U.S. patent application number 10/760524 was filed with the patent office on 2004-10-28 for fluorescent lamp capable of cleaning air.
Invention is credited to Wang, Wei-Hong.
Application Number | 20040213899 10/760524 |
Document ID | / |
Family ID | 33297697 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040213899 |
Kind Code |
A1 |
Wang, Wei-Hong |
October 28, 2004 |
Fluorescent lamp capable of cleaning air
Abstract
A method of preparing semiconductor nano crystal anatase
TiO.sub.2 solution uses titanium alkoxide Ti(OR).sub.4 as a main
component in combination with chelating agents in aqueous solution.
A fluorescent lamp tube is coated with the semiconductor nano
crystal anatase TiO.sub.2 solution to form a photocatalytic coating
fluorescent lamp capable of cleaning air. Then a baking step is
carried out at a low temperature about 100-250.degree. C. By doped
anatase TiO2 with small amount about 0-1.0 wt % of precious metals
complex or transition metals oxides as nano-particle on or in the
anatase TiO2 nano-particle surface, the visible light
photocatalysis efficiency is increased for air cleaning. By doped
with small amount Eu.sup.+3 or rare earth metal ion on or in the
anatase TiO2 nano-particle surface, which is a photocatalytic
material acting as fluorescent agent, the fluorescent lamp has
increasing brightness of when it is turned on.
Inventors: |
Wang, Wei-Hong; (Tao Yuan
City, TW) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
33297697 |
Appl. No.: |
10/760524 |
Filed: |
January 21, 2004 |
Current U.S.
Class: |
427/67 ;
422/186 |
Current CPC
Class: |
H01J 61/48 20130101;
B01J 21/063 20130101; H01J 61/35 20130101; H01J 9/20 20130101; H01J
61/44 20130101; B01J 19/123 20130101; B01J 35/004 20130101; B01J
37/0215 20130101; B01J 2219/0892 20130101; B01J 2219/0875 20130101;
B01J 19/127 20130101 |
Class at
Publication: |
427/067 ;
422/186 |
International
Class: |
B05D 005/06; B01J
019/08 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2003 |
TW |
092109831 |
Claims
What is claimed is:
1. A method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness, comprising:
preparing semiconductor nano-crystalline anatase TiO.sub.2 sol
using titanium alkoxide Ti(OR).sub.4 as a main component in
combination with chelating agents in aqueous solution; dip coating
said semiconductor nano-crystalline anatase TiO.sub.2 sol on a
surface of a fluorescent lamp tube; and baking said fluorescent
lamp tube coated with said semiconductor nano-crystalline anatase
TiO.sub.2 sol to form a photocatalytic coating fluorescent lamp
capable of cleaning air; wherein said baking step is carried out at
a low temperature in a range of about 100-250.degree. C.; and
wherein when said photocatalytic coating fluorescent lamp is turned
on, brightness of said photocatalytic coating fluorescent lamp
increases because of a fluorescent property of said semiconductor
anatase TiO.sub.2 sol coating, and due to the anatase TiO.sub.2
coating have had visible light photocatalytic ability thereof, a
small amount of UV light (UVA) and blue light from the fluorescent
lamp is absorbed by said anatase TiO.sub.2 coating, thus generating
active species such as electron-hole pairs are capable of cleaning
the air.
2. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness as claimed in
claim 1, wherein the step of preparing semiconductor
nano-crystalline anatase TiO.sub.2 sol using said chelating agents
in aqueous solution comprises the following steps: using acid
process to prepare anatase TiO.sub.2 sol; and adding
H.sub.4TiO.sub.4 solution to a H.sub.4TiO.sub.4/TiO.sub.2 ratio of
about 0-10 wt %, thereby improving thickness, adhesion, and
hardness of said semiconductor nano-crystalline anatase TiO.sub.2
sol coating.
3. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness as claimed in
claim 1; wherein the step of preparing semiconductor
nano-crystalline anatase TiO.sub.2 sol using said chelating agents
in aqueous solution comprises the following steps: using alkaline
process to prepare anatase TiO.sub.2 sol; and adding
H.sub.4TiO.sub.4 solution to a H.sub.4TiO.sub.4/TiO.sub.2 ratio of
about 0-10 wt %, thereby improving thickness, adhesion, and
hardness of said semiconductor nano-crystalline anatase TiO.sub.2
sol coating.
4. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness as claimed in
claim 1; wherein the step of preparing semiconductor
nano-crystalline anatase TiO.sub.2 sol using said chelating agents
in aqueous solution comprises the following steps: using the
process to prepare anatase TiO.sub.2 sol; and adding water solution
of precious metal salts or transition metal salt to the anatase
TiO.sub.2 sol for the M.sup.+n/anatase TiO.sub.2 ratio of about
0-1.0 wt %, thereby improving visible light photocatalytic ability
for air cleaning.
5. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness as claimed in
claim 1; wherein the step of preparing semiconductor
nano-crystalline anatase TiO.sub.2 sol using said chelating agents
in aqueous solution comprises the following steps: mixing Eu or
rare earth metal salt alcoholic solution with Ti(OR).sub.4 for the
Eu.sup.+3 or rare earth metal.ions./TiO.sub.2 ratio of about 0-1.0
wt %, and using the process to prepare Eu or rare earth metal doped
anatase TiO.sub.2 sol, thereby improving brightness of the
fluorescent lamp coated with the anatase TiO.sub.2 sol.
6. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness as claimed in
claim 1; wherein the step of dip coating said semiconductor
nano-crystalline anatase TiO.sub.2 sol on the surface of said
fluorescent lamp tube further comprises the steps of: dipping a
coating frame arranged with an array of fluorescent lamp tubes into
said semiconductor nano-crystalline anatase TiO.sub.2 sol by using
a coating machine; dip coating said lamp tubes and readily pulling
out said coating frame and said lamp tubes at a fixed pull-out
speed of about 10-30 cm/min, wherein said pull-out speed depends on
a desired thickness of coating and concentration of said anatase
TiO.sub.2 sol; and wherein the step of baking said fluorescent lamp
tube coated with said semiconductor nano-crystalline anatase
TiO.sub.2 sol to form a photocatalytic coating fluorescent lamp
capable of cleaning air and increasing brightness, further
comprises the following steps of: placing said coated fluorescent
lamp tubes and said coating frame into an oven; and baking said
fluorescent lamp tubes to form a photocatalytic coating fluorescent
lamp; wherein said baking process is carried out at a temperature
of 150-250.degree. C. for 10-30 minutes, and accurate conditions
depend on types of said anatase TiO.sub.2 sol, heat resistance of
said fluorescent lamp tubes, hardness of said anatase TiO2 coating,
and manufacture throughput.
7. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increasing brightness as claimed in
claim 1; wherein the step of dip coating said semiconductor
nano-crystalline anatase TiO.sub.2 sol on surface of said
fluorescent lamp tube further comprises the steps of: dipping a
coating frame arranged with an array of fluorescent lamp tubes into
SiO.sub.2 sol or H.sub.4TiO.sub.4 solution by using a coating
machine; dip coating said fluorescent lamp tubes and readily
pulling out said coating frame and said lamp tubes at a fixed
pull-out speed of about 10-30 cm/min, wherein said pull-out speed
depends on desired thickness of coating and concentration of said
SiO.sub.2 sol or H.sub.4TiO.sub.4 solution; baking said fluorescent
lamp tubes dipped with SiO.sub.2 sol or H.sub.4TiO.sub.4 solution
at a temperature of about 50-100.degree. C. for about 10-30
minutes, wherein the advanced SiO.sub.2 sol or H.sub.4TiO.sub.4
solution dipping improves optical properties, adhesion, and
hardness of said semiconductor nano-crystalline anatase TiO.sub.2
sol coating; dip coating said lamp tubes in said anatase TiO.sub.2
sol; readily pulling out said coating frame and said lamp tubes at
a fixed pull-out speed of about 10-30 cm/min, wherein said pull-out
speed depends on desired thickness of coating and concentration of
said anatase TiO.sub.2 sol; and wherein the step of baking said
fluorescent lamp tube coated with said semiconductor
nano-crystalline anatase TiO.sub.2 sol to form a photocatalytic
coating fluorescent lamp capable of cleaning air and increasing
brightness further comprises the following steps of: placing said
coated fluorescent lamp tubes and said coating frame into an oven;
and baking said fluorescent lamp tubes to form a photocatalytic
coating fluorescent lamp; wherein said baking process is carried
out at a temperature of about 150-250.degree. C. for about 10-30
minutes, and accurate condition depends on types of said anatase
TiO.sub.2 sol, heat resistance of said fluorescent lamp tubes,
hardness of said anatase TiO.sub.2 coating, and designed
manufacture throughput.
8. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
1 wherein said fluorescent lamp comprises normal fluorescent lamps,
RGB three wave fluorescent lamps, and high frequency fluorescent
lamps.
9. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
1, wherein said fluorescent lamp comprises a straight tube, an
annular tube, a U-shaped tube, a spiral tube, and a special
dual-layer tube, and wherein when implementing said dip coating
step method for fixing said lamp includes a dual head fixing method
and a single end fixing method.
10. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
1, wherein before dip coating said semiconductor nano-crystalline
anatase TiO.sub.2 sol on the surface of a fluorescent lamp tube,
the method further comprises the following steps of: arranging said
fluorescent lamp tube on a coating frame; washing said fluorescent
lamp tube and said coating frame; and drying said fluorescent lamp
tube and said coating frame.
11. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
10, wherein said straight tube dual head fluorescent lamp uses said
dual head fixing method, the method further comprising the
following steps before arranging said fluorescent lamp tubes on
said coating frame: masking a metal portion at both ends of each
said straight tube dual head fluorescent lamps using protection
sleeves or thermal plastic sleeves; and arranging said straight
tube dual head fluorescent lamps through holes on said coating
frame and fixing said both ends of each said dual head fluorescent
lamps by means of a clipping mechanism disposed at an upper plate
and lower plate of said coating frame, so that about 1-100
fluorescent lamps can be arranged on said coating frame.
12. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air as claimed in claim 11, wherein said
straight tube dual head fluorescent lamps are fixed by using a dual
head fixing method, and wherein a method of washing said
fluorescent lamp tube and said coating frame comprises dipping said
fluorescent lamp tube and said coating frame into solution
containing surfactants for removing oil, followed by rinsing in
de-ionized water to removing said surfactants.
13. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
12, wherein said straight tube dual head fluorescent lamps are
fixed by using a dual head fixing method, and wherein method for
drying said fluorescent lamp tube and said coating frame comprises
placing said fluorescent lamp tube and said coating frame into a
drying apparatus, and drying said fluorescent lamp tube and said
coating frame with heated air.
14. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
13, wherein said straight tube dual head fluorescent lamps are
fixed by using a dual head fixing method, and said dried
fluorescent lamp tube and said coating frame are subjected to said
dip coating step as defined in claim 1.
15. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
14, wherein said straight tube dual head fluorescent lamps are
fixed by using a dual head fixing method, and said dried
fluorescent lamp tube and said coating frame are subjected to said
anatase TiO.sub.2 sol dip coating step as defined in claim 6.
16. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
15, wherein said straight tube dual head fluorescent lamps are
fixed by using a dual head fixing method, and said dried
fluorescent lamp tube and said coating frame are subjected to said
dip coating step as defined in claim 7, after SiO.sub.2 sol or
H.sub.4TiO.sub.4 solution dip coating is performed, followed by
anatase TiO.sub.2 sol dip coating.
17. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
8, wherein said single-end fluorescent lamps are fixed by using a
single-end fixing method, and a method for arranging said
fluorescent lamp tubes on said coating frame comprises: selecting
same type single-end fluorescent lamps or special fluorescent
lamps; and connecting and fixing said the single-end fluorescent
lamps to clipping mechanism on said coating frame; wherein about
1-100 pieces said the single-end fluorescent lamps can be arranged
on said coating frame depending on size of said coating frame and
pitch thereof.
18. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
17, wherein said single-end fluorescent lamps are fixed by using
single-end fixing method, and washing said single-end fluorescent
lamps and said coating frame comprises the steps of: placing said
single-end fluorescent lamps and said coating frame in a washing
machine; washing away oil with surfactant solution; and thereafter
washing away surfactant with de-ionized water.
19. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
1, wherein said single-end fluorescent lamps are fixed by using a
single-end fixing method, and drying said single-end fluorescent
lamps and said coating frame comprises the steps of: placing said a
cleaned single-end fluorescent lamps and said coating frame in a
drying machine; drying said cleaned single-end fluorescent lamps
and said coating frame with heated air.
20. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
19, wherein said single-end fluorescent lamps are fixed by using a
single-end fixing method, and said dried single-end fluorescent
lamp tube and said coating frame are subjected to dip coating step
as defined in claim 1.
21. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
20, wherein said single-end fluorescent lamps are fixed by using a
single-end fixing method, and said dried single-end fluorescent
lamp tubes and said coating frame are subjected to said dip coating
step as defined in claim 6.
22. The method for fabricating a photocatalytic fluorescent lamp
capable of cleaning air and increase brightness as claimed in claim
21, wherein said single-end fluorescent lamps are fixed by using
single-end fixing method, said dried single-end fluorescent lamp
tubes and said coating frame are subjected to said dip coating step
as defined in claim 7, after SiO.sub.2 sol or H.sub.4TiO.sub.4
solution dip coating is performed, followed by anatase TiO.sub.2
solution dip coating.
23. A photocatalytic fluorescent lamp capable of cleaning air and
increase brightness is fabricated by the process as described in
claim 1, comprising: a lamp tube comprising an anatase TiO.sub.2
coating film made of anatase TiO.sub.2 semiconductor
nano-crystalline particle packing; wherein when said photocatalytic
fluorescent lamp is turned on, brightness of said photocatalytic
fluorescent lamp increases because of a fluorescent property of
said anatase TiO.sub.2 coating film, and due to a porous
characteristic of said anatase TiO.sub.2 coating film and a visible
light photocatalytic ability thereof, a small amount of UV light
(UVA) and blue light transmitted from said photocatalytic
fluorescent lamp is absorbed by said anatase TiO.sub.2 coating film
and active species such as electron-hole pairs that are capable of
purifying air are generated.
24. The photocatalytic fluorescent lamp capable of cleaning air and
increase brightness as claimed in claim 23, wherein said anatase
TiO.sub.2 coating film is made from anatase TiO.sub.2 sol
comprising coagulated said anatase TiO.sub.2 semiconductor
nano-crystalline particles with at least about 80% of which are at
a particle size below about 20 nm.
25. The photocatalytic fluorescent lamp capable of cleaning air and
increase brightness as claimed in claim 23, wherein said
photocatalytic fluorescent lamp further comprises a base layer
coated underneath said anatase TiO.sub.2 coating film, said base
layer being made by sol-gel method, and wherein said base layer is
made from SiO.sub.2 sol or H4TiO4 solution, thereby preventing
alkaline ions on a lamp glass tube surface from thermal diffusing
out to said anatase TiO.sub.2 coating film to decrease the
photocatalytic efficiency, thereby improving optical properties,
adhesion, and hardness of said anatase TiO.sub.2 coating film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a fluorescent lamp capable
of cleaning air, and more particularly, to a fluorescent lamp
coated with nano-crystalline anatase TiO2 sol, which is a
photocatalytic material acting as fluorescent agent, which is
capable of increasing brightness of the fluorescent lamp when it is
turned on.
[0003] The present invention also discloses a method comprising the
steps of preparing semiconductor nano-crystalline anatase TiO.sub.2
solution using titanium alkoxide Ti(OR).sub.4 as a main component
in combination with chelating agents and than hydrolysis in aqueous
solution, which semiconductor nano-crystalline anatase TiO.sub.2
solution is then coated onto surface of a fluorescent lamp tube.
The fluorescent lamp tube coated with the semiconductor
nano-crystalline anatase TiO.sub.2 solution is then baked to form a
photocatalytic coating fluorescent lamp capable of cleaning air.
The baking step is carried out at a low temperature in a range of
100-250.degree. C. The fluorescent lamp comprises straight type
tubes, annular shaped tubes, U-shaped tubes, spiral-shaped tubes,
and special dual layer tubes.
[0004] 2. Description of the Related Art
[0005] Photocatalysts have been developed for treating waste gases
for the past few years, such as those described in, for example,
Gregory B. Roupp & Lynette A. Dibble, Arizona State University,
U.S. Pat. No. 5,045,288; Jeffrey G. Sczechowski et al., The
University of Colorado, U.S. Pat. No. 5,439,652; William A. Jacoby
& Daniel M. Blake, U.S. Pat. No. 5,449,443; Zhenyu Zhang &
James R. Gehlner, Inrad., U.S. Pat. No. 5,468,699; and Franz D.
Oeste & Olga Dietrich Neeleye, U.S. Pat. No. 5,480,524.
[0006] The above-mentioned patents relate to treatment of waste
gases, and were basically carried out in a hermetically sealed
reactor. Utilization or operation of granular photocatalysts or
photocatalysts coating granules therefore usually needs, in
general, complex equipment to handle.
[0007] The above-described prior art examples have disadvantages
making the prior art photocatalysts difficult to apply in the field
of air pollutant treatment for a living environment. Of them, one
waste water and/or waste gases disposal photocatalytic reactor
comprising a UV lamp inserted into matrix with photocatalysts
coated fibers, thereof is described in Michael K. Robertson &
Robert G. Henderson, Nutech Energy Systems Inc., U.S. Pat. No.
4,982,712. As mentioned above, such a reactor was a closed type one
such that counter-flow of gases must be forced by a blower that
makes such a reaction system impractical when used in living
environments.
