CN115776941A

CN115776941A - Optical laminate

Info

Publication number: CN115776941A
Application number: CN202180045371.XA
Authority: CN
Inventors: 矢野孝伸; 疋田贵巳; 渊田岳仁; 赵洪赞
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-06-24
Filing date: 2021-05-18
Publication date: 2023-03-10
Also published as: KR20230026309A; WO2021261119A1

Abstract

The invention provides an optical laminate (1) which is provided with a glass plate (2), an adhesive layer (3), a film (4) and an adhesive layer (12) in sequence towards one side in the thickness direction. The glass plate (2) has a thickness of 40 [ mu ] m or more and 60 or less. The average of tan delta of the film (4) at-100 ℃ to-50 ℃ is 0.06 or more as determined by a dynamic viscoelasticity test at a frequency of 10Hz, a temperature rise rate of 2 ℃/min and a stretching mode. The average tensile storage modulus E' of the film (4) at-100 ℃ to-50 ℃ is 3GPa or more and 6GPa or less as determined by a dynamic viscoelasticity test. The adhesive layer (12) has a thickness of 20 [ mu ] m or less.

Description

Optical laminate

Technical Field

The present invention relates to an optical laminate including glass plates.

Background

An optical laminate including a glass plate, an adhesive layer, and a polyethylene terephthalate film or a cellulose triacetate film is known (for example, see patent document 1 below). The glass plate is excellent in optical characteristics, while it is low in impact resistance. Impact resistance is a property of suppressing the occurrence of damage including cracks in a glass sheet when the glass sheet is subjected to impact. The optical laminate described in the example of patent document 1 has a three-layer laminate structure.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2019-25899

Disclosure of Invention

Problems to be solved by the invention

In recent years, higher levels of impact resistance have been demanded for optical laminates. For example, if the thickness of the glass plate is made very thick, the impact resistance is improved. However, thinner glass is desired from the viewpoint of reduction in thickness and weight.

The invention provides an optical laminate excellent in impact resistance.

Means for solving the problems

As a result of intensive studies, the inventors of the present invention have surprisingly found that the impact resistance of an optical laminate can be improved by providing the optical laminate with a thin glass plate having a thickness of 40 μm or more and 60 μm or less, providing the optical laminate with a film having a specific tan δ and a specific tensile storage modulus E' via an adhesive layer, and further providing the film with an adhesive layer having a thickness of 20 μm or less on the side opposite to the glass plate.

The present invention (1) is an optical laminate comprising, in order from one side in the thickness direction, a glass plate, an adhesive layer, a film, and an adhesive layer, wherein the glass plate has a thickness of 40 μm or more and 60 μm or less, the average of tan δ of the film at-100 ℃ to-50 ℃ as determined by a dynamic viscoelasticity test at a frequency of 10Hz, a temperature rise rate of 2 ℃/min, and a tensile mode is 0.06 or more, the average of tensile storage modulus E' of the film at-100 ℃ to-50 ℃ as determined by the dynamic viscoelasticity test is 3GPa or more and 6GPa or less, and the adhesive layer has a thickness of 20 μm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

The optical laminate of the present invention has a glass plate thickness of 40 to 60 μm, a film having a specific tan δ and a specific tensile storage modulus E' via an adhesive layer, and a pressure-sensitive adhesive layer having a thickness of 20 μm or less, and therefore has excellent impact resistance.

Drawings

Fig. 1 is a cross-sectional view of an embodiment of the optical laminate of the present invention.

Fig. 2 is a cross-sectional view of an organic electroluminescent display device including the optical laminate shown in fig. 1.

Description of the symbols

1. Optical laminate

2. Glass plate

3. Adhesive layer

4. Film

12. Adhesive layer

Detailed Description

< optical laminate 1 >

An embodiment of an optical laminate according to the present invention will be described with reference to fig. 1.

The optical layered body 1 has, for example, a flat plate shape extending in the plane direction. The plane direction is orthogonal to the thickness direction of the optical laminate 1. The optical laminate 1 includes, in order toward one side in the thickness direction: glass plate 2, adhesive layer 3, film 4, and adhesive layer 12.

