JP2001174610A - Method for producing optical collimator sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high performance optical collimator sheet which efficiently converges diffused light, has high directivity and gives high luminance collimated light. SOLUTION: A coating fluid containing a binder and a dispersed light scattering material is applied on a transparent substrate and many light transmissive spheres are scattered on the coating fluid. The light transmissive spheres not bonded to the coating fluid are removed, the light transmissive spheres bonded to the coating fluid in a monolayer are pressed and brought into contact with the substrate and then the coating fluid is hardened to produce the objective optical collimator sheet.

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 an optical collimator sheet for making diffused light parallel, and
The present invention relates to a method for manufacturing an optical collimator sheet capable of producing a high-performance optical collimator sheet capable of obtaining collimated light having high directivity and high brightness.

[0002]

2. Description of the Related Art In recent years, the frequency of use of liquid crystal displays (LCDs) as word processor and computer displays has been greatly increased. In addition, the use of the LCD as a monitor of a medical diagnostic apparatus such as an ultrasonic diagnostic apparatus, a CT diagnostic apparatus, and an MRI diagnostic apparatus, which has conventionally been mainly a CRT (Cathode Ray Tube), is being considered.

[0003] LCDs have numerous advantages, such as being easy to miniaturize, thin and lightweight. On the other hand, the viewing angle characteristics are poor (the viewing angle is narrow). That is, the contrast ratio of the image sharply decreases depending on the viewing direction and the angle, and the inversion of the gradation also 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.
Inappropriate recognition of an image causes erroneous diagnosis and discrepancy in diagnosis results. Therefore, especially over a wide viewing angle,
A display image with a high contrast ratio is required. further,
In a medical monitor, a display image is usually a monochrome image, and the image contrast greatly depends on the viewing angle, which is more problematic.

As a wide viewing angle LCD, IPS (In-Plan)
e Swiching) mode, MVA (Multidomaoin Vertical A)
lignement mode LCDs are also known. However, even with these, a sufficiently wide viewing angle has not been ensured for monochrome images, particularly for medical use.

On the other hand, as an LCD capable of obtaining an image having a good contrast ratio over a wide viewing angle, collimated light (parallel light) is used as light (backlight) illuminating the liquid crystal panel from the back (collimated backlight). Further, there is known an LCD in which light carrying an image passing through a liquid crystal panel is diffused by a diffusion plate. Also,
A PL-LCD that combines ultraviolet light and a fluorescent screen is also being studied. In these LCDs, higher contrast can be realized by using a backlight having higher directivity and higher luminance. Therefore, for medical applications requiring a high contrast and a wide viewing angle as described above, it is particularly preferable to use a backlight having strong directivity and high luminance. Therefore, an appearance of an optical collimator having strong directivity and capable of obtaining high-brightness collimated light is desired.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-performance optical collimator sheet capable of efficiently condensing diffused light, having strong directivity, and obtaining high-brightness collimated light. It is an object of the present invention to provide a method for manufacturing an optical collimator sheet that can be used. By using the optical collimator sheet manufactured by the manufacturing method of the present invention, a fluorescent lamp is used in a rear projection display such as a liquid crystal display of a type in which the distance from the image forming surface to the screen (observation surface) is relatively short. When used with a diffusion light source such as a liquid crystal panel, an image display element such as a liquid crystal panel, or a light diffusion screen (or a fluorescent screen), a high-quality image with a wide viewing angle can be displayed.

[0007]

In order to achieve the above object, the present invention provides a coating solution containing a binder and a light scattering substance dispersed on a transparent support. The transparent spheres that are not adhered to the coating liquid are removed by spraying the spheres, and the light-transmitting spheres that are adhered in a single layer to the coating liquid are pressed to contact the support, and then the coating liquid And a method for producing an optical collimator sheet, characterized by curing the sheet.

