JP2778448B2 - Driving method of electron gun and cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun using a field emission cathode as an electron source, and a method for driving a cathode ray tube (hereinafter abbreviated as CRT ) equipped with the electron gun.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional general CRT. The CRT 1 includes a neck 3 having an electron gun 2,
It has a funnel section 5 provided with a deflection electrode 4 for deflecting the electron beam emitted from the neck section 3, and a panel section 6 on which a phosphor excited and emitted by the electron beam is attached.

FIG. 8 shows a conventional electron gun 2 used in a conventional general CRT 1. The electron gun 2 has an indirectly heated cathode 7 for heating an oxide layer by a heater, an extraction electrode 8, and a focusing electrode 9.

According to the CRT 1 configured as described above, the focused electron beam emitted from the electron gun 2 at the neck is guided to a predetermined position on the panel 6 by the deflection electrode 4 of the funnel 5. As a result, the fluorescent screen is excited to emit light, and a desired display is performed.

[0005] The above-described conventional CRT using an electron gun has the following problems. (1) Since the cathode of the conventional electron gun is of an indirectly heated type, a heater power supply for heating the heater is required. (2) It took some time from when the heater power supply was turned on to when an electron beam was obtained.

(3) Since the life of the heater of the electron gun is short,
Long-life CRT could not be performed. (4) An electron source emitting an electron beam with a high current density could not be obtained.

(5) The diameter of the electron generating portion of the electron gun is several mm.
When the beam is minutely focused to a certain degree or less by the electron lens system, the beam shape is distorted due to aberration, and the electron density tends to be uneven within the beam diameter.

In order to solve the above-mentioned problems, in recent years, a field emission cathode (Field Emi
ssion Cathode, also called FEC. CRT using)
Has also been proposed. This can be said to focus on the advantages of FEC, which is small, does not require a heater, and can obtain a high current density.

[0009]

Some conventional CRTs using FEC include different numbers of FECs in a binary relationship.
Configure multiple groups that connect cells one after another,
Others have attempted to achieve different brightness by driving these groups in different combinations.

However, the CR having the above-described configuration has
In T, a plurality of groups in which a plurality of FEC cells are connected in a continuous predetermined pattern must be provided within a predetermined range. However, such a complicated structure has a problem of increasing the manufacturing cost. Further, depending on the selection or combination of groups, the driven FEC cells are not concentrated in a narrow range, and a gap may be generated between a plurality of driven FEC cells. In this case, the diameter of the electron generating portion of the electron gun becomes substantially large, and the beam shape is distorted due to aberration, and the electron density tends to be non-uniform within the beam diameter. .

The present invention provides an electron gun provided with an FEC having a small spot diameter of an electron beam, a high driving speed, and capable of controlling the luminance with a simple structure, a cathode ray tube having such an electron gun, and a method of driving a cathode ray tube. It is intended to be.

[0012]

According to the present invention, there is provided an electron gun comprising a cathode conductor and an emitter provided on the cathode conductor.
Electric field with a gate provided near the emitter and the emitter
An electron gun having an emission cathode, wherein the field emission cathode is
When the poles are composed of multiple small areas arranged in a matrix
In both cases, a part of the small area protrudes from the outer edge of the set of other small areas.
And the cathode conductor and gate of each small area are
It is configured to be driven for each row or column .

According to a second aspect of the present invention, there is provided a method of driving a cathode ray tube, wherein a field emission cathode having a cathode conductor, an emitter provided on the cathode conductor, and a gate provided near the emitter is arranged in a matrix. An electron gun divided into a plurality of small areas, an electron beam deflection electrode for deflecting the electron beam emitted from the electron gun, and a panel portion on which a phosphor that emits light by projecting the electron beam is attached. A method of driving a cathode ray tube having brightness control means for selecting a small region by driving a cathode conductor and a gate of each small region for each row or column in the electron gun, wherein the selected small region is always dense It is characterized in that the driving area of the field emission type cathode is controlled so as to form a set of and the luminance is controlled.

[0018]

The brightness control means selects the small area by driving the cathode conductor and the gate of each small area of the field emission cathode for each row or column. The amount of emitted electrons is adjusted according to the area of the selected small region, and the luminance is controlled. Since the selected small areas always form one dense group, a small spot diameter makes it possible to obtain a high-quality electron beam with little aberration and uniform electron density.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The basic configuration of the CRT 10 of the present embodiment is the same as the configuration of the conventional CRT 1 shown in FIG. That is, FIG.
As shown in (1), an electron gun 12 is provided on a neck portion 11a of a glass container 11 included in the CRT 10 of the present embodiment, and an electron beam emitted from the neck portion 11a is deflected by a deflection electrode of a funnel portion. And the electron beam is
The phosphor of the panel portion provided on the inner surface of the front surface of the glass container 11 collides with the phosphor to excite and emit light, thereby displaying a desired image. However, unlike the conventional CRT 1, the electron gun 12 of the CRT 10 of the present embodiment has a field emission cathode 20 as its electron source. The electron gun 12 includes the field emission cathode 20, first and second electron beam focusing electrodes 25 and 28, and the like.

