Active light curable composition and cured film

Abstract

The active light ray-curable composition according to the present invention is an active light ray-curable composition that cures by means of active light rays, and contains a (meth) acrylate having a hydroxyl group, an alkyl (meth) acrylate, a photopolymerization initiator, and an inorganic filler, the inorganic filler being contained in an amount of 10-50 mass% relative to the entire active light ray-curable composition, and the content of the (meth) acrylate having a hydroxyl group, the photopolymerization initiator, and the inorganic filler being contained in an amount of 10-50 mass% relative to the total amount of the active light ray-curable composition. The viscosity of the active light curable composition before curing is in the range of 5-200 mPas at 25 DEG C.

Description

Technical Field

[0001] This invention relates to active light-curable compositions and cured films. In particular, this invention relates to active light-curable compositions having adhesiveness, high transparency, and refractive index as post-film properties, as well as bending resistance and storage stability, and to cured films using the active light-curable compositions. Background Technology

[0002] It is known that liquid crystal display devices, organic electroluminescent (organic EL) display devices (hereinafter also referred to as "OLED") use high refractive index layers to improve the light extraction efficiency of optical devices.

[0003] Recently, a technology for improving the optical properties of each layer, such as high refractive index and high transparency, in foldable device applications was disclosed.

[0004] For example, Patent Document 1 discloses a technique involving a curable composition containing high refractive index particles, a (meth)acrylate having two or more olefinic unsaturated groups and having an alicyclic structure, an aromatic ring structure or a combination thereof, and a polymerization initiator.

[0005] Patent document 2 discloses a technique for using a high-refractive-index acrylic complex containing metal oxide nanocrystals smaller than 10 nm as a high-refractive-index, high-transparency coating for various optical applications, such as OLED lighting.

[0006] Patent document 3 discloses a formulation comprising: metal oxide nanocrystals, and a matrix containing at least one monomer, oligomer, or polymer. This formulation is used to manufacture high-refractive-index, high-transparency nanocomposites for various optical applications, including OLED lighting and displays.

[0007] On the other hand, in recent years, in addition to the aforementioned optical properties, bending resistance and storage stability have also been emphasized, and these properties are required to be combined. However, although the technologies described in the aforementioned patent documents 1 to 3 mention inkjet applicability, optical properties, and refractive index, they do not describe mechanical properties such as adhesive function and bending resistance.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2017-61606

[0011] Patent Document 2: Japanese Patent Publication No. 2019-507221

[0012] Patent Document 3: Japanese Patent Publication No. 2022-507821 Summary of the Invention

[0013] The present invention was made in view of the above-mentioned problems and circumstances, and its solution is to provide an active light-curable composition and a curable film capable of forming a curable film with high adhesion, bending resistance and storage stability and high refractive index.

[0014] In order to solve the aforementioned problems, the inventors investigated the causes of these problems. As a result, they incorporated hydroxyl-containing (meth)acrylates, alkyl (meth)acrylates, photopolymerization initiators, and inorganic fillers into the active light-curable composition, and maintained the content of the inorganic fillers and the viscosity of the active light-curable composition before curing within specific ranges. The inventors discovered that with this configuration, a cured film with high adhesion, high flexural strength, high storage stability, and high refractive index can be formed.

[0015] That is, the above-mentioned problems of the present invention are solved by the following method.

[0016] 1. An active light-curable composition, which is an active light-curable composition cured by active light.

[0017] It contains hydroxyl-containing (meth)acrylates, alkyl (meth)acrylates, photopolymerization initiators, and inorganic fillers.

[0018] The content of the inorganic filler is in the range of 10% to 50% by mass relative to the overall active light-curable composition described above, and

[0019] The viscosity of the above-mentioned active light-curable composition before curing is 5-200 mPa at 25°C. Within the range of s.

[0020] 2. The active light-curable composition according to item 1, wherein the refractive index of the inorganic filler at a wavelength of 589 nm is in the range of 1.9 to 3.0.

[0021] 3. The active light-curable composition according to item 1, wherein the composition contains either zirconium oxide or titanium oxide as the aforementioned inorganic filler.

[0022] 4. The active light-curable composition according to item 1, wherein the average primary particle size of the inorganic filler is 100 nm or less.

[0023] 5. The active light-curable composition according to claim 1, wherein the (meth)acrylate contained in the active light-curable composition as a whole does not contain sulfur.

[0024] 6. The active light-curable composition according to claim 1, wherein, relative to the entire active light-curable composition, it contains 5 to 50% by mass of the above-mentioned hydroxyl-containing (meth)acrylate, 5 to 50% by mass of the above-mentioned alkyl (meth)acrylate, and 0.1 to 5% by mass of the above-mentioned photopolymerization initiator.

[0025] 7. The active light-curable composition according to item 1, wherein the alkyl group of the above-mentioned (meth)acrylate has 8 to 24 carbon atoms.

[0026] 8. The active light-curable composition according to item 1, used in inkjet ink.

[0027] 9. A cured film, which is a cured product of the active light-curable composition described in any one of claims 1 to 8.

[0028] According to the method described above, it is possible to provide an active light-curable composition having adhesiveness, high transparency and refractive index as physical properties after film formation, as well as bending resistance and storage stability, and a cured film using the active light-curable composition.

[0029] The mechanism or mechanism of action of the effects of this invention is not yet clear, but the following is a conjecture.

