JP2000117901A - Release film for solid electrolyte casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film for solid electrolyte casting characterized by that the transfer amt. of a silicone resin of a release layer to other layer is extremely little or the surface shape of the release layer is not transferred. SOLUTION: In a release film obtained by providing a silicone release layer to at least the single surface of a polyester film, the center line average roughness (Ra) of the surface of the silicone release layer is 0.4 μm or less and the silicone transfer amt. of the silicone release layer measured by ESCA is set to 5 atom % or less as a silicon element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a release film for solid electrolyte casting using a polyester film as a base film. More particularly, the release layer has a very small amount of silicone resin and the surface shape of the release layer is different from that of another layer. The present invention relates to a release film for solid electrolyte casting which is not transferred to a film.

[0002]

2. Description of the Related Art At present, lithium ion secondary batteries are known as PDs.
A (portable information device terminal), etc., and have become the mainstream of secondary batteries.
As a next-generation lithium-ion secondary battery, a polymer battery using a solid electrolyte has been proposed. This polymer battery has a structure of a current collector / anode mixture / solid electrolyte / positive electrode mixture / current collector. Among the interfaces, the interfacial bonding between the solid electrolyte and the positive electrode mixture is most important. When the adhesion at the interface is good, Li ⁺ moves smoothly, and the performance as a battery is improved.

Conventionally, to form this solid electrolyte layer, a polymer precursor containing an electrolyte is applied on a release film coated with a silicone resin as a casting substrate, and various energy (heat, light, radiation) is applied to the coated surface. Has been used to polymerize and crosslink.

When storing the laminate, a protective film may be crimped on the surface opposite to the coated surface, and may be wound and stored in a sandwich shape. However, there has been a problem that the silicone resin is transferred to the surface of the solid electrolyte, which inhibits the formation of an interface with the positive (negative) electrode mixture, thereby deteriorating battery characteristics.

[0005] Further, it is generally practiced that a polyester film used as a film constituting a casting substrate is provided with a surface roughness by blending inorganic fine particles for imparting slipperiness.
If this surface shape is transferred to the surface of the solid electrolyte, there is also a problem that the interface cannot be formed well when pressed with the positive (negative) electrode mixture.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a release film which can solve the above-mentioned drawbacks of the prior art and can form a solid electrolyte surface without deteriorating the battery performance of a polymer battery. It is in.

[0007]

According to the present invention, an object of the present invention is to provide, on at least one side of a polyester film,
A release film provided with a silicone release layer, wherein the surface of the silicone release layer has a center line average roughness (Ra) of 0.4.
μm or less, and the amount of transferred silicone in the silicone release layer is 5 atom as a silicon element as measured by ESCA.
This is achieved by a release film for casting a solid electrolyte, which is characterized by being at most m%.

In the present invention, a polyester film having good transparency, especially a biaxially stretched polyester film, is blended for applications requiring transparency, and a pigment is blended for applications requiring light shielding properties. It is preferable to use a polyester film, particularly a biaxially stretched polyester film containing an inorganic pigment such as TiO ₂ or SiO ₂ .

The polyester constituting such a polyester film is preferably a crystalline linear saturated polyester comprising an aromatic dibasic acid component and a diol component. Examples of the polyester include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene-terephthalate. 2,6-naphthalate and the like can be mentioned.

In order to improve the slipperiness of the film, organic or inorganic fine particles are used as a lubricant in the above-mentioned polyester to improve the center line average roughness (Ra) of the surface of the silicone release layer.
Is 0.4 μm or less, the type, the average particle size, and the mixing ratio can be selected and contained. Specifically, the average particle size is in the range of 0.01 to 20 μm, and the mixing ratio is 0.00
It can be selected from the range of 5 to 20% by weight. Specific examples of the fine particles include inorganic particles such as alumina, calcium carbonate, kaolin, silicon oxide, and barium sulfate, and organic particles such as cross-linked polystyrene resin particles, cross-linked silicone resin particles, and cross-linked acrylic resin particles. . By depositing fine particles from the catalyst residue used in the polyester synthesis reaction, fine irregularities can be formed on the film surface, and the film can have good slipperiness.

Further, other modifiers can be blended with the polyester. For example, a compound having a sulfonate group such as sodium dodecylbenzene sulfonate can be contained as an antistatic agent. Polyesters without these modifiers can also be used.

