JP7631707B2 - Release Film - Google Patents

Description

The present invention relates to a release film.

Conventionally, a method for manufacturing optical devices and the like has been used in which a release film is placed in a mold with a cavity so as to fit the cavity, the cavity is filled with a curable composition, and the curable composition is compression molded while the support is pressed against the mold so that the optical element provided on the support is inserted into the curable composition in the cavity, thereby integrating the curable composition. Fluoroplastic resin films, polyester resin films, and polyolefin resin films have been used as the release film (Patent Document 1).

JP 2010-245477 A

However, as a result of the inventors' investigations, molded articles obtained using conventional fluororesin films, polyester resin films, and polyolefin resin films as described in the above Patent Document 1 sometimes had distortions at the edges or wrinkles formed on the surface. In other words, it was found that there is room for improvement in terms of obtaining a good appearance for the molded article.

The above problems also occur with release films used when hardening prepregs of thermosetting resins, such as CFRP (carbon fiber reinforced plastics), release films for molding thermosetting resins, and transfer release films for decoration, such as printing on products with three-dimensional shapes.

The inventors have thoroughly investigated the causes of distortion and wrinkles that occur in molded bodies and have found that when the release layer of a release film has certain physical properties, the release film can conform well to the mold and deformation due to heating and compression can be suppressed, thereby preventing distortion and wrinkles from occurring in the release film.
After further investigation, the inventors discovered that by controlling the integrated value of the tear strength and breaking elongation of the release layer, or the degree of change in tear strength before and after heat treatment, as indicators, it is possible to appropriately suppress the occurrence of distortion and wrinkles in the release film and improve the appearance of molded articles using the release film, thereby completing the present invention.

According to the present invention,
A release film in which a layer constituting at least one surface thereof is made of a cured product of a silicone rubber composition,
When the tear strength of the cured product of the silicone rubber composition is TS0 (N/mm) and the elongation at break is BE0s (%), the following properties are obtained:
There is provided a release film that satisfies 2.4×10 ⁴ ≦TS0×BE0s.
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared from the cured product of the silicone rubber composition in accordance with JIS K6252 (2001), and the tear strength of the obtained crescent-shaped test piece at 25° C. is measured and designated as TS0, expressed in N/mm.
(Procedure for measuring elongation at break)
A dumbbell-shaped No. 3 test piece is prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and the breaking elongation of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. The breaking elongation is calculated as [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and is designated as BE0s, and is expressed in %.

Further, according to the present invention,
When the tear strength of the cured product of the silicone rubber composition, measured by the following procedure, is TS0 (N/mm) and TS1 (N/mm),
There is provided a release film, in which ((TS1-TS0)/TS0) x 100 is -85% or more and 5% or less.
(Procedure for measuring tear strength)
A crescent-shaped test specimen is prepared from the cured product of the silicone rubber composition in accordance with JIS K6252 (2001), and the tear strength of the crescent-shaped test specimen obtained at 25° C. is designated as TS0 (N/mm). A crescent-shaped test specimen is prepared from the cured product of the silicone rubber composition in accordance with JIS K6252 (2001), and after holding at 100° C. for 30 minutes, the tear strength of the crescent-shaped test specimen obtained at 100° C. is designated as TS1 (N/mm).

The present invention provides a release film that can produce molded articles with good appearance.

1 is a cross-sectional view illustrating a cross section of a release film according to a first embodiment; FIG. 6 is a cross-sectional view that illustrates a cross section of a release film according to a second embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
In all drawings, similar components are given the same reference numerals, and explanations are omitted as appropriate. To avoid complexity, (i) when there are multiple identical components in the same drawing, only one of them is given a reference numeral, and not all of them are given a reference numeral, or (ii) especially in FIG. 2 and subsequent drawings, components similar to those in FIG. 1 are not given a reference numeral again. All drawings are for explanatory purposes only. The shapes and dimensional ratios of each member in the drawings do not necessarily correspond to the actual objects.

In this specification, the notation "a to b" in the explanation of a numerical range means from a to b, unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass to 5% by mass."

<Indicators of silicone rubber composition>
First, the indices of the silicone rubber composition in this embodiment will be described.
The silicone rubber composition of the present embodiment is specified by controlling each index, either alone or in combination, which is measured according to the following procedure.
In addition, in each index, the cured product of the silicone rubber composition is intended to mean a product that has been heated at 160° C. for 20 minutes (first curing) and then post-baked at 200° C. for 4 hours (second curing).

・Tear strength TS0 (N/mm)
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared from the cured product of the silicone rubber composition in accordance with JIS K6252 (2001), and the tear strength of the resulting crescent-shaped test piece is measured at 25° C. The unit is N/mm.

・Tear strength TS1 (N/mm)
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and then the test piece is held at 100°C for 30 minutes. The tear strength of the crescent-shaped test piece obtained at 100°C is defined as TS1 (N/mm).

・Tear strength TS2 (N/mm)
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and then the test piece is held at 150°C for 30 minutes. The tear strength of the crescent-shaped test piece obtained at 150°C is defined as TS2 (N/mm).

Breaking elongation BE0s (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, a dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004), and the breaking elongation of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. The breaking elongation is calculated as [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and is designated as BE0s. The unit is %.

Breaking elongation BE0 (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, a dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004), and the breaking elongation of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. The breaking elongation is calculated as [chuck movement distance (mm)]÷[initial chuck distance (60 mm)]×100, and is designated as BE0. The unit is %.

Breaking elongation BE1 (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, dumbbell-shaped No. 3 test pieces are prepared in accordance with JIS K6251 (2004), and after holding at 100° C. for 30 minutes, the breaking elongation of the resulting dumbbell-shaped No. 3 test pieces is measured at 100° C. The breaking elongation is calculated as [chuck movement distance (mm)]÷[initial chuck distance (60 mm)]×100, and is designated as BE1. The unit is %.

Breaking elongation BE2 (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, a dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004), and after holding at 150° C. for 30 minutes, the resulting dumbbell-shaped No. 3 test piece is measured for breaking elongation at 150° C. The breaking elongation is calculated as [chuck travel distance (mm)]÷[initial chuck distance (60 mm)]×100, and is designated as BE2. The unit is %.

Elongation E1 (%) at 1 MPa
(Procedure for measuring elongation at 1 MPa)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and a tensile test was conducted at 25°C at a tensile speed of 500 mm/min, and the elongation of the resulting dumbbell-shaped No. 3 test piece when the stress reached 1 MPa was calculated using the formula [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and designated as E1. The unit is %.

Elongation E2 (%) at 0.2 MPa
(Procedure for measuring elongation at 0.2 MPa)
Using the cured product of the silicone rubber-based curable composition, a dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004), and a tensile test is carried out under conditions of 25°C and a tensile speed of 500 mm/min, and the elongation of the obtained dumbbell-shaped No. 3 test piece when the stress reaches 0.2 MPa is calculated by the formula [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, in units of %.

Tensile strength S (MPa)
(Procedure for measuring tensile strength)
A dumbbell-shaped No. 3 test piece is prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and the tensile strength of the dumbbell-shaped No. 3 test piece at 25° C. is measured in units of MPa.

Stroke change rate after n hours SCn (%)
(Procedure for measuring stroke change rate)
A dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004) using the cured product of the silicone rubber composition, and the elongation of the resulting dumbbell-shaped No. 3 test piece is measured over time at 25°C when held between chucks at a stress of 1 MPa.
The time when the stress becomes 1 MPa is defined as 0h, and the stroke amount after a predetermined time n (h) is defined as En (%) = [chuck movement distance (mm)] ÷ [initial chuck distance (60 mm)] × 100. The stroke change rate is calculated from the measured stroke amount En based on the following formula.
Stroke change rate after n hours SCn (%) = (En-E0)/E0 x 100

・Durometer hardness A
(Procedure for measuring durometer hardness A)
A sheet-like test specimen is prepared using the cured product of the silicone rubber composition, and the durometer hardness A of the resulting sheet-like test specimen at 25° C. is measured in accordance with JIS K6253 (1997).

- Plasticity (Procedure for measuring plasticity)
The uncured silicone rubber composition is used as a test sample, and the plasticity of the resulting test sample at 25° C. is measured 10 minutes after the start of the measurement using a Williams plasticity meter in accordance with JIS K6249 (2003).

The above indexes can be controlled, for example, by appropriately selecting the type and blending amount of each component contained in the silicone rubber composition, the preparation method of the silicone rubber composition, etc. Among these, for example, suitable control of the type and blending ratio of the resin constituting the silicone rubber, the crosslink density and crosslinking structure of the resin, and improving the blending ratio of the inorganic filler and the dispersibility of the inorganic filler are listed as elements for setting the above indexes within the desired numerical range.
In addition, by adjusting the temperature and time when the silicone rubber composition is cured, the crosslink density and crosslink structure of the resin can be appropriately controlled, and the above-mentioned indexes can be set to the desired numerical range. In addition, for example, in the production process of the release film, when the film is sandwiched between substrates, it is also possible to change the surface roughness depending on the surface condition.

First Embodiment
FIG. 1 is a cross-sectional view that typically shows a cross section of a release film of a first embodiment.
As shown in FIG. 1, a release film 10 of the present embodiment includes a release layer 1, which is made of a silicone rubber composition and satisfies the following conditions.
In other words, by using a silicone rubber composition that satisfies specific parameters, a release film 10 having the desired characteristics can be obtained, and the mold conformability and dimensional stability of a molded article using the release film 10 can be improved, making it possible to maintain a good appearance.

The release film 10 of this embodiment is
The condition 2.4×10 ⁴ ≦TS0×BE0s is satisfied.

