Thermal printer

Abstract: Miniaturisation of a thermal head incorporated in a printer is attained without risking damage to electrical components by contact with paper being fed through the printer. A platen 2 is rotatably axially supported between left and right faces L and R of a frame 1. A thermal head 3 is also swingably supported between the left and right faces of the frame 1, and opens and closes with respect to the platen 2. The thermal head 3 comprises a ceramic substrate 11 and a support body 12 for fixing the ceramic substrate 11. A heater, a semiconductor device 13 for driving the heater, and sealing resin 14 for protecting the semiconductor device 13 are formed on the ceramic substrate 11 on the side facing the platen 2. In case a straight path is adopted, recording paper is fed between the platen 2 and the thermal head 3 from a bottom face D of the frame, and a sheet 16 for preventing recording paper from contacting with the exposed sealing resin 14 is attached along the straight path. When a curled path is adopted, recording paper is fed between the platen 2 and the thermal head 3 from a rear face B of the frame, and another sheet 15 for preventing recording paper from contacting with the exposed sealing resin 14 is attached at a different place along the curled path.

Description: The present invention relates to a printer for printing on recording paper, which comprises a platen and a thermal head. A known printer is shown in Fig. 2A, as including a platen 101 and a thermal head 102. The platen 101 is rotatably supported about an axis 101a along the width direction of recording paper. More specifically, a stepping motor 104 is connected with the axis 101a via a train of gears 103. The rotational motion of the stepping motor 104 is decelerated by the train of gears 103, and is transmitted to a rear axis 101a, and the platen 101 is appropriately intermittently rotated for feeding paper in the direction shown by an arrow in the figure. The thermal head 102 is disposed so as to face the platen 101 via recording paper The thermal head 102 is swingably supported about an axis 105. In printing operation, a heater of the thermal head 102 is pressed against the recording paper. With this state maintained, the heater is electrically energised to print a line of letters on the recording paper. After the printing of the line, the platen 101 is rotated in the direction shown by the arrow to feed the recording paper. Fig. 2B shows a schematic cross-sectional structure of the printer shown in Fig. 2A. The thermal head 102 is disposed so as to face the platen 101 via a recording paper 106 as shown in the figure. It should be noted that the direction of appearance of a printed face of the recording paper 106 is considered to be the front. When the thermal head 102 is swung counterclockwise about the axis 105 that is in parallel with but different from the axis 101a of the platen 101, the heater above the axis 105 is pressed against the platen 101. In order to provide the pressing force, a spring member 107 intervenes between the thermal head 102 and a frame 108 of the printer. On the contrary, when the thermal head 102 is swung clockwise against the urging force by the spring member 107, the heater of the thermal head 102 is retracted from the platen 101. This operation is carried out when, for example, the recording paper 106 is fed between the platen 101 and the thermal head 102. Fig. 3 is a sectional view of a specific structure of the conventional printer shown in Fig. 2, wherein like reference characters designate corresponding parts shown in Fig. 2 to promote understanding. A frame 108 is in the shape of a box having six faces, i.e., front, rear, left, right, top, and bottom faces. In the present specification, the front face, the rear face, the left face, the right face, the top face, and the bottom face are represented as F, B, L, R, U, and D, respectively. As mentioned in the above, the front face F is on the side of the printed face of recording paper. The platen 101 is rotatably, axially supported between the left and right faces of the frame 108. Similarly, the thermal head 102 is swingably supported between the left and right faces of the frame 108 about an axis different from that of the platen, and opens and closes with respect to the platen 101. With such a structure, printing is carried out on recording paper (not shown) fed between the platen 101 and the thermal head 102 from the bottom face D or the rear face B of the frame 108 and then the recording paper is discharged to the top face U of the frame 108. In the figure, a first supply path from an arrow SIN to an arrow OUT is referred to as a straight path, while a second supply path from an arrow CIN to the arrow OUT is referred to as a curled path. A sheet 110 intervenes between the straight path and the curled path so as to separate them. The thermal head 102 comprises a ceramic substrate 111 and a support body 112 for fixing the ceramic substrate 111. A heater 113 contacting with the platen 101, a semiconductor device 114 for driving the heater 113, and sealing resin 115 for protecting the semiconductor device 114 are formed on the ceramic substrate 111 on the side facing the platen 101. The sealing resin 115 is a relatively soft resin and is provided for the purpose of protecting against breakage extra fine gold wire or the like connected with the semiconductor device 114 such as an IC chip. Further, a cover 116 for mechanically protecting the semiconductor device 114 and the sealing resin 115 are attached to the support body 112 of the thermal head 102. The cover 116 is made of metal or resin and is provided for the purpose of mechanical protection of the semiconductor device 114 and preventing the sealing resin 115 from wearing out. If