Display device

Abstract

The present invention pertains to a display device (10) comprising: a display panel (14); a frame (18) that includes sections that are disposed outside the display panel (14); a cover glass (12) that has a first primary face (12A) and a second primary face (12B) and that is provided above the display panel (14) and the frame (18) so that the second primary face (12B) is on the display panel (14) side and the frame (18) side; and a first adhesive layer (20) that is disposed between the second primary face (12B) of the cover glass (12) and the frame (18) and that adheres the second primary face (12B) of the cover glass (12) and the frame (18). The first adhesive layer (20) has an elastic modulus of 5MPa to 400MPa.

Description

[Technical Field]

[0001] The present invention relates to a display device. [Background technology]

[0002] Liquid crystal displays and organic EL (Electro Luminescence) displays are often used in vehicle-mounted display devices that display information necessary while driving. These displays are sometimes equipped with a cover glass to protect the front surface. For example, Patent Document 1 describes a vehicle interior system in which a glass substrate is fixed with a highly elastic adhesive to improve the crack resistance of the glass substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japan Special Publication No. 2021-518296 Summary of the Invention [Problem to be solved by the invention]

[0004] However, cover glass tends to have low resistance to cracking at its edges due to latent scratches and other reasons. Therefore, even if the cover glass is broken from the edge, it is required to prevent the glass fragments generated when the cover glass is broken from floating up. Furthermore, when the cover glass is attached to a display device, it is also required to prevent uneven display on the display.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a display device that can suppress display unevenness while suppressing glass fragments from floating up when the display is broken. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the display device of the present disclosure comprises a display panel, a frame including a portion provided on the outside of the display panel, a cover glass having a first main surface and a second main surface and provided on the display panel and the frame so that the second main surface faces the display panel and the frame, and a first adhesive layer provided between the second main surface of the cover glass and the frame and bonding the second main surface of the cover glass to the frame, wherein the first adhesive layer has an elastic modulus of 5 MPa or more and 400 MPa or less in an indentation elastic modulus test. [Effects of the Invention]

[0007] According to the display device of the present invention, uneven display on the display can be suppressed while suppressing floating of glass fragments when the display device is broken. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a state in which a display device according to this embodiment is provided in a vehicle. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a part of one aspect of the display device according to this embodiment. [Figure 3] FIG. 3 is a schematic top view showing one aspect of the cover glass, the first adhesive layer, and the second adhesive layer in the display device according to this embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a part of one aspect of the display device according to this embodiment. [Figure 5] FIG. 5 is a schematic diagram for explaining the head impact test. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes configurations that are made by combining the respective embodiments. Furthermore, numerical values ​​include the range of rounding.

[0010] (display device) Fig. 1 is a schematic diagram showing a state in which a display device according to this embodiment is installed in a vehicle. As shown in Fig. 1, the display device 10 according to this embodiment is preferably installed in a vehicle, and is installed, for example, in front of a steering shaft 1 inside the vehicle. However, the configuration in Fig. 1 is only an example, and the display device 10 may have any configuration and may be installed in any position, and may be used for any purpose, not limited to vehicle use.

[0011] 2 is a schematic cross-sectional view showing a part of the display device, taken along a line passing through the center of the top view of FIG. 3 and perpendicular to the long side. As shown in FIG. 2, the thickness direction of the display device 10, i.e., the stacking direction, is defined as the Z direction, one direction perpendicular to the Z direction, i.e., the left-right direction in the example of FIG. 2, is defined as the X direction, and a direction perpendicular to the Z direction and the X direction, i.e., the direction perpendicular to the paper surface in the example of FIG. 2, is defined as the Y direction. Furthermore, one direction along the X direction, which in the example of Fig. 2 is the right direction, is referred to as direction X1, and the other direction along the X direction, which in the example of Fig. 2 is the left direction, is referred to as direction X2. Similarly, one direction along the Y direction, which in the example of Fig. 2 is the direction toward the back of the paper, is referred to as direction Y1, and the other direction along the Y direction, which in the example of Fig. 2 is the direction toward the front of the paper, is referred to as direction Y2. Furthermore, one direction along the Z direction, which is the direction from the display surface of the display device 10 toward the back, is referred to as direction Z1, and the other direction along the Z direction, which is the direction from the back of the display device 10 toward the display surface, is referred to as direction Z2.

[0012] As shown in FIG. 2, the display device 10 includes a cover glass 12, a display panel 14, a backlight unit 16, a frame 18, and a housing 19. The display device 10 is arranged in a stacked configuration, facing the Z1 direction, with the cover glass 12, display panel 14, and backlight unit 16 aligned in this order. The frame 18 is provided to surround the periphery of the display panel 14. When viewed from the Z direction, the frame 18 is a component provided on the outer side of the display panel 14. In other words, the frame 18 is located radially outward from the display panel 14, i.e., on the X1 side in the example of FIG. 2. The radial direction here refers to the radial direction when the direction along the central axis AX of the cover glass 12 is defined as the axial direction. The radially inward direction is the direction approaching the central axis AX as viewed from the Z direction, and the radially outward direction is the direction away from the central axis AX as viewed from the Z direction. The same applies hereinafter unless otherwise specified. The central axis AX is an axis along the Z direction that passes through the center position of the cover glass 12 as viewed from the Z direction. The central axis AX can also be referred to as an axis that passes through the center in the top view and is parallel to the Z direction. For example, the center of gravity in the top view is used as the center, and if the center of gravity is located outside the cover glass 12, a method is used in which coordinate data of the outline of the cover glass 12 is obtained and the coordinate center is determined. A first adhesive layer 20 is provided between the cover glass 12 and the frame 18 in the Z direction, and the cover glass 12 and the frame 18 are bonded and fixed to each other by the first adhesive layer 20. A second adhesive layer 22 is preferably provided between the cover glass 12 and the display panel 14 in the Z direction, and the cover glass 12 and the display panel 14 are preferably bonded and fixed to each other by the second adhesive layer 22. The housing 19 is a case that houses the cover glass 12, the display panel 14, the backlight unit 16, the frame 18, the first adhesive layer 20, and the second adhesive layer 22. The housing 19 is not an essential component.

