JP5526827B2 - Colored ink composition and visibility improving sheet using the same - Google Patents

Description

  The present invention relates to a colored ink composition. More specifically, the present invention relates to a color ink composition, which is installed on the front surface of a display device. In particular, the performance of the display device, in particular, contrast degradation, glare, and image reflection when the display device is exposed to external light. A colored ink composition used for producing a visibility-enhancing sheet having a function of preventing a decrease in performance due to engraving, a function of suitably diffusing effective light of a display device and widening a viewing angle, and the like, and The present invention relates to a visibility improving sheet using the colored ink composition.

  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) proposes a louver-type visibility improving sheet having a structure in which light transmission layers and light shielding layers are alternately arranged. As a light shielding layer, it is disclosed to use a material comprising a light transmission layer mixed 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, so that depending on the type of 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 part, a composition in which fine particles such as carbon pigment are mixed with a lens material such as an ionizing radiation curable resin is used, and this composition is filled in the wedge-shaped part and cured by irradiation with ionizing radiation. When the average particle size is too small as 1 μm, a sufficient light absorption effect cannot be obtained, and when the fine particles are too large, the wedge-shaped portions are formed into fine particles. It is also known that the filling rate of each wedge-shaped part varies, and optical spots occur (for example, JP 2006-184609 A: Patent Document 3).

JP 2006-119365 A JP 2006-85050 A JP 2006-184609 A

  As described above, when the light absorbing portion is formed by filling the wedge-shaped groove with an ink composition in which fine particles such as carbon pigment are mixed, it is necessary to use fine pigment particles having a somewhat large particle diameter. However, if carbon pigment fine particles having an average particle size of 1 μm or more are used, the carbon pigment fine particles settle in the ink composition when added to an ionizing radiation curable resin or the like to form an ink composition. In some cases, the storage stability of the product was insufficient. In addition, when carbon black particles having an average particle size of 1 μm or more are used, there is a limit to the filling rate when the carbon black particles are filled into the wedge-shaped grooves, so that the black density of the light absorbing portion is insufficient. was there.

  The present inventors have recently used an ink composition by using a mixture of a certain amount of carbon fibers in addition to a carbon black pigment as a colorant to be added to an ionizing radiation curable resin for forming a light absorbing portion. The knowledge that the black ink composition which is excellent in the black density of a light absorption part is realizable while the storage stability of a thing improves is obtained. The present invention is based on this finding.

  Accordingly, an object of the present invention is to provide a black ink composition that improves the storage stability of the ink composition and is excellent in the black density of the light absorbing portion.

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

The colored ink composition for a visibility-enhancing sheet according to the present invention is filled with a colored ink composition 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. A colored ink composition used for the visibility improving sheet,
A transparent ionizing radiation curable resin composition having a refractive index smaller than that of the material constituting the prism portion, a colored fibrous filler having an average fiber length in the major axis direction of 5 to 50 μm, and an aspect ratio of 10 or more; Comprising
The colored fibrous filler is contained in an amount of 1 to 30% on a weight basis with respect to the ionizing radiation curable resin composition.

  Moreover, as an aspect of the present invention, it is preferable to further include carbon black having an average particle diameter of 1 to 5 μm.

  Moreover, as an aspect of the present invention, it is preferable to further include colored fine particles having an average particle diameter of 1 to 5 μm.

  Moreover, as an aspect of the present invention, it is preferable that the ionizing radiation curable resin composition contains 10 to 50% of the carbon black and / or the colored fine particles on a weight basis.

  Moreover, as an aspect of the present invention, it is preferable that the colored fibrous filler and the carbon black and / or the colored fine particles are included in a ratio of 1:10 to 1: 1.

  Moreover, as an aspect of the present invention, the colored fibrous filler is preferably carbon fiber.

  Moreover, as an aspect of the present invention, the colored fine particles are preferably black.

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

  Furthermore, the display apparatus provided with said visibility improvement sheet | seat as another aspect of this invention is also provided.

