JPS61159682A - Transmission type liquid crystal display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] One hill! The present invention relates to a transmissive liquid crystal display device.

A transmission-type liquid crystal display device has a light source on the back side of a liquid crystal cell that houses a liquid crystal material, and selectively transmits or blocks light from the back side light source by applying a signal voltage to the electrodes. The system is designed to display one character, one figure, etc. Traditionally, fluorescent lamps or tungsten lamps have been used as backside light sources.

A diffuser plate was used to distribute the light evenly.

However, it tends to become darker due to the use of a diffuser plate, and due to the coloring of the polarizing plate, there are drawbacks such as the fact that the transparent area is difficult to turn white even when irradiated with a white fluorescent lamp, and the brightness and contrast of a single display There was a problem with this. Furthermore, even if a diffuser plate is used, there is a limit to the uniformity of backside illumination, which is particularly problematic for large screen displays.

SUMMARY OF THE INVENTION An object of the present invention is to provide a transmissive liquid crystal display device capable of displaying a bright and high-contrast display without providing a diffuser plate.

The transmission-type liquid crystal display device of the present invention is a device that selectively transmits and blocks light from a back light source using a liquid crystal element, and as a back light source, the color is changed to white or near-white by irradiation with electromagnetic waves. It is characterized by having a phosphor layer that emits light.

The present invention will be explained in more detail below.

FIG. 1 is a sectional view showing an embodiment of the present invention, in which a twisted nematic (TN) type liquid crystal cell 11 is arranged between a first polarizing plate 23 on the viewing side and a second polarizing plate 25 on the back side. are arranged to constitute a liquid crystal element. Transparent electrode 15.
An upper substrate 13 and a lower substrate 21 provided with 19, respectively.
A liquid crystal composition 22 is sealed between the upper and lower substrates 13 and 21 so as to be twisted by 90°. 17 represents a sealant.

The first polarizing plate 23 and the second polarizing plate 25 are arranged so that their absorption axes are orthogonal to each other, and the transparent electrode 15.1
When a voltage is applied to 7, the liquid crystal element 27 blocks light.

A phosphor layer 31 is provided below the second polarizing plate 25, and an ultraviolet light source 33 is provided further below.

The phosphor layer 31 includes a phosphor that emits light by ultraviolet light from the ultraviolet light source 35, and emits white or near-white light when irradiated with ultraviolet light. 33 is a substrate that supports the phosphor layer. Note that the phosphor layer 31 can be provided anywhere between the liquid crystal element and the ultraviolet light source 35; for example, it can also be formed on the surface of the second polarizing plate 25 on the ultraviolet light source 35 side. The phosphor layer 31 is made by mixing appropriate amounts of phosphors of three colors that emit red, green, and blue light based on the relationship between the luminance of each phosphor and the 1+'j point on the chromaticity diagram.
Visibility can be adjusted to emit white light.

The phosphor layer is formed by uniformly dispersing the phosphor in a resin binder and coating it on a suitable substrate such as glass or plastic film.

For example, as a red phosphor, MgO.
MgF2.GeO2:Mn compound.

Y, O,: Eu, Zn as green phosphor, 5in4:
M n # L a P O4: Cs g T b
, (SrCaBa)s (po4) as a blue phosphor,
cm: Eu, S r, (P o4), c Q:
Examples include Eu.

The binder is preferably one that has low absorption of ultraviolet light, and acrylic resin, nitrocellulose, triacetate, and other fiber-based resins are used.

When the ultraviolet lamp is turned on, the phosphor in the phosphor layer emits light. Since the phosphor layer is formed by dispersing fine particles of phosphor, it functions as a diffusion plate by itself, and is observed as uniform light over the entire surface. Therefore, even without a diffuser plate or a planel plate, it functions as a surface light source, and the light emitted from this surface light source is incident on the liquid crystal element. When a signal electrode is applied to the liquid crystal element and it becomes active, ll! To the celebrant, the areas where no voltage is applied appear white because light passes through them, while the areas where voltage is applied appear black because light is blocked. The light from the flat light source is directly observed through the liquid crystal element, and since this light is fluorescent and bright, a large contrast ratio can be obtained, making it possible to display clear images. Of course, by making the absorption axes of the polarizing plate parallel,
Negative display in which the voltage application section is displayed in white is also possible.

In the above explanation, the case where a TN type liquid crystal element is used has been explained, but any type of liquid crystal element that can control the transmission/blocking of light from the back side may be used.For example, a guest-host type liquid crystal element, a dual-frequency drive type liquid crystal element, etc. Both are used.

According to the present invention, by using a phosphor layer as a light source of a transmissive liquid crystal display element, the apparent contrast of a displayed image can be improved, and clear image display becomes possible. Furthermore, since the phosphor layer can be formed by a normal coating method, productivity is good and it is industrially advantageous.

The example phosphors include Mgo-MgF2.GeO2:Mn compound (red), Zn, 5i04:Mn (green) and (SrC
aBa), (PO4)zCn: Eu (blue) were mixed in equal weights, and nitrocellulose was kneaded as a binder at a weight ratio of 1/4.5 to the total phosphor.
It was coated on a triacetate film substrate and dried to form a phosphor layer with a thickness of about 6 μm. When this fluorescent plate was irradiated with ultraviolet rays, it emitted uniform white fluorescence over the entire surface and acted as a uniform surface light source even without a reflector or diffuser. When this light source and a liquid crystal cell were arranged in the configuration shown in Figure 1 and the liquid crystal cell was driven, black characters appeared on a white background, the apparent contrast was improved, and good display quality was obtained. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention.

Claims (1)

[Claims] 1. The liquid crystal element selectively transmits light from the backside light source.
What is claimed is: 1. A transmissive liquid crystal display device, characterized in that the transmissive liquid crystal display device is provided with a phosphor layer that emits white or near-white color when irradiated with electromagnetic waves as a backside light source.