JP2007207471A - Surface emitter and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To greatly enhance front luminance of light emitted from a surface emitter equipped with a surface light emitting element. <P>SOLUTION: This surface emitter is equipped with the surface light emitting element on the surface of the light emitting side of which a diffraction grating is formed, and a light control sheet having regular projecting and recessed parts on its one side, and this surface emitter makes light deflected by the diffraction grating diffract frontward by the light control sheet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface light emitter including a surface light emitting element and a display device.

  In recent years, with the diversification of information equipment, the need for surface light emitting devices with low power consumption and small volume has increased, and as such surface light emitting devices, surface light emitting devices such as organic electroluminescent devices and inorganic electroluminescent devices. Exists. However, it is known that such a surface light emitting element does not have a high ratio of emitted light into the air. The reason will be described by taking an organic electroluminescence element as an example.

  A schematic diagram of the structure of the organic electroluminescence element is shown in FIG. In the bottom emission type organic electroluminescence element 100, a transparent electrode 102, an organic layer 103, and a metal electrode 104 are sequentially laminated on a surface of the transparent substrate 101 opposite to the light emitting side surface, and the organic layer 103 has a light emitting layer. It is included. Light emitted from the organic layer 103 passes through the transparent electrode 102 and the transparent substrate 101 and is emitted into the air.

  Due to the difference in refractive index between the transparent electrode 102 and the transparent substrate 101, the light emitted from the organic layer 103 undergoes total reflection when reaching the interface between the transparent electrode 102 and the transparent substrate 101, and cannot enter the transparent substrate. Similarly, light reaching the interface between the transparent substrate 101 and the air at an angle greater than the critical angle causes total reflection, and cannot be extracted outside. Therefore, in general, in a surface light emitting device such as an organic electroluminescence device, 20 to 30% of light generated in the light emitting layer is confined to a transparent substrate, and 40% to 60% is confined to a transparent electrode or an organic layer. It is said that only the remaining 20-30% can be taken out into the air. Therefore, in the surface light emitting element, it is an important item to effectively use the light emitted from the light emitting layer.

  One means for effectively using light emitted from the light emitting layer is to extract light confined inside the element by total reflection (to improve light extraction efficiency). In the organic electroluminescence element described in Patent Document 1, a transmission-type fine uneven structure having a specific shape is provided on the light-emitting side surface of the light-emitting element, that is, the light extraction surface that is an interface between the light-emitting surface of the light-emitting element and the atmosphere, Due to the diffraction phenomenon of the structure, the light confined in the transparent substrate by total reflection is extracted, and the light extraction efficiency is improved.

  Another means for effectively using the light emitted from the light emitting layer includes condensing the emitted light to improve the luminance in a specific direction. In Patent Document 2, a light extraction sheet in which a plurality of first protrusions having a triangular cross section with respect to the light extraction surface are provided on the light extraction side of the organic EL device, and the light extraction sheet is provided on the light extraction sheet. It has been proposed to provide a light incident surface set substantially parallel to the surface and a prism sheet having a plurality of second convex portions having a triangular cross section convex to the light incident surface on the light exit side. In the device described in Patent Document 2, the incident angle light is incident on the slope of the convex portion provided on the light extraction sheet by causing the incident angle light that has been totally reflected in the conventional organic EL device to be greater than the critical angle. The light is extracted to the outside by refraction (improves the light extraction efficiency), and the light that travels in the oblique direction out of the light extracted by the light extraction sheet is incident on the slope of the convex portion of the prism sheet. It is said that the brightness in the front direction is improved by collecting (condensing) light in the direction perpendicular to the light emitting surface (front direction).

Furthermore, as another means for improving the light extraction efficiency, in Patent Document 3, a diffuser (volume diffuser, surface diffusion) in which fine particles having a refractive index different from that of the film are added to the light extraction surface of the light emitter. It has been proposed to provide a container. As a result, the light incident on the light extraction surface at an angle that is totally totally reflected hits the particles in the diffuser, and the angle is changed by being scattered, and light is extracted by taking out the light converted to an angle that does not cause total reflection. The extraction efficiency is improved.
JP 2004-3221 A JP 2005-63926 A JP-T-2004-513484

  However, in the organic electroluminescence element described in Patent Document 1, even if all of the light in the transparent substrate is taken out from the location and the ratio of the light of the element, the efficiency is about twice. Even in the experimental example, only 1.5 times the efficiency can be obtained.

