JP2003001711A - Method for producing laminate with adhesion-sealed peripheral fringe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a laminate with its adhesion-sealed peripheral fringe which can produce a laminate having a high thickness precision without generating a large amount of waste, and is excellent in work properties in place of a production method using a pressure sensitive adhesive double coated sheet with its middle part cut off which has been used generally so far. SOLUTION: A photo-reactive liquid adhesive, after being applied on the peripheral fringe of at least one base material by a screen printing method, is irradiated with light and laminated on the other base material to adhesion-seal the peripheral fringe.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminate having a peripheral portion adhesively sealed using a screen printing method. 2. Description of the Related Art When manufacturing a laminated product requiring strict thickness accuracy, a film material is bonded with a double-sided adhesive tape, or an adhesive is precisely formed by a precision dispenser, a screen printing method, or the like. A method of applying with a large application amount is adopted. However, strangely, in the case of manufacturing a laminated body in which the peripheral portion is adhesively sealed, only a method of attaching a double-sided pressure-sensitive adhesive tape having a good thickness accuracy to the peripheral portion of the film and laminating the film is adopted. In addition, it is surprisingly difficult to apply a double-sided adhesive tape to the edge of the film with strict thickness accuracy, and simply applying a double-sided adhesive tape along the edge of the film will produce a laminate with uniform thickness accuracy. It was difficult to manufacture. Also, the work was complicated. Therefore, at present, a method has been adopted in which a peripheral portion of a film is laminated using a double-sided pressure-sensitive adhesive sheet having substantially the same size as a film whose central portion has been cut out. This makes it possible to manufacture a laminated body with good thickness accuracy and excellent workability. However, this method has a problem that a large amount of the cut double-sided pressure-sensitive adhesive sheet is generated as waste. SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a method for manufacturing a laminated body having a peripheral portion bonded and sealed with a strict thickness accuracy. An object of the present invention is to provide a method for producing a laminate which can be performed, does not generate a large amount of waste, and is excellent in workability. According to the present invention, there is provided a method for producing a laminate having a peripheral portion bonded and sealed by applying a photoreactive liquid adhesive to at least one peripheral portion of a substrate by a screen printing method. It is characterized by being irradiated with light and bonded to one of the substrates. [0004] The laminate produced by the production method of the present invention is a laminate in which the central portion is not bonded, while the peripheral portion is adhesively sealed. Therefore, if the contents are stored in advance before performing the adhesive seal and then the adhesive seal is performed by the manufacturing method of the present invention, the package can be used as a packaging container. Further, the present invention can be applied to a method of manufacturing a product such as a touch panel, which requires only a peripheral portion to be adhesively sealed with strict thickness accuracy. In the present invention, the photoreactive liquid adhesive is applied to the substrate by a screen printing method, but the device used for the application operation does not need to be a special device. The adhesive may be applied only to the peripheral portion of the base material using a commercially available screen printing device. The screen printing plate used in the screen printing method is not special, and a general screen printing plate is sufficient. For example, polyamide resin,
A screen is made of a thin cloth made of mesh made of fibers of polyester resin, polyimide resin, stainless steel, etc. at a fine pitch and formed into a mesh.The screen is fixed to a wooden or metal rectangular frame to prevent wrinkles, and exposed to this screen. A screen printing plate obtained by superimposing and thermally transferring an emulsion film having an emulsified emulsion layer, printing a required pattern on the transferred photosensitive emulsion layer, and exposing and etching the emulsion film. Incidentally, the mesh of the screen does not immediately form a hole due to heating, and it is necessary to adjust the mesh to such an extent that the adhesive passes during screen printing. Usually, a screen made of polyester, silk, cotton, nylon, rayon, stainless steel or the like and having a mesh size of about 50 to 300 mesh is generally used. [0007] The screen printing method is a method of adjusting the amount of coating using a temperature change in viscosity. When the application temperature is set to room temperature or higher, the adhesive can be applied through the mesh of the screen, and when cooled to a certain temperature or lower, the flow of the adhesive is suppressed and the phenomenon that the adhesive does not flow out of the screen is used. Thus, the operation of applying the adhesive can be interrupted with high accuracy. Since the screen printing method is a coating method in which the accuracy of the coating amount is better than other coating methods and it is easy to apply in a planar manner, it meets the purpose of the present invention of strictly controlling the thickness accuracy of the adhesive layer in the laminate. It is a coating method. When the adhesive is applied by the screen printing method, the optimum working conditions should be considered. If the application temperature is too low, the viscosity does not increase so much even when the adhesive is cooled, so that the operation of applying the adhesive cannot be successfully interrupted, and the accuracy of the applied amount may deteriorate. If the application temperature is high, the laminated film may be thermally degraded. Although the description has been given from the viewpoint of the application temperature, in other words, it is equivalent to that it is necessary to examine whether the viscosity of the adhesive at the application temperature is within a practical range. That is, in order to apply the adhesive by the screen printing method, the viscosity of the adhesive at the application temperature is important, and if it is too low, precise thickness accuracy cannot be obtained after the adhesive is applied. On the other hand, if the viscosity is too high, transfer from the screen to the adherend becomes difficult. Therefore, in the screen printing method, the adhesive does not flow out of the screen at a very high viscosity at room temperature, and the viscosity at about 50 ° C. is 1000 to 30000.
