JP2017028190A - Flexible substrate for led element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible substrate for an LED element, which can avoid decrease in flexibility intrinsic to the flexible substrate due to a chromatic layer formed on a surface of the flexible substrate and which can reliably develop preferable characteristics intrinsic to the flexible substrate such as flexibility in designing and high productivity.SOLUTION: A flexible substrate 1 for an LED element includes a substrate film 11 having flexibility, a metal wiring part 13 formed on one surface of the substrate film 11, and a chromatic ink layer 15 that is formed in a region excluding a region for mounting an LED element on the substrate film 11 and the metal wiring part 13 and encloses the region for mounting an LED element. Each chromatic ink layer 15 is disposed corresponding to the region for mounting an LED element and spaced from others.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a flexible substrate for an LED element.

  In recent years, various LED display devices such as a liquid crystal display using an LED element as a backlight light source and a dot matrix display device that displays information such as desired characters and symbols by selectively emitting light from the LED element have been rapidly used. Is popular. In these LED display devices, in order to mount an LED element as a light source, it is usually a circuit board for various LED elements composed of a support substrate and a wiring portion (also referred to as “LED element substrate” in this specification). Say) is used.

  Conventionally, a rigid substrate in which an LED element is mounted on a rigid substrate made of a glass epoxy plate or the like has been widely used as the LED element substrate. However, in recent years, LED display devices have become larger and display screens have become more diversified. In recent years, a flexible substrate in which a metal circuit is formed on a flexible substrate such as a resin sheet has been developed (see Patent Document 1). . Since flexible substrates have higher design freedom and higher productivity than rigid substrates, further expansion is expected in the future.

  On the other hand, in the circuit boards for LED elements used in various LED display devices, various colored layers intended to improve optical characteristics are usually provided around the LED element mounting area. For example, a reflective layer for the purpose of increasing the light use efficiency in a liquid crystal display, or a black layer for the purpose of improving display contrast in a dot matrix display device.

  As a representative example of the colored layer for the purpose of improving the optical characteristics, the reflectance is improved by giving a constant thickness to the white resist layer formed on the substrate by printing. The thing which demonstrates a function (refer patent document 2) is mentioned.

  However, for example, when the white resist layer as described above is formed on the entire surface of the flexible substrate, the white resist layer that does not have sufficient flexibility may reduce the flexibility of the flexible circuit board, or This causes a problem that the white resist layer breaks without being able to follow the flexibility of the circuit board.

JP 2012-59867 A JP 2012-124358 A

  In the present invention, the colored layer formed on the surface of the flexible substrate avoids a decrease in the original flexibility of the flexible substrate, and more reliably satisfies the desirable characteristics inherent in the flexible substrate such as design freedom and high productivity. It aims at providing the flexible substrate for LED elements which can be made to express in.

  As a result of intensive studies, the present inventors have arranged the colored ink layer separately in the peripheral area of the LED element mounting region when arranging the colored ink layer on the surface of the flexible substrate for the LED element. As a result, it has been found that the effect of improving the desired optical characteristics can be ensured, and that the inherent flexibility of the flexible substrate can be avoided, and the present invention has been completed. Specifically, the present invention provides the following.

  (1) A region for LED element mounting in a region excluding a substrate film, a metal wiring part formed on one surface of the substrate film, and a LED element mounting region on the substrate film and the metal wiring part And a colored ink layer formed so as to surround the LED element, and each colored ink layer is disposed separately for each LED element mounting region.

  (2) The flexible substrate according to (1), wherein the surface coverage by the colored ink layer on the surface of the substrate film is less than 25%.

  (3) The flexible substrate as described in (1) or (2) whose thickness of the said colored ink layer is 5 micrometers or more and 100 micrometers or less.

  (4) The flexible substrate according to any one of (1) to (3), wherein the colored ink layer has a light reflectance in a visible light region of 90% or more.

  (5) The colored ink layer according to any one of (1) to (3), wherein a ΔL * value measured according to a D65 light source and a 10 ° viewing angle according to JIS-Z8722 is 60 or less. Flexible substrate.

  (6) The flexible film according to any one of (1) to (5), wherein an optical film in which an opening is formed in a portion corresponding to the LED element mounting region is further laminated on the colored ink layer. substrate.

