JP2001260100A - Driving method for minute object driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving method for a minute object driving device capable of generating linear movement or rotative movement in a minute object and of controlling the direction of the movement. SOLUTION: The minute object driving device is provided with: a pair of boards arranged in a form spaced apart at a predetermined distance; liquid crystal arranged in the space between the boards; at least one minute object movably arranged in the liquid crystal; a pair of electrodes arranged so as to interpose the liquid crystal; insulation films formed on the electrode surfaces with a horizontal orientation process applied; and a voltage application means for applying a voltage between the electrodes. This method for the movement of the minute object between the electrodes is controlled by the frequency of, an alternating voltage applied between the electrodes by the voltage application means, which is composed of a positive pulse and a negative pulse different in the absolute value of their peak value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method of a micro object driving device and a display method of a display element which can make a micro object make a linear motion or a curvilinear motion and reverse the direction of the motion.

[0002]

2. Description of the Related Art In recent years, with the development of micromechanical technology, biotechnology, and the like, interest in a small object driving device capable of causing a small object to perform a desired motion has been increasing. As a method of controlling the movement of a minute object, a technique using laser light or the flow of a liquid has been reported.

For example, Japanese Patent Application Laid-Open No. Hei 5-168265 discloses a method of rotating a minute object using a laser beam. In addition, there have already been many reports on a method of moving a small object in a desired direction in a state of being trapped by a laser beam and moving the object on a desired orbit (for example, a circle). The force for driving a minute object in these devices is caused by a change in momentum caused by refraction of the laser beam when the minute object is irradiated with laser light passed through the objective lens.

On the other hand, a new type of driving device for driving an object using an electric field induced type fluid flow has been reported. For example, Japanese Patent Application Laid-Open No. 6-294374 discloses a power generation device using liquid crystal as a fluid. The device according to the present invention generates a convection vortex outside the electrode end (not between the electrodes) by applying an electric field to the liquid crystal cell sealed between the opposing parallel electrodes. It is characterized in that the rotor is rotated by arranging the rotor in the area where the convection occurs.

[0005] The convection of the liquid crystal is driven by the liquid crystal at the electrode end moving from the negative electrode end to the plus electrode end facing the electrode end by an electric field formed between the electrodes. That is, the liquid crystal flow formed by the movement of the liquid crystal escapes to the outside of the electrode and then returns to the end of the negative electrode again, resulting in convection (the axis of the convection is parallel to the substrate surface). .

[0006]

However, the above-mentioned prior art has the following problems. First, there is a problem that it is difficult to reduce the size of a driving device using laser light. This is because an optical system such as a laser light source and an objective lens is required. Further, in order to move or rotate the minute object in a desired direction, an optical system or a mechanical system for moving the focal position of the laser beam in the desired movement direction is required. . Further, in order to rotate the minute object, a plurality of laser light sources and an optical system for circularly polarizing the laser light are required.

On the other hand, the invention disclosed in Japanese Patent Application Laid-Open No. 6-294374 has the following problems. First
In addition, there is a problem that only rotational movement can be formed.
Secondly, there is a problem that although a rotating motion is required in the apparatus, there is an area where the rotor cannot be arranged, and there is wasted space in the apparatus. In addition, there is a problem that it is difficult to reduce the size of the device due to the presence of this space. The region is a capacitor region composed of a pair of electrodes.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and is capable of causing a linear motion or a rotary motion to be exerted on a minute object and controlling the direction of the motion. Further, it is an object of the present invention to provide a driving method of a minute object driving device and a display method of a display element which have a simple structure and can be reduced in size.

[0009]

According to the present invention, there is provided a driving method of a micro object driving apparatus, comprising: a pair of substrates arranged at a predetermined interval; a liquid crystal disposed in a gap between these substrates; At least one minute object movably disposed therein, a pair of electrodes disposed so as to sandwich the liquid crystal, an insulating film provided on a surface of the electrode and subjected to a horizontal alignment process, and A voltage applying means for applying a voltage to the micro object driving device, comprising applying an alternating voltage between the electrodes by the voltage applying means,
The alternating voltage is composed of a positive pulse and a negative pulse having different absolute values of peak values, and the movement of the minute object between the electrodes is controlled at the frequency of the alternating voltage.

Preferred embodiments of the present invention are shown below. It is preferable that the magnitude of the dielectric anisotropy of the liquid crystal is a positive value of +5 or less. The viscosity of the liquid crystal is 2
It is preferably at most 0 mPa · s. It is preferable that the direction of the movement of the minute object is controlled by the frequency of the alternating voltage.

