JP7610089B2 - Display device - Google Patents

Description

The present invention relates to a display device having a flexible LED device and a porous material that covers at least a portion of the LED arrangement surface side of the LED device.

2. Description of the Related Art LED display devices, such as dot matrix display devices, which display information such as characters, symbols, and patterns by selectively emitting light from LED elements, are rapidly becoming popular.
Conventional LED display devices are widely used in which LED elements are mounted on a hard substrate that is substantially inflexible. However, such LED display devices have a low degree of freedom in design, and therefore their applications are limited.

Known LED display devices having flexibility that allows them to be deformed into a desired shape include those disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-233699 and Japanese Patent Application Laid-Open No. 2003-233699.
Patent Document 1 describes that the device can be wrapped around pillars or the like in underground malls and function as digital signage.
Patent Document 2 describes that in a flexible LED display device, in order to prevent the occurrence of wrinkles in the flexible substrate, an auxiliary substrate is laminated on the surface of the flexible substrate on which LED elements are not mounted.
The LED display devices described in these patent documents have excellent display effects when the LED elements are emitting light, but since the LED elements are conspicuous even when they are not emitting light, improvements in terms of design have been desired.

Patent No. 6738057 JP 2017-157837 A

The problem that this invention aims to solve is to obtain a display device with excellent design and flexibility, which makes the presence of the LED device unnoticeable when it is not emitting light, and provides an excellent display effect when the LED device is emitting light.

The present inventors have conducted extensive research to solve the above problems, and have found that the above problems can be solved by providing the following configuration, thereby completing the present invention.
Specifically, the following applies:
Item 1: A display device comprising an LED device having a plurality of LED elements solder-bonded onto one surface side of a flexible substrate, and a porous material covering at least a portion of the LED arrangement surface side of the LED device.
Item 2: The display device described in Item 1, wherein the LED device comprises a circuit provided on one surface of a flexible substrate, a circuit-side terminal provided on the circuit, and an LED element soldered to the circuit-side terminal by electromagnetic induction heating.
Item 3: The display device described in Item 1, wherein the LED device comprises a circuit provided on one surface of a flexible substrate, a circuit-side terminal provided on the circuit, a conductive pad provided on the other surface of the flexible substrate at a position corresponding to the circuit-side terminal, and an LED element soldered to the circuit-side terminal by electromagnetic induction heating.
Item 4: The LED device satisfies the following requirements (1) to (8):
(1) The thickness of the flexible substrate is 0.001 mm to 5.0 mm;
(2) The number of LED elements is 1/100 cm ² to 4,000/100 cm ² ,
(3) The circuit is formed by printing a conductive ink.
(4) The circuit is formed by plating after forming a plating resist.
(5) The circuit is formed by printing a plating seed layer and then plating it;
(6) The width of the circuit is 0.01 mm to 3.0 mm;
(7) The thickness of the circuit is 0.001 mm to 0.3 mm;
(8) It is possible to wrap the LED device around a cylinder with a diameter of 1 cm or more.
Item 4. The display device according to item 2 or 3, which satisfies at least one of the above requirements.
Item 5: The display device according to any one of items 1 to 4, wherein the porous material has an open area ratio of 3 to 80% and a visible light transmittance of 5% or more.
Item 6: A display device according to any one of items 1 to 5, wherein the LED device is formed by combining two or more sheets having a plurality of LED elements soldered onto one side of a flexible substrate and a connecting portion at at least a portion of an end of the flexible substrate into which at least some of the plurality of LED elements are fitted, and fitting the connecting portion and the LED elements together.
Item 7: The LED device and the porous material are bonded to one side of a flexible substrate by a double-sided adhesive sheet having recesses or holes corresponding to at least some of the LED elements soldered to one side of the flexible substrate. A display device according to any one of items 1 to 6.

