JPH02257551A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce unevenness of the brightness on an image by furnishing modulating grid electrodes for controlling passage and shutoff of an electron beam emitted from an electron emitting element, changing the area of an opening in each modulating grid electrode, and thereby making uniform the beam current. CONSTITUTION:Striped grid electrodes GR is furnished in the middle of a base plate S and a face plate FP. Each of these electrodes is provided with an open hole Gh to allow penetration by an electron beam. Therein open holes Gh in the grid electrodes have different opening areas in relationship as Gha<Ghb<Ghc. Usage of these grid electrodes GR shall be such that grid electrodes G1 and G200 at the two ends have the smallest opening, i.e., (a) the grid electrode G100 in the center has the greatest, (c), and ones between the ends and the center have middle opening area, (b).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention utilizes a large number of electron-emitting devices, a grid electrode for modulating a group of electron beams emitted from the large number of electron-emitting devices, and irradiation of the electron beam. The present invention relates to an image forming apparatus including a target for forming an image.

[Prior art] Conventionally, as an element that can emit electrons with a simple structure,
For example, M.I. Ellingson (M,I.

A cold cathode device announced by Elineon et al. is known. [Radio Engineering Electron Physics (Radio Eng, Electr
on.

Phys, ) Volume 10, pp. 1290-1296, 19
1 In 1965, this type of electron-emitting device includes one using the Snug (Sb) thin film developed by Ellingson et al., and one using an Au thin film [G. Dittmer: thi
nSolid Films”), volume 9, page 317,
(1972) 1. ITO thin film [M
Hartwell and C.G. Fonstad
“I EEE E Trance” E Deco
) (M, Hartwell and C,G,F
onstad: “IEEE Trans.

εD Conf,”) page 519, (1975)]
, by carbon thin film "Hisashi Araki et al.""Vacuum", No. 2
Vol. 6, No. 1, p. 22, (1983)].

In addition to the above, many promising electron-emitting devices such as thin-film thermal cathodes and MIM-type emitting devices have been reported.

Together with rapid advances in film-forming technology and photolithography technology, it is becoming possible to form a large number of elements on a substrate. Application to various image forming devices such as drawing devices is expected.

[Problems to be Solved by the Invention] However, when applying these elements to image forming devices, generally a large number of elements are arrayed on a substrate, and electrical connections are made between each element using thin or thick film electrodes. However, due to the voltage drop caused by the wiring resistance, a phenomenon occurs in which the voltage applied to each element varies. As a result, the amount of current of the electron beam emitted from each emitting element varies, causing a problem of uneven brightness (density) in the formed image forming device.

Figure 9 and Figure 1O are diagrams to explain this problem in more detail. In both figures, (a) is an equivalent circuit diagram including an electron-emitting element, wiring resistance, and power supply, and (b) is an equivalent circuit diagram of each electron-emitting element. A diagram showing the potentials of the positive and negative electrodes of the elements, and (C) a diagram showing the voltages applied between the positive and negative electrodes of each element.

FIG. 9(a) shows N electron-emitting devices D connected in parallel.
This shows a circuit that connects τ~DH' and the power supply VE.
The positive electrode of the power source and the positive electrode of the element DN are connected, and the negative electrode of the power source and the negative electrode of the element DN are connected. In addition, the common wiring that connects each element in parallel is r
It shall have a resistance component of (In the image forming device,
Pixels that are targets of electron beams are usually arranged at equal pitches. Therefore, the electron-emitting devices are also spatially arranged at regular intervals, and the wiring connecting these devices has the same resistance value between the devices as long as there is no manufacturing variation in width or film thickness. ) Furthermore, it is assumed that all the electron-emitting elements R, ~DN have approximately the same resistance value Rd.

In the circuit diagram of FIG. 9(a), FIG. 9(b) shows the potentials of the positive and negative electrodes of each element. The horizontal axis of the figure shows the element numbers D1 to DN, and the vertical axis shows the potential.・
The mark represents the positive electrode potential of each element, and the square mark represents the negative electrode potential.For convenience, the mark (■
) are connected with solid lines.

As is clear from this figure, the voltage drop due to the wiring resistance r does not occur uniformly (on the positive side, it is steeper the closer it is to the element DN, and conversely, on the negative side, the closer it is to the element DN, the steeper it is. This is because on the positive electrode side, the closer to D, the larger the current flows through the wiring resistance r, and on the negative electrode side, the closer to DN, the larger the current flows.

From this, the voltage applied between the positive and negative electrodes of each element is plotted in FIG. The horizontal axis of the figure is ~DN
The horizontal axis shows the applied voltage.
), 0 is connected with a solid line for convenience (to make it easier to see the trend).

