KR101722717B1 - Polyester release film - Google Patents

Abstract

More particularly, the present invention relates to a polyester release film, and more particularly to a polyester release film which solves the problem of increase in haze caused by lamination in two or more layers by controlling the amount of surface particles at the time of film production, Transparent window and a high transparency window release film for a window.

Description

POLYESTER RELEASE FILM [0002]

More particularly, the present invention relates to a polyester release film, and more particularly to a polyester release film, which solves the problem of increase in haze caused by lamination in two or more layers by controlling the amount of surface particles during the production of a film, , And a high coefficient of friction of 0.1 or more.

The release film is provided with a cured film of a silicone composition on the substrate surface in order to prevent peeling or sticking between a substrate such as paper or a plastic film and a sticky material, thereby imparting peelability. When the substrate surface is a plastic film, it is generally called a release film. Such a release film may be used as an adhesive surface protective film for a pressure-sensitive adhesive, an adhesive, a pasting medicine, etc., or a carrier for forming a sheet of resin For example, a ceramic sheet, an electrode sheet and the like. Examples of such release films include Korean Patent No. 10-0879003 (Jan. 09, 2009).

In recent years, as the use and variety of optical products have diversified, release films have been widely used in the production of window films in addition to the above applications. These release films for windows provide temporary protection of the adhesive adhesive surface of the adhesive product from contamination by dust, debris, moisture and other contaminants until the end customer is ready for use. In general, the release film is separated from the adhesive surface immediately prior to use of the adhesive product. Therefore, if the release film is bonded to the adhesive adhesive surface, it should not spontaneously fall off without peeling force, but it should be easily removed with relatively low peeling force (releasability), and the residual adhesive force of the adhesive should not be reduced. Further, when the release film is separated from the adhesion surface, the release coating layer of the release film itself remains intact, i.e., the internal adhesion of the release film is also important. However, in the case of a release film for a window, in addition to the above properties, a high transparency is additionally required since the product is shipped with the release film laminated to the end customer.

Korean Patent No. 10-0879003 (Jan. 09, 2009)

In order to solve the above problems, it is an object of the present invention to provide a polyester release film for a high transparency window having a haze level of 2.0 or less through controlling the content of silica, which is a particle used in the production of a release film.

It is another object of the present invention to provide a release film which does not cause any problem in winding characteristics that may occur when the silica particle content is reduced.

The present invention also provides a polyester release film which is excellent in releasability and excellent in transparency by using particles having a large particle diameter through surface modification of silica particles.

The present invention relates to a release film, and more particularly to a polyester release film having high transparency.

Specifically, the present invention relates to a polyester resin composition comprising a polyester resin, a base film comprising silica particles surface-treated with sodium aluminate, and a release layer formed on one side of the base film and having a haze according to ASTM D-1003 of not more than 2.0, ASTM D-1894 To a polyester releasing film having a coefficient of friction of 0.1 or more.

The silica particles are preferably contained in an amount of 30 to 500 ppm.

The silica particles preferably have an average particle diameter of 20 nm to 10 탆, more preferably an average particle diameter of 3.6 to 10 탆. At this time, it is preferable that the surface coating thickness of the surface-treated sodium aluminate is 30 to 60 nm.

The releasing layer is formed by coating and heat-treating an emulsion composition comprising 1 to 25% by weight of a silicone-based binder resin, 1 to 20 ppm of a platinum catalyst, 70 to 95% by weight of water and 0.5 to 10% by weight of an emulsifier.

The base film preferably has a thickness of 7 to 50 mu m.

As described above, the release film of the present invention can be applied to a releasing film for window which satisfies a level of 0 to 2.0 in haze and needs transparency by controlling the content of silica particles contained in the step of producing a polyester base material film It is effective.

In addition, the release film of the present invention minimizes the content of silica particles to be applied, thereby preventing cost loss due to excessive use of the particles.

Hereinafter, the present invention will be described in more detail.

In order to achieve the above object, it is possible to achieve high transparency through surface modification of the silica particles to be applied to the polyester base film (PET) and to control the content of silica particles.

It is characterized in that the haze according to ASTM D-1003 is 2.0 or less and the friction coefficient according to ASTM D-1894 is 0.1 or more. If the haze exceeds 2.0, it is not suitable for use as a release film for windows. If the coefficient of friction is less than 0.1, it may occur that the roll form is lost during film winding in the process. More preferably, the present invention relates to a polyester release film having a haze of 0.4 to 1.9 and a coefficient of friction of 0.1 to 0.2.

