JP2007000794A - Method for curing ultraviolet curing adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for curing an ultraviolet curing adhesive, in which the ultraviolet curing adhesive is prevented from coloring even if not heat-treated just after being cured by solving such a problem that the conventional ultraviolet curing adhesive colors with time when not heat-treated just after being cured. <P>SOLUTION: The method for curing the ultraviolet curing adhesive comprises the steps of: applying the ultraviolet curing adhesive to the surface of a substrate; and irradiating the applied adhesive with the light passing through a means for adjusting the total transmissivity of light beams of 300 nm to 380 nm to ≤20%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for curing an ultraviolet curable adhesive.

The ultraviolet curing technology is widely used in the electronics field, and the applications of the ultraviolet curable adhesive are various, such as photoresist, ink, adhesive, insulating material, and lens material. The performance required for the ultraviolet curable adhesive varies somewhat depending on the application, but when used in an optical element, transparency is not to mention, but weather resistance is also required. That is, it is required not to be colored over time while maintaining the adhesive force even under the temperature and humidity conditions to be used.
As a method for preventing the coloring of the ultraviolet curable adhesive, heat treatment is generally performed immediately after curing (see, for example, Non-Patent Documents 1 and 2). That is, by heating immediately after curing, coloring is suppressed by removing low molecular weight components that cause coloring remaining in the adhesive. However, when the substrate to which the ultraviolet curable adhesive is applied is a film or a sheet-like substance, heat treatment is not preferable because it may be deformed by heat. Therefore, there is a need for a method of curing an ultraviolet curable adhesive that does not color over time even if the ultraviolet curable adhesive immediately after curing is not heat-treated.
“Practical guide to photocuring technology”, Technonet, 2002 "Ultraviolet curing system", General Technology Center, 1989

  An object of the present invention is to provide a curing method in which coloring with time of an ultraviolet curable adhesive can be suppressed without performing heat treatment immediately after curing.

  As a result of intensive studies on the above problems, the present inventors have found that coloring can be suppressed by irradiating light through a specific means and curing the ultraviolet curable adhesive, and the present invention has been completed.

  That is, according to the first aspect of the present invention, an ultraviolet curable adhesive is applied to the substrate surface, and light irradiation is performed through a means that the total light transmittance at a wavelength of 300 nm to 380 nm is 20% or less. The present invention relates to a method for curing an ultraviolet curable adhesive characterized by curing.

  In the second aspect of the present invention, an ultraviolet curable adhesive is applied to the back surface of the substrate obtained by the first method of the present invention and coated on one side with an ultraviolet curable adhesive, and the entire surface at a wavelength of 300 nm to 380 nm is applied. The present invention relates to a method for curing an ultraviolet curable adhesive, characterized in that the ultraviolet curable adhesive is cured through a means that provides a light transmittance of 20% or less to obtain a substrate coated on both sides with the ultraviolet curable adhesive. .

According to a third aspect of the present invention, the ultraviolet curable adhesive is 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl-phenyl-ketone, benzophenone, 2-methyl-1- [4. -(Methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, bis (2,4,6-trimethylbenzoyl)- Phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (η ⁵ -2,4-cyclo Pentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) fe Nyl) titanium, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethyl-4-dimethylaminobenzoate, 2-ethylhexylaminobenzoate and 2,4-diethyl The present invention relates to the curing method according to the first aspect of the present invention or the second aspect of the present invention, comprising one or more photopolymerization initiators selected from thioxanthone.

4th of this invention is related with the hardening method in any one of the 1st thru | or 3rd of this invention characterized by not performing heat processing at the temperature of 40 degreeC or more immediately after hardening.
5th of this invention is related with the hardening method in any one of 1st thru | or 4th of this invention characterized by the thickness of the ultraviolet curable adhesive after hardening being 1-30 micrometers.

The present invention is described in detail below.
The curing method of the ultraviolet curable adhesive of the present invention is such that an ultraviolet curable adhesive is applied to the substrate surface, and the ultraviolet ray is irradiated with light through a means having a total light transmittance of 20% or less at a wavelength of 300 nm to 380 nm. A curable adhesive is cured.