Further, the contact between the light-transmitting sphere and the support due to the pressing is performed by setting the coating liquid to be semi-cured and having a thickness T of “(R / 10) <T <(R / 2)”. It is preferable to carry out under the conditions (in the above formula, R is the diameter of the light-transmitting sphere).

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing an optical collimator sheet according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 conceptually shows an example of a display device using an optical collimator sheet manufactured by the manufacturing method of the present invention. A display device 10 shown in FIG. 1 is a so-called liquid crystal display (hereinafter, referred to as an LCD) using a liquid crystal panel 12 as an image display means.
2, a backlight unit 14 that uses a light collimator sheet 20 manufactured by the manufacturing method of the present invention, in which a backlight is incident on the liquid crystal panel 12, and light that diffuses light carrying an image that has passed through the liquid crystal panel 12. And a diffusion plate 16.

The display device 10 includes a backlight unit 1
4 is a known LCD except that the optical collimator sheet according to the present invention is used. That is, the backlight unit 1
The collimated light (collimated backlight) emitted from 4 enters the liquid crystal panel 12 driven according to the display image and passes therethrough to become light carrying an image, which is diffused by the light diffusion plate 16. The image is displayed.

FIG. 2 shows a conceptual diagram of the optical collimator sheet 20. The light collimator sheet 20 according to the present invention includes a transparent support sheet 22 and a plurality of light-transmitting spheres 24 (hereinafter, beads 2) that are partially in contact with and fixed to the support sheet 22.
4) and a reflective layer 26 that diffuses light incident on portions other than the contact portion between the support sheet 22 and the beads 24 (or further in the vicinity of the contact portion) and fixes the beads 24 to the support sheet 22. It is configured to have.

As shown in FIG. 2, the optical collimator sheet 20 is arranged and held in the backlight unit 14 with the beads 24 facing the liquid crystal panel 12. Housing 18
The diffused light emitted from the light source inside enters from the support sheet 22 side, and enters the beads 24 from the contact portion between the beads 24 and the support sheet 22 by the action of the reflection layer 26,
The light is refracted by the spherical beads 24 and is appropriately condensed to be collimated light (parallel light). On the other hand, the diffused light other than the contact portion, that is, the diffused light incident on the reflective layer 26 is preferably diffused on the surface or inside of the reflective layer 26, that is,
Reflected by the optical collimator sheet 2, returned to the housing 18, reflected by the inner surface of the housing 18, and again
Incident at 0.

That is, the optical collimator sheet 20
Of the diffused light emitted from the light source, only the light appropriately incident on the beads 24 is collected and emitted as collimated light. On the other hand, the light incident on the reflection layer 26 is well reflected, so that the light emitted from the light source can be used without waste. Therefore, the optical collimator sheet 20
Can emit collimated light with high directivity and high luminance with little light passing through the reflective layer 26 (hereinafter referred to as leakage light), high light use efficiency, and high efficiency. Therefore, by using the optical collimator sheet 20, it is possible to realize a display device 10 which realizes a high contrast ratio over a wide viewing angle and is suitable for a monitor of a medical diagnostic apparatus.

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. The optical collimator sheet 20 is
It may be a rigid plate or a flexible sheet or film. The material and thickness of the support sheet 22 may be selected depending on the required mechanical strength and application.

The beads 24 are light-transmitting (substantially) spheres,
In the illustrated example, a part thereof is in contact with the support sheet 22 and is fixed to the support sheet 22 by the reflection layer 26 (the binder thereof). The material of the beads 24 is not particularly limited, and various materials can be used as long as they are transparent. For example, various examples of the material of the above-described sheet material 18 are provided.
Glass and (meth) acrylic resin are preferably used in terms of good optical characteristics.

