JP2960240B2 - Carbonless pressure-sensitive copy paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonless pressure-sensitive copying paper which has excellent color developability, stain resistance and appearance of a coated surface, enables high-speed coating, and enables stable production. .

[0002]

2. Description of the Related Art Carbonless pressure-sensitive copying paper usually has a colorless electron-donating dye (hereinafter referred to as a color former) on one side of a support.
It is basically composed of a so-called upper sheet coated with a microcapsule containing a solution of the above and a so-called lower sheet coated with a developer sheet coated with an electron-accepting acidic substance (hereinafter referred to as a developer), The color former is released from the microcapsules of the color former sheet by the writing pressure or the pressure of a typewriter or the like, and comes into contact with the developer of the color developer sheet to form a color, thereby obtaining an image.

[0003] Further, a middle sheet having a role of a color former sheet and a color developer sheet (a microcapsule coating layer containing a color former is provided on one surface of a support, and a developer is provided on the other surface). Many copies can be made by combining a large number of sheets (provided with a coating layer) between an upper sheet and a lower sheet.

A microcapsule containing a color former solution is coated on one surface of a support, and a color developer is further coated thereon or a microcapsule containing a color developer solution is applied. If a single coating is carried out by mixing the agents, a printed color image can be obtained on one sheet, and a self-coloring type sheet is obtained. Hereinafter, the self-coloring type sheet is basically considered to be handled in the same manner as the colorant sheet.

In general, there are the following four items as quality conditions required for a color former sheet for carbonless pressure-sensitive copying paper and main conditions required at the time of manufacturing. High color density, clear image can be obtained in a short time, and there is no deterioration over time. When color formation is not intended, that is, during the production process, various printing processes, cutting process, storage and handling in a sheet or wound state of the color former sheet for carbonless pressure-sensitive copying paper, no stain is generated. The coated surface has no streaks or bumps, no uncoated parts, etc., and the appearance is not bad. High-speed, high-concentration coating is possible.

Although the two items have conflicting characteristics, it is difficult to sufficiently satisfy both of them.
Improve by devising factors such as the manufacturing conditions of the microcapsules applied to the color former sheet, the type and amount of the protective agent and the type and amount of the binder, and also by the type and amount of the binder and the winding method, etc. And many suggestions have been made for them.

On the other hand, in order to obtain high productivity in the production of a color former sheet for carbonless pressure-sensitive copying paper, it is necessary to use a high coating liquid for the purpose of minimizing the drying energy during coating and increasing the coating speed. Densification is achieved. As a means,
Improvements have been made to the liquid properties of the coating solution and the coating method have been devised. Particularly, in the case of a color former sheet, a low-viscosity microcapsule emulsion (for example, JP-A-63-2875)
No. 42) or a method using a low-viscosity binder (for example, JP-A-2-3367).

However, the color former sheet obtained by the high concentration coating by the above-mentioned means causes a decrease in stain resistance due to rubbing during actual use, and sufficiently satisfies the quality as a color former sheet for carbonless pressure-sensitive copying paper. I could not say that I was doing it.

As a method for forming the microcapsule coating layer of the color former sheet, a method using an air knife coater has been conventionally used. However, such a method involves scraping off excess coating liquid with air and coating the required amount. It is. The main reason that air knife coaters have been used is
It is considered that the coating can be performed at a relatively high speed (300 m / min or more) and that the method has been conventionally used for coated paper for printing and the like. However, in such a method, generation of mist, noise, and the like poses a problem for recent demands for a higher speed (800 m / min or more).
Furthermore, a phenomenon in which the protective agent having a large particle diameter is selectively scraped off by excessive air causes a so-called classification effect, and as a result, the protective agent having a small particle diameter increases on the support and the stain resistance of the color former sheet is reduced. There was a problem of lowering.

In order to solve the above problem, a method using a so-called curtain coater for forming a free-fall vertical curtain (for example, Japanese Patent Publication Nos. 61-46187 and 63-239) has been devised. This method is a coating method which has already been widely used in the field of photosensitive recording materials (for example, JP-B-49-24133 and JP-B-49-3544).
No. 7) is applied to the coating of pressure-sensitive copying paper. It is a microcapsule that does not require any classification of protective agent and can be applied at a relatively high concentration compared to the air knife coater that is usually used. This is a method for forming a coating layer.

