JP2004085375A - Evaluation method and evaluation apparatus for photocatalyst activity and layer including photocatalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly evaluate photocatalyst activity in a manufacturing process of a layered structure by using an evaluation method and an evaluation apparatus for the photocatalyst activity of the layered structure having a photocatalyst layer disposed on a surface and including a photocatalyst. <P>SOLUTION: The evaluation method is provided with a process for dipping the layered structure 5 into an electrolyte after the layer having the photocatalyst (the photocatalyst layer) as a surface layer of the layered structure 5 has hydrophilic, bringing the electrolyte into contact with the surface of the photocatalyst layer, connecting an electrode of a potentiostat 39 to the layered structure 5 while a reference electrode 38 and the electrolyte are coupled through a salt bridge 37 and measuring a spontaneous potential, a process for radiating an active light having energy larger than band gap energy of the photocatalyst to the photocatalyst layer after the spontaneous potential is measured and measuring a surface potential generated during a radiation time of the active light and a process for evaluating the photocatalyst activity of the photocatalyst layer based on the maximum of an absolute value of a rise time (unit: V/sec) of the surface potential. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for evaluating the photocatalytic activity of a layered structure having a photocatalyst layer containing a photocatalyst on the surface.
[0002]
[Prior art]
As a general printing technique, digitization of a printing process is in progress. In this method, an image and a document are produced by a personal computer, or an image is read by a scanner or the like to digitize the image data, and a printing plate is produced directly from the digital data. This can save labor in the entire printing process and facilitate high-definition printing.
[0003]
The present inventors have proposed a printing plate material that can be reused while coping with the digitization of the printing process as described above, and a method of reproducing the printing plate material (see Patent Document 1).
That is, using a coating material containing a titanium oxide photocatalyst formed on a substrate as a printing plate material, in the initial state at the time of plate production, the surface of the coating layer is adjusted to show a hydrophobic state, This surface is irradiated with light (active light) having a wavelength higher than the band gap energy of the titanium oxide photocatalyst based on the above digital data, and a part of the surface is converted into a hydrophilic surface. A plate comprising a hydrophobic image portion and a hydrophilic non-image portion is prepared. After the printing is completed, the irradiation of the energy flux or the chemical conversion treatment is performed in combination or alone to convert the entire surface of the coat layer to the initial state at the time of producing the hydrophobic plate again.
[0004]
In addition, the present inventors apply a compound such as octadecyltrimethosisilane to the surface of the plate material to adjust the surface to a hydrophobic state, and then apply the compound again after printing. In addition, a technique has been proposed in which the surface of the coating layer is converted so as to be in an initial state at the time of producing a plate exhibiting hydrophobicity again (see Patent Document 2).
By the way, in the production and reproduction of the printing plate as described above, there is a demand that the writing of the image and the erasing of the image history by the light irradiation should be performed promptly and the printing preparation time in the printing process should be reduced as much as possible.
[0005]
In order to quickly perform image writing and image history deletion by light irradiation, the photocatalyst must have high photocatalytic activity, so in order to determine whether the photocatalyst has high photocatalytic activity, An evaluation method for evaluating the photocatalytic activity is required.
As a conventional method for evaluating photocatalytic activity, for example, the following method is known. That is, a method of forming an organic layer having a lower alcohol on a photocatalyst layer containing a photocatalyst, irradiating the photocatalyst layer with ultraviolet rays through the organic layer, and evaluating the activity of the photocatalyst layer by the contact angle of water (Patent Document 3) And a method in which an organic dye such as methylene blue is attached or adsorbed on the photocatalytically active surface of the photocatalytically active material, and the decomposition rate of the organic dye is measured to determine the photocatalytic activity (see Patent Document 4). A method of irradiating the photocatalytic film with light in an active gas atmosphere and an atmosphere containing oxygen and water vapor and comparing changes in the surface potential of the photocatalytic film (see Patent Document 5).
[0006]
[Patent Document 1]
JP-A-2000-62334
[0007]
[Patent Document 2]
JP-A-2000-62335
[0008]
[Patent Document 3]
JP 2001-183359 A
[0009]
[Patent Document 4]
JP-A-11-83833
[0010]
[Patent Document 5]
JP-A-11-258206
[0011]
[Problems to be solved by the invention]
However, the evaluation methods according to Patent Publications 3 and 4 require a great deal of time to evaluate the photocatalytic activity. Further, the evaluation method according to Patent Document 5 requires two steps of measuring the surface potential in an inert gas atmosphere and measuring the surface potential in an atmosphere containing oxygen and water vapor. It cannot be evaluated.
[0012]
The present invention has been made in view of such a problem, and is a method for evaluating a photocatalytic activity, in which a photocatalytic activity can be evaluated in a short time in a manufacturing process of a layered component having a layer containing a photocatalyst. And an evaluation device.
Still another object of the present invention is to provide a layer containing a photocatalyst, which can be evaluated as having high photocatalytic activity by the method for evaluating photocatalytic activity.
[0013]
[Means for Solving the Problems]
The present invention has taken the following means in order to solve the above-mentioned problems.
That is, the method for evaluating photocatalytic activity of the present invention (Claim 1) is a method for evaluating the photocatalytic activity of a layered composition having a photocatalyst layer containing a photocatalyst on its surface, wherein the photocatalyst layer has a bandgap energy of the photocatalyst. Irradiating the layered component having a surface hydrophilicized to a contact angle of water of 10 ° or less by irradiating an active light having a larger energy than the electrolyte to contact the electrolyte with the surface of the layered component, In a state where the reference electrode and the electrolytic solution are connected by a salt bridge, a step of connecting a potentiostat electrode to the layered structure to measure a natural potential on the surface of the layered structure, and after the measurement of the natural potential, Irradiating the photocatalytic layer with actinic light, measuring the change in surface potential of the layered component with the irradiation time of the actinic light, and the maximum value of the absolute value of the rising speed (unit: V / sec) of the surface potential Based on the photocatalyst layer It is characterized in that it includes a step of evaluating the photocatalytic activity. Hereinafter, light having effective energy for causing the photocatalyst of the present invention to exhibit catalytic activity will be referred to as active light.
[0014]
The electrolyte is Na ₂ SO ₄ (Claim 2).
An apparatus for evaluating photocatalytic activity of the present invention (claim 3) is an apparatus for evaluating the photocatalytic activity of a layered component having a photocatalyst layer containing a photocatalyst on its surface, and a surface potential for measuring the surface potential of the layered component. A measuring device, an active light irradiation device for irradiating the surface of the layered structure with active light having energy larger than the band gap energy of the photocatalyst, and irradiating the surface of the layered structure with the active light by the active light irradiation device And a calculating device for calculating the maximum value of the absolute value of the rising speed (unit: V / sec) of the surface potential from the surface potential measured by the surface potential measuring device and the light irradiation time. It is characterized by.
[0015]
The surface potential measuring device has a first insulating plate provided in close contact with the back surface of the layered structure, and a second insulating plate having an opening and provided in close contact with the surface of the layered structure. A plate, an electrolyte poured into the opening, a salt bridge connecting the electrolyte and the reference electrode, and a potentiostat having an electrode connected to the layered structure. Is preferable (claim 4). Further, the electrolyte is Na ₂ SO ₄ (Claim 5).
