WO2013035792A1 - Method for producing transparent adhesive sheet for optical applications, transparent adhesive sheet for optical applications, and display device using same - Google Patents

Abstract

[Problem] To provide: a transparent adhesive sheet for optical applications, which is able to have a good balance between adhesiveness and easy separability, in view of the above-mentioned problems of prior art; and a method for producing the transparent adhesive sheet for optical applications. [Solution] A method for producing a silicone-based transparent adhesive sheet for optical applications, specifically for assembly of optical components, which is characterized in that at least a part or the entire of an adhesive surface of the transparent adhesive sheet for optical applications, said adhesive surface being to be in contact with an object to which the transparent adhesive sheet for optical applications is bonded, is subjected to a surface activation treatment such as a corona discharge treatment or an atmospheric pressure plasma treatment so as to form an activated surface wherein the peel strength after bonding to the object is increased over time in comparison to the peel strength before bonding; and a transparent adhesive sheet for optical applications, which is obtained by the production method.

Description

Optical transparent adhesive sheet manufacturing method, optical transparent adhesive sheet, and display device using the same

The present invention relates to a method for producing an optical transparent adhesive sheet, an optical transparent adhesive sheet, and a display device using the same, and more specifically, a method for producing an optical transparent adhesive sheet capable of achieving both adhesion and reworkability, and optical transparency. The present invention relates to an adhesive sheet and a display device using the same.

Conventionally, functional adhesive sheets have been applied to assemblies of various optical devices, electrical devices, or electronic devices (including parts). In particular, from the viewpoint of productivity, an adhesive sheet that can handle rework of a bonded product is desired, and in particular, when bonding with a liquid crystal display device (hereinafter, also referred to as LCD) whose parts are expensive, rework can be supported. There is a strong demand for adhesive sheets.
On the other hand, it is also required to secure adhesion to an adherend (LCD, protective panel, etc.). However, it is difficult to achieve both adhesion and rework because of conflicting properties.
In recent years, a functional adhesive sheet having higher adhesion (adhesiveness) has been demanded from the viewpoint of practical reliability of an assembly part in which a functional adhesive sheet and an adherend are bonded. ) It can clear the point pressure test to confirm the peeling of the functional adhesive sheet and the generation of bubbles by applying a point load from the surface of the assembly product (for example, LCD / functional adhesive sheet / protective panel laminate) with a pressurizer. If large adhesion is ensured, on the other hand, (2) ensuring workability by maintaining the light release of the release protection sheet on the surface of the functional adhesive sheet in the assembly, and (3) adhesion displacement and parts repair The reworkability in replacement is significantly reduced. For this reason, it is more difficult to achieve both adhesion and reworkability.

Under the above circumstances, various techniques have conventionally been proposed as techniques for improving and solving the problem (1).
That is, (i) From the viewpoint of improving the adhesiveness, various techniques for improving the adhesiveness with the base material by subjecting the adhesive layer of the adhesive sheet to plasma treatment have been proposed (for example, Patent Documents 1 to 4). 4).
For example, Patent Document 4 discloses a surface protective film comprising a base material layer and an adhesive layer, the adhesive layer comprising a copolymer of specific ethylene and α-olefin, and the surface of the adhesive layer having a corona discharge. An activation treatment such as treatment or plasma treatment is performed, and from the viewpoint of adhesive strength, a surface protective film having a surface wetting index of 36 dyn / cm or more, preferably 40 dyn / cm or more is disclosed.
However, depending on the material of the pressure-sensitive adhesive, the adhesion improving effect and stability by the plasma treatment are different, and it is not always universal. In particular, for silicone adhesives that are attracting attention as optical materials due to their excellent transparency and heat resistance, the surface treatment effect is deactivated in a short time, so it is difficult to improve the adhesion by the surface activation treatment. (For example, refer nonpatent literature 1.).

Therefore, conventionally, in order to improve the adhesion or adhesion between the silicone resin and other materials, many approaches for hydrophilizing the silicone resin surface by plasma treatment have been studied. However, before 1980, since the plasma processing apparatus used at first required a vacuum or a low pressure, it was difficult to apply to a continuously produced silicone film or sheet.
Then, around 1990, atmospheric pressure glow discharge formation technology was proposed and demonstrated, and research on silicone surface treatment using atmospheric pressure plasma treatment has become active. However, since the hydrophilic silicone surface has a silicone-specific property of quickly hydrophobizing, it has been difficult to stably maintain hydrophilicity. Hydrophobic recovery (hydrophobic recovery) of this rapid hydrophobization is due to the fact that low molecular weight siloxane diffuses from the inside to the surface, and the methyl group component whose concentration has decreased due to the formation of hydrophilic groups on the surface is due to molecular motion. The re-orientation is caused by coming out on the surface, etc., and usually returns to the original hydrophobic state within about 24 hours after the plasma treatment. For this reason, various attempts have been made to suppress the restoration of hydrophobicity and to maintain stable hydrophilicity, but at present, no fundamental solution has been reached.

In addition, (ii) a method has been proposed in which, in the surface protective adhesive film, a plasma treatment or the like is performed on the adhesive layer to achieve both reworkability and adhesion (see, for example, Patent Documents 5 and 6).
However, the adhesive film for surface protection does not adhere firmly to the adherend for the purpose of its use, and it is difficult to ensure the adhesiveness that can pass the above point pressure test. A technique such as a surface protective film cannot be applied to the sheet.

