JPH1039118A - Ray-directional sheet, and directional surface light source formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ray-directional sheet with which the high directivity of an edge type surface light source is obtainable and the efficient utilization of rays is possible and a thin and uniform surface light source is obtainable, by forming microprojecfions in positions including the light condensing regions of unit lenses. SOLUTION: The one surface of the transparent substrate 2 of this ray- directional sheet is a microlens group 1 having arrayed unit lenses, and the array of the microprojections 3 is formed on the other surface. The microprojections 3 are formed to include the light condensing regions of the rays entering from the microlens group 1 side. The arraying pitch of the respective microlenses is preferably <=300μm in terms of uniformity when the surface light source is formed. Further, the pitch is preferably <=200μm and more preferably <=100μm. The height of the microprojections 3 is preferably in a range of 1 to 50μm. The width of the microprojections 3 is preferably <=1/3 the width of the unit lenses. Further, the microprojections 3 are preferably optically transparent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a light directing sheet and a directional planar light source using the same.

[0002]

2. Description of the Related Art A planar light source is widely used as a back light for a liquid crystal display device in addition to a signboard and various kinds of lighting.

[0003] A general planar light source uses various diffusion plates for randomly diffusing a light beam in order to ensure the uniformity of the luminance of the light beam exit surface. Therefore, the light beam emitted from the emission surface has no directivity and irradiates a wide range.

On the other hand, depending on the use of the planar light source, it is required to narrow the light emitting direction to a narrow range.

[0005] For example, as a method of improving the viewing angle dependency, which has greatly hindered the development of applications of liquid crystal display devices,
Various light diffusion sheets and microlens array sheets (JP-A-53-25399, JP-A-56-65175, JP-A-61-148430, JP-A-6-274)
54, etc.) on the observation surface of a liquid crystal display device. However, in these methods, in order to improve the light use efficiency and the image quality (contrast reduction, image bleeding). A rear light source having a high directivity such as a spread angle of 20 degrees is useful.

For this purpose, there is known a so-called louver sheet in which a large number of light-shielding walls extending along the traveling direction of a light beam are arranged. According to this louver sheet, for example, a surface light source having an arbitrary directivity by blocking a light beam traveling in a direction other than a desired direction from a light beam having a spread of 120 degrees or more on the light exit surface, for example. Is obtained.

In addition, as a backlight for a liquid crystal display device, in order to improve the brightness of the emission surface with respect to power consumption,
A prism sheet in which a large number of minute triangular prisms are arranged is used, and this is achieved by restricting the direction of light emission to some extent. According to this prism sheet, directivity of about 60 degrees can be obtained depending on the optical design of the combined planar light source and prism.

[0008]

However, in any of the conventional methods, a light source having a directivity such that the spread angle is 20 degrees or less without impairing the "thinness" characteristic of the planar light source. Was not obtained.

In particular, it has not been possible to obtain high directivity while ensuring "thinness", light use efficiency, and in-plane uniformity required for a backlight of a liquid crystal display device.

[0010] According to the louver sheet, it is possible to obtain high directivity as described above. However, since the louver sheet needs to form a light-shielding wall extending in the thickness direction of the sheet in the sheet, there is a limit in miniaturization. For this reason, there is a disadvantage that in order to obtain high directivity, a "high" light shielding wall, that is, a large sheet thickness is necessarily required. Furthermore, since there is a limit to the miniaturization of the light-shielding wall, the arrangement of the light-shielding wall can be seen as a backlight of a liquid crystal display device that can be seen up close, and there is a problem in terms of uniformity. Further, in the case of the louver sheet, since a light beam traveling in a direction other than the desired direction is absorbed by the light shielding wall, there is a drawback that the light use efficiency is low.

[0011] On the other hand, the method using the prism sheet provides high light use efficiency, but its directivity is limited, and as described above, its limit is about 60 degrees.

Accordingly, the present invention solves the above-mentioned drawbacks, and in particular, achieves high directivity in an edge type planar light source, enables efficient use of light beams, and provides a thin and uniform planar light source. A sheet and a directional planar light source using the same are provided.

