JPH09505440A - Color cathode ray tube with in-line electron gun - Google Patents

Abstract

(57) [Summary] A color cathode ray tube is equipped with a line electron gun having a main lens having an opening in a recess. The main lens is formed by two electrodes. These electrodes have an outer edge and three in-line electron beams that pass through and have openings in recesses located at distances d1 and d2 from the outer edge, respectively. The outermost aperture is asymmetric. The difference d1-d2 and the asymmetry of the outermost aperture are taken so that the beam displacement and the core haze asymmetry are minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION A color cathode ray tube with an in-line electron gun. The present invention has a main lens portion including first and second electrodes, wherein the first and second electrodes are respectively An electron gun having three in-line apertures and one outer edge, the outer edges of the electrodes facing each other, the holes being recessed with respect to the edge of the outer edge with which they are associated. The present invention relates to an equipped color cathode ray tube. The cathode ray tube described at the beginning of this kind is well known. The assembly of an electron gun must take into account several important parameters such as so-called spot error (SE), beam displacement (BD) and core haze asymmetry (C HA). The electron gun has several lenses that have a converging or diverging effect on the electron beam. The displacement or tilt of the electrodes used to form the lens causes the displacement of the lens, resulting in unwanted deflection of the electron beam. When this occurs in the main lens, the electron beam impinges on a bad place on the display screen, resulting in a spot error. Another effect that occurs when an electron beam passes off-center through the main lens is that the helicopter beam of the electron beam undergoes more deflection on one side than the other. The effect on the display screen is called core haze asymmetry. Furthermore, changes in the electric field at the main lens cause the displacement of the beam on the display screen, a phenomenon commonly referred to as beam displacement. As explained below, core haze asymmetry decreases as image sharpness increases. Problems with red-blue convergence occur as a result of beam displacement. These problems adversely affect image quality. The object of the present invention is to provide a cathode ray tube of the kind mentioned at the outset with which the image quality can be improved. In order to achieve this object, the color cathode ray tube according to the present invention has a core haze asymmetry of 50 V or less and a beam displacement of 0.2 mm or less, and a distance between the edges of a plurality of collars and a plurality of plates. In addition, the plurality of outermost apertures exhibit left-right asymmetry that is different and has a core haze asymmetry of 50 V or less and a beam displacement of 0.2 mm or less. Within the scope of the present invention, the outermost edge of one aperture at right angles to one (or n) (x or horizontal) line of the in-line plane and in the (x or horizontal) direction of the in-line plane. It should be understood that with respect to a line (y or vertical) passing through a point located at the center between the parts, it means that the planes of the aperture portions on both sides of the line are not mirror image symmetric with respect to the line. Is. An egg-shaped opening is an example of an opening that meets this condition. Each plate with three apertures is located at a distance d1 and d2 with respect to the first electrode and the second electrode, respectively, and this difference will hereinafter also be referred to as the "depth difference". Within the scope of the present invention, both core haze asymmetry and beam displacement vary as a function of depth difference and the "oval" of the outermost aperture, and the path of the outermost electron through the outermost aperture is the core haze. It is advantageous and feasible to choose the combination of depth differences and "oval" so that the asymmetry matches the negligible path and this path matches the path when the beam displacement is almost negligible. It has been recognized that there is. Core haze asymmetry is defined and measured by the difference in first electrode voltage when the left and right sides of the spots of the outermost beams are focused on the display screen (measured at the center of the display screen). In the color cathode ray tube according to the present invention, this difference is smaller than 50V. While the potential applied to the first electrode remains almost constant, the potential applied to the second electrode is changed