JPH0916330A - Transparent digitizer for display - Google Patents

Abstract

PURPOSE: To use a digitizer for a display device such as portable computer, word processor or various kinds of electronic guide board for selecting or confirming a menu by directly touching the screen of the display device with a pen or a finger. CONSTITUTION: Concerning a digitizer for coordinate detection provided with a tablet 2 having plural electrode wires mounted on a display 4 of liquid crystal or plasma and arranged for detecting X and Y coordinates to be used as the interface of application and an indicator for designating an input position, this one is the transparent digitizer for display which has plural shield layers 8 mounted on the display 4, and mounts the tablet 2 on these shield layers 8. Thus, since the digitizer can input the signal of no noise component having a high S/N, it is not necessary to perform a noise measure routine for increasing the number of data to be sampled, and high throughput can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention ensures the position of a signal when a tablet is touched with a coordinate indicator such as a finger or a detection pen, by preventing noise from the display and improving the S / N ratio. The present invention relates to a digitizer capable of inputting a signal, particularly when mounted on a large-sized display, the noise of this display is reduced.

[0002]

2. Description of the Related Art Thin and lightweight products, such as portable computers, word processors, and various electronic guide plates, that use liquid crystal as a display device are required and used in the market. Normally, these display devices are not equipped with a keyboard, and by touching the screen of the display device directly with a pen or finger,
The user's intention is entered instead. For example, it is used for menu selection and confirmation. In addition, this input method is considered to be more intuitive and easier to use than a keyboard or mouse because it is used to directly input a position, draw a picture, and sign. There is a digitizer as an input device that can be touched with a pen or a finger.The tablet, which is the input part of this digitizer, is composed of transparent electrodes, a transparent film, transparent spacers, and adhesives, and is highly transparent. Is designed so as not to interfere with the display of.

[0003]

When the distance between the input surface of the tablet and the display becomes large, a parallax is noticeable between the pointing point displayed on the screen called a pointer and the actual pointing pen or finger. Because,
I had to stick the digitizer device to the display surface. In the display device, noise due to the display portion and noise due to the backlight are induced on the tablet. This noise signal is larger as it is closer to the display device which is the source, and when the tablet is directly placed on the display device, it may detect the wrong coordinates by interfering with the position detection signal which is the original signal. ,
When noise countermeasures are taken by software When data is sampled and noise is identified, the number of coordinates generated per unit time is extremely low, making it difficult to use or not being able to detect the position. Was. In particular, when the display is large, not only the signal at the electrode used for position detection changes depending on the position, but also the electrode wire acts as an antenna with a long length and receives a lot of noise, which makes detection difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the conventional problems, and is provided for detecting X, Y coordinates used as an interface for an application mounted on a display such as liquid crystal or plasma. A tablet having a plurality of electrode lines, and a coordinate detection digitizer having an indicator for designating an input position of the tablet, wherein a plurality of shield layers placed on the display and a shield layer on the shield layer are provided. We propose a transparent digitizer for a display with a tablet mounted on it.

[0005]

According to the present invention, a plurality of shield layers are provided on the display surface side of the display of the digitizer tablet to prevent the influence of noise from the display on the electrode lines arranged on the tablet. The shield layer is subjected to treatment such as roughening the surface so that interference fringes do not enter, and is connected to the signal ground or the frame ground, which is a digitizer circuit. With respect to the noise generated from the display surface of the display, local large noise is reduced to a low level as a whole by the shield layer, and propagates in a direction away from the display surface.
The noise passing through the plurality of noise shields is reduced and the signal for position detection is not disturbed. Since the digitizer can input a signal that does not include a noise component having a high S / N ratio, it is not necessary to perform a noise countermeasure routine that increases the number of data samplings, and thus high processing capability can be obtained in coordinate generation. The change in the transmittance due to the shield layer is small, the display on the display is not difficult to see, and the input can be reliably performed, which improves the usability for the user.

[0006]

An embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of an input device embodying the present invention.
FIG. 2 is a development view of the digitizer, and FIG. 3 is an overall appearance view.
In this embodiment, a case where a capacitive coupling digitizer is attached to a plasma display will be described as an example. The digitizer 1 is composed of a main substrate (not shown), a transparent tablet 2 and a pen 3, is directly mounted on the plasma display 4, and is housed in the housing. The tablet 2 has comb-teeth-shaped electrode lines, and a certain signal is applied to this electrode line to detect the signal by capacitive coupling with the pen 3 and convert it into a voltage, the voltage level and the number of the electrode line. The position of the pen 3 is detected by the control circuit of the main board.

