Thermal Head Research Articles

Abrasion resistance of diamond-like carbon coatings on thick film resistor material

Thick film resistors used in thermal printing heads suffer from abrasion due to kilometres of paper sliding over the surface of the resistive material. In the present work we try to improve the long-term performance by the introduction of an abrasion-resistant coating in the contact area between resistor and paper. Since diamond-like carbon (i-C) is known to exhibit high hardness (3500–6000 HV) and low friction as well as good thermal conductivity and electrical insulation, we deposited 2–4 μm of carbon by ion-assisted chemical vapour deposition and tested it with respect to adhesion, crystal structure and abrasion resistance. After variation of the deposition parameters power, time and bias voltage, we discovered that the i-C layers are only adhesive to one of the two resistor pastes of different suppliers. For the abrasion resistance test, a special mechanical fixture was constructed comprising an excentrically rotating disc on a polishing wheel. The results in terms of time dependence of stylus profile depths are compared with those of uncoated samples. From this it is shown that for i-C-coated samples, the time scale for a fixed amount of thickness decrease is extended by more than one order of magnitude, representing an accordingly enlarged lifetime of the printing head.

Measurement of thermal transients in a thermal print head used for dye diffusion colour printing

An examination of a thermal print head used for dye diffusion thermal transfer printing (D2T2) is presented and the results related to the various problems that can arise when this printing technique is used. Transient measurements are described that show how the temperature distribution over the surface of the thermal print head changes with time. Irregularities in these thermal distributions can give rise to imperfections in the colour printing process.

A Study on the Low Energy Consumption Thermal Head Using Electroless Ni‐W‐P Alloy Films as Heating Resistors

The new type of thermal head with an electroless Ni‐W‐P film on a polyimide film substrate was investigated for the purpose of low cost and low energy consumption. The electroless plating method attained a fine patterned heating element and the polyimide substrate worked as a heat‐insulating layer with a lower heat conductivity. In our simulation, the applied power was reduced about 50% by using polyimide film as the heat‐insulating layer. The accumulation of heat could be suppressed by controlling the polyimide film thickness without reducing the advantage of low energy consumption. The new head, composed of screen‐printed polyimide resin with powder (10 μm thick) as the protective layer, an electroless Ni‐W‐P film (0.25 μm thick) as the heating element, a polyimide film (50 μm thick) as the heat‐insulating layer, and an Al board (3.0 mm) as the heat sink, was produced. The new head shows the same dot size as that of the conventional thin‐film‐type head produced by vacuum technology, and its cost is lower than that of the conventional thin‐film‐type head. The new head produces the good printing quality with 60% of the power required by the conventional one. Therefore, the new head provides low cost and low energy consumption.

感熱記録紙用微粉シリカの開発

Thermal recording paper typically used in facsmile system has been rapidly expanding to great proportions and has secured a firm position in an information-oriented society. This would result the systematic development between electronic technology in hardware industries and coating technology in paper industries including various raw material industries.The fine powdered silica, “Mizukasil”, has played an important role in the development of the thermal recording paper as a residue-preventing agent on a thermal head. Since this fine powdered silica has extremely fine particles and is inactive, it combines the following advantages in residue-prevention, sticking prevention, color-developing sensisivity, color intensity, dot minuteness, color gradient and runnability of the thermal head.

Development of heating resistor for versatile thermal print heads

Improvement in shock and heat resistance of meander-shaped tantalum nitride heating resistors used in facsimiles and other apparatuses is studied, and life prolongation is achieved under the condition of a large drive power. To solve the problem of resistor failure under high-power and high-speed conditions, the causes of heating resistor deterioration are studied. After predicting the temperature distribution at curves of the meander and confirming the effect of some measures, a simulation for thickness-wise temperature distributions is conducted that shows that the temperature rises and falls violently only in the vicinity of the heating resistor. As a means for improvement, the meander-shaped heating resistor is placed between SiO/sub 2/ layers. With this structure, the resistance to heat and to thermal shock is improved remarkably. Using the results of the analysis and experiments, a heating resistor is obtained with a remarkably improved resistance to thermal shock. >

A BiCMOS thermal head intelligent driver with density controllers for full-tone rendition printers

