JPH04221677A - Heat sensitive repeating recording material - Google Patents

Abstract

PURPOSE:To impart excellent stability with the elapse of time to a written printed character and to avoid the lowering of readability due to discoloration by using a polymer containing a crystalline olefin chain and a crystalline org. compound. CONSTITUTION:100 pts. of a hydrogenerated styrene/butadiene block copolymer as crystalline olefin and 40 pts.wt. of behenic acid as a crystalline org. compound are dissolved in p-xylene to prepare a 30wt.% solution mixture. This solution mixture is applied to a sheet with 0.08mm-thickness composed of polyglycol terephthalate and the solvent is volatilized to obtain a film with 0.1nm-thickness. The film thus obtained is cloudy and shows low light transmissivity but shows high light transmissivity when it is heated to about 100 deg.C and subsequently quenched in cold water.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to thermally writeable and erasable repetitive recording materials. More specifically, the present invention relates to a repetitive recording material in which various types of information can be thermally written in a visually visible manner by utilizing the thermal history dependence of the light transmittance of the material, and which can be repeatedly erased.

0002

2. Description of the Related Art Cards such as telephone cards, ticket purchase cards, expressway cards, cash cards, ID cards, and membership cards are currently in wide use. Functionally, many of these cards have various types of information written and stored using some method. Usually, various types of information are recorded in a magnetic recording layer or an IC provided on the card in a form that is not visible to the naked eye.

However, depending on the application, the magnetic recording layer or I
It may be preferable that some of the information recorded in C be visible. For example, in the case of a telephone card, it is preferable for the user to be able to see the number of used or remaining powers with the naked eye. It is preferable that the expressway card records and displays the date of use, etc. in a visible manner. In response to such demands, conventional methods have been adopted, such as punching holes in cards so that the roughness can be seen, or printing records on the cards so that they can be seen visually.

0004

The above-mentioned prior art display methods each have their own problems, and solutions have been sought. For example, in the punching method, it is difficult to display detailed information, and only a rough guideline can be displayed. In addition, in the method of printing records,
Since the surface area of the card itself is small and the area that can be used for one recording is naturally limited, there are problems such as a limit to the amount of information that can be displayed.

[0005] As a method to solve these problems in the conventional technology, there is already a known technology that enables repeated recording by using photomic materials or thermochromic materials that change color when exposed to light or heat. It has not yet been put into practical use, probably because there are problems with the weather stability and heat resistance stability of recording. Furthermore, techniques utilizing thermosensitive phase change of materials made of polymer compositions are already known.

[0006] For example, Japanese Patent Application Laid-open No. 119377/1983,
No. 55-154198, No. 58-7683, No. 58-109695, No. 57-82086, No. 57-82088, and JP-A-2-17
This method is known from Japanese Patent No. 5280, etc. These technologies reversibly change between a transparent state and a cloudy state by heat,
In addition, a material made of a polymer composition that maintains the above two states at room temperature is used.

Specific examples of these conventionally known heat-sensitive memory materials include polyvinyl chloride, vinyl chloride copolymers, vinylidene chloride copolymers, polyesters, polyamides, polyacrylates, polymethacrylates, silicone resins,
A thermoplastic resin such as vinyl acetate copolymer is used as a matrix, and an insoluble organic low-molecular compound is dispersed in this matrix.

[0008] These heat-sensitive recording materials have the property that when kept at a specific temperature above room temperature, ie above T0, the state changes depending on the temperature. That is, in the temperature range higher than T0, there are two state transition temperatures, T1 and T2 (T0<
T1<T2), and when the material is heated to T2 or higher and then cooled to T0 or lower, it becomes cloudy and exhibits minimal light transmittance.

