JP7443682B2 - Backlight module and display device - Google Patents

Description

The present disclosure relates to a direct type backlight module using light emitting diodes and a display device using 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 divided into direct type and edge light type. It is broadly divided into 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 viewpoint of brightness, direct-type LED backlight modules are used. This is being considered. On the other hand, in large display devices such as large-screen liquid crystal televisions, direct-type LED backlight modules are often used.

A direct-type LED backlight module has a configuration in which a plurality of LED elements are arranged on a substrate (Patent Document 1). Such direct-type LED backlight modules use so-called local dimming, which adjusts the brightness of each area of the LED backlight module according to the brightness of the displayed image by independently controlling multiple LED elements. It can be realized. This makes it possible to significantly improve contrast and reduce power consumption of the display device.

In a direct-type LED backlight module, an optical member such as a diffuser plate is disposed over the LED element in order 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 space the diffuser plate away from the LED mounting board on which the LED elements are mounted, so the diffuser plate is spaced apart from the LED mounting board. A plurality of columnar spacers are arranged for this purpose. Further, when a blue LED element is used as a light source, for example, whitening is achieved by arranging a wavelength conversion member containing a phosphor or a quantum dot on the side of the LED light emission surface.

Specifically, as shown in FIG. 4, the conventional direct-type LED backlight module 40 has spacers 43 provided on a support substrate 41 on which LED elements 42 are disposed, so that a diffusion plate 44 and a wavelength conversion A space is provided between the optical member such as the member 45 and the LED element 42 to improve the in-plane uniformity of brightness.

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

Here, as shown in FIG. 4, in the conventional backlight module using direct type LED elements, a spacer is arranged to maintain a predetermined distance between the LED element and the diffusion plate. However, uneven brightness may occur due to light emitted from the LED element being blocked or reflected by the spacer. Furthermore, although it is necessary to provide a large number of spacers, it is difficult to arrange a large number of spacers when the pitch is fine, such as in the case of the above-mentioned mini LED or micro LED, for example.

Therefore, in a backlight module using LED elements, a configuration has been proposed in which a sealing member for sealing the LED elements is disposed between the LED elements and the diffusion plate (see, for example, Patent Document 2). However, as described above, backlight modules using direct-type LED elements are disadvantageous in terms of thickness reduction compared to edge-light type backlight modules, and further improvements are required.

JP2010-272245A JP 2019-61954 Publication

The present disclosure has been made in view of the above circumstances, and its main purpose is to provide an LED backlight module and a display device that can be made thinner.

The present disclosure includes a support substrate, an LED substrate having an LED element disposed on one surface side of the support substrate, and an LED substrate disposed on a surface side of the LED element side of the LED substrate to seal the LED element. A sealing member, the sealing member containing a light diffusing agent, provides an LED backlight module.

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

The present disclosure has the advantage that it is possible to provide 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 of the present disclosure. FIG. 2 is a schematic cross-sectional view illustrating a conventional backlight module.

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. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each member compared to the embodiment, but this is only an example, and the interpretation of this disclosure is It is not limited to. In addition, in this specification and each figure, the same elements as those described above with respect to the previously shown figures are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

In this specification, when expressing the manner in which another member is placed on top of a certain member, when it is simply expressed as "on the surface side", unless otherwise specified, it means that it is in contact with a certain member, directly above or directly below it. This includes both a case where another member is placed above or below a certain member, and a case where another member is placed above or below a certain member via another member.
Moreover, in this specification, "LED" means a light emitting diode.

In order to make the backlight module thinner, the present inventors attempted to increase the number of LED elements and increase the arrangement density, but they were unable to make the backlight module thin enough, and the cost and consumption This was difficult in practice because it would lead to an increase in power consumption. Therefore, instead of arranging a spacer to create a space, an attempt was made to shorten the distance between the optical member and the LED board by filling the LED board with a sealing material, but this did not fully satisfy the demand for thinning. I couldn't do that.

By filling the LED elements in the backlight module with a sealing member, the present inventors can secure the distance between the LED substrate and the optical member, which was conventionally secured by a spacer, using the sealing member, and The present invention was completed based on the discovery that by incorporating a light diffusing agent into the member, it is not necessary to provide a diffuser plate as in the conventional case, thereby making it possible to reduce the thickness of the member.
Hereinafter, a backlight module of the present disclosure and a display device using the same will be described in detail.

