JP2011025653A - Color developing sheet for pressure-sensitive copying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color developing sheet for pressure-sensitive copying, excellent in coloration sensitivity and general printing aptitude. <P>SOLUTION: This color developing sheet for the pressure-sensitive copying contains a cellulose nano-fiber in a color developer layer, in the color developing sheet for the pressure-sensitive copying provided with the color developer layer containing an electron acceptable compound (color developer) on a support layer. An excellent effect is exhibited, in particular, by using the cellulose nano-fiber having a 0.5-20 nm width and a 0.1-15 μm length. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developer sheet for pressure-sensitive copying, and more particularly to a developer sheet for pressure-sensitive copying having an improved balance between coloring ability and printing strength.

  The pressure-sensitive copying paper is an “upper sheet” provided with a layer containing microcapsules containing an electron donating dye (hereinafter referred to as “dye”) on one side of a support, and an electron that develops color upon contact with the dye. "Lower paper" provided with a layer containing a receptive compound (hereinafter referred to as "developer"), a layer containing a microcapsule containing a dye on one side of the support, and a layer containing a developer on the other side Or “self-contained paper” in which a microcapsule containing a dye and a developer are laminated or mixed on the same surface of a support.

  Pressure-sensitive copying paper is applied to various forms because it has the function of being able to copy a large number of sheets, and is usually used for form printing by offset printing, ink-jet recording printing method, etc. When printing is performed on the provided developer sheet, paper powder or a part of the coating layer may be deposited on the blanket or plate, which may cause problems in printability such as color loss or printing stains.

  Therefore, for the purpose of improving printability, a method of preparing a binder ratio and using a binder having a strong bond strength is considered, and the use of an acrylamide polymer as the binder is disclosed (Patent Document 1, Patent Document). 2, Patent Document 3).

JP 63-170079 JP-A-01-234288 JP 06-227118 A

However, as disclosed in Patent Documents 1 to 3, when an acrylamide polymer is used as the binder, the penetration of oil in which the dye is dissolved into the developer layer is inhibited, and the color development sensitivity (color development) There is a tendency for speed and density) to decrease.
SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure-sensitive copying developer sheet excellent in color development sensitivity and general printability.

  As a result of intensive studies, the inventors of the present invention have developed a pressure-sensitive copying developer sheet provided with a developer layer containing a developer on a support, and the developer layer contains cellulose nanofibers. As a result, the inventors have found that a pressure-sensitive copying color-developing sheet having excellent color development sensitivity and printing strength can be obtained, leading to the present invention.

  According to the present invention, it is possible to obtain a pressure sensitive color developing sheet excellent in color development sensitivity and general printability.

Embodiments of the present invention will be described below.
The present invention has been made by finding that excellent color development sensitivity and printing strength can be obtained by containing cellulose nanofibers in a developer layer containing a developer.

Cellulose nanofibers used in the present invention are obtained by defibration (miniaturization) of cellulosic raw materials by chemical treatment or mechanical treatment.
As a method for producing cellulose nanofibers used in the present invention, a cellulose raw material such as finely divided cellulose oxidized by a catalyst is defibrated by a high-pressure homogenizer (cellulose nanofibers obtained by chemical treatment), a cellulose raw material Examples of the suspension obtained by defibration / classification using glass or zirconia beads as a grinding medium (cellulose nanofibers by mechanical treatment) can be exemplified, and the method is not limited to these production methods. However, from the viewpoint of improving the strength of the developer layer, it is particularly preferable to use cellulose nanofibers produced by performing an oxidation treatment with a catalyst.

  In the present invention, as cellulose nanofibers obtained by chemical treatment, (1) an oxidizing agent is used in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides and mixtures thereof. Use of cellulose nanofibers obtained by this method, which comprises a step of preparing oxidized cellulose, and (2) a step comprising wet-pulverizing the oxidized cellulose to form nanofibers. From the viewpoints of improving color development sensitivity and general printability (ink fixability).

