KR100233189B1 - Shadow mask type color cathode-ray tube and cathode-ray tube - Google Patents

Abstract

The shadow mask type color cathode ray tube used in a high resolution display device has a stripe-shaped fluorescent surface and a slotted shadow mask. The longitudinal spacing of the slots in the shadow mask is 0.2 to 0.3 mm and the bridge width between the slots is 0.02 to 0.08 mm. In addition, the bridge has a minimum width of 0.005 to 0.03 mm at the surface of the shadow mask. The electron beam is elliptical with a ratio of the longitudinal axis to the horizontal axis of 0.45 to 0.95. The shadow mask type color cathode ray tube has excellent sharpness for text and pictures.

Description

Shadow mask type color cathode ray tube and cathode ray tube device for high resolution display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to shadow mask type cathode ray tubes (CRTs) for high resolution displays, and more particularly to improving the shape of shadow masks and electron beam spots.

Shadow mask type color cathode ray tubes are commonly used in high resolution displays of television receivers and computer systems. 1 shows the form of a conventional cathode ray tube having a fluorescent surface 13 attached to an inner surface of a display panel 11. The fluorescent surface 13 includes a plurality of elongated strips of three colored phosphors, which extend perpendicular to the scanning line of the electron beam emitted by the electron gun assembly 12. The electron gun assembly 12 has three electron guns in the neck portion to form an in-line type electron gun assembly. The cone-shaped funnel 15 having the cylindrical neck portion 14 is connected to the display panel 11 to form a vacuum tube. A deflection yoke 16 for deflecting the electron beam surrounds the back outer periphery of the funnel 15 to provide a magnetic field in the longitudinal and transverse directions. A shadow mask 18 having a plurality of slots 17 therein is disposed opposite the fluorescent surface 13 on the inner surface of the display panel 11.

In the shadow mask type color cathode ray tube of the above-described configuration, the electron beam emitted by the electron gun assembly 12 is deflected by the horizontal and vertical magnetic fields formed by the deflection yoke 16 and the slot 17 in the shadow mask 18. Passing through, it collides with each fluorescent substance to excite and emit the fluorescent substance, thereby providing a color image on the screen 13.

As shown in FIG. 2, in the shadow mask 18, a plurality of square slots 17 are arranged in a plurality of slots 17 arranged at regular intervals PV of about 0.5 mm to 1.0 mm in the longitudinal direction of the screen. These are arranged in the transverse direction by the multi-row rule in parallel to form a mosaic image. A bridge 19 is formed between two adjacent longitudinally arranged slots 17 to provide mechanical strength to the shadow mask 18.

Viewed in the longitudinal direction, the center of each bridge 19 passes through the center of adjacent slots in adjacent rows. Since the bridge 19 does not pass through the electron beam, a shadow portion is generated on the screen 13. The smaller the size of the electron beam spot, the greater the difference in contrast of the display screen, and the influence by moire stripes becomes remarkable.

Shadow mask type color cathode ray tubes used in television receivers typically use a combination of a large stripe of fluorescent masks and a slotted shadow mask with square slots, while shadow mask type color used in high resolution displays. In the cathode ray tube, a combination of a dot-shaped fluorescent surface having a narrow interval of the shadow mask and a round hole shadow mask having round holes is used. The first combination using the stripe fluorescent surface and the slotted shadow mask can increase the aperture ratio with respect to the total area in the shadow mask as compared to the second combination using the dot phase fluorescent surface and the round hole shadow mask. The first combination is thus used in television receivers as described above.

However, if the slot spacing is very small, the first combination suffers from press molding causing the anisotropy of the shadow mask pattern, and has a difficulty in manufacturing a color cathode ray tube because the shadow mask does not have sufficient strength. For this reason, the first combination is rarely used for a high resolution display device requiring a narrow gap.

