JP2003004950A - Laminated light transmission plate and method of manufacturing for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated light transmission plate which hardly gives rise to molding strain, eliminates a possibility of exerting an adverse influence on a lens layer in non-reflection treatment of a light transmission plate layer in order to avert mirroring-in and the lens layer are deviated in a liquid crystal cell direction in order to prevent the interference fringes. SOLUTION: This laminated light transmission plate is a light transmission plate to be arranged in order to irradiate the surface of a liquid crystal display device and consists of a laminate of the lens layer 3 consisting of a lens array film continuously formed with many lenses having the respective ridge lines parallel to each other and a light transmission plate layer 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate arranged to illuminate a display surface of a liquid crystal display device, and more specifically, it is composed of a laminate of a lens layer and a light guide plate layer, and particularly, an auxiliary light source. The present invention relates to a laminated light guide plate suitable for a front light type illumination device arranged on the display surface side of a liquid crystal display device, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, various reflective liquid crystal display devices using liquid crystals have been developed as display devices for portable information equipment, which are thin, lightweight and have low power consumption. This reflection type liquid crystal display device is basically supposed to be used under bright illumination capable of obtaining outside light, but attempts have been made to use it in a dark place. Since the reflective liquid crystal display device has a reflective layer, a conventional backlight cannot be used, and a front light type illumination device using an auxiliary light source is required from the front of the display surface.

As shown in FIG. 7, a front-light type illuminating device emits light from a light source 11 which is incident from a light source 11 close to one side surface of the light guide plate while repeating total reflection at an interface between the light guide plate 12 and air. Propagate away. In the meantime, the light is reflected or refracted by the lens array 13 provided on the light guide plate 12 to be directed to the liquid crystal display surface side (a flat surface on the reflection side of the lens array). Reference numeral 14 is a reflector. In this case, the lens array includes prisms of an isosceles triangle (Patent No. 2925530).
No.) or projection-shaped transmission dots (Japanese Patent Laid-Open No. 11-326898).
No.), an arc-shaped groove (Japanese Patent Laid-Open No. 2000-98383), a special groove (SID95DIGEST, P376), and the like.

When a front light type illuminating device is incorporated into a display device to illuminate the liquid crystal display surface, the reflected light from the liquid crystal display surface is reflected again on the liquid crystal display surface side of the front light, and this is the liquid crystal. Since there is a reflection phenomenon visually recognized by an observer on the display surface, the liquid crystal contrast is lowered and the image quality such as a bright line is partially deteriorated. In order to prevent this, this surface is often subjected to antireflection treatment before use.

[0005]

A light guide plate used for a front light and provided with a lens array on one surface is formed by molding a transparent synthetic resin. The molding method is often made by injection molding, and a mold equipped with a precise lens array is required to achieve accurate optical functions. It is necessary to establish molding conditions for copying the shape of the surface. This molding condition is rather narrow and marginal.

[0006] Moreover, in recent years, the demand for thinner front lights has become stronger, and it is becoming a very marginal requirement for injection molding. Moreover, in order to copy the surface of a mold for obtaining a precise optical function, molding is required. In addition to the conditions, distortion due to the orientation of the resin flow peculiar to injection molding is likely to appear as interference fringes due to deflected light. Furthermore, if the surface opposite to the surface on which the lens array is formed (flat surface) is subjected to antireflection treatment to prevent reflection, this distortion causes deformation and causes defects.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have produced a lens layer and a light guide plate layer separately, and laminated the both layers to obtain an intended purpose. The inventors have found that they have been achieved and have reached the present invention.

That is, claim 1 for solving the above problems
The invention is a light guide plate arranged to illuminate a display surface of a liquid crystal display device, wherein the light guide plate is formed from a lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed. A laminated light guide plate characterized by comprising a laminate of a lens layer and a light guide plate layer.

The invention of claim 2 provides the laminated light guide plate according to claim 1, wherein the lens layer and the light guide plate layer are laminated by an adhesive layer or an adhesive layer.

