JP2010123436A - El element, display, display device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element advantageous in improving light extraction efficiency by optimizing light extraction efficiency; a display; a display device; and a liquid display device. <P>SOLUTION: A microlens sheet 7 is provided on a surface of a first transparent substrate 1A via an adhesive layer 6, wherein the surface is on an opposite side of a surface of the first transparent substrate 1A facing a positive electrode 3. The microlens sheet 7 has a surface facing an opposite side of the first transparent substrate 1A and micro unit lenses 5 arranged on the surface. The microlens sheet 7 is formed so as to have a region satisfying formula (1) of 0.3≤(T1/P1)≤(S1/S2), where P1 is an average diameter of the micro unit lenses 5, T1 is an average height of the micro unit lenses 5, S1 is the total of bottom areas of the micro unit lenses 5, and S2 is an area of a remaining part except for S1 of the surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an EL element (electroluminescence element) used for a flat panel display, a backlight for liquid crystal, a light source for illumination, an electrical decoration, a light source for sign, and the like, and a display device, a display device and a liquid crystal display using the EL element Relates to the device.

In general, an organic EL has a structure in which a light-emitting layer containing a fluorescent organic compound is sandwiched between an anode and a cathode on a translucent substrate.
Then, a DC voltage is applied to the anode and the cathode, electrons and holes are injected into the light emitting layer and recombined to generate excitons, and light emission when the excitons are deactivated is used. Leads to light emission.

Conventionally, in these EL elements, when the light emitted from the light emitting layer is emitted from the light transmitting substrate, there is a problem that the light is totally reflected on the light transmitting substrate and the light is lost.
The light extraction efficiency at this time is generally said to be about 20%. Therefore, there is a problem that the higher the luminance is, the more necessary the input power is. Not only that, the addition to the element increases and the reliability of the element itself is lowered.

In order to improve the external extraction efficiency of light, a method has been proposed in which fine irregularities are formed on the element substrate and a light beam lost due to total reflection is extracted to the outside.
For example, it has been proposed to form a microlens array in which a plurality of microlens elements are arranged in a plane on one surface of a translucent substrate (see Patent Document 1).
JP 2002-260845 A

However, it cannot be said that the above prior art is sufficient for improving the light extraction efficiency.
The present invention has been made in view of such circumstances, and provides an EL element, a display device, a display device, and a liquid crystal display device that are advantageous in improving the light extraction efficiency by optimizing the light extraction efficiency. With the goal.

  In order to achieve the above object, the present invention takes the following measures.

That is, the invention of claim 1 is an EL device comprising a light-transmitting substrate and a light-emitting layer provided on one surface of the light-transmitting substrate and sandwiched between an anode and a cathode. A microlens sheet is provided on the other surface of the substrate, and the microlens sheet has a surface and fine unit lenses arranged on the surface, and the fine unit lens has an average diameter P1, and the fine unit When the average height of the lens is T1, the total bottom area of the fine unit lens is S1, and the area of the remaining part excluding the S1 from the surface is S2,
0.3 ≦ (T1 / P1) ≦ (S1 / S2)
It has the area | region which satisfy | fills.

  That is, the invention of claim 2 is an EL element characterized in that the fine unit lens has a convex spherical shape.

  That is, the invention according to claim 3 is the EL element according to claim 1, wherein the fine unit lens has a convex aspherical shape.

  That is, the invention according to claim 4 is the EL element according to claim 1, wherein the fine unit lens includes a straight portion and a curved portion.

  That is, the invention according to claim 5 is the EL element according to claim 1, wherein the pitch of the fine unit lenses is random.

  That is, the invention of claim 6 is the EL device according to claim 1, wherein the arrangement of the fine unit lenses on a plane is a pattern.

  That is, the invention according to claim 7 is the EL element according to claim 1, wherein a light diffusion member is disposed on the surface of the microlens sheet.

