JP7031815B2 - Thermal printheads and thermal printers - Google Patents

Description

Embodiments of the present invention relate to thermal printheads and thermal printers.

The thermal print head (TPH) is an output device that heats a plurality of resistors arranged in a heat generating region and forms an image such as characters or figures on a heat-sensitive recording medium by the heat. This thermal printhead is widely used in recording equipment such as bar code printers, digital plate making machines, video printers, imagers, and seal printers.

The thermal print head includes a heat sink and a head board and a circuit board provided on the heat sink. A glaze layer is provided on the head substrate, and a plurality of heat generating elements are provided on the glaze layer. A drive IC for controlling the heat generation of a plurality of heat generating elements is mounted on the circuit board. The plurality of heat generating elements and the driving IC are electrically connected by a bonding wire.

A protective film is provided on the surface of the heat generating element to protect the heat generating element and the like. The drive IC and the bonding wire are covered with a sealant for protection.

A thermal printer using such a thermal print head is provided with a platen roller, and while pressing the image receiving paper and the ink ribbon inserted between the platen roller and the heat generating area against the heat generating area, the image receiving paper and the ink ribbon are mainly scanned in the main scanning direction. Move in the sub-scanning direction perpendicular to.

At this time, when the back surface of the ink ribbon comes into contact with the sealing body, there is a problem that the ink ribbon is rubbed and dust is generated. When this residue adheres to the heat generating element, uniform contact between the heat generating element and the ink ribbon is hindered, and the image quality of the image deteriorates.

Japanese Unexamined Patent Publication No. 2009-6638

Provided are a thermal print head capable of suppressing the generation of ink ribbon residue even when the ink ribbon comes into contact with a sealing body, and a thermal printer using the thermal print head.

According to one embodiment, the thermal print head is provided on the heat dissipation plate, the support substrate mounted on the heat dissipation plate, the glaze layer laminated on the support substrate, and the main scanning direction. A head substrate having a plurality of heat generating elements arranged in the above, a circuit board mounted on the heat radiating plate so as to be adjacent to the head substrate in the sub-scanning direction and provided with a connection circuit, and the head substrate of the head substrate. A control element placed on the upper surface near the circuit board or the upper surface near the head board of the circuit board and electrically connected to the heat generating element and the connection circuit, and the upper surface of the head board near the circuit board and An encapsulating body provided so as to cover the control element is provided on the upper surface of the circuit board near the head substrate. The encapsulant contains a filler, and the filler is distributed in a particle size range of 1 to 30 μm, and the occupancy rate of the filler having a particle size of 2 to 10 μm is 67% by weight. The surface roughness of the sealed body is 0.3 μm or less .

According to the present embodiment, even if the ink ribbon comes into contact with the sealing body, a thermal print head capable of suppressing the generation of ink ribbon residue and a thermal printer using the thermal print head can be obtained.

The figure which shows the thermal print head which concerns on Embodiment 1. The figure which shows the surface state of the sealed body which concerns on Embodiment 1 in comparison with the comparative example. The figure which shows the surface roughness of the sealed body which concerns on Embodiment 1 in comparison with the comparative example. The figure which shows the particle size distribution of the filler which concerns on Embodiment 1. FIG. The schematic diagram for demonstrating the relationship between the content rate of the filler which concerns on Embodiment 1 and the characteristic of a sealed body. The cross-sectional view which shows the thermal printer which concerns on Embodiment 2. FIG. 3 is a mock diagram for explaining the frequency of ink ribbon residue generation according to the second embodiment in comparison with a comparative example. FIG. 5 is a cross-sectional view showing another thermal printer according to the second embodiment. FIG. 3 is a cross-sectional view showing a main part of another thermal print head according to the second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The thermal print head according to this embodiment will be described with reference to FIGS. 1 to 4. 1 is a view showing a thermal print head, FIG. 1A is a plan view thereof, FIG. 1B is a sectional view taken along the line V1-V1 of FIG. 1A, and FIG. 2 is a surface state of a sealed body. 3 shows the surface roughness of the sealed body in comparison with the comparative example, FIG. 4 shows the abrasive grain distribution of the filler, and FIG. 5 shows the filler content. It is a schematic diagram for demonstrating the relationship with the characteristic of a sealed body. It should be noted that the present embodiment is merely an example, and the present invention is not limited thereto. The drawings are schematic, and the ratio of each dimension is different from the actual one.