[0008] UV lamp treatment for waste gases is generally based on the
sustained oxidative degradation against organic and/or inorganic
hazardous materials in the air by a photocatalytic reaction to
render them into non-harmful substances such as water or carbon
dioxide. For example, U.S. Pat. No. 6,135,838 and U.S. Pat. No.
6,336,998, which are owned by the applicants of the present
application, all describe such a UV lamp. Since the UV lamp is not
a commercially available lighting apparatus, some research has
focused on a commercial fluorescent lamp having a photocatalytic
coating for cleaning air.
[0009] Hiroshi Taoda and Watanabe, U.S. Pat. No. 5,650,126 and U.S.
Pat. No. 5,670,206, discloses a fluorescent lamp coated with
titanium dioxide sol, than baked to 350-500.degree. C., for
deodorized the air. And the U.S. Pat. No. 6,024,929 by Ichikawa
Shinichi, Furukawa Yashinori, and Azuhata Shigeru discloses a
light-transmissive and transparent film photocatalyst made of
anatase-type titanium dioxide and alpha type iron oxide formed on
an outside surface of a glass tube used for a fluorescent lamp. The
thin film photocatalyst is formed by sol-gel coating. But the
temperature for baking the solution adhered to the outside wall of
the glass tube is in a range of 450-600.degree. C. when forming the
thin film anatase-type titanium dioxide and is in a range of
560-770.degree. C. when forming the alpha iron oxide
.alpha.-Fe.sub.2O.sub.3. By baking the solution at so high
temperature in the above-mentioned ranges, which made the coating
too dense to work with high efficiency in photocatalysis for air
cleaning.
[0010] U.S. Pat. No. 6,242,862 by Akira Kawakatsu and Kanagawa-ken
discloses a photocatalytic membrane on a lamp with lighting
fixture. The membrane is formed using TiO.sub.2 anatase particle
dispersed liquid coating with a ground layer. The ground layer made
of a metallic oxide: such as silane coupling agent, SiO.sub.2 sol,
TiO.sub.2 sol, or Al.sub.2O.sub.3 sol, also with mutli-layer
structure provided lot of penetrating holes for increase the
photocatalytic efficiency. However, the anatase TiO2 particles are
obtained from a high temperature sinter process. Although the TiO2
Anatase particles are dispersed in an alcohol solvent, the hydroxyl
groups on the particle surfaces are still at a low level, resulting
in poor adhesion to the fluorescent lamp. For this reason,
inorganic materials for enhancing adhesion such as silane coupling
agent, SiO.sub.2 sol, TiO.sub.2 sol, or Al.sub.2O.sub.3 sol is
needed. This inorganic materials distributed in lower the
photocatalytic effect and lower the air cleaning efficiency,
too.
SUMMARY OF THE INVENTION
[0011] Accordingly, the primary object of the invention is to
provide a method for preparing anatase TiO.sub.2 nano-scale crystal
particle solution. The particle size of the anatase TiO.sub.2 is
below about 20 nm. Since the anatase TiO.sub.2 nano-crystalline
particle is made in a water-based solution, bountiful hydroxyl
groups are presented on the surface. When the anatase TiO.sub.2 sol
is baked at low temperatures in a range of about 100-250.degree. C.
for removing organic solvent and organic additives, thereby
obtaining a good adhesion and nano-scale anatase TiO.sub.2 porous
coating. Because the anatase TiO.sub.2 particle is below about 20
nm, the primary particle achieves at 1.0 nm scale. Due to the
characteristic of such nano-scale material, the anatase TiO.sub.2
coating presents photocatalystic effects even in the visible light
range. Further, since no high-temperature annealing is needed, the
nano-scale anatase TiO.sub.2 coating is porous. Air and
organic/inorganic pollutants more easily diffuse to the inside of
the TiO.sub.2 coating. On the other hand, the electron-hole pairs
originally generated inside the TiO.sub.2 Anatase crystal, more
easily migrate to the outer side of the TiO.sub.2 Anatase crystal,
thereby improving the deodorization effect, bactericidal and
fungicidal activity and contamination prevention effect.
[0012] It is another object of the present invention is to provide
a fluorescent lamp coating with the above-mentioned anatase
TiO.sub.2 nano-crystalline sol. Since the anatase TiO.sub.2 crystal
particle is in the nano scale, the photocatalytic reaction with
quantum effect to lower the activation energy. The activation
energy has an original maximum value of about 0.5 eV as band
bending energy. As a result of the reduction of particle size, the
activation energy is lower than about 0.3 eV, which means about a
0.2 eV energy shrinkage, at least. This enables the visible light
photocatalyst to be formed, which works originally under a 385 nm
UV light. It is evidenced that the anatase TiO.sub.2 crystal
particle formed according to the present invention can function at
about 425 nm, or at an even wavelength such as about 512 nm, when
the band bending energy approach zero.
[0013] To achieve these and other advantages and in accordance with
the purposes of the present invention, as embodied and broadly
described herein, the present invention provides a method for
fabricating a photocatalytic fluorescent lamp capable of cleaning
air. The method comprises preparing semiconductor nano crystalline
anatase TiO.sub.2 solution using titanium alkoxide Ti(OR).sub.4 as
a main component in combination with chelating agents in aqueous
solution, dip coating the semiconductor nano crystalline anatase
TiO.sub.2 solution on surface of a fluorescent lamp tube and baking
the fluorescent lamp tube coated with the semiconductor
nano-crystalline anatase TiO.sub.2 solution to form a
photocatalytic coating fluorescent lamp capable of cleaning air.
The baking temperature is carried out at a low temperature in a
range of about 100-250.degree. C., because the anatase TiO.sub.2
nano-crystalline already formed in solution. When the
photocatalytic coating fluorescent lamp is turned on, brightness of
the fluorescent lamp increases because of the fluorescent property
of the semiconductor nano crystalline anatase TiO.sub.2. Due to the
porous characteristic of the anatase TiO.sub.2 solution coating and
its visible light photocatalytic ability, a small amount of UV
light (UVA) and visible light generating by the fluorescence in the
lamp are absorbed by the nano anatase TiO.sub.2 coating, thus
generating active species such as electron-hole pairs that are
capable of cleaning air.
[0014] The anatase TiO.sub.2 solution, anatase TiO.sub.2 sol or
anatase TiO.sub.2 film developed according to this invention
features its ability to increase brightness of the fluorescent lamp
when the anatase TiO2 sol is coated on an outside wall of the glass
tube of the fluorescent lamp. It is surprisingly found that the
brightness of the coated fluorescent lamp is improved by 1.0% when
compared to a fluorescent lamp without an anatase TiO2 sol coating.
When we used fluorescent spectrometer to measure the nano-TiO2
Anatase materials, which had absorption band around 395 nm as
excitation, with fluorescent band around 480 nm as emission. It is
evident that the TiO.sub.2 sol developed according to this
invention also acts as fluorescent agent. It is known that a
fluorescent lamp typically has a phosphorous layer coated on the
inner wall of the vacuum glass tube. High energy ultraviolet (UV)
light are generated due to the collision between free accelerated
electrons and gaseous mercury between two electrode at high voltage
in high vacuum with small amount of inert gas. The high energy UV
light irradiates the phosphorous layer coated on the inner wall of
the vacuum glass tube and absorbed by the phosphorous and generated
fluorescence of visible light and a small amount of near UV (UVA).
It is known that only the small amount of UVA either generated, can
penetrates through the calcium glass tube. The fluorescent light
spectrum of a conventional fluorescent lamp is shown in FIG. 4.
Another fluorescent lamp with RGB composite fluorescent has the
visible RGB fluorescence with spectrum is shown in FIG. 5. It is
shown that all with a small amount of UVA (.lambda.=365 nm) photons
is present in the fluorescence. According to the present invention,
not only the small amount of UVA photons are absorbed by the
anatase TiO.sub.2 coating but also the violet even the blue light
can be absorbed, and thus induces photocatalytic reactions
(assisted by active electron-hole pairs) therefrom. The
photocatalytic reactions catalyze organic or inorganic gaseous
substance absorbed on the catalyst to be decomposed. If the organic
or inorganic gaseous substance is insufficient to attend the
photoreaction, excess excited electron-hole pairs will recombine to
their ground state and release fluorescent light or thermal
heat.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other objects, advantages and novel features of the
invention will become more clearly and readily apparent from the
following detailed description when taken in conjunction with the
accompanying drawings.