[0016]
The layer containing the photocatalyst of the present invention (claim 6) was measured using the evaluation method described in claim 2, and the surface potential induced by irradiating the active light was plotted against the active light irradiation time. The slope of the curve, that is, the maximum value of the absolute value of the rising speed (unit: V / sec) of the photovoltaic value is 10 mW / cm of the illuminance of the active light. ² Is 0.2 (unit: V / sec) or more under the condition of (1).
[0017]
In a layer containing a photocatalyst in which the maximum value of the absolute value of the rising speed (V / sec) of the photovoltaic value is 0.2 V / sec or more (hereinafter, also referred to as a photocatalyst layer), the surface of the photocatalyst layer is irradiated with active light. The decomposition of the organic compound present in the photocatalyst and the hydrophilization of the photocatalyst itself occur simultaneously and promptly.
Here, the photovoltaic value is such that at least the component (sample electrode) having a photocatalyst layer is 0.1 mol Na ₂ SO ₄ The potential of the sample electrode with respect to the saturated calomel electrode (abbreviated as SCE) when the active electrode is irradiated with active light in a state where the electrode is placed in an aqueous solution and the platinum electrode as a counter electrode is brought close to the surface of the photocatalyst layer.
[0018]
The layer containing the photocatalyst of the present invention (claim 7) is measured by the evaluation method according to claim 2, and the slope of a curve in which the surface potential is plotted against the active light irradiation time by irradiating the active light. That is, the maximum value of the absolute value of the rising speed (unit: V / sec) of the photovoltaic value is determined by the illuminance (W / cm) of the active light. ² ) Is 20 (unit: Vcm) ² / Sec · W) or more.
[0019]
That is, in the photocatalyst layer of the present invention according to claim 6, the illuminance of the active light is set to 10 mW / cm. ² It was found that the maximum value of the absolute value of the rising speed (unit: V / sec) of the photovoltaic value obtained by changing the illuminance was almost proportional to the illuminance. Therefore, the maximum value of the absolute value of the rising speed (unit: V / sec) of the photovoltaic value obtained by changing the illuminance of the active light for a specific photocatalytic layer is defined as the illuminance (unit: W / cm). ² ) Was found to be almost constant irrespective of the illuminance, and to be an index of the catalytic activity for the specific photocatalytic layer.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[A] Description of layered component
First, a layered component having a layer containing a photocatalyst to which the method for evaluating photocatalytic activity of the present invention is applied (hereinafter, simply referred to as a component) will be described.
[0021]
FIGS. 1 and 2 show a composition 5 according to an embodiment of the present invention, and FIG. 1 shows that the surface thereof is hydrophobic (here, the water 6 has a contact angle of 50 ° or more). FIG. 2 is a schematic cross-sectional view of the case where the surface shows hydrophilicity (here, the contact angle of water 6 is 10 ° or less).
As shown in FIGS. 1 and 2, the composition 5 is basically composed of a base material (or support) 1, an intermediate layer 2, and a layer containing a photocatalyst (hereinafter, referred to as a photocatalyst layer) 3. ing.
[0022]
The substrate 1 is made of a metal such as aluminum or stainless steel, a polymer film, or the like. However, the substrate 1 is not limited to a metal such as aluminum or stainless steel, or a polymer film, and is not limited to the properties required when the photocatalyst layer 3 is put to practical use. The selection may be made according to characteristics such as flexibility (which may be called hardness), thermal conductivity, electrical conductivity, and durability.
[0023]
The intermediate layer 2 is formed on the surface of the substrate 1 and functions to securely adhere the substrate 1 and a photocatalyst layer 3 described later and to improve the adhesion. However, if the adhesion strength between the substrate 1 and the photocatalyst layer 3 can be sufficiently ensured, the intermediate layer 2 may be omitted.
Further, the effect of preventing the impurities from thermally diffusing from the base material 1 and mixing into the photocatalyst layer 3 to reduce the photocatalytic activity when the intermediate layer 2 is subjected to heat treatment for forming the photocatalyst layer 3 described later. There is also. Further, when the substrate 1 is formed of a polymer film or the like, the intermediate layer 2 may be formed for protecting the substrate 1 as necessary.
[0024]
As the intermediate layer 2, for example, silica (SiO ₂ ), Silicon resin, silicon rubber, etc. are used as the material. Among them, silicon alkyd, silicone urethane, silicone epoxy, silicone acryl, silicone polyester, etc. are used as the silicone resin.
The intermediate layer 2 preferably functions to enhance the photocatalytic action of the photocatalyst layer 3. As such an intermediate layer 2, an oxide semiconductor, an electric conductor, or a solid acid catalyst can be applied.
[0025]
For example, when an oxide semiconductor is used, zinc oxide ZnO, tin oxide SnO ₂ , Tungsten oxide WO ₃ And the like are preferable. Note that it is preferable to form the intermediate layer 2 using these oxide semiconductors. However, the intermediate layer 2 may be formed by forming oxide semiconductor fine particles with another binder substance.
When an electric conductor is used, an oxide such as ITO (oxide of indium and tin), a metal such as aluminum, silver, and copper, carbon black, or a conductive polymer can be used. The intermediate layer 2 may be formed by using the electric conductor itself, or the electric conductor fine particles may be formed of another binder material to form the intermediate layer 2.
[0026]
Further, when a solid acid catalyst is applied, SiO 2 ₂ / TiO ₂ , SiO ₂ / Ai ₂ O ₃ , SiO ₂ / ZrO ₂ , TiO ₂ / ZrO ₂ , TiO ₂ / WO ₃ , WO ₃ / Fe ₂ O ₃ , WO ₃ / ZrO ₂ , WO ₃ / SnO ₂ , WO ₃ / SiO ₂ Etc. are available.
By providing such an intermediate layer 2 containing an oxide semiconductor, an electric conductor, or a solid acid catalyst, under irradiation of active light, the action of the photocatalyst to decompose organic substances is promoted, or the action of the photocatalyst itself to become hydrophilic. Has been confirmed to be promoted.
[0027]
When the composition 5 having the photocatalyst layer 3 is used as a lithographic printing plate material (also simply referred to as a plate material) by enhancing the action of the photocatalyst in this manner, the writing speed at the time of writing an image on the plate by actinic light is improved. To shorten the plate making time and reduce the light energy required for image writing. Further, it is possible to reduce the irradiation energy of the active light applied to the plate material surface (plate surface) in order to erase (eliminate) the image history when the plate is reproduced. Although the reason is not clear, it is presumed that the semiconductor or the electric conductor constituting the intermediate layer 2 enhances the function of a photocatalyst included in the photocatalyst layer 3 described later.
[0028]
On the intermediate layer 2, a photocatalyst layer 3 is formed. By irradiating the surface of the photocatalyst layer 3 with active light having energy higher than the band gap energy of the photocatalyst, the organic compound attached to the photocatalyst layer 3 is decomposed, and at the same time, the photocatalyst itself has high hydrophilicity. Will be shown.
