JP2009080208A - Liquid crystal screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal screen which is excellent in color reproduction of an image by eliminating yellowish coloring of a liquid crystal shutter. <P>SOLUTION: The liquid crystal screen 1 has an ITO containing transparent conductive thin film, and is constructed so as to have a liquid crystal shutter 2 with which the liquid crystal is switched between a transparent state and a nontransparent state according to presence/non presence of voltage application and a filter layer 3 of which the b<SP>*</SP>value in the L<SP>*</SP>a<SP>*</SP>b<SP>*</SP>color system is 0.5 or less. Also the b<SP>*</SP>value of the filter layer 3 is preferably 0 or less, and the lower limit of the b<SP>*</SP>value is preferably -0.4 or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal screen suitably used for video projection.

  Conventionally, an OHP or a slide projector has been used as a video projection device. Such a projector is an apparatus that enlarges an image formed on a film or the like by a projection lens and projects the image on a screen image. In addition, the image projected on the screen can be viewed by a large number of people because a large image can be obtained on the screen.

  In recent years, digital technology has made it possible to project digitized video onto a screen. For example, when personal computer data is converted into a video signal and input to a projector, an image enlarged by the projector can be projected on a screen.

  If there is a bias in the color of the image projected on the screen, the color will become unnatural and very difficult to see. For this reason, images with more natural color development have been desired. For this reason, a light source that has three wavelength components and can reproduce natural colors has been used as the light source of the projector. In addition, a screen with a high whiteness without unevenness in color development was used so that the projection surface can perform color development faithfully.

  On the other hand, there is a need for a screen that can be switched between a transparent state and an opaque state, and a video projection apparatus that uses a liquid crystal screen that can switch a liquid crystal between a transparent state and an opaque state according to the presence or absence of an applied voltage has been proposed. (See Patent Document 1).

  However, when such a liquid crystal screen is used as a projector screen, there is a problem in that the image projected on the screen is colored pale yellow for some reason and appears unnaturally colored.

Japanese Patent Laid-Open No. 6-82748 (Claims)

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal screen that eliminates coloring of the liquid crystal screen and is excellent in image coloration.

  In order to solve the above-mentioned problems, the present inventor has intensively studied and found that the transparent conductive thin film used in the liquid crystal screen contains ITO, and that the cause of the slight yellowishness is in the ITO. It came.

That is, the liquid crystal screen of the present invention includes a liquid crystal shutter having a transparent conductive thin film containing ITO and capable of switching the liquid crystal between a transparent state and an opaque state according to the applied voltage, and L ^* a ^* b ^*. And a filter layer having a b ^* value of 0.5 or less in the color system.

The L ^* a ^* b ^* color system means the color specification method defined in 1976 by the International Commission on Illumination (CIE), and the L ^* value, a ^* value, and b ^* value in the present invention. Is a value obtained by measurement by the method defined in JIS-Z8729: 1994.

The liquid crystal screen of the present invention has a transparent conductive thin film containing ITO, and a liquid crystal shutter capable of switching a liquid crystal to a transparent or opaque state according to the presence or absence of an applied voltage, and an L ^* a ^* b ^* color specification By having a filter layer having a b ^* value of 0.5 or less in the system, the color of the projected image can be made excellent.

  Such a liquid crystal screen can be installed in a show window, for example, so that a product can be seen when it is transparent, and an image projected on the screen can be seen with good color development when it is opaque.

The liquid crystal screen of the present invention has a transparent conductive thin film containing ITO, and a liquid crystal shutter capable of switching a liquid crystal to a transparent or opaque state according to the presence or absence of an applied voltage, and an L ^* a ^* b ^* color specification And a filter layer having a b ^* value of 0.5 or less in the system. Hereinafter, embodiments of each component will be described.

  1 to 4 are sectional views showing embodiments of the liquid crystal screen of the present invention. As shown in the figure, the liquid crystal screen 1 has a liquid crystal shutter 2 and a filter layer 3.