The polyester film of the present invention comprises:
It can be manufactured by a conventionally known method. For example, a biaxially stretched polyester film is obtained by drying a polyester, melting it with an extruder, and forming a die (for example, a T-die,
(I-die etc.), extruded onto a rotary cooling drum, quenched to obtain an unstretched film, and then stretched in the biaxial direction, and heat-fixed if necessary. The thickness of the film is not particularly limited, but is preferably 5 to 250 μm.

In the present invention, a silicone release layer, preferably a silicone release layer containing an addition polymerization type silicone resin as a main component, is provided on at least one surface of the polyester film. After the silicone resin is three-dimensionally cross-linked and cured by a catalyst, particularly a Pt catalyst, the silicone transfer amount of the silicone release layer needs to be 5 atom% or less as a silicon element as measured by ESCA. If the silicone transfer amount exceeds 5 atom%, the adhesion between the solid electrolyte and the positive (negative) electrode mixture is impaired, and the battery characteristics are undesirably reduced. There is no particular limitation on the method for setting the silicone transfer amount within such a range, but it is preferable to provide a silicone release layer provided by the means described below.

Here, the amount of the silicone release layer transferred to the silicone is determined by adding an adhesive tape (31B tape (acrylic adhesive) manufactured by Nitto Denko Corporation) or a 31D tape (rubber-based tape manufactured by Nitto Denko Corporation) to the silicone release layer. Adhesive)) and apply 7
After maintaining at 0 ° C. for 20 hours, the tape was peeled off, and the peeled surface was subjected to ESCA measurement, and the abundance ratio of the silicon element (atom)
%).

In the present invention, the silicone resin constituting the release layer may be, for example, a polydimethylsiloxane having a vinyl group represented by the following formula (A) and a hydrogensilane-based compound represented by the following formula (B): It can be obtained by addition polymerization using a system compound as a catalyst.

[0016]

Embedded image

In the above formula (A), m and n are numbers of 1 or more, where m is 1 to 100, n is 20 to 5000, and m + n
Is in the range of 30 to 5000, since the crosslinking reaction proceeds favorably and the layer becomes durable. Note that, in the above formula (A),

[0018]

Embedded image

It is to be understood that does not mean block connection, but merely indicates that the sum of the respective units is m, n. Therefore,
Each unit in the above formula (A) may be randomly bonded, or may be block-bonded.

[0020]

Embedded image

In the above formula (B), a and b are 1 or more, and a is 3 to 200, b is 1 to 20, and 5 ≦ a + b ≦
When it is in the range of 200, the crosslinking reaction proceeds favorably, and a durable layer is formed. Note that, in the above equation (B),

[0022]

Embedded image

It is to be understood that does not mean block connection, but merely indicates that the sum of the respective units is a and b. Therefore,
Each unit in the formula (B) may be randomly bonded, or may be block-bonded.

The ratio of the vinyl group-containing polydimethylsiloxane used for the above addition polymerization and the hydrogensilane-based compound is such that the ratio of the hydrogensilane-based compound is 1.0 mole of the vinyl group in the vinyl group-containing polydimethylsiloxane. It is preferable that the content of the SiH group is 1.0 to 2.0 mol. The addition polymerization referred to here is
~Si-CH = a functional group at the molecular ends or in the molecular side chains represented by CH _2, and a functional group in a molecular end or a molecular side chain represented by _{H-Si~, ~Si-CH 2} CH 2 - Si ~
It is a polymerization reaction that becomes However, “to” in the above functional group indicates that the molecule is further connected.

In the present invention, there are the following two methods for setting the transfer amount of the silicone resin constituting the release layer to 5 atom% or less as a silicon element measured by ESCA. (I) Use of a platinum catalyst in an amount of 10 to 500 ppm as platinum atoms. (II) In order to consume unreacted -SiH, after a silicone release layer is provided, the polyester film is subjected to Tg (glass transition temperature of polyester film)-40 to Tg-1.
Heat-treat at a temperature of 0 ° C. for 24-168 hours.

Various known additives can be added to the release layer in the present invention as long as the object of the present invention is not hindered. As this additive, for example, ultraviolet absorbers, pigments,
Examples include an antifoaming agent, a pot life extending agent, a crosslinking agent, and the like.

In the present invention, a silicone release layer is provided on at least one side of the polyester film. The release layer may be, for example, a polydimethylsiloxane having a vinyl group represented by the formula (A) or a silicone resin having the formula (B). Can be provided by applying a coating liquid containing a hydrogen silane-based compound and a Pt-based compound represented by the formula (1) to a film, followed by drying and curing reaction by heating. The heating conditions are preferably, for example, 80 to 160 ° C. for 10 to 120 seconds, particularly 100 to 150 ° C. for 15 to 60 seconds, since the drying and curing reaction will be sufficient. still,
As a method for applying the coating liquid, any known coating method can be applied, and examples thereof include a roll coater method and a blade coater method, but are not limited to these methods. Further, the coating liquid may be a coating liquid using an organic solvent, may be an aqueous coating liquid, it is preferably a solution in which polydimethylsiloxane or hydrogen silane compound is dissolved, for example, toluene and the like The coating liquid using an organic solvent is preferable.

