Interlayer filler, laminated glass, image display device, and touch panel

Abstract

In an interlayer filler according to the present invention, the range of the relative permittivity when the moisture content is 0% is 2.0-5.0, the range of the relative permittivity when the moisture content is 0.5% is 2.5-5.5, and the relative permittivity when the moisture content is 0.5% is larger than the relative permittivity when the moisture content is 0%. According to the present invention, it is possible to provide an interlayer filler in which the relative permittivity can be adjusted to a desired range even when the material system of a resin composition for forming an interlayer filler is the same.

Description

Interlayer filler, laminated glass, image display device, and touch panel

[0001] The present invention relates to an interlayer filler, a laminated glass, an image display device, and a touch panel.

[0002] Touch panels, which allow input operations to be performed by touching the screen, are used in in-vehicle displays, tablet computers, smartphones, and the like. Touch panels include various components such as touch sensors and front panels, and an interlayer filler is used as a pressure-sensitive adhesive (or adhesive) to secure the various components. For example, Patent Document 1 describes an invention relating to an adhesive composition for touch panels, which contains a compound having a glycidyl ether group and an alkoxysilyl group in its molecule, an epoxy resin, a phenolic curing agent, and a filler.

[0003] JP 2010-90320 A

[0004] In recent years, capacitive touch panel modules have adopted on-cell or in-cell structures, i.e., structures with touch sensors patterned directly on liquid crystal displays (LCDs). One drawback of these structures is that the distance between the touch sensor and the front panel is larger than in conventional structures, which tends to result in lower touch sensor sensitivity. In addition, because the distance between the touch sensor and the front panel and the material of the front panel vary depending on the type of touch panel module, achieving a touch panel with excellent operation sensitivity requires an interlayer filler with an appropriate thickness and dielectric constant for each type.

[0005] To achieve a touch panel with excellent operational sensitivity, an interlayer filler with an appropriate dielectric constant is required depending on the type of touch panel module or the location where the interlayer filler is attached within the touch panel. However, when attaching interlayer fillers of different materials (with different dielectric constants), the number of types of interlayer fillers to be handled increases, making management and design more complicated. Furthermore, adjusting the amount of metal additive added when fine-tuning the dielectric constant can easily change the optical properties, making management and design more complicated.

[0006] Therefore, an object of the present invention is to provide an interlayer filler whose relative dielectric constant can be adjusted to a desired range even when the resin composition material for forming the interlayer filler is the same.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by using an interlayer filler in which the relative dielectric constant (1 MHz) at a water content of 0% is in the range of 2.0 to 5.0 and the relative dielectric constant (1 MHz) at a water content of 0.5% is in the range of 2.5 to 5.5, and the relative dielectric constant (1 MHz) at a water content of 0.5% is greater than the relative dielectric constant (1 MHz) at a water content of 0%. This finding led to the completion of the present invention. That is, the gist of the present invention is as follows: [1] to

[13]

[0008] [1] An interlayer filler having a relative dielectric constant at 1 MHz of 2.0 or more and 5.0 or less when the moisture content is 0%, and a relative dielectric constant at 1 MHz of 2.5 or more and 5.5 or less when the moisture content is 0.5%, the relative dielectric constant at 0.5% being greater than the relative dielectric constant at 0% moisture content. [2] The interlayer filler according to [1] above, having a relative dielectric constant of 3.9 or more. [3] The interlayer filler according to [1] or [2] above, having a thickness of 380 μm or more and 760 μm or less. [4] The interlayer filler according to [1] above, having a relative dielectric constant of less than 3.9. [5] The interlayer filler according to [4] above, having a thickness of 380 μm or more and 760 μm or less. [6] The interlayer filler according to any of [1] to [5] above, containing a thermoplastic resin. [7] The interlayer filler according to any of [1] to [6] above, further containing a plasticizer. [8] A laminate having the interlayer filler according to any one of [1] to [7] above and at least one transparent substrate. [9] Laminated glass having the interlayer filler according to any one of [1] to [7] above.

[10] An image display device having the interlayer filler according to any one of [1] to [7] above.

[11] A touch panel having at least a first substrate, a first interlayer filler, a second substrate, a second interlayer filler, and a touch sensor, in this order, wherein the first interlayer filler and the second interlayer filler have different dielectric constants and the resin compositions constituting the first interlayer filler and the second interlayer filler are made of the same material system.

[12] The touch panel according to

[11] above, wherein the first interlayer filler and the second interlayer filler have different moisture contents.

[13] The touch panel according to

[11] or

[12] above, wherein the first interlayer filler and the second interlayer filler have different thicknesses.

[0009] The present invention can provide an interlayer filler whose relative dielectric constant can be adjusted to a desired range even when the resin composition material for forming the interlayer filler is the same.

[0010] 1 is a graph showing the relationship between moisture content and relative dielectric constant. FIG. 2 is a schematic cross-sectional view showing an embodiment of a laminate. FIG. 3 is a schematic cross-sectional view showing an embodiment of a laminate. FIG. 4 is a schematic cross-sectional view showing an embodiment of a laminate.

[0011] <Interlayer Filler> When the moisture content of the interlayer filler of the present invention is 0%, the relative dielectric constant at 1 MHz is in the range of 2.0 to 5.0, and when the moisture content is 0.5%, the relative dielectric constant at 1 MHz is in the range of 2.5 to 5.5. Furthermore, when the moisture content of the interlayer filler of the present invention is 0.5%, the relative dielectric constant at 1 MHz is greater than the relative dielectric constant at 1 MHz when the moisture content is 0%. Note that the 1 MHz frequency is the frequency used to measure the relative dielectric constant.

