JPH01284893A - Dot matrix system display device - Google Patents

Abstract

PURPOSE:To select a high definition display device by amplifying outputted results in case of reading out a test signal through an amplification circuit and discriminating the delicate difference of display luminance every picture element. CONSTITUTION:An invertor is constituted of a display body driving transistor Tr2, a readout Tr3, a column selection Tr4, a test signal output control Trsw and a load resistance Re. At such a time, the potential of the terminal T' of the invertor is determined according to the signals accumulated in a driving voltage accumulation capacity Cv if the circuit is normal. When the potential of the terminal T', determined thus, is inputted in the amplification circuit A, the potential of the terminal T' is a little lowered by the amount of the threshold voltage of a Trd and transmitted to a terminal Vv to be read by a tester T. Since the threshold voltage of the Trd can be controlled, the potential of the terminal T', that means, the potential of the accumulation capacity Cv, can be accurately read out if the Tr2, Tr3 and Tr4 accurately act.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a testable dot Φ matrix having a display drive transistor, a write transistor, and a read transistor for each unit pixel arranged in a dot matrix. Among the type display devices, this invention particularly relates to a fluorescent image display tube in which a phosphor is attached to IcLsI to display light.

<Prior Art> Conventionally, in a dot matrix type display device having a display drive transistor for each unit pixel, a method for determining whether each pixel is good or bad has been performed by manufacturing the display device. Although the conventional method was to actually perform display and then cut the image, electrical testing became possible by means of providing a readout transistor for each pixel in the technique described in Japanese Patent Application Laid-Open No. 57-99688. However, according to this method, when data corresponding to 1 open or 1 closed of the drive transistor is written in each pixel, and then an external determination circuit is driven through the read transistor to detect the state of the drive transistor, The disadvantage is that the load such as the capacitance and resistance of the connection line with the outside is large, and it takes time to make a determination for each pixel.

Therefore, the same applicant as the present applicant devised a dot matrix type display device that solved the above-mentioned drawbacks, and in 1985,
I have already filed the application on May 5th (Patent Application No. 1488-1488).
93. Japanese Patent Publication No. 62-9393”l.

To briefly explain this display device in the third drawing, dots and
In a device in which display elements 3 arranged in a matrix are driven by a vertical scanning circuit 1 and a horizontal scanning circuit 2, each display element 3 has a write transistor Tri,
Display drive transistor Tr2. A read transistor Tr3 and an input signal storage capacitor Cv are provided and selected by a column selection transistor Tr4. When testing a certain pixel, considering the case where the pixel in the i-th column and j-th row is tested, each transistor Tr2.
Tr3. Tr4. An inverter is formed by the control transistor Trsw and the load element Re. At this time,
If the circuit is normal, the potential at the terminal T' of the inverter is determined according to the signal stored in the storage capacitor Cv. The determination circuit Inv consisting of an inverter determines whether the potential of the terminal T' is high or low determined in this way, and the result is outputted through the output control transistor Trout.
l! When designing the constant circuit Inv, by determining the constants so as to be able to sufficiently drive the external circuit, it is possible to easily drive the externally connected load, and the test speed can be increased.

<Problems to be Solved by the Invention> Although the display device has the remarkable effect of speeding up the determination of whether a unit pixel is good or bad, a few problems remain. That is, with the above device, it is possible to determine whether the transistors constituting each pixel are short-circuited or disconnected, but! Since the 1-good and 1-bad judgment levels of the PIJ constant circuit Inv are always constant and cannot be changed, it is possible to detect differences in the driving ability of each transistor, that is, subtle differences in display brightness for each pixel. difficult to do. Particularly in fluorescent image display tubes, subtle differences in brightness deteriorate image quality. Therefore, in the test using the above-mentioned apparatus, it was not possible to determine whether the image quality was high or low.

Means for Solving the Problems> The present invention has been made in view of the above-mentioned conventional problems and in order to solve the problems. good,
The system is designed to determine defects, and the output result during readout is passed through an amplifier circuit to amplify the output result, making it possible to discern subtle differences in display brightness for each pixel. That is.

<Example> Hereinafter, one embodiment of the present invention will be explained in detail.

In FIG. 1, the same or equivalent components as in FIG. 3 are given the same reference numerals. 0 The operation of the embodiment device of the present invention shown in FIG. 1 will be explained. 0 First, consider the case where the pixel in column %i and row j is tested.〇 By turning on the input control transistor Trin, the column selection transistor Tr4, and the write transistor Trl'i, the signal input from the Vv terminal is transferred to the storage capacitor C.
It is stored in v. The signal accumulated in Cv controls the display drive transistor Tr2 to control the brightness of the display 3. At this time, the output control transistor Trou
t, the load control transistor 'l'r3w and the read transistor Tr3 are turned off. Through the operations up to this point, the test signal is written to the display body.

Next, the input control transistor Trin and write transistor Tri are turned off, and the output control transistor Tro
When ut, load control transistor Trsw, and read transistor Tr3 are turned on, a circuit as shown in FIG. 2 is formed. The operation when reading the test signal will be explained using FIG. 2.

Tr2. Tr3. Tr4. Trsw and Re form an inverter, and the potential of the terminal T' is determined depending on the potential of the test signal stored in the storage capacitor Cv and whether Tr 2 + Try and Tr4 are good or bad.0 Amplify the potential at this point. When input to circuit A, the potential of T' is slightly lowered by the threshold voltage of Trd (the voltage at which current starts flowing through the FET) and is transmitted to the Vv terminal, where it is read by test T. T
Since the threshold voltage of rd is controllable, T r
2, T r 3 *If Tr4 is working correctly,
The potential of T', ie, the potential of Cv, can be read accurately.

<Effects of the Invention> The purpose of incorporating the amplifier circuit of the present invention is not primarily to transmit electric potential, but particularly to a fluorescent image display tube. This operation is also possible with the Inv circuit shown in Figure %3, but according to the present invention, it is possible to detect differences and variations in the driving ability of the transistors in the pixel portion, and it is possible to select high-quality display devices. 0 is possible

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a dot matrix type display device of the present invention, FIG. 2 is an equivalent circuit diagram during test execution of the present invention, and FIG. 3 is a block diagram of a conventional device. Explanation of symbols l: Vertical scanning circuit 2: Horizontal scanning circuit Tr 1 : @ Reading transistor Tr 2 : Display element drive transistor Tr 3 : Read transistor 3 : Display element Tr 4 : Column selection transistor Cv : Drive voltage storage capacitance Re : Load Resistance A: Amplification circuit Trd: Amplification circuit transistor Rd: Amplification circuit resistance Trin: Video signal input control transistor Trou
t: Test signal output control transistor Trsw
:Test signal output control transistor T:Tester Rt:Tester internal resistance. Agent: Patent Attorney Takeshi Sugiyama (and 1 other person)

Claims (1)

[Claims] 1. Arrange unit pixels in a matrix, and for each pixel,
The circuit that constitutes each pixel has a drive transistor that drives the display, a write transistor that supplies a video signal for drive, and a read transistor that extracts the output level of the drive transistor to the outside. In dot-matrix display devices that allow tests to be performed electrically, particularly in fluorescent image display tubes that emit light by attaching phosphors to an LSI, the pixel portion of the circuit is driven by a minute current. A dot matrix type display device characterized in that, when reading a test signal, the output result is amplified by current, and the configuration is such that it is possible to discriminate subtle differences in display brightness for each pixel.