Hard coat resin composition and hard coat film

Abstract

To provide a photocurable resin composition which has low curing shrinkage and a small curl, has excellent abrasion resistance, and has an extremely small change rate of a water contact angle even when being scratched with an eraser, and a hard coat film having a resin curable layer of the same.SOLUTION: A hard coat resin composition contains polyfunctional urethane (meth)acrylate, a polythiophene-based compound, a fluorine-based compound having a reactive functional group, and a photopolymerization initiator, wherein the urethane (meth)acrylate is urethane (meth)acrylate derived from hexamethylene diisocyanate, a blending amount of the polythiophene-based compound is 0.2-1.3 pts.wt. with respect to 100 pts.wt. of a photopolymerization component, and a blending amount of the fluorine-based compound is 0.3-1.1 parts.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a photocurable hard coat resin composition and a hard coat film using the same. [Background technology]

[0002] In recent years, touch panels, which combine display and input methods, have been used in a wide range of fields. In particular, touch panels that utilize a stylus as an input method allow for more intuitive operation by directly inputting characters and complex shapes, and are widely adopted in tablet PCs, pen tablets, smartphones, portable gaming devices, and other devices.

[0003] Touch panels have exposed screens that come into direct contact with fingers, skin, pens, etc., making them susceptible to dirt from sebum and scratches. To address these issues, technologies have been developed to make the touch panel surface less prone to dirt, easier to clean, smoother, and more scratch-resistant. For example, a hard coat film has been proposed in which a hard coat layer containing hydrolyzable silyl or silanol groups, a radical polymerizable compound, and a polymerization initiator is sequentially laminated with a surface layer (Patent Document 1).

[0004] While the use of such hard-coat films has made it possible to significantly prevent dirt adhesion and scratches, there is a growing demand for high durability that can maintain surface functionality over long periods, especially when using touch pens. However, there are few hard-coat films that possess sufficient abrasion resistance along with basic properties such as good optical properties and low curl. For example, when rubbed with something that abrades the film surface, such as an eraser, the water contact angle changes significantly, reducing its stain resistance, and there is room for improvement. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6519771 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a photocurable resin composition that exhibits low curing shrinkage and small curl, has excellent abrasion resistance, and shows very little change in water contact angle even when rubbed with an eraser, and a hard coat (hereinafter referred to as HC) film having the resin cured layer thereof. [Means for solving the problem]

[0007] To solve the above problems, the invention of claim 1 is a composition comprising a polyfunctional urethane (meth)acrylate (A), a polythiophene compound (B), a fluorine compound having a reactive functional group (C), and a photopolymerization initiator (D), wherein (A) The urethane acrylate is a reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate or glycerin diacrylate, wherein (B) is poly(3,4-ethylenedioxythiophene) and poly(4-styrene sulfonate), and (C) has a fluoropolyether skeleton. Photopolymerization component 100 parts by weight (Except for (C) above) The amount of (B) in relation to is 0.2 to 1.3 parts by weight, and the amount of (C) in relation to is 0.3 to 1.1 parts. Yes, the amount of the previous stage (A) is 65-98% by weight of the total solid content. The present invention provides a hard coat resin composition characterized by certain features.

[0008] The invention of claim 2 is, A composition comprising a polyfunctional urethane (meth)acrylate (A), a polythiophene compound (B), a fluorine compound having a reactive functional group (C), and a photopolymerization initiator (D), wherein (A) is a urethane acrylate which is a reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate or glycerin diacrylate, and (B) is poly(3,4-ethylenedioxythiophene) and poly(4-styrene sulfonate), and ( C) has a fluoropolyether skeleton, the amount of (B) blended per 100 parts by weight of the photopolymerization component (excluding (C)) is 0.2 to 1.3 parts by weight, and the amount of (C) blended is 0.3 to 1.1 parts, and when the above composition is applied to a polyethylene terephthalate film with a thickness of 50 microns so that the film thickness after curing is 5 μm, cured with ultraviolet light, cut into 10 cm squares and fixed to the ground surface at the center, the average value of the height of the curl up from the ground surface at each vertex is 3.0 cm or less. The present invention provides a hard coat resin composition characterized by the following:

[0009] The invention of claim 3 is, A hard coat film characterized by having a cured resin composition layer according to claim 1 or 2 on a plastic film substrate. To provide.

