JP2006267412A - Anti-glare sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-glare sheet which suppresses and reduces light scattering due to external light and hardly deteriorates contrast, and also to provide a manufacturing method of the anti-glare sheet. <P>SOLUTION: In the anti-glare sheet 10, a plurality of fine particles 2 are dispersed with prescribed intervals on a substrate 3 and the plurality of fine particles 2 are covered with coating film. Therein, a refractive index of the plurality of fine particles is the same as the refractive index of the coating film, and the thickness of the coating film is 30 to 80% of average diameter of the plurality of fine particles 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antiglare sheet formed on a viewer-side surface of a screen for a transmissive projection TV (hereinafter referred to as a transmissive projection screen) and a method for manufacturing the same.

A screen for a transmissive projection TV (hereinafter also simply referred to as a transmissive projection screen) is generally configured by a combination of a Fresnel lens sheet and a lenticular sheet.
In order to improve the life, resolution and contrast of the screen, a hard coat layer for protecting the screen may be formed on the outermost surface on the viewer side, that is, on the flat surface opposite to the lenticular lens forming surface of the lenticular sheet corresponding to the outermost surface of the screen. It is common.

In some cases, a front plate is provided on the screen. In this case, the observer side surface of the front plate is the outermost surface of the screen, and thus it is necessary to form a hard coat layer for screen protection on this surface. .
In this way, a hard coat layer is formed on the surface on the viewer side of the screen, and the function of the hard coat layer requires sufficient strength to protect the screen and at the same time scatters light from the outside. Therefore, various functions such as an antiglare function for reducing reflection on the screen and an antistatic function for preventing contamination due to adhesion of dust and the like are required.

  In general, an antistatic agent is added to impart an antistatic function. In addition, in order to impart an antiglare function, a technique (anti-glare: AG) in which light diffusing fine particles are mixed in a hard coat coating solution to form irregularities on the surface of the hard coat layer is employed (for example, patents). Reference 1).

There are various types of light diffusing fine particles used here, from those using inorganic substances to those using organic substances (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 10-20105 JP 2003-66205 A

  By the way, if a light diffusing fine particle is added in a large amount to a thin hard coat layer to form an antiglare sheet, light scattering occurs on the surface of the light diffusing fine particle. There is a problem that the whole image appears white and the contrast of the screen is lowered.

  Contrast is indicated by “bright brightness / dark brightness” of the display image viewed on the screen. As described above, if light scattering occurs due to external light (sunlight or indoor illumination light) on the screen surface, And the dark luminance also increases, so that the overall contrast decreases. In particular, when observing obliquely from the front of the screen from which the projected video light from the projector is emitted, the weight occupied by the light scattering is higher than that of the projected video light, so that the contrast in the diagonal direction is significantly reduced. The cause is not elucidated in principle, and the phenomenon has only been confirmed experimentally, but this phenomenon is particularly noticeable when the lighting intensity in the room is low, and it is installed near the window. In addition, there is a problem that it is more noticeable when viewing a transmissive projection TV placed in a room where the sunset shines.

  Accordingly, an object of the present invention is to provide an antiglare sheet that solves the above-described problems, suppresses and reduces light scattering due to external light, and causes little reduction in contrast, and a method for manufacturing the same.

In a first invention of the present invention, in the antiglare sheet in which a plurality of fine particles are dispersed at a predetermined interval on a substrate and the plurality of fine particles are covered with a coating film, the refractive index of the plurality of fine particles is Provided is an antiglare sheet having the same refractive index as that of the coating film and having a thickness of 30 to 80% of an average diameter of the plurality of fine particles.
According to a second aspect of the present invention, there is provided a method for producing an anti-glare sheet in which a plurality of fine particles are dispersed at a predetermined interval on a substrate, and the plurality of fine particles are covered with a coating film. After the resin is mixed with a curing agent to form a suspension, the first ultraviolet curable resin is cured by irradiating with ultraviolet rays, and the cured first ultraviolet curable resin is taken out of the water. A step of drying to produce the plurality of fine particles, a step of mixing the curing agent with at least the second ultraviolet curable resin, and then adding the plurality of fine particles at a predetermined ratio to produce a fine particle-containing ultraviolet curable resin; And a step of irradiating the ultraviolet ray within 2 to 10 seconds after the fine particle-containing ultraviolet curable resin is coated on the substrate.

