Adhesives for transparent substrates

Abstract

To provide an adhesive having excellent transparency and bending resistance.SOLUTION: An adhesive for transparent substrates contains (A) a polyester polyol that is a product from the condensation of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid and an aliphatic diol, and (B) a polyisocyanate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive for transparent substrates. [Background technology]

[0002] Liquid crystal display devices are constructed by bonding together polarizing filters, color filters, electrode substrates, etc. with adhesive layers. Furthermore, laminated glass, in which an adhesive layer is interposed between two sheets of glass, is used for window glass in automobiles, aircraft, buildings, etc., to prevent glass fragments from scattering in the event of breakage. For example, Patent Document 1 discloses that the adhesive layer of laminated glass is formed from polyvinyl butyral or ethylene vinyl acetate.

[0003] Such adhesive layers require transparency, but conventional materials did not have sufficient transparency. Furthermore, conventional adhesive layers did not have sufficient flex resistance, and when used in flexible display devices, repeated bending of the screen could cause cracks or peeling inside the screen. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-066976 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an adhesive that is excellent in transparency and flex resistance. [Means for solving the problem]

[0006] As a result of intensive research to solve the above problems, the inventors discovered that in an adhesive made of polyurethane resin, the transparency and flex resistance of the adhesive layer can be improved by combining an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol as raw material components of a polyester polyol, and thus completed the present invention.

[0007] That is, the present invention relates to an adhesive for transparent substrates that contains (A) a polyester polyol that is a condensation reaction product of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol, and (B) a polyisocyanate.

[0008] The transparent substrate is preferably glass or a film.

[0009] The aliphatic diol preferably has an aliphatic skeleton having 2 to 6 carbon atoms.

[0010] The aromatic dicarboxylic acid is preferably selected from the group consisting of o-phthalic acid, m-phthalic acid and p-phthalic acid.

[0011] The (B) polyisocyanate is preferably an adduct of an aliphatic diisocyanate having 6 or more carbon atoms and an aliphatic polyol.

[0012] The adhesive for transparent substrates preferably further contains (C) a silicone compound having a reactive hydroxyl group.

[0013] The present invention also relates to a laminate comprising a first transparent substrate, an adhesive layer made of the adhesive for transparent substrates, and a second transparent substrate laminated in this order.

[0014] The present invention also relates to an automotive glass comprising the laminate.

[0015] The present invention also relates to a flexible display device including the laminate. [Effects of the Invention]

[0016] The adhesive for transparent substrates of the present invention makes it possible to obtain an adhesive layer that is excellent in transparency and flex resistance. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of the substrate and coating film used in Examples 8 to 13. DETAILED DESCRIPTION OF THE INVENTION

[0018] The adhesive for transparent substrates of the present invention is characterized by containing (A) a polyester polyol which is a condensation reaction product of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol, and (B) a polyisocyanate.

[0019] <(A) Polyester polyol> The polyester polyol (A) used in the present invention is a condensation reaction product of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol.

[0020] The aromatic dicarboxylic acid is not particularly limited, and examples thereof include o-phthalic acid (orthophthalic acid), m-phthalic acid (isophthalic acid), p-phthalic acid (terephthalic acid), naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and reactive derivatives thereof such as acid anhydrides, alkyl esters, and acid halides. Among these, from the viewpoints of ease of availability as a raw material and cost, aromatic dicarboxylic acids having 8 to 14 carbon atoms and their reactive derivatives are preferred, and o-phthalic acid, m-phthalic acid, p-phthalic acid, and their reactive derivatives are particularly preferred. These dicarboxylic acids can be used alone or in combination of two or more.

[0021] The aliphatic dicarboxylic acid is not particularly limited, and examples thereof include linear, branched, or cyclic aliphatic dicarboxylic acids and their reactive derivatives such as acid anhydrides, alkyl esters, and acid halides. Specific examples include succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid, maleic acid, fumaric acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and cyclopentanedicarboxylic acid. Among these, from the viewpoints of ease of availability as a raw material and cost, aliphatic dicarboxylic acids having 4 to 9 carbon atoms and their reactive derivatives are preferred, and linear aliphatic dicarboxylic acids and their reactive derivatives are more preferred, with adipic acid and its reactive derivatives being particularly preferred. These dicarboxylic acids can be used alone or in combination of two or more.

