WO2008069793A1

WO2008069793A1 - Anode button position for a cathode ray tube funnel

Info

Publication number: WO2008069793A1
Application number: PCT/US2006/046532
Authority: WO
Inventors: James John Maley
Original assignee: Thomson Licensing; Maley, Elaine
Priority date: 2006-12-06
Filing date: 2006-12-06
Publication date: 2008-06-12

Abstract

A cathode ray tube has an envelope including a panel and a neck connected by a funnel. The funnel includes a main body portion having first and second regions. The first and second regions have a higher tensile stress than other regions of the main body portion, and the second region has a higher tensile stress than the first region. An anode button is provided in the first region of the main body portion. An exterior surface of the main body portion has first and second protective coatings. The first protective coating covers at least a portion of the first and second regions and is of a composition and thickness such that the first protective coating substantially reduces the susceptibility of the at least one region from incurring mechanical damage. The second protective coating covers at least a portion of the first protective coating and is of a composition and thickness such that the second protective coating protects the funnel from moisture contact.

Description

ANODE BUTTONPOSITIONFORA CATHODE RAY TUBE FUNNEL

Field of the Invention

The invention relates to cathode ray tubes and, more particularly, to a cathode ray tube having a glass funnel with first and second regions of high tensile stress, wherein an anode button is provided in the first region which has a lower tensile stress than the second region. The funnel may further be provided with a first protective coating on an external surface thereof for preventing mechanical damage to the funnel in the first and second regions of high tensile stress and a second protective coating on an external surface thereof for protecting the funnel from moisture contact. The invention further relates to a method of making the same.

Background of the Invention

As new types of image display devices, such as non-cathode ray tube flat panel displays, continue to be introduced into the marketplace, there is an increased demand to reduce the depth of conventional cathode ray tubes to remain competitive with the non- cathode ray tube flat panel displays. Because the depth of the cathode ray tube is largely determined by the depth of a glass funnel that forms the cathode ray tube, it is necessary to shorten the funnel to provide the cathode ray tube with a reduced depth. Shortening the funnel of the cathode ray tube requires increasing the deflection angle of the funnel. For example, the typical deflection angle of a reduced depth cathode ray tube is about 125-140 degrees. As the deflection angle of the funnel is increased, however, the tensile stress on the funnel is also increased.

Funnels having regions with tensile stress above 1350 pounds per square inch (PSI) are considered unsafe, because the funnel has a higher probability of mechanical failure if the funnel is exposed to moisture or incurs mechanical damage, such as a surface defect, scratch, ding, check, etc. In order to decrease the probability of mechanical failure, it is known to decrease the tensile stress on the funnel to 1350 PSI by increasing the glass thickness of the funnel. Increasing the glass thickness of the funnel, however, also increases the weight and cost of the cathode ray tube. For example, as shown in Figure 4, when the tensile stress on the funnel is maintained at a maximum of 1350 PSI and the deflection angle of the funnel is increased from 104 degrees to 118 degrees, the weight of the funnel increases by about 3 kilograms. Additionally, when the tensile stress on the funnel is maintained at a maximum of 1350 PSI and the deflection angle of the funnel is increased from 104 degrees to 130 degrees, the weight of the funnel increases by about 10.5 kilograms.

In order to enable the cathode ray tube to operate safely when the funnel has regions of tensile stress above 1350 PSI without having to increase the glass thickness of the funnel, coatings and/or tapes may be applied to an external surface of the funnel. The coatings and/or tapes help to prevent mechanical damage to the funnel in the regions of high tensile stress and help to protect the funnel from moisture contact. Because of high voltage leakage and breakdown, however, these coatings/and or tapes can not be applied in a region of an anode button, which is provided in the funnel. This is problematic in that the anode button in a standard cathode ray tube is provided along a minor axis of the funnel in the region with the highest tensile stress. Because of the location of the anode button, mechanical damage to the funnel and moisture penetration is therefore difficult to prevent in the region with the highest tensile stress.

