JPH07110473A - Optical coloring film for liquid crystal element - Google Patents

Abstract

PURPOSE:To make possible to high-luminance color display of a color liquid crystal element by forming a phosphor film which accepts light and emits color fluorescent light. CONSTITUTION:The coloring film consists of a phosphor film 1 which accepts light and emits color fluorescent light. The incident light entering through the top surface of the film 1 is transmitted through the film 1 shown as solid lines in the figure and is reflected on the reflecting film plane M. The reflected light is again transmitted through the film 1 to the outside. A certain proportion of the light collides with the phosphor material 3 during the light is transmitted through the film. The phosphor material 3 transmits or reflects light in a specified wavelength region, namely light in the same wavelength region as the fluorescence the phosphor material 3 emits. Further, the material 3 absorbs light in other wavelength region and emits light (fluorescence) in the specified wavelength region from the energy of the absorbed light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-colored film used in a color liquid crystal device.

[0002]

2. Description of the Related Art A liquid crystal device is one in which liquid crystal is sealed between a pair of transparent substrates provided with transparent electrodes. In a color liquid crystal device for displaying a color image, one of the substrates is used to identify visible light. Is provided with a color filter that transmits only the light in the wavelength range of 1 and absorbs the light in the other wavelength range.

[0003]

However, the color liquid crystal element using the above color filter has a problem that the display is dark. This is because the color filter transmits only light in a specific wavelength region of visible light and absorbs light in other wavelength regions and makes it colored light, so that the light absorption in this color filter is large. In particular, in a reflective liquid crystal element in which a reflection film is arranged on the back surface side, light incident from the front surface side is reflected by the reflection film on the back surface side through the color filter, and again passes through the color filter to the front surface. Since the light is emitted to the side, the light absorption in the color filter becomes larger, and the display becomes considerably dark. An object of the present invention is to provide a photo-coloring film for a liquid crystal element, which allows a color liquid crystal element to perform high-intensity color display.

[0004]

The photo-colored film of the present invention comprises a phosphor film which emits colored fluorescence upon receiving light. The phosphor film may be added with a pigment that transmits light in a wavelength range corresponding to the color of fluorescence emitted by the phosphor film and absorbs light in other wavelength ranges.

[0005]

That is, the present invention uses the phosphor film as a photo-coloring film. Since the phosphor film emits colored fluorescence upon receiving light, the photo-coloring film composed of this phosphor film is emitted. The emitted light is light colored in the color of fluorescence emitted by the phosphor film.

The phosphor film does not transmit only light in a specific wavelength region of visible light but absorbs light in other wavelength regions to obtain colored light, as in a color filter. Since it emits fluorescence by the energy of light, the intensity of light colored by this phosphor film is much higher than the intensity of colored light by the color filter.

Therefore, if the photo-coloring film of the present invention is used in a color liquid crystal element, color display can be performed by utilizing the light colored by the photo-coloring film, and the light intensity colored by the photo-coloring film can be displayed. Since the light has high intensity, the liquid crystal element can perform high-luminance color display.

In the photo-colored film of the present invention, a pigment that transmits light in a wavelength range corresponding to the color of fluorescence emitted from the fluorescent substance and absorbs light in other wavelength ranges is added to the phosphor film. If so, the color purity of the colored light can be improved.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a portion of a photo-coloring film showing a first embodiment of the present invention. The photo-coloring film is composed of a phosphor film 1 which emits colored fluorescence upon receiving light.

The phosphor film 1 is, for example, a transparent substrate 2 to which a fluorescent substance 3 is added. The phosphor film 1 is made of an acrylic resin, a vinyl chloride resin, an alkyd resin, an aromatic sulfonamide resin, or urea. A transparent resin made of a resin, a melamine resin, a benzoguanamine resin, and a copolycondensate thereof is used as the base material 2, and the fluorescent material 3 is mixed in the base material 2 in a scattered state.

The phosphor film 1 is prepared by mixing a resin material for the base material 2 and the phosphor 3 in a desired ratio.
It is formed by coating a substrate (not shown) of a color liquid crystal element by a printing method or a spin coating method to a predetermined film thickness, and then curing the resin material.

The fluorescent substance 3 is obtained by crushing a fluorescent material obtained by dyeing the resin used for the substrate 2 or another transparent resin with a fluorescent dye into fine particles.
Has a wavelength conversion function of absorbing light other than the specific wavelength range (the wavelength range of the fluorescent color emitted by the fluorescent substance 3) and emitting the light of the specific wavelength range by the energy of the light.

