Recording paper

Abstract

The present invention addresses the problem of providing a recording paper having both excellent heat-sensitive recording adaptability and ink-jet recording adaptability, and also having excellent heat resistance and strength of a recording layer. [Solution] A recording paper which comprises a support and a recording layer that is provided on the support and contains a leuco dye and an electron-accepting developer, the recording layer containing an electron-accepting developer, the solubility of the electron-accepting developer in ethanol being 0.3 g / ml or less, the recording layer containing silica as a pigment for accepting ink, and the recording layer containing silica as a pigment for accepting ink. And the solid content blending amount of the silica relative to the recording layer is 20 mass% or more.

Description

Technical Field

[0001] This invention relates to a recording paper adapted for inkjet recording. Background Technology

[0002] Generally, thermal recording papers are typically manufactured as follows: colorless or light-colored electron-donating leuco dyes (hereinafter also called "leuco dyes") and electron-accepting color developers such as phenolic compounds (hereinafter also called "color developers") are separately ground and dispersed into fine particles. These particles are then mixed, and binders, pigments, sensitivity enhancers (sensitizers), lubricants, and other additives are added. The resulting coating solution is then applied to a support such as paper, synthetic paper, film, or plastic. Color is developed through an instantaneous chemical reaction caused by heating from a thermal printhead, thermal embossing device, thermal pen, laser, etc., thus recording the image.

[0003] Thermal recorders have the following characteristics: no noise during recording, no need for development and fixing, maintenance-free, relatively inexpensive equipment, compact structure, and very clear color reproduction. Therefore, they are widely used in fax machines, computer terminal printers, automatic ticket vending machines, measuring recorders, handheld terminals, etc.

[0004] Furthermore, for thermal recorders, sometimes it is necessary not only to possess thermal recording performance but also inkjet recording adaptability. For example, in applications such as ATMs and tags, UV inks are first printed using a general layout, and then various different information such as amounts and barcodes are recorded thermally. However, when printing on thermal recorders or other recording paper using inkjet recording, problems such as darkening or blurring of the inkjet-recorded image occur due to the color development of the base layer caused by the color development of the thermal recording layer overlaid on the recording area.

[0005] Therefore, it is known that a technique exists for making a thermal recorder adaptable to inkjet recording by using a colorimetric agent with a specific solubility in acetonitrile (Patent Document 1).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2003-226076

[0009] Patent Document 2: Japanese Patent Application Publication No. 2022-151636 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the heat resistance is not sufficient when using the color developer described in Patent Document 1.

[0012] Furthermore, in the case of the technology described in Patent Document 2, since ethanol is used as the solvent in the coating solution for the recording layer, the strength of the recording layer is insufficient. When the strength of the coating layer is weak, undesirable conditions may occur during printing using an inkjet continuous ticket printer, reducing the adaptability of inkjet recording.

[0013] Therefore, the object of the present invention is to provide recording paper that has both excellent thermal recording adaptability and inkjet recording adaptability, and has excellent heat resistance and recording layer strength.

[0014] Methods for solving problems

[0015] The inventors conducted in-depth research and found that by specifying the solubility of the electron-accepting colorimetric reagent in ethanol, the above-mentioned problems could be solved, thus completing the present invention.

[0016] That is, the present invention comprises a support body and a recording layer disposed on the support body and containing a leuco dye and an electron-accepting color developer. The recording layer contains the electron-accepting color developer, and the solubility of the electron-accepting color developer in ethanol is less than 0.3 g / ml. In the recording layer, the pigment that receives ink contains silicon dioxide, and the solid content of the silicon dioxide relative to the recording layer is 20% by mass or more.

[0017] Invention Effects

[0018] According to the present invention, it is possible to provide recording paper that has both excellent thermal recording adaptability and inkjet recording adaptability, as well as excellent heat resistance and recording layer strength. Detailed Implementation

[0019] The specific details of the present invention will be described below.

[0020] The recording paper of the present invention has a support body and a recording layer disposed on the support body and containing a leuco dye and an electron-accepting developer. The recording layer contains an electron-accepting developer, and the solubility of the electron-accepting developer in ethanol is 0.3 g / ml or less. Furthermore, the recording layer contains silica as a pigment that receives ink, and the solid content of silica relative to the recording layer is 20% by mass or more.

[0021] Hereinafter, various materials used in the recording layer of the recording paper of the present invention are illustrated. However, binders, crosslinking agents, pigments, etc., may also be used in each coating layer provided as needed, without impairing the desired effect on the above-mentioned issues.

[0022] The recording layer is, for example, a thermal recording layer or an ink receiving layer.

[0023] The recording layer contains an electron-accepting colorimetric agent, and the solubility of the electron-accepting colorimetric agent in ethanol is less than 0.3 g / ml.

[0024] If the solubility of the developer in ethanol is below 0.3 g / ml, it exhibits excellent adaptability to both thermal recording and inkjet recording. Although the reason is unclear, it can be assumed that since organic solvents are typically used as solvents in inkjet inks, the lower the solubility of the developer in ethanol, the more the melting of the developer caused by the inkjet ink is suppressed.

[0025] Furthermore, if the solubility of the color developer in ethanol is below 0.3 g / ml, it exhibits excellent heat resistance. This is because if the solubility of the color developer in ethanol is greater than 0.3 g / ml, the color development onset temperature of the color developer becomes lower.

[0026] Here, solubility refers to the value obtained as follows: at room temperature, the colorimetric reagent powder is dissolved in 10 ml of 99.5% ethanol until supersaturated. After suction filtration, the weight of the incompletely dissolved powder remaining on the filter paper is measured, and the weight dissolved in 1 ml of ethanol is calculated based on the difference between the weight of the powder and the weight of the powder added.