[0010] The invention of claim 4 is, Touch panel using the hard coat film described in claim 3 To provide. [Effects of the Invention]

[0011] The resin composition of the present invention exhibits low curl and good optical properties, as well as excellent abrasion resistance, with a very small rate of change in the water contact angle even when rubbed with an eraser. Therefore, it is useful as an HC resin for HC films used in touch panels that use a stylus as an input means. [Modes for carrying out the invention]

[0012] The present invention will be described in detail.

[0013] The HC resin composition of the present invention comprises a polyfunctional urethane (meth)acrylate (hereinafter referred to as urea) (A), a polythiophene compound (B), a fluorine compound having a reactive functional group (C), and a photopolymerization initiator (D). In this specification, (meth)acrylate includes both acrylate and methacrylate.

[0014] The polyfunctional urea(A) used in the present invention is a urea derived from hexamethylene diisocyanate (hereinafter referred to as HDI), which has excellent weather resistance and stretchability, and is a binder that has excellent scratch resistance due to the cohesive force of hydrogen bonds derived from urethane bonds. Examples include reaction products of HDI with (meth)acrylate having hydroxyl groups.

[0015] Examples of the (meth)acrylate having a hydroxyl group used in the synthesis of the above (A) include monofunctional (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, difunctional (meth)acrylates such as glycerin di(meth)acrylate, trifunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate and diglycerin tri(meth)acrylate, tetrafunctional (meth)acrylates such as dipentaerythritol tetra(meth)acrylate, pentafunctional (meth)acrylates such as dipentaerythritol penta(meth)acrylate, etc. They can be used alone or in combination of two kinds. Among these, 2 to 4 functional groups are preferable and 2 to 3 functional groups are more preferable in view of the balance between reactivity and curing shrinkage. In particular, pentaerythritol triacrylate (hereinafter referred to as PETA) is preferable in that a film with good reactivity and high hardness can be obtained, and glycerin diacrylate (hereinafter referred to as GDA) is preferable in that curl can be made very small.

[0016] There is no particular limitation on the synthesis method of the above (A), and known methods can be used. The reaction may be carried out without a solvent, but since the viscosity may increase and stirring may become difficult as the molecular weight of (A) increases, ketones such as butanone and aromatic inert solvents such as xylene may be used. In addition, it is preferable to use a catalyst for the reaction between the hydroxyl group of the (meth)acrylate and the isocyanate group. Examples in that case include tin-based ones such as dibutyltin dilaurate and metal alkoxide-based ones such as cobalt naphthenate. The reaction temperature can be set as appropriate, but 40 to 120°C is preferable and 60 to 100°C is more preferable.

[0017] The number of functional groups of the above (A) is preferably 3 to 9 functional groups, and more preferably 4 to 6 functional groups. By setting the number of functional groups to 3 or more, sufficient reactivity can be ensured, and by setting it to 9 or less, curing shrinkage can be controlled and curl can be controlled to be small.

[0018] The weight average molecular weight of the above (A) (hereinafter referred to as Mw) is preferably 500 to 10,000, more preferably 1,000 to 5,000. By setting it to 500 or more, sufficient film strength and low curl property can be ensured, and by setting it to 10,000 or less, it can be easily adjusted to a viscosity with good workability. Note that Mw was measured and calculated by gel permeation chromatography using a column with a styrene divinylbenzene-based filler and a tetrahydrofuran eluent to measure the molecular weight in terms of standard polystyrene.

