Backlight module and display device

Abstract

To provide an LED backlight module that can reduce the thickness, and a display device.SOLUTION: There is provided a display device in which a backlight module includes: a light-emitting diode substrate 1 including a support substrate 11 and a light-emitting diode element 12 arranged on a side of one surface of the support substrate; and an encapsulation member 2 arranged on a side of a surface, of the light-emitting diode substrate, on a light-emitting diode element side and brought into close contact with the light-emitting diode substrate to encapsulate the light-emitting diode element. The encapsulation member comprises three layers 21, 22, 21, and includes a light diffusion agent 50 only in the layer 22 that is the center of the three layers. The encapsulation member contains, together with the three layers, an olefin resin and a silane copolymer obtained by copolymerization of α olefin and an ethylenically unsaturated silane compound, as a comonomer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a direct-type backlight module using light-emitting diodes, and a display device using the same. [Background technology]

[0002] In recent years, display devices such as liquid crystal display devices have rapidly become popular. Backlight modules (hereinafter sometimes referred to as LED backlight modules) using light-emitting diode (hereinafter sometimes referred to as LED) elements used in display devices can be broadly divided into direct-type and edge-light-type. Edge-light-type LED backlight modules are typically used in small and medium-sized display devices such as smartphones and other mobile terminals, but the use of direct-type LED backlight modules is being considered from the perspective of brightness, etc. On the other hand, direct-type LED backlight modules are often used in large display devices such as large-screen LCD TVs.

[0003] A direct-type LED backlight module has a configuration in which multiple LED elements are arranged on a substrate (Patent Document 1). In such a direct-type LED backlight module, by independently controlling the multiple LED elements, it is possible to achieve so-called local dimming, which adjusts the brightness of each area of ​​the LED backlight module according to the brightness and darkness of the displayed image. This makes it possible to significantly improve the contrast of the display device and reduce power consumption.

[0004] In direct-type LED backlight modules, optical components such as a diffuser plate are placed on the LED elements to improve the in-plane uniformity of brightness. In this case, to improve the in-plane uniformity of brightness, it is necessary to separate the diffuser plate from the LED mounting board on which the LED elements are mounted, so multiple columnar spacers are placed to separate the diffuser plate from the LED mounting board. Furthermore, when using blue LED elements as the light source, for example, a wavelength conversion material containing phosphor or quantum dots is placed on the LED light output surface to whiten the light.

[0005] Specifically, as shown in FIG. 4, a conventional direct-type LED backlight module 40 has spacers 43 provided on a support substrate 41 on which LED elements 42 are arranged, thereby creating a space between the LED elements 42 and optical components such as a diffuser plate 44 and a wavelength conversion member 45, thereby improving the in-plane uniformity of brightness.

[0006] Recently, research and development into miniaturization and high-density LED elements has been progressing, and LEDs with small chip sizes, so-called mini LEDs and micro LEDs, have been attracting attention. Furthermore, it has been considered to put the technology for miniaturization and high-density LED elements into practical use as a backlight module using LED elements (see, for example, Patent Document 2).

[0007] As shown in Figure 4 above, in backlight modules using conventional direct-type LED elements, spacers are placed to maintain a predetermined distance between the LED elements and the diffuser. However, the light emitted from the LED elements can be blocked or reflected by the spacers, resulting in uneven brightness. Furthermore, multiple spacers are required, but this is difficult to achieve with the fine pitch of mini LEDs and micro LEDs mentioned above.

[0008] Therefore, in a backlight module using LED elements, a configuration has been proposed in which a sealing member that seals the LED elements is placed between the LED elements and the diffusion plate (see, for example, Patent Document 2). However, as mentioned above, backlight modules using direct-type LED elements are at a disadvantage in terms of thinning compared to edge-light-type backlight modules, and further improvements are required. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-272245 [Patent Document 2] Japanese Patent Application Publication No. 2019-61954 Summary of the Invention [Problem to be solved by the invention]

[0010] The present disclosure has been made in view of the above circumstances, and has as its main object to provide an LED backlight module and a display device that can be made thinner. [Means for solving the problem]

[0011] The present disclosure provides an LED backlight module comprising: a support substrate; an LED substrate having LED elements arranged on one side of the support substrate; and a sealing member arranged on the side of the LED substrate facing the LED elements and sealing the LED elements, wherein the sealing member contains a light diffusing agent.

[0012] The present disclosure provides a display device including a display panel and the above-described LED backlight module disposed on the rear surface of the display panel. [Effects of the Invention]

[0013] The present disclosure provides an effect of providing an LED backlight module and a display device that can be made thinner. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional view illustrating a backlight module of the present disclosure. [Figure 2] 1 is a schematic cross-sectional view illustrating a backlight module of the present disclosure. [Figure 3] 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. [Figure 4] FIG. 1 is a schematic cross-sectional view illustrating a conventional backlight module. DETAILED DESCRIPTION OF THE INVENTION

[0015] The backlight module and display device of the present disclosure will be described below. However, the present disclosure can be implemented in many different embodiments, and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each component more schematically than in the embodiments. However, these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those previously described with reference to the previous drawings will be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0016] In this specification, when expressing an aspect in which another component is placed on top of a component, the term "on the surface side" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below a component so as to be in contact with the component, and a case in which another component is placed above or below a component with another component in between. In this specification, "LED" means a light-emitting diode.

[0017] In order to reduce the thickness of the backlight module, the inventors attempted to increase the number of LED elements and increase their arrangement density, but this was not possible to achieve a sufficient thickness, and was practically difficult because it led to increased costs and power consumption. Therefore, instead of providing space by placing spacers, they attempted to shorten the distance between the optical component and the LED substrate by filling the LED substrate with a sealing material, but this did not fully satisfy the requirement for a thinner backlight module.

[0018] The inventors discovered that by filling the LED elements in a backlight module with a sealing material, the distance between the LED substrate and the optical component, which was previously ensured by a spacer, can be ensured by the sealing material, and by incorporating a light diffusing agent into the sealing material, there is no need to provide a diffusion plate as in the past, thereby achieving a thinner design, and thus completed the present invention. The backlight module of the present disclosure and a display device using the same will be described in detail below.

