CN116893465A

CN116893465A - optical laminate

Info

Publication number: CN116893465A
Application number: CN202310308804.7A
Authority: CN
Inventors: 神野亨; 松野健次
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2022-03-30
Filing date: 2023-03-27
Publication date: 2023-10-17

Abstract

The invention provides an optical laminate, which can inhibit uneven generation caused by tiny foreign matters even when tiny foreign matters are mixed in an adhesive layer during manufacturing of the optical laminate. The optical laminate comprises a 1 st retardation plate and a 1 st optical layer bonded to one surface of the 1 st retardation plate, wherein the 1 st retardation plate comprises a 1 st retardation layer as a cured layer of a polymerizable liquid crystal compound, and the 1 st retardation layer has a normalized DMT elastic modulus of 0.65 or more.

Description

Optical laminate

Technical Field

The present invention relates to an optical laminate.

Background

A circular polarizing plate, which is an optical laminate, is an optical member in which a polarizing plate and a phase difference plate are laminated, and is used for preventing reflection of light at electrodes constituting an organic EL image display device or the like, for example, in a device that displays an image in a planar state. As a retardation plate constituting the circularly polarizing plate, a so-called λ/4 plate is generally used. In recent years, with the diversification of displays, the thinning of circular polarizing plates has been demanded. As one method for thinning a circularly polarizing plate, a retardation plate having a liquid crystal layer obtained by changing a stretched retardation plate used for a circularly polarizing plate to a retardation plate having a liquid crystal layer obtained by curing a polymerizable liquid crystal compound in an aligned state is known. For example, patent document 1 proposes a retardation plate having a horizontally aligned liquid crystal layer and a vertically aligned liquid crystal layer formed by polymerizing and curing a polymerizable liquid crystal compound in a state of being aligned in a vertical direction with respect to a plane of the retardation plate (patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2015-163935

Disclosure of Invention

Problems to be solved by the invention

However, the liquid crystal layer included in the circularly polarizing plate is formed by a method of forming a liquid crystal layer on a substrate and laminating the liquid crystal layer on other functional layers via an adhesive layer and peeling off only the substrate, in order to make the liquid crystal layer thinner, however, in the conventional circularly polarizing plate, there is a case where color unevenness caused by deformation of the liquid crystal retardation layer due to a minute foreign matter mixed in the adhesive layer is observed. In the case where the liquid crystal layer is a horizontally aligned liquid crystal layer, unevenness is more easily observed.

The invention provides an optical laminate, which can inhibit uneven generation caused by tiny foreign matters even when the tiny foreign matters are mixed in an adhesive layer during manufacturing of the optical laminate.

Means for solving the problems

The present invention provides the following optical layered body.

An optical laminate comprising a 1 st phase difference plate and a 1 st optical layer bonded to one surface of the 1 st phase difference plate,

the 1 st retardation plate comprises a 1 st retardation layer as a cured layer of a polymerizable liquid crystal compound,

The normalized DMT elastic modulus of the 1 st retardation layer is 0.65 or more.

[ 2 ] an optical laminate comprising a 1 st phase difference plate and a 1 st optical layer bonded to one surface of the 1 st phase difference plate,

the ratio (nIT) of the elastic deformation work amount (Japanese: elastic deformation work amount) of the 1 st retardation layer calculated by the following formula (1) is 25% or more.

Formula (1):

nIT (%) = { elastic deformation work amount/(elastic deformation work amount+plastic deformation work amount) } ×100

The optical laminate according to [ α2 ], wherein the normalized DMT elastic modulus of the 1 st retardation layer is 0.65 or more.

The optical laminate according to any one of [ α1 ] to [ 3 ], wherein the 1 st optical layer is a linear polarizing plate or a 2 nd phase difference plate.

The optical laminate according to any one of [ 1 ] to [ 4 ], wherein the 1 st optical layer is bonded to the 1 st phase difference plate via a 1 st adhesive layer,

the thickness of the 1 st adhesive layer is 4 μm or less.

The optical laminate according to [ 6 ], wherein the 1 st adhesive layer contains an adhesive.

The optical laminate according to any one of [ 1 ] to [ 6 ], further comprising a 2 nd optical layer bonded to the other surface of the 1 st retardation plate,

one of the 1 st optical layer and the 2 nd optical layer is a linear polarizing plate, and the other is a 2 nd phase difference plate.

The optical laminate according to [ 8 ], wherein the 2 nd optical layer is bonded to the 1 st phase difference plate via a 2 nd adhesive layer,

the thickness of the 2 nd adhesive layer is 4 μm or less.

The optical laminate according to [ 9 ], wherein the 2 nd pressure-sensitive adhesive layer contains an adhesive.

The optical laminate according to any one of [ 1 ] to [ 9 ], wherein the 1 st retardation plate satisfies the following formula (2).

100nm＜Re(550)＜160nm (2)

[ Re (550) represents the in-plane phase difference value at a wavelength of 550 nm. ]

The optical laminate according to any one of [ 1 ] to [ 10 ], which comprises a 2 nd retardation plate,

the 2 nd retardation plate comprises a 2 nd retardation layer as a cured layer of a polymerizable liquid crystal compound,

the ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer calculated by the formula (1) is 10% or more.

The optical laminate according to any one of [ 1 ] to [ 11 ], further comprising at least one of a front panel and a touch sensor panel laminated on the observation side of the 1 st phase difference plate.

An image display device comprising the optical laminate according to any one of [ 1 ] to [ 12 ].

Effects of the invention

According to the present invention, it is possible to provide an optical laminate in which generation of unevenness due to fine foreign matters is suppressed even when fine foreign matters are mixed in an adhesive layer at the time of manufacturing an optical laminate or the like.

Drawings

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

Fig. 2 is a schematic cross-sectional view schematically showing an example of a modification of the optical laminate according to embodiment 1 of the present invention.

Fig. 3 is a schematic cross-sectional view schematically showing an example of an optical laminate having a base material layer of the present invention.

Fig. 4 is a schematic cross-sectional view schematically showing an example of a modification of the optical laminate having the base material layer of the present invention.

Fig. 5 is a schematic cross-sectional view schematically showing an example of a process for producing an optical layered body according to embodiment 1 of the present invention.

Fig. 6 is a schematic cross-sectional view schematically showing another example of the process for producing an optical layered body according to embodiment 1 of the present invention.

Fig. 7 is a schematic cross-sectional view schematically showing an example of an optical laminate according to embodiment 2 of the present invention.

Fig. 8 is a schematic cross-sectional view schematically showing an example of an optical laminate having a base material layer of the present invention.

Description of the reference numerals

1. 1a, 1b, 1c, 1d: optical laminate, 10, 50: 1 st phase difference plate, 11, 51: 1 st orientation layer, 12, 52: 1 st phase difference layer, 15, 55: substrate layer 1, 18: 1 st retardation plate with base material layer, 20: 2 nd phase difference plate, 21: 2 nd orientation layer, 22: phase difference layer 2, 25: substrate layer 2, 28: 2 nd retardation plate with base material layer, 31: adhesive layer (a), 32: adhesive layer (B), 40: linear polarizing plate, 61: laminate 1, 62: laminate 2, 63: 3 rd laminate, 64: and 4 th laminate.

Detailed Description

Hereinafter, preferred embodiments of the optical laminate and the method for producing the same according to the present invention will be described with reference to the accompanying drawings.

< optical laminate >

The optical laminate of the present invention is an optical laminate comprising a 1 st phase difference plate and a 1 st optical layer bonded to one surface of the 1 st phase difference plate. The 1 st retardation plate comprises a 1 st retardation layer as a cured product of a polymerizable liquid crystal compound. The 1 st retardation layer satisfies at least one of the following conditions (i) or (ii).

(i) The elastic modulus of the standardized DMT is more than 0.65

(ii) The ratio (nIT) of the elastic deformation work is 25% or more

The ratio (nIT) of the elastic deformation work is calculated by the following formula (1).

Formula (1):

The ratio (nIT) of the elastic deformation work amount of the retardation layer obtained by curing the polymerizable liquid crystal compound will be described. In the present invention, the ratio (nIT) of the elastic deformation work amount means the ratio (Welast/wtotal×100) of the elastic deformation work (Welast) in the total deformation work amount (Wtotal) shown by the press-in work amount composed of the plastic deformation work (Wplast) and the elastic deformation work (Welast) obtained in the instrumented indentation test based on the hardness and various material parameters of ISO-14577. The device for measuring the ratio (nIT) of the elastic deformation work amount is a micro hardness measuring device. Specifically, fischer scope HM2000 (manufactured by Helmut Fischer) and the like are mentioned.

The 1 st optical layer is, for example, a polarizing plate or a 2 nd phase difference plate. In the step of bonding the 1 st optical layer to one surface of the 1 st retardation plate via the 1 st adhesive layer, a minute foreign matter may be mixed into the 1 st adhesive layer when the 1 st adhesive layer is formed.

The present inventors have made intensive studies to suppress unevenness occurring in the optical laminate when a fine foreign matter is mixed in the 1 st pressure-sensitive adhesive layer, and as a result, have found that unevenness can be suppressed by setting the normalized DMT elastic modulus to 0.65 or more (condition (i) above) or setting the ratio of the elastic deformation work amount (nIT) to 25% or more (condition (ii) above) for the 1 st retardation layer, and have completed the present invention.

The optical laminate of the present invention may further have a 2 nd optical layer bonded to the other surface of the 1 st retardation plate. In this configuration, for example, one of the 1 st optical layer and the 2 nd optical layer is a linear polarizing plate, and the other is a 2 nd phase difference plate. In the step of bonding the 2 nd optical layer to the other surface of the 1 st retardation plate via the 2 nd adhesive layer, a minute foreign matter may be mixed into the 2 nd adhesive layer at the time of forming the 2 nd adhesive layer.

The present inventors have found that, in the 1 st retardation layer, the normalized DMT elastic modulus is 0.65 or more (condition (i) above), or the ratio of the elastic deformation work amount (nIT) is 25% or more (condition (ii) above), and that even when fine foreign matter is mixed in the 1 st adhesive layer and the 2 nd adhesive layer, the unevenness generated in the optical laminate can be suppressed.

The optical laminate of the present invention preferably has a structure including a linear polarizing plate. Hereinafter, a specific example of the structure and manufacturing method of the optical laminate (embodiment 1) including the layer of "linear polarizing plate/adhesive layer (a)/1 st retardation plate/adhesive layer (B)/2 nd retardation plate" and the optical laminate including the layer of "linear polarizing plate/adhesive layer (a)/1 st retardation plate (embodiment 2)" will be described. In embodiment 1, one of the adhesive layer (a) and the adhesive layer (B) corresponds to the 1 st adhesive layer, and the other corresponds to the 2 nd adhesive layer. In the linear polarizing plate and the 2 nd retardation plate, the side closer to the 1 st adhesive layer corresponds to the 1 st optical layer, and the side closer to the 2 nd adhesive layer corresponds to the 2 nd optical layer. Hereinafter, the case where the adhesive layer (a) corresponds to the 1 st adhesive layer, the adhesive layer (B) corresponds to the 2 nd adhesive layer, the linear polarization plate corresponds to the 1 st optical layer, and the 2 nd retardation plate corresponds to the 2 nd optical layer will be described. In embodiment 2, the adhesive layer (a) corresponds to the 1 st adhesive layer, and the linear polarizing plate corresponds to the 1 st optical layer.

< optical laminate of embodiment 1 >

Fig. 1 to 4 are schematic cross-sectional views schematically showing an example of an optical layered body according to the present embodiment. As shown in fig. 1 to 4, the optical layered bodies 1a, 1B, 1c, and 1d (hereinafter, these may be collectively referred to as "optical layered body 1") of the present embodiment include, in order, a linear polarizing plate (corresponding to "1 st optical layer") 40, an adhesive layer (a) (corresponding to "1 st adhesive layer") 31, a 1 st phase difference plate 10, an adhesive layer (B) (corresponding to "2 nd adhesive layer") 32, and a 2 nd phase difference plate (corresponding to "2 nd optical layer") 20. The 1 st retardation plate 10 is a cured layer of a polymerizable liquid crystal compound, and includes a 1 st retardation layer 12 having a retardation. The 2 nd retardation plate 20 is a cured layer of a polymerizable liquid crystal compound, and includes a 2 nd retardation layer 22 having a retardation. The 2 nd retardation plate 20 may be a stretched film having a retardation. From the viewpoint of reducing the thickness of the optical laminate 1, the 2 nd retardation layer 20 is preferably a structure having a 2 nd retardation layer 22 as a cured layer of a polymerizable liquid crystal compound. Hereinafter, the case where the 2 nd retardation layer 22 is a cured layer of a polymerizable liquid crystal compound will be described.

In the optical laminate 1, the 1 st retardation layer 12 satisfies at least one of a normalized DMT elastic modulus of 0.65 or more (condition (i) above) and an elastic deformation work amount ratio (nIT) of 25% or more (condition (ii) above). Embodiment 1 is a configuration effective for suppressing occurrence of unevenness caused by fine foreign matters even when fine foreign matters are mixed in the adhesive layer (a) 31.

As shown in fig. 3 and 4, the optical laminate 1 may have the 2 nd base material layer 25 on the opposite side of the 2 nd phase difference plate 20 from the side of the adhesive layer (B) 32. The 2 nd base layer 25 is preferably provided so as to be separable between the 2 nd base layer 25 and the 2 nd phase difference layer 22 included in the 2 nd phase difference plate 20.

The fact that the 2 nd base material layer 25 and the 2 nd retardation layer 22 are separable means that the 2 nd base material layer 25 is peelable from the 2 nd retardation layer 22, or that the 2 nd alignment layer 21 is peelable from the 2 nd alignment layer 21 when the 2 nd alignment layer 21 is present between the 2 nd base material layer 25 and the 2 nd retardation layer 22, or that the 2 nd alignment layer 21 is peelable from the 2 nd retardation layer 22. Therefore, in the case where the 2 nd base material layer 25 is peelable from the 2 nd alignment layer 21, if the 2 nd base material layer 25 is separated from the optical layered body 1c, 1d (fig. 3 and 4), the 2 nd alignment layer 21 remains on the 2 nd retardation layer 22 (fig. 1 and 2). In the case where the 2 nd alignment layer 21 is peelable from the 2 nd retardation layer 22, if the 2 nd base material layer 25 is separated from the optical laminate 1a, the 2 nd alignment layer 21 is peeled together with the 2 nd base material layer 25.

(1 st phase plate)

The 1 st retardation plate 10 may be the 1 st retardation layer 12 itself, which is a cured layer of a polymerizable liquid crystal compound, or may be a laminate of the 1 st retardation layer 12 and the 1 st alignment layer 11. When the 1 st retardation plate 10 has the 1 st alignment layer 11, the 1 st alignment layer 11 may be provided on the opposite side of the 1 st retardation layer 12 from the 2 nd retardation plate 20 side (fig. 1), or may be provided on the 2 nd retardation plate 20 side of the 1 st retardation layer 12 (fig. 2). The 1 st retardation layer 12 satisfies at least one of the following conditions (i) or (ii).

(i) The elastic modulus of the standardized DMT is more than 0.65

(ii) The ratio (nIT) of the elastic deformation work is 25% or more

The normalized DMT elastic modulus of the 1 st retardation layer 12 is preferably 0.65 or more, more preferably 0.75 or more, and still more preferably 0.85 or more. By setting the normalized DMT elastic modulus of the 1 st retardation layer 12 to the above range, unevenness can be suppressed even when fine foreign matters are mixed in the adhesive layer (a) 31 in the optical laminate 1. The upper limit of the normalized DMT elastic modulus of the 1 st retardation layer 12 is not particularly limited, but is, for example, 3.0 or less, preferably 2.0 or less, from the viewpoints of process suitability and handleability after the formation of the 1 st retardation layer 1 2.

The "DMT elastic modulus" is an elastic modulus calculated based on a theory constructed by Derjaguim-Muller-Toporov et al (DMT theory) by evaluating mechanical properties of a cross section of a retardation layer using an Atomic Force Microscope (AFM). The "normalized DMT elastic modulus" is obtained by dividing the DMT elastic modulus of the evaluation sample by the DMT elastic modulus of the standard. The normalized DMT elastic modulus of the 1 st retardation layer 12 is a value at a temperature of 23℃and a relative humidity of 50%, and is measured and calculated by the method described in examples described later.

The ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer 12 is preferably 25% or more, more preferably 26% or more, still more preferably 28% or more, and still more preferably 30% or more. The upper limit of the ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer 12 is not particularly limited, but is, for example, 70% or less, preferably 50% or less, from the viewpoints of process suitability and handleability after the formation of the 1 st retardation layer 12.

The ratio (niT) of the elastic deformation work amount of the 1 st retardation layer 12 is a value at a temperature of 23 ℃ and a relative humidity of 50%, and can be calculated from the above formula (1) by using a value measured by a method for measuring the ratio (nIT) of the elastic deformation work amount described in examples described later.

According to the optical laminate 1 of the present embodiment, even when fine foreign matter is mixed in the adhesive layer (a) 31, unevenness can be suppressed. The method for producing the optical laminate comprises the following steps: when the 1 st optical layer and the 1 st phase difference plate are bonded together via the 1 st adhesive layer, for example, the 1 st optical layer and the 1 st phase difference plate are bonded together by a bonding roller, and a force is applied to the optical layer from the outside thereof. The present inventors have established the following hypothesis: when a minute foreign matter is mixed in the 1 st adhesive layer, a force from the minute foreign matter mixed in the 1 st adhesive layer is applied to the 1 st retardation plate in the above-described step, and as a result, local deformation occurs in the 1 st retardation layer in the 1 st retardation plate, and deformation of the 1 st retardation layer is maintained in the optical laminate, and unevenness occurs. Based on this hypothesis, the following findings were obtained by verifying the ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer: by setting the ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer to 25% or more, even when a minute foreign matter is mixed in the 1 st adhesive layer, unevenness generated in the optical laminate can be suppressed, and the structure of the optical laminate of the present embodiment can be obtained. Based on this hypothesis, the following findings were obtained: by setting the normalized DMT elastic modulus of the 1 st retardation layer to 0.65 or more, even when a minute foreign matter is mixed in the 1 st adhesive layer, unevenness occurring in the optical laminate can be suppressed, and the structure of the optical laminate of the present embodiment can be obtained.

In addition, the optical laminate 1 of the present embodiment can suppress unevenness even when fine foreign matter is mixed in the adhesive layer (B) 32. The method for producing the optical laminate comprises the following steps: when the 1 st phase difference plate and the 2 nd optical layer are bonded together via the 2 nd adhesive layer, for example, the 1 st phase difference plate and the 2 nd optical layer are laminated together by passing the layers through a bonding roller, and a force is applied to the layers from the outside. The present inventors have assumed that: when a minute foreign matter is mixed in the 2 nd adhesive layer, a force from the minute foreign matter mixed in the 2 nd adhesive layer is applied to the 1 st phase difference plate in the above-described step, and as a result, local deformation occurs in the 1 st phase difference layer in the 1 st phase difference plate. The 1 st retardation layer is presumed to have a normalized DMT elastic modulus of 0.65 or more (condition (i) above) or a ratio of elastic deformation work (nIT) of 25% or more (condition (ii) above), whereby even when a minute foreign matter is mixed in the 2 nd adhesive layer, unevenness occurring in the optical laminate can be suppressed.

Regarding the 1 st retardation layer 12, it is considered that if the proportion (nIT) of the DMT elastic modulus or the elastic deformation work amount is increased, the 1 st retardation layer 12 is easily restored to its original shape even if the 1 st retardation layer 12 is deformed at the time of bonding the 1 st retardation plate 10 and the linear polarizing plate 40 due to the inclusion of the minute foreign matter in the adhesive layer (a) 31.

The optical laminate 1 generally has an adhesive layer, and deformation due to foreign matter, which is easily observed on the spacer side of the adhesive, may become undetectable due to the relaxing effect of the adhesive layer after the panel is bonded. However, even if the deformation is relaxed in the structure of the optical laminate 1, unevenness may be observed when the deformation in the 1 st retardation layer 12 is maintained. In the present invention, the effect of suppressing the occurrence of unevenness caused by deformation due to a minute foreign matter whose size is such that the deformation is relaxed when the thin film is bonded to a panel is remarkable. For example, the effect of suppressing the occurrence of unevenness is remarkable in the mixing of fine foreign matters having a diameter of 100 μm or less, further 50 μm or less, particularly 30 μm or less. The lower limit of the diameter of the fine foreign matter is not limited, but in general, in the case of a fine foreign matter having a diameter of less than 1 μm, the diameter is preferably 1 μm or more because the fine foreign matter is less likely to be uneven. Such fine foreign matters are assumed to be aggregates of components in the adhesive composition, fine foreign matters from a container used in preparing the adhesive composition, and the like.

The ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer 12 or the value of the DMT elastic modulus can be adjusted by, for example, the kind of the polymerizable liquid crystal compound constituting the 1 st retardation layer 12, the degree of polymerization (curing degree), the kind and amount of the polymerization initiator, the reactive additive, the leveling agent, the polymerization inhibitor, the crosslinking agent and other additives contained in the 1 st retardation layer 12, the thickness of the 1 st retardation layer 12, and the like. The inventors have found that: if the degree of polymerization (curing) of the polymerizable liquid crystal compound increases, the ratio of the amount of elastic deformation work (nIT) and the value of DMT elastic modulus also increase. The ratio of the elastic deformation work amount (nIT) of the 1 st retardation layer 12 and the value of the DMT elastic modulus can also be adjusted by the crosslink density of the 1 st retardation layer 12. In order to increase the crosslinking density, a polyfunctional polymerizable liquid crystal compound having 2 or more polymerizable groups in the molecule may be used as the polymerizable liquid crystal compound.

In order to set the ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer 12 to a predetermined range, for example, a preliminary experiment for controlling the polymerization degree (curing degree) of the polymerizable liquid crystal compound may be performed, and the ratio (nIT) of the desired elastic deformation work amount may be set. As such a preliminary experiment, for example, in the case of controlling the polymerization degree of the 1 st retardation layer 12, the following can be performed. First, a coating layer of a composition for forming a retardation layer containing a polymerizable liquid crystal compound is provided on a 1 st base layer (the 1 st alignment layer may be provided), and ultraviolet rays or the like are irradiated to the coating layer, whereby the 1 st retardation layer is formed on the 1 st base layer. The degree of polymerization (degree of curing) is determined by measuring the ratio (relative value) of the amount of polymerizable groups of the polymerizable liquid crystal compound contained in the coating layer to the amount of polymerizable groups of the polymerizable liquid crystal compound contained in the 1 st retardation layer by infrared absorption (IR) spectrometry or the like. The ratio (nIT) of the elastic deformation work of the 1 st retardation layer obtained at this time was measured, and the above-determined polymerization degree was correlated with the ratio (nIT) of the elastic deformation work. This step is performed by changing the type of the polymerizable liquid crystal compound, the irradiation amount of ultraviolet rays, and the like. By thus obtaining the correlation between the degree of polymerization and the ratio (nIT) of the amount of elastic deformation work, the degree of polymerization of the ratio (nIT) for obtaining the desired amount of elastic deformation work can be determined. The present inventors have found that: when the coating layer of the composition for forming a retardation layer is irradiated with ultraviolet light or the like, the coating layer is heated, for example, to 30 to 70 ℃, whereby a desired ratio of the amount of elastic deformation work (nIT) can be easily obtained, and further, the process suitability as a base layer is also desired. The heating is desirably performed uniformly, and for example, it is preferable to irradiate ultraviolet rays to the coating layer of the composition for forming a phase difference in a state where the substrate surface is provided on the metal after temperature adjustment. In addition to the heating, the ultraviolet irradiation is preferably performed under a nitrogen atmosphere excluding oxygen which is a main cause of the inhibition of curing. By these methods, the polymerization degree can be increased and adjusted so that the ratio (nIT) of the desired elastic deformation work amount is obtained.

The value of the DMT elastic modulus of the 1 st retardation layer 12 can also be adjusted by the same method as the ratio (nIT) of the amount of elastic deformation work.

The thickness of the 1 st phase difference plate 10 is preferably 1.0 μm or more, more preferably 1.5 μm or more, and may be 1.7 μm or more, or may be 2.0 μm or more. The 1 st phase difference plate 10 has a thickness of usually 8 μm or less, and may have a thickness of 5 μm or less or 3 μm or less.

(No. 2 phase plate)

The 2 nd retardation plate 20 may be the 2 nd retardation layer 22 itself, which is a cured layer of a polymerizable liquid crystal compound, or may be a laminate of the 2 nd retardation layer 22 and the 2 nd alignment layer 21. When the 2 nd retardation plate 20 has the 2 nd alignment layer 21, the 2 nd alignment layer 21 is provided on the opposite side of the 2 nd retardation layer 22 from the 1 st retardation plate 10 side.

The thickness of the 2 nd retardation plate 20 is preferably 1.0 μm or more, and may be 1.5 μm or more, or may be 2.0 μm or more, or may be 2.5 μm or more. The thickness is usually 8 μm or less, may be 5 μm or less, may be 3.5 μm or less, or may be 3.0 μm or less.

The ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer 22 is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. If the content is less than 10%, plastic deformation due to foreign matter may become a bright point in the vertical alignment liquid crystal layer in which unevenness is not easily observed, for example. The upper limit of the ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer 22 is not particularly limited, but is, for example, 70% or less, preferably 50% or less, from the viewpoints of process suitability and handling property after formation of the 2 nd retardation layer 22.

The ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer 22 can be measured and calculated by the same method as the ratio (nIT) of the elastic deformation work amount of the 1 st retardation layer 12, and can be adjusted so as to be the desired ratio (nIT) of the elastic deformation work amount by the same method as the 1 st retardation layer 12.

It is considered that the greater the ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer 22, the greater the force with which the 2 nd retardation layer 22 is restored to its original shape even if deformed, and that, for example, in the step of bringing the 1 st retardation plate and the 2 nd retardation plate together by the bonding roller and applying the force to be sandwiched from the outside thereof, the greater the ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer 22, the greater the force with which the foreign matter is pushed back, and the greater the force from the minute foreign matter to the 1 st retardation layer 12, the more likely the unevenness is considered to be generated. Therefore, when the ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer 22 is large, the effect of suppressing unevenness is more remarkable.

(combination of the 1 st phase plate and the 2 nd phase plate)

As a combination of the 1 st phase difference plate 10 and the 2 nd phase difference plate 20 in the optical laminate 1, for example, there may be mentioned:

i) A combination of a 1/4 wave plate and an optical compensation layer,

ii) a combination of a reverse-dispersive 1/4 wave plate and an optical compensation layer,

iii) A combination of a 1/2 wave plate and a 1/4 wave plate,

iv) a combination of a 1/2 wave plate and an optical compensation layer, etc. The optical laminate 1 composed of the combination of i) to iv) described above can be used as a circularly polarizing plate.

In the 1 st retardation plate 10, when the 1 st retardation layer 12 is oriented horizontally, unevenness due to the inclusion of minute foreign matters in the adhesive layer (a) 31 is more remarkably observed. In the present invention, even if the 1 st retardation layer 12 is a combination of the above i) and ii) which are horizontally oriented, unevenness can be suppressed, and therefore, the combination of the above i) and ii) which is more remarkable in the effect of the present invention is a suitable combination.

The 1/4 wave plate imparts a phase difference of pi/2 (=λ/4) to the electric field oscillation direction (polarization plane) of incident light, and has a function of converting linearly polarized light of a specific wavelength into circularly polarized light (or converting circularly polarized light into linearly polarized light).

The 1/4 wave plate is a layer whose in-plane retardation value at a specific wavelength λnm, that is, re (λ) satisfies Re (λ) =λ/4, and can be realized at an arbitrary wavelength in the visible light region, but is preferably realized in the vicinity of wavelength 550 nm. The in-plane retardation value at wavelength 550nm, re (550), preferably satisfies the formula (2): re (550) is less than 100nm and less than 160nm. In addition, it is more preferable that Re (550) is less than 150nm at 1.0 nm.

The retardation value in the thickness direction of the lambda/4 plate measured at a wavelength of 550nm, that is, rth (550), is preferably-120 to 120nm, more preferably-80 to 80nm.

The 1/2 wave plate imparts pi (=λ/2) phase difference to the electric field vibration direction (polarization plane) of the incident light, and has a function of changing the direction of the linearly polarized light (polarization direction). In addition, if light of circularly polarized light is incident, the rotation direction of the circularly polarized light can be reversely rotated.

The 1/2 wave plate is a layer whose in-plane retardation value at a specific wavelength λnm, i.e., re (λ), satisfies Re (λ) =λ/2. As long as Re (λ) =λ/2 is realized at an arbitrary wavelength in the visible light region, of which it is preferably realized in the vicinity of wavelength 550 nm. The in-plane retardation value at wavelength 550nm, re (550), preferably satisfies 21 nm.ltoreq.Re (550). Ltoreq.300 nm. In addition, it is more preferable that Re (550) to 290nm is not more than 220 nm.

The retardation value in the thickness direction of the 1/2 wave plate, that is, rth (550), measured at a wavelength of 550nm is preferably-150 to 150nm, more preferably-100 to 100nm.

Examples of the optical compensation layer include a positive a plate and a positive C plate. The positive a plate satisfies the relationship Nx > Ny, where Nx is the refractive index in the slow axis direction in the plane, ny is the refractive index in the fast axis direction in the plane, and Nz is the refractive index in the thickness direction. The positive A plate preferably satisfies the relation that Nx > Ny > Nz. The positive a plate can also function as a 1/4 wavelength layer. The positive C plate meets the relation that Nz is more than Nx and more than or equal to Ny.

The inverse wavelength dispersion refers to an optical characteristic in which the in-plane retardation value of the liquid crystal at a short wavelength is smaller than the in-plane retardation value of the liquid crystal at a long wavelength, and preferably satisfies the following formula (a):

Re(450)≤Re(550)≤Re(650) (a)。

re (λ) represents an in-plane phase difference value with respect to light having a wavelength of λnm.

The optical characteristics of the retardation plate can be adjusted by the alignment state of the liquid crystal compound constituting the liquid crystal layer.

(adhesive layer (A))

The adhesive layer (a) 31 is a layer for bonding the linear polarizing plate 40 to the 1 st phase difference plate 10. The adhesive layer (a) 31 may be in direct contact with the polarizing plate 40 and the 1 st phase difference plate 10. The thickness of the adhesive layer (A) 31 is preferably 0.1 μm to 50. Mu.m, more preferably 0.1 μm to 10. Mu.m, still more preferably 0.5 μm to 5. Mu.m.

When fine foreign matter is mixed into the adhesive layer (a) 31 when the adhesive layer (a) 31 is formed, the thicker the adhesive layer (a) 31, the less the influence on the deformation of other layers due to the mixing of fine foreign matter into the adhesive layer (a) 31 itself can be reduced, and the occurrence of unevenness can be reduced. The invention exerts the following effects: even in the case where the thickness of the adhesive layer (a) 31 is thin, that is, even in the case where the effect of reducing the deformation caused by the incorporation of the minute foreign matter into the adhesive layer (a) 31 itself is low or none, the occurrence of unevenness caused by the minute foreign matter can be suppressed. Therefore, from the viewpoint of making the effect of the present invention more remarkable, the thickness of the adhesive layer (a) 31 is preferably 4 μm or less, and the effect is more remarkable when it is 3 μm or less and the effect is more remarkable when it is 2 μm or less.

(adhesive layer (B))

The pressure-sensitive adhesive layer (B) 32 is a layer for bonding the 1 st phase difference plate 10 and the 2 nd phase difference plate 20 to each other. The adhesive layer (B) 32 may be in direct contact with the 1 st phase difference plate 10 and the 2 nd phase difference plate 20. The thickness of the adhesive layer (B) 32 is preferably 0.1 μm to 50pm, more preferably 0.1 μm to 10pm, and still more preferably 0.5pm to 5pm.

When fine foreign matter is mixed into the adhesive layer (B) 32 when the adhesive layer (B) 32 is formed, the thicker the adhesive layer (B) 32, the less the influence on the deformation of other layers due to the mixing of fine foreign matter into the adhesive layer (B) 32 itself can be reduced, and the occurrence of unevenness can be reduced. The invention exerts the following effects: even in the case where the thickness of the adhesive layer (B) 32 is thin, that is, even in the case where the effect of reducing the deformation caused by the incorporation of the minute foreign matter into the adhesive layer (B) 32 itself is low or none, the occurrence of unevenness caused by the minute foreign matter can be suppressed. Therefore, from the viewpoint of making the effect of the present invention more remarkable, the thickness of the adhesive layer (B) 32 is preferably 4 μm or less, and the effect is more remarkable when it is 3 μm or less, and the effect is more remarkable when it is 2 μm or less. The thickness of the adhesive layer (B) 32 may be the same as or different from the adhesive layer (a) 31.

(Linear polarization plate)

The linear polarization plate 40 includes a linear polarization layer; a polarizing plate having a protective layer provided on one or both sides of the linear polarizing layer; a polarizing plate with a protective film, etc. having a protective film provided on one surface of the polarizing plate. When the linear polarizing plate 40 is a polarizing plate having a protective layer on only one side of the linear polarizing layer, the linear polarizing layer side of the polarizing plate is preferably bonded to the 1 st phase difference plate 10. When the linear polarizing plate 40 is a polarizing plate with a protective film, the polarizing plate side of the polarizing plate with a protective film is preferably bonded to the 1 st phase difference plate 10.

The optical laminate 1 can be used by being attached to an image display element of an image display device such as a liquid crystal display device or an organic EL (electro luminescence) display device. The image display device of the present embodiment includes an optical laminate 1. The optical laminate 1 may be bonded with at least one of a front panel and a touch sensor panel on the observation side of the 1 st phase difference plate 50. More specifically, at least one of the front panel and the touch sensor panel may be attached to the surface of the linear polarizing plate 40 of the optical laminate 1 on the opposite side of the 1 st phase difference plate 50 side. As the touch sensor panel, various methods such as a resistive film method, a surface elastic wave method, an infrared method, an electromagnetic induction method, and a capacitance method have been proposed, and any method can be used. Among them, the electrostatic capacitance system is preferable.

(method for producing an optical laminate of embodiment 1)

Fig. 5 and 6 are schematic cross-sectional views schematically showing an example of a process for producing an optical layered body according to the present embodiment (embodiment 1). The optical layered bodies 1a, 1B manufactured by the manufacturing method of the optical layered body 1 sequentially include the above-described linear polarizing plate 40, adhesive layer (a) 31, 1 st phase difference plate 10, adhesive layer (B) 32, and 2 nd phase difference plate 20. The 1 st retardation layer 12 of the 1 st retardation plate 10 satisfies the normalized DMT elastic modulus (condition (i)) described above or the ratio of the elastic deformation work amount (nIT) (condition (ii)) described above.

The method for manufacturing the optical layered bodies 1a, 1b includes:

a step of preparing a 1 st phase difference plate 18 having a 1 st base layer 15 and a 1 st phase difference plate 10 and a tape base layer (fig. 5 (a));

a step of preparing a 2 nd retardation plate 28 (a retardation layer (X) of the tape base layer) having a 2 nd base layer 25 (a base layer (X)) and a 2 nd retardation plate 20 (a retardation layer (X)) (fig. 5 (b));

a step of preparing a laminate having, in order, a linear polarizing plate 40, an adhesive layer (a) 31, a 1 st retardation plate 10, an adhesive layer (B) 32, a 2 nd retardation plate 20, and a 2 nd base material layer 25; and

And separating the 2 nd base material layer 25 from the laminate.

The method for producing the optical laminate 1 may further include the steps of: from the exposed surface side exposed through the step of separating the 2 nd base material layer 25, another adhesive layer and a release film different from the adhesive layer (a) 31 and the adhesive layer (B) are sequentially formed. The other adhesive layer may be used for, for example, an image display element attached to a display device. The release film may cover the surface of the other adhesive layer opposite to the 2 nd phase difference plate 20 side, and may be provided so as to be peelable from the other adhesive layer.

In the method for producing the optical laminate 1, the 1 st retardation layer 12 of the 1 st retardation plate 10 satisfies the normalized DMT elastic modulus in the above range (condition (i)), or the ratio of the elastic deformation work amount (nIT) described above (condition (ii)). Therefore, in the step of bonding the 1 st phase difference plate 10 and the 2 nd phase difference plate 20 (fig. 5 (c), fig. 6 (c)) and the step of bonding the 1 st phase difference plate 10 and the linear polarizing plate 40 (fig. 5 (e), fig. 6 (B)), even if the 1 st phase difference layer 12 of the 1 st phase difference plate 10 is deformed by the minute foreign matter mixed into the adhesive layer (a) 31 or the adhesive layer (B), the deformation is relaxed, and the occurrence of unevenness in the optical laminate 1 can be suppressed.

The method for producing the optical laminate 1 includes the above steps, but the steps included in the step of preparing the laminate are different from those included in the case of obtaining the optical laminate 1a shown in fig. 1 and the case of obtaining the optical laminate 1b shown in fig. 2. First, the process of preparing the laminate when the optical laminate 1a shown in fig. 1 is obtained will be described. In the method for manufacturing the optical laminate 1a, the step of preparing the laminate may include:

a step of preparing a 2 nd retardation plate 28 having the 2 nd base material layer 25 and the 2 nd retardation plate 20 and having a base material layer (fig. 5 (b));

a step of bonding the 1 st phase difference plate 10 side of the 1 st phase difference plate 18 with the base layer and the 2 nd phase difference plate 20 side of the 2 nd phase difference plate 28 with the base layer via the 2 nd adhesive layer 32 (fig. 5 (c));

a step of separating the 1 st base material layer 15 after the bonding step via the adhesive layer (B) 32 (fig. 5 (d)); and

a step of bonding the exposed surface exposed by separating the 1 st base layer 15 to the linear polarizing plate 40 via the adhesive layer (a) 31 (fig. 5 (e)).

The 1 st retardation plate 10 includes a 1 st retardation layer 12 formed by polymerizing a polymerizable liquid crystal compound on the 1 st base layer 15, and the 2 nd retardation plate 20 includes a 2 nd retardation layer 22 (liquid crystal layer X) formed by polymerizing a polymerizable liquid crystal compound on the 2 nd base layer 25. Accordingly, the step of preparing the 1 st retardation plate 18 with the base material layer may include a step of forming the 1 st retardation layer 12 by polymerizing a polymerizable liquid crystal compound on the 1 st base material layer 15. The step of preparing the 2 nd retardation plate 28 with a base material layer may include a step of forming the 2 nd retardation layer 22 by polymerizing a polymerizable liquid crystal compound on the 2 nd base material layer 25.

The 1 st retardation layer 12 may be formed by polymerizing a polymerizable liquid crystal compound on the 1 st alignment layer 11 provided on the 1 st base layer 15. Similarly, the 2 nd retardation layer 22 may be formed by polymerizing a polymerizable liquid crystal compound on the 2 nd alignment layer 21 provided on the 2 nd base material layer 25. In this case, the step of preparing the 1 st retardation plate 18 with the base material layer may include a step of forming the 1 st alignment layer 11 on the 1 st base material layer 15. The step of preparing the 2 nd retardation plate 28 with a base material layer may include a step of forming the 2 nd alignment layer 21 on the 2 nd base material layer 25.

In the method for producing the optical laminate 1a (fig. 1), for example, in the step of bonding via the adhesive layer (B) 32, a layer of the adhesive composition for forming the adhesive layer (B) 32 is first formed on the 1 st retardation plate 10 side of the 1 st retardation plate 18 of the tape base layer and/or on the 2 nd retardation plate 20 side of the 2 nd retardation plate 28 of the tape base layer. Next, an adhesive layer (B) 32 is formed from the adhesive composition layer. The method of forming the adhesive layer (B) 32 from the adhesive composition layer may be selected according to the kind of the adhesive composition layer. For example, in the case where the adhesive composition is an adhesive composition, the adhesive layer (B) 32 as an adhesive cured layer may be formed by curing the adhesive by irradiation with active energy rays, heat treatment, or the like, and in the case where the adhesive composition is an adhesive composition, the adhesive composition layer may be used as the adhesive layer (B) 32, or the adhesive layer (B) 32 may be formed from the adhesive composition layer. As a result, as shown in fig. 5 (c), the 1 st laminate 61 in which the 1 st base layer 15, the 1 st phase difference plate 10, the adhesive layer (B) 32, the 2 nd phase difference plate 20, and the 2 nd base layer 25 are laminated in this order can be obtained.