In the present invention, in order to enhance the adhesion between the polyester film and the silicone release layer, it is preferable to provide an adhesive layer on at least one side of the polyester film and provide a silicone release layer on the adhesive layer. .
For this adhesive layer, for example, a silane coupling agent can be preferably used. As the silane coupling agent include those represented by the general formula Y-Si-X _3. Here, Y represents a functional group represented by, for example, an amino group, an epoxy group, a vinyl group, a methacryl group, a mercapto group, and X represents a hydrolyzable functional group represented by an alkoxy group.

The preferred thickness of the adhesive layer is 0.01 to
It is about 5 μm, particularly about 0.02 to 2 μm.
When the thickness of the adhesive layer is in the above range, the adhesion between the polyester film and the release layer becomes good, and the polyester film provided with the adhesive layer is difficult to block, so that it is hard to cause trouble in handling.

The center line average roughness (Ra) of the surface of the silicone release layer of the release film of the present invention must be 0.4 μm or less. If Ra exceeds 0.4 μm, the surface of the formed solid electric field juice becomes rough, and when the positive (negative) mixture is pressed, good interfacial adhesion cannot be obtained and the battery performance is undesirably reduced.

[0031]

EXAMPLES The present invention will be further described below with reference to examples. In addition, each characteristic value of the film was measured by the following method.

(1) Peel strength A crosslinkable polymer having the following chemical structure is dissolved in an organic solvent, an isocyanate crosslinker having the following chemical structure is added, and the coating thickness is 200 g / m ² on the silicone release layer of the release film. An appropriate amount was applied, dried at 150 ° C. for 5 minutes, and cured at 60 ° C. for 3 days to form a crosslinked polymer layer. This laminate was cut out to a width of 1 inch, and the peeling force between the formed crosslinked polymer layer and the release film was measured by a tensile tester. The preferable range of the peel strength is 10 to 300 g / in. When the peel strength is less than 10 g / in, delamination occurs during storage or transportation of the release film, and on the other hand, 300
If it exceeds g / in, the adhered layer is firmly adhered and there is a problem in peeling.

[0033]

Embedded image

(2) Residual Adhesion Rate A polyester adhesive tape (Nitto Denko, 31B) was prepared using JI
Cold rolled stainless steel sheet (SU
The peeling force after application in S304) is measured, and the measured value is defined as a basic adhesive force (f ₀ ). Further, the polyester adhesive tape was pressed against the release layer coating surface of the sample film with a 5 kg pressure roller, left for 30 seconds, and then the adhesive tape was peeled off. And stick the peeled adhesive tape on the stainless steel plate,
The peeling force of the bonded portion was measured and defined as a residual adhesive force (f).
From the obtained basic adhesive strength (f ₀ ) and residual adhesive strength (f),
The residual adhesion rate was determined using the following equation. Residual adhesion rate (%) = (f / f ₀ ) × 100 The preferable range of the residual adhesion rate is 85% or more. When the residual adhesion ratio is less than 85%, for example, when the release film is wound up in a roll and stored, the components constituting the release layer are transferred to the surface of the adjacent film (so-called backside transfer).
However, the properties of the release layer may be poor, or the properties such as adhesiveness of the adjacent film surface may be poor, which is not preferable.

(3) Amount of transfer of silicone in silicone release layer Silicon element and N on the surface of silicone release layer were measured by ESCA method.
The count numbers of the element and the C element were measured. That is,
X-ray electron analyzer (ESCA RAB2 manufactured by VG, UK)
00 type machine), MgKα ray (125
Using 3.6 eV), photoelectrons are irradiated to the release layer surface at a photoelectron extraction angle (θ) of 45 degrees, and the photoelectrons emitted from the release layer surface are applied to a concentric cylindrical mirror type or concentric hemisphere type electron energy analyzer. The peak of the Si element was measured using a continuous multistage amplification type electron multiplier, and the peak height was used as the count.