[0030] The active photocurable composition of the present invention contains: a hydroxyl-containing (meth)acrylate, an alkyl (meth)acrylate, and a photopolymerization initiator. It is known that alkyl (meth)acrylates, even alone, possess adhesive properties through polymerization. However, in the present invention, it is believed that by adding a hydroxyl-containing (meth)acrylate as a comonomer, the adhesive properties, i.e., the wetting state, are more stably maintained after polymerization. Furthermore, the adhesive properties are improved because the surface irregularities of the coated material are easily filled in.

[0031] Furthermore, it is known that increasing the refractive index can be achieved by adding inorganic fillers. When the content of inorganic fillers is low, the effect of increasing the refractive index is insufficient; when the content is high, increasing the refractive index may be achieved on its own. However, the rigidity of inorganic fillers has properties opposite to adhesion, thus resulting in a loss of adhesion.

[0032] Therefore, in this invention, by setting an appropriate amount of inorganic filler, the surface states of the inorganic filler, such as charge and hydrophilicity, are maintained in a certain dispersion state after the active light-curing composition is cured. As a result, it is believed that this invention can improve the overall average refractive index of the material while maintaining adhesion and high transparency.

[0033] Generally, the addition of moisture and temperature promotes yellowing during storage. In this invention, it is believed that yellowing progresses through chromophores generated from sulfur oxides produced by sulfur oxidation, or from a reaction between sulfur oxides and the active light-curing composition, or between sulfur oxides and the coated material. Therefore, in this invention, it is believed that excellent storage stability is achieved by making the active light-curing composition sulfur-free.

[0034] In summary, it has been found that the active light-curable composition of the present invention, by containing the aforementioned hydroxyl-containing (meth)acrylate and the aforementioned alkyl (meth)acrylate, enables the cured product to exhibit adhesiveness under the action of active light. Furthermore, while exhibiting adhesiveness, mechanical strength can also be obtained through the use of inorganic fillers. Moreover, it is believed that flexural strength can be obtained by achieving a balance between adhesiveness and mechanical strength. Attached Figure Description

[0035] Figure 1A This is a schematic diagram illustrating an exemplary configuration of a curing film manufacturing apparatus according to one embodiment of the present invention.

[0036] Figure 1B This is a schematic diagram illustrating an exemplary configuration of a curing film manufacturing apparatus according to one embodiment of the present invention.

[0037] Figure 1C This is a schematic diagram illustrating an exemplary configuration of a curing film manufacturing apparatus according to one embodiment of the present invention. Detailed Implementation

[0038] The active light-curable composition of the present invention is an active light-curable composition that is cured by active light, comprising: (meth)acrylate having hydroxyl groups, alkyl (meth)acrylate, a photopolymerization initiator, and an inorganic filler. The active light-curable composition contains 10-50% by mass of the aforementioned inorganic filler relative to the total active light-curable composition. The viscosity of the active light-curable composition before curing is 5-200 mPa at 25°C. Within the range of s.

[0039] This feature is a technical feature shared by or corresponding to the following embodiments.

[0040] As an embodiment of the present invention, it is preferable that the refractive index of the inorganic filler at a wavelength of 589 nm is in the range of 1.9 to 3.0. If the refractive index of the inorganic filler is in the range of 1.9 to 3.0, then even if the content of the inorganic filler is low, the effect of increasing the refractive index is high.

[0041] In terms of achieving high refractive index, it is preferable that the above-mentioned inorganic filler contains one or more of zirconium oxide and titanium oxide.

[0042] In terms of high transparency, it is preferable that the average primary particle size of the aforementioned inorganic filler is below 100 nm.

[0043] Regarding excellent storage stability, it is preferable that the (meth)acrylate contained in the above-mentioned active light-curable composition as a whole does not contain sulfur.

[0044] In terms of adhesion, high refractive index, bending resistance and storage stability, it is more preferable, relative to the above-mentioned active light curable composition as a whole, to contain 5 to 50% by mass of the above-mentioned hydroxyl-containing (meth)acrylate, 5 to 50% by mass of the above-mentioned alkyl (meth)acrylate, and 0.1 to 5% by mass of the above-mentioned photopolymerization initiator.

[0045] From the perspective of ensuring greater transparency in the composition of the present invention, it is preferable that the alkyl group of the above-mentioned (meth)acrylate has 8 to 24 carbon atoms.

[0046] The active light-curable composition of the present invention is suitable for inkjet inks.

[0047] The cured film of the present invention is characterized in that the above-mentioned active light curable composition is cured using active light. This results in the formation of a cured film with high adhesion, high bending resistance, high storage stability, and a high refractive index.

[0048] The present invention, its constituent elements, and the forms for carrying out the present invention will be described below. The method of explanation is as follows. It should be noted that in this application, "~" is used to include the numerical values ​​stated before and after it as lower and upper limits.

[0049] [Summary of the active light-curable composition of the present invention]

[0050] The active light-curable composition of the present invention is an active light-curable composition that is cured by active light. It contains hydroxyl-containing (meth)acrylate, alkyl (meth)acrylate, a photopolymerization initiator, and an inorganic filler. Relative to the total active light-curable composition, it contains 10-50% by mass of the aforementioned inorganic filler. The viscosity of the active light-curable composition before curing is 5-200 mPa at 25°C. Within the range of s.

[0051] In this invention, "(meth)acrylate" refers to acrylate or methacrylate. "(meth)acryloyl" refers to acryloyl or methacryloyl, and "(meth)acrylic acid" refers to acrylic acid or methpropylene.

[0052] The active light-curable composition of the present invention is a composition that can be cured by active light.

[0053] "Active light" refers to a type of light that can impart energy to initiate the formation of substances in a curable composition through irradiation, including alpha rays, gamma rays, X-rays, ultraviolet rays, electron beams, etc. Among these, from the viewpoint of curing sensitivity and ease of obtaining the apparatus, ultraviolet rays and electron beams are preferred, and ultraviolet rays are more preferred.

