JP2000275411A - Collimating plate and backlight system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collimating plate capable of providing coHimated light that is made sufficiently convergent so that the angle at which the light intensity is 50% is within ±15 deg., the plate having a good contrast ratio over a wide angle of visibility and providing a 1iquid crystal display suitable for use as the monitor of a medical diagnostic device and to provide a backlight system using the same. SOLUTION: This backlight system comprises a collimating plate 20 having transparent support 22, a number of light-transmitting spheres 24 each partially contacted with and secured to the support 22, and a light passage blocking part 27 for blocking the passage of light in areas other than a light-transmitting portion consisting of the portion of contact between the support 22 and the spheres 24 and nearby areas. In this case, the backlight system has a housing optically closed by the collimator plate and having an inner surface provided with a reflection characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a collimating plate for collimating diffused light and a backlight system using the same, and more particularly, a liquid crystal display capable of obtaining a sufficiently focused collimated light. And a backlight system using the same.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display (LCD; Li;
The frequency of use of quid crystal displays has increased significantly. The LCD is an ultrasonic diagnostic device, a CT diagnostic device,
Conventionally, a CRT (Cathode Ray Tub) such as an MRI diagnostic apparatus is used.
The use as a monitor for medical diagnostic equipment, which was mainly used in e), is also being considered.

[0003] LCDs have many advantages such as easy miniaturization, thinness and light weight, but have poor viewing angle characteristics (narrow viewing angle). The contrast ratio sharply drops, and the inversion of the gradation occurs, so that the image looks different.
Therefore, there is a problem that the image cannot be properly observed depending on the position of the observer or the like. In particular, in medical applications such as those described above, diagnosis is performed based on the density of the image, so an image with a high contrast ratio is required. In addition, improper recognition of the image is a cause of misdiagnosis and discrepancies in the diagnostic results. Becomes Therefore, a display image with a high contrast ratio is required particularly over a wide viewing angle. Further, in a medical monitor, a display image is usually a monochrome (black and white) image, and thus the image contrast greatly depends on the viewing angle, which is more problematic.

Further, as a wide viewing angle LCD, IPS (I
n-Plane Swiching mode, MVA (Multidomaoin Vert)
Although LCDs of the Alignment mode are known, they have not been able to secure a sufficiently wide viewing angle for monochrome images, particularly for medical applications.

On the other hand, as an LCD capable of obtaining an image having a good contrast ratio over a wide viewing angle, collimated light (straight light) is used as a backlight (collimated backlight), and furthermore, light passing through a liquid crystal panel is used. Is diffused by a diffusion plate. here,
In order to realize an LCD with a wide viewing angle, it is necessary to condense the diffused light emitted from the backlight light source and use well-collimated light, especially for the aforementioned medical applications. In order to realize an LCD with a wide viewing angle,
It is preferable to use collimated light whose angle at which the light intensity becomes 50% is within ± 15 °.

Normally, collimated light is obtained by condensing diffused light using a light-collecting sheet. However, in a conventional light-collecting sheet, the obtained collimated light has a light intensity of 50%.
% Is about ± 20 °, and it is difficult to obtain sufficient collimated light even when used for the above-mentioned LCD backlight for medical use.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to have excellent light-collecting performance, and to set the angle at which the light intensity becomes 50% within ± 15 °. , It is possible to obtain a sufficiently focused collimated light, for example,
A collimator plate that has a good contrast ratio over a wide viewing angle by being used as a collimator of a backlight of a liquid crystal display and can realize a liquid crystal display suitable for a monitor of a medical diagnostic apparatus, and a backlight using the same It is to provide a system.

[0008]

In order to achieve the above object, a first aspect of the present invention is to provide a transparent support, and a plurality of light transmitting members, a part of which is in contact with and fixed to the support. A collimator plate comprising: a spherical body; and a light-passing inhibition section that inhibits light from passing through a contact portion between the support and the sphere and a region other than a light-transmitting portion formed in the vicinity of the contacting portion.