[0016] FIG. 1 shows Raman spectrum of anatase TiO2 powder;
[0017] FIG. 2 shows Raman spectrum of anatase TiO2 sol;
[0018] FIG. 3 shows DLS particle size analysis on anatase TiO2
sol;
[0019] FIG. 4 is a spectrum of a conventional fluorescent lamp;
[0020] FIG. 5 is a spectrum of a RGB composite fluorescent
lamp;
[0021] FIG. 6A is a diagram showing a straight tube fluorescent
lamp;
[0022] FIGS. 6B, 6C, and 6D are schematic diagrams showing
single-end fluorescent lamps;
[0023] FIG. 7A is a cross section view showing the fluorescent lamp
coated with anatase TiO.sub.2;
[0024] FIG. 7B is a schematic diagram showing reactions at the
surface of the fluorescent lamp coated with anatase TiO.sub.2;
[0025] FIG. 8 is a schematic diagram showing the coating frame for
dip coating straight tube fluorescent lamps in array;
[0026] FIG. 9A is a schematic diagram showing the coating frame for
dip coating single-end fluorescent lamps in array; and
[0027] FIG. 9B is a cross section view showing the mechanism for
fixing the single-end fluorescent lamp.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The present invention uses sol-gel technique to prepare
anatase TiO2 semiconductor nano-crystalline solution, hereinafter
referred to as anatase TiO2 sol, which is used for the
photocatalytic coating of substrate, such as glass, ceramic, active
carbon, metals, plastics or synthesis fiber clothes. The coating is
air dried at room temperature and then baked at temperatures about
100-250.degree. C. For increase waste gas decomposed efficiency (or
water treatment efficiency), precious metals or transition metal
oxides are added to the prepared anatase TiO2 solution.
Alternatively, the coating may be dipped in a solution containing
precious metals or transition metals ions, followed by thermal
drying and photo-reduction.
[0029] After the fluorescent lamp for lighting purposes is coated
with TiO2 anatase sol or doped with rare earth metal (less than 10
wt %) TiO2 anatase sol to maintain the maximum photocatalysis for
air cleaning ability but also could increase the brightness cause
the fluorescent property of the photocatalyst materials. It is
advanced to use the present invention because the anatase TiO.sub.2
or Eu doped anatase TiO.sub.2 particle in the nano-scale has
photo-luminescence with 480 nm or 615 nm fluorescence property and
quantum well effect, and thus cause have photocatalystic effect but
also increase the brightness of the fluorescent lamp when it turn
on.
[0030] 1. Preparation of Anatase TiO2 Solution.
[0031] The photocatalyst solution used in the above-said process
for coating photocatalyst contains as the main component a titanium
alkoxide such as Ti(OR)4, wherein R is a hydrocarbon group,
C.sub.nH.sub.2n+1, where n=1-5, and is, for example, methyl, ethyl,
n-propyl, isopropyl, n-butyl, t-butyl, sec-butyl, pentyl and the
like. Since the anatase TiO.sub.2 particle is stable in a pH<2.5
acid solution and a pH>7.0 alkaline solution, both acid-type
anatase TiO.sub.2 solution and alkaline-type anatase TiO.sub.2
solution have been developed. To ensure that about 80% of TiO.sub.2
particles are under a particles size of about 10 nm size, chelating
agents are incorporated with the titanium alkoxide Ti(OR).sub.4
hydrolysis in water or water contained solvent as TiO.sub.2 gel.
Acids or Alkali are used for peptizing this TiO2 gel by adjust the
pH value of the solution. Organic acids include CH.sub.3COOH or
RCOOH. Inorganic acids lnclude HNO.sub.3 or HCl. Organic alkali
include quadruped alkyl ammonium (R.sub.4NOH) or alkyl amine
NR.sub.3. Strong chelating agents such as Acetonacetate
[RC(O)CH.sub.2C(O)R], amino acid [RCH(NH.sub.2)COOH], succinic acid
[HOOCCH(R)COOH], and organic alcohol [RC.sub.6H.sub.3(OCH.sub.3)OH]
are also used. The amount of strong chelating agent added should be
within a molar ratio of 0.01-1.0 for chelating agent/Ti(OR).sub.4.
The chelating agent is used before the hydrolysis of the
Ti(OR).sub.4 and reacts with the Ti(OR).sub.4 to form
Ti(OR).sub.4-SCA complex, SCA meaning Strong Chelating Agent. The
complex is then added into water or water-containing solution for
hydrolysis so as to form H.sub.xTiO.sub.[(3-x)/2+x]-SCA. Since the
molar ratio of chelating agent/Ti(OR).sub.4 is less than about 1.0,
after hydrolysis, the H.sub.yTiO.sub.[(4-y)/2+y] mixes with the
H.sub.xTiO.sub.[(3-x)/2+x]-- SCA to form a gel. Alternatively,
Ti(OR).sub.4 can be added into water to form a
H.sub.yTiO.sub.[(4-y)/2+y] gel and then a chelating agent is added
to form the H.sub.yTiO.sub.[(4-y)/2+y]-SCA gel.
[0032] Both the above
H.sub.yTiO.sub.[(4-y)/2+y]/H.sub.xTiO.sub.[(3-x)/2+x- ]-SCA gel or
H.sub.yTiO.sub.[(4-y)/2+y] gel are hereinafter referred to as
TiO.sub.2-SCA gel. To prepare the anatase TiO2 nano-crystalline,
acids such as HNO.sub.3, HCl, or HF, and alkali such as NH.sub.3 or
NH.sub.4OH are used to adjust the pH value. Acids are used to
adjust the solution to about pH<2.5, while the alkali are used
to adjust the solution to about pH>7.0. After adjusting the pH
value, most of the TiO.sub.2 gel begins to be peptized, and
undergoes rapid peptizing when heated. At this phase, crystalline
particles form after the hydrothermal process. To obtain
crystalline TiO.sub.2 particles, the process temperature has to be
kept above 100.degree. C. as hydrothermal process. The resultant
anatase TiO.sub.2 particle size relates to the type of chelating
agent, chelating agent concentration and dispersion technique which
applied in peptizing or hydrothermal process. It is found that a
high efficiency dispersing technique can lower the anatase
TiO.sub.2 particle size. The hydrothermal time and temperature both
are factors for yield of the anatase TiO.sub.2 particle. A higher
temperature or a longer hydrothermal results in anatase TiO.sub.2
particles having better crystal structure. Preferably, the
temperature is below 250.degree. C. However, it is noted that a
higher temperature or longer time for hydrothermal also results in
a larger crystal size exceeding 100 nm. The type of chelating agent
and its concentration depend on process, properly pH value and
temperature are selected, about 1 to 7-hour hydrothermal is
preferably carried out to form anatase TiO2 sol.
[0033] Typically, the anatase TiO.sub.2 sol is an aqueous solution.
When applying above-said sol to coat a fluorescent lamp by using an
outside coating method, the anatase TiO.sub.2 sol of this invention
either made from acid process or alkaline process has a particle
size below about 20 nm and extensive surface with hydroxyl
group(--OH), thereby promoting adhesion to the lamp surface. When
dip coating, a uniform anatase TiO.sub.2 gel film can be formed. In
one embodiment, alcoholic solvent may be added into the anatase
TiO.sub.2 sol. In another embodiment, anatase TiO.sub.2 sol made
from alcoholic aqueous solution is used, in which alcohol
concentration to water is lower than about 50% by weight, to
improve the properties of the anatase TiO.sub.2 sol coating and the
adhesion ability thereof.
[0034] In one embodiment, the H.sub.4TiO.sub.4 solution added to
the main component anatase TiO2 sol. The H.sub.4TiO.sub.4 solution
can be made from titanium alkoxide such as Ti(OR).sub.4, where R is
a hydrocarbon group, C.sub.nH.sub.2n+1 and n=1-5, and is, for
example, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl,
sec-butyl, pentyl and the like. The titanium alkoxide is slowly
added into water with water/titanium alkoxide molar ratio of
100-1000. The solution is stirred to hydrolyze so as to form the
above-said H.sub.yTiO.sub.[(4-y)/2+y] gel solution. The above-said
H.sub.yTiO.sub.[(4-y)/2+y] gel solution is filtered and washed, and
re-filtered to obtain H.sub.yTiO.sub.[(4-y)/2+y] gel. The
thus-formed H.sub.yTiO.sub.[(4-y)/2+y] gel is then dispensed into
water to form water/titanium dioxide with a mole ratio of about
100-1000. After that, the thus-formed H.sub.yTiO.sub.[(4-y)/2+y]
gel solution is cooled down using ice water to below about
4.0.degree. C. Then, a 33% H.sub.2O.sub.2 solution is added to the
cooled H.sub.yTiO.sub.[(4-y)/2+y] gel solution. The
H.sub.2O.sub.2/titanium oxide molar ratio is 4.0. The temperature
of the H.sub.yTiO.sub.[(4-y)/2+y] gel solution is kept below
6.degree. C. waiting for the H.sub.yTiO.sub.[(4-y)/2+y] gel to be
completely dissolved into transparent yellow H.sub.4TiO.sub.4. In
practice, the concentration of the H.sub.4TiO.sub.4 may be adjusted
to 1.0% by weight and stored in a PP plastic tank at 4.degree. C.
to become H.sub.4TiO.sub.4 gel-solution.