Furthermore, (iii) the present applicant has also proposed a silicone-based pressure-sensitive adhesive sheet that has both reworkability and adhesion (see Patent Document 7), but in ensuring the adhesion that can pass the point pressure test described above. However, there is still room for improvement. In particular, with a low-hardness silicone gel, it is difficult to ensure adhesion, and technical hurdles for improving the adhesion are high.
In addition, (iv) as a means of achieving both adhesion ensuring and reworkability that can pass the above point pressure test, initially, the adherend is low adhesiveness that can be reworked, and after sticking A means for increasing the adhesive force over time is effective, for example, a pressure-sensitive adhesive in which the pressure-sensitive adhesive surface is modified with a functional group exhibiting adhesive reactivity by an interfacial contact reaction and a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive are proposed. (For example, refer to Patent Document 8).
However, in the above means and method, it is necessary to optimize the functional group exhibiting adhesion reactivity for each adherend, and there is a problem that requires a lot of labor.
As described above, the techniques (i) to (iv) and means (methods) have been proposed as techniques for improving and solving the problems. However, (1) ensuring adhesion and (2) It is not enough as a technical idea that can solve the problem of workability and (3) reworkability by maintaining light peelability, and for optical use that can achieve both reworkability and ensuring adhesion that can pass the above point pressure test A transparent adhesive sheet is desired.

Japanese Patent Laid-Open No. 07-173448 JP 2000-256247 A JP 2009-064552 A JP 2009-148996 A JP 2001-240820 A JP 2005-200606 A Japanese Patent No. 4500908 (WO / 2009/063847) JP 2001-323247 A

An object of the present invention is to provide an optical transparent pressure-sensitive adhesive sheet that can achieve both adhesion and reworkability, and a method for producing the same, in view of the above-described problems of the prior art.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention are initially low-adhesiveness capable of reworking the adherend, and after sticking, as means for increasing the adhesive force over time. As a result of paying attention and considering various experiments and their experimental results,
(A) By applying a specific plasma treatment to the adhesive surface, it has an appropriate adhesive force when bonded to an adherend, and is excellent in workability (including reworkability). The ability to produce a transparent adhesive sheet for silicone-based optics that increases the adhesiveness to the adherend and (B) the effect of increasing the adhesiveness to the adherend over time is the specific peelable surface By laminating a layer (in other words, an active sustaining layer),
I found. The present invention has been completed based on these findings.

That is, according to the first invention of the present invention, a method for producing a transparent adhesive sheet for silicone-based optics for assembling optical components,
The surface of the pressure-sensitive adhesive surface that is in contact with the adherend of the optical transparent pressure-sensitive adhesive sheet is subjected to surface activation treatment, and the peel strength after bonding to the adherend is compared with the peel strength before bonding. Thus, there is provided a method for producing an optical transparent pressure-sensitive adhesive sheet, characterized by forming a surface activation-treated surface that increases with time.

According to a second aspect of the present invention, there is provided the method for producing an optical transparent adhesive sheet according to the first aspect, wherein the surface activation treatment is a corona discharge treatment or an atmospheric pressure plasma treatment. The
According to a third aspect of the present invention, in the second aspect, the surface activation treatment is an atmospheric pressure plasma treatment, and the treatment is performed using a plasma derived from corona discharge. A method for producing an adhesive sheet is provided.
According to the fourth invention of the present invention, in the second or third invention, the surface activation treatment is an atmospheric pressure plasma treatment, and the treatment is performed by an afterglow of plasma generated by corona discharge. The manufacturing method of the optical transparent adhesive sheet characterized by the above is provided.
Furthermore, according to the fifth invention of the present invention, in the first invention, the peel strength (B) after 24 hours of bonding to the adherend is relative to the peel strength (A) at the initial stage of bonding. There is provided a method for producing an optical transparent adhesive sheet, wherein the increase in peel strength (BA) is 1 N / 20 mm or more in a 90-degree peeling mode of an adhesive strength test according to JIS Z0237.

According to a sixth aspect of the present invention, there is provided the method for producing an optical transparent pressure-sensitive adhesive sheet according to the first aspect, further comprising laminating an activity maintaining layer on the surface activation treatment surface. .
According to a seventh aspect of the present invention, in the sixth aspect of the invention, the activity maintaining layer is an alkyd resin-based or aliphatic amide-based release film. A method is provided.
Furthermore, according to an eighth aspect of the present invention, there is provided an optical transparent pressure-sensitive adhesive sheet obtained from the production method according to any one of the first to seventh aspects.

Further, according to the ninth aspect of the present invention, a protective panel, a polarizing plate, a phase difference, and a surface active treatment surface of the optical transparent adhesive sheet obtained from the manufacturing method according to any one of the first to fifth aspects are provided. There is provided a method for producing a laminate comprising bonding an adherend comprising an optical component selected from a plate, a diffusion film, or a liquid crystal display device.
Furthermore, according to the tenth aspect of the present invention, there is provided a laminate characterized in that it is obtained from the manufacturing method according to the ninth aspect.

According to the eleventh aspect of the present invention, there is provided an optical component using the optical transparent adhesive sheet or laminate according to the eighth or tenth aspect.
Furthermore, according to the twelfth aspect of the present invention, there is provided an optical transparent pressure-sensitive adhesive sheet manufacturing apparatus used in the method for manufacturing an optical transparent pressure-sensitive adhesive sheet according to any one of the first to seventh aspects of the invention. Is done.

As described above, the present invention relates to a method for producing a silicone-based transparent adhesive sheet for optical use for assembling optical components, and preferred embodiments thereof include the following.
(1) In the first invention, the transparent adhesive sheet for silicone-based optics has an Asker C hardness of 0 to 30 according to SRIS 0101 standard, or a penetration according to JIS K2207 “Petroleum Asphalt” (25 A method for producing a transparent optical adhesive sheet, characterized by comprising a silicone gel having a temperature of 20 to 200 ° C.).
(2) In the twelfth invention, an apparatus for producing a transparent optical adhesive sheet, comprising a surface activation treatment apparatus.