< glass plate 2 >

The glass plate 2 extends in the plane direction. The glass plate 2 forms the other surface of the optical laminate 1 in the thickness direction. The glass plate 2 has a total light transmittance of, for example, 80% or more, preferably 85% or more, and, for example, 99% or less. As the glass plate 2, commercially available products, for example, G-leaf series (registered trademark, manufactured by Nippon Denko Co., ltd.) can be used.

< thickness of glass plate 2 >

The thickness of the glass plate 2 is 40 μm to 60 μm. If the thickness of the glass plate 2 is sufficiently thick, impact resistance is improved. From this viewpoint, it is considered that the impact resistance is higher as the thickness of the glass plate 2 is larger, but the impact resistance of the optical laminate 1 can be improved by making the thickness of the glass plate 2 40 μm or more and 60 μm or less, providing the film 4 having a specific tan δ and a specific tensile storage modulus E' via the adhesive layer 3 in the optical laminate 1, and further providing the adhesive layer 12 of 20 μm or less.

The thickness of the glass plate 2 is preferably 42 μm or more, more preferably 45 μm or more, and further preferably 48 μm or more. The thickness of the glass plate 2 is, for example, 58 μm or less, preferably 55 μm or less, and more preferably 52 μm or less. The glass plate 2 is referred to as a thin glass plate because it has the above thickness.

< adhesive layer 3 >

The adhesive layer 3 extends in the planar direction. The adhesive layer 3 is disposed on one surface of the glass plate 2 in the thickness direction. Specifically, the adhesive layer 3 is in contact with one surface of the glass plate 2 in the thickness direction. The adhesive layer 3 is not an adhesive layer (pressure-sensitive adhesive layer) formed of an adhesive (pressure-sensitive adhesive), but is a cured product of a curable adhesive. Specifically, the adhesive layer 3 is a cured product of a curable adhesive that undergoes a curing reaction by irradiation or heating with an active energy ray.

The curable adhesive is a curing material of the adhesive layer 3, and examples thereof include an active energy curable type and a thermosetting type, and a preferred example thereof is an active energy curable type. Specifically, examples of the curable adhesive include: the acrylic adhesive composition, the epoxy adhesive composition, and the silicone adhesive composition may be exemplified as the epoxy adhesive composition from the viewpoint of obtaining excellent impact resistance.

The epoxy adhesive composition contains an epoxy resin as a main agent. Examples of the epoxy resin include: a bifunctional epoxy resin having 2 epoxy groups, a polyfunctional epoxy resin having 3 or more epoxy groups, and the like. These epoxy resins may be used alone or in combination of two or more. A combination of a bifunctional epoxy resin and a polyfunctional epoxy resin is preferably used.

Examples of the bifunctional epoxy resin include: aromatic epoxy resins such as bisphenol epoxy resin, novolak epoxy resin, naphthalene epoxy resin, fluorene epoxy resin and triphenylmethane epoxy resin, nitrogen-containing epoxy resins such as trisepoxypropyl isocyanurate and hydantoin epoxy resin, aliphatic epoxy resins, glycidyl ether epoxy resins and glycidyl amine epoxy resins. The bifunctional epoxy resin is preferably an aliphatic epoxy resin. The aliphatic epoxy resin includes an aliphatic alicyclic epoxy resin. The epoxy equivalent of the bifunctional epoxy resin is, for example, 100 g/eq.or more, preferably 120 g/eq.or more, and is, for example, 250 g/eq.or less, preferably 150 g/eq.or less. The proportion of the bifunctional epoxy resin in the epoxy resin is, for example, 80 mass% or more, preferably 90 mass% or more, and is, for example, 99 mass% or less, preferably 97 mass% or less.

Examples of the polyfunctional epoxy resin include: a multifunctional epoxy resin having three or more functions such as a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, a trishydroxyphenylmethane type epoxy resin, a Tetraphenylolethane type epoxy resin, a dicyclopentadiene type epoxy resin, a trifunctional aliphatic epoxy resin, and the like. As the polyfunctional epoxy resin, a trifunctional aliphatic epoxy resin can be preferably mentioned. The epoxy equivalent of the polyfunctional epoxy resin is, for example, 130g/eq. Or more, preferably 150g/eq. Or more, and is, for example, 220g/eq. Or less, preferably 200g/eq. Or less. The proportion of the polyfunctional epoxy resin in the epoxy resin is, for example, 1 mass% or more, preferably 3 mass% or more, and is, for example, 20 mass% or less, preferably 10 mass% or less.

