TWI474036B - Optical sheet and touch panel - Google Patents

Description

Optical sheet and touch panel

The present invention relates to an optical sheet and a touch panel suitable for use in a liquid crystal display device.

The liquid crystal display module (LCD) is mostly used as a flat panel display because of its thinness, lightness, low power consumption, etc., and the display device for information such as mobile phones, personal digital assistants (PDAs), personal computers, and televisions is expanding year by year. In recent years, as a characteristic required for a liquid crystal display module, various characteristics are required depending on the application, and examples thereof include bright (high luminance), easy viewing (wide viewing angle), energy saving, thin weight, and large size. Screening and so on.

As the liquid crystal display module described above, there is also a touch panel mounted thereon for improving the ease of operation, rapidity, and the like of a person who views. The liquid crystal display module with the touch panel described above generally has a structure in which a touch panel, a liquid crystal are superposed in order from a surface side to a back side in accordance with a touch panel, a liquid crystal display element, various optical sheets, and a backlight. Display elements, various optical sheets, and backlights.

The touch panel includes a capacitive touch panel, a resistive film method, an electromagnetic induction method, and the like. For example, the capacitive touch panel has a touch panel in which electrodes extend in directions intersecting each other. Detecting a change in capacitance between electrodes when a finger or the like is touched to detect an input position; applying an alternating current having the same phase and the same potential to both ends of the light-transmitting conductive film, and detecting a weak flow when a capacitor is formed when the finger is in contact or close to each other The current thus detects the input position and the like.

In addition, in the foregoing touch panel, in order to effectively prevent reflection of external light, the polarizing plate and the first retardation film are disposed on the outermost surface of the touch panel. A polarizing plate and a first retardation film are disposed in the order of (1/4 λ plate), and a second retardation film (1/4 λ plate) is disposed on the back side of the touch panel (refer to Japanese Laid-Open Patent Publication) 2010-204480).

However, in the case where the surface of the retardation film described above is damaged at the time of production or transportation, there is a problem that the optical function of the damaged portion is lowered and the appearance is deteriorated. Such a problem also exists in other types of touch panels such as a resistive film method and an electromagnetic induction method.

Prior art literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-204480.

In view of the foregoing, it is an object of the present invention to provide an optical sheet and a touch panel using the optical sheet, which are capable of preventing deterioration of optical function and deterioration of appearance by being damaged during manufacturing and transportation.

In order to solve the aforementioned problems, the present invention provides an optical sheet comprising: a retardation film comprising a polycarbonate resin as a main component; a hard coat layer laminated on one side of the retardation film; and an adhesive layer And laminated on the other surface side of the aforementioned retardation film.

Since the optical sheet has a hard coat layer on one surface side of the retardation film, it is possible to improve the performance of preventing damage during manufacturing and transportation, and it is possible to prevent deterioration of optical function and deterioration of appearance. Further, since the optical sheet is made of a polycarbonate resin as a main component of the retardation film, impact resistance can be improved. Even if the optical sheet is used for a touch panel or the like, in the case of pressing or pressing the surface of the touch panel, the retardation film and the adhesive layer laminated on the other surface side of the retardation film are used. It is also possible to prevent the glass substrate of the touch panel from being damaged. The result is the optical sheet It is possible to effectively prevent scattering of fragments or the like of the glass substrate.

It is preferable that the retardation film of the optical sheet has a photoelastic coefficient of 40 × 10 ^-12 /Pa or less. By setting the photoelastic coefficient of the retardation film to the above range, it is possible to suppress a change in phase difference caused by direct sunlight and heat generation of the display. Therefore, the optical sheet can well maintain the birefringence imparted by the orientation and can display a fine image.

It is preferable that the retardation film of the optical sheet has an average thickness of 10 μm or more and 500 μm or less. By setting the average thickness of the retardation film to the above range, it is possible to suppress a decrease in luminance of the liquid crystal display device, and it is possible to improve the strength of the optical sheet and to improve characteristics such as bending prevention performance.

It is preferable that the optical sheet has a haze of 2% or less. By setting the haze to the above range, it is possible to suppress the deterioration of the visibility of the image displayed on the liquid crystal display device, and it is possible to maintain the sharpness of the displayed image.

It is preferable that the optical sheet has a total light transmittance of 87% or more. By making the total light transmittance into the above range, light can be sufficiently transmitted, and visibility can be improved.

It is preferable that the retardation film of the optical sheet has a glass transition temperature (Tg) of 120 ° C or more and 180 ° C or less. By setting the glass transition temperature of the retardation film to the above range, thermoforming can be easily and reliably performed, and birefringence can be favorably maintained.

Preferably, the optical sheet is adhered to the glass substrate of the touch panel through the adhesive layer. Thereby, it is possible to effectively prevent the glass substrate of the touch panel from being damaged, and it is possible to improve the function of preventing scattering of debris generated during breakage or the like.

In addition, in order to solve the foregoing problems, the present invention further provides a touch panel including: a glass substrate; and the foregoing optical sheet, through the foregoing The adhesive layer is adhered to the aforementioned glass substrate.

