JP5481245B2 - Active energy ray-curable white resin composition and printed wiring board having an insulating layer made of the cured product - Google Patents

Description

  The present invention relates to an active energy ray-curable white resin composition useful as an insulating layer of a printed wiring board on which a light emitting element such as a light emitting diode (LED) is mounted, and a print having an insulating layer made of a cured product of the composition. The present invention relates to a wiring board.

  In recent years, printed wiring boards have been increasingly used by being mounted directly on LEDs that emit light at low power, such as backlights for liquid crystal displays such as portable terminals, personal computers and televisions, and light sources for lighting fixtures (for example, , See Patent Document 1).

  In that case, the insulating film that is formed as a protective film on the printed wiring board is not only the characteristics required for the solder resist film, such as solvent resistance, hardness, solder heat resistance, and electrical insulation, but also LED emission. It is desirable that the light reflectivity is excellent so that can be used effectively.

  However, in the conventionally used white solder resist composition, the oxidation of the resin proceeds due to light or heat generated from the LED, and the yellowing occurs, and the reflectance and whiteness decrease with time. there were. Under such circumstances, a titanium oxide powder specific to the thermosetting diallyl phthalate resin composition in order to obtain a thermosetting resin composition having high whiteness and good heat discoloration resistance and light discoloration resistance. Has been proposed (see, for example, Patent Document 2). However, as a result of intensive studies by the present inventors, it was found that this resin composition has a problem in storage stability at room temperature.

JP 2007-249148 A (paragraphs 0002 to 0007) JP 2008-255338 A

  An object of the present invention is to provide an active energy ray-curable white resin composition having a high reflectance and whiteness and excellent in light resistance and heat resistance, and a printed wiring board having an insulating layer made of a cured product of the composition. Is to provide.

The problems of the present invention have been solved by the invention described below.
(1) An active energy ray-curable white resin composition containing a diallyl phthalate-based prepolymer, a photopolymerizable monomer, a photopolymerization initiator containing neither a heterocyclic group nor a polycyclic aromatic group, and titanium oxide.

  (2) The active energy ray-curable composition according to (1), wherein the diallyl phthalate-based prepolymer contains either or both selected from a diallyl orthophthalate prepolymer and a diallyl isophthalate prepolymer. White resin composition.

  (3) The active energy ray-curable white resin composition according to (1) or (2), wherein the diallyl phthalate-based prepolymer has a weight average molecular weight of 20,000 to 60,000.

  (4) The active energy ray-curable white resin composition according to any one of (1) to (3), wherein the titanium oxide is a rutile type.

  (5) The active energy ray-curable white resin according to any one of (1) to (4), wherein the photopolymerizable monomer contains a bifunctional or higher functional acrylic monomer or methacrylic monomer, or a mixture thereof. Composition.

(6) The active energy ray-curable white resin composition according to any one of (1) to (5), wherein the average reflection of light of a cured product obtained by curing the composition with a wavelength of 400 to 700 nm The ratio is 80% or more, and the difference between the average reflectance with respect to light having a wavelength of 400 to 700 nm after irradiating the cured product with light having a wavelength of 350 nm so that the integrated light amount is 150 J / cm ² is less than 2.0 An active energy ray-curable white resin composition characterized by

(7) The active energy ray-curable white resin composition according to any one of (1) to (5), which is a hunter represented by formula (1) of a cured product obtained by curing the composition The initial value of the whiteness (HW) is 90 or more, and the cured product is irradiated with light having a wavelength of 350 nm so that the integrated light quantity becomes 150 J / cm ^2. An active energy ray-curable white resin composition having a difference from HW) of less than 2.0.

HW = 100 − [(100−L) ² + a ² + b ² ] ^1/2 (1)
(In the formula, L represents lightness, a represents redness, and b represents yellowness.)
(8) A cured product formed using the active energy ray-curable white resin composition according to any one of (1) to (7).

  (9) A printed wiring board having an insulating layer made of a cured product of the active energy ray-curable white resin composition according to any one of (1) to (7).

