Vacuum fluorescent display and manufacturing method therefor

Abstract: A vacuum fluroescent display and a manufacturing method therefor. The vacuum fluroescent display has a faceplate (10) and a substrate (20) defining a vacuum-space, segments (24), filaments (50), grids (60), pin leads (80), stands (40) for fixing filaments (50) and a pair of setters (91) for fixing the stands. In manufacture, the setters form opposite sides of a hollow rectangular base (90) and they are provided for welding the stands (40) on opposing sides of the substrate (20). The other two sides of the base form a pair of spacing strips (92) for maintaining the interval between the setters (91). The setters (91) are fixed to the substrate (20), and then are separated from each other by removing the spacing strips (92). The ends of the setters (91) extend outwardly from the vacuum-space to serve as conductors for the filament (50).

Description: The present invention relates to a vacuum fluorescent display and a manufacturing method thereof, and particularly to an improved vacuum fluorescent display and a manufacturing method thereof, which enables the pattern to be arranged as desired, the vacuum state within the tube to be stable, and automation to enhance productivity. US-A-4263700, US-A-4047073 and JP-A-60198043 (English language abstract in Patent Abstracts of Japan, Vol. 10, no. 42 (E-382) 19 February 1986) disclose prior art techniques and structures for a vacuum fluorescent display. On particular, US-A-4 047 073, discloses a display having connectors along one edge of the substrate (Figure 1) and a display having lead-in wires along one edge of the substrate (Figure 3). Vacuum fluorescent displays can be classified according to the form of the connecting lead. For example, in a frame-lead type, leads are integrally formed with the frame as a single body, and in a pin-lead type, the leads are composed of a plurality of separate pins. Figure 1 of the accompanying drawings illustrates a conventional vacuum fluorescent display of pin-lead type, partially exposed. In the display tube, a vacuum is formed between a faceplate 1 and a substrate 2 with an interposing spacer 3. All of the functional parts of the display are provided on the substrate 2. The following components can be given as examples of the functional parts: a segment (not shown) placed on the substrate below a grid (to be described later) providing an alphanumeric pattern; a filament 5 arranged over the segment; a grid 6 positioned between the segment and filament 5 for controlling a low-speed thermoelectron emission; a getter (now shown) for additional enhancement of the vacuum in the tube; and a contact spring for applying a negative potential to a transparent conductive layer 1' which is formed on the faceplate's inner surface to assist the effective concentration of electrons. In this vacuum fluorescent display structure, the functional parts are divided into two groups, some are formed directly on the substrate while others are spaced from the first group and formed over the substrate. The latter group includes the grid 6 and filament 5. The grid 6 is installed above the substrate 2 at a predetermined height by contacts 6' at both ends thereof which are used for fixing the grid to the substrate and for electrical conduction. The filament 5 is positioned at the utmost top portion of the functional layer by bridge-type supports 4 which are provided at both edges of the inner surface of substrate 2. In order to operate, the functional layer must be supplied with external control voltages and provided with internal electrical circuits formed on the functional layer. To accomplish this, a plurality of exposed contacts 2' along the edge of substrate 2 form signal paths. A pin-lead 8 with U-shaped clamps 8' is used for convenient connection with a driving circuit on a separate printed circuit board. Respective pin-leads 8 arranged in a row along one edge of substrate 2 are engaged with the exposed contacts 2', and are permanently fixed by a sealing material such as frit glass 7. In Figure 2, a conventional frame-lead type vacuum fluorescent display is illustrated, which has similar functional parts as the foregoing pin-lead type vacuum fluorescent display. In more detail, all of the functional parts are provided on a substrate 2 below a faceplate 1 which together with substrate 2, encases a vacuum space. The functional layer includes an alphanumeric segment, a filament 5 disposed above the segment, and a grid 6 positioned between the segment and filament 5 for controlling low-speed thermoelectron emission. Here, filament 5 and grid 6 are directly connected to the inner ends of selected leads 8b bent in crank-form and arranged parallel with one another along one edge of the substrate, different from the fixing construction of the pin-lead type. More specifically, grid 6 is fixed overlying the inner fixed end 8b' of lead 8b bent in crank-form, and the filament 5 is fixed by interposing a stand 4b with welding stop 4b' by the leads 8b placed at both ends. By contrast, the segment makes contact with the inner end 8b of other leads 8b of inverted "V" shape through the corresponding signal line connector 2'', thereby forming an electrical circuit. According to the above-described lead characteristics, the two aforementioned conventional vacuum fluorescent displays have merits and demerits as follows. Since the functional layer pattern is independent of the shape of the lead, the pin-lead type vacuum