JP2013068872A - Lens sheet and el light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a lens sheet preventing reduction in brightness increase rate even when a unit lens is downsized, and inconspicuous in change in chromaticity at different view angles; and an EL light-emitting device using the lens sheet.SOLUTION: A lens sheet includes on its front face side a lens array in which unit lenses 2 each having a convex lens shape are arranged in a hexagonal packing arrangement state. A ratio L2/L1 of a length L2 of a portion where the longest diagonal line 4 of a hexagon lattice 3 dividing the lens array into each unit lens 2 is overlapped with the unit lens 2, to a length L1 of the longest diagonal line 4 is 87-93%. An EL light-emitting device has the lens sheet adhered thereto.

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 and increases the light emission efficiency, and an EL light-emitting device that is attached with this lens sheet, and in particular, even when the unit lens is miniaturized, the luminance is increased. The present invention relates to a lens sheet in which the rate does not decrease and the chromaticity change is not conspicuous when the viewing angle is changed, and an EL light emitting device to which the lens sheet is attached.

2. Description of the Related Art Conventionally, liquid crystal display devices have been widely used as display devices for information devices, particularly portable information devices. In recent years, demands for reducing the weight, thickness, and power consumption of display devices have become stricter. In order to satisfy such demands, the use of EL light-emitting devices as backlights has been promoted.
Since the EL light emitting device emits light as a surface light source from the beginning, a light guide plate or a diffusion plate for changing a point light source or a line light source to a surface light source is unnecessary, which is excellent in terms of weight reduction and thickness reduction. On the other hand, since the transparent electrode for energizing the EL light-emitting device has a high refractive index, there is a drawback that total reflection occurs easily between the transparent electrode and the glass substrate and between the glass substrate and the atmosphere, and the light emission efficiency is poor. is there. Therefore, the EL light-emitting device has much room for improvement in terms of high brightness and labor saving.

As a technique for increasing the light emission efficiency, for example, as described in Patent Document 1, an optical sheet provided with a three-dimensional pattern (hereinafter sometimes referred to as a unit lens) having an optical function on a glass substrate is used. There is a method to paste. However, if the unit lens has a shape that can fill the entire surface of the lens sheet, such as a prism shape, semi-cylindrical shape, pyramid shape, triangular pyramid shape, hexagonal pyramid shape, etc., the chromaticity of the screen changes depending on the viewing direction. Therefore, a so-called microlens sheet in which a large number of circular unit lenses in a plan view are arranged is preferably used.
In addition, there are microlens sheets with unit lenses randomly arranged and those with regular arrangements such as a lattice or hexagonal packing arrangement. Those arranged in are preferred.

On the other hand, if the unit lenses of the microlens sheet are regularly arranged, the size of the pitch in which the pixels of the liquid crystal device are provided and the arrangement pitch of the unit lenses of the microlens sheet used for the backlight are approximately the same. For example, the light that has passed through the unit lens of the microlens may not be able to illuminate the pixel well, and may become partially dark. In order to avoid this phenomenon, a method of precisely aligning the pixels of the liquid crystal device and the unit lens of the microlens in a one-to-one correspondence can be considered. Become high.
Therefore, as a microlens sheet for low-priced products, the arrangement pitch of unit lenses is set to a fraction to a fraction of the pitch of the liquid crystal device pixels, and the microlens sheet is arranged at any position. Even so, a method of enabling the liquid crystal pixels to be irradiated with the light passing through one of the unit lenses is conceivable.

JP 2003-197364 A

  The microlens sheet as described above usually supplies a resin on an original plate in which a female mold in the shape of a unit lens is engraved, and if necessary, applies a pressing force with a roll or the like to make the thickness uniform, It is manufactured by curing by a method suitable for the supplied resin (for example, UV irradiation in the case of UV curable resin, cooling in the case of thermoplastic resin). A gap of about 1 to several microns is generated between the arranged unit lenses.

