CN115803410A

CN115803410A - Impact absorbing material

Info

Publication number: CN115803410A
Application number: CN202180045601.2A
Authority: CN
Inventors: 英翔; 宫崎香织; 仓知毅; 名塚正范; 小野洋介
Original assignee: Taica Corp; Panasonic Holdings Corp
Current assignee: Taica Corp; Panasonic Holdings Corp
Priority date: 2020-07-21
Filing date: 2021-07-20
Publication date: 2023-03-14
Also published as: WO2022019285A1; JPWO2022019285A1; TW202219143A; KR20230042270A

Abstract

The invention provides an impact absorbing material having adhesive property and light shielding property. The impact absorbing material (1) is obtained by adding an insulating inorganic black pigment (3) to a silicone composition (2) having adhesive properties and stress relaxation properties. The adhesive force of the impact absorbing material (1) to the glass plate is 2N/20mm or more. The transmittance of light having a wavelength of 300nm to 850nm of the impact absorbing material (1) is 0.6% or less. The penetration at 25 ℃ of the impact absorbing material (1) is 90 to 160 in accordance with JIS K2207. The impact absorption rate of the impact absorption material (1) is 20% or more.

Description

Impact absorbing material

Technical Field

The present invention relates generally to an impact absorbing material, and more particularly to an impact absorbing material that imparts light-shielding properties to a silicone composition having adhesive properties.

Background

Patent document 1 describes an impact absorbing film having a laminate. The laminate comprises a 1 st stretchable film and a foam laminated thereon. The 1 st stretch film has a tensile strength of 0.15 to 0.5N/10mm at a 10% modulus and has stretchability which returns to its original length when the stretching force is removed. The foam is a foam having a thickness of 0.05mm to 0.5mm, and the elastic stress of a sheet formed only of the foam is 0.02MPa to 3.0MPa when the sheet is compressed to a thickness of 50% after a plurality of sheets are stacked to a thickness of 1 cm.

Such impact absorbing films are used for protecting display panels, electronic circuits, batteries, and the like of products such as smart phones, tablet terminals, and notebook computers. That is, the above-described impact absorbing film is used as a material for absorbing impact so that the display panel is not broken when a product such as a smartphone or a tablet terminal is subjected to impact due to dropping or the like.

The shock absorbing film of patent document 1 is difficult to impart light-shielding properties to the shock absorbing film itself, and the light-shielding film needs to be attached to the shock absorbing film via an adhesive layer. That is, since the impact absorption film has a foam, surface scattering occurs due to surface voids, and thus it is difficult to impart light-shielding properties to the foam itself, and it is necessary to attach a light-shielding film to the impact absorption film separately.

In addition, when the impact absorption film of patent document 1 is attached to a display panel or the like, an adhesive layer for bonding the impact absorption film to the display panel or the like is necessary. In addition, when the light shielding film is required, an adhesive layer for bonding the light shielding film and the impact absorbing film is also required. Therefore, the display panel or the like to which the light shielding film and the impact absorbing film are attached becomes rigid as a laminate, and it is easily prevented that the display panel or the like can freely perform functions such as bending and stretching which are originally required.

Foam or rubber-like impact absorbing materials of urethane, acrylic, and silicone are often used as the impact absorbing material, but silicone is advantageous in the case of display applications in which performance stability during repeated use is often required. Further, since the impact absorbing material is effective when it comes into contact with the object to be protected, it is necessary to have adhesiveness such that the impact absorbing material and the object to be protected are not peeled off when repeated impacts are applied. Further, reworkability is required for displays in which parts are expensive, and therefore control of the adhesion of the impact absorbing material is important.

Patent document 2 describes an adhesive sheet of an addition curing silicone composition having light-shielding properties. The adhesive sheet is intended to shield and protect the electrodes from light. Among them, since the adhesive sheet is pressed against a protection object in a state of a semi-cured (a-stage) sheet and cured by heat to obtain adhesiveness, the production process becomes complicated. In addition, in order to maintain the semi-cured sheet, low-temperature storage is required, and production management is difficult.

Patent document 3 describes a material that can be formed into a sheet as an addition curing type silicone composition. This material can be provided with light-shielding properties, thermal conductivity, and vibration-absorbing properties by adding a material, but there is no description about the adhesive strength of the material.

Patent documents

4 and 5 describe silicone compositions having adhesive properties. The silicone composition is bonded by heat after being brought into contact with a protection object. Patent document 4 does not describe light-shielding properties. Such a silicone composition is not useful because it has a high possibility of breaking the display during reworking.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2016-30394

Patent document 2: japanese patent laid-open No. 2010-90363

Patent document 3: japanese laid-open patent publication No. 2010-144133

Patent document 4: japanese patent laid-open No. 2002-173661

Patent document 5: japanese laid-open patent publication No. 62-240361

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an impact absorbing material having adhesiveness and light shielding properties.