Since the touch panel has a hard coat layer on one surface side of the retardation film of the optical sheet, it is possible to improve the performance of preventing damage of the optical sheet during production and transportation, and to prevent deterioration of optical function and appearance. Getting worse. Further, since the touch panel uses a polycarbonate resin as a main component of the retardation film of the optical sheet, impact resistance can be improved. Even when the touch panel surface is pressed hard or dropped, the touch panel can prevent touch by the retardation film and the adhesive layer laminated on the other surface side of the retardation film. The glass substrate of the panel is damaged. As a result, it is possible to effectively prevent the scattering of the fragments or the like of the glass substrate of the touch panel.

Further, in the present invention, the "photoelastic coefficient" is a coefficient indicating the degree of difficulty in changing the refractive index due to an external force, and is a value obtained by C _R [/Pa] = Δn / σ _R . Here, σ _R is a tensile stress [Pa], Δn is a refractive index when stress is applied, and Δn is defined by the following formula.

△n=n ₁ -n ₂

(wherein n ₁ is a refractive index in a direction parallel to the tensile stress, and n ₂ is a refractive index in a direction perpendicular to the stretching direction.)

Further, the "average thickness" is an average value of values measured in accordance with the A-2 method of 5.1.2 prescribed in JIS K 7130. "Haze" is a value obtained in accordance with JIS K 7136. "Full light transmittance" is a transmittance measured by a haze meter manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K 7361.

As described above, the optical sheet of the present invention can be prevented from being damaged during the production and transportation, and thus the optical function can be prevented from being lowered and the appearance can be deteriorated. Therefore, the optical sheet according to the present invention and the touch panel using the optical sheet can suppress the reduction in optical function and the appearance change Poor, able to display images with high visibility and contrast. Further, the light emitted from the liquid crystal panel becomes polarized light. In the case of wearing polarized sunglasses in an in-vehicle environment, sometimes the polarized light axis cannot be aligned when the head is tilted, resulting in the inability to see polarized light. A touch panel may be disposed on the surface side of the vehicle-mounted liquid crystal panel, and PET may be used as a film for preventing glass from scattering. In the case where PET is used as a film for preventing scattering of glass, there is a case where the polarization axis cannot be aligned and the polarized light cannot be seen. However, according to the optical sheet of the present invention, polarized light can be seen from all angles.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The optical sheet 1 of FIG. 1 includes a retardation film 2, a hard coat layer 3, and an adhesive layer 4.

The retardation film 2 is transparent because it is to transmit light, and is particularly colorless and transparent. The retardation film 2 is a 1/4 λ retardation film containing a polycarbonate resin as a main component.

The retardation film 2 may contain other optional components as long as it does not impair transparency and desired strength, and is preferably a main component composed of a polycarbonate resin having 90% by mass or more, and more preferably 98% by mass or more. The main component of the polycarbonate resin. Here, examples of the optional component include an ultraviolet absorber, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact modifier, a phase difference reducing agent, a matting agent, an antibacterial agent, and an antifungal agent.

The polycarbonate resin forming the retardation film 2 is not particularly limited, and any of a linear polycarbonate resin or a branched polycarbonate resin can be used. Further, as the polycarbonate-based resin forming the retardation film 2, a linear polycarbonate-based resin and a branched polycarbonate may also be used. A polycarbonate resin composed of a resin.

The linear polycarbonate-based resin is a linear aromatic polycarbonate-based resin produced by a known phosgene method or a melting method, and is composed of a carbonate component and a diphenol component. Examples of the precursor for introducing the carbonate component include carbonium chloride, diphenyl carbonate, and the like. Further, as the diphenol, there may be exemplified: 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 1,1. - bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)fluorene Alkane, 1,1-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclodecane, 1,1-bis(3,5-dimethyl-4-hydroxybenzene Base) cyclododecane, 4,4'-dihydroxydiphenyl ether, 4,4'-diphenyl sulfide, 4,4'-dihydroxy-3,3-dichlorodiphenyl ether, and the like. They may be used singly or in combination of two or more. The linear polycarbonate-based resin described above can be produced, for example, by the method described in U.S. Patent No. 3,896,672.

The branched polycarbonate resin is a polycarbonate resin produced by using a branching agent, and examples of the branching agent include: phloroglucinol, trimellitic acid, 1, 1, 1-three (4) -hydroxyphenyl)ethane, 1,1,2-tris(4-hydroxyphenyl)ethane, 1,1,2-tris(4-hydroxyphenyl)propane, 1,1,1-tri(4 -hydroxyphenyl)methane, 1,1,1-tris(4-hydroxyphenyl)propane, 1,1,1-tris(2-methyl-4-hydroxyphenyl)methane, 1,1,1- Tris(2-methyl-4-hydroxyphenyl)ethane, 1,1,1-tris(3-methyl-4-hydroxyphenyl)methane, 1,1,1-tris(3-methyl- 4-hydroxyphenyl)ethane, 1,1,1-tris(3,5-dimethyl-4-hydroxyphenyl)methane, 1,1,1-tris(3,5-dimethyl-4 -hydroxyphenyl)ethane, 1,1,1-tris(3-chloro-4-hydroxyphenyl)methane, 1,1,1-tris(3-chloro-4-hydroxyphenyl)ethane, 1 , 1,1 - tris(3,5-dichloro-4-hydroxyphenyl)methane, 1,1,1-tris(3,5-dichloro-4-hydroxyphenyl)ethane, 1,1,1-tri ( 3-bromo-4-hydroxyphenyl)methane, 1,1,1-tris(3-bromo-4-hydroxyphenyl)ethane, 1,1,1-tris(3,5-dibromo-4- Hydroxyphenyl)methane, 1,1,1-tris(3,5-dibromo-4-hydroxyphenyl)ethane, 4,4'-dihydroxy-2,5-dihydroxydiphenyl ether, and the like.

