experimental study of the transcription of minute width grooves by injection molding.

With the latest progress in the optical industry, many molded plastic products, such as optical lenses, disc substrates, mirrors and diffraction grating, have been widely used.
As a sequence, the requirements associated with dimensional accuracy and optical properties become extremely strict.
Especially in the injection molding of the disc substrate, the following have become important technical issues:)
Accurate transcription of pits, slots and records (1-8), b)
Reduce the refraction (9-22), and c)
Improvement of Shape Accuracy of substrate (23-25).
Especially for higher storage density, molding transcription becomes more important.
Regarding transcription and aiming to minimize disc noise caused by substrate surface roughness, we have previously studied transcription of smooth and flat surfaces with surface roughness at The nm scale (3-5).
In these previous studies, the relationship between molding conditions and transcription was quantitatively verified.
In addition, trace of micro flow (
Its height is on the order of magnitude of several nm to fewhundred nm)
They are considered to be the cause of poor transcription and clarify their production mechanisms.
At the same time, studies related to the transcription of grooves in the sub-upper width
Micron level executed (6-8)
, And verified the relationship between the molding conditions and the transcription height.
In addition, by introducing the concept of the equivalent thickness of the ceramic layer, a transcription model related to the width of the tiny groove is proposed.
By using the above transcription model, the degree of transcription under various regulatory conditions can be estimated.
The purpose of this paper is to clarify the transcription of various molding resins and to determine the relationship between the properties of these resins and the molding transcription.
The material used by the experimental method and the shape of the molded part the resin used in this experiment is polycarbonate (
Taijin Chemical Co. , Ltd.
, Panlite ad3)
Amorphous olefin (Nihon Zeon Ltd.
Zeonex280 and Japan Synthetic Rubber Co. , Ltd. , Arton F)
, And Poly a fat (
Mitsubishi Lei Yong Co. , Ltd. , Acrypet TF-3).
The main properties of these resins are listed in Table 1.
As shown in the figure.
1. the molded part is a disc with a diameter of 130 and a thickness of 1. 2 mm.
The door is a disc-
Shape and located in the center of the molded disk. [
Figure 1 illustration omitted]
On one side of the surface of the molded disk, use a nickel die cross slot with a tiny rectangular groove (width 0. 55[micro]m, depth 70 nm)
As shown in the figure. 2. [
Figure 2 illustration omitted]
Injection molding machine driven by electric servo motor (
Toy machinery and metals, Ltd. )
In this experiment, the screw with a diameter of 28mm and the aclamping force of 780 kN were used.
The mold is shown in the figure.
3, the experiment is carried out with the above pressure die installed in the cavity. [
Figure 3 illustration omitted]
As shown in Table 2, the experiment is carried out at the same time as changing the mold temperature and other conditions.
The mold temperature and the pressure in the mold cavity are the use of heat-
Coupling and pressure sensors placed in the mold (see Fig. 3).
Methods for measuring the height of transcription measure the extent of transcription by atomic force microscopy (
Digital instruments, Nano Mirror III)
As shown in the figure. 4.
In order to evaluate transcription, the transcription height is defined as shown in the figure5. [Figures 4-
5 illustration omitted]
The measurement position is in the internal part of the disc (
R = 30mm from center)
And the external part (
R = 60mm from center).
The molding transcription model of tiny grooves was studied using basic elasticity and heat transfer theory. (1)
Transcription model: glass layer at glass transition temperature, as shown in the figure6.
The transcription height h entering the groove is related to the degree of bending deformation of the hyaluronic layer. [
Figure 6 illustration omitted]
When the bending of the glazed layer is considered to be the result of a uniform load on a beam fixed at both ends, its deflection ,[Delta]
, Can be expressed in the following formula :(1)[
Mathematical expressions that cannot be reproduced in ASCII]Where, [P. sub. c]
: Cavity pressure w: slot width E: elastic modulus d: thickness of glass layer.
However, since d is not an actual measurement, the thickness of the equivalent glass layer can be measured.
According to the previous investigation (25)
, The equivalent glass layer thickness d at the completion of the filling is estimated to be about 100 to 150 nm, in which case the polyresin is formed under the following conditions: the melting temperature is 330 [degrees]
C The temperature of the mold is 120 [degrees]
C. Injection speed is 75 [cm. sup. 3]/s. (2)
The relationship between the thickness of the glass layer and the insulation factors.
The heat transfer coefficient of stable flow is expressed by the following formula (4). (2)[
Mathematical expressions that cannot be reproduced in ASCII]
Where, k: unchanged [[Lambda]. sub. r]
: Thermal conductivity of hot resin [Gamma]
: Shear rate a: resin thermal diffusion rate r: distance from the center of the molded disk, Ie. flow length.
The effect due to the melting on the groove can be ignored.
Because the area of the existing grooves is very small (0. 1mm in length)
As shown in the figure. 2.
