CN115715255A - Impact absorbing sheet - Google Patents
Impact absorbing sheet Download PDFInfo
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- CN115715255A CN115715255A CN202180045535.9A CN202180045535A CN115715255A CN 115715255 A CN115715255 A CN 115715255A CN 202180045535 A CN202180045535 A CN 202180045535A CN 115715255 A CN115715255 A CN 115715255A
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- silicone
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
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Abstract
The impact-absorbing sheet (1) is provided with a silicone-containing layer (2) containing a silicone resin, and an elastic layer (3) that overlaps the silicone-containing layer (2). The thickness of the silicone-containing layer (2) is 50% to 98% of the thickness of the impact absorption sheet (1). The silicone-containing layer (2) has a penetration at 25 ℃ of 80 to 160 in accordance with JIS K2207. The elastic layer (3) has a tensile modulus of elasticity of 1X 10 6 Pa or more and 1X 10 9 Pa or less, and the elastic layer (3) has an elongation at break of 100% or more.
Description
Technical Field
The present description relates to an impact absorbing sheet, and more particularly, to an impact absorbing sheet including a silicone-containing layer and an elastic layer.
Background
A display of a display device used in various electronic apparatuses such as a smartphone, a tablet terminal, and a notebook computer is provided with an impact absorbing sheet for absorbing impact and vibration generated when the display device is dropped or the like. In recent years, the size and thickness of these electronic devices have been rapidly reduced, and in response to this, impact absorbing sheets that can exhibit excellent impact absorbing properties even when the impact absorbing layer is made thin have been studied (see patent documents 1, 2, and 3).
Recently, flexible displays such as organic EL displays have come to be used in foldable terminals, electronic paper, and the like. The impact absorption sheet used in a display device including such a flexible display may have the following disadvantages: deformation such as unevenness is caused by collision with an object such as falling.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2016-030394
Patent document 2: international publication No. 2018/131619
Patent document 3: japanese patent laid-open No. 2012-102878
Disclosure of Invention
The present invention addresses the problem of providing an impact-absorbing sheet having excellent impact-absorbing properties and excellent resilience to uneven deformation.
An impact absorption sheet according to one embodiment of the present description includes a silicone-containing layer containing a silicone resin, and an elastic layer overlapping with the silicone-containing layer. The thickness of the silicone-containing layer is 50% to 98% of the thickness of the impact absorption sheet. The penetration degree of the silicone-containing layer at 25 ℃ is 60 to 160 in accordance with JIS K2207. The elastic layer has a tensile modulus of elasticity of 1X 10 6 Pa or more and 1X 10 9 Pa or less, and the elastic layer has an elongation at break of 100% or more.
Drawings
Fig. 1 is a schematic cross-sectional view of an impact absorption sheet according to an embodiment of the present description.
Fig. 2 is a schematic sectional view of an impact absorption sheet according to another embodiment of the present description.
Detailed Description
< impact absorption sheet >
The impact absorbing sheet of the present embodiment (hereinafter also referred to as an impact absorbing sheet 1) includes a silicone-containing layer containing a silicone resin and an elastic layer overlapping the silicone-containing layer. The thickness of the silicone-containing layer is 50% to 98% of the thickness of the impact absorption sheet 1. The silicone-containing layer has a penetration at 25 ℃ of 60 to 160 in accordance with JIS K2207. The elastic layer has a tensile modulus of elasticity of 1X 10 6 Pa or more and 1X 10 9 Pa or less, and the elastic layer has an elongation at break of 100% or more. The term "overlap" means that the silicone-containing layer and the elastic layer overlap each other in a plan view.
The present inventors have found that in the impact absorbing sheet 1 including the silicone-containing layer and the elastic layer, there is a correlation between the efficiency of absorbing energy generated by impact and the ability to return to its original state when the concave-convex deformation occurs, and the penetration of the silicone-containing layer, and the tensile elastic modulus and the elongation at break of the elastic layer. That is, it was found that the penetration of the silicone-containing layer was set to the above-mentioned specific range and the tensile modulus of elasticity of the elastic layer was 1X 10 6 Pa or more and 1X 10 9 Pa or less and an elongation at break of 100% or more, the impact absorption sheet 1 can improve the restorability against concave-convex deformation without impairing the impact absorption. Thus, according to the present description, it is possible to provide an impact absorbing sheet excellent in both impact absorbing property and recovery property against concave-convex deformation. When the penetration of the silicone-containing layer is outside the above range, or the tensile elastic modulus of the elastic layer is outside the above range, or the elongation at break is less than the above value, the flexibility and the like of the silicone-containing layer or the elastic layer become uncomfortable, and the recovery property against the concave-convex deformation is lowered. It was also found that in order to obtain excellent impact absorption properties and excellent recovery properties against irregular deformation of the impact absorption sheet 1, in addition to these properties, the thickness of the silicone-containing layer needs to be 50% or more and 98% or less of the thickness of the impact absorption sheet 1. When the thickness is less than 50%, the flexibility of the impact-absorbing sheet 1 becomes uncomfortable, and the impact-absorbing property is loweredLow. When the thickness exceeds 98%, the elastic layer becomes thinner, and the resilience to the uneven deformation becomes lower.