  The cellulose raw material used as the raw material of the cellulose nanofiber of the present invention is not particularly limited, and kraft pulp or sulfite pulp derived from various woods, powdered cellulose obtained by pulverizing them with a high-pressure homogenizer or a mill, or the like. Microcrystalline cellulose powder purified by chemical treatment such as acid hydrolysis can be used. In addition, plants such as kenaf, hemp, rice, bagasse and bamboo can also be used. Among these, when bleached kraft pulp, bleached sulfite pulp, powdered cellulose, and microcrystalline cellulose powder are used, it is easy to handle and has a relatively low viscosity (2% (w / v) B-type viscosity of 500% in aqueous dispersion). Cellulose nanofibers of about ˜2000 mPa · s) can be efficiently produced, and powdered cellulose and microcrystalline cellulose powder are more preferable.

Powdered cellulose is a rod-like particle made of microcrystalline cellulose obtained by removing a non-crystalline part of wood pulp by acid hydrolysis and then pulverizing and sieving. The degree of polymerization of cellulose in the powdered cellulose is preferably about 100 to 500, the degree of crystallinity of the powdered cellulose by X-ray diffraction is preferably 70 to 90%, and the volume average particle size by a laser diffraction type particle size distribution measuring device. Is preferably 100 μm or less, more preferably 50 μm or less. When the volume average particle size is 100 μm or less, a cellulose nanofiber dispersion having excellent fluidity can be obtained. As the powdered cellulose used in the present invention, for example, a fixed particle size in the form of a rod shaft produced by a method of purifying and drying an undegraded residue obtained after acid hydrolysis of a selected pulp, pulverizing and sieving. it may be a crystalline cellulose powder having a distribution, (manufactured by Nippon Paper Chemicals Co.) KC flock ^R, Ceolus ^TM (manufactured by Asahi Kasei Chemicals Corporation), a commercially available product may be used, such as Avicel ^R (FMC Corp.) .

（式１中、Ｒ¹〜Ｒ⁴は同一又は異なる炭素数１〜４程度のアルキル基を示す。）
式１で表される化合物のうち、２，２，６，６−テトラメチル−１−ピペリジン−Ｎ−オキシラジカル（以下、ＴＥＭＰＯと称する）、及び４−ヒドロキシ−２，２，６，６−テトラメチル−１−ピペリジン−Ｎ−オキシラジカル（以下、４−ヒドロキシＴＥＭＰＯと称する）を発生する化合物が好ましい。また、ＴＥＭＰＯ又は４−ヒドロキシＴＥＭＰＯから得られる誘導体も好ましく用いることができ、特に、４−ヒドロキシＴＥＭＰＯの誘導体が最も好ましく用いることができる。４−ヒドロキシＴＥＭＰＯ誘導体としては、４−ヒドロキシＴＥＭＰＯの水酸基を、炭素数４以下の直鎖或いは分岐状炭素鎖を有するアルコールでエーテル化して得られる誘導体か、あるいは、カルボン酸又はスルホン酸でエステル化して得られる誘導体が好ましい。４−ヒドロキシＴＥＭＰＯをエーテル化する際には、炭素数が４以下のアルコールを用いれば、アルコール中の飽和、不飽和結合の有無に関わらず、得られる誘導体が水溶性となり、酸化触媒として良好に機能する４−ヒドロキシＴＥＭＰＯ誘導体を得ることができる。 As the N-oxyl compound used for oxidizing the cellulosic raw material, any compound can be used as long as it promotes the target oxidation reaction. For example, the N-oxyl compound used in the present invention includes a substance represented by the following general formula (Formula 1).

(In Formula 1, R ^{1 to} R ⁴ represent the same or different alkyl groups having about 1 to 4 carbon atoms.)
Among the compounds represented by Formula 1, 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter referred to as TEMPO), and 4-hydroxy-2,2,6,6- A compound that generates a tetramethyl-1-piperidine-N-oxy radical (hereinafter referred to as 4-hydroxy TEMPO) is preferable. Moreover, the derivative | guide_body obtained from TEMPO or 4-hydroxy TEMPO can also be used preferably, and the derivative | guide_body of 4-hydroxy TEMPO can be used most preferably especially. The 4-hydroxy TEMPO derivative is a derivative obtained by etherifying the hydroxyl group of 4-hydroxy TEMPO with an alcohol having a linear or branched carbon chain having 4 or less carbon atoms, or esterified with carboxylic acid or sulfonic acid. The derivatives obtained are preferred. When 4-hydroxy TEMPO is etherified, if an alcohol having 4 or less carbon atoms is used, the resulting derivative becomes water-soluble regardless of the presence or absence of saturated or unsaturated bonds in the alcohol, making it an excellent oxidation catalyst. A functional 4-hydroxy TEMPO derivative can be obtained.

