JP2006093060A - Image display device - Google Patents

Abstract

Provided is an image display device capable of effectively utilizing fluorescence from a phosphor layer as much as possible, improving luminance and extending the lifetime of the phosphor.
A fluorescence comprising a light-shielding layer patterned on a front substrate disposed opposite to a rear substrate on which a large number of electron-emitting devices are arranged, and a plurality of phosphor segments provided in a portion where the light-shielding layer does not exist. A body layer and a metal back layer 7A having a reflecting surface in which a longitudinal section in at least one of the long side and the short side of the front substrate has a substantially concave shape as a longitudinal section facing the phosphor segment.
[Selection] Figure 1

Description

  The present invention relates to a flat image display device that displays an image by irradiating a phosphor screen with electrons from an electron-emitting device.

  Recently, as a next-generation image display device, development of a flat-type image display device in which a large number of electron-emitting devices are arranged so as to be opposed to a phosphor screen has been advanced. There are various types of electron-emitting devices, all of which basically use field emission, and display devices using these electron-emitting devices are generally called field emission displays (hereinafter referred to as FED). )is called. A display device using a surface conduction electron-emitting device among FEDs is also called a surface conduction electron-emission display (hereinafter referred to as SED). In this specification, the display device is generally called FED. Use terminology.

In the FED, in order to obtain practical display characteristics, as described in Patent Document 1, a phosphor screen in which an aluminum thin film called a “metal back” is formed on a phosphor is used.
Japanese Patent Laid-Open No. 10-326583

  The metal back has an anode electrode function for the electron-emitting device and a mirror function for reflecting light emitted from the phosphor toward the front substrate side. The light emitted from the phosphor consists of a transmissive component that directly goes out to the front substrate and a reflective component that is reflected off the metal back on the back, but in order to improve the brightness of the screen Is required to increase the light of both these components. In order to increase the former transmitted component light, it is necessary to increase the luminous efficiency, but in order to increase the latter reflected component light, it is necessary to examine the structure of the metal back.

  Incidentally, in order to display a bright and clear image over a long period of time, it is desired to extend the lifetime of the phosphor as much as possible. The lifetime of the phosphor is determined by the amount of electron beam irradiation. When receiving the same electron beam dose, it is possible to obtain a brighter screen by using the light emitted from the phosphor as efficiently as possible, and when displaying the screen with the same brightness, the light emitted from the phosphor should be as efficient as possible. When used, the irradiation amount of the electron beam can be reduced, so that the lifetime of the phosphor is extended.

  As shown in FIGS. 2A and 3A, the conventional metal back layer has a substantially flat cross-sectional shape, so that part of the emitted light is not directed toward the front substrate 2 and left and right. It will be scattered. That is, most of the light emitted from the phosphor 6a is the light 18a that passes through the front substrate 2 as it is and the reflected light 18b that is reflected by the metal back layer 7 and travels toward the front substrate 2, but part of the light is metal. Without being reflected by the back layer 7, it leaks to both sides and becomes scattered light 18c. Since the scattered light 18c is absorbed by the light shielding layers 13V and 13H adjacent to each other, it does not contribute to the improvement of luminance.

  The present invention has been made in order to solve the above-described problems, and is capable of effectively utilizing the fluorescence from the phosphor layer as much as possible, improving the luminance, and extending the lifetime of the phosphor. An object is to provide an apparatus.

  An image display device according to the present invention includes a light shielding layer patterned on a front substrate disposed opposite to a rear substrate on which a large number of electron-emitting devices are arranged, and a plurality of light shielding layers provided in a portion where the light shielding layer is not present. A phosphor layer comprising a phosphor segment, and a metal back layer having a reflecting surface in which at least one longitudinal section of the long side and the short side of the front substrate is substantially concave as a longitudinal section facing the phosphor segment It is characterized by comprising.

  The phosphor layer is formed by arranging a plurality of types of phosphor segments containing different phosphors in a predetermined repeating pattern. These phosphor segments have a rectangular shape or a strip shape, and the same type (for example, red (R) and red (R)) is patterned with a predetermined interval and between different types (for example, Red (R), green (G), and blue (B)) are also patterned at predetermined intervals.

The thickness of the phosphor layer (height from the bottom to the top) depends on the particle size of the phosphor particles, the coating method, and the coating thickness, but is usually in the range of about 7 to 10 μm. As the phosphor layer, a ZnS-based, Y ₂ O _3- based, Y ₂ O ₂ S-based phosphor or the like generally used for a color TV CRT can be used. The phosphor of the color TV CRT has a high luminance performance even though it is relatively inexpensive because it emits electrons accelerated by a voltage of several kV to several tens of kV to obtain good luminance and color development. is there.