Further, an object of the present invention is to provide an impact absorbing material which can be stored at normal temperature and does not require post-curing.

An impact absorbing material according to one embodiment of the present invention contains an insulating inorganic black pigment in a silicone composition having adhesiveness and stress relaxation properties. The adhesive force of the impact absorbing material to the glass plate is 2N/20mm or more. The impact absorbing material has a light transmittance of 0.6% or less at a wavelength of 300nm to 850 nm. The penetration at 25 ℃ of the impact absorbing material according to JIS K2207 is 90 to 160 inclusive. The impact absorption rate of the impact absorption material is 20% or more.

Drawings

Fig. 1A is a schematic view showing a shock absorbing material according to an embodiment of the present invention. Fig. 1B is an explanatory view showing a shock-absorbing laminate of a comparative example.

Fig. 2 is a schematic view showing a test for measuring the adhesive force of the impact absorbing material according to the embodiment of the present invention.

Fig. 3 is a schematic diagram showing a test for measuring the impact acceleration of the impact absorbing material according to the embodiment of the present invention.

Detailed Description

(outline of impact absorber)

Fig. 1A shows a shock absorbing material 1 according to the present embodiment. The impact absorbing material 1 contains an insulating inorganic black pigment 3 in a silicone composition 2. Silicone composition 2 is the reaction product of an organosilicon compound and has adhesion and stress relaxation properties.

Fig. 1B shows an impact absorbing laminate 100 in a case where it is desired to obtain impact absorbing properties, light shielding properties, and adhesion properties equivalent to those of the impact absorbing material 1. The impact absorbing laminate 100 has a porous structure layer 101 for obtaining impact absorbability. The porous structure layer 101 is formed from a foam such as polypropylene, polyethylene, polyacrylic acid, or polyurethane, and has a thickness of 50 to 1000 μm. The shock absorbing laminate 100 is provided with a light-shielding base material 102 having a low light transmittance in order to obtain light-shielding properties. The light-shielding base 102 is formed to have a thickness of 5 to 50 μm, and is attached to one surface of the porous structure layer 101 by an adhesive layer 103 having a thickness of 3 to 50 μm. The impact-absorbing laminate 100 has two

adhesive layers

104 and 105 having a thickness of 3 to 50 μm for adhesion. The adhesiveness is a property of being able to adhere the impact absorption laminate 100 to another member. Therefore, one adhesive layer 104 is provided on the other surface (the surface without the light-shielding substrate 102) of the porous structure layer 101. The other adhesive layer 105 is provided on one surface (surface without the adhesive layer 103) of the light-shielding substrate 102.

In this way, the shock absorbing laminate 100 is formed of the porous structure layer 101 for obtaining shock absorption, the light-shielding substrate 102 for obtaining light shielding properties, the two

adhesive layers

104 and 105 for obtaining adhesion properties, and the adhesive layer 103 for adhering (bonding) the light-shielding substrate 102 to the porous structure layer 101, and thus has a very large thickness. On the other hand, since the impact absorbing material 1 of the present embodiment contains the insulating inorganic black pigment 3 in the silicone composition 2 having adhesiveness and stress relaxation properties, the impact absorbing property and the adhesion property are obtained by the silicone composition 2, and the light shielding property is obtained by the insulating inorganic black pigment 3. Therefore, even without the light-shielding base material 102 and the three

adhesive layers

103, 104, and 105, the impact-absorbing laminate 100 has the same degree of impact absorbability, light-shielding property, and adhesiveness. Therefore, the impact absorbing material 1 of the present embodiment has impact absorbing properties, light blocking properties, and adhesion properties, and can be made thinner (thinner) than the impact absorbing laminate 100. Specifically, the impact absorbing material 1 of the present embodiment may be formed to have a thickness equal to or thinner than the porous structure layer 101 by 80 μm to 500 μm. The thickness of the impact absorber 1 is preferably 100 μm or more and 450 μm or less. The thickness of the impact absorbing material 1 is more preferably 150 μm or more and 300 μm or less.

The impact absorbing material 1 of the present embodiment is preferably used for light shielding and impact absorption of a display panel, for example. This makes it easy for the display panel to be protected from impact by the impact absorbing material 1. Further, the display panel is shielded from light by the shock absorbing material 1, and the display is easily made clear. The display panel is a liquid crystal panel, an organic EL panel, or the like.