  The substrate to which the ultraviolet curable adhesive to which the curing method of the present invention is applied is not particularly limited, but a material that is easily deformed when heated is preferable because the effect of the present invention is exhibited. For example, a film or sheet-like substance made mainly of a thermoplastic polymer such as polyethylene, polystyrene, or polyethylene terephthalate is particularly preferable.

The ultraviolet curable adhesive is roughly classified into a radical polymerization system such as an acrylic type and a cationic polymerization system such as an epoxy type according to the mechanism of the curing reaction. The ultraviolet curable adhesive used in the present invention is divided into a raw material, Acrylic materials are preferred because of the abundance and availability of various acrylic monomers and oligomers. In addition, the photopolymerization initiator is more of a radical polymerization system than a cationic polymerization system, and an acrylic adhesive is preferable from this aspect.
Examples of the raw material constituting the acrylic UV curable adhesive are commercially available from Toagosei Co., Ltd., Osaka Organic Chemical Co., Ltd., Nippon Kayaku Co., Ltd., Shin Nakamura Chemical Co., Ltd., etc. Examples include various acrylates and methacrylates, and oligomers such as epoxy acrylate, polyester acrylate, and urethane acrylate.

  It is preferable to add a photopolymerization initiator to the ultraviolet curable adhesive used in the present invention. The photopolymerization initiator that can be used in the present invention must be capable of exhibiting a function by light irradiation in a wavelength region longer than 380 nm. Therefore, in the present invention, the photopolymerization initiator preferably has a higher extinction coefficient (ε) at 405 nm, and specifically, preferably has a ε = 10 ml / g · cm or more in methanol, and 100 ml / g. -More than cm is more preferable. Further, it is also preferable to use a combination of a plurality of photopolymerization initiators or to use a photosensitizer in combination with the photopolymerization initiator.

Examples of the photopolymerization initiator that can be used in the present invention include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl-phenyl-ketone, benzophenone, 2-methyl-1- [ 4- (Methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, bis (2,4,6-trimethylbenzoyl) -Phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (η ⁵ -2,4- Cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1- Yl) phenyl) titanium, 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethyl-4-dimethylaminobenzoate, 2-ethylhexylaminobenzoate, 2,4 -Diethyl thioxanthone etc. are mentioned. You may use these in combination of 2 or more types.

Of these, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl -Diphenyl-phosphine oxide, bis (η ⁵ -2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium, etc. Particularly preferred is the high extinction coefficient (ε) at 405 nm.

  In addition, even a photopolymerization initiator that has almost no absorption region at a wavelength of 380 nm or more alone can be used as a photopolymerization initiator by light irradiation in a long wavelength region in combination with another photopolymerization initiator. For example, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one alone does not absorb 405 nm light at all, but when used in combination with 2,4-diethylthioxanthone, The sensitizing action of 2,4-diethylthioxanthone increases the extinction coefficient (ε) at 405 nm, and can function as a photopolymerization initiator in the present invention.

  The addition amount of the photopolymerization initiator to the ultraviolet curable adhesive is preferably 10 mass ppm to 10 mass%, more preferably 50 mass ppm to 5 mass%, and most preferably 100 mass based on the total amount of the adhesive composition. It is the range of ppm-3 mass%. When the amount is less than 10 ppm by mass, the polymerization does not proceed sufficiently, and the adhesive force with the film or sheet-like substance may not be sufficient. On the other hand, when the content is more than 10% by mass, the remaining photopolymerization initiator decomposition residue increases, and coloring may become intense.

Moreover, you may add various thickeners to the ultraviolet curable adhesive used in this invention in order to improve adhesiveness or adhesiveness. In addition, various stabilizers, leveling agents, surfactants, and the like may be added to improve storage stability and uniform coatability. Further, if necessary, a dye or pigment, a filler such as silica or aluminum hydroxide, or a solvent may be added to control fluidity.
The thickener is not particularly limited as long as it can be dissolved in the ultraviolet curable adhesive of the present invention, and various commonly used thickeners such as rosin resins, polyterpene resins, rubbers. System, petroleum hydrocarbon resin, (crosslinked type) acrylic resin, and the like.