The present invention provides a display device that is excellent in design and flexibility, that makes the presence of an LED device unnoticeable when the LED device is not emitting light, and that provides an excellent display effect when the LED device is emitting light.
The display device of the present invention can be a display device with excellent design without impairing the aesthetic appearance of buildings or the scenery in towns because its LED device is not noticeable when it is not emitting light. Furthermore, because it has excellent flexibility, it can be installed by wrapping it around a traffic sign pole or a roadside tree, or installed on a curtain or banner. It can be used as a display device at any time, and because its presence is not noticeable when it is not used as a display device, it can blend in with the scenery.

FIG. 1 is a schematic diagram of a display device according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the display device of FIG. FIG. 1 is a schematic diagram of a display device according to another embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of the display device of FIG. 3 . 1 is a schematic diagram of a display device according to a third embodiment of the present invention; FIG. 6 is a schematic exploded view of the display device of FIG. FIG. 6 is a schematic cross-sectional view of the display device of FIG.

A preferred embodiment of the display device according to the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiment. In addition, appropriate modifications can be made without departing from the scope of the effects of the present invention. Note that the use of the same reference numbers in different drawings indicates similar or identical items or features.

1, a display device D according to an embodiment of the present invention includes an LED device L and a porous material 1. The LED device L includes a flexible substrate 2 and a plurality of LED elements 3 soldered onto one surface of the substrate 2.
3, the display device D according to another embodiment of the present invention may be formed by coupling two LED devices La and Lb, each of which has a plurality of LED elements 3 soldered onto one surface of a flexible substrate 2 and an LED device connector 22 into which at least some of the LED elements 3 are fitted, at least at a portion of an end of the flexible substrate 2, by fitting the LED device connector 22 with the LED elements 3. The number of connected LED devices may be two or more.
As shown in FIG. 5 , a display device D according to another embodiment of the present invention may be configured such that the LED device L and the porous material 1 are bonded together by a double-sided adhesive sheet 7 having an LED element fitting portion 71 corresponding to at least a portion of a plurality of LED elements 3 solder-bonded onto one surface of a flexible substrate 2.
The LED device L, the porous material 1 and the display device D will be described in detail below.

[LED Device]
<Flexible Substrate>
The flexible substrate 2 in the LED device L is made of an insulating material. For example, the insulating material may be a resin film, paper, cloth, or the like, as long as it is flexible. It is preferable to have a resin film, since it is easy to impart the desired physical properties.
Examples of the resin that can be used to form the resin film include, without particular limitation, polyester-based resins, polyamideimide-based resins, polyimide-based resins, polyamide-based resins, polyether ether ketone-based resins, polysulfone-based resins, polyphenylene sulfide-based resins, polysulfone-based resins, polyether sulfone-based resins, fluororesins, ABS resins, polyphenylene oxide-based resins, acrylic resins, polycarbonate-based resins, polybutadiene-based resins, polyurethane-based resins, polyolefin-based resins, polyvinyl chloride-based resins, polystyrene-based resins, and the like.
Furthermore, the resin may be a mixture of these resins, and may contain functional materials such as colorants, ultraviolet absorbing agents, infrared reflective materials, and light scattering particles, as necessary.
Furthermore, the material may be a laminate formed by combining any of these resin films, papers, and cloths.

The thickness of the flexible substrate 2 is not particularly limited as long as it has flexibility, and may be, for example, 0.001 mm to 5.0 mm. From the viewpoints of strength and flexibility, the thickness is preferably 0.01 mm to 3.0 mm, and more preferably 0.02 mm to 1.0 mm.
The optical properties of the flexible substrate 2 are not particularly limited and may be any of colorless and transparent, colored and transparent, semi-transparent, and opaque, and can be appropriately selected depending on the application and installation location of the display device.
The shape of the flexible substrate 2 is not particularly limited and may be polygonal or circular. In addition, the flexible substrate 2 may have a three-dimensional structure by combining the same or different shapes.

