U.S. patent application number 11/993870 was filed with the patent office on 2010-04-08 for optical resin composition and method for producing the same.
This patent application is currently assigned to FUJIFILM Corporation. Invention is credited to Tatsuya Ishizaka, Tetsuo Kawano.
Application Number | 20100087578 11/993870 |
Document ID | / |
Family ID | 37570374 |
Filed Date | 2010-04-08 |
United States Patent
Application |
20100087578 |
Kind Code |
A1 |
Kawano; Tetsuo ; et
al. |
April 8, 2010 |
OPTICAL RESIN COMPOSITION AND METHOD FOR PRODUCING THE SAME
Abstract
To provide an optical resin composition containing carbonate
crystals, which have oriented birefringence, have a needle- or
rod-like shape, and are able to negate the birefringence without
sacrificing the light transmittance of a transparent polymeric
resin where the carbonate crystal exists, and a method for
producing the resin composition. To achieve this provided are an
optical resin composition containing a resin and carbonate
crystals, wherein the carbonate crystals have a specific surface
area of 4 m.sup.2/g or more, and the carbonate crystals dispersed
into the resin have an average dispersion diameter of 500 nm at a
maximum, and a method for producing the optical resin
composition.
Inventors: |
Kawano; Tetsuo; (Kanagawa,
JP) ; Ishizaka; Tatsuya; (Kanagawa, JP) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
FUJIFILM Corporation
Minato-ku, Tokyo
JP
|
Family ID: |
37570374 |
Appl. No.: |
11/993870 |
Filed: |
June 16, 2006 |
PCT Filed: |
June 16, 2006 |
PCT NO: |
PCT/JP2006/312141 |
371 Date: |
December 24, 2007 |
Current U.S.
Class: |
524/424 ;
252/182.12 |
Current CPC
Class: |
C08K 3/26 20130101; C08L
1/12 20130101; C08L 1/10 20130101 |
Class at
Publication: |
524/424 ;
252/182.12 |
International
Class: |
C08K 3/26 20060101
C08K003/26; C01F 11/18 20060101 C01F011/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 24, 2005 |
JP |
2005-185822 |
Mar 9, 2006 |
JP |
2006-064653 |
Claims
1. An optical resin composition comprising: a resin; and carbonate
crystals having a specific surface area of 4 m.sup.2/g or more,
wherein the carbonate crystals dispersed into the resin have an
average dispersion diameter of 500 nm at a maximum.
2. The optical resin composition according to claim 1, wherein the
optical resin composition has a light transmittance of 86% or
greater at a wavelength of 450 nm.
3. The optical resin composition according to claim 1, wherein the
content of the carbonate crystals relative to the resin is 0.01% by
mass to 15.00% by mass.
4. The optical resin composition according to claim 1, wherein the
resin is any one selected from a cellulose acylate resin, a
polyethylene terephthalate resin, a polyethylene naphthalate resin
and a polycarbonate resin.
5. The optical resin composition according to claim 1, wherein the
carbonate crystals have an aspect ratio of 2 or greater, an average
major axis length of 400 nm or shorter, and a variation coefficient
of the major axis expressed by Formula (1) of 0.40 or less: 1 r
.times. { 1 n - 1 i = 1 n ( r i - r ) 2 } 1 2 Formula ( 1 )
##EQU00003## wherein r denotes an average major axis length, n
denotes the number of particles whose major axis length is
measured, and r.sub.i denotes the major axis length of the i.sup.th
particle measured.
6. A method for producing an optical resin composition comprising:
producing carbonate crystals, and dispersing the produced carbonate
crystals into a resin, wherein the step of producing carbonate
crystals comprises reacting a metal ion source that contains at
least one metal ion selected from Sr.sup.2+, Ca.sup.2+, Ba.sup.2+,
Zn.sup.2+ and Pb.sup.2+ with a carbonate source in liquid.
7. The method for producing an optical resin composition according
to claim 6, wherein the carbonate crystals have a specific surface
area of 4 m.sup.2/g or more, and the carbonate crystals dispersed
into the resin have an average dispersion diameter of 500 nm at a
maximum.
8. The method for producing an optical resin composition according
to claim 6, wherein the step of producing carbonate crystals
comprises removing an adsorbate from surfaces of the carbonate
crystals.
9. The method for producing an optical resin composition according
to claim 8, wherein the step of removing an adsorbate comprises any
one of a method for washing the carbonate crystal at least once by
decantation and a method for subjecting the carbonate crystal to
ultrafiltration at least once.
10. The method for producing an optical resin composition according
to claim 9, wherein a supernatant obtained by the decantation or a
filtrate obtained by the ultrafiltration has a conductivity of 100
.mu.S/cm or less.
11. The method for producing an optical resin composition according
to claim 6, wherein the step of producing carbonate crystals
comprises increasing, at least once, the number of the carbonate
crystal in liquid, and increasing, at least once, only the volume
of the carbonate crystals in liquid.
12. The method for producing an optical resin composition according
to claim 11, wherein the temperature of the step of increasing the
number of the carbonate crystals is -10.degree. C. to 40.degree.
C., and a temperature of the step of increasing the volume of the
carbonate crystal is 1.degree. C. to 60.degree. C. and not less
than the temperature of the step of increasing the number of the
carbonate particles.
13. The method for producing an optical resin composition according
to claim 6, wherein the step of dispersing the carbonate crystals
into the resin comprises dispersing the carbonate crystal into the
resin by kneading.
14. The method for producing an optical resin composition according
to claim 13, wherein a method for molding the optical resin
composition in which the carbonate crystal is dispersed is any one
of an injection molding, press molding and extrusion molding.
Description
TECHNICAL FIELD
[0001] The present invention relates to an optical resin
composition containing carbonate crystals which have oriented
birefringence, have a needle- or rod-like shape and are able to
negate the birefringence without sacrificing the light
transmittance of a transparent resin where the carbonate crystal
exists, and a method for producing the optical resin
composition.
BACKGROUND ART
[0002] Carbonates such as calcium carbonate have long been widely
used in areas such as rubber, plastics and papermaking. Recently,
many types of carbonates with high functionality have been
developed and put into practical use for a variety of applications
and purposes according to particle shapes and diameters.
[0003] Examples of crystal forms of the carbonates include calcite,
aragonite and vaterite. Of these, the aragonite is needle-like and
has superior hardness and coefficient of elasticity, and it may be
used for versatile applications.
[0004] Commonly known methods for producing the carbonates are, for
example: (1) a reaction of a solution containing carbonate ions
with a chloride solution, and (2) a reaction of chloride with
carbon dioxide. Also, Patent Literature 1 proposes a method
regarding the method (1) to produce a needle-like carbonate having
aragonite structure, wherein a reaction of a solution containing
carbonate ions with a chloride solution takes place under
ultrasonic irradiation. However, the carbonate obtained by the
production method described in Patent Literature 1 is not only
oversized of 30 .mu.m to 60 .mu.m in length but also has a wide
distribution in the particle size; a carbonate controlled for a
desired particle size may not be obtained.
[0005] In addition, regarding a method of introducing carbon
dioxide into water slurry of Ca(OH).sub.2, Patent Literature 2
proposes a method to place a seed crystal of needle-like aragonite
in Ca(OH).sub.2 water slurry and grow the seed crystal only in a
certain direction. Furthermore, there is a problem that only a
large particle of 20 .mu.m to 30 .mu.m in length may be obtained
even with the method for producing a carbonate described in Patent
Literature 2.
[0006] On the other hand, in recent years, the majority of
optical-glass products such as glass lens and camera lens have been
replaced by polymeric optical materials in view of their lightness,
easy processing, superior mass productivity, and simplicity in
application of molding technologies such as injection molding and
extrusion molding. For materials of optical components for
opto-electronics, especially for optical components used for
laser-related devices such as optical disc devices for recording
sounds, images, literal information and the like, there is a strong
tendency to use polymeric materials.
[0007] A polymeric material having birefringence does not cause a
problem when it is applied to optical components which do not
require relatively high precision. However, optical components
requiring higher precision have been demanded recently, and
birefringence is a big issue in case of, for example, a
writable/erasable magneto-optical disc. Birefringence is a property
that a light beam passing through a certain substance is separated
into two light beams depending on the conditions of polarized light
beams. Birefringence index is given as the difference in refractive
index between the directions of the polarized lights in the
substance.
