JP6001948B2 - Seal member, composite seal member, and integrated product with seal member - Google Patents

Description

  The present invention relates to a seal member that is sandwiched between a first member and a second member, and in particular, when a silicone gel material is used as a base material, fine particles are adhered to the surface of the seal member, and the bleed component over time The present invention relates to a seal member with less surface transition to the first member and the second member, a composite seal member using the seal member, and an integrated product with the seal member using the seal member.

  Generally, a seal member using silicone rubber or the like is sandwiched between a first member and a second member, and therefore requires a certain degree of adhesiveness and softness. Ingredients are added. However, there is a problem that these oil components bleed with time.

  As a method for solving the bleeding of the oil component, for example, a method of adding a filler having a high affinity to the oil component in a flexible material described in JP 2011-137104 A (Patent Document 1), -65122 (Patent Document 2), a method of coating the surface by painting or the like, and a method of attaching inorganic or organic fine particles to the surface are known.

JP 2011-137104 A JP 2010-65122 A

  However, among the above techniques, the method of adding a filler has problems in product production such as problems in product characteristics such as an increase in product hardness and difficulty in molding due to an increase in the viscosity of the composition. Moreover, in the case of the method of coating on the surface, there exists a subject that the surface followability and adhesiveness as packing parts are impaired.

In contrast to such a silicone rubber-based member, a sealing member using a silicone gel as a base has no or no added oil component because the silicone gel itself is soft and sticky. It is. Therefore, the bleed problem is unlikely to occur. However, since the silicone gel itself is sticky, an attempt was made to apply a method of attaching fine particles to the gel surface in order to improve handling.
However, when starch particles are attached to the silicone gel, bleed that hardly occurs without such fine particles is likely to occur, and a new problem arises that the bleed component adheres to the surface of the housing or electronic component. Rose. This bleed component was found to have more unreacted components in the raw material than the oil component added in a small amount to the raw material.

  Accordingly, the present invention provides a seal member without a bleed from silicone gel, or a seal member in which a bleed component does not transfer to a first member or a second member such as a housing or an electronic component even when there is a bleed from silicone gel, and The object is to provide a composite seal member using a seal member and an integrated product with the seal member.

  That is, as a result of repeated research for the purpose of suppressing the adhesiveness of the silicone gel surface and obtaining a seal member that does not cause bleed, the first member and the second member are selected even if bleed occurs due to selection of fine particles to be adhered. The inventors have found that the migration of the bleed component to the surface can be suppressed and completed the present invention.

  The present invention is a seal member sandwiched in a compressed state between a first member and a second member, and comprises a silicone gel molded body and fine particles covering a predetermined surface of the silicone gel molded body, 70% or more of the surface is covered with the fine particles, and the fine particles are hydrophobic silica particles or silicone resin particles having an average particle diameter of 20 μm or less, and the particle diameter is 2 μm or more within 100 μm square of the surface. Provided is a sealing member having 50 or less particles visible with an electron microscope.

  Since a silicone gel molded body is used as a base member, a seal member is constituted by the silicone gel molded body and fine particles covering the predetermined surface, and 70% or more of the predetermined surface is coated with the fine particles. Even without this, bleeding of unreacted components during curing becomes a problem. However, the fine particles are hydrophobic silica particles or silicone resin particles having an average particle diameter of 20 μm or less, and the number of particles that can be visually recognized by an electron microscope as a size of 2 μm or more in a 100 μm square of the surface coated with the fine particles is 50. Therefore, even if bleed occurs, the bleed component is hardly transferred to the surface of the first member or the second member, the seal member is excellent in handleability, and suppresses the seepage of the uncured component.

Moreover, the composite sealing member which laminated | stacked such a sealing member with the resin film is provided. Since the sealing member is a composite sealing member laminated with a resin film, if the sealing member is pressed against either the first member or the second member through a non-adhesive resin film, the sealing member can be easily attached to the first member or the first member. It can be fixed to either one of the two members. That is, the handleability and storage stability of the sealing member are improved by the resin film. Furthermore, if this resin film is peeled off, the exposed seal member can be easily fixed to either the first member or the second member.
Further, the seal member and at least one of the first member and the second member can be integrally formed with the seal member. Since the seal member and the first member or at least one of the second member are integrally formed with the seal member, the integrated member having excellent adhesion between the first member and the second member is used. Can do.

  According to the sealing member, even if there is a bleed from the silicone gel, the surface migration to the first member or the second member is suppressed, the handling property is excellent, and the tactile sensation and texture are good.