  In addition, when light extraction is performed using refraction as in the light emitting device described in Patent Document 2, the light emitted in the front direction from the light emitting layer in the conventional organic EL device can be directly extracted into the air. On the contrary, there is a problem that the light emitted from the light emitting layer in the front direction is totally reflected and cannot be used. That is, even if some of the light generated in the light emitting layer can be extracted in a diagonal direction, the extraction of outgoing light in the front direction is hindered, and the efficiency cannot be improved sufficiently.

  Furthermore, in Patent Document 3, the problems in Documents 1 and 2 are unlikely to occur. However, since the optical path of light is changed by randomly added particles, there is no wavelength selectivity and it is not suitable for particularly increasing the luminance of a specific wavelength. is there.

  Thus, in the conventional surface light emitter, the effect is not yet sufficient in that light is effectively used and the luminance of light of a specific wavelength, particularly in the front direction, is improved.

  Accordingly, an object of the present invention is to more easily and effectively use light of a specific wavelength intended to be generated in a surface light emitting device, and particularly to improve the brightness in the front direction as compared with a conventional device. An object of the present invention is to provide a light emitter and a display device using the same.

  The inventor conducted extensive research and was able to solve the above problems with any of the configurations described below.

1.
A surface light-emitting element having a diffraction grating formed on the surface on the light emitting side, and a light control sheet having regular irregularities on at least one side arranged to face the diffraction grating through a space,
The diffraction grating biases the direction of light emitted from the surface light emitting element in a predetermined direction different from a direction perpendicular to the light emitting surface of the surface light emitting element by diffraction, and the light control sheet includes the diffraction light A surface light emitter that emits, in a direction perpendicular to the light emitting surface, refraction of light that is strongly emitted out of the light that is biased by a grating.

2.
2. The surface light emitter according to 1, wherein a period of the diffraction grating is 1 to 10 times a wavelength of light to be diffracted.

3.
3. The surface light emitter according to 1 or 2, wherein the diffraction grating has unit gratings periodically and two-dimensionally arranged.

4).
4. The surface light emitter according to claim 1, wherein the diffraction grating and the light control sheet have the same rotational symmetry. 5.

5).
The surface light emitter according to any one of claims 1 to 4, wherein the unit cell includes a substantially prismatic or substantially cylindrical structure.

6).
The surface light emitter according to any one of claims 1 to 4, wherein the unit cell includes a substantially pyramid or substantially conical structure.

7).
The surface light emitter according to any one of claims 1 to 6, wherein the light control sheet is a laminate of a plurality of sheets.

8).
The surface light emitter according to any one of 1 to 7, wherein the light control sheet has regular irregularities with a period of 10 μm or more and 1 mm or less on any one surface.

9.
A display device comprising: a display element; and the surface light emitter according to any one of 1 to 8, wherein the surface light emitter is used as a backlight of the display element.

10.
9. A display device comprising the surface light emitter according to any one of 1 to 8, wherein the surface light emitting elements constituting the surface light emitter include a plurality of pixels arranged in a matrix in a planar shape. .

  According to the present invention, a surface light emitting device having a diffraction grating formed on the surface on the light emitting side, a light control sheet having regular irregularities on at least one surface disposed so as to face the diffraction grating through a space, The diffraction grating biases the direction of the light emitted from the light emitting element in a predetermined direction different from the direction perpendicular to the light emitting surface of the light emitting element by diffracting, Of the light deflected by the diffraction grating, by using a surface light emitter that emits light in the direction of intense emission in a direction perpendicular to the light emitting surface by refraction, the surface light emitting element has a specific wavelength intended. Light can be used more easily and effectively, and in particular, the brightness in the front direction can be significantly improved compared to conventional elements.

