Double-sided adhesive sheet and image display device

Abstract

The present invention relates to a double-sided adhesive sheet and an image display device. The image display device (100) comprises: a panel array (1) obtained by arranging a plurality of display panels (11, 12, 13) side by side in the same plane; a front transparent plate (5) arranged on the visible side surface of the panel array; and an adhesive sheet (2) disposed between the panel array and the front transparent plate. The adhesive sheet has a light-transmitting region and a light-shielding region (56, 57) having a relatively low visible light transmittance, and the light-shielding region of the adhesive sheet is arranged on the boundary between adjacent display panels in the panel array.

Description

Technical Field

[0001] The present invention relates to an image display device obtained by arranging a plurality of display panels side by side, and a double-sided adhesive sheet used for forming the image display device. Background Art

[0002] Micro-LED displays are attracting attention as next-generation displays. Micro-LED displays achieve high definition and wide viewing angles by densely stacking LED elements. Furthermore, since LED displays do not require color filters, they can achieve low power consumption and high brightness.

[0003] As a technology for scaling up display devices such as LED displays, splicing technology is known, which uses multiple display panels arranged side by side on the same surface to form a single image. In a spliced display device created by arranging multiple display panels side by side, it is conceivable that viewers will observe the seams (boundaries) between adjacent display panels. Patent Document 1 improves the positional accuracy of splicing by providing alignment members on the sides of the display panels.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-45718 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In a spliced display device, even when display panels are arranged without gaps, external light or light from the display panels may be diffusely reflected at the boundaries between adjacent display panels, making the boundaries visible. In view of this problem, an object of the present invention is to provide an image display device in which the boundaries (seam) between display panels are less visible.

[0009] Means used to solve problems

[0010] The image display device of the present invention comprises: a panel array formed by arranging a plurality of display panels side by side within a common plane; and a front transparent plate disposed on a visible side surface of the panel array, wherein the display panels constituting the panel array and the front transparent plate are bonded to each other via a double-sided adhesive sheet. The display panels may be LED panels.

[0011] The adhesive sheet has a light-transmitting region and a light-blocking region. The light-blocking region has a lower visible light transmittance than the light-transmitting region, and the visible light transmittance of the light-blocking region is preferably 50% or less. The light-blocking region of the adhesive sheet is arranged at the boundary between adjacent display panels in the panel array. For example, if multiple display panels are arranged in a tiled pattern in the panel array, the light-blocking region has a grid-like pattern that covers the boundary between the display panels.

[0012] The adhesive sheet may be an adhesive sheet having a patterned colored layer on a transparent adhesive layer. The colored layer is preferably provided on the main surface of the adhesive layer on the display panel side. The adhesive sheet may be an adhesive sheet having transparent adhesive layers laminated on both sides of a transparent substrate film, or an adhesive sheet having a colored layer provided on one or both main surfaces of the film substrate. The colored layer is preferably provided on the main surface of the transparent substrate film on the display panel side. In these adhesive sheets, the colored layer is provided on the light-shielding area.

[0013] Effects of the Invention

[0014] By arranging the light-shielding region of the adhesive sheet at the boundary between adjacent display panels in the panel array, the boundary between the display panels is less easily visible from the outside, thereby achieving seamless display. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a three-dimensional exploded view of the image display device.

[0016] Figure 2 is a cross-sectional view of an image display device.

[0017] Figure 3 A cross-sectional view of an LED panel array.

[0018] Figure 4 A cross-sectional view of the adhesive sheet.

[0019] Figure 5 is a cross-sectional view of an image display device.

[0020] Figure 6 A cross-sectional view of the adhesive sheet.

[0021] Figure 7 is a cross-sectional view of an image display device.

[0022] Figure 8 A cross-sectional view of the adhesive sheet.

