JP2015105993A - Protective sheet for liquid crystal screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective sheet whose impact resistance and scratch resistance are improved more than before.SOLUTION: A protective sheet includes a composite base material 4 formed by adhering two transparent sheet-like substrates 1, 2 having different hardness via an adhesive layer 3. A hard coat layer 5 is provided on the surface of the side of the base material (base material 2) having large hardness of the composite base material, and on the surface of the side of the base material (base material 1) having small hardness of the composite base material, a silicon adhesive layer 6 having a self-suction property is provided. Low reflective treatment, antifouling treatment and antibacterial treatment are applied to the hard coat layer 5.

Description

  The present invention relates to a protective sheet attached to a liquid crystal screen of a portable information terminal such as a smartphone or a tablet personal computer.

  The touch panel type liquid crystal display of the portable information terminal is always exposed to the outside. Therefore, if the portable information terminal is accidentally dropped on the ground or the floor, the liquid crystal screen may be damaged due to the impact. There is a problem that scratches can easily occur when rubbed by a pointed object.

  In addition, light incident from the periphery of the portable information terminal is reflected on the liquid crystal screen, making it difficult to see the screen, and fingerprints or finger oil on the liquid crystal screen and causing the screen to become dirty. Furthermore, recently, there has been a medical report that light in a wavelength range of 380 to 500 nm (so-called “blue light”) emitted from a liquid crystal backlight can have various adverse effects on the human eye. Long-term viewing has become a problem.

  For this reason, in the prior art, various protective sheets to be mounted on a liquid crystal screen have been proposed. By these protective sheets, the impact resistance, scratch resistance and optical performance (antireflection function, blue light, etc.) of the liquid crystal screen have been proposed. Cutting function, etc.) and antifouling property (fingerprint adhesion prevention function, etc.).

  As this type of protective sheet, for example, an inorganic layer deposited on one surface of a substrate and an optically active polymer layer (400 nm to 400 nm) formed by in-situ curing of the curable composition on the inorganic layer. And a protective sheet having a refractive index of about 1.53 or less over a wavelength range of 700 nm and a thickness of about 20 to 200 nm) and an adhesive layer deposited on the other surface of the substrate. (For example, refer to Patent Document 1).

  For example, it consists of a base material made of PET resin and a silicon layer having a thickness of 200 to 500 μm provided on one side surface of the base material. On the other side surface of the base material, antireflection treatment, low reflection gloss treatment, blue A protective sheet is known that has been subjected to any one surface treatment of light cut treatment, hard coat treatment, antibacterial treatment or a combination of at least two (see, for example, Patent Document 2).

  In these conventional protective sheets, the scratch resistance is mainly brought about by the hard coat layer provided on the entire surface of the substrate. However, the hard coat layer is merely a coating of the curable composition, and therefore, about 9H. According to a pencil with a sharp point, scratches that penetrate the protective sheet and reach the liquid crystal screen are relatively easily generated.

In these protective sheets, the impact resistance is mainly brought about by the relatively soft base material and the adhesive layer (silicon layer) absorbing the impact force (low repulsion against the impact force). It is.
However, the impact resistance is maximized by a good balance between the repulsion to the impact force and the absorption of the impact force. In view of this point, the impact resistance provided by the conventional protective sheet. Is not enough.

JP-T-2005-524113 Utility Model Registration No. 3183062

  Accordingly, an object of the present invention is to provide a protective sheet having improved impact resistance and scratch resistance than before.

  In order to solve the above problems, the present invention is a protective sheet for a liquid crystal screen, wherein a plurality of transparent sheet-like base materials having different hardnesses are laminated so that the hardnesses increase in order, and the base materials adjacent to each other A composite base material made by bonding the surfaces of the composite base material through an adhesive layer, a hard coat layer provided on the base material side surface having the largest hardness of the composite base material, and the hardness of the composite base material A self-adsorbing silicon adhesive layer or polyurethane adhesive layer provided on the surface of the smallest substrate, and the hard coat layer has a low reflection treatment, an antifouling treatment, an antibacterial treatment or a combination thereof. The protective sheet is characterized in that the above combination is applied and the silicon adhesive layer or the polyurethane adhesive layer is attached to the liquid crystal screen by adhering to the liquid crystal screen. It is intended.

