JP7525824B2 - Polymerizable composition, cured product, and method for producing the cured product - Google Patents

Description

The present invention relates to a polymerizable composition, a cured product, and a method for producing the cured product.

Photosensitive compositions that can be rapidly cured by irradiation with light are used in coatings, inks, adhesives, and various photoresists. For example, Patent Document 1 describes a benzophenone group-containing polyvalent peroxyester as a photopolymerization initiator contained in the photosensitive composition.

In general, photosensitive compositions contain additives such as colorants depending on the application, in addition to photopolymerization initiators and radically polymerizable compounds. Additives such as colorants absorb the irradiated light and attenuate it, or block the irradiated light, which can prevent the light from reaching the depths of the applied coating film and cause poor curing. Therefore, in order to improve curing properties, heat curing by high-temperature treatment may be used in combination.

On the other hand, there are plans to switch from the conventional glass substrate to a resin substrate for liquid crystal display elements in order to make them lighter and more flexible. However, resin substrates have inferior heat resistance compared to glass substrates, and there have been problems with this, such as the inability to carry out the high-temperature processing required for manufacturing liquid crystal display elements, as with conventional materials.

In order to solve the above problems, Patent Document 2 describes a polymerizable composition containing a benzophenone group-containing polyperoxyester and a specific epoxy compound, and describes that the benzophenone group-containing polyperoxyester acts as both a photopolymerization initiator and a thermal polymerization initiator, allowing for curing at low temperatures and making the composition suitable for use on resin substrates.

Japanese Unexamined Patent Publication No. 59-197401 JP 2003-113224 A

However, in Patent Document 2, a specific epoxy compound is essential, which limits the composition of the polymerizable composition and requires high-temperature treatment at 150°C or higher. Therefore, a polymerizable composition that can be cured at an even lower temperature is desired.

In addition, Patent Document 2 suggests that a polymerizable composition containing a benzophenone group-containing polyhydric peroxyester can be thermally cured. However, it has been found that thermal curing takes longer than photocuring, and therefore uneven shrinkage occurs during curing, resulting in a loss of smoothness on the coating surface.

The object of the present invention was made in consideration of the above-mentioned circumstances, and is to provide a polymerizable composition that can be sufficiently cured at low temperature in a short time, and that can produce a cured product with excellent surface smoothness.

That is, the present invention relates to a compound represented by the general formula (1):
(in general formula (1), R ¹ and R ² are independently an alkyl group having 4 to 8 carbon atoms or an aralkyl group having 9 to 12 carbon atoms, and R ³ and R ⁴ are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 4 to 8 carbon atoms, or an aralkyloxy group having 9 to 12 carbon atoms), a cobalt-based curing accelerator, and a radically polymerizable compound.

The present invention also relates to a cured product formed from the polymerizable composition.

The present invention also relates to a method for producing a cured product, which includes a step of heating the polymerizable composition.

The polymerizable composition of the present invention contains the benzophenone group-containing polyhydric peroxyester, a cobalt-based curing accelerator, and a radically polymerizable compound. Generally, curing accelerators include, for example, amine compounds, thiourea compounds, and compounds of fourth-period transition metals such as vanadium, cobalt, and copper. In the present invention, the use of a cobalt-based curing accelerator allows sufficient curing at low temperatures and in a short time, and a cured product with excellent surface smoothness can be obtained.

The polymerizable composition of the present invention contains a benzophenone group-containing polyperoxyester represented by the following general formula (1), a cobalt-based curing accelerator, and a radically polymerizable compound.

<Polyfunctional peroxyester containing a benzophenone group>
The benzophenone group-containing polyvalent peroxyester of the present invention can be represented by the following general formula (1): The benzophenone group-containing polyvalent peroxyester may be used alone or in combination of two or more kinds.
(In general formula (1), ^R1 and ^R2 are independently an alkyl group having 4 to 8 carbon atoms or an aralkyl group having 9 to 12 carbon atoms, and ^R3 and ^R4 are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 4 to 8 carbon atoms, or an aralkyloxy group having 9 to 12 carbon atoms.)