fluorescent display offers a wide choice in selecting patterns of the functional layer, and it's vacuum tube has low probability of leakage. However, while the assembling jigs are simple, the process for manufacturing and assembling the leads is exacting due to the use of a plurality of separate pin-type leads. Furthermore, the substrate may be damaged whilst fixing the leads, which makes automation in manufacturing the product difficult. As for the frame-lead type vacuum fluorescent display, the functional part placed over the substrate such as the metallic components including the grid and filament is first fixed to the frame lead, separately from the substrate, and then is fixed to the substrate. Therefore, this type of display takes very little time to manufacture, and is favorable for automation. Further, since the lead itself is used for direct electrical connection to the filament, grid, and segment, connections between circuits are very stable and accurate. However, the orientation of the grid is determined by the direction of the leads, which offers a narrower choice in selecting the desired pattern. Particularly, since a predetermined width of the lead must enter the vacuum space, the seal is apt to leak. This type is also disadvantageous in that the frame lead is integrally formed with the filament contacts, grid contacts, and segment contacts, thus, the material cost is expensive. Moreover, the manufacturing process of the frame lead itself is necessarily accompanied by punching and pressing while considering the position and/or height of each component. Once manufactured, the frame lead is restricted to a specific model, impeding common usage of components. During the assembling process, strict management of the size is required to secure a stable connection of each lead to the connectors as the functional part. Accordingly, it is an object of the present invention to provide an improved vacuum fluorescent display and a manufacturing method thereof, such that the merits of the two above-described types of vacuum fluorescent displays, are mutually complementary. It is another object of embodiments of the present invention to provide an improved vacuum fluorescent display which enables most of the components to be used commonly to reduce the material cost, the productivity to be improved by low manufacturing cost and easy automation, and the reliability of the product to be enhanced. According to the present invention as claimed, there is provided a vacuum fluorescent display comprising: a substrate provided with a plurality of signal lines of a predetermined pattern thereon; a faceplate opposite said substrate which together define a vacuum-space; an anode segment of a predetermined pattern formed on the substrate, and electrically connected to a corresponding signal line among said signal lines; a filament over said anode segment and serving as a thermoelectron emitting source; a grid interposed between said filament and said anode segment for controlling the thermoelectrons; a plurality of pin leads each for clamping onto one edge of said substrate on which a connector for each of said signal lines is formed, one to connect electrically with each of the signal lines respectively connected to said grid and said anode segment, and each having a pair of U-shaped grippers for clamping said substrate; a pair of stands one on each side of said substrate at a predetermined interval for supporting respective ends of said filament; and a pair of parallel setters to each of which a respective stand is fixed, which setters are located on opposing sides of said substrate, wherein at least one end of each setter extends outwards from said vacuum-space to function as a conductor for said filament. A method for manufacturing the vacuum fluorescent display according to the present invention as claimed having the above-described structure is performed by combining the methods for manufacturing the conventional pin-lead type and frame-lead type vacuum fluorescent displays, in which the stationary base for fixing the filament may correspond to the conventional frame lead. However, the stationary base is a substantially hollow rectangle and a separately formed grid, functioning as the lead by removing an unnecessary portion of the completed vacuum fluorescent display. Accordingly, the present invention as claimed further comprises a method of manufacturing a vacuum fluorescent display comprising the steps of: forming a first functional layer on a substrate by: forming a plurality of signal lines on said substrate, and a connector for each signal line along one edge of said substrate; forming internal functional parts including an anode segment of a predetermined pattern, electrically connected to a corresponding one of said signal lines; fixing a grid having fixing means at each end, over said substrate on which said anode segment is formed, so that said grid is spaced from said anode segment by a predetermined height while being electrically connected to a corresponding one of said signal lines, and coupling a plurality of pin leads to one edge of said substrate where each of said connectors of said signal lines are provided, one for electrical connection with each of said segment and grid; and forming a second functional layer by: fixing each of a pair of stands to a respective one of a pair of parallel setters, said stands being for supporting a filament which supplies thermoelectrons, wherein said setters are long enough to extend beyond opposite sides of said substrate, and have spacing strips shorter than the distance between the other opposite sides of said substrate, for maintaining the interval between said setters, said parallel setters and spacing strips forming a base; and welding said filament to said stands; securing said second functional layer to said first functional layer by securing said setters to said substrate, such that said filament extends crossing said signal lines, and said spacing strips are positioned beyond said substrate; and removing said spacing strips, such that said setters extend outwardly from said substrate to serve as leads for said filament. Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a partially-exposed perspective view of a conventional pin-lead type vacuum fluorescent display; Figure 2 is a partially-exposed perspective view of a conventional frame-lead type vacuum fluorescent display; Figure 3 is a partially-exposed perspective view of a vacuum fluorescent display according to an embodiment of the present invention; and Figure 4 is an exploded perspective view of parts of a vacuum fluorescent display for illustrating a method for manufacturing a vacuum fluroescent display according to an embodiment of the present invention. A vacuum fluorescent display according to an embodiment of the present invention is illustrated in Figures 3A and 3B. A vacuum space is formed between a faceplate 10 and a substrate 20 by interposing a spacer 30, and all functional parts are provided internally on substrate 20. Signal line connectors 23 which are electrically connected to the internal functional parts are provided along one exposed edge of the substrate, protruding from the vacuum-space. The functional parts include: an anode segment 24 capable of forming alphanumeric patterns coated with a low-speed electron activated fluorescent; a filament 50 positioned over the segment for supplying the thermoelectrons; and a grid 60 placed between the segment 24 and filament 50 for controlling the low-speed thermoelectrons from the filament 50. The grid 60 being of the same net-like shape as conventional ones, is installed over the substrate at a predetermined height using fixed ends 60a on both ends thereof, in which the fixed ends allow the grid to electrically connect with a corresponding signal line 23a formed on the substrate 20. An insulating layer 12 is formed on the surface of substrate 20 as a protection layer for preventing the electrical shorting of the signal lines running beneath the insulating layer. A connecting section 26 for electrical connection is partially exposed via a through-hole 25 formed in insulating layer 12. Here, fixed end 60a of grid 60 overlaps the connecting section, thereby fixing the grid to the connecting section 26 by a material such as, for example, conductive paste. Since filament 50 is positioned over grid 60, a support of a considerable height is required which includes an L-shaped stand 40 and a setter 91 which during construction forms part of a base 90 used for fixing the stand to substrate 20. (Here, the base is a principle feature of the present invention as claimed, which will be described later.) The stand 40 having welding stops 41 on its top to which filaments 50 can be welded at predetermined intervals, is indirectly fixed to substrate 20 via setter 91. Since the functional layer, i.e., the segment and grid 60 formed on substrate 20 must be supplied with corresponding external signals, they are electrically connected to the outside through corresponding signal lines 23. For this purpose, the signal lines 23 extend to connectors 23a tightly arranged in a row along one edge of substrate 20, and then connected to pin leads 80 with a pair of U-shaped grippers 80a for clamping the edge of substrate 20 where connectors 23a are formed. The pin leads 80 are regularly arranged along the edge of substrate 20 and permanently secured thereto by frit glass 70. Base 90 is used for supporting and fixing filament 50 during manufacture as mentioned above, and is secured by means of the frit glass 70a to the upper surface of the insulating layer 12 or to a portion of the substrate without a signal line. The base 90 is long enough to extend beyond the edge of substrate 20. A slot 93 is formed in the extending portion so that the protrusion of base 90 can be easily bent. As illustrated in Figure 4, the base 90 is a hollow rectangle before completion, and includes a pair of parallel setters 91 facing each other on which stands 40 and 40a are welded, and a pair of spacing strips 92 functioning as a spacer determining the relative position of both setters 91. In a base having the above-described structure, stands 40 and 40a are welded, and in turn filament 50 is welded to welding stop 41 and 41a of stands 40 and 40a before being fixed to the substrate, nearly completing the base as one display tube component. To fix the semi-processed base 90 to the substrate, the base 90 is seated in its predetermined position as shown in Figure 4 and fixed by the frit glass 70a. Then, the setters 91 is cut into a pair of separate pieces by removing the unnecessary sections of the base, i.e., the spacing strips 92. Both ends of the setters 91 are exposed from the vacuum-space, functioning as a conductor to the filament. The vacuum fluorescent display having the above-described structure can be called a hybrid type which partially unites the structures of the pin-lead type fluorescent display and the frame-lead type fluorescent