[0035] When adding the H.sub.4TiO.sub.4 gel-solution into the
anatase TiO.sub.2 solution, the H.sub.4TiO.sub.4 to anatase
TiO.sub.2 ratio is 0-10% by weight. During the addition of the
H.sub.4TiO.sub.4 gel-solution, the anatase TiO.sub.2 solution is
cooled in iced water at 4.degree. C. The mixture is then stirred
and coated on the glass tube of a fluorescent lamp and then baked
at 100-250.degree. C., it is found that the adhesion ability,
thickness, and solidity of the coated film are improved, without
affecting its porosity.
[0036] The thus-formed anatase TiO.sub.2 solution is analyzed with
Fourier-Transform Raman (FT-Raman) spectroscopy. The resultant
Raman shift spectrum is illustrated in FIG. 2. The spectrum is
measured by using 15 wt % anatase TiO.sub.2 solution, which is
irradiated by a 750 mW laser at a wavelength of 1060 nm. As shown
in FIG. 2, split high-intensity peaks present at Raman shift 204
cm.sup.-1, 398 cm.sup.-1, 515 cm.sup.-1, and 638 cm.sup.-1, which
are analogous to the solid anatase TiO.sub.2 Raman shift spectrum
as shown in FIG. 1. The particle size is analyzed by a Dynamic
Laser Scattering method. As shown in FIG. 3, the result shows that
about 80% of the anatase TiO.sub.2 crystals have a particle size
around 10 nm.
[0037] 2. Photocatalytic Coating
[0038] The developed anatase TiO.sub.2 solution, either acidic or
alkaline, has a dominant particle size below 20 nm. To increase
wetness when coating glass and to get a uniform photocatalytic
coating, either the anatase TiO.sub.2 solution prepared by using
alcohol-containing solution or anatase TiO.sub.2 solution added to
a proper alcoholic solution is used. By utilizing such
characteristics, a high-quality optical level anatase TiO2 solution
photocatalytic coating on a fluorescent lamp can be achieved. As
mentioned, to improve adhesion ability, thickness, and solidity of
the coated film, proper H.sub.4TiO.sub.4 gel-solution may be
added.
[0039] The refraction index of the glass tube of the fluorescent
lamp is about 1.52, and the refraction index of the anatase
TiO.sub.2 is about 2.2. It is found that the anatase TiO.sub.2
coating has a refraction index of 1.6-1.75, which is close to the
refraction index of the glass tube of the fluorescent lamp. It is
believed that the anatase TiO.sub.2 has a complete crystal
structure in the TiO.sub.2 solution, and the baking process does
not decrease the porosity of the particles in the coating. The
natural packing of such particles can have a porosity of 37.5% to
50%.
[0040] There are two methods for coating the anatase TiO.sub.2
solution film onto the glass tube of the fluorescent lamp. The
first method is coated the anatase TiO.sub.2 on the glass before
the fluorescent lamp fabricated. When the clean glass tube is cut
and finished with a side melting process, the two ends of the clean
glass tube are sealed or capped. The capped clean glass tube is
then dipped into the anatase TiO.sub.2 solution in a vertical
manner relative to the solution surface, then pulled out from the
anatase TiO.sub.2 solution in constant velocity. After this, the
caps at both ends of the tube are removed, followed by baking at
150-250.degree. C. for 10-60 minutes. The baking of the coating may
be carried out in a baking machine, to avoid severely grinding the
coating, the two ends of the glass tube are in contact with the
clipper or a high-temperature transfer wheel.
[0041] The second method is employed after the fluorescent lamp is
completed. Additional capping nuts are used to mask the electrode
bases at both ends of the glass tube of the fluorescent lamp. The
masked glass tube is then dipped into the anatase TiO.sub.2
solution in a vertical manner relative to the solution surface and
pulled out from the anatase TiO.sub.2 solution in constant
velocity. The fluorescent lamp is next baked at 150-250.degree. C.
for 10-60 minutes. The baking may be carried out in a batch type or
continues type oven.
[0042] When coating anatase TiO.sub.2 solution onto the surface of
the glass tube of the fluorescent lamp, the key to control the
uniformity and thickness of the coating is avoiding vibration of
the coating machine while pulling the glass tube from the anatase
TiO.sub.2 solution, and also the precise control of humidity and
air cleanness. If the pullout speed is set at 30 cm/min, the
concentration of the anatase TiO.sub.2 solution is adjustable, such
that the coating thickness can achieve the desired value. The
control of the coating thickness is based on the coating thickness
after finishing baking to finely tune the pullout speed. The
thus-formed anatase TiO.sub.2 solution coated fluorescent lamp is
illustrated in FIG. 7A. The thus-formed anatase TiO.sub.2 solution
coated fluorescent lamp includes anatase TiO.sub.2 sol coating
(10), glass tube (20), and fluorescent coating (30).
[0043] FIG. 7B is a schematic diagram depicting how the anatase
TiO.sub.2 sol coated fluorescent lamp capable of cleaning air. Most
fluorescent lamps have a vacuum tube having fluorescent materials
coated on its interior walls. When the lamp is turned on, the
electron cloud is generated by the heated electrodes under very low
pressure. At AC or DC voltage, the electrons and charged atoms
leave the electrode and move through the tube toward the opposite
electrode, some of them collide with the gaseous mercury atoms.
These collisions excite the atoms, bumping electrons up to higher
energy levels. When the electrons return to their original energy
level, they release UV (and also visible) light photons. The UV
light photons have energy distributed mainly at 365 nm (UVA), 315
nm (UVB), 254 nm (UVC), and 184 nm (UVD). The main energy bands of
the visible light photons are 400-500 nm (blue light as VisB),
500-600 nm (green light as VisG), and 600-650 nm (red light as
VisR). Hereinafter, the UV light intensities (UV light is generated
by gaseous mercury atoms excited by free electrons) are presented
with UVA, UVB, UVC, and UVD, and the visible light intensities are
presented with VisB, VisG, and VisR. When the generated UV and
visible light irradiate internal walls to be coated with
fluorescent materials, the fluorescent materials absorb UVA, UVB,
UVC, or UVD to produce different fluorescent light, which are
mainly VisB, VisG, and VisR. The UV light not absorbed by the
fluorescent materials transmitted through the glass tube and are
mostly absorbed by the glass tube. At this phase, the UV
intensities decrease to UVA' and UVB', wherein the UVB' is almost
zero. As for visible light intensities, the fluorescent visible
light produced by the fluorescent materials mix with original
visible light generated by the electron collided with the gaseous
of mercury or inert gas, after transmitting through the glass tube
is increased to intensities of VisB', VisG' and VisR' for
illumination. Due to the different spectrum and intensities of the
VisB', VisG' and VisR', the color temperature and brightness are
thus different. But in real fluorescent Lamp, which have the
visible light with the intensities of VisB', VisG' and VisR' and a
small amount of UVA' of near UV light, some of them are absorbed by
the anatase TiO.sub.2 coating after transmitting through the glass
tube. Depending on the structure and the photocatalytic ability of
the TiO.sub.2 coating, a small amount of UVA' and near UV light are
absorbed to generate photocatalytic effects and fluorescent
effects. Accordingly, the anatase TiO.sub.2 coated fluorescent lamp
capable of cleaning air and generating visible light with visible
fluorescence having intensities as VisB", VisG", and VisR", and a
remaining small amount of UVA" as near UV light. The photocatalytic
anatase TiO.sub.2 after absorbing UV light generates electron-hole
pairs, which carry out oxidation-reduction reactions for air
cleaning. If the produced electron-hole pairs do not react with
organic or inorganic substances in the air timely, the electrons
and the holes recombine to generate fluorescent as blue light. Most
important, used the pure TiO.sub.2 Anatase solution can be doped
with Zn.Eu or like rare earth metal compounds by added to the TiO2
Anatase solution for coating on the fluorescent lamp can generate
not only blue light but also generate green or red fluorescent
light.
[0044] 3. The Procedure and Apparatus for Fabricating the Anatase
TiO.sub.2 Coated Fluorescent Lamp for Air Cleaning.
[0045] The glass tube of the fluorescent lamp is made of sodium
calcium glass. The fabrication of the glass tube is known in the
art. After the gradients of the glass to be hot melting and tube
shaping, the long and straight glass tube is cut into certain
lengths. The cut glass tube is subjected to cleaning, drying, and
then fluorescent film coating. Fluorescent slurry comprising
inorganic fluorescent agents, inorganic binders, organic dispenser,
and organic solvent is injected from the upper end of the glass
tube and flows down along the interior wall of the glass tube to
form a fluorescent film thereon. The glass tube coated with
fluorescent film is then baked at 400-600.degree. C. in a
continuous tunnel oven to get rid of organic substances and
moisture. After this, an opaque white color fluorescent film is
adhered onto the interior wall of the glass tube.
