JPH0430005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvement of a liquid crystal device that utilizes the electro-optic effect of liquid crystal, and more specifically to the improvement of the birefringence of liquid crystal molecules, that is, the birefringence of liquid crystal molecules, that is, the long axis direction of liquid crystal molecules and the direction orthogonal thereto. This invention relates to a liquid crystal device that utilizes the characteristics of light having different refractive indexes.

In recent years, liquid crystal devices have been widely used as display devices for numeric display panels such as watches and calculators by applying the electro-optical effect exhibited by liquid crystals, and are also used in fields other than display devices, such as optical image scanning devices for cameras and printers. Applications are also being developed in the field of optoelectronics, such as optical shutters.

However, when using the electro-optic effect of conventional liquid crystal devices to perform, for example, a light shutter operation, the orientation of the liquid crystal in two directions to form the ON and OFF states of light passage is difficult, one being relative to the other. An electric field is applied between facing electrodes to forcibly change the alignment of the liquid crystal molecules interposed between the two electrodes, whereas the other method relies only on the molecular orientation based on the initial liquid crystal molecule alignment. , the response speed is tens to hundreds
It was extremely slow (msec) and did not completely block light, so it was completely unusable as an optical shutter. Therefore, in order to improve the shortcomings of the response speed of the conventional liquid crystal device and the contrast ratio of the ON/OFF state of light passage, the present inventors first connected one of the opposing electrodes of the liquid crystal cell to a plurality of electrodes. A ground electrode having a comb-teeth portion and a ground electrode located between the comb-teeth portions,
We proposed a liquid crystal device with a three-electrode structure in which one dot that forms ON and OFF states and a drive electrode having the same width are arranged in a line.

A liquid crystal device using a liquid crystal cell with this three-electrode structure takes advantage of the birefringence of liquid crystal molecules. The liquid crystal cell 1 is arranged such that the length direction (y-axis direction) of the drive electrode L ₀ and the ground electrode L ₂ of the liquid crystal cell 1 is parallel to the polarization axis of either one of the polarizers Po or An. The drive electrode Lo of the liquid crystal cell 1 is grounded,
When a voltage Vc is applied between the driving and grounding electrodes L ₀ and L ₂ and the opposing electrode L ₁ , the liquid crystal 5 is vertically aligned (in the Z-axis direction in Figure 1B), and the light passes through the liquid crystal cell as it is. Therefore, the light is completely blocked by the two polarizing plates Po and An whose polarization axes are perpendicular to each other, and the passage of light becomes OFF, while the ground electrode L ₂ and the drive electrode
When a voltage Vd is applied between the electrode L1 and the ground electrode _L2 , and a voltage Vc is applied between the opposing electrode L1 and the ground electrode _L2 , the liquid crystal 5
is the direction due to the combination of the electric fields of both voltages (Z in Fig. 1B)
A portion of the light polarized in the y-axis direction by the polarizing plate Po, which is oriented in the y-axis direction (by combining the axis and x-axis) and has a polarization axis in the y-axis direction, is rotated by the liquid crystal 5 in the The light passes through the cell 1 and directly passes through the polarizing plate An having the polarization axis in the x-axis direction, thereby forming an ON state in which light passes.

In this way, the ON/OFF state of light passage is determined by the voltage.
Controlled by switching the application of Vc and Vd. This 3
A liquid crystal device using a liquid crystal cell with an electrode structure has a fast response speed of several milliseconds because the liquid crystal orientation to form ON and OFF states for light passage is forced by the application of voltages Vc and Vd. obtained,
Moreover, since the ON/OFF state of light passage is perfect, a high contrast ratio can be obtained.

However, although this liquid crystal device shows great improvement in its response speed, it
Since the part that forms the OFF state is dot-shaped, multiple rows of signals are sequentially scanned row by row, and the ON and OFF states of light passage are formed in response to the scanning signals.For example, optical image scanning for printers When the scanning speed of an optical shutter used in equipment is high, such as several milliseconds or less, the ON and OFF states of the light passing through the liquid crystal device cannot be accommodated, and the function as an optical shutter is hindered. It has the disadvantage that it can cause problems.