  In the present invention, in the 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, the wedge-shaped groove is provided. As the colored ink composition filled in the grooves, a transparent ionizing radiation curable resin composition having a refractive index smaller than that of the material constituting the prism portion, an average fiber length in the major axis direction of 5 to 50 μm, and an aspect ratio 10 or more colored fibrous fillers, and using the colored ink composition containing 1 to 30% of the colored fibrous filler on a weight basis with respect to the ionizing radiation curable resin composition, an ink composition It is possible to form a light absorbing portion having a high storage stability and a high black density.

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.

  First, the colored ink composition according to the present invention will be described. 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. A transparent ionizing radiation curable resin composition having a refractive index smaller than that of the material constituting the prism portion, an average fiber length in the major axis direction of 5 to 50 μm, and an aspect ratio 10 or more colored fibrous fillers are included as essential components.

  As a transparent ionizing radiation curable resin composition having a refractive index smaller than the material constituting the prism portion of the visibility improving sheet as described later, ionization used for conventionally known visibility improving sheets and viewing angle improving sheets, etc. A radiation curable resin composition 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.

  In the present invention, an ink composition is used in which the above-mentioned ionizing radiation curable resin composition is mixed with a colored fibrous filler having an average fiber length of 5 to 50 μm in the major axis direction and an aspect ratio of 10 or more. By using the colored fibrous filler having such an outer shape, the thixotropic property of the ink composition is improved, so that the storage stability of the ink is improved. The colored fibrous filler may be organic or inorganic, but preferably carbon fiber is used. By adding carbon fiber to the ionizing radiation curable resin composition, it is possible to achieve both the storage stability of the ink and the blackness of the wedge-shaped groove. The average fiber length of the colored fibrous filler is more preferably 10 to 30 μm, and particularly preferably 15 to 20 μm. In this specification, an average fiber length means the number average of the length of an actual fibrous filler. Moreover, 10-50 are preferable and, as for an aspect-ratio (fiber length with respect to a fiber diameter), 10-30 are more preferable. As such a colored fibrous filler, VGCF, VGCF-H, etc. commercially available from Showa Denko KK can be suitably used. The fiber length and fiber diameter of the colored fibrous filler can be measured from an image observed with a scanning electron microscope (SEM) or the like.

  The colored fibrous filler is contained in an amount of 1 to 30% on a weight basis with respect to the ionizing radiation curable resin composition. When the content is less than 1%, the thixotropic property of the ink composition is not improved, and the storage stability of the ink composition becomes insufficient. On the other hand, if it exceeds 30%, the viscosity of the ink composition increases and the filling suitability deteriorates, and the colored fibrous filler tends to settle in the ink composition.

  In the present invention, carbon black having an average particle diameter of 1 to 5 μm may further be included. By containing carbon black having a predetermined average particle diameter, the storage stability of the ink composition and the black density when the light absorbing portion is formed can be made more compatible. The average particle size can be measured, for example, with a particle size distribution measuring device (LA-920, manufactured by Horiba, Ltd.).

  The average particle size of the carbon black affects the process suitability and the filling rate when filling the wedge-shaped groove with the ink composition. A higher filling rate is preferable, but for that purpose, it is necessary that the average particle diameter of the carbon black be sufficiently smaller than the depth and width of the groove to be filled. The average particle diameter of the carbon black is preferably L / 2 or less, and L / 3 or less with respect to the narrower interval L of the width dimension and the depth dimension of the groove filled with carbon black. More preferably. For example, if the wedge-shaped groove has a sufficient depth and the groove opening width is 10 μm, the average particle diameter of the carbon black is preferably 5 μm or less, and more preferably 3.3 μm or less. If the average particle size of the carbon black is larger than L / 2, the carbon black is substantially not aligned in the width direction of the groove, and the filling rate is lowered. In addition, it is difficult in terms of process to efficiently fill carbon black having an average particle size larger than half of the size of the groove to the back of the groove.