(4) Center line surface roughness (Ra) of the silicone release layer According to JIS B0601, the radius of the needle is measured using a high-precision surface roughness meter (SE-3FAT) manufactured by Kosaka Laboratory Co., Ltd. A surface roughness curve was measured under the conditions of 2 μm, a load of 30 mg, an enlargement magnification of 200,000, and a cutoff of 0.08 mm. From the surface roughness curve, a portion of the length (L) measured in the direction of the center line was extracted. When the center line of the sampled portion was defined as the X axis and the longitudinal magnification direction was defined as the Y axis, and the roughness curve was represented as Y = f (x), the value obtained by the following equation was represented in μm units. Note that the measurement was performed with n = 4 with the reference length set to 1.25 mm, and expressed as an average value.

[0037]

(Equation 1)

Example 1 In the above formula (A), polydimethylsiloxane in which m is 10 and n is 2000,
In the formula (B), a mixed solution of a hydrogensilane-based compound in which a is 100 and b is 10 (the vinyl group in the polydimethylsiloxane is 1.0 mole to the SiH group in the hydrogensilane-based compound) Pt catalyst (methanol solution of chloroplatinic acid)
2 as Pt metal for the silicone polymer obtained
In addition to the amount corresponding to 00 ppm, a toluene solution having a total solid content of 0.8% was prepared. This solution was applied to a biaxially stretched polyethylene terephthalate film (thickness: 38).
μm, Ra on the film surface; 0.03 μm) to 6 g / m
² (wet) was applied, and drying and addition polymerization were performed at a heating temperature of 140 ° C. and a heating time of 1 minute to prepare a release film. Table 1 shows the characteristics of the release film.

Example 2 The amount of the Pt catalyst to be added was 500
ppm, and the resulting release film was further post-cured at 40 ° C. for 72 hours.
A release film was prepared in the same manner as described above. Table 1 shows the characteristics of the release film.

Example 3 A release film was prepared in the same manner as in Example 1 except that a biaxially stretched polyethylene terephthalate film having a center line surface roughness (Ra) of 0.2 μm on the film surface was used. Table 1 shows the characteristics of the release film.

Comparative Example 1 A release film was prepared in the same manner as in Example 1 except that a biaxially stretched polyethylene terephthalate film having a center line surface roughness (Ra) of 0.6 μm on the film surface was used. Table 1 shows the characteristics of the release film.

[Comparative Example 2] The amount of the Pt catalyst added was 1 ppm as Pt metal with respect to the obtained silicone polymer.
A release film was prepared in the same manner as in Example 1 except for the following. Table 1 shows the characteristics of the release film.

[Comparative Example 3] The amount of the Pt catalyst to be added was 1000 relative to the obtained silicone polymer as Pt metal.
ppm, the pot life of the coating solution was short, application to the polyester film was not possible, and release film could not be prepared.

[Comparative Example 4] Instead of the addition type silicone of Example 1, a condensation type silicone (Toshiba Silicone Co., Ltd.)
Manufactured by YSR-3022) and replaced with Sn instead of the Pt catalyst.
Example 1 was repeated except that a coating solution was prepared by adding a recommended amount of a catalyst.
A release film was prepared in the same manner as described above. Table 1 shows the characteristics of the release film.

[0045]

[Table 1] ---------------------------------------------- -------------------- Peel strength Residual adhesion rate Silicone transfer amount Release layer Ra (g / in) (%) (atom%) (μm) --- -------------------------------------------------- ------------- Example 1 20 92 1.2 0.028 Example 2 48 98-0 0.029 Example 3 16 93 1.0 0.203 Comparative Example 1 12 91 1.1 0.599 Comparative Example 2 576 8.9 0.026 Comparative Example 3----Comparative Example 4 12 84 12 0.023 ----------------- ------------------------------------------------- table As is clear from FIG. 1, the release films of Examples 1 to 3 are excellent in peel strength, residual adhesion, silicone transfer amount and surface roughness.

[0046]

According to the present invention, there is provided a release film for solid electrolyte casting in which the amount of the silicone resin of the release layer transferred to another layer is extremely small, or the surface shape of the release layer is not transferred. be able to.

Claims (3)

[Claims] 1. A release film provided with a silicone release layer on at least one surface of a polyester film,
The center line average roughness (Ra) of the surface of the silicone release layer is 0.4 μm or less, and the silicone transfer amount of the silicone release layer is 5 as silicon element as measured by ESCA.
A release film for solid electrolyte casting, which is at most atom%. 2. The polyester film is polyethylene-
The release film for solid electrolyte casting according to claim 1, which is a 2,6-naphthalate film. 3. The release film for solid electrolyte casting according to claim 1, wherein the polyester film is a polyethylene terephthalate film.