It would therefore be desirable to develop a cathode ray tube that can safely operate when the funnel has regions of tensile stress above 1350 PSI so that the glass thickness of the funnel does not have to be increased to prevent mechanical failure. Summary of the Invention

The invention relates to a cathode ray tube having an envelope including a panel and a neck connected by a funnel. The funnel includes a main body portion having first and second regions. The first and second regions have a higher tensile stress than other regions of the main body portion, and the second region has a higher tensile stress than the first region. An anode button is provided in the first region of the main body portion. An exterior surface of the main body portion has first and second protective coatings. The first protective coating covers at least a portion of the first and second regions and is of a composition and thickness such that the first protective coating substantially reduces the susceptibility of the at least one region from incurring mechanical damage. The second protective coating covers at least a portion of the first protective coating and is of a composition and thickness such that the second protective coating protects the funnel from moisture contact.

Brief Description of the Drawings

The invention will now be described by way of example with reference to the accompanying drawings.

Figure 1 is a cross sectional view of a cathode ray tube.

Figure 2 is a top view of a funnel of the cathode ray tube. Figure 3 is rear partial sectional view of the funnel of Figure 2.

Figure 4 is a graph illustrating how the weight of the funnel generally increases as the deflection angle of the funnel increases when the funnel is maintained at a given tensile stress. Detailed Description of the Invention

Figure 1 shows a cathode ray tube 1 having a glass envelope 2. The glass envelope 2 includes a rectangular faceplate panel 3 and a tubular neck 4 connected by a funnel 5. The funnel 5 has a deflection angle 15 of at least 125 degrees. In the illustrated embodiment, the deflection angle 15 is about 125-140 degrees. The deflection angle 15, however, may vary depending on the desired dimensions of the funnel 5. The funnel 5 is provided with an anode button 6. An internal conductive coating (not shown) extends from the anode button 6 toward the faceplate panel 3 and to the neck 4. The faceplate panel 3 consists of a viewing faceplate 8 and a peripheral flange or sidewall 9, which is sealed to a seal edge 17 of the funnel 5 by a glass frit 7. A phosphor screen 12 is carried by an inner surface of the faceplate panel 3. The screen 12 can be a line screen with phosphor lines arranged in triads, wherein each of the triads includes three phosphor lines.

A mask frame assembly 10 is removably mounted in predetermined spaced relation to the screen 12. An electron gun 13, shown schematically by dashed lines in Figure 1, is centrally mounted within the neck 4. The electron gun 13 can generate and direct three inline electron beams, a center beam and two side or outer beams, along convergent paths through the mask frame assembly 10 to the screen 12. The cathode ray tube 1 is designed to be used with an external magnetic deflection yoke 14 shown in a neighborhood of the funnel-to-neck junction. When activated, the yoke 14 subjects the three beams to magnetic fields that cause the beams to scan horizontally and vertically in a rectangular raster over the screen 12.

The funnel 5 will now be described in greater detail. As shown in Figures 2-3, the funnel 5 includes a main body portion 16. The main body portion 16 has a glass thickness 18 and first and second regions 22, 23, respectively. In the illustrated embodiment, the first regions 22 lie along a major (horizontal) axis X of the funnel 5, and the second regions 23 lie along a minor (vertical) axis Y of the funnel 5. The second regions 23 have a higher tensile stress than the first regions 22. Both the first and second regions 22, 23 have a higher tensile stress than other regions of the main body portion 16. For example, the first and second regions 22, 23 may have a tensile stress above 1350 PSI. Although the main body portion 16 is illustrated as having two of the first regions 22 and two of the second regions 23, the number and dimensions of the first and second regions 22, 23 may vary depending on the thickness 18 and/or the deflection angle 15 of the funnel 5.

As shown in Figures 2-3, the anode button 6 is provided in the main body portion 16 along the major axis X of the funnel 5. In the illustrated embodiment, the anode button 6 is attached to the main body portion 16 in the first region 22. Alternatively, the anode button 6 may be attached along the major axis X of the funnel 5 in an area of the first region 22. The anode button 6 may be any conventional anode button used as an anode terminal of a cathode ray tube. Because the configuration and operation of anode buttons are well known in the art, further description thereof will not be provided herein. As shown in Figures 2-3, the main body portion 16 has a first protective coating 20 on an external surface 19 thereof. The first protective coating 20 covers at least a portion of the first and second regions 22, 23. The first protective coating 20 is not applied to the anode button 6. The first protective coating 20 is of a composition and thickness such that the first protective coating 20 substantially reduces the susceptibility of the first and second regions 22, 23 from incurring mechanical damage, such as a surface defect, scratch, ding, check, etc. The first protective coating 20 should also be made to be capable of withstanding cathode ray tube processing temperatures, to be discussed later. The first protective coating 20 may be, for example, a silicate layer containing inorganic fillers. The silicate layer may be, for example, a potassium silicate layer, a lithium silicate layer, or a sodium silicate layer, and the inorganic fillers may be, for example, an aluminum oxide, a silicon carbide, a boron carbide, or a titanium carbide.

