Inkjet resin composition

Abstract

The purpose of this invention is to provide a resin composition for inkjet printing, which, after curing, produces a coating with high toughness, resistance to chemical gold plating solutions, resistance to high-temperature solder, and good uniformity. It is suitable for use as a solder resist in printed circuit boards, electronic materials, and for marking symbols. The inkjet resin composition of this invention comprises (A) a photopolymerizable prepolymer (oligomer): 20-40% by weight, such as A1 or A2, having a carboxyl group (-COOH) and a photocurable unsaturated functional group. Its preparation involves reacting (a1) 2,2-dialkylmethylbutyric acid or (a2) 2,2-dialkylmethylpropionic acid with (b) 3-isocyanate-methylene-3,5,5-trimethylcyclohexyl isocyanate (IPDI), followed by (c) a resin containing a vinyl group. (A) Monocarboxylic acid reaction; (B) Photopolymerizable alkyl difunctional acrylate monomer: 20-40 wt%; (C) Hyperbranched polyester acrylate: 5-10 wt%; (D) Epoxy resin: 5-15 wt%; (E) α-aminoalkylbenzophenone-based photopolymerization initiator and acetylated phosphine oxide-based photopolymerization initiator: 3-10 wt%; (F) Nano-scale highly dispersible titanium dioxide: 5-20 wt%; (G) Accelerator: 0.5-2.0 wt%.

Description

[Technical Field]

[0001] The present invention provides a resin composition for inkjet printing, which, after curing, forms a tough coating that is resistant to chemical gold plating solutions, electroplating gold solutions, and heat, and has good uniformity. It is suitable for use as a solder resist for printed circuit boards, electronic materials, and for marking symbols, etc. [Previous Technology]

[0002] In recent years, inkjet printing has replaced screen printing for printed circuit boards, forming etching resists, solder resists, and markings. Inkjet printing reduces ink consumption and allows direct drawing from digital data. Using the printhead of an inkjet printer and its attached UV irradiation device, graphic printing and temporary UV curing can be performed simultaneously. Inkjet equipment requires ink viscosity below 40 mPa·s at 25°C and different physical properties from inks used in conventional screen printing.

[0003] The curable components of inkjet coatings are easily affected by oxygen in the air. The surface curing of the coating under UV irradiation is poor, and the patterns formed by inkjet printing are prone to ink bleeding, and may even contaminate the inkjet printing device's stage. If photopolymerization initiators are added to improve the surface curing of the coating, there will be problems with reduced heat resistance or chemical resistance.

[0004] The present invention provides a resin composition for inkjet printing that effectively solves the above-mentioned problems, thereby improving the surface hardening properties of the coating formed by inkjet printing, maintaining the high temperature resistance to soldering and the properties of resistance to chemical gold and electroplating solutions, and can be used as solder resist and marking agent for printed circuit boards and electronic materials. [Summary of the Invention]

[0005] The inkjet resin composition of the present invention contains photocurable and thermocurable resins, nano-level highly dispersible pigments, photopolymerization initiators and thermopolymerization accelerators.

[0006] This invention uses photopolymerizable prepolymers (oligomers) of the A1 or A2 type, which have carboxyl (-COOH) and photocurable unsaturated functional groups, in combination with hyperbranched polyester acrylates and difunctional acrylate compounds of the alkyl group, such as 1,6-hexanediol diacrylate monomers, to obtain a composition suitable for inkjet printing. Furthermore, by using an aminoalkylbenzophenone-based photopolymerization initiator, such as 4,4”-bis(N,N-diethylamino)benzophenone, and an oxophosphine oxide-based photopolymerization initiator, such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, the absorbance is adjusted to an appropriate range to achieve good surface hardening and coating properties.

[0007]

[0008]

[0009] The present invention is characterized by forming the above-mentioned inkjet resin composition on a substrate and then shaping it by light irradiation. Curing is then completed by heat baking.

[0010] The resin composition for inkjet printing according to the present invention can improve the surface hardening properties of the coating caused by inkjet printing, and has heat resistance for subsequent soldering processes and chemical resistance for chemical gold or electroplated gold.

[0011] The inkjet resin composition of the present invention is characterized by containing (A) a photopolymerizable prepolymer (oligomer): 20-40% by weight, such as A1 (I) or A2 (II), having a carboxyl group (-COOH) and a photocurable unsaturated functional group. It is prepared by reacting (a1) 2,2-dialkylmethylbutyric acid or (a2) 2,2-dialkylmethylpropionic acid with (b) 3-isocyanate-methylene-3,5,5-trimethylcyclohexyl isocyanate IPDI, and then with... (c) Obtained by reaction of a monocarboxylic acid containing one vinyl group; (B) Photopolymerizable alkyl difunctional acrylate monomer: 20-40 wt%; (C) Hyperbranched polyester acrylate: 5-10 wt%; (D) Epoxy resin: 5-15 wt%; (E) α-aminoalkylbenzophenone-based photopolymerization initiator and acetylated phosphine oxide-based photopolymerization initiator: 3-10 wt%; (F) Nanoscale highly dispersible titanium dioxide: 5-20 wt%; (G) Accelerator: 0.5-2.0 wt%.

