JPH11170440A - Release polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film excellent in release characteristics, where a release layer having high surface hardness and excellent resistance to scratching is provided. SOLUTION: A release polyester film is formed by providing, on a polyester film 1, a coated film (a release layer) 2 composed of a composition, where 0.3-10 pts.wt. graft-type silicone resin having an acrylic skeleton is mixed with respect to 100 pts.wt. melamine hardening epoxy resin and/or acrylic/melamine thermosetting resin. The thickness of the coated film 2 is 0.03-1 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a releasable polyester film, and more particularly, to a film having excellent adhesion between a base film and a releasable coating film, and having releasability and scratch resistance on the surface of the coating film. The present invention relates to a polyester film having excellent properties.

[0002]

2. Description of the Related Art A biaxially stretched polyester film represented by polyethylene terephthalate has excellent properties such as transparency, dimensional stability, mechanical properties, and chemical resistance. Are used in various industrial fields such as graphic materials.

By the way, in applications such as various process papers, since a resin is cast on a polyester film and then separated from the film, at least release performance is required. However, if the conventional polyester film is used as it is in applications requiring release properties as described above, the peeling strength is too high, so that peeling becomes impossible or peeling failure occurs, resulting in production. There was a problem of causing troubles in the process.

[0004] For this reason, a so-called releasable film, which is provided with a coating film made of a silicone resin or the like in order to impart releasability to the film surface, is usually used for such applications.

[0005] Silicone resins applied to impart such release properties are roughly classified into two types: addition type and condensation type. There is a problem that a part of the layer easily migrates to the adjacent film surface. Such a problem is, for example, when used in a thermal transfer application in which a transfer ink layer and an adhesive layer are sequentially provided on a release layer, the release layer transfers onto the transfer ink, and is used to protect the subsequent ink. Impede processing.

In order to solve such a problem, it is effective to improve the adhesion between the silicone resin and the base film and the surface hardness of the release layer to improve the scratch resistance. There is a release film in which a release layer is formed using a composition in which a binder resin is mixed with a silicone resin. However, in this film, since the compatibility between the silicone resin and the binder resin is low, it was difficult to satisfy both the adhesiveness and the releasability in the first place.

Therefore, if the silicone resin can be uniformly dispersed in the hard coat agent based on the thermosetting resin, the silicone resin is present on the surface of the coating film. The moldability can be obtained, and the surface hardness can be increased. Furthermore, it is easy to adjust the releasability (peeling strength) by changing the content of the silicone resin in the mixed composition. However, a silicone-based resin having a practical composition in a usual hard coat agent and uniformly dispersing and dissolving and a combination thereof have not been found.

[0008]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention aims to provide a polyester film having a release layer which is excellent in releasability and has a high surface hardness and excellent scratch resistance. Is what you do.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve this problem, and have found that a melamine-cured epoxy resin and / or an acrylic / melamine-based thermosetting resin and a specific silicone-based resin are used. When they are combined, they are uniformly dispersed and compatible, and it has been found that a polyester film having both releasability and scratch resistance can be obtained by applying this mixed solution, and the present invention has been achieved.

That is, the gist of the present invention is to provide a polyester film having a graft type silicone resin having an acrylic skeleton per 100 parts by weight of a melamine-cured epoxy resin and / or an acrylic / melamine-based thermosetting resin.
A releasable polyester film provided with a coating film comprising a composition in which parts by weight are mixed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the present invention, the base polyester film is a uniaxially or biaxially stretched film made of a polyester-based resin, as long as it has excellent strength and transparency. The polyester that makes up the film
Any type may be used as long as it has a film forming property, and the type thereof is not particularly limited, but aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid and diols such as ethylene glycol, propylene glycol, and 1,4-butanediol. Polyester obtained by polycondensation with terephthalic acid and ethylene glycol is particularly preferable.

The base polyester film is preferably subjected to physical and chemical treatments in advance in order to improve the adhesion to the coating film.

[0014] The polyester film of the present invention is characterized in that at least one surface is provided with a coating film composed of a mixture of a specific thermosetting resin and a silicone resin. By providing this coating film, a film having excellent release properties can be obtained, and since the silicone resin is dispersed in the thermosetting resin, the surface hardness of the coating film surface is increased and the scratch resistance is improved. And the transfer of the silicone resin to the adjacent film surface, which is a problem of the conventional film, is suppressed.

In the present invention, the thermosetting resin includes
Melamine-cured epoxy resin and / or acrylic / melamine-based thermosetting resin is used. Specific examples of such a thermosetting resin include SF manufactured by Dainippon Ink and Chemicals, Inc.
-409, SF-413, SF-910H, A-911, A-914
, A-915 and EX 114D media manufactured by Dainichi Seika Kogyo Co., Ltd. and the like.

