JP2008027619A - Surface emitter and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface emitter that has sufficient bonding strength even in storage under a high-temperature high-humidity environment and maintains light extraction efficiency and frontal luminance, while greatly improving the light extraction efficiency and frontal luminance of light emitted from the surface emitter in the surface emitter provided with a surface light-emitting element and a display device using the surface emitter. <P>SOLUTION: The surface emitter at least has the surface light-emitting element 20 and a light-control sheet 10A. The light-control sheet 10A has a plurality of convexes 12 at least on its one face. Each tip of the convexes 12 is in contact with an emission face 14 of the surface light-emitting element 20 via adhesive layers 100, 101. A part of each tip of the convexes 12 is embedded inside the adhesive layers 100, 101. The adhesive layers 100, 101 are respectively composed of two or more adhesive layers made of more than one kind of adhesive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface light emitter and a display device using the same.

  In recent years, with the diversification of information equipment and the like, the need for a surface light-emitting element with low power consumption and a small volume has increased, and an electroluminescence element (hereinafter abbreviated as EL element) is one of such surface light-emitting elements. Is attracting attention.

  Such EL elements are roughly classified into inorganic EL elements and organic EL elements depending on the materials used.

  Here, the inorganic EL element generally causes a high electric field to act on the light emitting portion, accelerates electrons in the high electric field to collide with the light emission center, thereby exciting the light emission center to emit light. On the other hand, the organic EL element injects electrons and holes from the electron injection electrode and the hole injection electrode, respectively, into the light emitting layer, and combines the injected electrons and holes in the light emitting layer to form an organic material. When the organic material returns from the excited state to the ground state, the organic material emits light, which has the advantage that it can be driven at a lower voltage than the inorganic EL element, and has the advantage of emitting light on the surface. It is expected to be used for thin and flexible lighting applications.

  In the case of an organic EL element, a light emitting element that emits light in an appropriate color can be obtained by selecting a light emitting material, and white light can be obtained by appropriately combining light emitting materials. It is also expected to be used as a backlight for elements and the like.

  When used as illumination, low power consumption is required, and generally brightness of about 50 lm / W is desired. However, when a surface light emitting element such as an inorganic or organic EL element emits light, the light emitted inside the light emitting layer having a high refractive index travels in various directions and is totally reflected on the emission surface of the surface light emitting element. There is also a lot of light confined inside the surface light emitting element. Generally, only 20 to 30% of the light emitted from the surface light emitting element can be taken out of the surface light emitting element. The brightness of inorganic EL elements and organic EL elements is about 30 to 40 lm / W even with high luminance elements, and there is a problem that sufficient brightness cannot be obtained.

In addition, when used as a backlight for liquid crystal display elements and the like, generally a front luminance of about 2000 to 4000 cd / m ² is required, but there is a lot of light confined inside the surface light emitting element as described above, and sufficient In particular, in the case of an organic EL element, only a front luminance of about 1000 to 1500 cd / m ² can be obtained in order to obtain a sufficient light emission lifetime. There was a problem.

  Conventionally, when a surface light-emitting element such as an organic EL element emits light, a diffusion structure is provided on the emission surface of the surface light-emitting element in order to extract the light confined in the surface and improve the front luminance. There have been proposed (for example, Patent Document 1) or a prism or lens-like sheet attached to the exit surface of the surface light emitting element so that the surface has irregularities (for example, Patent Document 2). reference.).

  However, when a minute unevenness is provided on the exit surface of the surface light emitting element as described above, or a flat member provided with an unevenness on the exit surface of the surface light emitting element is attached so that the unevenness appears on the surface. There is a problem that light is scattered by the unevenness on the surface and the front luminance cannot be sufficiently improved. As another means for improving the front luminance of a surface light emitting element such as an organic EL light emitting device, a prism array sheet having an uneven surface is provided on the surface where light is emitted, and the prism side faces the emission surface. It has been devised (for example, see Patent Documents 3 and 4). As a method for bonding the prism array sheet and the substrate, a method of bonding with a UV curable resin has been proposed. However, there is a problem that it is difficult to uniformly apply the UV curable resin to the substrate. Moreover, in order to cure by UV irradiation, the prism array sheet has a problem that it is limited to a material that transmits ultraviolet rays. Further, when used for an organic EL light emitting device, there has been a problem that UV irradiation during curing deteriorates the organic material.

