EP0360627B1 - Face plate for a colour television tube - Google Patents

Description

The present invention relates to a screen for a three-color television tube. It finds application for the reception of television broadcasts in high definition. (HDTV)

• pluralité de langues dans les programmes reçus,
• systèmes à son stéréophonique,
• son de qualité numérique,
• nouveaux services comme le télétexte,
• ouverture sur la télévision de norme HDTV (télévision à haute définition).

High definition television requires a redefinition of the manufacturing parameters of color television tubes. In particular, the European standard D2-MAC brings the following advantages to the user:

• multiple languages in the programs received,
• stereophonic sound systems,
• digital quality sound,
• new services like teletext,
• opening to HDTV standard television (high definition television).

• amélioration de la taille de l'impact des faisceaux électroniques sur l'écran,
• choix des réglures d'écran et de masque (screen et mask pitches) sensiblement constantes sur toute la surface éclairée,
• écran "plat" et "large" au format "cinémascope" de rapport égal en général à 16/9,
• bonne tolérance du tube au niveau de blanc et à la pureté de couleur dans toute la gamme des intensités de faisceaux d'électrons,
• bons paramètres de brillance et de contraste,
• amélioration des qualités antivibratoires du masque (insensibilité améliorée aux effets microphoniques dus en particulier aux chocs sur le téléviseur et aux vibrations produites par les haut-parleurs du téléviseur).

Such advantages require from the tubes:

• improvement in the size of the impact of the electron beams on the screen,
• choice of screen and mask pitches that are substantially constant over the entire illuminated area,
• "flat" and "wide" screen in "cinemascope" format with a ratio generally equal to 16/9,
• good tolerance of the tube at the level of white and at the purity of color in all the range of the intensities of electron beams,
• good brightness and contrast settings,
• improvement of the anti-vibration qualities of the mask (improved insensitivity to microphonic effects due in particular to impacts on the television and vibrations produced by the television's speakers).

In the prior art, the aesthetics of television tubes are oriented towards increasingly flat screen tubes. One type of "flat" slab currently used is called "planar", and is described in particular in French patent applications FR-A-2 541 817 and FR-A-2 541 820. Such tubes work correctly but require corrections to obtain good image geometry, corrections which cannot be obtained by the deflector alone.

On the other hand, the flatness of the screen has repercussions on the geometry of the mask and induces problems of thermomechanical behavior which are manifested by the defects of "doming" and "blister".

The present invention firstly relates to the production of a screen, for high-definition television, of a trichromatic tube with a "wide" screen (of 16/9 ratio) but which can also have the standard 4/3 ratio, of which the screen is as flat as possible and requires the least possible correction of geometry, slab which allows to realize a very wide range of tubes of very different dimensions and flatnesses and this, in the simplest way possible without using cylindrical element in the slab insolation light box.

The present invention also relates to a panel for a three-color television tube for high-definition television, in particular with a "wide" screen whose coefficient called "screen pitch" or screen ruler is as constant as possible, the edges of the screen being as straight as possible, the geometrical characteristics of the screen making the linearity of the phosphor lines optimal without using a cylindrical element in the insolation light box of the slab, the performance of the tube being optimized on the coefficients of "doming", of "blister", of microphonicity and on the tolerance of color purity.

EP-A-0 283 129 shows the common characteristics of a cathode ray tube comprising a surface of the rectangular plate where a long edge of the surface of the plate is substantially parallel to the long axis of the tube and a short edge of the surface of the plate is substantially parallel to the minor axis of the tube, the surface of the plate having a non-spherical external surface having curvatures both along the minor axis and the major axis and where the external surface comprises a substantially rectangular outline near the periphery of the surface of the plate which lies substantially in a plane perpendicular to the longitudinal central axis of the tube.

où Z est la distance de tout point de la surface au plan tangent à cette surface en son centre, la somme portant sur l'indice fini entier i, x et y étant les coordonnées cartésiennes des points de cette surface et j et k étant des coefficients entiers respectivement égaux à 4,2,0,4,2,0,4,2 pour j, à 4,0,2,0,2,4,2,4 pour k lorsque i varie de 1 à 8. Les coefficients C(i) étant d'équation : ${\text{C(i) = Co(i).F}}^{\text{-(j(i)+k(i)-1)}}$