Here, it is preferable that the aperture ratio of the light transmitting portion on the surface of the support is 3 to 10%. Further, it is preferable that the light passage inhibiting section is any one of a light diffusing unit, a light absorbing unit and a light reflecting unit, and the light diffusing unit includes a binder for fixing the sphere to the support. , A material having a refractive index of 1.3 or more dispersed therein.
The light-transmitting sphere preferably has a reflectance of 80% or more at a thickness of half the average particle diameter.

According to a second aspect of the present invention, there is provided the collimating plate of the first aspect, and a housing which is optically sealed by the collimating plate and whose inner surface has reflection characteristics. A backlight system is provided. In addition, the housing,
Of course, it has a light source. Here, the reflectivity of the inner surface of the housing is preferably 80% or more.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A collimating plate according to the present invention and a backlight system using the same will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

FIG. 1 conceptually shows an embodiment of a display device using a backlight system according to a second aspect of the present invention using the collimating plate according to the first aspect of the present invention. FIG.
Is a so-called liquid crystal display (Li) using a liquid crystal panel 12 as an image display means.
A liquid crystal panel 12, a light diffusion plate 16 for diffusing light carrying an image passing through the liquid crystal panel 12, and collimated light (straight light) incident on the liquid crystal panel 12. And a backlight unit 14 utilizing the collimating plate 20 of the present invention. Here, the backlight unit 14 is obtained by applying the backlight system of the present invention. A driver (not shown) for driving the liquid crystal panel 12 is connected to the liquid crystal panel 12.
Further, various members included in a known LCD are arranged on the display device 10 as necessary. Since the display device 10 of the present invention including the collimating plate 20 of the present invention and the backlight unit 14 to which the backlight system using the same is applied can realize a high contrast ratio over a wide viewing angle, the monitor of a medical diagnostic device can be used. It can be suitably used.

In the display device 10 using the collimating plate 20 and the backlight unit 14 of the present invention, the liquid crystal panel 12 is filled with liquid crystal between transparent supports arranged with a predetermined gap therebetween, and the transparent liquid crystal is filled. It may be a known liquid crystal panel used for various LCDs, in which electrodes are arranged, and an analysis plate is arranged on one surface of the sheet and a polarizing plate is arranged on the other surface. Therefore,
The liquid crystal panel 12 may be either color or monochrome, and the operation mode is TN (Twisted Nematic) mode, S mode.
TN (Super Twisted Nematic) mode, ECB (Electri
All operation modes such as a cally controlled birefringence mode, an IPS mode, and an MVA mode are available. Among them, a TN mode liquid crystal panel is particularly preferable. Although the liquid crystal display of the TN mode has a low viewing angle characteristic, the configuration of the liquid crystal panel itself is simpler than the high viewing angle mode such as the IPS mode and the MVA mode. Therefore, the use efficiency of the backlight at the time of high resolution is high, and high-definition image display can be easily performed. Further, there is no limitation on the switching element or the matrix.

The light diffusing plate 16 is not particularly limited, and various known light diffusing plates (light diffusing sheets) can be used. As a preferred light diffusing plate, a light diffusing plate having a transparent electron conductive layer between a transparent support and a light diffusing layer disclosed in JP-A-5-333202; A light diffusion plate containing an organic polymer binder and organic polymer particles on one surface of a transparent support; a light diffusion layer on one surface of a transparent support, and a binder and a weight average on the other surface disclosed in JP-A-6-230230. Japanese Patent Application Laid-Open No. 7-5306 discloses light diffusion plates each having a back layer containing 0.0001% by weight to 1% by weight (relative to a binder) of organic polymer particles having a particle diameter of 3 μm to 25 μm and partially projecting therefrom. A light diffusion plate having a layer of a crosslinked body of an ionic conductive resin having a cationic quaternary ammonium base in a side chain between a transparent support and a light diffusion layer; disclosed in JP-A-7-174909. Transparent branch It has a diffusion layer containing an organic polymer binder and organic polymeric particles to one side of the body, binder and the refractive index difference between the particles of 0.05 or less, the weight average particle diameter of the particles 1
0 μm to 21 μm, the weight ratio of binder to particles is 1.9 to
3.6, both the coating weight is ^{10g / m 2 ~17g / m 2} , the light diffusing plate standard deviation of the size distribution of the particles is within 3.5 [mu] m; and the like. It is preferable that the diffusion plate 16 has a black mask other than the light passage area. Thus, it is possible to preferably prevent the contrast of the observed image from being lowered due to the reflection and diffusion of the external light.