[0009] When this cloudy material is heated and maintained at a temperature range of T0 or higher and lower than T1, and then cooled to a temperature below T0, the cloudiness of the material becomes less and the light transmittance increases. Also, T1 or higher,
It becomes transparent when it is heated to a temperature below T2 and then cooled to below T0. Therefore, the material in its minimally transparent state is
After heating and maintaining at a temperature in the range of T0 or higher and lower than T1, T
When cooling to below 0, the heating holding temperature is from T0 to T1.
As the temperature increases, the light transmittance of the material upon cooling will exhibit a continuous light transmittance change from a minimum to a maximum.

[0010] As described above, this type of heat-sensitive recording material can reversibly repeat a cloudy state and a transparent state depending on the heat treatment conditions. As described above, the heat-sensitive recording materials of the prior art exhibit a dependence of light transmittance on thermal history, and their use as recording materials is being considered by utilizing this performance. However, the thermal history dependence of its optical transparency is complex;
The conditions for the heat treatment process to fully develop the performance are severe. Furthermore, the difference in light transmittance caused by thermal history is not necessarily large enough, and improvements are required.

[0011] In order to improve this, a material (Pol
ymer Preprint, Japan Vol.
．． 39, No. 3,491 (1990)) is publicly known. This material exhibits high light transmittance at temperatures above the melting point, Tm, of the organic acid compound in the material, and exhibits low light transmittance when gradually cooled. However, when it is rapidly cooled, high light transmittance is maintained.

[0012] This material has the characteristics that the heat treatment process for developing its performance is simple, and the difference in light transmittance developed depending on the thermal history is also remarkable. However, the high light transmittance during quenching results in poor stability over time at room temperature, and the resin material itself has high unsaturated bonding properties based on conjugated dienes, resulting in poor weather resistance.

[0013]

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive studies to improve the problems of the above-mentioned prior art. In other words, a composition of a polymer containing a crystalline olefin chain and a crystalline organic low-molecular compound undergoes a reversible change in light transmittance through a simple heat treatment process, and this change is extremely remarkable, and the light transmittance at around room temperature decreases. The inventors have discovered that the resin material has excellent stability over time, and has excellent weather resistance and physical properties as a resin material, and has arrived at the present invention.

The recording material of the present invention has a crystalline melting point Tm or higher of the organic low-molecular compound in the material, preferably 10° C. below Tm.
It exhibits high light transmittance in the higher temperature range. When this is gradually cooled to room temperature, the organic low-molecular compound crystallizes and scatters light, making the material opaque. However, when rapidly cooled from a molten state, organic low-molecular compounds remain amorphous, or even if they crystallize, growth is inhibited and the crystal size is small, so high visible light scattering does not occur and high light transmittance is maintained. It turns out.

As a result of our studies, we have found that these phenomena can be observed to some extent in combinations of various polymers and crystalline organic low-molecular compounds. However, in general, the organic low-molecular-weight compound in the material does not grow quickly enough to a crystal size sufficient for light scattering, or conversely, the crystal size grows and expands gradually even at room temperature, so when rapidly cooled, It has fatal drawbacks such as extremely low stability over time at room temperature due to its high light transmittance. The effects achieved by the present invention, that is, the excellent effects in terms of thermal history changes in light transmittance, stability over time of light transmittance at room temperature, etc., are surprising. The present invention comprises (a) 100 parts by weight of at least one type of polymer that is substantially transparent at room temperature and contains a crystalline olefin chain;
) A heat-sensitive repetitive recording material comprising 5 to 200 parts by weight of at least one organic low molecular compound having a crystal point in the range of 40 to 200°C.

The polymer (
A) can be selected from various polymers that have crystalline olefin chains and are substantially transparent at room temperature. Preferred examples of polymers containing crystalline olefin chains include crystalline polymers containing chains of polyethylene, polypropylene, polybutene, hydrogenated polybutadiene, and the like. More specifically, LDPE (low density polyethylene)
, LLDPE (linear low density polyethylene), ethylene-
Propylene copolymer, ethylene-vinyl acetate copolymer,
Examples include crystalline hydrogenated polybutadiene polymers and block copolymers or graft copolymers containing these polymer blocks.

