JPH11208106A - Decomposing recording sheet and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording sheet useful for an OHP recording material in particular by preparing a layer consisting mainly of a hydrophilic high molecular compound on a base material consisting of a polylactic acid polymer, and further having a specific straight line light permeability. SOLUTION: A polylactic acid polymer forming a base material is polylactic acid on most general. Such polylactic acid having a glass transition point being a room temperature or higher is a decomposable copolymer capable of obtaining a transparent base sheet. A hydrophilic high molecular compound is naturally existing one or synthetic one. A natural hydrophilic high molecular compound is hyaluronic acid of a polysaccharide, agarese, a collagen of a protein, or the like. A synthetic polymer compound is polyvinyl alcohol or the like. Among these substances, most preferable one is a polyvinyl alcohol copolymer which is good for an OHP recording sheet particularly in terms of a transparency, ink fixation, and decomposition property. Besides, it is needed to have a straight line light permeability of 70% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a sheet having a characteristic of disintegrating in a natural environment and having excellent transparency. In particular, the present invention relates to a decomposable recording sheet having excellent ink jet recording characteristics and a method for producing the same.

[0002]

2. Description of the Related Art A recording sheet provided with a recording layer mainly composed of a hydrophilic polymer compound is currently used as a recording material, particularly as a transparent recording material for OHP. Recently, water-soluble inks containing water or alcohol as a main component have often been used as recording inks from the viewpoint of safety. In particular, in an ink jet recording method in which ink droplets are ejected and adhered to a recording material to perform recording, a water-soluble ink is often used from the viewpoint of high-speed printing suitability and multicolor printing suitability. In order to meet these requirements, recently, a recording sheet provided with a recording layer mainly composed of a hydrophilic polymer compound as a receiving layer capable of absorbing and fixing a water-soluble ink on a plastic sheet has been used. ing.

[0003] By the way, as a substrate for supporting the recording layer, physically stable polyethylene or polypropylene,
Many are produced from synthetic polymers such as aromatic polyesters. In particular, when transparency is required, a sheet of biaxially oriented polypropylene (OPP), biaxially oriented aromatic polyester (OPET), or the like is used. However, these plastic sheets do not collapse in the natural environment, and do not lose underground even when landfilled.
This is one of the factors that hinder the extension of landfill life.

On the other hand, a sheet made of a biodegradable polymer, which has been actively studied in recent years, is expected to solve the above problems. Above all, aliphatic polyester is
After biodegradation, it is a non-toxic and safe low-molecular compound, and is particularly studied. As the biodegradable aliphatic polyester, a polyester obtained by ring-opening polymerization of a cyclic lactone, a synthetic aliphatic polyester, a polyester biosynthesized in a bacterial cell, an aliphatic polyfunctional alcohol and an aliphatic polyfunctional carboxylic acid are condensed. The resulting polyester and the like can be mentioned.

More specifically, typical polyesters obtained by ring-opening polymerization of cyclic lactones include poly-ε-caprolactone, poly-δ-valerolactone, poly-β-methyl-δ-valerolactone and the like. It is listed. Examples of the synthetic aliphatic polyester include a cyclic acid anhydride and an oxirane, for example, a copolymer of succinic anhydride and ethylene oxide, propylene oxide, or the like. Examples of the polyester biosynthesized in the cells include polyhydroxybutyrate, polyhydroxybutyrate / valylate, and the like. Further, as the polyester obtained by condensing an aliphatic polyfunctional alcohol and an aliphatic polyfunctional carboxylic acid, succinic acid or adipic acid, or a dicarboxylic acid component consisting of both, and ethylene glycol or butanediol, or both of these. Representative examples thereof include aliphatic polyesters having a diol component as a main structural unit. Further, as a different polyester, a compound such as suberic acid, sebacic acid, dodecanedioic acid, or a polyester obtained by condensing an anhydride or a derivative thereof with an acid component, or hexanediol, octanediol, or cyclohexanedimethanol with an alcohol component. Or a polyester obtained by condensing these derivatives, or a very small amount of a trifunctional or higher carboxylic acid, alcohol or hydroxycarboxylic acid for the purpose of providing a branch in the polymer to improve the melt viscosity. Polyester obtained by the above method.