[0022] The ratio of aromatic dicarboxylic acid to aliphatic dicarboxylic acid is preferably 20 to 80 weight percent, more preferably 30 to 70 weight percent, of a total of 100 parts by weight of aromatic dicarboxylic acid and aliphatic dicarboxylic acid. If it is less than 20 weight percent, adhesion to the substrate tends to decrease, and if it exceeds 80 weight percent, the elasticity and flexibility of the adhesive layer tends to decrease.

[0023] The aliphatic diol is not particularly limited, and examples thereof include linear (ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, etc.), branched (1,2-propanediol (propylene glycol), neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, etc.) and cyclic (1,4-bis(hydroxymethyl)cyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane) aliphatic diols. These diols can be used alone or in combination of two or more. Among these, from the viewpoints of ease of availability as a raw material and cost, those having 2 to 8 carbon atoms are preferred, and those having 2 to 6 carbon atoms are more preferred.

[0024] As the diol component, an aliphatic diol and an aromatic diol may be used in combination, but the proportion of the aliphatic diol in the total diol components is preferably 60 to 100% by weight, more preferably 70 to 100% by weight, and even more preferably 80 to 100% by weight. If it is less than 60% by weight, the elasticity and flexibility of the adhesive layer tend to decrease.

[0025] The number average molecular weight (Mn) of the (A) polyester polyol is preferably 1,000 to 30,000, more preferably 10,000 to 20,000. If it is less than 1,000, elasticity tends to decrease, and if it exceeds 30,000, viscosity tends to increase, significantly decreasing handleability. The number average molecular weight can be determined in terms of polystyrene using gel permeation chromatography (GPC).

[0026] The weight-average molecular weight (Mw) of the (A) polyester polyol is preferably 2000 to 60000, more preferably 20000 to 40000. If it is less than 2000, elasticity tends to decrease, and if it exceeds 60000, viscosity tends to increase, significantly decreasing handleability. The weight-average molecular weight can be determined in terms of polystyrene using GPC.

[0027] The hydroxyl value of the (A) polyester polyol is preferably 5 to 100 mgKOH / g, more preferably 5 to 50 mgKOH / g. If it is less than 5 mgKOH / g, the crosslinking density tends to decrease, resulting in a decrease in adhesive strength. If it exceeds 100 mgKOH / g, the water resistance of the adhesive layer tends to decrease. The hydroxyl value can be determined by esterifying the polyester polyol with a pyridine solution of phthalic anhydride and titrating the excess phthalic anhydride with a sodium hydroxide solution (in accordance with JIS K 1557-1).

[0028] The polyester polyol (A) can be obtained by dehydration condensation of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol by a known method.

[0029] The ratio of the dicarboxylic acid components (aromatic dicarboxylic acid and aliphatic dicarboxylic acid) to the diol component is preferably such that the ratio of the total number of moles of hydroxyl groups contained in the diol component to the total number of moles of carboxyl groups contained in the dicarboxylic acid (hydroxyl groups / carboxy groups) is 0.5 to 1.5, more preferably 0.8 to 1.2.

[0030] <(B) Polyisocyanate> The polyisocyanate (B) used in the present invention is not particularly limited, and examples thereof include linear, branched, or cyclic aliphatic polyisocyanates and aromatic polyisocyanates. Examples of aliphatic polyisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of aromatic diisocyanates include toluene diisocyanate, naphthylene diisocyanate, and xylylene diisocyanate. Adducts obtained by addition reaction of these polyisocyanates with polyols such as glycerin and trimethylolpropane can also be used. These polyisocyanates can be used alone or in combination of two or more.

[0031] Among these, those having an aliphatic skeleton (aliphatic polyisocyanate or an adduct of an aliphatic polyisocyanate and an aliphatic polyol) are preferred because they provide an adhesive layer with high elasticity and flexibility. Furthermore, from the viewpoints of ease of availability as a raw material and cost, an adduct of an aliphatic diisocyanate having 6 or more carbon atoms, preferably 6 to 12 carbon atoms, such as hexamethylene diisocyanate, and an aliphatic polyol is more preferred, and an adduct of hexamethylene diisocyanate and trimethylolpropane is particularly preferred.