Fig. 1 shows an example of the shock absorbing sheet of the present embodiment. The impact absorbing sheet 1 of fig. 1 is provided with a silicone-containing layer 2 and an elastic layer 3 directly overlapping the silicone-containing layer 2.
[ Silicone-containing layer ]
The silicone-containing layer 2 contains a silicone resin. The silicone-containing layer 2 preferably contains a silicone resin as a main component. The term "main component" means a component having the largest mass ratio, and means a component containing preferably 50 mass% or more, more preferably 70 mass% or more, and further preferably 90 mass% or more.
The impact absorption sheet 1 may have 1 silicone-containing layer 2, or may have 2 or more layers, usually 1 layer. The shape of the silicone-containing layer 2 is, for example, a film, a sheet, a plate, or the like.
The thickness of the silicone-containing layer 2 is 50% to 98% of the thickness of the impact absorption sheet 1. The thickness of the silicone-containing layer 2 is preferably 63% or more, more preferably 70% or more, still more preferably 80% or more, and particularly preferably 83% or more. The thickness of the silicone-containing layer 2 is preferably 96% or less, more preferably 94% or less, further preferably 92% or less, and particularly preferably 90% or less. By setting the thickness of the silicone-containing layer 2 to the above range, the impact absorbability and the recovery property against concave-convex deformation can be further improved.
The thickness of the silicone-containing layer 2 is preferably 50 μm or more. In this case, the impact absorption of the impact absorption sheet 1 can be further improved. The thickness is more preferably 100 μm or more, still more preferably 150 μm or more, and particularly preferably 200 μm or more. The thickness of the silicone-containing layer 2 is preferably 500 μm or less. In this case, the bending resistance of the impact absorption sheet 1 can be further improved. The thickness is more preferably 400 μm or less, still more preferably 350 μm or less, and particularly preferably 300 μm or less.
The penetration degree of the silicone-containing layer 2 is 60 or more and 160 or less. The penetration was as follows: according to JIS K2207, the needle holder and the needle were vertically inserted into a sample at 25 ℃ under the condition that the total weight of the needle holder and the needle was 50g using a penetration tester RPM-201 manufactured by Clutch Co, and the depth (mm) of insertion of the needle in 5 seconds was multiplied by 10 times to obtain a value. The penetration degree is preferably 70 or more, more preferably 80 or more, further preferably 90 or more, and particularly preferably 100 or more. In this case, the impact absorbability can be further improved. The penetration degree is preferably 150 or less, more preferably 140 or less, still more preferably 130 or less, and particularly preferably 120 or less. In this case, the recovery property against the concave-convex deformation can be further improved.
The storage modulus at-20 ℃ (G1) and the storage modulus at 25 ℃ (G2) of the silicone-containing layer 2 are both preferably 1X 10 4 Pa is not less than 1X 10 6 Pa. In this case, a decrease in the adhesive strength between the silicone-containing layer 2 and the elastic layer 3 at low temperatures can be reduced, and the peeling resistance of the impact absorption sheet 1 can be further improved. In this case, it is considered that the wettability of the silicone-containing layer 2 and the elastic layer 3 at low temperatures can be maintained, and the peeling resistance at low temperatures is further improved without significantly reducing the interlayer adhesive force. At least one of G1 and G2 is less than 1 x 10 4 Pa or 1X 10 6 When Pa or more is used, the interlayer adhesive force is reduced at low temperature, the peeling resistance is lowered, and the impact resistance and the recovery from uneven deformation are lowered in some cases. At least one of G1 and G2 is more preferably 1.5X 10 4 Above and 1X 10 5 Hereinafter, more preferably 1.8 × 10 4 Above and 5X 10 4 Hereinafter, 2 × 10 is particularly preferable 4 Above and 3X 10 4 Hereinafter, it is more particularly preferably 2.2 × 10 4 Above and 2.7X 10 4 The following. Further, both G1 and G2 are most preferably in the above range. By setting G1 and G2 in the above range, the peeling resistance and the bending resistance at low temperatures can be further improved.