  (7) An LED display device comprising an LED element mounted on the flexible substrate according to any one of (1) to (6).

  According to the present invention, the colored layer formed on the surface of the flexible substrate avoids the decrease in flexibility inherent in the flexible substrate, and the flexible substrate inherent favorable characteristics such as design freedom and high productivity, The flexible substrate for LED elements which can be made to express more reliably can be provided.

It is a disassembled perspective view with which it uses for description of a structure of the LED mounting module formed by mounting an LED element on the flexible substrate for LED elements of this invention. It is the elements on larger scale of the flexible substrate for LED elements of this invention. It is a fragmentary sectional view of the LED mounting module of FIG. FIG. 2 is a partially enlarged plan view schematically showing a state when a peripheral portion of an LED element mounting region of the LED mounting module of FIG. 1 is viewed from the upper surface side. It is a perspective view which shows typically the outline of the layer structure of the LED display apparatus which uses the LED mounting module of FIG.

  Hereinafter, embodiments of a flexible substrate for an LED element of the present invention (hereinafter also simply referred to as “flexible substrate”) and an LED display device in which the LED element is mounted on the flexible substrate will be sequentially described. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

<Flexible substrate>
As shown in FIGS. 1 to 3, the flexible substrate 1 is a circuit board for an LED element in which a metal wiring portion 13 is formed on the surface of a flexible substrate film 11. In addition, as shown in FIG. 1, the flexible substrate 1 is usually further laminated with an optical film 16 for the purpose of improving optical characteristics in a region on the metal wiring portion 13 excluding a portion to be an LED element mounting region. Used. Here, the “LED element mounting region” in this specification is a region composed of a portion to be joined to the metal wiring portion 13 of the LED element 2 in the flexible substrate 1 and its peripheral portion. It means the area directly below the space that is at least necessary as an optical path to the outside of the light emitted from the LED element.

  Such a flexible substrate 1 constitutes the LED mounting module 10 by mounting the LED element 2 thereon. The LED mounting module 10 is disposed as an LED light source, for example, as the light source of the LED display device 100 as shown in FIG.

  There is no particular limitation on the size of the flexible substrate 1. Since the flexible substrate 1 has a high degree of freedom in design, for example, it can be easily installed in an LED display device having a large display screen with a diagonal length of 32 inches or more, more preferably 65 inches or more.

  Moreover, the flexible substrate 1 has flexibility and extremely excellent shape followability to various installation surfaces. Therefore, it can be very preferably used for various LED display devices having display screens including curved surfaces having various shapes.

  The flexible substrate of the present invention has, for example, a multilayer circuit board in which metal wiring portions are respectively formed on both surfaces of the substrate film 11 and are electrically connected through through holes penetrating the inside of the substrate film 11. It may be.

[Substrate film]
The substrate film 11 is not particularly limited, but is preferably made of a thermoplastic resin. The substrate film 11 is required to have high heat resistance and insulation. Preferable examples of such material resins include polyimide (PI), polyethylene naphthalate (PEN), amorphous polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyetherimide, fluororesin, A liquid crystal polymer etc. can be mentioned. Among these, polyethylene naphthalate (PEN) whose heat resistance and dimensional stability are improved by performing a heat resistance improvement treatment such as an annealing treatment can be particularly preferably used. In addition, polyethylene terephthalate (PET) whose flame retardancy is improved by addition of a flame retardant inorganic filler or the like can also be selected as a material resin for the resin base.

  As the resin for forming the substrate film 11, a resin having a thermal shrinkage start temperature of 100 ° C. or higher, or a resin having improved heat resistance so that the temperature becomes 100 ° C. or higher by the above-described annealing treatment or the like is used. preferable. Usually, the peripheral portion of the element may reach a temperature of about 90 ° C. due to heat generated from the LED element. From this viewpoint, it is preferable that the thermoplastic resin forming the substrate film has heat resistance equal to or higher than the above temperature. In this specification, “thermal shrinkage start temperature” means that a sample film made of a thermoplastic resin to be measured is set in a TMA apparatus, a load of 1 g is applied, and the temperature is increased to 120 ° C. at a rate of temperature increase of 2 ° C./min. Measure the amount of shrinkage (in%) at that time, output this data and record the temperature and amount of shrinkage, read the temperature that deviates from the 0% baseline due to shrinkage, and heat shrink the temperature This is the starting temperature. In addition, the “thermosetting temperature” in the present specification is the measurement and calculation of the temperature at the rising position of the thermosetting reaction when the thermosetting resin to be measured is heated, and that temperature is the thermosetting temperature. .