[0027] Furthermore, the recording layer preferably contains only one of the aforementioned specific electron-accepting color developers. This is because if two or more electron-accepting color developers are included, a situation will arise in inkjet recording adaptability where a "base color" occurs after inkjet recording, resulting in the inkjet-recorded image sometimes becoming dark or blurry.

[0028] Although the reason is not yet clear, it can be assumed that the use of two or more color developers to form a eutectic mixture increases reactivity compared to using only one color developer.

[0029] In addition, because the use of two or more color developers to form a eutectic mixture will lower the melting point, the heat resistance will also decrease.

[0030] It should be noted that the statement that the recording layer "contains only one" electron-accepting colorimetric agent means that it contains only one electron-accepting colorimetric agent whose solubility in ethanol is within the aforementioned range. That is, even if the electron-accepting colorimetric agent has a solubility in ethanol that meets the aforementioned range, the recording layer does not contain more than two electron-accepting colorimetric agents.

[0031] If the solubility of the aforementioned electron-accepting color developer in 99.7% IPA (isopropanol) is less than 0.5 g / ml, the melting of the color developer caused by inkjet ink is further suppressed, which is therefore preferred.

[0032] The solubility in IPA is calculated as follows: at room temperature, the colorimetric reagent powder is dissolved in 10 ml of IPA until supersaturated. After suction filtration, the weight of the incompletely dissolved powder remaining on the filter paper is measured. The weight dissolved in 1 ml of IPA is calculated based on the difference between the weight of the undissolved powder and the weight of the added powder.

[0033] As a specific example of the aforementioned electron-accepting colorimetric reagent, a urea compound represented by the general formula (Chemical 1) can be shown.

[0034] [Chemistry 1]

[0035]

[0036] (In the formula, X represents -O- or -NH-, R) 1 Represents a hydrogen atom or -SO2-R 3 R 3 Indicates substituted or unsubstituted alkyl, aralkyl, or aryl groups, R 2 (This represents a hydrogen atom or an alkyl group, where m represents an integer from 0 to 1.)

[0037] In the above general formula (Chemistry 1), R 3 Preferably, it is a substituted or unsubstituted aryl group, more preferably a group represented by the following formula.

[0038] [Chemistry 2]

[0039]

[0040] (where R) 4 ~R 8 These can be the same or different, representing hydrogen atoms, halogen atoms, nitro groups, amino groups, alkyl groups, alkoxy groups, aryloxy groups, alkyl carbonyloxy groups, aryl carbonyloxy groups, alkyl carbonyl amino groups, aryl carbonyl amino groups, alkyl sulfonyl amino groups, aryl sulfonyl amino groups, monoalkyl amino groups, dialkyl amino groups, or aryl amino groups.

[0041] In general formula (Chemistry 1), R 3 This indicates an alkyl, aralkyl, or aryl group that may or may not be substituted. The alkyl group is, for example, a straight-chain, branched, or alicyclic alkyl group, and preferably has 1 to 12 carbon atoms. The aralkyl group preferably has 7 to 12 carbon atoms, and the aryl group preferably has 6 to 12 carbon atoms. Furthermore, when they are substituted, the substituents are preferably alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, aryl groups having 6 to 12 carbon atoms, or halogen atoms. Additionally, multiple R... 3 They can be the same or different.

[0042] R in the benzene ring of general formula (Chem. 1) 1 The positions of -O- can be the same or different, preferably 3, 4 or 5.

[0043] R in the benzene ring of general formula (Chem. 1) 3 The positions of -SO2-O- can be the same or different, preferably 3, 4 or 5.

[0044] Examples of such alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclopentyl, hexyl, cyclohexyl, 2-ethylhexyl, lauryl, etc.

[0045] Examples of such aralkyl groups include benzyl, 1-phenylethyl, 2-phenylethyl, 3-phenylpropyl, p-methylbenzyl, m-methylbenzyl, m-ethylbenzyl, p-ethylbenzyl, p-isopropylbenzyl, p-tert-butylbenzyl, p-methoxybenzyl, m-methoxybenzyl, o-methoxybenzyl, m-, p-dimethoxybenzyl, p-ethoxy-m-methoxybenzyl, p-phenylmethylbenzyl, p-cumylbenzyl, p-phenylbenzyl, o-phenylbenzyl, m-phenylbenzyl, p-tolylbenzyl, m-tolylbenzyl, o-tolylbenzyl, p-chlorobenzyl, and other unsubstituted or substituted aralkyl groups, alkoxy groups, aralkyl groups, aryl groups, or halogen atoms.

[0046] Examples of aryl groups include phenyl, p-tolyl, m-tolyl, o-tolyl, 2,5-dimethylphenyl, 2,4-dimethylphenyl, 3,5-dimethylphenyl, 2,3-dimethylphenyl, 3,4-dimethylphenyl, mesitylene, p-ethylphenyl, p-isopropylphenyl, p-tert-butylphenyl, p-methoxyphenyl, 3,4-dimethoxyphenyl, p-ethoxyphenyl, p-chlorophenyl, 1-naphthyl, 2-naphthyl, tert-butylated naphthyl, and other unsubstituted or substituted aryl groups with alkyl, alkoxy, aralkyl, aryl, or halogen atoms.

[0047] R 2 The symbol represents a hydrogen atom or an alkyl group, preferably a hydrogen atom. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, etc.

[0048] R in the benzene ring of general formula (Chem. 1) 2 The positions can be the same or different, preferably 3, 4 or 5.