[0054] <Viscosity>

[0055] The viscosity of the active light-curable composition before curing is 5–200 mPa at 25°C. Within the range of s.

[0056] In this invention, "viscosity of the active light-curable composition before curing" refers to the viscosity obtained by measuring the active light-curable composition before curing by active light under the following conditions.

[0057] Viscosity was measured using a rheometer MCR302 (manufactured by Anton Paar Japan Co., Ltd.) and a cone-plate CP75-1 (manufactured by Anton Paar Japan Co., Ltd.) with a diameter of 75 mm and an angle of 1° at 25°C and a shear rate of 1000 (S). －1 ).

[0058] The viscosity of the above-mentioned active light-curable composition before curing is preferably 5-200 mPa at 25°C. Within the range of s, 10–100 mPa is particularly preferred. Within the range of s.

[0059] In order to make the viscosity of the active light-curable composition before curing within the above-mentioned range, examples include: the total content of (meth)acrylates, (meth)acrylates and other acrylates having hydroxyl groups in the active light-curable composition being in the range of 50 to 90% by mass.

[0060] [Composition of the active light-curable composition]

[0061] The active light-curable composition of the present invention contains: a hydroxyl-containing (meth)acrylate, an alkyl (meth)acrylate, a photopolymerization initiator, and an inorganic filler. Hereinafter, the hydroxyl-containing (meth)acrylate, the alkyl (meth)acrylate, the photopolymerization initiator, and the inorganic filler will be described.

[0062] <Hydroxy-containing (meth)acrylates>

[0063] Examples of hydroxyl-containing (meth)acrylates of the present invention include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, ethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, propylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, cyclohexyldiethanol mono(meth)acrylate, and caprolactone acrylate, etc. These (meth)acrylates can be used alone or in combination of two or more.

[0064] In this invention, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate are particularly preferred as hydroxyl-containing methacrylates.

[0065] Alkyl (meth)acrylates

[0066] Examples of alkyl (meth)acrylates of the present invention include n-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecanyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, and other linear-chain types. Branched methacrylates include isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, isoamyl methacrylate, ethylhexyl methacrylate, isononyl methacrylate, isodecanyl methacrylate, isostearyl methacrylate, isobornyl methacrylate, dicyclopentyl methacrylate, cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, and cyclooctyl methacrylate. These methacrylates can be used alone or in combination with two or more.

[0067] The alkyl group of the above-mentioned (meth)acrylate preferably has 8 to 24 carbon atoms.

[0068] As for the aforementioned alkyl methacrylates, in addition to linear types such as octyl methacrylate (8 carbon atoms) and benzyl methacrylate (22 carbon atoms), branched types such as isostearyl methacrylate (18 carbon atoms) are particularly preferred, but not limited to these.

[0069] The active light-curable composition of the present invention is preferably free of sulfur in the (meth)acrylate contained in the entire active light-curable composition, which has excellent storage stability.

[0070] Specifically, it is preferable that the aforementioned hydroxyl-containing (meth)acrylates and alkyl (meth)acrylates do not contain sulfur. Furthermore, it is preferable that these hydroxyl-containing (meth)acrylates and alkyl (meth)acrylates, other than these, also do not contain sulfur.

[0071] In terms of adhesion, high refractive index, flexural strength and storage stability, the content of hydroxyl-containing (meth)acrylate is preferably in the range of 5 to 50% by mass relative to the total active light-curable composition.

[0072] In terms of adhesion, high refractive index, flexural strength and storage stability, the content of alkyl (meth)acrylate is preferably in the range of 5 to 50% by mass relative to the total active light-curable composition.

[0073] <Photopolymerization Initiator>

[0074] The photopolymerization initiator is a free radical photopolymerization initiator.

[0075] Photopolymerization initiators can be either intramolecular bond-breaking free radical polymerization initiators or intramolecular hydrogen-abstraction free radical polymerization initiators.

[0076] Among them, intramolecular bond-breaking free radical polymerization initiators are less likely to initiate polymerization starting from the hydroxyl groups of (meth)acrylates, which have hydroxyl groups, compared to intramolecular hydrogen abstraction free radical polymerization initiators. Therefore, intramolecular bond-breaking free radical polymerization initiators are less likely to form cross-linked structures through polymerization starting from the aforementioned hydroxyl groups, which makes the cured film more flexible and improves the durability of the cured film when bent.

[0077] Examples of intramolecular bond-breaking free radical polymerization initiators include: acetophenone-based initiators containing diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzoylayl dimethyl ketal, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)one, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propane-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, benzoylaine-based initiators containing benzoylaine, benzoylaine methyl ether and benzoylaine isopropyl ether, acylphosphine oxide-based initiators containing 2,4,6-trimethylbenzoylaine diphenylphosphine oxide, and benzyl and methylphenylacetalates, etc.

[0078] Among these intramolecular bond-breaking free radical polymerization initiators, acylphosphine oxide-based polymerization initiators are preferred because they also possess sufficient curing properties (polymerization initiation properties) when used with a UV-LED light source to reduce damage to the substrate. The aforementioned intramolecular bond-breaking free radical polymerization initiators can be used alone or in combination of two or more.

[0079] Examples of intramolecular hydrogen-abstracting free radical polymerization initiators include: benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxydibenzophenone. Initiators include benzophenone-based initiators, thioxanthone-based initiators including 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone, aminobenzophenone-based initiators including Michlechone and 4,4'-diethylaminobenzophenone, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-phenanthroquinone, and camphorquinone. These intramolecular hydrogen-extraction type free radical polymerization initiators can be used alone or in combination of two or more.

