Surface light emitting device, display device, manufacturing method of surface light emitting device, and sealing member sheet for surface light emitting device

Abstract

To provide a surface light emitting device capable of preventing an occurrence of warpage in manufacturing, etc. and improving a yield in manufacturing the surface light emitting device.SOLUTION: A surface light emitting device includes a sealing member for sealing a light emitting diode element, and a foam formation prevention layer arranged on a surface opposite to a light emitting diode substrate of the sealing member. A reflection layer is arranged in a region other than a mounting region of the light emitting diode element in the surface of the light emitting diode substrate on the side where the light emitting diode element is arranged. The sealing member has polyethylene-based resin as base resin, and includes a core layer and a skin layer arranged at least on one surface side of the core layer. The skin layer is arranged on a light emitting diode substrate side of the sealing member. The melting point of the skin layer is 50-100°C, the thickness of the foam formation prevention layer is 35 μm or more, and the modulus of elasticity of a material constituting the foam formation prevention layer is 500 MPa or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a surface light-emitting device, a display device using the same, a method for manufacturing the surface light-emitting device, and a sealing member sheet for the surface light-emitting device.

Background Art

[0002] In recent years, in the field of display devices, higher image quality displays have been demanded. Display devices using light-emitting diode elements have attracted attention and are being developed because they have advantages such as high brightness and high contrast. In the following description, "light-emitting diode" may be referred to as "LED" in some cases. For example, the development of a backlight using LED elements as a backlight used in a liquid crystal display device has been advanced. The above backlight is also referred to as a mini-LED backlight.

[0003] Here, LED backlights are roughly classified into a direct-lit type and an edge-lit type. In small and medium-sized display devices such as mobile terminals such as smartphones, an edge-lit type LED backlight is usually used, but from the viewpoint of brightness and the like, using a direct-lit type LED backlight has been considered. On the other hand, in large display devices such as large-screen liquid crystal televisions, a direct-lit type LED backlight is often used.

[0004] A direct-lit type LED backlight has a configuration in which a plurality of LED elements are arranged on a substrate. In such a direct-lit type LED backlight, by independently controlling a plurality of LED elements, so-called local dimming can be realized in which the brightness of each region of the LED backlight is adjusted according to the brightness and darkness of the display image. Thereby, it is possible to significantly improve the contrast and reduce the power consumption of the display device.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] International Publication No. 2013 / 018902 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In a surface light-emitting device such as a direct-type LED backlight, a diffusion plate or a transmissive-reflective plate (hereinafter referred to as a diffusion member) is disposed above the LED element from the viewpoint of suppressing luminance unevenness. In order to suppress luminance unevenness, it is necessary to dispose the LED element and the diffusion member apart from each other. Therefore, conventionally, pins or spacers are disposed to maintain a predetermined interval between the LED element and the diffusion member (for example, Patent Document 1). FIG. 12(a) shows a conventional LED backlight 60 in which a pin 65 is disposed to secure a distance d between an LED element 63 and a diffusion member 66 on a support substrate 62. FIG. 12(b1) shows a conventional LED backlight 61 in which a spacer 67 is disposed between the support substrate 62 and the diffusion member 66, and FIG. 12(b2) is a schematic plan view of the spacer 67.

[0007] As described above, when pins or spacers are disposed, luminance unevenness may occur because the light emitted from the LED element is blocked or reflected by the pins or spacers. Therefore, for example, in Patent Document 1, it is necessary to further dispose a diffusion plate or the like above the transmissive-reflective plate, and it is difficult to make the module thinner. Thus, in the conventional surface light-emitting device, there is a problem that it is difficult to simultaneously achieve in-plane luminance uniformity and thinning.

[0008] In order to solve such problems, it is also conceivable to dispose a sealing member having light diffusibility between the LED support substrate that supports the LED and the diffusion member. Thereby, it is possible to improve the in-plane luminance uniformity and to achieve thinning, and there is a possibility of solving the above problems. However, in the surface light-emitting device including the LED support substrate and the sealing member, there may be a problem that warping may occur during manufacturing or the like.

[0009] The present disclosure has been made in view of the above problems, and a main object thereof is to provide a surface light-emitting device capable of preventing warpage during manufacturing or the like and improving the yield during the manufacturing of the surface light-emitting device.

Means for Solving the Problems

[0010] In order to achieve the above object, in the present disclosure, a sealing member for sealing a light-emitting diode element, and a warpage prevention layer disposed on the sealing member and having a linear expansion coefficient in the range of -15×10 -6 / °C or more and 10×10 -6 / °C or less are provided, and a sealing member sheet for a surface light-emitting device is provided.

[0011] The present disclosure also provides a sealing member sheet for a surface light-emitting device, which is formed by laminating a sealing member for sealing a light-emitting diode element and an anti-foaming layer disposed on one surface side of the sealing member, and is used for a surface light-emitting device, wherein the elastic modulus of the material constituting the anti-foaming layer is 500 MPa or more.

[0012] The present disclosure also provides a sealing member sheet for a surface light-emitting device, which is formed by laminating a sealing member for sealing a light-emitting diode element and an anti-foaming layer disposed on one surface side of the sealing member, and is used for a surface light-emitting device, wherein the melting point of the material constituting the anti-foaming layer is 140 °C or more.

[0013] The present disclosure also provides a surface light-emitting device having a support substrate, a light-emitting diode substrate having a light-emitting diode element disposed on one surface side of the support substrate, a sealing member disposed on the surface of the light-emitting diode substrate on the light-emitting diode element side for sealing the light-emitting diode element, a warpage prevention layer disposed on the surface of the sealing member opposite to the light-emitting diode substrate, and a diffusion member disposed on the surface of the warpage prevention layer opposite to the light-emitting diode substrate, wherein the sealing member has a haze value of 4% or more, a thickness thicker than the thickness of the light-emitting diode element, and the linear expansion coefficient of the material constituting the warpage prevention layer is -15×10 -6above 10×10 / °C -6 A surface light-emitting device is provided within a range of / °C or lower.

[0014] The present disclosure further provides a surface light-emitting device having a support substrate, a light-emitting diode substrate having a light-emitting diode element disposed on one surface side of the support substrate, a sealing member disposed on the surface of the light-emitting diode substrate on the light-emitting diode element side for sealing the light-emitting diode element, a diffusion member disposed on the surface of the sealing member opposite to the light-emitting diode substrate, and a warpage prevention layer disposed on the surface of the light-emitting diode substrate opposite to the light-emitting diode element, wherein the sealing member has a haze value of 4% or more, a thickness greater than the thickness of the light-emitting diode element, and a linear expansion coefficient of the material constituting the warpage prevention layer is equal to or greater than the linear expansion coefficient of the material constituting the sealing member.

[0015] The present disclosure provides a display device including a display panel and the above-described surface light-emitting device disposed on the back surface of the display panel.

[0016] The present disclosure provides a method for manufacturing the above-described surface light-emitting device, including preparing a laminate in which the warpage prevention layer, the sealing member, and the light-emitting diode substrate on which the light-emitting diode element is disposed so as to be on the sealing member side are arranged in this order, and thermocompression bonding the laminate.

[0017] The present disclosure provides a method for manufacturing the above-described surface light-emitting device, including a step of thermocompression bonding a first laminate in which the warpage prevention layer and the sealing member are laminated, and a step of thermocompression bonding a second laminate in which the light-emitting diode substrate on which the light-emitting diode element is disposed so as to be on the sealing member side is disposed on the surface of the thermocompression-bonded first laminate on the sealing member side.

Advantages of the Invention

[0018] The present disclosure can provide a surface light-emitting device capable of preventing the occurrence of warping during manufacturing or the like and improving the yield during the manufacture of the surface light-emitting device, and has the effect of achieving this.

Brief Description of the Drawings

[0019]

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Figure 12

Embodiments for Carrying Out the Invention

[0020] Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different modes and is not to be construed as limited to the description of the embodiments exemplified below. Also, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each member as compared with the embodiments, but this is merely an example and does not limit the interpretation of the present disclosure. Further, in this specification and each drawing, elements similar to those described above with respect to the previously presented drawings may be denoted by the same reference numerals, and detailed descriptions thereof may be omitted as appropriate.

[0021] In this specification, when expressing the mode of arranging one member on another member, when simply described as "on the surface side", unless otherwise specified, it includes both the case where another member is arranged directly above or below so as to be in contact with one member, and the case where another member is arranged above or below one member via yet another member.

[0022] Also, in this specification, terms such as "sheet", "film", "plate", etc. are not distinguished from each other based only on the difference in name. For example, "sheet" is used in the sense that it includes members that may also be called film or plate.

[0023] As described above, in the surface light-emitting device including the newly proposed LED support substrate and the sealing member, there has been a problem that warping may occur during manufacturing or the like.

[0024] As a result of intensive studies to solve the above new problems, the inventors have found that warping occurs because the linear expansion coefficients of both are different after thermocompression bonding the LED support substrate and the sealing member during manufacturing. Thus, the above problem has been solved by arranging an anti-warping layer having a predetermined relationship with respect to the linear expansion coefficient of the sealing member at an appropriate position with respect to the sealing member.

[0025] A. Surface light-emitting device The surface light-emitting device in the present disclosure can be divided into three aspects. Hereinafter, it will be described separately for each embodiment.

[0026] I. First Embodiment Hereinafter, the surface light-emitting device of this embodiment will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the surface light-emitting device of this embodiment. As illustrated in FIG. 1, the surface light-emitting device 1 includes a support substrate 2, an LED substrate 4 having an LED element 3 disposed on one surface side of the support substrate 2, a sealing member 5 disposed on the surface side of the LED substrate 4 on the LED element 3 side for sealing the LED element 3, a diffusion member 6 disposed on the surface side of the sealing member 5 opposite to the LED substrate 4 side, and a warpage prevention layer 7 disposed between the sealing member 5 and the diffusion member 6. The sealing member 5 in this embodiment has a haze value of 4% or more and a thickness d that is thicker than the thickness of the LED element 3, and the linear expansion coefficient of the material constituting the warpage prevention layer 7 is in the range of -15×10 -6 / °C or more and 10×10 -6 / °C or less.

[0027] Generally, in a surface light-emitting device, for example, when means such as thermocompression bonding are used to join the sealing member and the LED substrate, warpage may occur due to the difference in the linear expansion coefficients of the LED substrate and the sealing member during subsequent cooling. In addition, when the surface light-emitting device is used at extremely high or low temperatures, warpage may occur due to the difference in the linear expansion coefficients of the LED substrate and the sealing member described above.

[0028] This embodiment is made to solve such problems. The warpage prevention layer is disposed between the sealing member and the diffusion member, and the linear expansion coefficient of the material constituting the warpage prevention layer is in the range of -15×10 -6 / °C or more and 10×10 -6 / °C or less, thereby solving the problem of the occurrence of warpage described above.

[0029] In addition, in a conventional surface light-emitting device, for example, when the surface light-emitting device is used at an extremely high temperature for a long time, there is also a problem that bubbles are generated between the LED substrate and the sealing member. This is caused by gas generated from the LED substrate due to heating, or when a reflective layer or the like is provided on the LED substrate, air existing between the LED substrate and the reflective layer or the like oozes out along the interface due to air entrapment or the like.

[0030] The LED element sealed in the sealing member has the light-emitting surface of the sealing member and the LED element directly joined, and since the refractive index difference at the interface is small, the light extraction efficiency is improved compared to an unsealed LED element. However, if such bubbles are present, the improvement in light extraction efficiency as described above cannot be obtained, and as a result, there occurs a problem of reducing the light-emitting efficiency of the surface light-emitting device. In the present embodiment, by providing the anti-warpage layer, the above problem is also solved. Hereinafter, the surface light-emitting device of the present embodiment will be described for each configuration.

[0031] 1. Sealing member The sealing member in the present embodiment has a haze value of 4% or more and a thickness thicker than that of the LED element. The sealing member has light transmissivity and is disposed on the light-emitting surface side of the LED substrate.

[0032] (1) Haze value The haze value of the sealing member in the present embodiment is 4% or more, preferably 8% or more, and more preferably 10% or more. If it is smaller than the above value, luminance unevenness cannot be suppressed. On the other hand, the upper limit value is not particularly limited, but for example, it is 85% or less, preferably 60% or less, and more preferably 30% or less. In this specification, the haze value is a value for the entire sealing member, and can be measured by a method conforming to JIS K7136:2000 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory) by cutting out the sealing member from the surface light-emitting device.

[0033] As a method for adjusting the haze value for obtaining the above-described haze value, although not particularly limited, examples thereof include a method using the degree of crystallinity of the resin and a method of changing the content of fine particles in the resin. Among them, a method of adjusting the degree of crystallinity of the resin is preferable. This is because when the haze value is increased by increasing the degree of crystallinity of the resin, an effect of reducing the directly transmitted light can be obtained.

[0034] (2) Thickness The thickness of the sealing member in the present embodiment may be greater than that of the above-described LED element. Specifically, it is preferably 50 μm or more, more preferably 80 μm or more, and particularly preferably 200 μm or more. On the other hand, the thickness of the LED element is preferably 800 μm or less, more preferably 750 μm or less, and particularly preferably 700 μm or less.

[0035] Note that the "thickness" in this specification is measured using a contact-type film thickness measuring device (Mitutoyo thickness gauge 547-301). The same applies to the measurement of sizes such as "size".

[0036] If it is smaller than the above thickness, the thickness is insufficient and the light emitted from the LED element cannot be diffused over the entire light emitting surface, and the luminance cannot be improved uniformly in the plane. Further, if it is larger than the above thickness, thinning cannot be achieved.

[0037] (3) Material of the sealing member The material contained in the sealing member in the present embodiment is not particularly limited as long as it is a material that provides the above-described haze value, but a thermoplastic resin or the like is preferable. By using a thermoplastic resin, for example, the haze value can be adjusted to be higher than in the case of using a thermosetting resin, and further, the sealing member can be formed at a low temperature.

[0038] In addition, when the sealing member contains a thermoplastic resin, a sheet-like sealing member composed of a sealing material composition containing the thermoplastic resin (hereinafter sometimes referred to as a sealing member sheet) can be used. FIG. 2 is a process diagram showing an example of a method for forming a sealing member in the present embodiment. For example, as shown in FIG. 2(a), an LED substrate 4 and a sealing member sheet 5a having a warpage prevention layer 7 disposed on one surface are prepared, and the surface of the LED substrate 4 on the side of the LED element 3 is laminated with the surface of the sealing member sheet 5a opposite to the warpage prevention member 7. Then, by pressing them using, for example, a vacuum lamination method, a laminate of a sealing member 5 having a warpage prevention layer 7 disposed on one side and the LED substrate 4 can be formed as shown in FIG. 2(b).

[0039] On the other hand, when the sealing member contains a curable resin such as a thermosetting resin or a photocurable resin, usually, a liquid sealing material is used. When a liquid sealing material is used, due to factors such as surface tension, a phenomenon may occur in which the thickness at the end is thicker or thinner compared to the central portion. Also, in the case of a curable resin, volume shrinkage during curing is likely to occur, and as a result, the thickness of the central portion and the end portion of the cured sealing member may become non-uniform. If the thickness of the sealing member is non-uniform in this way, luminance unevenness may occur.

[0040] In contrast, when using a sheet-like sealing material, it is possible to avoid the occurrence of surface irregularities of the sealing member such as the occurrence of a thickness distribution of the coating film due to surface tension and the occurrence of a thickness distribution due to thermal shrinkage or photo shrinkage, which occur when using a liquid sealing material. Therefore, a sealing member with good flatness can be obtained, and a higher-quality display device can be provided.

[0041] (a) Thermoplastic resin In the present embodiment, as the thermoplastic resin, an olefin-based resin, an ethylene-vinyl acetate copolymer (EVA), a polyvinyl butyral-based resin, or the like can be used.

