Method for manufacturing optical laminate, and method for manufacturing image display device

Abstract

This disclosure provides a method for manufacturing an optical laminate capable of effectively reducing reflection unevenness of external light reflection. According to an embodiment of the present invention, this method serves to manufacture an optical laminate in which a first translucent optical film and a second translucent optical film are bonded by an adhesive layer. The method includes: a bonding step for bonding the first translucent optical film and the second translucent optical film via an aqueous adhesive solution; and a curing step for curing the aqueous adhesive solution to form the adhesive layer, which has a thickness of 50 nm or less.

Description

Method for manufacturing optical laminate and method for manufacturing image display device

[0001] The present invention relates to a method for manufacturing an optical laminate and a method for manufacturing an image display device.

[0002] Image display devices such as liquid crystal display devices and organic EL display devices typically include an optical laminate including a plurality of light-transmitting optical films. In such optical laminates, a pressure-sensitive adhesive is used to bond the plurality of light-transmitting optical films together.

[0003] 2. Description of the Related Art In image display devices, the occurrence of reflection unevenness that is visually recognized due to reflection of external light in a non-illuminated (OFF) state has become a problem.

[0004] Recently, a molecular adhesive technique for bonding by chemical bonding has been reported as a pressure-sensitive adhesive used in optical laminates (Patent Document 1).

[0005] International Publication No. 2022 / 172755

[0006] An object of the present invention is to provide a method for producing an optical laminate that can effectively reduce reflection unevenness in external light reflection.

[0007] An image display device typically includes an optical laminate in which many optical films are laminated, in addition to a display element that forms an image. This optical laminate serves to improve the display performance of the image display device and to add an anti-reflection function, and is an essential component of the image display device. From the viewpoint of power consumption, the mainstream image display device typically displays black in a non-illuminated state, which is called normally black.

[0008] When external light (visible light) enters an image display device, reflection occurs at the interfaces of the optical elements that make up the optical laminate. Such reflection of light at the interfaces of the optical elements is particularly noticeable in organic EL displays when the display is not lit. Furthermore, when the thickness between optical elements is in the range of several hundred nanometers to several micrometers, the reflected light appears colored due to interference of the reflected light at adjacent interfaces.

[0009] Recently, the occurrence of reflection unevenness, which is visible due to the reflection of external light when the image display device is turned off, has become a problem. Such reflection unevenness is observed as a change in the reflection spectrum, and is typically seen as a relatively strong pink reflection in a weak green reflected light. It is thought that the cause of reflection unevenness is coloration that occurs when reflected light interferes at two thin interfaces between optical elements.

[0010] Therefore, the present inventors have investigated the cause of such reflection unevenness. First, they considered that the reflection unevenness is caused by a change in wavelength of constructive interference caused by a change in thickness of two thin interfaces between optical elements, resulting in a strong observed color change. Then, they considered that the optical elements, particularly the interface between the adhesive layer bonding the translucent optical film and the translucent optical film as an adjacent layer, have a significant influence on this reflection unevenness. They considered that the occurrence of unevenness or waviness in the thickness of the adhesive layer causes a change in the interference wavelength at which the reflected light generated at the two interfaces sandwiching the adhesive layer constructively or destructively interferes, and that this is observed as color unevenness.

[0011] Furthermore, it is considered that when there is a large difference in refractive index between the pressure-sensitive adhesive layer and the light-transmitting optical film bonded adjacent to it, the presence of an interface between the pressure-sensitive adhesive layer and the optical element bonded adjacent to it, particularly the light-transmitting optical film, causes noticeable reflection of external light.

[0012] Therefore, the present inventors considered that when thickness unevenness or waviness occurs in the pressure-sensitive adhesive layer, there are parts where the optical path length of reflected light (the product of thickness and refractive index) differs within the plane, causing interference unevenness of reflected light at the interface, and as a result, the reflection unevenness becomes noticeable. They investigated whether the problem could be solved by technical means that take the optical path length into consideration, and considered that if the optical path length is made sufficiently small for the target visible light wavelength, the pressure-sensitive adhesive layer will lose its sensitivity to light and interference of reflected light will not occur.

[0013]

[0013] Based on the above-mentioned concept, the present inventors have conducted extensive studies and have found that, taking a thickness of 1 / 10 of the wavelength of external light as a standard, if an adhesive layer having a thickness thinner than 1 / 10 of the wavelength of external light is used as the pressure-sensitive adhesive layer, even if there is a large difference in refractive index between the adhesive layer and the adjacent light-transmitting optical film laminated thereto, the optical path length (product of thickness and refractive index) of the adhesive layer can be made small because the thickness of the adhesive layer is thin, thereby eliminating the sensitivity of the adhesive layer to light and preventing interference of reflected light. This is thought to be because, when the thickness of the adhesive layer is set as above, the adhesive layer can be treated as if it does not exist to light, and even if there is thickness unevenness in the adhesive layer, the adhesive layer itself is in a state that is not detectable to light in the first place, so there is no interference of reflected light due to interfacial reflection at the two interfaces between the adhesive layer and the adjacent layer, and therefore the reflection unevenness itself is not observed. In particular, since the wavelength of external light with high luminosity is in the 500 to 610 nm range, centered around 555 nm, where the maximum relative luminosity is achieved, it was discovered that if the thickness of the adhesive layer is 1 / 10 of 500 nm, i.e., 50 nm or less, reflection unevenness at wavelengths longer than 500 nm is further suppressed, and the thinner the thickness, the greater the effect of suppressing reflection unevenness. If the thickness of the adhesive layer is further reduced, for example to 30 nm, even if the adhesive layer has a high refractive index of about 1.60, the optical path length will be 48 nm, which is about 1 / 8 to 1 / 16 of the visible light wavelength (380 nm to 780 nm). For light with wavelengths of 500 nm or longer, which are particularly influential as a cause of reflection unevenness, the optical path length will be less than 1 / 10, resulting in an extremely high effect of suppressing reflection unevenness.

[0014] When the adhesive layer is sufficiently thick, for example, more than 20 μm, there are many wavelengths in the visible light range that interfere with each other constructively and destructively due to the interference of reflected light at the interface, and therefore the order of interference is sufficiently large, making it difficult to observe interference colors and resulting in achromatic reflected light. Therefore, even if the thickness of the adhesive layer varies, reflection unevenness as color unevenness is not observed in practice.

[0015] [1] A method for producing an optical laminate according to an embodiment of the present invention is a method for producing an optical laminate in which a first light-transmitting optical film and a second light-transmitting optical film are bonded together with an adhesive layer, the method comprising: a laminating step of laminating the first light-transmitting optical film and the second light-transmitting optical film together via an aqueous adhesive solution; and a curing step of curing the aqueous adhesive solution to form the adhesive layer having a thickness of 50 nm or less. [2] In the production method described in [1] above, water may be removed from the aqueous adhesive solution in the curing step. [3] The production method described in [1] or [2] above may further comprise a contacting step of contacting the aqueous adhesive solution with at least one selected from the group consisting of the first light-transmitting optical film and the second light-transmitting optical film. [4] In the production method described in [3] above, a liquid layer of the aqueous adhesive solution may be formed in the contacting step, and the liquid layer may not come into contact with air between performing the contacting step and performing the laminating step. [5] In the manufacturing method according to [3] or [4] above, the time from carrying out the contacting step to carrying out the laminating step may be 1 second or less. [6] In the manufacturing method according to any of [3] to [5] above, the contacting step may be carried out by placing the second light-transmitting optical film on the surface of the first light-transmitting optical film and supplying the aqueous adhesive solution to the laminating portion between the first light-transmitting optical film and the second light-transmitting optical film. [7] In the manufacturing method according to [6] above, a puddle of the aqueous adhesive solution may be formed by supplying the aqueous adhesive solution to the laminating portion. [8] In the manufacturing method according to any of [1] to [7] above, the laminating step may involve laminating the first light-transmitting optical film and the second light-transmitting optical film by pressure bonding. [9] In the manufacturing method according to any of [1] to [8] above, the aqueous adhesive solution may contain at least one amino compound.

[10] In the production method according to the above [9], the amino compound may be an amino-based silane coupling agent.

[11] In the manufacturing method according to any one of [1] to [8] above, the aqueous adhesive solution may contain at least one amino compound and one epoxy compound.

[12] In the manufacturing method according to

[11] above, the total content of the amino compound and the epoxy compound in the aqueous adhesive solution may be 0.5% by weight to 10% by weight.

[13] In the manufacturing method according to any one of [1] to

[12] above, at least one of the first light-transmitting optical film and the second light-transmitting optical film may have an in-plane refractive index of 1.50 or more.

[14] In the manufacturing method according to any one of [1] to

[13] above, at least one of the first light-transmitting optical film and the second light-transmitting optical film may be a retardation film.

[15] In the manufacturing method according to any one of [1] to

[14] above, the thickness of the adhesive layer may be less than 30 nm.

[16] A method for manufacturing an image display device according to an embodiment of the present invention includes forming an image display device using an optical laminate formed by the manufacturing method described in any one of [1] to

[15] above.

[0016] According to an embodiment of the present invention, it is possible to provide a method for manufacturing an optical laminate that can effectively reduce reflection unevenness in external light reflection.

[0017] Fig. 1 is a schematic cross-sectional view showing an example of an optical laminate produced by the production method of this embodiment. Fig. 2 is a view for explaining a preferred example of a method for producing an optical laminate according to an embodiment of the present invention. Fig. 3 is a view for explaining a preferred example of a method for producing an optical laminate according to an embodiment of the present invention. Fig. 4 is a view for explaining a preferred example of a method for producing an optical laminate according to an embodiment of the present invention. Fig. 5 is a schematic cross-sectional view showing an example of an optical member including an optical laminate produced by the production method of this embodiment.