[0006]

However, these fatty acid polyesters have a glass transition point of room temperature or lower, have high crystallinity, and are in a crystalline state at room temperature. These resins are difficult to suppress the growth of spherulites even after being melt-extruded and quenched, making them opaque and unsuitable as a transparent sheet.

For example, Japanese Patent Application Laid-Open No. 6-239014 discloses recording base materials using various biodegradable materials described above, but all of them have difficulty in transparency. In particular, when used as an OHP recording sheet, at least a linear light transmittance of 70% or more is required, and if it is less than this, a clear image cannot be obtained when projected on an OHP. Furthermore, O which is widely used at present
Compared to the PET sheet, the stiffness (elastic modulus) is clearly insufficient, and the thickness has to be increased to compensate for this, resulting in a further decrease in transparency.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention comprises a water-soluble ink receiving layer (recording layer) and a biodegradable substrate, and has a collapsible and linear light transmittance as a whole. An object of the present invention is to provide a high recording material, particularly a recording material for OHP, and a method for manufacturing the same.

First, the gist of the present invention is that a recording layer containing a hydrophilic polymer compound as a main component is provided on a substrate made of a polylactic acid-based polymer, and the linear light transmittance is 70% or more. Characteristic degradable recording sheet.

A second aspect of the present invention resides in the first degradable recording sheet wherein the hydrophilic polymer compound is a polyvinyl alcohol-based polymer represented by the following general formula (1).

[0011]

Embedded image

[In the above formula, m and n are 0 or 1 or more positive numbers satisfying the following relational expression: m + n ≧ 150 100 ≧ 100 m / (m + n) ≧ 30. ]

A third feature is that the base material is a biaxially oriented polylactic acid-based polymer sheet.
Decomposable recording sheet.

Fourth, after applying a solution of the polyvinyl alcohol-based polymer represented by the general formula (1) to a non-oriented sheet or a uniaxially-oriented sheet made of a polylactic acid-based polymer, the sheet is biaxially oriented. A third aspect of the present invention is a method for producing a degradable recording sheet, which comprises orienting and heat-treating.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described.
In the sheet of the present invention, polylactic acid is the most common polylactic acid-based polymer constituting the base material. Polylactic acid having a glass transition point of room temperature or higher is a degradable polymer that can obtain a transparent base sheet, depending on the molding method. The structural units of polylactic acid include two types of optical isomers, L-lactic acid unit and D-lactic acid unit.
The crystallinity differs depending on the ratio of the kinds of structural units. For example, the ratio of L-lactic acid units to D-lactic acid units is approximately 80:20 to 2
The random copolymer having a ratio of 0:80 has no crystallinity, and becomes a transparent completely amorphous polymer which softens at a glass transition point of about 60 ° C. On the other hand, a homopolymer composed of only an L-lactic acid unit or only a D-lactic acid unit is a semicrystalline polymer having a glass transition point of about 60 ° C and a melting point of 180 ° C or more. This semi-crystalline polylactic acid, after melt extrusion,
Immediate quenching results in an amorphous material with excellent transparency. Further, a more preferable method of obtaining a transparent polylactic acid material is to heat-treat the polylactic acid after uniaxially or biaxially stretching the molecules to orient the molecules. This makes it possible to crystallize while suppressing the growth of spherulites having a size equal to or greater than the wavelength of visible light.

The polylactic acid-based polymer may be not only the above-mentioned polylactic acid but also a copolymer of another hydroxycarboxylic acid or the like to the extent that the required properties of the polylactic acid are not impaired. Further, the molecular weight may be increased by using a small amount of a chain extender, for example, a diisocyanate compound, an epoxy compound, an acid anhydride or the like. The weight average molecular weight is preferably in the range of 60,000 to 700,000. When it is below this range, practical physical properties are hardly exhibited, and when it is above this, the melt viscosity is too high and the moldability is poor.

