THIN-TYPE DISPLAY DEVICE

Abstract: The thin-type display device (1) has a transparent front wall (3), which is provided with a display screen, and a rear wall (24) which extends parallel to said front wall (3), and said display device comprises at least an electron source and a duct structure. The display device (1) is characterized in that the rear wall (24) and walls (22, 22', 22") of the ducts of the duct structure are manufactured in a single piece. Preferably, the walls (22, 22', 22") of the ducts widen in the direction of the rear wall (24), with the angle, which opposing faces of the walls (22, 22', 22") of the ducts make with each other, ranging from 1 DEG to 30 DEG . Preferably, the rear wall (24) further comprises at least an upright side wall (32), which is integral with the rear wall (24). Preferably, the walls (22, 22', 22") are made from a glass having a temperature interval between the operating temperature and the softening temperature of less than 420 DEG , preferably less than 360 DEG , and the duct structure and the side walls (32) can be pressed in one process step.

Description: Thin-type display device. The invenuon relates to a thin-type display device which comprises a transparent front wall which is provided with a display screen having a pattern of pixels, and a rear wall which extends parallel to said front wall, which display device includes at least an electron source and a duct structure, which cooperates with said electron source and extends substantially parallel to the front wall, and which comprises walls which are transverse to the rear wall, said rear wall and the walls forming the ducts of the duct structure. Thin-type display devices are used for displaying monochromatic or colour images in vacuum tubes, plasma displays and plasma-addressed liquid-crystal display devices (PALC display devices). A display device of the type mentioned in the opening paragraph is disclosed in United States Patent document US 5,347,199 (PHN 13.197), in which a description is given of a display device which employs (multiple or ribbon-shaped) electron currents which initially extend substantially parallel to the plane of the front wall and, finally, are constrained to move in a direction transverse to the display screen so as to address the desired (luminescent) pixels of the display screen, either directly or by means of, for example, an addressing system. In the known display device, the ducts of the duct structure comprise so-called electron-propagation means which cooperate with the electron source to transport emitted electrons through vacuum. The electron currents, which are to be guided by the electron-propagation means, can be generated by means of an electron source or by means of an arrangement of a number of electron sources which are parallel to (an edge of) the front wall. The electron currents generated by the electron source(s) are guided by means of die propagation means (beam-guiding means) over at least a part of the height (or width) of the display device in the direction of one of the edges of the display screen. To make it possible for the electron current to leave the electron-propagation means in desired (successive) places, a beam-guiding means can be provided with a row of apertures with electrodes which can be energized either to withdraw or not to withdraw electron currents from the propagation means at the location of an aperture. In plasma displays, electrons are generated in the ducts of the duct structure, which electrons address desired (luminescent) pixels of the display screen, either directly or by means of, for example, an addressing system. In plasma-addressed LCDs (PALC displays), a plasma having a relatively low energy level is generated in the ducts of the duct structure, which plasma converts the (plasma) duct of an (electrically neutral) insulator into a conductor. If a suitable voltage is applied to an electrode in a corresponding LCD element, the plasma provides for the conduction which is necessary to set the voltage across the LC element and hence control d e transparency of d e element. A disadvantage of the known display device is mat, during the manufacture of the duct structure, the interspace between me walls of the ducts, and hence the width of the ducts extending (transverse) to the rear wail is not constant. As a result, differences in (beam) intensity between adjacent ducts develop, which give rise to annoying streaks in the image displayed on the display screen by the pixels. It is an object of me invention to provide a display device in which intensity differences between adjacent ducts of the duct structure are minimized. To this end, me display device in accordance with the invention is characterized in that the rear wall and the walls of the ducts of the duct structure are constructed in one piece. The expression "in one piece" is to be understood to mean herein that the rear wall and the walls are manufactured from a single, solid piece of one material (for example glass, ceramics or synthetic resin) and that the assembly of rear wall and walls of the ducts of the duct structure is not obtained by means of a connection technique. The inventors have recognized that me walls of the ducts of the duct structure, which extend transverse to the rear wall, should not be individually manufactured, positioned on the rear wall and subsequendy connected to the rear wall by means of a connection technique (for example by means of an adhesive or by die so-called "fritting"), because this would be unfavorable. A further drawback of walls which are connected to the rear wall by means of a connection technique is that stresses can develop in these connections, while, in addition, undesirable properties of die material used to connect the walls of the ducts to me rear wall, may adversely affect the quality (for example the service life) of the display device. By manufacturing me rear wall and the walls of the ducts in a single piece, an accurate positioning of the walls relative to each other is obtained. By virtue thereof, a variation in the interspace between ie walls of the ducts is effectively precluded. If walls are accurately provided, the wid i of the individual ducts of the duct structure are substantially identical and, consequently, differences in (beam) intensity between two (adjacent) ducts are precluded, so that annoying streaks in the image displayed on the display screen by ie pixels are precluded or reduced. A further advantage obtained by manufacturing the rear wall and the walls of me ducts of me duct structure in a single piece is that the number of parts of the display device is reduced substantially. Instead of individually manufacturing many hundred to several thousand (thin) walls, the number depends on die dimensions of the display device, (for example by cutting the walls from a suitable plate material), the ducts can now be provided in a suitable substrate material, thereby forming the rear wall and the walls. The walls are provided in the substrate in one operation whenever possible. Suitable mediods of manufacturing the rear wall and the walls of the ducts of me duct structure in a single piece include (selective) etching or sand blasting of transport ducts in a substrate on which, during the manufacture, for example a mask (such as a photoresist or a suitable (ductile) layer) is provided. In an alternative method, the transport ducts can be ground into a substrate, ei ier by successively grinding adjacent ducts of d e desired depm into a substrate or by simultaneously providing a number of ducts in a substrate by means of, for example, a number of parallel, juxtaposed (rotating) saw blades. In a further method of manufacturing die rear wall and the walls of the electron-transport ducts in a single piece, the ducts are pressed into a suitable substrate material. On the one hand, "pressing" is to be understood to mean herein mat a profiled structure is formed in a quantity of glass, which may be unformed or preformed, by a movement of a mould. On the odier hand, "pressing" refers to the process in which a pre-formed (glass) plate is provided with a profiled structure by a (horizontal) movement of a mould (for example rolling). An embodiment of the display device in accordance with die invention is characterized in mat die walls of the ducts of the duct structure widen in me direction of the rear wall, the angle which opposing faces of the walls of the ducts make with a normal, which extends perpendicularly to die rear wall, ranging from 1 ° to 30°. A more robust construction of the duct structure and hence of the display device is obtained if the walls of the ducts of the duct structure widen in the direction of the rear wall. The angle, which opposing (side) faces of the walls of the ducts make with the rear wall, is measured at the location of the portion of the walls of the ducts of the duct structure which is (most) remote from the rear wall. An upper limit of 30° is maintained to preclude that d e ducts of die duct structure become too narrow in the vicinity of the rear wall. If the ducts of die duct structure are very shallow, for example wi a depd (measured relative to die rear wall) of less than 1 mm, the angle which the walls make with the rear wall can be chosen to be larger man 30° (for example 60°). The widening of ie walls of the ducts in the direction of me rear wall can take place in accordance wid a straight line or a curved line. In the first case, the walls of me ducts form rectangular faces which make the same angle everywhere with the rear wall. If the widening takes place in accordance with a curved line, the angle made by the walls relative to die rear wall increases gradually in die direction of die rear wall. In a particularly suitable method of manufacturing e rear wall and the walls of the ducts of the duct structure in a single piece, and in which the walls of the ducts of the duct structure widen in the direction of die rear wall, said ducts are pressed in a suitable substrate material. The desired angle, which opposing faces of die walls of the ducts make with the rear wall, can be formed in the substrate in a single pressing step by suitably choosing the shape of the pressing member. An embodiment of d e display device in accordance widi die invention is characterized in diat ie angle ranges from 3° to 10°. If the opposing faces of die walls make a relatively small angle ( ≤ 10°) with ie rear wall, the widdi of the ducts of the duct structure remains reasonably large in the vicinity of e rear wall. The lower limit of the angle (≥ 3°) leads to a substantial increase in strength of the construction. A preferred embodiment of the display device in accordance with the invention is characterized in diat the depth of d e ducts of the duct structure, measured in a direction peφendicular to the rear wall, ranges from 0.1 