JP5141555B2 - Surface light emitter and display device - Google Patents

Description

  The present invention relates to a surface light emitter with high front luminance and a bright display device using the same as a backlight.

  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, an organic EL element excites an organic material by injecting electrons and holes from an electron injection electrode and a hole injection electrode into the light emitting layer, respectively, and combining the injected electrons and holes in the light emitting layer. The organic material emits light when the organic material returns from the excited state to the ground state, and has an advantage that it can be driven at a lower voltage than the inorganic EL element.

  Utilizing the advantage of emitting light on the surface, it is expected to develop as a thin and flexible lighting application.

  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 display devices such as devices.

  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 EL element is caused to emit 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 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.

Here, when used as a backlight of a liquid crystal display element or 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, It is difficult to obtain a sufficient front luminance. 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. Therefore, there is a demand for a solution that provides a light extraction efficiency of 1.3 times or more, a front brightness improvement magnification of 1.6 times or more, and more preferably a front brightness improvement magnification of 2 times or more.

  Conventionally, when a surface light emitting device such as an organic EL device is made to emit light, a diffusion structure is provided on the exit surface of the surface light emitting device in order to extract light confined in the surface and improve the front luminance. There have been proposed ones (for example, see Patent Documents 1 and 2) and those in which prisms or lens-like sheets are attached to the exit surface of the surface light-emitting element so that irregularities appear on the surface (for example, see Patent Documents 2 and 3). ).

  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. However, there is a problem that light is scattered by the unevenness on the surface and the front luminance cannot be sufficiently improved.

  In addition, as another means for improving the front luminance of the surface light emitting element such as an organic EL light emitting device, a light control sheet provided with unevenness on the surface where light is emitted is arranged such that the prism side faces the light emitting surface. A configuration has been devised (see Patent Document 4).

  In the structure in which the concavo-convex surface proposed in Patent Document 4 is directed toward the surface light emitting element and the convex portion is in close contact with the light emitting surface of the surface light emitting element, the characteristics of the surface light emitting element and the structure of the light control sheet are optimized. Since this was not taken into consideration, a sufficient front luminance improvement effect could not be obtained. Therefore, it has been a problem to obtain a further luminance improvement effect by designing the surface light emitting element and the light control sheet.

In particular, white light-emitting elements that emit light of three colors of R, G, and B, or two colors of Y and B vary greatly depending on the wavelength, and the effect of improving the front luminance and improving the light extraction efficiency is greatly improved. Therefore, it has been desired that front luminance and light extraction efficiency be improved at as many emission wavelengths as possible.
JP 2000-323272 A JP 2005-63926 A JP 2005-353431 A JP 2006-59543 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface light emitter with high front luminance and a bright display device using the surface light emitter for a backlight.

  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 device having a transparent substrate and a light control sheet, the light control sheet has a plurality of frustoconical convex portions without gaps , and a tip portion of the convex portion is the surface light emitting device. Embedded in the adhesive layer and in contact with the adhesive layer through the adhesive layer, the convex portion has an apex angle θ and a refractive index n, and the luminance in the front direction in the transparent substrate of the surface light emitting element is I0, Θ ′ = arcsin (n / n ′ × sin θ), where I ′ ′ is the luminance at the angle θ ′ from the front, n ′ is the refractive index of the transparent substrate, and R is the reflectance of the surface light emitting element.
0.7 <R × (Iθ ′ / cos θ ′) / I0
A surface light emitter characterized by the above.

2. 2. The surface light emitter according to 1 above, wherein the adhesive used for the adhesive layer is an adhesive .

  3. 3. A display device using the surface light emitter according to 1 or 2 above.

  According to the present invention, it is possible to provide a surface light emitter with high front luminance and a bright display device using the same as a backlight.

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 a schematic diagram which shows the structure of the brightness | luminance measurement inside a transparent substrate. It is a graph which shows the relationship between U value and the front luminance of a surface light emitting element.

Explanation of symbols

10A, 10B 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 40 Spherical lens 100 Adhesive layer

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

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

  As a light control sheet, as shown in FIGS. 1 (a) and 1 (b), a prism array in which frustum-shaped convex portions 12 whose front end side contracts on one side of a translucent substrate 11 are formed continuously in the vertical and horizontal directions. The sheet 10A was used. In the present specification, the fact that the front end side of the convex portion 12 contracts means that the convex portion 12 is formed so as to gradually decrease as the distance from the prism array sheet 10A increases. In FIG. It is in the shape of a lower dent.