The method for producing polylactic acid is not particularly limited, and various known methods such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the polycondensation method, L-lactic acid, D-lactic acid or a mixture thereof can be directly subjected to dehydration polycondensation to obtain polylactic acid having an arbitrary composition. In the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, can be polymerized in the presence of a selected catalyst using a polymerization regulator or the like, if necessary, to obtain polylactic acid. Lactide includes L-lactide which is a dimer of L-lactic acid, D-lactide which is a dimer of D-lactic acid, and DL which comprises L-lactic acid and D-lactic acid.
-Lactide, and polylactic acid having an arbitrary composition and crystallinity can be obtained by mixing and polymerizing these in an appropriate ratio. In particular, after biaxially stretching polylactic acid,
By performing heat treatment, crystallization can be performed while maintaining transparency, and heat shrinkage can be suppressed. In this case, considering the crystallinity, the ratio of the L-lactic acid unit to the D-lactic acid unit in the polymer is 100: 0 to 94: 6 or 6:94 to 0:
Preferably it is in the range of 100. Outside this range, a degree of crystallinity sufficient to sufficiently suppress heat shrinkage cannot be obtained.

Any known method can be used for forming the base sheet. For example, a polymer composition obtained by mixing additives such as a lubricant and an antistatic agent with the above polylactic acid-based polymer, if necessary, is melt-extruded from a T-die and rapidly cooled while being taken up by a rotating casting drum. Then, a solidification method may be used, or an inflation method may be used in which the molten polymer is pulled up from a round die into a cylindrical shape, and while being air-cooled, is simultaneously expanded into a balloon to form a film. In general, the latter has a lower cooling rate, tends to be crystallized, and is disadvantageous to the transparency of the sheet. However, water can be used instead of air to increase the cooling efficiency.

The biaxially oriented substrate sheet is formed by, for example, stretching a sheet formed by the above method using an existing roll-type or tenter-type flat stretching machine, tubular stretching machine, or the like. It is obtained by doing. The stretching temperature may be selected within the range of the glass transition temperature to the crystallization temperature of the polylactic acid-based polymer, and the stretching ratio may be selected within a range of at least 6 times or less in one axial direction while taking into account the degree of orientation of the sheet. it can. To minimize heat shrinkage, use a polylactic acid-based polymer having crystallinity, and keep the sheet under tension for several seconds within the range from the crystallization temperature to the melting point of the sheet after biaxial stretching. The above is obtained by heat treatment.

In the sheet of the present invention, an appropriate hydrophilic polymer is selected from various compounds having an affinity for water as the main component of the water-soluble ink-receiving layer (recording layer). Many of the hydrophilic compounds have a property of being easily soluble in water, and therefore, when the water-soluble ink is placed on the recording layer, there is also a problem that the ink flows out or becomes blurred before fixing. Regarding the fixing property of the ink, it is preferable that the ink is quickly absorbed by the recording layer. Conversely, the one in which the recording layer component is absorbed by the ink has poor fixing property. Therefore, the recording layer is preferably composed of a component having a large molecular weight, that is, a high molecular compound, and it is important that the recording layer is not easily peeled off from the substrate with a small amount of water.

In the present invention, the “recording layer containing a hydrophilic polymer compound as a main component” refers to a component constituting the recording layer.
It means that the hydrophilic polymer compound is the largest in weight ratio, preferably 50% or more. The compound contained in the recording layer is not particularly limited as long as it does not inhibit the above-mentioned properties desired for the recording layer. For example, it may contain an inorganic or organic filler, a surfactant, a thickener, and the like.

The hydrophilic polymer compound (hydrophilic resin) selected in consideration of such points includes a naturally occurring compound and a synthesized compound. Specifically, examples of natural hydrophilic high molecular compounds include polysaccharides such as hyaluronic acid, agarose, and proteins such as collagen. Examples of modified natural hydrophilic polymer compounds include starch and cellulose obtained by graft polymerization of acrylonitrile, acrylic acid, vinylsulfonic acid, acrylamide, and the like. Examples of the synthetic polymer compound include a polyvinyl alcohol polymer, an acrylic polymer such as sodium polyacrylate and polyhydroxyethyl methacrylate, a polyether polymer such as polyethylene glycol, and a maleic anhydride polymer. And vinylpyrrolidone-based polymers.