It is recommended to select an adhesive with mPa · s. [0010] The substrate used in the present invention is not particularly limited in shape and thickness. Therefore, it may be any of a film, a sheet, and a plate. Examples of the substrate include a composite sheet of metal and plastic, such as a plastic film, paper, metal foil, a plastic sheet, a metal sheet, and an aluminum laminated sheet, and a glass plate. The photoreactive liquid adhesive used in the present invention is a generic term for a liquid adhesive in which a trigger for initiating a reaction of a polymerization component or a crosslinking component contained in the adhesive or an energy source for promoting the reaction is light. It is. When the photoreactive liquid adhesive is irradiated with light capable of activating the reaction, the curing reaction of the adhesive proceeds to develop heat resistance and adhesive strength. Photoreactive liquid adhesives are broadly classified into radical-reactive photoreactive adhesives and cation-reactive photoreactive adhesives. In the present invention, light is not limited to mere visible light, but refers to electromagnetic waves including not only ultraviolet rays and infrared rays but also high energy rays such as electron beams and radiation. The radical-reactive photoreactive adhesive is an adhesive that undergoes a curing reaction only during irradiation with light, except for a special adhesive. Therefore, it is suitable for use when laminating a substrate made of a light-transmitting material such as a transparent film. [0014] The cation-reactive photoreactive adhesive is suitable for use when the substrate is an opaque material, since once the light is irradiated, the curing reaction continues even after the light irradiation. When comparing the cation-reactive photoreactive adhesive with the radical-type photoreactive liquid adhesive, the radical-reactive photoreactive adhesive requires that the base material be a material that transmits light. At least after bonding the substrates, it is necessary to irradiate light until a sufficient adhesive strength is exhibited. On the other hand, in the case of a cation-reactive photoreactive adhesive, once light is irradiated, the curing reaction continues after irradiation, so that the substrate may be an opaque material. If light is once irradiated before bonding, the curing reaction of the adhesive proceeds as a dark reaction, and sufficient bonding strength will be developed shortly after bonding the substrates without irradiating light. Less work efficiency. Accordingly, as the photoreactive liquid adhesive, a cation-reactive photoreactive adhesive is more preferable. The cation-reactive photoreactive liquid adhesive is an adhesive comprising a cationically polymerizable substance and a cationic photopolymerization initiator as essential components. The details will be described below, but this is only one example, and the cation-reactive photoreactive liquid adhesive generates a cationic active species when irradiated with light, and the cationic active species contains a polymerization component contained in the adhesive. It is a general term for adhesives that cure with reaction with a crosslinking component. A cationically polymerizable substance is a substance that can react with a cationically active species generated by irradiating an adhesive with light to cause a polymerization reaction. The type of the substance is not particularly limited as long as it is a substance that causes the following.Examples thereof include a cyclic ether compound such as an epoxy group-containing compound, an oxetane compound, and an oxolane compound, a cyclic ester compound, a vinyl ether compound, and a propenyl ether compound. These are suitably used as a polymerization component in an adhesive. The photo-cationic polymerization initiator is a substance which generates a cationic active species when irradiated with light,
The generated cationic active species acts as a polymerization initiator for the cationically polymerizable substance to promote the polymerization reaction. For example, there are onium salts such as aromatic diazonium salts, aromatic halonium salts and aromatic sulfonium salts, organic metal complexes such as iron-allene complexes, titanocene complexes and arylsilanol-aluminum complexes, and pyridinium. The above-mentioned aromatic iodonium salt, aromatic sulfonium salt and metallocene salt effective as a photocationic polymerization initiator are described, for example, in US Pat. No. 4,256,828, US Pat.
No. 306346 and the like. By incorporating these cationic photopolymerization initiators, the adhesive can be rapidly cured by irradiating light having a wavelength of 200 to 400 nm.