[0019] A. Backlight module The backlight module of the present disclosure comprises a support substrate, an LED substrate having LED elements arranged on one side of the support substrate, and a sealing member arranged on the side of the LED substrate facing the LED elements and sealing the LED elements, wherein the sealing member contains a light diffusing agent.

[0020] According to the present disclosure, since there is no need to provide a diffusion plate as in conventional backlight modules, the number of parts can be reduced, making it possible to achieve a thinner design. In addition, since the process of providing a diffusion plate is no longer necessary, the manufacturing process can be simplified.

[0021] The backlight module of the present disclosure will be described with reference to the drawings, in which: Figure 1 is a schematic cross-sectional view showing an example of a backlight module of the present disclosure. The backlight module 10 shown in Fig. 1 includes an LED substrate 1 having a support substrate 11 and LED elements 12 arranged on one side of the support substrate 11, and a sealing member 2 containing a light diffusing agent 50 arranged on the side of the LED substrate 1 facing the LED elements 12 to seal the LED elements 12. The LED substrate 1 is an LED substrate for a direct-type backlight module. Fig. 1 shows an example in which a wavelength conversion member 3 is arranged on the sealing member 2.

[0022] The backlight module of the present disclosure is characterized by having a sealing member that seals the LED elements, and this sealing member contains a light diffusing agent. Each component of the backlight module of the present disclosure will be described below.

[0023] 1. Sealing member The sealing member in the present disclosure is a member that seals the LED element and is disposed on the LED element side of the LED substrate, between the LED substrate and an optical member such as a wavelength conversion member.

[0024] In this specification, "transparent" and "transparency" refer to transparency to the extent that it does not impede the visibility of light from the LED element.

[0025] (1) Light diffusing agent The sealing member in the present disclosure contains a light diffusing agent that diffuses the light emitted from the LED element.

[0026] The light diffusing agent is usually dispersed in a transparent resin layer. The material of the light diffusing agent is not particularly limited as long as it can diffuse light from the LED element, and may be, for example, an organic material or an inorganic material. Examples of organic light diffusing agents include synthetic resins such as polymethyl methacrylate (PMMA) resin particles, melamine resin particles, silicone resin particles, styrene resin, polyurethane resin, polyester resin, fluorine-based resin, and copolymers thereof. These may be used alone or in combination. On the other hand, examples of inorganic light diffusing agents include TiO2, SiO2, Al2O3, silicon, zirconia, glass, smectite, and kaolinite. These may be used alone or in combination.

[0027] The refractive index of the light diffusing agent is not particularly limited as long as it can diffuse the light from the LED element, but it is, for example, 1.4 to 2.2. Such a refractive index can be measured by the Becke method, minimum deviation method, deviation angle analysis, mode line method, ellipsometry, Abbe method, etc.

[0028] The refractive index of the light diffusing agent preferably has a predetermined difference from that of the resin constituting the sealing material, specifically, a refractive index difference of 0.03 or more, particularly 0.05 or more.

[0029] The light diffusing agent is preferably in the form of particles from the viewpoint of dispersibility in the resin.

[0030] Average primary particle size of the light diffusing agent (D 50 ) is, for example, 0.1 μm or more and 50 μm or less, preferably 1 μm or more and 20 μm or less.

[0031] The proportion of the light diffusing agent in the sealing member is not particularly limited as long as it can diffuse the light from the LED element, and is, for example, 0.1 mass % or more and 10 mass % or less. Within this range, the light from the LED element can be reliably diffused, and the light diffusing agent is unlikely to disperse and form clumps, which is preferable. Note that when the sealing member has a multilayer structure described below, the proportion of the light diffusing agent refers to the proportion of the light diffusing agent in the light diffusing agent-containing layer.

[0032] (2) Resin In the sealing member of the present disclosure, the light diffusing agent is dispersed in a resin. The resin constituting the sealing member of the present disclosure is not particularly limited as long as it has high light transmittance and can disperse the light diffusing agent, and any resin generally used in the field of display devices can be used. Examples include thermoplastic resins and curable resins, but thermoplastic resins are preferred.

[0033] When using a thermosetting resin or a photocurable resin, a liquid resin composition is usually applied to the LED substrate and then cured. However, when a liquid resin composition is applied, the film thickness may not be uniform between the center and the periphery of the LED substrate. In this case, it may be difficult to control the film thickness in the periphery. Furthermore, in the case of the above-mentioned curable resin, shrinkage occurs during curing, making it difficult to control the film thickness in the periphery of the LED substrate.

[0034] Display devices using the backlight module of the present disclosure may be used, for example, in tiling, and in such cases, if the film thickness around the periphery of each display device is not uniform, the periphery of each display device may be seen as a line, which may cause problems in terms of display quality.

[0035] In the present disclosure, by using a thermoplastic resin as the sealing member, it is possible to seal the LED elements with the sealing member by thermocompressing a sheet-shaped thermoplastic resin. In this case, it is possible to control the film thickness around the periphery of the backlight module, thereby achieving the effect of preventing the above-mentioned problems.

[0036] As the thermoplastic resin, a resin that does not substantially generate components that deteriorate the LED substrate (deterioration components) is usually used. Here, "resin that does not substantially generate deteriorating components" refers to a resin that does not contain any deteriorating components, or if it does contain any, the amount is so small that it does not affect the deterioration of the LED substrate, or a resin that does not generate any deteriorating components during the manufacture and use of the backlight module, or if it does generate any, the amount is so small that it does not affect the deterioration of the LED substrate.

[0037] Examples of resins that generate such degradation components include ethylene-vinyl acetate (EVA) copolymers, which generate acid components as degradation components.

[0038] Furthermore, the thermoplastic resin used in the present disclosure is preferably one that has a melt viscosity that, when heated, allows it to conform to the unevenness of the LED elements and other components arranged on the LED substrate and to penetrate into gaps.