[0023] Label Description

[0024] 1 Panel Array

[0025] 11~19 Display Panel

[0026] 7 Display components

[0027] 8 Support substrate

[0028] 2, 41, 43, 44 adhesive sheets

[0029] 21, 23, 25 adhesive layer

[0030] 31~39 light-transmitting area

[0031] 51, 53, 56, 58 shading area

[0032] 5. Front transparent panel

[0033] 81 transparent substrate film

[0034] 66, 68, 76, 78 coloring layer (light-shielding area)

[0035] 100, 101, 103 Image display device DETAILED DESCRIPTION

[0036] Figure 1 This is an exploded perspective view of an image display device according to one embodiment. Image display device 100 includes a panel array 1 formed by arranging multiple display panels 11 to 19 in a tile-like pattern on the same surface. A front transparent plate 5 is disposed on the visible side (light-emitting side) of panel array 1. The display panels 11 to 19 and front transparent plate 5 that constitute panel array 1 are bonded together with an adhesive sheet 2 interposed therebetween.

[0037] The adhesive sheet 2 has light-transmitting regions 31-39 and a grid-patterned light-shielding region. The grid-patterned light-shielding region includes strips 51 and 53 extending in the x-direction and strips 56 and 58 extending in the y-direction. The visible light transmittance of the light-shielding region is lower than that of the light-transmitting region. The light-transmitting regions 31-39 correspond to the positions of the display panels 11-19 that make up the panel array 1. The light-shielding regions 51, 53, 56, and 58 of the adhesive sheet 2 are arranged on the boundaries between adjacent display panels.

[0038] The adhesive sheet 2 is a double-sided adhesive sheet. The first main surface of the visible side of the adhesive sheet 2 is bonded to the front transparent plate 5, and the second main surface of the adhesive sheet 2 is bonded to the display panel. In the following, for each component, the main surface of the visible side is sometimes described as the "first main surface", and the main surface of the opposite side (panel array side) is sometimes described as the "second main surface". The adhesive sheet can be a substrate-free adhesive sheet or a substrate-free adhesive sheet such as Figure 6 and Figure 8 The adhesive sheet shown here has adhesive layers laminated on both sides of a transparent base film. The light-shielding region of the adhesive sheet 2 may not have adhesive properties.

[0039] A front transparent plate 5 is disposed on the visible side of the panel array 1. Each display panel 11 to 19 constituting the panel array 1 is bonded to the front transparent plate 5 via an adhesive sheet 2. The front transparent plate 5 is a transparent plate made of glass or resin with suitable mechanical strength and thickness. The front transparent plate prevents damage and scratches to the image display panels caused by external impacts. Position sensors such as touch panels may be provided on the front transparent plate.

[0040] Figure 2 for Figure 1 Cross-sectional view taken along line AA. Display panels 11-13 include display element 7 on a supporting substrate 8. Examples of display panels include self-luminous display panels such as LED panels and organic electroluminescent (EL) panels, and non-luminous display panels such as liquid crystal panels and electronic paper. The supporting substrate 8 and display element 7 in the display panel are appropriately determined depending on the type of display panel.

[0041] The following description will be made by taking the case where the display panel is an LED panel as an example. Figure 3 1 is a cross-sectional view of a panel array 1 obtained by arranging LED panels 11 , 12 , and 13 having LED arrays in a tile shape on a support substrate 8 .

[0042] Support substrate 8 supports the LED elements that make up display element 7. Glass or various resin materials are used for support substrate 8. The support substrate can be transparent or opaque. The thickness of the support substrate is not particularly limited as long as it can support display element 7; for example, it ranges from about 10 μm to about 2 mm.

[0043] The display element 7 of the LED panel is an LED array including a plurality of LED elements. Typically, three colors of LED elements, namely a red LED element 6R, a green LED element 6G and a blue LED element 6B, constitute a pixel P, and a plurality of pixels are arranged in a tile shape. LED elements are suitable for high definition because they can be miniaturized. In a micro-LED, the size of an LED element (the length of one side) is, for example, about 5 μm to about 200 μm, and the pixel pitch is about 20 μm to about 1 mm. A transparent resin layer (not shown) can be provided on the surface of the LED element in a manner covering the LED element.

