JPH08313937A - Method for driving high-polymer liquid crystal and liquid crystal shutter - Google Patents

Abstract

PURPOSE: To facilitate the control to change over a transparent state and an opaque state by heating high-polymer liquid crystals, then allowing the liquid crystals to cool, heating the high-polymer liquid crystals, allowing the liquid crystals to cool under impression of an electric field thereon, releasing the impressed electric field and maintaining the light transparent state. CONSTITUTION: The high-polymer liquid crystals 302 are held between a pair of substrates 300 and 304 arranged in such a manner that transparent electrodes 301, 303 face each other. After the high-polymer liquid crystals 302 are heated near to the transparent temp., the liquid crystals are allowed to cool, by which an opaque light scattering state is formed and the high-polymer liquid crystals 302 are heated near to the transparent temp. The high-polymer liquid crystals are allowed to cool under the impression of the electric field thereon, by which the transparent light transparent state is maintained and thereafter, the impressed electric field is released to maintain the light transparent state. The transparent temp. in such a case refers to the temp. at which the liquid crystals shift from the liquid crystal state (liquid crystal phase) to the isotropic liquid crystal state (isotropic phase). As a result, the electric power consumption is needed at the time of switching between the transparent state and the opaque state. There is no more need for the consumption of the electric power in holding of the respective states occupying most of the time as an optical shutter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal shutter for light control capable of electrically controlling the amount of light transmission. In particular, by utilizing the phase change of the nematic state-random alignment state of the polymer liquid crystal, the driving method of the polymer liquid crystal which alternately switches between the opaque light scattering state and the transparent light transmitting state, and the two states are alternately switched. The present invention relates to a liquid crystal shutter that does not require power consumption to hold both states.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for light control glass capable of electrically controlling the transmission and blocking of the sunlight dose in order to save energy consumption such as heating and cooling and lighting. There is great potential demand for a light control glass or a light control film capable of exhibiting a blinding effect at any time in offices and homes. In general, these are a pair of transparent substrates sandwiching a substance whose color and light transmission amount change due to changes in electric field and temperature. In particular, as a condition for exhibiting highly efficient dimming ability, it is necessary that the forward transmittance in the transparent state and the light scattering state is large.

As a means for realizing these functions, there is one utilizing an electrochronism phenomenon or a sol-gel change. The former utilizes the color change of a substance due to an electrochemical reaction that occurs in a solution, an electrode surface, a solid electrolyte, or the like. Tungsten oxide WO ₃ is used for light control glass. Both of the two coloring states have a memory property and are extremely preferable in terms of characteristics. However, it has been pointed out that one of the states is close to blue and the light transmittance is low. At least one of the substrates needs to be made of glass, and it is difficult to form a lightweight film. Further, in the case of utilizing the latter sol-gel change, stability of the gel state becomes a problem, and the change speed is slow and the difference in light transmission amount is not large.

Another technique utilizes the shutter property of liquid crystal. Well known is polymer dispersed liquid crystal. This is disclosed in JP-A-60-252687, JP-A-63-43993, JP-A-2-53022, JP-A-4-42213 and the like.
A low molecular weight nematic liquid crystal of submicron order is dispersed in a polymer binder in a granular or network form and sandwiched between films with electrodes. When an electric field is applied, the liquid crystal molecules are aligned in one direction, the difference in the refractive index with the surrounding binder is reduced, and a transparent state is obtained. This transparent state is maintained by continuously applying an electric field,
Next, when the electric field is cut off, the difference in refractive index between the liquid crystal component and the surroundings, which are in a random arrangement state, increases, and light is scattered to make it opaque. A phase separation phenomenon is used as a means for dispersing liquid crystal in a polymer binder. For example, a binder and liquid crystal are dissolved in a common solvent and coated on a substrate. When the solvent evaporates, the compatibility between the binder and the liquid crystal disappears and the liquid crystal part and the binder part undergo phase separation on the order of submicrons. Alternatively, when the photoreactive resin and the liquid crystal are uniformly mixed and then the resin is cured by irradiation with ultraviolet rays or electron beams, the compatibility between the polymerized resin and the liquid crystal is also lowered and the phases are separated. However, even if the manufacturing process is complicated, there is a problem that the phase separation state is not stable in the long term, the interface is blurred, and it becomes difficult to respond to an electric field.

