JPH0519477B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a thermal transfer recording paper and a thermal transfer recording device using the same, and particularly to a thermal transfer recording paper excellent in color recording, high-speed recording, and high-resolution recording, and a transfer recording device using the same. [Technical background of the invention and its problems] In recent years, following the development of office automation, there has been a demand for a recording device that can record on plain paper. A typical example of this is the thermal transfer recording device, which is currently aiming for color recording, high-speed recording, and high-resolution recording.
Further development is underway. Thermal transfer recording devices perform recording using the simple principle of melting or softening ink with heat and transferring it to recording paper, so they have a simple structure and are maintenance-free. Since image quality is determined by accuracy, it is necessary to perform ink transfer accurately. However, when thermal transfer recording is performed at high speed, or
When color recording is performed by overlapping inks of a plurality of colors, missing pixels occur as shown in FIG. 1a, or missing pixels as shown in FIG. 1b. Furthermore, in high-resolution recording, the clarity of characters is noticeably lacking. Problems such as color unevenness in color images occur. In order to solve this problem, it is generally known that the smoothness of paper should be increased.
In other words, it is said that the smoother the paper, the more efficiently ink is transferred. However, when the present inventor conducted an experiment, it was found that ink transfer to the paper became unreliable when paper had a high degree of smoothness. [Object of the invention] The present invention eliminates the above-mentioned drawbacks and achieves high-speed recording and
An object of the present invention is to provide a thermal transfer recording sheet on which ink can be reliably transferred even during color recording, and a thermal transfer recording device using the same. [Summary of the Invention] This invention provides an ink-receiving surface of thermal transfer recording paper.
It is characterized by imposing a condition that the Beck smoothness is 300 seconds or more and 2500 or less, and a condition that the print surf roughness is 0.6 μ or more and 5 μ or less. Prior to this invention, as stated in [Technical background of the invention and its problems], the inventor discovered the following based on the fact that when recording paper with high smoothness is used, ink transfer becomes uncertain. I made a similar inference. That is, the transfer of ink to paper is carried out by contacting the ink and paper in the desired transfer area (this is called a contact step), and after heating the ink, the ink is transferred to the paper by the cohesive force of the ink, or by the ink forming a film that is the carrier of the ink. The adhesion force is stronger than the adhesion force to the ink ribbon (called the adhesion step), and is achieved by peeling the ink ribbon from the paper. Although improved smoothness is useful to ensure the contact step, It is believed that it is not necessarily useful in the attachment step. When considering the factors governing this adhesion step, it was found that the surface of the paper 21 is not smooth as shown in FIG. 2a, but rather has a suitable roughness as shown in FIG. 2b. We have come to the conclusion that the ink adhesion is improved when Furthermore, in thermal transfer recording, since recording is performed with the ink carrier and recording paper in pressure contact,
The roughness achieved on the paper surface when under a given pressure appears to be important. The present invention has been made by paying attention to the above points. As specified in JISP8119, Beck's smoothness here is defined by the time it takes for a given amount of fluid to flow between a surface to be measured of a given area and an ideal smooth surface, and for all of this to flow out. Ru. The unit is seconds. This Beck smoothness indicates that
It is the overall smoothness of the paper surface. On the other hand, print surf roughness indicates the degree of local unevenness of the surface under pressure, and is measured as follows. That is, as shown in FIG. 3, there is an air inlet 31 adjusted to a low pressure and an air outlet 32 connected to a flow meter (not shown).
Then, the paper 36 is placed between the measuring head 34 having a partition wall 33 of a predetermined area and the back support 35 having a predetermined hardness so that the ink-receiving surface faces the measuring head 34. 35, while applying a constant pressure to the paper 36, the air is moved from the air inlet 31 to the air outlet 32 via the partition wall 33 at a constant time.