to 10 mm. Relatively shallow ducts in die duct structure (0.1 mm ≤ depth < 2 mm) are used, in particular, in plasma displays and plasma-addressed liquid-crystal display devices, while relatively deeper ducts in die duct structure (2 mm ≤ depth ≤ 10 mm) are used, in particular, in diin-type vacuum tubes. A further embodiment of the display device in accordance with the invention is characterized in that die rear wail further comprises at least an upright side wall to obtain a vacuum-tight connection between the front wall and die rear wall. The expression "upright side wall" can mean mat one (or more) of the (four) side walls of the display device is (or are) integral with d e rear wall or diat the rear wall is integral with one upright wall, which extends (all round) at the corners of the display device. In die manufacture r r the known display device, so-called spacer strips are arranged near the edge of die rear wall to connect said rear wall to the front wall, said front wall being positioned on die spacer strips, which are subsequently connected to the front wall, die rear wall and, near the corners of the display device, to each odier by means of a connection technique (for example by means of adhesives or by so-called "fritting"). By manufacturing die rear wall, die walls of me ducts of die duct structure and one or more upright side walls in a single piece, a further simplification of the manufacturing process of die display device is achieved. Preferably, the side wall is further provided widi an upright edge on the inside of which the front wall is positioned. By virtue diereof, the positioning of die front wall and its connection to die rear wall via the side walls in a vacuum-tight manner is simplified further. If necessary, die shape of die upright edge can be chosen to be such (for example by providing die upright edge widi a horizontal protuberance) that die front wall is (partly) enclosed by die upright edge. A further embodiment of the display device in accordance with the invention is characterized in that the walls of the ducts of the duct structure are made from a glass having a temperature interval between me operating temperature and the softening temperature of less than 420°, preferably less dian 360 °C. Preferably, the rear wall and the side walls of the display device are made of the same material as the walls of the ducts of the duct structure. In general, die viscosity TJ of a glass at die melting temperature η = IO 2 dPa.s (0.1 Pa.s = 1 dPa.s corresponds to 1 poise). At the so-called operating temperature of the glass, at which most shaping processes, such as bending, blowing, drawing, pressing and casting, take place, die viscosity of the glass 17 = 10* dPa.s. At d e so-called "American" softening temperature of die glass, at which d e glass products deform widiin a very short period of time (for example a few seconds) under die influence of dieir own weight, die viscosity of die glass TJ = IO 7,6 dPa.s. The so-called softening range of a glass or glass-processing range comprises a temperature range in which the viscosity of die glass changes from 77 = 10 3 dPa.s to TJ = 10 7 dPa.s and in which shaping of the glass takes place. If this range is relatively small (a temperature interval of approximately 150 to approximately 250 °C) the glass is referred to as short glass, if this range is large (larger than approximately 300 °C), the glass is referred to as long glass. If, in me manufacture of the display device, the rear wall and the walls of die ducts of die duct structure are manufactured in a single piece, and if use is made of a pressing process, it is desirable that die viscosity TJ of the glass used ranges between 10" dPa.s and IO 7 6 dPa.s. In this operating range between, respectively, the operating temperature and the softening temperature of die glass, also die side walls and the walls of the ducts of die duct su-ucture can be formed simultaneously (i.e. in a single pressing step). Preferably, an operating temperature of the glass is chosen which is above 1,050 °C. A further preferred operating temperature of the glass is chosen above 920 °C. These and other aspects of the invention will be apparent from and elucidated wiώ reference to die embodiments described hereinafter. In the drawings: Fig. IA is a schematic, perspective view, partly broken away, of a part of a construction of a thin-type display device; Fig. IB shows, in cross-section, a plan view of the construction of Fig. IA; Fig. 2A is a schematic block diagram of a conventional flat panel display system; Fig. 2B is a perspective view of a part of a conventional PALC display device; Figs. 3A, 3B and 3C are cross-sectional views of embodiments of the rear wall and die walls of die ducts of die duct structure in accordance with the invention, and Figs. 4A and 4B are cross-sectional views of embodiments of the thin-type display device in accordance widi die invention. The Figures are purely schematic and not drawn to scale. In particular for clarity, some dimensions are strongly exaggerated. In the Figures, like reference numerals refer to like parts whenever possible. Fig. IA is a schematic, perspective view, partly broken away, of a part of a construction of a min-type display device 1. The invention is important, in particular, for is kind of diin-type display devices. The display device comprises a front wall (window) 3 and an oppositely located rear wall 4, which is