  Next, 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 a range not changing the gist thereof.

(First embodiment)
The configuration of the surface light emitter 20 according to the first embodiment of the present invention will be described below. FIG. 2 shows the configuration used in the first embodiment, in which a diffraction grating 202 is formed on the light emitting side surface of a light emitting element 201 having a light emitting layer having a surface emission function. The diffraction grating 202 has a structure in which cylinders are periodically arranged two-dimensionally. Further, on the diffraction grating 202, a light control sheet 203 having a periodic triangular roof structure on the light emission side surface is disposed so as to face each other through a space, and further on the light control sheet, A light control sheet 204 having a periodic triangular roof structure on the light emission side surface is disposed so as to face each other through a space such that the directions of the light control sheet and the triangular roof structure are substantially orthogonal to each other.

Here, the reason why the front luminance of the device is remarkably improved in this embodiment will be described. First, light emitted from the light emitting layer reaches the diffraction grating 202. For the sake of simplicity, the effect of the diffraction grating will be described by taking a one-dimensional diffraction grating as an example. For example, the incident light as shown in FIG. 3 and the light diffracted in the θ direction by a certain diffraction grating and the next diffraction grating θ When the optical path difference of the light diffracted in the direction becomes an integral multiple of the wavelength λn of the incident light, the light emitted in that direction is strengthened by interference. In particular, in the case of FIG. 3, the relationship between the direction θ of the strengthening light, the period d of the diffraction grating, and the wavelength λn of the incident light is
(1-cos θ) d = N · λn (N is a natural number) (1)
It is expressed by the following formula. As a result, the alignment characteristics of the light passing through the diffraction grating are biased in a specific direction. The direction in which the orientation characteristic is biased can be easily obtained from the period and refractive index of the diffraction grating and the wavelength of the light emitted into the air as shown in the above formula. On the contrary, in the element design, when it is desired to bias the orientation characteristics of a specific wavelength in the intended direction, the wavelength of light emitted into the air is determined by the design, and the refractive index of the diffraction grating is also determined by the material of the diffraction grating. Therefore, it is possible to easily bias the orientation characteristics in the intended direction by changing the period of the diffraction grating.

  Here, biasing the orientation characteristic means biasing emitted light in a specific direction, and the same applies hereinafter.

  Therefore, a device having a dimming function intended as compared with a device using random diffusion such as the diffuser of Patent Document 3 can be easily obtained, and the wavelength of light to be extracted can be easily controlled. In addition, since this diffraction phenomenon occurs with respect to light incident from various directions, the conventional surface light emitting device can also extract light incident at an angle that has been totally reflected. Therefore, the light extraction efficiency is also improved. Furthermore, since the light deflected in a specific direction by diffraction is refracted in the front direction, the light traveling in a certain direction can be extracted instead of the device of Patent Document 2 using light extraction by refraction. In principle, it does not occur that the light traveling in the direction cannot be extracted. Therefore, the light extraction efficiency can be improved as compared with light extraction by refraction. In this way, the light that has passed through the diffraction grating 202 has improved light utilization efficiency due to the diffraction grating, and the orientation characteristics are biased in a specific direction. Therefore, the intensity of light in the direction in which the orientation characteristics are biased is very high. growing. When a diffraction grating having a structure as shown in FIG. 2 is used, the intensity of light emitted in four directions having four-fold symmetry increases as shown in FIGS. 4 (a) and 4 (b).

  Next, the light that has passed through the diffraction grating 202 reaches the light control sheet 203 provided on the diffraction grating 202. As shown in FIG. 5, the light control sheet 203 applies light incident in an oblique direction to a slope of a triangular roof structure provided on the light emission side surface and refracts the light, thereby changing the light traveling direction. . For this reason, when light that has passed through the diffraction grating 202 and whose orientation characteristics are biased in four directions enters the light control sheet 203, the light control sheet 203 has a one-dimensional periodic structure, and the roof has two directions. Therefore, as shown in FIG. 6, two directions of light in four directions are emitted in the same direction, and the orientation characteristics are biased in two directions. At this time, since the two directions of light in the two directions are condensed, the intensity in each direction is greater than that before passing through the light control sheet.

