JPH1048625A - Touch panel for liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent light from an outside from being reflected by a transparent conductive film and to make possible transmitting through the light of a liquid crystal display without loss by arranging a first 1/4 wavelength plate, two pieces of transparent conductive films opposite to each other through a spacer, a second 1/4 wavelength plate and a polarizing plate successively from the liquid crystal display side. SOLUTION: This panel is constituted so as to arrange a first 1/4 wavelength plate 4, two pieces of transparent conductive films 2 opposite to each other through a spacer 3, a second 1/4 wavelength plate 5 and a polarizing plate successively from a liquid crystal display 7 side. This first 1/4 wavelength plate 4 eliminates a phase difference together with a second 1/4 wavelength plate 5, or gives an effect as a 1/2 wavelength plate. Although a first 1/4 wavelength plate 4 is set on the phase difference plate of the liquid crystal display 7 or the polarizing plate 6, only it may be put on simply, and it may be arranged in the state stuck to the phase difference plate or the polarizing plate 6 also. Further, the conductive film 2 becomes an electrode of a touch panel, and generally, is formed on transparent base material to be arranged so that two pieces of conductive films are confronted with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a touch panel provided on a liquid crystal display.

[0002]

2. Description of the Related Art A touch panel, which is arranged on the front of a display and serves as an input switch integrated with the display,
It is widely used because of its ease of use. As a touch panel system, an optical system, an ultrasonic system, an electromagnetic induction system, and a resistive film system are generally used, but a resistive film system is most often used in combination with a small liquid crystal display. This resistive touch panel is an input switch using a transparent conductive film as a conductor, and has a structure in which two transparent conductive films are opposed to each other via a spacer as shown in FIG. By pressing this with a finger or a pen or the like, the opposing conductive films come into contact with each other and are input. The transparent conductive film used here is formed on a transparent substrate such as glass or a transparent resin film, and the conductive film may be a metal oxide such as indium tin oxide or tin antimonic acid, or gold, palladium, aluminum, silver, or the like. Metal thin film is used.

[0003] However, these metal oxides or metal thin films have a large reflection, and when used integrally with a liquid crystal display, the contrast of the liquid crystal display is remarkably reduced, resulting in a screen which is extremely difficult to see. To solve such a problem, Japanese Patent Publication No. 2509215 proposes to provide an antireflection film between a transparent conductive film and a transparent substrate. Japanese Patent Application Laid-Open No. 5-127822 discloses a touch panel having a structure in which two transparent conductive films disposed in front of a liquid crystal display are opposed to each other via a spacer, or on the opposite side of the liquid crystal display or between the liquid crystal displays. It has been proposed that a retardation plate and a polarizing plate are sequentially laminated on at least one of them.

[0004]

However, in the method disclosed in Japanese Patent Publication No. 2509215, the thickness of the transparent conductive film is limited in order to form an antireflection film, and the conductive performance can be selected in a wide range. Can not. Further, even if an antireflection film is formed, sufficient antireflection performance cannot be obtained because the conductive film must be disposed on the outermost layer. In the device disclosed in JP-A-5-127822, reflection by the transparent conductive film is reduced, but the screen is dark and very difficult to see.

In view of such circumstances, the present inventors have made intensive studies to eliminate reflection from the transparent conductive film and improve the visibility of the liquid crystal display. As a result, the first quarter wavelength plate and the spacer were sequentially arranged from the liquid crystal display side. It has been found that the visibility of a liquid crystal display equipped with a touch panel can be improved by arranging two transparent conductive films, a second quarter-wave plate, and a polarizing plate that face each other through the substrate, and complete the present invention. Reached.

[0006]

That is, the present invention relates to a touch panel arranged on the front surface of a liquid crystal display, comprising: a first quarter-wave plate in order from the liquid crystal display side;
This is a touch panel for a liquid crystal display in which two transparent conductive films facing each other via a spacer, a second quarter-wave plate, and a polarizing plate are arranged.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, the first quarter-wave plate, together with the second quarter-wave plate, eliminates a phase difference or has an effect as a half-wave plate. The first quarter-wave plate is set on the retardation plate or the polarizing plate of the liquid crystal display, but may be simply placed, or may be arranged in a state of being bonded to the retardation plate or the polarizing plate. .