Applying the alternating voltage having a first frequency higher than the critical frequency causes the minute object to move in a predetermined direction, and applying the alternating voltage having a second frequency lower than the critical frequency. It is preferable to move the minute object in a direction opposite to the predetermined direction.

Applying said alternating voltage at said critical frequency;
It is preferable that the movement of the minute object is substantially stopped. It is preferable that the magnitude of the critical frequency is 10 Hz or more and 200 Hz or less. It is preferable that the electric field intensity formed between the electrodes by the alternating voltage is 1 V / μm or more. It is preferable that the horizontal alignment process is a rubbing process.

The rubbing direction of the rubbing process applied to the insulating film on one electrode surface of the pair of electrodes is opposite to the rubbing direction of the rubbing process applied to the insulating film on the other electrode surface. Preferably it is. It is preferable that the rubbing treatment is performed along a band-like region closed with respect to the insulating film. It is preferable that the predetermined direction is parallel to the rubbing direction.

It is preferable that the trajectory of the movement of the minute object is a linear movement of the minute object in a plane substantially parallel to the electrode surface. It is preferable that the trajectory of the movement of the minute object is a closed curve movement of the minute object in a plane substantially parallel to the electrode surface. It is preferable that the speed of movement of the minute object in the predetermined direction is controlled by the first frequency.

It is preferable that the speed of the movement of the minute object in the direction opposite to the predetermined direction is controlled by the second frequency. It is preferable that the direction of movement of the minute object is controlled by the polarity of the alternating voltage. It is preferable to invert the direction of movement of the minute object by inverting the polarity of the alternating voltage.

According to the present invention, a pair of transparent substrates arranged at a predetermined interval, a liquid crystal disposed in a gap between these substrates, and at least one transparent substrate movably disposed in the liquid crystal. A minute object, a pair of transparent electrodes arranged so as to sandwich the liquid crystal, a horizontally oriented insulating film provided on the electrode surface, and voltage applying means for applying a voltage between the electrodes. A method of displaying a display element comprising: applying an alternating voltage between the electrodes by the voltage applying means, wherein the alternating voltage includes a positive pulse and a negative pulse having different absolute values of peak values, and By forming a state in which the minute object is dispersed between the transparent electrodes and a state in which the minute object is localized near the edge of the transparent electrode, the transparent state and the non-transparent state are formed on the display element. Express state A display method of a display device, characterized in that for displaying by causing.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a micro object driving device according to the present invention will be described with reference to FIG. In FIG. 1, 11 and 12 are substrates. 13 and 14 are electrodes provided on the substrate 11 and the substrate 12, respectively. In FIG. 1, an insulating film provided on each electrode surface is omitted.
Further, a spacer for maintaining a gap between the substrate 11 and the substrate 12 is also omitted. Reference numeral 15 denotes a liquid crystal filled between the electrodes. Reference numeral 16 denotes a minute object dispersed in the liquid crystal. FIG. 1 shows only one minute object, but two or more minute objects may be dispersed. Reference numeral 17 denotes voltage applying means for applying a voltage between the electrodes 13 and 14.

The insulating film has been subjected to a horizontal alignment process. Rubbing treatment can be given as a horizontal alignment treatment method. In the present invention, there are two types of rubbing treatment methods for the insulating film. One is a linear rubbing process, and the other is a closed curve rubbing process.

Further, the rubbing treatment according to the present invention is performed on the insulating film on each electrode so as to satisfy the following conditions. That is, the rubbing direction of the rubbing treatment applied to the insulating film on one electrode surface of the pair of electrodes is opposite to the rubbing direction of the rubbing treatment applied to the insulating film on the other electrode surface. .

FIG. 2 is a schematic diagram for explaining a linear rubbing process according to the present invention. FIG. 2 shows only the electrode unit of the micro object driving device shown in FIG. FIG.
In FIG. 2, the insulating film 18 on the electrode 14 is subjected to rubbing in the + x-axis direction shown in the drawing, and the insulating film 19 on the electrode 13 is subjected to rubbing in the -x-axis direction.

FIG. 3 is a schematic diagram for explaining a closed curve rubbing process according to the present invention. In FIG. 3, FIG.
Only the electrode section of the micro object driving device shown in FIG. In FIG. 3, the insulating film 18 on the electrode 14 is subjected to a rubbing process along a closed band shape (hatched portion in the drawing). The rubbing direction is a counterclockwise direction when observed from the upper surface of the electrode 14 (indicated by an arrow in the figure).