  On the other hand, as the resolution and miniaturization of liquid crystal display devices progress, it is desirable to further reduce the arrangement pitch of the unit lenses of the microlens sheet, but the width of the gap generated between the unit lenses as described above is constant. The smaller the arrangement pitch is, the larger the proportion of the gap is, and the lower the luminance tends to be. If the unit lens is shaped like a regular triangle, regular square, or regular hexagon so that it can be spread without gaps, the decrease in luminance can be suppressed, but as described above, the phenomenon of chromaticity changing depending on the viewing angle is conspicuous. It becomes like this.

  In view of such a current situation, the present invention can efficiently extract light even if the arrangement pitch is reduced, and can obtain an EL light emitting device in which change in chromaticity is not noticeable when the viewing angle is changed. An object of the present invention is to provide a sheet and an EL light emitting device to which the lens sheet is attached.

  In order to solve the above-described problem, a first feature of the present invention is a lens sheet that is attached to a light emission surface of an EL light-emitting device, in which convex lens-shaped unit lenses are arranged in a hexagonal filling arrangement. Is provided on the surface side, and the ratio L2 / L1 of the length L2 of the portion where the longest diagonal line overlaps the unit lens to the longest diagonal length L1 of the hexagonal lattice dividing the lens array into unit lenses is The content of the lens sheet is 87 to 93%.

  The second feature of the present invention is the above lens sheet, in which the radius of curvature of the portion adjacent to the vertex of the hexagonal lattice in the planar shape of the unit lens is one half or more of the radius of the inscribed circle of the hexagonal lattice. To do.

  A third 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, the ratio L2 / L1 of the length L2 of the portion where the longest diagonal line overlaps the unit lens with respect to the longest diagonal line length L1 of the hexagonal lattice that divides the lens array into unit lenses. By setting the ratio to 87% or more, even when the size of the unit lens is reduced and the ratio of the gap between the adjacent unit lenses is increased, it is possible to suppress a decrease in luminance.
In addition, by setting the ratio to 93% or less, a change in chromaticity due to a different viewing angle can be suppressed in an inconspicuous range.
Furthermore, if the radius of curvature of the unit lens near the apex of the hexagonal lattice is set to half or more of the radius of the inscribed circle of the hexagonal lattice, the change in chromaticity can be further suppressed.

FIG. 1 is a schematic explanatory view showing a lens array provided on the lens sheet of the present invention. FIG. 2 is a schematic explanatory view showing the shape of unit lenses arranged on the lens sheet of the present invention. FIG. 3 is a schematic explanatory view showing another example of unit lenses that can be arranged on the lens sheet of the present invention. FIG. 4 is a schematic explanatory view showing still another example of unit lenses that can be arranged on the lens sheet of the present invention. FIG. 5 is a schematic explanatory diagram for explaining a place indicated by a word indicating a dimensional relationship used in this specification.

The lens sheet of the present invention is affixed to the light emission surface of an EL light emitting device, and as shown in FIGS. 1, 2, and 5, the convex lens unit lenses 2 are arranged in a hexagonal filling arrangement. The lens array 1 is provided on the surface side, and the portion of the hexagonal lattice 3 that divides the lens array 1 into each unit lens 2 with respect to the length L1 of the longest diagonal 4 is overlapped with the unit lens 2. The ratio L2 / L1 of the length L2 is 87 to 93%.
Moreover, the EL light-emitting device of the present invention is characterized in that the lens sheet is attached to the light-emitting surface side of the glass substrate.

  In the present invention, the lens array 1 is provided on the surface side of the lens sheet. In this lens array 1, as shown in FIG. 1, convex lens-like unit lenses 2 are arranged in a hexagonal filling arrangement. The distance between the unit lenses 2 is preferably narrow, and ideally, it is most preferable if the distance between the lenses is zero. However, in reality, the distance between the unit lenses 2 is 1 to several μm depending on the resin roundness and the processing accuracy of the original. A gap of a degree is generated. However, in the present invention, such a gap is permissible.