[0080] The content of the polymerization initiator only needs to be within the range that allows the active light-curable composition to be fully cured, and is preferably in the range of 0.01 to 10% by mass relative to the total mass of the active light-curable composition. The content of the polymerization initiator is preferably in the range of 0.1 to 5% by mass relative to the total mass of the active light-curable composition.

[0081] <Inorganic packing>

[0082] Examples of inorganic fillers in this invention include silicon monoxide (nano-SiO2 silicon monoxide powder: Xinglu Chemicals), zirconium oxide (Zirconeo-Cp, Zirconia-Rp: ITEC Corporation, Zircostar ZP-153, Zircostar HR-101: Nippon Catalyst Co., Ltd.), titanium oxide (AMT-100, AMT-600, TKP-101, TKP-102: Tayca Corporation, ultrafine titanium oxide TTO series: Ishihara Kogyo Co., Ltd.), tantalum pentoxide (Hongwu International Group Ltd.), niobium pentoxide (Baylar series: Nb-G6000, Nb-G6100, Nb-G6600: Tagi Chemical Co., Ltd.), cerium oxide (ITEC Corporation), silicon (Si nanoparticles: Nisshin Kasei Corporation), and germanium (Hongwu International Group Ltd.). These inorganic fillers can be used individually or in combination with two or more types.

[0083] Alternatively, it can be like a nucleus. Like a shell, it contains multiple metal oxides in a single particle.

[0084] In this invention, the inorganic filler preferably contains one or more of silicon monoxide, zirconium oxide, titanium oxide, tantalum pentoxide, niobium pentoxide, cerium oxide, silicon monomer, and germanium monomer. It is particularly preferred that the inorganic filler contains one or more of zirconium oxide and titanium oxide.

[0085] In terms of achieving high refractive index even with a low content of inorganic filler, the refractive index of the aforementioned inorganic filler at a wavelength of 589 nm is preferably in the range of 1.9 to 3.0.

[0086] The refractive index of the above-mentioned inorganic filler was determined by the following method.

[0087] A thin film of less than 1 μm made of inorganic filler was formed on a substrate such as glass or silicon wafer using a sputtering method. Then, for example, measurements were performed using an ellipsometry M-2000 (JA Woolam Japan Co., Ltd.).

[0088] In terms of ensuring optical transparency, the average primary particle size of the inorganic filler is preferably 100 nm or less, and more preferably in the range of 1 to 50 nm.

[0089] The average primary particle size of the above-mentioned inorganic filler was determined using the following values.

[0090] For the ZetaSizer Nano ZS (manufactured by Malvern Panaritical), which uses dynamic light scattering as the measurement principle, the liquid sample before solidification was introduced into a glass sample cell (manufactured by Malvern Panaritical), and the Z-Average value was used as the average primary particle size.

[0091] The inorganic filler of the present invention is contained in the range of 10 to 50% by mass relative to the total amount of the active light-curable composition (the total amount of acrylic monomer and inorganic filler).

[0092] When the content of the aforementioned inorganic filler is not more than 10% by mass, its contribution to the high refractive index is minimal. On the other hand, if the content of the aforementioned inorganic filler is less than 50% by mass, adhesion can be maintained. The content of the aforementioned inorganic filler is preferably in the range of 20% to 50% by mass, and more preferably in the range of 25% to 50% by mass.

[0093] <Other Acrylates>

[0094] The active light-curable composition of the present invention may include aromatic ring-containing monomers, multifunctional monomers, crosslinking agents, etc., to improve refractive index, elastic modulus, and adhesion.

[0095] As the aforementioned monomer containing an aromatic ring, any compound having an aromatic ring and one olefinic unsaturated group within its molecule is acceptable. Examples of such functional groups containing olefinic unsaturated groups include (meth)acryloyl, crotonyl, vinyl, and allyl, among which (meth)acryloyl is preferred in terms of excellent reactivity.

[0096] Furthermore, examples of such aromatic rings include benzene rings, naphthalene rings, anthracene rings, biphenyl rings, and fluorene rings. The number of aromatic rings can be one or more. However, in terms of achieving a balance in adhesive properties, compounds containing one aromatic ring are preferred, while compounds containing two aromatic rings are preferred in terms of efficiently controlling the refractive index and birefringence of the adhesive layer.

[0097] Examples of the aforementioned monomers containing aromatic rings include benzyl (meth)acrylate, benzyloxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, biphenoxyethyl (meth)acrylate, and styrene, among which benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred. These can be used alone or in combination of two or more.

[0098] Furthermore, any compound containing two or more (meth)acrylate groups within its molecule can be used as a multifunctional monomer. Multifunctional (meth)acrylates can appropriately increase the hardness of the cured film.

[0099] Examples of multifunctional (meth)acrylates include triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, dimethyloltricyclodecane dimethacrylate, bisphenol A PO adduct dimethacrylate, neopentyl glycol dimethacrylate with hydroxypentanoic acid, and polytetramethylene glycol dimethacrylate. Difunctional (meth)acrylates such as dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate; trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerol propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate; and other (meth)acrylates with more than three functions, as well as their modified forms.

[0100] Examples of the modified materials mentioned above include ethylene oxide-modified (EO-modified) (meth)acrylates with inserted ethylene oxide alkyl groups and propylene oxide-modified (PO-modified) (meth)acrylates with inserted propylene oxide alkyl groups. They can be used alone or in combination of two or more.

[0101] <Other Ingredients>

[0102] The following components may be incorporated into the active light-curable composition of the present invention without impairing the effects of the present invention.

