KR20200016320A - Release film and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a release film and a manufacturing method thereof. The release film of the present invention comprises: a polyester base layer having average surface roughness (SRa) of a 3D center line of 20 to 50 nm; and a release layer formed on at least one surface of the base layer and including an addition-reactive silicone release composition. Since the thickness of the release layer is 0.5 to 2 μm, the surface roughness of a typical substrate layer can be significantly lowered through a thick release layer, thereby reducing pinhole defects and reducing costs when applied to an MLCC manufacturing process. In addition, the release film of the present invention is capable of a winding process of winding the release film even if the thick release layer is included, blocking does not occur.

Description

Release film and its manufacturing method {RELEASE FILM AND MANUFACTURING METHOD THEREOF}

The present invention relates to a release film and a method of manufacturing the same, and more particularly, to prepare a multilayer ceramic capacitor (MLCC) process by providing a thick release layer including an addition-reactive silicon release composition to significantly lower the surface roughness of the release layer. It relates to a release film and a method for manufacturing the same that can suppress pinhole defects when applied to.

A release film is a protective film for adhering to a pressure-sensitive adhesive film and protecting an adhesive component from foreign substances or unwanted adherends in the air, and a structure having a release layer containing silicone polymer as a main component on one surface of a base layer is common.

Another special use of release films is in the manufacturing process of multilayer ceramic capacitors (MLCC). MLCC is manufactured by laminating several hundred layers of ceramic sheets and metal electrodes of a thin film. At this time, a release film is used as a carrier film for manufacturing a thin ceramic sheet. That is, a thin ceramic sheet is obtained by coating a ceramic slurry on a release film and then peeling off the dried ceramic slurry from the release film. In the case of the release film applied in the MLCC process, projections or irregularities on the release film cause pin hole defects of the ceramic sheet, and thus surface roughness showing the surface roughness of the release film is the most important characteristic. For this reason, efforts have been made in the industry to reduce surface roughness.

In the general release film of the art, the surface roughness of the polyester film used as the substrate is 20 to 50 nm, since the coating thickness of the release layer is as thin as 100 nm, the surface roughness of the release film is usually determined by the surface roughness of the substrate.

Therefore, in order to reduce the surface roughness of the release film, a method of preparing a polyester film having a low surface roughness and using it as a substrate is common. However, in order to reduce the surface roughness of the polyester film manufacturing process, special particles are required, and since the yield and productivity of the film are reduced, the application of such a film as a substrate inevitably raises the release film manufacturing cost.

As a method for obtaining a release film having a low surface roughness using a polyester film having a normal level of surface roughness as a substrate, a method of coating a separate smoothing layer on the substrate and coating the release layer on the smoothing layer again is proposed. It has been made [Patent Document 1]. However, since this method requires a separate coating process, the process cost increases and the yield falls.

One of ordinary skill in the art can easily think of making the coating thickness of the release layer sufficiently thicker than the surface roughness of the substrate without a separate smoothing layer. However, since the conventional release layer is mainly composed of silicone polymer, when a certain coating thickness (about 300 nm) is exceeded, a so-called blocking phenomenon occurs in which the release layer is sticky due to the low viscoelasticity of the silicone polymer. The winding process becomes impossible.

Accordingly, a method of adding metal oxide particles having a diameter of 2 to 5 µm to the release layer has been proposed as a method of solving the conventional blocking phenomenon and obtaining a release layer having a coating thickness of 2 µm [Patent Document 2]. However, the added metal oxide particles may also cause pinhole defects in the MLCC, so this solution is not suitable as a release film for MLCC.

On the other hand, as a method for providing a release layer having a thickness of 0.3 to 2 µm without containing particles without a blocking phenomenon, a method of coating an ultraviolet curable silicone has been proposed [Patent Document 3]. However, UV curable silicone is very expensive compared to thermosetting (additional reactive) silicone widely used in the art, and thus there is a problem in that the productivity of the release film is lowered.

Republic of Korea Patent Publication No. 10-2016-0127036 Republic of Korea Patent No. 10-1715688 Republic of Korea Patent Publication No. 10-2016-0140662

An object of the present invention is to provide a release film comprising a conventional substrate layer and addition reaction type silicone release composition, the surface roughness of the release layer is lower than the surface roughness of the base layer.