For example, the above-mentioned branched polycarbonate resin can be produced by exemplifying the method of arranging the aromatic diphenols from the aromatic phenols in the turbulent manner. The mixed solution of the polycarbonate oligomer, the aromatic diphenol, and the terminal blocking agent derived from the carbon bismuth chloride is stirred and reacted, and the alkalinity is added at the time when the viscosity of the reaction mixture solution is increased. The aqueous solution is passed, and the reaction mixture solution is brought into a laminar flow to carry out a reaction. The branched polycarbonate resin of the resin composition of the present invention in a range of from 5% by weight to 80% by weight in the polycarbonate resin is preferably contained in a range of from 10% by weight to 60% by weight. A branched polycarbonate resin of the resin composition of the present invention. This is because when the branched polycarbonate resin is less than 10% by weight, the tensile viscosity is lowered, and it is difficult to mold in extrusion molding. If the branched polycarbonate resin exceeds 80% by weight, the resin is sheared. The viscosity is increased and the moldability is lowered.

The photoelastic coefficient of the retardation film 2 is not particularly limited, and is, for example, preferably 40 × 10 ^-12 /Pa or less, more preferably 20 × 10 ^-12 /Pa or less. When the photoelastic coefficient of the retardation film 2 exceeds the above-described upper limit, the fluctuation of the phase difference due to the stress becomes large, and there is a problem that a desired phase difference cannot be obtained due to tension applied during the production of the optical sheet 1 or the like. In addition, there is also a problem that a change in phase difference due to direct sunlight and heat generation of the display increases. On the other hand, when the photoelastic coefficient of the retardation film 2 is within the above range, it is possible to suppress variation in phase difference when the retardation film 2 or the like is manufactured, and it is possible to suppress generation of direct sunlight and heat generation of the display. The change in phase difference. As a result, the optical sheet 1 can well maintain the birefringence imparted by the orientation, and can display a fine image.

The thickness (average thickness) of the retardation film 2 is not particularly limited, and is preferably, for example, 10 μm or more and 500 μm or less, more preferably 50 μm or more and 300 μm or less, and particularly preferably 100 μm or more and 200 μm or less. When the thickness of the retardation film 2 exceeds the above upper limit, there is a problem that the luminance of the liquid crystal display device is lowered, and there is a problem that the thickness of the liquid crystal display device is reduced. On the other hand, when the thickness of the retardation film 2 is less than the aforementioned lower limit, characteristics such as strength of the film and prevention of bending property are lowered, and there is a problem that the scattering prevention function is lowered. On the other hand, when the thickness of the retardation film 2 is within the above range, it is possible to suppress a decrease in the brightness of the liquid crystal display device, and it is possible to improve the strength of the film and to improve characteristics such as prevention of bending performance.

The glass transition temperature of the retardation film 2 is not particularly limited, and is, for example, preferably 120° C. or higher and 180° C. or lower, more preferably 130° C. or higher and 170° C. or lower, and particularly preferably 140° C. or higher and 160° C. the following. When the glass transition temperature of the retardation film 2 of the optical sheet 1 exceeds the above upper limit, there is a problem that stretching unevenness of the film is likely to occur at the time of stretching, and it is difficult to thermoform. On the other hand, if the glass transition temperature of the retardation film 2 of the optical sheet 1 is less than the aforementioned lower limit, there is a problem that heat resistance is deteriorated. On the other hand, when the glass transition temperature of the retardation film 2 of the optical sheet 1 is within the above range, thermoforming can be easily and reliably performed, and birefringence can be favorably maintained.

The method for producing the retardation film 2 is not particularly limited and can be used. A composition obtained by using a polycarbonate resin as a main component is formed into a film and stretched.

The film forming method is not particularly limited, and examples thereof include a known film forming method such as a solvent casting method, a melt extrusion method, and a calendering method.

Further, as a solvent used in a solvent casting method such as a casting method and a doctor blade method for extruding a solution from a die, dichloromethane, chloroform, dioxane, toluene, dimethylformamide may be exemplified. An organic solvent such as N-methylpyrrolidone. The solution concentration is, for example, preferably 10% by mass or more, and more preferably 15% by mass or more.

On the other hand, the melt extrusion method has high productivity because no solvent is used. Therefore, it is preferred to manufacture the retardation film 2 by a melt extrusion method.

As a production method by the melt extrusion method, a method may be exemplified by preparing a composition by a solution mixing method, a melt mixing method, or the like, and then performing film formation by melt-extruding the composition; directly by melt-extrusion combination A dry mixture of the materials is subjected to film formation or the like.

The solution mixing method may, for example, be a method (solution mixing) or the like: a polycarbonate resin and an optional additive added as needed are dissolved in a solvent for dissolution, uniformly mixed, and then filtered as needed. The foreign matter is removed by filtration (filtering or the like), and the mixture is poured into a solvent (or a poor solvent) in which the polycarbonate resin is insoluble, whereby the composition is recovered and further dried to obtain a composition as a target.