Among the above hydrophilic polymer compounds, the most preferred is a polyvinyl alcohol-based polymer,
It is particularly excellent as a P recording sheet in terms of transparency, fixing property of ink and decomposability. In addition, many of the hydrophilic polymer compounds have the property of dissolving in water, and are so-called disintegrable materials.
Materials with a high saponification rate are biodegradable materials, which are decomposed into water and carbon dioxide by microorganisms in the environment. Furthermore, the degree of crystallinity of the polyvinyl alcohol-based polymer is increased by heat treatment, and the polyvinyl alcohol-based polymer has a physically crosslinked structure. This means
Suppresses leaching due to water and improves ink fixation.

That is, the hydrophilic polymer compound used for the decomposable recording sheet is preferably a polyvinyl alcohol polymer represented by the following general formula (1).

[0025]

Embedded image

[Wherein, m and n are 0 or 1 or more positive numbers satisfying the following relational expression: m + n ≧ 150 100 ≧ 100 m / (m + n) ≧ 30. ]

The polyvinyl alcohol-based polymer preferably has a degree of polymerization (m + n in the above formula (1)) of at least 150 from the viewpoint of fixability of the water-soluble ink. In addition, the saponification rate, that is, the ratio of the hydroxyl group formed by the saponification (100 m / (m +
n)) is preferably at least 30%, more preferably at least 40%. If the saponification ratio is smaller than this, the affinity with water becomes small, and the fixability of the water-soluble ink may be deteriorated. On the other hand, if the saponification rate is too large, the proportion of hydroxyl groups increases,
By increasing intramolecular and intermolecular hydrogen bonds,
Crystallinity is increased, the affinity between molecules and water is relatively reduced, and the absorption of water-soluble ink may be hindered. Considering these, the saponification rate is more preferably 85% or less.

The method for producing the sheet of the present invention is not particularly limited as long as a recording layer containing a hydrophilic polymer compound as a main component can be provided on a substrate made of a polylactic acid-based polymer. Various known lamination methods can be employed. Among them, the following methods are important. A method in which a hydrophilic polymer compound (polyvinyl alcohol-based polymer) film is bonded to a base sheet via an adhesive, and the hydrophilic polymer compound (polyvinyl alcohol-based polymer) is converted into an aqueous solution, an alcohol solution, or the like. , A method of applying to a substrate sheet and then drying, and a method of simultaneously stretching and heat-treating after the steps of

The glass transition point of the polylactic acid-based polymer is 60 ° C.
At temperatures above this, the sheet may soften and flow through a rubbery state. Since the biaxially oriented polylactic acid-based polymer sheet is crystallized even above this temperature, it does not become rubbery if it is at or below the melting point, but the elastic modulus is still inevitably reduced. In particular, at a temperature of 100 ° C. or higher, the sheet shrinks greatly, and the dimensional stability is poor. Therefore,
It is necessary to laminate the polylactic acid-based polymer sheets in consideration of these drawbacks.

The laminating method can be performed by a so-called wet lamination method or a dry lamination method. As the adhesive at the time of lamination, vinyl, acrylic, polyamide, polyester, urethane, rubber, etc. are used.If the adhesive is also made biodegradable, starch, amylose, amylopectin, etc. Preferred are polysaccharides, proteins such as glue, gelatin, casein, zein and collagen, polypeptides, unvulcanized natural rubber, aliphatic polyesters and modified products thereof. Normally, when laminating with a laminator, the sheet is preheated before lamination, and after lamination, it is often aged to dry the solvent and cure the adhesive, but the sheet softens. The heating temperature for preheating or aging needs to be 80 ° C. or less so as not to lose the flatness or shrink. In addition, when the recording layer is made extremely thin, if the hydrophilic polymer film unwound during lamination has no strength or stiffness, the film may be broken when stretched or stretched and cannot be laminated precisely. Be careful as there are.

In the laminating method, a hydrophilic polymer compound solution is sprayed onto a polylactic acid-based polymer sheet, preferably a biaxially oriented sheet, by spraying from a nozzle or by a roller, and then the sheet is dried. . It is preferable that the drying temperature at this time does not exceed 80 ° C. In the case of an aqueous solution, drying at a temperature of 80 ° C. or less requires a long time, and drying in a reduced pressure is required for finishing in a short time, which is disadvantageous in the process. From the viewpoint of facilitating drying, it is preferable to use a low boiling point solvent such as alcohol.