[0008] However, there is a problem that an optical component
obtained by molding the common polymeric materials exhibits
birefringence. A semiconductor laser beam is used for reading and
writing this kind of magneto-optical disc; the existence of an
optical component with birefringence in the disc itself or in the
lens, for example, on the light path may adversely affect the
precision in reading or writing.
[0009] Given this factor, Patent Literature 3 proposes a
non-birefringent optical resin material containing a polymeric
resin and an inorganic fine particle having different signs of
birefringence for the purpose of reducing the birefringence. The
non-birefringent optical resin material of this proposal is
obtained by a method called crystal doping, wherein, for example, a
number of inorganic fine particles are dispersed in a polymeric
resin, and the bonding chains in the polymeric resin and the
inorganic fine particles are oriented in an approximately parallel
direction by externally applying a molding force such as drawing so
as to diminish the birefringence caused by the orientation of the
bonding chain in the polymeric resin with the birefringence of the
inorganic fine particles having an opposite sign.
[0010] As stated above, inorganic fine particles that may be used
for a crystal doping is essential in order to obtain a
non-birefringent optical resin material through the crystal doping.
The inorganic fine particles are required to have a shape with a
high aspect ratio such as a needle- or rod-like shape to align the
carbonate particles along the orientation of the bonding chain in
the polymeric resin. Carbonate particles which do not influence a
light transmittance, which is an important function as an optical
material, is demanded. In addition, the average particle size of
carbonate crystals need to be sufficiently small compared to the
wavelength of a light source to reduce the effect of light
scattering by particles as much as possible so that it does not
affect the light transmittance.
[0011] However, it is difficult to disperse carbonate crystals in a
resin without causing flocculation, and merely designing individual
carbonate crystal particles to have a desired form or size is not
necessarily satisfactory. Therefore, development of a technology
for preventing decrease in transmittance of the optical resin
material caused by the flocculation of carbonate crystal particles
is highly demanded.
[0012] Patent Literature 1 Japanese Patent Application. Laid-Open
(JP-A) No. 59-203728
[0013] Patent Literature 2 U.S. Pat. No. 5,164,172
[0014] Patent Literature 3 International Publication WO No.
01/25364
DISCLOSURE OF INVENTION
[0015] An object of the present invention aims to solve the
conventional problems and achieve the following objects.
Specifically, the object of the present invention is to provide an
optical resin composition containing a carbonate crystal
(hereinafter may be referred to as "carbonate particle" or
"carbonate crystal particle"), which has oriented birefringence, is
needle- or rod-like, and is able to negate the birefringence
without sacrificing the light transmittance of a transparent
polymeric resin where the carbonate crystal exists, and a method
for producing the optical resin composition.
[0016] In view of the above-mentioned shortcomings, the inventors
of the present invention have conducted extensive studies and
established that in order for resin to keep high transparency, it
is critical that carbonate crystal fine particles having a specific
surface area of 4 m.sup.2/g or more be taken out beforehand as a
dry powder with no flocculated particles by removing adsorbates
from the particle surfaces prior to addition into resin, and then
the carbonate crystal fine particles are dispersed into the resin,
whereby an optical resin composition can be obtained that negates
birefringence without sacrificing light transmittance.
[0017] The present invention is based on the findings of the
inventors, and the means for solving the problem is as follows:
<1> An optical resin composition containing a resin and
carbonate crystals having a specific surface area of 4 m.sup.2/g or
more, wherein the carbonate crystals dispersed into the resin have
an average dispersion diameter of 500 nm at a maximum. <2>
The optical resin composition according to <1>, wherein the
optical resin composition has a light transmittance of 86% or
greater at a wavelength of 450 nm. <3> The optical resin
composition according to any one of <1> and <2>,
wherein the content of the carbonate crystals relative to the resin
is 0.01% by mass to 15.00% by mass. <4> The optical resin
composition according to any one of <1> to <3>, wherein
the resin is any one selected from a cellulose acylate resin, a
polyethylene terephthalate resin, a polyethylene naphthalate resin
and a polycarbonate resin. <5> The optical resin composition
according to any one of <1> to <4>, wherein the optical
resin composition is used in a drawn film. <6> The optical
resin composition according to any one of <1> to <5>,
wherein the carbonate crystals have an aspect ratio of 2 or
greater, an average major axis length of 400 nm or shorter, and a
variation coefficient of the major axis expressed by Formula (1) of
0.40 or less:
1 r .times. { 1 n - 1 i = 1 n ( r i - r ) 2 } 1 2 Formula ( 1 )
##EQU00001##
[0018] wherein r denotes an average major axis length, n denotes
the number of particles whose major axis length is measured, and
r.sub.i denotes the major axis length of the i.sup.th particle
measured.
<7> The optical resin composition according to any one of
<1> to <6>, wherein the carbonate crystals are produced
by reacting a metal ion source containing at least one metal ion
selected from Sr.sup.2+, Ca.sup.2+, Ba.sup.2+, Zn.sup.2+ and
Pb.sup.2+ with a carbonate source in liquid. <8> The optical
resin composition according to <7>, wherein the carbonate
crystals are produced by the method including increasing, at least
once, the number of the carbonate crystals in liquid, and
increasing, at least once, only the volume of the carbonate
crystals in liquid. <9> The optical resin composition
according to any one of <7> to <8>, wherein the optical
resin composition is formed by reacting the metal ion source with
the carbonate source in liquid by a single-jet method. <10>
The optical resin composition according to any one of <1> to
<9>, wherein the optical resin composition is used in an
optical element. <11> The optical resin composition according
to <10>, wherein the optical element is a magneto-optical
disc. <12> A method for producing an optical resin
composition including: producing carbonate crystals, and dispersing
the produced carbonate crystals into a resin, wherein the step of
producing carbonate crystals includes reacting a metal ion source
containing at least one metal ion selected from Sr.sup.2+,
Ca.sup.2+, Ba.sup.2+, Zn.sup.2+ and Pb.sup.2+ with a carbonate
source in liquid. <13> The method for producing an optical
resin composition according to <12>, wherein the carbonate
crystals have a specific surface area of 4 m.sup.2/g or more, and
the carbonate crystals dispersed into the resin have an average
dispersion diameter of 500 nm at a maximum. <14> The method
for producing an optical resin composition according to any one of
<11> to <13>, wherein the step of producing carbonate
crystals includes removing an adsorbate from surfaces of the
carbonate crystals. <15> The method for producing an optical
resin composition according to <14>, wherein the step of
removing an adsorbate includes any one of a method for washing the
carbonate crystal at least once by decantation and a method for
subjecting the carbonate crystal to ultrafiltration at least once.
<16> The method for producing an optical resin composition
according to <15>, wherein a supernatant obtained by
decantation or a filtrate obtained by the ultrafiltration has a
conductivity of 100 .mu.S/cm or less. <17> The method for
producing an optical resin composition according to any one of
<12> to <16>, wherein the step of producing carbonate
crystals includes increasing, at least once, the number of the
carbonate crystal in liquid, and increasing, at least once, only
the volume of the carbonate crystals in liquid. <18> The
method for producing an optical resin composition according to any
one of <12> to <17>, wherein the step of producing
carbonate crystals includes reacting the metal ion source with the
carbonate source in liquid by a single-jet method. <19> The
method for producing an optical resin composition according to any
one of <12> to <18>, wherein the temperature of the
step of increasing the number of the carbonate crystals is
-10.degree. C. to 40.degree. C., and a temperature of the step of
increasing the volume of the carbonate crystal is 1.degree. C. to
60.degree. C. and not less than the temperature of the step
increasing the number of the carbonate particles. <20> The
method for producing an optical resin composition according to
<12>, wherein the step of dispersing the carbonate crystals
into the resin includes dispersing the carbonate crystal into the
resin by kneading. <21> The method for producing an optical
resin composition according to <12>, wherein in the step of
dispersing the carbonate crystal into the resin the carbonate
crystals are added into the resin at least before completion of the
polymerization reaction for the preparation of the resin.
<22> The method for producing an optical resin composition
according to any one of <20> and <21>, wherein a method
for molding the optical resin composition in which the carbonate
crystal is dispersed is any one of an injection molding, press
molding and extrusion molding. <23> The method for producing
an optical resin composition according to <22>, wherein the
optical resin composition obtained by the injection molding, press
molding and extrusion molding is drawn so as to form a film.