The melt-mixing method may be a method in which a polycarbonate resin and any additives added as needed are mixed as needed, and then melt-mixed (melt-kneaded) to obtain a composition. The solution mixing method can obtain a composition having a small heat history (heat history), but a large amount of solvent is used for the composition, and sometimes there is a solvent remaining in the composition. problem. The melt mixing method is preferred because the melt mixing method has no solvent problem and is economically advantageous.

As a method of forming a film by dry melt extrusion of a dry mixture of a composition containing a polycarbonate resin as a main component, a method of using a V-type mixer, a Henschel mixer, or a mechanical chemical device can be exemplified. After the mixing device is sufficiently mixed with the composition containing the polycarbonate resin as a main component, it is granulated by an extrusion granulator or a pelletizing machine as necessary, and melted by a vented twin-screw extruder or the like. The extruder was melt-kneaded and extruded from a flat mold (T-die) to thereby form a film by melting. Further, in the method of forming a film by directly melt-extruding a dry mixture, a part of each component may be premixed and supplied to the melt extruder independently of the remaining components.

In order to obtain a uniform retardation film 2, a melt extruder having no vent method can be used as the melt extruder. Further, it is also possible to use a melt extruder having a discharge port which can deaerate the moisture in the raw material and the volatile gas generated from the melt-kneaded resin. It is preferable to provide a vacuum pump on the exhaust port for efficiently discharging the generated moisture and volatile gas to the outside of the melt extruder. Further, a screen for removing foreign matter or the like mixed in the extruded raw material may be placed in a region before the mold portion of the melt extruder, so that foreign matter can be removed. Examples of the mesh described above include a metal mesh, a screen changer, a sintered metal plate (a disk screening program, etc.).

When the glass transition temperature of the composition is Tg, the resin temperature at the time of melt extrusion is preferably Tg or more, more preferably Tg + 50 ° C to Tg + 250 ° C, further preferably Tg + 80 ° C. ~Tg+200°C. The retardation film 2 can be stretched at the same time as the film formation or continuously with the film formation, thereby forming the desired 1/4 λ retardation film 2. In addition, it is also possible to use the aforementioned film formation. The film obtained by the method was additionally stretched, whereby a 1/4 λ retardation film 2 was obtained.

After the composition is formed into a film, the retardation film 2 can be obtained by uniaxial stretching or biaxial stretching. As the uniaxial stretching method, any method such as transverse uniaxial stretching by a tenter method, longitudinal uniaxial stretching between rolls, and roll-to-roll calendering method can be used. The stretching ratio is usually in the range of 1.01 to 5 times, and can be carried out depending on the tensile properties and optical properties (for example, refractive index distribution, in-plane retardation value, thickness direction retardation value, Nz coefficient) of the film. The stretching can be carried out in a one-stage manner or in a plurality of stages. Further, the temperature at the time of stretching is Tg - 30 ° C - Tg + 50 ° C, more preferably Tg - 10 ° C - Tg + 30 ° C. This is because if the molecular motion of the polymer is moderate within the aforementioned temperature range, the orientation is not easily relaxed by stretching, the orientation is easily suppressed, and desired optical characteristics are easily obtained, so the above range is ideal. .

The hard coat layer 3 is laminated on one surface side of the retardation film 2 to increase the hardness of the optical sheet 1. The material forming the hard coat layer 3 is not particularly limited. The hard coat layer 3 may be formed only of a resin, or may contain cerium oxide fine particles, a polymerization initiator, or the like.

Examples of the resin forming the hard coat layer 3 include a thermosetting resin, an active energy ray-curable resin, and the like.

For example, a coating composition containing a polymerizable monomer or a polymerizable oligomer of an active energy ray-curable resin is applied onto one surface of the retardation film 2 to crosslink the polymerizable monomer or the polymerizable oligomer. And/or polymerization, whereby the hard coat layer 3 can be formed.

The functional group of the above-mentioned active energy ray-curable polymerizable monomer or polymerizable oligomer is preferably an ultraviolet ray, an electron ray or a radiation polymerizable functional group, and particularly preferably an ultraviolet ray polymerizable functional group. As The ultraviolet-polymerizable functional group may, for example, be a vinyl-type unsaturated polymerizable functional group such as a (meth)acryl fluorenyl group, a vinyl group, a styryl group or an allyl group.

The coating composition is not particularly limited, but is preferably a coating composition containing an acrylic monomer or a urethane acrylate oligomer as a main component. The hardness can be improved by forming the hard coat layer 3 from the composition containing the above-mentioned single monomer or oligomer as a main component. Among them, it is particularly preferable to form the hard coat layer 3 from a composition containing both urethane acrylate and (meth) acrylate.

The total content of the urethane acrylate and the (meth) acrylate forming the hard coat layer 3 is preferably 45 mass% or more and 99 mass% or less, more preferably 50 mass% or more and 95 mass% or less. It is 60% by mass or more and 90% by mass or less. When the total content of the urethane acrylate and the (meth) acrylate forming the hard coat layer 3 exceeds the above upper limit, the start of photopolymerization becomes slow, and there is a problem that productivity is lowered. Further, when the total content of the urethane acrylate and the (meth) acrylate forming the hard coat layer 3 is less than the aforementioned lower limit, there is a problem that the flexibility, the abrasion resistance, the scratch resistance, and the like are lowered. On the other hand, if the total content of the urethane acrylate and the (meth) acrylate forming the hard coat layer 3 is within the above range, the productivity can be improved, and the flexibility and abrasion resistance can be well maintained. Scratch resistance and the like.