A. Backlight Module The backlight module of the present disclosure includes a support substrate, an LED board having an LED element disposed on one surface side of the support substrate, and an LED substrate disposed on a surface side of the LED element side of the LED substrate, and a sealing member that seals the LED element, and the sealing member contains a light diffusing agent.

According to the present disclosure, unlike conventional backlight modules, there is no need to provide a diffusion plate, so the number of parts can be reduced and the device can be made thinner. Furthermore, since the step of providing a diffusion plate is not necessary, the manufacturing process can be simplified.

The backlight module of the present disclosure will be explained using figures. FIG. 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 board 1 having a support substrate 11 and an LED element 12 arranged on one side of the support substrate 11, and an LED board 1 arranged on the side of the LED element 12 side of the LED board 1. , a sealing member 2 containing a light diffusing agent 50 and sealing the LED element 12. Moreover, the LED board 1 is an LED board for a direct type backlight module. In FIG. 1, an example is shown in which a wavelength conversion member 3 is provided on a sealing member 2.

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

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

Note that "transparent" and "transparency" in this specification may be used as long as they are transparent to the extent that the visibility of light from the LED element is not inhibited.

(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.

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 the light from the LED element, and for example, it may be 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, fluororesin, or a copolymer thereof. Examples include synthetic resins such as. 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, examples thereof include TiO ₂ , SiO ₂ , Al ₂ O ₃ , silicon, zirconia, glass, smectite, and kaolinite. 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 or more and 2.2 or less. Such a refractive index can be measured by the Becke method, the minimum argument method, the argument analysis, the mode line method, the ellipsometry method, the Abbe method, or the like.

Moreover, it is preferable that the refractive index of the light diffusing agent has a predetermined difference in refractive index from that of the resin constituting the sealing material. Specifically, it is preferable that the refractive index difference is 0.03 or more, particularly 0.05 or more.

The shape of the light diffusing agent is preferably particulate from the viewpoint of dispersibility in the resin.

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, 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, 0.1% by mass or more and 10% by mass or less.
If it is within this range, the light from the LED element can be reliably diffused, and the light diffusing agent is difficult to disperse and there is no possibility of forming lumps, which is preferable. In addition, when a sealing member has a multilayer structure mentioned later, the ratio of the light diffusing agent mentioned above refers to the ratio of the light diffusing agent in the light diffusing agent-containing layer.

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

When a thermosetting resin or a photocurable resin is used, a liquid resin composition is usually applied onto the LED substrate and then cured; however, when a liquid resin composition is applied, the LED The film thickness may not be uniform between the center and the periphery of the substrate. In this case, it may be difficult to control the film thickness in the peripheral area. Furthermore, in the case of the above-mentioned curable resin, curing shrinkage occurs during curing, so that it becomes difficult to control the film thickness at the peripheral portion of the LED board in this case as well.

A display device in which the backlight module of the present disclosure is used may be used, for example, in tiling, and in that case, if the film thickness at the periphery of each display device is not uniform, the periphery of each display device may be may be visually recognized as a line, which may cause problems in terms of display quality.

In the present disclosure, by using a thermoplastic resin as the sealing member, it is possible to seal the LED element with the sealing member by thermocompression bonding the sheet-shaped thermoplastic resin. In this case, since it becomes possible to control the film thickness of the peripheral portion of the backlight module, the above-mentioned problems can be prevented.

As the thermoplastic resin, a resin that does not substantially generate components that degrade the LED board (degrading components) is usually used. Here, "resin that does not substantially generate deteriorating components" refers to resins that do not contain degrading components themselves, or even if they do, do not affect the deterioration of LED boards, or resins that are manufactured for backlight modules. Refers to a resin that does not generate deteriorating components during time and use, or even if it does, does not affect the deterioration of the LED board.

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

Further, as the thermoplastic resin in the present disclosure, it is preferable to use a resin having a melt viscosity that allows it to follow the irregularities of the LED elements and other members arranged on the LED board and enter into the gaps when heated. used for.

Specifically, the melt mass flow rate (MFR) of the thermoplastic resin used is preferably 0.5 g/10 minutes or more and 40 g/10 minutes or less, and 2.0 g/10 minutes or more and 40 g/10 minutes or less. It is more preferable. By having an MFR within the above range, the sealing member can penetrate into the gaps between the LED elements, exhibit sufficient sealing performance, and have excellent adhesion to the LED board. This is because it can be done.

Note that MFR in the present disclosure refers to a 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 at 230° C. and a load of 2.16 kg, also according to JIS K7210.