As is clear from the figure, in the case of the circuit shown in figure (a), the closer the elements at both ends (D, and ) are, the greater the voltage is applied, and the applied voltage is lower to the elements near the center. becomes smaller.

Therefore, the electron beam emitted from each electron-emitting device is
The beam current increases toward the elements at both ends, which is extremely inconvenient when applied to an image forming apparatus. (For example, the image near both ends will have a high density, and the image near the center will have a low density.) On the other hand, what is shown in Figure 1O is one side of an element array connected in parallel (in this figure, element D1 This is the case when the positive and negative poles of the power supply are connected to the In the case of such a circuit, as shown in FIG. 3(b), the voltage drop due to the wiring resistance r becomes thicker as the positive electrode side and the negative electrode side are closer to each other.

Therefore, the voltage applied to each element becomes larger as it approaches D, as shown in FIG.

As shown in the two examples above, the degree of variation in the applied voltage for each element depends on the total number of elements connected in parallel N, the ratio of element resistance Rd to wiring resistance r (= Rd/r), or power supply connection. Although it differs depending on the position, in general, the larger N is and the smaller Rd/r is, the more pronounced the variation is.Furthermore, the connection method shown in Fig. 1θ has a larger variation in the voltage applied to the element than the connection method shown in Fig. 9. .

For example, with the connection method shown in Figure 9, the element resistance Rd = 1, Ω, r =
In the case of lOmΩ, if N = 100, comparing the element with the largest applied voltage and the element with the smallest applied voltage, V +
maX:v++t1゜=about 102:100, but if N=1000, then V, , :V,, n=
The dispersion ratio becomes large at 472:100.

Also, N = 1000. Rd = 1 kΩ, r=
In the case of 1 mΩ, V , , :V 111 = 127
: About 100, but when r = 10mΩ,
The degree of variation becomes large, such as V +++ax:Vat, = about 472:100.

As explained above, when multiple electron-emitting devices with the same characteristics are connected in parallel, the voltage effectively applied to each device varies due to the voltage drop caused by wiring resistance. The amount of emitted electron beam becomes non-uniform, which is inconvenient when applied as an image forming apparatus.

In particular, when attempting to realize a large-capacity display device with a large number of pixels (that is, a large number of N), the rate of variation becomes significant, and uneven brightness (density) of images becomes a major problem.

[Means for Solving the Problems (and Effects)] According to the present invention, a modulation grid electrode is provided for controlling passage and blocking of electron beams emitted from each electron-emitting device, and an aperture of each modulation grid electrode is provided. By changing the area of the holes (holes), the target is irradiated with the same beam current from all elements.

More specifically, when the electron-emitting device has wiring as shown in FIG. 9, the opening area of the grid electrode at the center is made larger than at both ends. In addition, in the case of wiring as shown in FIG. 1O, the grid electrode farther from the power supply side of the element has a larger opening area.

By the above means, the decrease in the amount of electron beam emitted per unit area from the electron emitting part caused by the voltage drop is compensated for by increasing the effective electron beam by expanding the aperture area of the modulation grid electrode, and as a result, the effective electron beam is increased. This has the effect of producing uniform image density on the forming surface.

[Example J The present invention will be specifically explained in detail below using examples.

1 to 7 illustrate a flat plate image forming apparatus which is an embodiment of the present invention.

FIG. 1 shows the structure of a display panel. In the figure, VC is a glass vacuum container, and FP, which is a part of the vacuum container, is a face plate on the display side.

A transparent electrode made of, for example, ITO is formed on the inner surface of the face plate FP, and a red,
Green and blue phosphors are painted separately in a mosaic pattern, and a metal back treatment known in the CRT field is applied. (The transparent electrode, phosphor, and metal back are not shown.) Furthermore, the transparent electrode is electrically connected to the outside of the vacuum vessel through a terminal EV in order to apply an accelerating voltage.

Further, S is a glass substrate fixed to the bottom surface of the vacuum container VC, and on the top surface thereof, the electron-emitting devices exemplified in the prior art section are arranged in 200 pieces x 200 rows. The electron-emitting device groups are electrically connected in parallel in each column, and the positive electrode side wiring (negative electrode side wiring) of each column is connected to the terminal op.
l~Dp3゜. (Terminals Dm+ to Dllio.) are electrically connected to the outside of the vacuum container. That is, in this device, 200 element rows are formed on the substrate S using the power feeding method shown in FIG. 9 described above. (The number of elements per row is 200.) Furthermore, a striped grid electrode GR is provided between the substrate S and the face plate FP, and the grid electrode GR is perpendicular to the element row. 200 electrodes are provided, and each electrode has a hole G for transmitting the electron beam.
R (opening) is provided. In the example shown in FIG. 1, one hole Gh is provided corresponding to each electron-emitting device, but as will be described later, the feature is that the opening area of the hole can be changed as appropriate depending on the electrode. .

