U.S. patent number 10,385,145 [Application Number 16/281,143] was granted by the patent office on 2019-08-20 for liquid photo initiating compound and uses of the same.
This patent grant is currently assigned to CHITEC TECHNOLOGY CO., LTD.. The grantee listed for this patent is CHITEC TECHNOLOGY CO., LTD.. Invention is credited to Wei-Chun Chang, Chingfan Chris Chiu, Huang-Min Wu.
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United States Patent |
10,385,145 |
Chang , et al. |
August 20, 2019 |
Liquid photo initiating compound and uses of the same
Abstract
A liquid photo initiating compound and uses of the same are
provided. The compound is represented by the following Formula I:
##STR00001## in Formula I, R.sub.1 and R.sub.2 are independently H
or C.sub.1-C.sub.3 alkyl, and R.sub.3 is H or methyl.
Inventors: |
Chang; Wei-Chun (Taipei,
TW), Chiu; Chingfan Chris (Taipei, TW), Wu;
Huang-Min (Taipei, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
CHITEC TECHNOLOGY CO., LTD. |
Taipei |
N/A |
TW |
|
|
Assignee: |
CHITEC TECHNOLOGY CO., LTD.
(Taipei, TW)
|
Family
ID: |
66182336 |
Appl.
No.: |
16/281,143 |
Filed: |
February 21, 2019 |
Foreign Application Priority Data
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Jul 17, 2018 [TW] |
|
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107124654 A |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F
2/48 (20130101); C08F 2/50 (20130101); C08F
20/18 (20130101); C08K 5/5397 (20130101); C08K
5/08 (20130101); C08K 5/353 (20130101); C08K
5/06 (20130101); G03F 7/031 (20130101) |
Current International
Class: |
C08F
2/46 (20060101); C08K 5/06 (20060101); C08G
61/04 (20060101); C08F 2/50 (20060101); C08K
5/08 (20060101); C08F 20/18 (20060101); C08K
5/353 (20060101); C08K 5/5397 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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I277834 |
|
Apr 2007 |
|
TW |
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I564276 |
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Jan 2017 |
|
TW |
|
Primary Examiner: Whiteley; Jessica
Attorney, Agent or Firm: McClure, Qualey & Rodack,
LLP
Claims
What is claimed is:
1. A liquid photo initiating compound, which is represented by the
following Formula I: ##STR00015## wherein, in Formula I, R.sub.1
and R.sub.2 are independently H or C.sub.1-C.sub.3 alkyl, and
R.sub.3 is H or methyl.
2. The compound of claim 1, wherein R.sub.1 and R.sub.2 are
independently methyl, ethyl, n-propyl or isopropyl.
3. The compound of claim 2, which is represented by the following
Formula Ia: ##STR00016##
4. A method of initiating a chemical reaction by using the liquid
photo initiating compound of claim 1.
5. The method of claim 4, wherein, in Formula I, R.sub.1 and
R.sub.2 are independently methyl, ethyl, n-propyl or isopropyl.
6. The method of claim 5, wherein the liquid photo initiating
compound is represented by the following Formula Ia:
##STR00017##
7. A photopolymerizable composition, comprising: a first
photoinitiator, which is the liquid photo initiating compound of
claim 1; a photopolymerizable component; and an optional
solvent.
8. The photopolymerizable composition of claim 7, wherein, in
Formula I, R.sub.1 and R.sub.2 are independently methyl, ethyl,
n-propyl or isopropyl.
9. The photopolymerizable composition of claim 8, wherein the
liquid photo initiating compound is represented by the following
Formula Ia: ##STR00018##
10. The photopolymerizable composition of claim 7, wherein the
photopolymerizable component is an olefinic unsaturated monomer, an
olefinic unsaturated oligomer, or a combination thereof.
11. The photopolymerizable composition of claim 10, wherein the
photopolymerizable component is an acrylate-based monomer, an
acrylate-based oligomer, or a combination thereof.
