JP2016186007A - Ultraviolet-curable adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet-curable adhesive composition which achieves both a high moist heat resistance and a high step followability of an adhesive used for an optical member having a multilayer structure.SOLUTION: There is provided an ultraviolet-curable adhesive composition, which comprises: a polyurethane (meth)acrylate (A) obtained by reacting a polyether polyol, a diisocyanate and a (meth)acrylate having an isocyanato group; a monofunctional (meth)acrylate (B) having an alkyl group having 8 to 16 carbon atoms; a monofunctional (meth)acrylate (C) having a primary hydroxyl group; one or a combination (D) of 4-t-butyl cyclohexyl acrylate, isobornyl acrylate and dicyclopentanyl acrylate; a liquid rosin derivative and/or a liquid acrylic polymer (E) having a glass transition temperature of -80 to 0°C; and a photopolymerization initiator (F), and has a solvent content of less than 1 wt.%, a viscosity at 25°C of 100 to 10000 mPa s and a Gardner color scale of 1 or less.SELECTED DRAWING: None

Description

The present invention relates to an ultraviolet curable pressure-sensitive adhesive composition. More specifically, the present invention relates to an ultraviolet curable pressure-sensitive adhesive composition suitable for bonding optical members and parts in various optical devices and the like.

In recent years, a touch panel using a liquid crystal display device is often used in digital information devices such as a mobile phone, a portable game machine, and a car navigation system. The touch panel is an electronic component that combines a display device and a position input device, and displays the image information received from the outside on the liquid crystal display, and senses the touched screen position information and outputs it as an information signal to the outside. Have. There are mainly control methods such as resistive film type, electrostatic capacity method, electromagnetic induction method, optical method, and acoustic method for touch panel position input devices. It has become a method.

The above resistive film type and capacitive type touch panel is a front protective film, glass and a film provided with a transparent conductive layer such as indium oxide (hereinafter referred to as ITO) film, glass, liquid crystal display device, and other functionalities. Consists of sheets. Among these, a film, glass, and a functional sheet are usually bonded together with an optical pressure-sensitive adhesive. Since it is used for bonding with each member constituting the display device, performance such as transparency, weather resistance and metal corrosion prevention is required.

On the other hand, in some display devices such as a touch panel, decorative printing may be applied to the frame portion in order to improve design, and a step is generated between the printing portion and the non-printing portion. The pressure-sensitive adhesive sheet is required to have a performance (step difference followability) for filling a printing step in the frame portion. If the pressure-sensitive adhesive sheet has insufficient step following capability, bubbles or voids are generated around the edge of the printed layer, which may reduce the visibility of the display device.

On the other hand, there exists an example which level | step difference followability improves by setting it as the adhesion composition which added the hydrogenation type | mold terpene phenol resin whose softening point is 70 to 150 degreeC to an acrylic base polymer. (See Patent Document 1). However, since the pressure-sensitive adhesive composition contains a solvent, a process for removing the solvent is required during film formation.

In addition, there is an example in which the step following ability is improved by improving the resin composition and the monomer composition in the solventless ultraviolet curable pressure-sensitive adhesive (see Patent Documents 2 and 3). However, the obtained adhesive layer is not sufficient because it can only follow a step of 30% with respect to the thickness of the adhesive layer. In particular, in recent years, demands for thinning and weight reduction of optical members have increased, and accordingly, followability to high steps when using a thin adhesive layer is required.
JP 2014-198798 A JP 2014-5368 A JP 2014-196422 A

The problem to be solved by the present invention is to provide an ultraviolet curable pressure-sensitive adhesive composition that achieves both high heat-and-moisture resistance and followability to a high level difference used in an optical member having a multilayer structure.

As a result of intensive studies on the composition and blending of the adhesive to solve the above problems, the present inventors have found that the problem can be solved by an ultraviolet curable adhesive composition satisfying specific conditions, and to complete the present invention. It came.

That is, the present invention provides a polyurethane (meth) acrylate (A) obtained by reacting polyether polyol (а-1), diisocyanate (а-2) and (meth) acrylate (а-3) having an isocyanato group, Monofunctional (meth) acrylate (B) having an alkyl group having a glass transition temperature of −70 to 40 ° C. in the case of a homopolymer having an alkyl group of 8 to 16 and a primary hydroxyl group, (C), 4 One or a combination (D) in t-butylcyclohexyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, a liquid rosin derivative and / or a liquid acrylic polymer having a glass transition temperature of −80 to 0 ° C. (E) and a photopolymerization initiator (F), the solvent content is less than 1% by weight, and the viscosity at 25 ° C. is 100. 10,000 mPa · s, Gardner color number is an ultraviolet curable adhesive composition is 1 or less (the present invention 1).

Invention 2 is an ultraviolet curable pressure-sensitive adhesive composition according to Invention 1, wherein the component (A) has a weight average molecular weight (polystyrene conversion value by gel permeation chromatography) of 10,000 to 90,000.

Invention 3 is the ultraviolet curable pressure-sensitive adhesive composition according to Invention 1 or 2, wherein the urethane equivalent (mol / g) of the component (A) is 400 to 5000 mol / g.

This invention 4 is an ultraviolet-ray adhesive composition whose average functional group number of (A) component is 1.5-4.0 in any one of this invention 1-3.

This invention 5 is 8-16 which is the glass transition temperature -70-40 degreeC at the time of making polyurethane (meth) acrylate (A) 10-50 weight part and a homopolymer in any one of this invention 1-4. 10 to 78.9 parts by weight of a monofunctional (meth) acrylate (B) having an alkyl group, 5 to 25 parts by weight of a monofunctional (meth) acrylate (C) having a primary hydroxyl group, 4-t-butylcyclohexyl acrylate, Liquid rosin derivative and / or liquid acrylic in which one or a combination amount (D) in isobornyl acrylate and dicyclopentanyl acrylate is 5 to 40 parts by weight and glass transition temperature is −80 to 0 ° C. It is an ultraviolet curable adhesive composition in which the polymer (E) is 1 to 20 parts by weight and the photopolymerization initiator (F) is 0.1 to 5 parts by weight.