In the general formula (1), R ¹ and R ² are independently an alkyl group having 4 to 8 carbon atoms or an aralkyl group having 9 to 12 carbon atoms. Among these, a tertiary alkyl group having 4 to 8 carbon atoms is preferred from the viewpoint of excellent sensitivity.

In the general formula (1), ^R3 and ^R4 are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 4 to 8 carbon atoms, or an aralkyloxy group having 9 to 12 carbon atoms. Among these, a tertiary alkoxy group having 4 to 8 carbon atoms is preferred from the viewpoint of excellent sensitivity.

Examples of the compound represented by the general formula (1) include 3,3',4,4'-tetra-(tert-butylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra-(tert-amylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra-(tert-hexylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra-(tert-octylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra-(cumylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra-(p-isopropylcumylperoxycarbonyl)benzophenone, 3, Examples of the benzophenone include 3'-di-(methoxycarbonyl)-4,4'-di-(tert-butylperoxycarbonyl)benzophenone, 3,4'-di-(methoxycarbonyl)-4,3'-di-(tert-butylperoxycarbonyl)benzophenone, and 4,4'-di-(methoxycarbonyl)-3,3'-di-(tert-butylperoxycarbonyl)benzophenone. Among these, 3,3',4,4'-tetra-(tert-butylperoxycarbonyl)benzophenone and 3,3',4,4'-tetra-(tert-amylperoxycarbonyl)benzophenone are preferred from the viewpoint of excellent sensitivity.

The method for producing the benzophenone group-containing polyhydric peroxyester represented by the general formula (1) is not particularly limited, and for example, the production method described in JP-A-59-197401 can be used as a reference.

<Cobalt-based curing accelerator>
Examples of the cobalt-based hardening accelerator include fatty acid cobalt salts such as cobalt octylate, cobalt naphthenate, and cobalt rhodanate, and cobalt octylate and/or cobalt naphthenate are preferred, and cobalt octylate is more preferred. The cobalt-based hardening accelerators may be used alone or in combination of two or more kinds.

<Radical Polymerizable Compound>
As the radical polymerizable compound, a compound having an ethylenically unsaturated group can be preferably used. Examples of the radical polymerizable compound include (meth)acrylic acid esters, styrenes, maleic acid esters, fumaric acid esters, itaconic acid esters, cinnamic acid esters, crotonic acid esters, vinyl ethers, vinyl esters, vinyl ketones, allyl ethers, allyl esters, N-substituted maleimides, N-vinyl compounds, unsaturated nitriles, and olefins. Among these, it is preferable to include (meth)acrylic acid esters having high reactivity. The radical polymerizable compound may be used alone or in combination of two or more kinds.

The (meth)acrylic acid esters may be monofunctional or polyfunctional compounds. Examples of the monofunctional compounds include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; ester compounds of (meth)acrylic acid and aliphatic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate; and aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate. Monomers having a hydroxy group, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-hydroxy-1-adamantyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; methoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, 2-phenylphenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, and (3-ethyloxetan-3-yl). Monomers having a chain or cyclic ether bond, such as methyl (meth)acrylate and cyclic trimethylolpropane formal (meth)acrylate; monomers having a nitrogen atom, such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, diacetone (meth)acrylamide, (meth)acryloylmorpholine, and N-(meth)acryloyloxyethylhexahydrophthalimide; monomers having an isocyanate group, such as 2-(meth)acryloyloxyethyl isocyanate; glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether monomers having an epoxy group such as ter; monomers having a phosphorus atom such as 2-((meth)acryloyloxy)ethyl phosphate; monomers having a silicon atom such as 3-(meth)acryloxypropyltrimethoxysilane; monomers having a fluorine atom such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, and 2-(perfluorohexyl)ethyl (meth)acrylate; monomers having a carboxyl group such as (meth)acrylic acid, mono(2-(meth)acryloyloxyethyl) succinate, mono(2-(meth)acryloyloxyethyl) phthalate, mono(2-(meth)acryloyloxyethyl) maleate, and ω-carboxy-polycaprolactone mono(meth)acrylate.

