KR20020080093A - Cathode ray tube - Google Patents

Abstract

PURPOSE: A cathode ray tube is provided to improve quality of screen by preventing distortion of screen caused due to inflection, while allowing shaping and processing for the face panel to be easily performed. CONSTITUTION: A cathode ray tube comprises a face panel(2) having an inner surface on which a phosphor screen(10) is formed; an electron gun(14) for emitting three electron beams toward the phosphor screen; a deflection yoke(16) for generating magnetic field for deflection of electron beam; and a color discrimination unit(12) for dividing three electron beams to the designated phosphor screen. The face panel has an outer surface substantially flat and an inner surface having a predetermined curvature. When the formula for the curvature of the inner surface of the face panel, is approximate to the polynomial, based on the central point of the inner surface of the face panel, by the three-dimensional orthogonal coordinate defined by x, y and z-axes, wherein the polynomial is z(x,y) = a20x¬2 + a40x¬4 + a02y¬2 + a04y¬4 + a24x¬2y¬4 + a42x¬4y¬2 + a22x¬2y¬2 + a44x¬4y¬4, coefficients of the polynomial are selected from a predetermined range, such that the inner surface of the face panel avoids inflection.

Description

Cathode Ray Tube {CATHODE RAY TUBE}

The present invention relates to a cathode ray tube, and more particularly, to a cathode ray tube which provides a face panel having an improved structure having no inflection point, thereby facilitating forming and processing of a face panel while preventing screen distortion caused by inflection.

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 electron beam is deflected by a magnetic field in which a deflection yoke has been generated, The R, G, and B fluorescent films are separated to emit all pixels in a specific color.

Here, the face panel forms a fluorescent screen on the inner surface, forms a body of the CRT together with the funnel, and serves to mount a shadow mask therein.

As a result, the face panel must have a mechanical strength capable of withstanding external pressure, and the screen characteristics of the cathode ray tube are greatly influenced by the shape characteristics of the face panel since the face panel transmits light emitted from the fluorescent screen to the outside.

9 shows a face panel 1 of known structure. The face panel 1 may formulate a shape of the face panel 1 to a z-axis position at each x and y coordinates based on a center point using a three-dimensional rectangular coordinate system.

For example, U.S. Patent Nos. 4,924,140 and 5,495,140 describe the outer surface of the face panel as polynomials for the x and y axes, and limit the coefficients of each polynomial to a specific range to minimize the problem caused by mask dominance. Disclosed is a planarizing panel and preventing distortion of the screen.

However, the face panel disclosed in the above-described patent is formed on both the outer surface and the inner surface with a predetermined curvature, and the shadow mask mounted thereon is a molding mask manufactured using a known press machine after a plurality of beam passing apertures are formed. .

Since the molding mask is easy to design curvature in the horizontal and vertical directions, a curvature design is mainly performed after face panel design and corresponding to electron beam landing characteristics. As a result, the problem of the face panel can be compensated by changing the curvature of the mask.

However, since the forming mask changes the path of the electron beam by causing a doming phenomenon by the electron beam collision, it is difficult to realize stable screen quality with the forming mask while the screen becomes large and high resolution. Therefore, a tensile mask was applied to give a tensile force to the mask, and a planar face panel having a substantially flat outer surface was developed.

The tensile mask has an advantage of effective anti-domming, but its shape is entirely determined by the frame shape, it is not easy to change the curvature of the mask. As a result, in the cathode ray tube to which the tensile mask is applied, the shape design of the face panel becomes more important, and a strict design is required.

However, most of the face panel design methods including the aforementioned patents mainly define the shape of the curvature of the horizontal axis and the vertical axis, and the above conditions do not define the shape of the curvature in the diagonal direction.

For example, in case of face panel design considering beam sigma characteristics (how the gap between the fluorescent film and the electron beam coincides), the diagonal curvature may be larger than the horizontal curvature. Inflection is more likely to occur on the surface of the surface.

Accordingly, there is a part in which the curvature function is reversed at the diagonal end or the vertical end of the screen, and an inflection occurs in this part.