12. The photopolymerizable composition of claim 7, further
comprising a second photoinitiator selected from the group
consisting of acylphosphine oxides, 9,10-dialkyloxyanthracene, and
combinations thereof.
13. The photopolymerizable composition of claim 7, further
comprising a photosensitizer selected from the group consisting of
benzophenones, thioxanthones, Michler's ketones, anthraquinone, and
combinations thereof.
14. The photopolymerizable composition of claim 7, further
comprising an additive selected from the group consisting of
pigments, amine synergists, and combinations thereof.
15. The photopolymerizable composition of claim 7, wherein the
content of the first photoinitiator ranges from 0.1 wt % to 15 wt %
based on the total weight of the photopolymerizable composition.
Description
CLAIM FOR PRIORITY
This application claims the benefit of Taiwan Patent Application
No. 107124654 filed on Jul. 17, 2018, the subject matters of which
are incorporated herein in their entirety by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a liquid photo initiating compound
and photopolymerizable compositions using the same.
Descriptions of the Related Art
A photoinitiator is a substance that forms free radicals via
Norrish Type I photo-fragmentation after absorbing the energy of
visible or UV light, which can initiate polymerization of monomers
or oligomers to provide a curing effect.
In 1990, Ciba Specialty Corporation introduced Irgacure.RTM. 369,
which is the first photoinitiator specifically designed for dark
color UV ink (related patent: U.S. Pat. No. 5,077,402).
Irgacure.RTM. 369 is in solid form and its structure is shown
below.
##STR00002##
Irgacure.RTM. 369 has an outstanding photo speed and other
advantages like odorless prior to and after curing. However, it
suffers from poor solubility in most UV inks and thus requires
additional grinding and heating processes to facilitate
dissolution. Even though, Irgacure.RTM. 369 is prone to precipitate
when dosage is over 4 wt % and when handled in cold areas.
Irgacure.RTM. 369 has recently been shown to have reproductive
toxicity and thus is under radar in EU to be prohibited from use in
food contact applications.
In order to improve the solubility issue, Ciba Specialty
Corporation introduced another solid photoinitiator product, i.e.,
Irgacure.RTM. 379 (related patent: U.S. Pat. No. 7,247,659 B2).
Irgacure.RTM. 379 does have improved solubility in some monomers
and resins than Irgacure.RTM. 369. Still, it is not easy to use in
its solid form that requires grinding and heating processes in
order to dissolve into an ink composition. Furthermore,
Irgacure.RTM. 379 also has reproductive toxicity.
##STR00003##
In recent years, the demand for low viscosity UV inks such as
digital UV and flexo UV inks has increased significantly. A
photoinitiator in liquid form with high solubility is therefore
highly desired to the low viscosity ink as these inks do not
provide sufficient shearing force to perform the grinding and
dispersion processes for solid photoinitiators.
Examples of liquid photoinitiators include the following compounds
93, 95, 96 and 100 as disclosed in U.S. Pat. No. 5,077,402. But
these compounds are not commercialized because their poor
photospeeds as well as odor issues.
##STR00004##
TW 1277834 discloses a liquid photoinitiator in Example 3. Even
though the liquid photoinitiator is odorless, it is not
commercialized due to its poor photo speed which is about one tenth
that of Irgacure.RTM. 369.
Example 3 of TW 1277834
##STR00005##
The following compound I is also a liquid photoinitiator and has a
photo speed comparable to that of Irgacure.RTM. 369. Unfortunately,
the compound I has a serious odor issue after curing.
##STR00006##
TW 1564276 also discloses a liquid photoinitiator, i.e., the
following compound IIa, which is comparable to Irgacure.RTM. 369 in
terms of photo speed and is odorless prior to or after curing.
However, the compound IIa has high acute oral toxicity. Besides, it
is in dark-brown color which is not satisfactory for some
colors.
##STR00007##
Therefore, conventional liquid photoinitiators with individual
defects for dark and black inks are far from satisfactory.