[0019] The blending amount of the above (A) is preferably 55 to 98% by weight, more preferably 60 to 97% by weight, and particularly preferably 65 to 96% by weight based on the total solid content. By setting it within this range, sufficient optical properties and low curl property can be ensured, and at the same time, the property that the change rate of the water contact angle is very small even when rubbed with a rubbing rubber can be obtained.

[0020] The polythiophene-based compound (B) used in the present invention is a polymer of thiophene, which is a sulfur-containing heterocyclic compound, and becomes conductive when electrons are added to or removed from the conjugated n-orbit by doping. In particular, poly(3,4-ethylenedioxythiophene) (hereinafter referred to as PEDOT) is preferable in that its conductivity is improved by a combination with poly(4-styrenesulfonate) (hereinafter referred to as PSS), it has high environmental stability, and it has high light transmittance in a thin film. The inventor has found that by combining this polythiophene-based compound with a specific binder, low curl property can be ensured and water repellency can be stably maintained.

[0021] The blending amount of the above (B) is 0.2 to 1.3 parts by weight with respect to 100 parts by weight of the photopolymerizable component, preferably 0.25 to 1.2 parts by weight, and more preferably 0.3 to 1.1 parts by weight. If it is less than 0.2 parts by weight, the water contact angle after rubbing with a rubbing rubber tends to decrease, and the water repellency cannot be stably maintained. Similarly, if it exceeds 1.3 parts by weight, the stable maintenance of water repellency tends to be impossible, and the total light transmittance also tends to decrease.

[0022] The surface resistivity of the cured film containing the above (B) is 1.00×10 at the initial stage9 ~9.99 × 10 11 A value of Ω / □ is preferable. This range allows for stable maintenance of water repellency. The reason why improved conductivity suppresses the decrease in the water contact angle is not clear, but it is presumed that by making it difficult to generate static electricity when rubbing with an eraser, damage to the coating can be reduced, and as a result, the decrease in the water contact angle can be suppressed.

[0023] The fluorine-based compound (C) having a reactive functional group used in this invention is added for the purpose of imparting antifouling (anti-fingerprint) and water-repellent properties. Because it has a reactive functional group that polymerizes with (A), it does not peel off from the cured film over time, and the effect can be sustained for a long period of time. In particular, the effect can be greatly enhanced when photocured under nitrogen purging (deoxygenation) conditions. Commercially available products include KY-1216 (product name: manufactured by Shin-Etsu Chemical Co., Ltd.), Megafac RS-851 (product name: manufactured by DIC Corporation), Opstar TU2225 (product name: manufactured by JSR Corporation), etc.

[0024] The amount of (C) is 0.30 to 1.1 parts by weight per 100 parts by weight of the photopolymerization component, preferably 0.35 to 1.0 parts by weight, and more preferably 0.40 to 0.8 parts by weight. If the amount is less than 0.3 parts by weight, the water contact angle after rubbing with an eraser decreases, and it tends not to be possible to stably maintain water repellency. Similarly, if the amount exceeds 1.1 parts by weight, it also tends not to be possible to stably maintain water repellency.

[0025] The photopolymerization initiator (D) used in this invention generates radicals upon irradiation with ultraviolet light or electron beams, and these radicals trigger the polymerization reaction. General-purpose photopolymerization initiators such as benzyl ketal, acetophenone, and phosphine oxide can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, examples include 2,2-dimethoxy-1,2-diphenylethane-1-one as a benzyl ketal, 1-hydroxycyclohexyl-phenyl-ketone and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one as α-hydroxyacetophenones, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one as an α-aminoacetophenone, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide as acylphosphine oxides, which can be used individually or in combination of two or more. Among these, it is preferable to include α-hydroxyacetophenones that are less prone to yellowing, and commercially available products include Irgacure 184 and 2959 (product names: manufactured by BASF Japan, α-hydroxyacetophenone type).

[0026] The amount of (D) is preferably 0.5 to 10 parts by weight, and more preferably 3 to 8 parts by weight, per 100 parts by weight of the photopolymerization component. An amount of 0.5 parts by weight or more allows for sufficient curing, while an amount of 10 parts by weight or less prevents excessive addition, thus preventing yellowing of the coating film and a decrease in shelf life.

