JP5963035B2 - Colored ink composition and visibility improving sheet using the same - Google Patents

Description

  The present invention relates to a colored ink composition, and more particularly, is installed on the front surface of a display device, and the performance of the display device, in particular, contrast reduction, glare, and image reflection when the display device is exposed to external light. The present invention relates to a colored ink composition used for producing a visibility-enhancing sheet having a function of preventing a decrease in performance due to engraving and a function of appropriately diffusing effective light of a display device to widen a viewing angle.

  In a liquid crystal display device, it is usually preferred that the viewing angle is wide so that a good image can be obtained from any position of the observer. On the other hand, for example, when working on a commuter train or in a liquid crystal display device installed in a public place such as an ATM, it may be difficult to see the screen from people around you. There is a demand for a peeping prevention function for protecting privacy so that it can be seen only by an observer of the display device and cannot be seen by others. In car-mounted liquid crystal display devices such as car navigation systems, the screen of the liquid crystal display device is reflected on the window glass at night and the like, and the phenomenon of blocking the field of view occurs. Control of the light emission angle is desired.

  In response to such a demand, for example, JP 2006-119365 A (Patent Document 1) discloses a louver-type visibility improving sheet having a structure in which light transmission layers and light shielding layers are alternately arranged. It has been proposed that the light shielding layer is made by mixing a material constituting the light transmission layer with a filler such as carbon black or carbon fiber.

  On the other hand, the louver-type visibility improving sheet as described above simply cuts the image light in the oblique direction, and depending on the type of the display device, the diffusion light source of the image light that should reach the observer is reduced. As a result, the brightness of the display screen may be lowered.

  In order to solve the above problems, a visibility improving sheet capable of improving the contrast by shielding outside light and reducing the occurrence of double images should be installed between the light source of the liquid crystal display device and the liquid crystal panel. Has been proposed. As such a visibility improving sheet, sheets having various structures have been proposed. For example, a lens portion having a trapezoidal cross-sectional shape is arranged at a predetermined interval, and a wedge portion between adjacent lens portions is provided with a lens portion. A material having a structure filled with a material having a lower refractive index and a carbon pigment or the like has been proposed (for example, JP-A-2006-85050, etc .: Patent Document 2).

  Then, as a material constituting the wedge-shaped portion, a composition in which a colored resin bead is mixed with a lens material such as an ionizing radiation curable resin is used. The composition is filled in the wedge-shaped portion and irradiated with ionizing radiation to be cured. A wedge-shaped portion is formed, and colored resin beads having a particle size of 3.5 μm to 20 μm are actually used due to process restrictions when filling the wedge-shaped portion with the composition (for example, International Application Publication WO 2006/090784: Patent Document 3).

  As described above, when the light absorbing portion is formed by filling the wedge-shaped groove with the resin composition mixed with resin beads, those having an average particle diameter of about 3.5 μm to 20 μm are actually used as the resin beads. It was. In recent years, as a result of high definition display devices, there has been a demand for a visibility-enhancing sheet having a narrower line width, that is, a narrow wedge-shaped groove (that is, a base of a substantially triangular light absorbing portion). When this ink composition was used, there was a problem that the wedge-shaped groove was not sufficiently filled with colored resin beads and the contrast was lowered. Further, since the filling rate when the colored resin beads are filled into the wedge-shaped grooves is low, the black density of the light absorbing portion may be insufficient.

  In order to solve the above problem, a visibility improving sheet in which a light absorbing portion is formed using a colored ink containing colored beads having an average particle diameter of about 1 to 3 μm as colored fine particles has been proposed (Patent Document 4).

JP 2006-119365 A JP 2006-85050 A International Application Publication WO2006 / 090784 JP 2011-170344 A

  As proposed in Patent Document 4, when manufacturing a visibility improving sheet in which the line width of the light absorbing portion is narrow, that is, the length of the base of the substantially triangular cross section of the light absorbing portion is about 5 to 15 μm, If fine particles having an average particle size of about 1 to 3 μm are used as the colored beads, it is considered that the colored beads enter the top of the substantially triangular cross section of the light absorbing portion (in other words, the bottom of the wedge-shaped groove). However, even when a colored ink containing colored fine particles having an average particle diameter of about 1 to 3 μm is used, the visibility-improving sheet is caused by poor filling of the colored beads into the wedge-shaped groove when forming the light absorbing portion. In some cases, a streak pattern was generated in the light-absorbing part.