The photocatalyst layer 3 according to the present embodiment is formed using a photocatalyst in which the active light is light having a wavelength of 600 nm or less. Therefore, by irradiating light having a wavelength of 600 nm or less, the surface of the photocatalyst layer 3 shows high hydrophilicity at the same time as decomposing the organic compound.
[0029]
Essentially, a photocatalyst does not exhibit photocatalytic activity unless irradiated with light having an energy higher than the band gap energy. For example, an anatase-type titanium oxide photocatalyst has a bandgap energy of 3.2 eV, and therefore responds only to ultraviolet light having a wavelength of 380 nm or less.
In this embodiment, a photocatalyst that responds to light having a wavelength of 600 nm or less may be used by forming a new level between the band gaps. The light having a wavelength of 600 nm or less includes ultraviolet rays, but the photocatalyst according to the present embodiment operates similarly whether or not the active light contains ultraviolet rays. ing.
[0030]
As a method for producing such a photocatalyst that responds to light having a wavelength of 600 nm or less, a known method may be used. For example, JP-A-2001-207082 discloses a visible light responsive photocatalyst doped with a nitrogen atom, and JP-A-2001-205104 discloses a visible light responsive photocatalyst doped with a chromium atom and a nitrogen atom. ing. Furthermore, Japanese Patent Application Laid-Open No. 11-197512 discloses a visible light responsive photocatalyst in which metal ions such as chromium are ion-implanted. In addition, a visible light responsive photocatalyst using low-temperature plasma and a visible light responsive photocatalyst carrying platinum have been published. In manufacturing the component 5 having the photocatalyst layer 3 according to the present embodiment, a visible light responsive photocatalyst manufactured by a known manufacturing method may be used.
[0031]
In order to maintain the above-mentioned property, that is, the hydrophilic property, or to improve the strength of the photocatalyst layer 3 and the adhesion to the substrate 1, the following substances are added to the photocatalyst layer 3. You may.
Examples of the substance include silica-based compounds such as silica, silica sol, organosilane, and silicon resin; metal oxides and hydroxides such as zirconium, aluminum, and titanium; and fluorine-based resins. .
[0032]
Further, as the titanium oxide photocatalyst, there are a rutile type, an anatase type and a brookite type. In the present embodiment, any of them can be used, and a mixture thereof may be used. In addition, as a photocatalyst, a titanium oxide photocatalyst is suitable, but it is not limited to this.
Further, the thickness of the photocatalyst layer 3 is preferably in the range of 0.005 to 1 μm. This is because, if the film thickness is too small, it is difficult to make full use of the above-mentioned properties, and if the film thickness is too large, the photocatalyst layer 3 is liable to crack, which causes a reduction in printing durability. It is because it becomes. Since the crack is remarkably observed when the film thickness exceeds 10 μm, it is necessary to recognize 10 μm as the upper limit even if the above range is relaxed. In practice, it is more preferable to set the thickness to about 0.03 to 0.5 μm.
[0033]
Furthermore, as a method for forming the photocatalyst layer 3, a sol coating method, an organic titanate method, a sputtering method, a CVD method, a PVD method, or the like may be appropriately selected and formed. Among them, the sol-gel method is particularly preferable in that the process is simple, and the sputtering method has high film strength. When the component 5 having the photocatalyst layer 3 is used as a plate material, high printing durability can be obtained. There is an advantage that is.
[0034]
For example, if the sol-gel method is used, the sol used in the sol includes, in addition to the above-mentioned various substances for improving the strength of the titanium oxide photocatalyst and the photocatalyst layer 3 and the adhesion to the substrate 1, a solvent, A crosslinking agent, a surfactant and the like may be added. The sol may be a room temperature drying type or a heat drying type, but the latter is more preferable. This is because increasing the strength of the photocatalytic layer 3 by heating is advantageous for improving the printing durability of the plate.
[0035]
Further, a photocatalyst layer responding to light having a wavelength of 380 nm or less is further provided as a protective layer on the photocatalyst layer 3 responding to light having a wavelength of 600 nm or less, or a silica layer is provided for the purpose of easily maintaining hydrophilicity. May be. In addition, the photocatalyst layer 3 in this embodiment may include the above layers.
In the present embodiment, basically, the composition 5 having the photocatalyst layer 3 may be used as a plate material. For example, when aluminum is used as the substrate 1, the surface may be anodized as necessary. The base material 1 which has been subjected to a treatment called a so-called graining treatment, which has been roughened by performing, for example, may be used. Therefore, the composition 5 having the photocatalyst layer 3 can be used as a plate material as it is, or has a function suitable for printing by using the substrate 1 subjected to the graining treatment. It may be an improved one.
[0036]
Furthermore, since the composition 5 of the present invention has the feature that the oxidative decomposition performance of the organic compound and the hydrophilization performance of the photocatalyst itself are both high, in addition to the plate material, for example, the outer wall of a building or a structure is used. When used for indoor wall surfaces, tiles, window glass, etc., there is an effect that dirt is hardly adhered.
When the layered component 5 is used as a lithographic printing plate material, the organic compound that renders the photocatalyst layer 3 hydrophobic is supplied to the plate surface (the surface of the photocatalyst layer 3), and is dried or heated and dried as necessary. It is preferable that the surface of the plate is made hydrophobic by reacting or strongly interacting with the plate, and decomposed and removed from the plate by the action of a photocatalyst. As such an organic compound, specifically, an organic titanium compound, an organic silane compound, an isocyanate compound, or an epoxide compound is preferable. These compounds react with hydroxyl groups present on the hydrophilic printing plate and are fixed to the surface, so that an organic compound layer (not shown) is formed on the printing plate in principle as a monomolecular layer. Since the plate surface is hydrophobized with the monomolecular layer in this manner, the organic compound can be easily decomposed under the irradiation of active light.
[0037]
[B] Description of evaluation method for photocatalytic activity
Next, the maximum value of the absolute value of the rising speed of the photovoltaic value, which is a feature of the present invention, for the composition 5 having the photocatalytic layer 3 or the planographic printing plate material (hereinafter, represented by the composition). The relationship between and the catalytic activity will be described.
First, a method for measuring a photovoltaic value will be described with reference to a schematic diagram of a measuring device (surface potential measuring device) shown in FIG. Two Teflon (registered trademark) plates (here, 10 mm thick) [a first insulating plate and a second insulating plate. The upper one (the second insulating plate) is hollowed out to form an opening as shown in FIG. 3), and the photocatalyst layer 3 is oriented in the active light irradiation direction. The object 5 is set between the two Teflon (registered trademark) plates in the measurement cell 36 (Step S10 shown in FIG. 12; only the steps are shown). In the hollow portion of the measurement cell 36 shown in FIG. ₂ SO ₄ Fill the aqueous solution (that is, the depth of the electrolyte solution is about 10 mm) (Step S20).
