JP7420533B2 - Double-sided adhesive sheet and image display device - Google Patents

Description

The present invention relates to an image display device in which a plurality of display panels are arranged side by side, and a double-sided adhesive sheet used for forming the image display device.

Micro LED displays are attracting attention as the next generation of displays. A micro LED display can achieve high definition and a wide viewing angle by densely laying out LED elements. Furthermore, since LED displays do not require color filters, they can achieve low power consumption and high brightness.

As a technique for increasing the size of a display device such as an LED display, a tiling technique is known in which a plurality of display panels are arranged side by side within the same plane to form one image. In a tiling display device in which a plurality of display panels are arranged side by side, it is assumed that a viewer will recognize the joints (boundaries) between adjacent display panels. In Patent Document 1, the positional accuracy of tiling is improved by providing an alignment member on the side surface of the display panel.

JP 2019-45718 Publication

In a tiling display device, even when the display panels are arranged without any gaps, the boundary may be visible due to diffuse reflection of outside light or light from the display panels at the boundary between adjacent display panels. In view of this problem, an object of the present invention is to provide an image display device in which boundaries (joints) between display panels are difficult to see.

The image display device of the present invention includes a panel array in which a plurality of display panels are arranged side by side in the same plane, and a front transparent plate placed on the viewing side surface of the panel array, and includes display panels constituting the panel array and a front transparent plate. The board is attached via a double-sided adhesive sheet. The display panel may be an LED panel.

The adhesive sheet has a light-transmitting area and a light-blocking area. The light-shielding region is a region whose visible light transmittance is lower than that of the light-transmitting region, and the visible light transmittance of the light-shielding region is preferably 50% or less. The light blocking area of the adhesive sheet is arranged on the boundary between adjacent display panels of the panel array. For example, in a panel array, when a plurality of display panels are arranged in a tile shape, the boundary area has a grid pattern so as to cover the boundary line between the display panels.

The adhesive sheet may include 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 one in which transparent adhesive layers are laminated on both sides of a transparent base film, or a colored layer may be provided on one or both main surfaces of the transparent base film. The colored layer is preferably provided on the main surface of the transparent base film on the display panel side. In these pressure-sensitive adhesive sheets, a colored layer is provided in the light-shielding area.

By arranging the light-shielding area of the adhesive sheet on the boundary between adjacent display panels in the panel array, the boundary between the display panels is difficult to see from the outside, and seamless display can be realized.

FIG. 2 is an exploded perspective view of the image display device. FIG. 2 is a cross-sectional view of an image display device. FIG. 2 is a cross-sectional view of an LED panel array. It is a sectional view of an adhesive sheet. FIG. 2 is a cross-sectional view of an image display device. It is a sectional view of an adhesive sheet. FIG. 2 is a cross-sectional view of an image display device. It is a sectional view of an adhesive sheet.

FIG. 1 is an exploded perspective view of an image display device according to an embodiment. The image display device 100 includes a panel array 1 in which a plurality of display panels 11 to 19 are arranged in the form of tiles on the same plane, and a front transparent plate 5 is arranged on the viewing side (light output side) of the panel array 1. There is. The display panels 11 to 19 constituting the panel array 1 and the front transparent plate 5 are bonded together with an adhesive sheet 2 placed between them.

The adhesive sheet 2 has light-transmitting regions 31 to 39 and light-shielding regions in a lattice pattern consisting of strip-shaped regions 51, 53 extending in the x direction and strip-shaped regions 56, 58 extending in the y direction. The visible light transmittance of the light-blocking region is smaller than the visible light transmittance of the light-transmitting region. The light transmission areas 31 to 39 correspond to the positions of the display panels 11 to 19 forming the panel array 1. The light shielding areas 51, 53, 56, and 58 of the adhesive sheet 2 are arranged on the boundary line between adjacent display panels.