The conductive film serves as an electrode of the touch panel, and is usually formed on a transparent base material, and two conductive films are arranged so as to face each other. In the present invention, the first 1
Two transparent conductive films formed on a transparent substrate may be arranged on the 波長 wavelength plate, or the transparent conductive film on the liquid crystal display side is formed directly on the first 波長 wavelength plate. May be used. These configurations are as follows.・ (First 波長 wavelength plate) / (transparent substrate / transparent conductive film /
(Spacer / transparent conductive film / transparent substrate) ・ (first quarter wave plate / transparent conductive film / spacer / transparent conductive film / transparent substrate)

As the transparent conductive film, generally used metal oxides such as indium tin oxide (ITO) and tin antimonic acid, or thin films of metals such as gold, silver, copper, and aluminum are used. These transparent conductive films are formed by a conventional method such as a physical method such as vacuum evaporation, sputtering, ion plating, or ion beam evaporation, or a chemical vapor deposition method.

The second quarter-wave plate is used to form a circularly polarized antireflection filter in combination with the outermost polarizing plate. The second quarter-wave plate reflects reflected light on the transparent conductive film surface of light entering from the outside. Cut efficiently. The optical axis of the second quarter-wave plate is arranged in the same direction or perpendicular to the optical axis of the first quarter-wave plate, but is arranged in a direction perpendicular to the visibility. Is particularly preferred.

A transparent conductive film may be formed on the second quarter-wave plate, or a transparent conductive film formed on a transparent substrate may be arranged below the second quarter-wave plate. Is also good. In the latter case, it is preferable to adjust so that the combination of the second quarter-wave plate and the transparent substrate on which the transparent conductive film is formed has a quarter-wave retardation.

The polarizing plate used in the outermost layer of the present invention is combined with a second quarter-wave plate to form a circularly polarizing type antireflection filter, and is used in a liquid crystal display without a polarizing plate. When a touch panel is provided, the touch panel also functions as a polarizing plate. The absorption axis of the polarizing plate is 45 ° or 13 ° with the optical axis of the second quarter-wave plate.
It is arranged to be 5 °.

The surface of the polarizing plate of the present invention is further improved in visibility,
Various surface treatments may be applied to improve durability. As the surface treatment, surface hardening treatment, anti-reflection treatment,
Examples include a stain prevention treatment and an anti-glare treatment.

[0014]

The touch panel for a liquid crystal display according to the present invention can prevent reflection of external light on the transparent conductive film and can transmit light of the liquid crystal display with almost no loss. The visibility is improved.

[0015]

The present invention will be described in more detail with reference to the following examples. The optical axis of the quarter-wave plate and the absorption axis of the polarizing plate are displayed counterclockwise with the right horizontal direction being 0 ° (shown in FIG. 3). The evaluation of the visibility was performed based on the color change of the screen when the viewing angle was changed.

Example 1 As shown in FIG. 2, a first quarter-wave plate (Sumikalite SEF-380135, manufactured by Sumitomo Chemical Co., Ltd.) was interposed through a spacer made of an ITO film provided on a glass plate. Two opposing transparent conductive films and a second quarter-wave plate (Sumikalite SEF-380135 Sumitomo Chemical Co., Ltd.)
) And a polarizing plate (Sumikaran SQ-1852AP manufactured by Sumitomo Chemical Co., Ltd.) were arranged on a liquid crystal display in which the absorption axis of the polarizing plate on the display surface rises to the right and rises 45 °. At this time, the optical axis of the first quarter-wave plate was arranged in the 0 ° direction, the optical axis of the second quarter-wave plate in the 90 ° direction, and the absorption axis of the polarizing plate in the 45 ° direction. . When the visibility of the liquid crystal display was evaluated, the liquid crystal display was very bright, had no reflection by the transparent conductive film, and had a very good contrast.

Comparative Example 1 An arrangement was made in the same manner as in Example 1 except that the first quarter-wave plate was omitted. As a result, although the reflection by the transparent conductive film was reduced, the screen was dark and very difficult to see.

Example 2, Comparative Example 2 The visibility was examined in the same manner as in Example 1 except that the optical axis of the quarter-wave plate and the absorption axis of the polarizing plate were changed. Table 1 shows the conditions.
The results are shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conventional general resistive touch panel.

FIG. 2 is a diagram illustrating a cross section of an arrangement of a touch panel according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating directions of an optical axis of a quarter-wave plate and an absorption axis of a polarizing plate.

Claims (3)

[Claims] 1. A touch panel disposed on a front surface of a liquid crystal display, comprising:
A touch panel for a liquid crystal display, comprising a １ ／ wavelength plate, two transparent conductive films facing each other via a spacer, a second ４ wavelength plate, and a polarizing plate. 2. The touch panel for a liquid crystal display according to claim 1, wherein the first quarter-wave plate and the second quarter-wave plate are arranged so that their optical axes are perpendicular to each other. 3. The touch panel for a liquid crystal display according to claim 1, wherein the transparent conductive film is provided on the transparent plate.