où les coefficients C(i) décrivent la famille de dalles selon l'invention pour des formes d'écran déterminées par F, F étant le rapport des diagonales d'une même famille et égal à 1 pour un écran de rapport 16/9 et de diagonale égale à 83 cm (33 pouces) ou un écran de rapport 4/3 et de diagonale 68 cm (27 pouces), les coefficients Co(i) étant donnés dans les tableaux ci-dessous pour des rapports de 16/9 et 4/3.
Pour 16/9 : i Co(i) j(i) k(i) 1 -.23773301E-18 4 4 2 .84293632E-04 2 0 3 .43121367E-03 0 2 4 .18365999E-08 4 0 5 -.17170219E-08 2 2 6 .79434857E-09 0 4 7 -.57689504E-14 4 2 8 .24894724E-13 2 4
Pour 4/3 : i Co(i) j(i) k(i) 1 -.58544384E-18 4 4 2 .11218491E-03 2 0 3 .35359521E-03 0 2 4 .43294582E-08 4 0 5 -.23872190E-08 2 2 6 .65136582E-09 0 4 7 -.14001255E-13 4 2 8 .35119581E-13 2 4 The panel according to the invention, for color television tube, suitable for high definition HDTV television, of the type defined by a surface (S) of equation: ${\text{Z = Σ (C (i) .x}}^{\text{j (i)}}{\text{. y}}^{\text{k (i)}}\text{)}$

where Z is the distance from any point on the surface to the plane tangent to this surface at its center, the sum relating to the integer finite index i, x and y being the Cartesian coordinates of the points on this surface and j and k being integer coefficients respectively equal to 4,2,0,4,2,0,4,2 for j, to 4,0,2,0,2,4,2,4 for k when i varies from 1 to 8. The coefficients C (i) being of equation: ${\text{C (i) = Co (i) .F}}^{\text{- (j (i) + k (i) -1)}}$

where the coefficients C (i) describe the family of tiles according to the invention for screen shapes determined by F, F being the ratio of the diagonals of the same family and equal to 1 for a screen of ratio 16/9 and diagonal equal to 83 cm (33 inches) or a 4/3 ratio screen and diagonal 68 cm (27 inches), the coefficients Co (i) being given in the tables below for 16/9 ratios and 4/3.
For 16/9: i Co (i) j (i) k (i) 1 -.23773301E-18 4 4 2 .84293632E-04 2 0 3 .43121367E-03 0 2 4 .18365999E-08 4 0 5 -.17170219E-08 2 2 6 .79434857E-09 0 4 7 -.57689504E-14 4 2 8 .24894724E-13 2 4
For 4/3: i Co (i) j (i) k (i) 1 -.58544384E-18 4 4 2 .11218491E-03 2 0 3 .35359521E-03 0 2 4 .43294582E-08 4 0 5 -.23872190E-08 2 2 6 .65136582E-09 0 4 7 -.14001255E-13 4 2 8 .35119581E-13 2 4

In a practical way, any surface (S1) is said to belong to the family (S) according to the invention if the difference Z1-Z of their respective equations taken at the center of the screens is:
100.ABS (Z1-Z) <5. Zd where Zd is the maximum value of Z on the long diagonal of the slab.

On the other hand, it is possible to vary the degree of flatness by the coefficients C (2) and C (4) by taking values proportional to the values calculated according to the equation giving Z (1). Thus, for F given, it is possible to work on surfaces (S) of various flatnesses:

$\text{C (i) = k.Co (i) for 1 = 2 and 4 only.}$

• la figure 1 est un schéma d'un tube de télévison dans un exemple de réalisation selon l'invention,
• la figure 2 représente deux demi-vues en coupe de dalles de verre selon l'invention,
• la figure 3 représente des demi-vues en coupe d'une dalle de verre selon l'invention et selon trois plans de coupe caractéristiques.

Other characteristics and advantages of the present invention will be better understood with the aid of the description of an embodiment, taken as a nonlimiting example and illustrated by the appended drawing, in which:

• FIG. 1 is a diagram of a television tube in an exemplary embodiment according to the invention,
• FIG. 2 shows two half-section views of glass slabs according to the invention,
• FIG. 3 represents half-sectional views of a glass slab according to the invention and according to three characteristic cutting planes.

The manufacture of color television tubes poses a large number of problems which interact with each other. Thus, the problem of glassware, that is to say the problem which tends to the production of glass slabs on which a display screen is intended to be produced, implements questions of physics of electromagnetic and optical deflectors electronics at the level of the electron gun, but also mechanical questions linked to the presence of the mask and physical chemistry linked to the receptivity properties of electron beams and transformation into visible radiation from the screen to the user.

