roughness density) is 17 to 28 per 1 mm length. As a stretching roll, the centerline average roughness of surface roughness is 0.5 to 1.5 μm, and the maximum depth is 10.0.
A method for producing a polyester film, comprising using a ceramic roll having a number of recesses (roughness density) of not more than 0.5 μm and not less than 0.5 μm per 1 mm length.