  That is, the invention according to claim 8 is the EL element according to claim 7, wherein the surface of the substantially microlens sheet and the light diffusing member are bonded via an adhesive layer.

  That is, the invention of claim 9 is a display device characterized in that the EL element of claim 1 is used as a backlight.

  That is, the invention of claim 10 is a display device characterized in that the EL element of claim 1 is pixel driven.

  That is, the invention of claim 11 is a liquid crystal display device comprising the backlight according to claim 9 on the back surface of the image display element.

According to the present invention, the average diameter of the fine unit lens is P1, the average height of the fine unit lens is T1, the total bottom area of the fine unit lens is S1, and the area of the remaining portion excluding S1 from the surface Is S2,
0.3 ≦ (T1 / P1) ≦ (S1 / S2)
Use of a lens sheet having a region satisfying the conditions is advantageous in improving the light extraction efficiency by optimizing the light extraction efficiency.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 2 is a diagram showing the configuration of the EL element (electroluminescence element) of the present embodiment.
As shown in FIG. 2, the EL element includes first and second translucent substrates 1A and 1B, a light emitting layer 2, an anode 3, a cathode 4, a microlens sheet 7, and the like. Yes.

An anode 3 is formed on one surface of the light emitting layer 2 and a cathode 4 is formed on the other surface.
A light emitting structure is configured including the light emitting layer 2, the anode 3, and the cathode 4. Various known configurations can be employed as the light emitting structure.

  The light emitting layer 2 may be a white light emitting layer, or may be a light emitting layer of blue, red, yellow, green, or the like. In the case of a white light emitting layer, the structure of the light emitting layer 2 is, for example, ITO / CuPc (copper phthalocyanine) / α-NPD doped with rubrene 1% / dinactylanthracene perylene 1% doped / Alq 3 / lithium fluoride. / The cathode may be made of Al. However, the present invention is not limited to this configuration, and an arbitrary configuration using an appropriate material that can set the wavelength of light emitted from the light emitting layer to R (red), G (green), and B (blue) is adopted. It is possible. Further, when used in a full-color display application, full-color display can be performed by separately applying three types of light emitting materials corresponding to R, G, and B, or by superimposing a color filter on white light.

The first translucent substrate 1 </ b> A is formed on the surface opposite to the surface where the anode 3 faces the light emitting layer 2.
The second translucent substrate 1 </ b> B is formed on the surface opposite to the surface where the cathode 4 faces the light emitting layer 2.
As materials for the first and second light-transmitting substrates 1A and 1B, various glass materials can be used, and plastic materials such as PMMA, polycarbonate, and polystyrene can be used. Although materials can be used, a cycloolefin-based polymer is particularly preferable, and this polymer is excellent in all of processability and material properties such as heat resistance, water resistance, and optical translucency. .
Further, the first light-transmitting substrate 1A is formed of a material capable of making the total light transmittance 50% or more so that light from the light-emitting structure (light-emitting layer 2) can be transmitted as much as possible. Is preferred.