(10) The printed wiring board according to (10), wherein the insulating layer is a light emitting element reflecting plate.
(11) The printed wiring board according to (10), wherein the insulating layer is an electroluminescence reflector.

  (12) The printed wiring board according to (10), wherein the insulating layer is a light-emitting diode reflector.

  The active energy ray-curable white resin composition according to the present invention has a high reflectance and whiteness, and the reflectance and whiteness are not easily deteriorated by light and heat. When used as an insulating layer (a solder resist or a light-emitting element reflector) of a wiring board, light from an LED or the like can be used efficiently, and the illuminance can be increased over a long period as a whole. The active energy ray-curable white resin composition according to the present invention is not limited to a printed wiring board, but is required to have a high reflectivity and is exposed to light or heat, such as EL and LED. It can be used over a wide range as a reflector for a light emitting element.

FIG. 1 is a top view schematically showing a printed wiring board on which a light emitting element is mounted. FIG. 2 is a cross-sectional view schematically showing a printed wiring board on which a light emitting element is mounted. FIG. 3 is a schematic view schematically showing a part of the manufacturing process of the printed wiring board on which the light emitting element is mounted. FIG. 4 is a top view schematically showing a substrate including a light emitting element reflecting plate. FIG. 5 is a cross-sectional view schematically showing a printed wiring board on which a light emitting element is mounted.

  The active energy ray-curable white resin composition of the present invention contains a diallyl phthalate-based prepolymer, a photopolymerizable monomer, a photopolymerization initiator that does not contain any of a heterocyclic group and a polycyclic aromatic group, and titanium oxide.

[Diallyl phthalate prepolymer]
The diallyl phthalate prepolymer used in the present invention is not limited as long as it contains a diallyl phthalate repeating unit, and is a homopolymer of a diallyl phthalate monomer, a copolymer of two or more diallyl phthalate monomers, A diallyl phthalate monomer and another monomer copolymerizable with the monomer (for example, an aromatic compound having an ethylenic double bond, an aliphatic compound having an ethylenic double bond, or a (meth) allyl compound) A copolymer may also be used. In a copolymer of a diallyl phthalate monomer and another monomer copolymerizable with the monomer, a diallyl phthalate repeating unit is usually the main component.

  The diallyl phthalate monomer used as the raw material for the diallyl phthalate prepolymer is a compound selected from diallyl orthophthalate monomer, diallyl isophthalate monomer, and diallyl terephthalate monomer, and one or more of these compounds are used. Synthesis of diallyl phthalate-based prepolymers and synthesis of diallyl phthalate-based prepolymers using these diallyl phthalate-based monomers and other monomers that can be polymerized with the monomers may be performed by known polymerization reactions. It can be obtained by the polymerization reaction described in JP-A-2-024850, JP-A-11-147917.

  Examples of the diallyl phthalate prepolymer used in the present invention include a diallyl orthophthalate prepolymer which is a homopolymer, such as “Dup-A” (registered trademark) manufactured by Daiso Corporation, and a diallyl isophthalate prepolymer such as Daiso. “Isodap” (registered trademark) and diallyl terephthalate prepolymer manufactured by Co., Ltd. are preferable, and diallyl orthophthalate prepolymer and diallyl isophthalate prepolymer are more preferable.

  The diallyl phthalate-based prepolymer that can be suitably used in the present invention has a weight average molecular weight (polystyrene conversion) measured by GPC (gel permeation chromatography) of 20,000 to 60,000, more preferably 50,000. ~ 60,000. When the weight average molecular weight exceeds 60,000, the curability is deteriorated, and when it is less than 20,000, the heat resistance is deteriorated.

