WO2007138909A1

WO2007138909A1 - Surface area light emitting body, method of producing surface area light emitting body, and display device

Info

Publication number: WO2007138909A1
Application number: PCT/JP2007/060356
Authority: WO
Inventors: Akira Sato; Manami Kuiseko
Original assignee: Konica Minolta Holdings, Inc.
Priority date: 2006-05-31
Filing date: 2007-05-21
Publication date: 2007-12-06
Also published as: JPWO2007138909A1; JP5304242B2

Abstract

Provided are a surface area light emitting body with a surface area light emitting element and a display device using the surface area light emitting body. Taking-out efficiency and front luminance of light emitted from the surface area light emitting body are uniformly and greatly improved. The surface area light emitting body has at least the surface light emitting element and a light regulating sheet. The light regulating sheet has projections on at least one side of the sheet, and the top ends of the projections are in contact with the light emitting surface of the surface area light emitting element with an adhesion layer inbetween. The top ends of the projections are adhered to the adhesion layer, embedding a portion of each top end in the adhesion layer. The ratio of the total area of the adhesion between the projections and the adhesion layer to the area of the emitting surface of the light emitting element is not less than 10% and less than 30%.

Description

Specification

Surface light emitter, method for manufacturing surface light emitter, and display device

Technical field

TECHNICAL FIELD [0001] The present invention relates to a surface light emitter and a display device, and more particularly to a surface light emitter provided with a surface light emitter, and the front luminance and luminance uniformity of light emitted from the surface light emitter force are large. The present invention relates to an improved surface light emitter and a display device.

Background art

[0002] In recent years, with the variety of information devices, the need for surface light emitting devices with low power consumption and small volume has increased, and as one of such surface light emitting devices, an electroluminescent device (hereinafter, referred to as an electroluminescent device). It is abbreviated as EL element.)

[0003] Such EL elements are roughly classified into inorganic EL elements and organic EL elements depending on the materials used.

Here, an inorganic EL element generally causes a high electric field to act on a light emitting portion, accelerates electrons in the high electric field and collides with a light emission center, thereby exciting the light emission center to emit light. ing. On the other hand, an organic EL element injects electrons and holes from an electron injection electrode and a 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, and has the advantage that it can be driven at a lower voltage than the inorganic EL element. Therefore, it is expected to be developed as a thin and flexible lighting application by making use of the advantages.

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 the light emitting materials. It is expected to be used as a backlight for liquid crystal display devices.

[0006] When used as illumination, low power consumption is required, and generally brightness of about 501 mZW is desired. However, when a surface light emitting device such as an inorganic or organic EL device emits light, the light emitted inside the light emitting layer having a high refractive index travels in various directions. There is also a lot of light that is totally reflected on the emission surface of the surface light emitting element and confined inside the surface light emitting element. Generally, 20-30% of the light emitted from the surface light emitting element cannot be extracted outside the surface light emitting element. Inorganic EL elements and organic EL elements have high brightness, and the elements are about 30 to 401 mZW, and there was a problem that sufficient brightness could not be obtained!

[0007] In addition, when used as a backlight of a liquid crystal display element or the like, a force that generally requires a front luminance of about 2000 to 4000 cd Zm ² is present, as described above, there is a lot of light confined inside the surface light emitting element, It is difficult to obtain sufficient front luminance. Especially in the case of organic EL elements, in order to obtain a sufficient emission lifetime, the front luminance of about 1000 to 1500 cdZm ² cannot be obtained. There was a problem.

Conventionally, when a surface light emitting device such as an organic EL device emits light, the light confined inside the surface light emitting device is extracted and diffused to the emission surface of the surface light emitting device in order to improve the front luminance. A structure with a structure (see, for example, Patent Documents 1, 2, 3, and 4), or a prism or lens-like sheet that is attached to the surface of the light emitting element so that irregularities appear on the surface. Has been proposed (see, for example, Patent Documents 5, 6, 7, and 8;).

However, as described above, a minute unevenness is provided on the exit surface of the surface light emitting element, or a flat member having an unevenness on the exit surface of the surface light emitting element is provided so that the unevenness appears on the surface. When attached, the light is scattered by unevenness on the surface, and there is still a problem that the front brightness cannot be sufficiently improved. As another means to improve the front brightness of surface light emitting devices such as organic EL light emitting devices, there is a configuration in which a light control sheet with irregularities on the surface is arranged on the light emitting surface, and the prism side faces the light emitting surface. It has been devised (Patent Documents 9 and 10).