[0039] Specifically, the melt mass flow rate (MFR) of the thermoplastic resin used is preferably 0.5 g / 10 min or more and 40 g / 10 min or less, and more preferably 2.0 g / 10 min or more and 40 g / 10 min or less. By having an MFR in the above range, the resin can penetrate into the gaps between the LED elements, exhibit sufficient sealing performance, and provide a sealing member with excellent adhesion to the LED substrate.

[0040] In this disclosure, MFR refers to the value measured at 190°C under a load of 2.16 kg according to JIS K7210. However, for polypropylene resins, MFR refers to the MFR value measured at 230°C under a load of 2.16 kg according to JIS K7210.

[0041] When the sealing member is a multilayer member as described below, the MFR is measured using the above-mentioned measurement method while all layers remain in a multilayer state where they are laminated together, and the obtained measurement value is taken as the MFR value of the multilayer sealing material.

[0042] The melting point of the thermoplastic resin used in the present disclosure is not particularly limited as long as it can encapsulate the LED element within a temperature range that does not degrade the LED substrate, and is preferably, for example, 55° C. or higher and 135° C. or lower. The melting point of the thermoplastic resin can be measured, for example, by differential scanning calorimetry (DSC) in accordance with the method for measuring the transition temperature of plastics (JIS K7121).

[0043] In the present disclosure, examples of the thermoplastic resin that can be used include olefin-based resins, ionomer-based resins, and polyvinyl butyral-based resins.

[0044] Among these, in the present disclosure, olefin-based resins are preferred. This is because olefin-based resins are particularly unlikely to produce components that deteriorate the LED substrate and have low melt viscosity, allowing them to effectively encapsulate the above-mentioned LED elements. Furthermore, among olefin-based resins, polyethylene-based resins or polypropylene-based resins are preferred.

[0045] The polyethylene resins used in the present disclosure include not only ordinary polyethylene obtained by polymerizing ethylene, but also resins obtained by polymerizing compounds having ethylenically unsaturated bonds such as α-olefins, resins obtained by copolymerizing a plurality of different compounds having ethylenically unsaturated bonds, and modified resins obtained by grafting other chemical species onto these resins.

[0046] Among these, a silane copolymer (hereinafter also referred to as "silane copolymer") obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer can be preferably used, because the use of such a resin can achieve higher adhesion between the LED substrate and the sealing member. The silane copolymer described in JP-A-2018-50027 can be used.

[0047] Furthermore, as the resin material used for the sealing member, a curable resin such as a photocurable resin or a thermosetting resin can also be used. When a curable resin is used, a liquid sealant composition containing the curable resin and a light diffusing agent is filled and cured to obtain a sealing member.

[0048] Such curable resins include those conventionally used as sealing materials, such as epoxy resins, acrylic resins, and silicone resins.

[0049] (3) Structure of sealing material The sealing member in the present disclosure may be, for example, a single-layer member in which the sealing member 2 is composed of a single resin layer, as shown in FIG. 1, or a multi-layer member in which the sealing member 2 is composed of multiple resin layers (three layers in FIG. 2) stacked together, as shown in FIG. By using the above multilayer member, it is possible to use a material that is usually expensive but has good adhesion and molding properties that allow it to penetrate into gaps in LED elements, etc., for the layer on the LED substrate side of the layer containing the light diffusing agent.

[0050] In the present disclosure, the multilayer member may have a two-layer structure, but preferably has a three-layer structure in which a light-diffusing agent-containing layer containing a light-diffusing agent is disposed in the central layer and adhesive layers with good adhesion are disposed on both sides of the central layer.

[0051] In the present disclosure, the material constituting the layer disposed on the LED substrate side is not particularly limited as long as it has high adhesion and molding properties. For example, it is preferable to use the above-mentioned silane copolymer, silane coupling agent, etc., and additives such as antioxidants and light stabilizers may also be added.

[0052] When the sealing member of the present disclosure is a multilayer member, it is sufficient that at least one layer contains a light diffusing agent. However, in the present disclosure, it is preferable that the light diffusing agent be contained in a layer other than the layer closest to the LED light-emitting diode substrate, i.e., a layer other than the layer that is in close contact with the LED substrate. This is because if the light diffusing agent is contained in the layer that is in close contact with the LED substrate, it may adversely affect adhesion to the LED substrate. Furthermore, by containing the light diffusing agent in a layer other than the layer that is in close contact with the LED substrate, it is possible to prevent the layer containing the light diffusing agent from becoming thin directly above the LED element, thereby enabling more uniform brightness. In the present disclosure, when the sealing member is configured with three layers, it is preferable that the central layer (resin layer 22 in FIG. 2) contains a light diffusing agent.

[0053] The thickness of the sealing member is not particularly limited and can be appropriately selected depending on the layer structure of the LED substrate, etc. For example, the thickness of the sealing member may be 100 μm or more and 600 μm or less, and more preferably 300 μm or more and 550 μm or less. If the thickness is less than 100 μm, the sealing member cannot fully function as a sealing material, and if the thickness is 600 μm or more, it may have an adverse effect on light transmittance.

[0054] When the sealing member is formed as a three-layer member, the thickness of the central layer (resin layer 22 in FIG. 2) is preferably 60 μm to 400 μm, more preferably 250 μm to 350 μm. In this case, the thickness of each outer layer (resin layer 21 in FIG. 2) is preferably 15 μm to 200 μm.

[0055] In particular, the sealing member of the present disclosure is preferably a multilayer member having a central layer and an adhesive layer disposed closer to the LED substrate than the central layer. In this case, the thickness of the adhesive layer disposed closer to the LED substrate is preferably greater than the height of the LED element. This is because the thickness of the central layer can be made uniform across the backlight module, both in the portion directly above the LED element and in the portion other than the portion directly above the LED element. The light diffusing agent is preferably contained in the central layer, as described above. In this case, the central layer is referred to as a light diffusing agent-containing layer in the present disclosure.