On the other hand, the second combination using a dot-shaped fluorescent surface and a round hole shadow mask has practically no problem in manufacturing color cathode ray tubes even at narrow intervals due to the uniformity of the shadow mask pattern and is used for high resolution display devices.

In recent years, more attention has been paid to stripe-shaped fluorescent surfaces in the field of high-resolution displays because of the following advantages when compared to dot-shaped fluorescent surfaces. Firstly, the stripe fluorescent surface in the human eye can express characters and pictures more clearly than the dot fluorescent surface. 3 and 4 show the sharpness of lines appearing on the screen in the case of a dot fluorescent surface and in the case of a striped fluorescent surface, respectively. Both figures show images of four horizontal lines with the same width superimposed on a uniform screen emitting only green light. As can be seen from Fig. 3, in the case of a dot fluorescent surface, the sharpness of the line depends on the positional relationship between the line and the dot arrangement, whereby the dot fluorescent surface gives different results. On the other hand, as shown in Fig. 4, the striped fluorescent surface may give different results due to the shadow image formed by the bridge if the fluorescent surface emits light, but provide a clear image for all four lines.

In addition, in the case of a dot-shaped fluorescent surface, when the electron beam is concentrated in a small diameter spot, a bugging phenomenon occurs, and the display line does not have a uniform width as if the display line is eaten by a bug or bug. As a result, compared with the case of the combination of the slotted shadow mask and the stripe fluorescent surface, the beam diameter cannot be made too small for the dot-shaped fluorescent surface, which makes the stripe-shaped fluorescent surface more clear in characters and pictures. It means that there is.

In addition, in the case of the raster moiredo dot fluorescent surface generated by the interference of light between the scanning line of the electron beam called the moire fringe and the opening of the shadow mask, it appears more clearly, which makes it difficult to reduce the spot size of the electron beam.

In view of the above, it is an object of the present invention to determine a pattern of a shadow mask and a shape of an electron beam, and to provide a shadow mask type color cathode ray tube having a slotted shadow mask and used in a high resolution display device.

According to the present invention, a shadow mask type includes an electron gun assembly for emitting a plurality of electron beams scanned in a lateral direction, a shadow mask having a plurality of slots through which the electron beam passes, and a fluorescent surface for receiving an image by receiving the electron beam passing through the slots. A color cathode ray tube is provided, wherein the slots are arranged longitudinally at regular intervals between 0.2 mm and 0.3 mm and the electron beam is elliptical with a larger transverse axis than the longitudinal axis.

In the shadow mask type color cathode ray tube according to the present invention, when a stripe fluorescent surface is used, the combination of a predetermined longitudinal interval of the slot and the spot shape of the electron beam more clearly shows characters and pictures.

By explaining the present invention in detail with reference to the accompanying drawings, the above and other objects, features and advantages of the present invention will become more apparent.

1 is a cross-sectional view of a conventional shadow mask type color cathode ray tube.

2 is a plan view of a shadow mask used in a conventional color cathode ray tube.

3 is a plan view of an image obtained by a simulation in which four lines are shown on a dot fluorescent surface.

4 is a plan view of an image obtained by a simulation in which four lines are shown on a stripe fluorescent surface.

5 is a partially enlarged plan view of a shadow mask in a shadow mask type color cathode ray tube according to an embodiment of the present invention;

FIG. 6A is a top view of a slot in the shadow mask of FIG. 5; FIG.

6B is a cross-sectional view of the shadow mask of FIG. 6A taken along line A-A '.

Fig. 7 is a plan view of an image formed by an electron beam on a fluorescent surface in a shadow mask type color cathode ray tube according to an embodiment of the present invention.