Further, the substrate film 11 is required to be a resin having high insulating properties. In general, the substrate film 11 has a volume resistivity of preferably 10 ¹⁴ Ω · cm or more, and more preferably 10 ¹⁸ Ω · cm or more.

  The thickness of the substrate film 11 is not particularly limited, but is approximately 10 μm to 500 μm, preferably 30 μm to 200 μm, from the viewpoint of having heat resistance and insulating properties and a balance of manufacturing costs. Preferably there is. Also, the thickness is preferably within the above-mentioned thickness range from the viewpoint of maintaining good productivity when manufacturing by the roll-to-roll method.

[Adhesive layer]
As shown in FIG. 3, the formation of the metal wiring portion 13 on the surface of the flexible substrate 1 is preferably performed by a dry laminating method with an adhesive layer 12 interposed. As the adhesive forming the adhesive layer 12, a known resin adhesive can be used as appropriate. Of these resin adhesives, urethane-based, polycarbonate-based, or epoxy-based adhesives can be particularly preferably used.

[Metal wiring section]
The metal wiring portion 13 is a wiring pattern formed on a conductive substrate such as a metal foil on at least one surface of the substrate film 11 in the flexible substrate 1. The arrangement of the metal wiring part 13 is preferably an arrangement in which the LED elements 2 can be mounted in a matrix at a desired pitch. However, the arrangement is not limited to a specific arrangement in both the horizontal direction and the vertical direction.

  Examples of the metal used as the material of the metal wiring part 13 include metal foils such as aluminum, gold, silver, and copper. The thickness of the metal wiring portion 13 may be set as appropriate according to the magnitude of the withstand current required for the flexible substrate 1 and is not particularly limited, but examples include a thickness of 10 μm to 50 μm. If the metal layer thickness is less than the above lower limit value, the influence of thermal shrinkage of the substrate is large, and the warp after the treatment is likely to increase during the solder reflow process, so the thickness of the metal wiring part 13 may be 10 μm or more. preferable. On the other hand, when the thickness is 50 μm or less, preferable flexibility of the flexible substrate 1 can be maintained, and a reduction in handling property due to an increase in weight can be prevented.

[Solder layer]
In the flexible substrate 1, when the metal wiring portion 13 and the LED element 2 are bonded, bonding is performed via the solder layer 14. Details of the soldering method will be described later, but can be roughly classified into either a reflow method or a laser method.

[Colored ink layer]
The colored ink layer 15 formed mainly to improve the optical characteristics of the flexible substrate 1 has the LED element mounting area on the surface of the metal wiring portion 13 and the substrate film 11 except for the LED element mounting area. In a surrounding manner, it is formed with colored ink such as thermosetting ink.

  As illustrated in Patent Document 2, when a colored ink layer is formed on the surface of a conventional flexible substrate, the colored ink layer is integrally formed on substantially the entire surface except for the LED mounting area on the substrate. It was. On the other hand, in the flexible substrate 1 of the present invention, the colored ink layer 15 is provided for each LED mounting region with respect to the LED element mounting regions existing on the flexible substrate 1 as shown in FIGS. In addition, the respective colored ink layers 15 are arranged separately from other adjacent colored ink layers in such a manner as to individually surround each region.

  The planar shape of the individual colored ink layers 15 arranged separately is not limited to a specific shape as long as the arrangement as described above can be realized. However, as shown in FIG. 2 and FIG. 4, the planar shape of each colored ink layer 15 is the same donut shape, specifically, a circular ink non-stacked portion including the same region for each LED element mounting region However, it is preferable that the shape be present on the flexible substrate 1. By unifying the shapes of the individual colored ink layers in this way, it is possible to ensure the uniformity of the optical effects imparted to the LED elements 2 included in the individual colored ink layers 15. Moreover, since it can shape | mold by printing of the same pattern, the fall of productivity by arrangement | positioning of the colored ink layer in this invention can also be stopped to the minimum.