The adhesive sheet 2 is a double-sided adhesive sheet, and the first main surface on the viewing side is bonded to the front transparent plate 5, and the second main surface is bonded to the display panel. Hereinafter, for each member, the main surface on the viewing side may be referred to as the "first main surface" and the main surface on the opposite side (panel array side) may be referred to as the "second main surface." The adhesive sheet may be a base material-less adhesive sheet, or may be one in which adhesive layers are laminated on both sides of a transparent base film, as shown in FIGS. 6 and 8. The light-shielding area of the adhesive sheet 2 does not need to have adhesive properties.

A front transparent plate 5 is arranged on the viewing side surface of the panel array 1, and each of the display panels 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 having appropriate mechanical strength and thickness, and by providing the front transparent plate, it is possible to prevent the image display panel from being damaged or scratched due to impact from the outer surface. . The front transparent plate may be provided with a position sensor such as a touch panel.

FIG. 2 is a cross-sectional view taken along line AA in FIG. The display panels 11 to 13 include a display element 7 on a support substrate 8. Types of display panels include self-luminous display panels such as LED panels and organic electroluminescence (EL) panels; and non-luminous display panels such as liquid crystal panels and electronic paper. The support substrate 8 and display element 7 in the display panel are appropriately determined depending on the type of display panel.

In the following, a case where the display panel is an LED panel will be described as an example. FIG. 3 is a cross-sectional view of a panel array 1 in which LED panels 11, 12, and 13 each having an LED array are arranged in a tile shape on a support substrate 8.

The support substrate 8 is a member that supports the LED elements that constitute the display element 7, and is made of glass or various resin materials. The supporting substrate may be transparent or opaque. The thickness of the support substrate is not particularly limited as long as it can support the display element 7, and is, for example, about 10 μm to 2 mm.

The display element 7 of the LED panel is an LED array including a plurality of LED elements, and usually, three color LED elements of a red LED element 6R, a green LED element 6G, and a blue LED element 6B constitute one pixel P, Multiple pixels are arranged in tiles. Since LED elements can be miniaturized, they are suitable for high definition. In a micro LED, the size of one LED element (length of one side) is, for example, about 5 μm to 200 μm, and the pixel pitch is about 20 μm to 1 mm. A transparent resin layer (not shown) may be provided on the surface of the LED element so as to cover the LED element.

A gap 96 exists at the boundary between adjacent display panels 11 and 12, and a gap 98 exists at the boundary between adjacent display panels 12 and 13. Even if the gap between adjacent display panels is made as small as possible, a step may occur due to a slight difference in the height of the upper surface (element forming surface) of the support substrate 8. When external light from the viewing side or light from an LED element is irradiated onto a gap between panels or a stepped portion at a boundary, the light is diffusely reflected. Therefore, in the boundary portion, the intensity and color of the reflected light are different from those in other areas of the display array, which causes the boundary to be visually recognized (recognized).

As shown in FIG. 2, if the light shielding regions 56 and 58 of the adhesive sheet 2 are arranged on the boundary between adjacent display panels, it is possible to reduce the incidence of external light into the boundary region between the display panels. Further, even when the boundary area is irradiated with light from the display element 7, the reflected light is blocked by the light shielding areas 56 and 58, so that it is possible to reduce the amount of reflected light from the boundary area that is emitted toward the viewing side. Therefore, the boundaries (joints) between display panels are difficult to see (recognize) from the outside, and seamless display can be achieved. In addition, since a light-shielding area is provided in the adhesive sheet 2 used for bonding the display panels 11, 12, 13 and the front transparent plate 5, the distance from the image display panel to the light-shielding area is small, and the border between adjacent display panels is It can also efficiently block out light that is diffusely reflected.

The width of the light-shielding area of the adhesive sheet 2 may be appropriately set depending on the gap between display panels, the gap between adjacent pixels, etc., and is, for example, about 5 μm to 200 μm. When a gap exists between adjacent display panels, the width of the light-blocking area is preferably larger than the width of the gap between the panels. Further, the width of the light shielding area is preferably smaller than the distance L between display elements of adjacent display panels.