The proportion of the epoxy resin in the epoxy adhesive composition is, for example, 60 mass% or more, preferably 75 mass% or more, and is, for example, 90 mass% or less, preferably 80 mass% or less.

The epoxy resin may be a commercially available one, and as the aliphatic alicyclic epoxy resin, CELLOXIDE 2021P (manufactured by xylonite chemical corporation) may be used, and as the trifunctional aliphatic epoxy resin, EHPE3150 (manufactured by xylonite chemical corporation) and the like may be mentioned.

The epoxy adhesive composition contains a photoacid generator if it is an active energy curable type. Examples of the photoacid generator include: triarylsulfonium salts, and the like. As the photoacid generator, a commercially available product can be used, and as the triarylsulfonium salt, CPI101A (manufactured by San-Apro corporation) or the like can be used. The proportion of the photoacid generator in the epoxy adhesive composition is, for example, 1 mass% or more, preferably 10 mass% or more, and is, for example, 30 mass% or less, preferably 20 mass% or less.

The epoxy adhesive composition may contain additives such as an oxetane resin and a silane coupling agent at an appropriate ratio.

Examples of the oxetane resin include: monofunctional oxetanes such as 3-ethyl-3-oxetanemethanol and 2-ethylhexyl oxetane, and difunctional oxetanes such as xylylene-bisoxetane and 3-ethyl-3 { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetane. As the OXETANE resin, commercially available products such as ARON OXETANE (available from Toyo chemical Co., ltd.) can be used.

Examples of the silane coupling agent include: epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane. As the silane coupling agent, commercially available silane coupling agents can be used, and examples thereof include KBM series (manufactured by Shin-Etsu Silicone Co., ltd.).

The thickness of the adhesive layer 3 is not limited. The thickness of the adhesive layer 3 is, for example, 0.1 μm or more, and is, for example, 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less.

The adhesive layer 3 has a total light transmittance of, for example, 80% or more, preferably 85% or more, and, for example, 99% or less.

The tensile storage modulus E' of the adhesive layer 3 at 25 ℃ is, for example, 1GPa or more, preferably 2GPa or more, more preferably 3GPa or more, further preferably 4GPa or more, and, for example, 100GPa or less. The tensile storage modulus E' of the adhesive layer 3 at 25 ℃ can be determined by measuring the dynamic viscoelasticity in a temperature dispersion mode under the conditions of a frequency of 1Hz and a temperature rise rate of 5 ℃/min. The elastic modulus of the adhesive layer 3 at 25 ℃ measured by the nanoindentation method is, for example, 1GPa or more, preferably 2GPa or more, more preferably 3GPa or more, further preferably 4GPa or more, and further, for example, 100GPa or less. The measurement conditions of the nanoindentation method are as follows.

The device comprises the following steps: triboindenter (manufactured by Hysitron Inc.)

Sample size: 10X 10mm

Pressure head: consial (spherical indenter: curvature radius 10 μm)

The determination method comprises the following steps: single indentation assay

Measuring temperature: 25 deg.C

Pressing depth of the pressing head: 100nm

Temperature: 25 deg.C

And (3) resolving: oliver Pharr resolution based on load-displacement curve

< Membrane 4 >

The film 4 is located on the side of the adhesive layer 3 opposite the glass plate 2. The film 4 extends in the plane direction. The film 4 is disposed on one surface of the adhesive layer 3 in the thickness direction. The film 4 is in contact with one surface of the adhesive layer 3 in the thickness direction. Thereby, the adhesive layer 3 comes into contact with one surface of the glass plate 2 in the thickness direction and the other surface of the film 4 in the thickness direction, and bonds (bonds) the glass plate 2 and the film 4 together.

Average of tan delta < film 4 >

The average of tan delta of the film 4 at-100 ℃ to-50 ℃ as determined by a dynamic viscoelasticity test at a frequency of 10Hz, a temperature rise rate of 2 ℃/min, a data acquisition interval of 0.5min, and a stretching mode is 0.06 or more. When the average of tan δ of the film 4 at-100 ℃ to-50 ℃ is less than 0.06, the impact resistance of the optical laminate 1 is lowered. The average of tan δ of the film 4 at-100 ℃ to-50 ℃ is an index representing the responsiveness when an object collides with the optical laminate 1 at high speed. As the average of tan δ is higher, the film 4 can sufficiently alleviate the impact applied to the glass plate 2, and the impact resistance of the optical laminate 1 can be improved.