In Figure 1, there is shown a television tube according to the invention 83 cm diagonal and 16/9 ratio. The Z axis is the central axis of the tube which corresponds substantially to the central electron beam with zero deflection, that is to say when the barrel 2 emits its three electron beams without the deflector 3, installed around the neck of the tube, receives the least deflection current.

The glass slab 1 on which the display screen will be formed is connected to a flared section 6 of the tube by a skirt 5 which is substantially parallel to the axis Z.

Inside the tube, there is a frame-shadow mask assembly intended mainly to achieve a good selection of colors on the phosphors formed in parallel strips on the internal face of the slab. There is shown in the cutaway in Figure 1 a section of the glass slab according to the invention, the layer 8 of phosphors intended to convert the electron beams from the barrel 2 into visible radiation through the glass slab 1 in the direction of the Z axis, and a shadow mask 7.

For a given value of the deflection currents on the deflector, a hole 12 in the mask is selected. This oblong-shaped hole is crossed by the RED, GREEN and BLUE beams which excite the corresponding band of electroluminescent phosphors 9, 10 or 11.

It is an advantage of the present invention to take into account the geometric requirements of correspondence between each hole of the mask and the arrangement of the phosphor strips. Indeed, the radius of curvature of the glass slab 1 is not constant at any point on its surface, it is necessary to take into account the distribution of the bands 9, 10, 11 so as to avoid that the edge of a beam do not strike a portion of a strip that does not correspond to it (lack of color purity).

In Figure 2, there are shown the half-sections of the exterior surfaces of glass slabs according to the invention made parallel to their major axis Ox (a) in the 83 cm (33 inch) version 16/9 for the curves (a ) and 69 cm (27 inches) 4/3 for the curves (b). In each set (a) and (b), the upper curve is made along the axis Ox passing through the center of the slab and the lower curve is made at the horizontal edge of the screen, respectively.

équation dans laquelle j et k sont des coefficients entiers dont les valeurs sont données dans les deux tableaux ci-dessus qui sont établis pour Co(i) correspondant à une dalle 83 cm 16/9 et à une dalle 68 cm 4/3 respectivement avec

${\text{C(i) = Co(i).F}}^{\text{-(j(i)+k(i)-1)}}\text{,}$

expression dans laquelle F est le rapport des diagonales d'une même famille et égal à 1 pour un écran de rapport 16/9 et de diagonale égale à 83 cm ou pour un écran de rapport 4/3 et de diagonale 68 cm, les coefficients Co(i) étant fournis par les tableaux précités. Ainsi, pour un écran de diagonale 112 cm (44 pouces) F = 4/3 et pour un écran de diagonale 28 cm (11 pouces) F = 1/3.The invention consisted in taking into account each of the conventional parameters linked to the manufacture of a television tube, then in defining by the method, finite elements the equation of the internal surface S2 by the Z coordinate of any point of this surface:

${\text{Z = Σ (C (i) .x}}^{\text{j (i)}}{\text{.y}}^{\text{k (i)}}\text{)}$

equation in which j and k are integer coefficients whose values are given in the two tables above which are established for Co (i) corresponding to a 83 cm 16/9 slab and a 68 cm 4/3 slab respectively with

${\text{C (i) = Co (i) .F}}^{\text{- (j (i) + k (i) -1)}}\text{,}$

expression in which F is the ratio of the diagonals of the same family and equal to 1 for a screen of ratio 16/9 and diagonal equal to 83 cm or for a screen of ratio 4/3 and diagonal 68 cm, the coefficients Co (i) being provided by the above tables. Thus, for a screen 112 cm (44 inches) F = 4/3 and for a screen 28 cm (11 inches) F = 1/3.

In a second step, the mask, made of appropriate material, is calculated using conventional materials such as steel and invar, taking into account the thermomechanical holding performance. In a practical manner, the optimized compromise is achieved by iterations of the calculation of the internal surface S2 and of the geometry of the mask so as to obtain an aspect of flatness as good as possible.

In an exemplary embodiment, it has been possible to have substantially constant screen rulings. They range from 0.7 mm (millimeter) in the center of the screen to 0.8 mm (millimeter) on a corner.

Once the internal surface S1 has been determined, the mask calculated at the same time, the method of the invention makes it possible to calculate the geometry of the external surface S2.

This surface is subject to the same requirements of flatness, but must also have good mechanical qualities in anti-implosion. To this end, the thickness t and the height H of the skirt are determined to have the best value. In an exemplary embodiment, shown in FIG. 3, these two parameters are checked on the large dimension edge m, the small dimension edge m and the corner D. The corresponding values found are: m M D t 20 18 18 H 102 79 73
where the dimensions are given in millimeters, for a 33 "16/9 panel.