（式２〜４中、Ｒは炭素数４以下の直鎖又は分岐状炭素鎖である。）
さらに、下記式５で表されるＮ−オキシル化合物のラジカル、すなわち、アザアダマンタン型ニトロキシラジカルも、短時間で、均一なセルロースナノファイバーを製造できるため、特に好ましい。

（式５中、Ｒ⁵及びＲ⁶は、同一又は異なる水素又はＣ₁〜Ｃ₆の直鎖若しくは分岐鎖アルキル基を示す。） セルロース系原料を酸化する際に用いるＴＥＭＰＯや４−ヒドロキシルＴＥＭＰＯ誘導体などのＮ−オキシル化合物の量は、セルロース系原料をナノファイバー化できる触媒量であれば特に制限されない。例えば、絶乾１ｇのセルロース系原料に対して、０．０１〜１０ｍｍｏｌ、好ましくは０．０１〜１ｍｍｏｌ、さらに好ましくは０．０５〜５ｍｍｏｌ程度である。 Examples of the 4-hydroxy TEMPO derivative include compounds of the following formulas 2 to 4.

(In formulas 2 to 4, R is a linear or branched carbon chain having 4 or less carbon atoms.)
Furthermore, a radical of an N-oxyl compound represented by the following formula 5, that is, an azaadamantane type nitroxy radical, is particularly preferred because it can produce uniform cellulose nanofibers in a short time.

(In the formula 5, R ⁵ and R ⁶ are the same or. Shows different hydrogen or straight-chain or branched-chain alkyl group of C ₁ -C ₆₎ TEMPO or 4-hydroxy TEMPO derivative used in oxidizing the cellulosic material The amount of the N-oxyl compound, such as, is not particularly limited as long as it is a catalyst amount capable of converting the cellulose-based material into nanofibers. For example, it is about 0.01 to 10 mmol, preferably about 0.01 to 1 mmol, and more preferably about 0.05 to 5 mmol with respect to 1 g of an absolutely dry cellulosic material.

  As the bromide or iodide used in oxidizing the cellulosic raw material, a compound that can be dissociated and ionized in water, such as an alkali metal bromide or an alkali metal iodide, can be used. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. For example, it is about 0.1 to 100 mmol, preferably about 0.1 to 10 mmol, and more preferably about 0.5 to 5 mmol, with respect to 1 g of cellulosic raw material.

  As the oxidizing agent used for oxidizing the cellulosic raw material, the target oxidation reaction such as halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide can be promoted. Any oxidizing agent can be used as long as it is an oxidizing agent. Among these, from the viewpoint of production cost, sodium hypochlorite, which is the most widely used in industrial processes and has a low environmental load, is particularly suitable. The amount of the oxidizing agent used can be selected within a range that can promote the oxidation reaction. For example, it is about 0.5 to 500 mmol, preferably 0.5 to 50 mmol, and more preferably about 2.5 to 25 mmol with respect to 1 g of cellulosic raw material.

  As described above, the oxidation of the cellulose-based raw material in the present invention is the presence of a compound selected from the group consisting of (1) N-oxyl compounds such as 4-hydroxy TEMPO derivatives and (2) bromides, iodides and mixtures thereof. Below, it is characterized by oxidizing a cellulosic raw material in water using an oxidizing agent such as sodium hypochlorite. This method has a feature that the oxidation reaction of the cellulosic raw material can proceed smoothly and efficiently even under mild conditions. Therefore, the reaction temperature may be about 15 to 30 ° C. In addition, since a carboxyl group produces | generates in a cellulose with progress of reaction, the fall of pH of a reaction liquid is recognized. In order to advance the oxidation reaction efficiently, it is desirable to maintain the pH of the reaction solution at about 9 to 12, preferably about 10 to 11, by adding an alkaline solution such as an aqueous sodium hydroxide solution.