(Silicone resin)
"Silicone resin" refers to a compound that contains a polysiloxane chain (-Si-O-) composed of siloxane bonds as a main skeleton. The silicone resin preferably contains a silicone gel from the viewpoint of impact absorption performance, and more preferably contains an addition reaction type silicone gel from the viewpoint of easier adjustment of the penetration of the silicone-containing layer 2 to the above range. The addition reaction type silicone gel is obtained, for example, by using an organohydrogenpolysiloxane and an alkenyl polysiloxane described later as raw materials and subjecting them to a hydrosilylation reaction (addition reaction) in the presence of a catalyst. The organohydrogenpolysiloxane is represented by, for example, the following formula (1).
[ chemical formula 1]
In the formula (1), R 1 Represents the same or different kinds of substituted or unsubstituted hydrocarbon groups having a valence of 1. R 2 、R 3 And R 4 Represents R 1 or-H, R 2 、R 3 And R 4 At least two of them represent-H. x and y represent the number of each unit, and are each independently an integer of 0 or more. x + y is an integer of 5 to 300 inclusive.
x is preferably 10 or more and 30 or less. y is preferably 1 to 10 inclusive. x + y is preferably 30 or more and 200 or less. y/(x + y) is preferably 0.1 or less. If y/(x + y) exceeds 0.1, the number of crosslinking points increases, and the impact absorbability may decrease.
The arrangement of each unit in the formula (1) may be random or block, and is preferably random.
The hydrogen atom (Si — H) directly bonded to the silicon atom is required for the addition reaction (hydrosilylation reaction) with the alkenyl group directly or indirectly bonded to the silicon atom, and preferably has at least 2 in the molecule of the organohydrogenpolysiloxane.
The alkenyl polysiloxane is represented by, for example, the following formula (2).
[ chemical formula 2]
In the formula (2), R 1 Represent the same or differentSubstituted or unsubstituted hydrocarbyl of 1 valence. R 5 、R 6 And R 7 Represents R 1 Or an alkenyl group. R 5 、R 6 And R 7 At least 2 of (a) represent an alkenyl group. s and t represent the number of units, and are each independently an integer of 0 or more. s + t is an integer of 10 to 600 inclusive.
s is preferably 10 or more and 30 or less. t is preferably 1 or more and 10 or less. t/(s + t) is preferably 0.1 or less. If t/(s + t) exceeds 0.1, the number of crosslinking points increases, and the impact absorbability may decrease.
Alkenyl groups (vinyl groups, allyl groups, etc.) directly or indirectly bonded to silicon atoms are necessary for the addition reaction (hydrosilylation reaction) with hydrogen atoms (Si — H) directly bonded to silicon atoms, and it is preferable that at least 2 groups are present in the molecule of the alkenyl polysiloxane.
As R in the formulae (1) and (2) 1 Examples thereof include alkyl groups such as methyl, ethyl, propyl and butyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aryl groups such as phenyl and tolyl; aralkyl groups such as benzyl and phenethyl; halogenated hydrocarbon groups obtained by substituting a part or all of the hydrogen atoms of these groups with chlorine atoms, fluorine atoms, or the like.
The hydrosilylation reaction can be carried out using known techniques. Examples of the catalyst for the hydrosilylation reaction include chloroplatinic acid, a complex obtained from chloroplatinic acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, and a platinum-phosphorus complex. The amount of the catalyst used is usually 1ppm to 500ppm, preferably 3ppm to 200ppm, in terms of platinum atom, relative to the alkenyl polysiloxane.
The silicone-containing layer 2 may contain other resins than silicone resins, pigments, heat-dissipating fine particles, flame retardants, heat stabilizers, and other components, as long as the effects of the present description are not impaired.
The method for forming the silicone-containing layer 2 is not particularly limited, and examples thereof include a method in which a silicone resin is applied to the surface of the elastic layer 3, a method in which a composition containing a precursor of a silicone resin is molded by a molding method such as an extrusion molding method, and then a curing reaction such as a hydrosilylation reaction is performed to form a silicone resin, and the like.
[ elastic layer ]
The elastic layer 3 is disposed to overlap the silicone-containing layer 2. The elastic layer 3 had a tensile modulus of elasticity of 1X 10 6 Pa or more and 1X 10 9 Pa or less and an elongation at break of 100% or more. The impact absorption sheet 1 may have 1 elastic layer 3, 2 layers, or 3 or more layers.
The elastic layer 3 has a film, sheet, plate or the like shape, for example.
The thickness of the elastic layer 3 is preferably 5 μm or more. In this case, the impact absorbability can be further improved. The thickness is more preferably 10 μm or more, and still more preferably 20 μm or more. The thickness is preferably 100 μm or less. In this case, the bending resistance can be further improved. The thickness is more preferably 70 μm or less, and still more preferably 50 μm or less.