[0042] Among them, the thermoplastic resin is preferably an olefin resin. This is because olefin resins are particularly unlikely to produce components that deteriorate the LED substrate and have a low melt viscosity, so that the above-described LED elements can be well encapsulated. Among olefin resins, polyethylene resins, polypropylene resins, and ionomer resins are preferred.

[0043] Here, the polyethylene resin in this specification includes not only ordinary polyethylene obtained by polymerizing ethylene, but also resins obtained by polymerizing compounds having ethylenic unsaturated bonds such as α-olefins, resins obtained by copolymerizing a plurality of different compounds having ethylenic unsaturated bonds, and modified resins obtained by grafting another chemical species onto these resins.

[0044] In particular, from the viewpoint of obtaining the above haze value, the encapsulating member in the present embodiment preferably 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. In particular, it is preferable to use a polyethylene resin having a density of 0.890 g / cm 3 or more and 0.930 g / cm 3 or less as a base resin. When the encapsulating member is a multilayer member as described later, it is preferable to use a polyethylene resin having the above density as the base resin of the core layer. The above density is measured in accordance with JIS Z 8807:2012. Here, in the present disclosure, the "base resin" refers to the resin having the largest content mass ratio among the resin components of the resin composition containing the base resin.

[0045] A silane copolymer obtained by copolymerizing α-olefin and an ethylenically unsaturated silane compound as comonomers (hereinafter also referred to as "silane copolymer") can be preferably used. By using such a resin, higher adhesion between the LED substrate and the encapsulating member can be obtained. As the above silane copolymer, those described in JP-A-2018-50027 can be used.

[0046] (b) Melting point The melting point of the thermoplastic resin used in this embodiment is not particularly limited as long as it can encapsulate the LED element. For example, it is preferably 90°C or higher and 135°C or lower. Among them, it is preferably not softened by the heat generation during LED emission, and it is preferable to use a thermoplastic resin of 90°C or higher and 120°C or lower.

[0047] Note that the melting point of the thermoplastic resin can be measured by differential scanning calorimetry (DSC) in accordance with, for example, the plastic transition temperature measurement method (JIS K7121:2012). In the case where a plurality of thermoplastic resins are included, it is the value of the highest melting point. When the encapsulating member is a multilayer member as described later, it is preferable to use a thermoplastic resin as the base resin of the core layer having the above melting point.

[0048] (c) Melt mass flow rate (MFR) Further, as the thermoplastic resin in this embodiment, those having a melt viscosity that can follow the unevenness of the LED element and other members arranged on one surface side of the LED substrate and enter the gaps by heating are preferably used.

[0049] Specifically, the melt mass flow rate (MFR) of the thermoplastic resin to be used is preferably 0.5 g / 10 min or more and 40 g / 10 min or less, more preferably 2.0 g / 10 min or more and 40 g / 10 min or less, and still more preferably 2.0 g / 10 min or more and 20 g / 10 min or less. When the MFR is within the above range, it can enter the gaps such as those of the LED element, can exhibit sufficient encapsulation performance, and further can be an encapsulating member having excellent adhesion to the LED substrate.

[0050] In addition, the MFR in this specification refers to the value at 190°C and a load of 2.16 kg measured according to Method A of JIS K7210-1:2014. However, for the MFR of polypropylene resin, it refers to the value of MFR at 230°C and a load of 2.16 kg, also according to Method A of JIS K7210-1:2014.

[0051] Regarding the MFR when the sealing member is a multilayer member as described later, measurement shall be carried out by the above measurement method while all the layers are in a multilayer state of integral lamination, and the obtained measurement value shall be taken as the MFR value of the multilayer sealing member.

[0052] d) Tensile modulus Further, as the thermoplastic resin in this embodiment, the tensile modulus at room temperature (25°C) is preferably 20 MPa or more and 300 MPa or less, and particularly preferably 20 MPa or more and 200 MPa or less. It can exhibit sufficient adhesion to the LED substrate and can be a sealing member with excellent impact resistance, for example, when an external impact is applied to the surface light-emitting device. When the sealing member is a multilayer member as described later, it is preferable to use a thermoplastic resin as the base resin of the core layer having the above modulus of elasticity. The above tensile modulus uses the value measured according to JIS K7127:1999.

[0053] Note that the modulus of elasticity is measured by the tensile measurement shown below. · Measuring device: Instron universal material testing machine 5565 · Load cell: 1 kN · Specimen width: 10 mm · Distance between chucks: 50 mm · Speed: 300 mm / min

[0054] In addition to the above thermoplastic resin, additives such as antioxidants and light stabilizers may be added to the sealing member.

[0055] e) Coefficient of linear expansion In this embodiment, the above-described sealing member has a higher coefficient of linear expansion than the LED substrate described later. Therefore, as described above, after thermocompression bonding the sealing member and the LED substrate in the manufacturing process, the shrinkage rate of the sealing member becomes larger than that of the LED substrate, and as a result, there arises a problem that warping occurs such that the sealing member side is recessed. As the coefficient of linear expansion of the material constituting the sealing member used in this embodiment, the lower limit value is preferably 20×10 -6 / °C or more, particularly preferably 150×10 -6 / °C or more. On the other hand, the upper limit value is preferably 1500×10 -6 / °C or less, particularly preferably 1000×10 -6 / °C or less. Specifically, it is preferably in the range of 20×10 -6 / °C or more and 1500×10 -6 / °C or less, particularly preferably 20×10 -6 / °C or more and 1000×10 -6 / °C or less, and most preferably in the range of 150×10 -6 / °C or more and 1000×10 -6 / °C or less. The above coefficient of linear expansion uses the value measured according to JIS K7197:2012.

[0056] (4) Structure of the sealing member In the surface light-emitting device in this embodiment, the sealing member may be, for example, as shown in FIG. 1, a single-layer member in which the sealing member 5 is composed of a single resin layer, or as shown in FIG. 3, the sealing member 5 may be a multilayer member in which a plurality of resin layers (two layers in FIG. 3(a) and three layers in FIG. 3(b)) including a core layer 51 and a skin layer 52 disposed on at least one surface of the core layer 51 are laminated. In particular, a two-layer structure having a core layer or the like and a skin layer disposed on the LED substrate side of the core layer is preferable. Note that FIG. 3 shows an example in which a reflective layer R is disposed around the LED element 3.

[0057] When the sealing member in the present embodiment is a multi-layer member having a two-layer structure including a core layer and a skin layer disposed on the LED substrate side of the core layer, the film thickness ratio of the skin layer to the core layer (skin layer: core layer), when the skin layer: core layer is 1:X, the lower limit value of X is preferably 0.1 or more, particularly preferably 0.5 or more. On the other hand, as the lower limit value, 10 or less is preferable, particularly preferably 6 or less. That is, 1:0.1 to 1:10 is preferable, and particularly preferably 1:0.5 to 1:6.

[0058] Further, when the sealing member in the present embodiment is a multi-layer member having a three-layer structure, when the film thickness ratio of the skin layer to the core layer (skin layer: core layer: skin layer) is 1:Y:1, Y is preferably 1 or more, particularly preferably 2 or more. On the other hand, Y is preferably 10 or less, particularly preferably 8 or less. That is, the film thickness ratio of the skin layer to the core layer (skin layer: core layer: skin layer) is preferably 1:1:1 to 1:10:1, and particularly preferably 1:2:1 to 1:8:1.

[0059] When the sealing member in the present embodiment is a multi-layer member, it is preferable that the core layer and the skin layer have the above-mentioned thermoplastic resin with different density ranges, melting points, etc. as the base resin. This is because it becomes easy to ensure the haze value in the core layer and to ensure the adhesion to the LED substrate and the molding characteristics in the skin layer.

[0060] In the case of the above multi-layer member, it is possible to use a material with good adhesion and molding characteristics that can enter the gaps such as LED elements, which is usually expensive, in the skin layer located on the LED substrate side of the multi-layer member. In the above multi-layer member, the material constituting the skin layer disposed on the LED substrate side is not particularly limited as long as it has high adhesion and high molding characteristics. However, in the case of the above thermoplastic resin, it is preferable to use the above-mentioned silane copolymer or the like. Further, in the case of the above thermoplastic resin, it is also preferable that the material contains the above olefin-based resin and a silane coupling agent. In addition, additives such as an antioxidant and a light stabilizer may be added to this layer.

[0061] (5) Preferred sealing member The sealing member in the present embodiment is preferably a multilayer member composed of a plurality of layers including a core layer and a skin layer disposed on at least one outermost surface. The core layer has a density of 0.900 g / cm 3 or more and 0.930 g / cm 3 or less, and it is preferable to use a polyethylene-based resin as the base resin. For the skin layer, the density is 0.875 g / cm 3 or more and 0.910 g / cm 3 or less, and it is preferable to use a polyethylene-based resin having a lower density than the base resin for the core layer as the base resin.

[0062] As the base resin for the core layer, a low-density polyethylene-based resin (LDPE), a linear low-density polyethylene-based resin (LLDPE), or a metallocene-based linear low-density polyethylene-based resin (M-LLDPE) can be preferably used. Among them, from the viewpoint of long-term reliability, a low-density polyethylene-based resin (LDPE) can be particularly preferably used as the base resin for the core layer.

[0063] The density of the polyethylene-based resin used as the base resin for the core layer is 0.900 g / cm 3 or more and 0.930 g / cm 3 or less, and more preferably 0.920 g / cm 3 or less. By setting the density of the base resin for the core layer within the above range, the haze value of the sealing member in the present embodiment can be made equal to or higher than the above specific value. In addition, sufficient heat resistance can be provided to the sealing member without undergoing a cross-linking treatment.

[0064] Regarding the melting point of the polyethylene-based resin used as the base resin for the core layer, it is preferably 90°C or higher and 135°C or lower, more preferably 90°C or higher and 115°C or lower. By setting the melting point within the above range, the heat resistance and molding characteristics of the sealing member can be maintained within a preferable range. In addition, by adding a high-melting resin such as polypropylene to the sealing material composition for the core layer, it is possible to increase the melting point of the sealing member to about 165°C. In this case, polypropylene is preferably contained in an amount of 5% by mass or more and 40% by mass or less based on all the resin components of the core layer.

[0065] The polypropylene contained in the core layer is preferably a homopolypropylene (homo-PP) resin. Since homo-PP is a polymer composed only of polypropylene and has high crystallinity, it has higher rigidity compared to block PP and random PP. By using this as the additive resin to the sealing material composition for the core layer, the dimensional stability of the sealing member can be enhanced. Further, the homo-PP used as the additive resin to the sealing material composition for the core layer preferably has an MFR of 5 g / 10 min or more and 125 g / 10 min or less at 230°C and a load of 2.16 kg measured in accordance with JIS K7210:2014 Method A. If the above MFR is too small, the molecular weight becomes large and the rigidity becomes too high, making it difficult to ensure the preferable sufficient flexibility of the sealing material composition. Also, if the above MFR is too large, the fluidity during heating is not sufficiently suppressed, and sufficient heat resistance and dimensional stability cannot be imparted to the sealing member sheet.

[0066] The melt mass flow rate (MFR) of the polyethylene-based resin used as the base resin for the core layer is preferably 1.0 g / 10 min or more and 7.5 g / 10 min or less at 190°C and a load of 2.16 kg, more preferably 1.5 g / 10 min or more and 6.0 g / 10 min or less. By setting the MFR of the base resin for the core layer within the above range, the heat resistance and molding characteristics of the sealing member can be maintained within a preferable range. In addition, it can sufficiently enhance the processing suitability during film formation and contribute to the improvement of the productivity of the sealing member.

[0067] The content of the above base resin with respect to all resin components of the above core layer is 70% by mass or more and 99% by mass or less, preferably 90% by mass or more and 99% by mass or less. As long as it contains a base resin within the above range, it may contain other resins.

[0068] As the base resin for the skin layer of the above sealing member, similar to the sealing material composition for the core layer, a low-density polyethylene resin (LDPE), a linear low-density polyethylene resin (LLDPE), or a metallocene linear low-density polyethylene resin (M-LLDPE) can be preferably used. Among them, from the perspective of molding characteristics, the metallocene linear low-density polyethylene resin (M-LLDPE) can be particularly preferably used as the sealing material composition for the skin layer.

[0069] The density of the above polyethylene resin used as the base resin for the skin layer is 0.875 g / cm 3 or more and 0.910 g / cm 3 or less, and more preferably 0.899 g / cm 3 or less. By setting the density of the base resin for the skin layer within the above range, the adhesion of the sealing member can be maintained within a preferable range.

[0070] Regarding the melting point of the above polyethylene resin used as the base resin for the skin layer, it is preferably 50°C or more and 100°C or less, and more preferably 55°C or more and 95°C or less. By setting it within the above range, the adhesion of the sealing member can be more surely improved.

[0071] The melt mass flow rate (MFR) of the polyethylene-based resin used as the base resin for the skin layer is preferably 1.0 g / 10 min or more and 7.0 g / 10 min or less at 190 °C under a load of 2.16 kg, and more preferably 1.5 g / 10 min or more and 6.0 g / 10 min or less. By setting the MFR of the base resin for the skin layer within the above range, the adhesion of the sealing member can be maintained within a more preferable range. In addition, the processing suitability during film formation can be sufficiently enhanced, contributing to an improvement in the productivity of the sealing member.

[0072] The content of the above base resin with respect to all resin components 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. As long as it contains the base resin within the above range, it may contain other resins.

[0073] It is more preferable to contain a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as comonomers in each of the above-described sealing material compositions in a certain amount as required. Such a graft copolymer can improve the adhesion of the sealing member to other members because the degree of freedom of the silanol group that contributes to the adhesive force is increased.

[0074] Examples of the silane copolymer include the silane copolymer described in JP-A-2003-46105. By using the above silane copolymer as a component of the sealing material composition, it is excellent in strength, durability, etc., and also excellent in weather resistance, heat resistance, water resistance, light resistance, and other various properties. 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 a sealing member can be obtained stably and at low cost.

[0075] As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used, but a graft copolymer is more preferable, and a graft copolymer having a polyethylene for polymerization as a main chain and an ethylenically unsaturated silane compound polymerized as a side chain is even more preferable. Such a graft copolymer has a high degree of freedom of silanol groups contributing to adhesion, and thus the adhesiveness of the sealing member can be improved.

[0076] When it comes to the content of the ethylenically unsaturated silane compound in forming the copolymer of an α-olefin and an ethylenically unsaturated silane compound, based on the total mass of the copolymer, for example, it is desirably 0.001% by mass or more and 15% by mass or less, preferably 0.01% by mass or more and 10% by mass or less, and particularly preferably 0.05% by mass or more and 5% by mass or less. When the content of the ethylenically unsaturated silane compound constituting the copolymer of an α-olefin and an ethylenically unsaturated silane compound is large, it is excellent in mechanical strength, heat resistance, etc., but when the content becomes excessive, it tends to be inferior in tensile strain, heat fusion property, etc.

[0077] The content of the above silane copolymer with respect to all the resin components of the sealing material composition is preferably 0% by mass or more and 20% by mass or less in the sealing material composition for the core layer, and 5% by mass or more and 40% by mass or less in the sealing material composition for the skin layer. Particularly for the sealing material composition for the skin layer, it is more preferable that it contains 5% by mass or more of the silane copolymer. Incidentally, the silane modification amount in the above silane copolymer is preferably about 0.1% by mass or more and 2.0% by mass or less. The preferable content range of the silane copolymer in the above sealing material composition is premised on the silane modification amount being within this range, and it is desirable to make appropriate fine adjustments according to the variation of this modification amount.

[0078] Additives such as an antioxidant and a light stabilizer may be added to all the layers of the sealing member. In addition, an adhesion improver can be added as appropriate. By adding the adhesion improver, the adhesion durability with other members can be made higher. As the adhesion improver, a known silane coupling agent can be used, and a vinyl group-containing vinyltrimethoxysilane, vinyltriethoxysilane, a silane coupling agent having an epoxy group, or a silane coupling agent having a mercapto group can be particularly preferably used.