8 is a perspective view of an electron gun assembly in a shadow mask type color cathode ray tube according to an embodiment of the present invention;

9 is a diagram illustrating a time-dependent dynamic focusing waveform used in an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

11: display panel 12: electron gun assembly

13: fluorescent surface 14: neck

16: deflection yoke 17: slot

18: Shadow Mask 19: Bridge

32: control electrode 34: acceleration electrode

PV: Slot spacing BW: Bridge width

In order to achieve the object of the present invention, the reason why the image of the shadow mask type color cathode ray tube becomes poor is analyzed, and the spot shape of the electron beam forming the pixel on the display screen as well as the slot spacing and the bridge width in the shadow mask are analyzed. By forming, a number of experiments are carried out to construct a certain type of shadow mask type color cathode ray tube, which has a strong mechanical strength suitable for the finished product, has sufficient screen brightness, and provides a clear image for fine characters and pictures. .

In the case of the stripe fluorescent surface, it should be noted that when the bridge width is sufficiently small, the longitudinal width of the slot does not affect the resolution of the color cathode ray tube. In general, when the longitudinal spacing of the slot is large, the aperture ratio in the mask can be increased to brighten the screen, but the strength of the shadow mask is lowered, whereas when the width of the bridge is large, the strength of the shadow mask is improved. , The brightness is lowered.

In high-resolution displays, particularly, the formation of bridge shadows is found when the longitudinal spacing of slots is large. Note the special bridge shadow that appears on the screen, then the bridge shadow will look like black dust to the human eye, while if viewed from a wider range on the screen, then multiple bridge shadows as a whole degrade the screen quality. It will be seen as a line letting. In addition, the overlapping of the pixels and bridge shadows that make up the character sometimes interferes with the recognition of the character, depending on the degree of the overlapping.

The number of pixels that can appear on the screen is usually determined by technical standards. If a standard number of pixels appears on the screen, the moire should be as small as possible. The inventors of the present invention have determined the following conditions in order to achieve sufficient mechanical strength and screen brightness of the shadow mask while minimizing the above-mentioned problems.

First, the longitudinal spacing of the slots was 0.2 to 0.3 mm, and the spot shape for the electron beam was determined to be elliptical with the horizontal axis larger than the vertical axis. Secondly, when viewed in the thickness direction of the shadow mask, the maximum width of the bridge at the center of the bridge was determined to be 0.02 to 0.08 mm. At that time, the minimum width of the bridge, that is, the width of the bridge at the surface of the shadow mask was determined to be 0.005 to 0.030 mm. At that time, the ratio of the longitudinal axis to the horizontal axis of the elliptical electron beam was determined to be 0.45 to 0.95. As noted above, slots are provided that extend vertically at the surface of the accelerating electrode near the focusing electrode of the electron gun assembly to achieve an elliptical electron beam having a larger horizontal axis than the longitudinal axis in the electron beam.

In addition, a modulating means is provided in the color cathode ray tube having the combination of the stripe fluorescent surface and the electron beam to obtain a high resolution display device. The focusing voltage for the display device is determined to obtain an elliptical electron beam having a horizontal axis larger than the longitudinal axis over the entire area of the screen. Therefore, a display device using a color cathode ray tube and a color cathode ray tube exhibiting low bugging and moire is manufactured.

The present invention will now be described in detail through the preferred embodiment of the present invention shown in FIG.

5, an arrangement of shadow masks used in a color cathode ray tube according to an embodiment of the present invention is shown. The shadow mask 18 has a plurality of square slots 17 having a longitudinal side longer than the transverse side. The slots are arranged in each row having a longitudinal spacing PV, and a bridge is formed between adjacent slots 17, the bridge having a bridge width BW. The rows of slots 17 are arranged apart by the transverse spacing PH, and in one row the center of the bracing 19 passes through the center of the adjacent slots 17 in the adjacent rows.

6A and 6B show the shadow mask shown in FIG. 5 in detail, FIG. 6A shows a top view of a slot row, and FIG. 6B shows a cross sectional view taken along the line A-A 'of FIG. 6A, respectively. As shown in Fig. 6A, when viewed in the thickness direction of the shadow mask, the bridge 19 has a maximum width (BW, briefly referred to as bridge width) at the center portion. The bridge 19 has a flat portion 21 of the same shape as the rear surface of the shadow mask 18. The bridge width BW is larger than the width BC of the flat portion 21, and its shape is similar to the conventional shadow mask type color cathode ray tube except for the size of the bridge width.