Patent Document 1: Japanese Unexamined Patent Publication No. 2000-323272

Patent Document 2: JP 2000-231985

Patent Document 3: Japanese Patent Laid-Open No. 7-162037

Patent Document 4: JP-A-11-111464

Patent Document 5: Japanese Unexamined Patent Publication No. 2005-63926

Patent Document 6: Japanese Patent Laid-Open No. 2003-59641 Patent Document 7: JP-A-6-265888

Patent Document 8: Japanese Patent Laid-Open No. 2005-353431

Patent Document 9: Japanese Patent Laid-Open No. 2000-148032

Patent Document 10: Japanese Patent Application Laid-Open No. 2006-59543

Disclosure of the invention

Problems to be solved by the invention

[0010] As described above, in the configuration in which the light control sheet with the unevenness on the surface is bonded so that the uneven surface side faces the light emitting surface of the surface light emitting element, as a bonding means between the light control sheet and the surface light emitting element Is preferably an adhesive.

[0011] When the prismatic convex portion is bonded to the surface light emitting element with the adhesive, a part of the tip of the convex portion is buried in the adhesive. Since the optical characteristics such as magnification of the front brightness vary depending on the amount of embedding of the convex portion, it is desirable that the amount of embedding in the adhesive is constant.

However, the amount of burying of the prismatic convex portions immediately after bonding tends to be non-uniform due to non-uniformity in the bonding pressure during bonding and uneven thickness of the adhesive. In particular, if an adhesive is to be applied to a light control sheet that has been cut in the same size as the surface light emitting element, when a sufficiently high pressure is applied to the light control sheet and the adhesive, On the other hand, since the force is concentrated near the periphery, the above non-uniformity increases.

[0013] In addition, a phenomenon was observed in which the amount of burying fluctuated when the adhesive interface between the pressure-sensitive adhesive and the convex portion of the light control sheet became familiar and left at room temperature after bonding.

[0014] Further, by leaving it under conditions of high temperature, low temperature and high humidity, stress is applied to the light control sheet due to thermal expansion, thermal contraction, hygroscopic expansion, etc. of the light control sheet, and it is embedded in the adhesive. The phenomenon that the amount changed was observed.

[0015] As described above, fluctuations in the amount of burial of the convex portion of the light control sheet and in-plane unevenness affect optical functions such as normal luminance, resulting in a decrease in luminance and in-plane luminance. It appears as an adverse effect such as unevenness.

Therefore, according to the present invention, in a surface light emitter provided with a surface light emitting element and a display device using the surface light emitter, the extraction efficiency of light emitted from the surface light emitter force and front luminance can be greatly improved without unevenness. Is an issue. Means for solving the problem

[0017] The above object of the present invention is achieved by the following constitution.

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 emission surface of the surface light emitting device. The surface light emitter is in a state in which a part of the tip of the convex portion is buried in the adhesive layer.

2. The surface light emitting device according to 1 above, wherein a ratio of a total area of the convex portion and the adhesive layer bonded to an area of an emission surface of the surface light emitting element is 10% or more and less than 30%. body.

3. The surface light emitter according to 1 or 2 above, wherein the convex portion has a truncated cone shape.

4.Vertical angle Θ force of the convex part of the frustoconical shape When the refractive index of the light control sheet is n, (1 Zn—0.1) <5ίη θ <(1 / η + 0.25) 4. The surface light emitter according to 3 above.

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

6. The method for producing a surface light emitter according to any one of 1 to 4 above, wherein the adhesive layer becomes an adhesive or adhesive force, and the light control sheet is larger than the area of the light emitting surface of the surface light emitting element. A step of applying a sheet-like pressure-sensitive adhesive or adhesive, a step of cutting the light-adjusting sheet to which the pressure-sensitive adhesive or adhesive has been applied, into a size of the emission surface, and a surface light emission of the cut light-controlling sheet. A method of manufacturing a surface light emitter, comprising the step of adhering to an emission surface of an element. The invention's effect

[0018] According to the present invention, a surface light emitter having high luminance and high in-plane luminance uniformity can be obtained. Further, by using such a surface light emitter as a backlight, a bright display device with high uniformity of in-plane luminance can be obtained.

Brief Description of Drawings

FIG. 1 is an example of a light control sheet of the present invention.

FIG. 2 is an example of an embodiment of a surface light emitter of the present invention.

FIG. 3 is a schematic view showing light emission by the surface light emitter according to the present invention.