The microlens sheet 7 is provided on the surface opposite to the surface on which the first transparent substrate 1 </ b> A faces the anode 3 with the adhesive layer 6 interposed therebetween.
Examples of the adhesive / adhesive constituting the adhesive layer 6 include acrylic, urethane, rubber, and silicone adhesives / adhesives. In any case, since it is used in a high-temperature backlight, it is desirable that the storage elastic modulus G ′ is 1.0E + 04 (Pa) or more at 100 ° C. If the value is lower than this, the light diffusion layer 25 and the lens sheet 1 may be displaced during use. In order to secure the gap 200 stably, transparent fine particles, for example, beads may be mixed in the contact / adhesive layer.
The adhesive may be a double-sided tape or a single layer.
The microlens sheet 7 has a surface facing the side opposite to the first transmissive substrate 1 </ b> A and the fine unit lenses 5 arranged on the surface.
In other words, the EL element includes a translucent substrate 1A and a light emitting layer 2 provided on one surface of the translucent substrate 1A and sandwiched between an anode 3 and a cathode 4. A microlens sheet 7 is provided on the other surface of the translucent substrate 1A, and the microlens sheet 7 has a surface and fine unit lenses 5 (microlenses) arranged on the surface.
Microlens shapes include lenticular, trapezoidal, and prismatic structures extending in one direction, polygonal cones, cones (or polygonal truncated cones, truncated cones, etc.), polygonal columns, columnar cylinders, rectangular parallelepipeds, and spherical shapes. (Or hemispherical) or an ellipsoidal structure.
Depending on the method of manufacturing the microlens, the shape of the side surface may be an unspecified shape as long as the height of the microlens is constant. When securing a space | gap with these microlenses, you may use said 1 type of microlens structure for the whole, or may use it combining several types of microlens structure. The arrangement of these microlenses may be periodic such as a stripe shape or a dotted line, or may be random, and is appropriately selected according to the design.

FIG. 1A is a top view of the microlens sheet 7 of the EL element of the present embodiment, and FIG.
As shown in FIGS. 1A and 1B, the microlens sheet 7 is configured such that the average diameter of the fine unit lens 5 is P1, the average height of the fine unit lens 5 is T1, and the bottom area of the fine unit lens 5 is When the total is S1 and the area of the remaining part excluding S1 from the surface is S2, the area is formed so as to have a region satisfying the following formula (1).
0.3 ≦ (T1 / P1) ≦ (S1 / S2) (1)
As a material for forming the microlens sheet 7, PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), acrylonitrile styrene copolymer, acrylonitrile polystyrene copolymer, or the like is used. be able to.
Further, when the area of the light emitting surface range a of the light emitting layer 2 shown in FIG. 2 is Sa and the area of the region where the microlens sheet 7 satisfies the formula (1) is Sb, Sb satisfies 50% of Sa. Is preferable, and it is more preferable when Sb satisfies 90% of Sa. In addition, it is not so preferable when Sb satisfies 10% of Sa.

Here, a method for measuring the areas S1, S2, the height T1, and the average diameter P1 will be described.
FIG. 14 is a schematic diagram of the microlens sheet 7.
In FIG. 14, the black portion indicates each fine unit lens 5.
Therefore, the total area of the black portion corresponds to the total bottom area S1 of the fine unit lens 5, and the total area of the white portion corresponds to the area S2 of the remaining portion excluding S1 from the surface of the microlens sheet 7. It corresponds.
The height T1 is an average of 100 or more samples.
The measurement of these areas S1, S2 and height T1 is not limited to this, but a confocal laser microscope such as Olympus scanning confocal infrared laser microscope LEXT OLS3000-IR can be used.
When the number of the fine unit lenses 5 in a unit area having 100 or more fine unit lenses 5 is N, the average diameter P1 of the fine unit lenses 5 is expressed by the following formula.

As shown in FIG. 9, the light emitted from the light emitting layer 2 is efficiently emitted not only in the front direction but also in various directions by the fine unit lens 5, and a wide field of view range is obtained.
In order to efficiently extract the light emitted from the light emitting layer 2, in other words, in order to improve the light extraction efficiency, the fine unit lens 5 has a convex spherical shape, a convex aspherical shape, a linear portion, A shape including a curved portion is preferable.

  The random pitch of the fine unit lenses 5 is advantageous for improving the light extraction efficiency by optimizing the light extraction efficiency.

3 and FIG. 4, the arrangement of the micro unit lenses 5 on the plane may be periodic, or the arrangement of the micro unit lenses 5 on the plane may be aperiodic as shown in FIG. Also good.
If the arrangement of the fine unit lenses 5 on the plane is periodic, it is advantageous for increasing the density of the fine unit lenses 5, and if the arrangement of the fine unit lenses 5 on the plane is aperiodic, it is difficult to see the EL emission defect. This is advantageous.