  The light finally reaching the light control sheet 204 is converted in the light traveling direction by the light control sheet in the same manner as before. At this time, since the light control sheet 204 is disposed so that the direction of the triangular roof structure is substantially orthogonal to the light control sheet 203, the effect of changing the direction of light is 90 ° different from that of the light control sheet 203. As a result, the light whose orientation characteristics are biased in two directions by the light control sheet 203 is changed in the front direction by the light control sheet 204 as shown in FIG. At this time, since the light in two directions is condensed, the intensity thereof further increases. As a result, the luminance in the front direction is significantly improved.

  The regular unevenness used in the light control sheet is not limited to the triangular roof structure, but may be any shape that can change light whose orientation characteristics are biased by refraction in the front direction. Moreover, as for the period of the unevenness | corrugation of this light control sheet, 10 micrometers or more and 1 mm or less are preferable. Since the light emission wavelength of the light emitting element used in the present embodiment is assumed to be in the visible range, if it is 10 μm or less, the period of unevenness becomes about ten times the light emission wavelength, and a diffraction phenomenon starts to occur in the light control sheet, which is not preferable. On the other hand, when the thickness is 1 mm or more, the size of the surface light emitter itself is increased, which is not preferable in terms of size reduction, weight reduction, and thickness reduction.

(Second Embodiment)
Next, the structure of the surface light emitter 30 according to the second embodiment will be described. FIG. 8 shows the configuration used in the second embodiment. A diffraction grating 302 is formed on a light emitting side surface of a light emitting element 301 having a light emitting layer having a surface emitting function. The diffraction grating has a structure in which cylinders are periodically arranged two-dimensionally. On the diffraction grating, a light control sheet 303 having a periodic quadrangular pyramid structure on the light emitting side surface is disposed so as to face each other through a space. Here, the behavior of the light until it enters the light control sheet 303 is the same as that in the first embodiment, and is omitted. Here, the light control sheet 303 has the effect of changing the direction of the emitted light in the same manner as the light control sheet having the triangular roof structure used in the first embodiment. It has a dimensional square pyramid structure, and slopes exist in four directions. Accordingly, when the light control sheet 303 is used as shown in FIG. 9, the traveling direction of light whose orientation characteristics are biased in four directions by the diffraction grating 302 can be converted to the front direction at a time. Also at this time, since the emitted light is collected in four directions, its intensity becomes very large.

  Next, details of each component will be described.

  The light emitting element may be an element having a surface light emitting function such as an organic electroluminescence element or an inorganic electroluminescence element.

  The shape of the diffraction grating may be a shape in which unit gratings are periodically arranged in a one-dimensional manner, but is preferably a shape in which unit gratings are periodically arranged in a two-dimensional manner. This is because the light emitter emits light two-dimensionally, so that light can be extracted more efficiently when the unit cells are periodically arranged two-dimensionally. For example, a shape in which cones and cylinders, pyramids and prisms are arranged in a square lattice shape, and a shape in which cones, cylinders, pyramids and prisms are arranged in a triangular lattice shape are conceivable.

  The period of the periodic structure of the diffraction grating is preferably 1 to 10 times the wavelength of the light to be diffracted. This is because the period in which the effect of diffraction rather than refraction is obtained is approximately in the above range. More preferably, the period of the periodic structure of the diffraction grating is 1 to 2 times the wavelength of light to be diffracted. This is because when the diffraction phenomenon occurs, high-order diffracted light is not generated, so that the light control sheet described later can be designed only for the first-order diffracted light, which simplifies the design. .