In particular, when a light diffusing sheet (diffusion plate or microlens array sheet) as described above is mounted on a liquid crystal display device, the liquid crystal display device having a widened viewing angle has reduced light use efficiency and display contrast. Decline,
An object of the present invention is to provide a directional planar light source effective for compensating for problems such as image bleeding.

[0014]

The present invention has the following arrangement to solve the above-mentioned problems.

That is, according to the present invention, one surface is a microlens surface on which unit lenses are arranged, and the other surface is provided with an array of microprojections, and the microprojections are incident on the microlens group. And a light directing sheet provided so as to include the light condensing area of the present invention.

According to a second aspect of the present invention, there is provided a structure having a structure in which a light beam introduced into a light guide plate from a linear light source disposed on a side surface of a transparent light guide plate is emitted from at least one surface of the light guide plate. In the planar light source, the light flux traveling inside the light guide plate is introduced into the light directing sheet by optically adhering only the minute projections of the light directing sheet to the surface of the light guide plate. The present invention is directed to a directional planar light source characterized in that directivity is given in an emission direction by a unit lens of a surface sheet.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a light-directing sheet means that a light beam containing light rays in various traveling directions incident from one surface of the sheet is transmitted through the sheet and emitted to the other surface. Sometimes refers to a sheet that can have directivity.

In the present invention, the directivity refers to the degree to which the traveling directions of the light beams emitted from the sheet are uniform. Here, as a scale, the direction of the highest luminance is centered on the direction in which the highest luminance is observed. It is assumed that the angle of the solid angle at which the luminance of 1/2 is observed is expressed as a directivity angle.

The directivity aimed at by the present invention has a high directivity such that the directivity angle is 60 degrees or less, further 40 degrees or less, and further 20 degrees or less.

In the light directing sheet of the present invention, one surface is a microlens group in which unit lenses are arrayed, and the other surface is formed with an array of microprojections, and the microprojections are arranged on the microlens group side. The purpose of the present invention is to provide a light directing sheet provided to include a light condensing area of light rays incident from the light source, and this is schematically illustrated in FIG.

The unit lens constituting the microlens group used in the present invention is a convex lens, and the light beam incident on the unit lens from the normal direction of the microlens group forming surface of the light directing sheet is collected, and the light beam density is highest. After passing through a condensing point (in the case of a one-dimensional lens array, it becomes a "condensing line, but here, it is also referred to as a" condensing point ") according to a custom, it travels while diffusing.

It is preferable that the focal point distance of each microlens is smaller than the microlens array period from the viewpoint of light use efficiency. Here, the “condensing point distance” refers to the distance between the microlens array surface and the converging point assuming that the light directing sheet has a sufficient thickness.

Here, the "microlens array surface"
Means at least 2 irregularities on the surface of each unit lens.
It means a plane inside the light directing sheet that touches and does not intersect at a point.

In a second aspect of the present invention, the light beam directing sheet has a surface on which the minute projections are formed on a light guide plate side and a microlens surface on an observation surface side. The directional planar light source provided in the above is a gist of the invention.

Hereinafter, the present invention will be described using a typical application of the present invention to a backlight for a liquid crystal display device (hereinafter, may be referred to as “LCD”).

The term "backlight" as used herein refers to a light source that uniformly illuminates the liquid crystal cells constituting the LCD from the back, and is roughly classified into an edge type and a direct type according to the position of the light source with respect to the display surface. An edge type backlight is basically a fluorescent lamp that is a line light source installed on the side of the display surface,
A light guide plate having extremely high transparency is arranged, and the light is scattered on the lower surface (FIG. 2) or the upper surface (FIG. 3) of the light guide plate to emit light toward the display surface side. Here, as a method of scattering light rays on the upper surface, a method of irregularly reflecting the reflection surface of a single light guide plate by hairline processing, a method of partially changing the shape of the light guide plate, and a matte reflection surface of one side And those in which a reflective surface is coated with aluminum vapor deposition or a highly reflective film are known. The direct backlight is a method in which one or several light sources are installed directly below a display surface, and a diffusion plate is installed on the display surface side to uniformly emit light rays.