Examples of the polyfunctional compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, glycerin propoxy tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol di(meth)acrylate monostearate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and neopen hydroxypivalate. Polyhydric alcohols such as ethyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 9,9-bis(4-(2-(meth)acryloyloxyethoxy)phenyl)fluorene, and 9,9-bis(4-(2-(2-(meth)acryloyloxyethoxy)ethoxy)phenyl)fluorene. and (meth)acrylic acid ester compounds; bis(4-(meth)acryloxyphenyl)sulfide, bis(4-(meth)acryloylthiophenyl)sulfide, tris(2-(meth)acryloyloxyethyl)isocyanurate, ethylene bis(meth)acrylamide, zinc (meth)acrylate, zirconium (meth)acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, epoxy acrylate, polyester acrylate, etc.

The polymerizable composition may contain a copolymer obtained from the radically polymerizable compound.

The content of the benzophenone group-containing polyvalent peroxyester is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1 to 15 parts by mass, relative to 100 parts by mass of the radical polymerizable compound. If the content of the benzophenone group-containing polyvalent peroxyester is less than 0.1 parts by mass relative to 100 parts by mass of the radical polymerizable compound, the curing reaction does not proceed, which is not preferable. In addition, if the content of the benzophenone group-containing polyvalent peroxyester is more than 40 parts by mass relative to 100 parts by mass of the radical polymerizable compound, the solubility in the radical polymerizable compound reaches saturation, crystals of the benzophenone group-containing polyvalent peroxyester are precipitated during film formation of the polymerizable composition, and roughness of the film surface may become a problem, or the strength of the coating film of the cured product may decrease due to an increase in decomposition residues of the benzophenone group-containing polyvalent peroxyester. This is not preferable.

The content of the cobalt-based curing accelerator is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the radical polymerizable compound. If the content of the cobalt-based curing accelerator is less than 0.01 parts by mass per 100 parts by mass of the radical polymerizable compound, the curing acceleration effect is not exhibited, which is not preferable. If the content of the cobalt-based curing accelerator is more than 20 parts by mass per 100 parts by mass of the radical polymerizable compound, the strength of the coating film of the cured product may decrease, which is not preferable.

<Solvent>
The polymerizable composition may further contain a solvent in order to improve the viscosity, coatability, and smoothness of the cured film. The solvent that can be used in the present invention is not particularly limited as long as it is capable of dissolving or dispersing the benzophenone group-containing polyvalent peroxyester, the cobalt-based curing accelerator, and the radical polymerizable compound, and is volatilized at the drying temperature.

Examples of the solvent include aprotic solvents such as hydrocarbon solvents and unsaturated hydrocarbon solvents, water, alcohol solvents, carbitol solvents, ester solvents, ketone solvents, ether solvents, lactone solvents, cellosolve acetate solvents, carbitol acetate solvents, propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, etc. The solvents may be used alone or in combination of two or more.

The amount of the solvent used is preferably 1 to 1000 parts by mass, and more preferably 2 to 500 parts by mass, per 100 parts by mass of the solid content of the polymerizable composition. If the amount of the solvent used is less than 1 part by mass per 100 parts by mass of the solid content of the polymerizable composition, the coatability will deteriorate, which is not preferred. If the amount of the solvent used is more than 1000 parts by mass per 100 parts by mass of the solid content of the polymerizable composition, the thermosetting property will deteriorate, which is not preferred.

<Polymerizable Composition>
The polymerizable composition of the present invention contains the benzophenone group-containing polyhydric peroxyester, the cobalt-based curing accelerator, and the radical polymerizable compound. The polymerizable composition may contain other components in appropriate combination.

<Other ingredients>
As the other components, the polymerizable composition may contain additives that are generally used in applications such as coating agents, paints, printing inks, photosensitive printing plates, adhesives, and various photoresists such as color resists and black resists. Examples of additives include sensitizers (isopropylthioxanthone, diethylthioxanthone, 4,4'-bis(diethylamino)benzophenone, 9,10-dibutoxyanthracene, coumarin, ketocoumarin, acridine orange, camphorquinone, etc.), polymerization inhibitors (p-methoxyphenol, hydroquinone, 2,6-di-t-butyl-4-methylphenol, phenothiazine, etc.), ultraviolet absorbers, infrared absorbers, light stabilizers, antioxidants, leveling agents, surface conditioners, surfactants, thickeners, defoamers, adhesion promoters, plasticizers, epoxy compounds, thiol, etc. Examples of the additives include all compounds, resins having ethylenically unsaturated bonds, saturated resins, coloring dyes, fluorescent dyes, pigments (organic pigments, inorganic pigments), carbon-based materials (carbon fibers, carbon black, graphite, graphitized carbon black, activated carbon, carbon nanotubes, fullerenes, graphene, carbon microcoils, carbon nanohorns, carbon aerogels, etc.), metal oxides (titanium oxide, iridium oxide, zinc oxide, alumina, silica, etc.), metals (silver, copper, etc.), inorganic compounds (glass powder, layered clay minerals, mica, talc, calcium carbonate, etc.), dispersants, flame retardants, etc. The additives may be used alone or in combination of two or more.