As for the MFR when the sealing member is a multilayer member as described later, the measurement is performed using the above measurement method while all the layers are in a multilayer state, and the obtained measurement value is applied to the multilayer sealant. The MFR value shall be .

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

In the present disclosure, as the thermoplastic resin, for example, olefin resin, ionomer resin, polyvinyl butyral resin, etc. can be used.

Among these, in the present disclosure, olefin resins are preferred. This is because olefin resins are particularly unlikely to produce components that degrade LED substrates, and have low melt viscosity, so that they can seal the above-mentioned LED elements well. Among the olefin resins, polyethylene resins or polypropylene resins are preferred.

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. These include 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.

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. This is because by using such a resin, higher adhesion between the LED board and the sealing member can be obtained.
As the silane copolymer, those described in JP-A-2018-50027 can be used.

Further, as the resin material used for the sealing member, it is also possible to use a photocurable or thermosetting resin. When using a curable resin, a sealing member can be obtained by filling a liquid sealant composition containing a curable resin and a light diffusing agent and curing the composition.

Examples of such curable resins include those conventionally used as sealing materials, such as epoxy resins, acrylic resins, and silicone resins.

(3) Structure of sealing member The sealing member in the present disclosure may be a single-layer member in which the sealing member 2 is composed of a single resin layer, as shown in FIG. 1, for example, or as shown in FIG. As shown, the sealing member 2 may be a multilayer member in which a plurality of resin layers (three layers in FIG. 2) are laminated.
By using the above multilayer member, it is possible to use a normally expensive material with good adhesion and moldability that can fit into the gaps of LED elements etc. in the layer closer to the LED substrate than the layer containing the light diffusing agent. Because it will be.

In the present disclosure, the multilayer member may have a two-layer structure, but 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. A three-layer structure is preferable.

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 moldability, but for example, the above-mentioned silane copolymer It is preferable to use silane coupling agents, etc., and additives such as antioxidants and light stabilizers may be added.

When the sealing member in the present disclosure is a multilayer member, it is sufficient that at least one layer contains a light diffusing agent, but in the present disclosure, layers other than the layer closest to the LED light emitting diode substrate among the multilayers, That is, it is preferable that the light diffusing agent is contained in 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 a layer that is in close contact with the LED board, it may have a negative effect on the adhesion with the LED board. 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 immediately above the LED element, thereby increasing the brightness. This is because it becomes possible to achieve more uniformity.
In the present disclosure, when the sealing member is composed of 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 can be appropriately selected depending on the layer structure of the LED board, etc., and is not particularly limited. 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. This is because if the thickness is less than 100 μm, it will not be able to fully exhibit its function as a sealing material, and if the thickness is 600 μm or more, it may have an adverse effect on light transmittance.

Further, when the sealing member is formed as a multilayer member having three layers, the thickness of the center layer (resin layer 22 in FIG. 2) is preferably 60 μm or more and 400 μm or less, more preferably 250 μm or more and 350 μm or less. It is as follows. Further, in this case, the thickness of each outer layer (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 multilayer member having a center layer and an adhesive layer disposed closer to the LED substrate than the center layer. Preferably, the thickness of the layer is greater than the height of the LED element. This is because the thickness of the center layer in the portion directly above the LED element and the portion other than the portion directly above the LED element can be made uniform within the plane of the backlight module. Note that the light-diffusing agent is preferably contained in the center layer as described above, and in the present disclosure, the center layer in this case is referred to as a light-diffusing agent-containing layer.

In addition, "thickness" in this specification can be measured using a known measurement method capable of measuring a size on the μ order, for example, using an optical microscope or a scanning electron microscope (SEM). It can be measured using an observed image. The same applies to measurements of sizes such as "size".

(4) Others The sealing material composition for forming the sealing member of the present disclosure may contain a light diffusing agent, a resin, a crosslinking agent as necessary, and other additives. Further, by containing a wavelength conversion material used in a wavelength conversion member to be described later, it becomes possible to incorporate the function of the wavelength conversion member into the sealing member, and it becomes possible to provide a thinner backlight module.

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

Specifically, an LED substrate and a sealing material sheet are prepared, the sealing material sheet is laminated on the LED element side of the LED substrate, and then the sealing material sheet is placed on the LED substrate by using, for example, a vacuum lamination method. A sealing member can be formed by pressing the sealing material sheet.
When a sheet-shaped sealing material is used in this manner, the dispersibility of the light diffusing agent is better than when forming a sealing member using a liquid sealing material composition. In addition, by using a sheet-shaped sealing material containing a thermoplastic resin, the flatness is better than that of a sealing member obtained by curing a liquid thermosetting resin composition or a photocurable resin composition. A sealing member is obtained.