As shown in FIG. 10, the generation of the inflection causes distortion of the screen by distorting the emission of the fluorescent screen, and this problem is caused by the convergence characteristics of the screen diagonally declining as the electron beam is deflected toward the periphery of the screen. It acts as a major cause of deterioration of the image quality characteristics.

Therefore, the present invention is to solve the above problems, an object of the present invention is to provide a face panel of an improved structure having no inflection point on the inner surface to facilitate the forming and processing of the face panel while preventing the screen distortion caused by inflection. To provide a cathode ray tube.

1 is a perspective view of a cathode ray tube according to the present invention.

2 is a cross-sectional view of a cathode ray tube according to the present invention.

3 is a front view of the face panel shown in FIG.

4A to 4C are cross-sectional views of the x-x axis, the y-y axis and the w-w axis of the face panel shown in FIG. 3, respectively.

5 is a view for explaining the inner curvature of the face panel;

6 is a front view of a face panel.

7 is a view for explaining the inner surface shape of the face panel quarter.

8 is a perspective view of the color screening apparatus shown in FIG.

9 is a perspective view of a face panel according to the prior art;

FIG. 10 is a front view of the face panel shown in FIG. 9. FIG.

In order to achieve the above object, the present invention,

A face panel having a fluorescent screen formed on its inner surface, an electron gun that emits a three-stage electron beam toward the fluorescent screen, a deflection yoke that generates a magnetic field for electron beam deflection, and a color that separates the three-strip electron beam into a designated fluorescent film A sorting device,

The face panel has a substantially flat outer surface, the inner surface has a predetermined curvature shape, and the curvature of the inner surface is polynomial based on the center point of the inner surface by a three-dimensional rectangular coordinate system defined by the x, y, and z axes.

z (x, y) = a ₂₀ x ² + a ₄₀ x ⁴ + a ₀₂ y ² + a ₀₄ y ⁴ + a ₂₄ x ² y ⁴ + a ₄₂ x ⁴ y ² + a ₂₂ x ² y ² + a ₄₄ x ⁴ y ⁴

(Where x, y, and z axes are the horizontal and vertical axes of the screen and the tube axis perpendicular to them, and the sum of all coefficients is 1)

When approximating to, it provides a cathode ray tube, characterized in that the coefficients of the polynomial are selected in a range satisfying the following conditions so that inflection does not occur on the inner surface.

/ sin xy <0,

/ sin xy <0,

/ sin xy <0,

/ sin xy <0.

Where sin xy> 0 if the position on the z-axis for each x, y coordinate with respect to the inner center point is negative, and sin xy <0 if the face panel inside has a positive value)

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

1 is a perspective view of a cathode ray tube according to an embodiment, and FIG. 2 is a cross-sectional view of a cathode ray tube, in which a horizontal axis of the screen is defined as an x axis, a vertical axis of the screen as a y axis, and a vertical tube axis is defined as a z axis.

The cathode ray tube combines the face panel 2, the funnel 4, and the neck portion 6 to form a vacuum bulb 8, and the face panel 2 has a plurality of R, G, B fluorescent films on its inner surface. The fluorescent screen 10 is formed, and the color screening device 12 is fixed therein by means not shown so as to face the fluorescent screen 10. The electron gun 14 and the deflection yoke 16 are integrally mounted to the inside of the neck portion 6 and the outside of the funnel 4, respectively.

As a result, when the electron gun 14 emits a three-stage electron beam corresponding to the screen signal, the electron beam is deflected by the magnetic field in which the deflection yoke 16 is generated to form a raster, and the corresponding R is selected by the color screening device 12. Landing on the G, B fluorescent film causes the designated fluorescent film to emit light.

Here, the face panel 2 is a planar shape having an outer surface substantially flat, and its inner surface is concave with a predetermined curvature.

3 is a front view of the face panel, and FIGS. 4A to 4C are xx-axis cross sections, yy-axis cross sections, and ww-axis cross sections of the face panel shown in FIG. 3, respectively, and show only a quarter of the face panel. .