The impact absorbing material 1 of the present embodiment is preferably formed of a single layer. That is, the impact absorbing material 1 is preferably not laminated with other layers, but has adhesiveness, light-shielding property, and impact absorption in one layer. Thus, the impact absorbing material 1 of the present embodiment can be easily formed thin. The adhesiveness refers to a function capable of adhering to other members. The adhesiveness of the impact absorbing material 1 of the present embodiment is defined by the adhesive force to the glass plate. The light-shielding property refers to a function of shielding light. The light-shielding property of the impact absorbing material 1 of the present embodiment is defined by the transmittance of light having a wavelength of 300nm to 850 nm. The impact absorbability means a function capable of absorbing an impact. The impact absorption performance of the impact absorbing material 1 of the present embodiment is defined by an impact absorption rate.

The impact absorbing material 1 of the present embodiment is used in a state of being disposed on the back surface of the display panel. That is, the impact absorbing material 1 is used by being laminated on the back surface of a display panel such as a liquid crystal panel used for a flat panel display or the like. The impact absorbing material 1 of the present embodiment does not need to be post-cured by heat or ultraviolet rays in a state of being disposed on the back surface of the display panel. Here, the post-curing refers to a curing step in the final stage of the manufacturing process. Therefore, the impact absorbing material 1 of the present embodiment does not require a step of finally curing the material by heat or ultraviolet rays in a state of being disposed on the back surface of the display panel. That is, the impact absorbing material 1 of the present embodiment can be bonded to the back surface of the display panel without post-curing by heat or ultraviolet rays. Therefore, the impact absorbing material 1 of the present embodiment can reduce the adverse effect of heat and ultraviolet rays on the display panel and can bond the display panel.

The impact absorbing material 1 of the present embodiment can be stored at room temperature. That is, the impact absorbing material 1 can be stored without being set at a low temperature for a long period of time with almost no change in properties. Here, the normal temperature means 25 ℃. The impact absorbing material 1 can be stored at room temperature for 6 months so that the adhesiveness, light-shielding property, penetration and impact absorption properties are hardly changed.

(Silicone composition)

The silicone composition 2, which is a reaction product of the silicone compound, constitutes the main body of the impact absorbing material 1. That is, the silicone composition 2 has a function of inherently holding the matrix of the insulating inorganic black pigment 3. In addition, the impact absorbing material 1 can physically alleviate the impact energy mainly by the silicone composition 2 without using a porous structure.

In the impact absorbing material 1 of the present embodiment, the silicone composition 2 has a sheet-like, plate-like, or film-like form. The thickness of the silicone composition 2 in these forms is 80 μm or more and 500 μm or less. That is, the thickness of the silicone composition 2 is the thickness of the impact absorbing material 1.

The silicone composition 2 has adhesiveness. Here, the adhesiveness refers to a function of being able to adhere (bond) the silicone composition 2 to another member. Specifically, the force required to peel off soda glass is specified in a 90-degree peel mode of an adhesive force test according to JIS Z0237. In this case, the adhesive strength of the silicone composition 2 is preferably 2N/20mm or more. In the method for measuring the adhesiveness in the present invention, the drawing speed was 300mm/min, and the test piece was a long strip having a width of 20mm, a length of 100mm and a thickness of 150 μm. The test piece was attached to the soda glass by reciprocating the roller 2kg 1 time, and then left at 23 ℃ for 24 hours.

Silicone composition 2 has stress relaxation properties. Here, the stress relaxation property means a function of absorbing impact energy generated by stress when the stress is applied to the silicone composition 2 by deforming or converting the impact energy into thermal energy, and making the stress less likely to be transmitted. Specifically, the stress relaxation property of silicone composition 2 is defined as a complex elastic modulus of 10 in the dynamic viscoelasticity measurement (torsional shear mode) at 0 ℃ to 200 ℃ ³ Pa is 10 or more ⁵ Pa or less, and tan delta of 10 ^-2 The above range and 1 or less. The complex elastic modulus and tan. Delta. Were measured under the conditions of a strain of 1% and an oscillation frequency of 10Hz using a disk-shaped test piece having a diameter of 25mm (diameter of 25 mm) and a thickness of 2 mm.

The dynamic elastic modulus includes a storage modulus G' (Pa) and a loss modulus G "(Pa). The storage modulus G' (Pa) is a component stored in the body among the energy generated by the body due to external force and strain, and the loss modulus G "(Pa) is a component diffused to the outside. The complex elastic modulus G (Pa) is G = (G' ² +G“ ² ) ^1/2 The expression indicates the hardness of the object. In addition, tan δ is a loss coefficient and is a ratio of G ″ to G '(tan δ = G "/G' = loss modulus/storage modulus).