[0056] In this specification, "thickness" can be measured using a known measurement method capable of measuring sizes on the order of μm, and for example, can be measured using images observed with an optical microscope or a scanning electron microscope (SEM). The same applies to measurements of size such as "size."

[0057] (4) Other The encapsulant composition for forming the encapsulant of the present disclosure may contain a light diffusing agent, a resin, and, if necessary, a crosslinking agent and other additives. Furthermore, by containing a wavelength converting material used in the wavelength converting material described below, it is possible to incorporate the function of the wavelength converting material into the encapsulant, thereby enabling a thinner backlight module.

[0058] The sealing member of the present disclosure can be formed using a sheet-shaped sealing material (sealant sheet) composed of a sealing material composition containing a light diffusing agent and a thermoplastic resin. The method for molding the sealing material sheet can be the same as the molding method for a general resin sheet. One example is the T-die method, but is not limited to this.

[0059] Specifically, an LED substrate and an encapsulant sheet are prepared, the encapsulant sheet is laminated on the side of the LED substrate facing the LED elements, and then the encapsulant sheet is pressed onto the LED substrate using, for example, a vacuum lamination method, thereby forming the encapsulant. When a sheet-like encapsulant is used in this way, the dispersibility of the light diffusing agent is better than when a encapsulating member is formed using a liquid encapsulant composition. Furthermore, by using a sheet-like encapsulant containing a thermoplastic resin, a encapsulating member with better flatness can be obtained than a encapsulating member obtained by curing a liquid thermosetting resin composition or a liquid photocurable resin composition.

[0060] The sealing member of the present disclosure can also be formed by applying a liquid sealing material composition containing a light diffusing agent and a curable resin such as a thermosetting or photocurable resin onto an LED substrate and then thermally curing the composition.

[0061] (5) Specific Embodiments of the Sealing Member As described above, the sealing member preferably contains a thermoplastic resin, more preferably an olefin-based resin, and even more preferably a polyethylene-based resin. 3 More than 0.930g / cm 3 The following polyethylene resins are preferably used as the base resin, as such sealing members have good adhesion to the LED substrate and good conformability to components arranged on the LED substrate.

[0062] A suitable sealing member will now be described in detail. The sealing member has a density of 0.870 g / cm 3 More than 0.930g / cm 3 It is formed of a resin film having the following polyethylene-based resin as a base resin: That is, the sealing member is formed of a sealing material sheet having the above-mentioned polyethylene-based resin as a base resin.

[0063] The sealing material sheet is preferably a multilayer film composed of a plurality of layers including a core layer and skin layers disposed on both outermost surfaces. In this case, the core layer has a density of 0.910 g / cm 3 More than 0.930g / cm 3The following polyethylene resin is preferably used as the base resin, and the skin layer has a density of 0.890 g / cm 3 More than 0.910g / cm 3 It is preferable to use a polyethylene-based resin having a density of 1000 kJ / cm or less and lower than that of the base resin for the core layer as the base resin. When the encapsulant sheet is a multilayer film having three or more layers, it is preferable that the core layer contains a light diffusing agent.

[0064] In the case of the above multilayer film, the total thickness is, for example, preferably 100 μm or more, more preferably 250 μm or more, and even more preferably 300 μm or more. The total thickness is, for example, preferably 600 μm or less, more preferably 550 μm or less. If the total thickness is too thin, it will not be possible to adequately cushion impact, but if the total thickness is within the above range, it will be possible to achieve both molding properties and heat resistance at a sufficiently desirable level. If the total thickness is too thick, it will be difficult to achieve further improvements in impact cushioning, it will not be possible to meet the demand for thinner films, and it will be uneconomical.

[0065] The thickness of the core layer in the multilayer film is, for example, preferably 60 μm or more, more preferably 100 μm or more, and even more preferably 250 μm or more. The thickness of the core layer is, for example, preferably 400 μm or less, more preferably 350 μm or less. In this case, the thickness of each skin layer can be, for example, 15 μm or more, or 30 μm or more, or 200 μm or less. By setting the thickness of each layer within such ranges, the heat resistance and molding properties of the encapsulant sheet can be maintained within good ranges.

[0066] The encapsulant sheet is obtained by molding an encapsulant composition, which will be described in detail below, into a sheet shape by a conventionally known method.

[0067] When the above-mentioned encapsulant sheet is formed as an encapsulating member, the encapsulant composition used to produce each layer has a base resin that is different in density range or the like for each layer.

[0068] In this case, the encapsulant composition for the core layer and the encapsulant composition for the skin layer are used to form the respective layers, and by molding a multilayer film of a predetermined thickness having a three-layer structure in which skin layers are disposed on both outermost surfaces using the encapsulant compositions for the core layer and the skin layer, it is possible to produce an encapsulating member 21 having a three-layer structure consisting of a skin layer 22a, a core layer 23, and a skin layer 22b, as shown in Fig. 8, for example.

[0069] As the base resin of the encapsulant composition for the core layer of the encapsulant sheet, a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), or a metallocene linear low-density polyethylene resin (M-LLDPE) can be preferably used. Among these, from the viewpoint of long-term reliability, low-density polyethylene resin (LDPE) can be particularly preferably used as the composition for the core layer.

[0070] The density of the polyethylene resin used as the base resin of the encapsulant composition for the core layer is 0.910 g / cm 3 More than 0.930g / cm 3 More preferably, it is 0.920 g / cm or less. 3 By setting the density of the base resin of the encapsulant composition for the core layer within the above range, the encapsulant sheet can be provided with necessary and sufficient heat resistance without undergoing a crosslinking treatment.

[0071] The melting point of the encapsulant composition for the core layer is preferably 90°C or higher and 135°C or lower, and more preferably 100°C or higher and 115°C or lower. By setting the melting point of the core layer within the above melting point range, the heat resistance and molding properties of the encapsulant composition can be maintained within preferred ranges. The melting point of the encapsulant composition can be increased to about 135°C by adding a high-melting point resin such as polypropylene to the encapsulant composition for the core layer. In this case, the polypropylene content is preferably 5% by mass or higher and 40% by mass or lower of the total resin components of the core layer.