display. Here, the setters 91 for fixing the filament corresponds to the frame lead. A method of manufacturing the vacuum fluorescent display having the aforesaid structure is performed such that the functional layer on the substrate 20 is separated into a first functional layer and a second functional layer to be manufactured by different processes. These separately processed layers are ultimately united. This method will be described in detail below with reference to Figure 4. In the present invention as claimed, the segment formed on the substrate 20 and the grid 60 directly over the segment are included in the first functional layer, and the filament 50 positioned over the grid 60 and the supporting elements 60a thereof are included in the second functional layer. (A) Each signal line 23 for the grid 60 and segment 24 is formed on the substrate 20. At this time, the connectors 23a of respective signal lines 23 are arranged along the edge of the substrate. The processing is performed by common metal sputtering and photolithography methods. (B) The insulating layer 12 is formed over the signal lines 23 at the desired position. Then, an exposed portion of the signal line 23 allows for connection to the segment 24 and the supporting element 60a of the grid via the through-hole 25. (C) The segment 24 of a predetermined pattern with a fluorescent layer 24a thereon is formed over the insulating layer 12 to electrically connect to a corresponding signal line 23 via the through hole 25. A silk screen printing method is used here. (D) Using a conductive material, the grid 60 provided with the supporting elements 60a at both ends thereof is fixed over the substrate 20 having the segment 24 formed thereon, which allow the grid 60 to stand off from the segment while being electrically connected to a corresponding signal line 23. The net-like structure of the grid is formed by a photolithography method, and the outer structure is completed by molding. (E) The pin lead 80 is coupled to the connector 23a of the signal line 23 provided along one edge of the substrate 20, so that the pin lead 80, the segment 24, and the grid 60 are electrically connected through corresponding signal lines 23, completing the formation of the first functional layer on the substrate. (F) A pair of stands 40 are manufactured by pressing, which support the filament 50 used for supplying thermoelectrons. The stands 40 are positioned over the grid 60 to be equally spaced apart from each other. (G) The stationary base 90 is manufactured by pressing, which is a substantially hollow rectangle and is medium to fix the stands 40 to the substrate 20. The base includes two parallel setters 91 for supporting the stands, and is long enough to extend beyond parallel sides of the substrate 20, and a pair of spacing strips 92 shorter than the width between the other parallel sides of the substrate to maintain the interval between the setters at both ends of the setters. (H) The stands 40 are welded to the setters 91 of the stationary base, so that the setters maintain a predetermined distance between the stands. (I) The filament 50 is welded to the setters 91 of the base 90, thereby completing the formation of the second functional layer. (J) The second functional layer is fixed over the substrate on which the first functional layer is provided, such that the filaments 50 extend crossing the signal lines 23, and the base 90 is fixed by way of frit glass 70 so that the spacing strips 92 are positioned beyond the edges of the substrate. (K) The spacing strips 92 which are beyond the edge of the substrate, are removed using a cutting apparatus, so that the setters 91 extending beyond the substrate serve as the filament leads. By the above-described steps, both functional layers for the substrate are completed, and if necessary, further components besides the aforesaid functional parts are additionally formed. Then, manufacture of the product is completed by fixing the spacer and faceplate. The embodiment of the method for manufacturing the vacuum fluorescent display according to the present invention as claimed is performed by combining methods for manufacturing conventional pin-lead type and frame-lead type vacuum fluorescent displays, in which the stationary base 90 for fixing the filament 50 corresponds to the conventional frame lead. However, the stationary base 90 is a substantially hollow rectangle and separately formed grid 60, functioning as a lead in the completed vacuum fluorescent display by removing an unnecessary extending portion. The method of manufacturing the vacuum fluorescent display according to the present invention as claimed has advantages as follows. First, as the conventional frame-lead type, the pattern's disposition or configuration of each functional layer of the present invention is not determined by the shape of the leads. Additionally, the number of leads entering the vacuum-space is few, lowering the possibility of leakage due to lead entry. Moreover, the filament is welded to the separate stationary base independent of the substrate, greatly reducing the welding time. The display is completed by forming the filament as a separate component, which makes manufacturing favorable for automation. Further, the structure of the base 90 for supporting the filament is simple, so that the cost for the component is lower than that of a frame-lead type display. Also, in this structure, whole parts are independently formed, enabling common usage of components.