Furthermore, the sealing member of the present disclosure can be obtained by applying a liquid sealing material composition containing a light diffusing agent and a curable resin such as a thermosetting resin or a photocurable resin onto an LED substrate and thermally curing the liquid sealing material composition. It can also be formed with.

(5) Specific aspects of the sealing member As described above, the sealing member preferably contains a thermoplastic resin, more preferably an olefin resin, and preferably a polyethylene resin. More preferred. In particular, it is preferable that the sealing member uses a polyethylene 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 board and good followability to the members arranged on the LED board.

Hereinafter, details of a suitable sealing member will be explained.
The sealing member is formed of a resin film whose base resin is a polyethylene resin of 0.870 g/cm ³ or more and 0.930 g/cm ³ or less. That is, the sealing member is formed of a sealing material sheet whose base resin is the above-mentioned polyethylene 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 preferably has a base resin of polyethylene resin having a density of 0.910 g/cm ³ or more and 0.930 g/cm ³ or less, and the skin layer has a density of 0.890 g/cm 3 or less. ³ or more and 0.910 g/cm ³ or less, and a polyethylene resin having a density lower than that of the base resin for the core layer is preferably used as the base resin.
When the encapsulant sheet is a multilayer film having three or more layers as described above, it is preferable that the core layer contains a light diffusing agent.

In the case of the multilayer film, the total thickness thereof is, for example, preferably 100 μm or more, more preferably 250 μm or more, and even more preferably 300 μm or more. Further, the total thickness is preferably, for example, 600 μm or less, and more preferably 550 μm or less. If the total thickness is too thin, it will not be possible to sufficiently cushion the impact, but if the total thickness is within the above range, moldability and heat resistance can be combined at sufficiently desirable levels. Note that if the total thickness is too thick, it is difficult to further improve the impact mitigation effect, it cannot meet the demand for thinning, 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 still more preferably 250 μm or more. Further, the thickness of the core layer is preferably, for example, 400 μm or less, more preferably 350 μm or less. Further, the thickness of each layer of the skin layer in this case can be, for example, 15 μm or more, 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 properties of the encapsulant sheet can be maintained within a favorable range.

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

When forming the above-mentioned sealing material sheet as a sealing member, the sealing material composition used for manufacturing each layer uses a composition having a different density range, etc. for each layer as a base resin.

In this case, the encapsulant composition for the core layer and the encapsulant composition for the skin layer are selectively used to form each layer. Then, by forming a multilayer film with a three-layer structure in which skin layers are arranged on both outermost surfaces to a predetermined thickness using each of the sealing material compositions for the core layer and the skin layer, for example, as shown in FIG. As shown in FIG. 2, a sealing member 21 having a three-layer structure including a skin layer 22a, a core layer 23, and a skin layer 22b can be manufactured.

The base resin of the encapsulant composition for the core layer of the encapsulant sheet is low density polyethylene resin (LDPE), linear low density polyethylene resin (LLDPE), or metallocene linear low density polyethylene resin. Resin (M-LLDPE) can be preferably used. Among them, 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. It is. By setting the density of the base resin of the core layer encapsulant composition within the above range, the encapsulant sheet can be provided with necessary and sufficient heat resistance without undergoing crosslinking treatment.

The melting point of the sealing material 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 preferable ranges. Note that by adding a high melting point resin such as polypropylene to the core layer encapsulant composition, it is possible to raise the melting point of the encapsulant composition to about 135°C. In this case, the content of polypropylene is preferably 5% by mass or more and 40% by mass or less based on the total resin components of the core layer.

The polypropylene contained in the core layer is preferably a homopolypropylene (homoPP) resin. Homo-PP is a polymer consisting only of polypropylene and has high crystallinity, so it has higher rigidity than block PP or random PP. By using this as an additive resin to the sealing material composition for the core layer, the dimensional stability of the sealing member can be improved. Furthermore, homo PP used as an additive resin to the encapsulant composition for the core layer has an MFR of 5 g/10 minutes or more and 125 g/10 minutes or less at 230°C and a load of 2.16 kg, as measured in accordance with JIS K7210. It is preferable that there be. If the MFR is too small, the molecular weight will become too large and the rigidity will become too high, making it difficult to ensure the preferable and sufficient flexibility of the encapsulant composition. Furthermore, if the MFR is too large, the fluidity during heating will not be sufficiently suppressed, making it impossible to impart sufficient heat resistance and dimensional stability to the encapsulant sheet.

