JP2002226610A - Polypropylene release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene release film that is hardly transferred to an opposite material and can be easily peeled at the next step. SOLUTION: This polypropylene release film comprises an antioxidant that does not contain any carbonyl groups in the film, wherein it is characterized in that the center line average roughness Ra of the sticking face is less than 0.04 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polypropylene film for mold release.

[0002]

2. Description of the Related Art Polypropylene films are widely used for industrial applications because of their excellent smoothness and transparency. Recently, there has been a remarkable increase in demand for protection during the processing of a laminated film for optical use or a printed wiring board and subsequent release material, and improvement of the quality and workability has become an important requirement.

[0003] In these applications, as a protective layer of the body material during processing, it is often attached to the body material once and then peeled off again in the next step.

In general, the surface in contact with the main body material is required to be smooth so that the surface irregularities of the release film are not transferred to the adhesive layer or the photosensitive layer applied to the main body material, and to be easily peeled off in the next step. . For this reason, measures have been taken by adjusting processing conditions such as a bonding pressure and a bonding temperature between the release film and the main body material and a peeling speed at the time of peeling in the next step.

[0005]

However, in these methods, not only the degree of freedom of the bonding conditions is small, but also when the bonding pressure is increased, the transfer of the surface irregularities of the release film to the main body film becomes strong. In addition, since the peeling force in the next step is increased, the peeling speed, that is, the processing productivity is lowered, and it is not sufficient to satisfy the above-mentioned requirements.

On the other hand, when the bonding pressure is reduced, a gap is formed between the release film and the main body material, and the protective effect which is the original function of the release film is reduced, which is also insufficient. there were.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polypropylene film for mold release which improves the disadvantages of the prior art, has less transfer to the body material, and facilitates peeling in the next step.

[0008]

Means for Solving the Problems In order to achieve the above object, the polypropylene film for release of the present invention comprises at least an antioxidant containing no carbonyl group in the film, The center line average roughness Ra of the bonding surface is 0.04 μm or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with preferred embodiments. The center line average roughness Ra of at least the bonding surface of the release polypropylene film of the present invention needs to be 0.04 μm or less. If it exceeds 0.04 μm, the transfer to another material to be bonded becomes strong, which is inappropriate. It is preferably 0.03 μm or less, more preferably 0.02 μm
It is as follows.

The antioxidant contained in the releasing polypropylene film of the present invention must be an antioxidant containing no carbonyl group, and is preferably used alone. Antioxidants containing a carbonyl group are unsuitable because they may bond to other substance molecules due to the nature of the double bond possessed by the carbonyl group, resulting in poor releasability. Antioxidants that do not contain carbonyl groups include
1,3,5 trimethyl-2,4,6-tris (3,5-
Di-tert-butyl-4-hydroxybenzyl) benzene, 2,6-di-tert-butyl-4-methylphenol, 2,4-bis-[(n-octylcio) -6
(4-hydroxy-3,5-di-tertiarybutyranilino) -1,3,5-triazine], and the like, but a phenolic antioxidant is preferred from the viewpoint of handleability and economy, and among others, 1,3,5 trimethyl-2,
4,6-Tris (3,5-di-tert-butyl-4hydroxybenzyl) benzene is more preferred.

On the other hand, if the content of the antioxidant containing no carbonyl group is too small, the original antioxidant effect is weakened.
In consideration of economy, the content is preferably 0.02 wt% or more and 2 wt% or less. More preferably 0.04 wt% or more and 1.5 wt%
% Or less.

Further, when the polypropylene film for release of the present invention is bonded to another material as a protective layer, it is better that the contact surface with the other material is easy to observe, and in this respect, the haze is 2.5% or less. It is preferred that It is more preferably at most 2%.

The polypropylene film for release of the present invention is preferably subjected to a surface treatment such as a corona discharge treatment on the non-bonded surface for the purpose of imparting a running property to the film, and its wetting tension is too low. The effect of improving the running property is small, and if it is too high, blocking may be caused. Therefore, it is preferably from 33 mN / m to 37 mN / m.

The sum of the longitudinal heat shrinkage and the transverse heat shrinkage of the polypropylene film of the present invention is 4%.
The following is preferred. If it exceeds 4%, deformation at the time of processing becomes large, and light distortion or the like may be caused in optical applications and the like, which is not preferable, and is more preferably 3.5% or less.