  On the other hand, when the average particle size of carbon black is reduced, the filling rate improves because it follows the shape of the wedge-shaped groove, but the number of carbon blacks per unit volume and the specific surface area increase, so that the flow of the black ink composition This lowers the property and reduces the scraping property, making it difficult to form a wedge-shaped light absorbing portion. However, in the present invention, as described above, the colored fiber filler having an average fiber length in the major axis direction of 5 to 50 μm and an aspect ratio of 10 or more is included, so that the thixotropy of the ink composition is high. Compared with a conventional black ink composition containing only fine particles such as black, carbon black having a smaller average particle diameter can be used. As a result, since the filling rate of the colorant in the wedge-shaped groove is improved, it becomes possible to manufacture a visibility improving sheet having a light absorbing portion with a high black density with less color unevenness.

  In the present invention, in addition to the above-described carbon black, colored fine particles having an average particle diameter of 1 to 5 μm may be added. As colored fine particles, resin beads or glass beads colored with pigments or dyes can be suitably used. Such colored fine particles may selectively absorb a specific wavelength in accordance with the characteristics of the image light, but preferably black resin beads are used. 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, acrylic crosslinked fine particles containing carbon black, urethane crosslinked fine particles containing carbon black, and the like may be used. Also, silicon-based beads can be preferably used. Moreover, in order to improve the dispersibility in the ink composition, these colored fine particles may be obtained by surface-treating resin beads. Furthermore, it is preferable to use a resin bead having a refractive index difference of about 0.1 with the ionizing radiation curable resin composition described above.

  When using colored fine particles containing carbon black in transparent resin beads, it is preferable to use carbon black having an average particle diameter of about 10 to 500 nm. The amount of carbon black kneaded into the resin beads is about 0.1 to 0.7 parts by weight, preferably 0.15 to 0.5 parts by weight of carbon black with respect to 1 part by weight of the resin beads. More preferably, it is 0.2-0.35 weight part. If the amount of carbon black kneaded is more than 0.7 parts by weight, the resin beads may be easily broken. On the other hand, if the amount is less than 0.1 parts by weight, colored fine particles having desired blackness cannot be obtained. There is a case.

  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 with plasma or the like.

  Similarly to carbon black, the above-mentioned colored fine particles have an average particle size that affects process suitability and filling rate when filling the wedge-shaped groove with the ink composition. Although it is preferable that the filling rate of the colored fine particles is high, for that purpose, the average particle diameter of the colored fine particles needs to be sufficiently small with respect to the depth and width of the groove to be filled. The average particle diameter of the colored fine particles is preferably L / 2 or less with respect to the interval L, which is the narrower one of the width dimension and the depth dimension of the groove filled with the colored fine particles, and is L / 3 or less. More preferably. For example, if the wedge-shaped groove has a sufficient depth and the groove opening width is 10 μm, the average particle diameter of the colored fine particles is preferably 5 μm or less, and more preferably 3.3 μm or less. When the average particle diameter of the colored fine particles is larger than L / 2, substantially only one colored fine particle is arranged in the width direction of the groove, and the filling rate is lowered. In addition, it is difficult in terms of process to efficiently fill colored grooves having an average particle diameter larger than half the dimension of the groove to the back of the groove.

  On the other hand, if the average particle size of the colored fine particles is reduced, the filling rate is improved because it follows the shape of the wedge-shaped groove, but the number of colored fine particles per unit volume and the specific surface area increase, so that the flow of the black ink composition This lowers the property and reduces the scraping property, making it difficult to form a wedge-shaped light absorbing portion. However, in the present invention, as described above, since the average fiber length in the major axis direction is 5 to 50 μm and the colored fibrous filler having an aspect ratio of 10 or more is included, the thixotropic property of the ink composition is high, and thus coloring is performed. Compared with the conventional black ink composition containing only fine particles, colored fine particles having a smaller average particle size can be used. As a result, since the filling rate of the colorant (colored fine particles) into the wedge-shaped groove is improved, it becomes possible to produce a visibility improving sheet having a light absorbing portion with a high black density and less color unevenness.