[0018] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is commonly used as an SI unit indicating weight, and vice versa.

[0019] The definitions of terms and symbols used in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. Note that, when the expression "in-plane refractive index" appears in this specification, it refers to "nx". (2) In-Plane Retardation (Re) "Re(λ)" is the in-plane retardation of a film measured at 23°C with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation of a film measured at 23°C with light having a wavelength of 550 nm. Re(λ) is calculated by the formula: Re = (nx - ny) × d, where d (nm) is the thickness of the film. (3) Thickness Direction Retardation (Rth) "Rth(λ)" is the thickness direction retardation of a film measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the thickness direction retardation of a film measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth = (nx - nz) x d, where d (nm) is the thickness of the film.

[0020] 1. Method for Producing an Optical Laminate A production method according to an embodiment of the present invention is a method for producing an optical laminate in which a first light-transmitting optical film and a second light-transmitting optical film are bonded together with an adhesive layer. This production method includes a laminating step of bonding the first light-transmitting optical film and the second light-transmitting optical film together via an aqueous adhesive solution, and a curing step of curing the aqueous adhesive solution to form an adhesive layer having a thickness of 50 nm or less. In this specification, the term "aqueous adhesive solution" refers to an adhesive solution containing water as a solvent. In this specification, the first light-transmitting optical film and the second light-transmitting optical film may be simply referred to as "light-transmitting optical films" for convenience of explanation.

[0021] Fig. 1 is a schematic cross-sectional view showing an example of an optical laminate produced by the production method of this embodiment. The optical laminate 100 shown in Fig. 1 includes a first light-transmitting optical film 10, an adhesive layer 30, and a second light-transmitting optical film 20, in this order. In the optical laminate 100, the first light-transmitting optical film 10 and the second light-transmitting optical film 20 are bonded together by the adhesive layer 30. The components of the optical laminate will be described in detail below.

[0022] <1-1. Contacting Step> The manufacturing method according to an embodiment of the present invention further includes, for example, a contacting step of contacting at least one selected from the group consisting of a first light-transmitting optical film and a second light-transmitting optical film with an aqueous adhesive solution. In the contacting step, it is preferable to contact both the first light-transmitting optical film and the second light-transmitting optical film with the aqueous adhesive solution. In detail, the contacting step can be a coating step of coating the aqueous adhesive solution on at least one selected from the group consisting of the first light-transmitting optical film and the second light-transmitting optical film.

[0023] Any appropriate method can be used to bring the aqueous adhesive solution into contact with the light-transmitting optical film as long as the effects of the present invention are not impaired. Examples of such methods include a method of immersing the light-transmitting optical film in the aqueous adhesive solution (dip coating), curtain coating, spray coating, bar coating, rod coating, roll coating, die coating, and gravure coating. The contacting step is preferably carried out by the method described below in Section <1-4. A Preferred Example of the Method for Producing an Optical Laminate>.

[0024] In the contacting step, the aqueous adhesive solution comes into contact with the translucent optical film, thereby forming a liquid layer (coating film) of the aqueous adhesive solution. In the manufacturing method according to an embodiment of the present invention, it is preferable that the liquid layer of the aqueous adhesive solution does not come into contact with the external atmosphere (particularly air) between the contacting step and the laminating step. In this case, drying of the liquid layer tends to be suppressed. However, in some cases, the liquid layer may come into contact with the external atmosphere between the contacting step and the laminating step.

[0025] The thickness of the liquid layer formed in the contacting step is not particularly limited as long as an adhesive layer of the desired thickness is formed in the curing step, and may be, for example, 10 μm or less, 5 μm or less, 3 μm or less, or even 1 μm or less. The lower limit of the thickness is, for example, 0.05 μm or more.

[0026] The contact step is typically performed before the laminating step. In the manufacturing method according to the embodiment of the present invention, the laminating step is preferably performed immediately after the contact step. As an example, the time from performing the contact step to performing the laminating step is preferably 5 seconds or less, and may be 3 seconds or less, 1 second or less, 0.5 seconds or less, 0.1 seconds or less, or even 0.01 seconds or less. The contact step and the laminating step may be performed approximately simultaneously.

[0027] In the manufacturing method according to an embodiment of the present invention, before the contacting step, any appropriate activation treatment may be applied to the surface of at least one selected from the group consisting of the first light-transmitting optical film and the second light-transmitting optical film, as long as the effects of the present invention are not impaired (activation step). Examples of such activation treatments include corona treatment, plasma treatment, saponification treatment, and low-pressure UV treatment. In particular, when a light-transmitting optical film made of a material that does not have polar groups is used, polar groups such as hydroxyl groups may be introduced into the surface of the light-transmitting optical film by the activation treatment.

[0028] <1-2. Bonding Step> As described above, the bonding step is performed by bonding the first light-transmitting optical film and the second light-transmitting optical film together via the aqueous adhesive solution. In particular, the first light-transmitting optical film and the second light-transmitting optical film can be bonded together via the liquid film of the aqueous adhesive solution formed in the contacting step.

[0029] Any appropriate method can be used to bond the first and second light-transmitting optical films together, as long as the effects of the present invention are not impaired. Examples of such methods include bonding by pressure using a laminator or the like. In the bonding step, the first and second light-transmitting optical films are preferably bonded together by pressure bonding. The bonding step is preferably carried out by the method described below in Section <1-4. A Preferred Example of the Method for Manufacturing an Optical Laminate>.

[0030] <1-3. Curing step> As described above, the curing step is performed by curing the aqueous adhesive solution to form an adhesive layer having a thickness of 50 nm or less. In detail, the adhesive layer can be formed by curing a liquid film of the aqueous adhesive solution.

[0031] Any appropriate method can be used to cure the aqueous adhesive solution as long as it does not impair the effects of the present invention. Examples of such methods include curing by heating. Conditions for curing by heating, such as temperature and time, can be any appropriate conditions depending on the composition of the aqueous adhesive solution. Examples of such conditions include a heating temperature of 40°C to 150°C and a heating time of 1 minute to 20 minutes.

[0032] In the curing step, it is preferable to remove water from the aqueous adhesive solution. Specifically, it is preferable that water is removed from the aqueous adhesive solution by migrating from the aqueous adhesive solution to the translucent optical film and then releasing the water in a gaseous state to the outside of the translucent optical film. In the manufacturing method according to an embodiment of the present invention, water is easily removed from the aqueous adhesive solution when the aqueous adhesive solution is heated and cured. Note that, when the aqueous adhesive solution contains a solvent other than water, it is preferable that the other solvent is also removed from the aqueous adhesive solution in the curing step. If water is sufficiently removed from the aqueous adhesive solution in the curing step, in the produced optical laminate, little water migrates from the adhesive layer to the translucent optical film, and as a result, the translucent optical film tends to be less susceptible to appearance defects such as galvanized iron wrinkles.

[0033] 2A to 2C are views for explaining a preferred example of a manufacturing method according to an embodiment of the present invention. In detail, Fig. 2A is a schematic perspective view of an apparatus that performs the contacting step and the laminating step, Fig. 2B is a schematic side view of the apparatus, and Fig. 2C is a schematic cross-sectional view of the apparatus.

[0034] 2A to 2C, in this example, the first light-transmitting optical film 10 and the second light-transmitting optical film 20 are each transported between a pair of rolls (laminating device) 4 and pass between the rolls 4 from top to bottom. However, the transport direction of the light-transmitting optical films 10 and 20 is not limited to the example of FIGS. 2A to 2C. The light-transmitting optical films 10 and 20 may also be transported so as to pass between the rolls 4 in the horizontal direction.

[0035] 2A to 2C, the first light-transmitting optical film 10 and the second light-transmitting optical film 20 are preferably both long. The first light-transmitting optical film 10 and the second light-transmitting optical film 20 may each be laminated with a substrate. The transport speeds of the first light-transmitting optical film 10 and the second light-transmitting optical film 20 are preferably the same, for example, 2 m / min to 50 m / min.

[0036] In the example of FIGS. 2A to 2C , the second light-transmitting optical film 20 is disposed on the surface of the first light-transmitting optical film 10 near the gap between the rolls 4. In other words, the first light-transmitting optical film 10 and the second light-transmitting optical film 20 are superimposed. An aqueous adhesive solution is supplied from a supply nozzle 1 to the bonded portion (the superimposed portion) of the first light-transmitting optical film 10 and the second light-transmitting optical film 20. The above-mentioned contacting step can be carried out by supplying the aqueous adhesive solution to the bonded portion. The method for supplying the aqueous adhesive solution is not particularly limited, and for example, a dropping method can be employed. The position from which the aqueous adhesive solution is supplied is not particularly limited, and may be determined appropriately as needed. For example, the aqueous adhesive solution may be dropped from near the bonded portion, near the center in the width direction of the light-transmitting optical films 10 and 20. Alternatively, the aqueous adhesive solution may be dropped at a position a predetermined distance away from the bonded portion of the translucent optical films 10 and 20, and the aqueous adhesive solution may be poured into the bonded portion. In this case, the translucent optical films 10 and 20 must be inclined at a predetermined angle above the horizontal. Furthermore, the dropping position may be multiple positions.

[0037] By supplying the aqueous adhesive solution to the bonded portion, a puddle 31 of the aqueous adhesive solution may be formed. The puddle 31 is, for example, above the bonded portion and in contact with the bonded portion. The puddle 31 may be formed over the entire width of the translucent optical films 10 and 20. By the translucent optical films 10 and 20 passing through the puddle 31, the aqueous adhesive solution can be evenly applied to the translucent optical films 10 and 20.

[0038] The supply amount and supply speed of the aqueous adhesive solution are appropriately set to optimal values ​​depending on the type, viscosity, etc. of the aqueous adhesive solution used. The type and viscosity of the aqueous adhesive solution will be described later in the section <1-5. Aqueous adhesive solution>.