In the present invention, after the ultraviolet curable adhesive is applied to the substrate surface, the ultraviolet curable adhesive is cured by irradiating with light through means having a total light transmittance of 20% or less at a wavelength of 300 nm to 380 nm. is there.
There is no particular limitation on the means for setting the total light transmittance at a wavelength of 300 nm to 380 nm to 20% or less, and various means can be used as long as the object can be achieved. For example, the filter which makes 20% or less the total light transmittance in the wavelength of 300 nm-380 nm is mentioned. Specifically, there is a filter made of a transparent glass plate with ultraviolet (UV) cut coating, a transparent film containing a commercially available ultraviolet absorber mainly made of polyethylene terephthalate (PET), triacetyl cellulose (TAC), or the like. Can be mentioned.
In the present invention, the total light transmittance at a wavelength of 300 nm to 380 nm is more preferably 15% or less, further preferably 10% or less, and most preferably 5% or less. If the total light transmittance at a wavelength of 300 nm to 380 nm is higher than 20%, it is not preferable because various decomposition products are generated due to an increase in the amount of irradiation with short wavelength light and cause coloring.
In addition, the total light transmittance in the wavelength of 300 nm-380 nm in this invention means the light transmittance in the whole wavelength range of 300 nm-380 nm measured based on the method as described in JISK7361-1.

  Naturally, a filter having a total light transmittance of 20% or less at a wavelength of 300 nm to 380 nm needs to transmit light in the vicinity of 405 nm. That is, a major feature of the present invention is that the ultraviolet curable adhesive is cured by light having a wavelength of about 405 nm included in the irradiation light.

  In the present invention, the light source used for light irradiation is preferably one that emits light having a wavelength longer than 380 nm, and examples thereof include a high-pressure mercury lamp, a metal halide lamp, and a xenon lamp. In particular, a high-pressure mercury lamp is generally used for photochemical reactions and is preferable because it has a line spectrum in a wide range.

  In the present invention, it is desirable not to perform the heat treatment at a temperature of 40 ° C. or higher immediately after the ultraviolet curable adhesive is cured. In normal cases, if the heat treatment is not performed immediately after curing, the coloring has already become intense, or the coloring is often severe over time even if the coloring is not noticeable immediately after curing, thus preventing coloring. In order to achieve this, heat treatment is performed on the ultraviolet curable adhesive immediately after curing. On the other hand, when light is irradiated through a filter having a total light transmittance of 20% or less at a wavelength of 300 nm to 380 nm of the present invention to cure the ultraviolet curable adhesive, the irradiated light is limited to a long wavelength region. Therefore, generation of undesirable components that cause coloring is suppressed, and coloration with time of the ultraviolet curable adhesive is suppressed.

  Although the thickness of the ultraviolet curable adhesive after hardening is not specifically limited, 1-30 micrometers is desirable, Preferably it is 1-10 micrometers, More preferably, it is 1-5 micrometers. If the cured UV curable adhesive is thinner than 1 μm, the adhesive strength with the substrate may not be sufficient. Moreover, when it is thicker than 30 μm, it is difficult to apply the UV curable adhesive on the substrate with a uniform thickness, which is not preferable.

  According to the method for curing an ultraviolet curable adhesive of the present invention, the coloration with time of the ultraviolet curable adhesive can be suppressed without performing a heat treatment immediately after curing, and thus the process is simplified.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
(1) Curing method of ultraviolet curable adhesive A high pressure mercury lamp UVL-3204RS-N (manufactured by Ushio Inc.) was used for irradiation at a distance of 40 cm from the light source.
(2) Measurement of color value The color value was measured using a spectrocolorimeter CM-3500d (manufactured by Konica Minolta).
(3) Measurement of total light transmittance It measured using the ultraviolet visible spectrophotometer JASCO V-500 (made by JASCO Corporation).

[Reference Example 1]
In a three-neck flask, 30 g of M-1100 (manufactured by Toagosei), 5 g of M-313 (manufactured by Toagosei), 20 g of M-5710 (manufactured by Toagosei), 40 g of N-vinylpyrrolidone, 4 g 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 1 g 2,4-diethylthioxanthone, 5 g thickener (adjusted by the method of Reference Example 3) Each was added and stirred at 65 ° C. for 1 hour under light shielding to obtain an ultraviolet curable adhesive 1.

