JP2010123322A - Surface light source element and display device including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source element that achieves high efficiency of using light emitted from a surface light emitter including a self light emitting element and enhances front luminance, when light absorption in the surface light emitter is comparatively high. <P>SOLUTION: The surface light source element 1 includes a surface light emitting element 3 having a self light emitting element as a light emitting source, and an emission light control sheet 2 provided on the light emitting surface of the surface light emitting element and having a plurality of protrusions 10 formed on at least one surface thereof. The protrusions 10 are optically in tight contact with an emission surface 13 of the surface light emitting element, and the emission surface 13 is not flat in portions not in contact with the protrusions 10. The refractive index of regions (sometimes referred to as voids) 11 formed between the protrusions 10 and the emission surface 13 of the light emitting element is lower than the refractive index of the protrusions 10. A display device including the surface light source element 1 is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface light emitter provided with a self-luminous surface light emitting element and a display device using the same.

  In recent years, with the diversification of information equipment, there is an increasing need for surface light emitting devices with low power consumption and small volume. Among surface emitting devices, attention is focused on the electroluminescence (EL) method.

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

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

  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 advertising media.

Here, when used as a backlight of a liquid crystal display device or the like, generally a front luminance of about 2000 to 4000 cd / m ² is required. However, when a surface light emitting device such as an EL device as described above is caused to emit light, light is emitted. The emitted light travels in various directions, and since there is a lot of light confined inside the surface light emitting element by being totally reflected on the emission surface of the surface light emitting element, it is difficult to obtain sufficient front luminance. In particular, in the case of an organic EL element, there is a problem that only a front luminance of about 1000 to 1500 cd / m ² can be obtained in order to obtain a sufficient light emission lifetime.

  Therefore, when a surface light emitting device such as an organic EL device emits light, the light confined in the surface is taken out, and the emission surface of the surface light emitting device is provided with unevenness in order to improve the front luminance. Or (for example, patent document 1, nonpatent literature 1), what attached the flat member in which the unevenness | corrugation was provided in the output surface of the surface light emitting element so that the unevenness might appear on the surface is proposed. (Patent Document 2)

  However, if the surface of the light emitting surface of the surface light emitting element is provided with minute irregularities as described above, or a member having irregularities on the light emitting surface of the surface light emitting element is bonded via an adhesive, the surface There was a problem that light was scattered by the unevenness in the surface, and the front luminance could not be sufficiently improved.

  In order to solve such a problem, in Patent Documents 3 and 4, the shape of the convex portion contracts toward the light-transmitting substrate exit surface, and the tip surface is adhered to the light exit surface of the light-transmitting substrate. The front luminance of the light emitted from the surface light emitter provided with the surface light emitting element is increased by making the refractive index lower than the refractive index of the light control sheet in the space formed between the light emitting surface of the surface light emitting element. It is improving. Light can be extracted from the portion where the convex portion and the emission surface are bonded, and the light utilization efficiency and front luminance are improved. However, total reflection cannot be suppressed except for the bonded surface. In addition, since the unbonded area is very large, the light is gradually emitted while being reflected many times inside the surface light emitting element. If there is no absorption inside the surface light emitter, light is extracted sufficiently. However, if there is absorption inside the light emitting element, there is a problem that the loss of light increases and the efficiency of light utilization and the front luminance improvement rate decrease.

JP-A-9-63767 JP-A-5-45505 JP 2007-149591 A JP 2000-148032 A Journal of applied physics Volume 91, Number5 3324-3327 (2002)

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a surface light source element that enhances the use efficiency of light emitted from the surface light emitter and greatly improves the front luminance in a state where there is absorption inside the surface light emitter composed of the self light emitting element. There is.

The surface light source element of the present invention comprises a surface light emitting element having a self light emitting element as a light source, and an emitted light control sheet provided with a plurality of convex portions on at least one surface provided on the light emitting surface of the surface light emitting element, The projection is optically in close contact with the emission surface of the surface light emitting element, and the emission surface not bonded to the projection is not flat, and is formed between the projection and the emission surface of the light emitting element. It is obtained by making the refractive index of the region (hereinafter sometimes referred to as a void) lower than that of the convex portion.
The surface light-emitting device described in this specification includes both single-sided light emission and double-sided light emission. In the case of double-sided light emission, the outgoing light control sheet may be attached to only one side or may be attached to both sides.

  In the surface light source element of the present invention, a region formed between the convex portion and the emission surface of the light emitting element is filled with a translucent material having a refractive index lower than that of the convex portion. Alternatively, the area may be filled with air.