(Photopolymerizable monomer)
The photopolymerizable monomer may be any compound that can be cured by irradiation with active energy rays to form a resin exhibiting electrical insulation.
In the present invention, a compound having at least one ethylenically unsaturated bond in the molecule and containing no aromatic ring is preferably used. As the compound having an ethylenically unsaturated bond in the molecule and not containing an aromatic ring, a known and commonly used photopolymerizable vinyl monomer or the like is used.
Examples of the photopolymerizable vinyl monomer include known and commonly used styrene derivatives such as styrene, chlorostyrene, and α-methylstyrene; vinyl esters such as vinyl acetate, vinyl butyrate, and vinyl benzoate; vinyl isobutyl ether, vinyl Vinyl ethers such as n-butyl ether, vinyl-t-butyl ether, vinyl-n-amyl ether, vinyl isoamyl ether, vinyl-n-octadecyl ether, vinyl cyclohexyl ether, ethylene glycol monobutyl vinyl ether, triethylene glycol monomethyl vinyl ether; acrylamide , Methacrylamide, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, N-methoxymethyl acrylamide, N-ethoxymethyl amide (Meth) acrylamides such as rilamide and N-butoxymethylacrylamide; allyl compounds such as triallyl isocyanurate, diallyl phthalate and diallyl isophthalate; 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tetrahydrofurfuryl Esters of (meth) acrylic acid such as (meth) acrylate, isobornyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, pentaerythritol Hydroxyalkyl (meth) acrylates such as tri (meth) acrylate; Alkyl such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate Coxyalkylene glycol mono (meth) acrylates; ethylene glycol di (meth) acrylate, butanediol di (meth) acrylates, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, tri Alkylene polyol poly (meth) acrylates such as methylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate; diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate Polyoxyalkylene glycol poly, such as ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane tri (meth) acrylate Meth) acrylates; poly (meth) acrylates such as hydroxypivalic acid neopentyl glycol ester di (meth) acrylate; isocyanurate-type poly (meth) acrylates such as tris [(meth) acryloxyethyl] isocyanurate Can be mentioned.
In addition, in this specification, (meth) acrylate is a term that collectively refers to acrylate, methacrylate, and mixtures thereof, and the same applies to other similar expressions.

In the present invention, it is particularly preferable to contain a bifunctional or higher functional (meth) acrylic monomer as the photopolymerizable monomer. A bifunctional or higher (meth) acrylic monomer is a compound having a plurality of acryloyl groups in the molecule. Specifically, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipenta Examples include erythritol hexa (meth) acrylate. Of these, trimethylolpropane tri (meth) acrylate is preferable.
These can be used alone or in combination of two or more according to the requirements on the properties of the coating film.

  Further, in the active energy ray-curable white resin composition of the present invention, a carboxyl group having no ethylenically unsaturated bond is used together with a compound having a carboxyl group introduced as a photopolymerizable monomer or the above compound having an ethylenically unsaturated bond. Group-containing compounds can be used.

  The blending ratio of the photopolymerizable monomer is preferably 65 to 240 parts by mass, and more preferably 100 to 150 parts by mass with respect to 100 parts by mass of the diallyl phthalate prepolymer. When the blending ratio of the photopolymerizable monomer exceeds 240 parts by mass, the heat resistance is deteriorated. On the other hand, when it is less than 65 parts by mass, it is difficult to form a liquid paste and printability cannot be obtained.

(Photopolymerization initiator)
The photopolymerization initiator used in the present invention is characterized by containing neither a heterocyclic group nor a polycyclic aromatic group. Here, the heterocyclic group is a compound having a ring structure composed of both carbon and other elements, and means both a non-aromatic heterocyclic ring and an aromatic heterocyclic ring. The polycyclic aromatic group represents an aromatic ring formed by condensing three or more rings.

  Examples of the photopolymerization initiator that can be used in the present invention include benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzyl methyl ketone, and the like. Alkyl ethers; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, diethoxyacetophenone, 2,2-diethoxy-2-phenylacetophenone, Acetophenones such as 1,1-dichloroacetophenone and 1-hydroxycyclohexyl phenyl ketone; Ketals such as acetophenone dimethyl ketal and benzyl dimethyl kettle; Benzophenone, 4,4-bismethylaminobenzofe Such as benzophenone such as emissions, and the like. These can be used alone or in admixture of two or more. Further, tertiary amines such as triethanolamine and methyldiethanolamine; 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate and the like Can be used in combination with photopolymerization initiation assistants such as benzoic acid derivatives.