  Further, as shown in FIG. 6, the arrangement on the plane of the fine unit lenses 5 may be a pattern, and in this case, the pattern can be displayed by the light emitted from each fine unit lens 5. Such a picture includes a logo, a mark, a pattern, and the like.

As shown in FIG. 7, a light diffusion member 8 may be disposed on the surface of the microlens sheet 7.
Further, as shown in FIG. 8, the surface of the microlens sheet 7 and the light diffusing member 8 may be bonded via an adhesive layer 6.
As shown in FIG. 10, when the light diffusion member 8 is disposed on the surface of the microlens sheet 7, the light emitted from each fine unit lens 5 can be diffused by the light diffusion member 8. Therefore, it is even more advantageous to obtain a wide field of view by efficiently emitting light in various directions.
Examples of such transparent resin for the diffusing member 8 include polycarbonate resin, acrylic resin, fluorine acrylic resin, silicone acrylic resin, epoxy acrylate resin, polystyrene resin, cycloolefin polymer, methylstyrene resin, fluorene resin, and PET. Polypropylene or the like can be used.
Moreover, as the encapsulated transparent particles, transparent particles made of inorganic oxide or transparent particles made of resin can be used. For example, examples of the transparent particles made of an inorganic oxide include particles made of silica, alumina or the like. Further, transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP (tetrafluoroethylene). Fluoropolymer particles such as fluoroethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene-tetrafluoroethylene copolymer), silicone resin particles, and the like. These transparent particles may be used as a mixture of two or more.

(Production method of microlens sheet)
Next, an example of a manufacturing method of the microlens sheet 7 will be described.
Example 1
An ultraviolet curable resin (urethane acrylate resin (refractive index: 1.5) made by Nippon Kayaku Co., Ltd.) having a urethane acrylate as a main component for forming a pattern of the lens sheet 1 on an optically biaxially stretchable and easy-adhesive PET film (film thickness 125 μm). 51)) is applied, and UV light is exposed from the PET film side while conveying a film coated with UV curable resin using a cylinder die cut into the shape of the lens sheet 1, thereby UV curable The resin was cured. After curing, the mold was released from the PET film, thereby producing a microlens group having a lens diameter of 140 μm.

(Example 2)
A cylinder mold in which a polycarbonate resin, which is a thermoplastic resin, is heated to about 300 ° C., formed into a 0.3 mm thick film while being stretched along a roll, and then a concave microlens shape is etched into the cylinder. Then, the heated film was cooled while being pressurized (the cylinder mold itself was at room temperature of 25 ° C.), and the film in which the microlens shape was formed was completely cured.
As a result, a microlens group with a lens array lens diameter of 50 μm was produced.

(Example)
Next, examples will be described.
FIG. 11 is a diagram showing measured values when (S2 / S1 = 0.785) in the microlens sheet of the present invention.
FIG. 12 is a diagram showing measured values when (S2 / S1 = 0.81) in the microlens sheet of the present invention.
FIG. 13 is a diagram showing measured values when (S2 / S1 = 0.92) in the microlens sheet of the present invention.
Comparing FIG. 11, FIG. 12, and FIG. 13, as (S2 / S1) is larger numerically, the lens area of the surface portion of the lens sheet 7 (lens area of the fine unit lens 5) increases. The lens effect is exhibited and the light extraction efficiency is increased.
However, if (S2 / S1) is less than (T1 / P1), the influence amount of the fine unit lens 5 in the microlens sheet 7 is reduced, the light extraction efficiency is weakened, and the flat part outside the fine unit lens 5 is reduced. The light extraction efficiency is declining and just falls to around T1 / P1 = 0.785.
Also, the light extraction efficiency drops sharply when T1 / P1 is about 0.3, and it can be seen that the microlens sheet 7 has almost no effect when T1 / P1 is 0.3 or less.