That is, in this embodiment, the phosphor film 1 in which the fluorescent substance 3 is added to the transparent substrate 2 is used as a photo-coloring film, and the phosphor film 1 receives the light and emits the colored fluorescence. Since the light is emitted, the light emitted from the photo-coloring film formed of the phosphor film 1 is the light colored in the color of the fluorescence emitted by the phosphor film 1.

The phosphor film 1 does not transmit only light in a specific wavelength region of visible light and absorbs light in other wavelength regions to form colored light, unlike a color filter. Since the fluorescent light is emitted by the energy of the absorbed light, the intensity of the light colored by the phosphor film 1 is much higher than the intensity of the colored light by the color filter.

The coloring of light by the phosphor film 1 will be described. For example, when the reflection film M is arranged on the back surface side of the phosphor film 1 as shown by the chain line in FIG.
The light incident from the front surface side passes through the phosphor film 1 and is reflected by the reflection film M surface as shown by the solid arrow in FIG. 1, and the reflected light is emitted again through the phosphor film 1. Some of the light strikes the fluorescent substance 3 as it passes through the phosphor film 1.

Then, the fluorescent substance 3 is a light in a specific wavelength range of the light that has hit the fluorescent substance 3, that is, the fluorescent substance 3
The light of the same wavelength range as the fluorescent color emitted by is transmitted or reflected, the light of another wavelength range is absorbed, and the energy of the light emits the light (fluorescence) of the specific wavelength range.

The fluorescence emitted by the fluorescent substance 3 is emitted to the periphery of the fluorescent substance 3 as indicated by the broken line arrow in FIG. The reflected light is reflected by the reflection film M and is reflected by the reflection film M to be emitted to the front surface side of the phosphor film 1.
The same applies to the light transmitted or reflected by the fluorescent substance 3.

Therefore, the reflected light emitted to the surface side of the phosphor film 1 is the light that has passed through the phosphor film 1 without hitting the phosphor substance 3, the fluorescence emitted by the phosphor substance 3, and the fluorescence. Light that is transmitted or reflected by the substance 3 (light in the same wavelength range as the fluorescent color emitted by the fluorescent substance 3) and that is transmitted through the fluorescent substance film 1 without hitting the fluorescent substance 3 is white light, so that The color of the light emitted from the body film 1 is the color of the fluorescence emitted by the fluorescent substance 3. The color density of the emitted light is determined by the amount of the fluorescent substance 3 mixed in the phosphor film 1.

Further, unlike the color filter, the phosphor film 1 does not transmit only light in a specific wavelength region of visible light and absorbs light in other wavelength regions to obtain colored light. The fluorescent substance 3 in the phosphor film 1 absorbs visible light and ultraviolet rays other than the specific wavelength range by absorbing the energy of the absorbed light, and absorbs visible light and ultraviolet rays other than the specific wavelength range, and the energy of the light absorbs light in the specific wavelength range. Therefore, the intensity of the light colored by the phosphor film 1 is much higher than the intensity of the colored light by the color filter.

FIG. 3 shows the measurement results of the intensity distribution of the light colored by the phosphor film 1 and the intensity distribution of the light colored by the color filter by arranging a reflective film on the back surface side of each. In this case, the reflective film has an Al reflective film having a roughened surface (hereinafter referred to as Al rough surface reflective film) and a white reflective film having a light scattering surface made of Ba SO ₄ (barium sulfate). Hereinafter referred to as Ba SO ₄ reflective film),
The measurement results are shown when three types of reflective films, namely a specular reflective film made of Ag (silver) (hereinafter referred to as Ag specular reflective film) are used.

The phosphor film used for measuring the intensity distribution of the colored light is a green phosphor film using a phosphor material of product number FA-22 manufactured by Shin Loihi Co., Ltd. The mixing amount is 60/160 by weight ratio. Further, the color filter is a green color filter formed by coating a mixture of a transparent resin material and a green pigment on the reflection film, and then curing the resin material. The film thickness of the phosphor film was 7.5 μm.

As shown in FIG. 3, in the phosphor film 1, the intensity of the emitted light is much higher than that of the color filter, and the reflection film is an Al rough surface reflection film, a Ba SO ₄ reflection film, The intensity distribution of the emitted light is almost unchanged regardless of whether the Ag specular reflection film is used.

As described above, the light emitted from the phosphor film 1 is light colored in the color of the fluorescence emitted by the phosphor film 1, and the intensity of the light colored by the phosphor film 1 is It is much higher than the intensity of colored light by the color filter.

