GB2236428A

GB2236428A - Process for coating phosphor slurry on a cathode ray tube

Info

Publication number: GB2236428A
Application number: GB9020504A
Authority: GB
Inventors: Seong-Ha Lim
Original assignee: Samsung Electron Devices Co Ltd
Current assignee: Samsung SDI Co Ltd
Priority date: 1989-09-20
Filing date: 1990-09-20
Publication date: 1991-04-03
Anticipated expiration: 2010-09-20
Also published as: GB9020504D0; KR910007042A; CN1050466A; CN1031086C; GB2236428B; KR920001340B1

Abstract

Phosphor slurry 12 from nozzle 11 coats the inner surface of CRT panel 10 which is mounted on a rotating support carrier 20, wherein the inclination of this axis of rotation X-X is varied by swinging the support carrier about a further axis 22. In the process, the support carrier 20 swings irregularly or regularly within a predetermined angle ( theta ) to reciprocate the panel 10 within a predetermined distance in relation to the nozzle 11. The panel (10) preferably reciprocates within said predetermined distance in such a manner that the panel (10) advances a distance, and then returns a distance which is shorter than the distance of advance, so that the entire surface of the phosphor screen is evenly coated. <IMAGE>

Description

PROCESS FOR COATING PHOSPHOR SLURRY ON A CATHODE RAY TUBE The present invention relates to an improved process for coating a phosphor slurry on the inner surface of the panel of a cathode ray tube (CRT).

Conventionally, the process for manufacturing a screen of a CRT comprises the steps of forming a coated layer by applying phosphor slurry onto the inner bottom surface of a panel, forming an unprocessed phosphor layer by drying the coated layer, exposing the phosphor layer in the shape of dot or stripe, and developing the exposed phosphor layer to obtain a desired phosphor layer.

A general method for providing a phosphor slurry on the inner surface of the panel is described in relative detail in U.S. Pat. No. 4,035,524. As illustrated in Fig. 1, of the accompanying drawings, for example, a panel 10 is held by a head 21 of a support carrier 20, which is designed to rotate about its axis x-x tilted at a predetermined angle, so that a.phosphor slurry 12 is supplied onto the inner bottom surface of the panel 10 which is rotated at a predetermined speed of revolution. In the above-mentioned method, if the phosphor slurry 12 is supplied onto the inner surface of the panel 10 rotating around a revolution axis, the coated layer of a phosphor slurry can be uniformly formed over the entire inner surface of the panel in a relatively short time.

Recently, a method of applying a phosphor slurry onto the panel which is improved compared with the aforementioned prior art was disclosed in the Korean Patent Publication No. 832602. The invention disclosed in that publication is a process for applying a stream of phosphor slurry onto a panel wherein said process includes rotating the panel at a low speed during the applying of a phosphor slurry onto the inner surface of the panel, and subsequently rotating at high speed during a predetermined time interval, after the coating operation of the phosphor slurry is completed.

As compared with the conventional methods for applying phosphor slurry, a more uniformly coated layer of a phosphor slurry can be obtained by the use of the aforesaid process.

However, this method is not sufficient to manufacture a CRT having an improved high image quality which meets the consumers' demands. Also, in the conventional methods, a coated region of a phosphor slurry is too wide to obtain a desired uniform thickness in a larger-sized CRT.

In more detail, according to the conventional method for applying a phosphor slurry, since the panel on which the phosphor slurry is coated is rotated only in one direction at low or high speed, non-uniformity of the coating due to the flowing of the phosphor slurry in any one way may occur. Furthermore, in order to manufacture a screen for use in a larger-sized CRT, it may well take a longer time to rotate the panel, so that the coating layer on the peripheral region of the inner surface of the panel is thicker than the coating layer on the central region thereof. In particular, because a large quantity of the phosphor slurry is thickly formed on the corner region of the panel, the layer on the peripheral region of the screen may be abnormally formed.

An object of the present invention is to provide a method for applying a phosphor slurry on the inner surface of the panel of a CRT, by which the coating layer is uniformly formed, and the flatness and smoothness of the coating are markedly improved, resulting in high image quality.

According to the present invention, there is provided a method for applying a phosphor slurry onto the inner surface of the panel of a cathode ray tube which comprises rotating said panel such that the rotating axis of the panel swings regularly or irregularly.

According to the method of the present invention, centrifugal force facilitating the spread of a phosphor slurry across the entire inner surface of the panel, is altered regularly or irregularly and relative position between the nozzle and panel varies, achieving the uniform distribution of the phosphor slurry over the entire inner surface of the panel.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: FIG. 1 is a schematic side view of a device for applying a phosphor slurry, for explaining à conventional method for applying phosphor slurry; FIG. 2 is a schematic side view of a device for applying a phosphor slurry for explaining the method for applying phosphor slurry according to the present invention; FIG. 3 illustrates the relative position of the panel moving within a predetermined distance in relation to the nozzle when the phosphor slurry is applied to and is coated on the inner surface of the panel by a method according to an embodiment of the present invention; and FIG. 4 illustrates the relative position of the panel in relation to the nozzle in another embodiment of the present invention.