FIG. 4 is a schematic diagram showing a configuration of a light control sheet, an adhesive layer, and a surface light emitting device according to the present invention. FIG. 5 is a schematic view in which the vicinity of the front end surface of the convex portion of the light control sheet is bonded in a form embedded in an adhesive layer.

FIG. 6 is a schematic view of a light control sheet having a frustum-shaped convex part with a contracted tip side.

Explanation of symbols

[0020] 10A, 10B Light control sheet

11 Translucent substrate

12 Convex

13 Space

14 Output surface

20 Surface light emitting device

21 Transparent substrate

22 Transparent electrode

23 OLED layer

24 Counter electrode

100 adhesive layer

BEST MODE FOR CARRYING OUT THE INVENTION

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

[0022] The surface light emitter of the present invention is 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. The front end portion is in contact with the emission surface of the surface light emitting element via an adhesive layer, and a part of the front end portion of the convex portion is embedded in the adhesive layer.

[0023] Further, the ratio of the total area where the convex portion and the adhesive layer are bonded to the area of the emission surface of the surface light emitting element is 10% or more and less than 30%.

[0024] In the case where a pressure-sensitive adhesive is used for the above-mentioned adhesion, if the convex portion is optically bonded, the tip portion of the convex portion is buried in the pressure-sensitive adhesive. At this time, the variation in the amount of embedding leads to non-uniformity of the front luminance, and there is a disadvantage in that luminance unevenness occurs.

[0025] There are two main causes of non-uniform embedding amounts that cause variations. It is.

[0026] The first variation is a variation in the initial embedding amount due to a sticking pressure at the time of adhesion, uneven film thickness of the adhesive or the adhesive, and the like.

[0027] The second variation is a variation that occurs when the embedding amount changes with time due to aging after being pasted (leaving for a certain period of time), temperature, and humidity.

[0028] As a result of intensive studies on the above-mentioned variation, the present inventors have verified by experiment using a light control sheet having a plurality of prism-shaped convex portions, and found that the amount of embedding of the prism-shaped convex portions varies. On the other hand, the shape of the light control sheet with less fluctuation of the front luminance was found.

[0029] That is, in a surface light emitter in which a light-modulating sheet having a plurality of convex protrusions is in contact with the light emitting surface of the surface light emitting element via an adhesive layer, the light emitting sheet of the surface light emitting element The ratio of the total area where the convex portion and the adhesive layer are bonded to the surface area is 10% or more and less than 30%. It was found that the effect of less fluctuation of the front brightness can be obtained.

[0030] Further, regarding the variation in bonding, when the pressure is applied to the light control sheet with a roller and is attached to the surface light emitting element via an adhesive, the amount of embedding increases especially at the end of the light control sheet. It was confirmed. This seems to be due to the pressure on the center becoming higher due to the concentration of stress at the edge of the dimming sheet due to the elasticity of the roller. In particular, when the area ratio of the bonded portion is 10% or less, the variation of the bonded area due to the pressure difference increases.

[0031] In order to eliminate such inconvenience, the light control sheet having a size larger than the light emitting area of the surface light emitter and the adhesive are first bonded at a high pressure (first pressure), and the peripheral portion is used. It is possible to paste with a uniform burying amount by cutting it to the size of the light emitting area of the surface light emitter so that it does not, and then applying it to the surface of the surface light emitter with a lower pressure (second pressure) than before. I found out.

[0032] 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 without changing the gist thereof. In the light control sheet according to the present invention, as shown in FIGS. 1 (a) and 1 (b), a square pyramid-shaped convex portion 12 whose front end side contracts on one side of a light-transmitting substrate 11 is continuous vertically and horizontally. The light control sheet 10 A formed in this way can be used. In the present 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 light control sheet 10A force increases, as shown in FIG. 1 (b) and FIG. In the examples 2-6, it means that the shape of the bottom dent.

FIG. 2 shows a surface light emitter according to the present invention. The surface light emitting element 20 having the organic EL element power provided with the organic EL layer 23 and the counter electrode 24 is provided on the surface of the transparent substrate 21 provided with the transparent electrode 22, and the light emitted from the surface light emitting element 20 is emitted. The front end surface 12a of the convex portion 12 having a square frustum shape in the light control sheet 10A was adhered to the emission surface 21a of the transparent substrate 21 to be adhered with an adhesive.

[0035] As described above, when the tip surface 12a of the convex portion 12 in the square frustum shape of the light control sheet 10A is adhered to the emission surface 21a of the surface light emitting element 20 with an adhesive, the convex portion of the light control sheet 10A 12 has a shape contracted toward the exit surface 21a of the surface light emitting element 20, and the space 13 between the convex portion 12 of the light control sheet 10A and the exit surface 21a of the surface light emitting element 20 is an air layer. Become.