parallel to said front wall. A display screen which includes a (regular) pattern of pixels luminescing, respectively, in red, green and blue is provided on the inner surface of die front wall 3. Near an upright side wall 2, which interconnects die front wall 3 and the rear wall 4, at least an electron source 5 is arranged. This electron source 5 comprises, for example, a cadiode arrangement which includes one or more line caώodes or a large number of separate electrodes. In this example, above the electron source 5, diere is arranged a number of electron-propagation means, which cooperate with the electron source and which are formed by ducts 6, 6', 6" etc., which are separated from the electron-propagation means by walls 11, 11', 11 " etc., which extend at right angles to the rear wall 4 so as to form the ducts of a so-called duct structure. The electron-propagation means extend substantially parallel to die front wall and serve to transport die electrons emitted by the electron source d rough vacuum. In a plate 10, which closes the ducts 6, 6', 6" etc., apertures 7, T , 7" etc. are provided for guiding electrons to die display screen. Said plate 10 may also comprise an assembly of various plates. In general, an addressing system for addressing desired pixels is provided between the duct structure and die front wall 3. Fig. IB schematically shows, in cross-section, a plan view of die construction of ie thin-type display device 1 in accordance with the state of die art. The front wall (window) 3 and die rear wall 4 are spaced apart by the upright side walls 2 (the so-called spacer strips). The electron-propagation means cooperating with die electron source (not shown) are formed by die ducts 6, 6', 6" etc., which are separated from each other by walls 11, I T, 11 " etc., which extend at right angles to the rear wall 4 so as to form the ducts of a so-called duct structure. Electrons are guided to die display screen via apertures (not shown) in plate 10. Plate 10 generally comprises an addressing system to address desired (luminescent) pixels and may also comprise, if desired, an assembly of various plates. The side walls 2 are connected to the front wall 4 and the rear wall 3 by means of vacuum-tight connections 15 (using, for example, a suitable adhesive or a so-called (glass) frit). A disadvantage of the use of said connections 15 is diat the walls may be inaccurately positioned relative to each odier during the connecting process, which is undesirable. A further disadvantage of walls which are connected to the rear wall by means of a connection technique is mat stresses may develop in diese connections, while, in addition, undesirable properties of the material with which die walls of die ducts are connected to e rear wall, may adversely affect die quality (for example die service life) of the display device. A further disadvantage resides in that the connections 15 must seal the display device 1 in a vacuum-tight manner. The risk of undesirable leakage increases wid die number of necessary connections 15. The walls 11 , 11', 11 " etc. of die ducts of the duct structure are connected to the rear wall by means of connections 16. Alternatively, the walls 11 , 11', 11 " 8 etc. may be mounted first on (and connected to) an auxiliary plate, whereafter said auxiliary plate, which is provided with die walls 11, 11', 11 ", etc. is positioned on die rear wall 3 and, if necessary, connected thereto. The use of an auxiliary plate on which the walls 11 , 11 ', 11" etc. are provided has advantages if die material used for the walls 11, 11', 11 " etc. differs from that used for the rear wall 4. A disadvantage of the use of the connections 16 is diat inaccuracies in the positioning of die walls 11, 11', 11 " etc. relative to each odier may occur during die connecting operation, which is undesirable. This inaccuracy in die positioning of die walls 11, 11', 11" etc. causes die interspace between the walls 11 , 11', 11 " etc. and hence the widdi of die ducts of the duct structure extending (at right angles) to die rear wall 4 to be inconstant, which brings about differences in (beam) intensity between (in particular) adjacent propagation means, which differences in intensity give rise to annoying streaks in the image displayed on die display screen by the luminescent pixels. Figure 2A shows a flat panel display system 10, which represents a typical PALC display device and die operating electronic circuitry, widi reference to Figure 2A, die flat panel display system comprises a display panel 62 having a display surface 64 diat contains a pattern formed by a rectangular planar array of nominally identical data storage of display elements 66 mutually spaced apart at predetermined distances in the vertical and horizontal directions. Each display element 66 in the array represents the overlapping portions of thin, narrow electrodes 68 arranged in vertical columns and elongate narrow channels 70 arranged in horizontal rows. (The electrodes 68 are hereinafter referred to from time to time as "column electrodes"). The display elements 66 in each of the row of channels represent one line of data. The widdis of column electrodes 68 and channels 70 determine e dimensions of display elements 66, which are typically rectangular shape. Column electrodes 68 are deposited on a major surface of a first electrically nonconductive, optically transparent substrate 84 (Fig. 2), and the channel rows are usually