[0013] (cover glass) The cover glass 12 is a transparent plate-like member that transmits visible light. The cover glass 12 has a first main surface 12A that faces the Z2 direction, i.e., the display surface side, a second main surface 12B that faces the Z1 direction, i.e., the back surface side, and an end surface 12C that connects the first main surface 12A and the second main surface 12B. The end surface 12C is the radially outer end surface of the cover glass 12 and can also be considered a side surface of the cover glass 12.

[0014] The thickness D0 of the cover glass 12 is preferably 0.3 mm or more and 2.5 mm or less. The lower limit of the thickness D0 is preferably 0.3 mm or more, more preferably 0.4 mm or more, and even more preferably 0.6 mm or more. The upper limit of the thickness D0 of the cover glass 12 is preferably 2.5 mm or less, more preferably 2.0 mm or less, and even more preferably 1.3 mm or less. That is, when the lower limit of the thickness D0 is set to the above value, the rigidity of the cover glass 12 can be ensured and cracking can be suppressed, and when the upper limit of the thickness D0 is set to the above value, peeling of the cover glass 12 from the frame 18 can be easily suppressed. In particular, in the case of a cold-formed product described below, a thickness D0 of 1.3 mm or less is preferable because it can be easily bent. The thickness D0 is the length in the Z direction from the first main surface 12A to the second main surface 12B.

[0015] In this embodiment, the cover glass 12 has a flat, rectangular shape when viewed from the Z direction. For example, when the cover glass 12 is rectangular, the size of the cover glass 12 may be such that the length in the longitudinal direction, i.e., in this embodiment, the X direction, is 100 mm to 800 mm, and the length in the lateral direction, i.e., in this embodiment, the Y direction, is 40 mm to 300 mm. However, the cover glass 12 is not limited to a flat, rectangular shape when viewed from the Z direction, and may have any shape, such as an elliptical shape when viewed from the Z direction, or a curved shape. The size of the cover glass 12 may also be arbitrary. When the cover glass 12 has a curved shape, the Z direction may be the thickness direction of the cover glass 12 at the center position of the main surface of the cover glass 12. In other words, the direction perpendicular to the main surface of the cover glass 12 at the center position of the main surface may be the Z direction. The method for forming the curved shape is not particularly limited, and may be, for example, a hot forming method or a cold forming method. Cold forming refers to a method of bending glass into a desired shape without raising the temperature of the glass to its softening point. In the cold forming method, the cover glass 12 is formed by bending a flat glass plate by cold forming and attaching it to the frame 18. In the cold forming method, a relatively thin glass is preferably used, which is prone to fragments being generated upon impact. However, by using the cover glass 12 of this embodiment, floating fragments can be significantly suppressed.

[0016] The Young's modulus of the cover glass 12 is preferably 60 GPa or more, more preferably 70 GPa or more. The Young's modulus of the cover glass 12 is preferably 90 GPa or less, more preferably 80 GPa or less, and even more preferably 75 GPa or less. That is, the Young's modulus of the cover glass 12 is preferably 60 GPa or more and 90 GPa or less, more preferably 70 GPa or more and 80 GPa or less, and even more preferably 70 GPa or more and 75 GPa or less. Having the Young's modulus within this range can suppress cracking. The Young's modulus of each member, including the cover glass 12, may be determined by a tensile test in accordance with JIS K7161 (2014).

[0017] The cover glass 12 is made of glass. The cover glass 12 is preferably tempered glass, and the tempered glass is preferably chemically tempered glass. When the cover glass 12 is chemically strengthened glass, the thickness (DOL) of the compressive stress layer of the cover glass 12 is, for example, preferably 10 μm or more, more preferably 15 μm or more, even more preferably 25 μm or more, and even more preferably 30 μm or more. The thickness (DOL) of the compressive stress layer is, for example, preferably 180 μm or less, more preferably 50 μm or less. The depth (DOL) of the compressive stress layer of at least one of the first main surface 12A and the second main surface 12B of the cover glass 12 is preferably within the above range, and more preferably both are within the above range. The surface compressive stress (CS) of the compressive stress layer is preferably 500 MPa or more, more preferably 650 MPa or more, and even more preferably 750 MPa or more. There is no particular upper limit, but for example, CS is preferably 1200 MPa or less. The surface compressive stress of at least one of the first main surface 12A and the second main surface 12B of the cover glass 12 is preferably within the above range, and more preferably both are within the above range. By keeping the DOL and CS within this range, cracking can be suppressed. A typical method for obtaining chemically strengthened glass by chemically strengthening glass is to immerse the glass in molten KNO, perform an ion exchange treatment, and then cool it to near room temperature. The treatment conditions, such as the temperature of the molten KNO and the immersion time, can be set so that the surface compressive stress and the thickness of the compressive stress layer reach the desired values. Examples of glass types include soda lime glass, aluminosilicate glass (SiO2-Al2O3-Na2O-based glass), etc. Among these, aluminosilicate glass is preferred from the viewpoint of strength. Examples of glass materials include glass materials containing, in mole percent based on oxides, 50% to 80% SiO2, 1% to 20% Al2O3, 6% to 20% Na2O, 0% to 11% K2O, 0% to 15% MgO, 0% to 6% CaO, and 0% to 5% ZrO2. Chemically strengthened glass based on aluminosilicate glass is also preferably used, for example, "Dragon Trail (registered trademark)" manufactured by AGC.

