JP2576085B2 - Liquid crystal element - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a liquid crystal element suitable for two-frequency driving.

[Technical background of the invention]

In recent years, liquid crystal elements have been applied to image display on television receivers, computer displays, and the like, and optical writing of optical writing printers used as computer terminals or office equipment.

The liquid crystal element used for image display, optical writing, etc.
Micro shutter parts for controlling light transmission are arranged at close intervals, and the shutter parts have transparent electrodes formed on a pair of transparent substrates facing each other with a liquid crystal layer interposed therebetween. It is constituted by.

A liquid crystal element used for image display or the like is normally driven by selectively applying a voltage equal to or higher than a threshold voltage of the electro-optical effect and a voltage lower than the threshold voltage to the shutter section.

However, in such a driving method, for example, in the case of a liquid crystal element using a liquid crystal composition having positive dielectric anisotropy, liquid crystal molecules are vertically aligned with respect to the substrate by applying a voltage higher than the threshold. Sometimes the applied voltage causes the liquid crystal molecules to behave immediately, but when the liquid crystal molecules are oriented parallel to the substrate by applying a voltage lower than the threshold value, the liquid crystal molecules are moved between the liquid crystal composition and the alignment film of the substrate. Since the liquid crystal molecules behave slowly because they are aligned only by the alignment regulating force acting on the shutter, there is a problem that the shutter cannot be opened and closed at high speed.

For this reason, when it is necessary to drive a large number of shutter sections at a high speed and a high contrast is obtained, a two-frequency driving method utilizing the dielectric dispersion phenomenon of liquid crystal is adopted.

The two-frequency driving method is such that when a high-frequency electric field is applied to the liquid crystal, the liquid crystal molecules try to be oriented so as to be orthogonal to the electric field, and when a low-frequency electric field is applied, the liquid crystal molecules are parallel to the electric field. The TN type (twisted nematic type) liquid crystal element of the positive display by this driving method (twisted nematic type in which the polarization axes of the polarizing plates are arranged orthogonal to each other) by this driving method has a shutter portion opened by application of a high frequency. The shutter section is closed (non-transparent) by applying a low frequency and a low frequency. In the case of a GH type (guest-host type) liquid crystal element, the shutter section is closed (non-transparent ... coloring) by applying a high frequency. The application of the frequency causes the shutter portion to open (light transmission ... no coloring).

[Problems of background technology]

However, when driving the liquid crystal element at two frequencies,
A high frequency (100 KHz or more) and a low frequency are applied to the liquid crystal. However, if the application time of the high frequency is long, there is a problem that the response of the liquid crystal to the next application of the low frequency is deteriorated.

This is due to the hysteresis effect of the liquid crystal. Since the hysteresis effect of the liquid crystal occurs particularly at high frequencies, the influence of the high frequency remains strong when the application time of the high frequency is long, and even when the low frequency is applied next. This is because the liquid crystal stops responding immediately.

That is, when the liquid crystal element is driven at two frequencies, the liquid crystal behaves by applying high and low frequencies so that the liquid crystal molecules are aligned parallel and perpendicular to the substrate. Instead of being oriented completely parallel and perpendicular to it, it behaves over a range of angles. However, when the application time of the high frequency is long, the applied electric field is accumulated and acts on the liquid crystal, so that the liquid crystal molecules are strongly aligned parallel to the substrate. Can not stand up.

For this reason, when the conventional liquid crystal element is driven at two frequencies, in the case of a TN type liquid crystal element for positive display, the operation when the shutter unit switches from the open state to the closed state is delayed, and
In the case of a liquid crystal element of the type, the operation when the shutter section switches from the closed state to the open state is delayed, so that, for example, in an optical writing type printer, the light on the photosensitive drum is not irradiated with light. When a liquid crystal element used as an optical writing element is driven by two frequencies, although a development-type electrophotographic process that attaches toner is used, in the case of a TN type liquid crystal element, the start of a print pixel is delayed due to a delay in the closing operation of the shutter. Portion is blurred or not printed, and in the case of a GH type liquid crystal element, the end portion of the print pixel is trailed due to a delay in the opening operation of the shutter unit.