In any of the above backlights, the light emitted to the display surface side has no directivity, but rather emits uniformly in all directions, and its directional angle is generally about 90 to 120 degrees.

The light directing sheet of the present invention can impart excellent directivity to edge type backlights, that is, those in which a fluorescent lamp is arranged on a side surface of a transparent light guide plate. it can.

FIG. 4 shows an example in which a light directing sheet of the present invention is mounted on an edge type backlight in which a fluorescent lamp is arranged on the side of a transparent light guide plate, and the concept of the present invention will be described with reference to FIG. .

Of the light rays 111 that are repeatedly reflected in the light guide plate 4, the light rays 222 that enter the light directivity sheet of the present invention from the minute projections 3 are refracted at the interface 10 between the lens and air.
The light beam 333 emitted therefrom becomes a light beam having directivity.

The microprojections of the present invention need to be formed at positions including the condensing area of the unit lens. Here, the “light-condensing area of the unit lens” means that a light beam incident from the normal direction of the microlens forming surface of the light-directing sheet is condensed by each unit lens to form a projection of the light-directing sheet. It refers to the area that passes through the surface. If the minute projections do not include the light converging region, the directivity of the light beam emitted to the display surface side cannot be obtained. However, it is not necessary that the microprojections are formed uniformly on the entire surface of the sheet, and it is preferable that the arrangement density has a distribution in order to obtain uniformity of luminance when a planar light source is used.

That is, uniform brightness can be obtained in a plane by giving a distribution such that the light sources are arranged coarsely in a part near the light source such as a fluorescent tube and densely arranged in a part far from the light source. Conventionally, in an edge type backlight, a dot pattern of a diffuse reflection ink that extracts a light beam traveling while reflecting multiple times inside the light guide plate to the observation surface side, a projection formed on the light guide plate surface for the same purpose, This is the same idea that grooves, depressions, and the like are arranged with a density distribution.

In this case, the unit lens covers the entire surface of the sheet,
There is no problem that it is formed uniformly, and therefore, there may be a unit lens or a unit lens portion having no projection in the light-collecting region.

In the present invention, the width of the minute projection is preferably 1/3, more preferably 1/5 or less of the unit lens width.
Also, from the viewpoint of light use efficiency, it is preferable that the width of the projection is 1/20 or more of the unit lens width. If the width of the opening exceeds the above range, it is difficult to obtain sufficient directivity of light rays.

In order to form such a small projection, it is necessary to make the light-collecting area smaller than the unit lens width as a characteristic of the unit lens. For this purpose, the distance between the unit lens array surface and the projection forming surface, that is, the thickness of the light beam directing sheet is assumed to be close to the focal point distance of the unit lens.
Further, it is necessary to perform an optical design such as controlling a unit lens shape, a refractive index, a refractive index wavelength dependency, and the like to obtain a lens having small aberration.

The height of the fine projections is preferably in the range of 1 to 50 μm. If the height of the projections is 1 μm or less, light rays repeatedly reflected in the light guide plate cannot be taken into the light directing sheet. If it exceeds 50 μm, the thickness of the entire sheet becomes too thick, which is not preferable.

The microprojections are preferably optically transparent, but are also preferably light diffusing.

In order to make the fine projections light diffusing, a method of adding organic or inorganic particles having different refractive indices to a transparent resin as a material for forming the fine projections, or a method of adding two or more resins having different refractive indices is used. And the like. In order to obtain “light diffusivity”, the surface is generally roughened. However, in the case of the fine projections of the present invention, the light use efficiency is undesirably reduced.

In the present invention, the shape of the minute projection is not particularly limited, but typical cross-sectional shapes include a rectangular cross-sectional shape as shown in FIG. 1 and a trapezoidal shape as shown in FIG. There are a cross-sectional shape, a semi-circular or semi-elliptical cross-sectional shape as shown in FIG. 6, and a triangular or inverted T-shaped cross-sectional shape as shown in FIG.

With the above configuration, the light directing sheet of the present invention can obtain a light beam having high directivity through the microlens through the light beam introduced from the projection.

In the present invention, the size and shape of each micro lens are as follows.