  In order to form the phosphor layer in a convex shape for each RGB segment, a photolithography method can be used. The photolithography method may be either a wet process or a dry process. In an optimal wet process, a mixed solution in which phosphor particles are mixed at a predetermined ratio with respect to a photoresist solution (including a solvent) is applied onto the front substrate using a spin coating method, a bar coater method, or a roll coater method. It is applied, dried by heating, exposed, developed, and finally baked to burn off the photoresist to obtain a phosphor layer having a predetermined pattern. In the case of forming a color phosphor screen, the photolithography method is repeated three times for each of red (R), green (G), and blue (B) so that rectangular or strip-like phosphor pixels are regularly arranged in the vertical and horizontal directions. A color pattern is formed.

  In addition, the phosphor layer is preferably formed by stacking a plurality of layers on the top and bottom, and the diameter of the upper layer is preferably smaller than the diameter of the lower layer in a two-dimensional planar view. For the formation of the phosphor layer, a photolithography method or a screen printing method can be used. In the case of the screen printing method, a plurality of plates having different pattern opening diameters are prepared, the diameter of the phosphor pattern of the first printing is increased (see FIG. 6 (a)), and the second printed on top of this. The diameter of the phosphor pattern for printing is reduced (see FIG. 6B). Note that the number of superimposed phosphor layers is not limited to two, but can be three or more, such as three, four, or five.

  The reflection efficiency in the metal back layer largely depends on the shape and thickness of the metal back layer. In the present invention, in order to improve the reflection efficiency from the metal back layer, the inner surface (surface on the phosphor side) of the metal back layer is formed as a concave surface, and all the emitted light from the phosphor is reflected to the front substrate side, and the scattered light (See FIGS. 2B and 3B).

  In order to form a concave metal back layer for each phosphor segment, first, a resin film as a base is adhered along the convex upper surface of the phosphor layer, or a resin solution is applied and dried by heating. Is formed, metal aluminum is vapor-deposited along the unevenness of the base film, and finally baked to disappear the resin film. When the resin film is adhered to the phosphor layer, a nitrocellulose film is used. When the resin solution is applied to the phosphor layer, a hemispherical resin film layer is formed around the phosphor with a highly viscous resin by surface tension. The average thickness of the metal back layer deposited on these resin film layers is in the range of about 50 to 200 nm (0.05 to 0.2 μm).

  The metal back layer is usually formed on the convex phosphor layer into a semi-cylindrical surface or a hemispherical curved surface. However, the method is not limited to this method. It is also possible to form the upper and lower or left and right black matrix light-shielding layers or the resistive material in a convex shape, and laminate the film on the convex shape. That is, after a more vertical line is formed under the portion to be convex, it can be laminated and formed thereon by a printing method or a photolithography method. Since the adhesion of the metal back layer is performed not by the phosphor but by the black matrix light shielding layer, the phosphor does not necessarily have to be convex and may be flat. In this case, the metal back layer can be curved by curving the light shielding layer higher than the height of the phosphor layer. In such a method, it is preferable to deposit a metal back layer using a nitrocellulose film on the phosphor layer.

  Further, the metal back layer is electrically divided at an appropriate interval so that the occurrence of discharge is effectively prevented. The width of the vertical partition lines that divide the rectangular or strip-shaped phosphor pixels is set in the range of 20 to 50 μm, and the width of the horizontal partition lines (stripes) is set in the range of 50 to 300 μm.

  According to the present invention, all the emitted light is reflected to the front substrate side by the concave surface of the metal back layer, and no scattered light is generated. Therefore, when the same electron beam irradiation amount is set, the screen brightness is improved as compared with the conventional case. . In addition, when the screen is set to the same luminance, the electron beam irradiation amount can be made lower than before, so that the life of the phosphor is extended.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows the structure of the front substrate 2, particularly the phosphor screen 6, common to the embodiments of the present invention. The phosphor screen 6 has a number of strip-shaped phosphor layers that emit red (R), green (G), and blue (B). When the long side direction of the front substrate 2 is the X axis and the short side direction orthogonal thereto is the Y axis, the phosphor layers R, G, and B are repeatedly arranged at a predetermined gap interval in the X axis direction. In the axial direction, phosphor layers of the same color are repeatedly arranged at a predetermined gap interval. Note that the gap distance between the phosphor layers 6a in the XY plane is allowed because the gap distance is allowed to vary within a manufacturing error range or within a design tolerance range. Although it cannot be said that is a constant value, it is assumed here that it is a substantially constant value for convenience.