This phenomenon is caused by the fact that a liquid crystal element driven in a time-division manner at two frequencies, in which a shutter portion formed by opposing portions of an electrode formed on one substrate and an electrode formed on the other substrate is arranged in a matrix, has It appears more prominently because the high frequency component of the applied electric field increases.

[Object of the invention]

The present invention has been made to solve the above-described problem, and an object of the present invention is to allow liquid crystal molecules to rise immediately by applying the next low frequency even when a high frequency is applied for a relatively long time. It is an object of the present invention to provide a liquid crystal element suitable for two-frequency driving, which can open and close the shutter portion with high responsiveness at high speed.

[Summary of the Invention]

That is, according to the present invention, the liquid crystal layer has a dielectric anisotropy Δε _L at a low frequency of positive and an absolute value | Δε _L | of 5.3 or more, and a dielectric anisotropy Δε _H at a high frequency of negative and an absolute value | Δε _H | is 3.
By using a liquid crystal composition exhibiting a dielectric dispersion phenomenon in which the ratio of | Δε _L | to | Δε _H | is 1.47 ≦ | Δε _L | / | Δε _H | This is to prevent the history effect from appearing greatly.

Explaining the liquid crystal composition used in the present invention,
FIG. 1 shows the frequency f (K) of the liquid crystal composition used in the present invention.
Hz), the dual-frequency driving liquid crystal composition exhibits a frequency in a low-frequency region showing a constant Δε.
The value of f _L and the frequency f _H f _L = f _C / 10 f _H = 10 · f _C in the high frequency region (f _C is the crossover frequency where Δε crosses zero and is 100 KHz or less) is Δε _L ≧ This shows a dielectric dispersion phenomenon in which 5.3 Δε _H ≧ 3.6 and the ratio between | Δε _L | and | Δε _H | is 1.47 ≦ | Δε _L | / | Δε _H | <5.

This liquid crystal composition has a small hysteresis effect with respect to a high frequency, and has a very short response time of standing and falling of liquid crystal molecules of 0.5 ms or less, and is excellent in responsiveness.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings, taking a liquid crystal element used for optical writing of an optical writing printer as an example.

First, the configuration of the optical writing type printer will be described. In FIG. 2, 1 is a photoconductive photosensitive drum, 2 is a charger for uniformly charging the surface of the photosensitive drum 1, and 3 is a charged surface of the photosensitive drum 1. The optical recording unit 3 is driven by a recording control unit 4 that controls timing and the like based on recording information such as an image, and irradiates the surface of the photosensitive drum 1 with light. The optical writing is performed by erasing the charge on the light-irradiated portion of the photosensitive drum surface.

The electrostatic latent image on the surface of the photosensitive drum formed by the optical writing of the optical recording unit 3 is developed by the developing unit 5 with toner.

The recording paper 6 is fed by a paper feed roll 7, temporarily stopped by a standby roll 8, and then sent to a transfer unit 9 in synchronization with the toner image on the surface of the photosensitive drum. The toner image on the drum surface is transferred to the paper 6 in the transfer unit 9. This paper 6
At 10, the toner image is separated from the photosensitive drum 1, the toner image is fixed by a fixing device 11, and is sent out by a paper discharge roller 12.

The photosensitive drum 1 on which the toner image has been transferred onto the paper 6 is
After the toner charge is neutralized by the static eliminator 13, the cleaner 14
Thus, the remaining toner is cleaned, and the surface charge is neutralized by the eraser 15.

The optical recording unit 3 includes, as shown in FIG.
It comprises a liquid crystal element 20 for optical writing and an imaging lens 17, and irradiates light from the light source 16 to the surface of the photosensitive drum via the liquid crystal element 20 and the imaging lens 17.

The liquid crystal element 20 is horizontally long along the axial direction of the photosensitive drum 1. The liquid crystal element 20 has a large number of minute shutters for controlling light transmission at close intervals along the length direction. It is formed.

That is, FIGS. 4 to 9 show the above-mentioned liquid crystal element 20. Here, a GH type liquid crystal element is shown.

The structure of the liquid crystal element 20 will be described. In the figure, reference numerals 21 and 22 denote a pair of upper and lower transparent substrates made of a glass plate having a thickness of about 0.7 mm. A laterally long frame-shaped outer sealing material 23a as shown in the figure, and a pair of mutually parallel inner sealing materials formed inside the outer sealing material 23a at an interval d of about 2 mm with respect to both side portions thereof.
23b, 23b.

