Patent ID: 12215972

DESCRIPTION OF EMBODIMENTS

A. Overall Configuration of Sensor Device

FIG.1is a schematic sectional view of a sensor device according to one embodiment of the present invention. A sensor device100ofFIG.1includes: an optical laminate10including a glass film11, an adhesive layer12, a resin layer13, and a pressure-sensitive adhesive layer14in the stated order; and a strain-sensing unit20. The strain-sensing unit20is arranged on the pressure-sensitive adhesive layer14side of the optical laminate10. The thickness of the glass film11is from 20 μm to 150 μm. It is preferred that the glass film11and the resin layer13be arranged directly via the adhesive layer12(i.e., while no layer other than the adhesive layer12is caused to exist between the glass film11and the resin layer13).

The optical laminate10includes the glass film11, and hence has high hardness. In an electronic device including the sensor device of the present invention, the optical laminate10may be arranged so that the glass film11may serve as the outermost surface. The use of the optical laminate10including the glass film11can effectively protect the electronic device including the sensor device of the present invention. In addition, the optical laminate10includes the resin layer13on one side of the glass film11, and hence the breakage of the glass film11can be prevented, and the laminate is excellent in impact resistance and puncture resistance. In the present invention, the laminate is considered to be excellent in impact resistance as described above because impact applied to the surface of the glass film11can be effectively caused to escape toward the resin layer13. In addition, the glass film11has a function of protecting the resin layer13. That is, in the present invention, the glass film11and the resin layer13protect each other. Accordingly, the number of members for protection can be reduced, and hence a lightweight and thin optical laminate can be obtained.

Further, in the present invention, the thin glass film11can be adopted, and hence the sensing sensitivity of the strain-sensing unit20is hardly inhibited. The strain-sensing unit20includes strain sensors21, and the strain sensors21each read a resistance value, which changes at the time of the occurrence of strain in the strain-sensing unit20, to detect a strain amount. In actuality, an external force applied from the glass film11side deflects the strain-sensing unit20, and hence the strain amount is detected. In general, when it is assumed that an external force is applied to the center of the sample (glass film) supported at two points, its strain amount is represented by the expression “{(external force)×(distance between support points)3}/{48×(modulus of elasticity of sample)×(second moment of area}.” Further, the second moment of area of the sample at this time is represented by the expression “{(sample depth)×(sample thickness)3}/12,” and is hence proportional to the cube of the thickness of the sample. That is, the strain amount is inversely proportional to the cube of the thickness of the sample (glass film). In the present invention, the thin glass film can be used when combined with the resin layer, and as a result, a sensor device in which the sensitivity of its strain-sensing unit is hardly inhibited can be provided.

The sensor device of the present invention may further include any appropriate other member to the extent that the effect of the present invention is obtained, though the member is not shown. For example, a liquid crystal cell, a member for a display, such as an organic light-emitting display, or an optical film, such as a polarizing plate, may be arranged between the optical laminate and the strain-sensing unit.

B. Optical Laminate

As described above, the optical laminate includes a glass film, an adhesive layer, a resin layer, and a pressure-sensitive adhesive layer in the stated order. The optical laminate may further include other layers. Examples of the other layers include an antireflection layer, an antiglare layer, an antistatic layer, and a conductive layer.

The thickness of the optical laminate is preferably from 60 μm to 550 μm, more preferably from 100 μm to 300 μm.

B-1. Glass Film

Any appropriate glass film may be adopted as the glass film. According to classification based on composition, examples of the glass film include soda-lime glass, borate glass, aluminosilicate glass, and quartz glass films. In addition, according to classification based on an alkali component, examples of the glass film include alkali-free glass and low-alkali glass films. The content of an alkali metal component (e.g., Na2O, K2O, Li2O) in the glass is preferably 15 wt % or less, more preferably 10 wt % or less.

The thickness of the glass film is from 20 μm to 150 μm, preferably from 30 μm to 150 μm, more preferably from 50 μm to 100 μm. When the thickness falls within such ranges, an optical laminate having the following features can be obtained: the optical laminate is excellent in flexibility; and the glass film hardly breaks, and hence the laminate is excellent in productivity.

The glass film preferably has a light transmittance at a wavelength of 550 nm of 85% or more. The glass film preferably has a refractive index at a wavelength of 550 nm of from 1.4 to 1.65.