The backlight unit 14 is a part of the backlight system of the present invention, and emits collimated light (straight light) for displaying an image on the liquid crystal panel 12, as shown in FIG. A so-called collimating backlight system, comprising a housing 18, a light source 19 disposed in the housing 18, a collimating plate 20 of the present invention for condensing light emitted from the light source 19 and emitting the collimated light. Having.

Here, the housing 18 is, as shown in FIG.
A housing that is optically sealed by a collimating plate 20 and has an inner surface, that is, an inner wall surface 18 of the housing 18.
a has the property of reflecting light. The shape of the housing 18 is not particularly limited, and may be any shape as long as it is light-tight by the collimator plate 20. The housing 18 has an inner wall surface 18.
It is preferable that the reflectance of a is 80% or more. The reason for this is that, as will be described later, at 80% or more, it exceeds at least the efficiency of the backlight of a normal liquid crystal display. Of course, the higher the internal reflectivity, the better.
00% is ideal, but the higher the reflectance, the higher the cost of the housing 18. Therefore, the cost may be appropriately selected according to the performance and cost required for the backlight system. The method and means for imparting the reflection characteristic to the inner wall surface 18a of the housing 18 are not particularly limited, and any conventionally known methods, means and members may be used. For example,
As will be described in detail later, a light diffuser (binder 26) in which a light diffusion material such as alumina, barium sulfate, titanium oxide, and calcium carbonate fine particles are dispersed in various adhesives may be applied to the inner surface of the housing 18. , Aluminum (A
l) A thin metal film such as copper (Cu) or the like may be deposited on the inner surface of the housing 18. The material of the housing 18 is not particularly limited, and may be a general plastic or metal.

The collimating plate 20 of the present invention is shown in FIG.
And (B), a transparent support 22, a light-transmitting sphere (hereinafter simply referred to as a bead) 24 fixed in a state where a part of the support 22 is in contact with the support 22, and a support 22.
A light-excluding portion (hereinafter simply referred to as an obstructing portion) 27 that obstructs the passage of light in a region other than the light-transmitting portion 25, that is, a region in contact with the bead 24 and the vicinity thereof, that is, a region other than the light-transmitting portion 25. The beads 24 are arranged and held with the beads 24 facing the liquid crystal panel 12. Therefore, FIG.
As shown conceptually in FIGS. 2 and 3B, the diffused light emitted from the light source 19 (see FIG. 2) is transmitted from the contact portion between the beads 24 and the support 22 and the vicinity thereof under the action of the inhibition portion 27. The light enters the beads 24 only from the light transmitting portion 25 (see FIG. 3B), is refracted by the spherical beads 24, and is appropriately condensed into collimated light. Therefore,
According to the collimating plate 20 of the present invention, it is possible to obtain a sufficiently condensed collimated light such that the angle at which the light intensity becomes 50% is within ± 15 °, and prevent the passage of diffused light. Therefore, by using the collimator plate 20 of the present invention, it is possible to realize a display device (LCD) 10 that can obtain a good contrast ratio over a wide viewing angle.

As the light source 19 of the backlight unit 14,
There is no particular limitation as long as the light source does not have directivity and emits light in random directions, but any light source that can emit a sufficient amount of light as a backlight light source according to the use of the display device 10 is provided. Various backlight light sources such as fluorescent lamps used in known LCDs can be used.

FIG. 4A conceptually shows one embodiment of the collimating plate of the present invention. The collimating plate 20a fixes a light-transmitting, that is, a transparent, sheet-like support (hereinafter, simply referred to as a support sheet) 22, beads 24 that are fixed by partially contacting the support sheet 22, and beads 24. And a binder 26. Here, in the illustrated example, the binder 26 functions as the inhibiting portion 27, and the binder 26 has a light diffusion substance dispersed therein, that is, the binder 26 functions as a light diffuser.