[0012] The interlayer filler of the present invention, with its above-described configuration, can provide an interlayer filler whose dielectric constant can be adjusted to a desired range, even when the resin composition used to form the interlayer filler is made of the same material system. Therefore, interlayer fillers with different dielectric constants can be produced using the same resin composition, making it easier to prepare interlayer fillers suitable for different touch panel models. Furthermore, when it is necessary to use interlayer fillers with different dielectric constants depending on the position of the interlayer filler in the touch panel, it becomes easier to prepare interlayer fillers with the desired dielectric constant. Note that resin compositions made of the same material system refer to resin compositions containing the same types of resin components, preferably resin compositions containing the same types of resin components and additives, and more preferably resin compositions containing the same components except for the water content.

[0013] From the viewpoint of further enhancing the effects of the present invention, the interlayer filler of the present invention has a relative dielectric constant of preferably 2.1 to 4.9, more preferably 2.2 to 4.8, when the moisture content is 0%. Also, the relative dielectric constant of preferably 2.6 to 5.3, more preferably 2.6 to 5.1, when the moisture content is 0.5%.

[0014] As described above, the interlayer filler of the present invention has a higher dielectric constant at a water content of 0.5% than at a water content of 0%. The difference between the dielectric constant at a water content of 0.5% and the dielectric constant at a water content of 0% is preferably 0.1 or more, more preferably 0.2 or more, and preferably 0.5 or less. Methods for adjusting the dielectric constants of the interlayer filler at water contents of 0% and 0.5% and the difference between these dielectric constants as described above include methods for adjusting the composition of the resin composition used in the interlayer filler, the thickness of the interlayer filler, etc.

[0015] Furthermore, when the moisture content of the interlayer filler of the present invention is X (%) and the relative dielectric constant is Y, it is preferable that the following formulas (1) and (2) are satisfied: Y≧0.66X+2.28 Formula (1) Y≦0.46X+4.80 Formula (2) The range satisfying formulas (1) and (2) is the region between the two straight lines in Figure 1. From the viewpoint of suppressing whitening of the interlayer filler, it is preferable that the moisture content be adjusted to a certain level or less. From this viewpoint, the moisture content (X) is preferably 0% or more and 1% or less, more preferably 0% or more and 0.7% or less, and even more preferably 0% or more and 0.5% or less.

[0016] When the interlayer filler of the present invention is used in a touch panel, the appropriate dielectric constant varies depending on its placement in the touch panel, i.e., whether it is located closer to the finger-operated portion of the surface or closer to the liquid crystal display. In the former case, a high dielectric constant is preferable, while in the latter case, a low dielectric constant is preferable. Therefore, the interlayer filler of the present invention is preferably one whose dielectric constant is adjusted to be low or high. From this perspective, when the dielectric constant is adjusted to be low, the dielectric constant of the interlayer filler of the present invention is preferably less than 3.9, more preferably 3.5 or less, even more preferably 3 or less, and preferably 1.5 or more, more preferably 2.0 or more. When the dielectric constant is adjusted to be high, the dielectric constant of the interlayer filler of the present invention is preferably 3.9 or more, more preferably 4 or more, even more preferably 4.5 or more, and preferably 6.0 or less, more preferably 5.5 or less.

[0017] (Thermoplastic resin) The interlayer filler preferably contains a thermoplastic resin as a resin component. As the thermoplastic resin contained in the interlayer filler, polyvinyl acetal resin is preferred, and polyvinyl butyral resin is more preferred, from the viewpoint of adjusting the relative dielectric constant at the water content of 0% and 0.5% to the desired range. By using such a resin, it becomes easier to adjust the relative dielectric constant to the desired range by adjusting the water content of the interlayer filler, and it also becomes easier to adjust the relative dielectric constant by adjusting the thickness of the interlayer filler. Furthermore, by using such a resin, the impact energy absorption of the interlayer filler is also improved.

[0018] (Polyvinyl acetal resin) The polyvinyl acetal resin used as the thermoplastic resin of the interlayer filler may be a modified polyvinyl acetal resin or an unmodified polyvinyl acetal resin. As described below, the modified polyvinyl acetal resin may have a structure (modifying group) other than an acetal group, a hydroxyl group, and an acetyl group, and preferably has a modifying group on a side chain. The polyvinyl acetal resin is obtained by acetalizing polyvinyl alcohol with an aldehyde, and then reacting it with a modifier or subjecting it to a reacetylation treatment as necessary. In addition, to obtain the modified polyvinyl acetal resin, modified polyvinyl alcohol may be used as the raw material polyvinyl alcohol.

[0019] <Degree of Acetalization> The degree of acetalization of the polyvinyl acetal resin used as the thermoplastic resin of the interlayer filler is preferably 65 mol% or more and 75 mol% or less. When the degree of acetalization of the polyvinyl acetal resin is 65 mol% or more, the number of hydroxyl groups in the polyvinyl acetal resin is reduced, and the polyvinyl acetal resin has sufficient flexibility. When the degree of acetalization of the polyvinyl acetal resin is 75 mol% or less, the adhesion to transparent substrates such as glass is improved. From this perspective, the degree of acetalization of the polyvinyl acetal resin is more preferably 67 mol or more and 74 mol or less, even more preferably 68 mol or more and 73 mol or less, and even more preferably 69 mol or more and 72 mol or less. Note that the degree of acetalization refers to the degree of butyralization when the acetal group is a butyral group and the polyvinyl acetal resin is a polyvinyl butyral resin.

