JPH04269581A - No-carbon paper for ion jet printing - Google Patents

Abstract

PURPOSE: To exhibit high quality resolution and rapid drying of an image and durability against water by associating a carbonless paper set involving a first sheet containing high surface area silica particles in a coloring developer and a second sheet containing a support covered with a colorant within an ink jet printer. CONSTITUTION: The carbonless paper is performed by providing a method for forming an image comprising a step of forming the image on a first sheet by discharging an ink in small droplet state to a surface containing a coloring developer, and a step of forming the image on a second sheet by discharging the ink in the small droplet state on an opposite surface to the surface covered with a colorant. To optimize an ink jet printing quality of the second sheet, a surface not covered with the colorant of the second sheet ma be further arbitrarily modified by a suitable treatment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet printing method using a special recording sheet. In particular, the present invention uses a suitable color developer (
The present invention relates to an inkjet printing method using a recording paper coated with a color developer layer. One embodiment of the invention includes a color former.
) a first sheet comprising a support comprising a color developer capable of reacting with a color developer to form a color image, the color developer being coated with a first sheet comprising high surface area silica particles and a color former. incorporating into an inkjet printing apparatus a carbonless paper set comprising a second sheet comprising a support, forming an image on the first sheet by ejecting ink in droplets onto the surface comprising a color developer; and forming an image on a second sheet by ejecting ink in droplets onto a surface opposite the surface coated with a color former.

0002

BACKGROUND OF THE INVENTION Carbonless paper sets are often used in forms in which a number of sets are printed with standard text or materials, leaving a blank space for inscribing individual information, for example by impact typesetting or by hand. is printed as . Typically, carbonless printing forms are manufactured by techniques such as offset printing. However, offset printing and other large scale printing methods require complex and expensive equipment and are not commonly found in office or small office environments. Thus, those desiring forms printed on carbonless paper must arrange them from specialized printing presses, and therefore especially the relatively small number of pre-printed forms.
is required, incurring extra cost and inconvenience. Thus, the ability to make preprinted carbonless foam on standard office equipment may be desirable, especially when small quantities of foam are desired.

Although known compositions and methods are adequate for their intended purposes, there remains a need for carbonless papers suitable for use in ink jet printing machines. Additionally, there is a need for a printing method that allows the production of preprinted carbonless forms on commercially available office machines. Additionally, there is a need for carbonless papers that are compatible with aqueous inkjet inks. The images show high quality resolution, fast drying time and resistance to water. There is also a need for carbonless papers that can be printed with water-based inkjet inks.

0004

SUMMARY OF THE INVENTION It is an object of the present invention to provide a carbonless paper suitable for use in inkjet printers.

[0005]

SUMMARY OF THE INVENTION This and other objects of the invention (or special embodiments of the invention)
a color developer that can react with a color former to form a color image
a first sheet comprising a support comprising:
incorporating into an inkjet printing apparatus a carbonless paper set, the color developer comprising a first sheet comprising high surface area silica particles and a second sheet comprising a support coated with a color former; forming an image on the first sheet by ejecting the ink in droplets onto a surface containing the color former; and forming an image on the first sheet by ejecting the ink in droplets onto a surface opposite the surface coated with the color former. This is accomplished by providing an image forming method that includes the steps of forming images on two sheets. Optionally, the second sheet can be further modified by suitable treatments on the surfaces not coated with color former to optimize the quality of the inkjet print of the second sheet. In another embodiment of the invention, the carbonless paper set also includes one or more intermediate paper sheets containing a color developer comprising high surface area silica particles on one surface and a color former on the opposite surface. include. When one or more additional intermediate sheets are present, the method of the invention also includes the step of forming an image on the intermediate sheet by ejecting ink in droplets onto a surface containing a color developer.

The carbonless paper set used in the method of the present invention comprises at least two sheets of base paper, each containing either a color former or a color developer on one surface. The optional intermediate sheet is coated with a color former on one surface and a color developer on the other surface. The support or base paper can include pulp fibers derived from bleached hardwood and softwood fibers, bleached mechanical pulp fibers, cotton fibers, and synthetic fibers and blends thereof. More specifically, examples of suitable cellulose fibers include Domtar Seagul
W and Q90, 75/25% bleached hardwood and softwood fiber blends, and 100% bleached framewood pulp (Acadi
a Forest Products Ltd. ) is included. Generated sheets derived from cellulose pulp (
The formed sheets must be appropriately sized to minimize penetration of subsequent coatings. Internal and surface sizing treatments include, for example, rosin acid/alum, alkyl ketene dimers, starch, and
or) various synthetic polymers.