[0019] The present invention can solve the conventional problems
and provide an optical resin composition containing a carbonate
crystal which has oriented birefringence, is needle- or rod-like
and is able to negate the birefringence without sacrificing light
transmittance of a transparent polymeric resin where the carbonate
crystal exists, and a method for producing the optical resin
composition.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a process drawing illustrating an example of
process of producing carbonate crystals by means of a double jet
method in the method for producing an optical resin composition of
the present invention.
[0021] FIG. 2 is a process drawing illustrating an example of
process of producing a carbonate crystal by means of a single-jet
method in the method for producing an optical resin composition of
the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Optical Resin Composition
[0022] An optical resin composition of the present invention
contains a carbonate crystal in the invention dispersed into a
resin, and optionally other components.
--Carbonate Crystal--
[0023] The carbonate crystals can be obtained by reacting a metal
ion source with a carbonate source in liquid, and their specific
surface area, aspect ratio, average major axis length and
variations in the major axis fall within respective predetermined
ranges. The carbonate crystal is added to resin for use and has a
relative value for light transmittance at a wavelength of 450 nm of
not less than a predetermined value.
--Metal Ion--
[0024] The metal ion source is not particularly limited and may be
suitably selected in accordance with the intended use as long as it
contains a metal ion. Examples of the metal ion sources include
Sr.sup.2+ ion, Ca.sup.2+ ion, Ba.sup.2+ ion, Zn.sup.2+ ion and
Pb.sup.2+ ion. Of these, Sr.sup.2+ ion, Ca.sup.2+ ion, and
Ba.sup.2+ ion, each of which is an alkali earth metal ion, are
particularly preferable from the perspective of reactivity. A metal
ion source capable of reacting with a carbonate source and forming
a carbonate having any one of crystal forms of calcite, aragonite,
vaterite, and amorphous is preferable, and a metal source capable
of forming a carbonate having an aragonite crystal structure is
particularly preferable.
[0025] The aragonite crystal structure is represented by
CO.sub.3.sup.2- unit, a plurality of the CO.sub.3.sup.2- unit are
formed in a laminate structure to form a carbonate crystal having a
needle-like shape or a rod-like shape. Thus, anisotropy arises in
the crystal structure, the refractive index varies depending on the
axial direction of the crystal, and the crystal results in a
biaxial and negative optical crystal. Table 1 shows respective
refractive indexes of crystals in each of crystal axial directions
of carbonates of which the metal ion is Ca.sup.2+, Sr.sup.2+,
Ba.sup.2+, or Pb.sup.2+ in carbonate particles. For the reason, the
carbonate is drawn in arbitrarily determined one direction by a
drawing process, which will be described below, and crystal
molecules are arrayed in a state where the major axis direction of
the particles corresponds to the drawing direction. Thus, the
orientation birefringence of the resin can be controlled by mixing
the resin to a resin having a positively orientated
birefringence.
TABLE-US-00001 TABLE 1 Specific .alpha. .beta. .gamma. .delta.
gravity CaCO.sup.3 1.530 1.681 1.685 0.155 2.94 SrCO.sup.3 1.520
1.667 1.669 0.149 3.75 BaCO.sup.3 1.529 1.676 1.677 0.148 4.29
PbCO.sup.3 1.804 2.076 2.078 0.274 6.55
[0026] The metal ion source is not particularly limited and may be
suitably selected in accordance with the intended use as long as it
contains Sr.sup.2+ ion, Ca.sup.2+ ion, Ba.sup.2+ ion, Zn.sup.2+
ion, and Pb.sup.2+ ion and examples thereof include at least one of
nitrate salts, chlorides, and hydroxides selected from Sr, Ca, Ba,
Zn, and Pb. Of these, hydroxides and chlorides are particularly
preferable from the perspective of reactivity.
[0027] Preferably, the metal ion source contains at least any one
of NO.sub.3.sup.-, Cl.sup.-, and OH.sup.-. Specifically, examples
of the metal ion sources include Sr (NO.sub.3).sub.2,
Ca(NO.sub.3).sub.2, Ba(NO.sub.3).sub.2, Zn(No.sub.3).sub.2,
Pb(No.sub.3).sub.2, SrCl.sub.2, CaCl.sub.2, BaCl.sub.2, ZnCl.sub.2,
PbCl.sub.2, Sr(OH).sub.2, Ca(OH).sub.2, Ba(OH).sub.2, Zn(OH).sub.2,
Pb(OH).sub.2, and hydrates thereof.
--Carbonate Source--
[0028] The carbonate source is not particularly limited and may be
suitably selected in accordance with the intended use as long as it
generates CO.sub.3.sup.2- ion. Examples thereof include sodium
carbonate [Na.sub.2CO.sub.3], sodium hydrogen carbonate
[NaHCO.sub.3], carbon dioxide gas and urea [(NH.sub.2).sub.2CO]. Of
these, sodium carbonate, ammonium carbonate, and carbon dioxide gas
are particularly preferable from the perspective of reactivity.
--Specific Surface Area, Aspect Ratio, Average Major Axis Length
and Variation in Major Axis--
[0029] It is required that the specific surface area of the
carbonate crystal particles or surface treated carbonate crystal
particles, as measured prior to addition to resin, be 4 m.sup.2/g
or more, more preferably 6 m.sup.2/g or more, and particularly
preferably 8 m.sup.2/g or more. When the specific area is less than
4 m.sup.2/g, it is often the case that the crystal carbonate
particles have already flocculated at the time of producing the
crystal carbonate, and even when the crystal carbonate is added to
and dispersed into the resin, the flocculated crystal carbonate is
further flocculated to cause a greater size of aggregate, resulting
in significant decrease in light transmittance.
[0030] The specific surface area of the crystal carbonate can be
measured using a commercially available nitrogen-adsorption
apparatus. For example, the specific surface area can be measured
using an automatic specific surface area/micropore distribution
analyzer (BELSORP-mini, manufactured by BEL JAPAN Inc.).
[0031] The aspect ratio of the carbonate particle is required to be
2 or more, preferably 3 to 20, and particularly preferably 3 to
8.
[0032] When the aspect ratio is less than two, the shape of the
carbonate crystal is closer to a granulated shape or a spherical
shape, the occurrence of the particle orientation along the
molecular orientation of the transparent resin becomes less
probable, or it does not occur at all. Consequently, the present
invention becomes ineffective. When the aspect ratio of the
carbonate particle is more than 20, the carbonate particles are
destructed in the course of producing the optical resin
composition, and resultingly, the major axis direction of the
carbonate particle may not be aligned in one direction, although
the present invention relates to a technique of compensating
orientation birefringence associated with molecular orientation by
making the orientation of molecules develop in accordance with the
molecular orientation of the transparent resin.
[0033] The average of the major axis length which is the maximum
length of a needle- or rod-like shaped carbonate crystal along its
long axis direction is preferably shorter than the wavelength of
visible light (approximately 400 nm to 780 nm) in order to suppress
the decrease in transmittance of the transparent optical resin as
much as possible. Therefore, the average major axis length of the
carbonate crystal should be 400 nm or shorter. It is preferably 300
nm or shorter, and more preferably 200 nm or shorter. The effect of
Mie scattering by particles increases when the average major axis
length is longer than 400 nm. This accelerates the decrease in the
light transmittance, and the material loses its value as a
transparent optical material.
[0034] Regarding the variation in the major axis, the variation
coefficient of the major axis should be 0.40 or less in order to
reduce the content of the particles that cause transmittance
reduction by light scattering and thereby to achieve a practically
low light-scattering status. The variation coefficient of a major
axis is expressed as a ratio of the standard deviation of the major
axis to the average major axis length, and it may be obtained from
Formula (1):
1 r .times. { 1 n - 1 i = 1 n ( r i - r ) 2 } 1 2 Formula ( 1 )
##EQU00002##
[0035] where r denotes the average major axis length, n the number
of particles used for measurement of the major axis length, and
r.sub.i the major axis length of the i.sup.th particle
measured.
[0036] The value of n is preferably large. Although it is set at
100 or greater, the value of n is more preferably 200 or greater.
The particle distribution may not be accurately represented with
the value of n less than 100. When the variation coefficient is
expressed in percentage, the value obtained from Formula (1) is
multiplied by 100. For example, the variation coefficient of 0.40
or less may be expressed as the variation coefficient of 40% or
less.