The tensile modulus of elasticity of the elastic layer 3 is preferably 2.5X 10 6 Above and 5.0X 10 8 Hereinafter, more preferably 5.0X 10 6 Above and 2.5X 10 8 Hereinafter, more preferably 1.0 × 10 7 Above and 1.0X 10 8 Hereinafter, 2.5X 10 is particularly preferable 7 Above and 7.5X 10 7 The following. In this case, the restorability against concave-convex deformation can be further improved without impairing the impact absorbability.
The material usable for the elastic layer 3 is not particularly limited as long as it is a resin having a tensile elastic modulus and an elongation at break within the above ranges. Examples of the resin include (meth) acrylic resins, polyester resins, urethane resins, polyvinyl resins (polyvinyl alcohol, vinyl chloride-vinyl acetate copolymers, and the like), epoxy resins, and the like. The (meth) acrylic resin includes both an acrylic resin and a methacrylic resin, and includes a structural unit derived from a (meth) acrylate ester.
From the viewpoint of further improving the recovery from uneven deformation, the elastic layer 3 preferably contains an elastic resin having elasticity.
Examples of the elastic elastomer resin include acrylic elastomers, urethane elastomers, olefin elastomers, amide elastomers, styrene elastomers, and ester elastomers.
Examples of the acrylic elastomer include copolymers in which the hard segment includes a (meth) acrylate unit and the soft segment includes an acrylonitrile unit, an ethylene unit, a (meth) acrylate unit, and the like.
Examples of the urethane elastomer include copolymers in which the hard segment includes a polyurethane structure and the soft segment includes a polyester structure, a polyether structure, a polycaprolactone structure, and the like.
Examples of the olefinic elastomer include polymer alloys in which olefinic rubbers such as ethylene-propylene rubber and ethylene-propylene-diene terpolymer are finely dispersed in a matrix of an olefinic resin such as polypropylene and polyethylene; copolymers in which the hard segment contains a polybutadiene structure and the soft segment contains a polyether structure, a polyester structure, and the like.
Examples of the amide-based elastomer include copolymers in which the hard segment includes a polyamide structure and the soft segment includes a polyether structure, a polyester structure, and the like.
Examples of the styrene-based elastomer include copolymers in which the hard segment contains styrene units and the soft segment contains butadiene units, hydrogenated butadiene units, isoprene units, hydrogenated isoprene units, and the like.
Examples of the ester-based elastomer include copolymers in which the hard segment has a polyester structure and the soft segment has a polyether structure, a polyester structure, and the like.
The elastic layer 3 preferably contains at least one of a (meth) acrylic resin and an acrylic elastomer from the viewpoint of adhesiveness, transparency, and weather resistance.
Examples of the (meth) acrylic acid ester that provides the (meth) acrylic resin and the acrylic elastomer include (meth) acrylic monomers such as (meth) acrylic acid esters having a substituted or unsubstituted 1-valent hydrocarbon group.
Examples of the 1-valent hydrocarbon group include an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group; a cycloalkyl group having 3 to 20 carbon atoms such as a cyclopentyl group and a cyclohexyl group; an aryl group having 6 to 20 carbon atoms such as a phenyl group or a tolyl group; aralkyl groups having 7 to 20 carbon atoms such as benzyl and phenethyl.
From the viewpoint of further improving the recovery from uneven deformation, the (meth) acrylic resin and the acrylic elastomer preferably include a copolymer of a (meth) acrylic monomer (hereinafter, also referred to as monomer a) having a homopolymer glass transition temperature (Tg) of-10 ℃ or lower and a (meth) acrylic monomer (hereinafter, also referred to as monomer B) having a homopolymer Tg of 60 ℃ or higher.
Examples of the monomer A include n-butyl acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl (meth) acrylate, isononyl (meth) acrylate, and lauryl methacrylate. Examples of the monomer B include methyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, isobornyl (meth) acrylate and the like.
In the (meth) acrylic resin and the acrylic elastomer, the proportion of the structural unit derived from the monomer a is preferably 45 mass% or more with respect to the total structural units constituting the (meth) acrylic resin and the acrylic elastomer. In this case, the adhesive strength between the elastic layer 3 and the silicone-containing layer 2 can be further increased, and as a result, the peeling resistance and the bending resistance can be further improved. The proportion is more preferably 50% by mass or more, still more preferably 55% by mass or more, and particularly preferably 60% by mass or more. The proportion of the structural unit derived from the monomer a is preferably 95% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less.
The elastic layer 3 preferably contains a (meth) acrylic block copolymer elastomer having a block composed of a structural unit derived from the monomer a and a block composed of a structural unit derived from the monomer B, and more preferably contains a (meth) acrylic block copolymer elastomer having a butyl acrylate unit and a methyl methacrylate unit.