between 20 and 30 kV, and the beam displacement of the outermost electron beam, that is, 20 at the center of the display screen, respectively. By measuring the difference in position at a potential of 30 kV, the beam displacement is also measured at the center of the display screen. In the color cathode ray tube according to the present invention, the beam displacement is 0.2 mm or less. Preferably, the left-right asymmetry expressed by the left-right asymmetry factor p and the difference between the edge of the collar and the plate distance (d1-d2) is defined by lines corresponding to beam displacements of 0.2 mm and -0.2 mm. 8 is within the range indicated by the area in FIG. Preferably, the depth difference (d1-d2) is approximately 0 mm. This allows the use of two identical electrodes. These and further scope of the invention are explained in more detail below by means of examples with reference to the accompanying drawings. The drawings are: FIG. 1 shows a sectional view of a display device; FIG. 2 shows a sectional view of an electron gun; FIG. 3 shows an outline of an electron gun used in a display device according to the present invention; Fig. 5 shows a plan view of a portion of Fig. 5; Fig. 5 shows several possible shapes of apertures and associated left-right asymmetry factors; Fig. 6 shows beam displacements; Figs. 7A and 7B show core haze asymmetry; FIG. 9 shows the relationship between the electro-optical pitch and the geometrical pitch of the electrodes. FIG. 10 shows a sectional view of the electrodes. The above drawings do not have a scale. Generally, the same reference numerals correspond to the same parts on the drawings. In FIG. 1, a display device according to the present invention has a cathode ray tube having an evacuated envelope 2 consisting of a display window 3, a conical portion 4 and a neck portion 5, in this example a color display tube 1. There is. The neck 5 is provided with an electron gun 6 for generating three electron beams 7, 8 and 9 which extend in one plane, the in-line plane, in this case the plane of FIG. A display screen 10 is provided inside the display window. The display screen 10 comprises a number of phosphor elements that emit red, green and blue. On the way to the display screen, a plurality of electron beams are deflected by the electromagnetic deflection unit 11 in a direction crossing the display screen 10, and the color selection electrode 12 provided on the front surface of the display window 3 and having a thin plate having an opening 13 is provided. pass. The color selection electrodes are suspended in the display window by suspension elements 14. The three electron beams 7, 8 and 9 pass through the apertures 13 of the color selection electrode at a slight angle to each other, so that each electron beam impinges on the phosphor elements of only one color. . The display further comprises means 15 for generating a voltage applied to each part of the electron gun via a feedthrough 16 during operation. FIG. 2 is a sectional view of the electron gun 6. The electron gun comprises three cathodes 21, 22 and 23. The electron gun further comprises a first common electrode 20 (G ₁ ), a second common electrode 24 (G ₂ ), a third common electrode 25 (G ₃ ) and a fourth common electrode 26 (G ₄ ). I am. These electrodes have voltage application connections. The display device comprises leads, not shown, for applying the voltage generated by the means 15 to said plurality of electrodes. By applying a voltage, in particular a voltage difference between the electrodes and / or the sub-electrodes, an electro-optical electric field is generated. The electrode 26 (G ₄ ) and the sub-electrode 25 (G ₃ ) constitute an electro-optical element that generates a main lens electric field formed between these electrodes during operation. The plurality of these electrodes are interconnected by connecting elements, in this example glass rods 27. FIG. 3 is a schematic sectional view of the electron gun shown in FIG. Electrodes 25 (G ₃ ) and 26 (G ₄ ) respectively comprise plates 30 and 40 having apertures 31, 32, 33 and 41, 42, 43 respectively. These plates are recessed against the outer edges of the collars 34 and 44 of the electrodes 25 and 26, respectively. The distance between the outer edge and the plate is shown in the figure in the z direction and is equal to d1 and d2 respectively. FIG. 4 is a plan view of a plate 30 having openings 31, 32 and 33. The outermost apertures 31 and 33 are asymmetrical with the sense that they are asymmetrical with respect to a line 51 extending at a right angle to a line 52 passing through the centers of the plurality of apertures. The line 51 divides the openings 31 and 33 into two parts 53 and 54, the line segment lengths 55 and 56 being the same. However, the surface areas of these parts 53 and 54 are not the same. The openings 31 and 33 have left-right asymmetry. This asymmetry is represented by the factor p, where p is the difference in surface area between the portions 53 and 54 divided by the sum of the two surface areas. This factor p is p = (54− when the “innermost” part (53), ie the part of the aperture closest to the central aperture, has a larger surface area than the part farthest from the central aperture (54). 