JPH0545678A - Color liquid crystal display - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] Color display including black display is possible,
Provided is a color liquid crystal display device capable of obtaining a bright and high-contrast color display. [Structure] Transparent substrates 11a and 11b, and transparent substrates 11a and 11b
It is provided with transparent electrodes 12a and 12b made of ITO, which are respectively formed inside 11b, and a liquid crystal composite 17 containing red, green, blue and black droplet liquid crystals 13, 14, 15 and 16. .. The red droplet liquid crystal 13 is formed of a p-type nematic liquid crystal and an n-type dichroic dye, and the green droplet liquid crystal 14 is a dual-frequency driving nematic liquid crystal whose dielectric anisotropy changes with the driving frequency and a p-type liquid crystal. The blue droplet liquid crystal 15 is formed of a dichroic dye, the p-type nematic liquid crystal and the p-type dichroic dye are formed, and the black droplet liquid crystal 16 is a negative-type nematic liquid crystal and a p-type dichroic dye. It is formed from pigments.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device has a wide range of applications regardless of whether it is a consumer product such as a clock, a calculator, a computer terminal, a word processor or a television, or an industrial product.
In the fields of graphic display and image display, multi-color and full-color liquid crystal display devices have been put to practical use.

In a conventional color liquid crystal display device capable of color display, a so-called twisted nematic (TN) mode in which liquid crystal molecules in a liquid crystal panel are twisted by 90 degrees is used. A blue mosaic color filter is provided, and a liquid crystal panel is sandwiched between two deflecting plates, and a multi-color display is performed by utilizing a shutter effect in a TN mode by turning on / off an applied voltage.

In the additive color mixture using the TN display mode in such a conventional color liquid crystal display device, since the color filters are formed side by side on the transparent substrate, the transmittance when displaying white is 20% to Reduced to 30%. or,
Even in the single color display, since the color filters are juxtaposed on the transparent substrate, the transmittance is reduced to about 1/3. Furthermore, in the display mode using the polarizing plate, the transmittance of the polarizing plate itself is reduced to 30% to 40%, and the total transmittance is 6% to 12%.
However, there is a problem in that the display becomes extremely dark.

Recently, a polymer dispersed liquid crystal display has been in the spotlight as a new display mode in which a deflecting plate is not used in order to improve the brightness of the display. It was announced that multi-color display would be performed by adding dichroic dyes of different colors (BZ Wu et al .: SID 90 Digest (B.
G.Wu et al .: SID 90 DIGEST) 217).

According to this announcement, it is not necessary to specifically stack the red, green and blue droplet liquid crystal layers, and the liquid crystal layer in which the red, green and blue droplet liquid crystals are mixed together is formed by two transparent substrates. It has a sandwiched panel structure.

Here, as the structure of the droplet liquid crystal, a bipolar structure in which the liquid crystal molecules are arranged in parallel so as to contact the boundary surface of the droplet liquid crystal, and an axial structure in which the liquid crystal molecules are arranged vertically to the boundary surface. Structure 2
There are different types, the red and green droplet liquid crystals have an axial structure, and the blue droplet liquid crystals have a bipolar structure.

Regarding the red droplet liquid crystal,
A red dichroic dye is added to a nematic liquid crystal with a negative dielectric anisotropy.
The dichroic anisotropy of the liquid crystal changes from negative to positive depending on the driving frequency, and a green dichroic dye is added to the liquid crystal for two-frequency driving. A blue dichroic dye is added to a positive nematic liquid crystal.

In this case, various colors as shown in Table 1 below can be displayed depending on the voltage applied to the liquid crystal and the driving frequency.

[0010]

[Table 1]

In the table, Nn is a nematic liquid crystal having a negative dielectric anisotropy, Np is a nematic liquid crystal having a positive dielectric anisotropy, and Δε is a dielectric constant in the major axis direction and a dielectric constant in the minor axis direction of liquid crystal molecules. The difference with the rate is shown.