Examples of the epoxy resin include bisphenol a type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, aralkyl epoxy resin, phenol novolac type epoxy resin, alkylphenol novolac type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, epoxy of a condensate of a phenol and an aromatic aldehyde having a phenolic hydroxyl group, triglycidyl isocyanurate, and alicyclic epoxy resin. These can be used alone in 1 kind, also can be combined with more than 2 kinds.
As the epoxy resin, for example, a stretchable epoxy elastomer containing 2 or more epoxy groups and 3 methyl groups in 1 molecule and having a molecular weight of 500 or more is more preferably exemplified. The epoxy resin can be cured by using an additive such as a curing agent or a curing accelerator.
The elastic layer 3 preferably contains at least one of a (meth) acrylic block copolymer elastomer and an epoxy resin, and more preferably contains at least one of a (meth) acrylic block copolymer elastomer having a butyl acrylate unit and a methyl methacrylate unit and an epoxy resin.
The method for forming the elastic layer 3 is not particularly limited, and examples thereof include a method of applying a material constituting the elastic layer 3 to the surface of the silicone-containing layer 2, a method of applying a material constituting the silicone-containing layer 2 to the surface of the elastic layer 3, a method of co-extruding a material constituting the silicone-containing layer 2 and a material constituting the elastic layer 3, a method of forming the elastic layer 3 and the silicone-containing layer 2 separately and bonding them, and the like.
The adhesion of the silicone-containing layer 2 to the elastic layer 3 at room temperature is preferably 2N/25mm or more. In this case, the peeling resistance and the bending resistance can be further improved. The adhesive strength is more preferably 3N/25mm or more, still more preferably 5N/25mm or more, and particularly preferably 7N/25mm or more.
[ other layers ]
The impact absorption sheet 1 may include other layers in addition to the silicone-containing layer 2 and the elastic layer 3. The other layer may have a film shape, a sheet shape, a plate shape, or the like, and may include an adhesive layer.
Examples of the other layer include a heat diffusion layer having heat diffusion properties, a shielding layer having electromagnetic wave shielding properties, and a protective layer such as a spacer.
[ layer constitution ]
Examples of the layer structure of the impact absorption sheet 1 of the present embodiment include the following (a) to (p). Hereinafter, the expression a/B/C indicates, for example, stacking a, B, and C in this order from the back side of the display.
(a) Elastic layer/silicone-containing layer
(b) Elastic layer/silicone-containing layer/elastic layer
(c) Elastic layer/silicone-containing layer/thermal diffusion layer
(d) Elastic layer/silicone-containing layer/thermal diffusion layer/adhesive layer
(e) Elastic layer/silicone-containing layer/thermal diffusion layer/adhesive layer/barrier layer
(f) Elastic layer/silicone-containing layer/thermal diffusion layer/adhesive layer/shielding layer/adhesive layer
(g) Elastic layer/silicone-containing layer/adhesive layer/thermal diffusion layer/adhesive layer/barrier layer
(h) Elastic layer/silicone-containing layer/adhesive layer/thermal diffusion layer/adhesive layer/barrier layer/adhesive layer
(i) Spacer/adhesive layer/elastic layer/silicone containing layer
(j) Spacer/adhesive layer/elastic layer/silicone-containing layer/elastic layer/adhesive layer/spacer
(k) Spacer/adhesive layer/elastic layer/silicone-containing layer/thermal diffusion layer
(l) Spacer/adhesive layer/elastic layer/silicone-containing layer/thermal diffusion layer/adhesive layer/spacer
(m) spacer/adhesive layer/elastic layer/silicone-containing layer/thermal diffusion layer/adhesive layer/barrier layer
(n) spacer/adhesive layer/elastic layer/silicone-containing layer/thermal diffusion layer/adhesive layer/barrier layer/adhesive layer/spacer
(o) spacer/adhesive layer/elastic layer/silicone-containing layer/adhesive layer/thermal diffusion layer/adhesive layer/barrier layer
(p) spacer/adhesive layer/elastic layer/silicone-containing layer/adhesive layer/thermal diffusion layer/adhesive layer/barrier layer/adhesive layer/spacer
Fig. 2 shows a shock-absorbing sheet having the layer structure of (j) above. The impact absorbing sheet 1 of fig. 2 is provided with a silicone-containing layer 2; 2 elastic layers 3 and 3 directly laminated on both surfaces of the silicone-containing layer 2; 2 adhesive layers 4, 4 directly laminated on these elastic layers 3, 3; and spacers 5 and 5 directly laminated on the adhesive layers 4 and 4.