  As described above, in the presence of (1) N-oxyl compound and (2) bromide, iodide, or a mixture thereof, an oxidized cellulose material obtained using an oxidizing agent is treated with wet fine particles. Cellulose nanofibers can be produced by fibrillation and defibration. As the wet atomization treatment, for example, a mixing / stirring and emulsifying / dispersing device such as a high-speed shear mixer or a high-pressure homogenizer can be used alone or in combination of two or more. In particular, when wet atomization is performed using an ultrahigh pressure homogenizer that enables a pressure of 100 MPa or more, preferably 120 MPa or more, more preferably 140 MPa or more, a relatively low viscosity (2% (w / v) aqueous dispersion Cellulose nanofibers having a B-type viscosity of about 500 to 2000 mPa · s) can be efficiently produced, which is preferable.

The cellulose nanofiber of the present invention is 0.5 mmol / g or more, preferably 0.9 mmol / g or more, more preferably 1.2 mmol / g or more, as the amount of carboxyl groups in 1 g of completely dried cellulose nanofiber. This is desirable because it results in a uniform dispersion. The amount of carboxyl groups in cellulose nanofibers was prepared by adding 60 ml of a 0.5% by weight slurry of cellulose nanofibers, adding 0.1M hydrochloric acid aqueous solution to pH 2.5, and then dropping 0.05N sodium hydroxide aqueous solution dropwise. Then, the electrical conductivity is measured until the pH reaches 11, and can be calculated from the amount of sodium hydroxide (a) consumed in the weak acid neutralization stage where the change in electrical conductivity is gradual, using the following equation. .
Amount of carboxyl group [mmol / g pulp] = a [ml] × 0.05 / oxidized pulp mass [g]

In the present invention, the B-type viscosity (60 rpm, 20 ° C.) in a concentration of 2% (w / v) of cellulose nanofiber (that is, 2 g of cellulose nanofiber (dry mass) is contained in 100 ml of dispersion) is 500. An aqueous dispersion of cellulose nanofibers having a viscosity of ˜7000 mPa · s, preferably 500 to 2,000 mPa · s is desirable because it can be suitably used as a coating material. A relatively low B-type viscosity in a 2% (w / v) aqueous dispersion of cellulose nanofibers is preferred because it is easy to handle when preparing a coating, and specifically, 500 to 2000 mPa · s. The degree is preferable, about 500 to 1500 mPa · s is more preferable, and about 500 to 1000 mPa · s is more preferable.
The B-type viscosity of the aqueous dispersion of cellulose nanofibers of the present invention can be measured by a known method. For example, it can be measured using a VICOMETER TV-10 viscometer manufactured by Toki Sangyo.

  In the present invention, (1) a step of preparing cellulose oxidized with an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides and mixtures thereof, (2) The width and length of cellulose nanofibers obtained by a method comprising the step of wet atomization of oxidized cellulose to form nanofibers can be controlled by the oxidation treatment time, wet atomization treatment time or treatment pressure. it can. Further, the viscosity of the cellulose nanofiber dispersion can be controlled by the oxidation treatment time, the wet atomization treatment time or the treatment pressure, and the carboxy amount can be adjusted by changing the oxidation treatment conditions.

  In the present invention, the reason why the developer layer strength is improved and the general printability is excellent by containing cellulose nanofibers in the developer layer is presumed as follows. This is because cellulose nanofibers produced by oxidation treatment with a catalyst are in a state where carboxyl groups or aldehyde groups are introduced at a high density on the surface, and these carboxyl groups or aldehyde groups are in the developer layer. This is considered to be because the contained pigment and binder are chemically bonded. For this reason, in order to obtain a favorable developer layer strength, the carboxy content of the cellulose nanofiber is desirably 0.3 to 5 mmol / g, and more desirably 0.8 to 2 mmol / g.

  In the present invention, the reason why good general printability (ink fillability) can be obtained is that the surface of the developer layer is uneven as in the case of silica or aluminum hydroxide widely used in the developer layer. Therefore, it is considered that the anchor effect for the ink is obtained.

  In the present invention, the reason why excellent color development sensitivity can be obtained by containing cellulose nanofibers in the developer layer is presumed as follows.