Light diffusing materials generally reflect nearly 100% of incident light without attenuation. Therefore, the light incident not on the beads 24 but on the binder 26, which is a light diffuser, is reflected on the surface or inside of the binder 26 by the light diffusing substance without being substantially attenuated.
8 and the inner wall surface 18a of the housing 18
, And re-enter the collimator plate 20a. Therefore, according to this aspect, the light emitted from the light source 19 can be used very efficiently, and the backlight unit 14 with high efficiency can be realized.

The support sheet 22 is not particularly limited, and various materials can be used as long as they have a sufficient light transmittance and a sufficient mechanical strength according to the application. Specifically, various types of glass, polyester, polyolefin, polyamide, polyether, polystyrene,
Various resin materials such as polyesteramide, polycarbonate, polyphenylene sulfide, polyetherester, polyvinyl chloride, and polymethacrylic acid ester are preferably exemplified. Note that the collimating plate 20a in the illustrated example is used.
First, the collimating plate of the present invention may be in the form of a rigid plate, or may be in the form of a flexible sheet or film. The material and thickness of the sheet 22 may be selected.

The beads 24 are light-transmitting (substantially) spheres,
With a part of the binder 2 in contact with the support sheet 22,
6 fix to the support sheet 22. There is no particular limitation on the material of the beads 24, and various materials can be used as long as they are transparent. For example, various materials of the above-described support sheet material 22 are exemplified, and particularly, the optical characteristics are good. In this respect, a (meth) acrylic resin or glass is preferably used.

The adhesive used for the binder 26 is not particularly limited, and various adhesives can be used as long as the beads 24 can be fixed to the support sheet 22. Examples of the adhesive include vinyl acetate resin and ethylene-acetic acid. Vinyl copolymer,
Vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer, (meth) acrylate resin, butyral resin, silicone resin, polyester, vinylidene fluoride resin, nitrocellulose resin, polystyrene, styrene
Acrylic copolymers, urethane resins, polyethylene, polypropylene, polyethylene chloride, rosin derivatives, and mixtures thereof are preferably exemplified. In particular, an acrylic resin and a silicone resin are preferably used.

As described above, the light diffusing substance is dispersed in the binder 26, so that the binder 26 functions as a light diffuser. There is no particular limitation on the light diffusing substance,
Preferably, a substance having a refractive index of 1.3 or more is preferable. This ensures a refractive index difference between the adhesive and the light diffusing material,
Efficient light diffusion (reflection) with little attenuation can be performed.

In particular, alumina (Al ₂ O ₃ ), barium sulfate (B
aSO ₄ ), titanium oxide (TiO ₂ ), and calcium carbonate (CaC
The fine particles of O ₃ ) are suitably used. These fine particles are not (substantially) spherical, but have many irregularities on the surface.
Therefore, a gap is formed between the contacting fine particles,
In addition, the binder does not flow into this gap, and there are many regions where air exists. Since the refractive index of the fine particles is about 1.7, the refractive index is 1 in many regions in the binder 26.
Therefore, it is possible to secure a large difference in refractive index between the air and the air, and therefore, it is possible to perform highly efficient diffusion (reflection) with greatly reduced attenuation of light in the binder 26.

In particular, by setting the volume ratio of air and the other components (adhesive and fine particles) in the binder 26 to 1: 4 to 3: 2 in the ratio of "air: others", the adhesive force and the reflection are improved. Good results can be obtained in terms of efficiency and the like.
The volume ratio can be achieved, for example, by adjusting the weight ratio between the adhesive and the fine particles.

The size of the light diffusing substance is not particularly limited, but fine particles of 0.2 μm to 1.2 μm are preferred. In addition, although there is no particular limitation on the amount ratio with the adhesive, in terms of inhibition of light passage of the collimating plate 20a, adhesive force, reflection efficiency, and the like,
5: 1 to 50: 1 by weight ratio of "adhesive: light diffusing substance"
It is preferred that

Here, in the collimating plate 20 of the present invention, in a mode in which a light diffuser is used as the inhibition portion 27, in order to emit collimated light with higher efficiency, as shown conceptually in FIG. , Average particle size d of the beads 24
_Diffuser (Binder 26 in the example shown) with half the thickness of _av
Reflectivity of the emitted light I _o / incident light I _i] is, is preferably 80% or more. [I _o / I _i ]> 80% (at d _av / 2) Therefore, in order to realize this, it is necessary to appropriately select the amount ratio of the adhesive and the light diffusing substance, the material, the size of the light diffusing substance, and the like. Is preferred.