The glass film has a density of preferably from 2.3 g/cm3to 3.0 g/cm3, more preferably from 2.3 g/cm3to 2.7 g/cm3. When the glass film has a density falling within the ranges, a lightweight optical laminate is obtained.

Any appropriate method may be adopted as a forming method for the glass film. The glass film is typically produced by melting a mixture containing a main raw material, such as silica or alumina, a fining agent, such as salt cake or antimony oxide, and a reducing agent, such as carbon, at a temperature of from 1,400° C. to 1,600° C., and forming the molten mixture into a thin sheet shape, followed by cooling. Examples of the forming method for the glass film include a slot down-draw method, a fusion method, and a float method. The glass film formed in a sheet shape by any one of those methods may be chemically polished with a solvent, such as hydrofluoric acid, as required, in order to reduce its thickness or enhance its smoothness.

B-2. Adhesive Layer

The term “adhesive layer” as used herein refers to a layer capable of bonding substances to each other by being interposed between the substances. Accordingly, when an adherend bonded to the adhesive layer is peeled, the adhesive layer is free of any practical adhesive strength. Meanwhile, the term “pressure-sensitive adhesive layer” refers to a substance that has an adhesive property at normal temperature, and that is bonded to an adherend with a light pressure. Accordingly, even when the adherend bonded to the pressure-sensitive adhesive layer is peeled, the pressure-sensitive adhesive layer holds a practical pressure-sensitive adhesive strength. In the present invention, the glass film and the resin layer are laminated via the adhesive layer, and hence both of the glass film and the resin layer can be effectively protected.

The adhesive layer is formed of any appropriate adhesive. Examples of the adhesive include a polyester-based adhesive, a polyurethane-based adhesive, a polyvinyl alcohol-based adhesive, and an epoxy-based adhesive. Of those, an epoxy-based adhesive is preferred. This is because particularly satisfactory adhesiveness can be obtained.

In one embodiment, a curable adhesive, such as a thermosetting, photocurable, or moisture-curable adhesive, is used as the adhesive. When the adhesive is a thermosetting adhesive, the adhesive layer can exhibit a peel-resisting force by being cured (solidified) through heating. In addition, when the adhesive is a photocurable adhesive, such as a UV-curable adhesive, the adhesive layer can exhibit a peel-resisting force by being cured through irradiation with light, such as UV light. In addition, when the adhesive is a moisture-curable adhesive, the adhesive may react with, for example, moisture in air to cure. Accordingly, the adhesive layer can cure to exhibit a peel-resisting force even by being left to stand.

For example, a commercial adhesive may be used as the adhesive, or the adhesive may be prepared as an adhesive solution (or dispersion liquid) by dissolving or dispersing various curable resins in a solvent.

The thickness of the adhesive layer is preferably from 0.1 μm to 30 μm, more preferably from 0.5 μm to 20 μm, still more preferably from 1 μm to 10 μm. When the thickness falls within such ranges, an optical laminate that is excellent in flexibility and is excellent in puncture resistance can be obtained.

The modulus of elasticity of the adhesive layer at 23° C. is preferably from 0.5 GPa to 15 GPa, more preferably from 0.8 GPa to 10 GPa, still more preferably from 1 GPa to 5 GPa. When the modulus of elasticity falls within such ranges, an optical laminate that is excellent in flexibility and is excellent in puncture resistance can be obtained. Herein, the modulus of elasticity may be measured with an autograph under the following conditions.

<Method of Measuring Modulus of Elasticity>

Measurement temperature:23° C.Sample size:50 μm thick by 2 cm wide by 15 cmlongChuck-to-chuck distance:10 cmTensile rate:10 mm/min

B-3. Resin Layer

Examples of the resin layer include a polarizing plate, a retardation plate, an isotropic film, and a conductive film. The resin film may include a single layer, or may include a plurality of layers.

Any appropriate material is used as a material for forming the resin layer. Examples of the material for forming the resin layer include a polyolefin-based resin, a cyclic olefin-based resin, a polycarbonate-based resin, a cellulose-based resin, a polyester-based resin, a polyamide-based resin, a polyimide-based resin, a polyether-based resin, a polystyrene-based resin, a (meth)acrylic resin, a (meth)acrylic urethane-based resin, a polysulfone-based resin, an acetate-based resin, an epoxy-based resin, a silicone-based resin, a polyarylate-based resin, a polysulfone-based resin, a polyetherimide-based resin, an epoxy-based resin, a urethane-based resin, a silicone-based resin, and a polyvinyl alcohol (PVA)-based resin.

