EP1469502A1 - Colour display tube having an improved magnetic shield - Google Patents

Abstract

The picture tube has a shielding cap (14) mounted on a mask frame that composed of transverse bars (11) and longitudinal bars (12). A shielding plate is secured to the longitudinal bar of the mask frame and covers a part of an outer side of the longitudinal bar. The plate is provided with a slot for influencing a magnetic flux. A position of the plate is oriented according to a position of the slot provided in the cap. Independent claims are also included for the following: (A) a colour monitor or television set with a colour picture tube (B) a manufacturing method for a colour picture tube comprising a glass body, which is composed of a screen tray and a cone.

Description

The invention relates to a color picture tube with improved shielding against external magnetic fields and a manufacturing process for such color picture tubes. In particular The invention relates to a color television and a color monitor with a such color picture tube are equipped.

Fig. 1 shows a cross section through a conventional color picture tube. A color picture tube consists essentially of a glass body 1, which in the manufacture of a front section, the "umbrella pan", and a conically shaped rear section is put together. On the inside of the front screen 2 of the color picture tube a phosphor layer with phosphor dots or strips is applied. The electron beams to control the phosphor dots are from an electron gun 3 generated, which is arranged in the neck of the color picture tube. The electrical signals to control the electron gun 3, these are supplied from outside via contact pins. By means of a deflection unit 4 mounted on the outside of the electron gun the electron beams generated by the electron gun 3 are deflected so that one after the other all pixels of the fluorescent screen can be controlled.

At a distance of about 15 mm in front of the fluorescent screen is inside the Color picture tube a shadow mask, which is held in a mask frame 5. The Shadow mask has a plurality of holes, each hole a color triple is assigned to the fluorescent screen. The holes are in the regular intervals Shadow mask etched and have a diameter of about 0.25 mm. The Shadow mask is held by the mask frame 5 in order to make the mask sufficient give mechanical stability and ensure their manageability.

The electron beams on their way from the electron gun 3 to the fluorescent screen The color picture tube has shielding against the influence of the earth's magnetic field inside a shielding hood 6. With such a shielding hood you can Color impurities in the image reproduction are avoided, which result from that the electron beams no longer exactly match the corresponding color point or color stripe to meet. The shielding hood 6 arranged in the glass body 1 is made of a highly permeable material Made of material.

In many color picture tubes, the mask frame 5 also provides a shield from the earth's magnetic field. However, modern color picture tubes often have mask frames, due to additional requirements made of materials with a poorer shielding effect are made. For example, the frame for tension masks is in SST technology (semi-stretch tension technology) is often made from iron. Due to the high mechanical stress on this stenter, it has a lower magnetic permeability than the material of the shielding hood. The poorer shielding effect of the mask frame 5 affects in particular that axial field (Z field) in the direction of the tube axis.

To avoid the poorer shielding effect of color picture tubes with a mask frame To compensate for less permeable material, the shield can move towards the The screen can be extended so that the screening hood also covers the mask frame shields. The shielding hood is extended so that in particular the longitudinal spars of the mask frame are shielded.

So that the magnetic flux is guided to the mask as well as possible, the extended one is Shield hood welded to the mask frame. This can cause interruptions of the magnetic flux can be avoided. Interruptions of the magnetic Flow to the mask cause components of the magnetic flux in a vertical direction (Y-) direction so that the electron beams are deflected in the horizontal (X-) direction become.

Welding the shielding hood to the mask frame, however, brings special Problems with themselves. Only then can the shielding hood be welded to the mask frame when the so-called "shielding process", i.e. the applying the phosphor layer on the inside of the screen, is completed, so immediately before "frying together" the components of the screen pan and cone of the vitreous.

