JP2008084776A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of maintaining high display performance for a long time and realizing reduction in the manufacturing cost. <P>SOLUTION: The image display device is provided with a housing 10, having a first substrate 11 and a second substrate 12 of which peripheral parts are jointed, a phosphor screen 16 arranged on the first substrate, electron sources 18 arranged on the second substrate, and a getter for adsorbing the gas in the housing. The getter includes a non-evaporation type getter formed on the phosphor screen and an evaporation type getter, containing at least barium installed at the peripheral part of the housing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an envelope and an image display device in which a getter is provided inside the envelope.

  In recent years, as a lightweight and thin image display device, a liquid crystal display (hereinafter referred to as LCD) that controls the intensity of light using the orientation of liquid crystal, a plasma display panel (hereinafter referred to as LCD) that emits phosphors by ultraviolet rays of plasma discharge. (Referred to as PDP), field emission display (hereinafter referred to as FED) that emits a phosphor with an electron beam of a field emission electron emitter, and surface conduction electron that emits a phosphor with an electron beam of a surface conduction electron emitter. Emission displays (hereinafter referred to as SEDs) have been developed.

  For example, an FED generally has a front substrate and a rear substrate that are opposed to each other with a predetermined gap, and these substrates are surrounded by a vacuum by surrounding each other through a rectangular frame-shaped side wall. Make up the vessel. A phosphor screen is formed on the inner surface of the front substrate, and a number of electron-emitting devices are provided on the inner surface of the rear substrate as electron emission sources that excite the phosphor to emit light.

  In order to support an atmospheric pressure load applied to the back substrate and the front substrate, a plurality of support members are disposed between these substrates. The potential on the back substrate side is almost the ground potential, and 10 kV, for example, is applied as an anode voltage to the phosphor screen. An image is displayed by irradiating the phosphors of red, green, and blue constituting the phosphor screen with the electron beams emitted from the electron-emitting devices and causing the phosphors to emit light.

  In such an FED, it is important to maintain a high degree of vacuum inside the vacuum envelope. This is because if the degree of vacuum is low, stable electron emission cannot be performed, and the life of the image display device is reduced.

Therefore, in order to maintain a high degree of vacuum inside the vacuum envelope over a long period of time, it is usual to provide a getter layer that adsorbs undesired gas molecules inside the vacuum envelope. As such a getter layer, for example, a method of forming a non-evaporable getter layer in a region adjacent to the panel side of the PDP has been proposed (see, for example, Patent Document 1). In addition, a method has been proposed in which a front substrate is placed in a vacuum chamber, the vacuum chamber is evacuated, and then an evaporative getter layer is deposited on the phosphor screen region of the front substrate (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 11-191378 JP 2001-229824 A

  However, in the method of forming a non-evaporable getter film in the area adjacent to the side of the panel, undesired gas molecules existing in the area away from the getter, that is, in the central portion of the phosphor screen, are efficiently adsorbed to the getter. Can not do it. Therefore, the gas pressure at the center of the vacuum envelope increases, and the brightness at the center of the display device decreases. That is, during the operation of the FED, an electron beam is irradiated onto the phosphor, and unwanted gas molecules are emitted from the phosphor screen. However, since there is no getter in the central part of the vacuum envelope, the emitted gas molecules in the central part are more likely to contaminate the electron-emitting device before being adsorbed by the peripheral getter. Characteristics deteriorate. The contaminated electron-emitting device cannot emit sufficient electrons, and the luminance at the central portion is lower than the luminance at the peripheral portion of the FED.

  Further, since the non-evaporable getter generally has a small amount of adsorption of carbon monoxide and carbon dioxide, it becomes impossible to adsorb carbon monoxide and carbon dioxide after a while after operating the FED. For this reason, the gas pressure in the entire vacuum envelope is increased, and the electron-emitting device is destroyed and stable electron emission cannot be performed. As a result, there arises a problem that the life of the FED is reduced.

  On the other hand, in a method in which a front substrate is placed in a vacuum chamber, the vacuum chamber is evacuated, and then an evaporation type getter film is deposited on the phosphor screen region of the front substrate, undesired gas molecules are efficiently removed by a getter film. To be adsorbed. For this reason, the inside of the vacuum envelope of the FED is maintained at a high degree of vacuum over a long period of time.