According to the method for producing an optical transparent pressure-sensitive adhesive sheet of the present invention, the obtained silicone-based optical transparent pressure-sensitive adhesive sheet for assembling optical components has an appropriate pressure-sensitive adhesive force when bonded to an adherend. The productivity and cost of the combined work are improved, and after bonding, the adhesion with the adherend increases with time, so that problems such as peeling are prevented and stable quality can be realized.
In addition, by covering with a release film that functions as an active maintenance layer until pasting, the surface activation treatment effect such as plasma treatment effect, which has been considered difficult in the past, is maintained, and the peel strength increases over time. Therefore, it is excellent in storage property and can realize stable bonding.
In the present invention, the surface of the silicone-based cured body is subjected to surface activation treatment such as plasma treatment, thereby continuously producing an optical transparent adhesive sheet having improved adhesion (adhesiveness) to an adherend. Further, it has a remarkable effect that high adhesion (adhesiveness) can be stably obtained.
Furthermore, the present invention can be applied not only to optical applications but also to silicone-based pressure-sensitive adhesive sheets that are not transparent, and can be used for a wider range of applications.

FIG. 1 is a schematic diagram for explaining a configuration example of the optically transparent adhesive sheet laminate of the present invention. FIG. 2 is a schematic view of a method of processing by an afterglow of plasma generated by a corona discharge generated by an alternating electric field applied between two coaxial cylindrical electrodes. FIG. 3 is a schematic view for explaining the method for producing the optical transparent adhesive sheet of the present invention. FIG. 4 is a schematic diagram for explaining another embodiment of the method for producing an optical transparent adhesive sheet of the present invention. FIG. 5 is a schematic diagram for explaining another embodiment of the method for producing the optical transparent pressure-sensitive adhesive sheet of the present invention. FIG. 6 is a graph showing the relationship between the peel strength and the irradiation distance in the examples of the method for producing the optical transparent adhesive sheet of the present invention. FIG. 7 is a graph showing the relationship between peel strength and processing output in an example of the method for producing an optical transparent adhesive sheet of the present invention. FIG. 8 is a graph showing the change over time of the increase in peel strength with respect to the pasting time after pasting to the adherend in the example of the method for producing the optical transparent adhesive sheet of the present invention. FIG. 9 is a graph showing the change over time in the amount of increase in peel strength with respect to the pasting time for the case of coating with the surface activity maintaining layer in the example of the method for producing the optical transparent adhesive sheet of the present invention. FIG. 10 is a graph showing the relationship between the storage elapsed time in the state covered with the surface activity maintaining layer and the peel strength from the adherend after storage in the example of the method for producing the transparent optical adhesive sheet of the present invention. It is. FIG. 11 is a schematic diagram illustrating the configuration and test mode of a sample for a peel force test.

The method for producing a silicone-based optical transparent adhesive sheet for assembling an optical component according to the present invention comprises subjecting at least a part of or the entire adhesive surface in contact with the adherend of the optical transparent adhesive sheet to surface activation treatment, It is a method for producing a transparent adhesive sheet for optics, characterized in that the surface activation treatment surface is formed such that the peel strength after bonding to an adherend increases with time compared to the peel strength before bonding. .
As another aspect of the present invention, the method for producing a silicone-based transparent optical adhesive sheet for assembling an optical component according to the present invention is characterized in that an active maintenance layer is further laminated on the surface activation-treated surface. It is a manufacturing method of the transparent adhesive sheet for optics to do.
Hereinafter, each item will be described.

1. Optical transparent pressure-sensitive adhesive sheet (1) Pressure-sensitive adhesive The optically transparent pressure-sensitive adhesive sheet according to the present invention has, as a pressure-sensitive adhesive, a transparent silicone gel, acrylic gel, polyolefin gel, polyurethane gel, butadiene gel, isoprene gel, A transparent adhesive composed of at least one transparent gel selected from butyl gel, styrene butadiene gel, ethylene vinyl acetate copolymer gel, ethylene-propylene-diene terpolymer gel or fluorine gel is used. Is preferred.
Especially as said silicone type gel, what is formed from the addition reaction type silicone gel which has adhesiveness is preferable.
As for the hardness of the silicone-based gel, the Asker C hardness of SRIS 0101 standard is preferably 0 to 30, or the penetration (25 ° C.) according to JIS K2207 “Petroleum Asphalt” is preferably 20 to 200.

In the present invention, the term “transparent” means colorless transparent, colored transparent, and translucent. The transparent silicone gel used in the present invention has a total light transmittance (JIS) of visible light having a wavelength of 380 to 780 nm. K7105 “Testing method for optical properties of plastic”) is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more.
The transmittance is an index of the transparency of the transparent member. When the transmittance is less than 80%, for example, light emitted from the screen is difficult to transmit through the transparent member, and thus visibility is deteriorated. In addition, when the wavelength region where the transmittance is 80% or more is narrower than the region of 380 nm to 780 nm, the light transmittance on the red side (high wavelength side) or blue side (low wavelength side) decreases. It is not preferable. Here, the transmittance is a value measured using a spectrophotometer or the like.

As the above addition reaction type silicone gel, silicon compounds that have been conventionally known and are generally used as various commercially available silicone materials can be appropriately selected and used. Therefore, any of a heat curable type or a room temperature curable type, a condensed type or an addition type curing mechanism can be used, and a silicone gel obtained from an addition type silicone composition is particularly preferable. In addition, the group bonded to the silicon atom is not particularly limited, for example, an alkyl group such as a methyl group, an ethyl group, or a propyl group, a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group, a vinyl group, an allyl group, or the like. In addition to aryl groups such as alkenyl groups, phenyl groups, and tolyl groups, those in which the hydrogen atoms of these groups are partially substituted with other atoms or bonding groups.