[0044] There is a gap 96 at the boundary between adjacent display panels 11 and 12, and a gap 98 at the boundary between adjacent display panels 12 and 13. Even if the gap between adjacent display panels is minimized as much as possible, there is sometimes a height difference caused by a slight difference in the height of the upper surface (element forming surface) of the support substrate 8. When external light from the visible side or light from the LED element hits the gap between the panels or the height difference portion of the boundary, the light is diffusely reflected. Therefore, at the boundary portion, the intensity and color tone of the reflected light are different from those in other areas of the display array, causing the boundary to be observed (recognized).

[0045] If Figure 2 As shown, the shading areas 56 and 58 of the adhesive sheet 2 are arranged on the boundaries between adjacent display panels, which can reduce the incidence of external light on the boundary areas between the display panels. In addition, even if the light from the display element 7 is irradiated on the boundary area, since the reflected light is shielded by the shading areas 56 and 58, it is possible to reduce the reflected light in the boundary area from being emitted to the visible side. Therefore, it is difficult to observe (identify) the boundaries (seams) between the display panels from the outside, and seamless display can be achieved. In addition, since the shading area is provided on the adhesive sheet 2 used in the bonding of the display panels 11, 12, 13 and the front transparent plate 5, the distance from the image display panel to the shading area is small, and it is also possible to effectively shield the light that is diffusely reflected at the boundaries between the adjacent display panels.

[0046] The width of the light-shielding region of the adhesive sheet 2 can be appropriately set based on the gap between display panels, the spacing between adjacent pixels, and other factors, and can be, for example, approximately 5 μm to approximately 200 μm. If there is a gap between adjacent display panels, the width of the light-shielding region is preferably greater than the width of the gap between the panels. Furthermore, the width of the light-shielding region is preferably less than the distance L between the display elements of adjacent display panels.

[0047] The visible light transmittance of the light-blocking region of the adhesive sheet 2 is preferably 50% or less, more preferably 30% or less, and even more preferably 10% or less. The visible light transmittance of the light-blocking region may be 5% or less, 3% or less, or 1% or less. From the perspective of efficiently transmitting light from the display panel to the visible side, the visible light transmittance of the light-transmitting region is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or less.

[0048] Adhesive sheet 2 is an adhesive sheet obtained by forming an adhesive into a layer. As the adhesive, an adhesive having a base polymer such as an acrylic polymer, a polysiloxane polymer, a polyester, a polyurethane, a polyamide, a polyvinyl ether, a vinyl acetate / vinyl chloride copolymer, a modified polyolefin, an epoxy polymer, a fluorine-containing polymer, a natural rubber, a synthetic rubber or the like can be appropriately selected. In particular, from the viewpoint of excellent optical transparency, moderate wettability, cohesiveness, and adhesiveness, acrylic adhesives or rubber adhesives are preferred.

[0049] As the adhesive constituting the adhesive sheet 2, a photocurable adhesive can also be used. The photocurable adhesive comprises a base polymer and a photocuring agent, and further comprises a photopolymerization initiator and / or a sensitizer. The photocurable adhesive is soft before photocuring and has high adaptability to uneven surfaces and height differences. Therefore, even on the surface of the LED array where there are gaps between adjacent LED elements, it is easy to fill the adhesive without gaps. By photocuring the adhesive after the display panel is bonded to the front transparent plate, the bonding reliability can be improved.