[0007] Color formers generally consist of a binder and a color forming substance dissolved in a suitable solvent.
material). Generally, the color-forming material can be a substantially colorless basic dye intermediate, or an organic complexing agent, or a combination of both. Color-forming substances include, for example, benzoylleucomethylene blue; 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (Cry
stal Violet Lactone) and 3,
3-bis(4-dimethiaminophenyl)phthalide (Ma
other phenyl-, indolepyrrole-, and carbazole-substituted phthalides; leukauramines; acylauramines; unsaturated aryl ketones; basic monoazo dyes; rhodamine B lactones; polyarylcarbinols ;3-diethylamino-6-methyl-7
- nitro-, amino-, amido-, sulfonamido-, aminobenzylidene-, halo- and anilino-substituted fluoranes such as anilinofluoranes; spirodipyrans;
It can be a colorless basic dye precursor such as pyridine and pyrazine compounds. Examples of colorless basic dye precursors include U.S. Pat. No. 2,417,897, 3,6
No. 72,935, No. 3,681,390, No. 4,
No. 202,820 and No. 4,675,706, the entire contents of which are hereby incorporated by reference. The color-forming substance can also be an organic complexing agent. Examples of organic complexing agents include U.S. Pat.
No. 481,759, No. 4,334,015, and No. 4,372,582, all of which are hereby incorporated by reference. Examples of organic complexing agents include N,N'-di-
Dithiooxamides and derivatives thereof, such as benzyl-dithiooxamide, N,N'-bis(2-octanyloxyethyl)dithiooxamide and di-dodecyldithiooxamide; as described in U.S. Pat. No. 4,334,015; Includes aromatic substituted hydrazones.

Typically, the selected chromogenic material or combination of chromogenic materials is dissolved in a suitable organic solvent and encapsulated in a rigid polymeric shell by one of several known encapsulation methods. . Examples of suitable solvents include alkyl biphenyls such as propyl biphenyl and butylbiphenyl; dialkyl phthalates such as diethyl phthalate, dibutyl phthalate, dioctyl phthalate, dinonyl phthalate and ditridecyl phthalate; alkylnaphthalene; C such as dodecylbenzene
10-C14 alkylbenzene; alkyl or aralkyl benzoate such as benzyl benzoate; benzyl xylene; benzyl butyl phthalate; ethyl diphenylmethane; 2,2,4-trimethyl-1,3-pentanediol diisobutyrate; partially hydrogenated Included are terphenyl; cyclohexane; toluene; 3-heptanone; tributyl phosphate and mixtures thereof. The solvent for the color former can include any of the above solvents that have sufficient solubility for the color former. A suitable solvent must be capable of dissolving at least 1% by weight of the color former, preferably from about 2 to about 10% by weight. In the case of basic dye/acidic polymer developer systems or organic complexing agent/transition metal salt systems, the color former solvent preferably contains the color developer material (
color developer material)
It is also a co-solvent of Of course, a suitable solvent must also be a non-solvent of the chosen microcapsule wall material.

[0009] Droplets of color former solution are created by emulsifying a solvent oil in an aqueous medium. This color former solution droplet is
It can then be encapsulated into a polymeric shell by any one of a number of known microencapsulation methods, such as coacervation, complex coacervation, interfacial polymerization, in situ polymerization, and the like. Methods for encapsulating droplets of color former solutions in polymeric shells are described, for example, in U.S. Pat.
, No. 800,458, No. 3,418,250 and No. 3,516,941. Capsule wall-forming agents include gelatin wall-forming agents such as gum arabic, polyvinyl alcohol, and carboxymethylcellulose; isocyanate wall-forming agents; urea-formaldehyde and urea-resorcinol-formaldehyde; melanin-formaldehyde; polyureas; polyurethanes; polyamides; These include, but are not limited to, polyester. The finished microcapsules typically have a diameter of about 1 to about 50 μm, preferably about 5 to about 10 μm. The capsule filler of color former in a solvent typically comprises from about 50 to about 95 percent by weight of the total capsule weight.