[0020] The degree of acetalization is a molar fraction obtained by subtracting the amount of ethylene groups having hydroxyl groups and the amount of ethylene groups having acetyl groups from the total amount of ethylene groups in the main chain, and dividing the result by the total amount of ethylene groups in the main chain, and the percentage is expressed as the molar fraction. The degree of acetalization (degree of butyralization) may be calculated from the results of measurements made, for example, according to JIS K6728 "Testing Methods for Polyvinyl Butyral."

[0021] <Aldehyde> The polyvinyl acetal resin used as the thermoplastic resin of the interlayer filler is preferably a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol (PVA) with an aldehyde. The aldehyde is not particularly limited, but generally, an aldehyde having 1 to 10 carbon atoms is preferably used. The aldehyde having 1 to 10 carbon atoms is not particularly limited, and examples thereof include n-butyl aldehyde, isobutyraldehyde, n-valeraldehyde, 2-ethylbutyraldehyde, n-hexyl aldehyde, n-octyl aldehyde, n-nonyl aldehyde, n-decyl aldehyde, formaldehyde, acetaldehyde, and benzaldehyde. These aldehydes may be used alone or in combination of two or more. Among the above, n-butylaldehyde, n-hexylaldehyde, and n-valeraldehyde are preferred, and n-butylaldehyde is more preferred. Therefore, the polyvinyl acetal resin is preferably a polyvinyl butyral resin.

[0022] <Polyvinyl Alcohol (PVA)> Polyvinyl alcohol (PVA) can be obtained, for example, by saponifying a polyvinyl ester such as polyvinyl acetate. The degree of saponification of polyvinyl alcohol is generally 70 to 99.9 mol%. The average degree of polymerization of PVA is preferably 200 or more, more preferably 500 or more, even more preferably 1000 or more, and even more preferably 1500 or more. When the average degree of polymerization is equal to or greater than the above-mentioned lower limit, the penetration resistance of laminated glass is improved when used in laminated glass. Furthermore, the average degree of polymerization of PVA is preferably 5000 or less, more preferably 4000 or less, even more preferably 3500 or less, and even more preferably 2500 or less. The average degree of polymerization of polyvinyl alcohol is determined by a method in accordance with JIS K6726 "Testing Methods for Polyvinyl Alcohol."

[0023] <Hydroxyl Group Amount> The hydroxyl group amount of the polyvinyl acetal resin used as the thermoplastic resin of the interlayer filler is preferably 15 mol% or more, and preferably 38 mol% or less. By setting the hydroxyl group amount to 15 mol% or more, adhesion to the transparent substrate is likely to be good. Furthermore, by setting the hydroxyl group amount to 38 mol% or less, flexibility is likely to be ensured. The hydroxyl group amount is more preferably 20 mol% or more, and even more preferably 25 mol% or more. Furthermore, the hydroxyl group amount is more preferably 35 mol% or less, and even more preferably 33 mol% or less. When a polyvinyl butyral resin is used as the polyvinyl acetal resin, from the same viewpoint, the hydroxyl group amount is 15 mol% or more, and preferably 38 mol% or less, more preferably 20 mol% or more, even more preferably 25 mol% or more, more preferably 35 mol% or less, and even more preferably 33 mol% or less. The amount of hydroxyl groups in the polyvinyl acetal resin is the molar fraction calculated by dividing the amount of ethylene groups having hydroxyl groups by the total amount of ethylene groups in the main chain, and is expressed as a percentage. The amount of ethylene groups having hydroxyl groups can be measured, for example, in accordance with JIS K6728 "Testing Methods for Polyvinyl Butyral."

[0024] <Degree of Acetylation> The degree of acetylation of the polyvinyl acetal resin used as the thermoplastic resin of the interlayer filler is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and even more preferably 2 mol% or less. When the degree of acetylation is below the upper limit, the moisture resistance of the interlayer filler is increased. Furthermore, the degree of acetylation is not particularly limited, but is preferably 0.01 mol% or more, more preferably 0.1 mol% or more. The degree of acetylation is a molar fraction calculated by dividing the amount of ethylene groups bonded to acetyl groups by the total amount of ethylene groups in the main chain, expressed as a percentage. The amount of ethylene groups bonded to acetyl groups can be measured, for example, in accordance with JIS K6728 "Test Methods for Polyvinyl Butyral."

[0025] <Modified Polyvinyl Acetal Resin> The polyvinyl acetal resin used as the thermoplastic resin of the interlayer filler may be an unmodified polyvinyl acetal resin, but may also be a modified polyvinyl acetal resin. The modified polyvinyl acetal resin has a structure (modifying group) other than an acetal group, a hydroxyl group, and an acetyl group, and preferably has a modifying group on the side chain. Examples of the modifying group include those having a polyalkylene oxide structure on the side chain, and those having an acetal group or an alkyl group other than an acetyl group (e.g., having approximately 2 to 30 carbon atoms) on the side chain. A preferred modified polyvinyl acetal resin is a polyalkylene oxide-modified polyvinyl acetal resin, and a more preferred modified polyvinyl acetal resin is a polyethylene oxide-modified polyvinyl acetal resin. The modification amount is not particularly limited, but is, for example, 0.1 mol% to 10 mol%. The modification amount refers to the ratio of functional groups to all vinyl monomer units constituting the polyvinyl acetal resin.

[0026] (Plasticizer) The interlayer filler preferably contains a plasticizer as an additive in addition to the thermoplastic resin. By containing a plasticizer, the interlayer filler becomes more flexible and has higher impact energy absorption.