Still another technique using liquid crystals is to use polymer liquid crystals. The one using the ferroelectric polymer liquid crystal disclosed in JP-A No. 62-277412 can be formed into a film, but since the polarizing plate is used, the light transmittance is small and it is not preferable for dimming. On the other hand, a material exhibiting a nematic phase, a cholesteric phase, or a smectic phase can be used as a light control glass because the phase itself has a light scattering ability. Since the smectic phase does not respond to the electric field,
There must be a nematic phase or cholesteric phase on the high temperature side. When the dielectric anisotropy of the phase that responds to the electric field is positive, the application of an alternating electric field causes the liquid crystal molecules to change to a homeotropic state in which they are perpendicular to the substrate surface. This is transparent. When the electric field is cut off, it returns to a random orientation and an opaque state is obtained. These are single-phase, and there is an advantage that the light control glass is provided only by sandwiching the polymer liquid crystal between the substrates. However, the polymer liquid crystal except the ferroelectric liquid crystal generally has difficulty in operating at room temperature because the temperature range responding to an electric field is higher than room temperature. Moreover, even if it operated, a high voltage of 3 to 400 V was required. For this reason, it is used as a mixture with a low-molecular liquid crystal (see, for example, Japanese Patent Application Laid-Open No. 4-260024), but in this case, the self-supporting property is lost and it becomes difficult to form a film.

By the way, the one using the polymer liquid crystal has another problem other than the above. That is, it is necessary to continuously apply an electric field in order to maintain either the transparent state or the opaque state. This also applies to polymer-dispersed liquid crystals. In most cases, an AC voltage is applied to maintain the transparent state. This is extremely disadvantageous in terms of energy consumption. Therefore, unlike in the past, there has been a strong demand for an operation method that does not require continuous application of an electric field to maintain the transparent or opaque state.

In order to achieve the desired functions described above, it is necessary to switch between a transparent state and an opaque state, and these states need to be maintained without application of an electric field. In general,
If the polymer liquid crystal is in a randomly aligned state in any of the nematic state, the cholesteric state, and the smectic state, the spatial spatial fluctuation of the density is large, and a strong light scattering ability is exhibited when the thickness is about 10 microns or more. In this case, the turbidity, which is a measure of opacity, can be controlled by the thickness of the liquid crystal layer. Japanese Patent Laid-Open No. 4-
Japanese Patent Publication No. 295820 discloses a recording and erasing method by a heat mode and its material. This method will be described with reference to FIG. In FIG. 1, a liquid crystal molecule 100 (in this case, a liquid crystal group of a polymer liquid crystal, a portion of a chemical bond connecting the liquid crystal groups is omitted) is sandwiched between two substrates, and is transparent at a high temperature. The two states obtained by changing the cooling rate from the different liquid state (200) will be described. When rapidly cooled, the liquid crystal molecule 100 cannot change to a stable state because of its high viscosity, and the transparent liquid state is frozen (202) as it is and maintained at low temperature. On the contrary, if it is slowly cooled, the phase changes to a nematic state or a cholesteric state, so that it becomes opaque (201). However, as the light control means, switching by controlling the cooling rate is not preferable because the control is difficult.

[0008]

An object of the present invention is to easily control switching between a transparent state and an opaque state in an optical shutter using a polymer liquid crystal, and to apply an electric field only when performing the switching control. The purpose of the present invention is to provide a driving method that does not require continuous application of an electric field when maintaining both states, and a liquid crystal shutter using the driving method.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have found that an opaque light-scattering state is obtained by heating a polymer liquid crystal near a transparent temperature and then allowing it to cool. On the other hand, the light transmission state can be formed by heating the polymer liquid crystal near the transparent temperature and allowing it to cool while applying an electric field. The inventors have found that they are maintained and have completed the present invention.