As shown in the figure, the face panel 2 is formed to be concave at a predetermined curvature, and the face shape of the face panel 2 is about the x and y coordinates based on the inner center point (O point). It can be formulated by the position on the z-axis, that is, the height difference Δh from the center point.

Specifically, the inner surface shape of the face panel 2 may be expressed as a fourth order polynomial with respect to the x and y axes, as shown in the following equation.

z (x, y) = a ₂₀ x ² + a ₄₀ x ⁴ + a ₀₂ y ² + a ₀₄ y ⁴ + a ₂₄ x ² y ⁴ + a ₄₂ x ⁴ y ² + a ₂₂ x ² y ² + a ₄₄ x ⁴ y ⁴

At this time, the sum of all coefficients is 1, and the height difference Δh from the center point at all points has a negative value on the z-axis. Therefore, the height H of the horizontal end of the face panel 2, the height V of the vertical end, and the height D of the diagonal end of the face panel 2 represent negative values with respect to the inner center point.

In formulating the inner surface shape of the face panel 2 under such conditions, the coefficients of the polynomial are selected in a range that satisfies the condition of the following equation so that no inflection occurs on the inner surface of the face panel 2.

= 2a ₂₀ + 12a ₄₀ x ² <0,

= 2 (a ₂₀ + a ₂₂ + a ₂₄ ) + 12 (a ₄₀ + a ₄₂ + a ₄₄ ) x ² <0,

= 2a ₀₂ + 12a ₀₄ y ² <0,

= 2 (a ₀₂ + a ₂₂ + a ₄₂ ) + 12 (a ₀₄ + a ₂₄ + a ₄₄ ) y ² <0.

That is, when the inner surface shape of the face panel 2 approximates a fourth order polynomial, and the heights of H, V, and D each have a negative value, the condition that the second derivative with respect to the x and y axes is negative is satisfied. The coefficients should be defined so that inverse curvature does not occur in all directions including horizontal, vertical, and diagonal, and as a result, no inflection point occurs in the face panel inner surface.

On the other hand, the inner surface shape of the face panel 2 can be plotted so that the height difference (Δh) at each x, y coordinate with respect to the inner surface center point has a positive value, as shown in FIG.

In this case, when the inner surface shape of the face panel 2 is expressed by the above-described polynomial of Equation 1, the coefficients of the polynomial satisfy the condition of the following equation so that no inflection occurs on the inner surface of the face panel 2. Is selected from the range.

= 2a ₂₀ + 12a ₄₀ x ² > 0,

= 2 (a ₂₀ + a ₂₂ + a ₂₄ ) + 12 (a ₄₀ + a ₄₂ + a ₄₄ ) x ² > 0,

= 2a ₀₂ + 12a ₀₄ y ² > 0,

= 2 (a ₀₂ + a ₂₂ + a ₄₂ ) + 12 (a ₀₄ + a ₂₄ + a ₄₄ ) y ² > 0.

That is, in the case where the heights of H, V, and D each have a positive value, the coefficients must be limited so as to satisfy the condition that the second derivative with respect to the x and y axes is positive. Inverse curvature does not occur at, and as a result, it is possible to prevent the occurrence of inflection.

Therefore, when the curvature shape of the inner surface of the face panel 2 is expressed by Equation 1, both the case where the inner surface shape is expressed to have a negative height difference Δh and the positive height difference Δh are represented. The conditions corresponding to are shown in the following equation.

/ sin xy <0,

/ sin xy <0,

/ sin xy <0,

/ sin xy <0.

That is, when the inner surface shape of the face panel 2 has a negative height difference Δh, it is a case where the condition that the second derivative with respect to the x and y axes becomes negative when x> 0 and y> 0 is satisfied. In the case where the inner surface shape of the face panel 2 has a positive height difference Δh, it is a case where the condition that the second derivative is positive for the x and y axes when x> 0 and y <0 is satisfied.

Therefore, sin xy> 0 when the inner surface of the face panel 2 has a negative height difference Δh, and sin xy <0 when having a positive height difference Δh.

