JP2008081514A - Epoxy resin-based composition and epoxy resin-based thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin-based thin film having a high glass transition temperature (Tg) and excellent heat yellowing resistance and to provide an epoxy resin-based composition capable of forming the thin film. <P>SOLUTION: The epoxy resin-based composition comprises an epoxy resin, an acid anhydride-based curing agent and a compound represented by general formula (1) [wherein, R<SP>1</SP>to R<SP>4</SP>are each same or different and represent each a phenyl group, a 1-16C linear or branched chain alkyl group or a 5-12C cycloalkyl group; and X represents an anion residue of a 10-16C aliphatic monocarboxylic acid]. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thin film encapsulant for semiconductor packages and light emitting elements, an epoxy resin composition used for forming a surface coating of a display device such as a liquid crystal display device, and an epoxy resin obtained by curing the composition. The present invention relates to a light-emitting element sealed with a thin film, a method for forming an epoxy resin thin film, and a method for preventing yellowing of an epoxy resin thin film.

  In recent years, semiconductor devices (transistors, field effect transistors (FETs), thyristors (SCRs), diodes (rectifiers), light, etc., as represented by the development of portable electronic devices such as mobile phones, digital cameras, and notebook computers. Electronic components such as semiconductors (photocouplers, light emitting diodes (LEDs), photointerrupters, etc.) tend to be smaller and thinner with higher density and higher integration. As a technique that can be highly integrated without taking up a mounting area, BGA (ball grid array), CSP (chip size package), COG (chip on glass), COB (chip on board), Methods such as MCM (multi-chip module) and LGA (land grid array) have been developed. . The chip type capable of surface mounting with regard LED light semiconductor has been developed.

  Since these semiconductor elements generate a large amount of heat, the resin encapsulant has not only workability, electrical properties of cured products, mechanical properties, adhesiveness, water resistance, solvent resistance, but also heat resistance. In general, a liquid epoxy resin is used.

  As a curing agent for such a liquid epoxy resin, it is excellent in workability because of its low viscosity, and can be blended with a large amount of fillers, and also has excellent electrical characteristics, mechanical characteristics, and heat resistance. A lot of things are used. The type is appropriately selected according to the application. For example, as an acid anhydride curing agent for an epoxy resin encapsulant of a semiconductor package, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, methylnorbornene-2,3-dicarboxylic anhydride, Trialkyltetrahydrophthalic anhydride and the like are used. In addition, since chip-type LEDs and optical semiconductor encapsulants are required to be transparent, acid anhydrides having no double bonds such as methylhexahydrophthalic anhydride and hexahydrophthalic anhydride are used. .

  The sealing material is usually applied in a thin film (for example, 2 mm or less) or potted by a dispenser method, an atmospheric pressure screen printing method or a vacuum screen printing method after an element is mounted on a substrate on a bare chip. The gap between the semiconductor element and the substrate is impregnated. Further, usually, after being stored for a predetermined period, curing is performed in a curing furnace.

  However, when a liquid epoxy resin composition using a conventional acid anhydride curing agent is cured to form a thin film, there are problems such as a decrease in the glass transition temperature (Tg) of the cured product and occurrence of cracks. In addition, when colorless transparency is required, yellowing under high temperature and high energy light irradiation conditions (hereinafter referred to as “yellowing” or “thermal yellowing”) becomes a problem. Therefore, the applications that can use epoxy resin thin films with acid anhydride curing agents are limited to applications that do not affect yellowing or thermal yellowing (red LEDs, etc.), and yellowing or thermal yellowing is quality. It was difficult to use for applications that affect the color (such as blue and white LEDs).

  In order to solve these problems, methylnorbornane-2,3-dicarboxylic acid anhydride, or methylnorbornane-2,3-dicarboxylic acid anhydride and norbornane-2,3-dicarboxylic acid in which the amount of impurities is a specific amount or less is used. An epoxy resin-based composition using a mixture of acid anhydrides as a curing agent has been proposed (Patent Document 1). However, because this epoxy resin composition is an imidazole curing accelerator, initial transparency (that is, the yellow index value after curing is low and colorless and transparent) and heat yellowing (that is, the above-mentioned) Further improvement is required in terms of the property of suppressing yellowing or thermal yellowing.

  On the other hand, DBU (1,8-diazabicyclo (5.4.0) undecene-7) type curing accelerators and ammonium salt-based curing accelerators are widely used for LED applications and the like because of their good curability. However, cured epoxy resins using these curing accelerators are relatively excellent in initial colorless transparency, but have a drawback of poor heat-resistant yellowing (see Comparative Examples 9 and 10 described later).

