JPS5824765B2 - display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-optical display device to which a dichroic dye is added.

In recent years, liquid crystal display devices, electrochromic display devices, and the like have been developed as non-emissive display devices.

Since electrochromic display devices do not use polarizing plates, they can display images with good contrast and a wide viewing angle.

However, it has not been put into practical use due to problems with reliability such as longevity.

On the other hand, liquid crystal display devices have been put into practical use because their power consumption is extremely low and their reliability, such as longevity, has been almost established.

Since most of these liquid crystal display devices use polarizing plates, the entire display device is dark and there are problems in terms of contrast.

In addition, in terms of colorization, there are methods using color reflectors, dichroic polarizing plates, liquid crystal glue dision, guest-host effects, etc., but in reflective display devices, j is There's a problem.

The present invention is intended to eliminate the above-mentioned drawbacks, and aims to provide a display device with a bright display surface and high contrast without using a polarizing plate due to the polarization dichroism effect of a dichroic dye.

It is also an object of the present invention to provide a display device that can be colored by changing the dichroic pigment in various ways and has a high decorative effect.

Next, the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of the display device of the present invention, in which transparent electrodes 5 are provided on both sides of a transparent substrate 2 such as glass, and a transparent substrate 2 with electrodes 4 and 6 on both sides is oriented in a certain direction. The structure of a reflective display device is shown in which a liquid crystal 7 and a dichroic dye 8 are sealed in substrates 1 and 3 via spacers 9, and a reflective plate 12 is provided.

Regarding the material of the liquid crystal 7, either P-type or N-type liquid crystal can be used, but if it is a reflective type and a bright display is desired without applying an electric field, the electrode surface as shown in Figure 1 can be used. An N-type liquid crystal such as methoxybenzylidene-butylaniline (MBBA), ethoxybenzylidene-butylaniline (EBBA) or a mixture thereof is preferable.

The treatment method required for so-called vertical alignment, which is perpendicular to the electrode surface, is to apply lecithin dissolved in a solvent such as ether to the substrate and rub it in a certain direction with absorbent cotton or gauze, or to Treat with chromium complex and rub with absorbent cotton.

The rubbing directions are perpendicular to each other for the first and second layers.

Although a rubbing step is generally not required in the vertical alignment process, rubbing is necessary in order to orient the molecules in a certain direction by applying a voltage.

Another method of orienting the molecules in a constant force direction by applying a voltage is to orient the molecules obliquely by about 5 to 10 degrees instead of oriented completely vertically in the initial state.

The dichroic dyes to be added are methyl red, methylene blue,
Japanese photosensitive pigment film NK1321 (blue color) is preferred, and the amount added is 0.4 to 2 Wt.

For NK1321, 0.8Wt is the best.

When an electric field is applied to a vertically aligned cell as shown in FIG. 1 using a common electrode 5 on both sides of the substrate 2 through a power source 10 and a switch 11, the dipole of the liquid crystal 7 rotates in the direction of the electric field.
Accordingly, the dichroic dye 8 also rotates so that each molecule becomes approximately parallel to the electrode surface as shown in FIG. 2, and the orientation directions of the molecules in each layer are perpendicular to each other.

In the vertically aligned state, there is almost no absorption by the dichroic dye, and the light is not polarized.

Application of an electric field causes parallel orientation, absorption by the dichroic dye, and a polarization dichroism effect in which light is linearly polarized in a direction parallel to the molecules.

For example, NK1321 has polarization around 6100λ, but 4500 (blue)
In this case, there is almost no polarization.

Displays in which dye molecules are added to liquid crystals and an electric field is applied to change the absorption of light by the dye molecules, and displays in which these are multilayered to improve contrast are known as displays based on the guest-host effect.

The feature of the present invention is that, in addition to such absorption of light, the part of the light that becomes linearly polarized light is further cut by forming two layers and orthogonal to each other, thereby improving contrast. .

Furthermore, by adding dye molecules with different polarization dichroism to each layer, it becomes possible to obtain a change in hue between the initial state and the state in which an electric field is applied, thereby facilitating colorization.

FIG. 3 shows another embodiment according to the invention. As shown in FIG. 3, the electrodes are comb-shaped electrodes.

The electrode spacing direction is the first layer electrodes 13a, 13b
yl 4a, 14b, the second layer electrodes 15a, 15b, 16a, 16b in the X-axis direction
At t, the direction is the y-axis.

In this case, the liquid crystal material can be either P-type or N-type, but if P-type liquid crystal is used, the orientation direction of the liquid crystal molecules is parallel to the electrode plane and 45 degrees to the X axis. .

When oriented in this manner, the dye molecules are also oriented parallel to the electrode surface and at 45 degrees to the X-axis (y-axis), as shown in FIG.

In this state, between each electrode 13a-13b) 14a
When an electric field is applied to 14b, 15a, 15b, and 16a-16b, an electric field is applied in the X-axis direction in the first layer, and an electric field is applied in the y-axis direction in the second layer, and the dichroic dyes 8', 8 The dye molecules are oriented as shown in FIG.

Transmission type with the same structure as shown in Figure 1, in which P-type liquid crystal is sealed, the first and second layers are oriented parallel and orthogonal, and dye molecules are made perpendicular to the electrode surface by applying an electric field. or,
It is clear that it is also possible to encapsulate an N-type liquid crystal in the comb-shaped electrode structure shown in FIG. 3 and to make the initial state vertically aligned.

Alternatively, the first layer may be vertically oriented and the second layer may be parallelly oriented.
Alternatively, the first layer may have the electrode structure shown in FIG. 1, and the second layer may have a comb-shaped electrode structure.

As described above, according to the present invention, it is extremely bright without using a polarizing plate and due to the polarization dichroism effect of the dichroic dye.
A display device with high contrast can be provided.

In addition, by selecting a dye, colorization becomes easy and a display device with a high decorative effect can be provided.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a two-layer vertically aligned display device according to the present invention, and FIG. 2 shows electrode surfaces, liquid crystals, and pigments when an electric field is applied to the display device of FIG. 1. FIG. 3 is a perspective view showing an example of the electrode arrangement of a comb-shaped electrode type display device, and FIG. 4 is an explanatory diagram showing the orientation state of dye molecules in FIG. 3. be. 1.2,3...board, 4,5,6...
Electrode, 7...Liquid crystal, 8...Dichroic dye, 9...Spacer, 10...Power supply, 1
2...Reflector, 13 a t 13 b ~ 16
a, 16 b...Comb-shaped electrode.

Claims (1)

[Claims] 1. In a display device in which a pair of transparent substrates, a pair of transparent electrodes, first and second cells having a liquid crystal and a pleochroic dye are laminated, the inner surfaces of the transparent substrates of the first and second cells are substantially perpendicular to each other. A first state in which the liquid crystal molecules in the first and second cells are both aligned substantially perpendicular to the transparent substrate by applying or not applying a voltage; A display device characterized by displaying a second state in which liquid crystal molecules in the cells are aligned substantially in the direction of the rubbing orientation.