In the 1 st layered body 61, the 1 st base material layer 15 is preferably provided so as to be separable between the 1 st base material layer 15 and the 1 st phase difference layer 12. The fact that the 1 st base material layer 15 and the 1 st retardation layer 12 are separable means that the 1 st base material layer 15 is peelable from the 1 st retardation layer 12, or that the 1 st alignment layer 11 is peelable from the 1 st alignment layer 11 when the 1 st alignment layer 11 is present between the 1 st base material layer 15 and the 1 st retardation layer 12, or that the 1 st alignment layer 11 is peelable from the 1 st retardation layer 12. Therefore, in the case where the 1 st base material layer 15 can be peeled off from the 1 st alignment layer 11, if the 1 st base material layer 15 is separated from the 1 st laminate 61 as described later, the 1 st alignment layer 11 remains on the 1 st retardation layer 12. In the case where the 1 st alignment layer 11 is peelable from the 1 st retardation layer 12, if the 1 st base material layer 15 is separated from the 1 st laminate 61, the 1 st alignment layer 11 is peeled together with the 1 st base material layer 15.

In the step of separating the 1 st base material layer 15, the 1 st base material layer 15 is separated from the 1 st laminate 61 obtained in the step of bonding via the 2 nd adhesive layer 32. In the step of separating the 1 st base material layer 15, only the 1 st base material layer 15 may be peeled off, or in the case where the 1 st alignment layer 11 is present, the 1 st alignment layer 11 may be peeled off together with the 1 st base material layer 15. Thus, a 2 nd laminate 62 (fig. 5 (d)) in which the 1 st retardation plate 10 (the 1 st alignment layer 11, the 1 st retardation layer 12), the adhesive layer (B) 32, the 2 nd retardation plate 20 (the 2 nd retardation layer 22, the 2 nd alignment layer 21) and the 2 nd base material layer 25 were laminated in this order was obtained.

In the step of bonding the linear polarizing plate 40 via the adhesive layer (a) 31, for example, first, an adhesive composition layer is formed on the exposed surface side exposed by separating the 1 st base material layer 15 of the 2 nd laminate 62 shown in fig. 5 (d) and/or the linear polarizing plate 40. Next, the 2 nd laminate 62 is laminated and bonded to the linear polarizing plate 40 via an adhesive composition layer, and the adhesive composition layer is used as the adhesive layer (B) 31, or the adhesive composition layer is used to form the adhesive layer (a) 31. Thus, an optical laminate 1c (fig. 5 (e), 3) in which the linear polarizing plate 40, the adhesive layer (a) 31, the 1 st retardation plate 10 (the 1 st alignment layer 11, the 1 st retardation layer 12), the adhesive layer (B) 32, the 2 nd retardation plate 20 (the 2 nd retardation layer 22, the 2 nd alignment layer 21), and the 2 nd base material layer 25 were laminated in this order was obtained.

In the method for manufacturing the optical laminate 1a shown in fig. 1, in the step of separating the 2 nd base material layer 25, the 2 nd base material layer 25 is separated from the optical laminate 1 c. In the step of separating the 2 nd base material layer 25, only the 2 nd base material layer 25 may be peeled off, or in the case where the 2 nd alignment layer 21 is present, the 2 nd alignment layer 21 and the 2 nd base material layer 25 may be peeled off together. Thus, the optical laminate 1a shown in fig. 1 can be obtained.

Next, a process for preparing the laminated body when the optical laminated body 1b shown in fig. 2 is obtained will be described. In the method for manufacturing the optical laminate 1b, the step of preparing the laminate may include:

a step (fig. 6 (a)) of bonding the linear polarizing plate 40 to the 1 st phase difference plate 1O side of the 1 st phase difference plate 18 of the tape base layer via the adhesive layer (a) 31;

a step of separating the 1 st base material layer 15 after the bonding step via the adhesive layer (a) 31 (fig. 6 (b)); and

a step of bonding the exposed surface exposed by separating the 1 st base layer 15 to the 2 nd phase difference plate 20 side of the 2 nd phase difference plate 28 with the base layer via the adhesive layer (B) 32 (fig. 6 (c)).

The method for obtaining the 1 st retardation plate 18 with a base layer and the 2 nd retardation plate 28 with a base layer is the above-described method. Fig. 6 shows a case where the 1 st retardation plate 18 is a laminate of the 1 st alignment layer 11 and the 1 st retardation layer 12, but the 1 st retardation plate 18 may not include the 1 st alignment layer 11. Similarly, fig. 6 shows a case where the 2 nd retardation plate 28 is a laminate of the 2 nd alignment layer 21 and the 2 nd retardation layer 22, but the 2 nd retardation plate 28 may not include the 2 nd alignment layer 21.

In the bonding step via the adhesive layer (a) 31, for example, first, an adhesive composition layer is formed on the 1 st retardation plate 10 side of the 1 st retardation plate 18 with the base layer and/or on the linear polarizing plate 40. Next, the 1 st retardation plate 18 with the base layer and the linear polarizing plate 40 are laminated and bonded via an adhesive composition layer, and the adhesive composition layer is set as the adhesive layer (a) 31, or the adhesive layer (a) 31 is formed of the adhesive composition layer. Thus, the 3 rd laminate 63 (fig. 6 (a)) in which the linear polarizing plate 40, the adhesive layer (a) 31, the 1 st retardation plate 10 (the 1 st alignment layer 11, the 1 st retardation layer 12) and the 1 st base material layer 15 are laminated in this order can be obtained.

In the step of separating the 1 st base material layer 15, the 1 st base material layer 15 is separated from the laminate shown in fig. 6 (a). In the step of separating the 1 st base material layer 15, only the 1 st base material layer 15 may be separated, or in the case where the 1 st alignment layer 11 is present, the 1 st alignment layer 11 and the 1 st base material layer 15 may be peeled together. Thus, the 4 th laminate 64 (fig. 6 (b)) in which the linear polarizing plate 40, the adhesive layer (a) 31, and the 1 st retardation plate 10 (the 1 st retardation layer 12, the 1 st alignment layer 11) are laminated in this order can be obtained.

In the bonding step via the adhesive layer (B) 32, for example, a bonding agent composition layer for forming the adhesive layer (B) 32 is first formed on the exposed surface side of the 4 th laminate 64 shown in fig. 6 (B) where the 1 st base layer 15 is separated and exposed, and/or on the 2 nd phase difference plate 20 side of the 2 nd phase difference plate 28 with the base layer. Next, after the 4 th laminate 64 and the 2 nd retardation plate 28 with the base layer are laminated and bonded via the adhesive composition layer, the adhesive layer (B) 32 is formed from the adhesive composition layer. The method of forming the adhesive layer (B) 32 from the adhesive composition layer may be the above-mentioned method. Thus, an optical laminate 1d (fig. 6 (c) and 4) in which the linear polarizing plate 40, the adhesive layer (a) 31, the 1 st retardation plate 10 (the 1 st retardation layer 12 and the 1 st alignment layer 11), the adhesive layer (B) 32, the 2 nd retardation plate 20 (the 2 nd retardation layer 22 and the 2 nd alignment layer 21), and the 2 nd base material layer 25 were laminated in this order was obtained.

In the method of manufacturing the optical laminate 1b shown in fig. 2, in the step of separating the 2 nd base material layer 25, the 2 nd base material layer 25 is separated from the optical laminate 1 d. In the step of separating the 2 nd base material layer 25, only the 2 nd base material layer 25 may be peeled off, or in the case where the 2 nd alignment layer 21 is present, the 2 nd alignment layer 21 and the 2 nd base material layer 25 may be peeled off together. Thus, the optical laminate 1b shown in fig. 2 can be obtained.

< optical laminate of embodiment 2 >

Fig. 7 and 8 are schematic cross-sectional views schematically showing an example of an optical laminate according to this embodiment (embodiment 2). As shown in fig. 7 and 8, the optical layered bodies 2a and 2b (hereinafter, these may be collectively referred to as "optical layered body 2") of the present embodiment include, in order, a linear polarizing plate 40, a pressure-sensitive adhesive layer (a) 31, and a 1 st phase difference plate 50. The 1 st retardation plate 50 includes a 1 st retardation layer 52 as a cured layer of a polymerizable liquid crystal compound. The 1 st retardation layer 52 of the 1 st retardation plate 50 satisfies at least one condition that the normalized DMT elastic modulus is 0.65 or more and the ratio (nIT) of the elastic deformation work amount is 25% or more.

As shown in fig. 8, the optical laminate 2 may have a 1 st base material layer 55 on the opposite side of the 1 st phase difference plate 50 from the side of the adhesive layer (a) 31. The 1 st base layer 55 is preferably provided so as to be separable between the 1 st base layer 55 and the 1 st phase difference layer 52 included in the 1 st phase difference plate 50.

The fact that the 1 st base material layer 55 and the 1 st retardation layer 52 are separable means that the 1 st base material layer 55 is peelable from the 1 st retardation layer 52, or that the 1 st alignment layer 51 is peelable from the 1 st alignment layer 51 when the 1 st alignment layer 51 is present between the 1 st base material layer 55 and the 1 st liquid crystal layer 52, or that the 1 st alignment layer 51 is peelable from the 1 st retardation layer 52. Therefore, in the case where the 1 st base material layer 55 is peelable from the 1 st alignment layer 51, if the 1 st base material layer 55 is separated from the optical laminate 2b (fig. 8), the 1 st alignment layer 51 remains on the 1 st retardation layer 52 (fig. 7). In the case where the 1 st alignment layer 51 is peelable from the 1 st retardation layer 52, if the 1 st base material layer 55 is separated from the optical laminate 2b, the 1 st alignment layer 51 is peeled together with the 1 st base material layer 55.

The 1 st retardation plate 50 may be the 1 st retardation layer 52 itself, which is a cured layer of a polymerizable liquid crystal compound, or may be a laminate of the 1 st retardation layer 52 and the 1 st alignment layer 51. In the case where the 1 st retardation layer 50 has the 1 st alignment layer 51, the 1 st alignment layer 51 is provided on the opposite side of the 1 st retardation layer 52 from the side of the adhesive layer (a) 31.

Details of the 1 st retardation plate 50, the linear polarizing plate 40, and the adhesive layer (a) 31 in the optical laminate 2 of the present embodiment are applicable to the description of the 1 st retardation plate 10, the linear polarizing plate 40, and the adhesive layer (a) 31 in the optical laminate 1 of the 1 st embodiment.

According to the optical laminate 2 of the present embodiment, even when fine foreign matter is mixed in the adhesive layer (a) 31, unevenness can be suppressed. The process for producing the optical laminate comprises the steps of: when the 1 st optical layer and the 1 st phase difference plate are bonded together via the 1 st adhesive layer, for example, the 1 st optical layer and the 1 st phase difference plate are bonded together by a bonding roller, and a force is applied to the optical layer from the outside thereof. The present inventors have established the following hypothesis: when a minute foreign matter is mixed in the 1 st adhesive layer, a force from the minute foreign matter mixed in the 1 st adhesive layer is applied to the 1 st retardation plate in the above-described step, and as a result, the 1 st retardation layer in the 1 st retardation plate is locally deformed, and deformation of the 1 st retardation layer is maintained in the optical laminate, and unevenness occurs. Based on this hypothesis, it was verified that at least one of the ratio (nIT) of the normalized DMT elastic modulus and the elastic deformation work amount was adjusted for the 1 st retardation layer, and as a result, the following findings were obtained: the 1 st retardation layer satisfies at least one of a normalized DMT elastic modulus of 0.65 or more and an elastic deformation work amount ratio (nIT) of 25% or more, whereby even when a minute foreign matter is mixed in the 1 st adhesive layer, unevenness occurring in the optical laminate can be suppressed, and the optical laminate of the present embodiment is obtained.

The optical stack 2 may be a circular polarizing plate. In this case, the 1 st phase difference plate 50 is a 1/4 wavelength phase difference plate or a 1/4 wavelength phase difference plate having inverse wavelength dispersion. The optical laminate 2 can be used by being attached to an image display element of an image display device such as a liquid crystal display device or an organic EL (electro luminescence) display device. The image display device of the present embodiment includes an optical laminate 2. The optical laminate 2 may be bonded with at least one of a front panel and a touch sensor panel on the observation side of the 1 st phase difference plate 50. More specifically, at least one of the front panel and the touch sensor panel may be bonded to the surface of the linear polarizing plate 40 of the optical laminate 2 on the opposite side of the 1 st phase difference plate 50.

(method for producing an optical laminate of embodiment 2)

The optical laminate 2a manufactured by the manufacturing method of the optical laminate 2 includes the linear polarizing plate 40, the adhesive layer (a) 31, and the 1 st phase difference plate 50 described above in this order. The 1 st retardation layer 52 of the 1 st retardation plate 50 satisfies at least one condition that the normalized DMT elastic modulus is 0.65 or more and the ratio (nIT) of the elastic deformation work amount is 25% or more.

The method for manufacturing the optical laminate 2a includes:

A step of preparing a retardation plate with a base material layer having a 1 st base material layer 55 and a 1 st retardation plate 50;

the 1 st retardation plate 50 includes a 1 st retardation layer 52 formed by polymerizing a polymerizable liquid crystal compound on a 1 st base layer 55,

a step of preparing a laminate having a linear polarizing plate 40, an adhesive layer (a) 31, a 1 st retardation layer 52, and a 1 st base material layer 55 in this order (fig. 8); and

and separating the 1 st base material layer 55 from the laminate.

In the method for producing the optical laminate 2, the 1 st retardation layer 52 of the 1 st retardation plate 50 has a normalized DMT elastic modulus in the above range or a ratio of the elastic deformation work amount in the above range (nIT). Therefore, in the step of bonding the linear polarizing plate 40 and the 1 st phase difference plate 50, even if the 1 st phase difference layer 52 of the 1 st phase difference plate 50 is deformed by the minute foreign matter mixed into the adhesive layer (a) 31, the deformation is relaxed, and the occurrence of unevenness in the optical laminate 2 can be suppressed.

The 1 st retardation plate 50 includes a 1 st retardation layer 52 formed by polymerizing a polymerizable liquid crystal compound on a 1 st base layer 55. Accordingly, the step of preparing the retardation plate with the base material layer may include a step of forming the 1 st retardation layer 52 by polymerizing the polymerizable liquid crystal compound on the 1 st base material layer 55. The 1 st retardation layer 52 may be formed by polymerizing a polymerizable liquid crystal compound on the 1 st alignment layer 51 provided on the 1 st base layer 55. In this case, the step of preparing the retardation plate with the base material layer may include a step of forming the 1 st alignment layer 51 on the 1 st base material layer 55.

The step of preparing the laminate may include a step of bonding the linear polarizing plate 40 to the 1 st retardation layer 52 side of the retardation plate with the base layer via the adhesive layer (a) 31. In the bonding step via the adhesive layer 31, for example, an adhesive composition layer is first formed on the 1 st retardation layer 52 side of the retardation plate with the base layer and/or the linear polarizing plate 40. Next, the retardation plate with the base layer and the linear polarizing plate 40 are laminated via an adhesive composition layer, so that the adhesive composition layer is the adhesive layer (a) 31, or the adhesive layer (a) 31 is formed from the adhesive composition layer. Thus, an optical laminate 2b (fig. 8) in which the linear polarizing plate 40, the adhesive layer (a) 31, and the 1 st retardation plate 50 (the 1 st retardation layer 52, the 1 st alignment layer 51) were laminated in this order was obtained.

The step of separating the 1 st base material layer 55 is to separate the 1 st base material layer 55 from the optical laminate 2 b. In the step of separating the 1 st base material layer 55, only the 1 st base material layer 55 may be peeled off, or in the case where the 1 st alignment layer 51 is present, the 1 st alignment layer 51 may be peeled off together with the 1 st base material layer 55. Thus, the optical laminate 2a shown in fig. 7 can be obtained.

The method for producing the optical laminate 2a may further include the steps of: another pressure-sensitive adhesive layer and a release film different from the pressure-sensitive adhesive layer (a) 31 are formed in this order from the exposed surface side exposed in the step of separating the 1 st base layer 55. The other adhesive layer may be used for, for example, an image display element attached to a display device. The release film may be provided so as to cover the surface of the other adhesive layer opposite to the 1 st phase difference plate 50 side and be peelable from the other adhesive layer.

The optical laminate of the present embodiment and the method for producing the same will be described in detail below.

(No. 1 phase plate, no. 2 phase plate)

The 1 st phase difference plate and the 2 nd phase difference plate (hereinafter, these may be collectively referred to as "phase difference plates") are layers having phase difference characteristics, and include a 1 st phase difference layer and a 2 nd phase difference layer which are cured layers of polymerizable liquid crystal compounds, respectively. The 1 st retardation plate may have a 1 st alignment layer in addition to the 1 st retardation layer. The 2 nd retardation plate may have a 2 nd alignment layer in addition to the 2 nd retardation layer in the same manner.

(No. 1 phase difference layer, no. 2 phase difference layer)

The 1 st phase difference layer and the 2 nd phase difference layer (hereinafter, they may be collectively referred to as "phase difference layers") are cured layers of polymerizable liquid crystal compounds. As the polymerizable liquid crystal compound, a rod-shaped polymerizable liquid crystal compound and a disk-shaped polymerizable liquid crystal compound may be used, one of them may be used, or a mixture containing both may be used. When the rod-shaped polymerizable liquid crystal compound is oriented horizontally or vertically with respect to the base material layer (1 st base material layer or 2 nd base material layer), the optical axis of the polymerizable liquid crystal compound coincides with the long axis direction of the polymerizable liquid crystal compound. When the disk-shaped polymerizable liquid crystal compound is aligned, the optical axis of the polymerizable liquid crystal compound is present in a direction perpendicular to the disk surface of the polymerizable liquid crystal compound. As the rod-like polymerizable liquid crystal compound, for example, a polymerizable liquid crystal compound described in JP-A-11-513019 (claim 1 and the like) can be suitably used. As the disk-shaped polymerizable liquid crystal compound, those described in JP-A2007-108732 (paragraphs [0020] to [0067] and the like) and JP-A2010-244038 (paragraphs [0013] to [0108] and the like) can be suitably used.

In order to cause the retardation layer formed by polymerizing the polymerizable liquid crystal compound to exhibit an in-plane retardation, the polymerizable liquid crystal compound may be aligned in an appropriate direction. When the polymerizable liquid crystal compound is rod-shaped, the optical axis of the polymerizable liquid crystal compound is aligned horizontally with respect to the plane of the base material layer, and thus an in-plane retardation is exhibited, and in this case, the optical axis direction coincides with the slow axis direction. When the polymerizable liquid crystal compound has a discotic shape, the optical axis of the polymerizable liquid crystal compound is aligned horizontally with respect to the plane of the substrate layer, whereby an in-plane retardation is exhibited, and in this case, the optical axis is orthogonal to the slow axis. The alignment state of the polymerizable liquid crystal compound can be adjusted by a combination of the alignment layer and the polymerizable liquid crystal compound.

The polymerizable liquid crystal compound is a liquid crystal compound having a polymerizable group, particularly a photopolymerizable group, and as the polymerizable liquid crystal compound, for example, a conventionally known polymerizable liquid crystal compound in the field of a retardation film can be used. The photopolymerizable group means a group that can participate in polymerization reaction by a reactive species generated by a photopolymerization initiator, for example, a reactive radical, an acid, or the like. Examples of the photopolymerizable group include vinyl, vinyloxy, 1-chlorovinyl, isopropenyl, 4-vinylphenyl, acryloyloxy, methacryloyloxy, epoxyethyl, oxetanyl, and the like. Among them, acryloyloxy, methacryloyloxy, ethyleneoxy, ethyleneoxide, and oxetanyl groups are preferable, and acryloyloxy is more preferable. The liquid crystal property may be a thermotropic liquid crystal or a lyotropic liquid crystal, and the thermotropic liquid crystal is preferable in view of being capable of controlling the film thickness in a compact state. The phase-ordered structure in the thermotropic liquid crystal may be a nematic liquid crystal or a smectic liquid crystal. The liquid crystal may be a rod-like liquid crystal or a discotic liquid crystal. The polymerizable liquid crystal compound may be used singly or in combination of two or more.

The polymerizable liquid crystal compound is preferably a T-shaped or H-shaped liquid crystal having a mesogenic structure, which is further birefringent in a direction perpendicular to the molecular long axis direction, from the viewpoint of exhibiting inverse wavelength dispersion, and is more preferably a T-shaped liquid crystal from the viewpoint of obtaining stronger dispersion, and specifically, for example, a compound represented by the following formula (I) is given as a structure of the T-shaped liquid crystal.

[ chemical formula 1]

In the formula (I), ar represents a divalent aromatic group which may have a substituent. The divalent aromatic group preferably contains at least 1 or more of nitrogen atom, oxygen atom and sulfur atom. When the number of aromatic groups contained in the divalent group Ar is 2 or more, 2 or more aromatic groups may be bonded to each other through a divalent bonding group such as a single bond, -CO-O-, -O-.

