JP2005085503A - Fluorescent screen with metal back, and picture display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent screen with metal back of a picture display device such as an FED with increased adhesiveness of a metal back layer and a phosphor layer as a lower layer and improved pressure withstanding property. <P>SOLUTION: On the screen with a metal back, a coating layer, having a heat-resistant particulate such as SiO<SB>2</SB>, Al<SB>2</SB>O<SB>3</SB>as main components, is formed on a metal back layer, and when the average thickness of a light absorption layer is made a and the average thickness of the phosphor layer is made b, thickness of each layer is adjusted so that the formula -5μm<(a-b)<1μm may apply. It is desirable that the coating layer is formed in a pattern and the pattern of this coating layer is formed at a position corresponding to the light absorption layer on the metal back. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a phosphor screen with a metal back and an image display device such as a field emission display (FED) having a phosphor screen with a metal back.

  Conventionally, an image display device such as a cathode ray tube (CRT) or a field emission display (FED) uses a metal back type phosphor screen in which a metal film such as an Al film is formed on a phosphor layer.

  This metal film (metal back layer) on the phosphor screen increases the brightness by reflecting the light traveling from the phosphor to the face plate side out of the light emitted from the phosphor by the electrons emitted from the electron source. In addition, it is intended to impart conductivity to the phosphor layer and to serve as an anode electrode. It also has a function of preventing the phosphor layer from being damaged by ions generated by ionization of the gas remaining in the vacuum envelope.

  However, in the phosphor screen having such a metal back layer, the thickness of the light absorption layer and the thickness of the phosphor layer are greatly different, and there is a large step on the upper surface of these layers. It was bad. In addition, there are problems such as low withstand voltage characteristics because the metal back layer is not sufficiently close to the phosphor layer, such as unevenness and wrinkles are likely to occur.

  In particular, in the FED, a gap (interval) between a face plate having a phosphor screen and a rear plate having an electron-emitting device is extremely narrow, about 1 mm to several mm, and a high voltage of about 10 kV is applied to the narrow interval. Since a strong electric field is formed, if the metal back layer has irregularities, the electric field concentrates on the protrusions, and discharge (vacuum arc discharge) may occur from there. When such an abnormal discharge occurs, a large discharge current ranging from several A to several hundred A instantaneously flows, so that the electron-emitting device in the cathode part and the phosphor screen in the anode part may be destroyed or damaged. there were.

  In order to suppress such a decrease in pressure resistance, an overcoat layer is formed on the entire surface of the metal back layer by a method such as screen printing of a paste mainly composed of heat-resistant fine particles. It has been proposed to improve the adhesion between the absorption layer and the metal back layer. (For example, see Patent Document 1)

However, in the phosphor screen with a metal back described in Patent Document 1, the degree of improvement in adhesion due to the overcoat layer is easily affected by the step between the light absorption layer and the phosphor layer, and if this step is too large. Even when the overcoat layer was formed, the adhesion with the lower phosphor layer could not be sufficiently improved. In addition, since the formation of the overcoat layer may cause a decrease in light emission luminance, the production conditions are narrow and the manufacture is difficult.
JP 2003-229074 A (page 1-2)

  The present invention has been made to solve these problems. The metal back layer has good film formability and excellent adhesion to the lower layer, and has good withstand voltage characteristics (high limit holding voltage). It is another object of the present invention to provide a phosphor screen with a metal back that is easy to form, and an image display device having high luminance and excellent withstand voltage characteristics to which such a phosphor screen with a metal back is applied.

  The phosphor screen with a metal back of the present invention is a phosphor screen having a light absorption layer and a phosphor layer on the inner surface of the face plate, and having a metal back layer on the phosphor layer, and has heat resistance on the metal back layer. -5 μm <(ab) where a coating layer having fine particles as a main component and an average value of the thickness of the light absorption layer is a and an average value of the thickness of the phosphor layer is b <1 μm holds.

  An image display device of the present invention includes a face plate, a rear plate disposed to face the face plate, a number of electron-emitting devices formed on the rear plate, and the face plate facing the rear plate. And a phosphor screen that emits light by an electron beam emitted from the electron-emitting device, and the phosphor screen is the above-described phosphor screen with a metal back.

  In the phosphor screen with a metal back according to the present invention, when the average thickness of the light absorption layer is a and the average thickness of the phosphor layer is b, a step between the upper surface of the light absorption layer and the upper surface of the phosphor layer is shown. Since the value of (a−b) is adjusted to a range larger than −5 μm and smaller than 1 μm, and the coating layer mainly composed of heat-resistant fine particles is formed on the metal back layer, the coating layer can be easily formed. In addition, the followability of the metal back layer is enhanced, and the adhesion between the phosphor screen composed of the light absorption layer and the phosphor layer and the metal back layer is greatly improved. Therefore, abnormal discharge hardly occurs and the withstand voltage characteristic is improved.

