JPH04328524A - liquid crystal curved display element - Google Patents

Abstract

PURPOSE:To enable curved surface display to be conducted by forming plastic film substrate of specific completely fluorinated polyimide, thereby obtaining the optically isotropic films having good transparency and excellent heat resistance and water repellency. CONSTITUTION:This display element is constituted of a liquid crystal layer and a pair of the plastic film substrates which are formed with transparent electrodes and a pair of transparent electrodes crimping this liquid crystal layer. The plastic film substrates are formed of the completely fluorinated polyimide having the repeating unit expressed by formula I. In the formula I, R1 denotes the group expressed by formula II, etc.; R2 denotes the group expressed by formula III, etc.; Rf denotes fluorine, perfluoroalkyl group. The above-mentioned completely fluorinated polyimide has not only the good heat resistance but has also the excellent transparency and water repellency by the introduction of the fluorine group. The optical anisotropy is extremely small. Since all the constituting elements of the liquid crystal display element are the films, the carrying in the curved state and curved surface display are possible.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention is a method for displaying a curved surface using a film-formable polymer liquid crystal or its composition and a plastic film substrate with improved moisture resistance and optical properties. The present invention relates to a liquid crystal display element. BACKGROUND OF THE INVENTION Liquid crystal display elements are characterized by being small, lightweight, and low power consumption, and in recent years, studies have been made to put them into practical use, and their diversification has attracted attention. Among these, there is a polymer liquid crystal display element that aims at display on a curved surface. By using a polymer liquid crystal that has film-forming ability and responds to external factors such as electric fields as a liquid crystal display medium, and sandwiching it between plastic film substrates, it has excellent reliability and is easy to manufacture. A liquid crystal display element can be provided. Conventionally, it has been proposed to use a film made of, for example, polyether sulfone (PES) or uniaxially oriented polyethylene terephthalate (PET) for such a liquid crystal substrate. [Problems to be Solved by the Invention] However, when a transparent electrode made of indium-tin oxide (ITO) is formed on a PES film or a uniaxially stretched PET film and used as a substrate, the water absorption rate is 1%. Because of this, it is susceptible to the effects of moisture in the air, which poses reliability problems. On the other hand, in these films that have strong optical anisotropy, misalignment between the polarizing plate and the polarization direction causes a decrease in contrast. For this reason, conventional liquid crystal display elements are time-consuming to manufacture, and improvements have been desired. The present invention has been made in view of these problems,
The purpose is to provide a liquid crystal display element capable of displaying a curved surface using an optically isotropic film that has good transparency, heat resistance, and water repellency. Means for Solving the Problems To summarize the present invention, the present invention relates to a liquid crystal display element, and includes a plastic film substrate on which a liquid crystal layer and a pair of transparent electrodes sandwiching the liquid crystal layer are formed. In a liquid crystal display element composed of
The plastic film substrate has the following general formula (Chemical formula 1):
[Formula 1] [In the formula, R1 is any group represented by the following formula (Chemical formula 2): [Chemical formula 2], R2 is the following formula (Chemical formula 2):
Chemical formula 3): Any of the groups represented by the following formula (Chemical formula 3), where Rf is fluorine or a perfluoroalkyl group, and X is the following formula (Chemical formula 4): [Chemical 4] (wherein, Rf' is a perfluoroalkylene group, and n is a number from 1 to 10). It is characterized by being made of polyimide. These perfluorinated polyimides not only have good heat resistance, but also have excellent transparency and water repellency due to the introduction of fluorine groups. Moreover, optical anisotropy is extremely small. Materials for forming the transparent electrodes of this liquid crystal display element include:
An example is ITO. To form this transparent electrode,