[0037] The variation coefficient of the major axis is preferably
small. More specifically, it is preferably 0.30 or less, and more
preferably 0.20 or less. The variation coefficient of the major
axis of greater than 0.40 increases the proportion of particles
having a major axis of longer than the average major axis length,
and the light transmittance in the resin may be decreased.
[0038] The each method of measuring the major axis length, aspect
ratio, variation coefficient and the like of the carbonate crystal
is not particularly limited and may be suitably selected in
accordance with the intended use. For example, adequately dispersed
carbonate particles are observed through the use of a transmission
electron microscope (TEM); the shot image of particles is scanned
and stored as an image file; the image file information is opened
with Mac-View Ver. 3, a particle size distribution analysis
software manufactured by Mountech Co., Ltd., and each of the
particles is measured; and finally the results are calculated.
--Dispersion Diameter and Dispersion Content--
[0039] A dispersion diameter means the average of maximum long axis
lengths of individual dispersed particles, and also encompasses the
dispersion diameters of primary particles, secondary particles,
lattice-shaped particles, chain-linked particles, and amorphous
cubic particles. When an average dispersion diameter is defined as
an average size of the carbonate crystal particles actually
residing in the resin after the carbonate crystal particles are
mixed with the resin by kneading or the like, the average
dispersion diameter of the carbonate crystal particles dispersed
into the resin is preferably 500 nm at a maximum, more preferably
450 nm or less, and particularly preferably 400 nm or less. When
the average dispersion diameter is greater than 500 nm, the
transparency of the resin containing the carbonate crystals may be
significantly decreased. The average dispersion diameter of the
carbonate crystals can be determined by observing the carbonate
crystals residing in the resin using a scanning electron microscope
(SEM); the shot image of the particles is scanned and stored as an
image file; the image file information is opened with Mac-View Ver.
3, a particle size distribution analysis software manufactured by
Mountech Co., Ltd., and the maximum major axis length of each
particle is measured; and finally the results are averaged.
[0040] The content of the carbonate crystal relative to the resin
is preferably 0.01% by mass to 15.00% by mass, more preferably
0.05% by mass to 3.00% by mass, and particularly preferably 0.10%
by mass to 2.00% by mass. When the content of the carbonate crystal
is less than 0.01% by mass, an effect of controlling birefringence
by adding the particles may not be exerted. When the content of the
carbonate crystal is more than 15.00% by mass, the optical resin
composition has an effect of controlling birefringence, but may not
keep necessary transparency.
--Resin--
[0041] The resin is not particularly limited and may be suitably
selected in accordance with the intended use as long as it is
generally used in optical components, and has a certain degree of
transparency. Examples of the resins include polyolefins such as
polyethylene and polypropylene; aromatic vinyl polymers such as
polystyrene; a poly(meth)acrylic esters such as
polymethylmethacrylate; polyphenylene oxide, polycarbonate,
polyvinyl chloride, polyethylene terephthalate, polyethylene
naphthalate, cyclohexyl methacrylate, cellulose acylate, alicyclic
polyolefin (for example, a cyclic olefin ring-opening polymer or
copolymer such as norbornene polyolefin); and a copolymer of
alicyclic(meth)acrylate such as isobornyl methacrylate and
(meth)acrylphenylene ether. Of these, the polyethylene
terephthalate, the polyethylene naphthalate, the cellulose acylate
and the polycarbonate as a resin having preferable optical and
physical properties, and the polycarbonate is most preferable since
it sufficiently develops an advantageous effect of the present
invention even with an incident light in an oblique direction.
--Light Transmittance at Wavelength of 450 nm--
[0042] The light transmittance at a wavelength of 450 nm is
preferably 86% or more in the optical resin composition in which
the carbonate crystal is added to the resin, more preferably 86.5%
or more, and particularly preferably 87% or more. When the light
transmittance is less than 86%, the transparency of the resin is
lowered and then the optical information may be decreased.
[0043] When the film thickness of the resin is set at 100 .mu.m,
the light transmittance at a wavelength of 450 nm in the resin
before the carbonate crystal being added thereto is taken as x %,
and the light transmittance at a wavelength of 450 nm in the resin
after the carbonate crystal being added thereto is taken as y %,
the value y/x is preferably 0.98 or more, particularly preferably
0.99 or more, and 1 is the most preferable. When the value y/x is
less than 0.98, the transparency of the resin to which the
carbonate crystal is added may be impaired.
--Application--
[0044] The characteristic birefringence values of resins containing
birefringence have been documented, for example, by Fumio Ide on
page 29 of "Contemporary transparent resins--the world of
high-performance optical material for challenging IT--" (Kogyo
Chosakai Publishing, Inc.; first edition), and are listed in Table
2. Table 2 indicates that the most of the resins contain positive
birefringence. Also, when strontium carbonate particles with a
shape having a high aspect ratio such as a needle- or rod-like
shape are employed as the carbonate and added for example to
polycarbonate used as the optical polymer followed by drawing of
the polycarbonate, the carbonate particles align along the
orientation of the polymer molecules For example, Yasuhiro Koike
and Tagaya Akihiro "Polymer and Advanced Materials One Point 1
Photonics Polymer" (KYORITSU SHUPPAN Co., Ltd.; first edition)
discloses that selection of inorganic crystals having a high aspect
ratio and birefringence whose sign is opposite to the sign of the
birefringence of the polymer in the aligned state leads to
cancellation of birefringence. Thus, it is made possible not only
to exactly cancel birefringence, but also to make the relative
birefringence negative. Therefore, the carbonate crystals may be
suitably employed for optical components, and more preferably
resins make up optical elements in which the birefringent
properties is important and high precision is required.
TABLE-US-00002 TABLE 2 Polymer Birefringence Polystyrene -0.10
Polyphenylene ether 0.21 Polycarbonate 0.106 Polyvinyl chloride
0.027 Polymethylmethacrylate -0.0043 Polyethylene terephthalate
0.105 Polyethylene 0.044
(Method for Producing Optical Resin Composition)
[0045] The method for producing the optical resin composition
includes a process of producing a carbonate crystal, and a process
of dispersing the produced carbonate crystal into a resin, and
further includes other processes in accordance with the
necessity.
--Process of Producing Carbonate Crystal--
[0046] A process of producing a carbonate crystal includes a
treatment of reacting the metal ion source with the carbonate
source in liquid so as to obtain a carbonate crystal, and a
treatment of removing an adsorbate from a carbonate crystal surface
(hereinafter may be simply referred to as an adsorbate removal
treatment), and further includes other treatments in accordance
with the necessity. In the treatment of reacting the metal ion
source with the carbonate source in liquid so as to obtain
carbonate crystals, a treatment of increasing the number of
carbonate particles and a treatment of increasing only the volume
of carbonate particles (hereinafter may be simply referred to as
volume increasing treatment) may be separately performed.
--Reaction Method--
[0047] The method of reacting the metal ion source with the
carbonate source in liquid is not particularly limited and may be
suitably selected in accordance with the intended use, for example,
a method in which the metal ion source and the carbonate source are
added in liquid at the same time to react them, from the
perspective of reactivity. Examples of the methods include a
double-jet method and a single-jet method. To obtain a carbonate
crystal in the invention, both methods can be used, however, when a
metal hydroxide is used as the metal ion source, the single-jet
method is preferably used. Further, specifically, when a solvent
used in the reaction contains water, the concentration of a metal
hydroxide is increased because of the metal hydroxide having a low
solubility to water. Thus, all the metal hydroxide is not dissolved
in water and forms suspension. Then, the suspension is left at
rest, the undissolved metal hydroxide is settled out. In most
cases, a raw material tank used for the double-jet method or
single-jet method is not equipped with a stirring equipment, and
therefore, it is unfavorable that a suspension is poured into the
raw material tank. It is most preferable that the metal hydroxide
suspension is previously put in a reaction vessel equipped with
stirring blades, and the carbonate source is preferably added in
the suspension using a nozzle. Thus, the single-jet method is
preferably used.
--Double Jet Method--
[0048] In the double-jet method, the metal ion source and the
carbonate source are respectively added on surfaces of individual
reaction liquids or in individual liquids by spraying to react
them. For example, as shown in FIG. 1, a liquid containing the
metal ion source (Liquid A) and a liquid containing the carbonate
source (Liquid B) are sprayed in Liquid C at the same time to react
the metal ion source and the carbonate source in Liquid C.