[0050] From the viewpoint of improving the filling property of height difference and unevenness, the shear storage modulus of the light-transmitting region of the pressure-sensitive adhesive sheet 2 at a frequency of 1 Hz and 25° C. is preferably 1×10 6 Pa or less, more preferably 5×10 5 Pa or less. It should be noted that the light-shielding area of the adhesive sheet 2 is not arranged on the display element of the display panel, so the characteristics of the light-shielding area may be different from those of the light-transmitting area. From the perspective of preventing adhesive from protruding from the end and contamination caused by adhesive transfer, the shear storage modulus of the adhesive sheet at a frequency of 1 Hz and 25°C is preferably 1×10 4 Pa or more, more preferably 3×10 4 Pa or more. When the pressure-sensitive adhesive sheet is photocurable, the shear storage modulus before photocuring is preferably within the above range.

[0051] The thickness of the adhesive sheet 2 is not particularly limited, but may range from about 10 μm to about 500 μm, or may be about 20 μm to about 300 μm. The adhesive strength of the light-transmitting area of the adhesive sheet 2 to the glass plate is preferably 3 N / 20 mm or greater. If the adhesive sheet is photocurable, the adhesive strength to the glass after photocuring is preferably 3 N / 20 mm or greater. The adhesive strength is the test force when a 20 mm wide adhesive sheet is attached to a glass plate and subjected to a 180° peel test at a peel speed of 300 mm / min.

[0052] The method for providing a patterned light-shielding area on the adhesive sheet 2 is not particularly limited. For example, by impregnating a dye or pigment into the adhesive in the light-shielding area and coloring it, it can be made to have light-shielding properties. The light-shielding area of the adhesive sheet 2 does not need to have light-shielding properties throughout the thickness direction of the adhesive sheet. For example, the light-shielding area can also be formed by impregnating a dye or pigment near the surface of the adhesive layer. The light-shielding area of the adhesive sheet does not require the adhesive itself to be colored. For example, the light-shielding area can also be formed by providing a colored layer on the transparent adhesive layer by printing or the like.

[0053] Figure 4 This is a cross-sectional view of a pressure-sensitive adhesive sheet 41 in which colored layers 66 and 68 are provided on one main surface of a transparent pressure-sensitive adhesive layer 21. In this pressure-sensitive adhesive sheet 41, the area where the colored layers 66 and 68 are provided serves as a light-shielding area. As the transparent pressure-sensitive adhesive layer 21, a pressure-sensitive adhesive layer containing the same pressure-sensitive adhesive as described above for the pressure-sensitive adhesive sheet can be suitably used.

[0054] Figure 5 This is a cross-sectional view of an image display device 101, in which the colored layer-forming surface of adhesive sheet 41 is positioned facing the panel array. In this structure, colored layers 66 and 68 are positioned in the gaps between display elements 7 of adjacent display panels, making the boundaries between the display panels difficult to observe from the outside. Furthermore, external light is prevented from entering the gaps between the panels, and light reflected in the boundary regions between adjacent panels is shielded by colored layers 66 and 68, making the boundaries of the panel array difficult to observe.

[0055] The colored layer 66, 68 may be provided on either the first or second principal surface of the transparent adhesive layer 21, or may be provided on both surfaces of the transparent adhesive layer 21. If the colored layer is provided on the second principal surface (the surface facing the panel array), since the colored layer is disposed immediately above the image display panel or in the gap between adjacent image display panels, reflected light is less likely to be emitted to the outside, and the boundary area is even less likely to be observed.

[0056] The method for providing the colored layer on the transparent adhesive layer is not particularly limited, and various printing methods such as inkjet printing and screen printing can be applied. Instead of forming the colored layer directly on the transparent adhesive layer, a colored pattern can be printed on another substrate and the colored layer can be transferred to the adhesive layer.

[0057] The thickness of the colored layer is not particularly limited and can be set based on the transmittance of the light-shielding area. To sufficiently reduce the light transmittance of the light-shielding area, the thickness of the colored layer is preferably 2 μm or greater, more preferably 5 μm or greater, and even more preferably 10 μm or greater. The thickness of the colored layer can be 50 μm or less, 40 μm or less, or 30 μm or less. Furthermore, the thickness of the colored layer is preferably 50% or less, and more preferably 40% or less of the thickness of the adhesive layer.