The silica particles used in the present invention are not limited in size or shape, but preferably have an average particle diameter of 20 nm to 10 탆, a spherical shape, and an average particle size of 3.6 to 10 탆. Further, the present invention improves the dispersibility of the particles through the surface modification of the silica particles, and satisfies the target level of 0 to 2.0 even when large particles having a size of 3.6 to 10 탆 are used, A film can be provided. As the surface modifying material, sodium aluminate is used. The sodium aluminate is used for enhancing the affinity between the spherical silica particles and the polyester resin, thereby improving the dispersibility of the particles and suppressing the voiding phenomenon that may occur during the stretching. have. The surface coating thickness of the sodium aluminate is preferably 30 to 60 nm, and the desired haze can be satisfied in the above range.

These silica particles are used as factors that provide stability in the on-going operation of the polyester base film-forming process. That is, if the content of the silica particles is insufficient, the film roll foam may be deformed at the time of winding the product, or workability problems such as scratches occurring at the time of roll passing may occur, resulting in poor workability.

The present invention satisfies the target level of releasability and haze level through the control of the silica particle content and also solves the problem of winding and scratches. The silica particles are preferably contained in an amount of 30 to 500 ppm, Is better. When the silica particles are contained in an amount of less than 30 ppm, workability problems such as deformation of the film roll foams or occurrence of scratches during roll passing occur at the time of winding described above. When the silica particles exceed 500 ppm, 2.0 or more, which makes it difficult to apply to window applications requiring high transparency.

The polyester base film layer is preferably a uniaxially or biaxially stretched polyethylene terephthalate film. After the surface treatment such as corona treatment is performed for strong chemical bonding between the base material and the coating layer, the composition of the coating layer of the present invention The thickness of the base film layer is preferably 7 to 50 mu m, more preferably 15 to 25 mu m. When the thickness is less than 7 mu m, the elasticity is insufficient and the peeling is difficult to occur at the time of releasing. When the thickness exceeds 50 mu m, the haze increases and it is difficult to apply to window applications.

The composition of the coating layer of the release film of the present invention can be prepared in an emulsion or a solvent form, and a coating layer can be formed by selecting an appropriate method according to the application. The following examples are merely illustrative of the results of using emulsion-type compositions in order to more specifically illustrate the present invention, and the scope of the present invention is not limited to these examples.

The emulsion-type composition may contain 1 to 25% by weight of a silicone-based binder resin, 1 to 20 ppm of a platinum catalyst, 70 to 95% by weight of water and 0.5 to 10% by weight of an emulsifier. The composition described above may be used, but not limited to, those described in Patent Documents 10-1049527 and 10-2009-0070204.

The method of coating the polyester base film with the emulsion-type composition is not particularly limited, but it is preferable to proceed with in-line coating, and the release film of the present invention can be produced by proceeding to the following process.

 a) melt-extruding the polyester resin and the silica particles surface-treated with sodium aluminate, and then uniaxially stretching in the machine direction to produce a polyester base film;

b) coating the emulsion-type composition on one surface of the substrate film to form a coating layer; And

c) drying the film having the coating layer formed thereon at 200 to 230 ° C for 5 to 30 seconds to stretch the film in the width direction to form a release film;

.

At this time, in the step b), the coating method may be applied by a gravure or bar coating method, and the coating amount is preferably applied by 1 to 100 탆 (wet).

It is preferable that the stretching is performed 2 to 6 times in the machine direction in the step c).

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

The requirements of the present invention and specific details for the measurement are as follows.

(1) Release force: FINAT 10 (Standard Tape: Nitto 31B)

The Nitto31B tape was placed on the release coating layer, and the sample was rubbed twice using 2 kg of rubber rolls, followed by cutting to a size of 50 mm × 15 cm. The prepared sample was allowed to stand at 70 DEG C for 1 day under a load of 70 g / cm < 2 > and subjected to a peel tester (ChemInstrument, AR-1000) The peeling speed was 300 mm / minute (0.3 mpm).

(2) Adhesion: KOLON METHOD

The adhesion can be roughly classified into two types.

① Smear (phenomenon that the surface of the silicone coating layer is pushed like oil)

② Rub-off (phenomenon that the silicon coating layer is pushed like the case)

The evaluation method of adhesion is as follows. The peel-off coating layer was strongly rubbed by reciprocating 5 times using a thumb, and the degree of peeling of the coating layer was evaluated by observing the degree of ink wetting using a lubricant pen. If the adhesion is weak and smear and love-off have occurred, ink wetting will occur on that area.

<Classification level>

  Class A: Smear is not observed at all.

