JPS632231A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To shorten the time until normal image is obtained without compromising the aging change of static convergence, by constituting an electron gun so that thermal expansion rates of all of the 1st to 5th grid are arranged in particular relationships among them. CONSTITUTION:Thermal expansion rates of 1st grid 31, 2nd grid 32 and 3rd grid 33 which constitute a triode, alpha1, alpha2 and alpha3, respectively, and thermal expansion rates of 4th grid 34 and 5th and the following grids which constituted a main lens, alpha4 and alphag, respectively, are related to each other as alpha2<=alpha1<alpha4<alphag<=alpha3, alpha2<=alpha1<=11.0X10<-6> and 10.0X10<-6=alpha4<alphag<=alpha3. With the respective grids of an electron gun which emits multiple electron beams made in such a constitution, flying characteristic can be optimized and secular change in the static convergence can be reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention has an electron gun that emits a plurality of electron beams, and displays an image by concentrating the electron beams on a phosphor screen. related to cathode ray tubes.

(Prior Art) Usually, a color cathode ray tube has an electron gun that emits three electron beams, and displays images (including characters) by concentrating the three electron beams emitted from the electron gun on a phosphor screen. is configured to do so. Just in case.

If these three electron beams are not properly focused on the phosphor screen, color shift will occur, resulting in incomplete image display.

Among this concentration of electron beams, what is the concentration of electron beams at the center of one screen (static convergence)?

Methods such as giving an inclination angle to the unit electron guns that emit each electron beam, shifting some electrodes that make up the main lens from the central axis of the electron gun, and tilting the main lens with respect to the direction in which the electron beam passes, etc. It is being done. Also, the concentration of electron beams around one screen (dynamic convergence)
This is accomplished by using a convergence correction device, or by using a non-uniform magnetic field of the deflection device itself.

On the other hand, in a cathode ray tube that has been sufficiently heat-run and has a cut-off setting, a stable electron beam current can be obtained by suppressing the so-called flying phenomenon in which the electron beam current at the time of image output changes greatly relative to the set current value. It is necessary to do so. In particular, for display tubes that display negative images such as characters and figures in one gradation in a non-luminous dark area, stability during image output is extremely important. If the electron beam current during image output is large compared to the set current value, phenomena such as the background on the screen floating or being out of focus will occur.

In particular, with color cathode ray tubes, reproduction of colors as well as images is incomplete.

In order to reduce the flying amount of the electron beam current and quickly stabilize it, it was recommended in 1983 that the first grid of the electron gun should be made of a material with a low coefficient of thermal expansion (approximately 12, OX 10-'). It is shown in the publication No.-35163. However, when the first grid is made of a material with a low coefficient of thermal expansion, on the other hand, the static convergence deteriorates.

To explain this about a uni-bipotential integrated electron gun that integrates three unit electron guns commonly used in color cathode ray tubes, this electron gun has three cathodes, each of which is heated separately. Consisting of a heater, fourth and second grids that are sequentially arranged on the cathode to control the electron beam emitted from the cathode, and third to sixth grids that constitute a lens system that focuses the electron beam. 0 Normally, the voltages shown in Table 1 are applied to the heater, cathode, and each grid of this electron gun, a video signal is input to the cathode, and the electron beam is cut off by the cathode voltage.

The first and second grids are control electrodes for extracting an electron beam faithfully to the video signal, and the electron beam is once focused near the fourth and second grids, forms a crossover, and then While diverging, the light enters the third grid U, is focused by a lens system consisting of the third to sixth grids, and is concentrated on the phosphor screen.

Table 1 This series of effects is realized because the cathode is heated by the heater and is in a state where it can always emit a stable electron beam. However, due to the heating of the cathode, the stable temperature of each electrode becomes the distribution shown in Table 2, and the time it takes to reach this stable temperature is about 5 seconds for the cathode, about 10 minutes for the first and second grids, and about 10 minutes for the third grid. ~Grid 6 takes about 15-20 minutes. Then, until this stable temperature is reached, each electrode expands in the tube axis direction and on a plane perpendicular to the tube axis due to thermal expansion.