it were not for the cover 116, the sealing resin 115 would wear out due to repeated contact with recording paper. In addition, the cover 116 prevents recording paper from catching on the sealing resin 115. In this way, in a conventional printer, the cover 116 is an essential composing element. However, provision of the cover 116 inevitably narrows the paper feed path. Therefore, the heater 113 and the semiconductor device 114 can not be disposed so as to be adjacent to each other on the ceramic substrate 111, and thus, it is difficult to miniaturise the ceramic substrate 111. Since the number of ceramic substrates gotten from a wafer can not be large without miniaturisation of the ceramic substrate, the cost can not be lowered. Even if the ceramic substrate 111 is miniaturised to dispose the semiconductor device 114 closer to the heater 113, the cover 116 comes closer to the side of the heater 113 accordingly. Since the cover 116 oppresses the paper feed path, recording paper can not be fed smoothly. SUMMARY OF INVENTION Accordingly, in order to solve the above-mentioned problems of a conventional printer, an object of the present invention is to miniaturise a ceramic substrate in printer. In a first aspect, the present invention provides a printer comprising a frame having a platen rotatably axially supported between opposed left and right faces of the frame; a thermal head pivotally supported between the left and right frame faces for movement between engaging and non-engaging positions with the platen, for printing on recording paper fed between the platen and the thermal head, wherein the thermal head comprises a support body mounting a ceramic substrate, the ceramic substrate carrying a heater for contacting the platen, a semiconductor device for driving the heater, and sealing resin for protecting the semiconductor device, wherein the printer is configured to have a first paper feed path, whereby recording paper is adapted to be fed from a back face of the frame, and a second paper feed path whereby recording paper is adapted to be fed from a bottom face of the frame, said printer further comprising a sheet member and first and second portions for alternatively attaching the sheet member, wherein when the sheet member is attached using the first portion, the sheet member is adapted to prevent paper fed along the first paper feed path from contacting with the exposed sealing resin and when the sheet member is attached using the second portion, the sheet member is adapted to prevent paper fed along the second paper feed path from contacting with the exposed sealing resin. In a second aspect, the present invention provides a method of manufacturing a printer comprising a frame having a platen rotatably axially supported between opposed left and right faces of the frame; a thermal head pivotally supported between the left and right frame faces for movement between engaging and non-engaging positions with the platen, for printing on recording paper fed between the platen and the thermal head, wherein the thermal head comprises a support body mounting a ceramic substrate, the ceramic substrate carrying a heater for contacting the platen, a semiconductor device for driving the heater, and sealing resin for protecting the semiconductor device, wherein the printer is configured to have a first paper feed path, whereby recording paper is adapted to be fed from a back face of the frame, and a second paper feed path whereby recording paper is adapted to be fed from a bottom face of the frame, said method comprising attaching a sheet member and to either a first or a second portion of the printer, wherein when the sheet member is attached using the first portion, the sheet member is adapted to prevent paper fed along the first paper feed path from contacting with the exposed sealing resin and when the sheet member is attached using the second portion, the sheet member is adapted to prevent paper fed along the second paper feed path from contacting with the exposed sealing resin. A printer according to the present invention comprises a frame, a platen, and a thermal head as a basic structure. The frame is in the shape of a box having six faces, i.e., front, rear, left, right, top and bottom faces. The platen is rotatably axially supported between the left and right faces of the frame. Similarly, the thermal head is swingably supported between the left and right faces of the frame, and opens and closes with respect to the platen. With such a structure, printing is carried out on recording paper fed between the platen and the thermal head from the bottom face or the rear face of the frame and then the recording paper is discharged to the top face of the frame. The thermal head comprises a ceramic substrate and a support body for fixing the ceramic substrate. A heater contacting with the platen, a semiconductor device for driving the heater, and sealing resin for protecting the semiconductor device are formed on the ceramic substrate on the side facing the platen. First and second paper feed paths to be alternatively adopted are made inside the frame. In case that the first paper feed path is adopted, recording paper is fed between the platen and the thermal head from the bottom face of the frame, and a sheet member for preventing recording paper from contacting with the exposed sealing resin is attached along the first paper feed path. Adversely, in case that the second paper feed path is adopted, recording paper is fed between the platen and the thermal head from the rear face of the frame, and another sheet member for preventing recording paper from contacting with the exposed sealing resin is attached at another place along the second paper feed path. According to the present invention, a printer with a small line