  In the surface light source element of the present invention, the exit surface of the surface light emitting element may be in close contact with the tip of the convex portion of the exit light control sheet and the bottom surface of the recess of the exit surface of the surface light emitting element.

  The present invention also provides a display device comprising a display element and the surface light source element described above, wherein the surface light source element is a backlight of the display element.

  In this invention, the refractive index of the region (gap portion) formed between the convex portion and the emission surface of the light emitting element is made lower than the refractive index of the convex portion, thereby the convex portion and the emission surface. The light which is originally totally reflected is transmitted at the portion where the adhesive is adhered, and is reflected at the interface between the extension of the convex portion of the outgoing light control sheet and the gap portion. The reflected light is brought closer to the main surface of the outgoing light control sheet in the vertical direction, so that it is emitted from the outgoing light control sheet without being totally reflected, and the front luminance is significantly increased by the light collecting effect.

  Here, the portion where the convex portion of the emission light control sheet and the emission surface of the surface light emitting element are not bonded occupies more than half of the entire area. Conventionally, the light incident on this part has a great amount of components that are totally reflected and are not emitted, but in the present invention, it is not flat, so the total reflected component is reduced and light can be extracted more efficiently. Become.

  In addition, since the exit surface of the surface light emitting element is in close contact with the top of the convex portion of the exit light control sheet and the bottom surface of the concave portion of the exit surface of the surface light emitting element, the light at the angle that is originally totally reflected once After exiting to the low refractive index region, the inside of the convex part proceeds at the same angle as the angle of traveling through the surface light source element to the convex part of the outgoing light control sheet. Thereafter, the light is reflected at the boundary between the convex portion and the low refractive index region, and is brought closer to the main surface of the outgoing light control sheet in the vertical direction, whereby the front luminance is increased and the light utilization efficiency is greatly improved.

  Furthermore, in the surface light source element described above, when a concavo-convex shape is provided on the exit surface which is the surface opposite to the surface of the exit light control sheet provided with a convex portion to be bonded to the exit surface of the surface light emitting element, the exit light Total reflection on the exit surface of the control sheet is suppressed, and the light utilization efficiency is further improved.

  Next, a surface light source element according to an embodiment of the present invention will be described with reference to the drawings. The surface light source element 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.

[Embodiment 1]
FIG. 1 shows a schematic view of a surface light source element 1 of the present invention. In the present invention, a configuration that does not include the light emission control sheet 2 of FIG.
The surface light emitting element 3 has a structure in which a self-luminous light emitting layer 5 is sandwiched between a transparent electrode 4 and a reflective electrode 6. Further, in the surface light source element 1, a quadrangular pyramid-shaped convex part 10 whose tip side contracts is continuously formed in a two-dimensional manner on a surface facing the light emitting surface 13 of the surface light emitting element 3 as the emitted light control sheet 2. Sheet. That the front end side contracts means that the cross-sectional area obtained by cutting the convex portion 10 along a plane parallel to the main surface of the sheet is smaller on the front end side than on the sheet side. The shape of the convex portion 10 is not limited to a quadrangular pyramid, and may be any shape that contracts the tip side, such as a conical shape.

  Further, the light exit surface 13 is not flat but has an uneven shape 14. The shape of the unevenness is not particularly defined, and examples thereof include a circle, an ellipse, a square, and a rectangle. The definition of non-flat here indicates that there are 40% or more of the total area with unevenness of 1 μm or more in height.

  By adhering the top of the convex portion 10 of the outgoing light control sheet 2 to the light outgoing surface 12, a gap 11 is provided between the side surface of the convex portion 10 and the outgoing surface 13 of the surface light emitting element. The gap 11 is usually filled with air having a low refractive index. A material having a refractive index lower than that of the convex portion 10 may be filled instead of air.

  By adopting such a configuration, when the outgoing light control sheet 2 is not provided, the light is totally reflected inside the surface light emitting element 3 and emitted from the side surface of the surface light emitting element 3 or absorbed in the light emitting element. The light which has become is taken in from the adhesion part of the convex part 10 of the outgoing light control sheet 2 and the outgoing face 13 of the light emitting element. The taken-in light is totally reflected at the interface between the convex portion 10 and the gap portion 11 and exits in the direction perpendicular to the main surface of the surface light source element 1.

  The difference between the refractive index of the convex portion 10 and the refractive index of the gap portion 11 is desirably 0.2 or more, more desirably 0.3 or more, and further desirably 0.4 or more. When the difference in refractive index is small, total reflection does not occur at the convex portion 10 and the gap portion 11, and the emitted light does not face in the direction perpendicular to the main surface of the surface light source element 1, so that the effect of the present invention is reduced.

