JPH09258179A - Liquid crystal panel and its driving method, as well as on-vehicle display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal panel designed to enhance visibility by effectively utilizing a scattering transmission type liquid crystal and devising the constitution of both electrode substrates interposing the scattering transmission type liquid crystal between them and its driving method, as well as an on-vehicle display device. SOLUTION: The electrode substrate 10 is provided with figure display patterns 14 to 16 facing ground surface electrodes 12, unit display patterns 17a, 17b, wiring electrodes 18a to 18d and external connecting terminals 19a to 19d via transparent insulating films 13. On the other hand, the electrode substrate 20 is provided with seven segments 24 to 26 facing the ground surface electrodes 22, both unit display patterns 27a, 27b, wiring electrodes 28a to 28p and external connecting terminals 29a to 29p via insulating films 23. Only the figure display patterns 14 to 16, the unit display patterns 17a, 17b and the seven segments 24 to 26 and both unit display patterns 27a, 28b exist by facing each other via high polymer dispersion liquid crystals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel using a scattering / transmissive liquid crystal such as polymer dispersed liquid crystal, a driving method thereof and a display device.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal panel using polymer-dispersed liquid crystals, the polymer-dispersed liquid crystals maintain a scattering state (white turbid state) when no voltage is applied, and become transparent when a voltage is applied.

[0003]

In such a liquid crystal panel, it is possible to make only a part of the liquid crystal panel in which the polymer dispersed liquid crystal is in the scattering state (white turbid state) transparent.
It is difficult to make only part of the liquid crystal panel, which is entirely transparent, cloudy. For this, JP-A-3-28
As disclosed in Japanese Patent No. 2416, a segment portion of a liquid crystal panel is formed by screen printing of a polymer dispersed liquid crystal layer, and a portion other than the segment portion is formed of a transparent resin layer. There is something.

However, in such a liquid crystal panel, the polymer-dispersed liquid crystal layer and the transparent resin layer are made of different materials. Therefore, when the polymer-dispersed liquid crystal layer and the transparent resin layer are in a transparent state, light is not emitted. The transmittance is different. Therefore, when this liquid crystal panel is directly viewed, the transparent state of the polymer dispersed liquid crystal layer and the transparent resin layer are different from each other. Therefore, the transparent state of the liquid crystal panel as a whole varies, resulting in poor visibility.

Therefore, in order to cope with such a situation, the present invention makes effective use of the scattering transmission type liquid crystal and devises the structure of both electrode substrates having the scattering transmission type liquid crystal interposed. Accordingly, it is an object of the present invention to provide a liquid crystal panel, a driving method thereof, and a vehicle display device, which are improved in visibility in terms of making a transparent state uniform.

[0006]

In order to achieve the above object, according to the invention described in claim 1 or 2, both electrode substrates of the liquid crystal panel are respectively provided between the transparent substrate and the scattering transmission type liquid crystal. And a transparent base electrode and an insulating film sequentially laminated on the transparent substrate. In addition, display electrodes are provided on both insulating films so as to face each other with a scattering / transmissive liquid crystal interposed therebetween.

As described above, since the base electrode, the insulating film, and the display electrode are laminated on each electrode substrate, the scattering transmission type liquid crystal is provided between the base electrodes and between the display electrodes. Exists. Therefore, if both the base electrodes and the display electrodes are properly driven, only the portion of the scattering / transmissive liquid crystal located between the display electrodes is set to a white display state, or the entire liquid crystal panel is transparent. Can be in a state. In this case, since the scattering / transmissive liquid crystal in the transparent state is in a uniform transparent state over the entire liquid crystal panel, the transparent state of the region which should be transparent in the liquid crystal panel varies regardless of whether it is in the white display state or not. There is no such thing. Therefore, the visibility of this liquid crystal panel can be improved.

According to the second aspect of the invention, the external connection portion provided on the one insulating film and the external connection portion provided on the other insulating film do not face each other with the scattering transmission type liquid crystal interposed therebetween. Is located. Therefore, even if the liquid crystal portion of the scattering / transmissive liquid crystal located between the display electrodes is in a white display state, the portion of the scattering / transmissive liquid crystal facing the external connection portions is different. The liquid crystal part can be kept transparent by the voltage applied to both base electrodes. Therefore,
Even if both external connection parts are present, only the liquid crystal part between both display electrodes can be displayed in white.