  Class B: The smear phenomenon begins to be observed.

  Class C: The Rub-Off phenomenon begins to be observed.

Class D: Love-off phenomenon is easily observed.

(3) Transfer rate (Silicone Transfer): KOLON METHOD

The residual adhesion rate was measured by measuring the transfer of the remaining silicone to the opposite side of contact.

Residual Adhesion Ratio: A method for confirming the transfer of a silicone release film to a pressure sensitive adhesive after laminating the pressure sensitive adhesive. The releasing film is laminated on a pressure sensitive adhesive to induce transfer in a severe condition, and then the adhesiveness of the pressure sensitive adhesive do. In general, a residual adhesion rate of 95% or more is required.

The evaluation method is as follows.

The Nitto31B tape was placed on the release coating layer, and the sample was rubbed twice using 2 kg of rubber rolls, followed by cutting to a size of 50 mm × 15 cm. The prepared sample is subjected to a load of 70 g / cm &lt; 2 &gt; and left at 70 DEG C for 1 day. In addition, Nitto31B tape is laminated to a Teflon tape in the same manner as above, and the same pretreatment is carried out at 70 DEG C for 1 day. In both samples, the Nitto31B tape attached to the release coating layer was removed, and the tape was laminated to a separate PET film. Finally, the difference in adhesion between the two types of tapes and PET determines how much silicone in the release coating layer is transferred to the tape.

Residual adhesion rate (%) = (Adhesion of release film Lami.Tape to polyethylene terephthalate (PET) film) X 100 / (Adhesion of Teflon Lami.Tape to polyethylene terephthalate (PET) film)

 <Classification level>

  ◎ Grade: Residual adhesion rate 95% or more.

  ○ Rating: Residual adhesion rate 90 ~ 95%

  △ grade: residual adhesion rate 80 to 90%

× grade: residual adhesion rate less than 80%

(4) Haze: ASTM D-1003

Haze is measured using an NDH-5000 product (NIPPON DENSHOKU INDUSTRIES).

When the haze exceeds 2.0, it is unsuitable for use as a release film for windows.

(5) Coefficient of friction: ASTM D-1894

The workability associated with winding can be expected mainly by measuring the coefficient of friction. Generally, when the coefficient of friction is less than 0.1, there is a problem of roll-form drop-out during the process winding in the workability, but when the friction coefficient is 0.1 or more, the work is smooth. Friction Tester TR-2 product (TOYOSEIKI) is used as the friction coefficient gauge.

(6) Appearance

In order to be used as a release film for windows, visual evaluation of the appearance is required and it is defined as occurrence of scratches, foam dropping, and surface opacity. Scratches are generally caused by the difference in peripheral velocity between the film and the guide roll during running. Form dropping occurs due to tension nonconformity at the time of winding, and surface whitening phenomenon is a phenomenon in which the degree of dispersion of particles is poor, It says. The criteria for appearance are as follows. A case where all three items below are satisfied is indicated as X, and a case where any of the following three items are unsatisfied is regarded as X.

<Criteria>

1. Scratch: Scratches with a size of 1 cm or more of 0.15ea / m ² or less are managed (visual evaluation)

2. Foam dropout: No dropout problem

3. Surface cloudiness: No cloudiness

[Example (1)]

Preparation of coating liquid (A)

The silicone binder resin was mixed in an amount of 50 wt% of the total solid content, 10 wt% of the crosslinking agent containing the phenyl group, and 40 wt% of the total solid content of the crosslinking agent containing no phenyl group, Water was added so that the content was 10% each. The platinum catalyst was used as an additive in an amount of 100 ppm based on the resin content. The emulsifier was used in an amount of 5 parts by weight based on 100 parts by weight of the solid content of the coating liquid, and the adhesion promoter was mixed with 0.2% by weight of the total solids content of the coating liquid.

As the binder resin, divinylpolydimethylsiloxane (viscosity 14000, mPa.s) was used, and as the crosslinking agent containing a phenyl group, the following structural formula 1 was used.

[Structural formula 1]

(m = 10, n = 10, o = 10)

As the crosslinking agent not containing a phenyl group, the following structural formula 2 was used,

[Structural formula 2]

(a = 10, b = 10)

The catalyst was a platinum catalyst (Na ₂ PtCl ₄ .4H ₂ O), an emulsifier polyvinyl alcohol (Stroust Co., Mowiol 4-80), and an adhesion promoter γ-acryloxypropyltrimethoxysilane.

