JPS6012633B2 - liquid crystal display device - Google Patents

Description

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

A conventional field-effect type liquid crystal display device displays polarizing plates by disposing them before and after a cell and performing a display by a light valve-like effect.

However, polarizing plates have the problem that their performance deteriorates due to humidity, ultraviolet rays, etc., and this is one of the factors that determines the lifespan of a liquid crystal display device. It had the disadvantage that it gradually decreased. SUMMARY OF THE INVENTION An object of the present invention is to provide a field-effect liquid crystal display device that does not require the use of polarizing plates, is simple in construction, and is easy to manufacture.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. 1
, 2 are electrode substrates, at least one of which 1 is transparent.

3 is a transparent display electrode formed on the inner surface of the electrode substrate 1 and is formed of a plurality of segments in a desired pattern; 4 is a reflective electrode formed on almost the entire inner surface of the electrode substrate 2; and 5 is a thin film formed on the surface of the reflective electrode 4. , 6 is a liquid crystal material sealed in the gap between the electrode substrates 1 and 2, and 7 is a spacer.

The liquid crystal substance 6 used in the present invention is dielectrically anisotropic, and has a dielectric constant (refractive index) different in the direction of the dipole axis of the molecule and in the direction orthogonal thereto. The thin film 5 is a liquid crystal material 6
Any material having a different refractive index may be used. In this example, the thin film 5 was formed by the following method. That is, the reflective electrode 4
Materials include tantalum, niobium, titanium, stainless steel,
Using a metal such as aluminum on which an oxide film is formed by anodic oxidation, this surface is anodized to form an oxide film, that is, a thin film 5.
I got it. Next, the operating principle of the present invention will be explained.

The liquid crystal substance 6 is subjected to a well-known molecular alignment treatment so that the dipole axes of its molecules are aligned parallel to the electrode substrates 1 and 2 when no electric field is applied. Since the liquid crystal substance 6 and the thin film 5 have different refractive indexes from each other, the light reflected on the surface of the thin film 5 is out of phase with the light that passes through this thin film and is reflected on the surface of the reflective film 4. Therefore, interference colors occur. Therefore, when an electric field is applied between the reflective electrode 4 and the desired display electrode 3, the dipole axes of the molecules of the liquid crystal material 6 in this area are aligned in the direction of the electric field, that is, perpendicular to the electrode substrates 1 and 2. Turn.
Therefore, the dielectric constant, that is, the refractive index, of the liquid crystal material 6 in the electric field application section changes, and the hue and intensity of the interference color differ between the electric field application section and the non-electric field EO application section, and a desired display is produced. It is. Next, a description will be given of how changes in the intensity and hue of interference colors are determined.

In the liquid crystal substance 6, the dielectric constant in the axial direction of the molecules and the dielectric constant in the direction orthogonal to the axial direction are different.

Furthermore, the refractive index of light is determined mostly by the dielectric constant of this molecule. The dipole axis usually coincides with the molecular axis. In other words, when the axes of liquid crystal molecules are oriented parallel to the electrodes,
The dielectric constant in the axial direction of the molecule mainly affects light, and the refractive index is determined by the dielectric constant in the axial direction of the molecule. Also, if the orientation of the liquid crystal molecules is perpendicular to the electrodes,
The dielectric constant in the direction perpendicular to the molecular axis acts on light, and the refractive index is determined by the dielectric constant in the direction perpendicular to the molecular axis. Applying this, in the present invention, a transparent thin film 5 is formed on the surface of the reflective electrode 4, and the apparent refractive index of the liquid crystal layer is changed by changing the alignment direction of liquid crystal molecules near this thin film using an electric field. Intensifies the interference color of a thin film or changes its hue. Further, this point will be explained in detail using a specific example. Assume that a liquid crystal material is used in which the dipole axis coincides with the long axis of the liquid crystal molecules, and the dielectric constant is large in the direction parallel to this molecular axis and small in the direction orthogonal to the axis. Then, a transparent electrode is used on one side of this liquid crystal, a reflective electrode is used on the other side, and a transparent thin film is applied on the reflective electrode. In addition, the surface of each electrode is coated with polyimide Teflon or the like and subjected to rubbing treatment in the same manner as in ordinary liquid crystal display cells. When the above liquid crystal is placed in such a cell, the liquid crystal molecules become parallel to the electrode plane, and the refractive index of the liquid crystal near the reflective electrode is determined by the dielectric constant in the direction parallel to the molecular axis, that is, the dipole axis, and increases. .

As a result, if the refractive index of the m-thin film is selected to be large, the difference in the refractive index between the two will be almost eliminated, and the interference color will be hardly visible. Also, if you select a thin film with a small refractive index and apply it, the difference in refractive index between the two will be large.
The more reflections occur at this interface, the stronger the interference color becomes. Next, when an electric field is applied in a desired pattern for display, the liquid crystal in the area where the electric field is applied becomes a dipole, that is, the molecular axis is perpendicular to the electrode plane, and the refractive index of the liquid crystal in this area is It is determined by the dielectric constant perpendicular to the molecular axis and becomes small.

Therefore, as shown in m above, when the refractive index of the thin film is large, the difference between the two becomes large and the interference color becomes strong.

Further, as in the case (2) above, when the refractive index of the thin film is small, the difference from the liquid crystal layer becomes small, and the interference color becomes almost invisible. Furthermore, if the strength of the applied electric field is appropriately selected, a change in hue may also occur.

Although the principle behind this is still unclear, a part of the liquid crystal layer near the thin film forms a layer with the same refractive index as the thin film due to the electric field, and this changes the hue as if the thickness of the thin film layer had changed. considered to be a thing. In this way, changes in the intensity and hue of interference colors are determined by the relationship between the dipole axis of the liquid crystal used and the long axis of the molecules, the dielectric constant in the direction parallel to the dipole axis, and the dielectric constant in the direction perpendicular to the dipole axis. It is determined by the dielectric constant. Of course, the liquid crystal material 6 only needs to have dielectric anisotropy, and it does not matter whether it is positive or negative. As described above, according to the present invention, a field effect type liquid crystal display is possible without using a polarizing plate, there is no problem such as deterioration of the performance of the polarizing plate, and the life is long.

Further, when a thin film (oxide film) is formed by anodic oxidation, the thickness can be easily adjusted by voltage, and the film can be manufactured at low cost. Furthermore, since oxide films generally have high resistance, they exhibit remarkable effects such as preventing short circuits between opposing electrodes.

[Brief explanation of drawings]

The drawing is a longitudinal sectional view of an embodiment of the present invention. 1, 2... Electrode substrate, 3... Display electrode, 4
...Reflecting electrode, 5... Thin film, 6...
・Liquid crystal substance.

Claims (1)

[Claims] 1. Two parallel electrode substrates sandwiching a dielectrically anisotropic liquid crystal material, a transparent display electrode formed on the inner surface of one electrode substrate, and a transparent display electrode formed on the inner surface of the other electrode substrate. A reflective electrode and a thin film formed on the surface of the reflective electrode and having a different refractive index with respect to the liquid crystal material are provided, and interference colors are produced due to the difference in refractive index between the liquid crystal material and the thin film, and a desired color is produced. By applying an electric field between the electrodes, the permittivity of the liquid crystal substance differs between the electric field applied part and the non-electric field applied part, and the state of the interference color differs, so that a desired display is performed. LCD display device. 2. The liquid crystal display device according to claim 1, wherein the thin film is an oxide film obtained by anodic oxidation of the surface of the reflective electrode. 3. The liquid crystal display device according to claim 1, wherein the thin film has high insulation resistance.