Another object of the present invention to provide a method for producing the release film.

In order to achieve the above object, the present invention is a release film formed of a polyester base layer and a release layer formed of an addition reaction type silicone release composition on at least one surface of the base layer, the three-dimensional center line average roughness of the surface of the base layer ( SRa) is 20 to 50nm, provides a release film having a three-dimensional centerline average roughness (SRa) of the surface of the release layer is 1 to 10nm, the release layer without containing particles for lowering the surface roughness The layer is characterized in that formed to a thickness of 0.5 to 2㎛.

In this case, the addition-reaction type silicone release composition comprises a polydimethylsiloxane having an alkenyl group, wherein the siloxane unit having an alkenyl group in the polydimethylsiloxane is characterized in that 5 to 10% by weight of the total siloxane units.

Thus, the surface hardness of the release layer of the present invention is characterized by measuring 2.0 to 5.0Gpa by nanoindentation.

In addition, the static friction coefficient between the release layer and the base layer satisfies 0.2 to 0.5.

Furthermore, the present invention provides a step of preparing an addition reaction type silicone release composition in which the siloxane unit having an alkenyl group in the polydimethylsiloxane skeleton is 5 to 10% by weight of the total siloxane units, wherein the addition reaction type silicone release composition is formed at least on the base layer. It provides a method for producing a release film to perform a step and the heat curing step of coating to a thickness of 0.5 to 2㎛ on one surface.

According to the release film of the present invention, by providing a thick release layer comprising an addition-reactive silicone release composition to significantly lower the surface roughness of the release layer than the surface roughness of the base layer to suppress pinhole defects when applied to the MLCC manufacturing process Can be.

In addition, even if the release film of the present invention includes a thick release layer, blocking does not occur, so the winding process of winding the release film is possible, thereby reducing costs.

1 is a schematic cross-sectional view of a release film according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a schematic cross-sectional view of a release film according to an embodiment of the present invention, the release film 100 of the present invention is a polyester base layer 110 and the addition reaction type silicon on at least one surface of the base layer 110 It is a release film formed with a release layer 120 formed of a release composition, the three-dimensional center line average roughness (SRa) of the surface of the base layer 110 is 20 to 50nm, the three-dimensional center line of the surface of the release layer 120 It provides a release film having an average roughness (SRa) of 1 to 10nm, the release layer thickness is 0.5 to 2㎛ without the particles for lowering the surface roughness of the release layer surface of the base layer through a thick release layer Roughness can be significantly lowered.

1. Base layer 110

As the base layer 110, any commercial polyester film may be used, and a biaxially stretched polyethylene terephthalate film having a thickness of 20 to 100 μm may be used.

The surface roughness of the polyester film surface is preferably 20 to 50nm based on the three-dimensional center line average roughness (SRa). At this time, if the surface roughness of the polyester film is less than 20nm, the surface roughness of the substrate is sufficiently low, so the surface roughness reduction effect by the coating of the release layer 120 provided by the present invention is insignificant, resulting in poor economical efficiency. On the other hand, if the surface roughness exceeds 50nm, even if the release layer 120 provided in the present invention surface roughness of the release layer 120 exceeds the preferred range (1 to 10nm), pinhole defects during the MLCC manufacturing process May occur.

2. Release layer 120

The release layer 120 may be formed by coating an addition reaction type silicone release composition on at least one surface of the substrate layer 110, followed by heat drying and curing.

The addition-reaction type silicone release composition may include a polydimethylsiloxane main chain having an alkenyl group, a polydimethylsiloxane curing agent having a hydroelectricity, a platinum catalyst, and a residual organic solvent. Specifically, addition reaction type silicone which comprises a mold release layer is obtained by addition reaction of the main chain which has polydimethylsiloxane which has an alkenyl group as a main component, and the hardening | curing agent which has polydimethylsiloxane which has a hydroelectric as a main component. In the case of using a commercially available silicone product, it is preferable to use a two-component product in which a silicone polymer product containing a main chain and a curing agent and a platinum catalyst are mixed and used at an appropriate ratio.

