JP7485189B2 - BACKLIGHT MODULE AND DISPLAY DEVICE - Google Patents

Description

This disclosure relates to a direct-type backlight module that uses light-emitting diodes, and a display device that uses the same.

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 are broadly divided into direct-type and edge-light-type. Edge-light-type LED backlight modules are usually used in small and medium-sized display devices such as mobile terminals such as smartphones, but from the standpoint of brightness, etc., the use of direct-type LED backlight modules is being considered. On the other hand, direct-type LED backlight modules are often used in large display devices such as large-screen LCD TVs.

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 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.

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, in order 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. In addition, when blue LED elements are used as the light source, for example, a wavelength conversion material containing phosphors or quantum dots is placed on the LED light emission surface side to whiten the light.

Specifically, as shown in FIG. 4, a conventional direct-type LED backlight module 40 has a spacer 43 provided on a support substrate 41 on which LED elements 42 are arranged, providing 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.

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

As shown in FIG. 4 above, in a backlight module using conventional direct-type LED elements, spacers are arranged to maintain a predetermined distance between the LED elements and the diffusion plate. However, the light emitted from the LED elements may be blocked or reflected by the spacers, resulting in uneven brightness. In addition, a large number of spacers must be provided, but when the pitch is fine, such as in the mini-LEDs and micro-LEDs described above, it is difficult to arrange a large number of spacers.

Therefore, in a backlight module using LED elements, a configuration has been proposed in which a sealing member that seals the LED elements is disposed 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 thinness compared to edge-light type backlight modules, and further improvements are required.

JP 2010-272245 A JP 2019-61954 A

This disclosure has been made in consideration of the above circumstances, and its main objective is to provide an LED backlight module and display device that can be made thinner.

The present disclosure provides an LED backlight module that includes 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, the sealing member containing a light diffusing agent.

The present disclosure provides a display device including a display panel and the above-mentioned LED backlight module disposed on the rear surface of the display panel.

The present disclosure has the effect of providing an LED backlight module and a display device that can be made thinner.

1 is a schematic cross-sectional view illustrating a backlight module of the present disclosure. 1 is a schematic cross-sectional view illustrating a backlight module of the present disclosure. 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a conventional backlight module.

The backlight module and display device of the present disclosure are described below. However, the present disclosure can be implemented in many different embodiments, and should not be interpreted as being limited to the description of the embodiments exemplified below. In addition, in order to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each component as compared to the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each figure, elements similar to those described above with respect to the previous figures are given the same reference numerals, and detailed explanations may be omitted as appropriate.

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

The inventors attempted to increase the number of LED elements and increase their arrangement density in order to make the backlight module thinner, but this was not possible to make the module sufficiently thin, and was practically difficult to achieve as it would lead to increased costs and power consumption. Therefore, instead of providing space by arranging spacers, they attempted to shorten the distance between the optical component and the LED substrate by filling the LED substrate with a sealant, but this did not fully satisfy the demand for a thinner module.

The inventors discovered that by filling the LED elements in a backlight module with a sealing material, the distance between the LED board 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 in the sealing material, it is no longer necessary 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.

A. Backlight Module The backlight module of the present disclosure includes a support substrate, an LED substrate having LED elements arranged on one surface of the support substrate, and a sealing member arranged on the surface of the LED substrate facing the LED elements and sealing the LED elements, the sealing member containing a light diffusing agent.

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 and a thinner design can be achieved. In addition, since the process of providing a diffusion plate is no longer necessary, the manufacturing process can be simplified.

The backlight module of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing an example of the backlight module of the present disclosure.
The backlight module 10 shown in Fig. 1 includes a support substrate 11, an LED substrate 1 having LED elements 12 arranged on one surface of the support substrate 11, and a sealing member 2 containing a light diffusing agent 50 arranged on the surface of the LED substrate 1 facing the LED elements 12 and sealing 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 provided on the sealing member 2.

The backlight module of the present disclosure is characterized in that it has a sealing member that seals the LED elements, and that this sealing member contains a light diffusing agent. Each component of the backlight module of the present disclosure is described below.

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. The sealing member is disposed between the LED substrate and an optical member such as a wavelength conversion member.