In the method (1), a hydrophilic polymer compound solution is applied to a polylactic acid-based polymer sheet, preferably a uniaxially oriented (longitudinal stretch) sheet, and the solution is stretched (transversely stretched) and heat-treated. This is a method in which the solvent is volatilized while the biaxially oriented polymer sheet is oriented. In particular, when the hydrophilic polymer compound is a polyvinyl alcohol-based polymer, the crystallization of the polyvinyl alcohol-based polymer can be promoted simultaneously with the evaporation of the solvent. In this method, a tenter-type flat biaxial stretching apparatus can be used, particularly under the conditions for stretching and heat-treating the polylactic acid-based polymer described in detail above.

For example, in a preferred embodiment of the sequential biaxially stretched sheet production, a substantially non-oriented polylactic acid-based polymer sheet produced by extrusion is first stretched in the flow direction (longitudinal direction) to obtain a uniaxially oriented sheet. And a polyvinyl alcohol-based polymer solution is uniformly applied to the uniaxially oriented (longitudinal stretched) sheet using a roll or the like. Subsequently, the sheet is guided to a tenter and subjected to transverse stretching, and then heat-treated to obtain a heat-set sheet.

When the solvent of the coating solution (polyvinyl alcohol-based polymer solution) is water, it is hardly dried in the stretching step, and the coating solution can be spread following the stretching of the base sheet. . The heat treatment step is performed at a temperature of at least 100 ° C. for the purpose of so-called heat fixation, during which time moisture is evaporated to dry the coating liquid. On the other hand, when a low-boiling solvent (methanol, ethanol, etc.) is used, the solvent may be volatilized in the stretching step, and care must be taken not to complete the drying before the stretching is completed. Regardless of which solvent is used, it is important to set the polymer concentration of the coating solution in consideration of the volatility and stretchability of the solvent. In particular, in consideration of coatability and stretchability, it is preferable to set the viscosity of the coating solution at 20 ° C. in the range of 50 to 10,000 poise. When it is in this range, it can easily follow the stretching of the base material sheet and can be applied to a uniform thickness. This method does not require any additional steps such as laminating after film formation, so there is no need to consider thermal deformation of the sheet, and there is also an advantage that it can be manufactured at low cost.

In the sheet of the present invention, the linear light transmittance must be 70% or more. If it is less than this, a clear image cannot be obtained when projected by OHP.
Thus, here, the linear light transmittance is, as incident light,
The ratio of the amount of transmitted light to the amount of incident light when a parallel light beam perpendicular to the sample sheet surface is used is determined by JISK
It was measured according to 7105. Generally, light transmittance is divided into linear transmittance and diffuse transmittance, and these are collectively referred to as total transmittance. Of these, diffuse transmission refers to transmission of incident light without depending on the refractive index of a normal medium. Therefore, even if the sheet is entirely transparent and has a high diffuse transmittance, a problem such as blurring of an image occurs even when the sheet is projected by the OHP, and the entire image becomes unclear.

[0036]

The present invention is not limited by the following examples. In addition, the measurement and evaluation of the physical properties of the recording sheet obtained in each example were performed under the following conditions.

(1) Linear light transmittance The measurement was performed according to JIS K 7105. The larger the value, the better the transparency.

(2) Inflow of ink Printing was performed with black ink using an ink jet printer. It was visually observed to determine whether or not ink had flowed out on the recording sheet surface. When the ink flow did not occur and the ink flow did not occur, x indicates that the ink flow did not occur, and when the ink flow did not occur, the character was blurred.

(3) OHP suitability Using an overhead projector (OHP),
The recorded image printed in (2) was projected on a screen, and OHP suitability was determined by visual observation. When the unprinted portion was bright and the balance with the print was clear and easy to see, the unprinted portion was dark, and when the printed portion was not clearly displayed, the cross was marked X.

(4) Degradability test for burying in soil The test was performed in accordance with the test method conducted by the Biodegradable Plastics Research Society. That is, a grassland having a sunny place and a poor drainage was excavated 10 cm, and then the excavated soil was sifted through a 1 cm sieve and returned to a depth of 5 cm. The sample was placed on top of it and the sieved soil was returned to completely fill the sample. After standing for 3 years, the sample was dug up and the change in the appearance of the sample was observed.