[0072] The polypropylene contained in the core layer is preferably a homopolypropylene (homoPP) resin. HomoPP is a polymer consisting only of polypropylene monomer and has high crystallinity, resulting in higher rigidity compared to block PP or random PP. Using this as an additive resin to the encapsulant composition for the core layer can improve the dimensional stability of the encapsulating member. Furthermore, the homoPP used as an additive resin to the encapsulant composition for the core layer preferably has an MFR of 5 g / 10 min or more and 125 g / 10 min or less at 230°C under a load of 2.16 kg, as measured in accordance with JIS K7210. If the MFR is too small, the molecular weight increases, resulting in excessive rigidity, making it difficult to ensure the desired sufficient flexibility of the encapsulant composition. If the MFR is too large, the flowability during heating is not sufficiently suppressed, and the encapsulant sheet cannot be provided with sufficient heat resistance and dimensional stability.

[0073] The melt mass flow rate (MFR) of the polyethylene resin used as the base resin of the encapsulant composition for the core layer is preferably 2.0 g / 10 min or more and 7.5 g / 10 min or less, and more preferably 3.0 g / 10 min or more and 6.0 g / 10 min or less, at 190°C and a load of 2.16 kg. By setting the MFR of the base resin of the encapsulant composition for the core layer within the above range, the heat resistance and molding properties of the encapsulating member can be maintained within preferred ranges. In addition, the processability during film formation can be sufficiently improved, contributing to improved productivity of the encapsulating member.

[0074] The content of the base resin relative to all resin components in the encapsulant composition for the core layer is 70% by mass or more and 99% by mass or less, and preferably 90% by mass or more and 99% by mass or less. As long as the content of the base resin is within the above range, other resins may be contained.

[0075] As with the encapsulant composition for the core layer, a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), or a metallocene linear low-density polyethylene resin (M-LLDPE) can be preferably used as the base resin of the encapsulant composition for the skin layer of the encapsulant sheet. Among these, from the viewpoint of molding properties, a metallocene linear low-density polyethylene resin (M-LLDPE) can be particularly preferably used as the encapsulant composition for the skin layer.

[0076] The density of the polyethylene resin used as the base resin of the encapsulant composition for the skin layer is 0.890 g / cm 3 More than 0.910g / cm 3 More preferably, it is 0.899 g / cm or less. 3 By setting the density of the base resin of the encapsulant composition for the skin layer within the above range, the adhesion of the encapsulating member can be maintained within a preferred range.

[0077] The melting point of the encapsulant composition for the skin layer is preferably from 55° C. to 100° C., and more preferably from 80° C. to 95° C. By setting the melting point of the encapsulant composition for the skin layer within the above range, the adhesion of the encapsulating member can be further reliably improved.

[0078] The melt mass flow rate (MFR) of the polyethylene resin used as the base resin of the encapsulant composition for the skin layer is preferably 2.0 g / 10 min or more and 7.0 g / 10 min or less, and more preferably 2.5 g / 10 min or more and 6.0 g / 10 min or less, at 190°C and a load of 2.16 kg. By setting the MFR of the base resin of the encapsulant composition for the skin layer within the above range, the adhesion of the encapsulating member can be more reliably maintained within a preferred range. In addition, the processability during film formation can be sufficiently improved, contributing to improved productivity of the encapsulating member.

[0079] The content of the base resin relative to all resin components in the encapsulant composition for the skin layer is 60% by mass or more and 99% by mass or less, and preferably 90% by mass or more and 99% by mass or less. As long as the content of the base resin is within the above range, other resins may be contained.

[0080] It is more preferable that all of the above-described sealant compositions contain, as necessary, a certain amount of a silane copolymer obtained by copolymerizing an α-olefin with an ethylenically unsaturated silane compound as a comonomer. Such a graft copolymer increases the degree of freedom of silanol groups that contribute to adhesive strength, thereby improving the adhesion of the sealing member to other members.

[0081] Examples of the silane copolymer include the silane copolymer described in JP-A-2003-46105. By using the silane copolymer as a component of a sealing material composition, it is possible to obtain a sealing member that is excellent in strength, durability, and other properties, as well as in weather resistance, heat resistance, water resistance, light resistance, and other properties, and that has extremely excellent heat-sealing properties unaffected by manufacturing conditions such as heat-compression bonding when arranging the sealing member, and that can be obtained stably and at low cost.

[0082] The silane copolymer can be any of random copolymer, alternating copolymer, block copolymer and graft copolymer, but more preferably graft copolymer, and more preferably graft copolymer in which polyethylene for polymerization is used as the main chain and ethylenically unsaturated silane compound is polymerized as a side chain. Such graft copolymer has high flexibility of silanol group that contributes to adhesive strength, so that it can improve the adhesiveness of sealing member.

[0083] The content of the ethylenically unsaturated silane compound in the copolymer of an α-olefin and an ethylenically unsaturated silane compound is, for example, 0.001% by mass to 15% by mass, preferably 0.01% by mass to 5% by mass, and particularly preferably 0.05% by mass to 2% by mass, based on the total mass of the copolymer. When the content of the ethylenically unsaturated silane compound in the copolymer of an α-olefin and an ethylenically unsaturated silane compound is high, the mechanical strength and heat resistance are excellent, but if the content is excessive, the tensile elongation and heat fusion bondability tend to be poor.

[0084] The content of the silane copolymer relative to the total resin components of the encapsulant composition is preferably 2% by mass or more and 20% by mass or less in the encapsulant composition for the core layer, and 5% by mass or more and 40% by mass or less in the encapsulant composition for the skin layer. It is particularly preferable that the encapsulant composition for the skin layer contains 10% by mass or more of the silane copolymer. The silane modification amount in the silane copolymer is preferably about 1.0% by mass or more and 3.0% by mass or less. The preferred range of the silane copolymer content in the encapsulant composition is based on the assumption that the silane modification amount is within this range, and it is desirable to fine-tune it appropriately depending on the variation in the modification amount.