[0039] Note that the aqueous adhesive solution that tends to flow toward both ends in the width direction of the translucent optical films 10 and 20 may be supplied from both ends in the width direction of the translucent optical films 10 and 20 toward the center. The supply of the liquid is performed, for example, using a supply nozzle 2. The supply nozzles 2 may be disposed at both ends in the width direction of the translucent optical films 10 and 20. This configuration is suitable when the bonded portion extends approximately horizontally and excess aqueous adhesive solution flows toward both ends in the width direction. However, when the translucent optical films 10 and 20 are disposed tilted to one side or when the pair of rolls 4 are disposed tilted, the bonded portion is also correspondingly tilted, so the aqueous adhesive solution flows to one side. In this case, it is sufficient to dispose the supply nozzle 2 only downstream of the aqueous adhesive solution. The supply of liquid from the supply nozzle 2 blocks excess aqueous adhesive solution that tends to flow toward both ends in the width direction of the translucent optical films 10 and 20, thereby preventing leakage of the aqueous adhesive solution.

[0040] It is preferable that the amount and pressure of the liquid discharged from the supply nozzle 2 be kept within a range that can prevent the flow of the aqueous adhesive solution. If the amount of liquid discharged is greater than necessary, the aqueous adhesive solution may be excessively diluted, resulting in a decrease in adhesiveness. Furthermore, the direction of the liquid discharge is not limited to the direction toward the center in the width direction, and various changes are possible within a range that can prevent the outflow of the aqueous adhesive solution.

[0041] The supply nozzle 2 is provided, for example, so that its supply port 2 a is located inside in the width direction of both ends of the light-transmitting optical films 10 and 20. This makes it possible to prevent the liquid from leaking from both ends of the light-transmitting optical films 10 and 20.

[0042] The liquid to be ejected from the supply nozzle 2 is not particularly limited, and examples thereof include organic solvents such as alcohols such as methanol, ethanol, and propyl alcohol; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as methylene chloride and chloroform, as well as water.

[0043] 2A and 2B , a suction nozzle 3 may be further provided for suctioning and removing excess aqueous adhesive solution that does not contribute to bonding the translucent optical films 10 and 20. This allows the optimal amount of aqueous adhesive solution for bonding to be evenly supplied to the entire surfaces of the translucent optical films 10 and 20, including both ends, resulting in an optical laminate with uniform in-plane adhesion and no in-plane unevenness. More specifically, the suction nozzle 3 preferably does not suction excess aqueous adhesive solution itself, but rather suctions aqueous adhesive solution that has been diluted with liquid. This is because suctioning the aqueous adhesive solution itself would hinder smooth suction, and the aqueous adhesive solution would eventually solidify and clog the suction port 3 a of the suction nozzle 3.

[0044] The suction nozzle 3 is preferably provided so that its suction ports 3a are located near both ends in the width direction of the light-transmitting optical films 10 and 20. This is because suction is performed on the aqueous adhesive solution diluted with liquid. By arranging the suction nozzle 3 separately from the supply nozzle 2, the structure can be simplified, making cleaning and maintenance easier.

[0045] The shape of the opening of the suction port 3 a of the suction nozzle 3 is preferably flattened in a predetermined direction. Examples of the shape of the opening include various shapes such as an ellipse, a semicircle, a rectangle, a rectangle with rounded chamfered corners, a flattened diamond, and a flattened cloud shape. The suction port 3 a is preferably positioned so that the flattening direction of the opening is approximately parallel to the width direction of the translucent optical films 10 and 20. This allows the suction port 3 a to be brought close to the bonded portion of the translucent optical films 10 and 20, allowing excess aqueous adhesive solution to be efficiently removed by suction.

[0046] 2A to 2C , the light-transmitting optical films 10 and 20 pass through the liquid puddle 31, thereby forming a liquid layer 35 ( FIG. 2C ) of the aqueous adhesive solution between the light-transmitting optical films 10 and 20. With the liquid layer 35 formed, the light-transmitting optical films 10 and 20 continuously pass between the pair of rolls 4. By passing between the pair of rolls 4, the first light-transmitting optical film 10 and the second light-transmitting optical film 20 can be bonded together via the liquid layer 35 by pressure bonding (laminating step). In the example of FIGS. 2A to 2C , the laminating step is performed immediately after the liquid layer 35 is formed, and therefore the liquid layer 35 does not come into contact with the external atmosphere during the period from the contacting step to the laminating step.

[0047] The roll 4 is not particularly limited, and various conventionally known rolls can be used. However, from the viewpoint of improving the appearance of the optical laminate to be produced, a roll with high surface precision is preferred. The material of the roll 4 is not particularly limited, and examples thereof include metal and rubber. Note that the lamination step may be performed using a lamination device other than the roll 4 (for example, a planar pressure-bonding means).

[0048] The translucent optical films 10 and 20 that have passed between the pair of rolls 4 are transported, for example, in a state of being stuck together to an apparatus (not shown) for carrying out a curing step, and the curing step is carried out in the apparatus. Examples of this apparatus include a heating apparatus such as an oven.

[0049] When the contacting step and the laminating step are performed using the method shown in FIGS. 2A to 2C, there is a tendency that poor appearance of the adhesive layer due to the generation of air bubbles or the inclusion of foreign matter is less likely to occur compared to coating methods such as gravure coating.

[0050] <1-5. Water-Based Adhesive Solution> The water-based adhesive solution preferably includes a solution containing polyvinyl alcohol and a solution containing at least one amino compound. The water-based adhesive solution may also be a solution containing at least one amino compound and an epoxy compound. By employing such a water-based adhesive solution and by making the adhesive layer very thin, as described above, it is possible to more effectively reduce reflection unevenness in external light reflection. In particular, even if there is a large difference in refractive index between the adhesive layer and the light-transmitting optical film attached adjacent to it, it is possible to more effectively reduce reflection unevenness in external light reflection.

[0051] In one embodiment, the solution containing polyvinyl alcohol may contain a metal compound colloid. The metal compound colloid is a dispersion of metal compound fine particles in a dispersion medium, which is electrostatically stabilized due to mutual repulsion of like-charged particles of the fine particles, and may have permanent stability.

[0052] The average particle size of the fine particles forming the metal compound colloid can be set to any appropriate value as long as it does not adversely affect optical properties such as transparency and polarization characteristics. It is preferably 1 nm to 100 nm, and more preferably 1 nm to 50 nm, because this allows the fine particles to be uniformly dispersed in the adhesive layer.

[0053] Any suitable compound can be used as the metal compound. Examples include metal oxides such as alumina, silica, zirconia, and titania; metal salts such as aluminum silicate, calcium carbonate, magnesium silicate, zinc carbonate, barium carbonate, and calcium phosphate; and minerals such as celite, talc, clay, and kaolin. A colloidal metal compound having a positive charge is preferably used as the metal compound. Examples of such metal compounds include alumina and titania, with alumina being particularly preferred.

[0054] As the amino compound that can be contained in the aqueous adhesive solution, any appropriate amino compound can be used as long as it does not impair the effects of the present invention. The amino compound may be only one type or two or more types. Examples of such amino compounds include amino-based silane coupling agents.

[0055] As the amino silane coupling agent, any suitable amino silane coupling agent can be used as long as it is an organosilicon compound having an amino group, so long as it does not impair the effects of the present invention. Examples of such amino silane coupling agents include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and hydrochlorides thereof. Commercially available amino silane coupling agents include, for example, KBM-602, KBM-603, KBM-903, KBE-603, KBE-903, and X-12-972F (all manufactured by Shin-Etsu Chemical Co., Ltd.), Z-6011, Z-6020, Z-6026, Z-6032, Z-6094, and Z-6610 (all manufactured by Dow Corning Toray Co., Ltd.), and A-1100, A-1110, A-1120, A-2120, and Y-9669 (all manufactured by Momentive Performance Materials).

[0056] As the amino compound that can be contained in the aqueous adhesive solution, in addition to an amino-based silane coupling agent, a compound having an amino group at the terminal is preferable, and examples thereof include polyethyleneimine, polyetheramine, etc. Commercially available polyethyleneimine products include SP-200, P-1000, and SP-006 (all manufactured by Nippon Shokubai Co., Ltd.), and commercially available polyetheramine products include PEA D230, PEA D400, and PEA D2000 (all manufactured by Mitsui Fine Chemicals, Inc.).

[0057] As the epoxy compound that can be contained in the aqueous adhesive solution, any appropriate epoxy compound can be used as long as the effects of the present invention are not impaired. The epoxy compound may be one type or two or more types. Examples of such epoxy compounds include epoxy-based silane coupling agents.

[0058] As the epoxy-based silane coupling agent, any appropriate epoxy-based silane coupling agent can be used as long as it is an organosilicon compound having an epoxy group and does not impair the effects of the present invention. Examples of such epoxy-based silane coupling agents include 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane. Commercially available epoxy silane coupling agents include, for example, KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KR-516, and X-12-981S (all manufactured by Shin-Etsu Chemical Co., Ltd.), SH6040, Z-6040, Z-6042, Z-6043, and Z-6044 (all manufactured by Dow Corning Toray Co., Ltd.), and A-186, A-187, and A-1871 (all manufactured by Momentive Performance Materials, Inc.).

[0059] Examples of epoxy compounds that can be contained in the aqueous adhesive solution include epoxy silane coupling agents, as well as sorbitol polyglycidyl ethers and water-soluble epoxy resins. Commercially available epoxy compounds include Denacol EX-612, EX-614, and EX-622 (all manufactured by Nagase ChemteX Corporation), W2801, W2821R70, and WD11M60 (all manufactured by Mitsubishi Chemical Corporation).