Thus, this embodiment provides the face panel 2 which does not have an inflection point on the inner surface by limiting the range so that the coefficients of each polynomial satisfy the above conditions. As a result, the face panel 2 prevents screen distortion caused by inflection as shown in FIG. 6, and particularly, prevents screen distortion at the diagonal ends of the screen, thereby improving the quality of the screen.

In this case, the face panel 2 may be formed in a shape having the same radius of curvature in all directions while satisfying the condition that there is no inflection on the inner surface.

7 is a diagram illustrating the inner shape of the face panel in the quadrant of the face panel with respect to the inner center point of the face panel. Expressed as Rd.

In the face panel 2 provided in this embodiment, the inner surface of the face panel 2 has the same value as the Rh, the Rv, and the Rd, all have the same value. As such, when the inner surface of the face panel 2 has a single radius of curvature, it is possible not only to prevent the inflection at the diagonal end but also to be advantageous for forming and processing the face panel, and to facilitate the manufacturing process of the fluorescent film screen. have.

For such a shape design, first, the radius of curvature Rh in the horizontal direction may be determined, and the same may be applied to Rv and Rd. Based on Equation 1, the curvature shape z (x) on the horizontal axis is expressed as follows. Shown in the formula.

z (x) = a ₂₀ x ² + a ₄₀ x ⁴

As such, the shape of the x-axis curvature of the inner surface of the face panel 2 is determined by the a ₂₀ and a ₄₀ coefficients. Therefore, the curvature of the x-axis must have a moderate curvature so that Rh can be applied to both Rv and Rd. The generation of the inflection can be suppressed.

Therefore, the a ₂₀ and a ₄₀ coefficients are selected in a range that satisfies the following condition so as to form a gentle curvature on the x-axis.

0.9 ≤ p (x) ≤ 1.0

Where p (x) = a ₂₀ x ² / (a ₂₀ x ² + a ₄₀ x ⁴ )

That is, in the above condition, in the a ₂₀ coefficient and the a ₄₀ coefficient for determining the x-axis curvature shape, the x-axis curvature shape is dominant by predominantly a ₂₀ value, which is a quadratic coefficient of x, rather than a ₄₀ , which is a quadratic coefficient of x. It is to let.

In other words, the larger the four linear expression coefficient, a ₄₀ value is that the face panel (2) inner surface forms a sharp curvature, difficult to achieve a single radius of curvature, on the contrary has the four linear expression coefficient, a ₄₀ value is too small, the curvature This reversal occurs, so the above conditions are set.

That is, when p (x) is smaller than 0.9, the a ₄₀ coefficient becomes larger than the a ₂₀ coefficient beam, so that it is difficult to form a single radius of curvature. When p (x) is larger than 1.0, the inner surface of the face panel 2 is larger. Curvature breaks up.

Meanwhile, as another embodiment, the face panel 2 may have a shape having a larger radius of curvature in the vertical direction corresponding to the tensile mask property while satisfying the condition of no inflection on the inner surface.

That is, the color screening apparatus 12 of this cathode ray tube supports the tensile mask 18 which forms the several beam passage aperture 18a as shown in FIG. 8, and this mask 18 is supported. It consists of a frame 20. Since the mask 18 is mainly fixed to the supporting member 22 of the frame 20 in a state of being stretched in the y-axis direction, the mask 18 has a straight radius of curvature while forming a straight line in the vertical direction.

As a result, the face panel 2 corresponds to the shape of the tensile mask 18 so that the radius of curvature Rv in the vertical direction is larger than the radius of curvature Rh in the horizontal direction.

In a specific embodiment, the face panel 2 is formed such that the wedge rate Wh of the horizontal end is 130% or more and the wedge rate Wv of the vertical end is within 110%.

That is, the wedge ratio means the thickness ratio of the center and the peripheral portion of the face panel. The wedge ratio Wh of the horizontal end and the wedge ratio Wv of the vertical end may be expressed by the following Equations 7 to 8, respectively.

Wh = (effective part thickness / center part thickness) × 100

Wv = (effective part thickness / center part thickness) × 100

In addition, the face panel has to have a total transmittance of 50% or more in consideration of luminance characteristics, and is formed to maintain a B / U (diagonal transmittance / center transmittance) characteristic of 75% or more.