By measuring the amount of air leaking into
It derives the minute surface roughness of the paper surface under pressure, and this value is referred to as print surf roughness. As a device having such means, H,
PARKER of E,MESSMER LIMITED
There is a series of PRINT-SURF (product name) models. The print surf roughness value of the paper according to the present invention is PARKER PRINT−SURF
Measured with MODEL750, pressure conditions
It is 1960kP ^A. [Effects of the Invention] According to the present invention, the surface not only has high smoothness but also locally has minute irregularities, so that when ink is transferred, the ink and paper come into close contact and the ink and paper are It also has strong adhesion to the paper. Therefore, ink transfer is performed more reliably. In particular, the effect is remarkable in high-speed recording and color recording. Furthermore, high resolution is also achieved. [Embodiments of the Invention] Next, a thermal transfer recording paper according to the present invention and a thermal transfer recording apparatus using the same will be described in detail with reference to the drawings. The thermal transfer recording paper in this example is NBKP,
Bleached chemical pulp such as LBKP, NBSP, LBSP alone or mixed pulp with mechanical pulse, semi-chemical pulp, chemical ground pulp such as GP, RGP, TMP, pine resin acid maleate, alkyl ketene dimer, synthetic polymer Sizing agents such as clay, calcium carbonate,
It is normally produced by paper machines such as fourdrinier paper machines by adding fillers such as white carbon and talc, starch, paper strength agents such as melamine formaldehyde resin, urea form, and aldehyde resin, and fixing agents such as aluminum sulfate. , non-coated paper or 4th grade paper calendered with a super calender, etc., with external addition of sizing agents and paper strength enhancers as necessary.
As shown in the figure, pigment 42 is applied to the surface of base paper 41,
Coated paper provided with a coating layer made of binder 43 is used. Base paper 41 generally includes NBKP, LBKP,
Bleached chemical pulp such as NBSP and LBSP,
Mechanical pulp such as GP, RGP, TMP, semi-chemical pulp, chemical ground pulp, etc., suitably sized or unsized medium-quality paper, wood-free paper, thermoplastic resin film such as polyester, polystyrene, or synthetic paper are used. However, the composition of the base paper itself is not particularly limited. Alternatively, a base paper smoothed by a supercalender or the like may be used. The pigment 42 is preferably an acicular inorganic pigment with an average length of less than 0.5μ, such as acicular light calcium carbonate, or preferably an average particle size of 0.5μ, such as powdered urea formaldehyde resin or powdered polystyrene resin. Particulate synthetic resins with an average particle size of less than 0.5μ, or synthetic silicas such as natural or white carbon, clays, talc, aluminum sulfate, tyrene dioxide, zinc oxide, etc., can be used, preferably with an average particle size of less than 0.1μ. Synthetic silica such as the following white carbon, and inorganic pigments such as light or heavy calcium carbonate can be used. The pigments used in the present invention are inorganic pigments and granular synthetic resins with the above-mentioned shapes and particle sizes, but if these specific pigments are included as pigment components in an amount of 30% or more, other pigments with shapes other than the above may be used. , may be used in combination with pigments of particle size. In addition, inorganic ingredients such as funnel oil, sodium dodecyl sulfate, organic amines, metal soaps,
non-ionic, such as sodium ligninsulfonate,
By treating with a cationic or amphoteric activator, the wetting of the ink ribbon with the ink is improved and it can be used suitably. The binder 43 is made of rubber such as styrene-butadiene rubber (SBR) or nitrile rubber (NBR).
Adhesive alone consisting of water-insoluble polymers such as vinyl chloride-vinyl acetate copolymer, acrylic resin, methacrylic resin, urethane resin, vinyl acetate-ethylene copolymer, ethylene cellulose, petroleum resin, or carnauba wax, Used in combination with solid waxes such as vegetable waxes such as wood wax, animal waxes such as beeswax and serratus wax, petroleum waxes such as microcrystalline waxes and paraffin waxes, and synthetic waxes such as oxidized waxes and ester waxes. It becomes. The requirements for adhesives are film formability and small size, preferably 40 dyn/
The surface energy is less than cm. The proportion of solid wax to adhesive is between 5 and 50%, preferably between 5 and 25%. This is because if the content is less than 5%, the effect of the wax mixture will be lost, and if it is more than 50%, problems will arise in film forming properties. Pigment 42 and binder 43 forming coating layer 34
The solid content ratio is 100% pigment to 100% binder.