[0049] In addition, examples of urea compounds of the present invention include N,N'-bis[3-(benzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(benzenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-bis[3-(benzenesulfonyloxy)-4-ethyl-phenyl]urea, N,N'-bis[3-(benzenesulfonyloxy)-5-methyl-phenyl]urea, N,N'-bis[3-(benzenesulfonyloxy)-4-propyl-phenyl]urea, N,N'-bis[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-bis[3-(m-toluenesulfonyloxy)phenyl]urea, and N,N'-bis[3-(p-toluenesulfonyloxy)phenyl]urea. [N,N'-di[3-(p-toluenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di[3-(m-toluenesulfonyloxy)phenyl]urea, N,N'-di[3-(tris(toluenesulfonyloxy)phenyl]urea, N,N'-di[3-(1-naphthalenesulfonyloxy)phenyl]urea, N,N'-di[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di[3-(p-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di[3-(p-propylbenzenesulfonyloxy)phenyl]urea, N,N'-di[3-(p-isopropylbenzenesulfonyloxy)phenyl]urea N,N'-bis[3-(p-tert-butylbenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(m-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(o-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(m-,p-dimethoxybenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(p-ethoxybenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(p-propoxybenzenesulfonyloxy)phenyl]urea, N,N'-bis[3-(p-butoxybenzenesulfonyloxy)phenyl]urea, N,N '-Di[3-(p-cumylbenzylsulfonyloxy)phenyl]urea, N,N'-Di[3-(p-cumylbenzylsulfonyloxy)phenyl]urea, N,N'-Di[3-(o-phenylbenzylsulfonyloxy)phenyl]urea, N,N'-Di[3-(p-phenylbenzylsulfonyloxy)phenyl]urea, N,N'-Di[3-(p-chlorobenzylsulfonyloxy)phenyl]urea, N,N'-Di[4-(benzylsulfonyloxy)phenyl]urea, N,N'-Di[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-Di[3-(ethanesulfonyloxy)phenyl]urea, N,N'-Di[3-(benzylsulfonyloxy)phenyl]urea, etc., but not limited to them.

[0050] Alternatively, as the urea compound of the present invention, a urea urethane compound represented by chemical formula (Chemical 3) (manufactured by FINE ACE Corporation, trade name UU) can be used.

[0051] [Chemistry 3]

[0052]

[0053] The content (solid component) of the electron-accepting colorimetric agent in the recording layer of the present invention is 1.0 to 70.0% by weight, preferably 5.0 to 65.0% by weight, and more preferably 10.0 to 60.0% by weight.

[0054] The same content of the urea compound in the recording layer of the present invention is 1.0 to 50.0% by weight, preferably 5.0 to 40.0% by weight.

[0055] In the recording layer, the pigment that receives the ink contains silicon dioxide, and the amount of the solid component of the silicon dioxide relative to the recording layer is 20% by mass or more.

[0056] Examples of silica include sedimentation silica and gel silica.

[0057] Using silica not only improves the color intensity (concentration) of inkjet-recorded images but also enhances the ink's drying properties. Other pigments (such as kaolin) cannot fully absorb the ink, leading to issues like ink bleeding in the inkjet-recorded images.

[0058] The solid content of silica relative to the recording layer is typically 10% to 12% by weight. If the solid content of silica is less than 10% by weight, the ink acceptability of the recording layer decreases, resulting in reduced inkjet recording adaptability.

[0059] There is no upper limit to the amount of solid silica in the formulation, as long as it is within a range that can balance thermal recording and inkjet recording compatibility, for example, 45.0% by mass. The amount of solid silica in the formulation is preferably 25.0 to 45.0% by mass, more preferably 25.0 to 40.0% by mass.

[0060] If the ink absorption capacity of silica is above 130ml / 100g, the ink accepting capacity of the recording layer increases, and the adaptability of inkjet recording is further improved.

[0061] As the leuco dye used in this invention, any known leuco dye in the field of pressure-sensitive or thermal recording paper can be used without particular limitation; however, triphenylmethane compounds, fluorane compounds, fluorene compounds, and divinyl compounds are preferred. Specific examples of representative colorless or light-colored dyes (dye precursors) are given below. Furthermore, these dye precursors can be used alone or in mixtures of two or more.

[0062] <Triphenylmethane-based leuco dyes>

[0063] 3,3-Bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone) and 3,3-bis(p-dimethylaminophenyl)phthalide (also known as malachite green lactone)