53) / (54 + 53) has a negative sign. FIG. 5 shows various shapes of the openings 31 and 33 together with the related factor p. 5a to 5e, the central aperture (not shown) is located to the left of the aperture shown. For circles (Fig. 5a) and ellipses (Fig. 5b), p = 0, and for equilateral triangles (Fig. 5c), p = -0.5. In the case of a semicircle (Fig. 5d), p = -0.218, and in the case of a combination of two semi-ellipses whose equal vertical and horizontal axes are a1 and a2, respectively (Fig. 5e), a first-order approximation (a1 It is p = -0.273 (a1-a2) / (a1 + a2) in -a2 <a1 + a2). In FIG. 5e, the boundaries of the two semi-ellipses are indicated by dashed lines. In this example, the main lens formed by the electrodes G3 and G4 focuses the electron beam on the display screen. The error occurs during this focusing operation. The first error is the so-called beam displacement. FIG. 6 schematically shows this error. In this example, the triode and the main lens are shown schematically by lenses 61 and 62. The electron beam is off center and enters the main lens. When the voltage of G4 changes (the voltage of G3 remains the same), the electron beam position at the center of the screen 63 changes. Beam displacement BD is usually measured as the difference in electron beam position on the screen that occurs when the voltage on G4 changes from 20 to 30 kV. The main reason why the beam displacement constitutes a problem is that the beam displacements of the outermost electron beams R and B have opposite signs. This causes a change in voltage on G4 to produce a red / blue convergence error. In practice, the change in voltage on G4 is a few kV. The second error is the so-called core haze asymmetry. 7A and 7B show a schematic of this effect. The electron beam 71 formed by the three-pole portion 72 of the electron gun enters the main lens 73 and is focused on the screen 74. An asymmetrical haze 76 is formed around the core 75 of the electron spot when the spherical aberration of the lens causes the helicopter electron beam to be deflected more strongly by the main lens on one side than the other. Such haze reduces the sharpness of the image. The magnitude of this effect is expressed as the potential difference, ie the potential difference on G3 such that the left side of the core or the right side of the core is in focus with respect to the center of the display screen. When this difference is approximately 0 V, the electron beam follows a so-called coma-free path through the main lens. The loss of sharpness is caused by the fact that the higher of the two focus voltages V _G3 is actually set. FIG. 7B shows the loss of sharpness. The voltage V _G3 is plotted on the horizontal axis. The edges of the core 75 are shown in solid line in the vertical axis direction, and the edges of the haze 76 are shown in dashed lines. Haze does not occur at high values of V _G3 . The solid line 81 and the broken line 82 represent the situation when there is no core haze asymmetry. When V _G3 <V _foc , haze asymmetry occurs. In such a case, the voltage on G 3 is adjusted so that V _G3 = V _foc . The size of the spot is indicated by the length of arrow 83. Lines 84 and 85 represent the spot sizes on the right and left sides of the core of the spot when the core haze asymmetry occurs. Lines 86 and 87 represent the haze magnitudes on the right and left sides of the spot, respectively. In this example, the core haze asymmetry occurs because the right haze of the spot is larger than the left haze of the spot. In this example haze occurs on the right side of the spot when the _{V G3} <V foc.R, generated for the left of the spot when the _{V G3} <V foc.L. The voltage on G3 is adjusted so that no haze occurs, ie V _G3 <V _foc.R. The size of the spot at this setting is represented by the size of the arrow 88. It is clear that the spot size has been expanded relative to the ideal size (without core haze asymmetry). Koaheizu asymmetry is defined by _V foc.R -V _f oc.L = CHAX. FIG. 8 is formed by the depth difference (d1-d2, mm) plotted along the horizontal axis and the two semi-ellipses as a function of p plotted along the vertical axis, as shown in FIG. 5e. 2 shows the beam displacement (BD) in mm for an electrode having an outermost aperture formed. The lens is constructed so that the core haze asymmetry is