10-50. Preferably 15 to 100 pigments
It is 40. The coating liquid that forms the coating layer 44 includes various auxiliary agents, waterproofing agents for the coating layer, fluidity improvers during coating, gloss finishing agents, preservatives, antifoaming agents, dyes, etc. You can enter it accordingly. The coating layer is formed using a conventional coating machine such as a blade coater, an air knife coater, a roll coater, or a bar coater, or a size press, a gate roll device, or the like. In addition, the surface of paper with only a coating layer is inferior in smoothness and uniformity.
After application and drying, compress with supercardan etc. to adjust smoothness. The thermal transfer recording paper according to the present invention has a smoothness of
300 seconds or more, 2500 seconds or less, print surf roughness 0.6μ or more and 5μ or less, preferably Beck smoothness 500
2000 seconds or more, print surf roughness 0.8μ
It has a surface characteristic of 3μ or less. This is because if the Beck smoothness is less than 300 seconds and the print surf roughness is less than 5 μ, the contact of the ink to the paper becomes uneven, causing chipping of the image dots.
The adhesion of the ink is not enough and the ink often remains untransferred. This is particularly likely to occur when the paper surface becomes uneven due to previously transferred inks, such as in a color thermal transfer recording device that creates a color image by sequentially transferring a plurality of inks onto paper. Next, FIG. 5 shows the basic configuration of the thermal transfer recording apparatus according to the present invention. The ink ribbon 50 is transferred from an ink ribbon supply reel 51 to an ink ribbon supply roller 52.
It is played out by. Paper 53 is fed out from paper supply reel 54 by ink ribbon supply roller 55 . The fed-out ink ribbon 50 and paper 53 are transferred to rollers 56, 57 and platen roller 5.
Ink ribbon-paper pressure contact means 5 composed of 8
9 onto the platen roller 58 via the ink of the ink ribbon (not shown). The ink ribbon 50 in the press-contact state is heated by a heating means 60 that selectively generates heat temporally and spatially according to recorded information by a drive circuit (not shown) from the opposite side to which the paper 53 is in contact. Ru. Heating means 60
This eliminates the structure in which the ink ribbon 50 and paper 53 are pressed together in cooperation with the platen roller 58. After heating recording, the ink ribbon 50 is separated from the paper 53 at the roller 57 by driving the ink ribbon discharge roller 61, and the ink is transferred. The paper 5 is discharged to the outside of the apparatus by a paper discharge roller 62. Thermal transfer recording is completed by this series of processes. In the case of color printing, the conveyance control of the paper and ink ribbon differs depending on whether it is surface sequential printing or line sequential printing, but this process is repeated according to the number of colors. Ink ribbon 50 is made of a resin film such as 4-20μ polyester, a base film such as paper such as condenser paper, solid waxes such as carnauba wax and paraffin wax, low molecular weight polyethylene, petroleum resin, etc. with a melting point of 65-150. For adhesives made of resins that can be easily melted at ℃,
Pigments and dyes commonly used in the printing field such as carbon black and phthalocyanine blue, or dispersed monoazo dyes, dispersed anthraquinone dyes, and anthracene dyes that are solid at room temperature and have a sublimation temperature of 65 to 200°C. 2~ ink
It is applied at a coating weight of 20g/ ^m2 . In addition, there are various forms of ink application, such as a single color ribbon, a color ink ribbon in which multiple ink layers of different colors for approximately one screen are repeatedly provided in the longitudinal direction, or a color ink ribbon in which colored ink areas are divided in the longitudinal direction. , ribbon width and length can also be arbitrarily determined. Paper 53 is the paper according to the present invention. It can be used in the form of roll paper, cut paper, etc.