The shielding process in the manufacture of a color picture tube requires that Mask-frame combination, i.e. the shadow mask held in the frame into which Shield tray is inserted. This is the only way to apply the phosphor layer exactly possible. Welding the shielding hood after the application of the phosphor layer leads to welding spatter damage to the fluorescent layer. To one To avoid damaging the fluorescent layer are therefore additional work steps required. To do this, the mask-frame combination is removed from the Umbrella pan "unbuttoned" and removed. After the welding process the mask frame with the shielding hood attached to it again in the Umbrella pan "buttoned". Unbuttoning and buttoning in and out of the umbrella tray makes expensive and complex manufacturing steps necessary.

The object of the invention is to provide a color tube that is easier to manufacture and a corresponding one Specify manufacturing process for color picture tubes.

This object is with the feature of claim 1 for a color picture tube and solved the features of claim 15 for a manufacturing method.

According to the invention, an additional shielding plate is attached to the mask frame, which is shielded from external magnetic fields. The shield is on the outside a longitudinal spar of the mask frame mounted. Because of such a shield it is no longer necessary to extend the shielding hood towards the shield and welded to the mask frame. The shield can be a very much earlier in the manufacturing process than the shield are attached to the mask frame, in particular before the application of the phosphor layer. In addition, the shielding hood itself no longer has to be with the mask frame can be welded, but can finally be easily with the mask frame get connected. It is a particular advantage of the present invention that complex removal and insertion of the mask-frame combination after the shielding process. It is therefore possible to use a color picture tube to produce good imaging properties in a simple manner.

The shielding plate is preferably welded to the mask frame. To this A particularly good magnetic flux to the mask can be achieved in this way.

In order to achieve a good shielding effect, the shielding plate is preferably made of made of a highly permeable material.

According to a preferred embodiment, the shielding plate is constructed in several parts or provided with slots that run transversely to the longitudinal direction of the shielding plate. Such a multi-part embodiment and also a slotted version of the shield plate allow the magnetic flux in the shield plate to influence. This makes it possible to have harmful influences on the movement of the electron beams and thus to avoid the reproduction quality of the color picture tube. According to a simple embodiment, the shield is formed in two parts or with provided with a single slot. A more complex control of the magnetic flux is with a plurality of slots or with a larger number of components of the shielding plate possible.

According to a preferred embodiment, the slot or slots are in the shielding plate arranged so that they position the vertical slots in the shielding hood correspond.

According to a further advantageous embodiment, the shielding plate is designed that in addition to the function of shielding external magnetic fields, Function of an electron shield fulfilled. The shield is also on the in Arranged in the direction of the electron gun side of the mask frame. The in The part of the shield plate pointing towards the electron gun reflects those Electrons hitting the mask frame in a direction away from that Illuminated screen to a backlight caused by scattered electrons on the To prevent fluorescent screen. The one perpendicular to it, arranged on the outside of the mask frame In contrast, the section of the shielding plate shields the movement of the electron beams inside the color picture tube against external magnetic fields. Thanks to the multiple functionality of the shielding can continue the manufacture of the color picture tube simplified and reduced in manufacturing costs.

Preferably, the shielding plate is attached to the longitudinal bars, i.e. at the top and lower spar of the mask frame attached.

The shielding hood is removed before the shielding trough and the cone are fritted the glass body of the color picture tube simply clipped onto the mask frame.

Further advantageous embodiments are the subject of the dependent claims.

Fig. 1

den schematischen Aufbau einer herkömmlichen Farbbildröhre;

Fig. 2

eine perspektivische Ansicht einer Masken-Rahmen-Kombination einer Farbbildröhre einer ersten Ausführungsform der Erfindung mit einer an der Masken-Rahmen-Kombination befestigten Abschirmhaube;

Fig. 3

eine Ansicht gemäß Fig. 2, jedoch ohne Abschirmhaube;

Fig. 4

eine Ansicht gemäß Fig. 3 mit an den Längsholmen der Masken-Rahmen-Kombination befestigten Abschirmblechen;