  Further, under the condition that the inside of the surface light emitting element 3 is absorbed, the light incident on the portion where the convex portion 10 and the emission surface 13 of the surface light emitting element are bonded is extracted while reflecting the inside of the light emitting element 3 many times. The amount of light that is absorbed in the device is very large. In particular, when the portion where the convex portion 10 and the emission surface 13 of the surface light emitting element are not in contact is flat, the light incident on the portion is totally reflected as it is, and this tendency becomes remarkable. Here, by providing the concavo-convex shape 14 in the portion where the convex portion 10 and the emission surface 12 of the surface light emitting device are not in contact with each other on the emission surface 11 of the surface light emitting device, a part of the light incident on the portion is entirely provided. The amount of light that is transmitted without being reflected can be increased. For this reason, the loss in the surface light emitting element 3 can be reduced.

  The inclination angle of the side surface of the convex portion 10 of the emitted light control sheet 2 is preferably such that the apex angle θ1 of the convex portion 10 shown in FIG. 2 is in the range of 30 ° to 70 °, and is in the range of 40 ° to 60 °. Is more desirable. When the apex angle θ1 is too small, the light totally reflected by the side surface of the convex portion 10 is reduced, and the light emitted in the front direction of the surface light source element 1 tends to be reduced. On the other hand, if the apex angle θ1 is too large, the area where the convex portion 10 and the emission surface 13 of the surface light emitting element element are in contact with each other tends to decrease, and the light extraction efficiency tends to decrease. Tends to be difficult to condense. The proportion of the convex portion 10 is preferably 80% or more of the light control sheet 2, and in order to capture the light beam at the tip of the convex portion 10 most efficiently, it is more desirable to arrange in a fine state. The interface between the exit surface 13 of the surface light emitting element and the tip of the convex portion 10 is optically bonded, and there is almost no air interface. Further, the range that the height h of the convex portion 10 can take is limited by the size A of the convex portion 10 shown in FIG. In general, if the height h of the convex portion 10 is too low, even if light that is totally reflected when the outgoing light control sheet 2 is not provided on the light outgoing surface 13 of the surface light emitting element, even if the light that is totally reflected is guided to the outgoing light control sheet 2 The light does not hit the slope of the convex portion 10, and is totally reflected on the exit surface 12 of the exit light control sheet 2 and returns. On the other hand, if the height h of the convex portion 10 is too high, the area where the convex portion 10 is in contact with the emission surface 13 of the surface light emitting element is reduced, and the light guided to the outgoing light control sheet 2 is reduced. For this reason, it is desirable that the height h of the convex portion 10 satisfy the condition of 0.3 × A ≦ h ≦ 1.0 × A with respect to the size A of the convex portion 10.

  The uneven shape 14 on the exit surface of the surface light emitting element is not particularly limited, but the cross section may be a semicircular shape as shown in FIG. 3, or any shape that inhibits total reflection, such as a trapezoidal shape or a pyramid shape. Further, it is desirable that the uneven shape 14 of the exit surface of the surface light emitting element is present in 70% or more of the area where the convex portion 10 of the exit light control sheet 2 and the exit surface 13 of the surface light emitting element are not in contact.

  Further, the surface shape of the outgoing light control sheet 2 is formed on a transparent substrate by using a stamper or a female die, etc. by a hot press method, a photopolymer method by ultraviolet curing, a casting method by thermal curing, an injection molding method, or the like. Can be formed. As the transparent substrate, resins such as acrylic resin, polycarbonate resin, polyethylene terephthalate, polystyrene resin, or glass are used. The stamper used for the production of the outgoing light control sheet 2 is, for example, coating a negative or positive photosensitive resin on a glass substrate, exposing the photosensitive resin through a photomask, developing, and electroforming. It can produce by performing, and can also produce by a cutting process. The emitted light control sheet 2 does not have to be in the form of a sheet, but may be in the form of a film. Further, the convex portion 10 provided in the outgoing light control sheet 2 in the present invention may be a two-dimensionally arranged lens array type in addition to a pattern like a one-dimensionally arranged lenticular lens.