  However, since this method uses a large vacuum chamber, the manufacturing cost increases, and as a result, the cost of the image display device also increases. In addition, since a drive mechanism for getter vapor deposition must be provided in the vacuum chamber, the reliability and maintainability of the apparatus are extremely deteriorated. Further, when an evaporation type getter film is formed over the entire surface of the phosphor screen, there is a problem in performance that the luminance is lowered.

  The present invention has been made in view of the above points, and an object thereof is to provide an image display device capable of maintaining high display performance over a long period of time and capable of reducing the manufacturing cost.

An image display device according to an aspect of the present invention includes an envelope having a first substrate and a second substrate whose peripheral portions are joined to each other, a phosphor screen disposed on the first substrate, and the second substrate An electron source disposed on the substrate, and a getter that adsorbs the gas in the envelope,
The getter includes a non-evaporable getter formed on the phosphor screen, and an evaporative getter provided at a peripheral edge of the envelope and containing at least barium.

  According to the image display device according to the aspect of the present invention, the non-evaporable getter is formed on the phosphor screen, and the evaporative getter including the barium getter having a large adsorption amount of carbon monoxide and carbon dioxide is provided around the envelope. By forming it in the part, undesired gas molecules can be efficiently adsorbed for a long period of time without lowering the luminance, and the inside of the vacuum envelope can be maintained at a high degree of vacuum for a long period of time. There is no need to use an expensive vacuum chamber for the production, the production cost can be reduced, and the reliability and maintainability of the apparatus are also improved. As a result, it is possible to provide an image display device that can maintain high display performance over a long period of time and can reduce the manufacturing cost.

Hereinafter, an embodiment in which an image display device of the present invention is applied to an SED will be described in detail with reference to the drawings.
As shown in FIGS. 1 and 2, the SED includes a front substrate 11 and a rear substrate 12 each made of a rectangular glass plate, and these substrates are arranged to face each other at a predetermined interval. The back substrate 12 as the second substrate is formed with a size larger than that of the front substrate 11 as the first substrate. The front substrate 11 and the back substrate 12 constitute a flat envelope 10 whose peripheral portions are joined to each other through a rectangular frame-shaped side wall 13 and the inside is maintained in a vacuum state. The side wall 13 functioning as a bonding member is sealed to the peripheral edge of the front substrate 11 and the peripheral edge of the back substrate 12 by, for example, a sealing material 25 such as low melting glass or low melting metal, and bonds these substrates together. is doing.

  A plurality of plate-like support members 14 are provided inside the envelope 10 in order to support an atmospheric pressure load applied to the front substrate 11 and the rear substrate 12. These support members 14 extend in a direction parallel to one side of the envelope 10 and are arranged at a predetermined interval along a direction orthogonal to the one side. Both ends in the longitudinal direction of each support member 14 are opposed to the side wall 13 with a gap.

  As shown in FIGS. 2 to 4, a phosphor screen 16 that functions as an image display surface is formed on the inner surface of the front substrate 11. The phosphor screen 16 is configured by arranging red, green, and blue phosphor layers R, G, and B, and a black light-shielding layer 20 positioned between the phosphor layers. The phosphor layers R, G, and B of three colors of red, green, and blue are formed alternately with a gap in the first direction, and the phosphor layers of the same color are in the second direction orthogonal to the first direction. Are arranged with a gap in between. Each of the phosphor layers R, G, and B constitutes a subpixel with single colors of red, green, and blue, and constitutes one pixel by combining the subpixels of three colors.

  A matrix-shaped dividing layer 31 is formed so as to overlap the light shielding layer 20 of the phosphor screen 16. A metal back layer 17 made of an aluminum film or the like is formed on the phosphor screen 16. According to this embodiment, the metal back layer 17 is divided in the vertical direction and the horizontal direction by the dividing layer 31 and has a plurality of divided regions that are electrically separated from each other. The metal back layers 17 that are electrically separated from each other by the dividing layer 31 are positioned so as to overlap the phosphor layers R, G, and B, respectively.