[0038]
Next, the salt bridge 37 of the reference electrode [Saturated Calomel Electrode (SCE)] 38 is immersed in the electrolytic solution (Step S30), and the electrode of the potentiostat 39 is connected to the end of the component 5 (Step S40). . When active light is irradiated from above the cell in this state, a potential is generated in the component 5 by the action of the photocatalyst (in this case, a negative potential is generated). Note that the potential induced by this light is called a photovoltaic value. This photovoltaic value is measured by the potentiostat 39.
[0039]
The rising speed of the photovoltaic value was measured as follows.
As shown in FIG. 3, the constituent 5 serving as a measurement sample is set, and a potential generated in the constituent 5 without irradiating the active light, more specifically, an interface potential between the surface of the constituent 5 and the electrolyte solution (hereinafter, referred to as “potential”) (Referred to as “self-potential”) is stable (step S50), and then the illuminance is 10 mW / cm. ² Is irradiated for 15 seconds. Since the photocatalyst generates a negative potential by light induction, a decrease in the potential on the surface of the component 5 is observed simultaneously with the irradiation of light (step S60).
[0040]
FIG. 4 shows an example of a graph showing the change of the photovoltaic value (unit: V) with respect to the active light irradiation time (unit: sec) measured in this way.
Since a negative potential is generated as described above, when the slope (V / sec) of the graph of the change in the photovoltaic value with respect to the light irradiation time is obtained by the computer (calculation device) 40, the slope becomes a negative value. The absolute value of the slope was used as the absolute value of the rising speed of the photovoltaic value, and the maximum value of the absolute value was determined (step S70).
[0041]
In this measurement, active light having a wavelength of 254 nm was irradiated. However, if the photocatalyst contained in the constituent 5 is a photocatalyst that responds to visible light, light containing visible light having a wavelength of 600 nm or less may be used as the active light. Needless to say.
When the photocatalyst layer 3 of the composition 5 is irradiated with active light and subjected to the above measurement in a state where the photocatalyst layer 3 is hydrophilized to a contact angle of 10 ° or less, a measurement result with high reproducibility is obtained. This is because if the surface of the photocatalyst layer 3 is contaminated with an organic substance or the like, an error easily occurs in a later-described natural potential or photovoltaic value. Therefore, it is necessary to clean the surface of the photocatalyst layer 3 by irradiating with actinic light before the start of the measurement. If the contact angle is 10 ° or less as a measure of cleanliness, the measured value is stable and the reproducibility is low. Is a good thing.
[0042]
Next, a method for evaluating photocatalytic activity will be described.
First, the surface of the component 5 is irradiated with an energy flux such as light or electricity singly or in combination, and a mechanical stimulus such as friction is applied to the surface of the component 5. The surface of the composition 5 (that is, the surface of the photocatalyst layer 3) is hydrophobized by any of the methods of supplying an organic compound that interacts with the surface of the composition 5.
[0043]
In addition, as a standard of the hydrophobicity, for example, when the composition 5 is used as a plate material, the contact angle of the water 6 is preferably 50 ° or more, and more preferably, the contact angle is 80 ° or more. The surface of the hydrophobized component 5 is irradiated with active light, and the surface of the component 5 has a contact angle of 10 ° or less, that is, the active light irradiation time required until the surface becomes hydrophilic, and the illuminance of the active light is measured. X The energy required for hydrophilization (hereinafter referred to as hydrophilization energy) was estimated from the irradiation time of the active light (see FIG. 5).
[0044]
The conversion of the photocatalyst layer 3 from hydrophobic to hydrophilic by irradiation with actinic light is because the photocatalyst itself is hydrophilized, and when the surface of the photocatalyst layer 3 is hydrophobized by an organic compound, the organic compound is It means that the decomposing action occurred at the same time. Therefore, it can be said that the photocatalytic action is stronger when the surface is hydrophilized with a smaller hydrophilization energy.
The present inventors have found that the maximum value of the absolute value of the rising speed of the photovoltaic value is related to the hydrophilizing energy of the catalyst.
[0045]
The dotted line shown in FIG. 6 indicates that the type of the photocatalyst and the type of the intermediate layer 2 were changed to adjust the composition 5 having various photocatalyst layers 3, and the rise of the photovoltaic value of the composition 5 measured by the method described above. It is the graph which arranged the maximum value of the absolute value of the velocity and the hydrophilization energy.
Note that the maximum value of the absolute value of the rising speed of the photovoltaic value and the hydrophilizing energy were all 10 mW / cm of illuminance of active light. ² It was measured in. In addition, this hydrophilizing energy is measured in the case where the constituent 5 is hydrophobized by an organic compound capable of hydrophobizing the surface of the constituent 5 with a monolayer in principle.
[0046]
When an image is written on a plate material using active light, the light energy that can be used for writing is up to 500 mJ / cm. ² From FIG. 6, it can be seen from FIG. 6 that when the organic compound is hydrophobized, the hydrophilizing energy is 500 mJ / cm when the maximum value of the rising speed of the photovoltaic value is about 0.3 V / sec or more. ² The results are as follows, and it is understood that the photocatalytic activity of the photocatalyst layer 3 is at a practical level. In other words, when the composition 5 having the photocatalyst layer 3 is used as a plate material, if the maximum value of the absolute value of the rising speed of the photovoltaic value is 0.3 V / sec or more, the image writing with the active light can be performed at a practical level. Complete in an acceptable limit of time.
[0047]
In erasing the history of a plate by irradiating with active light in the plate reproducing process, the active light can be irradiated to a large area at a time, so that the light irradiation conditions are not so limited as in writing. If so, it is possible to eliminate the history of the plate by irradiation with actinic light.
Further, when the organic compound has a large molecular weight, or when the organic compound is hydrophobized with a large amount of organic compound instead of a monolayer, the organic compound is decomposed within a predetermined time, and the surface of the component 5 becomes hydrophilic. Needless to say, the maximum value of the absolute value of the rising speed of the photovoltaic value, which is a measure of the activity of the photocatalyst, must be larger than 0.3 V / sec.
[0048]
Further, the solid line shown in FIG. 6 shows the measurement results of the maximum value of the absolute value of the rising speed of the photovoltaic value and the hydrophilization energy in the case where the hydrophobization was performed without using the organic compound (individual measurement). Data omitted). In this case, since only the photocatalyst itself needs to be hydrophilized without decomposing the organic compound, even if the maximum value of the absolute value of the rising speed of the photovoltaic value is 0.2 V / sec, it is a practically acceptable limit. It can be seen that hydrophilization is completed in time.
From the above results, it was found that the maximum value of the absolute value of the rising speed of the photovoltaic value needs to be about 0.2 V / sec or more in order to use it at a practical level.
[0049]
Further, as shown in FIG. 7, the maximum value of the absolute value of the rising speed of the photovoltaic value was measured while changing the illuminance of the active light.
The constituent 5 as a measurement sample (sample) is set, and after confirming that the spontaneous potential has stabilized, active light is irradiated for 15 seconds. The illuminance of the active light is 3, 10, 20 mW / cm ² The maximum value of the absolute value of the rising speed of the photovoltaic value was measured, and the results were 0.29, 0.93, and 1.88 (V / sec), respectively.