  Hereinafter, modes for carrying out the present invention will be described.

  FIG. 1 is a cross-sectional view showing a phosphor screen with a metal back according to the first embodiment of the present invention. In the figure, reference numeral 1 denotes a glass substrate constituting the face plate. On the inner surface of the glass substrate 1, a light absorption layer 2 having a predetermined pattern (for example, stripe shape) made of a black pigment such as carbon is formed by a photolithography method or the like.

Further, between the patterns of the light absorption layer 2, the patterns (for example, stripes) of the phosphor layers 3 of red (R), green (G), and blue (B) are ZnS-based and Y ₂ O ₃ -based. , Y ₂ O ₂ S-based resin paste containing a phosphor is formed by a method such as screen printing. The phosphor layers 3 of the respective colors can be formed by a method of applying a phosphor slurry containing a photosensitive material and performing patterning by a photolithography method.

  And in the phosphor screen comprised by the pattern of such a phosphor layer 3 of three colors and the light absorption layer 2, the average of the thickness of the light absorption layer 2 is set to a, and the average of the thickness of the phosphor layer 3 is set to In the case of b, the light is such that −5 μm <(ab) <1 μm holds for (ab) which is the difference between the average thickness a of the light absorption layer 2 and the average thickness b of the phosphor layer 3. The thicknesses of the absorption layer 2 and the phosphor layer 3 are adjusted.

  Here, the reason why the value of (ab) is limited to the above range is as follows. That is, when the value of (a−b) is −5 μm or less, it is not preferable because the edge of the concave portion of the lower metal back layer is easily scratched when a coating layer pattern to be described later is formed. Further, when the value of (a−b) is 1 μm or more, a metal gap is generated at the step portion between the upper surface of the light absorption layer 2 and the upper surface of the phosphor layer 3 when the metal back layer is formed. Since the adhesion between the back layer and the lower layer is deteriorated, the pressure resistance characteristics are greatly reduced.

  A metal back layer 4 made of a metal film such as an Al film is formed on the phosphor screen configured as described above. In order to form the metal back layer 4, for example, a metal film such as an Al film is vacuum-deposited on a thin film made of an organic resin such as nitrocellulose formed by a spin method, and further baked (baked). A method for removing organic substances (lacquer method) can be employed.

  Moreover, the metal back layer 4 can also be formed by the transfer method using the transfer laminated film (transfer film) shown below. The transfer film has a structure in which a metal film such as Al and an adhesive layer are sequentially laminated on a base film via a release agent layer (a protective film as necessary). This transfer film is disposed such that the adhesive layer is in contact with the phosphor layer and the light absorption layer, and is subjected to a pressing treatment. Examples of the pressing method include a stamp method and a roller method. In this way, the transfer film is pressed with heating, the metal film is adhered, the base film is peeled off, and then the organic film is decomposed and removed by heating and baking to form a metal film on the phosphor screen. it can.

  Further, on such a metal back layer 4, a pattern of a coating layer (overcoat layer) 5 mainly composed of heat-resistant fine particles is formed at a position corresponding to the light absorption layer 2 described above by a printing method such as screen printing. It is formed using.

The kind of heat-resistant fine particles is not particularly limited. For example, Fe ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , TiO ₂ , MnO ₂ , In ₂ O ₃ , Sb ₂ O ₅ , SnO ₂ , WO ₃ , At least one kind of inorganic fine particles selected from metal oxides such as NiO, ZnO, ZrO ₂ , ITO, and ATO can be used. The particle diameter of the heat-resistant fine particles is preferably 5 nm to 30 μm, and more preferably 5 μm or less so that the coating layer can be precisely patterned.

Such a coating layer 5 can contain a binding inorganic material together with the heat-resistant fine particles. Examples of the binding inorganic material include low melting point glass and water glass, and it is particularly desirable to use low melting point glass. Examples of the low melting point glass include a composition formula (SiO ₂ · B ₂ O ₃ · PbO), (B ₂ O ₃ · Bi ₂ O ₃ ), (SiO ₂ · PbO), or (B ₂ O ₃ · PbO). The glass represented can be used.

  The thickness of the coating layer 5 is not particularly limited because it itself does not cause discharge, but is preferably 1.0 to 10.0 μm. If the thickness of the coating layer is less than 1.0 μm, the effect of improving the adhesion of the metal back layer 4 cannot be obtained sufficiently. On the other hand, when the thickness of the covering layer 5 exceeds 10.0 μm, the pressure resistance characteristics deteriorate, which is not preferable.