The silicone resin has a structure in which a silicone component is grafted on an acrylic skeleton, and has a glass transition temperature (Tg) of 150 ° C. or less, preferably 60 to 100 ° C.

Specific examples of such silicone resins include Cymac US-120 and US-15 manufactured by Toa Gosei Co., Ltd.
0, US-210, US-270, US-300, US-350
And Aaron GS-30.

The ratio of the thermosetting resin to the silicone resin should be 0.3 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the thermosetting resin. . If the proportion of the silicone resin is smaller than this, the release performance is poor, while if the proportion of the silicone resin is too large, the curing reaction of the thermosetting resin is inhibited, and the adhesion to the base film and the surface hardness decrease. .

What is important when mixing the silicone resin and the thermosetting resin is the dispersibility or compatibility of the two, and if these are insufficient, uniform release performance cannot be obtained. However, there is a problem in the curability of the thermosetting resin. The thermosetting resin and the silicone resin in the present invention can be uniformly dispersed and form a coating film having a sufficient surface hardness.

The thickness of the coating film is 0.03 to 1 μm after drying and curing.
m, preferably in the range of 0.05 to 0.8 μm. If the thickness of the coating film is less than 0.03 μm, satisfactory release performance cannot be obtained. On the other hand, if the thickness of the coating film is 1
If it is larger than μm, it takes time for drying and curing, which is not only inconvenient in production, but also may cause curling of the polyester film with the coated surface as the inner surface.

The coating film is formed by dissolving and diluting a thermosetting resin in a solvent, adding a silicone-based resin, applying a uniformly dispersed coating liquid to a polyester film, and then drying and curing. Will be As the application method,
Known methods such as a gravure roll method, a spray method, a roll coater method, and a reverse roll coating method can be adopted,
The gravure roll method is suitable for adjusting the coating amount.

The drying and curing conditions after application are as follows: temperature 80 to 200
C., preferably 150-190.degree. C., and the time is suitably in the range of 5-30 seconds, preferably 10-20 seconds. Dry and harden the coating film sufficiently so that the physical properties can be fully expressed.
The curing temperature and time may be appropriately combined within the above range. However, if the drying / curing temperature is lower than 80 ° C., the curing reaction does not proceed sufficiently, and the adhesion to the base film, the solvent resistance and the surface hardness become insufficient. If the drying / curing temperature is higher than 200 ° C., wrinkles due to heat loss of the polyester film are strongly generated, and spots may be generated when ink or the like is applied in the next step.

If necessary, a curing catalyst such as an organic acid may be contained in the coating solution as long as the physical properties of the coating film are not impaired.

Further, the polyester film of the present invention comprises:
In order to suppress the silicone resin from falling off or set off from the coating film and to prevent blocking, it is desirable that the surface hardness of the coating film surface be H or higher in pencil hardness. When the pencil hardness is lower than H, scratch resistance is poor, and when the film is wound into a roll, blocking may occur between adjacent films. The higher the surface hardness is, the more preferable. The upper limit is not particularly limited, but it is difficult to make the pencil hardness higher than 3H. In addition, the surface hardness of the coating film surface can be adjusted by the composition and application amount of the coating solution.

The polyester film of the present invention is used, for example, as heat transfer paper in a film configuration as shown in FIG. In FIG. 1, a coating film (release layer) 2, an ink layer 3, and a hot-melt adhesive layer 4 are sequentially coated on one side of a polyester film 1.

The film shown in FIG. 1 is used by being thermally transferred onto a transfer substrate via a hot-melt adhesive. Examples of the hot-melt adhesive include a polyester-based adhesive and a polyolefin-based adhesive mainly containing an ethylene-vinyl acetate copolymer.

[0027]

Next, the present invention will be described specifically with reference to examples. In addition, the raw materials and evaluation methods used in the examples are as follows.

1. Ingredients ・ Thermosetting resin “EX114D Medium” Acrylic / melamine thermosetting resin liquid (solid content: 75% by weight) manufactured by Dainichi Seika Kogyo Co., Ltd. ・ Silicone resin “CYMAC US-270” manufactured by Toa Gosei Co., Ltd. , Graft type silicone resin having an acrylic skeleton, solid content concentration 30% by weight) ・ Polyester film “Emblet” Biaxially oriented polyethylene terephthalate film (25 μm thick) manufactured by Unitika Ltd.