As a method for bonding the prism array sheet and the substrate, a method using an adhesive and a pressure sensitive adhesive on these bonding surfaces (see, for example, Patent Document 5) or between the prism array sheet and the emission surface of the surface light emitting element. A method of using an adhesive on both sides of an intermediate film and bonding them together (see, for example, Patent Document 6) has been reported, but in order to obtain the peel strength required for recent surface light emitters. It was still insufficient. In addition, the storage stability at high temperature or high humidity is still insufficient, peeling of the adhesive surface due to the difference in the expansion coefficient of the materials constituting the prism array sheet and the surface light emitting element, and lifting from the adhesive surface of the prism array sheet, etc. The light extraction efficiency and the front luminance due to the light are easily changed, which has been a problem in practical use.
JP 2000-323272 A JP-A-6-265888 JP 2000-148032 A JP 2006-59543 A JP 2001-357709 A JP 2001-356704 A

  It is an object of the present invention to greatly improve the extraction efficiency and front luminance of light emitted from a surface light emitter provided with a surface light emitting element and a display device using the surface light emitter. is there.

  It is another object of the present invention to provide a surface light emitter that has sufficient adhesive strength even when stored in a high temperature and high humidity environment, and maintains light extraction efficiency and front luminance.

  The above object of the present invention is achieved by the following configurations.

  1. In a surface light emitter having at least a surface light emitting element and a light control sheet, the light control sheet has a plurality of convex portions on at least one surface, and a tip portion of the convex portion is an adhesive layer on an emission surface of the surface light emitting device. A part of the tip of the convex portion is embedded in the adhesive layer, and the adhesive layer is composed of two or more adhesive layers each composed of one or more adhesives. A surface light emitter characterized by comprising:

  2. In the two or more pressure-sensitive adhesive layers, a ratio B / A of a convex portion burying load A to the pressure-sensitive adhesive layer in contact with the light control sheet and a convex portion burying load B to the pressure-sensitive adhesive layer in contact with the emission surface of the surface light emitting element is 0 <B / A <1 in the range, The surface light emitter according to 1 above.

  3. 3. The surface light emitter according to 2 above, wherein the ratio B / A is in a range of 0 <B / A <0.7.

  4). 4. The surface light emitter according to any one of items 1 to 3, wherein the convex portion has a truncated cone shape.

  5. 5. A display device using the surface light emitter according to any one of 1 to 4 as a backlight.

  According to the present invention, the extraction efficiency and front luminance of light emitted from the surface light emitter are greatly improved, the reliability of adhesion to the light control sheet is improved, the impact resistance is increased, and the strength against bending of the substrate is increased. Thus, it is possible to provide a highly durable surface light emitting body with improved resistance.

  In addition, since the optical action at the convex portion embedded in the adhesive is reduced, variation in the shape of the convex portion embedded in the adhesive does not affect the optical performance. In general, in the manufacture of a light control sheet, it is difficult to accurately create the shape near the apex of the convex portion, so that the influence of the variation in the shape of the convex portion on the performance of the surface light emitter is minimal as in the present invention. This improves the ease of manufacturing.

  Furthermore, it is possible to provide a surface light emitter that has sufficient adhesive strength even when stored in a high temperature and high humidity environment, and maintains excellent light extraction efficiency and front luminance.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The surface light emitter according to the present invention includes at least a surface light emitting element and a light control sheet, and the light control sheet has a plurality of convex portions on at least one surface, and a tip portion of the convex portion is the surface light emitting device. 2 is in contact with the light-exiting surface via an adhesive layer, a part of the tip of the convex portion is embedded in the adhesive layer, and each of the adhesive layers is made of one or more kinds of adhesives. It is characterized by comprising an adhesive layer of more than one layer.

  Further, in this surface light emitter, in the two or more adhesive layers, the convex portion burying load A on the adhesive layer in contact with the light control sheet and the convex portion burying load on the adhesive layer in contact with the emission surface of the surface light emitting element. The ratio B / A to B is in the range of 0 <B / A <1.

  In the surface light emitter, the ratio B / A is in a range of 0 <B / A <0.7.

  In the surface light emitter, the convex portion is more preferably a truncated cone.

  Further, the surface light emitter is used as a backlight of a display device.

  In the present invention, the light control sheet has a plurality of convex portions on at least one surface, and a tip portion of the convex portion is in contact with an emission surface of the surface light emitting element via an adhesive layer. A part of the adhesive layer is embedded in the adhesive layer, and the adhesive layer is composed of two or more adhesive layers each made of one or more adhesives. It is preferable that the convex portion is buried in the adhesive layer when adhering to the outgoing surface. At that time, the difference between the refractive index of the convex portion and the refractive index of the adhesive layer is preferably 0.2 or less.

  In addition, in the surface light emitter according to the present invention, when the convex portion of the light control sheet is bonded to the output surface of the surface light emitting element, the light emitted from the output surface of the surface light emitting element is appropriately applied to the convex portion of the light control sheet. In order to be guided, it is desirable to bond with a highly transparent adhesive.