  Patent Document 2 discloses that a liquid epoxy resin composition containing an acid anhydride as a curing agent and tetrabutylphosphonium octate as a curing accelerator is excellent in transparency when used as a sealing material. Yes. However, a cured product (particularly a thin film) obtained using this composition has a small decrease in Tg, but is not necessarily satisfactory in terms of heat-resistant yellowing (see Comparative Example 1 described later).

  Patent Document 3 discloses that an epoxy resin composition for encapsulating an optical semiconductor containing an acid anhydride as a curing agent and a tetraalkylphosphonium carboxylate as a curing accelerator is excellent in colorless transparency. Acetate is exemplified as a preferred carboxylate. However, a cured product (especially a thin film) obtained using this acetate salt as an epoxy resin curing accelerator has a small decrease in Tg, but is not necessarily satisfactory in improving heat-resistant yellowing (Comparative Example 2 described later). reference).

  Patent Document 4 discloses that an epoxy resin composition for a laminated board containing an acid anhydride as a curing agent and a quaternary phosphonium salt as a curing accelerator has a high curing rate and excellent moldability. Among the quaternary phosphonium salts, examples of the aliphatic monocarboxylate include acetate, propionate and stearate. However, cured products obtained by using these acetates and propionates as curing accelerators for epoxy resins, particularly thin films, have little decrease in Tg, but heat yellowing is not always satisfactory (Comparative Example 2 described later). On the other hand, a cured product obtained using stearate as an epoxy resin curing accelerator, particularly a thin film, has good heat yellowing resistance, but has a large decrease in Tg (see Comparative Example 6 described later), Both require further improvement.

Patent Document 5 discloses that a quaternary phosphonium carboxylate containing a carboxylic acid having 8 to 18 carbon atoms is useful as an epoxy resin curing agent, curing accelerator, flame retardant and the like. However, this document only discloses these carboxylates themselves and the production method thereof, and does not describe a blend with an epoxy resin.
JP 2003-2951 A (refer to claim 1 etc.) JP-A-7-196774 (refer to claim 1 etc.) Japanese Patent Laying-Open No. 2005-325178 (see paragraph 0021) Japanese Patent Laid-Open No. 11-158251 (see paragraph 0015, etc.) Japanese Patent Laid-Open No. 62-87595 (see claim 1, table 1)

  The main object of the present invention is to provide an epoxy resin thin film having a high glass transition temperature (Tg) and excellent heat-resistant yellowing, and an epoxy resin composition capable of forming such a thin film.

  The present inventors have repeatedly studied to solve the above-mentioned problems, and have obtained the following knowledge.

  (i) Thin film formation with an epoxy resin composition is usually carried out at a high temperature. However, since the acid anhydride of the curing agent volatilizes at a high temperature, poor curing occurs and the glass transition temperature (Tg) of the cured product is lowered. In order to provide practically sufficient deterioration resistance and moisture resistance, the thin film needs to have a high Tg. When the amount of the curing accelerator used is increased in order to obtain a high Tg, the thin film is easily yellowed by heat during use. For example, when it is used as a coating film on the display surface or when it is used as a thin film encapsulant for a white light emitting element, it is important that it does not turn yellow during use. However, at present, an epoxy resin thin film having a high Tg and excellent heat-resistant yellowing has not been obtained.

  (ii) an epoxy resin, an acid anhydride curing agent, and the following general formula (1)

[Wherein R ^{1 to} R ⁴ are the same or different and each represents a phenyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, X represents an anion residue of an aliphatic monocarboxylic acid having 10 to 16 carbon atoms. ]
The epoxy resin-based composition containing the compound represented by the formula (1) has a high Tg and is excellent in heat-resistant yellowing even when a thin film having a thickness of 1 mm or less, particularly 0.4 mm or less is formed. .

  The present invention has been completed based on the above findings, and provides the following epoxy resin-based compositions and the like.

Item 1 (a) epoxy resin,
(b) an acid anhydride curing agent, and
(c) The following general formula (1)

[Wherein R ^{1 to} R ⁴ are the same or different and each represents a phenyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, X represents an anion residue of an aliphatic monocarboxylic acid having 10 to 16 carbon atoms. ]
An epoxy resin composition comprising a compound represented by:

  Item 2 The composition according to Item 1, wherein the content of the compound represented by General Formula (1) is 0.1 to 5 parts by weight with respect to 100 parts by weight of the epoxy resin.

Item 3 The composition according to Item 1 or 2, wherein, in General Formula (1), R ^{1 to} R ⁴ represent a linear or branched alkyl group having 1 to ⁴ carbon atoms.

