KR100344517B1 - Cathode ray tube having upf type electron gun - Google Patents

Abstract

The present invention relates to a lens structure of a prefocus portion of a Hi-UPF electron gun used for a cathode ray tube. In the Hi-UPF electron gun, a cathode, a control electrode, an acceleration electrode, a first anode, a focus electrode, and a second anode are arranged in this order, the anode voltage is commonly applied to the first anode and the second anode, and the focus electrode is focused. Voltage is applied. In the cathode ray tube of the present invention, in the prefocus portion, the electron beam passing hole of the control electrode is 0.57 mm or less, and the distance in the vicinity of the electron beam passing hole of the acceleration electrode and the first anode is 1.9 mm or less.

Description

Cathode ray tube with JP type electron gun {CATHODE RAY TUBE HAVING UPF TYPE ELECTRON GUN}

The present invention relates to a cathode ray tube having a UPF electron gun.

Large 40-inch or larger TVs are more popular than projection TVs. Projection TV projects a 5.5-inch CRT image onto an 40-inch screen using optical lenses, mirrors, and so on. In general, a color image is obtained by projecting images of three CRTs on a screen to produce a monochrome, red, green screen.

The CRT used for this is called a projection tube (PRT). In the projection type, for example, a 5.5-inch image on a PRT is projected onto a 40-inch screen, so that the image is enlarged by 50 times in area. Therefore, the PRT image needs to be very high in brightness and very good in focus.

In order to realize high brightness, it is necessary to flow a large current. The PRT has a problem of maintaining good focus characteristics even when a large current flows. Therefore, in the PRT, so-called Hi-UPF electron guns, which have relatively good focus characteristics even in a large current region, are widely used. An example of this Hi-UPF electron gun is disclosed in US Pat. No. 4,178,532.

In the PRT, attention has been paid to mainly increasing the main lens diameter. This is to maintain the focus characteristic even in the high current region. In order to further improve the large current region, a so-called large diameter electron gun has also been proposed, in which the lens diameter of the main lens is increased. Such an example is disclosed in US Pat. No. 4,271,374.

In addition to the main lens, for example, US Patent No. 4,318, 027 may be cited as a prior art that discloses a means for improving focus with a prefocus structure. This is a disclosure of a BPF electron gun, in which the electron gun structure is completely different. In addition, as a method of improving the focus, it may be considered to increase the main lens diameter by making the electron gun larger, but in order to do this, it is necessary to increase the neck diameter and increase the deflection power.

According to the present invention, it is possible to achieve an improvement in focus characteristics equivalent to that in the case where the main lens diameter is increased without having to increase the neck portion diameter.

According to a first aspect of the present invention, in the Hi-UPF type electron gun, the hole diameter of the control grid G1 is φ0.57 mm or less, and the distance between the acceleration electrode G2 and the first anode electrode G3 is 1.9 mm or less. As a result, the focus characteristic is improved in both the large current region and the small current region.

The second feature of the present invention is that the diameter of the G2 side hole of G3 is not more than 2.0 mm, thereby improving the focus of the large current region.

A third feature of the present invention is to improve the focus characteristic in the small current region by setting the thickness of the G2 to 0.37 mm or less.

A fourth feature of the present invention is that excellent life characteristics are obtained by using an oxide containing barium scandate in the cathode.

The fifth feature of the present invention is that the lens characteristic of the above-described prefocus structure is combined with a large-diameter main lens to further improve the focus characteristic.

1 is a schematic diagram of a PRT.

2 is a front view of a Hi-UPF electron gun.

Fig. 3 is a side view of a Hi-UPF electron gun.

4 is a schematic diagram of a prefocus unit;

Fig. 5 is a graph showing the relationship between the G1 hole diameter and focus characteristics under specific conditions of a Hi-UPF electron gun.

Fig. 6 is a graph showing the relationship between the G2-G3 spacing and the focus characteristic in the Hi-UPF electron gun.

Fig. 7 is a graph showing the relationship between the G1 hole diameter and the focus characteristic under other specific conditions of the Hi-UPF electron gun.

8 is a graph showing the relationship between the G3 bottom hole diameter and the focus characteristic.

Fig. 9 is a graph showing the relationship between G2 plate thickness and focus characteristics.