Considering basic polymer material properties such as tensile strength, impact resistance, weather resistance, and abrasion resistance, a more preferable polymer containing a crystalline olefin chain has at least one hydrogenated block of a polybutadiene polymer. Most preferably, it is a block copolymer having at least one hydrogenated block of polybutadiene polymer and at least two blocks of aromatic vinyl polymer. When the crystalline olefin chain of the polymer consists of hydrogenated butadiene block chains, the bonding mode of the butadiene before hydrogenation is such that the 1,4-bond chains account for at least 75%, preferably 80% or more, particularly preferably 85%. Unless it is above, sufficient crystallinity cannot be achieved.

The polymer containing a crystalline olefin chain of the present invention may of course be a mixture of these polymers, or may contain other polymers as long as the intended effects of the present invention are not impaired. It doesn't matter. It is generally preferred that the weight content of olefin chains in the polymer in the heat-sensitive repeating material be greater than 20%. It is more preferably 40% or more, particularly preferably 60% or more. 20
%, it may not be possible to achieve a sufficient heat-sensitive change in light transmittance.

The degree of crystallinity is preferably at least 5% by weight of the crystalline olefin chain, more preferably 10% by weight or more.
wt% or more. If the crystallinity is less than 5 wt%, the stability of light transmittance over time at room temperature may be significantly reduced. In addition, its crystal melting point is preferably 40 to 200°C
, more preferably in the range of 60 to 150°C. If the crystal melting point is less than 40°C, the stability of light transmittance over time at room temperature may be significantly reduced. Also, the crystal melting point is 2
If the temperature exceeds 00°C, processability and information writing operability may be significantly reduced.

[0020] The weight average molecular weight of these polymers is usually 50, considering the physical performance such as strength of the resulting material.
00 to 1 million, more preferably 10,000 to 50
20,000, particularly preferably in the range of 20,000 to 200,000. The organic low-molecular compound (b), which is the other component constituting the heat-sensitive repetitive memory material of the present invention, undergoes a first-order transition, that is, crystallization or melting, when heated or cooled, and upon rapid cooling due to interaction with the polymer. Selected from those that maintain the state at high temperatures. Specifically, the crystal melting point in the material is 4
0 to 200°C, preferably 60 to 150°C, particularly preferably -30°C of the melting point of the polymer containing crystalline olefin chains
It is in the range of ℃ to +30℃.

[0021] The crystal melting point of the material does not necessarily correspond to the melting point of a single organic low-molecular compound. Depending on the type of polymer, the purity of the organic low-molecular compound, the presence or absence of a third component not specified as a component of the present invention, and the composition thereof, the crystal melting point may be slightly lowered. The molecular weight of the organic low molecular compound is preferably 100 to 10,000, more preferably 120 to 5,000, particularly preferably 150 to 100.
It is in the range of 0. Too high a molecular weight is undesirable because it lowers the heat sensitivity of the resulting repeat recording material.

[0022] The organic low molecular compounds that can be used are:
Examples include alcohols, phenols, carboxylic acids, salts of carboxylic acids, amides, ethers, and ester compounds having aliphatic hydrocarbon or substituted aromatic hydrocarbon groups. Preferred specific examples of these include crystalline fatty acids having 10 to 30 carbon atoms, such as palmitic acid, stearic acid, arachidic acid, behenic acid, benzoic acid, P-tertbutylbenzoic acid, and P-toluic acid; Examples include carboxylic acids, and derivatives thereof such as esters, amides, salts, and various metal salts. Moreover, if necessary, two or more of these can be used in combination.

The composition of the components constituting the heat-sensitive repetitive memory material of the present invention is as follows: component (a), 100 parts by weight of the polymer containing crystalline olefin chains, component (b), 5 parts by weight of the organic low molecular compound; ~200 parts by weight. Preferably 10-1
00 parts by weight, particularly preferably 20 to 60 parts by weight. If the composition of the organic low-molecular compound of component (b) is less than 5 parts by weight, a sufficient heat-sensitive change in the light transmittance of the material cannot be expected;
If the amount exceeds 0.00 parts by weight, various physical properties such as strength and rigidity of the material will drop significantly, which is not preferable.