  Item 4 Any one of Items 1 to 3, wherein in General Formula (1), X is an anion residue of at least one aliphatic monocarboxylic acid selected from the group consisting of decanoic acid, lauric acid, myristic acid and palmitic acid. A composition according to 1.

Item 5 The composition according to any one of Items 1 to 4, wherein in the general formula (1), all of R ^{1 to} R ⁴ are butyl groups.

  Item 6 The epoxy resin is bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, naphthalenediol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, and hydrogenated bisphenol A diglycidyl. Item 6. The composition according to any one of Items 1 to 5, which is at least one selected from the group consisting of ethers.

  Item 7 The acid anhydride-based curing agent is at least one selected from the group consisting of 3-methylhexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride. Composition.

  Item 8: The above item, wherein the content of the acid anhydride curing agent is such that the equivalent ratio of the acid anhydride group in the acid anhydride curing agent to the epoxy group in the epoxy resin is 0.9 to 1.2. The composition in any one of 1-7.

  Item 9 (a) an epoxy resin, and (b) at least one acid anhydride curing agent selected from the group consisting of 3-methylhexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride, c) at least one compound selected from the group consisting of tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, tetrabutylphosphonium myristate and tetrabutylphosphonium palmitate, an acid anhydride curing agent An epoxy resin composition in which the content ratio of the acid anhydride group in the acid anhydride curing agent with respect to the epoxy group in the epoxy resin is 1 to 1.1.

  Item 10 A method for preventing yellowing of an epoxy resin-based thin film, wherein the epoxy resin-based thin film is represented by the following general formula (1)

[Wherein R ^{1 to} R ⁴ are the same or different and each represents a phenyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, X represents an anion residue of an aliphatic monocarboxylic acid having 10 to 16 carbon atoms. ]
The method using the compound represented by these.

  Item 11: Forming an epoxy resin thin film, wherein the composition according to any one of Items 1 to 9 is applied on a substrate, and the coating film is cured to form a thin film having a thickness of 1 mm or less. Method.

  Item 12 A thin film having a thickness of 1 mm or less obtained by curing the composition according to any one of Items 1 to 9.

  Item 13 The thin film according to Item 12, wherein the thin film is a sealing material for a light emitting device.

  Item 14. The thin film according to Item 12, wherein the thin film is a display coating material.

  Item 15 A light emitting device encapsulated with the thin film according to Item 12.

  The composition of the present invention is a composition containing an epoxy resin, an acid anhydride curing agent, and a curing accelerator, and the curing accelerator contains a compound represented by the above general formula (1). Thereby, the thin film obtained by curing this composition is excellent in initial transparency, hardly yellowed by heat, and has a high Tg.

  A sealing film of a light emitting element and a hard coating film of a display device are required to be hardly yellowed by heat generated from a light emitting element, a liquid crystal backlight, plasma emission, or the like. The thin film formed by curing the epoxy resin composition of the present invention can be suitably used for such applications. For example, white light-emitting diodes require that the encapsulant be non-yellowing in order to maintain clear white light, so thin-film sealing using a conventional epoxy resin-based composition that tends to yellow could not. According to the present invention, a white light emitting diode sealed with a thin film of an epoxy resin composition was realized.

  The epoxy resin composition of the present invention is easy to use because it has less odor than conventional epoxy resin compositions using curing accelerators. Moreover, since the compound represented by the general formula (1) is easily dissolved in an acid anhydride curing agent even at a low temperature, the epoxy resin composition can be easily prepared and stored at a low temperature.

  Hereinafter, the present invention will be described in detail.

  The epoxy resin composition of the present invention is basically a composition containing an epoxy resin, an acid anhydride curing agent, and a compound represented by the above general formula (1).

As the epoxy resin epoxy resin, a known epoxy resin can be used without limitation. In particular, a liquid epoxy resin containing two or more epoxy groups in the molecule is preferable. For example, bisphenol A diglycidyl ether, diglycidyl ether of bisphenol A ethylene oxide adduct, diglycidyl ether of bisphenol A propylene oxide adduct, Glycidyl ether type epoxy resins such as bisphenol F diglycidyl ether, bisphenol AD diglycidyl ether, naphthalenediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of hydrogenated bisphenol F Glycidyl ester type epoxy resin such as hexahydrophthalic acid diglycidyl ester; 3,4-epoxycyclohexylmethyl- ', 4'-epoxycyclohexane carboxylate, and alicyclic epoxy resins such as vinylcyclohexene diepoxide is.