[0049] The addition rate of the metal ion source and the carbonate
source by the double-jet method is not particularly limited and may
be suitably adjusted in accordance with the intended use. Further,
it is preferable to determine the molar addition rate such that the
final product can take the stoichiometric mixture ratio. In the
present invention, an equimolar addition rate is most preferable.
When the treatment of increasing the number of the carbonate
particle and the treatment of increasing the volume of the
carbonate particle are separately performed in the course of
forming the final product, the addition rate and the reaction
temperature used in each treatment are sometimes varied.
[0050] The double-jet method can be carried out using, for example,
a double-jet reactive crystallization apparatus disclosed in
Japanese Patent Application Laid-Open (JP-A) No. 05-107668. The
apparatus includes a reaction vessel, stirring blades equipped in
the reaction vessel and near the stirring blades provided with two
or more nozzles for supplying raw material solutions. The metal ion
source (Liquid A) supplied from a nozzle and the carbonate source
(Liquid B) supplied from another nozzle are mixed in an uniform
state at a high speed by the stirring blades, and it is possible to
uniformly mix and react the both liquids in Liquid C in a moment of
time.
[0051] The stirring rate in the double-jet method is preferably 500
rpm to 1,500 rpm from the perspective of uniformizing concentration
distributions of the reaction system, which continuously vary.
--Single-Jet Method--
[0052] In the single-jet method, any one of the metal ion source
and the carbonate source is added on the liquid surface of the
other source or in the other source liquid by spraying to react
them.
[0053] The single-jet method can also be performed using the
above-noted double-jet reactive crystallization apparatus. However,
the single-jet method requires only one nozzle. For example, as
shown in FIG. 2, a carbonate source (Liquid B) sprayed from a
nozzle is added to a metal ion source (Liquid A) in a tank, thereby
the metal ion source can be reacted with the carbonate source just
as in the double-jet method.
[0054] The addition rate of the metal ion source and the carbonate
source, and the stirring rate in the single-jet method are not
particularly limited and may be suitably selected in accordance
with the intended use, however, the addition rate and the stirring
rate in the single-jet method are preferably within the same range
as those in the double-jet method. In the single-jet method, when
the treatment of increasing the number of the carbonate particle
and the treatment of increasing the volume of the carbonate
particle are separately performed, in the course of forming the
final product, the addition rate and the reaction temperature used
in each treatment may also be varied.
--Treatment of Increasing the Number of Carbonate Particle--
[0055] The treatment of increasing the number of the carbonate
particle is not particularly limited and may be suitably selected
in accordance with the intended use as long as the number of a
carbonate particle can be increased after formation of carbonate.
Examples thereof include a method in which any one of a metal ion
source and a carbonate source is added to and mixed with a liquid
of which a reaction temperature is set at a given temperature.
[0056] Examples of the methods using the single-jet method include
a method in which an aqueous solution containing the carbonate
source is added at a given addition rate and then mixed to either
an aqueous solution containing the metal ion source or a suspension
containing the metal ion source while maintaining the aqueous
solution or the suspension at a given reaction temperature.
[0057] The reaction temperature is preferably -10.degree. C. to
40.degree. C., and more preferably 1.degree. C. to 25.degree. C.
When the temperature used in the treatment of increasing the number
of the carbonate particle is less than -10.degree. C., a carbonate
formed in a needle-like shape or a rod-shape cannot be obtained,
and a spherically shaped or an ellipsoid-shaped carbonate may be
yielded. When the temperature is more than 40.degree. C., a
carbonate having a shape of an aspect ratio greater than 2 within a
nanometer size region may not be yielded due to oversized primary
particles.
[0058] The addition rate is not particularly limited and may be
suitably adjusted in accordance with the intended use.
Specifically, the addition rate is preferably 0.01 mL/min to 500
mL/min, and more preferably 0.01 mL/min to 100 mL/min.
--Treatment of Increasing the Volume of Carbonate Particle--
[0059] The treatment of increasing the volume of the carbonate
particle is not particularly limited and may be suitably selected
in accordance with the intended use as long as the volume of the
carbonate particle can be increased without increasing the number
of the carbonate particles. Examples thereof include a method in
which at least any one of a metal ion source and a carbonate source
is added to and mixed with the other source under the condition of
a reaction temperature higher than that used in the treatment of
increasing the number of the carbonate particles and at an addition
rate faster than that used in the treatment of increasing the
number of the carbonate particles. The term "without increasing the
number of the carbonate particle" in the treatment of increasing
the volume of the carbonate particle means that the number of
carbonate particles upon completion of the treatment of increasing
the volume of the carbonate particle is increased not over 40% of
the number of carbonate particles upon completion of the treatment
of increasing the number of the carbonate particle. The number of
carbonate particles upon completion of the treatment of increasing
the volume of the carbonate particle is preferably increased not
over 30%, and more preferably, not over 20% of the number of
carbonate particles upon completion of the treatment of increasing
the number of the carbonate particle.
[0060] Examples of the addition and mixing methods include a method
in which any one of the aqueous solution containing the carbonate
source or a gas containing the carbonate source is added to and
mixed with the metal ion source under the conditions of a reaction
temperature higher than that used in the treatment of increasing
the number of the carbonate particle and an addition rate faster
than that used in the treatment of increasing the number of the
carbonate particle.
[0061] The reaction temperature is preferably 1.degree. C. to
60.degree. C., and more preferably 1.degree. C. to 55.degree. C.
When the reaction temperature is lower than 1.degree. C., handling
of formed particles may be troublesome because a solvent to be used
is subjected to restraints. When the reaction temperature is higher
than 60.degree. C., a solvent other than water may be
evaporated.
[0062] The addition rate is not particularly limited and may be
suitably adjusted in accordance with the intended use as long as it
is faster the addition rate used in the treatment of increasing the
number of the carbonate particle. For example, the addition rate is
preferably 0.1 mL/min to 100 mL/min, and more preferably 0.1 mL/min
to 50 mL/min. When the addition rate is slower than the addition
rate in the treatment of increasing the number of the carbonate
particle, the shape of the obtained aspect ratio may not be
controlled.
--pH--
[0063] The pH of a liquid in which the metal ion source is reacted
with the carbonate source is preferably in an alkali atmosphere in
terms that a needle-like or a rod-like shaped carbonate crystal is
easily obtainable. Specifically, the pH of the liquid is preferably
9 or more, and more preferably 9.5 or more. When the pH of the
liquid is less than 9, the transparency of a resin to which the
carbonate crystal of the present invention is added may be
lowered.
[0064] When the metal ion source contains an OH group, it is
preferable to keep the pH of the liquid from the start of reaction
to the reaction end. When the metal ion source does not contain an
OH group, it is preferred that an agent for forming an alkali
atmosphere such as NaOH is added to a liquid such that the pH of
the liquid is within the above-noted range, and then reaction is
performed.
--Concentration of Metal Ion Source and Carbonate Source in
Reaction--
[0065] The metal ion concentration in the metal ion source and the
carbonic acid ion concentration in the carbonate source used in the
reaction are not particularly limited and may be suitably adjusted
in accordance with the intended use, however, the metal ion
concentration in the metal ion source is preferably 0.05 mol/L or
more, and more preferably 0.10 mol/L or more from the perspective
of reactivity.
--Other Processes--
[0066] When the metal ion source is reacted with the carbonate
source, it is preferable to react them in the presence of an
organic solvent.
[0067] The organic solvent is not particularly limited and may be
suitably selected in accordance with the intended use. Examples of
the organic solvent include methanol, ethanol, 1-propanol,
isopropyl alcohol, 2-aminoethanol, 2-methoxy ethanol, acetone,
tetrahydrofuran, 1,4-dioxane, N,N-dimethylformamide,
N,N-dimethylacetoamide, N-methylpyrrolidone,
1,3-dimethyl-2-imidazolidone, and dimethylsulfoxide. Each of these
may be used alone or in combination of two or more. Of these, the
alcohols are preferably used. From the perspective of reactivity
and easy availability of materials, methanol, ethanol, isopropyl
alcohol, and 2-aminoethanol are more preferably used.
[0068] The content of the solvent is preferably 1% by volume to 80%
by volume, and more preferably 20% by volume to 80% by volume,
relative to an amount of a solvent after the carbonate is
produced.