The melt mass flow rate (MFR) of the polyethylene resin used as the base resin of the encapsulant composition for the core layer is 2.0 g/10 minutes or more and 7.5 g/10 minutes or less at 190°C and a load of 2.16 kg. It is preferable that it is, and it is more preferable that it is 3.0 g/10 minutes or more and 6.0 g/10 minutes or less. By setting the MFR of the base resin of the core layer encapsulant composition within the above range, the heat resistance and molding properties of the encapsulant can be maintained within preferred ranges. In addition, it is possible to sufficiently improve processing suitability during film formation and contribute to improvement in productivity of the sealing member.

The content of the base resin based on all the resin components in the core layer encapsulant composition is 70% by mass or more and 99% by mass or less, preferably 90% by mass or more and 99% by mass or less. Other resins may be included as long as the base resin is included within the above range.

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

The density of the polyethylene resin used as the base resin of the sealing material 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. ³ or less. By setting the density of the base resin of the skin layer sealing material composition within the above range, the adhesion of the sealing member can be maintained within a preferable range.

The melting point of the sealing material composition for the skin layer is preferably 55°C or more and 100°C or less, and more preferably 80°C or more and 95°C or less. 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 sealant composition for the skin layer is 2.0 g/10 minutes or more and 7.0 g/10 minutes or less at 190°C and a load of 2.16 kg. It is preferable that it is, and it is more preferable that it is 2.5 g/10 minutes or more and 6.0 g/10 minutes or less. By setting the MFR of the base resin of the skin layer sealing material composition within the above range, the adhesion of the sealing member can be more reliably maintained within a preferable range. Further, it is possible to sufficiently improve processing suitability during film formation and contribute to improvement in productivity of the sealing member.

The content of the base resin based on all the resin components in the sealing material composition for the skin layer is 60% by mass or more and 99% by mass or less, preferably 90% by mass or more and 99% by mass or less. Other resins may be included as long as the base resin is included within the above range.

In all of the encapsulant compositions explained above, a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer is added to each encapsulant composition as necessary. It is more preferable to contain a certain amount. In such a graft copolymer, the degree of freedom of the silanol groups that contribute to adhesive strength is increased, so that the adhesiveness of the sealing member to other members can be improved.

Examples of the silane copolymer include the silane copolymers described in JP-A No. 2003-46105. By using the above-mentioned silane copolymer as a component of the sealant composition, it has excellent strength, durability, etc., as well as weather resistance, heat resistance, water resistance, light resistance, and other various properties, and furthermore, It has extremely excellent heat fusion properties without being affected by manufacturing conditions such as heat-pressure bonding when arranging the sealing member, and the sealing member can be stably obtained 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 preferable. More preferred is a graft copolymer in which polymerizable polyethylene is used as the main chain and an ethylenically unsaturated silane compound is polymerized as the side chain. In such a graft copolymer, the degree of freedom of the silanol groups that contribute to adhesive strength is increased, so that the adhesiveness of the sealing member can be improved.

The content of the ethylenically unsaturated silane compound when constituting the copolymer of α-olefin and the ethylenically unsaturated silane compound is, for example, 0.001% by mass or more 15% by mass based on the total mass of the copolymer. It is desirable that the amount is 0.01% by mass or more and 5% by mass or less, particularly preferably 0.05% by mass or more and 2% by mass or less. If the content of the ethylenically unsaturated silane compound constituting the copolymer of α-olefin and ethylenically unsaturated silane compound is high, it will have excellent mechanical strength and heat resistance, but if the content becomes excessive, Tensile elongation and heat fusion properties tend to be poor.

The content of the silane copolymer based on the total resin components of the encapsulant composition for the core layer is 2% by mass or more and 20% by mass or less for the encapsulant composition for the skin layer. In the composition, it is preferably 5% by mass or more and 40% by mass or less. In particular, it is more preferable that the sealing material composition for the skin layer contains 10% by mass or more of a silane copolymer. Note that the amount of silane modification in the above-mentioned silane copolymer is preferably about 1.0% by mass or more and 3.0% by mass or less. The preferable content range of the silane copolymer in the above-mentioned sealant composition is based on the assumption that the above-mentioned amount of silane modification is within this range, and may be finely adjusted as appropriate according to fluctuations in the amount of modification. desirable.