On the other hand, the insulating film 19 on the electrode 13 is also subjected to a rubbing process along a closed band (hatched portion in the figure). The rubbing direction is clockwise as viewed from the upper surface of the electrode 14 (indicated by an arrow in the figure). The material used for the insulating film laminated on the electrode surface is not particularly limited. For example, a polyimide film can be used.

The type and structure of the liquid crystal used in the present invention are not particularly limited as long as the desired motion can be exerted on the minute object by the voltage applied between the electrodes. However, it is preferable that the liquid crystal is a nematic liquid crystal having a positive dielectric anisotropy and the magnitude of the dielectric anisotropy is a positive value of at least +5 or less. This is because, if the magnitude of the dielectric anisotropy is greater than +5 and the magnitude of the frequency of the alternating voltage applied between the electrodes is changed, the motion direction of the minute object may not be controlled. If it cannot be reversed, the minute object may show random motion without directionality. Further, the viscosity of the liquid crystal is preferably 20 mPa · s or less. It is preferable that the magnitude of the dielectric anisotropy of the liquid crystal and the magnitude of the viscosity are simultaneously satisfied.

The type of the minute object according to the present invention is as follows.
There is no particular limitation as long as it is chemically stable to the liquid crystal. For example, polymer beads, metal oxide fine particles, organic molecular aggregates, and the like can be given. In addition, the shape is not particularly limited as long as the desired motion can be expressed by the minute object. For example, it may be spherical, flat, or acicular.

Next, a driving method of the minute object driving device according to the present invention will be described. According to the present invention, by applying the alternating voltage having a first frequency higher than the critical frequency, the minute object is moved in a predetermined direction, and the alternating voltage having a second frequency lower than the critical frequency is applied. By doing so, the minute object is moved in a direction opposite to the predetermined direction.

Even when the alternating voltage of the critical frequency is applied between the electrodes, the minute object is almost stopped or does not show a predetermined direction and the movement in the opposite direction to the predetermined direction. Further, even when an alternating voltage having a frequency that is too high than the critical frequency is applied between the electrodes, the minute object does not show any motion. That is, the first frequency according to the present invention has a maximum value.
Even when an alternating voltage having a frequency lower than the critical frequency is applied between the electrodes, the minute object is almost stopped in many cases. That is, the second frequency according to the present invention has a minimum value.

The critical frequency, the first frequency, the second
The magnitude and range of the frequency may vary greatly depending on the type of liquid crystal used in the device, the material and size of the driver, the type of insulating film, and the like. Therefore, in the present invention, it is only necessary to select an appropriate magnitude and range of frequency in which a desired motion can be expressed in the minute object.

FIG. 4 schematically shows the relationship between the magnitude of the frequency of the alternating voltage applied between the electrodes and the moving speed of the minute object. The direction in which the minute object advances when the alternating voltage of the first frequency is applied is defined as plus. Fc shown in FIG. 4 corresponds to the critical frequency. Further, the first frequency exists in the frequency range from fc to f1 shown in FIG. In the case of the present invention, the magnitude of f1 is 5 kHz or less. On the other hand, the second frequency exists in a frequency range from f2 to fc. In the case of the present invention, the magnitude of f2 is 0.5 Hz or more.

The value of the critical frequency fc tends to increase as the electric field strength formed between the electrodes due to the alternating voltage increases. If the liquid crystal used in the device according to the present invention is the same, the value of the critical frequency fc is uniquely determined by the magnitude of the electric field intensity. The range of the critical frequency may be 10 Hz or more and 200 Hz or less. For example, when an electric field of a predetermined electric field strength is applied between the electrodes, the magnitude of the critical frequency fc is 50
Hz. In this case, the first frequency has a value of 50 Hz or more and 5 kHz or less. On the other hand, the second frequency has a value of 0.5 Hz or more and 50 Hz or less.

As shown in FIG. 4, there are two alternating voltage frequencies that maximize the speed of movement of the minute object.
One is between fc and f1 (this frequency is f1a). The other exists between the above f2 and fc (this frequency is f2a). The speed of the minute object when the frequency of the alternating voltage is f1a (v1 shown in FIG. 4) and the speed of the minute object when the frequency of the alternating voltage is f2a (v2 shown in FIG. 4) Varies greatly depending on the type of liquid crystal used in the device, the material and size of the driver, the type of insulating film, the electric field strength, and the like. However, regardless of the type of liquid crystal, the material of the driver, and the like, the higher the electric field strength, the higher the speed tends to be. The magnitudes of v1 and v2 tend to be substantially equal.