Next, the configuration of the electron gun 12 will be described with reference to FIG.
This will be described in detail with reference to FIG. On the ceramic substrate 13, a substrate 14 made of an insulating material such as Si or glass is provided. On the substrate 14, a Spindt-type field emission cathode 20 (FEC20) has a diameter of about 0.5 to 0.6 m.
Many are formed in the range of m. That is, the cathode conductor 15 is formed on the substrate 14 by a conductive thin film,
An insulating layer 16 and a gate 17 are stacked thereon.
A hole 18 is formed in the insulating layer 16 and the gate 17 by a photolithography method, and a cone-shaped emitter 19 is formed on the cathode conductor 15 in the hole 18 by a vapor deposition method. In this embodiment, the emitter 19 is of the Spindt type. However, in addition to the Spindt-type deposition emitter, a vertical field emission emitter by etching may be used, or a plane field emission emitter may be used as long as the directionality is excellent.

The cathode conductor 15 of the FEC 20 is connected to a cathode stem 21 provided on a ceramic substrate 13.
Is drawn out of the neck portion 11a.

The gate 17 of the FEC 20 is connected to a plate-shaped conductor 22 having a hole formed in the center. Both ends of the conductor 22 penetrate the ceramic substrate 13 and are FE
It is connected to one end of each of two gate stems 23 protruding toward the C20 side. The other end of at least one gate stem 23 projects outward through the neck 11a of the glass container 11.

On the ceramic substrate 13, an insulating layer 24 is formed on the conductor 22.
The first electron beam focusing electrode 25 is provided on the first. The first electron beam focusing electrode 25 is a metal plate having a hole 25a having a diameter of 0.5 to 0.6 mm facing the FEC 20 formed on the substrate 14, and a gate 17 of the FEC 20 near the hole 25a. Distance is 0.08 ~
0.1 mm. Both ends of the first electron beam focusing electrode 25 are supported by rod-shaped lead terminals 26, and at least one of them is led out of the glass container 11.

A second electron beam focusing electrode 28 is provided above the first electron beam focusing electrode 25 via a ceramic insulating material 27 of 0.1 to 0.2 mm. The configuration of the second electron beam focusing electrode 28 is the same as that of the first electron beam focusing electrode 25, and at least one of the lead terminals 29 is led out of the glass container 11.

The CRT 10 according to the present embodiment includes the electron gun 12
And a circuit for applying a predetermined voltage to each of the electrodes. In this example, the emitter 19 is grounded, and
50V, 0-150 for the first electron beam focusing electrode 25
V, 200-500 V for the second electron beam focusing electrode 28
Are applied.

Alternatively, the gate 17 may be grounded to give the same potential difference between the electrodes as described above. Although the electron gun 12 of this embodiment has the FEC 20 and the first and second electron beam focusing electrodes 25 and 28, the third and fourth focusing electrodes may be further provided as necessary. Is also good.

Next, the FEC 20 in this embodiment is divided into a plurality of small areas S as shown in FIG. FIG.
As shown in the figure, the set of the plurality of small areas S is arranged in a matrix of 8 rows and 8 columns including 8 rows from the 0th row to the 7th row and 8 columns from the 0th to the 7th columns. It is arranged. Here, a row indicates a row in the horizontal direction, and a column indicates a row in the vertical direction. However, since there are no small areas S at four locations corresponding to the 0th, 1st, 6th, and 7th rows in the seventh column, the total number of the small areas S is 60 pieces. That is, the set of the 60 small areas S in total is composed of a rectangular main part 30 composed of 56 small areas S arranged in 8 rows and 7 columns, and the outer side while being in contact with the outer edge of the main part 30. The protruding portion 31 includes four protruding small regions S.

Each of the small regions S has a cathode conductor, an emitter, a gate and the like as described in FIG. The cathode conductor of each small region S is commonly connected for each row, and the gate of each small region S is commonly connected for each column.

The FEC 20 divided into a number of small areas S is driven by an X decoder 40 and a Y decoder 41 as brightness control means shown in FIG. The X decoder 40 has output terminals X ₀ to X ₇ connected to columns 0 to 7 respectively, and scans the gate of each small area S column by column. The Y decoder is used for Y ₀ to Y ₇
Are connected to the 0th to 7th rows, respectively, and scan the cathode conductor of each small area S row by row. Luminance data of an image to be displayed is input to the X decoder 40 and the Y decoder 41 in synchronization with a control signal given to the deflection electrode.

FIG. 4 shows the relationship between the combination of input signals and the output in each small area S of the FEC 20. That is, in each small area S, when the signal input to the gate from the X decoder 40 is ON and the signal input to the cathode conductor from the Y decoder 41 is OFF, electrons are emitted from the emitter.

FIG. 5 shows the above-mentioned F consisting of 60 small areas S.
9 is a table showing combinations of decoder outputs when performing luminance control of 16 gradations using EC20. In this embodiment, the brightness is controlled by adjusting the number of the small areas S that emit electrons when selected. As shown in FIG. 5, the 4-bit luminance data represents 16 gradations from No. 1 to No. 15, and the X decoder 40 is configured to increase the number of selected small areas S every time the gradation increases. And a combination of signals output by the Y decoder 41 are determined for each gradation.