The diameter R of the beads 24 is not particularly limited, and may be appropriately selected according to the use and size (area) of the optical collimator sheet 20. If the beads 24 are too small, the reflection layer 26 described later must be thinned.
Leakage light and the like increase, and as a result, the directivity and efficiency of the optical collimator sheet 20 (that is, the luminance of the emitted light) decrease. Therefore, the diameter R of the beads 24 is preferably set to 40 μm or more. Conversely, if the size of the beads 24 is too large, the shape of the beads 24 causes noise to the image. Therefore, empirically, the size of the beads 24 is preferably set to 5 mm or less. Therefore, the diameter R of the beads 24
Is preferably 40 μm to 5 mm, particularly preferably 100 μm to 2 mm.

Although the degree of dispersion of the beads 24 is not particularly limited, it is preferable that the diameter of the beads 24 is as uniform as possible (monodispersion). For example, if the beads 24 have an average diameter R of 800 μm as in the examples described later, the beads 24 have a diameter of 600 μm to 10 μm.
It is preferably within 00 μm. That is, the average particle diameter is preferably within ± 25%.

The reflection layer 26 is formed of the beads 24 as described above.
In addition to blocking the passage of light in areas other than the contact portion between the sheet and the support sheet 22, the beads 24 are fixed (adhered) to the support sheet 22. Basically, the entire surface of the support sheet 22 at least in a region where the beads 24 are fixed. Formed so as to cover The reflective layer 26 is used to wrap the beads 24 on the support sheet 22.
The light scattering substance is dispersed in a binder (adhesive) fixed to the substrate.

The binder used for the reflection layer 26 is not particularly limited, and various binders can be used as long as the beads 24 can be fixed to the support sheet 22. Therefore,
A binder that dissolves the solid binder in a solvent and then evaporates the solvent after application, may be a UV-curable or electron beam-curable binder, or may be a binder using a curing agent, A curable binder may be used, or a self-curing binder such as a two-component type may be used.

Examples of the material include urethane resin, vinyl acetate resin, ethylene-vinyl acetate copolymer, vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer, (meth) acrylate resin, butyral resin, silicone resin, and polyester. , Vinylidene fluoride resin, nitrocellulose resin, polystyrene, styrene-acrylic copolymer, polyethylene, polypropylene, polyethylene chloride, rosin derivative, and mixtures thereof. In particular, urethane resins, acrylic resins and silicone resins are preferably used. In the present invention, it goes without saying that the binder may have various components contained in a normal binder such as a plasticizer, in addition to the adhesive component.

On the other hand, the light scattering substance used for the reflection layer 26 is not particularly limited, and various substances can be used as long as they do not absorb the light emitted from the light source. Preferably, fine particles of a substance having a refractive index of 1.6 or more are preferred. Thus, efficient light diffusion (reflection) with little attenuation can be performed. Specifically, yttrium oxide (Y ₂ O
₃ ), zirconium oxide (ZrO ₂ ), gadolinium oxide (Gd
₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), hafnium oxide (Hf
One or more of fine particles such as O ₂ ), barium sulfate (BaSO ₄ ), alumina (Al ₂ O ₃ ), and titanium oxide (TiO ₂ ) are preferably exemplified. In particular, yttrium oxide, zirconium oxide, gadolinium oxide, lanthanum oxide, hafnium oxide, titanium oxide, and the like are preferable.

In the reflective layer 26, a gap is formed between the contacting fine particles, and if the ratio of the binder is appropriate, the binder does not sufficiently flow into the gap and the area where air exists is provided. Often occur. Therefore, a large difference in the refractive index between the air (refractive index 1) and the light scattering substance can be secured, whereby the attenuation of light in the reflective layer 26 is greatly reduced, The light incident on the housing 26 can be returned to the inside of the housing 18 with high efficiency.

Although the particle size of the light scattering substance is not particularly limited, fine particles having a D50% particle diameter of 0.1 μm to 2 μm in a laser diffraction method, for example, are preferable in that good optical characteristics can be obtained. is there.

Hereinafter, such an optical collimator sheet 20 will be described.
The manufacturing method of the present invention for fabricating is described with reference to FIG.