That is, according to the present invention, in a polymer liquid crystal sandwiched between a pair of substrates arranged so that transparent electrodes are opposed to each other, the polymer liquid crystal is heated to near the transparent temperature and then left to cool. An opaque light-scattering state is formed, the polymer liquid crystal is heated to near the transparent temperature, and allowed to cool while applying an electric field to form a transparent light-transmitting state, and then the applied electric field is released to allow light transmission. The present invention relates to a method for driving a polymer liquid crystal, which is characterized by maintaining a state. In addition,
In the present invention, the transparent temperature means a temperature at which a liquid crystal state (liquid crystal phase) transitions to an isotropic liquid state (isotropic phase).

The present invention also relates to the following liquid crystal shutters. That is, the first liquid crystal shutter according to the present invention sandwiches a polymer liquid crystal between a pair of substrates arranged so that transparent electrodes face each other, and alternates between an opaque light scattering state and a transparent light transmitting state. In a switchable liquid crystal shutter, the light-scattering state is formed by heating the polymer liquid crystal near the transparent temperature and then allowing it to cool, and the light-transmitting state applies the polymer liquid crystal near the transparent temperature. Warm
The liquid crystal shutter is characterized in that it is formed by allowing it to cool while applying an electric field, and then releases the applied electric field to maintain it.

The second liquid crystal shutter according to the present invention is characterized in that the polymer liquid crystal exhibits a nematic phase near the transparent temperature.

Further, the third liquid crystal shutter according to the present invention is characterized in that the transparent temperature of the polymer liquid crystal is in the range of 40 ° C to 100 ° C.

Further, the fourth liquid crystal shutter according to the present invention is characterized in that the means for heating the polymer liquid crystal is heat generation by energizing the transparent electrode.

Further, in a fifth liquid crystal shutter according to the present invention, the polymer liquid crystal has the following general formula (I):

[0016]

Embedded image

(Wherein R is a hydrogen atom, a halogen atom, an alkyl group or a phenyl group, X is a single bond, an oxygen atom, or a group represented by --COO-- or --OCO--, Q ¹ is a liquid crystal group, and k is A repeating unit represented by the following general formula (II).

[0018]

[Chemical 4]

(In the formula, R'may be the same as or different from R, a hydrogen atom, a halogen atom, an alkyl group or a phenyl group, and R ^{1 to} R ⁶ may be the same or different, and an alkyl group or a phenyl group. , X is a single bond, an oxygen atom, or a group represented by -COO- or -OCO-, Q ² is a liquid crystal group which is the same as or different from Q ^1, and m and p are 2
Is an integer of 10 and n is an integer of 0-10. ), The molar ratio of the repeating unit represented by the general formula (I) to the repeating unit represented by the general formula (II) is in the range of 95/5 to 20/80, and the number average is It is a copolymer having a liquid crystal group in the side chain having a molecular weight of 1,000 or more.

In the driving method and the liquid crystal shutter of the present invention, the opaque state and the transparent state are selected by the presence or absence of an electric field near the transparent temperature. Also, the cooling process uses only the difference between the temperature of the polymer liquid crystal itself and the ambient temperature. That is, as shown in FIG. 2, a transparent homeotropic state (203) is formed by heating by applying an electric field, and if the liquid crystal molecule 100 is allowed to cool to a temperature at which the liquid crystal molecule 100 does not move due to the temperature difference, the transparent state is changed. It is fixed as it is. Once the temperature drops, the liquid crystal molecules cannot move, so that state can be maintained even if the electric field is cut off. On the other hand, if no electric field is applied during cooling, the state changes to an opaque nematic state or cholesteric state (201). In this way, the transparent / opaque state can be switched and maintained.