In the invention of claim 3, the lens array film is an isosceles prism array film.
The laminated light guide plate described is included.

A fourth aspect of the present invention includes the laminated light guide plate according to any one of the first to third aspects, in which the lens array film is obtained by extrusion molding.

A fifth aspect of the present invention includes the laminated light guide plate according to any one of the first to fourth aspects, which is for a front light.

Further, according to the invention of claim 6 for manufacturing the laminated light guide plate, when manufacturing the light guide plate arranged to illuminate the display surface of the liquid crystal display device, the respective ridge lines are parallel to each other. A method for manufacturing a laminated light guide plate, which comprises manufacturing a lens array film in which a large number of lenses are continuously formed, and then laminating a lens layer made of the lens array film and a light guide plate layer. .

According to a seventh aspect of the present invention, in a lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed, a molten resin is provided between a molding roll having the shape of the lens and a rubber roll. 7. The manufacturing method according to claim 6, wherein the molten resin is extruded to press the molten resin between the molding roll and the rubber roll to form a mold.

According to an eighth aspect of the present invention, there is provided a lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed between the lens array molding film and the rubber roll, which are molded in the seventh aspect. The manufacturing method according to claim 6, wherein the molten resin is extruded into the mold and the molten resin is pressed between the lens array molding film and the rubber roll to form a mold.

According to a ninth aspect of the present invention, a lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed is curable by ultraviolet rays or heat on a mold roll on which the lens shape is formed. The manufacturing method according to claim 6, wherein a resin is applied, and the resin is cured by irradiation with ultraviolet rays or heating to mold the resin.

According to a tenth aspect of the invention, a lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed is provided on the lens array patterning film molded according to the seventh aspect by ultraviolet rays or heat. The manufacturing method according to claim 6, wherein the curable resin is applied, and the resin is cured by irradiation with ultraviolet rays or heating to mold the resin.

The invention of claim 11 is characterized in that the lens layer and the light guide plate layer are laminated via a pressure-sensitive adhesive layer or an adhesive layer.
The manufacturing method according to any one of 10 is included.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 7, the light source of the front light is usually a linear light source composed of a cold cathode tube, a light emitting diode or the like installed near one end face of the light guide plate. The back surface is surrounded by a reflection plate, and the light is incident from the side surface of the light guide plate.

The light guide plate according to the present invention is characterized by comprising a laminate of a lens layer and a light guide plate layer. The lens layer is
Those continuously manufactured by extrusion molding are preferably used. The reason is that excellent quality backlights for transmissive liquid crystal display devices are being mass-produced, and in addition, those continuously manufactured by extrusion molding are those obtained by injection molding. Compared to the lens surface, it is possible to perform non-reflective processing of the liquid crystal display surface to avoid the reflection phenomenon, and to avoid adverse effects on the lens surface. Is
In order to prevent interference fringes that occur between a large number of lens shapes in which the ridges of the liquid crystal cell and the front light are parallel to each other, you can freely set the direction angle to shift this ridgeline from the liquid crystal cell direction. This is because it has the advantage of

In order to obtain a lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed, a molding roll having the lens shape on the surface is required. This embossing roll is usually manufactured by engraving the lens shape on the surface of a metal roll, but a roll of other material may be used. Usually, a device equipped with a surface temperature such as heating or cooling to keep it constant is used.

As a method for producing a lens array film in which the lenses are continuous, a method of extruding a molten resin between the molding roll and the rubber roll and pressing the molten resin between the two rolls to obtain a mold, and a method of patent The method according to No. 2925069 is mentioned. In the method of the patent, a molten resin is extruded between a molding roll having a lens shape formed on the surface and a rubber roll to form a film in which the lens shape is copied, and then the film is used as a shaping film, and a metal roll having a mirror surface is used. It is manufactured by extruding the film and molten resin between rubber rolls and pressing them to copy the shape of the film onto the molten resin.