[0050]
Thus, by changing the illuminance, the maximum value of the absolute value of the rising speed of the photovoltaic value changes, but the value obtained by dividing the maximum value of the absolute value of the rising speed of the photovoltaic value by the illuminance of light. Is the illuminance of the active light 3, 10, 20 mW / cm ² Respectively, 96.7, 93, 94 (unit: Vcm) ² / Sec · W).
That is, the value obtained by dividing the maximum value of the absolute value of the rising speed of the photovoltaic value by the illuminance of light is a substantially constant value regardless of the illuminance of the component 5 having one photocatalytic layer 3 of the present invention. I found that. The value obtained by dividing the maximum value of the absolute value of the rising speed of the photovoltaic value by the illuminance of light is referred to as a photocatalytic activity index value (unit: V · cm ² / Sec · W) ”.
[0051]
Regarding the composition 5 having the various photocatalyst layers 3 used for the measurement in FIG. 6, the illuminance of the active light was adjusted to 3, 10, and 20 mW / cm in the same manner as in FIG. ² FIG. 8 is a graph in which the average value of the photocatalytic activity index values measured in three stages is plotted against the hydrophilization energy.
[0052]
For example, as described above, the illuminance of the active light is set to 3, 10, 20 mW / cm. ² When the photocatalytic activity index values when changed are 96.7, 93, and 94, respectively, the average value is 94.6.
The hydration energy was 10 mW / cm of illuminance of active light as in the measurement of FIG. ² Is used, but when the hydrophilicity is measured by changing the illuminance of the active light, the illuminance of the active light (mW / cm ² ) × Hydrophilic energy (mJ / cm) estimated by irradiation time (sec) until hydrophilization ² ) Is constant regardless of the illuminance, and the illuminance is 1 to 1000 mW / cm. ² Confirmed in the range.
[0053]
As described above, when an image is written on a plate using actinic light, the light energy that can be used for writing is up to 500 mJ / cm. ² Assuming that the photocatalytic activity index value is about 30 or more when hydrophobized with a monolayer of an organic compound, and the photocatalytic activity index value is about 20 or more when hydrophobized without using an organic compound. It turns out that it is a practical level. Therefore, from the results of FIG. 8, in order to use the photocatalyst at a practical level, the value obtained by dividing the maximum value of the absolute value of the rising speed of the photovoltaic value by the illuminance of light, that is, the “photocatalytic activity index value (unit: V · cm ² /Sec.W) "is required at least 20 or more.
[0054]
In the present embodiment, Na ₂ SO ₄ Although the evaluation is performed using the electrolytic solution, it is needless to say that the evaluation can be similarly performed using another electrolytic solution. In that case, the rising speed of the photovoltaic value usable at a practical level can be obtained. The maximum absolute value and the photocatalytic activity index value vary depending on the electrolyte.
[0055]
[C] Explanation of the method of preparing and regenerating a lithographic printing plate
Next, a method of producing a lithographic printing plate (also simply referred to as a plate) and a method of reproducing the same when the component 5 having the photocatalyst layer 3 according to the present embodiment is used as a lithographic printing plate material will be described.
[0056]
First, a method of manufacturing a plate will be described. Here, the plate refers to a plate material having an image area for printing formed on the surface. In the following, "preparation of a plate" means that after making the plate surface hydrophobic, at least a part of the plate surface is irradiated with light having a wavelength of visible light or less based on digital data to form a hydrophilic non-image area. In addition to forming a latent image consisting of a hydrophobic image portion and a hydrophilic non-image portion on the plate surface, together with the hydrophobic portion of the plate surface that has not been irradiated with light having a wavelength of visible light or less. I do.
[0057]
First, the surface of the photocatalyst layer 3 is irradiated with the active light to make the entire surface of the printing plate 5 a hydrophilic surface having a contact angle of water 6 of 10 ° or less, and the state as shown in FIG. This eliminates the history of the plate.
Next, the plate is irradiated with an energy flux such as light or electricity, mechanical stimulus such as friction is applied to the plate, or an organic compound interacting with the plate is supplied to the plate to make the photocatalytic property hydrophilic. Is converted to hydrophobic to make the entire surface of the plate material 5 hydrophobic. FIG. 9A shows a state in which the entire surface of the plate material 5 has been hydrophobized. The term "hydrophobic plate surface" as used herein means a plate surface having a contact angle of water 6 of 50 ° or more, preferably 80 ° or more, to which hydrophobic ink for printing easily adheres, while it is difficult to attach dampening water. It is in a state.
[0058]
This state on the surface of the photocatalyst layer 3 is referred to as an “initial state at the time of plate production”. The "initial state at the time of plate production" mentioned above may be regarded as the start of the actual printing process. More specifically, for an arbitrary image, it can be regarded as indicating a state where digitized data is already prepared and this is to be written on the plate material.
[0059]
As an image writing step, a non-image area is written with actinic light on the plate surface in the hydrophobic state.
This non-image portion is performed in accordance with digital data relating to an image so as to correspond to the data. Here, the non-image portion is a hydrophilic portion where the contact angle of water 6 is 10 ° or less, and the dampening solution easily adheres thereto, while the adhesion of the printing ink becomes difficult. ing.
[0060]
As a method for exposing the hydrophilic non-image area based on image data, the photocatalyst layer 3 is irradiated with active light, and the plate surface is hydrophilized by the action of the photocatalyst. On the other hand, the plate surface not irradiated with the active light remains hydrophobic, so that a plate can be manufactured.
Here, as shown in FIG. 9B, a non-image portion is written by a writing head using a violet laser having a wavelength of 405 nm, for example, and a non-image portion is formed on a hydrophobic printing plate. ing. Thus, as shown in FIG. 9C, the formation of the image portion and the non-image portion on the plate surface is completed, and the printable state is established.
[0061]
As a method for exposing a hydrophilic non-image area based on image data, besides a writing head using a violet laser having a wavelength of 405 nm, for example, a UV setter 710 published by Basis Print (Germany) is available. Any device capable of writing an image using active light, such as a writing head using a UV light source and a micro mirror used in the above-described method, may be used.
[0062]
After the above-mentioned processing is completed, a so-called emulsified ink obtained by mixing a dampening solution and a hydrophobic ink for printing with a dampening solution is applied to the plate surface. Thus, for example, a plate as shown in FIG. 10 is produced.
In FIG. 10, the shaded portion shows a state in which hydrophobic ink has adhered to the hydrophobic image portion 3b. This shows a state in which the dampening solution adheres preferentially to the remaining white background, that is, the hydrophilic non-image area 3a, while the hydrophobic ink is repelled and does not adhere. As the pattern emerges in this manner, the plate material has a function as a plate. Thereafter, a normal printing process is executed, and the process is terminated.
[0063]
Next, a method of reproducing a plate will be described.