G ¹ And G ² Each independently represents a divalent aromatic group or a divalent alicyclic hydrocarbon group. The hydrogen atom contained in the divalent aromatic group or the divalent alicyclic hydrocarbon group may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group or a nitro group, and the carbon atoms constituting the divalent aromatic group or the divalent alicyclic hydrocarbon group may be substituted with an oxygen atom, a sulfur atom or a nitrogen atom.

L ¹ 、L ² 、B ¹ And B ² Each independently is a single bond or a divalent linking group.

k. 1 each independently represents an integer of 0 to 3, satisfying the relationship of 1.ltoreq.k+1. Here, B is, in the case of 2.ltoreq.k+1 ¹ And B ² 、G ¹ And G ² Respectively may or may not be identical to each otherAnd the same is true.

E ¹ And E is ² Each independently represents an alkanediyl group having 1 to 17 carbon atoms, wherein hydrogen atoms contained in the alkanediyl group may be substituted with halogen atoms, and wherein-CH contained in the alkanediyl group ₂ Can be substituted by-O-, -S-, -a substitution of the COO-group, having a plurality of-O-, -S-, -COO-in case of non-adjacent to each other. P (P) ¹ And P ² Independently of one another, a polymerizable group or a hydrogen atom, at least 1 of which is a polymerizable group.

G ¹ And G ² Each independently is preferably a 1, 4-phenylenediyl group (Japanese: 1, 4-fecuna group) which may be substituted with at least 1 substituent selected from the group consisting of a halogen atom and an alkyl group having 1 to 4 carbon atoms, a 1, 4-cyclohexanediyl group which may be substituted with at least 1 substituent selected from the group consisting of a halogen atom and an alkyl group having 1 to 4 carbon atoms, more preferably a 1, 4-phenylenediyl group substituted with a methyl group, an unsubstituted 1, 4-phenylenediyl group, or an unsubstituted 1, 4-trans-cyclohexanediyl group, particularly preferably an unsubstituted 1, 4-phenylenediyl group, or an unsubstituted 1, 4-trans-cyclohexanediyl group.

In addition, a plurality of G's are preferably present ¹ And G ² At least 1 of them is a divalent alicyclic hydrocarbon group, and further, more preferably with L ¹ Or L ² Bonded G ¹ And G ² At least 1 of them is a divalent alicyclic hydrocarbon group.

L ¹ And L ² Each independently is preferably a single bond, an alkylene group having 1 to 4 carbon atoms, -O-, -S-, -R ^a1 OR ^a2 -、-R ^a3 COOR ^a4 -、-R ^a5 OCOR ^a6 -、R ^a7 OC＝OOR ^a8 -、-N＝N-、-CR ^c ＝CR ^d -, or C-tric-. Here, R is ^a1 ～R ^a8 Each independently represents a single bond or an alkylene group having 1 to 4 carbon atoms, R ^c And R is ^d Represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom. L (L) ¹ And L ² More preferably each independently is a single bond, -OR ^a2-1 -、-CH ₂ -、-CH ₂ CH ₂ -、-COOR ^a4-1 -, or OCOR ^a6-1 -. Here, R is ^a2-1 、R ^a4-1 、R ^a6-1 Each independently represents a single bond, -CH ₂ -、-CH ₂ CH ₂ -any one of the following. L (L) ¹ And L ² Each independently further preferably is a single bond, -O-, -CH ₂ CH ₂ -、-COO-、-COOCH ₂ CH ₂ -, or OCO-.

B ¹ And B ² Each independently is preferably a single bond, an alkylene group having 1 to 4 carbon atoms, -O-, -S-, -R ^a9 OR ^a10 -、-R ^a11 COOR ^a12 -、-R ^a13 OCOR ^a14 -, or R ^a15 OC＝OOR ^a16 -. Here, R is ^a9 ～R ^a16 Each independently represents a single bond or an alkylene group having 1 to 4 carbon atoms. B (B) ¹ And B ² More preferably each independently is a single bond, -OR ^a10-1 -、-CH ₂ -、-CH ₂ CH ₂ -、-COOR ^a12 ^-1 -, or OCOR ^a14-1 -. Here, R is ^a10-1 、R ^a12-1 、R ^a14-1 Each independently represents a single bond, -CH ₂ -、-CH ₂ CH ₂ -any one of the following. B (B) ¹ And B ² Each independently further preferably is a single bond, -O-, -CH ₂ CH ₂ -、-COO-、-COOCH ₂ CH ₂ -, -OCO-, or OCOCH ₂ CH ₂ -。

From the viewpoint of exhibiting inverse wavelength dispersion, k and 1 are preferably in the range of 2.ltoreq.k+1.ltoreq.6, preferably k+1=4, more preferably k=2 and 1=2. K=2 and 1=2 are preferable because they have a symmetrical structure.

E ¹ And E is ² Each independently is preferably an alkanediyl group having 1 to 17 carbon atoms, more preferably an alkanediyl group having 4 to 12 carbon atoms.

As P ¹ Or P ² Examples of the polymerizable group include an epoxy group, a vinyl group, an ethyleneoxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an ethyleneoxy group, and an oxetanyl group. Among them, preferred are acryloyloxy, methacryloyloxy, ethyleneoxy, ethyleneoxide, and oxetanyl groups, and more preferred is acryloylAn oxy group.

Ar preferably has at least one selected from the group consisting of an aromatic hydrocarbon ring which may have a substituent, an aromatic heterocyclic ring which may have a substituent, and an electron withdrawing group. Examples of the aromatic hydrocarbon ring include benzene ring, naphthalene ring, and anthracene ring, and benzene ring and naphthalene ring are preferable. Examples of the aromatic heterocycle include a furan ring, a benzofuran ring, a pyrrole ring, an indole ring, a thiophene ring, a benzothiophene ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a triazole ring, a triazine ring, a pyrroline ring, an imidazole ring, a pyrazole ring, a thiazole ring, a benzothiazole ring, a thienothiazole ring, an oxazole ring, a benzoxazole ring, and a phenanthroline ring. Among them, a thiazole ring, a benzothiazole ring, or a benzofuran ring is preferable, and a benzothiazolyl group is more preferable. In addition, in the case where Ar contains a nitrogen atom, the nitrogen atom preferably has pi electrons.

In the formula (I), the total number of pi electrons contained in the 2-valent aromatic group represented by Ar is preferably 8 or more, more preferably 10 or more, further preferably 14 or more, and particularly preferably 16 or more. The content is preferably 30 or less, more preferably 26 or less, and even more preferably 24 or less.

Examples of the aromatic group represented by Ar include the following groups.

[ chemical formula 2]

In the formulae (Ar-1) to (Ar-23), the symbol represents a connecting portion, Z ⁰ 、Z ¹ And Z ² Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyano group, a nitro group, an alkylsulfinyl group having 1 to 12 carbon atoms, an alkylsulfonyl group having 1 to 12 carbon atoms, a carboxyl group, a fluoroalkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 12 carbon atoms, an N-alkylamino group having 1 to 12 carbon atoms, an N, N-dialkylamino group having 2 to 12 carbon atoms, an N-alkylsulfonyl group having 1 to 12 carbon atoms or an N, N-dialkylsulfamoyl group having 2 to 12 carbon atoms.

Q ¹ 、Q ² And Q ³ Each independently represents-CR ^2’ R ^3’ -、-S-、-NH-、-NR ^2’ -, -CO-or O-, R ^2’ And R is ^3’ Each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

J ¹ And J ² Each independently represents a carbon atom, or a nitrogen atom.

Y ¹ 、Y ² And Y ³ Each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may be substituted.

w ¹ And W is ² Each independently represents a hydrogen atom, a cyano group, a methyl group or a halogen atom, and m represents an integer of 0 to 6.

As Y ¹ 、Y ² And Y ³ Examples of the aromatic hydrocarbon group in (a) include aromatic hydrocarbon groups having 6 to 20 carbon atoms such as phenyl, naphthyl, anthryl, phenanthryl and biphenyl, and preferably phenyl and naphthyl, more preferably phenyl. Examples of the aromatic heterocyclic group include an aromatic heterocyclic group having 4 to 20 carbon atoms and containing at least 1 hetero atom such as a nitrogen atom, an oxygen atom, a sulfur atom, etc., such as a furyl group, a pyrrolyl group, a thienyl group, a pyridyl group, a thiazolyl group, a benzothiazolyl group, etc., and a furyl group, a thienyl group, a pyridyl group, a thiazolyl group, a benzothiazolyl group are preferable.

Y ¹ 、Y ² And Y ³ Each independently may be a polycyclic aromatic hydrocarbon group or a polycyclic aromatic heterocyclic group which may be substituted. Polycyclic aromatic hydrocarbon group refers to a condensed polycyclic aromatic hydrocarbon group or a group derived from an aromatic ring set. Polycyclic aromatic heterocyclic groups refer to fused polycyclic aromatic heterocyclic groups or groups derived from an aromatic ring set.

Z ⁰ 、Z ¹ And Z ² Each independently is preferably a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cyano group, a nitro group, an alkoxy group having 1 to 12 carbon atoms, Z ⁰ More preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, a cyano group, and Z ¹ And Z ² Further preferred are a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group and a cyano group.

Q ¹ 、Q ² And Q ³ preferably-NH-, -S-, -NR ^2’ -、-O-，R ^2’ Hydrogen atoms are preferred. Wherein, the method comprises the steps of, particularly preferred are-S-, -O-, -NH-.

Of the formulae (Ar-1) to (Ar-23), the formulae (Ar-6) and (Ar-7) are preferable from the viewpoint of stability of the molecule.

In the formulae (Ar-16) to (Ar-23), Y ¹ To which nitrogen atoms and Z can be bound ⁰ Together forming an aromatic heterocyclic group. Examples of the aromatic heterocyclic group include aromatic heterocyclic groups which may be contained in Ar and are described above, and examples thereof include pyrrole rings, imidazole rings, pyrroline rings, pyridine rings, pyrazine rings, pyrimidine rings, indole rings, quinoline rings, isoquinoline rings, purine rings, pyrrolidine rings, and the like. The aromatic heterocyclic group may have a substituent. In addition, Y ¹ To which nitrogen atoms and Z can be bound ⁰ Together are the above-mentioned polycyclic aromatic hydrocarbon group or polycyclic aromatic heterocyclic group which may be substituted. For example, a benzofuran ring, benzothiazole ring, benzoxazole ring, and the like can be cited.

Among the polymerizable liquid crystal compounds, compounds having a maximum absorption wavelength of 300 to 400nm are preferable. When the photopolymerization initiator is contained in the polymerizable liquid crystal composition, there is a concern that the polymerization reaction and gelation of the polymerizable liquid crystal compound proceed during long-term storage. However, if the maximum absorption wavelength of the polymerizable liquid crystal compound is 300 to 400nm, the generation of reactive species derived from the photopolymerization initiator and the progress of polymerization and gelation of the polymerizable liquid crystal compound due to the reactive species can be effectively suppressed even when exposed to ultraviolet light during storage. Therefore, the composition is advantageous in terms of long-term stability of the polymerizable liquid crystal composition, and the alignment property and uniformity of film thickness of the obtained liquid crystal cured film can be improved. The maximum absorption wavelength of the polymerizable liquid crystal compound can be measured in a solvent using an ultraviolet-visible spectrophotometer. The solvent is a solvent capable of dissolving the polymerizable liquid crystal compound, and examples thereof include chloroform.

The content of the polymerizable liquid crystal compound in the polymerizable liquid crystal composition is, for example, 70 to 99.5 parts by mass, preferably 80 to 99 parts by mass, more preferably 85 to 98 parts by mass, and even more preferably 90 to 95 parts by mass, relative to 100 parts by mass of the solid content of the polymerizable liquid crystal composition. If the content of the polymerizable liquid crystal compound is within the above range, it is advantageous from the viewpoint of the orientation of the obtained liquid crystal cured film. In the present specification, the solid content of the polymerizable liquid crystal composition means all components obtained by removing volatile components such as an organic solvent from the polymerizable liquid crystal composition.

The thickness of the retardation layer is not particularly limited, but is preferably 0.5pm or more, and may be 1 μm or more, usually 8 μm or less, and may be 5 μm or less, and preferably 3 μm or less.

(1 st orientation layer, 2 nd orientation layer)

The 1 st alignment layer and the 2 nd alignment layer (hereinafter, they may be collectively referred to as "alignment layers") have an alignment control force for aligning the polymerizable liquid crystal compound contained in the retardation layer formed on these alignment layers in a desired direction. It is preferable to have solvent resistance that is not dissolved by coating or the like of a composition for forming a retardation layer, which will be described later, and heat resistance for heat treatment for removing the solvent and aligning the polymerizable liquid crystal compound.

The alignment layer may be a vertical alignment layer that aligns the molecular axis of the polymerizable liquid crystal compound vertically with respect to the base material layer, a horizontal alignment layer that aligns the molecular axis of the polymerizable liquid crystal compound horizontally with respect to the base material layer, or an oblique alignment layer that aligns the molecular axis of the polymerizable liquid crystal compound obliquely with respect to the base material layer.

Examples of the alignment layer include an alignment polymer layer made of an alignment polymer, a photo-alignment polymer layer made of a photo-alignment polymer, and a groove alignment layer having a concave-convex pattern and a plurality of grooves (grooves) on the layer surface. The 1 st alignment layer and the 2 nd alignment layer may be the same alignment layer or different alignment layers.

The alignment polymer layer can be formed by applying a composition in which an alignment polymer is dissolved in a solvent to a base material layer (1 st base material layer or 2 nd base material layer) and removing the solvent, and if necessary, subjecting it to a rubbing treatment. In this case, in the alignment polymer layer formed of the alignment polymer, the alignment control force can be arbitrarily adjusted according to the surface state of the alignment polymer and the friction condition.

The photo-alignment polymer layer can be formed by applying a composition containing a polymer having a photoreactive group or a monomer and a solvent to a substrate layer (substrate layer 1 or substrate layer 2) and irradiating light such as ultraviolet rays. Particularly, when the orientation control force is exhibited in the horizontal direction, the optical element can be formed by irradiating polarized light. In this case, in the photo-alignment polymer layer, the alignment control force can be arbitrarily adjusted by the polarized light irradiation condition or the like for the photo-alignment polymer.

The groove orientation layer may be formed, for example, by the following method or the like: a method of forming a concave-convex pattern on the surface of the photosensitive polyimide film by exposing and developing the film through an exposure mask having a slit in a pattern shape; a method in which an uncured layer of an active energy ray-curable resin is formed on a plate-shaped master having grooves on the surface, and the layer is transferred to a base material layer (1 st base material layer or 2 nd base material layer) to be cured; an uncured layer of an active energy ray-curable resin is formed on a base layer, and a master having a concave-convex shape in a roll shape is pressed against the layer to form concave-convex shapes and cure the concave-convex shapes.

When the alignment layer is peeled off together with the base material layer, the alignment layer preferably contains a resin obtained by polymerizing a polymerizable compound, from the viewpoint of easy peeling off and removal of the alignment layer together with the base material layer. The polymerizable compound is a compound having a polymerizable group, and is usually a non-liquid crystalline polymerizable non-liquid crystalline compound which does not become a liquid crystalline state. The polymerizable groups of the polymerizable compound react with each other to polymerize the polymerizable compound, thereby forming a resin.

When the alignment layer is peeled off together with the base material layer, the alignment layer preferably contains a resin such as a cured product obtained by curing a known monofunctional or polyfunctional (meth) acrylate monomer with a polymerization initiator. Examples of the (meth) acrylic acid ester monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, urethane acrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol polyacrylate, dipentaerythritol hexaacrylate, and the like. The resin may be 1 kind of the resin, or may be a mixture of 2 or more kinds of the resin. In the case of using such a resin as an alignment layer, after the formation of the retardation plate, the alignment layer may be peeled off together with the substrate layer when the substrate layer is separated from the retardation plate of the tape base layer (the 1 st retardation plate of the tape base layer or the 2 nd retardation plate of the tape base layer) before and after the step of laminating the obtained laminate with other layers such as a polarizing plate. In the present specification, "meth) acrylic acid" means either acrylic acid or methacrylic acid. (meth) acrylate and the like are also defined as "(meth)" as well.

When the alignment layer is not peeled off together with the base material layer and remains on the retardation layer side, the alignment layer preferably contains a resin such as a cured product obtained by curing a 3-functional or higher (meth) acrylate monomer, an imide monomer or a vinyl ether monomer, and more preferably contains a cured product obtained by curing a 3-functional or higher (meth) acrylate monomer.

In the case where the orientation layer is formed by curing the polymerizable compound in the composition for forming an orientation layer by irradiation with ultraviolet rays, the irradiation intensity of ultraviolet rays is not particularly limited, and is preferablyIs 10-1000 mW/cm ² More preferably 100 to 600mw/cm ² . If the light irradiation intensity of the composition for forming an alignment layer coated on the substrate layer is less than 10mW/cm ² The reaction time becomes too long, if it exceeds 1000mW/cm ² The substrate layer may be wrinkled due to heat radiated from the light source, and there is a concern that unevenness in phase difference may occur. The irradiation intensity is an intensity in a wavelength region effective for activation of the polymerization initiator, preferably the photo radical polymerization initiator, more preferably an intensity in a wavelength region of 400nm or less, and still more preferably an intensity in a wavelength region of 280 to 320 nm. Preferably, the irradiation is performed 1 or more times at such a light irradiation intensity that the cumulative light amount thereof becomes 10mJ/cm ² The above is preferably 100 to 1000mJ/cm ² More preferably 400 to 1000mJ/cm ² Further preferably 600 to 1000mJ/cm ² Particularly preferably 600 to 1000mJ/cm ² Is set by the mode of (2). If the cumulative light amount of the composition for forming an alignment layer coated on the substrate layer is less than 10mJ/cm ² The generation of active species derived from the polymerization initiator is insufficient, and the curing of the composition for forming an alignment layer becomes insufficient. In addition, if the accumulated light quantity exceeds 1000mJ/cm ² The irradiation time becomes very long, which is disadvantageous in that productivity is improved. Depending on the thickness and type of the base material layer, the type of the component contained in the composition for forming an alignment layer, the combination of the components in the composition for forming an alignment layer, and the like, the wavelength (UVA (320 to 390 nm), UVB (280 to 320 nm), and the like) at the time of light irradiation varies, and the required cumulative light amount also varies depending on the wavelength at the time of light irradiation.

In the case of curing the polymerizable compound in the composition for forming an alignment layer by ultraviolet irradiation, the temperature at the time of ultraviolet irradiation is preferably 25 ℃ or higher, more preferably 50 ℃ or higher, and still more preferably 80 ℃ or higher, from the viewpoint of sufficiently improving the polymerization degree. In addition, when the temperature is too high, wrinkles may occur in the base material layer and uneven phase difference may occur, so that the temperature at the time of ultraviolet irradiation is preferably 200 ℃ or less, more preferably 150 ℃ or less, and further preferably 120 ℃ or less. The upper limit value and the lower limit value may be arbitrarily combined.

The thickness of the alignment layer is not particularly limited, but is preferably 0.01 μm or more, and may be 0.05 μm or more, and may be 0.1 μm or more, and is usually 5 μm or less, and may be 2.5 μm or less, and may be 1 μm or less.

(1 st phase plate with base layer and 2 nd phase plate with base layer)

The 1 st retardation plate with a base layer and the 2 nd retardation plate with a base layer (hereinafter, these may be collectively referred to as "retardation plate with a base layer") can be obtained by applying a composition for forming a retardation layer containing a polymerizable liquid crystal compound onto a base layer, and drying the composition to form a retardation layer as a cured layer formed by polymerizing the polymerizable liquid crystal compound. When the alignment layer is formed on the base layer, the composition for forming a retardation layer may be applied to the alignment layer, and when the retardation layer has a multilayer structure of 2 or more layers, the composition for forming a retardation layer may be applied in order to form a multilayer structure. The method for forming the alignment layer may use the above method.

The composition for forming a retardation layer generally contains a solvent in addition to the polymerizable liquid crystal compound. The composition for forming a retardation layer may further contain a polymerization initiator, a reactive additive, a polymerization inhibitor, and the like. These components may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

As the solvent that can be contained in the composition containing the polymerizable liquid crystal compound, a solvent that can dissolve the polymerizable liquid crystal compound and is inactive to the polymerization reaction of the polymerizable liquid crystal compound is preferable.

Examples of the solvent include alcohol solvents such as methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, and phenol; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, cycloheptanone, methyl amyl ketone, methyl isobutyl ketone, and N-methyl-2-pyrrolidone; non-chlorinated aliphatic hydrocarbon solvents such as pentane, hexane, heptane, etc.; non-chlorinated aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as propylene glycol monomethyl ether, tetrahydrofuran, and dimethoxyethane; chlorinated hydrocarbon solvents such as chloroform and chlorobenzene. The solvents may be used alone or in combination.