The temperature Ts to which the alternating electric field for switching is applied needs to include a state responsive to the electric field, and is generally in the vicinity of the transparent temperature Tc which is the transition temperature of the nematic phase-liquid phase. Higher voltage and longer time are required as the temperature goes away from the transparent temperature Tc to the lower temperature side. The applied voltage is preferably as low as 100 V or less. The temperature Ts is set to the lowest temperature in view of this voltage and the time allowed for switching. However, this temperature is preferably higher than atmospheric temperature or a temperature that can be reached under direct sunlight. Otherwise, at atmospheric temperature or under direct sunlight, the state change of liquid crystal molecules occurs without application of an electric field.

Therefore, in order to obtain a state capable of responding to the electric field, it is preferable to raise the temperature of the polymer liquid crystal to the temperature Ts which is higher than the atmospheric temperature. Generally, a heater is used to heat the liquid crystal to raise the temperature, but a desirable means is to use the transparent electrode for driving directly as a heater for heating. Therefore, if the temperature Ts is too high, it takes time to raise the temperature. Under these conditions, Ts is preferably about 40 ° C to 100 ° C.

The liquid crystal shutter may be a flat electrode, but is preferably a striped electrode connected for the purpose of heating. In this case, the amount of heat generation is proportional to I ² R, where R is the resistance of the transparent electrode and I is the current. Therefore, the length and width are determined so that R is appropriate for obtaining the desired amount of heat generation. Both of the pair of electrodes may be formed in this manner, or only one of them may be formed. Depending on the length and width of the transparent electrode, a constant current of about 30 mA can be applied to obtain a temperature of 40 to 100 ° C. relatively easily, and the polymer liquid crystal can be brought into a nematic phase near the transparent temperature in response to an electric field. In the case of a transparent state, an AC electric field of about 50 Hz or higher may be applied. In this way, the polymer liquid crystal is heated to make it respond to an electric field, and then it is recooled. At this time, transparent or opaque can be selected depending on whether or not an AC electric field is applied.
When transparent, the electric field can be cut off after becoming transparent. Therefore, it is not necessary to constantly apply the electric field.

In the liquid crystal shutter of the present invention, the transparent temperature Tc is in the range of 40 ° C. to 100 ° C.
It is preferable to use a high-speed polymer liquid crystal having a response speed of several hundred milliseconds or less under an alternating current of V50 Hz. Therefore, it is desirable that the polymer liquid crystal used in the present invention exhibits a nematic phase near the transparent temperature. From this point of view, the copolymer composed of the repeating units represented by the general formulas (I) and (II) is preferable in that the above-mentioned properties can be satisfied. Further, the same effect can be obtained by mixing a chiral component with a polymer liquid crystal and using it as a cholesteric phase.

In the copolymer used in the present invention,
Q in the general formulas (I) and (II) ¹And Q²Represented by
The liquid crystal group to be used may be any of the conventionally known liquid crystallinity imparting groups.
They may be offset, and there is no particular limitation on the structure. liquid crystal
Examples of the group include biphenyl and biphe
Nyl ether, benzoic acid phenyl ester, benzoic acid vinyl ester
Phenyl ester, benzylidene aniline, stilbe
Amine, azoxybenzene, azobenzene, Schiff base,
Chlorohexyl phenyl ether, cyclohexylbenze
, Cyclohexylcarboxylic acid phenyl ester, chrysanthemum
Lohexyl carboxylic acid biphenyl ester, cholesteric
From liquid crystal molecules such as amine, cholestane and their derivatives
A group formed by removing one hydrogen atom can be mentioned.

The substituents represented by R and R'in the above general formulas (I) and (II) include a hydrogen atom, a halogen atom such as fluorine, chlorine, bromine and iodine, a methyl group,
Ethyl group, propyl group, iso-propyl group, butyl group, t-
Examples thereof include a linear or branched alkyl group such as a butyl group and a hexyl group, and a phenyl group. However, a hydrogen atom or a methyl group is more preferable as the substituent represented by R because of ease of synthesis.

