KR102193476B1 - 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 a three-dimensional centerline average roughness (SRa) of 20 to 50 nm and a release layer formed on at least one side of the base layer and comprising an addition-reactive silicone release composition. In addition, since the release layer has a thickness of 0.5 to 2 μm, the surface roughness of the conventional base layer can be significantly reduced through the thick release layer, so that pinhole defects can be suppressed and cost can be reduced when applied to the MLCC manufacturing process. In addition, even if the release film of the present invention includes a thick release layer, blocking does not occur, so that a winding process of winding the release film is possible.

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, a process of manufacturing a multilayer ceramic capacitor (MLCC) by significantly reducing the surface roughness of the release layer by providing a thick release layer containing an addition reaction-type silicone release composition. It relates to a release film capable of suppressing pinhole defects when applied to and a method of manufacturing the same.

A release film is a protective film that is usually attached to an adhesive film to protect the adhesive component from foreign substances or unwanted adhesives in the atmosphere, and has a structure including a release layer mainly composed of a silicone polymer on one side of the substrate layer.

Another special use of the release film is for the manufacturing process of laminated ceramic capacitors (hereinafter, MLCC). MLCC is manufactured by laminating several hundred layers of thin ceramic sheets and metal electrodes. In this case, a release film is used as a carrier film for manufacturing a thin ceramic sheet. That is, after coating the ceramic slurry on the release film, the dried ceramic slurry is peeled from the release film to obtain a thin ceramic sheet. In the case of a release film applied to such an MLCC process, the surface roughness indicating the surface roughness of the release film is the most important characteristic because the protrusions or irregularities on the release film cause pin hole defects in the ceramic sheet. Therefore, the industry has been making efforts to lower the surface roughness.

A typical release film in the art has a surface roughness of 20 to 50 nm of a polyester film used as a substrate, and 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 lower the surface roughness of the release film, it is common to prepare a polyester film with a low surface roughness and use it as a substrate. However, in order to lower the surface roughness in the polyester film manufacturing process, special particles are required, and the yield and productivity of the film are low, so applying such a film as a substrate inevitably causes an increase in the production cost of the release film.

As a method for obtaining a release film with a low surface roughness by 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 done [Patent Document 1]. However, since this method requires a separate coating process, there are disadvantages in that the process cost increases and the yield decreases.

Those skilled in the art can easily think of making the coating thickness of the release layer sufficiently thick compared to the surface roughness of the substrate without a separate smoothing layer. However, since the typical release layer is made of silicon polymer as a main component, when the coating thickness exceeds a certain level (about 300 nm), the so-called blocking phenomenon in which the release layer has adhesiveness due to the low viscoelasticity of the silicon polymer occurs. The winding-up process becomes impossible.

Accordingly, as a method of obtaining a release layer having a coating thickness of 2 μm by solving the conventional blocking phenomenon, a method of adding metal oxide particles with a diameter of 2 to 5 μm to the release layer has been proposed [Patent Document 2]. However, since added metal oxide particles can also cause pinhole defects in MLCC, 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 a blocking phenomenon without containing particles, a method of coating an ultraviolet curable silicone has been proposed [Patent Document 3]. However, UV-curable silicone is very expensive compared to thermosetting (addition-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 Korean Patent Registration 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 base layer and an addition reaction-type silicone release composition, wherein the surface roughness of the release layer is lower than that of the base layer.

Another object of the present invention is to provide a method of manufacturing the release film.

In order to achieve the above object, the present invention is a release film having a polyester base layer and a release layer formed of an addition-reactive silicone release composition on at least one side of the base layer, and the three-dimensional centerline average roughness of the surface of the base layer ( SRa) is 20 to 50 nm, and provides a release film having a three-dimensional centerline average roughness (SRa) of 1 to 10 nm on the surface of the release layer, and the release layer does not contain particles for lowering the surface roughness. It is characterized in that the layer is formed to a thickness of 0.5 to 2㎛.

At this time, the addition reaction-type silicone release composition includes polydimethylsiloxane having an alkenyl group, and the siloxane unit having an alkenyl group in the polydimethylsiloxane is 5 to 10% by weight of the total siloxane units.

Thus, the surface hardness of the release layer of the present invention is characterized in that the measured 2.0 to 5.0 Gpa by nano-indentation.

In addition, the coefficient of static friction 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, the addition reaction type silicone release composition at least of the base layer. It provides a method for producing a release film performing a step of coating a thickness of 0.5 to 2㎛ on one side and a thermal curing step.

According to the release film of the present invention, by providing a thick release layer containing an addition-reactive silicone release composition, the surface roughness of the release layer is significantly lower than that of the base layer, thereby suppressing pinhole defects when applied to the MLCC manufacturing process. I can.

In addition, even if the release film of the present invention includes a thick release layer, blocking does not occur, so that a winding process of winding the release film is possible, so that cost can be reduced.

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 an addition reaction-type silicone on at least one side 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 50 nm, and the three-dimensional center line of the surface of the release layer 120 Provides a release film having an average roughness (SRa) of 1 to 10 nm, and the release layer has a thickness of 0.5 to 2 µm, without containing particles for lowering the surface roughness, and the surface of the base layer through a thick release layer. The illuminance can be significantly reduced.