  The proportion of the photopolymerization initiator used is usually a quantitative ratio, and for example, with respect to 100 parts by mass of the total amount of diallyl phthalate prepolymer and photopolymerizable monomer, preferably 0.1 to 20 parts by mass. More preferably, it is 1-10 mass parts. When the blending ratio of this photopolymerization initiator is less than 0.1 parts by mass, it does not cure even when active energy rays are irradiated, or it is necessary to increase the irradiation time. There is no change in curability, which is economically undesirable.

[Titanium oxide]
In the present invention, titanium oxide is used as a white pigment. The titanium oxide may be rutile titanium oxide or anatase titanium oxide, but rutile titanium is preferably used. Anatase-type titanium oxide has a high whiteness compared to rutile-type titanium oxide and is often used as a white pigment. However, anatase-type titanium oxide has photocatalytic activity, and therefore, particularly by light irradiated from an LED, It may cause discoloration of the resin in the insulating resin composition. In contrast, rutile-type titanium oxide is slightly inferior to anatase-type in whiteness, but has almost no photoactivity, so that the resin is deteriorated by light due to the photoactivity of titanium oxide (yellowing). Is remarkably suppressed and is stable against heat. For this reason, when it is used as a white pigment in the insulating layer of the printed wiring board on which the LED is mounted, a high reflectance can be maintained over a long period of time.

  A well-known thing can be used as a rutile type titanium oxide. There are two types of production methods for rutile titanium oxide, a sulfuric acid method and a chlorine method. In the present invention, those produced by any of the production methods can be suitably used. Here, the sulfuric acid method uses ilmenite ore or titanium slag as a raw material, dissolves this in concentrated sulfuric acid, separates iron as iron sulfate, and hydrolyzes the solution to obtain a hydroxide precipitate. A production method in which rutile titanium oxide is taken out by baking at a high temperature. On the other hand, the chlorine method uses synthetic rutile or natural rutile as a raw material, reacts with chlorine gas and carbon at a high temperature of about 1000 ° C to synthesize titanium tetrachloride, and oxidizes this to extract rutile titanium oxide. Say. Among them, rutile-type titanium oxide produced by the chlorine method is particularly effective in suppressing the deterioration (yellowing) of the resin due to heat, and is more preferably used in the present invention.

  Examples of commercially available rutile-type titanium oxides include, for example, Typek R-820, Typek R-830, Typek R-930, Typek R-550, Typek R-630, Typek R-680, Typek R-670, and Typek R. -680, Type R-670, Type R-780, Type R-850, Type CR-50, Type CR-57, Type CR-80, Type CR-90, Type CR-93, Type CR-95, Type CR -97, Type CR-60, Type CR-63, Type CR-67, Type CR-58, Type CR-85, Type UT771 (Ishihara Sangyo Co., Ltd.), Type Pure R-100, Type Pure R-101, Type Pure R -102, Ipure R-103, Taipure R-104, Taipure R-105, Taipure R-108, Taipure R-900, Taipure R-902, Taipure R-960, Taipure R-706, Taipure R-931 (manufactured by DuPont) , R-25, R-21, R-32, R-7E, R-5N, R-61N, R-62N, R-42, R-45M, R-44, R-49S, GTR-100, GTR -300, D-918, TCR-29, TCR-52, FTR-700 (manufactured by Sakai Chemical Industry Co., Ltd.) and the like can be used.

  Among them, the Taipei CR-50, the Taipei CR-57, the Taipei CR-80, the Taipei CR-90, the Taipei CR-93, the Taipei CR-95, the Taipei CR-97, the Taipei CR-60, and the Taipei manufactured by the chlorine method. CR-63, Taipei CR-67, Taipei CR-58, Taipei CR-85, Taipei UT771 (manufactured by Ishihara Sangyo Co., Ltd.), Taipei Pure R-100, Taiwan Pure R-101, Taiwan Pure R-102, Taiwan Pure R-103, Taiwan Pure R-104, Tai Pure R-105, Tai Pure R-108, Tai Pure R-900, Tai Pure R-902, Tai Pure R-960, Tai Pure R-706, Tai Pure R-931 (manufactured by DuPont Co., Ltd.) can be used more preferably. .