The content of the solvent in the polymerizable liquid crystal composition is usually preferably 10 to 10000 parts by mass, more preferably 50 to 5000 parts by mass, per 100 parts by mass of the solid content. The solid component refers to the total of components other than the solvent in the polymerizable liquid crystal composition.

The polymerization initiator that may be contained in the composition containing the polymerizable liquid crystal compound is a compound capable of initiating polymerization of the polymerizable liquid crystal compound, and a photopolymerization initiator is preferable in view of initiating polymerization under a lower temperature condition. Specifically, a photopolymerization initiator capable of generating a living radical or an acid by the action of light is exemplified, and among them, a photopolymerization initiator capable of generating a radical by the action of light is preferable. Examples of the photo radical polymerization initiator include benzoin compounds, benzophenone compounds, benzil ketal compounds, α -hydroxyketone compounds, α -aminoketone compounds, oxime compounds, triazine compounds, iodonium salts, and sulfonium salts. As the photo radical polymerization initiator, only 1 kind may be used, or 2 or more kinds may be used in combination.

As the photo radical polymerization initiator, commercially available ones can be used. Specific examples of such commercial products include Irgacure, registered trademark) 907, irgacure 184, irgacure 651, irgacure 819, irgacure 250, irgacure 369, irgacure 379, irgacure 127, irgacure 2959, irgacure 754, irgacure 379EG (above BASF Japan), seikuol BZ, seikuol Z, seikuol BEE (above Seikuol bez), kayacure BP100 (manufactured by kayaure corporation), kayaure UVI-6992 (manufactured by DOW corporation), adeka Optomer SP-152, adeka Optomer SP-170, adeka Optomer N-1717, adeka Optomer N-1919, eka Arkls NCI-831, seka arkul-62 (above taki) and TAZ-930 (above TAZ-38).

The content of the polymerization initiator is usually 0.1 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, relative to 100 parts by mass of the total amount of the polymerizable liquid crystal compound. Within this range, the reaction of the polymerizable group proceeds sufficiently, and the alignment state of the polymerizable liquid crystal compound is easily stabilized.

The crosslinking agent that may be contained in the composition containing the polymerizable liquid crystal compound is a compound having 1 or more photoreactive groups in the molecule. By using the crosslinking agent, the crosslinking density of the liquid crystal layer is changed, and the film strength can be easily adjusted. Examples of the crosslinking agent include polyfunctional acrylate compounds, epoxy compounds, oxetane compounds, methylol compounds, isocyanate compounds, and the like. Among them, the polyfunctional acrylate compound is preferable from the viewpoints of uniformity of the coating film and adjustment of film strength. The crosslinking agent preferably has 2 or more and 8 or less reactive groups in the molecule, more preferably 2 or more and 6 or less polymerizable groups.

As the multifunctional acrylate, commercially available ones can be used. As such a commercially available product, specifically, examples of the "A-DOD-N, A-HD-N, A-NOD-N, APG-100", "APG-200", "APG-400", "A-GLY-9-E, A-GLY-20-E, A-TMM-3", "A-TMPT", "AD-TMP", "ATM-35-E, A-TMMT", "A-9550", "A-DPH", "HD-N, NOD-N, NPG, TMPT", "ARONIX M-220", "ARONIX M-325", "ARONIX M-240", "ARONIX M-270", "ARONIX M-309", "ARONIX M-310", "ARONIX M-321", "ARONIX M-350", etc. may be given ARONIX M-360, ARONIX M-305, ARONIX M-306, ARONIX M-450, ARONIX M-451, ARONIX M-408, ARONIX M-400, ARONIX M-402, ARONIX M-403, ARONIX M-404, ARONIX M-405, ARONIX M-406 (manufactured by east Asia Synthesis Co., ltd.), EBECRYL11, EBECRYL145, EBECRYL150, EBECRYL40, EBECRYL140, EBECRYL180, DPGDA, HDDA, TPGDA, HPNDA, PETIA, PETRA, TMPTA, TMPEOTA, DPHA, EBECRYL series (manufactured by Daicel-Cytec Co., ltd.), and the like.

The content of the crosslinking agent is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, relative to 100 parts by mass of the total amount of the polymerizable liquid crystal compound. If the content of the crosslinking agent is not more than the lower limit, defects are likely to occur during processing such as polishing, and if it is not less than the upper limit, the alignment state of the liquid crystal compound becomes unstable and alignment defects are likely to occur.

As the reactive additive that can be contained in the composition containing the polymerizable liquid crystal compound, a reactive additive having a carbon-carbon unsaturated bond and an active hydrogen reactive group in its molecule is preferable. The term "active hydrogen-reactive group" as used herein means a group selected from the group consisting of carboxyl group (-COOH), hydroxyl group (-OH), and amino group (-NH) ₂ ) Typical examples of the reactive group include a group having active hydrogen such as a glycidyl group, an oxazoline group, a carbodiimide group, an aziridine group, an imide group, an isocyanate group, a thioisocyanate group, and a maleic anhydride group. The number of carbon-carbon unsaturated bonds and active hydrogen reactive groups in the reactive additive is usually 1 to 20, preferably 1 to 10, respectively.

In the reactive additive, the active hydrogen reactive groups are preferably present in at least 2 in the molecule. In this case, the plurality of active hydrogen reactive groups may be the same or different.

The carbon-carbon unsaturated bond of the reactive additive in the molecule means a carbon-carbon double bond or a carbon-carbon triple bond, preferably a carbon-carbon double bond. Among them, as the reactive additive, it is preferable to contain carbon-carbon unsaturated bonds as vinyl groups and/or (meth) acryl groups in the molecule. In addition, the active hydrogen reactive group is preferably at least 1 selected from the group consisting of an epoxy group, a glycidyl group and an isocyanate group. Particularly preferred are reactive additives having an acryl group as a carbon-carbon double bond and an isocyanate group as an active hydrogen reactive group.

Examples of the reactive additive include compounds having a (meth) acryloyl group and an epoxy group, such as methacryloxyglycidyl ether and acryloxyglycidyl ether; compounds having a (meth) acryloyl group and an oxetanyl group, such as oxetane acrylate and oxetane methacrylate; compounds having a (meth) acryloyl group and a lactone group, such as lactone acrylate and lactone methacrylate; compounds having vinyl groups and oxazolinyl groups such as vinyl oxazoline and isopropenyl oxazoline; and compounds having a (meth) acryloyl group and an isocyanate group such as methyl acrylate, methyl methacrylate, 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate, and oligomers of these monomers. Examples of the compound include methacrylic anhydride, acrylic anhydride, maleic anhydride, and vinyl maleic anhydride, and compounds having a vinyl group, vinylidene group, and anhydride. Among them, methacryloxyglycidyl ether, acryloxyglycidyl ether, isocyanatomethyl acrylate, isocyanatomethyl methacrylate, vinyloxazoline, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, or an oligomer of these monomers is preferable, and isocyanatomethyl acrylate, 2-isocyanatoethyl acrylate, or an oligomer of these monomers is particularly preferable.

When the polymerizable liquid crystal composition contains the reactive additive, the content thereof is usually 0.1 part by mass or more and 30 parts by mass or less, preferably 0.1 part by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the polymerizable liquid crystal compound.

In order to make the coating film obtained by coating the composition flatter, the composition containing the polymerizable liquid crystal compound may contain a leveling agent. Examples of the leveling agent include silicone-based, polyacrylate-based, and perfluoroalkyl-based leveling agents.

The content of the leveling agent is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound. If the content of the leveling agent is within the above range, the polymerizable liquid crystal compound is easily oriented, and the resulting liquid crystal cured film (cured layer of the polymerizable liquid crystal compound) tends to be smoother, which is preferable.

The composition for forming the retardation layer can be applied by a known method such as spin coating, extrusion, gravure coating, die coating, slit coating, bar coating, coating by an applicator, or printing by a flexography. After the composition for forming a retardation layer is applied, the solvent is preferably removed under the condition that the polymerizable liquid crystal compound contained in the applied layer is not polymerized. Examples of the drying method include a natural drying method, a ventilation drying method, a heat drying method, and a reduced pressure drying method.

The polymerization of the polymerizable liquid crystal compound performed after the drying of the coating layer can be performed by a known method of polymerizing a compound having a polymerizable functional group. Examples of the polymerization method include thermal polymerization and photopolymerization, and photopolymerization is preferable from the viewpoint of ease of polymerization. When polymerizing a polymerizable liquid crystal compound by photopolymerization, it is preferable to use a composition containing a photopolymerization initiator as a composition for forming a retardation layer, apply and dry the composition for forming a retardation layer, orient a liquid crystal of the polymerizable liquid crystal compound contained in the dried film after drying, and perform photopolymerization while maintaining the liquid crystal oriented state.

The photopolymerization may be performed by irradiating the polymerizable liquid crystal compound having undergone liquid crystal alignment in the dried film with active energy rays. The active energy ray to be irradiated may be appropriately selected depending on the type and amount of the polymerizable group included in the polymerizable liquid crystal compound, the type of the photopolymerization initiator, and the like, and examples thereof include at least 1 active energy ray selected from the group consisting of visible rays, ultraviolet rays, laser light, X rays, α rays, β rays, and γ rays. Among them, ultraviolet rays are preferable from the viewpoint of easiness in controlling the progress of the polymerization reaction and that a device widely used in the art can be used as a photopolymerization device, and the types of the polymerizable liquid crystal compound and the photopolymerization initiator are preferably selected so that photopolymerization can be performed by ultraviolet rays. In photopolymerization, the polymerization temperature may be controlled by irradiation of active energy rays while cooling the dried film by an appropriate cooling means.

When the coating layer of the composition for forming a retardation layer is cured by irradiation with ultraviolet rays, the irradiation intensity of the ultraviolet rays is not particularly limited, and is preferably 10 to 1000mW/cm ² More preferably 100 to 600mW/cm ² . If the light irradiation intensity to the coating layer is less than 10mW +.cm ² The reaction time becomes too long, if it exceeds 1000mW/cm ² The substrate layer may be wrinkled by heat radiated from the light source, and there is a concern that unevenness in phase difference may occur. The irradiation intensity is an intensity in a wavelength region effective for activation of the polymerization initiator, preferably the photo radical polymerization initiator, more preferably an intensity in a wavelength region of 400nm or less, and still more preferably an intensity in a wavelength region of 280 to 320 nm. Preferably, the irradiation is performed 1 or more times at such a light irradiation intensity that the cumulative light amount thereof becomes 10mJ/cm ² The above is preferably 100 to 1000mJ/cm ² More preferably 400 to 1000mJ/cm ² Further preferably 600 to 1000mJ/cm ² Particularly preferably 600 to 1000mJ/cm ² Is set by the mode of (2). If the cumulative light quantity to the coating layer is less than 10mJ/cm ² The generation of active species derived from the polymerization initiator is insufficient, and the curing of the coating layer becomes insufficient. In addition, if the accumulated light quantity exceeds 1000mJ/cm ² The irradiation time becomes very long, which is disadvantageous in improving productivity. Depending on the thickness and type of the base material layer, the type of the component contained in the composition for forming a retardation layer, the combination of the components in the composition for forming a retardation layer, and the like, the wavelength (UVA (320 to 390 nm), UVB (280 to 320 nm), and the like) at the time of light irradiation varies, and the required cumulative light amount also varies depending on the wavelength at the time of light irradiation.

In the case of curing the coating layer of the composition for forming a retardation layer by ultraviolet irradiation, the temperature at the time of ultraviolet irradiation is preferably 30℃or higher, more preferably 40℃or higher, still more preferably 50℃or higher, still more preferably 65℃or higher, from the viewpoint of sufficiently improving the polymerization degree. In addition, when the temperature is too high, wrinkles may occur in the base material layer and there is a concern that the phase difference may be uneven, and therefore the temperature at the time of ultraviolet irradiation is preferably 200 ℃ or less, more preferably 120 ℃ or less, further preferably 90 ℃ or less, and particularly preferably 75 ℃ or less. The upper limit value and the lower limit value may be arbitrarily combined.

(substrate layer 1. Substrate layer 2)

The 1 st and 2 nd base material layers (hereinafter, they may be collectively referred to as "base material layers") function as support layers for supporting alignment layers and retardation layers, which will be described later, formed on these base material layers. The base material layer is preferably a film formed of a resin material.

As the resin material, for example, a resin material excellent in transparency, mechanical strength, thermal stability, stretchability, and the like is used. Specifically, examples thereof include polyolefin resins such as polyethylene and polypropylene; cyclic polyolefin resins such as norbornene polymers; polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate; (meth) acrylic resins such as (meth) acrylic acid and polymethyl (meth) acrylate; cellulose ester resins such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; vinyl alcohol resins such as polyvinyl alcohol and polyvinyl acetate; a polycarbonate resin; a polystyrene resin; polyarylate-based resins; polysulfone-based resin; polyether sulfone resin; a polyamide resin; polyimide resin; polyether ketone resin; polyphenylene sulfide resin; polyphenylene ether resins, and mixtures and copolymers thereof. Among these resins, any one of a cyclic polyolefin resin, a polyester resin, a cellulose ester resin, and a (meth) acrylic resin or a mixture thereof is preferably used.

The thickness of the base material layer is not particularly limited, but is usually preferably 1 to 300pm, more preferably 10 to 200pm, and even more preferably 30 to 120 μm in view of workability such as strength and handling property.

In the case where the 1 st phase difference plate having the base layer has the 1 st orientation layer and the 2 nd phase difference plate having the base layer has the 2 nd orientation layer, in order to improve the adhesion between the 1 st base layer and the 1 st orientation layer and the adhesion between the 2 nd base layer and the 2 nd orientation layer, at least the surface of the 1 st base layer on the side where the 1 st orientation layer is formed and the surface of the 2 nd base layer on the side where the 2 nd orientation layer is formed may be subjected to corona treatment, plasma treatment, flame treatment, or the like, or may be formed with an undercoat layer or the like.

The substrate layer can be peeled off from the liquid crystal layer or the alignment layer, and the magnitude of the peeling force between the substrate layer and the liquid crystal layer or the alignment layer needs to be determined in consideration of the order in which the substrate layers are separated. The peel force of the 1 st base material layer separated from the 1 st laminate at first is preferably smaller than the peel force of the 2 nd base material layer separated later.

In the bonding step, when the 1 st base material layer of the 1 st phase difference plate is present (for example, (c) of fig. 5, and (a) of fig. 6), if the hardness of the 1 st base material layer is too high, the force applied to the 1 st phase difference layer by the curing of the polymerizable liquid crystal compound cannot be relaxed when the layer formed by the curing of the polymerizable liquid crystal compound is sandwiched between the fine foreign matter and the 1 st base material layer, and the 1 st phase difference layer formed by the curing of the polymerizable liquid crystal compound is likely to be deformed. The Martin hardness of the 1 st substrate layer is preferably 220N/mm ² Hereinafter, the lower limit is 70N/mm in consideration of process suitability and the like ² The above is preferably 100N/mm ² The above is more preferably 130N/mm ² The above. From the viewpoint of the mahalanobis hardness, a substrate selected from any of triacetyl cellulose, polymethacrylate, and polyethylene terephthalate is more preferable. As a device for measuring such a mahalanobis hardness, a minute hardness measuring device is exemplified. Specifically, fischer scope HM2000 (manufactured by Helmut Fischer) and the like are mentioned.

(adhesive layer (A) and adhesive layer (B))

The adhesive layer (a) and the adhesive layer (B) (hereinafter, these may be collectively referred to as "adhesive layer"), for example, may be formed of an adhesive, an aqueous adhesive, an active energy ray-curable adhesive, or a combination thereof. Even if the thickness is 4 μm or less, the adhesive force is easily and sufficiently obtained, and therefore, an aqueous adhesive or an active energy ray-curable adhesive is preferable.

As the adhesive, an acrylic adhesive containing an acrylic resin having a glass transition temperature Tg of 0 ℃ or less obtained by radical polymerization of an acrylic monomer mixture containing a (meth) acrylic acid ester as a main component and a small amount of a (meth) acrylic monomer having a functional group in the presence of a polymerization initiator and a crosslinking agent is generally preferably used.

The weight average molecular weight Mw of the acrylic resin constituting the acrylic adhesive is preferably in the range of 100 to 200 tens of thousands in terms of standard polystyrene based on Gel Permeation Chromatography (GPC). If the weight average molecular weight Mw is 100 ten thousand or more, the adhesion at high temperature and high humidity is improved, the possibility of floating or peeling between the glass substrate and the adhesive layer constituting the liquid crystal cell is reduced, and the reworkability is improved, which is preferable. In addition, if the weight average molecular weight Mw of the acrylic resin is 200 ten thousand or less, the pressure-sensitive adhesive layer tends to follow the dimensional change even if the size of the polarizing plate changes, and thus tends to suppress light leakage and color unevenness of the display. The molecular weight distribution represented by the ratio Mw/Mn of the weight average molecular weight Mw to the number average molecular weight Mn is preferably in the range of 3 to 7.

The acrylic resin contained in the acrylic adhesive may be composed of only the acrylic resin having a relatively high molecular weight as described above, or may be composed of a mixture of the acrylic resin and an acrylic resin different from the acrylic resin. Examples of the acrylic resin that can be used in combination include an acrylic resin having a structural unit derived from the (meth) acrylic ester represented by the above formula (I) as a main component and having a weight average molecular weight in the range of 5 to 30 ten thousand.

The acrylic resin thus obtained was blended with a crosslinking agent to prepare an adhesive. The crosslinking agent is a compound having at least 2 functional groups capable of undergoing a crosslinking reaction with a structural unit derived from a monomer having a polar functional group in the acrylic resin in a molecule, and examples thereof include isocyanate compounds, epoxy compounds, metal chelate compounds, and aziridine compounds.

As a method for forming an adhesive layer on an optical film, for example, a method of forming an adhesive layer by coating the adhesive composition using a release film as a base material, and transferring the obtained adhesive layer to the surface of the optical film; and a method of forming an adhesive layer by directly coating the adhesive composition on the surface of an optical film. Alternatively, a double-sided spacer type adhesive sheet may be produced by forming an adhesive layer on 1 release film, and then further bonding another release film to the adhesive layer. Such a double-sided spacer type pressure-sensitive adhesive sheet is bonded to an optical film by peeling off a single-sided release film at a necessary timing. Examples of the commercial products of the double-sided spacer type adhesive sheet include a carrier-free adhesive film and a carrier-free adhesive sheet sold by lindaceae, and the company nito.

As the aqueous adhesive, for example, a polyvinyl alcohol resin or a urethane resin is used as a main component, and in order to improve the adhesion, a composition containing a crosslinking agent such as an isocyanate compound or an epoxy compound or a curable compound is usually prepared.

In the case of using a polyvinyl alcohol resin as a main component of the aqueous adhesive, a modified polyvinyl alcohol resin such as carboxyl-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol and amino-modified polyvinyl alcohol may be used in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol. The aqueous solution of the polyvinyl alcohol resin is used as an aqueous adhesive, and the concentration of the polyvinyl alcohol resin in the aqueous adhesive is usually 1 to 10 parts by mass, preferably 1 to 5 parts by mass, relative to 100 parts by mass of water.

As described above, in order to improve the adhesion, a curable compound such as a polyaldehyde, a water-soluble epoxy resin, a melamine compound, a zirconia compound, and a zinc compound may be blended into the aqueous adhesive containing the aqueous solution of the polyvinyl alcohol resin. Examples of the water-soluble epoxy resin include a water-soluble polyamide epoxy resin obtained by reacting epichlorohydrin with a polyamide polyamine obtained by reacting a polyalkylene polyamine such as diethylenetriamine and triethylenetetramine with a dicarboxylic acid such as adipic acid. As the commercial products of such polyamide epoxy resins, there are "Sumirez Resin 650" and "Sumirez Resin 675" sold by Kagaku chemical CHEMTEX Co., ltd., and "WS-525" sold by Japanese PMC Co., ltd. When the water-soluble epoxy resin is blended, the amount of the water-soluble epoxy resin is usually about 1 to 100 parts by mass, preferably about 1 to 50 parts by mass, based on 100 parts by mass of the polyvinyl alcohol resin.

In addition, when a urethane resin is used as a main component of the aqueous adhesive, it is effective to use a polyester ionomer urethane resin as a main component of the aqueous adhesive. The polyester ionomer type urethane resin as referred to herein means a urethane resin having a polyester skeleton, into which a small amount of ionic component (hydrophilic component) is introduced. The ionomer urethane resin is emulsified in water directly without using an emulsifier to form an emulsion, and thus can be made into an aqueous adhesive. When a polyester ionomer type urethane resin is used, it is effective to blend a water-soluble epoxy compound as a crosslinking agent. For example, JP-A2005-70140 and JP-A2005-208456 describe a polyester ionomer type urethane resin as an adhesive for a polarizing plate.