≥ 75%

Here, k is an absorption coefficient, t ₀ is the thickness of the center portion of the face panel, and t ₁ means the thickness of the peripheral portion of the face panel.

For example, in a 29-inch cathode ray tube having a thickness of 17 mm in the center portion, the shape characteristics of the face panel satisfying the above-described shape characteristics are shown in the table below.

Inner curvature Effective part thickness at the tip Wedge rate B / U Horizontal (H) 6,416 (5.4R) 22.61 mm 133% 76% Vertical (V) 20,564 (17R) 17.85 mm 105% Diagonal (D) 10,024 (8.4R) 22.61 mm 133%

As described above, the face panel according to the present exemplary embodiment is formed to satisfy the above-described conditions in response to the shape characteristics of the tensile mask while satisfying the condition where no inflection occurs on the inner surface. This has the advantage of preventing the distortion of the screen due to the inflection and facilitates the design of the tensile mask.

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 such, the present invention provides a face panel which does not incur in all directions including horizontal, vertical, and diagonal by limiting the coefficient of each polynomial to the above-described conditions when the inner surface shape of the face panel approximates a fourth order polynomial. . Therefore, by preventing the distortion of the screen caused by the inflection effectively improves the quality of the screen, has the advantage of facilitating the forming and processing of the face panel.

Claims (7)

A face panel having an inner surface of the fluorescent film screen; An electron gun that emits three stem electron beams toward the fluorescent screen; A deflection yoke for generating a magnetic field for electron beam deflection; And A color screening device for separating the three stem electron beam into a designated fluorescent film, The face panel has a substantially flat outer surface, the inner surface has a predetermined curvature shape, and the curvature of the inner surface is polynomial based on the center point of the inner surface by a three-dimensional rectangular coordinate system defined by the x, y, and z axes. z (x, y) = a ₂₀ x ² + a ₄₀ x ⁴ + a ₀₂ y ² + a ₀₄ y ⁴ + a ₂₄ x ² y ⁴ + a ₄₂ x ⁴ y ² + a ₂₂ x ² y ² + a ₄₄ x ⁴ y ⁴ (Where x, y, and z axes are the horizontal and vertical axes of the screen and the tube axis perpendicular to them, and the sum of all coefficients is 1) Approximate to, the cathode ray tube, characterized in that the coefficient of the polynomial is selected in a range that satisfies the following conditions so that inflection does not occur on the inner surface. / sin xy <0, / sin xy <0, / sin xy <0, / sin xy <0. Where sin xy> 0 if the position on the z-axis for each x, y coordinate with respect to the inner center point is negative, and sin xy <0 if the face panel inside has a positive value) The method of claim 1, And Rh, Rv, and Rd have the same value when a horizontal radius of curvature of the face panel is Rh, a vertical radius of curvature is Rv, and a diagonal radius of curvature is Rd. The method of claim 2, The horizontal axis curvature shape of the inner face panel is approximated by the polynomial below, z (x) = a ₂₀ x ² + a ₄₀ x ⁴ The cathode ray tube, characterized in that the a ₂₀ and a ₄₀ coefficient is selected in the range satisfying the following conditions. 0.9 ≤ p (x) ≤ 1.0 Where p (x) = a ₂₀ x ² / (a ₂₀ x ² + a ₄₀ x ⁴ ) The method of claim 1, And a tensile mask in which the color screening device forms a plurality of beam passing apertures and is tensioned in the vertical axis direction of the screen, and a frame supporting the tensile mask. The method of claim 4, wherein And Rh and Rv satisfy the following conditions when a horizontal radius of curvature of the face panel is Rh and a vertical radius of curvature is Rv. Rv> Rh The method of claim 4, wherein The face panel is a cathode ray tube, characterized in that the wedge rate (Wh) of the horizontal end is more than 130%, the wedge rate (Wv) of the vertical end is made within 110%. The method of claim 1, The face panel is a cathode ray tube, characterized in that the B / U (diagonal transmittance / center transmittance) value is made of 75% or more.