As shown in the table, when no voltage is applied to the liquid crystal panel (when the voltage is off), absorption occurs in the blue droplet liquid crystal and the display color becomes blue. The liquid crystal panel operates so as to display each color by the absorption of the red liquid crystal and the display color becomes green, and the absorption of the red liquid crystal of the red color causes the absorption when the high voltage is applied at a low frequency.

[0013]

In such a conventional color liquid crystal display device, since a polarizing plate is not used in the polymer dispersion type liquid crystal display, it is essential to use the polarizing plate in the TN display mode. Although brighter display can be realized, black display cannot be performed, so that there is a problem in that display is not vivid and high-contrast display cannot be obtained.

Therefore, the present invention provides a color liquid crystal display device capable of color display including black display and capable of obtaining bright and high-contrast color display.

[0015]

A color liquid crystal display device sandwiching a liquid crystal composite composed of a liquid crystal, a dichroic dye, and a polymer resin supporting them between two transparent substrates facing each other. The liquid crystal composite is composed of four types of droplet liquid crystals using nematic liquid crystals, and two types of p-type and n-type which show different colors in the droplet liquid crystals and absorb in the major axis and minor axis directions of the dye molecule. The liquid crystal material forming the droplet liquid crystal, which contains a chromatic dye, is composed of a nematic liquid crystal having a positive dielectric anisotropy, a nematic liquid crystal having a negative dielectric anisotropy, and a nematic liquid crystal for dual frequency driving. There is.

Of the four types of liquid crystal materials that compose the droplet liquid crystal, three types of liquid crystal materials are made of nematic liquid crystals having different threshold voltages, and the remaining one type is made of a nematic liquid crystal for dual frequency driving. Made of

Further, among the three kinds of liquid crystal materials constituting the droplet liquid crystal, two kinds are nematic liquid crystals having a positive dielectric anisotropy and one kind is a nematic liquid crystal having a negative dielectric anisotropy.

[0018]

The liquid crystal layer provided between the substrates each having an electrode is composed of a nematic liquid crystal having a positive dielectric anisotropy and a first liquid crystal formed of an n-type dichroic dye, and a two-frequency liquid crystal. A second liquid crystal formed of a driving nematic liquid crystal and a p-type dichroic dye, and a third liquid crystal formed of a nematic liquid crystal having a positive dielectric anisotropy and a p-type dichroic dye. It includes a liquid crystal and a nematic liquid crystal having a negative dielectric anisotropy and a fourth liquid crystal formed of a p-type dichroic dye. Depending on the combination of the applied voltage level and the driving frequency, the first, second, third and fourth liquid crystals respectively absorb the incident light, so that red, green, blue and black display can be freely performed. Therefore, color display including black display is possible, and bright and high-contrast color display can be obtained.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a panel structure included in a color liquid crystal display device which is an embodiment of the present invention.

As shown in the figure, the color liquid crystal display device of this embodiment includes transparent substrates 11a and 11b and a transparent electrode 12a.
And 12b, and a liquid crystal composite 17 including a red droplet liquid crystal 13, a green droplet liquid crystal 14, a blue droplet liquid crystal 15 and a black droplet liquid crystal 16.

The transparent electrodes 12a and 12b are made of indium oxide (ITO) and are formed inside the transparent substrates 11a and 11b, respectively.

The liquid crystal composite 17 is sandwiched between the transparent electrodes 12a and 12b, and the droplet liquid crystals 13, 14, 15 and
Includes a polymeric resin to support 16.

Red, green, blue and black droplet liquid crystal 1
3, 14, 15 and 16 respectively contain a dichroic dye, and the liquid crystal material of these droplet liquid crystals and the dichroic dye are formed from the following in this embodiment.

The red droplet liquid crystal 13 is formed of a p (positive) type nematic liquid crystal having a positive dielectric anisotropy and an n (negative) type dichroic dye exhibiting the largest absorption in the dye molecule short axis. There is.

The green droplet liquid crystal 14 is formed of a two-frequency driving nematic liquid crystal whose dielectric anisotropy changes according to the driving frequency and a p-type dichroic dye in which absorption is greatest in the dye molecule long axis. ..