The present invention 6 has any one of the present inventions 1 to 5 wherein the alkyl group having a glass transition temperature of −70 to 40 ° C. in the case of a homopolymer has a carbon number of 8 to 16 monofunctional (meth) acrylate (B). And an ultraviolet curable pressure-sensitive adhesive composition containing a linear alkyl group having 8 to 16 carbon atoms and / or a branched alkyl group having 8 to 16 carbon atoms.

INDUSTRIAL APPLICABILITY According to the present invention, it can be widely used as an ultraviolet ray curable pressure sensitive adhesive for optical applications, which is applied to a display panel having a multilayer structure in a digital display device. For example, when it is used for a touch panel, when adhering a decorative plate or icon sheet on the panel, or when adhering a transparent substrate and a transparent plate on which a transparent electrode is formed in a capacitive touch panel, In addition, the adhesive layer can be processed without bubbles (high step followability), and the adhesive layer obtained by UV ray curing is colorless and transparent, and has excellent visible light permeability. Excellent durability without deformation.

The ultraviolet curable pressure-sensitive adhesive composition of the present invention comprises polyether polyol (а-1) (hereinafter also referred to as “(a-1) component”), diisocyanate (а-2) (hereinafter referred to as “(a-2) component”. As well as (meth) acrylate (а-3) having an isocyanato group (hereinafter also referred to as “component (a-3)”), and a polyurethane (meth) acrylate (A) ( Hereinafter, also referred to as “component (A)”), when the homopolymer is used, the glass transition temperature of the alkyl group having a glass transition temperature of −70 to 40 ° C. is 8-16 monofunctional (meth) acrylate (B) (hereinafter referred to as “( B) component "), monofunctional (meth) acrylate (C) having a primary hydroxyl group (hereinafter also referred to as" (C) component "), 4-t-butylcyclohexyl acrylate, isobornyl acrylate, dicyclo One or a combination (D) in the tanyl acrylate (hereinafter also referred to as “component (D)”), a liquid rosin derivative and / or a liquid acrylic polymer (E) having a glass transition temperature of −80 to 0 ° C. "(E) component") and a photopolymerization initiator (F) (hereinafter also referred to as "(F) component"), the solvent content is less than 1% by weight, and the viscosity at 25 ° C is 100 to 100%. 10,000 mPa · s and Gardner color number is 1 or less.

When the solvent content exceeds 1% by weight, the resulting composition foams when cured by irradiation with ultraviolet rays, and bubbles are likely to be generated in the adhesive layer, which may impair the value of the application member and the final product.

The solvent content of the ultraviolet curable resin composition of the present invention is less than 1% by weight. If it exceeds 1% by weight, the resulting composition foams when it is cured with ultraviolet rays, and bubbles are likely to be generated in the cured layer, which may impair the value of the applied member and the final product. The solvent content is measured under the following conditions using a gas chromatograph apparatus.
(Analysis equipment)
GC: Agilent 6850 (manufactured by Agilent Technologies)
(GC measurement conditions)
GC column: HP-1 (manufactured by Agilent Technologies)
Column temperature: 50 ° C. (10 min) → 10 ° C./min→300° C. (10 min)
Column flow rate: 2.0 ml / min
Carrier gas: Helium injection method: Split (50: 1)
Detection temperature: 300 ° C

When the viscosity is out of the range of 100 to 10,000 mPa · s, the coating workability at normal temperature and normal pressure tends to decrease. The viscosity is measured at 25 ° C. with an E-type viscometer.

When the color tone exceeds the Gardner color number 1, there is a tendency that the color tone and transparency of the resulting adhesive layer are lowered, and there is a concern about application restrictions in optical applications. The Gardner color number is measured according to JIS K5600.

The component (a-1) is obtained, for example, by addition polymerization of one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, etc., to a compound having two or more hydroxyl groups. One or more of polytetramethylene ether glycol obtained by ring-opening polymerization of tetrahydrofuran, modified polytetramethylene ether glycol obtained by copolymerizing tetrahydrofuran and alkyl-substituted tetrahydrofuran, and the like can be used.

Examples of the compound having two or more hydroxyl groups include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5 -Hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,1,1-undecanediol, 1,12-dodecanediol, 2, -Methyl-1, Propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-propanediol, 3-methyl-1 , 5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, hydroquinone, resorcin, bisphenol A, bisphenol F, and other relatively low molecular weight dihydroxy compounds, 3-cyclopentanediol, 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, 1,4-cyclohexanedimethanol, hydroxypropylcyclohexanol, butylcyclohexanediol, 1,1'-bicyclo Xylylene Denji ol, cyclohexane triol, hydrogenated bis fail A, 1, 3 - cycloaliphatic polyols such as adamantane diol, polyethylene glycol, polypropylene glycol, polyether polyol of polytetramethylene glycol.

Although the molecular weight of the said (a-1) component is not specifically limited, It is preferable that it is 700-4,000 from the point of adhesive force and holding power. When the molecular weight of the component (a-1) is excessively small, the pressure-sensitive adhesive sheet adhesive strength and flexibility obtained are lowered. On the other hand, when the molecular weight of the component (a-1) is excessively large, the holding force of the obtained pressure-sensitive adhesive sheet is deteriorated, and there is a concern of heat dripping after the wet heat resistance test.

Examples of the component (a-2) include dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate, and these can be used alone or in combination. By using the component (a-2), it is possible to provide a pressure-sensitive adhesive layer excellent in adhesive strength and durability.

