JP2015109213A - Lens sheet and el light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens sheet with which a brightness increase rate becomes high and also a color temperature difference for each irradiation angle becomes small, and to provide an EL light-emitting device using the same.SOLUTION: A lens sheet 1 to be pasted to an exit plane of light of an EL light-emitting device includes a lens layer 2, including a layer composed of a transparent resin containing a diffusion agent, on an exit plane side of which a number of concave lens-shaped unit lenses 2a are arranged. The lens sheet 1 is pasted to the EL light-emitting device.

Description

  The present invention relates to a lens sheet that is attached to the surface of a glass substrate of an EL light-emitting device to increase the light extraction efficiency, and an EL light-emitting device to which the lens sheet is attached. The present invention relates to a lens sheet in which the difference in color temperature is reduced and an EL light emitting device to which the lens sheet is attached.

In recent years, demands for power saving, weight reduction and thinning of display devices have become strict, and in order to satisfy such demands, development of EL light emitting devices as illumination devices and backlights has been promoted.
The EL light-emitting device has a high refractive index for the transparent electrode for energizing the light-emitting layer, and therefore it is easy to cause total reflection between the transparent electrode and the glass substrate, and between the glass substrate and the air, and the light extraction efficiency is poor. There is. Therefore, the EL light-emitting device has much room for improvement in terms of increasing the brightness.

Further, when an EL light emitting device is used as a lighting device or a backlight, the emitted light needs to be white light including light of various wavelengths in a balanced manner. On the other hand, since the light emitted from a single EL element has a narrow spectrum width, the EL light emitting device combines a plurality of phosphors and phosphors to cover all wavelengths in the visible light region in order to obtain white light. Designed as such.
However, the phosphors and phosphors used have different light emitting layer structures and arrangements, and therefore have different optical characteristics such as light distribution. Therefore, white light as designed is irradiated in the front direction, but light having a spectral distribution different from that of the front side is emitted in the oblique direction. Such a difference in spectral distribution can be measured as a difference in color temperature.

  Among the above-mentioned problems, a technique for improving the light extraction efficiency has been proposed for increasing the brightness, for example, by providing a transparent substrate and / or a transparent layer on which the transparent particles are partially projected on the transparent substrate. (Patent Document 1). However, even with such a technique, it cannot be said that the light extraction efficiency is sufficiently improved. In addition, no problem has been proposed regarding the problem that the color temperature differs for each light emission direction.

JP 2009-522737 A

  In view of such a current situation, the present invention can further improve the light extraction efficiency to increase the brightness of the EL lighting device, and further reduce the difference in color temperature for each irradiation angle, An object of the present invention is to provide an EL light emitting device to which the lens sheet is attached.

  In order to solve the above problems, a feature of the present invention is a lens sheet that is attached to the light emission surface of an EL light-emitting device, including a layer made of a transparent resin containing a diffusing agent, and a concave lens on the emission surface side. The lens sheet has a lens layer in which a large number of unit lenses are arranged.

  Another feature of the present invention includes a base material layer, a lens layer provided on one surface side of the base material layer, and an adhesive layer provided on the other surface side of the base material layer, and the diffusing agent is a lens. The above-described lens sheet blended in the layer and / or the pressure-sensitive adhesive layer is included.

  Still another feature of the present invention includes the above lens sheet in which unit lenses are arranged in a hexagonal filling arrangement in the lens layer.

  Still another feature of the present invention includes an EL light-emitting device in which the lens sheet is attached to the light-emitting surface side of the glass substrate.

  According to the lens sheet of the present invention, when including a layer made of a transparent resin containing a diffusing agent and a large number of concave lens unit lenses are arranged on the exit surface side, when convex lens unit lenses are arranged The difference in color temperature is reduced as compared with the above, and the light extraction performance is increased.

Fig.1 (a) is a top view which shows the lens sheet of this invention, (b) is AA sectional drawing of (a). FIG. 2A is a schematic explanatory view showing the operation of the present invention, and FIG. 2B is a schematic explanatory view showing the operation of a conventional lens sheet.

The lens sheet of the present invention is affixed to the light emission surface of an EL light-emitting device, includes a layer made of a transparent resin containing a diffusing agent, and has many concave lens unit lenses 2a on the emission surface side. It has the lens layer arranged.
Moreover, the EL light-emitting device of the present invention is characterized in that the above-described lens sheet is attached to the emission surface side of the glass substrate.