The content of the additive is appropriately selected depending on the purpose of use and is not particularly limited, but is usually preferably 500 parts by mass or less, and more preferably 100 parts by mass or less, per 100 parts by mass of the radical polymerizable compound.

<Method for preparing polymerizable composition>
When preparing the polymerizable composition, the benzophenone group-containing polyvalent peroxyester, the cobalt-based curing accelerator, the radically polymerizable compound, and, if necessary, the solvent and other components may be charged into a container, and dissolved or dispersed according to a conventional method using a paint shaker, a bead mill, a sand grind mill, a ball mill, an attritor mill, a two-roll mill, a three-roll mill, etc. Furthermore, if necessary, the mixture may be filtered through a mesh or membrane filter, etc.

In addition, in preparing the polymerizable composition, the benzophenone group-containing polyvalent peroxyester and the cobalt-based hardening accelerator may be added to the polymerizable composition from the beginning, but when the polymerizable composition is to be stored for a relatively long period of time, it is preferable to dissolve or disperse the benzophenone group-containing polyvalent peroxyester and the cobalt-based hardening accelerator in a composition containing a radical polymerizable compound immediately before use.

<Method of producing the cured product>
The cured product of the present invention is formed from the polymerizable composition. The method for producing the cured product is a production method including a step of applying the polymerizable composition onto a substrate and then heating the polymerizable composition. The method may also include a step of irradiating the composition with active energy rays before the heating step. In particular, a cured film having excellent surface smoothness can be obtained by quickly curing the surface by light irradiation and then further curing by heating.

Examples of the coating method include various methods such as spin coating, bar coating, spray coating, dip coating, flow coating, slit coating, doctor blade coating, gravure coating, screen printing, offset printing, inkjet printing, and dispenser printing. Examples of the substrate include films and sheets of glass, silicon wafers, metals, plastics, etc., and molded products with three-dimensional shapes, and the shape of the substrate is not limited.

In the step of heating the polymerizable composition, examples of the heating method include heating and ventilation heating. The heating method is not particularly limited, but examples include an oven, a hot plate, infrared irradiation, and electromagnetic wave irradiation. In addition, examples of the ventilation heating method include a ventilation drying oven.

The active energy rays are preferably light having a wavelength of 250 to 450 nm. As a light source for irradiating the light, a low pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, an ultraviolet electrodeless lamp, a light emitting diode (LED), a xenon arc lamp, a carbon arc lamp, sunlight, a solid-state laser such as a YAG laser, a semiconductor laser, a gas laser such as an argon laser, and the like can be used. The exposure dose of the active energy rays should be appropriately set according to the wavelength, intensity, and the like of the active energy rays.

In the step of heating the polymerizable composition, the heating temperature is preferably 80 to 140°C, and more preferably 100 to 130°C. At this temperature, the composition can be cured without deteriorating the resin substrate, etc. The heating time is preferably 1 to 180 minutes, and more preferably 5 to 120 minutes.

The dry film thickness of the polymerizable composition (film thickness of the cured product) is set appropriately depending on the application, but is preferably 0.05 μm to 500 mm, and more preferably 0.1 μm to 10 mm.