In the following, “reproduction of a printing plate” refers to a method in which at least a portion of a printing plate surface is hydrophobic and the remaining portion is hydrophilic, and the entire printing plate surface is uniformly hydrophilized. By irradiating the plate with a single or a plurality of energy fluxes, applying a mechanical stimulus such as friction to the plate, or supplying an organic compound interacting with the plate to the plate surface, thereby forming a catalyst on the surface of the photocatalyst layer 3. By changing the characteristic from hydrophilic to hydrophobic, it means to restore the "initial state at the time of plate production" again.
[0064]
First, as an ink removing step, ink, fountain solution, paper dust and the like adhering to the plate surface after printing are removed. This method includes stopping the supply of ink to the plate surface to reduce printing, wiping the ink on the plate surface with a mechanism that winds up a cloth tape for wiping ink, and using a roller around which a cloth material for wiping ink is wrapped. The method of wiping the ink and the method of spraying the cleaning liquid onto the plate surface with a spray to wash the ink may be appropriately used.
[0065]
Thereafter, the entire surface of the plate, which is at least partially hydrophobic, is irradiated with active light. By doing so, it becomes possible to render the image area hydrophilic and make the entire plate surface a hydrophilic surface with a contact angle of water 6 of about 10 °, that is, the state shown in FIG.
By irradiating the actinic light, the characteristic that the hydrophobic image portion existing on the plate surface is converted into a surface having high hydrophilicity is achieved by using a titanium oxide photocatalyst or a visible light responsive titanium oxide photocatalyst. be able to. Here, as shown in FIG. 9 (e), using a UV irradiation lamp (UV lamp), the hydrophobic image portion is converted to hydrophilic by UV irradiation, the plate surface is made entirely hydrophilic, and the plate history is changed. Is erased.
[0066]
Irradiate the plate surface with a single or a combination of energy fluxes such as light and electricity, or apply mechanical stimuli such as friction to the plate surface, or interact with the plate surface to the plate surface that has been restored to full hydrophilicity by ultraviolet irradiation. By supplying the compound to the plate surface, it is possible to return the plate surface, that is, the catalytic properties of the photocatalyst layer 3 from hydrophilic to hydrophobic, to return to the initial state at the time of plate production.
[0067]
The step of FIG. 9E is provided to completely eliminate the history of the plate, but the removal of the ink attached to the plate surface in the step of FIG. 9D at least affects the next printing. If it is sufficiently removed to the extent that it does not occur, the process of FIG. 9E may be skipped and the process may immediately proceed to the process (a) from the process (d).
[0068]
What has been described above is shown collectively in the graph shown in FIG. This is a graph in which the horizontal axis represents time (or operation) and the vertical axis represents the contact angle of water 6 on the plate surface. With respect to the plate in this embodiment, the contact angle of the surface of the photocatalytic layer 3 (that is, hydrophobic, (Hydrophilic state) changes with time or operation. In FIG. 11, a dashed line indicates a non-image portion of the photocatalyst layer 3, and a solid line indicates an image portion.
[0069]
First, the plate surface is irradiated with actinic light so that the contact angle of water 6 on the plate surface shows high hydrophilicity of 10 ° or less.
First, as a hydrophobizing treatment step (step A), the plate surface is irradiated with an energy flux such as light or electricity, alone or in combination, or a mechanical stimulus such as friction is applied to the plate surface. By supplying the interacting organic compound to the printing plate, the photocatalytic properties are converted from hydrophilic to hydrophobic. That is, the contact angle of the water 6 becomes 50 ° or more, preferably 80 ° or more. The time when the hydrophobic treatment is started (point a) and the state after the hydrophobic treatment is the “initial state at the time of plate production” (point b).
[0070]
Next, as a non-image portion writing step (step B), writing of the non-image portion on the hydrophobic printing plate is started with active light (point b). In this way, the plate surface irradiated with the active light is converted from hydrophobic to hydrophilic by the action of the photocatalyst, that is, the contact angle of water 6 on the plate surface becomes 10 ° or less.
On the other hand, the plate surface that has not been irradiated with active light maintains a hydrophobic state, so that the plate surface becomes a non-image region where the active light-irradiated portion is hydrophilic and the active light-irradiated portion is a hydrophilic non-image region. Therefore, it can function as a plate.
[0071]
After the writing of the non-image area is completed, printing is started as a printing step (step C) (point c).
When printing is completed, ink, stains, and the like on the plate surface are removed as an ink removing step (step D) (points d to e).
After the completion of the ink removal, actinic light irradiation to the plate surface is started as a step of hydrophilizing the image area (step E) (point e). By doing so, the hydrophobic image portion is converted into a hydrophilic non-image portion by the action of the photocatalyst, and the entire printing plate returns to hydrophilic again.
[0072]
Thereafter, as a next hydrophobic treatment step (step A '), the plate is irradiated with an energy flux such as light or electricity, alone or in combination, or a mechanical stimulus such as friction is applied to the plate or By supplying the interacting organic compound to the plate surface (point a '), the plate returns to the "initial state at the time of plate preparation", and the plate is reused.
[0073]
[D] Example
Hereinafter, more specific examples which have been confirmed by the present inventors and related to the method of manufacturing and regenerating the plate material 5 will be described.
(Catalyst preparation)
Aqueous ammonia was added to the raw material titanium sulfate (Wako Pure Chemical) while stirring to obtain a hydrolyzate of titanium sulfate. This hydrolyzate was filtered using a Nutsche, and washed with ion-exchanged water until the electric conductivity of the filtrate became 2 μS / cm or less. After washing, the hydrolyzate was dried at room temperature and then calcined in the air at 400 ° C. for 2 hours. This calcined product was first ground in a mortar to obtain a photocatalyst powder.
[0074]
(Confirmation of visible light activity)
0.2 g of the photocatalyst powder was collected and uniformly spread on the bottom of a Pyrex (registered trademark) glass cylindrical container (capacity: 500 mL) which can be sealed. Next, the inside of the reaction vessel was evacuated and then replaced with high-purity air. Then, acetone was injected so that the concentration in the reaction vessel became 500 ppm, and the mixture was adsorbed at 25 ° C. for 10 hours in a dark place until the adsorption became parallel. Thereafter, irradiation was performed with a blue LED (main wavelength 470 nm) manufactured by Nichia Chemical Co., Ltd. ₂ As a result of tracking the amount by a gas chromatograph made by Shimadzu, acetone disappeared after 20 hours of irradiation with the blue LED, and instead, CO2 corresponding to the stoichiometric ratio of acetone was used. ₂ Occurrence was confirmed. That is, it was confirmed that the photocatalyst powder exhibited catalytic activity with light having a wavelength of 470 nm.
[0075]
[Plate material creation]
(1) Preparation of photocatalyst dispersion liquid and substrate
The photocatalyst powder was dispersed in ion-exchanged water to obtain a slurry having a solid content of 20% by weight. After adding 1% by weight of a polycarboxylic acid-based dispersing agent to the photocatalyst to this slurry, it was pulverized with a wet mill (trade name: Dino Mill PILOT) to obtain a photocatalyst dispersion liquid. A base material 1 made of stainless steel (SUS301) having a size of 280 × 204 mm and a thickness of 0.1 mm was prepared and subjected to alkali degreasing treatment to obtain a plate material substrate.