When the light diffusing substance is alumina or the like,
80% reflectivity can be obtained with a thickness of approximately 20 μm. Therefore, the average particle size d _av of the beads 24 is 40 μm.
It is preferable to make the above. If the size of the bead 24 is too large, the shape of the bead 24 causes noise to the image.
mm or less is preferable. Therefore, the average particle size d _av of the beads 24 is 40 μm to 5 mm, particularly 100 μm to 2 mm.
It is preferred that

The method of manufacturing the collimating plate 20a is not particularly limited. For example, a coating is prepared by dispersing beads 24 in a binder 26, and the coating is applied to the support sheet 2.
2 may be dried (cured), or the binder 26 may be applied to the support sheet 22 and the beads 2
4 may be sprayed over the entire surface, and then the binder 26 may be dried.

In the present invention, in order to obtain a suitable collimated light, the beads 24 can be uniformly fixed to the support sheet 22 over the entire surface, and the beads 24 should not be buried in the light diffuser. Preferably all beads 2
Binder 2 so that more than half is exposed from the light diffuser.
It is necessary to adjust the amount of 6. Further, if necessary, the beads 24 are pressed or settled by gravity, and the beads 24 are brought into contact with the support sheet 22.
May be dried.

In the above example, by dispersing the light diffusing substance in the binder 26, the binder 26 acts as a light diffuser to form the inhibition section 27, and the diffused light from the light source 19 of the backlight section 14 is transmitted to the beads 24. Although the light is incident on the beads 24 only from the light transmitting portion 25 that is in contact with the support sheet 22 and the vicinity thereof, the present invention is not limited to this. The diffused light may be incident by forming a black mask other than the light transmitting portion 25 including the contact portion and the vicinity thereof.

For example, in the case of the above example, instead of the light diffusing substance, a light absorbing agent such as carbon black is dispersed in an adhesive, and the binder 26 is prepared. A collimator plate having a black mask that allows the diffused light from the light to enter the beads 24 only from the contact portion between the beads 24 and the support sheet 22 and the light transmitting portion 25 formed in the vicinity thereof can be manufactured. According to this aspect, although the efficiency is slightly reduced, it is still possible to obtain the collimated light suitably collected by the beads 24.

In the collimating plate of the present invention, as a mode using a black mask, as shown in a collimating plate 20b shown in FIG. The light transmitting portion 2 formed of the contact portion between the beads 24 and the support sheet 22 and the vicinity thereof using a heat-sensitive developing material or a heat-sensitive ablation material.
In addition to 5, a black mask 28 serving as the inhibition portion 27 may be formed. As shown in FIG. 4 (B), also in this example, diffused light is incident on the beads 24 only from the light transmitting portion 25 which is the contact portion between the beads 24 and the support sheet 22 and the vicinity thereof, and is preferably collected. The emitted collimated light can be obtained.

The collimating plate 20b shown in FIG. 4 (B) and the collimating plate 20c shown in FIG. 4 (C), which will be described later, are similar to the collimating plate 20a shown in FIG. 4 (A). Since they are common, the same components are denoted by the same reference numerals, and a detailed description thereof will be omitted below, and different portions will be mainly described.

The positive photosensitive heat-developable material (hereinafter, referred to as a color-forming material) is a material in which the exposed portion becomes non-color-developed by exposure to light and only the non-exposed portion develops color by subsequent heating. Preferred examples include a thermoresponsive microcapsule containing a colorless electron-donating dye, a compound having an electron acceptor and a polymerizable vinyl monomer in the same molecule, and a color former containing a photopolymerization initiator. . In this coloring material, the compound and the photopolymerization initiator exist outside the thermoresponsive microcapsules. This coloring material
By exposure, the composition outside the thermoresponsive microcapsules is cured, and by heating, a compound having a mobile electron-accepting portion and a polymerizable vinyl monomer portion or an electron-accepting compound moves in the coloring material. Then, the electron-donating colorless dye in the microcapsules is colored to form a positive image. This coloring material is described in detail in JP-A-10-226174. In addition, other than the above, if the material is a positive material, JP-A-3-87827 and JP-A-4-21125
The photosensitive heat-developable material disclosed in JP-A No. 2 can be suitably used.