Table 2 The above elongation in the tube axis direction indicates that even if the electron gun is assembled with a predetermined precision, the spacing between each electrode will change due to the temperature of each electrode and the difference in time required to reach a stable temperature. In particular, when the distance between the cathode and the first grid changes, the amount of flying changes with respect to the set current value of the electron beam. Further, the elongation on the plane perpendicular to the tube axis changes the distance between the axes of each unit electron gun assembled with a predetermined precision, and changes the concentration of the three electron beams.

Therefore, static convergence and cutoff are generally set after the electron gun has been sufficiently heat-run.

In a normal electron gun, each grid has a thermal expansion coefficient α of 17 and O
Although it is made of a stainless steel member with a temperature of about 10-' The amount of flying of this electron gun changes significantly depending on the elongation of the grid. In addition, in Figure 11, 1 curve (2)
is the second grid, song 4! (3) shows the elongation of the cathode.

By the way, the cutoff voltage Ee is expressed by the following equation, and as the value of the right term increases, the electron beam current increases.

However, φ: diameter of the electron beam passage hole of the first grid mini-1st
Distance f between grid and cathode: Distance t between first grid and second grid: Thickness He of first grid: Applied voltage of second grid In the above equation, φ, t, and Ec are the same electron gun. are always constant, but a and f change over time due to the ignition of the heater. Now, when the heater is ignited, a and f are a
1+fl and a, f after sufficient heat run are azyfz, then the product of a, f is constant, that is,
If it is a engineering・fl”a2・f2, the flying characteristics are
Curve (5) in Figure 12 shows an almost ideal electron beam current, curve (6) when a1+fl > am @ f, and curve (7) when a, -fl<a2・f2. ).

Therefore, if the first grid is made of a material with a low coefficient of thermal expansion, changes in af can be reduced, and song 5 (6)
, (7) can be brought closer to curve (5). Note that the straight line (8) shown in Fig. 12 is
This is the set current value of the electron beam.

However, even if the first grid is made of a material with a low coefficient of thermal expansion, although the flying characteristics can be improved, the static convergence cannot be improved.In other words, even if the electron gun is assembled with a predetermined precision, As there is a difference in the stable temperature of each grid and the time it takes to reach the stable temperature,
This causes a shift in the center of the hole in each grid, which greatly impedes the concentration of the three electron beams.

(Problems to be Solved by the Invention) As described above, if the first grid is formed of a material with a low coefficient of thermal expansion, the flying characteristics can be optimized.

However, if only a material with a low coefficient of thermal expansion is used for the first grid, the change in static convergence over time deteriorates, which poses a major problem in concentrating the electron beam.

This invention was made to solve these problems, and it is possible to properly image an electron gun that emits multiple electron beams without impairing the change in static convergence over time. The purpose of this invention is to obtain a cathode ray tube that shortens the time it takes to become visible.

[Structure of the invention]

(Means for solving the problem) It has an electron gun consisting of a plurality of grids that emit a plurality of electron beams, and displays an image by concentrating the plurality of electron beams emitted from this electron gun on a phosphor screen. In a cathode ray tube, the coefficient of thermal expansion of the first to fourth grids is α1, respectively.
~α4, and the coefficient of thermal expansion after the fifth grid is αg, and the electron gun was constructed so that α2≦α1<α, and <αg≦α3.

(Function) By configuring each grid of the electron gun that emits a plurality of electron beams as described above, it is possible to optimize the flying characteristics, and at the same time, it is possible to reduce the change in static convergence over time.

(Example) Hereinafter, the present invention will be described based on an example with reference to the drawings.

FIG. 1 shows a color cathode ray tube according to an embodiment of the present invention, and FIG. 2 shows the structure of its electron gun.

This color cathode ray tube has a fluorescent screen (22) made of three-color phosphors formed on the inner surface of a panel (21) that constitutes the front part of an envelope (20), and faces the fluorescent screen (22) and is spaced at a constant distance. Separately, shadow mask inside (23)
is installed. In addition, three electron beams (25
B) An electron gun (26) that emits , (25G) and (25R) is installed, and these three electron beams (25B)
, (25G), (25R) with shadow mask (2
By making the light incident on the phosphor screen (22) through the light source 3) and concentrating on the phosphor screen (22), a color image can be displayed.