[0103] Examples of this component include antistatic agents, other acrylic adhesives, and other adhesives. Additionally, examples of this component include adhesives such as polyurethane resins, rosin, rosin esters, hydrogenated rosin esters, phenolic resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, and xylene resins. Furthermore, examples of this component include various additives such as colorants, fillers, anti-aging agents, ultraviolet absorbers, and functional pigments, as well as compounds that cause color development or discoloration upon exposure to ultraviolet light or radiation.

[0104] In addition to the additives mentioned above, small amounts of impurities contained in the raw materials used to manufacture the components of the active light-curable composition may also be included. The amount added should be appropriately set in a way that yields the desired physical properties.

[0105] <Uses>

[0106] The active light-curable composition of the present invention is used for the formation of cured films in various applications using inkjet printing to form cured films in the form of so-called inkjet inks that can be ejected from an inkjet printhead.

[0107] The active light-curable composition of the present invention is suitable for use as a transparent layer in image display devices due to the high adhesiveness and sufficiently high transparency of the cured film. It is particularly suitable for forming transparent layers used to bond various components of an image display device.

[0108] Examples of the above-mentioned transparent layers include: transparent layers for bonding transparent electrodes formed on a substrate to transparent protective layers made of glass or resin; transparent layers for bonding various panels such as liquid crystal display panels, organic EL display panels, and touch panels to transparent protective layers; transparent layers for bonding display panels such as liquid crystal display panels and organic EL display panels to touch panels; and transparent layers for bonding other components, etc.

[0109] [Cured film]

[0110] The cured film of the present invention is characterized in that the above-described active light curable composition of the present invention is cured using active light.

[0111] <Physical Properties>

[0112] The refractive index of the cured film of the present invention at 25°C and 589nm is preferably 1.5 or higher, and more preferably 1.55 or higher.

[0113] The refractive index described above can be determined as follows. First, the active light-curable composition is placed on the prism of an Abbe refractometer (NAR-1T SOLID: manufactured by Atago Corporation). Next, an ultraviolet irradiation device (manufactured by Phoseon Corporation) is used at an intensity of 2000 mW / cm². 2 Cumulative light intensity 1000 mJ / cm 2 By irradiating the film with ultraviolet light at a wavelength of 395 nm, the refractive index (nD) of the cured film at 25 °C and a wavelength of 589 nm can be measured.

[0114] The total light transmittance of the cured film of the present invention is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more.

[0115] The above-mentioned total light transmittance can be measured as follows: An active light-curable composition is coated onto a 50mm × 50mm × 1mm quartz substrate (manufactured by Matsunami Glass Co., Ltd.) to achieve a film thickness of 50μm. After being clamped onto the same quartz substrate, it is irradiated using an ultraviolet light irradiation device (manufactured by Phoseon Co., Ltd.) at an intensity of 2000mW / cm². 2 Cumulative light intensity 1000 mJ / cm 2 A cured film is formed by irradiating with ultraviolet light with a wavelength of 395nm. The total light transmittance of the cured film is measured using a haze meter NDH-5000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JISK7361-1.

[0116] [Method for forming the cured film]

[0117] The curing film of the present invention is obtained by applying the above-mentioned active light-curing composition to a substrate or a bonded component and irradiating it with active light to cure the above-mentioned active light-curing composition.

[0118] The method for applying the above-mentioned active light-curable composition is not particularly limited, and known methods such as spraying, dipping, screen printing, gravure printing, offset printing, and inkjet printing can be used. One of the above-mentioned methods can be used alone, or two or more can be used in combination. From the viewpoint of forming a finely textured cured film with high precision to create a high-precision pattern (image, etc.), or applying it to curved portions, inkjet printing is preferred.

[0119] The active light-curable composition can be applied to various substrates or to a component that is bonded together when two parts are attached. The material of the substrate or component to which it is applied is not particularly limited; it can be inorganic materials such as glass, metal, and ceramics, or organic materials such as resin films. Regardless of the type of material, the aforementioned active light-curable composition can achieve excellent adhesion.

[0120] At this point, active rays that are not fully cured can be irradiated to temporarily cure the aforementioned active ray-curable composition.

[0121] When forming a transparent layer for bonding two different components, another component is bonded to the aforementioned active light-curing composition that has been applied (or temporarily cured). At this time, at least one of the bonded components is a component that transmits active light.

[0122] Components that transmit active light include those made of materials such as glass, (meth)acrylate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polycarbonate resin, polyimide resin, and cyclic olefin polymers. Transparent functional components, such as transparent electrodes, can be formed within these components.

[0123] As components that do not transmit active light, they include: liquid crystal display panels, organic EL display panels, protective panels, touch panels, organic EL elements, and components with color filters formed thereon.

[0124] After bonding, appropriate pressure can be applied to ensure a tight fit between the components or to make the thickness of the active light-curable composition uniform.

[0125] Then, the active light curable composition is irradiated with active light to cure (or perform primary curing), thereby obtaining a cured film. The active light can be any active light such as an electron beam, ultraviolet light, alpha rays, gamma rays, and X-rays, but from the viewpoint of suppressing damage to other components, ultraviolet light is more preferred. In addition, from the viewpoint of suppressing damage to other components caused by radiant heat, ultraviolet light using a light-emitting diode (UV-LED) emitting ultraviolet light as a light source is more preferred.

[0126] The cured film formed by the active light-curing composition of the present invention has high adhesion and maintains good adhesion even in high temperature and high humidity environments and low temperature environments. Therefore, when used to bond two components, it is less likely for these components to detach, especially during long-term use.

