KR20040008366A - Tension mask type cathode ray tube - Google Patents

Abstract

PURPOSE: A tension mask type cathode ray tube is provided to achieve improved purity and convergence characteristics and screen quality by using an inner terrestrial magnetic field shield for minimizing variance of landing of electron beams. CONSTITUTION: A tension mask type cathode ray tube comprises a vacuum tube(18) including a panel(12) having a phosphor screen(20), a funnel(14) attached to the panel, and a neck portion(16) connected to the funnel; an electron gun(24) mounted in the neck portion; a tension mask(26) for discriminating colors of electron beams emitted from the electron gun; a mask frame(28) for supporting the tension mask at the tension state; a deflection yoke(22) for deflecting electron beams emitted from the electron gun; and an inner shield(30) arranged in the vacuum tube so as to shield terrestrial magnetic fields. The ratio of the characteristic value(Br/HC) of the inner shield with respect to the characteristic value(Br/HC) of the mask frame ranges from 0.94 to 2.00, wherein BR is a remanent magnetic flux density and Hc is a coercive force.

Description

Tension mask type cathode ray tube {TENSION MASK TYPE CATHODE RAY TUBE}

The present invention relates to a cathode ray tube having a tensile mask to which a tensile force is applied in one axis or two axes, and more particularly to a tensile mask type cathode ray tube having an inner shield capable of minimizing the amount of landing change of the electron beam by a geomagnetic field. It is about.

In general, a cathode ray tube is a display device that implements a predetermined screen by scanning a fluorescent film screen with three stem electron beams emitted from an electron gun, and the path of the electron beam is changed by a geomagnetic field generated along the north and south poles of the earth. Purity characteristics, raster position, and convergence characteristics are affected.

These geomagnetic fields are divided into vertical components perpendicular to the ground (vertical geomagnetic field) and horizontal components parallel to the ground (horizontal geomagnetic field), and represent different values depending on the place on the earth. The electron beam movement can be explained by dividing the NS movement amount and the EW movement amount according to the direction in which the cathode ray tube is directed.

In this case, the NS movement amount refers to the electron beam movement amount by the component that matches the tube axis of the cathode ray tube in the horizontal geomagnetic field, and the EW movement amount refers to the electron beam movement amount by the component perpendicular to the tube axis of the cathode ray tube in the horizontal geomagnetic field.

On the other hand, the landing change amount of the electron beam appearing on the screen under the influence of the geomagnetic field can be analyzed by dividing it into a horizontal component and a vertical component.

At this time, in both the shadow mask which is mainly applied to the commercial cathode ray tube and has a long slot in the vertical direction, and the shadow mask which is mainly applied to the industrial cathode ray tube and has a dot-shaped hole, the horizontal moving component of the electron beam is defined as the electron beam. Because of the distance away from the slot or hole, suppressing this horizontal shift component is an important task.

Therefore, an inner shield is mounted inside the cathode ray tube for the purpose of reducing the amount of change in the landing of the electron beam due to the geomagnetic field. Generally, a cathode ray tube having a formed mask by press molding (hereinafter referred to as a cathode ray tube) In this case, the inner shield is manufactured using a material with high permeability to reduce the amount of beam movement caused by the geomagnetic field. The reason is as follows.

As shown in FIG. 1, when the cylindrical shield 110 is formed using two materials 112 and 112 having the same level of permeability, the magnetic force lines due to the geomagnetic field are internal to the materials 112 and 112 as shown by the arrows. By passing through the internal magnetic field of the shield 110 becomes constant (see FIG. 1A).

On the other hand, a cylindrical shield 110 'is formed by joining two materials having different permeability, that is, a material having a high permeability 112 and a material having a low permeability (114: the permeability is about 1/10 of that of a high permeability material). In the case of forming a magnetic field leakage occurs at the junction 116 of the two materials (112, 114) as shown by the arrow, the internal magnetic field is non-uniform, and as a result, the shielding efficiency is reduced (see Fig. 1b).