[0018] More specifically, the following glass compositions are preferred for the glass used for the cover glass 12. For example, "containing 0 to 25% MgO" means that MgO is not essential but may be contained in an amount of up to 25%. The following glass (i) is included in soda-lime silicate glass, the following glasses (ii) and (iii) are included in aluminosilicate glass, and the following glasses (iv) to (vi) are included in lithium aluminosilicate glass. (i) A glass having a composition expressed in mole percent on an oxide basis of 63 to 73% SiO2, 0.1 to 5.2% Al2O3, 10 to 16% Na2O, 0 to 1.5% K2O, 0 to 5.0% Li2O, 5 to 18% MgO, and 1 to 10% CaO. (ii) A glass having a composition expressed in mole percent on an oxide basis of 50 to 74% SiO2, 5 to 15% Al2O3, 10 to 20% Na2O, 0 to 8% K2O, 0 to 5.0% Li2O, 2 to 15% MgO, 0 to 6% CaO, and 0 to 5% ZrO2, with the total content of SiO2 and Al2O3 being 65 to 85%, the total content of Na2O and K2O being 12 to 25%, and the total content of MgO and CaO being 1 to 15%. (iii) A glass having a composition expressed in mole percent on an oxide basis of 68 to 80% SiO2, 4 to 10% Al2O3, 5 to 15% Na2O, 0 to 1% K2O, 0 to 5.0% Li2O, 4 to 15% MgO, and 0 to 1% ZrO2. (iv) A glass having a composition expressed in mole percent on an oxide basis of 67 to 75% SiO2, 0 to 4% Al2O3, 7 to 15% Na2O, 1 to 9% K2O, 0 to 5.0% Li2O, 6 to 14% MgO, and 0 to 1.5% ZrO2, with the total content of SiO2 and Al2O3 being 71 to 75%, the total content of Na2O and K2O being 12 to 20%, and if CaO is contained, its content is less than 1%. (v) Glass having a composition expressed in mole percent on an oxide basis of 50 to 73% SiO2, 5 to 20% Al2O3, 0 to 6% B2O3, 0 to 10% P2O5, 4 to 12% Li2O, 3 to 20% Na2O, 0 to 5% K2O, 0 to 8% MgO, 0 to 2% CaO, 0 to 5% SrO, 0 to 5% BaO, 0 to 5% ZnO, 0 to 2% TiO2, and 0 to 4% ZrO2. (vi) Glass having a composition expressed in mole percent on an oxide basis of 58 to 80% SiO2, 13 to 18% Al2O3, 0 to 5% B2O3, 0.5 to 4% P2O5, 3 to 10% Li2O, 5 to 20% Na2O, 0 to 2% K2O, 0 to 11% MgO, 0 to 20% CaO, 0 to 20% SrO, 0 to 15% BaO, 0 to 10% ZnO, 0 to 1% TiO2, and 0 to 2% ZrO2.

[0019] The tensile stress of the cover glass 12 is preferably 5 MPa or more, more preferably 5 MPa to 100 MPa, even more preferably 8 MPa to 80 MPa or 5 MPa to 70 MPa, and even more preferably 8 MPa to 70 MPa. By keeping the tensile stress within this range, cracking can be suppressed. Note that the tensile stress of the cover glass 12 refers to the internal tensile stress CT of the cover glass 12.

[0020] (Display panel) The display panel 14 is a panel that displays images, and is disposed on the Z1 direction side of the cover glass 12 so as to overlap the cover glass 12. The display surface of the display panel 14, which is the surface on the Z2 direction side, may be adhered to the second main surface 12B of the cover glass 12 by a second adhesive layer 22.

[0021] The display panel 14 may be a liquid crystal panel, an organic EL panel, a flexible organic EL panel, a PDP (plasma display), an electronic ink panel, or the like, and may also have a touch panel, etc. When the display panel 14 has a glass substrate, the glass substrate is the thickest and determines the rigidity of the entire display panel. Therefore, the Young's modulus of the glass substrate may be considered to be the Young's modulus of the display panel 14. The Young's modulus of the display panel 14 is preferably 2 GPa or more, more preferably 60 GPa or more, and even more preferably 70 GPa or more. The Young's modulus of the display panel 14 is preferably 90 GPa or less, and more preferably 75 GPa or less. That is, the Young's modulus of the display panel 14 is preferably 20 GPa or more and 90 GPa or less, more preferably 60 GPa or more and 75 GPa or less, and even more preferably 70 GPa or more and 75 GPa or less.