SUMMARY OF THE INVENTION
In view of the unsatisfaction of conventional photoinitiators, the
present invention provides a photoinitiator derived from
oxazolidine, which improves all the aforementioned defects
associated conventional liquid photoinitiators for the black ink
system as: (1) it becomes a liquid state at 50.degree. C.; (2) it
has a photo speed comparable to that of Irgacure.RTM. 369; (3) it
is odorless prior to and after curing; and (4) it does not have
acute oral toxicity. Furthermore, its light color and high purity
perfectly meet the requirements of the industry regarding liquid
photoinitiators. Accordingly, the present invention involves at
least the objectives described below.
It should be noted that neither U.S. Pat. No. 5,077,402 nor U.S.
Pat. No. 7,732,504 B2 discloses the photoinitiator of the present
invention, even though the photoinitiators disclosed in these
patents may have an oxazolidine structure. Furthermore, persons
having ordinary skill in the art cannot expect the advantages of
the photoinitiator of the present invention based on the general
teaching of U.S. Pat. Nos. 5,077,402 or 7,732,504 B2. The
advantages include being liquid at a low temperature of 50.degree.
C., high solubility in various monomers and oligomers, odorless,
comparable photo speed to Irgacure.RTM. 369, and no acute oral
toxicity.
An objective of the present invention is to provide a liquid photo
initiating compound, which is represented by the following Formula
.quadrature.:
##STR00008## wherein, in Formula I, R.sub.1 and R.sub.2 are
independently H or C.sub.1-C.sub.3 alkyl, and R.sub.3 is H or
methyl. Examples of C.sub.1-C.sub.3 alkyl include methyl, ethyl,
n-propyl and isopropyl.
In some embodiments of the present invention, the aforementioned
compound is represented by the following Formula Ia:
##STR00009##
Another objective of the present invention is to provide a method
of initiating a chemical reaction by using the aforementioned
liquid photo initiating compound.
Yet another objective of the present invention is to provide a
photopolymerizable composition, comprising:
a first photoinitiator, which is the aforementioned liquid photo
initiating compound;
a photopolymerizable component; and
an optional solvent.
In some embodiments of the present invention, the
photopolymerizable component is an olefinic unsaturated monomer, an
olefinic unsaturated oligomer, or a combination thereof. Examples
of the olefinic unsaturated monomer include acrylate-based
monomers. Examples of the olefinic unsaturated oligomer include
acrylate-based oligomers.
In some embodiments of the present invention, the
photopolymerizable composition further comprises a second
photoinitiator selected from the group consisting of acylphosphine
oxides, 9,10-dialkyloxyanthracene
##STR00010## wherein R is alkyl), and combinations thereof.
In some embodiments of the present invention, the
photopolymerizable composition further comprises a photosensitizer
selected from the group consisting of benzophenones, thioxanthones,
Michler's ketones, anthraquinone, and combinations thereof.
In some embodiments of the present invention, the
photopolymerizable composition further comprises an additive
selected from the group consisting of pigments, amine synergists,
and combinations thereof.
In some embodiments of the present invention, the content of the
first photoinitiator ranges from 0.1 wt % to 15 wt % based on the
total weight of the photopolymerizable composition.
To render the above objectives, technical features and advantages
of the present invention more apparent, the present invention will
be described in detail with reference to some embodiments
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Not applicable.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinafter, some specific embodiments of the present invention
will be described in detail. However, without departing from the
spirit of the present invention, the present invention may be
embodied in various embodiments and should not be limited to the
specific embodiments described in the specification.
Unless it is additionally explained, the expressions "a,", "an",
"the," or the like recited in the specification (especially in the
claims) should include both the singular and the plural forms.
Unless it is additionally explained, the term such as "first",
"second" or the like is used to distinguish different elements or
components, not terms supplying a numerical limit.
Unless it is additionally explained, the term "alkyl" recited in
the specification (especially in the claims) includes linear,
branched and/or cyclic alkyl groups.
