JP5442053B2 - Release film - Google Patents

Description

  The present invention relates to a release film, and more particularly, to provide a release film that is lightly peeled but has little silicone migration.

  The release film based on polyester film is used when manufacturing flat sheet displays such as process sheets for green sheet forming used in the production of various ceramic electronic parts such as ceramic multilayer capacitors and ceramic substrates, and polarizing plates and optical filters. It is often used for adhesive separators for optical members.

  In recent years, with the progress of miniaturization and increase in capacity of ceramic multilayer capacitors, there is a tendency that a green sheet becomes thinner and a film having a lighter peeling force is required. Even in the production of flat panel displays, since the screen is enlarged and the width of the film to be peeled is widened, a separator that is lightly peeled is also required in such applications.

  In response to such requirements, silicone having a long dimethylpolysiloxane molecular chain with few branches is selected as a release coating, but if the required light release cannot be obtained, non-reactive silicone may be added. Generally done.

  However, the non-reactive silicone bleeds out to the surface of the release layer to form a liquid film to achieve light release, and therefore it is undesirable for the non-reactive silicone to move to the adherend and to contaminate the adherend with silicone and reduce the adhesive strength. Bring about an effect.

JP 2005-343073 A JP-A-2005-47176

Kunio Ito, “Silicone Handbook”, Nikkan Kogyo Shimbun, 1990, p. 535

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the release film with little silicone transfer, although it is light peeling.

As a result of intensive studies in view of the above problems, the present inventor has found that the use of silicone having a specific structure as a coating material makes it possible to easily solve the above problems, and has completed the present invention. That is, the gist of the present invention is a release film having a release layer provided by applying a coating containing an addition reaction type curable silicone having a group having a silicon-hydrogen bond on at least one side of a polyester film. Yes, the cured silicone contains silicone having only one vinyl group in the molecule, and an adhesive tape (A7475 manufactured by tesa) is attached to the surface of the release layer, and the tensile speed is 180 m / min. ° A release film having a peeling force of 94 mN / 2.5 cm or less when peeled exists.

  According to the present invention, it is possible to provide a release film with little silicone migration while being lightly peeled, and its industrial value is extremely high.

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

In the present invention, the polyester used for the polyester film may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. On the other hand, in the case of a copolymerized polyester, a copolymer containing 30 mol% or less of the third component is preferable. Examples of the dicarboxylic acid component of the copolyester include one or two of isophthalic acid, terephthalic acid phthalate, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  In any case, the polyester referred to in the present invention is usually 80 mol% or more, preferably 90 mol% or more of polyethylene terephthalate in which ethylene terephthalate units are formed, or polyethylene-2,6- in which ethylene-2,6-naphthalate units are formed. Refers to polyester such as naphthalate.

  In the polyester layer in the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and magnesium phosphate. , Particles of kaolin, aluminum oxide, titanium oxide and the like. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more if necessary.

  Moreover, it is preferable that the average particle diameter of the particle | grains contained in a polyester film in this invention satisfies 0.1-5 micrometers, More preferably, it is 0.5-3 micrometers, Most preferably, it is the range of 0.5-2 micrometers. . If the average particle size is less than 0.1 μm, the particles tend to aggregate and the dispersibility tends to be insufficient. On the other hand, if it exceeds 5 μm, the surface roughness of the film becomes too rough, Problems may occur when a release layer is provided in a subsequent process.

  Furthermore, the particle content in the polyester preferably satisfies 0.01 to 5% by weight, more preferably 0.01 to 3% by weight. When the particle content is less than 0.01% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the smoothness of the film surface is insufficient. It may become.

  In addition, conventionally known antioxidants, heat stabilizers, lubricants, dyes, pigments and the like can be added to the polyester film in the present invention within the range not impairing the gist of the present invention in addition to the above-mentioned particles.

  The thickness of the polyester film constituting the release film of the present invention is preferably a thin film in order to reduce the influence of the waist of the film, but on the other hand, it is necessary to ensure film flatness. When the thickness of the polyester film constituting the release film is too thin, the film flatness is often impaired by wrinkles due to heat treatment during processing. From this viewpoint, the thickness of the polyester film constituting the release film in the present invention is preferably 12 to 100 μm, and more preferably 25 to 50 μm.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all.

  That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction.