In a conventional shadow mask, reducing the bridge width BW has a problem of lowering the strength of the shadow mask. A similar problem occurs when the inner surface of the slot 17 is etched in the bridge 19 so that the bridge 19 has an almost flat surface along the thickness direction.

However, it was found that if the minimum bridge width was maintained at 0.005 mm, it would have sufficient strength at the longitudinal spacing (PV) of the slot of 0.3 mm or less. This is considered to be because the number of bridges increases in inverse proportion to the longitudinal spacing PV of the slot, and as a result, the strength of the shadow mask is improved.

In consideration of the variation in the bridge width of the shadow mask generated in the manufacturing process, in order to keep the flat portion 21 of the bridge 19 as small as possible, the flat portion 21 has a width of 0.005 to 0.03 mm. The inventors have found out by experiment that the bridge 19 must have a maximum width (or bridge width) of 0.04 to 0.08 mm. In the manufacturing process, if the width of the bridge is to be the same at any position along the thickness direction of the shadow mask, that is, if the width of the bridge can be exactly matched with the width of the flat portion of the bridge, then the width of the bridge is 0.3 mm between slots. About 0.02 mm is sufficient.

A typical shadow mask used in a 15 inch color cathode ray tube according to an embodiment of the present invention is preferably composed of Invar ash, has a thickness of 0.1 to 0.13 mm, and is about 1000 pixels arranged in the transverse direction. Slot lateral spacing of 0.25 mm. If the vertical spacing (PV) is selected below 0.3 mm under conditions where moire is difficult to form, for a pattern of representative display pixels 1024 × 768, 800 × 600, or 640 × 480 HZ, the appropriate slot spacing (PV) is About 0.235 mm.

Referring to Fig. 7, each of the elliptical electron beams 20 having a horizontal axis longer than the longitudinal axis is shown on the fluorescent surface 13 of the color cathode ray tube according to the embodiment of the present invention. The elliptical electron beam 20 having a long horizontal axis improves the sharpness of the scanning line, so that characters and pictures are displayed more clearly.

The elliptical electron beam can be obtained by the configuration of the electron gun assembly of FIG. 8 provided in the color cathode ray tube of the embodiment according to the present invention. The inline electron gun assembly is composed of three cathodes, a control electrode 32, an acceleration electrode 34, a focusing electrode not shown in the drawing, and an anode not shown in the drawing, and are arranged in this order. The control electrode 32 has three circular holes 33 through which the electron beam radiated by one cathode 31 passes, while the acceleration electrode 34 has a surface of an adjacent control electrode 31. It has three circular holes 35 on it, which correspond to three square openings 36 on the surface of the accelerating electrode near the focusing electrode. Each of the three square openings 36 has a shape whose longitudinal side is longer than the transverse side. The combination of the circular hole 35 and the square opening 36 on the accelerating electrode 34 provides an elliptical electron beam as described above. The form of the inline electron gun assembly of FIG. 8 is disclosed in Japanese Patent No. 90-12739.

The ratio of the longitudinal axis to the abscissa of the electron beam should be determined according to the position in the screen. In order to obtain a substantially satisfactory image without other odd shapes, the ratio should be 0.45 to 0.95, even if the ratio is different at the center and perimeter of the screen. The specific ratio of the ellipses displays characters and pictures more clearly when compared to the case of other ratios of elliptical or round electron beams having a longitudinal axis longer than the abscissa.

If the sharpness of the scanning line is excessive and the image on the scanning line is degraded, the elliptical electron beam and the slotted shadow mask applied in the present invention can improve the sharpness of the rub and drawing even if the combination of the elliptical electron beam and the dot shadow mask enhances the raster moire. Significantly improve.