According to the invention described in claim 3, both the external connection parts are grounded together in the state where an AC voltage is applied between both base electrodes of the liquid crystal panel described in claim 2, and the scattering transmission is performed. The liquid crystal is put into a scattering state, and one of the both external connection portions is grounded, and the same voltage as the amplitude value of the AC voltage is applied to the other external connection portion to bring the scattering transmission type liquid crystal into a transparent state. As a result, the function and effect of the liquid crystal panel according to the second aspect can be reliably achieved.

According to the invention described in claim 4, the amplitude value of the AC voltage is applied between both external connection parts in a state where the AC voltage is applied between both base electrodes of the liquid crystal panel described in claim 2. An AC voltage having an amplitude value of ½ of is applied between both external connections. As a result, it is possible to achieve the function and effect of the invention described in claim 2 while preventing display burn-in due to AC driving of both display electrodes.

According to a fifth aspect of the invention, there is provided a vehicle display device in which the liquid crystal panel according to the second aspect is erected in the vicinity of a lower portion of a front windshield of a vehicle. As a result, it is possible to provide a display device for a vehicle, which has the effect of the invention described in claim 2 and has good visibility.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a vehicle head-up display. This head-up display is provided with a liquid crystal panel P. The liquid crystal panel P is opposed to the visual direction of the driver seated in the driver's seat of the vehicle (direction opposite to the double arrow directions Ao and Ap in the figure), It is erected on the upper wall D of the dash panel inside the lower part of the front windshield W. The arrow direction Ao indicates the direction of light that passes through the front windshield W and passes through the liquid crystal panel P from the front to enter, and the arrow direction Ap indicates the direction of light that represents the display content of the liquid crystal panel P.

The liquid crystal panel P is provided with upper and lower electrode substrates 10 and 20 facing each other with a large number of spherical spacers made of resin interposed therebetween.
A polymer dispersed liquid crystal 30 is formed between 20.
The polymer dispersed liquid crystal 30 includes a liquid crystal 31 and a matrix resin 32. The upper electrode substrate 10 includes a transparent substrate 11 such as a glass substrate, and a transparent base electrode 12 and a transparent insulating film 13 are sequentially laminated on the inner surface of the transparent substrate 11. As shown in FIG. 5A, one corner of the base electrode 12 has an external connection terminal 12 for the base electrode.
a is formed.

The inner surface of the transparent insulating film 13 has a structure shown in FIG.
As shown in FIG. 5A, the numerical display patterns 14 to 16 and the unit display pattern 17 representing the three-digit numerical display.
a, 17b, the wiring electrodes 1 extending from the numeral display patterns 14 to 16 and the unit display pattern 17, respectively.
8a to 18d and these wiring electrodes 18a to 18d
Segment external connection terminals 19a extending from the respective
To 19d are formed.

On the other hand, the lower electrode substrate 20 includes a transparent substrate 21 such as a glass substrate, and a transparent base electrode 22 and a transparent insulating film 23 are sequentially laminated on the inner surface of the transparent substrate 21. There is. As shown in FIG. 5B, one corner portion of the base electrode 22 has an external connection terminal 22 for the base electrode.
a is formed. Further, as shown in FIG. 2 to FIG. 5B, 7 segments 24 to 26 representing a three-digit numerical value display, both unit display patterns 27a, 27b, and 7 segment 24 are formed on the inner surface of the transparent insulating film 23. Wiring electrodes 28a to 28r extending from the respective segments of Nos. 26 to 26 and both unit display patterns 27a and 27b, and segment external connection terminals 29a to 29r extending from the wiring electrodes 28a to 28r, respectively.

Here, each of the seven segments 24 to 26 and the unit display pattern 25 is formed so as to be able to face each of the number display patterns 14 to 16 and the unit display patterns 17a and 17b. Also, the external connection terminal 2
2a, wiring electrodes 28a to 28r, and external connection terminals 29
a to 29r are external connection terminals 1 as shown in FIG.
2a, wiring electrodes 18a to 18d, and external connection terminal 19
They are formed at positions upside down from a to 19d. As a result, the voltage applied between the base electrodes 12 and 22 acts on the polymer dispersed liquid crystal 30 without being electrically interrupted by the external connection terminal and the wiring electrode.