The upper limit of the average of tan δ of the film 4 at-100 ℃ to-50 ℃ is not limited. The average of tan δ of the film 4 at-100 ℃ to-50 ℃ is, for example, 0.50 or less. The dynamic viscoelasticity test is described in the examples below.

< average of tensile storage modulus E' of film 4 >

The average tensile storage modulus E' of the film 4 at-100 ℃ to-50 ℃ as determined by a dynamic viscoelasticity test at a frequency of 10Hz, a temperature rise rate of 2 ℃/min, a data acquisition interval of 0.5min, and a stretching mode is 3GPa or more, preferably 4GP or more, more preferably 5GP or more, and further 6GPa or less. If the average tensile storage modulus E' of the film 4 at-100 ℃ to-50 ℃ exceeds 6GPa, the film 4 becomes too hard and the impact resistance of the optical laminate 1 is reduced. On the other hand, if the average tensile storage modulus E' of the film 4 at-100 ℃ to-50 ℃ is less than 3GP, the film 4 becomes too soft, and as a result, the impact resistance of the optical laminate 1 cannot be sufficiently improved.

Examples of the film 4 include a polyester film. Examples of the polyester film include: polyethylene terephthalate films (PET), polybutylene terephthalate (PBT) films, and polyethylene naphthalate (PEN) films. The film 4 is preferably a PET film in view of improving the impact resistance of the optical laminate 1.

The thickness of the film 4 is not limited. The thickness of the film 4 is, for example, 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and further preferably 40 μm or more, and is, for example, 150 μm or less, preferably 100 μm or less, and preferably 75 μm or less.

The total light transmittance of the film 4 is, for example, 80% or more, preferably 85% or more, and is, for example, 99% or less.

< adhesive layer 12 >

The adhesive layer 12 forms one side in the thickness direction of the film 4. The adhesive layer 12 is disposed on one surface of the film 4 in the thickness direction. Specifically, the adhesive layer 12 is in contact with one surface of the film 4 in the thickness direction. The adhesive layer 12 is a bonded body that is pressure-sensitive bonded without being accompanied by a curing reaction.

The material of the adhesive layer 12 is not limited. Examples of the material of the pressure-sensitive adhesive layer 12 include: acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine adhesives, epoxy adhesives, and polyether adhesives. As the material, an acrylic adhesive is preferably used. The formulation and physical properties of the pressure-sensitive adhesive layer 12 are described in detail in, for example, japanese patent application laid-open No. 2018-28573.

The shear storage modulus G' of the pressure-sensitive adhesive layer 12 at 25 ℃ is, for example, 0.01MPa or more, and is, for example, 0.20MPa or less. The shear storage modulus G' can be determined by a dynamic viscoelasticity test in a shear (torsion) mode at a frequency of 1Hz and a temperature rise rate of 5 ℃/min.

The thickness of the pressure-sensitive adhesive layer 12 is 20 μm or less. If the thickness of the adhesive layer 12 exceeds 20 μm, the impact resistance of the optical laminate 1 is lowered. The thickness of the pressure-sensitive adhesive layer 12 is, for example, 5 μm or more, preferably 10 μm or more.

The thickness of the optical laminate 1 is, for example, 70 μm or more and, for example, 250 μm or less.

< method for producing optical laminate 1 >

A method for producing the optical laminate 1 will be described. In the method for producing the optical laminate 1, for example, a curable adhesive is first disposed (applied) on one surface in the thickness direction of the glass plate 2 and/or the other surface in the thickness direction of the film 4, and then the curable adhesive is sandwiched between the glass plate 2 and the film 4.

Then, the curable adhesive is cured. If the curable adhesive is an active energy curable adhesive, the curable adhesive is irradiated with active energy including ultraviolet rays. Specifically, the curable adhesive is irradiated with ultraviolet rays from the glass plate 2 side. If the curable adhesive is a thermosetting adhesive, the curable adhesive is heated. This forms the adhesive layer 3 that strongly adheres the glass plate 2 and the film 4 to each other.