As described above, the shadow mask of the high resolution display device using the color cathode ray tube may be provided with a focusing electrode having a dynamic focusing waveform as shown in FIG. 9, which is also disclosed in the above-mentioned patent publication. By properly applying the focusing voltage across the screen in the focusing waveform, clearer characters and pictures can be displayed.

In the shadow mask type color cathode ray tube of the above type, the spot shape of the electron beam can be generally adjusted to a predetermined shape by setting the focusing voltage. Therefore, in the color cathode ray tube according to the embodiment of the present invention, during the initial adjustment of the cathode ray tube to suppress the generation of the bugging and moire, by setting the elliptical electron beam in combination with the stripe-like fluorescent surface as described above, Characters and pictures can be represented. In particular, when combining a color cathode ray tube having a double focusing electron gun assembly having a so-called quadrupole, an elliptical electron beam having a horizontal axis longer than the longitudinal axis can be formed, and characters and pictures can be displayed more clearly. Also in this case, the ratio of the longitudinal axis to the horizontal axis in the spot shape of the elliptical electron beam should preferably be 0.45 to 0.95 in order to obtain an excellent phase balance.

Although the present invention has been described through its preferred embodiments, the present invention is not limited thereto and may be readily modified by those skilled in the art without departing from the scope of the present invention.

According to the present invention, the longitudinal spacing of the slotted shadow mask is limited to 0.2 to 0.3 mm, and the electron beam spot shape is combined with an electron gun such that the ratio of the longitudinal axis to the horizontal axis becomes an ellipse with a ratio of 0.45 to 0.95, thereby making the characters and pictures more clearly Provided are a colored cathode ray tube and a cathode ray tube device capable of representing.

Claims (8)

A shadow mask type color cathode ray comprising an electron gun assembly that emits a plurality of transversely scanned electron beams, a shadow mask having a plurality of slots through which the electron beam passes, and a fluorescent surface for receiving the electron beam passing through the slots to represent an image. In the tube, the slots are arranged in the longitudinal direction at regular intervals between 0.2 mm and 0.3 mm, the spot shape of the electron beam is a shadow mask type color, characterized in that the oval having a longer horizontal axis than the longitudinal axis throughout the fluorescent surface Cathode ray tube. 2. The slot according to claim 1, wherein the slot forms a bridge between two adjacent slots arranged in the longitudinal direction, and when viewed in the longitudinal direction, the maximum width of the bridge is at the center of the bridge in the thickness direction of the shadow mask. A shadow mask type color cathode ray tube, characterized in that about 0.02 to 0.08 mm. The shadow mask type color cathode ray tube according to claim 2, wherein the bridge has a minimum width of 0.005 to 0.030 mm when viewed in the longitudinal direction from the surface of the shadow mask. The shadow mask type color cathode ray tube according to claim 1, wherein the ratio of the longitudinal axis to the horizontal axis of the elliptical electron beam is 0.45 to 0.95. The electron gun assembly of claim 1, wherein the electron gun assembly has an acceleration electrode and a focusing electrode arranged in a direction of the electron beam, the acceleration electrode has a plurality of slots through which the electron beam passes, and the slot is located near the focusing electrode. The shadow mask type color cathode ray tube, characterized in that formed on the surface of the acceleration electrode in a square. A shadow mask type color cathode ray tube device, comprising: a focusing voltage generator for providing the focusing electrode having a focusing voltage according to the deflection voltage with respect to the electron beam, and a shadow mask type color cathode ray tube according to claim 5 . A shadow mask type color cathode ray tube device comprising a focusing voltage generator for providing a focusing voltage to form the electron beam, and a shadow mask type color cathode ray tube according to claim 1. 8. The shadow mask type color cathode ray tube device according to claim 7, wherein the ratio of the vertical axis to the horizontal axis of the spot shape of the electron beam is 0.45 to 0.95.

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