[0079] (6) Total light transmittance The encapsulating member in this embodiment is not particularly limited as long as it can function as a surface light-emitting device, but is preferably 70% or more, and particularly preferably 80% or more. The total light transmittance of the encapsulating member can be measured, for example, by a method conforming to JIS K7361-1:1997.

[0080] (7) Method for forming the encapsulating member As described above, the encapsulating member in this embodiment can be formed using an encapsulating member sheet composed of the above-mentioned thermoplastic resin and other components contained in an encapsulating material composition. The above-mentioned encapsulating member sheet is obtained by molding an encapsulating material composition into a sheet shape by a conventionally known method.

[0081] When the encapsulating member is a multilayer member, a two-layer structure multilayer film composed of a core layer and a skin layer disposed on one surface of the core layer with a predetermined thickness is formed by using each encapsulating material composition for the core layer and the skin layer. Thus, as shown in FIG. 3(a), for example, an encapsulating member 5 having a two-layer structure of a core layer 51 and a skin layer 52 can be manufactured. Alternatively, it is also possible to form a three-layer structure multilayer film in which skin layers are disposed on both surfaces of the core layer. Thereby, as shown in FIG. 3(b), for example, an encapsulating member 5 having a three-layer structure of a skin layer 52, a core layer 51, and a skin layer 52 can be manufactured. Note that the configurations other than the encapsulating member 5 and the reflective layer R in FIG. 3 are the same as those in FIG. 1, and thus the description thereof is omitted here.

[0082] 2. Anti-warping layer The anti-warping layer in the present embodiment is a layer disposed between the above-mentioned sealing member and a diffusion member described later.

[0083] In the present embodiment, warping can be prevented by setting the linear expansion coefficient of the material constituting the anti-warping layer in a predetermined range at a high temperature region. The reason why warping can be prevented by setting the linear expansion coefficient of the material constituting the anti-warping layer within a predetermined range is as follows.

[0084] That is, when manufacturing a surface light-emitting device, it may have a step of thermocompression bonding the sealing member and the LED substrate. However, during cooling after thermocompression bonding, the sealing member behaves to contract more greatly than the LED substrate. At this time, since an anti-warping layer with a small linear expansion coefficient is disposed on the side of the sealing member opposite to the LED substrate, it becomes possible to reduce the degree of contraction on the sealing member side. As a result, the occurrence of warping can be suppressed.

[0085] Further, in the present embodiment, by disposing the anti-warping layer, it becomes possible to suppress deformation of the sealing member that occurs when bubbles are generated at the site where bubbles are generated. Thereby, it becomes possible to prevent the generation of bubbles between the sealing member and the LED substrate as described above. In particular, the above effects can be effectively obtained by an anti-warping layer having a predetermined elastic modulus and a predetermined melting point.

[0086] a) Linear expansion coefficient The linear expansion coefficient of the material constituting the anti-warping layer in the present disclosure is -15×10 -6 / °C or more and 10×10 -6 / °C or less. In the present disclosure, among others, it is preferable that the lower limit value of the linear expansion coefficient is -10×10 -6 / °C or more. On the other hand, the upper limit value is preferably 5×10 -6 / °C or less, and particularly preferably 0 or less. That is, it is preferably -10×10 -6 / °C or more and 5×10 -6 / °C or less, and particularly preferably -10×10-6 / °C or higher 0×10 -6 / °C or lower is preferable. On the other hand, considering the materials used, etc., usually, -10×10 -6 / °C or higher 5×10 -6 / °C or lower. If it is smaller than this, it will cause reverse warping. On the other hand, if it is larger than this, the warpage prevention effect will be insufficient.

[0087] As the method for measuring the linear expansion coefficient in this embodiment, it is carried out by the following method. For a sheet cut to 5 mm × 20 mm, after heating in accordance with JIS K 7197:2012, the dimensional change during cooling from the elevated temperature to room temperature was measured, and the linear expansion coefficient from 100°C to 25°C was averaged and calculated. Here, the linear expansion coefficient is a positive value during contraction and a negative value during expansion. The measurement was carried out under the following measuring apparatus and measuring conditions. · Measuring apparatus: Thermal mechanical apparatus (TMA / SS-6000) manufactured by Seiko Instruments Inc. · Constant load tension mode: 0.1 mN · Measuring temperature range: -50°C or higher and 160°C or lower · Linear expansion coefficient calculation temperature range: 25°C or higher and 100°C or lower

[0088] b) Elastic modulus The elastic modulus of the warpage prevention layer used in this embodiment is preferably 500 MPa or higher, particularly preferably 1000 MPa or higher, and most preferably 4000 MPa or higher. If the elastic modulus is lower than the above range, the effect of suppressing bubble generation and the warpage prevention effect will be reduced. Considering the materials usually used, it is 5500 MPa or lower.

[0089] As the method for measuring the elastic modulus in this embodiment, it is carried out by the tensile measurement shown below. (Measurement method) · Measuring apparatus: Universal material testing machine 5565 manufactured by Instron · Load cell: 1 kN · Sample width: 10 mm · Distance between chucks: 50 mm · Speed: 300 mm / min

[0090] c) Thickness The thickness of the warpage prevention layer in this embodiment is preferably in the range of 35 μm or more and 188 μm or less, more preferably in the range of 50 μm or more and 150 μm or less, and particularly preferably in the range of 100 μm or more and 125 μm or less. Within the above range, it is possible to obtain a warpage prevention effect and an effect of suppressing the generation of bubbles, and it does not hinder the miniaturization of the device.

[0091] d) Transmittance and haze value The haze value of the warpage prevention layer in this embodiment is preferably 40% or less, more preferably 20% or less, and particularly preferably 10% or less. Within the above range, it is possible to improve the in-plane uniformity of luminance. When the haze value exceeds the above range, light is absorbed while being scattered inside the sealing member, resulting in a decrease in luminance. As the method for measuring the haze value, the same method as the method for measuring the haze value of the above sealing member can be used.

[0092] On the other hand, the total light transmittance of the warpage prevention layer in this embodiment is preferably 80% or more, and particularly preferably 90% or more. By having such a high total light transmittance, it is possible to prevent a decrease in the luminance of the surface light-emitting device.

[0093] Here, the total light transmittance of the warpage prevention layer can be measured in accordance with JIS K7361-1, and can be measured by a haze meter HM150 manufactured by Murakami Color Technology Laboratory.

[0094] e) Melting point The melting point of the warpage prevention layer in this embodiment is preferably 140°C or more, and particularly preferably 260°C or more. Considering the materials usually used, the upper limit is 350°C or less. In this embodiment, the melting point can be measured by differential scanning calorimetry (DSC) in accordance with, for example, the method for measuring the transition temperature of plastics (JIS K7121).

[0095] In this embodiment, since the warpage prevention layer has the above-described melting point, it is possible to effectively prevent the generation of bubbles even when the surface light-emitting device is used in a high-temperature environment for a long time.

[0096] f) Material The material constituting the warpage prevention layer used in this embodiment is not particularly limited as long as it has the above characteristics, and examples thereof include polyolefin, polyester, celluloses, acrylic resins, and polyimide resins. Examples of polyolefin include polypropylene (PP). Examples of polyester include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). Examples of celluloses include triacetyl cellulose (TAC). In this embodiment, among them, PP and PET are preferable from the viewpoints of versatility and the like.

[0097] g) Others In this embodiment, it is preferable that the warpage prevention layer and the sealing member are in close contact with each other. This is because the warpage prevention effect can be more efficiently exhibited. In this embodiment, "the warpage prevention layer and the sealing member are in close contact with each other" means a state in which they do not peel off by their own weight when taken out. Specifically, it is preferable that the adhesion strength is 1 N or more. As a method for measuring the adhesion strength, the following method can be used in accordance with JIS K 6854-2:1999.

[0098] (Measurement method) Cut out the sealing member adhered to the PCB substrate to a width of 25 mm, and perform a vertical peeling (300 mm / min) test with a peeling tester (Tensilon universal testing machine RTF-1150-H) to measure the adhesion strength.

[0099] In order to closely adhere the anti-warping layer and the sealing member, methods such as disposing both of them via an adhesive layer or melting and adhering them by thermocompression bonding can be mentioned.

[0100] 3. LED Substrate The LED substrate in the present embodiment is a member in which a plurality of LED elements are arranged on one surface side of a support substrate.

[0101] (1) LED Element The LED element is a member arranged on one surface side of the support substrate and functions as a light source. The LED element is not particularly limited as long as it can irradiate white light when it is a surface light-emitting device, and examples thereof include LED elements that can emit white, blue, ultraviolet, or infrared light.

[0102] The LED element can be a chip-shaped LED element. As the form of the LED element, for example, it may be the light-emitting part itself (also referred to as an LED chip), or a packaged LED (also referred to as a chip LED) such as a surface-mount type or a chip-on-board type. The 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, as the LED element, for example, a blue LED element, an ultraviolet LED element, or an infrared LED element can be used. Also, when the LED element is a packaged LED, as the LED element, for example, a white LED element can be used.

[0103] When the surface light-emitting device of the present embodiment irradiates white light by combining an LED element and the wavelength conversion member, the LED element is preferably a blue LED element, an ultraviolet LED element, or an infrared LED element. The blue LED element can generate white light, for example, by combining with a yellow phosphor or by combining with a red phosphor and a green phosphor. Further, the ultraviolet LED element can generate white light, for example, by combining with a red phosphor, a green phosphor, and a blue phosphor. Among them, it is preferable that the LED element is a blue LED element. This is because the surface light-emitting device of the present embodiment can irradiate white light with high luminance.

[0104] In addition, when the LED element is a white LED element, the white LED element is appropriately selected according to the light-emitting method of the white LED element or the like. Examples of the light-emitting 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.

[0105] Therefore, as the white LED element, for example, it may have a red LED light-emitting portion, a green LED light-emitting portion, and a blue LED light-emitting portion, or it may have a blue LED light-emitting portion and a protective portion containing a red phosphor and a green phosphor, or it may have a blue LED light-emitting portion and a protective portion containing a yellow phosphor, or it may have an ultraviolet LED light-emitting portion and a protective portion containing a red phosphor, a green phosphor, and a blue phosphor.

[0106] Among them, the white LED element preferably has a blue LED light-emitting portion and a protective portion containing a red phosphor and a green phosphor, a blue LED light-emitting portion and a protective portion containing a yellow phosphor, or an ultraviolet LED light-emitting portion and a protective portion containing a red phosphor, a green phosphor, and a blue phosphor.

[0107] Among these, the white LED element preferably has 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. This is because the surface light-emitting device of the present embodiment can irradiate white light with high luminance. The structure of the LED element can be the same as that of a general LED element.

[0108] The LED elements are usually arranged at equal intervals on one surface side of the support substrate. The arrangement of the LED elements is appropriately selected according to the application and size of the surface light-emitting device of the present embodiment, the size of the LED elements, etc. Also, the arrangement density of the LED elements is appropriately selected according to the application and size of the surface light-emitting device of the present embodiment, the size of the LED elements, etc.

[0109] The size (chip size) of the LED element can be a general chip size, but among them, it is preferably a chip size called a mini LED. The size of the LED element may be, for example, several hundred micrometers square or several tens of micrometers square. Specifically, the size of the LED element can be 100 μm square or more and 2000 μm square or less. Since the size of the LED element is small, the LED elements can be arranged at a high density, that is, the interval (pitch) between the LED elements can be reduced, and the distance between the LED substrate and the diffusion member can be shortened, that is, the thickness of the sealing member can be reduced. Thereby, the surface light-emitting device can be made thinner and lighter.

[0110] (2) Support substrate The support substrate in the present embodiment is a member that supports the above-mentioned LED elements, sealing members, diffusion members, etc.

[0111] The support substrate may be transparent or opaque. Also, the support substrate may have flexibility or rigidity. The material of the support 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.

[0112] 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 can be used as the support substrate. Also, for example, a metal core substrate can be used as the support substrate. As the support substrate, a printed circuit board on which a circuit is formed by printing can also be used.

[0113] The thickness of the support substrate is not particularly limited and is appropriately selected according to the presence or absence of flexibility or rigidity, the application and size of the surface light-emitting device of the present embodiment, etc. In the present embodiment, the above support substrate has a lower linear expansion coefficient than the above-described sealing member. Therefore, as described above, after thermocompression bonding the above sealing member in the manufacturing process, a problem of warpage occurs.

[0114] The linear expansion coefficient of the support substrate used in the present embodiment is usually 5×10 -6 / °C or more and 100×10 -6 / °C or less.

[0115] (3) Others The LED substrate in the present embodiment is not particularly limited as long as it has the above-described support substrate and LED element, and can appropriately have a necessary configuration. Examples of such a configuration include a wiring portion, a terminal portion, an insulating layer, a reflective layer, a heat radiating member, etc. Each configuration can be the same as those used in known LED substrates.

[0116] The wiring portion is electrically connected to the LED element. The wiring portion is usually arranged in a pattern. Also, the wiring portion can be arranged on the support base material via an adhesive layer. As the material of the wiring portion, a metal material, a conductive polymer material, etc. can be used.

[0117] The wiring part is electrically connected to the above LED element by a joint part. As the material of the joint part, an adhesive or solder having a conductive material such as metal or conductive polymer can be used.

[0118] On the surface of the support substrate where the LED element is arranged, a reflective layer can be arranged in the area other than the LED element mounting area. For example, the light reflected by the second layer of the diffusion member can be reflected by the reflective layer of the support substrate and then incident on the first layer of the diffusion member again, thereby improving the light utilization efficiency.

[0119] The reflective layer can be the same as the reflective layer generally used for an LED substrate. Specifically, examples of the reflective layer include 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 a desired reflectance can be obtained, and it is set appropriately. The method for forming the LED substrate can be the same as a known forming method.

[0120] 4. Diffusion member The diffusion member is arranged on the surface side opposite to the LED substrate side of the sealing member. The diffusion member is not particularly limited as long as it has a function of diffusing the light emitted from the LED element and emitting it uniformly in the plane direction, and the following first diffusion member, second diffusion member, and third diffusion member can be mentioned.

[0121] 4.1 First diffusion member The first diffusion member usually has at least a resin layer in which a diffusing agent is dispersed. The above diffusion member may be, for example, a resin sheet in which a diffusing agent is dispersed, or a laminate having a resin layer in which a diffusing agent is dispersed on a transparent substrate, but the former is more preferable. The resin contained in the resin layer is not particularly limited as long as a diffusing agent can be dispersed, but it is preferably a thermoplastic resin. This is because a diffusion member can be formed using a resin sheet in which a diffusing agent is dispersed, and good flatness can be achieved.

[0122] The thermoplastic resin used for the above diffusion member is not particularly limited as long as it has a high light transmittance, and those generally used in the display device field can be used.

[0123] The material of the above diffusing agent is not particularly limited as long as it can diffuse the light from the LED element. For example, it may be an organic material or an inorganic material. When the material of the diffusing agent is an organic material, for example, polymethyl methacrylate (PMMA) can be mentioned. On the other hand, when the material of the diffusing agent is an inorganic material, TiO 2 、SiO 2 、Al 2 O 3 、silicon, etc. can be mentioned.

[0124] The refractive index of the diffusing agent is not particularly limited as long as it can diffuse the light from the LED element. For example, it is 1.4 or more and 2 or less. Such a refractive index can be measured by an Abbe refractometer, the Becke method, the minimum deviation method, deviation analysis, the mode-line method, the ellipsometry method, etc. The shape of the diffusing agent can be, for example, particulate. The average particle size of the diffusing agent is, for example, 1 μm or more and 100 μm or less.

[0125] The ratio of the diffusing agent in the diffusion member is not particularly limited as long as it can diffuse the light from the LED element. For example, it is 40% by weight or more and 60% by weight or less.