  The diffraction grating may be formed using a conventional fine processing process such as dry etching or imprinting on the light emitting side surface of the light emitting element. In addition, a film or a substrate on which a diffraction grating is formed may be bonded to the surface of the light emitter with an adhesive tape or a curable resin. However, when bonding, the refractive index of the material forming the diffraction grating is preferably within ± 0.5 with respect to the refractive index of the material on the light emitting side surface of the light emitter. More preferably, the refractive index of the material forming the diffraction grating is within ± 0.1 with respect to the refractive index of the material on the light emitting side surface of the light emitter. Moreover, it is preferable not to leave bubbles on the bonding surface. This is because if there are portions having different refractive indexes, light that cannot be extracted into the air is generated due to total reflection.

  The distance between the diffraction grating and the light control sheet is preferably 1 to 200 μm, more preferably 1 to 10 μm. This is because even light emitted from the vicinity of the end face of the diffraction grating toward the outside of the element is incident on the light control sheet as much as possible.

  The unevenness of the light control sheet is, for example, a shape in which a triangular roof is periodically provided on one side, a shape in which a quadrangular pyramid or a triangular pyramid is provided periodically on one side, and the apex angle of a quadrangular pyramid or a triangular pyramid on one side For example, a shape in which a structure having a rounded shape is provided periodically. Further, a light control sheet may be placed on the light control sheet via a space. In this case, the distance between the light control sheets is preferably 1 to 200 μm, and more preferably 1 to 10 μm, similarly to the distance between the diffraction grating and the light control sheet.

  Regarding the correspondence between the diffraction grating and the light control sheet, it is preferable that the diffraction grating and the light control sheet have the same rotational symmetry. This is because, for example, the diffraction grating used in the description of the embodiment has a four-fold symmetry, and in this case, the orientation characteristics of light that has passed through the diffraction grating are biased in four directions reflecting the four-fold symmetry. On the other hand, the light control sheet having the quadrangular pyramid structure used in the second embodiment also has fourfold symmetry, and in this case, light in four directions can be collected. Therefore, when the diffraction grating and the light control sheet have the same rotational symmetry, the direction in which the orientation characteristics are biased can coincide with the direction in which light can be collected, and thus the front luminance can be improved very efficiently.

  In addition, the light control sheet is simulated by using a plurality of sheets in a manner similar to the case where light in four directions is collected using the light control sheet having two-fold symmetry in a substantially orthogonal manner in the first embodiment. The same rotational symmetry as that of the diffraction grating may be realized. Of course, the rotational symmetry may be replaced with other symmetries such as 2-fold symmetry and 6-fold symmetry other than the 4-fold symmetry.

  Further, in the present invention, among the light whose orientation characteristics are biased by the diffraction grating, it is characterized in that the light in the direction of intense emission is collected in the front direction by the light control sheet. Can be done as follows. First, the wavelength of light to be diffracted is determined. For example, when producing a monochromatic device, the determination method may be adjusted to the emission wavelength. As another example, a white device is produced by stacking light emitting layers emitting red, green, and blue in an organic electroluminescence element. In this case, in order to make up for the emission intensity, it may be adjusted to the wavelength of a light having a low emission intensity, or in order to extend the lifetime of the element, it may be adjusted to the emission wavelength of a light emitting body that is severely deteriorated. Next, the period of the diffraction grating is determined in order to determine the direction of strong emission by the diffraction grating. The relationship between the period of the diffraction grating and the direction of the strongly emitted light can be easily obtained from equation (1). Next, the refractive index of the light control sheet and the apex angle of the convex portion are determined so that the direction of light strongly emitted by the diffraction grating is converted to the front direction. In this case, the front direction is preferably within ± 5 °, more preferably within ± 2 ° with respect to the direction perpendicular to the light emitting surface. In addition, when a plurality of light control sheets are used, the refractive index and the apex angle of the convex portion should be designed so that the above effects can be obtained as a result of adding the refraction effects of all the light control sheets. That's fine. The refractive index is determined by the physical properties of the material, and the apex angle can be obtained from Snell's law because the relationship between the incident angle and the outgoing angle of light can be easily obtained.