The urethane acrylate is not particularly limited, and a monomer or an oligomer may be used. Further, the number of functional groups of the urethane acrylate is not particularly limited, and may be a monofunctional group or a polyfunctional group. However, it is preferably a bifunctional group or more and a 6 functional group or less, and more preferably a bifunctional group or more and a trifunctional group or less. By making the number of functional groups of urethane acrylate in the aforementioned range Inside, the hard coat layer 3 can well maintain a balance of hardness and elongation. The urea alkane acrylate may be used singly or in combination of two or more.

The elongation of the urethane acrylate is preferably 20% or more and 80% or less, more preferably 25% or more and 75% or less. If the elongation of the urethane acrylate exceeds the above upper limit, there is a problem that the durability of the hard coat layer 3 is lowered. Further, if the elongation of the urethane acrylate is less than the aforementioned lower limit, there is a problem that cracks are generated at the time of molding. On the other hand, when the elongation of the urethane acrylate is within the above range, durability can be improved, and cracking during molding or the like can be prevented.

Further, the "elongation ratio" as used herein means a value measured in accordance with JIS K 5600.

The glass transition temperature of the resin formed of urethane acrylate is not particularly limited, but is preferably 40° C. or higher and 100° C. or lower, and more preferably 40° C. or higher and 80° C. or lower. By setting the glass transition temperature of the resin formed of urethane acrylate within the above range, the hardness and durability of the hard coat layer 3 at normal temperature can be improved.

The content of the urethane acrylate forming the hard coat layer 3 is not particularly limited, but is preferably 10% by mass or more and 90% by mass or less, and more preferably 15% by mass or more and 85% by mass or less. It is 20% by mass or more and 80% by mass or less. If the content of the urethane acrylate forming the hard coat layer 3 exceeds the above upper limit, there is a problem that abrasion resistance and coating film hardness are lowered. Further, if the content of the urethane acrylate forming the hard coat layer 3 is less than the aforementioned lower limit, the flexibility is lowered, and the risk of occurrence of cracks becomes high. On the other hand, if the content of the urethane acrylate forming the hard coat layer 3 is within the above range, the abrasion resistance and the coating film hardness can be well maintained, and moderate flexibility can be maintained, and cracking can be suppressed. produce.

The (meth) acrylate is not particularly limited, and a monomer or an oligomer may be used. The number of functional groups of the (meth) acrylate is not particularly limited, and may be a monofunctional group or a polyfunctional group. Further, by using a trifunctional or higher (meth) acrylate, the durability of the hard coat layer 3 can be improved. Further, the aforementioned (meth) acrylate may be a molecular structure having a polar group or a molecular structure having a low polarity. The (meth) acrylate may be used singly or in combination of two or more.

The polar group of the (meth) acrylate may, for example, be a hydroxyl group, a carboxyl group, an amine group or a guanamine group.

Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (methyl). Acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-(methyl) propylene methoxyethyl 2-hydroxypropyl phthalate, glycerol single (meth)acrylic acid ester, 3-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. Ester and the like.

The (meth) acrylate containing a carboxyl group may, for example, be a vinyl-type unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid or citraconic acid; It is also exemplified by 2-(methyl)acryloxyethyl succinic acid, 2-(methyl) propylene methoxyethyl phthalic acid, 2-(methyl) propylene methoxyethyl hexa Hydrogen phthalic acid and the like.

The (meth) acrylate containing an amino group may, for example, be monomethylaminoethyl (meth)acrylate or monoethylaminoethyl (meth)acrylate. A monoalkylamino (meth)acrylate such as an ester, monomethylaminopropyl (meth)acrylate or monoethylaminopropyl (meth)acrylate.

Examples of the (meth) acrylate-containing (meth) acrylate include (meth) acrylamide, N-methyl (meth) acrylamide, and N-methylol (meth) propylene hydride. Acrylamide such as amine.

Further, as the (meth) acrylate having a low polar molecular structure, a (meth) acrylate cyclic ester or an alkyl (meth) acrylate may be exemplified.

Examples of the (meth) acrylate alicyclic ester include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentenyloxyethyl (A). Acrylate, dicyclopentadienyl (meth) acrylate, tricyclodecenyl (meth) acrylate, norbornene (meth) acrylate, and the like.

The alkyl (meth)acrylate may, for example, be lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate or benzene. Methyl (meth) acrylate, stearyl (meth) acrylate, butyl (meth) acrylate, 1,6-hexanediol diacrylate, and the like.

The content of the (meth) acrylate forming the hard coat layer 3 is not particularly limited, but is preferably 5% by mass or more and 85% by mass or less, and more preferably 10% by mass or more and 80% by mass or less. Particularly preferred is 15% by mass or more and 75% by mass or less. If the content of the (meth) acrylate forming the hard coat layer 3 exceeds the above upper limit, the risk of occurrence of cracks during molding becomes large. Further, if the content of the (meth) acrylate forming the hard coat layer 3 is less than the aforementioned lower limit, there is a problem that abrasion resistance and coating film hardness are lowered. On the other hand, if the (meth) acrylate of the hard coat layer 3 is formed When the content is within the above range, the abrasion resistance and the coating film hardness can be well maintained, and moderate flexibility can be maintained, and cracking can be suppressed.