The distance e between the pair of inner seal members 23b, 23b is about 1 mm, and the length of the narrow gap between the inner seal members 23b, 23b is, for example, for a printer for recording on a maximum B4 size sheet. It is 249 mm in the case of a liquid crystal element. Further, both ends of the inner seal members 23b, 23b are connected to both side portions of the outer seal member 23a, respectively, and the inner seal members 2 between the substrates 21, 22 are formed.
Spaces 30, 30 are defined by portions surrounded by 3b, 23b and both side portions of the outer sealing material 23a. In FIG. 5, reference numerals 31 and 31 denote substrates 2 when the pair of substrates 21 and 22 are superposed and bonded.
This is an air hole for allowing the air between 1 and 22 to escape to the outside, and the air holes 31 and 31 are sealed with sealing materials 32 and 32 applied after bonding the substrates 21 and 22. . Therefore, the space 30,
The space 30 is filled with air (clean air) left when the substrates 21 and 22 are bonded.

Also, both ends of the narrow gap between the inner seal members 23b, 23b are communicated with the wide gaps at both ends surrounded by the outer seal material 23a, and the narrow gap and the wide gap between the substrates 21, 22 are provided. The gap is filled with a liquid crystal composition 24 to which a dichroic dye is added. Reference numeral 33 denotes a liquid crystal injection hole provided at one end of the outer sealing material 23a.
Is also used as an air hole for releasing air between the substrates 21 and 22 to the outside when the pair of substrates 21 and 22 are superimposed and bonded,
The liquid crystal injection hole 33 is sealed by applying a sealing material 34 after injecting the liquid crystal composition 24 (injecting by a vacuum injection method).

In addition, one of the substrates 21 and 22
As shown in FIG. 5 and FIG. 7, the inner surface of the segment substrate (hereinafter referred to as a segment substrate) has a length of about one side over the entire length thereof in the narrow gap between the inner seal members 23b. 180μm, almost square segment electrodes S1, S1,
.., S2, S2,...
As shown in FIG. 6, two strip-shaped common electrodes C1 and C2 each having a width of 3 mm are provided on the inner surface of the common substrate 2 (hereinafter referred to as a common substrate) as shown in FIG.
They are formed in parallel with a minute gap of about 30 μm.

The segment electrodes S1, S1,..., S2, S2,.
1 and C2 are transparent electrodes, and a shutter section a for controlling light transmission at a portion where the segment electrodes S1, S1,..., S2, S2,. , a,... are formed.

.., S2, S2,... Among the two rows of segment electrodes S1, S1,. .. Are arranged in two rows with a shift of 1/2 pitch.

The reason why the shutter units a, a,... Are arranged in two rows while being shifted by 1/2 pitch is that the shutter units a, a,.
Between the rows of irradiation points on the surface of the photosensitive drum irradiated with light passing through the shutter section a, a,. This is for forming a latent image. The shutter sections a, a,... Are a liquid crystal element for a printer that records on a maximum B4 size sheet, and are arranged 587 per row, and the shutter sections a, a,. (The distance between the centers of the shutter sections a, a) P1 and P2 are about 200 μm, respectively, and the pitch between the shutter sections a, a,... In one row and the shutter sections a, a,. The distance D between the centers is about 260 μm.

Also, the segment electrodes S1, S1,... Of one row and the segment electrodes S2, S2,... Of the other row are adjacent to each other with a shift of 1/2 pitch. Are connected by the electrodes 25, 25,..., And the drive circuit connection leads 26, 26,... Of the segment electrodes are alternately led out from one of the commonly connected segment electrodes S1, S2. The reason why the segment electrodes S1, S1,... Of one row are commonly connected to the segment electrodes S2, S2,.
If the drive circuit connection leads are individually derived from 2, S2, ..., the number of drive circuit connection leads becomes so large that it is difficult to route the leads. Therefore, in this liquid crystal element, Segment electrode S1, S in one row
Are connected in common with the segment electrodes S2, S2,... Of the other row, and the common electrodes C1, C2 are opposed to the respective segment electrode rows to drive the liquid crystal element in a time-division manner.

