JPS623929B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display using a transparent conductive film, and more specifically, the present invention relates to a liquid crystal display using a transparent conductive film, and more specifically, a base film is a polyester film in which the difference in extinction position at any point between crossed nicols is within 5 degrees. This invention relates to a liquid crystal display using a transparent conductive film.

2. Description of the Related Art Conventionally, transparent conductors for liquid crystal displays have been made of glass whose surface is made transparent and conductive. However, liquid crystal displays are becoming increasingly lighter and thinner, and in order to increase the contrast of the display,
Attempts have also been made to install a liquid crystal panel between two opposing polarizing plates. Under such circumstances, it is not possible to make the glass plate thinner due to the mechanical strength of the glass and manufacturing constraints, and the glass surface is said to be thinner than 0.5 mm. Therefore, in order to apply it to the above purpose,
It has its own limitations, and furthermore, because of its vulnerability to impact, it tends to be easily damaged and unreliable during the assembly process of the elements and the completed display.

On the other hand, an attempt has been made to utilize a transparent conductive film, which is a transparent conductive thin film provided on the surface of a polymer molded product, in a liquid crystal display by utilizing the dynamic alignment change of a nematic phase liquid crystal material. For the purpose of improving durability, there are encapsulated liquid crystal displays (see JP-A No. 47-22694), and cases where metal or alloy is used as the transparent electrode coating material (see JP-A-53-74055). reference)
It has been known. In particular, when tin oxide or indium oxide is used as the transparent electrode coating material, it is possible to achieve this with inorganic glass, but it is difficult to do so with synthetic resin, by using metal or alloy as the material. It is noteworthy that it has also been made available for use.

However, the present inventors have discovered that it is possible to form a transparent conductive film such as tin oxide and/or indium oxide on a synthetic resin molded product, which has been considered difficult or impossible in the past. In display materials, the difference in extinction position at any point between orthogonal nicols is 5, even in synthetic resin molded products.
It was discovered that polyester within the range of
We have arrived at the present invention. That is, the present invention provides a voltage application type liquid crystal display in which a transparent conductive film formed by providing a transparent conductive thin film on the surface of a polymer molded product is used in combination with a polarizing plate as a pair of transparent electrodes that sandwich a liquid crystal substance. The liquid crystal display is characterized in that the polymer molded product is a polyester film in which the difference in extinction position at any point between crossed nicols is within 5 degrees, and in particular, the optical axis of the extinction position of the polyester film is or the extinction position of the polyester film is within 5 degrees with respect to the width direction, and the transparent conductive thin film is made of indium oxide containing tin oxide or tin oxide containing antimony oxide. It is a thin film liquid crystal display.

The liquid crystal display of the present invention is of a type that uses a polarizing plate to improve its display effect, and has a structure as shown in FIG. 1, for example. That is, a polyester film 1 is used as a base material, a transparent conductive thin film 2 is provided thereon, and a liquid crystal composition 4 is sealed between the facing films. The liquid crystal composition is sealed using a suitable spacer 3. However, the seal does not necessarily have to be the spacer 3; a separate sealing material may be used, or the film 1 may be fused together. Further, the spacers 3 do not necessarily need to be provided only at both ends, and spacers of an appropriate number and shape may be provided in order to make the thickness of the liquid crystal layer uniform. The liquid crystal display element assembled in this manner is inserted between two polarizing plates 5 whose polarization angles are vertically perpendicular to each other to form a liquid crystal display. At this time, the polyester film 1 and the polarizing plate 5 can be laminated in advance. The polyester film has a difference in extinction position at any point between crossed nicols within 5 degrees.

Generally, the extinction positions of a polyester film that has been biaxially stretched (for example, 2.5 to 5 times) are distributed in the width direction as shown in FIG. For example, part 1 has an extinction position of 30±2.5° with respect to the width direction, and can be cut out in any shape parallel to the extinction position from this part and used in the present invention. In particular, the extinction position of the second part, which is approximately in the center of the polyester film, is within 5 degrees with respect to the width direction.
Electrodes can be punched out parallel to the longitudinal (longitudinal) direction of the film, and continuous production is possible, so it is preferably used. When constructing a liquid crystal panel, by aligning the optical axes at the extinction position and facing each other, a liquid crystal panel with extremely excellent contrast can be obtained. The thickness of the polyester film is preferably in the range of 50 μm to 500 μm. 500μm
If it exceeds this, it deviates from the purpose of making the liquid crystal display thinner. Further, if the thickness is less than 50 μm, it is difficult to maintain a constant distance between the electrodes of the liquid crystal display because of flexibility. Therefore, a range of 75 μm to 200 μm is particularly preferable from the viewpoint of keeping the electrode spacing constant and making it thinner, and from the viewpoint of producing a transparent conductive film.

The transparent conductive thin film provided on the polyester film includes an indium oxide thin film doped with a small amount of tin oxide, a tin oxide thin film doped with a small amount of antimony oxide, and cadmium/tin oxide (Cd ₂ SnO ₄ ).
From the viewpoint of transparency and etching resistance, indium oxide thin films doped with a small amount of tin oxide and tin oxide thin films doped with a small amount of antimony oxide are particularly suitable, and in particular, isodium oxide thin films doped with a small amount of tin oxide. is preferred. In addition, the transparent conductive thin film usually has a visible light (550 nm) transmittance of at least 75% and a surface resistance of 10KΩ/□ or less, and preferably has a transmittance of at least 80% and a surface resistance of at least 10KΩ/□. Low resistance is 5KΩ/□ or less.