The visible light transmittance in the light-blocking area 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 viewpoint of efficiently emitting light from the display panel to the viewing side, the visible light transmittance in the light transmission region is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or less.

The adhesive sheet 2 is a layered adhesive. Adhesives include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride copolymers, modified polyolefins, epoxy-based polymers, fluorine-based polymers, rubber-based polymers such as natural rubber, synthetic rubber, etc. The base polymer can be appropriately selected and used. In particular, acrylic adhesives or rubber adhesives are preferred because they have excellent optical transparency and exhibit appropriate adhesive properties such as wettability, cohesiveness, and adhesiveness.

As the adhesive constituting the adhesive sheet 2, a photocurable adhesive may be used. The photocurable adhesive includes a base polymer and a photocuring agent, and further includes a photopolymerization initiator and/or a sensitizer. Photo-curing adhesives are soft before photo-curing, and have a high ability to follow irregularities and steps. Therefore, even the surface of the LED array that has gaps between adjacent LED elements is likely to be filled with the adhesive without any gaps. By photo-curing the adhesive after bonding the display panel and front transparent plate together, the reliability of adhesion can be increased.

From the viewpoint of improving the filling property to steps and unevenness, the light transmission region of the adhesive sheet 2 preferably has a shear storage modulus of 1×10 ⁶ Pa or less at a frequency of 1 Hz and 25° C., and 5×10 ⁵ Pa or less. It is more preferable that Note that the light-shielding region of the adhesive sheet 2 is not arranged on the display element of the display panel, and therefore may have different characteristics from the light-transmitting region. From the viewpoint of preventing contamination due to extrusion of the adhesive from the edges or transfer of the adhesive, 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, and 3 × 10 ⁴ Pa or more is more preferable. When the pressure-sensitive adhesive sheet is photocurable, it is preferable that the shear storage modulus before photocuring is within the above range.

The thickness of the adhesive sheet 2 is not particularly limited, but is, for example, about 10 to 500 μm, and may be about 20 to 300 μm. The light-transmitting area of the adhesive sheet 2 preferably has an adhesive force of 3 N/20 mm or more to the glass plate. When the adhesive sheet is photocurable, it is preferable that the adhesive strength of the adhesive to glass after photocuring is 3 N/20 mm or more. The adhesive strength is the test force obtained by laminating a 20 mm wide adhesive sheet to a glass plate and conducting a 180° peel test at a peeling rate of 300 mm/min.

The method of providing patterned light-shielding areas on the adhesive sheet 2 is not particularly limited. For example, the light-shielding property can be imparted by impregnating the adhesive in the light-shielding area with a dye or pigment to color it. The light-shielding region of the adhesive sheet 2 does not need to have light-shielding properties over the entire thickness direction of the adhesive sheet. For example, a light-shielding region may be formed by impregnating a dye or a pigment near the surface of the adhesive layer. In the light-shielding area of the adhesive sheet, the adhesive itself does not need to be colored. For example, a colored layer may be provided on the transparent adhesive layer by printing or the like to form a light-shielding area.

FIG. 4 is a cross-sectional view of an adhesive sheet 41 in which colored layers 66 and 68 are provided on one main surface of the transparent adhesive layer 21. In this adhesive sheet 41, the area where the colored layers 66 and 68 are provided is a light-shielding area. As the transparent adhesive layer 21, an adhesive layer made of the same adhesive as that described for the above-mentioned adhesive sheet is preferably used.

FIG. 5 is a cross-sectional view of the image display device 101 in which the colored layer forming surface of the adhesive sheet 41 is arranged to face the panel array. In this configuration, the colored layers 66 and 68 are arranged in the gaps between the display elements 7 of adjacent display panels, so that the boundaries between the display panels are difficult to see from the outside. In addition, the incidence of external light into the gaps between panels is suppressed, and furthermore, the colored layers 66 and 68 block light reflected at the boundary areas between adjacent panels, making it difficult to recognize the boundaries of the panel array. .

