JPH03126984A - Thin film transistor control type fluorescent display panel - Google Patents

Abstract

PURPOSE:To prevent the brightness of emitted light from being reduced even in the case that the number of a picture element increases by disposing two P type TFTs in one picture element so that they may be connected. CONSTITUTION:On a glass substrate in a vacuum envelope, two P type thin film transistors (TFT) 1 and 4 are formed in one picture element. A gate signal line 2 and a data signal line 3 are respectively connected to the gate electrode and the drain electrode of a 1st transistor 1, and a source electrode is connected to the gate electrode of a 2nd transistor 4, and the source electrode of the 2nd transistor 4 is connected to a ground wire 5, and also, the drain electrode is connected to an anode phosphor layer 6 respectively. And the picture element being constituted of the two TFTs 1 and 4 and the anode phosphor layer 6 is arranged in a matrix state so as to manufacture a graphic fluorescent display panel. Thus, even in the case that the number of the picture element increases, the high-brightness graphic display whose brightness of the emitted light is not reduced can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fluorescent display panel incorporating a thin film transistor for controlling light emission inside a vacuum envelope, and particularly to a thin film transistor-controlled fluorescent display panel in which two thin film transistors are connected. Regarding.

[Conventional technology]

Fluorescent display panels are highly bright, highly visible, and can be easily converted into color, making them ideal for VTRs.

It has been used in a wide range of applications, from audio and other home appliances to various office automation equipment and data terminals. With the advancement of the information society, there has been an increasing demand for diversification of display contents, and in addition to alphabets and numbers, graphic display fluorescent display panels have been developed that display complex patterns such as kanji shapes and graphs.

It has come into production. However, because graphic fluorescent display panels use a so-called dynamic drive method in which a scanning potential is applied to the grid electrode and a data potential is applied to the anode, the duty factor decreases as the number of pixels increases, resulting in a decrease in brightness. Ta. For example, horizontal 256
A standard fluorescent display panel with 64 vertical dots
When driving at a duty ratio of 260, the grid voltage is set to 8
Under conditions of 0 V and anode voltage of 150 V, the luminance was only about 150 to 200 fL. Naturally, brightness can be increased by increasing the grid voltage and anode voltage, but this increases the price of the driving IC, making it impractical as a commercial product.

In addition, in the conventional structure in which a matrix structure is formed by a grid electrode and an anode, the manufacturing method, especially the method for installing the grid electrode, is complicated and increases the manufacturing cost.

The brightness decreases regardless of the increase in the number of pixels! In order to obtain a fluorescent display panel with a structure that is compact and does not have a control grid, there has been a strong demand for the development of a fluorescent display panel with a new structure in which a switching element is connected to each anode pixel.

On the other hand, in the field of liquid crystal displays, so-called active matrix type displays with good display contrast have been developed due to multiplex drive. This is a thin film transistor (hereinafter referred to as TPT) formed of amorphous silicon or polysilicon for each liquid crystal cell, and a typical example is as shown in FIG. 2, a connection configuration diagram. One of the source and drain electrodes of the TPT 51 is connected to the data signal line 52 , the gate electrode is connected to the gate signal line 53 , and the other source and drain electrode of the TPT 51 is connected to the liquid crystal cell 54 .

[Problem to be solved by the invention]

When using the TPT structure as described above as a switching element for the anode of a fluorescent display panel, there are the following problems and it is not practical (θ). In other words, the scanning signal line is connected to the gate line, and the data signal line is connected to the source electrode. connection,
With a connection structure in which a positive voltage is applied from the source electrode to the cathode filament at a predetermined timing, and the anode phosphor layer connected to the drain electrode emits light, it is possible to control the light emission, but the light emission time is determined by the scanning signal. As the number of scanning signal lines, that is, the number of pixels increases, the luminance of one light emission decreases in proportion to the duty factor.

The present invention makes effective use of the operating principle of TPT, and enables a high-brightness graphic display without reducing luminance even when the number of pixels increases.

[Means to solve the problem]

The thin film transistor controlled fluorescent display panel of the present invention has two P-type TFTs formed in one pixel on an anode glass substrate,
All gate signal lines and data signal lines are connected to the gate electrode and drain electrode of the first TPT, respectively.
The source electrode of the second TPT is connected to the gate electrode of the second TPT, while the drain electrode of the second TPT is connected to the anode phosphor layer, and the source electrode is connected to the ground line.

Further, the anode glass substrate forms a vacuum container together with the cover glass, in which a cathode filament and, if necessary, a grid electrode for electron beam acceleration are installed.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows the elements constituting one pixel of the present invention, and shows the connection state of two P-type TFTs.
A gate signal line 2 and a data signal line 3 are connected to the gate electrode and drain electrode of the first transistor l, respectively. The source electrode of the first transistor 1 is connected to the gate electrode of the second transistor 4. The source electrode of the second transistor 4 is connected to the ground line 5, and the drain electrode is connected to the anode phosphor.