built into a second transparent substrate 86. Skilled persons will appreciate diat certain systems, such as a reflective display of eidier the direct view or projection type, would require diat only one substrate be optically transparent. Column electrodes 68 receive data drive signals developed on output conductors 72' by different ones of output amplifiers 73 (Fig. 2B) of a data driver or drive circuit 74, and channels 70 receive data strobe signals developed on output conductors 76' by different ones of output amplifiers 71 (Fig. 2B) of a data strobe circuit 78. Between die channels walls 81 are present and at each side of a wall electrodes are present. Electrodes at opposite sides of a wall (and dius in adjacent channels) are electrically interconnected. To syndiesize an image on the entire area of the display surface 64, display systems 60 employs a scan control circuit 82 that coordinates the function of data drive 74 and data strobe 78 so diat all columns of display elements 66 of display panel 62 are addressed row by row in, for instance, row scanning fashion. Display panel 62 may employ electro-optical materials of different types. For example, if it uses such material that changes the polarization state of incident light rays, display panel 62 is positioned between a pair of light polarizing filters, which cooperate with display panel 62 to change die luminance of light propagating through them. The use of a scattering liquid crystal cell as the electro-optical material would not require the use of polarizing filters, however. All such materials or layers of materials which attenuate transmitted or reflected light in response to the voltage across it are referred to herein as electro-optic materials. As LC materials are presendy the most common example, the detailed description will refer to LC materials but it will be understood diat the invention is not limited thereto. A colour filter (not shown) may be positioned widiin display panel 62 to develop multi-coloured images of controllable colour intensity. For a projection display, colour can also be achieved by using diree separate monochrome panels 62, each of which conttOls one primary colour. Fig. 2B illustrates the PALC version of such a flat display panel using LC material. Only 3 of the column electrodes 68 are shown. The row electrodes are constituted by a plurality of parallel elongated sealed channels 70 underlying a layer 92 of LC material. Each of the channels 70 is filled widi an ionizable gas 94, closed off with a diin dielectric sheet 95 typically of glass, and contains on an interior channel surface first and second elongated electrodes 82 and 83. Electrodes at opposites sides of die wall 81 between channels are electrically interconnected. The interconnected electrodes have leads 91 through which pulses are supplied to die electrodes 82, 83. Supplying pulses as shown in Figure 2 to die interconnected electrode will ignite channel 94 since the voltage difference between die electrodes in channel 94 is +V-(-V) where V is for instance 150 Volt = 150-(-150)= 300 Volt which is enough to form a plasma discharge. In neighbouring channels die voltage difference is 150 Volt which is not enough to form a plasma discharge. By choosing die proper pulses to be fed to the electrodes it is possible to form a plasma discharge in one and only one of the channels. The channels are filled with ionizable gas and dius form a gas-tight enclosure. (If this would not be the case, the channels would be contaminated wid odier gases or gas would leak out of die channels). The leads 91 are brought out from the gas-tight enclosure. As can be seen in Figure 2A conventionally the leads are all parallel to each odier and to the channels. In such an arrangement the pitch p2 of the leads equals die pitch pl of die channels. At or near positions 98 where the leads 91 exit die gas-tight enclosure, diere usually are made connectors to connect leads 71 to output conductors (which serve as supply lines) 76'. Fig. 3 A is a schematic, cross-sectional view of an embodiment of the rear wall 24 and die walls 21, 21', 21" etc. of the ducts of the duct structure in accordance with die invention. The depdi of die ducts and die widdi of die walls 21, 21', 21" etc. of d e ducts of the duct structure (die ducts) are labeled Sj and Wj, respectively, in Fig. 3A. In this example, die oppositely located faces of the walls 21, 21', 21 " etc. extend parallel to each otiier. The rear wall 24 and die walls 21, 21', 21" etc. are in a single piece, diat is the rear wall 24 and die walls 21, 21, 21" etc. are manufactured from a single, solid piece of one material, without die use of a connection technique. The advantages of such a construction are diat connection techniques are superfluous, an accurate positioning of die walls 21, 21', 21 " etc. on die rear wall is achieved, and diat me number of parts of which me display device is built up is considerably reduced. In suitable methods of manufacturing the rear wall 24 and the walls 21, 21', 21" etc. of die electron-transport ducts in a single piece, transport ducts are formed in a substrate material by means of (selective) etching, sand blasting, grinding or pressing. Fig. 3B is a schematic, sectional view of a preferred embodiment of the rear wall 24 and die walls 22, 22', 22" etc. of die ducts of die duct structure, said walls 22, 22', 22" etc. widening gradually in die direction of die rear wall 