(Third embodiment)
FIG. 10 shows a display device 60 according to the third embodiment of the present invention. The display device 60 includes a surface light emitter 20 having one of the configurations described in the first and second embodiments (here, the configuration of the first embodiment is illustrated) and the light modulation element 50. Is done. As the light modulation element 50, a transmissive or semi-transmissive liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of translucent substrates each having a transparent electrode is employed. Here, the surface light emitter 20 is used as a backlight of the light modulation element 50. The light emitted from the surface light emitter 20 toward the light modulation element 50 is modulated by switching the light modulation element in units of pixels by a drive circuit and recognized as an image by the observer. The

(Fourth embodiment)
FIG. 11 shows a display device 70 according to the fourth embodiment of the present invention. The display device 70 forms pixels arranged two-dimensionally in a matrix by patterning at least one of the transparent electrode and the counter electrode of the organic EL element 201 which is a surface light emitting element, and can generate an arbitrary image. Is used as a surface light emitting element. The surface emitting element 20 (here, the configuration of the first embodiment) is formed by forming the diffraction grating 202 described in the first or second embodiment on the light emission surface of the surface light emitting element 201 and attaching a light control sheet. (Shown). Such a display device is suitable for applications having a relatively large pixel size, such as a large display installed in a public place.

  Next, the surface light emitter according to the embodiment of the present invention is compared with the surface light emitter of the comparative example, and in the surface light emitter according to the embodiment of the present invention, the front luminance of the light emitted from the surface light emitter is Make a big improvement.

(Examples 1-8)
In Example 1, the thing of the structure shown to said 1st Embodiment (refer FIG. 2) was used. The organic EL element is a so-called bottom emission type organic EL element in which a transparent anode is formed on the upper surface of a transparent substrate, an organic EL layer is provided on the upper surface of the anode, and light is emitted to the transparent substrate side. . A hole transport layer is provided on the upper surface of the anode. Further, a light emitting layer is provided on the upper surface of the hole transport layer, and a hole blocking layer is provided on the upper surface. An electron transport layer is provided on the upper surface of the hole blocking layer, and a cathode is further provided on the upper surface of the electron transport layer. An alkali-free glass (thickness 0.7 mm, size 40 mm × 52 mm) was used as a transparent substrate, and an electrode shape was patterned by a general photolithography method on a substrate on which ITO was formed to a thickness of 150 nm as an anode. The resistance of the anode at this time was 20 Ω / □ measured using a Loresta manufactured by Mitsubishi Chemical Corporation. The size of the anode was 35 × 46 mm. A triazole derivative was used as a hole transport material, and was formed to a thickness of 100 nm on the upper surface of the thin anode by vacuum deposition. As the light emitting layer, tris (8-quinolinolato) aluminum was formed to a thickness of 100 nm by vacuum deposition. As the hole blocking layer, a triazine derivative was formed to a thickness of 100 nm by vacuum deposition. As the electron transport layer, a nitro-substituted fluorene derivative was formed to a thickness of 100 nm by vacuum deposition. As the cathode, aluminum was formed to a thickness of 100 nm by sputtering. The refractive index at the exit surface of the surface light emitting element 20 was 1.517.

  A sheet on which the diffraction grating 202 was formed was attached to the emission surface side of the surface light emitting element 201. This sheet has a refractive index of 1.52, and on its surface, a cylinder having a height of 400 nm and a diameter of 560 nm is arranged in a square lattice pattern with a period (d) from 400 nm to 6000 nm according to each example shown in Table 1. (See FIG. 12). This sheet was bonded to the emission surface side of the surface light emitting element with a thermosetting resin. Next, two light control sheets having a triangular roof structure were arranged on the diffraction grating 202 so that the directions of the triangular roof structure were substantially orthogonal to each other, thereby producing Examples 1 to 8. The structure of the light control sheet used for FIG. 13 is shown. This light control sheet has a refractive index of 1.5, an apex angle of 100 °, and a period of a triangular roof of 50 μm.

Example 9
In Example 2, the configuration shown in the second embodiment (see FIG. 8) is used, and the light control sheet 303 is the same as that of Example 1, except that the light control sheet 303 shown in FIG. 14 is used. Produced. FIG. 14A shows a cross-sectional view of the light control sheet 303, and FIG. 14B shows a structural view thereof. It has a quadrangular pyramid structure with an apex angle of 90 °. The refractive index is 1.5 and the period of the square pyramid is 50 μm.