Fig. 5

eine perspektivische Prinzipskizze eines erfindungsgemäßen Abschirmblechs;

Fig. 6

eine perspektivische Ansicht eines zweiteiligen Abschirmblechs;

Fig. 7

eine perspektivische Ansicht eines vierteiligen Abschirmblechs;

Fig. 8

eine perspektivische Ansicht eines erfindungsgemäßen Abschirmblechs mit einem Schlitz;

Fig. 9

eine perspektivische Ansicht eines erfindungsgemäßen Abschirmblechs mit einer Mehrzahl von Schlitzen;

Fig. 10

eine perspektivische Ansicht einer Masken-Rahmen-Kombination mit Abschirmhaube gemäß einer zweiten Ausführungsform der vorliegenden Erfindung;

Fig. 11

eine perspektivische Ansicht gemäß Fig. 10 ohne Abschirmhaube;

Fig. 12

eine perspektivische Ansicht gemäß Fig. 11, bei der die Befestigung eines Abschirmblechs auf einem der Längsholme der Farbbildröhre angedeutet ist;

Fig. 13

eine perspektivische Detailansicht eines L-förmigen Abschirmblechs;

Fig. 14

eine perspektivische Detailansicht des L-förmigen Abschirmblechs aus Fig. 13 mit Cliplöchern;

Fig. 15

eine perspektivische Detailansicht einer Ausführungsform eines U-förmigen Abschirmblechs mit Cliplöchern; und

Fig. 16

eine Seitenansicht des U-förmigen Abschirmblechs aus Fig. 15.

Preferred embodiments of the invention are explained below with reference to the drawings. Show in detail:

Fig. 1

the schematic structure of a conventional color picture tube;

Fig. 2

a perspective view of a mask-frame combination of a color picture tube of a first embodiment of the invention with a shield attached to the mask-frame combination;

Fig. 3

a view of Figure 2, but without a shield.

Fig. 4

a view of Figure 3 with attached to the longitudinal spars of the mask-frame combination shielding plates.

Fig. 5

a perspective schematic diagram of a shielding plate according to the invention;

Fig. 6

a perspective view of a two-part shielding plate;

Fig. 7

a perspective view of a four-part shield plate;

Fig. 8

a perspective view of a shield plate according to the invention with a slot;

Fig. 9

a perspective view of a shield plate according to the invention with a plurality of slots;

Fig. 10

a perspective view of a mask-frame combination with shielding hood according to a second embodiment of the present invention;

Fig. 11

a perspective view of FIG 10 without a shield.

Fig. 12

a perspective view of Figure 11, in which the attachment of a shield on one of the longitudinal spars of the color picture tube is indicated.

Fig. 13

a detailed perspective view of an L-shaped shielding plate;

Fig. 14

a detailed perspective view of the L-shaped shielding plate of Figure 13 with clip holes.

Fig. 15

a detailed perspective view of an embodiment of a U-shaped shielding plate with clip holes; and

Fig. 16

15 shows a side view of the U-shaped shielding plate from FIG. 15.

A first embodiment of the present invention is shown in FIGS. 2 to 5. A mask frame is composed of longitudinal bars 11 and transverse bars 12. A shadow mask 10 is inserted into the mask frame, so that the shadow mask 10 and the mask frame 11, 12, form a "mask-frame combination". The mask-frame combination has 13 fastening devices at the corners the mask-frame combination on the tubular glass.

A shielding hood 14 is mounted on the mask frame 11, 12. The shielding hood 14 can be easily attached to the mask frame using clips. to Influencing the magnetic flux in the shielding hood 14 indicates this Longitudinal sides of vertical openings or slots 15. The vertical openings 15 allow a targeted control of the magnetic flux in the shielding hood 14.

3 are those for fastening the shielding hood 14 to the mask frame 11, 12 provided to recognize clip holes 17. The shield 14 can therefore be easier Way to be attached to the mask frame without the risk of damage the phosphor layer as in the conventional fastening.