[Embodiment 2]
In the second embodiment, as shown in FIG. 7, the exit surface of the surface light emitting element is other than the tip of the convex portion 10 of the outgoing light control sheet 2 and the concave portion 15 of the exit surface of the surface light emitting element being in close contact with each other. Is the same as in the first embodiment. Here, as shown in FIG. 7, it is preferable that the side surface of the convex portion 10 of the emission light control sheet 2 and the emission surface 13 of the surface light emitting element are not in contact with each other, but if the gap portion 11 is provided. In addition, a part of the side surface of the convex portion 10 is not prevented from contacting a part of the emission surface 13 of the surface light emitting element. In FIG. 7, the shape of the convex portion 10 of the outgoing light control sheet is a quadrangular pyramid shape, and the concave portion 15 of the outgoing surface of the surface light emitting element is formed in a quadrangular pyramid shape so that the shape of the outgoing surface matches the convex portion 10. . The tip of the convex portion 10 and the bottom surface of the concave portion 15 are optically bonded. Further, the side surfaces of the convex portion 10 and the concave portion 15 are not in contact with each other and are separated by the gap portion 11. The shape of the concave portion 15 does not have to be exactly the shape corresponding to the convex portion 10, and may be a similar shape.

  By adopting such a configuration, the portion where the bottom surface of the concave portion 15 and the tip portion of the convex portion 10 are not in contact with each other is totally reflected when the outgoing light control sheet 2 is not provided as shown in FIG. The emitted light is taken into the outgoing light control sheet 2 without being totally reflected as shown in FIG. A part of the taken-in light is reflected by the side surface of the convex portion 10, directed in a direction perpendicular to the main surface of the surface light source element 1, and emitted without being totally reflected by the emission surface 12 of the emission light control sheet. It becomes possible. This improves the front brightness and light utilization efficiency. Moreover, since the shape of the concave portion 15 corresponding to the shape of the convex portion 10 is provided, the tip of the convex portion 10 and the bottom surface of the concave portion 15 can be bonded without accurate alignment. There is also an advantage that is easy. It is desirable that the apex angle θ2 of the concave portion 15 matches within ± 10 degrees as compared with the apex angle θ1 of the convex portion convex portion 10. If the angle θ2 is too small, the bottom surface of the recess 15 becomes large, and the area that inhibits total reflection tends to be narrowed. Even if the angle θ2 is too large, the effect of inhibiting total reflection tends to be small. The recesses 15 may be connected as shown in FIG. 5, or may be arranged at a distance as shown in FIG.

[Embodiment 3]
In Embodiment 3, as shown in FIG. 9, the uneven | corrugated shape 16 is formed in the output surface 12 of the output light control sheet | seat which is a surface on the opposite side to the convex part 10 of an output light control sheet | seat being provided. Other than the above, the second embodiment is the same as the second embodiment. Since the uneven surface 16 is formed on the output surface 12 of the output light control sheet, the light that is totally reflected when the uneven surface 16 is not provided on the output surface 12 is output without being totally reflected. Light utilization efficiency is improved. The uneven shape 16 of the emission surface 12 may be arranged at random, but the effect is further enhanced by aligning with the convex portion 10.

  The material for forming the electroluminescent layer of an EL light source used as a light source in the present invention may be either organic or inorganic. Further, the present invention is intended to extract light confined in the EL light source by total reflection occurring in the EL light source covered with the transparent substrate, and can be used regardless of the configuration of the EL light source. The present invention can be used regardless of the EL light source as long as the light source emits light from a material having a high refractive index.

The present invention is illustrated by examples. The present invention is not limited to the examples.
<Example 1>
In Example 1, as shown in Embodiment 1 above, a square pyramid-shaped convex part having a vertex angle θ1 of 50 ° and a height of 25 μm contracted on one side of a PET film having a refractive index of 1.57. 10 is an emission light control sheet 2 continuously formed of a photocurable resin having a refractive index of 1.51 in a two-dimensional direction, and a transparent substrate 7 having a convex shape 14 on an emission surface 13 as shown in FIG. Were bonded together with an adhesive. The pressure-sensitive adhesive layer 8 was formed on the flat surface of the transparent substrate 7, and the transparent electrode 4, the light emitting layer 5, and the reflective electrode 6 were bonded to a glass substrate 10 to obtain the surface light source element 1. The reflectance of the reflective electrode 6 of the surface light emitting element 3 is 93%, and the combined absorptivity of the light emitting layer and the transparent electrode is 10%.

<Example 2>
In Example 2, as shown in Embodiment 1 above, a truncated pyramid-shaped convex portion having a vertex angle θ1 of 50 degrees and a height of 25 μm, which is contracted on one side of a PET film having a refractive index of 1.57. 10 is an emission light control sheet 2 formed by continuously aligning in a two-dimensional direction with a photocurable resin, and a concave and convex shape 14 is provided on the emission surface 13 of the surface light emitting element as shown in FIG. The transparent substrate 7 was pasted with an adhesive. The pressure-sensitive adhesive layer 8 was formed on the flat surface of the transparent substrate 7, and the transparent electrode 4, the light emitting layer 5, and the reflective electrode 6 were bonded to a glass substrate 10 to obtain the surface light source element 1. The reflectance of the reflective electrode 6 of the surface light emitting device 3 is 93%, and the combined absorption rate of the surface light emitting device 3 and the transparent electrode 4 is 10%.