Then, the adhesive layer 12 is disposed on one surface of the film 4 in the thickness direction. For example, a varnish containing an adhesive is applied to one surface of the film 4 in the thickness direction and dried. Alternatively, the pressure-sensitive adhesive layer 12 formed on a release sheet, not shown, may be transferred to one surface of the film 4 in the thickness direction.

In this way, an optical laminate 1 including the glass plate 2, the adhesive layer 3, the film 4, and the pressure-sensitive adhesive layer 12 was obtained. The optical laminate 1 may include a release sheet not shown. In this case, the optical laminate 1 includes: glass plate 2, adhesive layer 3, film 4, pressure-sensitive adhesive layer 12, and a release sheet not shown.

< use of optical laminate 1 >

The optical laminate 1 can be used for various optical applications, and for example, can be disposed in an image display device. Examples of the image display device include an organic electroluminescence display device (hereinafter, simply referred to as an "organic EL display device").

Next, the organic EL display device 10 including the optical laminate 1 will be described with reference to fig. 2.

< organic EL display device 10 >

The organic EL display device 10 has a flat plate shape extending in the plane direction. The organic EL display device 10 includes the conductive film 13 described below, and thus functions as a touch panel type input display device. The organic EL display device 10 includes: an optical laminate 1, a conductive film 13, a 2 nd pressure-sensitive adhesive layer 14, and an image display member 15. In the organic EL display device 10, the upper side of the drawing is the front side (corresponding to the other side in the thickness direction of fig. 1) which is visible to the user, and the lower side of the drawing is the rear side (corresponding to the one side in the thickness direction of fig. 1).

< optical layered body 1 >

The optical laminate 1 includes a glass plate 2, an adhesive layer 3, a film 4, and a pressure-sensitive adhesive layer 12 in this order toward the back side.

< conductive film 13 >

The conductive film 13 includes a conductive layer 16 and a base material layer 17 in this order toward the back side.

< conductive layer 16 >

The conductive layer 16 has a given pattern. The surface and side surfaces of the conductive layer 16 are in contact with the adhesive layer 12. Examples of the material of the conductive layer 16 include: metal oxides, conductive fibers (fibers), and metals. Examples of the metal oxide include a composite oxide. Examples of the complex oxide include: indium zinc complex oxide (IZO), indium gallium zinc complex oxide (IGZO), indium gallium complex oxide (IGO), indium tin complex oxide (ITO), and antimony tin complex oxide (ATO). Examples of the conductive fiber include: metal nanowires, and carbon nanotubes. Examples of the metal include: gold, platinum, silver, and copper. The conductive layer 16 integrally has a sensor electrode portion 18 located at the center in the plane direction and a lead wiring portion 19 located at the periphery of the sensor electrode portion 18. Details of the conductive layer 16 are described in, for example, japanese patent laid-open nos. 2017-102443, 2014-113705, and 2014-219667.

< substrate layer 17 >

The base layer 17 is disposed on the back surface of the conductive layer 16 and the back surface of the adhesive layer 12. The base material layer 17 extends in the planar direction. The base material layer 17 is, for example, a resin layer. Examples of the material of the base layer 17 include: olefin resins, polyester resins, (meth) acrylic resins, polycarbonate resins, polyethersulfone resins, polyarylate resins, melamine resins, polyamide resins, polyimide resins, cellulose resins, and polystyrene resins. Examples of the olefin resin include: polyethylene, polypropylene, and Cyclic Olefin Polymer (COP). Examples of the polyester resin include: PET, PBT, and PEN. Examples of the (meth) acrylic resin include: a poly (meth) acrylate resin. The details of the base material layer 17 are described in, for example, japanese patent laid-open No. 2018-181722.

< 2 nd adhesive layer 14 >

The 2 nd adhesive layer 14 is disposed on the back surface of the conductive film 13. Specifically, the 2 nd adhesive layer 14 is in contact with the back surface of the conductive film 13. The material of the 2 nd adhesive layer 14 is the same as that of the adhesive layer 12.