[0022] The thickness of the display panel 14 is preferably 0.05 mm or more, more preferably 1.0 mm or more, and even more preferably 1.1 mm or more. The thickness of the display panel is preferably 2.0 mm or less, and more preferably 1.3 mm or less. That is, the thickness of the display panel 14 is preferably 0.05 mm or more and 2.0 mm or less, more preferably 1.0 mm or more and 1.3 mm or less, and even more preferably 1.1 mm or more and 1.3 mm or less. The thickness of the display panel 14 is the length in the Z direction from the main surface of the display panel 14 on the Z1 direction side to the main surface of the display panel 14 on the Z2 direction side.

[0023] (backlight unit) The backlight unit 16 is a light source that irradiates the display panel with light for displaying an image, and is disposed on the Z1 side of the display panel so as to overlap the display panel .

[0024] The backlight unit 16 is generally composed of components such as a lens sheet, a diffusion sheet, a light guide plate, lamps, and a reflector. Of these components, the light guide plate is usually the thickest, and it determines the rigidity of the entire backlight unit 16. For this reason, the Young's modulus of the light guide plate can be considered to be the Young's modulus of the backlight unit 16. The Young's modulus of the backlight unit 16 is preferably 1 GPa or more and 5 GPa or less, and more preferably 2 GPa or more and 5 GPa or less.

[0025] The thickness of the backlight unit 16 is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 3 mm or more. The thickness of the backlight unit 16 is preferably 10 mm or less, more preferably 6 mm or less, and even more preferably 5 mm or less. That is, the thickness of the backlight unit 16 is preferably 1 mm or more and 10 mm or less, more preferably 2 mm or more and 6 mm or less, and even more preferably 3 mm or more and 5 mm or less. The thickness of the backlight unit 16 is the length in the Z direction from the main surface of the backlight unit 16 on the Z1 direction side to the main surface on the Z2 direction side.

[0026] The display device 10 does not necessarily need to be provided with a backlight unit 16. When the backlight unit 16 is not provided, a self-luminous display panel that does not require the backlight unit 16, such as an organic EL panel or a micro LED panel, is selected as the display panel 14.

[0027] (frame) The frame 18 is a member that includes a portion that is provided on the outer side of the display panel 14 when viewed from the Z direction. That is, the frame 18 is a member that has at least a portion that is provided on the outer side of the display panel 14 when viewed from the Z direction. The frame 18 preferably has a Young's modulus of 1.5 GPa or more and 250 GPa or less, more preferably 10 GPa or more and 230 GPa or less, and even more preferably 60 GPa or more and 230 GPa or less.

[0028] The material of the frame 18 is arbitrary, but is preferably a metal or alloy containing a metal element such as aluminum or magnesium. The material of the frame 18 may also be a resin or a laminate of a resin layer and a metal layer.

[0029] 2, the frame 18 includes a bottom member 18A and a side wall member 18B, with the bottom member 18A being provided on the Z1 direction side of the display panel 14, and the side wall member 18B being provided radially outward from the display panel 14. That is, in the example of FIG. 2, the side wall member 18B includes a portion that is provided on the outer side of the display panel 14 when viewed from the Z direction. 2, the bottom member 18A has a plate-shaped bottom portion 18A1 and a frame-shaped frame portion 18A2 that protrudes from the periphery of the bottom portion 18A1 toward the Z2 side. The bottom member 18A houses the backlight unit 16 by disposing the backlight unit 16 in the space formed by the bottom portion 18A1 and the frame portion 18A2. In the example of FIG. 2, the sidewall member 18B is a frame-shaped member that surrounds the periphery of the display panel 14 and is supported by the frame portion 18A2 at a position 18B3 between positions 18B1 and 18B2. Note that the position 18B1 is located radially inward of the sidewall member 18B, i.e., on the X2 side in the example of FIG. 2, and the position 18B2 is located radially outward of the sidewall member 18B, i.e., on the X1 side in the example of FIG. 2. Also, in the example of FIG. 2, the position 18B1 of the sidewall member 18B is disposed between the display panel 14 and the backlight unit 16 in the Z direction and is adhered to the surface of the backlight unit 16 on the Z2 side by an adhesive layer 24. Also, in the example of FIG. 2, the frame 18 is fixed to the second main surface 12B of the cover glass 12 via a first adhesive layer 20 at the position 18B2 of the sidewall member 18B.

[0030] However, the shape of the frame 18 is not limited to the example in Fig. 2 and may be any shape. The frame 18 may be any member that includes a portion that is provided on the outer side of the display panel 14 when viewed from the Z direction, and the portion that is provided on the outer side of the display panel 14 is adhered to the second main surface 12B of the cover glass 12 via a first adhesive layer 20. For example, as shown in Fig. 4 described below, the frame 18 may be a housing that houses the cover glass 12, the display panel 14, and the backlight unit 16. In addition, in FIG. 2, the frame 18 may not include the bottom member 18A, and may be composed of only the frame-shaped side wall member 18B.

[0031] (1st adhesive layer) 3 is a schematic top view showing one embodiment of the cover glass, the first adhesive layer, and the second adhesive layer in the display device. As shown in FIG. 2, the first adhesive layer 20 is an adhesive layer provided between the cover glass 12 and the frame 18 in the Z direction to bond the cover glass 12 to the frame 18. The first adhesive layer 20 bonds the surface 18BA of the frame 18 on the Z2 side to the second main surface 12B of the cover glass 12. As shown in FIGS. 2 and 3, in this embodiment, the surface 18BA of the frame 18 is provided so as to surround the periphery of the display panel 14, and therefore the first adhesive layer 20 is also provided so as to surround the periphery of the display panel 14.