Fig. 10 shows the structure near the cathode;

Fig. 11 is a diagram showing the structure of another Hi-UPF electron gun.

<Description of the code | symbol about the principal part of drawing>

1: electron gun

2: neck part

3: panel

4: phosphor

5 funnel

6: vapor deposition film

10: cathode

11: control electrode

12: acceleration electrode

13: first anode

14: focus electrode

15: second anode

101: oxide layer

1 is an external view of a PRT. One electron beam is generated from the electron gun 1 accommodated in the neck 2. The neck portion 2 has a diameter of 29.1 mm and one built-in electron gun. Therefore, PRT has a large electron gun compared with the normal color CRT. The reason for this is to increase the lens diameter of the main lens. The phosphor 4 is formed on the inner surface of the panel 3, and a screen having a diagonal of about 5.5 inches is formed. The panel 3 has a thick center of the screen and a thin peripheral portion. This is to give a lens action to the panel glass. An aluminum vapor deposition film 6 is formed inside the funnel portion 5. The deflection yoke 7 deflects the electron beam. In this embodiment the diagonal deflection angle is 90 degrees. The contrast of the image is improved by the speed modulating coil 8. The terminal 9 supplies a voltage to each electrode of the electron gun.

2 is a front view of the electron gun of the present invention. Typical operating conditions are an average of about 190 V on the cathode 10, an earth potential on the control electrode G1; 11, and 550-600 V on the accelerating electrode G2 12. A positive voltage of 30 KV is applied to the first anode G3 13, a focus voltage of about 7.7 KV is applied to the focus electrode G4 14, and a maximum voltage of 30 KV is applied to the second anode G5 15. . The focus electrode G4 has three different outer diameters. The second anode 15 has two different outer diameters. The main lens is formed by the diameter expanding portion 14c of G4 and the diameter expanding portion 15b of G5. G4 is inserted in G5 in order to make the main lens diameter as large as possible with respect to the determined neck shape. The bead glass 16 fixes each electrode while insulating each other. 3 is a side view of the electron gun of the present invention. The same components as in FIG. 2 are shown with the same reference numerals.

4 is an enlarged model of a prefocus part. The same components as in FIG. 2 are shown with the same reference numerals. The oxide layer 101 emitting electrons contains barium scandate. C-G1 is the gap between cathode and G1, G1-G2 is the gap between G1 and G2, and G2-G3 is the gap between G2 and G3. TG1 is the thickness of the G1 electrode, which is thinned by so-called coining of the material of the G1 electrode, for example, 0.18 mm. TG2 is a sheet thickness of the G2 electrode, which is also slightly thinned by the so-called coining of the sheet thickness, for example, 0.4 mm. φG1 is the G1 hole diameter, φG2 is the G2 hole diameter, and φG3 is the G3 hole diameter.

The inventors of the present application have found that, particularly, by optimizing the prefocus lens system for the Hi-UPF electron gun used for PRTs, the focus characteristic can be dramatically improved compared to the prior art without increasing the neck portion diameter.

Fig. 5 shows focus characteristics when the G1 hole diameter is changed. In order to correct the change of the cutoff voltage by the G1 hole diameter change, the dimension of each part was changed as shown in Table 1. Dimensions other than these are constant. The focus voltage was adjusted to the correct focus when the cathode current Ik was 2 mA.

G1 hole diameter (φG1) φ0.65 φ0.60 φ0.55 G1 plate thickness 0.08 0.08 0.08 G2 hole diameter (φG2) φ0.65 φ0.60 φ0.55 G2 plate thickness 0.39 0.39 0.36 C-G1 gap 0.13 0.115 0.115 G1-G2 gap 0.32 0.305 0.195

Unit [mm]

Here, the C-G1 gap is a dimension when the electron gun is assembled. In actual operation, the C-G1 gap becomes smaller than this value because the cathode is thermally expanded. The same applies to the embodiments shown below. In addition, G2 hole diameter was made the same as G1 hole diameter. As can be seen from Fig. 5, the spot diameter at low current (0.5 mA) can be reduced by decreasing the G1 hole diameter. Fig. 5 shows that almost 7% improvement in the focus characteristic at low current can be seen when G1 becomes 0.57 mm or less.