[0046] The glass tube coated with fluorescent film is then
connected with electrode bases at both ends by using conventional
melting joint method. The electrode bases are made from tungsten
wiring melted with glass having thereon a glass venting tube.
Through the venting tube, the glass tube is evacuated to a very low
pressure, followed by injection of an amount of mercury and inert
gas such as argon or helium. Then, the both ends of the glass tube
are sealed by melt the venting tube. There are many types of
fluorescent lamp, for example, straight tube shaped, ball shaped, U
shaped, spiral shaped, annular shaped, or the like. Preferably, the
anatase TiO.sub.2 solution is carried out by dip coating. For
straight tube or annular lamp products or semi-products without
electrode bases and pins yet, a protection sleeve or protection
plastic film can be used to mask the electrode bases and pins
before the coating. After finishing coating, the protection sleeve
or protection plastic film is removed and baking is performed.
Alternatively, after coating, the lamp is directly baked without
removing the protection sleeve or protection plastic film. For
single-end connector lamps, the lamp products are coated by a base
fixing method, while the semi-product lamps are coated by a
clipping fix method.
[0047] It is advantageous to use the present invention anatase TiO2
solution to coat the lamps by dip coating method thereof, because
the resultant TiO.sub.2 coating can achieve a high-quality optical
level, which cannot be achieved by conventional spray coating,
brush coating, roller coating, or shower coating. According to the
dip coating method of this invention, the lamp is fixed on a
coating frame, to ensure high quality of coat, the coating speed is
kept to below 30 cm/min. By way of example, a 120 cm, 40 W
fluorescent lamp needs at least 4 minutes for completion. The use
of the coating frame enables 100 tubes to be coated at one time,
that is, 3 seconds for each tube, thereby facilitating industrial
mass production.
[0048] This invention also proposes anatase TiO2 solution coating
methods for either straight tube two-end fluorescent lamps or
single-end fluorescent lamps. As shown in FIG. 6A, the straight
tube two-end fluorescent lamp (40) has lamp cap and lamp pin at its
two ends. To prevent contact with the anatase TiO2 solution during
the dip coating process, the lamp cap and lamp pin are protected by
a protection sleeve or thermal plastic film. The protected straight
tube two-end fluorescent lamp (40) is then fixed on the coating
frame. The coating frame is schematically shown in FIG. 8. The
coating frame, which is made of stainless steel, has a hook at its
top surface, with an upper and lower flushing plates with
apertures. The upper plate has a clipping mechanism at the center
of four apertures for fixing lamp cap and lamp pin. The distance
between the upper and the lower flushing plates is adjustable and
is adjusted to a condition that the lamps can easily enter and get
out from the side or the lower apertures plate with the fixing
mechanism on the aperture. By doing this, the lamps can be placed
in the frame in an array, as shown in FIG. 8. The coating frame
(60) has capacity of 7.times.7=49 tubes each time or
10.times.10=100 tube array.
[0049] The sol-gel coating for straight tube fluorescent lamp is
carried out by first washing the lamp product in a washer or
cleaning machine to remove surface oil and inorganic alkali. Acid
or alkaline cleaning solution is not suitable at his stage, because
the two ends of the lamp contain metal. Preferably, the lamp is
brush washed using non-ionic surfactant solution, then washed by
de-ionized water, followed by baking. After washing, the two ends
of the lamp are covered with protection sleeve or thermal plastic
film. The covered tubes are arranged and positioned on the coating
frame, which is thereafter connected to the coating machine through
the hook. The coating machine transfers the coating frame to dip
into the anatase TiO.sub.2 solution, and then pulls out the coating
frame steadily at a pull speed of about 30 cm/min, such that a
uniform coating of anatase TiO.sub.2 is formed. After draining the
excess anatase TiO.sub.2 solution from the bottom, the coated tubes
are transferred to an oven to bake at 150-250.degree. C. for 30-60
minutes. To improve the hardness and strength of the anatase TiO2
coating, the tube may be coated with SiO.sub.2 sol or
H.sub.4TiO.sub.4 sol in advance by a dip coating method. After
drying at room temperature, the tube is then subjected to an
anatase TiO.sub.2 coating and subsequent baking. It is understood
that the thickness control of the coating by the gel-solution
depends on gel-solution concentration and coating speed to achieve
desired optical coating quality.
[0050] FIGS. 6B, 6C, and 6D illustrate various single-end
fluorescent lamps, which are the current trend in fluorescent
lamps. FIG. 6B shows a U-shaped lamp. The U-shaped lamp includes a
single tube, dual tubes, and triple tubes. FIG. 6C shows a spiral
lamp. FIG. 6D shows a special dual-layer lamp. The relative coating
frames are shown in FIG. 9A and FIG. 9B. The coating frames shown
in FIG. 9A has a frame height L'. The lamp base is fixed on a
corresponding aperture of the coating frame (70). As shown in FIG.
9B, the working depth is L. The single-end lamp is screwed into the
lamp connecter or clipped to the lamp base with lamp tube facing
down, dipping into alcohol for minute to remove oil and residuals
with air dried, then dipped into the anatase TiO2 solution, and
then baked in the oven at 150-250.degree. C. Since the length of
the single-end lamp is relatively short, and the tube is bent with
large angle, the pull speed is preferably 10-15 cm/min to ensure
better quality.
[0051] 4. Preferred Embodiments of this Invention.
[0052] The fabrication of the anatase TiO.sub.2 solution coated
fluorescent lamp capable of cleaning air involves the preparation
of the anatase TiO.sub.2 solution and the photocatalytic coating
for fluorescent lamps. The currently adapted procedure for
fabricating the photocatalytic coating fluorescent lamp includes
the lamp product going through anatase TiO.sub.2 solution dipping
and coating, followed by 150-250.degree. C. baking. In one
embodiment, the semi-product glass tube goes through anatase
TiO.sub.2 sol dip coating, followed by 150-250.degree. C. baking.
The decomposition efficiency of the coated lamp is measured as
evidence of the ability of the anatase TiO.sub.2 sol coated
fluorescent lamp for air cleaning.
EXAMPLE 1
[0053] About 1 mole titanium alkoxide such as Ti(OR).sub.4, where R
is a hydrocarbon group, C.sub.nH.sub.2+1 and n=1-5, and is, for
example, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl,
sec-butyl, pentyl and the like, is incorporated with chelating
agents. Strong chelating agents such as organic acid RCOOH, Organic
acetate CH.sub.3(O)CCH.sub.2C(O)R, amino acid RCH(NH.sub.2)COOH,
succinic acid HOOCCH(R)COOH, and organic alcohol
RC.sub.6H.sub.3(OCH.sub.3)OH are used. The amount of strong
chelating agent added should be controlled to a chelating
agent/Ti(OR).sub.4 mole ratio of 0.01-2.0, and preferably 0.1-1.0.
Preferably, the chelating agent is mixed with alcoholic solvent
such as ethanol, propanol, iso-propanol, butanol, iso-butanol, or
methanol before mixing with the titanium alkoxide. The amount of
alcoholic solvent blended should be controlled to an alcoholic
solvent/chelating agent mole ratio of 1-100, preferably diluted to
a mole ratio of 10. The mixture of alcoholic solvent and the
chelating agent is slowly mixed with the titanium alkoxide. The
chelating agent reacts with the Ti(OR).sub.4 to form
Ti(OR).sub.3-SCA complex, where SCA means Strong Chelating Agent.
The complex is then added into water or alcohol-containing aqueous
solution to hydrolyze. The water/ titanium alkoxide mole ratio is
1-400, preferably 100. After hydrolysis, a white colored gel slurry
is obtained, which is then subjected to inorganic acid titration.
Suitable inorganic acid includes nitric acid, hydrochloric acid,
hydrofluoric acid, or the like. After the titration, the pH value
of solution is 1.0-2.0. Preferably, nitric acid is used for the
titration. The gel solution is stirred and heated under normal
atmospheric conditions. When the pH below 2.0 the gel begin to
peptize and the solution becomes transparent. The hydrothermal
temperature is further raised and pressure increases, but those
were kept below 250.degree. C. to prevent boiling. As mentioned, a
higher hydrothermal temperature or a longer hydrothermal results in
anatase TiO.sub.2 particle having a better crystal structure.
However, a higher hydrothermal temperature or longer hydrothermal
also results in larger crystal size. To ensure that the anatase
TiO.sub.2 sol coating has good transmittance and planar topography,
it is preferable that the anatase TiO.sub.2 sol particle size is
maintain between 10-100 nm. In practice, the actual anatase TiO2
sol particle size is 1-10 nm. In addition to hydrothermal
conditions, temperature, time, stirring, and pH, the control
factors for the particle size of the anatase TiO.sub.2 sol further
include the property and quantity of chelating agent as well as the
property and quantity of titanium alkoxide. The resultant acidic
anatase TiO.sub.2 solution has a TiO.sub.2 concentration of 0.2-10%
by weight and is slightly yellow color transparent liquid.