[0064] <Fluorane leuco dyes>

[0065] 3-Diethylamino-6-methylfluorane, 3-Diethylamino-6-methyl-7-aniline fluorane, 3-Diethylamino-6-methyl-7-(o,p-dimethylaniline)fluorane, 3-Diethylamino-6-methyl-7-chlorofluorane, 3-Diethylamino-6-methyl-7-(m-trifluoromethylaniline)fluorane, 3-Diethylamino-6-methyl-7-(o-chloroaniline)fluorane, 3-Diethylamino-6-methyl-7-(p-chloroaniline)fluorane, 3-Diethylamino-6-methyl-7-(o-fluoroaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-methylaniline)fluorane, 3-Diethylamino-6-methyl-7-n-octylaniline ...(m-methylaniline)fluorane, 3-Diethylamino-6-methyl-7-n-octylaniline fluorane, 3-Diethylamino-6-methyl-7-(m-methylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-methylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-methylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-methylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-ethylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-ethylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m-ethylaniline)fluorane, 3-Diethylamino-6-methyl-7-(m 3-Methyl-7-n-octylaminofluorane, 3-diethylamino-6-methyl-7-benzylaminofluorane, 3-diethylamino-6-methyl-7-dibenzylaminofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-chloro-7-aniline fluorane, 3-diethylamino-6-chloro-7-p-methylaniline fluorane, 3-diethylamino-6-ethoxyethyl-7-aniline fluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-(m-trifluoromethylaniline)fluorane, 3-diethylamino-7-(o-chloroaniline)fluorane, 3-diethylamino-7-(p-chloroaniline)fluorane, 3-diethylamino-7-(m-trifluoromethylaniline)fluorane, 3-diethylamino-7-(o-chloroaniline)fluorane, 3-diethylamino-7-(p-chloroaniline)fluorane, 3-diethylamino-7- -(o-fluoroaniline)fluorane, 3-diethylamino-benzo[a]fluorane, 3-diethylamino-benzo[c]fluorane, 3-dibutylamino-6-methylfluorane, 3-dibutylamino-6-methyl-7-aniline fluorane, 3-dibutylamino-6-methyl-7-(o,p-dimethylaniline)fluorane, 3-dibutylamino-6-methyl-7-(o-chloroaniline)fluorane, 3-dibutylamino-6-methyl-7-(p-chloroaniline)fluorane, 3-dibutylamino-6-methyl-7-(o-fluoroaniline)fluorane, 3-dibutylamino-6-methyl-7-(m-trifluoromethylaniline)fluorane, 3-dibutylamino-6-methyl-7-chlorofluorane, 3-dibutylamino-6-ethoxyethyl 3-Anilinefluorane, 3-Dibutylamino-6-chloro-7-anilinefluorane, 3-Dibutylamino-6-methyl-7-p-methylanilinefluorane, 3-Dibutylamino-7-(o-chloroaniline)fluorane, 3-Dibutylamino-7-(o-fluoroaniline)fluorane, 3-Di-n-pentylamino-6-methyl-7-anilinefluorane, 3-Di-n-pentylamino-6-methyl-7-(p-chloroaniline)fluorane, 3-Di-n-pentylamino-7-(m-trifluoromethylaniline)fluorane, 3-Di-n-pentylamino-6-chloro-7-anilinefluorane, 3-Di-n-pentylamino-7-(p-chloroaniline)fluorane, 3-pyrrolidinyl-6-methyl-7-anilinefluorane, 3-piperidinyl-6-methyl-7-anilinefluorane3-(N-methyl-N-propylamino)-6-methyl-7-anilinofluorane, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-cyclohexylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-hexylamino)-6-methyl-7-(p-chloroanilino)fluorane, 3-(N-ethyl-p-toluidine)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isopentylamino)-6 3-Chloro-7-anilinofluorane, 3-(N-ethyl-N-tetrahydrofurfurylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isobutylamino)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-ethoxypropylamino)-6-methyl-7-anilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-(4-oxahexyl)-3-dimethylamino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-diethylamino-6-methyl-7-anilinofluorane, 2-(4-oxahexyl)-3-dipropyl Amino-6-methyl-7-aniline fluorane, 2-methyl-6-p-(p-dimethylaminophenyl)aminoaniline fluorane, 2-methoxy-6-p-(p-dimethylaminophenyl)aminoaniline fluorane, 2-chloro-3-methyl-6-p-(p-phenylaminophenyl)aminoaniline fluorane, 2-chloro-6-p-(p-dimethylaminophenyl)aminoaniline fluorane, 2-nitro-6-p-(p-diethylaminophenyl)aminoaniline fluorane, 2-amino-6-p-(p-diethylaminophenyl)aminoaniline fluorane, 2-diethylamino-6-p-(p-diethylaminophenyl)amino Aniline fluorane, 2-phenyl-6-methyl-6-p-(p-phenylaminophenyl)aminoaniline fluorane, 2-benzyl-6-p-(p-phenylaminophenyl)aminoaniline fluorane, 2-hydroxy-6-p-(p-phenylaminophenyl)aminoaniline fluorane, 3-methyl-6-p-(p-dimethylaminophenyl)aminoaniline fluorane, 3-diethylamino-6-p-(p-diethylaminophenyl)aminoaniline fluorane, 3-diethylamino-6-p-(p-dibutylaminophenyl)aminoaniline fluorane, 2,4-dimethyl-6-[(4-dimethylamino)aniline]-fluorane.

[0066] <Fluorene Leuco Dyes>

[0067] 3,6,6'-tris(dimethylamino)spiro[fluorene-9,3'-phthalide], 3,6,6'-tris(diethylamino)spiro[fluorene-9,3'-phthalide].

[0068] <Divinyl Leuco Dyes>

[0069] 3,3-Bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)vinyl]-4,5,6,7-tetrabromophthalide, 3,3-Bis[2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)vinyl]-4,5,6,7-tetrachlorophthalide, 3,3-Bis[1,1-bis(4-pyrrolylphenyl)vinyl-2-yl]-4,5,6,7-tetrabromophthalide, 3,3-Bis[1-(4-methoxyphenyl)-1-(4-pyrrolylphenyl)vinyl-2-yl]-4,5,6,7-tetrachlorophthalide.

[0070] <Other>

[0071] 3-(4-Diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-octyl-2-methylindole-3-yl)-4-azaphthalide, 3-(4-cyclohexylethylamino-2-methoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3,3-bis(1-ethyl-2-methylindole-3-yl)phthalide, 3,6-bis(diethylamino)fluorane-γ-(3'-nitro)anilinolactam, 3,6-bis( Diethylamino)fluorane-γ-(4'-nitro)anilinolactam, 1,1-bis[2',2',2'',2''-tetra(p-dimethylaminophenyl)-vinyl]-2,2-diacetonitrile ethane, 1,1-bis[2',2',2'',2''-tetra(p-dimethylaminophenyl)-vinyl]-2-β-naphthoyl ethane, 1,1-bis[2',2',2'',2''-tetra(p-dimethylaminophenyl)-vinyl]-2,2-diacetyl ethane, bis[2,2,2',2'-tetra(p-dimethylaminophenyl)-vinyl]-dimethylmalonate.

[0072] Previously known sensitizers can be contained in the recording layer.