Therefore, if the photo-coloring film made of the phosphor film 1 is used for a color liquid crystal element, color display can be performed by utilizing the light colored by the photo-coloring film, and the photo-coloring film is used for coloring. Since the emitted light is high-intensity light, the color liquid crystal element can perform high-intensity color display.

The photo-coloring film of the above embodiment is composed of the phosphor film 1 in which only the fluorescent substance 3 is mixed in the transparent substrate 2, but like the second embodiment shown in FIG. In addition, a color pigment (a pigment used in a color filter) that allows the phosphor film 1 to transmit light in a wavelength range corresponding to the color of fluorescence emitted by the phosphor film 1 and absorb light in other wavelength ranges. If 4 is added, the color purity of colored light can be improved.

In this case, since the light passing through the phosphor film 1 is absorbed to some extent by the pigment, the intensity of the emitted light is slightly reduced by that amount, but if the addition amount of the pigment is adjusted, the color purity is improved. Moreover, it is possible to obtain colored light having sufficient intensity.

FIG. 4 is a sectional view of a part of a liquid crystal element showing an example in which the photo-coloring film is used in a polymer dispersion type liquid crystal element. This liquid crystal element is a reflection type active matrix liquid crystal element in which a reflective film is provided on the inner surface of the back side substrate.

In FIG. 4, the lower substrate 11 is the back side substrate of the liquid crystal element, and the upper substrate 12 is the front side substrate. The back side substrate 11 is an insulating substrate made of a glass plate or the like (however, it need not be transparent), and the back side substrate 11 has a plurality of transparent pixels arranged in rows and columns. An electrode 13 and a plurality of active elements 14 corresponding to the respective pixel electrodes 13 are arranged.

The active element 14 is, for example, a TFT (thin film transistor), and the TFT 14 includes a gate electrode 15 formed on the substrate 11, a gate insulating film 16 covering the gate electrode 15, and the gate insulating film 16. A semiconductor film 17 made of a-Si (amorphous silicon) or the like which is formed on the semiconductor film 17 so as to face the gate electrode 15, and a source electrode 18 which is formed on both sides of the semiconductor film 17.
And a drain electrode 19.

Although not shown, a gate line (address line) for supplying a gate signal to the TFT 14 and a data line for supplying a data signal corresponding to image data to the TFT 14 are provided on the rear substrate 11. , The gate electrode 15 of the TFT 14 is formed integrally with the gate line, and the drain electrode 19 is connected to the data line.

A reflective film 20 is formed on the back-side substrate 11 so as to correspond to all the pixel electrodes 13 provided on the back-side substrate 11 so as to face substantially the entire surface of the pixel electrode 13. It is provided. The reflective film 20
Is the Al rough reflective film, Ba SO ₄ reflective film, Ag
Although it may be any specular reflection film, if the reflection film 20 and the gate electrode 15 and the gate line of the TFT 14 are the same metal film (for example, Al film), they can be formed at the same time.

The photo-coloring film made of the phosphor film described above is provided on each of the reflection films 20.
In this embodiment, as the photo-coloring film, a plurality of phosphor films that emit fluorescence of different colors, for example, a yellow phosphor film 1 is used.
a, the red phosphor film 1b, and the green phosphor film 1c described above are used, and these phosphor films 1a, 1b, and 1c are alternately arranged and provided on each reflection film 20.

The fluorescent substance used for the yellow fluorescent substance film 1a has a COLOUR INDEX number of "CI.562".
05 "or" CI.46040 "fluorescent dyes. The fluorescent color of these fluorescent dyes when irradiated only with ultraviolet rays is green to yellow green for the dye of "CI.56205" and green yellow to yellow for the dye of "CI.46040". The colors under light are all yellow.

The fluorescent substance used for the red phosphor film 1b has a COLOUR INDEX number of "C.I.
45380 "or" CI.45160 "fluorescent dye. All of these fluorescent dyes have a yellow to orange fluorescent color when irradiated with only ultraviolet rays, and have a red color under daylight.

The red phosphor film 1b may be a pink phosphor, and the phosphor used for the pink phosphor film has a COLOUR INDEX number of "C.I.4."
5170 "fluorescent dye. The fluorescent color of this fluorescent dye when it is irradiated with only ultraviolet rays is orange ~
It is red and the color in daylight is pink.

The reflective film 20 and the phosphor films 1a, 1b and 1c formed thereon are covered with the gate insulating film 16 of the TFT 14. This gate insulating film 16 is S
The pixel electrode 13 is a transparent film made of iN (silicon nitride) or the like, is formed on the gate insulating film 16, and is connected to the source electrode 18 of the corresponding TFT 14 at one end thereof.