An aqueous dispersion of microcapsules containing a color former solution and an aqueous dispersion of a suitable binder such as starch, polyvinyl alcohol, latex, etc. are typically mixed in a ratio of about 9:1 to about 7:3. Prepare the coating formulation by mixing the capsule:binder ratio. This capsule+binder dispersion is then coated onto a paper support using any one of a number of known paper coating methods such as roll, gravure, air knife, rod or slot die coating. However, methods that cause minimal capsule disruption, such as rolls and air knives, are preferred.

Optionally, the color former coating comprises from about 5 to about 10% by weight of particles having a particle size somewhat larger than the microcapsules.
can also be included. See, for example, U.S. Pat.
As described in No. 630,079, the color former coating includes particles that are slightly larger than the capsules to prevent or reduce accidental or premature destruction of the microcapsules. Such particles typically include finely divided cellulose powder, starch granules, or various types of plastic beads. The dry code weight of the color former coating is typically about 2 to about 10 g/m2, and typically about 1 to about 5 g/m2.
m2 of solvent and about 0.01 to about 0.1 g/m2 of color former.

When present as a coating, the color developer generally comprises high surface area silica particles dispersed in a water-soluble binder. Inkjet paper or transparency (
Any water-soluble binder material can be used, such as those commonly used in coatings for transparencies. Examples of suitable binders include, but are not limited to, Air
VINOL 3 released by Products
Polyvinyl alcohol such as 50 and Hercul
These include carboxymethyl cellulose sold by E.S. and mixtures thereof. The additional binder material in the coating composition for the paper of the present invention, when present in combination with the pigment and polyvinyl alcohol, improves surface friction, optical density, adhesion of the coating to the paper, reduces chalking, makes the paper more normal Improved properties such as similar feel, water fastness and uniform solid area color can be imparted to the paper. Additional binder is styrene-butadiene latex,
It can be a cationic polyamine, a styrene-vinylpyrrolidone copolymer, a styrene-maleic anhydride copolymer, a polyvinylpyrrolidone, or a vinylpyrrolidone-vinyl acetate copolymer, or a mixture of two or more of these substances. It can also be. If desired, additional additives can be incorporated into the color developer coating provided that these additives do not interfere with image development upon destruction of the color developer material.

[0013] The high surface area silica particles provide a surface that is compatible with aqueous inkjet inks, in contrast to the low surface area (ie, less than 25 m2/g) clays commonly used in carbonless paper color developer coatings. The surface area of the silica particles is sufficiently high to provide effective absorption of ink upon contact with the coated paper. Generally, the particles are at least about 1
00 m2/g, preferably at least about 100 to about 19
5 m2/g, and the surface area is typically about 15
0 to about 375 m2/g, preferably about 250 to about 375 m2/g
m2/g, but the surface area may be outside this range. Examples of suitable silica particles include Grace-Dav
Sy released by ison Company
synthetic amorphous colloidal silica, such as loid 74;
Calcium silicate containing XP974 sold by Huber Corporation, and
Ze released by Corporation
sodium aluminum silicate, such as Olex 80;
and synthetic precipitated silicas such as Zeo and Zeothix 265 from Huber Corporation. The particles are present in the binder in an effective amount, typically from about 50 to about 90% by weight, preferably from about 60 to about 80% by weight, although amounts may be outside this range.

The coating formulation consists of pre-dispersing the silica in water, then adding a pre-heated binder and adjusting the pH.
and finally by mixing in other additives such as additional binders and surfactants. The color developer coating is applied by a laboratory draw-down method using a wire-wound rod or in a pilot coater equipped with an inverted roll coating station and dried in a hot air dryer. Typical coating thicknesses are about 5 to 25 μm, preferably about 10 to about 20 μm, although coating thicknesses may be outside this range.