(Comparative Example 1)
In Comparative Example 1, the surface light emitting device 20 used in Example 1 is used as it is as a surface light emitter as shown in FIG. 15 without providing a diffraction grating on its exit surface and without using a light control sheet. Except for the above, it was produced in the same manner as in Example 1.

(Comparative Example 2)
In Comparative Example 2, the configuration shown in FIG. 16 in which a square light extraction sheet 90 was bonded instead of the diffraction grating on the emission surface of the surface light emitting element 20 used in Example 1 was used. It produced similarly. 17 and 18 are a cross-sectional view and a structural diagram of the light extraction sheet 90. The period of the square pyramid is 50 μm and the apex angle is 90 °.

  The surface light emitting elements in the respective surface light emitters of Examples 1 to 9 and Comparative Examples 1 and 2 were caused to emit light, and the light distribution characteristics of the respective surface light emitters were examined. The front luminance of each surface light emitter when the front luminance was set to 1 was determined. In addition, the orientation characteristic is the luminance in a direction forming a predetermined angle with respect to the normal in the plane including the normal direction when the normal direction of the surface light emitter is set to 0 ° by an angle-luminance measuring device. It was determined by measuring while changing the angle.

  The measurement results of the alignment characteristics of Example 1 at a measurement wavelength of 550 nm are shown in FIG. 19, the measurement results of the alignment characteristics of Comparative Example 1 are shown in FIG. 20, and the measurement results of the alignment characteristics of Comparative Example 2 are shown in FIG. Table 1 summarizes the measurement results of the front luminance at the measurement wavelength of 550 nm in Examples 1 to 9 and Comparative Examples 1 and 2. Table 2 shows the front luminance when the measurement wavelength is changed in Example 1.

  The evaluation results were evaluated as Δ when the front luminance was 1.5 times or more and less than 1.7 times, and ◯ when the front luminance was 1.7 times or more and less than 1.9 times.

  From the results shown in Table 1, it can be seen that the front luminance can be greatly improved by providing a diffraction grating on the emission surface of the light emitting element and refracting the diffracted light in the front direction by the light control sheet. In addition, the effect is great if it is 1 to 10 times the wavelength of light (550 nm in this case) to obtain the period of the diffraction grating, and if it is 1 to 2 times, the front luminance is greatly improved. I understand. Table 2 shows the front luminance when the period of the diffraction grating is fixed at 800 nm and the measurement wavelength is changed in the same configuration as in the first embodiment. In this case, the front luminance with respect to light having a wavelength of 585 nm is the largest. This indicates that a wavelength capable of increasing the front luminance can be selected depending on the setting conditions of the diffraction grating. For example, when a white device is produced using an organic electroluminescence element, the present invention is effective if the emission intensity of the light emitter itself is low by 585 nm. It can be seen that the strength can be compensated by using. Needless to say, when the light with low intensity has other wavelengths, it can be optimized to make up the intensity of the wavelength by changing the period of the diffraction grating.

(Example 10)
In Example 10, a display device 60 having the configuration shown in FIG. 10 was produced using the surface light emitter 20 produced in the same manner as in Example 1 and the liquid crystal display element 50. The liquid crystal display element 50 is a transmissive type in which a liquid crystal layer is sandwiched between a pair of translucent substrates each having a transparent electrode formed thereon. Light as a backlight emitted from the surface light emitter is emitted toward the liquid crystal display element 50 provided on the observation side. Light that has entered the liquid crystal display element 50 is modulated by switching a liquid crystal layer in units of pixels by a drive circuit (not shown), and is recognized as an image by an observer. Here, the alignment characteristic of the light emitted from the surface light emitter is the alignment characteristic shown in FIG. This alignment characteristic shows the tendency of the same alignment characteristic even after passing through the liquid crystal display element. Thus, by providing a diffraction grating on the light emitting surface of the surface light emitting element and using a light control sheet that refracts light deflected by the diffraction grating in the front direction, it has orientation characteristics with high front luminance required for a display device. A display device can be provided.

