JP2018091993A - Protective cover for flat display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective cover for a flat display in which tempered glass is not easily broken even when strong impact is locally applied to the protective cover.SOLUTION: A protective cover protects a display part of a flat display and includes tempered glass and an adhesive layer for bonding the tempered glass to the display part. Between the tempered glass and the adhesive layer, provided is an impact absorbing layer, in which a first resin sheet, a first impact absorbing silicone layer, a second resin sheet, and a second impact absorbing silicone layer are laminated in order from the tempered glass.SELECTED DRAWING: Figure 1

Description

  The technology disclosed in the present specification relates to a protective cover for protecting a display unit of a flat display device such as a smartphone or a tablet PC.

  In recent years, flat display devices represented by, for example, smartphones and tablet PCs are rapidly spreading. Among them, portable flat display devices, for example, can be carried in a bag or pocket, placed carelessly on a desk, etc., or in close contact with the skin when the telephone function is used. Therefore, a protective cover is often used to prevent the display unit from being damaged or dirty during use.

  Such a protective cover has, for example, a structure in which an adhesive layer is provided on a hard plate material such as tempered glass or PMMA, which is excellent in properties such as transparency, mechanical strength, and antifouling property, and is attached to a display unit of a flat display device. Has been.

  In order to impart shock absorption, a configuration in which a urethane shock absorption layer is provided between a hard plate material and an adhesive layer has been proposed.

JP 2007-331996 A Utility Model Registration No. 3196581

  However, when an impact is applied to the protective cover such as inadvertently dropping the flat display device, the display portion can be protected, but the protective cover itself may be damaged. In particular, when tempered glass is used as a hard plate material, tempered glass is harder and more fragile than resin, so it is relatively easier to break than a resin-made one when a strong impact is applied locally. There is a problem. Even with a conventional protective cover provided with a shock absorbing layer made of urethane, it is still not sufficient to prevent damage to the protective cover.

  The technology disclosed in this specification has been conceived in view of the above circumstances. For example, in a protective cover made of tempered glass that protects a display unit of a flat display device such as a smartphone or a tablet PC, locally An object of the present invention is to provide a protective cover in which tempered glass is not easily damaged even when an impact is applied.

  The technology disclosed in the present specification is a protective cover for protecting a display unit of a flat display device, and includes a tempered glass and an adhesive layer to be attached to the display unit, and the tempered glass and the adhesive A shock absorbing layer in which a first resin sheet, a first shock absorbing silicone layer, a second resin sheet, and a second shock absorbing silicone layer are laminated in order from the tempered glass side is provided between the layers. ing.

  According to the above configuration, when a strong impact is applied to the tempered glass, for example, the impact is first transmitted from the tempered glass to the first resin sheet. Since the first resin sheet is made of resin, it is softer than tempered glass and harder than the adjacent first shock absorbing silicone layer. Therefore, the first resin sheet suppresses partial deformation of the tempered glass due to local impact, and disperses the impact within the sheet to a certain extent, while the impact is absorbed by the first impact absorbing silicone. Transmit to the layer side. That is, the first resin sheet can release an impact to the first shock absorbing silicone layer side while suppressing excessive deformation of the tempered glass.

  If it explains supplementarily, when the 1st resin sheet is not provided, the local impact which tempered glass received will be transmitted to the soft 1st shock absorption silicone layer as it is, and will be absorbed, 1 The shock-absorbing silicone layer is easily deformed with partial deformation of the tempered glass, so that the tempered glass is also easily deformed and easily damaged. However, when the first resin sheet is provided, as described above, the relatively hard first resin sheet suppresses the deformation of the tempered glass and disperses the received impact. Since it escapes to the absorption silicone layer side, the tempered glass is less likely to be broken than when the first resin sheet is not provided.