The molten resin is a resin for optical products, and for example, acrylic resin, polyvinyl chloride, polystyrene, polyester resin such as polyethylene terephthalate and polyethylene naphthalate, transparent resin such as polycarbonate and cyclic polyolefin are used. Particularly, a high refractive index material such as polycarbonate or polyethylene naphthalate is preferable. In addition, the molten resin as the shaped film is 4-
Crystalline polyolefin resins such as methylpentene-1 resin are preferred.

Another method for producing a lens array film having continuous lenses is a method using a resin which is cured by ultraviolet rays or heat as disclosed in JP-A-10-158349. In this case, after applying a liquid curable resin to a molding roll having a lens shape formed on the surface, the resin is cured by ultraviolet rays or heat to take a mold, and then the mold roll is peeled from the molding roll. Usually, a substrate is often used, and after being integrated with a substrate film before curing or after coating a curable resin on the substrate film, it is pressed against a molding roll having a lens shape on the surface, After curing with ultraviolet rays or heat to mold the lens shape into a curable resin,
It is peeled off from the patterning roll. Then, it is used as a lens array film while being integrated with the substrate. An example of this product is a lens array film in which an acrylic ultraviolet curable resin is used for the lens portion and a biaxially stretched polyethylene terephthalate film is used as the base material.

It is known that the shape of the lens array in which the ridge lines are parallel to each other effectively illuminates the liquid crystal display surface as a front light and does not easily distort or blur the display screen. This shape is also convenient for manufacturing a continuous lens array, and it is easy to manufacture a continuous lens array by forming the ridge line in the circumferential direction of the patterning roll. A triangular prism, a quadrangular protrusion, a circle, a trapezoid, or a special shape has been proposed for the cross-sectional shape in a plane perpendicular to the ridgeline, but the shape of the triangular prism is the normal direction of the liquid crystal display surface. Easy to brighten. Triangles are most efficient when they are unequal sides.

The repeating unit of the ridgeline of the lens array in which the ridgelines are parallel to each other is arbitrary, but if it is too large, the ridgeline is visually recognized by the observer of the liquid crystal display surface, and if it is too small, the illumination efficiency between the liquid crystal displays is small. Is thin, the preferable range is 300 to 50 μm. The thickness of the lens array film is arbitrary, but a range of 50 to 500 μm is suitable for practical use.

A transparent synthetic resin is used for the light guide plate layer laminated with the lens layer formed of the lens array film.
As the example, the synthetic resins used for the lens array film described above are used, but the most typical example is acrylic resin. Its shape is flat or wedge-shaped. In the latter case, the light source is often arranged on the side having a thick cross section, and it is easy to uniformly distribute the light over the entire surface of the light guide plate. The thickness of the light guide plate is arbitrary. Recently, there is a strong demand for a thin type, and it is selected according to the thickness or size of the light source, but most of them are 1 mm or less. Various synthetic resin molding methods are selected as the manufacturing method of the light guide plate, but in the case of a flat plate shape, the one obtained by the acrylic resin casting method is preferable from the viewpoint of strain and surface smoothness. In the case of the wedge shape, it is manufactured by injection molding of transparent synthetic resin, profile extrusion molding, cast molding of UV curable resin, or the like.

In order to prevent reflection on the side facing the liquid crystal display surface and prevent the reflection phenomenon, the light guide plate is often subjected to antireflection treatment on the opposite surface on which the lens layers are laminated. The antireflection treatment is a treatment in which substances having various refractive indexes are formed into thin films and laminated in multiple layers to extremely reduce the reflectance on the surface. The processing method is often produced by vapor deposition and requires some heating. When the molded light guide plate is subjected to anti-reflection treatment, deformation and other troubles are likely to occur due to distortion during molding, resulting in a low yield rate and a disadvantage in terms of cost. In particular,
Molding of a light guide plate having a lens layer has severe processing conditions at the time of injection molding, and since it is subjected to antireflection treatment, it is difficult to achieve both. In this respect, since the laminated light guide plate of the present invention is manufactured by laminating the lens layer and the light guide plate layer separately and is laminated, there is no problem as described above, which is a great advantage.