thermal head mounted thereon comprises a thermal head incorporating a ceramic substrate provided with a heater and a semiconductor device for driving the heater (driver IC). Further, relatively hard sealing resin is used for protecting the semiconductor device. By making the sealing resin hard different from the conventional soft sealing resin, the cover is eliminated. The printer according to the present invention has two paper feed paths. Sheet members (polyimide films, for example) for guiding recording paper are stuck at appropriate places for the respective paper feed paths to prevent the sealing resin from wearing out due to friction with recording paper. With this structure, the semiconductor device is protected sufficiently even if the cover is eliminated, and further, recording paper is inserted and fed in an improved manner. BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Fig. 1A is a sectional view of a printer according to an embodiment of the present invention illustrating a curled paper feed path; Fig. 1B is a sectional view of the printer of figure 1A illustrating a straight paper feed path; Fig. 2A is a schematic view illustrating a prior art printer; Fig. 2B is a schematic sectional view illustrating the prior art printer; and Fig. 3 is a sectional view illustrating a specific structure of the prior art printer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, which is a sectional view of a printer according to the present invention, Fig. 1A illustrates a structure of the printer in case one paper feed path (curled path) is adopted, while Fig. 1B illustrates a structure of the printer in case the other paper feed path (straight path) is adopted. As shown in the figures, the printer comprises a frame 1, a platen 2, and a thermal head 3. The frame 1 is moulded out of resin, and is in the shape of a box having six faces, i.e., front, rear, left, right, top, and bottom faces F, B, L, R, U, and D. The platen 2 is rotatably, axially supported between the left and right faces L and R of the frame 1. Similarly, the thermal head 3 is swingably supported between the left and right faces L and R of the frame 1, and opens and closes with respect to the platen 2. It is to be noted that a pressure spring 4 and a pressure cam 5 are used to press the thermal head 3 against the platen 2. Further, the thermal head 3 is swingably supported by bearings 6 integrally formed with the left and right faces L and R of the frame 1. More specifically, rotation shafts 7 protruding at both ends of the lower end portion of the thermal head 3 are fit in the bearings 6. With such a structure, the printer carries out printing on recording paper (not shown) fed between the platen 2 and the thermal head 3 from the rear face B of the frame 1 and then the recording paper is discharged to the top face U of the frame 1. This paper feed path is referred to as a curled path and is shown as from an arrow CIN to an arrow OUT. It is to be noted that, in order to carry out paper feed in this way, a paper feed motor 8 for driving the platen 2 to rotate via a decelerating train of gears (not shown) is housed in the frame 1. The thermal head 3 comprises a ceramic substrate 11 and a support body 12 for fixing the ceramic substrate 11. A heater H contacting with the platen 2, a semiconductor device 13 for driving the heater, and sealing resin 14 for protecting the semiconductor device 13 are formed on the ceramic substrate 11 on the side facing the platen 2. The sealing resin 14 is hard, thereby eliminating a conventionally essential cover. Two paper feed paths (a curled path and a straight path) to be alternatively adopted are made in advance inside the frame 1. In Fig. 1A, the curled path as one of the paper feed paths is adopted. In this case, recording paper (not shown) is fed between the platen 2 and the thermal head 3 from the rear face B of the frame 1 as shown by an arrow CIN, and a sheet 15 for preventing recording paper from contacting with the exposed sealing resin 14 is attached with adhesive or the like along this paper feed path. Sheet 15 also functions to lead the paper in path CIN to the thermal head. On the other hand, as shown in Fig. 1B, in case the other paper feed path (straight path) is adopted, recording paper is fed between the platen 2 and the thermal head 3 from the bottom face D of the frame 1 as shown by an arrow SIN, and the recording paper is discharged from the top face U of the frame 1 as shown by an arrow OUT. In this case, another sheet 16 for preventing recording paper from contacting with the exposed sealing resin 14 is attached along the straight path. Sheet 16 also functions to lead the paper in path SIN to the thermal head. As is clear from comparison between Fig. 1A and Fig. 1B, the sheet 15 used in the curled path and the sheet 16 used in the straight path are different in shape and are attached with adhesive or the like at different places. It is to be noted that the frame 1 has a built-in paper sensor 20 for detecting recording paper fed through the curled path or the straight path. As shown in Fig. 1A, in case the curled path is adopted, the paper sensor 20 is attached upward, while, as shown in Fig. 1B, in case the straight path is adopted, the paper sensor 20 is attached toward the front. As is clear from the above, according to the present invention, a printer can have a very small line thermal head. The heater and the semiconductor device 13 for driving the heater are formed on the ceramic substrate 11 incorporated in the thermal head 3. The hard sealing resin 14 is provided so as to cover the semiconductor device 13. By providing the hard sealing resin 14, a cover is eliminated. The printer has two paper feed paths for recording paper, i.e., a curled path and a straight path. Two kinds