  According to the present invention, the refractive index of the plurality of fine particles is the same as the refractive index of the coating film, and the thickness of the coating film is 30 to 80% of the average diameter of the plurality of fine particles. In addition, there is an effect that it is possible to provide an anti-glare sheet that suppresses and reduces light scattering due to external light and causes little reduction in contrast. A step of curing the first ultraviolet curable resin by irradiating ultraviolet rays after mixing a curing agent with the first ultraviolet curable resin not containing a hydroxyl group in water to produce a suspension, and curing the first (1) The step of taking out the ultraviolet curable resin from the water and drying it to produce the plurality of fine particles, and at least mixing the curing agent with the second ultraviolet curable resin and then adding the plurality of fine particles at a predetermined ratio And a step of irradiating the ultraviolet ray within 2 to 10 seconds after coating the fine particle-containing ultraviolet curable resin on the substrate. The shape can be made spherical, and productivity can be improved.

Embodiments of the present invention will be described below with reference to the drawings.
In this embodiment, the antiglare sheet provided on the transmission projection screen front plate and the method of manufacturing the antiglare sheet will be described. It is the same.

FIG. 1 is a configuration diagram showing an embodiment of an antiglare sheet of the present invention. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line MM shown in FIG.
As shown in the figure, the antiglare sheet 10 of the present embodiment is formed on a transparent substrate 3 and has a configuration in which fine particles 2 are dispersed and the fine particles 2 are covered with a coating film 1. Yes. The surface of the coating film 1 is uneven according to the shape of the fine particles 2.
Here, the coating film 1 and the spherical fine particles 2 have the same refractive index.

First, the coating film 1 will be described.
As the coating film (binder) 1, it is preferable to use an ultraviolet curable resin made of (meth) acrylic acid ester as a main component. 4 to 6 (in one molecule, such as pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate ( A (meth) acrylic acid ester having a (meth) acrylic functional group is suitable.

If the number of functional groups is 3 or less, and the molecular chain between functional groups is 2 or less carbon atoms, the hardness after resin curing will be at the required level, but the resin after curing will be rigid and brittle. There is a defect that disappears. When the number of functional groups is 7 or more, the number of functional groups in the molecule increases and the curing action increases, but the resin viscosity changes due to a slight temperature change and the handling of the resin becomes unstable. Due to subtle changes in temperature, the drawback that the coating film thickness greatly fluctuates becomes significant.
That is, it is preferable to use an ultraviolet curable resin having a functional group number of 4 to 6 as a main component.
Furthermore, in addition to the main component, monomers may be mixed as appropriate, or an ultraviolet curable resin having a functional group number other than 4 to 6 may be mixed.

Next, a method for producing spherical fine particles 2 and a method for producing an antiglare sheet using the same will be described with reference to FIG.
FIG. 2 is a process diagram for producing an embodiment of the antiglare sheet of the present invention.
As described above, the fine particles 2 have the same refractive index as the coating film 1.
The main point of production of the fine particles 2 is to use a product obtained by curing an ultraviolet curable resin by a suspension polymerization method. The suspension polymerization method is a resin production method in which a water-insoluble material is generally suspended in an aqueous solution to make a polymer having a uniform particle diameter. It is often used.

  The suspended state is a physical phenomenon in which a water-insoluble substance exists stably by reducing its surface area as much as possible in order for a water-insoluble substance to exist in an aqueous solution. The state with the smallest surface area in the substance is a sphere. In a suspended state in an aqueous solution, spherical particulate matter (fine particles) exists.

  As shown in step S1 of FIG. 2, first, a curing agent for causing a radical reaction to an ultraviolet curable resin having low solubility in water is sufficiently mixed.

  Next, as shown in step S2, the mixture of the ultraviolet curable resin and the curing agent is dropped into water, and the water is stirred in a turbulent state.

Next, as shown in step S3, the ultraviolet curable resin is suspended in a turbulent state of water, and then stirred in a laminar state to obtain a suspension having a constant particle size distribution. That is, the fine particles of the ultraviolet curable resin float in a suspended state in water.
Here, the factors that determine the particle size distribution include the amount of water flow in the vertical direction in the bed in a turbulent state and the number of stirrings per hour. When the amount of water flow in the vertical direction and the number of stirrings per hour are increased, fine particles 2 having a finer particle size can be obtained. By changing the stirring state, fine particles having various particle size distributions (the average particle diameter can be changed or the standard deviation value can be changed) can be obtained.