<Example 3>
In Example 3, as shown in FIG. 7, the shape of the emission surface 13 of the surface light emitting device was the surface light emitting device 3 in which the concave portion 15 corresponding to the shape of the convex portion 10 of the outgoing light control sheet 2 was formed. The angle θ2 of the side surface of the recess 15 is 45 degrees and the height is 23 μm. The tip of the convex part 10 and the bottom part of the concave part 15 were adhered with an adhesive. Other than that was carried out in the same configuration as in Example 1.

<Example 4>
In Example 4, a cylindrical shape having a height of 10 μm and a radius of 10 μm was formed as the concavo-convex shape 16 on the emission surface 12 which is the opposite surface of the surface on which the convex portion 10 is formed in the emission light control sheet 2. The same configuration as in No. 2 was performed.

<Comparative Example 1>
The same procedure as in Example 1 was performed except that the emission light control sheet 2 was not provided and the emission surface 13 of the surface light emitting element was flat.

<Comparative example 2>
Comparative Example 2 was the same as Example 1 except that the emission surface 13 of the surface light emitting element was flat.

  Table 1 shows the results obtained by calculating the front luminance and the light utilization efficiency by ray tracing for each of the examples and comparative examples. In the table, the front brightness and the light use efficiency are normalized by setting the front brightness and the light use efficiency in Comparative Example 1 to 1.0.

From these results, it can be seen that in the present invention, the front brightness is the same as that of Comparative Example 2, but the efficiency is improved.
<Example 5>
A display device can be configured by using the surface light source element 1 obtained in any of Examples 1 to 4 as a backlight and combining it with a transmissive display element.

It is a schematic side view of the surface light source element according to the first embodiment. It is a schematic side view of the emitted light control sheet which concerns on said Embodiment 1. FIG. It is a schematic side view of said Example 2. FIG. It is a schematic plan view of the outgoing light control sheet according to the second embodiment. It is a schematic side view of the light control sheet and the emission surface according to the second embodiment. It is a schematic diagram which shows the advancing direction of the light in said comparative example 2. It is a schematic diagram which shows the advancing direction of the light in said Example 3. FIG. It is said Embodiment 2, and is a schematic diagram in case there exists a space | interval in the recessed part of a light-projection surface. It is a schematic side view of the light control sheet and the emission surface in the third embodiment. It is a schematic plan view of the light control sheet and the emission surface in the third embodiment.

Explanation of symbols

1: Surface light source element, 2: Emission light control sheet, 3: Surface light emitting element 4: Transparent electrode, 5: Light emitting layer, 6: Reflective electrode 7: Transparent base material, 8: Adhesive, 9: Glass substrate 10: Convex Part, 11: area (gap part) formed between the convex part and the emission surface of the light emitting element
12: exit surface of the exit light control sheet, 13: exit surface of the surface light emitting element 14: uneven shape of the exit surface of the surface light emitting element, 15: recess of the exit surface of the surface light emitting element 16: exit surface of the exit light control sheet Uneven part

Claims (6)

  A surface light emitting element having a self light emitting element as a light source, and an emission light control sheet provided with a plurality of convex portions on at least one surface provided on a light emitting surface of the surface light emitting element, wherein the convex portions of the surface light emitting element The exit surface that is optically in close contact with the exit surface and is not bonded to the projection is not flat, and the refractive index of the region formed between the projection and the exit surface of the light emitting element is A surface light source element characterized by being lower than a convex part.   A region formed between the convex portion and the emission surface of the light emitting element is filled with a translucent material having a refractive index lower than that of the convex portion of the outgoing light control sheet. Item 2. A surface light source element according to Item 1.   2. The surface light source element according to claim 1, wherein air is filled in a region formed between the convex portion and an emission surface of the light emitting element.   The surface light source element according to claim 1, wherein unevenness is formed on an emission surface of the surface light source element.   2. The surface light source element according to claim 1, wherein an exit surface of the surface light emitting element is in close contact with a front end of a convex portion of the output light control sheet and a bottom surface of a concave portion of the exit surface of the surface light emitting element.   A display element comprising the display element and the surface light source element according to claim 1, wherein the surface light source element is a backlight of the display element.

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