  Even if the present inventors use fine particles having an average particle diameter of about 1 to 5 μm, the fine particles aggregate to form a wedge-shaped groove as large as the width of the light-absorbing portion. I realized that And when scraping off the surplus ink after filling the colored ink, it was found that the streaky pattern was generated by dragging the aggregate that was not filled in the wedge-shaped groove by the doctor blade. Based on this knowledge, if the colored beads of the colored ink to be used are 15 μm or less in the dispersity test based on JIS K5600-2-5, a uniform visibility-improving sheet is generated without causing a streak pattern. It was found that can be manufactured.

  Accordingly, an object of the present invention is to provide a visibility improving sheet in which a colored ink composition is filled in a wedge-shaped groove provided in parallel between a plurality of prism portions capable of transmitting light and cured to form a light absorbing portion. In the above, a stripe-like pattern is generated on the visibility improving sheet for a high-definition display device in which the width of the wedge-shaped groove (that is, the length of the bottom of the substantially triangular cross section of the light absorbing portion) is 5 to 15 μm. It is providing the coloring ink composition which can form a uniform light absorption part, without.

  Another object of the present invention is to provide a visibility improving sheet in which a light absorbing portion is formed using the above colored ink composition.

The colored ink composition for a visibility improving sheet according to the present invention is filled with a colored ink composition in a wedge-shaped groove having a width of 5 to 15 μm provided in parallel between a plurality of prism portions capable of transmitting light, A colored ink composition used for a visibility improving sheet, which is cured to form a light absorbing portion,
A transparent ionizing radiation curable resin composition having a refractive index smaller than the material constituting the prism part;
Colored fine particles having an average particle diameter of 1 to 5 μm;
Comprising
The dispersity of the colored fine particles is 15 μm or less in a dispersity test based on JIS K5600-2-5.

  As an aspect of the present invention, it is preferable that the colored fine particles are made of resin beads in which carbon black is kneaded in a resin.

  Moreover, as an aspect of the present invention, the resin is preferably a colored resin.

  Moreover, as an aspect of the present invention, the colored resin is preferably a black colored resin.

  Moreover, as an aspect of the present invention, it is preferable that the colored fine particles are included in an amount of 10 to 50% based on the mass of the ionizing radiation curable resin composition.

  Moreover, as an aspect of the present invention, the carbon black preferably has an average particle size of 10 to 500 nm.

  Further, as an aspect of the present invention, the ionizing radiation curable resin composition comprises a polyester resin, a polyether resin, an acrylic resin, an epoxy resin, a urethane resin, an alkyd resin, a spiroacetal resin, a polybutadiene resin, a polythiol polyene resin, and many It is preferably composed of an oligomer or prepolymer such as (meth) arylate of a polyfunctional compound selected from polyhydric alcohols.

Moreover, the manufacturing method of the colored ink composition by another aspect of this invention prepares the mixture containing an ionizing-radiation-hardening-type resin composition and the coloring microparticles | fine-particles with an average particle diameter of 1-5 micrometers,
The dispersion of the colored fine particles conformed to JIS K5600-2-5 by using any one kind of kneader selected from a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, and a high-speed stirring type disperser. In the dispersity test, kneading is performed until the dispersion is in the range of 5 to 15 μm.

  Moreover, the visibility improvement sheet | seat produced using the said colored ink composition as another aspect of this invention is also provided.

  According to the present invention, the colored fine particles contained in the colored ink composition are those having an average particle diameter of 1 to 5 μm, and the dispersity of the colored fine particles is set to 15 μm or less. Even when manufacturing a visibility-enhancing sheet having a width (that is, the length of the base of a substantially triangular cross section of the light absorbing portion) of 5 to 15 μm, uniform light is generated without causing streak-like unevenness. An absorption part can be formed.

The figure which shows the cross section of the one direction of the visibility improvement sheet | seat in 1st embodiment of this invention. The enlarged view of the one-way cross section of a visibility improvement sheet | seat. It is the schematic cross section which expanded a part of the prism part 4 and the light absorption part 5 of the visibility improvement sheet | seat obtained in the Example.