By making the complex elastic modulus G (Pa) 10 between 0 ℃ and 200 DEG C ³ Pa or more and 10 ⁵ Pa or less and tan delta of 10 ^-2 The range of 1 or less is set as above, so that the silicone composition 2 can exhibit a characteristic of gradually diffusing to the outside in the form of thermal energy after storing energy in the silicone composition 2 when external force, strain, or the like is applied, and thus can exhibit an impact absorption characteristic. Within the range other than the above, the silicone composition 2 does not accumulate energy generated by external force, strain, or the like in the interior but generates elastic repulsive force toward the outside or plastic deformation, and the impact absorbing material 1 is difficult to maintain the original shape.

More preferably, the silicone composition 2 has a complex elastic modulus G (Pa) in the range of 20,000pa or more and 80,000pa or less at 0 ℃ to 200 ℃, and tan δ of 0.1 or more and 0.9 or less.

As a measuring device for the complex elastic modulus G (Pa), "ARES G2" manufactured by TA Instruments co.

The silicone composition used in the present embodiment may be a known silicone composition having rubber elasticity and viscoelasticity, as long as the desired absorption buffering performance can be obtained, and from the viewpoint of absorption buffering, it is preferable to use a silicone gel as the silicone composition, and from the viewpoint of curability and the like, it is particularly preferable to use an addition reaction type (or crosslinked) silicone gel as the silicone composition. The addition reaction type silicone gel is not particularly limited, and is generally obtained by using, as an example of the silicone compound, an organohydrogenpolysiloxane and an alkenylpolysiloxane, which will be described later, as raw materials, and subjecting them to a hydrosilylation reaction (addition reaction) in the presence of a catalyst. That is, in the present embodiment, the silicone compound that can be a raw material of the silicone gel is often referred to as organohydrogenpolysiloxane and alkenylpolysiloxane. The organohydrogenpolysiloxane used as one of the raw materials is preferably represented by the following general formula (1).

[ chemical formula 1]

In the formula, R ¹ Represent the same or different kinds of substituted or unsubstituted hydrocarbyl radicals 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 2 of them represent-H, x and y are integers representing the number of the respective units, the respective units are arranged block-wise or randomly, preferably randomly, x is an integer of 0 or more, preferably 10 to 30, y is an integer of 0 or more, preferably 1 to 10.x + y is an integer of 5 to 300, preferably 30 to 200. Further, y/(x + y) ≦ 0.1 is preferable. If the amount exceeds this range, the crosslinking points increase, and the impact resistance may decrease.

As R ¹ Examples of the (b) 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 phenylethyl, and halogenated hydrocarbons in which hydrogen atoms are partially substituted by chlorine atoms, fluorine atoms and the like.

Hydrogen (Si — H) directly bonded to a silicon atom is necessary for the addition reaction (hydrosilylation reaction) with an alkenyl group directly or indirectly bonded to a silicon atom, and preferably has at least 2 in the molecule of the organohydrogenpolysiloxane.

The alkenyl polysiloxane, which is another raw material used in the production of the crosslinked silicone gel used in the present embodiment, is preferably represented by the following general formula (2).

[ chemical formula 2]

In the formula, R ¹ Represent the same or different kinds of substituted or unsubstituted hydrocarbyl radicals having a valence of 1, R ⁵ 、R ⁶ And R ⁷ Represents R ¹ Or alkenyl, R ⁵ 、R ⁶ And R ⁷ At least 2 of them represent an alkenyl group, s and t are integers representing the number of the respective units, the respective units are arranged in blocks or randomly, preferably randomly, s represents an integer of 0 or more, t represents an integer of 0 or more, s + t is an integer of 10 to 600, and t/(s + t) ≦ 0.1. In addition, the ratio t/(s + t) ≦ 0.1 is preferred. If the amount exceeds this range, the number of crosslinking points increases, and the impact absorbability may be lowered.

As R ¹ Examples of the (b) 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 phenylethyl, and halogenated hydrocarbons in which a hydrogen atom part thereof is substituted with a chlorine atom, a fluorine atom, and the like. The alkenyl group (vinyl group, allyl group, etc.) directly or indirectly bonded to the silicon atom is necessary for the addition reaction (hydrosilylation reaction) with hydrogen (Si — H) directly bonded to the silicon atom, and preferably has at least 2 in the molecule of the alkenyl polysiloxane.

In the present embodiment, since the hydrogenpolysiloxane represented by the general formula (1) has-H (hydrogen group) directly bonded to silicon atom and the alkenylpolysiloxane represented by the general formula (2) has carbon-carbon double bond, the addition reaction of the carbon-carbon double bond and-H (hydrogen group) is referred to as hydrosilylation reaction. The hydrogen polysiloxane represented by the general formula (1) can adjust the hardness and the cushioning property of the silicone composition 2 by adjusting the equivalent ratio of — H (hydrogen group) directly bonded to a silicon atom to the alkenyl group of the alkenyl polysiloxane represented by the general formula (2). The hydrosilylation reaction can be carried out by a known technique, and can be carried out using a catalyst such as chloroplatinic acid, a complex obtained from chloroplatinic acid and an alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, or a platinum-phosphorus complex. The amount of the catalyst used is usually 1ppm or more and 500ppm or less in terms of platinum atom relative to the alkenyl polysiloxane, and is preferably 3ppm or more and 250ppm or less in view of curability and physical properties of the cured product.