  A preferred embodiment of the lens sheet 1 according to the present invention will be described with reference to FIG. 1. In the present invention, a lens layer 2 in which a large number of concave lens-shaped unit lenses 2a are arranged is arranged on the exit surface side of the lens sheet 1. Yes. By making the unit lens 2a into a concave lens shape, the light extraction efficiency is improved and the reason for eliminating the color temperature difference is not fully understood, but it is estimated as follows.

That is, if a lens sheet is used to improve the light extraction efficiency, the light irradiated to the vicinity of the center of the unit lens 2a is preferably emitted from the lens sheet regardless of whether the unit lens is a convex lens or a concave lens ( In the case where the optical path (1) and (1 ′) in FIG. 2 is a convex lens, the light irradiated near the periphery is reflected to the light source side (optical path (2 ′) in FIG. 2). On the other hand, in the case of the present invention, the light irradiated to the peripheral portion of the unit lens 2a is once reflected by the unit lens 2a, but the reflected light is incident on the plane portion 2b of the lens sheet surface and is emitted therefrom. (The optical path (2) in FIG. 2), it is considered that the light extraction efficiency is improved accordingly.
When a convex lens is used as the unit lens, light having a short wavelength such as blue is likely to be reflected to the light source side as shown in the optical path (2 ′) of FIG. 2 depending on the angle, but has a long wavelength such as red. Light is not easily reflected. Therefore, depending on the angle, only the blue color is reflected and light with a small blue component (low color temperature) is emitted. On the other hand, when a concave lens is used as the unit lens 2a, even a light having a short wavelength such as blue is likely to be emitted, and a portion having a small blue component (color temperature is low) is reduced. Is thought to be resolved.

Even if the unit lens 2a is a concave lens, the light to be emitted may be reflected to the light source side by the unit lens 2a. However, since the light reflected by the concave lens-shaped unit lens 2a is mostly parallel to the lens sheet, the distance until it returns to the light source side and is absorbed becomes longer. Accordingly, there are many opportunities for the optical path to be changed to the exit surface side by the diffusing agent, which is considered to contribute to the improvement of light extraction efficiency.
On the other hand, since the light reflected by the conventionally used convex lens-shaped unit lens is mostly perpendicular to the lens sheet, the distance until the light is returned to the light source side and absorbed is shortened. Accordingly, the opportunity for the optical path to be changed to the exit surface side by the diffusing agent is reduced, and it is considered that this does not contribute to the improvement of the light extraction efficiency.

  In the present invention, the concave lens shape is a hollow shape in which the plan view is circular, the cross-sectional view is horizontal at the bottom portion, and the gradient becomes steeper as it approaches the edge portion.

The arrangement of the unit lenses 2a is not particularly limited, and the arrangement employed in a general lens sheet can be suitably employed in the present invention. In the example shown in FIG. 1A, the unit lenses 2a are arranged in a hexagonal filling arrangement, but may be arranged in a lattice form or in a random form.
When a conventional convex lens-shaped unit lens is employed, the interval between the unit lenses is made as narrow as possible, for example, 1 to several μm, in order to prevent total reflection at the plane portion 2b generated between the unit lenses and improve the luminance. It was formed to become. However, in the case of the present invention, the light having a shallow angle that is totally reflected by the planar portion 2b first enters the unit lens 2a having a concave lens shape, and thus is not easily incident on the planar portion 2b. Therefore, even if the planar portion 2b between the unit lenses is narrowed as in the prior art, there is almost no effect of improving the luminance.

  The method of providing the unit lens 2a on the surface side of the lens sheet 1 of the present invention is not particularly limited. For example, in the method of pressing the resin extruded into a sheet shape with two metal cooling rolls, In the method of disposing a female mold in the shape of the unit lens 2a on the surface, and the method of pressing the resin extruded in a sheet shape with a metal cooling roll and a rubber roll, the shape of the unit lens 2a on the surface of the metal cooling roll And a method of arranging a mold film in which the female mold in the shape of the unit lens 2a is transferred on the rubber roll side.