[0060] When the aqueous adhesive solution contains both at least one amino compound and one epoxy compound, the molar ratio of the amino compound to the epoxy compound in the aqueous adhesive solution is preferably 8:92 to 60:40, or alternatively 10:90 to 55:45, 15:85 to 50:50, 20:80 to 45:55, or 25:75 to 40:60. When the molar ratio of the amino compound to the epoxy compound in the aqueous adhesive solution is within the above range, the effects of the present invention can be more effectively exhibited.

[0061] The total content of the amino compound and the epoxy compound in the aqueous adhesive solution is preferably less than 50% by weight, and may be 0.01% by weight to 40% by weight, 0.1% by weight to 30% by weight, 0.1% by weight to 20% by weight, 0.3% by weight to 10% by weight, 0.4% by weight to 5% by weight, or 0.5% by weight to 2% by weight. In another embodiment, the content may be 0.5% by weight to 10% by weight.

[0062] As described above, the aqueous adhesive solution used in the manufacturing method according to the embodiment of the present invention contains water as a solvent. The aqueous adhesive solution preferably contains only water as a solvent. However, the aqueous adhesive solution may further contain an organic solvent in addition to water. Examples of organic solvents include esters such as ethyl acetate, butyl acetate, and 2-hydroxyethyl acetate; ketones such as methyl ethyl ketone, acetone, cyclohexanone, methyl isobutyl ketone, diethyl ketone, methyl n-propyl ketone, and acetylacetone; cyclic ethers such as tetrahydrofuran (THF) and dioxane; aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; aliphatic or alicyclic alcohols such as methanol, ethanol, n-propanol, isopropanol, and cyclohexanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and diethylene glycol monoethyl ether; and glycol ether acetates such as diethylene glycol monomethyl ether acetate and diethylene glycol monoethyl ether acetate.

[0063] The water content in the solvent is preferably 50% by weight to 100% by weight, and may be 60% by weight to 100% by weight, 70% by weight to 100% by weight, 80% by weight to 100% by weight, 90% by weight to 100% by weight, 95% by weight to 100% by weight, 98% by weight to 100% by weight, or substantially 100% by weight. When the water content of the solvent is within the above range, the solvent evaporates easily when the aqueous adhesive solution is applied and dried, making it easier to achieve a thinner film. Furthermore, water causes less damage to the polarizer and the translucent optical film, and is therefore effective in preventing deterioration of product quality when, for example, an optical component including an optical laminate according to an embodiment of the present invention and a polarizer is produced.

[0064] The solvent may not contain an aliphatic or alicyclic alcohol. The content of the aliphatic or alicyclic alcohol in the solvent is preferably 0% by weight to 50% by weight, may be 0% by weight to 40% by weight, may be 0% by weight to 30% by weight, may be 0% by weight to 20% by weight, may be 0% by weight to 10% by weight, may be 0% by weight to 5% by weight, may be 0% by weight to 2% by weight, or may be substantially 0% by weight.

[0065] The content of the solvent in the aqueous adhesive solution is preferably 50% by weight or more, and may be 60% by weight to 99.99% by weight, 70% by weight to 99.9% by weight, 80% by weight to 99.8% by weight, 90% by weight to 99.7% by weight, 95% by weight to 99.6% by weight, or 98% by weight to 99.5% by weight.

[0066] The aqueous adhesive solution may contain any suitable additives as long as they do not impair the effects of the present invention. Such additives may be used alone or in combination of two or more. Examples of such additives include binder resins, surfactants, plasticizers, tackifiers, low-molecular-weight polymers, polymerizable monomers, surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, UV absorbers, polymerization inhibitors, silane coupling agents, titanium coupling agents, inorganic or organic fillers, metal powders, particles, and foil-like materials. Examples of binder resins include acrylic resins, styrene resins, polyvinyl alcohol resins, urethane resins, polyester resins, polypropylene resins, polyethylene resins, epoxy resins, and polycarbonate resins.

[0067] The content of the additive in the aqueous adhesive solution is preferably 0% by weight to 10% by weight, and may be 0% by weight to 5% by weight, 0% by weight to 3% by weight, 0% by weight to 2% by weight, 0% by weight to 1% by weight, or 0% by weight to 0.5% by weight.

[0068] The viscosity of the aqueous adhesive solution is preferably in the range of 1 to 1000 mPa s, more preferably in the range of 1 to 100 mPa s. If the viscosity is in the above range, it tends to be easier to carry out the production method described in the section <1-4. A preferred example of the method for producing an optical laminate>.

[0069] <1-6. Adhesive Layer> As described above, in the curing step of the manufacturing method according to the embodiment of the present invention, the aqueous adhesive solution is cured to form an adhesive layer. Note that when the aqueous adhesive solution contains at least one amino compound (particularly an amino-silane coupling agent), the adhesive layer formed from the aqueous adhesive solution preferably contains an organosilicon compound.

[0070] The thickness of the adhesive layer is preferably thinner than 1 / 10 of the wavelength of external light. In this way, if the thickness of the adhesive layer is thinner than 1 / 10 of the wavelength of external light, even if there is a large difference in refractive index between the adhesive layer and the adjacent light-transmitting optical film attached thereto, the optical path length of the adhesive layer (the product of the thickness and the refractive index) can be reduced due to the thin thickness of the adhesive layer, which can eliminate the sensitivity of the adhesive layer to light and prevent interference of reflected light, and the thinner this thickness is, the greater the effect of suppressing uneven reflection can be.

[0071] The thickness of the adhesive layer is preferably 1 / 10 of the wavelength of 500 nm, which has a particularly high visibility, i.e., a thickness of 50 nm or less. Furthermore, even with light having a wavelength shorter than 500 nm, interference is sufficiently suppressed and coloring is lighter than when the adhesive layer is about 1 μm thick, making it fully practical. Furthermore, since visible light is 380 nm to 780 nm, the thickness of the adhesive layer is more preferably 38 nm or less, and even more preferably 30 nm or less. Furthermore, considering that the optical path length is preferably 1 / 10 of the target visible light wavelength and that the refractive index of the adhesive layer is typically around 1.40 to 1.60, the thickness of the adhesive layer is preferably 30 nm or less. Furthermore, when manufacturing industrially, considering the margin of the adhesive layer, it is preferable that the maximum thickness of the adhesive layer does not exceed 30 nm, and the average thickness is preferably 25 nm or less.

[0072] From the above, in the optical laminate produced by the production method of this embodiment, the thickness of the adhesive layer is very small, preferably 50 nm or less, and may be 40 nm or less, 38 nm or less, 35 nm or less, 30 nm or less, less than 30 nm, 25 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less. The lower limit of the thickness of the adhesive layer is, for example, 1 nm or more, or 2 nm or more. In the optical laminate produced by the production method of this embodiment, by setting the thickness of the adhesive layer as described above, an unexpectedly excellent effect can be achieved, in particular, that uneven reflection of external light can be effectively reduced, even if there is a large difference in refractive index between the adhesive layer and the light-transmitting optical film bonded adjacent to it.

[0073] In an optical laminate produced by the manufacturing method of this embodiment, reflection unevenness in external light reflection can be effectively reduced even if there is a large difference in refractive index between the adhesive layer and the adjacently bonded light-transmitting optical film. Therefore, in the optical laminate, the in-plane refractive index difference between the first light-transmitting optical film and the adhesive layer may be large, and the in-plane refractive index difference between the second light-transmitting optical film and the adhesive layer may be large. That is, a light-transmitting optical film having a high refractive index can be used as the first light-transmitting optical film or the second light-transmitting optical film. Conventionally, optical laminates in which two light-transmitting optical films having high refractive indexes are bonded together with an adhesive have exhibited noticeable reflection unevenness in external light reflection. However, according to the present invention, reflection unevenness in external light reflection can be effectively reduced even when a light-transmitting optical film having a high refractive index is used as the first light-transmitting optical film or the second light-transmitting optical film.

[0074] The in-plane refractive index difference (absolute value) between the first light-transmitting optical film and the adhesive layer is preferably 0.05 or more, and may be 0.08 or more, 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more. The upper limit of the in-plane refractive index difference (absolute value) between the first light-transmitting optical film and the adhesive layer is, for example, 0.26 or less.

[0075] The in-plane refractive index difference (absolute value) between the second light-transmitting optical film and the adhesive layer is preferably 0.05 or more, and may be 0.08 or more, 0.10 or more, 0.12 or more, 0.14 or more, or 0.16 or more. The upper limit of the in-plane refractive index difference (absolute value) between the second light-transmitting optical film and the adhesive layer is, for example, 0.26 or less.

[0076] <1-7. Light-Transmitting Optical Film> The first light-transmitting optical film and the second light-transmitting optical film may be the same type of light-transmitting optical film, or may be different types of light-transmitting optical films.

[0077] The thickness of each of the first light-transmitting optical film and the second light-transmitting optical film may be any appropriate thickness as long as the effects of the present invention are not impaired. Such a thickness is, for example, 0.5 μm to 200 μm, or may be 1 μm to 100 μm, or may be 1 μm to 50 μm. From the viewpoint of thinning, the thickness of the light-transmitting optical film is, for example, 0.5 μm to 50 μm, or may be 1 μm to 40 μm, or may be 1 μm to 30 μm, or may be 1 μm to 20 μm, or may be 1 μm to 10 μm, or may be 1 μm to 5 μm.

[0078] The in-plane refractive index of the first translucent optical film is preferably 1.50 or more, and may be 1.52 or more, 1.54 or more, 1.56 or more, 1.58 or more, 1.60 or more, 1.61 or more, or 1.62 or more. There is a tendency that the higher the upper limit of the in-plane refractive index of the first translucent optical film, the better, but based on realistic material selection, etc., it is, for example, 1.72 or less. The optical laminate produced by the production method of this embodiment can effectively reduce reflection unevenness of external light reflection even if the in-plane refractive index of the first translucent optical film is as high as described above.