First, the thermal print head will be described.
As shown in FIG. 1, the thermal print head 10 has a heat sink 12, a head substrate 13, a circuit board 14, a driving IC 15, and bonding wires 24, 25 as its main parts. Here, the head substrate 13 and the circuit board 14 adjacent to each other are adhered and placed on the main surface of the heat radiating plate 12 via the adhesive 23.

A drive IC 15 which is a control element is mounted on the circuit board 14, and is airtightly sealed by a sealing body 26 made of, for example, an epoxy resin which is a rigid sealing material. The sealing body 26 is provided so as to straddle the circuit board 14 and the head board 13.

The heat radiating plate 12 is made of a metal such as aluminum or stainless steel, and has a strip shape extending in the main scanning direction S1. The adhesive 23 is made of a double-sided adhesive tape or a thermosetting resin adhesive having a soft property such as a silicon resin.

The head substrate 13 extends in the main scanning direction S1 and is mounted on the heat sink 12. The head substrate 13 has a support substrate 16 and a glaze layer 17. The support substrate 16 is made of a heat-resistant insulator material, and is made of ceramics such as alumina. In addition, fine ceramics containing SiN, SiC, quartz, AlN, Si, Al, O, N and the like may be used. The glaze layer 17 is made of, for example, a glass film or a resin film made of SiO ₂ , and is laminated on the support substrate 16.

On the upper surface of the glaze layer 17, a plurality of heat generating resistors 18 extending in the sub-scanning direction S2 in which the print medium runs perpendicular to the main scanning direction S1 and arranged at intervals in the main scanning direction S1 are formed. ing. Then, the individual electrodes 20 and the common electrodes 19 are arranged on the heat generation resistor 18 so as to face each other with the gap G interposed therebetween. Here, the pair of electrodes composed of the individual electrodes 20 and the common electrodes 19 are layered on the heat generation resistor 18 and electrically connected. Then, the heat generation resistor 18 exposed in these gaps G becomes the heat generation resistance portion. The heat generation resistance portion constitutes one heat generation element together with a pair of electrodes serving as the energizing electrodes, and is arranged in a band shape at a required pitch (dpi: dots / inch) in the main scanning direction S1 to form a heat generation region 21. The individual electrode 20 is electrically connected to the driving IC 15 via the bonding wire 24 as described later.

Here, the head substrate 13 is formed, for example, as follows. For example, an elongated support substrate 16 having a plate thickness of about 0.5 mm to 1.0 mm made of alumina ceramics is prepared, and a glaze layer 17 made of glass is fused and fired on the upper surface thereof. Next, the resistor layer and the conductor layer are sequentially laminated on the entire upper surface of the glaze layer 17 by a thin film forming device such as a sputtering device. Then, the conductor layer and the resistor layer are processed into a shape pattern of the heat-generating resistor portion by a photo-engraving process. Subsequently, the conductor layer in the gap G is removed by etching to obtain a predetermined individual electrode 20 and a common electrode 19. Further, a protective film 22 that covers the individual electrode 20, the common electrode 19, and the heat generation resistance portion is formed, and an opening is formed in the protective film 22 above the connection point of the individual electrode 20 with the bonding wire 24.

Here, the resistor layer is made of, for example, a TaSiO, NbSiO, TaSiNO, or TiSiCO-based electric resistor material. The conductor layer is mainly made of a metal such as Al, Cu or an AlCu alloy. The protective film 22 is made of a hard, dense, thermally conductive insulator material such as a SiO ₂ film, a SiN film, a SiON film, or a SiC film. Here, it is preferable that the outermost surface of the protective film 22 contains at least Si and carbon because the thermal conductivity becomes high. The protective film 22 has a function of at least covering the pair of electrodes of the heat generating element array and the heat generating region 21 to protect the recording medium from wear due to pressure contact or sliding contact, and corrosion due to contact with moisture contained in the atmosphere. Has.