  As another method, after injecting or coating a radiation curable resin on a mold in which a female mold having the shape of the unit lens 2a is engraved, a resin sheet made of another material is covered as necessary. A method may be used in which the base material layer 3 is formed and solidified by actinic radiation that matches the characteristics of the resin to be used, such as heat, ultraviolet rays, or electron beams. Further, after applying a radiation curable resin on the resin sheet to be the base material layer 3, a mold in which a female mold in the shape of the unit lens 2 a is engraved is applied from above, and the resin used in that state is covered. It may be a method of solidifying by actinic radiation that matches the characteristics.

  The thickness of the lens layer 2 is not particularly limited as long as the thickness is sufficient to support the concave lens unit lens 2a, but is preferably 25 to 75 μm, and particularly preferably 38 to 50 μm.

  The resin used as the material of the lens layer 2 in the present invention is not particularly limited as long as it is a transparent resin. For example, polyolefins such as acrylic, polycarbonate, polystyrene, polyvinyl chloride, polyethylene, polypropylene, and polymethylpentene, cyclic polyolefins, Examples thereof include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides, polyarylate, and polyimide. These may be used alone or in combination of two or more as required.

The base material layer 3 is for supporting the lens layer 2, and the same material as the lens layer 2 can be used. Among them, polyethylene terephthalate (PET) has good adhesion to the lens layer. Is preferable.
Although the thickness of the base material layer 3 will not be specifically limited if it is a grade which can support the lens layer 2, Preferably it is 38-400 micrometers, Especially preferably, it is 50-200 micrometers.
The lens layer 2 and the base material layer 3 may be laminated by coextrusion, or may be bonded together with an adhesive or a pressure-sensitive adhesive. The lens layer 2 may be extruded and laminated on the base material layer 3. Moreover, when it has sufficient intensity | strength only with the lens layer 2, the base material layer 3 can also be abbreviate | omitted.

In order to make it easy to attach the lens sheet 1 to an EL light emitting device or the like, an adhesive layer or an adhesive layer (hereinafter collectively referred to as an adhesive layer 4) is usually provided on the back surface of the lens sheet 1.
The method of providing the pressure-sensitive adhesive layer 4 is not particularly limited, but there is a method of removing the release paper after bonding the double-sided adhesive or pressure-sensitive adhesive prepared on the release paper to the back surface of the lens layer 2 or the base material layer 3. Preferably used. Normally, the release paper is removed immediately before being attached to the surface of the EL light emitting device.

  The pressure-sensitive adhesive or adhesive used as the pressure-sensitive adhesive layer 4 is preferably optical and highly transparent. The refractive index is not particularly limited and can be used as long as it is an ordinary polymer material. However, the refractive index of the material constituting the lens sheet is equal to or higher than the refractive index of the glass substrate of the EL light emitting layer. It is preferable to make them equal or lower because loss due to total reflection at the joint surface can be minimized. The same applies to the adhesive used to bond the lens layer 2 and the base material layer 3 together.

  In the present invention, a diffusing agent is blended in any layer constituting the lens sheet 1. In the present invention, this diffusing agent diffuses light emitted from EL elements or the like having different optical characteristics such as light distribution, thereby emitting the light after eliminating the difference in optical characteristics of each EL element or the like. To eliminate the color temperature difference.

  Any layer containing a diffusing agent may be used, but in a mode in which the lens layer 2 is provided on one surface side of the base material layer 3 and the pressure-sensitive adhesive layer 4 is provided on the other surface side as shown in FIG. As the material layer 3, it is preferable to use a film containing no diffusing agent and blend the diffusing agent into the lens layer 2 and / or the pressure-sensitive adhesive layer 4.

  The diffusing agent that can be used in the present invention is not particularly limited, and examples thereof include organic particles such as crosslinked polyacrylate and silicon resin, and inorganic particles such as aluminum silicate, calcium silicate, silica, alumina, and calcium carbonate. In the case of a spherical shape, a diameter of about 2 to 20 μm can be used, but 2 to 4 μm is preferable. If the size is smaller than this range, there is a disadvantage that the wavelength dependence of the light extraction efficiency increases. If it is larger than this range, the effect of improving the luminance increase rate and the effect of eliminating the color temperature difference tend to decrease. These may be used alone or in combination of two or more as required.