[0027] Examples of the plasticizer include organic ester plasticizers, organic phosphorus-based plasticizers such as organic phosphate ester plasticizers and organic phosphite ester plasticizers, organic ether-based plasticizers such as polyalkylene glycol-based plasticizers and polyoxyalkylene ether-based plasticizers, and alcohol-based plasticizers. One type of plasticizer may be used alone, or two or more types may be used in combination. Among the above, organic ester plasticizers and organic ether-based plasticizers are preferred.

[0028] Preferred organic ester plasticizers include monobasic organic acid esters and polybasic organic acid esters. Examples of monobasic organic acid esters include esters of glycols and monobasic organic acids. Examples of glycols include polyalkylene glycols in which each alkylene unit has 2 to 4 carbon atoms, preferably 2 or 3 carbon atoms, and the number of repeating alkylene units is 2 to 10, preferably 2 to 4. Examples of glycols include monoalkylene glycols having 2 to 4 carbon atoms, preferably 2 or 3 carbon atoms (i.e., one repeating unit). Specific examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, and butylene glycol. Examples of the monobasic organic acid include organic acids having 3 to 10 carbon atoms, and specific examples thereof include butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptyl acid, n-octylic acid, 2-ethylhexyl acid, n-nonylic acid, and decylic acid.

[0029] Specific monobasic organic acids include triethylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol dicaprylate, triethylene glycol di-n-octanoate, triethylene glycol di-n-heptanoate, tetraethylene glycol di-n-heptanoate, tetraethylene glycol di-2-ethylhexanoate, diethylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, and triethylene glycol. Di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate, diethylene glycol dicaprylate, triethylene glycol di-n-heptanoate, tetraethylene glycol di-n-heptanoate, triethylene glycol di-2-ethylbutyrate, ethylene glycol di-2-ethylbutyrate, 1,2-propylene glycol di-2-ethylbutyrate, 1,3-propylene glycol di-2-ethylbutyrate, 1,4-butylene glycol di-2-ethylbutyrate, 1,2-butylene glycol di-2-ethylbutyrate, and the like.

[0030] Examples of polybasic organic acid esters include ester compounds of dibasic organic acids having 4 to 12 carbon atoms, such as adipic acid, sebacic acid, and azelaic acid, with alcohols having 4 to 10 carbon atoms. The alcohols having 4 to 10 carbon atoms may be linear, branched, or cyclic. Specific examples include dibutyl sebacate, dioctyl azelaate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl carbitol adipate, and mixed adipates. Oil-modified alkyd sebacate is also suitable. Examples of mixed adipates include adipates prepared from two or more alcohols selected from alkyl alcohols having 4 to 9 carbon atoms and cyclic alcohols having 4 to 9 carbon atoms.

[0031] The organic ester plasticizer is not limited to the complete esters of the above-mentioned esters, but may also be a partial ester. For example, it may be a partial ester of a glycol and a monobasic organic acid, or a partial ester of a dibasic organic acid and an alcohol. Specific examples include triethylene glycol-mono-2-ethylhexanoate. Furthermore, it may be a partial ester of a monobasic organic acid with a trihydric or higher alcohol, such as glycerin. Examples of monobasic organic acids include monobasic organic acids having 3 to 24 carbon atoms, preferably 6 to 18 carbon atoms. Specific examples of partial esters of a trihydric or higher alcohol and a monobasic organic acid include a mono- or diester of glycerin and stearic acid, and a mono- or diester of glycerin and 2-ethylhexyl acid. Among the organic ester plasticizers listed above, triethylene glycol-di-2-ethylhexanoate (3GO) is particularly preferred.

[0032] Examples of organic phosphorus-based plasticizers include phosphate esters such as tributoxyethyl phosphate, isodecylphenyl phosphate, and triisopropyl phosphate. Examples of polyalkylene glycol-based plasticizers include polyethylene glycol, polypropylene glycol (PPG), poly(ethylene oxide / propylene oxide) block copolymers, poly(ethylene oxide / propylene oxide) random copolymers, and polytetramethylene glycol. Among these, polypropylene glycol is preferred.

[0033] The polyoxyalkylene ether plasticizer is an ether compound of a monohydric or polyhydric alcohol and a polyoxyalkylene. Specific examples of the polyoxyalkylene ether plasticizer include polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene allyl ether, polyoxypropylene allyl ether, polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, polyoxyethylene diglyceryl ether, polyoxypropylene diglyceryl ether (DGP), and polyoxyalkylene pentaerythritol ether. The polyoxyalkylene ether plasticizer is preferably an ether compound of a polyhydric alcohol and a polyoxyalkylene, more preferably an ether compound of glycerin or diglycerin and a polyoxyalkylene, and even more preferably an ether compound of glycerin or diglycerin and a polyoxypropylene. Examples of alcohol-based plasticizers include various polyhydric alcohols such as butanediol, hexanediol, trimethylolpropane, pentaerythritol, etc. Among these, trimethylolpropane is preferred.

[0034] The above plasticizers can be used alone or in combination of two or more. Among the above plasticizers, triethylene glycol-di-2-ethylhexanoate (3GO), polyoxypropylene diglyceryl ether (DGP), and polypropylene glycol (PPG) are preferred, with triethylene glycol-di-2-ethylhexanoate (3GO) being more preferred.