On the other hand, when the shear flow and compression generate heat, the following equation for the ceramic layer is established :(3)[
Mathematical expressions that cannot be reproduced in ASCII]Here, [T. sub. g]
Temperature of glass transition and [T. sub. s]
Temperature of resin-
Given mold contact surface (26)by (4)[
Mathematical expressions that cannot be reproduced in ASCII]
In the above equation ,[b. sub. r]and [b. sub. mo]
The thermal permeability of resin and mold materials is expressed (5)[
Mathematical expressions that cannot be reproduced in ASCII](6)[
Mathematical expressions that cannot be reproduced in ASCII]where [[Rho]. sub. r]and [[Rho]. sub. mo]
Is it density ,[c. sub. r]and [c. sub. mo]
Is the specific heat, and [[Lambda]. sub. r], and[[Lambda]. sub. mo]
It is the thermal conductivity of resin and old materials.
From Eqs 2 and 3 ,(7)[
Mathematical expressions that cannot be reproduced in ASCII]
Where is the shear rate 【Gamma]
In the glazed layer (8)[
Mathematical expressions that cannot be reproduced in ASCII]
Where Q: flow rate H: cavity thickness n: Power-
In the case of a circular molded part, the relationship between the flow distance r and the elapsed time t is expressed as follows. (9)[
Mathematical expressions that cannot be reproduced in ASCII]
Since d is negligible compared to H in Eq 8, from Eqs 7 and 8, d can be expressed as follows. (10)[
Mathematical expressions that cannot be reproduced in ASCII]where [Theta]= ([T. sub. g]-[T. sub. mo])/([T. sub. me]-[T. sub. g])
Infinite temperature
Therefore, the thickness d of the equivalent glass layer can be obtained as follows :(11)d ~ [[Theta]. sup. A][multiplied by][t. sup. B]
Among them, A and B are the definite values obtained by the experiment greater than 0.
With Eqs 1 and 11, the transcription height can be expressed as follows. (12)h ~ [[Theta]. sup. -3A][multiplied by][t. sup. -3B]
According to equation 12, the transcription height h can be considered as a heat transfer factor for the filling stage and an initial temperature setting factor for melting and mold temperature.
The relationship between the results and the temperature of the discussion mold [T. sub. mo]
Infinite temperature [Theta]
The transcription height of various molding resins is shown in the figure. 7-14.
In all cases, transcription of the external part (r = 60 mm)
Almost the same as the internal part (r = 30 mm).
However, when the injection rate is low, the transcription of downstream melt flow is worse than that of upstream melt flow (8).
This trend becomes more evident as the injection speed decreases.
The following results have been achieved. [Figure 7-
14 illustration omitted]1)
Influence of mold temperature (
[Dimensionless temperature words]Theta])
: The transcription height increases as the mold temperature increases.
That is, the temperature without cause [Theta]
As shown in the figure, the transcription height is increased and decreased. 8, 10, 12, 14.
Relationship between logs ([Theta])and log(h)
Is linear, Index (-3A)
In Eq 9, it\'s probably-1 to -1.
3, produce ~ 0.
4 for resins used in this study.
This theoretical value of less than 1 may be due to the deformation analysis of the glass layer in equation 1, in order to make the analysis simpler, only elastic analysis deformation is considered.
Therefore, the effect of introducing plastic deformation should be considered in this analysis. 2)
Effect of heat diffusion rate of resin (a)
: As shown in the figure.
15, the effect of the thermal diffusion rate of the resin cannot be clearly recognized. [
Figure 15 illustration omitted]3)
Dependence on elastic modulus (E)
: The relationship between elastic modulus and transcription height is shown in the figure16.
According to the estimation of equation 1, the transcription height increases when the elastic modulus decreases.
In other words, h ~ [E. sup. c]
Where the theoretical value of c is-1. From Fig.
16, the experimental value of C is-1. 4.
The experimental value is basically the same as the theoretical value. [
Figure 16 illustration omitted]
From above, also from the previous results (8)
, The conditions required to improve transcription by injection molding are:)
Low elastic modulus of molded resin, B)
C) higher melting temperature
D) higher mold temperature
High injection rate, e)
Keep the pressure high, f)
Keep the pressure for a long time, g)
Ashorter gate shortened the time.
Conclusion The molding transcription of injection molding micro grooves was studied.
A transcription model was proposed and molded transcription of tiny rectangular grooves by the use of polycarbonate, amorphous olefin, and multi-Alpha-shrinkage resin (width 0. 55[micro]m, depth 70 nm)
Was investigated.
We have reached the following conclusions. (1)
By introducing the concept of equivalent thickness of ceramic layer, a transcription model of tiny width grooves is proposed. (2)
As a non-dimensional temperature [Theta]
The transcription height increased and the transcription height decreased.
Relationship between logs ([Theta])and log(h)
Is linear, Index (-3A)
About-in Eq 12-1to -1.
3 resin used in this study. (3)
The effect of the thermal diffusion rate of the resin cannot be clearly reflected. (4)
With the decrease of elastic modulus, the transcription height increases.
Therefore, the amorphous olefin Zeonex has the highest conversion rate among these resins.
We sincerely thank the doctor.
Dr. Hongji Songcun
Dr. Hashizume Shin.
Susumu Aiuchi, Production Engineering Research Laboratory, Hitachi Ltd.
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21. 1997 revised July 1997, Production Engineering Research Laboratory of Hitachi masaki yoshii, kurki KURAMOTO and YUUJI ochiaiprodution292Yoshida-cho, Totsuka-