of sheets 15 and 16 for guiding recording paper are provided accordingly. It is to be noted that both of the sheets 15 and 16 are made of a polyimide film or the like. The sheets 15 and 16 are stuck at appropriate places for the respective paper feed paths to prevent the sealing resin 14 from wearing out due to friction with recording paper. Further, by attaching the sheets 15 and 16 at appropriate places, recording paper is inserted and fed in an improved manner. By making the sealing resin hard, the semiconductor device (driver IC) is directly protected from external shocks. Further, since the sheets stuck to the side of the frame intervenes between the recording paper and the sealing resin, the sealing resin is prevented from wearing out. By this, a cover conventionally attached can be eliminated. Elimination of the cover makes it possible to secure the paper feed path even the sealing resin and the heater are disposed close to each other. This makes it possible to miniaturise the ceramic substrate attached to the thermal head. Since the number of ceramic substrates gotten from a large wafer is increased, the cost can be lowered. As described in the above, according to the present invention, by making the sealing resin hard, the semiconductor device is protected against shocks. The sheets are stuck at different places according to the two paper feed paths such that one of the sheets always intervenes between recording paper and the sealing resin. By this, the sealing resin can be prevented from wearing out, and thus, a cover conventionally attached can be eliminated from the thermal head. Elimination of the cover makes it possible to dispose the sealing resin and the heater close to each other. As a result, miniaturisation of the ceramic substrate can be attained, and the cost can be lowered. The aforegoing description has been given by way of example only and it will be appreciated by a person skilled in the art that modifications can be made without departing from the scope of the present invention.

Claims: A printer comprising a frame having a platen (2) rotatably axially supported between opposed left and right faces (L, R) of the frame; a thermal head pivotally supported (7) between the left and right frame faces for movement between engaging and non-engaging positions with the platen, for printing on recording paper fed between the platen and the thermal head, wherein the thermal head comprises a support body (12) mounting a ceramic substrate (11), the ceramic substrate carrying a heater (H) for contacting the platen, a semiconductor device (13) for driving the heater, and sealing resin (14) for protecting the semiconductor device, wherein the printer is configured to have a first paper feed path (CIN), whereby recording paper is adapted to be fed from a back face (B) of the frame, and a second paper feed path (SIN) whereby recording paper is adapted to be fed from a bottom face (D) of the frame, said printer further comprising a sheet member (15, 16) and first and second portions for alternatively attaching the sheet member, wherein when the sheet member is attached using the first portion, the sheet member is adapted to prevent paper fed along the first paper feed path from contacting with the exposed sealing resin and when the sheet member is attached using the second portion, the sheet member is adapted to prevent paper fed along the second paper feed path from contacting with the exposed sealing resin. A printer according to claim 1, wherein said frame has front (F), rear (B), left (L), right (R), top (U), and bottom (D) faces, and said first and second paper feed paths partly extend respectively from the rear face (B) and the bottom face (D) of the frame and discharge the recording paper to the top face (U) of the frame. A printer according to any preceding claim, wherein the sheet member is fixed in position to the frame by adhesive. A printer according to any preceding claim, wherein the sheet member comprises a polyimide film. A printer according to any preceding claim, wherein the sheet member extends to contact the platen at a position adjacent the thermal head. A method of manufacturing a printer comprising a frame having a platen (2) rotatably axially supported between opposed left and right faces (L, R) of the frame; a thermal head pivotally supported (7) between the left and right frame faces for movement between engaging and non-engaging positions with the platen, for printing on recording paper fed between the platen and the thermal head, wherein the thermal head comprises a support body (12) mounting a ceramic substrate (11), the ceramic substrate carrying a heater (H) for contacting the platen, a semiconductor device (13) for driving the heater, and sealing resin (14) for protecting the semiconductor device, wherein the printer is configured to have a first paper feed path (CIN), whereby recording paper is adapted to be fed from a back face (B) of the frame, and a second paper feed path (SIN) whereby recording paper is adapted to be fed from a bottom face (D) of the frame, said method comprising attaching a sheet member (15, 16) to either a first or a second portion of the printer, wherein when the sheet member is attached using the first portion, the sheet member is adapted to prevent paper fed along the first paper feed path from contacting with the exposed sealing resin and when the sheet member is attached using the second portion, the sheet member is adapted to prevent paper fed along the second paper feed path from contacting with the exposed sealing resin.

Inventors: IMAI SABURO, NAITO AKIO, SEKIYA HIROAKI, IMAI, SABURO, NAITO, AKIO, SEKIYA, HIROAKI
Applicants: SEIKO INSTR INC, SEIKO INSTRUMENTS INC.
Application year: 1997
Main classification: B41J2
IPC codes: B41J13, B41J2