  The phosphor screen 6 includes a light shielding layer. As shown in FIG. 1, the light shielding layer has a rectangular frame light shielding layer 13F extending along the peripheral edge of the front substrate 2, and the phosphor layer R, G, B is disposed in the X direction inside the rectangular frame light shielding layer 13F. The pattern light shielding layer 13V extends and the pattern light shielding layer 13H extends in the Y direction. By these vertical and horizontal pattern light shielding layers 13V and 13H, the surrounding area of the RGB phosphor segment 6a is shielded in a matrix. Since the phosphor layer 6a is aligned with R, G, and B in the X direction, the vertical light shielding layer 13V is much narrower than the horizontal light shielding layer 13H. For example, in the case of a square pixel with a pitch of 600 μm, the width of the vertical light shielding layer 13V is set to 30 to 40 μm, and the width of the horizontal light shielding layer 13H is set to 200 to 300 μm.

  The phosphor layer 6a is formed in a convex shape for each of red (R), green (G), and blue (B) segments. A metal back layer 7A is formed on these convex phosphor layers 6a. The metal back layer 7A has a concave surface facing the convex upper portion of the phosphor layer 6a, and reflects the emitted light from the phosphor layer 6a toward the front substrate 2. That is, as shown in FIGS. 2B and 3B, the light 18d reflected by the metal back layer 7A travels toward the front substrate 2 without being scattered to the periphery, and displays an image. Contribute. For this reason, the brightness of the screen is improved.

7 and 8 show the structure of the FED common to this embodiment. The FED has a front substrate 2 and a rear substrate 1 each made of rectangular glass, and both substrates 1 and 2 are arranged to face each other with an interval of 1 to 2 mm. The front substrate 2 and the rear substrate 1 are joined to each other through a rectangular frame-shaped side wall 3, and a flat rectangular vacuum envelope whose inside is maintained at a high vacuum of about 10 ⁻⁴ Pa or less. 4 is configured.

  A phosphor screen 6 is formed on the inner surface of the front substrate 2. The phosphor screen 6 is composed of a phosphor layer 6a that emits light of three colors of red (R), green (G), and blue (B) and matrix-shaped light shielding layers 13V and 13H. On the phosphor screen 6, a metal back layer 7A that functions as an anode electrode and functions as a light reflecting film that reflects the light of the phosphor layer 6a is formed. During the display operation, a predetermined anode voltage is applied to the metal back layer 7 by a circuit (not shown).

  On the inner surface of the back substrate 1, a large number of electron-emitting devices 8 that emit an electron beam for exciting the phosphor layer 6a are provided. These electron-emitting devices 8 are arranged in a plurality of columns and a plurality of rows corresponding to each pixel. The electron-emitting devices 8 are driven by wiring (not shown) arranged in a matrix. In addition, a large number of plate-like or columnar spacers 10 are provided between the rear substrate 1 and the front substrate 2 as reinforcement in order to withstand the atmospheric pressure acting on the substrates 1 and 2. .

  An anode voltage is applied to the phosphor screen 6 through the metal back layer 7A, and the electron beam emitted from the electron-emitting device 8 is accelerated by the anode voltage and collides with the phosphor screen 6. As a result, the corresponding phosphor layer 6a emits light and an image is displayed.

Next, an example of a method for manufacturing the FED as the image display apparatus of the present embodiment will be described with reference to FIG.
The glass substrate 2 serving as the front substrate of the FED was washed with a predetermined chemical solution and dried by heating to obtain a desired clean surface (Step S1). A light shielding layer forming solution containing a light absorbing material such as a black pigment was applied to the inner surface of the cleaned front substrate 2. After the coating film is heated and dried, it is exposed using a screen mask having openings at positions corresponding to the matrix pattern, and developed to form matrix pattern light-shielding layers 13V and 13H shown in FIG. 1 (step S2). ).