  Moreover, the shock absorbing layer of the present invention is provided with two shock absorbing silicone layers, and the second resin sheet is also provided between the two shock absorbing silicone layers. While suppressing excessive deformation by the first resin sheet, the first shock absorbing silicone layer, the second resin sheet, the second shock absorbing silicone layer, and the first and second resin sheets, and dispersing the received shock Attenuate step by step with the first and second shock absorbing silicone layers. That is, an excellent shock absorbing effect can be obtained while suppressing deformation as compared with a configuration in which only one shock absorbing silicone layer having the same thickness as the total thickness of the first and second shock absorbing silicone layers is provided. Can do.

  In addition, since the silicone used as a material of the shock absorbing layer has an appropriate hardness that suppresses breakage of the tempered glass, it is more suitable than a conventionally used urethane having a lower hardness.

  The protective cover may have the following configuration.

  The shock absorbing layer may have a configuration in which a base sheet, a pressure-sensitive adhesive layer, and a release sheet are laminated on a base sheet of a pressure-sensitive adhesive sheet that is laminated in order.

  According to such a configuration, for example, by using a general-purpose surface-protective pressure-sensitive adhesive sheet comprising a base sheet, a pressure-sensitive adhesive layer, and a release sheet, the pressure-sensitive adhesive layer can be easily provided on the protective cover. Manufacturing cost can be reduced.

  Moreover, the adhesion layer may be comprised with the silicone type adhesive. When a silicone-based adhesive is used, it is difficult for air bubbles to enter between the display part, and it can be repeatedly attached to and removed from the display part.

  According to the technology disclosed in this specification, it is possible to provide a protective cover for a flat display device in which the tempered glass is hardly damaged even when a strong impact is applied locally.

Schematic sectional view showing the configuration of the protective cover of one embodiment (Example 1) Schematic sectional view showing the structure of the protective cover of Comparative Example 1 Schematic sectional view showing the structure of the protective cover of Comparative Example 2 Schematic sectional view showing the structure of the protective cover of Comparative Example 3

  One embodiment is illustrated by FIG.

  For example, the protective cover 10 according to the present embodiment is mounted so as to cover a display unit of a flat display device such as a smartphone or a tablet PC, and protects the display unit. In the following description, the upper side of FIG.

  As shown in FIG. 1, the protective cover 10 of the present embodiment includes a tempered glass 11, an acrylic adhesive layer 12, a first resin sheet 14, a first shock absorbing silicone layer 15, a second resin sheet 16 in order from the upper layer side. The second shock absorbing silicone layer 17, the base material sheet 19, the silicone adhesive layer 20, and the release sheet 21 are formed in a flat plate shape. The protective cover 10 has a configuration in which a silicone-based adhesive layer 20 exposed by peeling the release sheet 21 is attached to the display unit of the flat display device, and the tempered glass 11 is disposed on the outer side opposite to the display unit. It is.

  The tempered glass 11 mentioned above is not specifically limited, A general purpose thing can be used. Specifically, Gorilla Glass (made by Corning Inc.), Dragontrail (made by Asahi Glass Co., Ltd.), etc. can be used. The thickness of the tempered glass is preferably 0.3 mm or less, and more preferably 0.2 mm or less. If it is thicker than 0.3 mm, the flexibility is lowered, and the impact resistance is lowered.

  The acrylic pressure-sensitive adhesive layer 12 is an optically transparent adhesive sheet (OCA: Optical Clear Adhesive) having adhesiveness, and the tempered glass 11 and the first resin sheet 14 are laminated. In the present embodiment, the acrylic adhesive layer 12 has a thickness of about 25 μm.

  As the first resin sheet 14 and the second resin sheet 16, a general-purpose resin sheet made of a transparent material such as polyethylene terephthalate (PET), polypropylene (PP), and polyvinyl chloride (PVC) can be used. Among these, although the thing made from PET is preferable, it is good also as a structure from which the kind of the 1st resin sheet 14 and the 2nd resin sheet 16 differs.