On the side of the mask frame 11, 12 facing the electron gun 3 is a Electron shield 18 provided. The electron shield 18 reflects on the mask frame hitting electrons, so that these as scattering electrons are not undesirable Generate backlights of the screen.

In the mask frame shown in FIG. 4, there is 11 on each of the longitudinal spars a corresponding shield plate attached. The shielding plates 20 are used for shielding external magnetic fields, especially the earth's magnetic field, and are external welded to the longitudinal spars 11 via welding spots 22. The attachment of the Shielding plate 20 on the longitudinal spar 11 is preferably carried out at an early stage during the manufacturing process, in any case before the shielding process, where the phosphor layer is applied to the inside of the screen trough becomes. The shielding plate 20 is preferably attached to the longitudinal spar 11 before inserting the mask-frame combination into the screen trough and preferably also before inserting the mask 10 into the mask frame.

According to a preferred embodiment, the shielding plate 20 has a rectangular one (L-shaped) profile with a bending edge 21. The shield plate 20 is so attached to the mask frame that it was the outside and that of the electron gun, respectively facing side completely or at least partially covers.

Examples of possible designs for the shielding plate are shown in FIGS. 5 to 9 shown. FIG. 5 shows the shielding plate 20 from FIG. 4 in detail. The shielding plate 20 consists of two arranged at right angles to each other around a bending edge 21 Sections 24, 25. The shielding plate is made for a good shielding effect made of a highly permeable material, preferably from the same material which the shield 14 is made.

It is the task of the shielding sheet 20, the poorer magnetic properties of the mask frame compared to that of the shielding hood. In particular improves the shielding plate 20 through the material of the mask frame conditional poorer magnetic properties that only a weak Allow magnetic flux from the shielding hood into the mask frame. About the shielding plate according to the invention, the magnetic flux of the axial field is clear interrupted less than conventional, so only fewer vertical components of the magnetic field and thus lower charge shifts.

To reduce the horizontal component (i.e. in the X direction) of the magnetic field the shielding plate 20 is additionally provided with vertical slots or openings. exemplary Embodiments are shown in Figures 6 to 9.

6 shows a two-part shielding plate made from sections 30 and 31, which are mounted on the frame spar with a gap 32 of predefined width.

Another embodiment is shown in FIG. 7, in which the shielding plate 20 is made of there are a total of four sections 33, 34, each with a lying between them Gap 35 of predefined width can be mounted on the frame rail.

Analog designs of the shielding plate 20 to that of Figures 6 and 7 are in the Figures 8 and 9 reproduced. Instead of a gap of predefined width between the parts of the shield plate, however, the shield plate is arranged accordingly Provide slots 40, 41.

The position of the slots 40, 41 or column 32, 35 preferably corresponds to that of Vertical slots 15 in the shielding hood 14, as can be seen, for example, in FIG. 2 are.

According to a further preferred embodiment, the shielding plate 20 is simultaneous designed as an electron shutter / electron shield. In this embodiment the portion of the shield plate facing the electron gun serves as Electron shield and the section covering the outside of the longitudinal spar in whole or in part covers the shield.

Another embodiment of the invention for a different shape of the mask frame is shown in Figures 10 to 12. The mask-frame combination of these The embodiment essentially has no planar surfaces Longitudinal spars on. In contrast to the mask-frame combination shown in the figures 2 to 5 is shown, the attachment of a shielding hood is therefore more complex.

In FIGS. 10 to 12 there are corresponding reference symbols for the same components have been used, even if the two configurations differ from one another in detail differ.

The mask frame of the embodiment shown in FIGS. 10 to 12 is made from longitudinal spars 11 and transverse spars 12 welded onto them. The transverse spars 12 are welded to the longitudinal spars 11 via curved ends 12a. Both the Cross bars as well as the longitudinal bars are preferably made of iron. For fixing the mask-frame combination on the glass body of the color picture tube is at this embodiment, a spring holder 51 is provided on each side. Besides, is a contact spring 52 is shown which is a conductive connection to an inner coating of the vitreous body.