  Among these, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, naphthalene diol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexanecarboxylate, and hydrogenated bisphenol A diglycidyl ether Bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, and hydrogenated bisphenol A diglycidyl ether are more preferred. By using these epoxy resins, a low-viscosity epoxy resin composition can be obtained, and good workability can be obtained.

  An epoxy resin can be used individually or in mixture of 2 or more types.

As the acid anhydride-based curing agent , a known acid anhydride-based curing agent can be used without limitation. For example, hexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, 1-methylnorbornane-2,3-dicarboxylic anhydride, 5-methylnorbornane-2, 3-dicarboxylic acid anhydride, norbornane-2,3-dicarboxylic acid anhydride, 1-methylnadic acid anhydride, 5-methylnadic acid anhydride, nadic acid anhydride, phthalic acid anhydride, tetrahydrophthalic acid anhydride, Examples include 3-methyltetrahydrophthalic anhydride, 4-methyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, and the like.

  Among them, hexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, which are acid anhydrides that do not have a double bond in the compound and hardly volatilize, 1- Methylnorbornane-2,3-dicarboxylic acid anhydride, 5-methylnorbornane-2,3-dicarboxylic acid anhydride, norbornane-2,3-dicarboxylic acid anhydride are preferable, and 3-methylhexahydrophthalic acid anhydride, 4 -More preferred is methylhexahydrophthalic anhydride. By using a compound which does not have a double bond and hardly volatilizes, an epoxy resin composition having a high Tg and further excellent in initial transparency and heat-resistant yellowing can be obtained.

  An acid anhydride type hardening | curing agent can be used individually by 1 type or in combination of 2 or more types.

  The content of the acid anhydride curing agent is preferably such that the equivalent ratio of the acid anhydride group in the acid anhydride curing agent to the epoxy group in the epoxy resin is about 0.9 to 1.2, An amount of about 1.1 is more preferable. If it is the said range, hardening reaction will fully advance. Moreover, if it is the said range, the hardened | cured material which is excellent in transparency and heat-resistant yellowing will be obtained.

Curing accelerator The epoxy resin composition of the present invention has the following general formula (1):

[Wherein R ^{1 to} R ⁴ are the same or different and each represents a phenyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, X ⁻ represents an anion residue of an aliphatic monocarboxylic acid having 10 to 16 carbon atoms, particularly a saturated aliphatic monocarboxylic acid. ]
Is included as a curing accelerator.

  The compound represented by General formula (1) can be used individually by 1 type or in combination of 2 or more types.

  In the epoxy resin composition of the present invention, since the curing accelerator is a compound represented by the above general formula (1), the curing agent is hardly volatilized and cured even when it is cured at a high temperature to form a thin film. A cured product having a high Tg is obtained sufficiently. Further, the cured product of this composition is excellent in initial transparency and excellent in heat-resistant yellowing.

  Further, the compound represented by the general formula (1) is more preferable than the compound in which X is an anion residue of an aliphatic monocarboxylic acid having a smaller carbon number in the general formula (1). In addition, the odor is low and the solubility at room temperature is better than that of a compound in which X is an anion residue of an aliphatic monocarboxylic acid having a larger carbon number, and it is easy to use.

In the general formula (1), R ^{1 to} R ⁴ are preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and more preferably a butyl group.

  The compound of the general formula (1) is excellent in heat yellowing resistance, has no odor, and has excellent solubility in an acid anhydride because X is an aliphatic monocarboxylic acid anion having 10 to 16 carbon atoms. ing. The organic acid anion represented by X is, in particular, a linear decanoate anion (carbon number 10), a linear laurate anion (carbon number 12), a linear myristic acid anion (carbon number 14). It is preferably a linear palmitate anion (16 carbon atoms), more preferably a linear decanoate anion (10 carbon atoms) or a linear laurate anion (12 carbon atoms). .

  About 0.1-5 weight part is preferable with respect to 100 weight part of epoxy resins, and, as for content of the compound represented by General formula (1), about 0.5-2 weight part is more preferable. If it is the said range, sufficient hardening speed will be obtained and the hardened | cured material which is excellent in initial transparency and heat-resistant yellowing will be obtained.

Other Components The epoxy resin composition of the present invention may contain known additives that are added to the epoxy resin composition. Examples of such known additives include antioxidants such as phenolic antioxidants and amine antioxidants, ultraviolet absorbers such as benzophenone ultraviolet absorbers, and light stabilizers such as hindered amine light stabilizers. And release agents such as hydrocarbon lubricants and higher fatty acid lubricants. Moreover, resin other than an epoxy resin can also be included.

