JPH07225370A - Liquid crystal element and irts production - Google Patents

Abstract

PURPOSE:To obtain liquid crystal element which has excellent high-speed responsiveness and self-supportability and is operative over a wide temp. range by clamping a film mixture contg. a specific liquid crystalline high polymer, a low-molecular liquid crystal material and an electrolyte. CONSTITUTION:A coating liquid prepd. by dissolving the side chain type liquid crystal high polymer compd. expressed by formula bonding a mesogene group to the main chain of polyoxycetane, the low-molecular liquid crystal material and the electrolyte into a common solvent is applied on one surface of a pair of base materials and is dried to form the film mixture and thereafter the other base material is laminated on this film mixture. (In the formula, X denotes an electron-withdrawing group or alkoxyl group). The operative temp. of the liquid crystal element is expanded particularly on a high-temp. side if such a side chain type liquid crystal high polymer compd. is used. The low-molecular liquid crystal material which has high dielectric anisotropy and refractive anisotropy and exhibits a smectic phase in the service temp. region of the element when mixed with the liquid crystalline high polymer is preferable for the properties of this material. Consequently, the memory characteristic of the liquid crystal element is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended for a TV screen, a general OA device, a display screen for vehicle-mounted navigation or the like which is mounted on an automobile to provide a driver with information such as a map display and a guidance display, or light shielding. The present invention relates to a liquid crystal element preferably used for a sun shade and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A conventional liquid crystal element is formed by injecting a low molecular weight liquid crystal material between a pair of base materials fixed at intervals of several μm. However, with such a configuration, it is difficult to create a large-area display. In addition, due to the operating principle of the device, it is necessary to attach a pair of polarizing plates to the pair of base materials that enclose the liquid crystal, with their polarization axes orthogonal to each other, so the screen brightness and viewing angle are insufficient. There is a problem that becomes.

Further, since the conventional liquid crystal element has no memory property in the alignment state except when the ferroelectric liquid crystal is used, for a display screen with a large number of pixels, an active matrix using a TFT or the like having a low manufacturing yield is used. Since driving is required, there is a problem that a failure or the like is likely to occur, reliability is low, an element is expensive, and the like. If a ferroelectric liquid crystal is used, active matrix drive is not necessary, but it is far from practical use because it requires an extremely thin cell gap control of 1 to 2 μm and uniform liquid crystal alignment control, and a satisfactory display even with a small area. The current situation is that no one can get it.

Further, these conventional liquid crystal elements require a polarizing plate as described above, but the polarizing plate has a problem that it cannot be used in a high temperature environment because of its large light absorption and heat generation. A liquid crystalline group consisting of a group (mesogenic group) corresponding to the chemical structure of the core part of a low-molecular liquid crystal material and a flexible bent chain (spacer part) connecting this mesogenic group to the main chain is used as a side chain. A side chain type liquid crystalline polymer bonded to the skeletal chain (main chain) of a molecule is mixed with a normal low molecular weight liquid crystal material and a small amount of an electrolyte to form a polymer liquid crystal / low molecular liquid crystal mixed film, A liquid crystal element has been developed in which a liquid crystal element is sandwiched between a pair of base materials arranged at regular intervals [JP-A-2-193115, JP-A-2-127494, Chem. Lett., 817.
(1989), Polym. Preprints, Japan 39 (8) 2373 (199
0) etc.].

The side chain type liquid crystalline polymer is obtained by radically polymerizing a monomer in which a bent chain and a mesogenic group are bonded to an ester portion of (meth) acrylic acid, or a polysiloxane polymer main chain. It is known that a bent chain and a mesogenic group are added to each other by a hydrosilylation reaction.
In the liquid crystal element, a liquid crystal polymer, a low molecular weight liquid crystal material, and an electrolyte are dissolved or dispersed in these common solvents, and cast and coated on one substrate, and dried and solidified to form a mixed film. Then, another base material is superposed on the mixed film, or both liquid crystal materials and electrolytes are dissolved in these common solvents, mixed and dried to obtain a paste-like mixture. It is produced by sandwiching the mixture between two substrates or by injecting the mixture between a pair of substrates arranged at a certain distance.