There is no particular restriction on the platinum catalyst, and commercial products consisting of 5000 to 10000 ppm of platinum and the residual amount of organic solvent may be used. Toluene is generally applied to the organic solvent, and in order to secure coating uniformity, one or more organic solvents such as n-hexane, n-heptane and n-octane may be mixed.

There is no particular limitation on the method of coating the release composition on the base layer 110, and bar coating, gravure coating, die coating, comma coating, or the like may be utilized.

It is preferable to apply a hot air dryer for drying and curing after the release composition coating, and the cured release film 100 may be obtained by heating at a temperature of 140 ° C. for 30 seconds.

3D center line average roughness SRa of the surface of the release layer 120 is preferably 1 to 10nm. At this time, the average roughness has a technical limit to achieve a surface roughness of less than 1nm, if it exceeds 10nm, pinhole defects may occur during the MLCC manufacturing process due to the projection of the surface of the release layer 120.

In the release film 100 of the present invention, the thickness of the release layer 120 is preferably 0.5 to 2㎛. At this time, if the thickness is less than 0.5㎛, the smoothing function of the release layer 120 is insufficient, the average roughness of the three-dimensional centerline of the surface of the release layer 120 is out of the above range, if the thickness exceeds 2㎛, release film (100) The surface roughness reduction effect is similar to that when the thickness is 2 μm or less, resulting in poor economic efficiency.

In order to prevent the blocking phenomenon without the release layer 120 containing particles, the present invention provides a release film 100 having a surface hardness value of 2.0 to 5.0 GPa measured by the nanoindentation method. In this case, if the surface hardness value of the release layer is less than 2.0 GPa, blocking phenomenon may occur due to viscosity. On the other hand, if it exceeds 5.0 GPa, the surface hardness value of the release layer may be achieved by using a commercial addition reaction type silicone polymer. It is difficult.

In order to provide the release layer 120 having the above preferred surface hardness value, in the present invention, it is preferable that the siloxane units having alkenyl groups in the polydimethylsiloxane skeleton having alkenyl groups are 5 to 10% by weight of all the siloxane units.

Since the siloxane unit having an alkenyl group in the polydimethylsiloxane skeleton acts as a crosslinking point when curing the silicone and determines the surface hardness of the release layer 120 after curing, the polydimethylsiloxane having an alkenyl group in the above preferred range has a sufficient number of crosslinking points. By having it has a preferred surface hardness. In this case, when the number of siloxane units having the alkenyl group is less than 5% by weight in the total number of siloxane units, the surface hardness value of the release layer 120 may be out of the preferred range (2.0 to 5.0 GPa), and blocking may occur. If the weight percentage is exceeded, curing of the release layer 120 becomes poor, and therefore, a commercial release agent is preferably 10% by weight or less.

In addition, the release layer 120 of the present invention preferably has a static friction coefficient of 0.2 to 0.5 with the base layer 110. At this time, if the static friction coefficient is less than 0.2, the slip property (sliding property) of the release layer is excessive and defects often occur in the cross section during the winding process often occur, and if it exceeds 0.5, blocking occurs and the film is stored for a long time. There is a problem that is bumpy and strong static electricity occurs.

The release film 100 of the present invention has a structure as described above, the release layer 120 thick enough to the surface roughness of the base film to cover the projections, irregularities, etc. of the base film, the surface of the release layer 120 Roughness is significantly lower than the surface roughness of the base layer 110.

Therefore, in the present invention, even if the release layer 120 has a thick coating thickness, blocking does not occur, and this is coated on the base layer 110 to a desired thickness to provide a release film 100 and the release film of the present invention Low surface roughness is suitable for MLCC manufacturing process.

In addition, the release film of the present invention can significantly reduce the surface roughness through the coating from the conventional level of the base film, thereby suppressing pinhole defects when applied to the MLCC manufacturing process and at the same time can contribute to cost reduction.

Hereinafter, the present invention will be described in more detail with reference to Examples.

This embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited by these examples.