Implementation Method

[0012] To make the present invention clearer, preferred embodiments will be further described in detail according to the following embodiments.

[0013] Synthesis Example 1: Photopolymerizable and Thermally Polymerizable Prepolymer (oligomer)-A1

[0014] 1000g of 2,2-dialkylmethylbutyric acid was added to 400g of monomer 1,6-hexanediol diacrylate, heated to 100℃, and stirred until dissolved. Then, 1000g of IPDI was added dropwise to the aforementioned solution for a reaction time of 100 minutes at a temperature of 100℃. After the addition was completed, the temperature was maintained at 100℃ for a maturation reaction for 4 hours. 1.0g of hydroquinone HQ was added, followed by 324g of acrylic acid AA, which was added dropwise to the aforementioned solution for a reaction time of 60 minutes at a temperature of 100℃. After the addition was completed, the temperature was raised to 120℃ for a maturation reaction for 5 hours, yielding photopolymerizable prepolymer A1. The acid value was 145mgKOH / g, and the weight average molecular weight (Mw) was 980.

[0015] Synthesis Example 2: Photopolymerizable and Thermally Polymerizable Prepolymer (oligomer)-A2

[0016] 1000g of 2,2-dialkylmethylpropionic acid was added to 400g of monomer 1,6-hexanediol diacrylate, heated to 100℃, and stirred until dissolved. Then, 1100g of IPDI was added dropwise to the above solution for 100 minutes and 100℃. After the addition was completed, the temperature was maintained at 100℃ for 4 hours for maturation. 1.0g of hydroquinone HQ was added, and then 358g of acrylic acid AA was added dropwise to the above solution for 60 minutes and 100℃. After the addition was completed, the temperature was raised to 120℃ for 5 hours for maturation, thus obtaining photopolymerizable prepolymer A2. The acid value was 155mgKOH / g, and the weight average molecular weight Mw was 928.

[0017] The component (B) of the inkjet resin composition of the present invention is a photopolymerizable alkyl difunctional acrylate monomer, such as 1,6-hexanediol diacrylate, in an amount of 20 to 40% by weight.

[0018] The component (C) of the inkjet resin composition of the present invention is photopolymerizable hyperbranched polyester acrylate, for example 6362-100, and the amount is preferably 5 to 10% by weight.

[0019] As the crosslinking agent (D), any suitable thermosetting resin may be used within the scope that does not impair the effects of the present invention. The thermosetting resin crosslinking agent may be only one type, or it may be two or more types, and the thermosetting resin crosslinking agent may be used in conjunction with prepolymer A1 or A2. Examples of thermosetting resin crosslinking agents include, for example, bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0020] The weight-average molecular weight of the epoxy resin can be any suitable weight-average molecular weight without impairing the effects of the present invention. For aspects that further enhance the effects of the present invention, a weight-average molecular weight of 500 to 15000 is preferred. The weight-average molecular weight can be determined, for example, by GPC (gel permeation chromatography, standard material: polystyrene conversion).

[0021] The photopolymerization initiator content (E) of the inkjet resin composition of the present invention is preferably 3 to 10% by weight. α-aminoalkylphenyl ketone and acetophosphine oxide photopolymerization initiators are used.

[0022] The component (F) of the inkjet resin composition of the present invention is a nano-level highly dispersible pigment: preferably 5 to 20% by weight, for example, nano-level highly dispersible titanium dioxide AUV1-W001.

[0023] The amount of accelerator in component (G) of the inkjet resin composition of this invention is 0.5 to 2.0% by weight. The curing accelerator can be selected from imidazoles, with dimethylimidazolium, diphenylimidazolium, dihydroxymethyldiphenylimidazolium, etc. being commonly used.

[0024] Examples 1-2

[0025] Using prepolymer A1 or A2 as a substitute for the inkjet ink formulation composition (details of which are shown in Table 1), the ink composition is obtained by thorough grinding using a bead mill. The resulting ink composition is then coated onto a 3cm x 3cm polyimide (PI) test plate using an inkjet printer to obtain a coating film with a thickness of 5 to 10 μm. The coating film is then irradiated with LED UV light and baked at 130 to 180°C for 0.5 to 1 hour to obtain a fully cured coating film.

[0026] In Table 1, the information of each component is as follows: hyperbranched polyester acrylate model 6362-100, bisphenol A type epoxy resin model NPEL-127E, nano-grade highly dispersible titanium dioxide model AUV1-W001, the photopolymerization initiator selected is α-aminoalkyl benzophenone EMK (4,4'-bis(N,N-diethylamino)benzophenone) and acetylated phosphine oxide TPO (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), and the imidazole is 2-methylimidazole.

[0027]

[0028] In Table 1, the viscosity values ​​are obtained by measuring the inkjet resin compositions of Examples 1-2 and Comparative Example 1 using a cone-plate viscometer (Toki Sangyo TV-35). The obtained inkjet resin compositions have a viscosity of 40 mPa·s or less at 25°C.