The above liquid crystal element operates so as to show either a cloudy state or a transparent state depending on the frequency of the electric field applied to the mixed film. That is, when a low-frequency or direct-current electric field is applied to the mixed film, the ions move along with the electric field in the mixed film and collide with the main chain of the side chain type liquid crystalline polymer to disturb the alignment of the liquid crystal. In the element, incident light is scattered and becomes an opaque white turbid state. On the other hand, when a high-frequency electric field is applied to the mixed film, the liquid crystal molecules in the film are homeotropically oriented in the electric field direction, and the incident light can pass through without being scattered, so that the device becomes transparent.

Further, since the mixed film forms a smectic phase structure, the liquid crystal element has both a transparent state and a cloudy state.
It has a so-called memory property that is stably held even after the application of an electric field is stopped. Therefore, in the liquid crystal element using the above-mentioned polymer liquid crystal / low molecular weight liquid crystal mixed film, active matrix driving is unnecessary due to its memory property, and the control circuit for driving can be simplified.

Further, since this mixed film contains a polymer, it has self-supporting property and does not require strict cell gap control as in the ferroelectric liquid crystal. As can be seen, the mixed film also does not require uniform alignment control of the liquid crystal. Therefore, there is also an advantage that the area of the liquid crystal element can be easily increased in combination with the fact that the liquid crystal element can be formed by a simple process such as application of the coating liquid, drying, lamination of the mixture, and injection as described above. It can also be used as a curved surface by combining it with a flexible substrate such as a plastic film.

[0009]

However, a liquid crystalline polymer having a (meth) acrylic acid-based main chain has a high glass transition temperature, so that a smectic phase is difficult to form at room temperature, which makes it difficult to operate at room temperature. is there. On the other hand, a liquid crystalline polymer having a polysiloxane-based main chain exhibits a smectic phase in a wide range including room temperature, but if the degree of polymerization (molecular weight) is lowered to obtain a practical response speed, an isotropic phase transition of the liquid crystal phase occurs. Since the temperature becomes low, it becomes difficult to maintain the smectic phase in the high temperature range, and the upper limit of the operable temperature becomes low, so that there is a problem that it cannot be used at high temperature. Further, if the degree of polymerization is lowered as described above, the self-supporting property of the mixed film is deteriorated, and there is a possibility that the mixed film may be lifted up or the substrates may be short-circuited especially when the element is formed into a curved surface.

Therefore, in a curved state, the sunshade for automobiles used in a wide temperature range from high temperature during the day in summer to severe cold in the winter and also in a wide temperature range from high temperature to severe cold Automotive display device,
Attempts have been made to form a liquid crystal device provided with the above mixed film, but at present it has not yet been put to practical use.

The present invention has been made in view of the above circumstances, and is excellent in high-speed response and self-supporting property, and can operate in a wide temperature range. In particular, the upper limit of operable temperature is high. An object of the present invention is to provide a liquid crystal device including a molecular liquid crystal / low molecular liquid crystal mixed film and a method for manufacturing the liquid crystal device.

[0012]

In order to solve the above-mentioned problems, the inventors of the present invention have previously proposed the structure of a liquid crystal element having a relatively wide operable temperature, which has been proposed by the present inventors. It was also considered to apply to the sun shade of the above (see JP-A-5-107530). The liquid crystal element proposed by the present inventors in the above publication is a ring-opening polymer of trimethylene oxide (oxetane).
(2):

[0013]

[Chemical 2]

[In the formula, R ¹ and R ² are the same or different groups. ] The main feature is to use a side chain type liquid crystalline polymer in which a side chain liquid crystal group is bonded to the R ¹ or R ² portion of the polyoxetane main chain composed of the repeating unit represented by However, automobile sunshades and the like are required to operate in a wide temperature range far exceeding the operable temperature range achieved in the embodiments of the above publications. It was found that the performance was not sufficient.