By the way, the electron gun (26) has three cathodes (2
8a), (28b), (28c), heaters (29a), (29b), (29c) that individually heat these cathodes (28a) to (28c), and the cathodes (28a) to (28c) Fourth and second grids (31) and (32) are sequentially arranged along the tube axis in the direction of the phosphor screen (22) to control the three electron beams emitted from the cathode, and It is composed of third to sixth glisodes (33) to (36) that constitute a focusing lens system. Each grid (3
1) to (36) are formed in a plate or cylinder shape with three electron beam passage holes (37), and the electron gun (26) includes the cathodes (28a) to (28c) and the heater (29a).
) to (29c) and grids (31) to (36) form an integrated structure in which three unit electron guns are integrated. In addition.

The electron beam (25B) of this electron gun (26), (2
5G), each grid (31) for (25R) ~
The basic operation of (36) is the same as that of the conventional electron gun, so its explanation will be omitted. In this electron gun (26), the coefficients of thermal expansion of each of the grids (31) to (36) are formed so as to have the relationship described below.

Now, according to experiments conducted by the inventors, in a color cathode ray tube whose static convergence was adjusted after being sufficiently heat-run, the static convergence after being sufficiently cooled changes over time as shown in Figure 3. There was found. FIG. 3 shows the measurement results when each grid of the electron gun is formed of a commonly used stainless steel member, and the curve (39) is the first. The static convergence change over time curve 1 (40) that occurs between the second grid is
゜Curve (41) shows the change over time in the static convergence that occurs between the third and fourth grids.Curve (42) shows the change over time in the static convergence that occurs between the third and fourth grids.
It shows the change in static convergence that occurs between grids over time, and the change in overall static convergence over time is
The sum of these results in an attenuation curve shown in curve (43).

Here, in order to optimize the flying characteristics of the electron beam during image output, the first and second grids are set.

The coefficient of thermal expansion α is 12. When formed with a low thermal expansion material of OX 10-" or less, the insufficient concentration component of static convergence shown in curve (39) in FIG.
The overconcentration component shown in 40) also decreases, and based on the difference in their contribution rates, the change in static convergence over time changes from curve 2 (43) to curve (44a), as shown in Figure 4.
, (44b). The curve (44a) in FIG. 4 shows that the fourth and second grids have a thermal expansion coefficient of 5.
The third grid is made of 42% Ni-Fe alloy (NSD) with a thermal expansion coefficient of 17.
When formed with stainless steel of OX 10-', the curve (4
4b) The first grid has a thermal expansion coefficient of 9.4 to 10.4
50% Ni-Fe at X 10-' (30-400°C)
This is a case where the second grid is made of N5C1 and the third grid is made of stainless steel.

As can be seen from Fig. 4, when the coefficient of thermal expansion of the first grid is α0, the coefficient of thermal expansion of the second grid is α2°, and the coefficient of thermal expansion of the third grid is α, then α2≦α, ≦α ,
・・・・・・・・・(1), the curve in Figure 3 (39
) By increasing the component, overconcentration can be alleviated. However, as shown in curves 1 (44a) and (44b), overconcentration is still large.

In order to further reduce the change in static convergence over time, as shown in curve (44b).

The coefficient of thermal expansion α2 of the second grid may be further reduced, but at present there is no material that can be put into practical use that satisfies the characteristics required for the grid and has a coefficient of thermal expansion smaller than that of the NSD.

Therefore, the inventors conducted further experiments and found that in order to make the overconcentration component smaller than that shown in FIG. 4 and to reduce the change in static convergence over time, the curve shown in FIG. It has been found that a method of increasing the (42) component and decreasing the one curve (42) component is extremely effective.

That is, the fourth and second grids have low coefficients of thermal expansion and α2≦α1.

5th grid or 5th grid with α coefficient of thermal expansion of 4th grid
When the coefficient of thermal expansion of the grid after the grid is αg, by setting α,〈αg≦α, ・・・・・・・・・(2), it is possible to significantly reduce the change in static convergence over time. did it. In this way, together with the low thermal expansion of the fourth and second grids, it has become possible to reproduce a screen with little color shift on one screen and little change in static convergence over time.