Next, as shown in step S4, the agitation state is maintained, and the suspension is irradiated with a desired amount of ultraviolet rays to cure the ultraviolet curable resin in water to obtain a spherical curable resin (fine particles) having a desired particle size distribution. 2) is obtained.
At this time, it can be cured by heating an aqueous solution instead of ultraviolet rays. In the case of heating an aqueous solution, since a temperature of about 100 ° C. is necessary, care must be taken so that the suspension system does not change due to boiling.

  As the ultraviolet curable resin having low solubility in water, a resin having no hydroxyl group in its structure is desirable. For example, glycerin acrylate obtained by esterifying glycerin and acrylic acid shows water-soluble properties even in the state where one hydroxyl group in glycerin remains and the other two hydroxyl groups are esterified. Therefore, when the suspension polymerization is performed, a good spherical suspended substance cannot be obtained, so that the cured product does not become spherical even when cured. In order to avoid such a situation, it is desirable to use an esterified product having no hydroxyl group.

  The same applies to the ultraviolet curing agent (polymerization initiator) added to the ultraviolet curable resin. When a hydroxyl group is present in the polymerization initiator, the polymerization initiator diffuses into water during suspension in water, When it is attempted to cure by irradiating with ultraviolet rays, the ultraviolet curable resin will not be cured.

  Next, as step S5, after spherical hardening resin (fine particle 2) arises in water, water is filtered.

Next, in step S6, the spherical cured resin (fine particles 2) taken out is dried to obtain desired fine particles 2. The average particle diameter (diameter D) of the fine particles 2 is in the range of 10 to 30 μm ± 2 μm.
Here, the drying is desirably performed at 90 ° C. or lower. Instead of lowering the temperature in this way, it is desirable to use a drying method that promotes air agitation by sending air. When dried at a temperature exceeding 100 ° C., the UV curable resin constituting the fine particles 2 may undergo a post-curing phenomenon called after-curing, and the fine particles 2 may be cracked or cracked. Absent.
The production of the fine particles 2 has been described above.

Next, preparation of the coating material containing the fine particles 2 will be described.
As a coating material constituting the coating film 1 after curing, it is desirable to use an ultraviolet curable resin having a composition similar to that of the material constituting the fine particles 2 basically. The reason is that the coating material thus prepared has a refractive index similar to that of the fine particles 2 after curing, and when an antiglare layer (hereinafter also simply referred to as AG layer) is formed, This is because the effect of eliminating the reflection of light is produced by this, and irregular reflection from the fine particles 2 can be prevented particularly when viewed from an oblique direction.

  As a material of the coating material, the main component is an ultraviolet curable resin before curing, and serves as a binder for the fine particles 2 to be added later. As the ultraviolet curable resin, 4 or more in one molecule such as pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate By using a (meth) acrylic acid ester having 6 or less (meth) acryl functional groups, the AG layer automatically becomes a hard coat layer by curing after coating.

In step S7, a curing agent, a leveling agent, a dispersing agent, and the like are added to the ultraviolet curable resin, and finally, the fine particles 2 are added at a predetermined ratio while stirring, and the mixture is further thoroughly stirred, whereby the ultraviolet curable resin coating material containing the fine particles 2 is obtained. Get.
Here, by adding the fine particles 2 in a state in which the main component of the paint is stirred, the fine particles 2 can be efficiently and satisfactorily dispersed without being unevenly distributed.

  An effective ultraviolet curable resin for use as a coating material is trimethylolpropane tri (meth) acrylate. Since this resin is a hexafunctional group and has a low viscosity of 0.05 Pa · s, it acts as a good binder after the next coating, and the fine particles 2 can be spread on the coated surface. Can be coated with a uniform thickness to obtain a desired uneven shape.

Next, as step S8, an ultraviolet curable resin coating is applied on the substrate 3 to a predetermined thickness.
As the substrate 3, a transparent polycarbonate film, a polyethylene terephthalate (PET) film, a polyethylene terephthalate (PET) film subjected to easy adhesion treatment, or an amorphous polyolefin film is used. The thickness of the film is a standard thickness and is appropriately selected from 50 μm, 75 μm, 100 μm, 135 μm, and 150 μm.
For coating, a general roll coating method, curtain coating method, gravure coating method, and die coating method can be used.