  In this surface light emitter, as shown in FIG. 2, a surface light emitting element comprising an organic EL element in which an organic EL layer 23 and a counter electrode 24 are provided on the surface of a transparent substrate 21 provided with a transparent electrode 22. 20, the tip surface 12a of the convex portion 12 in the prism array sheet 10A is attached to the emission surface 21a of the transparent substrate 21 from which the light emitted from the surface light emitting element 20 is emitted. It was made to adhere with. Here, as the adhesive layer, a UV-curable adhesive, a curable adhesive such as a thermosetting adhesive, or a pressure-sensitive adhesive can be used, but an acrylic adhesive or pressure-sensitive adhesive can be used. A material with excellent transparency is desirable.

  As described above, when the tip surface 12a of the convex portion 12 in the prism array sheet 10A having the truncated cone shape is adhered to the emission surface 21a of the surface light emitting element 20 with the adhesive layer, the convex portion 12 of the prism array sheet 10A is surface-attached. The shape shrinks toward the emission surface 21a of the light emitting element 20, and the space 13 between the convex portion 12 of the prism array sheet 10A and the emission surface 21a of the surface light emitting element 20 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. As shown in FIG. 3, in the case where the light control sheet is not provided, the light totally reflected on the emission surface 21a of the surface light emitting element 20 is applied to the portion where the tip surface 12a of the convex portion 12 of the prism array sheet 10A is bonded. Then, 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 introduced into the prism array sheet 10A from the front end surface 12a of the convex portion 12. In order to be guided appropriately, 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 is preferably within 0.2. Further, it is desirable that the difference in refractive index between the adhesive layer and the prism array sheet 10A is within 0.2. More preferably, the difference between the refractive index of the adhesive layer and the average value of 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 and the refractive index of the adhesive layer is within 0.1. It is desirable.

  Further, when the convex portion 12 having a truncated cone shape is provided on the prism array sheet 10A 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 strike 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 with 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 totally reflected at 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. The light passes again and is guided into 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 of the prism array sheet 10A. The intensity of light emitted from 14 decreases.

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

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 impinged on the inclined surface 12b of the convex portion 12, but is guided to the exit surface 14 of the prism array sheet 10A, and is totally reflected back on the exit surface 14 of the prism array sheet 10A. On the other hand, when 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 obtained. 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, the optical height h of this convex part 12 is with respect to the pitch p of the convex part 12.
0.28p ≦ h ≦ 1.1p
It is preferable to satisfy the following condition.

  A portion where the prism array 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 prism array sheet 10A are laminated in this order on the emission surface 21a of the surface light emitting element 20, and the tip surface 12a of the convex portion 12 of the prism array sheet 10A, 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.

  Adhesives used for the adhesive layer include highly transparent adhesives such as thermosetting acrylic adhesives, UV curable acrylic adhesives, and other highly transparent curable adhesives, and acrylic adhesives. An agent is preferably used. In addition, when the transparent substrate 11 forming the prism array sheet 10A is made of an acrylic resin and the transparent substrate 20 is a glass substrate, the adhesive having a high stress relaxation property is used. An agent is desirable.

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

  In bonding using an adhesive or a pressure-sensitive adhesive, bonding is performed in such a manner that the vicinity of the front end surface 12a of the convex portion 12 of the prism array sheet 10A is buried in the bonding layer 100 as shown in FIG. Since the adhesive layer 100 and the convex portion 12 of the prism array sheet are selected so as to have substantially the same refractive index, the width in which the prism array sheet 10A is optically adhered to the emission surface 21a of the surface light emitting element is 5 is a width corresponding to X. Further, the height of the convex portion 12 is a value obtained by subtracting the embedding depth Y shown in FIG. 5 from the height of the convex portion of the prism array sheet 10A, and the optical height of the convex portion of the optical prism array sheet. It corresponds to.

  The width X, which is optically adhered, can be easily obtained by observing the surface light emitting element in a state in which the prism array sheet 10A is attached to the surface light emitting element 20 and focusing on the attached portion with a microscope. Can be measured.

  In the above description, the circular pedestal shown in FIG. 1 has been described as an example of the shape of the prism array sheet 10A. However, as a shape that enhances light extraction efficiency and front luminance, a square frustum, a triangular frustum, a hexagonal frustum You may use the prism array sheet | seat in which the shape like this was formed continuously vertically and horizontally.

  Next, an embodiment of a surface light emitting device that can increase the light extraction efficiency and the front luminance in combination with the light control sheet described above will be described in detail.