  Although the thickness of the 1st resin sheet 14 and the 2nd resin sheet 16 can be changed suitably, it is preferable that all are in the range of 25-50 micrometers. Moreover, the thickness of the 1st resin sheet 14 and the 2nd resin sheet 16 may be equal, and may differ. In the present embodiment, the thicknesses of the first resin sheet 14 and the second resin sheet 16 are both about 25 μm.

  The first shock absorbing silicone layer 15 and the second shock absorbing silicone layer 17 are formed of a shock absorbing silicone adhesive. The impact-absorbing silicone pressure-sensitive adhesive has excellent impact absorbability and is excellent in flexibility, high extensibility, heat resistance and the like. The impact-absorbing silicone layer of the present embodiment comprises an impact-absorbing silicone adhesive having a Young's modulus of less than 0.3 Mpa, a Poisson's ratio of 0.4 to 0.5, and a linear expansion coefficient of 200 to 300 ppm / ° C. I use it.

  Although the thickness of the 1st shock absorption silicone layer 15 and the 2nd shock absorption silicone layer 17 can be changed suitably, it is preferable that all are in the range of 25-75 micrometers. The thicknesses of the first shock absorbing silicone layer 15 and the second shock absorbing silicone layer 17 may be the same or different. In the present embodiment, the thicknesses of the first shock absorbing silicone layer 15 and the second shock absorbing silicone layer 17 are both about 50 μm.

  In the present embodiment, the laminated portion of the first resin sheet 14, the first shock absorbing silicone layer 15, the second resin sheet 16, and the second shock absorbing silicone layer 17 described above is the shock absorbing layer 13.

  In the present embodiment, among the above-described layers, three layers from the lower layer side, that is, a laminated portion of the release sheet 21, the silicone pressure-sensitive adhesive layer 20, and the base material sheet 19 is a general-purpose pressure-sensitive adhesive sheet 18 for surface protection. It is. The silicone-based adhesive layer 20 has adsorptivity and can be repeatedly attached to or removed from the display unit. The release sheet 21 and the base sheet 19 are made of PET. The thicknesses of the release sheet 21, the silicone pressure-sensitive adhesive layer 20, and the base sheet 19 are all about 50 μm.

<Evaluation method of impact absorption rate and cracking>
In the present embodiment, the impact absorption rate of the protective cover 10 is evaluated by the following method.

  The drop height of the iron ball is such that a load of 13 kN, 15 kN, 17 kN, 19 kN, 21 kN, and 25 kN is applied when an iron ball with a weight of 0.2 kgf and a diameter of 34 mm is dropped freely on a load cell without a sample. Is set, and an iron ball is dropped from the set height, and an average value F1 of measured values measured ten times is calculated. Thereafter, the silicone adhesive layer 20 of the sample with the release sheet 21 peeled off is attached to the mounting surface of the load cell, and the iron ball is dropped from the same height with respect to the sample with the tempered glass 11 positioned above. The average value F2 of the measured values measured five times is calculated. The number represented by the following formula (1) is defined as the impact absorption rate.

Impact absorption rate = (1-F2 / F1) × 100 (%)
Moreover, it is confirmed visually whether the tempered glass is broken when the iron ball is dropped.

<Example>
EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not restrict | limited to a following example, unless the summary is exceeded.

  A sample for comparing the impact absorption rate and crack evaluation between the protective cover 10 of the present embodiment and the protective covers 30, 40, 50 having a configuration different from that of the present embodiment was produced as follows.

Example 1
The protective cover 10 having the configuration shown in FIG. 1 was produced. Specifically, a 0.2 mm tempered glass 11 (Dragontrail (manufactured by Asahi Glass Co., Ltd.)), a 25 μm acrylic adhesive layer 12 and a shock absorbing layer 13, a 25 μm PET first resin sheet 14, 50 μm First shock absorbing silicone layer 15 (consisting of a silicone adhesive having a Young's modulus of less than 0.3 Mpa, a Poisson's ratio of 0.4 to 0.5, and a linear expansion coefficient of 200 to 300 ppm / ° C.), 25 μm Second resin sheet 16 made of PET, second shock absorbing silicone layer 17 of 50 μm (made of the same material as first shock absorbing silicone layer 15), and general-purpose adhesive sheet 18, 50 μm substrate sheet 19, 50 μm The protective cover 10 in which the silicone pressure-sensitive adhesive layer 20 and the 50 μm release sheet 21 were sequentially laminated was prepared.