The shape of the unit lens 2 is a convex lens shape, that is, a shape in which the plan view is close to a circle, a cross-sectional view is horizontal at the apex portion, and the gradient becomes steeper as it approaches the edge portion.
However, the shape in plan view is not a perfect circle, and protrudes outward from the ideal inscribed circle 5 of the hexagonal lattice 3 that divides the lens array 1 into unit lenses 2 at a portion near the vertex of the hexagonal lattice 3. It is also a shape close to a regular hexagon with six parts. That is, as shown in FIG. 2, the ratio L2 / L1 of the length L2 of the portion where the longest diagonal 4 overlaps the unit lens 2 with respect to the length L1 of the longest diagonal 4 of the hexagonal lattice 3 (see FIG. 5). Hereinafter, the ratio of the lens in the diagonal portion is 87 to 93%.
In addition, the longest diagonal line 4 said here means three diagonal lines which pass through the hexagonal center point among the nine diagonal lines of the hexagonal lattice 3, as shown in FIG.

In the present invention, if the ratio of the lenses in the diagonal portion is less than 87%, there is no great difference in luminance increase rate from the microlens sheet in which circular convex lenses are arranged in a normal sectional view, and the unit lens 2 is Even when the ratio of the interval between the unit lenses 2 is increased with respect to the size of the unit lens 2, the effect of preventing the luminance from being lowered is small. On the other hand, if the ratio of the lenses in the diagonal portion exceeds 93%, the radius of curvature of the portion close to the apex of the hexagonal lattice 3 becomes too small, and the change in chromaticity depending on the viewing angle starts to stand out.
Not only the ratio of the lens in the diagonal portion is 93% or less, but also the radius of curvature of the unit lens 2 near the vertex of the hexagonal lattice 3 is set to the inscribed circle 5 of the hexagonal lattice 3 as shown in FIG. If the radius is set to more than half of the radius, the change in chromaticity depending on the viewing angle becomes more inconspicuous.
Also, as shown in FIG. 4, if a shallow depression is provided at the edge of the unit lens 2 and close to the side of the hexagonal lattice 3, the change in chromaticity depending on the viewing angle becomes more inconspicuous.

  The resin used as a material for the lens sheet 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, polymethylpentene, cyclic polyolefin, polyethylene Examples thereof include polyesters such as terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamide, polyarylate, and polyimide.

  The method of providing the lens array 1 on the surface side of the lens sheet 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, the surface of one metal cooling roll In the method of engraving the female mold of the lens array 1 and the method of pressing the resin extruded into a sheet shape between the metal cooling roll and the rubber roll, the female mold of the lens array 1 is engraved on the surface of the metal cooling roll. For example, a method of placing a mold film on which the female mold of the lens array 1 is transferred on the rubber roll side can be exemplified.

  In addition, after injecting or coating a radiation curable resin on the mold in which the female mold of the lens array 1 is engraved, it is solidified by heat, active radiation that matches the characteristics of the resin used, such as ultraviolet rays and electron beams. And a manufacturing method may be used.

  The surface of the lens sheet where the lens array 1 is not provided is substantially a plane. However, the surface on which the lens array 1 is not provided may be a fine concavo-convex structure surface in order to improve the peel strength and adhesive strength of the joint surface with the glass substrate on which the EL light emitting layer is formed.

The lens sheet of the present invention is optically integrated with the exit surface of the glass substrate of the EL light emitting device with the surface on which the lens array 1 is provided facing the light exit side. Thereby, the light emission efficiency is improved and the luminance is increased.
In addition, although the EL light-emitting device used by this invention is divided into inorganic EL and organic EL by the kind of light emitting layer, either EL can be used in this invention. Although the structure differs slightly depending on the type of the light emitting layer, a thin light emitting layer is usually provided on the ITO transparent electrode on the glass substrate, and a 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.