  In the above-described configuration, 380 to 380 between the composite base material and the hard coat layer, or between the composite base material and the silicon adhesive layer or the polyurethane adhesive layer, or between adjacent base materials in the composite base material. A blue light cut layer that shields light in the wavelength range of 500 nm at a predetermined ratio can also be provided.

The said structure WHEREIN: It is preferable that the said several base material consists of a different kind of synthetic resin sheet, respectively.
Further, when the composite base material is composed of two types of base materials, a first base material and a second base material having a hardness higher than that of the first base material, the first base material is used. The material is preferably a PET sheet, a polycarbonate resin sheet, or a polyurethane resin sheet, and the second substrate is preferably an acrylic resin sheet. In this case, it is sufficient that the hardness of the second base material is larger than the hardness of the first base material. Therefore, the first base material is made of a PET sheet, and the second base material is made of a polycarbonate resin sheet. It may be.
The adhesive forming the adhesive layer is preferably an ultraviolet curable resin or a thermosetting resin.

According to the present invention, a composite base material comprising a plurality of base materials having different hardnesses bonded to each other so as to increase in hardness is provided, and the composite base material is generated from one side to the other side. By using the gradient of the hardness, the composite substrate exhibits high scratch resistance and resilience to impact force on the surface side, while the composite substrate surface has low impact force absorbability. Is expressed.
Further, a hard coat layer is provided on the surface side of the composite substrate having a high hardness, and a silicon adhesive layer or a urethane adhesive layer having self-adsorption is provided on the surface side of the composite substrate having a low hardness.

In this way, the scratch resistance is greatly improved by the cooperation of the hard coat layer and the surface of the composite substrate having the higher hardness, and the impact resistance is improved by the cooperation of the entire composite substrate and the silicon adhesive layer or the polyurethane adhesive layer. The characteristics are greatly improved.
In addition, the surface of the composite substrate with high hardness may crack when subjected to impact force exceeding the limit, but at that time, the substrate with low hardness of the composite substrate is less likely to crack, so it breaks. The broken pieces are held on a base material having a low hardness and are less likely to scatter outside.
Moreover, the said effect is acquired in the state which maintained the whole protective sheet to the fixed extent by reducing the number of base materials which comprise a composite base material as much as possible.

It is sectional drawing which showed typically the laminated structure of the protection sheet of the liquid crystal screen by this invention. It is the perspective view of the Example which adapted the protective sheet of the liquid crystal screen by this invention to the touchscreen type liquid crystal display of a smart phone.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view schematically showing a laminated structure of a liquid crystal screen according to an embodiment of the present invention.

Referring to FIG. 1A, in this embodiment, the protective sheet is composed of a composite base material 4 formed by adhering two transparent sheet-like base materials 1 and 2 having different hardnesses with an adhesive layer 3 interposed therebetween. I have.
Then, the hard coat layer 5 is provided on the surface of the base material (in this embodiment, the second base material 2) side with the higher hardness of the composite base material 4, and the hardness of the composite base material 4 is smaller. A silicon adhesive layer 6 having self-adsorption is provided on the surface of the base material (first base material 1 in this embodiment). In this case, a urethane adhesive layer may be provided instead of the silicon adhesive layer.

For example, a PET sheet, a polycarbonate resin sheet, or a polyurethane resin sheet can be used as the first substrate 1, and an acrylic resin sheet can be used as the second substrate 2, for example. In this case, a PET sheet can be used as the first base material 1 and a polycarbonate resin sheet can be used as the second base material 2.
As an adhesive for forming the adhesive layer 3, for example, an ultraviolet curable resin or a thermosetting resin can be used.

  The hard coat layer 5 is formed using, for example, a known curable resin composition containing a binder component made of a curable resin and inorganic fine particles or organic fine particles. As the binder component, for example, a thermosetting resin, an ultraviolet curable resin, or the like can be used. Examples of the inorganic fine particles include silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, calcium phosphate, and the like. As the organic fine particles, resin particles such as crosslinked polyacrylic acid particles, methyl methacrylate / styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethyl methacrylate particles, silicon resin particles, or polyimide particles can be used. .