  As described above, the mechanism for improving the front luminance of the light control sheet described in the present invention is the front end surface of the convex portion 12 of the prism array sheet 10 </ b> A that transmits the light beam that is totally reflected in the transparent substrate 21 of the surface light emitting element. This is due to the action of being guided from the vicinity of 12a into the convex portion 12 and being totally reflected by the inclined surface 12b of the convex portion 12 and guided in the front direction.

Here, in more detail, as shown in FIG. 6, the light rays extracted in the front direction, that is, the normal direction of the surface light emitting element, are the same as the light rays just before being totally reflected in the convex portion 12 and the surface light emission. Assuming that the angle formed with the normal line of the element is θ1, θ1 = θ with respect to the apex angle θ of the convex portion 12. Further, if the angle formed between the light ray in the transparent substrate 21 before the same light ray enters the convex portion 12 and the normal of the surface light emitting element is θ2, and the refractive index of the transparent substrate 21 is n2,
n2sinθ2 = nsinθ1 = nsinθ
This relationship holds.

Therefore, from the normal direction of the surface light emitting element, θ2 = arcsin (n / n2sinθ)
It can be seen that the light emitted in the direction of 1 contributes mainly to the front luminance.

  Further, a part of the light beam emitted at the angle θ2 does not enter the convex portion 12 but is totally reflected and confined by the exit surface 21a of the transparent substrate 21, and is projected after being reflected by the counter electrode 24 one or more times. The optical path incident on the part 12 is traced. At this time, when the transparent substrate 21 is a parallel plate, the incident angle of the light incident on the convex portion 12 remains θ2 and does not change.

  Therefore, with respect to the light beam that follows the optical path reflected by the counter electrode 24, the higher the light beam reflectivity when passing through the transparent electrode 22, the organic EL layer 23, and the counter electrode 24, the less loss, and the light can be used.

As a result of further examination through experiments, the reflectance of the surface light emitting element is R, the luminance in the front direction of the surface light emitting element is I0 (cd / m ² ), and the luminance in the θ2 direction inside the transparent substrate 21 is Iθ2 (cd / m). ² )
U = R × (Iθ2 / cos θ2) / I0
It has been found that the larger the value of, the higher the front luminance improvement magnification.

  Here, as shown in FIG. 7, the brightness inside the transparent substrate 21 is measured by using a plano-convex spherical lens 40 having substantially the same refractive index as that of the transparent substrate 21 on the outgoing surface of the transparent substrate 21 and the spherical lens. A matching oil having substantially the same refractive index as 40 was applied and measured. At this time, the radius of curvature of the spherical lens 40 was the same as the thickness D of the transparent substrate 21 and the core thickness of the spherical lens. For the measurement, a spectral luminance meter CS1000 (manufactured by Konica Minolta Sensing) was used, and the luminance was measured while tilting the angle from the front direction.

  Further, the reflectance R was obtained from the light emitting surface side of the surface light emitting element, and the spectral reflectance R (λ) was obtained using a spectral reflection film thickness meter. The product of the emission spectra P (λ) and R (λ) of the surface light emitting element is obtained, and the spectrum P (λ) and P (λ) × R (λ) are integrated in the visible region (420 to 680 nm), and the ratio Was defined as reflectance R.

  Based on the above definition, the value of U was measured while changing the configuration of the surface light emitting element, and the improvement factor of the front luminance was measured, and the result of FIG. 8 was obtained.

  The larger the value of U is, the higher the front luminance improvement magnification is. However, when the value is 0.7 or more, the front luminance improvement magnification is 1.6 or more, and it can be seen that a sufficient effect can be obtained. It was.

  Further, when the value of U is 0.9 or more, the improvement factor of the front luminance becomes 2 times or more, and it was found that this is a more desirable combination.

  At this time, in order to obtain a desired U value, it is desirable that the spectral reflectance of the light emitting element is high, and the reflectance R is desirably 70% or more. Moreover, it is more desirable that it is 85% or more.

  In order to obtain a high spectral reflectance, it is desirable to use a material having a high reflectance such as aluminum or silver as the material of the counter electrode. Further, it is desirable that the organic layer forming the light emitting layer has a high transmittance. Further, it is desirable to use a transparent electrode material having a high transmittance such as ITO.