Claims: A method of manufacturing a vacuum fluorescent display comprising the steps of: forming a first functional layer on a substrate (20) by: forming a plurality of signal lines (23) on said substrate (20), and a connector (23a) for each signal line along one edge of said substrate; forming internal functional parts including an anode segment (24) of a predetermined pattern, electrically connected to a corresponding one of said signal lines; fixing a grid (60) having fixing means (60a) at each end, over said substrate on which said anode segment is formed, so that said grid is spaced from said anode segment by a predetermined height while being electrically connected to a corresponding one of said signal lines (23), and coupling a plurality of pin leads (80) to one edge of said substrate where each of said connectors (23a) of said signal lines are provided, one for electrical connection with each of said segment (24) and grid (60); and forming a second functional layer by: fixing each of a pair of stands (40) to a respective one of a pair of parallel setters (91), said stands (40) being for supporting a filament (50) which supplies thermoelectrons, wherein said setters are long enough to extend beyond opposite sides of said substrate, and have spacing strips (92) shorter than the distance between the other opposite sides of said substrate, for maintaining the interval between said setters (91), said parallel setters (91) and spacing strips (92) forming a base (90); and welding said filament (50) to said stands (40); securing said second functional layer to said first functional layer by securing said setters (91) to said substrate (20), such that said filament (50) extends crossing said signal lines, and said spacing strips (92) are positioned beyond said substrate; and removing said spacing strips (92), such that said setters (91) extend outwardly from said substrate to serve as leads for said filament. A method of manufacturing a vacuum fluorescent display as claimed in claim 1, wherein a slot (93) is formed in a bending portion of said setter (91). A method of manufacturing a vacuum fluorescent display as claimed in claim 1 or 2, wherein said grid (60) is fixed using a conductive adhesive. A vacuum fluorescent display comprising: a substrate (20) provided with a plurality of signal lines (23) of a predetermined pattern thereon; a faceplate (10) opposite said substrate which together define a vacuum-space; an anode segment (24) of a predetermined pattern formed on the substrate, and electrically connected to a corresponding signal line among said signal lines; a filament (50) over said anode segment (24) and serving as a thermoelectron emitting source; a grid (60) interposed between said filament and said anode segment for controlling the thermoelectrons; a plurality of pin leads (80) each for clamping onto one edge of said substrate on which a connector (23a) for each of said signal lines (23) is formed, one to connect electrically with each of the signal lines respectively connected to said grid and said anode segment, and each having a pair of U-shaped grippers (80a) for clamping said substrate; a pair of stands (40) one on each side of said substrate at a predetermined interval for supporting respective ends of said filament; and a pair of parallel setters (91) to each of which a respective stand (40) is fixed, which setters are located on opposing sides of said substrate, wherein at least one end of each setter extends outwards from said vacuum-space to function as a conductor for said filament (50). A vacuum fluorescent display as claimed in claim 4, wherein a slot (93) is provided in a bending portion of each of said setters (91).

Inventors: JANG CHEOL-HYEON, JANG, CHEOL-HYEON
Applicants: SAMSUNG DISPLAY DEVICES CO LTD, SAMSUNG DISPLAY DEVICES CO., LTD.
Application year: 1992
Main classification: H01J31
IPC codes: H01J9, H01J31, H01J29