[0076]
(2) Intermediate layer formation
Li ₂ O-containing water glass LSS-35 (manufactured by Nissan Chemical Industries) ₂ Diluted to 5 wt% solids, SiO ₂ A solution was prepared. Next, this SiO ₂ Titanium oxide coating agent TKC-301 manufactured by Teica Co., Ltd. ₂ / TiO ₂ = 50/50 and uniformly mixed, ₂ / TiO ₂ The coating solution was used. The substrate 1 is made of SiO ₂ / TiO ₂ The coating solution is dip-coated, air-dried, and baked at 500 ° C. for 1 hour to obtain a solid acid SiO. ₂ / TiO ₂ A layer was formed. SiO ₂ / TiO ₂ The thickness of the layer was about 0.10 μm.
[0077]
(3) Photocatalyst layer formation
The photocatalyst dispersion liquid and a titanium oxide coating agent TKC-301 manufactured by Teika Co., Ltd. ₂ A liquid mixed at a weight ratio of 6: 4 was dip-coated on the plate material substrate, air-dried, and baked at 350 ° C. for 1 hour to form a layer containing a photocatalyst, thereby obtaining a plate material. The thickness of the photocatalyst layer was about 0.1 μm. The plate material surface was measured for the contact angle of water with a CA-W type contact angle meter manufactured by Kyowa Interface Science. The contact angle was 8 °, indicating sufficient hydrophilicity.
[0078]
(Hydrophobicity of plate surface)
Next, 1,2-epoxide dodecane (Wako Pure Chemical Industries, Ltd.) was dissolved in isoparaffin (trade name: Isopar L, manufactured by ExxonMobil) to obtain a 1 wt% solution. This 1,2-epoxide decane solution was roll-coated on the plate surface and dried at 60 ° C. for 10 minutes. Then, when the contact angle of the water was measured by the contact angle meter, the contact angle was 83 °, showing sufficient hydrophobicity, and it was confirmed that the plate material was in an initial state at the time of plate production.
[0079]
[Hydrophilic energy measurement]
A wavelength of 360 nm and an illuminance of 10 mW / cm are applied to the hydrophobized plate material. ² Activated light was applied, and the active light irradiation time until the contact angle became 10 ° or less was measured to be 15 seconds. Therefore, the hydrophilization energy, which is the product of the illuminance of the active light and the irradiation time, is 150 mJ / cm. ² Met.
[0080]
(Measurement of maximum value of absolute value of rising speed of photovoltaic value)
After irradiating the surface of the plate with actinic light and confirming that the contact angle became 10 ° or less, the plate was set in the measuring cell shown in FIG. / Cm ² Under the condition, the light irradiation time vs. as shown in FIG. The curve of the photovoltaic value was measured. When the maximum value of the slope (absolute value) of this curve was determined, it was 0.51 (V / sec).
[0081]
(Measurement of photocatalytic activity index value)
In the same manner as the measurement of the maximum value of the absolute value of the rising speed of the photovoltaic value, the illuminance of the active light was set to 3 mW / cm. ² , 20mW / cm ² When the maximum value of the absolute value of the rising speed of the photovoltaic value was measured in the same manner, the values were 0.15 and 1.03 V / sec, respectively.
[0082]
Activated light illuminance 10 mW / cm ² Activated light illuminance including the case of 3,10,20mW / cm ² The photocatalytic activity index value is determined for each of ² / Sec · W), and these average values are 50.8 (V · cm ² / Sec · W).
[0083]
[Image writing]
Next, using the UV setter 710 published by Basis Print (Germany), which can write an image (non-image area) by exposing to ultraviolet light having a wavelength of 360 to 450 nm, the printing plate subjected to the hydrophobic treatment. A halftone dot image with an image ratio of 10% to 100% was written in 10%. The illuminance of this UV setter 710 at a wavelength of 360 nm is 200 mW / cm. ² Therefore, the image writing was performed by setting the exposure time of one area to 0.75 seconds based on the measurement result of the hydrophilization energy. Since the size of one area is 17 mm × 13 mm, it took four minutes to write an image on a plate having a size of 280 × 204 mm (the image area was 272 mm × 195 mm). When the contact angle of water on the surface of the plate after the writing was completed was measured by the contact angle meter, the contact angle of the written portion was 8 °, which was a hydrophilic non-image portion, and the contact angle of 83 ° was the non-written portion. It was confirmed that the image area had hydrophobicity.
[0084]
〔printing〕
This plate material was installed on a New Ace Pro desktop offset printing machine of Alpha Giken Co., Ltd., and printed on iBest paper using the ink HYECOOB Beni MZ manufactured by Toyo Ink and a 1% solution of fountain solution lysoferro manufactured by Mitsubishi Heavy Industries. Printing was started at a speed of 3500 sheets / hour. A halftone dot image was printed on the paper from the first sheet of printing.
[0085]
〔Playback〕
Next, an embodiment relating to the reproduction of the plate material will be described.
After printing, apply a low-pressure mercury lamp at a wavelength of 254 nm and an illuminance of 10 mW / cm over the entire surface of the plate from which ink, dampening water, paper powder, etc. attached to the plate have been wiped clean. ² For 15 seconds. Then, the contact angle of water was immediately measured with the contact angle meter on the portion where the halftone dot was written, and the contact angle was 8 °, indicating sufficient hydrophilicity. Next, the 1,2-epoxide dodecane solution was roll-coated on the plate material surface and dried at 60 ° C. for 10 minutes. After measuring the contact angle of water with the contact angle meter, the contact angle was 84 °. And the plate material returned to the "initial state at the time of plate production", and it was confirmed that the plate could be reproduced.
[0086]
(Comparative example)
A plate material was prepared in the same manner as in the above example, except that the photocatalyst layer was formed directly on the stainless steel substrate without providing the intermediate layer in the example (Comparative Example 1).
The hydrophilicity, the maximum value of the absolute value of the rising speed of the photovoltaic value, and the index value of the photocatalytic activity, which were measured for the plate material of Comparative Example 1 in the same manner as in the above example, were 700 mJ / cm. ² , 0.15 V / sec, 16.1 (V · cm ² / Sec · W).
[0087]
In Comparative Example 1, an image was written using the UV setter 710 with an exposure time of 0.75 seconds for one area (total time of image writing was 4 minutes). When the contact angle of water on the surface of the plate material after writing was measured by the contact angle meter, the contact angle of the written portion was 37 ° and the hydrophilicity was insufficient. Attach to a tabletop offset printing machine New Ace Pro of Alpha Giken Co., Ltd., and print at 3500 sheets / hour on ibest paper using Toyo Ink's HYECOOB Red MZ and Mitsubishi Heavy Industries' dampening solution lysoferro 1% solution. When printing was carried out, ink was attached to places that should originally be non-image lines, and only printing where the entire printed matter was soiled could be performed.
[0088]
As described above, according to the method and the apparatus for evaluating the photocatalytic activity according to the present embodiment, the photocatalytic activity can be evaluated in a short time in the manufacturing process of the component 5 having the photocatalytic layer 3.