This can prevent the release film 10 from being wrinkled or distorted, and can improve the appearance of the resulting molded article.
Although the detailed mechanism is unclear, it is believed that by using the integrated value of the tear strength and the breaking elongation as an indicator, the balance of the rigidity, elastic recovery, extensibility, etc. of the release film 10 can be controlled, and good conformability to the mold can be obtained, thereby effectively suppressing the occurrence of wrinkles and distortion.

The lower limit of TS0×BE0s is preferably 2.5×10 ⁴ or more, more preferably 2.8×10 ⁴ or more. This makes it possible to improve the mold followability and dimensional stability, and to stably obtain a molded article having a good appearance.
On the other hand, the upper limit of TS0×BE0s is not particularly limited, but may be, for example, 5.0×10 ⁵ or less, 1.0×10 ⁵ or less, or 9.0×10 ⁴ or less. This allows the properties of the release film 10, such as mold followability, dimensional stability, and releasability, to be well balanced.

Alternatively, the release film 10 of the present embodiment is
((TS1-TS0)/TS0) x 100 satisfies -85% or more and 5% or less.

The inventors focused on the fact that the rubber properties deteriorate when a cured silicone rubber composition is heated and conducted further research. As a result, they discovered that by using the degree of change in the physical properties of the cured silicone rubber composition when heated from room temperature to a high temperature (change in thermal physical properties) as a guideline, it is possible to appropriately control the degree of deformation when heated and the durability of a release film 10 using a cured silicone rubber composition.
That is, by controlling the degree of change in tear strength before and after heating, i.e., ((tear strength TS1-tear strength TS0)/tear strength TS0) x 100, within a specific numerical range, it is possible to improve the dimensional stability against heat while maintaining good mold followability of the release film 10, and to improve the appearance of a molded article using the same. Furthermore, by controlling (tear strength TS1-tear strength TS0)/tear strength TS0) x 100 within a specific numerical range, repeated use of the release film 10 can be expected.

The upper limit of ((tear strength TS1-tear strength TS0)/tear strength TS0) x 100 is, for example, 5% or less, preferably 0% or less, more preferably -5% or less, and may be -10% or less.
On the other hand, the lower limit of the above (tear strength TS1-tear strength TS0)/tear strength TS0) x 100 is -85% or more, preferably -70% or more, more preferably -55% or more, and even more preferably -45% or more. By making it equal to or more than the above lower limit, it is possible to obtain good mold followability, improve dimensional stability in a high temperature environment, and improve mechanical strength. In addition, by making it equal to or more than the above lower limit, repeated use of the release film 10 can be expected.

The release film of this embodiment satisfies the numerical ranges specified by the above-mentioned indices, thereby appropriately suppressing the occurrence of warping and wrinkles in the release film and improving the appearance of the molded article using the release film. In addition, by satisfying the numerical ranges specified by the following indices, the occurrence of warping and wrinkles can be more stably suppressed.

The release film 10 of this embodiment is
The characteristic may be such that 2.8×10 ⁵ ≦TS0×BE0s×S is satisfied.
The lower limit of TS0×BE0s×S is 1.4×10 ⁵ or more, preferably 2.8×10 ⁵ or more, and more preferably 3.0×10 ⁵ or more. This makes it possible to improve the mold followability and dimensional stability, and to stably obtain a molded product having a good appearance.
On the other hand, the upper limit of TS0×BE0s×S is not particularly limited, but may be, for example, 6.0×10 ⁶ or less, 2.0×10 ⁶ or less, or 1.0×10 ⁶ or less. This makes it possible to achieve a good balance of the properties of the release film 10, such as mold followability, dimensional stability, and releasability.

The lower limit of the tear strength is, for example, 25 N/mm or more, preferably 28 N/mm or more, more preferably 30 N/mm or more, even more preferably 33 N/mm or more, and still more preferably 35 N/mm or more. This can improve the durability of the release film 10.
On the other hand, the upper limit of the tear strength is not particularly limited, but may be, for example, 80 N/mm or less, or 70 N/mm or less, which allows the properties of the release film 10, such as mold followability, dimensional stability, and releasability, to be well balanced.

The release film 10 of this embodiment is
The material may have a characteristic that ((breaking elongation BE1-breaking elongation BE0)/breaking elongation BE0) x 100 satisfies -50% or more and 0% or less.

In addition, the release film 10 of the present embodiment is
The material may have a characteristic that ((breaking elongation BE2-breaking elongation BE0)/breaking elongation BE0) x 100 satisfies -65% or more and 0% or less.

The upper limit of ((breaking elongation BE2-breaking elongation BE0)/breaking elongation BE0) x 100 is not particularly limited, but may be, for example, 0% or less, preferably -20% or less, and more preferably -30% or less.
On the other hand, the lower limit of the above ((breaking elongation BE2-breaking elongation BE0)/breaking elongation BE0) x 100 is, for example, -65% or more, preferably -60% or more, and more preferably -55% or more. This makes it possible to suppress changes in dimensional stability and durability in a high-temperature environment.

The upper limit of the breaking elongation BE1 may be, for example, 1500% or less, preferably 1200% or less, more preferably 1000% or less, and even more preferably 900% or less. This can improve the mechanical strength of the release film 10.
On the other hand, the lower limit of the breaking elongation BE1 is 250% or more, preferably 300% or more, and more preferably 350% or more, which can suppress changes in dimensional stability and durability in a high-temperature environment.

The release film 10 of this embodiment is
The characteristic may be such that ((TS2-TS0)/TS0) x 100 is equal to or greater than -88% and equal to or less than 5%.

The upper limit value of ((tear strength TS2-tear strength TS0)/tear strength TS0) x 100 is, for example, 5% or less, preferably 0% or less, and may be -20% or less, or further -30% or less.
On the other hand, the lower limit of the above (tear strength TS2-tear strength TS0)/tear strength TS0) x 100 is -88% or more, preferably -70% or more, more preferably -60% or more, and even more preferably -50% or more. By making it equal to or more than the above lower limit, the dimensional stability against heat can be improved while maintaining good mold followability of the release film 10, and the appearance of a molded article using the same can be improved.

The upper limit of the tear strength TS1 is not particularly limited, but may be, for example, 60 N/mm or less, 50 N/mm or less, or 40 N/mm or less.
On the other hand, the lower limit of the tear strength TS1 is, for example, 10 N/mm or more, preferably 20 N/mm or more, more preferably 25 N/mm or more, and even more preferably 30 N/mm or more.

The upper limit of the tear strength TS2 is not particularly limited, but may be, for example, 50 N/mm or less, 40 N/mm or less, or 35 N/mm or less, which allows a balance with other physical properties to be achieved.
On the other hand, the lower limit of the tear strength TS2 is, for example, 6.5 N/mm or more, preferably 10 N/mm or more, more preferably 15 N/mm or more, which can improve the dimensional stability against heat while maintaining good mold followability of the release film 10, and can improve the appearance of a molded article using the same.

The release film 10 of this embodiment is
It may have the characteristics that 15≦E1 and 20≦TS0 are satisfied.

In other words, by using the elongation at low stress (E1) and tear strength (TS0) as indicators and controlling them simultaneously, a good balance between mold conformity and dimensional stability can be stably achieved.

The lower limit of E1 is 15 or more, preferably 30 or more, and more preferably 50 or more. This increases the ease of deformation, and more stably maintains mold followability and dimensional stability, resulting in a molded product with good appearance.
On the other hand, the upper limit of E1 is not particularly limited, but may be, for example, 500 or less, 400 or less, 300 or less, or, depending on the purpose, 100 or less. This allows the properties of the release film 10, such as mold followability, dimensional stability, and releasability, to be well balanced.

The release film 10 of this embodiment is
E1 and E2 may have the property that 10≦|E1−E2| is satisfied.

The lower limit of |E1-E2| is at least 10, preferably at least 20, and more preferably at least 30. This makes it easier to improve the mold followability and dimensional stability.
On the other hand, the upper limit of |E1-E2| is not particularly limited, but may be, for example, 500 or less, 400 or less, 300 or less, or, depending on the purpose, 90 or less. This allows the properties of the release film 10, such as mold followability, dimensional stability, and releasability, to be well balanced.

According to the study by the present inventors, the elongation amount at low stress (E1) and the tear strength (TS0) are in a trade-off relationship, in that the elongation amount at low stress can be increased by reducing the amount of filler in the silicone rubber, but on the other hand, the tear strength decreases and the durability of the silicone rubber decreases. As a result of further intensive study, it was found that by appropriately selecting the components of the silicone rubber composition, such as the vinyl group-containing organopolysiloxane described below, it is possible to control the uneven distribution of crosslinking density and crosslinking structure, and to increase the elongation amount at low stress in a wide strain range while increasing the tear strength of the cured product of the silicone rubber composition. Although the detailed mechanism is unclear, it is believed that the crosslinking state can be appropriately controlled by using two different types of vinyl group-containing organopolysiloxanes in combination or by using a low vinyl group organopolysiloxane, so that the tear strength of the cured product of the silicone rubber composition can be increased while improving the elongation amount at stress.

The release film 10 of this embodiment is
When the stroke change rate after 1 hour of the cured product of the silicone rubber-based curable resin composition is defined as SC1 (%),
It may have the characteristics that SC1≦50 and 20≦TS0 are satisfied.

In other words, by using the initial stroke change rate and tear strength as indicators and controlling them simultaneously, a good balance of mechanical strength, durability, mold conformity, and dimensional stability can be stably achieved.

The upper limit of SC1 may be not more than 50, preferably not more than 40, and more preferably not more than 30. This makes it possible to more stably maintain mold followability and dimensional stability, and to obtain a molded article having a good appearance.
On the other hand, the lower limit of SC1 is not particularly limited, but may be equal to or greater than 1, or may be equal to or greater than 2. This makes it possible to improve the mechanical strength while achieving a good balance between the properties of the release film 10, such as mold followability and dimensional stability.