The circuit board 14 is arranged on the main surface of the heat radiating plate 12 so as to be adjacent to the head board 13 and the sub-scanning direction S2, and is arranged in the main scanning direction S1 in parallel with the head board 13.

A required number of drive ICs 15 are mounted on the upper surface of the circuit board 14 near the head substrate 13 along the main scanning direction S1. The drive IC 15 is a control element having a switching function capable of controlling the heat generating element. It is electrically connected to the individual electrode 20 via the bonding wire 24.

The driving IC 15 and the bonding wires 24 and 25 are sealed by a sealing body 26 made of an epoxy resin. The sealing body 26 seals the driving IC 15 and the bonding wires 24 and 25 on the upper surface of the head substrate 13 near the circuit board 14. The sealing body 26 is formed at a predetermined position through application of an epoxy resin coating liquid which is a thermosetting resin and heat curing by heat treatment at about 100 ° C. for several hours.

The sealing body 26 mainly uses an epoxy resin coating liquid which is a thermosetting resin, and the driving IC 15 and the bonding wires 24 and 25 are held and formed on the head substrate 13 and the circuit board 14 by the thermosetting by heat treatment. The purpose is to (protect). The sealing body 26 may use a silicone-based resin or the like having a certain softness after heat curing.

Since the purpose of the sealing body 26 is to hold and protect the driving IC 15 and the bonding wires 24 and 25, the sealing body 26 has characteristics such as insulation, heat resistance, aspect ratio, wettability, surface tension, and solvent resistance. It is needed and various fillers are mixed to meet the properties.

Most resins often have some kind of filler added to them, and even if the same resin has different fillers, the properties will change. Therefore, when considering resin-based materials, it is important to consider what kind of filler is added and how. Many types include ceramics, fibers, and oxides, but basically the properties of this filler are reflected as they are. However, even with the same filler, the properties exhibited differ depending on the size, shape, and method of addition.

In practice, resins play such an important role that it is difficult to use industrially without the presence of fillers.

By putting the above-mentioned filler in the resin, it is possible to impart functions, properties, and physical properties that were not found in the original material. The filler specifically used is mainly determined by the type, size, and shape of the filler, but some fillers can obtain multiple properties even with one type of filler.

For example, calcium carbonate, talc, silica, clay, etc. for increasing the amount, wollastonite, potassium titanate, zonotrite, gypsum fiber, aluminum borate, MOS, aramid fiber, various fiber type, carbon fiber (carbon) for reinforcement. Fiber), glass fiber (glass fiber), talc, mica, glass flakes, polyoxybenzoyl whiskers, etc., in order to impart conductivity, carbon black, graphite, carbon fiber, metal powder, metal fiber, metal foil, etc. Examples of the flame-retardant imparting include antimony oxide, aluminum hydroxide, magnesium hydroxide, zinc borate, red phosphorus, zinc carbonate, hydrotalcite, dosonite and the like.

Fillers are materials that usually have a considerable range in size from 100 μm to about 10 nm, and are classified into macrofillers (100 μm to 10 μm), microfillers (10 μm to 100 nm), and nanofillers (100 nm to 10 nm). Will be done. Since the size of the particles directly affects the performance, it is necessary to use them properly according to the desired characteristics.

In general, the smaller the particles, the higher the expression of the performance of the filler, for example, the improvement of mechanical strength, but the handling becomes difficult. Fillers are basically used in the form of particles and powders, so like other powders, when they reach a certain size, they behave differently from solids and liquids, and powders. Body control and powder processing technologies are involved.

The particle size of the filler used in the resin of the encapsulant used in the conventional thermal print head is 20 μm (1 μm to 100 μm) on average. At this time, the average surface roughness of the sealed body is Ra 0.45 μm and Rmax 0.55 μm.