[0032] Polyisocyanates having an aliphatic skeleton and polyisocyanates having an aromatic skeleton may be used in combination, but the proportion of polyisocyanates having an aliphatic skeleton in the total polyisocyanate components is preferably 50 to 100% by weight, more preferably 70 to 100% by weight or more, and even more preferably 80 to 100% by weight or more. If it is less than 50% by weight, the elasticity and flexibility of the adhesive layer tend to decrease.

[0033] NCO%, which indicates the weight percentage of NCO groups in the polyisocyanate, is preferably 2 to 30%, and more preferably 2 to 20%.

[0034] <(C) Silicone Compound Having a Reactive Hydroxyl Group> The adhesive for transparent substrates of the present invention preferably further contains (C) a silicone compound having a reactive hydroxyl group. "Reactive hydroxyl group" refers to a hydroxyl group that is reactive with an isocyanate group. Because the silicone compound that acts as a slip agent has a reactive hydroxyl group, it reacts with the polyisocyanate and is fixed to the cured adhesive layer, allowing the adhesive layer to maintain its flexibility for a long period of time.

[0035] In the silicone compound (C) having a reactive hydroxyl group, the reactive hydroxyl group may or may not be directly bonded to Si. The reactive hydroxyl group may also be generated by hydrolysis of an alkoxysilyl group or the like. The silicone compound (C) having a reactive hydroxyl group may have, in addition to the reactive hydroxyl group, a reactive group such as a (meth)acrylic group, a vinyl group, an amino group, or an epoxy group, or a non-reactive group such as an alkyl group, an ester group, an aralkyl group, a phenyl group, or a polyether group. Two or more of these silicone compounds may be used in combination.

[0036] The number average molecular weight of the (C) silicone compound having a reactive hydroxyl group is preferably 1000 to 20000, more preferably 3000 to 15000. If it is less than 1000, it will tend to separate from the adhesive layer and the effect will not last, and if it exceeds 20000, it will tend to be difficult to orient in the adhesive layer.

[0037] The weight-average molecular weight of the silicone compound having a reactive hydroxyl group (C) is preferably 2000 to 40000, more preferably 6000 to 30000. If it is less than 2000, it will tend to separate from the film and the effect will not last, and if it exceeds 40000, it will tend to be difficult to orient in the adhesive layer.

[0038] The hydroxyl value of the silicone compound (C) having a reactive hydroxyl group is preferably 30 to 200 mgKOH / g, more preferably 80 to 150 mgKOH / g. If it is less than 30 mgKOH / g, it tends to separate from the film and its effect will not last, while if it exceeds 200 mgKOH / g, its water solubility increases and it tends to separate from the film due to moisture.

[0039] <Other additives> Various additives such as dispersants, solvents, leveling agents, curing catalysts, thickeners, ultraviolet absorbers, light stabilizers, antioxidants, and silane coupling agents may be added to the adhesive for transparent substrates of the present invention as needed.

[0040] The dispersant is not particularly limited, and examples thereof include polycarboxylic acid dispersants, polyamine dispersants, etc. The blending amount is also not particularly limited, and for example, 0.1 to 10 parts by weight can be added per 100 parts by weight of (A) polyester polyol.

[0041] The solvent is not particularly limited, and examples thereof include cyclohexanone, butyl acetate, ethyl acetate, xylene, toluene, methyl isobutyl ketone, and methyl ethyl ketone. These solvents can be used alone or in combination of two or more. The content of the solvent in the adhesive for transparent substrates is not particularly limited, and can be adjusted as needed.

[0042] The leveling agent is not particularly limited, and examples thereof include polyether-based leveling agents, fluorine-based leveling agents, polyester-based leveling agents, siloxane-based leveling agents, silicone-based leveling agents, acrylic-based leveling agents, etc. The amount of the leveling agent to be added is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, per 100 parts by weight of (A) polyester polyol.