As a specific addition reaction type silicone gel material, trade name: CF-5106 (penetration 150) manufactured by Toray Dow Corning Co., Ltd. is preferable, and this silicone gel material is a silicone as a raw material. The resin is divided into A liquid and B liquid. By mixing and heating both liquids at a predetermined ratio, a silicone gel material having a desired penetration can be obtained.

The production method of the addition reaction type (or cross-linked) silicone gel used in the present invention is not particularly limited. Usually, however, an organohydrodiene polysiloxane and an alkenyl polysiloxane, which will be described later, are used as raw materials, and both are hydrolyzed in the presence of a catalyst. It can be obtained by a silylation reaction (addition reaction).

The silicone gel has adhesiveness derived from the non-crosslinked functional group on the surface. For example, the silicone gel is formulated with an MQ resin-type tackifier component, the addition of a non-reactive adhesive component, the non-crosslinked functional group What applied the well-known tackiness imparting methods, such as expressing the adhesiveness by adjusting the length of a side chain, the kind of terminal functional group, etc. can also be used.

(2) Activity maintenance layer The manufacturing method of the optical transparent adhesive sheet of this invention is characterized by further laminating an activity maintenance layer on the surface activation treatment surface.
By laminating the activity maintaining layer on the surface activation treatment surface, it is possible to suppress a decrease in the surface activation treatment effect. The mechanism is unknown at present.

The activity maintaining layer is required to be peelable from the surface activation treatment surface in addition to being laminated on the surface activation treatment surface to suppress a decrease in the surface activation treatment effect. Therefore, since the activity maintaining layer also functions as a release film (also referred to as a release liner), a known release film can be used as the activity maintaining layer.
Examples of release films include polyethersulfone resins, cellulose acetate resins, polyimide resins, polyester resins, polyether resins, epoxy resins, phenol resins, polyamide resins, polyolefin (eg polypropylene), and other organic resins; these organic resins Is a film formed by laminating with another peelable organic resin, or a film in which these organic resins cover the surface of a peelable substrate film. In the present invention, the film is used as an activity maintaining layer. Since the release film is peeled and removed when laminated on the adherend, an alkyd resin release film and an aliphatic amide release film that are excellent in peelability are preferable.

2. Manufacturing method of optical transparent pressure-sensitive adhesive sheet The method for manufacturing an optical transparent pressure-sensitive adhesive sheet according to the present invention comprises subjecting at least a part or the entire surface of the pressure-sensitive adhesive surface in contact with the adherend to a surface activation treatment. The surface activation treatment surface is formed such that the peel strength after bonding to the adherend increases with time as compared to the peel strength before bonding.

(1) Surface activation treatment The method for producing an optical transparent pressure-sensitive adhesive sheet of the present invention is characterized in that surface activation treatment is performed on at least a part or the entire surface of the pressure-sensitive adhesive surface in contact with the adherend of the optical transparent pressure-sensitive adhesive sheet. As the surface activation treatment, it is possible to form a surface activation treatment surface in which the peel strength after bonding to the adherend increases with time compared to the peel strength before bonding. There is no particular limitation.
In the present invention, the surface activation treatment is a known method such as corona discharge treatment (in air, nitrogen, carbon dioxide, etc.), plasma treatment (high pressure, low pressure), alkali metal solution treatment, high-frequency sputtering etching treatment. Chemical surface treatment methods such as these are preferable, and corona discharge treatment or plasma treatment is preferred, plasma treatment is more preferred, and atmospheric pressure plasma treatment is even more preferred.

Furthermore, atmospheric pressure plasma treatment is roughly classified into, for example, thermal equilibrium plasma typified by arc discharge and non-thermal equilibrium plasma typified by corona discharge and dielectric barrier discharge. Atmospheric pressure plasma is preferred.
Corona discharge that generates atmospheric pressure plasma is known to take various discharge modes depending on the type of atmospheric gas, voltage application method (direct current, alternating current, pulse) and the magnitude of the applied voltage. In the present invention, a method of treating with a plasma afterglow generated by a corona discharge generated by an alternating electric field applied between two coaxial cylindrical electrodes can be adopted. (See FIG. 2) is more preferable.
In addition, since the plasma afterglow treatment is performed in an environment where the plasma energy is low as compared with the plasma treatment method (plasma treatment) in which the plasma is directly treated, the effects of the present invention are exhibited. One factor suggests that treatment in a plasma energy environment as low as the afterglow of the plasma is effective.
In addition, since the definition in the classification of the surface treatment technology is not constant at present, a method of treating with a plasma afterglow generated by a corona discharge generated by an alternating electric field applied between the two coaxial cylindrical electrodes. the, Claire Tendero, Christelle Tixier, Pascal Tristant, Jean Desmaison, Philippe Leprince: Atmospheric pressure plasmas: a review: Spectrochimica are described in Acta Part B 61 (2006) 2-30 "the derived-from-Corona processes" It is equivalent to.

Hereinafter, the treatment conditions and the like will be specifically exemplified by taking the surface treatment of the silicone adhesive as an example.

(I) Type of gas Examples of the type of gas include nitrogen, oxygen, hydrogen, carbon dioxide, etc. The effect varies depending on the gas type. The time-dependent change width of the adhesive force after pasting can be adjusted. The time-varying width contributes to reworkability and adhesion after lamination to the adherend, and the larger the width, the more advantageous. For example, in the case of treatment with a plasma afterglow generated by corona discharge generated by an alternating electric field applied between two coaxial cylindrical electrodes, the above gas species is, for example, an adhesive when PMMA is used as an adherend. The magnitude of the force UP effect is in the order of O ₂ > H ₂ > CO ₂ , and the magnitude of the temporal change width is O ₂ > H ₂ ≈CO ₂ .
The active maintenance layer is required to have low adhesion (high peelability). However, when the active maintenance layer is an alkyd resin release film or an aliphatic amide release film, the gas type The dependence of is small. As an example, oxygen gas is preferable from the viewpoint of the balance between the improvement of adhesiveness and the light release property of the release film.
On the other hand, the effect of gas concentration is small compared to the effect of gas type.