The total of the thickness of the silicone-containing layer 2 and the thickness of the elastic layer 3 in the impact absorption sheet 1 is preferably 50 μm or more. In this case, the impact absorption of the impact absorption sheet 1 can be further improved. The thickness is more preferably 100 μm or more, and still more preferably 200 μm or more. The total thickness is preferably 500 μm or less. In this case, the bending resistance can be further improved. The thickness is more preferably 400 μm or less, and still more preferably 350 μm or less.
The thickness of the impact absorption sheet 1 is preferably 50 μm or more. In this case, the strength of the impact absorption sheet 1 can be further improved. The thickness is more preferably 100 μm or more, and still more preferably 200 μm or more. The thickness of the impact absorption sheet 1 is preferably 500 μm or less. In this case, the display device including the display can be further thinned. The thickness is more preferably 400 μm or less, and still more preferably 350 μm or less.
The impact absorption rate of the impact absorption sheet 1 is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, and particularly preferably 40% or more. The upper limit value of the impact absorption rate may be 100%. The impact absorption rate of the impact absorption sheet 1 is a value measured by a steel ball drop method, for example. The method for measuring the impact absorption rate is described in the column of examples described later.
The impact absorbing sheet 1 of the present embodiment can be suitably used for a flexible display. The impact absorption sheet 1 is preferably used by being disposed on the back side or the front side of a flexible display such as an organic EL display, more preferably disposed on the back side, and even more preferably directly laminated on the back side of the flexible display. By using the impact absorbing sheet 1 of the present embodiment, which is excellent in both impact absorbability and resilience to uneven deformation, in a display device including a flexible display, the flexible display can be effectively protected from impact and vibration.
Examples
The present description will be described in more detail below with reference to examples, but the present description is not limited to these examples at all.
1. Manufacture of impact-absorbing sheet
Silicone resin providing a silicone-containing layer
Resin A: two-component addition reaction type Silicone gel (product No. KE-104, curing agent (B) having Main agent (A), manufactured by shin-Etsu chemical industries, ltd.)
Resin B: two-component addition reaction type Silicone gel (product No. X32-3443, manufactured by shin-Etsu chemical Co., ltd., product No.: X32-3443, having a base (A) and a curing agent (B))
Resin C: addition curing type Silicone adhesive (product No. X-40-3240, manufactured by shin-Etsu chemical Co., ltd., product No.: X-40-3240, having a base agent (A) and a curing agent (B))
The resins a to C were used by mixing the main agent (a) and the curing agent (B) at the mixing ratios shown in table 1.
-elastomer resins providing the elastic layer
And an acrylic elastomer (a block copolymer of Butyl Acrylate (BA) and Methyl Methacrylate (MMA), manufactured by Kuraray Co., ltd., product No. LA 4285) and an acrylic elastomer (a block copolymer of Butyl Acrylate (BA) and Methyl Methacrylate (MMA), manufactured by Kuraray Co., ltd., product No. LA 2270) were used in combination so that the BA/MMA ratio (mass ratio) was 55/45 (example 1, example 2, example 4, example 8 and example 12) or 52/48 (example 3 and comparative example 4). In addition, LA4285 and an acrylic elastomer (a block copolymer of Butyl Acrylate (BA) and Methyl Methacrylate (MMA), manufactured by Kuraray Co., ltd., product No. LA 2250) were mixed and used so that the ratio of BA/MMA was 65/35 (example 5, example 13 and example 14). Further, LA4285 and an acrylic elastomer (a block copolymer of Butyl Acrylate (BA) and Methyl Methacrylate (MMA), manufactured by Kuraray Co., ltd., product No. LK 9243) were mixed and used so that the BA/MMA ratio was 80/20 (comparative example 2).
As the stretchable epoxy elastomer, an epoxy resin (product No. JER1003, manufactured by Mitsubishi Chemical Co., ltd.) and a polyrotaxane (product No. SH3400P, manufactured by ASM Co., ltd.) were used in combination in the form of a mixture of JER1003/SH3400P as shown in Table 1. 1 part by mass of an acid anhydride (YH-307, monofunctional acid anhydride, functional group equivalent: 231, manufactured by Mitsubishi Chemical Co., ltd.) as a curing agent and 0.5 part by mass of an imidazole-based curing accelerator (2E 4MZ, 2-ethyl-4-methylimidazole, manufactured by four Chemical industries) as a curing accelerator were mixed with 100 parts by mass of the stretchable epoxy elastomer.
Production of impact-absorbing sheet
(i) The two-component addition reaction type silicone gel was formed into a sheet by extrusion molding, and then dried and cured, thereby forming a silicone-containing layer having a thickness shown in table 1.
(ii) Next, the elastomer resin synthesized as described above was applied to the release-treated surface of the release polyethylene terephthalate film and dried, thereby forming the elastic layer 1 and the elastic layer 2 of the types and thicknesses of resins shown in table 1.