--Treatment of Removing Adsorbate--
[0069] Before carbonate crystals obtained by reacting the metal ion
source with the carbonate source is dried in a subsequent dry
process, it is preferable to remove adsorbates from surfaces of
carbonate crystal particles. In the process of producing carbonate
crystals, ions derived from the starting materials used in
preparing particles and reaction by-products and the like are
adsorbed on surfaces of the carbonate crystal particles in liquid,
and may often affect interaction between particles, such as changes
in electrostatic repulsive forces, and flocculation of particles in
liquid is inconveniently accelerated. Drying the carbonate crystals
in such a condition only gives rise to flocculated carbonate
particles. As a result, even if the flocculated particles are added
to the resin, the flocculated particles cannot be dispersed, and
thus the flocculated carbonate crystal particles may be sometimes
contained in the resin.
[0070] The method of removing adsorbates is not particularly
limited, and a method of separating and removing unnecessary
components from a particle surface may be suitably selected in
accordance with the intended use. Examples thereof include a method
that includes the steps of adding pure water to the carbonate
crystal particles, sufficiently stirring the mixture, allowing the
mixture to stand, and washing the carbonate crystal particles
washed at least once by decantation; and a method in which a liquid
containing carbonate crystal particles is subjected to
ultrafiltration at least once using a function-separated polymer
membrane. It is preferable to perform at least one of these
methods. The extent of removing the adsorbates can be determined by
measuring the conductivity of a supernatant obtained by decantation
or a filtrate obtained by ultrafiltration. The supernatant or the
filtrate has a conductivity of preferably 100 .mu.S/cm or less, and
more preferably 50 .mu.S/cm or less. When the optical resin
composition is produced using carbonate particles obtained from the
supernatant or the filtrate having a conductivity of greater than
100 .mu.S/cm, foaming may be observed in kneading.
[0071] The function-separated polymer membrane is not particularly
limited and may be suitably selected in accordance with the
intended use. Preferred examples thereof include ion exchange
resins such as strongly basic or weakly basic anionic exchange
resins, strongly acidic or weakly acidic cationic exchange resins,
porous ion exchange resins having a large mesh structure, and
chelate resins. Preferred examples of the function-separated
polymer membrane include reverse osmosis membranes (such as a
cellulose acetate membrane, a cellulose triacetate membrane, a
polypiperazine amide membrane, a all aromatic polyamide membranes,
a polybenzimidazolone membrane, a crosslinked polyether membrane,
an alkylallylpolyamide-polyurea membrane, a polyacrylonitrile
membrane, and a sulfone polysulfone membrane); microfiltration
membranes (such as a acetylcellulose membrane, a polypropylene
membrane, a polyvinyl chloride membrane, a polyvinyl alcohol
membrane, a polyester membrane, a polyamide membrane, and a
polyimide membrane); ultrafiltration membranes (such as a cellulose
membrane, a cellulose/reproduced cellulose membrane, a polyimide
membrane, a polysulfone membrane, a polyamide membrane, a polyvinyl
chloride membrane, a polypropylene membrane, and a polyvinylidene
chloride; a flat membrane, a tube-like membrane, a hollow fiber
membrane, a spiral membrane, and a pleated membrane may be used);
dialysis membranes (a cellulose membrane, an acrylonitrile-based
hollow fiber membrane, an ethylene/vinyl alcohol copolymer hollow
fiber membrane, a polymethyl methacrylate membrane, a hollow fiber
membrane, a polysulfone hollow fiber membrane, a polypropylene
hollow fiber membrane, and a reproduced cellulose membrane); and
ion exchange membranes used in electrodialysis (an inorganic ion
exchange membrane, a sulfonated styrene/divinyl benzene crosslinked
polymer membrane, an aminated chloromethylstyrene/divinyl benzene
crosslinked polymer membrane, a N-methylated vinylpyridine/divinyl
benzene crosslinked polymer membrane, a perfluorocarbon-based
carboxylic acid membrane, and a styrene/butadiene membrane). Of
these function-separated membranes, the ultrafiltration membranes
or the dialysis membranes are more preferable. The molecular mass
cut off of the ultrafiltration membrane or the dialysis membrane
which is preferably used in the present invention is not
particularly limited as long as the effect of the present invention
can be exerted. However, the molecular mass cut off is typically
about 3,000 to 50,000.
[0072] These materials are described in detain in Chapters of 16th
and 17th of "Functional Polymer Materials, Products and Market Ver.
1994" (issued by Tokyo Techno Brain). These products are available
from, as ion exchange resins, Rohm & Haas Japan K.K. (Amber
Light, Duo Light), Dow Chemical Co. (Dow X) etc.; as ion exchange
films, Asahi Kasei Corporation (Asiplex), Asahi Glass Co.
(Celemion), Tokuyama Sotatsu K.K. (Neocepta), DUPONT (Nafion) etc.;
as microfiltration membranes, FUJIFILM Corporation (Microfilter)
etc.; as ultrafiltration membranes, Asahi Kasei Corporation
(Microza UF Lab module), KURARAY Co. Ltd. (MU), DAICEL CHEMICAL
INDUSTRIES, LTD. (MOLSEP) etc.; as reverse osmasis membranes, Toray
Industries, Inc. (PEC-1000), DNV Japan (NTR7250), DUPONT (B9, and
B10) etc.: and as dialysis membranes, Sanko Junyaku Co. (dialysis
membranes, cellulose tubes, manufactured by VISKASE).
--Dry Treatment--
[0073] The carbonate crystal that has been subjected to the
treatment of removing an adsorbate is preferably subjected to a dry
treatment.
[0074] The method for drying the carbonate crystal is not
particularly limited and may be suitably selected. Examples thereof
include a filtration.
--Application--
[0075] According to the process of producing a carbonate crystal, a
carbonate having a predetermined specific surface area, an
orientation birefringence, and a large aspect ratio can be
efficiently and simply formed without having flocculation of
particles because the adsorbate on particle surfaces have been
removed.
--Process of Dispersing Carbonate Crystal--
[0076] A process of dispersing a carbonate crystal includes a
treatment of dispersing the carbonate crystal of the present
invention in the resin and further includes other treatments
suitably selected in accordance with the intended use.
[0077] A method for dispersing a carbonate crystal in the resin is
not particularly limited and may be suitably selected in accordance
with the intended use as long as the objects of the present
invention can be achieved. For example, the carbonate crystals may
be dispersed into the resin by kneading the carbonate crystals with
the resin, or when the resin is subjected to a polycondensation
reaction so as to synthesize the resin, the carbonate crystal may
be added and dispersed into the resin before completion of the
polycondensation reaction. The temperature at which the carbonate
crystal particles are dispersed in the resin by kneading depends on
the resin to be used. When the resin mainly contains polycarbonate,
the dispersion temperature is preferably 200.degree. C. to
290.degree. C., and more preferably 220.degree. C. to 280.degree.
C. When the dispersion temperature is less than 200.degree. C., the
carbonate may not be mixed with the resin. When the dispersion
temperature is more than 290.degree. C., the physical properties of
the resin may be greatly changed.
[0078] A method for molding a resin composition in which carbonate
crystals are dispersed is not particularly limited and may be
suitably selected in accordance with the intended use. Examples
thereof include an injection molding, press molding and extrusion
molding. These molding methods may be used alone or in combination
of two or more. The form of the obtained molded article is not
particularly limited and may be suitably selected in accordance
with the intended use. Examples thereof include a plane shape such
as a sheet shape and film shape, an indeterminate form of solid
such as a columnar shape, and a block shape.
[0079] The temperature for the injection molding depends on a resin
to be used. When a resin mainly contains polycarbonate, the
temperature of the injection molding is preferably 150.degree. C.
to 270.degree. C., more preferably 150.degree. C. to 240.degree. C.
When the temperature of the injection molding is less than
150.degree. C., or more than 270.degree. C., a desired molded
article may not be obtained.
[0080] The temperature and pressure for the press molding are
preferably 150.degree. C. to 240.degree. C. and 15 MPa to 45 MPa,
more preferably 160.degree. C. to 230.degree. C. and 10 MPa to 40
MPa, respectively. When the molding temperature is less than
150.degree. C., a desired film thickness cannot be obtained by the
press molding. When the temperature is more than 240.degree. C., a
film-shaped may not be obtained. When the molding pressure is less
than 10 MPa, a desired film thickness may not be obtained by the
press molding. When the pressure is more than 40 Mpa, the resin
composition may not be adjusted to a desired film thickness,
however, it also depends on a spacer for adjusting a film
thickness.