[0085] All of the encapsulant compositions may also contain an adhesion improver as needed. The addition of an adhesion improver can improve adhesion durability with other components. As the adhesion improver, known silane coupling agents can be used, but silane coupling agents having an epoxy group or silane coupling agents having a mercapto group are particularly preferred.

[0086] 2.Light-emitting diode board The LED substrate of the present disclosure includes a support substrate and an LED element. The LED substrate of the present disclosure is preferably an LED substrate for a backlight module, particularly a direct-type backlight module. The LED substrate is also preferably an LED substrate for a mini LED backlight module.

[0087] The structure of the LED substrate is not particularly limited as long as it includes a support substrate and an LED element, and can emit white light with uniform brightness when used as a backlight module with a sealing member containing a light diffusing agent.

[0088] (1) Support substrate The support substrate is a member that supports the LED element, the sealing member, and the like. The support substrate may or may not be transparent. The support substrate may be soft (flexible) or rigid. The material of the support substrate may be an organic material, an inorganic material, or a composite material that combines both an organic material and an inorganic material.

[0089] When the material of the support substrate is an organic material, a resin substrate can be used as the support substrate. On the other hand, when the material of the support substrate is an inorganic material, a ceramic substrate or a glass substrate can be used as the support substrate. Furthermore, when the material of the support substrate is a composite material, a glass epoxy substrate (e.g., an FR-4 substrate) can be used as the support substrate. Furthermore, for example, a metal core substrate can be used as the support substrate.

[0090] The support substrate is usually a flat substrate, but may have at least one curved surface, for example, on the side on which the LED elements are disposed or on the opposite side.

[0091] The thickness of the support substrate is, for example, 0.05 mm or more and 10 mm or less, and preferably 0.1 mm or more and 5 mm or less.

[0092] The shape of the support substrate in plan view can be appropriately selected without any particular limitation, but is typically rectangular. The support substrate may be a printed circuit board on which a circuit is formed by printing.

[0093] (2) Light-emitting diode element The LED element is a component disposed on one surface of the support substrate, and the light-emitting portion of the LED element functions as a light source for the display device, which will be described later.

[0094] The backlight module of the present disclosure may be a white LED. The LED element is not particularly limited as long as it can emit white light when used in a backlight module, and examples thereof include LED elements that can emit white, blue, ultraviolet, infrared, etc.

[0095] The LED element can be a chip-shaped LED element. The form of the LED element can be, for example, the light-emitting portion (also referred to as an LED chip) itself, or a packaged LED (also referred to as a chip LED) such as a surface-mounted type or a chip-on-board type. The packaged LED can have, for example, a light-emitting portion and a protective portion that covers the light-emitting portion and contains resin. Specifically, when the LED element is the light-emitting portion itself, the LED element can be, for example, a blue LED element, an ultraviolet LED element, or an infrared LED element. When the LED element is a packaged LED, the LED element can be, for example, a white LED element.

[0096] When the backlight module of the present disclosure emits white light by combining an LED element with a wavelength conversion member (described later), the LED element is preferably a blue LED element, an ultraviolet LED element, or an infrared LED element. A blue LED element can generate white light by combining it with, for example, a yellow phosphor, or a red and green phosphor. Furthermore, an ultraviolet LED element can generate white light by combining it with, for example, a red, green, and blue phosphor. Of these, it is preferable that the LED element be a blue LED element. This is because the backlight module of the present disclosure can emit white light with high brightness.

[0097] Furthermore, when the LED element is a white LED element, the white LED element is appropriately selected depending on the light-emitting method of the white LED element. Examples of light-emitting methods of white LED elements include a combination of a red LED, a green LED, and a blue LED, a combination of a blue LED, a red phosphor, and a green phosphor, a combination of a blue LED and a yellow phosphor, and a combination of an ultraviolet LED, a red phosphor, a green phosphor, and a blue phosphor. Therefore, the white LED element may have, for example, a red LED light-emitting portion, a green LED light-emitting portion, and a blue LED light-emitting portion, a blue LED light-emitting portion and a protective portion containing red and green phosphors, a blue LED light-emitting portion and a protective portion containing yellow phosphors, or a ultraviolet LED light-emitting portion and a protective portion containing red, green, and blue phosphors.

[0098] Among these, the white LED element preferably has a blue LED light-emitting unit and a protective unit containing red and green phosphors, a blue LED light-emitting unit and a protective unit containing yellow phosphors, or an ultraviolet LED light-emitting unit and a protective unit containing red, green, and blue phosphors. Among these, the white LED element preferably has a blue LED light-emitting unit and a protective unit containing red and green phosphors, or a blue LED light-emitting unit and a protective unit containing yellow phosphors. This is because the backlight module of the present disclosure can emit white light with high brightness. Instead of the phosphor, quantum dots can also be used as a wavelength conversion material.

[0099] The structure of the LED element can be the same as that of a general LED element. The LED elements are typically arranged at equal intervals on one side of the support substrate. The arrangement of the LED elements is appropriately selected depending on the application and size of the backlight module of the present disclosure, the size of the LED elements, etc. The arrangement density of the LED elements is also appropriately selected depending on the application and size of the backlight module of the present disclosure, the size of the LED elements, etc.

[0100] The size (chip size) of the LED element can be a general chip size, but is preferably a chip size known as a mini LED or micro LED. The size of the LED element may be, for example, several hundred micrometers square or several tens of micrometers square. Specifically, in the case of a mini LED, the size of the LED element is preferably 100 μm square to 1000 μm square, more preferably 100 μm square to 500 μm square, and may be 100 μm square to 300 μm square.

[0101] The small size of the LED elements allows for high density arrangement of the LED elements, i.e., a small spacing (pitch) between the LED elements, which allows for a thinner sealing material, resulting in a thinner and lighter device.