24. The depth of the ducts of die duct structure (the ducts) is labeled s 2 in Fig. 3B, said deptii s 2 ranging preferably from 0.1 to 10 mm. In Fig. 3B, the width of and distance between the walls 22, 22', 22" etc. of the ducts, measured at the location of die portion of die walls 22, 22', 22" etc., which is (most) remote from me rear wall 24, are labeled w, and p,, respectively, and die widdi of the walls 22, 22', 22" etc., measured at the location of die rear wall 24, is labeled w 2 . Particularly if the ratio between s 2 and die widdi w, of the walls 22, 22', 22" etc. is greater than 2, in odier words, if _i ≥ 2 w ι it is very important to strengdien the walls 22, 22', 22" etc. (at die base), i.e. widening of the walls 22, 22', 22" etc. in the direction of the rear wall 24 to preclude that the construction becomes too fragile. The angle a, which opposing (side) faces of the walls 22, 22', 22" etc. make witii the rear wall 24 is measured, as shown in Fig. 3B, at the location of the portion of the walls 22, 22', 22" etc. which is (most) remote from the rear wall 24. In the embodiment shown in Fig. 3B, the walls 22, 22', 22" etc. of the ducts widen in accordance witii a straight line in the direction of die rear wall 24. The angle α suitably ranges between 1° and 30°, preferably between 3° and 10°. A simple, geometric relation between the angle α, the deptii s 2 of the walls 22, 22', 22" etc., the width Wi of the walls 22, 22', 22" etc., measured at the location of die portion of die walls 22, 22', 22" etc., which is (most) remote from the rear wall 24, and die widdi w 2 of the walls 22, 22', 22" etc., measured at die location of the rear wall 24, can be derived, which relation can be expressed as follows: tanα = - — - 2 s. If, for example, the angle a = 3°, the depth s 2 = 5.0 mm and the widdi w, = 0.5 mm, then me widdi w 2 = 1.0 mm, that is the walls 22, 22', 22" etc. widen in the direction of the rear wall 24 by 0.5 mm. If the distance between the walls 22, 22', 22" etc., p, = 2.5 mm, the distance can be expressed, in this example, as p 2 = p l + w ϊ - w 1 = 2 , 0 mm Fig. 3C is a schematic, sectional view of a preferred embodiment of the rear wall 24 and walls 23, 23', 23" etc. of die ducts of the duct structure, said walls 23, 23", 23" etc. widening gradually in the direction of die rear wall 24. The angle a, which opposing (side) faces of die walls 23, 23', 23" etc. make with the rear wall 24, is measured, as shown in Fig. 3C, at the location of the portion of the walls 23, 23', 23" etc., which is (most) remote from the rear wall 24. In the embodiment shown in Fig. 3C, the walls 23, 23', 23" etc. widen in accordance with a curved line in die direction of the rear wall 24. If the ducts of the duct structure become very shallow (see, for example, Fig. 3C), i.e. the deptii is less than 1 mm measured relative to the rear wall 24, the angle a, which the walls 23, 23', 23" etc. make with the rear wall 24 can be greater than 30° (for example 60°). A very suitable method of manufacturing the exemplary embodiments shown in Figs. 3B and 3C, in which the rear wall 24 and the walls 22, 22', 22" etc. and 23, 23', 23" etc. of the ducts of die duct structure are manufactured in a single piece, and in which die walls 22, 22', 22" etc. and 23, 23', 23" etc. widen in the direction of die rear wall 24, consists in pressing ducts in a suitable substrate material (for example glass). The term "pressing" is to be understood to mean, on the one hand, the provision of a profiled sdructure (for example walls) in a quantity of glass, which may be unformed or pre-formed (for example a (flat) glass plate of die desired thickness) by a movement of a mould, and on die odier hand, the provision of a profiled structure (for example walls) in a pre-formed (flat) glass plate by a (horizontal) movement of a mould (for example by means of rolling). The desired angle, which opposing faces of d e walls make with the rear wall, is obtained by using a suitably chosen shape of the pressing member. In this manner, the desired structure is pressed in die substrate in a single process step. Other methods, such as (selective) etching, sand blasting and grinding are not always suitable for forming such well-defined profiles in d e substrate. Fig. 4A is a schematic, cross-sectional view of an embodiment of die thin-type display device 1 in accordance with the invention. Apart from the rear wall 24 and the walls 22, 22', 22" etc. of the ducts of the duct structure, in this embodiment, also the upright side walls 32 are manufactured in a single piece. This results in a further simplification of the manufacturing process of the display device 1. The upright side walls 32 may have side faces which extend perpendicularly to the rear wall, but they may alternatively (as shown in Fig. 4A) widen in die direction of die rear wall, i.e. they have bevelled side faces. A vacuum-tight connection 15 is provided only between the upright side walls 32 and die front wall 3, so tiiat the risk of undesirable leakage is reduced considerably. As a result of die absence of a (vacuum-tight) connection between die side walls 32 and the rear wall 24, the positional accuracy of the display device is improved considerably. In accordance widi Fig. 3B, ώe walls 22, 22', 22" etc. of the ducts of the duct structure widen in the direction of die rear wall 24. Fig. 4B is a schematic, cross-sectional view of an embodiment of the thin- type