   Dans un exemple de réalisation, ces facteurs sont tous égaux à 1 sauf les coefficients pour i=2 et i=4 pour lesquels

$\text{C'(2) = C(2).p et}$

$\text{C'(4) = C(4).p.}$

The flatness is regulated by coefficients C (i) assigned a multiplicative factor p:

$\text{C '(i) = c (i) .p}$

In an exemplary embodiment, these factors are all equal to 1 except the coefficients for i = 2 and i = 4 for which

$\text{C '(2) = C (2) .p and}$

$\text{C '(4) = C (4) .p.}$

When p is greater than 1, the surface S2 is less planar, and when p is less than 1, the surface S2 is more planar.

où Z est la cote du point homologue d'une surface étalon appartenant à la famille de surfaces de l'invention définies par les coefficients C(i) détaillés plus haut et Zd est la valeur de la plus grande cote de cette surface prise sur la grande diagonale.In general, we say that a surface Sn belongs to the family meeting the requirements of the invention, if its dimension Zn is such that: $\text{100.ABS (Zn-Z) <5.Zd}$

where Z is the dimension of the homologous point of a standard surface belonging to the family of surfaces of the invention defined by the coefficients C (i) detailed above and Zd is the value of the largest dimension of this surface taken on the large diagonal.

Claims (4)

1. Envelope for a screen of a colour television tube appropriate for high definition television, each of the internal (S2) and external (S1) faces is of a type defined by an equation surface (S) :
   
   ${\text{Z = Σ (C(i)·x}}^{\text{j(i)·yk(i)}}\text{)}$

   

   
   
   where Z is the distance of any point of the surface to the plane tangent to this surface in its center, characterized in that the coefficients C(i) are those of the equation :
   
   ${\text{C(i) = C₀(i)·F}}^{\text{-(j(i)+k(i)-1)}}$

   

   
   
   where the coefficients C(i) describe the series of envelopes according to the invention, F being the ratio of the diagonals of a same series and being equal to 1 for a screen with the ratio 16/9 and a diagonal of 83 cm (33 inches) or a screen with a ratio 4/3 and a diagonal of 68 cm (27 inches), the sum concerning the integral finite index i, x and y being the cartesian coordinates of the points of this surface and j and k being the integral coefficients respectively equal to 4,2,0,4,2,0,4,2 for j, to 4,0,2,0,2,4,2,4 for k when i varies from 1 to 8, the coefficients C₀(i) being given in the tables below for the ratio of 16/9 and 4/3.
   For 16/9 : i C₀(i) j(i) k(1) 1 -0,23773301·10⁻¹⁸ 4 4 2 0,84293632·10⁻⁰⁴ 2 0 3 0,43121367·10⁻⁰³ 0 2 4 0,18365999·10⁻⁰⁸ 4 0 5 -0,17170219·10⁻⁰⁸ 2 2 6 0,79434857·10⁻⁰⁹ 0 4 7 -0,57689504·10⁻¹⁴ 4 2 8 0,24894724·10⁻¹³ 2 4 For 4/3: i C₀(i) j(i) k(1) 1 -0,58544383·10⁻¹⁸ 4 4 2 0,11218491·10⁻⁰³ 2 0 3 0,35359521·10⁻⁰³ 0 2 4 0,43294582·10⁻⁰⁸ 4 0 5 -0,23872190·10⁻⁰⁸ 2 2 6 0,65136582·10⁻⁰⁹ 0 4 7 -0,14001255·10⁻¹³ 4 2 8 0,35119581·10⁻¹³ 2 4
2. Envelope according to claim 1, characterized in that the flatness of the screen is determined by the changing of the coefficients C(i) into $\text{p·C(i) = C'(i)}$

   

   , p being a multiplication factor higher than zero assigned to the coefficient C(i).
3. Envelope according to claim 2, characterized in that the only variable coefficients are C(2) and C(4).
4. Envelope characterized by the fact that, if Z_n is the distance of a point of its internal or external surface to a plane tangent to the center of this surface and if Z is the distance of an homologous point of a second surface according to any of the preceding claims to a plane tangent to this second surface in its center, we have :
   
   ${\text{100·ABS(Z}}_{\text{n}}{\text{-Z) < 5·Z}}_{\text{d}}\text{,}$

   

   
   
   Z_d being the maximal value of Z on its big diagonal of the envelope.

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