[0073] Examples of such sensitizers include stearamide, palmitamide and other fatty acid amides, ethylene diamide, lignite wax, polyethylene wax, 1,2-bis(3-methylphenoxy)ethane, p-benzylbiphenyl, β-benzyloxynaphthalene, 4-biphenyl-p-tolyl ether, m-terphenyl, 1,2-diphenoxyethane, dibenzyl oxalate, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate, dibenzyl terephthalate, and benzyl p-benzyloxybenzoate. Esters, phenyl-α-naphthyl carbonate, 1,4-diethoxynaphthalene, phenyl 1-hydroxy-2-naphthoic acid ester, o-xylene-bis(phenyl ether), 4-(m-methylphenoxymethyl)biphenyl, dibenzyl 4,4'-ethylenedioxy-bisbenzoate, dibenzoyloxymethane, 1,2-di(3-methylphenoxy)ethylene, bis[2-(4-methoxy-phenoxy)ethyl] ether, methyl p-nitrobenzene, phenyl p-toluenesulfonate, o-toluenesulfonamide, p-toluenesulfonamide, etc. These sensitizers can be used alone or in combination of two or more.

[0074] If the total content of the above-mentioned sensitizers relative to the recording layer is 30% by weight or less, the heat resistance is improved and the substrate color development is suppressed, which is therefore preferred.

[0075] Examples of binders used in this invention include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, acetylated polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, olefin-modified polyvinyl alcohol, nitrile-modified polyvinyl alcohol, pyrrolidone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, other modified polyvinyl alcohols, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, and cellulose derivatives such as ethyl cellulose and acetylated cellulose, casein, gum arabic, oxidized starch, etherified starch, dialdehyde starch, esterified starch, polyvinyl chloride, polyvinyl acetate, polyacrylamide, polyacrylate, polyvinyl butyral, polystyrene and its copolymers, polyamide resins, silicone resins, petroleum resins, terpene resins, ketone resins, coumarone resins, etc. These polymers can be used not only in solvents such as water, alcohols, ketones, esters, and hydrocarbons, but also in emulsified or dispersed into a paste state in water or other media. They can also be used in combination depending on the required quality.

[0076] Examples of lubricants used in this invention include fatty acid metal salts such as zinc stearate and calcium stearate, waxes, and silicone resins.

[0077] In this invention, without impairing the desired effects on the aforementioned issues, 4,4'-butyride (6-tert-butyl-3-methylphenol), 2,2'-di-tert-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-tert-butylphenyl)butane, etc., can be added as stabilizers to improve the oil resistance of the image section. Furthermore, benzophenone-based and triazole-based ultraviolet absorbers, dispersants, defoamers, antioxidants, fluorescent dyes, etc., can be used.

[0078] The types and amounts of leuco dyes, developers, sensitizers, and other components used in the recording layer of this invention can be determined according to the required performance and recording suitability, and are not particularly limited. Generally, relative to 1 part by weight of leuco dye, the amounts of developer, sensitizer, stabilizer, and other components are approximately 0.01 to 10 parts by weight. The binder is suitable to be approximately 5 to 25% by weight in the solid components of the recording layer.

[0079] In this invention, the leuco dye, color developer, and other materials to be added as needed are micronized to a particle size of less than a few micrometers using a ball mill, grinder, sand mill, or other suitable emulsification device. A binder and various additives used for the intended purpose are then added to prepare the coating liquid. Water or alcohol can be used as the solvent in this coating liquid, with a solid content of approximately 20-40% by weight.

[0080] Especially when alcohol is used as a solvent, the coating solution can penetrate into the paper, resulting in a decrease in the strength of the coating layer. Therefore, water is preferred as the solvent.

[0081] In the recording paper of the present invention, an undercoat layer may also be provided between the support and the recording layer.

[0082] The base coat mainly consists of binders and pigments.

[0083] As the adhesive used in the base coat, the adhesives applicable to the recording layers described above can be appropriately used. One or more of these adhesives can be used.

[0084] Pigments used in the base coating can include, for example, inorganic pigments such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, magnesium hydroxide, kaolin, calcined kaolin, clay, and talc, as well as organic pigments such as hollow plastic particles. One or more of these pigments can be used. Calcined kaolin is preferred as a pigment other than hollow plastic particles.

[0085] The pigment content in the base coat is typically 50-95% by weight, preferably 70-90% by weight, relative to the base coat (solid component). The content of hollow plastic particles in the base coat is 50% by weight or more, preferably 70-100% by weight, and more preferably 80-100% by weight, relative to the pigment (solid component) in the base coat.

[0086] In the coating liquid of the primer layer, various additives such as dispersants, plasticizers, pH adjusters, defoamers, water-retaining agents, preservatives, coloring dyes, and UV inhibitors can be appropriately added as needed.

[0087] In this invention, it is preferable that no protective layer or other layers are provided on the surface of the recording layer, and that the recording layer is the outermost layer of the recording paper (exposing the surface of the recording layer).

[0088] In cases where a protective layer is not placed on the recording layer, the water resistance and adhesion are improved.

[0089] Regarding water resistance and adhesion, tap water was dripped onto the surface of the recording layer (or protective layer) of the recording paper, and the paper was folded in half with the surface facing inwards. After standing for a while, the paper was peeled off, and the peeling was evaluated to determine whether the recording layer (or protective layer) peeled off.

[0090] The reason for improved water resistance and adhesion without a protective layer is that the protective layer usually contains a lot of adhesives such as PVA (polyvinyl alcohol). Therefore, when a protective layer is applied, the adhesive will bond the coated surfaces together with water.

[0091] In this invention, the method for coating the recording layer and other coating layers besides the recording layer, i.e., the protective layer, the primer layer, etc., is not particularly limited, and coating can be carried out according to commonly known techniques. For example, an external coating machine or an internal coating machine equipped with various coating machines such as an air knife coating machine, a bar blade coating machine, an exhaust blade coating machine, an angled blade coating machine, a roller coating machine, and a curtain coating machine can be appropriately selected.