[0126] 4.2 Second Diffusion Member The second diffusion member is a member having a first layer and a second layer in this order from the above LED substrate side. The first layer has light transmissivity and light diffusibility, and the second layer has a reflectance that increases as the absolute value of the incident angle of light with respect to the surface of the second layer on the first layer side decreases, and a transmittance that increases as the absolute value of the incident angle of light with respect to the surface of the second layer on the first layer side increases. In this embodiment, by having the above-described diffusion member, it is possible to improve the in-plane uniformity of the luminance further while achieving thinning. Also, it is possible to reduce the cost and power consumption.

[0127] Hereinafter, the second diffusion member will be described with reference to the drawings. FIG. 4 is a schematic cross-sectional view showing an example of the second diffusion member. As illustrated in FIG. 4, the diffusion member 11 has a first layer 12 and a second layer 13 in this order. The first layer 12 has light transmissivity and light diffusibility, and transmits and diffuses the incident lights L1 and L2 from the surface 12A opposite to the surface on the second layer 13 side of the first layer 12. Further, in the second layer 13, the reflectance increases as the absolute value of the incident angle of light with respect to the surface 13A on the first layer 12 side of the second layer 13 decreases, and the transmittance increases as the absolute value of the incident angle of light with respect to the surface 13A on the first layer 12 side of the second layer 13 increases. Therefore, in the second layer 13, the light L1 incident at a low incident angle θ1 with respect to the surface 13A on the first layer 12 side of the second layer 13 can be reflected, and the light L2 incident at a high incident angle θ2 with respect to the surface 13A on the first layer 2 side of the second layer 13 can be transmitted. Note that the low incident angle means an incident angle with a small absolute value, and the high incident angle means an incident angle with a large absolute value.

[0128] FIG. 5 is a schematic cross-sectional view showing an example of the surface light-emitting device of the present embodiment including the second diffusion member shown in FIG. 4. As illustrated in FIG. 5, the surface light-emitting device 10 has an LED substrate 4 in which an LED element 3 is disposed on one surface of a support substrate 2, a sealing member 5 disposed on the surface side of the LED substrate 4 on the LED element 3 side for sealing the LED element 3, and a diffusion member 11 disposed on the surface side opposite to the LED substrate 4 side of the sealing member 5. The diffusion member 11 is disposed such that the surface 11A on the first layer 12 side faces the sealing member 5.

[0129] As shown in FIG. 4, the light incident from the surface 11A on the first layer 12 side of the diffusion member 11 is diffused by the first layer 12, and among the light that has passed through and diffused through the first layer 12, for the light L1 incident on the surface 13A on the first layer 12 side of the second layer 13 at a low incident angle θ1, as shown in FIG. 5, it can be reflected by the surface 13A on the first layer 12 side of the second layer 13 and incident on the first layer 12 again for diffusion. And among the light that has passed through and diffused through the first layer 12, for the light L2, L2' incident on the surface 13A on the first layer 12 side of the second layer 13 at a high incident angle θ2, it can pass through the second layer 13 and be emitted from the surface 11B on the second layer 13 side of the diffusion member 11.

[0130] Also, by combining the first layer and the second layer, for the light incident from the surface on the first layer side of the diffusion member, especially the light incident at a low incident angle from the surface on the first layer side of the diffusion member, it can be made to pass through the first layer and be diffused many times, so that it can be emitted from the surface on the second layer side of the diffusion member at a high emission angle. Therefore, a surface light emitting device having such a diffusion member (especially a direct - type LED backlight) can diffuse the light emitted from the LED element over the entire light emitting surface and further improve the in - plane uniformity of luminance.

[0131] Also, by combining the first layer and the second layer, for the light incident at a low incident angle from the surface on the first layer side of the diffusion member, it can pass through the first layer many times. Therefore, the optical path length from when the light enters from the surface on the first layer side of the diffusion member until it is emitted from the surface on the second layer side of the diffusion member can be lengthened. As a result, a part of the light emitted from the LED element and then emitted from the surface on the second layer side of the diffusion member can be made to be emitted from a position away from the LED element in the in - plane direction rather than directly above the LED element.

[0132] (1) The first layer The first layer in this embodiment is a member that is disposed on one surface side of the second layer described later and has light transmissivity and light diffusibility. As the light transmissivity of the first layer, for example, it is preferable that the total light transmittance of the first layer is 50% or more, more preferably 70% or more, and particularly preferably 90% or more. By the total light transmittance of the first layer being within the above range, the luminance of the surface light-emitting device of this embodiment can be increased.

[0133] Note that the total light transmittance of the first layer can be measured, for example, by a method conforming to JIS K7361-1:1997.

[0134] As the light diffusibility of the first layer, for example, it may be light diffusibility that diffusely scatters light randomly, or it may be light diffusibility that diffusely scatters light mainly in a specific direction. The light diffusibility that diffusely scatters light mainly in a specific direction is a property of deflecting light, that is, a property of changing the traveling direction of light. When the light diffusibility of the first layer is light diffusibility that diffusely scatters light randomly, for example, the diffusion angle of the light incident on the first layer can be 10° or more, may be 15° or more, and may be 20° or more. Also, the diffusion angle of the light incident on the first layer can be, for example, 85° or less, may be 60° or less, and may be 50° or less. By the diffusion angle being within the above range, the in-plane uniformity of the luminance of the surface light-emitting device of this embodiment can be further improved.

[0135] Here, the diffusion angle will be described. FIG. 6 is a graph illustrating the transmitted light intensity distribution and is a diagram for explaining the diffusion angle. In this specification, the full width at half maximum (FWHM), which is the difference between two angles that become half of the maximum transmitted light intensity Imax of the light emitted from the other surface of the first layer when light is perpendicularly incident on one surface of the first layer constituting the diffusion member, is defined as the diffusion angle α.

[0136] Note that the diffusion angle can be measured using a variable-angle photometer or a variable-angle spectrophotometer. For measuring the diffusion angle, a variable-angle photometer (goniophotometer) GP-200 manufactured by Murakami Color Research Laboratory can be used.

[0137] The first layer is not particularly limited as long as it has the above-described light transmissivity and light diffusibility, and examples thereof include a transmissive diffraction grating, a microlens array, a diffusing agent-containing resin film containing a diffusing agent and a resin, and the like. Specifically, when the first layer has light diffusibility that mainly diffuses light in a specific direction, a transmissive diffraction grating and a microlens array can be mentioned. On the other hand, when the first layer has light diffusibility that diffuses light randomly, a diffusing agent-containing resin film can be mentioned. Among them, from the viewpoint of light diffusibility, a transmissive diffraction grating and a microlens array are preferable. Note that the transmissive diffraction grating is also referred to as a transmissive diffractive optical element (DOE).

[0138] When the first layer is a transmissive diffraction grating, the transmissive diffraction grating is not particularly limited as long as it has the above-described light transmissivity and light diffusibility. The pitch and the like of the transmissive diffraction grating may be appropriately adjusted as long as the above-described light transmissivity and light diffusibility can be obtained. Specifically, when the wavelength output from the LED element is a single color such as red, green, or blue, the light from the LED element can be effectively bent by setting the pitch according to each wavelength.

[0139] The material constituting the transmissive diffraction grating is not particularly limited as long as it can obtain a transmissive diffraction grating having the above-described light transmissivity and light diffusibility, and those generally used for transmissive diffraction gratings can be adopted. Also, the formation method of the transmissive diffraction grating can be the same as the general formation method of transmissive diffraction gratings.

[0140] When the first layer is a microlens array, the microlens array is not particularly limited as long as it has the above-described light transmittance and light diffusibility. The shape, pitch, size, etc. of the microlenses may be appropriately adjusted as long as the above-described light transmittance and light diffusibility are obtained. As the material constituting the microlenses, any material can be adopted as long as it can obtain microlenses having the above-described light transmittance and light diffusibility, and generally, those commonly used for microlenses can be employed. Also, the method for forming the microlenses can be the same as the general method for forming microlenses.

[0141] When the first layer is a resin film containing a diffusing agent, the resin film containing a diffusing agent is not particularly limited as long as it has the above-described light transmittance and light diffusibility.

[0142] The first layer only needs to have a structure capable of exhibiting light diffusibility. For example, it may exhibit light diffusibility throughout the layer or may exhibit light diffusibility on the surface. Examples of those that exhibit light diffusibility on the surface include relief type diffraction gratings and microlens arrays. On the other hand, examples of those that exhibit light diffusibility throughout the layer include volume type diffraction gratings and resin films containing diffusing agents. Examples of the method for laminating the first layer and the second layer include a method of bonding the first layer and the second layer via an adhesive layer or a pressure-sensitive adhesive layer, and a method of directly forming the first layer on one surface of the second layer. Examples of the method of directly forming the first layer on one surface of the second layer include a printing method and resin shaping using a mold.

[0143] (2) The second layer In the present embodiment, the second layer is disposed on one surface side of the first layer, and has a reflectance angle dependence such that the reflectance increases as the absolute value of the incident angle of light with respect to the surface of the second layer on the first layer side decreases, and a transmittance angle dependence such that the transmittance increases as the absolute value of the incident angle of light with respect to the surface of the second layer on the first layer side increases.

[0144] The second layer has a reflectance angle dependence such that the reflectance increases as the absolute value of the incident angle of light with respect to the surface of the second layer on the first layer side decreases. That is, the reflectance of light incident at a low incident angle with respect to the surface of the second layer on the first layer side is greater than the reflectance of light incident at a high incident angle with respect to the surface of the second layer on the first layer side. Among them, it is preferable that the reflectance of light incident at a low incident angle with respect to the surface of the second layer on the first layer side is large.

[0145] Specifically, the specular reflectance of visible light incident within an incident angle of ±60° with respect to the surface of the second layer on the first layer side is preferably 50% or more and less than 100%, more preferably 80% or more and less than 100%, and particularly preferably 90% or more and less than 100%. It is preferable that the specular reflectance of visible light satisfies the above range at all incident angles within ±60° of the incident angle. By the specular reflectance being within the above range, the in-plane uniformity of the luminance of the surface light-emitting device of the present embodiment can be further improved.

[0146] Further, the average value of the specular reflectance of visible light incident within an incident angle of ±60° with respect to the surface of the second layer on the first layer side is preferably, for example, 80% or more and 99% or less, more preferably 90% or more and 97% or less. The average value of the specular reflectance refers to the average value of the specular reflectance of visible light at each incident angle. By the average value of the specular reflectance being within the above range, the in-plane uniformity of the luminance of the surface light-emitting device in the present embodiment can be further improved.

[0147] Also, the specular reflectance of visible light incident at an incident angle of 0° (vertically incident) with respect to the surface of the second layer on the first layer side is preferably, for example, 80% or more and less than 100%, more preferably 90% or more and less than 100%, and particularly preferably 95% or more and less than 100%. By the specular reflectance being within the above range, the in-plane uniformity of the luminance of the surface light-emitting device of the present embodiment can be further improved.

[0148] Note that, in this specification, "visible light" means light with a wavelength of 380 nm or more and 780 nm or less. The regular reflectance can be measured using a variable-angle photometer or a variable-angle spectrocolorimeter. For measuring the regular reflectance, a variable-angle photometer (goniophotometer) GP-200 manufactured by Murakami Color Research Laboratory can be used.

[0149] The second layer has a transmittance angle dependence such that the transmittance increases as the absolute value of the incident angle of light with respect to the surface of the second layer on the first layer side increases. That is, the transmittance of light incident at a high incident angle with respect to the surface of the second layer on the first layer side is greater than the transmittance of light incident at a low incident angle with respect to the surface of the second layer on the first layer side. Among them, it is preferable that the transmittance of light incident at a high incident angle with respect to the surface of the second layer on the first layer side is large. Specifically, it is preferable that the total light transmittance of light incident at an incident angle of 70° or more and less than 90° with respect to the surface of the second layer on the first layer side is 30% or more, preferably 40% or more, and particularly preferably 50% or more. Note that it is preferable that the total light transmittance satisfies the above range at all incident angles of 70° or more and less than 90°. Also, when the absolute value of the incident angle is 70° or more and less than 90°, it is preferable that the total light transmittance satisfies the above range. By the total light transmittance being in the above range, the in-plane uniformity of the luminance of the surface light-emitting device of the present embodiment can be further improved.

[0150] Note that the total light transmittance of the second layer can be measured, for example, using a variable-angle photometer or a variable-angle spectrocolorimeter by a method conforming to JIS K7361-1:1997. For measuring the total light transmittance, an ultraviolet-visible-near-infrared spectrophotometer V-7200 manufactured by JASCO Corporation can be used.

[0151] The second layer is not particularly limited as long as it has the above-described incident angle dependencies of reflectance and transmittance, and various configurations having the above-described incident angle dependencies of reflectance and transmittance can be adopted. As the second layer, for example, a dielectric multilayer film, a reflective structure having a patterned first reflective film and a patterned second reflective film in order from the first layer side, where the openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are arranged apart from each other in the thickness direction, a reflective diffraction grating, and the like can be mentioned.

[0152] Hereinafter, the case where the second layer is a dielectric multilayer film, a reflective structure, or a reflective diffraction grating will be described.

[0153] a) Dielectric multilayer film When the second layer is a dielectric multilayer film, examples of the dielectric multilayer film include a multilayer film of an inorganic compound in which inorganic layers having different refractive indices are alternately laminated, and a multilayer film of a resin in which resin layers having different refractive indices are alternately laminated.

[0154] (Multilayer film of inorganic compound) When the dielectric multilayer film is a multilayer film of an inorganic compound in which inorganic layers having different refractive indices are alternately laminated, the multilayer film of the inorganic compound is not particularly limited as long as it has the above-described incident angle dependencies of reflectance and transmittance.

[0155] Among the inorganic layers having different refractive indices, the inorganic compound contained in the high refractive index inorganic layer having a high refractive index can have a refractive index of, for example, 1.7 or more, and may be 1.7 or more and 2.5 or less. Examples of such an inorganic compound include those mainly composed of titanium oxide, zirconium oxide, tantalum pentoxide, niobium pentoxide, lanthanum oxide, yttrium oxide, zinc oxide, zinc sulfide, indium oxide, and containing a small amount of titanium oxide, tin oxide, and cerium oxide.

[0156] Among the inorganic layers with different refractive indices, examples of the inorganic compound contained in the low refractive index inorganic layer with a low refractive index include those having a refractive index of 1.6 or less, and may be 1.2 or more and 1.6 or less. Examples of such inorganic compounds include silica, alumina, lanthanum fluoride, magnesium fluoride, sodium hexafluoroaluminate, and the like.

[0157] The number of stacked layers of the high refractive index inorganic layer and the low refractive index inorganic layer may be appropriately adjusted as long as the above-described incident angle dependencies of the reflectance and transmittance are obtained. Specifically, the total number of stacked layers of the high refractive index inorganic layer and the low refractive index inorganic layer can be 4 layers or more. Further, although the upper limit of the total number of stacked layers is not particularly limited, when the number of stacked layers increases, the number of processes increases. Therefore, for example, it can be 24 layers or less.

[0158] The thickness of the multilayer film of the inorganic compound may be appropriately adjusted as long as the above-described incident angle dependencies of the reflectance and transmittance are obtained. For example, it can be 0.5 μm or more and 10 μm or less. Examples of the method for forming the multilayer film of the inorganic compound include a method of alternately stacking a high refractive index inorganic layer and a low refractive index inorganic layer by a CVD method, a sputtering method, a vacuum evaporation method, a wet coating method, or the like.

[0159] (Multilayer film of resin) When the dielectric multilayer film is a multilayer film of resin in which resin layers with different refractive indices are alternately stacked, the multilayer film of resin is not particularly limited as long as it has the above-described incident angle dependencies of the reflectance and transmittance.

[0160] Examples of the resin constituting the resin layer include thermoplastic resins and thermosetting resins. Among them, thermoplastic resins are preferred because of their good moldability.

[0161] Various additives, such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducers, heat stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, and dopants for refractive index adjustment, may be added to the resin layer.