Then, the surface light emitting element 20 is caused to emit light by adhering the front end surface 12a of the convex portion 12 having a quadrangular pyramid shape in the light control sheet 10A to the emission surface 21a of the surface light emitting element 20 in this way. Then, as shown in FIG. 3, when the light control sheet is not provided, the light totally reflected on the emission surface 21a of the surface light emitting element 20 is converted to the tip surface 12a of the convex portion 12 of the light control sheet 10A. In the part to which is adhered, the light is guided to the light control sheet 10A without being totally reflected.

Then, most of the light guided into the light control sheet 10A in this way is a convex portion that 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 light is reflected on the twelve inclined surfaces 12b, and the reflected light is guided to the emission surface 14 of the light control 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 light control sheet 10A is not attached is emitted from the emission surface 21a in the vertical direction. Although the traveling direction of the light is slightly changed by the inclined surface 12b of the convex portion 12, it is emitted to the front side of the light control sheet 10A, and the convex portion 12 of the light control sheet 10A from the output surface 21a. The light emitted in a direction perpendicular to the inclined surface 12b of the Then, the light is guided into the convex portion 12, reflected by the inclined surface 12b opposite to the convex portion 12, and emitted to the front side of the light control sheet 10A.

[0038] Here, in the case where 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 reflected from the front end surface 12a of the convex portion 12 in this light control. In order to be appropriately guided into the light sheet 10A, the difference between the refractive index of the light control sheet 10A and the refractive index of the exit surface 21a of the surface light emitting element 20 should be within 0.2. Is preferred

[0039] Further, when the convex portion 12 having a square frustum shape is provided on the light control sheet 10A as described above, the apex angle Θ at which the inclined surfaces 12b of the convex portion 12 intersect each other is large, If the inclination angle oc of the inclined surface 12b of the convex portion 12 with respect to the emission surface 21a of the surface light emitting element 20 is too small, the light totally reflected on the emission surface 21a of the surface light emitting element 20 is not obtained when a light control sheet is not provided. Even if the light is guided to the inside of the light control sheet 10A, the light is not applied to the inclined surface 12b of the convex part 12 but is guided to the light output surface 14 of the light control sheet 10A, and the light output on the light output surface 14 of the light control sheet 10A. The light is totally reflected and returned, and the intensity of the light emitted from the emission surface 14 of the light control sheet 10A decreases.

[0040] On the other hand, when the apex angle Θ at which the inclined surfaces 12b intersect each other in the convex portion 12 becomes small, the inclination angle oc 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 force guided into the light control sheet 10A is not reflected by the inclined surface 12b of the convex portion 12, but passes through the convex portion 12 and is guided to the space portion 13. The light passes through the portion 13 and is again guided to the inside of the light control sheet 10A. As described above, the light is totally reflected and returned by the light exit surface 14 of the light control sheet 10A, and the light control sheet. The intensity of light emitted from the exit surface 14 of 10A decreases.

[0041] For this reason, the apex angle Θ at which the inclined surfaces 12b of the convex portion 12 intersect each other is (lZn-0.35) where n is the refractive index for light having a wavelength of 550 nm in the light control sheet 10A. ) <sin 0 <(1 / η + Ο. 3) It is preferable to satisfy the condition (lZn— 0. l) <s ίη θ <(1 / η + Ο. 25) More preferably. A specific apex angle Θ of the convex portion is particularly preferably in the range of 45 degrees or more and less than 55 degrees as a light control sheet for obtaining the effects of the present invention. A portion where the light control sheet 10A is bonded to the emission surface of the surface light emitting element 20 will be described in detail. As shown in FIG. 4, the transparent adhesive layer 100 and the light control sheet 10A are laminated in this order on the light emission surface 21a of the surface light emitting element 20, and the tip surface 12a of the convex portion 12 of the light control sheet 10A and the adhesive layer 100 and the surface are laminated. The light emitting element 20 is configured so as to be in optical contact with the emission surface 21a. Here, the thickness of the adhesive layer is preferably 5 m or more. If it is less than 5 m, sufficient adhesive strength cannot be obtained.

[0043] The height of the prismatic convex portion before the light control sheet is bonded to the surface light emitting element is the height required optically in consideration of the fact that the top portion of the convex portion is buried by bonding. Created higher than h. In order to obtain stable adhesion and sufficient adhesive strength, it is desirable that the depth buried by bonding be 3 μm or more.