However, it was found that simply reducing the G1 hole diameter deteriorates the focus characteristic in a large current region such as 6 mA. Thus, as described below, improvements in the high current region are possible by combining improvements such as narrowing the G2 and G3 gaps, but even in this case, slight improvements (around 3%) in the low current region are possible. . Therefore, by improving the G1 hole diameter to 0.57 mm or less, focus characteristic improvement of 10% or more in the low current region is possible.

Fig. 6 shows a change in beam spot diameter when the gap between G2 and G3 is changed. Although the luminance distribution of the beam spot generally forms a bell curve, the beam diameter in this embodiment is a measure of the diameter when the luminance is 5% of the highest value. The same applies to the following examples. The measurement conditions of FIG. 6 are as shown in Table 2.

Anode voltage (Eb) 30 KV Cathode voltage (Ek) 190 V Focus voltage (EG4) Accurate focus at 2 mA G1 hole diameter (φG1) φ0.55 mm G2 hole diameter (φG2) φ0.55 mm G3 Bottom Hole Diameter (φG3) φ1.98 mm G1-G2 gap 0.275 mm

Generally, it is thought that the smaller the G1 hole diameter improves the focus characteristic, but this is a case where the beam current is small, and in the case of a large current region, an intended degree of effect cannot be obtained. In addition, when the G1 hole diameter is reduced, the cathode loading becomes large and the service life characteristics become a problem. Therefore, 0.6 mm or more of G1 hole diameters were used conventionally.

The inventors of the present application have found that the G2-G3 gap has a great influence on the improvement of the focus characteristic at a large current. Experiments have shown that when this value is 1.9 mm or less, a remarkable effect can be obtained in a large current region. 6 shows that by setting the G2-G3 gap appropriately, a significant improvement effect is obtained in the high current region without sacrificing the improvement effect of the low current region obtained by reducing the G1 hole diameter. Therefore, the effect of reducing the G1 hole diameter in this case can sufficiently cope with the risk of increasing the cathode loading.

5 and 6 together, the G2-G3 gap is 1.9 mm or less, and the G1 hole diameter is 0.57 mm or less, resulting in a beam of 10% or more than the conventional PRT in both the high current region and the low current region. It can be seen that the spot can be improved.

6 shows that the focus in the high current region is improved by reducing the G2-G3 gap, but the characteristic improvement tends to be saturated when the G2-G3 gap is smaller than 1.73 mm. As a characteristic of the UPF gun, a large voltage close to 30 KV is applied between G2-G3. This means that the withstand voltage characteristic between G2 and G3 is very strict. Fig. 6 suggests that even if the G2-G3 gap is 1.5 mm or less, the improvement of the focus characteristic is not so large, so that the G2-G3 gap is advantageously 1.5 mm or more.

Fig. 7 is a focus characteristic when the G1 hole diameter is changed while the G3 bottom hole diameter is changed. By changing the G3 bottom hole diameter, it can be seen that the focus characteristic is dramatically improved as compared with the case of FIG. 7 shows that when the G1 hole diameter becomes 0.57 mm or less, a remarkable improvement in focus characteristics is obtained. The main conditions of Fig. 7 are as shown in Table 3. The focus voltage is adjusted to achieve the correct focus when the cathode current Ik is 2 mA.

G1 hole diameter (φG1) φ0.65 φ0.60 φ0.55 G1 plate thickness 0.08 0.08 0.07 G2 hole diameter (φG2) φ0.65 φ0.60 φ0.55 G2 plate thickness 0.39 0.39 0.36 G3 Bottom Hole Diameter (φG3) φ2.2 φ2.2 φ1.98 C-G1 gap 0.13 0.115 0.115 G1-G2 gap 0.32 0.305 0.195

Unit [mm]

Fig. 8 shows the relationship between the G3 bottom hole diameter and the focus characteristic when the G2-G3 gap is 1.53 mm. Even in this region, there is a significant dependence of the focus characteristic on the G3 bottom hole diameter in the high current region. Other conditions are as shown in Table 4. The focus voltage is adjusted to achieve the correct focus when the cathode current Ik is 2 mA.