[0092] The coating weight of the recording layer and other coating layers can be determined based on the required performance and recording suitability, and there are no particular limitations. However, the typical coating weight of the recording layer, based on solids, is 2–12 g / m². 2 The coating weight of the protective layer, based on solid content, is preferably 0.5–5.0 g / m². 2 .

[0093] In addition, various well-known techniques in the field of recording paper can be applied as needed after each coating layer is applied, such as smoothing treatments such as supercalendering.

[0094] If the coating layer, which serves as the recording layer, is weak, the printed portion may peel off along with the coating layer after printing using an inkjet continuous printing press. To maintain its proper function after inkjet printing, the coating layer needs to have sufficient strength, for example, the strength to prevent peeling when adhesive tape is peeled off from the substrate.

[0095] Specifically, the force required to peel the tape (peel strength) is determined using a digital force gauge in the cellophane tape peel test described later. A peel strength of 150 N / m or higher is acceptable, but to ensure sufficient strength, it is preferably set to 250 N / m or higher.

[0096] If the longitudinal tensile strength (JIS P8113) of the recording paper is 3 kN / m or higher, its operability in inkjet continuous ticket printers is improved, and therefore it is preferred. Even in the field of inkjet paper, continuous ticket printers that print continuously, like offset printing presses, are used in industrial applications. In this case, with low tensile strength, it is impossible to apply tension during printing, resulting in poor travel performance; if tension is forcibly applied, paper breakage may occur.

[0097] To achieve a tensile strength of 3 kN / m or higher, one could increase the basis weight and thickness of the base paper, or increase the amount of paper strength enhancer in the base paper.

[0098] If the color concentration obtained by contacting the recording layer side of the recording paper with a hot plate at 90°C for 5 seconds at 0.1 MPa is 0.40 or less, the base color development caused by drying during printing using an inkjet continuous ticket printer is suppressed, which is therefore preferred.

[0099] Methods for setting the color concentration to below 0.40 include reducing the coating amount of the recording layer, changing the color developer, reducing the proportion of the sensitizer, or not using the sensitizer at all.

[0100] Example

[0101] The present invention will be illustrated below with reference to examples, but it is not intended to limit the present invention. It should be noted that, unless otherwise specified, in the various embodiments and comparative examples, "parts" means "parts by weight" and "%" means "% by weight".

[0102] To manufacture recording paper, the various dispersions and coating solutions are prepared as follows.

[0103] [Preparation of each coating solution]

[0104] The complex containing the following compounds is stirred and dispersed to prepare a coating liquid for the primer layer.

[0105] <Coating liquid for primer>

[0106] Calcined kaolin (ANCILEX 90) 100.0 parts

[0107] Styrene-butadiene copolymer latex (ST5526) 10.0 parts

[0108] 50.0 parts water

[0109] The color developer dispersion (A1-5), leuco dye dispersion (B), and sensitizer dispersion (C) were wet-milled using a sand mill until the average particle diameter was 0.5 μm.

[0110] Colorimetric reagent dispersion (A1 solution)

[0111] N,N'-Bis[3-(p-toluenesulfonyloxy)phenyl]urea

[0112] (Hereinafter referred to as "Urea Compound 1 (represented as U1 in Table 1)"). 6.0 parts

[0113] Fully saponified polyvinyl alcohol aqueous solution (manufactured by Kuraray, trade name:

[0114] PVA117 (10% solids) 5.0 parts

[0115] 1.5 parts water

[0116] Colorimetric reagent dispersion (A2 solution)

[0117] N-[2-(3-phenylureo)phenyl]benzenesulfonamide

[0118] (Hereinafter referred to as "Urea compound 2 (represented as U2 in Table 1)"). 6.0 parts

[0119] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0120] 1.5 parts water

[0121] Colorimetric reagent dispersion (A3 solution)

[0122] Urea ester compounds represented by chemical formula (Chem. 3)

[0123] (Made by FINE ACE) 6.0 copies

[0124] [Chemistry 3]

[0125]

[0126] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0127] 1.5 parts water

[0128] Colorimetric reagent dispersion (A4 solution)

[0129] 4,4'-Dihydroxydiphenyl sulfone

[0130] (Manufactured by Konishi Chemical Industry Co., Ltd., Trade Name: 44BPS) 6.0 parts

[0131] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0132] 1.5 parts water

[0133] Leuco dye dispersion (solution B)

[0134] 3-Dibutylamino-6-methyl-7-anilinefluorane (manufactured by Yamamoto Chemical Co., Ltd.)

[0135] Product Name: ODB-2) 6.0 servings

[0136] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0137] 1.5 parts water

[0138] Sensitizer dispersion (C solution)

[0139] 1,2-Bis(3-methylphenoxy)ethane (manufactured by Sanko Co., Ltd.)

[0140] Product Name: KS232) 6.0 servings

[0141] 5.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0142] 1.5 parts water

[0143] Then, the dispersions are mixed in the following proportions to prepare a coating solution for the recording layer.

[0144] <Coating solution for recording layer>

[0145] Colorimetric reagent dispersion (A1 solution) 36.0 parts

[0146] Leuco dye dispersion (solution B) 18.0 parts

[0147] Sensitizer dispersion (C solution) 18.0 parts

[0148] Silica dispersion (manufactured by Mizusawa Chemical Co., Ltd., MIZUKASIL P-537)

[0149] (25% solids) 140.0 parts

[0150] 25.0 parts of fully saponified polyvinyl alcohol aqueous solution (PVA117)

[0151] Then, the coating liquid for the protective layer is prepared by mixing the complexes in the following proportions.

[0152] <Protective Coating Liquid>

[0153] Aluminum hydroxide dispersion (manufactured by Martinswerk)

[0154] Product Name: Martifin OL (50% Solids) 9.0 parts

[0155] Carboxyl-modified polyvinyl alcohol aqueous solution (manufactured by Kuraray, trade name:

[0156] KL318, degree of polymerization: approximately 1800, degree of saponification: 85–90 mol%.