[0035] The content of the plasticizer in the interlayer filler is not particularly limited, but is preferably 10 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of the polyvinyl acetal resin. When the content of the plasticizer is 10 parts by mass or more, the interlayer filler becomes moderately flexible, and the impact energy absorption of the interlayer filler can be further improved. On the other hand, when the content of the plasticizer is 100 parts by mass or less, separation of the plasticizer from the interlayer filler is prevented. The content of the plasticizer is more preferably 20 parts by mass or more, even more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more, and more preferably 70 parts by mass or less, even more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less.

[0036] The interlayer filler may preferably be mainly composed of a thermoplastic resin, or a thermoplastic resin and a plasticizer, and the total amount of the thermoplastic resin and the plasticizer in the interlayer filler is usually 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more but less than 100% by mass, based on the total amount of the interlayer filler.

[0037] (Metal-Based Additive for Adjusting the Dielectric Constant) The interlayer filler of the present invention may contain a metal-based additive capable of adjusting the dielectric constant. By incorporating a metal-based additive, the dielectric constant of the interlayer filler can be adjusted to a high value. As the metal-based additive, for example, metal oxide-based additives such as indium tin oxide (ITO), tin oxide, antimony tin oxide (ATO), indium gallium oxide (IGO), indium zinc oxide (IZO), and zinc oxide are preferred. Among these, ITO is preferred. When a metal-based additive capable of adjusting the dielectric constant is used, the content of the metal-based additive is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and even more preferably 0.01% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, based on the total amount of the resin composition for forming the interlayer filler.

[0038] (Other Additives) The interlayer filler may contain other additives in addition to the above-mentioned plasticizers and metal-based additives. Specific examples of the other additives include adhesion modifiers, moisture resistance improvers, light stabilizers, antioxidants, dispersants, ultraviolet absorbers, infrared absorbers, heat-shielding substances, pigments, dyes, fluorescent brighteners, crystal nucleating agents, antistatic agents, antiblocking agents, refractive index modifiers, and light scattering agents.

[0039] (Thickness) The thickness of the interlayer filler of the present invention is not particularly limited, but from the viewpoint of adjusting the relative dielectric constant to a desired range and ensuring impact absorption, it is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 380 μm or more, and is preferably 1000 μm or less, more preferably 760 μm or less.

[0040] (Film Shape) From the viewpoint of being easily attached to a transparent substrate, the interlayer filler of the present invention is preferably in the form of a film. In this case, the interlayer filler of the present invention may be obtained, for example, by mixing a resin and various additives to be blended as necessary, and molding the obtained resin composition by extrusion molding, press molding, or the like.

[0041] The interlayer filler of the present invention may be a film having a single layer structure or a film having a multilayer structure. A single-layer film may be made of the thermoplastic resin described above, or may be made of a resin composition containing, in addition to a thermoplastic resin, additives such as plasticizers and metal-based additives, as needed. The content of each additive in the resin composition of the single layer structure may be adjusted as described above. Furthermore, when the interlayer filler is a film having a multilayer structure, each layer may be made of a thermoplastic resin as described above, or may be made of a resin composition containing, in addition to a thermoplastic resin, additives such as plasticizers and metal-based additives, as needed. In the case of a multilayer structure, the interlayer filler only needs to have the overall composition described above, and the resin composition constituting each layer only needs to contain the respective components as described above. When the interlayer filler is a film having a multilayer structure, it can be obtained by molding each layer by extrusion molding, press molding, or the like, and then laminating them. For example, a method of co-extrusion using two or more extruders and attaching multilayer feed blocks to the tips of multiple extruders is preferred. Furthermore, when a plurality of layers are provided and two or more layers have the same composition, two or more layers having the same composition may be extruded from one extruder.

[0042] [Laminate, Laminated Glass, Image Display Device] The laminate of the present invention comprises the interlayer filler of the present invention and at least one transparent substrate. Examples of the transparent substrate include an organic material substrate and an inorganic material substrate.

[0043] Examples of organic material substrates include organic resin plates and resin films. Organic resin plates are also called organic glass plates. Examples of organic resin plates include, but are not limited to, polycarbonate plates, (meth)acrylic plates such as polymethyl methacrylate plates, polyester plates such as acrylonitrile-styrene copolymer plates, acrylonitrile-butadiene-styrene copolymer plates, and polyethylene terephthalate plates, and various organic glass plates such as fluorine-based resin plates, polyvinyl chloride plates, chlorinated polyvinyl chloride plates, polypropylene plates, polystyrene plates, polysulfone plates, epoxy resin plates, phenolic resin plates, unsaturated polyester resin plates, and polyimide resin plates. The organic resin plates may be subjected to appropriate surface treatments. Among the above, polycarbonate plates are preferred because of their excellent transparency and impact resistance, and (meth)acrylic plates are preferred because of their high transparency, weather resistance, and mechanical strength, with polycarbonate plates being more preferred. The thickness of the organic resin plate is not particularly limited, but is preferably 0.1 mm or more, more preferably 0.4 mm or more, and is preferably 5.0 mm or less, more preferably 3.0 mm or less.

[0044] The resin film is not particularly limited, but examples thereof include polyester resin films such as (meth)acrylic resin film, polycarbonate film, polyethylene terephthalate (PET) film, and polyethylene naphthalate (PEN) film; polyolefin resin films such as polyethylene film and polypropylene film; cyclic polyolefin (COP) film, triacetyl cellulose (TAC) film, polyethersulfone (PES) resin film, and polyimide resin film. Furthermore, a surface layer such as a hard coat layer made of a (meth)acrylic resin may be provided on the surface of the resin film. The thickness of the resin film is not particularly limited, but is preferably 30 μm or more, more preferably 50 μm or more, and also preferably 500 μm or less, and more preferably 450 μm or less. While a relatively thick, low-flexibility, and generally unbendable material is referred to as an organic resin plate, a relatively thin, generally bendable material is generally referred to as a resin film, but these are not clearly distinguishable.