In addition, when the stroke change rate after 5 hours is defined as SC5 (%), the upper limit of SC5 may be 70 or less, preferably 50 or less, and more preferably 40 or less. This makes it possible to obtain a molded product having good durability, mold followability and dimensional stability, and a good appearance.
On the other hand, the lower limit of SC5 is not particularly limited, but may be equal to or greater than 1, or may be equal to or greater than 3. This makes it possible to improve the mechanical strength while achieving a good balance between the properties of the release film 10, such as mold followability and dimensional stability.

The release film 10 of this embodiment is
It may have the property that |SC5-SC1|≦20 is satisfied.

The upper limit of |SC5-SC1| may be equal to or less than 20, preferably equal to or less than 15, and more preferably equal to or less than 10. This makes it easier to improve durability and more stably maintain mold followability and dimensional stability.
On the other hand, the lower limit of |SC5-SC1| is not particularly limited, but may be equal to or greater than 1. This makes it possible to realize a silicone rubber composition that is well balanced with other properties.

The lower limit of the tear strength TS0 is, for example, 25 N/mm or more, preferably 28 N/mm or more, more preferably 30 N/mm or more, even more preferably 33 N/mm or more, and still more preferably 35 N/mm or more. This can improve the durability of the release film 10 during repeated use.
On the other hand, the upper limit of the tear strength TS0 is not particularly limited, but may be, for example, 80 N/mm or less, or 70 N/mm or less, which can provide a good balance between the properties of the release film 10, such as mold followability and dimensional stability, while maintaining mechanical strength.

The upper limit of the durometer hardness A of the cured product of the silicone rubber composition of this embodiment is not particularly limited, but may be, for example, not more than 80, preferably not more than 65, and more preferably not more than 60. This improves the curability of the silicone rubber composition, enhances the deformability that makes it easy to deform, and improves the mold followability and dimensional stability.
On the other hand, the lower limit of the durometer hardness A is not particularly limited, but is, for example, not less than 20, preferably not less than 25, and more preferably not less than 30. This can increase the mechanical strength of the release film 10.

The lower limit of the plasticity of the silicone rubber composition is, for example, not less than 80, preferably not less than 90, and more preferably not less than 100. This can improve the stability during film formation using the silicone rubber composition.
On the other hand, the upper limit of the plasticity of the silicone rubber composition is, for example, not more than 340, preferably not more than 320, and more preferably not more than 300. This can improve the stability during film formation.

The release film 10 of the present embodiment preferably has a surface free energy on one surface of 10 mJ/m ² or more and 20 mJ/m ² or less.
By adjusting the surface free energy to be equal to or higher than the above lower limit, good releasability can be achieved.

In this embodiment, it is preferable that at least one surface of the release film 10 has the above surface free energy, but it is more preferable that the release surface 3 has the above surface free energy. In addition, both the release surface 3 and the surface opposite the release surface 3 may have the above surface free energy.

The surface free energy can be measured using a general-purpose contact angle meter (for example, Drop Master DM-501, a contact angle meter manufactured by Kyowa Interface Science Co., Ltd.).
Specifically, water, diiodomethane, and hexadecane are used as three types of liquids whose surface free energy and each of its components (dispersive force, polar force, and hydrogen bonding force) are known, and the contact angle (θ) of each liquid on the release layer 11 is measured using a contact angle meter at 23° C. and 65% RH. From the contact angle (θ) value and the known values of each liquid (the numerical values of Panzer's Method IV (described in Vol. 15, No. 3, page 96 of the Journal of the Japan Adhesion Association)), the values of each component are calculated using the following formula introduced from the Kitazaki-Hata formula.
(γSd・γLd)1/2+(γSp・γLp)1/2+(γSh・γLh)1/2=γL(1+cosθ)/2
Here, γLd, γLp, and γLh respectively represent the components of dispersion force, polar force, and hydrogen bonding force of the measurement liquid. θ represents the contact angle of the measurement liquid on the measurement surface. γSd, γSp, and γSh respectively represent the values of the components of dispersion force, polar force, and hydrogen bonding force of the release layer surface. γL represents the surface energy of each liquid. The values of the three components of the measurement surface (release layer surface) are obtained by solving the simultaneous equations obtained by substituting the known values and θ into the above formula.
Then, the sum of the determined dispersion force component value, polar force component value, and hydrogen bonding force component value can be calculated as the surface free energy (E) using the following formula.
E=γSd+γSp+γSh

The release film 10 of this embodiment is made up of a release layer 1. The release layer 1 will be described below.

[Release layer]
The release surface 3 of the release layer 1 is the surface that comes into contact with a sealing resin, which will be described later, when the release film 10 is used. The surface roughness Rz of the release surface 3 is 0.1 to 10 μm, preferably 1 to 7 μm, and more preferably 1 to 5 μm.
By setting the surface roughness Rz of the release surface 3 to be equal to or greater than the above lower limit, a good balance between releasability and mold followability during molding can be achieved. On the other hand, by setting the surface roughness Rz of the release surface 3 to be equal to or less than the above upper limit, good releasability can be achieved while maintaining mold followability and dimensional stability.

The surface roughness of the release surface 3 can be controlled by known methods, such as transferring an embossed pattern to the film using an embossed roll during the production process of the release film, or by incorporating particles into the material of the release layer.

The surface roughness Rz of the release layer 1 is measured in accordance with JIS B0601:2013.

The thickness of the release layer 1 is preferably 30 μm or more and 500 μm or less, more preferably 100 μm or more and 400 μm or less, and even more preferably 150 μm or more and 300 μm or less.
By setting the thickness of the release layer 1 to the above lower limit or more, the rigidity of the release film 10 is increased, and excessive deformation and wrinkles are easily suppressed. As a result, mold followability and dimensional stability are obtained. On the other hand, by setting the thickness of the release layer 1 to the above upper limit or less, the rigidity of the release film 10 can be controlled, and a good balance between mold followability and releasability can be achieved.

The release layer 1 is made of a silicone rubber composition.
In this embodiment, the silicone rubber composition is a rubber material having rubber-like properties such as elasticity, compressibility, etc. of silicone having a siloxane bond (-Si-O-Si-) as the main skeleton. The present inventors focused on release films as a new application of the silicone rubber composition and realized a new release film using the silicone rubber composition.
The silicone rubber composition of this embodiment will now be described.

<<Vinyl Group-Containing Organopolysiloxane (A)>>
The silicone rubber composition of the present embodiment may contain a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) is a polymer that is the main component of the silicone rubber composition.

The vinyl group-containing organopolysiloxane (A) may include a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, which become crosslinking points during curing.

The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but for example, it is preferable that the vinyl group content is 15 mol% or less and that the vinyl group content is 2 or more in the molecule. This optimizes the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1), and ensures the formation of a network with each component described below.

In this specification, the vinyl group content refers to the mole percent of vinyl group-containing siloxane units when all units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mole percent. However, it is considered that there is one vinyl group per vinyl group-containing siloxane unit.

The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably within the range of about 1,000 to 10,000, and more preferably about 2,000 to 5,000. The degree of polymerization can be determined, for example, as the number average degree of polymerization (or number average molecular weight) in terms of polystyrene in gel permeation chromatography (GPC) using chloroform as a developing solvent.

Furthermore, the specific gravity of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of about 0.9 to 1.1.

By using a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and specific gravity within the above ranges, the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber can be improved.

The vinyl group-containing linear organopolysiloxane (A1) preferably has a structure represented by the following formula (1):

In formula (1), R ¹ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group consisting of a combination thereof, each having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group, with a vinyl group being preferred. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Furthermore, ^R2 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group that is a combination of these groups, each having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

^R3 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

In addition, examples of the substituents of R ¹ and R ² in the formula (1) include a methyl group and a vinyl group, and examples of the substituent of R ³ include a methyl group.

In formula (1), the R ^1s are independent of each other and may be different from each other or may be the same. The same applies to R ² and R ³ .

Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), where m is an integer from 0 to 2000 and n is an integer from 1000 to 10000. m is preferably 0 to 1000, and n is preferably 2000 to 5000.

Specific examples of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) include those represented by the following formula (1-1):

In formula (1-1), R ¹ and R ² each independently represent a methyl group or a vinyl group, and at least one of them is a vinyl group.

The vinyl group-containing linear organopolysiloxane (A1) may contain a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more vinyl groups in the molecule and having a vinyl group content of 0.4 mol% or less. The vinyl group content of the first vinyl group-containing linear organopolysiloxane (A1-1) may be 0.1 mol% or less.

The vinyl group-containing linear organopolysiloxane (A1) may also contain a first vinyl group-containing linear organopolysiloxane (A1-1) and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of 0.5 to 15 mol %.

By combining a first vinyl group-containing linear organopolysiloxane (A1-1) and a second vinyl group-containing linear organopolysiloxane (A1-2) with a high vinyl group content as the raw rubber, which is the raw material of the silicone rubber, it is possible to unevenly distribute the vinyl groups and more effectively form a crosslinking density distribution in the crosslinked network of the silicone rubber. As a result, the tear strength of the cured product of the silicone rubber composition is more effectively increased, and dimensional stability and transferability are easier to control.

Specifically, as the vinyl group-containing linear organopolysiloxane (A1), it is preferable to use, for example, a first vinyl group-containing linear organopolysiloxane (A1-1) having in the molecule two or more units in which R ¹ is a vinyl group and/or units in which R ² is a vinyl group, and containing 0.4 mol % or less of these units in the above formula (1-1), and a second vinyl group-containing linear organopolysiloxane (A1-2) containing 0.5 to 15 mol % of units in which R ¹ is a vinyl group and/or units in which R ² is a vinyl group.