Next, a method of manufacturing the liquid crystal panel configured as described above will be described. First, a method of forming the electrode substrate 10 will be described. Transparent substrate 11 made of glass plate
A transparent conductive film is formed on the inner surface of the substrate to form the base electrode 12. Then, an amorphous silicon nitride film is formed on the inner surface of the base electrode 12 by plasma chemical vapor deposition to form a transparent insulating film 13.

After that, a transparent insulating film is formed on the inner surface of the transparent insulating film 13, and then the numeral display patterns 14 to 16 and the unit display patterns 17a and 17 are formed by photoetching.
b and the wiring electrodes 18a to 18d are formed by patterning. Then, one corner portion of the transparent insulating film 13 exposed by this patterning is removed to form the external connection terminal 12 a on the base electrode 12. After that, the external connection terminals 19a to 19d are formed on the inner surface of the transparent insulating film 13 by the lift-off method.

On the other hand, in the electrode substrate 20, a transparent conductive film is formed on the inner surface of a lower transparent substrate 21 made of a glass plate to form a base electrode 22. Then, an amorphous silicon nitride film is formed on the inner surface of the base electrode 22 by plasma chemical vapor deposition to form a transparent insulating film 23. After that, a transparent insulating film is formed on the inner surface of the transparent insulating film 23, and then the 7 segments 24 to 2 are formed by photoetching.
6. Both unit display patterns 27a and 27b, both unit display patterns 27a and 27b, and wiring electrodes 28a to 28r are formed by patterning.

Then, one corner portion of the transparent insulating film 23 exposed by this patterning is removed to form the external connection terminal 22a on the base electrode 22. After that, the segment external connection terminals 29a to 29r are formed on the inner surface of the transparent insulating film 23 by the lift-off method. The two electrode substrates 10 and 20 thus formed are stacked on each other via spherical spacers (not shown) made of a large number of resins.
As shown in FIG. 6, this superposition is carried out by the numeral display patterns 14 to 16 and the unit display patterns 17a and 17b.
Are 7 segments 24 to 26 and both unit display patterns 2
7a, 27b and external connection terminal 12
a, wiring electrodes 18a to 18d, and external connection terminal 19a
Through 19d are arranged so as to be vertically opposite to the external connection terminal 22a, the wiring electrodes 28a through 28r, and the external connection terminals 29a through 29r.

Then, a mixture of an uncured product of an ultraviolet curable resin and a liquid crystal is injected between both electrode substrates 10 and 20,
After that, the polymer dispersed liquid crystal 30 is formed by irradiating ultraviolet rays through the liquid crystal panel as shown by the arrow in FIG. As a result, a good polymer-dispersed liquid crystal can be obtained as compared with the case of the solvent evaporation method. From the above,
Liquid crystal panel manufacturing is completed.

In FIG. 2, reference numeral P1 indicates the background area of the liquid crystal panel P, and reference numeral P2 indicates the display area of the liquid crystal panel P. Further, in FIG. 3, reference numeral P3 exemplifies the upper wiring region portion of the liquid crystal panel P, and FIG.
In the figure, reference numeral P4 exemplifies the lower wiring area portion of the liquid crystal panel P. Next, the operation of this embodiment configured as described above will be described.

The voltage for driving the polymer dispersed liquid crystal 30 is applied to both the external connection terminals 12 with respect to the background area P1.
applied between a and 22a. Further, to the display area portion P2, the voltage is applied between the external connection terminals 19a to 19d and the external connection terminals 29a to 29r. However, the voltage applied to the polymer-dispersed liquid crystal 30 is, as described below, the background area P1, the display area P2, and the both wiring area P3,
Different in P4.

First, in order to display the display area P2 in white, the external connection terminal 12a of the base electrode 12 is connected to the external connection terminal 12a shown in FIG.
While applying the rectangular wave voltage shown in FIG.
The rectangular wave voltage shown in FIG. 8B is applied to the external connection terminal 22a. In this case, the phase of the rectangular wave voltage shown in FIG. 8A is shifted by a half cycle (t0 to t1) from the phase of the rectangular wave voltage shown in FIG. The peak level is the predetermined voltage V.