Liquid Photo Initiating Compound
The liquid photo initiating compound of the present invention is
represented by the following Formula .quadrature.:
##STR00011##
In formula I, R.sub.1 and R.sub.2 are independently H or
C.sub.1-C.sub.3 alkyl, and R.sub.3 is H or methyl. In some
embodiments of the present invention, R.sub.1 and R.sub.2 are
independently methyl, ethyl, n-propyl or isopropyl, and R.sub.3 is
H. In the appended examples, the first photoinitiator is
represented by the following Formula Ia:
##STR00012##
The synthesis of the liquid photo initiating compound of the
present invention will be described in the appended examples.
Uses of Liquid Photo Initiating Compound
The liquid photo initiating compound of the present invention is
liquid at a low temperature of 50.degree. C. Therefore, it can be
used as a liquid photoinitiator to trigger polymerization and
crosslinking of photopolymerizable monomers or oligomers and thus,
provide a curing effect. The liquid photo initiating compound of
the present invention surprisingly shows properties quite different
from conventional photoinitiators and has many advantages.
Specifically, the liquid photo initiating compound of the present
invention has excellent photo speed performance, excellent
solubility and light color and is in liquid state at a low
temperature of 50.degree. C. When used in a photopolymerizable
system, the influence of the liquid photo initiating compound of
the present invention on viscosity is very minor. The liquid photo
initiating compound of the present invention also has long storage
stability. Therefore, the liquid photo initiating compound of the
present invention is particularly useful for low viscosity UV inks
(e.g., an ink with a viscosity of less than 1000 cP), light color
UV inks, color resists, black matrixes and solder masks.
Furthermore, the liquid photo initiating compound of the invention
has high purity that can meet the chemical substance registration
regulations of nations of the world.
Accordingly, the present invention also provides a
photopolymerizable composition, comprising a first photoinitiator,
a photopolymerizable component and an optional solvent, wherein the
first photoinitiator is the compound represented by Formula I.
The species of the photopolymerizable component is not particularly
limited and can be any substance that is photopolymerizable in the
presence of a photoinitiator, including the substance that is
generally used in photopolymerizable systems, like UV inks. In some
embodiments of the present invention, the photopolymerizable
component is selected from the group consisting of olefinic
unsaturated monomers, olefinic unsaturated oligomers and
combinations thereof. Examples of the olefinic unsaturated monomer
include but are not limited to acrylate-based monomers, and
examples of the olefinic unsaturated oligomer include but are not
limited to acrylate-based oligomers.
The solvent is optional and can be any solvent that dissolves or
disperses the components of the composition but does not react with
the components, including those generally used in
photopolymerizable systems such as UV inks. Examples of the solvent
include but are not limited to water; aliphatic hydrocarbons, such
as dichloromethane, trichloromethane, tetrachloromethane, n-hexane,
and cyclohexane; aromatic hydrocarbons, such as toluene, benzene,
and xylene; ketones, such as acetone, methyl ethyl ketone, isobutyl
ketone and cyclohexanone; esters, such as ethyl acetate and butyl
acetate; alcohols, such as methanol, ethanol, n-propanol and
isopropanol; and ethers, such as dimethylether, diethylether, and
methylethylether.
In the photopolymerizable composition of the present invention, the
amount of the first photoinitiator is not particularly limited and
can be optionally adjusted by persons having ordinary skill in the
art. To obtain a better photocuring efficacy, the amount of the
photoinitiator is usually from 0.1 wt % to 15 wt %, such as 1 wt %,
2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, or 9 wt %,
based on the total weight of the photopolymerizable composition.
However, the present invention is not limited thereto.
In addition to the first photoinitiator, the photopolymerizable
composition of the present invention can optionally further include
other components that are advantageous to the efficacy of
photoinitiation, like photosensitizing components or other photo
initiating components. Therefore, in some embodiments of the
present invention, the photopolymerizable composition further
comprises a second photoinitiator, a photosensitizer, or a
combination thereof.