First, a predetermined amount of a binder is dissolved in an appropriate solvent, a predetermined amount of a light-scattering substance is added to this solution, and the mixture is stirred, and a coating liquid (hereinafter referred to as a paint) in which the light-scattering substance is dispersed. Is prepared. When a binder that is a liquid in an uncured state, such as an ultraviolet-curable resin or a moisture-curable resin, is used, a solvent may not be used as long as the binder can have an appropriate viscosity. In this paint (that is, the reflective layer 26), the amount ratio of the binder and the light scattering substance is not particularly limited. However, in consideration of the adhesive force of the beads 24 and the optical characteristics of the reflective layer 26,
0.5: 1 to 2 by weight ratio of “light scattering material: binder”
It is preferably 0: 1. In addition, in this quantity ratio,
The binder also contains components such as a plasticizer.

The viscosity of the prepared paint is adjusted if necessary.
After performing processes such as filtration and defoaming, this coating material is applied to the support sheet 22 as shown in FIG. At this time, the applied amount of the paint (thickness of the paint layer 28) depends on the target paint layer 28 when the beads 24 described later are pressed.
Is appropriately determined according to the thickness T of the substrate. The method of applying the paint is not particularly limited, and any known application methods such as a doctor blade, a roll coater, and a knife coater can be used.

The paint is dried (or cured in accordance with the type of binder), and the paint layer 28 (particularly the surface) is semi-cured, has an appropriate adhesive strength (adhesive strength), and is preferably The beads 24 are in a state where they do not settle under their own weight. In addition,
Drying may be natural drying, heating drying, or drying under reduced pressure.

In this semi-cured state, as shown in FIG. 3 (B), a predetermined area of the paint layer 28 (the light passing area of the light collimator sheet 20 to be produced) is sufficiently covered so as to cover the entire area. Spray an amount of beads 24. In addition, even immediately after the application, if the paint layer 28 has appropriate adhesive strength and hardness, beads may be sprayed immediately.

Further, the beads 24 are leveled as a whole, and then the beads 24 not adhered to the paint layer 28 are removed. Preferably, the beads 24 are entirely leveled while being pressed. As a result, as shown in FIG. 3C, one layer of beads 24 covers the entire predetermined area of the paint layer 28 at a high density (optimally, a close-packed state), and is in a state of being suitably bonded. .

The pressing force at this time is not particularly limited, and may be appropriately determined according to the hardness, adhesive strength, and the like of the paint layer 28, but may be from 10 g / cm ^{2 to} 1000 g / cm ^2.
Is preferred. The pressing may be performed by hand, or may be performed using a jig such as a roller or a plate material. Further, the beads 24 not adhering to the paint layer 28 may be removed by slanting the support sheet 22, lightly wiping, or gently tapping the support sheet 22 obliquely or upside down.
Particularly when pressure is applied, the beads 24 that have not adhered can be easily removed by these operations.

Next, the beads 24 adhered to the paint layer 28 are pressed by using an elastic member (jig) such as a rubber roller or an elastic plate, and as shown in FIG.
Part of each bead 24 (optimally part of all beads 24)
Are in contact with the support sheet 22. Thereafter, the paint layer 28 is completely dried (cured), and the support sheet 22,
An optical collimator sheet 20 having beads 24 fixed in a state of being partially in contact with the support sheet 22 and a reflection layer 26 for diffusing light incident to portions other than the contact portion and fixing the beads 24 is completed.

Here, in the manufacturing method of the present invention, preferably, the contact between the beads 24 and the support sheet 22 by the pressing of the beads 24 is performed when the paint layer 28 is in a semi-cured state.
In addition, the process is performed in a state where the layer thickness T satisfies (R / 10) <T <(R / 2).
Diameter). Normally, when the paint layer 28 is semi-cured and the layer thickness T satisfies the above condition, the beads 24 are sprayed, and if the subsequent operation is continued, the layer at the time of pressing the beads 24 is obtained. The thickness T satisfies the above condition.