(insulating inorganic black pigment)

The insulating inorganic black pigment 3 is contained in the silicone composition 2 mainly for the purpose of imparting light-shielding properties to the impact absorbing material 1. That is, the impact absorbing material 1 obtains a desired light-shielding property by the insulating inorganic black pigment 3.

The insulating inorganic black pigment 3 has electrical insulation. In the present invention, the electrical insulation property refers to a function of being large in resistance value and hard to be energized. The resistivity of the insulating inorganic black pigment 3 is preferably set to 1X 10 ⁵ Omega cm or more and 1X 10 ¹⁹ The range of Ω · cm or less makes it easy to obtain the electrical insulation of the impact absorbing material 1. The resistivity of the insulating inorganic black pigment 3 is more preferably set to 1X 10 ¹¹ Omega cm or more and 1X 10 ¹⁹ The range of Ω · cm or less is more preferably 1 × 10 ¹⁵ Omega cm or more and 1X 10 ¹⁹ The range of not more than Ω · cm.

The insulating inorganic black pigment 3 contains an inorganic material. In the present invention, examples of the inorganic material include insulating metals, metal oxides, metal nitrides, ceramics, and the like. Specifically, the insulating inorganic black pigment 3 may use a simple substance or an alloy of a metal containing at least one element selected from titanium, iron, zinc, titanium oxide, titanium nitride, and aluminum oxide, an oxide, a nitride, and a ceramic. The insulating inorganic black pigment 3 containing an inorganic material is not easily discolored and has stable properties, and thus the light-shielding property of the impact absorbing material 1 is not easily lowered.

The insulating inorganic black pigment 3 is black. In the present invention, black means that in coordinates of a color code using CIE 1976L a b color space (measurement light source C: color temperature 6774K), 0. Ltoreq. L.ltoreq.14, 6. Ltoreq. A.ltoreq.8, 10. Ltoreq. B.ltoreq.5, most preferably L is 1.26, a is 6.9, and b is-8.12. The insulating inorganic black pigment 3 is, for example, jet black having a color code of #0d 0015. If the insulating inorganic black pigment 3 is black, the desired light-shielding property of the impact absorbing material 1 can be obtained. The insulating inorganic black pigment 3 is a particle. The insulating inorganic black pigment 3 is approximately spherical, but has various shapes. The average primary particle diameter of the insulating inorganic black pigment 3 is preferably in the range of 10nm to 300 nm. Thereby, the insulating inorganic black pigment 3 is easily uniformly dispersed in the organic silicon compound and the organic silicon composition 2. Here, uniform means that the composition of the impact absorbing material 1 per unit volume is substantially the same. The average primary particle diameter of the insulating inorganic black pigment 3 is more preferably in the range of 20nm to 150 nm.

In the present invention, the average primary particle size is determined by the following method. The particles of the pigment contained in the silicone composition 2 were observed at a magnification of 5000 times or more using a Transmission Electron Microscope (TEM), a Scanning Transmission Electron Microscope (STEM), or a Scanning Electron Microscope (SEM). Among a plurality of particles observed by TEM or STEM images or SEM, particles of the pigment that did not form aggregates were regarded as primary particles. The major axis of the primary particle is regarded as the primary particle diameter. The primary particle size was measured for one hundred primary particles. The arithmetic mean of the number references of the primary particle diameters was calculated as the average primary particle diameter.

The content of the insulating inorganic black pigment 3 in the impact absorbing material 1 is in the range of 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the silicone composition 2. If the content of the insulating inorganic black pigment 3 is within this range, the light-shielding property of the impact absorbing material 1 can be easily obtained without impairing the adhesion and stress relaxation properties of the silicone composition 2. The content of the insulating inorganic black pigment 3 is more preferably in the range of 7 parts by mass or more and 35 parts by mass or less, and still more preferably in the range of 10 parts by mass or more and 30 parts by mass or less, with respect to 100 parts by mass of the silicone composition 2.

In addition, in order to improve the dispersibility in the organosilicon compound and the organosilicon composition 2, the insulating inorganic black pigment 3 is preferably surface-treated with a silicone-based treating agent.