[0079] The in-plane refractive index of the second translucent optical film is preferably 1.50 or more, and may be 1.52 or more, 1.54 or more, 1.56 or more, 1.58 or more, 1.60 or more, 1.61 or more, or 1.62 or more. There is a tendency that the higher the upper limit of the in-plane refractive index of the second translucent optical film, the better, but based on realistic material selection, etc., it is, for example, 1.72 or less. The optical laminate produced by the production method of this embodiment can effectively reduce reflection unevenness of external light reflection even if the in-plane refractive index of the second translucent optical film is as high as described above.

[0080] In one preferred embodiment of the present invention, the in-plane refractive index of at least one of the first light-transmitting optical film and the second light-transmitting optical film is 1.50 or more, and it is preferred that the in-plane refractive index of both the first light-transmitting optical film and the second light-transmitting optical film is 1.50 or more.

[0081] Any suitable light-transmitting optical film can be used as the light-transmitting optical film as long as the effects of the present invention are not impaired. Examples of such light-transmitting optical films include retardation films (retardation layers), polarizers, polarizing films (laminated films including a polarizer and a polarizer protective film), polarizer protective films, brightness-enhancing films, and resin substrate films.

[0082] Any suitable material can be used as the material for the light-transmitting optical film as long as it does not impair the effects of the present invention. Examples of such materials include polycarbonate resins (including polyester carbonate resins), polyester resins (PET, etc.), polyvinyl acetal resins, polyarylate resins, polyolefin resins, cyclic polyolefin resins (e.g., norbornene resins), cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, acrylic resins, and polyvinyl alcohol resins. These resins may be used alone or in combination (e.g., blends or copolymers).

[0083] In one preferred embodiment of the present invention, at least one of the first and second light-transmitting optical films may be a retardation film, and both the first and second light-transmitting optical films may be retardation films. When both the first and second light-transmitting optical films are retardation films, they may be a combination of a λ / 2 plate and a λ / 4 plate, or a λ / 3 plate and a λ / 6 plate, a λ / 2 plate and a C plate, or a λ / 4 plate and a C plate. Note that an optical element in which the relationship between the in-plane refractive indexes nx and ny and the refractive index nz in the thickness direction satisfies nx = ny > nz is called a negative C plate, and an optical element in which nx = ny < nz is called a positive C plate. These are collectively called C plates. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the retardation film can be 20 nm or less, preferably 10 nm or less, and more preferably 5 nm or less.

[0084] The light-transmitting optical film may have any appropriate treatment layer formed on its surface, as long as the effects of the present invention are not impaired. Examples of such treatment layers include a hard coat layer, an easy-adhesion layer, an anti-reflection treatment, an anti-glare treatment, and an anti-sticking treatment layer.

[0085] The surface of the light-transmitting optical film may be subjected to any appropriate activation treatment within the scope of the present invention, for the purpose of improving adhesiveness, etc. Examples of such activation treatments include corona treatment, plasma treatment, saponification treatment, and low-pressure UV treatment.

[0086] The light-transmitting optical film may be a stretched film. Generally, optical anisotropy is imparted to a retardation film or a polarizer by orienting a polymer chain or a dichroic material through stretching. In the present invention, an optical laminate may be produced using a light-transmitting optical film that has been stretched in advance to impart optical anisotropy, or an optical laminate produced using a light-transmitting optical film may be stretched to impart optical anisotropy.

[0087] The light-transmitting optical film may contain any appropriate additive as long as it does not impair the effects of the present invention. Such additives may be contained alone or in combination of two or more. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0088] As described above, any appropriate light-transmitting optical film can be used as the light-transmitting optical film as long as the effects of the present invention are not impaired. Hereinafter, as one embodiment of the light-transmitting optical film, a case where the light-transmitting optical film is a retardation film will be described.

[0089] <1-7-a. First Retardation Film> When the first light-transmitting optical film is a retardation film, it is referred to as a first retardation film.

[0090] In one embodiment, the first retardation film has a refractive index characteristic of nx>ny. Here, the relationship between ny and nz may be ny<nz, ny=nz, or ny>nz. In one embodiment, the first retardation film may function as a λ / 2 plate. In one embodiment, the first retardation film may function as a λ / 3 plate.

[0091] In one embodiment, the first retardation film has a refractive index characteristic of nx=ny, where nx and nz may have a relationship of nx<nz or nx>nz. In one embodiment, the first retardation film may function as a C-plate.

[0092] Examples of the first retardation film include a retardation film that is a λ / 2 plate having a front retardation of 200 nm or more and a thickness direction retardation of 0 nm or more. The front retardation is usually controlled in the range of 200 nm to 350 nm, and the thickness direction retardation is usually controlled in the range of 0 nm to 450 nm. Another example is a retardation film that is a C plate having a front retardation of 0 nm and a thickness direction retardation of −50 nm or less or 50 nm or more. The front retardation is usually controlled in the range of −10 nm to 10 nm, and the thickness direction retardation is usually controlled in the range of −200 nm to 200 nm.

[0093] The first retardation film may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light.

[0094] The first retardation film may be, for example, a positive wavelength dispersion retardation film that satisfies the following conditions: 1.00<Re(450) / Re(550)<1.20 0.08<Δn<0.15 1.00<NZ<1.20, where Re(450) and Re(550) are in-plane retardations measured with light having wavelengths of 450 nm and 550 nm at 23° C., nx and ny are refractive indices of the retardation film in the slow axis direction and the fast axis direction, respectively, nx-ny is in-plane birefringence, Δn is in-plane birefringence, and Nz is the ratio of nx-nz, which is thickness direction birefringence, to nx-ny, which is in-plane birefringence, where nz is the refractive index in the thickness direction of the retardation film.

[0095] The Re(550) of the first retardation film is, for example, 130 nm to 350 nm, may be 160 nm to 330 nm, or may be 200 nm to 300 nm.

[0096] The first retardation film is formed of any appropriate material that can satisfy the above characteristics. The first retardation film can be composed of, for example, a resin film or an oriented and solidified layer of a liquid crystal compound, and is preferably an oriented and solidified layer of a liquid crystal compound. By using an oriented and solidified layer of a liquid crystal compound as the retardation film, it is possible to achieve a desired in-plane retardation with a thickness that is significantly thinner than that of a resin film. As a result, it is possible to significantly reduce the thickness of the optical laminate.

[0097] Examples of resins contained in the resin film include polycarbonate resins (including polyester carbonate resins), polyester resins, polyvinyl acetal resins, polyarylate resins, polyolefin resins, cyclic polyolefin resins (e.g., norbornene resins), cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, acrylic resins, and polyvinyl alcohol resins. These resins may be used alone or in combination (e.g., blends or copolymers).

[0098] When the first retardation film exhibits reverse dispersion wavelength characteristics, a resin film containing a polycarbonate-based resin (including a polyester carbonate-based resin) can be suitably used.

[0099] As the polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as it does not impair the effects of the present invention. The polycarbonate-based resin contains, for example, structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri-, or polyethylene glycols, and alkylene glycols or spiroglycols. The polycarbonate-based resin preferably contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, structural units derived from an alicyclic dimethanol and / or structural units derived from di-, tri-, or polyethylene glycol; more preferably, it contains structural units derived from a fluorene-based dihydroxy compound, structural units derived from an isosorbide-based dihydroxy compound, and structural units derived from di-, tri-, or polyethylene glycol. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds as necessary. Details of polycarbonate-based resins that can be suitably used for the first retardation film are described in, for example, JP 2014-10291 A, JP 2014-26266 A, JP 2015-212816 A, JP 2015-212817 A, and JP 2015-212818 A, and the descriptions of these publications are incorporated herein by reference.

[0100] When the first retardation film exhibits flat wavelength dispersion characteristics, a resin film containing a cycloolefin resin can be suitably used.

[0101] Cycloolefin resin is a general term for resins polymerized using cycloolefins as polymerization units, and examples thereof include resins described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, etc. Examples of cycloolefin resins include ring-opening (co)polymers of cycloolefins, addition polymers of cycloolefins, copolymers (typically random copolymers) of cycloolefins with α-olefins such as ethylene and propylene, graft modified products obtained by modifying these with unsaturated carboxylic acids or derivatives thereof, and hydrogenated products thereof. Specific examples of cycloolefins include norbornene monomers.Examples of norbornene-based monomers include norbornene and its alkyl and / or alkylidene substituted derivatives and polar group substituted derivatives such as halogen (for example, 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene), dicyclopentadiene, 2,3-dihydrodicyclopentadiene, dimethanooctadecane, and the like. Hydronaphthalene and its alkyl and / or alkylidene substituted derivatives and polar group substituted derivatives such as halogen (for example, 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7,8, 8a-Octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano Examples of suitable cycloolefins include 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydronaphthalene, and trimers and tetramers of cyclopentadiene (e.g., 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene). Other cycloolefins capable of ring-opening polymerization may be used in combination. Examples of such other cycloolefins include compounds having one reactive double bond, such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

[0102] Various cycloolefin resin products are commercially available. Specific examples of commercially available cycloolefin resin products include "ZEONEX" and "ZEONOR" manufactured by Zeon Corporation, "Arton" manufactured by JSR Corporation, "TOPUS" manufactured by TICONA, and "APEL" manufactured by Mitsui Chemicals, Inc.