In the present embodiment, the size of the filler (filler) is mainly 2 to 7 μm in particle size (1 μm to 30 μm), and the filler (filler) separated into the resin is mixed with about 60% of the filler after curing. The surface property of the encapsulant is Ra 0.3 μm or less, and the surface property is improved. Therefore, even when the ink ribbon or the like comes into contact with the sealed body, the generated debris is not generated, and the generated debris moves to the heat generation resistor and prints. Good printing can be obtained without causing any troubles.

Next, the sealing body 26 will be described.
The sealed body of the thermal print head is required to have characteristics such as insulation, heat resistance, aspect ratio, wettability, surface tension, and solvent resistance in order to hold and protect the driving IC and the bonding wire. In order to meet these requirements, various fillers are mixed in the resin as a sealant.

As will be described later, in the encapsulant, a resin mixed with a filler is placed near the boundary between one surface of the head substrate 13 and one surface of the circuit board 14 together with a plurality of driving ICs 15 and a plurality of bonding wires 24 and 25, for example, by potting. It is formed by applying and thermosetting. Therefore, the shape of the sealed body, particularly the height, varies depending on the amount of the resin applied, the viscosity of the resin, and the like.

As will be described later, a thermal printer using a thermal print head is provided with a platen roller. The thermal printer moves the image receiving paper and the ink ribbon inserted between the platen roller and the heat generating region 21 in the sub-scanning direction S2 by the rotation of the platen roller.

Generally, ink ribbons are composed of a resin base film (thickness of about 2.5 to 12 μm) coated with a heat-resistant and slippery layer (thickness of about 0.1 to 2 μm) and an ink layer (thickness of about 1 to 10 μm). It is composed of.

The base film of the ink ribbon is softer than the epoxy resin of the encapsulant. When the back surface of the ink ribbon is rubbed against the sealing body, the ink ribbon is scraped according to the surface roughness of the sealing body, and residue is generated. It is presumed that the residue is the heat-resistant / slippery layer peeled off from the base film and the cutting debris of the base film base material. As the ink ribbon moves, this residue is carried to the heat generating element and adheres to the heat generating element. As a result, uniform contact between the heat generating element and the ink ribbon is hindered, resulting in deterioration of image quality.

Therefore, the sealing body of the thermal print head is further required to have smoothness so that the ink ribbon is not scraped even if the ink ribbon comes into contact with the sealing body.

The sealing body 26 of the present embodiment is a thermosetting epoxy resin containing a filler and has a surface roughness of 0.3 μm or less.

Whether there are various definitions of surface roughness, it will be described here as arithmetic mean roughness Ra. Arithmetic mean roughness Ra is obtained by extracting only the reference length L from the roughness curve in the direction of the average line, taking the X-axis in the direction of the average line of the extracted portion, and taking the Y-axis in the direction of the vertical magnification. When the Sa curve is expressed by y = f (x), the value obtained by the following equation is expressed in micrometer (μm). Ra = (1 / L) ∫ | f (x) | dx, but the integration range is from 0 to L.

Further, Rmax is described here as the maximum height Ry. The maximum height Ry is obtained by extracting only the reference length from the roughness curve in the direction of the average line, and measuring the distance between the peak line and the valley bottom line of the extracted portion in the direction of the vertical magnification of the roughness curve. The value is expressed in micrometers (μm). However, when Ry is obtained, only the standard length shall be extracted from the part where there are no extraordinarily high peaks and low valleys that are considered to be scratches.

The sealant 26 is mainly mixed with a filler having a particle size of 2 μm to 7 μm and having a particle size distribution within 1 μm to 30 μm by weight ratio of about 60%.

The sealing body 26 is formed, for example, as follows.
After the filler is mixed with the epoxy resin and sufficiently stirred, the epoxy resin is potted together with a plurality of driving ICs 15 and a plurality of bonding wires 24 and 25 near the boundary between one surface of the head substrate 13 and one surface of the circuit board 14, for example. Apply by.