(Circuit and circuit side terminal)
At least a circuit and circuit side terminals 21 (hereinafter, the circuit and the circuit side terminals 21 may be collectively referred to as wiring) provided on one side of the flexible substrate 2 on which the LED elements 3 are mounted by soldering are formed. Furthermore, the ends of the circuit have connection terminals for connecting to a power source or a control device.
The wiring is made of one or more conductive materials selected from the group consisting of metal materials such as gold, silver, copper, aluminum, nickel, and chromium, conductive polymers, and conductive carbon.
The wiring can be formed by one or more methods selected from the group consisting of screen printing, inkjet printing, gravure offset printing, flexographic printing, etching, metal vapor deposition, plating, silver salt, and the like.

The width of the wiring, particularly the circuit, is preferably 0.01 mm to 3.0 mm, more preferably 0.03 mm to 2.0 mm, and even more preferably 0.1 mm to 1.0 mm.
If the width of the wiring is less than 0.01 mm, it may be difficult to form the wiring, and the wiring may break due to being unable to withstand the generated stress when the display device D and/or the LED device L are deformed. If the width of the wiring exceeds 3.0 mm, when the display device D is formed using a transparent flexible base material 2, the wiring may be conspicuous and may impair the design.

The wiring, especially the circuit, preferably has a thickness of 0.001 mm to 0.3 mm.
In the LED device L of the present invention, the solder joint 4 to which the LED element 3 is soldered is rigid and does not have flexibility, and the part to which the LED element 3 is not soldered is bent to exhibit flexibility. When the display device D and/or the LED device L of the present invention is bent, stress is applied to the solder joint 4 to which the LED element 3 is soldered. For this reason, if the thickness of the wiring is less than 0.001 mm, the wiring may not be able to withstand the generated stress when the display device D and/or the LED device L is deformed, and peeling or destruction may occur between the flexible substrate 2 and the wiring near the solder joint 4 of the LED element 3. On the other hand, if the thickness of the wiring exceeds 0.3 mm, the wiring may become more rigid, and the flexibility of the display device D and/or the LED device L may decrease. The thickness of the wiring is more preferably 0.003 mm to 0.2 mm, even more preferably 0.003 mm to 0.1 mm, even more preferably 0.003 mm to 0.08 mm, and most preferably 0.005 mm to 0.06 mm.

In the present invention, the wiring provided on one surface of the flexible substrate 2 can be formed by printing a conductive ink. As the printing method, screen printing, inkjet printing, and gravure offset printing are particularly preferable. By forming the circuit by printing, it becomes possible to mass-produce it cheaply and easily.
In the present invention, the wiring provided on one side of the flexible substrate 2 can be formed by forming a plating resist by printing or the like and then plating, or by printing a plating seed layer and then plating. Such methods also allow for easy mass production at low cost.

(LED element)
In the LED device L of the present invention, a plurality of LED elements 3 are soldered onto one surface of a flexible substrate 2 .
The number of LED elements 3 is not particularly limited and can be appropriately determined according to the dot density required for the LED device L. For example, the number of LED elements 3 can be set to 1/100 cm ² to 4000/100 cm ² , preferably 30/100 cm ² to 3000/100 cm ² , more preferably 60/100 cm ² to 3000/100 cm ² , and even more preferably 80/100 cm ² to 2500/100 cm ² .
The LED elements 3 may be provided at a constant pitch on one surface of the flexible substrate 2. Alternatively, the LED elements 3 may be provided in any arrangement on one surface of the flexible substrate 2.

The LED element 3 is not particularly limited, and any LED element such as a single-color LED element or a full-color LED element can be used. In the present invention, it is preferable to use a full-color LED with a built-in control unit from the viewpoint of the expressive power of the display device D. A full-color LED has at least three LED elements of red (R), green (G), and blue (B) and a control unit in one LED element component. The control unit is configured to selectively emit light from one or more of the LED elements of each color based on an external command signal, thereby enabling emission of any color tone.
A signal generated by an external main control unit is sent to each of the full-color LEDs built into the control unit to control the LEDs, so that the LEDs function as a color display.
By increasing the dot density of the LEDs, a more detailed display can be achieved, but flexibility may decrease.