, S2, S2,..., Common connection electrodes 25, 25, and drive circuit connection leads 26, 26,.
Is integrally formed of a transparent conductive material such as indium oxide.

In FIGS. 7 and 9, 27, 27,... Are the common connection electrodes 25, 25,.
Are low-resistance metal films made of chromium or gold or the like, which are deposited on the common connection electrodes 2.
5, 25,... And the drive circuit connection leads 26, 26,. The drive circuit connection leads 26, 26,...
The metal films 27, 27,... that cover the drive circuit connection leads 26, 26,. , Except for the drive circuit connection terminal portions 26a, 26a,.

In FIGS. 6 and 9, reference numerals 28, 28 denote low-resistance metal films applied to the common electrodes C1, C2 except for the shutter portions a, a,. 28 is to reduce the electric resistance of the common electrodes C15 and C2,
are provided to regulate the light transmission area of a, a,.
28a, 28a,... Indicate light transmitting portions (portions where the transparent common electrodes C1, C2 are exposed) regulated by the metal films 28, 28. The light transmitting portions 28a, 28a,. Length l1, l
2 (see FIG. 7) each have a square shape of about 90 μm.

, S2, S2,... And the common electrodes C1, C2 have a thickness of 200 to 300 mm, and the metal films 27, 27,.
And the thickness of 28,28 is about 1700mm.

Reference numerals 29, 29 denote liquid crystal alignment films formed on the inner surfaces of both substrates 21, 22, and the thickness of the alignment films 29, 29 is 200 to 400 °.

The segment substrate 21 and the common substrate 22 have a distance between the alignment films 29, 29 in each shutter portion a, a, that is, a layer thickness G of the liquid crystal layer of each shutter portion a, a,. The outer sealing material 23a and the inner sealing materials 23b, 23b
Is glued through.

In this embodiment, inner sealing members 23b, 23b are provided on both sides of an array portion of the segment electrodes S1, S1,..., S2, S2,. The reason why the liquid crystal filling area of the portion is narrowed is that when the filling area of the liquid crystal composition 24 is widened, the leads 26, 26, ... of the segment electrodes S1, S1, ... S2, S2, ... when a high frequency signal is applied. This is because a high-frequency current flows through the common electrodes C1 and C2 through the liquid crystal composition 24 to promote heat generation of the common electrodes C1 and C2. , S1,... S2, S2,..., And the common electrodes C1, C2 should be prevented from interposing the liquid crystal composition as much as possible at the portions where the leads 26, 26,. can do. Also, in this embodiment,
Since the segment electrodes S1, S1,..., S2, S2,... Are arranged on both sides of the liquid crystal material filling portion, a double wall structure including an inner sealing material 23b and an outer sealing material 23a is provided. It is possible to completely prevent dust and moisture from entering the liquid crystal layer.

On the other hand, in FIG. 5, S0 and S0 are the segment electrodes S
1, S1,..., S2, S2,... Are laterally elongated auxiliary segment electrodes formed at both ends of the array portion.
S0 and S0 face the common electrodes C1 and C2 of the common substrate 22 to form a margin erasing shutter unit. The margin erasing shutter section includes the two rows of shutter sections a, used for optical writing.
a,… irradiate light to both ends of the photosensitive drum (corresponding to the margins on both sides of the recording paper) that are not irradiated with the light passing therethrough to erase the charged charges on both ends of the photosensitive drum, The margin erasing shutter is driven to be always open (light transmitting). In FIG. 5, St and St are test segment electrodes formed outside the auxiliary segment electrodes S0 and S0. The test segment electrodes St and St are also connected to the common electrodes C1 and C2 of the common substrate 22. A test shutter section is formed facing the test shutter section. Reference numerals 23c, 23c denote spacers provided on both sides of the test segment electrodes St, St to maintain an interval between the substrates 21, 22.

The auxiliary segment electrodes S0, S0 and the test segment electrodes St, St are connected to the common electrodes C1, C2 of the common substrate 22.
The common electrodes C1 and C2 of the common substrate 22
The metal films 28, 28 deposited on the auxiliary segment electrodes S0, S0 of the common electrodes C1, C2 and the test segment electrodes St,
It is attached so as to expose portions 28b, 28b and 28c, 28c facing St (see FIG. 6).