To attach the shield 14 are at the curved ends of the side rails 12a clip holder 56 provided with clip holes.

In contrast to the embodiment of Figures 2 to 5, the shield plate is not direct attached to the surface of the longitudinal spar 11, but on the curved ends 12a of the sides spars. The L-shaped curved shield plate 60 is on the curved Mounted ends 12a of the side rails and in this way bridges the height differences the frame construction.

Variants for exemplary embodiments of the shielding plate 60 are shown in the figures 13 to 16 reproduced. 13 shows a perspective view of the shielding plate 60 with a section 64 which shields the mask frame on its outside, and a section 65 arranged at right angles thereto on the in the direction of FIG Electron gun-facing side of the longitudinal spar 11.

According to an advantageous embodiment shown in FIGS Color picture tubes are clip holes 66 in instead of the clip holder 56 on the mask frame the shielding plate 60 introduced, so that the complex welding of clip holders 56 on the mask frame is omitted. The clip holes 66 are on the section 65 of the Shielding plate provided.

The fact that the shielding plate 60 the height differences on the long side of the Bridged frame, the shielding can essentially in these areas just be designed, which also simplifies their manufacture.

The shielding plate 60 preferably has an L-shape in cross section (cf. FIGS. 13 and 14) or a U-shape (see FIGS. 15 and 16). The shield is for this Purpose in the manufacture either bent only once around 90 ° or for the U shape twice by about 90 ° each. While the shield plate 60 with an L-shaped Cross section only on the outer side of the mask frame via welding spots 61 is attached, the U-shaped shielding plate 60 is also on the inside welded to the frame. For this purpose, the shielding plate has at least one additional one Section 67, which at least on the inside of the curved ends 12a of the Crossbars 12, preferably also on the inside of the longitudinal spar 11 and is attached. In this way, the mechanical stability of the shielding plate can be clearly seen increased and a mechanically firm attachment of the shield to the shield can be achieved in a simple manner.

A further increase in the mechanical stability of the shielding plate 60 can be achieved by an additional section 68 can be achieved. The shield plate is used during this the manufacture is bent again in the opposite direction by approximately 90 °. While the section 67 at its ends on the extensions 12a of the cross bars 12 is attached and fastened (i.e. usually welded on), the additional section lies 68 again on the longitudinal spar. An increase in strength is first already achieved through the additional bending edge. This can result in a further increase are caused that this section is firmly connected to the surface of the longitudinal spar 11 will, i.e. is preferably also welded.

Although in the embodiments shown, the NS shield plate 20, 60 is essentially the same The shielding plate can extend over the entire length of the longitudinal spar extend just as well over part of the spar. That way the resulting component of the magnetic field can be influenced further favorably.

In summary, the invention relates to a color picture tube and a production method for a color picture tube. The color picture tube contains a shadow mask attached to one Mask frame is attached. To improve the shielding effect is at least A shield plate is attached to a longitudinal spar of the mask frame, the external magnetic fields shields. With such a shielding plate, the picture quality of a Color picture tube improve and the manufacturing costs compared to conventional Simplify color picture tubes.

Claims (29)