A 3- mu m BiCMOS thermal head driver using pulsewidth modulation dealing with eight-bit density input data (256 gray levels) is described. Circuits composed of 64*8-bit complex counters, which function as eight-line parallel 64-bit shift registers (shift mode) and as 64 counters which have eight bits (count mode) by alteration of their mutual connections according to the mode signals, have been developed. The complex counter controls the output pulse width according to the binary data and the clock intervals (minimum 100 ns). The shift registers can operate using a 20-MHz clock. The driver consists of about 4500 CMOS gates and 128 bipolar transistors in a 2.8-mm*8.8-mm chip size. The breakdown voltage of the bipolar transistor BV/sub cbo/ is more than 35 V. The driver is especially suited for full-tone rendition printers. Applications of the driver include use in thermal print heads, LED print heads, and LCD print heads. >

画像プリンタ

PURPOSE:To obtain a printed image with high color-reproducibility, by a method wherein a color masking treatment is applied to density data converted from pixel data of a television image to eliminate a turbidity of color contained in a coloring material etc. CONSTITUTION:Each image data for one line respectively outputted from line memories 40, 42, 44 is subjected to a reverse gamma correction in a reverse gamma correction circuit 48 and operated by a digital logarithmic computing element, whereby density data Db, Dg, and Dr are generated. the density data Db, Dg, and Dr are supplied to a color masking circuit 50 and operated, whereby density data DY, DM, and DC are outputted to be supplied to a density-time conversion circuit 52. Gradation data CY, CM, and CC for one line respectively corresponding to the density data DY, DM, and DC are supplied to a thermal head 54 in a predetermined order from the density-time conversion circuit 52. Here, one line of heating resistors generte heat for a time directed by the corresponding gradation data CY, CM, and CC, whereby pixels corresponding to respective pixels of a television image are printed on one printing line.

Ta-Si-C High Resistivity Thin Films for Thermal Printing Heads

Ta-Si-C thin films have been developed for thermal printing heads, and the effect of composition on the film properties was studied. The results of these investigations show that (1) when Ta-Si-C thin films are formed, the composition of the film does not agree with the target composition, (2) addition of carbon to Ta/SiC mixtures suppresses recrystallization during high temperature treatment, (3) excellent characteristies are achieved with thermal printing heads using Ta-Si-C thin films formed using a target with more than 20-percent carbon in a SiC/C mixture, and (4) irreversible resistance changes are very small in thermal printing heads containing more than 20-percent carbon when external heat is applied. These results show that Ta-Si-C is an excellent material for use in thermal printing heads.

A mixed CMOS-DMOS-JFET technology for switching circuits with high voltage output stages

This paper describes the development of a technology that incorporates low voltage CMOS and high voltage JFET and DMOS transistors on the same chip. The fabrication sequence is based on a metal gate CMOS process. The influence of the process variables and trade-offs in the characteristics of the devices have been discussed. The successful application of the technology to a thermal printer head driver circuit has been demonstrated.

Observation of the Gold Plated Surface of Flexible Printed Circuits (FPC) by Electron Probe X-ray Micro-Analyzer (EPMA) .

Recently fine line Flexible Printed Circuits (FPC) are used in many applications such as Thermal Head Printers and Faximille. In these applications very precise control of plating thickness is required and leads us to difficult problem both in design and in measurment of plating thickness.The conventional β-ray method and Fluoro X-ray method are not sufficient to answer the above requirement. The Electron-Probe X-ray Micro Analyzer (EPMA) is recently developped surface measuring method which is especially suitable for these purposes.We applied this new technique to analyze the degrading problem in gold plated surface of FPC. Also the authors summarized the circuit resistivity effect on plating thickness control.

Zirconium Nitride Thin-Film Resistors With High Thermal Durability

A ZrN thin-film resistor is proposed as a promising heating resistor for a future thermal printing head used in high-resolution highspeed printing. The ZrN film is prepared by nonreactive sputtering with a hot-pressed ZrN target. The present method is able to control the film characteristics mainly through the nitrogen content in the sputtering atmosphere as well as achieve good reproducible results. Practical films, which have a small resistance change with temperature as well as during aging tests, are provided with resistivities of 0.5 to 5 m <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Omega</tex> .cm. Thermal printing element test pieces with 16-dot/mm resolution are fabricated to examine the thermal durability of the ZrN thin-film resistor when applied to high-speed printing. The results of heat pulse life tests make clear that the elements are applicable to high-speed (a 0.3-ms duration and a 1.0-ms repetition interval) printing of excellent quality and sufficient thermal durability.