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

2. Release layer (120)

The release layer 120 may be formed by coating an addition-reactive silicone release composition on at least one surface of the base 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 amount of an organic solvent. Specifically, the addition reaction-type silicone constituting the release layer is obtained by addition reaction of a curing agent containing polydimethylsiloxane having an alkenyl group as a main component and polydimethylsiloxane having a hydroelectricity as a main component. When 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 in an appropriate ratio.

There is no particular restriction on the platinum catalyst, and a commercial product consisting of 5000 to 10000 ppm platinum and the remaining amount of organic solvent can be used. In general, toluene is applied to the organic solvent, and one or more organic solvents such as n-hexane, n-heptane, and n-octane may be mixed and used to ensure coating uniformity.

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, etc. may be used.

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

It is preferable that the three-dimensional centerline average roughness (SRa) of the surface of the release layer 120 is 1 to 10 nm. At this time, there is a technical limitation in achieving the surface roughness of the average roughness less than 1 nm, and if it exceeds 10 nm, pinhole defects may occur during the MLCC manufacturing process due to the protrusions on 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 μm, the smoothing function of the release layer 120 is insufficient and the average roughness of the three-dimensional center line on the surface of the release layer 120 is out of the above range, and if the thickness exceeds 2 μm, the release film (100) The effect of reducing the surface roughness is similar to the case where the thickness is less than 2㎛, so economical efficiency is poor.

In order to prevent the blocking phenomenon while the release layer 120 does not contain particles, the present invention provides a release film 100 having a surface hardness value of 2.0 to 5.0 GPa measured by a nano-indentation method. At this time, if the surface hardness value of the release layer is less than 2.0 GPa, blocking may occur due to viscosity. On the other hand, if it exceeds 5.0 GPa, the surface hardness value of the release layer can be achieved with a commercial addition reaction silicone polymer. it's difficult.

In order to provide the release layer 120 having the preferable surface hardness value, in the present invention, it is preferable that the siloxane unit having an alkenyl group in the polydimethylsiloxane skeleton having an alkenyl group is 5 to 10% by weight of the total siloxane units.

Since the siloxane unit having an alkenyl group in the polydimethylsiloxane skeleton acts as a crosslinking point when curing silicone and determines the surface hardness of the release layer 120 after curing, polydimethylsiloxane having an alkenyl group in the preferred range has a sufficient number of crosslinking points. It has a desirable surface hardness by having At this time, if the number of siloxane units having an alkenyl group is less than 5% by weight of the total number of siloxane units, the surface hardness value of the release layer 120 may be outside the preferred range (2.0 to 5.0 GPa), and blocking may occur, 10 If the weight% is exceeded, the release layer 120 is poorly cured, so a commercial release agent is preferably 10% by weight or less.

In addition, it is preferable that the release layer 120 of the present invention has a static friction coefficient of 0.2 to 0.5 with the base layer 110. At this time, if the coefficient of static friction is less than 0.2, the slipping property (sliding property) of the release layer is excessive, causing a defect in which the cross section is removed during the winding process, and if it exceeds 0.5, blocking occurs and the film is There is a problem that it becomes uneven and static electricity is strong.

The release film 100 of the present invention has the above-described configuration, so that the release layer 120 that is sufficiently thick compared to the surface roughness of the base film covers the protrusions and irregularities of the base film, so that the surface of the release layer 120 The 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 it is coated with a preferred thickness on the base layer 110 to provide a release film 100, and the release film of the present invention It has low surface roughness and is suitable for MLCC manufacturing process.

In addition, since the release film of the present invention can significantly reduce the surface roughness through coating from a conventional base film, when applied to the MLCC manufacturing process, pinhole defects can be suppressed and cost reduction can be contributed.

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

These examples are for explaining the present invention in more detail, and the scope of the present invention is not limited by these examples.

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

1. Base layer

A polyethylene terephthalate film (manufacturer: Toray Advanced Materials, product name: XD500P) having a three-dimensional centerline surface roughness (SRa) of 23 nm was used as the 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 base layer of.

2. Addition reaction type silicone release composition

A polydimethylsiloxane main chain in which the siloxane unit having a vinyl group is 3% by weight of the total siloxane units; And a curing agent; a polymer silicone product a (manufacturer: Shin-Etsu, product name: KS-847H\),

A polydimethylsiloxane main chain in which the siloxane unit having a vinyl group is 5% by weight of the total siloxane units; And a curing agent; Polymer silicone product b (manufacturer: Shin-Etsu, product name: KS-839L) or

A polydimethylsiloxane main chain in which the siloxane unit having a vinyl group is 8% by weight of the total siloxane units; And a curing agent; Polymer silicone product c (manufacturer: Shin-Etsu, product name: KS-3601) and

After mixing the platinum catalyst mixture of 5000 ppm concentration (manufacturer: Shin-Etsu, product name: PL-50T) and the remaining amount of toluene in the same amount as in Examples 1 to 6 and Comparative Examples 1 to 9 in Table 1 below, by stirring at room temperature for 60 minutes An addition reaction type silicone release composition was prepared.