Next, a mixed solution prepared by mixing red (R) phosphor particles at a predetermined ratio with respect to the photoresist solution (including a solvent) was applied to the front substrate 2 with a predetermined film thickness by, for example, a spin coating method. After the coating film was dried by heating, it was exposed and developed using a screen mask having openings at positions corresponding to the red (R) pattern. For green (G) and blue (B), a predetermined pattern was formed using the same photolithography method. In this example, Y ₂ O ₂ S: Eu ³⁺ is used as the red (R) phosphor, ZnS: Cu, Al is used as the green (G) phosphor, and ZnS: Ag is used as the blue (B) phosphor. Then, patterning was performed by a photolithography method to form a phosphor layer having a convex red (R), green (G), and blue (B) repeating pattern (step S3). Finally, the substrate 2 was baked to burn off the photoresist, and the phosphor screen 6 in which the phosphor layers 6a having a rectangular or strip-shaped three-color pattern shown in FIG. In this example, square pixels with a pitch of 600 μm were formed, and the width of the vertical division lines of the phosphor layer 6a was set to a range of 20 to 50 μm. The width of the vertical division line of the phosphor layer 6a is defined by the bottom interval between the adjacent phosphor layers 6a. Since the phosphor layer 6a has a convex profile, the width of the top (top) is 5 to 15 μm, which is smaller than the bottom. In addition, the width | variety of the horizontal division line (stripe) of the fluorescent substance layer 6a was made into the range of 50-300 micrometers, for example. Matrix pattern light shielding layers 13 </ b> V and 13 </ b> H exist on these vertical and horizontal division lines, and are shielded so that light does not leak toward the front substrate 2.

  Next, a metal back layer 7A was formed on the convex surface of the R, G, B phosphor segment pattern (step S4), and this was divided into a predetermined pattern (step S5). As shown in FIGS. 2B and 3B, the metal back layer 7A has a concave inner surface facing the phosphor. In the case of a square pixel with a pitch of 600 μm, the radius of curvature of the concave surface of the metal back layer 7A formed on the upper surface of the phosphor layers R, G, B is in the range of 30 to 300 μm, and the X of the metal back layer 7A The direction width is set to a range of 140 to 180 μm, for example.

  In order to form the metal back layer 7A, an aluminum (Al) film is formed on a thin film made of an organic resin such as nitrocellulose applied by a spin coating method, for example, by a vacuum evaporation method. Furthermore, this was heated and fired at a temperature of 450 ° C. for 30 minutes to decompose and remove organic components. The metal back layer 7A is divided by dividing the underlying resin film using mechanical means such as a roller cutter or thermal means such as a resistance heating wire cutter, and Al is formed on the divided resin film. This is done by vapor deposition. Further, a predetermined getter material (Ti, Ba, etc.) was deposited on the metal back layer 7A in a vacuum atmosphere.

The panel having the phosphor screen was used as a front substrate, and an FED was assembled by a conventional method (step S6). A back substrate 1 was prepared by fixing an electron source having a large number of surface conduction electron-emitting devices formed in a matrix to a glass substrate. Next, as shown in FIGS. 7 and 8, the back substrate 1 and the front substrate 2 were disposed to face each other through the side wall 3 and the spacer 10 and sealed with frit glass. The gap between the back substrate 1 and the front substrate 2 was about 2 mm. Next, after evacuation, Ba was vapor-deposited toward the panel surface, and a getter film having a pattern reverse to the SiO ₂ layer pattern was formed on the Al film.

  Thus, as a result of examining the brightness of the FED screen obtained in Example 1 (with the electron beam irradiation amount fixed), an improvement in brightness of several percent was seen compared to the conventional one.

Next, another embodiment of the present invention will be described with reference to FIGS.
In the present embodiment, the phosphor layer is laminated in two steps, divided into two steps, and a metal back layer 7A having a concave reflecting surface is formed thereon.

  The glass substrate 2 serving as the front substrate of the FED was washed with a predetermined chemical solution and dried by heating to obtain a desired clean surface (step S21).

  A solution prepared by dissolving red (R) phosphor particles in a solvent at a predetermined ratio was printed on the front substrate 2 by a screen printing method through a screen of a first plate having a predetermined pattern. Thereby, the first-stage phosphor layer 6a1 shown in FIG. 6A was formed on the front substrate 2. For green (G) and blue (B), a predetermined pattern was formed using the same screen printing method (step S22).

  Next, a solution obtained by dissolving the red (R) phosphor particles used in step S22 in a solvent at a predetermined ratio is passed through a second pattern screen of a predetermined pattern on the first pattern by a screen printing method. Printed on top of each other. As a result, the second-stage phosphor layer 6a2 shown in FIG. 6B was formed on the first-stage phosphor layer 6a1. The diameter d2 of the pattern hole of the second plate screen was made smaller than the diameter d1 of the pattern hole of the first plate screen (0.3 · d1 <d2 <0.5 · d1).

