JP2005187540A - Invisible water-based ink composition and composite writing tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an invisible ink composition which can easily visually be checked on learning by heart or the like and can easily and accurately be written on writing, and to provide a composite writing tool using the ink composition. <P>SOLUTION: This invisible water-based ink composition comprising the first coloring agent, the second coloring agent, water and a water-soluble organic solvent is characterized by the following characteristics. The first coloring agent comprises 0.01 to 5 wt. % (based on the total amount of the composition) of a fluorescent colorant or fluorescent brighter which can visually not be checked under visible light or daylight but can visually be checked under the irradiation of ultraviolet rays. The second coloring agent is a pH-corresponding indicator. The pH of the composition is ≥9.5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a so-called invisible ink composition capable of visually observing a handwriting by irradiating ultraviolet rays only when it is desired to visually recognize a handwritten character, figure or the like, and a composite writing instrument using the composition.

  In recent years, the number of mark sheet questions and the problem of answering blanks have increased due to the increase in opportunities for center examinations, qualification acquisition, and lifelong learning. For this reason, various attempts have been made in applications such as memorization learning. For example, Patent Document 1 discloses a combination of a pen and a sheet that are a complementary color pair. However, in this memorization pen, when checking the handwriting, the sheet must be opened and closed, which is annoying to the user. Patent Document 2 discloses a method using a thermochromic handwriting. Patent Document 3 discloses a method using handwriting that can be erased with an eraser. However, these require an operation of rubbing with an eraser when confirming the handwriting, which is troublesome for the user who confirms the handwriting many times.

  On the other hand, barcodes are used for product price, number of products sold, inventory management, etc., but conventional barcodes are printed in black and white so that they can be seen with the naked eye, which is undesirable in the design of the product itself, There was a drawback that it could not be applied to dirty parts. In addition, there is a drawback in that a large amount of postal items are not efficiently handled manually. In order to solve these problems, according to Patent Document 4 and Patent Document 5, ink added with a fluorescent whitening agent that is not visible with visible light but develops color with ultraviolet light is printed on a product or the like. An invention is disclosed in which a printed matter is confirmed by irradiating ultraviolet rays or the like. However, these are examinations as printing inks, and when used as writing inks, the viscosity and solvent used are not appropriate, and bleeding and leakage occur.

  In Patent Document 6 and Patent Document 7, it is proposed to apply a fluorescent substance such as a fluorescent brightening agent to ink for writing instruments. Patent Document 8 proposes a fluorescent writing instrument including a writing unit having a pen tip containing fluorescent ink, a light emitting unit that emits ultraviolet light, and a driving unit that drives the light emitting unit. However, when these inks are used, they cannot be visually recognized under visible light, which is a normal writing environment, so that there has been a problem that accurate characters and figures cannot be written.

Japanese Patent Publication No.57-37871 JP-A-7-186588 JP-A-8-199102 JP-A-8-199101 JP 11-152436 A JP-A-5-98202 Japanese Patent Laid-Open No. 2001-214095 JP-A-7-195890

  An object of the present invention is to provide an invisible ink composition and a composite writing instrument using the invisible ink composition that are not troublesome to visually recognize in memorization learning and the like and that are easy to write accurately.

As a result of intensive research on the above problems, the present inventor has made it possible to visually recognize handwriting at the time of writing by newly adding a PH response indicator as a colorant in addition to the fluorescent colorant or the fluorescent whitening agent. The inventors have found that the object can be achieved, and have reached the present invention.

  That is, the present invention is a water-based ink composition comprising a first colorant, a second colorant, water and a water-soluble organic solvent, wherein the first colorant is not visible under visible light or daylight, It consists of 0.01 to 5% by weight (in the total amount of the composition) of a fluorescent colorant or whitening agent that is visible when irradiated with ultraviolet light, the second colorant consists of a PH response indicator, and the composition has a pH of 9 The present invention provides an invisible water-based ink composition characterized by being 5 or more. The present invention also provides a composite writing instrument comprising at least an ink containing part containing the invisible water-based ink composition and a light emitting part having an ultraviolet irradiation light driving device.

  Since the water-based ink composition of the present invention can visually recognize the handwriting by coloring the PH response indicator during writing, it can accurately write letters, symbols, etc., and the handwriting is not visible under visible light thereafter. Therefore, when irradiated with ultraviolet light, it emits fluorescence and becomes visible, so that visualization and invisibility can be repeated any number of times, and it can be easily used as a marker for learning learning. In addition, information can be written on merchandise, mail, etc. without causing discomfort in appearance to the consumer, and it can be used as a security marker that can be sorted and managed. Furthermore, it can be used for notes that you want to share with specific people only.

  In the invisible water-based ink composition of the present invention, the first colorant is a fluorescent colorant that is not visible under visible light or daylight and becomes visible when irradiated with ultraviolet light, and is 315 nm to 450 nm, preferably There is no particular limitation as long as it emits light from colorless to colored by changing from the ground state to the excited state when absorbing ultraviolet rays of 350 nm to 410 nm, and it is not particularly limited, such as fluorescent colorant, fluorescent whitening agent, etc. Either can be used and may be a dye or a pigment.

  Currently available fluorescent whitening dyes include diaminostilbene, imidazole, thiazole, oxazole, triazole, oxadiazole, coumarin, naphthalimide, and pyrazoline. These may be solutions so that they can be easily added.