  A light-emitting element having a high ratio (Iθ2 / cos θ2) / I0 can be achieved by setting the film thickness of the organic layer and the film thickness of ITO within a preferable range. In particular, the ratio depends on the distance from the counter electrode to the light emission position (the position of the point where electrons and holes combine to emit light in the organic layer), and the light emission wavelength λ is from the counter electrode to the light emission position. When the distance is x1 and the refractive index of the organic layer is n1, it is more desirable that x1 × d1 is set to a value close to 1 / 4λ and further larger so that the ratio becomes 1 or more.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example [Production of surface light emitter 1]
According to the method for producing a surface light emitter of the present invention, a surface light emitter was produced 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 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.

(Production of surface light emitting device A)
Here, the surface light emitting element 20 uses non-alkali glass having a thickness of 0.7 mm and a size of 40 mm × 52 mm as the transparent substrate 21, and ITO is formed to a thickness of 110 nm as a transparent electrode 22 on one side of the transparent substrate 21. A film was formed and patterned into an electrode shape by a photolithography method to obtain a size of 35 × 46 mm.

Next, a hole injection layer having a film thickness of 100 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, on the hole injection layer, α-NPD was used as a hole transport material, and a hole transport layer having a thickness of 10 nm was formed by a vacuum deposition method. 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 included as a dopant material in an amount of 6% by mass. A light emitting layer having a thickness of 20 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 the hole blocking layer, Alq ₃ was formed to have a thickness of 55 nm by vacuum deposition to form an electron transport layer. Furthermore, 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.

(Preparation of light control sheet A)
Next, as shown in FIG. 4, using the light control sheet 10A in which convex portions 12 having a truncated cone shape are continuously formed on one surface of the light-transmitting substrate 11, the convex portions 12 of the light control sheet 10A are used. The light control sheet 10A was bonded to the emission surface 21a of the surface light emitting device 20 so that the surface light emitting device 21 was opposed to the emission surface 21a of the surface light emitting device 20, and the surface light emitter 1 was produced.

  Sekisui Chemical's transparent double-sided tape double tack tape # 5511 was used for adhesion. The thickness of the adhesive excluding the substrate was 25 μm. The light control sheet 10A 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 portion 12 is 50 °, the height of the convex portion 12 is 25 μm, and the convex portion. The pitch of 12 was 30 μm. The adhesion width X was 10 μm. Moreover, the refractive index with respect to the light of wavelength 550nm of an adhesive was 1.48.

[Production of surface light emitter 2]
A surface light emitter 2 was produced using the same light control sheet A as the surface light emitter 1. A surface light emitting device was manufactured as shown below.

(Production of surface light emitting element B)
The transparent substrate and the ITO film were formed in the same manner as the surface light emitting device A.

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, on the hole injection layer, α-NPD was used as a hole transport material, and a hole transport layer having a thickness of 20 nm was formed by a vacuum deposition method. 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 included as a dopant material in an amount of 6% by mass. 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. Furthermore, on this hole blocking layer, Alq ₃ was formed to 40 nm by vacuum deposition to form an electron transport layer. Furthermore, 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.

  As described above, the surface light emitter 2 was produced by bonding the light control sheet A to the produced surface light emitter B in the same manner as the surface light emitter 1. The adhesion width X was 10 μm.

[Production of surface light emitter 3]
A surface light emitter was produced using the same light control sheet A as the surface light emitter 1. A surface light emitting device was manufactured as shown below.

(Production of surface light emitting element C)
The transparent substrate and the ITO film were formed in the same manner as the surface light emitting device A.

Next, a hole injection layer having a film thickness of 110 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, on the hole injection layer, α-NPD was used as a hole transport material, and a hole transport layer having a film thickness of 15 nm was formed by a vacuum deposition method. 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 included as a dopant material in an amount of 6% by mass. A light emitting layer having a thickness of 20 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 a thickness of 60 nm by vacuum deposition to form an electron transport layer. Furthermore, 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.

  As described above, the surface light emitter 3 was produced by bonding the light control sheet A to the produced surface light emitter C in the same manner as the surface light emitter 1. The adhesion width X was 10 μm.

[Production of surface light emitter 4]
A surface light emitter was produced using the same light control sheet A as the surface light emitter 1. A surface light emitting device was manufactured as shown below.

(Production of surface light emitting element D)
The transparent substrate and the ITO film were formed in the same manner as the surface light emitting device A.

Next, a hole injection layer having a film thickness of 85 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, on the hole injection layer, α-NPD was used as a hole transport material, and a hole transport layer having a thickness of 10 nm was formed by a vacuum deposition method. 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 included as a dopant material in an amount of 6% by mass. A light emitting layer having a thickness of 20 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 the hole blocking layer, Alq ₃ was formed to 45 nm by vacuum deposition to form an electron transport layer. Furthermore, 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.