For the heat-sensitive repetitive memory material of the present invention, modifications of the resin material such as stabilizers, ultraviolet stabilizers, colorants, etc.
The additives used for modification can of course also be used in the present invention to achieve similar effects. Various known methods can be used to mix the components in the heat-sensitive repetitive memory material of the present invention. For example, a solution mixing method, a physical mixing method using a roll, a plastomill, a resin extrusion device, etc. can be used.

The use of the heat-sensitive repeat recording material of the present invention is as follows:
Although the explanation was limited to the use of cards as recording materials,
Naturally, its uses are not limited to these, but it can be used in various uses that utilize its excellent performance, that is, the dependence of light transmittance on thermal history. Examples of this include use in recording materials for information equipment such as computers, light-shielding films with variable light transmission applied to window glass, toys, and the like.

[0026]

[Examples] The present invention will be specifically explained with reference to Examples below, but the scope of the present invention is not limited to these Examples.

[0027]

Example 1 100 parts by weight of a crystalline hydrogenated styrene-butadiene block copolymer and 40 parts by weight of behenic acid are mixed into a 30 wt % p-xylene solution. This solution is 0
．． Coated onto a sheet of polyterephthalic acid glycol ester with a thickness of 0.08 mm, and then evaporated the solvent to form a 0.1 m
A film of m thickness is obtained. The film thus obtained is cloudy and has low light transmittance, and when heated to about 100° C. and then quenched in cold water, it exhibits high light transmittance. When this was heated again to 100°C and slowly cooled to 50°C at a rate of about 2°C/min, the cloudy state was recovered. Figure 1 shows the relationship between temperature and haze of this material.

However, the following crystalline hydrogenated styrene-butadiene-styrene triblock copolymer was used. (1) Bonding mode of hydrogenated butadiene moiety: 1.4-bond content 89% (2) Weight average molecular weight: 45,000 (3) Amount of bound styrene: 35 wt% (4) Hydrogenation rate of butadiene moiety: 99% or more (5) Crystal melt peak measured by differential thermal analyzer of hydrogenated butadiene part
temperature: 93°C, crystallinity: 32%. In addition, cloudiness (Haz
e) is Color and color dif
Fe-rence meter Model l
Measured using 00lDP (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0029]

[Examples 2 to 4 and Comparative Examples 1 and 2] In Examples 2 to 4, stearic acid, p-aminobenzoic acid, and o
- The same procedure as in Example 1 was carried out except that toluic acid was used. Examples 5 to 7 were carried out by varying the amount of behenic acid mixed. Further, Comparative Example 1 shows an example in which no organic low-molecular compound was mixed, and Comparative Example 2 shows an example in which paraffin wax (HNP-10, manufactured by Nippon Seiro Co., Ltd.) was similarly evaluated. The results obtained are shown in Table-1.

[0030]

Examples 8 and 9 The same procedure as in Example 1 was carried out except that the solvent was changed to p-xylene, dichlorobenzene was used in Example 8, and tetralin was used in Example 9. Table 1 shows the results obtained.
Shown below.

[0031]

[Example 10] 100 parts by weight of the same crystalline hydrogenated styrene-butadiene block copolymer as used in Example 1 and 40 parts by weight of behenic acid were heated at 180°C using a Laboplastomill.
The mixture was kneaded and mixed for 10 minutes, and the resulting material was press-molded at 180°C to obtain a film with a thickness of 0.1 mm. The film thus obtained is opaque (white cloudy) and exhibits high light transmittance when heated to about 100°C and then rapidly cooled. After heating this again to 100℃, it is heated to 50℃, about 2℃/
The opaque state was restored by slow cooling at a rate of 10 min.