Next, the structure of the tablet 2 will be described. For the purpose of preventing friction from the pen 3 and deterioration of the electrode wire, the input surface 5 with which the pen 3 is abutted is subjected to a transparent acrylic or glass antiglare treatment. The input surface 5 is bonded with an electrode layer in which electrode wires 6 and 7 in the X and Y directions for position detection are laminated with a transparent insulating adhesive. A layer having resistance is adhered as the shield layer 8. Each layer except the input surface 5 is preferably a substrate having a high transmittance, for example, an ITO film or other transparent low resistance film may be formed on PET having a thickness of about 125 μ. Has a 200 Ω / □ ITO film uniformly deposited. The resistance film of the shield layer 9 can be directly connected to the signal ground or the frame ground through the main board and the connector. The X and Y electrode lines 6 and 7 are etched in a long comb-like shape on a film-like dielectric layer similar to the shield layer 8, and the X electrode line 6 and the Y electrode line 7 are bonded so as to be orthogonal to each other. ing.
Further, the respective layers are adhered by a transparent adhesive agent and processed so that interference fringes cannot be seen even when placed on the display 4.

As the operation of the digitizer 1, a signal is applied to each electrode line from the main substrate, and a minute current is induced in the pen 3 due to capacitive coupling between the tip of the pen 3 and the electrodes 6 and 7.
The main board sends a carrier signal to the X or Y electrode lines 6 and 7, and inputs a signal electrostatically coupled to the electrode lines from the pen 3 to reproduce the waveform. In the signal input from the pen 3, not only the signal coupled with the electrode line but also external noise is picked up, so that only the signal from the electrode line is taken out by a bandpass filter. The signal that has passed through the bandpass filter is detected and changed to a DC signal, which is then A / D changed and digitized by the control circuit. The location of the pen is calculated from the relationship between the data level and the electrode line to which the signal is applied. However, when the above-mentioned operation is carried out by mounting it on the large-sized display device 4, backlight noise of this large-sized display 4 and spark noise from each pixel on the display surface for displaying, DC before A / D conversion are generated. The signal level is affected so that the DC signal cannot be stably measured, and the proper A / D conversion value cannot be taken out. The signal level at which a large signal is supposed to be input due to the presence of the pen 3 is actually In some cases, the location of the pen 3 is not correctly indicated due to the fact that the pen 3 is small or a large signal is input due to noise at a place where the pen 3 is not originally present and the signal is small.

As a countermeasure against this noise, it is conceivable to increase the sampling frequency by scanning the same point several times by software to prevent noise from being detected and incorrect coordinates are calculated. Depending on the number of times and the method of judging noise, if input is not possible due to the effect of noise, or if the number of coordinates per unit time is reduced or the pen is moved fast, it will not be possible to input and the usability will deteriorate. . When considering a shield method by hardware, a resistance film having a low electric resistance as a normal electrostatic shield generally has low transparency,
Since it looks silvery, brown, or green, what seems to be the most suitable was not suitable for a transmissive tablet.

Therefore, by using a plurality of the above-mentioned sheets, a shield function is obtained. Even if a plurality of the above-mentioned sheets are used, the sheet has a high transparency and the ITO film is uniformly vapor-deposited. It is possible to use without unevenness without causing unevenness. The image of the plasma display 4 has a strong reddish color as a whole, and since the color filter 9 is attached to the outside of the display 4 to perform color correction, the shield layer 1 is provided between the color filter 9 and the display 4.
The tablet 2 is attached to the upper part of the color filter 9 with 0 interposed therebetween. These shields are connected to the signal ground or frame ground of the main board, and display noise will fall to the ground.

Gas is enclosed in each pixel of the plasma display 4, and a pair of electrode lines are provided to repeatedly charge and discharge the electrode lines to generate ultraviolet rays. Since this ultraviolet ray excites the phosphor to perform color display, the voltage fluctuation is large and noise is generated due to its nature. The maximum noise actually generated was + 12V on the plus side and -12V on the minus side. Generally, the display method of the display 4 is to display each pixel in the horizontal direction from top to bottom. The electrodes of the tablet 2 arranged in the horizontal direction, that is, the electrode lines 7 for detecting the Y-axis direction are arranged parallel to the noise source, and the noise of each pixel is continuously received in time. Furthermore, the Y electrode line 7 is longer than the X-axis electrode line 6 which is the vertical direction, and the electrode line 1 has an electrical characteristic.
Since the resistance value of the book needs to be low, the electrode width must be wide. Since the Y electrode 7 must be below the X electrode 6 as viewed from the input side so that the Y electrode 7 does not block the X electrode 6, the Y electrode layer is formed on the display 4 surface with the X electrode line. Since it is closer to the 6th layer and a crosstalk phenomenon occurs, noise is more likely to occur than the X electrode 6.