[0162] As the thermoplastic resin, polyolefin resin, alicyclic polyolefin resin, polyamide resin, aramid resin, polyester resin, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, fluororesin such as tetrafluoroethylene resin, trifluoroethylene resin, vinylidene chloride fluoride resin, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride resin, acrylic resin, methacrylic resin, polyacetal resin, polyglycolic acid resin, polylactic acid resin can be used. Examples of the above polyolefin resin include polyethylene, polypropylene, polystyrene, and polymethylpentene. Examples of the polyamide resin include nylon 6 and nylon 66. Further, examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polybutyl succinate, and polyethylene-2,6-naphthalate. In the present disclosure, among them, from the viewpoints of strength, heat resistance, and transparency, polyester is more preferable.

[0163] In this specification, the polyester refers to a homopolyester or a copolyester which is a polycondensate of a dicarboxylic acid component skeleton and a diol component skeleton. Here, examples of the homopolyester include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and polyethylene diphenylate. Among them, polyethylene terephthalate is preferable because it is inexpensive and can be used for a very wide range of applications.

[0164] In addition, in this specification, the copolyester is defined as a polycondensate composed of at least three or more components selected from components having a dicarboxylic acid skeleton and components having a diol skeleton listed below. Examples of the component having a dicarboxylic acid skeleton include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, 4,4-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid, and their ester derivatives. Examples of the component having a diol skeleton include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, diethylene glycol, polyalkylene glycol, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, isosorbide, 1,4-cyclohexanedimethanol, and spiroglycol.

[0165] Among the resin layers with different refractive indices, the difference in the in-plane average refractive index between the high refractive index resin layer with a high refractive index and the low refractive index resin layer with a low refractive index is preferably 0.03 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. If the difference in the in-plane average refractive index is too small, sufficient reflectivity may not be obtained.

[0166] In addition, the difference between the in-plane average refractive index and the refractive index in the thickness direction of the high refractive index resin layer is preferably 0.03 or more, and the difference between the in-plane average refractive index and the refractive index in the thickness direction of the low refractive index resin layer is preferably 0.03 or less. In this case, even when the incident angle increases, a decrease in the reflectivity of the reflection peak is less likely to occur.

[0167] As a preferable combination of the high refractive index resin used for the high refractive index resin layer and the low refractive index resin used for the low refractive index resin layer, first, it is preferable that the absolute value of the difference in the SP value between the high refractive index resin and the low refractive index resin is 1.0 or less. When the absolute value of the difference in the SP value is within the above range, delamination between layers is less likely to occur. In this case, it is more preferable that the high refractive index resin and the low refractive index resin contain the same basic skeleton. Here, the basic skeleton refers to the repeating unit that constitutes the resin. For example, when one resin is polyethylene terephthalate, ethylene terephthalate is the basic skeleton. Also, for example, when one resin is polyethylene, ethylene is the basic skeleton. When the high refractive index resin and the low refractive index resin are resins containing the same basic skeleton, delamination between layers is even less likely to occur.

[0168] As a preferable combination of the high refractive index resin used for the high refractive index resin layer and the low refractive index resin used for the low refractive index layer, second, it is preferable that the difference in the glass transition temperature between the high refractive index resin and the low refractive index resin is 20°C or less. If the difference in the glass transition temperature is too large, the thickness uniformity may be poor when forming the laminated film of the high refractive index resin layer and the low refractive index resin layer. Also, when molding the above laminated film, overstretching may occur.

[0169] Further, it is preferable that the high refractive index resin is polyethylene terephthalate or polyethylene naphthalate, and the low refractive index resin is a polyester containing spiroglycol. Here, the polyester containing spiroglycol refers to a copolyester copolymerized with spiroglycol, or a homopolyester, or a polyester blended with them. The polyester containing spiroglycol is preferable because the difference in the glass transition temperature from polyethylene terephthalate or polyethylene naphthalate is small, so it is less likely to be overstretched during molding and is also less likely to cause delamination between layers.

[0170] More preferably, the high refractive index resin is polyethylene terephthalate or polyethylene naphthalate, and the low refractive index resin is preferably a polyester containing spiroglycol and cyclohexanedicarboxylic acid. When the low refractive index resin is a polyester containing spiroglycol and cyclohexanedicarboxylic acid, the difference in in-plane refractive index from polyethylene terephthalate or polyethylene naphthalate becomes large, so that a high reflectance is easily obtained. In addition, the difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate is small, and the adhesiveness is excellent. Therefore, it is not easily overstretched during molding and is also less likely to cause delamination between layers.

[0171] Also, it is preferable that the high refractive index resin is polyethylene terephthalate or polyethylene naphthalate, and the low refractive index resin is a polyester containing cyclohexanedimethanol. Here, the polyester containing cyclohexanedimethanol refers to a copolyester obtained by copolymerizing cyclohexanedimethanol, or a homopolyester, or a polyester blended therefrom. The polyester containing cyclohexanedimethanol is preferable because the difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate is small, so that it is not easily overstretched during molding and is also less likely to cause delamination between layers. In this case, the low refractive index resin is more preferably an ethylene terephthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is 15 mol% or more and 60 mol% or less.

[0172] By doing so, while having high reflection performance, particularly, the change in optical properties due to heating or over time is small, and delamination between layers is less likely to occur. The ethylene terephthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is within the above range adheres very strongly to polyethylene terephthalate. In addition, the cyclohexanedimethanol group has a cis or trans geometric isomer and also has an is or boat conformational isomer. Therefore, even when co-stretched with polyethylene terephthalate, it is difficult to undergo orientation crystallization, has a high reflectance, the change in optical properties due to thermal history is even less, and breakage during film formation is less likely to occur.

[0173] In the above multilayer film of resin, it is sufficient that there is a portion having a structure in which a high refractive index resin layer and a low refractive index resin layer are alternately laminated in the thickness direction. That is, it is preferable that the arrangement sequence of the high refractive index resin layer and the low refractive index resin layer in the thickness direction is not in a random state, and the arrangement sequence of the resin layers other than the high refractive index resin layer and the low refractive index resin layer is not particularly limited. Further, when the above multilayer film of resin has a high refractive index resin layer, a low refractive index resin layer, and other resin layers, as the permutation of their arrangement, when the high refractive index resin layer is A, the low refractive index resin layer is B, and other resin layers are C, A(BCA) n , A(BCBA) n , A(BABCBA) n etc., it is more preferable that the layers are laminated in a regular permutation. Here, n is the number of repeating units. For example, in A(BCA) n , when n = 3, it represents that the layers are laminated in the order of ABCABCABCA in the thickness direction.

[0174] Further, the number of laminations of the high refractive index resin layer and the low refractive index resin layer may be appropriately adjusted as long as the above-described reflectance and transmittance angle dependencies are obtained. Specifically, the high refractive index resin layer and the low refractive index resin layer can be alternately laminated 30 layers or more each, and each can be laminated 200 layers or more. Further, the total number of laminations of the high refractive index resin layer and the low refractive index resin layer can be, for example, 600 layers or more. If the number of laminations is too small, sufficient reflectance may not be obtained. Also, by having the number of laminations within the above range, a desired reflectance can be easily obtained. Further, although the upper limit of the above total number of laminations is not particularly limited, considering the increase in the size of the apparatus and the decrease in lamination accuracy due to too many layers, it can be, for example, 1500 layers or less.

[0175] Furthermore, it is preferable that the multi-layer film of the above resin has a surface layer containing polyethylene terephthalate or polyethylene naphthalate with a thickness of 3 μm or more on at least one side, and among them, it is preferable to have the above surface layer on both sides. Moreover, it is more preferable that the thickness of the surface layer is 5 μm or more. By having the above surface layer, the surface of the multi-layer film of the above resin can be protected.

[0176] Examples of the method for manufacturing the multi-layer film of the above resin include the co-extrusion method. Specifically, reference can be made to the method for manufacturing a laminated film described in JP-A-2008-200861.

[0177] Moreover, as the multi-layer film of the above resin, a commercially available laminated film can be used. Specifically, examples include Picassus (registered trademark) manufactured by Toray Industries, Inc., and ESR manufactured by 3M.

[0178] b) Reflective structure The reflective structure has a patterned first reflective film and a patterned second reflective film in order from the first layer side, and the openings of the first reflective film and the openings of the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are arranged apart in the thickness direction.

[0179] The reflective structure has two modes. The first mode of the reflective structure includes a transparent substrate, a patterned first reflective film disposed on one surface of the transparent substrate, and a patterned second reflective film disposed on the other surface of the transparent substrate. The openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are spaced apart in the thickness direction. Further, the second mode of the reflective structure includes a transparent substrate, a patterned convex portion having light transmissivity disposed on one surface of the transparent substrate, a patterned first reflective film disposed on the surface side opposite to the surface of the convex portion on the transparent substrate side, and a patterned second reflective film disposed in the opening of the convex portion on one surface of the transparent substrate. The openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are spaced apart in the thickness direction. Hereinafter, it will be described separately for each mode.

[0180] (The first mode of the reflective structure) The first mode of the reflective structure in the present embodiment includes a transparent substrate, a patterned first reflective film disposed on one surface of the transparent substrate, and a patterned second reflective film disposed on the other surface of the transparent substrate. The openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are spaced apart in the thickness direction. In the case of the reflective structure of this mode, in the second diffusing member, the first layer is disposed on the surface side of the first reflective film side of the reflective structure.

[0181] Figs. 7(a) and 7(b) are a schematic plan view and a cross-sectional view showing an example of the reflection structure of this aspect. Fig. 7(a) is a plan view seen from the surface on the first reflection film side of the reflection structure, and Fig. 7(b) is a cross-sectional view taken along line A-A in Fig. 7(a). As shown in Figs. 7(a) and 7(b), the reflection structure 20 has a transparent substrate 21, a pattern-shaped first reflection film 22 disposed on one surface of the transparent substrate 21, and a second reflection film 24 disposed on the other surface of the transparent substrate 21. The opening 23 of the first reflection film 22 and the opening 25 of the second reflection film 24 are positioned so as not to overlap in plan view. Further, the first reflection film 22 and the second reflection film 24 are disposed on both surfaces of the transparent substrate 21, respectively, and are spaced apart in the thickness direction. In Fig. 7(a), the opening of the second reflection film is indicated by a dashed line. Fig. 7(c) is a schematic cross-sectional view showing an example of a surface light-emitting device including a diffusion member having the reflection structure of this aspect.

[0182] In such a reflection structure, since the pattern-shaped first reflection film and the second reflection film are laminated and the openings of the first reflection film and the second reflection film are positioned so as not to overlap in plan view, when a diffusion member having the reflection structure of this aspect is used in a surface light-emitting device, for example, as shown in Fig. 7(c), at least one of the first reflection film 22 and the second reflection film 24 will necessarily exist directly above the LED element 3. Therefore, for example, as shown in Fig. 7(b), the light L11 incident at a low incident angle with respect to the surface on the first reflection film 22 side of the reflection structure 20, that is, the surface 13A on the side where the first layer (not shown) of the reflection structure 20 (second layer) is disposed, can be reflected by the first reflection film 22 and the second reflection film 24.

[0183] Further, since the openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are arranged apart from each other in the thickness direction, light L12 and L13 that are incident on the surface of the reflective structure 20 on the side of the first reflective film 22, that is, the surface 13A on the side where the first layer (not shown) of the reflective structure 20 (second layer) is arranged, at a high incident angle can be emitted from the opening 23 of the first reflective film 22 and the opening 25 of the second reflective film 24. As a result, a part of the light emitted from the LED element and then emitted from the surface on the second layer side of the diffusion member can be emitted from a position away from the LED element in the in-plane direction instead of directly above the LED element. Therefore, the in-plane uniformity of the luminance can be improved.

[0184] As the first reflective film and the second reflective film, general reflective films can be used, such as metal films and dielectric multilayer films. As the material of the metal film, metal materials used for general reflective films can be adopted, such as aluminum, gold, silver, and their alloys. Further, as the dielectric multilayer film, those used for general reflective films can be adopted, such as multilayer films of inorganic compounds such as a multilayer film in which zirconium oxide and silicon oxide are alternately laminated. The materials included in the first reflective film and the second reflective film may be the same or different from each other.

[0185] The pitch of the openings of the first reflective film and the second reflective film only needs to obtain the above-described incident angle dependence of the reflectance and transmittance, and is appropriately set according to the light distribution characteristics, size, pitch, and shape of the LED elements in the surface light-emitting device in which the diffusion member of this aspect is used, and the distance between the LED substrate and the diffusion member, etc. The pitches of the openings of the first reflective film and the second reflective film may be the same or different from each other.

[0186] The pitch of the opening of the first reflective film may be larger than the size of the LED element, for example. Specifically, the pitch of the opening of the first reflective film can be set to be 0.1 mm or more and 20 mm or less.

[0187] Also, the pitch of the openings of the second reflective film is not particularly limited as long as luminance unevenness can be suppressed. Among these, it is preferably equal to or less than the pitch of the openings of the first reflective film, and more preferably smaller than the pitch of the openings of the first reflective film. Specifically, the pitch of the openings of the second reflective film can be set to be 0.1 mm or more and 2 mm or less. By making the pitch of the openings of the second reflective film fine as described above, it is possible to make it difficult to visually recognize the pattern between the portion of the second reflective film and the portion of the opening of the second reflective film, enabling surface light emission without unevenness.

[0188] Note that the pitch of the openings of the first reflective film refers to the distance P1 between the centers of adjacent openings 23 of the first reflective film 22, as shown in, for example, FIG. 7(a). Also, the pitch of the openings of the second reflective film refers to the distance P2 between the centers of adjacent openings 25 of the second reflective film 24, as shown in, for example, FIG. 7(a).

[0189] The size of the openings of the first and second reflective films only needs to provide the above-described incident angle dependence of the reflectance and transmittance, and is appropriately set according to the light distribution characteristics, size, pitch, and shape of the LED element, and the distance between the LED substrate and the diffusion member. The sizes of the openings of the first and second reflective films may be the same or different from each other.

[0190] Specifically, when the shape of the opening of the first reflective film is rectangular, the length of the opening of the first reflective film can be set to be 0.1 mm or more and 5 mm or less.

[0191] In addition, the size of the opening of the second reflective film is not particularly limited as long as it can suppress luminance unevenness. Among these, it is preferably equal to or smaller than the size of the opening of the first reflective film, and more preferably smaller than the size of the opening of the first reflective film. Specifically, when the shape of the opening of the second reflective film is rectangular, the length of the opening of the second reflective film can be set to be 0.05 mm or more and 2 mm or less. By making the size of the opening of the second reflective film fine as described above, it is possible to make it difficult to visually recognize the pattern between the portion of the second reflective film and the portion of the opening of the second reflective film, and surface light emission without unevenness becomes possible.

[0192] Note that the size of the opening of the first reflective film, for example, when the shape of the opening of the first reflective film is rectangular, refers to the length x1 of the opening 23 of the first reflective film 22 as shown in FIG. 7(a). Also, the size of the opening of the second reflective film, for example, refers to the length x2 of the opening 25 of the second reflective film 24 as shown in FIG. 7(a).

[0193] The shapes of the openings of the first reflective film and the second reflective film can be any shape such as rectangular or circular. The thicknesses of the first reflective film and the second reflective film only need to obtain the above-described reflectance and transmittance angle dependencies, and are adjusted as appropriate. Specifically, the thicknesses of the first reflective film and the second reflective film can be set to be 0.05 μm or more and 100 μm or less.

[0194] The first reflective film and the second reflective film may be formed on the surface of a transparent substrate, or may be sheet-like reflective films. The method for forming the first reflective film and the second reflective film is not particularly limited as long as it can form a reflective film in a pattern on the surface of a transparent substrate, and examples include a sputtering method and a vacuum evaporation method. Also, when the first reflective film and the second reflective film are sheet-like reflective films, examples of the method for forming the opening include a method of forming a plurality of through-holes by punching or the like. In this case, as a method for laminating the transparent substrate and the sheet-like reflective film, for example, a method of bonding the sheet-like reflective film to the transparent substrate via an adhesive layer or an adhesive layer can be used.