These components constituting the aqueous adhesive are usually used in a state of being dissolved in water. The adhesive layer can be obtained by applying an aqueous adhesive to an appropriate substrate and drying the same. The water-insoluble component may be in a state dispersed in the system.

Examples of the method for forming the adhesive layer on the optical film include a method for forming an adhesive layer by directly applying the adhesive composition to the surface of the optical film.

In addition, for example, the obtained aqueous adhesive is injected between the polarizing plate and the optical film, and then heated, thereby evaporating water and simultaneously performing a thermal crosslinking reaction, whereby sufficient adhesiveness can be imparted to both.

The active energy ray-curable adhesive is an adhesive cured by irradiation with active energy rays, provided that a puncture slope per unit film thickness of 6kg/mm can be obtained ² ～15kg/mm ² The composite phase difference plate 5 is not limited. Examples thereof include cationically polymerizable active energy ray-curable adhesives containing an epoxy compound and a cationic polymerization initiator, and adhesives containing an acrylic curing component and a free radicalAn active energy ray-curable adhesive having radical polymerization properties of a radical polymerization initiator, an active energy ray-curable adhesive containing both a cationically polymerizable curing component such as an epoxy compound and a radically polymerizable curing component such as an acrylic compound and containing a cationic polymerization initiator and a radical polymerization initiator incorporated therein, an electron beam-curable adhesive cured by irradiation of an electron beam to the active energy ray-curable adhesive containing no initiator, and the like. The active energy ray-curable adhesive preferably contains an acrylic curing component and a radical polymerization initiator. In addition, a cationically polymerizable active energy ray-curable adhesive containing an epoxy compound and a cationic polymerization initiator, which can be used substantially in the absence of a solvent, is preferable.

An active energy ray-curable adhesive which is a cationically polymerizable epoxy compound and which is itself liquid at room temperature, has moderate fluidity even in the absence of a solvent, can impart an appropriate cured adhesive strength, and is blended with a cationic polymerization initiator suitable for the epoxy compound, and in a production facility for a composite retardation plate, a drying facility normally required in a step of bonding a 1 st retardation layer and a 2 nd retardation layer can be omitted. In addition, by irradiating an appropriate amount of active energy rays, the curing speed can be accelerated, and the production speed can be increased.

Examples of the epoxy compound used in such an adhesive include glycidyl ethers of aromatic compounds or chain compounds having a hydroxyl group, glycidyl amino compounds of compounds having an amino group, epoxides of chain compounds having a c—c double bond, alicyclic epoxy compounds having a glycidyl oxy group or an epoxy group directly bonded to a saturated carbon ring or via an alkylene group, and epoxy groups directly bonded to a saturated carbon ring. These epoxy compounds may be used alone or in combination of two or more. Among them, alicyclic epoxy compounds are preferably used because they are excellent in cationic polymerization.

The glycidyl etherate of an aromatic compound or a chain compound having a hydroxyl group can be produced, for example, by a method of addition-condensing epichlorohydrin with the hydroxyl group of the aromatic compound or the chain compound under alkaline conditions. Such glycidyl ethers of aromatic compounds or chain compounds having a hydroxyl group include diglycidyl ethers of bisphenols, polyaromatic epoxy resins, diglycidyl ethers of alkylene glycols or polyalkylene glycols, and the like.

Examples of the diglycidyl ether of bisphenol include glycidyl etherate of bisphenol a and oligomer thereof, glycidyl etherate of bisphenol F and oligomer thereof, and glycidyl etherate of 3,3', 5' -tetramethyl-4, 4' -biphenol and oligomer thereof.

Examples of the polyaromatic epoxy resin include a glycidyl etherate of a phenol novolac resin, a glycidyl etherate of a cresol novolac resin, a glycidyl etherate of a phenol aralkyl resin, a glycidyl etherate of a naphthol aralkyl resin, and a glycidyl etherate of a phenol dicyclopentadiene resin. In addition, glycidyl ethers of triphenols, oligomers thereof, and the like are also polyaromatic epoxy resins.

Examples of the diglycidyl ether of an alkylene glycol or polyalkylene glycol include a glycidyl ether of ethylene glycol, a glycidyl ether of diethylene glycol, a glycidyl ether of 1, 4-butanediol, and a glycidyl ether of 1, 6-hexanediol.

The glycidyl amide of a compound having an amino group can be produced, for example, by a method of addition-condensing epichlorohydrin with an amino group of the compound under alkaline conditions. The compound having an amino group may have a hydroxyl group at the same time. Among the glycidyl amide compounds of such an amino group-containing compound, there are those of 1, 3-phenylenediamine and its oligomer, those of 1, 4-phenylenediamine and its oligomer, those of 3-aminophenol and its oligomer, those of 4-aminophenol and its oligomer, and the like.

Epoxides of a chain compound having a C-C double bond can be produced by a method of epoxidizing the C-C double bond of the chain compound under alkaline conditions using a peroxide. Butadiene, polybutadiene, isoprene, pentadiene, hexadiene, and the like are contained in the chain compound having a C-C double bond. In addition, terpenes having a double bond can be used as an epoxidation raw material, and linalool and the like are used as acyclic monoterpenes. The peroxide used in the epoxidation may be, for example, hydrogen peroxide, peracetic acid, t-butyl hydroperoxide, etc.

The alicyclic epoxy compound having a glycidoxy group or an epoxyethyl group directly or via an alkylene group bonded to a saturated carbocyclic ring may be a glycidyl etherate of a hydrogenated polyhydroxy compound obtained by hydrogenating an aromatic ring of an aromatic compound having a hydroxyl group represented by bisphenols, a glycidyl etherate of a cycloalkane compound having a hydroxyl group, an epoxide of a cycloalkane compound having a vinyl group, or the like.

The EPOXY compounds described above are readily available commercially, and are represented by trade names, for example, by the "jER" series sold by mitsubishi Chemical corporation, by the "epicron" sold by DIC corporation, by the "EPOTOTO (registered trademark)" sold by eastern Chemical corporation, by the "ADEKA RESIN (registered trademark)" sold by ADEKA corporation, by the "degacol (registered trademark)" sold by Nagase chemmex corporation, by the "DOW EPOXY" sold by DOW Chemical corporation, by the "TEPIC (registered trademark)" sold by daily Chemical industry corporation, and the like.

On the other hand, an alicyclic epoxy compound having an epoxy group directly bonded to a saturated carbocyclic ring can be produced, for example, by a method of epoxidizing a C-C double bond of a non-aromatic cyclic compound having a C-C double bond in the ring with a peroxide under alkaline conditions. Examples of the non-aromatic cyclic compound having a c—c double bond in the ring include a compound having a cyclopentene ring, a compound having a cyclohexene ring, and a polycyclic compound in which at least 2 carbon atoms are further bonded to the cyclopentene ring or the cyclohexene ring to form an additional ring. The non-aromatic cyclic compound having a C-C double bond in the ring may have other C-C double bonds outside the ring. Examples of the non-aromatic cyclic compound having a C-C double bond in the ring include cyclohexene, 4-vinylcyclohexene, limonene as a monocyclic monoterpene, and α -pinene.

The alicyclic epoxy compound having an epoxy group directly bonded to a saturated carbocyclic ring may be a compound having an alicyclic structure in which at least 2 epoxy groups directly bonded to a ring as described above are formed in a molecule via a suitable linking group. The linking group herein includes, for example, an ester bond, an ether bond, an alkylene bond, and the like.

The following compounds are examples of alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbon ring.

3, 4-epoxycyclohexylmethyl 3, 4-epoxycyclohexane carboxylate,

1, 2-epoxy-4-vinylcyclohexane,

1, 2-epoxy-4-epoxyethylcyclohexane,

1, 2-epoxy-1-methyl-4- (1-methyl-epoxyethyl) cyclohexane,

3, 4-epoxycyclohexylmethyl (meth) acrylate,

Adducts of 2, 2-bis (hydroxymethyl) -1-butanol with 4-epoxyethyl-1, 2-epoxycyclohexane,

Ethylene bis (3, 4-epoxycyclohexane carboxylate),

Oxydiethylene bis (3, 4-epoxycyclohexane carboxylate),

1, 4-cyclohexanedimethylbis (3, 4-epoxycyclohexane carboxylate),

3- (3, 4-epoxycyclohexylmethoxycarbonyl) propyl 3, 4-epoxycyclohexane carboxylate, and the like.

The alicyclic epoxy compounds in which an epoxy group is directly bonded to a saturated carbon ring as described above can be easily obtained as commercial products, and examples thereof are "Celloxide" series and "cycler" sold by Daicel, inc., and "Cyracure UVR" series sold by DOW CHEMICAL, inc., respectively, and the like.

The curable adhesive containing an epoxy compound may further contain an active energy ray-curable compound other than the epoxy compound. Examples of the active energy ray-curable compound other than the epoxy compound include oxetane compounds and acrylic compounds. Among them, the oxetane compound is preferably used in combination, since it is possible to promote the curing rate in the cationic polymerization.

The oxetane compound is a compound having a 4-membered cyclic ether in the molecule, and examples thereof include the following.

1, 4-bis [ (3-ethyloxetan-3-yl) methoxymethyl ] benzene,

3-ethyl-3- (2-ethylhexyl oxymethyl) oxetane,

Bis (3-ethyl-3-oxetanylmethyl) ether,

3-ethyl-3- (phenoxymethyl) oxetane,

3-ethyl-3- (cyclohexyloxymethyl) oxetane,

Phenol novolac oxetane,

Xylylene dioxetane,

1, 3-bis [ (3-ethyloxetan-3-yl) methoxy ] benzene, and the like.

The Oxetane compound is also easily available in the market, and is represented by trade names, for example, the "Aron oxide (registered trademark)" series sold by eastern synthetic corporation, the "ETERNACOLL (registered trademark)" series sold by yu xiang corporation, and the like.

In order to make the adhesive containing the epoxy compound and the oxetane compound solvent-free, it is preferable to use a curable compound which is not diluted with an organic solvent or the like. As other components constituting the adhesive, and including a small amount of a cationic polymerization initiator and a sensitizer described later, it is also preferable to use a powder or a liquid of the compound alone, which is obtained by removing and drying an organic solvent, instead of using a substance dissolved in an organic solvent.

The cationic polymerization initiator is a compound that generates cationic species upon irradiation with active energy rays, for example, ultraviolet rays. The adhesive to which the adhesive is blended may be provided with a desired adhesive strength and curing speed, and examples thereof include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes, and the like. These cationic polymerization initiators may be used alone or in combination of two or more.

Examples of the aromatic diazonium salt include the following compounds.

Diazobenzene hexafluoroantimonate,

Diazobenzene hexafluorophosphate,

And diazonium benzohexafluoroborate.

Examples of the aromatic iodonium salts include the following compounds.

Diphenyliodonium tetrakis (pentafluorophenyl) borate,

Diphenyl iodonium hexafluorophosphate,

Diphenyl iodonium hexafluoroantimonate,

Bis (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

Examples of the aromatic sulfonium salt include the following compounds.

Triphenylsulfonium hexafluorophosphate,

Triphenylsulfonium hexafluoroantimonate,

Triphenylsulfonium tetrakis (pentafluorophenyl) borate,

Diphenyl (4-phenylsulfanyl) sulfonium hexafluoroantimonate,

4,4' -bis (diphenylsulfonium) diphenyl sulfide bis hexafluorophosphate,

4,4' -bis [ bis (. Beta. -hydroxyethoxyphenyl) sulfonium ] diphenyl sulfide bis hexafluoroantimonate,

4,4' -bis [ bis (. Beta. -hydroxyethoxyphenyl) sulfonium ] diphenyl sulfide bis hexafluorophosphate salt,

7- [ bis (p-benzoyl) sulfonium ] -2-isopropylthioxanthone hexafluoroantimonate,

7- [ bis (p-benzoyl) sulfonium ] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,

4-phenylcarbonyl-4' -diphenylsulfonium diphenyl sulfide hexafluorophosphate,

4- (p-tert-butylphenylcarbonyl) -4' -diphenylsulfonium diphenyl sulfide hexafluoroantimonate,

4- (p-tert-butylphenylcarbonyl) -4' -bis (p-benzoyl) sulfonium-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

Examples of the iron-aromatic hydrocarbon complex include the following compounds.

Xylene-cyclopentadienyl iron (II) hexafluoroantimonate,

Cumene-cyclopentadienyl iron (II) hexafluorophosphate,

Xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) methanation, and the like.

Among the cationic polymerization initiators, aromatic sulfonium salts have ultraviolet absorption characteristics even in a wavelength region of 300nm or more, and thus can provide an adhesive layer excellent in curability and having good mechanical strength and adhesive strength, and thus are preferably used.

The cationic polymerization initiator can also be easily obtained as a commercially available product, for example, each of which is represented by a trade name, examples thereof include "Kayard (registered trademark)" series sold by Japan CHEMICAL Co., ltd., "Cyracure UVI" series sold by DOW CHEMICAL Co., ltd., photo acid generator "CPI" series sold by Sun-apo Co., ltd., photo acid generators "TAZ", "BBI" and "DTS" sold by Midori CHEMICAL Co., ltd., adeka Optomer "series sold by Kadskin Co., ltd., rhodia Co., ltd., RHOORSIL (registered trademark)", and the like.

In the active energy ray-curable adhesive, the cationic polymerization initiator is usually blended in a proportion of 0.5 to 20 parts by mass, preferably 1 to 15 parts by mass, relative to 100 parts by mass of the total active energy ray-curable adhesive. If the amount is too small, curing becomes insufficient, and the mechanical strength and adhesive strength of the adhesive layer may be lowered. If the amount is too large, the ionic substance in the adhesive layer increases, and the hygroscopicity of the adhesive layer increases, which may reduce the durability of the resulting polarizing plate.

In the case of using an active energy ray-curable adhesive in an electron beam-curable type, it is not necessary to intentionally include a photopolymerization initiator in the composition, but in the case of using an ultraviolet ray-curable type, a photoradical generator is preferably used. Examples of the photoradical generator include hydrogen abstraction type photoradical generators and cleavage type photoradical generators.

Examples of the hydrogen abstraction type photoradical generator include naphthalene derivatives such as 1-methylnaphthalene, 2-methylnaphthalene, 1-fluoronaphthalene, 1-chloronaphthalene, 2-chloronaphthalene, 1-bromonaphthalene, 2-bromonaphthalene, 1-iodonaphthalene, 2-iodonaphthalene, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 2-methoxynaphthalene, 1, 4-dicyanonaphthalene, anthracene, 1, 2-benzanthracene, 9, 10-dichloroanthracene, 9, 10-dibromoanthracene, 9, 10-diphenylanthracene, 9-cyanoanthracene, 9, 10-dicyanoanthracene, 2,6,9, 10-tetracyanocarbazole, pyrene derivatives, carbazole, 9-methylcarbazole, 9-phenylcarbazole, 9-prop-2-ynyl-9H-carbazole, 9-propyl-9H-carbazole, 9-vinylcarbazole, 9H-carbazole-9-ethanol, 9-methyl-3-nitro-9H-carbazole, 9-methyl-3, 6-dinitrocarbazole, 9-H-nitrocarbazole, 9-dicarbazole, 9- (9-dicyanocarbazole, 9-ethylcarbazole), 9- (9-ethylcarbazole) and 9-ethylcarbazole, 9-ethoxycarbazole, 9- (ethylcarbazole) and 9-ethylcarbazole, 9-propylmorpholine, 9-ethylcarbazole, carbazole derivatives such as 9-benzyl-9H-carbazole, 9-carbazole acetic acid, 9- (2-nitrophenyl) carbazole, 9- (4-methoxyphenyl) carbazole, 9- (1-ethoxy-2-methyl-propyl) -9H-carbazole, 3-nitrocarbazole, 4-hydroxycarbazole, 3, 6-dinitro-9H-carbazole, 3, 6-diphenyl-9H-carbazole, 2-hydroxycarbazole, 3, 6-diacetyl-9-ethylcarbazole, benzophenone, 4-phenylbenzophenone, 4 '-bis (dimethoxy) benzophenone, 4' -bis (dimethylamino) benzophenone, 4 '-bis (diethylamino) benzophenone, and the like benzophenone derivatives such as 2-benzoylbenzoic acid methyl ester, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 3' -dimethyl-4-methoxybenzophenone, 2,4, 6-trimethylbenzophenone, etc., thioxanthone derivatives such as aromatic carbonyl compounds, [4- (4-methylbenzothio) phenyl ] -phenylketone, xanthone, thioxanthone, 2-chlorothioxanthone, 4-chlorothioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diethylthioxanthone, 1-chloro-4-propoxythioxanthone, etc., thioxanthone derivatives such as, coumarin derivatives, and the like.

The cleavage type photoradical generator is a type of photoradical generator that generates radicals by cleavage of the compound by irradiation with active energy rays, and specific examples thereof include aryl alkyl ketones such as benzoin ether derivatives and acetophenone derivatives, oxime ketones, acyl phosphine oxides, S-phenyl thiobenzoate, titanocenes, and derivatives obtained by increasing the molecular weight thereof, but are not limited thereto. Examples of the commercially available cleavage type photoradical generator include 1- (4-dodecylbenzoyl) -1-hydroxy-1-methylethyl, 1- (4-isopropylbenzoyl) -1-hydroxy-1-methylethyl, 1-benzoyl-1-hydroxy-1-methylethyl, 1- [4- (2-hydroxyethoxy) -benzoyl ] -1-hydroxy-1-methylethyl, 1- [4- (acryloyloxyethoxy) -benzoyl ] -1-hydroxy-1-methylethyl, diphenyl ketone, phenyl-1-hydroxy-cyclohexylketone, benzildimethyl ketal, bis (cyclopentadienyl) -bis (2, 6-difluoro-3-pyrrolyl-phenyl) titanium (. Eta.6-isopropylphenyl) - (. Eta.5-cyclopentadienyl) -iron (II) hexafluorophosphate, trimethylbenzoyl diphenylphosphine oxide, bis (2, 6-dimethoxy-benzoyl) - (2, 4-trimethyl-pentyl) -phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2, 4-dipentylphenyl phosphine oxide or bis (2, 6-trimethylbenzoyl) phosphine oxide (4-morpholinobenzoyl) -1-benzyl-1-dimethylaminopropane, 4- (methylthiobenzoyl) -1-methyl-1-morpholinoethane, and the like, but are not limited thereto.

In the active energy curable adhesive used in the present invention, the photo radical generator contained in the electron beam curable type, that is, the hydrogen abstraction type or the cleavage type photo radical generator may be used alone, or a plurality of the photo radical generators may be used in combination, and from the viewpoint of stability and curability of the photo radical generator monomer, a combination of 1 or more of the cleavage type photo radical generators is more preferable. Among the cleavage type photoradical generators, acyl phosphine oxides are preferable, and more specifically, trimethylbenzoyl diphenyl phosphine oxide (trade name "DAROCURE TPO"; ciba japan corporation), bis (2, 6-dimethoxy-benzoyl) - (2, 4-trimethyl-pentyl) -phosphine oxide (trade name "CGI 403"; ciba japan corporation), or bis (2, 4, 6-trimethylbenzoyl) -2, 4-dipentyloxyphenyl phosphine oxide (trade name "Irgacure819"; ciba japan corporation) is preferable.

The active energy ray-curable adhesive may contain a sensitizer as required. By using the sensitizer, the reactivity is improved, and the mechanical strength and the adhesive strength of the adhesive layer can be further improved. As the sensitizer, the above-mentioned sensitizer can be suitably used.

When the sensitizer is blended, the blending amount is preferably in the range of 0.1 to 20 parts by mass based on 100 parts by mass of the total amount of the active energy ray-curable adhesive.

The active energy ray-curable adhesive may contain various additives within a range that does not impair the effect thereof. Examples of the additive that can be blended include an ion scavenger, an antioxidant, a chain transfer agent, a thickener, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent.

These components constituting the active energy ray-curable adhesive are usually used in a state of being dissolved in a solvent. When the active energy ray-curable adhesive contains a solvent, the active energy ray-curable adhesive is applied to the coated surface and dried, whereby an adhesive layer is obtained. The solvent-insoluble component may be in a state of being dispersed in the system.