  In the embodiment of the present invention, it is possible to form a dividing portion in the metal back layer 4 in order to further improve the breakdown voltage characteristics. At this time, it is desirable to provide a dividing portion on the light absorption layer 2 in order to obtain a high-luminance phosphor screen.

  In order to form the dividing portion in the metal back layer 4, the metal film formed on the entire surface of the phosphor screen by the lacquer method or the transfer method is cut by a laser or the like, or the metal formed on the entire surface of the phosphor screen in the same manner. A method of dissolving the film by applying an acid or alkali aqueous solution or increasing the resistance by applying an oxidizing solution can be employed. It is also possible to form a metal back layer having a predetermined pattern dividing portion in one step by depositing a metal film such as Al using a metal mask having a predetermined negative pattern opening. .

  Further, when the dividing portion is provided in the metal back layer 4 in this way, the end portion of the dividing portion formed on the light absorption layer 2 with the coating layer 5 mainly composed of the heat-resistant fine particles described above is provided. By providing the cover, it is possible to further improve the breakdown voltage characteristics.

  In the embodiment of the phosphor screen with a metal back configured as described above, when the average thickness of the light absorption layer 2 is a and the average thickness of the phosphor layer 3 is b, the upper surface of the light absorption layer 2 and the phosphor layer The value of (ab) indicating the step with respect to the upper surface of 3 is adjusted in the range of −5 μm to 1 μm, and the coating layer 5 mainly composed of heat-resistant fine particles is formed on the metal back layer 4. In addition, since the followability of the metal back layer 4 is enhanced, the adhesion between the metal back layer 4 and the lower phosphor screen is excellent. Therefore, abnormal discharge hardly occurs and the withstand voltage characteristics are greatly improved. Further, the coating layer 5 can be easily formed, and the metal back layer 4 which is the lower layer is hardly scratched when the coating layer 5 is formed. Furthermore, since the pattern of the covering layer 5 is formed only at the position corresponding to the light absorption layer 2, the luminance characteristics do not deteriorate.

  Next, an FED according to a second embodiment of the present invention, in which a phosphor screen with a metal back is used as an anode electrode, will be described.

  In this FED, as shown in FIG. 2, a face plate 7 having a phosphor screen 6 with a metal back according to the first embodiment, and a rear plate 10 having electron-emitting devices 9 arranged in a matrix on a substrate 8; Are arranged so as to face each other through a narrow gap of about 1 mm to several mm, and a high voltage of 5 to 15 kV is applied to a very narrow gap between the face plate 7 and the rear plate 10. In the figure, reference numeral 11 denotes a glass substrate of the face plate 7, and 12 denotes a support frame (side wall).

  The gap between the face plate 7 and the rear plate 10 is very narrow, and electric discharge (dielectric breakdown) is likely to occur between them. This FED has a smooth metal back layer free from cracks, pinholes, scratches, etc. Since the adhesion between the metal back layer and the lower phosphor screen is also extremely high, the occurrence of discharge is suppressed and the withstand voltage characteristics are greatly improved. Further, in the FED of this embodiment, the pattern of the coating layer formed on the metal back layer is limited to the region corresponding to the light absorption layer. A luminance display is obtained.

  Next, specific examples in which the present invention is applied to an image display device will be described.

Example 1
A striped light absorbing layer (average thickness a 7 μm) made of a black pigment is formed on a glass substrate by a photolithographic method, and then, between the light absorbing layers, red (R), green (G), and blue (B) Each of the resin pastes containing the three phosphors was screen printed. Then, stripe-like three-color phosphor layers (average thickness b 10 μm) were formed so as to be adjacent to each other with the light absorption layer interposed therebetween. Thus, a phosphor screen having a step (ab) between the light absorption layer and the phosphor layer of −3 μm was obtained.

  Next, a metal back layer was formed on such a phosphor screen by a transfer method. That is, an Al transfer film in which an Al film is laminated on a polyester resin base film through a release agent layer and an adhesive layer is applied thereon is placed so that the adhesive layer is in contact with the phosphor screen. From the top, it was heated and pressed with a heating roller to make it adhere. Next, the base film was peeled off and an Al film was adhered on the phosphor screen, and then heated and baked at a temperature of 450 ° C. for 30 minutes to decompose and remove organic components. Thus, a substrate having a phosphor screen on which the metal back layer was transferred and formed was obtained.

  Next, a paste of heat-resistant fine particles having the following composition is screen-printed at a position corresponding to the upper side of the light absorption layer in the metal back layer of the substrate, and then heated and fired at 450 ° C. for 30 minutes to mainly produce silica. A coating layer as a component was formed. The thickness of the coating layer was 5 μm.