The polymerization initiator may, for example, be benzophenone, benzophenone, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoin ethyl ether or benzoin isopropyl ether. Benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzoin dimethyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-hydroxy- 2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylacetone- 1, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, bis(2,4-cyclopentadienyl)- Bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium(IV), 2-benzyl-2-dimethylamino-1-(4-morpholinium) Butylketone-1, 2,4,6-trimethylbenzimidyldiphenylphosphine oxide, and the like. These compounds may be used singly or in combination of a plurality of these compounds.

The pencil hardness of the hard coat layer 3 is not particularly limited, and is preferably, for example, H or more, more preferably 2H or more, and particularly preferably 3H or more. If the pencil hardness of the hard coat layer 3 of the optical sheet 1 is less than the aforementioned lower limit, there is a problem that the hardness is not good. On the other hand, if the pencil hardness of the hard coat layer 3 of the optical sheet 1 is within the above range, the hard coat layer 3 can be maintained in a desired hardness. Thereby, the performance of preventing the hard coat layer 3 of the optical sheet 1 from being damaged can be improved, and the processing of the optical sheet 1 can be further facilitated. In addition, "pencil hardness" means a value obtained based on the pencil scratch value described in 8.4 of the test method specified in JIS K5400.

The thickness (average thickness) of the hard coat layer 3 is not particularly limited, and for example, the thickness (average thickness) of the hard coat layer 3 can be 3 μm or more and 50 μm or less.

The method for producing the hard coat layer 3 is not particularly limited, and the active energy ray-curable resin may be applied to one surface of the retardation film 2, dried, and then irradiated with an active energy ray to be produced. The coating method of the active energy ray-curable resin is not particularly limited as long as it can uniformly apply the active energy ray-curable resin to one surface of the retardation film 2, and examples thereof include a spin coating method and a spray coating method. Various methods such as a slide coat method, a dipping method, a bar coating method, a roll coater method, and a screen printing method.

The adhesive layer 4 is laminated on the other surface side of the retardation film 2. The adhesive layer 4 can be formed using a known adhesive resin such as an acrylic resin or a urethane resin. Further, in the above-mentioned known adhesive resin, a thermoplastic resin such as a high-pressure method low-density polyethylene, an elastomer such as a synthetic rubber or a natural rubber, a bonding aid such as a terpene resin or a petroleum resin may be mixed. The adhesive layer 4 is formed.

As the adhesive resin forming the adhesive layer 4, an acrylic copolymer containing a structural unit derived from an alkyl acrylate monomer having an alkyl group having 8 or more and 20 or less carbon atoms is preferably used; a structural unit of at least one alicyclic monomer selected from the group consisting of cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and tricyclodecyl (meth) acrylate; and derived from a functional group The structural unit of the monomer. From the viewpoint of adhesion and suppression of generation of bubbles from the bonding target, as the alkyl acrylate monomer, 2-ethylhexyl acrylate, isooctyl acrylate, lauryl acrylate, and stearyl group are preferable. Acrylate, particularly preferred is 2-ethylhexyl acrylate. When the adhesion is small, the trace gas component generated from the adhering object stays on the interface to become a bubble, and there is a problem that the adhesion performance is lowered and the appearance is deteriorated. As the aforementioned alkyl acrylic acid The content of the structural unit of the ester monomer is preferably from 29.9% by mass to 55% by mass based on the total structural unit constituting the acrylic copolymer, from the viewpoint of maintaining the content of the other structural unit and maintaining a predetermined adhesive strength. More preferably, it is 35 mass% or more and 50 mass% or less. Further, cyclohexyl acrylate is suitably used as the alicyclic monomer from the viewpoint of adhesion and suppression of generation of bubbles from the bonded article. The content of the structural unit derived from the alicyclic monomer is preferably 50% by mass or more and 70% by mass or less, and more preferably 55% by mass or more, based on the entire structural unit constituting the acrylic copolymer. Below mass%. If the content of the structural unit derived from the alicyclic monomer exceeds the above upper limit, there is a problem that the viscosity is insufficient and the adhesive strength is lowered. On the other hand, if the content of the structural unit derived from the alicyclic monomer is less than the aforementioned lower limit, there is a problem that the generation of bubbles from the bonded article cannot be effectively prevented. The functional group-containing monomer may, for example, contain a hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate or various hydroxypropyl (meth) acrylates or a carboxyl group. Examples of the unsaturated monomer include (meth)acrylic acid, crotonic acid, fumaric acid, itaconic acid, and maleic acid. Among them, 2-hydroxyethyl acrylate is preferred from the viewpoint of adhesion and suppression of generation of bubbles from the adhesive member. The content of the structural unit derived from the functional group-containing monomer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less. When the content of the structural unit derived from the monomer having a functional group exceeds the above upper limit, the polarity of the adhesive layer 4 becomes large, and the adhesion to the low-polar surface is lowered. On the other hand, when the content of the structural unit derived from the monomer having a functional group is less than the above lower limit, the cohesive force of the adhesive layer 4 is lowered, and it is difficult to maintain the shape for the stress in the shear direction.

A well-known radical polymerization method etc. are mentioned as a manufacturing method of the said acrylic copolymer. For example, in an ester-based organic solvent such as a hydrocarbon or ethyl acetate such as toluene or xylene, the monomer is dissolved, and azobisisobutyronitrile, azobisisovaleronitrile, and benzoyl peroxide are added. The polymerization initiator is polymerized at about 50 to 90 ° C for about 3 to 20 hours to obtain an organic solvent solution of the acrylic copolymer.