less than 50V and equal to approximately 0V. In this example, the inter-aperture electro-optical pitch, which is equal to the geometric center distance (geometric pitch) of the apertures in the 0th-order approximation, is equal to 5.5 mm (in the first-order approximation, the geometric pitch is the electro-optical pitch). A few (1/10) mm larger, in this example between 5.7 and 6.3 mm). FIG. 9 shows the relationship between the electro-optical pitch and the geometrical pitch. FIG. 10 shows depths d1 and d2 which are about 3.2 mm in this example. In FIG. 10, apertures are provided in the plate 101 attached to the electrode 102. This is the preferred embodiment. The electrodes may be deep drawn (as shown in the cross-sectional view of Figure 3). However, the use of the plate 101 as shown in FIG. 10 is preferable because the distances d1 and d2 can be set more accurately, the openings can be made more accurately, and the design can be made more freely. For example, for an electrode such as that shown in FIG. 3, there should always be a distance between the edge of the aperture 31 and the edge 34. This limitation does not apply to the apertures in plate 101. FIG. 8 shows that by changing the depth difference (d1-d2) and the core haze asymmetry factor p, which is approximately 0 (<50 V), a beam displacement of approximately 0 is reached. In the color cathode ray tube according to the present invention, the edge of the collar is different from the plate distance (d1, d2), the outermost holes (31, 33) exhibit left-right asymmetry, and the core haze asymmetry is 50 V during operation. The feature below is that the beam displacement is 0.2 mm or less in absolute value. This is 0. It is indicated by the in-line area defined by 2 and -0.2. In this region, p has a negative value. This is the case when a1 is smaller than a2. A factor p of −0.04 corresponds to a value for a1 / (a1 + a2) of 0.427, and a factor p of −0.01 corresponds approximately to a value of a1 / (a1 + a2) of 0.4818. A preferred embodiment is characterized in that d1-d2 is zero. In this case the use can be made with the same configuration for both electrodes of the main lens, resulting in cost savings. In FIG. 8, this corresponds to line intercepts AD. Although some embodiments have been described above, it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the invention.

────────────────────────────────────────────────── ─── Continuation of front page    (81) Designated countries EP (AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LU, M C, NL, PT, SE), JP, KR (72) Inventor Spaniel Thierk Herrit             Netherlands 5621 Beer Aindow             Fennefleune Wautzwach 1 (72) Inventor Los Abraham Adrians             Netherlands 5621 Beer Aindow             Fennefleune Wautzwach 1 (72) Inventor Peninhus Antonius Jacob             Netherlands 5621 Beer Aindow             Fennefleune Wautzwach 1

Claims (1)

[Claims] 1. Having a main lens portion including first and second electrodes, the first and second lens portions Each of the electrodes has three in-line apertures and one collar, The collars face each other and the apertures are recessed with respect to the edge of the outer edge with which they are associated In a color cathode ray tube equipped with an electron gun with a core haze asymmetry of 50 V or less As long as the beam displacement is 0.2 mm or less, the distance between the edge of the collar and the aperture (d1 , D2) are different, the outermost aperture has a core haze asymmetry of 50 V or less, and the beam displacement is Color cathode-ray tube characterized by being asymmetrical so as to be 0.2 mm or less . 2. Having a main lens portion including first and second electrodes, the first and second lens portions Each of the electrodes has three in-line apertures and one collar, The collars face each other and the apertures are recessed with respect to the edges of the associated collar In a color cathode ray tube equipped with an electron gun, the distance between the color edge and the plate (d1 , D2) are different, the outermost aperture shows left-right asymmetry, and the left-right asymmetry factor p and color The left-right asymmetry represented by the difference (d1-d2) between the edge portion and the plate distance is Note that it is in the range shown in the area of FIG. 8 defined by lines 0.2 and -0.2. Color cathode ray tube to collect. 3. Due to the left-right asymmetry factor p and the difference between the edge of the collar and the distance between the plates (d1-d2) The represented left-right asymmetry is shown in the region of Figure 8 defined by lines 0.2 and -0.2. The color cathode ray tube according to claim 1, wherein 4. 3. The depth difference (d1-d2) is substantially equal to 0 mm. Or the color cathode ray tube described in 3.