A suitable method is to sputter ITO by electron cyclotron resonance (ECR) while heating the polyimide film to 200 to 400°C. The liquid crystal polymer constituting the liquid crystal layer of the liquid crystal display element of the present invention may be a polymer or copolymer having repeating units represented by the following general formulas (5) to (7), or other polymers or polymers added thereto. A liquid crystal composition containing a molecular liquid crystal compound is preferably used. The polymer liquid crystals exemplified below have a strong response to electric fields and are suitable for displaying moving images. Furthermore, since it itself has film-forming ability, it is suitable for large screen display elements and curved display elements. (1) Polymer liquid crystal with polysiloxane as the main chain [Formula (5), R3 is a lower alkyl group, k is 1 to 2
0 integer, R4 is the following formula (Chemical formula 8): [Chemical formula 8] (X is hydrogen, hydroxyl group, halogen, or nitrile group, Y is -COO-, -OCOCH2 O-, or -OCH2
-, R5 is -COR6, -COOR6, -OCO
(R6, -OR6, or -R6, R6 represent optically active alkyl groups)] (2) Polymer liquid crystal having a main chain of polyacrylate or polymethacrylate [Formula (Chemical 6)] where k is an integer of 1 to 20, R8 is the following formula (Chemical formula 9): [Chemical formula 9] (X is hydrogen, hydroxyl group, halogen, or nitrile group, Y is -COO-, -OCOCH2 O-, or -OCH2
-, R9 is -COR10, -COOR10, -OCO
R10, -OR10, or -R10, R10 represents an optically active alkyl group), R7 represents hydrogen or CH3] (3) Polymer liquid crystal having polyester as the main chain [Formula (Chemical formula 7)] 7), R11 is hydrogen, CH3, or C2
H5, k is an integer from 1 to 20, l is an integer from 1 to 30, Z
is oxygen or COO, m is 0 or 1, R12 is the following formula (Chemical formula 10): [Chemical formula 10] (X is hydrogen, hydroxyl group, halogen, or nitrile group, Y is -COO-, -OCOCH2 O-, or - OCH2
-, R13 is -COR14, -COOR14, -OCO
R14, -OR14, or -R14, R14 represents an optically active alkyl group] [Example] The present invention will be explained in more detail with reference to Examples below. Not limited to examples. Embodiment 1 FIG. 1 is a sectional view showing an embodiment of the liquid crystal curved display element of the present invention, which is formed in an arcuate cross section. Reference numeral 1 in FIG. 1 is a polymer liquid crystal layer. The polymer crystal layer 1 is sandwiched between plastic film substrates 4 on which an alignment film 2 and a transparent electrode 3 are formed, and a polarizing plate 5 is laminated on the outside of the plastic film substrate 4 . The polymer liquid crystal layer 1 of this liquid crystal display element is formed to have a thickness of 4 μm. Further, the substrate is formed to have a thickness of 70 μm, and the transparent electrode 3 is formed to have a film thickness of 1800 Å. The polymer liquid crystal layer 1 of this liquid crystal curved display element is manufactured by uniaxially stretching a polymer liquid crystal containing a repeating unit represented by the following structural formula (Chemical Formula 11). [Chemical formula 11] This polymer liquid crystal is a patent application filed by the present inventors
It was manufactured in the same manner as the manufacturing method described in No. 181298. That is, first, 4-hydroxybenzoic acid and potassium hydroxide are dissolved in a mixed solution of ethanol and water, 8-bromooctene is added to this solution, the mixture is stirred under reflux for a predetermined period of time, the solvent is distilled off, and dimethyl sulfoxide and dilute hydrochloric acid are dissolved. added. This solution was poured into cold water, and the precipitate was purified to obtain substituted benzoic acid. Furthermore, it was made into an acid chloride with thionyl chloride. Under ice cooling, 4-(1-oxo-2
Triethylamine was added to a solution of -methyloctyl)phenol in tetrahydrofuran, and the substituted benzoate chloride was added dropwise, followed by stirring. After the reaction, the crude product obtained by removing the solvent was purified by column chromatography and recrystallization to obtain an intermediate. Further, polysiloxane and a platinum acid catalyst were added to a toluene solution of this intermediate, and after reaction for a predetermined time, reprecipitation was performed from methanol to obtain a polymer liquid crystal. A perfluorine polyimide film containing a repeating unit represented by the following structural formula (Chemical formula 12) was used as the substrate of the liquid crystal display element of Example 1. This polyimide film is 1,
4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride and 2,4,5,6