(Ii) Plasma irradiation conditions As plasma irradiation conditions, irradiation distance and output are typical factor conditions.
When processing is performed by a plasma afterglow generated by a corona discharge generated by an alternating electric field applied between two coaxial cylindrical electrodes, the irradiation distance has a peak in adhesive strength in a small region regardless of the gas type. Specifically, the adhesive force changes when the irradiation distance is in the range of 5 to 20 mm, and has a peak near the center of the range.
Further, the output tends to increase the adhesive force as the output increases, but the contribution to the adhesive force is small compared to the irradiation distance.

Further, in the surface activation treatment, the surface once activated may be further treated with a different surface activation treatment method and / or different surface activation treatment conditions (for example, different gas types). By combining different treatment methods, it is possible to variously adjust the temporal change width of the adhesive strength and the adhesion after pasting to the adherend.

In the present invention, the mechanism (mechanism) for improving the adhesive force of the pressure-sensitive adhesive layer different from the conventional one by surface activation treatment such as corona discharge treatment or plasma treatment and its maintenance is not clear at present, As a result of the roughening of the surface of the pressure-sensitive adhesive layer by the activation treatment, the pressure-sensitive adhesive easily enters the slits on the surface of the adherend, and the pressure-sensitive adhesive that has penetrated into the slits lowers the wrinkles. A composite effect is that the anchoring effect that exhibits strong adhesive force occurs, or that the adhesive force is improved by the occurrence of carbonyl groups, carboxyl groups, etc. on the adhesive surface and the surface being polarized. Is considered.

In addition, it is preferable to further laminate the above-mentioned activity maintaining layer on the surface activation treatment surface. For example, if the silicone gel treatment surface is covered with a release film (sheet-like or roll-like), rework is possible. Adhesive strength is maintained, and after bonding to the adherend, the adhesive strength improves over time, and the adhesion is ensured.

(2) Manufacturing method of optical transparent adhesive sheet The manufacturing method of the optical transparent adhesive sheet of this invention consists of the formation process and surface activation processing process of the optical transparent adhesive sheet which carry out surface activation processing, and surface activation processing process Is a step of performing a surface activation treatment on a portion that is desired to be surface activated by a surface treatment apparatus, while a known method can be applied to the step of forming the optical transparent adhesive sheet.
Hereinafter, although it demonstrates concretely using the form which manufactures a thermosetting (silicone) transparent adhesive sheet for optics continuously as an example using FIG. 3, it is not limited to this embodiment.
FIG. 3 is a schematic diagram of a continuous optical transparent adhesive sheet manufacturing apparatus.
First, an uncured pressure-sensitive adhesive composition is applied to a predetermined thickness on a release film, and the optically transparent pressure-sensitive adhesive sheet discharged from the curing zone is cured by curing in the curing zone while leaving the coated surface open. The surface is surface activated with a surface activation processing apparatus, and then a release film to be an activity maintaining layer is laminated to obtain an optical transparent adhesive sheet having the configuration of FIG. .

As another embodiment, as shown in FIG. 4, an uncured pressure-sensitive adhesive composition is applied to a predetermined thickness on a release film that has been subjected to a release treatment on both sides, and the application surface is left open as it is in a curing zone. The surface of the transparent adhesive sheet for optics discharged from the curing zone is activated by a surface activation treatment device, and the surface of the transparent adhesive sheet for optics discharged from the curing zone is activated. It is good also as a form of the structure of FIG.1 (b) wound in roll shape, making the said surface activation process surface contact the back surface of the said peeling film after surface activation process with an apparatus. In this case, the release treatment functional part of the release film functions as an activity maintaining layer.
Furthermore, as another form of FIG. 4, as shown in FIG. 5, after curing in a state where an uncured adhesive composition is sandwiched between different base materials at the time of curing, one base material is peeled off, It is good also as a form which performs a surface activation process to a peeling surface.
In addition, the transparent adhesive sheet for optics before the surface activation process formed by the method of FIG. 3 and FIG. Since it can be set in advance before the re-treatment, it is useful because the degree of freedom in designing the front-back different adhesion can be expanded without relying only on the surface activation treatment for the front-back different adhesion required for the peeling selectivity at the time of rework. Also in the method of FIG. 5, by adjusting the type of base material surface to be brought into contact with both surfaces of the uncured pressure-sensitive adhesive composition to a different kind of combination, the same adjustment of front and back different tackiness as in FIGS. 3 and 4 can be achieved. Is possible.

3. Properties and performance of the optical transparent adhesive sheet The optical transparent adhesive sheet obtained by the method for producing the optical transparent adhesive sheet of the present invention is applied to the adherend on at least a part of or the entire adhesive surface in contact with the adherend. Compared with the peel strength before pasting, the peel strength after pasting has a surface activation treatment surface that increases with time, so it has moderate adhesive strength when pasting to the adherend. Therefore, productivity and cost of bonding work are improved, and after bonding, adhesiveness with the adherend increases with time, so troubles such as peeling are prevented and stable quality is realized. it can. That is, the optical transparent pressure-sensitive adhesive sheet of the present invention can achieve both adhesion and reworkability.
Even with conventional adhesives, the adhesion may increase over time depending on the temperature, compatibility with the adherend, etc., but the present invention significantly accelerates the increase in adhesion over time due to the surface activation treatment. In addition, the amount of increase in adhesion over time can be adjusted according to the surface activation treatment conditions.