  When using additional components, such as said additive and resin, those content should just be taken as the range which does not impair the effect of this invention, for example, the sum total of an epoxy resin, a hardening | curing agent, and a hardening accelerator is 100. If it is the range of 10 weight part or less with respect to a weight part, it may be contained.

Epoxy resin composition The epoxy resin composition of the present invention can be prepared by mixing the components described above. As a preferred preparation method, a curing agent and a curing accelerator are stirred and mixed at a temperature of about 20 to 80 ° C., an epoxy resin is added to the obtained homogeneous mixture, and the mixture is uniformly stirred at a temperature of about 20 to 80 ° C., The method of mixing can be mentioned.

  Each component of the epoxy resin, the curing agent, and the curing accelerator may be added at once, or may be added little by little in several times. Other components such as antioxidants, UV absorbers, light stabilizers, mold release agents, and resins other than epoxy resins are added before curing of epoxy resin before addition of epoxy resin when mixing curing agent and curing accelerator. It can be added and mixed at any time, such as at or after.

  The above-described epoxy resin-based composition of the present invention has a high Tg and a cured product excellent in initial transparency and heat-resistant yellowing even when cured at a relatively high temperature. Therefore, it is particularly suitable for forming a thin film that needs to be cured at a relatively high temperature.

Epoxy resin-based thin film A thin film, particularly a thin film having a thickness of 1 mm or less, can be formed by applying the above-described epoxy resin-based composition of the present invention on a substrate and curing the coating film, for example. The thickness of the thin film is preferably about 0.4 mm or less. The lower limit of the thickness of the thin film is usually about 0.01 mm.

  Although it does not specifically limit as a base | substrate, For example, glass, a ceramic, aluminum, CCL (copper clad laminated board), a heat resistant polymer film, etc. are mentioned.

  As a method for applying the epoxy resin-based composition of the present invention onto a substrate, a conventionally known method can be employed without any particular limitation. For example, screen printing, die coater, comma coater, roll coater, bar coater, gravure, etc. Known methods such as a coater curtain coater, a spray coater, an air knife coater, a reverse coater, and a dip squeeze coater can be exemplified.

  The method for curing the coating film is not particularly limited, and a known method can be employed. For the curing, a conventionally known curing apparatus such as a closed curing furnace or a tunnel furnace capable of continuous curing can be used. Heating can be performed by a conventionally known method such as hot air circulation, infrared heating, and high frequency heating.

  The curing temperature and curing time can be about 80 to 250 ° C. and about 30 seconds to 15 hours. To reduce the internal stress of the cured product, after pre-curing at about 80 ° C. to 130 ° C. for about 0.5 hours to about 5 hours, then at about 130 to 180 ° C. for about 0.1 hours to about 15 hours It is preferable to perform post-curing. When aiming at short-time curing, curing is preferably performed at about 150 to 250 ° C. for about 30 seconds to 30 minutes.

  In particular, when forming a thin film of about 0.01 to 1 mm, particularly about 0.01 to 0.4 mm, the curing temperature and the curing time are about 100 ° C. to 130 ° C. and about 0.5 to 2 hours. After curing, post-curing is preferably performed at about 130 ° C. to 180 ° C. for about 0.5 to 5 hours.

  In addition, the epoxy resin-type composition of this invention can also be used as a material for forming thick film hardened | cured material other than thin film hardened | cured material. For example, when the composition of the present invention is used as a sealing material, it can be sealed by a known method such as a casting method, a potting method, a dipping method, an underfill method, or a printing method. For example, a thick film cured product such as a bullet-type LED encapsulant can be obtained by pouring the epoxy resin composition into a bullet mold and curing it by the above method.

  Further, for example, a thin film such as a surface mount type LED sealing material can be obtained by applying by a method such as screen printing or a dispenser method and curing by the above method.

  For example, when forming a surface coating material, it can be obtained by applying the epoxy resin composition of the present invention to a substrate by the above method and then curing it by the above method. The thickness of the surface coating material thus obtained is also preferably about 0.01 to 1 mm, particularly about 0.01 to 0.4 mm.

  The thin film cured product obtained by curing the epoxy resin composition of the present invention has a high Tg, excellent initial transparency, and excellent heat yellowing. This thin film cured product has a very slight degree of yellowing even after giving a heat history at a high temperature of, for example, 150 ° C. for 5 days (see Examples described later).