In this specification, "transparent" and "transparency" refer to transparency that does not impair the visibility of the light from the LED element.

(1) Light Diffusing Agent The encapsulating member in the present disclosure contains a light diffusing agent that diffuses light emitted from the LED element.

The light diffusing agent is usually dispersed in a resin layer having transparency. The material of the light diffusing agent is not particularly limited as long as it can diffuse the light from the LED element, and may be, for example, an organic material or an inorganic material. When the material of the light diffusing agent is an organic material, for example, polymethyl methacrylate (PMMA) resin particles, melamine resin particles, silicone resin particles, styrene resin, polyurethane resin, polyester resin, fluorine-based resin, and synthetic resins such as copolymers thereof can be mentioned. These may be used alone or in combination of two or more. On the other hand, when the material of the light diffusing agent is an inorganic material, for example, TiO ₂ , SiO ₂ , Al ₂ O ₃ , silicon, zirconia, glass, smectite, kaolinite, etc. can be mentioned. These may be used alone or in combination of two or more.

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 is, for example, 1.4 to 2.2. Such a refractive index can be measured by the Becke method, minimum deviation method, deviation analysis, mode line method, ellipsometry, Abbe method, etc.

In addition, it is preferable that the refractive index of the light diffusing agent has a predetermined refractive index difference from the resin that constitutes the sealing material. Specifically, it is preferable that the refractive index difference is 0.03 or more, and particularly 0.05 or more.

From the viewpoint of dispersibility in the resin, the shape of the light diffusing agent is preferably particulate.

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

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, from 0.1 mass % to 10 mass %.
Within such a range, the light from the LED element can be reliably diffused, and the light diffusing agent is unlikely to disperse and form a lump, which is preferable. In addition, when the sealing member has a multi-layer structure described later, the proportion of the light diffusing agent refers to the proportion of the light diffusing agent in the light diffusing agent-containing layer.

(2) Resin In the sealing member of the present disclosure, the light diffusing agent is dispersed in the 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 display device field can be used. For example, thermoplastic resin, curable resin, etc. can be used, and preferably, thermoplastic resin.

When using a thermosetting resin or a photocurable resin, a liquid resin composition is usually applied onto 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. In addition, in the case of the above-mentioned curable resin, curing shrinkage occurs as the resin cures, so in this case too, it is difficult to control the film thickness in the periphery of the LED substrate.

Display devices using the backlight module of the present disclosure may be used, for example, in tiling. In such cases, if the film thickness of 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.

In the present disclosure, by using a thermoplastic resin as a 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, which has the effect of preventing the above-mentioned problems.

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 deteriorating components, or that contains deteriorating components to an extent that does not affect the deterioration of the LED substrate, or a resin that does not generate deteriorating components during the manufacture and use of the backlight module, or that generates deteriorating components to an extent that does not affect the deterioration of the LED substrate, even if they do.

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

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

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, it is possible for the resin to penetrate into the gaps in the LED element, thereby providing sufficient sealing performance and, furthermore, forming a sealing member with excellent adhesion to the LED substrate.

In this disclosure, MFR refers to the value measured according to JIS K7210 at 190°C and a load of 2.16 kg. However, the MFR of polypropylene resin refers to the MFR value measured according to JIS K7210 at 230°C and a load of 2.16 kg.

When the sealing material is a multi-layer material as described below, the MFR is measured using the above-mentioned measurement method while all layers are in a multi-layered state where they are laminated together, and the measured value obtained is regarded as the MFR value of the multi-layer sealing material.

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 in a temperature range that does not deteriorate 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).

In the present disclosure, the thermoplastic resin may be, for example, an olefin resin, an ionomer resin, or a polyvinyl butyral resin.

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 a low melt viscosity, allowing them to encapsulate the above-mentioned LED elements well. Furthermore, among olefin-based resins, polyethylene-based resins or polypropylene-based resins are preferred.

The polyethylene resins used in this 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 multiple different compounds having ethylenically unsaturated bonds, and modified resins obtained by grafting other chemical species onto these resins.

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

In addition, a curable resin such as a photocurable or heat-curable resin can be used as the resin material used for the sealing member. When a curable resin is used, the sealing member can be obtained by filling a liquid sealing material composition containing the curable resin and a light diffusing agent and curing it.