(iii) Next, the elastic layer 1 and the elastic layer 2 formed as described above were bonded to both sides of the silicone-containing layer. Thus, a shock-absorbing sheet was produced.
The "-" in the elastic layer 1 and the elastic layer 2 in table 1 indicates that the respective elastic layers were not used.
2. Measurement of physical Properties
[ storage modulus of Silicone-containing layer ]
The silicone-containing layer was cut into a size of 10mm in width and 20mm in length to prepare a test piece. The test piece was measured for storage modulus (Pa) at-20 ℃ and 25 ℃ under the conditions of a frequency of 10Hz and a temperature rise rate of 5 ℃/min using a dynamic viscoelasticity measuring apparatus (DVA-200, manufactured by IT measurement control Co., ltd.).
[ tensile elastic modulus of elastic layer ]
The elastic layer was cut into a size of 10mm in width and 20mm in length to prepare a test piece. The tensile modulus (Pa) at 25 ℃ was measured using a dynamic viscoelasticity measuring apparatus (DVA-200, manufactured by IT measurement and control Co., ltd.) at a frequency of 10Hz and a temperature rise rate of 5 ℃/min.
[ elongation at Break of elastic layer ]
(preparation of test piece)
A No. 6 dumbbell test piece defined in JIS K6251 was punched out to prepare a test piece.
(measurement of elongation at Break)
Using the test piece thus obtained, a tensile test was carried out under the following conditions by using Autograph (AGS-X) manufactured by Shimadzu corporation.
Temperature: 25 deg.C
A force sensor: 50N
Distance between initial clamps: 35mm in diameter
Stretching speed: 25mm/min
(calculation of elongation at Break)
The elongation at break (%) was calculated by using the moving distance of the jig at the time of breaking and by the following formula.
Elongation at break (%) = (L-Lo). Times.100/Lo
Lo: length of sample before test, L: length of specimen at break
[ adhesive force of Silicone-containing layer with respect to elastic layer ]
The silicone-containing layer was cut into a size of 25mm in width and 100mm in length, laminated on the elastic layer, and the silicone-containing layer and the elastic layer were bonded by reciprocating the rubber roller once on the laminate at a speed of 300 mm/min using a 2.0kg rubber roller. Then, the sample was left at 25 ℃ for 20 minutes to prepare a test piece. The test piece was measured at normal temperature (23 ℃ C.) in an environment according to JIS-Z0237 "test method for adhesive tape/sheet" (bonding conditions: 1 reciprocating motion of 2kg roller, peeling speed: 300 mm/min, peeling angle: 180 ℃ C.).
3. Evaluation of
[ impact absorption Rate ] (Steel ball drop test)
(sample preparation)
The impact absorbing sheet was cut into 5cm × 5cm in size to prepare a sample for a steel ball drop test.
(evaluation method)
An acceleration sensor element of a digital accelerometer (MODEL-1340B, manufactured by showa-measuring corporation) was fixed to one surface of a 10 cm-square aluminum plate having a thickness of 2mm by using a general-purpose adhesive tape having a thickness of 25 μm. Next, the aluminum plate was fixed to the mount with the acceleration sensor facing downward. Next, the cut sample was placed on an aluminum plate, and a steel ball drop test was performed using SUS balls having a diameter of 20mm and a weight of 14g under a condition of a drop height of 10 cm.
(calculation of impact absorptivity)
The impact absorption rate (%) was calculated by the following formula.
Shock absorption (%) = (peak acceleration of aluminum alone-peak acceleration when using test piece) × 100/(peak acceleration of aluminum alone)
[ test for recovery from indentation ] (Steel ball drop test)
(sample preparation)
The impact absorbing sheet was cut into 5cm × 5cm in size to prepare a sample for a steel ball drop test.
(evaluation method)
The cut sample was placed on an aluminum plate having a thickness of 2mm and a square of 10cm, and a steel ball drop test was carried out under a condition that the drop height was 10cm by using SUS balls having a diameter of 20mm and a weight of 14 g.
(evaluation of unevenness)
The test specimen was visually observed for the dent immediately after the steel ball fell, and the impact absorption sheet was evaluated for the recovery from the concave-convex deformation according to the following criteria.
A: without recesses
B: disappearance of dishing within 2 hours
C: the depressions are not disappeared
[ bending test ]
The bending resistance of the impact absorption sheet was evaluated by performing the bending test described below.