There are roughly two types of microlenses. One is a one-dimensional lens array sheet in which curved surfaces represented by trajectories obtained by translating a curve such as an arc like a lenticular lens are arranged in one direction, and the second is a rectangular, triangular, hexagonal, etc. This is a two-dimensional lens array sheet in which dome-shaped curved surfaces having a low surface are arranged vertically and horizontally.

In the case of a one-dimensional lens array sheet, it is possible to obtain a luminous flux provided with directivity in one direction in the sheet surface, and in the case of a two-dimensional lens array sheet, directivity is obtained in various directions in the sheet surface. Can be obtained.

In the case of a one-dimensional lens array sheet,
Each microlens is a cylindrical lens, and strictly speaking, it is not condensed at one point and is condensed in a line, so it does not connect the “condensed point”. Refers to the focal point.

In the present invention, the arrangement pitch of each microlens is preferably 300 μm or less from the viewpoint of uniformity when a planar light source is used.

Further, 200 μm or less, further 100
It is preferable that the diameter be equal to or less than μm, since the lens arrangement will not be recognized even when viewed close up, such as when used as a backlight of a liquid crystal display device.

Methods for adjusting the focal point and the width of the minute projection include adjusting the refractive index of the material forming the unit lens, adjusting the curved surface shape of the unit lens, and adjusting the distance between the lens and the minute projection. There are methods such as adjustment,
The methods and and especially the method are preferably applied. As a method of adjusting the distance between the unit lens array surface and the microprojection group forming surface, it is possible to adjust the film thickness of the material constituting the lens. In particular, a minute lens having a unit lens array period of 20 μm or less is used. Sometimes,
The simplest and most accurate method of adjusting the distance by the thickness of the transparent substrate, particularly the thickness of the plastic film, by forming the microlens group and the microprojection group array on both sides of the flat transparent substrate, respectively. Is preferably applied. Of course, in this case, the adjustment of the material constituting the lens and the adjustment of the thickness of the transparent substrate may be combined.

Next, the materials constituting the light directing sheet of the present invention and the manufacturing method thereof will be described.

First, the material constituting the microlens is not particularly limited as long as it is a substance transparent to at least visible light. Examples of the material include glass and various plastic materials. Is preferably used. Examples of the plastic material include a polyester resin, an acrylic resin, a urethane resin, an epoxy resin, a polycarbonate resin, a polystyrene resin, and a mixture thereof, but are not limited thereto, and handling properties such as viscosity, refractive index, etc. Is appropriately selected in consideration of the optical characteristics and the like. When the microlens is very fine, an ultraviolet curable resin is also preferably used.

Examples of the method for forming the microlens group include a method using a mold, a method using a photolithography method and its application, and the method using a mold is most preferable in terms of productivity and the like. At this time, a UV-curable resin, a thermosetting resin, a thermoplastic resin, or the like can be appropriately selected and used as a material for forming a microlens, but it can be cured in a short time, and is easy in equipment. The method using a resin is most preferable.

When the microlens group has an arrangement pitch of 200 μm or less, the focal point distance of those lenses is also 2
It is often about 00 μm to several tens μm.

When such a microlens group is used, it is necessary to adjust the distance between each microlens and the minute projection group formed on the back surface near the focal point distance of each microlens. ,
A method in which a microlens group is formed on one side and a microprojection group is formed on the other side is preferably used.

Further, in this case, a biaxially stretched film, especially a polyester film, is preferably used as a base plastic film from the viewpoint of strength and handleability.

Needless to say, a base film that is as transparent as possible to visible light and free from turbidity is preferred.

The material for forming the microprojection group is not particularly limited, but various resins such as acrylic resin, polyester resin, urethane resin, epoxy resin, polycarbonate resin, styrene resin, and novolak resin are used. can do.

As a method of uniformly forming the microprojections on the surface opposite to the surface on which the microlenses are formed, there is a method of using a mold whose positions are perfectly matched. Specifically, the following method can be applied as a method for accurately aligning the converging point of the microlens with the position of the minute projection.