  For this reason, it is particularly suitable as an insulating sealing material of the surface mounting type, and BGA (ball grid array), CSP (chip size package), COG (chip on glass), COB (chip on glass). Board), MCM (multi-chip module) or LGA (land grid array) or other surface mounting type semiconductor device sealing material, chip type LED or other light emitting element or optical semiconductor sealing material It can be used in a wide range of industrial fields including insulating materials such as the above.

  In particular, since it is important that the sealing material of the light emitting element is not easily yellowed by heat generated from the light emitting element itself, the composition of the present invention can be suitably used as a thin film sealing material of the light emitting element.

  The light emitting element sealed with the epoxy resin thin film obtained by curing the epoxy resin composition of the present invention maintains the initial color tone even after long-term use. In particular, the white light emitting device encapsulated with the thin film of the present invention is useful in that transparent white light is maintained even after long-term use.

  Moreover, since this thin film is excellent in transparency and heat-resistant yellowing, it can be suitably used as a transparent hard coating material for various glass substrates, automobile parts, display devices such as liquid crystal display devices and plasma displays. In particular, since it is important that the liquid crystal display device is not easily yellowed by the high heat of the backlight, the composition of the present invention can be suitably used as a coating material for the liquid crystal display device. Thus, the thin film of the present invention is also useful as a coating material for displays.

  In the present invention, as described above, yellowing of the epoxy resin thin film can be suppressed or prevented. Accordingly, the present invention prevents yellowing of an epoxy resin thin film characterized by using a compound represented by the above general formula (1) as an epoxy resin curing accelerator when producing an epoxy resin thin film. It also provides a way to do that.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Test Examples, but the present invention is not limited thereto.

Physical property evaluation method
<Yellow Index (YI)>
In this example, the yellow index before heat treatment of each cured film (hereinafter referred to as “YI”) and the YI after heat treatment at 150 ° C. for 5 days were measured, and the difference between them was taken as ΔYI. YI indicates the yellowness of the cured film. The smaller this value, the better the colorless transparency, and the yellowness increases as the value increases. ΔYI indicates the degree of yellowing when subjected to heat history, that is, heat yellowing, and the smaller this value, the better the heat yellowing of the cured film. In the present invention, YI is a value calculated by measuring reflectance using a spectrocolorimeter in accordance with ASTM D1925.

  Specifically, a liquid epoxy resin composition as a test sample is poured into a metal dish with a diameter of 68 mm on which an aluminum foil is laid so that the thickness after curing is 5 mm, 1 mm, and 0.4 mm, and 120 The composition was cured at 1 ° C. for 1 hour and further at 150 ° C. for 3 hours. With respect to this disk-like cured product, the reflectance was measured using a spectrocolorimeter (manufactured by Minolta, CM-3500d) with the aluminum foil adhered to one side. YI was calculated from the reflectance according to ASTM D1925.

<Glass transition temperature (Tg)>
The glass transition temperature of a disk-shaped cured product having a thickness of 5 mm and 0.4 mm prepared by the method described in the section of yellow index (YI) is measured using a DSC method at a heating rate of 20 ° C./min. did.

  As the value of Tg is larger, deterioration, particularly deterioration due to heat is suppressed, and a film having excellent moisture resistance is obtained.

<Film thickness>
The film thickness after curing was measured using a coolant proof micrometer (manufactured by Mitutoyo Corporation).

<Odor test>
Ten panelists compared and evaluated the odor of the epoxy resin composition before curing with the case where no curing accelerator was blended. The evaluation criteria are as follows:
○: It is determined that everyone does not feel odor ×: It is determined that 5 or more people feel odor
Example 1
Curing agent Rikacid MH-T (manufactured by Shin Nippon Rika Co., Ltd .; the main component is 4-methylhexahydrophthalic anhydride) (acid anhydride equivalent 168) 99.9 parts by weight (based on the epoxy group in the epoxy resin) Then, 1 part by weight of tetrabutylphosphonium decanoate as a curing accelerator is added to the amount in which the equivalent ratio of acid anhydride groups in the curing agent becomes 1.1), heated at 60 ° C. for 30 minutes, and further stirred and dissolved. Then, it cooled to room temperature and obtained the transparent liquid hardening | curing agent liquid at normal temperature. To this was added 100 parts by weight of epoxy resin bisphenol A glycidyl ether (Etototo YD-128, Epoxy Equivalent 185, manufactured by Tohto Kasei Co., Ltd.). I got a thing.

Example 2
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium laurate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Example 3
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium myristate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Example 4
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium palmitate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 1
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium octanoate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 2
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium acetate was used instead of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 3
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium heptanoate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 4
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium 2-ethylhexanoate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 5
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium 3,5,5-trimethylhexanoate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 6
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium stearate was used in place of the curing accelerator tetrabutylphosphonium decanoate.