<Colored ink composition>
The colored ink composition according to the present invention improves the visibility by filling the colored ink composition into a wedge-shaped groove provided in parallel between a plurality of prism parts capable of transmitting light and curing it to form a light absorbing part. As an essential component, a transparent ionizing radiation curable resin composition having a refractive index smaller than that of the material constituting the prism portion and colored fine particles having an average particle diameter of 1 to 5 μm are used for a sheet. Including. In this specification, “average particle size” is defined as a statistical average value of particle size distribution measured on a volume basis, and is a known particle size distribution measuring device (for example, LA-920, manufactured by Horiba, Ltd.). ) Means the value measured by.

  Since the above-mentioned colored fine particles having an average particle diameter of 1 to 5 μm have a large surface energy, an attractive force acts between the colored fine particles. In order to stably disperse the colored fine particles in the colored ink composition, it is considered to be obtained when a repulsive force sufficient to repel the attractive force generated between the colored fine particles is generated. This repulsive force is said to be due to the surface potential of the colored fine particles and due to steric hindrance due to the adsorption layer adsorbed on the surface of the colored fine particles and spreading from the surface. When these repulsive forces are large and the repulsive force extends farther from the surface of the colored fine particles, it is considered that stable dispersion can be obtained. In the present invention, if the dispersion is 15 μm or less in a dispersion test based on JIS K5600-2-5, the width of the wedge-shaped groove (that is, the length of the bottom of the substantially triangular cross section of the light absorbing portion). Even in the case where a visibility improving sheet having a thickness of 5 to 15 μm is produced, a uniform light absorbing portion can be formed without causing streaky irregularities. If the degree of dispersion exceeds 15 μm, streaky irregularities are generated when the visibility improving sheet is produced due to the aggregates of the colored fine particles.

  A colored ink composition in which the colored fine particles have the above-described degree of dispersion can be obtained by specific kneading or by adding a surfactant to the ink composition. For example, the colored fine particles, the ionizing radiation curable resin composition to be described later, and an appropriate solvent are mixed using a normal mixing and stirring device such as an anchor blade or a turbine blade, and then the mixture is kneaded using a kneader or the like. Further, it is preferable to disperse the colored fine particles using a ball mill, roll mill, bead mill, high-pressure homogenizer, high-speed stirring type disperser, or the like. Specifically, by using the dispersing apparatus as described above, a coloring ink composition in which the dispersion time of the colored fine particles is 15 μm or less by increasing the dispersion time and increasing the shear stress applied in the dispersion process. Can be prepared. In addition, the dispersity test based on JIS K5600-2-5 means that the ink is applied to the top surface of the gauge, the excess ink is scraped off using a scraper, and the position of the granular marks or linear marks on the top surface of the gauge. And the degree of dispersion (μm) is measured by reading the gauge.

  Moreover, you may remove a coarse particle after a dispersion process as needed. For example, the colored ink composition obtained as described above can be filtered under pressure with a filter or treated with a centrifuge to remove particles having a size exceeding 15 μm or aggregates thereof.

  Hereinafter, each component which comprises the coloring ink composition by this invention is demonstrated. The colored ink composition according to the present invention includes a transparent ionizing radiation curable resin composition having a lower refractive index than the material constituting the prism portion of the visibility improving sheet as the binder resin component constituting the light absorbing portion. . As such an ionizing radiation curable resin composition, a conventionally known ionizing radiation curable resin composition used for a visibility improving sheet or a viewing angle improving sheet can be used. For example, those having an acrylate functional group can be suitably used. Specifically, polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetals having a relatively low molecular weight can be used. Examples thereof include oligomers or prepolymers such as (meth) allylates of polyfunctional compounds such as resins, polybutadiene resins, polythiol polyene resins, and polyhydric alcohols. Although depending on the material constituting the prism portion of the visibility improving sheet, a resin having a refractive index smaller than that of the material constituting the prism portion may be selected from these resins.

  In addition, a reactive diluent may be added to the resin composition. Examples of such a reactive diluent include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N- Monofunctional monomers such as vinyl pyrrolidone and polyfunctional monomers may be used. Specifically, dimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di ( Examples include meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like.

  In order to convert the ionizing radiation curable resin composition into an ultraviolet curable resin composition, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethylchuram mono as a photopolymerization initiator in the composition. A mixture of sulfides, thioxanthones, n-butylamine, triethylamine, poly-n-butylphosphine, or the like as a photosensitizer can be used. In particular, in the present invention, it is preferable to mix urethane acrylate as an oligomer and dipentaerythritol hexa (meth) acrylate as a monomer.