[0058] Figure 6 This is a cross-sectional view of an adhesive sheet 43 according to another embodiment. Adhesive sheet 43 is a double-sided adhesive sheet with a substrate, in which adhesive layers are laminated on both sides of a transparent base film 81. A first transparent adhesive layer 23 is laminated on the first principal surface of the transparent base film 81, and a second transparent adhesive layer 25 is laminated on the second principal surface of the transparent base film 81. Colored layers 76 and 78 are provided on the second principal surface of the transparent base film 81. In this adhesive sheet 44, the area on the transparent base film 81 where the colored layers 76 and 78 are provided is a light-shielding area.

[0059] Examples of the plastic material comprising the transparent base film 81 include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, polyetheretherketone, and polyethersulfone. The visible light transmittance of the transparent base film 81 is preferably 80% or greater, more preferably 85% or greater, and even more preferably 90% or greater. The thickness of the transparent base film is, for example, approximately 10 μm to 100 μm.

[0060] There is no particular limitation on the method of providing the coloring layer on the transparent substrate film, and various printing methods such as inkjet printing and screen printing can be applied. Compared with printing on the adhesive layer, forming the coloring layer on the transparent substrate film has the advantages of excellent printing workability and improved printing accuracy. The thickness of the coloring layer, the transmittance of the light-shielding area, etc. are as described above. Figure 4 as described in the way.

[0061] The first transparent adhesive layer 23 and the second transparent adhesive layer 25 are preferably adhesive layers containing the same adhesive as described above for the adhesive sheet. The composition and thickness of the first transparent adhesive layer 23 and the second transparent adhesive layer 25 may be the same or different. Either or both of the first transparent adhesive layer 23 and the second transparent adhesive layer 25 may be a photocurable adhesive layer. The adhesion strength of the first transparent adhesive layer 23 and the second transparent adhesive layer 25 to the glass plate is preferably 3N / 20mm or greater. The adhesion strength of the second transparent adhesive layer 25 to the glass plate, at least in contact with the display panel, is preferably 3N / 20mm or greater.

[0062] Figure 7This is a cross-sectional view of image display device 103, arranged with second transparent adhesive layer 25 of adhesive sheet 43 facing the panel array. In this structure, colored layers 76 and 78 provided on the second main surface of transparent base film 81 have the effect of suppressing the entry of external light into the gaps between panels and shielding light reflected in the boundary region between adjacent panels, making the boundary of the panel array less visible.

[0063] The colored layers 76 and 78 may be provided on either the first or second principal surface of the transparent base film 81, or may be provided on both surfaces of the transparent base film 81. If the colored layer is provided on the second principal surface (the surface facing the panel array), the distance between the image display panel and the colored layer is small, so reflected light is less likely to be emitted to the outside, and the boundary area is even less visible.

[0064] From the perspective of reducing the distance between the image display panel and the colored layer to prevent the boundary region from being observed, the thickness of the second transparent adhesive layer 25 can be made thinner than the thickness of the first transparent adhesive layer 23. From the perspective of ensuring that the adhesive fills the uneven surface of the image display panel (for example, the gaps between adjacent LED elements) without gaps and improving the adhesive reliability, a photocurable adhesive can be used as the second transparent adhesive layer 25.

[0065] exist Figure 6 In the embodiment shown, an example is shown in which the colored layer is provided on the surface of the transparent base film 81, but it is also possible to Figure 8 Similarly, the adhesive sheet 44 shown above forms light-shielding regions by coloring the resin constituting the transparent substrate film 82 in regions 86 and 88. The method for coloring the resin constituting the substrate film is not particularly limited. For example, a colored resin material can be used to form the light-shielding regions, while a transparent resin material can be used to form the light-transmitting regions, using 3D printing technology. Alternatively, the resin constituting the substrate film can be colored by impregnating the transparent resin film with a dye or pigment.