The external connection terminals 19a of the electrode substrate 10 are also provided.
To 19d and the external connection terminals 29a to 29r of the electrode substrate 20 are grounded together (see FIG. 8C). As a result, the voltage as shown in FIG. 9 is applied to the background area portion P1, the display area portion P2, and both wiring area portions P3 and P4. To make the entire surface of the liquid crystal panel P transparent, the external connection terminals 19a to 19d of the electrode substrate 10 are grounded (see FIG. 8C). Also, the external connection terminal 12
8a, the rectangular wave voltage shown in FIG. 8A is applied to the external connection terminals 29a to 29r and the external connection terminal 2.
The rectangular wave voltage shown in FIG. 8B is applied to 2a. As a result, the voltage shown in FIG.
1, the display area portion P2, and both wiring area portions P3 and P4.

In both Figures 9 and 10, the applied voltage is represented by positive and negative values (potential of the upper electrode substrate 10-potential of the lower electrode substrate 20). It becomes transparent with V. By applying the voltages shown in Table 9 above, the background region P1 is always transparent when a positive or negative constant voltage V is applied. Since the voltage is always zero, the display area P2 is in white display (corresponding to the scattering state of the polymer dispersed liquid crystal 30).

Further, a positive or negative voltage V is alternately applied to both wiring region portions P3 and P4. FIG. 8A,
When the frequency of the rectangular wave voltage in (b) is 60 Hz, it always looks visually transparent. This is the rise of the response speed of the polymer dispersed liquid crystal 30 (speed from white to transparent).
Is about 2 msec, while the trailing edge (speed from transparent to white) is about 15 msec.

Further, by applying the voltage as shown in the above chart 10, the positive voltage V or the negative voltage V is applied to the background area portion P1 and the wiring area portion P4, so that the background area portion P1 and the wiring area portion P4 are always transparent. Further, the display region P2 and the upper wiring region P3 are transparent by being applied with the negative voltage V for only half the period. As a result, the entire liquid crystal panel becomes transparent. As described above, in the electrode substrate 10, the numeral display patterns 14 to 16, the unit display patterns 17a and 17b, and the wiring electrodes 18a to 1 are opposed to the base electrode 12 with the transparent insulating film 13 interposed therebetween.
8d and external connection terminals 19a to 19d are provided, while
In the electrode substrate 20, the base electrode 22 is provided via the transparent insulating film 23.
7 segments 24 to 26, both unit display patterns 27a and 27b, wiring electrodes 28a to 28r, and external connection terminals 29a to 29r are provided facing each other.

Then, the voltage shown in FIG.
By applying to the display area portion P2 and both wiring area portions P3 and P4, the display area portion P2 is displayed in white, and the background area portion P1 and both wiring area portions P3 and P4 are made transparent. On the other hand, by applying the voltage shown in FIG. 10 to the background area P1, the display area P2, and both wiring area parts P3 and P4, the entire surface of the liquid crystal panel is made transparent.

In this case, since the liquid crystal of the liquid crystal panel is only the polymer dispersed liquid crystal 30, the light transmittance of the polymer dispersed liquid crystal 30 in the transparent state is uniform over the entire liquid crystal panel. Therefore, during operation of the liquid crystal panel, the regions other than the display region P2 of the liquid crystal panel are maintained in a uniform transparent state, regardless of whether the display region P2 is transparent and white display is performed. Therefore, it is possible to always visually recognize only the white display in the display area portion P2 without causing variations in the transparent state of the liquid crystal panel.

As a result, when the driver directly looks at the liquid crystal panel, the front of the vehicle can be visually recognized through the liquid crystal panel when the liquid crystal panel is entirely transparent.
When the display area P2 of the liquid crystal panel is in the white display state, both the front of the vehicle and the white display state can be visually recognized. In this case, since the region of the liquid crystal panel that should be transparent is in a uniform transparent state, good visibility can be maintained.

FIG. 11 shows a modification of the above embodiment. In this modified example, when the display area P2 is displayed in white, the rectangular-wave AC voltage shown in FIG. 11A is applied to the external connection terminals 12a of the base electrode 12 and the base electrode 22 is externally connected. The terminal 22a is shown in FIG.
A rectangular wave AC voltage shown in (b) is applied. In this case, the phase of the AC voltage shown in FIG.
The phase of the alternating voltage is shifted by a quarter cycle, and the peak levels of both alternating voltages are positive and negative predetermined voltages V.