On the other hand, the front side substrate 12 is a transparent substrate made of a glass plate, a transparent resin film or the like, and on the front side substrate 12, almost all the pixel electrodes on the back side substrate 11 are covered. A transparent counter electrode 21 that faces 13 is provided.

The back-side substrate 11 and the front-side substrate 12 are bonded to each other at their outer peripheral edges via a frame-shaped sealing material (not shown), and are surrounded by the sealing material between the substrates 11 and 12. A liquid crystal / polymer composite film 22 is provided in the opened region.

The liquid crystal / polymer composite film 22 is one in which liquid crystal is dispersed in a polymer layer.
A liquid crystal is confined in each void of the polymer layer 23 polymerized so as to have a cross section like a sponge. In FIG. 4, reference numeral 24 denotes a liquid crystal part (a part in which the liquid crystal is confined) in the composite film 22.

In this liquid crystal element, the composite film 22 is used.
Nematic liquid crystal with positive dielectric anisotropy is used for the liquid crystal of
A black dichroic dye is mixed in this liquid crystal. FIG. 5 is an enlarged cross-sectional view of one liquid crystal part 24 of the composite film 22 in a non-electric field state and an electric field applied state.
A indicates a molecule of liquid crystal, and B indicates a molecule of the dichroic dye.

This liquid crystal element has, for example, a pair of substrates 1
After joining 1 and 12 with a sealant, both substrates 1
1 and 12, a mixed solution of a polymer material polymerized by light and a liquid crystal to which a dichroic dye is added is vacuum-injected through an injection port formed by removing a part of the sealing material. It can be manufactured by a method in which the polymer material is photopolymerized by irradiating the filling solution with ultraviolet rays from the surface side substrate 11 side which is a transparent substrate. The injection port is sealed after filling the solution or after photopolymerization of the polymer.

As described above, when the mixed solution filled between the substrates 11 and 12 is irradiated with ultraviolet rays, the polymer material in the monomer or oligomer state is radicalized by the dissolution of the double bond, and adjacent molecules are adsorbed. The radicals are combined with each other to form a polymer by radical polymerization reaction, and the liquid crystal is phase-separated by polymerizing the polymer material.

For this reason, the polymerized polymer layer 23 has a cross section like a sponge, and the liquid crystal is confined in the gaps of the polymer layer 23, so that the liquid crystal / polymer composite film 22 having the above-described structure is formed. Is formed. The method for forming the composite film 22 is a method called a photopolymerization phase separation method.

The above liquid crystal element has a liquid crystal / polymer composite film 22.
It is displayed by using the scattering and transmission of light at
The molecules A of the liquid crystal of the liquid crystal part 24 dispersed in the polymer layer 23 of the composite film 22 are oriented in various directions as shown in FIG. 5A when no electric field is applied. Similarly, since the dichroic dye molecule B also faces various directions,
In this non-electric field state, the light incident from the surface side of the liquid crystal element is scattered by the interface between the liquid crystal part 24 and the polymer layer 23 and the light scattering action of the liquid crystal of the liquid crystal part 24 when passing through the composite film 22. At the same time, most of the scattered light is absorbed by the dichroic dye.

Therefore, in the non-electric field state, the composite film 2 is
2 through the phosphor film 1a, 1b, 1 on the rear substrate 12
c, the amount of light reaching the reflection film 20 is extremely small, and therefore, the amount of fluorescence emitted from the phosphor films 1a, 1b, 1c and the amount of light reflected from the reflection film 20 are small, and
Since these lights are scattered and absorbed as described above when passing through the composite film 22 again, almost no light is emitted to the surface side, and the display is in a substantially black dark state.

When an electric field is applied between the pixel electrode 13 of the back side substrate 11 and the counter electrode 21 of the front side substrate 12, the liquid crystal part 2 of the composite film 22 is formed as shown in FIG. 5B.
Since the liquid crystal molecules A of No. 4 are uniformly rise-orientated so as to be substantially perpendicular to the surfaces of the substrates 11 and 12, and the molecules B of the dichroic dye are also rise-oriented, the electric field application state is The light incident from the front surface side of the liquid crystal element receives the composite film 22.
The light is transmitted through the composite film 22 with almost no light-scattering effect in the above and almost no absorption by the dichroic dye.