An adhesion improver can also be added to all the sealant compositions as appropriate. By adding an adhesion improver, the durability of adhesion to other members can be made higher. As the adhesion improver, a known silane coupling agent can be used, and a silane coupling agent having an epoxy group or a silane coupling agent having a mercapto group can be particularly preferably used.

2. Light Emitting Diode Substrate The LED substrate in the present disclosure includes a support substrate and an LED element. The LED board in the present disclosure is preferably an LED board for a backlight module, particularly for a direct type backlight module. Moreover, it is preferable that the LED board is an LED board 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 can emit white light with uniform brightness by using a sealing member containing a light diffusing agent as a backlight module.

(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 have transparency. Further, the support substrate may have softness (flexibility) or rigidity (rigidity). The material of the support substrate may be an organic material, an inorganic material, or a composite material made of both an organic material and an inorganic material.

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. Further, when the material of the support substrate is a composite material, a glass epoxy substrate (eg, FR-4 substrate) can be used as the support substrate. Further, as the support substrate, for example, a metal core substrate can be used.

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

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

The shape of the support substrate in plan view can be appropriately selected and is not particularly limited, but is typically rectangular.
As the support substrate, a printed circuit board on which a circuit is formed by printing can also be used.

(2) Light-emitting diode element The LED element is a member disposed on one surface side of the support substrate, and the light-emitting part of the LED element functions as a light source of a display device to be described later.

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

When the backlight module of the present disclosure irradiates white light by combining an LED element and a wavelength conversion member described below, the LED element is a blue LED element, an ultraviolet LED element, or an infrared LED element. is preferred. A blue LED element can generate white light, for example, in combination with a yellow phosphor, or in combination with a red phosphor and a green phosphor. Furthermore, ultraviolet LED elements can generate white light when combined with, for example, red phosphors, green phosphors, and blue phosphors. Among these, it is preferable that the LED element is a blue LED element. This is because the backlight module of the present disclosure can emit white light with high brightness.

Further, 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, etc. Examples of the light emitting method of a 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 and a blue LED. Examples include a combination of 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, and the blue LED light emitting part and a protective part containing a red phosphor and a green phosphor. It may have a blue LED light emitting part and a protective part containing a yellow phosphor, and it may have an ultraviolet LED light emitting part and a red phosphor, a green phosphor and a blue phosphor. It may also have a protective part.

Among these, the white LED element has a blue LED light emitting part and a protective part containing a red phosphor and a green phosphor, a blue LED light emitting part and a protective part containing a yellow phosphor, or an ultraviolet LED light emitting part. It is preferable to have a protection part containing a red phosphor, a green phosphor, and a blue phosphor. Among these, a white LED element may have a blue LED light emitting part and a protective part containing a red phosphor and a green phosphor, or a blue LED light emitting part and a protective part containing a yellow phosphor. preferable. This is because the backlight module of the present disclosure can emit white light with high brightness. Quantum dots can also be used as a wavelength conversion material instead of the phosphor described above.

The structure of the LED element can be similar to that of a general LED element.
The LED elements are usually arranged at equal intervals on one side of the support substrate. The arrangement of the LED elements is appropriately selected depending on the purpose and size of the backlight module of the present disclosure, the size of the LED elements, and the like. Furthermore, the arrangement density of the LED elements is also appropriately selected depending on the use and size of the backlight module of the present disclosure, the size of the LED elements, and the like.

Although the size (chip size) of the LED element can be a general chip size, a chip size called a mini LED or a micro LED is particularly preferable. 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 or more and 1000 μm square or less, more preferably 100 μm square or more and 500 μm square or less, and 100 μm square or more and 300 μm square or less. There may be.

This is because the small size of the LED elements allows the LED elements to be arranged at high density, that is, the interval (pitch) between the LED elements can be reduced, and the thickness of the sealing member can be reduced. Thereby, it is possible to achieve a reduction in thickness and weight.

The LED element used in the present disclosure is arranged on one side of the support substrate. In the present disclosure, it is sufficient that at least one LED element is disposed on one side of the support substrate, but normally, a plurality of LED elements are disposed. Although the arrangement of the plurality of LED elements is not particularly limited, it is preferable, for example, that they are arranged in an X×Y matrix (X and Y are each an integer of 1 or more). The numbers of X and Y are appropriately selected depending on the use of the backlight module.

(3) Others The LED board in the present disclosure is not particularly limited as long as it has the above-mentioned support board and LED element, and necessary configurations can be selected and added as appropriate. Examples of such a structure include a wiring part, a terminal part, an insulating layer that protects these parts, and the like. When having a wiring part, the wiring part is electrically connected to the LED element. The wiring section, the terminal section, and the insulating layer can be the same as those used in known LED boards, so their individual descriptions will be omitted.