Such curable resins include those that have traditionally been used as sealing materials, such as epoxy resins, acrylic resins, and silicone resins.

(3) Structure of the sealing member The sealing member in the present disclosure may be, for example, as shown in FIG. 1, a single-layer member in which the sealing member 2 is composed of a single resin layer, or may be a multilayer member in which a plurality of resin layers (three layers in FIG. 2) are laminated, as shown in FIG. 2.
By using the above-mentioned 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.

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

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 be added.

In the case where the sealing member in the present disclosure is a multi-layer member, it is sufficient that at least one layer contains a light diffusing agent, but in the present disclosure, it is preferable that the light diffusing agent is 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 adheres to the LED substrate, among the multi-layer members. This is because if the light diffusing agent is contained in the layer that adheres to the LED substrate, it may adversely affect the adhesion to the LED substrate. In addition, by containing the light diffusing agent in a layer other than the layer that adheres to the LED substrate, it is possible to prevent the layer containing the light diffusing agent from becoming thin directly above the LED element, and it is possible to make the brightness more uniform.
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.

The thickness of the sealing member is not particularly limited and can be appropriately selected depending on the layer structure of the LED substrate. 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, and if the thickness is 600 μm or more, it may have a negative effect on light transmittance.

When the sealing member is formed as a three-layered multilayer member, the thickness of the central layer (resin layer 22 in FIG. 2) is preferably 60 μm or more and 400 μm or less, and more preferably 250 μm or more and 350 μm or less. In this case, the thickness of each of the outer layers (resin layer 21 in FIG. 2) is preferably 15 μm or more and 200 μm or less.

In particular, the sealing member in the present disclosure is preferably a multi-layer member having a central layer and an adhesive layer disposed on the LED substrate side of the central layer, and in this case, the thickness of the adhesive layer disposed on the LED substrate side is preferably greater than the height of the LED element. This is because the thickness of the central layer can be made uniform within the backlight module surface in the areas directly above the LED element and other than the areas directly above it. The light diffusing agent is preferably contained in the central layer as described above, and in this disclosure, the central layer in this case is referred to as a light diffusing agent-containing layer.

In this specification, "thickness" can be measured using a known measurement method capable of measuring sizes on the order of μm. For example, it 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".

(4) Others 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. In addition, by containing a wavelength conversion material used in the wavelength conversion material described later, it is possible to incorporate the function of the wavelength conversion material into the encapsulant, and it is possible to obtain a backlight module with a thinner thickness.

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 molding method for 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.

Specifically, an LED substrate and a sealing material sheet are prepared, the sealing material sheet is laminated on the side of the LED substrate facing the LED elements, and then the sealing material sheet is pressed against the LED substrate, for example by using a vacuum lamination method, to form the sealing member.
In the case of using a sheet-like encapsulant in this way, the dispersibility of the light diffusing agent is better than when a encapsulant is formed using a liquid encapsulant composition. In addition, by using a sheet-like encapsulant containing a thermoplastic resin, a encapsulant having better flatness can be obtained than a encapsulant obtained by curing a liquid thermosetting resin composition or a liquid photocurable resin composition.

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

(5) Specific embodiment of sealing member As described above, the sealing member preferably contains a thermoplastic resin, more preferably contains an olefin-based resin, and further preferably contains a polyethylene-based resin. In particular, the sealing member preferably uses a polyethylene-based resin having a density of 0.870 g/cm ³ or more and 0.930 g/cm ³ or less as a base resin. This is because such a sealing member has good adhesion to the LED substrate and good conformability to the members arranged on the LED substrate.

A suitable sealing member will now be described in detail.
The sealing member is formed of a resin film having a polyethylene-based resin of 0.870 g/ ^cm3 or more and 0.930 g/ ^cm3 or less 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.

The encapsulant 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 is preferably made of a polyethylene-based resin having a density of 0.910 g/ ^cm3 or more and 0.930 g/cm3 or ^less as a base resin, and the skin layer is preferably made of a polyethylene-based resin having a density of 0.890 g/ ^cm3 or more and 0.910 g/ ^cm3 or less and a lower density than the base resin for the core layer as a base resin.
In the case where the encapsulant sheet is a multilayer film having three or more layers, it is preferable that the core layer contains a light diffusing agent.