 In FIG. 8, reference numeral 35 denotes a polarizing plate.

As shown in FIG. 4, the driving circuit 40 connected to the liquid crystal element 20 supplies the segment electrodes S1, S1,..., S2,
Apply drive signal between S2, ... and common electrode C1, C2
It is driven in a time-division manner at a frequency, and is basically controlled by applying an electric field having a waveform as shown in FIG. 10 to the liquid crystal composition. That is, when the shutter portions a, a,... Are opened (light transmission), the segment electrodes S1, S1,..., S2, S2,.
When a drive voltage having a waveform as shown in FIG. 10 (a) is applied between the common electrode C1 and the common electrode C1, and the shutter portions a, a,. S1,…, S2, S2,…
A drive voltage having a waveform as shown in FIG. 10 (b) is applied between and the common electrodes C1 and C2. FIG. 10 shows a waveform of one cycle T1 for controlling the shutter sections a, a,..., And the shutter section is opened and closed by a holding signal (a signal in a time zone of T3), and a start signal ( Signal in the time zone of T2).

Describing a specific drive signal for controlling this liquid crystal element, in FIG. 11, COM1 is a common signal applied to one common electrode C1, and COM2 is a common signal applied to the other common electrode C2. Yes, this common signal CO
M1 and COM2 have the same waveform, but the phases are T2 and T3 (T2 and T3
= 1 msec) and applied at a period of T1. Also SE
G1 to SEG4 are segment signals applied to the commonly connected segment electrodes S1 and S2 with the application of the common signal and the period, and the segment signal SEG1 is the segment electrode S
1, S2 and the common electrode C1, C2 are applied when both of the two shutter sections a, a facing each other are closed, and the segment signal SEG2 is applied to the segment electrodes S1, S2 and the common electrode C1, C2.
The segment is applied when the shutter section on the side of the common electrode C1 to which the common signal COM1 is applied is closed and the other shutter section is opened, out of the two shutter sections a and a facing C2. The signal SEG3 is applied when the shutter section on the side of the common electrode C2 to which the common signal COM2 is applied is closed and the other shutter section is opened, and the segment signal SEG4 is used when both shutter sections are opened. Applied when

In the FIG. 11, only the low-frequency component f _L shown in pulse waveform, the high frequency component f _H represents hatched in that portion. Further, ▲ and ▼ show signals applied in a reversed manner.

FIG. 12 shows a waveform of an electric field applied to the liquid crystal composition between the segment electrodes S1, S2 and the common electrodes C1, C2 of the shutter portions a, a, and FIG. 5 shows the electric field applied to the liquid crystal when the segment signal SEG1 is applied to the segment electrodes S1 and S2. At this time, the common signal CO
A liquid crystal between the common electrodes C1 and C2 to which M1 and COM2 are applied and the segment electrodes S1 and S2 is applied with a closing activation electric field (high frequency) for laying down the liquid crystal molecules during the time period of T2.
In the time zone of, an electric field for holding the liquid crystal molecules in a lying state is applied. Further, at the end of the time zone of T3, an open starting electric field (low frequency) for causing the liquid crystal molecules to stand is applied, and then, after entering the time zone of T2, a closed starting electric field is applied. When the opening start electric field is applied, the liquid crystal molecules rise and the shutter opens, but since the time Δt is very short, the opening of the shutter does not affect the optical writing.
Also, if the liquid crystal molecules are allowed to stand momentarily immediately before the application of the closing activation electric field, it is possible to prevent the liquid crystal molecules from being strongly aligned parallel to the substrate every time the closing activation electric field is applied. Can be.

FIG. 12 (b) shows an electric field applied to the liquid crystal when the segment signal SEG2 is applied to the segment electrodes S1 and S2. In this case, the common electrode C1 to which the common signal COM1 is applied is shown. An electric field similar to the above is applied to the liquid crystal in the shutter portion, and the liquid crystal of the shutter portion on the side of the common electrode C2 to which the common signal COM2 is applied has an open starting electric field (low frequency) for causing liquid crystal molecules to stand and its hold. An electric field is applied.