In this embodiment, the composite base material is formed from two base materials having different hardnesses, but the composite base material may be composed of two or more base materials having different hardnesses.
That is, according to the present invention, the composite base material is formed by laminating a plurality of transparent sheet-like base materials having different hardnesses so that the hardnesses increase in order, and the surfaces of the base materials adjacent to each other are adhesive layers. It consists of what is glued through.
When the composite substrate is composed of three or more substrates, the hard coat layer is provided on the surface on the substrate side where the hardness of the composite substrate is the largest, and the silicon adhesive layer having self-adsorption is The composite base material is provided on the surface on the base material side having the smallest hardness.

Further, the hard coat layer 5 is subjected to low reflection treatment, antifouling treatment, antibacterial treatment, or a combination of two or more thereof.
The low reflection treatment, the antifouling treatment and the antibacterial treatment are performed using known techniques. The low reflection treatment is performed, for example, by performing fine embossing on the surface of the hard coat layer 5, and the antifouling treatment (providing a fingerprint adhesion preventing function, etc.) The antibacterial treatment is performed, for example, by mixing silver nanoparticles into the hard coat layer 5.

FIG. 2 is a perspective view of an embodiment in which the protective sheet according to the present invention is adapted to a touch panel type liquid crystal display of a smartphone.
As shown in FIG. 2, the protective sheet 10 is cut to a size that covers the liquid crystal display 12 of a portable information terminal to be worn such as the smartphone 11. In the illustrated embodiment, the size is cut to cover the entire front surface of the smartphone 11 including the liquid crystal display 12. In this case, the protective film 10 is provided with holes 10a and 10b corresponding to the camera 13 and the operation buttons 14 of the smartphone 11 as necessary.

  The protective sheet is attached to the liquid crystal screen when the silicon adhesive layer 6 is in close contact with the liquid crystal screen of the portable information terminal.

  Thus, the protective sheet of the present invention includes the composite base material 4 formed by bonding the two base materials 1 and 2 having different hardnesses to each other. On the substrate 2 side), scratch resistance and resilience to impact force are exhibited, while on the surface side where the composite substrate 4 has low hardness (first substrate 1 side), impact force absorbability is exhibited. It is supposed to let you.

Furthermore, the hard coat layer 5 is provided on the surface side (second substrate 2 side) where the hardness of the composite substrate 4 is large, and the surface side (first substrate 1 side) where the hardness of the composite substrate 4 is small. Is provided with a silicon adhesive layer 6 having self-adsorption.
Thus, the scratch resistance of the liquid crystal screen is greatly improved by the cooperation of the hard coat layer 5 and the surface of the composite substrate 4 having a high hardness, and at the same time, the cooperation of the entire composite substrate 4 and the silicon adhesive layer 6 is improved. The impact resistance of the LCD screen is greatly improved.
Further, the second base material 2 is made of an acrylic resin sheet or the like and is very hard. Therefore, the second base material 2 may be cracked when subjected to an impact force exceeding the limit. In this case, the first base material 1 is soft. It is less likely to break, whereby the fragments of the second substrate 2 are held on the first substrate 1 and less likely to scatter outside.

In addition, according to the protective sheet of the present invention, the hard coat layer 5 is subjected to low reflection treatment, antifouling treatment, antibacterial treatment, or a combination of two or more thereof. It is prevented that the screen is difficult to see due to reflection on the liquid crystal screen, fingerprints or finger oils are less likely to adhere to the liquid crystal screen, and bacteria are prevented from growing on the liquid crystal screen.
And since the composite base material 4 was comprised from two types of base materials, the 1st and 2nd base materials and 2, the protective sheet is maintained to a certain amount of thinness.