The insulating inorganic black pigment 3 may be titanium oxynitride (titanium oxynitride). The nitrogen content of the titanium oxynitride is high, and the titanium oxynitride is represented by the general formula TiO _x N _y The resin composition has a composition of x =0.05 or more and 0.50 or less, and y =0.6 or more and 1.0 or less. If the oxygen amount x is less than 0.05, the insulation property tends to be insufficient, and if it is more than 0.50, the light-shielding property tends to be lowered, which is not preferable. If the nitrogen amount y is less than 0.60, the light-shielding property tends to be low, and if it is more than 1.0, the insulation property tends to be insufficient, which is not preferable.

The impact absorbing material 1 may contain components such as heat dissipating fine particles, flame retardants, and thermal stabilizers, as long as the effects of the present invention are not impaired.

(Heat-dissipating particle)

The heat dissipating fine particles 4 are mainly included to impart heat dissipation to the impact absorbing material 1, and for example, inorganic materials such as aluminum hydroxide, magnesium oxide, anhydrous magnesium carbonate, alumina, silica, aluminum nitride, and boron nitride can be used.

Since the hardness and viscoelastic properties of the impact absorbing material 1 change by adding the heat dissipating fine particles 4, the particle diameter and content of the heat dissipating fine particles 4 may be appropriately set within a range in which desired light shielding properties and impact cushioning properties of the impact absorbing material 1 can be obtained.

(method for producing impact-absorbing Material)

The impact absorbing material 1 is manufactured as follows: the organic silicon compound and the insulating inorganic black pigment 3 are mixed and kneaded, and molded by a molding method such as an extrusion molding method, and then the organic silicon compound is dried, reacted and cured to form the organic silicon composition.

(physical Properties of impact absorbing Material)

The adhesive force of the impact absorbing material 1 to the glass plate is 2N/20mm or more. The adhesion was measured as follows. The adhesive strength was measured by a 90-degree peel test machine at a tensile speed of 300mm/min using the peel strength at 90-degree peel in the adhesive strength test according to JIS Z0237 "test methods for adhesive tapes and adhesive sheets" as the adhesive strength. As schematically shown in fig. 2, the test specimen for adhesion evaluation was prepared by bonding a glass plate 300 to one surface of the impact absorbing material 1, and then bonding a resin film (PET, embet, manufactured by Unitika) 301 to the other surface (back surface) via a primer (primer a, manufactured by shin-Etsu chemical industries). The above bonding conditions were set to 1 round trip using a 2kg roller, and then left at 23 ℃ for 24 hours. The glass plate 300 is a soda glass plate (made by Laoka glass Co., ltd.) having a thickness of 1 mm.

Since the impact absorbing material 1 has an adhesive force of 2N/20mm or more to a glass plate, it is easily attached to a glass plate constituting a display panel such as a liquid crystal panel or an organic EL panel, and is not easily detached because of adhesion (adhesion). From the viewpoint of workability such as re-attachment (reworking) of the display panel, the adhesion strength of the impact absorbing material 1 to the glass plate of the impact absorbing material 1 is preferably 6.5N/20mm or less, and more preferably 5N/20mm or less.

The transmittance of light having a wavelength of 300nm to 850nm of the impact absorbing material 1 is 0.6% or less. The transmittance was measured according to JIS K7136.

The lower the light transmittance of the impact absorbing material 1, the lower the transmittance is preferably 0%.

The penetration of the impact absorbing material 1 at 25 ℃ is 90 to 160 inclusive. 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. If the penetration of the impact absorbing material 1 is less than 90, the impact absorbing material 1 is too hard to bend or elongate and is difficult to cope with soft deformation. If the penetration of the impact absorbing material 1 is greater than 160, the impact absorbing material 1 is too soft, and the workability such as adhesion to other members is reduced. The penetration under the above conditions of the impact absorbing material 1 is preferably in the range of 100 to 135 inclusive, and more preferably in the range of 110 to 135 inclusive.

The impact absorption rate of the impact absorption material 1 is 20% or more. The impact absorption rate was measured as follows. The impact absorption rate was calculated by the following equation after measuring the impact acceleration at a swing angle of 18 degrees using a pendulum impact test apparatus PST-300 manufactured by SHINEI TESTING MACHINERY in accordance with JISC 60068-2-27.

Impact absorption rate (%) = (1- (impact acceleration of test piece with impact absorbing material)/(impact acceleration of PC board alone)) × 100

The test piece for measuring the impact acceleration was produced by bonding an impact absorbing material 1 to a polycarbonate plate (PC plate) 400 having a thickness of 1.0mm, and further bonding a metal cylinder 401 having a thickness of Φ 16mm (= diameter 16 mm) and a thickness of 4mm to the plate. This test piece is schematically shown in FIG. 3.