[0195] The transparent substrate in the reflection structure of this aspect is a member that supports the above-described first reflection film, second reflection film, etc., and is also a member for disposing the first reflection film and the second reflection film apart from each other in the thickness direction.

[0196] The transparent substrate has light transmissivity. As for the light transmissivity of the transparent substrate, it is preferable that the total light transmittance of the transparent substrate is, for example, 80% or more, and particularly preferably 90% or more. Note that the total light transmittance of the transparent substrate can be measured by a method conforming to JIS K7361-1:1997.

[0197] As the material constituting the transparent substrate, any material having the above-described total light transmittance may be used, and examples thereof include resins such as polyethylene terephthalate, polycarbonate, acrylic, cycloolefin, polyester, polystyrene, and acrylic styrene, and glasses such as quartz glass, Pyrex (registered trademark), and synthetic quartz.

[0198] As the thickness of the transparent substrate, as shown in FIG. 7(b), for example, light L12 incident at a high incident angle with respect to the surface on the first reflection film 22 side of the reflection structure 20, that is, the surface 13A on the side where the first layer (not shown) of the reflection structure 20 (second layer) is disposed, is preferably a thickness such that it can be emitted from the opening 23 of the first reflection film 22 and the opening 25 of the second reflection film 24, and is appropriately set according to the pitch and size of the openings of the first reflection film and the second reflection film, the thickness of the first reflection film and the second reflection film, and the like. Specifically, the thickness of the transparent substrate can be 0.05 mm or more and 2 mm or less, and particularly preferably 0.1 mm or more and 0.5 mm or less.

[0199] (Second aspect of the reflection structure) The second aspect of the reflective structure includes a transparent substrate, a pattern-shaped convex portion having light transmissibility disposed on one surface of the transparent substrate, a pattern-shaped first reflective film disposed on the surface opposite to the surface of the convex portion on the transparent substrate side, and a pattern-shaped second reflective film disposed in the opening of the convex portion on one surface of the transparent substrate, wherein the openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view, and the first reflective film and the second reflective film are spaced apart in the thickness direction. In the case of the reflective structure of this aspect, in the second diffusion member, a first layer is disposed on the surface side of the reflective structure on the first reflective film side.

[0200] Figs. 8(a) and (b) are a schematic plan view and a cross-sectional view showing an example of the second aspect of the reflective structure in the present embodiment. Fig. 8(a) is a plan view seen from the surface of the reflective structure on the first reflective film side, and Fig. 8(b) is a cross-sectional view taken along line A-A in Fig. 8(a). As shown in Figs. 8(a) and (b), the reflective structure 20 includes a transparent substrate 21, a pattern-shaped convex portion 26 having light transmissibility disposed on one surface of the transparent substrate 21, a pattern-shaped first reflective film 22 disposed on the surface opposite to the surface of the convex portion 26 on the transparent substrate 21 side, and a pattern-shaped second reflective film 24 disposed in the opening of the convex portion 26 on one surface of the transparent substrate 21. The openings 23 of the first reflective film 22 and the openings 25 of the second reflective film 24 are positioned so as not to overlap in plan view. Also, the first reflective film 22 and the second reflective film 24 are separated by the convex portion 26 and are spaced apart in the thickness direction.

[0201] In such a reflective structure, a patterned first reflective film and a second reflective film are laminated, and the openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view. Therefore, in a surface light-emitting device (particularly, an LED backlight) using a diffusion member having the reflective structure of this embodiment, at least one of the first reflective film and the second reflective film will necessarily exist directly above the LED element. Thus, similar to the first aspect of the above-described reflective structure, for example, as shown in FIG. 8(b), light L11 incident at a low incident angle with respect to the surface on the first reflective film 22 side of the reflective structure 20, that is, the surface 13A on the side where the first layer (not shown) of the reflective structure 20 (second layer) is disposed, can be reflected by the first reflective film 22 and the second reflective film 24.

[0202] Also, since the openings of the first reflective film and the second reflective film are positioned so as not to overlap in plan view and the first reflective film and the second reflective film are disposed apart from each other in the thickness direction, light L12 incident at a high incident angle with respect to the surface on the first reflective film 22 side of the reflective structure 20, that is, the surface 13A on the side where the first layer (not shown) of the reflective structure 20 (second layer) is disposed, can be emitted from the side surface of the convex portion 26 and the opening 25 of the second reflective film 24. As a result, a part of the light emitted from the LED element and then emitted from the surface on the second layer side of the diffusion member can be emitted from a position away from the LED element in the in-plane direction rather than directly above the LED element. Therefore, the in-plane uniformity of the luminance can be improved. Further, in this embodiment, since there are convex portions, self-alignment of the openings of the first reflective film and the second reflective film is possible, and the manufacturing cost can be reduced.

[0203] Note that regarding the materials of the first reflective film and the second reflective film, the pitch of the openings of the first reflective film and the second reflective film, the size of the openings of the first reflective film and the second reflective film, the shape of the openings of the first reflective film and the second reflective film, the thickness of the first reflective film and the second reflective film, and the method of forming the first reflective film and the second reflective film, etc., they can be the same as those in the above-described first aspect. Also, regarding the transparent base material, it can be the same as that in the above-described first aspect.

[0204] The convex portion in the reflection structure of this aspect is a member for disposing the above-described first reflection film and second reflection film apart from each other in the thickness direction. The convex portion has light transmissivity. As for the light transmissivity of the convex portion, it is preferable that the total light transmittance of the convex portion is, for example, 80% or more, and particularly preferably 90% or more. The total light transmittance of the convex portion can be measured by a method conforming to JIS K7361-1:1997.

[0205] As the material constituting the convex portion, any material that can form a pattern-shaped convex portion and has the above-described total light transmittance may be used, and examples thereof include thermosetting resins and electron beam curable resins.

[0206] As for the height of the convex portion, as shown in, for example, FIG. 8(b), with respect to the surface on the first reflection film 22 side of the reflection structure 20, that is, the surface 13A on the side where the first layer (not shown) of the reflection structure 20 (second layer) is disposed, it is preferable that the height is such that the light L12 incident at a high incident angle can be emitted from the side surface of the convex portion 26 and the opening 25 of the second reflection film 24, and it is appropriately set according to the pitch and size of the openings of the first reflection film and the second reflection film, the thickness of the first reflection film and the second reflection film, etc. Specifically, the height of the convex portion can be 0.05 mm or more and 2 mm or less, and particularly preferably 0.1 mm or more and 0.5 mm or less.

[0207] Regarding the pitch, size, and planar shape of the convex portion, they can be the same as those of the opening of the second reflection film. The surface of the convex portion may be, for example, a smooth surface as shown in FIG. 8(b) or a rough surface as shown in FIG. 9(a). When the surface of the convex portion is a rough surface, light diffusibility can be imparted to the convex portion.

[0208] Also, as the shape of the surface of the convex portion, it may be a flat surface as shown in, for example, FIG. 8(b) or a curved surface as shown in FIG. 9(b). When the surface of the convex portion is a curved surface, light diffusibility can be imparted to the convex portion.

[0209] The method for forming the convex portions is not particularly limited as long as it can form pattern-shaped convex portions, and examples include printing methods, resin shaping using a mold, and the like.

[0210] c) Reflective diffraction grating When the second layer is a reflective diffraction grating, the reflective diffraction grating is not particularly limited as long as it has the above-described incident angle dependence of reflectance and transmittance.

[0211] Regarding the pitch of the reflective diffraction grating and the like, it is sufficient that the above-described incident angle dependence of reflectance and transmittance can be obtained, and it is adjusted as appropriate. Specifically, when the wavelength output from the LED element is a single color such as red, green, or blue, by setting the pitch according to each wavelength, it is possible to effectively reflect the light of the LED element.

[0212] As the material constituting the reflective diffraction grating, any material can be used as long as it can obtain a reflective diffraction grating having the above-described incident angle dependence of reflectance and transmittance, and generally, those commonly used for reflective diffraction gratings can be adopted. Also, as the method for forming the reflective diffraction grating, it can be the same as the general method for forming a reflective diffraction grating.

[0213] 4.3 Third diffusing member The third diffusing member is a resin plate having a light-transmissive resin such as polystyrene (PS) or polycarbonate, which has a large number of voids inside or has irregularities on the surface, and generally, those commonly used in the display device field can be used.

[0214] 5. Wavelength conversion member In the surface light-emitting device of the present embodiment, for example, the wavelength conversion member may be disposed on the surface side opposite to the LED substrate side of the diffusing member, or the wavelength conversion member may be disposed on the LED substrate side of the diffusing member.

[0215] The wavelength conversion member is a member containing a phosphor that absorbs light emitted from an LED element and emits excitation light. The wavelength conversion member has a function of generating white light when combined with an LED substrate.

[0216] The wavelength conversion member usually has at least a wavelength conversion layer containing a phosphor and a resin. The wavelength conversion member may be, for example, a single wavelength conversion layer, or may be a laminate having a wavelength conversion layer on one surface side of a transparent substrate. Among them, from the viewpoint of thinning, a single wavelength conversion layer is preferable. More preferably, a sheet-like wavelength conversion member is used.

[0217] The above phosphor can be appropriately selected according to the emission color from the LED element, and examples thereof include a blue phosphor, a green phosphor, a red phosphor, and a yellow phosphor. For example, when the LED element is a blue LED element, as the phosphor, a green phosphor and a red phosphor may be used, or a yellow phosphor may be used. Further, for example, when the LED element is an ultraviolet LED element, as the phosphor, a red phosphor, a green phosphor, and a blue phosphor can be used.

[0218] As the phosphor, for example, a phosphor used for the wavelength conversion member of an LED backlight can be adopted. Also, quantum dots can be used as the phosphor. The content of the phosphor in the wavelength conversion member layer is not particularly limited as long as it can generate desired white light, and can be the same as the content of the phosphor in the wavelength conversion member of a general LED backlight.

[0219] Also, the resin contained in the wavelength conversion member is not particularly limited as long as it can disperse the phosphor. The above resin can be the same as the resin used for the wavelength conversion member of a general LED backlight, and examples thereof include thermosetting resins such as silicone-based resins and epoxy-based resins.

[0220] The thickness of the wavelength conversion member is not particularly limited as long as it can generate desired white light when used in the surface light emitting device. For example, it can be set to 10 μm or more and 1000 μm or less.

[0221] 6. Other optical members In the surface light emitting device of the present embodiment, for example, an optical member may be further disposed on the side opposite to the surface of the diffusion member on the LED substrate side. Examples of the optical member include a prism sheet and a reflective polarizing sheet.

[0222] (1) Prism sheet The prism sheet in the present embodiment has a function of condensing the incident light and intensively improving the luminance in the front direction. The prism sheet is, for example, a sheet in which a prism pattern containing an acrylic resin is disposed on one surface side of a transparent resin substrate. As the prism sheet, for example, the brightness enhancement film BEF series manufactured by 3M can be used.

[0223] (2) Reflective polarizing sheet The reflective polarizing sheet in the present embodiment has a function of transmitting only the first linearly polarized light component (for example, P-polarized light) and reflecting the second linearly polarized light component (for example, S-polarized light) orthogonal to the first linearly polarized light component without absorption. The second linearly polarized light component reflected by the reflective polarizing sheet is reflected again and enters the reflective polarizing sheet again in a state where the polarization is canceled (a state including both the first linearly polarized light component and the second linearly polarized light component). Therefore, the reflective polarizing sheet transmits the first linearly polarized light component among the light incident again, and the second linearly polarized light component orthogonal to the first linearly polarized light component is reflected again.

[0224] By repeating the above process, light that is 70% or more and 80% or less of the light emitted from the second layer is emitted as light that has become the first linearly polarized component. Therefore, when the surface light-emitting device of the present embodiment 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 surface light-emitting device can be used for image formation on the display panel. Therefore, even when the light energy input from the LED element is the same, higher-brightness image formation is possible compared to the case where the reflective polarizing sheet is not arranged.

[0225] Examples of the reflective polarizing sheet include the brightness enhancement film DBEF series manufactured by 3M. Also, as the reflective polarizing sheet, for example, the high-brightness polarizing sheet WRPS manufactured by Shinwha Intertek or a wire grid polarizer can also be used.

[0226] 7. Applications The application of the surface light-emitting device in the present embodiment is not particularly limited, but it can be suitably used in a display device. It can also be used in a lighting device or the like.

[0227] II. Second Embodiment Next, a second embodiment of the surface light-emitting device of the present embodiment will be described. FIG. 10 is a schematic cross-sectional view showing an example of the surface light-emitting device of the present embodiment. As illustrated in FIG. 10, the surface light-emitting device 1 of the present embodiment includes a support substrate 2, an LED substrate 4 having an LED element 3 disposed on one surface side of the support substrate 2, a sealing member 5 disposed on the surface side of the LED substrate 4 on the LED element 3 side for sealing the LED element 3, a diffusion member 6 disposed on the surface side of the sealing member 5 opposite to the LED substrate 4 side, and a warpage prevention layer 7 disposed on the surface of the LED substrate 4 opposite to the sealing member 5. The sealing member 5 in the present embodiment has a haze value of 4% or more and a thickness greater than that of the LED element 3, and is characterized in that the linear expansion coefficient of the material constituting the warpage prevention layer 7 is equal to or greater than the linear expansion coefficient of the material constituting the sealing member 5.

[0228] In the surface light-emitting device of this embodiment, when means such as thermocompression bonding is used to bond the sealing member and the LED substrate, warping may occur due to the difference in the linear expansion coefficients of the LED substrate and the sealing member during subsequent cooling. Also, when the surface light-emitting device is used at extremely high or low temperatures, warping may occur due to the difference in the linear expansion coefficients of the LED substrate and the sealing member described above.

[0229] This embodiment, like the first embodiment, is made to solve such problems. By arranging the anti-warping layer on the surface of the LED substrate opposite to the sealing member and making the linear expansion coefficient of the material constituting the anti-warping layer equal to or greater than the linear expansion coefficient of the material constituting the sealing member, the problem of the occurrence of warping described above is solved.

[0230] Hereinafter, the surface light-emitting device of this embodiment will be described. Note that this embodiment is the same as the first embodiment except that the arrangement position of the anti-warping layer and the material constituting the anti-warping layer are different. Therefore, the description of the configuration other than the anti-warping layer will be omitted.

[0231] 1. Anti-warping layer The anti-warping layer in this embodiment is a layer arranged on the surface of the LED substrate opposite to the sealing member. In this embodiment, the linear expansion coefficient of the material constituting the anti-warping layer is equal to or greater than the linear expansion coefficient of the material constituting the sealing member. The reason why warping can be prevented by making the linear expansion coefficient of the material constituting the anti-warping layer equal to or greater than the linear expansion coefficient of the material constituting the sealing member is as follows.

[0232] That is, when manufacturing a surface light-emitting device, it has a step of thermocompression bonding a sealing member and an LED substrate. However, when cooling after thermocompression bonding, the sealing member behaves to shrink more than the LED substrate. At this time, since an anti-warping layer having a linear expansion coefficient equal to or greater than that of the sealing member is disposed on the surface of the LED substrate opposite to the sealing member, the anti-warping layer also shrinks with respect to the shrinkage on the sealing member side, so that the degree of warping of the LED substrate can be reduced. As a result, the occurrence of warping can be suppressed.

[0233] a) Linear expansion coefficient In the present embodiment, the larger the difference between the linear expansion coefficient of the material constituting the anti-warping layer and the linear expansion coefficient of the material constituting the sealing member, the more preferable. However, considering the material used for the sealing member, it is limited to a certain extent. Therefore, the difference in the linear expansion coefficient is usually 400×10 -6 / °C or less, and they may be equivalent.