[0027] Furthermore, the HC resin composition of the present invention may optionally contain ultraviolet absorbers, antioxidants, colorants, defoaming agents, thickeners, anti-precipitation agents, antistatic agents, anti-fogging agents, slip agents, antibacterial agents, antiviral agents, organic fine particles, inorganic fillers, etc.

[0028] The HC resin composition of the present invention is diluted with a solvent to a solid content of 10-90% in order to improve its coating properties on organic plastic films. Examples of solvents include alcohol-based solvents such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and diacetone alcohol; ketone-based solvents such as acetone, methyl ethyl ketone (hereinafter referred to as MEK), methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate and butyl acetate; and ether-based solvents such as PGM, diethyl ether, and diisopropyl ether. These can be used individually or in combination of two or more types.

[0029] Examples of plastic film substrates to which the HC resin of the present invention is coated include polyester film, polyethylene film, polypropylene film, diacetylcellulose film, triacetylcellulose film, acetylcellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, polyimide film, fluororesin film, nylon film, acrylic film, cycloolefin (co)polymer film, and the like.

[0030] Among these, biaxially oriented polyester film is preferred due to its price, processability, and dimensional stability, while acrylic film and polycarbonate film are preferred due to their weather resistance. The film thickness should generally be between 23 μm and 250 μm.

[0031] The method for applying the HC resin composition of the present invention is not particularly limited, and known coating methods such as spray coating, roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, and wire bar coating, or gravure printing, screen printing, offset printing, and inkjet printing can be used. The dry film thickness is preferably 0.5 μm to 20 μm.

[0032] After applying the HC resin composition of the present invention, it is dried at 60-120°C and cured using an ultraviolet irradiation device. Examples of light sources for ultraviolet irradiation include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, electrodeless ultraviolet lamps, and LED lamps, and the curing conditions are 500 mW / cm². 2 ~3000mW / cm 2 At this irradiation intensity, the integrated light dose is 50-2,000 mJ / cm². 2 Examples include the following. The irradiation atmosphere can be air, but an inert gas such as nitrogen or argon is preferred.

[0033] The initial water contact angle of the HC film having the cured layer of the HC resin composition of the present invention is preferably 105° or higher, and more preferably 110° or higher. Furthermore, the water contact angle after 1000 reciprocating strokes with an eraser under a load of 1 kgf is preferably 100° or higher, and more preferably 105° or higher. If a water contact angle of 100° or higher is secured after rubbing with an eraser, it can be determined that the film has excellent stain resistance and excellent abrasion resistance.

[0034] Furthermore, the decrease in the water contact angle after rubbing with an eraser is preferably 10% or less, and more preferably 7% or less. If the decrease is 10% or less, it can be considered that most of the antifouling components remain without being scraped off by the eraser test, thus indicating stable antifouling and abrasion resistance, and that there is little decrease in antifouling properties over time when rubbed with a touch-up pen.

[0035] The reason for using an eraser as described above is that the rubbing with an eraser is similar to rubbing with a stylus, and this evaluation allows for an approximate assessment of abrasion resistance to styluses. While the scratch resistance of optical films is generally evaluated using steel wool, steel wool is literally a hard, thin metal wire, and the degree of rubbing with a stylus is completely different, so abrasion resistance to styluses cannot be evaluated with steel wool.

[0036] The eraser used in the above eraser test is a MINOAN eraser made in Korea (product name: MUNBANGSAWOO Co., Ltd., diameter 6 mm), which is used in abrasion resistance tests. Using a flat friction tester manufactured by Toyo Seiki Seisakusho, the eraser is rubbed 1000 times back and forth under the conditions of a load of 1 kg, a rubbing speed of 40 rpm, and a stroke width of 50 mm, and the water contact angle before and after the rub is measured. In this specification, the water contact angle is the value measured based on the static drop method of JIS R 3257:1999.