Since the reaction is activated by light of a relatively short wavelength, it is not necessary to apply the adhesive under a strict light-shielding environment because the adhesive does not cure immediately even under visible light for a short time. Absent. In addition, ordinary opaque substrates block wavelengths in this region, so that if they are light-shielded, they exhibit relatively excellent storage stability even when stored for a long period of time. Among the above-mentioned cationic photopolymerization initiators, aromatic iodonium salts and aromatic sulfonium salts do not produce cations when exposed to light other than in the ultraviolet region, but are known in the art such as aromatic amines and polycyclic aromatic hydrocarbons. By using a sensitizer in combination, cations can be generated even with light in the near ultraviolet region or visible region. When a metallocene salt is used, an oxalate ester of tertiary alcohol may be used as a reaction accelerator. Commercially available photocationic polymerization initiators are broadly classified into ionic photoacid generating types and nonionic photoacid generating types. Examples of ionic photoacid generating type photocationic polymerization initiators include, for example, trade names " Adeka Optomer SP150 "," Adeka Optomer SP170 "
(Above, manufactured by Asahi Denka Kogyo Co., Ltd.), trade name "UVE-101
4 (manufactured by General Electronics), trade name "CD
-1012 "(manufactured by Sartomer) and the like. Examples of the nonionic photoacid generating type cationic photopolymerization initiator include nitrobenzyl ester, sulfonic acid derivative, phosphoric acid ester, phenolsulfonic acid ester, diazonaphthoquinone, N-hydroxyimidosulfonate and the like. No. As the light irradiation device used in the present invention, any device having a wavelength of 200 to 800 nm can be used, but an ultraviolet irradiation device that is easy to handle and can obtain relatively high energy is more preferably used. . The irradiation device is not particularly limited, but includes, for example, a carbon arc, a mercury vapor arc, a fluorescent lamp, an argon glow lamp, a halogen lamp, an incandescent lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a flash UV lamp, and a deep UV. lamp,
Irradiation can be performed using an appropriate light source such as a xenon lamp or a tungsten filament lamp. In addition, you may use sunlight. Although the amount of light irradiation varies depending on the type and amount of each component constituting the photoreactive liquid adhesive, the coating thickness, the light irradiation source, and the like, it cannot be uniquely determined. Alternatively, the irradiation amount at a wavelength effective for crosslinking is 0.01 to 100 J
/ Cm ² is desirable. Heretofore, light irradiation devices have been mainly intended for application to photocurable inks, and there has been no device for producing a laminate using a photoreactive liquid adhesive.
Therefore, in a generally used light irradiation device, heat generated from a light source sometimes heats the photoreactive liquid adhesive. Although it depends on the light amount of the light source and the light irradiation time, the production method of the present invention generally has a temperature of 60 ° C. during the light irradiation time.
° C or higher. In such a conventional light irradiation device, the pot life of the photoreactive liquid adhesive is extremely reduced, and in some cases, it becomes impossible to adhere after irradiation. Therefore,
In the production method of the present invention, it is preferable to modify the light irradiation device to cool the space between the light source and the photoreactive liquid adhesive. As a method of cooling the space between the light source and the photoreactive liquid adhesive, a method of circulating water, air, a refrigerant or the like while blocking them between them is suitable. In particular, water and air are preferable as the medium to be circulated because of easy maintenance. The water cooling method includes, for example, a method of cooling by flowing circulating water around an irradiation lamp. The method is commercially available from Eye Graphics, Oak Manufacturing, and others. The air-cooled type is commercially available from USHIO Inc. or the like. By modifying the light irradiation device as described above, it is possible to irradiate light sufficiently while keeping the applied adhesive at a low temperature, and the photoreactive liquid bonding that the pot life could not be used with the conventional light irradiation device was short Agents can also be used. Further, it has become possible to use a cation-reactive photoreactive liquid adhesive in which a polymerization reaction sufficiently proceeds even after irradiation with light. Further, even in the case of the radical-reactive photoreactive liquid adhesive, the adhesive is not exposed to a high temperature, so that the phenomenon in which the polymerization component is reduced in molecular weight during the progress of the curing reaction is suppressed, so that the adhesive is prevented from deteriorating at a high temperature. In the present invention, light is applied to bond a substrate having a photoreactive liquid adhesive applied only to its peripheral portion to another substrate. The light may be applied either before bonding the substrates or after bonding the substrates. Therefore, the light irradiation device may be installed before the step used for bonding or after the step.
Here, irradiating light after bonding the base material includes the case where light is irradiated at the same time as bonding the base material. Therefore, a light irradiation device may be incorporated in the bonding device. The step of adhering and adhering the substrates can be carried out using a device such as a roll laminator or a press. Further, if necessary, heating may be performed at the time of close contact.
Since the photoreactive liquid adhesive is liquid, it can be adhered at room temperature. According to the production method of the present invention, since the photoreactive liquid adhesive is applied to a precise thickness by a screen printing method, the adhesive layer of the laminate has extremely excellent thickness accuracy. are doing. Further, the production method of the present invention does not generate a large amount of waste. Excellent workability.

Claims (1)

Claims 1. A photoreactive liquid adhesive is applied to at least one peripheral portion of a base material by a screen printing method, and then irradiated with light to be bonded to the other base material. A method for producing a laminate in which a peripheral portion is adhesively sealed.