The thickness of the resin layer is preferably from 5 μm to 300 μm, more preferably from 30 μm to 250 μm, still more preferably from 50 μm to 200 μm, particularly preferably from 50 μm to 100 μm.

The modulus of elasticity of the resin layer at 23° C. is preferably from 1 GPa to 10 GPa, more preferably from 2 GPa to 7 GPa, still more preferably from 2 GPa to 5 GPa. When the modulus of elasticity falls within such ranges, an optical laminate excellent in impact resistance and puncture resistance can be obtained.

B-3-1. Polarizing Plate

As described above, in one embodiment, the resin layer is a polarizing plate. The polarizing plate includes a polarizer and a protective film arranged on at least one side of the polarizer. The thickness of the polarizing plate is preferably from 5 μm to 300 μm, more preferably from 10 μm to 250 μm, still more preferably from 25 μm to 200 μm, particularly preferably from 25 μm to 150 μm.

(Polarizer)

The thickness of the polarizer is not particularly limited, and an appropriate thickness may be adopted depending on purposes. The thickness is typically from about 1 μm to about 80 μm. In one embodiment, a thin polarizer is used, and the thickness of the polarizer is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, particularly preferably 6 μm or less. With the use of such thin polarizer, a thin optical laminate can be obtained.

The polarizer preferably exhibits absorption dichroism at any wavelength in the wavelength range of from 380 nm to 780 nm. The polarizer has a single layer transmittance of preferably 40.0% or more, more preferably 41.0% or more, still more preferably 42.0% or more, particularly preferably 43.0% or more. The polarizer has a polarization degree of preferably 99.8% or more, more preferably 99.9% or more, still more preferably 99.95% or more.

The polarizer is preferably an iodine-based polarizer. More specifically, the polarizer may be formed of an iodine-containing polyvinyl alcohol-based resin (hereinafter referred to as “PVA-based resin”) film.

Any appropriate resin may be adopted as a PVA-based resin for forming the PVA-based resin film. Examples of the resin include polyvinyl alcohol and an ethylene-vinyl alcohol copolymer. The polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is typically from 85 mol % to 100 mol %, preferably from 95.0 mol % to 99.95 mol %, more preferably from 99.0 mol % to 99.93 mol %. The saponification degree may be determined in conformity with JIS K 6726-1994. The use of the PVA-based resin having such saponification degree can provide a polarizer excellent in durability. When the saponification degree is excessively high, gelling may occur.

The average polymerization degree of the PVA-based resin may be appropriately selected depending on purposes. The average polymerization degree is typically from 1,000 to 10,000, preferably from 1,200 to 5,000, more preferably from 1,500 to 4,500. The average polymerization degree may be determined in conformity with JIS K 6726-1994.

A production method for the polarizer is, for example, a method (I) including stretching and dyeing a PVA-based resin film alone, or a method (II) including stretching and dyeing a laminate (i) having a resin substrate and a polyvinyl alcohol-based resin layer. Detailed description of the method (I) is omitted because the method is well known and commonly used in the art. The production method (II) preferably includes the step of stretching and dyeing the laminate (i) having the resin substrate and the polyvinyl alcohol-based resin layer formed on one side of the resin substrate to produce a polarizer on the resin substrate. The laminate (i) may be formed by applying an application liquid containing a polyvinyl alcohol-based resin onto the resin substrate and drying the applied liquid. In addition, the laminate (i) may be formed by transferring a polyvinyl alcohol-based resin film onto the resin substrate. For example, the details of the production method (II) are described in JP 2012-73580 A, which is incorporated herein by reference.

(Protective Film)

Any appropriate resin film may be adopted as the protective film. As a material for forming the protective film, there are given, for example: a polyester-based resin, such as polyethylene terephthalate (PET); a cellulose-based resin, such as triacetylcellulose (TAC); a cycloolefin-based resin, such as a norbornene-based resin; an olefin-based resin, such as polyethylene or polypropylene; and a (meth)acrylic resin. The term “(meth)acrylic resin” refers to an acrylic resin and/or a methacrylic resin.

In one embodiment, a (meth)acrylic resin having a glutarimide structure is used as the (meth)acrylic resin. The (meth)acrylic resin having a glutarimide structure (hereinafter sometimes referred to as glutarimide resin) is described in, for example, JP 2006-309033 A, JP 2006-317560 A, JP 2006-328329 A, 2006-328334 A, JP 2006-337491 A, JP 2006-337492 A, JP 2006-337493 A, JP 2006-337569 A, JP 2007-009182 A, JP 2009-161744 A, and JP 2010-284840 A, the descriptions of which are incorporated herein by reference.