The substituents represented by R ^{1 to} R ⁶ in the above general formulas (I) and (II) include a methyl group, an ethyl group, a propyl group, an iso-propyl group, a butyl group and an iso-butyl group. Examples thereof include linear or branched alkyl groups such as t-butyl group, pentyl group, hexyl group and phenyl group. However, the methyl group is most preferable among the above substituents in order to facilitate the synthesis and to take advantage of the characteristics of the polymer having a liquid crystal group of the present invention. Further, the methylene chains in the above general formulas (I) and (II) need to have a certain length, and therefore the number of methylene groups represented by k in the formula is in the range of 2 to 20, m and p. The number of methylene groups is in the range of 2-10. However, m and p are more preferably in the range of 3 to 6 in order to facilitate the synthesis and to take advantage of the characteristics of the polymer having a liquid crystal group of the present invention. Further, the number of siloxane units represented by n in the general formula (II) is in the range of 0 to 10, and particularly 0
It is preferably in the range of to 3 in order to take advantage of the ease of synthesis and the characteristics of the polymer liquid crystal obtained.

The copolymer used in the present invention has the following general formula (III):

[0029]

Embedded image

(Wherein R is a hydrogen atom, a halogen atom, an alkyl group or a phenyl group, X is a single bond, an oxygen atom or a group represented by --COO-- or --OCO--, Q ¹ is a liquid crystal group, and k is A monomer represented by the following general formula (IV).

[0031]

[Chemical 6]

(In the formula, R ′ may be the same as or different from the above R, a hydrogen atom, a halogen atom, an alkyl group or a phenyl group, and R ^{1 to} R ⁶ may be the same or different, and an alkyl group or a phenyl group. , X is a single bond, an oxygen atom, or a group represented by -COO- or -OCO-, Q ² is a liquid crystal group which is the same as or different from Q ^1, and m and p are 2
Is an integer of 10 and n is an integer of 0-10. ) And a monomer represented by the formula (1) are mixed and polymerized.
In that case, known addition polymerization methods such as radical polymerization, anionic polymerization, and cationic polymerization can be used. In this case, the radical polymerization method is preferably used as the simplest method.

When the radical polymerization method is used, known methods such as bulk polymerization, solution polymerization and emulsion polymerization can be used. The radical polymerization reaction is initiated simply by irradiation with heat, ultraviolet rays or addition of a radical initiator. Radical initiators preferably used in the reaction include organic peroxides such as dilauroyl peroxide, di-t-butyl peroxide, benzoyl peroxide, t-butyl hydroperoxide and cumene hydroperoxide, or α, α'-azobisisode. Examples thereof include azo compounds such as butyronitrile and azobiscyclohexanecarbonitrile. The organic solvent that can be used in the radical polymerization reaction in this case is, for example, benzene, toluene, chlorobenzene, tetrahydrofuran, chloroform, methyl ethyl ketone, fluorobenzene, methanol, ethanol, n-.
Alternatively, i-propanol, N, N-dimethylformamide, N, N-dimethylacetamide and the like can be used, but the invention is not limited thereto. The polymerization reaction normally proceeds smoothly in the range of 40 ° C to 100 ° C. Moreover, the molecular weight of the obtained polymer can be controlled to some extent by adding a chain transfer agent during the polymerization reaction. Examples of the chain transfer agent used here include carbon tetrachloride, bromotrichloromethane, p-benzoquinone, chloroanil, n-butanethiol, and n-dodecanethiol.

The monomer represented by the general formula (III) is a known compound, and its manufacturing method is described in many documents. (For example, H. Finkelmann, H. Ringsdor
f and JH Wendorff, Makromol. Chem., Vol.179, p.
273 (1978); V. Shibaev, A. Kostromin and N. Plate,
Eur. Polym. J., Vol.18, p.651 (1982); R. Zenteland
H. Ringsdorf, Makromol. Chem., Rapid Commun., Vo
l.5, p.393 (1984); V. Shibaev and N. Plate, Pure an
d Appl. Chem., Vol.57, p.1589 (1985); CS Hsu and
V. Percec, J. Polym. Sci., Polym. Chem. Ed., Vol.
26, p.2047 (1988); Vol.27, 453 (1989), etc.) Further, the monomer represented by the general formula (IV) is also a known compound (for example, JP-A-4-218513,
JP-A-6-256355, WO 94/2418
No. 0, etc.).