As described above, the surface light emitter 4 was produced by bonding the light control sheet A to the produced surface light emitting element D in the same manner as the surface light emitter 1. The adhesion width X was 10 μm.
(Production of surface light emitting element E)
The transparent substrate and the ITO film were formed in the same manner as the surface light emitting device A.
Next, a hole injection layer having a film thickness of 40 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, α-NPD was formed to a thickness of 10 nm as a hole transport layer. Next, a luminescent material that emits blue light is co-evaporated on the hole transport layer so that the compound (1) is used as a host material and BD-1 is included as a dopant material in an amount of 3% by mass. The light emitting layer 1 was formed. Subsequently, the compound (2) was formed as an intermediate layer 1 with a film thickness of 5 nm by vapor deposition. Next, a light-emitting material that emits red light is co-evaporated on the intermediate layer 1 so that the compound (1) is used as a host material and Ir-9 is included as a dopant material in an amount of 8% by mass. Layer 2 was formed. Subsequently, the compound (1) was formed as the intermediate layer 2 with a film thickness of 3 nm by vapor deposition. Next, a light-emitting material that emits green light is co-evaporated on the intermediate layer 2 so that the compound (1) is used as a host material and Ir-1 is included as a dopant material in an amount of 5% by mass. Layer 3 was formed.
Further, a hole blocking layer made of BAlq was formed to 5 nm by vapor deposition, and then an electron transport layer having a ratio of BCP 75% and Cs 25% was provided with a thickness of 70 nm. Furthermore, 100 nm of aluminum was vapor-deposited to form a cathode, and a surface light emitting device E was produced. 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.

As described above, the surface light emitter 9 was manufactured by bonding the light control sheet A to the manufactured surface light emitting element E in the same manner as the surface light emitter 1. The adhesion width X was 10 μm.
(Production of surface light emitting element F)
The transparent substrate and the ITO film were formed in the same manner as the surface light emitting device A.
Next, a hole injection layer having a film thickness of 40 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, α-NPD was formed to a thickness of 10 nm as a hole transport layer. Next, a luminescent material that emits blue light is co-evaporated on the hole transport layer so that the compound (1) is used as a host material and BD-1 is included as a dopant material in an amount of 3% by mass. The light emitting layer 1 was formed. Subsequently, the compound (2) was formed as an intermediate layer 1 with a film thickness of 5 nm by vapor deposition. Next, a light-emitting material that emits red light is co-evaporated on the intermediate layer 1 so that the compound (1) is used as a host material and Ir-9 is included as a dopant material in an amount of 8% by mass. Layer 2 was formed. Subsequently, the compound (1) was formed as the intermediate layer 2 with a film thickness of 3 nm by vapor deposition. Next, a light-emitting material that emits green light is co-evaporated on the intermediate layer 2 so that the compound (1) is used as a host material and Ir-1 is included as a dopant material in an amount of 5% by mass. Layer 3 was formed.
Further, a hole blocking layer made of BAlq was formed to 5 nm by vapor deposition, and then an electron transport layer having a ratio of BCP of 75% and Cs of 25% was provided with a thickness of 50 nm. Furthermore, 100 nm of aluminum was vapor-deposited to form a cathode, and a surface light emitting device E was produced. 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.

As described above, the light control sheet A was adhered to the manufactured surface light emitting element F in the same manner as the surface light emitter 1, and the surface light emitter 10 was manufactured. The adhesion width X was 10 μm.
(Production of surface light emitting element G)
The transparent substrate and the ITO film were formed in the same manner as the surface light emitting device A.
Next, a hole injection layer having a film thickness of 40 nm was formed on the transparent electrode 22 by vacuum deposition using m-MTDATA as a hole injection material. Next, α-NPD was formed to a thickness of 10 nm as a hole transport layer. Next, a luminescent material that emits blue light is co-evaporated on the hole transport layer so that the compound (1) is used as a host material and BD-1 is included as a dopant material in an amount of 3% by mass. The light emitting layer 1 was formed. Subsequently, the compound (2) was formed as an intermediate layer 1 with a film thickness of 5 nm by vapor deposition. Next, a light-emitting material that emits red light is co-evaporated on the intermediate layer 1 so that the compound (1) is used as a host material and Ir-9 is included as a dopant material in an amount of 8% by mass. Layer 2 was formed. Subsequently, the compound (1) was formed as the intermediate layer 2 with a film thickness of 3 nm by vapor deposition. Next, a light-emitting material that emits green light is co-evaporated on the intermediate layer 2 so that the compound (1) is used as a host material and Ir-1 is included as a dopant material in an amount of 5% by mass. Layer 3 was formed.
Further, a hole blocking layer made of BAlq was formed to 5 nm by vapor deposition, and then an electron transport layer having a ratio of BCP of 75% and Cs of 25% was provided with a thickness of 30 nm. Furthermore, 100 nm of aluminum was vapor-deposited to form a cathode, and a surface light emitting element G was produced. 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.