The surface activation treatment surface of the optical transparent pressure-sensitive adhesive sheet of the present invention is an increase in peel strength (B) after 24 hours with respect to the peel strength (A) at the initial adhesion when bonded to an adherend ( B-A) is characterized in that it is 1 N / 20 mm or more in the 90-degree peeling mode of the adhesive strength test according to JIS Z0237. In addition, the said adhesion | attachment initial stage is 20 minutes after surface activation process (including the bonding operation | work to a to-be-adhered body).
In addition, until the pasting to the adherend, by covering with an activity maintenance layer, while maintaining the adhesive improvement effect and surface adhesion improvement effect by surface activation treatment such as plasma treatment effect, Since it is possible to suppress an increase in peel strength over time with the active maintenance layer in the storage state before pasting to the adherend, it is possible to secure the peel stability of the active maintenance layer, so that it has excellent storability and stable pasting. Can also be realized.

4). Optical transparent pressure-sensitive adhesive sheet laminate, production method thereof The optical transparent pressure-sensitive adhesive sheet laminate of the present invention is obtained by closely laminating optical components on the surface activation-treated surface of the optical transparent pressure-sensitive adhesive sheet, As an optical component, a protective panel, a polarizing plate, a retardation plate, a diffusion film, a liquid crystal display device, a light guide plate, a touch panel element, a planar light emitting device, and the like can be applied depending on applications and purposes. For example, a display device unit Used as a touch panel unit, lighting unit, or a component thereof. Typically, as shown in FIG. 1 (c), a configuration in which an optical component is attached to one side (the other may be attached with a release film (B), for example, and the release film (B) is peeled off during use). Alternatively, as shown in FIG. 1D, optical components are laminated on both sides.
The optical transparent adhesive sheet laminate may be laminated to an optical component on the optical transparent adhesive sheet immediately after the surface activation treatment, or using an optical transparent adhesive sheet in which an activity maintaining layer is laminated, You may laminate on the surface activation treatment surface which peeled.

Although lamination | stacking of the transparent adhesive sheet for optics and an optical component will not be specifically limited if it can be bonded so that a bubble may not be caught, A roller bonding method, a vacuum bonding method, etc. are applicable.
If the transparent adhesive sheet for optics is bonded to an optical component within a certain period of time, it can be re-attached (reworked). A transparent adhesive sheet laminate for optics is obtained in which the transparent adhesive sheet and the optical component are firmly adhered in a state where no peeling or bubbles are generated in the point pressure test.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not particularly limited to these examples.

[Examples 1 to 25]
The optical transparent adhesive sheet laminate was produced by the following procedure.
(I) Supplying an uncured liquid viscoelastic material onto the release film (B) and setting the thickness; (ii) Opening and heating curing without attaching the release film (A) after molding And (iii) forming a transparent adhesive sheet for optics through a cooling step for cooling the cured sheet obtained in the heat curing step, and (iv) on the surface cured by heating in the heating step. Then, after forming a surface activation treatment surface by surface activation treatment in an atmospheric pressure plasma treatment apparatus, a release film attachment step of attaching a release film (A) as an active maintenance layer to the surface activation treatment surface, An optical transparent adhesive sheet laminate having a penetration of 100 and a hardness of 200 mm × 200 mm × thickness 0.5 mm was obtained, in which the release film (A), the optical transparent adhesive body, and the release film (B) were laminated in this order.
The uncured liquid silicone gel raw material is a two-component addition reaction type silicone gel (model: SLJ3363, total light transmittance in air of 90%) manufactured by Asahi Kasei Wacker Silicone Co., Ltd., liquid A (main agent + crosslinking catalyst) / Liquid B (main agent + crosslinking agent) blended at 55 parts by weight / 45 parts by weight was used.
The release film (A) is an alkyd resin release film (model: T-9, film thickness: 0.1 mm) manufactured by Panac Co., Ltd., and the release film (B) is fluorosilicone manufactured by Unitika Ltd. A system release film (model: FZ, film thickness: 0.1 mm) was used.

As the procedure of the molding step, the thickness setting in the molding step (i) is carried out by placing the release film (B) on the flat glass substrate with the release action surface facing upward, and further, aluminum on the release film (B). Place a frame-shaped spacer with an inner dimension of 200 mm × 200 mm × thickness 0.5 mm and pour the uncured silicone gel raw material into the mold, and then squeeze it along the upper surface of the mold with a squeegee plate. The method was performed by removing the cured silicone gel raw material.
The curing of (ii) was performed by heating and curing in a hot air oven at 75 ° C. for 1 hour, and the cooling of (iii) was naturally cooled on a wooden board at room temperature (25 ° C.).

In addition, the surface activation treatment of (iv) is performed by an atmospheric pressure plasma apparatus (ULD manufactured by AcXys Technologies, ULD) that performs treatment with a plasma after glow generated by a corona discharge generated by an alternating electric field applied between two coaxial cylindrical electrodes. -120) was carried out at a transfer speed of 4 m / min under the conditions of gas type, irradiation distance, and output shown in Table 1.

[Comparative Example 1]
An optical transparent adhesive sheet laminate was obtained in the same manner as in Example 1 except that the surface activation treatment was not performed in Example 1.

In the examples and comparative examples, the performance and the like related to the optical transparent adhesive sheet were evaluated according to the following evaluation methods.

1. Evaluation method (1) Hardness:
It calculated | required by the penetration measuring method based on JISK2207 "petroleum asphalt", or the Asker C hardness of SRIS 0101 specification was calculated | required.