[0102] The LED elements used in the present disclosure are arranged on one side of the support substrate. In the present disclosure, it is sufficient that at least one LED element is arranged on one side of the support substrate, but typically, multiple LED elements are arranged. The arrangement of the multiple LED elements is not particularly limited, but it is preferable that they are arranged in an X x Y matrix (X and Y are each an integer of 1 or greater). The numbers X and Y are selected appropriately depending on the application of the backlight module.

[0103] (3) Other The LED substrate of the present disclosure is not particularly limited as long as it has the above-mentioned support substrate and LED element, and necessary components can be appropriately selected and added. Such components can include, for example, wiring sections, terminal sections, and insulating layers for protecting these. When wiring sections are included, the wiring sections are electrically connected to the LED elements. The wiring sections, terminal sections, and insulating layers can be the same as those used in known LED substrates, so individual descriptions are omitted.

[0104] In the LED substrate of the present disclosure, a reflective layer can be disposed on the surface of the support substrate on which the LED elements are disposed, in an area other than the LED element mounting area.

[0105] The reflective layer can be the same as the reflective layer generally used in LED substrates. Specifically, the reflective layer can be a white resin film containing metal particles, inorganic particles, or pigments and resin, a metal film, a porous film, or the like. The thickness of the reflective layer is not particularly limited as long as it can obtain the desired reflectance, and can be set appropriately.

[0106] The method for forming the LED substrate can be the same as a known method, and therefore a description thereof will be omitted here.

[0107] 3. Other configurations The backlight module of the present disclosure is not particularly limited as long as it includes a sealing member containing a light diffusing agent and an LED substrate, and necessary components can be selected and added as appropriate. Examples of such components include the optical members described below.

[0108] (1) Wavelength conversion material The backlight module of the present disclosure may optionally include a wavelength conversion member. The wavelength conversion member functions to generate white light when combined with an LED substrate. The wavelength conversion member is disposed on the light-emitting surface side of the LED substrate, and can be disposed closer to the viewer than the LED elements and sealing member. The wavelength conversion member contains a wavelength conversion material, such as a phosphor or quantum dots.

[0109] When the wavelength conversion member is positioned closer to the viewer than the LED element and the sealing member, it may be, for example, a resin sheet in which the wavelength conversion member is dispersed, or a laminate having a resin layer in which the wavelength conversion member is dispersed on a transparent substrate, but the former is more preferable from the viewpoint of thinning. The resin used for the resin sheet is not particularly limited as long as it can disperse the wavelength conversion material, but is preferably a thermoplastic resin. This is because the wavelength conversion member can be formed using a resin sheet in which the wavelength conversion material is dispersed, thereby achieving good flatness. The thermoplastic resin is not particularly limited as long as it has high light transmittance, and general-purpose resins can be used.

[0110] The phosphor can be appropriately selected depending on the color of light emitted from the LED element, and examples thereof include blue phosphor, green phosphor, red phosphor, amber phosphor, yellow phosphor, etc. For example, when the LED element is a blue LED element, it is preferable to use a yellow phosphor as the phosphor. Furthermore, when the LED element is an ultraviolet LED element or an infrared LED element, it is preferable to use three color phosphors, i.e., red phosphor, blue phosphor, and green phosphor. The shape of the phosphor is, for example, particulate. The average primary particle size (D 50) is, for example, 1 μm or more and 100 μm or less. The average particle size is the average value when 20 random phosphor particles are measured in an image of the cross section of the wavelength conversion member observed with a scanning electron microscope (SEM).

[0111] The proportion of the phosphor in the wavelength conversion member is not particularly limited as long as it is sufficient to generate the desired white light, and is, for example, 40% by mass or more and 60% by mass or less.

[0112] The quantum dots are not particularly limited as long as they are conventionally used in backlight modules. As quantum dot particle diameter decreases, the energy band gap increases. In other words, as the crystal size decreases, the quantum dot emission shifts toward blue, i.e., toward higher energy. Therefore, by changing the quantum dot particle diameter, the emission wavelength can be adjusted across the entire wavelength range of the ultraviolet, visible, and infrared spectrum. For example, quantum dots with a particle diameter of 2.0 nm to 3.5 nm emit blue light; quantum dots with a particle diameter of 4.0 nm to 5.0 nm emit green light; and quantum dots with a particle diameter of 5.5 nm to 6.5 nm emit red light.

[0113] Information such as the particle size, average particle size, shape, and dispersion state of quantum dots can be obtained using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). The average particle size of quantum dots can be determined by observing the cross section of a wavelength conversion member using a transmission electron microscope or a scanning transmission electron microscope, and calculating the average diameter of 20 quantum dots measured from the observed image.

[0114] The wavelength conversion member of the present disclosure may use one type of quantum dot, but it is also possible to use two or more types of quantum dots that each have an emission band in a single wavelength range due to differences in particle size or material, etc.

[0115] The content of the quantum dots in the wavelength conversion member is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.2% by mass or more and 5% by mass or less. If the content of the quantum dots is less than the above lower limit, sufficient luminescence intensity may not be obtained.

[0116] The thickness of the wavelength conversion member is not particularly limited as long as it can generate the desired white light, but is, for example, 10 μm or more and 1000 μm or less.

[0117] (2) Reflective material In the backlight module of the present disclosure, a reflective member is preferably disposed at least directly above the LED element. By providing the reflective member directly above the LED element in this manner, even if the thickness of the sealing member directly above the LED element is thin, the reflective member can reflect and diffuse the light directly above the LED element to the surroundings, thereby improving the in-plane uniformity of brightness due to the light diffusing agent contained in the sealing material.

[0118] Examples of such reflective members include a dielectric multilayer film, a reflective structure having a patterned first reflective film arranged on one surface of a transparent substrate and a patterned second reflective film arranged on one or the other surface of the transparent substrate, in which the openings of the first reflective film and the openings of the second reflective film are positioned so as not to overlap in a planar view, and the first reflective film and the second reflective film are arranged apart in the thickness direction, and a reflective diffraction grating.