  In addition to high transparency, cellulose nanofibers have a refractive index of 1.49 at room temperature, and polyvinyl alcohol (refractive index of 1.49) and acrylic resin (refractive index of 1.49) used as a binder for the developer layer. Since the refractive index is close to 1.49), scattering of incident / reflected light hardly occurs in the developer layer, and excellent color development sensitivity can be obtained.

In the present invention, it is preferable to use a cellulose nanofiber having a width of 0.5 to 20 nm and a length of 0.1 to 15 μm, and a cellulose nanofiber having a width of 2 to 5 nm and a length of 1 to 5 μm. More preferably it is used.
When the length of the cellulose nanofiber is 0.1 μm or less, the anchor effect is difficult to be exhibited, so that sufficient general printing suitability (ink fixability) may not be obtained, and the gap between the fillers of the developer layer is filled. It becomes difficult for the dye to penetrate into the developer layer, causing deterioration of color development. On the other hand, when it exceeds 15 μm, the smoothness of the developer layer is lowered, the surface strength is deteriorated, and the color development sensitivity tends to be lowered.

In the developer layer of the present invention, cellulose nanofibers can be used alone or in combination with various pigments. The blending amount of cellulose nanofibers is a solid content with respect to 100 parts by weight of the total amount of cellulose nanofibers and pigments. It is desirable to make it contain 0.005 weight part or more, More preferably, it is 0.1-50 weight part.
The developer layer of the present invention can contain cellulose nanofibers and an arbitrary binder. Water-soluble polymers such as starch, polyvinyl alcohol, methylcellulose, and carboxymethylcellulose, styrene / butadiene copolymers, and acrylic acid type Examples thereof include synthetic resin emulsions such as copolymers. Among these binders, starch, polyvinyl alcohol, and styrene / butadiene copolymers are preferably used.
In the developer layer of the present invention, the blending amount of the binder is desirably about 1 to 300 parts by weight, more desirably about 1 to 300 parts by weight, based on 100 parts by weight of the total amount of cellulose nanofibers and pigments. 30 parts by weight.

  The pressure-sensitive copying color developer sheet of the present invention is produced according to a conventional method. For example, the developer layer coating solution prepared by dispersing the developer in the binder together with the pigment is applied on the support. Obtained by coating and drying.

  As the developer used in the present invention, any known developer in the field of conventional pressure-sensitive or heat-sensitive recording paper can be used, and is not particularly limited. For example, activated clay, attapulgite, colloidal silica Inorganic inorganic substances such as aluminum silicate, 4,4′-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 4 , 4′-dihydroxydiphenyl sulfide, hydroquinone monobenzyl ether, benzyl 4-hydroxybenzoate, 4,4′-dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 4-hydroxy-4′-isopropoxydiphenyl sulfone, 4-Hydroxy-4′-n-propoxydiphenyls Hong, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 3,4-dihydroxyphenyl-4'-methyl Phenylsulfone, aminobenzenesulfonamide derivatives described in JP-A-8-59603, bis (4-hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, bis (p -Hydroxyphenyl) butyl acetate, methyl bis (p-hydroxyphenyl) acetate, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α-methyl-α- (4′- Hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4′-hydroxy) Phenyl) ethyl] benzene, di (4-hydroxy-3-methylphenyl) sulfide, 2,2′-thiobis (3-tert-octylphenol), 2,2′-thiobis (4-tert-octylphenol), International Publication WO97 No. 16420, a phenolic compound such as a diphenylsulfone cross-linking compound, an international publication WO 02/0812229 or JP 2002-301873, a phenolic compound, an international publication WO 02/098774 or WO 03/029017 Phenol novolac type condensation compositions, urea urethane compounds described in International Publication WO 00/14058 or JP 2000-143611, thiourea compounds such as N, N′-di-m-chlorophenylthiourea, p-chlorobenzoic acid, Stearyl gallate Bis [4- (n-octyloxycarbonylamino) salicylate zinc] dihydrate, 4- [2- (p-methoxyphenoxy) ethyloxy] salicylic acid, 4- [3- (p-tolylsulfonyl) propyloxy] Salicylic acid, 5- [p- (2-p-methoxyphenoxyethoxy) cumyl] salicylic acid aromatic carboxylic acid, and zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. of these aromatic carboxylic acids Examples thereof include a salt with a polyvalent metal salt, an antipyrine complex of zinc thiocyanate, and a composite zinc salt of terephthalaldehyde acid and other aromatic carboxylic acid. These developers can be used alone or in combination of two or more. In addition, a metal chelate color-developing component such as a higher fatty acid metal double salt and a polyvalent hydroxyaromatic compound described in JP-A-10-258577 can also be contained.