  A non-evaporable getter film 23 is formed so as to overlap the light shielding layer 20 of the phosphor screen 16 and, here, to the dividing layer 31. The getter film 23 is disposed on the phosphor screen 16 with a predetermined area. That is, the getter film 23 is formed so as to overlap the dividing layer 31 so as to avoid the phosphor layers R, G, and B, and has a plurality of regions that are electrically separated from each other. Further, on the inner surface of the front substrate 11, a getter film 28 containing barium is formed as an evaporation type getter in a region outside the phosphor screen 16.

  First, the evaporation type getter film 28 will be described in detail. The getter film 28 is formed with a thickness of 30 nm between the peripheral portion of the envelope 10, for example, between the phosphor screen 16 and the side wall 13. The getter film 28 is formed on the inner surface of the front substrate 11 at both ends of the support member 14 and is provided continuously or intermittently along a direction orthogonal to the support member.

As a material for the evaporable getter containing barium, a reactive getter in which nickel is added to powder of an intermetallic compound BaAl ₄ of barium and aluminum can be used. This is a general evaporative getter used for CRT. When the sealing process of the envelope 10 is performed in the atmosphere, it is desirable to select a fritterable getter as the oxidation resistant getter. The getter film 28 is formed by heating and evaporating the getter material in a vacuum.

  Next, the non-evaporable getter film 23 will be described in detail. As shown in FIGS. 3 to 5, the getter film 23 includes non-evaporable getter powder 41, non-evaporable getter powders, and adhesive particles 43 for bonding the non-evaporable getter powder to the front substrate. have. As the non-evaporable getter, various types that are generally used can be selected. However, when used for an SED, a type having a relatively low activation temperature is desirable.

  The particle size of the powder 41 is determined by the vacuum characteristics of the device used, such as the ultimate vacuum and the amount of gas released. In this embodiment, the 50% diameter is 1 to 10 μm, preferably 1 to 5 μm. If the particle size is larger than this, the specific surface area of the non-evaporable getter powder becomes small. Therefore, the gas adsorption speed of the getter is reduced, and it becomes difficult to maintain the inside of the SED envelope 10 at a high degree of vacuum. If the particle diameter is smaller than this, the getter powder 41 becomes very active even at room temperature, and handling becomes difficult.

  Various kinds of adhesive particles 43 that are generally used can be selected, but adhesive particles having a particle diameter smaller than that of the non-evaporable getter powder 41 are used. When the particle size of the adhesive particles 43 is equal to or larger than the particle size of the non-evaporable getter powder 41, most of the powder surface of the non-evaporable getter is shaded by the adhesive particles 43, and the gas Molecules are less likely to be adsorbed on the getter powder. As a result, the adsorption speed of the getter decreases, and the inside of the SED envelope cannot be maintained at a high degree of vacuum.

  Desirable adhesive particles 43 include silver powder having a 50% diameter of 0.1 to 1 μm. The silver powder 41 adheres the non-evaporable getter powder 41 to each other, and simultaneously bonds the non-evaporable getter powder and the front substrate to each other, thereby forming the getter film 23 on the phosphor screen 16. The getter film 23 can be formed by, for example, a screen printing method, a dispensing method, a spray coating method, or the like.

  The non-evaporable getter film 23 is formed so that the region located in the central portion of the phosphor screen 16 is thicker and becomes thinner as the region is closer to the peripheral portion of the front substrate 11. That is, the film thickness of the getter film 23 located at the central portion of the phosphor screen 16 is thicker than the film thickness of the getter film 23 located at the peripheral portion of the phosphor screen.

  As described above, the envelope 10 of the SED is flat and has a small internal conductance. Therefore, in the envelope, gas molecules existing in the peripheral part are easily adsorbed by the evaporation type getter film 28 formed in the peripheral part, but gas molecules existing in the central part are difficult to be adsorbed by the getter film 28. . Therefore, the amount of gas molecules staying in the central part is larger than the amount of gas molecules staying in the peripheral part. Therefore, the non-evaporable getter film 23 is formed thick so that the adsorption ability of the getter film located at the center is not exhausted first.