Further, according to the present invention, the speed of the minute object can be controlled by changing the magnitude of the frequency of the alternating voltage applied between the electrodes. That is, the frequency of the alternating voltage applied between the electrodes is changed from the frequency fc shown in FIG.
By changing between 1a, the speed of the minute object can be controlled between 0 and v1. Similarly, the frequency of the alternating voltage applied between the electrodes is changed to the frequency f shown in FIG.
By changing between c and f2a, it is possible to control the speed of the minute object between 0 and v2.

Next, a driving method according to the present invention will be described.
This will be specifically described. <Driving method of micro-object driving device subjected to linear rubbing process> A micro-object driving device having a configuration shown in FIG. 1 is applied to an insulating film on each electrode as shown in FIG. A driving method of the minute object driving device when a linear rubbing process is performed will be described.

The voltage applying means 17 applies a rectangular wave (V 1> V 2) having a polarity in the first frequency range as shown in FIG.
Is grounded). In this case, the minute object 1
6 shows a linear movement between the electrodes in the + x-axis direction. That is, the minute object moves in a plane substantially parallel to the electrode surface.

On the other hand, a bipolar short wave (V1> V2) as shown in FIG.
4 is grounded), and a rectangular wave having a frequency in the second frequency range is applied. In this case, the minute object 16 linearly moves between the electrodes in the −x-axis direction.

That is, the peak value on the plus side of the short wave (V1 in the above description) and the peak value on the minus side (−V in the above description)
By changing the magnitude of the frequency of the rectangular wave without changing 2), the motion direction of the minute object can be reversed.

Similar results can be obtained even if a plurality of minute objects are dispersed between the electrodes. That is, when a rectangular wave having a frequency in the first frequency range as shown in FIG. 5 is applied, all the minute objects show a linear motion in the −x-axis direction. On the other hand, FIG. 5 having a frequency in the second frequency region
When a rectangular wave as shown in is applied, all minute objects are
It shows a linear motion in the + x-axis direction.

When a short wave having a frequency in the first frequency range, which is a short wave having a polarity opposite to that of the short wave shown in FIG. 5 (see FIG. 6), is applied to the minute object. −
The linear motion in the x-axis direction is shown. 5 is a short wave having a polarity opposite to that of the short wave shown in FIG. 5 (see FIG. 6).
When a short wave having a frequency within the second frequency range is applied, the minute object shows a linear motion in the + x-axis direction. That is, the minute object driving device according to the present invention can control the direction of movement of the minute object without changing the frequency and also by the polarity of the alternating voltage applied between the electrodes.

<Driving Method of Micro-Object Driving Device Performed with Closed Curve Rubbing Process> A micro-object driving device having the structure shown in FIG. 1 is shown in FIG. A driving method of the minute object driving device when rubbing processing is performed along such a closed curve will be described.

The voltage applying means 17 applies a rectangular wave (V1> V2) having both polarities as shown in FIG. 5 and having a frequency in the first frequency range (electrode 14).
Is grounded). In this case, the minute object 1
Numeral 6 shows a counterclockwise rotational movement between the electrodes when observed from the upper surface of the electrodes 14. That is, the minute object moves in a plane substantially parallel to the electrode surface.

On the other hand, the voltage application means 17 applies a rectangular wave having a frequency within the second frequency range, which is a rectangular wave having both polarities (V1> V2) as shown in FIG. 14 is grounded). In this assembling, the minute object 16 shows a clockwise rotational movement between the electrodes when observed from the upper surface of the electrode 14.

That is, the peak value on the plus side (V1 in the above description) and the peak value on the minus side (−V in the above description) of the rectangular wave.
By changing the magnitude of the frequency of the rectangular wave without changing 2), the direction of the rotational movement of the minute object can be reversed.

Similar results can be obtained even if a plurality of minute objects are dispersed between the electrodes. That is, when a rectangular wave having a frequency within the first frequency range as shown in FIG. 5 is applied, all the minute objects show a clockwise rotation. On the other hand, when a rectangular wave having a frequency in the second frequency range as shown in FIG. 5 is applied, all the minute objects show a counterclockwise rotation.

When a rectangular wave having a frequency in the first frequency range, which is a rectangular wave having a polarity opposite to that of the rectangular wave shown in FIG. 5 (see FIG. 6), is applied, the minute object rotates clockwise. Shows the rotational movement of. 5 is a rectangular wave having a polarity opposite to that of the rectangular wave shown in FIG. 5 (see FIG. 6).
Applying a rectangular wave having a frequency within the frequency range of
The minute object shows a counterclockwise rotation. That is, the minute object driving device according to the present invention can control the direction of movement of the minute object without changing the frequency and also by the polarity of the alternating voltage applied between the electrodes.