That is, a microlens array having a desired arrangement pitch is formed on a transparent substrate such as a plastic film by a mold or the like, and a resin composition which is cured by a curing energy beam on a surface opposite to the surface on which the microlenses are formed. An object (hereinafter, simply referred to as “photo-curable resin”) is applied or laminated, and a curing energy ray having relatively high parallelism is irradiated from the microlens side, and light at a position corresponding to the vicinity of the converging point of the microlens is irradiated. This is a method in which a curable resin is cured, and an uncured portion is dissolved and removed with an appropriate developer to form the resin. In this case, the thickness of the transparent substrate is adjusted by the focal point distance of the microlens. However, the focal point does not exist inside the transparent substrate, but is slightly outside the transparent substrate to uniformly remove the fine protrusions. Preferred for molding. This theory will be specifically described with reference to FIG. The curing energy ray 9 irradiated from the microlens 1 side is refracted and condensed by passing through the microlens 1 and converges on a converging point 11. Since the converging point 11 is inside the photocurable resin 3 ', the photocurable resin can be cured uniformly and with high curability.

The photocurable resin preferably used in the present invention is mainly composed of a monomer and / or a prepolymer having at least one functional group. In some cases,
In addition to the main component, it is necessary to add a substance that generates ions or radicals by irradiation with a curing energy beam, a so-called photopolymerization initiator. The term “main component” as used herein refers to a substance containing 50% or more, preferably 60%, of all components of the paint.

The term "functional group" as used herein means an atomic group or a bonding mode, such as a vinyl group, a carboxyl group, or a hydroxyl group, which causes reactivity. In the present invention, the resin composition is cured by irradiation with a curing energy ray. From the viewpoint of stiffness, those having a vinyl group such as an acryloyl group are preferably used in terms of curability and the like.

Such an acryloyl group-containing monomer can be appropriately selected from known ones and can be used without any particular limitation. Typical examples thereof include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate and 2-hydroxyethyl acrylate. Monofunctional ones such as propyl acrylate, acrylates of tetrahydrofuryl and its derivatives, dicyclopentenyl acrylate, 1,3-
Butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, hydroxypivalic acid ester neopentyl glycol and its derivatives diacrylate, tripropylene glycol diacrylate There are bifunctional compounds such as acrylate and dimethylol tricyclodecane diacrylate, and trifunctional or higher compounds such as trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythrol hexaacrylate.

Among the above-mentioned monomers, those having three or less functional groups have a film hardness after curing of not more than HB and are excellent in flexibility, many have low crosslinking density and low volume shrinkage, and It is preferably used because it has excellent properties.

In the present invention, in addition to the above monomers, a prepolymer is often used in combination with the above monomers. The prepolymer used in the present invention is not particularly limited as well as the monomer, but is represented by polyester acrylate, epoxy acrylate, urethane acrylate, etc., and is trifunctional for reasons of low volume shrinkage and flexibility. Hereinafter, a bifunctional or trifunctional one is preferably used.

The curing energy rays referred to in the present invention include visible rays, ultraviolet rays, electron beams, etc., and ultraviolet rays are most preferably applied in view of versatility of resin, workability and equipment.

When the curing energy rays are ultraviolet rays, it is necessary to add a substance which generates ions or radicals upon irradiation with ultraviolet rays, that is, a photopolymerization initiator, in addition to the monomers and prepolymers.

The photopolymerization initiator used in the present invention is not particularly limited, but typical examples include acetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoin ether, benzyldimethyl ketal. System, benzoin benzoate system, α
Carbonyl compounds such as -acyloxime esters, sulfur compounds such as tetramethylthiuram monosulfide and thioxanthone, and phosphorus compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide. These may be used alone or in combination. Used mixed.

In the present invention, the photopolymerization initiator is added in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 20 parts by weight, per 100 parts by weight of the monomer and / or prepolymer component.
It is preferably 15 parts by weight. If the photopolymerization initiator is less than the above range, the curability will be low, and if the photopolymerization initiator exceeds the above range, bleed out after curing will occur, which is not preferable.

In the present invention, various additives may be used before, during and after the curing of the resin composition for the purpose of controlling the physical properties and properties of the resin or cured film.