The first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of 0.01 to 0.2 mol %. The second vinyl group-containing linear organopolysiloxane (A1-2) preferably has a vinyl group content of 0.8 to 12 mol %.

Furthermore, when the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2) are combined and blended, the ratio of (A1-1) to (A1-2) is not particularly limited, but for example, the weight ratio of (A1-1):(A1-2) is preferably 50:50 to 95:5, and more preferably 80:20 to 90:10.

The first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may each be used alone or in combination of two or more.

The vinyl group-containing organopolysiloxane (A) may also contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

<<Organohydrogenpolysiloxane (B)>>
The silicone rubber composition of the present embodiment can contain an organohydrogenpolysiloxane (B).
The organohydrogenpolysiloxane (B) is classified into a linear organohydrogenpolysiloxane (B1) having a linear structure and a branched organohydrogenpolysiloxane (B2) having a branched structure, and may contain either one or both of these.

Linear organohydrogenpolysiloxane (B1) has a linear structure and a structure in which hydrogen is directly bonded to Si (≡Si-H), and is a polymer that undergoes a hydrosilylation reaction with the vinyl groups of vinyl group-containing organopolysiloxane (A) and with vinyl groups of components blended into the silicone rubber composition, crosslinking these components.

The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited, but for example, the weight average molecular weight is preferably 20,000 or less, and more preferably 1,000 or more and 10,000 or less.

The weight average molecular weight of the linear organohydrogenpolysiloxane (B1) can be measured, for example, by polystyrene conversion using GPC (gel permeation chromatography) with chloroform as the developing solvent.

In addition, it is generally preferred that the linear organohydrogenpolysiloxane (B1) does not have a vinyl group. This effectively prevents the crosslinking reaction from proceeding within the molecule of the linear organohydrogenpolysiloxane (B1).

As the linear organohydrogenpolysiloxane (B1) described above, for example, one having a structure represented by the following formula (2) is preferably used.

In formula (2), ^R4 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these groups, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

Furthermore, ^R5 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, a hydrocarbon group combining these groups, or a hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, and a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In addition, in formula (2), the multiple ^R4s are independent of each other and may be different from each other or may be the same. The same applies to ^R5 . However, among the multiple ^R4s and ^R5s , at least two or more are hydrido groups.

Furthermore, ^R6 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group that is a combination of these. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. The multiple ^R6s are independent of each other and may be different from each other or the same.

In addition, examples of the substituents R ⁴ , R ⁵ and R ⁶ in the formula (2) include a methyl group and a vinyl group, and from the viewpoint of preventing an intramolecular crosslinking reaction, a methyl group is preferable.

Furthermore, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), where m is an integer from 2 to 150 and n is an integer from 2 to 150. Preferably, m is an integer from 2 to 100 and n is an integer from 2 to 100.

The linear organohydrogenpolysiloxane (B1) may be used alone or in combination of two or more.

The branched organohydrogenpolysiloxane (B2) has a branched structure, and therefore forms regions with high crosslink density, making it a component that contributes greatly to the formation of a sparsely-dense crosslink structure in the silicone rubber system. In addition, like the linear organohydrogenpolysiloxane (B1), it has a structure in which hydrogen is directly bonded to silicon (≡Si-H), and undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with the vinyl groups of the components blended into the silicone rubber composition, forming a polymer that crosslinks these components.

The specific gravity of the branched organohydrogenpolysiloxane (B2) is in the range of 0.9 to 0.95.

Furthermore, it is generally preferred that the branched organohydrogenpolysiloxane (B2) does not have a vinyl group. This effectively prevents the crosslinking reaction from proceeding within the molecule of the branched organohydrogenpolysiloxane (B2).

The branched organohydrogenpolysiloxane (B2) is preferably one represented by the following average composition formula (c):

Average composition formula (c)
(H _a (R ⁷ ) _3-a SiO _1/2 ) _m (SiO _4/2 ) _n
(In formula (c), ^R7 is a monovalent organic group, a is an integer ranging from 1 to 3, m is the number of H _a ( ^R7 ) _3-a SiO _1/2 units, and n is the number of SiO _4/2 units.)

In formula (c), ^R7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si) and is an integer ranging from 1 to 3, preferably 1.

In addition, in formula (c), m is the number of H _a (R ⁷ ) _3-a SiO _1/2 units, and n is the number of SiO _4/2 units.

Branched organohydrogenpolysiloxane (B2) has a branched structure. Linear organohydrogenpolysiloxane (B1) and branched organohydrogenpolysiloxane (B2) differ in that their structures are linear or branched, and the number of alkyl groups R bonded to Si (R/Si), where the number of Si is 1, is in the range of 1.8 to 2.1 for linear organohydrogenpolysiloxane (B1) and 0.8 to 1.7 for branched organohydrogenpolysiloxane (B2).

In addition, because the branched organohydrogenpolysiloxane (B2) has a branched structure, for example, when heated in a nitrogen atmosphere to 1000°C at a heating rate of 10°C/min, the amount of residue is 5% or more. In contrast, because the linear organohydrogenpolysiloxane (B1) is linear, the amount of residue after heating under the above conditions is almost zero.

Specific examples of branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3):

In formula (3), ^R7 is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group consisting of a combination thereof, or a hydrogen atom. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group. Examples of the substituent of ^R7 include a methyl group.

In addition, in formula (3), multiple R ^7s are independent of each other and may be different from each other or may be the same.

In addition, in formula (3), "-O-Si≡" indicates that Si has a branched structure that extends three-dimensionally.

The branched organohydrogenpolysiloxane (B2) may be used alone or in combination of two or more.

In addition, the amount of hydrogen atoms (hydride groups) directly bonded to Si in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is not particularly limited. However, in the silicone rubber composition, the total amount of hydride groups in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is preferably 0.5 to 5 moles, more preferably 1 to 3.5 moles, per mole of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1). This ensures that a crosslinked network is formed between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organopolysiloxane (A1).

<<Inorganic particles (C)>>
The silicone rubber composition of this embodiment may contain inorganic particles (C) in addition to the vinyl group- containing organopolysiloxane (A).

The inorganic particles (C) are not particularly limited, but may be particles made of one or more selected from the group consisting of diatomaceous earth, iron oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, magnesium carbonate, zinc carbonate, glass wool, mica, calcium carbonate, zinc oxide, alumina, crystalline silica, amorphous silica, fused silica, and zeolite. Among these, one or more selected from the group consisting of calcium carbonate, zinc oxide, alumina, crystalline silica, amorphous silica, fused silica, and zeolite are preferred.
Furthermore, depending on the synthesis method of silica, fumed silica (flame-processed silica), fired silica, precipitated silica, etc. may be used.
The inorganic particles (C) may be used alone or in combination of two or more kinds.

The inorganic particles (C) preferably have a specific surface area, as measured by the BET method, of, for example, 50 to 400 ^{m 2} /g, and more preferably 100 to 400 m ² /g.
The average primary particle size of the inorganic particles (C) is preferably, for example, from 1 to 100 nm, and more preferably from about 5 to 20 nm.

By using inorganic particles (C) that have a specific surface area and average particle size within this range, the hardness and mechanical strength of the release layer 1 that is formed can be improved, and the balance between releasability, mold conformability, and dimensional stability can be improved.

<<Silane coupling agent (D)>>
The silicone rubber composition of the present embodiment may contain a silane coupling agent (D).
The silane coupling agent (D) may have a hydrolyzable group. The hydrolyzable group is hydrolyzed by water to become a hydroxyl group, and the hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the inorganic particles (C), thereby modifying the surface of the inorganic particles (C).

The silane coupling agent (D) may contain a silane coupling agent having a hydrophobic group. This provides the surface of the inorganic particles (C) with this hydrophobic group, which reduces the cohesive force of the inorganic particles (C) in the silicone rubber composition and thus in the silicone rubber (in the case of silica particles, the cohesion caused by hydrogen bonds due to silanol groups is reduced). As a result, it is presumed that the dispersibility of the inorganic particles (C) in the silicone rubber composition is improved. This increases the interface between the inorganic particles (C) and the rubber matrix, and increases the reinforcing effect of the inorganic particles (C). Furthermore, it is presumed that the slipperiness of the inorganic particles (C) in the matrix is improved during deformation of the rubber matrix. And, due to the improvement in the dispersibility and slipperiness of the inorganic particles (C), the mechanical strength (e.g., mold followability, dimensional stability, etc.) of the release layer 1 due to the inorganic particles (C) is improved.

Furthermore, the silane coupling agent (D) may contain a silane coupling agent having a vinyl group. This introduces a vinyl group onto the surface of the inorganic particles (C). Therefore, when the silicone rubber composition is cured, that is, when the vinyl group of the vinyl group-containing organopolysiloxane (A) and the hydride group of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction to form a network (crosslinked structure), the vinyl group of the inorganic particles (C) (in the case of silica particles) also participates in the hydrosilylation reaction with the hydride group of the organohydrogenpolysiloxane (B), so that the inorganic particles (C) are also incorporated into the network. This allows the release layer 1 to be formed with a low hardness and high modulus.

As the silane coupling agent (D), a silane coupling agent having a hydrophobic group and a silane coupling agent having a vinyl group can be used in combination.

Examples of the silane coupling agent (D) include those represented by the following formula (4):

Y _n -Si-(X) _4-n (4)
In the above formula (4), n represents an integer of 1 to 3. Y represents any functional group having a hydrophobic group, a hydrophilic group, or a vinyl group, and when n is 1, it is a hydrophobic group, and when n is 2 or 3, at least one of them is a hydrophobic group. X represents a hydrolyzable group.