The impact absorption rate of the impact absorption material 1 is preferably 25% or more. The upper limit of the impact absorption rate of the impact absorption material 1 is 100% as it is higher, but the upper limit of the impact absorption rate of the impact absorption material 1 obtained in the present state is 85%.

(Filler)

The impact absorbing material 1 preferably contains the filler 5 made of a resin in an amount of 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the silicone composition 2. By containing the filler 5, the penetration of the impact absorbing material 1 becomes 90 or more, the softness becomes high, and the shape is maintained and the workability is not easily lowered. When the content of filler 5 is less than 0.5 parts by mass with respect to 100 parts by mass of silicone composition 2, the shape of impact absorbing material 1 is difficult to maintain, and when it exceeds 50 parts by mass, the light transmittance of impact absorbing material 1 tends to be high. The content of the filler 5 is preferably 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the silicone composition 2.

The filler 5 is preferably in the form of particles, and the long diameter is preferably 5 μm or more and 25 μm or less, and more preferably 10 μm or more and 20 μm or less. In the present invention, the "major axis" refers to the diameter of the longest portion of the cross section of the particulate filler 5.

For example, silicone-based fine particles or acrylic fine particles can be used as the filler 5. In this case, the filler 5 contains a silicone resin or an acrylic resin. The filler 5 may be formed of a resin. That is, filler 5 may be formed of only a resin, or may contain another inorganic material or the like in the resin.

(use of impact-absorbing Material)

The impact absorbing material 1 of the present embodiment is used by being attached to another member. In this case, since the impact absorbing material 1 has adhesiveness, the surface of the impact absorbing material 1 can be brought into contact with the surface of another member and attached. However, when the impact absorbing material 1 is to be firmly attached to another member, an adhesive or an adhesive may be used in combination.

The other member is a member which is easily broken when an impact is applied, and examples thereof include a display panel such as a liquid crystal panel and an organic EL panel. The impact absorbing material 1 is attached to the back surface (surface opposite to the side on which characters and images are displayed) of the display panel. Examples of the display panel include a flexible Organic Liquid Crystal Display (OLCD), an electronic Paper (E Paper), an organic EL display (OLED), a quantum dot display (QLED), and a micro LED display (μ LED).

The impact absorbing material 1 of the present embodiment can be suitably used for a display having flexibility such as a foldable terminal. A flexible display is provided with a sheet-like impact absorbing material on the back surface thereof, and if the impact absorbing material has a low impact property, the display may be broken by a collision at the time of falling. Manufacturers of smart phones and the like have studied making the structure of the display simpler and thinner in order to evolve the foldable function. Therefore, in such applications, the level of impact properties required of the impact absorbing material becomes higher. Among these, in the impact absorbing material using the silicone composition, in order to achieve further softening, improvement in the cohesive property of the blocks such as the filler and the pigment becomes a problem, but in the impact absorbing material 1 of the present embodiment, it is possible to suppress the deformation of the projections and depressions on the surface at the time of a drop impact, and to absorb the impact energy at the time of the drop, and it is possible to obtain an impact absorbing material having high impact absorbability. In addition, the shock absorbing material 1 of the present embodiment has a light shielding property so that the illuminance of the display does not leak from the rear surface, as in the conventional case.

The impact absorbing material 1 of the present embodiment has a thinner, more flexible structure than the conventional one, is lightweight, has a function of folding, and has a light-shielding property. Therefore, even when the optical display unit is attached to a display panel such as a liquid crystal panel or an organic EL panel, the optical display unit can be formed to have a large screen in use and to be small in size by being folded in transportation or the like.

For example, acrylic foams and the like that have been conventionally used as impact absorbing materials are foams and have closed cells, and thus it is difficult to impart light-shielding properties. Further, although an impact absorbing material using a conventional silicone composition may have light-shielding properties and impact properties, the impact absorbing material may have problems in shape maintenance and handling properties due to softening, and an upper limit is set to the penetration. That is, since further softening of the impact absorbing material is difficult, there is a limit to improvement of the impact absorbability. Therefore, in the present embodiment, for example, the penetration is increased (softened) by the balance of the blending amounts of the main agent and the curing agent of the silicone composition, and the impact absorbability is improved. In the impact absorbing material of the present embodiment, the filler having a major diameter of 5 to 25 μm is added to the silicone composition in an amount of 0.5 to 50 mass%, thereby suppressing excessive softening of the impact absorbing material.

Examples

(example 1)

As the silicone composition, a two-component addition reaction type silicone gel (model: X32-3443) manufactured by shin-Etsu chemical Co., ltd was used. The organosilicon compound which can be a raw material of the silicone composition contains a main agent (a) and a curing agent (B), and the smaller the blending ratio of the curing agent (B) to the main agent (a), the larger the penetration (i.e., the softer) of the obtained silicone composition.