[Composition of paste of heat-resistant fine particles]
Silica fine particles (particle size: 3.0μm) …… 40wt%
Resin (Ethylcellulose) …… 6wt%
Solvent (Butyl Carbitol Acetate) …… 54wt%

  Next, on the phosphor screen with the metal back of the substrate thus obtained, the presence or absence of scratches on the metal back layer was examined.

  Moreover, FED was produced using the board | substrate (panel) which has a fluorescent surface with a metal back obtained in this way. That is, an electron generation source in which a large number of surface conduction electron-emitting devices are formed in a matrix on a substrate is fixed to a rear glass substrate to form a rear plate, and the rear plate and the panel (face plate) are connected to a support frame and They were placed facing each other through a spacer and sealed with frit glass. The gap between the face plate and the rear plate was 2 mm. Next, necessary processing such as evacuation and sealing was performed to complete the FED.

  Subsequently, the pressure resistance characteristics (discharge voltage) of the obtained FED were measured by a conventional method. The measurement results are shown in Table 1 together with the presence or absence of scratches on the metal back layer. A withstand voltage of 8 kV or higher is a practical level.

A paste of heat-resistant fine particles was prepared by using 20 wt% of silica particles and 20 wt% of low melting point glass material (SiO ₂ · B ₂ O ₃ · PbO) instead of 40 wt% of silica fine particles. Similar measurement results were obtained with the FED having the coating layer formed thereon.

Example 2
A phosphor screen with a metal back was prepared in the same manner as in Example 1 except that the average thicknesses of the light absorption layer and the phosphor layer were changed to the values shown in Table 1, and the pattern of the coating layer mainly composed of silica thereon. Formed.

  Further, as Comparative Examples 1 and 2, the average thickness of the light absorption layer and the phosphor layer is set to the value shown in Table 1, and the step (ab) between the light absorption layer and the phosphor layer is −5 μm to 1 μm. A phosphor screen was formed out of the range. And the metal back layer was formed on it similarly to Example 1, and also the pattern of the coating layer was formed.

  Next, on the phosphor screen with metal back thus obtained, the presence or absence of scratches on the metal back layer was examined. Moreover, FED was produced using the panel which has this fluorescent screen with a metal back, and the pressure | voltage resistance characteristic of obtained FED was measured similarly to Example 1. FIG. The measurement results are shown in Table 1 together with the presence or absence of scratches on the metal back layer.

  As is clear from Table 1, the metal back-equipped phosphor screens obtained in Examples 1 and 2 have no scratch on the metal back layer and have good adhesion to the lower layer. And FED provided with such a fluorescent screen with a metal back has a high discharge voltage compared with what was obtained in Comparative Examples 1 and 2, and has a favorable pressure | voltage resistant characteristic.

  According to the present invention, it is possible to form a smooth metal back layer having high adhesion with the lower phosphor layer, without scratches, and obtain a phosphor screen with a metal back having a high limit holding voltage. it can. Therefore, by providing such a phosphor screen with a metal back, it is possible to realize an image display device having excellent withstand voltage characteristics and high luminance.

It is sectional drawing which shows the structure of the fluorescent screen with a metal back which is the 1st Embodiment of this invention. It is a figure which shows typically the structure of FED which is the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ...... Glass substrate, 2 ...... Light absorption layer, 3 ...... Phosphor layer, 4 ...... Metal back layer, 5 ...... Cover layer, 6 ...... Phosphor screen with metal back, 7 ... …… Face plate, 10 ……… Rear plate.

Claims (5)

A phosphor screen having a light absorption layer and a phosphor layer on the inner surface of the face plate, and a metal back layer on the phosphor layer;
When the metal back layer has a coating layer mainly composed of heat-resistant fine particles, and the average thickness of the light absorption layer is a, and the average thickness of the phosphor layer is b, A phosphor screen with a metal back characterized by the following formula:
−5 μm <(ab) <1 μm   The coating layer containing the heat-resistant fine particles as a main component is formed in a pattern, and the pattern of the coating layer is formed on the metal back layer at a position corresponding to the light absorption layer. The fluorescent screen with a metal back according to claim 1.   3. The phosphor screen with a metal back according to claim 1, wherein the coating layer containing the heat-resistant fine particles as a main component includes a layer having a function of removing the metal back layer or increasing the resistance.   4. The phosphor screen with a metal back according to claim 1, wherein the coating layer containing the heat-resistant fine particles as a main component has a thickness of 1.0 to 10.0 μm.   A face plate; a rear plate disposed opposite to the face plate; a plurality of electron-emitting devices formed on the rear plate; and the electron-emitting device formed on the face plate so as to face the rear plate. 5. An image display device comprising: a phosphor screen that emits light by an electron beam emitted from the image display device, wherein the phosphor screen is a phosphor screen with a metal back according to claim 1.

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