計測自動制御学会 東北支部

第 232 回研究集会(2006.11.24)

資料番号 232－20

オンデマンド・オンデマンド・マイクロジェットを
マイクロジェットを用いた光学
いた光学レンズ
光学レンズのレンズの形成
Producing MicroMicro-Optical Lenses using MicroMicro-jet
DropDrop-OnOn-Demand○古畑 義治, 坂野 進
Yoshiharu Furuhata ，Susumu Sakano
日本大学大学院工学研究科
College of Engineering, Nihon University
Abstract. MEMS (Micro-Electro-Mechanical System) is the integration of mechanicalelements, sensors, actuators, and electronics on a silicon substrate through the micro
fabrication technology, in general. Another MEMS formation technology is proposed in thisstudy. The improved drop-on-demand ink jet heads are used and the Memes are formed on
the plastics and silicon substrate. The transparent ultraviolet curing resins are injected fromthe drop-on-demand head to the plastics panel for the micro lenses formation.
Keywords：MEMS(Micro Electro Mechanical System)，マイクロ光学レンズ(Optical-Microlenses), オンデマンド微小ジェット(On demand micro-jet), 液晶用バックライト(Back light for liquid crystal devices)
連絡先：〒963-8642 郡山市田村町得定字中河原 1,

日本大学工学部機械工学科

メカトロニクス研究室，TEL:0249568774 Fax:024-956-8860
e-mail:sakano@mech.ce.nihon-u.ac.jp

Producing Micro-Optical Lenses using Micro-jet
Drop-On-DemandYoshiharu Furuhata1,a, Kazuya Oyoshi2,b, Susumu Sakano1,c1

College of Engineering, Nihon University, Nakagawara Tokusada
Tamura-cho Koriyama 963-8642 Japan
2Tohoku Electronics Company, 1-114 Nawatesita Kitada Futaba-cho
Futaba 979-0604 Japan2bkoyoshi@mcp-hybec.co.jp, 1c sakano@mech.ce.nihon-u.ac.jp
Keywords: MEMS, On demand micro-drop, Optical micro-lenses, Back light

Abstract. MEMS (Micro-Electro-Mechanical System) is the integration of mechanicalelements, sensors, actuators, and electronics on a silicon substrate through the micro
fabrication technology, in general. Another MEMS formation technology is proposed inthis study. The improved drop-on-demand ink jet heads are used and the Memes areformed on the plastics and silicon substrate. The transparent ultraviolet curing resins are
injected from the drop-on-demand head to the plastics panel for the micro lenses
formation.
Introduction
MEMS technologies have been exposed to the attention recently. The representative
example of MEMS technology is the semiconductor technology. MEMS is produced
using the exposure and the etching technologies of the semiconductor technology.
MEMS is formed on the silicon substrate using the micro fabrication technology of thesemiconductor. Another MEMS formation technology is proposed in this paper. The
drop-on-demand system is one of the ink jet printing technologies. This technology is themethod that spews the ink from the inkjet head by the trigger of outside and prints. This
inkjet method is used for the formation of the micro mechanisms. However, it isnecessary that the head is improved because the medium discharged from the head is theplastics or metallurgy genus, and keeps the head and the medium to the high temperature.
The micro lenses for the back light of the liquid crystal display are produced by theimproved on-demand-drop jet head. The transparent ultraviolet curing resins are injectedto the plastic panel and the micro lenses are formed on the panel. The small quantity of
the resins makes the desired dimension lenses by repeating the jet drop and irradiating theultraviolet ray. In this study, the following researches are practiced and the optimum
conditions are clarified in the respect of the micro lenses formation high-reproducibly andstably.
(1) The clarification of the lenses curvature change by the resin materials and the drop
head control parameters.
(2) Optimization of the resin spewed conditions from the nozzle of the drop head.

Drop-on-demand jet
There are three types of the ink jet printing. They are the continuous delivery type, thedrop-on-demand type and the bubble jet type. The bubble jet printing is very popular andis used for the precise color printing and the photo printing. But the control of theindividual bubble is difficult. The on-demand-drop is applied to the forming the MEMS
because of controlling the jet easily. Fig. 1 shows the on-demand-drop. It is called
ODMD (On-Demand-Micro-Drop). The data pulse The piezoelectric device of the jethead is supplied with the voltage power in proportion to the data pulse, and the mediumof the head is spewed from the nozzle of the head tip by the impulsive deformation of thepiezoelectric device.
Piezoelectric
deviceDrop head

Substrate
Fig. 1 The conceptual scheme of ODMD (On-Demand-Micro-Drop)In this study, the epoxy resin of the liquid is used as the medium, and the micro lens ofabout 100 µm is formed. The viscosity of the epoxy resin of the liquid is high in theordinary temperature. The delivery from the drop head is difficult for the viscosity. The
head is retained in the high temperature in order to solve the problem of the viscosity.
The drop head is retained at the 60° C and the resin medium can be discharged.
The experimental equipment is shown in Fig.2. The central is a part of the drop head andThe epoxy liquid is spewed on the plastic board. The dropped liquid balls are hardened
by UV irradiation device in the right hand part of the experiment equipment.
Drop head

UV device

Fig.2 Experimental equipment

Experiment
The example of the micro lenses formation in spewing the epoxy resin liquid on theepoxy resin board is shown in Fig. 3. The lenses from big one to small one can be formedby the drop frequencies of the epoxy resin from the drop head. However, the height anddiameter of the formed lenses slightly vary even in the equal size lens. The reason of thisdispersion is that the optimum conditions of the parameters which affect the drops of theepoxy resin are not being obtained. The shape of one lens is shown in Fig.4. The shape ofthe lens is slightly different in X axis and Y axis. This is also the cause of the above
dispersion. The experiments of the enormous quantity are required for the optimization of
the conditions, if the experiments intend to be practiced on the combination of theparameter conditions. The technique of the Quality Engineering may be used in order tosolve this problem. The optimum conditions of the parameter can be confirmed using theQuality Engineering experiment and analysis.