The second photoinitiator can be any photo initiating component
other than the first photoinitiator. Examples of the second
photoinitiator include but are not limited to acylphosphine oxides,
9,10-dialkyloxyanthracene, and combinations thereof. The species of
the photosensitizer is not particularly limited. Examples of the
photosensitizer include but are not limited to benzophenones,
thioxanthones, Michler's ketones, anthraquinone, and combinations
thereof. In the appended examples, 2,4-diethylthioxanthone (product
name: Chivacure.RTM. DETX) is used as a second photosensitizer in
the photopolymerizable composition. The amount of the second
photoinitiator or the photosensitizer is not particularly limited
and can be optionally adjusted by persons having ordinary skill in
the art depending on the need.
The photopolymerizable composition of the present invention may
optionally further comprise one or more additives to impart desired
properties to the cured product of the composition. For example, a
pigment can be added to provide color to the cured product, and an
amine synergist can be added to improve curing performance, for
example, to improve the surface curing speed of composition and to
enhance the mirror surface effect after curing. Examples of the
pigment include titanium oxide, carbon black, cadmium red,
molybdate red, chrome yellow, cadmium yellow, titanium yellow,
chromium oxide, cobalt titanate green, cerulean blue, copper blue,
azo pigments, phthalocyanine pigments, quinacridone based pigments,
isoindolinone based pigments, perylene based pigments, thio indigo
based pigments, and metal complex pigments. As used herein, an
amine synergist is well-known to persons having ordinary skill in
the art and refers to a reactive amine that can promote the
photoinitiation, such as a low-molecular weight tertiary amine.
Examples of the amine synergist include but are not limited to
methyldiethanolamine, dibutylethanolamine, triethylamine and
triethanolamine. Commercially available products of the amine
synergist include Chivacure.RTM. 115, Chivacure.RTM. EPD,
Chivacure.RTM. OPD, etc. available from Chitec Technology Co.,
Ltd.
The present invention is further illustrated by the following
embodiments.
EXAMPLES
Example 1: Preparation of Liquid Photo Initiating Compound
Represented by Formula Ia
34 g
2-(dimethylamino)-1-[4-[(2-hydroxyethyl)amino]phenyl]-2-(phenylmethy-
l)-1-butanone (CAS 862589-48-8); the synthesis method of it may
refer to TW 1277834), 13.0 g 2,2-dimethoxybutane (CAS 3453-99-4),
0.17 g PTSA (p-toluenesulfonic acid), and 100 mL toluene were added
in sequence to a 250 mL three-necked flask at room temperature and
then the reaction as shown below was carried out at reflux. The
by-product methanol produced by this reaction was removed by
Dean-Stark evaporator.
##STR00013##
The reaction was monitored by High Performance Liquid
Chromatography (HPLC). After the reaction was completed, the
reaction product was cooled to room temperature and washed with 17
g pure water for three times. The organic layer was collected and
then concentrated under vacuum to obtain the compound represented
by Formula Ia (hereinafter "photo initiating compound Ia") as a
yellowish and viscous liquid. The yield is 95%.
The photo initiating compound Ia was subjected to nuclear magnetic
resonance analysis, and the results are as follows:
TABLE-US-00001 Nuclear .sup.1H NMR (500 MHz, CDCl.sub.3): 0.70 (t,
J = 7.5 Hz, 3H), magnetic 0.82 (t, J = 7.5 Hz, 3H), 1.85-1.89 (m,
1H), 1.94-1.99 resonance (m, 1H), 2.04-2.09 (m, 1H), 2.13-2.18 (m,
1H), 2.36 analysis: (s, 6H), 3.16-3.23 (m, 2H), 3.18 (d, J = 14.0
Hz, 1H), 3.22 (d, J = 14.0 Hz, 1H), 4.06-4.10 (m, 1H), 4.12-4.26
(m, 1H), 6.60 (d, J = 9.0 Hz, 2H), 7.16-7.28 (m, 6H), 8.34 (d, J =
9.0 Hz, 2H) .sup.13C NMR (500 MHz, CDCl.sub.3): 7.7, 9.8, 23.8,
27.8, 31.0, 35.5, 39.1, 48.4, 63.2, 73.8, 96.2, 111.5, 125.8,
125.9, 127.9, 131.3, 132.2, 139.6, 147.1, 201.6
Example 2: Preparation of a Liquid Photo Initiating Compound
Represented by Formula Ib
34 g
2-(dimethylamino)-1-[4-[((2-hydroxyethyl)amino]phenyl]-2-(phenylmeth-
yl)-1-butanone, 12.0 g 2,2-dimethoxypropane (CAS 77-76-9), 0.17 g
PTSA (p-toluenesulfonic acid), and 100 mL toluene were added to a
250 mL three-necked flask at room temperature in sequence and the
reaction as shown below was carried out at a condition the same as
the previous example.