[0032] The first adhesive layer 20 has an elastic modulus in an indentation elastic modulus test of 5 MPa to 400 MPa, preferably 8 MPa to 400 MPa, more preferably 10 MPa to 400 MPa, even more preferably 12 MPa to 350 MPa, even more preferably 15 MPa to 300 MPa, and particularly preferably 100 MPa to 300 MPa. The lower limit of the elastic modulus is 5 MPa, preferably 8 MPa or more, more preferably 10 MPa or more, even more preferably 12 MPa or more, even more preferably 15 MPa or more, and particularly preferably 100 MPa or more. The upper limit of the elastic modulus is 400 MPa, preferably 350 MPa or less, and more preferably 300 MPa or less. Having an elastic modulus of 5 MPa or more ensures sufficient strength against peeling, preventing glass fragments from floating up when the edge of the cover glass 12 is broken. Having an elastic modulus of 400 MPa or less reduces display unevenness.

[0033] The indentation elastic modulus test in this embodiment is carried out by the following method. The first adhesive layer 20 bonded to the second main surface 12B of the cover glass 12 and the frame is exposed facing vertically upward and placed in a creep meter (e.g., Yamaden Corporation, Model No. RE2-33005C). A plunger (Yamaden Corporation, Cylindrical Plunger, Model No. P-61, 1.5 mm diameter, 40 mm height) is pressed against the first adhesive layer 20 at room temperature (e.g., 20°C) and a relative humidity of 50% at a pressing speed of 0.05 mm / sec. The load acting on the plunger and the displacement of the plunger in the pressing direction are sequentially measured. The measured load and displacement are plotted over time, and the slope of the approximation line between the plotted points in the section where the pressing depth is 5% to 10% of the thickness of the first adhesive layer 20 is calculated as the elastic modulus of the first adhesive layer 20. The method for exposing the first adhesive layer 20 is not particularly limited, but a method that does not denature the adhesive is preferred. For example, a thin metal plate or the like may be inserted between the first adhesive layer 20 and the adherend, i.e., the cover glass 12 or the frame 18, to physically separate them. If the first adhesive layer 20 breaks partway through the thickness direction during the separation, it is preferable to measure the elastic modulus of the thicker remaining portion. It is also preferable to measure the elastic modulus using the adhesive layer remaining on the side of the frame or the cover glass that has the higher Young's modulus. That is, it is preferable to measure the elastic modulus by leaving the adhesive layer on the frame side when the frame is made of metal, or on the cover glass side when the frame is made of resin with a low Young's modulus. Here, the meaning of the indentation elastic modulus test in this embodiment will be explained. In glass articles, adhesives bond the glass surface of a cover glass or a printed surface on the glass surface to a metal or resin frame. When attempting to peel the bonded glass surface from the frame, the adhesive is generally designed to break, resulting in peeling. It is known that the adhesive strength at which the adhesive breaks depends on the tensile elastic modulus of the adhesive. However, existing adhesive strength tests, such as the cross-type adhesive strength test and the H-type adhesive strength test, have been difficult to measure on glass articles in which the cover glass and frame are bonded. In this embodiment, an indentation elastic modulus test is adopted as an evaluation method to replace the existing adhesive strength test, which can also be verified on glass articles in which the cover glass and frame are bonded. In this embodiment, since it is known that the adhesive breaks when the glass article and frame are peeled, and that there is generally a positive correlation between the tensile elastic modulus and the indentation elastic modulus, it is presumed that there is also a correlation between the adhesive strength and the elastic modulus in the indentation test.

[0034] The thickness D1 of the first adhesive layer 20 is preferably 0.2 mm to 4.0 mm, more preferably 0.5 mm to 3.5 mm, and even more preferably 1.0 mm to 3.0 mm. The lower limit of the thickness D1 of the first adhesive layer 20 is preferably 0.2 mm, more preferably 0.5 mm or more, and even more preferably 1.0 mm or more. The upper limit of the thickness D1 is preferably 4.0 mm, more preferably 3.5 mm or less, and even more preferably 3.0 mm or less. By setting the thickness D1 within this range, the elastic modulus can be adjusted to an appropriate range, which can effectively prevent glass fragments from floating up when the cover glass is broken and also effectively suppress display unevenness. The thickness D1 is the length in the Z direction from the surface of the first adhesive layer 20 facing the Z1 direction to the surface facing the Z2 direction.

[0035] FIG. 3 is a schematic top view showing the second main surface of the cover glass 12 as viewed from the Z direction. The area of ​​the second main surface 12B of the cover glass 12 is defined as area AR0, and the area of ​​the first adhesive layer 20 is defined as area AR1. In this case, the ratio of the area AR1 of the first adhesive layer 20 to the area AR0 of the second main surface 12B is preferably 5% to 65%, more preferably 8% to 50%, and even more preferably 10% to 40%. The lower limit of this area ratio is preferably 5%, more preferably 8% or more, and even more preferably 10% or more. The upper limit of the ratio is preferably 65%, more preferably 50% or less, and even more preferably 40% or less. By ensuring that the ratio of the area AR1 of the first adhesive layer 20 falls within this range, cracking of the cover glass 12 can be suitably suppressed.