  In the surface light emitter according to the present invention, the adhesive layer is composed of two or more pressure-sensitive adhesive layers each composed of one or more pressure-sensitive adhesives, but is preferably composed of three or more pressure-sensitive adhesive layers. Each adhesive layer may be composed of two or more kinds of adhesives. The pressure-sensitive adhesive used in each pressure-sensitive adhesive layer is preferably different, and is preferably selected appropriately in consideration of the emission surface of the surface-emitting element to be bonded, the surface characteristics of the light control sheet, the required adhesive strength, and the like. .

  In the surface light emitter according to the present invention, in the two or more adhesive layers, the convex portion burying load A to the adhesive layer in contact with the light control sheet and the convex to the adhesive layer in contact with the emission surface of the surface light emitting element. The ratio B / A to the partial burying load B is preferably in the range of 0 <B / A <1, more preferably in the range of 0 <B / A <0.7, 0 <B / A More preferably, it is in the range of <0.5.

  The ratio B / A of the convex portion burying load to the pressure-sensitive adhesive layer according to the present invention is the transparent substrate having the pressure-sensitive adhesive layer formed by cutting and bonding the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer in contact with the light control sheet, A transparent substrate having an adhesive layer formed by cutting and adhering the adhesive used for the adhesive layer in contact with the emission surface of the surface light emitting element is prepared, and further, a convex portion apex angle θ described later is provided on at least one side thereof. A dimming sheet having a plurality of frustoconical convex portions each having a convex portion height of 50 °, a convex portion height of 26.6 μm, and a convex pitch of 35 μm is cut out from the same area, and the leading end of the convex portion is interposed through an adhesive layer The ratio of the load per unit area necessary for burying the frustoconical convex portion in the adhesive layer to a depth of 5 μm when bonding to the transparent substrate is defined.

  Heat in the light control sheet and the adhesive layer is prevented in order to prevent peeling of the adhesive surface and lifting from the adhesive surface of the light control sheet due to differences in the expansion coefficient of the materials constituting the light control sheet and the surface light emitting element. The difference between the expansion coefficient and the hygroscopic expansion coefficient is preferably small, and the ratio of the thermal expansion coefficient and the hygroscopic expansion coefficient is preferably 1/10 to 10.

  The pressure-sensitive adhesive in the present invention is widely used in the industrial field, and is bonded by pressurization among agents or materials used in designations such as pressure-sensitive adhesives, adhesives, pressure-sensitive adhesives, adhesives, etc. It means something that is not accompanied.

  The present invention will be described in detail below.

  First, a surface light emitter according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. The surface light emitter according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within the scope not changing the gist thereof.

  Hereinafter, the light control sheet | seat which concerns on this invention is called the prism array sheet | seat which is the one form.

(Embodiment 1)
In the first embodiment, as a light control sheet, as shown in FIGS. 1A and 1B, a square pyramid-shaped convex part 12 whose front end side contracts on one side of a light-transmitting substrate 11 continues vertically and horizontally. The prism array sheet 10A formed in this way was used. In this specification, the contraction of the front end side of the convex portion 12 means that the convex portion 12 is formed so as to gradually decrease as the distance from the prism array sheet 10A increases. FIG. In the examples shown in FIGS. 2 to 7, this means that the shape of the lower dent is formed.

  In the surface light emitter of the first embodiment, as shown in FIG. 2, the organic EL element in which the organic EL layer 23 and the counter electrode 24 are provided on the surface of the transparent substrate 21 provided with the transparent electrode 22 is used. The front surface of the convex portion 12 in the form of a square frustum in the prism array sheet 10A is used as the light emitting surface 21a of the transparent substrate 21 that emits the light emitted from the surface light emitting device 20. It was made to adhere by the adhesive layer which consists of the adhesion layers 100 and 101 which provided 12a 12a.

  In this way, when the tip surface 12a of the convex portion 12 having a square frustum shape in the prism array sheet 10A is adhered to the emission surface 21a of the surface light emitting element 20 with an adhesive layer composed of two adhesive layers 100 and 101. The convex portion 12 of the prism array sheet 10 </ b> A has a shape contracted toward the emission surface 21 a of the surface light emitting element 20, and between the convex portion 12 of the prism array sheet 10 </ b> A and the emission surface 21 a of the surface light emitting element 20. The space 13 becomes an air layer.

  Then, when the tip surface 12a of the convex portion 12 in the prism array sheet 10A is bonded to the emission surface 21a of the surface light emitting element 20 in this way, the surface light emitting element 20 emits light. In the case where the light sheet is not provided, the light totally reflected on the emission surface 21a of the surface light emitting element 20 is, as shown in FIG. 3, in the portion where the tip surface 12a of the convex portion 12 of the prism array sheet 10A is bonded. The light is guided into the prism array sheet 10A without being totally reflected.