The above-mentioned free fall vertical curtain coating method solves the problem of the air knife or the blade coater. However, the curtain film is formed by free fall from the head height from the upper end of the liquid level in the liquid supply head. When the viscosity of the coating solution is increased due to the high concentration of the coating solution, a desired amount of the solution may not be obtained. Accordingly, in order to obtain a desired amount of liquid, the opening width of the outlet slit of the head is increased to reduce the flow pressure loss, and the length of the outlet slit in the vertical direction is reduced to reduce the flow pressure loss. It is necessary to take any measures such as increasing the height of the liquid supply surface to increase the head difference.

At this time, when the opening width of the outlet slit of the head is increased, the flow velocity at the slit outlet is reduced as compared with the case where the same flow rate is obtained without changing the opening width. Therefore, the collision speed at the contact point between the support and the curtain film is reduced if the height of the curtain film is the same. When the speed at the contact point between the support and the curtain film is reduced, it becomes difficult to break through the boundary layer of air on the surface of the support, and in particular, high-speed coating exceeding 800 m / min becomes impossible.

Further, when the length of the exit slit of the head is shortened, the flow turbulence due to the narrowing of the flow path shape in the slit tends to flow out of the slit exit without being sufficiently rectified, and a stable curtain film is formed. I can't get it.

Further, when the liquid supply surface is increased, it is necessary to increase the height of the liquid retaining portion of the head. Further, when the amount of staying liquid increases, the staying time of the liquid becomes longer, and the aggregation of the liquid proceeds, which may block the slit portion. The aggregation of the liquid
When the concentration of the solution is increased, the solution becomes more remarkable. In addition, a method of adding a dispersant or an anti-agglomeration agent to prevent aggregation of the liquid is conceivable, but it should be avoided in consideration of the influence on the quality of the product.

As described above, the free-fall vertical curtain type head cannot cope with a further increase in the concentration of the coating solution, and the concentration range of the coating solution has an upper limit, which is extremely narrow. Is a method in which the pressure in the head must be as low as possible in order to make the profile uniform.For this reason, in the current situation, it is easier to close than in the pressurized curtain coater that forces the pressure in the head as described below. is there.

On the other hand, when the solid content concentration of the coating liquid decreases,
Since the viscosity tends to be low, the pressure of the liquid supply head decreases, and considerable restrictions are imposed on the hard surface in order to form a uniform curtain film. Furthermore, the amount of movement of water and the binder with respect to the capsule at the time of drying increases, and the water and the binder tend to be unevenly distributed on the surface of the coating layer, and uneven distribution of the binder tends to occur on the surface. Color formation is suppressed in the portion where the binder is localized on the surface, and conversely, in the portion where the binder is sparse, the color formation tends to be accelerated, and color unevenness is likely to occur.

In recent years, a demand for high-speed and high-concentration coating exceeding 1000 m / min has started to appear. In this method, as the speed increases, the curtain film fluctuates due to the flow of air accompanying the support, and at the same time, the air on the support surface The boundary layer becomes thicker, so that the curtain film cannot break down the boundary layer, causing the so-called "repelling phenomenon" that eventually disturbs the curtain film and does not receive the coating liquid on the support surface. There has been a problem that coating unevenness or an uncoated portion occurs.

In order to solve these problems, a method of providing a wind shield plate (for example, Japanese Patent Publication No. Sho 53-31005) and a method of covering the entire portion of a liquid supply head where a curtain film is formed (for example, Japanese Patent Publication No. Sho 57-105) Japanese Patent Application Laid-Open No. 2005-54969) and a method of installing a suction device immediately before a curtain film (for example, Japanese Patent Publication No. 62-186966) have been devised, but no solution has yet been found.

In addition to these methods, in general, it can be improved to some extent by increasing the free fall speed of the curtain to increase the collision speed, and by giving the free fall curtain sufficient momentum to sufficiently shoot through the boundary layer of air. In addition to the reasons described above, if the height is too high, the effect is limited because the curtain is disturbed by the resistance of the air, even if the flow of air accompanying the support is relatively small.