As described above, according to the EL element of the present embodiment, the use of the lens sheet 7 having a region satisfying the expression (1) is advantageous in improving the light extraction efficiency.
In addition, the EL device according to the present invention is driven by pixels, in other words, a display device can be configured by having a light emitting structure of an EL device having a pixel structure, and a display configured as such Devices are also within the scope of the present invention.
Furthermore, since the EL element according to the present invention has excellent light extraction efficiency, it can be suitably used for various other applications. For example, the EL element according to the present invention can be suitably used as a backlight device for a display device or a liquid crystal display device, and a backlight device configured as such is also included in the scope of the present invention.

(A) is a top view of the microlens sheet 7 of the EL element of this Embodiment, (b) is a side view. It is a figure which shows the structure of the EL element of this Embodiment. It is a figure which shows an example of the grid | lattice-like arrangement | positioning of the micro unevenness | corrugation shape of the micro lens sheet. 3 is a diagram showing an example of a substantially square pyramid honeycomb arrangement of a microlens sheet. FIG. It is a figure which shows an example of the substantially square pyramid-shaped random arrangement | positioning of the microlens sheet | seat. It is a figure which shows an example of the substantially square pyramid-shaped pattern arrangement | positioning of the microlens sheet | seat. It is a figure which shows the structure which provided the light-scattering means on the EL element of this Embodiment. It is a figure which shows the structure which provided the light-scattering means on the EL element of this Embodiment, and has arrange | positioned the contact bonding layer to the light-scattering means. It is a figure which shows an example which provided the example of the light ray from an EL element part on the EL element of this Embodiment. It is a figure which shows an example which provided the light-scattering means on the EL element of this Embodiment, arrange | positioned the contact bonding layer in the light-scattering means, and provided the example of the light ray from an EL element part. In the microlens sheet | seat of this invention, it is a figure which shows the measured value in case it is (S2 / S1 = 0.785). In the microlens sheet of this invention, it is a figure which shows a measured value in case it is (S2 / S1 = 0.81). In the microlens sheet | seat of this invention, it is a figure which shows the measured value in the case of (S2 / S1 = 0.92). 3 is a schematic diagram of a microlens sheet 7. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1A ... 1st translucent board | substrate, 2 ... Light emitting layer, 3 ... Anode, 4 ... Cathode, 5 ... Fine unit lens, 6 ... Adhesion layer, 7 ... Micro lens sheet, 8 ... Light scattering means.

Claims (11)

An EL device comprising a translucent substrate and a light emitting layer provided on one surface of the translucent substrate and sandwiched between an anode and a cathode,
A microlens sheet is provided on the other surface of the translucent substrate,
The microlens sheet has a surface and fine unit lenses arranged on the surface,
The average diameter of the fine unit lens is P1,
The average height of the fine unit lens is T1,
S1 is the total bottom area of the fine unit lens,
When the area of the remaining part excluding the S1 from the surface is S2,
0.3 ≦ (T1 / P1) ≦ (S1 / S2)
An EL element characterized by having a region satisfying the above.   The EL device according to claim 1, wherein the minute unit lens has a convex spherical shape.   2. The EL element according to claim 1, wherein the fine unit lens has a convex aspherical shape.   The EL device according to claim 1, wherein the fine unit lens includes a linear portion and a curved portion.   The EL device according to claim 1, wherein the pitch of the fine unit lenses is random.   2. The EL element according to claim 1, wherein the arrangement of the fine unit lenses on a plane is a pattern.   The EL device according to claim 1, wherein a light diffusion member is disposed on a surface of the microlens sheet.   The EL device according to claim 7, wherein the surface of the substantially microlens sheet and the light diffusing member are bonded via an adhesive layer.   A display device, wherein the EL element according to claim 1 is used as a backlight.   2. A display device, wherein the EL element according to claim 1 is pixel driven.   A liquid crystal display device comprising the backlight according to claim 9 on the back surface of the image display element.

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