  Then, most of the light guided into the prism array sheet 10A in this way is an inclined surface of the convex portion 12 which is an interface between the convex portion 12 and the space portion 13 contracted toward the emission surface 21a of the surface light emitting element 20. The reflected light is reflected at 12b, and the reflected light is guided to the emission surface 14 of the prism array sheet 10A and emitted. Further, as shown in FIG. 3, even light emitted from the portion of the emission surface 21a where the tip surface 12a of the convex portion 12 of the prism array sheet 10A is not bonded is emitted from the emission surface 21a in the vertical direction. Although the traveling direction of the light is slightly changed on the inclined surface 12b of the convex portion 12, it is emitted to the front side of the prism array sheet 10A, and the inclination of the convex portion 12 in the prism array sheet 10A is emitted from the emission surface 21a. The light emitted in the direction orthogonal to the surface 12b is guided into the convex portion 12 from the inclined surface 12b, reflected by the inclined surface 12b opposite to the convex portion 12, and the front side of the prism array sheet 10A. Are emitted.

  Here, when the light control sheet is not provided as described above, the light totally reflected on the emission surface 21a of the surface light emitting element 20 is transmitted from the front end surface 12a of the convex portion 12 related to the surface light emitter of the present invention. In order to be appropriately guided into the prism array sheet 10A, the difference between the refractive index of the prism array sheet 10A and the refractive index of the exit surface 21a of the surface light emitting element 20 should be within 0.2. It is preferable to do.

  Further, in providing the prism array sheet 10A with the convex portion 12 having a square frustum shape as described above, the apex angle θ at which the inclined surfaces 12b of the convex portion 12 intersect each other is increased, and the surface light emitting element described above is obtained. If the inclination angle α of the inclined surface 12b of the convex portion 12 with respect to the 20 emission surface 21a becomes too small, the light that is totally reflected on the emission surface 21a of the surface light emitting element 20 when the light control sheet is not provided is the prism array sheet. Even if the light is guided into the interior of 10A, this light does not hit the inclined surface 12b of the convex portion 12, but is guided to the output surface 14 of the prism array sheet 10A, and is totally reflected by the output surface 14 of the prism array sheet 10A. Accordingly, the intensity of the light emitted from the emission surface 14 of the prism array sheet 10A is reduced.

  On the other hand, when the apex angle θ at which the inclined surfaces 12b of the convex portion 12 intersect each other becomes small and the inclination angle α of the inclined surface 12b of the convex portion 12 with respect to the emission surface 21a of the surface light emitting element 20 becomes too large, as described above. The light guided to the inside of the prism array sheet 10A is not reflected by the inclined surface 12b of the convex portion 12, but is guided to the space portion 13 through the convex portion 12, and further passes through the space portion 13. Then, the light is again guided to the inside of the prism array sheet 10A, and the light is totally reflected and returned by the light exit surface 14 of the prism array sheet 10A as described above, and the light exit surface 14 of the prism array sheet 10A. The intensity of light emitted from the light source decreases.

  For this reason, the apex angle θ at which the inclined surfaces 12b of the convex portion 12 intersect each other is (1 / n−0.35) when the refractive index for light having a wavelength of 550 nm in the prism array sheet 10A is n. It is preferable that the condition <sin θ <(1 / n + 0.3) is satisfied, and it is more preferable that the condition 1 / n <sin θ <(1 / n + 0.25) is satisfied.

  Further, the range that the optical height h of the convex portion 12 can take varies depending on the apex angle θ of the convex portion 12 and the pitch p of the convex portion 12, but generally the optical property of the convex portion 12 is not limited. If the typical height h is too low, even if light totally reflected when no light control sheet is provided on the emission surface 21a of the surface light emitting element 20, even if the light is guided into the prism array sheet 10A, this light Is not directed to the inclined surface 12b of the convex portion 12, but is guided to the emission surface 14 of the prism array sheet 10A, and is totally reflected and returned by the emission surface 14 of the prism array sheet 10A. On the other hand, if the optical height h of the convex portion 12 becomes too high, a portion that is not used for light reflection occurs on the inclined surface 12b of the convex portion 12, and the surface of the convex portion 12 having the same pitch p The area of the front end surface 12a of the convex portion 12 bonded to the emission surface 21a of the light emitting element 20 is reduced, and the amount of light guided to the inside of the prism array sheet 10A is reduced. For this reason, it is preferable that the optical height h of the convex portion 12 satisfies the condition of 0.28p ≦ h ≦ 1.1p with respect to the pitch p of the convex portion 12.