Incidentally, in order to improve the adhesion between the thin film and the polyester film serving as the substrate, undercoating may be performed using a silane coupling agent or the like in a conventional manner.

Examples of methods for providing the transparent conductive thin film on the surface of the polyester film include physical means such as vacuum evaporation, sputtering, and ion plating. For example, in the case of an indium oxide thin film doped with a small amount of tin oxide, the substance is vacuum-deposited in a vacuum, and the resulting low-oxide thin film is heated to the desired high Next, a method of converting into an oxide; a method of reactive vapor deposition in an oxygen atmosphere or a method of sputtering can be selected depending on the type of the polymer molded product.

An example of the structure of a liquid crystal display using the transparent conductive film thus obtained is shown in FIG.

Since the liquid crystal display of the present invention uses crossed nicols and there is little difference in optical anisotropy of the transparent conductive film, there is no coloring of the film within the crossed nicols, and since it is dark, it cannot use white light. When a voltage is applied to the liquid crystal display while transmitting light, the liquid crystal molecules rotate, producing birefringence and changing the hue, resulting in a display effect with excellent contrast. Moreover, since the thickness of the element of the liquid crystal display can be made thin, it is possible to fully satisfy the purpose of making the liquid crystal display lightweight and thin.

Further, the polyester film used as the base film of the transparent conductive film has excellent transparency, heat resistance, chemical resistance, and surface smoothness, and is therefore extremely advantageous in achieving the above-mentioned effects.

Example 1 In a 100 μm thick polyethylene terephthalate film stretched 3 times in length and width, a uniform portion was formed over the entire surface with an extinction position of 30 ± 2.5 degrees in the width direction of the film.
It was slit across a width of 20cm. After priming the film with a silane coupling agent, 95 parts of In ₂ O ₃ ;
The deposition was carried out using a mixture of 5 parts of SnO ₂ at a deposition rate of 20 Å/sec under 5×10 ⁻⁵ Torr. Deposited film thickness is
It was 130Å/. Subsequently, it was heat-treated at 150°C to produce a transparent conductive film with a resistance of 3KΩ/□ and a transmittance of 89%. A 2 x 5 cm punched electrode was prepared parallel to the extinction position. When making these electrodes face each other, the optical axes at the extinction position are aligned and overlapped.
When observed between crossed nicols, it turned dark and could be used as a liquid crystal electrode.

Adhesion between the transparent conductive material and the film substrate was good, and when rubbed under a load of 100 g/cm ² , the resistance value after 10 rubbings was within 6 times the resistance value before friction.

When a liquid crystal display having the structure shown in FIG. 1 was assembled using the film and a voltage was applied between the transparent conductive layers, a change in hue occurred and a display effect with excellent contrast was exhibited. In addition, the display body was extremely thin at 0.7 mm in thickness compared to conventional displays using glass, and was also lightweight.

Example 2 A polyethylene terephthalate film with a thickness of 100 μm and stretched 4 times in length and width was slit in a 10 cm width portion where the extinction position was within 0 to 5 degrees with respect to the width direction of the film. After undercoating the film with a silane coupling agent, a transparent conductive film was prepared under the same conditions as in Example 1, and the resistance value was 28K.
Ω/□, transmittance was 87%.

This film has a small extinction position of less than 5 degrees in the width direction, so it is
Electrodes 5 cm in size were fabricated continuously by a combination of gravure printing and etching methods. Thereafter, when two of the electrodes were cut out and observed in crossed nicols, they turned dark and could be used as electrodes for liquid crystals.

Furthermore, the adhesion between the transparent conductive layer and the film substrate was comparable to that of Example 1.

When a liquid crystal display having the structure shown in FIG. 1 was assembled using the film and a voltage was applied between the transparent conductive layers, a change in hue occurred and a display effect with excellent contrast was exhibited. Furthermore, the display body is extremely thin compared to those using conventional glass;
Moreover, it was lightweight. Furthermore, the display did not break even when dropped from a height of 1 m.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a liquid crystal display. 1 is a polyester film, 2 is a transparent conductive coating, 3
4 represents a liquid crystal composition, and 5 represents a polarizing plate. Moreover, FIG. 2 shows the distribution of the extinction position of the biaxially stretched polyester film in the width direction. 1 represents a portion where the extinction position is 30±2.5 degrees with respect to the width direction, and 2 represents a portion within 5 degrees.

Claims (1)

[Claims] 1. A transparent conductive film formed by providing a transparent conductive thin film on the surface of a polymer molded product is combined with a polarizing plate,
A voltage application type liquid crystal display used as a pair of transparent electrodes that sandwich a liquid crystal substance, characterized in that the polymer molded product is a polyester film in which the difference in extinction position at any point between crossed nicols is within 5 degrees. LCD display. 2. The liquid crystal display according to claim 1, wherein the optical axes of the polyester film at the extinction position are made to coincide with each other and face each other. 3. The liquid crystal display according to claim 1, wherein the extinction position of the polyester film is within 5 degrees with respect to the width direction. 4. The liquid crystal display according to claim 2 or 3, wherein the transparent conductive thin film is a thin film of indium oxide containing tin oxide or tin oxide containing antimony oxide.