Therefore, as a result of further study on the structure of the side chain type liquid crystalline polymer of the polyoxetane main chain type, the present inventors have found that the polyoxetane main chain has a special structure not disclosed in the above publication. With a general mesogen group, the general formula (1):

[0016]

[Chemical 3]

[In the formula, X represents an electron-withdrawing group or an alkoxy group, n is the degree of polymerization, and m is an integer of 1-12. ]
It has been found that the operable temperature of the liquid crystal element can be dramatically expanded particularly on the high temperature side by using the side chain type liquid crystalline polymer represented by the following, and the present invention has been completed. That is, the liquid crystal element of the present invention has a side chain type liquid crystalline polymer represented by the above general formula (1) between a pair of base materials having an electrode layer formed on at least one surface and arranged at a constant distance. When,
It is characterized in that a mixed film containing a low-molecular liquid crystal material and an electrolyte is sandwiched.

In the liquid crystal device of the present invention having the above structure, the liquid crystalline polymer forming the mixed film has a main chain skeleton made of polyoxetane, which is difficult to rotate in the molecule, through an alkylene group as a spacer portion. Since it has a structure in which a relatively large mesogenic group consisting of three benzene rings sandwiching an ester bond is bonded on the way, the movement of the polymer chain is weakened and the phase transition temperature of the mixed film becomes high. Therefore, the liquid crystal element using the above side chain type liquid crystalline polymer can have a wider operable temperature than ever before, especially on the high temperature side.

In order to manufacture the above liquid crystal device of the present invention,
The first production method of the present invention is a coating solution prepared by dissolving the side chain type liquid crystalline polymer represented by the general formula (1), a low molecular weight liquid crystal material, and an electrolyte in these common solvents. After being coated on one surface of the pair of base materials and dried to form a mixed film, the other base material is laminated on the mixed film.

In the second production method of the present invention, a mixture containing a side chain type liquid crystalline polymer represented by the general formula (1), a low molecular weight liquid crystal material, and an electrolyte is mixed in a fixed amount. It is characterized in that a mixed film is formed by injecting between a pair of base materials arranged at a distance. Furthermore, the third production method of the present invention is to arrange a mixture containing a side chain type liquid crystalline polymer represented by the general formula (1), a low molecular weight liquid crystal material, and an electrolyte at a constant distance. The mixed film is formed by injecting between the pair of base materials.

According to the above-mentioned first to third manufacturing methods of the present invention, the liquid crystal element of the present invention can be manufactured simply and efficiently by the same operation as in the conventional case. The present invention will be described below. In the side chain type liquid crystalline polymer represented by the general formula (1) used in the liquid crystal device of the present invention, a group X
Is an important factor for imparting liquid crystallinity to the polymer. Examples of the group X include electron withdrawing groups and alkoxy groups as described above.

Examples of the electron-withdrawing group include a cyano group, a nitro group, an acyl group (acetyl group and the like), a halogen atom (F, Cl, Br, I) and the like. Examples of the alkoxy group include methoxy group, ethoxy group, n
A propoxy group, iso-propoxy group, n-butoxy group, iso-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group and the like having 1 to 6 carbon atoms are preferably used.

Of these groups, it is most preferable to use a cyano group (-CN) or a fluorine atom, which is an electron-withdrawing group, in order to raise the phase transition temperature of the liquid crystal phase.
The degree of polymerization n is not particularly limited, but is usually 2 to 1000.
The degree is appropriate. The polymerization can be carried out, for example, by cationic polymerization. The carbon number m of the alkylene group is 1 to 12
Is limited to integers. When m is 0, the mobility of the side-chain liquid crystalline group is remarkably reduced and liquid crystallinity is not exhibited. When it exceeds 12, the motion of the polymer chain is strengthened and the phase transition temperature of the mixed film is lowered.

The liquid crystalline polymer used in the mixed film may be one kind alone, or two or more kinds having different groups X, m, n and the like may be used in combination. Further, other conventionally known liquid crystal polymer of main chain type or side chain type can be used in combination within a range that does not impair the effects of the present invention. A low molecular weight compound that forms a mixed film together with the above liquid crystalline polymer (the term "low molecular weight" here means that it does not have a main chain structure or a side chain structure like a liquid crystalline polymer, and never a molecular weight. As liquid crystal materials, various commercially available or publicly known and commonly used single-component or multi-component liquid crystal materials excluding main chain type or side chain type liquid crystalline polymers are used as liquid crystal materials. Materials (eg nematic liquid crystals, smectic liquid crystals, chiral smectic liquid crystals, etc.) can be used.