Here, as a substance for controlling properties and physical properties before curing, there are a paint stabilizer (anti-gelling, anti-curing), a thickener (improvement of coating properties) and the like.

Materials controlling the properties during curing include a photopolymerization accelerator and a light absorber (both of which adjust the curing behavior).
and so on.

Further, as a substance for controlling film properties after curing, there are a plasticizer (improving flexibility), an ultraviolet absorber (imparting light resistance), and the like.

The light directing sheet of the present invention may be further provided with antireflection, antistatic, hard coat, adhesive processing, and other substrates, depending on the application and required characteristics. Various processes such as matching can also be performed.

A directional planar light source according to a second aspect of the present invention is a light source that emits a light flux introduced into a light guide plate from a linear light source disposed on a side surface of a transparent light guide plate, at least in the light guide plate. In a planar light source having a structure of emitting light from one surface, only the minute projections of the above-mentioned light directing sheet are optically brought into close contact with the surface of the light guide plate so that the light flux traveling inside the light guide plate is directed to the light beam. The light-directing sheet is introduced into the light-directing sheet, and has a directivity in the emission direction by the unit lens.

As a method of adhering only the projecting portions of the light directing sheet to the surface of the light guide plate, a method of sticking with various adhesives and / or adhesives (hereinafter, collectively referred to as “adhesives”) can be applied. . In this case, an adhesive or the like is applied to the entire surface of the light guide plate in advance, and the light directing sheet is attached to the light directing sheet, or the minute projections of the light directing sheet are made of an adhesive and / or adhesive resin. Preferably, a method in which an adhesive or the like is applied only to the minute projections of the light directing sheet and is attached to the light guide plate is preferably used. In addition, when an adhesive or the like is applied to the entire surface of the light guide plate, it is preferable to apply the adhesive at a thickness equal to or less than the projection height of the light directing sheet, since the light directing sheet can be easily attached.

As other constituent elements of the planar light source, those used in the conventional planar light source can be applied.

[0075]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments, but is not limited thereto.

(1) Formation of Microlens Group (a) A microlens group molding die in which a groove having a side surface shape of an elliptical cylinder is dug at a period of 175 μm in a stripe shape is prepared.
This was filled with an ultraviolet curable resin (acrylic resin / urethane resin) having a refractive index of 1.54. The converging point distance of the microlens group obtained by this is indicated by the distance from the concave portion of the lens to 145 μm (calculated value in the polyester film when the concave portion is assumed to be continuous with polyester having a refractive index of 1.63). ).

Next, an ultraviolet curable resin filled in the mold was placed on a polyester film having a thickness of 125 μm, irradiated with ultraviolet rays, and after curing, the mold was peeled off to obtain a microlens group having a pitch of 175 μm. (Example 1) (b) A mold of a microlens group in which a groove having a side surface of an elliptical cylinder was dug at a period of 55 μm in a stripe shape was prepared, and this was filled with the ultraviolet curable resin described in the preceding paragraph. The focal point distance of the micro lens group obtained by this is also 43 μm.
m.

Next, an ultraviolet curable resin filled in the mold was placed on a 38 μm-thick polyester film, irradiated with ultraviolet rays, and after curing, the mold was peeled off to obtain a 50 μm pitch microlens group. (Example 2) (2) Formation of microprojections Urethane acrylate oligomer ("Kayarad" U)
X4101: 40 parts by weight of Nippon Kayaku Co., Ltd., 60 parts by weight of acrylic monomer (“Kayarad” HX220: Nippon Kayaku Co., Ltd.), 10 parts by weight of photopolymerization initiator (“Irgacure” 184: Ciba Geigy) Part, photopolymerization accelerator ("Kayacure" EPA: manufactured by Nippon Kayaku Co., Ltd.)
5 parts by weight and 2 parts by weight of an ultraviolet absorber ("Tinuvin" PS: manufactured by Ciba Geigy) were added, and the mixture was stirred until the powder was dissolved to obtain a resin for forming fine projections. The resin is applied with a thickness of 40 μm on the surface opposite to the surface on which the microlens array is formed, and ultraviolet rays having a high degree of parallelism are irradiated from the microlens formation surface side to cure the microlens focal point portion,
The uncured portions were dissolved and removed with methyl isobutyl ketone to form minute projections, thereby obtaining a light directing sheet of the present invention.