  When the gas adsorption speed of the non-evaporable getter film 23 is high, gas molecules in the envelope 10 are adsorbed to the non-evaporable getter film 23 before the getter film 28. In a high vacuum region such as the inside of the SED, carbon monoxide and carbon dioxide are dominant gas molecules. However, the amount of adsorption of these gas molecules is smaller in the non-evaporable getter film 23 than in the evaporable getter film 28. For this reason, if gas molecules are first adsorbed on the non-evaporable getter film 23, the gas pressure at the center of the envelope increases and the life of the SED decreases.

  Therefore, according to the present embodiment, for carbon monoxide and carbon dioxide, the gas adsorption rate per unit area of the evaporable getter film 28 is higher than the gas adsorption rate per unit area of the non-evaporable getter film 23. It is set large. As a result, the gas adsorption amount is earned by the evaporative getter film 28, and the entire vacuum inside the envelope 10 is maintained by the non-evaporable getter film 23 formed in a planar shape.

  As shown in FIG. 2, on the inner surface of the back substrate 12, a number of surface conduction type electron emitters each emitting an electron beam as an electron source for exciting the phosphor layers R, G, B of the phosphor screen 16 are provided. An element 18 is provided. These electron-emitting devices 18 are arranged in a plurality of columns and a plurality of rows corresponding to each pixel. Each electron-emitting device 18 includes an electron emitting portion (not shown) and a pair of device electrodes for applying a voltage to the electron emitting portion. A large number of wirings 21 for supplying a potential to the electron-emitting devices 18 are provided in a matrix on the inner surface of the rear substrate 12, and end portions thereof are drawn out of the vacuum envelope 10.

  Exhaust holes 29 for exhausting the inside of the vacuum envelope 10 are formed through the peripheral edge of the back substrate 12, for example, the corner, in the exhaust process. The exhaust hole 29 is provided at a position away from the phosphor screen 16, that is, at a position away from the effective display area. The exhaust hole 29 is hermetically sealed by the lid member 30. The number of exhaust holes 29 is not limited to one, and can be increased as necessary.

  In such an SED, when displaying an image, an anode voltage is applied to the phosphor screen 16 and the metal back layer 17, and the electron beam emitted from the electron-emitting device 18 is accelerated by the anode voltage to the phosphor screen. Collide. Thereby, the phosphor layers R, G, and B of the phosphor screen 16 are excited to emit light, and a color image is displayed.

  According to the SED configured as described above, the getter film 23 formed of a non-evaporable getter is formed over the entire surface of the phosphor screen 16 and avoids over the phosphor layers R, G, and B. It is formed on the light shielding layer 20. For this reason, the entire interior of the envelope 10 can be maintained at a high degree of vacuum without lowering the luminance by the getter film 23. Further, a getter film 28 containing barium having a large adsorption amount of carbon monoxide and carbon dioxide is formed in the peripheral portion of the envelope, and the gas adsorption rate per unit area of the getter 28 is set to be low for carbon monoxide and carbon dioxide. The gas adsorption rate per unit area of the evaporation type getter film 23 is set larger. Therefore, the gas adsorption amount can be earned by the evaporation type getter film 28, and a long-life SED capable of adsorbing the generated gas over a long period of time can be obtained. Furthermore, it is not necessary to use an expensive vacuum chamber when forming the getter film, and an increase in manufacturing cost can be suppressed, and the reliability and maintainability of the apparatus are also improved. As described above, a display device with low image quality, long life, and low cost can be provided.

  Next explained is an SED according to the second embodiment of the invention.

  As shown in FIGS. 6 and 7, according to the second embodiment, the evaporative getter film 28 made of a thin film of barium on the peripheral edge of the envelope 10, for example, both side edges of the inner surface of the front substrate 11. Are formed respectively. The getter film 28 is formed so that a part thereof overlaps the phosphor screen 16. That is, the evaporation type getter film 28 is formed to have a larger area than in the first embodiment. In this case, the side edge portion of the getter film 28 on the phosphor screen 16 side is formed in an uneven shape, for example, is formed in a comb blade shape, and is formed so as to overlap the light shielding layer 20 in the phosphor screen 16.

When the area of the getter film 28 is increased, the amount of gas adsorption is improved. Therefore, it is effective for further extending the life of the SED. As a material for the evaporable getter containing barium, a reactive getter in which nickel is added to a powder of an intermetallic compound BaAl ₄ of barium and aluminum can be used.
Other configurations of the SED excluding the getter film 28 are the same as those in the first embodiment described above, and the same portions are denoted by the same reference numerals and detailed description thereof is omitted.