[0081] Alternatively, a sheet may be produced by means of the
injection molding at low cost, in which molded bodies can be
obtained continuously by injecting the resin composition without a
mold. The temperature of the injection molding is preferably
220.degree. C. to 280.degree. C., and more preferably 230.degree.
C. to 270.degree. C. When the temperature of the injection molding
is less than 220.degree. C., the resin may be stabilized and not be
injected. When the temperature of the injection molding is more
than 280.degree. C., a film surface may not be satisfactorily
obtained.
[0082] A method for aligning molecules in a molded sheet is not
particularly limited and may be suitably selected in accordance
with the intended use as long as the objects of the present
invention can be achieved. Examples there of include a uniaxial
drawing method and biaxial drawing method. The biaxial drawing
method can longitudinally and laterally draw the molded sheet in
sequence or at the same time. The molded sheet may be drawn after
it has been cut in a predetermined size; alternatively, the molded
sheet may be molded and then sent to a drawing device for
drawing.
[0083] A film of the optical resin composition can be obtained by
drawing a 100 .mu.m-thick sheet, which is drawn to 2 times the
original size by the injection molding or press molding, at
165.degree. C. and at a speed of 3 mm/min by a biaxial drawing
device. Alternatively, a sheet obtained by the injection molding
can be consecutively drawn to 2 times the original size at
165.degree. C. and at a speed of 3 mm/min by a biaxial drawing
device.
EXAMPLES
[0084] Hereinafter, Examples of the present invention will be
explained, but the present invention is not limited thereto.
Example 1
Production of Carbonate Crystal
[0085] As shown in FIG. 2, carbonate was produced by means of the
single-jet method.
--Treatment of Increasing the Number of Carbonate Particle--
[0086] 375 mL (75 ml of water, 300 ml of methanol) of a 0.08 mol/L
strontium hydroxide [Sr(OH).sub.2] suspension which had been
prepared from strontium hydroxide octahydrate as a metallic ion
source in a stainless-steel pot was taken as Liquid A. While, 500
mL of a 0.2 mol/L ammonium carbonate [(NH.sub.4).sub.2CO.sub.3]
aqueous solution as a carbonate source was taken as Liquid. B,
Liquid B was then poured into two feed tanks separately, and the
temperature was maintained at 10.degree. C. While stirring Liquid A
at 1,000 rpm with the temperature maintained at 10.degree. C., 62.5
mL of Liquid B in each of the two feed tanks was respectively added
to Liquid A in the stainless-steel pot at an addition rate of 0.5
mL/min and then mixed.
--Treatment of Increasing the Volume of Carbonate Particle--
[0087] Next, 250 mL of a 0.1 mol/L strontium hydroxide
[Sr(OH).sub.2] suspension
[0088] (Liquid A) was poured into the mixture of Liquid A and
Liquid B while stirring Liquid A at 1,000 rpm with the temperature
raised to 50.degree. C., and then 250 mL of a 0.1 mol/L ammonium
carbonate [(NH.sub.4).sub.2CO.sub.3] aqueous solution was slowly
added thereto at an addition rate of 1 mL/min.
--Treatment of Removing Adsorbate--
[0089] A cycle of adding 1 liter of pure water to the mixed liquid,
allowing the mixture to stand, and removing the water by
decantation was repeated until the supernatant had a conductivity
of 52 .mu.S/cm.
[0090] To the liquid, PLENACT KR44, manufactured by Ajinomoto
Fine-Techno Co., Ltd., was added to a concentration of 3% by mass
relative to a generated sediment, and was sufficiently stirred for
surface treatment.
--Drying Process--
[0091] Finally, the obtained sediment in the liquid was subjected
to suction filtration using a Buchner funnel, and a cake was dried
at 150.degree. C. for 2 hours to obtain a white dry powder.
--Evaluation of Carbonate--
[0092] The dried powder was measured using an X-ray diffractometer,
and the measurement result showed that the powder was comprised of
strontium carbonate crystals. Further, the strontium carbonate
crystals were observed using a transmission electron microscope
(TEM). From a TEM picture of particles, a particle size, aspect
ratio, variation coefficient obtained from Formula (1) were found.
The variation coefficient was obtained by measuring each of the
particles in an image file using image analysis type of particle
distribution measuring software "Mac-View" Ver. 3 (manufactured by
MOUNTECH Co., Ltd.) and counting the measured values. The specific
surface area was measured using an automatic specific surface
area/micropore distribution analyzer (BELSORP-mini, manufactured by
BEL JAPAN Inc.). The strontium carbonate crystals were heated at
200.degree. C. for pretreatment. The results are shown in Table
3.
--Process of Dispersing Carbonate Crystal and Evaluation of Optical
Resin Composition--
[0093] The obtained carbonate particles and polycarbonate resins
were kneaded at 220.degree. C. by a small kneader, so that the
content of the carbonate particles was 1% by mass relative to the
resin, thereby obtained a composite resin in a form of a pellet.
The resin was injection molded at 220.degree. C., and a sheet
having a thickness of 100 .mu.m was produced by press molding at
220.degree. C./30 MPa as an optical resin composition. At this
step, the light transmittance of the composition was measured and
its dispersibility was evaluated by SEM. Moreover, the 100
.mu.m-thick sheet was cut out in a size of 55 mm.times.30 mm, and
was uniaxially drawn to 1.5 times the original size at 165.degree.
C. and at a speed of 3 mm/min by a biaxial drawing device by Imoto
seisakusho to obtain an optical resin composition having a
thickness of 68 .mu.m. The results are shown in Table 3.
Example 2
[0094] A treatment of increasing the number of carbonate particles
was conducted as in Example 1 except that 375 mL of the suspension
of Liquid A (50 ml of water, 325 ml of methanol) was maintained at
5.degree. C., and Liquid B was added at an addition rate of 0.3
mL/min.
[0095] A treatment of increasing the volume of carbonate particles
was conducted as in Example 1 except that 250 mL of an ammonium
carbonate [(NH.sub.4).sub.2CO.sub.3] aqueous solution was added at
an addition rate of 0.5 mL/min.
[0096] A treatment of removing adsorbates from particle surfaces
was conducted by subjecting the mixed liquid to ultrafiltration by
means of Microza UF Lab module (by Asahi Kasei Chemicals) made of
polysulfone and having a molecular mass cut off of 6,000 until a
filtrate had a conductivity of 28.6 .mu.S/cm.
[0097] Finally, a cake was dried at 150.degree. C. for 2 hours to
obtain a white dry powder. The obtained carbonate crystal and
optical resin composition were evaluated in the same manner as in
Example 1. The results are shown in Table 3.
Example 3
[0098] A treatment of increasing the number of carbonate particles
was conducted as in Example 2 except that Liquid B was added at an
addition rate of 0.4 mL/min.
[0099] A treatment of increasing the volume of carbonate particles
was conducted as in Example 2 except that 250 mL of an ammonium
carbonate [(NH.sub.4).sub.2CO.sub.3] aqueous solution was added at
an addition rate of 0.7 mL/min.
[0100] The adsorbates on particle surfaces were removed by
subjecting the mixed liquid to ultrafiltration until a filtrate had
a conductivity of 27.2 .mu.S/cm.
[0101] Finally, a cake was dried at 150.degree. C. for 2 hours to
obtain a white dry powder. The obtained carbonate crystal and
optical resin composition were evaluated in the same manner as in
Example 1. The results are shown in Table 3.
Example 4
[0102] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 3 except that a calcium
hydroxide suspension was used instead of the strontium hydroxide
suspension of Liquid A in Example 3. The results are shown in Table
3.
Example 5
[0103] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 3 except that a barium
hydroxide suspension was used instead of the strontium hydroxide
suspension of Liquid A in Example 3. The results are shown in Table
3.
Example 6
[0104] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 3 except that a zinc
hydroxide suspension was used instead of the strontium hydroxide
suspension of Liquid A in Example 3. The results are shown in Table
3.
Example 7
[0105] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 3, except that a lead
hydroxide suspension was used instead of the strontium hydroxide
suspension of Liquid A in Example 3. The results are shown in Table
3.