This is because the segment signal S is applied to the segment electrodes S1 and S2.
The same applies to the case of FIG. 12 (c) where EG3 is applied.

FIG. 12D shows an electric field applied to the liquid crystal when the segment signal SEG4 is applied to the segment electrodes S1 and S2. In this case, an opening for causing liquid crystal molecules to stand on the liquid crystal in both shutter portions. A starting electric field (low frequency) and its holding electric field are applied.

Next, the liquid crystal composition 24 filled in the liquid crystal element will be described.

 The table below shows examples of the liquid crystal composition 24.

In addition, among the liquid crystal compounds of 1 to 21 in this table, the compounds of Group I are the bases of the liquid crystal composition, and the compounds of Group I have low viscosity and excellent compatibility with other compounds. (However, Δε is small and does not show the dielectric dispersion phenomenon). Group II liquid crystal materials exhibit a dielectric dispersion phenomenon in which Δε on the low frequency f _L side is positively large and | Δε | on the high frequency f _H side is relatively small. This compound gives the liquid crystal composition dielectric properties. Mixed for. In the case of the compounds of group III, the desired dielectric properties could not be obtained only by mixing the compound of group II with the compound of group I as the base, or the viscosity of the liquid crystal composition was increased by mixing the compounds of group II. In some cases, this is mixed to fine-tune it (however, the Group III compounds need not be mixed if the desired dielectric properties are obtained by mixing the Group II compounds alone). The compounds of group IV, together with lowering the overall dielectric properties of the liquid crystal composition on the negative side, intended to be mixed to lower the f _C, the compounds of this group IV, [Delta] [epsilon] is greater on the negative side, viscosity high.

Each of the above (1) to (6) liquid crystal compositions as a dichroic dye, Each of the two dyes was added in an amount of 1.2% by weight, respectively, and the liquid crystal element 20 having the above-described structure filled with the liquid crystal composition was used for optical writing of the optical writing printer described above. The emission wavelength band of the light source of the optical recording unit of the printer is 543 ± 20 nm, and the absorption wavelength band of the dichroic dye is 560 ± 40 nm.

This liquid crystal element is driven by the driving signal having the waveform shown in FIG. 10 at V _OP 25V T1 = 2 ms T2 = T3 = 1 ms Low frequency driving frequency f _L = 5 KHz High frequency driving frequency f _H = 320 KHz Temperature 20-30 ° C When the shutter was driven and the shutter characteristics were examined, the results shown in the following table were obtained.

As can be seen from this table, in each of the liquid crystal elements filled with the liquid crystal compositions of the respective examples, the switching time from the opening of the shutter portion to the closing, that is, the rise time of the liquid crystal molecules due to the application of the high frequency after the application of the low frequency. It is very short, less than 0.5 ms. This is because the value of | Δε |
This is because | Δε _H |> 2.0 in all cases.

In addition, when the value of | Δε _H | of the liquid crystal composition is large, the time required for switching from opening to closing of the shutter portion is shortened, but the high-frequency hysteresis effect is increased and the shutter characteristics are affected, and the responsiveness and stability are reduced. Although worse, the liquid crystal compositions of the above examples each had a value of | Δε | at low frequency of Δε _L > 3.5, and the ratio of | Δε _L | to | Δε _H | was | Δε _L | / | Δε _H |> 1.0, that is, a dielectric dispersion phenomenon in which the value of | Δε | at a high frequency is smaller than the value of | Δε | at a low frequency. Can greatly prevent the history effect from appearing.

Note that to reduce the hysteresis effect for high frequencies, | Δ
The larger the value of ε _L | / | Δε _H |, the better, but | Δε _L | / | Δε
_H | When the value is large, practical because not the viscosity of the liquid crystal composition becomes too _{high, | Δε L | / | Δε} H | is the _{value, | Δε L | / | Δε} H | <5 range Is desirable.