Each grid electrode GR has a terminal G, ~G2°. It is electrically connected to the outside of the vacuum vessel.

This display panel has 200 electron-emitting device rows and 20
An XY matrix is composed of zero grid electrode rows. Sequentially driving (scanning) electron emission columns one by one
By simultaneously applying a modulation signal for one line of the image to the grid electrode array in synchronization with this, the irradiation of each electron beam onto the phosphor is controlled, and the image is displayed line by line.

Next, FIG. 2 is a plan view showing a part of the grid electrode GR used in the display panel of FIG. 1, and (a)
Three types are shown: , , (b), and (c). As is clear from this figure, the holes Gh of each grid electrode have different opening areas and have a size relationship of Gha < Ghb < Ghc.

These grid electrodes GR having different opening areas are used in the display panel shown in FIG. 1 in the following manner. That is, for the grid electrodes at both ends (G and Gaoo), use the one with the smallest opening (a), and for the central grid electrode GR (G+o.), use the one with the largest opening (c
), and (b) with an intermediate opening area is used between both ends and the center.

Specifically, for example, G, ~G8° and GI'FI-Gl
. (a) in a, Gs+-Gyo and Gtst-Gty
. (b) to G? By constructing a display panel using (C) in 1-GI30, it has become possible to significantly reduce the uneven brightness (density) of images, which has been a problem in the past.

In order to explain the effects of grid electrodes having different opening areas, the output characteristics of the electron-emitting device are shown in FIG. 3, and the operating characteristics of the grid electrode are shown in FIG. 4.

FIG. 3 shows an example of the output characteristics of the electron-emitting device used in this display panel. (Electron-emitting devices include cold cathode devices, thin film hot cathodes, and MI
Any device capable of arraying a large number of M-type emitting devices or devices similar to these devices may be used. Therefore, the output characteristics shown in FIG. 3 are only one example of these, but the present invention Even if the characteristics of the elements are different, similar effects can be achieved by appropriately adjusting the opening area of the grid electrode. ) In this figure, the horizontal axis is the voltage applied to the electron-emitting device, and the vertical axis is the output beam current emitted from the electron-emitting device. Figure 9 (C)
As explained above, in electron-emitting devices connected in parallel, variations occur in the applied voltage (for convenience, the maximum value of the applied voltage is expressed as Vmax, and the minimum value as Vmin), which is clear from the graph in Figure 3. As shown, from the element to which Vmax is applied (both ends of the column, i.e., and D2°), EBm
EB is emitted from the element (center of the column, ie Dl...) to which the electron beam of ax is emitted and VIIIin is applied.
An electron beam of min is emitted.

To simplify the explanation, only the elements that output EBmax and EBmin will be described, but according to the present invention,
The grid electrode with the smallest opening area is used for the element that outputs EBmax, and the grid electrode with the largest opening area is used for the element that outputs EBmin.

Therefore, as shown in FIG. 4, when the phosphor screen potential (acceleration voltage) of the display panel is kept constant (for example, 10 KV) and the grid electrode extraction voltage is kept constant (for example, 15 KV), the grid electrode void Gh The current reaching the phosphor screen through the EBmax element and the EBmin element are equal.

As is clear from the above description, by appropriately changing the opening area of the grid electrode in accordance with the output beam current of the electron-emitting device, it is possible to significantly reduce the brightness (density) unevenness of the display panel. As mentioned above, in this embodiment, FIG. 2(a).

Although three types of opening areas (b) and (e) were used, in order to more precisely reduce unevenness in brightness (density), the opening area may be changed for each grid electrode.

FIG. 5 schematically shows the opening area of each grid electrode.
It is easily possible to form different openings for each grid electrode using photolithography and etching techniques.

The inventors prototyped a planar image forming apparatus using grid electrodes as shown in FIG. The luminance (density) unevenness of the emitted light is 1/. We succeeded in reducing it to below.

Next, the outline of the method for driving the display panel of this embodiment will be explained.

FIG. 6 shows a block diagram of an electric circuit for driving the display panel shown in FIG.
1 is the display panel shown in FIG.