[0054] In accordance with this preferred embodiment of the present
invention, a 4 wt % anatase TiO.sub.2 solution prepared by
above-said process is used to coat various 40 W fluorescent lamps
including FL-40-W, FL-40-D, FL-40-WEX, and FL-40-DEX. The FL-40-W
(white light) and the FL-40-D (sun light) use single visible light
fluorescent agent such as Ca.sub.10(PO.sub.4).sub.6FCl:(Sb,Mn)
(Nichia NP10, NP20). The FL-40-WEX (strong white light) and
FL-40-DEX (strong sun light) may use three wave mixed fluorescent
agent including Sr.sub.5(PO.sub.4).sub.3Cl:Eu (Nishia Np-103) blue
light fluorescent agent, LaPO4:(Ce, Tb) (Nishia NP-220) green light
fluorescent agent, and Y.sub.2O.sub.3:Eu (Nishia NP-340) red light
fluorescent agent, or mixed-type fluorescent agent such as NP-93 or
NP-96 by Nishia. The above-said fluorescent lamps are coated with
anatase TiO.sub.2 solution and baked at 150.degree. C. The
decomposition efficiency of the above-said fluorescent lamps
regarding organic substance butyl acetate is measured in a 5-liter
close chamber system. 5.0 .mu.l butyl acetate is injected into the
5-liter close chamber system and measured by using FTIR during the
irradiation of 40 W fluorescent lamps. The results are shown in
Table 1.
1TABLE 1 UV 365 nm intensity Butyl acetate decomposition rate
(mW/cm.sup.2) constant (min.sup.-1) FL-40-WA 0.144 0.0324 FL-40-DA
0.119 0.0309 FL-40-WEXA 0.110 0.0434 FL-40-DEXA 0.071 0.0253 Note:
40 W fluorescent lamps; acidic 4 wt % anatase TiO.sub.2 solution
coating.
[0055] Comparison Table 2 shows the color temperatures and
brightness (Lm) before and after photocatalytic coating of the
lamps.
2 TABLE 2 Color temperature (.degree. K) Brightness (Lm) Before
After Before After coating coating coating coating FL-40-WA 4212
4196 3037 3059 FL-40-DA 6099 6104 2792 2803 FL-40-WEXA 3929 3893
3500 3524 FL-40-DEXA 6860 6875 3309 3319 Note: 40 W fluorescent
lamps; acidic 4 wt % anatase TiO2 solution coating.
[0056] From the above, it is evident that the illumination ability
of the lamps after coating with anatase TiO.sub.2 does not degrade,
while the ability in decomposing organic gas is improved. On
average, the decomposition rate of butyl acetate in rate constant
is 0.025-0.043 min.sup.-1, that is, the lamps coated with anatase
TiO.sub.2 can decompose 2.5-4.3% of surrounding organic gas every
single minute.
EXAMPLE 2
[0057] 1.0 mole titanium alkoxide is added into water for
hydrolysis. The resultant solution has a H.sub.2O/titanium alkoxide
mole ratio of about 100. The titanium alkoxide is hydrolyzed to
become white H.sub.xTiO.sub.[(4-x)/2+x].nH.sub.2O gel solution.
After filtrating and then water-washing the hydrolysate solution,
H.sub.xTiO.sub.[(4-x)/2+x].n- H.sub.2O gel is obtained, which is
then diluted with water that is 0.1-1.0 times the weight of the
gel. The pH value of the diluted gel solution is thereafter
adjusted by alkaline substance such as NH.sub.4OH, N(R).sub.4OH, or
N(R).sub.3. The pH value is adjusted to above 9.0-12.0. The
alkaline substance/titanium alkoxide mole ratio is in a range of
0.05-0.5. After adjusting the pH value, the solution is stirred and
heated in a hydrothermal reactor for 1-25 hours. The temperature of
the hydrothermal is 100-250.degree. C. After the hydrothermal,
alkaline anatase TiO.sub.2 solution gel, which is a yellow
transparent liquid, is obtained. The resultant anatase TiO.sub.2
sol contains 2-20 wt % TiO.sub.2. The thus-formed anatase TiO.sub.2
sol is analyzed by a FT-Raman spectrometer, and the result is shown
in FIG. 2. The DLS particle size analysis is shown in FIG. 3. At
least 80% of the particles suspended in the thus-formed anatase
TiO.sub.2 solution gel have particle size below 20 nm.
[0058] In this example, the 20 wt % alkaline anatase TiO.sub.2 sol
is used to coat various lamps (those as example 1). The fluorescent
lamps are coated with anatase TiO.sub.2 sol and baked at
150.degree. C. The decomposition efficiency of the above
fluorescent lamps regarding organic substance butyl acetate is
measured in a 5-liter close chamber system. 5.0 .mu.l butyl acetate
is injected into the 5-liter close chamber system and measured by
using FTIR during the irradiation of 40 W fluorescent lamps.
Brightness (Lm) before and after photocatalytic coating of the
lamps is also taken. The results are shown in Table 3.
3TABLE 3 Butyl acetate decomposition rate Brightness (Lm) constant
(min.sup.-1) Before coating After coating FL-40-WB 0.1036 3016 3042
FL-40-DB 0.1885 2741 2771 FL-40-WEXB 0.269 3476 3504 FL-40-DEXB
0.1646 3315 3326 Note: 40 W fluorescent lamps; coated by 20 wt %
anatase TiO.sub.2 alkaline solution.
[0059] It is evident that the illumination ability of the lamps
after coating with 20 wt % anatase TiO.sub.2 does not degrade. It
is found that the decomposition rate of butyl acetate is basically
proportional to the thickness of the anatase TiO.sub.2 coating.
Compared with example 1, the thickness of the 20 wt % alkaline
anatase TiO.sub.2 coating is 5 times the thickness of the 4 wt %
acidic anatase TiO.sub.2 coating, and the decomposition rate of
butyl acetate is also 5 times the decomposition rate of example
1.
[0060] According to example 1 and example 2 of fabrication of the
anatase TiO.sub.2 solution coated fluorescent lamp capable of
cleaning air, it is evident that either the fluorescent lamps or
RGB fluorescent lamps, after coating with anatase TiO.sub.2, go
through change on photocatalytic function and increase in
illumination ability. The comparison is shown in Table 4.
4 TABLE 4 Butyl acetate Relative de- UV bright- composition- 365 nm
Brightness (Lm) ness rate constant intensity After Before ratio
(min.sup.-1) (mW/cm.sup.2) coating coating (note 1) FL-40-W-0A
0.0309 0.144 3037 3059 1.0072 FL-40-W-0B 0.1036 0.144 3016 3042
1.0086 FL-40-D-0A 0.0324 0.119 2792 2803 1.0039 FL-40-D-0B 0.1885
0.119 2741 2771 1.0109 FL-40-WEX-0A 0.0434 0.110 3500 3524 1.0068
FL-40-WEX-0B 0.2690 0.110 3476 3504 1.0080 FL-40-DEX-0A 0.0253
0.071 3309 3319 1.0030 FL-40-DEX-0B 0.1646 0.071 3315 3326 1.0033
Note 1: Relative brightness ratio: Brightness of the lamps coated
with anatase TiO.sub.2 (Lm a)/Brightness of the lamps not coated
with anatase TiO.sub.2 (Lm b).
[0061] From Table 4, the RGB fluorescent lamp FL-40-WEX coated with
4 wt % acidic anatase TiO.sub.2 sol presents superior
photocatalytic ability amount the four fluorescent lamp, with butyl
acetate decomposition rate of 0.0434 min.sup.-1. When coated with
20 wt % alkaline anatase TiO.sub.2 sol, the RGB fluorescent lamp
FL-40-WEX also shows highest butyl acetate decomposition rate of
0.269 min.sup.-1. The illumination ability of the lamps after
coated with anatase TiO.sub.2 does not degrade. It is surprisingly
found that most lamps coated with anatase TiO.sub.2 can increase
illumination ability. Taking FL-40-D and FL-40-WEX as an example,
their brightness increase 0.74%.
EXAMPLE 3
[0062] In this example, spiral fluorescent lamps are used. The
spiral-type single end fluorescent lamps are coated with anatase
TiO.sub.2 by the above dip coating process to form a photocatalytic
coating air cleaning fluorescent lamp. The air cleaning ability
test is conducted in an 8-liter closed system. In the closed
system, the spiral fluorescent lamp coated with anatase TiO.sub.2
is installed therein and 2 .mu.L butyl acetate is injected. The
lamp is turned on and the gas concentration is measured by standard
equipment. The result is shown in Table 5.