In the above description, a rectangular wave has been described as an example of an electric signal for driving a minute object. In the present invention, the electric signal for driving the minute object is not limited to a rectangular wave. At least an alternating voltage is acceptable. And
The alternating voltage is composed of a positive pulse and a negative pulse, and the peak value of the positive pulse is different from the peak value of the negative pulse. Further, it is preferable that the electric field intensity formed between the electrodes by the alternating voltage according to the present invention is 1 V / μm or more. However, the range of the electric field strength may vary greatly depending on the type of liquid crystal used in the device, the material and size of the driving body, the type of insulating film, and the like. Therefore, in the present invention, an appropriate electric field intensity that can cause a desired motion to be exerted on the minute object may be selected.

The details of the mechanism of the movement of the minute object in the liquid crystal as described above are unknown, but the present inventors speculate that the electric field-induced liquid crystal flow may drive the minute object. That is, when the rectangular waves shown in FIGS. 6 and 5 are applied, the minute object is attracted to one of the electrodes according to the charge sign in the liquid crystal. It is presumed that an electric field-induced liquid crystal flow is formed in the vicinity of the attracted electrode. However, it is assumed that the direction of the liquid crystal flow formed when the rectangular wave in FIG. 6 is applied is opposite to the direction of the liquid crystal flow formed when the rectangular wave in FIG. 5 is applied. I guess. For this reason, it is considered that when the polarity of the rectangular wave is changed, the moving direction of the minute object is reversed. Further, the direction of the liquid crystal flow formed when the frequency of the rectangular wave shown in FIG. 5 is the first frequency is changed when the frequency of the rectangular wave shown in FIG. 5 is the second frequency. It is presumed that the direction is opposite to the direction of the liquid crystal flow. For this reason, it is estimated that the direction of movement of the minute object can be controlled by the frequency of the rectangular wave.

On the other hand, the above-mentioned minute object driving device may be provided with a mechanism for taking the movement of the minute object out of the wall surface of the driving device. For example, when a minute object is caused to linearly move, a minute rod may be connected to the minute object, and the rod may be put out of the substrate of the driving device. In this case, it is possible to extract the linear motion of the minute object. Alternatively, application to a micropump that induces liquid crystal flow by an electric field instead of driving a minute object in the liquid crystal is also possible. Alternatively, the present invention can be applied to a display element that forms two optically different states (for example, a transparent state and a non-transparent state) by moving a minute object between electrodes and changing the distribution state.

[0047]

The present invention will be described below in detail with reference to examples.

Embodiment 1 FIG. 7 is a schematic diagram of a micro object driving device according to this embodiment. In FIG. 7, reference numerals 71 and 72 denote glass substrates (15 mm × 15 mm) disposed to face each other. 73 and 74
Are transparent electrodes (10 mm × 10 mm) provided on the substrate 71 and the substrate 72, respectively. A polyimide thin film is laminated on the surfaces of the electrodes 73 and 74 (omitted in FIG. 7). The polyimide thin film laminated on the electrode 73 is subjected to a rubbing treatment in the −x-axis direction. The polyimide thin film laminated on the electrode 74 has been subjected to a rubbing treatment in the + x-axis direction.

75 is a nematic liquid crystal (trade name: MLC-
6225-000, manufactured by Merck & Co., Ltd.). Reference numeral 76 denotes a minute object, a polymer bead having a diameter of 3 μm (trade name: Micropearl SP-203, Sekisui Fine Chemical Co., Ltd.)
Made). Reference numeral 77 denotes voltage applying means for applying a voltage between the electrode 73 and the electrode 74. The electrode 74 is grounded. In FIG. 7, the spacer for maintaining the gap (12.5 μm in this embodiment) between the pair of electrodes is omitted.

A rectangular wave of V1 = 82 V, V2 = 18 V and a frequency of 300 Hz was applied between the electrodes 73 and 74 as shown in FIG. During the rectangular wave application,
The response of the polymer beads disposed between the electrodes was observed with a microscope from the upper surface of the electrode 73. As a result, it was observed that all the polymer beads existing between the electrodes moved in the + x-axis direction. When the application of the square wave is continued,
A state in which the polymer beads were gathered at one electrode edge (the left electrode edge in FIG. 7) could be formed.