Color picture tube with a substantially rectangular shadow mask (10), a mask frame made of transverse (12) and longitudinal spars (11) carrying the shadow mask (10) and a shielding hood (14) mounted on the mask frame, characterized by a shield on a longitudinal spar (11) shielding plate (20; 60) attached to the mask frame and covering at least part of the outside of the longitudinal spar (11). Color picture tube according to claim 1, characterized in that the shielding plate (20; 60) is welded to the mask frame. Color picture tube according to claim 1 or 2, characterized in that the shielding plate (20; 60) is made of highly permeable material. Color picture tube according to one of claims 1 to 3, characterized in that the shielding plate (20) is constructed in several parts. Color picture tube according to claim 4, characterized in that the shielding plate (20) is formed in two parts. Color picture tube according to claim 4, characterized in that the shielding plate (20) is formed in four parts. Color picture tube according to one of claims 1 to 6, characterized in that the shielding plate (20) is provided with at least one slot (40) for influencing the magnetic flux. Color picture tube according to claim 7, characterized in that the at least one slot (40) in the shielding plate (20) is aligned perpendicular to the longitudinal direction of the spar (11). Color picture tube according to claim 7 or 8, characterized in that the at least one slot (40) in the shielding plate (20) is aligned in its position with that of a slot (15) provided in the shielding hood (14). Color picture tube according to one of claims 1 to 9, characterized in that the shielding plate (20; 60) is designed such that it also fulfills the function of an electron shield (18). Color picture tube according to Claim 10, characterized in that the shielding plate (20; 60) essentially faces the side of the longitudinal spar (11) of the mask frame, in the direction of the electron gun (3) of the color picture tube, to which the shielding plate (20; 60) is attached covers. Color picture tube according to one of claims 1 to 11, characterized in that the shielding plate (60) is L-shaped. Color picture tube according to one of claims 1 to 11, characterized in that the shielding plate (60) is U-shaped. Color picture tube according to claim 13, characterized in that the shielding plate (60) is welded to both sides of the longitudinal spar (11). Color picture tube according to claim 13, characterized in that the shielding plate (60) is additionally welded to the ends (12a) of the cross bars (12). Color picture tube according to one of claims 13 to 15, characterized in that the shielding plate (60) on the inside of the mask frame has a further section (68) pointing into the interior of the color picture tube. Color picture tube according to claim 15, characterized in that the further section (68) of the shielding plate (60) is welded to the longitudinal spar (11). Color picture tube according to one of claims 1 to 17, characterized in that clip holes for fastening the shielding hood (14) are provided in the shielding plate (60). Color picture tube according to one of claims 1 to 18, characterized in that the shielding hood is designed to be clipped onto the mask frame. Color monitor or television with a color picture tube according to one of the claims 1 to 19. Production method for a color picture tube with a glass body, which is composed of a screen trough and a cone, with the steps: Production of a mask frame from transverse (12) and longitudinal spars (11), Inserting a mask (10) into the mask frame, which together form a mask-frame combination, Inserting the mask-frame combination into the screen pan, Applying a layer of fluorescent material on the inside of the screen, Attach a shield (14) to the mask frame and Connecting the screen trough and cone characterized in that
Before inserting the mask-frame combination into the shield trough, a shielding plate (20, 60) is mounted on at least one longitudinal spar (11) of the mask frame. Manufacturing method according to claim 21, characterized in that the shielding plate (20; 60) is welded to the mask frame. Manufacturing method according to claim 22, characterized in that the shielding plate (20; 60) is welded to the outside of the longitudinal spar (11). Manufacturing method according to claim 22 or 23, characterized in that the shielding plate (20; 60) is additionally welded to the inside of the mask frame. Manufacturing method according to claim 24, characterized in that the shielding plate (20; 60) is welded to the side of the longitudinal spar (11) pointing into the interior of the color picture tube. Manufacturing method according to claim 24, characterized in that the shielding plate (20; 60) is welded to the ends (12a) of the cross bars (12). Manufacturing method according to claim 26, characterized in that the shielding plate (20; 60) is welded to an additional section (68) on the side of the longitudinal spar (11) pointing in the direction of the electron gun (3) of the color picture tube. Manufacturing method according to one of claims 21 to 27, characterized in that the shielding hood (14) is clipped onto the mask frame in the fastening step. Manufacturing method according to claim 28, characterized in that the shielding hood (14) is clipped onto the mask frame via clip holes provided in the shielding plate (20; 60).

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