[0234] Note that the equivalent in the present embodiment means the case within the range of 0.8 or more and 1.2 or less, particularly within the range of 0.95 or more and 1.0 or less, when the linear expansion coefficient of the material constituting the sealing member is set to 1.

[0235] As the linear expansion coefficient of the material constituting such an anti-warping layer, it is usually within the range of 300×10 -6 / °C or more and 500×10 -6 / °C or less, particularly within the range of 350×10 -6 / °C or more and 450×10 -6 / °C or less is used. As the method for measuring the linear expansion coefficient in the present embodiment, it is performed by the same method as the method described in the first embodiment.

[0236] b) Thickness In this embodiment, the thickness of the warpage prevention layer is preferably 25% or more of the thickness of the above-mentioned sealing member, particularly preferably 35% or more, and most preferably 45% or more. The upper limit is set to 50% or less from the concept of downsizing the device. Within the above range, it is possible to obtain a warpage prevention effect and it does not hinder the downsizing of the device.

[0237] c) Elastic modulus The elastic modulus of the warpage prevention layer used in this embodiment is preferably equal to or higher than the elastic modulus of the above-mentioned sealing member. Specifically, when the elastic modulus of the sealing member is set to 1, it is preferably 0.8 or more, particularly preferably 0.9 or more. Usually, it is 2.5 or less.

[0238] Also, as an actual value, it is preferably 35 MPa or more, particularly preferably 40 MPa or more, and most preferably 85 MPa or more. This is because if the elastic modulus is lower than the above range, the warpage prevention effect will be reduced. Considering the materials commonly used, it is 300 MPa or less.

[0239] The elastic modulus is measured by the tensile measurement shown below. · Measuring device: Universal material testing machine 5565 manufactured by Instron · Load cell: 1 kN · Sample width: 10 mm · Distance between chucks: 50 mm · Speed: 300 mm / min

[0240] d) Material The material constituting the warpage prevention layer used in this embodiment is not particularly limited as long as it has the above characteristics, but among them, the same materials as those that can be used as the sealing member can be used. Preferred materials are preferably olefin resins. Among olefin resins, polyethylene resins, polypropylene resins, and ionomer resins are preferred.

[0241] (2) Others In this embodiment, the warpage prevention layer is preferably in close contact with the LED substrate, because the warpage prevention effect can be further improved. Since the specific degree of adhesion is the same as that in the first embodiment, the description thereof is omitted here. As a method of bringing the warpage prevention layer into close contact with the LED substrate, methods such as disposing an adhesive layer between the two and bonding them, or thermocompression bonding to melt and bond the warpage prevention layer can be mentioned.

[0242] III. Third Embodiment The surface light-emitting device of this embodiment uses a foam prevention layer instead of the warpage prevention layer in the first embodiment, and has two modes: a mode in which the elastic modulus of the foam prevention layer is 500 MPa or more, and a mode in which the melting point of the foam prevention layer is 140 °C or more.

[0243] In a conventional surface light-emitting device, for example, when the surface light-emitting device is used at an extremely high temperature for a long time, there is also a problem that bubbles are generated between the LED substrate and the sealing member. This is caused by gas generated from the LED substrate due to heating, or air existing between the LED substrate and a reflective layer or the like oozing out along the interface due to air entrapment or the like when a reflective layer or the like is provided on the LED substrate.

[0244] The LED element sealed in the sealing member has its light-emitting surface directly joined to the sealing member, and the refractive index difference at the interface is small, so the light extraction efficiency is improved compared to an unsealed LED element. However, if such bubbles exist, the improvement in light extraction efficiency as described above cannot be obtained, and as a result, a problem occurs in that the light-emitting efficiency of the surface light-emitting device is reduced.

[0245] In this embodiment, by providing a foam prevention layer having the above-described characteristics, it is possible to suppress the deformation in which the surface shape of the sealing member that is assumed to occur during foaming becomes convex portions. Accordingly, even when gas is generated from, for example, an LED substrate, the presence of the anti-foaming layer causes pressure to be applied to the sealing member, thereby preventing the generated gas from forming bubbles.

[0246] The elastic modulus of the anti-foaming layer used in this embodiment may be 500 MPa or more, preferably 1000 MPa or more, and particularly preferably 4000 MPa or more.

[0247] This is because when the elastic modulus is lower than the above range, the effect of suppressing bubble generation is reduced. In consideration of commonly used materials, it is 5500 MPa or less.

[0248] The melting point of the anti-foaming layer in this embodiment may be 140°C or more, preferably 260°C or more. In consideration of commonly used materials and the like, the upper limit is 350°C or less.

[0249] In this embodiment, it is more preferable to use an anti-foaming layer having the above-described elastic modulus and the above-described melting point. The measuring methods for the elastic modulus and the melting point are the same as those described in the first embodiment above.

[0250] Unlike the warpage prevention layer, the anti-foaming layer used in this embodiment does not necessarily require the linear expansion coefficient to be within a predetermined range. However, since the anti-foaming layer having the same linear expansion coefficient as that of the warpage prevention layer in the first embodiment can obtain the same warpage prevention effect as that of the first embodiment, it can be made preferable.

[0251] Other aspects of the surface light-emitting device of this embodiment are the same as those obtained by reading the warpage prevention layer of the surface light-emitting device of the first embodiment as the anti-foaming layer, and thus the description here is omitted.

[0252] B. Display device The present disclosure provides a display device including a display panel and the surface light-emitting device disposed on the back surface of the display panel as described above.

[0253] FIG. 11 is a schematic diagram showing an example of the display device of the present disclosure. As illustrated in FIG. 11, the display device 100 includes a display panel 31 and the surface light-emitting device 1 in the present disclosure disposed on the back surface of the display panel 31.

[0254] According to the present disclosure, by having the above-described surface light-emitting device, it is possible to achieve thinning while improving the in-plane uniformity of luminance. Therefore, a high-quality display device can be obtained.

[0255] 1. Surface light-emitting device The surface light-emitting device in the present disclosure is the same as that described in the section of "A. Surface light-emitting device" above.

[0256] 2. Display panel The display panel in the present disclosure is not particularly limited, and for example, a liquid crystal panel can be mentioned.

[0257] C. Method for manufacturing a surface light-emitting device In the present disclosure, a method for manufacturing the surface light-emitting device of the first embodiment is provided. In the present disclosure, it can be divided into two embodiments.

[0258] I. First embodiment The method for manufacturing the surface light-emitting device of this embodiment is the manufacturing method described in the first embodiment of the surface light-emitting device above, and is characterized by including a step of preparing a laminate in which the anti-warpage layer, the sealing member, and the LED substrate on which the LED elements are disposed on the sealing member side are arranged in this order, and thermocompression bonding the laminate. In this embodiment, first, a laminate in which the LED substrate, the sealing member, and the anti-warpage layer are arranged in this order is prepared.

[0259] Here, since the LED substrate, the sealing member, and the anti-warping layer are the same as those described in the first embodiment of the surface light-emitting device, the description here is omitted. Next, a step of thermocompression bonding the laminate is performed.

[0260] As the thermocompression bonding method in this embodiment, as long as it is a method capable of thermocompression bonding these, it is not particularly limited, but a vacuum lamination method, a vacuum pack method, a thermal lamination method, etc. can be used.

[0261] In this embodiment, a diffusion member is arranged on the anti-warping layer side of the pressure-bonded laminate, and the surface light-emitting device can be manufactured by bonding using an adhesive or the like.

[0262] II. Second Embodiment The manufacturing method of the surface light-emitting device of this embodiment is the manufacturing method described in the first embodiment of the surface light-emitting device, and includes a step of thermocompression bonding a first laminate in which the anti-warping layer and the sealing member are laminated, and a step of thermocompression bonding a second laminate in which the LED substrate arranged such that the LED element faces the sealing member side is arranged on the surface of the thermocompression-bonded first laminate on the sealing member side.

[0263] In this embodiment, first, a first laminate in which the anti-warping layer and the sealing member are laminated is prepared. Next, the first laminate is thermocompression bonded by the same method as in the first embodiment.

[0264] Next, a second laminate in which the LED substrate is arranged on the surface of the thermocompression-bonded first laminate on the sealing member side is thermocompression bonded by the same method as in the first embodiment. In this embodiment, a diffusion member is arranged on the anti-warping layer side of the pressure-bonded second laminate, and the surface light-emitting device can be manufactured by bonding using an adhesive or the like.

[0265] D. Sealing Member Sheet for Surface Light-Emitting Device The sealing member sheet for the surface light-emitting device of the present disclosure has the following two modes.

[0266] 1. First Aspect The encapsulation member sheet for a surface light-emitting device of this aspect is formed by laminating an encapsulation member for encapsulating an LED element and a warpage prevention layer disposed on one surface side of the encapsulation member, and is an encapsulation member sheet for a surface light-emitting device used in a surface light-emitting device, wherein the linear expansion coefficient of the material constituting the warpage prevention layer is -15×10 -6 / °C or more and 10×10 -6 / °C or less.

[0267] The surface light-emitting device includes a support substrate, an LED substrate having the LED element disposed on one surface side of the support substrate, the encapsulation member disposed on the LED element side of the LED substrate, the warpage prevention layer, and a diffusion prevention member, which are laminated in this order.

[0268] The warpage prevention layer used in this aspect is the same as that described in the first embodiment of the surface light-emitting device. Also, since the LED substrate, the encapsulation member, and the reflection prevention member are the same as those described in the surface light-emitting device, the description here is omitted.

[0269] 2. Second Aspect The encapsulation member sheet for a surface light-emitting device of this aspect is formed by laminating an encapsulation member for encapsulating an LED element and a foam prevention layer disposed on one surface side of the encapsulation member, and is an encapsulation member sheet for a surface light-emitting device used in a surface light-emitting device, which has two forms: a form in which the elastic modulus of the material constituting the foam prevention layer is 500 MPa or more, and a form in which the melting point of the material constituting the foam prevention layer is 140°C or more.

[0270] The surface light-emitting device includes a support substrate, an LED substrate having the LED element disposed on one surface side of the support substrate, the encapsulation member disposed on the LED element side of the LED substrate, the foam prevention layer, and a diffusion prevention member, which are laminated in this order.

[0271] The anti-foaming layer used in this aspect is the same as that described in the third embodiment of the above surface light-emitting device. Also, since the above LED substrate, the above sealing member, and the above anti-reflection member are the same as those described in the above surface light-emitting device, the description here is omitted.

[0272] Note that the present disclosure is not limited to the above embodiments. The above embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

Examples

[0273] Hereinafter, experimental examples related to the sealing member will be shown, and then examples and comparative examples of the present disclosure will be shown to explain the present disclosure in more detail.

[0274] A. Experimental Examples (Experimental Example 1) As shown in FIG. 11, a surface light-emitting device 1 having a support substrate 2, a light-emitting diode substrate 4 having a light-emitting diode element 3, a sealing member A (thickness 450 μm) 5, a diffusion member A 6, and a wavelength conversion member 9 was manufactured. Table 1 shows the haze value, layer structure, density, and transmittance at a wavelength of 450 nm of the sealing member A. Table 2 shows the evaluation results of luminance unevenness evaluated by the following method.

[0275] The members used are as follows. · Light-emitting diode substrate LED chips B0815ACQ0 (chip size 0.2 mm × 0.4 mm, manufactured by Genelite) were arranged in a square pattern on a support substrate (reflectivity 95%) at a 6 mm pitch. · Diffusion member A (diffusion plate) 55K3 (manufactured by Entire) · Wavelength conversion member (QD) QF-6000 (manufactured by Showa Denko Materials)

[0276] The thickness of the sealing member and the optical properties shown in Table 1 are the measured values of the sample for the sealing member after sandwiching the sealing member sheet with an ETFE film (thickness 100 μm) and performing heat treatment by vacuum lamination. The optical properties were measured by peeling off the ETFE film and measuring only the sample for the sealing member. The vacuum lamination conditions were as follows.

[0277] (Vacuum lamination conditions) (a) Vacuum evacuation: 5.0 minutes (b) Pressurization: Changed from 0 kPa to 100 kPa in 5 seconds (c) Pressure holding: (100 kPa): 7 minutes (d) Temperature: 150 °C

[0278] (Experimental Example 2) The occurrence of brightness unevenness was evaluated in the same manner as in Experimental Example 1, except that the following Diffusion Member B was used instead of Diffusion Member A. The results are shown in Table 2. · Diffusion Member B A second diffusion member having a prism structure with a prism surface formed on the light-emitting diode element side as the first layer and a dielectric multilayer film as the second layer

[0279] (Experimental Examples 3, 4) The occurrence of brightness unevenness was evaluated in the same manner as in Experimental Examples 1 and 2, except that Sealing Member B (thickness 450 μm) shown in Table 1 was used instead of Sealing Member A.

[0280] (Experimental Examples 5, 6) The occurrence of brightness unevenness was evaluated in the same manner as in Experimental Examples 1 and 2, except that Sealing Member D (thickness 450 μm) shown in Table 1 was used instead of Sealing Member A.

[0281] (Comparative Experimental Examples 1, 2) The occurrence of brightness unevenness was evaluated in the same manner as in Experimental Examples 1 and 2, except that pins were provided between the diffusion member and the light-emitting diode substrate instead of Sealing Member A. The results are shown in Table 2. At this time, the distance between the light-emitting diode element and the diffusion member was 500 μm.

[0282] (Comparative Experimental Examples 3, 4) Except for providing a Si cured product (thickness: 450 μm) using a highly transparent potting type liquid silicone composition instead of the sealing member A, the occurrence of brightness unevenness was evaluated in the same manner as in Experimental Examples 1 and 2. The results are shown in Table 2.

[0283] (Comparative Experimental Examples 5 and 6) Except for using the sealing member C (thickness: 450 μm) shown in Table 1 instead of the sealing member A, the occurrence of brightness unevenness was evaluated in the same manner as in Experimental Examples 1 and 2. The results are shown in Table 2.

[0284]

Table 1

[0285] [Brightness Unevenness Evaluation Method] For the obtained surface light-emitting device, the brightness during LED emission was measured using a two-dimensional color brightness meter CA2000, and the brightness unevenness was evaluated. The index of brightness unevenness was judged as follows based on the uniformity value.

[0286] [Evaluation Criteria] Uniformity = Minimum value of front brightness / Maximum value of front brightness A: Uniformity > 0.9 B: 0.8 ≤ Uniformity ≤ 0.9 C: Uniformity < 0.8

[0287]

Table 2

[0288] In the surface light-emitting devices (Experimental Examples 1 to 6) in the present disclosure, the occurrence of brightness unevenness could be suppressed. On the other hand, in Comparative Experimental Examples 1 and 2 where pins were provided instead of the sealing member A, Comparative Experimental Examples 3 and 4 using a cured product of liquid Si, and Comparative Experimental Examples 5 and 6 using the sealing member C with a low haze value, the occurrence of brightness unevenness could not be suppressed.

[0289] B. Examples of the First Embodiment and the Second Embodiment Examples of the surface light-emitting device according to the first embodiment and the second embodiment are shown below.

[0290] [Example B-1] (Formation of a laminate of a sealing member and an anti-warping layer) Based on 100 parts by mass of the following Base Resin 1, 5 parts by mass of Additive Resin 1 (weathering agent masterbatch) and 20 parts by mass of Additive Resin 2 (silane-modified polyethylene resin) were mixed to obtain a composition for a sealing member for forming a PET film-integrated sealing member.

[0291] ·Base Resin 1 Metallocene linear low-density polyethylene resin (M-LLDPE) with a density of 0.901 g / cm 3 , a melting point of 93°C, and an MFR of 2.0 g / 10 min at 190°C.

