JPS62256021A - Display device with touch panel - Google Patents

Abstract

PURPOSE:To enable an image to be visualized even under more intense external light, by constituting a display device such that the contrast ratio of the display screen in which there is added the influence of reflection on the display device and a touch panel of an external light is a maximum. CONSTITUTION:Assuming that reflectance of the first and the second transparent substrates 21 and 22, and a display device 1 are set as R1-R3, light transmittance of the substrates 21 and 22, as T1 and T2, the light emitting luminance of the display device 1, as B when lightening, and as O when no lightening, and external luminance, as E, the contrast ratio CR by appearances of the display picture plane of the device can be reduced to the value in which both the R1 and the R2 are sufficiently small values compared with 1, that is, to a glass 0.07 in thickness. Therefore, an expression can be obtained approximating (1-R1) or (1-R2) to 1, neglecting multipath reflection because it is so small, and furthermore, finding a condition in which the CR reaches a maximum by approximating to 1 because the T2 is sufficiently in the neighborhood of 1. And the contrast ratio of the display picture plane can be optimized by reducing the light transmittance T1 considerably so as to almost satisfy the expression.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a display device with a touch panel (tentacle input device) used in a man-machine interface part of various information systems. Figure 2 is for example U, 8, Patent 4.2.
20,815 is a partial sectional view showing a conventional display device with a touch panel, in which (1) is a display device, (2) is a CRT (cathode, cathode ray tube), and (2) is a display device (CRT). 1) is a touch panel placed on the display screen.

The touch panel (2) has a suitably flexible first transparent substrate (21) and second transparent substrate (22). These transparent substrates (21) (22) are made of transparent glass or transparent plastic, and have a transparent electrode (211) @1 and a second transparent F! A
It has an electrode (221).

The transparent electrodes (211) (221) are made of metal oxide such as indium oxide. (23) is a spacer that maintains the distance between the first transparent substrate (21) and the second transparent substrate (22).

Next, the operation will be explained.

First, the electrical operation will be explained. When a specific part of the first transparent substrate (21) is pressed with a finger according to the display screen of the display device (1), the first transparent substrate (21) is elastically deformed and the first transparent electrode (211 ) is the second transparent electrode (22
1) come into contact with. The contact point is, for example, a transparent electrode (21
1) , (221) can be regarded as resistive sheets facing each other, so by applying a gradient potential to one electrode and measuring the voltage appearing on the other electrode, the position in the direction of the gradient can be detected.

By switching the inclination direction at high speed, the position of the two-dimensional child surface can be electrically detected at high speed.

Next, the optical operation, which is the key point of this invention, will be explained. The light exiting the display device (1) passes through the second transparent substrate (2
2) and the first transparent substrate (21) to reach the opening. On the other hand, in the observer, external light passes through the first transparent substrate (21) and the second transparent substrate (22) and reaches the display device (1), and the light reflected there returns to the display device (21) (22). ) and the first transparent substrate (
The reflected light at 21) and the reflected light at the second transparent substrate (22) are seen at the same time as the above-mentioned light.

The transmittance of both transparent substrates (21) (22) is made as high as possible in order to keep the display brightness as high as possible.
It is usually 7096 or more.

[Problems to be Solved by the Invention] Since the conventional display device with a touch panel is configured as described above, when strong external light is incident, reflected light from the first and second transparent substrates and the display device is However, there is a problem in that the signal light is stronger than the signal light emitted by the display device itself, resulting in poor visibility.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a display device with a touch panel that can maintain a high display contrast ratio even with relatively strong external light.

[Means for solving problems]

In the display device with a touch panel according to the present invention, the light transmittance of the touch panel is given by the light reflectance of the display device and the light reflectance of the transparent substrate constituting the touch panel, and the light transmittance of the touch panel is given by the light reflectance of the transparent substrate constituting the touch panel. This is the value when the contrast ratio of the display screen including the influence of reflection is at its maximum.

[Effect]

In the display device with a touch panel according to the present invention, the light transmittance of the touch panel is set to a value at which the contrast ratio of the display screen given by considering the influence of reflection of external light is maximum, that is, the light transmittance of the conventional device. Since the value is set to a relatively small value, the light intensity of the external light reflected by the display device and entering the eyes of the optical device is greatly reduced because the light passes twice through the touch panel with low light transmittance.

On the other hand, since the light emitted from the display device 1' passes only once, attenuation is relatively small. Therefore, when the intensity of external light is strong, the contrast ratio of the display is greatly improved.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a partial sectional view showing a display device with a touch panel according to an embodiment of the present invention. This is similar to the conventional one shown.

(2) is a touch panel, which is structurally the same as the conventional one, except that the first transparent substrate (21) has a predetermined light absorption property.