As a method for attaching the lens sheet to the EL light emitting device, other methods are particularly applicable as long as the method can eliminate the air between the back surface of the lens sheet and the light emitting surface of the glass substrate of the EL light emitting device. Although it is not limited, what is necessary is just to fix through the adhesive and adhesive agent which have a refractive index equivalent to a glass substrate or a lens sheet.
Specifically, there can be exemplified a method in which an optical adhesive or pressure-sensitive adhesive is applied to any one of the rear surface of the lens sheet or the light-emitting surface of the glass substrate of the EL light-emitting device and attached to the other surface. In this case, a method in which the release paper is removed after being bonded to one of the surfaces on which the adhesive or pressure-sensitive adhesive on both sides prepared on the release paper is bonded is also preferably used. Moreover, by pressurizing the EL light emitting device with the lens sheet attached in an autoclave, the strength of the attachment can be increased and air between the lens sheet and the EL light emitting device can be completely eliminated.

  The adhesive and pressure-sensitive adhesive for attaching the lens sheet to the EL light emitting device are 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.

  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
A polycarbonate transparent resin “Panlite L-1225Y (trade name)” manufactured by Teijin Chemicals Ltd. is used as a material for the lens sheet, and this is extruded into a sheet form from a T-die at a resin temperature of 300 ° C. A lens sheet was manufactured by a method in which the resin was compressed between a metal cooling roll and a rubber roll. As the cooling roll, one in which a female mold of a lens array in which unit lenses are arranged in a hexagonal filling array was engraved was used.
The shape of the unit lens 2 constituting the lens array 1 is a convex lens shape that fits in a hexagonal lattice in which the length L1 of the longest diagonal is 12.13 μm and the diameter of the inscribed circle 5 is 10.51 μm. With respect to the ideal inscribed circle, it was a shape close to a hexagon, protruding outward at a portion near the vertex of the hexagonal lattice and retracted inward at a portion close to the side. Specifically, the length L3 (see FIG. 5) of the overlapping portion of the line 6 connecting the hexagonal center point and the midpoint of the side and the unit lens (hereinafter this portion may be referred to as a transverse line) is 9 .49 μm, and the length L2 of the overlapping portion of the longest diagonal L1 and the unit lens 2 is 10.84 μm (89.37% of the longest diagonal L1, that is, L2 / L1 = 89.37%). It was.
The thickness of the obtained lens sheet was 240 μm, and the height (difference in height) of the lens array was 5.2 μm.

(Comparative Example 1)
A commercially available diffusion sheet (manufactured by Keiwa Co., Ltd., model number: BS-702) in which resin beads having a diameter of 10 to 20 μm were bonded to a resin sheet with a binder was used as the lens sheet of Comparative Example 1.

(Comparative Example 2)
A lens sheet of Comparative Example 2 was obtained in the same manner as in Example 1 except that the unit lens 2 had a true circle shape with a diameter of 9.50 μm.

(Comparative Example 3)
The unit lens 2 is formed in a hexagonal shape with the longest diagonal corresponding to L2 having a length of 11.53 μm (L2 / L1 = 95.05%) and a transverse line having a length of 9.50 μm. The lens sheet of Comparative Example 3 was obtained in the same manner as Example 1.

(Reference example)
Except for the size of the hexagonal lattice, the length L1 of the longest diagonal is 93.0 μm, the diameter of the inscribed circle 5 is 80.5 μm, and the shape of the unit lens 2 is a true circle with a diameter of 79.5 μm. A lens sheet of a reference example was obtained in the same manner as Example 1.
Note that the reference example is an example of a lens sheet in which the unit lens 2 is sufficiently large, and even if a gap of about 1 to several μm occurs between the unit lenses 2, a problem such as a decrease in luminance is hardly noticeable. The stability of the color tone depending on the height and viewing angle is a goal of the present invention.