On the other hand, a coating method in which a curtain is formed by forcible pressure has been considered in order to compensate for the drawbacks of the above-mentioned coating method. That is, a curtain film of a coating liquid containing a microcapsule containing an electron-donating dye as a main component is formed from a pressure type liquid supply head having a slit, and the height of the liquid supply head is kept at an appropriate height. In addition, it can be achieved by providing a coating layer by colliding the support with a predetermined speed or more by forcible pressure. Here, the forcible pressurization means that a structure other than the liquid supply port and the liquid outflow slit has a hermetically closed structure. When pressurized to cm ² or more, it is fundamentally different from the free-fall curtain described above. That is, in the free-fall type, it is necessary to reduce the pressure in the liquid supply head as low as possible in order to make the profile uniform, and it is difficult to remove the obstruction once formed in the slit. On the other hand, in the pressurized type handled by the present invention,
Since sufficient pressure is applied, an obstruction is hardly generated, and even if it is generated, it is needless to say that the obstruction is more easily removed than the free type.

Although these solve the problem of the air knife coater, all of these methods are
This method forms a curtain film of the coating liquid from the slit and collides with the support, which greatly affects the compatibility (wettability) between the support and the coating liquid. No. 57-39985), but at present, improvement from a support is still unsatisfactory.

[0022]

SUMMARY OF THE INVENTION The present invention is to overcome the problems in quality and production of the conventional color former sheet for carbonless pressure-sensitive copying paper. It is to provide a satisfactory color former sheet.
High-density color development can be obtained by writing pressure or pressure from a typewriter or the like. That is, clear also in a number of copies
Images can be obtained. Prevents contamination when color development is not intended. In other words, there is little friction stain generated at the time of rubbing, and pressure stain applied during storage of the color former sheet, at the time of printing, at the time of cutting, and the like, and the stain resistance is excellent. There is no unevenness of coating, uncoated portion or dropout, and the appearance of the coated surface is good. High-speed, high-concentration coating is possible, and there is little adverse effect of slit blockage.
That is, the drying load can be reduced by the high-concentration coating solution, and high productivity without deterioration in quality can be obtained because of the measures against clogging.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a coating liquid containing microcapsules containing an electron-donating dye as a main component from a liquid supply head having a slit. In a method of forming a curtain film and colliding with a support to provide a coating layer,
It is achieved by setting the air permeability based on the ISP8117 method to 60 seconds or less.

Conventionally, in a curtain coater, a method of lowering the surface tension of the coating solution has been used in order to improve the compatibility (wetting property) between the coating solution and the support. A problem arises in that printability and set-glue suitability, which are one of the important characteristics, cannot be maintained.
That is, when the surface tension of the coating liquid is low, the wettability of the coated surface is improved as it is, and it is difficult to achieve balance in a printing method based on a difference in interfacial tension as represented by offset printing. Regarding the set glue aptitude, although the glue itself easily penetrates and the adhesive strength is increased, the whole becomes wavy after drying, and the appearance is poor and the commercial value is low.
Furthermore, it adheres to the surface to be coated (generally the base paper surface), which is an unnecessary part of adhesion, resulting in a fatal defect that it cannot be set properly,
There was a limit to improvement from the coating solution.

Therefore, if the air permeability of the support is 60 seconds or less, more preferably 40 seconds or less as in the present invention,
When the curtain of the coating liquid collides with the support, the air in the boundary layer on the surface of the support can easily escape, so that the coating liquid can be uniformly fixed to the support. On the other hand, when the air permeability exceeds 60 seconds, the air in the boundary layer loses a refuge, so that the curtain film is disturbed and the coating liquid is not received on the surface of the support. This results in uneven coating or uncoated portions.

The air permeability of a support which has been conventionally used in an air knife coater is not particularly limited as compared with other coating methods. In particular, there is no practical upper limit since the film can be coated. However, if the lower limit is extremely low, the coating method of the air knife coater is a coating method in which excess coating liquid is scraped to the required amount by air pressure. Is pushed into the inside of the support and further escapes to the opposite side of the coated surface, so-called danger of strikethrough increases. In the case of medium paper (in which a microcapsule coating layer containing a color developing agent is provided on one side of the support and a color developing agent coating layer is provided on the other side), the strike-through is particularly caused by the developer coating. Since there is a great possibility of coloring in the working layer, the commercial value is significantly reduced.