It is a schematic cross section of a sealing member. 2 is an electron micrograph of Sample 2. 4 is an electron micrograph of Sample 3. 4 is an electron micrograph of Sample 6. 2 is an electron micrograph of Sample 11.

Further details will be described based on specific embodiments.
The seal member 11 seals between the first member and the second member by sandwiching the first member and the second member (not shown) in an electronic device or the like in a compressed state. For example, various parts and casings made of various materials such as resin, metal, glass, etc., such as between a circuit board and a casing (panel) in a portable communication terminal and between a circuit board and an electronic component in a personal computer. Used by being sandwiched between bodies.
That is, the sealing member 11 is sandwiched in a compressed state between the first member and the second member, thereby contributing to sealing for waterproofing, filling for preventing slippage, protection from vibration and impact, and the like. is there.

  The silicone gel molded body 12 that forms the sealing member 11 is made of a silicone gel that is a cured product of low crosslink density that partially has a three-dimensional network structure. The silicone gel can be formed using a general silicone gel which is a cured product obtained by thermally curing a composition containing an addition reaction catalyst such as an organopolysiloxane having an alkenyl group, an organohydrogenpolysiloxane, and a platinum-based catalyst.

In the sealing member 11, since the surface of the silicone gel molded body 12 has adhesiveness, in consideration of convenience of handling, as shown in FIG. 1, at least one surface 12a of the coating layer having predetermined fine particles adhered thereto 13 is formed.
It is necessary that 70% or more of the surface 12a of the silicone gel molded body covered with such particles is covered with the fine particles. This is because when the ratio is less than 70%, the ratio of the surface of the silicone gel molded body not coated with the fine particles is increased, resulting in stickiness.

The fine particles (hereinafter also referred to as “coated particles”) covering one surface 12a of the silicone gel are predetermined hydrophobic silica particles or silicone resin particles.
The average particle size of the coated particles is 20 μm or less, and preferably 10 μm or less. When it exceeds 20 μm, the surface area of the entire coated particle adhered to the surface of the silicone gel molded body becomes small, and it becomes difficult to obtain the holding power of the bleed component. If it is 10 μm or less, the surface area is large, and the bleed component can be sufficiently spread on the surface of the coated particles.
On the other hand, the average particle diameter of the coated particles is preferably 0.5 μm or more. This is also because when the particle size is smaller than 0.5 μm, the surface area of the coated particles is small, so that the bleed component may not be effectively dispersed on the surface of the fine particles.

  The bleed component that bleeds out from the silicone gel molded body mainly includes unreacted components such as vinyl silicone before being cured. Such an unreacted component hardly appears on the surface of the silicone gel when the surface of the silicone gel is not covered with fine particles, and often does not cause a problem of bleeding. However, it is considered that when fine particles such as starch adhere to the surface, unreacted components move up the surface of the fine particles and are transmitted to promote bleeding. In addition, when oil components such as silicone oil are included in advance for imparting flexibility, bleeding of these oil components also becomes a problem.

Even if bleed occurs when fine particles are adhered to the surface of the silicone gel molded body, it has been found that the degree of bleed on the surface of the first member or the second member differs depending on the kind and particle size of the fine particles to be adhered. It was. It has also been found that the presence or absence of such transition can be assumed from an enlarged photograph of the surface of the silicone gel molded body by an electron microscope.
When particles are placed on the surface of the molded body without bleed, the particle shape is clearly visually recognized, and the shape of the adhered particles can be observed as it is. On the other hand, in the silicone gel molded body in which the bleed component is present, the surface of the coated particle is partially covered with the bleed component, and the apparent particle shape and particle size change as the particle size appears small or disappears. When the bleed becomes excessive, the particles are hidden in the bleed component and the particle shape becomes invisible. That is, the surface of the silicone gel molded body is photographed with an electron microscope, the state of the particles shown in the photograph is observed, and the number of particles having a predetermined size is obtained, thereby transferring the bleed component to the first member or the second member. The presence or absence could be judged.

  Specifically, the experiment was conducted as follows. Different types of materials and fine particles having an average particle diameter were applied to the surface of the flat silicone gel molded body through a mesh. Fine particles excessively adhering to the surface of the silicone gel molded body were removed from the surface by air blow. In this way, several samples with different kinds and particle sizes of the particles attached to the surface were prepared. The sample was sandwiched between protective films, allowed to stand at room temperature and normal condition (uncompressed) for one month, and then a silicone gel molded body sprayed with fine particles with an electron microscope (scanning electron microscope S-3000N (manufactured by Hitachi High-Technologies Corporation)). The surface state was observed and photographed, and the kind and average particle size of the fine particles used are shown in Table 1 below.

Further, the weight reduction rate of each sample was measured as follows, and the state of migration of the bleed component to the first member or the second member was observed. Each sample was a test piece having a diameter of 20 mm and a thickness of 1 mm, and was placed on a polycarbonate (PC) plate. A PET film was placed on the test piece so that the state after compression could be observed. Then, a spacer having a thickness of 0.5 mm was placed between the PC plate and the PET film so that the test piece was compressed by 50%, and the test piece was pressed with a compression jig. In this state, the sample was left in an atmosphere of 85 ° C. for 168 hours, and then the test piece was taken out from the compression jig, the polycarbonate plate and the PET film were peeled off, and the weight after the bleed component was transferred was measured to determine the weight reduction rate. Moreover, the state of the surface of the PET film was observed.
And the case where it was recognized that there was no transfer of the bleed component to the PET film was evaluated as “◯”, and the case where it was recognized that there was no bleed was evaluated as “x”. Table 1 shows the weight loss rate and the evaluation results.

When the difference between the case where the evaluation is “◯” and the case where “×” is observed with the previous electron micrograph, the number of particles that can be grasped as a particle size of 2 μm or more in a 100 μm square is 50 or less (however, 0 In the case of (except), it was “◯”, and when the number of particles exceeded 50, it was found to be “x”. Here, the evaluation is for the case where the coated particles are coated on the silicone gel molded body, and it is assumed that the coated particles are attached to 70% or more of the predetermined surface to be coated.
2 shows a state in which the number of particles having a particle diameter of 2 μm or more is counted on the electron micrographs of the sample 2, FIG. 3 in the sample 3, FIG. 4 in the sample 6, and FIG. The five photographs shown in each figure are electron micrographs obtained by enlarging five points arbitrarily selected from a predetermined surface to 100 μm square, and the number of particles having a size of 2 μm or more was counted at each point. Results (numbers) are shown (black dots on the photo represent check marks when counting). The upper limit value and the lower limit value of these five locations are shown in Table 1 above. Samples other than Samples 2, 3, 6, and 11 also show the upper limit value and lower limit value of 5 points by the same method.

  Sample 2, Sample 3 and Sample 5 that have no migration of bleed components to the PET film surface and are evaluated as “◯” have 1 to 50 particles that can be visually recognized as a particle diameter of 2 μm or more in a 100 μm square. Is in range. On the other hand, when the evaluation is “x”, the number of particles that can be visually recognized as a particle size having a diameter of 2 μm or more in a 100 μm square exceeds 50 particles. The sample with an evaluation of “◯” is a hydrophobic silica or silicone resin having a particle size of 20 μm or less as a coated particle. However, as in Sample 4, even if it is a hydrophobic silica, the average particle size is more than 20 μm. It can be seen that even when coated with large particles, the bleed component migrates and the evaluation is “x”. Moreover, it turns out that the sample whose evaluation is "x" is starch, hydrophilic silica, and polyethylene. In addition, the sample 1 which does not provide a covering particle is excluded from the judgment here.

The shape of the silicone gel molded body may be any shape, but it can be made into a thin plate shape from the versatility and convenience of handling.
The predetermined surface to be coated with the coating particles may be either one of the front and back surfaces, preferably the front and back surfaces, and more preferably the entire surface of the seal member, as long as it is a thin seal member.
The seal member can be a composite seal member provided on a resin film or the like. Moreover, it can be set as the integrated product with a sealing member integrated with this sealing member and the back surface of a housing | casing, for example, a cover member with a sealing member, SUS components with a sealing member, etc.

  In addition, the said embodiment is an example of this invention and is not limited to such a form, The arbitrary modification which does not contradict the meaning of this invention is included.

DESCRIPTION OF SYMBOLS 11 Seal member 12 Silicone gel molded object 12a One side 13 Coating layer

Claims (4)

A sealing member sandwiched in a compressed state between the first member and the second member, comprising a silicone gel molded body and fine particles covering a predetermined surface of the silicone gel molded body,
70% or more of the surface is covered with the fine particles,
The fine particles are hydrophobic silica particles or silicone resin particles having an average particle size of 20 μm or less,
A sealing member having a particle diameter of 2 μm or more in a 100 μm square of the surface and having 50 or less particles visible with a scanning electron microscope.   The seal member according to claim 1, wherein the fine particles are porous particles.   A composite seal member in which the seal member according to claim 1 or 2 is laminated with a resin film.   An integrated product with a seal member, wherein the seal member according to any one of claims 1 to 3 and at least one of the first member and the second member are integrally formed.