  A portion where the prism array sheet 10A of Embodiment 1 is bonded to the emission surface of the surface light emitting element 20 will be described in detail. As illustrated in FIG. 4, the adhesive layer 100 including the transparent adhesive layer 100 and the transparent adhesive layer 101 and the prism array sheet 10 </ b> A are sequentially stacked on the emission surface 21 a of the surface light emitting element 20, and the convex portion 12 of the prism array sheet 10 </ b> A. The front end surface 12 a and the adhesive layer 100, and the adhesive layer 101 and the emission surface 21 a of the surface light emitting element 20 are configured to be in optical contact with each other. Here, the thickness of the adhesive layer composed of the adhesive layer 100 and the adhesive layer 101 is desirably 5 microns or more. If it is less than 5 microns, sufficient adhesive strength cannot be obtained.

  The type of the pressure-sensitive adhesive used for the adhesive layer of the present invention is not particularly limited. For example, urethane-based, epoxy-based, aqueous polymer-isocyanate-based, acrylic-based pressure-sensitive adhesive, polyether methacrylate type, ester methacrylate type, Anaerobic adhesives such as oxidized polyether methacrylate are exemplified. Moreover, you may mix an antistatic agent and various fillers in an adhesive using a well-known method.

  The method for forming the adhesive layer is not particularly limited, and examples thereof include general methods such as gravure coater, micro gravure coater, comma coater, bar coater, spray coating, and ink jet method.

  As shown in FIG. 5, the vicinity of the tip surface 12 a of the convex portion 12 of the prism array sheet 10 </ b> A is embedded in an adhesive layer made of the adhesive layer 100 and the adhesive layer 101. Since the adhesive layer composed of the adhesive layer 100 and the adhesive layer 101 and the convex portion 12 of the prism sheet are selected so as to have substantially the same refractive index, the prism array sheet 10A is optically in close contact with the emission surface 21a of the surface light emitting element. In FIG. 5, the width is the width corresponding to X. Further, the height of the convex portion 12 is obtained by subtracting the burying depth Y shown in FIG. 5 from the height Z of the convex portion of the prism array sheet 10A, so that the optical height of the convex portion of the optical prism array sheet is obtained. It corresponds to. The ratio Y / Z of the buried depth Y to the height Z of the convex portion of the prism array sheet 10A is preferably 0.1 to 0.5, more preferably 0.2 to 0.4, Most preferably, it is 0.25 to 0.35.

  In the above description, the prism array sheet 10A has been described with reference to the square pedestal shown in FIG. 1 as an example. However, as the light control sheet, as shown in FIGS. 6A and 6B, a translucent substrate is used. Alternatively, a prism array sheet 10E may be used in which a square portion is formed by cutting the periphery of the truncated cone-shaped convex portion 12 whose tip side is contracted on one side of the plate 11 in the vertical and horizontal directions.

  Here, if the prism array sheet 10E is provided with the convex portion 12 having a frustum shape, the front luminance of the light emitted through the prism array sheet 10E is further greatly improved. Although the detailed reason is unknown, according to the study by the present inventors, for example, as shown in FIG. 1, when the convex portion 12 has a square frustum shape, the top of the ridge line in the cross section in the ridge line direction is formed. Since the corner is smaller than the apex angle in the cross section in the arrangement direction of the convex portions 12 having a square frustum shape, outgoing light that cannot sufficiently contribute to the improvement of the front luminance is generated, In the case of the convex portion 12 having a frustum shape, the apex angle is constant in the cross section in any direction, and thus sufficient to improve the front luminance which has occurred in the case of the convex portion 12 having a square frustum shape. This is considered to be because no outgoing light that cannot contribute is generated.

  With the surface light emitter of Embodiment 1 described above, a surface light emitter with high light extraction efficiency and high front luminance can be obtained.

  FIG. 7 shows Embodiment 2 according to the present invention, which is the same as Embodiment 1 except that the adhesive layer is composed of three adhesive layers 100 to 102. In the surface light emitters of the first and second embodiments, the description has been given of the case where the shape of the convex portion 12 of the prism array sheet is a quadrangular thrust base and a truncated cone. However, as shapes for improving light extraction efficiency and front luminance, The shape is not limited to this, and may be a triangular pyramid or a hexagonal frustum.

  In the surface light emitters of Embodiments 1 and 2, an organic EL element is used as the surface light emitting element 20, but the surface light emitting element 20 may be any element that emits light in a planar shape, such as an inorganic EL element. However, it is particularly effective to use an organic EL element that is expected to greatly improve luminance.