An object of the present invention is to provide a liquid crystal device, which was previously proposed by the inventors, in which perfect ON and OFF states of light passage are formed even if the scanning speed of input signals is increased. It is in.

In the present invention, the cell is interposed between a liquid crystal sealed between a pair of transparent substrates and 22 polarizing plates whose polarization axes are orthogonal to each other, and has a plurality of comb teeth and is set at a ground potential. A comb-shaped electrode that is a combination of a ground electrode and a driving electrode that is located between the comb-teeth portions and has approximately the same dimensions as one dot to form an ON/OFF state for light passage; and a common electrode that faces the comb-shaped electrode. electrodes are respectively provided on the pair of transparent substrates, and the polarization axis of one of the two polarizing plates is set to be parallel to the longitudinal direction of the comb-shaped electrode to prevent light from passing through. OFF to prevent
When setting the ON state, the drive electrode is set to the ground potential and a potential difference is created between the common electrode and the common electrode to allow light to pass through.When the ON state is set, the drive electrode is set to the same potential as the common electrode, and a potential difference is created between the drive electrode and the common electrode. In a liquid crystal device that generates a potential difference,
A plurality of drive electrodes are formed in the longitudinal direction of the comb-shaped electrode, and the drive electrodes are arranged in a direction perpendicular to the longitudinal direction of the comb-shaped electrode.

Hereinafter, the present invention will be explained in detail based on FIGS. 2 and 3.

In the figure, the same parts as in the conventional product are given the same reference numerals.

2A and 2B show the basic structure of the liquid crystal device of the present invention, where 1 is a liquid crystal cell and Po and An are polarizing plates.

The liquid crystal cell 1 has a comb-shaped ground electrode L ₂₁ on the inner surface and two rows of drive electrodes located between the comb-shaped parts of the ground electrode.
A transparent substrate 2 having L ₀₁ and L ₀₂ and a common electrode on the inner surface.
A transparent substrate 3 having a dielectric constant L ₁₁ and a transparent substrate 3 are placed close to each other via a spacer 4 so as to form a predetermined gap between the two substrates, and a liquid crystal 5 exhibiting positive dielectric anisotropy is sealed in the gap.

The inner surfaces of the transparent substrates 2 and 3 are subjected to a molecular alignment treatment to facilitate the molecular alignment of the liquid crystal 5.

The ground electrode L ₂₁ , drive electrodes L ₀₁ , L ₀₂ and common electrode L ₁₁ are made of a transparent conductive material such as tin oxide or indium oxide, and are formed by employing a conventionally well-known thin film method and etching method.

The ground electrode L ₂₁ has _a concave shape with two comb teeth L _21a and L _21b as _shown in FIG. Two drive electrodes L ₀₁ and L ₀₂ having the same width as one dot forming a state are arranged in two rows. That is, the two drive electrodes L ₀₁ and L ₀₂ are arranged in the longitudinal direction of the comb-shaped electrode, and the two drive electrodes L ₀₁ and L ₀₂ are further arranged in a line shape ( (not shown). This concave ground electrode L ₂₁
is grounded as an electrode common to electrodes L ₀₁ and L ₀₂ ,
Further, the drive electrodes L ₀₁ and L ₀₂ are connected to an external power source (not shown) or to a ground terminal by switching the switches S ₁ and S ₂ .

Further, the common electrode _L11 is connected to an external power source (not shown) as a control electrode.

When the drive electrode L ₀₁ is connected to the ground terminal by the switch S ₁ , the drive electrode L ₀₁ and the ground electrode L ₂₁ are all grounded, and the drive and ground electrodes L ₀₁ ,
A control voltage Vc is applied between _L21 and common electrode _L11 . By applying this control voltage Vc, the drive electrode L ₀₁
The liquid crystal 5 between the common electrode _L11 and the substrate 2 of the liquid crystal cell 1,
3 is forced to be oriented perpendicularly to 3. Furthermore, when the drive electrode L ₀₁ is connected to the drive power supply, the drive electrode
A drive voltage Vd is applied between L ₀₁ and the ground electrode L ₂₁ , and a control voltage is applied between the common electrode L ₁₁ and the ground electrode L ₂₁ .
Vc is applied, and this drive voltage Vd and control voltage
By applying Vc, the liquid crystal 5 between the drive electrode L ₀₁ and the common electrode L ₁₁ is aligned in a direction due to the combination of the electric fields of both voltages, that is, in a diagonal direction with respect to the substrates 2 and 3 of the liquid crystal cell 1.