The polymer constituting the polypropylene film according to the present invention is not particularly limited. In addition to a homopolymer of polypropylene, a copolymer of propylene and another α-olefin (eg, ethylene, butene, etc.) may be used. Alternatively, a blend of polypropylene and another α-olefin polymer (eg, polyethylene, polybutene, polymethylpentene, etc.) may be used.

Further, the polypropylene film according to the present invention may be obtained by any of the tenter method and the inflation method, and the stretching method is not particularly limited. Biaxial stretching is preferred.

Next, an example of the method for producing the polypropylene film for release of the present invention will be described, but the present invention is not particularly limited thereto. 0.5 wt% of polymethylpentene in a polypropylene resin containing 0.1 to 1 wt% of 1,3,5 trimethyl-2,4,6-tris (3,5-di-tert-butyl-4hydroxybenzyl) benzene ~ 5wt
The polymer with the% added is supplied to an extruder at a temperature of 200 to 270 ° C to be melted, extruded into a sheet shape from a slit T die, and cooled and solidified by a cooling roll at a temperature of 20 to 75 ° C. At this time, the higher the melt index of the polypropylene resin is, the smaller the heat shrinkage ratio is. In general, the higher the temperature of the cooling roll, the greater the surface roughness and haze. Therefore, the temperature of the cooling roll may be appropriately selected.

Next, the film is stretched 3 to 7 times in the longitudinal direction by a stretching roll at 115 to 155 ° C. Also in this case, the magnitude of the surface roughness can be changed by selecting the stretching temperature.
Next, the film is stretched 7 to 12 times in the width direction at a temperature of 155 to 175 ° C, and further subjected to a heat treatment at 140 to 165 ° C. Generally, the lower the stretching temperature or the heat treatment temperature, and the higher the stretching ratio, the greater the heat shrinkage. Therefore, these conditions may be appropriately selected. The non-bonded surface of the thus obtained polypropylene film is subjected to a corona discharge treatment and wound up by a winder.

Next, the measurement method and the evaluation method used in the present invention will be described. (1) Film peeling force A sample having a size of 10 cm in the longitudinal direction and 5 cm in the width direction is collected, and the two samples are overlapped so that a certain surface and an opposite surface are in contact with each other. 5cm x 5c
m) is sandwiched between two glass plates, and a weight is applied so that the load applied to the area becomes 1 kg. The sample thus set is heat-treated for 1 hour in a hot-air circulation oven heated to 90 ° C., and then left to cool for 1 hour or more at room temperature. The two samples were peeled at an angle of 180 °, the peeling force was read with a spring, and the average value of n = 3 was determined.

(2) Center line average roughness (Ra) Measured according to JIS B-0601 (1982). However, the cutoff was 0.25 mm.

(3) Haze Measured according to 6.4 of JIS K-7105 (1981).

(4) Heat shrinkage rate According to JIS C-2330 (1995),
After measuring the heat shrinkage in each of the width directions, the sum of the heat shrinkage in the longitudinal direction and the heat shrinkage in the width direction was obtained.

(5) Wetting tension Measured according to JIS K-6768 (1995).

[0024]

Next, an embodiment of the present invention will be described. Example 1 1,3,5 trimethyl-2,4,6-tris (3,5-
26-polypropylene resin containing 0.5% by weight of di-tert-butyl-4hydroxybenzyl) benzene
It is fed to an extruder at 0 ° C., melted, extruded into a sheet from a T-die, cooled and solidified by a cooling roll at a temperature of 35 ° C., stretched 5 times in the longitudinal direction at a temperature of 140 ° C., and then in a width direction. Stretched 10 times at a temperature of 167 ° C.
Heat treatment was performed at a temperature of 65 ° C. Thereafter, the non-bonded surface was subjected to a corona discharge treatment and wound up with a winder.

At this time, the film thickness is 15 μm, and the center line average roughness Ra of the surface to be bonded to another material is 0.02 μm.
m, center line average roughness of the opposite surface is 0.03 μm, haze is 0.5%, heat shrinkage in the longitudinal direction is 2.8%, heat shrinkage in the width direction is 0.5%, non-bonded surface Has a wetting tension of 3
5 mN / m, and the film peeling force was 1.0 g.

Further, the film was adhered to an adhesive tape (splicing tape No. 322 manufactured by Nitto Denko Corporation) using a polyethylene terephthalate film as a base layer, and then the transfer trace to the adhesive layer was observed when the film was peeled off again. However, there were no transfer marks.

Example 2 A polypropylene film was obtained under the same conditions as in Example 1 except that the polymer extruded into a sheet from a T-die was cooled and solidified by a cooling roll at a temperature of 65 ° C.