The weight average molecular weight of the acrylic copolymer is, for example, 200,000 or more, preferably 400,000 or more and 2,000,000 or less, and more preferably 500,000 or more and 1.5 million or less. When the weight average molecular weight of the acrylic copolymer exceeds the above upper limit, there is a problem that polymerization at the time of polymer synthesis is difficult. On the other hand, if the weight average molecular weight of the acrylic copolymer is less than the aforementioned lower limit, the risk of generation of bubbles becomes large. Further, the weight average molecular weight is a value in terms of standard polystyrene measured by gel permeation chromatography.

In order to obtain sufficient adhesion as an adhesive, the glass transition temperature of the acrylic copolymer is usually -10 ° C or lower, preferably -70 ° C or higher and -20 ° C or lower.

The adhesive layer 4 can be laminated on the retardation film 2 by applying the adhesive solution to the other surface side of the retardation film 2 and drying it. Further, the adhesive solution may be previously coated on one surface of a separator and dried, and then bonded to the retardation film 2, whereby the adhesive layer 4 may be laminated on the retardation film. 2 on.

The thickness (average thickness) of the adhesive layer 4 is not particularly limited, and the thickness (average thickness) of the adhesive layer 4 can be, for example, 10 μm or more and 40 μm or less.

Although the haze of the optical sheet 1 is not particularly limited, the haze of the optical sheet 1 is preferably 2% or less, more preferably 0.5% or less. Such as If the haze of the optical sheet 1 exceeds the above upper limit, there is a problem that the sharpness of the image displayed by the liquid crystal display device is lowered and the visibility of the image is lowered.

The outer haze of the optical sheet 1 obtained as a difference (Ha-Hw) between the haze (Ha) of the film in air and the haze (Hw) of the film in water is preferably 1.0% or less. More preferably, it is 0.5% or less. When the external haze of the optical sheet 1 exceeds the above upper limit, there is a problem that the unevenness of the surface becomes relatively large and the phase difference accuracy is lowered.

The total light transmittance of the optical sheet 1 is not particularly limited, but is preferably 87% or more, and more preferably 90% or more. If the total light transmittance of the optical sheet 1 is less than the aforementioned lower limit, there is a problem that the light cannot be sufficiently transmitted, resulting in a decrease in visibility.

When the optical sheet 1 is adhered to the glass substrate of the touch panel by the adhesive layer 4, the glass substrate of the touch panel can be effectively prevented from being damaged, and the function of preventing scattering of debris generated during breakage or the like can be improved. In particular, by adhering the adhesive layer 4 of the optical sheet 1 to the back surface of the glass substrate of the touch panel, it is possible to effectively improve the function of preventing scattering of the glass substrate fragments or the like when the touch panel is broken.

Since the optical sheet 1 has the hard coat layer 3 on one surface side of the retardation film 2, it is possible to improve the performance of preventing damage during manufacturing and transportation, and to prevent deterioration of optical function and deterioration of appearance. In addition, since the optical sheet 1 uses a polycarbonate resin as a main component of the retardation film 2, impact resistance can be improved. Even if the optical sheet 1 is used for a touch panel or the like, in the case where the surface of the touch panel is pressed hard or dropped, the phase difference film 2 and the other layer side laminated on the retardation film 2 are bonded. The layer 4 can also prevent the glass substrate of the touch panel from being damaged. As a result, the optical sheet 1 can effectively prevent scattering of the glass substrate fragments and the like.

The touch panel 11 of FIG. 2 includes glass substrates 12, 14, an electrode layer 13, and an optical sheet 1. An input region in which a finger tip is input is formed in a substantially central region on the surface side of the glass substrate 12. The optical sheet 1 is laminated on the back surface of the glass substrate 12 by adhering the adhesive layer 4 to the back surface of the glass substrate 12. The electrode layer 13 is a transparent conductive film, and the first electrode and the second electrode extend in a direction crossing each other. The electrode layer 13 is laminated on the surface side of the glass substrate 14. The capacitance of the touch panel 11 changes before and after the input area of the finger touch glass substrate 12. The touch panel 11 is configured in such a manner that the first electrode and the second electrode detect a change in capacitance to determine a touch position. Further, a liquid crystal panel (not shown) is disposed on the back side of the touch panel 11.

Since the optical sheet 1 is disposed on the touch panel 11, the linearly polarized light emitted from the liquid crystal display panel is converted into circularly polarized light by the optical sheet 1. Therefore, in the case where the person watching is viewing the touch panel 11 with the polarized sunglasses, it is possible to suppress the occurrence of the rainbow pattern and to see the polarized light at all angles.

The touch panel 21 of FIG. 3 includes glass substrates 12, 14, an electrode layer 13, a polarizing plate 22, and an optical sheet 1. The optical sheet 1 (first optical sheet) is laminated on the polarizing plate 22 by adhering the adhesive layer 4 to the back side of the polarizing plate 22. Further, the optical sheet 1 (second optical sheet) is laminated on the glass substrate 14 by adhering the adhesive layer 4 to the back side of the glass substrate 14.