Therefore, in the electric field applied state, the incident light passes through the composite film 22 and the phosphor film 1a on the rear substrate 2
1b, 1c and the reflection film 20 thereunder, this light causes the fluorescent films 1a, 1b, 1c to generate colored fluorescence and is reflected by the reflection film 20 to be again composite film 2.
The light is emitted to the surface side of the liquid crystal element through 2 and the display is in a bright state.

The color of this bright display is the phosphor film 1a, 1
b, 1c are the colors of fluorescence emitted by this liquid crystal element.
Since the yellow-based phosphor film 1a, the red-based phosphor film 1b, and the green-based phosphor film 1c are provided alternately facing each pixel electrode 13, the pixels of three colors of yellow, red, and green are provided. A color image is displayed by combination.

The phosphor films 1a, 1b, 1c are
Like a color filter, it does not transmit only light in a specific wavelength range of visible light and absorbs light in other wavelength ranges to make colored light, but it emits fluorescence by the energy of absorbed light. , These phosphor films 1a, 1b, 1c
The intensity of the light colored by is much higher than the intensity of the colored light by the color filter.

The liquid crystal element is composed of the phosphor film 1 described above.
Since color display is performed by using light colored with the photo-coloring film consisting of a, 1b, and 1c, a color filter having a large light absorptance is unnecessary, and light colored by the photo-coloring film is not necessary. Since the light has high intensity, color display with high brightness can be performed.

In the above liquid crystal element, a photo-coloring film (phosphor film 1) is formed on the substrate 11 on which the pixel electrode 13 and the TFT 14 are provided.
a, 1b, 1c), the photo-colored film may be provided on the substrate 12 provided with the counter electrode 21 or on both substrates 11 and 12, respectively.

Furthermore, in the above-mentioned liquid crystal element, the substrate 11 provided with the pixel electrodes 13 and the TFTs 14 is used as the back side substrate, but conversely, the substrate 12 provided with the counter electrode 21 may be used as the back side substrate. Well (in that case, the substrate 11 on which the pixel electrode 13 and the TFT 14 are provided becomes the front-side substrate,
The substrate 12 needs to be a transparent substrate), and the reflective film 20 may be provided on the outer surface of the backside substrate.

Further, the photo-coloring film of the present invention can be used not only in the reflection type but also in the transmission type color liquid crystal element,
Further, the invention is not limited to polymer-dispersed liquid crystal elements, but may be TN type,
It can be widely used for various liquid crystal elements such as an N-type liquid crystal element and a liquid crystal element using a ferroelectric liquid crystal or an antiferroelectric liquid crystal. These liquid crystal elements are not limited to the active matrix type, but may be simple matrix type, or a segment display type in which a segment having a shape corresponding to the display pattern is provided on one substrate and a common electrode is provided on the other substrate. It may be one.

[0054]

The photo-colored film of the present invention comprises a phosphor film which emits colored fluorescence upon receiving light. Therefore, when the photo-colored film of the present invention is used in a color liquid crystal element, the photo-colored film is Color display can be performed using colored light, and since the light colored with the photo-coloring film has high intensity, the liquid crystal element can perform color display with high brightness.

In the photocoloring film of the present invention, a pigment that transmits light in a wavelength range corresponding to the color of fluorescence emitted by the phosphor film and absorbs light in other wavelength ranges is added to the phosphor film. If so, the color purity of the colored light can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a portion of a photo-coloring film showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a portion of a photo-coloring film showing a second embodiment of the present invention.

FIG. 3 is a result of measuring the intensity distribution of light colored by the photo-coloring film of the first embodiment and the intensity distribution of light colored by the color filter by disposing a reflecting film on each back surface side. FIG.

FIG. 4 is a partial cross-sectional view of a liquid crystal element showing an example in which the photo-coloring film of the present invention is used in a polymer dispersion type liquid crystal element.

FIG. 5 is an enlarged cross-sectional view of one liquid crystal part of a liquid crystal / polymer composite film in a polymer dispersed liquid crystal element in a non-electric field state and an electric field applied state.

[Explanation of symbols]

 1 ... Fluorescent substance film (light coloring film) 2 ... Transparent base material 3 ... Fluorescent substance 4 ... Coloring pigment

Claims (2)

[Claims] 1. A photocoloring film for a liquid crystal element, which is a photocoloring film used for a color liquid crystal element and is formed of a phosphor film which emits colored fluorescence upon receiving light. 2. A pigment is added to the phosphor film, which transmits light in a wavelength range corresponding to the color of fluorescence emitted by the phosphor film and absorbs light in other wavelength ranges. The photo-colored film for a liquid crystal device according to claim 1.