Next, a protective sheet having the same configuration as that shown in FIG. 1A was actually manufactured, and the impact resistance and scratch resistance of the protective sheet were tested.
The structure of the laminated structure of the manufactured protection sheet is as follows.
-1st base material of the composite base material 4: PET sheet | seat, thickness 188 micrometers
-Second base material of composite base material 4: acrylic resin sheet, thickness 200 μm
・ Adhesive layer: UV curable resin ・ Hard coat layer: 4μm thick
・ Silicon adhesive layer: thickness 35μm

A puncture impact test was performed using a 50 mm × 50 mm test piece obtained from the protective sheet (JIS K 7211-2).
The test was performed by dropping a striker having a diameter of 12.7 mm from a height of 1 m above the hard coat layer of the test piece.
As a result of the test, the drop strength of the protective sheet was 320 g / m.

Next, the scratch resistance of the produced protective sheet was tested by measuring the pencil hardness using a pencil hardness tester (JIS K 5600).
As a result of the test, the pencil hardness at a load of 500 g was 9H.

FIG. 1B is a view similar to FIG. 1A showing a laminated structure of protective sheets according to another embodiment of the present invention.
This example differs from the example shown in FIG. 1A only in the configuration of the composite substrate. Therefore, in FIG. 1B, the same components as those shown in FIG. 1A are denoted by the same reference numerals, and detailed description thereof will be omitted below.

In this embodiment, a blue light cut layer 7 is provided between the first substrate 1 and the adhesive layer 3 in the composite substrate 4 ′ to block light in the wavelength range of 380 to 500 nm at a predetermined ratio. .
The blue light cut layer 7 shields light by reflecting or absorbing a certain amount of light in a wavelength range of 380 to 500 nm, and is formed from a known composition.
In this embodiment, the blue light cut layer 7 is formed by dispersing a metal oxide such as titanium dioxide or zinc oxide in a liquid medium to prepare a coating composition, and laminating the composition by coating or the like. The Alternatively, the blue light layer 7 can be formed by using silicon oxide reacted with dimethylsiloxane as a coating composition and laminating it by coating or the like.

  In this embodiment, the blue light cut layer is arranged between the adjacent substrates of the composite substrate. Instead, the blue light cut layer is replaced with the composite substrate and the hard coat layer, or the composite substrate. It is good also as a structure arrange | positioned between a base material and a silicon adhesion layer.

  According to this embodiment, in addition to the effects obtained by the embodiment of FIG. 1A, a certain amount of blue light emitted from the rear surface of the liquid crystal and harmful to the human body can be shielded.

DESCRIPTION OF SYMBOLS 1 1st base material 2 2nd base material 3 Adhesive layer 4, 4 'Composite base material 5 Hard-coat layer 6 Silicon adhesion layer 7 Blue light cut layer 10 Protective sheet 10a, 10b Hole 11 Smart phone 12 Liquid crystal display 13 Camera 14 Operation buttons

Claims (6)

A protective sheet for an LCD screen,
A plurality of transparent sheet-like base materials having different hardnesses are laminated so that the hardness increases in order, and a composite base material made by adhering surfaces of adjacent base materials through an adhesive layer;
A hard coat layer provided on the substrate-side surface having the largest hardness of the composite substrate;
Provided with a self-adsorbing silicon adhesive layer or polyurethane adhesive layer provided on the surface of the base material side having the smallest hardness of the composite base material,
The hard coat layer is subjected to low reflection treatment, antifouling treatment, antibacterial treatment or a combination of two or more thereof.
The protective sheet, wherein the silicon adhesive layer or the polyurethane adhesive layer is attached to the liquid crystal screen by being in close contact with the liquid crystal screen   A wavelength range of 380 to 500 nm between the composite substrate and the hard coat layer, or between the composite substrate and the silicon adhesive layer or the polyurethane adhesive layer, or between adjacent substrates in the composite substrate. The protective sheet according to claim 1, wherein a blue light cut layer that shields the light at a predetermined ratio is provided.   The protective sheet according to claim 1, wherein the plurality of base materials are made of different types of synthetic resin sheets.   The protection according to claim 1 or 2, wherein the composite base material comprises a first base material and a second base material having a hardness higher than that of the first base material. Sheet.   The protective sheet according to claim 4, wherein the first substrate is a PET sheet, a polycarbonate resin sheet, or a polyurethane resin sheet.   The protective sheet according to claim 4 or 5, wherein the second base material is an acrylic resin sheet.

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