Next, as step S9, after elapse of a predetermined time after coating, the ultraviolet curable resin paint is irradiated with ultraviolet rays and cured. The paint becomes the coating film 1.
In addition, the time until the coating material is cured after coating is an item to be managed.
Due to the kinematic viscosity characteristics of the paint, the particulate matter is concealed in the paint immediately after coating, and thus a desired surface irregularity shape cannot be obtained. Since the general coating viscosity when using a roll coat or the like is 0.1 to 1 Pa · s, when the coating is applied to the surface of the fine particles 2 by irradiating with ultraviolet rays after leaving for 2 seconds or more after coating. It can be covered with a uniform thickness, and a surface irregularity shape corresponding to the added fine particles 2 can be obtained. If it is 2 seconds or less, the coating thickness near the top of the fine particles and the vicinity of the side surface changes depending on the standing time, and a uniform coating film cannot be formed. On the other hand, if the coating is allowed to stand for a long period of time exceeding 10 seconds after curing, the uneven shape of the coating film surface will be more tightly formed, but the production efficiency will be degraded. The time until post-curing is preferably within 2 seconds to 10 seconds.

  As described above, as step S10, the anti-glare sheet 10 having the uneven surface on the surface obtained by covering the surface of the fine particles 2 with the coating film 1 is obtained.

  In addition, when demonstrating another coating additive, the coloring agent may be disperse-mixed with the said coating material. As an effect of the colorant, a transmission projection screen in which only the extraneous light is absorbed and the contrast is improved by a synergistic effect with the fine particles 2 by configuring the surface on the viewer side of the anti-glare sheet 10 to be colored. Can be obtained.

  Colorants to be dispersed and mixed include azo dyes, anthraquinone dyes, quinophthalone dyes, methine dyes, condensed polycyclic dyes, reactive dyes, carbon black, inorganic pigments such as titanium white, titanium yellow, and oxidation. Selected from iron (red, yellow brown), ultramarine, cobalt blue, chromium oxide green, spinel green, cadmium yellow, cadmium red, organic pigment aniline black, phthalocyanine, perylene, pyrrole alone or in a mixture The The addition amount of the colorant dispersed and mixed in the paint is preferably 0.01 to 1.0% by weight with respect to the ultraviolet curable resin.

In addition, as shown in FIG. 3, there exists an optimum value also about the thickness t of the coating film 1 after coating.
FIG. 3 is a graph showing the relationship between the ratio of the coating thickness and fine particle diameter to the antiglare life and quality of the antiglare sheet according to the present invention. The vertical axis represents the life and quality of the antiglare property, and the longer the life is, the higher the quality is. The horizontal axis indicates the ratio between the thickness t of the coating film 1 constituting the antiglare sheet 10 and the diameter D of the fine particles 2.

As shown in the figure, the antiglare life and quality are related to the thickness t of the coating film and the diameter D of the fine particles 2 to be mixed in the paint. A coating film thickness t of 80% or less and 30% or more is suitable for the average particle diameter (diameter D) of the fine particles 2. When the coating film 1 is formed with a thickness t exceeding 80% of the diameter D of the fine particles 2, the amount of unevenness on the coating film 1 decreases, and good external light reflectivity cannot be obtained. On the other hand, when the coating film 1 is formed with a thickness t of 30% or less of the diameter D of the fine particles 2, protrusions having a diameter D or more of the fine particles 2 are formed on the coating film 1, and the antiglare sheet 10 is cleaned. The probability that the fine particles 2 are peeled off due to the shearing force on the fine particles 2 due to the wiping and cleaning of the surface of the anti-glare sheet 10 increases, resulting in a disadvantage that the life of the anti-glare sheet 10 is reduced.
Here, the coating film thickness t is generally preferably in the range of 5 to 35 μm.