5TABLE 5 Butyl acetate UV TiO.sub.2 Butyl acetate decomposition
intensity anatase concentration rate constant (mW/ Lamp Type Sol
Type (ppm) (min.sup.-1) cm.sup.2) Spiral lamp as 53 0.027 0.189
Example 1 23 W, D-type as 53 0.0676 0.254 Example 2 Spiral lamp as
53 0.004 0.217 Example 1 21 W, D-type as 53 0.0718 0.215 Example 2
Spiral lamp as 53 0.021 0.476 Example 1 21 W, L-type as 53 0.1474
0.583 Example 2
[0063] In this experiment, different spiral type lamps are dip
coated in anatase TiO.sub.2 solution. The air cleaning ability is
proportional to the UV intensities of the lamps, and is also
proportional to the anatase TiO.sub.2 coating thickness. From Table
5, it is seen that the Spiral lamp (21 W, L-type) coated with 20 wt
% alkaline anatase TiO.sub.2 sol as in example 2 presents a butyl
acetate decomposition rate of 0.1474 min.sup.-1, and is thus the
most effective one.
EXAMPLE 4
[0064] In this example, a spiral type fluorescent lamp is used. The
spiral-type single end fluorescent lamp is coated with anatase
TiO.sub.2 by the above dip coating process to form a photocatalytic
coating air cleaning fluorescent lamp. To improve the thickness,
adhesion ability, and hardness of the photocatalytic coating,
H.sub.4TiO.sub.4 sol is added into the anatase TiO.sub.2 solution,
with a maximum (H.sub.4TiO.sub.4 gel/anatase TiO.sub.2 solution)
ratio of 10% in weight. The air cleaning ability test is carried in
an 8-liter closed system. In this closed system, the spiral
fluorescent lamp coated anatase TiO.sub.2 with a little of
H.sub.4TiO.sub.4 sol, is installed therein and 2.0 .mu.l butyl
acetate is injected. The lamp is turned on and the gas
concentration is measured by standard equipment. The results are
shown in Table 6.
6TABLE 6 Butyl acetate TiO2 H.sub.4TiO.sub.4/ Butyl acetate
decomposition anatase anatase TiO.sub.2 concentration rate constant
Lamp Type Sol Type wt % (ppm) (min.sup.-1) Spiral lamp as 1 53
0.0201 21 W, Example 1 L-type as 1 53 0.1286 Example 2 as 5 53
0.0204 Example 1 as 5 53 0.0971 Example 2 as 10 53 0.0193 Example 1
as 10 53 0.0462 Example 2
[0065] It is evident from example 3 and example 4 that the
H.sub.4TiO.sub.4/anatase TiO.sub.2 solution can improve the
thickness, adhesion ability, and hardness of the photocatalytic
coating. From Table 6, it is found that adding H.sub.4TiO.sub.4 sol
into the 4 wt % acidic anatase TiO.sub.2 solution in a
H.sub.4TiO.sub.4/anatase TiO.sub.2 ratio of 1-10 wt %, and then
using this mixture to coat the spiral lamp (21 W, L-type) does not
degrade the air cleaning ability of the lamp. However, the air
cleaning ability of the spiral lamp (21 W, L-type) are affected
when H.sub.4TiO.sub.4 gel is added into the 20 wt % alkaline
anatase TiO.sub.2 solution in a H.sub.4TiO.sub.4/anatase TiO.sub.2
ratio of 1-10 wt %, and this mixture is then used to coat the
spiral lamp. It is also found that a higher the
H.sub.4TiO.sub.4/anatase TiO.sub.2 ratio results in a lower butyl
acetate decomposition rate. It may be concluded that the
H.sub.4TiO.sub.4/anatase TiO.sub.2 mixture solution at a
H.sub.4TiO.sub.4/anatase TiO.sub.2 ratio below 10 wt % about 1.0 wt
% is suitable for acidic anatase TiO2 sol for fabricating the air
cleaning fluorescent lamp of this invention.
EXAMPLE 5
[0066] In this example, a spiral-type fluorescent lamp (FSL-23 W
EXL-type) is used. The spiral-type single end fluorescent lamp is
coated with anatase TiO.sub.2 one to four times by using the
above-mentioned dip coating process to form a photocatalytic
coating air cleaning fluorescent lamp. Likewise, the air cleaning
ability test is carried out in an 8-liter closed system. In the
closed system, the spiral-type single end fluorescent lamp coated
with anatase TiO.sub.2 is installed therein and 2 .mu.L butyl
acetate is injected. The lamp is turned on and the gas
concentration is measured by standard equipment. The result is
shown in Table 7.
7TABLE 7 Butyl acetate TiO.sub.2 Butyl acetate decomposition Lamp
Anatase Numbers of dip concentration rate constant Type Sol Type
coating (ppm) (min.sup.-1) Spiral as 1 53 0.0127 lamp Example 1
FSL-23 W as 2 53 0.0704 EXL-type Example 1 as 3 53 0.1075 Example 1
as 4 53 0.1495 Example 1 as 1 53 0.0676 Example 2 as 2 53 0.1988
Example 2 as 3 53 0.3049 Example 2 as 4 53 0.3089 Example 2
[0067] According to example 5, it is evident that when using the
spiral-type single end fluorescent lamp coated with anatase
TiO.sub.2 (as used in example 1) one to four times by using the
above-mentioned dip coating process to form a photocatalytic
coating air cleaning fluorescent lamp, the air cleaning ability of
the photocatalytic coating is proportional to the thickness of the
coating thereof. The anatase TiO.sub.2 solution adopted in example
1 is 4 wt % acidic anatase TiO.sub.2 sol. The thickness of the
coating is proportional to the number of duplicate dipping-coating,
and is also proportional to butyl acetate decomposition rate. In
Table 7, it is seen that the butyl acetate decomposition rate
increases from 0.0127 cm.sup.-1 to 0.1495 cm.sup.-1. This indicates
that the acidic anatase TiO2 coating is still not at its optimal
coating thickness. That is, the butyl acetate decomposition rate of
the acidic anatase TiO.sub.2 coating may further increase if the
thickness of the coating increases.
[0068] The anatase TiO.sub.2 solution adopted in example 2 is 20 wt
% alkaline anatase TiO.sub.2 sol. The thickness of the coating is
also proportional to the number of duplicate dip coating for 20 wt
% alkaline anatase TiO.sub.2 sol. For a lamp with three duplicate
dip coatings in the 20 wt % alkaline anatase TiO.sub.2 sol, the
butyl acetate decomposition rate increases from 0.0676 cm.sup.-1 to
0.3049 cm.sup.-1. But for a lamp with four duplicate dip coatings
in the 20 wt % alkaline anatase TiO.sub.2 sol, the butyl acetate
decomposition rate slows up to 0.3089 cm.sup.-1. This suggests that
the coating film from three 20 wt % alkaline anatase TiO.sub.2 sol
duplicate dip coatings is at its optimal thickness, and there is a
balance between the diffusion rate of the air and organic
substances between the air and the coating film to got the maximum
rate about the photocatalytic reaction. After three duplicate dip
coatings in the 20 wt % alkaline anatase TiO.sub.2 sol, the
thickness of the anatase TiO.sub.2 coating is about 10 microns,
which is deemed the optimal thickness of the anatase TiO.sub.2 sol
coating developed according to the present invention.
[0069] To sum up, the present invention provides methods for
preparing nano-scale semiconductor crystalline anatase TiO.sub.2
particle solution, which is used to coating various fluorescent
lamps by the above-mentioned dip coating method. The coated
fluorescent lamps are baked to form photocatalytic fluorescent
lamps capable of cleaning air. The photocatalytic fluorescent lamps
have improved brightness and illumination ability. Due to the
porous characteristic of the anatase TiO.sub.2 coating and its
visible light photocatalytic ability, a small amount of UV light
(UVA) and visible light are absorbed by the anatase TiO.sub.2
coating and thus active species such as electron-hole pairs that
are capable of purifying air are generated. The alkaline anatase
TiO.sub.2 nano-crystalline solution can reach a concentration of 20
wt %. For the lamp having three duplicate dip coatings in the 20 wt
% alkaline anatase TiO.sub.2 sol, the butyl acetate decomposition
rate increases from 0.0676 cm.sup.-1 to 0.3049 cm.sup.-1, which is
about 10-100 times the magnitude of the most efficient prior art
TiO.sub.2 coating.
[0070] The anatase TiO.sub.2 nano-crystalline or doped with Eu or
rare earth metal oxide on anatase TiO.sub.2 nano-crystalline
solution functions like fluorescent agents. The coating is carried
out on outer walls of the lamps and only low temperature baking is
needed. It is surprisingly found that the coating according to the
present invention can increase the brightness of the lamps, which
is not disclosed in any prior art.
[0071] Various types of fluorescent lamps may incorporate the
present invention recipe and process thereof. The anatase TiO.sub.2
sol dip coating process proposed by the present invention may be
used either before the lamps fabricated or after the completion of
the lamps. Furthermore, it is understood the concentration of
chemicals and types of additives in this application are for
illustration. Changes may be made in detail, especially in matters
of shape, size, and arrangement of parts within the principles of
the invention to the full extent indicated by the broad general
meaning of the terms in which the appended claims are
expressed.
* * * * *