The heating means 60 can be a moving head type, a line head type thermal head, a hot wire, a hot matrix type, or the like. platen roller 58
Thermal heads, ink ribbons, etc. that cannot be heated without contact, such as thermal heads,
It is preferable to use an elastic material such as silicone rubber so that the paper can be pressed under appropriate conditions. Further, it is preferable that the ink ribbon and paper move as one between the heating recording point and the peeling point. Next, the recording results obtained when the above-described apparatus is operated will be described. Here, we will evaluate the performance of the thermal transfer recording paper according to the present invention, which is equipped with a thermal head with a heating element density of 12 dots/mm, and has a heating element density of 12 dots/mm in both the horizontal and vertical directions.
Using an evaluation device that records images at a resolution of
I did this on the item. Recording conditions such as recording voltage and applied pulse width are constant except for 4. Ink ribbons (1), (2), and (4) are black ink ribbons with the same specifications, and (3) is color ink with the same specifications. I used ribbon. (1) Establishment of transfer: Record dots consisting of 2 dots x 2 dots at a paper feed speed of 2.5 cm/min, observe the number of dots that are 7/8 or more of the regular dot size,
The percentage was calculated based on the total number of observations of 50. (2) Resolution characteristic A; Checkerboard pattern with side length n is N=
1, 2, 3, 4, 6 (respectively, resolution 12, 6, 4,
The transfer density was measured using a Macbeth densitometer RD-2, and the maximum resolution was determined in an area of equal density. (3) Resolution characteristic B; Checkerboard pattern with side length n is N=
1, 2... (respectively, resolution 12, 6,... dots/mm
After recording the first color in the empty part of the checkered pattern with the second color, observe the dots of the second color under magnification, and check the shape of the dots as A and A.
It was evaluated in three stages: B and C. Those that are close to square are rated A, those with slight chips are rated B, and those with significant chips are rated C. (4) High-speed recording performance: Transfer probability evaluation pattern recording was performed at a paper feed speed of 250 cm/min, and the transfer probability was determined using the same evaluation criteria as for the transfer probability in (1). Evaluation example 1 15 parts by weight of talc and 2 parts by weight of aluminum sulfate were added to a mixed pulse consisting of 80 parts by weight of beaten LBKP and 20 parts by weight of GP, and paper was made using a Fourdrinier paper machine in a conventional manner, followed by size pressing with oxidized starch. , I made ^a base paper of 50g/m2. This base paper was passed through a super calender and three types of recording paper (1) to (3) having a Beck smoothness of 300 seconds or more and a print surf roughness of 5μ or less were placed. Further, as comparative examples, commercially available medium-quality paper, high-quality paper, and gravure paper having a Beck smoothness of 300 seconds or less and a print surf roughness of 5 μ or more were used as comparative papers (1) to (3). Table 1 shows the base smoothness, print surf roughness, and evaluation results of these recording papers.

[Table] As is clear from Table 1, the recording papers (1) to (3) of the present invention exhibit superior suitability as thermal transfer recording papers compared to Comparative Examples (1) to (3). Evaluation example 2 100 parts by weight of beaten LBKP, 8 parts by weight of white clay,
After adding 2 parts by weight of aluminum sulfate and making paper using a Fourdrinier paper machine in a conventional manner, size press is performed using oxidized starch, and machine calender treatment is performed to obtain
A base paper of 50 g/m ² was made. 15 parts by weight (solid content) of styrene-butadiene latex were mixed with 100 parts by weight (solid content) of light calcium carbonate with an average particle size of 0.1μ and synthetic silica with an average particle size of 0.03μ.
Types of paints A and B were adjusted. These paints are applied onto the base paper using an air knife coater so that the coating amount on one side is 8 g/ ^m2 , and after drying, the coated surface has a Bekku smoothness of 300 seconds or more and 250 seconds or less, and a print surf roughness of 0.6 μ or more and 5 μ or less. Six types of recording sheets 4 to 9 were obtained by supercalendering so that the results were as follows. In addition, as a comparative example, a paint was prepared by mixing 8 parts by weight (solid content) of styrene butadiene latex with 100 parts by weight (solid content) of Sachin White with an average particle size of 0.1μ, and the coating amount on one side was 20 g on the base paper. /m ² using an air knife coater, and after drying, super calender treatment is performed to ensure that the coated surface has a Bekku smoothness of 2500 seconds or more and a print surf roughness.