  The surface light emitter of the present invention can be applied to various display devices as a backlight, but it is a reflective, transmissive, transflective LCD or TN, STN, OCB, HAN, VA (PVA type). , MVA type), IPS type and the like, and is preferably used as a backlight of a liquid crystal display device having an LCD of various driving methods. In particular, a large-screen display device having a screen of 30 or more screens, particularly 30 to 54 screens, has an effect of obtaining an image with high front luminance and high contrast.

  The surface light emitter according to the example of the present invention is compared with the surface light emitter of the comparative example, and in the surface light emitter according to the embodiment of the present invention, the extraction efficiency and front luminance of light emitted from the surface light emitter are high. It will be described that a surface light emitter that is greatly improved and has high reliability can be obtained. However, the present invention is not limited to these.

(Example 1)
In Example 1, similarly to the surface light emitter of Embodiment 1 described above, the prism array sheet 10A was bonded to the surface light emitting element 20 using an adhesive layer composed of two adhesive layers.

  As the surface light emitting element 20, the surface light emitting element 20 composed of the organic EL element in which the organic EL layer 23 and the counter electrode 24 are provided on the surface of the transparent substrate 21 provided with the transparent electrode 22 as described above is used. I made it.

  Here, in the surface light emitting element 20, non-alkali glass having a thickness of 0.7 mm and a size of 40 mm × 52 mm is used as the transparent substrate 21, and ITO ( Indium oxide doped with tin) was formed to a thickness of 150 nm and patterned into an electrode shape by photolithography to obtain a size of 35 × 46 mm. The resistance of the transparent electrode 22 was measured using Loresta (manufactured by Mitsubishi Chemical Corporation) and found to be 20Ω / □.

Next, a hole injection layer having a film thickness of 20 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, a hole transport layer having a thickness of 20 nm was formed on the hole injection layer by vacuum evaporation using NPD as a hole transport material. Next, a luminescent material that emits green light is deposited on the hole transport layer by vacuum deposition so that CBP is used as a host material and Ir (ppy) ₃ is contained as a dopant material in an amount of 6 mass percent. A light emitting layer having a thickness of 30 nm was formed. On this light emitting layer, BAlq was vapor-deposited with a thickness of 10 nm by a vacuum vapor deposition method to form a hole blocking layer. Further, on this hole blocking layer, Alq ₃ was formed to 40 nm by vacuum deposition to form an electron transport layer. Further, LiF was formed to 0.5 nm by a vacuum deposition method to form an electron injection layer. A counter electrode 24 made of aluminum and having a thickness of 100 nm was formed on the electron injection layer by sputtering. In addition, the refractive index with respect to the light with a wavelength of 550 nm of the transparent substrate 21 on the emission surface 21a side of the surface light emitting element 20 was 1.517.

  Next, a prism array sheet 10A in which convex portions 12 each having a quadrangular pyramid shape are continuously formed on one surface of the translucent substrate 11 is used. As shown in FIG. The prism array sheet 10 </ b> A was bonded to the emission surface 21 a of the surface light emitting element 20 so that the convex portion 12 faces the emission surface 21 a of the surface light emitting element 20. An acrylic adhesive with a thickness of 25 μm (double tack tape manufactured by Sekisui Chemical Co., Ltd.) is used for the adhesive layer in contact with the prism array sheet 10A, and an acrylic adhesive with a thickness of 10 μm is used for the adhesive layer in contact with the emission surface of the surface light emitting device. The agent (Sekisui Chemical Co., Ltd. double tack tape) was used. The ratio B / A related to the above-described convex burying load was 1.35. The prism array sheet 10A has a refractive index of 1.495 with respect to light having a wavelength of 550 nm, the apex angle θ of the quadrangular frustum-shaped convex portion 12 is 50 °, and the height of the quadrangular frustum-shaped convex portion 12. Was 32.9 μm, and the pitch of the convex portions 12 was 35 μm.

  After the prism array sheet 10A was attached to the emission surface 21a side of the surface light emitting element, the buried depth was measured and found to be 7 μm. The ratio Y / Z of the buried depth Y to the height Z of the convex portion of the prism array sheet is 0.213, and the front luminance and light extraction efficiency of the surface light emitter without the prism array sheet 10A attached are 1 The front luminance of the surface light emitter of Example 1 was 1.71, and the light extraction efficiency was 1.55.

(Example 2)
In Example 2, in the manufacture of the surface light emitting device according to Example 1, a 10 μm-thick acrylic adhesive (double tack tape manufactured by Sekisui Chemical Co., Ltd.) was used for the adhesive layer in contact with the prism array sheet 10A. A surface light emitter was produced in the same manner except that an acrylic pressure-sensitive adhesive having a thickness of 25 μm (double tack tape manufactured by Sekisui Chemical Co., Ltd.) was used for the adhesive layer in contact with the emission surface of the light emitting element.