  Note that the antiglare sheet 10 produced in this way has a feature that, when the cross-sectional structure is observed, the uneven shape of the cross section is the same material and the same refractive index, as shown in FIG. When closely observed, since the polymerization environment of the resin is different, observing the birefringence distribution in the cross section, it can be seen from the change in birefringence between the fine particles 2 and the coating film 1 that the internal structure has two layers. Also, on the boundary of the layer, there are minute cracks, and it can be seen that there are still two layers. In this way, if the structure is not observed closely with a microscope, the structure content is so uniform that the structure content is not known.

  As described above, according to the present invention, it is possible to provide an antiglare sheet that suppresses and reduces light scattering due to external light and causes little reduction in contrast, and a method for manufacturing the same.

Trimethylolpropane triacrylate fine particles having an average particle diameter of 10 μm and a standard deviation of the average particle diameter of 2 μm were prepared using a suspension polymerization method. Solid 100 parts by weight of UV-curable acrylic resin containing 10 parts by weight of trimethylolpropane triacrylate polymer particles, 5 parts by weight of photopolymerization initiator and 50 parts by weight of trimethylolpropane triacrylate in a mixed solvent of cyclohexane and isopropyl alcohol. After stirring at high speed so that the content becomes 35% by weight, it is applied to one side of a polycarbonate film having a film thickness of 75 μm by a roll coating method, and the solvent is evaporated so that the surface is 5 μm thick. Worked. This was cured by irradiating light of 80 W / cm ² with a high-pressure mercury lamp to obtain an anti-glare sheet of the example.

The obtained anti-glare sheet is a front plate for a transmissive projection screen. This was mounted on a 52-inch D-ILA set manufactured by Victor Co., Ltd. together with a Fresnel lens sheet and a lenticular sheet, and contrast and external light reflectance were measured.
The angle dependency of contrast and external light reflectivity is less than that of an object that does not form an antiglare layer, and the angle dependency of contrast is not confirmed at the measurement angle up to 45 ° from the front of the screen, and the external light reflectivity is also 4%. It was the following, and it was in the favorable state that the outline of the indoor fluorescent lamp reflected by the screen was not confirmed.

Further, the surface of the antiglare sheet (layer) could secure 2H even with pencil hardness, and the screen surface was not damaged even when the screen was wiped.
As described above, since the anti-glare layer using the fine particles of the same material as the hard coat material is formed on the surface on the viewer side, the transmissive projection screen has a configuration in which light scattering due to external light is reduced and contrast is hardly reduced. Can be obtained.

  As described above, the example used for the projection screen has been described. However, the antiglare layer of this configuration is effective in preventing reflection of external light, and this effect is caused by a plasma type flat display using plasma emission or liquid crystal. It is also suitable to install on the viewer side of the surface panel of liquid crystal type flat display that changes the light transmittance by changing the refractive index, light emitting type flat display using organic EL light emitting material, light emitting display using field emission It can be used for.

It is a partial section lineblock diagram showing an embodiment of an antiglare sheet of the present invention. It is process drawing for manufacturing embodiment of the anti-glare sheet of this invention. It is a graph which shows the relationship of the ratio of the coating-film thickness and fine particle diameter with respect to the lifetime and quality of the anti-glare property of the anti-glare sheet which concerns on this invention.

Explanation of symbols

1 Coating 2 Fine Particle 3 Substrate 10 Antiglare Sheet

Claims (2)

In the anti-glare sheet in which a plurality of fine particles are dispersed at a predetermined interval on the substrate, and the plurality of fine particles are covered with a coating film,
The antiglare sheet, wherein a refractive index of the fine particles is the same as a refractive index of the coating film, and a thickness of the coating film is 30 to 80% of an average diameter of the plurality of fine particles. In the method for producing an antiglare sheet, wherein a plurality of fine particles are dispersed at a predetermined interval on the substrate, and the plurality of fine particles are covered with a coating film.
A step of mixing a curing agent with a first ultraviolet curable resin not containing a hydroxyl group in water to form a suspension, and then irradiating with ultraviolet rays to cure the first ultraviolet curable resin;
Removing the cured first ultraviolet curable resin from the water and drying to produce the plurality of fine particles;
A step of preparing a fine particle-containing ultraviolet curable resin by adding a plurality of fine particles at a predetermined ratio after mixing a curing agent with at least the second ultraviolet curable resin;
Irradiating the ultraviolet rays within 2 to 10 seconds after coating the fine particle-containing ultraviolet curable resin on the substrate;
A method for producing an antiglare sheet, comprising: