JPH0340343A - Cathode-ray tube - Google Patents

Abstract

PURPOSE: To conduct the beam focusing operation of an electron gun with accuracy by preventing the deposition of a getter on the inner surface of an open hollow tube of electric insulating material which is the focusing structure portion of the electron gun. CONSTITUTION: In a cathode-ray tube 1, an electron gun 3 is disposed in a neck portion, a luminescence screen 41 is disposed on the opposite side end thereof, and a getter 43 is provided between the electron gun 3 and the luminescent screen 41. A focusing structure portion 10 constituting the electron gun 3 comprises a hollow tube 12 of electric insulating material such as ceramics or the like, and its inner face is equipped with a layer 14 of material having high electric resistance. For example, an open auxiliary tube 45 of the electric insulating material is provided on a coaxial line with the hollow tube 12 at the end portion 15 of the hollow tube 12 so that focusing effect is not deteriorated resulting from the deposition of the getter on the layer 14. Thereby, the almost all getter is deposited on the open auxiliary tube 45.

Description

TECHNICAL FIELD The present invention relates to cathode ray tubes, which include a luminescent screen on one side.
), an electron gun having a neck portion on the other side, and an electron gun positioned in the neck and including a beam forming portion and a focusing structure, where the focusing structure is made of an electrically insulating material. open-ended hollow tube
an inner surface (hollowtube) and on which a layer of material with high electrical resistance is deposited.
ace) and a getter array (get
ter arrangement).

Such cathode ray tubes can be used in black and white televisions, projection televisions, character image displays (data graphic displays) and other devices in which cathode ray tubes are used.

BACKGROUND ART Even though, in theory, precise focusing can be obtained by a layer of material with high electrical resistance, for example in the form of a helical structure, at both ends of which a potential difference is applied, It has been found that in practice the focusing is not always as expected.

DISCLOSURE OF THE INVENTION It is an object of the invention to provide a cathode ray tube with an electron gun having a focusing structure of the type defined in the opening article so as to provide particularly accurate focusing.

According to the invention, a cathode ray tube of the type defined in the opening article is characterized in that a layer on the inner surface of the hollow tube is shielded from the getter arrangement.

The present invention is based on the following recognition.

Typically, the envelope is evacuated during manufacture of the cathode ray tube. Cathode ray tubes have approximately 400
It is heated to a temperature of degrees Celsius. It is customary to place a getter array in a cathode ray tube to combine gases released during pumping and during the operating life of the tube. The getter array includes a material capable of binding the emitted gas. In television tubes, the material includes, for example, inter alia metallic barium. In order to obtain sufficient gas coupling, the getter material is generally placed in an envelope and evaporated during the manufacturing process (gettering), so that a finely distributed layer of getter material is e.g. The present invention provides that the desired high electrical resistance of the layer (for example of the order of 10I6Ω) is insidiously reduced during this gettering operation due to the deposition of the conductive getter material onto the resistive material layer. It is based on the recognition that If the high ohmic resistance layer has a helical structure, the generated focused electric field will be disturbed because the deposited getter material will create short circuits between the individual turns.

In the cathode ray tube according to the invention, the inner surface of the hollow tube is shielded from the getter array, which means that the layer of material with high electrical resistance of the focusing array is shielded from the getter material deposited thereon during the gettering operation. It means that This shielding is carried out by specific positioning of the hollow tubes and the use of getter arrangements and/or shielding means relative to each other.

In a conventional electron gun with a focusing lens formed from a metal can, the fact that the getter material falls or does not fall onto the focusing lens part has no consequence on the focusing effect of the electron gun. .

In cathode ray tubes in which a getter array is provided between the end of the hollow tube and the luminescent screen, for example on the anode contact, the inner surface of the hollow tube is effectively shielded from the getter array in one embodiment of the invention. ing. This is because an open auxiliary tube (o
pen-ended auxiliary tube)
is provided, the axis of which is substantially aligned with the axis of the hollow tube. In practice, it has been found that the evaporated getter material is deposited primarily at the end of the hollow tube facing the luminescent screen. By providing a hollow tube with an open auxiliary tube, the getter material evaporated toward the end of the hollow tube will be deposited mostly or completely on the auxiliary tube and not on the high ohmic resistance layer.

Sealing of the resistive layer from evaporated getter material by the auxiliary tube, even if the getter arrangement is not provided between the end of the hollow tube and the luminescent screen, but is provided, for example, around the hollow tube. ding is even more efficient. This auxiliary tube has a cylindrical or conical shape, for example.

In a preferred embodiment of the cathode ray tube according to the invention, the minimum internal diameter of the auxiliary tube is smaller than the internal diameter of the hollow tube. If the inner diameter of the auxiliary tube is smaller than the inner diameter of the hollow tube, the auxiliary tube also functions as a diaphragm. The shielding of the highly ohmic layer on the inner surface of the hollow tube is efficient as a result of acting as a partition.

Accurate shielding is also obtained if the septum is attached to the end of the hollow tube.

Another preferred embodiment of the cathode ray tube according to the invention is characterized in that the auxiliary tube is made of an electrically insulating material.

Generally, during operation of a cathode ray tube, the generated electron beam is deflected across a luminescent screen by a deflection unit. The deflection electric field generated by the deflection unit can extend far beyond or even into the focusing structure. i!
By manufacturing the auxiliary tube from electrically insulating material, the deflection electric field is not adversely affected. It is advantageous for the auxiliary tube to be part of the hollow tube. This requires fewer individual parts in the cathode ray tube.

A further embodiment of the cathode ray tube according to the invention, in which the deflection electric field to be generated is not substantially adversely affected, provides that the auxiliary tube is made of an electrically insulating material and that the auxiliary tube is substantially attached to the axis of the hollow tube. It is characterized by having at least one void extending in parallel.

The air gap in the auxiliary tube prevents excessive currents occurring in the auxiliary tube that may interfere with the deflection field.

A getter array is mounted in a position between said end and a luminescent screen at said end of the hollow tube, so that the getter array with a focusing structure is integrated and requires fewer separate parts in the cathode ray tube. It is preferable that

Another preferred embodiment according to the invention is characterized in that the getter arrangement is located in the neck between the hollow tube and the inner surface of the neck. As a result, the evaporated getter material is largely or completely deposited on the outer surface of the hollow tube and the inner surface of the neck, and the electrical resistance of the layer on the inner surface of the hollow tube is adversely affected. minimize.

A cathode ray tube according to the invention is preferred in order to prevent the evaporated getter material from depositing on the high ohmic resistance layer through the end of the hollow tube facing away from the luminescent screen during gettering. In an embodiment, a shield is placed between the end of the hollow tube opposite the fluorescent screen and the inner surface of the neck of the cathode ray tube. This causes the evaporated getter material to adhere to the shield.

Some embodiments of cathode ray tubes according to the invention will be explained in detail by way of example with reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a cathode ray tube is shown with a luminescent screen, such as a fluorescent screen 40 deposited on a display window 41, and an electron gun 3 mounted on the neck 2.

A Gl (grid) electrode structure is provided with a typical opening behind which a cathode 4 with an electron-emitting surface is placed with a heater 5 in contact with it. The G2 electrode structure, which in this case is constituted by a thin metal plate 6 with a central opening, is further located on the front side adjoining the G1 electrode structure.

A G3 electrode structure composed of a thin metal plate is located further in front of the front surface. To form the assembly, the electrode structures Gl, G2 and G3 constituting the beam-generating part of the electron gun, in this case the triode part, are attached via pins (or brackets) to an insulating mounting rod, which One (8) is shown in FIG. Two rods are used in this case. However, the invention is not limited thereto. For example, four or three mounting rods could alternatively be used and are themselves used in a conventional manner. The focusing structure 10 includes a hollow tube 12 of electrically insulating material, such as glass or ceramic, and
The hollow tube 12 is coated with an inner surface having a layer 14 of material with high electrical resistance. The hollow tube 12 is rigidly connected at its end 13 to a fold edge 17 of a sheet metal 16, which fold edge 17
The attachment which surrounds the opening 18 of 6 and to which the beam forming part of the electron gun is fixed via the thin metal plate 16 is attached to the rod. The tube 12 is fixed at its end 15 to the mounting rod in a similar manner by means of a sheet metal 31.

To obtain precise focusing, a potential difference is applied across the edges of the layers by connecting the metal sheets 16 and 31 to an external voltage source (not shown in Figure 1). layer 14
may have the shape of one or more rings or may have a combination with one or more rings, for example a helical shape or a helix. electron gun 3
is a flexible element in this example.
element) is positioned on the neck 2 by a centering unit with 32. The flexible element 32 also provides an electrical connection between the thin plate 31 and a conductive layer 33 deposited on the inner surface of the tube envelope.

In the envelope, the anode contact 42 is connected to the conductive layer 33
exists so as to apply a desired potential to.

A getter array 43 is provided on the anode contact 42 .