##STR00014##
The reaction was monitored by High Performance Liquid
Chromatography (HPLC). After the reaction was completed, the
reaction product was extracted with 17 g pure water for three
times. The organic layer was collected and then concentrated under
vacuum to obtain the compound represented by Formula Ib
(hereinafter referred to as "photo initiating compound Ib") as a
yellowish and viscous liquid. The yield is 93%.
The photo initiating compound Ib was subjected to nuclear magnetic
resonance analysis, and the results are as follows:
TABLE-US-00002 Nuclear .sup.1H NMR (500 MHz, CDCl.sub.3): 0.69 (t,
J = 7.5Hz, 3H), magnetic 1.64 (s, 6H), 1.83-1.90 (m, 1H), 2.02-2.17
(m, 1H), resonance 2.36 (s, 6H), 3.17 (d, J = 14.0 Hz, 1H), 3.22
(d, J = analysis: 14.0 Hz, 1H), 3.53 (t, J = 6.5 Hz, 2H), 4.11 (t,
J = 6.5 Hz, 2H), 6.60 (d, J = 9.0 Hz, 2H), 7.15-7.28 (m, 6H), 8.35
(d, J = 9.0 Hz, 2H) .sup.13C NMR (500 MHz, CDCl.sub.3): 9.8, 25.4,
27.8, 35.5, 39.1, 47.8, 62.9, 73.9, 93.9, 111.8, 125.8, 125.9,
127.9, 131.3, 132.2, 139.6, 147.0, 201.6
Example 3: Solubility Test
Mixtures I to III were prepared according to the composition
provided below, and then 6 parts by weight of photoinitiator
Trgacure.RTM. 369 (available from IGM), photoinitiator R-gen.RTM.
919 (available from Chitec Technology Co., Ltd.) or photo
initiating compound Ia was added to each of the mixtures I to III.
The obtained mixtures were ultrasonicated for 1 hour at room
temperature, and the dissolution of each of Irgacure.RTM. 369,
R-gen.RTM. 919 and photo initiating compound Ia was observed and
described in the following Table 1.
TABLE-US-00003 Mixture I: a mixture of 50 parts by weight of
1,6-hexanediol diacrylate (product name: EM221, Eternal Materials
Co., Ltd.) and 50 parts by weight of polyester tetraacrylate
(product name: Oligomer 6325-100, Eternal Materials Co., Ltd.) with
a viscosity of 41.2 cP Mixture II: a mixture of 50 parts by weight
of trimethylolpropane triacrylate (product name: EM231, Eternal
Materials Co., Ltd.) and 50 parts by weight of polyester
tetraacrylate (product name: Oligomer 6325-100, Eternal Materials
Co., Ltd.) with a viscosity of 349.5 cP Mixture III: a mixture of
50 parts by weight of ethoxylated pentaerythritol tetraacrylate
(product name: EM2411, Eternal Materials Co., Ltd.) and 50 parts by
weight of polyester tetraacrylate (product name: Oligomer 6325-100,
Eternal Materials Co., Ltd.) with a viscosity of 433.0 cP
TABLE-US-00004 TABLE 1 Dissolution of Irgacure .RTM. 369, R-gen
.RTM. 919 and photo initiating compound Ia after one-hour
ultrasonication at room temperature Photoinitiator Mixture I
Mixture II Mixture III Irgacure .RTM. 369 Completely Only a small
part Only a small part dissolved was dissolved was dissolved R-gen
.RTM. 919 Completely Completely Completely dissolved dissolved
dissolved Photo initiating Completely Completely Completely
compound Ia dissolved dissolved dissolved
As shown in Table 1, the photo initiating compound Ia completely
dissolved in each of the three mixtures after one-hour
ultrasonication at room temperature. The results indicate that the
photo initiating compound Ia is much better than the solid
photoinitiator Irgacure.RTM. 369 and comparable to R-gen.RTM. 919
in terms of solubility.