Therefore, in the case of the molded mask type cathode ray tube, the initial permeability (μ _0.35 ) of the molded mask is about 600, the maximum permeability (μ _max ) is about 3200, and the mask frame used to support the molded mask is initially The magnetic permeability (μ _0.35 ) is at a level of 800 or more, and the maximum permeability (μ _max ) is made of a material having a level of approximately 4000 to 8000.

Here, the initial permeability is a value measured at a magnetic flux density of 350 milligauss (mG).

Therefore, when the inner shield material has the same high permeability as that of the mask frame, as shown in FIG. 1A, as in the case where two materials 112 and 112 having the same level of permeability are joined, the magnetic line flow is smoothly shielded. The efficiency is increased, which reduces the amount of electron beam movement.

Therefore, in the related art, as disclosed in Korean Patent Laid-Open Publication Nos. 1998-077085, 1998-077088, and 1999-026171, the method of improving permeability of an inner shield material using heat treatment has been mainly studied.

However, unlike a molded mask type cathode ray tube, in a cathode ray tube using a tensile mask (hereinafter referred to as a tensile mask type cathode ray tube), the tensile mask and the mask frame supporting the mask must maintain high strength, so that the tensile mask And the permeability of the material forming the mask frame is relatively lower than that of the molded mask type cathode ray tube.

Table 1 below shows the magnetic properties of a typical mask frame, which is characterized by blackening the mask frame at a temperature of 460 ° C., and applying a tensile mask to a force of 15 kgf / mm ² in one or two axes. It was measured while being mounted in the cathode ray tube after being tensioned, and Hc and Br represent coercive force and residual magnetic flux density, respectively.

Magnetic properties Remarks μ _max Hc (Oe) Br (kG) Hc × Br Material name Mask frame 1080 5.42 11.59 62.82 SCM415

As shown in Table 1, the mask frame of the tensile mask method has a permeability (μ) of approximately 20% compared to the components of the molded mask method cathode ray tube.

Therefore, when a high permeability inner shield is attached to the tensile mask type cathode ray tube, a phenomenon as shown in FIG. 1B occurs. That is, since the high permeability inner shield and the low permeability mask frame are used, the shielding effect inside the inner shield may be satisfactory, but the local magnetic field distribution changes due to the magnetic leakage at the part where the inner shield and the frame are welded. As a result, the amount of electron beam movement increases.

Accordingly, the present invention is to solve the above problems, to provide a tensile mask type cathode ray tube with improved quality by providing an inner shield for shielding the geomagnetic field that can minimize the amount of the landing change of the electron beam by the geomagnetic field.

The object of the present invention described above,

A tensile mask type cathode ray tube having a tensile mask applied with a tensile force in one or two axes, a mask frame supporting the mask, and an inner shield fixed to the mask frame to shield the geomagnetic field, wherein the characteristic value of the mask frame The ratio of the characteristic value (Br x Hc) of the inner shield to (Br x Hc) is achieved by a tensile mask type cathode ray tube satisfying 0.94 to 2.00 times. Here, Br is the residual magnetic flux density (kG) and Hc is the coercive force (Oe).

The mask frame is formed of a material having a coercive force (Hc) of 3.0 Oe or more. In other words, in the tensile mask type cathode ray tube, a certain amount (15 kgf / 인장) of tensile force must be applied to the tensile mask, and in particular, the rigidity at high temperature (above 450 ° C) such as blackening process and sealing process is required, so that the high temperature yield as a material of the mask frame High strength materials should be used, and these materials have a high carbon content and a small grain size, and thus have a coercive force (Hc) of 3.00 e or more. If a material having a coercive force of 3.00 e or less is used as a frame, the above-described high temperature strength characteristics are not satisfied, and thus a certain amount of tensile force required in the tensile mask type cathode ray tube cannot be applied to the tensile mask.

In the case of the inner shield, a material of 0.15 mm thickness is widely used in a conventional cathode ray tube of a molded mask, but in the case of a tensile mask type cathode ray tube, the weight of the mask and the frame structure is about 6 kg or more, and thus the molded mask type cathode ray tube 2 times more heavy than Therefore, since the inner shield must support the mask and the frame structure during the manufacturing process of the cathode ray tube, the inner shield has a thickness of 0.20 to 0.50 mm to secure a certain level or more.