  In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, the extending | stretching temperature orthogonal to the extending | stretching direction of the 1st step is 130-170 degreeC normally, and a draw ratio is 3.0-7 times normally, Preferably it is 3.5-6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges. It is also possible to perform simultaneous biaxial stretching. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. As for the simultaneous biaxial stretching apparatus using the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, a linear drive method, or the like can be adopted. The “screw method” is a method in which a clip is placed in the groove of the screw to increase the clip interval. The “pantograph method” is a method of expanding the clip interval using a pantograph. The “linear motor system” has an advantage that the clip interval can be arbitrarily adjusted by applying the linear motor principle and controlling the clips individually.

  Further, simultaneous biaxial stretching may be performed in two or more stages. In that case, stretching may be performed in one tenter or a plurality of tenters may be used in combination.

  In the present invention, when the polyester film constituting the release film is stretched by simultaneous biaxial stretching, conventionally, when the area magnification becomes large by sequential biaxial stretching, a problem such as breaking at the time of stretching occurs. However, since the film following property is good in the simultaneous biaxial stretching, the area magnification can be further increased in the film longitudinal direction and the width direction as compared with the sequential biaxial stretching. It is preferable because a polyester film having a small thickness can be produced.

  In addition, a so-called coating stretching method (in-line coating) for treating the film surface during the above-described stretching process of the polyester film can be performed.

  Although it is not limited to the following, for example, in the sequential biaxial stretching, in particular, the first-stage stretching is completed, and the coating treatment can be performed before the second-stage stretching.

  The release layer constituting the release film of the present invention is a curable silicone resin having releasability and includes a reaction with a vinyl group in the curing process. The type of reaction is not particularly limited, and examples thereof include a radical reaction of a vinyl group, an addition reaction of a group having a silicon-hydrogen bond, and an addition reaction of a group having a sulfur-hydrogen bond. Of these, an addition reaction of a group having a silicon-hydrogen bond (so-called addition type silicone) is preferably used. The energy source in the curing process is not limited, and examples thereof include heat treatment, ultraviolet irradiation, and electron beam irradiation. Although these are used alone or in combination, heat treatment alone or combined treatment of heat and ultraviolet light is preferably used.

  The silicone compound having only one vinyl group in the molecule used in the present invention is produced by a known method. In the present invention, it may be obtained by any production method. For example, the object can be obtained by reacting a mixture of octamethylcyclotetrasiloxane, divinyltetramethyldisiloxane, and hexamethyldisiloxane in the presence of an acid or alkali catalyst. (This is described in Kunio Ito, “Silicone Handbook”, Nikkan Kogyo Shimbun, 1990, p. 99).

  The position of the vinyl group contained in the silicone having only one vinyl group in the molecule used in the present invention is not particularly limited, but it is preferably at the molecular end in terms of light release and reactivity.

  The molecular weight of the silicone compound having only one vinyl group in the molecule used in the present invention is not particularly limited, but the viscosity is preferably in the range of 30 to 100,000 mPa · s, more preferably 100 to 5000 mPa · s. If the molecular weight is too small, it may volatilize during coating and contaminate the inside of the coating system, and the light release effect is also reduced. On the other hand, if the molecular weight is too large, the reactivity is lowered and the migration is increased.

  The proportion of the silicone compound having only one vinyl group in the molecule contained in the cured silicone paint is 0.1 to 90%, preferably 1 to 70%, more preferably 5 to 5% by weight in terms of solid content. The range is 50%. If the content is too small, the light release effect may be small, and if it is too large, there is a concern that the adhesiveness and the coating film strength will deteriorate.

  The form of the cured silicone paint containing a silicone compound having only one vinyl group in the molecule in the present invention is not particularly limited. A so-called solvent type, in which high-viscosity products are diluted with a solvent. Examples thereof include a solventless type in which a product having a relatively low viscosity is applied as it is, and an emulsion type in which it is dispersed in an aqueous solvent. Diluting solvents for solvent dilution include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane and heptane, esters such as ethyl acetate and butyl acetate, ethyl methyl ketone (MEK), isobutyl methyl ketone, etc. Ketones, alcohols such as ethanol and 2-propanol, and ethers such as diisopropyl ether and dibutyl ether can be exemplified, and they are used alone or in combination in consideration of solubility, coating property, boiling point and the like.

  Further, in order to adjust the properties of the release layer, auxiliary agents such as a reaction modifier, an adhesion enhancer, and a release control agent may be used in combination as long as the gist of the present invention is not impaired.