Example 4: Viscosity Variation Test
4 parts by weight of photoinitiators Irgacure.RTM. 369, R-gen.RTM.
919, and photo initiating compound Ia were individually added to
each of the mixtures I to III, and the obtained mixtures were
exposed to a 0.degree. C. atmosphere for 7 days. The viscosities
before and after the exposure were measured and tabulated in the
following Table 2.
TABLE-US-00005 TABLE 2 Viscosities (cP) before and after exposure
to 0.degree. C. atmosphere for 7 days Mixture I Mixture II Mixture
III Photoinitiator Initial 7 days Initial 7 days Initial 7 days
None 41.2 50.1 349.5 401.0 433.0 548.0 Irgacure.RTM. 369 52.7 60.4
385.0 Precipitate 487.0 Precipitate R-gen.RTM. 919 42.2 51.0 354.0
408.0 445.5 544.0 Photo initiating 41.6 51.2 351.3 406.7 433.1
547.8 compound Ia
As shown in Table 2, the photo initiating compound IA has the
lowest influence on the viscosity of the mixture. In addition,
after the exposure to a 0.degree. C. atmosphere for 7 days, the
viscosity variation of the mixture with the photo initiating
compound Ia is similar to that of the mixture without
photoinitiator, and no precipitate was observed in the mixture with
the photo initiating compound Ia. The results indicate that the
photo initiating compound Ia is better than Irgacure.RTM. 369 in
terms of solubility and resin compatibility and therefore is very
useful.
Example 5: Photo Speed Performance Test
The black flexo formulation containing Oligomer 6325-100, EM2411
and carbon black (viscosity: 1750 cP) was mixed with a
photoinitiator to carry out the photo speed performance test.
Specifically, 100 parts by weight of the black flexo formulation
and 2 parts by weight of Chivacure.RTM. DETX (available from Chitec
Technology Co., Ltd.) were mixed, and then 6 parts by weight of
Irgacure.RTM. 369, R-gen.RTM. 998 (available from Chitec Technology
Co., Ltd.), R-gen.RTM. 919, or photo initiating compound Ia was
added to the obtained mixture. The resultant mixture was coated on
a printable pearlescent film (wet film thickness: 25.15 .mu.m); and
the coated printable pearlescent film was exposed to an UV light
(Fusion F300, D-bulb, 300 W/inch) for curing. The photo speed
performance was observed and tabulated in the following Table
3.
TABLE-US-00006 TABLE 3 Photo speed performance of photoinitiator
Photo initiating compound Photoinitiator Irgacure .RTM. 369 R-gen
.RTM. 998 R-gen .RTM. 919 Ia Photo speed 120 70 120 120
(m/minute)
Theoretically, photoinitiators with electron withdrawing groups,
such as the photo initiating compound Ia, usually have a lower
photo speed due to the blue shift effect. However, as shown in
Table 3, the photo initiating compound Ia surprisingly has an
outstanding photo speed which is comparable to those of
Irgacure.RTM. 369 and R-gen.RTM. 919 and significantly better than
that of R-gen.RTM. 998.