In the light collimator sheet 20, if the thickness of the reflection layer 26 is too small, a large amount of leakage light is generated, the directivity and luminance of the collimated light are reduced, and the bonding strength of the beads 24 is weak. High mechanical strength cannot be obtained. Conversely, if the beads 24 are buried in the reflective layer 26 more than half, the light incident on the beads 24 is reflected by the reflective layer 26, and the efficiency is reduced, and the directivity and the brightness are also reduced. In consideration of the above, it is preferable that the thickness (the thickness of the maximum portion) of the reflective layer 26 be R / 5 to R / 2.

In the manufacturing method of the present invention, preferably, the thickness T of the paint layer 28 satisfies the above condition.
The beads 24 are pressed to come into contact with the support sheet 22, and then the paint layer 28 is dried. Thereby, the reflection layer 2
6 having a sufficient mechanical strength,
In addition, it is possible to manufacture the optical collimator sheet 20 having strong directivity and capable of obtaining high-luminance collimated light.

More specifically, by setting the thickness T of the paint layer 28 at the time of pressing to be more than (R / 10), the reflective layer 26 having a sufficient thickness can be obtained, and the mechanical strength can be reduced. The above-mentioned disadvantages such as an increase in leaked light can be more suitably prevented. On the other hand, by setting the same layer thickness T to less than (R / 2), the amount of buried beads 24 in the paint layer 28 after pressing is prevented from becoming too large, and the amount of buried beads 24 in the reflective layer 26 is prevented. Is too large, and when the paint layer 28 contracts due to curing, the contamination of the beads 24 with the paint can be suitably prevented. Therefore, by setting the layer thickness T of the paint layer 28 at the time of pressing to the above range, it is possible to more reliably manufacture an optical collimator sheet that emits collimator light with sufficient directivity and luminance and with high efficiency. Become. In addition, the layer thickness T of the paint layer 28 when pressing the beads 24 is particularly preferably (R / 5) <T <(R /
2) is preferred.

There is no particular limitation on the method of adjusting the layer thickness of the semi-cured paint at the time of spraying the beads 24, and various methods according to the paint can be used. For example, a method of controlling the thickness T of the paint layer 28 when the beads 24 are pressed by adjusting the thickness of the paint applied is exemplified.
In addition, when a solvent is used in the preparation of the paint or in the case of a binder whose curing involves shrinkage, as shown in FIGS. 3A to 3C, the layer thickness of the paint is reduced by evaporation or curing of the solvent. Since the resin hardens while gradually decreasing, the time when the layer thickness T falls within the above range is found by using this, and the bead 2 is accordingly determined.
The method of pressing 4 is illustrated. In this case, two kinds of solvents having different boiling points are used, and when the solvent having a low boiling point evaporates, the quantitative ratio of each component is examined so that the layer thickness T falls within the above range. Good.

The paint layer 2 when pressing the beads 24
Considering the change in the layer thickness T of 8 and the thickness of the reflective layer 26 obtained by drying (curing), the smaller the change, the easier it is to control the coating thickness of the paint and the preparation of the paint. This is advantageous in that dirt on the beads 24 can be reduced. Most ideally, when the beads 24 are pressed, the beads 2
4 is half-buried in the paint layer 28 (reflection layer 26), and the paint layer 28 is cured as it is without shrinking. In this regard, there is no need to use a solvent, or
An ultraviolet-curing type binder that can eliminate (reduce) the solvent existing in the paint layer 28 in a semi-cured state is advantageous.

Although the method of manufacturing the optical collimator sheet of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the gist of the present invention. Of course, you can.

