Microcircular Holes Research Articles

Innovative design of reel-to-reel hot embossing system for production of plastic microlens array films

This paper reports an innovative design of reel-to-reel hot embossing system for the production of plastic microlens array films. The novel system mainly consists of a reel-to-reel mechanism with tension rollers, a gas-assisted hot embossing module and a vacuum-assisted de-molding unit. During this new process operation, a thin steel mold with large-area micro-circular hole array pattern was fixed on the bottom hot plate of this system. The part of plastic film roll was placed on the mold by tension rollers. Under the proper processing conditions, the softened polymer will just partially fill the micro-circular holes of the mold and, due to surface tension, form a convex lens surface. After a proper cooling process, the plastic film with a large-area microlens array pattern was de-molded from the mold by reverse pressure activated through the vacuum system. In this way, a roll of plastic film with a large-area microlens array can be successfully fabricated. In addition, the sag height, curvature, and focal length of the fabricated microlens arrays could be changed and controlled. The embossing by gas pressure is uniform and the de-molding by a vacuum system is running smooth. This technique shows great potential for mass production of plastic optical films with various large-area microlens arrays.

Development of a continuous roll-to-roll processing system for mass production of plastic optical film

This paper reports a highly effective method for the mass production of large-area plastic optical films with a microlens array pattern based on a continuous roll-to-roll film extrusion and roller embossing process. In this study, a thin steel mold with a micro-circular hole array pattern is fabricated by photolithography and a wet chemical etching process. The thin steel mold was then wrapped onto a metal cylinder to form an embossing roller mold. During the roll-to-roll process operation, a thermoplastic raw material (polycarbonate grains) was put into the barrel of the plastic extruder with a flat T-die. Then, the molten polymer film was extruded and immediately pressed against the surface of the embossing roller mold. Under the proper processing conditions, the molten polymer will just partially fill the micro-circular holes of the mold and due to surface tension form a convex lens surface. A continuous plastic optical film with a microlens array pattern was obtained. Experiments are carried out to investigate the effect of plastic microlens formation on the roll-to-roll process. Finally, the geometrical and optical properties of the fabricated plastic optical film were measured and proved satisfactory. This technique shows great potential for the mass production of large-area plastic optical films with a microlens array pattern.

Rapid hot embossing of polymer microfeatures

Although the hot embossing process is gaining popularity in molding polymer micro/nano structures, it needs a breakthrough improvement in reducing cycle time before it can become a mass-production process. In this study, an embossing tool with a rapid heating and cooling capability was investigated to reduce the cycle time. During the process, the embossing tool was rapidly heated to above the polymer softening temperature (in less than a couple of seconds), pressed against a room-temperature polymer substrate, and subsequently rapidly cooled for mold separation. Different miniaturized features including microsquare and hexagonal wells, microcircular holes, and submicron surface features were successfully produced using the new process with a total embossing cycle time around 20 s. The fatigue test result indicated that the new embossing technology is durable and reliable for microscale feature replication.

Measurement of Mean Stress Using Nickel Alloy Foil with Microcircular Holes (Improvement of Accuracy and Influence of Frequency)

The mean stress detecting method by the nickel foil with microcircular holes uses the propagation rate of the fatigue crack, which propagates from the edge of microcircular holes. However, since the crack propagation rate does not change considerably even if the mean stress changes, it cannot be said that the accuracy of the conventional method is enough. From the above viewpoint, in this report using the nickel alloy foil with higher hardness than the nickel foil, the improvement of accuracy of this method is investigated. Namely, the effect of mean stress on fatigue crack propagation is examined under constant temperature and frequency at first. Moreover, the influence of the frequency on the sensitivity of this method is investigated. Namely, the fatigue crack propagation is examined under various frequencies, and the basic equations are proposed to obtain mean stress.

102 微小円孔を有する電着銅薄膜による成長粒子の分布形状を利用した二軸応力検出法 : 被測定物の弾性係数の影響(材料力学I)

102 微小円孔を有する電着銅薄膜による成長粒子の分布形状を利用した二軸応力検出法 : 被測定物の弾性係数の影響(材料力学I)

103 微小円孔を有するニッケル合金薄膜による平均応力検出法 : 被測定物の弾性係数の影響(材料力学I)

103 微小円孔を有するニッケル合金薄膜による平均応力検出法 : 被測定物の弾性係数の影響(材料力学I)

Measurement of Biaxial Stress Using Electrodeposited Copper Foil with a Microcircular Hole (Effect of Frequency and Wave Form on Strain Sensitivity)

In order to examine the effects of frequency and the wave form of cyclic stress on the strain sensitivity of biaxial stress measurement method using an electrodeposited copper foil with microcircular holes, pulsating tension tests are done to the stainless steel specimen glued the copper foil and recrystallized copper foil. The higher the frequency becomes, the lower the strain sensitivity becomes.And in the case of sine wave, the relationship between stress amplitude σph0.5 corresponding to slip occurrence rate of 50% at the periphery of micro circular holes and the mean strain rate 4nσph0.5/Eper one forth cycle, where n is the frequency expressed by Hertz and K is Young's modulus of the material stress measured, is expressed as σph0.5=.4109 (4nσph0.5/E) +B. So, σph0.5 to optional frequency can be estimated by this equation. Also, the strain sensitivity is affected by wave form and it becomes highest in the case of square wave and becomes lower in ramp wave than sine wave. If the copper foil is recrystallized, the strain sensitivity increases but the effect of the difference of wave form decreases.