The applied epoxy resin is kept at a high temperature of, for example, about 100 ° C. and heat-treated for several hours. In this high temperature state, the polymers of the epoxy resin are crosslinked and thermally cured.

Since the epoxy resin is cured and shrunk during thermal curing, inclusions such as fillers are deposited on the surface, and surface roughness is likely to occur.

However, the epoxy resin of the sealant 26 of the present embodiment has an appropriate size of 2 μm to 7 μm in particle size and 1 μm to 30 μm in particle size distribution, and a filler having good adhesion is 60 in weight ratio. Since it is contained in an amount of about%, surface precipitation of the filler is suppressed, and a surface roughness Ra of 0.3 μm or less can be obtained. Therefore, even if the ink ribbon is rubbed against the sealing body 26, it is possible to obtain sufficient smoothness so that the ink ribbon is not scraped.

FIG. 2 is a differential interference contrast micrograph showing the surface state of the sealed body 26 in comparison with the comparative example. FIG. 2 (a) shows the surface state of the sealed body 26, and FIG. 2 (b) shows the surface state of the comparative example. be. Here, the comparative example is a sealed body using an epoxy resin containing a filler having an average particle size of 20 μm and a particle size distribution of 1 μm to 100 μm in a weight ratio of about 60%.

As shown in FIG. 2A, in the sealed body 26 of the present embodiment, minute irregularities are uniformly distributed, and it can be seen that the surface is fine. No noticeable surface precipitation of the filler is seen.

On the other hand, as shown in FIG. 2B, in the comparative example, it can be seen that relatively large lumps are scattered and the filler is deposited on the surface and aggregated. In addition, the swell of the surface is also inferred.

FIG. 3 is a diagram showing the surface roughness of the sealed body 26 in comparison with the comparative example. FIG. 3 (a) shows the surface roughness of the sealed body 26, and FIG. 3 (b) shows the surface roughness of the comparative example. be. In FIGS. 3A and 3B, the upper row shows a three-dimensional map of surface roughness, and the lower row shows a line profile. The surface roughness was measured by a laser roughness meter. The area of the measurement area is approximately 500 μm □.

As shown in FIG. 3A, it can be seen that in the sealed body 26 of the present embodiment, the surface irregularities are round and the surface roughness Ra is about 0.21 μm.

On the other hand, as shown in FIG. 3B, in the comparative example, it can be seen that the unevenness of the surface is convex with large undulations and the surface roughness Ra is about 0.46 μm.

FIG. 4 is a diagram showing the particle size distribution of various fillers. Here, the horizontal axis is the particle size and the vertical axis is the frequency. The comparative example is a commercially available filler. Samples A to D are fillers obtained by sieving the filler of the comparative example through a sieve in which the mesh size is gradually reduced.

As shown in FIG. 4, in the comparative example, the particle size of the filler is distributed in the range of about 1 μm to 100 μm, a large first peak is distributed in the vicinity of the particle size of 20 μm, and a small second peak is distributed in the vicinity of the particle size of 2 μm to 3 μm. Peak can be seen.

In Sample A and Sample B, the particle size of the filler is distributed in the range of about 1 μm to 100 μm, and the large first peak is still present in the vicinity of the particle size of 20 μm. However, the frequency of fillers having a large particle size has decreased slightly, and the number of fillers having a particle size near the second peak has increased. The large particle size filler has not yet been sufficiently removed.

In Sample C and Sample D, the particle size of the filler is distributed in the range of about 1 μm to 30 μm, and a remarkable change is observed in the particle size distribution. Due to the smaller mesh size, the filler with a large particle size has been sufficiently removed.

Sample C has a large first peak near the particle size of 10 μm and a medium second peak near the particle size of 2 μm to 3 μm. The basic pattern of particle size distribution has not changed, but the difference in frequency between the first and second peaks is small.

On the other hand, in sample D, the first peak and the second peak are not seen in the particle size distribution. The particle size distribution is monomodal, with a substantially flat peak near the particle size of 2 μm to 7 μm. It can be seen that the particle sizes of the fillers have become uniform.