The lens layer and the light guide plate layer, which are separately manufactured, are laminated with an adhesive or an adhesive. Both the adhesive and the adhesive must be transparent. The refractive index is preferably close to that of the light guide plate layer or the lens array film layer, but 88% or more can be preferably used. The pressure-sensitive adhesive or adhesive may be of a solvent type, an emulsion type, a hot melt type or the like depending on its form, and an acrylic type, a rubber type, a silicone type, a polyester type, an isocyanate type or the like is used from the viewpoint of components. Furthermore, a pressure-sensitive adhesive that has an adhesive function or a pressure-sensitive adhesive that hardens to become an adhesive can be freely selected.

Since acrylic adhesives are mainly used in liquid crystal display devices, acrylic adhesives are suitable for laminating the lens layer and the light guide plate layer. The sticking of the pressure-sensitive adhesive and the sticking of the adhesive is carried out by sticking to either one layer or both layers and laminated. Further, it is possible to adopt a method in which a so-called double-sided adhesive layer coated on a release paper is used to adhere to one surface and then laminated to the other surface. The thickness of these tacky or adhesive layers is arbitrary, but is usually in the range of about 25 to 50 μm.

The lamination is performed by cutting a continuous lens array film into a desired size and then laminating it with a light guide plate of a desired size. The continuous lens array film is laminated with a light guide plate of a desired size. After that, the lens array film may be cut, or particularly in the case of a flat light guide plate, a method in which the lens array film and the light guide plate are laminated and then cut into a desired size may be selected. Upon stacking, it is preferable to stack so that the antireflection treated surface is located on the surface opposite to the lens array stacked surface of the light guide plate.

When a laminated light guide plate composed of a lens layer and a light guide plate layer is used as a front light, the laminated light guide plate is in front of the reflective liquid crystal display surface, and the lens layer faces a person who observes the liquid crystal display surface. It is installed to do. In this case, the ridge lines of the prism array may be placed so as to be offset from the direction of the liquid crystal cell so that interference fringes that occur with the liquid crystal cell do not occur, and the laminated light guide plate of the present invention is designed for this purpose. It also has the advantage that it can be changed freely.

[0033]

The present invention will be described in more detail below with reference to examples, but it goes without saying that the present invention is not limited to these examples.

Examples 1 and 2 (a) Fabrication of lens layer A crystalline polyolefin film 4 was formed between a metal roll and a rubber roll, each of which had the shape of an isosceles triangle shown in FIG.
A polymer of methylpentene-1 was melt extruded to obtain a shaped film. Next, the melted polycarbonate resin was inserted at the same time between the mirror-shaped metal roll and the rubber roll together with the shaped patterning film, and the thickness of the film having a prism array structure of an isosceles triangle whose ridge lines were parallel to each other was formed on the surface of the film. 200 μm, refractive index 1.585
A polycarbonate film of was obtained.

(B) Manufacture of flat light guide plate layer One side of cast acrylic resin plate (trade name: Acrylite, manufactured by Mitsubishi Rayon Co., Ltd.) with a thickness of 1.0 mm is formed by multi-phase vapor deposition containing zirconia as a component. A reflection treatment was applied. This was cut to a size of 50.2 mm in length and 67.2 mm in width and the cut surface was polished to obtain a flat light guide plate layer having a refractive index of 1.490.

(C) Manufacture of wedge-shaped light guide plate layer As shown in FIG. 2, an acrylic resin having a refractive index of 1.490 (trade name: Acrypet, manufactured by Mitsubishi Rayon Co., Ltd.) is used.
1.06 when the thickness is the same as the flat light guide plate layer and the thickness is larger
mm, the smaller one being 0.5 mm, was obtained by injection molding a wedge-shaped forming plate in the longitudinal direction. The molded body was aged at a temperature of 90 ° C. for 6 hours, and then the surface having a gradient of 0.644 ° was subjected to the same antireflection treatment as the flat light guide plate.