[0036] As shown in FIG. 2, the minimum radial distance from the central axis AX of the cover glass 12 to the end face 12C, i.e., the distance in the X direction in the example of FIG. 2, is defined as distance L0. Furthermore, the minimum radial distance from the end face 12C of the cover glass 12 to the outer end 20A of the first adhesive layer 20, i.e., the distance in the X direction in the example of FIG. 2, is defined as distance L1A. End 20A is the radially outer end of the first adhesive layer 20, i.e., the end on the X1 direction in the example of FIG. 2. Furthermore, the minimum radial distance from the end face 12C of the cover glass 12 to the inner end 20B of the first adhesive layer 20, i.e., the distance in the X direction in the example of FIG. 2, is defined as distance L1B. End 20B is the radially inner end of the first adhesive layer 20, i.e., the end on the X2 direction in the example of FIG. 2. In this case, the ratio of distance L1A to distance L0 is preferably 0% or more and 10% or less, more preferably 0.3% or more and 8% or less, and even more preferably 0.5% or more and 5% or less. Furthermore, distance L1A is preferably 0 mm or more and 10 mm or less, more preferably 0.1 mm or more and 8 mm or less, and even more preferably 0.2 mm or more and 5 mm or less. Here, the lower limit of distance L1A is 0 mm, preferably 0.1 mm or more, and even more preferably 0.2 mm or more. Furthermore, the upper limit of distance L1A is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 5 mm or less. Furthermore, the ratio of distance L1B to distance L0 is preferably 0.1% or more and 50% or less, more preferably 1% or more and 40% or less, and even more preferably 2% or more and 10% or less. Furthermore, distance L1B is preferably 0.5 mm or more and 60 mm or less, more preferably 1 mm or more and 30 mm or less, and even more preferably 3 mm or more and 10 mm or less. Here, the lower limit of distance L1B is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 3 mm or more. Furthermore, the upper limit of distance L1B is preferably 60 mm or less, more preferably 30 mm or less, and even more preferably 10 mm or less. By setting the distance L1A and the distance L1B within this range, the vicinity of the edge of the cover glass 12 can be properly bonded, and when the edge of the cover glass 12 is broken, the floating of broken pieces can be suitably prevented.

[0037] The first adhesive layer 20 may be any adhesive, and examples of the material for the first adhesive layer 20 include epoxy resin, urethane resin, and acrylic resin.

[0038] (Second adhesive layer) As shown in FIG. 2, the second adhesive layer 22 is an adhesive layer provided between the cover glass 12 and the display panel 14 in the Z direction and bonds the cover glass 12 to the display panel 14. The second adhesive layer 22 bonds the display surface, which is the surface 14A of the display panel 14 facing Z2, to the second main surface 12B of the cover glass 12. The second adhesive layer 22 is preferably located radially inward of the first adhesive layer 20 and separated from the first adhesive layer 20. Note that, in the example of FIG. 3, the second adhesive layer 22 is provided over the entire area of ​​the display panel 14, but this is not limiting and the second adhesive layer 22 may be provided only in a portion of the display panel 14 or over an area larger than the display panel 14.

[0039] The second adhesive layer 22 preferably has a lower modulus of elasticity in an indentation elastic modulus test than the first adhesive layer 20. The second adhesive layer 22 preferably has a modulus of elasticity in an indentation elastic modulus test of 0.5 MPa to 100 MPa, more preferably 1 MPa to 80 MPa, and even more preferably 2 MPa to 50 MPa. Having a modulus of elasticity within this range makes it possible to appropriately bond the display panel 14 and the cover glass 12 while suppressing display unevenness. The indentation elastic modulus test for the second adhesive layer 22 is also performed in the same manner as for the first adhesive layer 20.

[0040] The thickness D2 of the second adhesive layer 22 is preferably 0.05 mm to 4.0 mm, more preferably 0.1 mm to 3.5 mm, and even more preferably 0.2 mm to 3 mm. Having the thickness D2 within this range allows the elastic modulus to be within an appropriate range, thereby appropriately bonding the display panel 14 and the cover glass 12 and suppressing display unevenness. The thickness D2 is the length in the Z direction from the surface of the second adhesive layer 22 facing the Z1 direction to the surface facing the Z2 direction.

[0041] 3, the area of ​​the second adhesive layer 22 when viewed in the Z direction is defined as area AR2. In this case, the ratio of the area AR2 of the second adhesive layer 22 to the area AR0 of the second main surface 12B of the cover glass 12 is preferably 30% to 90%, more preferably 40% to 85%, and even more preferably 50% to 80%. When the area AR2 of the second adhesive layer 22 is within this range, the display panel 14 and the cover glass 12 can be appropriately bonded together.

[0042] 2, the distance in the radial direction from the inner end 20B of the first adhesive layer 20 to the outer end 22A of the second adhesive layer 22 (i.e., the distance in the X direction in the example of FIG. 2) is defined as distance L2. End 22A is the end of the second adhesive layer 22 on the outer side in the radial direction (i.e., the X1 side in the example of FIG. 2). In this case, the ratio of distance L2 to distance L0 is preferably 0.5% to 15%, more preferably 1% to 12%, and even more preferably 2% to 10%. Furthermore, distance L2 is preferably 0.1 mm to 10 mm, more preferably 0.3 mm to 8 mm, and even more preferably 0.5 mm to 5 mm.