The filler of sample D is distributed in a range of about 1 to 30 μm in particle size, and the occupancy rate of the filler having a particle size of about 2 to 10 μm is about 67% by weight. The occupancy rate of the filler having a particle size of about 2 to 10 μm is not fixed, and varies depending on the conditions of the sieve and the like, and is generally expected to fluctuate by about 10%.

FIG. 5 is a schematic diagram for explaining the relationship between the content of the filler in the epoxy resin and the characteristics of the encapsulant. Here, the horizontal axis shows the filler content, the left vertical axis shows smoothness, and the right vertical axis shows durability. Smoothness means the reciprocal of surface roughness.

The sealed body is required to have strength (durability) in addition to having a small surface roughness (smoothness). As shown in FIG. 5, the smoothness is better as the content of the filler is smaller, but it shows a characteristic that it deteriorates sharply when the content of the filler becomes excessive. On the other hand, with regard to durability, when the filler content is low, there is no reinforcing effect and the resin exhibits the original characteristics, and when the filler content is above a certain value, sufficient durability can be obtained.

That is, since smoothness and durability have a trade-off relationship with respect to the filler content, it is desirable to determine the filler content so as to satisfy both characteristics. When various investigations were made on smoothness and durability while changing the content using the filler of Sample D, the content was preferably about 50% to 70%, and more optimally about 60% was obtained. ..

As described above, the epoxy resin which is the sealing body 26 of the present embodiment has an appropriate particle size of 2 μm to 7 μm and a particle size distribution of 1 μm to 30 μm, and has good adhesion. Is contained in an amount of about 60% by weight.

As a result, precipitation of the filler due to thermal curing of the epoxy resin is suppressed, and a sealed body 26 having a surface roughness Ra of 0.3 μm or less can be obtained. The sealing body 26 has sufficient smoothness so that the ink ribbon is not scraped even if the ink ribbon is rubbed against the sealing body 26. Therefore, a thermal print head capable of suppressing the generation of ink ribbon residue can be obtained.

Although the case where the sealing body 26 is an epoxy-based resin has been described, it is also possible to use a silicon-based resin or the like from the viewpoint of suppressing the generation of ink ribbon residue. Silicone resin has some flexibility even after thermosetting. Therefore, even if the back surface of the ink ribbon is rubbed against the silicon-based resin that is the encapsulant, the generation of debris due to the scraping of the ink ribbon is suppressed.

However, an epoxy resin is more suitable from the viewpoint of durability in which the encapsulant holds and protects the driving IC and the bonding wire.

The filler is not limited to one type such as silica and calcium carbonate, and a plurality of types of fillers may be mixed.

(Embodiment 2)
The thermal printer according to this embodiment will be described. FIG. 6 is a cross-sectional view showing the thermal printer of the present embodiment, and FIG. 7 is a mock diagram for explaining the frequency of ink ribbon residue generation in comparison with a comparative example.

As shown in FIG. 6, the thermal printer 40 of the present embodiment uses the thermal print head 10 having the sealing body 26 shown in FIG. The thermal printer 40 includes a platen roller 41. The platen roller 41 is arranged so that its side surface is in contact with a heat generation region (a band-shaped region in which a plurality of heat generation elements are arranged) 21 with the main scanning direction S1 as an axis, and is rotatably provided around the shaft 42. ing.

The thermal printer 40 moves the image receiving paper 43 and the ink ribbon 44 inserted between the platen roller 41 and the heat generating region 21 in the sub-scanning direction S2 perpendicular to the main scanning direction S1 by the rotation of the platen roller 41. A desired image is formed by selectively heating a plurality of heat generating resistors 18 with the movement of the image receiving paper 43 and the ink ribbon 44.

The platen roller 41 stops rotating when the plurality of heat generating resistors 18 are selectively generated, and presses the image receiving paper 43 and the ink ribbon 44 against the protective film 22 covering the heat generating resistors 18. The platen roller 40 starts rotating when the heat generation of the plurality of heat generating resistors 18 is stopped, and stops rotating when the thermal paper 43 rotates by the angle required to move by the scanning distance in the sub-scanning direction S2.