  In addition, about arrangement | positioning of the individual colored ink layer 15 arrange | positioned spaced apart, each colored ink layer 15 includes the LED element mounting area | region corresponding to planar view, and each colored ink layer It is preferable that the center of 15 and the center of the corresponding LED element mounting region are arranged at the same position. Specific examples of the arrangement include an example in which each colored ink layer 15 and the LED element mounting region included in the above-described embodiment are circular and are arranged concentrically with each other. With such an arrangement, it is possible to minimize the area of each colored ink layer 15 that is necessary to develop the effect of improving desired optical characteristics.

  Regarding the areas of the individual colored ink layers 15 that are spaced apart from each other, each colored ink is so arranged that the surface coverage by the colored ink layer 15 on the surface of the substrate film 11 is less than 40%, preferably less than 25%. It is preferable to adjust the size of the layer. “The surface coverage by the colored ink layer 15 on the surface of the substrate film 11” means that the surface area of the surface of the substrate film 11 on the side where the colored ink layer 15 is formed is the same surface. It means the ratio of the total area of all the colored ink layers. When the surface coverage is less than 40%, the preferable flexibility of the flexible substrate 1 due to the flexibility of the substrate film 11 can be sufficiently retained. In addition, when the flexible substrate 1 is installed following the curved surface, cracking of the colored ink layer can be sufficiently avoided.

  Further, the thickness of the colored ink layer 15 is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. In order to improve optical characteristics and ensure insulation, it is generally required to be at least 5 μm. On the other hand, by setting the thickness to 100 μm or less, the flexibility of the flexible substrate 1 can be maintained at a more preferable level.

  As the thermosetting ink for forming the colored ink layer 15, a known ink can be suitably used as long as the thermosetting temperature is about 100 ° C. or less. Specifically, as a representative example of an ink that can preferably use an insulating ink having a polyester resin, an epoxy resin, an epoxy resin and a phenol resin, an epoxy acrylate resin, a silicone resin, or the like as a base resin, respectively. Can be mentioned. Among these, polyester-based thermosetting insulating ink is particularly preferable as a material for forming the colored ink layer 15 of the flexible substrate 1 because of its excellent flexibility.

  In addition, formation of the colored ink layer 15 by the above insulating thermosetting ink can be performed by well-known methods, such as screen printing.

(White reflective layer)
The colored ink layer 15 is a white reflective layer having a good light reflectance by, for example, using a thermosetting ink forming the same layer as a white ink further containing an inorganic white pigment such as titanium dioxide. Can do. Thereby, in the LED display apparatus 100, it can contribute to the improvement of the utilization factor of the light light-emitted from the LED element 2 which is a light source. Here, the good light reflectivity specifically means that the light reflectivity in the visible light region (with a wavelength of 450 to 700 nm) is 80.0% or more, preferably 90.0% or more. More preferably, the reflectance is 93.0% or more. In addition, since it is difficult to strictly measure the absolute reflectance, the relative reflectance with the reference standard sample is usually used for the reflectance. In the present invention, barium sulfate is used as a comparative standard sample. In the present invention, the above-mentioned light reflectance means that an integrating sphere attachment device (for example, ISR2200 manufactured by Shimadzu Corporation) is attached to a spectrophotometer (for example, Shimadzu Corporation UV2450), and barium sulfate is used as a standard plate. And a value that can be obtained by measuring the relative reflectance with the standard plate as 100%.

  For example, the light reflectance according to the above standard of a white layer having a thickness of 30 μm that can be obtained by adding titanium oxide to a general-purpose silicone resin at a content ratio of 40% by mass is about 93%. By setting it as a white reflective layer, it can be set as the flexible substrate 1 which has the sufficiently excellent reflective performance.