Examples of the component (a-3) include 2-isocyanatoethyl (meth) acrylate and 1,1- (bisacryloyloxymethyl) ethyl isocyanate, and these can be used alone or in combination.

The component (A) is obtained by reacting the component (a-1) with the component (a-2) to obtain a hydroxyl-terminated polyurethane, and then reacting the hydroxyl-terminated polyurethane with the component (a-3). Can be manufactured. In the production of the component (A), a method in which the components (a-1), (a2) and (a3) are reacted together can be adopted. However, the former is preferred because the weight average molecular weight of the component (A) can be easily controlled. It is preferable to adopt.

The weight average molecular weight (polystyrene conversion value by gel permeation chromatography) of the component (A) is not particularly limited, but is 10,000 to 90,000 from the viewpoint of the adhesive strength and flexibility of the adhesive layer. Preferably, it is 30,000-70,000.

The urethane equivalent (mol / g) of the component (A) is preferably 400 to 5000 mol / g, and more preferably 500 to 2000 mol / g, from the viewpoint of the holding power and flexibility of the adhesive layer. By making the urethane equivalent to be 400 mol / g or more, the flexibility of the adhesive layer can be improved, and by making the urethane equivalent to be 5000 mol / g or less, the holding power of the adhesive layer can be improved (such as misalignment after the moisture and heat resistance test). Does not occur). In particular, when a liquid rosin derivative and / or a liquid acrylic polymer (component (E)) is added, the holding power of the resulting adhesive layer is reduced, and there is a tendency for positional displacement and the like to occur after the wet heat resistance test. It is necessary to design a component (A) having an appropriate urethane equivalent.

The urethane equivalent (mol / g) is a polyurethane (meth) acrylate weight (g) for making the urethane bond (-OCONH-) 1 mol. The smaller the urethane equivalent, the more the density of the urethane bond. Get higher.
The urethane equivalent can be calculated as in the following formula.
Urethane equivalent = reciprocal of molar concentration of urethane bond = 1 / (number of moles of urethane bond / molecular weight of polyurethane (meth) acrylate)
Here, the theoretical molecular weight is used as the molecular weight of the polyurethane (meth) acrylate.

The average functional group number of the component (A) is not particularly limited, but is preferably 1.5 to 3.0, more preferably 1 from the viewpoint of durability and curability of the obtained adhesive layer. .8 to 2.2. The average number of functional groups means the average number of (meth) acryloyl groups present in one molecule of the component (A).

The amount of component (A) used is preferably 10 to 50% by weight and more preferably 25 to 35% by weight in 100 parts by weight of the present composition. By making the proportion of the component (A) 10% by weight or more, the adhesive strength / durability of the present composition / this adhesive layer can be improved, and by making the proportion of the component (A) 50% by weight or less, The handleability of the composition can be improved.

Carbon number of the alkyl group of the said (B) component is 8-16. If it is less than 8, the curability or durability is lowered, and if it exceeds 16, the compatibility is lowered. It can be used alone or in combination of two or more. In particular, a combination of a monofunctional (meth) acrylate having a branched structure and a monofunctional (meth) acrylate having a linear structure is preferable, and a combination of lauryl (meth) acrylate and / or cetyl (meth) acrylate is more preferable. By such a combination, the step following ability can be improved.

Specific examples of the component (B) include 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, and decyl (meth) acrylate. , (Meth) acrylates having a chain structure such as isodecyl (meth) acrylate, lauryl (meth) acrylate, and cetyl (meth) acrylate.

The glass transition temperature of the homopolymer of the said (B) component is -70-40 degreeC. By setting the glass transition temperature of the (B) component homopolymer to −70 ° C. or higher, it is possible to prevent a decrease in the curability of the present adhesive layer, and the glass transition temperature of the (B) component homopolymer to 40 ° C. or lower. By doing so, a compatibility fall can be prevented. The glass transition temperature is measured by dynamic viscoelasticity measurement.

The amount of component (B) used is preferably 10 to 50% by weight, more preferably 20 to 40% by weight, in 100 parts by weight of the present composition. By making the proportion of the component (B) 10% by weight or more, the handleability of the composition can be improved, and by making the proportion of the component (B) 78.9% by weight or less, the composition can be cured. Can be improved.

When the component (C) does not have a primary hydroxyl group, the durability is lowered. Specific examples of the component (C) include hydroxyalkyl (meth) acrylates having a primary hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and cyclohexanedimethanol mono (meth) acrylate. Can be mentioned.

The amount of component (C) used is preferably 5 to 25% by weight and more preferably 10 to 20% by weight in 100 parts by weight of the present composition. By making the proportion of the component (C) 5% by weight or more, the heat and moisture resistance and curability of the present adhesive layer can be improved, and by making the proportion of the component (C) 25% by weight or less, This is to prevent a decrease in compatibility.

Examples of the component (D) include 4-t-butylcyclohexyl acrylate, isobornyl acrylate and acrylate having a cyclic structure of dicyclopentanyl acrylate. Thereby, the sclerosis | hardenability of this composition and the adhesive force of this adhesion layer can be improved.

The amount of component (D) used is preferably 10 to 40% by weight in 100 parts by weight of the present composition. By making the ratio of the component (D) 10% by weight or more, the adhesive strength of the adhesive layer can be improved, and by making the ratio of the component (D) 40% by weight or less, the durability of the adhesive layer can be improved. Can be improved.