  The liquid crystal shutter is formed by sandwiching a liquid crystal between two sheets of glass having a transparent conductive thin film. When a voltage is applied to the liquid crystal shutter formed in this manner by a liquid crystal shutter driving circuit that can apply a voltage between the transparent conductive thin films, the liquid crystal responds to the opaque state (voltage is reduced). The state can be instantaneously changed from when it is not applied) to a transparent state (when voltage is applied). In this way, when a voltage is alternately applied to the liquid crystal, the liquid crystal can alternately change between an opaque state and a transparent state in response thereto. In this way, when the liquid crystal is in an opaque state, the liquid crystal is in a cloudy state and cannot transmit light. Thus, the liquid crystal in the opaque state can project an image. When the liquid crystal is transparent, the light is not blocked by the liquid crystal and the light is transmitted as it is. For this reason, an image cannot be projected.

  When a projector that can project an image is projected on a liquid crystal screen using such a liquid crystal shutter, the liquid crystal shutter can project an image when the liquid crystal state is opaque, and the liquid crystal state is transparent. The screen will not be able to project video.

  As such a liquid crystal shutter, known ones can be used (for example, Japanese Patent Application Laid-Open No. 2004-325497, Japanese Patent Application Laid-Open No. 3-11619, Japanese Patent Application Laid-Open No. 5-107562, Japanese Patent Application Laid-Open No. 5-188353, Japanese Patent Application Laid-Open No. 2004-69978).

  The transparent conductive thin film used for the liquid crystal shutter generally contains indium-tin oxide (ITO). Research has confirmed that this transparent conductive thin film containing ITO appears light yellow regardless of whether it is observed with transmitted light or reflected light. The reason why it looks yellow is presumed to be yellow because the transparent conductive thin film containing ITO absorbs blue and transmits or reflects light with wavelengths of green and red.

  For this reason, when a liquid crystal shutter containing ITO is used as a screen, the image projected on the screen is colored yellow under the influence of the transparent conductive thin film and appears unnaturally colored, which is preferable. That's not true.

  Therefore, further research was conducted on a method for removing the yellow color of the liquid crystal screen.

  As a result, in order to solve this problem, the inventors have come up with the idea that a filter layer that can be corrected by suppressing the yellow coloring of the liquid crystal shutter is used for the liquid crystal screen.

The color coordinate value b ^* value in the L ^* a ^* b ^* color system of such a filter layer is set to 0.5 or less, preferably 0 or less. Further, the lower limit of the b ^* value is −0.4 or more, preferably −0.3 or more. That is, the design is such that the hue is adjusted so that the saturation of yellow is lowered and blue is exhibited. When the filter layer is designed in this manner, the filter layer transmits or reflects blue light, but can absorb yellow due to the influence of the transparent conductive thin film containing ITO. In this way, a natural color can be obtained without affecting the light quality of green or red.

The L ^* a ^* b ^* color system is a color specification method defined by the International Commission on Illumination (CIE) in 1976, and the b ^* value in the present invention is defined in JIS-Z8729: 1994. It is a value obtained by measuring by the method. As a measuring method of JIS-Z8729: 1994, there are a measuring method by reflection and a measuring method by transmission. In this embodiment, a value measured by transmission is used. Although it is possible to use a measurement method by reflection, a preferable value as the b ^* value in the L ^* a ^* b ^* color system in that case is not the same as the measurement value by transmission, and is preferably experimentally conducted in advance. Find and use the value.

The filter layer may be provided on one side of the liquid crystal shutter or on both sides of the liquid crystal shutter. Moreover, a filter layer can be used in a sheet form in a plurality of layers. When the filter layers are used on both sides or a plurality of layers, the b ^* value is a value obtained by measuring each filter layer.

  When a plurality of filter layer sheets are used in a stacked manner, light is reflected inside and outside each interface of the filter layer, resulting in a loss of light amount. For this reason, the projected image becomes dark. For these reasons, it is preferable to use a minimum number of filter layers.

In the present embodiment, as a method for setting the b ^* value in the L ^* a ^* b ^* color system of the filter layer to 0.5 or less, a method in which a pigment is contained in the transparent polymer film can be used. In addition to this method, a resin layer containing a pigment may be provided on the transparent polymer film.

The b ^* value can be adjusted to the above-described range by appropriately changing the kind of the dye, the amount of the dye, and the thickness of the filter layer.