< image display means 15 >

The image display member 15 forms the back surface of the organic EL display device 10. The image display member 15 is disposed on the back side of the conductive film 13 via the 2 nd adhesive layer 14. The image display member 15 extends in the plane direction. The image display member 15 is specifically an organic EL element. Although not shown, the image display member 15 includes, for example, a display substrate, two electrodes, an organic EL layer sandwiched between the two electrodes, and a sealing layer. The structure and physical properties of the image display member 15 are described in detail in, for example, japanese patent application laid-open No. 2018-28573.

< Effect of one embodiment >

The optical laminate 1 comprises a glass plate 2 having a thickness of 40 μm to 60 μm, an adhesive layer 3, and a film 4 having an average tan delta of 0.06 or more at-100 ℃ to-50 ℃ and an average tensile storage modulus E' of 3GPa or more and 6GPa or less at-100 ℃ to-50 ℃, and further comprises an adhesive layer 12. In addition, the adhesive layer 12 has a thickness of 20 μm or less. Therefore, the optical laminate 1 has excellent impact resistance.

< modification example >

In the following modification, the same members and steps as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Unless otherwise specified, the modified examples can exhibit the same operational effects as the one embodiment.

In one embodiment, the film 4 is a single layer, but the number of layers of the film 4 is not limited.

The film 4 may also be multilayered.

The optical laminate of the present invention has excellent impact resistance, and therefore, has sufficient impact resistance even when the glass plate has a thickness of 40 μm or more and 60 μm or less. On the other hand, the optical laminate of the present invention can be suitably used for flexible displays such as a folding display and a roll display because of its excellent bendability of a glass plate having a thickness of 40 μm or more and 60 μm or less.

As shown by the one-dot chain line in fig. 1, the optical laminate 1 may further include a functional layer 37. The functional layer 37 is disposed on the other surface in the thickness direction of the glass plate 2. Examples of the functional layer 37 include: a hard coat layer, a scattering prevention layer, an antifouling layer, and an antireflection layer. These layers may be a single layer or a plurality of layers may be stacked.

Examples

Specific numerical values such as the blending ratio (content ratio), the physical property value, and the parameter used in the description below may be replaced with upper limit values (numerical values defined as "lower" and "lower") or lower limit values (numerical values defined as "upper" and "lower") described in association with the blending ratio (content ratio), the physical property value, and the parameter described in the above-described "embodiment". In the following description, "part" and "%" are based on mass unless otherwise specified.

Example 1

A glass plate 2 (G-leaf) having a thickness of 50 μm and a film 4 (DIAFOIL S100, manufactured by Mitsubishi chemical corporation) formed of a polyethylene terephthalate film having a thickness of 50 μm were prepared. An epoxy adhesive composition was prepared by mixing 70 parts by mass of an aliphatic alicyclic epoxy resin (CELLOXIDE 2021P, epoxy equivalent 128 to 133g/eq., manufactured by Dailuo chemical Co., ltd.), 5 parts by mass of a trifunctional aliphatic epoxy resin (EHPE 3150, epoxy equivalent 170 to 190g/eq., manufactured by Dailuo chemical Co., ltd.), 19 parts by mass of an OXETANE resin (ARON OXETANE, manufactured by Toyo Synthesis Co., ltd.), 4 parts by mass of a silane coupling agent (KBM-403, 3-glycidoxypropyltrimethoxysilane, manufactured by shin chemical industries, ltd.) and 2 parts by mass of a photoacid generator (101A, triarylsulfonium salt, manufactured by San-Apro). The epoxy adhesive composition was sandwiched between the glass plate 2 and the film 4.

Then, the curable adhesive is irradiated with ultraviolet rays from the glass plate 2 side. This forms the adhesive layer 3 having a thickness of 1 μm, which is formed of a cured product and firmly bonds the glass plate 2 and the film 4. The elastic modulus of the adhesive layer 3 at 25 ℃ measured by the nanoindentation method was 4.9GPa.

Next, the adhesive layer 12 having a thickness of 15 μm was disposed on one surface of the film 4 in the thickness direction by transfer. The adhesive layer 12 was prepared as follows.

A base polymer composition (polymerization rate: about 10%) was obtained by polymerizing 43 parts by mass of Lauryl Acrylate (LA), 44 parts by mass of 2-ethylhexyl acrylate (2 EHA), 6 parts by mass of 4-hydroxybutyl acrylate (4 HBA), 7 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 0.015 part by mass of IRGACURE 184 manufactured by BASF, by irradiating with ultraviolet light.