[0119] Furthermore, a conventionally known transmissive reflector can be used as the reflective member. For example, a transmissive substrate can be used, which includes a reflective portion made of a reflective material laminated in a predetermined pattern on at least one surface of the transmissive support substrate, and a transmissive portion formed in an area of ​​the transmissive support substrate where the reflective portion is not formed. In such a transmissive support substrate, the central portion around the position directly above the LED element can be composed only of the reflective portion.

[0120] In the present disclosure, the "directly above" portion of the LED element refers to the region of the light-emitting region of the LED element that is shifted vertically relative to the surface of the support substrate for the LED element. In the present disclosure, it is sufficient that a reflective member is disposed at least in this region.

[0121] (3) Other The backlight module of the present disclosure may further include known optical members that are conventionally used in backlight modules, such as a prism sheet, a reflective polarizing sheet, and the like.

[0122] The prism sheet in the present disclosure has a function of concentrating incident light and improving luminance in a concentrated front direction. The prism sheet is, for example, a transparent resin substrate having a prism pattern including an acrylic resin or the like disposed on one side thereof.

[0123] As the prism sheet, for example, a brightness enhancement film BEF series manufactured by 3M can be used.

[0124] The reflective polarizing sheet according to the present disclosure has the function of transmitting only a first linearly polarized light component (e.g., P-polarized light) and reflecting a second linearly polarized light component (e.g., S-polarized light) that is orthogonal to the first linearly polarized light component without absorbing it. The second linearly polarized light component reflected by the reflective polarizing sheet is reflected again and re-enters the reflective polarizing sheet in a depolarized state (a state containing both the first linearly polarized light component and the second linearly polarized light component). Thus, the reflective polarizing sheet transmits the first linearly polarized light component of the re-entering light, and reflects again the second linearly polarized light component that is orthogonal to the first linearly polarized light component. By repeating the above process, approximately 70% to 80% of the light output from the diffusing member is output as the first linearly polarized light component. Therefore, when the backlight module of the present disclosure is used in a display device, by aligning the polarization direction of the first linearly polarized component (transmission axis component) of the reflective polarizing sheet with the transmission axis direction of the polarizer of the display panel, all of the light emitted from the backlight module can be used to form images on the display panel. As a result, even if the light energy input from the LED elements is the same, it is possible to form images with higher brightness than when a reflective polarizing sheet is not provided.

[0125] Examples of the reflective polarizing sheet include the DBEF series brightness enhancement film manufactured by 3M Co., Ltd. Also, examples of the reflective polarizing sheet that can be used include the WRPS high brightness polarizing sheet manufactured by Shinwha Intertek Co., Ltd. and a wire grid polarizer.

[0126] The optical member may be attached to the sealing member using, for example, an adhesive layer. The adhesive used for the adhesive layer may be the same as that used in general display devices, and therefore, a description thereof will be omitted here.

[0127] 4. Backlight module using light-emitting diodes The backlight module using the LED of the present disclosure is used as a direct type backlight module.

[0128] The method for manufacturing the backlight module of the present disclosure is not particularly limited as long as it is a method that can obtain a backlight module having the above-mentioned configuration, and can be manufactured by a conventional method. For example, the present disclosure can also provide a method for manufacturing a backlight module that includes a step of preparing an LED substrate, a step of preparing an encapsulant sheet containing a light diffusing agent and a thermoplastic resin, and a step of arranging the encapsulant by laminating the encapsulant sheet on the LED element side of the LED substrate using a lamination method.

[0129] B.Display device The display device of the present disclosure is characterized by including a display panel and the above-described backlight module disposed on the rear surface of the display panel.

[0130] A display device (liquid crystal display device) according to the present disclosure will be described with reference to the drawings. Fig. 3 is a schematic cross-sectional view showing an example of a display device according to the present disclosure. The liquid crystal display device 100 shown in Fig. 3 comprises a backlight module 10 including a support substrate 11, an LED substrate 1 having LED elements 12 arranged on one side of the support substrate, and a sealing member 2 containing a light diffusing agent that seals the LED elements 12, and a liquid crystal panel 20 arranged on the light-emitting surface side of the backlight module. In Fig. 3, the backlight module 10 has a wavelength conversion member 3.

[0131] According to the present disclosure, a display device having a reduced thickness can be provided. Hereinafter, each configuration of the display device of the present disclosure will be described.

[0132] 1. Backlight module The backlight module in the display device of the present disclosure can be the same as that described in the above section "A. Backlight Module," and therefore will not be described here.

[0133] 2. Display panel A display panel is typically a component having a color filter substrate, a counter substrate, and a liquid crystal layer disposed between the color filter substrate and the counter substrate. The color filter substrate, counter substrate, and liquid crystal layer used in a display panel can be similar to those used in known liquid crystal panels, and therefore will not be described here.

[0134] 3.Other The display device of the present disclosure is not particularly limited as long as it includes a backlight module using the above-described LED elements and a display panel, and any necessary components can be appropriately selected and added, such as a polarizing plate, a front panel, etc. The display device of the present disclosure may be a tiling display device in which a plurality of display devices are arranged in parallel. When a sealing material sheet is used, the sealing material can be a sealing member with good flatness, so that the boundaries between the display devices are less likely to be observed as seams by an observer, and a tiling display device with good display visibility can be obtained.

[0135] The tiling method of the display device can be the same as a general tiling method.

[0136] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Explanation of symbols]

[0137] 1...LED board 2... Sealing member 3... Wavelength conversion material 10, 40...Backlight module 11, 41 ... Support substrate 12, 42... LED element 43...Spacer 20...LCD panel 100…Liquid crystal display device

Claims

[Claim 1] a light-emitting diode substrate having a support substrate and a light-emitting diode element disposed on one surface side of the support substrate; a sealing member that is disposed on a surface of the light-emitting diode substrate that faces the light-emitting diode element and that seals the light-emitting diode element by being in close contact with the light-emitting diode substrate, the sealing member is composed of three layers, and only the central layer of the three layers contains a light diffusing agent; The display device, wherein all three layers of the sealing member contain an olefin resin and a silane copolymer obtained by copolymerizing an α-olefin with an ethylenically unsaturated silane compound as a comonomer.

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