The impact absorption sheet was cut into a rectangular piece of 2X 10cm to prepare a test piece. The test piece was fixed to a planar unloaded U-shaped extension and contraction tester (manufactured by Yuasa System Instruments, model: DMLHB, main body, jig: planar unloaded U-shaped extension and contraction test jig) so that the bending radius became 5 mm. The bending test was performed 1 ten thousand times by repeating the operation of bending and the operation of restoring the impact absorption sheet at a speed of 30 times for 1 minute. The test piece after the bending test was visually observed, and the bending resistance of the impact absorption sheet was evaluated according to the following criteria.
A: no appearance change and no wrinkle
B: wrinkle disappearance within 24 hours
C: the wrinkles did not disappear.
[ Table 1]
Description of the reference numerals
1. Impact absorbing sheet
2. Layer containing organic silicon
3. Elastic layer
4. Adhesive layer
5. Spacer member
Claims (5)
1. An impact absorbing sheet comprising:
a silicone-containing layer comprising a silicone resin; and
an elastic layer overlapping the silicone-containing layer,
the thickness of the silicone-containing layer is 50% or more and 98% or less of the thickness of the impact absorption sheet,
the silicone-containing layer has a penetration at 25 ℃ of 60 to 160 in accordance with JIS K2207,
the elastic layer has a tensile modulus of elasticity of 1X 10 6 Pa or more and 1X 10 9 Pa or less, and the elastic layer has an elongation at break of 100% or more.
2. The impact-absorbing sheet according to claim 1, wherein the impact absorption rate measured by a steel ball drop method is 20% or more.
3. The impact-absorbing sheet according to claim 1 or 2, wherein the adhesion force of the silicone-containing layer to the elastic layer is 2N/25mm or more.
4. The impact-absorbing sheet according to any one of claims 1 to 3, having a thickness of 50 μm or more and 500 μm or less.
5. The impact-absorbing sheet according to any one of claims 1 to 4, wherein the elastic layer comprises at least one of a (meth) acrylic block copolymer elastomer having a butyl acrylate unit and a methyl methacrylate unit, and an epoxy resin.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US202063054434P | 2020-07-21 | 2020-07-21 | |
| US63/054,434 | 2020-07-21 | ||
| PCT/JP2021/027061 WO2022019286A1 (en) | 2020-07-21 | 2021-07-20 | Shock absorbing sheet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115715255A true CN115715255A (en) | 2023-02-24 |
Family
ID=79728789
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180045535.9A Pending CN115715255A (en) | 2020-07-21 | 2021-07-20 | Impact absorbing sheet |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPWO2022019286A1 (en) |
| KR (1) | KR20230041697A (en) |
| CN (1) | CN115715255A (en) |
| TW (1) | TW202204140A (en) |
| WO (1) | WO2022019286A1 (en) |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6151035A (en) * | 1984-08-16 | 1986-03-13 | Kiyuubitsuku Eng:Kk | Preparation of impact absorber |
| JPS6428974A (en) * | 1987-07-24 | 1989-01-31 | Toyama Prefecture | Piezoelectric pressure sensitive element and manufacture thereof |
| JPH0717039B2 (en) * | 1989-02-22 | 1995-03-01 | イナバゴム株式会社 | Buffer body and manufacturing method thereof |
| JP4820597B2 (en) * | 2005-07-25 | 2011-11-24 | 株式会社タイカ | Cosmetic compact container |
| JP5352661B2 (en) | 2011-11-22 | 2013-11-27 | 株式会社タイカ | Thin impact cushioning material and thin impact cushion laminate |
| JP2016030394A (en) | 2014-07-29 | 2016-03-07 | 岩谷産業株式会社 | Impact absorption film |
| JP6470968B2 (en) * | 2014-12-26 | 2019-02-13 | 株式会社潤工社 | Rubber or thermoplastic elastomer composition and molded article comprising the composition |
| JP2018032397A (en) * | 2016-08-17 | 2018-03-01 | 株式会社半導体エネルギー研究所 | Touch input pen, electronic device, and method for input to electronic device with touch input pen |
| WO2018131619A1 (en) | 2017-01-11 | 2018-07-19 | 積水化学工業株式会社 | Shock-absorbing sheet |
-
2021
- 2021-07-20 JP JP2022538011A patent/JPWO2022019286A1/ja active Pending
- 2021-07-20 TW TW110126620A patent/TW202204140A/en unknown
- 2021-07-20 CN CN202180045535.9A patent/CN115715255A/en active Pending
- 2021-07-20 WO PCT/JP2021/027061 patent/WO2022019286A1/en active Application Filing
- 2021-07-20 KR KR1020237001954A patent/KR20230041697A/en active Search and Examination
Also Published As
| Publication number | Publication date |
|---|---|
| TW202204140A (en) | 2022-02-01 |
| WO2022019286A1 (en) | 2022-01-27 |
| JPWO2022019286A1 (en) | 2022-01-27 |
| KR20230041697A (en) | 2023-03-24 |
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