(3) Preparation of Directional Planar Light Source A transparent acrylic plate having a width of 212 mm × a length of 159 mm and a thickness of 3 mm was prepared as a transparent light guide plate, a fluorescent lamp was arranged on the side surface, and the light guide plate was placed on the light guide plate. The surface of the light directing sheet on which the microprojections were formed was adhered with an acrylic adhesive to obtain a directional planar light source.

(4) Evaluation of Characteristics The degree of emission of the light emitted from the directional planar light source obtained as described above is set in the horizontal direction (microlens group arrangement direction) with the normal direction of the display surface being 0 degree. The luminance of the emission surface was measured up to ± 60 degrees (total 120 degrees) in two-degree increments. The evaluation results are shown in Table 1 (data is described in steps of 20 degrees).

[0081]

[Table 1] Table 1 shows that the directional planar light source provided with the light directivity sheet of the example of the present invention has excellent directivity and high luminance.

In Table 1, Comparative Example 1 A conventional LCD backlight (edge type) equipped with a normal microprism array (pitch: 31 μm), Comparative Example 2 uses a louver sheet, Comparative Example Reference numeral 3 denotes a conventional backlight in which nothing is performed.

[0083]

According to the present invention, it is possible to provide a sheet which can be provided with directivity only by being superposed on a light guide plate, and a directional planar light source using the same.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a light directivity sheet of the present invention.

FIG. 2 is a schematic diagram illustrating an example of an edge type backlight.

FIG. 3 is a schematic view showing an example of an edge type backlight.

FIG. 4 is a schematic view showing an example of a directional planar light source according to the present invention.

FIG. 5 is a schematic view showing an example of the light directivity sheet of the present invention.

FIG. 6 is a schematic view showing an example of the light directivity sheet of the present invention.

FIG. 7 is a schematic view showing an example of the light directivity sheet of the present invention.

FIG. 8 is an example of a method for producing a light directivity sheet of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Micro lens group 2 ... Transparent substrate 3 ... Microprojection 4 ... Light guide plate 5 ... Diffusion plate 6 ... ... Scattering surface 7 ... Reflection plate 8 ... Fluorescent lamp 9 ... Curing energy ray 10 ... Interface between microlens and air 11 ... ... Condensed point 111 ... Light rays that are repeatedly reflected in the light guide plate 222 ... Light rays emitted from the minute protrusions 333 ... Light rays that are refracted at the interface 10 and imparted with directivity

Claims (9)

[Claims] 1. One surface is a microlens surface on which unit lenses are arrayed, and the other surface is formed with an array of microprojections, and the microprojections collect light rays incident from the microlens group side. A light directivity sheet provided including a region. 2. The light directivity sheet according to claim 1, wherein the arrangement pitch of the unit lenses is 300 μm or less. 3. The light directing sheet according to claim 1, wherein the height of the minute projections is in a range of 1 to 50 μm. 4. The light directivity sheet according to claim 1, wherein the width of the minute projection is equal to or less than １ ／ of the unit lens arrangement pitch. 5. The light directing sheet according to claim 1, wherein the unit lens array surface is formed on one surface of a transparent substrate, and the fine projections are formed on the back surface. 6. The light directing sheet according to claim 5, wherein the transparent substrate is a plastic film. 7. The light directing sheet according to claim 6, wherein the plastic film is a polyester film. 8. The light directing sheet according to claim 1, wherein the fine projections have an array density distribution in the plane of the light directing sheet. 9. A planar light source having a structure in which a light beam introduced into a light guide plate from a linear light source disposed on a side surface of a transparent light guide plate is emitted from at least one surface of the light guide plate.
A light beam traveling inside the light guide plate is introduced into the light directing sheet by optically adhering only the minute projections of the light directing sheet according to claims 1 to 8 to the surface of the light guide plate. A directional planar light source characterized in that directivity is provided in an emission direction by a unit lens of a light beam directing sheet.