  As shown in FIG. 8, according to the SED according to the third embodiment of the present invention, an evaporation type consisting of a thin film of barium on the peripheral edge of the envelope 10, for example, both side edges of the inner surface of the front substrate 11. Each getter film 28 is formed. The getter film 28 is formed so that a part thereof overlaps the phosphor screen 16. That is, the evaporation type getter film 28 is formed to have a larger area than in the first embodiment.

  In this case, the side edge of the getter film 28 on the phosphor screen 16 side is patterned so as to avoid the phosphor layers R, G, and B of the phosphor screen 16 and is electrically separated on the light shielding layer 20. It is formed in a state.

  In order to improve the gas adsorption characteristics of the getter film 28, it is effective to increase the getter formation area and at the same time increase the film thickness. However, if the film thickness is too large, the luminance of the region where the getter film is formed increases. descend. As in this embodiment, such a problem can be avoided by forming the getter film 28 on the light shielding layer 20 so as to avoid the phosphor layers R, G, and B16.

When the patterned evaporation type getter film 28 is formed, the getter may be deposited through a mask corresponding to the divided structure. When vapor deposition is performed on the side edge portion of the phosphor screen 16 through a mask, the size of the mask can be reduced unlike the case of vapor deposition on the entire surface of the phosphor screen 16. Therefore, it is easy to align the phosphor screen 16 and the mask, and it is possible to easily pattern and deposit a getter film having a divided structure.
Other configurations of the SED excluding the getter film 28 are the same as those in the first embodiment described above, and the same portions are denoted by the same reference numerals and detailed description thereof is omitted.

  Next explained is an SED according to the fourth embodiment of the invention.

According to this embodiment, the SED includes a getter box 50 fixed to the outer surface side of the back substrate 12, and an evaporation type getter film 28 containing barium is formed in the getter box. The getter box 50 is formed of, for example, glass with a rectangular cross section, is fixed to the bottom surface of the back substrate 12, and extends along the side edge of the back substrate. The internal space of the getter box 50 communicates with the inside of the envelope 10 through the exhaust hole 29 formed in the back substrate 12. The getter film 28 is formed on the inner surface of the getter box and in the vicinity thereof by evacuating the inside of the envelope 10 and then heating and evaporating the evaporation getter disposed in the getter box 50.
The size of the getter box 50 and the number of installations can be variously selected as necessary.

  According to the fourth embodiment, the film thickness and area of the evaporation type getter film 28 can be set relatively freely. That is, when the getter box 50 is provided separately from the front substrate 11 and the back substrate 12 and the evaporation type getter film 28 is formed therein, the structural restrictions of the phosphor screen 16 and the electron-emitting device 18 are imposed. Disappears. Therefore, the getter film 28 can be formed in accordance with the gas release characteristics of the phosphor screen 16 and the performance of the image display device. Such a structure is particularly effective for a large image display apparatus having a large screen size.

  As shown in FIG. 10, according to the SED according to the fifth embodiment of the present invention, the getter film 28 from the evaporation type getter is added to the inside of the envelope 10, for example, the first in addition to the inside of the getter box 50. As in the first embodiment, the inner periphery of the front substrate 11 is provided. In this case, the formation area of the evaporation type getter film 23 can be further increased, which is effective for a large image display device.

  In the fourth and fifth embodiments, the other configurations of the SED excluding the getter box and the getter film 28 are the same as those in the first embodiment described above, and the same parts are denoted by the same reference numerals. The detailed explanation was omitted.

  The present invention is not limited to the above-described embodiment, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. Some constituent elements may be deleted from all the constituent elements shown in the embodiments, or constituent elements over different embodiments may be appropriately combined.

  In the above-described embodiment, the SED provided with the front substrate having the phosphor screen on the inner surface has been described as an example of the member to be the getter film. However, the present invention is not limited to this, and the FED and PDP are not limited thereto. The present invention can also be applied to other devices such as other vacuum apparatuses, fluorescent display tubes, and semiconductor sensors. The material of the non-evaporable getter powder, the adhesive particles, and the insulating adhesive layer is not limited to the above embodiment, and various materials can be used according to the vacuum characteristics, emission gas characteristics, heat resistance, etc. of the device to be used. it can.