(Comparative Example 1)
A protective cover 30 having the structure shown in FIG. 2 is used as the shock absorbing layer 33 having the single layer structure, which is the shock absorbing layer 13 having the two layer structure of the resin sheets 14 and 16 and the shock absorbing silicone layers 15 and 17 of the first embodiment. Was made. Specifically, 0.2 mm tempered glass 11 (Dragontrail (manufactured by Asahi Glass Co., Ltd.)), 25 μm acrylic adhesive layer 12 and shock absorbing layer 33, 25 μm PET resin sheet 34, 50 μm shock absorbing. Silicone layer 35 (consisting of a silicone adhesive having a Young's modulus of less than 0.3 Mpa, a Poisson's ratio of 0.4 to 0.5, and a linear expansion coefficient of 200 to 300 ppm / ° C.), and a general-purpose adhesive sheet 18 A protective cover 30 was prepared in which a 50 μm base material sheet 19, a 50 μm silicone adhesive layer 20, and a 50 μm release sheet 21 were sequentially laminated.

(Comparative Example 2)
In place of the shock absorbing silicone layers 15 and 17 used in Example 1, an acrylic optical transparent adhesive sheet (OCA: Optically Clear Adhesiv) made of the same material as the acrylic adhesive layer 12 described above is used, as shown in FIG. The protective cover 40 having the configuration was produced. Specifically, 0.2 mm tempered glass 11 (Dragontrail (manufactured by Asahi Glass Co., Ltd.)), 25 μm acrylic adhesive layer 12, shock absorbing layer 43, 25 μm PET first resin sheet 44, 50 μm The first acrylic pressure-sensitive adhesive layer 45, the 25 μm second resin sheet 46 made of PET, the 50 μm second acrylic pressure-sensitive adhesive layer 47, and the general-purpose pressure-sensitive adhesive sheet 18, the 50 μm base material sheet 19, the 50 μm silicone-based pressure sensitive adhesive A protective cover 40 in which the layer 20 and the 50 μm release sheet 21 were sequentially laminated was produced.
The acrylic adhesive layer is made of an acrylic adhesive.

(Comparative Example 3)
A protective cover 50 having the structure shown in FIG. 4 was prepared, in which no shock absorbing layer was provided. Specifically, 0.2 mm tempered glass 11 (Dragontrail (manufactured by Asahi Glass Co., Ltd.)), 25 μm acrylic adhesive layer 12, general-purpose adhesive sheet 18, 50 μm substrate sheet 19, 50 μm silicone adhesive A protective cover 50 in which the layer 20 and the 50 μm release sheet 21 were sequentially laminated was produced.

  For Example 1 and Comparative Examples 1 to 3, the impact absorption rate and cracking were evaluated based on the evaluation method described above. The experimental results are shown in Table 1. In addition, regarding the evaluation of a crack, the thing which was not cracked is represented by (circle) and the thing which cracked is represented by x.

  As can be seen from Table 1, the sample of Example 1 in which two shock absorbing silicone layers were provided had the highest shock absorption rate, and no cracking occurred in the glass up to 13-21 kN.

  On the other hand, in the comparative example 1 which made the impact-absorbing layer 1 layer structure, the impact absorption rate fell 2% from Example 1, and the crack generate | occur | produced at 19 kN or more. Further, in Comparative Example 2 in which an acrylic adhesive layer was provided instead of the impact-absorbing silicone layer, although an impact absorption rate equivalent to that in Example 1 was obtained, cracking occurred at 15 kN or more. Furthermore, in Comparative Example 3 having a conventional configuration in which no shock absorbing layer was provided, the shock absorption rate was the lowest at 73%, and cracking occurred at 15 kN or more as in Comparative Example 2.