The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group that is a combination of these. Examples include a methyl group, an ethyl group, a propyl group, and a phenyl group, and among these, a methyl group is preferable.

The hydrophilic group may be, for example, a hydroxyl group, a sulfonic acid group, a carboxyl group, or a carbonyl group, and among these, a hydroxyl group is preferred. Note that a hydrophilic group may be included as a functional group, but it is preferable that it is not included from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

Further, examples of the hydrolyzable group include alkoxy groups such as methoxy and ethoxy groups, chloro groups, and silazane groups, among which silazane groups are preferred due to their high reactivity with inorganic particles (C) (in the case of silica particles). Note that those having silazane groups as hydrolyzable groups have two (Y _n -Si-) structures in the above formula (4) due to their structural characteristics.

Specific examples of the silane coupling agent (D) represented by the above formula (4) include, for example, alkoxysilanes such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and phenyltrichlorosilane; and hexamethyldisilazane, which have a hydrophobic group as a functional group. Examples of the silane having a vinyl group include alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane. Among these, taking into consideration the above description, it is particularly preferable that the silane having a hydrophobic group is hexamethyldisilazane, and the silane having a vinyl group is divinyltetramethyldisilazane.

<<Platinum or platinum compound (E)>>
The silicone rubber composition of the present embodiment can contain platinum or a platinum compound (E).
The platinum or platinum compound (E) is a catalytic component that acts as a catalyst during curing. The amount of platinum or platinum compound (E) added is a catalytic amount.

As the platinum or platinum compound (E), known substances can be used, such as platinum black, platinum supported on silica or carbon black, chloroplatinic acid or an alcohol solution of chloroplatinic acid, a complex salt of chloroplatinic acid and an olefin, and a complex salt of chloroplatinic acid and a vinyl siloxane.

The platinum or platinum compound (E) may be used alone or in combination of two or more.

<<Water (F)>>
Furthermore, the silicone rubber composition of this embodiment may contain water (F) in addition to the above components (A) to (E).

Water (F) functions as a dispersion medium to disperse each component contained in the silicone rubber composition, and is also a component that contributes to the reaction between the inorganic particles (C) and the silane coupling agent (D). Therefore, the inorganic particles (C) and the silane coupling agent (D) can be more reliably linked to each other in the silicone rubber, and uniform properties can be exhibited overall.

Furthermore, the silicone rubber composition of this embodiment may contain, in addition to the above components (A) to (F), known additive components that are blended into silicone rubber compositions. Examples of known additive components that can be blended appropriately include dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, and thermal conductivity improvers.

In addition, the content ratio of each component in the silicone rubber composition is not particularly limited, but is set, for example, as follows.

In this embodiment, the upper limit of the content of the inorganic particles (C) may be, for example, 60 parts by weight or less, preferably 50 parts by weight or less, and more preferably 40 parts by weight or less, relative to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). This improves the mechanical strength, such as the hardness and tear strength, of the release film 10, and improves the balance of releasability, mold followability, and dimensional stability. In addition, the lower limit of the content of the inorganic particles (C) is not particularly limited, but may be, for example, 10 parts by weight or more, relative to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A).

The silane coupling agent (D) is preferably contained in an amount of 5 parts by weight or more and 100 parts by weight or less, and more preferably 5 parts by weight or more and 40 parts by weight or less, per 100 parts by weight of the vinyl group-containing organopolysiloxane (A). This can reliably improve the dispersibility of the inorganic particles (C) in the silicone rubber composition.

The content of organohydrogenpolysiloxane (B) is preferably, for example, 0.5 parts by weight or more and 20 parts by weight or less, and more preferably 0.8 parts by weight or more and 15 parts by weight or less, per 100 parts by weight of the total amount of vinyl group-containing organopolysiloxane (A), inorganic particles (C), and silane coupling agent (D). By keeping the content of (B) within the above range, a more effective curing reaction may be achieved.

The content of platinum or platinum compound (E) means a catalytic amount and can be set appropriately, but specifically, it is an amount in which the platinum group metal in this component is 0.01 to 1000 ppm by weight, preferably 0.1 to 500 ppm, relative to the total amount of vinyl group-containing organopolysiloxane (A), inorganic particles (C), and silane coupling agent (D). By making the content of platinum or platinum compound (E) equal to or greater than the above lower limit, the obtained silicone rubber composition can be sufficiently cured. By making the content of platinum or platinum compound (E) equal to or less than the above upper limit, the curing speed of the obtained release layer 1 can be improved.

Furthermore, when water (F) is contained, its content can be set appropriately, but specifically, for example, it is preferably in the range of 10 to 100 parts by weight, and more preferably in the range of 30 to 70 parts by weight, per 100 parts by weight of the silane coupling agent (D). This allows the reaction between the silane coupling agent (D) and the inorganic particles (C) to proceed more reliably.

The silicone rubber composition of the present embodiment may be a paste containing the solvent (G).
Examples of the solvent (G) include aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, methylcyclohexane, ethylcyclohexane, octane, decane, dodecane, and tetradecane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, trifluoromethylbenzene, and benzotrifluoride; ethers such as diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, 1,4-dioxane, 1,3-dioxane, and tetrahydrofuran; haloalkanes such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane; carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; and sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide. These may be used alone or in combination of two or more.
The solvent used here may be appropriately selected from among solvents capable of uniformly dissolving or dispersing the components in the paste.

[Method of manufacturing the release layer]
Next, a method for producing the release layer 1 of this embodiment will be described.
In the method for producing the release layer 1 of this embodiment, the above-mentioned silicone rubber composition is prepared, and the silicone rubber composition is formed into a film, which is then cured to obtain the release layer 1.
Details are provided below.

First, the silicone rubber composition components are mixed uniformly using any kneading device to prepare the silicone rubber composition.

[1] For example, a vinyl group-containing organopolysiloxane (A), inorganic particles (C), and a silane coupling agent (D) are weighed out in predetermined amounts, and then kneaded using any kneading device to obtain a kneaded product containing these components (A), (C), and (D).

It is preferable to prepare this mixture by first kneading the vinyl group-containing organopolysiloxane (A) with the silane coupling agent (D) and then kneading (mixing) the inorganic particles (C). This further improves the dispersibility of the inorganic particles (C) in the vinyl group-containing organopolysiloxane (A).

When obtaining this kneaded mixture, water (F) may be added to the kneaded mixture of components (A), (C), and (D) as necessary. This allows the reaction between the silane coupling agent (D) and the inorganic particles (C) to proceed more reliably.

Furthermore, it is preferable that the kneading of each of the components (A), (C), and (D) is carried out through a first step of heating at a first temperature and a second step of heating at a second temperature. This allows the surfaces of the inorganic particles (C) to be surface-treated with the coupling agent (D) in the first step, and allows the by-products generated by the reaction between the inorganic particles (C) and the coupling agent (D) to be reliably removed from the kneaded mixture in the second step. Thereafter, component (A) may be added to the obtained kneaded mixture as necessary, and further kneaded. This allows the compatibility of the components in the kneaded mixture to be improved.

The first temperature is preferably, for example, about 40 to 120°C, and more preferably, for example, about 60 to 90°C. The second temperature is preferably, for example, about 130 to 210°C, and more preferably, for example, about 160 to 180°C.

The atmosphere in the first step is preferably an inert atmosphere such as a nitrogen atmosphere, and the atmosphere in the second step is preferably a reduced pressure atmosphere.

Furthermore, the time for the first step is, for example, preferably about 0.3 to 1.5 hours, and more preferably about 0.5 to 1.2 hours. The time for the second step is, for example, preferably about 0.7 to 3.0 hours, and more preferably about 1.0 to 2.0 hours.

By setting the above conditions for the first and second steps, the above effects can be obtained more significantly.

[2] Next, predetermined amounts of organohydrogenpolysiloxane (B) and platinum or platinum compound (E) are weighed out, and then, using any kneading device, the components (B) and (E) are kneaded into the mixture prepared in the above step [1] to obtain a silicone rubber composition. The obtained silicone rubber composition may be a paste containing a solvent.

When mixing the components (B) and (E), it is preferable to first mix the mixture prepared in step [1] above with the organohydrogenpolysiloxane (B), and then mix the mixture prepared in step [1] above with platinum or a platinum compound (E), and then mix the mixtures together. This allows the components (A) to (E) to be reliably dispersed in the silicone rubber composition without allowing the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) to proceed.

The temperature at which components (B) and (E) are kneaded is, for example, preferably about 10 to 70°C, and more preferably about 25 to 30°C, as the roll setting temperature.

Furthermore, the kneading time is preferably, for example, about 5 minutes to 1 hour, and more preferably about 10 to 40 minutes.

In the above steps [1] and [2], by setting the temperature within the above range, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) can be more accurately prevented or inhibited. In addition, in the above steps [1] and [2], by setting the kneading time within the above range, the components (A) to (E) can be more reliably dispersed in the silicone rubber composition.

The kneading device used in each step [1] and [2] is not particularly limited, but may be, for example, a kneader, a two-roll mill, a Banbury mixer (continuous kneader), a pressure kneader, etc.

In addition, in this step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded mixture. This makes it possible to more accurately prevent or inhibit the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) even if the temperature of the kneaded mixture is set to a relatively high temperature.

[3] Next, the silicone rubber composition obtained in step [2] may be made into a paste by dissolving it in a solvent.

[4] Next, the silicone rubber composition is processed into a film and cured to form the release layer 1.
Specifically, the silicone rubber composition is formed into a film by extrusion molding, calendar molding, press molding, coating, etc. During film formation, the surface shape of a roll or the like may be transferred or embossed.