  The above-described carbon black and / or colored fine particles are preferably contained in an amount of 10 to 50% on a weight basis with respect to the ionizing radiation curable resin composition. If it is less than 10%, the light-shielding property of the light-absorbing part having a wedge shape may be insufficient. On the other hand, if it exceeds 50%, the resin beads may come into contact with each other, causing a problem of cracking or chipping. It becomes easy to do.

  In the present invention, it is preferable that the colored fibrous filler and the carbon black and / or the colored fine particles are included in a ratio of 1:10 to 1: 1. If the amount of the colored fibrous filler added is less than the above range, the thixotropic property of the ink will not be improved, so that resin beads will settle out and the storage stability of the ink composition will be insufficient. On the other hand, when the addition amount of the colored fibrous filler is larger than the above range, the viscosity of the ink composition is increased and the filling suitability is deteriorated, and the colored fibrous filler is liable to settle in the ink composition.

  The colored ink composition containing each component described above is prepared by mixing a predetermined amount of colored fibrous filler, carbon black, and colored fine particles into an ionizing radiation curable resin composition, and adding a polymerization initiator or the like as desired. Is done. In the preparation of the ink composition, as will be described later, the amount of each component and the type of each component can be appropriately selected so that the ink viscosity is 1500 to 5000 mPa · s. In addition, the viscosity of an ink composition shall mean the value measured in 25 degreeC environment using a B-type viscosity meter etc.

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. 1, 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 coloring ink composition in 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 properly and provide bright images to the observer. Further, since a part of the external light from the observer side is absorbed, the contrast is improved.

  The light absorption part 5 is formed by filling the above-described colored ink composition. That is, it is cured in a state in which fibrous fillers 7 (and carbon black 8 and / or colored fine particles 9) having a predetermined length are dispersed in the ionizing radiation curable resin composition 6. As a result, stray light incident on the inner side of the light absorbing portion 5 without being reflected at the boundary surface between the light absorbing portion 5 and the prism portion 4 is converted into the fibrous filler 7 (and carbon black 8 and / or carbon black in the light absorbing portion 5). Or it is absorbed by the colored fine particles 9). In addition, since the external light from the observer side incident at a predetermined angle can be appropriately absorbed, the contrast can also be improved.

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

  The base material layer 2 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, the density | concentration of a colored fibrous filler etc.) 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. Preparation of an ink composition can select suitably the compounding quantity of each component and the kind of each component so that ink viscosity may be 1500-5000 mPa * s as mentioned above. This 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 method for filling the ink composition, it is possible to fill the wedge-shaped groove with the ink composition by dropping with a dispenser, coating with 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 ink composition is filled into the wedge-shaped groove, that is, the depressions between the plurality of prism portions, the excess ink composition is scraped to fill the wedge-shaped groove with the ink composition. In order to improve the ink scraping property, a continuous wiping device using a doctor blade or a wiping roll is used. When the ink viscosity is less than 1500 mPa · s, the ink scraping property is good, but it becomes difficult to fill the wedge-shaped groove with the 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 ink composition, the light absorbing portion is formed by curing the ink composition. 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>
As ionizing radiation curable resin, urethane acrylate 33.6 parts by weight, epoxy acrylate 14.4 parts by weight, tripropylene glycol diacrylate 28 parts by weight, and methoxytriethylene glycol acrylate 4 parts by weight, and Irgacure as a photopolymerization initiator 184 was mixed with 4 parts by weight, and 1.6 parts by weight of carbon fiber (VGCF-H, Showa Denko KK) and 16 parts by weight of carbon black (average particle size 2 μm) were mixed. An ink composition was prepared. The viscosity of the obtained ink composition was 3000 mPa · s when measured in a 25 ° C. environment using a B-type viscometer.

<Preparation of a sheet for improving visibility>
On a PET substrate (A4300, manufactured by Toyobo Co., Ltd.) with a thickness of 100 μm, using a urethane-based ultraviolet curable resin having a refractive index after curing of 1.55, a continuous molding process is performed with a molding die, and a plurality of prisms And a wedge-shaped groove provided in parallel between the prism portion. Next, the ink composition obtained above is filled into a wedge-shaped groove, and after scraping off the excess ink composition with a metal doctor blade, the ink composition is cured by irradiating with ultraviolet rays, A light absorbing portion was formed. In the obtained visibility improving sheet, the opening width of the light absorbing portion (wedge-shaped groove) was 12 μm, the width of the tip portion of the wedge-shaped groove was 3 μm, and the depth was 105 mm.