<Soldering>
In the present invention, the means for soldering onto one side of the flexible substrate is not particularly limited and can be appropriately determined in consideration of the physical properties of the solder used, such as the melting point, the heat resistance of the flexible substrate 2 and the LED element 3, workability, and the like.
For example, an LED element may be placed on the circuit-side terminal via solder, and the circuit-side terminal and the electronic component-side terminal may be soldered together by heating the LED element in this state to melt the solder. As a result, for example, as shown in Figures 2(a) and 2(b), the circuit-side terminal 21 provided on the circuit formed on one surface of the flexible substrate 2 and the LED element-side terminal 31 of the LED element 3 are connected together via the solder joint 4.
The type of solder used for soldering is not particularly limited. In the present invention, it is preferable to use lead-free solder from the viewpoint of environmental aspects, etc. For example, solders ranging from high-temperature solders (SnAgCu-based solders, melting point of about 220° C., etc.) to low-temperature solders (SnBi-based solders, melting point of about 140° C., etc.) can be used.

As a means for soldering, for example, solder flow, solder reflow, soldering using electromagnetic induction heating technology (IH technology), or the like can be used.
In particular, when joining a large number of LED elements to increase the dot density, workability can be improved by using a heat-resistant flexible base material such as a polyimide resin and using a method such as solder reflow.
Furthermore, when a polyester resin, such as polyethylene terephthalate resin (PET resin), which does not have a very high heat resistance, is used as the flexible substrate, a soldering means using electromagnetic induction heating technology (IH technology) can be used. A soldering means using electromagnetic induction heating technology (IH technology) (soldering means using electromagnetic induction heating) generates Joule heat by passing an eddy current through a conductive material, and can cause the conductive material to self-heat.
As a soldering means using electromagnetic induction heating technology (IH technology), for example, the means described in the above-mentioned Patent Document 1 can be used.

For example, when using a flexible substrate 2 that is not very heat resistant, as shown in Fig. 2(b), a conductive pad 5 is provided at a position corresponding to a circuit terminal 21 provided on one surface of the flexible substrate 2 on the other surface of the flexible substrate 2, so that the LED element 3 can be reliably soldered onto the circuit terminal 21 by electromagnetic induction heating technology (IH technology). This allows the LED element 3 to be easily positioned at any desired position.
In the LED device L, the conductive pad 5 provided on the other side of the flexible substrate 2 has a larger volume than the circuit-side terminals 21, the solder, etc., and therefore generates a large amount of heat due to electromagnetic induction heating. Heat generated in the conductive pad 5 by electromagnetic induction heating is transferred to the solder through the flexible substrate 2 and the circuit-side terminals 21, so that the solder is efficiently heated and melted, and the LED element 3 is soldered. At this time, the heat generated in the conductive pad 5 by electromagnetic induction heating is quickly transferred to the solder, which has a high thermal conductivity, and the temperature rise of the flexible substrate 2 is suppressed, so that the flexible substrate 2 can be made of a non-heat-resistant material.

The conductive pad is formed of a metal-based material containing one or more metal elements selected from the group consisting of gold, silver, copper, aluminum, nickel, palladium, chromium, etc. The conductive pad 5 can be formed by the same method as the wiring. The conductive pad 5 has a size that includes the circuit side terminal 21 located on the opposite surface of the flexible substrate 2, and the shape is not particularly limited, but can be a circle, a polygon, etc. For example, it can be a circle with a diameter of 3 mm. The thickness of the conductive pad 5 is preferably 0.001 mm to 0.3 mm, more preferably 0.003 mm to 0.2 mm, and even more preferably 0.005 mm to 0.06 mm, the same as the wiring.
The conductive pad 5 increases the heat generated by electromagnetic induction heating, and can particularly increase the temperature in the area in which the conductive pad 5 is formed, making it possible to perform solder bonding more reliably.