It is the schematic of the general structure of an organic electroluminescent element. It is the schematic which showed the surface emitting body which concerns on the 1st Embodiment of this invention. It is the schematic which showed the mode of diffraction of the one-dimensional diffraction grating. It is the schematic which showed that the light which passed the diffraction grating in the 1st Embodiment of this invention is biased to a specific direction. It is the schematic which showed that the direction to which light advances is converted by the effect of a light control sheet. It is the schematic which showed the condensing effect of the 1st light control sheet in the 1st Embodiment of this invention. It is the schematic which showed the condensing effect of the 2nd light control sheet in the 1st Embodiment of this invention. It is the schematic which showed the surface emitting body which concerns on the 2nd Embodiment of this invention. It is the schematic which showed the condensing effect of the light control sheet in the 2nd Embodiment of this invention. It is the schematic which showed the structure of the display element which concerns on the 3rd Embodiment of this invention. It is the schematic which showed the structure of the display element which concerns on the 4th Embodiment of this invention. It is the schematic of the diffraction grating used for the Example of this invention. It is a schematic sectional drawing of the light control sheet used for the Example of this invention. It is a schematic structure figure of the light control sheet used for the example of the present invention. 6 is a schematic cross-sectional view showing a surface light emitter used in Comparative Example 1. FIG. 3 is a schematic configuration showing a surface light emitter used in Comparative Example 2. 6 is a schematic cross-sectional view of a light extraction sheet used in Comparative Example 2. FIG. 6 is a schematic view of a light extraction sheet used in Comparative Example 2. FIG. FIG. 3 is a diagram showing the orientation characteristics obtained in Example 1. FIG. 6 is a diagram showing the orientation characteristics obtained in Comparative Example 1. FIG. 6 is a diagram showing the orientation characteristics obtained in Comparative Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Organic electroluminescent element 101 Transparent substrate 102 Transparent electrode 103 Organic layer 104 Metal electrode 20, 30 Surface light-emitting body 201, 301 Light emitting element 202, 302 Diffraction grating 203, 204, 303 Light control sheet 50 Light modulation element 60, 70 Display apparatus

Claims (10)

A surface light-emitting element having a diffraction grating formed on the surface on the light emitting side, and a light control sheet having regular irregularities on at least one side arranged to face the diffraction grating through a space,
The diffraction grating biases the direction of light emitted from the surface light emitting element in a predetermined direction different from a direction perpendicular to the light emitting surface of the surface light emitting element by diffraction, and the light control sheet includes the diffraction light A surface light emitter that emits, in a direction perpendicular to the light emitting surface, refraction of light that is strongly emitted out of the light that is biased by a grating. 2. The surface light emitter according to claim 1, wherein a period of the diffraction grating is 1 to 10 times a wavelength of light to be diffracted. 3. The surface light emitter according to claim 1, wherein unit gratings of the diffraction grating are periodically arranged two-dimensionally. 4. The surface light emitter according to any one of claims 1 to 3, wherein the rotational symmetry of the diffraction grating and the light control sheet is the same. The surface light emitter according to any one of claims 1 to 4, wherein the unit cell includes a substantially prismatic or substantially cylindrical structure. 5. The surface light emitter according to claim 1, wherein the unit cell includes a substantially pyramid or substantially conical structure. 6. The surface light emitter according to any one of claims 1 to 6, wherein the light control sheet is obtained by superposing a plurality of sheets. The surface light emitter according to any one of claims 1 to 7, wherein the light control sheet has regular irregularities with a period of 10 µm or more and 1 mm or less on any one surface. A display device comprising a display element and the surface light emitter according to claim 1, wherein the surface light emitter is used as a backlight of the display element. A surface light emitter according to claim 1, wherein the surface light emitting element constituting the surface light emitter includes a plurality of pixels arranged in a matrix in a planar shape. Display device.

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