The blue droplet liquid crystal 15 is formed of a p-type nematic liquid crystal having a positive dielectric anisotropy and a p-type dichroic dye.

The black droplet liquid crystal 16 is composed of an n-type nematic liquid crystal having a negative dielectric anisotropy and a p-type dichroic dye.

2A and 2B are explanatory views of the bipolar structure of the droplet liquid crystal. FIG. 2A shows a state where the electric field E is not applied, and FIG. 2B shows a state where the electric field E is applied. ..

3A and 3B are explanatory views of the axial structure of the droplet liquid crystal. FIG. 3A shows a state where the electric field E is not applied, and FIG. 3B shows a state where the electric field E is applied. ..

In these figures, the droplet liquid crystal 21,
In addition, the nematic liquid crystal molecules 22 and the dichroic dye 23 contained in the droplet liquid crystal 21 are shown. The droplet liquid crystal 21 is the red, green, blue and black droplet liquid crystals 13, 14 shown in FIG. It corresponds to either 15 or 16.

The droplet liquid crystal 21 shown in FIGS. 2 and 3 generally has an elongated, elliptical shape, and as shown in FIG. 2A, the nematic liquid crystal contained in the droplet liquid crystal 21. The molecule 22 and the dichroic dye 23 are processed so as to be aligned substantially parallel to the wall surface 25 of the droplet liquid crystal 21, and this structure is a bipolar structure.

When an electric field E is applied in this state,
As shown in (B), the nematic liquid crystal molecules 22 and the dichroic dye 23 rotate so as to be aligned along the direction E of the applied electric field.

Red and blue droplet liquid crystals shown in FIG.
13 and 15 form this bipolar structure.

On the other hand, as shown in FIG. 3A, the nematic liquid crystal molecules 22 and the dichroic dye 23 are droplet liquid crystals.
It is processed so as to be aligned almost perpendicularly to the wall surface 25 of 21, and this structure is an axial structure.

When an electric field E is applied in this state, the state shown in FIG.
As shown in (B), the nematic liquid crystal molecules 22 and the dichroic dye 23 rotate so as to be aligned along the direction E of the applied electric field.

Green and black droplet liquid crystals shown in FIG.
14 and 16 form this axial structure.

Next, the operating principle of the color liquid crystal display device of this embodiment will be described.

4 to 8 are operation principle diagrams for explaining the operation of the color liquid crystal display device which is one embodiment of the present invention.

As shown in these figures, the liquid crystal panel of the color liquid crystal display device of this embodiment has the same structure as the liquid crystal panel of the color liquid crystal display device shown in FIG. 1, and the transparent electrodes 12a and 12b. Red, green, blue and black droplet liquid crystals 13, 14, 15 and contained in the liquid crystal composite 17 between
16 contains dichroic dyes 31, 32, 33 and 34, respectively. However, the transparent substrates 11a and 11b are omitted in the figure.

In the figure, Nn is a nematic liquid crystal having a negative dielectric anisotropy, Np is a nematic liquid crystal having a positive dielectric anisotropy, and Np / Nn is a nematic liquid crystal for driving two frequencies. Represent

FIG. 4 shows red, green, and
When the display color is BLUE (blue) in the state of the blue and black droplet liquid crystals 13, 14, 15 and 16, FIG. 5 shows a case where the low voltage V ₁ is applied and the liquid crystal is driven at the low frequency f ₁ . When the display color is COLORLESS (colorless) in the state of the droplet liquid crystals 13, 14, 15 and 16, FIG. 6 shows the droplet liquid crystal 13 when the low voltage V ₁ is applied and it is driven at the high frequency f _2. 7, 14, 15 and 16 and the display color is GREEN (green), FIG. 7 shows the droplet liquid crystal 13, 14, 15 when the high voltage V ₂ is applied and driven at the low frequency f _1. And 16 states and the display color is RED
In the case of (red), and in FIG. 8, when the high voltage V ₃ is applied and the liquid crystal is driven at the low frequency f ₁ , the droplet liquid crystal 13,
The display color is BLACK (black) in the state of 14, 15 and 16
It is explanatory drawing which respectively shows the case where it becomes.