The colored layers 66 and 68 may be provided on either the first principal surface or the second principal surface of the transparent adhesive layer 21, or colored layers may be provided on both surfaces. If a colored layer is provided on the second principal surface (the surface facing the panel array), the colored layer will be placed directly above the image display panel or in the gap between adjacent image display panels, so that reflected light will not be reflected outside. This makes it difficult for the boundary area to be seen.

The method of 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 a colored layer directly on the transparent adhesive layer, a colored pattern may be printed on another base material and the colored layer may be transferred onto the adhesive layer.

The thickness of the colored layer is not particularly limited, and may be set according to the transmittance of the light-blocking area. In order to sufficiently reduce the light transmittance of the light shielding region, the thickness of the colored layer is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The thickness of the colored layer may be 50 μm or less, 40 μm or less, or 30 μm or less. Moreover, the thickness of the colored layer is preferably 50% or less of the thickness of the adhesive layer, more preferably 40% or less.

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

Examples of the plastic material constituting the transparent base film 81 include polyester resin, polyolefin resin, cyclic polyolefin resin, polyamide resin, polyimide resin, polyether ether ketone, polyether sulfone, and the like. The visible light transmittance of the transparent base film 81 is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The thickness of the transparent base film is, for example, about 10 to 100 μm.

The method of providing the colored layer on the transparent base film is not particularly limited, and various printing methods such as inkjet printing and screen printing can be applied. When a colored layer is formed on a transparent base film , compared to printing on an adhesive layer, there are advantages in that printing workability is excellent and printing accuracy is improved. The thickness of the colored layer, the transmittance of the light-shielding region, etc. are as described above for the form of FIG.

As the first transparent adhesive layer 23 and the second transparent adhesive layer 25, an adhesive layer made of the same adhesive as that described for the above-mentioned adhesive sheet is preferably used. 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 photocurable adhesive layers. It is preferable that both the first transparent adhesive layer 23 and the second transparent adhesive layer 25 have an adhesive force to the glass plate of 3 N/20 mm or more. At least the second transparent adhesive layer 25 bonded to the display panel preferably has an adhesive strength to glass of 3 N/20 mm or more.

FIG. 7 is a cross-sectional view of the image display device 103 arranged so that the second transparent adhesive layer 25 of the adhesive sheet 43 faces the panel array. In this configuration, the colored layers 76 and 78 provided on the second main surface of the transparent base film 81 suppress the incidence of external light into the gap between the panels and the light reflected at the boundary area between adjacent panels. This has a shielding effect, making it difficult to recognize the boundaries of the panel array.

The colored layers 76 and 78 may be provided on either the first principal surface or the second principal surface of the transparent base film 81, or colored layers may be provided on both surfaces. If a 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, making it difficult for reflected light to exit to the outside and making the boundary area more difficult to see. Become.

The thickness of the second transparent adhesive layer 25 is made smaller than the thickness of the first transparent adhesive layer 23 from the viewpoint of reducing the distance between the image display panel and the colored layer and suppressing the boundary area from being visible. You can. A photocurable adhesive is used as the second transparent adhesive layer 25 in order to fill the unevenness of the surface of the image display panel (for example, gaps between adjacent LED elements) with the adhesive without any gaps and to improve the adhesion reliability. May be used.

In the embodiment shown in FIG. 6, an example is shown in which a colored layer is provided on the surface of the transparent base film 81, but as in the adhesive sheet 44 shown in FIG. By coloring the resin, it may be used as a light-shielding area. The method of coloring the resin constituting the base film is not particularly limited. For example, a colored resin material may be used to form the light-blocking area, and a transparent resin material may be used to form the light-transmitting area, using 3D printing technology or the like. Furthermore, the resin constituting the base film may be colored by impregnating the transparent resin film with a dye or pigment.