The protective film and the polarizer are laminated via any appropriate adhesive layer. The resin substrate used at the time of the production of the polarizer may be peeled before the lamination of the protective film and the polarizer, or after the lamination.

The thickness of the protective film is preferably from 4 μm to 250 μm, more preferably from 5 μm to 150 μm, still more preferably from 10 μm to 100 μm, particularly preferably from 10 μm to 50 μm.

The modulus of elasticity of the protective film at 23° C. is preferably from 1 GPa to 10 GPa, more preferably from 2 GPa to 7 GPa, still more preferably from 2 GPa to 5 GPa. When the modulus of elasticity falls within such ranges, an optical laminate excellent in impact resistance and puncture resistance can be obtained.

B-4. Pressure-Sensitive Adhesive Layer

The pressure-sensitive adhesive layer is formed of any appropriate pressure-sensitive adhesive. A pressure-sensitive adhesive containing, for example, an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyamide, polyether, or a fluorine-based or rubber-based polymer as a base polymer is used as the pressure-sensitive adhesive. Of those, an acrylic pressure-sensitive adhesive is preferably used. This is because the acrylic pressure-sensitive adhesive is excellent in optical transparency, shows moderate wettability, moderate cohesiveness, and a moderate pressure-sensitive adhesive characteristic, such as an adhesive property, and may be excellent in, for example, weatherability and heat resistance. An acrylic pressure-sensitive adhesive formed of an acrylic polymer having 4 to 12 carbon atoms is particularly preferred.

The thickness of the pressure-sensitive adhesive layer is preferably from 1 μm to 100 μm, more preferably from 3 μm to 80 μm, still more preferably from 3 μm to 50 μm. When the thickness falls within such ranges, an optical laminate that is excellent in flexibility and is excellent in impact resistance and puncture resistance can be obtained.

The modulus of elasticity of the pressure-sensitive adhesive layer at 23° C. is preferably from 0.00001 GPa to 10 GPa, more preferably from 0.001 GPa to 8 GPa, still more preferably from 0.001 GPa to 5 GPa. When the modulus of elasticity falls within such ranges, an optical laminate that is excellent in flexibility and is excellent in impact resistance and puncture resistance can be obtained.

C. Strain-Sensing Unit

The strain-sensing unit is configured to sense strain caused by an external force applied to the surface (surface opposite to the strain-sensing unit) of the optical laminate laminated on the strain-sensing unit. The strain-sensing unit may be of any appropriate configuration as long as the unit has such function.

In one embodiment, as illustrated inFIG.1, the strain-sensing unit20includes the at least one strain sensor21. More specifically, the strain-sensing unit20includes a transparent substrate22and the strain sensor21arranged on at least one side of the transparent substrate22. When the strain sensors21are arranged on both sides of the transparent substrate22, the strain sensor21arranged on one surface and the strain sensor21arranged on the other surface are preferably opposite to each other through the transparent substrate22. The strain sensors21are arranged in any appropriate form on the transparent substrate22. The strain sensors21are arranged in, for example, a grid form.

In one embodiment, the strain sensors each include a strain gauge formed from a transparent material. The strain gauge is configured to measure strain by sensing a change in resistance value intrinsic to a metal material through utilization of the fact that the resistance value changes at the time of the compression/elongation of the metal material. The strain gauge may be formed from a plurality of nanostructures, such as a nanomesh structure and a nanowire structure. A material having a low strain gauge factor is preferably used as a material for forming the strain gauge. The strain gauge factor is a characteristic intrinsic to the material for forming the strain gauge, and represents the sensitivity of the material to the strain. A strain amount ε is represented by the expression “(resistance change amount/gauge resistance)/gauge factor,” and a material having a lower gauge factor has higher sensitivity to the strain. Examples of the material for forming the strain gauge include Cu, Ni, Cr, and alloys thereof.

The strain-sensing unit may include a sense-processing circuit connected to the strain sensors through wires, though the circuit is not shown. The sense-processing circuit can relate a change in resistance value of the strain gauge and the magnitude of the external force applied to the surface of the optical laminate to each other on the basis of a signal from the strain sensor that has detected the change in resistance value.

The details of the strain-sensing unit are described in, for example, US 2017/0075465 A1, the description of which is incorporated herein by reference in its entirety.