[0043] The silane coupling agent is not particularly limited, and examples thereof include vinyl-based silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane, (meth)acrylic-based silane coupling agents such as γ-methacryloxypropyltrimethoxysilane, epoxy-based silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and amine-based silane coupling agents such as γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane. The amount of the silane coupling agent to be added is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, per 100 parts by weight of the (A) polyester polyol.

[0044] <Adhesive for transparent substrates> The adhesive for transparent substrates of the present invention may be in the form of either a one-component type or a two-component type, but is preferably a two-component type from the viewpoint of ensuring the toughness of the film.

[0045] The blending ratio of the components is preferably such that the ratio of the total number of moles of isocyanate groups contained in (B) polyisocyanate to the total number of moles of hydroxyl groups contained in (A) polyester polyol and (C) silicone compound having a reactive hydroxyl group (isocyanate groups / hydroxyl groups) is 0.7 to 1.5, and more preferably 0.8 to 1.2.

[0046] The amount of (C) silicone compound having a reactive hydroxyl group is preferably 0.3 to 25 parts by weight, more preferably 0.3 to 10 parts by weight, and even more preferably 0.5 to 5 parts by weight, per 100 parts by weight of (A) polyester polyol. If it is less than 0.3 parts by weight, the flexibility of the adhesive layer may be insufficient, and if it exceeds 25 parts by weight, the water resistance may be reduced.

[0047] <Laminate> The laminate of the present invention is formed by laminating a first transparent substrate, an adhesive layer made of the adhesive for transparent substrates, and a second transparent substrate in this order.

[0048] The material of the transparent substrate is not particularly limited, and examples thereof include resin, rubber, and glass. Examples of resins include electrostatically processed polypropylene, polycarbonate resin, nylon 6, polyethylene terephthalate resin, acrylic resin, polyurethane resin, polyester resin, ABS resin, hard vinyl chloride, soft vinyl chloride, vinyl acetate resin, and polystyrene. Examples of rubber include butyl rubber, urethane rubber, and silicone rubber. Examples of glass include heat-absorbing glass, heat-reflecting glass, green glass, lined plate glass, and colored glass. The transparent substrate may be a composite material combining two or more of these materials. The shape of the substrate is also not particularly limited, and examples thereof include flat, curved, and spherical surfaces. Furthermore, the first transparent substrate and the second transparent substrate may be the same or different.

[0049] The method for forming the adhesive layer is not particularly limited, and examples thereof include a method in which an adhesive for transparent substrates is applied to a first substrate, a second substrate is laminated onto the applied layer, and then the applied layer is cured. Examples of application methods include brushing, roller coating, bar coating, spin coating, dipping, spraying, printing, and inkjet coating. The curing method is also not particularly limited, and examples thereof include known methods such as curing by drying at room temperature and accelerated curing by heating. If necessary, the adhesive layer may be cured while degassing using a vacuum degassing method, a nip roll method, or the like. When heating, the temperature is preferably 30 to 150°C, and more preferably 50 to 100°C.

[0050] The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 2000 μm. If it is less than 5 μm, the strength may be insufficient and the adhesive layer may be prone to breakage, while if it exceeds 2000 μm, the reactivity tends to be non-uniform. In particular, when applied to automotive glass, the thickness of the adhesive layer is preferably 300 to 2000 μm, more preferably 400 to 1000 μm. Because the adhesive layer obtained by the present invention has high transparency, the transparency of the entire laminate can be ensured even if the adhesive layer is thick. When applied to a flexible display device, the thickness of the adhesive layer is preferably 5 to 400 μm, more preferably 10 to 200 μm. Note that if a thickness of more than 100 μm is required, coating may be performed in several steps, and finally, a second transparent substrate may be attached and cured.

[0051] The adhesive layer preferably exhibits an elongation of 300% or more, more preferably 350% or more, when the thickness is 50 μm, where the elongation is a value measured by a tensile test on a free film.

[0052] The laminate of the present invention preferably has a total light transmittance of 75% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. The total light transmittance of the adhesive layer alone is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more. The total light transmittance can be evaluated by the total light transmittance test of JIS K 7375 using a visible light transmittance meter.