The above explanation has focused on the case where the display panel is an LED panel (LED array), but the technique of using an adhesive sheet with a light-blocking area to make it difficult for the gaps between panels to be seen is applicable to display panels other than LED panels. can also be applied. Further, the arrangement of the plurality of display panels does not need to be in a tile shape (lattice shape), and can be changed as appropriate depending on the shape of the display panels, the shape of the array, etc. The pattern shape of the light-shielding area of the adhesive sheet may be designed to cover the boundary line between display panels.

1 Panel array 11 to 19 Display panel 7 Display element 8 Support substrate 2, 41, 43, 44 Adhesive sheet 21, 23, 25 Adhesive layer 31 to 39 Light transmission area 51, 53, 56, 58 Light blocking area 5 Front transparent plate 81 Transparent base film 66, 68, 76, 78 Colored layer (light shielding area)
100, 101, 103 Image display value increase

Claims (12)

A panel array in which multiple display panels are arranged side by side in the same plane;
a front transparent plate disposed on the viewing side surface of the panel array; and an adhesive sheet provided between the panel array and the front transparent plate,
A first main surface of the adhesive sheet is bonded to the transparent plate, and a second main surface of the adhesive sheet is bonded to the display panel,
The adhesive sheet includes a transparent adhesive layer and a patterned colored layer provided on a second main surface of the transparent adhesive layer that is the side to be bonded to the display panel,
The adhesive sheet has a light-transmitting region and a light-blocking region having a lower visible light transmittance than the light-transmitting region due to the colored layer being provided ,
An image display device, wherein a light-shielding region of the adhesive sheet is arranged on a boundary between adjacent display panels of the panel array. A panel array in which multiple display panels are arranged side by side in the same plane;
a front transparent plate disposed on the viewing side surface of the panel array; and an adhesive sheet provided between the panel array and the front transparent plate,
A first main surface of the adhesive sheet is bonded to the transparent plate, and a second main surface of the adhesive sheet is bonded to the display panel,
The adhesive sheet includes a transparent base film, a first transparent adhesive layer provided on the first main surface of the transparent base film, and a second transparent adhesive layer provided on the second main surface of the transparent base film. Equipped with an adhesive layer,
The first transparent adhesive layer is bonded to the transparent plate, and the second transparent adhesive layer is bonded to the display panel,
The pressure-sensitive adhesive sheet has a light-transmitting region and a light-blocking region whose visible light transmittance is lower than that of the light-transmitting region due to the transparent base film being colored ;
An image display device, wherein a light-shielding region of the adhesive sheet is arranged on a boundary between adjacent display panels of the panel array. The image display device according to claim 2 , wherein the transparent base film is colored by providing a colored layer on a light-shielding region of at least one main surface. The image display device according to claim 3 , wherein the colored layer is provided on a light-shielding region of the second main surface of the transparent base film. The image display device according to any one of claims 1 to 4 , wherein in the panel array, the plurality of display panels are arranged in a tile shape. The image display device according to claim 1 , wherein the display panel is an LED panel. The image display device according to any one of claims 1 to 6 , wherein the second main surface of the adhesive sheet has an adhesive force to glass of 3 N/20 mm or more. A transparent base film, a first transparent adhesive layer provided on the first main surface of the transparent base film, and a second transparent adhesive layer provided on the second main surface of the transparent base film. A double-sided adhesive sheet comprising :
A double-sided pressure -sensitive adhesive sheet having a light-transmitting area and a light-blocking area having a lower visible light transmittance than the light-transmitting area due to the transparent base film being colored . The double-sided pressure-sensitive adhesive sheet according to claim 8 , wherein the light-shielding region has a band-like region with a width of 5 to 200 μm. The double-sided pressure-sensitive adhesive sheet according to claim 8 or 9 , wherein the light shielding area has a grid pattern. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 10 , wherein the transparent base film is colored by providing a colored layer on a light-shielding region on at least one main surface. Used for bonding a panel array in which a plurality of display panels are arranged side by side in the same plane and a front transparent plate arranged on the viewing side surface of the panel array,
The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 11 , wherein the light-shielding region is arranged in a region corresponding to a boundary between adjacent display panels of the panel array.

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