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, and more preferably 550 μm or less. If the total thickness is too thin, it is not possible to sufficiently cushion the impact, but if the total thickness is within the above range, it is possible to achieve a sufficiently favorable level of both molding properties and heat resistance. However, if the total thickness is too thick, it is difficult to achieve any further improvement in the impact cushioning effect, it is not possible to meet the demand for a thinner film, and it is uneconomical.

The thickness of the core layer in the multilayer film is preferably, for example, 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 preferably, for example, 400 μm or less, and more preferably 350 μm or less. In this case, the thickness of each layer of the skin layer can be, for example, 15 μm or more, or may be 30 μm or more, or 200 μm or less. By setting the thickness of each layer within such a range, the heat resistance and molding characteristics of the encapsulant sheet can be maintained within a good range.

The above-mentioned encapsulant sheet is formed by molding and processing the encapsulant composition, which will be described in detail below, into a sheet shape using a conventionally known method.

When the above-mentioned encapsulant sheet is formed as an encapsulating member, the encapsulant composition used to manufacture each layer has a base resin that has a different density range, etc. for each layer.

In this case, the above-mentioned encapsulant composition is used for forming each layer, with a encapsulant composition for the core layer and a encapsulant composition for the skin layer. Then, by forming a multilayer film with a predetermined thickness and a three-layer structure in which skin layers are arranged on both outermost surfaces using each of the encapsulant compositions for the core layer and the skin layer, it is possible to manufacture a sealing member 21 with a three-layer structure of a skin layer 22a, a core layer 23, and a skin layer 22b, as shown in FIG. 8, for example.

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.

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 or more and 0.930 g/cm ³ or less, more preferably 0.920 g/cm ³ or less. 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.

The melting point of the encapsulant composition for the core layer is preferably 90°C or more and 135°C or less, and more preferably 100°C or more and 115°C or less. By setting the melting point of the core layer within the above melting point range, the heat resistance and molding properties of these encapsulant compositions can be maintained within a preferred range. It is possible to increase the melting point of the encapsulant composition 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, it is preferable that the polypropylene content is 5% by mass or more and 40% by mass or less of the total resin components of the core layer.

The polypropylene contained in the core layer is preferably a homopolypropylene (homoPP) resin. HomoPP is a polymer consisting of only polypropylene alone and has high crystallinity, so it has higher rigidity than block PP or random PP. By using it as an additive resin to the encapsulant composition for the core layer, the dimensional stability of the encapsulating member can be improved. In addition, it is preferable that the homoPP used as an additive resin to the encapsulant composition for the core layer has an MFR of 5 g/10 min to 125 g/10 min at 230 ° C and a load of 2.16 kg measured in accordance with JIS K7210. If the MFR is too small, the molecular weight becomes large and the rigidity becomes too high, making it difficult to ensure the desired sufficient flexibility of the encapsulant composition. In addition, if the MFR is too large, the fluidity during heating is not sufficiently suppressed, and the encapsulant sheet cannot be provided with sufficient heat resistance and dimensional stability.

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 characteristics of the encapsulating member can be maintained within a preferred range. In addition, the processability during film formation can be sufficiently improved, which contributes to improving the productivity of the encapsulating member.

The content of the base resin relative to the total 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 base resin is contained within the above range, other resins may be contained.

As with the encapsulant composition for the core layer, low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), or 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 them, from the viewpoint of molding properties, metallocene linear low-density polyethylene resin (M-LLDPE) can be particularly preferably used as the encapsulant composition for the skin layer.

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 or more and 0.910 g/cm ³ or less, more preferably 0.899 g/cm ³ or less. 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.

The melting point of the sealing material composition for the skin layer is preferably 55°C or higher and 100°C or lower, and more preferably 80°C or higher and 95°C or lower. By setting the melting point of the sealing material composition for the skin layer within the above range, the adhesion of the sealing member can be further reliably improved.

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.

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

It is more preferable that all of the above-described sealing material compositions contain a certain amount of a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as comonomers, as necessary. Such a graft copolymer increases the degree of freedom of the silanol groups that contribute to adhesive strength, and therefore can improve the adhesion of the sealing material to other members.