In the copolymer used in the present invention, the molar ratio of the repeating unit represented by the general formula (I) to the repeating unit represented by the general formula (II) is 95/5.
˜20 / 80 mol%, more preferably 95/5 to 50 /
It is in the range of 50 mol%. From this, the above general formula (II)
When the content of the repeating unit represented by is low, the transparent temperature Tc of the obtained copolymer is in a high temperature range, and when it is high, the copolymer may have difficulty in exhibiting liquid crystallinity. In addition,
The above molar ratio, that is, the copolymer composition, can be easily controlled by changing the charging ratio of the monomer represented by the general formula (III) and the monomer represented by the general formula (IV) in the above-mentioned copolymerization reaction. . The number average molecular weight of the copolymer of the present invention is preferably 1,000 or more in order to take advantage of the characteristics of the polymer. The molecular weight is measured by a known method such as gel permeation chromatography, osmotic pressure method, light scattering method and viscosity method.

Hereinafter, the present invention will be described in more detail with reference to Examples and Examples. However, it goes without saying that the present invention is not limited to these.

[0037]

【Example】

 Reference example 1

[0038]

[Chemical 7]

The monomers represented by the above structural formulas (1) to (4) were synthesized according to the method described in WO 94/24180. Next, the monomer A
[(1)] and Monomer B [(2) to (4)] were mixed at the ratios shown in Table 1, and the total monomer concentration was 0.5 mol /
It was dissolved in toluene so that the concentration became l, and α, α′-azobisisobutyronitrile (AIBN) was further added so as to have a concentration of 25 mmol / l. After thoroughly degassing this solution,
The polymerization reaction was carried out at ℃ for 24 hours. The reaction solution was poured into excess methanol, the obtained precipitate was recovered, further dissolved in toluene, and reprecipitation was repeated twice in methanol. The obtained polymer was subjected to ¹ H-NMR spectrum analysis to determine the copolymerization composition x / y, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) were obtained as a polystyrene conversion value by gel permeation chromatography. It was The results are summarized in Table 1.

[0040]

[Table 1] ────────────────────────────────── Sample Monomer A Monomer B Monomer A / Monomer B x / y Mn Mw No. (molar ratio) (molar ratio) x10 ^-3 x10 ^-3 ──────────────────────────────── ─── CP-1 (1) (2) 90/10 92/8 3.21 4.32 CP-2 (1) (2) 75/25 76/24 3.70 4.87 CP-3 (1) (3) 95/5 94 / 6 5.74 9.54 CP-4 (1) (3) 92/8 90/10 8.39 16.4 CP-5 (1) (4) 90/10 89/11 8.56 29.4 CP-6 (1) (4) 70/30 70/30 13.2 19.7 ───────────────────────────────────

Reference Example 2

[0042]

Embedded image

The monomers represented by the above structural formulas (5) to (7) were synthesized according to the method described in WO 94/24180. Next, the monomer A
[(5) or (6)] and monomer B [(7) or (2)] were mixed in the ratios shown in Table 2, and dissolved in tetrahydrofuran so that the total monomer concentration was 0.5 mol / l. Then, α, α′-azobisisobutyronitrile (AIBN) was further added so as to have a concentration of 25 mmol / l.
After this solution was sufficiently degassed by freezing, a polymerization reaction was carried out at 60 ° C. for 24 hours. The reaction solution was poured into excess methanol, the obtained precipitate was recovered, further dissolved in tetrahydrofuran, and reprecipitation was repeated twice in methanol. The obtained polymer was subjected to ¹ H-NMR spectrum analysis to determine the copolymerization composition x / y, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) were obtained as a polystyrene conversion value by gel permeation chromatography. It was The results are summarized in Table 1.