Furthermore, even if the flexible substrate 2 does not have a conductive pad 5 on the other side, as shown in FIG. 2(a), for example, by lengthening the heating time, increasing the current, reducing the resistance, etc., the heat generated inside the circuit side terminals 21 and the solder, etc. by electromagnetic induction heating can be used to perform solder joining at the solder joint portion 4.
Furthermore, if the flexible substrate 2 and the LED element 3 are heat resistant, the entire assembly can be heated using a reflow furnace or the like for soldering.

<Characteristics of LED devices>
The LED device L constituting the display device D of the present invention has flexibility. For example, the LED device L can be wrapped around a cylinder having a diameter of 1 cm or more. Here, being capable of being wrapped means that even after being wrapped around a cylinder, damage to the function of the LED device, such as breakage of wiring or peeling or falling off of the LED element 3, does not occur.
In the present invention, it is possible to wind the wire around a cylinder having a diameter of 1 cm or more, for example, a diameter of 10 cm or more. It is also possible to follow a corrugated plate or the like having a series of arcs having a diameter of 1 cm or more.

[Porous materials]
The porous material 1 in the display device is not particularly limited as long as it has flexibility. Examples include cloth (woven fabric, nonwoven fabric, knitted fabric), net, paper, porous film, resin foam, punching material (punching metal, perforated (hole) resin film, mesh, etc.) For example, when cloth is used as the porous material 1, it can be used as a curtain, a banner, a curtain, a wall cloth, a flag, clothing, etc.
When a resin foam, a porous film, or a punched material is used, it can be used as a building material, an interior material, a signboard, or the like.
The porous material 1 can be printed or the like as necessary to improve its design.

In the present invention, the porous material 1 preferably has an open area ratio of 3 to 80%, more preferably 5 to 75%, and further preferably 10 to 70%. The open area ratio means the ratio of the area of the pores (openings) formed on the surface of the porous material 1.
If the opening area ratio is less than 3%, there is a risk that the porous material 1 will not substantially exhibit the characteristics of the porous material 1. Furthermore, if the opening area ratio exceeds 80%, there is a risk that the porous material 1 will be difficult to form and may not be practical from the standpoint of strength, etc.

In the present invention, the porous material 1 preferably has a visible light transmittance of 5% or more. In the present invention, the wavelength range of visible light is 360 nm to 830 nm. The visible light transmittance is determined by a test method specified in ISO 9050 using a spectrophotometer. For example, it can be determined in accordance with JIS S 3107 (note that in JIS S 3107, a resin film is attached to glass and measured, but in the present invention, the porous material 1 itself is measured without being attached to glass).

If the visible light transmittance is less than 5%, it may become difficult to visually recognize the light emitted from the LED element 3 in the LED device L through the porous material 1 .
The upper limit of the visible light transmittance may be, for example, 80%. If the visible light transmittance exceeds 80%, the LED device L located below the porous material 1 can be easily recognized by the naked eye, which may result in poor design.
In the present invention, the visible light transmittance of the porous material 1 is more preferably 7 to 75%, and further preferably 10 to 70%.

[Display device configuration and uses]
In the present invention, as shown in FIG. 3, a large-screen LED device L can be formed by connecting two or more LED devices La, Lb, . . .
These LED devices La, Lb... comprise, for example, a plurality of LED elements 3 solder-joined onto one side of the flexible substrate 2, and an LED device connecting portion 22 at at least a portion of the end of the flexible substrate 2, into which at least a portion of the plurality of LED elements 3 can be fitted.
Two or more LED devices La and Lb can be connected, for example, as shown in Figures 3 and 4, by fitting a plurality of LED elements 3 solder-joined on one side of a first LED device La into an LED device connecting portion 22 provided on an end of a flexible substrate 2 of a second LED device Lb.
With this configuration, it is possible to easily form a display device D or an LED device L having a large screen.