Next, a rectangular wave of V1 = 82 V, V2 = 18 V, and a frequency of 20 Hz was applied between the electrode 73 and the electrode 74 as shown in FIG. During the application of the rectangular wave, the response of the polymer beads placed between
3 was observed with a microscope from above. As a result, it was observed that all the polymer beads existing between the electrodes moved in the −x-axis direction. When the rectangular wave was continuously applied, a state where the polymer beads were gathered at one electrode edge (the right electrode edge in FIG. 7) could be formed. That is, the polymer beads moved from near the left electrode edge to near the right electrode edge. Further, in this embodiment, when the above-mentioned two types of rectangular waves were alternately applied, the movement direction of the polymer beads could be reversibly reversed. That is, by changing the magnitude of the frequency of the square wave applied between the electrodes,
The direction of movement of the polymer beads could be controlled.

In the rectangular wave shown in FIG. 5, V1
= 82V, V2 = 18V, and a rectangular wave having a frequency of 40 Hz were applied between the electrodes. However, no clear movement of the polymer beads was observed.

Embodiment 2 In this embodiment, the same minute object driving device as in Embodiment 1 was used. In this example, the following short-wave was applied. [Square wave 1] In the short wave shown in FIG. 5, V1 = 98.4V, V2
= 21.6V, frequency 500Hz and frequency 2
0Hz square wave. -Square wave 2 In the square wave shown in Fig. 5, V1 = 131.2V, V
2 = 28.8 V, a rectangular wave having a frequency of 500 Hz and a frequency of 20 Hz.

While the rectangular wave 1 and the rectangular wave 2 were applied between the electrodes, the response of the polymer beads existing between the electrodes was observed. As a result, both rectangular waves are 500 Hz
It was observed that the polymer beads moved in the + x-axis direction in the case of, and in the -x-axis direction in the case of 20 Hz.

When a rectangular wave having the same peak value as the rectangular wave 1 and a frequency of 60 Hz was applied, no clear movement of the polymer beads was observed. On the other hand, when a rectangular wave having the same crest value as the rectangular wave 2 and a frequency of 80 Hz was applied, clear movement of the polymer beads was not observed.

Embodiment 3 In this embodiment, the same minute object driving device as in Embodiment 1 was used. In this embodiment, the following rectangular wave was applied.

Square wave 3 In the short wave shown in FIG. 5, V1 = 98.4V, V2
= 21.6V and the frequency is changed from 60Hz to 500H
z. -Square wave 4 In the square wave shown in FIG. 5, V1 = 98.4V, V2
= 21.6V and varied between 60Hz and 30Hz.

While the rectangular bridge 3 is being applied between the electrodes,
The response of the polymer beads between the electrodes was observed. As a result, it was observed that as the frequency increased from 60 Hz to 500 Hz, the speed of movement of the polymer beads in the + x-axis direction increased.

On the other hand, while the rectangular wave 4 was applied between the electrodes, the response of the polymer beads existing between the electrodes was observed. As a result, it was observed that the movement speed of the polymer beads in the −x-axis direction increased as the frequency decreased from 60 Hz to 30 Hz.

Embodiment 4 In this embodiment, the same minute object driving device as in Embodiment 1 was used. In this embodiment, the following rectangular wave was applied. Short wave 5 In the rectangular wave shown in FIG. 5, V1 = 98.4V, V2
= 21.6 V, 500 Hz frequency square wave. Short wave 6 In the short wave shown in FIG. 5, V1 = 21.6 V, V2
= 98.4V, 500Hz frequency square wave. The rectangular wave 6 is a short wave having a polarity opposite to that of the short wave 5.

While the rectangular wave 5 is being applied between the electrodes,
The response of the polymer beads existing between the electrodes was observed. As a result, it was observed that the polymer beads moved in the + x-axis direction. On the other hand, while the rectangular wave 6 was applied between the electrodes, the response of the polymer beads existing between the electrodes was observed. As a result, it was observed that the polymer beads moved in the −x axis direction.

Embodiment 5 In this embodiment, a micro object driving device having the same configuration as that of Embodiment 1 was used except that the following items were changed. What has been changed is a rubbing treatment for the polyimide films laminated on the electrodes 73 and 74, respectively.

In this embodiment, rubbing treatment was performed on each polyimide film along the circumference to form a closed band-shaped rubbed region. FIG. 8 is a schematic view of the rubbing treatment performed on the electrodes 73 and 74. FIG.
Shows only the electrode 73 and the electrode 74. The arrow shown in the figure is the rubbing direction of the rubbing process. Electrode 7
Rubbing 3 is performed in a clockwise direction as viewed from the upper surface of the electrode 73. On the other hand, the electrode 74 is
The rubbing process is performed in a counterclockwise direction when observed from the upper surface of the third sample.