At the same time, switch S ₂ is also activated on drive electrode L ₀₂ .
When the drive electrode L ₀₂ is connected to the ground terminal or the drive power source, the liquid crystal 5 between the drive electrode L ₀₂ and the common electrode L ₂₁ is connected to the ground terminal or the drive power supply, as in the case of the drive electrode L ₀₁ described above.
are forcibly aligned perpendicularly or obliquely to the substrates 2 and 3.

Incidentally, the comb teeth of the ground electrode L ₂₁ are 2 as shown in FIG.
It is not specific to each individual liquid crystal cell 1
The number of teeth can be arbitrarily changed depending on the size of the drive electrodes L 01 and L 02 , and the number of drive electrodes L ₀₁ and L ₀₂ is not limited to two, but can be changed to two depending on the scanning speed of the input signal, etc. It is also possible to have more than one.

The polarizing plates Po and An are respectively disposed at the front and rear of the liquid crystal cell 1, that is, on the light incident side and the light output side, and their polarization axes are orthogonal to each other. In addition, the polarizing axis of the polarizing plate Po is parallel to the driving electrode and the ground electrode of the liquid crystal cell 1, but instead of this, the polarizing plate An is arranged so that its polarizing axis is parallel to the driving electrode and the grounding electrode of the liquid crystal cell 1. It can also be arranged so that

Thus, in the liquid crystal device of the present invention, the polarizing plate
When a small lamp (not shown) having tungsten as a light emitting element is placed in front of Po as a light source and a scanning input signal is applied to the liquid crystal device,
The drive electrode L ₀₁ of the liquid crystal device is connected to the ground terminal or the drive power source in response to the input signal of the first scan, and the drive electrode L ₀₂ is connected to the input signal of the second scan. At this time, if drive electrode L ₀₁ or L ₀₂ is connected to the ground terminal, drive electrode L ₀₁
Alternatively, L ₀₂ is grounded together with the ground electrode L ₂₁ , and the control voltage Vc is applied between it and the common electrode L ₁₁ . This allows the drive electrode L ₀₁ or L ₀₂ and the common electrode L ₁₁
The molecules of the liquid crystal 5 existing between the liquid crystal cell 1 and
The light polarized in the y-axis direction by the polarizing plate Po, which is oriented perpendicularly to the substrate (BZ-axis direction in Figure 2) and has a polarization axis in the y-axis direction, is directly transmitted to the liquid crystal cell without being absorbed by the liquid crystal 5. Pass through 1. The light in the y-axis direction passing through this liquid crystal cell 1 is x
The light is completely absorbed and blocked by the polarizing plate An having the polarization axis in the axial direction, forming an OFF state in which light passes through.

At this time, since each electrode of the liquid crystal cell 1 has a certain thickness, even if the liquid crystal located on the side surface of the electrode is aligned in the x-axis direction, the alignment direction will be different from that of the polarizing plate. Since the direction is perpendicular to the polarization axis (y-axis direction) of Po, the y
The light in the axial direction is completely absorbed by the liquid crystal (liquid crystal aligned in the x-axis direction) on the side surface of the electrode, and the liquid crystal cell 1
will not pass through. Therefore, in this liquid crystal device, even at the electrode side portions of the liquid crystal cell 1, an OFF state is formed in which light is completely transmitted.