In this embodiment, the curing process of the silicone rubber composition is carried out, for example, by heating at 100 to 250°C for 1 to 30 minutes (first curing) and then post-baking at 100 to 250°C for 1 to 4 hours (secondary curing).

Through the above steps, a release layer 1, i.e., a release film 10, is obtained using the silicone rubber composition of this embodiment.

[Uses and methods of use of release film]
The release film 10 of the present embodiment is used in a resin-encapsulating process for a semiconductor device, in which it is disposed between a mold to which an encapsulating resin is supplied and a semiconductor device to be encapsulated with the resin.
Hereinafter, an example of a method for manufacturing a resin-encapsulated semiconductor device using the release film 10 will be described. However, the use of the release film 10 is not limited to this. For example, it can be used as a release film when hardening a prepreg of a thermosetting resin such as CFRP, a release film for molding a thermosetting resin, a transfer release film for decoration in which printing or the like is applied to a product having a three-dimensional shape, and the like.

The method for manufacturing a resin-encapsulated semiconductor device includes the following steps.
(Step 1) Preparation of the semiconductor device (Step 2) Installation of a release film (Step 3) Supply of sealing resin (Step 4) Hardening (Step 5) Demolding of molded body Each step will be described in detail below.

(Step 1) Preparation of Semiconductor Device A semiconductor device is formed by electrically connecting electrode pads on circuit wiring provided on a support and electrodes provided on a semiconductor element.
Examples of the semiconductor element include optical elements such as a light emitting element and a light receiving element. An example of the light emitting element is an LED chip (light emitting diode), and an example of the light receiving element is an image sensor.
The support is a substrate formed in any shape such as a circle or a polygon. Examples of the support include a ceramic substrate, a silicone substrate, a metal substrate, a rigid substrate such as an epoxy resin or a BT resin, or a flexible substrate such as a polyimide resin or a polyethylene substrate.

(Step 2) Step of Setting Release Film The release film 10 is placed in a mold having a recess for supplying the sealing resin. At this time, the release surface 3 of the release film 10 is placed on the front side, that is, in contact with the sealing resin to be supplied later.
The release film 10 may also be disposed within the recess of the mold and along the surface of the flat portion surrounding the recess. At this time, it is preferable to use a suction device or the like to suck and discharge the air, moisture, gas, etc. in the space between the release film 10 and the mold, so that the release film 10 follows the shape of the recess of the mold, and to perform vacuum adsorption. Furthermore, in order to firmly fix the release film 10 to the mold, the release film 10 may be clamped by a chuck mechanism arranged at a position corresponding to the outer periphery of the sealing resin injection area, the outer periphery of the entire release film 10, or the outer periphery of the entire mold.
Examples of the mold include a known metal mold and a resin mold.

(Step 3) Sealing resin supply step Next, the sealing resin is supplied to the recessed portion of the mold where the release film 10 is disposed. A known method can be used as the supply method. In addition, the sealing resin can be a known resin, for example, silicone-based resin, epoxy-based resin, acrylic-based resin, fluorine-based resin, polyimide-based resin, silicone-modified epoxy-based resin, etc., or a mixture of these, and precursors thereof.
In this embodiment, when the release film 10 is applied to a compression molding method, the sealing resin is preferably processed into a tablet, granule, sealed particle, or sheet shape.
In the mold, the sealing resin is heated to a predetermined temperature and is in a fluid state.

(Step 4) Curing Step Next, the surface of the prepared semiconductor device on which the semiconductor element is provided is pressed against a mold in which the sealing resin is supplied into the recess. This causes the semiconductor element to be covered with the sealing resin. The sealing resin is then cured by applying heat and pressure to obtain a molded body.
When the sealing resin is a precursor of a curable resin, it may be cured by heating and irradiation with active energy rays, examples of which include radiation, ultraviolet rays, visible light, and electron beams.

(Step 5) Demolding step of molded body After that, the molded body is demolded. In the demolding step of the molded body, air, moisture, gas, etc. are supplied between the release film 10 and the mold, so that the release film 10 is peeled off from the mold and the molded body is demolded. At the same time or after this, the release film 10 is demolded from the molded body.
When there is one semiconductor element provided on the support, this molded body becomes a resin-sealed semiconductor device.

Second Embodiment
In the first embodiment, the release film 10 is described as being composed of the release layer 1, but in the second embodiment, an example will be described in which the release film 11 is configured by laminating the release layer 1 and the base layer 2. In the following, a description of the same configuration and effects as those in the first embodiment will be omitted.

FIG. 2 is a cross-sectional view that typically shows a cross section of a release film of a second embodiment.
As shown in FIG. 2 , the release film 11 of the present embodiment includes a base layer 2 and a release layer 1 laminated on the base layer 2 .

The thickness of the release film 11 is preferably 25 μm or more and 150 μm or less, more preferably 35 μm or more and 100 μm or less, and even more preferably 40 μm or more and 50 μm or less.

[Base layer]
The base material layer 2 is used from the viewpoint of imparting appropriate rigidity to the release film 11 .

The thickness of the base layer 2 is preferably 5 μm or more and 50 μm or less, more preferably 9 μm or more and 35 μm or less, and even more preferably 12 μm or more and 25 μm or less.
By setting the thickness of the base layer 2 to the above-mentioned lower limit or more, the rigidity of the release film 11 is increased, and excessive deformation and wrinkles are easily suppressed. As a result, mold followability and dimensional stability are obtained. On the other hand, by setting the thickness of the base layer 2 to the above-mentioned upper limit or less, the rigidity of the release film 11 can be controlled, and a good balance between mold followability and releasability can be achieved.

The material of the base layer 2 may be one or more selected from the group consisting of polyester resin, poly-4-methyl-1-pentene resin, polyamide resin, and polypropylene resin.
Examples of the polyester resin include polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), polyhexamethylene terephthalate resin (PHT), and polyethylene naphthalate resin (PEN).
Examples of the polyamide resin include aliphatic polyamides, aromatic polyamides, etc. Specific examples of the aliphatic polyamides include polyamide 6, polyamide 6,6, polyamide 6-6,6 copolymer, polyamide 11, and polyamide 12. Specific examples of the aromatic polyamides include polyamide 61, polyamide 66/6T, polyamide 6T/6, and polyamide 12/6T.
Among these, polyethylene terephthalate resin, polybutylene terephthalate resin, and polyamide resin are preferable.

A stretched film may also be used as the substrate layer 2, and the stretching can be performed using known methods such as sequential biaxial stretching, simultaneous biaxial stretching, and tubular stretching.

[Method of producing release film]
The release film 11 can be formed by a known method such as co-extrusion, extrusion lamination, dry lamination, inflation, etc. The release layer 1 may be formed on the base layer 2 by applying a silicone rubber composition prepared in a paste form to the surface of the base layer 2.
In the release film 11 of the second embodiment, for example, the release layer 1 and the base layer 2 may be produced separately and then bonded together by a laminator, etc. In addition, the release layer 1 and the base layer 2 may be bonded together as they are, or may be bonded together via an adhesive layer.
The method for producing the base layer 2 is not limited, and specific examples thereof include an inflation extrusion method and a T-die extrusion method.
In the second embodiment, the silicone rubber composition, paste, and film-like cured product of the silicone rubber composition described in the first embodiment can be used.

The above describes the embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements that can achieve the object of the present invention are included in the present invention.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the description of these examples.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the description of these examples.

(1) Raw Materials The raw material components used in the Examples and Comparative Examples shown in Table 1 are as follows.
(Vinyl Group-Containing Organopolysiloxane (A))
Low vinyl group-containing linear organopolysiloxane (A1-1): a vinyl group-containing dimethylpolysiloxane synthesized according to Synthesis Scheme 1 (a structure represented by formula (1-1) in which only R ¹ (terminal) is a vinyl group)
High vinyl group-containing linear organopolysiloxane (A1-2): A vinyl group-containing dimethylpolysiloxane synthesized according to Synthesis Scheme 2 (a structure represented by formula (1-1) in which R ¹ and R ² are vinyl groups).
Low vinyl group-containing linear organopolysiloxane (A1-3): A vinyl group-containing dimethylpolysiloxane synthesized according to Synthesis Scheme 3 (a structure represented by formula (1-1) in which R ¹ and R ² are vinyl groups).

(Organohydrogenpolysiloxane (B))
・Momentive: "TC-25D"

(Inorganic particles (C))
Silica particles (C-1): silica fine particles (particle size 7 nm, specific surface area 300 m ² /g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL300"
Silica particles (C-2): silica fine particles (particle size 7 nm, specific surface area 240 m2/g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL R976"

(Silane Coupling Agent (D))
Silane coupling agent (D-1): hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)"
Silane coupling agent (D-2): Divinyltetramethyldisilazane, manufactured by Gelest, "1,3-DIVINYLTETRAMETHYLDISILAZANE (SID4612.0)"

(Platinum or platinum compound (E))
・Momentive: "TC-25A"

(Synthesis of vinyl group-containing organopolysiloxane (A))
[Synthesis Scheme 1: Synthesis of low-vinyl-group-containing linear organopolysiloxane (A1-1)]
A low-vinyl-group-containing linear organopolysiloxane (A1-1) was synthesized according to the following formula (5).
That is, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium siliconate were placed in a 300 mL separable flask equipped with a cooling tube and stirring blade and substituted with Ar gas, and the temperature was raised and the mixture was stirred for 30 minutes at 120° C. During this time, an increase in viscosity was confirmed.
The temperature was then raised to 155° C. and stirring was continued for 3 hours. After 3 hours, 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added and the mixture was further stirred at 155° C. for 4 hours.
After 4 hours, the mixture was diluted with 250 mL of toluene and washed three times with water. The washed organic layer was washed several times with 1.5 L of methanol for reprecipitation purification, and the oligomer and polymer were separated. The resulting polymer was dried overnight under reduced pressure at 60° C. to obtain a low-vinyl-group-containing linear organopolysiloxane (A1-1) (Mn=2.2×10 ⁵ , Mw=4.8×10 ⁵ ). The vinyl group content calculated by H-NMR spectrum measurement was 0.04 mol%.