[0032]

[Example 11] Except for using LLDPE (linear low-density polyethylene, trade name: Tafmer A-4085, manufactured by Mitsui Petrochemical Industries, Ltd.) instead of the crystalline hydrogenated styrene-butadiene block copolymer. It was evaluated in the same manner as in Example 10, and the same effect on light transmittance was achieved. However, the heat resistance of the material when heated to about 100° C. was slightly inferior, and shrinkage and deformation of the film was observed.

[0033]

[Comparative Example 3] Tufprene A (trade name of styrene-butadiene block copolymer, which is an amorphous thermoplastic rubber manufactured by Asahi Kasei Corporation) in place of crystalline hydrogenated styrene-butadiene block copolymer. It was carried out in the same manner as in Example 1. As a result, almost no difference was observed in the history of light transmittance due to heat treatment.

[0034]

[Comparative Example 4] Asmer (trade name of a shape memory resin made of a crystalline styrene-butadiene complex manufactured by Asahi Kasei Industries, Ltd.) was used instead of the crystalline hydrogenated styrene-butadiene block copolymer. It was carried out in the same manner as in Example 1. The results showed that the light transmittance and stability over time were inferior.

(a) Type of polymer component in the material (A):
Crystalline hydrogenated styrene-butadiene-styrene triblock copolymer (B): LLDPE (linear low density polyethylene) (C)
:Styrene-butadiene block copolymer rubber (D):
Shape Memory Resin Comprised of Styrene-Butadiene Complex (b) Amount of Organic Low-Molecular Compound The amount of the organic low-molecular compound component is expressed in parts by weight based on 100 parts by weight of the polymer component.

(c) Haze measurement conditions Haze (haze value) is expressed as a percentage of the ratio of the diffuse transmission amount Td to the total transmitted light amount T. Haze=Td/T×100 Haze during quenching is the value measured after 2 hours at room temperature of a test piece that was quenched by placing it in water at room temperature after heating.

[0037] Haze during slow cooling is a value measured after 2 hours at room temperature of a test piece that was slowly cooled to 50°C at a rate of about 2°C/minute after heating.

[0038]

[Table 1]

[0039]

[Effects of the Invention] When a heat-sensitive recording layer made of the material of the present invention is formed on a support base material such as resin, metal, or ceramics, and this layer is heated to a temperature higher than the melting point Tm of an organic low-molecular compound and then gradually cooled, The whole becomes cloudy and becomes a state of minimal light transmission,
When printing is performed on this with a thermal head of a printer or the like at a temperature higher than Tm, since the printing area is extremely small, after heating, it is rapidly cooled and transparent characters are printed. Furthermore, if the entire surface is heated again to a temperature higher than Tm after the characters are formed, these characters are erased and printing becomes possible again.

[0040] Prints written in this manner have excellent stability over time, and since the material has excellent weather resistance and various physical properties, there is no reduction in readability due to surface roughness, roughness, or discoloration. Extremely good effects can be achieved.

[Brief explanation of the drawing]

FIG. 1: Temperature and haze of Example 1 of the present invention
shows the relationship between

Claims (4)

[Claims] Claim 1: (a) 100 parts by weight of at least one polymer containing a crystalline olefin chain that is substantially transparent at room temperature; and (b) an organic low-molecular compound having a crystalline melting point in the range of 40 to 200°C. A heat-sensitive repeat recording material comprising 5 to 200 parts by weight of at least one species. 2. The heat-sensitive repeat recording material according to claim 1, wherein the organic low-molecular compound is a compound containing at least one element selected from oxygen, sulfur, nitrogen, and halogen. 3. The heat-sensitive repeat recording material according to claim 1, wherein at least 70% by weight of the olefin chains of the polymer containing crystalline olefin chains are ethylene segments. 4. The heat-sensitive repeat recording material according to claim 1, wherein the polymer containing crystalline olefin chains is a hydrogenated polybutadiene polymer.