At this time, when the ink ribbon 44 is in contact with the sealing body 26 (the scratched portion 45 surrounded by the broken line in the figure), the back surface of the ink ribbon 44 (the surface opposite to the ink layer, the heat-resistant / slippery layer is coated). The surface) is rubbed intermittently with the intermittent movement of the ink ribbon 44.

As described above, since the sealing body 26 has a smoothness with a surface roughness Ra of 0.3 μm or less, the back surface of the ink ribbon 44 is slightly worn by being rubbed intermittently by the sealing body 26. Is. Therefore, it is possible to prevent the back surface of the ink ribbon 44 from being scraped to generate debris (heat-resistant / slippery layer peeling pieces, cutting chips of the base film base material, etc.).

A test was conducted in which an image was continuously formed on an A4 size image receiving paper 43 using a thermal printer 40 and the generation of residue was confirmed from the ink ribbon 44. As a result, even after printing 20,000 sheets, no deterioration in image quality due to the residue generated from the ink ribbon 44 was observed.

In addition, no scratch marks or the like were found on the back surface of the used ink ribbon 44. The scratch marks on the back surface of the ink ribbon 44 were made by pulling out the used ink ribbon 44 wound on the reel from the reel and observing it with a loupe.

FIG. 7 is a schematic diagram for explaining the relationship between the encapsulant formed by using the above-mentioned various fillers and the frequency of residue generation of the ink ribbon. The residue occurrence frequency is a relative value based on the comparative example. The frequency of residue generation in Sample A, Sample B, and Sample C was equal to or slightly reduced from that of Comparative Example.

On the other hand, it was confirmed that the residue generation frequency of the sample D was significantly reduced as compared with the residue generation frequency of the comparative example.

As described above, the thermal printer 40 of the present embodiment uses a thermal print head 10 having a sealing body 26 having a smoothness with a surface roughness Ra of 0.3 μm or less. As a result, even if the ink ribbon 44 comes into contact with the sealing body 26, the generation of residue on the ink ribbon 44 is suppressed. Therefore, it is possible to obtain the thermal printer 40 in which the image quality deterioration of the image caused by the residue of the ink ribbon 44 is prevented.

Incidentally, in the sealed body of the comparative example shown in FIG. 2B, it is necessary to polish the surface with polishing paper or the like in order to prevent the ink ribbons from coming into contact with each other and generating residue. As a result, the work requires a great deal of time and money.

In the case of a thermal print head in which the paper guide is arranged on the sealing body, the back surface of the ink ribbon comes into contact with the paper guide. Since the paper guide is originally arranged for the purpose of contacting the ink ribbon, such a residue problem does not occur.

In the above-mentioned thermal print head 10, the case where the drive IC 15 is mounted on the upper surface of the circuit board 14 near the head board 13 has been described, but the drive IC 15 is mounted on the upper surface of the head board 13 near the circuit board 14. It doesn't matter. Further, the case where the glaze layer 17 has a protruding portion extending along the main scanning direction S1 slightly toward the opposite direction of the sub-scanning direction with respect to the central portion in the sub-scanning direction S2 has been described, but the glaze layer is flat. It doesn't matter.

FIG. 8 is a cross-sectional view showing a thermal printer having a thermal print head in which a drive IC is mounted on the upper surface of the head substrate near the circuit board. As shown in FIG. 8, in the thermal printer 50, the drive IC 15 is mounted on the upper surface of the head substrate 13 near the circuit board 14.

When the drive IC 15 is placed on the upper surface of the head substrate 13 near the circuit board 14, the distance between the drive IC 15 and the heat generation resistor 18 becomes short, so that the heat generation resistor 18 and the sealing body 26 come close to each other. .. As a result, the probability that the ink ribbon 44 and the sealing body 26 come into contact with each other (the scraped portion 51 surrounded by the broken line in the figure) is high, but the effect of suppressing the generation of ink ribbon residue can be similarly obtained.