display device 1 in accordance witii the invention. Apart from the rear wall 24 and die walls 23, 23', 23" etc. of die ducts of die duct structure, in this embodiment, also the upright side walls 42 having upright edges 43 are manufactured in a single piece. This results in a further simplification of the manufacturing process of the display device 1. In the embodiment of Fig. 4B, the upright side wall 42 is bevelled and provided with a (bevelled) upright edge 43 on die inside of which the front wall 3 is positioned. If desired, the edge 43 may extend beyond die front wall 3. If d e edge 43 is provided widi a further, projecting edge which extends parallel to the rear wall 24 (not shown in Fig. 4B), the projecting edge of the edge 43 can enclose the front wall 3 partly. If necessary, this can further increase die strength of die display device. A vacuum-tight connection 15 is provided only between the upright side walls 42 and die front wall 3, so that the risk of undesirable leakage is reduced considerably. The positional accuracy of the display device is improved considerably by die absence of a vacuum-tight connection between the side walls 32 and the rear wall 24. In accordance widi Fig. 3B, the walls 22, 22', 22" etc. of the ducts of the duct structure widen in die direction of the rear wall 24. A very suitable method of manufacturing the preferred embodiments shown in Figs. 4A and 4B, in which d e rear wall 24 and the walls 22, 22', 22" etc. and 23, 23', 23" etc. of the ducts of die duct structure and ώe upright side walls 32, and 42 and 43 are made in a single piece, and in which die walls 22, 22', 22" etc. and 23, 23', 23" etc. and the upright side walls 32, and 42 and 43 widen in die direction of the rear wall 24, consists in pressing the desired shapes (ducts) in a suitable substrate material (for example glass). If a pressing process is used for said construction, preferably, a glass is utilized whose temperature interval between die operating temperature, at which TJ = 10 4 dPa.s, and d e softening temperature, at which TJ = 10 76 dPa.s, is less than 420°, preferably less than 360 °C. Satisfactory results are obtained at an operating temperature of die glass above 1 ,050 °C, preferably above 920 °C. The coefficient of expansion of the material of the walls 22, 22', 22" preferably ranges from 35. IO "7 to 50.10- /°C, preferably from 40. IO "7 to 45.10 "7 /°C. The rear wall and die side walls of the display device 1 are preferably made from the same material as the walls 22, 22', 22" of the ducts of die duct structure. Materials which can suitably be pressed into die desired shapes include borosilicate glass, borofloate glass and soda-lime glass. In the case of plasma displays and plasma-addressed LCDs, a further preferred material for pressing into die desired shapes is lead glass. Lead glass yields good results at an operating temperature of the glass of 1,000 °C and higher. Preferably, a space 26, 27 for holding further elements of the display device is present in said display device 1 between die side wall 32, 42 and the walls 22, 22', 22" etc. and 23, 23', 23" etc. of the ducts of the duct structure. Elements which can be accommodated in said space 26, 27 are, for example, the electron source, a getter, wiring for driving (the ducts of) the duct structure and for the addressing system for addressing desired pixels, as well as an exhaust tube. In a particularly preferred embodiment of the display device in accordance with the invention, the rear wall, the duct structure and, if necessary, the upright side walls are manufactured in a single piece, preferably of glass, which is shaped by means of a pressing process. In die case of thin-type display devices having standard picture dimensions (for example a lengtii-width ratio of 3:4, 9: 16, 10:16 or 9:21) and comprising a (vertically) arranged duct structure, die lengtii of the ducts of die duct structure ranges from 50 to 750 mm, and die depth of die ducts of die duct structure ranges between 2 and 10 mm, the (average) ώickness of the walls of the ducts of die duct structure ranges between 0.1 and 5 mm, and die distance between the ducts of the duct structure (die so-called "pitch") preferably ranges between 1 and 10 mm. In plasma displays and plasma-addressed LCDs, die depth of the duct structure ranges between 0.1 and 0.5 mm. It will be obvious tiiat within the scope of the invention many variations are possible to those skilled in die art. In general, the invention relates to a diin-type display device comprising a transparent front wall, which is provided witii a display screen, and a rear wall which extends parallel to said front wall, and comprising at least an electron source and a duct structure. The display device is characterized in tiiat the rear wall and walls of the ducts of the duct structure are manufactured in a single piece. Preferably, die walls of the ducts widen in the direction of die rear wall, witii the angle, which opposing faces of the walls make with each other, ranging from 1 ° to 30°. Preferably, the rear wall further comprises at least an upright side wall which is integral witii the rear wall. Preferably, the walls are manufacmred from a glass having a temperature interval between the operating temperature and die softening temperature of less than 420°, preferably less than 360°; and the rear wall with the duct structure and the side walls can be pressed in one process step.