[0053] The laminate of the present invention preferably has a haze of 5% or less, more preferably 2% or less. The haze of the adhesive layer alone is preferably 1% or less, more preferably 0.5% or less. The haze can be measured and calculated using a visible light transmittance measuring device.

[0054] The refractive index of the adhesive layer can be appropriately set depending on the application of the laminate, and can be, for example, 1.2 to 1.7 at a wavelength of 550 nm.

[0055] The laminate of the present invention preferably has excellent flexibility. Flexibility can be evaluated by the flexibility test of JIS K 5600-5-1. It is preferable that the laminate of the present invention does not suffer from cracking or peeling of the coating film when tested using a 2 mm diameter mandrel in the test apparatus of 3.1.2 Type 1 in Part 5: Mechanical properties of coating films, Section 1: Flex resistance (cylindrical mandrel method) of the JIS.

[0056] The adhesive for transparent substrates of the present invention can be used in flexible display devices and flexible touch panels to bond polarizing filters, color filters, electrode substrates, etc. The adhesive for transparent substrates of the present invention can also be used for laminated glass for automobiles, laminated glass for aircraft, laminated glass for ships, and laminated glass for buildings, and is particularly suitable for use in bonding laminated glass used in automobile windshields. [Example]

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Furthermore, unless otherwise specified, "parts" means parts by weight.

[0058] (1) Various chemicals used in the examples and comparative examples Silicone compound 1: KR-500 (a silicone compound having a methoxysilyl group. Contains 28% by weight of methoxy groups), manufactured by Shin-Etsu Chemical Co., Ltd. Silicone compound 2: BYK-330 (BYK) Silane coupling agent: BYK-4512 (BYK) Adduct of hexamethylene diisocyanate and trimethylolpropane: Duranate E402-90T (NCO%: 8.5%) manufactured by Asahi Kasei Corporation Adduct of m-xylene diisocyanate and trimethylolpropane: Desmodur L75 (NCO%: 13.3%), manufactured by Sumika Covestro Urethane Co., Ltd. Dispersant: BYK-161 (BYK)

[0059] (2) The prepared resin compositions were evaluated by the following methods. <Adhesion> The resin composition was applied to various substrates listed in Table 1, and then dried to obtain a 15 μm-thick coating film. 1 mm square grid-like cuts were made in the film with a cutter knife, and adhesive tape was then applied and peeled off to check the proportion of the film remaining on the substrate, and the adhesion was evaluated on the following 7-point scale (based on the JIS K 5600-5-6 cross-cut test method). 6: The coating film adhered to the substrate and no peeling occurred. 5: The coating peeled off in the range of more than 0% to 5%. 4: More than 5% but not more than 15% of the coating peeled off. 3: More than 15% but not more than 35% of the coating peeled off. 2: More than 35% but not more than 65% of the coating peeled off. 1: More than 65% of the coating peeled off. However, the coating did not peel off when peeled off only with adhesive tape without making a cross-cut incision. 0: More than 65% of the coating peeled off. Furthermore, the coating peeled off simply by attaching and peeling off adhesive tape without making cross-cut cuts.

[0060] <Growth rate> The resin composition was applied to a natural rubber substrate to form a coating film with a thickness of 50 μm, and both ends were tensile-deformed to measure the elongation of the coating film. The elongation (%) is expressed as the ratio of the length of the substrate at the time when the coating film is stretched to the length before stretching.

[0061] (3) Evaluation of adhesion and elongation rate 1 Example 1 A dicarboxylic acid mixture was obtained by mixing 14 parts of aromatic dicarboxylic acids, terephthalic acid and 14 parts of isophthalic acid, with 30 parts of adipic acid, an aliphatic dicarboxylic acid. This mixture was then mixed with 8 parts of aliphatic diols, ethylene glycol, 17 parts of neopentyl glycol, and 17 parts of 1,6-hexanediol, and subjected to a condensation reaction by a known method to obtain polyester polyol (A1). The Mn of (A1) was 17,400, the Mw was 34,100, and the hydroxyl value (solid) was 10 mgKOH / g. 100 parts of the obtained (A1) were mixed with 1 part of silicone compound 1, and then 100 parts of cyclohexanone as a solvent to form a base resin. 4 parts of an adduct of hexamethylene diisocyanate and trimethylolpropane as a curing agent were mixed thereto to obtain a resin composition. The evaluation results of adhesion and elongation are shown in Table 1.