[0103] The first retardation film composed of a resin film can be obtained, for example, by stretching an unstretched resin film. Any appropriate stretching method and stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction) can be employed for stretching. The stretching temperature is, for example, Tg-30°C to Tg+60°C, and may be Tg-10°C to Tg+50°C, relative to the glass transition temperature (Tg) of the resin film. In one embodiment, the first retardation film can be obtained by uniaxially stretching or fixed-end uniaxially stretching an unstretched resin film. A specific example of fixed-end uniaxial stretching is a method in which a resin film is stretched in the width direction (transverse direction) while traveling in the longitudinal direction. The stretching ratio is preferably 1.1 to 3.5 times. The thickness of the first retardation film made of a resin film is, for example, 10 μm to 100 μm, may be 10 μm to 70 μm, may be 10 μm to 60 μm, or may be 20 μm to 50 μm.

[0104] When the first retardation film is composed of an oriented and solidified layer of a liquid crystal compound, the first retardation film is typically oriented in a state where rod-shaped liquid crystal compounds are aligned in the slow axis direction of the first retardation film (homogeneous orientation). Examples of rod-shaped liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable. If the liquid crystal compound is polymerizable, the orientation state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.

[0105] An alignment and solidification layer of a liquid crystal compound (liquid crystal alignment and solidification layer) can be formed by performing an alignment treatment on the surface of a predetermined substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. Any appropriate alignment treatment can be used as the alignment treatment. Examples of the alignment treatment include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photoalignment treatment. Any appropriate treatment conditions can be used for the alignment treatment depending on the purpose.

[0106] The alignment of liquid crystal compounds can be achieved by treating them at a temperature at which they exhibit a liquid crystal phase depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compounds assume a liquid crystal state and are aligned in accordance with the alignment treatment direction of the substrate surface.

[0107] In one embodiment, the alignment state is fixed by cooling the aligned liquid crystal compound. When the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the aligned liquid crystal compound to a polymerization treatment or a crosslinking treatment.

[0108] Any suitable liquid crystal polymer and / or liquid crystal monomer can be used as the liquid crystal compound. The liquid crystal polymer and liquid crystal monomer may each be one type only, or two or more types. Specific examples of liquid crystal compounds and methods for producing a liquid crystal alignment solidified layer are described in, for example, JP 2006-163343 A, JP 2006-178389 A, and WO 2018 / 123551 A. The descriptions in these publications are incorporated herein by reference.

[0109] When the first retardation film is constituted by a liquid crystal compound alignment solidified layer, the thickness of the first retardation film which is the liquid crystal alignment solidified layer is, for example, 0.5 μm to 10 μm, may be 0.5 μm to 8 μm, may be 0.5 μm to 6 μm, or may be 0.5 μm to 4 μm.

[0110] <1-7-b. Second Retardation Film> When the second light-transmitting optical film is a retardation film, it is referred to as a second retardation film.

[0111] In one embodiment, the second retardation film has a refractive index characteristic of nx>ny. Here, the relationship between ny and nz may be ny<nz, ny=nz, or ny>nz. In one embodiment, the second retardation film may function as a λ / 4 plate. In one embodiment, the second retardation film may function as a λ / 5 plate or a λ / 6 plate.

[0112] In one embodiment, the second retardation film has a refractive index characteristic of nx=ny, where nx and nz may have a relationship of nx<nz or nx>nz. In one embodiment, the second retardation film may function as a C-plate.

[0113] Examples of the second retardation film include a retardation film that is a λ / 4 plate having a front retardation of 90 nm or more and a thickness direction retardation of 0 nm or more. The front retardation is usually controlled in the range of 90 nm to 200 nm, and the thickness direction retardation is usually controlled in the range of 0 nm to 240 nm. Another example is a retardation film that is a C plate having a front retardation of 0 nm and a thickness direction retardation of −50 nm or less or 50 nm or more. The front retardation is usually controlled in the range of −10 nm to 10 nm, and the thickness direction retardation is usually controlled in the range of −200 nm to 200 nm.

[0114] The second retardation film may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light.

[0115] The second retardation film may be, for example, a positive wavelength dispersion retardation film that satisfies the following conditions: 1.00<Re(450) / Re(550)<1.20 0.08<Δn<0.15 1.00<NZ<1.20, where Re(450) and Re(550) are in-plane retardations measured with light having wavelengths of 450 nm and 550 nm at 23° C., nx and ny are refractive indices of the retardation film in the slow axis direction and the fast axis direction, respectively, nx-ny is in-plane birefringence, Δn is in-plane birefringence, and Nz is the ratio of nx-nz, which is thickness direction birefringence, to nx-ny, which is in-plane birefringence, where nz is the refractive index in the thickness direction of the retardation film.

[0116] The Re(550) of the second retardation film is, for example, 70 nm to 200 nm, may be 90 nm to 160 nm, or may be 120 nm to 140 nm.

[0117] The arrangement order of the first retardation film and the second retardation film may be reversed.

[0118] The second retardation film is formed of any appropriate material that can satisfy the above characteristics. The second retardation film can be composed of, for example, a resin film or an oriented and solidified layer of a liquid crystal compound, and is preferably an oriented and solidified layer of a liquid crystal compound. By using an oriented and solidified layer of a liquid crystal compound as the retardation film, it is possible to achieve a desired in-plane retardation with a thickness that is significantly thinner than that of a resin film. As a result, it is possible to significantly reduce the thickness of the optical laminate.

[0119] The second retardation film made of a resin film may be referred to in the above description of the first retardation film made of a resin film. The second retardation film made of a layer of a liquid crystal compound with a fixed orientation may be referred to in the above description of the first retardation film made of a layer of a liquid crystal compound with a fixed orientation.

[0120] <1-8. Optical Laminate> The thickness of the optical laminate produced by the production method of this embodiment can be any appropriate thickness as long as the effects of the present invention are not impaired. Such a thickness is, for example, 1 μm to 400 μm, or may be 2 μm to 200 μm. From the perspective of thinning, the thickness of the light-transmitting optical film is, for example, 1 μm to 100 μm, or may be 2 μm to 80 μm, 2 μm to 60 μm, 2 μm to 40 μm, 2 μm to 20 μm, or 2 μm to 10 μm.

[0121] The optical laminate preferably has an adhesive strength of 0.2 N / 15 mm or more, and may have an adhesive strength of 0.5 N / 15 mm or more, 0.8 N / 15 mm or more, 1.0 N / 15 mm or more, 1.3 N / 15 mm or more, 1.5 N / 15 mm or more, 1.8 N / 15 mm or more, 2.0 N / 15 mm or more, 2.3 N / 15 mm or more, or even 2.5 N / 15 mm or more. The upper limit of the adhesive strength is not particularly limited, and may be, for example, 10 N / 15 mm or less.

[0122] The adhesive strength can be measured by the following method. First, a 15 mm wide strip sample is prepared from the optical laminate (when the second translucent optical film is a λ / 4 retardation film, a sample cut to a width of 15 mm along the slow axis). The first translucent optical film is fixed to a glass plate with adhesive tape (e.g., Nitto Denko Corporation, product name "No. 5000NS", thickness: 160 μm), and the second translucent optical film is backed with polyimide tape (e.g., Nitto Denko Corporation, product name "No. 360A", thickness: 25 μm) using a hand roller. The second translucent optical film backed with polyimide tape is peeled at a peel angle of 90° and a peel rate of 20,000 mm / min under an environment of a temperature of 23° C. and a humidity of 50% RH. The force (peel strength) required to peel the second translucent optical film is determined as the adhesive strength. The adhesive strength is evaluated within 30 minutes after the optical laminate is produced by the above-mentioned curing step, in an environment of a temperature of 23° C. and a humidity of 50% RH.

[0123] The optical laminate can be used in any suitable application, for example, in image display devices such as liquid crystal display devices and organic EL display devices.

[0124] The optical laminate can be used by laminating any other appropriate optical film, and can be used by providing any other appropriate layer. Examples of other optical films include a retardation film, a polarizer, a polarizing film (a laminate film including a polarizer and a polarizer protective film), a polarizer protective film, a brightness-enhancing film, and a resin substrate film. Examples of other layers include a pressure-sensitive adhesive layer, another adhesive layer, a hard coat layer, an antireflection layer, and an antiglare layer.

[0125] Fig. 3 is a schematic cross-sectional view showing an example of an optical member including an optical laminate produced by the production method of this embodiment. The optical member 1000 shown in Fig. 3 includes a polarizing film 40, an adhesive layer 50, an optical laminate 100 (a first light-transmitting optical film 10, an adhesive layer 30, and a second light-transmitting optical film 20) produced by the production method of this embodiment, and a panel-side pressure-sensitive adhesive layer 60. The panel-side pressure-sensitive adhesive layer 60 enables the optical member 1000 to be attached to an image display cell, thereby constituting an image display device.

[0126] 2. Manufacturing Method of Image Display Device A manufacturing method of an image display device according to an embodiment of the present invention includes forming an image display device using an optical laminate formed by the manufacturing method of this embodiment. As an example, the image display device can be manufactured by appropriately assembling the optical laminate with other optical films, an image display cell, a backlight, etc., and incorporating a drive circuit. In configuring the image display device, the optical laminate can be used on one or both sides of the image display cell.

[0127] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The test and evaluation methods used in the examples are as follows. The term "parts" means "parts by weight" unless otherwise specified, and the term "%" means "% by weight" unless otherwise specified.

[0128] <Measurement of adhesive layer thickness> Using an apparatus named "HT7820" manufactured by Hitachi High-Technologies Corporation, cross-sectional TEM observation was performed by a frozen ultrathin section method including heavy metal staining to measure the thickness of the adhesive layer. The accelerating voltage during the measurement was 100 kV.