[0037] The present invention will be described in detail below based on examples and comparative examples, but these are merely examples and the invention is not limited to them. Unless otherwise stated, measurements were taken under conditions of room temperature of 25°C and relative humidity of 65%. The amounts of ingredients are expressed in parts by weight and are expressed on a solid content basis.

[0038] Examples 1-8 Examples 1-8, which are HC resin compositions, were prepared by stirring until uniformly dissolving and dispersing the following compounds: (A) Ureac 1 (hexafunctional, Mw 2,600, obtained by reacting HDI and PETA), Ureac 2 (tetrafunctional, Mw 1,900, obtained by reacting HDI and GDA), and Ureac 3 (neptafunctional, Mw 4,300, obtained by reacting HDI nurate and PETA); (B) PEDOT / PSS dispersion (solids content 2.2%); (C) KY-1216 (product name: manufactured by Shin-Etsu Chemical Co., Ltd., solids content 20%); (D) Omnirad 2959 (product name: manufactured by iGM, α-hydroxyacetophenone type); DPHA (dipentaerythritol hexaacrylate) as the monomer; and a mixed solvent of butyl acetate, MEK, and PGM (mixing ratio 50:10:40) as the diluent. The compounds were then mixed according to the formulations shown in Table 1 (the amount of diluent resulting in a solids content of 30%).

[0039] Comparative Examples 1-8 In addition to the materials used in the examples, Ureac A (a 9-functional compound, Mw 4800, obtained by reacting isophorone diisocyanurate with PETA) was used as a binder, and a mixed solvent of butyl acetate, MEK, and PGM (mixing ratio 50:10:40) was used as a diluent. Comparative Examples 1 to 8, which are HC resin compositions, were prepared by stirring until uniformly dissolved and dispersed according to the formulations shown in Table 2 (the amount of diluent solvent was such that the solid content was 30%).

[0040] Adjustment of HC film A4-sized polyethylene terephthalate film U403 (product name: Toray Industries, Inc., 50 μm thick, with easy-adhesion layers on both sides) was coated to a curing thickness of 5 μm. After drying in a constant temperature bath at 80°C for 1 minute, it was purged with nitrogen and cured with ultraviolet light using a Fusion UV System Japan F300S / LC-6B electrodeless UV irradiation device with an H bulb output of 1200 mW / cm2 and an integrated light intensity of 200 mJ / cm2.

[0041] Table 1 JPEG0007842603000001.jpg62135

[0042] Table 2 JPEG0007842603000002.jpg61135

[0043] The evaluation method was as follows.

[0044] Total light transmittance: In accordance with JIS K7361-1, it was measured using Haze-GARD2 manufactured by Toyo Seiki Seisakusho. If it exceeded 90%, it was rated as ◎; if it was between 90% and 85%, it was rated as 〇; if it was less than 85%, it was rated as ×.

[0045] Surface resistivity: The coated surface of the HC film prepared above was measured in accordance with JIS K6911 using a high resistivity meter HIRESTA-UX manufactured by Nitto Seiko Analytic. If it was less than 1.00×10 10 Ω / □, it was rated as ◎; if it was between 1.00×10 10 Ω / □ and 1.00×10 12 Ω / □, it was rated as 〇; if it exceeded 1.00×10 12 Ω / □, it was rated as ×.

[0046] Water contact angle: Using MINOAN (product name: manufactured by MUNBANGSAWOO, diameter 6 mm), and a planar friction tester manufactured by Toyo Seiki Seisakusho, it was rubbed 1000 times back and forth under the conditions of a load of 1 Kg, a rubbing speed of 40 rpm, and a stroke width of 50 mm. The water contact angles before and after that were measured. The water contact angle was measured in accordance with the sessile drop method of JIS R 3257:1999 using DMs-400 manufactured by Kyowa Interface Science Co., Ltd. Water was dropped at room temperature and left standing for 30 seconds before measurement. The evaluation was as follows: if the initial water contact angle was 110° or more and the water contact angle after abrasion with a rubber was more than 105°, it was rated as ◎; if it was between 105° and 100° or more, it was rated as 〇; if it was less than 100°, it was rated as ×.