  For example, phosphoric acid-based frit glass may be used as the material for the adhesive particles. Various organic materials can be used for pasting non-evaporable getter powders, such as ethyl acetate, butyl acetate, nitrocellulose, elbasite, and polyethylene carbonate, according to the characteristics of the device used and non-evaporable getter materials. Various types may be selected and used as appropriate. In addition, the mixing ratio of pasting, the forming method of the paste, the firing conditions for forming the getter film, and the like can be variously changed as long as the activated non-evaporable getter can exhibit sufficient gas adsorption performance.

  Needless to say, it is possible to select a suitable shape, size, arrangement, or material of the structure constituting the SED. Various formation dimensions, shapes, arrangements, and film thicknesses of the getter film can be used in accordance with the vacuum characteristics, emission gas characteristics, heat resistance, etc. of the device to be used. Regarding the sealing of the front substrate and the rear substrate, in addition to the in-line type continuous furnace, a batch-type atmospheric firing furnace may be used, or the sealing may be performed in a vacuum. As the electron-emitting device, a pn-type cold cathode device or a field-emission type electron-emitting device may be used.

FIG. 1 is a perspective view showing a partially broken SED according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the SED along line AA in FIG. FIG. 3 is an enlarged plan view showing a part of the front substrate and phosphor screen of the SED. 4 is a cross-sectional view of the front substrate along the line BB in FIG. 3. FIG. 5 is a sectional view showing a non-evaporable getter film of the SED. FIG. 6 is a sectional view showing an SED according to a second embodiment of the present invention. FIG. 7 is an enlarged plan view showing a part of a front substrate and a phosphor screen of the SED according to the second embodiment. FIG. 8 is an enlarged plan view showing a part of the front substrate and the phosphor screen of the SED according to the third embodiment. FIG. 9 is a cross-sectional view showing an SED according to a fourth embodiment of the present invention. FIG. 10 is a sectional view showing an SED according to a fifth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Envelope, 11 ... Front substrate, 12 ... Back substrate, 13 ... Side wall,
14 ... support member, 16 ... phosphor screen, 17 ... metal back layer,
18 ... electron-emitting device, R, G, B ... phosphor layer, 20 ... light shielding layer,
23 ... Non-evaporable getter film, 28 ... Evaporative getter film, 41 ... Getter powder,
43 ... Adhesive particles, 50 ... Getter box

Claims (8)

An envelope having a first substrate and a second substrate joined together at the periphery;
A phosphor screen disposed on the first substrate;
An electron source disposed on the second substrate;
A getter that adsorbs the gas in the envelope,
The getter is an image display device having a non-evaporable getter formed on the phosphor screen and an evaporating getter provided at a peripheral portion of the envelope and containing at least barium.   The image display device according to claim 1, wherein the evaporable getter is formed on the first substrate or the second substrate in the envelope.   The image display device according to claim 1, wherein the evaporable getter is formed on the first substrate and outside the phosphor screen. The phosphor screen has a light shielding layer formed between a plurality of phosphor layers and the phosphor layer,
The image display device according to claim 3, wherein a part of the evaporative getter is formed so as to overlap the light shielding layer at a peripheral portion of the phosphor screen.   4. The getter box that is joined to the periphery of the envelope and that communicates with the inside of the envelope, and the evaporative getter is provided in the getter box. 5. The image display device according to item 1.   The non-evaporable getter is formed so as to overlap the phosphor screen, and the film thickness of the non-evaporable getter located in the central part of the phosphor screen is the film of the non-evaporable getter located in the peripheral part of the phosphor screen. The image display device according to claim 1, wherein the image display device is formed thicker than the thickness.   The phosphor screen includes a plurality of phosphor layers and a light shielding layer formed between the phosphor layers, and the non-evaporable getter is formed to overlap the light shielding layer. Image display device.   4. The gas adsorption rate per unit area of the evaporable getter is higher than the gas adsorption rate per unit area of the non-evaporable getter for at least carbon monoxide and carbon dioxide. The image display device described.

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