The external connection terminals 19a of the electrode substrate 10 are also provided.
To 19d and the external connection terminals 29a to 29r of the electrode substrate 20 are applied with a rectangular wave AC voltage shown in FIG. 11C. In this case, the peak level of this AC voltage is one half of the predetermined voltage V. As a result, Chart 1
The voltage as shown by 2 is applied to the background area P1, the display area P2, and both wiring area parts P3 and P4.

In order to make the entire surface of the liquid crystal panel P transparent, the external connection terminals 19a to 1a of the electrode substrate 10 are formed.
The alternating voltage shown in FIG. 11C is applied to 9d.
In addition, the AC voltage shown in FIG.
2a and the AC voltage shown in FIG. 11B is applied to the external connection terminals 29a to 29r and the external connection terminal 2
2a is applied. As a result, the voltage as shown in FIG. 13 is applied to the background area portion P1, the display area portion P2, and both wiring area portions P3 and P4.

By the application of the voltage shown in FIG. 12, the background area P1 is AC-driven by the voltage V,
Always transparent. The display area P2 is always displayed in white because the voltage is zero. Further, the voltage polarities of both wiring region portions P3 and P4 change, but the voltage is always ½ of V, and the wiring regions are transparent. In this case, the polymer-dispersed liquid crystal used should become transparent at a voltage of ½ V or more.

Further, by applying a voltage as shown in the above chart 13, the polarity of the voltage changes in the background area P1 and the wiring area P4, but since the voltage is always V, it becomes transparent. Further, in the display area portion P2 and the upper wiring area portion P3, the polarity of the voltage changes, but the voltage is always ½ of V and is in a transparent state. Therefore, the entire liquid crystal panel becomes transparent.

In other words, by using the voltage application patterns of the charts 12 and 13, in order to secure the white display of the display area P2 and the transparent state of the entire liquid crystal panel, the applied voltage to any area of the liquid crystal panel The polarities are alternately inverted. Therefore, the direction of current flow between the two electrode substrates 10 and 20 is alternately changed, so that the burn-in of the display of the liquid crystal panel can be prevented. Other configurations, functions and effects are the same as those of the above-described embodiment.

In the above embodiments, the polymer dispersed liquid crystal 30 is used as the liquid crystal layer of the liquid crystal panel, but the present invention is not limited to this, and the light scattering property or the coloring property is obtained when no voltage is applied. And any liquid crystal that exhibits transparency when a voltage is applied (scattering transparent liquid crystal) may be used. Further, in the above-described embodiment, an example in which the polymer-dispersed liquid crystal is formed by irradiation with ultraviolet rays has been described, but the invention is not limited to this, and the polymer-dispersed liquid crystal may be formed by an emulsion method using a water-soluble resin and a liquid crystal. You may

In the above embodiment, an example in which the polymer-dispersed liquid crystal is formed by irradiation with ultraviolet rays has been described.
Not limited to this, the polymer dispersed liquid crystal may be formed by utilizing the interference of laser light. In this case, it is necessary to employ a resin that is cured by laser light as the resin used. Here, the polymer-dispersed liquid crystal is formed by irradiating laser light from the outside of each of the electrode substrates 10 and 20 of the liquid crystal panel, as shown by the double-headed arrow in FIG. Thus, when no voltage is applied to the liquid crystal panel, only the light used as the laser light is selectively reflected and the light of other wavelengths is transmitted. Further, when a voltage is applied to the liquid crystal panel, light of all wavelengths is transmitted.

Therefore, while the ordinary polymer dispersed liquid crystal has no dependence on the wavelength of light and is white, the polymer dispersed liquid crystal by the laser light can display a specific color. Also,
In carrying out the present invention, the polymer-dispersed liquid crystal described in the above embodiment may be added with a dichroic dye. In such a case, white display when no voltage is applied to the liquid crystal panel is displayed. , The color of the added dichroic dye can be changed.

For example, if a red dichroic dye is added to the polymer-dispersed liquid crystal, the display area P2 is displayed red when no voltage is applied to the liquid crystal panel, and the display area P2 is transparent when a voltage is applied. Become. Further, instead of the example in which the dichroic dye is added to the polymer-dispersed liquid crystal as described above, a cholesteric liquid crystal to which the dichroic dye is added may be adopted as the liquid crystal layer of the liquid crystal panel.