Claims: Claims: 1. A thin-type display device (1) which comprises a ti-ansparent front wall (3) which is provided witii a display screen having a pattern of pixels, and a rear wall (24) which extends parallel to said front wall (3), which display device (1) includes at least an electron source (5) and a duct structure, which cooperates with said electron source (5) and extends substantially parallel to the front wall (3), and which comprises walls (22, 22', 22") which are transverse to the rear wall (24), said rear wall (24) and the walls (22, 22' 22") forming the ducts of die duct structure, characterized in that the rear wall (24) and the walls (22, 22', 22") of the ducts of die duct structure are constructed in one piece. 2. A display device (1) as claimed in Claim 1, characterized in that die walls of the ducts of the duct structure widen in the direction of the rear wall (24), the angle made by opposing faces of d e walls (22, 22', 22") of the ducts widi a normal, which extends perpendicularly to the rear wall (24), ranging from 1 ° to 30°. 3. A display device (1) as claimed in Claim 2, characterized in that the angle ranges from 3° to 10°. 4. A display device (1) as claimed in Claim 1, 2 or 3, characterized in that the deptii of the ducts of the duct structure, measured in a direction peφendicular to the rear wall (24), ranges from 0.1 to 10 mm. 5. A display device (1) as claimed in any one of d e preceding Claims, characterized in tiiat the rear wall (24) further comprises at least an upright side wall (32; 42) to obtain a vacuum-tight connection between the front wall (3) and die rear wall (24). 6. A display device (1) as claimed in Claim 5, characterized in that the side wall (32; 42), viewed from the rear wall (24), extends beyond the walls (22, 22', 22"; 23, 23', 23") of the ducts of the duct structure. 7. A display device (1) as claimed in Claim 5 or 6, characterized in diat the side wall (42) further comprises an upright edge (43) on d e inside of which the front wall (3) is positioned. 8. A display device (1) as claimed in Claim 5, 6 or 7, characterized in that a space (26; 27) for holding further elements of the display device (1) is present between die side wall (32; 42) and the walls (22, 22', 22"; 23, 23', 23") of the ducts of the duct structure. 9. A display device (1) as claimed in any one of die preceding Claims, characterized in that the walls (22, 22', 22"; 23, 23', 23") are made from a glass having a temperature interval between the operating temperature and die softening temperature of less than 420°, preferably less than 360 °C. 10. A display device (1) as claimed in Claim 9, characterized in that the operating temperature of the glass is higher than 1,050 °C, preferably higher than 920 °C. 11. A display device as claimed in any one of the preceding Claims, characterized in that the coefficient of expansion of the material of the walls (22, 22', 22"; 23, 23', 23") ranges from 35. IO" 7 to 50. i /°C, preferably from 40. IO" 7 to 45.10" 7 /°C. 12. A display device as claimed in any one of die preceding Claims, characterized in that the material of the walls (22, 22', 22"; 23, 23', 23") comprises a borosilicate glass or a soda-lime glass.

Inventors: DAMEN JOHANNES HERMANUS MARIA, LEIJTEN JOHANNES THEODORUS HEN, NIESTADT MARCEL, SANDERS MARTINUS GERARDUS FRAN, SELTEN WILHELMUS NICOLAAS MARI, TUIN HERMANUS NICOLAAS, VAN BOMMEL CERNELUS HUBERTUS M, VAN LAARHOVEN FRANCISCUS MARTI, DAMEN, JOHANNES, HERMANUS, MARIA, LEIJTEN, JOHANNES, THEODORUS, HENRICUS, NIESTADT, MARCEL, SANDERS, MARTINUS, GERARDUS, FRANCISCUS, CHRISTIAA, SELTEN, WILHELMUS, NICOLAAS, MARIA, TUIN, HERMANUS, NICOLAAS, VAN BOMMEL, CERNELUS, HUBERTUS, MARIA, VAN LAARHOVEN, FRANCISCUS, MARTINUS, HENRICUS
Applicants: PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, PHILIPS ELECTRONICS N.V.
Application year: 1997
Main classification: H01J31
IPC codes: G02F1, H01J1, H01J5, H01J9, H01J11, H01J17, H01J29, H01J31