  The ratio B / A related to the above-described convex burying load was 0.74. The prism array sheet 10A has a refractive index of 1.495 with respect to light having a wavelength of 550 nm, the apex angle θ of the quadrangular frustum-shaped convex portion 12 is 50 °, and the height of the quadrangular frustum-shaped convex portion 12. Was 32.9 μm, and the pitch of the convex portions 12 was 35 μm.

  After the prism array sheet 10A was attached to the emission surface 21a side of the surface light emitting element, the buried depth was measured and found to be 7 μm. The ratio Y / Z of the buried depth Y to the height Z of the convex portion of the prism array sheet is 0.213, and the front luminance and light extraction efficiency of the surface light emitter without the prism array sheet 10A attached are 1 The front luminance of the surface light emitter of Example 2 was 1.71, and the light extraction efficiency was 1.55.

(Example 3)
In Example 3, in the manufacture of the surface light emitting device according to Example 2, instead of the prism array sheet 10A, the convex portion 12 having a truncated cone shape was continuously formed on one surface of the translucent substrate 11. The prism array sheet 10E is used, and the prism-shaped convex portion 12 of the prism array sheet 10E is opposed to the emission surface 21a of the surface light emitting element 20, and the prism array sheet 10E is used as the surface light emitting element 20. A surface light emitter was produced in the same manner except that it was adhered to the light emitting surface 21a. The ratio B / A related to the above-described convex burying load was 0.74. The prism array sheet 10E has a refractive index of 1.495 with respect to light having a wavelength of 550 nm, the apex angle θ of the truncated cone-shaped projection 12 is 50 °, and the height of the truncated cone-shaped projection 12 is 26.6 μm, and the pitch of the convex portions 12 was 35 μm.

  After the prism array sheet 10E was attached to the emission surface 21a side of the surface light emitting element, the buried depth was measured and found to be 7 μm. The ratio Y / Z of the buried depth Y to the height Z of the convex portion of the prism array sheet is 0.263, and the front luminance and light extraction efficiency of the surface light emitter without the rhythm array sheet 10E attached are 1 The front luminance of the surface light emitter of Example 3 was 2.09, and the light extraction efficiency was 1.65.

Example 4
In Example 4, in the manufacture of the surface light emitting device according to Example 3, an acrylic pressure-sensitive adhesive having a thickness of 25 μm (double tack tape manufactured by Sekisui Chemical Co., Ltd.) was used for the adhesive layer in contact with the prism array sheet 10E. A surface light emitter was prepared in the same manner except that an acrylic adhesive having a thickness of 25 μm (CS9621 manufactured by Nitto Denko Corporation) was used for the adhesive layer in contact with the emission surface of the light emitting element.

  The ratio B / A related to the above-described convex burying load was 0.30.

  The prism array sheet 10E has a refractive index of 1.495 with respect to light having a wavelength of 550 nm, the apex angle θ of the truncated cone-shaped projection 12 is 50 °, and the height of the truncated cone-shaped projection 12 is 26.6 μm, and the pitch of the convex portions 12 was 35 μm.

  After the prism array sheet 10E was attached to the emission surface 21a side of the surface light emitting element, the buried depth was measured and found to be 7 μm. The ratio Y / Z of the buried depth Y to the height Z of the convex portion of the prism array sheet is 0.263, and the front luminance and light extraction efficiency of the surface light emitter without the prism array sheet 10E attached are 1 The front luminance of the surface light emitter of Example 4 was 2.09, and the light extraction efficiency was 1.65.

(Comparative Example 1)
In the manufacture of the surface light emitting device according to Example 1, the square frustum-shaped convex portion 12 of the prism array sheet 10A is opposed to the emission surface 21a of the surface light emitting device 20 without using two adhesive layers. Then, a surface light emitting device was prepared in the same manner except that only one adhesive layer having a thickness of 25 μm was used for adhesion, and used as a comparative example. The buried depth of the prism array sheet was measured to be 7 μm, the ratio Y / Z of the buried depth Y to the height Z of the convex portion of the prism array sheet was 0.213, and the prism array sheet 10A was not attached. When the front luminance and light extraction efficiency of the surface light emitter in the state were 1, the front luminance of the surface light emitter was 1.71 and the light extraction efficiency was 1.55.

[Evaluation of storage stability]
After the surface light emitting devices of Examples 1 to 4 and Comparative Example 1 were stored at 85 ° C. for 20 hours, the change in outer shape and the change in light extraction efficiency were measured, respectively, and compared with those before the storage stability evaluation.