In the initial state where no voltage is applied to the liquid crystal panel of the color liquid crystal display device of this embodiment, that is, when the applied voltage level is 0 as shown in FIG. 4, the transparent electrode 12b is used.
The light 35 incident through the droplet liquid crystal 13 and 14
And red, green and black dichroic dyes 31, 32 contained in 16 and 16
And is hardly absorbed by 34, and the dichroic dye 33 contained in the blue droplet liquid crystal 15 (the dichroic dye
33 (in the long axis direction of the dye molecule), and a blue display is obtained.

As shown in FIG. 5, a low voltage V is applied to the liquid crystal panel.
_{When 1} is applied and driving is performed at a low frequency f ₁ , the blue droplet liquid crystal 15 responds by this voltage level, and the blue droplet liquid crystal 15 itself faces the direction of the electric field (the direction of the arrow shown in the figure). As described above, the absorption by the dichroic dye 33 does not occur and the display becomes colorless.

In general, when a liquid crystal material for dual frequency driving is used, when the driving frequency is increased from a low frequency to a high frequency with a low voltage applied, the dielectric constant of the liquid crystal itself changes. It exhibits a negative dielectric anisotropy. Therefore, in the case of the green droplet liquid crystal 14 formed of the liquid crystal material for driving two frequencies, when the low voltage V ₁ is applied to the liquid crystal panel as shown in FIG. 6 and the driving is performed at the high frequency f ₂ ,
The green droplet liquid crystal 14 rotates so as to face the direction of the electric field (the direction of the arrow shown in the figure), and the light 35 incident through the transparent electrode 12b is absorbed by the dichroic dye 32 (the dichroic dye 35 It is absorbed (in the long axis direction of the dye molecule) and becomes a green display.

As shown in FIG. 7, when the driving frequency is returned to the low frequency f ₁ and the high voltage V ₂ is further applied to the liquid crystal panel, the red droplet liquid crystal 13 is in the direction of the electric field (the direction of the arrow shown in the figure). The light 35 which is rotated so as to face the light and is incident through the transparent electrode 12b is reflected by the dichroic dye 31 (the dichroic dye 31).
31 dye molecules (in the minor axis direction) and the driving frequency of the green droplet liquid crystal 14 is low frequency f ₁
As a result, the dielectric anisotropy of the liquid crystal changes positively, and the absorption by the droplet liquid crystal 14 disappears.
Displayed in red.

Finally, as shown in FIG. 8, the voltage level V
Higher voltage V ₃ than ₂ is applied to the liquid crystal panel and low frequency f
_When driven at ₁ , the black droplet liquid crystal 16 is rotated and arranged so as to face the direction of the electric field (the direction of the arrow shown in the figure). At this time, according to the arrangement 36 of the liquid crystal molecules of the droplet liquid crystal 16, the liquid crystal molecules contained in the droplet liquid crystal 16 are
The chromatic dye 34 is also arranged perpendicularly to the direction of the electric field, and the light 35 incident through the transparent electrode 12b is absorbed by the dichroic dye 34 (in the long axis direction of the dye molecule of the dichroic dye 34). , Is displayed in black.

In this case, the incident light 35 is also absorbed by the red dichroic dye 31, but the black color is displayed as a result of the color mixture of red and black.

The above operation is summarized in Table 2 below.

[0050]

[Table 2]

In the table, V ₁ , V ₂ and V ₃ representing the voltage level applied to the liquid crystal panel are V ₁ <V ₂ <V
There is a relationship of ₃ , and the driving frequencies f ₁ and f ₂ are f ₁ <f
There is a relationship of ₂ .