(D) Lamination of lens layer and light guide plate layer The lens layer obtained in (a) above is used in (b) or (c) above.
It was cut into the same size as the light guide plate layer obtained in. On the other hand, the light guide plate layer is a double-sided adhesive tape in which an acrylic adhesive having a refractive index of 1.481 has a thickness of 25 μm and both sides are covered with release paper (Polatechno Co., Ltd., trade name AD-ROC) Was cut into the same size as the light guide plate layer, the release paper was peeled off, and the light guide plate layer was attached to the surface opposite to the antireflection surface. Further, peel off the other release paper so that the ridgeline direction of the prism is parallel to the lateral direction of the light guide plate layer, that is, the long side direction, and in the case of the wedge type, the prism long side direction is the thick end face. To the surface opposite to the surface of the prism array structure, and pressure-bonded by roll to obtain a laminated light guide plate as shown in FIG. 3 (Example 1) and FIG. 4 (Example 2).

(E) Evaluation of the laminated light guide plate as a front light A cold cathode tube having a thickness of about 1 mm and a length of 7.5 mm is used as a light source. In that case, it was installed on the thick side end face, and a voltage of 11.25 V was applied through the inverter to light it. Light incident from the end face is refracted and reflected by the prism face and is mainly emitted from the non-reflection processed face, so that the light is reflected in the direction normal to the anti-reflection treated face.
A luminance meter (manufactured by Topcon Corporation, color luminance meter BM5) was installed at a distance of 0 mm, and measurement was performed with a measuring unit candela (cd) in a measurement area with a measurement angle of 0.1 degree. Three measurement points were measured: the center of the light guide plate and the light source side were 12.5 mm from the center and 12.5 mm away from the center, and the average value was also calculated.

(F) Actually Measured Values The types of the light guide plate were measured for the flat plate type and the wedge type.

Comparative Examples 1 to 4 In the case where the lens layer is simply superposed on the light guide plate layer without interposing the adhesive layer (FIG. 5: Comparative example 1, FIG. 6: Comparative example 2), and the light guide plate without using the lens layer. The same measurement was carried out when only the layers were used (flat plate type: Comparative Example 3, wedge type: Comparative Example 4), and the results are shown in Table 1.

[0041]

[Table 1]

As is clear from the results shown in Table 1, it is impossible to expect the emission of light in a desired direction unless the lens layer is provided (Comparative Examples 3 and 4). Moreover, when the lens layer and the light guide plate are not laminated via the adhesive layer but simply superposed, the lens effect cannot be obtained, or even if it is obtained, it becomes very unstable (Comparative Examples 1 and 2). Therefore, it is important to make sure that the lens layer and the light guide plate are integrated into a laminated body.

Next, the non-reflection treated surface of the laminated light guide plates of Examples 1 and 2 was placed so as to face the display surface of the 3.5-inch reflective TFT liquid crystal cell. Then, by observing from the lens surface side, the luminance when the display surface was displayed in white and when the display surface was displayed in black was measured, and this ratio is shown in Table 2 as a contrast ratio.

[0044]

[Table 2]

As can be seen from Table 2, the laminated light guide plates of Examples 1 and 2 can be sufficiently put into practical use without any interference fringes or other troubles.

[0046]

As described above, since the laminated light guide plate of the present invention is manufactured by laminating and laminating the lens layer and the light guide plate layer separately, the lens layer is continuously formed by extrusion molding with almost no molding distortion. Can be used, and since the antireflection treatment of the light guide plate layer to avoid the reflection phenomenon can be performed separately from the lens layer, the lens layer is not adversely affected in the antireflection treatment process. There is no fear of giving it. Further, even when the ridge line of the lens layer is displaced from the liquid crystal cell direction in order to prevent interference fringes, there are many advantages such that the direction angle can be freely set.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a lens (isosceles triangle).

FIG. 2 is a schematic view showing an example of a wedge-shaped light guide plate layer.