[0044]

[Table 2] ────────────────────────────────── Sample Sample Monomer A Monomer B Monomer A / Monomer B x / y Mn Mw No. (molar ratio) (molar ratio) x10 ^-4 x10 ^-4 ──────────────────────────────── ─── CP-7 (5) (7) 50/50 47/53 3.57 5.45 CP-8 (6) (2) 50/50 49/51 2.15 2.88 ────────────── ─────────────────────

Example 1 A glass substrate 300 having a flat transparent electrode of A3 size with a sheet resistance of 10Ω was prepared, and the striped electrode 3 having the pattern of FIG. 3 was formed by a conventional photolithography method.
01 was formed. This transparent electrode has a width of 5 mm and a length of 2
It is 6 cm and the distance between the lines is 10 μm. The striped transparent electrodes are connected in series via the same transparent electrodes.

Polymer liquid crystal C obtained in Reference Examples 1 and 2
P-1 to CP-8 were dissolved in THF (5% by weight), and uniformly coated on the substrate by the bar coating method. Then, when dried in an oven at about 60 ° C., a polymer liquid crystal coating film 302 having a thickness of 15 μm was obtained. Next, at about 50 degrees, a polyether sulfone (P
ES) film 304 was laminated. In this way, the liquid crystal shutter having the structure shown in FIG. These liquid crystal shutters are heated to a certain temperature (driving temperature), and the transparent electrodes facing each other are heated to 50H.
The time (response speed) from the moment when the alternating current of z was applied and the time when the light transmittance was maximized was measured. Table 3 shows the glass transition temperature (Tg), the transparent temperature (Tc), the driving temperature (Ts), the driving voltage and the response speed of the polymer liquid crystal used here. Each of these polymer liquid crystals exhibited a nematic phase in the temperature range between Tg and Tc.
Further, at room temperature, all of these liquid crystal shutters exhibited a white turbid state (opaque state) with a haze value of 80, but even if the temperature was set to Ts shown in Table 3, no change occurred.

[0047]

[Table 3] ─────────────────────────────────── Sample Tg Tc Ts Drive voltage Response speed No. ( ℃) (℃) (℃) (V) (msec) ─────────────────────────────────── CP -1 13 82 70 70 100 80 CP-2 8 48 46 46 200 350 CP-3 28 95 95 90 100 60 CP-4 24 85 75 75 100 200 CP-5 29 89 81 81 100 100 CP-6 17 48 45 200 200 CP-7 12 66 60 100 330 330 CP-8 19 64 57 100 250 250 ────────────────────────────────────

Next, after releasing the electric field of these liquid crystal shutters and cooling it to room temperature again to make it cloudy, when a direct current of 30 mA is applied to the transparent electrode 301 in stripes, it becomes a liquid phase in about 20 seconds. It was transferred and a transparent state was obtained.
When switching to an alternating voltage of 50 Hz and 100 V in this state, the temperature of the liquid crystal dropped to around room temperature in a transparent state. Even after the voltage application was stopped after 20 seconds, the transparent state was maintained. When a current of 30 mA was applied again for heating and then the application of a current was stopped, white turbidity began after about 5 seconds, equilibrium was reached in 20 seconds, and a white turbid state with a haze value of 80 was obtained. Therefore, it was confirmed that the liquid crystal shutter can be switched between the transparent state and the opaque state by applying an electric field in the above-described procedure, and that it is not necessary to energize between the electrodes when maintaining both states. Since the gap between the striped transparent electrodes was as narrow as 10 μm, the polymer liquid crystal in that portion was squeezed by the surroundings to respond, and there was no hindrance during switching.