Getter array 43 includes getter material capable of binding the emitted gas and providing a vacuum to the envelope. To obtain proper gas coupling, getter material 44 is evaporated during the manufacturing process, thus forming a finely distributed getter material. An open auxiliary tube 45 is connected to the end 15 of the hollow tube 12 facing the fluorescent screen 14, the axis 46 of which lies substantially in the extension of the axis 47 of the hollow tube 12. hollow tube 1
Due to the fact that the getter material evaporated in direction 2 is mostly or completely deposited in the auxiliary tube 45, the resistive layer 1
The inner surface of the hollow tube 12 provided with 4 is shielded from getter material. The electrical resistance of resistor [14] and the focusing of focusing structure 10 are not adversely affected substantially or to a large extent by the deposited getter material due to the presence of auxiliary tube 45.

FIG. 2 shows a longitudinal sectional view of another embodiment of the cathode ray tube according to the invention. Like reference symbols in FIGS. 1 and 2 indicate like components. In this embodiment, the getter array 43 is provided with a shield 50. This shield 50 is located between the getter material 43 and the hollow tube 12. The evaporated getter material will deposit on the shield 50 and substantially no getter material will adhere to the high ohmic resistance layer 14, resistor N14 is thus shielded from the getter array 43.

During operation of the cathode ray tube, the generated electron beam is deflected across the fluorescent screen 40 by a deflection unit (not shown). The deflection electric field generated by the deflection unit will extend far beyond or even into the hollow tube 12 of the focusing structure. The auxiliary tube 45 should not have a substantial detrimental effect on this deflection field, especially at high frequencies.

If the auxiliary tube 45 is made of metal as shown in FIG. 1, the deflection field will not be substantially adversely affected if the auxiliary tube 45 is provided with one or more slots 51. The number of slots 51 made in the auxiliary tube 45 depends on the extent of the adverse influence of the auxiliary tube 45 on the deflection electric field.

Preferably, the auxiliary tube 45 is made of an electrically insulating material, such as glass. In this way, the deflection electric field generated is not adversely affected in a simple manner. In FIG. 1, the inner diameter of the auxiliary tube 45 is equal to the inner diameter of the hollow tube 12. Preferably, the inner diameter of the auxiliary tube 45 is smaller than the inner diameter of the hollow tube 12, so that the resistive layer 14 is shielded to an improved degree from getter alignment.

FIG. 3 is a longitudinal sectional view of another embodiment of the cathode ray tube according to the present invention. In this embodiment, the hollow tube 12 contains both the focusing structure 10 and the electrodes of the beam forming section. The potential is supplied to the electrodes of the beam forming part, for example, through a through conductor (f
eed-through wire) (not shown in FIG. 3). The hollow tube 12 is suspended from the connecting pin 23 to the neck 2 and by a flexible element 32. In this embodiment, the auxiliary tube 45 is an extension of the hollow tube 12. Auxiliary pipe 4
The end of 5 is closed by a partition wall 52, onto which a portion of the evaporated getter material is deposited. The resistance 1i14 on the inner surface of the hollow tube 12 extends to the auxiliary tube 45.

In fact, if the auxiliary tube 45 has an inner diameter equal to the inner diameter of the hollow tube 12 and a length of 15 mm, substantially all of the evaporated getter material will be deposited on the inner surface of the auxiliary tube 45. In this case, the partition wall 52, on which a portion of the evaporated getter material is deposited, is even redundant. Resistive layer 14 is thus shielded from the getter array without unnecessarily increasing the number of cathode ray tube components.

FIG. 4 shows a part of a cathode ray tube according to the invention,
Here, the hollow tube 12 has both the focusing structure 10 and the auxiliary tube 45, as well as a getter array 44.

The getter array 44 is attached to the centering unit with the flexible element 32 by a metal strip 48.

In this example, the getter array is the fluorescent screen 4
It is located 22 mm from the end of the hollow tube 12 in the direction of 0. The hollow tube 12 has an inner diameter of 10 mm.

The auxiliary pipe 45 has seven lengths and six inner diameters. Due to the fact that the auxiliary tube 45 has a smaller internal diameter than the hollow tube 12, the auxiliary tube 45 functions as a septum.

A length of 7IIIw has been found to be sufficient to ensure that virtually no evaporated getter material is deposited on the resistive layer 14. In this way, an integrated unit is created, which can be well processed during the manufacture of cathode ray tubes, and which resistive layer 14 has a getter arrangement 44 despite its compact structure, in which getter array 44 is located at a relatively short distance from hollow tube 12. It is well shielded from array 44.