  As described above, the surface light emitter 11 was produced by bonding the light control sheet A to the produced surface light emitting element G in the same manner as the surface light emitter 1. The adhesion width X was 10 μm.

[Production of surface light emitters 5 to 8 and 12 to 14]
Using the same surface light emitting elements A to D and E to G as the surface light emitters 1 to 4 and 9 to 11, surface light emitters 5 to 8 and 12 to 14 were prepared by attaching a light control sheet B described below. .

(Preparation of light control sheet B)
Next, as shown in FIG. 4, using the light control sheet 10A in which convex portions 12 having a truncated cone shape are continuously formed on one surface of the light-transmitting substrate 11, the convex portions 12 of the light control sheet 10A are used. The light control sheet 10A was bonded to the emission surface 21a of the surface light emitting element 20 so as to face the emission surface 21a of the surface light emitting element 20, and surface light emitters 5-8 and 12-14 were produced.

  Sekisui Chemical's transparent double-sided tape double tack tape # 5511 was used for adhesion. The thickness of the adhesive excluding the substrate was 25 μm. The light control sheet 10A 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 portion 12 is 55 °, the height of the convex portion 12 is 25 μm, and the convex portion. The pitch of 12 was 30 μm. The adhesion width X was 11 μm. Moreover, the refractive index with respect to the light of wavelength 550nm of an adhesive was 1.48.

[Evaluation of surface emitter]
The produced surface light emitter was evaluated in the following manner.

(Front brightness)
Using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing), emission luminance from the front (2 ° viewing angle front luminance) was measured. The front luminance is expressed as a relative value where the front luminance of the surface light emitting element in a state where the light control sheets A and B are not attached is 1.

(Measurement of brightness inside transparent substrate)
With the configuration shown in FIG. 7, a spherical lens was pasted with matching oil, and the luminance I0 was measured from the front direction. Next, the luminance Iθ ′ was measured by tilting the surface light emitting element by 50 degrees with the spherical lens attached with matching oil.

(Measurement of reflectance R)
Spectral reflectance R (λ) was measured from the exit surface side of the surface light emitting device using a reflective spectral film thickness meter. Next, the spectrum P (λ) and the value obtained by multiplying P (λ) by the spectral reflectance R (λ) were integrated in the visible region (wavelength 420 nm to 680 nm). The ratio of the integrated value was defined as the reflectance R of the surface light emitting element.

  The results of evaluation are shown in Tables 1 and 2.

  The correlation between the U value in Tables 1 and 2 and the front luminance is shown in a graph in FIG.

  From Table 1, Table 2, and FIG. 8, when the value of U exceeds 0.7, a value exceeding 1.6 times is obtained as the front luminance, and it was confirmed that a sufficient effect can be obtained. .

  Further, when the value of U exceeded 0.9, a value exceeding twice as large as the front luminance was obtained, and it was confirmed that it was more desirable.

Claims (3)

In a surface light emitter having at least a surface light emitting device having a transparent substrate and a light control sheet, the light control sheet has a plurality of frustoconical convex portions without gaps , and a tip portion of the convex portion is the surface light emitting device. Embedded in the adhesive layer and in contact with the adhesive layer through the adhesive layer, the convex portion has an apex angle θ and a refractive index n, and the luminance in the front direction in the transparent substrate of the surface light emitting element is I0, Θ ′ = arcsin (n / n ′ × sin θ), where I ′ ′ is the luminance at the angle θ ′ from the front, n ′ is the refractive index of the transparent substrate, and R is the reflectance of the surface light emitting element.
0.7 <R × (Iθ ′ / cos θ ′) / I0
A surface light emitter characterized by the above. The surface light emitter according to claim 1, wherein the adhesive used for the adhesive layer is a pressure-sensitive adhesive.   A display device using the surface light emitter according to claim 1 or 2.