[0043] The second adhesive layer 22 is preferably an adhesive having a different composition from that of the first adhesive layer 20. The second adhesive layer 22 may be, for example, an acrylic resin or a silicone resin. By making the second adhesive layer 22 and the first adhesive layer 20 different, it is possible to suppress uneven display on the display while also making it easier to suppress cracks from the edge of the cover glass 12.

[0044] (Other configuration examples) 4 is a schematic cross-sectional view showing a part of another aspect of the display device according to the present embodiment. In the example of FIG. 2, the frame 18 and the cover glass 12 housed in the housing 19 are bonded together with the first adhesive layer 20. However, this is not limiting, and as shown in FIG. 4, the housing that houses the cover glass 12 and the display panel 14 may be the frame 18. In other words, the frame 18, which is the housing that houses the cover glass 12 and the display panel 14, and the cover glass 12 may be bonded together with the first adhesive layer 20.

[0045] (effect) As described above, in the display device 10 according to this embodiment, the first adhesive layer 20 that bonds the cover glass 12 and the frame 18 has an elastic modulus of 5 MPa or more and 400 MPa or less. This makes it possible to suppress display unevenness while also suppressing glass fragments from floating up when the edge (periphery) of the cover glass 12 is broken.

[0046] (Head impact test) Whether or not glass fragments float up when the edge of the cover glass 12 is broken can be evaluated by a head impact test. The head impact test will be described below.

[0047] Fig. 5 is a schematic diagram for explaining a head impact test. As shown in Fig. 5, when conducting a head impact test, the display device 10 is placed on a horizontal surface so that the first main surface 12A of the cover glass 12 faces vertically upward. Then, a spherical rigid model (not shown) (material: iron, diameter: 165 mm, mass: 19.6 kg) is dropped from a height of 793 mm at an impact speed of 3.944 m / s to impact the first main surface 12A of the cover glass 12 at impact position P so that the impact energy is 152.4 J. For the test method, you may refer to "Article 20: Passenger Devices" of the "Safety Standards for Road Transport Vehicles" set forth by the Ministry of Land, Infrastructure, Transport and Tourism, "Attachment 28: Technical Standards for Impact Absorption of Instrument Panels" (hereinafter simply referred to as "Standards"). This "Standards" requires that a spherical rigid model (material: iron, diameter: 165 mm, mass: 6.8 kg) be projected and impacted at a collision speed of 6.7 m / s, resulting in a collision energy of 152.4 J. In other words, in a head impact test, it is preferable to ensure that the collision energy is equivalent to that of the "Standards." The collision position P on the cover glass 12 where the rigid body model is to be collided is located on the first main surface 12A of the cover glass 12, at the center position of the first main surface 12A in the X direction, and at a position 1 mm away in the Y direction from the end face 12C of the cover glass 12 on the Y1 side toward the Y2 direction.

[0048] A head impact test is performed under the above conditions, and when the edge of the cover glass 12 (near the impact position P) is broken, the degree to which the fragments of the cover glass 12 float up can be evaluated by observing, for example, the distance in the Z direction from the uncracked part of the first main surface 12A to the tip of the fragment.

[0049] (Uneven display) Because the second main surface 12B of the cover glass 12 and the surface 18BA of the frame 18 are not strictly flat, when the second main surface 12B and the surface 18BA are brought into contact with each other, the gap between them varies from position to position. This variation in the gap causes variations in the way light emitted from the display panel 14, e.g., from the backlight unit 16 in this embodiment, passes through the cover glass 12, resulting in variations in brightness and display unevenness. In contrast, in this embodiment, the first adhesive layer 20, which has a relatively soft elastic modulus of 400 MPa or less, is provided between the second main surface 12B and the surface 18BA to absorb the gap variation and suppress display unevenness. On the other hand, if the first adhesive layer 20 were made harder and did not satisfy the elastic modulus requirement of 400 MPa or less, the gap variation would not be absorbed, and display unevenness would not be suppressed.

[0050] This disclosure describes the following inventions, but is not limited thereto.

[0051] (1) A display device comprising: a display panel; a frame including a portion provided on the outside of the display panel; a cover glass having a first main surface and a second main surface, and provided on the display panel and the frame so that the second main surface faces the display panel and the frame; and a first adhesive layer provided between the second main surface and the frame, and bonding the second main surface to the frame; wherein the first adhesive layer has an elastic modulus of 5 MPa or more and 400 MPa or less in an indentation elastic modulus test.

[0052] (2) The display device according to (1), wherein the cover glass 12 is chemically strengthened glass having a compressive stress layer with a thickness of 10 μm or more, a thickness D0 of 0.3 mm to 2.5 mm, and a tensile stress of 5 MPa or more.

[0053] (3) The display device according to (1) or (2), wherein the thickness D1 of the first adhesive layer 20 is 0.2 mm or more and 4.0 mm or less.

[0054] (4) The display device according to any one of (1) to (3), wherein the ratio of the area AR1 of the first adhesive layer 20 to the area AR0 of the second main surface 12B of the cover glass 12 is 5% or more and 65% or less.

[0055] (5) The display device according to any one of (1) to (4), wherein the distance L1A from the end surface 12C of the cover glass 12 to the outer end 20A of the first adhesive layer 20 is 0 mm or more and 10 mm or less.