  Transparent polymer films that do not impair transparency such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polystyrene, polyarylate, cyclic olefin, triacetyl cellulose, acrylic, polyvinyl chloride, etc. Can be used. Among these, a polyethylene terephthalate film that has been stretched, in particular biaxially stretched, is preferred because of its excellent mechanical strength and dimensional stability. Moreover, what improved the adhesiveness with a resin layer by giving a corona discharge process to the surface or providing an easily bonding layer is also used suitably. The thickness of such a transparent polymer film is generally 25 to 500 μm, preferably 50 to 200 μm.

  As the coloring matter, colored inorganic pigments, colored organic pigments, dyes, and the like can be used, but from the viewpoint of excellent weather resistance, cadmium red, red pepper, molybdenum red, chrome vermilion, chromium oxide, viridian, titanium cobalt green, Cobalt green, cobalt chrome green, Victoria green, ultramarine blue, ultramarine blue, bitumen, Berlin blue, Milori blue, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc blue, manganese violet, mineral violet, cobalt violet, etc. Pigments and organic pigments such as phthalocyanine pigments are preferably used.

  The resin constituting the resin layer is polyester resin, acrylic resin, acrylic urethane resin, polyester acrylate resin, polyurethane acrylate resin, epoxy acrylate resin, urethane resin, epoxy resin, polycarbonate resin, and cellulose resin. Thermoplastic resins such as resin, acetal resin, vinyl resin, polyethylene resin, polystyrene resin, polypropylene resin, polyamide resin, polyimide resin, melamine resin, phenol resin, silicone resin, fluorine resin , Thermosetting resin, ionizing radiation curable resin, and the like. Among these, thermosetting resins and ionizing radiation curable resins are preferable, and ionizing radiation curable resins are particularly preferable. When the resin layer is composed of a thermosetting resin and an ionizing radiation curable resin to form a transparent hard coat film, the heat resistance and scratch resistance of the filter layer can be improved. In particular, if the resin layer is formed as a transparent hard coat film and the transparent hard coat film is used so as to be positioned on the outermost surface of the liquid crystal screen, it is preferable in that the liquid crystal screen can be prevented from being damaged.

  The liquid crystal screen of the present invention can be used as a screen capable of projecting a projector image when the liquid crystal is opaque. In addition, when the liquid crystal is transparent, the background can be seen through.

  As described above, when used as a liquid crystal screen, a transmissive screen or a reflective screen can be used, but it is preferably used as a transmissive screen capable of absorbing the yellow coloring of the liquid crystal screen.

  When used as a transmissive screen, in FIGS. 1 and 2, projection of an image by a projector may be performed from either side. However, in the observation, the screen is observed from the side opposite to the projection side.

  Further, when it is not desired to show the room from the outside, when the transmissive liquid crystal screen is used, the liquid crystal is made opaque to prevent the room from being shown from the outside.

  As described above, the liquid crystal screen can be suitably used as a transmissive screen. However, as shown in FIGS. 3 and 4, a reflective layer may be provided to form a reflective screen. In this case, the reflective layer 4 is provided so as to be the last of the layers constituting the liquid crystal screen 1 when the liquid crystal screen is viewed. For example, in the case of FIG. 3, the filter layer 3, the liquid crystal shutter 2, and the reflective layer 4 are provided in this order from the viewing side. In the case of FIG. 4, the liquid crystal shutter 2, the filter layer 3, and the reflective layer 4 are provided in this order from the viewing side. Further, the projection and observation of the image by the projector is performed from the side of the filter layer 3 opposite to the reflective layer 4.

  The reflective layer is preferably composed of a metal thin film layer. By using a reflective layer made of a metal thin film layer, the surface of the reflective layer can be made into a mirror. By providing the reflective layer on the liquid crystal screen in this way, a reflective screen can be obtained. In the liquid crystal screen having the reflective layer, when the liquid crystal is transparent, the reflective layer becomes a mirror and can project a landscape on the near side.

  The metal thin film layer is formed by vacuum deposition, sputtering, electroless plating, or a combination of this and electrolytic plating using a material made of a known metal and metal compound such as aluminum, zinc, gold, silver, copper, and nickel. Or can be obtained by thinly extending a material made of the metal or metal compound to form a metal foil. Among these metal thin film layers, a thin film formed by vacuum deposition, sputtering, electroless plating, or a combination of this and electrolytic plating is preferable in that the thickness can be reduced. The thickness of the metal thin film layer is preferably 10 to 1000 nm, and more preferably 10 to 300 nm.