[0127] Furthermore, the adhesion of the cured film does not easily decrease even with repeated bending. Therefore, when used in flexible displays, it is less likely for the aforementioned components to detach, especially during prolonged use.

[0128] Therefore, devices having the above-mentioned cured film, such as image display devices having the above-mentioned cured film, can be used for a long time.

[0129] [Apparatus for manufacturing cured film]

[0130] Figures 1A to 1C This is a schematic diagram showing the configuration of a curing film manufacturing apparatus for carrying out the above-described curing film manufacturing method.

[0131] The curing film manufacturing apparatus 100 includes: an application section 120 for applying the above-mentioned active light-curable composition to the surface of a component 110, and an irradiation section 130 for irradiating the surface of a component 110 that has been applied with the active light-curable composition with active rays.

[0132] In this embodiment, the application unit 120 applies the active light-curable composition by inkjet printing. The application unit 120 ejects the active light-curable composition from the nozzle 121, applying the active light-curable composition 122 (see reference) to the location on the surface of a component 110 where a cured film is to be formed. Figure 1A ).

[0133] Then, another component 150 is applied to the surface of the applied active light-curable composition 122 using the bonding section, so that one component 110 is bonded to the other component 150. In this embodiment, for the bonding section, the other component 150, which is a transparent film, is conveyed by the conveying roller 142 and applied to the surface of the active light-curable composition. Subsequently, pressure is applied using the pressure roller 144 to make one component 110 and the other component 150 adhere tightly (see reference). Figure 1B ).

[0134] It should be noted that when one component 110 is a component that transmits active light and the other component 150 is a component that does not transmit active light, the manufacturing apparatus 100 may have a reversing part that reverses them.

[0135] The irradiation unit 130 irradiates the surface of a component 110 with active rays towards the surface to which the active ray-curable composition 122 is applied. As a result, the irradiation unit 130 cures the active ray-curable composition 122 applied to the surface of the component 110 to form a cured film. In this embodiment, the irradiation unit 130 irradiates the active ray-curable composition 122 with active rays that have passed through another component 150 (see reference). Figure 1C ).

[0136] It should be noted that, in the above description, an active ray curable composition is applied to the surface of a component 110 by inkjet printing. However, the method of applying the active ray curable composition is not particularly limited, and known methods such as spraying, dipping, screen printing, gravure printing, and offset printing can be used.

[0137] Example

[0138] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. It should be noted that, unless otherwise specified, the operation in the following examples is carried out at room temperature (25°C). In addition, unless otherwise specified, "%" and "parts" refer to "mass %" and "parts by mass", respectively.

[0139] [Preparation of Active Light-Curing Composition 4]

[0140] Add the materials shown below and heat at 90°C for 1 hour to prepare active light-curable composition 1.

[0141] (Meth)alkyl acrylate: Octyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd., linear structure, 4 carbon atoms) 9 parts by weight

[0142] Hydroxyl-containing (meth)acrylates: 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 9 parts by weight

[0143] Inorganic filler: DZM-003 (DZM-003 contains 60% by mass ZrO2, primary particle size of ZrO2: 10 nm, manufactured by Daiken Chemical Co., Ltd.) 79 parts by mass

[0144] Polymerization inhibitor: 0.02 parts by weight of bis(2,2,6,6-tetramethyl-4-piperidinyl-1-oxy) sebacate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0145] Photopolymerization initiator: 3 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resin).

[0146] It should be noted that the 60% by mass ZrO2 contained in the above-mentioned DZM-003 contains 79 parts by mass × 0.6 = 47.4 parts by mass relative to the total active light-curable composition.

[0147] [Preparation of active light-curable compositions 2-23]

[0148] In the preparation of the above-mentioned active light-curable composition 4, the types and contents of alkyl methacrylate, hydroxyl-containing methacrylate, inorganic filler, polymerization inhibitor, and photopolymerization initiator are changed as shown in the table below. Otherwise, each active light-curable composition is prepared by the same operation.

[0149] It should be noted that the compounds shown in the table below are as follows.

[0150] Octyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd., linear structure, 8 carbon atoms)

[0151] Isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., branched structure, 18 carbon atoms)

[0152] Succinate acrylate (manufactured by Tokyo Chemical Industry Co., Ltd., linear structure, 22 carbon atoms)

[0153] 2-Hydroxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0154] Caprolactone acrylate (manufactured by Miwon Specialty Chemicals)

[0155] 9869 ZR (Contains 20% by mass of ZrO2, primary particle size of ZrO2: 63 nm, manufactured by TAYCA Corporation)

[0156] NS483 (Contains 20% by mass TiO2, primary particle size of TiO2: 6.8 nm, manufactured by Tayca Corporation)

[0157] In addition, the sulfur-containing acrylate (compound 1) used in the preparation of the active light-curable composition 16 is synthesized as described below.

[0158] <Synthesis of Compound 1>

[0159] Add the following materials to a 300ml three-necked round-bottom flask.

[0160] 2-(Octylthio)ethanol (manufactured by Fluorochem Ltd.) 47.5g

[0161] Triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 29.7g

[0162] Salicylic aldehyde oxime (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.01g

[0163] 2,3,5,6-Tetramethyl-1,4-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.01g

[0164] tert-Butyl methyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) 430g

[0165] The flask containing the mixture was heated to 40°C in a water bath, and 24.4 g of acryloyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise to the reaction. The reaction was maintained at 40°C for 1 hour until the reaction was complete, and then cooled to room temperature. 400 g of water was added to the flask. 5 g of hydrochloric acid (35-37%, manufactured by Kanto Chemical Co., Ltd.) was then added, and after thorough stirring, the aqueous phase was separated.

[0166] The organic phase was washed with a mixture of 300g water and 30g sodium carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.), and then washed with a mixture of 300g water and 30g sodium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.). The solvent was removed using a rotary evaporator to obtain 45g of a pale yellow liquid containing sulfur acrylate (compound 1).

[0167]

[0168] <Viscosity>

[0169] The viscosity of each of the prepared active light-curable compositions was measured as described below.

[0170] The rheometer MCR302 (manufactured by Anton Paar Japan Co., Ltd.) used a CP75-1 cone plate (manufactured by Anton Paar Japan Co., Ltd.) with a diameter of 75 mm and an angle of 1° to measure at 25°C and a shear rate of 1000 (S). －1 The viscosity of the active light-curable composition was determined. The results are shown in the table below.

[0171] <Refractive Index>

[0172] The refractive index of the cured film of each of the prepared active light-curable compositions was measured as described below.

[0173] The active light-curable composition was placed on the prism of an Abbe refractometer (NAR-1T SOLID: manufactured by Atago Corporation). An ultraviolet irradiation device (manufactured by Phoseon Corporation) was used at an intensity of 2000 mW / cm². 2 Cumulative light intensity 1000 mJ / cm 2 After irradiation with ultraviolet light at a wavelength of 395 nm, the refractive index (nD) of the cured film at 25 °C and a wavelength of 589 nm was measured.

[0174] The obtained refractive index is evaluated in three stages: AA, A, and B. "AA" and "A" are considered to be practically sound.

[0175] (Benchmark)

[0176] AA: (nD) ≥ 1.55

[0177] A: 1.50 ≤ (nD) < 1.55

[0178] B: (nD) < 1.50

[0179] <Adhesive Force>

[0180] The adhesive force mentioned in this specification refers to the adhesive force on the glass plate, which is measured as described below.

[0181] An inkjet printhead (Konica Minolta, KM1024iLHE-30) was mounted on an inkjet image forming apparatus (Tritek). Each photopolymerizable composition was coated onto a 75μm thick PET film LUMIRROR T60 (Toray Industries, Inc.) at a resolution of 360dpi × 360dpi, achieving a film thickness of 50μm. Then, ultraviolet light irradiation (Phoseon) was applied at an intensity of 2000mW / cm². 2 Cumulative light intensity 1000 mJ / cm 2 A cured film is formed by irradiating with ultraviolet light with a wavelength of 395nm.

[0182] The obtained PET film with cured film was sampled at 25mm × 100mm and attached to the surface of a clean soda glass plate (manufactured by Matsunami Glass Co., Ltd.). It was then pressed twice back and forth using a 2kg pressing roller. After 24 hours at room temperature, the adhesive force (N / 25mm) was measured using a peel tester VPA-H200 (manufactured by Kyowa Interface Science Co., Ltd.) at a tensile speed of 300mm / min, according to the 180-degree peel test method specified in JIS-Z-0237. The obtained adhesive force was evaluated according to four stages: AAA, AA, A, and B. "AAA", "AA", and "A" were considered to be practically problem-free.

[0183] (Benchmark)

[0184] AAA: (Adhesive strength) ≥30 [N / 25mm]

[0185] AA: 20 [N / 25mm] ≤ (adhesive strength) < 30 [N / 25mm]

[0186] A: 10 [N / 25mm] ≤ (adhesive strength) < 20 [N / 25mm]

[0187] B: (Adhesive strength) <10 [N / 25mm]

[0188] <Transmittance>

[0189] The transmittance of the cured film is evaluated as follows.

[0190] Using the same method as the <adhesion strength> test described above, each active light-curable composition was coated onto a 50mm × 50mm × 1mm quartz substrate (manufactured by Matsunami Glass Co., Ltd.) to achieve a film thickness of 50μm. After being clamped onto the same quartz substrate, it was irradiated using an ultraviolet light irradiation device (manufactured by Phoseon Co., Ltd.) at an intensity of 2000mW / cm². 2 Cumulative light intensity 1000 mJ / cm 2 A cured film is formed by irradiating with ultraviolet light with a wavelength of 395nm.

[0191] The total light transmittance of the cured film was measured using a haze meter NDH-5000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JIS K7361-1. The obtained total light transmittance was evaluated in four stages: AAA, AA, A, and B. "AAA", "AA", and "A" were considered to be practically acceptable.

[0192] (Benchmark)

[0193] AAA: (Total light transmittance) ≥95%

[0194] AA: 90% ≤ (total light transmittance) < 95%

[0195] A: 80% ≤ (total light transmittance) < 90%

[0196] B: (Total light transmittance) < 80%

[0197] <Preservation Stability>

[0198] The preservation stability was evaluated as described below.

[0199] Using the same method as described above for <adhesion strength>, each active light-curable composition was coated onto a 75 μm thick PET film LUMIRROR X10S (manufactured by Toray Industries, Inc.) to achieve a film thickness of 50 μm. After being clamped in the same PET film, it was irradiated using an ultraviolet light irradiation device (manufactured by Phoseon Corporation) at an intensity of 2000 mW / cm². 2 Cumulative light intensity 1000 mJ / cm 2 A cured film, sandwiched between two PET films, was formed by irradiation with ultraviolet light at a wavelength of 395 nm. The sample with the cured film was placed in an environmental testing chamber (ESPEC) at 85°C and 85% RH for 1000 hours. The yellowness ΔYI (=YI2-YI1) was calculated based on the yellowness YI1 immediately after curing and the yellowness YI2 after placement in the environmental testing chamber, calculated using a color evaluation program on a V-780 UV-Vis near-infrared spectrophotometer (Japan Spectrophotometer Co., Ltd.). The obtained yellowness was evaluated in four stages: AAA, AA, A, and B. "AAA", "AA", and "A" were considered practically acceptable.

[0200] (Benchmark)

[0201] AAA: ΔYI < 1.0

[0202] AA: 1.0 ≤ ΔYI < 3.0

[0203] A: 3.0 ≤ ΔYI < 5.0

[0204] B: 5.0≤ΔYI

[0205] <Bending resistance>

[0206] Bending resistance was evaluated as described below.

[0207] Using the same method as described above for <adhesion strength>, each active light-curable composition was coated onto a 200mm × 200mm × 75μm PET film LUMIRROR T60 (manufactured by Toray Industries, Inc.) to achieve a film thickness of 50μm. After being clamped with the same PET film, it was irradiated using a UV irradiation device (manufactured by Phoseon Corporation) at an intensity of 2000mW / cm². 2Cumulative light intensity 1000 mJ / cm 2 A cured film, sandwiched between two PET films, is formed by irradiating the sample with ultraviolet light at a wavelength of 395 nm. The sample, sandwiched between PET films on both sides, is placed in a clamshell-type bending tester (manufactured by Yuasa Systems Machinery Co., Ltd.). The sample is bent at a bending radius of 2 mm and a speed of 20 cycles per minute. The change in appearance after 100,000 cycles is evaluated using three stages: AA, A, and B. "AA" and "A" are considered to indicate no practical problems.

[0208] (Benchmark)

[0209] AA: The part that is not cracked and has turned white.

[0210] A: I see one or two cracks, and the parts have turned white.

[0211] B: If you see more than 3 cracks, white areas, or the cured film protruding beyond the PET film.

[0212]

[0213]

[0214]

[0215] Based on the results shown in Tables I to III, it is believed that, compared with active light-curable compositions 19 to 23 (comparative examples 1 to 5), active light-curable compositions 1 to 18 (1 to 18 of the present invention) not only maintain high transparency as a physical property after film formation, but also have high refractive index, and excellent bending resistance and storage stability.

[0216] That is, it can be understood that the active light-curable composition of the present invention exhibits adhesiveness by using ultraviolet irradiation to obtain a cured film that is composed of a specific combination of acrylates, and the effects of the present invention are obtained by further combining these acrylates with specific inorganic fillers.

[0217] In addition, it is known that, as with active light-curable compositions 4 to 18, the type and proportion of monofunctional acrylates, the chain length of monofunctional alkyl acrylates, and the proportion of acrylates containing sulfur elements also slightly affect the physical properties.

[0218] On the other hand, in the active light-curable compositions 19 and 20 (Comparative Examples 1 and 2), the refractive index was as low as 1.48 because there was no inorganic filler or the amount added was small. In addition, because these active light-curable compositions 19 and 20 were too soft, the cured film protruded from the PET film during the bending resistance test, indicating that sufficient bending resistance could not be obtained.

[0219] Furthermore, in the active light-curable composition 21 (Comparative Example 3), no adhesive force was obtained, and cracks and white areas were observed during the bending resistance test due to the curing film being too hard.

[0220] In the active light-curable composition 22 (Comparative Example 4), there is no acrylate with hydroxyl groups, only alkyl acrylate. Due to poor compatibility, a decrease in transparency can be observed. In the active light-curable composition 23 (Comparative Example 5), the result is that the cured film has insufficient cohesion, cannot exert adhesive force, and also has insufficient bending resistance.

[0221] Industrial availability

[0222] This invention can be used for active light-curable compositions that possess adhesiveness, high transparency, and refractive index as physical properties after film formation, as well as bending resistance and storage stability, and for cured films using the active light-curable compositions.

[0223] Symbol Explanation

[0224] Manufacturing apparatus for 100-degree cured film

[0225] 110 One component

[0226] 120 Assigned to the Department

[0227] 122 Active X-ray Curable Composition

[0228] 130 Irradiation Department

[0229] 142 Conveyor Rollers

[0230] 144 pressure rollers

[0231] 150 Another component.

Claims

1. An active light-curable composition, which is an active light-curable composition cured by active light. It contains hydroxyl-containing (meth)acrylates, alkyl (meth)acrylates, photopolymerization initiators, and inorganic fillers. The content of the inorganic filler relative to the total active light-curable composition is in the range of 10% to 50% by mass, and, The viscosity of the active light-curable composition before curing is 5–200 mPa at 25°C. Within the range of s.

2. The active light-curable composition according to claim 1, wherein, The inorganic filler has a refractive index in the range of 1.9 to 3.0 at a wavelength of 589 nm.

3. The active light-curable composition according to claim 1, wherein it contains either zirconium oxide or titanium oxide as the inorganic filler.

4. The active light-curable composition according to claim 1, wherein, The average primary particle size of the inorganic filler is less than 100 nm.

5. The active light-curable composition according to claim 1, wherein, The active light-curable composition contains no sulfur in the (meth)acrylate it comprises.

6. The active light-curable composition according to claim 1, wherein, The active light-curable composition contains, relative to the total composition, 5-50% by mass of the hydroxyl-containing (meth)acrylate, 5-50% by mass of the alkyl (meth)acrylate, and 0.1-5% by mass of the photopolymerization initiator.

7. The active light-curable composition according to claim 1, wherein, The alkyl group of the (meth)acrylate has 8 to 24 carbon atoms.

8. The active light-curable composition according to claim 1, used in inkjet inks.

9. A cured film, which is a cured product of the active light-curable composition according to any one of claims 1 to 8.

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