[0047] Contact angle reduction rate: The difference between the initial water contact angle and the water contact rate after abrasion with a rubber was defined as the contact angle reduction rate. If it was less than 7%, it was rated as ◎; if it was between 7% and 10%, it was rated as 〇; if it exceeded 10%, it was rated as ×.

[0048] Curling: The HC film was cut into a 10 cm square, the center of the test piece was fixed to the grounding surface, and the height of the upward warping from the grounding surface at each vertex was measured. If the average value of the four locations was less than 1.5 cm, it was rated as ◎; if it was between 1.5 cm and 3.0 cm, it was rated as 〇; if it exceeded 3.0 cm, it was rated as ×.

[0049] Flexibility: With the coated surface of the HC film prepared above facing outwards, the flexibility was measured in accordance with JIS K6911, and values ​​of less than 3 mm were marked with ◎, 3 to 6 mm with ○, and more than 6 mm with ×.

[0050] Evaluation Result 1 JPEG0007842603000003.jpg106139

[0051] Evaluation Result 2 JPEG0007842603000004.jpg107139

[0052] The examples showed no problems in any aspect, including total light transmittance, surface resistivity, water contact angle, contact angle reduction rate, curl, and flexibility.

[0053] On the other hand, Comparative Examples 1 and 2, in which (B) was not included or was below the lower limit, showed inferior surface resistivity, water contact angle, and contact angle reduction rate. Comparative Examples 3 and 4, in which (B) exceeded the upper limit, showed inferior contact angle and contact angle reduction rate, and in particular, Comparative Example 4, which had a large amount of (B), also showed low total light transmittance. Furthermore, Comparative Examples 5 and 6, and Comparative Example 7, in which (C) was below the lower limit and above the upper limit, also showed inferior contact angle and contact angle reduction rate. Comparative Example 8, which used ureaq not derived from HDI, showed similar results, and all of these were unsuitable for the present invention.

Claims

1. A hard coat resin composition comprising a polyfunctional urethane (meth)acrylate (A), a polythiophene compound (B), a fluorine compound (C) having a reactive functional group, and a photopolymerization initiator (D), wherein (A) is a urethane acrylate which is a reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate or glycerin diacrylate, (B) is poly(3,4-ethylenedioxythiophene) and poly(4-styrene sulfonate), (C) has a fluoropolyether skeleton, the amount of (B) is 0.2 to 1.3 parts by weight per 100 parts by weight of the photopolymerization component (excluding (C)), the amount of (C) is 0.3 to 1.1 parts, and the amount of (A) is 65 to 98% by weight of the total solid content.

2. A composition comprising a polyfunctional urethane (meth)acrylate (A), a polythiophene compound (B), a fluorine compound (C) having a reactive functional group, and a photopolymerization initiator (D), wherein (A) is a urethane acrylate which is a reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate or glycerin diacrylate, (B) is poly(3,4-ethylenedioxythiophene) and poly(4-styrene sulfonate), (C) has a fluoropolyether skeleton, the amount of (B) blended per 100 parts by weight of the photopolymerization component (excluding (C)) is 0.2 to 1.3 parts by weight, and the amount of (C) blended is 0.3 to 1.1 parts. A hard coat resin composition characterized in that, when the composition is applied to a polyethylene terephthalate film with a thickness of 50 microns so that the film thickness after curing becomes 5 μm, cured with ultraviolet light, cut into 10 cm squares, and the central part is fixed to the ground surface, the average value of the height of each vertex rising from the ground surface is 3.0 cm or less.

3. A hard coat film characterized by having a cured resin composition layer according to claim 1 or 2 on a plastic film substrate.

4. A touch panel using the hard coat film described in Claim 3.

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