The LED device connecting portion 22 is not particularly limited as long as it has a shape that can fit the LED element 3, and examples of the shape include a hole and a recess. For example, it is preferable that the LED device 22 is a hole, which is convenient. The shape of the hole is not particularly limited as long as the LED element 3 can fit therein, and examples of the shape include a circle, a polygon, an ellipse, etc.
When two or more LED devices La, Lb, ... are connected to each other, it is preferable to form an LED device connection part bonding layer 6 that bonds the respective LED devices. The LED device connection part bonding layer 6 can be composed of an adhesive, a bonding agent, an adhesive sheet, etc., and can ensure the connection between the LED devices in the two or more LED devices La, Lb, .... As the adhesive or bonding agent, for example, a silicone resin-based, urethane resin-based, polyolefin resin-based, acrylic resin-based, rubber-based, epoxy resin-based, etc. can be used. By using an elastic material, it is possible to provide the display device D in a place that is subjected to impact, such as a floor.
By constructing the LED device connection portion bonding layer 6 from an adhesive, glue, adhesive sheet, etc., the LED elements 3 are fixed to the LED device connection portion 22 and become less likely to move when two or more LED devices La, Lb, ... are connected, so that the arrangement of the LED elements 3 can be prevented from being disturbed and the awkward feeling in the display portion caused by the connection of two or more LED devices La, Lb, ... can be reduced.

The large-screen LED device formed by connecting the LEDs retains flexibility even after connecting, and can be handled in the same way as an LED device formed on a single large flexible substrate.
Furthermore, if the LED device connecting portion bonding layer 6 is made of a removable adhesive, even if a dot is missing due to a malfunction of the LED element 3, only the LED device L on which the corresponding LED element 3 is mounted needs to be replaced, which is excellent in maintainability, etc. As the removable adhesive, silicone resin-based, urethane resin-based, polyolefin resin-based, acrylic resin-based, etc. can be used without any particular restrictions.

In the present invention, the LED device L and the porous material 1 may or may not be fixed to each other. Alternatively, the LED device 3 may be enclosed in the porous material 1 formed into a bag shape.
When the LED device L and the porous material 1 are fixed to each other, for example, a pressure sensitive adhesive, a bonding agent, an adhesive sheet, etc. may be used. In addition, means such as sewing or fitting may be used.
When the LED device L and the porous material 1 are fixed to each other, they may be fixed partially or entirely.

In the present invention, when fixing the LED device L and the porous material 1, it is preferable to use a double-sided adhesive sheet 7 having an LED element fitting portion 71 corresponding to at least a part of the multiple LED elements 3 solder-joined on one side of the flexible substrate 2, as shown in Figures 5 to 7.
By using such double-sided adhesive sheet 7, it is possible to prevent the occurrence of contamination due to the adhesive or pressure-sensitive adhesive protruding, and it is also possible to easily fix the sheet by a simple means.

When the LED device L and the porous material 1 are not fixed, they may simply be sandwiched between them. For example, when fixing a porous material 1 that has been decorated by printing, dyeing, embroidery, etc. as necessary to a wall or the like, the LED device L may be sandwiched between the porous material 1 and the wall. When the display device D of the present invention is used as a shop curtain or a banner, the porous material 1 such as a cloth that has been decorated by printing, dyeing, embroidery, etc. and the LED device L may be suspended.
Furthermore, the porous material 1 and the LED device L can be fixed to each other by wrapping them around a pillar or the like without fixing them to each other.