Separately, 60 parts by mass of dicyclopentyl methacrylate (DCPMA), 40 parts by mass of Methyl Methacrylate (MMA), 3.5 parts by mass of α -thioglycerol, and 100 parts by mass of toluene were mixed, and the mixture was stirred at 70 ℃ for 1 hour in a nitrogen atmosphere. Then, 0.2 part by mass of 2,2' -Azobisisobutyronitrile (AIBN) was charged and reacted at 70 ℃ for 2 hours, and then the temperature was raised to 80 ℃ and reacted for 2 hours. Then, the reaction solution was heated to 130 ℃ to dry and remove toluene, the chain transfer agent and the unreacted monomer, thereby obtaining a solid acrylic oligomer. The weight average molecular weight of the acrylic oligomer was 5100. The glass transition temperature (Tg) was 130 ℃.

0.07 parts by mass of 1, 6-hexanediol diacrylate (HDDA), 1 part by mass of an acrylic oligomer, and 0.3 part by mass of a silane coupling agent ("KBM 403", manufactured by shin-Etsu chemical Co., ltd.) were added to 100 parts by mass of the solid content of the base polymer composition, and these were uniformly mixed to prepare a pressure-sensitive adhesive composition.

The adhesive composition was applied to the surface of a release sheet composed of a PET film (diaf MRF75, mitsubishi chemical), and then another release sheet composed of a PET film (diaf MRF75, mitsubishi chemical) was attached to the coating film. Then, the coating film was irradiated with ultraviolet rays to prepare an adhesive layer 12 having a thickness of 15 μm. The adhesive layer 12 had a shear storage modulus G' of 0.03MGPa at 25 ℃. The measurement method is as follows. The adhesive layer 12 was formed into a disk shape, sandwiched between parallel plates, and the shear storage modulus G' of the adhesive layer 12 at 25 ℃ was determined by dynamic viscoelasticity measurement under the following conditions using an Advanced Rheometric Expansion System (ARES) manufactured by Rheometric Scientific corporation.

[ Condition ]

Mode (2): torsion

Temperature: 40 ℃ below zero to 150 DEG C

Temperature rise rate: 5 ℃/min

Frequency: 1Hz

Thus, an optical laminate 1 including the glass plate 2, the adhesive layer 3, the film 4, and the pressure-sensitive adhesive layer 12 was produced.

Comparative example 1

An optical laminate 1 was produced in the same manner as in example 1. Here, the thickness of the adhesive layer 12 was changed to 25 μm.

Comparative example 2

An optical laminate 1 was produced in the same manner as in example 1. Here, the thickness of the glass plate 2 was changed to 70 μm.

Comparative example 3

An optical laminate 1 was produced in the same manner as in example 1. Here, as the film 4, a cellulose triacetate film (KC 4UYW, manufactured by Konika-Mentada) having a thickness of 40 μm was used.

Comparative example 4

An optical laminate 1 was produced in the same manner as in example 1. As the film 4, a cellulose triacetate film (KC 8UAW, manufactured by Konikamendata) having a thickness of 80 μm was used.

< evaluation >

The following items were measured and evaluated for each of examples and comparative examples. The results are set forth in Table 1.

Tan delta and tensile storage modulus E' > < film 4

The films 4 prepared in the respective examples and comparative examples were subjected to a dynamic viscoelasticity test. The apparatus and conditions are as follows.

The device comprises the following steps: multifunctional dynamic viscoelasticity measuring apparatus DMS6100 manufactured by Hitachi High-Tech Science corporation

Temperature range: 100 ℃ below zero to 200 DEG C

Temperature rise rate: 2 ℃/min

Mode (2): stretching

Width of the sample: 10mm

Distance between chucks: 20mm

Frequency: 10Hz

Strain amplitude: 10 μm

Atmosphere: atmosphere (250 ml/min)

Acquisition interval of data: 0.5min (per 1 deg.C)

The average of the tensile storage modulus E' of the film 4 at-100 ℃ to-50 ℃ was calculated by dividing the sum of all the data obtained above at-100 ℃ to-50 ℃ by the number of data, respectively. The average of tan δ of the film 4 at-100 ℃ to-50 ℃ was calculated by dividing the sum of all the data obtained above at-100 ℃ to-50 ℃ by the number of data, respectively.