  Even when the liquid crystal screen is used as a reflective screen, the liquid crystal screen can see an image in which the yellow coloring is corrected by the filter layer and a natural scene in which the coloring is corrected.

  As described above, even when the liquid crystal screen is of a transmissive type or a reflective type, the image and the scenery that are seen through and reflected by the liquid crystal screen are the image and the scenery in which the yellow coloration of the liquid crystal shutter is corrected by the filter layer. Can see.

  Hereinafter, the present invention will be described by way of examples. “Part” and “%” are based on weight unless otherwise specified.

1. Preparation of Filter Layer A filter layer having a transparent hard coat film on one or both sides of a transparent polymer film was prepared as the filter layers a to n. The filter layers a to n differ in the type and amount of pigment used in the transparent hard coat film.

(1) Filter layers a to g
First, a polyethylene terephthalate film (Cosmo Shine A4300: Toyobo Co., Ltd.) having a thickness shown in Table 1 was prepared as a transparent polymer film. Next, each of Examples 1 to 7 was prepared as a coating solution a for transparent hard coat film having the following composition containing pigments of the types shown in Table 1 as colored inorganic pigments in the addition amounts shown in Table 1. After the coating film coating solution a was applied to one surface of the transparent polymer film and dried, an ultraviolet ray was irradiated for 1 to 2 seconds with a high-pressure mercury lamp to form a transparent hard coat film of about 5 μm. Thus, filter layers a to g of Examples 1 to 7 each having a transparent hard coat film on one side of the transparent polymer film were produced.

<Coating liquid a for transparent hard coat film>
・ Ionizing radiation curable resin 60 parts (Diabeam UR6530: Mitsubishi Rayon Co., Ltd.)
-Colored inorganic pigments (pigments and parts listed in Table 1)
・ Photopolymerization initiator 1.8 parts (Irgacure 651: Ciba Specialty Chemicals)
・ Methyl ethyl ketone 80 parts ・ Toluene 60 parts

(2) Filter layer h
First, a polyethylene terephthalate film (Cosmo Shine A4300: Toyobo Co., Ltd.) having a thickness shown in Table 1 was prepared as a transparent polymer film. Next, a transparent hard coat film coating solution b having the following composition containing pigments of the types shown in Table 1 as colored inorganic pigments in the addition amounts shown in Table 1 is prepared. This transparent hard coat film coating solution b Was applied to both sides of the transparent polymer film, dried, and then irradiated with ultraviolet light for 1 to 2 seconds with a high-pressure mercury lamp to form a transparent hard coat film of about 5 μm on each side. This produced the filter layer h of Example 8 provided with a transparent hard coat film on both sides of the transparent polymer film.

<Coating liquid b for transparent hard coat film>
・ 58 parts of ionizing radiation curable resin (Diabeam UR6530: Mitsubishi Rayon Co., Ltd.)
-Colored inorganic pigments (pigments and parts listed in Table 1)
・ Photopolymerization initiator 1.8 parts (Irgacure 651: Ciba Specialty Chemicals)
・ Thermoplastic acetal resin 2 parts (ESREC BL-S: Sekisui Chemical Co., Ltd.)
・ 1 part of porous silica particles (Silysia 446 <average particle diameter 4.5 μm>: Fuji Silysia Chemical Ltd.)
・ Part 1 of fine powder silica particles (Aerosil 30 <average particle size 50 nm>: Nippon Aerosil Co., Ltd.)
・ Methyl ethyl ketone 80 parts ・ Toluene 60 parts

(3) Filter layers i to n
As the filter layers i to n, the colored inorganic pigments of the coating liquid a for the transparent hard coat film used in the filter layers a to g of Examples 1 to 7 were changed to those shown in Table 1, and the thickness of the transparent polymer film The filter layers i to n of Comparative Examples 1 to 6 were formed in the same manner as the filter layers a to g of Examples 1 to 7 except that the thickness was changed to Table 1 thickness. In addition, about the filter layer i of the comparative example 1 and the filter layer n of the comparative example 6, the coating liquid a for transparent hard coat films which does not contain a colored inorganic pigment was used.