The silane copolymer can be, for example, the silane copolymer described in JP 2003-46105 A. By using the above silane copolymer as a component of the sealing material composition, it is possible to obtain a sealing material 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 fusion properties without being affected by manufacturing conditions such as heat compression bonding when arranging the sealing member, and can be obtained stably and at low cost.

As the silane copolymer, any of random copolymers, alternating copolymers, block copolymers, and graft copolymers can be preferably used, but graft copolymers are more preferable, and graft copolymers in which polyethylene for polymerization is used as the main chain and an ethylenically unsaturated silane compound is polymerized as a side chain are even more preferable. Such graft copolymers have a high degree of freedom for the silanol groups that contribute to the adhesive strength, and can therefore improve the adhesiveness of the sealing member.

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 copolymer mass. When the content of the ethylenically unsaturated silane compound constituting the copolymer of an α-olefin and an ethylenically unsaturated silane compound is high, the mechanical strength and heat resistance are excellent, but when the content is excessive, the tensile elongation and heat fusion properties tend to be poor.

The content of the silane copolymer in 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. In particular, it is more preferable that the encapsulant composition for the skin layer contains 10% by mass or more of the silane copolymer. The amount of silane modification in the silane copolymer is preferably about 1.0% by mass or more and 3.0% by mass or less. The preferred content range of the silane copolymer in the encapsulant composition is based on the assumption that the amount of silane modification is within this range, and it is desirable to fine-tune it appropriately according to the fluctuation of the amount of modification.

All of the sealing material compositions may also contain an adhesion improver as appropriate. Addition of an adhesion improver can improve adhesion durability with other members. As the adhesion improver, a known silane coupling agent can be used, but a silane coupling agent having an epoxy group or a silane coupling agent having a mercapto group is particularly preferred.

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

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

(1) Support Substrate The support substrate is a member that supports the LED elements, the sealing member, etc.
The supporting substrate may be transparent or may not be transparent. The supporting substrate may be soft (flexible) or may be rigid. The material of the supporting substrate may be an organic material, an inorganic material, or a composite material in which both an organic material and an inorganic material are combined.

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.

The support substrate is usually a flat substrate, but for example, at least one of the side on which the LED elements are arranged or the opposite side may be curved.

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.

The planar shape of the support substrate can be appropriately selected without any particular limitation, but is typically rectangular.
The supporting substrate may be a printed circuit board on which a circuit is formed by printing.

(2) Light-Emitting Diode Element The LED element is a component disposed on one surface side of the support substrate, and a light-emitting portion of the LED element functions as a light source of the display device described below.

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 as a backlight module, and examples include LED elements that can emit white, blue, ultraviolet, or infrared light.

The LED element may be a chip-shaped LED element. The form of the LED element may be, for example, the light-emitting portion (also called an LED chip) itself, or may be a packaged LED (also called a chip LED) such as a surface-mount type or chip-on-board type. The packaged LED may 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 may 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 may be, for example, a white LED element.

When the backlight module of the present disclosure is one that irradiates 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. The blue LED element can be combined with, for example, a yellow phosphor, or with a red phosphor and a green phosphor to generate white light. The ultraviolet LED element can be combined with, for example, a red phosphor, a green phosphor, and a blue phosphor to generate white light. Of these, it is preferable that the LED element is a blue LED element. This is because the backlight module of the present disclosure can irradiate white light with high luminance.

In addition, when the LED element is a white LED element, the white LED element is appropriately selected depending on the light emission method of the white LED element. Examples of the light emission method of the white LED element 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 part, a green LED light-emitting part, and a blue LED light-emitting part, a blue LED light-emitting part and a protective part containing red phosphor and green phosphor, a blue LED light-emitting part and a protective part containing yellow phosphor, or an ultraviolet LED light-emitting part and a protective part containing red phosphor, green phosphor, and blue phosphor.

Among these, it is preferable that the white LED element has a blue LED light-emitting section and a protective section containing red and green phosphors, a blue LED light-emitting section and a protective section containing yellow phosphors, or an ultraviolet LED light-emitting section and a protective section containing red, green, and blue phosphors. Among these, it is preferable that the white LED element has a blue LED light-emitting section and a protective section containing red and green phosphors, or a blue LED light-emitting section and a protective section containing yellow phosphors. This is because the backlight module of the present disclosure can irradiate white light with high luminance. Quantum dots can also be used as a wavelength conversion material instead of the above phosphors.