Further, when the drive electrode L ₀₁ or L ₀₂ is connected to the drive power source, the drive voltage Vd is applied between the drive electrode L ₀₁ or L ₀₂ and the ground electrode L ₂₁ , and the common electrode
Control voltage Vd is simultaneously applied between L ₁₁ and ground electrode L ₂₁ , and drive electrode L ₀₁ or L ₀₂
The molecules of the liquid crystal 5 existing between the electrode _L11 and the common electrode L11 are arranged in an oblique direction (Z in FIG. 2B) with respect to the substrate of the liquid crystal cell 1.
The light polarized in the y-axis direction by the polarizing plate Po, which is oriented in the axial direction (combined axis and Pass through 1. The light that has passed through this liquid crystal cell 1 and has been rotated in the x-axis direction passes through a polarizing plate An that has its polarization axis in the x-axis direction,
An ON state for light passage is formed.

At this time, even if the liquid crystal in that area is oriented in a direction that forms an OFF state for light passage due to the large effect of the electric field between the opposing electrodes L ₁₁ and L ₂₁ , the ground electrode L ₂₁ is ON for light passage,
Since it is located on the outer periphery of the one dot that forms the OFF state, it does not prevent light from passing through, but it can make the light that passes through extremely strong.

As described above, the two drive electrodes L ₀₁ and L ₀₂ are arranged in the longitudinal direction of the comb-shaped electrode, and the two drive electrodes L ₀₁ and L ₀₂ are further arranged in the direction perpendicular to the longitudinal direction of the comb-shaped electrode. Because they are arranged in a line,
The scanning line in which the driving electrodes L ₀₁ are arranged and the scanning line in which the driving electrodes L ₀₂ are arranged are integrated,
Turning light on and off across two scan lines
states can be formed all at once, substantially doubling the response speed of the liquid crystal device. Therefore, even if a high-speed scanning input signal is applied to this liquid crystal device, a complete light transmission ON/OFF state corresponding to the applied input signal can be formed, and the function as a light shutter can be fully demonstrated.

Therefore, according to the liquid crystal device of the present invention, the liquid crystal cell is placed between two polarizing plates whose polarizing axes are orthogonal to each other, and the ground electrode and drive electrode of the liquid crystal cell are parallel to the polarizing axis of either one of the two polarizing plates. By arranging the driving electrodes in multiple rows, we have achieved a response speed that allows the ON and OFF states of light passage to be formed even in response to extremely high-speed input inputs, compared to conventional liquid crystal devices. An extremely fast liquid crystal device can be obtained.

Note that the present invention is not limited to the embodiments described above, and various changes can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

Figures 1A and B are diagrams for explaining the structure of a conventional liquid crystal device, Figures 2A and B are diagrams for explaining the structure of the liquid crystal device of the present invention, and Figure 3 is a diagram for explaining the drive electrode and ground electrode. It is a top view showing an example. 1...Liquid crystal cell, 2, 3...Transparent substrate, 5...Liquid crystal,
_L21 ...Ground electrode, _L01 , _L02 ...Drive electrode, _L11 ...Counter electrode, Po, An...Polarizing plate.

Claims (1)

[Claims] 1. A liquid crystal cell in which liquid crystal is sealed between two transparent substrates, and the cell is interposed between two polarizing plates whose polarization axes are perpendicular to each other, and has a plurality of comb teeth and is set at a ground potential. A comb-shaped electrode that is a combination of a ground electrode and a driving electrode that is located between the comb-teeth portions and has approximately the same dimensions as one dot to form an ON/OFF state for light passage; and a common electrode that faces the comb-shaped electrode. electrodes are respectively provided on the pair of transparent substrates, and the polarization axis of one of the two polarizing plates is set to be parallel to the longitudinal direction of the comb-shaped electrode to prevent light from passing through. OFF to prevent
When setting the ON state, the drive electrode is set to the ground potential and a potential difference is created between the common electrode and the common electrode to allow light to pass through.When the ON state is set, the drive electrode is set to the same potential as the common electrode, and a potential difference is created between the drive electrode and the common electrode. In a liquid crystal device that generates a potential difference,
A liquid crystal device characterized in that a plurality of the drive electrodes are formed in the longitudinal direction of the comb-shaped electrodes, and the drive electrodes are arranged in a direction perpendicular to the longitudinal direction of the comb-shaped electrodes.