  From this result, although it cannot be said that there is a correlation between the impact absorption rate and the occurrence of cracks, it was confirmed that the sample of Example 1 was excellent in both the impact absorption rate and cracking.

  Next, about the protective cover 10 of this embodiment shown in FIG. 1, the impact absorption rate and the crack were evaluated by changing the kind and thickness of the tempered glass 11.

(Example 2)
As tempered glass 11, Gorilla Glass (made by Corning Inc.) with a thickness of 95 μm was used. The other configurations were the same as those in Example 1.

(Example 3)
As the tempered glass 11, Gorilla Glass having a thickness of 150 μm was used. The other configurations were the same as those in Example 1.

Example 4
As the tempered glass 11, a Dragontrail (manufactured by Asahi Glass Co., Ltd.) having a thickness of 150 μm was used. The other configurations were the same as those in Example 1.

(Example 5)
As the tempered glass 11, Dragontrail X (made by Asahi Glass Co., Ltd.) having a thickness of 200 μm was used. The other configurations were the same as those in Example 1.

(Example 6)
As the tempered glass 11, Dragontrail X (two-stage tempered) having a thickness of 200 μm was used. The other configurations were the same as those in Example 1.

(Example 7)
As the tempered glass 11, Gorilla Glass having a thickness of 300 μm was used. The other configurations were the same as those in Example 1.

  Note that the two-stage tempering in Example 6 is a tempered glass obtained by performing ion exchange treatment of glass in two stages.

  About the sample of the said Example 1 and Example 2 thru | or Example 7, the iron ball was dropped so that the load of 15 kN might be applied by the method similar to the experimental method mentioned above, and the broken state of glass was confirmed visually. The experimental results are shown in Table 2. In addition, regarding evaluation of a crack, (circle) in a table | surface represents having not cracked.

  As can be seen from Table 2, in the samples of Examples 1 to 7 having the configuration of the present embodiment, no cracks occur at a load of 15 kN, regardless of the type and thickness of tempered glass. It could be confirmed.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) The thickness of each layer of the shock absorbing layer 13 is not limited to the above embodiment, and can be appropriately changed. For example, the thicknesses of the first resin sheet 14 and the second resin sheet 16 or the first shock absorbing silicone layer 15 and the second shock absorbing silicone layer 17 may not be the same.

  (2) The first and second resin sheets 14 and 16 are not limited to those made of PET, and other types of resin sheets may be used. Further, the first resin sheet 14 and the second resin sheet 16 may be different types of resin sheets.

  (3) In the above embodiment, the general-purpose pressure-sensitive adhesive sheet 18 is used to form the silicone-based pressure-sensitive adhesive layer 20, but it is not always necessary to use it.

  (4) Although the tempered glass 11 and the shock absorbing layer 13 are laminated by the acrylic adhesive layer 12 in the above embodiment, other types of adhesive layers can be used.

10: protective cover 11: tempered glass 12: acrylic adhesive layer 13: shock absorbing layer 14: first resin sheet 15: first shock absorbing silicone layer 16: second resin sheet 17: second shock absorbing silicone layer 18: general purpose Adhesive sheet 19: base material sheet 20: silicone-based adhesive layer 21: release sheet

Claims (3)

A protective cover for protecting the display unit of the flat display device,
Tempered glass, and an adhesive layer for attaching to the display unit,
Between the tempered glass and the adhesive layer, a first resin sheet, a first shock-absorbing silicone layer, a second resin sheet, and a second shock-absorbing silicone layer are laminated in order from the tempered glass side. A protective cover for a flat display device, provided with a shock absorbing layer. The protective cover for a flat display device according to claim 1, wherein the impact absorbing layer is laminated on the base material sheet of a pressure sensitive adhesive sheet in which a base material sheet, the adhesive layer, and a release sheet are laminated in order. . The protective cover of the flat display device according to claim 1, wherein the adhesive layer is made of a silicone-based adhesive.

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