However, in the curtain coater according to the present invention, it is needless to say that the above-mentioned problem hardly occurs even if the air permeability is slightly low because of the coating method in which pressure is not extremely applied as compared with the air knife coater. That is, the present inventor has found that a curtain coater has an upper limit of the air permeability of the support, and on the other hand, has substantially no lower limit, leading to the present invention.

As the support of the present invention, acidic paper and neutral paper mainly containing cellulose fibers are usually used. The air permeability of the support specified by the present invention is, for example, the length of pulp used in papermaking. Beating degree, filler, binder,
It can be easily performed by adjusting the size and the like, but is not necessarily limited to these.

The support of the present invention having the above characteristics can be obtained according to a conventionally known papermaking method.
For example, bleached kraft pulp and the like of hardwood and softwood are the main raw materials, and further, depending on the purpose, synthetic pulp, synthetic fiber,
Glass fiber etc. are used in combination, fillers as fillers,
It can be obtained by blending necessary additives such as a sizing agent, various binders, a dispersant, a water resistance agent, a retention improver, a fluorescent dye, and the like, and forming the paper.

Further, the support of the present invention may have a coating layer containing a pigment or the like formed on the surface thereof. Examples of raw materials used for forming such a coating layer include clay, talc, kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, and satin white.

The coating layer composed of the above pigment is formed by dispersing the pigment in a medium such as water, adding a suitable binder and adjusting the composition, and applying the coating by a known method. The support is JI
When the Beck smoothness based on the SP8119 method is 10 seconds or less, the air flow accompanying the support becomes thick, so that it is preferable to increase the air flow as much as possible.

In the present invention, in the coating process, the coating liquid is not subjected to an action such as high shearing stress from the outside, and since the pre-metering method is used, water is selectively absorbed by the support and the coating liquid becomes high. Since the composition does not change, the composition of the coating liquid does not change with time even if the coating liquid is recycled and reused, so that a stable color former sheet for carbonless pressure-sensitive copying paper is manufactured. This effect can be expected even when the coating speed is increased.

Since the amount of the coating solution is measured in advance and then applied onto the support, the amount is minimized, and the coating solution is excessively supplied like a blade or an air knife coater. The amount of liquid supply is 1/5 or less. In the method in which the coating liquid is formed into a curtain film by pressurization and is applied by colliding with the support, the amount of coating is determined by the traveling speed of the support and the supply amount of the coating liquid per unit time. However, theoretically, the minimum liquid supply amount is an amount capable of stably forming the curtain film, and is an extremely small amount.

In the present invention, the coating liquid containing microcapsules as a main component is generally a solution obtained by dissolving or dispersing microcapsules in a water together with a binder and a protective agent. Means 10 to 60% by weight. The mixing ratio of the microcapsule, the binder, and the protective agent is generally such that the ratio of the binder and the protective agent is 5 parts by weight or more, preferably 10 to 70 parts by weight, more preferably 30 to 60 parts by weight with respect to 100 parts by weight of the microcapsules. Parts, and the ratio of the binder to the protective agent is usually 50 to 200 parts by weight based on 100 parts by weight of the binder.

[0035] As coloring agents in the present invention, crystal violet lactone, 3, 3 - bis (p - dimethylaminophenyl) phthalide, 3- (p - dimethylaminophenyl) -3- (2-methyl-India Lumpur -3 -Ill)
Triarylmethane phthalide and methylene blue benzoyl, such as 6-dimethylamino phthalide, Anizoiru, acyl derivatives such as pin Baroiru; 3-diethylamino-6-methyl-7-chloro fluoran, 3-diethylamino-7- Xanthenphthalide such as dibenzylaminofluoran and the like.

Examples of the color developer include natural clay minerals such as acid clay and attapulgite as inorganic color developers, activated clay obtained by treating acid clay with a mineral acid, and semi-synthetic solid acids described in JP-A-57-15996. And various organic phenolic compounds, novolak-type phenolic resins, polyvalent metal salts of aromatic carboxylic acids, and the recently proposed
Polyvalent metal products of salicylic acid resins described in JP-A-186729 and JP-A-63-254124 have already been used.