As the insulating inorganic black pigment, product No. 13M-C manufactured by Mitsubishi materials corporation was used.

As the filler, product numbers AFX-8 (average particle size 8 μm), AFX-15 (average particle size 15 μm) and AFX-30 (average particle size 30 μm) manufactured by Hydrocarbon chemical Co., ltd were used. The resin contained in the filler is a crosslinked polyacrylate.

These materials were mixed and kneaded in the blending amounts shown in table 1, and then formed into a sheet by extrusion molding, and then dried and cured to form a silicone composition, thereby forming an impact absorbing material having a thickness of 200 μm.

(examples 2 to 8 and comparative examples 1 to 4)

As shown in table 1, in example 1, various impact absorbing materials having different physical properties were formed by changing the blending amount of the materials used.

(Properties)

The adhesive force to the glass plate, the transmittance of light having a wavelength of 300nm to 850nm, the penetration at 25 ℃ in accordance with JIS K2207, and the impact absorption were measured for each of the examples and comparative examples. The transmittance was measured using a spectrophotometer V-650 manufactured by japan spectrophotometer.

The impact absorbing material of the present invention was evaluated for workability in terms of ease of processing in examples and comparative examples from the viewpoint of processing such as cutting and lamination. The workability was evaluated by visually observing the appearance of the impact absorbing material when the impact absorbing material cut into 15cm × 15cm was laminated to a 20cm × 20cm glass plate as follows.

OK: the impact absorbing material is not broken even partially, and the end of the impact absorbing material is in a state of being bonded to the glass without being deformed by 1cm or more.

NG: the impact absorbing material is partially broken or the end of the impact absorbing material is deformed by 1cm or more and is bonded to the glass.

The storage stability at room temperature of the impact absorbing material of the present invention was determined as follows.

OK: after 6 months of storage at room temperature, the properties were almost unchanged from those before storage.

NG: after 6 months of storage at room temperature, there was a change in properties to such an extent that a problem occurred in use, as compared with before storage.

[ Table 1]

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7	Example 8	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4
													Film thickness (μm) of impact absorbing Material	200	200	200	200	200	80	200	200	200	200	200	80
Compounding amount (parts by mass) of Silicone composition	100	100	100	100	100	100	100	100	100	100	100	100
													(A) /(B) mixing ratio	54/46	56/44	54/46	56/44	58/42	54/46	55/47	56/44	51/49	56/44	58/42	54/46
Mixing amount (parts by mass) of black pigment	5	10	10	30	40	5	10	10	10	8	50	4
													Compounding amount of Filler (parts by mass)	20	7.5	40	20	20	20	45	2.5	20	0	20	20
Particle diameter (major axis) (μm) of filler	8	8	8	15	15	15	15	8	30		15	15
													Adhesion (N/20 mm)	6.5	6	5	4.5	2.5	3.5	2	6.5	4	8	2	3.5
Transmittance (%)	0.2	0.1	0.1	0.1	0.1	0.6	0.1	0.1	0.1	0.1	0.1	0.8
													Penetration degree	130	160	120	120	95	120	120	140	80	170	85	120
Impact absorption Rate (%)	32	31	34	33	30	21	29	25	23	29	24	19
													Operability of	OK	OK	OK	OK	OK	OK	OK	OK	OK	NG	OK	OK
Storage stability at ordinary temperature	OK	OK	OK	OK	OK	OK	OK	OK	OK	OK	OK	OK

Description of the reference numerals

1. Impact absorbing material

2. Silicone composition

3. Insulating inorganic black pigment

Claims

1. An impact absorber comprising an insulating inorganic black pigment in a silicone composition having adhesive properties and stress relaxation properties,

the adhesive force of the impact absorbing material to the glass plate is more than 2N/20mm,

the impact absorbing material has a light transmittance of 0.6% or less at a wavelength of 300nm to 850nm,

the impact absorbing material has a penetration at 25 ℃ of 90 to 160 in accordance with JIS K2207,

the impact absorption rate of the impact absorption material is 20% or more.

2. The impact absorbing material according to claim 1, wherein a filler containing a resin is contained in an amount of 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the silicone composition.

3. The impact absorbing material according to claim 2, wherein the filler has a major axis of 5 μm or more and 25 μm or less.

4. The impact absorbing material according to any one of claims 1 to 3, wherein the thickness is 80 μm or more and 500 μm or less.

5. The impact absorbing material according to any one of claims 1 to 4, wherein a content of the insulating inorganic black pigment is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the silicone composition.

6. The impact absorbing material according to any one of claims 1 to 5, which is used for light shielding and impact absorption of a display panel.