The coating amount of the release layer (after drying) is usually 0.01 to 1 g / m ² , preferably 0.04 to 0.5 g / m ² , more preferably 0.06 to 0.3 g / m ² . It is a range.

  When the coating amount of the release layer is too small, light peeling does not occur and the stability of the peeling force may be lacking. On the other hand, when there is too much coating amount, there exists a concern of an increase in transferability and blocking.

  In the present invention, conventionally known coating methods such as multi-roll coating, reverse gravure coating, direct gravure coating, bar coating, and die coating can be used as a method for providing a release layer on the polyester film. Regarding the coating method, there is a description example in Yuji Harasaki's “Coating Method”, published in 1979.

  Moreover, you may give surface treatments, such as a corona treatment and a plasma treatment, to the polyester film which comprises the release film in this invention previously. Furthermore, the polyester film constituting the release film in the present invention may be provided with a coating layer such as an adhesive layer and an antistatic layer in advance.

  In addition, the release layer which comprises the release film in this invention may be provided on the polyester film by the above-mentioned coating extending | stretching method (in-line coating).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measuring method used in the present invention is as follows.

(1) Measurement of tape A peeling force (peeling speed 0.3 m / min) After affixing an adhesive tape (“A7475” manufactured by tesa) to the release surface of the sample film, it is cut into a size of 25 mm × 300 mm, The peel force after standing for 1 hour at room temperature is measured. The peeling force was “Intesco Model 2001” manufactured by Intesco Co., Ltd., and 180 ° peeling was performed under the condition of a tensile speed of 0.3 (m / min).

(2) Measurement of tape B peeling force (peeling speed 0.3 m / min) After affixing an adhesive tape (“No. 31B” manufactured by Nitto Denko Corporation) to the release surface of the sample film, 50 mm × 300 mm Cut to size and measure the peel force after standing at room temperature for 1 hour. The peeling force was “Intesco Model 2001” manufactured by Intesco Co., Ltd., and 180 ° peeling was performed under the condition of a tensile speed of 0.3 (m / min).

(3) Measurement of tape B peeling force (peeling speed 3 m / min, 30 m / min) After sticking an adhesive tape (“No. 31B” manufactured by Nitto Denko Corporation) on the release surface of the sample film, 50 mm × Cut to 300 mm size and measure peel strength after standing at room temperature for 1 hour. The peel strength was measured using a high-speed peel tester “TE-702 type” manufactured by Tester Sangyo Co., Ltd. In the method of peeling the 31B pressure-sensitive adhesive tape side, 180 ° peeling was performed under the conditions of peeling speeds of 3 (m / min) and 30 (m / min), respectively.

(4) Transferability (residual adhesion rate) evaluation / residual adhesive strength of release film Nitto Denko Co., Ltd. No. The 31B adhesive tape is subjected to one reciprocating pressure bonding with a 2 kg rubber roller, and heat-treated at 100 ° C. for 1 hour. Next, no. The 31B pressure-sensitive adhesive tape is peeled off, and the adhesive strength is measured according to the method of JIS-C-2107 (adhesive strength to stainless steel plate, 180 ° peeling method). This is the residual adhesive strength.
-Fundamental adhesive force Using the same adhesive tape (No. 31B) as in the case of residual adhesive force, an adhesive tape is pressure-bonded to a stainless steel plate according to JIS-C-2107, and measurement is performed in the same manner. The value at this time is defined as the basic adhesive strength. Using these measured values, the residual adhesion rate is determined based on the following equation. Residual adhesion rate (%) = (residual adhesive force / basic adhesive force) × 100
The measurement is performed at 20 ± 2 ° C. and 65 ± 5% RH. If the residual adhesive strength is less than 80%, it becomes easy to cause a failure when the separator is peeled off due to show-through.

Example 1:
A release agent having the following composition is applied to a biaxially stretched PET film (Mitsubishi Chemical Polyester Film Co., Ltd .: Diafoil T100-38) with a thickness of 38 μm so that the coating amount (after drying) is 0.1 (g / m 2). And then heat treated at 120 ° C. for 30 seconds to obtain a release film.
<Releasing agent composition>
A silicone mixture having the following composition (hereinafter referred to as silicone A), where Me represents a methyl group.