The active energy ray-curable adhesive is applied to the adhesive surface of the 1 st retardation layer 1 with the 2 nd retardation layer 2, the adhesive surface of the 2 nd retardation layer 2 with the 1 st retardation layer 1, or both. The adhesive surface between the 1 st retardation layer 1 and the 2 nd retardation layer 2 and the adhesive surface between the 2 nd retardation layer 2 and the 1 st retardation layer 1 may be subjected to corona treatment, plasma treatment, flame treatment, etc., or may be provided with an undercoat layer, etc. The thickness of the undercoat layer is usually about 0.001 to 5. Mu.m, preferably 0.01 μm or more, and preferably 4 μm or less, more preferably 3 μm or less. If the undercoat layer is too thick, the composite phase difference plate 5 is liable to have poor appearance.

The viscosity of the active energy ray-curable adhesive may be any viscosity that can be applied by various methods, and the viscosity thereof at a temperature of 25 ℃ is preferably in the range of 10 to 1000 mPa-sec, more preferably in the range of 20 to 500 mPa-sec. If the viscosity thereof is too small, there is a tendency that it is difficult to form a layer at a desired thickness. On the other hand, if the viscosity is too high, it tends to be difficult to flow and to obtain a uniform coating film without unevenness. The viscosity herein is a value measured at 10rpm after the adhesive is temperature-controlled to 25℃by using an E-type viscometer.

The active energy ray-curable adhesive may be used in an electron beam-curable or ultraviolet-curable manner. In the present specification, an active energy ray is defined as an energy ray capable of decomposing a compound that generates an active species to generate an active species. Examples of such active energy rays include visible light, ultraviolet light, infrared light, X-rays, α -rays, β -rays, γ -rays, and electron beams.

In the electron beam curing type, any suitable conditions may be used as long as the irradiation conditions of the electron beam are such that the active energy ray curing type adhesive can be cured. For example, the acceleration voltage of electron beam irradiation is preferably 5kV to 300kV, and more preferably 10kV to 250kV. If the acceleration voltage is less than 5kV, there is a concern that the electron beam does not reach the adhesive and insufficient curing occurs, and if the acceleration voltage exceeds 300kV, the penetration force through the sample is too strong to rebound the electron beam, and there is a concern that the transparent protective film and the polarizing plate may be damaged. The irradiation dose is 5 to 100kGy, more preferably 10 to 75kGy. When the irradiation dose is less than 5kGy, the adhesive becomes insufficient to be cured, and when it exceeds 100kGy, the retardation plate is damaged, and the mechanical strength is lowered and yellowing occurs, so that the desired optical characteristics cannot be obtained.

The electron beam irradiation is usually performed in an inert gas, but may be performed under conditions of introducing a small amount of oxygen into the atmosphere as needed. By properly introducing oxygen, oxygen inhibition is generated on the surface of the retardation plate on which the electron beam is first irradiated, and damage to the retardation plate can be prevented, and only the adhesive can be irradiated with the electron beam effectively.

In the ultraviolet-curable adhesive, the irradiation intensity of the active energy ray-curable adhesive is determined according to each composition of the adhesive, and is not particularly limited, and is preferably 10 to 1000mW/cm ² . If the light irradiation intensity to the resin composition is less than 10mW/cm ² The reaction time becomes too long, if it exceeds 1000mW/cm ² Yellowing of the constituent materials of the adhesive may occur due to heat radiated from the light source and heat generated during polymerization of the composition. The irradiation intensity is preferably an intensity in a wavelength region effective for activation of the photo-cationic polymerization initiator, more preferably an intensity in a wavelength region having a wavelength of 400nm or less, and still more preferably an intensity in a wavelength region having a wavelength of 280 to 320 nm. Preferably, the irradiation is performed 1 or more times at such a light irradiation intensity that the cumulative light amount thereof becomes 10mJ/cm ² The above is preferably 100 to 1000mJ/cm ² Is set by the mode of (2). If the cumulative light quantity of the adhesive is less than 10mJ/cm ² The generation of active species derived from the polymerization initiator is insufficient, and the curing of the adhesive becomes insufficient. On the other hand, if the accumulated light amount exceeds 1000mJ/cm ² The irradiation time becomes very long, which is disadvantageous in that productivity is improved. In this case, the amount of accumulated light in which wavelength region (UVA (320 to 390 nm), UVB (280 to 320 nm), etc.) is required varies depending on the type of film of the retardation plate to be used, the combination of adhesive types, etc.

The light source used for polymerization curing of the adhesive by irradiation with active energy rays of the present invention is not particularly limited, and examples thereof include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excimer laser, an LED light source that emits light in a wavelength range of 380 to 440nm, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp. From the viewpoints of energy stability and device simplicity, an ultraviolet light source having a light emission distribution at a wavelength of 400nm or less is preferable.

(Linear polarization layer)

The linear polarization layer transmits linearly polarized light having a vibration plane orthogonal to an absorption axis when unpolarized light is incident. The linear polarization layer may include a polyvinyl alcohol (hereinafter, also simply referred to as "PVA") resin film, or may be a cured film obtained by aligning a dichroic dye in a polymerizable liquid crystal compound and polymerizing the polymerizable liquid crystal compound.

Examples of the linear polarizing layer including a PVA-based resin film include a product obtained by subjecting a hydrophilic polymer film such as a PVA-based film, a partially formalized PVA-based film, or an ethylene/vinyl acetate copolymer partially saponified film to a dyeing treatment with a dichroic substance such as iodine or a dichroic dye, and a stretching treatment. In view of excellent optical characteristics, a linear polarization layer obtained by dyeing a PVA-based resin film with iodine and uniaxially stretching the film is preferably used.

The PVA-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the PVA-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The PVA-based resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with an aldehyde may be used. The polymerization degree of the polyvinyl alcohol resin is usually about 1000 to 10000, preferably about 1500 to 5000.

A film formed of such a PVA-based resin film is used as a raw material film of the linear polarization layer. The method for forming the PVA-based resin into a film is not particularly limited, and the film may be formed by a known method. The thickness of the PVA-based resin raw material film is, for example, about 10 to 100 μm, preferably about 10 to 60 μm, and more preferably about 15 to 30 μm.

As another method for producing a linearly polarizing layer including a PVA-based resin film, there is a production method including the steps of: first, a base film is prepared, a solution of a resin such as a PVA-based resin is applied to the base film, and the resin layer is formed on the base film by drying the solution by removing the solvent. The primer layer may be formed on the surface of the base film on which the resin layer is formed. As the base film, a resin film such as PET can be used. Examples of the material of the primer layer include PVA resin obtained by crosslinking a hydrophilic resin used for the linear polarization layer.

Next, the amount of solvent such as moisture in the resin layer is adjusted as needed, then the base film and the PVA resin layer are uniaxially stretched, and then the PVA resin layer is dyed with a dichroic dye such as iodine, so that the dichroic dye is adsorbed and oriented to the PVA resin layer. Next, the PVA resin layer having the dichroic dye adsorbed and aligned thereto is treated with an aqueous boric acid solution as needed, and a washing step of washing away the aqueous boric acid solution is performed. Thus, a film having a linear polarization layer, which is a PVA resin layer having a dichroic dye aligned therein, adsorbed thereon was produced. The steps may be performed by a known method.

The uniaxial stretching of the base film and the PVA resin layer may be performed before dyeing, may be performed during boric acid treatment after dyeing, and may be performed in each of these multiple stages. The base film and the PVA resin layer may be uniaxially stretched in the MD direction (film conveying direction), in which case uniaxial stretching may be performed between rolls having different peripheral speeds, or uniaxial stretching may be performed using a hot roll. In addition, the base film and the PVA resin layer may be uniaxially stretched in the TD direction (direction orthogonal to the film conveying direction), in which case a so-called tenter method may be used. The stretching of the base film and the PVA resin layer may be dry stretching performed in the atmosphere, or wet stretching performed in a state where the PVA resin layer is swollen with a solvent. In order to exhibit the performance of the linearly polarizing layer, the stretching ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. The upper limit of the stretching ratio is not particularly limited, but is preferably 8 times or less from the viewpoint of suppressing breakage or the like.

The linearly polarizing layer produced by the above method can be obtained by peeling off a base film after lamination of a protective layer described later. According to this method, further thinning of the linear polarization layer can be achieved.

As a method for producing a linear polarization layer which is a cured film obtained by aligning a dichroic dye to a polymerizable liquid crystal compound and polymerizing the polymerizable liquid crystal compound, the following method can be mentioned: a composition for forming a polarizing layer, which comprises a polymerizable liquid crystal compound and a dichroic dye, is applied to a base film, and the polymerizable liquid crystal compound is polymerized and cured while maintaining a liquid crystal state, thereby forming a linearly polarizing layer. The thus obtained linear polarization layer is laminated on a base film, and the linear polarization layer with the base film can be used as a polarizing plate described later.

As the dichroic dye, a dye having a property that the absorbance in the long axis direction of the molecule is different from the absorbance in the short axis direction, for example, a dye having an absorption maximum wavelength (λmax) in a range of 300 to 700nm is preferable. Examples of such a dichroic dye include an acridine dye, an oxazine dye, a cyanine dye, a naphthalene dye, an azo dye, and an anthraquinone dye, and among them, an azo dye is preferable. Examples of the azo dye include monoazo dye, disazo dye, trisazo dye, tetrazo dye, stilbene azo dye, and the like, and more preferably disazo dye and trisazo dye.

The composition for forming a polarizing layer may contain a solvent, a polymerization initiator such as a photopolymerization initiator, a photosensitizer, a polymerization inhibitor, and the like. As the polymerizable liquid crystal compound, dichroic dye, solvent, polymerization initiator, photosensitizer, polymerization inhibitor, and the like contained in the composition for forming a polarizing layer, known ones can be used, and for example, ones exemplified in japanese patent application laid-open publication nos. 2017-102479 and 2017-83843 can be used. The polymerizable liquid crystal compound may be the same as the compound exemplified as the polymerizable liquid crystal compound used for obtaining the liquid crystal layers (the 1 st retardation layer and the 2 nd retardation layer) described later. As a method for forming a linearly polarizing layer using the composition for forming a polarizing layer, the method exemplified in the above publication may be employed.

The thickness of the linearly polarizing layer is preferably 2 μm or more, more preferably 3 μm or more. The thickness of the linearly polarizing layer is 25 μm or less, preferably 15 μm or less, and more preferably 13 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

(Linear polarization plate)

The linear polarization layer may be laminated with a protective layer on one or both sides thereof via a known adhesive layer or an adhesive cured layer to form a polarizing plate. The polarizing plate is a so-called linear polarizing plate. As the protective layer that can be laminated on one side or both sides of the linearly polarizing layer, for example, a film formed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, stretchability, and the like can be used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose; polyester resins such as PET and polyethylene naphthalate; polyether sulfone resin; polysulfone resin; a polycarbonate resin; polyamide resins such as nylon and aromatic polyamide; polyimide resin; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; a cyclic polyolefin resin having a ring system and a norbornene structure (also referred to as a norbornene-based resin); (meth) acrylic resins; a polyarylate resin; a polystyrene resin; polyvinyl alcohol resins, and mixtures thereof. In the case where the protective layers are laminated on both sides of the linear polarization layer, the resin compositions of the two protective layers may be the same or different.

In order to improve adhesion to the linear polarizing layer formed of the PVA-based resin and the dichroic material, the film formed of the thermoplastic resin may be subjected to a surface treatment (for example, corona treatment or the like), or may be formed with a thin layer such as an undercoat layer (also referred to as a primer layer).

The protective layer may be, for example, a protective layer obtained by stretching the thermoplastic resin, or may be an unstretched protective layer (hereinafter, sometimes referred to as "unstretched resin"). The stretching treatment includes uniaxial stretching, biaxial stretching, and the like.

The thickness of the protective layer is preferably 3 μm or more, more preferably 5 μm or more. The thickness of the protective layer is preferably 50 μm or less, more preferably 30 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

The surface of the protective layer on the opposite side from the linear polarization layer may have a surface treatment layer, for example, a hard coat layer, an antireflection layer, an anti-adhesion layer, an antiglare layer, a diffusion layer, or the like. The surface treatment layer may be other layers laminated on the protective layer, or may be a layer formed by surface-treating the surface of the protective layer.

The thickness of the polarizing plate is not particularly limited, and is usually 2 μm or more and 300 μm or less. The thickness of the polarizing plate may be 10 μm or more, 150 μm or less, 120 μm or less, or 80 μm or less.

(polarizing plate with protective film)

The polarizing plate may be generally manufactured by laminating a protective film on one side thereof. The protective film may be a protective film in which an adhesive layer is formed on a resin film for a protective film, or may be a self-adhesive film. The thickness of the protective film may be, for example, 30 to 200pm, preferably 40 to 150 μm, and more preferably 50 to 120pm.

Examples of the resin constituting the protective film resin film include polyolefin resins such as polyethylene resins and polypropylene resins; a cyclic polyolefin resin; polyester resins such as PET and polyethylene naphthalate; a polycarbonate resin; (meth) acrylic resins, and the like. Among them, polyester resins such as PET are preferable. The resin film for a protective film may have a 1-layer structure or a multilayer structure having 2 or more layers.

The self-adhesive film is a film which can be self-adhered without providing a means for adhesion such as an adhesive layer and can maintain its adhered state. The self-adhesive film can be formed using, for example, polypropylene resin, polyethylene resin, or the like.

The thickness of the polarizing plate with a protective film is preferably 32 μm or more and 500 μm or less. The thickness of the polarizing plate with the protective film may be 40 μm or more, or 350 μm or less, or 200 μm or less, or 150 μm or less.

(Release film)

The release film protects the other adhesive layer by coating or supports the other adhesive layer, and functions as a spacer that can be peeled from the other adhesive layer. As the release film, a film obtained by subjecting the surface of the base film on the pressure-sensitive adhesive layer side to a release treatment such as a silicone treatment can be exemplified. As the resin material forming the base film, the same resin material as that forming the protective layer described above can be used. The resin film may have a 1-layer structure or a multilayer structure of 2 or more layers.

Examples

Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" and "parts" are mass% and parts unless otherwise specified.

[ production of polarizer ]

A polyvinyl alcohol resin film having a thickness of 30 μm (average polymerization degree: about 2400, saponification degree: 99 mol% or more) was uniaxially stretched to about 5 times by dry stretching, immersed in pure water at a temperature of 60℃for 1 minute while maintaining a stretched state, and then immersed in an aqueous solution at a temperature of 28℃for 60 seconds at a mass ratio of iodine/potassium iodide/water of 0.05/5/100. Then, the mixture was immersed in an aqueous solution having a temperature of 72℃and a mass ratio of potassium iodide/boric acid/water of 8.5/8.5/100. Then, the mixture was washed with pure water at 26℃for 20 seconds, and then dried at 65 ℃. A polarizing plate having a thickness of 12 μm and having iodine adsorption oriented to a polyvinyl alcohol resin film was obtained.

[ preparation of aqueous adhesive ]

An aqueous polyvinyl alcohol solution was prepared by dissolving 3 parts by mass of carboxyl-modified polyvinyl alcohol (KL-318 manufactured by Kuraray, inc.) in 100 parts by mass of water. To the obtained aqueous solution, a water-soluble polyamide epoxy Resin (sumitez Resin650 (30), manufactured by the chemical industry, cyclobalanopsis glauca) was mixed at a ratio of 1.5 parts by mass relative to 100 parts by mass of water, and a water-based adhesive was obtained with a solid content concentration of 30% by mass.

[ production of Linear polarization plate ]

A water-based adhesive prepared as described above was applied to one surface side of the obtained polarizing plate (thickness: 12 μm), and a protective layer (triacetyl cellulose (TAC) film (thickness: 20 μm, in-plane phase difference at wavelength 590 nm: 1.2nm, in-plane phase difference at wavelength 590 nm: 1.3 nm) manufactured by Konikoku Meida Co., ltd.) was laminated. The aqueous adhesive prepared above was applied to the other surface side of the linear polarizer, and a surface-treated protective layer (a surface-treated COP film obtained by applying a surface-treating agent manufactured by Nippon paper Co., ltd., on a cycloolefin resin (COP) film (in-plane phase difference at a wavelength of 590 nm: 140 nm) manufactured by Nippon ZEON Co., ltd.) was applied at a thickness of 3. Mu.m. It was dried at a temperature of 80℃for 5 minutes, thereby obtaining a linear polarizing plate having protective layers on both sides of the polarizing plate.

[ production of 1 st phase-difference plate (i) with base layer ]

(preparation of composition (1) for Forming a photo-alignment layer)

The following components were mixed, and the resultant mixture was stirred at a temperature of 80℃for 1 hour, thereby obtaining a composition (1) for forming a photo-alignment layer.

Light-directing material (5 parts):

[ chemical formula 3]

Solvent (95 parts): cyclopentanone (CNG)

(preparation of composition for Forming liquid Crystal layer (A-1))

The following components were mixed, and the resultant mixture was stirred at 80℃for 1 hour, thereby obtaining a composition (A-1) for forming a liquid crystal layer. The polymerizable liquid crystal compound A1 and the polymerizable liquid crystal compound A2 were synthesized by the method described in japanese unexamined patent publication No. 2010-31223.

Polymerizable liquid crystal compound A1 (80 parts):

[ chemical formula 4]

Polymerizable liquid crystal compound A2 (20 parts):

[ chemical formula 5]

Polymerization initiator (6 parts):

2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one (manufactured by Irgacure 369;Ciba Specialty Chemicals Co., ltd.)

Solvent (400 parts): cyclopentanone (CNG)

(production of 1 st phase-difference plate (i) with base layer)

A polyethylene terephthalate (PET) film (substrate layer 1) having a thickness of 100 μm was subjected to 1 treatment using a corona treatment apparatus (AGF-B10, manufactured by Chun Motor Co., ltd.) at an output of 0.3kW and a treatment speed of 3 m/min. The composition (1) for forming a photo-alignment layer was applied to the corona-treated surface by a bar coater, and dried at 80℃for 1 minute. The cumulative light amount at the wavelength of 313nm was measured using a polarized UV irradiation apparatus (SPOTCURE SP-7; manufactured by USHIO Motor Co., ltd.): 100mJ/cm ² Polarized light UV exposure was performed at an axis angle of 45 ° to obtain a horizontally oriented layer. The thickness of the obtained alignment layer was measured by a laser microscope (LEXT, olympus corporation) and found to be 100nm.

Next, the composition (a-1) for forming a retardation layer was applied onto the horizontal alignment layer using a bar coater, and dried at 120 ℃ for 1 minute. The film was set on a hot plate set at 60℃in such a manner that the 1 st substrate layer of the obtained film was in contact with the hot plate. The hotplate was placed in the housing and sealed with nitrogen for 1 minute. Ultraviolet light (wavelength: 365nm, irradiation intensity at wavelength 365nm under nitrogen atmosphere) was applied to the coated surface of the composition for forming a retardation layer BY using a high-pressure mercury lamp (Unicure VB-15201BY-A, manufactured BY USHIO Motor Co., ltd.)Degree: 10mW/cm ² Cumulative light amount: 1000mJ/cm ² ) Thus, a 1 st retardation layer was formed, and a 1 st retardation plate (i) with a base material layer was obtained.

(production of 1 st phase plate (ii) with base layer)

Except that the hot plate set at 60 ℃ was not used, the 1 st retardation plate (ii) with the base layer was obtained by the same procedure as the production of the 1 st retardation plate (i) with the base layer.

(production of 1 st retardation plate (iii) with base layer)

Except that the setting of the hot plate was 70 ℃, the 1 st retardation plate (iii) with the base layer was obtained by the same procedure as the production of the 1 st retardation plate (i) with the base layer.

[ measurement of phase Difference value ]

The in-plane phase difference values Re (λ) of the 1 st phase difference plate (i) and the 1 st phase difference plate (ii) produced by the above-described method were measured by a measuring machine ("KOBRA-WPR", manufactured by prince measuring machine co.). The 1 st retardation plate (i) with the base layer, the 1 st retardation plate (ii) with the base layer, and the 1 st retardation plate (iii) with the base layer were bonded to glass via an adhesive, and then PET as a base was peeled off to prepare a sample for measurement. The measurement results of the phase difference value Re (λ) at each wavelength were Re (450) =121 nm, re (550) =142 nm, re (650) =146 nm, re (450)/Re (550) =0.85.