The color developer sheet may include high surface area silica particles dispersed between the pulp fibers rather than in a separate coating. Paper of this type may be made by any suitable method, such as that described in U.S. Pat. No. 4,734,336, the entire description of which is incorporated herein by reference. . In this case, another embodiment of the invention comprises a support paper substrate sheet having a thickness of 50 to 90 μm as a first layer and a paper sheet as a second layer thereon, the paper sheet having a thickness of about 5 μm. ~about 50μm
and a paper having a filler additive, e.g., about 25 to 75% by weight, attached to the fibers, where the additive is selected from the group consisting of synthetic silica, inorganic silica, such as sodium aluminosilicate, and inorganic oxide. Excellent drying, including sheet and
High image resolution, i.e. high edge clarity (edg
e definition) to obtain a composite sheet,
and to a two-layer uncoated paper for inkjet processes, wherein said sheet also has excellent waterfastness due to certain pigmented aqueous anionic dye-based inkjet compositions.

Optionally, the surfaces of the first sheet of the set are coated with a color former on one surface and a color developer coating comprising a water-soluble binder material and high surface area silica particles on the other surface. can enhance the paper surface's affinity for aqueous inkjet inks and improve image quality. Alternatively, the surface may be left uncoated or treated in any other desired manner to enhance the quality of the inkjet image formed thereon.

Conventional carbonless paper technology typically uses one of two methods. In the first method, the color former is a colorless dye precursor that develops color when it comes into contact with the relatively acidic surface of the color developer. One example of a commercially available carbonless paper that uses this method is Appleton Papers
Inc. , Appleton, Wl. This is NCR brand carbonless paper manufactured by. The recording paper of the present invention is suitable for this type of development. Typically SiO
High surface area silica, meaning 2, also contains physically or chemisorbed water on the surface. This bound water is
It is generally represented by a silanol group, Si-OH, and exhibits considerable acidity. The silica particles thus impart an acidic character to the color developer coating, resulting in the development of a color image when the precursor dye contacts the developer surface.

In the second method, the color former is a colorless substance that forms a colored metal complex when contacted with the color developer. An example of a commercially available carbonless paper using this method is M
innesota Mining and Manuf
Acturing Company, St. Pau
l, MN. It is 3M Tartan, which is colored by. The recording sheet of the present invention generally includes Ni, Cu, Co
Alternatively, the development surface can be made suitable for this type of development by treating it with an organic complexing agent color developer containing a salt of a transition metal such as Zn. Examples of transition metal salts for color developers include nickel 2-ethylhexanoate and nickel rosinate. A water-soluble rosin salt, such as sodium rosinate, is added to the initial paper pulp slurry along with a water-soluble metal salt, such as nickel sulfate, to precipitate the insoluble rosin acid metal salt, i.e., nickel rosinate, as a sizing onto the paper fibers. A color developer sheet can be manufactured by this method. The treated fibers are then formed into paper sheets using conventional papermaking techniques. Alternatively, an aqueous dispersion of nickel rosinate mixed with an inorganic pigment such as silica and a suitable binder can be applied onto the surface of the paper support by any of a number of known techniques.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the invention are described in detail below. These examples are illustrative and the invention is not limited to the materials, conditions or process parameters shown in these examples. Parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 A color developer coating formulation in which the solids portion was 74.3% by weight of high surface area silica particles (Grace-
Davison Chemical Division
12.0% by weight polyvinyl alcohol (Vinol 350, available from Air Products), 0.5% by weight cationic polyamine (American Cyanamid) with a surface area of 340 m2/g
e) Published by (ypro 514), 1
0% by weight of carboxylated styrene-butadiene latex co-binder (Poly
Pol released by sar Limited
ysar 478), 1.0% by weight of a nonionic surfactant (Triton X100 from Rhom and Haas) and the pH of the formulation was adjusted to 8.
．． A formulation containing 1.0% by weight of sodium hydroxide to adjust to 0 was prepared. A coating formulation containing approximately 18% solids by weight was prepared by pre-dispersing silica particles in water and thoroughly degassing. Next, advance 9
Polyvinyl alcohol that had been heated at 5° C. for about 1 hour was added, and the pH was adjusted to 8.0 with sodium hydroxide. Next, the cationic polyamine was added, followed by the styrene-butadiene latex, followed by the surfactant. All these process steps are performed at or near ambient room temperature and pressure. Brookfi
eld Engineering Labs, Sto.
Brookfield LV made in Ughton, MA
The viscosity of the coating formulation measured using a Type F viscometer and spindle #2 at 60 rpm is about 100 to about 15
It was 0 centipoise. This coating is then applied to heavily sized diazo base paper (Dom) weighing 71.5 g/m2.
tar Inc. Released from ) to Meyer rod #
22 draw-down coating (draw-d
Approximately 8 to 1
A coated paper was produced with a coating weight of 0 g/m2. The coating was dried with a hot air gun at approximately 100° C. for 1 minute.