High‐speed thin‐film thermal print head

AbstractThis paper describes the result of thermal analysis of the inner region of the thin film thermal print head and the effect of the shape of the meander type heating resistor. The thermal head allowing short pulse driving for higher speed with higher reliability has been demanded recently. The influence of the pulse duration on the temperature profile of the inner region of the head and the heating resistor shape have not been studied.We have studied various conditions affecting the temperature profile of the inner region of the thin film thermal print head and the shape of the meander type heating resistor, and obtained the following results:1. As the pulse applied to the heating resistor gets shorter, the necessary power for pulse application increases and the temperature slope in the heat insulating layer near the heating resistor becomes steeper.2. To lessen the temperature slope in the heat insulating layer, thinning the protective layer, increasing the thermal conductivity of the protective layer and preheating the whole inner region are effective.3. In surface temperature distribution, corners of the meander type heating register become hotter as the width of the pulse applied to it becomes shorter. Widening the heating register at corners, narrowing the straight parts and increasing the number of meanderings are effective.

Thermal groundwater movement and radionuclide transport in SW England

AbstractHeat flow in SW England is well above average for the UK as a whole, but northwards towards Bath and Bristol the values decrease rapidly. However, hot springs occur both in the Bath-Bristol area and in mines in Cornwall. The development of hydrothermal circulation systems is thus not controlled entirely by geothermal gradient: the presence of a suitable fracture permeability is the main requirement. The thermal ‘head’ produced, which nevertheless depends upon the temperature and volume of water in the system, theoretically can exceed local topographic heads even in areas of low geothermal gradient.Thermal groundwaters usually carry above average quantities of radioelements in solution because of the long residence times involved. 222Rn values are often particularly high. High concentrations of 222Rn in surface waters arise from the discharge of groundwater. The results of a survey of 222Rn in streams in SW England have established areas of high values which are interpreted as rising limbs of convection cells with dimensions in the order of 5–10 km.In SE Devon γ-ray spectrometry of soils shows two E.-W. belts of high activity. The northern is coincident with the faulted southern margin of the Crediton Trough, while the southern is coincident with the westerly extension of the Abbotsbury fault system. Groundwater movement along deep-seated fracture systems is considered to be the explanation of these features. The horizontal scale of the area involved suggests that a thermal rather than local topographic head is the driving force. Groundwater circulation within fractures, driven by a thermal head, may therefore occur even in areas of low geothermal gradient and should be considered when selecting waste disposal sites.

Development of 16 dots/mm Thermal Printing Head

The development of a high-speed thermal printing head with a resolution of 16 dots/ram is described. Main features of the present study are as follows. 1) A meander shaped heating resistor is suitable for high-resolution printing and has a life of more than 2 X l0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> pulses at the applied pulse width of 0.8 ms. 2) The deterioration characteristic of the meander shaped heating resistor depends on the pulse width. 3) The fabrication of a thermal printing head with 16 dots/mm resolution and high-speed drive was achieved by installing the integrated circuit (IC) containing a shift register, latch, and driver on the heating resistor board.

A 64 Bit Bi-CMOS Sink Driver for Thermal Head

A newly developed 64 bit sink driver for thermal print heads luSing Bi-CM0S technology has achieved the following characteristics: high input clock rate 10 MHz; low saturation voltage, Vsat 0.6 V1 at 60 mA output current; low power dissipation, 350 mW at 20 % duty and below 10 mW when all the output buffers are OFF; high output breakdown voltage, Vout 40 V. Sixty-four bipolar transistor buffers and about 2400 CMOS transistors for logic circuits are included in a 3.50 X 6.26 mm chip.'

A large scale hybrid thermal print head : Tamio Saito, Yoshikatsu Fukumoto, Mamoru Mizuguchi, Takahiko Abe and Masayoshi Nagashima. Electrocomponent Sci. Technol.10, 261 (1983)

A large scale hybrid thermal print head : Tamio Saito, Yoshikatsu Fukumoto, Mamoru Mizuguchi, Takahiko Abe and Masayoshi Nagashima. Electrocomponent Sci. Technol.10, 261 (1983)

Ta-SiC thin film resistors for highly reliable thermal printing heads : Keiji Nunomura, Nobuyoshi Koyama and Tetsujin Matsubara. IEEE Trans. Components Hybrids Mfg Technol.CHMT-6 (4), 377 (December 1983)