(2) Peel strength:
The 90-degree peeling adhesive strength in an adhesive strength test in accordance with JIS Z0237 “Testing method for adhesive tape / adhesive sheet” was measured with a 90-degree peel tester at a pulling speed of 300 mm / min.
The test sample for evaluation was obtained by bonding the adherend to the surface activation-treated surface of the optical transparent adhesive sheet with the release film (B) prepared in each Example and Comparative Example, and then the release film (B). Is peeled and removed, and a resin film (PET, emblet made by Unitika Co., Ltd.) is pasted on the surface from which the release film (B) is peeled, via a primer (Primer A made by Shin-Etsu Chemical Co., Ltd.) In this case, and for the case where the release film (A) was bonded, a test sample for evaluation of peel strength was produced with the configuration schematically shown in FIGS. 11 (a) and 11 (b), and the test was performed.
The pasting condition was one round trip at a speed of 300 mm / min with a 2 kg roller, and then left at 23 ° C. for 20 to 40 minutes.
The adherend was an acrylic plate (Mitsubishi Rayon Co., Ltd., MR-200) having a thickness of 1 mm and a glass plate (Hiraoka Glass Co., Ltd., soda glass).

(3) Change in peel strength over time when bonded to an adherend:
According to the above (2) peel strength evaluation method, the peel strength evaluation sample when bonded to the adherend in the configuration of FIG. 11 (a) and the peel film (A) in the configuration of FIG. 11 (b). The samples for evaluation of peel strength when bonded were prepared within 20 minutes after the surface activation treatment, and allowed to stand at room temperature (25 ° C.) for a predetermined time, and then the peel strength was measured. In addition, initial value 0hr used as the reference | standard of pasting elapsed time is 20 minutes after surface activation processing (including the pasting work to a to-be-adhered body), and measures the peeling strength in the pasting elapsed time of Table 2, respectively. did.

(4) Change in peel strength over time when the surface activation-treated surface is covered with the release film (A) and stored (verification of activity maintenance effect by the activity maintenance layer):
The transparent optical adhesive sheet laminate in which the release film (A) was bonded to the surface activation-treated surface of the optical transparent adhesive sheet with the release film (B) produced in each Example and Comparative Example was obtained at room temperature (25 C.), the release film (A) is peeled off after reaching a predetermined elapsed time (storage elapsed time) from the start of storage, and the adherend and surface activation treatment are performed in the configuration shown in FIG. A peel strength evaluation sample bonded to the surface was prepared, and the peel strength was measured by the test method for (2) peel strength. The initial value 0 hr as a reference for the storage elapsed time was 20 minutes after the surface activation treatment, and the peel strength at the storage elapsed time in Table 3 was measured.

As shown in Table 1, as is clear from the comparison between Examples 1 to 24 and Comparative Example 1, it can be seen that the surface activation treatment improves the peel strength in any of the Examples.
As for the influence of the surface activation treatment conditions, it can be seen from the results shown in FIG. 6 that any gas species has a peel strength peak in a specific irradiation distance range. Moreover, even if a to-be-adhered body is glass (FIG.6 (b)) and a PMMA board (FIG.6 (a)), it has the same tendency. Comparing the gas types, the irradiation distance ranges that show peaks in H ₂ / N ₂ gas and O ₂ / N ₂ gas are almost the same, but the effect of improving peel strength is greater in H _2. Recognize.
Furthermore, about peeling strength with a peeling film (A) from FIG.6 (c), when irradiation distance becomes large, there exists a tendency for it to fall and to be saturated, and shows a peak in FIG. 6 (a) and FIG.6 (b). It can be seen that, at the irradiation distance, the saturation level has already been reached, and within the irradiation distance range showing the peak, the peelability of the release film can be achieved while improving the adhesion to the adherend.
Further, regarding the influence of the processing output, from the result of FIG. 7, in any gas type, within the range of the conditions of this example, as the processing output increases, the resistance to PMMA (FIG. 7A) and the resistance to glass ( It can be seen from FIG. 7B that the peel strength is improved.
Therefore, it can be seen that the desired peel strength can be improved by adjusting the gas type, irradiation distance, and processing output.

Table 2 shows the results of comparative evaluation of the optical transparent adhesive sheets of Examples 1 and 13 and the optical transparent adhesive sheet of Comparative Example 1 with respect to the adhesiveness with time after bonding, which is a feature of the present invention. Furthermore, about the relationship between the increase amount (difference) of the peeling strength with respect to the peeling strength at the initial stage of bonding in Table 2 and the pasting elapsed time, it is applied to a PMMA plate, a glass plate, and a release film (active maintenance layer) The combined cases are shown in FIGS. 8 (a), 8 (b) and 9, respectively. In FIGS. 8A and 8B, the black plots and the bold underline notation in Table 2 indicate that the optical transparent adhesive sheet has been destroyed.
From the result of FIG. 8 (a), when PMMA is used as the adherend, the surface activation treatment is performed in comparison with Comparative Example 1 without the surface activation treatment, in which the adhesion gradually increases with time. In the optically transparent adhesive sheets of Example 1 (O ₂ / N ₂ gas) and Example 13 (H ₂ / N ₂ gas) subjected to the above, adhesion with time after bonding is promoted. I understand that. In addition, when Examples 1, 3, and 25 are compared, the degree of promotion of adhesion over time is different, and the optical transparent adhesive sheet of Example 1 has reached adhesion until the material is destroyed in a few hours.
Further, in the case of the optical transparent adhesive sheet of Example 13 in which the glass plate was used as an adherend, the optical transparent adhesive sheet of Example 13 was subjected to no surface activation treatment as shown in FIG. Compared with the optical transparent adhesive sheet of Comparative Example 1, it can be seen that the adhesiveness over time is promoted. In addition, in the case of the transparent adhesive sheet for optics of Example 1, it is the adhesiveness of the state which destroys a material from the initial stage of bonding, and measurement of peeling strength with time is impossible (only the material breaking strength of the transparent adhesive sheet for optics is measured) It was because it was not possible.
Furthermore, although not described in FIG. 8 (a), FIG. 8 (b), and Table 2, if it is within the pasting elapsed time in which the optical transparent adhesive sheet does not break the material when peeled from the adherend. The optical transparent adhesive sheets of Examples 1 and 13 were able to be peeled off from the PMMA and glass as adherends.
In this way, there is a difference in the behavior of adhesiveness over time depending on the type of adherend and surface treatment result treatment conditions, but in any case, the adhesion over time is promoted by the surface activation treatment, and bonding It can be seen that rework is possible within the range of pasting time that can be peeled later. Furthermore, it can be seen that by adjusting the surface treatment result processing conditions, it is possible to adjust the adhesiveness over time according to the type of adherend and the desired rework time.