FIG. 3 is a schematic view showing a laminated light guide plate of Example 1.

FIG. 4 is a schematic view showing a laminated light guide plate of Example 2.

5 is a schematic view showing a light guide plate of Comparative Example 1. FIG.

FIG. 6 is a schematic view showing a light guide plate of Comparative Example 2.

FIG. 7 is a schematic view showing an example of a conventional light guide plate.

[Explanation of symbols]

1 lens 2 lens film 3 Lens array film (lens layer) 4 Adhesive layer 5a Flat type light guide plate layer 5b Wedge type light guide plate layer 6 Anti-reflection treatment surface 11 light source 12 Light guide plate 13 lens array 14 Reflector

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // F21Y 103: 00 F21Y 103: 00 (72) Minor Tsuzuki Minoru Tsuzuki, 4-13 Anritsu, Suminoe-ku, Osaka-shi, Osaka No. 18 Inside Goyo Paper Co., Ltd. (72) Inventor Fumiya Terakado 4-13-18 Anchi, Suminoe-ku, Osaka-shi, Osaka Prefecture Within Goyo Paper Works Co., Ltd. (72) Inventor Jungo Hirose Suminoe-ku, Osaka City, Osaka Prefecture Anritsu 4-Chome 13-18 F-term in Goyo Paper Co., Ltd. (reference) 2H038 AA55 BA02 BA06 2H091 FA14X FA23X FA29X FA41X FB02 FB03 FB04 FC17 FC19 FC22 FC23 FD06 FD15 FD23 GA17 LA03 LA12 LA16 LA21 5G435 AA01 EE22 BB12 FF16H KK07

Claims (11)

[Claims] 1. A light guide plate arranged to illuminate a display surface of a liquid crystal display device, wherein the light guide plate has a large number of lenses whose ridge lines are parallel to each other. A laminated light guide plate, comprising a laminate of a lens layer and a light guide plate layer. 2. The laminated light guide plate according to claim 1, wherein the lens layer and the light guide plate layer are laminated by an adhesive layer or an adhesive layer. 3. The laminated light guide plate according to claim 1, wherein the lens array film is an isosceles prism array film. 4. The laminated light guide plate according to claim 1, wherein the lens array film is obtained by extrusion molding. 5. The laminated light guide plate according to claim 1, which is for a front light. 6. When manufacturing a light guide plate arranged to illuminate a display surface of a liquid crystal display device, a lens array film in which a large number of lenses whose respective ridge lines are parallel to each other are continuously formed is manufactured. Then, a method of manufacturing a laminated light guide plate, comprising laminating a lens layer formed of the lens array film and a light guide plate layer. 7. A lens array film, in which a large number of lenses whose ridge lines are parallel to each other are continuously formed, extrudes a molten resin between a molding roll having a shape of the lens and a rubber roll to melt the lens. The manufacturing method according to claim 6, wherein the resin is pressed by pressing between the molding roll and the rubber roll. 8. A lens array film in which a large number of lenses whose ridge lines are parallel to each other are continuously formed extrudes a molten resin between the lens array patterning film molded in claim 7 and a rubber roll. 7. The manufacturing method according to claim 6, wherein the molten resin is pressed between the lens array patterning film and the rubber roll to mold. 9. A lens array film, in which a large number of lenses whose ridge lines are parallel to each other are continuously formed, is coated with a curable resin by ultraviolet rays or heat on a molding roll having the shape of the lenses. The method according to claim 6, wherein the resin is molded by curing the resin by irradiation with ultraviolet rays or heating. 10. A lens array film in which a large number of lenses whose respective ridge lines are parallel to each other are continuously formed is formed on the lens array patterning film molded according to claim 7 by a curable resin by ultraviolet rays or heat. 7. The method according to claim 6, wherein the resin is applied, cured by irradiating with ultraviolet rays or heated to mold the resin. 11. The lens layer and the light guide plate layer are laminated via an adhesive layer or an adhesive layer.
The manufacturing method according to item.