At this time, the film thickness is 15 μm, and the center line average roughness Ra of the surface to be bonded to another material is 0.03 μm.
m, center line average roughness of the opposite surface is 0.07 μm, haze is 1.5%, heat shrinkage in the longitudinal direction is 2.8%, heat shrinkage in the width direction is 0.5%, non-bonded surface Has a wetting tension of 3
5 mN / m, and the film peeling force was 0.5 g.

This film was adhered to an adhesive tape (splicing tape No. 322, manufactured by Nitto Denko Corporation) using a polyethylene terephthalate film as a base layer, and then the transfer trace to the adhesive layer when peeled off again was observed. There were no traces.

Example 3 A polypropylene film was obtained under the same conditions as in Example 1 except that the corona discharge treatment was performed so that the wetting tension of the non-bonded surface was 37 mN / m.

At this time, the film thickness was 15 μm, and the center line average roughness Ra of the surface to be bonded to another material was 0.02 μm.
m, the center line average roughness of the opposite surface is 0.03 μm, the haze is 0.5%, the heat shrinkage in the longitudinal direction is 2.8%, the heat shrinkage in the width direction is 0.5%, and the film peeling force is It was 3.0 g.

Further, this film was adhered to an adhesive tape using a polyethylene terephthalate film as a base layer (splicing tape NO. 322 manufactured by Nitto Denko), and the transfer trace to the adhesive layer when the film was peeled off again was observed. However, there were no transfer marks.

Comparative Example 1 The same conditions as in Example 1 except that a polypropylene resin containing 0.5 wt% of tetrakis [methylene-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane was used. To obtain a polypropylene film.

At this time, the film thickness is 15 μm, and the center line average roughness Ra of the surface to be bonded to another material is 0.02 μm.
m, center line average roughness of the opposite surface is 0.03 μm, haze is 0.5%, heat shrinkage in the longitudinal direction is 2.8%, heat shrinkage in the width direction is 0.5%, non-bonded surface Has a wetting tension of 3
5 mN / m, and the film peeling force was 8.0 g.

This film was adhered to an adhesive tape (splicing tape No. 322, manufactured by Nitto Denko) using a polyethylene terephthalate film as a base layer, and then the transfer trace to the adhesive layer when peeled off again was observed. However, on the contrary, the adhesive layer was transferred to the release film, which was not practical.

Comparative Example 2 A polypropylene film was obtained under the same conditions as in Comparative Example 1 except that the polymer extruded into a sheet from a T-die was cooled and solidified by a cooling roll at a temperature of 95 ° C.

At this time, the film thickness is 15 μm, and the center line average roughness Ra of the surface to be bonded to another material is 0.05 μm.
m, center line average roughness of the opposite surface is 0.10 μm, haze is 3.5%, heat shrinkage in the longitudinal direction is 2.8%, heat shrinkage in the width direction is 0.5%, non-bonded surface Has a wetting tension of 3
5 mN / m, and the film peeling force was 6.0 g.

Further, this film was adhered to an adhesive tape (splicing tape NO. 322 manufactured by Nitto Denko) using a polyethylene terephthalate film as a base layer. It was not possible, and there were many traces of transfer to the adhesive layer when the film was peeled off again thereafter, which was not practical.

[0039]

According to the present invention, it is possible to obtain a releasing polypropylene film which can be easily peeled off after being bonded to another material and then peeled off, and a transfer mark after peeling is hardly left on the other material.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29L 7:00 B29L 7:00 (72) Inventor Tadashi Kawada 2-1 Kitakami Tatemachi, Tsuchiura City, Ibaraki Prefecture Toray Stock F-term in the Tsuchiura Plant (reference) 4F071 AA20 AC05 AC11 AC19 AE05 AF04Y AF30Y AH19 BC01 BC16 4F210 AA11 AB06 AF16 AG01 QC06 QG01 QG18 4J002 BB121 BB14W BB15W EC056 EJ026 EU186 FD076 GT00

Claims (4)

[Claims] An antioxidant contained in a film is an antioxidant containing no carbonyl group, and at least a center line average roughness Ra of a bonding surface is 0.04 μm or less. Polypropylene film for mold. 2. The release polypropylene film according to claim 1, wherein the film contains only a phenolic antioxidant containing no carbonyl group as an antioxidant in the film. 3. The release polypropylene film according to claim 1, wherein the haze is 2.5% or less. 4. The release polypropylene film according to claim 1, wherein the wet tension of the non-bonded surface of the film is 33 mN / m or more and 37 mN / m or less.