Comparative Example 7
The amount of Rikacid MH-T used was changed to 90.8 parts by weight (an amount in which the equivalent ratio of the acid anhydride group in the curing agent to the epoxy group in the epoxy resin was 1.0). An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylphosphonium bromide was used instead of tetrabutylphosphonium decanoate.

  In Comparative Example 7, the amount of Ricacid MH-T used was changed to 90.8 parts by weight (an amount in which the equivalent ratio of the acid anhydride group in the curing agent to the epoxy group in the epoxy resin was 1.0). The reason for this is that preliminary experiments confirmed that the amount of Tg was the highest and the transparency was good for this amount. When the amount of Rikacid MH-T used is the same amount as in Example 1 (the amount at which the equivalent ratio is 1.1), Tg and transparency are inferior compared to Comparative Example 7.

  In Tables 1 to 3, tetrabutylphosphonium bromide is abbreviated as “TBP bromide”.

Comparative Example 8
Changed to Ricacid MH-T 81.7 parts by weight (amount in which the equivalent ratio of acid anhydride groups in the curing agent to the epoxy groups in the epoxy resin is 0.9), tetrabutylphosphonium decanoic acid as a curing accelerator An epoxy resin composition was obtained in the same manner as in Example 1 except that tetraphenylphosphonium bromide was used instead of the salt.

  In Comparative Example 8, the amount of Ricacid MH-T used was changed to 81.7 parts by weight (the amount by which the equivalent ratio of acid anhydride groups in the curing agent to the epoxy groups in the epoxy resin was 0.9). The reason for this is that preliminary experiments confirmed that the amount of Tg was the highest and the transparency was good for this amount. When the amount of Rikacid MH-T used is the same amount as in Example 1 (the amount at which the equivalent ratio is 1.1), Tg and transparency are inferior compared to Comparative Example 8.

  In Tables 1 to 3, tetraphenylphosphonium bromide is abbreviated as “TPP-PB”.

Comparative Example 9
Implemented except that 1,8-diazabicyclo (5.4.0) undecen-7.octylate (U-CAT SA102, manufactured by San Apro) was used in place of the curing accelerator tetrabutylphosphonium decanoate. In the same manner as in Example 1, an epoxy resin composition was obtained. In Tables 1 to 3, 1,8-diazabicyclo (5.4.0) undecene-7.octylate is abbreviated as “DBU octylate”.

Comparative Example 10
An epoxy resin composition was obtained in the same manner as in Example 1 except that tetrabutylammonium bromide was used in place of the curing accelerator tetrabutylphosphonium decanoate.

  For the epoxy resin compositions of Examples 1 to 4 and Comparative Examples 1 to 10, the Tg of the cured product (5 mm thickness, 0.4 mm thickness), the yellow index immediately after curing (5 mm thickness, 1 mm thickness, 0.4 mm thickness) The yellow index (5 mm thickness, 1 mm thickness, 0.4 mm thickness) after heat treatment (aging) at 150 ° C. for 5 days and the odor of the epoxy resin composition were evaluated.

  The results are shown in Tables 1-3. In Tables 1 to 3, “TBP” refers to “tetrabutylphosphonium”.

  From the results shown in Tables 1 to 3, the following can be understood.

  (a) In a thin film having a thickness of 0.4 mm, if YI after heat treatment is 5 or less and ΔYI before and after heat treatment is 5 or less, yellowing does not occur due to heat generation of the light emitting element or the liquid crystal backlight. It can also be used for applications.

  In this regard, Comparative Examples 1-7, 9-10 have a YI after heat treatment greater than 5, and Comparative Examples 1-5, 7, 9-10 have a ΔYI before and after the heat treatment greater than 5, which is the point of thermal yellowing. It is difficult to use for the above purposes. On the other hand, the epoxy resin composition of Examples 1 to 4 in which the curing accelerator is an aliphatic monocarboxylate of tetrabutylphosphonium having 10 to 16 carbon atoms has a YI and ΔYI after heat treatment in the above range. It can be seen that a practical thin film can be formed.

  (b) Further, the higher the Tg, the more the deterioration, particularly the deterioration due to heat, is suppressed, and the film has excellent moisture resistance. When used as a thin film encapsulant or a coating material for a display device, it is difficult to be thermally deteriorated and moisture resistance is important. The Tg of a 0.4 mm-thick film is 140 ° C. or higher, and If the Tg difference (Tg difference) of the 0.4 mm thick film is smaller than 10 ° C., it can be used for these applications.