FIG. 9 is a cross-sectional view showing a main part of a thermal print head having a flat glaze layer. As shown in FIG. 9, a flat glaze layer 17 is provided on the support substrate 16. Similar to the thermal print head 10 shown in FIG. 1, a protective film 22 covering a plurality of heat generation resistors 18, common electrodes 19, and individual electrodes 20 is formed on one surface of the glaze layer 17.

The difference is that the protective film 22 is provided with a slightly recessed recess 22a in the portion covering the heat generation resistor 18. When the glaze layer is flat, the contact area between the ink ribbon sandwiched between the platen roller and the protective film increases, and the protective film is easily worn.

Therefore, in order to suppress an increase in the contact area with the ink ribbon, the protective film 22 has a slightly recessed recess 22a. It is also possible to use the encapsulant 26 of the present embodiment for this type of thermal print head.

When the glaze layer is flat, the distance between the platen roller 41 and the support substrate 16 becomes short, so that the platen roller 41 and the sealing body 26 come closer to each other. As a result, the probability that the ink ribbon 44 and the sealing body 26 come into contact with each other is further increased, but the effect of suppressing the generation of ink ribbon residue can be similarly obtained.

Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10 Thermal print head 11 Head unit 12 Heat sink 13 Head board 14 Circuit board 15 Drive IC
16 Support substrate 17 Glaze layer 18 Heat generation element 19 Common electrode 20 Individual electrode 21 Heat generation area 22 Protective film 22a Recess 23 Adhesive 24, 25 Bonding wire 26 Encapsulant 40, 50 Thermal printer 41 Platen roller 42 Axis 43 Image receiving paper 44 Ink Ribbons 45, 51 Scraped portion S1 Main scanning direction S2 Sub scanning direction

Claims (4)

With a heat sink,
A head substrate having a support substrate mounted on the heat sink, a glaze layer laminated on the support substrate, and a plurality of heat generating elements provided on the glaze layer and arranged in the main scanning direction.
A circuit board mounted on the heat sink so as to be adjacent to the head board in the sub-scanning direction and provided with a connection circuit, and a circuit board.
A control element placed on the upper surface of the head board near the circuit board or on the upper surface of the circuit board near the head board and electrically connected to the heat generating element and the connecting circuit.
An encapsulant provided so as to cover the control element on the upper surface of the head substrate near the circuit board and the upper surface of the circuit board near the head substrate.
Equipped with
The encapsulant is an epoxy resin containing a filler, and the filler is distributed in the range of 1 to 30 μm in particle size, and the occupancy rate of the filler having a particle size of 2 to 10 μm is 67% by weight. A thermal print head having a surface roughness of 0.3 μm or less. The thermal print head according to claim 1, wherein the filler is at least one of silica and calcium carbonate. The thermal print head according to claim 1, wherein the sealing body contains the filler in an amount of 50 to 70% by weight. A head substrate having a heat radiating plate, a support substrate mounted on the heat radiating plate, a glaze layer laminated on the support substrate, and a plurality of heat generating elements provided on the glaze layer and arranged in the main scanning direction. A circuit board mounted on the heat dissipation plate so as to be adjacent to the head board in the sub-scanning direction and provided with a connection circuit, and an upper surface of the head board near the circuit board or near the head board of the circuit board. The control element mounted on the upper surface and electrically connected to the heat generating element and the connection circuit, and the control element on the upper surface of the head substrate near the circuit board and the upper surface of the circuit board near the head substrate. The sealing body is provided with a sealing body provided so as to cover the sealing body, and the sealing body is an epoxy-based resin containing a filler. A thermal print head having a filler occupancy of 2 to 10 μm of 67% by weight and a surface roughness of the sealed body of 0.3 μm or less.
A platen roller that sandwiches the image receiving paper and the ink ribbon between the plurality of heat generating elements and moves the image receiving paper and the ink ribbon in the sub-scanning direction.
A thermal printer equipped with.

Images