  In the present invention, the developer layer can contain a sensitizer. Examples of such sensitizers include fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide, montanic acid wax, polyethylene wax, 1, 2-di- (3-methylphenoxy) ethane, p-benzylbiphenyl, β-benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, sulphur Di (p-chlorobenzyl) acid, di (p-methylbenzyl) oxalate, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate, phenyl-α-naphthyl carbonate, 1,4-di Ethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester, o -Xylene-bis- (phenyl ether), 4- (m-methylphenoxymethyl) biphenyl, 4,4'-ethylenedioxy-bis-benzoic acid dibenzyl ester, dibenzoyloxymethane, 1,2-di (3 -Methylphenoxy) ethylene, bis [2- (4-methoxy-phenoxy) ethyl] ether, methyl p-nitrobenzoate, phenyl p-toluenesulfonate, but are not particularly limited thereto. Absent. These sensitizers may be used alone or in combination of two or more.

  The binder used in the present invention includes fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetylated polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, and olefin-modified. Polyvinyl alcohol, nitrile modified polyvinyl alcohol, pyrrolidone modified polyvinyl alcohol, silicone modified polyvinyl alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and Cell like ethyl cellulose, acetyl cellulose Derivatives, casein, arabic gum, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylic ester, polyvinyl butyral, polystyrose and copolymers thereof Polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, coumaro resin and the like can be exemplified. These polymer substances are used by dissolving them in solvents such as water, alcohol, ketones, esters, hydrocarbons, etc., and are used in the state of being emulsified or pasted in water or other media to achieve the required quality. It can also be used in combination.

  Examples of the pigment used in the present invention include kaolin, (calcined) kaolin, calcium carbonate, aluminum oxide, titanium oxide, magnesium carbonate, aluminum silicate, magnesium silicate, calcium silicate, aluminum hydroxide, and silica. It is not limited to these.

  In the present invention, a crosslinking agent can be added to the developer layer as necessary. Cross-linking agents include glyoxal, methylol melamine, melamine formaldehyde resin, melamine urea resin, polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, potassium persulfate, ammonium persulfate, sodium persulfate, ferric chloride, magnesium chloride Borax, boric acid, alum, ammonium chloride and the like.

In the present invention, a lubricant can be added to the developer layer as necessary. Examples of the lubricant include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.
Further, in the present invention, 4,4′-butylidene (6-tert-butyl-3-methylphenol) is used as an image stabilizer exhibiting an oil resistance effect of a recorded image and the like within a range that does not hinder a desired effect on the above problems. ), 2,2′-di-t-butyl-5,5′-dimethyl-4,4′-sulfonyldiphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) Butane, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 4-benzyloxy-4 ′-(2,3-epoxy-2-methylpropoxy) diphenyl sulfone, etc. Can also be added.
In addition, benzophenone and triazole ultraviolet absorbers, dispersants, antifoaming agents, antioxidants, fluorescent dyes, and the like can be used.

  In the present invention, the developer and the material to be added as necessary are finely divided to a particle size of several microns or less by a pulverizer such as a ball mill, an attritor, or a sand glider, or an appropriate emulsifying device. Accordingly, various additive materials are added to obtain a coating solution. As a solvent used for the coating liquid, water, alcohol, or the like can be used.

In the present invention, the method for forming the developer layer is not particularly limited, and for example, an appropriate coating apparatus such as an air knife coater, a roll coater, a blade coater, a rod coater, or a curtain coater can be used. Further, the developer layer is high-quality paper, recycled paper, it is common to be formed to about ^2g / m ² ~7g / m 2 on a synthetic paper consisting of a support or the like.