  As a curing method of the ionizing radiation curable resin composition, the curing method of the ionizing radiation curable resin composition can be cured by a normal curing method, that is, irradiation with an electron beam or ultraviolet rays.

  For example, in the case of electron beam curing, 50 to 50 emitted from various electron beam accelerators such as a Cockloft Walton type, a bandegraph type, a resonant transformation type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type An electron beam having an energy of 1000 keV, preferably 100 to 300 keV is used. In the case of ultraviolet curing, ultraviolet rays emitted from rays such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, etc. Available.

  The colored ink composition according to the present invention includes colored fine particles having an average particle diameter of 1 to 5 μm. A light absorbing portion provided in parallel between the prism portions by using colored fine particles having an average particle diameter in the above range and having a dispersity in the ink composition of 15 μm or less as described above. Even if the sheet is a thin visibility improving sheet with a line width of 5 to 15 μm (that is, the length of the base of the substantially triangular light absorbing portion), a uniform light absorbing portion without streaks is formed. can do. When the average particle diameter of the colored fine particles exceeds 5 μm, the colored fine particles are hardly filled to the bottom of the groove, and the filling rate of the colored fine particles is reduced. On the other hand, if the average particle diameter is less than 1 μm, the surface area of the fine particles per unit volume increases, so that the colored ink composition tends to thicken and it is difficult to fill the wedge-shaped groove with the colored ink composition. It becomes. In addition, as described above, when the average particle size is small, the colored fine particles tend to aggregate, so that the handling of the fine particles when preparing the colored ink composition becomes complicated.

  The average particle diameter of the colored fine particles is preferably 1.5 to 2.5 μm. Further, two or more kinds of colored fine particles having different average particle diameters may be mixed and used.

  As the colored fine particles used in the present invention, resin beads or glass beads kneaded with carbon black can be used, but from the viewpoint of ease of kneading of carbon black, it is preferable to use resin beads. . As the resin beads, melamine beads, acrylic beads, acrylic-styrene beads, polycarbonate beads, polyethylene beads, polystyrene beads, polyvinyl chloride beads and the like can be suitably used. Further, urethane cross-linked fine particles and silicon-based beads can also be suitably used. These resin beads are preferably those having a refractive index difference of about 0.1 of the ionizing radiation curable resin composition described above.

  As the carbon black that can be used in the present invention, known carbon materials such as furnace black, channel black, acetylene black, and thermal black can be used. Among these, furnace black is particularly suitable because the particle size and structure can be easily controlled.

  Carbon black having an average particle diameter of about 5 to 600 nm is preferably used, and more preferably 10 to 500 nm. The average particle diameter means an arithmetic average diameter obtained by observing carbon black particles with an electron microscope.

  The amount of carbon black kneaded into the resin beads is about 0.1 to 0.7 parts by mass, preferably 0.15 to 0.5 parts by mass, more preferably 1 part by mass of the resin beads. 0.2 to 0.35 parts by mass. If the amount of carbon black kneaded is more than 0.7 parts by mass, the resin beads may be easily broken. On the other hand, if the amount is less than 0.1 parts by mass, colored fine particles having desired blackness cannot be obtained. There is a case.

  As the resin before kneading the carbon black, a transparent resin can be used, but it is preferable to use a resin colored with a pigment or a dye, and it selectively absorbs a specific wavelength according to the characteristics of the image light. However, resin beads colored in black are preferably used.

  In order to improve the dispersibility of the colored fine particles in the ionizing radiation curable resin composition, the colored fine particles may be surface-treated. Examples of the surface treatment include hydrophilic treatment with a conventionally known silica coating, and surface modification by plasma treatment or corona treatment.

  The colored fine particles described above are preferably contained in an amount of 10 to 50% on a mass basis with respect to the ionizing radiation curable resin composition. If it is less than 10%, the light shielding property of the wedge-shaped groove may be insufficient. On the other hand, if it exceeds 50%, the problem of cracking or chipping between resin beads tends to occur.

  The colored ink composition containing each component described above is prepared by mixing a predetermined amount of colored fine particles into an ionizing radiation curable resin composition and adding a polymerization initiator or the like as desired. In the preparation of the colored ink composition, as will be described later, the blending amount of each component and the type of each component can be appropriately selected so that the ink viscosity is 500 to 5000 mPa · s.