[0129] <Evaluation of Reflection Unevenness> [Evaluation 1] An adhesive tape was attached to the second light-transmitting optical film surface of the optical laminate obtained in the Examples and Comparative Examples, and this was then attached to a black acrylic plate. When a carrier was laminated on the light-transmitting optical film, the carrier film was peeled off before the film was attached to the acrylic plate. A fluorescent lamp was lit from the first light-transmitting optical film side, and observation was performed. The adhesive tape used was prepared by the following method. [Preparation of Acrylic Polymer] A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 92 parts by weight of butyl acrylate, 5 parts by weight of N-acryloylmorpholine (ACMO), 2.9 parts by weight of acrylic acid, 0.1 parts by weight of 2-hydroxyethyl acrylate, 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 200 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was maintained at around 55°C, and a polymerization reaction was carried out for 8 hours to prepare an acrylic polymer solution. The weight-average molecular weight of the resulting acrylic polymer was 1.78 million. [Preparation of Pressure-Sensitive Adhesive Tape] The acrylic polymer solution obtained above was applied to one side of a silicone-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical, thickness = 38 μm), and the film was dried and crosslinked at 150°C for 3 minutes to form a pressure-sensitive adhesive layer with a thickness of 5 μm after drying. The gel fraction of the pressure-sensitive adhesive layer at this time was 83 wt %, and the amount of decomposed peroxide after drying was 91 wt %. [Evaluation 2] In Evaluation 1, an irradiation-side linear polarizer was attached to the irradiation direction side of the fluorescent lamp used, and the fluorescent lamp was illuminated from the first light-transmitting optical film side through the irradiation-side linear polarizer. On the viewing side, a viewing-side linear polarizer was placed so as to be orthogonal (crossed Nicols) to the irradiation-side linear polarizer, and observation was performed from the first light-transmitting optical film side through the viewing-side linear polarizer. Observation was performed under conditions that suppressed surface reflection of the first light-transmitting optical film using the irradiation-side linear polarizer and the viewing-side linear polarizer. Evaluation was based on the following criteria: ⊚: No reflection unevenness was visible in either Evaluation 1 or Evaluation 2. ◯: Weak reflection unevenness was visible in Evaluation 2, but no reflection unevenness was visible in Evaluation 1. Δ: Reflection unevenness was visible in Evaluation 2, but no reflection unevenness was visible in Evaluation 1.x: Reflection unevenness was visible in evaluation 2, and weak reflection unevenness was visible in evaluation 1. xx: Reflection unevenness was visible in evaluation 2, and reflection unevenness was also visible in evaluation 1.

[0130] <Evaluation of Appearance> [Air Bubbles] Using an Olympus Corporation device named "DP74," the adhesive layers contained in the optical laminates obtained in the Examples and Comparative Examples were subjected to microscopic observation. The microscopic observation was performed at a magnification of 50 times and a 100 cm 2 The test was carried out for a range of 100 μm and 200 μm, and the number of bubbles of 3 μm or more that had occurred in the adhesive layer during production was counted. Evaluation was based on the following criteria: ◯: The number of bubbles was 0. Δ: The number of bubbles was 1 to 3. ×: The number of bubbles was 4 or more.

[0131] [Foreign matter] Using an Olympus DP74 instrument, the adhesive layers contained in the optical laminates obtained in the examples and comparative examples were observed under a microscope. The microscope observation was carried out at a magnification of 50x over an area of ​​297 mm length x 210 mm width, and the number of foreign particles of 5 μm or more in size that had been mixed into the adhesive layer during production was counted. Evaluation was based on the following criteria: ◯: The number of foreign particles was 0. Δ: The number of foreign particles was 1 to 3. ×: The number of foreign particles was 4 or more.

[0132] [Tin-like wrinkles] The translucent optical films contained in the optical laminates obtained in Examples and Comparative Examples were observed in an area of ​​297 mm length x 210 mm width to check for the presence or absence of tin-like wrinkles. Specifically, the optical laminate was placed on a smooth surface, and the presence or absence of lift of 2 mm or more due to tin-like wrinkles in the translucent optical film was checked. It is presumed that the tin-like wrinkles in the translucent optical film are caused by water moving from the adhesive layer to the translucent optical film.

[0133] <Evaluation of Adhesion Strength> A 15 mm wide strip sample (when the second translucent optical film was a λ / 4 plate retardation film, a sample cut to a width of 15 mm along the slow axis) was prepared from the optical laminate obtained in each of the Examples and Comparative Examples. The first translucent optical film was fixed to a glass plate with adhesive tape (manufactured by Nitto Denko Corporation, product name "No. 5000NS", thickness: 160 μm). The second translucent optical film was backed with polyimide tape (manufactured by Nitto Denko Corporation, product name "No. 360A", thickness: 25 μm) using a hand roller. Peeling of the polyimide tape-backed second translucent optical film was attempted at a peel angle of 90° and a peel rate of 20,000 mm / min under an environment of a temperature of 23° C. and a humidity of 50% RH. The force (peel strength) required to peel the second translucent optical film was determined to be the adhesive strength. The adhesive strength of all samples was evaluated within 30 minutes after the optical laminate was produced by the curing step, in an environment of a temperature of 23° C. and a humidity of 50% RH.

[0134] [Preparation Example 1] Preparation of Photopolymerizable Liquid Crystal Composition A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor LC242") was dissolved in cyclopentanone to prepare a solution with a solids concentration of 30% by weight. A surfactant (BYK-360, BYK-Chemie) and a photopolymerization initiator (IGM Resins B.V.'s "Omnirad 907") were added to this solution to prepare a liquid crystal composition solution. The amounts of the surfactant and photopolymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

[0135] [Production Example 2] Production of Retardation Film 1 (λ / 2 Retardation Film) A biaxially stretched norbornene film (manufactured by Zeon Corporation, trade name "ZEONORFILM", thickness = 33 μm, front retardation = 135 nm) was used as a substrate, and the liquid crystal composition solution prepared in Production Example 1 was applied to this substrate using a bar coater so that the phase difference was λ / 2, and the liquid crystal was aligned by heating at 100°C for 3 minutes. After cooling to room temperature, the film was irradiated with an accumulated light amount of 400 mJ / cm under a nitrogen atmosphere. 2The laminate (1) was photocured by irradiating it with ultraviolet light of 1000 W at ...

[0136] [Production Example 3] Production of Retardation Film 2 (λ / 4 Retardation Film) A biaxially stretched norbornene film (manufactured by Zeon Corporation, trade name "ZEONORFILM", thickness = 33 μm, front retardation = 135 nm) was used as a substrate, and the liquid crystal composition solution prepared in Production Example 1 was applied to this substrate using a bar coater so that the phase difference was λ / 4, and the solution was heated at 100°C for 3 minutes to align the liquid crystal. After cooling to room temperature, the film was irradiated with an accumulated light amount of 400 mJ / cm under a nitrogen atmosphere. 2 The laminate (2) was photocured by irradiating it with ultraviolet light of 1000 W at ...

[0137] [Production Example 4] Preparation of aqueous adhesive solution (1) 0.5 parts by weight of an amino silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-603"), 0.5 parts by weight of an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KBM-403"), and 99 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 1.0 wt%. To 100 parts by weight of the obtained aqueous solution, 0.2 parts by weight of a surfactant (manufactured by Nissin Chemical Co., Ltd., product name "EXP4200") was added, and an aqueous adhesive solution (1) was prepared.

[0138] [Production Example 5] Preparation of aqueous adhesive solution (2) The same procedure as in Production Example 4 was carried out, except that 0.25 parts by weight of an amino compound, 0.25 parts by weight of an epoxy compound, and 99.5 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 0.5 wt%. An aqueous adhesive solution (2) was prepared.

[0139] [Production Example 6] Preparation of aqueous adhesive solution (3) The same procedure as in Production Example 4 was carried out, except that 1.5 parts by weight of an amino compound, 1.5 parts by weight of an epoxy compound, and 97 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 3.0% by weight, to prepare an aqueous solution (3).

[0140] [Production Example 7] Preparation of aqueous adhesive solution (4) The same procedure as in Production Example 4 was carried out, except that 2.5 parts by weight of an amino compound, 2.5 parts by weight of an epoxy compound, and 95 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 5.0% by weight, to prepare an aqueous adhesive solution (4).

[0141] [Production Example 8] Preparation of aqueous adhesive solution (5) The same procedure as in Production Example 4 was carried out, except that 1.25 parts by weight of an amino compound, 1.25 parts by weight of an epoxy compound, and 97.5 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 2.5% by weight, to prepare an aqueous adhesive solution (5).

[0142] [Production Example 9] Preparation of aqueous adhesive solution (6) The same procedure as in Production Example 4 was carried out, except that 5 parts by weight of an amino compound, 5 parts by weight of an epoxy compound, and 90 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 10.0% by weight, to prepare an aqueous solution (6).

[0143] Production Example 10 Preparation of Water-Based Adhesive Solution (7) A water-based adhesive solution (7) was prepared by mixing 6.02 parts by weight of acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6%, degree of saponification 99.0 mol% or more, solids concentration 4%, manufactured by Mitsubishi Chemical Corporation, trade name "Gohsenex Z-200"), 25 parts by weight of an aqueous solution containing positively charged alumina colloid (average particle size 15 nm) at a solids concentration of 3.2%, and 18.98 parts by weight of pure water.

[0144] [Production Example 11] Preparation of aqueous adhesive solution (8) The same procedure as in Production Example 4 was carried out, except that 1.75 parts by weight of an amino compound, 1.75 parts by weight of an epoxy compound, and 96.5 parts by weight of water were mixed to prepare an aqueous solution with a solids concentration of 3.5% by weight, to prepare an aqueous adhesive solution (8).