As the physical properties of the low molecular weight liquid crystal material, those having a large dielectric anisotropy Δε and those having a large refractive index anisotropy Δn are preferable. Further, as a particularly important factor, it is possible to show a smectic phase in the operating temperature range of the device when mixed with a liquid crystalline polymer. As a result, the mixed film has the memory property as described above. Such liquid crystal materials may be used alone or in combination of two or more.

The mixing ratio of the liquid crystalline polymer and the low molecular weight liquid crystal material is not particularly limited, but a weight ratio of liquid crystalline polymer / low molecular weight liquid crystal material = 4/6 to 6/4 is preferable.
If the ratio of the liquid crystalline polymer exceeds the above range, the response speed of the device may be slower. Conversely, if the ratio of the liquid crystalline polymer is less than the above range, the self-supporting property of the mixed film is insufficient. As a result, there is a possibility that a flexible large-area liquid crystal element using a particularly flexible substrate cannot be formed.

A minute amount of electrolyte is mixed in the mixed film. By blending the electrolyte, the response speed of the device is enhanced by the ions derived from the electrolyte, and the change from transparent to cloudy and from cloudy to transparent can be reliably and reproducibly produced. Any electrolyte can be used as long as it can be dissolved in the coating liquid, for example, the general formula (3):

[0028]

[Chemical 4]

[Wherein R ³ , R ⁴ , R ⁵ and R ⁶ are the same or different and each represents a linear or branched alkyl group having 1 to 6 carbon atoms, and Y is F, Cl, Br or I. , ClO ₄ , PF
₄ , BF ₄ etc.] are preferred. The addition amount of the electrolyte is preferably 0.01 to 1% by weight with respect to the total amount of the mixed film. These electrolytes may be used alone or in combination of two or more.

Various known dichroic dyes can be added to the mixed film composed of the above components in order to color the display. Further, the mixed film may be mixed with various additives, a non-liquid crystal compound, or the like within a range that does not impair the property, to adjust the property. In addition, in order to keep the distance between the pair of base materials holding the mixed film constant, the mixed film is made of silica, glass fiber or resin, and a spacer material of any shape such as granular or needle-like. It can also be mixed and dispersed. The particle size of the spacer material is set according to the desired distance between the base materials (that is, the film thickness of the mixed film). The mixing ratio of the spacer material is not limited to this, but it is desirable that it is about 10 to 300 per 1 mm ^{2 of} liquid crystal area.

The mixture composed of the above components used as a material for the mixed film has a relatively high viscosity because it contains a liquid crystalline polymer, and therefore the spacer material is localized by the flow of the liquid crystal. There is no fear. Therefore, the spacer material is uniformly dispersed in the mixed film, and acts sufficiently to keep the distance between the base materials constant. The thickness of the mixed film is not particularly limited in the present invention, but considering the driving voltage of the element, the thickness of the mixed film is preferably 10 μm or less.

As the pair of base materials for sandwiching the mixed film, various base materials conventionally used as base materials for liquid crystal elements such as glass plates can be used, but they are heavy and easily broken. A plastic film or a plastic plate is preferably used as the base material in order to eliminate the drawbacks of the plate and obtain a lightweight and durable element. As a plastic film, for example, heat resistance, practical strength,
Polyethylene terephthalate (PET) film and polyether sulfone (PE) with excellent optical uniformity
S) film and the like. The thickness of the plastic film is not limited to this, but may be 50 to 50.
About 0 μm is preferable.

As the plastic plate, for example, various acrylic resin plates, polycarbonate plates, polystyrene plates, and other plastic plates having excellent optical characteristics are preferably used. The thickness of the plastic plate is not limited to this, but is preferably about 0.5 to 3 mm. An electrode layer for applying an electric field to the mixed film is formed on at least one surface of the pair of base materials. For transmissive elements,
As the electrode layer, a transparent conductive film made of a transparent conductive material such as ITO (Indium-Tin-Oxide) or SnO ₂ is preferably used. The transparent conductive film may be formed by a vacuum deposition method or a reactive sputtering method, or may be formed by applying or printing an ink containing the transparent conductive material on a substrate. When the liquid crystal device of the present invention is used for displaying data and the like, a predetermined display pattern can be formed on the electrode layer by etching or the like.