(Contrast improvement layer)
The colored ink layer 15 can be a black or dark contrast improving layer by using a thermosetting ink forming the same layer as a dark ink further containing a black or dark pigment. Thereby, for example, the contrast of display information in the dot matrix display device can be improved to improve visibility. Here, in the LED display device 100, it is possible to contribute to an improvement in the utilization rate of light emitted from the LED element 2 that is a light source. Here, about the color of a contrast improvement layer, it is preferable that (DELTA) L * value measured by the conditions of D65 light source and 10 degree viewing angle based on JIS-Z8722 is 60 or less, Preferably it is 10 or less. By setting the value of ΔL * of the contrast enhancement layer within the above range, the color of the layer can be sufficiently black or dark, and the visibility of display information due to the improvement of contrast can be sufficiently improved. Further, since ΔL * of the contrast improving layer is 60 or less, it is possible to prevent the luminance adjustment on the display of the LED dot matrix display device from being difficult due to the diffuse reflection of visible light in the same layer.

  As the black or dark pigment, various conventionally known pigments can be widely used. For example, an inorganic pigment such as carbon black and titanium pigment subjected to insulation reinforcement treatment, or oxazine, pyrrole, quinacridone, azo, perylene, dioxane, isoindolinone, induslen, A dark organic pigment such as quinophthalone, perinone, or phthalocyanine can be used. In addition, pigments obtained by mixing two or more of these pigments can be used in the same manner as long as they satisfy the above conditions of insulation and color.

[Optical film]
The optical film 16 is further laminated on the colored ink layer 15 as a member for improving the optical characteristics of the LED display device 100 using the flexible substrate 1 in a complementary manner with the colored ink layer 15. The optical film 16 may be a reflective film that exhibits a reflective performance in a complementary manner with the above-described white reflective layer, or may be a black film that contributes to an improvement in contrast in a complementary manner with the above-described contrast improving layer. . Hereinafter, a case where the optical film 16 is a reflective film will be mainly described.

  For the purpose of improving the optical characteristics of the LED mounting module 10, the optical film 16 is laminated on the outermost surface on the light emitting surface side of the flexible substrate 1 so as to cover an area excluding the LED element mounting area. The optical film 16 has openings 161 that can be adapted to the mounting pitch of the LED elements 2 and the shape and size of the mounting region by punching or the like.

  When the optical film 16 is a reflective film, as the material, for example, white polyester foam type white polyester, white polyethylene resin, silver vapor-deposited polyester, etc., are appropriately used according to the use of the final product and its required specifications. Can do.

  Here, as shown in FIGS. 3 and 4, in the state where the LED element 2 is mounted, there is a slight gap between the outer peripheral side surface of the LED element 2 and the colored ink layer 15 or the optical film 16. It will be. The maximum value of this gap is preferably 1 mm or less, and more preferably 0.01 mm or more and 0.1 mm or less. When the maximum value of the gap width exceeds 1 mm, the area where the colored ink layer or the optical film does not exist in the peripheral portion of the LED element 2 becomes relatively large, thereby reducing the optical performance to be exhibited by these layers. . By setting the maximum width of the gap to 1 mm or less, the light emitted from the LED element 2 can be effectively used to improve the brightness of the LED display device. The width of the gap is more preferably 0.1 mm or less. From the viewpoint of improving the luminance, the width is preferably as small as about 0.01 mm.

  The optical film 16 is laminated by positioning so that the opening 161 includes the LED element mounting region in the flexible substrate 1. In this case, it is difficult to strictly control the size of the opening 161 and the stacking position so that the gap between the inner periphery of the opening 161 of the optical film 16 and the outer peripheral side surface of the LED element 2 is 1 mm or less as described above. It is.

  However, as shown in FIG. 4, the colored ink layer 15 capable of complementarily improving the optical characteristics is laminated on the lower layer of the optical film 16, and the colored ink layer 15 and the outer peripheral side surface of the LED element 2 are By configuring the gap width to be smaller than the gap width between the opening 161 of the optical film 16 and the outer peripheral side surface of the LED element 2, it is assumed that the inner circumference of the opening 161 of the optical film 16 and the LED element Even if the width of the gap between the outer peripheral side surface of 2 and the outer peripheral side surface of the colored ink layer 15 exceeds 1 mm, the gap between the inner periphery of the opening of the colored ink layer 15 and the outer peripheral side surface of the LED element 2 is 1 mm or less. In particular, by exhibiting reflective performance, the optical characteristics can be improved to a sufficiently favorable level.