[0292] ·Additive Resin 1 (weathering agent masterbatch) Density 0.919 g / cm 3 , with respect to 100 parts by mass of a low-density polyethylene resin having an MFR of 3.5 g / 10 min at 190°C, 0.6 part by mass of KEMISTAB62 (HALS). A masterbatch to which 3.5 parts by mass of KEMISORB12 (UV absorber) and 0.6 part by mass of KEMISORB79 (UV absorber) were added

[0293] ·Additive Resin 2 (silane-modified polyethylene resin) Density 0.898 g / cm 3 , with respect to 95 parts by mass of a metallocene linear low-density polyethylene resin having an MFR of 3.5 g / 10 min, 5 parts by mass of vinyltrimethoxysilane and 0.15 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed and melted and kneaded at 200°C to obtain a silane-modified polyethylene resin. The density of this Additive Resin 2 is 0.901 g / cm 3 , and the MFR is 1.0 g / 10 min.

[0294] Next, as the anti-warp layer, a biaxially stretched polyethylene terephthalate film (optical grade) with a film thickness of 50 μm was used, and this was integrated by being pressure-bonded to the film obtained by melt-extruding the above-described composition for the sealing member, thereby forming an anti-warp layer laminate in which the anti-warp layer and the sealing member with a film thickness of 300 μm were laminated.

[0295] Next, using a vacuum laminator, lamination of the PCB substrate and the above anti-warp layer laminate was performed. The PCB substrate is one in which white coating, copper, and glass epoxy are laminated in this order.

[0296] From the hot plate side of the vacuum laminator, a hot plate, a 0.3 mm thick Teflon (registered trademark) coated glass sheet, a glass (3 mm thick), a release PET (release surface: up), the above PCB substrate with the glass epoxy surface on the above release PET side, the anti-warp layer laminate with the above sealing member on the above PCB substrate side, a release PET (release surface: down), a glass (3 mm thick), and a 0.3 mm thick Teflon (registered trademark) coated glass sheet were laminated, and under the conditions of the vacuum laminator, lamination treatment was performed with a vacuum heating laminator under the treatment conditions of 130°C for 8 minutes. After the lamination was completed, the entire glass sheet was moved to a cooling shelf and cooled over about 10 to 15 minutes to obtain the sealing member laminate of the first embodiment. Regarding the above sealing member laminate as a surface light-emitting device, various evaluations were performed.

[0297] [Example B-2] A sealing member laminate of the first embodiment was obtained in the same manner as in Example B-1, except that the film thickness of the anti-warp layer was 100 μm.

[0298] [Example B-3] The same composition for the sealing member as in Example B-1 and the same PCB substrate as in Example B-1 were used. First, a film obtained by melt-extruding the composition for the sealing member with a film thickness of 160 μm as an anti-warping layer was pressure-bonded to the glass epoxy surface of the PCB member. Next, a film obtained by melt-extruding the composition for the sealing member with a film thickness of 240 μm as a sealing member was pressure-bonded to the white-painted surface of the PCB member, and a sealing member laminate of the second embodiment was obtained.

[0299] [Example B-4] A sealing member laminate of the second embodiment was obtained in the same manner as in Example B-3, except that the film thickness as the sealing member was 320 μm and the film thickness as the anti-warping layer was 80 μm.

[0300] [Example B-5] A sealing member laminate of the first embodiment was obtained in the same manner as in Example B-2, except that a biaxially stretched polyethylene terephthalate film (general-purpose grade) different from that in Example 2 was used as the anti-warping layer. [Example B-6] A sealing member laminate was obtained in the same manner as in Example B-1, except that the sealing member laminate was produced by joining the sealing member and the anti-warping layer with a dry laminating adhesive. As the main component of the dry laminating adhesive, a polycarbonate urethane-based one was used, and as the material for the curing agent, an isocyanate-based curing agent was used. Also, the blending ratio of the main component and the curing agent was 10:1, and the main component and the curing agent were dissolved in a solvent to make 50% by mass (ethyl acetate solution) each for blending.

[0301] Using a two-component adhesive consisting of the above-mentioned main agent and curing agent, a laminator capable of dry lamination was used to join and laminate a PET and a sheet-shaped sealing member to produce a sealing member laminate for a backlight. As the PET film, a biaxially stretched polyethylene terephthalate film (optical grade) was used. This PET film was fed out from the first paper feed side of the laminator, and the adhesive was dissolved in solvent ethyl acetate and gravure-coated so that the solid content application amount was 2 to 15 g / m2 (film thickness after curing: 2 to 15 μm). The solvent was volatilized and dried in a drying hood at about 70 to 90 °C to produce an adhesive surface. Then, the sealing member was fed out from the second paper feed, laminated by nip rolls in the state of PET / adhesive / sealing member, and wound up by a winding unit to produce a sealing member laminate. Further, after producing the laminated roll, an aging treatment was performed at 30 to 50 °C for about 70 to 200 hours to cure it.

[0302] [Comparative Example B-1] A sealing member laminate was obtained in the same manner as in Example B-1, except that the above-mentioned warpage prevention layer laminate was used as a sealing member with a film thickness of 400 μm.

[0303] [Comparative Example B-2] A sealing member laminate of the first embodiment was obtained in the same manner as in Example B-1, except that a polycarbonate film (standard grade) with a film thickness of 100 μm was used as the above-mentioned warpage prevention layer.

[0304] [Evaluation Method] (Coefficient of Linear Thermal Expansion) For a sheet cut into 5 mm × 20 mm, after heating in accordance with JIS K7197, the dimensional change during cooling from the elevated temperature to room temperature was measured, and the coefficient of linear thermal expansion from 100 °C to 25 °C was averaged and calculated. Here, the coefficient of linear thermal expansion is a positive value during contraction and a negative value during expansion. The measurement was performed under the following measuring apparatus and measuring conditions. · Measuring apparatus: Thermomechanical apparatus (TMA / SS-6000) manufactured by Seiko Instruments · Constant load tension mode: 0.1 mN · Measuring temperature range: -50 °C to 160 °C ·Coefficient of linear expansion calculation temperature range: 25°C to 100°C

[0305] (Elastic modulus) It was carried out by the tensile measurement shown below. (Measurement method) ·Measuring device: Universal material testing machine 5565 manufactured by Instron ·Load cell: 1 kN ·Sample width: 10 mm ·Distance between chucks: 50 mm ·Speed: 300 mm / min

[0306] (Melting point) It was measured by a method conforming to JIS K 7121 using a differential scanning calorimeter (DSC-60 Plus, manufactured by Shimadzu Corporation).

[0307] (Total light transmittance) It was measured by a method conforming to JIS K7361-1:1997.

[0308] (Haze value) It was measured by a method conforming to JIS K7136 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory).

[0309] (Amount of warp) Each sealing member laminate immediately after vacuum lamination is left standing on a horizontal plane in a normal temperature environment for 24 hours or more. Then, the height from the horizontal plane at the corner to the lower side of the substrate was measured with a steel straight gauge conforming to JIS B 7514.

[0310] (Foaming test) Each sealing member laminate immediately after vacuum lamination was put into a constant temperature bath at 100°C for 1000 h in accordance with JIS C 60068-2-2, and the presence or absence of foaming was observed.

[0311] (Luminance unevenness) Diffusion members were placed on the surface of the sealing member side of the sealing member laminates obtained in Examples B-1 to B-6 and Comparative Examples B-1 to B-2, and corresponding surface light-emitting devices were obtained. The method for measuring luminance unevenness and the evaluation criteria were the same as those shown in the above experimental examples. Also, the same diffusion member as diffusion member B used in Experimental Example 2 above was used as the diffusion member.

[0312] The results are shown in Table 3.

[0313]

Table 3

[0314] C. Examples of the Third Embodiment Next, examples of the surface light-emitting device of the third embodiment are shown.

[0315] [Example C-1] A sealing member laminate of the third embodiment was obtained in the same manner as in Example B-1 above, except that a biaxially stretched polyethylene terephthalate film (optical grade) with a film thickness of 35 μm was used as the anti-foaming layer. Regarding the above sealing member laminate as a surface light-emitting device, various evaluations were performed.

[0316] [Example C-2] A sealing member laminate was obtained in the same manner as in Example B-1 above, except that the anti-warping layer was used as the anti-foaming layer.

[0317] [Example C-3] A sealing member laminate was obtained in the same manner as in Example B-2 above, except that the anti-warping layer was used as the anti-foaming layer.

[0318] [Example C-4] A sealing member laminate was obtained in the same manner as in Example B-1 above, except that random polypropylene with a film thickness of 100 μm was used as the anti-foaming layer.

[0319] [Example C-5] A sealing member laminate was obtained in the same manner as in Comparative Example B-2 above, except that the anti-warping layer was used as the anti-foaming layer.

[0320] [Comparative Example C-1] A sealing member laminate was obtained in the same manner as in Comparative Example B-1.

[0321] [Evaluation method] The elastic modulus, melting point, and foaming test were conducted in the same manner as in the above "B. Examples of the First and Second Embodiments". The results are shown in Table 4.

[0322]

Table 4

[0323] That is, in the present disclosure, the following inventions can be provided. [1] A sealing member sheet for a surface light-emitting device, which is laminated with a sealing member for sealing a light-emitting diode element and an anti-warping layer disposed on one surface side of the sealing member, and is used for a surface light-emitting device, wherein the linear expansion coefficient of the material constituting the anti-warping layer is -15×10 -6 / °C or more and 10×10 -6 / °C or less. [2] The sealing member sheet for a surface light-emitting device according to [1], wherein the thickness of the sealing member is 50 μm or more and 800 μm or less. [3] The sealing member sheet for a surface light-emitting device according to [1] or [2], wherein the sealing member contains a thermoplastic resin. [4] The sealing member sheet for a surface light-emitting device according to any one of [1] to [3], wherein the sealing member has a polyethylene-based resin with a density of 0.870 g / cm 3 or more and 0.930 g / cm 3 or less as a base resin. [5] The sealing member sheet for a surface light-emitting device according to any one of [1] to [4], wherein the sealing member has a core layer and a skin layer disposed on at least one surface side of the core layer. [6] The sealing member sheet for a surface light-emitting device according to [5], wherein the core layer and the skin layer have different melting points of the thermoplastic resin contained as a base resin. [7] The encapsulating member is the encapsulating member sheet for a surface light-emitting device according to [6] or [7], which has a thermoplastic resin with a melting point of 90°C or higher and 120°C or lower as the base resin of the core layer. [8] The core layer in the encapsulating member has a polyethylene-based resin with a density of 0.900 g / cm 3 or higher and 0.930 g / cm 3 or lower as the base resin, and the skin layer has a polyethylene-based resin with a density of 0.875 g / cm 3 or higher and 0.910 g / cm 3 or lower, and uses a polyethylene-based resin with a lower density than the base resin for the core layer as the base resin. The encapsulating member sheet for a surface light-emitting device according to any one of [5] to [7]. [9] An encapsulating member sheet for a surface light-emitting device, which is formed by laminating an encapsulating member for encapsulating a light-emitting diode element and an anti-foaming layer disposed on one surface side of the encapsulating member, and the elastic modulus of the material constituting the anti-foaming layer is 500 MPa or higher.

[10] An encapsulating member sheet for a surface light-emitting device, which is formed by laminating an encapsulating member for encapsulating a light-emitting diode element and an anti-foaming layer disposed on one surface side of the encapsulating member, and the melting point of the material constituting the anti-foaming layer is 140°C or higher.

[11] A surface light-emitting device having a support substrate, a light-emitting diode substrate having a light-emitting diode element disposed on one surface side of the support substrate, an encapsulating member disposed on the surface of the light-emitting diode substrate on the light-emitting diode element side for encapsulating the light-emitting diode element, a warpage prevention layer disposed on the surface of the encapsulating member opposite to the light-emitting diode substrate, and a diffusion member disposed on the surface of the warpage prevention layer opposite to the light-emitting diode substrate. The encapsulating member has a haze value of 4% or higher, a thickness thicker than the thickness of the light-emitting diode element, and the linear expansion coefficient of the material constituting the warpage prevention layer is in the range of -15×10 -6 / °C or higher and 10×10 -6 / °C or lower.

[12] A surface light-emitting device having a support substrate and a light-emitting diode substrate disposed on one surface side of the support substrate, the light-emitting diode substrate having a light-emitting diode element, a sealing member disposed on the surface of the light-emitting diode substrate on the side of the light-emitting diode element for sealing the light-emitting diode element, a diffusion member disposed on the surface of the sealing member opposite to the light-emitting diode substrate, and a warpage prevention layer disposed on the surface of the light-emitting diode substrate opposite to the light-emitting diode element, wherein the sealing member has a haze value of 4% or more, a thickness greater than the thickness of the light-emitting diode element, and the linear expansion coefficient of the material constituting the warpage prevention layer is equal to or greater than the linear expansion coefficient of the material constituting the sealing member.

[13] The surface light-emitting device according to

[11] or

[12] , wherein the thickness of the sealing member is 50 μm or more and 800 μm or less.

[14] The surface light-emitting device according to any one of

[11] to

[13] , wherein the sealing member contains a thermoplastic resin.

[15] The surface light-emitting device according to any one of

[11] to

[14] , wherein the sealing member has a polyethylene-based resin with a density of 0.870 g / cm 3 or more and 0.930 g / cm 3 or less as a base resin.

[16] The surface light-emitting device according to any one of

[11] to

[15] , wherein the sealing member has a core layer and a skin layer disposed on at least one surface side of the core layer.

[17] The surface light-emitting device according to

[16] , wherein the core layer and the skin layer have different melting points of the thermoplastic resin contained as the base resin.

[18] The surface light-emitting device according to

[16] or

[17] , wherein the sealing member has a thermoplastic resin with a melting point of 90 °C or more and 120 °C or less as the base resin of the core layer.

[19] In the sealing member, the core layer has a polyethylene-based resin with a density of 0.900 g / cm 3 or more and 0.930 g / cm 3 or less as a base resin, and the skin layer has a density of 0.875 g / cm 3 or more and 0.910 g / cm 3The surface light-emitting device according to any one of

[16] to

[18] , which uses a polyethylene-based resin having a lower density than the base resin for the core layer as the base resin.

[20] A display device including a display panel and the surface light-emitting device according to any one of

[11] to

[19] disposed on the back surface of the display panel.

[21] A method for manufacturing the surface light-emitting device according to

[11] , the method including preparing a laminate in which the anti-warpage layer, the sealing member, and the light-emitting diode substrate on which the light-emitting diode elements are disposed so as to face the sealing member side are arranged in this order, and thermocompression bonding the laminate.

[22] A method for manufacturing the surface light-emitting device according to

[11] , the method including thermocompression bonding a first laminate in which the anti-warpage layer and the sealing member are laminated, and thermocompression bonding a second laminate in which the light-emitting diode substrate on which the light-emitting diode elements are disposed so as to face the sealing member side is disposed on the surface of the thermocompression-bonded first laminate on the sealing member side.

Explanation of Reference Numerals

[0324] 1, 10... Surface light-emitting device 2... Support substrate 3... LED element 4... LED substrate 5... Sealing member 6... Diffusion member 7... Anti-warpage layer 100... Display device

Claims

1. a light emitting diode substrate having a support substrate and a light emitting diode element disposed on one surface side of the support substrate; a sealing member for sealing the light emitting diode element; a foaming prevention layer disposed on a surface of the sealing member opposite to the light emitting diode substrate; a reflecting layer is disposed in an area other than an area where the light emitting diode element is mounted on a surface of the light emitting diode substrate on which the light emitting diode element is disposed, the sealing member has a polyethylene-based resin as a base resin, a core layer, and a skin layer disposed on at least one surface side of the core layer; the skin layer is disposed on the light-emitting diode substrate side of the sealing member, and the melting point of the skin layer is 50° C. or more and 100° C. or less; The foaming prevention layer has a thickness of 35 μm or more, A surface emitting device, wherein the material constituting the foaming prevention layer has an elastic modulus of 500 MPa or more.

2. The surface emitting device according to claim 1 , wherein the material constituting the foaming prevention layer has a melting point of 140° C. or higher.

3. 3. The surface emitting device according to claim 1, wherein the foaming prevention layer is made of a material selected from the group consisting of random polypropylene.

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