The display device D of the present invention can be used as a conventionally known LED light-emitting device. The display device D of the present invention can be used for a wide variety of purposes, similar to the LED light-emitting device. Furthermore, the display device D of the present invention can be used for purposes that utilize its flexibility. Examples of uses of the display device D of the present invention include noren curtains, vertical curtains, curtains, wall cloth, flags, clothing, interior materials, buildings, signs, toys, gaming machines (pachinko machines, slot machines, etc.), game machines, lighting fixtures, tiles, medical equipment, inspection equipment, various industrial machines, transportation equipment, electrical equipment, agricultural equipment, fishing equipment, etc. In particular, the display device D of the present invention can be made to blend into the scenery without making its presence felt when the LED device L is not emitting light.
In addition, in emergencies and disasters such as accidents, fires, earthquakes, tsunamis, and floods, and during events such as concerts and festivals, the display device D (LED device L) in vehicles, on the streets, inside buildings, etc., and in some cases multiple display devices D (LED devices L) can be controlled and linked to display information, making it extremely useful for evacuation, guidance, warnings, etc.
Furthermore, by making it into clothing, it can be developed into safety vests for security guards, and goods for concerts and sporting events.

The power source of the display device D of the present invention is not particularly limited, and may be a battery, a household power source, a vehicle, etc. For example, the battery may be a dry cell or a lithium ion battery, and in particular, a lithium ion battery is preferred because the power source can be repeatedly used by charging.
The present invention can be developed as a product incorporating a power source such as a battery, and further including a control device and a control program for displaying necessary information such as characters and symbols.

Although the present invention has been described in detail above, various modifications can be made in the above configuration without departing from the scope of the present invention. Therefore, all matters contained in the above description or shown in the accompanying drawings should be interpreted as illustrative.

D display device L LED device La first LED device Lb second LED device 1 porous material 2 flexible substrate 21 circuit side terminal 22 LED device connecting portion 3 LED element 31 LED element side terminal 4 solder joint portion 5 conductive pad 6 LED device connecting portion bonding layer 7 double-sided adhesive sheet 71 LED element fitting portion

Claims (3)

A display device comprising: an LED device having a plurality of LED elements soldered onto one surface of a flexible substrate; and a porous material covering at least a portion of the LED arrangement surface of the LED device,
the LED device comprises a circuit provided on one surface of a flexible base material, a circuit-side terminal provided on the circuit, a conductive pad provided on the other surface of the flexible base material at a position corresponding to the circuit-side terminal, and an LED element soldered to the circuit-side terminal by electromagnetic induction heating;
The LED device satisfies the following requirements (a) to (c):
(a) the thickness of the flexible substrate is 0.001 mm to 5.0 mm;
(b) the thickness of the circuit is 0.001 mm to 0.3 mm;
(c) The LED device can be wrapped around a cylinder with a diameter of 1 cm;
and
The LED device is a large-screen device that is made by combining two or more sheets having a plurality of LED elements soldered onto one surface of a flexible substrate and a connecting portion at least at a portion of an end of the flexible substrate into which at least some of the LED elements are fitted, and the connecting portion is fitted into the LED elements at the end of the flexible substrate,
The porous material has an open pore area ratio of 5% or more and 75% or less and a visible light transmittance of 10% or more and 70% or less,
In the display device, when the LED device is not emitting light, the LED device cannot be easily recognized by visual inspection .
The display device. The LED device satisfies the following requirements (d) to (h):
(d) the number of LED elements is 1/100 cm ² to 4000/100 cm ² ,
(e) the circuit is formed by printing a conductive ink;
(f) the circuit is formed by plating after forming a plating resist;
(g) the circuit is formed by printing a plating seed layer and then plating;
(h) the width of the circuit is 0.01 mm to 3.0 mm;
The display device according to claim 1 , which satisfies at least one of the above requirements. 3. The display device according to claim 1, wherein the LED device and the porous material are bonded together by a double-sided adhesive sheet having recesses or holes corresponding to at least some of the LED elements soldered onto one side of a flexible substrate.

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