On the other hand, a heat-sensitive ablation material is a material that undergoes ablation (dissociation, release, etc.) by heating and is removed, and in the present invention, a light-absorbing layer,
Preferably, various materials can be used as long as they can form a black layer and generate ablation satisfactorily by heating with light. Specifically, U.S. Pat. No. 5,429,909 discloses a material which contains a dye and a light absorbing substance in a color-forming layer and evaporates the dye by heating as described in GB 2,083,726. Having a coloring layer containing an image dye, an infrared absorbing substance and a binder described in Japanese Patent Application Laid-Open No. 9-104173 and nitrocellulose and acetic acid described in JP-A-9-104174. Resin materials such as propion cellulose and cellulose acetate, infrared absorbing substances such as carbon black, or further foaming agents (such as azide), accelerators (4,
4'-diazidobenzophenone and 2,6-di (4-
Azidobenzal) -4-methylcyclohexanone)
Examples of such materials include an ablation enhancer and the like.

Such a collimating plate 20b can be manufactured as follows. First, the coloring material or the heat-sensitive ablation material is dissolved or dispersed in a solvent as necessary and applied to the support sheet 22, and dried to form a layer made of these materials (hereinafter, referred to as a material layer).
Next, the beads 24 are fixed on the material layer. For example, a paint in which beads 24 are dispersed in a binder is applied,
Alternatively, after the binder is applied, the beads 24 are scattered over the entire surface, and the binder is dried to fix the beads 24. Prior to the fixing of the beads 24, the beads 24 and the material layer may be brought into contact with each other by pressing or sedimentation as in the above-described example.

After the beads 24 are fixed, collimated light, preferably the same collimated light as that emitted from the backlight unit 14, is incident from the beads 24 side. This allows
The light incident on the beads 24 is refracted, and this light (and light not incident on the beads 24) is incident on the material layer.
Thereby, the bead 24 is refracted by the refractive power of the bead 24.
Light transmitting part 2 consisting of a contact part between the material and the material layer and its vicinity
Only 5 is exposed, and the area other than the light transmitting section 25 that becomes the inhibition section 27 is not exposed. This is because the light incident on the beads 24 is condensed on the light transmitting portion 25 by the beads 24, so that a material layer such as a coloring material or a thermal ablation material in the light transmitting portion 25 can be exposed. This is because the light incident on the other material layers is not collected by the beads 24, so that the material layers other than the light transmitting portion 25 cannot be well exposed. In some embodiments, the beads 24
Material layer (black mask 2)
8) is present and the beads 24 and the support sheet 22 may not directly contact each other, but if the material layer is formed thin, it can be optically ignored.

In an embodiment in which the material layer is formed of a coloring material, the region is exposed by light passing through the beads 24. That is, the light transmitting region of the material layer (the light transmitting portion 2)
Only 5) is exposed and becomes non-colored. Next, by heating and developing the material layer, only the unexposed portion develops color, resulting in a black mask 28 functioning as the inhibition portion 27. As described above, the color developed by this heat development is only at the light transmitting portion 25 consisting of the contact portion between the beads 24 and the material layer and the vicinity thereof, through which the light refracted by the beads 24 passes. The mask 28 is provided with
As a result, it is possible to preferably prevent light from entering the beads 24 from a region other than the light transmitting portion 25.

On the other hand, in the embodiment using the thermal ablation material, similarly, the light or the like refracted by the beads 24 causes the thermal ablation of only the light transmitting portion 25 consisting of the contact portion between the beads 24 and the material layer and the vicinity thereof. The material is heated, and the thermal ablation material in that region is removed by ablation, and the ablation material remains only in the region where the light serving as the inhibition portion 27 does not pass. Therefore, similarly to the above-described embodiment using the color forming material, the black mask 28 serving as the inhibition layer 27 that inhibits light from entering the beads 24 from portions other than the light transmission portion 25 near the contact portion between the beads 24 and the material layer. Is formed.