  Here, when the colored ink layer 15 is formed by screen printing, it is relatively easy to control the shape of about ± 0.1 mm. That is, at least for the colored ink layer, the gap portion can be easily set to 1 mm or less. By setting the width of the gap portion of the colored ink layer to 1 mm or less in this way, even if the width of the gap portion in the optical film 16 is not necessarily 1 mm or less, the effect of improving the optical characteristics by the colored ink layer 15 is complemented. Thus, the optical performance required for the flexible substrate 1 can be exhibited. In the case where the colored ink layer 15 is a black or dark contrast improving layer, the colored ink layer 15 can sufficiently supplement the lack of the optical property improving effect of the optical film 16 as described above.

<Manufacturing flexible substrates>
About the manufacturing method of the flexible substrate 1, it can be based on the manufacturing method of a conventionally well-known electronic substrate. For example, it can be manufactured by a conventional method in which each metal wiring portion is formed on each surface of the substrate film by an etching process involving chemical treatment. In this etching process, the unmasked portion of the copper foil and the like is removed to form a non-conductive portion, but the adhesive layer immediately below the portion remains on the substrate film, and the completed flexible substrate 1 It exists as an adhesive layer on substantially the entire surface of the substrate film 11.

<LED display device>
FIG. 5 is a perspective view schematically showing a configuration of the LED display device 100 using the LED mounting module 10 in which the LED element is mounted on the flexible substrate 1. The LED display device 100 includes an LED mounting module 10 and a display screen 3 such as a liquid crystal display panel. Further, in the LED display device 100, in order to radiate the heat radiated from the LED mounting module 10 to the outside more efficiently, the heat radiating structure 4 made of aluminum or the like is further installed on the back side of the flexible substrate 1. Is preferred. Each of these members actually constitutes an LED display device by being fixedly disposed at appropriate positions inside an external frame (not shown) made of metal or the like.

[LED element]
The LED element 2 constituting the LED display device 100 by being mounted on the flexible substrate 1 is a light emitting element utilizing light emission at a PN junction where a P-type semiconductor and an N-type semiconductor are joined. There are proposed a structure in which a P-type electrode and an N-type electrode are provided on the upper and lower surfaces of the element and a structure in which both the P-type and N-type electrodes are provided on one side of the element.

  The LED element 2 can be bonded to the metal wiring portion 13 in the flexible substrate 1 by solder bonding via the solder layer 14. This solder bonding can be performed by a reflow method or a laser method. In the reflow method, the LED element 2 is mounted on the metal wiring part 13 via solder, and then the flexible multilayer circuit board is transported into the reflow furnace, and hot air at a predetermined temperature is blown to the metal wiring part 13 in the reflow furnace. In this method, the solder paste is melted to attach the LED element 2 to the metal wiring portion 13. The laser method is a method of soldering the LED element 2 to the metal wiring portion 13 by locally heating the solder with a laser.

  According to the flexible substrate 1 of the present invention described above and the LED display device 100 using the same, the following effects can be obtained.

(1) In the flexible substrate for LED elements, each colored ink layer is an area for mounting LED elements with respect to the arrangement of the colored ink layers formed in the area excluding the area for mounting LED elements on the substrate film and the metal wiring portion. It was assumed that each was separated and arranged separately.
By limiting the arrangement range only to the range that contributes to the improvement of the optical characteristics, it is possible to avoid the decrease in flexibility of the flexible substrate accompanying the formation of the ink layer while enjoying the effect of the optical characteristics improvement effect. . Further, compared to the case where the ink layer is formed on substantially the entire surface, the cost of the ink material can be greatly saved, thereby contributing to the improvement of economy.