[0044] Here, the depth to be buried is measured by the following method.

[0045] First, with the light control sheet adhered to the surface light emitting device, the surface light emitting device is caused to emit light, and the surface light emitter is observed with a microscope from the light control sheet side. At this time, when focusing on the surface of the light control sheet on which the prism-shaped convex portions are formed, the ridge line between the portion where the prism-shaped convex portions are optically bonded and the portion where the prism-shaped convex portions are not bonded is clearly observed. . The adhesion width can be measured by measuring the diameter X of the optically bonded part with a microscope. From the bonding width, the buried depth L can be obtained from the apex angle Θ, pitch p, and prism-like convex height H of the light control sheet in the cross section of the light control sheet.

[0046] L = H— (p—w) Z2 X tan (w Z2— 0 Z2)

As shown in FIG. 5, the vicinity of the front end surface 12a of the convex portion 12 of the light control sheet 10A is bonded in a form embedded in the adhesive layer 100. The height h of the convex portion 12 is obtained by subtracting the burying depth Y shown in FIG. 5 from the height of the convex portion of the light control sheet 10A, and corresponds to the optical height of the convex portion of the light control sheet.

[0047] Regarding the range that the optical height h of the convex portion 12 can take, the above-described apex angle at the convex portion 12 is a force that also varies depending on the pitch p of the convex portion 12. If the typical height h is too low, even if the light totally reflected on the emission surface 21a of the surface light emitting element 20 is not provided with the light control sheet, even if the light is guided into the light control sheet 10A, The light is not applied to the inclined surface 12b of the convex portion 12 but is guided to the exit surface 14 of the light control sheet 10A. The light is totally reflected at the exit surface 14 of the gate 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 is generated on the inclined surface 12b of the convex portion 12, and the surface of the convex portion 12 having the same pitch p is As 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, the amount of light guided into the dimming sheet 10A is reduced. Therefore, it is preferable that the optical height h of the convex portion 12 satisfies the condition of 0.28p≤h≤l.lp with respect to the pitch p of the convex portion 12.

[0048] The surface light emitter according to the present invention has a plurality of convex portions on at least one surface, and the tip portions of the convex portions are in contact with the emission surface of the surface light emitting element via an adhesive layer. A part of the tip is bonded so as to be embedded in the adhesive layer, and the ratio of the total area of the convex portion and the adhesive layer bonded to the area of the emission surface of the surface light emitting element is 10% or more and less than 30%. It is a feature.

[0049] The total area where the convex portion and the adhesive layer are bonded is the width from X where the convex portion of the light control sheet 10A is optically in close contact with the emission surface 21a of the surface light emitting element in FIG. It is defined as the total area of optically effective convex portions obtained by the product of the required optically close area and the total number of convex portions.

[0050] The inventors of the present invention created four types of light control sheets composed of truncated cones having apex angles Θ of the convex portions of 45 degrees, 47 degrees, 50 degrees, and 55 degrees, and measured the front luminance. When the ratio of the optically bonded area to the area of the emission surface of the surface light emitting element is 10% or more and less than 30%, the front luminance is high and the front luminance is high with respect to the fluctuation of the bonding area ratio. We found that there was little fluctuation in Furthermore, as a result of experimenting by changing the bonding area ratio with each light control sheet when the front luminance of the surface light emitting element in the state where the light control sheet is not attached is set to 1, in the light control sheet of V, the apex angle of deviation However, when the adhesion area ratio was 10% to 20%, the front brightness showed almost the highest value. Further, when the adhesion area ratio exceeds 25%, the front luminance gradually decreases, and particularly when the adhesion area ratio exceeds 30%, the front luminance decreases rapidly, and as soon as the present invention has been achieved. It is.

[0051] From the results of this study, in order to obtain a relatively stable front luminance against the variation in the buried depth of the apex of the prism-shaped convex portion, that is, the variation in the adhesion area ratio, the front luminance is high. It was found that the adhesive area ratio of the light control sheet is preferably 10% or more and less than 30%. Furthermore, it is particularly preferable that the adhesive area ratio of the light control sheet is 10% or more and less than 20%, since the front luminance can be almost maximized.

Next, a method for bonding the surface light emitting element and the light control sheet will be described in detail.

[0053] Using the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive and the prismatic convex portion of the light control sheet are first bonded.