(Experimental Example 1) A saponification rate of about 80% was applied to a transparent OPET sheet having a thickness of 100 μm (trade name: Diafoil / H500 type (manufactured by Diafoil Hoechst Co., Ltd.) (product with easy surface adhesion)) , A 30% by weight aqueous solution of a polyvinyl alcohol polymer having a polymerization degree of 500 (viscosity of 600)
poise (20 ° C.)) was applied with a Mayer bar so that the thickness after drying became 3 μm, and then dried in an oven at 105 ° C. for 60 minutes. Table 1 shows the evaluation of the obtained recording sheets.
Shown in In addition, as a result of examining the soil decomposability of this sheet,
The polyvinyl alcohol-based polymer layer (hereinafter abbreviated as PVA layer) had collapsed and disappeared, but the substrate was not particularly changed.

(Experimental example 2) Polylactic acid (manufactured by Shimadzu Corporation, trade name: Lacti 1000, weight average molecular weight: about 20)
The ratio of L-lactic acid units and D-lactic acid units in the polymer is 9
9: 1) using a 30 mmφ small single screw extruder at 210 ° C.
After being melt-extruded from a T-die at a temperature of 57.degree.
A 0 μm transparent unstretched sheet was produced. After performing a corona treatment on the sheet at an energy of 25 W / m ² / min,
Polyurethane solvent adhesive (manufactured by Takeda Pharmaceutical Co., Ltd.
Takelac A-970 / Takenate A-19 = 15 /
1) is applied so as to be approximately 1 μm, and
A polyvinyl alcohol film (trade name: Boblon / EX, biaxially-stretched film, manufactured by Nichigo Film Co., Ltd.) having a saponification rate of about 99% and a thickness of 12 μm was bonded while being pressed with a hand roller. Drying was performed for the purpose of removing the solvent component of the adhesive of the bonded recording sheets. Drying temperature is 6
This was performed at 0 ° C. for 60 minutes, and further aged at 40 ° C. for 2 days to obtain a recording sheet shown in Table 1. As a result of examining the decomposability in the soil, the PVA layer had collapsed and disappeared. In addition, it was found that the polylactic acid of the base material was whitened, the surface was roughened, and the decomposition was progressing.

(Experimental Example 3) Polylactic acid (manufactured by Shimadzu Corporation, trade name: Lacti 1000, weight average molecular weight: about 20)
The ratio of L-lactic acid units and D-lactic acid units in the polymer is 9
9: 1) was extruded from a T-die at 210 ° C. with a 60 mmφ single screw extruder and rapidly cooled with a casting roll to obtain an unstretched sheet having a thickness of 600 μm. This unstretched sheet was roll-stretched 2.3 times at 75 ° C. in the longitudinal direction, and then stretched 2.5 times at 70 ° C. by a tenter in the width direction.
Subsequently, heat treatment was performed at a temperature of 13 in the heat treatment zone of the tenter.
About 100 μm of transparent 2
An axially oriented polylactic acid sheet was obtained.

The biaxially oriented sheet was subjected to an energy of 25 W
/ M ² / min after corona surface treatment, saponification rate about 8
0%, 30% by weight aqueous solution of a polyvinyl alcohol polymer having a polymerization degree of 500 (viscosity: 600 poise (20 ° C.))
Was applied with a Mayer bar so that the thickness after drying was 3 μm, and then dried in an oven at 70 ° C. for 30 minutes.
Was obtained. In the soil burial decomposability test, the PVA layer collapsed and disappeared, and although the biaxially oriented polylactic acid sheet as the base material did not collapse significantly, white spots were observed. Degradation appears to be progressing, albeit slightly.

(Experimental Example 4) A 30% by weight methanol solution of a polyvinyl alcohol polymer having a saponification rate of about 90% and a degree of polymerization of about 1700 (viscosity of about 250
A transparent recording sheet shown in Table 1 was obtained in the same manner except that 0 poise (20 ° C.) was used.