FIG. 4 shows a change in noise component when the shield layer 10 is attached as described above. Display 4
When the pixel display of 1 is used as the radiation source, the pointing vector of the display, which is the flow of the radiant energy density per unit area of the noise signal, is P, the magnetic field strength (component) is H, and the electric field strength (component) is E. Pointing The vector is represented as P = H × E and gives a flow of magnetic field energy, which is carried and propagated by the electric and magnetic fields. However, the use of the shield barrier 11 causes reflection loss, internal absorption loss, and repeated reflection loss in each magnetic field / electric field vector, resulting in signal attenuation. From the pointing vector P0 of display 4,
FIG. 4 shows a change in state due to passage to P ′ on the opposite side of the shield layer 10 as the shield barrier 11. When the component of the pointing vector P consists of Hz0 and Ey0, the shield barrier 11 causes the reflected components Ey'0 and Hz'0 to be lost at the time of input, the shield layer 10 internally absorbs Ey1 and Hz1, and finally the reflected component. Since the loss Hz2 and Ey2 are generated, finally E ″ y
It changes to 1 and H ″ z1 component.

Electromagnetic energy is carried by an electric vector and a magnetic vector, but in the conductor, the electric vector becomes smaller and the wavelength becomes shorter. When the plane wave travels in the shield barrier 10, the wavelength λ in the conductor is reduced as follows, where λ0 is the wavelength in vacuum.

(Equation 1) c: speed of light r: conductivity μ: permeability ω: each frequency

The display frequency of the display 4 is about 25.
The high frequency is around MHz, and the spark noise generated by each pixel for the actual display is higher. Generally, in the case of high frequency noise, the relationship between the thickness of the shield wall and the shield effect is invalid if the shield wall is too thin, but the thinner the better,
Although it depends on the material, it is said to have a maximum at several μm. Actually, the thickness of the ITO film is about 0.1 μ, and a sufficient shield effect can be expected by using a plurality of ITO films. The two shield layers with a distance serve as an electrostatic shield and an electromagnetic shield, and are separated by a distance to suppress the effect of display noise, and because they have high transparency, they work effectively as a digitizer shield.

An example of this application is a transparent conductive material in which a color filter is sandwiched in the middle, but it can be processed to suppress any tint. Therefore, by using a shield layer which also serves as a shield layer and a color filter, it is inexpensive and Parallax can be prevented by reducing the thickness of the color filter.

In the hardware of the main board, a signal is transmitted / input based on a fixed carrier signal, and noise is removed by applying a bandpass filter and a phase filter in particular, and noise emitted from the display 4 is eliminated. The noise level is reduced by the shield layer 10,
Similarly, noise is removed by the plurality of shield layers via the color filter 9, so that input from the pen 3 can be performed in a state where there is no noise in the electrode lines. This means that it is possible to take measures against noise without causing a problem of deterioration in processing capability due to an increase in the number of times data is sampled by software.

[0017]

According to the present invention, since the digitizer can input a noise component having a high S / N ratio by the above configuration,
It is not necessary to take a noise countermeasure routine that increases the number of data samplings, and high processing capability can be obtained. In addition, display noise is reduced even on large displays, and the digitizer can reliably input coordinates and improve operability.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an input device embodying the present invention.

[Figure 2] Development view of the digitizer

[Figure 3] Overall appearance

[Figure 4] Shield explanatory diagram

[Explanation of symbols]

 1 Digitizer 2 Tablet 3 Pen 4 Display 5 Input surface 6 X electrode 7 Y electrode 8 Shield layer 9 Color filter 10 Shield layer 11 Shield barrier

Claims (2)

[Claims] 1. A tablet having a plurality of electrode lines arranged to detect X and Y coordinates to be used as an interface of an application, which is mounted on a display such as liquid crystal or plasma, and an input position of the tablet is designated. A transparent digitizer for a display, comprising a plurality of shield layers mounted on the display, and a tablet mounted on the shield layer, the coordinate detection digitizer having an indicator. 2. The transparent digitizer for a display according to claim 1, wherein the shield layer is made of a transparent conductive material.