(Characteristic evaluation)
Lenses of the above-mentioned Examples, Comparative Examples, and Reference Examples through a contact liquid (refractive index of 1.53) for filling an air gap on the surface of a 2.8-inch two-wavelength white EL light emitting device (Tohoku Device Co., Ltd.) A sheet was attached and visually evaluated.
As a result of the evaluation, regarding the lens sheet of the example, although the size of the lens array is much smaller than that of the reference example, the change in color tone depending on the brightness of the front and the viewing angle is also inferior to that of the reference example. There was no.
On the other hand, the lens sheet of Comparative Example 1 was not much different from the reference example with respect to the change in color tone, but was very inferior in frontal brightness. This is thought to be because the lens array of Comparative Example 1 is randomly provided, so that the distance between the lens arrays is very wide, the ratio of light passing through the lens array is reduced, and the light collection efficiency is lowered.
Moreover, about the comparative example 2, although the change of the color tone was not very different from the reference example, it was inferior in the brightness of the front. This is because the distance between the lens arrays is the same as that of the reference example, but the lens array is smaller than that of the reference example, so the ratio of the distance between the lens arrays increases, and the light collection efficiency decreases accordingly. The cause is considered.
In Comparative Example 3, the brightness of the front was not much different from that in the Reference Example, but the change in color tone depending on the viewing angle was conspicuous. This is offset by the increase in the gap ratio between the lens arrays, because the corners of the hexagons overhang the case of the reference example, and the decrease in light collection efficiency is suppressed. Since the light refracted in this part is diffused non-uniformly, it is considered that the color tone changes greatly.
About an Example, the comparative example 1, a reference example, and the EL light-emitting device (control example) which does not stick a lens sheet, the brightness | luminance and chromaticity were measured with the following method.

(Measurement of brightness)
A color luminance meter (manufactured by Topcon Techno House Co., Ltd., model number: TOPCON BM-5A) was installed at a position 600 mm in front of the EL light emitting device, and the luminance was measured. Table 1 shows the luminance and the luminance increase rate based on the control example.

A color luminance meter (manufactured by Topcon Techno House Co., Ltd., model number: TOPCON BM-5A) was installed at a position 600 mm in front of the EL light emitting device, and chromaticity was measured. The results are shown in Table 1. Note that the chromaticity is indicated by an x value and a y value in the CIE Yxy color system.
In addition, without moving the color luminance meter from the above position, the direction of the EL light emitting device is tilted left and right to 60 ° in 10 ° increments, and the chromaticity is measured at each angle, and for each of the x value and the y value, The maximum value and the minimum value of the measured value at the front and the difference (change amount) from the measured value at the front were calculated. The results are shown in Table 1.

  As described above, according to the lens sheet of the present invention and the EL light emitting device using the same, even when the unit lens is made smaller, the luminance is not lowered as compared with the case where the unit lens is large, and the viewing angle is changed. Since the change in chromaticity in the case is small, it is useful as an EL light emitting device used as a backlight of a liquid crystal display device and a lens sheet used therefor.

DESCRIPTION OF SYMBOLS 1 Lens array 2 Unit lens 3 Hexagonal lattice 4 Longest diagonal 4h The upper limit of the unit lens in a diagonal part 4l The lower limit of the unit lens in a diagonal part 5 Inscribed circle 5 'Radius is more than half of the radius of an inscribed circle Circle 6 Line connecting the center point of the hexagon and the middle point of the side L1 Length of the longest diagonal line of the hexagonal lattice L2 Length of the part where the longest diagonal line overlaps the unit lens L3 Center point of the hexagon and the midpoint of the side The length of the overlap between the unit lens and the unit lens

Claims (3)

A lens sheet to be attached to the light emitting surface of the EL light emitting device,
A lens array in which convex lens-shaped unit lenses are arranged in a hexagonal filling arrangement is provided on the surface side,
The ratio L2 / L1 of the length L2 of the portion where the longest diagonal line overlaps the unit lens with respect to the longest diagonal length L1 of the hexagonal lattice dividing the lens array into the unit lenses is 87 to 93%. Lens sheet.   2. The lens sheet according to claim 1, wherein a radius of curvature of a portion adjacent to the vertex of the hexagonal lattice in the planar shape of the unit lens is at least half of the radius of the inscribed circle of the hexagonal lattice.   An EL light-emitting device, wherein the lens sheet according to claim 1 or 2 is attached to a light-emitting surface side of a glass substrate.

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