Production of release film

A polyethylene terephthalate resin containing 30 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded and then quenched to obtain a sheet. The sheet thus obtained was preheated at 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Example (2)]

Production of release film

A polyethylene terephthalate resin containing 50 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded and subjected to rapid cooling to obtain a sheet. The sheet thus obtained was preheated at 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Example (3)]

Production of release film

A polyethylene terephthalate resin containing 100 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded and subjected to rapid cooling to obtain a sheet. The sheet was preheated at 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Example (4)]

Production of release film

A polyethylene terephthalate resin containing 180 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded and then quenched to obtain a sheet. The sheet was preheated at 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Example (5)]

Production of release film

A polyethylene terephthalate resin containing 300 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded and then subjected to rapid cooling to obtain a sheet. The sheet thus obtained was preheated at 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Example (6)]

Production of release film

A polyethylene terephthalate resin containing 500 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded and subjected to rapid cooling to obtain a sheet. The sheet thus obtained was preheated at 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Comparative Example (1)]

The polyethylene terephthalate resin not containing silica particles (0 ppm) was melt-extruded, and the sheet obtained by quenching was preheated at 95 캜 in a preheating portion, and then stretched four times in the machine direction (MD). The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Comparative Example (2)]

A polyethylene terephthalate resin containing 800 ppm of silica particles having an average particle diameter of 3.8 탆 (surface coating thickness: 50 nm) surface-treated with sodium aluminate was melt-extruded, and the sheet obtained by quenching was pre-heated to 95 캜 in a pre- Direction (MD) and then cooled. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Comparative Example (3)]

A polyethylene terephthalate resin containing silica particles with a mean particle size of 3.8 mu m and a surface area of 3.8 mu m was melt-extruded, and then the sheet obtained by quenching was preheated at 95 DEG C in a preheating section, Followed by cooling. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Comparative Example (4)]

A polyethylene terephthalate resin containing silica particles having an average particle diameter of 3.8 탆 and a surface area of 3.8 탆 was melt-extruded, and the sheet obtained by quenching was preheated at 95 캜 in a preheating section, Followed by cooling. The coating solution (A) was applied to the cooled film using a gravure coater. After drying and preheating at 150 占 폚, the film was stretched 4 times in the transverse direction (TD), and the film was thermally fixed at 250 占 폚 to dry on a substrate film having a thickness of 23 占 퐉.

The physical properties and workability of the thus-prepared films were evaluated and are shown in Table 1 below.

[Table 1]

As can be seen from the results of Table 1, the haze value increases and the coefficient of friction also increases as the silica particle content increases. However, when the content of silica particles is 0 ppm, it can be seen that the workability is difficult due to the friction coefficient value of 0.1 or less. In fact, problems such as dropping of the roll form during winding and dropping of the roll form during transportation, I could confirm that there was a difficulty.

When the amount of silica particles is more than 500 ppm and 800 ppm, there is no problem in workability such as windability and scratching problem, but haze value is 3.7 and it is difficult to apply to window applications requiring transparency. That is, as can be confirmed in the case of Examples 1 to 6, it can be confirmed that the content of silica particles is most preferably 30 to 500 ppm, especially 30 to 180 ppm, when considering both haze and workability. In addition, it is also confirmed that the release properties such as the releasing force, the adhesion force, and the residual adhesion ratio of the silica particle content are largely irrelevant.

Further, as shown in Comparative Examples 3 and 4, when the surface-treated silica is used, it can be observed that the contrast haze is increased when the surface-treated silica is used. In the case of Comparative Example 4 in which 500 ppm of silica was applied, the haze was 3.2, which is unsuitable for use as a release film for windows. In Comparative Example 3, the haze was 1.3, The film is partially peeled off due to opacity and is also unsuitable for use as a release film for windows.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be obvious to the person.

Claims (6)

A base film comprising polyethylene terephthalate resin and 30 to 500 ppm of silica particles surface-treated with sodium aluminate having an average particle size of 3.6 to 10 탆, and a release layer formed on one surface of the base film,
A polyester release film having a haze of 2.0% or less according to ASTM D-1003 and a coefficient of friction of 0.1 or more according to ASTM D-1894. delete The method according to claim 1,
Wherein the surface coating thickness of the sodium aluminate is 30 to 60 nm. delete The method according to claim 1,
Wherein the releasing layer is formed by coating and heat-treating an emulsion composition comprising 1 to 25% by weight of a silicone-based binder resin, 1 to 20 ppm of a platinum catalyst, 70 to 95% by weight of water and 0.5 to 10% by weight of an emulsifier. The method according to claim 1,
Wherein the base film has a thickness of 7 to 50 占 퐉.