Meanwhile, the tensile mask may be tensioned with a greater tensile force around the center, and conversely, the tension mask may be tensioned with a greater tensile force than the center, and the cathode ray tube of the present invention may include a panel and a panel on which a fluorescent film screen is formed. And a deflection apparatus for deflecting a vacuum tube including a funnel sealed to the neck and a neck portion connected to the funnel, an electron gun installed on the neck portion, and an electron beam emitted from the electron gun.

1 is a view showing the direction and size of the internal magnetic field generated in the inner shield material, Figure 1a is a case formed by joining two kinds of materials having the same permeability, Figure 1b is a two kinds of different permeability This is the case where the raw materials are joined together.

Figure 2 is a plan sectional view of a tension mask type cathode ray tube equipped with an inner shield of the present invention.

3A and 3B are tensile force distributions applied to a tensile mask.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 2 shows a cross-sectional plan view of a tensile mask type cathode ray tube equipped with the inner shield of the present invention, Figures 3a and 3b shows a tensile force distribution applied to the tensile mask.

As shown, the cathode ray tube is a panel 12, the funnel 14 and the neck portion 16 is integrally combined to form a vacuum tube 18, a plurality of R, G, B on the inner surface of the panel 12 A fluorescent film screen 20 made of a fluorescent film is formed, and the deflection yoke 22 and the electron gun 24 are integrally mounted to the outer circumferential surface of the funnel 14 and the inner circumferential surface of the neck portion 16, respectively.

In addition, a tensile mask 26 having a plurality of electron beam through holes formed therein is fixed to the mask frame 28 and installed inside the tube 18 so as to face the fluorescent screen 20.

At this time, the tension mask 26 is fixed to the mask frame 28 in a state in which the tension mask 26 is tensioned in one axis (long axis) or two axes (long axis and short axis), and the tension mask 26 is shown in FIG. 3A. Peripheral relative to the center may be stretched with a large tensile force, or as shown in FIG.

According to the above-described configuration, when the electron gun 24 emits a three-stem electron beam corresponding to the screen signal, the electron beam is deflected by the magnetic field in which the deflection yoke 22 is generated to form a raster on the screen, and thus the tension mask 26. By the R, G, B fluorescent film is separated by the correct color and the screen is implemented.

In this way, the electron beam forms a raster designated by the deflection magnetic field, and the three-beam electron beam exactly moves in one electron beam passing hole (that is, achieves good convergence characteristics). have.

Therefore, inside the vacuum tube 18, an inner shield 30, which serves to provide a certain level of shielding of the magnetic field affecting the electron beam movement, is mounted so that one end thereof is fixed to the mask frame 28 to surround the electron beam path. .

However, in the tensile mask type cathode ray tube should pay special attention to the material selection of the inner shield (30).

Accordingly, the present invention intends to improve the quality of the tensile mask type cathode ray tube by proposing a new characteristic value that can be used to select the material of the inner shield.

As described above, the most important factor influencing smooth magnetic flow in the magnetic flow leading to the inner shield-mask frame-tensile mask can be expressed as permeability. However, it is impossible to accurately measure the permeability of materials with low permeability and use them as evaluation data. In particular, the initial permeability is difficult to be used as an evaluation criterion because it changes sensitively to the measurement equipment and the measurement conditions.

Therefore, the present inventors define 'residual magnetic flux density (Br) x coercive force (Hc)', which has a constant function relation with the 'maximum permeability (μ _max )', as a characteristic value, and properly correlate the correlation between the characteristic value of the inner shield and the mask frame. By selecting the material of the inner shield can reduce the landing error.

Table 2 below is a comparison of the magnetic properties of the various materials forming the inner shield 30, Table 3 is a measure of the electron beam movement of the inner shield formed by using the materials.