[0045] Examples of inorganic material substrates include inorganic glass plates. The inorganic glass plates are not particularly limited, but include various glass plates such as float glass, tempered glass, colored glass, polished glass, patterned glass, wired glass, lined glass, ultraviolet absorbing glass, infrared reflecting glass, infrared absorbing glass, and green glass. The inorganic glass may be subjected to surface treatment. The thickness of the inorganic glass is not particularly limited, but is preferably 0.1 mm or more, more preferably 1.0 mm or more, and is preferably 5.0 mm or less, more preferably 3.0 mm or less.

[0046] The organic material substrate or inorganic material substrate may be appropriately provided with an electrode, a sensor, or the like. The electrode is composed of a conductive layer laminated on each of the above substrates. A touch sensor may be laminated on each of the above substrates as a sensor to form a substrate with a touch sensor. The touch sensor is a sensor that detects touch input when a finger, a touch pen, or other object approaches or contacts the substrate, and is composed of a conductive layer laminated on the above substrate. When a finger, a touch pen, or other object approaches or contacts the substrate, an electrical change such as capacitance, current, or voltage occurs in the conductive layer, and the touch sensor detects the touch input based on this electrical change. The conductive layer is not particularly limited, and any conventionally known electrode material having transparency can be used without particular limitation, and examples thereof include an indium tin oxide (ITO) conductive film, a tin oxide conductive film, a zinc oxide conductive film, and a polymer conductive film.

[0047] Among the above, the inorganic material substrate is preferably selected from the group consisting of an inorganic glass plate and an inorganic glass plate to which at least one of an electrode or a sensor is attached. The organic material substrate is preferably at least one selected from the group consisting of a polycarbonate plate, a (meth)acrylic plate, a PET film, a COP film, a polycarbonate film, and a film to which at least one of an electrode or a sensor is attached. Furthermore, an organic material substrate (particularly a film) on which a conductive layer such as an electrode or a sensor is laminated may have the above-mentioned hard coat layer formed on the surface opposite to the surface on which the conductive layer is provided.

[0048] The laminate is not particularly limited, but preferably has a multilayer structure of three or more layers, including a pair of transparent substrates selected from inorganic material substrates and organic material substrates, and an interlayer filler disposed between the pair of transparent substrates. In such a multilayer structure, the interlayer filler may be bonded to both of the pair of transparent substrates, thereby bonding the pair of transparent substrates via the interlayer filler.

[0049] The laminate may also have a structure in which another intermediate member is disposed between the pair of transparent substrates. In such a structure, an adhesive film may be disposed between each transparent substrate and the intermediate member, resulting in a multilayer structure of five or more layers. Here, the adhesive film may be adhered to each transparent substrate and the intermediate member, thereby bonding the transparent substrate and the intermediate member via the adhesive film. In the multilayer structure of five or more layers described above, the adhesive film between the transparent substrate and the intermediate member is a resin film, and at least one of them may be the interlayer filler of the present invention, but it is preferable that both are the interlayer filler of the present invention. The intermediate member may have at least one of the inorganic material substrate and the organic material substrate described above, and at least one of the inorganic material substrate and the organic material substrate may be disposed at the position where the interlayer filler of the present invention is adhered. In addition, a multilayer structure of five or more layers may have three or more transparent substrates, for example, arranged in the order of transparent substrate, transparent substrate, intermediate member, and transparent substrate, with an adhesive film disposed between each of these members. In this case, it is sufficient that any one of the adhesive films is the interlayer filler of the present invention. Furthermore, the intermediate member may be a substrate with a touch sensor, as will be described later, but is not limited to this.

[0050] The laminate described above may constitute laminated glass, an image display device, a touch panel, or the like. In this case, the laminated glass comprises the interlayer filler of the present invention. The image display device comprises the interlayer filler of the present invention. Furthermore, the image display device may further comprise a cover glass and an image display panel in addition to the interlayer filler of the present invention. Furthermore, the touch panel comprises the interlayer filler of the present invention. Furthermore, the touch panel may further comprise a touch sensor, a cover glass, and an image display device. However, the laminate described above is not limited to these.

[0051] The image display device is preferably an in-vehicle display device, and is preferably provided in the front section in front of the driver's seat, and is particularly preferably disposed below the windshield of the automobile in front of either the driver's seat or the passenger seat. In other words, the image display device is preferably disposed in a position where a conventional instrument panel would be disposed.

[0052] The laminate of the present invention can be produced, for example, by preparing the interlayer filler of the present invention and compressing each component via the prepared interlayer filler. For example, it can be produced by stacking a transparent substrate, the interlayer filler of the present invention, and a transparent substrate in this order and compressing them together. Furthermore, when an intermediate component is provided, it can be produced, for example, by stacking a transparent substrate, an interlayer filler, an intermediate component, an interlayer filler, and a transparent substrate in this order and compressing them together.

[0053] Next, a specific example of the laminate will be described with reference to the drawings. Fig. 2 shows an example in which the laminate is a touch panel 50. The touch panel 50 is preferably an in-vehicle touch panel. The touch panel is preferably a capacitance type.