[0145] Example 1 The first liquid crystal alignment solidified layer side of the laminate (1) obtained in Production Example 2 and the second liquid crystal alignment solidified layer side of the laminate (2) obtained in Production Example 3 were treated with a corona treatment machine at a treatment density of 50 W·min / m 2 The corona treatment was performed. Using the apparatus described with reference to Figures 2A to 2C, the laminate (1) and the laminate (2) were each transported between a pair of rolls 4 and passed between the rolls 4 from top to bottom. At this time, the corona-irradiated surface of the laminate (1) and the corona-irradiated surface of the laminate (2) were bonded together, and the laminate (1) and the laminate (2) were transported so that the slow axis of the retardation film 2 (λ / 4 retardation film) was at a 60° angle with the slow axis of the retardation film 1 (λ / 2 retardation film). The aqueous adhesive solution (1) obtained in Production Example 4 was supplied to the bonded portion of the laminate (1) and the laminate (2) by a supply nozzle 1. As the laminate (1) and the laminate (2) passed between the pair of rolls 4, the laminate (1) and the laminate (2) were bonded together via a liquid layer (1 μm thick) of the aqueous adhesive solution (1). In Example 1, the laminates (1) and (2) were bonded together within 1 second after the aqueous adhesive solution (1) came into contact with them. That is, in Example 1, the time from the contacting step to the laminating step was 1 second or less. After lamination, the laminates were heated and dried at 60°C for 6 minutes to form an adhesive layer (1) from the aqueous adhesive solution (1). The biaxially stretched norbornene-based films on both sides of the resulting laminate were peeled off to obtain an optical laminate (1) having a configuration of retardation film 1 / adhesive layer (1) / retardation film 2. The results are shown in Table 1.

[0146] [Example 2] An optical laminate (2) having a configuration of retardation film 1 / adhesive layer (2) / retardation film 2 was obtained in the same manner as in Example 1, except that the aqueous adhesive solution (2) obtained in Production Example 5 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4. The results are shown in Table 1.

[0147] [Example 3] An optical laminate (3) having a configuration of retardation film 1 / adhesive layer (3) / retardation film 2 was obtained in the same manner as in Example 1, except that the aqueous adhesive solution (3) obtained in Production Example 6 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4. The results are shown in Table 1.

[0148] [Example 4] An optical laminate (4) having a configuration of retardation film 1 / adhesive layer (4) / retardation film 2 was obtained in the same manner as in Example 1, except that the aqueous adhesive solution (4) obtained in Production Example 7 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4. The results are shown in Table 1.

[0149] [Example 5] The same procedure as in Example 1 was carried out, except that the thickness of the liquid layer of the aqueous adhesive solution (1) was changed to 2 μm and that after lamination, the films were dried by heating at 60° C. for 10 minutes, to obtain an optical laminate (5) having a configuration of retardation film 1 / adhesive layer (5) / retardation film 2. The results are shown in Table 1.

[0150] [Example 6] The same procedure as in Example 1 was carried out, except that the aqueous adhesive solution (5) obtained in Production Example 8 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4, the thickness of the liquid layer of the aqueous adhesive solution (5) was changed to 2 μm, and after lamination, the films were dried by heating at 60° C. for 10 minutes, thereby obtaining an optical laminate (6) having a configuration of retardation film 1 / adhesive layer (6) / retardation film 2. The results are shown in Table 1.

[0151] [Example 7] The same procedure as in Example 1 was carried out, except that the aqueous adhesive solution (1) obtained in Production Example 4 was replaced with the aqueous adhesive solution (6) obtained in Production Example 9, and the thickness of the liquid layer of the aqueous adhesive solution (6) was changed to 0.5 μm, to obtain an optical laminate (7) having a configuration of retardation film 1 / adhesive layer (7) / retardation film 2. The results are shown in Table 1.

[0152] [Example 8] An optical laminate (8) having a configuration of retardation film 1 / adhesive layer (8) / retardation film 2 was obtained in the same manner as in Example 1, except that the aqueous adhesive solution (7) obtained in Production Example 10 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4. The results are shown in Table 1.

[0153] Example 9 The first liquid crystal alignment solidified layer side of the laminate (1) obtained in Production Example 2 and the second liquid crystal alignment solidified layer side of the laminate (2) obtained in Production Example 3 were treated with a corona treatment machine at a treatment density of 50 W·min / m 2 The corona treatment was carried out. Using an MCD coater (manufactured by Fuji Machine Co., Ltd.) (cell shape: honeycomb, gravure roll line count: 1000 / inch, rotation speed 130% / line speed), the aqueous adhesive solution (1) obtained in Production Example 4 was coated on the corona-irradiated surface of the laminate (1) to a coating thickness (liquid layer thickness) of 1 μm, and the laminate (2) was laminated using a lamination roll machine so that the corona-irradiated surface of the laminate (2) faced the coated surface. The lamination line speed was 15 m / min. The lamination was carried out so that the slow axis of the retardation film 2 (λ / 4 retardation film) was at a 60° angle with the slow axis of the retardation film 1 (λ / 2 retardation film). In Example 1, the laminate (1) and the laminate (2) were laminated together 2 seconds after the laminate (1) came into contact with the aqueous adhesive solution (1). That is, in Example 9, the time from the contacting step to the laminating step was 2 seconds. After lamination, the laminate was heated and dried at 60°C for 6 minutes to form an adhesive layer (9) from the aqueous adhesive solution (1), and the biaxially stretched norbornene-based films on both sides were peeled off from the resulting laminate to obtain an optical laminate (9) having a configuration of retardation film 1 / adhesive layer (9) / retardation film 2. The results are shown in Table 1.

[0154] [Example 10] The same procedure as in Example 9 was carried out, except that the aqueous adhesive solution (1) was applied so that the coating thickness (thickness of the liquid layer) was 5 μm, to obtain an optical laminate (10) having a configuration of retardation film 1 / adhesive layer (10) / retardation film 2. The results are shown in Table 1.

[0155] [Example 11] The same procedure as in Example 1 was carried out, except that after lamination, the adhesive layer (11) was formed from the aqueous adhesive solution (1) by drying at 23°C for 15 hours, to obtain an optical laminate (11) having a configuration of retardation film 1 / adhesive layer (11) / retardation film 2. The results are shown in Table 1.

[0156] [Example 12] The same procedure as in Example 4 was carried out, except that after lamination, the adhesive layer (12) was formed from the aqueous adhesive solution (4) by drying at 23°C for 15 hours, to obtain an optical laminate (12) having a configuration of retardation film 1 / adhesive layer (12) / retardation film 2. The results are shown in Table 1.

[0157] Comparative Example 1 An optical laminate (13) having a configuration of retardation film 1 / adhesive layer (13) / retardation film 2 was obtained in the same manner as in Example 1, except that the aqueous adhesive solution (4) obtained in Production Example 7 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4, the thickness of the liquid layer of the aqueous adhesive solution (4) was changed to 2 μm, and after lamination, the laminate was heated and dried at 60° C. for 10 minutes. The results are shown in Table 1.

[0158] Comparative Example 2 The same procedure as in Example 1 was carried out, except that the aqueous adhesive solution (8) obtained in Production Example 11 was used instead of the aqueous adhesive solution (1) obtained in Production Example 4, the thickness of the liquid layer of the aqueous adhesive solution (8) was changed to 2 μm, and after lamination, the films were dried by heating at 60° C. for 10 minutes, thereby obtaining an optical laminate (14) having a configuration of retardation film 1 / adhesive layer (14) / retardation film 2. The results are shown in Table 1.

[0159]

[0160] The optical laminate produced by the production method of the present invention can be used for any appropriate purpose, and can be suitably used for, for example, image display devices such as liquid crystal display devices and organic EL display devices.

Claims

1. A method for producing an optical laminate in which a first light-transmitting optical film and a second light-transmitting optical film are bonded together with an adhesive layer, the method comprising: a laminating step of bonding the first light-transmitting optical film and the second light-transmitting optical film together with an aqueous adhesive solution; and a curing step of curing the aqueous adhesive solution to form the adhesive layer having a thickness of 50 nm or less.

2. The manufacturing method according to claim 1, wherein water is removed from the water-based adhesive solution in the curing step.

3. The manufacturing method according to claim 1, further comprising a contacting step of contacting the aqueous adhesive solution with at least one selected from the group consisting of the first light-transmitting optical film and the second light-transmitting optical film.

4. The manufacturing method according to claim 3, wherein a liquid layer of the aqueous adhesive solution is formed in the contacting step, and the liquid layer does not come into contact with air during the period from when the contacting step is performed until when the laminating step is performed.

5. The manufacturing method according to claim 3, wherein the time from the contacting step to the laminating step is 1 second or less.

6. The manufacturing method according to claim 3, wherein the contacting step is carried out by placing the second light-transmitting optical film on the surface of the first light-transmitting optical film and supplying the aqueous adhesive solution to the bonded portion between the first light-transmitting optical film and the second light-transmitting optical film.

7. The manufacturing method according to claim 6, wherein a pool of the water-based adhesive solution is formed by supplying the water-based adhesive solution to the bonded portion.

8. The manufacturing method according to claim 1, wherein in the bonding step, the first light-transmitting optical film and the second light-transmitting optical film are bonded together by pressure bonding.

9. The manufacturing method according to claim 1, wherein the water-based adhesive solution contains at least one amino compound.

10. The method according to claim 9, wherein the amino compound is an amino-silane coupling agent.

11. The manufacturing method according to claim 1, wherein the water-based adhesive solution contains at least one of an amino compound and an epoxy compound.

12. The manufacturing method according to claim 11, wherein the total content of the amino compound and the epoxy compound in the aqueous adhesive solution is 0.5% by weight to 10% by weight.

13. The manufacturing method according to claim 1, wherein at least one of the first light-transmitting optical film and the second light-transmitting optical film has an in-plane refractive index of 1.50 or more.

14. The manufacturing method according to claim 1, wherein at least one of the first light-transmitting optical film and the second light-transmitting optical film is a retardation film.

15. The method of claim 1, wherein the adhesive layer has a thickness of less than 30 nm.

16. A method for manufacturing an image display device, comprising forming an image display device using an optical laminate formed by the manufacturing method according to any one of claims 1 to 15.

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