[Reference Example 2]
In a three-necked flask, 30 g of M-1100 (manufactured by Toagosei), 5 g of M-313 (manufactured by Toagosei), 20 g of M-5710 (manufactured by Toagosei), 40 g of N-vinylpyrrolidone, Darocur 5 g of TPO (Ciba Specialty Chemicals Photopolymerization Initiator) and 5 g of thickener (adjusted by the method of Reference Example 3) were added and stirred for 1 hour at 65 ° C. under light shielding. Got.

[Reference Example 3]
100 parts by weight of acrylic resin-based pressure-sensitive adhesive having a weight average molecular weight of 500,000 (resin component: n-butyl acrylate / methyl acrylate / 2-hydroxyethyl acrylate = 80% by weight / 18% by weight / 2% by weight copolymer) A thickener was obtained by blending 3 parts by weight of a trimethylolpropane (1 mol) adduct (crosslinking agent) of tolylene diisocyanate (3 mol).

[Reference Example 4]
100 g of UV curable adhesive Aronix UV-3610 (manufactured by Toagosei Co., Ltd.), 4 g of 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one and 2,4-diethyl 1 g of thioxanthone was added, and the mixture was stirred at 40 ° C. for 20 minutes under light shielding to obtain an ultraviolet curable adhesive 3.

[Comparative Example 1]
The ultraviolet curable adhesive 1 prepared in Reference Example 1 was applied on a polyethylene naphthalate film Teonex Q-51 (manufactured by Teijin DuPont) to a thickness of 5 μm, and a polytetrafluoroethylene film HSL-75 ( Teijin DuPont's film thickness: 75 μm) was laminated, and ultraviolet light was irradiated through the HSL-75 film for 22 seconds to cure the ultraviolet curable adhesive. After curing, the HSL-75 film was peeled off to obtain film 1.
The transmission spectrum of the HSL-75 film measured with an ultraviolet-visible spectrophotometer JASCO V-500 (manufactured by JASCO Corporation) is shown in FIG.

[Comparative Example 2]
The UV curable adhesive 1 prepared in Reference Example 1 was applied to the back surface of the film 1 obtained in Comparative Example 1, that is, the surface on which the adhesive was not applied, to a thickness of 5 μm, and an HSL-75 film was used. The laminate was laminated and irradiated with ultraviolet light through an HSL-75 film for 22 seconds to cure the ultraviolet curable adhesive. After curing, the HSL-75 film was peeled off to obtain film 2.

[Comparative Example 3]
The UV curable adhesive 2 prepared in Reference Example 2 was applied to a polyethylene naphthalate film Theonex Q-51 so as to have a thickness of 5 μm, laminated with an HSL-75 film, and passed through the HSL-75 film. The UV curable adhesive was cured by irradiating UV light for 2 seconds. After curing, the HSL-75 film was peeled off to obtain film 3.

[Comparative Example 4]
The UV curable adhesive 2 prepared in Reference Example 2 was applied to the back surface of the film 3 obtained in Comparative Example 3, that is, the surface on which the adhesive was not applied, so as to have a thickness of 5 μm, and an HSL-75 film was used. The laminate was laminated and irradiated with ultraviolet light through an HSL-75 film for 22 seconds to cure the ultraviolet curable adhesive. After curing, the HSL-75 film was peeled off to obtain film 4.

[Comparative Example 5]
The UV curable adhesive 3 prepared in Reference Example 4 was applied to a polyethylene naphthalate film Theonex Q-51 so as to have a thickness of 5 μm, laminated with an HSL-75 film, and passed through the HSL-75 film. The UV curable adhesive was cured by irradiating UV light for 2 seconds. After curing, the HSL-75 film was peeled off to obtain film 5.

[Comparative Example 6]
The UV curable adhesive 3 prepared in Reference Example 4 was applied to the back surface of the film 5 obtained in Comparative Example 5, that is, the surface on which the adhesive was not applied, so as to have a thickness of 5 μm, and an HSL-75 film was used. The laminate was laminated and irradiated with ultraviolet light through an HSL-75 film for 22 seconds to cure the ultraviolet curable adhesive. After curing, the HSL-75 film was peeled off to obtain a film 6.