(Experimental Example 5) In the process of producing a biaxially oriented polylactic acid sheet in the same manner as in Experimental Example 3, the original sheet was stretched in the flow direction (longitudinal uniaxial stretching), and then one-sided by a Mayer bar coating method. , An aqueous solution of a polyvinyl alcohol-based polymer was uniformly applied. The saponification rate of the used polyvinyl alcohol polymer is about 80%, the degree of polymerization is 1700, and the concentration of the aqueous solution is 10% by weight (viscosity: 60 poise (20 ° C.)).
Was adjusted. The coated sheet was directly stretched and heat-treated in a tenter to obtain a biaxially oriented sheet. Table 1 shows the evaluation of the obtained sheet.

(Experimental Examples 6, 7, and 8) In Experimental Example 5, the degree of polymerization was 1750,
A solution having a saponification rate of 88% and an aqueous solution concentration of 20% by weight (viscosity of 4500 poise (20 ° C.)), a
0, saponification rate 88%, aqueous solution concentration 15% by weight (viscosity 15
poise (20 ° C.)) and a degree of polymerization of 240
0, saponification rate 88%, concentration 20% by weight (viscosity 20,000
A recording sheet was obtained in the same manner except that the recording sheet was used. Table 1 shows the obtained recording sheets.

(Experimental Example 9) Polyhydroxybutyrate / valerate biosynthesized in the cells (manufactured by Monsanto Japan, trade name: Biopol D610G) was melted from a T-die at 190 ° C using a 30 mmφ small single screw extruder. After being extruded, the sheet was taken out while being rapidly cooled by a casting drum having a surface temperature of 30 ° C., to produce a 100 μm-thick non-stretched sheet. Instead of using a biaxially oriented polylactic acid sheet,
A recording sheet shown in Table 1 was obtained in the same manner as in Experimental Example 4, except that this sheet subjected to corona treatment at an energy of 20 W / m ² / min was used.

(Experimental example 10) Instead of polyhydroxybutyrate / valerate, polybutylene succinate (showa high) comprising a synthetic aliphatic polyester mainly composed of a condensate of 1,4-butanediol and succinic acid Molecular Corporation
Recording sheet shown in Table 1 was obtained in the same manner as in Experimental Example 9 except that Bionore # 1001) was used.

[0050]

[Table 1]

The recording sheets of Examples 2 to 6, which are examples of the present invention, have a high linear light transmittance and are excellent in OHP characteristics. Above all, the sheets of Experimental Examples 3 and 5 have no outflow of ink and are excellent in printability using water-soluble ink. In Experimental Examples 7 and 8, the occurrence of unevenness,
There was a defect in the thickness, and a sheet having a good appearance could not be obtained. In addition, the sheets of Experimental Examples 9 and 10, which are based on a biodegradable resin that is not a polylactic acid-based polymer as a comparative example, have excellent degradability, but have low linear light transmittance and low OHP suitability. It turns out there is no. The sheet of Experimental Example 1 has no decomposability.

[0052]

According to the present invention, a decomposable substrate composed of a polylactic acid-based polymer and a recording layer mainly composed of a hydrophilic polymer compound are provided. A high recording sheet, particularly a recording sheet useful as an OHP recording material, can be obtained.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 67/04 ZAB C08L 67/04 ZAB C09D 5/00 C09D 5/00 Z 129/04 129/04 Z // C08L 29:04

Claims (4)

[Claims] 1. A decomposable recording sheet comprising a recording layer mainly composed of a hydrophilic polymer compound on a substrate made of a polylactic acid-based polymer and having a linear light transmittance of 70% or more. . 2. The decomposable recording sheet according to claim 1, wherein the hydrophilic polymer compound is a polyvinyl alcohol polymer represented by the following general formula (1). Embedded image [In the above formula, m and n are 0 or 1 or more positive numbers satisfying the following relational expression: m + n ≧ 150 100 ≧ 100 m / (m + n) ≧ 30. ] 3. The decomposable recording sheet according to claim 1, wherein the substrate is a biaxially oriented polylactic acid-based polymer sheet. 4. A solution of a polyvinyl alcohol-based polymer represented by the general formula (1) is applied to a non-oriented sheet or a uniaxially-oriented sheet made of a polylactic acid-based polymer, and then the sheet is biaxially oriented. 4. The method for producing a degradable recording sheet according to claim 3, wherein the heat treatment is performed.