  The difference in refractive index between the diffusing agent and the resin in which the diffusing agent is blended is preferably about 0.08 to 0.12. If the difference is larger or smaller than this range, the luminance increase rate tends to decrease and the color temperature difference tends to increase.

The amount of the diffusing agent used is preferably 11 g or more per square meter of the lens sheet. When the amount was less than 11 g, it was confirmed that the luminance increase rate decreased and the color temperature difference increased. As long as the amount of the diffusing agent is 11 g or more per square meter of the lens sheet, even if the diffusing agent is reduced and the lens sheet is thickened, or the diffusing agent is increased and the lens sheet is thinned, the same Results are obtained.
The upper limit of the amount of the diffusing agent was increased to 50 g per square meter, but the peak of the luminance increase rate and the minimum point of the color temperature difference could not be found. From this, it is considered that there is no upper limit of the amount of the diffusing agent in the principle of the present invention. However, the thickness of the lens sheet used for light extraction of the EL light emitting device is usually required to be about 120 μm and at most about 500 μm, and the upper limit of the amount of the diffusing agent that can be added to the adhesive or the transparent resin is 30 wt. Therefore, the practical upper limit of the diffusing agent is about 23 g per square meter of the lens sheet. Of course, when making a lens sheet exceeding 500 μm, or when using a pressure sensitive adhesive or transparent resin that can contain a diffusing agent in excess of 30% by weight, the diffusing agent exceeds 23 g per square meter of lens sheet. There is no problem.

The lens sheet of the present invention is optically integrated with the emission surface of the glass substrate of the EL light emitting device. Thereby, the light extraction efficiency is improved and the luminance is increased.
In general, EL light-emitting devices are classified into inorganic EL and organic EL depending on the type of light-emitting layer, but the lens sheet of the present invention is used only for organic EL. The structure of the organic EL differs slightly depending on the type of the light emitting layer, but usually a thin light emitting layer is provided on the ITO transparent electrode on the glass substrate, and the metal electrode on the back is provided thereon. In general, light emitted from the light emitting layer is emitted through the ITO transparent electrode and the glass substrate.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited only to this Example.

Example 1
First, a PET sheet (trade name: Cosmo Shine, product number: A4300, thickness: 50 μm, refractive index: 1.60, manufactured by Toyobo Co., Ltd.) was prepared as a base material layer.
As the resin for the lens layer, an ultraviolet curable resin (trade name: JSR Opster, product number: KZ9886F, refractive index: 1.553, manufactured by JSR Corporation) and a diffusing agent (trade name: Tospearl 120, average particle diameter: 2 μm, Refractive index: 1.43, manufactured by Momentive Performance Materials), 11% by weight was prepared.
As the resin for the pressure-sensitive adhesive layer, a diffusing agent (trade name: Uni-Powder) is used for the selected pressure-sensitive adhesive (trade name: purple light, product number: UV-NS051, refractive index: 1.47, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). , Product number: NMB-025T, average particle size: 3 μm, refractive index: 1.57, manufactured by JX Nippon Oil & Energy Corporation) was used at a ratio of 25% by weight.

The lens layer resin is laminated on one side of the above-described PET sheet for the base layer so that the thickness is 38 μm, and a hemispherical projection having a diameter of 78 ± 2 μm and a height of 37 ± 1 μm is formed thereon. However, an original plate having a shape arranged in a hexagonal packing arrangement with a period of 88 μm was placed. In this state, by using an ultraviolet lamp GS UV system from the PET sheet side and irradiating ultraviolet rays under the condition of 1100 mJ / cm ² to cure the ultraviolet curable resin, a concave lens shape with a diameter of 78 ± 2 μm and a depth of 37 ± 1 μm is obtained. A lens layer was formed in which unit lenses were arranged in a hexagonal packing arrangement with a period of 88 μm.
On the other side of the PET sheet, the above adhesive layer resin is applied to a thickness of 30 μm, and then an ultraviolet curing device (trade name: Aicure Light, manufactured by iGraphics Co., Ltd.) is used. The pressure-sensitive adhesive layer was formed by fixing the pressure-sensitive adhesive resin to the PET sheet.