  Moreover, as an anatase type titanium oxide, a well-known thing can be used. Commercially available anatase-type titanium oxide includes TITON A-110, TITON TCA-123E, TITON A-190, TITON A-197, TITON SA-1, TITON SA-1L (manufactured by Sakai Chemical Industry Co., Ltd.), TA -100, TA-200, TA-300, TA-400, TA-500, TP-2 (manufactured by Fuji Titanium Industry Co., Ltd.), TITANIX JA-1, TITANIX JA-3, TITANIX JA-4, TITANIX JA-5 , TITANIX JA-C (manufactured by Takeka Co., Ltd.), KA-10, KA-15, KA-20, KA-30 (manufactured by Titanium Industry Co., Ltd.), Type A-100, Type A-220, Type W-10 ( Ishihara Sangyo Co., Ltd.) can be used.

  The blending ratio of titanium oxide is preferably 50 to 200 parts by mass, more preferably 100 to 150 parts by mass with respect to 100 parts by mass of the total amount of the diallyl phthalate prepolymer and the photopolymerizable monomer. If the titanium oxide content exceeds 200 parts by mass, the dispersibility of the titanium oxide is deteriorated and dispersion may be poor. On the other hand, if it is less than 50 parts by mass, the hiding power is small, and it may be difficult to obtain an insulating film having a high reflectance, which is not preferable.

[Other additives]
The active energy ray-curable white resin composition of the present invention may further comprise, as necessary, known and commonly used polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, pyrogallol, phenothiazine, fine silica, organic bentonite, and montmorillonite. Known and commonly used thickeners such as silicone, fluorine and polymer antifoaming agents and / or leveling agents, imidazole, thiazole and triazole silane coupling agents and the like Additives can be blended, and a colorant can be blended as long as the white color of the active energy ray-curable white resin composition of the present invention is not impaired.

[Cured product]
The active energy ray-curable white resin composition of the present invention can obtain a cured coating film by irradiating and curing an active energy ray after coating on a substrate or the like by the following coating method.

  As the irradiation source of the active energy ray, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a metal halide lamp, or the like is suitable. In addition, laser beams, electron beams, and the like can be used as active energy rays.

  As a coating method, any method such as a dip coating method, a flow coating method, a roll coating method, a bar coater method, a screen printing method, and a curtain coating method can be applied.

  The cured coating film obtained using the composition of the present invention has high reflectance and whiteness, and is excellent in light resistance and heat resistance. Here, the whiteness refers to the lightness (L value) and redness (a value) of the Hunter Lab color system using a Minolta spectrophotometer CM-2600d with respect to the test pieces described in the following examples. The yellowness (b value) is obtained, and the whiteness obtained from these values according to the following formula (1).

Whiteness = 100 − [(100−L) ² + a ² + b ² ] ^1/2 (1)
(In the formula, L represents lightness, a represents redness, and b represents yellowness.)
The active energy ray-curable white resin composition according to the present invention is not only suitably used as a solder resist layer in a printed wiring board, but also a component for which a high reflectance is required, for example, a reflection for light emitting elements such as EL and LED It can be used widely as a plate. 1 to 5 show usage examples when the active energy ray-curable white resin composition of the present invention is used for a solder resist layer and a reflector for light emitting elements such as EL and LED.

  1 and 2 are a top view and a cross-sectional view, respectively, of a printed wiring board 13 on which the light emitting element 12 is mounted, and for the light emitting element comprising the active energy ray-curable white resin composition of the present invention as the outermost layer. They are a top view and a cross-sectional view schematically showing a form in which a reflecting plate (11) is formed and the reflecting plate is a white resist having a high reflectance.