In this embodiment, the rubbing along the circumference was performed as follows. The method will be described with reference to FIG. First, a rubbing cloth 92 is pressed against the electrode 91 (a polyimide film is not shown) to rotate the electrode in one direction about a rotation axis 94 passing through the electrode center 93 of the electrode 91 and perpendicular to the electrode surface. As a result, a rubbing treatment was performed on the polyimide thin film on the electrode surface. By performing such a rubbing process, a rubbing region along the circumference was formed.

Next, the electrode 73 and the electrode 7 are
4, the following two types of rectangular wave voltages were alternately applied.
However, in each case, the electrode 74 is grounded. A rectangular wave of V1 = 82 V, V2 = 18 V, and a frequency of 500 Hz was applied between the electrodes 73 and 74 in the rectangular wave shown in FIG. During the application of the rectangular wave, the response of the polymer beads disposed between the electrodes was observed with a microscope from the upper surface of the electrode 73. As a result, it was observed that all the polymer beads present between the electrodes showed a counterclockwise rotation. That is, the minute object showed a rotational motion in a plane substantially parallel to the electrode surface.

Next, a rectangular wave of V1 = 82 V, V2 = 18 V, and a frequency of 20 Hz was applied between the electrode 73 and the electrode 74 as shown in FIG. During the application of the rectangular wave, the response of the polymer beads placed between
3 was observed with a microscope from above. As a result, it was observed that all the polymer beads present between the electrodes showed a clockwise rotational motion. Further, in the present embodiment, the above 2
When the different types of rectangular waves were applied alternately, the direction of movement of the polymer beads could be reversibly reversed. That is, the direction of movement of the polymer beads could be controlled by changing the magnitude of the frequency of the square wave applied between the electrodes.

In the rectangular wave shown in FIG. 5, V1
= 82 V, V2 = 18 V, and a rectangular wave having a frequency of 40 Hz were applied between the electrodes. However, no clear movement of the polymer beads was observed.

Embodiment 6 In this embodiment, a micro object driving device having the same configuration as that of Embodiment 1 was used except that the following items were changed. The difference is that a black plate is provided on the back surface of the substrate 72.

The apparatus of the present embodiment looked white when first observed from the upper surface of the substrate 71. In the rectangular wave shown in FIG. 5, V1 = 82 V, V2
= 18V, a rectangular wave having a frequency of 300 Hz was applied. During the application of the rectangular wave, the response of the polymer beads disposed between the electrodes was observed with a microscope from the upper surface of the substrate 71. As a result, all the polymer beads existing between the electrodes become +
Movement in the x-axis direction was observed. When the rectangular wave is continuously applied, the polymer beads are placed on one electrode edge (FIG. 7).
Thus, a state in which the electrodes were gathered at the left electrode edge portion) was formed. Observing the device in this state from the upper surface of the substrate 71,
The electrode area appeared black. This state was maintained even when the rectangular wave application was canceled.

Next, in the rectangular wave shown in FIG. 5 between the electrodes, V1 = 82 V, V2 = 18 V, frequency 20 Hz
Was applied. During the application of the rectangular wave, the response of the polymer beads disposed between the electrodes was observed with a microscope from the upper surface of the substrate 71. As a result, it was observed that all the polymer beads existing between the electrodes moved in the −x-axis direction. Continued application of the square wave formed a state in which the polymer beads were almost uniformly dispersed between the electrodes. When the device in this state was observed from the upper surface of the substrate 71, the electrode region again appeared white. This state was preserved even after the application of the short-wave application.

Further, in this embodiment, when the above-mentioned two types of rectangular waves were alternately applied, a black state and a white state could be formed alternately.

[0072]

As described above, according to the present invention, despite its simple structure, a minute object can exhibit linear motion or rotational motion, and the reversible reversal of the motion direction and the motion speed can be achieved. Thus, it is possible to provide a driving method of a micro-object driving device and a display method of a display element, which are capable of controlling the size of the micro-object driving device and having a simple structure and can be downsized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a structure of a minute object driving device according to the present invention.

FIG. 2 is an explanatory diagram showing a rubbing process in the present invention.

FIG. 3 is an explanatory diagram showing a rubbing process in the present invention.

FIG. 4 is a schematic diagram illustrating a relationship between a frequency of an alternating voltage and a moving speed of a minute object.

FIG. 5 is a waveform diagram showing a driving waveform of an alternating voltage applied to the minute object driving device according to the present invention.

FIG. 6 is a waveform diagram showing a driving waveform of an alternating voltage applied to the minute object driving device according to the present invention.

FIG. 7 is a sectional view showing another example of the structure of the minute object driving device according to the present invention.