Comparison papers (4) and (5) of 0.5μ or less were obtained. Table 2 shows the base smoothness, print surf roughness, and evaluation results of these recording papers and comparative papers.

[Table] As is clear from Table 2, even if the surface smoothness of the recording paper is too high, the adhesion of ink will be weakened, and the ink ribbon and recording paper will separate, making it difficult to use as a thermal transfer recording paper that transfers ink. , it turns out that it is not suitable. In addition, as shown in Tables 1 and 2, recording paper with surface characteristics (ink-receiving surface characteristics) of Beck's smoothness of 500 seconds to 2000 seconds and print surf roughness of 0.8 μ to 3 μ is particularly excellent. It shows ink receptivity, and is suitable for high-speed recording, high-resolution recording,
This shows that it is suitable as a recording paper for color recording. Evaluation Example 3 An example of a thermal transfer color recording apparatus according to the present invention using the recording paper 7 of Evaluation Example 2 will be described with reference to the drawings (FIG. 6). Thermal head 63 and thermal head 6 have 2624 resistive elements arranged in one row at 12 elements/mm.
The recording head assembly 66, which consists of a support plate 64 supporting the recording head 3 and an ink ribbon peeling roller 65 attached to the support plate 64, is moved by the action of a spring 67 and an electromagnetic lever 68.
A silicone rubber roller 69 with a rubber hardness (JIS hardness) of 40° is arranged opposite to the roller 6 and is rotated at a predetermined paper feed speed by a step motor (not shown).
It is designed so that it can be in either a pressed or separated state. The width is 210mm, and there are 297 inks in four colors: yellow, magenta, cyan, and black in the longitudinal direction.
The four-color ink ribbon 70 that appears repeatedly at mm pitch is guided from the ink ribbon supply roll 71 to guide rollers 72 and 73, passes between the recording head assembly 66 and the platen roller 69, and then passes through the peeling roller 65 and guide roller 74. and is driven by a motor (not shown). The ink ribbon is wound onto a take-up roll 75. The recording paper 76 is fed out from the recording paper supply roll 77, and is passed between the recording paper pressure roller 78 and the platen roller 6.
9 in close contact with the circumferential surface of the platen roller 69. Next, the recording operation of the apparatus will be explained. Star Next, the recording operation of the device will be explained. When the start signal is input, the ink ribbon sensor 79 detects yellow ink and sets the ink so that its leading end is located at the position of the heating element row of the thermal head 63. At this time, the recording head assembly 66
is in a state separated from the platen roller 69, and only the ink ribbon 70 is conveyed by the drive of the ink ribbon take-up roll 75. After that, the recording head assembly 66 is lowered, and the thermal head 63,
The ink ribbon 70, the recording paper 76, and the platen roller 69 are brought into pressure contact, and the recording preparation is completed. The drive circuit (not shown) of the thermal head 63 is driven by a recording signal corresponding to yellow recording from a recording information source (not shown), and the heating element is driven with a pulse width of 1 ms (maximum), a pulse period of 2 ms, and a pulse rate of 70 mJ/.