A polyamic acid solution obtained by reacting -tetrafluoro-1,3-phenylenediamine was cast on a silicon substrate, and in a nitrogen atmosphere at 70°C for 2 hours, 160°C for 1 hour, 250°C for 30 minutes, and 350°C. (The production of the polyamic acid solution was in accordance with the example of Japanese Patent Application No. 1-71737 filed by the present inventors). embedded image Next, an ITO film was formed on the fully fluorinated polyimide film using an ECR sputtering device. The properties of the obtained film are shown in Table 1 below along with other examples. Furthermore, a polyimide alignment film was attached thereon to form a substrate. A liquid crystal display element made of this substrate and the polymer liquid crystal described above could be easily manufactured with good contrast, and no problems occurred when used in a curved surface. Furthermore, no abnormalities occurred even after long-term use. Example 2 A liquid crystal curved display element was produced which differed from Example 1 only in that the perfluorinated polyimide film constituting the substrate 4 was changed to one containing a repeating unit represented by the following structural formula (Chemical formula 13). . [Chemical formula 13] This perfluorinated polyimide film has 1,4-bis(
A polyamic acid solution obtained by reacting 3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride and bis(2,3,5,6-tetrafluoro-4-aminophenyl)ether was placed on a silicon substrate. It was produced by casting and subjecting it to the same heat treatment as in Example 1 under a nitrogen atmosphere. Next, an ITO film was formed on this polyimide film by the same operation as in Example 1. The properties of this film are shown in Table 1. Furthermore, a polyimide alignment film was attached thereon to form a substrate. A liquid crystal display element made of this substrate and the polymer liquid crystal described above could be easily manufactured with good contrast, and could sufficiently withstand use in a curved state. Furthermore, no abnormalities occurred even after long-term use. Comparative Example 1 Compared to Example 1, the substrate was made of PE with a thickness of 70 μm.
A liquid crystal curved display element was manufactured with the only difference being that the S film was used. Table 1 shows the characteristics of a PES film with ITO deposited to a thickness of 1800 Å. When this liquid crystal display element was used for a long time, abnormal operation occurred. Comparative Example 2 Compared to Example 1, the substrate was made of PE with a thickness of 70 μm.
A liquid crystal curved display element was manufactured with the only difference being that the T film was used. Table 1 shows the characteristics of a PET film with ITO deposited to a thickness of 1800 Å. When this liquid crystal display element was used for a long time, abnormal operation occurred. [Table 1] [Effects of the Invention] As explained above, since all the constituent elements of the liquid crystal display element of the present invention are films, it is possible to carry the device in a curved state and display it on a curved surface. Since the optical anisotropy of the perfluorinated polyimide film serving as the substrate is extremely small, there is no need for alignment with the polarizing plate, making the device easy to manufacture. Furthermore, since the transparency is high, the contrast is good. At the same time, it has superior moisture resistance compared to conventional plastic film liquid crystal display elements, so it is possible to provide a highly reliable element.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a liquid crystal display element of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Polymer liquid crystal layer, 2... Alignment film, 3... Transparent electrode, 4... Plastic film substrate, 5... Polarizing plate

Claims (1)

[Claims] Claim 1: A liquid crystal display element comprising a plastic film substrate formed with a liquid crystal layer and a pair of transparent electrodes sandwiching the liquid crystal layer, wherein the plastic film substrate has the following general formula (Chemical formula 1): [Chemical formula 1] [In the formula, R1 is any group represented by the following formula (Chemical formula 2): [Chemical formula 2], R2 is a group represented by the following formula (Chemical formula 2):
Chemical formula 3): Any of the groups represented by the following formula (Chemical formula 3), where Rf is fluorine or a perfluoroalkyl group, and X is the following formula (Chemical formula 4): [Chemical 4] (wherein, Rf' is a perfluoroalkylene group, and n is a number from 1 to 10). A liquid crystal display element characterized by being formed of polyimide.