[0054] The pressure-sensitive adhesive sheet has a structure in which a pressure-sensitive adhesive of about 25 microns is sandwiched between two separators made of a transparent resin sheet such as PET. It is formed so that the peel strength of one of the two separators is strong and the peel strength of the other separator is weak. The separator with low peel strength is peeled off to expose the pressure-sensitive adhesive, and the pressure-sensitive adhesive and the side of the light control sheet on which the convex portions are formed are sandwiched with a roller or the like and bonded while applying pressure. At this time, bonding is performed while applying the first pressure so that the prismatic convex portion has a predetermined buried depth.

[0055] Next, the light control sheet is cut into a predetermined size according to the light emitting area of the surface light emitter. At this time, the cutting may be performed by pressing all of the light control sheet, the adhesive, and the separator, or only the light control sheet and the adhesive may be cut without cutting the separator. At this time, by cutting so as not to use the end portion of the pasting of the light control sheet and the pressure-sensitive adhesive, a more uniform embedding depth of the prismatic convex portion can be obtained.

[0056] Next, the cut light control sheet and the adhesive are also peeled off from the separator and attached to the surface of the surface light emitting element. Affixing is preferably performed using a roller because bubbles do not enter.

[0057] At this time, the adhering pressure is a pressure at which sufficient adhesion strength is obtained between the surface light emitting element and the adhesive. Also, if the pressure is too high, unevenness will occur in the buried depth of the prism-like convex vertices, so the layers are bonded at a pressure lower than the first pressure (pressure for bonding the light control sheet and adhesive sheet).

[0058] The type of the pressure-sensitive adhesive is not particularly limited, but an acrylic pressure-sensitive adhesive having high transparency is preferably used. A curable pressure-sensitive adhesive that forms a polymer or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded is suitably used. Moreover, you may mix an antistatic agent in an adhesive using a well-known method. Further, instead of the pressure-sensitive adhesive, a UV curable adhesive, a thermosetting adhesive, an anaerobic adhesive, a two-component adhesive, or the like in which an adhesive layer is applied on a substrate may be used. Adhesive material is solid and bonded before curing An adhesive that has strength and that enhances the adhesion after curing is desirable.

[0059] The method for forming the adhesive layer is not particularly limited, and includes general methods such as gravure coater, micro gravure coater, comma coater, percoater, spray coating, and ink jet method.

[0060] As the shape of the light control sheet 10A, the force described by taking the quadruple thruster shown in FIG. 1 as an example, it is possible to take the shape of a triangular frustum, a hexagonal frustum, a frustum, and the like without any limitation.

[0061] For example, as the light control sheet, as shown in FIGS. 6 (a) and 6 (b), the peripheral portion of the truncated cone-shaped convex portion 12 whose front end side contracts on one side of the translucent substrate 11 is cut. It is also preferable to use a light control sheet 10B that is formed into a square shape continuously and vertically and horizontally.

[0062] Here, when the convex portion 12 having a frustum shape is provided like the light control sheet 10B, the front luminance of the light emitted through the light control sheet 10B can be further greatly improved. become. The force that is unknown about this detailed reason According to the study by the present inventors, for example, as shown in FIG. 1, when the convex portion 12 has a quadrangular frustum shape, the apex angle formed by the ridge line in the cross section in the ridge line direction However, since it becomes smaller than the apex angle in the cross section in the alignment direction of the convex part 12 having a square pyramid shape, emitted light that cannot sufficiently contribute to the improvement of the front luminance is generated, In the case of the convex part 12 having the frustum shape, the apex angle is constant in the cross section in any direction, so that it is sufficient to improve the front luminance that occurred in the case of the convex part 12 having the square frustum shape. This is considered to be because no outgoing light that cannot contribute is generated. Therefore, in the present invention, the shape of the convex portion of the light control sheet is preferably a frustum shape like the light control sheet 10B.

[0063] By adhering the light control sheet to the surface light emitting element by the above-described steps, a surface light emitter with small in-plane luminance unevenness can be obtained.

[0064] In the surface light emitter, an organic EL element is used as the surface light emitting element 20. However, the surface light emitting element 20 may be an inorganic EL element or the like as long as it emits light in a planar shape. However, it is particularly effective to use organic EL elements that are expected to greatly improve brightness.

[0065] The surface light emitter of the present invention can be applied to various display devices as a backlight, but it is reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA. Type (P (VA type, MVA type), IPS type, etc. It 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 with a screen of 30-inch or larger, especially 30-54-inch, has the effect of high brightness and high contrast, and an image can be obtained!

Example

[0066] The surface light emitters according to the examples of the present invention are compared with the surface light emitters of the comparative examples. In the surface light emitters according to the examples of the present invention, the extraction efficiency of light emitted from the surface light emitters and It will be explained that the front luminance is greatly improved and a reliable surface light emitter can be obtained. However, the present invention is not limited to these.