2 is an element array drive circuit, 3 is a modulation grid drive circuit, and 4 is a high voltage power supply. In the electrode terminal EV of the display panel 1,
An accelerating voltage of about 10 KV is supplied from the high voltage power supply 4. In addition, the negative electrode side wiring terminals (Da, ~D
m*. . ) is grounded to the ground level (OV), and the positive electrode side wiring terminal (Dp-apl...) is connected to the element column drive circuit 2. In addition, the grid electrode has terminal G,
~G8°. It is connected to the modulation grid drive circuit 3 through.

Furthermore, an element array drive circuit 2 and a modulation grid drive circuit 3
From there, a signal voltage is output at the timing shown in the drive time chart of FIG. (a) to (d) in Figure 7 are
Dp+, Dps, of the display panel l from the element column drive circuit 2;
Dps, and D.I. . Indicates the signal applied to the terminal,
As you can see from the figure, Dp+, Da snow.

Driving pulses with an amplitude vi [V] are sequentially applied in the order of Dps, ass (DI)4-Dp+ss (in the figure), and 09*oo. In synchronization with this, the modulation grid drive circuit 3 sends a signal to the terminal GI-G ◎0 as shown in Fig. 3 (
A modulation signal (v6 (ON) or V, (OFF)) is applied at the timing shown in e). V for each terminal
, (ON) level, or Va (OFF) level is determined by the pattern of the displayed image.

Although one embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this. For example, when the electron-emitting device is wired using the power feeding method shown in the above-mentioned Fig. 1θ, the power feeding side Grid electrodes for elements close to (i.e. G,
It is effective to reduce brightness (concentration) unevenness by increasing the opening area of the holes as the grid electrode for the element is farther away from the power supply side (ie, on the a-OO side) than on the side).

Further, the number of holes provided in the grid electrode does not necessarily have to be one for each electron-emitting device;
As shown in the figure, a mesh-like structure consisting of a large number of holes may also be used.
As shown in c), it is possible to change the opening area by changing the number of holes to be formed.

[Effects of the Invention] As explained above, in the present invention, the opening area of the holes provided in the grid electrode is made to have different sizes depending on the variation in the electron beam current emitted from the electron-emitting device. , it is possible to make the beam current reaching the phosphor screen uniform regardless of the element. As a result, the conventional problem of uneven image brightness (density) can be solved, and the practical performance of a thin, large-area, large-capacity image forming apparatus can be greatly improved.

The present invention can be applied to most image forming apparatuses having an electron source section in which a large number of electron-emitting devices are connected in parallel, in addition to the flat image forming apparatus shown in the embodiments, such as electron beam lithography. It is also extremely effective in the field of devices and image recording devices.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a part of the display panel, and FIG. 2 is a perspective view showing a part of the display panel.
FIG. 3 is a partial plan view of a modulation grid electrode used in a display panel; FIG. 3 is a diagram showing the output characteristics of an electron-emitting device used in this image forming apparatus; FIG. 4 is a diagram showing operating characteristics of the modulation grid electrode. , FIG. 5 is a graph to simply show the area of the opening formed in each modulation grid electrode, FIG. 6 is a diagram showing a block circuit for driving the display panel, and FIG. 7 is a graph showing the area of the opening formed in each modulation grid electrode. FIG. 8 is a partial plan view of a grid electrode showing another embodiment; FIG. 9 and FIG. 1θ are diagrams for explaining conventional problems. 1 - Display panel GR - Grid electrode 2 - Element row drive circuit Gh - Hole 3 - Modulation grid drive circuit 4 - High voltage power supply

Claims (3)

[Claims] (1) A multi-electron beam source in which a plurality of electron-emitting devices are electrically wired in parallel, a plurality of modulation grid electrodes for passing and blocking the electron beams emitted from the electron-emitting devices, and a plurality of modulation grid electrodes for passing and blocking the electron beams emitted from the electron-emitting devices; a target for forming an image by irradiation, and each of the plurality of modulation grid electrodes has a hole through which an electron beam passes, the opening area of which varies depending on the voltage applied to the electron-emitting device. An image forming apparatus characterized by being provided with. (2) In the multi-electron beam source, a power feeding means is provided so that a positive voltage can be applied from one end of the parallel-connected electron-emitting device array and a negative voltage can be applied from the other end, and the power feeding means is provided on the modulation grid electrode. 2. The image forming apparatus according to claim 1, wherein the opening area of the hole is larger for an element at the center of the element array than for elements at both ends of the element array. (3) In the multi-electron beam source, means is provided at one end of the row of electron-emitting devices connected in parallel to supply a positive voltage and a negative voltage for driving the devices, and means is provided at the modulation grid electrode. The image forming apparatus according to claim 1, wherein the opening area of the hole is larger for an element far away than for an element near one end of the element array where the power feeding means is provided. .