Example 2 Another color developer formulation was prepared as described in Example 1. However, cationic polyamine Cypro
514 is present in an amount of 7% by weight and contains silica Syloid
74 was present in an amount of 69% by weight and the proportions of other components remained the same. The coater (Faustel
Inc. , Germantown, W1), the coating provided a waterfast surface treatment that was compatible with anionic dye-based inkjet inks.

Example 3 A two-ply paper was prepared as follows according to the method described in US Pat. No. 4,734,336, the entire disclosure of which is incorporated herein by reference. The base sheet is made of 75/25% bleached hardwood (Domatar Se) beaten to a Canadian standard freeness value of approximately 400-450.
agul W') and softwood fiber (Domtar Q9
0), and the second layer is made of high-quality furnish containing Gr.
It consisted of the same furnish blended with Syloid 74, a high surface area colloidal silica pigment filler available from Ace-Davison. More specifically, the first pulp suspension for the base layer is removed from the storage tank A.
．． A base sheet weighing 65 g/m2 was produced by feeding it onto forming wire through a vertically oscillating nozzle at a 4% consistency. a second comprising a blend of pulp and 50% silica filler;
of the agitated pulp suspension (storage tank B) is applied with a vibrating nozzle to the first preformed layer (maintained as a wet fiber slurry on the wire) and then drained. , a paper structure with two separate layers was formed having a total basis weight of about 75 g/m2. Therefore, the base layer or the second
The thickness of the layer can be varied by the number of passes through the nozzle. In this example, the number of passes through the nozzle was counted to obtain a two-layer sheet having an upper layer of 14% of the total sheet thickness. After draining the sheet to 20% dryness, a level with sufficient wet strength, peel the sheet from the wire, press the second (top) layer onto the smooth Teflon surface and press the base layer. Further dehydration was performed in a single nip wet press in a sandwich pressed onto felt, followed by drying in a photographic drum dryer. The combined thickness of the first and second layers was approximately 100 μm.

Example 4 Four carbonless paper sets were prepared and imaged as follows. Appleton Papers I
nc. , Appleton, W1 has a first sheet (a coloring agent coated on the surface opposite to the surface on which the image is to be formed).
and a second sheet (with color developer coated on the surface on which the image is to be formed). Both sheets were placed so that the color former coating on the first sheet was in contact with the color developer coating on the second sheet and the IBM
Incorporated into Selectric typewriter. An image was formed on the first sheet by typing on the surface opposite the surface having the color former coating. A corresponding image was formed on the surface of a second sheet coated with color developer.

Three other sets of NCR brand carbonless paper were dismantled, the second sheet of each was replaced with a recording sheet prepared as described in Examples 1, 2, and 3, and the second sheets were color developed. agent coating is the first
A new carbonless paper set was assembled in contact with the color former coating of the sheet. Each of these sets was placed so that the color former coating of the first sheet was in contact with the color developer coating of the second sheet and the IBM Se
Incorporated into the lsctric typewriter. An image was formed on the first sheet by typing on the surface opposite the surface having the color former coating. A corresponding image was formed on the surface of a second sheet coated with color developer.

The image formed on the recording paper of Example 1 was N
Exhibits edge sharpness comparable to images obtained with carbonless paper sets with CR color developer sheets and NCR
It exhibited improved optical density compared to that obtained with the carbonless paper set with a color developer sheet. Images formed on the recording papers of Examples 2 and 3 exhibited edge sharpness and optical density comparable to images obtained with carbonless paper sets with NCR color developer sheets. In all cases, carbonless image development was almost instantaneous.

Example 5 The inkjet printing performance of the carbonless paper set described in Example 4 was evaluated using HP Deskjet (registered trademark) black ink printer and Xerox (registered trademark).
Tested on a 4020 color printer. Examples 1 and 2
The text and solid area black images printed with the HP Deskjet® printer on the color developer sheets prepared as described in 3 and 3 have significantly superior optical density, solid area, and solid area images compared to the NCR color developer sheets. It showed area uniformity and edge sharpness. Similarly, Example 1,
The first and second color checkerboard patterns of colored inks printed with a Xerox® 4020 printer on color developer sheets prepared as described in 2 and 3 were much duller, exhibited intercolor bleed, and were highly pigmented. Compared to images printed on mottled NCR color developer sheets, the resulting image produced a much more vibrant solid area color image with no intercolor bleed and highly uniform optical density.