[0054] The touch panel 50 includes, in this order, a first substrate 20a, a first interlayer filler 10a, a second substrate 20c, a second interlayer filler 10b, and a touch sensor 20b. The first substrate 20a and the second substrate 20c are cover glasses, preferably organic resin plates or inorganic glass plates, with inorganic glass plates being preferred. The surface of the first substrate 20a serves as the operation surface that comes into contact with the user's fingers during touch operations. This structure, with two cover glasses and two interlayer fillers alternately, provides excellent shock absorption.

[0055] The touch sensor 20b is preferably a substrate with a touch sensor (such as sensor glass), and the substrate is preferably any of inorganic glass, an organic resin plate, or a resin film, and inorganic glass or a resin film is preferred. The substrate may also be a multilayer structure in which two or more of inorganic glass, an organic resin plate, or a resin film are laminated.

[0056] As shown in Fig. 3, the touch panel 50 may include an image display panel 30 on the surface of the touch sensor 20b opposite to the surface on which the second interlayer filler 10b is laminated, and an optically transparent resin (OCR) 40 may be provided between the touch sensor 20b and the image display panel 30. The optically transparent resin (OCR) 40 may be the interlayer filler of the present invention. Also, in Fig. 3, instead of the touch sensor 20b, the optically transparent resin (OCR) 40, and the image display panel 30, an image display device in which a touch sensor is directly patterned may be used, i.e., an on-cell or in-cell touch panel may be used.

[0057] Examples of the image display panel 30 include an organic EL display element and a liquid crystal display element. The image display panel 30 preferably has a polarizing plate (polarizing film) on its outermost surface on the front side. The outermost surface on the front side refers to the outermost surface on the cover glass side, and the opposite side is also referred to as the back side. A polarizing plate (polarizing film) generally has a configuration in which protective films are provided on both sides of a polarizer such as a polyvinyl alcohol resin film. The protective film is made of the above-mentioned resin film, preferably a PET film, a COP film, or a TAC film. Therefore, an organic material substrate is generally disposed on the outermost surface on the front side of the image display panel 30. Even if the image display panel 30 does not have a polarizing plate (polarizing film) on its front side, a protective film may be provided on the outermost surface on the front side. Therefore, even in such cases, the outermost surface on the front side of the image display panel 30 is composed of an organic material substrate.

[0058] The first interlayer filler 10a and the second interlayer filler 10b are the interlayer fillers of the present invention. The resin compositions constituting the first interlayer filler 10a and the second interlayer filler 10b are made of the same material. Specifically, the resin composition 10a constituting the first interlayer filler 10a and the resin composition 10b constituting the second interlayer filler preferably contain the same type of resin component. More specifically, both the resin composition 10a and the resin composition 10b preferably contain a polyvinyl acetal resin, more preferably a polyvinyl butyral resin, as a resin component. The resin composition 10a and the resin composition 10b preferably contain the same type of additive. Since the interlayer filler of the present invention can be adjusted to a desired dielectric constant even with resin compositions of the same material system, the first interlayer filler 10a and the second interlayer filler 10b can be made of the same material system, which facilitates the design and management of the interlayer filler.

[0059] The first interlayer filler and the second interlayer filler preferably have different water contents. By having different water contents, it is possible to adjust the dielectric constants to different values, thereby improving the operation sensitivity of the touch panel. Furthermore, it is preferable that the first interlayer filler and the second interlayer filler have different thicknesses. By having different thicknesses, it is possible to adjust the dielectric constants to different values, thereby improving the operation sensitivity of the touch panel.

[0060] The dielectric constant of the first interlayer filler is preferably higher than that of the second interlayer filler. Because the first interlayer filler is located close to the operating surface of the touch panel, a high dielectric constant is preferable from the viewpoint of followability to a human finger. From this viewpoint, the dielectric constant of the first interlayer filler is preferably 3.9 or more, more preferably 4 or more, even more preferably 4.5 or more, and preferably 6.0 or less, more preferably 5.5 or less. Furthermore, because the second interlayer filler is located close to the touch sensor or liquid crystal display, a low dielectric constant is preferable from the viewpoint of preventing malfunction. From this viewpoint, the dielectric constant of the second interlayer filler is preferably less than 3.9, more preferably 3.5 or less, even more preferably 3 or less, and preferably 1.5 or more, more preferably 2.0 or more.

[0061] 2 and 3, and may, for example, not use a second substrate, and may have a configuration having a first substrate 20a, a first interlayer filler 10a, a touch sensor 20b, a second interlayer filler 10b, and an image display device 30 in this order, as shown in Fig. 4. The first substrate 20a, the first interlayer filler 10a, the touch sensor 20b, the second interlayer filler 10b, and the image display device 30 are as described above.

[0062] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating the various physical properties in the present invention are as follows.

[0063] (Measurement of Relative Dielectric Constant) The relative dielectric constant was measured by the automatic balancing bridge method in accordance with JIS C 2138 under the following conditions: Measurement temperature: 23°C Frequency: 1 MHz Electrode material: tin foil Number of measurements: n=2 (measured at two locations and the average value was calculated) Test room environment: 23°C, 50% RH Measurement device: Precision LCR meter E4980A manufactured by Agilent Technologies

[0064] (Measurement of moisture content) A sample (5 cm long x 5 cm wide) was prepared from the obtained interlayer filler. The measurement sample was measured using a Karl Fischer moisture meter (MKC-610-DT, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) based on JIS K7251-B. Based on the measurement results, the moisture content was adjusted as necessary by the method described below, and adjustment and measurement were continued until the predetermined moisture content was reached.