EXAMPLES

The present invention is specifically described below by way of Examples, but the present invention is not limited to these Examples. In addition, in Examples, “part(s)” and “%” are by weight unless otherwise specified.

Production Example 1

(Preparation of Adhesive)

An epoxy-based resin (manufactured by Daicel Chemical Industries, Ltd., product name: “CELLOXIDE 2021P”), another epoxy-based resin (manufactured by Daicel Chemical Industries, Ltd., product name: “EHPE 3150”), an oxetane-based resin (manufactured by Toagosei Co., Ltd., product name: “ARON OXETANE OXT-221”), an epoxy group-terminated coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name: “KBM-403”), and a polymerization initiator (CPI-101A manufactured by San-Apro Ltd.) were mixed at a ratio of 60:10:20:4:2 to prepare a UV-curable adhesive.

Example 1

A glass film (manufactured by Nippon Electric Glass Co., Ltd., product name: “GA-10G,” thickness: 50 μm) and a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: “Lumirror S10,” thickness: 100 μm, modulus of elasticity: 4 GPa) were laminated via the adhesive prepared in Production Example 1. UV light (integrated light quantity: 300 mJ/cm2) was applied to the resultant laminate to provide a laminate A having the configuration “glass film/adhesive layer (thickness: 1 μm, modulus of elasticity: 1 GPa)/resin layer (PET).”

A pressure-sensitive adhesive film (manufactured by Nitto Denko Corporation, product name: “LUCIACS CS9861UAS,” pressure-sensitive adhesive layer thickness: 25 μm) was laminated on the resin layer (PET) side of the laminate A to provide a laminate B.

Next, a film present above a liquid crystal panel in a smartphone (manufactured by Apple Inc., product name: “i-Phone X”) was peeled, and the laminate B was mounted on the liquid crystal panel via the pressure-sensitive adhesive layer.

The moduli of elasticity of the adhesive layer and the resin layer were measured with an autograph (manufactured by Shimadzu Corporation, product name: “AG-IS”) under the following conditions.

<Method of Measuring Modulus of Elasticity>

Measurement temperature:23° C.Sample size:50 μm thick by 2 cm wide by 15 cmlongChuck-to-chuck distance:10 cmTensile rate:10 mm/min

Example 2

A sensor device was obtained in the same manner as in Example 1 except that the thickness of the glass film was changed to 100 μm.

Comparative Example 1

A sensor device was obtained in the same manner as in Example 1 except that the thickness of the glass film was changed to 300 μm.

Comparative Example 2

A sensor device was obtained in the same manner as in Example 1 except that the adhesive layer for forming the laminate A was changed to a pressure-sensitive adhesive layer (manufactured by Nitto Denko Corporation, acrylic pressure-sensitive adhesive, product name: “LUCIACS CS9861UAS,” pressure-sensitive adhesive layer thickness: 25 μm).

<Evaluation>

The sensor devices obtained in Examples and Comparative Examples were subjected to the following evaluations. The results are shown in Table 1.

1. Sensitivity

The glass surface of the laminate B mounted on the smartphone was pressed with a finger, and a case in which the display of the smartphone responded to the pressing was evaluated as “∘”, while a case in which the response delayed or the display did not respond thereto was evaluated as “x”. The response was recognized while one polarizing plate (manufactured by Nitto Denko Corporation, product name: “NPF-SEG1425DU”) was simply held up toward a viewer side (onto the glass) so that the display screen of the smartphone was able to be viewed.

2. Impact Resistance

A case in which when a 100-gram iron ball was dropped from a height of 50 mm toward the glass surface of the laminate B mounted on the smartphone, the glass film or display screen of the laminate did not break was evaluated as “∘”, and a case in which the glass film or the display screen broke was evaluated as “x”.

TABLE 1ModulusofThickness ofelasticity ofModulus ofglassresinelasticityfilmResinlayerAdhesiveof adhesiveImpact(μm)layer(GPa)layerlayer (GPa)SensitivityresistanceExample 150PET4Epoxy-based1∘∘adhesiveExample 2100PET4Epoxy-based1∘∘adhesiveComparative300PET4Epoxy-based1x∘Example 1adhesiveComparative100PET4Acrylic0.2∘xExample 2pressure-sensitiveadhesive

REFERENCE SIGNS LIST

10optical laminate11glass film12adhesive layer13resin layer20strain-sensing unit100sensor device