In the LED substrate according to the present disclosure, a reflective layer can be disposed on the surface of the support substrate on which the LED elements are disposed, and in a region other than the LED element mounting area.

The reflective layer can be similar to reflective layers commonly used in LED substrates. Specifically, examples of the reflective layer include a white resin film containing metal particles, inorganic particles, or pigments and a resin, a metal film, and a porous film. The thickness of the reflective layer is not particularly limited as long as it provides a desired reflectance, and is appropriately set.

The method for forming the LED board can be the same as a known method, so a description thereof will be 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 board, and necessary configurations can be selected and added as appropriate. Examples of such a configuration include the optical member described below.

(1) Wavelength Conversion Member In the backlight module of the present disclosure, a wavelength conversion member may be arranged as necessary. The wavelength conversion member has a function of generating white light when combined with the LED board. The wavelength conversion member is arranged on the light emitting surface side of the LED board, and can be arranged 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, quantum dots, and the like.

When the wavelength conversion member is placed closer to the viewer than the LED element and the sealing member, for example, it may be a resin sheet in which the wavelength conversion material is dispersed, or a resin sheet in which the wavelength conversion material is dispersed on a transparent substrate. Although a laminate having a resin layer may be used, 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 a thermoplastic resin is preferable. This is because the wavelength conversion member can be formed using a resin sheet in which the wavelength conversion material is dispersed, so that the flatness can be improved. The thermoplastic resin is not particularly limited as long as it has a high light transmittance, and any general-purpose thermoplastic resin can be used.

The above-mentioned phosphor can be appropriately selected depending on the color of light emitted from the LED element, and includes, for example, a blue phosphor, a green phosphor, a red phosphor, an amber phosphor, a yellow phosphor, and the like. For example, when the LED element is a blue LED element, it is preferable to use a yellow phosphor as the phosphor. Further, when the LED element is an ultraviolet LED element or an infrared LED element, it is preferable to use three color phosphors: a red phosphor, a blue phosphor, and a 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 diameter is an average value obtained when 20 arbitrary phosphors are measured in an observed image of a cross section of the wavelength conversion member using a scanning electron microscope (SEM).

The proportion of the phosphor in the wavelength conversion member is not particularly limited as long as the desired white light can be generated, 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 size of quantum dots decreases, the energy band gap increases. That is, as the crystal size becomes smaller, the emission of quantum dots shifts toward the blue side, that is, toward the higher energy side. Therefore, by changing the particle size of the quantum dots, the emission wavelength can be adjusted over the entire spectrum of the ultraviolet, visible, and infrared regions. For example, if the quantum dot particle size is 2.0 nm or more and 3.5 nm or less, blue light is emitted, and if the quantum dot particle size is 4.0 nm or more and 5.0 nm or less, green light is emitted. If the diameter 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 diameter of the quantum dots can be obtained by observing the cross section of the wavelength conversion member using a transmission electron microscope or a scanning transmission electron microscope, and finding it as the average value of the diameters of 20 quantum dots measured from this observed image. I can do it.

Although one type of quantum dot may be used for the wavelength conversion member in the present disclosure, it is also possible to use two or more types of quantum dots each having an individual emission band in a wavelength range due to different particle sizes or materials. is also possible.

The content of 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 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 desired white light can be generated, and is, for example, 10 μm or more and 1000 μm or less.

(2) Reflective Member In the backlight module of the present disclosure, it is preferable that a reflective member is disposed at least directly above the LED element. By providing a reflective member directly above the LED element in this way, even if the thickness of the sealing member directly above the LED element is thin, the light directly above the LED element is reflected by the reflective member and diffused into the surroundings. Therefore, the in-plane uniformity of brightness due to the light diffusing agent contained in the sealing material is improved.

Such reflective members include, for example, a dielectric multilayer film, a patterned first reflective film disposed on one side of the transparent base material, and a first reflective film disposed on one side or the other side of the transparent base material. a patterned second reflective film, the openings of the first reflective film and the openings of the second reflective film are located so as not to overlap in plan view, and the first reflective film and the second reflective film have a thickness. Examples include reflective structures arranged apart in the direction, reflective diffraction gratings, and the like.