<Visibility improvement sheet>
Next, the visibility improvement sheet | seat manufactured using the above-mentioned coloring ink composition is demonstrated, referring drawings. FIG. 1 is a view showing a cross section in one direction of a visibility improving sheet in the first embodiment of the present invention. As shown in FIG. 1, the visibility improving sheet 1 according to the present invention includes at least a base material layer 2 and an optical function sheet layer 3. As shown in FIG. 2, the optical function sheet layer 3 includes a substantially trapezoidal prism portion 4 in a cross section in the layer thickness direction, and a light absorbing portion 5 including wedge-shaped grooves arranged in parallel between the prism portions 4. It has.

  The prism portion 4 is an element having a substantially trapezoidal cross section arranged such that one sheet surface side is an upper base and the other sheet surface side is a lower bottom. The prism portion is made of a light transmissive resin. As such a resin, various transparent thermoplastic resins and the like can be used. As described later, in the present invention, the above-mentioned ionizing radiation curable resin can be preferably used.

  The light absorbing portion 5 is an element having a substantially triangular cross section formed by filling the above-described colored ink composition into the wedge-shaped groove 5 formed between the prism portions and curing. The surface corresponding to the bottom side of the triangular cross section is arranged in parallel so as to face the sheet surface on the upper bottom side of the prism portion. Thereby, one surface of the optical function sheet layer 3 is constituted by the bottom of the light absorbing portion 5 (wedge-shaped groove) and the upper bottom of the prism portion. The hypotenuse in the substantially triangular cross section preferably has an angle in the range of 0 to 10 degrees with respect to the normal direction of the sheet surface of the optical function sheet layer 3. When the angle of the hypotenuse is close to 0 degrees, it becomes a trapezoidal section or a rectangular section rather than a triangular section.

  Since the light absorption part 5 is formed of the above-described colored ink composition, it has a refractive index that is the same as or smaller than the refractive index of the prism part 4. Since the refractive index between the prism unit 4 and the light absorbing unit 5 is as described above, the image light from the light source incident on the prism unit under a predetermined condition is transmitted on the boundary surface between the light absorbing unit 5 and the prism unit 4. It can reflect appropriately and provide a bright image to the viewer. Further, since a part of the external light from the observer side is absorbed, the contrast is also improved.

  The light absorption part 5 is formed by filling the above-described colored ink composition. That is, it is cured in a state where colored fine particles 7 having a predetermined average particle diameter are dispersed in the ionizing radiation curable resin composition 6. As a result, the image light incident on the inner side of the light absorption unit 5 without being reflected at the boundary surface between the light absorption unit 5 and the prism unit 4 is absorbed by the colored fine particles 7 in the light absorption unit 5. In addition, since the external light from the observer side incident at a predetermined angle can be appropriately absorbed, the contrast can be improved.

  In the above-described embodiment, the configuration in which the cross-sectional shape of the light absorbing portion 5 is a substantially triangular shape having two oblique sides on a straight line has been described. However, the present invention is not limited to such a configuration. As long as has the above optical function, it may have any shape.

  The base material layer 2 is disposed on the incident side of the image light, and is a layer serving as a base for forming the prism portion 4 and the light absorbing portion 5 described above. As the base material layer, a transparent resin film, a transparent resin plate, a transparent resin sheet or transparent glass can be used. Transparent resin films include triacetate cellulose (TAC) film, polyester film such as polyethylene terephthalate (PET), diacetyl cellulose film, acetate butyrate cellulose film, polyethersulfone film, polyacrylic resin film, polyurethane resin film Polyester film, polycarbonate film, polysulfone film, polyether film, polymethylpentene film, polyether ketone film, (meth) acrylonitrile film, etc. can be suitably used. Among these, polyester films are preferably used. . Examples of the polyester film include polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, and polytrimethylene terephthalate.

  The visibility improving sheet according to the present invention may be provided with only one optical functional layer 3 as described above, but two or more layers may be laminated and laminated. When two layers of the optical function layer 3 are stacked, each optical function can be laminated via an adhesive or the like, or the optical function layer can be formed on both surfaces of the base material layer.