3. Coating and curing

The addition reaction-type silicone release composition prepared according to the conditions in Table 1 was coated on one side of the substrate layer with a Mayer bar (manufactured by Cheminstruments, #12 mesh), and then heated and 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. Release layer thickness measurement

After preparing the release films of Examples 1 to 6 and Comparative Examples 1 to 9, the coating thickness was measured using a calibrated X-ray fluorescent spectroscopy.

2. Measurement of surface hardness

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

3. Blocking evaluation

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

The superimposed release film was visually observed under a fluorescent lamp, and it was judged as'good' if no traces due to blocking were observed, and'defective' if blocking marks were observed.

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

The presence or absence of blocking was quantitatively evaluated by measuring the coefficient of static friction between the release layer and the substrate layer. HEIDON's TRIBOGEAR product was used to measure the static friction coefficient.

5. Measurement of surface roughness

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

6. Evaluation of pinhole defect

After mixing 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, stirring at room temperature for 12 hours, and then ball milling at 500 rpm for 24 hours to prepare a ceramic slurry. This was coated to a predetermined thickness using an applicator on the release layer of the release films of each of the Examples and Comparative Examples, and then hot air dried at 80° C. for 5 minutes to prepare a release film having an average thickness of 1 μm. Thereafter, an area of 1 mm ² was observed 10 times with an interferometric microscope, and if the number of pinholes exceeding 1 μm on average 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 examples are shown in Table 2 below.

As shown in Table 2, 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 backbone all satisfy the preferred range provided by the present invention. In the release film of, the surface hardness value of the release layer was within the preferred range suggested by the present invention, and accordingly, blocking did not occur.

In addition, the surface roughness of the release layer of Examples 1 to 6 is in the range of 1 to 10 nm, which is significantly lower than the surface roughness of the base layer of 23 nm, and it can be confirmed that the smoothing effect is large. It can be confirmed that it does not occur.

On the other hand, in Comparative Examples 1 to 3, in which the content of the siloxane unit having an alkenyl group in the silicon 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 blocking occurs strongly due to the viscosity of.

Even when a release layer is formed using a release agent containing a preferred polydimethylsiloxane main chain proposed in the present invention, the thickness of the release layer is less than the preferred range of the present invention (Comparative Examples 4 and 6), or the base layer When the three-dimensional 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. It can be seen that pinhole defects occur due to the protrusion of.

On the other hand, the release layer is constituted by a release agent containing a preferred polydimethylsiloxane main chain, but Comparative Examples 5 and 7 in which the coating thickness of the release layer exceeds the preferred range of the present invention are examples 3 and examples having a thinner coating thickness. Compared with Example 6, since there is no difference in the surface roughness of the release layer, it can be confirmed that the method is less economical than the same performance.

100: release film
110: base layer
120: release layer

Claims (3)

A polyester base layer and
It is a release film consisting of a release layer formed of an addition-reactive silicone release composition on at least one side of the base layer,
The release layer is formed to have a thickness of 0.5 to 2 μm of the addition-reactive silicone release composition, but the addition-reactive silicone release composition does not contain particles for adjusting surface roughness,
The addition reaction-type silicone release composition comprises a polydimethylsiloxane having an alkenyl group, and the siloxane unit having an alkenyl group in the polydimethylsiloxane is 5 to 10% by weight of the total siloxane units,
The addition reaction type silicone release composition is composed of 10 to 20 g of polydimethylsiloxane having an alkenyl group, 0.15 to 0.3 g of a platinum catalyst, and 80 to 90 g of an organic solvent,
The surface hardness of the release layer was measured to be 2.0 to 5.0 Gpa by nanoindentation,
The three-dimensional centerline average roughness (SRa) of the surface of the substrate layer is 20 to 50 nm,
A release film, characterized in that the surface roughness of the release layer is lowered compared to the base layer to a three-dimensional centerline average roughness (SRa) of the surface of the release layer of 1 to 10 nm.
The release film according to 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 in which the siloxane unit having an alkenyl group in the polydimethylsiloxane skeleton is 5 to 10% by weight of the total siloxane units,
Coating the addition reaction type silicone release composition to a thickness of 0.5 to 2 μm on at least one surface of the polyester substrate layer, and
To form a release layer by performing a thermal curing step,
The addition reaction type silicone release composition is composed of 10 to 20 g of polydimethylsiloxane having an alkenyl group, 0.15 to 0.3 g of a platinum catalyst, and 80 to 90 g of an organic solvent,
The surface hardness of the release layer was measured to be 2.0 to 5.0 Gpa by nanoindentation,
The three-dimensional centerline average roughness (SRa) of the surface of the substrate layer is 20 to 50 nm,
The method of manufacturing a release film, characterized in that the surface roughness of the release layer is lowered compared to the base layer to a three-dimensional centerline average roughness (SRa) of the surface of the release layer is 1 to 10 nm.

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