[0157] (10% solids) 30.0 parts

[0158] Polyamide epichlorohydrin resin (manufactured by Starlight PMC Company, trade name:

[0159] WS4030 (25% solids) 4.0 parts

[0160] Modified polyamine resin (manufactured by Taoka Chemical Co., Ltd., trade name: Sumirez Resin SPI)

[0161] -102A (45% solids) 2.2 parts

[0162] Zinc stearate (manufactured by Zhongjing Oils & Fats Co., Ltd., trade name: HYDRIN Z-7-30)

[0163] (30% solids) 2.0 parts

[0164] [Example 1]

[0165] In the support body (base weight 47g / m) 2 On one side of high-quality paper, a base coating liquid is applied using a doctor blade method, resulting in a coating weight of 10.0 g / m² based on solids. 2 Then it is dried to obtain the base coating paper.

[0166] On the base coating of the base-coated paper, a coating liquid for the recording layer is applied using a bar blade method, resulting in a coating weight of 6.0 g / m² based on solids. 2 Then it is dried and processed using a super calender to achieve a smoothness of 100-500 seconds, thus producing recording paper.

[0167] [Example 2]

[0168] The recording paper was produced in the same manner as in Example 1, except that liquid A2 was used instead of liquid A1 in the coating liquid for the recording layer.

[0169] [Example 3]

[0170] Except for changing the amount of silica dispersion in the coating solution for the recording layer to 100 parts, the recording paper was produced in the same manner as in Example 1.

[0171] [Example 4]

[0172] Except for changing the amount of silica dispersion in the coating solution for the recording layer to 200 parts, the recording paper was produced in the same manner as in Example 1.

[0173] [Example 5]

[0174] Except for changing the amount of liquid C in the coating solution for the recording layer to 48 parts, the recording paper was produced in the same manner as in Example 1.

[0175] [Comparative Example 1]

[0176] Except for changing the amount of A1 liquid in the coating liquid for the recording layer to 18 parts and adding 18 parts of A3 liquid to the coating liquid for the recording layer, the recording paper was produced in the same manner as in Example 1.

[0177] [Comparative Example 2]

[0178] The recording paper was produced in the same manner as in Example 1, except that liquid A4 was used instead of liquid A1 in the coating liquid for the recording layer.

[0179] [Comparative Example 3]

[0180] The recording paper was produced in the same manner as in Example 3, except that liquid A4 was used instead of liquid A1 in the coating liquid for the recording layer.

[0181] [Comparative Example 4]

[0182] Except for changing the amount of silica dispersion in the coating solution for the recording layer to 40 parts, the recording paper was produced in the same manner as in Example 1.

[0183] [Comparative Example 5]

[0184] Except for changing the amount of silica dispersion in the coating solution for the recording layer to 70 parts and adding 35 parts of aluminum hydroxide dispersion to the coating solution for the recording layer, the recording paper was produced in the same manner as in Example 1.

[0185] [Comparative Example 6]

[0186] The recording paper was prepared in the same manner as in Example 1, except that the same amount of 20% ethanol was used instead of water as a solvent in the developer dispersion (A1 solution), leuco dye dispersion (B solution), and sensitizer dispersion (C solution) in the coating solution for the recording layer.

[0187] The following evaluation is given to the produced recording paper.

[0188] <Thermal Recording Adaptability (Barcode Reading Adaptability)>

[0189] For the recording paper produced, a Zebra 140XiIII label printer was used to print barcodes (CODE39) in both the longitudinal (barcode orthogonal to the print head movement direction) and transverse (barcode parallel to the print head movement direction) conditions at a printing level of +10 and a printing speed of 30.4 cm / s (12 inches / s).

[0190] Then, the printed barcodes were read using a barcode verification machine (Honeywell QCPC600, 640nm light source) to evaluate their readability. The evaluation results were recorded using ANSI standard symbol levels.

[0191] Symbol rating: Divide the barcode into 10 parts along the direction perpendicular to the bar, perform a reading test on each part once, and use a 5-level evaluation of (excellent) A, B, C, D, F (poor) to represent its average value.

[0192] <Inkjet Recording Adaptability (Bleeding)>

[0193] For the prepared recording paper, solid printing in four colors—black, cyan, magenta, and yellow—was performed using a Canon PIXUS MG7130 inkjet printer (mode: plain paper / standard). The bleeding was evaluated according to the following criteria.

[0194] Advantages: The ink dries immediately after printing, without blurring or feathering of the text.

[0195] Acceptable: Although the ink dries immediately after printing, there are slight issues such as blurry text and feathering.

[0196] Unacceptable: The ink did not dry immediately after printing. Or the text is blurry or feathered.

[0197] <Inkjet Recording Adaptability (Substrate Color Development)>

[0198] For the prepared recording paper, a solid yellow print was made using a Canon PIXUS MG7130 inkjet printer (mode: plain paper / standard). The base color development of the solid print was evaluated one day later according to the following criteria.

[0199] Advantage: No base color was produced at all.

[0200] Good: Although it is difficult to distinguish with the naked eye, the Bk value increases slightly when measured with a concentration meter.

[0201] Acceptable: The base color is slightly produced at a level that can be judged by the naked eye.

[0202] Unacceptable: The base color is not produced.

[0203] <Heat resistance>

[0204] The recording paper was tested for color development using a thermal tilt tester (manufactured by Toyo Seiki Co., Ltd.) at a pressure of 0.1 MPa, a contact time of 5 seconds, and a temperature of 90°C. The color concentration of the recording section was determined using a Macbeth concentration meter (RD-914, using an amber filter) to measure the Bk concentration.