The component (E) is a liquid rosin derivative and / or a liquid acrylic polymer having a glass transition temperature (Tg) of −80 to 0 ° C. By setting it as Tg of this range, a softness | flexibility can be provided to the adhesion layer obtained by the ultraviolet curable adhesive composition of this invention, and level | step difference followable | trackability can be improved. The glass transition temperature is measured by dynamic viscoelasticity measurement. Specific examples of the component (E) include liquid rosin derivatives and liquid solvent-free acrylic polymers obtained by high-temperature continuous polymerization. Among these, those having a color tone of 1 or less Gardner colors are preferable. Examples of the color tone having a Gardner color number of 1 or less include liquid hydrogenated rosin derivatives and liquid solvent-free acrylic polymers. Since these resins usually have a Gardner color number of 1 or less and are excellent in transparency, the transparency and durability of the adhesive layer can be improved.

Examples of the liquid rosin derivative include a liquid rosin ester compound and a liquid disproportionated rosin. The liquid rosin ester compound is obtained by reacting a rosin compound with a monohydric alcohol compound having 1 to 10 carbon atoms.

As the rosin compound which is a constituent component of the liquid rosin ester compound, conventionally known various rosins can be used without particular limitation. Examples of rosin compounds include natural rosins such as gum rosin, tall oil rosin and wood rosin, purified rosin obtained by purifying natural rosin, hydrogenated rosin obtained by hydrogenating natural rosin, and disproportionation of natural rosin. Disproportionated rosin and the like obtained. More preferable rosin compounds are disproportionated rosin and hydrogenated rosin. By using these, it becomes easy to obtain a Gardner color tone of 1 or less of the obtained adhesive composition, and the heat resistance and light resistance of the adhesive composition can be further improved.

The purified rosin can be obtained using various known means such as a distillation method, an extraction method, and a recrystallization method. In the distillation method, for example, the natural rosin can be distilled under a temperature of about 200 to 300 ° C. and a reduced pressure of about 0.01 to 3 kPa. In the extraction method, for example, purified rosin can be obtained by using the above natural rosin as an alkaline aqueous solution, extracting an insoluble unsaponified product with various organic solvents, and then neutralizing the aqueous layer. In the recrystallization method, for example, the above-mentioned natural rosin is dissolved in an organic solvent as a good solvent, then the solvent is distilled off to obtain a concentrated solution, and further, an organic solvent as a poor solvent is added to obtain a purified rosin. it can.

The disproportionated rosin can be obtained using various known means. For example, a disproportionated rosin can be obtained by subjecting a raw natural rosin or a purified purified rosin to a heat reaction in the presence of a disproportionation catalyst. As the disproportionation catalyst, palladium-carbon, rhodium-carbon, platinum-carbon and other supported catalysts; nickel, platinum and other metal powders; Can do. The amount of the catalyst used is usually about 0.01 to 5 parts by weight, preferably about 0.01 to 1 part by weight, based on 100 parts by weight of rosin. The reaction temperature is about 100 to 300 ° C, preferably about 150 to 290 ° C.

The hydrogenated rosin can be obtained by hydrogenating a rosin compound using known rosin compound hydrogenation conditions. Specifically, for example, the rosin compound is hydrogenated by heating the rosin compound to about 100 to 300 ° C. in the presence of a hydrogenation catalyst in a hydrogen atmosphere at about 2 to 20 MPa. The reaction pressure is preferably about 5 to 20 MPa. The reaction temperature is preferably about 150 to 300 ° C. As the hydrogenation catalyst, various known catalysts such as a supported catalyst, metal powder, iodine, and iodide can be used. Examples of the supported catalyst include palladium-carbon, rhodium-carbon, ruthenium-carbon, platinum-carbon, and the like. Examples of the metal powder include nickel and platinum. Examples of the iodide include iron iodide. Among these, palladium, rhodium, ruthenium, and platinum-based catalysts are preferable because the hydrogenation rate of the rosin compound is increased and the hydrogenation time is shortened. In addition, the usage-amount of a hydrogenation catalyst is about 0.01-5 weight part normally with respect to 100 weight part of rosin compounds, Preferably it is about 0.01-2 weight part.

In order to obtain the liquid rosin ester compound, it is essential to use a monohydric alcohol having 1 to 10 carbon atoms as the alcohol compound. Among the monohydric alcohol compounds having 1 to 10 carbon atoms, monohydric alcohols having 1 to 8 carbon atoms can be preferably used because they are excellent in tack or adhesion balance. Examples of the alcohol compound include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol and the like. These can be used individually by 1 type or in combination of 2 or more types. More preferred is a monohydric alcohol having 1 to 4 carbon atoms, and most preferred is a monohydric alcohol having 1 carbon atom, that is, methanol.

It does not specifically limit as a manufacturing method of the said liquid rosin ester compound, A conventionally well-known esterification method is employable. The amount of each of the rosin compound and alcohol compound charged is not particularly limited, but usually the OH group of the alcohol compound / COOH group (equivalent ratio) of the rosin compound is 0.8 to 3.0, preferably 0.9. It is determined to be in the range of ~ 2.0. The reaction temperature of the esterification reaction is usually about 150 to 320 ° C, preferably about 150 to 300 ° C. The reaction time is usually about 2 to 24 hours, preferably about 2 to 7 hours. Furthermore, for the purpose of shortening the reaction time, the esterification reaction can proceed in the presence of a catalyst. Examples of the catalyst include acid catalysts such as p-toluenesulfonic acid; metal hydroxides such as calcium hydroxide and magnesium hydroxide; metal oxides such as calcium oxide and magnesium oxide. Since water is produced as a result of the esterification reaction, the reaction can proceed while removing the produced water out of the system. In consideration of the color tone of the obtained liquid rosin ester compound, it is desirable to carry out the reaction under an inert gas stream. The reaction can be performed under pressure if necessary. It is also possible to proceed the reaction in an organic solvent that is non-reactive with rosin compounds and alcohol compounds. Examples of the organic solvent include hexane, cyclohexane, toluene, xylene and the like. In addition, when an organic solvent is used, if it is necessary to distill off the solvent or an unreacted raw material, it can carry out under reduced pressure suitably.

The liquid solvent-free acrylic polymer is produced by, for example, placing a small amount of a polymerization solvent, a thermal polymerization initiator, and an ethylenically unsaturated monomer in a pressurizable continuous reactor, and continuously at 150 to 350 ° C. under high pressure. Polymerization is carried out, the unreacted monomer is passed through a separator and again put into a continuous reactor, and this recycling is repeated several times (2 to 60 minutes) to obtain a copolymer. Examples of commercially available products include solvent-free acrylic polymer “Alfon” manufactured by Toagosei Co., Ltd.

The amount of the component (E) used is preferably 5 to 20% by weight, more preferably 5 to 15% by weight, in 100 parts by weight of the present composition. By making the proportion of the component (E) 5% by weight or more, the step following property of the adhesive layer can be improved, and by making the proportion of the component (E) 20% by weight or less, the holding power of the adhesive layer. Can be improved.

As the component (F), various known compounds can be used without any particular limitation as long as they are photopolymerization initiators that decompose upon irradiation with ultraviolet rays to generate radicals. Examples include photopolymerization initiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and oxime ester compounds, and photosensitizers such as amines and quinones. 2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxy Ethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- [4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl] 2-methyl-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morph Linopropan-1-one, 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6-trimethylbenzoyl -Diphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine 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)], ethanone 1- [9-ethyl-6- (2- Methylbenzoyl) -9H-carbazol-3-yl] -1- (o-acetyloxime), and the like. It may be. Among these, the use of 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide is preferable because the step following ability of the composition can be further improved.

The amount of component (F) used is preferably 0.1 to 5% by weight, more preferably 0.2 to 2% by weight, in 100 parts by weight of the present composition. By making the proportion of component (F) 0.1% by weight or more, it is possible to prevent variation in curing polymerization due to ultraviolet irradiation, and by making the proportion 5% by weight or less, odor caused by the decomposition product of component (F) Generation | occurrence | production can be reduced and coloring of an adhesion layer can be prevented.

The ultraviolet curable pressure-sensitive adhesive composition of the present invention can be produced by mixing the components (A) to (F) at a desired ratio. There are no particular limitations on the mixing method and order of addition of the components.

Moreover, the adhesive composition of this invention can be made to contain various additives as long as the effect of this invention is not impaired as needed. For example, additives such as surface conditioners, surfactants, UV absorbers, antioxidants, inorganic fillers, silane coupling agents, colloidal silica, antifoaming agents, wetting agents, rust inhibitors, stabilizers, etc. be able to.

The pressure-sensitive adhesive composition of the present invention is bonded to a display panel and a decorative plate or an icon sheet, bonded to a transparent substrate on which a transparent electrode is formed on a touch panel and a transparent plate, and bonded to a display body and an optical functional material. It is suitably used for adhesive materials for various optical devices and optical members. Examples of the material of the member include polyethylene terephthalate, polycarbonate, glass, polycarbonate, and acrylic resin. As a display body, display elements, such as a liquid crystal display which stuck the polarizing plate on glass, EL display, EL illumination, electronic paper, and a plasma display, are mentioned. Examples of optical functional materials include acrylic plates (which may be treated with a single-sided or double-sided hard coating or antireflection coating), polycarbonate plates, polyethylene terephthalate plates for the purpose of improving visibility and preventing cracking of display elements from external impacts. And a transparent plastic plate such as a polyethylene naphthalate plate, tempered glass (which may have an anti-scattering film), and a touch panel input sensor.

Examples of the ultraviolet light source used for curing the pressure-sensitive adhesive composition of the present invention include an ultraviolet irradiation device having a xenon lamp, a high-pressure mercury lamp, a metal halide lamp, and an EB device capable of generating thermoelectrons. Moreover, what is necessary is just to adjust conditions, such as a light quantity, a light source, and a conveyance speed suitably, and a light quantity is about 80-160 W / cm normally, and a conveyance speed is about about 5-50 m / min normally.

The thickness of the pressure-sensitive adhesive layer obtained by applying and curing the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is usually about 10 to 1000 μm on average, preferably 25 to 500 μm. By making the thick film within this range, the impact resistance of the optical member / module can be improved.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “%” and “part” mean “% by weight” unless otherwise specified.

<Synthesis of component (A)>
Synthesis example 1
(A-1) Synthesis of component In a reactor equipped with a cooling paddle and a stirrer, 816 parts of polypropylene glycol having a weight average molecular weight of 1000 (ADEKA Corporation, trade name “Adeka Polyether P-1000”), isophorone diisocyanate 172 parts, 2-ethylhexyl acrylate (2-EHA) 176 parts and tin octylate 0.5 parts were added, the temperature was raised to 80 ° C. and kept for 3 hours, and the completion of the reaction was confirmed by NCO measurement. A 2-EHA solution of a hydroxyl-terminated urethane oligomer was obtained. Next, 12 parts of 2-isocyanatoethyl methacrylate was added, kept at 80 ° C. for 2 hours, and the completion of the reaction was confirmed by NCO measurement. Thus, the weight average molecular weight 42,000, urethane equivalent 646 mol / g, average number of functional groups A 2-EHA solution of 2.0 polyurethane methacrylate oligomer (hereinafter referred to as component (A-1)) was obtained. In addition, the said weight average molecular weight is the polystyrene conversion value by a gel permeation chromatography, and this measurement condition is as follows [a measuring apparatus main body (product name "HLC-8220GPC", the Tosoh Corporation make), column. (Product names “TSKGel G1000H”, “TSKGel G2000H”, manufactured by Tosoh Corporation), developing solvent (tetrahydrofuran)]. (The same applies hereinafter)

Synthesis example 2
(A-2) Synthesis of component In a reactor equipped with a cooling paddle and a stirrer, 897 parts of polypropylene glycol having a weight average molecular weight of 2000 (trade name “Adeka Polyether P-2000” manufactured by ADEKA Corporation), isophorone diisocyanate 93 parts, 250 parts of 2-ethylhexyl acrylate (2-EHA) and 0.5 parts of tin octylate were added, heated to 80 ° C. and kept for 3 hours, and then the completion of the reaction was confirmed by NCO measurement. A 2-EHA solution of a hydroxyl-terminated urethane oligomer was obtained. Next, 10 parts of 2-isocyanatoethyl methacrylate was added, the mixture was kept at 80 ° C. for 2 hours, and the completion of the reaction was confirmed by NCO measurement. As a result, the weight average molecular weight 42,000, urethane equivalent 1200 mol / g, average number of functional groups A 2-EHA solution of 2.0 polyurethane methacrylate oligomer (hereinafter referred to as component (A-2)) was obtained.

Synthesis example 3
(A-3) Synthesis of Component In the same reaction apparatus as in Synthesis Example 1, 928 parts of polytetramethylene glycol having a weight average molecular weight of 3000 (made by Hodogaya Chemical Co., Ltd., trade name “PTG-3000SN”), isophorone diisocyanate 60 parts, 176 parts of 2-ethylhexyl acrylate (2-EHA) and 0.5 part of tin octylate were added, the temperature was raised to 80 ° C. and kept for 3 hours, and the completion of the reaction was confirmed by NCO measurement. A 2-EHA solution of a hydroxyl-terminated urethane oligomer was obtained. Subsequently, 12 parts of 2-isocyanatoethyl methacrylate was added, and the mixture was kept at 80 ° C. for 2 hours, and the completion of the reaction was confirmed by NCO measurement. Thus, the weight average molecular weight 38,000, urethane equivalent 1848 mol / g, average number of functional groups A 2-EHA solution of 2.0 polyurethane methacrylate oligomer (hereinafter referred to as component (A-3)) was obtained.

Comparative Synthesis Example 1
Synthesis of Component (A-4) In the same reactor as in Synthesis Example 1, 986 parts of polypropylene glycol having a weight average molecular weight of 18000 (Asahi Glass Co., Ltd., trade name “PREMINOL S 4318F”), 6 parts of isophorone diisocyanate and octylic acid After adding 0.3 part of tin and raising the temperature to 80 ° C. and keeping the temperature for 2 hours, the completion of the reaction was confirmed by NCO measurement to obtain a hydroxyl group-terminated urethane oligomer as an intermediate. Next, 8 parts of 2-isocyanatoethyl methacrylate was added, and the mixture was kept at 80 ° C. for 2 hours. By confirming the completion of the reaction by NCO measurement, the weight average molecular weight 62,000, urethane equivalent 18266 mol / g, average number of functional groups 2.0 polyurethane methacrylate oligomer (hereinafter referred to as component (A-4)) was obtained.

Comparative Synthesis Example 2
Synthesis of Component (A-5) In the same reactor as in Synthesis Example 1, 980 parts of polypropylene glycol having a weight average molecular weight of 12000 (manufactured by NOF Corporation, trade name “PREMINOL S 4013F”), 15 parts of isophorone diisocyanate, 2 -After adding 333 parts of ethylhexyl acrylate (2-EHA) and 0.3 part of tin octylate and raising the temperature to 80 ° C. and keeping the temperature for 2 hours, the completion of the reaction was confirmed by NCO measurement. A 2-EHA solution of urethane oligomer was obtained. Next, 5 parts of 2-isocyanatoethyl methacrylate was added, and the mixture was kept at 80 ° C. for 2 hours. By confirming the completion of the reaction by NCO measurement, the weight average molecular weight was 105,000, the urethane equivalent was 7650 mol / g, and the average number of functional groups. A 2-EHA solution of 2.0 polyurethane methacrylate oligomer (hereinafter referred to as component (A-5)) was obtained.

Comparative Synthesis Example 3
Synthesis of Component (A-6) In the same reactor as in Synthesis Example 1, 637 parts of polypropylene glycol having a weight average molecular weight of 400 (trade name “Uniol D-400” manufactured by NOF Corporation), 330 parts of hexamethylene diisocyanate , 176 parts of 2-ethylhexyl acrylate (2-EHA) and 0.3 part of tin octylate were added, the temperature was raised to 80 ° C. and kept for 3 hours, and the completion of the reaction was confirmed by NCO measurement. A 2-EHA solution of a hydroxyl-terminated urethane oligomer was obtained. Subsequently, 33 parts of 2-isocyanatoethyl methacrylate was added, the mixture was kept at 80 ° C. for 2 hours, and the completion of the reaction was confirmed by NCO measurement, whereby the weight average molecular weight 28000, urethane equivalent 337 mol / g, average functional group number 2. A 2-EHA solution of 0 polyurethane methacrylate oligomer (hereinafter referred to as component (A-6)) was obtained.

<Preparation of pressure-sensitive adhesive composition>
Example 1
(A-1) Component 30 parts, (B) component, 2-ethylhexyl acrylate (Mitsubishi Chemical Co., Ltd., trade name "2-ethylhexyl acrylate, homopolymer glass transition temperature -70 ° C, below (B- (1) Component) 30 parts, (C) component, 2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Co., Ltd., trade name "HEA", hereinafter referred to as (C-1) component) 15 parts, (D) component As an isobornyl acrylate (manufactured by Osaka Organic Chemical Co., Ltd., trade name “IBXA”, hereinafter referred to as component (D-1)) 15 parts, as component (E), liquid solventless acrylic polymer (manufactured by Toa Gosei Co., Ltd.) , Trade name "ARUFON UH-2041, Tg-50 ° C, hereinafter referred to as (E-1) component) 10 parts and (F) component as 1-hydroxycyclohexyl phenyl ketone (BASF) One part of Japan Co., Ltd., trade name “Irgacure 184” (hereinafter referred to as “component (F-1)”) was blended in terms of pure matter to prepare an adhesive composition (see Table 1). Moreover, the Gardner color number, viscosity, solvent content and compatibility of the composition were evaluated, and the results are shown in Table 2 (the same applies hereinafter).

Example 2
The component (A-1) in Example 1 was replaced with 30 parts of the component (A-2), and other formulations were prepared as in Example 1 to prepare a pressure-sensitive adhesive composition.

Example 3
The component (A-1) in Example 1 was replaced with 30 parts of the component (A-3), and other formulations were prepared in the same manner as in Example 1 to prepare an adhesive composition.

Example 4
As component (B), 20 parts of component (B-1) and cetyl acrylate (manufactured by NOF Corporation, trade name “Blenmer CA”, homopolymer glass transition temperature is 35 ° C., hereinafter component (B-2)) 10 parts was used in combination, and the other composition was the same as in Example 1 to prepare a pressure-sensitive adhesive composition.

Example 5
It changed into 20 parts of (D-1) component of Example 1, and 5 parts of (E-1) components, and the other compounding prepared the adhesive composition similarly to Example 1. FIG.

Example 6
The component (E-1) of Example 1 was a liquid hydrogenated rosin resin (Arakawa Chemical Industries, trade name “Pink Listal ME-H”, Tg-20 ° C., hereinafter referred to as “E-2” component). The other composition was prepared in the same manner as in Example 1 to prepare an adhesive composition.

Example 7
As component (F), 0.6 part of component (F-1) and 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by Lambson, trade name “Speedcure TPO”, hereinafter referred to as component (F-2)) An adhesive composition was prepared in the same manner as in Example 5 except that 0.4 part was used in combination.

Comparative Example 1
The component (A-1) in Example 1 was replaced with 30 parts of the component (A-4), and other formulations were prepared in the same manner as in Example 1 to prepare an adhesive composition. (See Table 1). Moreover, the Gardner color number, viscosity, solvent content and compatibility of the composition were evaluated, and the results are shown in Table 2 (the same applies hereinafter).

Comparative Example 2
The component (A-1) in Example 1 was replaced with 30 parts of the component (A-5), and other formulations were prepared in the same manner as in Example 1 to prepare an adhesive composition.

Comparative Example 3
The component (A-1) was replaced with 30 parts of the component (A-6), and the other blends were prepared in the same manner as in Example 1 to prepare an adhesive composition.

Comparative Example 4
(C) The component was not used, but changed to 35 parts of (A-1) component and 40 parts of (B-1) component.

Comparative Example 5
The component (E-1) in Example 1 was replaced with a hydrogenated aromatic petroleum resin (Arakawa Chemical Industries, trade name “Arcon P-100”, Tg 50 ° C., hereinafter referred to as component (E-4)). The other compositions were prepared in the same manner as in Example 1.

Comparative Example 6
The component (E) was not used, and 40 parts of the component (A-1) and other formulations were prepared in the same manner as in Example 1.

Comparative Example 7
The component (E-1) of Example 1 was replaced with a solid hydrogenated rosin ester (Arakawa Chemical Industries, Ltd., trade name “Pink Listal KE-311”, Tg 30 ° C., hereinafter referred to as “E-3” component). The other compositions were prepared in the same manner as in Example 1.
(B-2): Cetyl acrylate (manufactured by NOF Corporation, trade name “Blemmer CA”, homopolymer glass transition temperature: 35 ° C.)
(E-1): Liquid solvent-free acrylic polymer (Tg-50 ° C)
(Product name “ARUFON UH-2041” manufactured by Toa Gosei Co., Ltd.)
(E-2): Liquid hydrogenated rosin derivative (Tg-20 ° C.)
(Arakawa Chemical Industries, Ltd., trade name "Pink Listal ME-H")
(E-3): Solid hydrogenated rosin ester (manufactured by Arakawa Chemical Industries, Ltd., trade name “Pink Listal KE-311”)
(E-4): Hydrogenated aromatic petroleum resin (Arakawa Chemical Industries, Ltd., trade name “Arcon P-100”)
(F-2): 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by Lambson, trade name “Speedcure TPO”)

<Gardner color number>
The Gardner color number was measured according to JIS K5600.

<Viscosity>
The viscosity (mPa · s) was measured with an E-type viscometer {TVE-10 (manufactured by Toki Sangyo Co., Ltd.)} at 25 ° C. for 5 minutes.

<Solvent content>
The solvent content was measured under the following conditions using a gas chromatograph apparatus.
(Analysis equipment)
GC: Agilent 6850 (manufactured by Agilent Technologies)
(GC measurement conditions)
GC column: HP-1 (manufactured by Agilent Technologies)
Column temperature: 50 ° C. (10 min) → 10 ° C./min→300° C. (10 min)
Column flow rate: 2.0 ml / min
Carrier gas: Helium injection method: Split (50: 1)
Detection temperature: 300 ° C

<Compatibility>
The compatibility was judged based on the following criteria by visually observing the obtained adhesive composition.
○: Uniform and completely transparent ×: Confirmation of white turbidity, sediment, insoluble matter or liquid layer separation

<Preparation of adhesive layer>
The compositions according to Examples 1 to 8 and Comparative Examples 1 to 6 are formed on a 100 μm film on a 75 μm thick heavy release polyester film (manufactured by Panac Corporation, trade name “SP-PET-03-75BU”). It was applied to a thickness, in the air, by passing once under high pressure mercury lamp ^{(100mW / cm 2, 100mJ /} cm 2), was pre-cured. The cured product coated surface and a 38 μm-thick lightly-released polyester film (manufactured by Panac Co., Ltd., trade name “SP-PET-01-38BU”) were bonded together so that the release-treated surface was in contact, and in air, a high-pressure mercury lamp (100 mW) / Cm ² , 300 mJ / cm ² ) was passed through 3 times for curing.

[Various tests on adhesive layer]
<Adhesion test>
The lightly release-treated polyester film on one side of the prepared adhesive layers of Examples 1 to 8 and Comparative Examples 1 to 6 was peeled off, and a 50 μm thick polyester film (manufactured by Toyobo Co., Ltd., trade name “Cosmo Shine A-4300”). ") Was pasted with a 2 kg roller and left for 2 hours. The remaining heavy release treated polyester film was peeled off and bonded to glass with a 2 kg roller. 50 μm PET / adhesive layer (100 μm) / glass test piece was prepared. After leaving at 25 ° C. and 50% RH for 24 hours, the adhesive strength was measured by peeling in the 180 ° direction at a speed of 300 mm / min (N / 25 mm).

<Haze value, transmittance>
A 50 μm PET / adhesive layer (100 μm) / glass test piece was prepared from the prepared adhesive layer in the same manner as the adhesive strength test, and the haze value was measured according to JIS K 5400 using a color haze meter manufactured by Murakami Color Research Laboratory. It was measured. The results are shown in Table 3. In addition, each haze value is a numerical value including the haze value of the polyester film which is a base material, and glass.

<Durability test>
In the moisture and heat resistance test, the test piece was left in a constant temperature and humidity chamber having a temperature of 85 ° C. and a humidity of 85% for 500 hours, and then the haze value and transmittance were measured by the same method as described above. The results are shown in Table 3. In addition, each haze value is a numerical value including the haze value of the glass which is a base material.
The durability was evaluated according to the following criteria.
○: No peeling, no adhesion layer misalignment, no bubbles and damage ×: Some peeling, adhesion layer misalignment, bubbles and damage

<Step following test>
The lightly peeled polyester film on one side of the prepared adhesive layer was peeled off and bonded to a 50 μm polyester film having a thickness of 50 μm, prepared on a test plate having a size of 8 cm × 8 cm, and left for 2 hours. After a 5 cm × 5 cm polyester film (film thickness 40 μm / 50 μm) is placed on the glass, the heavy release polyester film on the test plate is peeled off and bonded to cover the 5 cm × 5 cm polyester film, and then autoclaved ( 50 ° C., 0.5 MPa, 20 min). The embedding property around the 40 μm / 50 μm polyester film is visually confirmed.
1: Good embeddability, no bubbles around the polyester film 2: Slightly good embedment, less than 5 small bubbles around the polyester film 3: Embeddability normal, less than 10 small bubbles around the polyester film 4: Embed A test plate with large bubbles with a gap around the polyester film is left for 24 hours at 25 ° C. and 50% RH, and then placed in a constant temperature and humidity chamber at 85 ° C. and 85% humidity for 24 hours. After standing still, the embedding property around 40 μm / 50 μm PET was reconfirmed by visual observation. The results are shown in Table 4.

Claims (6)

Polyurethane (meth) acrylate (A) obtained by reacting polyether polyol (а-1), diisocyanate (а-2) and (meth) acrylate (а-3) having an isocyanate group, and a homopolymer Monofunctional (meth) acrylate (B) having an alkyl group having a glass transition temperature of −70 to 40 ° C. and an alkyl group having 8 to 16 carbon atoms, monofunctional (meth) acrylate (C) having a primary hydroxyl group, 4-t-butylcyclohexyl acrylate , One or more acrylates (D) selected from isobornyl acrylate and dicyclopentanyl acrylate, liquid rosin derivatives and / or liquid acrylic polymers (E) having a glass transition temperature of −80 to 0 ° C. And a photopolymerization initiator (F), the solvent content is less than 1% by weight, and the viscosity at 25 ° C. is 100 to 10, MPa · s, ultraviolet-curable pressure-sensitive adhesive composition, characterized in that the Gardner color number is 1 or less. The ultraviolet curable pressure-sensitive adhesive composition according to claim 1, wherein the component (A) has a weight average molecular weight (polystyrene conversion value by gel permeation chromatography) of 10,000 to 90,000. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1 or 2, wherein the urethane equivalent (mol / g) of the component (A) is 400 to 5000 mol / g. The ultraviolet curable adhesive composition according to claim 1, wherein the component (A) has an average functional group number of 1.5 to 4.0. Monofunctional (meth) acrylate (B) having 10 to 50 parts by weight of polyurethane (meth) acrylate (A) and a glass transition temperature of -70 to 40 ° C. when having a homopolymer and having 8 to 16 carbon atoms and having an alkyl group ) Is 10 to 78.9 parts by weight, monofunctional (meth) acrylate (C) having a primary hydroxyl group is 5 to 25 parts by weight, 4-t-butylcyclohexyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate One or a combination use amount (D) in the catalyst is 5 to 40 parts by weight, the liquid rosin derivative and / or the liquid acrylic polymer (E) is 1 to 20 parts by weight, and the photopolymerization initiator (F) is 0.1 to 0.1 parts by weight. The ultraviolet curable pressure-sensitive adhesive composition according to any one of 1 to 4, which is 5 parts by weight. When the above homopolymer is used, the alkyl group having a glass transition temperature of −70 to 40 ° C. and the monofunctional (meth) acrylate (B) having 8 to 16 carbon atoms is a linear alkyl group having 8 to 16 carbon atoms and 6. The ultraviolet curable pressure-sensitive adhesive composition according to any one of claims 1 to 5, comprising a branched alkyl group having 8 to 16 carbon atoms.