According to this embodiment, as shown in Table 2,
The red droplet liquid crystal contains a nematic liquid crystal (Np) having a positive dielectric anisotropy and an n-type dichroic dye, and the green droplet liquid crystal contains a nematic liquid crystal for driving two frequencies (Np / Nn) and The blue droplet liquid crystal contains a p-type dichroic dye, the nematic liquid crystal (Np) having positive dielectric anisotropy and the p-type dichroic dye, and the black droplet liquid crystal It contains a nematic liquid crystal (Nn) having a negative dielectric anisotropy and a p-type dichroic dye. In such a configuration, when the voltage level applied to the liquid crystal panel is 0, it is displayed in blue, and when the applied voltage is low voltage V ₁ and the driving frequency is low frequency f ₁ , it is displayed in colorless. If the applied voltage is a low voltage V ₁ and the driving frequency is a high frequency f ₂ , it is displayed in green. If the applied voltage is a high voltage V ₂ and the driving frequency is a low frequency f ₁ , it is displayed in red. When the applied voltage is the high voltage V ₃ and the drive frequency is the low frequency f ₁ , the display is black.

As described above, it is possible to freely display red, green, blue, and black depending on the combination of the voltage level applied to the liquid crystal panel and the driving frequency, and therefore, it is possible to perform color display including black display. Therefore, a bright color display with high contrast can be obtained without using a polarizing plate.

[0054]

As described above, the present invention is a color liquid crystal having a liquid crystal composite composed of a liquid crystal, a dichroic dye, and a polymer resin supporting them between two transparent substrates facing each other. In a display device, a liquid crystal composite is composed of four types of droplet liquid crystals using nematic liquid crystals, and the droplet liquid crystals have different colors and exhibit absorption in the long-axis and short-axis directions of dye molecules. Type and n-type dichroic dyes are contained, and the liquid crystal material constituting the droplet liquid crystal has nematic liquid crystal having positive dielectric anisotropy, nematic liquid crystal having negative dielectric anisotropy, and dual frequency driving Since it is made of the nematic liquid crystal, the color display including the black display is possible, and the bright and high-contrast color display can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a panel structure included in a color liquid crystal display device which is an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a bipolar structure of droplet liquid crystal.

FIG. 3 is an explanatory diagram of an axial structure of droplet liquid crystal.

FIG. 4 is an operation principle diagram for explaining the operation of the color liquid crystal display device which is an embodiment of the present invention.

FIG. 5 is an operation principle diagram for explaining an operation of the color liquid crystal display device which is one embodiment of the present invention.

FIG. 6 is an operation principle diagram for explaining the operation of the color liquid crystal display device which is an embodiment of the present invention.

FIG. 7 is an operation principle diagram for explaining the operation of the color liquid crystal display device which is an embodiment of the present invention.

FIG. 8 is an operation principle diagram for explaining the operation of the color liquid crystal display device which is one embodiment of the present invention.

[Explanation of symbols]

 11a, 11b Transparent substrate 12a, 12b Transparent electrode 13, 14, 15, 16 Droplet liquid crystal 17 Liquid crystal composite 31, 32, 33, 34 Dichroic dye

Claims (3)

[Claims] 1. A liquid crystal and a liquid crystal layer are provided between two transparent substrates facing each other.
What is claimed is: 1. A color liquid crystal display device, comprising a liquid crystal composite comprising a chromatic dye and a polymer resin supporting the same, the liquid crystal composite comprising four types of droplet liquid crystals using nematic liquid crystals. The liquid crystal material contains p-type and n-type dichroic dyes that have different colors and absorb in the major axis and minor axis directions of the dye molecule. A color liquid crystal display device comprising a nematic liquid crystal having a positive dielectric anisotropy, a nematic liquid crystal having a negative dielectric anisotropy, and a nematic liquid crystal for dual frequency driving. 2. Among the four kinds of liquid crystal materials constituting the droplet liquid crystal, three kinds of liquid crystal materials are made of nematic liquid crystals having different threshold voltages, and the remaining one kind is a nematic liquid crystal for dual frequency driving. The color liquid crystal display device according to claim 1, comprising: 3. Of the three types of liquid crystal materials constituting the droplet liquid crystal, two types are nematic liquid crystals having a positive dielectric anisotropy, and one type is a nematic liquid crystal having a negative dielectric anisotropy. The color liquid crystal display device according to claim 2.