G1 hole diameter (φG1) φ0.54 G1 plate thickness 0.08 G2 hole diameter (φG2) φ0.55 G2 plate thickness 0.36 C-G1 gap 0.105 G1-G2 gap 0.275 G2-G3 gap 1.53

Unit [mm]

6, 7 and 8, when the G3 bottom hole diameter is φ2.0 mm or less, a marked improvement in focus characteristics is observed, particularly in a large current region. However, in the vicinity of the bottom of the G3, the electron beam is widened. If the center of the G3 bottom hole is shifted from the center of the electron beam, the electron beam collides with the G3. In order to prevent this, considering the assembly precision of the electron gun, the G3 bottom hole diameter is preferably set to φ1.5 mm or more.

9 shows the relationship between the G2 sheet thickness TG2 and the focus characteristic. 9 shows that when the G2 plate thickness TG2 is 0.37 mm or less, the focus characteristic is improved when the low current region, in particular, the cathode current Ik is 0.5 mA. However, when the G2 plate thickness TG2 is 0.32 mm or less, the focus characteristic is deteriorated in a large current region under this condition, so the preferred G2 plate thickness TG2 is preferably 0.32 mm or more. Other conditions are as shown in Table 5.

G1 hole diameter (φG1) φ0.55 G1 plate thickness 0.08 G2 hole diameter (φG2) φ0.55 C-G1 gap 0.115 G1-G2 gap 0.255 G2-G3 gap 1.73

Unit [mm]

10 is a schematic diagram of a cathode used in this embodiment. The oxide 101 is divided into two layers, the lower layer 101b is a conventional oxide and the upper layer 101a is an oxide containing about 1.4 wt% of barium scandate. Moreover, it is effective to make content of barium scandate into 0.3 weight%-2 weight%. In this embodiment, the lower layer has a thickness of 20 µm and the upper layer has a thickness of 48 µm. Oxides containing barium scandate can withstand high cathode loading. The lower layer is an ordinary oxide because the adhesion to the cathode gap 102, which is mainly Ni, is good. The cathode sleeve 103 is made of a Ni—Cr alloy having a thickness of about 25 μm.

In the PRT of the present invention, compared to the conventional PRT, 17% in the low current region (cathode current Ik = 0.5 mA), 18% in the medium current region (Ik = 2.0 mA), 21% in the high current region (Ik = 6.0 mA) Focus improvement was possible. The dimensions of the electron gun used for the PRT having this characteristic are shown in Table 6.

G1 hole diameter (φG1) φ0.54 G1 plate thickness 0.07 G2 hole diameter (φG2) φ0.55 G2 plate thickness 0.36 C-G1 gap 0.105 G1-G2 gap 0.235 G2-G3 gap 1.73 Main lens Large diameter main lens shown in FIG.

Unit [mm]

The embodiment described so far has been directed to a large diameter electron gun in which the focus electrode G4 is fitted in the second anode G5, but the present invention can also be applied to the conventional Hi-UPF electron gun shown in FIG. In Fig. 11, the same reference numerals are used for the same electrodes as in Fig. 2. In FIG. 11, the focus electrode is divided into two, 14a and 14b, and is electrically connected by a metal strip 17. In FIG. The main lens is formed of the second anode 15 and the focus electrode 14b. In the example of FIG. 11, reference numeral 14b is slightly larger than the reference numeral 14a among the focus electrodes. This is to make the main lens diameter a little larger.

Although the above description is directed to a PRT whose performance requirements for focus are strict, the present invention is not limited to the PRT but can be applied to a three-electron gun-type color CRT using a Hi-UPF electron gun.

According to the present invention, it is possible to achieve an improvement in focus characteristics equivalent to that in the case where the main lens diameter is increased without having to increase the neck portion diameter.

Claims (25)

In a cathode ray tube having a panel having a fluorescent surface, a neck portion for embedding an electron gun, and a funnel portion for connecting the panel portion and the neck portion, In the electron gun, a cathode, a control electrode, an acceleration electrode, a first anode, a focus electrode, and a second anode electrode are arranged in this order toward the fluorescent surface, and an anode voltage is commonly applied to the first anode and the second anode, and to the focus electrode. A focus voltage is applied, an electron beam passing hole is formed in a portion where the control electrode, the acceleration electrode, and the first anode face toward the acceleration electrode, and the length in the tube axis direction of the focus electrode is the length in the tube axis direction of the first anode. And the diameter of the electron beam passing hole of the control electrode is 0.57 mm or less, and the distance in the vicinity of the outer circumference of the electron beam passing hole of the acceleration electrode and the first anode is 1.9 mm or less. The cathode ray tube according to claim 1, wherein the control electrode hole diameter is 0.50 mm or more and 0.57 mm or less. The cathode ray tube according to claim 1, wherein a distance in the vicinity of the outer circumference of the electron beam passing hole of the acceleration electrode and the first anode is 1.5 mm or more and 1.9 mm or less. The cathode ray tube according to claim 1, wherein the diameter of the electron beam passing hole of the first anode is 2.0 mm or less. The cathode ray tube according to claim 4, wherein the diameter of the electron beam passing hole of the first anode is 1.5 mm or more and 2.0 mm or less. delete The cathode ray tube according to claim 1, wherein the plate thickness in the vicinity of the electron beam passing hole of the acceleration electrode is 0.32 mm or more and 0.37 mm or less. The cathode ray tube according to claim 1, wherein the cathode has an oxide on the cathode ceiling surface, and the upper layer of the oxide includes barium scandate. 9. The cathode ray tube of claim 8, wherein the top layer of oxide comprises between 0.3% and 2.0% by weight of barium scandate. The cathode ray tube according to claim 1 or 2, wherein the hole diameter of the acceleration electrode is approximately equal to the hole diameter of the control electrode. In a cathode ray tube having a panel having a fluorescent surface, a neck portion for embedding an electron gun for generating a single electron beam, and a funnel portion for connecting the panel portion and the neck portion, In the electron gun, a cathode, a control electrode, an acceleration electrode, a first anode, a focus electrode, and a second anode electrode are arranged in this order toward the fluorescent surface, and an anode voltage is commonly applied to the first anode and the second anode, and to the focus electrode. A focus voltage is applied, an electron beam passing hole is formed in a portion where the control electrode, the acceleration electrode, and the first anode face toward the acceleration electrode, and the length in the tube axis direction of the focus electrode is the length in the tube axis direction of the first anode. And the diameter of the electron beam passing hole of the control electrode is 0.57 mm or less, and the distance in the vicinity of the outer circumference of the electron beam passing hole of the acceleration electrode and the first anode is 1.9 mm or less. 12. The cathode ray tube according to claim 11, wherein the panel has a glass thickness at the center of the screen larger than a thickness of the periphery of the screen, thereby forming an optical lens. The cathode ray tube according to claim 11, wherein the control electrode hole diameter is 0.50 mm or more and 0.57 mm or less. The cathode ray tube according to claim 11, wherein a distance in the vicinity of the outer circumference of the electron beam passing hole of the acceleration electrode and the first anode is 1.5 mm or more and 1.9 mm or less. The cathode ray tube according to claim 11, wherein the diameter of the electron beam passing hole of the first anode is 2.0 mm or less. The cathode ray tube according to claim 15, wherein the diameter of the electron beam passing hole of the first anode is 1.5 mm or more and 2.0 mm or less. delete 12. The cathode ray tube according to claim 11, wherein the plate thickness in the vicinity of the electron beam passing hole of the acceleration electrode is 0.32 mm or more and 0.37 mm or less. 12. The cathode ray tube according to claim 11, wherein the cathode has an oxide on the cathode ceiling surface and the upper layer of the oxide comprises barium scandate. 20. The cathode ray tube of claim 19, wherein the top layer of oxide comprises between 0.3% and 2.0% by weight of barium scandate. The cathode ray tube according to claim 11 or 13, wherein the hole diameter of the acceleration electrode is substantially the same as the hole diameter of the control electrode. 12. The cathode ray tube according to claim 11, wherein the tip of the focus electrode is inserted into the second anode, and the main lens is formed in the second anode. 23. The focusing electrode according to claim 22, wherein the focus electrode has a plurality of appearances, the panel portion side is a large diameter portion, the second anode has a plurality of appearances, the panel portion side is a large diameter portion, and the main lens has a large diameter of the focus electrode. A cathode ray tube, characterized in that formed in a portion having a large diameter between the portion and the second anode. The cathode ray tube according to claim 1, wherein the anode is 30 kV. 12. The cathode ray tube of claim 11, wherein the anode is 30 kV.