The color former is dissolved in a high boiling point solvent and used as microcapsules. Examples of the high-boiling solvent that dissolves the color former include alkylnaphthalenes represented by diisopropylnaphthalene, diallylalkanes represented by 1-phenyl-1-xylylethane, alkylbiphenyls represented by isopropylbiphenyl, and other triallyldienes. Aromatic hydrocarbons such as methanes, alkylbenzenes, benzylnaphthalenes, diallylalkylenes, and allylindanes; carboxylate compounds represented by dibutyl phthalate and dioctyl maleate; represented by tricresyl phosphate Phosphate oils; vegetable oils such as castor oil, soybean oil and cottonseed oil or modified oils thereof; and high-boiling fractions of natural products such as mineral oils (consisting of aliphatic hydrocarbons).

There are known methods for producing microcapsules containing a color developing agent, such as a coacervation method, an in-situ method, and an interfacial polymerization method. A synthetic resin capable of obtaining microcapsules at a high concentration is used as a wall material. Are preferred.

The microcapsules containing the color former are coated on a support such as paper together with a binder and a protective agent. Examples of the binder include a water-soluble polymer binder such as starch and polyvinyl alcohol, and styrene butadiene. Latex emulsion binders, which are hydrophobic polymers based on acrylic, acrylic, or vinyl acetate, are used. The protective agent is added to prevent unintended destruction of the microcapsules. Generally, a protective agent having a particle diameter of about 2 to 10 times the particle diameter of the microcapsules is used. Specifically, wheat starch, Potato starch, cellulose fine powder, synthetic resin fine particles and the like are used.

In the present invention, the weight solids concentration of the coating liquid containing microcapsules as a main component is not particularly limited. In the case of the mold viscosity, an arbitrary liquid concentration is preferably 30 cps or more, more preferably 70 to 500 cps. The coating amount on the support is 2 g / m ² or more, preferably ^{3 to 6} g, on a dry weight basis.
/ M ² is appropriate.

[0041]

Next, the effects of the present invention will be described more specifically with reference to examples. The following parts are all parts by weight, and all percentages represent% by weight. Example 1 [Coating liquid component] Crystal violet lactone (CV
L) 200 parts of a high boiling point oil (KMC-113 manufactured by Kureha Chemical Co., Ltd.) in which 5 parts were dissolved was added to 250 parts of a 5% aqueous solution of styrene-maleic anhydride copolymer (PH5.0), and the average particle diameter was 6 μm. And emulsified so that Next, a 40% melamine-formalin precondensate aqueous solution (Sumitomo Chemical Co., Ltd.)
(Sumitetsu Resin Co., Ltd.) was added to the above emulsion, the temperature was raised to 75 ° C., and the mixture was reacted for 2 hours. After that, the pH was adjusted to 9.0 with a 20% aqueous sodium hydroxide solution, and the mixture was cooled to room temperature.
A 0% microcapsule dispersion was obtained. 30% of the microcapsule dispersion liquid thus obtained is mixed with the following composition.
A coating solution having a concentration was obtained. 40% microcapsule dispersion 100 parts Wheat starch (particle size 20 μm) 50 parts 48% carboxy-modified styrene-butadiene copolymer latex emulsion 20 parts Water added 162 parts

[Support] 800 mm in width and 40 g / m in basis weight
^{2 Using} a gate roll coater, starch size of 0.2% solid content is applied to high quality paper, and the size amount is 0.8 g / m2.
A coating support of No. ² was obtained. The air permeability of the obtained support was measured to be 40 seconds. The thus obtained coating liquid and the support were formed into a uniform curtain coating liquid film at a supply rate of 9.6 l / min using a curtain coater head having a width of 900 mm and a slit gap of 0.3 mm. The coating was performed at a coating speed of 800 m / min and dried to obtain a color former sheet for carbon-free pressure-sensitive copying paper having a coating amount of 4 g / m ² in terms of absolute dry solids. At this time, the curtain coating liquid film was well adapted to the support, and a uniform coating layer of microcapsules was obtained without causing coating unevenness or uncoated portions.