FIG. 5 shows another embodiment of the cathode ray tube according to the invention. In this case, the getter array 9 is located in the neck 2 surrounding the hollow tube 12. The getter array 9 includes a getter material 19, which after gettering forms a finely distributed layer 20 of getter material. This layer 20 of evaporated getter material is substantially completely located on the outer surface of the hollow tube 12 and on the inner surface of the neck 2. Because of this structure, virtually no getter material is deposited on resistive layer 14.

In this embodiment, the getter array 9 is annular and attached to the centering unit by a strip 53. However, the invention is not limited thereto.

For example, the getter array can be attached to mounting rods, one of which (8) is shown, or supported by the hollow tube 12 or neck 2.

A shield 21 , in this case an annular shield, is provided near the end 13 of the hollow tube 12 between the hollow tube 12 and the inner surface of the neck 2 . During gettering, the getter material traveling towards the cathode 4 thus adheres to the annular shield 21. This prevents getter material from depositing on the high ohmic resistance layer through the end 13 of the hollow tube. The shield 21 may be made of a metallic or insulating material, for example.

In the embodiment of the cathode ray tube according to the invention, as shown in FIG. A structure is obtained. Prior to the gettering procedure, getter material is included in the channel.

After evaporation, the getter material is present at least partially on the outside of the hollow tube 12 and on the inside of the neck 2.

A conical shield 22, the diameter of which in this case tapers down towards the phosphor screen, is disposed between the hollow tube 12 and the inner surface of the neck 2 and is connected to the high ohmic resistance layer 14. prevents unwanted precipitation of getter material.

In the cathode ray tube according to the invention, proper focusing of the electron beam on the fluorescent screen is obtained because no or all getter material is deposited on the focusing structure.

Although the invention has been described with reference to a cathode ray tube with a single electron gun, it will be apparent to those skilled in the art that it is also suitable for use with color cathode ray tubes.

[Brief explanation of drawings]

FIG. 1 shows a longitudinal sectional view of a cathode ray tube according to the invention, and FIGS. 2 to 6 show longitudinal sectional views of other embodiments according to the invention. 1... Cathode ray tube 2... Neck 3... Electron gun 4... Cathode 5... Heater 6... Metal thin plate 8... Insulated mounting rod (one of them) 9... Getter Arrays 9a, 9b... Annular channel lO... Focusing structure 12... Hollow tube 13... End portion 14... Resistance layer 15... End portion 16... Metal thin plate 17... - Folded edge 18... Opening 19... Getter material 20... Layer 21... Annular shield 22... Conical shield 23... Connection bin 25... Envelope 31... Thin metal plate 32...Flexible element 33...Conductive layer 40...Fluorescent screen 41...Display window 42...Anode contacts 43, 44...Getter array 45...Auxiliary tubes 46, 47 ... Shaft 48 ... Metal strip 50 ... Shield 51 ... Slot 52 ... Partition wall 53 ... Strip

Claims (1)

[Claims] 1. having a luminescent screen on one side and a neck odor envelope on the other side, and having an electron gun positioned in the neck and including a beam forming part and a focusing structure. , in which the focusing structure comprises an open hollow tube of electrically insulating material and has a getter array provided in the envelope and an inner surface on which a layer of material with high electrical resistance is deposited, the hollow A cathode ray tube characterized in that the inner surface of the tube is shielded from the getter array. 2. At the end of the hollow tube facing the luminescent screen,
Cathode ray tube according to claim 1, characterized in that an open auxiliary tube is arranged, the axis of which is located substantially in the extension of the axis of the hollow tube. 3. The cathode ray tube according to claim 2, wherein the inner diameter of the auxiliary tube is smaller than the inner diameter of the hollow tube. 4. A cathode ray tube according to claim 2 or 3, characterized in that the auxiliary tube is made of an electrically insulating material. 5. The cathode ray tube according to claim 4, wherein the auxiliary tube is a part of a hollow tube. 6. Cathode ray tube according to claim 2 or 3, characterized in that the auxiliary tube is made of a conductive material and comprises at least one slot extending approximately parallel to the axis of the hollow tube. 7. Cathode ray according to any one of claims 2 to 6, characterized in that a getter arrangement is fixed in a position between said end and a luminescent screen at said end of the hollow tube. tube. 8. The cathode ray tube of claim 1, wherein the getter array is positioned in the neck of the cathode ray tube between the hollow tube and the inner surface of the neck. 9. A cathode ray tube according to any one of claims 1 to 8, characterized in that the getter arrangement comprises an annular channel. 10. The cathode ray according to any one of claims 1 to 9, characterized in that a shield is provided between the end of the hollow tube opposite the luminescent screen and the inner surface of the neck of the cathode ray tube. tube.