[Synthesis Scheme 2: Synthesis of Highly Vinyl Group-Containing Linear Organopolysiloxane (A1-2)]
A vinyl-rich linear organopolysiloxane (A1-2) was synthesized as shown in the following formula (6) by the same synthesis process as for (A1-1), except that 0.86 g (2.5 mmol) of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane was used in addition to 74.7 g (252 mmol) of octamethylcyclotetrasiloxane in the synthesis process for (A1-1) above. (Mn=2.3×10 ⁵ , Mw=5.0×10 ⁵ ). The vinyl group content calculated by H-NMR spectrum measurement was 0.93 mol%.

[Synthesis Scheme 3: Synthesis of low-vinyl-group-containing linear organopolysiloxane (A1-3)]
A linear organopolysiloxane (A1-3) having a low vinyl group content was synthesized as shown in formula (6) above by the same procedure as in the synthesis of (A1-2) above, except that 75.3 g (254 mmol) of octamethylcyclotetrasiloxane and 0.12 g (0.35 mmol) of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane were used and the stirring time after heating to 155° C. was changed to 3 hours. (Mn=2.5×10 ⁵ , Mw=5.0×10 ⁵ ). The vinyl group content calculated by H-NMR spectrum measurement was 0.13 mol %.

(2) Preparation of Silicone Rubber Composition A silicone rubber composition was prepared as follows.
First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D), and water (F) was pre-kneaded in the proportions shown in Table 1 below, and then inorganic particles (C) were added to the mixture and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after the addition of the inorganic particles (C) was carried out through a first step of kneading for 1 hour under conditions of 60 to 90°C in a nitrogen atmosphere for the coupling reaction, and a second step of kneading for 2 hours under conditions of 160 to 180°C in a reduced pressure atmosphere for the removal of the by-product (ammonia), followed by cooling, and then adding the remaining 10% of the vinyl group-containing organopolysiloxane (A) in two portions and kneading for 20 minutes.
Next, organohydrogenpolysiloxane (B) (TC-25D) and platinum or platinum compound (E) (TC-25A) were added in the ratios shown in Table 1 below to 100 parts by weight of the resulting kneaded product (silicone rubber compound), and the mixture was kneaded with a roll to obtain a silicone rubber composition.

(3) Measurement of Physical Properties of Silicone Rubber Composition The physical properties of the silicone rubber composition were measured according to the following procedures. The results are shown in Table 2.

Tear strength TS0
(Procedure for measuring tear strength)
A crescent-shaped test piece was prepared using the cured product of the silicone rubber composition in accordance with JIS K6252 (2001), and the tear strength of the resulting crescent-shaped test piece was measured at 25° C. The unit is N/mm.

・Tear strength TS1 (N/mm)
(Procedure for measuring tear strength)
A crescent-shaped test specimen was prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and then the specimen was held at 100°C for 30 minutes. The tear strength of the crescent-shaped test specimen obtained at 100°C was recorded as TS1 (N/mm).

・Tear strength TS2 (N/mm)
(Procedure for measuring tear strength)
A crescent-shaped test piece was prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and then the test piece was held at 150°C for 30 minutes. The tear strength of the crescent-shaped test piece obtained at 150°C was recorded as TS2 (N/mm).

Breaking elongation BE0s (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004), and the breaking elongation of the resulting dumbbell-shaped No. 3 test pieces was measured at 25°C. The breaking elongation was calculated as [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and was designated as BE0s. The unit is %.

Breaking elongation BE0 (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, a dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004), and the breaking elongation of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. The breaking elongation is calculated as [chuck movement distance (mm)]÷[initial chuck distance (60 mm)]×100, and is designated as BE0. The unit is %.

Breaking elongation BE1 (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004), and after holding at 100°C for 30 minutes, the breaking elongation of the resulting dumbbell-shaped No. 3 test pieces was measured at 100°C. The breaking elongation was calculated as [chuck travel distance (mm)]÷[initial chuck distance (60 mm)]×100, and designated as BE1. The unit is %.

Breaking elongation BE2 (%)
(Procedure for measuring elongation at break)
Using the cured product of the silicone rubber composition, dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004), and after holding at 150°C for 30 minutes, the breaking elongation of the resulting dumbbell-shaped No. 3 test pieces was measured at 150°C. The breaking elongation was calculated as [chuck travel distance (mm)]÷[initial chuck distance (60 mm)]×100, and was designated as BE2. The unit is %.

Elongation E1 (%) at 1 MPa
(Procedure for measuring elongation at 1 MPa)
Using the cured product of the silicone rubber composition, dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004), and a tensile test was carried out under conditions of 25°C and a tensile speed of 500 mm/min, and the elongation of the resulting dumbbell-shaped No. 3 test piece when the stress reached 1 MPa was calculated by the formula [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and designated as E1. The unit is %.

Elongation E2 (%) at 0.2 MPa
(Procedure for measuring elongation at 0.2 MPa)
Using the cured product of the silicone rubber-based curable composition, a dumbbell-shaped No. 3 test piece was prepared in accordance with JIS K6251 (2004), and a tensile test was carried out under conditions of 25°C and a tensile speed of 500 mm/min, and the elongation of the obtained dumbbell-shaped No. 3 test piece when the stress reached 0.2 MPa was calculated by the formula [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, with the unit being %.

Tensile strength S (MPa)
(Procedure for measuring tensile strength)
Dumbbell No. 3 test pieces were prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and the tensile strength of the dumbbell No. 3 test pieces at 25° C. was measured, the unit being MPa.

Stroke change rate after n hours SCn (%)
(Procedure for measuring stroke change rate)
Dumbbell-shaped No. 3 test pieces were prepared in accordance with JIS K6251 (2004) using the cured product of the silicone rubber composition, and the elongation of the resulting dumbbell-shaped No. 3 test pieces was measured over time at 25°C when held between chucks at a stress of 1 MPa.
The time when the stress became 1 MPa was defined as 0 h, and the stroke amount after a predetermined time n (h) was defined as En (%) = [chuck movement distance (mm)] ÷ [initial chuck distance (60 mm)] × 100. The stroke change rate was calculated from the measured stroke amount En based on the following formula.
Stroke change rate after n hours SCn (%) = (En-E0)/E0 x 100

・Durometer hardness A
(Procedure for measuring durometer hardness A)
A sheet-like test specimen was prepared using the cured product of the silicone rubber composition, and the durometer hardness A of the resulting sheet-like test specimen at 25° C. was measured in accordance with JIS K6253 (1997).

- Plasticity (Procedure for measuring plasticity)
The uncured silicone rubber composition was used as a test sample, and the plasticity of the resulting test sample at 25° C. was measured 10 minutes after the start of the measurement using a Williams plasticity meter in accordance with JIS K6249 (2003).

(4) Preparation of release layer (release film) <Example 1>
[Preparation of release film having only a release layer]
The silicone rubber composition prepared in (3) above was pressed at 160°C and 20 MPa for 20 minutes to form a film having a thickness of 300 μm, and was cured primarily. It was then heated at 200°C for 4 hours to be cured secondary, and a release film consisting of a release layer was prepared. In addition, in this procedure, the unevenness of the mold surface was transferred when the silicone rubber composition was pressed, thereby performing uneven processing.
The release layer of the obtained release film had a thickness of 300 μm, and the surface roughness Rz of the release surface of the release layer was 3 μm.

Example 2
[Preparation of release film having substrate layer]
A biaxially oriented polyethylene terephthalate film (Toyobo Co., Ltd., Toyobo Ester (registered trademark) film, 12 μm thick) was used as a substrate layer. A paste (solid content 25 mass%, decane solvent) made of the silicone rubber composition prepared in (3) above was applied onto the substrate layer using a bar coater and cured at 180° C. for 120 minutes to obtain a release film having a release layer on the substrate layer.
In this procedure, after the paste made of the silicone rubber composition was dried, a matte film was sandwiched between the two layers to provide an uneven surface to the release layer.
The release layer of the obtained release film had a thickness of 38 μm, and the surface roughness Rz of the release surface of the release layer was 2 μm.

<Comparative Example 1>
A biaxially oriented polyethylene terephthalate film (Toyobo Co., Ltd., Toyobo Ester (registered trademark) film, 12 μm thick) was used as a substrate layer. A paste (solid content 25 mass%, decane solvent) made of the silicone rubber composition prepared in (3) above was applied onto the substrate layer using a bar coater and cured at 180° C. for 120 minutes to obtain a release film having a release layer on the substrate layer.
In this procedure, after the paste made of the silicone rubber composition was dried, a matte film was sandwiched between the two layers to provide an uneven surface to the release layer.
The release layer of the obtained release film had a thickness of 38 μm, and the surface roughness Rz of the release surface of the release layer was 2 μm.

(5) Measurement and Evaluation The following measurements and evaluations were carried out using the obtained release film. The results are shown in Table 2.

(i) Measurement of surface roughness Rz of the release surface of the release layer The measurement was performed in accordance with JIS B0601:2013.