Blackening temperature (℃) Magnetic properties Remarks Hc (Oe) Br (kG) Hc × Br ratio Comparative material 1 460 ℃ 5.00 13.35 66.75 0.94 Posco 700ppm Comparative material 2 460 ℃ 4.03 15.10 60.85 1.03 Ultra Low Carbon FH Ash Comparative material 3 460 ℃ 3.46 14.28 49.41 1.27 Low Carbon CR Material Comparative material 4 460 ℃ 2.69 10.90 29.32 2.14 Ultra low carbon CR material Comparative material 5 460 ℃ 2.84 11.05 31.41 2.00 Posco 800ppm Comparative Material 6 460 ℃ 3.87 14.75 57.11 1.10 Low carbon FH ash Comparative material 7 460 ℃ 2.65 10.79 28.55 2.20 Posco 900ppm

In Table 2, the FH (full hard) material is a material in which annealing heat treatment is omitted after cold rolling, and the CR (cold rolled) material is a material in which annealing heat treatment and temper rolling are performed after cold rolling. The magnetic properties of the materials were measured at a temperature (460 ° C.) of blackening the inner shield in the tensile mask type cathode ray tube, and the ratio was the characteristic value of the inner shield with respect to the characteristic value (Br × Hc) of the mask frame. The ratio of Br x Hc) is shown.

That is, if the characteristic value of the mask frame is referred to as 'A' and the characteristic value of the inner shield is referred to as 'B', the ratio represents A / B.

Blackening temperature (℃) Electron beam shift amount (㎛) Diagonal Point EW Diagonal Branch NS (1/2) NS Vertical point NS TOTAL Comparative material 1 460 ℃ 43 72 71 70 114 Comparative material 2 460 ℃ 58 40 39 41 97 Comparative material 3 460 ℃ 41 29 44 41 85 Comparative material 4 460 ℃ 64 30 45 40 109 Comparative material 5 460 ℃ 55 41 50 45 105 Comparative Material 6 460 ℃ 47 43 45 42 92 Comparative material 7 460 ℃ 75 40 55 51 130

In Table 3, (1/2) NS refers to the amount of (NS) at the point moved by 1/2 from the diagonal end of the cathode ray tube to the vertical end.

Referring to Tables 2 and 3 above, it can be seen that the inner shield material satisfying the electron beam movement amount below a predetermined level (100 μm) is a comparative material 2, 3, 6, and the characteristics of the mask frame (Hc × Br) It turns out that ratio (A / B) of the characteristic value (Hc * Br) of the said comparative materials 2,3,6 exceeds 0.94 and is less than 2.00.

Therefore, when the inner shield is manufactured using a material belonging to the ratio (A / B) of more than 0.94 and less than 2.00 of the comparative materials 1 to 7, it is possible to minimize the amount of change in landing of the electron beam by the geomagnetic field.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

As described above, the present invention provides a more accurate electron beam path when the inner shield is manufactured using a material in which the ratio of the characteristic value (Br × Hc) of the inner shield to the characteristic value (Br × Hc) of the mask frame is within a certain range. It has the advantage of improving the quality of the screen, such as to improve the purity characteristics and convergence characteristics to ensure accurate raster.

Claims (5)

A vacuum tube comprising a panel on which a fluorescent film screen is formed, a funnel encapsulating the panel and a neck portion connected to the funnel; An electron gun installed in the neck portion; A tensile mask for color-selecting the electron beam emitted from the electron gun; A mask frame for supporting the tensile mask in a state in which the tensile mask is tensioned in one or two axes; A deflecting device for deflecting the electron beam emitted from the electron gun; An inner shield installed inside the vacuum tube to shield an earth magnetic field; A tensile mask type cathode ray tube satisfying a ratio of the characteristic value (Br / Hc) of the inner shield to the characteristic value (Br / Hc) of the mask frame is 0.94 to 2.00 times. Here, Br is the residual magnetic flux density (kG) and Hc is the coercive force (Oe). The tensile mask type cathode ray tube according to claim 1, wherein the coercive force (Hc) of the mask frame is 3.0 Oe or more. The tensile mask type cathode ray tube according to claim 1, wherein the inner shield has a thickness of 0.20 to 0.50 mm. The tensile mask type cathode ray tube according to any one of claims 1 to 3, wherein the tensile mask is tensioned with a greater tensile force around the center. The tensile mask type cathode ray tube according to any one of claims 1 to 3, wherein the tensile mask is tensioned with a greater tensile force in the center than the surroundings.