[0062] Example 2 A resin composition was obtained in the same manner as in Example 1, except that bisphenol A, an aromatic diol, was used instead of 1,6-hexanediol. The evaluation results of adhesion and elongation are shown in Table 1.

[0063] Example 3 A resin composition was obtained in the same manner as in Example 1, except that an adduct of hexamethylene diisocyanate and trimethylolpropane was not used, and instead 5 parts of an adduct of m-xylene diisocyanate having an aromatic skeleton and trimethylolpropane was blended. The evaluation results of adhesion and elongation are shown in Table 1.

[0064] Example 4 A resin composition was obtained in the same manner as in Example 1, except that Silicone Compound 1 was not used. The evaluation results of adhesion and elongation are shown in Table 1.

[0065] Comparative Example 1 A resin composition was obtained in the same manner as in Example 1, except that 29 parts of terephthalic acid and 29 parts of isophthalic acid were used as the dicarboxylic acids. The evaluation results of adhesion and elongation are shown in Table 1.

[0066] [Table 1]

[0067] As shown in Table 1, each example in which an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol were combined as raw material components for the polyester polyol showed a higher elongation rate than Comparative Example 1 in which no aliphatic dicarboxylic acid was used.

[0068] (4) Evaluation of adhesion and elongation rate 2 Example 5 A dicarboxylic acid mixture containing 14 parts terephthalic acid, 14 parts isophthalic acid, and 30 parts adipic acid was mixed with 11 parts neopentyl glycol, 17 parts 1,6-hexanediol, and 10 parts propylene glycol, and the mixture was subjected to a condensation reaction to obtain a polyester polyol (Mn: 10,000, Mw: 20,000, hydroxyl value (solid): 20 mg KOH / g). This polyester polyol was mixed with 1 part silicone compound 1 and 100 parts cyclohexanone to form a base resin. Four parts of an adduct of hexamethylene diisocyanate and trimethylolpropane were then added as a curing agent to obtain a resin composition. The evaluation results of adhesion and elongation are shown in Table 2.

[0069] Example 6 A resin composition was obtained in the same manner as in Example 5, except that 2 parts of a silane coupling agent was further added to the formulation of Example 5. The evaluation results of adhesion and elongation are shown in Table 2.

[0070] Example 7 A resin composition was obtained in the same manner as in Example 5, except that in the formulation of Example 5, 20 parts of silicone compound 1 was used, and further 0.5 parts of silicone compound 2 and 2 parts of a silane coupling agent were added. The evaluation results of adhesion and elongation are shown in Table 2.

[0071] [Table 2]

[0072] As shown in Table 2, Example 6 exhibited elongation and adhesion to a variety of substrates equivalent to those of Example 5. Example 7 also exhibited elongation and adhesion to a variety of substrates equivalent to those of Example 5.

[0073] (5) Elasticity and transparency evaluation of resin composition films Example 8 The resin composition of Example 1 was applied to a 0.1 mm thick acrylic resin substrate and then dried to obtain a 15 μm thick coating film. A schematic diagram of the substrate and coating film is shown in Figure 1. The modulus, load strain, haze, and total light transmittance of this coating film were measured using a texture analyzer TA.XTplus (Eiko Seiki). The evaluation results are shown in Table 3.

[0074] Example 9 The resin composition of Example 2 was applied to a 0.1 mm thick acrylic resin substrate and then dried to obtain a coating film with a thickness of 15 μm. This coating film was evaluated in the same manner as in Example 8. The results are shown in Table 3.

[0075] Example 10 The resin composition of Example 3 was applied to a 0.1 mm thick acrylic resin substrate and then dried to obtain a coating film with a thickness of 15 μm. This coating film was evaluated in the same manner as in Example 8. The results are shown in Table 3.

[0076] Example 11 The resin composition of Example 4 was applied to a 0.1 mm thick acrylic resin substrate and then dried to obtain a coating film with a thickness of 15 μm. This coating film was evaluated in the same manner as in Example 8. The results are shown in Table 3.