Selectively generates heat with exothermic energy of mm ² . Since this thermal head 63 is capable of driving all heating elements, the ink ribbon 70 and the recording paper 76 are conveyed by 1/12 mm every 2 ms by rotation of the platen roller 69 without shifting. Further, the driving of the thermal head 63 is controlled so that the heat generation temperature of the heating element remains constant regardless of the amount of recording signal. The partially adhered ink ribbon 70 and recording paper 76 are separated by a peeling roller 65, and the ink is transferred to the recording paper. At this time, ink ribbon 70
is stretched by the drive of the ink ribbon take-up roll 75, and prevents the ink ribbon 70 from fluttering, which may cause transfer defects. In this way, one screen is first recorded using yellow ink. During this time, the ink ribbon 70 and the recording paper 7
6 is transported at a constant speed. After yellow recording, record head assembly 7
6 is separated from the platen roller 69. The recording paper 76 causes a step motor connected to the platen roller 69 to rotate in reverse at double speed. By moving backward the same number of forward steps, the recording paper 76 is set at the initial position. During this time, magenta ink is set on the ink ribbon 70 by driving the ink ribbon take-up roll 75. After the ink ribbon 70 and recording paper 76 are set, the recording head assembly 66 is lowered and the thermal head 63, ink ribbon 70, recording paper 76, and platen roller 69 are brought into pressure contact again, completing magenta recording preparation. Similar to yellow recording, the thermal head 63 is driven by a recording signal corresponding to magenta recording from a recording information source (not shown), and magenta ink recording is superimposed on yellow recording. Similarly, cyan recording and black recording are performed. Here, the ink transfer state in the example will be described in more detail. FIG. 7 shows a state where the second color ink 82 is about to be transferred after the first color ink 80 has been transferred onto the recording paper 76. Since the recording of the first color has been completed, there is a spot pressure of the ink 80 on the recording paper 76. Here, for example, if a second color ink 82 is to be transferred between the first color ink 80, the object to be transferred is a composite of the recording paper 76 and the ink 80. The surface has larger irregularities than the surface of the recording paper 76 alone. Naturally, if this ink 82 is used, the state of contact between the ink 80 and the recording paper 76 is not favorable, and the ink 82 is pressed against the recording paper 76 with a weaker pressure. However, recording paper 7
If the print surf roughness of No. 6 is an appropriate value, the ink 82 and the recording paper 76 will be compatible with each other, wetting will be good, and the recording paper 76 will be printed more reliably even under weak pressure.
6 and the ink 82 are in close contact with each other. This is the mechanism for improving image quality. This recording device created a high-speed color thermal transfer recording device that can output an A4-sized blue color image with a resolution of 12 dots/mm in about 40 seconds. The obtained image was an excellent full-color image with extremely good gradation and clear dots since there were no missing or missing dots. In the color thermal transfer recording device configured using Comparative Paper 2 of Evaluation Example 1 and Comparative Paper 5 of Evaluation Example 2, only color images with a very rough feel and poor gradation could be obtained due to missing image dots. Ta. Although the embodiments of the present invention have been described above in detail, the present invention is not limited to the above embodiments. For example, the thermal transfer recording method is not particularly limited as long as it uses heat to change the ink on the ink carrier into a state such as melting, fluidization, sublimation, or evaporation. In this way, any modification is included in the invention as long as it does not depart from the spirit of the invention.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the problem of image dot formation in thermal transfer recording, Figure 2 is a diagram for explaining the relationship between the surface characteristics of recording paper and ink transfer, and Figure 3 is a diagram for explaining the relationship between the surface characteristics of recording paper and ink transfer.
The figure is an explanatory diagram of the print surf roughness measuring means.
FIG. 4 is a diagram for explaining the configuration of a recording paper according to an embodiment of the present invention, FIGS. 5 and 6 are diagrams illustrating the configuration of a thermal transfer recording apparatus according to an embodiment of the present invention, FIG. 7 is a schematic diagram for explaining ink transfer during color recording. 21,76...Paper, 22,80,82...Ink, 41...Base paper, 42...Pigment, 43...Binder, 44...Coating layer, 40...Ink ribbon, 53,76... Recording paper, 60...Heating source,
63... thermal head, 58, 69... platen roller, 70... color ink ribbon.

Claims (1)

[Claims] 1. Beck smoothness is 300 seconds or more and 2500 seconds or less, and
A thermal transfer recording paper having an ink-receiving surface having a print surf roughness of 0.6μ or more and 5μ or less. 2. A recording paper having an ink-receiving surface with a Beck smoothness of 300 seconds or more and 2500 seconds or less and a print surf roughness of 0.6 μ or more and 5 μ or less, an ink carrier carrying ink to be transferred to this recording paper, and this ink. 1. A thermal transfer recording device comprising: heating means for selectively applying heat to a carrier.