According to the decoder signals shown in the table of FIG.
The selected small area S in each gradation is arranged as shown in FIG. That is, a small area S that emits electrons when selected.
Are gradually increased from substantially the center of the main portion 30 to an adjacent portion as the luminance increases (as the number of gradations increases). Then, after the 11th gradation, the convex portions 31
Are turned ON / OFF simultaneously for each gradation, and when the convex portion 31 is turned OFF, the selected small regions S are increased by one line, and thus the selected small regions S
Are increased to reach 15 gradations in which the entire small area S is selected.

As described above, the FEC 20 according to the present embodiment is arranged in such a manner that a plurality of small areas S to be matrix-driven have the convex portions 31. Then, the plurality of small regions S are gradually selected from the central portion to the adjacent portion (or the selection is gradually released from the adjacent portion to the central portion) to change the gradation, so that the electrons are emitted. The selected small area S always forms one dense set. Therefore,
The spot diameter of the electron beam emitted from the FEC 20 is always the smallest.

In each small area S of the FEC 20, a capacitor is provided between the gate and the cathode conductor, so that there is a limit to the driving speed when ON / OFF of electron emission is repeated. Further, if the charging and discharging of such a capacitor is repeated, the reactive current increases, the energy loss increases, and the electron gun equipped with the FEC 20 cannot cope with the required driving speed.

However, according to the present embodiment, ON / OFF of each small area S is not repeated as much as possible. In particular, in the 10th to 15th gradations, control using the four small areas S of the convex portion 31 is performed so that the matrix of the matrix to which the signal is applied is not changed as much as possible. That is, the four small regions S of the convex portion 31 and the eight small regions S in a row are alternately turned ON / OFF to change the gradation, so that the selected small region S between successive gradations is changed. (Or the matrix of the small areas S) does not change as much as possible, and ON / OFF of each small area S is not repeated as much as possible. Therefore, the electron gun of this embodiment can be driven at a relatively high speed with little loss of energy.

[0036]

According to the present invention, the field emission cathode, which is the electron source of the electron gun, is divided into a plurality of small areas S and driven in a matrix, and the luminance is controlled by the number of selected small areas S. . Therefore, according to the present invention, the brightness control of an arbitrary number of gradations which is resistant to noise and excellent in linearity can be realized by an extremely simple configuration, and the convenience in applying a field emission cathode to an electron gun of a CRT is improved. Thus, an industrially remarkable effect of increasing the CRT functionality can be obtained. Further, in the present invention, if the electron gun is driven so that the selected small area S always forms one dense group,
The spot diameter of the electron beam is small, and the driving speed is high.

Further, since the present invention uses a field emission cathode as an electron source, an electron beam having a small aberration and a uniform electron density in the beam can be obtained only by providing a simple electrostatic lens. , The emission of the electron beam can be controlled, so that a compact electron gun can be obtained without having to provide a new control electrode.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electron gun according to one embodiment.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a drive block diagram of an FEC in one embodiment.

FIG. 4 is a table showing a relationship between an input signal and an output in a small area S of the FEC in one embodiment.

FIG. 5 is a table showing combinations of decoder outputs in a case where luminance control of 16 gradations is performed using FEC in one embodiment.

FIG. 6 is a diagram showing an emission area of FEC electrons at each gradation in one embodiment.

FIG. 7 is a sectional view showing a structure of a general cathode ray tube.

FIG. 8 is a sectional view of a conventional electron gun.

[Explanation of symbols]

 Reference Signs List 4 deflection electrode 6 panel unit 10 cathode ray tube (CRT) 12 electron gun 17 gate 19 emitter 20 field emission cathode (FEC) 30 luminance control circuit as luminance control means 32 image memory as storage means 33 CRT controller 34 gradation control D / A conversion circuit as a circuit 40 X decoder as luminance control means 41 Y decoder as luminance control means S Small area

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-37543 (JP, A) JP-A-5-343000 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 29 / 04,29 / 48,1 / 30,31 / 12 H04N 5/68

Claims (2)

(57) [Claims] 1. A cathode conductor and provided on the cathode conductor.
Having an emitter and a gate provided near the emitter
An electron gun provided with a field emission cathode.
The output cathode is composed of a plurality of small areas arranged in rows and columns.
And a part of the small area is an outer edge of a set of other small areas.
And the cathode conductor and gate of each small area
An electron gun configured to be driven for each row or column . 2. A cathode conductor and provided on the cathode conductor.
Having an emitter and a gate provided near the emitter
Field-emission cathodes are arranged in a plurality of small areas arranged in rows and columns.
An electron gun that is divided and an electron gun
An electron beam deflection electrode for deflecting the electron beam;
Panel coated with phosphor that emits light when the
And a cathode conductor and a gate of each small area in the electron gun.
Each row or column to select a small area.
A driving method of a cathode ray tube having a brightness control means,
Selected small areas always form a dense set
Control by controlling the driving area of the field emission cathode
A method of driving a cathode ray tube.