  FIG. 3 is a process diagram for explaining another embodiment of the printed wiring board including the light-emitting element reflector made of the active energy ray-curable white resin composition of the present invention.

  That is, a solder resist layer formed on a printed wiring board using a general colored or white solder resist such as green is processed so that a portion corresponding to the light emitting element 12 mounted on the printed wiring board 13 is cut out. (15 in FIG. 3A).

  Further, a plastic or metal sheet-like substrate having a light-emitting element reflector made of the active energy ray-curable white resin composition of the present invention is cut out in a portion corresponding to the light-emitting element 12 in the same manner as the solder resist layer 15. (11 (light emitting element reflector) and 20 (substrate) in FIG. 3A).

  And the board | substrate 20 which has the reflecting plate 11 for light emitting elements is piled up on a printed wiring board. By this step, it appears that the light-emitting element reflector 11 made of an active energy ray-curable white resin composition having a high reflectance is formed in the outermost layer (see FIGS. 3B and 3B). ).

  4 and 5 each show a light-emitting element reflector such as an EL or LED, and a printed wiring board provided with the light-emitting element reflector, formed by the following steps. That is, first, the printed wiring board 13 including the light emitting element reflecting plate 11 (white resist) shown in FIGS. 1 and 2 is formed. Then, the active energy ray-curable white resin composition of the present invention is applied in a specific pattern on a substrate 21 made of a transparent material such as glass, polyethylene terephthalate, or polyethylene naphthalate, thereby creating the light-emitting element reflector 11. . The transparent substrate 21 on which the light emitting element reflecting plate 11 is formed is overlaid on the printed wiring board 13 including the light emitting element reflecting plate 11 (white resist). By the said form, it becomes possible to make uniform illuminance because the light taken out diffuses. Here, in FIG. 5, it goes without saying that the printed wiring board 13 shown in FIG. 3 may be used instead of the printed wiring board 13 shown in FIGS.

  In any of the above forms, the active energy ray-curable white resin composition (cured product) is exposed to light emitted from the light emitting element and heat generation, which are deterioration factors such as yellowing. It becomes. Even in such a situation, the active energy ray-curable white resin composition of the present invention and the cured product thereof can maintain a high reflectance over a long period of time.

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.
Each component was kneaded with a three roll mill according to Table 1, and each active energy ray-curable white resin composition was obtained. The numbers in the table represent parts by mass.

(Preparation of coating film property evaluation board)
Each active energy ray-curable white resin composition was pattern-printed on a copper solid FR-4 substrate by screen printing so that the thickness of the coating film was about 20 μm, and 4 J / mm at a wavelength of 350 nm with a high-pressure mercury lamp. A test piece was obtained by irradiating and curing an integrated light quantity of cm ² . The characteristics of the obtained test piece were evaluated as follows.

(Measurement of initial value)
For each test piece, an initial value of reflectance and an initial value of Hunter whiteness were measured by the following method using a spectrocolorimeter CM-2600d manufactured by Minolta.

  The reflectance was measured at intervals of 10 nm over a wavelength range of 400 nm to 700 nm, and the average reflectance was determined from the average value of the obtained measured values.

  Hunter whiteness (HW) was determined by calculating the brightness (L value), redness (a value) and yellowness (b value) of the Hunter Lab color system, and using these values, the following equation (1) was obtained.

HW = 100 − [(100−L) ² + a ² + b ² ] ^1/2 (1)
(In the formula, L represents lightness, a represents redness, and b represents yellowness.)
(Light resistance evaluation method)
Each test piece was accelerated and deteriorated by irradiating 150 J / cm ² of light with a UV conveyor furnace (output 120 W / cm, metal halide lamp, cold mirror), and then using a Minolta spectrophotometer CM-2600d as described above. Each numerical value was measured by the method. Light resistance was evaluated by the difference between the initial value in the average reflectance of 400 to 700 nm and the value after light irradiation, and the difference between the initial value in Hunter whiteness and the value after light irradiation.