As shown in Figure 2-3, a second protective coating 21 covers the first protective coating 20. The second protective coating 21 can substantially cover the main body portion 16 and extend from proximate the neck 4 to the seal edge 17. The second protective coating 21 is not applied to the anode button 6. The second protective coating 21 is of a composition and thickness such that the second protective coating 21 protects the funnel 5 from moisture contact. The second protective coating 21 may be, for example, a poly-tetrafluoroethylene (TEFLON®) or silicone layer containing graphite. Although the second protective coating 21 is illustrated as substantially covering the main body portion 16 and the first protective coating 20, the second protective coating 21 may cover only a portion of the main body portion 16 or the first protective coating 20 depending on the desired moisture protection and cathode ray tube capacitance.

The method of manufacturing the cathode ray tube 1 will now be described in greater detail. The anode button 6 is attached in the first region 22 of the main body portion 16 of the funnel along the major axis X using known methods. The first protective coating 20 is applied to the external surface 19 of the funnel 5 such that the first protective coating 20 covers at least a portion of the first and second regions 22, 23. The first protective coating 20 is not applied to the anode button 6. The first protective coating 20 may be applied using any conventional coating methods, for example, by spraying, brushing, roller coating, etc.

The faceplate panel 3, having a screen 12 and the mask support frame assembly 10, is aligned with the funnel 5 and sealed to the seal edge 17 of the funnel 5 at the peripheral sidewall 9 by melting the glass frit 7. The electron gun 13 is aligned and permanently mounted in the neck 4 of the funnel 5 using known methods. The envelope 2 is evacuated and hermetically sealed to form the cathode ray tube 1 using known methods.

The second protective coating 21 is then applied to the external surface 19 of the funnel 5 such that the second protective coating 21 covers the first protective coating 20. The second protective coating is applied such that it substantially covers the main body portion 16 or covers a majority of the main body portion 16 and extends from the neck 4 to the seal edge 17. The second protective coating 21 is not applied to the anode button 6. The second protective coating 21 may be applied using any conventional coating methods, for example, by spraying, brushing, roller coating, etc. Although the first protective coating 20 is taught as being applied to the funnel 5 before sealing the funnel 5 to the faceplate panel 3, such that the first protective coating 20 is subject to cathode ray tube processing temperatures, the first protective coating 20 may alternatively be applied at any stage during the manufacture of the cathode ray tube 1.

The first protective coating 20 protects the external surface 19 of the funnel 5 in the first and second regions 22, 23 of high tensile stress from mechanical damage, because the first protective coating 20 incurs and/or prevents mechanical damage that would otherwise occur on the funnel 5. The second protective coating 21 further protects the external surface 19 of the funnel 5 from being exposed to moisture. The funnel 5, therefore, has a lower probability of mechanical failure in the first and second regions 22, 23 of higher tensile stress. Because there is a lower probability of mechanical failure in the first and second regions 22, 23 of higher tensile stress, the funnel 5 can be manufactured with regions of higher tensile stress and a low glass thickness 18. The preferred thickness of either coating is 0.25-2.5 mils (6.35-63,5 microns). Additionally, the funnel 5 can safely operate when the first and second regions 22, 23 have a tensile stress above 1350 PSI without having to increase the glass thickness 18 of the funnel 5. In this way, the weight of the cathode ray tube 1 can be kept at a minimum, which benefits manufacturing yields and lowers costs. For example, as shown in Figure 4, when the tensile stress on the funnel 5 is maintained at a maximum of 2000 PSI and the deflection angle 15 of the funnel 5 is increased from 104 degrees to 118 degrees, the weight of the funnel 5 can be reduced by about 3.1 kilograms. Additionally, when the tensile stress on the funnel 5 is maintained at a maximum of 2000 PSI and the deflection angle 15 of the funnel 5 is increased from 104 degrees to 130 degrees, the weight of the funnel 5 can be reduced by about 4.8 kilograms.