The structure and manufacturing method of the P"I TFT used here will be explained.The structures of the two P-type TFTs are basically the same, so here the cross-sectional structure of the second transistor is shown in Figure 2. A polysilicon film is formed on a glass substrate 21 by low pressure CVD, boron ions are implanted, and then buttered to form a polysilicon source electrode 22 and a polysilicon drain electrode 23.The thickness of the picture electrode is as follows. Both were set to about 1500 A.Next, a polysilicon active layer 24 was similarly formed using the low pressure CVD method.Ion implantation was not performed on this layer.After patterning the polysilicon active layer, a 5i02 layer 25, which will become a gate insulating film, was formed. Cr electrode layer 26.A is deposited by low pressure CVD and then patterned.
After forming the n-electrode layer 27 by sputtering, a passivation layer 28 was laminated.

The aluminum electrode layer 27 is connected to an anode phosphor layer 29 made of zinc oxide phosphor.

A graphic fluorescent display panel was manufactured by arranging pixels having the structure described above, each consisting of two TPTs and an anode phosphor layer, in a matrix. FIG. 3 shows the circuit connection m'x. Here, for convenience, a 4×3 matrix will be explained. Gn
A gate signal line 31 from Gn+3 is connected to the gate electrode of the first transistor 32, and a data signal line 33 from Dn to Dn+2 is connected to the drain electrode of the eleven transistors 32, respectively. second transistor 34
The drain electrodes of (n, n), (n, n+1), (n,
n+2), -= (n+1.n), (n+1, n+1)
, -, (n+2.n+2), (n+2, n+3), respectively.

Further, all the source electrodes of the second transistors are connected to a ground line (not shown). A positive potential is applied to the ground line with respect to the cathode filament, which corresponds to the anode voltage in a normal fluorescent display panel.

〔Effect of the invention〕

As explained above, since the present invention arranges and connects two P-type TFTs in one pixel, static operation is possible. This has the revolutionary effect of not causing any In order to clarify this, the operating state in the matrix structure shown in FIG. 3 will be explained using FIG. 4.

A negative scanning signal is applied to the gate signal lines On, . . . , Gn+3. Corresponding to this timing, a negative data signal for obtaining a desired light emission pattern is applied to the data signal line. For example 1. -1. In time, (n, n) (n+1, n), (n+2.n
) are turned on. Among these, only the second transistor of the pixel (n, n) connected to Dn has its gate electrode set to a negative potential, f, and the second transistor is turned on. A positive potential is applied to the anode phosphor layer (n, n) with respect to the cathode filament via the ground line, and when the second transistor is turned on, an anode current flows, that is, irradiation is performed from the cathode filament. The phosphor is excited and emits light by the emitted electrons. At time t2, the gate electrode of the first transistor of (n, n) is reversed from negative to positive, and the first transistor is OF
F. Therefore, the gate electrode of the second transistor is in an open state, and the negative charge accumulated from t to t2 is held in the gate capacitance, and the second transistor is turned on.
Persist state. Therefore, the scanning signal is applied again t1
The ON state of the second transistor continues for up to 1 hour, and t
A negative potential is applied to Dn between ll and t12, and (n
, n) are in a light emitting state, static operation becomes possible. Is the retention time due to the gate capacitance of the second transistor sufficient at approximately 100m5ec in the prototype manufactured this time? The j value was obtained, and it became clear that there was no problem in practical use. If this holding time is longer than the cycle of the scanning signal applied to the gate signal line, the auxiliary display panel will theoretically operate statically even if the number of pixels increases, and if applied to graphic displays, it will be significantly more effective than conventional fluorescent display panels. High luminance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, FIG. 2 is a structural sectional view of an embodiment of the present invention, FIG. 3 is a diagram showing a matrix pixel configuration of the present invention, and FIG. FIG. 5 is a timing diagram illustrating the operation of this embodiment. FIG. 5 is a circuit configuration diagram showing a liquid crystal cell driven by an R film transistor. 1.32...first transistor, 2,31...
・Gate signal line, 3, 33...data signal line,
4゜34... Second transistor, 5...
・Ground line, 6.29.35...Anode phosphor layer, 21...Glass substrate, 22...Polysilicon source electrode, 23...Polysilicon Drain IIL24...Polysilicon active layer, 25
...5i02 layer, 26...Cr electrode layer,
27...AA electrode layer, 28...passivation layer, 51...thin film transistor, 52...
・Data signal line, 53... Gate signal line, 54
...Liquid crystal cell.

Claims (1)

[Claims] In a thin film transistor controlled fluorescent display panel, two P-type thin film transistors are formed in one pixel on a glass substrate inside a vacuum envelope, and a signal for controlling light emission is applied to the gate electrode and drain electrode of the first transistor, respectively. the line is connected, the source electrode of the first transistor is connected to the gate electrode of the second transistor, the drain electrode of the second transistor is connected to the anode phosphor layer;
A thin film controlled fluorescent display panel characterized in that the other source electrode is connected to a ground line.