Further, the present invention is not limited to the head-up display, but the present invention may be applied to a direct-view liquid crystal panel in various display devices.

[Brief description of drawings]

FIG. 1 is a schematic side view showing a main part of a vehicle head-up display to which the present invention is applied.

FIG. 2 is a partial cross-sectional view taken along the line 2-2 of FIG.

FIG. 3 is a partial cross-sectional view taken along line 3-3 of FIG.

FIG. 4 is a partial cross-sectional view taken along the line 4-4 of FIG.

FIG. 5A is a plan view of an upper electrode substrate,
(B) is a plan view of the lower electrode substrate.

6 is a schematic perspective view showing a state in which both electrode substrates of FIG. 5 are opposed to each other with a polymer dispersed liquid crystal interposed therebetween.

FIG. 7 is a side view showing a state in which a liquid crystal panel is irradiated with ultraviolet rays.

FIG. 8 is a timing chart showing an applied voltage waveform of a liquid crystal panel.

FIG. 9 is a table showing values of applied voltage to each area of the liquid crystal panel when the display area of the liquid crystal panel is displayed in white.

FIG. 10 is a chart showing values of applied voltages to respective regions of the liquid crystal panel when the entire liquid crystal panel is made transparent.

FIG. 11 is a timing chart showing an applied voltage waveform of a liquid crystal panel showing a modified example of the above embodiment.

FIG. 12 is a table showing values of applied voltage to each area of the liquid crystal panel when the display area of the liquid crystal panel in the above modified example is displayed in white.

FIG. 13 is a table showing values of applied voltages to respective area portions of the liquid crystal panel when the entire liquid crystal panel in the modified example is made transparent.

FIG. 14 is a side view showing a state in which a liquid crystal panel is irradiated with a laser beam.

[Explanation of symbols]

10, 20 ... electrode substrate, 11, 21 ... transparent substrate, 12,
22 ... Base substrate, 13, 23 ... Transparent insulating film, 14 to 1
6 ... Numerical display pattern, 17a, 17b, 27a, 27
b ... Unit display pattern, 18a to 18d ... Wiring electrodes,
19a to 19d, 29a to 29r ... External connection terminals,
30 ... Polymer dispersed liquid crystal, liquid crystal panel P.

Claims (5)

[Claims] The two electrode substrates (10, 2) facing each other are provided.
In the liquid crystal panel in which the scattering transmission type liquid crystal (30) is interposed between 0), both electrode substrates are transparent substrates (11, 21), respectively.
And transparent base electrodes (12, 22) sequentially laminated on the transparent substrate between the transparent substrate and the scattering transmission type liquid crystal.
And insulating films (13, 23), and the display electrodes (14 to 16, 17) are provided on both insulating films.
a, 17b, 24 to 26, 27a, 27b) are provided so as to face each other with the scattering transmission type liquid crystal interposed therebetween. 2. An external connection portion (18a to 18d, 19a to 19d) extending from a display electrode provided on one of the two insulating films is provided on the one insulating film and the scattering transmission type. External connection portions (28a to 28r, 29a to 29r) provided between the other insulating film and extending from the display electrode provided on the other insulating film are provided on the other insulating film, and The liquid crystal according to claim 1, wherein the liquid crystal display device is provided between the liquid crystal display device and the scattering / transmission type liquid crystal, and the two external connection parts are located so as not to face each other with the scattering / transmission type liquid crystal interposed therebetween. panel. 3. The liquid crystal panel according to claim 2, wherein an AC voltage is applied between both base electrodes of the liquid crystal panel, the both external connection parts are grounded to bring the scattering transmission type liquid crystal into a scattering state, A method of driving a liquid crystal panel, wherein one of the external connection portions is grounded and a voltage equal to the amplitude value of the AC voltage is applied to the other external connection portion so that the scattering transmission type liquid crystal is brought into a transparent state. 4. The liquid crystal panel according to claim 2, wherein an AC voltage is applied between both base electrodes, a half amplitude value of the AC voltage is applied between the both external connection parts. A method of driving a liquid crystal panel, wherein an alternating voltage having the voltage is applied between the both external connection portions. 5. A display device for a vehicle, wherein the liquid crystal panel according to claim 2 is provided upright near a lower portion of a front windshield of the vehicle.