Example 8
[0106] A treatment of increasing the number of carbonate particles
was conducted as in Example 1 except that 375 mL of the suspension
of Liquid A (50 ml of water, 325 ml of methanol) was maintained at
3.degree. C. and, that Liquid B was added at an addition rate of
0.1 mL/min.
[0107] A treatment of increasing the volume of carbonate particles
was conducted as in Example 1 except that the temperature was
raised to 45.degree. C. and that 250 mL of an ammonium carbonate
[(NH.sub.4).sub.2CO.sub.3] aqueous solution was added at an
addition rate of 0.4 mL/min.
[0108] The adsorbates on particle surfaces were removed by
subjecting the mixed liquid to decantation continuously until a
filtrate had a conductivity of 28.6 .mu.S/cm.
[0109] Finally, a cake was dried at 150.degree. C. for 2 hours to
obtain a white dry powder. The obtained carbonate crystal and
optical resin composition were evaluated in the same manner as in
Example 1. The results are shown in Table 3.
Example 9
[0110] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 8 except that the
temperature of the treatment of increasing the number of the
carbonate particle was changed to 5.degree. C. The results are
shown in Table 3.
Example 10
[0111] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 9 except that the
temperature of increasing the volume of the carbonate particle was
changed to 47.degree. C. The results are shown in Table 3.
Comparative Example 1
[0112] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 1 except that the
content of the obtained carbonate particles was changed to 17% by
mass relative to resin in Example 1.
Comparative Example 2
[0113] The carbonate crystal and optical resin composition were
evaluated in the same manner as in Example 1 except that
decantation was not performed and the obtained sediment in the
liquid was subjected to suction filtration using a Buchner funnel
in Example 1. A filtrate had a conductivity of 9,735 .mu.S/cm. The
results are shown in Table 3.
Comparative Example 3
[0114] 250 mL (250 ml of water) of a 0.05 mold, strontium hydroxide
[Sr(OH).sub.2] suspension which had been prepared from strontium
hydroxide octahydrate as a metallic ion source in a stainless-steel
pot was taken as Liquid A, and a 4.00 g of sodium hydroxide
granulated powder was dissolved in Liquid A. While 500 mL of a 4
mol/L urea [(NH.sub.2).sub.2CO] aqueous solution was taken as
Liquid B. While stirring Liquid A at 1,000 rpm with a temperature
raised and maintained at 90.degree. C., 500 mL of Liquid B was
poured into one feed tank and added to Liquid A in the
stainless-steel pot at an addition rate of 250 mL/min and then
mixed. A cycle of adding 1 liter of pure water to the mixed liquid,
allowing the mixture to stand, and removing the water by
decantation was repeated until a supernatant having a conductivity
of 84 .mu.S/cm was obtained. Finally, a cake was dried at
150.degree. C. for 2 hours to obtain a white dry powder.
[0115] The obtained carbonate crystal and optical resin composition
were evaluated in the same manner as in Example 1. The results are
shown in Table 3.
Comparative Example 4
[0116] Only a polycarbonate resin was kneaded at 220.degree. C. by
a small kneader to obtain a resin in a form of pellet. The resin
was injection molded at 220.degree. C., and a sheet having a
thickness of 100 .mu.m was prepared by press molding at 220.degree.
C./30 MPa as an optical resin composition. At this step, the light
transmittance of the composition was measured. A 100 .mu.m-thick
sheet was cut out in a size of 55 mm.times.30 mm, and was
uniaxially drawn to 1.5 times the original size at 165.degree. C.
and at a speed of 3 mm/min by a biaxial drawing device by Imoto
seisakusho to obtain an optical resin composition having a
thickness of 68 .mu.m. The results are shown in Table 3.
TABLE-US-00003 TABLE 3 Average of Variation specific surface Aspect
maximum coefficient Added area *1) ratio major axis represented by
Composition amount [m.sup.2/g] [--] lengths [nm] Formula (1) [%] of
particles [%] Ex. 1 11 4.2 395 31 SrCO.sub.3 1 Ex. 2 15 4 267 38
SrCO.sub.3 1 Ex. 3 4 3.8 315 35 SrCO.sub.3 1 Ex. 4 4 3.4 363 40
CaCO.sub.3 1 Ex. 5 6 4.8 343 32 BaCO.sub.3 1 Ex. 6 8 4.4 345 28
ZnCO.sub.3 1 Ex. 7 10 3.9 334 33 PbCO.sub.3 1 Ex. 8 4 4 150 30
SrCO.sub.3 1 Ex. 9 4 4.4 300 25 SrCO.sub.3 1 Ex. 10 4 4.1 350 15
SrCO.sub.3 1 Comp. Ex. 1 11 4.2 395 31 SrCO.sub.3 17 Comp. Ex. 2 11
3.7 415 45 SrCO.sub.3 1 Comp. Ex. 3 3.5 23.5 27000 23 SrCO.sub.3 1
Comp. Ex. 4 -- -- -- -- -- 0 Light Average transmit- dispersion
Birefringence tance *2) diameter Dispersion Conductivity index *4)
Form [%] [nm] Condition *3) [.mu.S/cm] [--] Ex. 1 film 88.2 450 A
52 1 .times. 10.sup.-4 Ex. 2 film 89.4 387 A 28.6 1 .times.
10.sup.-4 Ex. 3 film 86.5 410 A 27.2 3 .times. 10.sup.-4 Ex. 4 film
86.9 436 A 43 6 .times. 10.sup.-4 Ex. 5 film 88 420 A 56 5 .times.
10.sup.-4 Ex. 6 film 87.8 487 A 42 2 .times. 10.sup.-4 Ex. 7 film
88.1 431 A 50 4 .times. 10.sup.-4 Ex. 8 film 89 290 A 26.7 4
.times. 10.sup.-5 Ex. 9 film 88 438 A 45 8 .times. 10.sup.-5 Ex. 10
film 88.2 473 A 50 1 .times. 10.sup.-4 Comp. Ex. 1 film 43.8 1248 C
52 Not measured Comp. Ex. 2 film 72.1 1912 C 9,735 Not measured
Comp. Ex. 3 film 35.4 34.1 A 84 4 .times. 10.sup.-4 Comp. Ex. 4
film 91.3 -- -- -- 1 .times. 10.sup.-3 *1) Values for dry power
before mixed with resin. *2) Values for light transmittance at a
wavelength of 450 nm in a sheet standardized to 100 .mu.m-thick.
*3) The dispersion condition was evaluated by SEM observation. A:
Excellent dispersion, B: Some amount of flocculation existed, C:
Severe flocculation *4) Values of birefringence obtained by
measuring a retardation at a wavelength 550 .+-. 5 nm by Automatic
Birefringence Analyzer (KOBRA-21ADH, manufactured by Oji Scientific
Instruments Co., Ltd.), and then dividing with a film
thickness.
[0117] From the results of Table 3, it is understood that the
optical resin compositions of Examples 1 and 2 in which dispersed
carbonate crystals are contained have high light transmittance at a
wavelength of 450 nm compared to Comparative Examples 1 to 3, and
that birefringence index can be changed in contrast to Comparative
Examples 1 to 3.
Example 11
[0118] A polyethylene terephthalate resin composition containing a
strontium carbonate crystal was obtained by adding 1% by mass of
the strontium carbonate crystal prepared in Example 1 in a
polycondensation reaction of terephthalic acid and ethylene glycol.
The transmittance and birefringence after the drawing process for
each of the obtained polyethylene terephthalate resin compositions
were measured in the same manner as in Example 1, and it was
confirmed that those are comparable with those measured in Example
1.
[0119] It was also confirmed that similar effects were obtained
with polyethylene naphthalate resin compositions and
triacetylcellulose resin compositions.
[0120] An optical resin composition containing the carbonate
crystal of the present invention is able to negate the
birefringence without sacrificing light transmittance; therefore,
it may be preferably used as a resin material that constitutes an
optical component, particularly optical elements with which
birefringent properties is important and high precision is
required.
[0121] A method for producing an optical resin composition
according to the present invention may easily and efficiently
produce a carbonate crystal having a predetermined specific surface
area, an oriented birefringence and high aspect ratio without
having flocculation of particles because adsorbates on particle
surfaces have been removed, and may be suitably used to produce an
optical resin composition of the present invention.
* * * * *