[0067] (Example 1)

(Create surface emitter 1)

In accordance with the method for producing a surface light emitter according to the present invention, a surface light emitter was formed by adhering a light control sheet 10B having a truncated cone shape to a surface light emitting element 20 using an adhesive.

As the surface light emitting element 20, the surface light emitting element 20 having the organic EL element force 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. Was used.

Here, the surface light emitting element 20 uses a non-alkali glass having a thickness of 0.7 mm and a size force of Om m X 52 mm as the transparent substrate 21, and the transparent electrode 22 is formed on one side of the transparent substrate 21 as I TO The film was formed to a thickness of 150 nm, patterned into an electrode shape by a photolithography method, and a size of 35 X 46 mm was used. When the resistance of the transparent electrode 22 was measured using a Loresta (manufactured by Mitsubishi Chemical Corporation), it was 20 Ω gloss.

[0070] Next, a hole injection layer having a thickness of 20 nm was formed on the transparent electrode 22 by vacuum evaporation 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, on this hole transport layer, CBP is used as a host material, and Ir (ppy) is contained as a dopant material, and a light emitting material that emits green light so as to contain 6 mass percent.

Three

The light emitting layer having a film thickness of 30 nm was formed by depositing the material by vacuum deposition. On this light emitting layer, BAlq was lOnm deposited by vacuum deposition to form a hole blocking layer. The In addition, on this hole blocking layer, Alq was formed to 40 nm by vacuum deposition to form an electron transport layer.

Three

did. Furthermore, LiF was formed to 0.5 nm by vacuum deposition to form an electron injection layer. A counter electrode 24 having an aluminum force and having a film thickness of lOOnm was formed on the electron injection layer by sputtering. The transparent substrate 21 on the emission surface 21a side of the surface light emitting element 20 had a refractive index of 1.517 with respect to light having a wavelength of 550 nm.

Next, as shown in FIG. 4, a light control sheet 10B in which convex portions 12 each having a truncated cone shape are continuously formed on one surface of the light transmissive substrate 11 is used. The light control sheet 10B was bonded to the emission surface 21a of the surface light emitting element 20 with the convex portion 12 opposed to the emission surface 21a of the surface light emitting element 20. For the bonding, Sekisui Chemical's transparent double-sided tape double tack tape # 5511 was used. The thickness of the adhesive, excluding the substrate, was 25 μm. The light control sheet 10B has a refractive index of 1.50 with respect to light having a wavelength of 550 nm, the apex angle Θ of the frustum-shaped convex part 12 is 45 °, and the height of the convex part 12 is 28 μm, The buried depth in the adhesive layer was 4.1 m, and the pitch of the protrusions 12 was 30 m. The adhesion width X is 10. The ratio of the total area where the convex part and the adhesive layer are bonded to the area of the light emitting surface of the surface light emitting element (referred to as the adhesion area ratio) is 9.1%. there were. The refractive index of the pressure-sensitive adhesive with respect to light having a wavelength of 550 nm was 1.48.

[0072] (Creation of surface light emitters 2 to 29)

The surface emitter 2 is the same as the surface emitter 1 except that the apex angle, pitch, height of the protrusion, buried depth, adhesion width X, and adhesion area ratio are changed as shown in Table 1. Created ~ 29.

It should be noted that the apex angles Θ of the convex portions described in Table 1 are (1 / n- O. I) <sin 0 <(1 / n + O when the refractive index of the light control sheet is n. 25).

[0074] <Evaluation>

The following evaluation was implemented about the obtained surface light emitters 1-29.

[0075] (Front brightness)

The front luminance of the surface light emitter of Example 1 is shown as a relative value when the front luminance of the surface light emitter in a state where the light control sheet 10B is not attached is 1. The measurement is performed using the spectral radiance meter CS-1000 (manufactured by Koyu Minolta Sensing) to measure the emission luminance from the front (2 ° C viewing angle front luminance). [0076] (Luminance unevenness)

Visually determine the brightness unevenness of the entire surface emitter and evaluate it according to the following criteria:

[0077] ○: No luminance unevenness is observed on the entire surface light emitter.

Δ: Brightness unevenness is observed in part of the surface light emitter

: Brightness unevenness is clearly observed on the entire surface light emitter

[0078] [Table 1]

From the above table, it can be seen that the surface light emitter using the light control sheet of the present invention has improved front brightness and further improved brightness unevenness. The bonding area ratio is 10% or more and less than 30%. In the case of surroundings, the front luminance and luminance unevenness are better.