  (2) The surface coverage by the colored ink layer on the surface of the substrate film was less than 25%. As a preferable specific example of the substrate film in such a coverage range, 16 × 16 LED elements are arranged in a matrix form at a pitch of 10 mm on a square substrate film (PET: thickness 50 μm) whose diagonal is 13 inches in size. In the flexible substrate disposed in the doughnut-shaped colored ink layer (silicone resin base, 40% by mass of titanium oxide) shown in FIG. ) Can be given at 16 × 16 locations. The thickness of the colored ink layer was 30 μm. In this case, the surface coverage is about 10%. In this case, it was confirmed that the flexible substrate can follow a curved surface having a curvature radius R = 20 mm without any visual gap. Further, in this case, no cracking of the colored ink layer accompanying the tracking of the curved surface was observed at all. On the other hand, the flexible substrate prepared in the same manner as described above except that the colored ink layer is formed on almost the entire surface excluding the LED mounting area is difficult to follow a curved surface with a radius of curvature R = 20 mm. In the installation, a plurality of gaps of about 0.5 mm were generated between the curved surface and fine ink cracks were observed at a plurality of locations. As can be seen from the above, according to the invention of (2), the effect that the flexible substrate of (1) can exhibit can be expressed more reliably.

  (3) The thickness of the colored ink layer was 5 μm or more and 100 μm or less. Thereby, according to invention of (2), the effect of invention of (1) and (2) can be expressed more reliably, ensuring the effect of the optical characteristic improvement calculated | required by a colored ink layer reliably. .

  (4) The light reflectance in the visible light region of the colored ink layer was 90% or more. Thereby, the flexible substrate for LED elements which can make the utilization efficiency of the light light-emitted from an LED element extremely high, maintaining extremely excellent flexibility can be obtained.

  (5) Based on JIS-Z8722 of the colored ink layer, the ΔL * value measured under the conditions of a D65 light source and a 10 ° viewing angle was set to 60 or less. Thereby, the quality of the display screen of the LED display device can be sufficiently improved while maintaining extremely excellent flexibility.

  (6) A flexible substrate in which an optical film having an opening formed in a portion corresponding to the LED element mounting region is further laminated on the colored ink layer. Thereby, it becomes the structure which a colored ink layer complements efficiently the effect of the optical characteristic improvement effect of an optical film. Therefore, the expression of the effects of the inventions (1) to (5) can be further promoted.

  (7) It was set as the LED display apparatus formed by mounting an LED element on the flexible substrate in any one of (1) to (6). Thereby, it is possible to obtain an LED display device having excellent optical characteristics while sufficiently enjoying the degree of freedom of design and high productivity due to the inherent flexibility of the flexible substrate.

  As described above, according to the present invention, it is possible to avoid the decrease in flexibility due to the lamination of the colored ink layer, which can contribute to the improvement of the optical characteristics, and to achieve the original preferable characteristics of the flexible substrate such as freedom of design and high productivity. It is possible to obtain a flexible substrate for an LED element that is more reliably expressed and has excellent flexibility and optical characteristics during installation, and an LED display device using the same.

DESCRIPTION OF SYMBOLS 1 Flexible substrate 11 Substrate film 12 Adhesive layer 13 Metal wiring part 14 Solder layer 15 Colored ink layer 16 Optical film 161 Opening part 2 LED element 3 Display screen 4 Heat dissipation structure 10 LED mounting module 100 LED display device

Claims (7)

Surrounding the LED element mounting region in a region excluding the substrate film, the metal wiring portion formed on one surface of the substrate film, and the LED element mounting region on the substrate film and the metal wiring portion A formed colored ink layer, and
Each colored ink layer is a flexible substrate for an LED element that is arranged separately for each LED element mounting region.   The flexible substrate according to claim 1, wherein the surface coverage of the colored ink layer on the surface of the substrate film is less than 25%.   The flexible substrate according to claim 1, wherein the colored ink layer has a thickness of 5 μm to 100 μm.   The flexible substrate according to claim 1, wherein the colored ink layer has a light reflectance in a visible light region of 90% or more.   4. The flexible substrate according to claim 1, wherein the colored ink layer has a ΔL * value of 60 or less measured according to a D65 light source and a 10 ° viewing angle in accordance with JIS-Z8722.   The flexible substrate according to claim 1, wherein an optical film in which an opening is formed in a portion corresponding to the LED element mounting region is further laminated on the colored ink layer.   An LED display device comprising an LED element mounted on the flexible substrate according to claim 1.

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