[0065] (Adjustment of moisture content) The moisture content of the interlayer filler was adjusted as follows. When increasing the moisture content of the interlayer filler, the sample was placed in a high-temperature, high-humidity chamber (manufactured by Yamato Scientific Co., Ltd., product name "IG420") at a temperature of 30°C and a humidity of 70% RH, and adjustment was performed. When decreasing the moisture content of the interlayer filler, the sample was placed in a vacuum dryer (manufactured by AS ONE Corporation, product name "AVO-310N") at a temperature of 50°C and a vacuum degree of 0.1 kPa, and adjustment was performed.

[0066] The following raw materials were used to prepare the interlayer filler: Thermoplastic resin: polyvinyl butyral resin (S-LEC BH-8 manufactured by Sekisui Chemical Co., Ltd.) Plasticizer: triethylene glycol-di-2-ethylhexanoate (3GO) Antioxidant: 2,6-di-t-butyl-p-cresol (BHT) Ultraviolet absorber: Tinuvin 326 manufactured by Ciba Specialty Chemicals ITO dispersion: a dispersion in which 100 parts by mass of ITO particles were dispersed in 125 parts by mass of 3GO, 12.5 parts by mass of ethanol, and 10 parts by mass of polyoxyethylene nonylphenyl ether phosphate ester (ITO concentration: approximately 40% by mass).

[0067] As the resin compositions for forming the interlayer filler, the following resin composition 1 and resin composition 2 were used. The concentration of the ITO dispersion in the resin composition 2 indicates the concentration of the ITO dispersion based on the entire resin composition.

[0068] (Preparation of Interlayer Filler: Sample 1) Resin composition 1 in Table 1, which was a mixture of polyvinyl butyral resin, plasticizer, antioxidant, and UV absorber, was press-molded using a heat molding machine under conditions of 180°C and 10 MPa to obtain a film with a thickness of 200 µm, which was used as an interlayer filler for Sample 1. The interlayer filler for Sample 1 was adjusted to each water content shown in Table 2, and the relative dielectric constant was measured.

[0069] (Preparation of Interlayer Filler: Samples 2 to 6) Interlayer fillers of Samples 1 to 6 were obtained in the same manner as the preparation method for the interlayer filler of Sample 1, except that the type of resin composition used and the thickness were changed as shown in Table 2. The interlayer fillers of Samples 1 to 6 were adjusted to the respective water contents shown in Table 2, and the relative dielectric constants were measured.

[0070] (Interlayer filler: Samples 7 and 8) Using a high-dielectric OCA (acrylic adhesive, relative dielectric constant 4.5) as Sample 7 and a low-dielectric OCA (acrylic adhesive, relative dielectric constant 2.5) as Sample 8, the change in relative dielectric constant in a humid and hot environment (an environment with various changes in humidity and temperature) was investigated. The results are shown in Table 3.

[0071] Examples 1 to 13 The interlayer fillers of Samples 1 to 6 were adjusted to have moisture contents as shown in Table 4, and the relative dielectric constants were measured.

[0072]

[0073]

[0074]

[0075] Samples 1 to 6 are interlayer fillers of the present invention, with a dielectric constant of 2.0 to 5.0 at a water content of 0% and a dielectric constant of 2.5 to 5.5 at a water content of 0.5%, which is greater than the dielectric constant at a water content of 0%. Furthermore, the results of Samples 1 to 6 demonstrate that even when the resin composition used to form the interlayer filler is the same, the dielectric constant can be adjusted to a desired range by changing the water content and thickness. Samples 7 and 8 are general adhesives used for touch panels, but their dielectric constants did not change even when the humid and hot environment was changed, and it was not possible to adjust the dielectric constant by changing the water content, etc., as with Samples 1 to 6.

[0076] 10a First interlayer filler 10b Second interlayer filler 20a First base material 20b Touch sensor 20c Second base material 30 Image display device 40 Optically transparent resin (OCR)

Claims

1. An interlayer filler having a relative dielectric constant at 1 MHz in the range of 2.0 to 5.0 when the moisture content is 0%, and a relative dielectric constant at 1 MHz in the range of 2.5 to 5.5 when the moisture content is 0.5%, the relative dielectric constant being greater than the relative dielectric constant when the moisture content is 0%.

2. The interlayer filler according to claim 1, having a dielectric constant of 3.9 or more.

3. The interlayer filler according to claim 2, having a thickness of 380 μm or more and 760 μm or less.

4. The interlayer filler of claim 1, having a dielectric constant of less than 3.

9.

5. The interlayer filler according to claim 4, having a thickness of 380 μm or more and 760 μm or less.

6. The interlayer filler according to any one of claims 1 to 5, which contains a thermoplastic resin.

7. The interlayer filler of claim 6, further comprising a plasticizer.

8. A laminate comprising the interlayer filler according to any one of claims 1 to 5 and at least one transparent substrate.

9. A laminated glass comprising the interlayer filler according to any one of claims 1 to 5.

10. An image display device comprising the interlayer filler according to any one of claims 1 to 5.

11. A touch panel having at least a first substrate, a first interlayer filler, a second substrate, a second interlayer filler, and a touch sensor, in that order, wherein the first interlayer filler and the second interlayer filler have different relative dielectric constants, and the material system of the resin composition constituting the first interlayer filler and the second interlayer filler is the same.

12. The touch panel according to claim 11, wherein the first interlayer filler and the second interlayer filler have different moisture contents.

13. The touch panel according to claim 11 or 12, wherein the first interlayer filler and the second interlayer filler have different thicknesses.

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