Moreover, a conventionally known transmission-reflection plate can be used as the reflection member. For example, a transparent substrate, a reflective part made of a reflective material laminated in a predetermined pattern on a portion of at least one surface of the transparent support substrate, and a reflective part formed on the transparent support substrate. It is possible to use a structure that includes a transparent part when formed in a region. In such a transparent support substrate, the central portion around the position directly above the LED element may be composed of only a reflective portion.

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

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

The prism sheet in the present disclosure has a function of condensing incident light and intensively improving brightness in the front direction. The prism sheet is, for example, one in which a prism pattern containing acrylic resin or the like is arranged on one side of a transparent resin base material.

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

The reflective polarizing sheet in the present disclosure transmits only a first linearly polarized light component (e.g., P-polarized light) and absorbs a second linearly polarized light component (e.g., S-polarized light) orthogonal to the first linearly polarized light component. It has the ability to reflect without any reflection. The second linearly polarized light component reflected by the reflective polarizing sheet is reflected again, and in a depolarized state (a state that includes both the first linearly polarized light component and the second linearly polarized light component), The light is incident on a reflective polarizing sheet. Therefore, the reflective polarizing sheet transmits the first linearly polarized light component of the light that enters again, and the second linearly polarized light component that is perpendicular to the first linearly polarized light component is reflected again. Thereafter, by repeating the same process as above, about 70% to 80% of the light emitted from the diffusion member is emitted as light having become the first linearly polarized component. Therefore, when the backlight module of the present disclosure is used in a display device, the polarization direction of the first linearly polarized light component (transmission axis component) of the reflective polarizing sheet must match the transmission axis direction of the polarizing plate of the display panel. Therefore, all 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 an image with higher brightness than when no reflective polarizing sheet is provided.

Examples of reflective polarizing sheets include the DBEF series of brightness enhancement films manufactured by 3M. Further, as the reflective polarizing sheet, for example, a high brightness polarizing sheet WRPS manufactured by Shinwha Intertek, a wire grid polarizer, etc. can also be used.

Further, the optical member described above may be bonded onto the sealing member using, for example, an adhesive layer. The adhesive used in the adhesive layer can be the same as the adhesive used in general display devices, so the explanation here will be omitted.

4. Backlight module using light emitting diodes The backlight module using 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-described configuration, and can be manufactured by a conventionally used method. In the present disclosure, for example, a step of preparing an LED substrate, a step of preparing a sealing material sheet containing a light diffusing agent and a thermoplastic resin, and a lamination method are used to attach the surface of the LED substrate to the surface on the LED element side. It is also possible to provide a method for manufacturing a backlight module, which includes a step of arranging the sealing member by laminating the sealing material sheet.

B. Display Device The display device of the present disclosure includes a display panel and the above-described backlight module arranged on the back surface of the display panel.

A display device (liquid crystal display device) according to the present disclosure will be explained using figures. FIG. 3 is a schematic cross-sectional view showing an example of the display device of the present disclosure. The liquid crystal display device 100 shown in FIG. 3 includes a support substrate 11, an LED substrate 1 having an LED element 12 disposed on one side of the support substrate, and a light diffusing agent that seals the LED element 12. and a liquid crystal panel 20 disposed on the light emitting surface side of the backlight module. In FIG. 3 , the backlight module 10 includes a wavelength conversion member 3 .

According to the present disclosure, it is possible to provide a thinner display device. Each configuration of the display device of the present disclosure will be described below.

1. Backlight Module The backlight module in the display device of the present disclosure can be the same as that described in the section “A. Backlight Module” above, so the description here will be omitted.

2. Display Panel A display panel is a member that typically includes 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 the display panel can be the same as those used in known liquid crystal panels, so their descriptions are omitted here.

3. Others The display device of the present disclosure is not particularly limited as long as it has a backlight module using the above-mentioned LED elements and a display panel, and necessary configurations can be selected and added as appropriate. Examples of such a structure include a polarizing plate, a front plate, and the like.
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 using an encapsulant sheet, the encapsulant can have good flatness, making it difficult for viewers to see the boundaries of each display device as a seam, making it possible to create a tiling display device with good display visibility. can do.

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

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

DESCRIPTION OF SYMBOLS 1... LED board 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 side of the support substrate;
a sealing member disposed on a surface side of the light emitting diode element side of the light emitting diode substrate, the sealing member sealing 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 above-mentioned sealing member is a backlight module , wherein all of the above-mentioned three layers contain an olefin resin and a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as comonomers. The backlight module according to claim 1, comprising a wavelength conversion member. The backlight module according to claim 1 or 2, further comprising a reflective member disposed at least directly above the light emitting diode element.

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