As shown in this table, looking at the shutter characteristics of the liquid crystal elements filled with the liquid crystal compositions of the respective examples, the shutter characteristics of the liquid crystal elements filled with the liquid crystal compositions of Examples (1) and (2) are the best. The shutter characteristics of the liquid crystal elements filled with the liquid crystal compositions of Examples (3) and (6) follow this. That is, as a two-frequency driving liquid crystal element, | Δ
It is optimal to use a liquid crystal composition having a value of ε _L | / | Δε _H | in the range of 1.2 to 5. The shutter characteristics of the liquid crystal elements filled with the liquid crystal compositions of Examples (4) and (5) are worse than those of the liquid crystal elements filled with the liquid crystal compositions of the other examples. The shutter characteristics are better than those of the above.

As described above, in each of the liquid crystal elements of the above embodiments, a liquid crystal composition exhibiting a dielectric dispersion phenomenon where the value of | Δε | at a high frequency is smaller than the value of | Δε | at a low frequency. In this liquid crystal element, even when a high frequency is applied for a long time, the liquid crystal molecules rise immediately upon application of a low frequency, so that the shutter portion can be driven to open and close with high responsiveness at high speed. Each liquid crystal composition has | Δε _H |, | Δε _L |
Since both values are large, this liquid crystal element can be driven at a low voltage.

In the above embodiment, a liquid crystal element used for optical writing of an optical writing type printer has been described. However, the present invention is also applicable to a liquid crystal element used for image display such as a television receiver or a computer display. Of course, it can be applied not only to the GH type but also to a TN type liquid crystal element.

〔The invention's effect〕

In the liquid crystal element of the present invention, the liquid crystal layer has a dielectric anisotropy Δε _L at a low frequency of positive and an absolute value | Δε _L | of 5.3 or more and a dielectric anisotropy Δε _H at a high frequency of negative and an absolute value of Δ 絶 対_L | | Δε _H | is 3.
Since a liquid crystal composition exhibiting a dielectric dispersion phenomenon in which the ratio of | Δε _L | to | Δε _H | is 1.47 ≦ | Δε _L | / | Δε _H | <5 is used, a high frequency Is applied for a relatively long period of time, the liquid crystal molecules are immediately raised by the application of the next low frequency, and the shutter portion can be opened and closed with high responsiveness and high speed.

[Brief description of the drawings]

FIG. 1 is a dielectric characteristic diagram of the liquid crystal composition used in the present invention. 2 and 3 are a schematic diagram of an optical writing type printer for performing optical writing using a liquid crystal element and a configuration diagram of an optical recording unit thereof. 4 to 12 show an embodiment of the present invention. FIG. 4 is a plan view of a liquid crystal element, FIGS. 5 and 6 are plan views of a segment substrate and a common substrate of the liquid crystal element, 7 is an enlarged plan view of a segment electrode forming portion of the segment substrate, FIG. 8 is a cross-sectional view of the liquid crystal element along the line AA in FIG. 7, FIG. 9 is an enlarged view of a shutter portion in FIG. FIG. 10 is a driving waveform diagram of the liquid crystal element, FIG. 11 is a waveform diagram of a common signal and a segment signal, and FIG. 12 is a waveform diagram of an electric field applied to the liquid crystal. 21,22 …… Substrate, S1, S2 …… Segment electrode, C1, C2 ……
Common electrode, a ... Shutter unit.

Claims (1)

(57) [Claims] 1. A semiconductor device having a positive dielectric anisotropy in a low-frequency electric field having a frequency lower than an intersection frequency fc at which a value of the dielectric anisotropy is 0 between a pair of substrates on which opposing electrodes are formed. A liquid crystal for two-frequency driving exhibiting negative dielectric anisotropy is sealed in a high-frequency electric field having a frequency higher than the frequency fc, and light is emitted by selectively applying the low-frequency electric field and the high-frequency electric field to the liquid crystal. In a liquid crystal element for controlling transmission, the liquid crystal includes:
The absolute value | Δε _L | of the dielectric anisotropy Δε _L in a low-frequency electric field having a frequency approximately 1/10 of the cross frequency fc is 5.3 or more, and the absolute value | Δε _L | The absolute value of the dielectric anisotropy Δε _H | Δε _H is 3.6 or more, and | Δ
A liquid crystal element using a liquid crystal composition exhibiting a dielectric dispersion phenomenon in which a ratio of ε _L | and | Δε _H | is 1.47 ≦ | Δε _L | / | Δε _H | <5.