  In addition, when two optical function layers are stacked, the respective optical function layers may have different structures. For example, the first optical functional layer and the second optical functional layer can change the width, pitch, depth (wedge shape depth) and shape of the light absorption part, or the direction of the light absorption part in the thickness direction. Or the bias angle of the light absorbing portion with respect to the image light (the inclination angle of the light absorbing portion with respect to the horizontal direction) can be changed. Moreover, the material (the kind of resin and the density | concentration of colored fine particles) which forms a light absorption part can also be changed. For example, the second layer is designed to cut outside light efficiently and focus on improving the contrast, and the second layer is designed to focus on the front brightness improvement effect using reflection. It is preferable.

  Next, the manufacturing method of an above-mentioned visibility improvement sheet | seat is demonstrated. First, the prism portion 4 is formed on the base material layer 2. Formation of this prism part 4 changes with kinds of resin to be used. For example, when the prism portion is formed using a transparent thermoplastic resin, a hot pressing method in which a heated mold is pressed against the thermoplastic resin, or a casting method in which the thermoplastic resin is injected into the mold and solidified. A prism portion having a desired shape can be formed by an injection molding method or the like. Also, when using ionizing radiation curable resin, especially UV curable resin, a prism portion having a desired shape is formed by a so-called UV method in which the resin is injected into a mold and irradiated with ultraviolet rays to be cured. can do. Among these methods, in the present invention, the UV method excellent in mass productivity can be suitably used. According to the UV method, the arranged prism units can be continuously produced using a roll-shaped mold.

  Next, the coloring ink composition for forming the light absorption part 5 is prepared. The colored ink composition is prepared by mixing the above-described components and subjecting them to a dispersion step so that the degree of dispersion of the colored fine particles in the ink is 15 μm or less. Specifically, it can be carried out by using a dispersing apparatus as described above. In the present invention, it is preferable to appropriately select the blending amount of each component and the type of each component so that the ink viscosity is 500 to 5000 mPa · s. This colored ink composition is filled into wedge-shaped grooves 5 arranged between the plurality of prism portions 4 formed on the base material layer 2. As a filling method of the colored ink composition, the colored ink composition can be filled into the wedge-shaped groove by dropping by a dispenser, coating by a die head, or a finisher roll. Among these, when the ink composition has poor fluidity and ink marks are conspicuous, coating with a die head is suitable.

  After the colored ink composition is filled in the wedge-shaped grooves, that is, the depressions between the plurality of prism portions, the excess colored ink composition is scraped to fill the wedge-shaped grooves with the colored ink composition. In the present invention, even when the colored ink composition containing the colored fine particles having an average particle size in the range of 1 to 5 μm is filled with the groove width of 5 to 15 μm, the colored fine particles are removed when the colored ink is scraped off. The agglomerates are not dragged and streak-like spots are not generated in the light absorption part. In order to improve the scraping property of the colored ink, it is preferable to use a continuous wiping device such as a doctor blade or a wiping roll. When the ink viscosity is less than 500 mPa · s, the ink scraping property is good, but it becomes difficult to fill the wedge-shaped groove with the colored ink composition, while when the ink viscosity exceeds 5000 mPa · s. The ink fluidity is poor and the ink scraping property is lowered or the ink marks are conspicuous, making it difficult to form a desired light absorbing portion.

  After filling the wedge-shaped groove with the colored ink composition, the colored ink composition is cured to form a light absorbing portion. As a curing method, it can be cured by a curing method usually used in a curing method of an ionizing radiation curable resin composition, that is, irradiation with an electron beam or ultraviolet rays. For example, in the case of electron beam curing, 50 to 50 emitted from various electron beam accelerators such as a Cockloft Walton type, a bandegraph type, a resonant transformation type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type An electron beam having an energy of 1000 keV, preferably 100 to 300 keV is used. In the case of ultraviolet curing, ultraviolet rays emitted from rays such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, etc. Available.

  By forming the prism part 4 and the light absorption part 5 on the base material layer 2 as mentioned above, the visibility improvement sheet | seat 1 as shown in FIG. 1 can be manufactured. The visibility improvement sheet | seat by this invention may contain the other functional layer employ | adopted as the conventional visibility improvement sheet | seat and the viewing angle expansion member. Specifically, an antireflection layer, an adhesive layer, an electromagnetic wave shielding layer, a wavelength filter layer, an antiglare layer, a hard coat layer, and the like may be appropriately combined. The stacking order and the number of stacks of these functional layers can be appropriately determined according to the use of the visibility improving sheet to be used.