[0040]

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. [Example] Pandex T-5265HM (manufactured by Dainippon Ink and Chemicals), which is a urethane resin binder, was dissolved in a 1/1 solution of diacetone alcohol / methyl ethyl ketone.
A 13% by weight binder solution was prepared. To 200 g of the binder solution, 52 g of fine yttrium oxide powder (produced by Nippon Yttrium Co., Ltd.) was added and dispersed by a homogenizer to prepare a coating material for forming the reflective layer 26.
It should be noted that Dt of the yttrium oxide fine powder by a laser diffraction method was measured.
The 50% particle size is 1.4 μm, FSSS (Fisher sub-sieve).
The average particle size measured by a sizer (Fisher air permeation apparatus) is 0.4 μm.

After the viscosity of the paint was adjusted to 30 poise, the paint was filtered and defoamed, and applied to a 180 μm-thick polyethylene terephthalate support sheet 22 by a doctor blade (800 μm clearance) to form a paint layer 28. After the paint layer 28 is air-dried for about 1 hour, the glass beads 24 having a diameter R of about 800 μm (R / 10 = 80, R / 2 = 400) (Hibee D24 manufactured by OHARA Co., Ltd., refractive index: 1.595) are added. A large amount was sprayed over the entire area where the paint was applied, and the whole was leveled while applying a pressure of about 10 g / cm ² . After removing the beads 24 not adhering to the paint, the beads 24 were pressed from above by a rubber roller, and the beads 24 were pushed into the paint layer 28 until they came into contact with the support sheet 22.

The paint layer 2 after being naturally dried for about 1 hour
The layer thickness T of No. 8 was about 200 μm. Further, immediately after measuring the layer thickness T, the beads 24 were sprayed, and the subsequent operation was continuously performed.
Is considered to be unchanged from about 200 μm (80 <
200 <400).

Thereafter, the coating layer 28 was completely dried (the binder was cured) to complete the optical collimator sheet.

With respect to the obtained optical collimator sheet, the luminous intensity of the light emitted from the light source, incident from the support sheet 22 side, and passing through the optical collimator sheet is measured, and the luminous intensity in the vertical direction becomes の of the vertical direction. The angle from was measured.
As a result, this angle was 17 °, and it was confirmed that the optical collimator sheet had good characteristics. From the above results, the effect of the present invention is clear.

[0045]

As described above in detail, according to the method of manufacturing the optical collimator sheet of the present invention, the diffused light is preferably condensed, and the collimated light having high directivity and high luminance is obtained. The obtained optical collimator sheet can be suitably manufactured. By using this optical collimator sheet, it is possible to display a high-quality image with a wide viewing angle on an LCD or the like in which the distance from the image forming surface to the screen is relatively short by using the optical collimator sheet together with a light diffusion screen or the like. .

[Brief description of the drawings]

FIG. 1 is an exploded perspective view conceptually showing a display device using an optical collimator sheet manufactured by a method for manufacturing an optical collimator sheet of the present invention.

FIG. 2 is a conceptual diagram of an example of an optical collimator sheet manufactured by the method for manufacturing an optical collimator sheet of the present invention.

FIGS. 3A to 3D are conceptual diagrams for explaining a method for manufacturing an optical collimator sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Liquid crystal panel 14 Backlight part 18 Housing 20 Optical collimator sheet 22 Support sheet 24 Bead 26 Reflection layer 28 Paint layer

Claims (2)

[Claims] 1. A coating solution containing a binder and a light-scattering substance dispersed therein is applied to a transparent support, and a large number of light-transmitting spheres are sprayed on the coating solution to form a light-transmitting sphere that is not adhered to the coating solution. A method for producing an optical collimator sheet, comprising removing a sex sphere, pressing a light-transmitting sphere adhered to a coating solution in a single layer to contact the support, and then curing the coating solution. 2. The contact between the light-transmitting sphere and the support due to the pressing, when the coating liquid is semi-cured and the thickness T is "(R
The method of manufacturing an optical collimator sheet according to claim 1, wherein the method is performed under the condition of (/ 10) <T <(R / 2) (where R is the diameter of a light-transmitting sphere).