[0066] The above description focuses on the case where the display panel is an LED panel (LED array). However, the technology of using an adhesive sheet with a light-shielding area to make the gaps between panels less visible can also be applied to display panels other than LED panels. In addition, the arrangement of multiple display panels does not need to be tile-shaped (grid-like) and can be appropriately modified according to the shape of the display panels, the shape of the array, etc. The pattern shape of the light-shielding area of the adhesive sheet can be designed so as to cover the boundary line between the display panels.

Claims

1. An image display device, wherein: The image display device comprises: A panel array, wherein the panel array is obtained by arranging a plurality of display panels side by side in the same plane; a front transparent plate, the front transparent plate being arranged on a visible side surface of the panel array; and an adhesive sheet disposed between the panel array and the front transparent plate, The first main surface of the adhesive sheet is bonded to the transparent plate, and the second main surface of the adhesive sheet is bonded to the display panel. The adhesive sheet has a light-transmitting region and a light-shielding region, the visible light transmittance of the light-shielding region is lower than the visible light transmittance of the light-transmitting region, and The light shielding region of the adhesive sheet is arranged on a boundary between adjacent display panels in the panel array.

2. The image display device according to claim 1, wherein The adhesive sheet includes a transparent adhesive layer and a patterned colored layer, wherein the patterned colored layer is provided on a light-shielding region of at least one main surface of the transparent adhesive layer.

3. The image display device according to claim 2, wherein: The colored layer is provided on the second main surface of the adhesive layer.

4. The image display device according to claim 1, wherein The adhesive sheet comprises: a transparent base film, a first transparent adhesive layer provided on a first main surface of the transparent base film, and a second transparent adhesive layer provided on a second main surface of the transparent base film. The first transparent adhesive layer is attached to the transparent plate, the second transparent adhesive layer is attached to the display panel, and The light-shielding region of the transparent base film is colored.

5. The image display device according to claim 4, wherein: A colored layer is provided on a light-shielding region of at least one main surface of the transparent base film.

6. The image display device according to claim 5, wherein: A colored layer is provided on the light-shielding region of the second main surface of the transparent base film.

7. The image display device according to claim 1, wherein: In the panel array, the plurality of display panels are arranged in a tile shape.

8. The image display device according to any one of claims 1 to 7, wherein: The display panel is an LED panel.

9. The image display device according to any one of claims 1 to 7, wherein The adhesive strength of the second main surface of the adhesive sheet to the glass is 3 N / 20 mm or more.

10. A double-sided adhesive sheet comprising a first main surface and a second main surface, wherein: The double-sided adhesive sheet has a light-transmitting area and a light-shielding area, wherein the visible light transmittance of the light-shielding area is lower than the visible light transmittance of the light-transmitting area. The light-shielding area is a lattice pattern.

11. The double-sided adhesive sheet according to claim 10, wherein The light shielding area has a strip-shaped area with a width of 5 μm to 200 μm.

12. The double-sided adhesive sheet according to claim 10 or 11, wherein The double-sided adhesive sheet includes a transparent adhesive layer and a patterned colored layer, wherein the patterned colored layer is provided on a light-shielding region of the transparent adhesive layer.

13. The double-sided adhesive sheet according to claim 10 or 11, wherein The double-sided adhesive sheet comprises: a transparent base film, a first transparent adhesive layer provided on a first main surface of the transparent base film, and a second transparent adhesive layer provided on a second main surface of the transparent base film, and The light-shielding region of the transparent base film is colored.

14. The double-sided adhesive sheet according to claim 13, wherein A colored layer is provided on a light-shielding region of at least one main surface of the transparent base film.

15. The double-sided adhesive sheet according to claim 10 or 11, wherein The double-sided adhesive sheet is used to bond a panel array to a front transparent plate. The panel array is obtained by arranging a plurality of display panels side by side in the same plane. The front transparent plate is arranged on the visible side surface of the panel array, and The light shielding region is arranged in a region corresponding to a boundary between adjacent display panels in the panel array.

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