  The surface light emitting devices according to Examples 1 to 4 had almost no change in outer shape, and hardly changed in light extraction efficiency and front luminance. On the other hand, in the surface light emitting device of Comparative Example 1, floating was observed in the peripheral portion of the prism array sheet, the light extraction efficiency was degraded by about 8%, and the front luminance was degraded by about 3%.

  Furthermore, after the surface light emitting devices of Examples 1 to 4 and Comparative Example 1 were stored at 85 ° C. for 100 hours, the change in outer shape and the change in light extraction efficiency were measured and compared with those before the storage stability evaluation. .

  In the surface light emitting device according to Example 1, several lifts were observed on the side portions of the prism array sheet on the surface light emission, and the light extraction efficiency was deteriorated by about 3%. The surface light emitting devices according to Examples 2 to 4 had almost no change in outer shape, and the light extraction efficiency was hardly changed. In addition, in the surface emitting element concerning Examples 1-4, the deterioration of front luminance was hardly confirmed. On the other hand, in the surface light emitting device of Comparative Example 1, a lot of floating was observed in the peripheral portion of the prism array sheet, the light extraction efficiency was deteriorated by about 15%, and the front luminance was deteriorated by about 6%.

  Subsequently, after the surface light emitting devices of Examples 1 to 4 and Comparative Example 1 were stored at 60 ° C. and 90% RH for 100 hours, the change in outer shape and the change in light extraction efficiency were measured, respectively, and the storage stability was evaluated. Compared to before.

  In the surface light emitting device according to Example 1, an increase in lifting of the side portion of the prism array sheet on surface light emission was observed, and the light extraction efficiency was deteriorated by about 5%. In the surface light emitting device according to Example 2, the lift of the prism array sheet was very small, but the light extraction efficiency was deteriorated by about 3%. The surface light emitting devices according to Examples 2 to 4 had almost no change in outer shape, and the light extraction efficiency was hardly changed. In addition, in the surface emitting element concerning Examples 1-4, the deterioration of front luminance was hardly confirmed. On the other hand, in the surface light emitter element of Comparative Example 1, the floating of the peripheral portion of the prism array sheet increased, the light extraction efficiency was degraded by about 20%, and the front luminance was degraded by about 8%.

  The surface light emitter according to the present invention was excellent in high-temperature and high-humidity resistance, and maintained high light extraction efficiency and high front luminance even after a storage stability test.

  Next, when the surface light emitters of Examples 1, 2, 3, and 4 of the present invention were used instead of the pre-built backlight of the 15-inch display VL-150SD manufactured by Fujitsu, which is a VA-type liquid crystal display device, it was excellent. It was found that a liquid crystal display device having high brightness was obtained.

It is an example of the light control sheet of this invention. It is an example of embodiment of the surface light-emitting body of this invention. It is a schematic diagram which shows light emission by the surface light emitter according to the present invention. It is a schematic diagram which shows the structure of the light control sheet | seat, adhesive layer, and surface emitting element which concern on this invention. It is the schematic diagram by which the vicinity of the front end surface of the convex part of the light control sheet is adhere | attached in the form embedded in the contact bonding layer. It is a schematic diagram of the light control sheet | seat which has a frustum-shaped convex part which the front end side contracted. It is an example of embodiment in case an adhesive layer is three layers.

Explanation of symbols

10A, 10E Light control sheet 11 Translucent substrate 12 Convex part 13 Space part 14 Output surface 20 Surface light emitting element 21 Transparent substrate 22 Transparent electrode 23 Organic EL layer 24 Counter electrode 100, 101, 102 Adhesive layer

Claims (5)

In a surface light emitter having at least a surface light emitting element and a light control sheet, the light control sheet has a plurality of convex portions on at least one surface, and a tip portion of the convex portion is an adhesive layer on an emission surface of the surface light emitting device. A part of the tip of the convex portion is embedded in the adhesive layer, and the adhesive layer is composed of two or more adhesive layers each composed of one or more adhesives. A surface light emitter characterized by comprising: In the two or more pressure-sensitive adhesive layers, a ratio B / A of a convex portion burying load A to the pressure-sensitive adhesive layer in contact with the light control sheet and a convex portion burying load B to the pressure-sensitive adhesive layer in contact with the emission surface of the surface light emitting element is The surface light emitter according to claim 1, wherein 0 <B / A <1. The surface light emitter according to claim 2, wherein the ratio B / A is in a range of 0 <B / A <0.7. The surface light emitter according to claim 1, wherein the convex portion has a truncated cone shape. 5. A display device using the surface light emitter according to claim 1 as a backlight.

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