The structure of the LED element can be the same as that of a general LED element.
The LED elements are usually arranged at equal intervals on one surface 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.

The size (chip size) of the LED element can be a general chip size, but is preferably a chip size called 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.

The small size of the LED elements allows the LED elements to be arranged at high density, i.e., the spacing (pitch) between the LED elements can be made small, allowing the thickness of the sealing material to be reduced. This allows for a thinner and lighter product.

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 more). The numbers X and Y are appropriately selected depending on the application of the backlight module.

(3) Others The LED substrate in the present disclosure is not particularly limited as long as it has the above-mentioned support substrate and LED element, and necessary configurations can be appropriately selected and added. Such configurations can include, for example, a wiring portion, a terminal portion, and an insulating layer that protects them. When the wiring portion is included, the wiring portion is electrically connected to the LED element. The wiring portion, the terminal portion, and the insulating layer can be the same as those used in known LED substrates, so that individual descriptions are omitted.

The LED substrate in this disclosure is the surface of the support substrate on which the LED elements are arranged, and a reflective layer can be arranged in areas other than the LED element mounting area.

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, etc. The thickness of the reflective layer is not particularly limited as long as the desired reflectance is obtained, and can be set appropriately.

The method for forming the LED substrate can be the same as known methods, so a detailed explanation is omitted here.

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

(1) Wavelength conversion member The backlight module of the present disclosure may be provided with a wavelength conversion member as necessary. The wavelength conversion member has a function of generating white light by combining with an LED substrate. The wavelength conversion member is provided on the light emitting surface side of the LED substrate, and can be provided closer to the viewer than the LED element and the sealing member. The wavelength conversion member contains a wavelength conversion material, and examples of the wavelength conversion material include phosphors and quantum dots.

When the wavelength conversion member is arranged on the observer side of the LED element and the sealing member, it may be, for example, a resin sheet in which the wavelength conversion member is dispersed, or it may be 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, and the flatness can be improved. The thermoplastic resin is not particularly limited as long as it has a high light transmittance, and a general-purpose resin can be used.

The phosphor can be appropriately selected according to 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. Also, when the LED element is an ultraviolet LED element or an infrared LED element, it is preferable to use three colors of phosphors, red phosphor, blue phosphor, and green phosphor. The shape of the phosphor is, for example, particulate. The average primary particle size (D ₅₀ ) of the phosphor is, for example, 1 μm or more and 100 μm or less. The average particle size is the average value when any 20 phosphors are measured in an observation image of a cross section of the wavelength conversion member by a scanning electron microscope (SEM).

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

The quantum dots are not particularly limited as long as they are conventionally used in backlight modules. As the particle diameter of the quantum dots becomes smaller, the energy band gap becomes larger. In other words, as the crystal size becomes smaller, the emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle diameter of the quantum dots, it is possible to adjust the emission wavelength over the entire wavelength range of the ultraviolet, visible, and infrared spectrum. For example, when the particle diameter of the quantum dots is 2.0 nm or more and 3.5 nm or less, blue light is emitted, when the particle diameter of the quantum dots is 4.0 nm or more and 5.0 nm or less, green light is emitted, and when the particle diameter of the quantum dots is 5.5 nm or more and 6.5 nm or less, red light is emitted.

Information on the particle size, average particle size, shape, dispersion state, etc. 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 the wavelength conversion material using a transmission electron microscope or a scanning transmission electron microscope, and taking the average value of the diameters of 20 quantum dots measured from the observed image.

In the wavelength conversion member of the present disclosure, one type of quantum dot may be used, but it is also possible to use two or more types of quantum dots that have different particle sizes or materials, each of which has an emission band in a single wavelength range.

The content of quantum dots in the wavelength conversion material 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 quantum dots is less than the above lower limit, sufficient luminescence intensity may not be obtained.

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.

(2) Reflective Member In the backlight module of the present disclosure, a reflective member is preferably disposed at least directly above the LED element. By providing a 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 the light directly above the LED element and diffuse it to the surroundings, thereby improving the in-plane uniformity of brightness due to the light diffusing agent contained in the sealing material.