By the way, according to experimental results, there is a relationship between the thermal expansion coefficient α of the first grid and the amount of flying as shown by the curve (46) in FIG. This is the amount of flying when the diameter of the electron beam passing holes in the first and second grids is 0.40 mm and the initial setting electron beam current is 10 μA, with 10 μA being 100%. In cathode ray tubes, especially display tubes, in order to reproduce images properly, it is desirable to have a ratio of 150% or less, so the curve (4
From 6), the coefficient of thermal expansion α of the first grid is 11.0X
It is sufficient if it is 10-' or less.

Considering the condition (1) above, it is desirable that the fourth and second grids satisfy the condition (3) below.

α2≦α□≦11. OX 10-@・・・・・・・・・
(3) Regarding the fourth grid, the coefficient of thermal expansion α of this fourth grid and the change over time of static convergence are
In Fig. 6, there is a straight line (47a), (4
There is a relationship shown in 7b). The third grid, the fifth grid, and the subsequent grids are made of stainless steel, and the straight line (47a) is connected to the fourth grid so that the relationship α2≦α is satisfied for the fourth and second grids. , the second grid is N5D (thermal expansion coefficient s, oxto-')
This is a case where the straight line (47b), the first grid, and the second grid are formed with TNFC (thermal expansion coefficient of 11.0×10−′ or less). In cathode ray tubes, particularly display tubes, it is desirable that the deviation after 5 minutes of static convergence changes over time is 0, but in practice, a maximum of ±0.2n+ is acceptable. Therefore, from straight lines (47a) and (47b), the coefficient of thermal expansion α of the fourth grid is.

10, OX 10-'≦α, ≦17. OX 10-', and considering the condition (2) above, the third and fourth
, for the fifth and subsequent grids, see below (4)
) should satisfy the following conditions.

10, OX 10-'≦α, ≦αg≦α, ...
(4) Thus, if the electron gun (26) is configured to satisfy the above conditions (3) and (4), the amount of flying can be reduced to 15
0% or less, static convergence change over time ±0, 2
mm or less, and can be used as a color cathode ray tube that displays an appropriate image on the phosphor screen (22).

This will be explained below using a specific example.

Specific example 1. In a 14 inch 29.1 mm diameter neck 90" deflection color cathode ray tube, the electron gun (26) is a uni-bipotential type integrated electron gun, and the third grid, fifth grid, and subsequent grids are made of stainless steel. Forming α, = αg = 17.OX 10-' (0~300
℃), and the fourth and second grids are formed of N5D (42%N1-Fe) in consideration of flying characteristics, and α1=α
, =5.0
%Cr-Ni alloy) and α, = 13.7
10-'' (0 to 100°C).

The time-dependent change in static convergence of this color cathode ray tube is shown by a curve (49a) in FIG. 7, and the flying characteristic is shown by a curve (50a) in FIG. From the curve (49a), the change in static convergence over time can be set to about 0.1 mm in 2 minutes, and as can be seen from the curve (50a), the flying characteristics can be made ideal. 5
1) As shown in (52), the third, fourth, and fifth
Compared to an electron gun in which the grid and subsequent grids are all made of stainless steel (the fourth and second grids are made of NSD), static convergence in particular is greatly improved.

Note that the above-mentioned measurement of the change in static convergence over time is performed using E.
b=25kV, Ec, =7.0kV (focus)
, Ec.

=600v, Ek=cutoff, Ec, = OV, E
After heat running for 1 hour at f=6.3V, static convergence was adjusted to O, and measurements were taken after cooling for 10 hours.

In addition, the measurement of flying characteristics is as follows: Eb = Ec, =
Ec, L=200V, Ek=barrier pull, Ec,
:=01Ik=10μA (per unit electron gun), after heat run for 1 hour, Ik was adjusted to exactly 10μA for each unit electron gun, and measured after cooling for 1 hour.

! In the color cathode ray tube of the above specific example 1, the third
, the fifth and subsequent grids are also made of stainless steel,
The fourth grid is formed with the same < IMO, the first grid is formed with TNF (50% N1-Fe alloy), and α□ = 9.4 ~ 10.4 X 10-' (30 ~ 40
0℃), and the second grid is formed using NSD to obtain α, =
5. OX 10-'' (0 to 300°C).