<Examples 1-6 and Comparative Examples 1-9>

1. Base layer

Polyethylene terephthalate film (manufacturer: Toray Advanced Materials, product name: XD500P) having a 3D centerline surface roughness (SRa) of 23 nm was used as a base layer of Examples 1 to 6 and Comparative Examples 1 to 7, and Comparative Examples 8 to 9 A polyethylene terephthalate film (manufacturer: Toray Advanced Materials, product name: XJSH) having a three-dimensional centerline surface roughness of 120 nm was used as the substrate layer of.

2. Addition Reaction Type Silicone Release Composition

Polydimethylsiloxane backbones wherein the siloxane units having vinyl groups are 3% by weight of the total siloxane units; And a polymeric silicone product a mixed with a curing agent (manufacturer: Shin-Etsu, product name: KS-847H \),

Polydimethylsiloxane backbones wherein the siloxane units having vinyl groups are 5% by weight of the total siloxane units; And curing agents; Mixed polymer silicone product b (manufacturer: Shin-Etsu, product name: KS-839L) or

Polydimethylsiloxane backbones wherein the siloxane units having vinyl groups are 8% by weight of the total siloxane units; And curing agents; Mixed polymer silicone product c (manufacturer: Shin-Etsu, product name: KS-3601)

Platinum catalyst mixture liquid (manufacturer: Shin-Etsu, product name: PL-50T) of 5000 ppm concentration and the remaining amount of toluene were mixed in the same amounts as in Examples 1 to 6 and Comparative Examples 1 to 9 of Table 1 and then stirred at room temperature for 60 minutes. An addition reaction silicone release composition was prepared.

3. Coating and Curing

The addition reaction type silicone release composition prepared according to the conditions of Table 1 was coated on one surface of the substrate layer with Meyer Bar (manufactured by Cheminstruments, # 12 mesh) and then heat-cured at 140 ° C. for 1 minute using a hot air dryer. The release films of Examples 1 to 6 and Comparative Examples 1 to 9 were prepared.

Experimental Example

1. Deformation layer thickness measurement

After the release films of Examples 1 to 6 and Comparative Examples 1 to 9 were prepared, the coating thicknesses were measured by using a calibrated X-ray fluorescent spectroscopy.

2. Measurement of surface hardness

The hardness (storage modulus) values of the release films of Examples 1 to 6 and Comparative Examples 1 to 9 were measured using the nanoindentation method. Measured using MTS nanoindenter XP equipment, and read the surface hardness value at the depth corresponding to the center of the release layer of each release film. In determining the surface hardness measurement depth, the coating thickness measurement value of the release layer measured by the X-ray fluorescence analyzer was used.

3. Evaluation of blocking

After the release layers of the respective release films prepared in Examples 1 to 6 and Comparative Examples 1 to 9 were overlaid so as to be in contact with the substrate layer surface of the substrate layer, the mixture was left for 24 hours under a load of 100 gf / cm 2, and then the blocking phenomenon The presence or absence was evaluated.

The overlapping release film was visually observed under a fluorescent lamp to determine 'good' when no marks due to blocking were observed, and 'bad' when blocking marks were observed.

4. Measurement of static friction coefficient between release layer and base layer

Quantitative evaluation of the presence or absence of blocking was performed by measuring the static friction coefficient between the release layer and the base layer. The static friction coefficient was measured using HEIDON's TRIBOGEAR product.

5. Measurement of surface roughness

Three-dimensional center line average roughness (SRa) of the surface of the release layer was measured using a contact three-dimensional roughness measuring instrument (manufactured by KOSAKA SE3300), and the average value measured five times with a standard measuring length of 0.08 cm was described.

6. Evaluation of Pinhole Defects

100 g of barium titanate particles having an average particle diameter of 0.2 μm, 10 g of polyvinyl butyral, 8 g of toluene, and 2 g of butanol were mixed, stirred at room temperature for 12 hours, and then ball milled at 500 rpm for 24 hours to prepare a ceramic slurry. This was coated with a certain thickness on the release layer of the release film of each Example and Comparative Example using an applicator to prepare a release film having an average thickness of 1㎛ by hot air drying at 80 ℃ for 5 minutes. Thereafter, an area of 1 mm ² was observed 10 times with an interferometer microscope. If the number of pinholes exceeding 1 μm was 1 or more per unit area (mm ² ), it was determined as defective.