  Specifically, Illuminal series (manufactured by Showa Kako Co., Ltd.), UVITEX series (manufactured by Ciba Specialty Chemicals), TINOPAL series (manufactured by Ciba Specialty Chemicals), Kayight series (manufactured by Nippon Kayaku Co., Ltd.) And fluorescent whitening agents such as Kaypol series (manufactured by Nippon Kayaku Co., Ltd.). In addition to these, red fluorescent dyes typified by europium compounds can also be used. These addition amounts are 0.01 to 5 weight%. When the added amount is less than 0.01% by weight, no color development is observed when irradiated with ultraviolet rays. When the added amount exceeds 5% by weight, the solubility is inferior, or the writing lines on the paper surface appear colored even under visible light. .

  The second colorant is not particularly limited as long as it is a PH response indicator having a color change range on the alkali side, colored on the alkali side from the color change range, and colorless on the acidic side. Specifically, cyanine, α-naphtholphthalein, ethylbis (2,4-dinitrophenyl) acetate, phenolphthalein sodium salt, 1,3,5-trinitrobenzene, nitramine, phenolphthalein, thymolphthalein, o -Cresolphthalein. These may be modified. Of these, phenolphthalein, thymolphthalein, and o-cresolphthalein are preferable because they have excellent solubility and are easily available at low cost. The second colorant may be used in combination of two or more.

  The amount of the second colorant added is preferably 0.01 to 5% by weight. If the added amount is less than 0.01% by weight, the visibility at the time of writing cannot be obtained. On the other hand, if it exceeds 5% by weight, the solubility is lowered, and if it is severe, writing may be impossible. Paper on which letters and figures are written is weakly acidic to neutral, so when writing, it is colored with a PH indicator and the handwriting can be visually recognized. However, when the ink composition soaks into the paper, the acid side becomes colorless from the discoloration range. , Handwriting becomes invisible.

  In the present invention, water and a water-soluble organic solvent are used as the solvent. The amount of water in the total amount of the composition is preferably 30 to 90% by weight.

  The organic solvent used in the present invention is preferably one that is compatible with water, which is the main component of the ink composition, and helps to dissolve the first and second colorants. Examples of such organic solvents include alcohols such as ethanol and isopropyl alcohol, glycols such as glycerin and propylene glycol, and ethers such as propylene glycol monomethyl ether and propylene glycol monoethyl ether. These can be blended by appropriately mixing two or more kinds. The organic solvent is preferably 10 to 70% by weight in the total amount of the ink composition. If it is less than 10% by weight, the first and second colorants will precipitate.

  Further, the ink composition of the present invention needs to have a pH of 9.5 or more, and preferably 10 or more. When the PH range is 9.5 or more, the second colorant is colored in response to the PH, and the handwriting can be visually recognized only immediately after writing. Additives for achieving a pH of 9.5 or higher include inorganic substances such as sodium hydroxide, potassium hydroxide and sodium carbonate, and organic substances such as amines such as monoethanolamine, diethanolamine, ammonia, monoethylamine, diethylamine and triethylamine. It is done. These may be added in combination.

  In addition to the ink composition of the present invention, additives such as a viscosity adjusting agent, a preservative, and an anti-drying agent can be appropriately added as necessary.

  The present invention also provides a composite writing instrument comprising at least a light emitting part having an ink containing part containing the invisible ink composition and an ultraviolet irradiation light driving device. The composite writing instrument is a light emitting device having an ink containing portion containing the invisible ink composition, and an ultraviolet irradiation light driving device for causing the UV lamp to emit light when a predetermined voltage is applied and making the handwriting visible by the invisible ink. At least a portion, and the ink containing portion is combined with a writing portion having a rod-like pen tip made of a material such as felt that has a hardness capable of penetrating ink and can withstand writing pressure.

  EXAMPLES The present invention will be described more specifically with reference to examples below, but the present invention is not limited to these examples.

(Examples 1-4, Comparative Examples 1-4)
The blends having the compositions shown in Table 1 below were blended for 1 hour by stirring with a stirrer, and the solution was filtered through a filter cloth to produce an invisible aqueous ink composition. Each obtained invisible water-based ink composition is mounted on a fluorescent marker (trade name: firefly coat, manufactured by Dragonfly Pencil Co., Ltd.), and a writing test is performed as a sample. Visibility during writing, visibility under black light The property (UV luminescence) was evaluated as follows. The results are also shown in Table 1.

(Visibility when writing)
After writing, it is confirmed whether or not the handwriting can be visually confirmed after 10 seconds, and the results are shown as follows.
Confirmed items: ○
Although it always disappears, the handwriting does not disappear even after 30 minutes: △
When handwriting cannot be seen at all: x

(Visibility with black light)
The handwriting that was allowed to stand for 24 hours or more after writing was irradiated with an ultraviolet diode 395 nm, and it was examined whether the handwriting could be confirmed.
Confirmable: ○
Cannot be confirmed: ×

Further, after filtering each ink composition, the presence or absence of insoluble matter in the ink composition when left overnight is confirmed with an optical microscope, and at the same time, the pH of each ink composition is measured with a PH meter (trade name: twin pH, Measured at normal temperature by HORIBA. The results are also shown in Table 1.
No deposit: ○
With deposit: ×

Claims (3)

An invisible water-based ink composition comprising a first colorant, a second colorant, water and a water-soluble organic solvent, wherein the first colorant is not visible under visible light or daylight and is irradiated with ultraviolet light It consists of 0.01 to 5% by weight (in the total amount of the composition) of a fluorescent colorant or brightener that is visible, the second colorant consists of a PH response indicator, and the composition has a pH of 9.5 or more. An invisible water-based ink composition characterized by that. The invisible water-based ink composition according to claim 1, wherein the second colorant is selected from the group consisting of phenolphthalein, thymolphthalein, and O-cresolphthalein. A composite writing instrument comprising at least a light-emitting unit having an ink storage unit storing the invisible water-based ink composition according to claim 1 and an ultraviolet irradiation light driving device.