Example 6: Photoinitiator Dosage Test
The commercially available black flexo ink without a photoinitiator
was mixed with a photoinitiator to carry out the photo speed
performance test, and the effect of the amount of photo initiating
compound Ia on the photo speed performance was evaluated.
Specifically, 100 parts by weight of the black flexo formulation
and 2 parts by weight of Chivacure.RTM. DETX (photoinitiator;
Chitec Technology Co., Ltd.) were mixed, and then a specific amount
of Irgacure.RTM. 369 or photo initiating compound Ia as shown in
Table 4 was added to the obtained mixture. The resultant mixture
was coated on a PET film with primer (means for improving adhesion)
(dry film thickness: 5 .mu.m). The coated PET film was exposed to
an UV light (wavelength: 365 nm; 4 W/inch) for curing. The photo
speed performance in each case was observed and tabulated in the
following Table 4.
TABLE-US-00007 TABLE 4 Photo speed performance of photoinitiator in
different amounts Amounts Curing performance (parts by (times of UV
light treatment) weight) 1 2 3 4 5 Irgacure.RTM. 369 4 X X X
.DELTA. O 8 Incomplete dissolution Photo 4 X X X .DELTA. O
initiating 8 .DELTA. O compound Ia 12 O
TABLE-US-00008 Description for curing results: X Not tack-free
.DELTA. Tack-free but not through-cure .largecircle. Tack-free and
through-cure
As shown in Table 4, the tested black flexo ink is an ink system
that is difficult to be photocured, and the photocuring efficiency
can be improved by increasing the amount of the photoinitiator.
However, when 8 parts by weight of Irgacure.RTM. 369 was added,
like the result of the solubility test, the photoinitiator could
not be completely dissolved in the ink system, making it impossible
to carry out a photo speed test. By contrast, when the amount of
the photo initiating compound Ia was increased, no solubility issue
was observed even if the amount reaches 12 parts by weight.
Furthermore, increasing the amount of the photo initiating compound
Ia from 4 parts by weight to 8 parts by weight can significantly
improve the photocuring speed; and only one time of UV light
treatment was required to achieve sufficient curing when the amount
of the photo initiating compound Ia was 12 parts by weight.
Example 7: Acute Oral Toxicity Test
The median lethal dose (LD50) test was carried out for each of
Irgacure.RTM. 369, R-gen.RTM. 998, R-gen.RTM. 919 and photo
initiating compound Ia in accordance with Test Guidelines 423:
acute oral toxicity, Organization for Economic Co-operation and
Development (OECD).
The results are tabulated in the following Table 5.
TABLE-US-00009 TABLE 5 Median lethal dose (LD50) of photoinitiator
Photo initiating compound Photoinitiator Irgacure .RTM. 369 R-gen
.RTM. 998 R-gen .RTM. 919 Ia LD50 >5000 2500 500 >5000
(mg/kg)
As shown in Table 5, the median lethal dose (LD50) of the photo
initiating compound Ia is comparable with that of Irgacure.RTM.
369, both exceeding 5000 mg/kg, which is considered as no acute
oral toxicity.
As can be seen from the results of Examples 1 to 7, the liquid
photo initiating compound of the present invention has excellent
photo speed performance, excellent solubility, light color and no
acute oral toxicity. The liquid photo initiating compound of the
present invention is in liquid state at a low temperature of
50.degree. C. When being used in a photopolymerizable system, the
influence of the liquid photo initiating compound of the present
invention on viscosity is very minor. The liquid photo initiating
compound of the present invention also has long storage stability.
Therefore, the liquid photo initiating compound of the present
invention is particularly useful for low viscosity UV inks, light
color UV inks, color resists, black matrixes and solder masks.
The above examples are used to illustrate the principle and
efficacy of the present invention and show the inventive features
thereof. People skilled in this field may proceed with a variety of
modifications and replacements based on the disclosures and
suggestions of the invention as described without departing from
the principle and spirit thereof. Therefore, the scope of
protection of the present invention is that as defined in the
claims as appended.
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