The results of evaluating the release films of Examples 1 to 6 and Comparative Examples 1 to 9 according to the experimental example are shown in Table 2 below.

As shown in Table 2, Examples 1 to 6 in which the three-dimensional centerline average roughness of the surface of the substrate layer, the thickness of the release layer, and the content of the siloxane unit having an alkenyl group in the silicon main chain all satisfy the preferable range provided by the present invention. The release film of the surface hardness value of the release layer was in the preferred range proposed by the present invention, thereby showing no blocking occurs.

In addition, the surface roughness of the release layer of Examples 1 to 6 in the range of 1 to 10nm, which is significantly lower than the surface roughness of the base layer 23nm it can be confirmed that the smoothing effect is large, pinhole defects even when coating the ceramic slurry You can see that it does not occur.

On the other hand, Comparative Examples 1 to 3 in which the content of the siloxane unit having an alkenyl group in the silicone main chain is less than the preferred range (5 to 10% by weight) of the present invention, the surface hardness of the release layer is outside the preferred range of the present invention. It can be seen that due to the viscosity of the blocking occurs strongly.

Even when the release layer is formed using a release agent containing a preferred polydimethylsiloxane backbone proposed in the present invention, the thickness of the release layer is not within the preferred range of the present invention (Comparative Example 4 and Comparative Example 6), or the base layer When the 3D centerline average roughness value of exceeds the preferred range of the present invention (Comparative Examples 8 to 9), the smoothing function of the release layer is insufficient and the surface roughness value of the release layer exceeds the preferred range of the present invention, so that the surface of the release layer is It can be seen that the pinhole defect occurs due to the projection of.

On the other hand, the release layer comprising a preferred polydimethylsiloxane backbone, but constituting the release layer, Comparative Example 5 and Comparative Example 7 in which the coating thickness of the release layer exceeds the preferred range of the present invention is thinner than Example 3 and practice Compared with Example 6, there is no difference in the surface roughness of the release layer, so it can be confirmed that the method is less economical than the same performance.

100: release film
110: substrate layer
120: release layer

Claims (3)

Polyester base layer and
It is a release film made of a release layer formed of an addition reaction type silicone release composition on at least one surface of the base layer,
Forming the release layer to a thickness of 0.5 to 2㎛ addition reaction silicone release composition, but does not contain particles for controlling the surface roughness in the addition reaction silicone release composition,
The addition-reaction type silicone release composition comprises a polydimethylsiloxane having an alkenyl group, the siloxane unit having an alkenyl group in the polydimethylsiloxane is 5 to 10% by weight of all the siloxane units,
The addition reaction silicone release composition comprises 10 to 19.9% by weight of polydimethylsiloxane having an alkenyl group and 80 to 89.8% by weight of an organic solvent,
The surface hardness of the release layer is measured by 2.0 to 5.0Gpa by nanoindentation,
Three-dimensional center line average roughness (SRa) of the surface of the substrate layer is 20 to 50nm,
3D center line average roughness (SRa) of the surface of the release layer is a release film, characterized in that to lower the surface roughness of the release layer compared to the base layer.
The release film of claim 1, wherein the coefficient of static friction between the release layer and the base layer is 0.2 to 0.5.
Preparing an addition reaction type silicone release composition wherein the siloxane units having alkenyl groups in the polydimethylsiloxane skeleton are 5 to 10% by weight of all the siloxane units;
Coating the addition-reactive silicon release composition to a thickness of 0.5 to 2 μm on at least one surface of a polyester base layer;
Perform a thermal curing step to form a release layer,
The addition reaction silicone release composition comprises 10 to 19.9% by weight of polydimethylsiloxane having an alkenyl group and 80 to 89.8% by weight of an organic solvent,
The surface hardness of the release layer is measured by 2.0 to 5.0Gpa by nanoindentation,
Three-dimensional center line average roughness (SRa) of the surface of the substrate layer is 20 to 50nm,
3D center line average roughness (SRa) of the surface of the release layer is 1 to 10nm, the method of manufacturing a release film, characterized in that the surface roughness of the release layer is lower than the base layer.

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