For the filter layers a to n of Examples 1 to 8 and Comparative Examples 1 to 6, the b ^* values in the L ^* a ^* b ^* color system are the SM color computer SM-4 (trade name) manufactured by Suga Test Instruments Co., Ltd. Table 1 shows the results of measurement by transmission.

[Table 1]

  Next, the filter layers a to n of Examples 1 to 8 and Comparative Examples 1 to 6 are applied to one surface of a liquid crystal shutter (UMU glass: Nippon Sheet Glass Co., Ltd.) having a transparent conductive thin film containing ITO. The transmissive liquid crystal screens of Examples 1 to 8 and Comparative Examples 1 to 6 were obtained. With regard to the transmissive liquid crystal screens of Examples 1 to 8 and Comparative Examples 1 to 6, the transparent conductive film is focused on the image projected on the screen when the liquid crystal is in an opaque state and the scenery seen when the liquid crystal is in a transparent state. The effect of removing the yellow color of the conductive film was evaluated.

As a result, the liquid crystal screens obtained in Examples 1 to 8 use a liquid crystal screen having a b ^* value of 0.5 or less in the L ^* a ^* b ^* color system as the filter layer. Since the image projected on the screen and the scenery seen beyond the screen were colored yellow, the yellow color of the transparent conductive thin film was not so noticeable.

In particular, in Examples 3 to 7, since the b ^* value was 0 or less, the yellow coloring of the transparent conductive thin film was less conspicuous.

Further, in Examples 3 to 6, since the lower limit of the b ^* value was −0.4 or more, yellow coloring of the transparent conductive thin film was not noticeable at all.

On the other hand, the liquid crystal screens obtained in Comparative Examples 1 to 6 use a liquid crystal screen having a b ^* value in the L ^* a ^* b ^* color system exceeding 0.5 as a filter layer. The projected image and the scenery on the other side of the screen looked yellow, and the yellow coloration of the transparent conductive thin film was conspicuous.

  Next, on the opposite surface of the hard coat film of the filter layers a to g of the liquid crystal screens obtained in Examples 1 to 7 and the filter layers i to n of the liquid crystal screens obtained in Comparative Examples 1 to 6, A silver vapor deposition film having a thickness of 100 nm was formed, and the hard coat film side was attached to the liquid crystal shutter to produce a reflective liquid crystal screen.

  With regard to the obtained reflective liquid crystal screen, paying attention to the image projected on the screen when the liquid crystal is opaque and the scenery that appears in the mirror when the liquid crystal is transparent, the yellow of the transparent conductive thin film The effect of color removal was evaluated.

As a result, the reflective liquid crystal screens of Examples 1 to 7 use a liquid crystal screen having a b ^* value of 0.5 or less in the L ^* a ^* b ^* color system as the filter layer. The projected image and the scenery reflected in the mirror were visible without being colored yellow, and the yellow coloring of the transparent conductive thin film was not so noticeable.

In particular, in the reflective liquid crystal screens of Examples 3 to 7, since the b ^* value was 0 or less, the yellow coloring of the transparent conductive thin film was less noticeable.

Furthermore, in the reflective liquid crystal screens of Examples 3 to 6, since the lower limit of the b ^* value was −0.4 or more, the yellow coloring of the transparent conductive thin film was inconspicuous.

On the other hand, the reflection type liquid crystal screens of Comparative Examples 1 to 6 are projected on the screen because a liquid crystal screen having a b ^* value exceeding 0.5 in the L ^* a ^* b ^* color system is used as a filter layer. The image and the scenery that was reflected in the mirror were colored yellow, and the yellow coloration of the transparent conductive thin film was conspicuous.

Sectional drawing which shows one Example of the liquid crystal screen of this invention Sectional drawing which shows the other Example of the liquid crystal screen of this invention Sectional drawing which shows the other Example of the liquid crystal screen of this invention Sectional drawing which shows the other Example of the liquid crystal screen of this invention

Explanation of symbols

1 ... Liquid crystal screen 2 ... Liquid crystal shutter 3 ... Filter layer 4 ... Reflective layer

Claims (1)

A liquid crystal shutter having a transparent conductive thin film containing ITO and capable of switching a liquid crystal to a transparent or opaque state according to the presence or absence of an applied voltage, and a b ^* value in an L ^* a ^* b ^* color system of 0 A liquid crystal screen having a filter layer of .5 or less.

Images