The polymerizable composition of the present invention is useful for FPD resists such as color resists, black resists, protective films for color filters, photospacers, black column spacers, frame resists, photoresists for TFT wiring, and interlayer insulating films; resists for printed circuit boards such as liquid solder resists and dry film resists; semiconductor resists, buffer coat films, and other semiconductor materials; printing inks such as offset printing inks, gravure printing inks, screen printing inks, inkjet printing inks, conductive inks, insulating inks, and inks for light guide plates; photosensitive printing plates; nanoimprint materials; resins for 3D printers; hard coat agents, photodisplays, and other optical devices. It can be used for a variety of purposes, including coatings for disks, coatings for optical fibers, paints for mobile devices, paints for home appliances, paints for cosmetic containers, paints for woodworking, internal anti-reflection paints for optical elements, high and low refractive index coatings, heat-shielding coatings, heat-dissipating coatings, and anti-fogging agents; holographic recording materials; dental materials; waveguide materials; black stripes for lens sheets; green sheets and electrode materials for capacitors; adhesives for FPDs, adhesives for HDDs, adhesives for optical pickups, adhesives for image sensors, adhesives for organic EL, OCA for touch panels, OCR for touch panels, and other adhesives and sealants, with no particular restrictions on their uses.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(1) Preparation of Polymerizable Compositions The radical polymerizable compound, benzophenone group-containing polyvalent peroxyester, thermal polymerization initiator, curing accelerator, and solvent in the amounts shown in Table 1 were mixed and stirred to prepare the polymerizable compositions of Examples 1 to 5 and Comparative Examples 1 to 4.

(2) Evaluation of curability The polymerizable composition prepared above was applied to a glass substrate to a thickness of 100 μm using a bar coater. After application, the composition was dried in an oven at 90° C. for 2.5 minutes, and then irradiated at 30 mJ/cm ² using a conveyor-type UV irradiation device equipped with a high-pressure mercury lamp. The composition was then heated in an oven at 100° C. for 30 minutes to obtain a cured film. The polymerization conversion rate of the obtained cured film was measured, and the curability was evaluated according to the following criteria. The polymerization conversion rate was measured by attenuated total reflection infrared spectroscopy (ATR-IR), and the polymerization conversion rate was calculated based on the following formula using the peak area A of the absorption spectrum (810 cm ⁻¹ ) derived from the double bond group and the peak area B of the absorption spectrum (1740 cm ⁻¹ ) derived from the carbonyl group that did not change before and after exposure. The results are shown in Table 1.
Polymerization conversion rate=(1-(A/B after curing)/(A/B before curing))×100
◎: Polymerization conversion rate is 80% or more. ◯: Polymerization conversion rate is 60% or more and less than 80%. ×: Polymerization conversion rate is less than 60%.

(3) Evaluation of Surface Smoothness The presence or absence of wrinkles on the surface of the cured film obtained above was observed under an optical microscope in a field of view of 70 μm × 70 μm, and evaluated according to the following criteria. The results are shown in Table 1.
◯: No wrinkles on the micrometer order are observed on the surface. ×: Wrinkles on the micrometer order are noticeable on the surface.

In Table 1 above, TMPTA is trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.);
PE4A, pentaerythritol tetraacrylate (Fujifilm Wako Pure Chemical Reagents);
Perbutyl O: t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corp.);
PGMEA, propylene glycol monomethyl ether acetate (Sigma-Aldrich Japan Reagent);
Mineral spirits refers to a mixed solvent of petroleum-based hydrocarbons.

The results in Table 1 clearly show that the polymerizable composition containing a benzophenone group-containing polyhydric peroxyester, a cobalt-based curing accelerator, and a radical polymerizable compound has excellent surface smoothness and can be cured sufficiently even at low temperatures.

Claims (5)

General formula (1):
(in general formula (1), R ¹ and R ² are independently an alkyl group having 4 to 8 carbon atoms or an aralkyl group having 9 to 12 carbon atoms, and R ³ and R ⁴ are independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 4 to 8 carbon atoms, or an aralkyloxy group having 9 to 12 carbon atoms), a cobalt-based curing accelerator, and a radically polymerizable compound. The polymerizable composition according to claim 1, characterized in that the cobalt-based curing accelerator is cobalt octylate and/or cobalt naphthenate. A cured product formed from the polymerizable composition according to claim 1 or 2. A method for producing a cured product, comprising a step of heating the polymerizable composition according to claim 1 or 2. The method for producing a cured product according to claim 4, characterized in that the heating step is performed at a heating temperature of 80 to 140°C.