The material is not glass or plastic, which is as transparent as possible, which has been used in the past, but glass or plastic that has been purposely made to have an appropriate light absorbing property, as will be described later, and has been made appropriately thin to make it flexible.

This first transparent substrate can be imparted with light absorption properties, for example, by applying it to the material itself, coating the surface with a substance that has light absorption properties, or pasting a sheet with similar properties. In such a display device with a touch panel, when the first transparent substrate (21) is pressed with a finger, an electrical signal corresponding to the pressed position is obtained, and a predetermined input is performed. Alternatively, the electrical operation is the same as the conventional one.

Next, the difference in optical characteristics, which is the key point of this invention, will be described below.

Now, the first transparent substrate (21), the second transparent substrate (22)
and the light reflectance of the display device (1) are R1%R25, respectively.
R3, the light transmittance of the first two (21) (22) is T, %T
2, the luminance brightness of the display device (1) is B (when lit) or 0 (when not lit), and the external light brightness is E, then the apparent contrast ratio C1 of the display screen of such a device is s R
Since both 1 and R2 can be set to sufficiently small values compared to IE (about 0.07 for glass), 1-E l or 1-R2 can be approximated by 1, and since multiple reflections are sufficiently small, this can be ignored. Furthermore, T2 is sufficiently close to 1, so if it is approximated by 1, = 1+ [R1+T1 (R2+R8) IE...
...(1).

Formula (1) is a general formula and naturally applies to conventional formulas.

It can be seen that using this formula to find the conditions under which OR is maximized. In this invention, the contrast ratio of the display screen is optimized by greatly reducing the light transmittance TI so as to substantially satisfy equation (2).

At this time, CR becomes.

As mentioned above, the conventional method is expressed by equation (1), and the value of T is set to be as large as possible (usually 70
92%), the display of the present invention, which provides the maximum contrast ratio expressed by equation (3), significantly improves the visibility of the display.

This showed very good agreement with the experimental results using the actual device.

Conventionally, there was a structure in which a light filter (including a color filter) with an experimentally determined light transmittance was placed in front of a light-emitting display device such as a CRT, but this did not have a touch panel and could not be touched. It was not possible to input data, and if a touch panel was simply placed on the front of such a device, visibility would be poor due to the reflection of outside light on the touch panel, and the significant effect of placing a filter would be poor. cannot be obtained.

In the above embodiment, the touch panel (2) is made up of two transparent substrates, but it may be made up of one or more transparent substrates.

Further, although a transparent type with a pole is shown, it would be better to use a type with a different position detection principle.

Furthermore, the contrast ratio may be further improved by subjecting the surface of the transparent substrate opposite to the display device (1) to a light reflectance reduction treatment such as multilayer coating.

Further, the same surface may be subjected to a process to impart light diffusivity, such as by providing unevenness, to eliminate specular reflection so that the specularly reflected image does not appear to overlap the displayed image.

In addition, a sheet may be attached to the surface of the transparent substrate to reduce the light transmittance and the surface has been treated to reduce the light reflectance or to have a light diffusive property. [Effects of the Invention] As described above, According to this invention, the light transmittance of the touch panel is given by the light reflectance of the display device and the light reflectance of the transparent substrate constituting the touch panel, and the influence of reflection of external light on the display device and the touch panel is added. Since the contrast ratio of the display screen is set to the maximum value, it is possible to obtain a display device with a touch panel that is visible even under stronger external light.

[Brief explanation of drawings]

1 is a partial sectional view showing a display device with a touch panel according to an embodiment of the present invention, and FIG. 2 is a partial sectional view showing a conventional display device with a touch panel. (1) Display device, (2) Touch panel,
(21)...first transparent substrate, (22)...second
Note that in the figures, the same reference numerals indicate the same or equivalent S portions.

Claims (6)

[Claims] (1) In a light-emitting type display device and a device equipped with a touch panel placed on the display screen of this display device, the light transmittance of the touch panel is defined as the light reflectance of the display device,
and the light reflectance of the transparent substrate constituting the touch panel, and is the value when the contrast ratio of the display screen is maximized, including the influence of reflection of external light on the display device and the touch panel. A display device with a touch panel. (2) A display device with a touch panel according to claim 1, wherein a predetermined light transmittance is obtained depending on the material of the transparent substrate. (3) A display device with a touch panel according to claim 1, wherein a coating layer is provided on a transparent substrate to obtain a predetermined light transmittance. (4) A display device with a touch panel according to claim 1, wherein a light-absorbing sheet is attached to a transparent substrate to obtain a predetermined light transmittance. (5) The display device with a touch panel according to any one of claims 1 to 4, wherein the transparent substrate surface on the side opposite to the display device is subjected to a light reflectance reduction treatment. (6) A display device with a touch panel according to any one of claims 1 to 4, wherein a light-diffusing treatment is applied to the surface of the transparent substrate opposite to the display device.