Fig. 3 Experimental example of optical lenses

Fig. 4 Shape of one lensOptimization of parameter conditions
The experiments are carried out using the L18 orthogonal array and the evaluation iscarried out for data at S/N ratio and sensitivity. The parameters in the experiment are
shown in Table. 1. The experiments using the orthogonal array and the evaluation using
S/N ratio and sensitivity is the technique of the Quality Engineering. It is called theparameter design. The S/N ratio and sensitivity are calculated from the next equations as
the data of the experiments on the NO.1 row of the orthogonal array.

Where,SNratio (η ) = 10 log(S β − V e) / r V e(1)

Sensitivity ( S ) = 10 log( S β − V e) / r(2)

V = ( S − S β ) /(2 − 1)

(3)e

T

221112S =y +yT(4)2Sβ = L / r(5)

L = M1 y + M 2 y112(6)

122(7)

r = M1 + M 2

The SN ratio (η) and Sensitivity (S) are calculated using these equations.

Table.1 Parameters and levelsParameterA. Room temperature
B. Head temperature
C. Head gap
D. Curing time
E. UV exposure time
F. UV gap
G. Head voltage

Drop frequency
Array NO.1

Level 120˚
40˚
0.5 mm50 min
5 min
100 mm18 V

Level 225˚
50˚
1.0 mm80 min10 min
120 mm22 V

Table.2

Array NO.1 data

M1y11

Level 360˚
1.5 mm
100 min15 min
150 mm24 V

M2y12

The SN ratio and Sensitivity calculated from the orthogonal array experiments are shownin Fig. 5 and Fig.6. It is shown that the dispersion of the data is small if the SN ratio ishigh, if not; the dispersion of the data from the orthogonal array is large. The sensitivity
means the height of the lens. If the sensitivity is high, the parameter of the experimentcondition generates the large high lens.
The combination of the best level of the parameters becomes A2, B2, C1, D3, E1, F3, andG1. In these parameters, the effects of C, D, E, F, are large. The height of the lens may bechanged by adjusting the parameter of the Sensitivity which does not affect the SN ratio.
The height of the lens is adjusted by changing the temperature of the drop head. It ispossible to change the lens height from 8.18 micron to 8.73 micron for one drop bychoosing the level of the parameter B(head temperature).

dB-6.5-7.0-7.5-8.0

1 2A

1 2 3 1 2 3
BCFig. 5

1 2 3 1 2 3 1 2 3 1 2 3
DEFGSN ratio and parameters

dB
10.0

9.50
.

9.0

1 2A

1 2 3 1 2 3BCFig. 6

1 2 3 1 2 3 1 2 3 1 2 3DEFGSensitivity and parameters

Application to the back light of the liquid crystal device

The back light is used in the liquid crystal display. The principle of the back light isshown in Fig.7. The light from the LED is guided to the light guide board and the lightfrom the light guide board is transmitted to the liquid crystal. As shown in Fig. 8, theliquid crystal device can displays the screen using reflected light such as the solar light in
the outdoor and in the indoor using transmitted light from the light guide board. The
micro lenses are formed on the light guide board and it is possible to get the higherbrightness back light. It was required that the luminance of the back light was uniform on
the display until now and that the brightness of the back light was high. However, it isrequired that distribution of the luminance on the display is Gaussian distribution atpresent. The luminance distribution of the back light using the results of the study cansatisfy the demand.

Back light

light guide board
LED

Fig. 7 Composition of the back light
Reflecting light

Color filter

Glass

Liquid crystal

Back light

Reflecting layer

Polarizing plate

Fig. 8 Back light of the liquid crystal deviceConclusions

The plastic resin liquid was dropped using the improved ink jet head and the formation ofMEMS was proposed using the head. As an example of the MEMS production, theformation of the micro lenses were taken up and the application to the back light of theliquid crystal device was shown. The production of the MEMS using metallic solution isalso possible by the result of the study.
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Microfluidics and BioMEMS, October, 2001.
[2] R.L. Adams, J. Roy: A one dimensional numerical model of a drop-on-demand inkjet, J.A of Appl. Mech, 53, pp.193-197, 1986.
[3] J. Caruso, M. Hampden-Smith, T. Kodas, K. Kunze, A. Ludviksson, S. Pennino andD. skamser: Color flat panel manufacturing using ink jet technology, Display
Works’99, 1999.
[4] W.T. Pimbley: Drop formation from a liquid jet: a linear one-dimensional analysis
considered as a boundary value problem, IBM Journ. Res. Dev. 29, p.148, 1984.