Example 2 [Coating liquid component] The same coating liquid as in Example 1 was used. [Support] A high quality paper having a width of 800 mm and a basis weight of 40 g / m ² was subjected to starch size with a solid concentration of 0.3% using a gate roll coater to obtain a coating support having a size of 1.2 g / m ^2. Was. When the air permeability of the obtained support was measured, it was 6
It was 0 seconds. The coating solution thus obtained and the support were used in the same manner as in Example 1 using a curtain coater to obtain a color-forming sheet for carbon-free pressure-sensitive copying paper having a coating amount of 4 g / m ^{2 in} absolute dry solids. At this time, the curtain coating liquid film was slightly unstable with the support, but a uniform microcapsule coating layer was obtained without any coating unevenness or uncoated portion.

Comparative Example 1 [Support] A high-quality paper having a width of 800 mm and a basis weight of 40 g / m ² was subjected to starch sizing with a solid content concentration of 0.5% using a gate roll coater to obtain a coating having a size of 1.5 g / m ² . An industrial support was obtained. When the air permeability of the obtained support was measured, it was 8
It was 0 seconds. The coating solution thus obtained and the support were used in the same manner as in Example 1 using a curtain coater to obtain a color-forming sheet for carbon-free pressure-sensitive copying paper having a coating amount of 4 g / m ^{2 in} absolute dry solids. At this time, the curtain coating liquid film did not fit well with the support, causing coating unevenness, and a very uniform microcapsule coating layer could not be obtained.

[0045] Comparative Example 2 [Support] Size amount 2.0 g / m ² performs the quality paper of width 800 mm · basis weight 40 g / m ² starch size of solid concentration of 0.7% using a gate roll coater coating An industrial support was obtained. When the air permeability of the obtained support was measured, it was 1
20 seconds. The coating solution thus obtained and the support were used in the same manner as in Example 1 using a curtain coater to obtain a color-forming sheet for carbon-free pressure-sensitive copying paper having a coating amount of 4 g / m ^{2 in} absolute dry solids. At this time, the curtain coating liquid film was considerably poorly adapted to the support, causing coating unevenness, and no uniform microcapsule coating layer was obtained.

(Coloring Agent Sheet Evaluation Method) 組合 せ The obtained coloring agent sheet was combined with a commercially available Mitsubishi NCR paper super lower paper (N-40) to obtain a super calender (100).
kg / cm ² × 2 times) to evaluate the color developability. The color density was measured using a Macbeth densitometer. ◎ 15cm x 15cm x 35cm x 25cm
Combine a 15 cm wide color former sheet and place 3500 on it
g was placed on a weight for evaluating stain resistance, and the stain resistance was evaluated by the degree of stain when the color former sheet was pulled at a constant speed. The color density was measured using a Macbeth densitometer.更 に Further, the presence or absence of coating unevenness / uncoated was evaluated as the surface quality of the coated paper with the naked eye. Table 1 shows the results of evaluating the above items.

[0047]

[Table 1] Evaluation results

* Evaluation Criteria Coloring property: The larger the value, the better (the printing density is higher).
··· 0.83 or more Stain resistance: The larger the value, the worse (easy to be stained) ………
… · 0.47 or less Surface quality: ◎ Excellent, ○ Excellent, △ Slightly inferior,
× Problem ・ ・ ・ ・ ・ ・ ・ ・ ・ ○ Above Overall evaluation: ◎ Excellent, ○ Excellent, △ Slightly inferior, × Problem ・ ・ ・ ・ ・ ・ ・ ○

[0049]

As is clear from the above examples, according to the present invention, it is possible to obtain a carbonless pressure-sensitive copying paper having high productivity, good coloring properties, excellent stain resistance and a uniform coated surface. Was.

Claims (3)

(57) [Claims] 1. A carbonless pressure-sensitive copying paper, in which a coating liquid is formed on a curtain film from a liquid supply head having a slit and collides with a support to apply the coating liquid, the JISP8 of the support is used.
A carbonless pressure-sensitive copying paper characterized in that the air permeability based on the 117 method is 60 seconds or less. 2. The carbonless pressure-sensitive copying paper according to claim 1, wherein the coating speed is 800 m / min or more. 3. The coating liquid comprising a microcapsule containing an electron-donating dye as a main component, or a microcapsule containing an electron-donating dye and a coating material containing a developer as a main component. 3. The carbonless pressure-sensitive copying paper according to claim 1, wherein the paper is a liquid.