FIG. 4C shows a conceptual diagram of another example of the collimating plate of the present invention. This collimating plate 20c reflects the diffused light incident on the housing 18 as an obstructing portion 27, in addition to the black mask 28, in addition to the light transmitting portion 25 formed by the contact portion between the beads 24 and the support sheet 22 and the vicinity thereof. In this example, a metal thin film 30 is formed on a support sheet 22 in the illustrated example. Therefore, also in this embodiment, the beads 2 are formed only by the light transmitting portion 25 formed between the contact portion between the beads 24 and the support sheet 22 and the vicinity thereof.
4, the collimated light can be emitted, and the light emitted from the light source 19 of the backlight unit 14 can be emitted in the same manner as in the above-described embodiment in which the binder 26 is used as the light diffuser as the blocking unit 27. Can be efficiently used to emit collimated light with high efficiency.

There is no particular limitation on the method of forming the metal thin film 30 such as aluminum (Al) or copper (Cu) other than the contact portion between the beads 24 and the support sheet 22 and the light transmitting portion 25 formed in the vicinity thereof. Although various methods can be used, as an example, a method using metal of a thin film is exemplified. When the metal thin film is irradiated with high-power collimated light such as a laser from the bead 24 side, the light is narrowed at a contact portion with the bead 24 and generates high heat. This heat causes the metal to melt and agglomerate spherically due to surface tension. Around the agglomerated metal, the metal thin film is not melted and disappears, becomes light transmissive, and the light transmissive portion 25 is formed. On the other hand, the remaining metal thin film that has not melted functions as the light passage inhibiting section 27.

In addition, a metal thin film forming technique such as printing or a metal thin film forming technique such as sputtering or photolithography may be used to form a metal thin film having a large number of openings corresponding to the size of the beads 24 to be used. An aperture grill is formed on the support sheet 22 and the beads 24 are formed.
The beads 24 may be housed in the aperture by a method such as spraying, and the beads may be fixed using a binder or the like. Thus, the collimator plate 20 of the present invention can be manufactured.

The collimator plate of the present invention thus produced
In 20, the light transmission on the entire surface of the support sheet 22 is performed.
The opening ratio of the excess part 25 is preferably 3 to 10%.
Here, the aperture ratio (R₀) Is the following formula
As shown in FIG. 2B, a table of the support sheet 22 is provided.
Total surface area (S₀), That is, the sum of all the light transmitting portions 25
Total area (Σs) and total area (S_i)When
Total area (S ₀) Total of all the light transmitting parts 25
Indicates the ratio of the area (Σs). That is, the light transmission portion 25
Opening ratio (R₀) Is represented by the following equation. R₀= Σs / S₀ S₀= Σs + S_i

In the present invention, the aperture ratio of the light transmitting portion 25 is limited to 3 to 10% for the following reasons. If the aperture ratio is less than 3%, the efficiency of light passing through the collimator plate is low, and it is difficult to obtain the brightness required for a backlight. On the other hand, when the aperture ratio is more than 10%, the efficiency of the light transmitted through the collimating plate is good, but the ratio of the collimated light is not good because the ratio is small. Light intensity is 5
The angle of 0% is within ± 15 °, that is, 15 in absolute value.
° collimated light that is sufficiently condensed to less than or equal to and cannot be emitted, resulting in poor collimating properties. As a result, it is not possible to obtain a sufficiently condensed collimated light, and thus lacks appropriateness as a backlight. Because.

By the way, in the backlight section 14 as shown in FIG. 2 manufactured using the collimating plate 20 shown in FIGS. 3A and 3B, the aperture ratio of the light transmitting section 25 is 3
%, The reflectance of the collimating plate 20 is 80%, and the light use efficiency η when the reflectance of the inner wall surface 18a of the housing 18 is 80% can be calculated as follows. First, 0.03 (3
%) Is directly emitted from the light transmitting portion 25, and the remaining (1-
0.03) (97%) is reflected by the collimator plate 20 at a reflectance of 0.8 (80%),
After being returned to the inside and being turned upside down at a reflectance of 80% on the inner wall surface 18 a, 0.03 is emitted from the light transmitting portion 25. The rest is similarly reflected by the collimating plate 20 and the inner wall surface 18a of the housing 18, and then the light transmitting portion 25
Is repeated.