The liquid crystal device of the present invention is not particularly limited in constitution except that the mixed film contains the liquid crystalline polymer represented by the general formula (1). For example, the polarizing plate may be arranged outside at least one of the pair of base materials sandwiching the mixed film. As the polarizing plate, various shapes such as a film shape and a plate shape can be used, and it is easy to use a commercially available product having these shapes. In addition, various design changes similar to those of the conventional liquid crystal element may be made within a range that does not change the gist of the present invention, such as providing a reflective film on the back surface of one of the substrates to form a reflective element. it can.

In order to manufacture the above liquid crystal device of the present invention,
The first production method of the present invention is a production method suitable for both the case where a flexible substrate such as a film is used and the case where a substrate such as a glass substrate or a hard plastic substrate is used. First, a liquid crystal polymer, a low-molecular liquid crystal material and an electrolyte are dissolved in an appropriate common solvent in the above-mentioned proportions, and a coating solution in which a spacer material is dispersed is further added to the surface of one substrate. And then dried to form a polymer liquid crystal / low molecular weight liquid crystal mixed film.

When the other base material is superposed on the formed mixed film, the liquid crystal element of the present invention in which the polymer liquid crystal / low molecular liquid crystal mixed film is sandwiched between the pair of base materials is completed. As a method of applying the coating liquid onto the surface of the substrate, various conventionally known coating methods such as a bar coating method, a spin coating method, a spray coating method and a roller coating method can be adopted.

On the other hand, the second production method of the present invention is a production method suitable when a flexible substrate such as a film is used. First, a liquid crystal polymer, a low molecular weight liquid crystal material and an electrolyte are used. Is dissolved in a suitable common solvent at the ratio described above,
A predetermined amount of spacer material is dispersed and then dried to obtain a paste-like mixture. Next, this mixture is placed on one base material, the other base material is overlaid thereon, and laminated by a laminating roll.

Then, the polymer liquid crystal /
The liquid crystal element of the present invention in which the low-molecular liquid crystal mixed film is sandwiched is completed. Furthermore, the third production method of the present invention is a production method suitable when using a base material such as a glass base material or a hard plastic base material. First, a pair of base materials is equivalent to the film thickness of the mixed film. Hold at a constant distance.

In order to hold a pair of base materials at a constant distance, both base materials are bonded together at their peripheral portions via a film-shaped spacer or the like, or one of the base materials is provided with the granular spacer material. After uniformly spraying, a method of laminating and sticking the other base material while pressing is adopted. Then, a liquid crystal polymer, a low-molecular liquid crystal material, and an electrolyte are mixed in the above-mentioned ratio between the two base materials, and a polymer liquid crystal / low-molecular liquid crystal mixed film is sandwiched between the pair of base materials. Thus, the liquid crystal element of the present invention is completed.

The method of injecting the mixture between the substrates is as follows:
Examples thereof include a method of impregnating the mixture between the base materials by a capillary phenomenon, and a method of sucking the mixture by reducing the pressure between the base materials. When injecting the mixture between the substrates by these methods, the viscosity may be lowered by heating the mixture in order to smoothly perform the injection. At the same time, the base material may be heated. The heating temperature of the mixture and the base material is not particularly limited, and may be a temperature range in which the liquid crystalline polymer, the polymer material and the like are not decomposed or deteriorated and the temperature at which the injection is smooth.

[0041]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1 In the general formula (1), the group X is a cyano group, the degree of polymerization n is 10,
Formula (4) in which the carbon number m of the linear alkylene group is 5:

[0042]

[Chemical 5]

30 parts by weight of the side chain type liquid crystalline polymer represented by the following formula is used as a low molecular weight liquid crystal material (E6 manufactured by Merck Japan Ltd.).
Acetone, together with 30 parts by weight of mixed liquid crystal which is assumed to contain three or more kinds of liquid crystal materials of different types) and 0.05% by weight with respect to the total amount of both liquid crystal materials, tetraethylammonium bromide as an electrolyte. A coating solution was prepared by dissolving it in a mixed solvent of dichloromethane / dichloromethane (1/1).