Example 2
Example 1 is the same as Example 1 except that 16 parts by weight of colored fine particles (Ganz Pearl, manufactured by Ganz Kasei Kogyo Co., Ltd.) having an average particle size of 4 μm are added in place of the carbon black used in the preparation of the ink composition of Example 1. An ink composition was prepared in the same manner. The viscosity of the obtained ink composition was 3200 mPa · s as measured in a 25 ° C. environment using a B-type viscometer. Subsequently, using the obtained ink composition, a visibility improving sheet was produced in the same manner as in Example 1.

Examples 3-7 and Comparative Examples 1-4
In the ink composition, a visibility improving sheet was produced in the same manner as in Example 1 except that the blending amounts of the ionizing radiation curable resin, carbon fiber, carbon black, and colored fine particles were changed according to Table 1 below.

<Contrast evaluation>
About the obtained visibility improvement sheet | seat, contrast was evaluated with the following evaluation methods. First, the visibility improving sheet was pasted on the display screen, the brightness of the white screen and the brightness of the black screen in the bright room and the dark room were measured, and the value of the white screen brightness / black screen brightness was calculated from each obtained brightness. . Next, measure the brightness of the white screen and the brightness of the black screen in the bright room and dark room of the display without attaching the visibility improving sheet, and calculate the value of the white screen brightness / black screen brightness from the obtained brightness. Calculated. Then, the value of white screen brightness / black screen brightness with the visibility improving sheet attached is divided by the white screen brightness / black screen brightness with no visibility improving sheet attached. did. The bright room means an environment where the fluorescent lamp is turned on in the room and the display screen used has a brightness of 170 cd / m ² when the brightness is 600 lux. The dark room means that the fluorescent lamp is turned off. It means an environment where there is no light source other than light from the display screen in the state. The obtained evaluation results were as shown in Table 1 below.

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 fibrous filler 8 carbon black 9 colored fine particles

Claims (9)

A visibility improving sheet in which a wedge-shaped groove provided in parallel between a plurality of prism portions capable of transmitting light is filled with a colored ink composition and cured to form a light absorbing portion, the colored ink composition Thing is,
A transparent ionizing radiation curable resin composition having a refractive index smaller than that of the material constituting the prism portion, a colored fibrous filler having an average fiber length in the major axis direction of 5 to 50 μm, and an aspect ratio of 10 or more; Comprising
A visibility improving sheet comprising 1 to 30% of the colored fibrous filler on a weight basis with respect to the ionizing radiation curable resin composition.   The visibility improving sheet according to claim 1, further comprising carbon black having an average particle diameter of 1 to 5 μm.   The visibility improving sheet according to claim 1 or 2, further comprising colored fine particles having an average particle diameter of 1 to 5 µm. The visibility improving sheet according to claim 3 , comprising 10 to 50% of the carbon black and / or the colored fine particles on a weight basis with respect to the ionizing radiation curable resin composition.   The visibility improvement sheet | seat of Claim 4 which contains the said colored fibrous filler and the said carbon black and / or the said color microparticles | fine-particles in the ratio of 1: 10-1: 1.   The visibility improvement sheet | seat as described in any one of Claims 1-5 whose said colored fibrous filler is carbon fiber.   The visibility improving sheet according to claim 3, wherein the colored fine particles are black. The ionizing radiation curable resin composition, polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd resin, spiroacetal resin, polybutadiene resin, polythiol polyene resin, and polyfunctional selected from polyhydric alcohols The visibility improving sheet according to any one of claims 1 to 7, comprising an oligomer or a prepolymer such as (meth) allylate of a compound.   The display apparatus provided with the visibility improvement sheet | seat as described in any one of Claims 1-8.

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