[0056] (6) The display device according to (5), wherein a distance L1B from the end surface 12C of the cover glass 12 to the inner end 20A of the first adhesive layer 20 is 0.5 mm or more and 60 mm or less.

[0057] (7) A display device described in any one of (1) to (6), further comprising a second adhesive layer 22 provided between the second main surface 12B of the cover glass 12 and the display panel 14 to bond the second main surface 12B of the cover glass 12 to the display panel 14, the second adhesive layer 22 being composed of an adhesive having a different composition from the first adhesive layer 20.

[0058] (8) The display device according to (7), wherein the modulus of elasticity of the second adhesive layer 22 in an indentation elasticity test is lower than the modulus of elasticity of the first adhesive layer 20 in the indentation elasticity test. [Example]

[0059] Next, examples will be described. Table 1 shows samples of each example relating to the adhesive that forms the adhesive layer. Examples 1 and 2 are comparative examples, and Examples 3 to 6 are examples. It should be noted that Examples 1 to 6 are examples related to adhesive layers, not display devices having a first adhesive layer, and are not provided between the cover glass and the frame to bond them together. However, when an adhesive is applied to the main surface of the cover glass and cured to form an adhesive layer, its elastic modulus can be used to predict the results regarding floating glass fragments when the edge of the cover glass is broken and display unevenness when used as the first adhesive layer of a display device, and therefore these examples are treated as examples or comparative examples.

[0060] [Table 1]

[0061] (Example 1) In Example 1, a two-component curing epoxy resin adhesive (EP21TDCHT-LO manufactured by Masterbond) was applied to the main surface of the cover glass to a thickness of 2 mm, and the adhesive was cured by heating at 200°C for 180 minutes to form an adhesive layer. An indentation elastic modulus test was then performed using the method described in this embodiment, and the elastic modulus of the formed adhesive layer was calculated. The elastic modulus of the adhesive layer in Example 1 was found to be 500 MPa.

[0062] (Examples 2 to 6) In Examples 2 to 6, adhesive layers were formed in the same manner as in Example 1, except that the adhesive material, adhesive layer thickness, and curing conditions were changed as shown in Table 1. The indentation modulus of the adhesive layer in each example was the value shown in Table 1.

[0063] In Examples 3 to 6, which are working examples, the adhesive layer has an elastic modulus of 5 MPa or more and 400 MPa or less, which can prevent glass fragments from floating up when the edge of the cover glass is broken, while also preventing uneven display. In particular, Examples 5 and 6, which have an elastic modulus of 100 MPa or more, can more effectively prevent glass fragments from floating up. On the other hand, in Comparative Example 1, the elastic modulus of the adhesive is too high at 500 MPa, so it cannot absorb variations in the gap amount and cannot suppress display unevenness when a display is installed.Furthermore, in Comparative Example 2, the elastic modulus of the adhesive is too low at 1 MPa, so it cannot suppress glass fragments from floating up when the edge of the cover glass breaks.

[0064] Although the embodiments of the present invention have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments. This application is based on Japanese patent applications filed on August 30, 2021 (Patent Application No. 2021-139604), April 26, 2022 (Patent Application No. 2022-072684), and August 8, 2022 (Patent Application No. 2022-126055), the contents of which are incorporated herein by reference. [Explanation of symbols]

[0065] 10 Display device 12 Coverslip 12A First principal surface 12B Second principal surface 12C End face 14 Display panel 18 frames 20 1st adhesive layer 22 Second adhesive layer

Claims

1. A display panel; a frame including a portion provided on the outer side of the display panel; a cover glass having a first main surface and a second main surface, the cover glass being provided on the display panel and the frame such that the second main surface faces the display panel and the frame; a first adhesive layer provided between the second main surface of the cover glass and the frame, the first adhesive layer adhering the second main surface of the cover glass to the frame; and A display device, wherein the first adhesive layer has an elastic modulus of 5 MPa or more and 400 MPa or less in an indentation elastic modulus test.

2. 2. The display device according to claim 1, wherein the cover glass is chemically strengthened glass having a compressive stress layer with a thickness of 10 [mu]m or more, a thickness of 0.3 mm to 2.5 mm, and a tensile stress of 5 MPa or more.

3. 3. The display device according to claim 1, wherein the first adhesive layer has a thickness of 0.2 mm or more and 4.0 mm or less.

4. 3 . The display device according to claim 1 , wherein a ratio of an area of ​​the first adhesive layer to an area of ​​the second main surface of the cover glass is 5% or more and 65% or less.

5. 3. The display device according to claim 1, wherein a distance from an end face of the cover glass to an outer end of the first adhesive layer is 0 mm or more and 10 mm or less.

6. The display device according to claim 5 , wherein the distance from the end face of the cover glass to the inner end of the first adhesive layer is 0.5 mm or more and 60 mm or less.

7. a second adhesive layer provided between the second main surface of the cover glass and the display panel, the second adhesive layer adhering the second main surface of the cover glass to the display panel; 3. The display device according to claim 1, wherein the second adhesive layer is made of an adhesive having a different composition from that of the first adhesive layer.

8. The display device according to claim 7 , wherein the modulus of elasticity of the second adhesive layer in the indentation elasticity test is lower than the modulus of elasticity of the first adhesive layer in the indentation elasticity test.

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