< pen drop burst test >

The optical laminate 1 of each example and comparative example was subjected to the pen-drop fracture test described below. As shown by the imaginary line in fig. 1, first, the optical laminate 1 is disposed on the surface of the resin film 34 so that the glass plate 2 faces upward. Specifically, the adhesive layer 12 is bonded to the surface of the resin film 34. The resin film 34 was Prescale (Prescale MS, manufactured by Fuji photo film, single sheet type for medium pressure, thickness 95 μm). The resin film 34 is disposed on the surface of a horizontal stage not shown. Next, a pen drop test was carried out in which a 7g pen 29 (Pentel ballpoint pen BK407 black, ball diameter 0.7 mm) was dropped from a height of 5cm from the glass plate 2. The height of 5cm is a distance between one surface of the glass plate 2 in the thickness direction and the tip 32 of the pen 29. The front end portion 32 is pointed toward the lower side. In the optical laminate 1, if the glass plate 2 is broken by the above-described dropping of the pen 29, the height H1 of the pen-drop breakage test is 5cm. If the glass plate 2 is not broken, the height is increased by 1cm in stages each time. This gives the height H1 at which the glass sheet 2 is broken.

< comparison of examples and comparative examples >

< evaluation of thickness of adhesive layer 12 >

The thickness of the adhesive layer 12 was evaluated. And example 1 was compared with comparative example 1. The thickness of the adhesive layer 12 of example 1 was 15 μm. On the other hand, the thickness of the pressure-sensitive adhesive layer 12 of comparative example 1 was 25 μm. The height H1 of the pen-drop breakage test of example 1 was 20cm, being higher than the height H1 of the pen-drop breakage test of comparative example 1 by 10 cm. Therefore, it is found that by setting the thickness of the pressure-sensitive adhesive layer 12 to 20 μm or less, the impact resistance of the optical laminate 1 is improved.

< evaluation of thickness of glass plate 2 >

The thickness of the glass plate 2 was evaluated. And example 1 was compared with comparative example 2. The thickness of the glass plate 2 of example 1 was 50 μm. The thickness of the glass plate 2 of comparative example 2 was 70 μm. The height H1 of the pen drop test of example 1 was 20cm, which was higher than the height H1 of the pen drop test of comparative example 2. Therefore, it is found that the impact resistance of the optical laminate 1 is improved by setting the thickness of the glass plate 2 to 60cm or less.

Evaluation of average of tan. Delta. < Membrane 4 >

The average of tan δ of the film 4 was evaluated. And example 1, comparative example 3 and comparative example 4 were compared. The average of tan δ of film 4 of example 1 was 0.062. The average of tan δ of the films 4 of comparative examples 3 and 4 was 0.047 μm. The height H1 of the pen-drop breakage test of example 1 was 20cm higher than the heights H1 cm and 10cm of the pen-drop breakage tests of comparative examples 3 and 4, respectively. Therefore, it is found that the impact resistance of the optical laminate 1 is improved by setting the average tan δ of the film 4 to 0.06 or more.

[ Table 1]

It should be noted that the above-mentioned invention is provided as an exemplary embodiment of the present invention, but it is only an example and is not to be construed as a limitation. It will be apparent to those skilled in the art that modifications of the present invention are encompassed by the appended claims.

Industrial applicability

The optical laminate may be provided in an image display device.

Claims

1. An optical laminate comprising a glass plate, an adhesive layer, a film, and an adhesive layer in this order toward one side in the thickness direction,

the glass plate has a thickness of 40 [ mu ] m or more and 60 [ mu ] m or less,

an average value of tan delta of the film at-100 ℃ to-50 ℃ as determined by a dynamic viscoelasticity test at a frequency of 10Hz, a temperature rise rate of 2 ℃/min and a stretching mode is 0.06 or more,

an average of tensile storage modulus E' of the film at-100 ℃ to-50 ℃ determined by the dynamic viscoelasticity test is 3GPa or more and 6GPa or less,

the adhesive layer has a thickness of 20 μm or less.