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, the openings of the first reflective film and the openings of the second reflective film being positioned so as not to overlap in a plan view, and the first reflective film and the second reflective film being spaced apart in the thickness direction, and a reflective diffraction grating.

In addition, a conventionally known transmissive reflector can be used as the reflective member. For example, a transmissive support substrate can be used that 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 a reflective portion.

In this disclosure, the portion directly above the LED element refers to the area where the light-emitting area of the LED element is moved vertically relative to the surface of the support substrate for the LED element. In this disclosure, it is sufficient that a reflective member is disposed at least in this area.

(3) Others The backlight module of the present disclosure may further include known optical members used in conventional backlight modules, such as a prism sheet, a reflective polarizing sheet, and the like.

The prism sheet in this disclosure has the function of concentrating incident light and improving the brightness 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 arranged on one side thereof.

As a prism sheet, for example, 3M's BEF series brightness enhancement film can be used.

The reflective polarizing sheet in the present disclosure has the function of transmitting only a first linearly polarized component (e.g., P-polarized light) and reflecting a second linearly polarized component (e.g., S-polarized light) that is orthogonal to the first linearly polarized component without absorbing it. The second linearly polarized component reflected by the reflective polarizing sheet is reflected again and enters the reflective polarizing sheet again in a depolarized state (a state containing both the first linearly polarized component and the second linearly polarized component). Thus, the reflective polarizing sheet transmits the first linearly polarized component of the light that re-enters the reflective polarizing sheet, and the second linearly polarized component that is orthogonal to the first linearly polarized component is reflected again. By repeating the above process, approximately 70% to 80% of the light emitted from the diffusion member is emitted as light that has become the first linearly polarized 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 polarizing plate of the display panel, all of the light emitted from the backlight module can be used for image formation on the display panel. Therefore, even if the light energy input from the LED element is the same, it is possible to form images with higher brightness than when the reflective polarizing sheet is not provided.

An example of a reflective polarizing sheet is the DBEF series of brightness enhancement films manufactured by 3M. In addition, examples of reflective polarizing sheets that can be used include the WRPS high brightness polarizing sheet and wire grid polarizer manufactured by Shinwha Intertek.

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

4. Backlight Module Using Light-Emitting Diodes The backlight module using the LEDs of the present disclosure is used as a direct-type backlight module.

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 it can be manufactured by a method that has been used conventionally. In the present disclosure, for example, it is also possible to 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 bonding the encapsulant sheet to the LED element side of the LED substrate using a lamination method.

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.

The display device (liquid crystal display device) of 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 of 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.

According to the present disclosure, a thin display device can be produced. Below, each component of the display device of the present disclosure is explained.

1. Backlight Module The backlight module in the display device of the present disclosure may be similar to the content described above in the section "A. Backlight Module," and therefore description thereof will be omitted here.

2. Display Panel A display panel is usually a member 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, the counter substrate, and the liquid crystal layer used in the display panel can be the same as those used in known liquid crystal panels, and therefore a description thereof will be omitted here.

3. Others 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 necessary components can be appropriately selected and added.
Examples of such components include a polarizing plate and a front plate.
The display device of the present disclosure may be a tiled 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 unlikely to be observed as seams by an observer, and the tiled display device can have good visibility of the display.

The tiling method for the display device can be the same as a general tiling method.

This disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical ideas described in the claims of this disclosure and provides similar effects is included within the technical scope of this disclosure.

REFERENCE SIGNS LIST 1 LED substrate 2 Sealing member 3 Wavelength conversion member 10, 40 Backlight module 11, 41 Support substrate 12, 42 LED element 43 Spacer 20 Liquid crystal panel 100 Liquid crystal display device

Claims (3)

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 facing 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 sealing member has a backlight module, and a display panel, each of the three layers containing an olefin resin and a silane copolymer obtained by copolymerizing an α-olefin with an ethylenically unsaturated silane compound as a comonomer;
The display device, wherein the backlight module is disposed on the rear surface of the display panel. The display device according to claim 1, comprising a wavelength conversion member. The display device according to claim 1 or 2, which has a reflective member disposed at least directly above the light-emitting diode element.

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