(ii) Evaluation of Mold Conformity, Dimensional Stability, and Mold Releasability First, tablets of the following thermosetting resin composition were prepared as a resin for encapsulation.
(Raw materials)
Epoxy resin 1: Biphenyl aralkyl type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., NC-3000)
Epoxy resin 2: Biphenyl type epoxy resin (manufactured by Mitsubishi Chemical Corporation, YL6677)
Hardener 1: Biphenylene skeleton-containing phenol aralkyl resin (manufactured by Nippon Kayaku Co., Ltd., GPH-65)
Hardener 2: Triphenylmethane type phenolic resin modified with formaldehyde (HE910-20, manufactured by Air Water Corporation)
Curing accelerator: Triphenylphosphine (TPP, manufactured by Hokko Chemical Industry Co., Ltd.)
Inorganic filler: fused spherical silica (manufactured by Denki Kagaku Kogyo Co., Ltd., FB-950FC)
Colorant: Carbon black (Mitsubishi Chemical Corporation, MA-600)
Coupling agent: N-phenyl-γ-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-573)
Release agent: Carnauba wax (Nikko Fine Co., Ltd., Nikko Carnauba)
(procedure)
The above-mentioned epoxy resin 1 was prepared in an amount of 4.5 parts by mass, epoxy resin 2 in an amount of 4.5 parts by mass, curing agent 1 in an amount of 2.8 parts by mass, curing agent 2 in an amount of 2.8 parts by mass, curing accelerator in an amount of 0.4 parts by mass, inorganic filler in an amount of 84.2 parts by mass, colorant in an amount of 0.2 parts by mass, coupling agent in an amount of 0.4 parts by mass, and release agent in an amount of 0.2 parts by mass. Next, the raw material components were mixed at room temperature using a mixer, and then roll-kneaded while being heated with two rolls at 45°C and 90°C to obtain a kneaded product. Next, the kneaded product was cooled and then pulverized to obtain a pulverized product. Next, the pulverized product was tableted to obtain a tablet-shaped thermosetting resin composition.

Next, using each release film, curing of the thermosetting resin composition (resin sealing) was carried out in the following procedure.
First, a COSMO-TFlex Series manufactured by Asahi Engineering Co., Ltd. was used as a hybrid molding machine for transfer molding and compression molding.
First, each release film of the examples and comparative examples was placed inside a mold equipped in a molding machine, and the space inside the mold was evacuated to a vacuum, thereby allowing the release film to conform to the mold.
Next, the tablet of the thermosetting resin composition was placed at a predetermined position. After that, the mold of the molding machine was clamped under a clamp pressure of 300 kg/ ^cm2 , and the above-mentioned thermosetting resin composition in a molten state was poured into the internal space of the mold of the molding machine under an injection pressure of 80 kg/ ^cm2 . Next, the mold cavity was moved to mold the thermosetting resin composition at 175°C for 2 minutes while applying pressure of 6 kg/ ^cm2 . Then, the upper and lower molds were opened to release the cured product of the thermosetting resin composition and the release film.

[Mold followability]
In the above procedure, the degree of air entrapment between the release film and the four corners of the mold when the release film was made to follow the mold by vacuum drawing was evaluated according to the following criteria.
◎: No air pockets were found. ◯: Small air pockets were found, but no practical problems were found. △: Small air pockets were found, and the degree of vacuum for film adsorption was reduced. ×: Large air pockets caused poor tracking (or evaluation was impossible).

[Dimensional stability]
In the above procedure, the appearance (wrinkles, etc.) of the cured product after it was released from the release film after molding was evaluated according to the following criteria.
◯: No wrinkles or deformations, no problem △: Some wrinkles, but no practical problem ×: Large wrinkles and molding defects

[Releasability]
In the above procedure, the release behavior when the cured product was released from the release film after molding and the state of the cured product (displacement, bending, etc.) were evaluated according to the following criteria.
◯: No problems with demolding or molded product △: The molded product shifted or warped when demolded, but no practical problems ×: Demolding was impossible, or large wrinkles were transferred to the cured product

1 Release layer 2 Base layer 3 Release surface 10 Release film 11 Release film

Claims (14)

A release film in which a layer constituting at least one surface thereof is made of a cured product of a silicone rubber composition,
the silicone rubber composition comprises a vinyl group-containing organopolysiloxane, an organohydrogenpolysiloxane, inorganic particles, and a silane coupling agent;
When the tear strength of the cured product of the silicone rubber composition is TS0 (N/mm) and the elongation at break is BE0s (%), the following properties are obtained:
2.4×10 ⁴ ≦TS0×BE0s is satisfied,
The surface roughness Rz of the one surface of the release film is 0.1 to 3 μm.
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared from the cured product of the silicone rubber composition in accordance with JIS K6252 (2001), and the tear strength of the obtained crescent-shaped test piece at 25° C. is measured and designated as TS0, expressed in N/mm.
(Procedure for measuring elongation at break)
A dumbbell-shaped No. 3 test piece is prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and the breaking elongation of the resulting dumbbell-shaped No. 3 test piece is measured at 25° C. The breaking elongation is calculated as [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and is designated as BE0s, and is expressed in %. When the tensile strength of the cured product of the silicone rubber composition is S (MPa), which is measured by the following procedure,
The release film according to claim 1 , which satisfies 1.4×10 ⁵ ≦TS0×BE0s×S.
(Procedure for measuring tensile strength)
A dumbbell-shaped No. 3 test piece is prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and the tensile strength of the dumbbell-shaped No. 3 test piece at 25° C. is measured and represented as S. The unit is MPa. A release film in which a layer constituting at least one surface thereof is made of a cured product of a silicone rubber composition,
the silicone rubber composition comprises a vinyl group-containing organopolysiloxane, an organohydrogenpolysiloxane, inorganic particles, and a silane coupling agent;
When the tear strength of the cured product of the silicone rubber composition, measured by the following procedure, is TS0 (N/mm) and TS1 (N/mm),
((TS1-TS0)/TS0) x 100 is -85% or more and 5% or less,
The surface roughness Rz of the one surface of the release film is 0.1 to 3 μm.
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and the tear strength of the obtained crescent-shaped test piece at 25° C. is designated as TS0 (N/mm).
A crescent-shaped test piece is prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and then the test piece is held at 100°C for 30 minutes. The tear strength of the crescent-shaped test piece obtained at 100°C is defined as TS1 (N/mm). When the tear strength of the cured product of the silicone rubber composition is TS2 (N/mm), which is measured by the following procedure,
The release film according to claim 3, wherein ((TS2-TS0)/TS0) x 100 is -88% or more and 5% or less.
(Procedure for measuring tear strength)
A crescent-shaped test piece is prepared in accordance with JIS K6252 (2001) using the cured product of the silicone rubber composition, and then the test piece is held at 150°C for 30 minutes. The tear strength of the crescent-shaped test piece obtained at 150°C is defined as TS2 (N/mm). 5. The release film according to claim 1, wherein the durometer hardness A of a cured product of the silicone rubber composition is 20 or more and 80 or less, as measured by the following procedure.
(Procedure for measuring durometer hardness A)
A sheet-like test specimen is prepared using the cured product of the silicone rubber composition, and the durometer hardness A of the resulting sheet-like test specimen at 25° C. is measured in accordance with JIS K6253 (1997). When the elongation of the cured product of the silicone rubber composition at 1 MPa is defined as E1 (%), which is measured by the following procedure,
The release film according to claim 1 , wherein 15≦E1 and 20≦TS0 are satisfied.
(Procedure for measuring elongation at 1 MPa)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the silicone rubber composition in accordance with JIS K6251 (2004), and a tensile test was conducted at 25°C at a tensile speed of 500 mm/min, and the elongation of the resulting dumbbell-shaped No. 3 test piece when the stress reached 1 MPa was calculated using the formula [gauge line movement distance (mm)]÷[initial gauge line distance (20 mm)]×100, and designated as E1. The unit is %. When the stroke change rate after 1 hour of the cured product of the silicone rubber composition is measured by the following procedure and defined as SC1 (%),
The release film according to claim 1 , wherein SC1≦50 and TS0 are satisfied.
(Procedure for measuring stroke change rate)
A dumbbell-shaped No. 3 test piece is prepared in accordance with JIS K6251 (2004) using the cured product of the silicone rubber composition, and the elongation of the resulting dumbbell-shaped No. 3 test piece is measured over time at 25°C when held between chucks at a stress of 1 MPa.
The time when the stress becomes 1 MPa is defined as 0h, and the stroke amount after a predetermined time n (h) is defined as En (%) = [chuck movement distance (mm)] ÷ [initial chuck distance (60 mm)] × 100. The stroke change rate is calculated from the measured stroke amount En based on the following formula.
Stroke change rate after n hours SCn (%) = (En-E0)/E0 x 100
The stroke change rate when n=1 is defined as SC1 (%). The release film according to claim 1 , wherein the surface free energy of the one surface is 10 mJ/m ² or more and 20 mJ/m ² or less. 9. The release film according to claim 1, wherein the content of the inorganic particles is 10 to 60 parts by weight based on 100 parts by weight of the vinyl group-containing organopolysiloxane. The release film according to any one of claims 1 to 9 , wherein the inorganic particles are particles made using one or more types selected from the group consisting of calcium carbonate, zinc oxide, alumina, crystalline silica, amorphous silica, fused silica, and zeolite. The release film according to claim 1 , which is constituted by a layer made of a cured product of the silicone rubber composition. The release film according to claim 1 , wherein the release film has a structure in which a base layer and a layer made of a cured product of the silicone rubber composition are laminated together. The release film according to claim 12 , wherein the base layer is one or more resins selected from the group consisting of polyester resin, poly 4-methyl 1-pentene resin, polyamide resin, and polypropylene resin. The release film according to claim 1 , which is intended to be disposed between a mold to which a sealing resin is supplied and a semiconductor device to be resin-encapsulated in a resin-encapsulating process of a semiconductor device.

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