Moreover, from the result of FIG. 9, when a peeling film (A) was bonded, the change of the peeling strength with respect to pasting elapsed time is slight, and the optical transparent adhesive sheet of Comparative Example 1 without surface activation treatment It is considerable, and even in the storage state before bonding to optical parts, the ease of removing the release film does not change, so the stable release property of the release film is maintained, so before bonding to optical parts It can be seen that the storability is excellent.

Furthermore, the surface activated surface is coated with the release film (A) that is the active maintenance layer, and the optically transparent adhesive laminate that has been stored is peeled and removed from the time and the release film (A) that has been coated and stored with the active maintenance layer. Table 3 shows the relationship between the peel strength and the adherend (PMMA and glass). Further, in Table 3, the relationship between the storage elapsed time and the change in peel strength when the adherend is PMMA is shown in FIG. The amount of change in Table 3 is a value obtained by subtracting the peel strength at the storage elapsed time of 0 hr from the peel strength at each storage elapsed time. Moreover, the bold underline notation in Table 3 represents that the optical transparent adhesive sheet was destroyed.
From this result, the peel strength from the adherend hardly changes with the time of coating and storing with the active maintenance layer, and the surface activation treatment effect is maintained by coating (lamination) with the active maintenance layer. You can see that

Since the optical transparent adhesive sheet obtained by the method for producing an optical transparent adhesive sheet of the present invention can achieve both adhesion and reworkability, a display device such as a mobile phone, a liquid crystal monitor, and a liquid crystal television, indoors or It can be used for outdoor signs, advertisements, lighting signs for posting, lighting fixtures, tail lamps, vehicle optical parts such as interior lighting, and the like. Moreover, it can be applied not only to optical applications but also to silicone-based pressure-sensitive adhesive sheets that are not transparent, and can be used for a wider range of applications.

DESCRIPTION OF SYMBOLS 1, 10, 100, 101 Optical transparent adhesive sheet laminated body 2 Optical transparent adhesive body 21 Surface activation surface 3 Release film (A)
4 Release film (B)
4S resin film 5 Uncured transparent adhesive body material for optics 6 Adhered body 7 Primer 75 Core 80 Heating device (heater)
81 Doctor blade (squeegee board)
82 Raw material supply device 83 Cooling device 84, 841, 842, 843, 844, 845 Conveying device (conveyor)
85 Calendar roll 86 Sheet cutting device 87 Peeling film (A) sticking device 91 Peeling film (B) feeding device (roll)
92 Peeling film (A) supply device (roll)
93 Peeling film (A) Peeling / collecting device (roll)
94 Peeling film (A) supply device for sticking (roll)
95 Surface activation treatment equipment

Claims (12)

1. A method for producing a silicone-based transparent adhesive sheet for optical use for assembling optical components,
   The surface of the pressure-sensitive adhesive surface that is in contact with the adherend of the optical transparent pressure-sensitive adhesive sheet is subjected to surface activation treatment, and the peel strength after bonding to the adherend is compared with the peel strength before bonding. And forming a surface activation-treated surface that increases with time.
2. The method for producing a transparent adhesive sheet for optics according to claim 1, wherein the surface activation treatment is corona discharge treatment or atmospheric pressure plasma treatment.
3. The method for producing a transparent adhesive sheet for optical use according to claim 2, wherein the surface activation treatment is atmospheric pressure plasma treatment, and treatment is performed with plasma derived from corona discharge.
4. The method for producing an optical transparent adhesive sheet according to claim 2 or 3, wherein the surface activation treatment is atmospheric pressure plasma treatment, and treatment is performed by afterglow of plasma generated by corona discharge.
5. The peel strength (B) after 24 hours of bonding to the adherend is an adhesive strength test in which the amount of increase in peel strength (BA) is in accordance with JIS Z0237 relative to the initial peel strength (A). The method for producing a transparent adhesive sheet for optical use according to claim 1, wherein the 90 ° peeling mode is 1 N / 20 mm or more.
6. The method for producing a transparent adhesive sheet for optics according to claim 1, wherein an activity maintaining layer is further laminated on the surface activation treated surface.
7. The method for producing an optical transparent adhesive sheet according to claim 6, wherein the activity maintaining layer is an alkyd resin-based or aliphatic amide-based release film.
8. An optical transparent pressure-sensitive adhesive sheet obtained from the production method according to any one of claims 1 to 7.
9. 6. An optical component selected from a protective panel, a polarizing plate, a retardation plate, a diffusion film, or a liquid crystal display device on the surface active treatment surface of the optical transparent adhesive sheet obtained from the production method according to claim 1. The manufacturing method of the laminated body characterized by bonding the adherend which consists of.
10. A laminate obtained from the production method according to claim 9.
11. An optical component using the optically transparent adhesive sheet or laminate according to claim 8 or 10.
12. An optical transparent pressure-sensitive adhesive sheet manufacturing apparatus, which is used in the method for manufacturing an optical transparent pressure-sensitive adhesive sheet according to any one of claims 1 to 7.

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