[0080] (Example 2)

Instead of the light control sheet 10B in which the convex part 12 having the truncated cone shape used in Example 1 is continuously formed, the light control sheet 10A in which the convex part 12 in the shape of a quadrangular pyramid is formed is used. In the same manner as in 1, the apex angle, pitch, height of the convex portion, buried depth, adhesion width X, and adhesion area ratio were changed and adhered to the emission surface 21a of the surface light emitting element 20.

The same evaluation as in Example 1 was performed using the obtained surface light emitter, and the surface light emitter of the present invention reproduced the improvement in luminance unevenness. The front luminance was the surface light emitter of Example 1 respectively. It was lower.

[0082] Example 3

The surface light emitters 4, 10, 18, and 24 according to the present invention of Example 1 were prepared by the following procedure.

[0083] (Procedure for creating a surface light emitter)

(1) Using a 60 mm square adhesive sheet, the 60 mm square dimming sheet-shaped convex part and the adhesive were first bonded. As a pressure-sensitive adhesive sheet, Sekisui Chemical's transparent double-sided tape, double tack tape # 5511 was used. The pressure-sensitive adhesive sheet has a structure in which a 25-micron pressure-sensitive adhesive is sandwiched between two separators made of a transparent resin sheet such as PET. It is formed so that the peel strength of one of the two separators is strong and the peel strength of the other separator is weak. The separator with weak peel strength was peeled off to expose the pressure-sensitive adhesive, and the pressure-sensitive adhesive and the light control sheet were sandwiched between rollers and bonded together while being pressurized. At this time, bonding was performed while applying a first pressure so that the convex portion had a predetermined buried depth.

(2) The light control sheet was cut into a predetermined size according to the light emitting area of the surface light emitter. The surface light emitting device had a light emitting area of 35 mm x 46 mm, and the light control sheet was cut so that each side was 37 mm x 48 mm so that each side was 1 mm larger than the light emitting area. At this time, the central partial force of the 60 mm square light control sheet was also completely punched out with a press so that the end portion of the light control sheet and the adhesive was not used.

[0085] (3) The cut light control sheet and the adhesive were also peeled off from the separator and attached to the surface of the surface light emitting device. Affixing was performed using a roller to prevent bubbles and the like from entering. At this time, the adhering pressure is a pressure at which sufficient adhesion strength can be obtained between the surface light emitting element and the adhesive. Do. In addition, if the pressure is too high, unevenness will occur in the buried depth of the prism-like convex and convex vertices, so bonding was performed at a pressure lower than the first pressure (pressure for bonding the light control sheet and adhesive sheet). .

[0086] With respect to the surface light emitters 4, 10, 18, and 24 prepared as described above, the burial depth was observed with a microscope, and it was confirmed that the burial depth of the prismatic convex portions was extremely uniform. . In addition, the variation in front luminance across the entire surface light emitter was extremely small.

[0087] Example 4

The surface light emitter according to the present invention of Example 1 was previously incorporated into a VA-type liquid crystal display device, 15-inch display VL-150SD, manufactured by Fujitsu, and used instead of a backlight. As a result, it was possible to obtain a liquid crystal display device having excellent front luminance.

Claims

The scope of the claims

[1] In a surface light emitter having at least a surface light emitting device 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 portions is an emission surface of the surface light emitting device. The surface light emitter is in a state in which a part of the tip of the convex portion is buried in the adhesive layer.

[2] The ratio of the total area where the convex portion and the adhesive layer are bonded to the area of the emission surface of the surface light emitting element is 10% or more and less than 30%, according to claim 1 The surface light emitter described.

[3] The surface light emitter according to [1] or [2], wherein the convex portion has a truncated cone shape.

[4] The shape of the convex part is a truncated cone, and its apex angle Θ force When the refractive index of the light control sheet is n, (lZn—O. 1) <5ίη θ <(1 / η + The surface light emitter according to claim 3, wherein the surface light emitter is 0.25).

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

[6] The method for manufacturing a surface light emitter according to any one of claims 1 to 4, wherein the adhesive layer is made of an adhesive or an adhesive, and the area of the emission surface of the surface light emitting element. A step of attaching a sheet-like pressure-sensitive adhesive or adhesive to a larger light-control sheet, a step of cutting the light-control sheet on which the pressure-sensitive adhesive or adhesive is affixed, and a size of the cut surface And a step of adhering a light sheet to an emission surface of the surface light emitting element.