[0049]

According to the present invention, power consumption is required when switching between a transparent state and an opaque state, and there is no need for power consumption in maintaining these states, which requires most of the time as an optical shutter. A driving method and a liquid crystal shutter are provided. In addition, it can be driven at a low voltage, the state can be switched at high speed, and the heating means is built in the liquid crystal shutter in common with the voltage applying means, so that it is easy to manufacture and has a high front transmittance. A liquid crystal shutter having a good light-shielding property is provided, which is suitable for a display element, light control glass, light control film, and the like.

[0050]

[Brief description of drawings]

FIG. 1 is a diagram illustrating two states obtained by cooling a polymer liquid crystal from a transparent liquid state.

FIG. 2 is a diagram illustrating a state obtained by cooling a polymer liquid crystal from a transparent liquid state while applying an electric field, and a state obtained without applying the electric field.

FIG. 3 is a drawing schematically showing a transparent electrode pattern for heating a liquid crystal.

FIG. 4 is a drawing schematically showing a cross-sectional structure of a liquid crystal shutter of the present invention.

[Explanation of symbols]

 100 Liquid Crystal Molecules 201 Minute Nematic Domains 202 Frozen Liquid State 203 Homeotropic Alignment State 300 Transparent Substrate 301 Striped Transparent Electrode 302 Polymer Liquid Crystal 303 Opposing Planar Transparent Electrode 304 Counter Substrate

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location G02F 1/1333 G02F 1/1333 G09G 3/36 G09G 3/36 (72) Inventor Takao Minato Taito-ku, Tokyo Taito-ku 1-5-1 Toppan Printing Co., Ltd.

Claims (6)

[Claims] 1. In a polymer liquid crystal sandwiched between a pair of substrates with transparent electrodes facing each other, opaque light scattering is achieved by heating the polymer liquid crystal to near the transparent temperature and then allowing it to cool. After forming a state, the polymer liquid crystal is heated to near the transparent temperature and allowed to cool while applying an electric field to form a transparent light transmitting state, and then the applied electric field is released to maintain the light transmitting state. A method for driving a polymer liquid crystal, which is characterized in that 2. A liquid crystal shutter in which a polymer liquid crystal is sandwiched between a pair of substrates arranged so that transparent electrodes face each other, and an opaque light scattering state and a transparent light transmitting state can be alternately switched. The light-scattering state is formed by heating the polymer liquid crystal near the transparent temperature and then allowing it to cool, and the light-transmitting state heats the polymer liquid crystal near the transparent temperature and is discharged while applying an electric field. A liquid crystal shutter, characterized in that it is formed by cooling, and then the applied electric field is released to maintain it. 3. The liquid crystal shutter according to claim 2, wherein
A liquid crystal shutter, wherein the polymer liquid crystal exhibits a nematic phase near a transparent temperature. 4. The liquid crystal shutter according to any one of claims 2 to 3, wherein the transparent temperature is in the range of 40 ° C to 100 ° C. 5. The liquid crystal shutter according to any one of claims 2 to 4, wherein the means for heating is by energizing the transparent electrode. 6. The liquid crystal shutter according to any one of claims 2 to 5, wherein the polymer liquid crystal has the following general formula (I): (In the formula, R is a hydrogen atom, a halogen atom, an alkyl group or a phenyl group, X is a single bond, an oxygen atom, or a group represented by -COO- or -OCO-, Q ¹ is a liquid crystal group, and k is 2 to 2.
It is an integer of 0. ) And the following general formula (II): (In the formula, R ′ may be the same as or different from the above R,
A hydrogen atom, a halogen atom, an alkyl group or a phenyl group, R ^{1 to} R ⁶ may be the same or different, an alkyl group or a phenyl group, X is a single bond, an oxygen atom, or -C.
A group represented by OO- or -OCO-, Q ² is a liquid crystal group which is the same as or different from Q ¹ , m and p are integers of 2 to 10,
n is an integer of 0-10. ), The molar ratio of the repeating unit represented by the general formula (I) to the repeating unit represented by the general formula (II) is in the range of 95/5 to 20/80, and the number average is A liquid crystal shutter, which is a copolymer having a liquid crystal group in a side chain having a molecular weight of 1,000 or more.