The time-dependent change in static convergence of this color cathode ray tube is shown in FIG. 9 as a curve (49b), and the flying characteristic is shown in FIG. 10 as a curve (sob). These curves (49b
), (50b), this electron gun (2
In 6), we estimate the change in static convergence over time to approximately 0.1.
It can be kept below 1I11, and the flying characteristics are also almost ideal.

In the color cathode ray tube of the above specific example 1,
Third. The 5th and subsequent grids are made of stainless steel, the 4th grid is made of 0, and the 4th and 2nd grids are made of KOV (29%Ni-17%Co-Fe alloy).
Form it with.

α1=α, = 4.54 X 10-' (30~4
0d'C), it was possible to obtain a color cathode ray tube exhibiting static convergence change over time and flying characteristics almost similar to those of Example 1.

In the color cathode ray tube of the above specific example 1, the third, fifth and subsequent grids are also made of stainless steel, the fourth and second grids are also made of NSD, and the fourth grid is made of ICL (16% Cr- α, = 13.5 x 10-' (30-400℃
), it was possible to obtain a color cathode ray tube exhibiting static convergence changes over time and flying characteristics almost similar to those of Example 1.

〔Effect of the invention〕

In a cathode ray tube that has an electron gun consisting of a plurality of grids that emit a plurality of electron beams, and displays an image by concentrating the plurality of electron beams emitted from the electron gun on a phosphor screen, first to fourth The coefficient of thermal expansion of the grid is α1
~ α, and the coefficient of thermal expansion of the fifth grid and subsequent grids is αg, and the configuration is such that α2≦α1≦α〈αg≦α〈αg≦α〉, so that the change in static convergence over time is impaired. This has made it possible to shorten the time it takes for the screen to look normal.

[Brief explanation of drawings]

1 to 10 are detailed explanatory diagrams of the present invention. FIG. 1 is a sectional view showing the structure of a color cathode ray tube according to an embodiment of the invention, FIG. 2 is a sectional view showing the structure of the electron gun, and FIG. 3
The figure is a diagram for explaining the change in static convergence over time. Figure 4 is a diagram showing the change in static convergence over time when the fourth and second grids are formed of a material with a low coefficient of thermal expansion. Figure 5 FIG. 6 is a diagram showing the relationship between the coefficient of thermal expansion of the first grid and flying, and FIG. 6 is a diagram showing the relationship between the coefficient of thermal expansion of the fourth grid and the change in static convergence over time. FIG. 7 is a diagram showing the change in static convergence over time of one specific example, FIG. 8 is a diagram showing the same flying characteristics, FIG. Figure 1O is also a diagram showing its flying characteristics.
FIG. 11 is a diagram showing the extension of the cathode and grid in the tube axis direction, and FIG. 12 is a diagram illustrating the flying characteristics of the electron beam current.

Claims (1)

[Claims] (1) A triode section consisting of a cathode, a first grid, and a second grid, and a plurality of grids constituting a main lens system adjacent to this triode section are disposed to generate a plurality of electron beams. In a cathode ray tube that has an electron gun that emits an electron beam, and displays an image on the phosphor screen by concentrating a plurality of electron beams emitted from the electron gun on the phosphor screen, a first grid forming the triode section; The coefficient of thermal expansion of α_1
, the coefficient of thermal expansion of the second grid is α_2, the coefficient of thermal expansion of the third grid is α_3, the coefficient of thermal expansion of the fourth grid constituting the main lens is α_4, and the coefficient of thermal expansion of the fifth and subsequent grids is α_2.
A cathode ray tube characterized in that g is α_2≦α_1<α_4<αg≦α_3. (2) The coefficient of thermal expansion of each grid is α_2≦α_1≦11.0×10^-^6 10.0×10^-^6≦α_4<αg≦α_3 The cathode ray tube according to item 1. (3) The cathode ray tube according to claim 2, wherein the first grid and the second grid are made of an iron-nickel alloy. (4) The cathode ray tube according to claim 2, wherein the first grid and the second grid are made of an iron-nickel-cobalt alloy. (5) The cathode ray tube according to claim 2, wherein the fourth grid is made of a nickel-chromium alloy. (6) The cathode ray tube according to claim 2, wherein the fourth grid is made of a nickel-chromium-iron alloy.