FIG. 2 illustrates a method for applying a phosphor slurry according to an embodiment of the present invention.

Referring to Fig. 2, the panel 10 onto which the phosphor slurry is applied, is supported by support carrier 20 used in a manufacturing process of a cathode ray tube, and is then rotated therewith. The support carrier 20 stays in a fixed position when it arrives at the line for coating phosphor slurry on the panel, then the support carrier 20 is rotated by means of a driving apparatus which is not shown. A nozzle 1.1 is positioned above the panel 10. Phosphor slurry 12 ejected from the nozzle 11, is applied onto the inner surface of the panel. As illustrated, the inner surface of the panel 10 is directed upwardly. When the phosphor slurry is ejected from the nozzle, the panel 10 is rotated at a predetermined velocity according to the movement of the head 21 of the support carrier 20.At the same time, the inclination of a revolution axis of the panel 10 is continuously varied by swinging the support carrier 20 about an axis 22. The angle e of swing is limited between the revolutional axes X-X and X'-X'. In more detail, the angle 9 is defined within the extent that the nozzle 11 is not deviated from the inner surface of the panel 10 to reciprocate a predetermined distance t as shown in FIG. 3.

If the phosphor slurry is applied to the inner surface of the panel 10 through the method as described above, the centrifugal force due to the rotation of the panel 10 is compositely varied according to the swing of the panel 10, so that spreading of the phosphor slurry over the panel is actively carried out. Noreover, the formation of the phosphor slurry concentrated at the corners of the panel is reduced by the composite centrifugal force. Therefore, the thickness of the coating layer of the phosphor slurry formed on the inner surface of the panel becomes uniform and smooth.

FIG. 4 illustrates another embodiment of the method for applying phosphorslurry to the panel according to the present invention.

In FIG. 4, a panel 10 is designed to reciprocate within the distance Q in a similar way to the first method. However, the reciprocating motion of the panel 10 is repeated within the distance Q divided into a plurality of sections, in which the panel advances the distance ', then retreats the distance e" which is shorter than the advancing distance '.

That is, the swinging angle of the panel 10 is determined within the angle 6, and the panel is reciprocated within the divided short distance in such a tanner that the panel does not swing in the angle 9 at one time, but swings through an smaller than 9 at a time. In FIGS. 3 and 4, the rotating state of the panel was not illustrated to avoid complexities and confusion.

In addition, through the repeated reciprocating motion within the divided distance as described above, impulsive force of inertia may come into being and be applied to the panel by shortening the retreat distance e" and by quickening the swing speed.

When the phosphor slurry is applied onto the inner surface of the panel to be coated according to the above described method, the phosphor slurry spreads across the entire surface of the panel by the centrifugal forces, which are altered compositely. Further, because the impulsive force by the reciprocating motion within the limited narrow distance is applied to the phsphor slurry, the efficiency of spreading is increased by the force of inertia and the sedimentation rate of the phosphor particles in the phosphor slurry can be enhanced.

According to the embodiment of the present invention as described above, the flatness of the surface of the panel is improved, and the phosphor screen layer can be formed uniformly by changing the inclination of the revolutional axis and by applying impulsive forces to the phosphor slurry.

Therefore, the deterioration of the image quality of the phosphor screen caused by the uneven thickness of the coating layer is avoided, and the phosphor screen having high luminance is obtained.

Claims

CLAIMS:

1. A process for coating phosphor slurry on the inner surface of a cathode ray tube comprising applying a phosphor slurry ejected from a nozzle onto the inner surface of the panel held by a support means rotating about an axis thereof, wherein said axis of the support means swings within a predetermined angle to reciprocate the panel within a predetermined distance in relation to the nozzle, whereby the centrifugal force facilitating spread of the phosphor slurry across the entire inner surface of the panel is altered.

2. A process according to claim 1 wherein said axis of the support means swings such that the centrifugal force is altered regularly.

3. A process according to claim 1 wherein said axis of the support means swings such that the centrifugal force is altered irregularly.

4. A process as claimed in claim 1 or 3, wherein.said panel reciprocates in such a manner that the panel advances a predetermined distance, and then retreats a distance which is shorter than the distance of advance and repeats advancing and retreating in a similar manner.

5. A process for coating phosphor slurry on the inner surface of a cathode ray tube substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.

6. A panel for cathode ray tube coated with phosphor slurry by the process claimed in any preceding claim.

7. A cathode ray tube comprising the panel of claim 6.