_{H 2 C = CH-Si (} Me) 2 O (-Si (Me) 2 -O) n-Si (Me) 2 -CH = CH 2 to about 60 mole%
_{H 2 C = CH-Si (} Me) 2 O (-Si (Me) 2 -O) n-SiMe 3 to about 35 mole%
Me ₃ SiO (—Si (Me) ₂ —O) n-SiMe ₃ About 5 mol% (average value of n about 104, viscosity about 200 mPa · s) 100 parts by weight Light release solvent type silicone with low migration (Shin-Etsu Chemical) KK-847H, non-volatile content 30%) 83 parts by weight Me3SiO (-SiH (Me) -O) m-SiMe3 silicone (Gelest: HMS-991, viscosity about 20 mPa · s) 3.3 parts by weight Platinum-containing catalyst (manufactured by Shin-Etsu Chemical Co., Ltd .: catPL-50T) 4 parts by weight This is diluted with a mixed solvent of MEK / hexane (mixing ratio is 1: 3), and the solid content concentration is 2% by weight. A coating solution was prepared.

Example 2:
A release agent having the following composition is applied to a 38 μm thick biaxially stretched PET film (Mitsubishi Chemical Polyester Film Co., Ltd .: Diafoil T100-38) so that the coating amount (after drying) is 0.1 (g / m 2). After applying and heat-treating at 90 ° C. for 30 seconds, a release film was obtained by irradiating with ultraviolet rays at a dose of about 200 mJ / cm 2 using a high-pressure mercury lamp.
<Releasing agent composition>
Silicone A 100 parts by weight Combined heat / ultraviolet curing solvent type silicone (Toray Dow Corning Co., Ltd .: LTC851, nonvolatile content 30%) 83 parts by weight Me ₃ SiO (—SiH (Me) —O) _m —SiMe ₃ Silicone (manufactured by Gelest: HMS-991, viscosity: about 20 mPa · s) 3.3 parts by weight Curing catalyst (manufactured by Toray Dow Corning: BY24-835) 6 parts by weight These are mixed solvents of MEK / hexane ( The mixture was diluted 1: 3) to prepare a coating solution having a solid concentration of 2% by weight.

Comparative Example 1:
In Example 1, a release film was obtained in the same manner as in Example 1 except that the release agent composition was changed to the following release agent composition.
<Releasing agent composition>
Light release solvent type silicone (Made by Shin-Etsu Chemical Co., Ltd .: KS-847H, non-volatile content 30%) 100 parts by weight Platinum-containing catalyst (manufactured by Shin-Etsu Chemical Co., Ltd .: catPL-50T) 1 part by weight These are MEK This was diluted with a mixed solvent of / hexane (mixing ratio 1: 3) to prepare a coating solution having a solid content concentration of 2% by weight.

Comparative Example 2:
In Example 1, a release film was obtained in the same manner as in Example 1 except that the release agent composition was changed to the following release agent composition.
<Releasing agent composition>
Migrating light release solvent type silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: KS-778, nonvolatile content 30%) 100 parts by weight Platinum-containing catalyst (manufactured by Shin-Etsu Chemical Co., Ltd .: catPL-50T) 1 part by weight These are MEK This was diluted with a mixed solvent of / hexane (mixing ratio 1: 3) to prepare a coating solution having a solid content concentration of 2% by weight.

  The characteristics of each film obtained in the above Examples and Comparative Examples are summarized in Table 1 below.

  The films of Example 1 and Example 2 achieved light peeling without significantly reducing the residual adhesion rate as compared with Comparative Example 1 with less migration. On the other hand, the film described in Comparative Example 2, which was lightly peeled by the conventional technique, was lightly peeled, but the residual adhesion rate was greatly reduced. The peeling force at higher speed of each film is as shown in Table 2 below.

  The film of Example 1 and Example 2 showed light peeling also in the peeling speed range (3-30 m / min) actually used in a polarizing plate separator and a polarizing plate protective film separator use.

  The film of the present invention is, for example, a process sheet for forming green sheets used in the production of various ceramic electronic components such as ceramic multilayer capacitors and ceramic substrates, and an adhesive for optical members used in the production of flat panel displays such as polarizing plates and optical filters. As a separator, it can utilize suitably.

Claims (1)

A release film having a release layer provided by applying a coating containing an addition reaction type curable silicone having a group having a silicon-hydrogen bond on at least one surface of a polyester film, and the cured silicone is in the molecule Contains a silicone having only one vinyl group, and an adhesive tape (A7475 manufactured by tesa) is attached to the surface of the release layer, and the peeling force when peeled 180 ° at a tensile speed of 0.3 m / min is A release film characterized by being 94 mN / 2.5 cm or less.