The criteria for determining the reflectance are as follows.
A: The initial value is 80% or more, and the difference from the initial value is less than 2.0.
X: The initial value is less than 80%. Alternatively, the difference from the initial value is 2.0 or more.
The criteria for determining the Hunter whiteness are as follows.
○: The initial value is 90 or more, and the difference from the initial value is less than 2.0.
X: The initial value is less than 90. Alternatively, the difference from the initial value is 2.0 or more.
The results are shown in Table 2-1.

(Heat resistance evaluation method)
Each specimen was allowed to stand for 50 hours in a 150 ° C. hot air lubrication drying oven and accelerated to deteriorate, and then each numerical value was measured by the same method as described above using a Minolta spectrophotometer CM-2600d. The heat resistance was evaluated by the difference between the initial value in the average reflectance of 400 to 700 nm and the value after heat treatment, and the difference between the initial value in Hunter whiteness and the value after heat treatment.

The criteria for determining the reflectance are as follows.
A: The initial value is 80% or more, and the difference from the initial value is less than 4.0.
X: The initial value is less than 80%. Alternatively, the difference from the initial value is 4.0 or more.
The criteria for determining the Hunter whiteness are as follows.
A: The initial value is 90 or more, and the difference from the initial value is less than 4.0.
X: The initial value is less than 90. Alternatively, the difference from the initial value is 4.0 or more.

The results are shown in Table 2-2.

  As is clear from the results shown in Tables 2-1 and 2-2, the active energy ray-curable white resin composition of the present invention contains an aromatic ring in the molecule even after accelerated deterioration by light and heat. Compared with the case where a compound, for example, a bisphenol type epoxy acrylate is used, the present invention is remarkably improved in light resistance and heat resistance.

11: Reflective plate for light-emitting element comprising the active energy ray-curable white resin composition of the present invention 12: Light-emitting element 13: Printed wiring board 14: Cut-out portion 15: Solder resist 20, 21: Substrate

Claims (8)

An active energy ray-curable white resin composition containing a diallyl phthalate-based prepolymer, a photopolymerizable monomer, a photopolymerization initiator containing neither a heterocyclic group nor a polycyclic aromatic group, and rutile titanium oxide.   2. The active energy ray-curable white resin composition according to claim 1, wherein the diallyl phthalate-based prepolymer includes one or both selected from a diallyl orthophthalate prepolymer and a diallyl isophthalate prepolymer. object.   2. The active energy ray-curable white resin composition according to claim 1, wherein the diallyl phthalate-based prepolymer has a weight average molecular weight of 20,000 to 60,000. The active energy ray-curable white resin composition according to any one of claims 1 to 3, wherein the photopolymerizable monomer contains a bifunctional or higher functional acrylic monomer or methacrylic monomer, or a mixture thereof. The active energy ray-curable white resin composition according to any one of claims 1 to 4 , wherein a cured product obtained by curing the composition has an average reflectance of 80 to light having a wavelength of 400 to 700 nm. %, And the difference between the average reflectance for light having a wavelength of 400 to 700 nm after irradiating the cured product with light having a wavelength of 350 nm so that the integrated light amount is 150 J / cm ² is less than 2.0. An active energy ray-curable white resin composition characterized by the above. The active energy ray-curable white resin composition according to any one of claims 1 to 5 , wherein the Hunter whiteness (1) represented by the formula (1) of a cured product obtained by curing the composition is provided. The initial value of (HW) is 90 or higher, and the cured product is irradiated with light having a wavelength of 350 nm so that the integrated light quantity is 150 J / cm ^2. The active energy ray-curable white resin composition is characterized by having a difference of less than 2.0.
HW = 100 − [(100−L) ² + a ² + b ² ] ^1/2 (1)
(In the formula, L represents lightness, a represents redness, and b represents yellowness.) Hardened | cured material formed using the active energy ray curable white resin composition of any one of Claims 1-6 . The printed wiring board which has an insulating layer which consists of hardened | cured material of the active energy ray curable white resin composition of any one of Claims 1-6 .

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