Measurement of Biaxial Stress Using Grown Grain Distributed Shape in Electrodeposited Copper Foil with Circular Holes

In order to measure cyclic biaxial stresses by an electrodeposited copper foil with microcircular holes, both occurrence rate of slip bands at the periphery of microcircular holes and the grown grain occurrence rate in copper foil itself have been used. However, this method needs a great many microcircular holes to obtain high accuracy. So, in this report the different method from that ever used is examined. Namely, as the biaxial stress ratio affects the stress distribution of the periphery of circular hole in a plate, it is also expected that the distributed shape of grown grains at the periphery of circular hole in a copper foil is different with biaxial stress ratio. From this viewpoint, the length of the circumferential direction and radial direction of grown grains appeared are measured under various biaxial stresses, and the basic equations are proposed to obtain principal stress.

微小円孔を有する電着金属薄膜による平均応力検出法 : 感度の向上および周波数の影響(材料力学III)

微小円孔を有する電着金属薄膜による平均応力検出法 : 感度の向上および周波数の影響(材料力学III)

Measurement of Mean Stress Using Electrodeposited Metal Foil with Microcircular Holes (Method by Fatigue Crack Propagation Rate)

The stress measurement method using an electrodeposited copper foil with microcircular holes has been developed to measure the cyclic biaxial stress. However, as shearing stress amplitude controls the phenomenon of grown grain occurrence, which is the principle of this method, the static mean stress acting on the elements cannot be measured only using this phenomenon. So the propagation of fatigue cracks from the periphery of microcircular holes are examined to measure mean stress. In this report, temperature and frequency, which affect the crack propagation mainly, are kept constant. And the effect of mean stress on fatigue crack propagation is investigated. Namely, using copper foil and nickel foil, fatigue crack lengths are measured under various combinations of stress amplitude and mean stress, and the basic equations connecting the crack propagation rate, stress amplitude, and mean stress are presented.

Measurement of Biaxial Stress Using Grown Grain Density Rate in Electrodeposited Copper Foil with a Microcircular Hole.

In order to measure biaxial stresses by an electrodeposited copper foil with a microcircular hole both occurrence rate of slip bands at the periphery of microcircular holes in a copper foil and the number of cycles of grown grain occurrence in copper foil itself are used. However, it is necessary to stop the test frequently to seek the latter. In this report, in order to overcome this weakness, the posssibility of the use of grown grain density, which can be obtained to optional number of cycles, is examined. Namely, using three kinds of material adhered copper foil, the stress component which controlls the grown grain density in copper foil is examined under the combination of plane bending and cyclic torsion and the basic equations connecting the grown grain density, the stress amplitude and number of cycles are presented.

115 微小円孔を有する電着金属薄膜による平均応力検出法 : 疲労き裂の進展速度を利用した測定法

115 微小円孔を有する電着金属薄膜による平均応力検出法 : 疲労き裂の進展速度を利用した測定法

103 微小円孔を有する電着銅薄膜による成長粒子の分布形状を利用した二軸応力検出法

103 微小円孔を有する電着銅薄膜による成長粒子の分布形状を利用した二軸応力検出法

413 微小円孔を有する電着銅薄膜による二軸応力検出法 : 成長粒子の発生密度を利用した測定法

413 微小円孔を有する電着銅薄膜による二軸応力検出法 : 成長粒子の発生密度を利用した測定法

414 微小円孔を有する電着銅薄膜による平均応力検出法 : 疲労き裂の進展速度を利用した測定法

414 微小円孔を有する電着銅薄膜による平均応力検出法 : 疲労き裂の進展速度を利用した測定法

105 微小円孔を有する電着銅薄膜による二軸応力検出法 : 成長粒子の発生密度を利用した測定法(材料力学II)

105 微小円孔を有する電着銅薄膜による二軸応力検出法 : 成長粒子の発生密度を利用した測定法(材料力学II)

Measurement of Biaxial Stress Using Electrodeposited Copper Foil with a Microcircular Hole. 5th Report. Effect of Modulus of Elasticity of the Material.

The condition of grain growth or slip line occurrence at the periphery of microcircular holes in a copper foil is fundamental to biaxial stress measurement by an electrodeposited copper foil with a microcircular hole, and that condition depends on the difference of the Poisson's ratio between the element where stress measured and a copper foil attached to it. In this report, basic equations of biaxial stress measurement, which takes into account of the difference of Poisson's ratio, are presented and the propriety of the equations is examined by plane bending and bending-torsion tests using materials with various Poisson's ratio and Young's modulus.

107 微小円孔を有する電着銅薄膜による二軸応力検出法 : 繰返し速度の影響(材料力学II)

107 微小円孔を有する電着銅薄膜による二軸応力検出法 : 繰返し速度の影響(材料力学II)

Measurement of Biaxial Stress Using Electrodeposited Copper Foil with a Microcircular Hole : Method Using the Probability of the Occurrence of Slip

The dependence of slip band occurrence at the periphery of microcircular holes formed by photoetching in electrodeposited copper foil upon the number of cycles and cyclic stress magnitude for plane bending and cyclic torsion is examined. The results show that the principal stresses in an element under biaxial stresses, which are undetectable by the conventional copper electroplating method, can be evaluated using an equation based on the probability of slip occurrence, which takes into account both cyclic stress magnitude and the number of cycles.

Measurement of Biaxial Stress Using an Electrodeposited Copper Foil with a Microcircular Hole. 4th Report. Method Using the Probability Process of the Occurrence of Slip Line.

The dependence of slip line occurrence at the periphery of microcircular holes formed by photoetching in an electrodeposited copper foil upon the number of cycles and cyclic stress magnitude for plane bending and cyclic torsion is examined. The results show that the principal stresses in the element under biaxial stress, which are undetectable by the conventional copper electroplating method, can be evaluated using the equation based on the probability process of slip line occurrence, which takes into account both cyclic stress magnitude and the number of cycles.