[0205] Advantages: Bk concentration is below 0.20.

[0206] Good: Bk concentration is above 0.21 and below 0.40.

[0207] Qualified: Bk concentration is above 0.41 and below 0.60.

[0208] Unacceptable: Bk concentration is above 0.61.

[0209] <Water Resistance and Adhesion>

[0210] For the prepared recording paper, drop 10ml of tap water onto the surface of the protective layer, fold it in half with the protective layer surface facing inward, and apply 20gf / cm. 2 After applying the load and allowing it to stand for 24 hours, peel it off. Visually evaluate the peeling of the protective layer and recording layer of the part where water was added according to the following criteria.

[0211] Advantages: No adhesion occurs at all, and there is no peeling of the protective layer or recording layer.

[0212] Acceptable: Adhesion occurs, the protective layer peels slightly, but the recording layer does not peel off.

[0213] Unacceptable: Strong adhesion occurs, the protective layer and the recording layer peel off; or the recording paper is damaged during peeling.

[0214] <Layer strength (peel strength) of the recording layer>

[0215] The layer strength of the recording layer (coating layer) was determined using a cellophane tape peel test (peel test) under ambient conditions of 23°C and 50%. The test was conducted as follows: a transparent adhesive tape (NICHIBAN Cellophane Tape (registered trademark), CT24, 24mm wide) was adhered to the surface of the recording layer, and a 2.0kg rubber roller was used to roll back and forth on the tape 20 times. The force required to peel the tape was then measured using a digital force gauge (SHIMPO FGX-2) (peeling speed 20m / min, peel angle 180 degrees).

[0216] The results are shown in Table 1.

[0217] It should be noted that Table 1 lists the types of electron-accepting colorimetric reagents and their solubility in 99.5% ethanol (Et) and 99.7% IPA.

[0218] In addition, the solid component amounts and total contents in Table 1 are values ​​relative to the recording layer.

[0219]

[0220] As shown in Table 1, it can be seen that in each embodiment, it has both excellent thermal recording adaptability and inkjet recording adaptability.

[0221] It should be noted that in Example 5, where the total content of the above-mentioned sensitizer relative to the recording layer is greater than 30% by weight, the heat resistance and substrate color development are slightly worse compared to other examples, but there is no problem in practical use.

[0222] On the other hand, in Comparative Example 1, where the recording layer contains two types of electron-receptive color developers, not only is the inkjet recording adaptability (substrate color development) poor, but the heat resistance is also poor.

[0223] In Comparative Example 2, where the solubility of the electron-accepting developer in the recording layer in ethanol is greater than 0.3 g / ml, inkjet recording adaptability (bleeding) and heat resistance are poor.

[0224] The reason for the decreased adaptability (bleeding) of inkjet recording is that inkjet inks come in both aqueous and solvent-based types, with solvent-based inks using organic solvents such as ethanol and IPA. Therefore, when using a color developer with high solubility in ethanol, the color developer melts in the inkjet ink and reacts with the dye to produce color, thus affecting the substrate color. The reason for the decreased heat resistance is that the color-developing onset temperature of the color developer is low.

[0225] In Comparative Example 3, where the surface of the recording layer was not exposed but covered by other layers (protective layers), the water resistance and adhesion were poor.

[0226] In Comparative Examples 4 and 5, where the amount of solid silica relative to the recording layer is less than 20% by mass, inkjet recording adaptability (bleeding) is poor.

[0227] In Comparative Example 6, where the solvent for the coating solution used as the recording layer contained ethanol, the strength of the recording layer decreased.

Claims

1. A recording paper having a support body and a recording layer disposed on the support body and containing a leuco dye and an electron-accepting developer. The recording layer contains the electron-accepting chromogenic agent, and the solubility of the electron-accepting chromogenic agent in 99.5% ethanol is less than 0.3 g / ml. In the recording layer, the pigment that receives the ink contains silicon dioxide, and the amount of solid component of the silicon dioxide relative to the recording layer is 20% by mass or more.

2. The recording paper according to claim 1, wherein, The recording paper is an inkjet recording medium with thermal recording adaptability.

3. The recording paper according to claim 1, wherein, The recording paper is a thermal recording paper adapted for inkjet recording.

4. The recording paper according to claim 1 or 2, wherein, The recording layer contains only one of the electron-accepting colorimetric agents.

5. The recording paper according to claim 1 or 2, wherein, The peel strength of the thermal recording layer, based on the cellophane tape peel test, is above 150 N / m.

6. The recording paper according to claim 1 or 2, wherein, The solubility of the electron-accepting colorimetric agent in 99.7% IPA is less than 0.5 g / ml.

7. The recording paper according to claim 1 or 2, wherein, The electron-accepting colorimetric agent is represented by a urea compound of the following general formula (1); Chemical Formula 1 In the formula, X represents -O- or -NH-, R 1 Represents a hydrogen atom or -SO2-R 3 R 3 Indicates substituted or unsubstituted alkyl, aralkyl, or aryl groups, R 2 This indicates a hydrogen atom or an alkyl group, and m represents 0 or 1.

8. The recording paper according to claim 1 or 2, wherein, The silica has an oil absorption capacity of over 130ml / 100g.

9. The recording paper according to claim 1 or 2, wherein, The recording layer contains a sensitizer, and the total content of the sensitizer relative to the recording layer is less than 30% by weight.

10. The recording paper according to claim 1 or 2, wherein, The recording paper has a longitudinal tensile strength of 3 kN / m or higher based on JIS P8113.

11. The recording paper according to claim 1 or 2, wherein, The color concentration obtained by contacting the recording paper with a hot plate at 90°C for 5 seconds at 0.1 MPa is 0.40 or less.

12. The recording paper according to claim 1 or 2, wherein, The recording layer is the outermost layer.

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