Also, paying attention to the maximum value of the absolute value of the rising slope of the photovoltaic value, which is an index of the catalytic activity, the illuminance of the active light is 10 mW / cm. ² It has been found that the photocatalytic activity of the photocatalyst layer 3 is at a practical level, especially at a practical level as a lithographic printing plate, when the maximum value obtained under the condition (1) is 0.2 V / sec or more.
[0089]
Furthermore, the maximum value of the absolute value of the rising slope of the photovoltaic value was measured by changing the illuminance of the active light, and the maximum value of the absolute value of the rising slope of the photovoltaic value was divided by the illuminance of the active light. The value (photocatalytic activity index value) was found to be substantially constant regardless of the illuminance of the active light, and the photocatalytic activity index value was 20 (unit: V · cm). ² / Sec · W) or more, it was found that the photocatalytic activity was at a practical level, especially at a practical level as a lithographic printing plate.
[0090]
Therefore, when the composition 5 having the photocatalyst layer 3 according to the present embodiment is applied to a lithographic printing plate material, the plate material can be reused, and at the same time, the photovoltaic value can be reduced. The high photocatalytic activity represented by the maximum value of the absolute value of the rising slope or the photocatalytic activity index value has an advantage that the cycle of plate production and plate reproduction can be accelerated. That is, by switching the properties of the surface of the photocatalyst layer 3 from hydrophobic to hydrophilic, the plate can be prepared, or the history of the plate can be erased in the plate regenerating step after printing. The work to realize it will not take much time. Therefore, it is possible to complete the entire printing process very quickly.
[0091]
【The invention's effect】
As described above, according to the photocatalytic activity evaluation method and the evaluation apparatus of the present invention, it is possible to evaluate the photocatalytic activity in a short time in the process of manufacturing a layered component having a layer containing a photocatalyst. is there.
Further, according to the layer containing a photocatalyst of the present invention, high photocatalytic activity can be exhibited. Therefore, if the layered structure having the layer containing the photocatalyst is used for a lithographic printing plate, the image writing time and the plate Can be shortened, and the printing preparation time in the printing process can be shortened.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a surface of a layered structure according to one embodiment of the present invention. This figure also shows a state where the surface of the photocatalyst layer shows hydrophobicity.
FIG. 2 is a cross-sectional view showing a surface of a layered structure according to one embodiment of the present invention. This figure also shows a state in which the photocatalytic layer surface is hydrophilic.
FIG. 3 is a schematic diagram schematically showing an evaluation device for evaluating the photocatalytic activity of the layered composition according to one embodiment of the present invention.
FIG. 4 is a graph showing a change in potential when a photocatalytic layer of a layered composition according to an embodiment of the present invention is irradiated with active light.
FIG. 5 is a graph showing a change in a contact angle of water with respect to UV irradiation energy in a layered composition according to one embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the hydrophilizing energy and the maximum value of the absolute value of the rising speed of the photovoltaic value in the layered composition according to one embodiment of the present invention. This shows a case where the treatment is performed and a case where the treatment is made hydrophobic without using an organic compound.
FIG. 7 is a graph showing a change in the maximum value of the absolute value of the rising speed of the photovoltaic value when the illuminance of active light of the layered structure according to the embodiment of the present invention is changed.
FIG. 8 is a graph showing the relationship between the hydrophilizing energy and the photocatalytic activity index value of the layered composition according to one embodiment of the present invention, in which the layered component is hydrophobized using an organic compound and does not use an organic compound. And the case where it is made hydrophobic.
FIG. 9 is a conceptual diagram showing the steps of producing and reproducing a plate when the layered composition according to one embodiment of the present invention is used as a planographic printing plate material.
FIG. 10 is a perspective view showing an example of an image portion and a non-image portion formed on a plate material surface.
FIG. 11 is a graph showing how the contact angle of water (that is, hydrophobic or hydrophilic state) on the plate material surface changes with time or operation.
FIG. 12 is a flowchart illustrating a method for evaluating photocatalytic activity according to one embodiment of the present invention.
[Explanation of symbols]
1 Substrate
2 Middle layer
3 Layer containing photocatalyst (photocatalyst layer)
3a Photocatalyst layer (non-image area)
3b Photocatalyst layer (image area)
5 Layered components
6 water
36 measuring cell
37 Shiohashi
38 Saturated calomel electrode (SCE)
39 potentiostat
40 Computer (Computing device)

Claims (7)

A method for evaluating the photocatalytic activity of a layered component having a photocatalyst layer containing a photocatalyst on the surface,
The photocatalyst layer is irradiated with active light having an energy larger than the band gap energy of the photocatalyst to immerse the layered composition in which the surface is hydrophilized to a contact angle of water of 10 ° or less in an electrolytic solution to form the layered product. In the state where the electrolyte is brought into contact with the surface of the component, and the reference electrode and the electrolyte are connected by a salt bridge,
Connecting an electrode of a potentiostat to the layered component and measuring the natural potential of the surface of the layered component,
After the measurement of the natural potential, irradiating the photocatalytic layer with active light, and measuring a change in the surface potential of the layered component with the irradiation time of the active light,
Evaluating the photocatalytic activity of the photocatalytic layer based on the maximum value of the absolute value of the rise rate of the surface potential (unit: V / sec). Electric Kaieki is characterized by a Na ₂ SO _4, Evaluation of the photocatalytic activity according to claim 1, wherein. An apparatus for evaluating the photocatalytic activity of a layered component having a photocatalyst layer containing a photocatalyst on its surface,
A surface potential measuring device for measuring the surface potential of the layered component,
An active light irradiation device that irradiates the surface of the layered structure with active light having energy larger than the band gap energy of the photocatalyst,
The active light irradiator irradiates the surface of the layered structure with the active light, and the surface potential rise rate (unit: V / sec) from the surface potential measured by the surface potential measuring device and the light irradiation time. An evaluation device for photocatalytic activity, comprising: a calculation device for calculating the maximum value of the absolute value of. The surface potential measuring device is
A first insulating plate provided in close contact with the back surface of the layered structure,
A second insulating plate having an opening and provided in close contact with the surface of the layered structure;
An electrolyte poured into the opening,
A salt bridge connecting the electrolyte and a reference electrode,
4. An apparatus for evaluating photocatalytic activity according to claim 3, wherein said layered structure is provided with a potentiostat connected to an electrode. Electric Kaieki is characterized by a Na ₂ SO _4, apparatus for evaluating photocatalytic activity according to claim 4. The maximum value of the absolute value of the rising speed (unit: V / sec) of the surface potential induced by irradiating the active light, which is measured using the evaluation method according to claim 2, is 10 mW of the illuminance of the active light. A layer containing a photocatalyst, which is 0.2 (unit: V / sec) or more under the condition of / cm ² . The maximum value of the absolute value of the rising speed (unit: V / sec) of the surface potential induced by irradiating the active light, which is measured using the evaluation method according to claim 2, is defined as the illuminance ( A layer containing a photocatalyst, wherein a value obtained by dividing by W / cm ² ) is 20 (unit: V · cm ² / sec · W) or more.

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