Example 1
<Preparation of colored ink composition>
Resin beads obtained by kneading carbon black (RCF # 45, manufactured by Mitsubishi Chemical Corporation) with an average particle size of 24 nm into acrylic resin (Hyperl, manufactured by Nemoto Kogyo Co., Ltd.) were used. The amount of carbon black kneaded was 35% based on the weight of the acrylic resin. It was 1.0 micrometer when the average particle diameter of this resin bead was measured with the particle size distribution measuring apparatus (LA-920, Horiba, Ltd. make).

  As ionizing radiation curable resin, urethane acrylate 33.6 parts by mass, epoxy acrylate 14.4 parts by mass, tripropylene glycol diacrylate 28 parts by mass, and methoxytriethylene glycol acrylate 4 parts by mass, Irgacure as a photopolymerization initiator 184 was mixed with 4 parts by mass, and further 16 parts by mass of the above resin beads were mixed to prepare a mixture.

  A colored ink composition was obtained by subjecting the mixture obtained as described above to a dispersion treatment.

  When the obtained colored ink composition was subjected to a dispersity test based on JIS K5600-2-5, the dispersity was 15 μm.

<Preparation of a sheet for improving visibility>
On a PET substrate (A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm, using a urethane-based ultraviolet curable resin having a refractive index after curing of 1.55, each is continuously molded using a molding die, A plurality of prism portions and wedge-shaped grooves provided in parallel between the prism portions were formed. Next, the colored ink composition obtained above is filled into a wedge-shaped groove, and after the excess colored ink composition is scraped off with a metal doctor blade, the colored ink composition is cured by irradiation with ultraviolet rays. Thus, a light absorption part was formed. At this time, when the formed light absorption part was confirmed by visual observation, streaky irregularities could not be confirmed. Moreover, when the cross section of the thickness direction of the obtained visibility improvement sheet | seat was observed with the optical microscope, it was as FIG. 3 shows. FIG. 3 is a schematic cross-sectional view in which a part of the prism portion 4 and the light absorbing portion 5 is enlarged.

Comparative Example 1
An ink composition was prepared in the same manner as in Example 1 except that the dispersion treatment was not performed. When the obtained colored ink composition was subjected to a dispersity test based on JIS K5600-2-5, the dispersity was 25 to 30 μm.

  Further, a visibility improving sheet was produced in the same manner as in Example 1. At this time, when the formed light absorption part was confirmed by visual observation, streaky irregularities were confirmed.

DESCRIPTION OF SYMBOLS 1 Visibility improvement sheet | seat 2 Base material layer 3 Optical function layer 4 Prism part 5 Light absorption part (wedge-shaped groove | channel)
6 ionizing radiation curable resin composition 7 colored fine particles

Claims (7)

A method for producing a visibility improving sheet comprising a plurality of prism parts capable of transmitting light and a light absorbing part provided in parallel between the prism parts ,
Preparing a mixture comprising an ionizing radiation curable resin composition and colored fine particles having an average particle size of 1 to 5 μm;
The dispersion of the colored fine particles conformed to JIS K5600-2-5 by using any one kind of kneader selected from a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, and a high-speed stirring type disperser. In the dispersity test, kneading is performed until it is 15 μm or less to prepare a colored ink composition,
The colored ink composition is filled in a wedge-shaped groove having a width of 5 to 15 μm provided in parallel between the prism portions,
Curing the colored ink composition to form a light absorbing portion;
Comprising
The said ionizing radiation curable resin composition has a refractive index lower than the material which comprises the said prism part, The manufacturing method of the visibility improvement sheet | seat characterized by the above-mentioned. The method according to claim 1, wherein the colored fine particles comprise resin beads in which carbon black is kneaded in a resin. The method of claim 2, wherein the carbon black is furnace black. The method according to claim 2 or 3, wherein the resin is a colored resin. The method according to claim 4, wherein the colored resin is a resin colored in black. The relative ionizing radiation curable resin composition, the comprising 10-50% in the colored particles mass A method according to any one of claims 1 to 5. The method according to claim 2 or 3 , wherein the carbon black has an average particle size of 10 to 500 nm.

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