Further, the anode button 6 is provided along the major axis X of the funnel 5 in the first region 22. Because the first region 22 has a lower tensile stress than the second regions 23 along the minor axis Y, the first and second coatings 20, 21 can adequately be provided on the second regions 23. The cathode ray tube 1 can therefore safely operate without having to increase the glass thickness of the funnel 5.

The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. Additional embodiments of the invention include the feature of the cathode ray tube 1 being a transposed scanning cathode ray tube, wherein the electron emitting cathodes are coplanar and oriented vertically and the electron beams emitted from the cathodes are scanned vertically. Other features include scenarios where only the first protective coating 20 is applied to at least a portion of the first and second regions 22, 23 of the funnel 5. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.

Claims

1. A cathode ray tube having an envelope including a panel and a neck connected by a funnel, the funnel comprising: a main body portion having a first region along a major axis of the runnel and a second region along a vertical axis of the funnel; and an anode button provided in the first region of the main body portion.

2. The cathode ray tube of claim 1, wherein the second region has a higher tensile stress than the first region.

3. The cathode ray tube of claim 1, wherein the funnel has a deflection angle of at least 125 degrees.

4. The cathode ray tube of claim 1, wherein the first and second regions have a tensile stress of at least 1350 pounds per square inch.

5. A cathode ray tube having an envelope including a panel and a neck connected by a funnel, the funnel comprising: a main body portion having a first region along a major axis of the funnel and a second region along a minor axis of the funnel; an anode button provided in the first region; a first protective coating on an exterior surface of the main body portion, the first protective coating covering at least a portion of the first and second regions; and a second protective coating on the exterior surface of the main body portion that covers at least a^' portion of the first protective coating.

6. The cathode ray tube of claim 5, wherein the second region has higher tensile stress and the first region funnel.

7. The cathode ray tube of claim 5, wherein the funnel has a deflection angle of at least 125 degrees.

8. The cathode ray tube of claim 5, wherein the first and second regions have a tensile stress of at least 1350 pounds per square inch.

9. The cathode ray tube of claim 5, wherein the second protective coating substantially covers the main body portion and extends from proximate the neck to the seal edge.

10. The cathode ray tube of claim 5, wherein the second protective coating is a silicone layer containing graphite or a poly-tetrafluoroethylene layer containing graphite.

11. The cathode ray tube of claim 5, wherein the first protective coating is a silicate layer.

12. The cathode ray tube of claim 11, wherein the silicate layer contains aluminum oxide, silicon carbide, titanium carbide, or boron carbide.

13. The cathode ray tube of claim 5, wherein the first protective coating has a thickness between 6.35 microns and 63.5 microns.

14. A method for making a cathode ray tube having an envelope including a panel and a neck connected by a funnel, comprising the steps of: providing the funnel with a main body portion having a first region along a major axis of the funnel and a second region along a minor axis of the funnel; attaching an anode button to the first region of the main body portion; attaching a seal edge of the main body portion to the panel; mounting an electron gun in the neck; and evacuating and sealing the envelope.

15. The method of claim 14, wherein the second region has a higher tensile stress than the first region.

16. The method of claim 14, further comprising forming the funnel to have a deflection angle of at least 125 degrees.

17. The method of claim 14, wherein the first and second regions have a tensile stress of at least 1350 pounds per square inch.

18. The method of claim 14, further comprising coating an external surface of the main body portion with a first protective coating such that the first protective coating covers at least a portion of the first and second regions, the first protective coating being of a composition and thickness to substantially reduce susceptibility of the at least one region to mechanical damage.

19. The method of claim 18, further comprising coating at least a portion of the first protective coating with a second protective coating, the second protective coating being of a composition and thickness to protect the funnel from moisture contact.

20. The method of claim 18, wherein the first protective coating has a thickness between 6.35 microns and 63.5 microns.