FIG. 8 is an explanatory diagram showing a rubbing process in the present invention.

FIG. 9 is an explanatory diagram illustrating a rubbing process according to the second embodiment of the present invention.

[Explanation of symbols]

 11, 12, 71, 72 Substrate 13, 14, 73, 74, 91 Electrode 15, 75 Liquid crystal 16, 76 Small object 17, 77 Voltage applying means 18, 19 Insulating film 92 Rubbing cloth 93 Electrode center 94 Rotation axis

Claims (19)

[Claims] 1. A pair of substrates disposed at a predetermined interval, a liquid crystal disposed in a gap between these substrates, at least one minute object movably disposed in the liquid crystal, A micro object driving device comprising: a pair of electrodes arranged so as to sandwich a liquid crystal; an insulating film provided on the surface of the electrodes, which has been subjected to a horizontal alignment process; and voltage applying means for applying a voltage between the electrodes. A driving method, wherein an alternating voltage is applied between the electrodes by the voltage applying means, and the alternating voltage is composed of a positive polarity pulse and a negative polarity pulse having different absolute values of the peak value, and the alternating voltage is applied at the frequency of the alternating voltage. A method for driving a minute object driving device, comprising controlling movement of the minute object between electrodes. 2. The method according to claim 1, wherein the magnitude of the dielectric anisotropy of the liquid crystal is +5.
2. The method according to claim 1, wherein the following positive values are set. 3. The liquid crystal having a viscosity of 20 mPa ·
2. The driving method of a small object driving device according to claim 1, wherein the distance is not more than s. 4. The method according to claim 1, wherein the direction of movement of the minute object is controlled by the frequency of the alternating voltage. 5. The small object is moved in a predetermined direction by applying the alternating voltage having a first frequency higher than a critical frequency, and the alternating voltage having a second frequency lower than the critical frequency is applied. 5. The method according to claim 4, further comprising: moving the minute object in a direction opposite to the predetermined direction. 6. The driving method for a micro object driving device according to claim 5, wherein the alternating voltage having the critical frequency is applied to substantially stop the motion of the micro object. 7. The method according to claim 5, wherein the magnitude of the critical frequency is not less than 10 Hz and not more than 200 Hz. 8. The method according to claim 1, wherein an electric field intensity formed between the electrodes by the alternating voltage is 1 V / μm or more. 9. The method according to claim 1, wherein the horizontal alignment process is a rubbing process. 10. A rubbing direction of a rubbing treatment applied to an insulating film on a surface of one of the pair of electrodes,
The method according to claim 9, wherein the rubbing direction of the rubbing process applied to the insulating film on the other electrode surface is opposite to the rubbing direction. 11. The method according to claim 9, wherein the rubbing process is performed along a band-like region closed with respect to the insulating film. 12. The rubbing direction according to claim 5, wherein the predetermined direction is parallel to the rubbing direction.
A driving method of the micro object driving device according to the above. 13. The device for driving a small object according to claim 9, wherein the trajectory of the movement of the small object is a linear movement of the small object in a plane substantially parallel to the electrode surface. Drive method. 14. The device for driving a minute object according to claim 11, wherein the trajectory of the movement of the minute object is a closed curve movement of the minute object in a plane substantially parallel to the electrode surface. Drive method. 15. The method according to claim 5, wherein the speed of movement of the minute object in the predetermined direction is controlled by the first frequency. 16. The driving of the device for driving a small object according to claim 5, wherein the speed of movement of the minute object in a direction opposite to the predetermined direction is controlled by the second frequency. Method. 17. The method according to claim 1, wherein a direction of movement of the minute object is controlled by a polarity of the alternating voltage. 18. The method according to claim 17, wherein the direction of movement of the minute object is inverted by inverting the polarity of the alternating voltage. 19. A pair of transparent substrates disposed at a predetermined interval, a liquid crystal disposed in a gap between these substrates, and at least one minute object movably disposed in the liquid crystal. A display element comprising: a pair of transparent electrodes disposed so as to sandwich the liquid crystal; an insulating film provided on the surface of the electrodes, which has been subjected to a horizontal alignment process; and voltage applying means for applying a voltage between the electrodes. In the display method, an alternating voltage is applied between the electrodes by the voltage applying means, and the alternating voltage is composed of a positive pulse and a negative pulse having different absolute values of the peak value, and the frequency of the alternating voltage, By forming a state in which the minute object is dispersed between the transparent electrodes and a state in which the minute object is localized near the edge of the transparent electrode, the display element expresses a transparent state and a non-transparent state. By thing A display method of a display element, which performs display.