Then, this coating solution was applied on a transparent conductive film (ITO-PES, thickness 100 μm) by a bar coating method and dried at room temperature for 30 minutes to form a mixed film, and then on this mixed film. A liquid crystal device was manufactured by laminating one transparent conductive film. Comparative Example 1 Instead of the liquid crystalline polymer represented by the formula (4), the formula (5):

[0045]

[Chemical 6]

A liquid crystal element was manufactured in the same manner as in Example 1 except that 30 parts by weight of the liquid crystalline polymer represented by Comparative Example 2 Instead of the liquid crystalline polymer represented by the formula (4), the formula (6):

[0047]

[Chemical 7]

Other than using 30 parts by weight of a liquid crystalline polymer having a polysiloxane-based main chain represented by
A liquid crystal element was manufactured in the same manner as in Example 1 above. Evaluation test The liquid crystal elements of the above-mentioned Examples and Comparative Examples were subjected to room temperature at 1 kHz,
He-Ne laser light (wavelength 633 nm) was used to examine the response time of transparent → white turbid when an alternating current of 90 V was applied and the response time of white turbid → transparent when a direct current of 90 V was applied.

Measurement of Smectic Temperature Range of Mixed Film The liquid crystal elements of Examples and Comparative Examples were set in a spectrophotometer, and an electric field of AC 1 kHz, 60 V was applied to change the transmittance of He—Ne laser light to a saturated transmittance of 90. %, Then in the memory state where the application of the electric field is stopped, the environmental temperature is changed,
The change rate of the He-Ne laser light was examined, and the change rate was 1%.
The temperature at which the temperature was maintained within the range was recorded and set as the smectic temperature range of the mixed film.

The above results are shown in Table 1.

[0051]

[Table 1]

From the results shown in Table 1 above, the liquid crystal element of Example 1 has a response speed of transparent → white turbid and white turbid → transparent to the same extent as that of the liquid crystal element of Comparative Example 1, and compared with the liquid crystal element of Comparative Example 2. It was found that it was possible to operate at high speed and in a wider temperature range and higher temperature than those of Comparative Examples 1 and 2.

[0053]

As described above in detail, in the liquid crystal device of the present invention, since the liquid crystalline polymer forming the mixed film has a unique structure, it is excellent in high-speed response, self-supporting property and wide temperature range. It is possible to operate in, and the upper limit of operable temperature is high. Therefore, the liquid crystal element of the present invention can be suitably used, for example, in a curved state in a curved state in a sunshade for an automobile that is used in a wide temperature range from a high temperature during the day in summer to a severe cold in the winter. .

Claims (4)

[Claims] 1. A general formula is provided between a pair of base materials having an electrode layer formed on at least one surface and arranged at a constant distance.
(1): [Chemical 1] [In the formula, X represents an electron-withdrawing group or an alkoxy group, and n
Is the degree of polymerization and m is an integer from 1 to 12. ] A liquid crystal element characterized by sandwiching a mixed film containing a side chain type liquid crystalline polymer represented by the following formula, a low molecular weight liquid crystal material, and an electrolyte. 2. A pair of base materials obtained by dissolving a side chain type liquid crystalline polymer represented by the general formula (1), a low molecular weight liquid crystal material, and an electrolyte in a common solvent of these liquids. A liquid crystal device according to claim 1, wherein the liquid crystal device according to claim 1 is manufactured by applying the composition on one of the surfaces and drying it to form a mixed film, and then laminating the other base material on the mixed film. Manufacturing method. 3. A mixture containing a side chain type liquid crystalline polymer represented by the general formula (1), a low molecular weight liquid crystal material, and an electrolyte is placed on one surface of a pair of base materials. The liquid crystal device according to claim 1, wherein the substrate is placed on the substrate, and the other substrate is laminated on the substrate and laminated to form a mixed film by sandwiching the mixture between the pair of substrates. A method for manufacturing a characteristic liquid crystal element. 4. A pair of base materials in which a mixture containing a side chain type liquid crystalline polymer represented by the general formula (1), a low molecular weight liquid crystal material, and an electrolyte is placed at a constant distance. A method for producing a liquid crystal element, comprising: injecting a mixture film to form a mixed film to produce the liquid crystal element according to claim 1.