[Example 1]
The ultraviolet curable adhesive 1 prepared in Reference Example 1 was applied on a polyethylene naphthalate film Theonex Q-51 so as to have a thickness of 5 μm, and a polytetrafluoroethylene film HB-25 (manufactured by Teijin DuPont: film) The UV curable adhesive was cured by irradiating with UV light for 22 seconds through the HB-25 film. After curing, the HB-25 film was peeled off to obtain film 7.
FIG. 2 shows the transmission spectrum of the HB-25 film measured with an ultraviolet-visible spectrophotometer JASCO V-500 (manufactured by JASCO Corporation).

[Example 2]
The UV curable adhesive 1 prepared in Reference Example 1 was applied to the back surface of the film 7 obtained in Example 1, that is, the surface on which the adhesive was not applied, to a thickness of 5 μm, and the HB-25 film The UV curable adhesive was cured by irradiating with UV light for 22 seconds through the HB-25 film. After curing, the HB-25 film was peeled off to obtain film 8.

[Example 3]
The UV curable adhesive 2 prepared in Reference Example 2 was applied on the polyethylene naphthalate film Teonex Q-51 so as to have a thickness of 5 μm, laminated with the HB-25 film, and passed through the HB-25 film. The UV curable adhesive was cured by irradiating UV light for 2 seconds. After curing, the HB-25 film was peeled off to obtain a film 9.

[Example 4]
The UV curable adhesive 1 prepared in Reference Example 1 was applied to the back surface of the film 9 obtained in Example 3, that is, the surface on which no adhesive was applied, to a thickness of 5 μm, and the HB-25 film The UV curable adhesive was cured by irradiating with UV light for 22 seconds through the HB-25 film. After curing, the HB-25 film was peeled off to obtain a film 10.

[Example 5]
The ultraviolet curable adhesive 3 prepared in Reference Example 4 was applied to a polyethylene naphthalate film Theonex Q-51 so as to have a thickness of 5 μm, laminated with an HB-25 film, and passed through the HB-25 film. The UV curable adhesive was cured by irradiating UV light for 2 seconds. After curing, the HB-25 film was peeled off to obtain a film 11.

[Example 6]
The UV curable adhesive 3 prepared in Reference Example 4 was applied to the back surface of the film 11 obtained in Example 5, that is, the surface on which no adhesive was applied, to a thickness of 5 μm, and the HB-25 film The UV curable adhesive was cured by irradiating with UV light for 22 seconds through the HB-25 film. After curing, the HB-25 film was peeled off to obtain a film 12.

[Example 7]
About the films 1-12 obtained in Comparative Examples 1-6 and Examples 1-6, after leaving still for 24 hours in a room at 23 ° C. and a relative humidity of 60%, CM-3500d (manufactured by Konica Minolta) was used. Each b value was measured with a Hunter Lab color system, and then the b value after being put in an oven at 90 ° C. for 250 hours was measured again. The results are shown in Table 1.

The transmission spectrum of the HSL-75 film measured by the comparative example 1 is shown. The transmission spectrum of the HB-25 film measured in Example 1 is shown.

Claims (5)

  An ultraviolet ray curable adhesive is applied to a substrate surface, and the ultraviolet ray curable adhesive is cured by irradiating with light through means having a total light transmittance of 20% or less at a wavelength of 300 nm to 380 nm. Curing method for curable adhesive.   An ultraviolet curable adhesive is applied to the back surface of the substrate coated with an ultraviolet curable adhesive on one side obtained by the method of claim 1, and the total light transmittance at a wavelength of 300 nm to 380 nm is 20% or less. A method for curing an ultraviolet curable adhesive, characterized in that the substrate is coated with an ultraviolet curable adhesive on both sides by irradiating light through means to cure the ultraviolet curable adhesive. UV curable adhesives are 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl-phenyl-ketone, benzophenone, 2-methyl-1- [4- (methylthio) phenyl]- 2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2 , 6-Dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (η ⁵ -2,4-cyclopentadien-1-yl)- Bis (2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethyl-4-dimethylaminobenzoate, 2-ethylhexylaminobenzoate and 2,4-diethylthioxanthone The curing method according to claim 1, wherein the curing method includes one or more photopolymerization initiators.   The curing method according to any one of claims 1 to 3, wherein heat treatment is not performed immediately after curing at a temperature of 40 ° C or higher. The curing method according to any one of claims 1 to 4, wherein the thickness of the cured ultraviolet curable adhesive is 1 to 30 µm.

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