Example 6 Two recording sheets as described in Example 2 were dip coated with an aqueous nickel chloride solution. The first sheet was dipped in a 1% solution (sheet 6a) and the second sheet was dipped in a 5% solution (sheet 66). Next, three types of carbonless paper sets were prepared and images were formed in the following manner. 3M
One set of Tartan carbonless papers consists of a first sheet (with a color former coating on the opposite surface from the surface on which the image is to be formed) and a second sheet (on the surface on which the image is to be formed). (with a color developer coating). Both sheets were placed so that the color developer coating on the first sheet was in contact with the color developer coating on the second sheet and the IBM Select
ric I incorporated it into my typewriter. An image was formed on the first sheet by typing on the surface opposite the surface having the color former coating. A corresponding image was formed on the surface of the second sheet coated with color developer.

The second set of 3M Tartan carbonless papers was dismantled and each second sheet was replaced with sheets 6a and 6b, respectively, so that the color developer coating of the second sheet was in contact with the color developer coating of the first sheet. Assembled a new carbonless paper set. Each of these sets was incorporated into an IBM Selectric typewriter with the color former coating of the first sheet in contact with the color developer coating of the second sheet. An image was formed on the first sheet by typing on the surface opposite the surface having the color former coating. A corresponding image was formed on the surface of a second sheet coated with color developer.

The images obtained on sheets 6a and 6b produced images of comparable quality to those obtained with carbonless paper sets, each having a 3M Tartan color developer sheet. The resulting image was somewhat wider and more magenta in comparison to the bluish-purple image obtained on the 3M Tartan color developer sheet. The development speed of the carbonless image was fastest for the set containing the 3M Tartan color developer sheet, somewhat slower for the set containing the color developer sheet 6b, and significantly slower for the set containing the color developer 6a. This development rate indicates that the absorbent silica coating of sheets 6a and 6b has a lower effective concentration of Ni2+ for complexation with the color former composition than the relatively less absorbent clay coating on the 3M Tartan developer coating. It suggests that. The images formed on sheets 6a and 6b were very clean and resisted background pressure development during transfer by the typewriter feed roll, whereas the carbonless paper set containing the 3M Tartan color developer sheet had very noticeable background development. showed that.

Example 7 The inkjet print quality performance of the carbonless paper set described in Example 6 was evaluated using an HP Deskjet® printer and a Xerox® 402 printer.
Evaluation was made using a 0 color printer. HP Deskjet
The color developer sheets of Examples 6a and 6b printed on a ® printer exhibited significantly superior optical density, solid area uniformity, and edge sharpness compared to the 3M color developer sheets. Similarly, Xe on Examples 6a and 6b
ROX® 4020 color prints have more vibrant solid area colors compared to images printed on 3M color developer sheets that are much duller, exhibit significant intercolor bleed, and exhibit highly mottled solid areas. Images formed with no intercolor bleed and highly uniform optical density.

Other embodiments and modifications of the invention may occur to those skilled in the art after reading the information presented herein. These embodiments and modifications and equivalents are intended to be included within the scope of the invention.

Claims (2)

[Claims] Claim 1: (1) Color former
er) a first sheet comprising a support comprising a color developer capable of reacting with the color developer to form a color image, the first sheet comprising a support comprising high surface area silica particles; a second sheet comprising a support coated with a color former into an inkjet printing apparatus;
) forming an image on a first sheet by ejecting ink in droplets onto a surface containing a color developer; and (3) forming a droplet of ink onto a surface opposite to the surface coated with color developer. An image forming method comprising the step of forming an image on a second sheet by discharging the image. 2. A first sheet comprising a support comprising a color developer capable of reacting with a color former to form a color image, wherein the color developer has an area of about 100 to about 195 m2/
A carbonless paper set comprising a first sheet comprising silica particles having a surface area of g and a second sheet comprising a support coated with a color former.