The obtained lens sheet was attached to a glass substrate of an organic EL light emitting device (trade name: white organic EL device panel, manufactured by Tohoku Device Co., Ltd.), and the luminance increase rate and the color temperature difference were measured in that state.
The luminance increase rate is measured by installing a color luminance meter (manufactured by Topcon Technohouse Co., Ltd., model number: BM-5A) at a position 600 mm in front of the organic EL light emitting device, and the obtained value is attached to a lens sheet. It was calculated by dividing by the value of the luminance of the organic EL light emitting device before.
The color temperature difference is determined by measuring the color temperature of the organic EL light emitting device every 5 degrees from the position 600 mm away from the position 600 mm away while rotating the organic EL light emitting device on a turntable. Calculation was performed by extracting the maximum value and the minimum value of the color temperature from the front of the light emitting device to a position of 80 degrees and subtracting the minimum value from the maximum value.

  Table 1 summarizes the shape of the unit lens, the thickness of the lens layer, the blending amount of the diffusing agent in the lens layer, the weight of the diffusing agent blended per square meter of the lens sheet, the luminance increase rate, and the color temperature difference.

Comparative Example 1
A lens sheet of Comparative Example 1 was prepared in the same manner as in Example 1 except that the shape of the unit lens of the lens layer was a convex lens having a diameter of 78 ± 2 μm and a height of 37 ± 1 μm. Was measured. Table 1 summarizes the shape of the unit lens, the thickness of the lens layer, the blending amount of the diffusing agent in the lens layer, the weight of the diffusing agent blended per square meter of the lens sheet, the luminance increase rate, and the color temperature difference.

  By comparing the lens sheets of Example 1 and Comparative Example 1, if the shape of the unit lens is a concave lens type, the luminance increase rate is remarkably increased and the color temperature difference is remarkably reduced as compared with the convex lens type. I understand that.

Examples 2 and 3
The lens sheets of Examples 2 and 3 were prepared in the same manner as in Example 1 except that the thickness of the resin laminated as the lens layer was 42 μm (Example 2) and 50 μm (Example 3), and the luminance was increased. The rate and color temperature difference were measured. Table 1 summarizes the shape of the unit lens, the thickness of the lens layer, the blending amount of the diffusing agent in the lens layer, the weight of the diffusing agent blended per square meter of the lens sheet, the luminance increase rate, and the color temperature difference.

  By comparing Examples 1 to 3, it can be seen that when the blending amount of the diffusing agent contained in the resin is constant, the thicker the lens layer, the higher the luminance increase rate and the smaller the color temperature difference.

Examples 4 and 5
The lens sheets of Examples 4 and 5 were prepared in the same manner as in Examples 2 and 3 except that the amount of the diffusing agent in the resin laminated as the lens layer was 25% by weight. The temperature difference was measured. Table 1 summarizes the shape of the unit lens, the thickness of the lens layer, the blending amount of the diffusing agent in the lens layer, the weight of the diffusing agent blended per square meter of the lens sheet, the luminance increase rate, and the color temperature difference.

  By comparing Example 2 and Example 4, Example 3 and Example 5, respectively, when the lens layer thickness is constant, the higher the amount of the diffusing agent contained in the resin, the higher the luminance increase rate It becomes clear that the color temperature difference is also reduced.

  As described above, according to the lens sheet of the present invention and the EL light emitting device using the lens sheet, it is possible to obtain an EL lighting device that has high luminance and a small color temperature difference of irradiated light.

DESCRIPTION OF SYMBOLS 1 Lens sheet 2 Lens layer 2a Unit lens 2b Plane part 3 Base material layer 4 Adhesive layer

Claims (4)

A lens sheet to be attached to the light emitting surface of the EL light emitting device,
Including a layer made of a transparent resin containing a diffusing agent,
A lens sheet comprising a lens layer on which a plurality of concave lens-shaped unit lenses are arranged on the exit surface side. A base material layer, a lens layer provided on one surface side of the base material layer, and an adhesive layer provided on the other surface side of the base material layer,
The lens sheet according to claim 1, wherein a diffusing agent is blended in the lens layer and / or the pressure-sensitive adhesive layer.   3. The lens sheet according to claim 1, wherein unit lenses are arranged in a hexagonal filling arrangement in the lens layer.   An EL light-emitting device, wherein the lens sheet according to any one of claims 1 to 3 is attached to an emission surface side of a glass substrate.

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