For green (G) and blue (B), a predetermined pattern was formed using the same screen printing method (step S23). In this example, YVO ₄ : Eu ³⁺ is used as a red (R) phosphor, (Zn, Cd) S: Cu, Al is used as a green (G) phosphor, and ZnS: Ag is used as a blue (B) phosphor. Each was used and patterned by a photolithography method to form a phosphor layer having a convex red (R), green (G), and blue (B) repeating pattern. Finally, a phosphor screen 6 was obtained in which phosphor layers 6a having a rectangular or strip-shaped three-color pattern shown in FIG. In this example, square pixels with a pitch of 600 μm were formed, and the width of the vertical division lines of the phosphor layer 6a was set to a range of 20 to 50 μm. The width of the vertical division line of the phosphor layer 6a is defined by the bottom interval between the adjacent phosphor layers 6a. Since the phosphor layer 6a has a convex profile, the width of the top (top) is 5 to 15 μm, which is smaller than the bottom.

  A light shielding layer forming solution containing a light absorbing material such as a black pigment was applied to the inner surface of the front substrate 2. After the coating film is heated and dried, it is exposed using a screen mask having openings at positions corresponding to the matrix pattern, and is developed to form matrix pattern light shielding layers 13V and 13H shown in FIG. 1 (step S24). ). In addition, the width | variety of the horizontal division line (stripe) of the fluorescent substance layer 6a was made into the range of 50-300 micrometers, for example. These vertical and horizontal dividing lines have matrix pattern light shielding layers 13 </ b> V and 13 </ b> H, and are shielded so that light does not leak toward the front substrate 2.

  Next, a metal back layer 7A was formed on the convex surface of the R, G, B phosphor segment pattern (step S25), and this was divided into a predetermined pattern (step S26). As shown in FIGS. 2B and 3B, the metal back layer 7A has a concave inner surface facing the phosphor. In the case of a square pixel with a pitch of 600 μm, the radius of curvature of the concave surface of the metal back layer 7A formed on the upper surface of the phosphor layers R, G, B is in the range of 30 to 300 μm, and the X of the metal back layer 7A The direction width is set to a range of 140 to 180 μm, for example.

  In order to form the metal back layer 7A, for example, an aluminum (Al) film is formed by a vacuum deposition method on a thin film made of an organic resin such as nitrocellulose applied by a spin coating method. Furthermore, this was heated and fired at a temperature of 450 ° C. for 30 minutes to decompose and remove organic components. The metal back layer 7A is divided by dividing a resin film as a base using a mechanical means such as a roller cutter or a thermal means such as a resistance heating wire cutter, and Al is formed on the divided resin film. This is done by vapor deposition. Further, a predetermined getter material (Ti, Ba, etc.) was deposited on the metal back layer 7A in a vacuum atmosphere.

  Finally, using the panel having the phosphor screen as a front substrate, an FED was assembled by a conventional method (step S27).

  As a result of examining the brightness of the FED screen obtained in Example 2 (with the electron beam irradiation amount fixed), an improvement in brightness of several percent was observed compared to the conventional one.

The top view which shows a fluorescent screen and a metal back layer of a front substrate by cutting out a part of an image display device (FED). (A) is sectional drawing which shows the conventional image display apparatus cut | disconnected along the AA line of FIG. 1, (b) shows the image display apparatus of this invention cut | disconnected along the AA line of FIG. Sectional drawing. (A) is sectional drawing which shows the conventional image display apparatus cut | disconnected along the BB line of FIG. 1, (b) shows the image display apparatus of this invention cut | disconnected along the BB line of FIG. Sectional drawing. Process drawing which shows an example of the method of manufacturing the image display apparatus of this invention. Process drawing which shows another example of the method of manufacturing the image display apparatus of this invention. (A) And (b) is a schematic diagram which shows the example of the formation process of a fluorescent substance layer. The perspective view which shows the outline | summary of an image display apparatus (FED). Sectional drawing cut | disconnected along CC line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Back substrate, 2 ... Front substrate, 3 ... Side wall,
6 ... phosphor screen, 6a ... phosphor layer,
7, 7A ... metal back layer 8 ... electron-emitting device, 10 ... spacer,
13V, 13H ... light shielding layer,
18a ... transmitted light,
18b ... reflected light,
18c ... scattered light,
18d: Reflected light.

Claims (2)

A light shielding layer patterned on a front substrate disposed opposite to a rear substrate on which a large number of electron-emitting devices are arranged;
A phosphor layer composed of a plurality of phosphor segments provided in a portion where the light shielding layer does not exist;
As a longitudinal section facing the phosphor segment, a metal back layer having a reflective surface having a substantially concave longitudinal section in at least one direction of the long side and the short side of the front substrate;
An image display device comprising: The image display device according to claim 1, wherein the phosphor layer has a plurality of layers stacked on top and bottom, and the diameter of the upper layer is smaller than the diameter of the lower layer in a two-dimensional planar field of view.

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