2. Evaluation method (a) Adhesion of coating film Cellophane tape (Nichiban Co., Ltd.,
Elpack LP-24) was pressed, and the cellophane tape was vigorously peeled off in the 180 ° direction (positive cellophane tape peeling). The degree of the adhesive strength of the cellophane tape was evaluated according to the following three grades. ：: Adhesive strength is maintained. Δ: Adhesion was partially impaired. X: The adhesive strength is completely impaired. (b) Blocking resistance A piece of film having a size of 7 cm x 7 cm was sampled, and then 15
The sheets were stacked and pressed under a load of 10 kg at a temperature of 40 ° C. for 24 hours, and evaluated according to the following three grades depending on the degree of blocking. ：: There is no blocking, and there is no catch when peeling. Δ: Slightly caught or a little sound was heard when peeling. ×: Strongly caught when peeled, damage is observed on the film surface. (c) Pencil hardness (scratch resistance) Measured according to JIS K 5400. (d) Peeling strength Adhesive tape 31B (tape width 50 mm) manufactured by Nitto Denko Corporation is applied to the coated surface of the film, and a load of 20 g / cm ² is applied at 70 ° C.
After leaving for 30 minutes, cool for 30 minutes, adjust the humidity in an atmosphere of 20 ° C and 65% RH,
The 180 ° peel strength was measured at 00 mm / min. (e) Residual adhesive rate The adhesive tape (peeled to the film and peeled off) used for the peel strength measurement was used as a sample, this was adhered to a clean stainless steel plate, and pressed with a rubber roll (one round trip of a 2 kg rubber roll). The peel strength was measured under the same conditions as above. As a blank, a new adhesive tape 31B manufactured by Nitto Denko Corporation was applied to a clean stainless steel plate, and pressed with a rubber roll (one reciprocation of a 2 kg rubber roll), and the peel strength was measured under the same conditions as above. Residual adhesion rate (%) = [(peeling strength of sample / peeling strength of blank)] × 100

Examples 1 to 4 A thermosetting resin "EX114D Medium" was diluted with methyl ethyl ketone (MEK) to prepare a resin solution having a solid content of 35% by weight. After adding MEK to this resin solution so as to have an appropriate solid content concentration according to the thickness of the coating film, the silicone resin “CYMAC US-270” was added to the thermosetting resin (TSR) and the silicone resin. (SiR) was added so as to have a weight ratio shown in Table 1 and sufficiently stirred at room temperature to obtain a uniform coating solution. This coating solution was applied to a polyester film “Embret” by a gravure roll method, and dried and cured at 190 ° C. for 20 seconds to obtain a coating film having a coating film thickness shown in Table 1. Table 1 shows the results of evaluating the characteristics of the obtained film.

Comparative Example 1 A coating film was prepared in the same manner as in Example 1 except that a resin solution prepared by diluting a thermosetting resin “EX114D Medium” with MEK to a solid content concentration of 35% by weight was used as a coating solution. A formed film was obtained. Table 1 shows the results of evaluating the characteristics of the obtained film.

Comparative Example 2 As a coating liquid, a silicone resin "CYMAC US-27" was used.
0 ", and a film-forming film was obtained in the same manner as in Example 1 except that the thickness of the coating film was 0.50 μm.

Table 1 shows the results of evaluating the properties of the obtained film.

[0034]

[Table 1]

[0035]

According to the present invention, it is possible to obtain a polyester film which has both releasability and scratch resistance, and in which, even when wound up in a roll, blocking of an adjacent surface and migration of a silicone resin are suppressed. be able to. And this polyester film can be used suitably as various process papers, such as a thermal transfer use.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a film configuration when a polyester film of the present invention is used as thermal transfer paper.

[Explanation of symbols]

 Reference Signs List 1 polyester film 2 coating film (release layer) 3 ink layer 4 hot melt adhesive layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 161/28 C09D 161/28 163/00 163/00 183/10 183/10 (72) Inventor Chiemi Nishitani Uji, Uji, Kyoto 31-3 Hinojiri Unitika Uji Plastic Factory Co., Ltd. (72) Inventor Tomoko Yamanaka 31-3 Uji Hinojiri Uji City, Kyoto Prefecture Unitika Uji Plastic Factory Co., Ltd.

Claims (3)

[Claims] 1. A composition obtained by mixing 0.3 to 10 parts by weight of a graft type silicone resin having an acrylic skeleton with respect to 100 parts by weight of a melamine-cured epoxy resin and / or an acrylic / melamine-based thermosetting resin in a polyester film. A releasable polyester film characterized by having a coating film formed thereon. 2. The polyester film according to claim 1, wherein the thickness of the coating film is 0.03 to 1 μm. 3. The polyester film according to claim 1, wherein the pencil hardness of the coated surface is H or higher.