The function of the touch panel 21 to block external light will be described. The external light incident from the surface of the polarizing plate 22 and transmitted through the polarizing plate 22 is converted into circularly polarized light by being transmitted through the first optical sheet. The circularly polarized light is reflected and incident from the back side of the first optical sheet. Here, the first optical sheet is disposed such that circularly polarized light incident from the back side becomes perpendicular to the transmission axis direction of the polarizing plate 22. The linearly polarized light is emitted from the surface side of the first optical sheet. Therefore, the linearly polarized light emitted from the surface side of the first optical sheet is blocked by the polarizing plate 22. In other words, the light incident on the surface of the polarizing plate 22 and transmitted through the polarizing plate 22 is reflected, and is incident on the back side of the polarizing plate 22 again. However, the reflected light is blocked by the polarizing plate 22 and cannot be removed from the touch panel 21. The side of the surface is shot. Thereby, the touch panel 21 can maintain excellent visibility.

On the other hand, the light emitted from the liquid crystal panel (not shown) disposed on the back side of the touch panel 21 is transmitted through the second optical sheet and the first optical sheet, and becomes a straight line in the transmission axis direction of the polarizing plate 22. The polarized light is incident on the back side of the polarizing plate 22. Therefore, according to the touch panel 21, the display of the liquid crystal panel (not shown) disposed on the back side of the touch panel 21 can be clearly seen.

Since the touch panel 21 has the hard coat layer 3 on one surface side of the retardation film 2 of the optical sheet 1, it is possible to improve the performance of preventing the optical sheet 1 from being damaged during the manufacturing and transportation. The optical function is reduced and the appearance is deteriorated. Further, in the touch panel 21, since the polycarbonate resin is used as the main component of the retardation film 2 of the optical sheet 1, the impact resistance can be improved. Even in the case where the surface of the touch panel 21 is pressed hard or the touch panel 21 is dropped, the phase difference film 2 and the adhesive layer 4 laminated on the other surface side of the retardation film 2 are also It is possible to prevent the glass substrates 12, 14 and the like of the touch panel 21 from being damaged. As a result, the touch panel 21 can effectively prevent the scattering of fragments or the like of the glass substrates 12 and 14.

Further, the optical sheet and the touch panel of the present invention can be variously modified and improved in addition to the foregoing. For example, the hard coat layer of the optical sheet may be composed of two or more layers. In addition, the optical sheet may also be laminated with other layers on the hard coat layer (for example, a UV absorbing layer, an antistatic layer, and an anti-static layer). Antireflection layer, etc.). The retardation film and the hard coat layer of the optical sheet, or the retardation film and the adhesive layer may be laminated via another layer. The optical sheet can be used for various liquid crystal display modules such as a stereoscopic image display device in addition to the touch panel. The optical sheet can be used for various touch panels such as a resistive film method, a capacitive method, or an electromagnetic induction method. Further, the touch panel need not include a pair of the aforementioned optical sheets (the first optical sheet and the second optical sheet). The optical sheet can be adhered to the surface of the glass substrate of the touch panel, or can be attached to the surface side and the back side of the touch panel. The retardation film of the optical sheet does not need to be a 1/4 λ retardation film, and may be a 1/2 λ retardation film, a 3/4 λ retardation film, or the like.

Industrial applicability

As described above, since the optical sheet of the present invention can be prevented from being damaged at the time of production and transportation, it is possible to prevent deterioration of optical function and deterioration of appearance. Therefore, the optical sheet of the present invention and the touch panel using the same can suppress the deterioration of the optical function and the deterioration of the appearance, and are suitable for use in a liquid crystal display device capable of performing image display with high visibility and contrast. .

1‧‧‧ optical film

2‧‧‧ phase difference film

3‧‧‧hard coating

4‧‧‧Adhesive layer

11‧‧‧Touch panel

12‧‧‧ glass substrate

13‧‧‧Electrode layer

14‧‧‧ glass substrate

21‧‧‧ touch panel

22‧‧‧Polar plate

Fig. 1 is a cross-sectional view schematically showing an optical sheet according to an embodiment of the present invention.

2 is a cross-sectional view schematically showing a touch panel according to an embodiment of the present invention.

3 is a cross-sectional view schematically showing a touch panel different from the touch panel of FIG. 2 .

1‧‧‧ optical film

2‧‧‧ phase difference film

3‧‧‧hard coating

4‧‧‧Adhesive layer

Claims (7)

An optical sheet comprising: a retardation film comprising a polycarbonate resin as a main component; a hard coat layer laminated on one surface side of the retardation film; and an adhesive layer laminated on the retardation film The other side of the surface; the adhesive layer is adhered to the glass substrate of the touch panel and has scattering prevention property; the hard coating layer contains urethane acrylate and (meth) acrylate, and urethane acrylic acid The elongation of the ester is 20% or more and 80% or less. The optical sheet according to claim 1, wherein the retardation film has a photoelastic coefficient of 40 × 10 ^-12 /Pa or less. The optical sheet according to claim 1, wherein the retardation film has an average thickness of 10 μm or more and 500 μm or less. An optical sheet as described in claim 1, wherein the haze is 2% or less. The optical sheet according to claim 1, wherein the total light transmittance is 87% or more. The optical sheet according to claim 1, wherein the retardation film has a glass transition temperature (Tg) of 120 ° C or more and 180 ° C or less. A touch panel comprising: a glass substrate; and the optical sheet according to any one of claims 1 to 6, which is adhered to the glass substrate by the adhesive layer.