Ta-SiC thin film resistors for highly reliable thermal printing heads : Keiji Nunomura, Nobuyoshi Koyama and Tetsujin Matsubara. IEEE Trans. Components Hybrids Mfg Technol.CHMT-6 (4), 377 (December 1983)

Ta-SiC Thin Film Resistors for Highly Reliable Thermal Printing Heads

A Ta-SiC thin film resistor has been newly developed for highly reliable thermal printing heads. The Ta-SiC film, which is formed by a sputtering technique, has a stable amorphous structure containing microcrystalline Tac. The film crystallization hardly develops, even at temperatures up to 800°C. In addition to this structural stability, it has chemical stability and oxidation resistance. A thermal printing element test piece has been fabricated composed of a 17 at% Ta-SiC heating resistor, Al conductor, and a sputtered SiC surface protective layer on a g!azed alumina substrate. High temperature resistor annealing and alkaline metal- and lead-free glaze substrate adoption are effective for stability improvement. As a result, highly reliable high speed thermal printing elements were realized, Which could generate more than 5 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> heatpulses at above 500°C peak temperature with 0.5-2.0 ms short electric current pulses.

New gray-scale printing method using a thermal printer

A 3-level dot-pattern method (the 3-L method) has been developed in order to achieve stable and many gradational-level thermal printing with minimal loss in print resolution. This 3-L method employs dot-pattern matrices which consist of three density level dots; black (saturation density of thermal paper), gray (half-black density), and white (paper brightness) dots. The matrices are assigned to picture elements of continuous tone images according to their gradational levels. A theoretical analysis of the gradational printing characteristics was carried out on the basis of a modified Yule-Nielsen equation and an equation describing the color change of thermal paper. Using these equations, the numbers of equally spaced gradational levels were studied, and an optimum gray density for maximizing them was found. To further ensure high quality printing, optimum dot patterns were selected by the introduction of an evaluation function based on a discrete Fourier transform. The 3-L method was demonstrated to have good performance in tests with a thermal printing fixture employing a high-resolution (16 dots/mm) thermal head.

Experimental study of heat transfer in He-I and He-II under stationary heat load

to know the critical heat flux qcr and its corresponding thermal head ATcr so as to prevent passage of the superconductor to the normal state. However, data for performing reliable thermal calculations associated with heat transfer in He-I and, expecially He-ll are still inadequate. We made an experimental study of heat transfer from a copper specimen to He-I and He-ll under a stationary heat load. The specimen was made in the form of a 0.005  0.I  0.I m plate of annealed M3 copper whose surface was machined. A heater was mounted on one side of the plate; the surface temperature of the opposite side of the plate was measured by three carbon resistors and the results of the measurements were recorded by a digital voltmeter. The experiments were performed on a horizontally placed plate facing the heater downward. The relative e error in temperature measurement was 2% at 4.2~ and 3% at 2~ A description of the experimental unit and some data are given in [3]. In Fig. la the experimental values of the heat flux from the specimen q to He-I (curve I) and the integral values of the heat transfer coefficient ~ (curve 3 constructed by the equation ~ = q/AT) have been plotted against the thermal head AT = Tw -- Ts (here T w is the wall temperature and T s is the saturation temperature). Typical heat exchange regions (convective, developed bubble boiling, transient, and steady film boiling) occur on experimental curve I of boiling in He-l. For the investigated, relatively massive, copper specimen the first critical density of heat flux qcrl ~8000 W/m = was noted at a thermal head ATcr1~ 0.9~ With the passage into the film boiling region the heat transfer coefficient diminishes, as is also evidenced by the course of curve 3. In [5, 6] less massive specimens were investigated and the first boiling crisis was noted at a critical heat flux density qcr1~ 8000-10,000 W/m 2 and the thermal head ATcrl ~ 0.7-1~ Typical heat exchange regions (Kapitsa resistance, nonfilm boiling, transient, and film boiling) are noted on experimental curve i (Fig. ib) by analogy with the data of [9]. It can be seen that for the investigated specimen a critical heat flux density qcr =2500 W/m 2 was observed at a temperature head ATcr =0.32~ The values obtained can be explained by the experimental conditions (a relatively massive specimen, a rough machined heat-exchanging surface) and, of course, by the mechanism of heat transfer in an He-ll medium. At high heat