[0029] The inkjet performance is confirmed by evaluating the printhead ejection state during inkjet printing based on the following criteria.

[0030] ○: Inkjet printing is good

[0031] △: Inkjet printing is not good, but inkjet printing is still possible.

[0032] ×: Inkjet printing failure

[0033] Apparatus: Piezoelectric inkjet printer (using Zheng Ye Technology PYB-100B)

[0034] The surface hardening property of the coating is the pattern formed by inkjet printing. The touch dryness of the hardened coating is confirmed and evaluated according to the following criteria.

[0035] ○: Non-adhesive to the coating surface.

[0036] △: The coating surface is sticky, and the stickiness can be confirmed.

[0037] ×: The coating surface is not hardened and is in a liquid state.

[0038] The edge neatness of the coating pattern is determined by observing the pattern formed by inkjet printing with an optical microscope, measuring the bleed width generated from the hardened coating on the substrate side, and evaluating it according to the following criteria.

[0039] ○: The width of the exudate is 0~10μm

[0040] △: The width of the exudate is 11~20μm

[0041] ×: The width of the exudate exceeds 20μm

[0042] The coating adhesion was tested according to the test method specified in JIS D 0202. The hardened film has a grid pattern. After a peel test was conducted using Cyrovan tape, the peel condition was assessed visually.

[0043] 100 / 100, meaning that none of the 100 parts peel off.

[0044] 50 / 100 to 90 / 100, that is, 50 to 90 of 100 remain unpeeled.

[0045] 0 / 100 to 50 / 100, that is, the 0 to 50 parts of 100 remain unpeeled.

[0046] Pencil Hardness

[0047] Using the same method as for adhesion, after making a test piece, use a Mitsubishi 2B~9H hardness pencil, with the tip flattened (at a right angle), and then scrape it on the test piece at a 45-degree angle until the coating is scratched.

[0048] Heat resistance of coated solder

[0049] Using the same sample as the one obtained from the above adhesion test, apply flux to the hardened coating and immerse it in tin at 270°C for 10 seconds each time. Each test should be performed after the board has cooled down. If no peeling or bulging occurs after 3 tests, the test should be stopped.

[0050] Electro-free gold plating durability

[0051] Using the same sample as obtained from the adhesion test described above, and using an electroless nickel plating bath and an electroless gold plating bath, the hardened coating was plated with nickel at 0.5 μm and gold at 0.03 μm, and the surface condition of the resulting hardened coating was observed. The judgment criteria are as described below.

[0052] ○: No changes were observed in the coating.

[0053] △: The coating film becomes white or cloudy.

[0054] ×: The coating film shows obvious whitening or turbidity.

[0055] The inkjet coatings of the present invention in Examples 1-2 have excellent surface hardening properties, neat pattern edges without exudation, and excellent adhesion. In addition, the coatings have excellent properties, such as heat resistance to post-processing solder and chemical resistance to chemical gold or electroplated gold. They are suitable for solder resists and markings on printed circuit boards and electronic materials.

Claims

1. A photocurable and thermocurable inkjet resin composition comprising (A) photopolymerizable prepolymers of formula A1 (a) and A2 (b), having carboxyl (-COOH) and photocurable unsaturated functional groups: 20-40 wt%; (B) photopolymerizable difunctional acrylate monomers of alkyl groups: 20-40 wt%; (C) hyperbranched polyester acrylate: 5-10 wt%; (D) epoxy resin: 5-15 wt%; (E) α-aminoalkylbenzophenone-based photopolymerization initiator and acetylated phosphine oxide-based photopolymerization initiator: 3-10 wt%; (F) nano-scale highly dispersible titanium dioxide: 5-20 wt%; (G) accelerator: 0.5-2.0 wt%; wherein, The photopolymerizable prepolymer (oligomer) A1 is shown in structural formula (I): The photopolymerizable prepolymer (oligomer) A2 is shown in structural formula (II):

2. The inkjet resin composition as described in claim 1, wherein, The photopolymerizable prepolymer (oligomer) A1 or A2 comprises a copolymer of a polymerizable monomer having a carboxyl group and a monomer including acrylate compounds, with an acid value of 80 to 180 mg KOH / g.

3. The inkjet resin composition as described in claim 1, wherein, This photopolymerized monopolymer 1,6-hexanediol diacrylate.

4. The inkjet resin composition as described in claim 1, wherein, The thermosetting resin is an epoxy resin, specifically bisphenol A type epoxy resin and bisphenol F type epoxy resin.

5. The inkjet resin composition as described in claim 1, wherein, The cured product includes: a structure of carboxyl groups of photopolymerizable prepolymer (oligomer) A1 or A2 and epoxy resin crosslinking; and a structure of unsaturated functional groups of photopolymerizable prepolymer (oligomer) A1 or A2 and photopolymerizable monomers crosslinked together, which is used as a solder resist and symbol marking in a printed circuit board inkjet device.

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