[0077] Example 12 The resin composition of Example 6 was applied to a 0.1 mm thick acrylic resin substrate and then dried to obtain a coating film with a thickness of 15 μm. This coating film was evaluated in the same manner as in Example 8. The results are shown in Table 3.

[0078] Example 13 The resin composition of Example 7 was applied to a 0.1 mm thick acrylic resin substrate and then dried to obtain a coating film with a thickness of 15 μm. This coating film was evaluated in the same manner as in Example 8. The results are shown in Table 3.

[0079] [Table 3]

[0080] As shown in Table 3, the adhesive layers made of the compositions of Examples 1 to 4 and 6 to 7 exhibited low haze values ​​of 0.5% or less and high total light transmittances of 93% or more.

[0081] (6) Transparency evaluation on glass substrate Example 14 The resin composition of Example 1 was spin-coated onto an alkali-free glass substrate (EagleXE, Corning Incorporated) to form a film. After film formation, it was dried to obtain a coating film with a thickness of 15 μm. The total light transmittance, haze, YI (yellow index), n (refractive index) at a wavelength of 550 nm, and k (extinction coefficient) of the laminate including this coating film and substrate were measured using an ellipsometer. The evaluation results are shown in Table 4.

[0082] Examples 15 to 17 The resin compositions of Examples 4, 6, and 7 were spin-coated onto alkali-free glass substrates (EagleXE, Corning Inc.) to form films. After film formation, the films were dried to obtain coatings with a thickness of 15 μm. The laminates including the coatings and the substrates were evaluated in the same manner as in Example 14. The results are shown in Table 4.

[0083] Comparative Example 2 The total light transmittance, haze, YI (yellow index), n (refractive index) and k (extinction coefficient) at a wavelength of 550 nm of the alkali-free glass substrate (EagleXE, Corning Inc.) used in Examples 14 to 17 were measured using an ellipsometer. The evaluation results are shown in Table 4.

[0084] [Table 4]

[0085] As shown in Table 4, the resin compositions of Examples 1, 4, 6, and 7 exhibited high total light transmittance and low haze values ​​even when coated on a glass substrate. They also exhibited sufficient values ​​for the yellow index (YI), refractive index, and extinction coefficient, which are important performance factors for laminates using glass as a substrate.

[0086] (7) Flexibility evaluation Each of the resin compositions of Examples 1, 4, 6, and 7 was applied to a 0.3 mm thick metal substrate and then dried to obtain a laminate having a 15 μm thick coating film on the substrate. The flexibility of this laminate was evaluated using the flex test of JIS K 5600-5-1. As a result, each of the laminates made from the resin compositions of Examples 1, 4, 6, and 7 did not experience cracking or peeling of the coating film when tested using a 2 mm diameter mandrel using the 3.1.2 Type 1 testing device in JIS Part 5: Mechanical Properties of Coating Films, Section 1: Flex Resistance (Cylindrical Mandrel Method).

Claims

1. (A) a polyester polyol which is a condensation reaction product of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic diol; (B) a polyisocyanate, and (C) Silicone compound having a reactive hydroxyl group An adhesive for bonding transparent substrates together, comprising:

2. The transparent substrate is glass or a film. An adhesive for bonding transparent substrates according to claim 1 together.

3. 3. The adhesive for bonding transparent substrates together according to claim 1, wherein the aliphatic diol has an aliphatic skeleton having 2 to 6 carbon atoms.

4. The adhesive for bonding transparent substrates together according to any one of claims 1 to 3, characterized in that the aromatic dicarboxylic acid is selected from the group consisting of o-phthalic acid, m-phthalic acid, and p-phthalic acid.

5. 5. The adhesive for bonding transparent substrates together according to claim 1, wherein the polyisocyanate (B) is an adduct of an aliphatic diisocyanate having 6 or more carbon atoms and an aliphatic polyol.

6. a first transparent substrate; An adhesive layer made of an adhesive for bonding the transparent substrates according to any one of claims 1 to 5 together; and The second transparent substrate is A laminate formed by stacking layers in this order.

7. 10. An automotive glass comprising the laminate of claim 6.

8. A flexible display device comprising the laminate of claim 6.

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