  In this respect, Comparative Examples 6 and 8 have a Tg lower than 140 ° C. and a Tg difference of 10 ° C. or more, and are difficult to use in the above applications from the viewpoint of heat resistance. On the other hand, the epoxy resin composition of Examples 1 to 4 in which the curing accelerator is an aliphatic monocarboxylate having 10 to 16 carbon atoms of tetrabutylphosphonium has a Tg of 0.4 mm thick cured film and It can be seen that the Tg difference is in the above range and a practical thin film can be formed.

  (c) Although the epoxy resin compositions obtained in Comparative Examples 1 to 5 and 9 have odor, the epoxy resin compositions of Examples 1 to 4 have no odor and are easy to prepare.

  The thin film obtained by curing the epoxy resin composition of the present invention has a high Tg, excellent initial transparency, and a slight degree of yellowing even after giving a thermal history at a high temperature. Since it has such excellent performance, it can be used in a wide range of industrial fields. It is particularly suitable as a surface mount type insulation sealing material, and is BGA (ball grid array), CSP (chip size package), COG (chip on glass), COB (chip on board), Suitable for use as an insulating material such as a sealing material for surface mount type semiconductor devices such as MCM (multi-chip module) or LGA (land grid array), or a sealing material for chip type LEDs or optical semiconductors. it can.

  The cured thin film can also be suitably used as a transparent hard coating material for various glass substrates, automobile parts, display devices and the like.

Claims (15)

(a) epoxy resin,
(b) an acid anhydride curing agent, and
(c) The following general formula (1)

[Wherein R ^{1 to} R ⁴ are the same or different and each represents a phenyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, X represents an anion residue of an aliphatic monocarboxylic acid having 10 to 16 carbon atoms. ]
An epoxy resin composition comprising a compound represented by:   The composition according to claim 1, wherein the content of the compound represented by the general formula (1) is 0.1 to 5 parts by weight with respect to 100 parts by weight of the epoxy resin. The composition according to claim 1 or 2, wherein in the general formula (1), R ^{1 to} R ⁴ represent a linear or branched alkyl group having 1 to ⁴ carbon atoms.   The general formula (1), wherein X is an anion residue of at least one aliphatic monocarboxylic acid selected from the group consisting of decanoic acid, lauric acid, myristic acid and palmitic acid. Composition. In General formula (1), all of R < ¹ > -R < ⁴ > is a butyl group, The composition in any one of Claims 1-4.   Epoxy resin from bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, naphthalene diol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, and hydrogenated bisphenol A diglycidyl ether The composition according to any one of claims 1 to 5, which is at least one selected from the group consisting of:   The composition according to any one of claims 1 to 6, wherein the acid anhydride curing agent is at least one selected from the group consisting of 3-methylhexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride. object.   The content of the acid anhydride curing agent is such that the equivalent ratio of the acid anhydride group in the acid anhydride curing agent to the epoxy group in the epoxy resin is 0.9 to 1.2. 8. The composition according to any one of 7.   (a) an epoxy resin, (b) at least one acid anhydride curing agent selected from the group consisting of 3-methylhexahydrophthalic anhydride and 4-methylhexahydrophthalic anhydride, and (c) Containing at least one compound selected from the group consisting of tetrabutylphosphonium decanoate, tetrabutylphosphonium laurate, tetrabutylphosphonium myristate and tetrabutylphosphonium palmitate, and containing an acid anhydride curing agent An epoxy resin composition in which the amount is such that the equivalent ratio of the acid anhydride group in the acid anhydride curing agent to the epoxy group in the epoxy resin is 1 to 1.1. A method for preventing yellowing of an epoxy resin-based thin film, and the following general formula (1) as an epoxy resin curing accelerator

[Wherein R ^{1 to} R ⁴ are the same or different and each represents a phenyl group, a linear or branched alkyl group having 1 to 16 carbon atoms, or a cycloalkyl group having 5 to 12 carbon atoms, X represents an anion residue of an aliphatic monocarboxylic acid having 10 to 16 carbon atoms. ]
The method using the compound represented by these.   A method for forming an epoxy resin thin film, comprising applying the composition according to any one of claims 1 to 9 on a substrate and curing the coating film to form a thin film having a thickness of 1 mm or less.   A thin film having a thickness of 1 mm or less obtained by curing the composition according to claim 1.   The thin film according to claim 12, wherein the thin film is a sealing material for a light emitting device.   The thin film according to claim 12, wherein the thin film is a display coating material.   A light emitting device sealed with the thin film according to claim 12.