  Hereinafter, the present invention will be described by way of examples. In the description, parts and% indicate parts by weight and% by weight, respectively. Each layer coating solution was prepared by stirring and dispersing various solutions, dispersions, or coating solutions of the following composition.

[Preparation of cellulose nanofiber]
15 g of powdered cellulose (manufactured by Nippon Paper Chemical Co., Ltd., particle size: 24 μm) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 755 mg (7 mmol) of sodium bromide were dissolved, Stir until the powdered cellulose is uniformly dispersed. After adding 50 ml of sodium hypochlorite aqueous solution (effective chlorine 5%) to the reaction system, the pH was adjusted to 10.3 with 0.5N hydrochloric acid aqueous solution, and the oxidation reaction was started. During the decreasing reaction, the pH in the system was adjusted to pH 10 by successively adding a 0.5N aqueous sodium hydroxide solution. After reacting for 2 hours, oxidized powdered cellulose was separated by centrifugal operation (6000 rpm, 30 minutes, 20 ° C.) and sufficiently washed with water to obtain oxidized powdered cellulose. A 2% (w / v) slurry of oxidized powdered cellulose was treated with a mixer at 12,000 rpm for 15 minutes, and the powdered cellulose slurry was further treated with an ultra-high pressure homogenizer (pressure 140 MPa), and the following transparent A cellulose nanofiber dispersion was obtained.
In addition, the width | variety and length of a cellulose nanofiber are randomly extracted from the photograph of the cellulose nanofiber image | photographed with the electron microscope (100 pieces), and are the measured average values.
-Cellulose nanofiber 1: Width 2.1 nm, Length 1.5 μm Solid content 2%
Cellulose nanofiber 2: width 4.9 nm, length 4.8 μm, solid content 2%

[Example 1]
22 parts of a 45% aqueous dispersion of 3,5-di (α-methylbenzyl) salicylic acid zinc salt having an average particle diameter of 2 μm by a sand grinder, 90 parts of calcium carbonate, 10 parts of kaolin, 10% polyvinyl alcohol (trade name) : Poval 117 (manufactured by Kuraray Co., Ltd.) 50 parts aqueous solution, 2 parts carboxy-modified SBR latex as solids, 200 parts of 2% dispersion of cellulose nanofiber 1 obtained above were mixed, and the concentration was adjusted with water. A coating solution having a concentration of 20% was obtained. This coating solution was applied to high-quality paper of 40 g / m ^{2 with} an air knife coater to obtain a pressure-sensitive copying color developing sheet having a solid coating amount of 5 g / m ² .

[Example 2]
A color developing sheet for pressure-sensitive copying was obtained in the same manner as in Example 1 except that the cellulose root fiber 1 was changed to cellulose nanofiber 2.

[Example 3]
A pressure-sensitive copying color developing sheet was obtained in the same manner as in Example 1 except that the blending part of the 2% cellulose nanofiber dispersion liquid blended in Example 1 was 400 parts.

[Example 4]
A pressure-sensitive copying color developing sheet was obtained in the same manner as in Example 1 except that the blending part of the cellulose nanofiber 2% dispersion blended in Example 1 was 100 parts.

[Comparative Example 1]
A pressure-sensitive copying developer sheet was obtained in the same manner as in Example 1 except that the number of parts of the cellulose nanofiber 2% dispersion compounded in Example 1 was 0.

The developer sheets prepared in Examples 1 to 4 and Comparative Example 1 were evaluated as follows. The evaluation results are shown in Table 1.
(1) Color development test The commercially available upper paper NW40T (Nippon Paper) and the coated surface of the developer sheet are overlapped, sandwiched between the base papers, and calendered at 20 ° C, 65% RH, 100 kg / cm ^2. went. The color density after 1 hour of calendar treatment was measured with a Macbeth densitometer (RD914, Latin # 25 filter, Macbeth).
(2) Printing strength test The color developing sheet 1500 m was printed with an offset rotary printing press (manufactured by Apollo Co., Ltd.).
○: No powder falling △: Powder falling

  As shown in Table 1, the pressure-sensitive copying developer sheet of the present invention has excellent color development performance and excellent printability.

Claims (1)

A pressure-sensitive copying developer sheet having a developer layer containing a developer on a support, wherein the developer layer contains cellulose nanofibers. .