This can be expressed by the following calculation formula. η = 0.03 + 0.03 × (1−0.03) × 0.8 × 0.8 + 0.03 × (1−0.03) ² × 0.8 ² × 0.8 ² + 0.03 × ( 1−0.03) ³ × 0.8 ³ × 0.8 ³ +... {0.03 / {1- (1-0.03) × 0.8 × 0.8}} 0.079 7.9% of the value of the light use efficiency η calculated as described above.
(0.079) is a sufficiently usable value in consideration that the utilization efficiency of the backlight of the ordinary liquid crystal display is 5 to 6%.

The light transmitting portion 25 has an aperture ratio of 5%, the collimating plate 20 has a reflectivity of 95%, and the housing 18 has
The light use efficiency η of the backlight unit 14 having a reflectivity of the inner wall surface 18a of 95% is 95% as follows, and the result is 35%. η ≒ 0.05 / {1− (1-0.05) × 0.95 × 0.95}｝ 0.35 Such a value of 35% is the light utilization efficiency η of the backlight.
Is extremely effective.

As described above, the collimating plate of the present invention and the backlight system using the same have been described in detail with reference to various embodiments. However, the present invention is not limited to the above-described embodiments and does not depart from the gist of the present invention. Of course, various improvements and design changes may be made.

[0051]

As described above in detail, according to the collimator plate of the present invention and the backlight system using the same, the collimator plate has excellent light condensing characteristics and a light intensity of 50%.
It is possible to obtain a sufficiently converged collimated light whose angle is within ± 15 °. Therefore, by using the collimating plate of the present invention as, for example, a collimator of a backlight device of a liquid crystal display, and by applying the backlight system of the present invention to a backlight device of a liquid crystal display, good collimating light can be obtained. Is incident on a liquid crystal panel, and has a good contrast ratio over a wide viewing angle, so that a liquid crystal display suitable for medical use can be realized.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view conceptually showing an embodiment of a display device using a collimating plate of the present invention and a backlight system using the same.

FIG. 2 is a schematic cross-sectional view conceptually showing one embodiment of the backlight system of the present invention using the collimating plate of the present invention.

FIGS. 3A and 3B are a schematic cross-sectional view and a schematic bottom view, respectively, conceptually showing an embodiment of the collimating plate of the present invention.

FIG. 4 shows (A), (B) and (C), respectively.
FIG. 1 is a schematic cross-sectional view conceptually showing one embodiment of a collimating plate of the present invention.

FIG. 5 is a conceptual cross-sectional schematic view for explaining a preferred embodiment of a collimating plate of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Liquid crystal panel 14 Back light part 18 Housing 18a Inner wall surface 19 Light source 20, 20a, 20b, 20c Collimate plate 22 Support body (support sheet) 24 Beads 25 Light transmission part 26 Binder (light diffuser) 27 Light transmission inhibition Part 28 black mask 30 metal thin film

Claims (7)

[Claims] 1. A transparent support, a large number of light-transmitting spheres partially fixed to the support in contact with each other, and a light transmission comprising a contact portion between the support and the sphere and its vicinity. A light-passing inhibiting portion that inhibits the passage of light in a region other than the portion. 2. The collimating plate according to claim 1, wherein the aperture ratio of the light transmitting portion on the surface of the support is 3 to 10%. 3. The collimating plate according to claim 1, wherein said light passage inhibiting portion is any one of a light diffusing means, a light absorbing means and a light reflecting means. 4. The collimating plate according to claim 3, wherein said light diffusing means is formed by dispersing a substance having a refractive index of 1.3 or more in a binder for fixing said sphere to said support. 5. The collimating plate according to claim 3, wherein said light diffusing means has a reflectance of 80% or more at a thickness of half the average particle diameter of said light transmitting sphere. 6. A collimating plate according to claim 1, wherein said collimating plate is optically sealed.
A backlight system having an inner surface having a housing having reflective characteristics. 7. The housing has an inner surface having a reflectance of 80%.
The backlight system according to claim 6, which is the above.