[ measurement of the ratio of the elastic deformation work (nIT) ]

The 1 st retardation plate (i), the 1 st retardation plate (ii) and the 1 st retardation plate (iii) from which the substrates were peeled off were placed on alkali-free glass (Eagle XG, manufactured by Corning Co., ltd.) and measured under the following measurement conditions using an ultra-fine hardness tester (Fischer Instruments Co., trade name: fischer scope. HM 2000). The elastic deformation work amount and the plastic deformation work amount of each sample were calculated by analysis software (WIN-HCU, manufactured by Fischer Instruments), and the ratio of the elastic deformation work amount was calculated by the above formula (1) (nIT). The ratio (nIT) of the elastic deformation work amount of the 1 st phase difference layer of the 1 st phase difference plate (i) was 29.3%, the ratio (nIT) of the elastic deformation work amount of the 1 st phase difference layer of the 1 st phase difference plate (ii) was 24.5%, and the ratio (nIT) of the elastic deformation work amount of the 1 st phase difference layer of the 1 st phase difference plate (iii) was 32.2%.

(measurement conditions)

Shape of the pressing head: vickers indenter of regular quadrangular pyramid (manufactured by diamond, opposite angle 136 °)

Measurement environment: the temperature is 23 ℃ and the relative humidity is 50%,

maximum test load: 1mN of the total weight of the fiber,

load speed: 1mN/5 seconds of the time,

unloading speed: 1mN/5 sec.

(production of the 2 nd phase plate with base layer)

As the composition for forming a vertical alignment layer, a composition prepared by mixing 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol triacrylate, and bis (2-ethyleneoxyethyl) ether in an amount of 1:1:4:5, and adding a polymerization initiator of LUCIRIN TPO at a ratio of 4%.

The composition (2) for forming a retardation layer is prepared by preparing a photopolymerizable nematic liquid crystal compound (RMM 28B, manufactured by merck corporation) and a solvent so that the solid content becomes 1 to 1.5 g. Solvent use Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK) and Cyclohexanone (CHN) were mixed in a mass ratio (MEK: MIBK: CHN) of 35:30:35, and a solvent mixture obtained by mixing the above components in proportion.

A polyethylene terephthalate (PET) film having a thickness of 38 μm was prepared as a base film. The composition for forming the vertical alignment layer was applied to one side of the base film so that the film thickness became 3. Mu.m, and irradiated with 200mJ/cm ² Is used for manufacturing a vertical alignment layer.

The composition (2) for forming a retardation layer is applied on the vertical alignment layer by die coating. The coating amount is 4 to 5g (wet). The coating film was dried by setting the drying temperature to 75℃and the drying time to 120 seconds. Then, ultraviolet (UV) light is irradiated to the coating film to polymerize the polymerizable liquid crystal compound.

Thus, a layer (a 2 nd retardation layer) obtained by curing a polymerizable liquid crystal compound, a vertical alignment layer, and a 2 nd retardation plate of a base film were laminated in this order. The 2 nd phase difference plate is a positive C plate. The total thickness of the retardation layer and the alignment layer of the 2 nd retardation plate was 4. Mu.m. After the 2 nd retardation plate with the base layer was bonded to glass via an adhesive, PET as a base material was peeled off to prepare a sample for measuring a phase difference value. Regarding the in-plane phase difference value Re (λ) of the 2 nd phase difference plate, the phase difference value at the wavelength of 550nm was measured by a measuring machine ("KOBRA-WPR", manufactured by prince measuring instruments co., ltd.) and as a result Re (550) =1 nm, rth (550) = -100nm. The ratio of the elastic deformation work amount of the 2 nd retardation layer of the 2 nd retardation plate was measured (nIT) in the same manner as described above. The ratio (nIT) of the elastic deformation work amount of the 2 nd retardation layer was 23.4%.

[ preparation of adhesive composition ]

The following cationic curable components a1 to a3 and a cationic polymerization initiator were mixed, and then the following cationic polymerization initiator and sensitizer were further mixed, followed by deaeration to prepare a photocurable adhesive composition. The following blending amount is based on the solid content.

Cationic curable component al (70 parts):

3',4' -epoxycyclohexane carboxylic acid 3',4' -epoxycyclohexyl methyl ester (trade name: CEL2021P, manufactured by Daicel Co., ltd.)

Cation curable component a2 (20 parts):

neopentyl glycol diglycidyl ether (trade name: EX-211, manufactured by NagaseChemteX Co., ltd.)

Cation curable component a3 (10 parts):

2-ethylhexyl glycidyl ether (trade name: EX-121, manufactured by NagaseChemteX Co., ltd.)

Cationic polymerization initiator (2.25 parts (solid component amount)):

trade name: 50% propylene carbonate solution of CPI-100 (San-Apro Co., ltd.)

Sensitizer (2 parts): 1, 4-Diethoxynaphthalene

[ production of adhesive ]

The adhesive was produced by the following method.

(production of adhesive 1)

Into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube, 95.0 parts by mass of n-butyl acrylate, 4.0 parts by mass of acrylic acid, 1.0 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate and 0.08 parts by mass of 2,2' -azobisisobutyronitrile were charged, and the air in the reaction vessel was replaced with nitrogen. The reaction solution was heated to 60℃under nitrogen with stirring, allowed to react for 6 hours, and then cooled to room temperature. As a result of measuring the weight average molecular weight of a part of the obtained solution, it was confirmed that 180 ten thousand (meth) acrylate polymers were produced.

100 parts by mass (solid content equivalent; hereinafter the same) of the (meth) acrylate polymer obtained in the above-mentioned step, 1.5 parts by mass of trimethylolpropane-modified toluene diisocyanate (trade name "Coronate (registered trademark) L", manufactured by Tosoh Co., ltd.), 0.30 parts by mass of 3-glycidoxypropyl trimethoxysilane (trade name "KBM403", manufactured by Xinyue chemical Co., ltd.), 7.5 parts by mass of ethoxylated isocyanuric acid triacrylate (trade name "A-9300", manufactured by Xinzhongcun chemical Co., ltd.) as an ultraviolet-curable compound, and 0.5 parts by mass of 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (Irgacure (registered trademark) 907, manufactured by BASF Co., ltd.) as a photopolymerization initiator were mixed and sufficiently stirred, and diluted with ethyl acetate, thereby obtaining a coating solution of the adhesive composition.

The coating solution was applied to the release surface (release layer surface) of the spacer (SP-PLR 382190, manufactured by Lindeke Co., ltd.) by an applicator so that the thickness after drying became 5 μm (adhesive A), and then dried at 100℃for 1 minute, and the other spacer (SP-PLR 381031, manufactured by Lindeke Co., ltd.) was bonded to the surface of the adhesive layer opposite to the surface to which the spacer was bonded. An ultraviolet irradiation device (manufactured by Fusion UV Systems Co., ltd., lamp using D-tube) was used to irradiate the adhesive layer with ultraviolet light (irradiation intensity 500 mW/cm) through a release sheet ² Cumulative light quantity 500mJ/cm ² ) An adhesive layer of the two-sided tape spacer was obtained. BondingThe storage modulus G' of agent 1 was 125000Pa at 25 ℃.

(production of adhesive 2)

Into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube, 97.0 parts by mass of n-butyl acrylate, 1.0 parts by mass of acrylic acid, 0.5 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate and 0.08 parts by mass of 2,2' -azobisisobutyronitrile were charged, and the air in the reaction vessel was replaced with nitrogen. The reaction solution was heated to 60℃under nitrogen with stirring, allowed to react for 6 hours, and then cooled to room temperature. As a result of measuring the weight average molecular weight of a part of the obtained solution, it was confirmed that 180 ten thousand (meth) acrylate polymers were produced.

100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth) acrylate polymer obtained in the above-described step, 0.30 part by mass of trimethylolpropane-modified toluene diisocyanate (trade name "Coronate (registered trademark) L" manufactured by Tosoh Co., ltd.) as an isocyanate-based crosslinking agent, and 0.30 part by mass of 3-glycidoxypropyl trimethoxysilane (trade name "KBM403" manufactured by Xinyue chemical Co., ltd.) as a silane coupling agent were mixed, stirred well, and diluted with ethyl acetate, thereby obtaining a coating solution of the adhesive composition.

The above-mentioned coating solution was applied to the release treated surface (release layer surface) of the spacer (SP-PLR 382190, manufactured by Lindeke Co., ltd.) by an applicator so that the thickness after drying became 25 μm (adhesive 2), and then dried at 100℃for 1 minute, and another spacer (SP-PLR 381031, manufactured by Lindeke Co., ltd.) was bonded to the surface of the adhesive layer opposite to the surface to which the spacer was bonded, to obtain an adhesive layer with spacers on both surfaces.

The storage modulus G' of the adhesive 2 was 25500Pa at 25 ℃.

[ measurement of weight average molecular weight (Mw) ]

The weight average molecular weight (Mw) of the (meth) acrylic resin for forming the adhesive layer is a polystyrene-equivalent weight average molecular weight measured using Gel Permeation Chromatography (GPC) under the following conditions.

[ measurement conditions ]

GPC measurement apparatus: HLC-8020 manufactured by Tosoh Co., ltd

GPC column (pass in the following order): manufactured by Tosoh Co., ltd

T SK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Measuring solvent: tetrahydrofuran (THF)

Measurement temperature: 40 DEG C

[ determination of storage modulus of adhesive ]

The storage modulus of the adhesive layer was measured by the following method. The adhesive layers were laminated so that the thickness reached 0.2 mm. A cylinder having a diameter of 8mm was punched out of the obtained adhesive layer, and this was used as a sample for measuring the storage modulus G'. For the above samples, storage modulus (MPa) was measured by torsional shear method using a viscoelasticity measuring apparatus (MCR 300, manufactured by Physica Co., ltd.) in accordance with JIS K7244-6 under the following conditions.

[ measurement conditions ]

Normal force F _N ：1N

Strain γ:1%

Frequency: 1Hz

Temperature: 25 DEG C

Example 1

The surface of the 2 nd retardation layer side of the prepared tape base layer (length 380mm in MD. Times. 180mm in TD) was subjected to corona treatment (800W, 10m/min, rod width 700mm,1 pass). The adhesive composition prepared above was formed into an adhesive composition layer by using an applicator (bar coater manufactured by first chemical Co., ltd.) to obtain a 2 nd retardation plate with an adhesive composition layer. Then, the surface of the 1 st retardation layer side of the prepared 1 st retardation plate (i) of the tape base layer (length 380mm in MD. Times. 180mm in TD) was subjected to corona treatment under the same conditions as described above, and the corona-treated surface was bonded to the adhesive composition layer of the 2 nd retardation plate of the tape adhesive composition layer using a bonding apparatus (LPA 3301 manufactured by FUJIPLA). From the first of the tape base material layersOn the 2 nd substrate layer side of the 2 nd retardation plate, an ultraviolet irradiation device (lamp using an "H tube" manufactured by Fusion UV Systems Co.) with a belt conveyor was used to irradiate an intensity of 390mW/cm in the UVA region ² The cumulative light quantity was 420mJ/cm ² In the UVB region, the irradiation intensity was 400mW/cm ² The cumulative light quantity was 400mJ/cm ² The adhesive composition was cured by irradiation with ultraviolet light to obtain a laminate of the 1 st phase difference plate and the 2 nd phase difference plate having both substrate layers. The thickness of the adhesive layer (hereinafter also referred to as "1 st adhesive layer") obtained by curing the adhesive composition layer was measured and found to be 1.5 μm.

The TAC film side of the linear polarizing plate was subjected to corona treatment. Then, the PET film on the 1 st retardation plate (i) side of the tape base layer was peeled off, and the peeled surface (alignment layer) side was subjected to corona treatment. Using the adhesive 1 from which the spacers were peeled, the TAC film surface side of the polarizing plate subjected to the corona treatment and the alignment layer of the laminate of the retardation plates were bonded so that the slow axis of the 1 st retardation plate (i) was rotated 45 degrees counterclockwise from the observation side with respect to the absorption axis of the polarizing plate, to obtain an optical laminate. Next, the PET film on the 2 nd retardation plate side of the base layer of the optical laminate obtained above was peeled off, corona-treated, and the adhesive 2 having one spacer peeled off from the adhesive layer having spacers on both sides was bonded to obtain a circularly polarizing plate of example 1. The obtained circularly polarizing plate had a structure consisting of COP film with surface-treated layer/aqueous adhesive/polarizer/aqueous adhesive/TAC film/adhesive 1/1 st retardation plate (i)/1 st adhesive layer (thickness 1.5 μm)/2 nd retardation plate/adhesive 2/spacer.

Example 2

A circularly polarizing plate of example 2 was obtained in the same manner as in example 1, except that the 1 st retardation plate (iii) with a base layer was used instead of the 1 st retardation plate (i) with a base layer in example 1. The obtained circularly polarizing plate had a structure consisting of COP film with surface-treated layer/aqueous adhesive/polarizer/aqueous adhesive/TAC film/adhesive 1/1 st retardation plate (iii)/1 st adhesive layer (thickness 1.5 μm)/2 nd retardation plate/adhesive 2/spacer.

Comparative example 1

A circular polarizing plate of comparative example 1 was obtained in the same manner as in example 1, except that the 1 st retardation plate (ii) with a base layer was used instead of the 1 st retardation plate (i) with a base layer in example 1. The obtained circularly polarizing plate had a structure consisting of COP film with surface-treated layer/aqueous adhesive/polarizer/aqueous adhesive/TAC film/adhesive 1/1 st retardation plate (ii)/1 st adhesive layer (thickness 1.5 μm)/2 nd retardation plate/adhesive 2/spacer.

Comparative example 2

In comparative example 1, a circularly polarizing plate of comparative example 2 was obtained in the same manner as in comparative example 1, except that the adhesive composition was applied to the 2 nd retardation layer of the 2 nd retardation plate with the base layer so that the thickness of the 1 st adhesive layer became 2.2 μm. The obtained circularly polarizing plate had a structure consisting of COP film with surface-treated layer/aqueous adhesive/polarizer/aqueous adhesive/TAC film/adhesive 1/1 st retardation plate (ii)/1 st adhesive layer (thickness 2.2 μm)/2 nd retardation plate/adhesive 2/spacer.

Comparative example 3

In comparative example 1, a circularly polarizing plate of comparative example 3 was obtained in the same manner as in comparative example 1, except that the adhesive composition was applied to the 2 nd retardation layer of the 2 nd retardation plate with the base layer so that the thickness of the 1 st adhesive layer became 4.3 μm. The obtained circularly polarizing plate had a structure consisting of COP film with surface-treated layer/aqueous adhesive/polarizer/aqueous adhesive/TAC film/adhesive 1/1 st retardation plate (ii)/1 st adhesive layer (thickness 4.3 μm)/2 nd retardation plate/adhesive 2/spacer.

[ measurement of DMT elastic modulus of the 1 st phase Density layer ]

For the circularly polarizing plates of example 1, example 2 and comparative examples 1 to 3, a cross-sectional processing was performed parallel to the slow axis of the 1 st retardation layer using an ultra-thin microtome (trade name "LEICA ultra-thin microtome EM UC7i", manufactured by LEICA corporation). The mechanical properties of the cross section of the obtained circular polarizing plate were evaluated under the following conditions using an atomic force microscope AFM (trade name: division Icon, bruker Co.) at the center in the thickness direction of the 1 st retardation layer, and DMT elastic modulus (GPa) was calculated based on the DMT theory, and normalized DMT elastic modulus was calculated. Values of normalized DMT elastic modulus are shown in Table 1.

First, the displacement amount of the piezoelectric scanner and the warp amount of the cantilever are measured and converted into a curve (force curve) indicating the relationship between the load F and the sample deformation amount δ. Fitting based on the DMT theory was performed on the pull-back process of the obtained force curve, and the elastic modulus at the measurement point was obtained. The cantilever used was OMCL-AC200TS-R3 (nominal spring constant k=9n/m, nominal probe tip radius r=7nm) manufactured by olynbas corporation. In the measurement, a force curve of 32×32 points (1024 points in total) in the range of 300nm×300nm was obtained under the condition that the cantilever was scanned in the pushing direction at a speed of 1 μm/sec while pushing the sample to 30 nN. In the analysis, the minimum to maximum values of the pull-back process of the force curve were set to 0 to 1, and a range of 0.05 to 0.8 was fitted. In the calculation of DMT elastic modulus, the Poisson's ratio of each of the sample and the standard was 0.3. The average value of the elastic modulus calculated at all points was taken as the DMT elastic modulus. By the above measurement method, DMT elastic modulus of a polystyrene standard (PSFILM-12M manufactured by Bruker) was measured as a standard sample, and then DMT elastic modulus of an evaluation sample was measured in the same manner. The DMT elastic modulus of the evaluation sample was divided by the DMT elastic modulus of the polystyrene standard, thereby giving a "normalized DMT elastic modulus".

[ measurement of the thickness of the adhesive layer ]

The thickness of the 1 st adhesive layer (adhesive layer for adhering the 1 st retardation plate and the 2 nd retardation plate) was measured by a contact film thickness meter (number die MH-15M, manufactured by Nikon Co., ltd.) as follows. First, the film thickness of each of the 1 st retardation plate with the base layer and the 2 nd retardation plate with the base layer was measured using the above-mentioned contact film thickness meter. Next, the film thickness of the laminated body of the two-sided tape base layer retardation plates obtained by bonding the 1 st retardation plate of the tape base layer and the 2 nd retardation plate of the tape base layer, the film thickness of which was measured, was measured at the same position as the positions of the film thicknesses of the 1 st retardation plate of the tape base layer and the 2 nd retardation plate of the tape base layer. The thickness of the 1 st adhesive layer was calculated from the difference between the measured film thickness of the laminated body of the retardation plates of the both-sided tape base layer and the total film thickness of the 1 st retardation plate of the tape base layer and the 2 nd retardation plate of the tape base layer.

[ method for measuring Martin hardness of the 1 st substrate layer ]

The 1 st base material layer was bonded to alkali-free glass (Eagle XG, manufactured by Corning Co., ltd.) via an adhesive 2, and measured under the measurement conditions described below using a ultra-small hardness tester (Fischer Instruments Co., ltd.: fischer scope HM 2000), and the Martin hardness was calculated by analytical software (WIN-HCU, manufactured by Fischer Instruments). The Martin hardness of the 1 st substrate layer was 184.7N/mm2.

maximum test load: 10mN of the total weight of the sample,

load speed: 10mN/5 seconds of the time,

unloading speed: 10mN/5 sec.

[ production of polarizing plate sample for inspection ]

An inspection circular polarizing plate was obtained in the same manner as in example 1 and comparative examples 1 to 3 except that in example 1 and comparative examples 1 to 3, the slow axis of the 1 st retardation plate was bonded so as to rotate 45 degrees clockwise from the observation side with respect to the absorption axis of the polarizing plate. The spacers of the obtained circular polarizing plate were peeled off and bonded to alkali-free glass (Eagle XG, manufactured by Corning corporation), to prepare a polarizing plate sample for inspection.

[ sample for uneven observation ]

The fluorescent lamps were observed by reflecting the surfaces of the spacers of the circularly polarizing plates obtained in example 1 and comparative examples 1 to 3, and the locations where minute deformations were observed were marked. For the marking position, a light microscope (product name BX5 3M manufactured by olympus corporation) was used for transmission observation, and a marking was selected in which minute foreign substances having a size of 10 μm to 20 μm were observed. For the selected marking position, layer cross-section analysis was performed using VS 1000 (Hitachi High-Tech Science, ltd.) as a scanning white interference microscope, and the marking position of the minute foreign matter was confirmed for the 1 st adhesive layer between the 1 st phase difference plate and the 2 nd phase difference plate, and unevenness was examined.

[ evaluation of unevenness ]

In a darkroom, a backlight (LED Viewer5000A4 manufactured by light corporation) was set to a normal mode (11800 lux), and a glass surface of the polarizing plate sample for inspection was set to face upward (COP film with a surface treatment layer was set as a light source side) on the backlight. The release spacer was arranged so that the adhesive faced the backlight side, and the sample for uneven observation was disposed. At this time, the absorption axis of the sample for uneven observation is parallel to the absorption axis of the polarizing plate for inspection. In the layer cross-section analysis, the marking position of the foreign matter was confirmed in the 1 st adhesive layer between the 1 st phase difference plate and the 2 nd phase difference plate, and unevenness was observed. The unevenness was evaluated using the following criteria. The results are shown in Table 1.

A+: no unevenness was observed.

A: no unevenness was substantially observed.

B: non-uniformity was observed.

C: unevenness was strongly observed.

TABLE 1

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Claims

1. An optical laminate comprising a 1 st phase difference plate and a 1 st optical layer bonded to one surface of the 1 st phase difference plate,

the normalized DMT elastic modulus of the 1 st phase difference layer is more than 0.65.

2. An optical laminate comprising a 1 st phase difference plate and a 1 st optical layer bonded to one surface of the 1 st phase difference plate,

the ratio nIT of the elastic deformation work amount of the 1 st phase difference layer calculated by the following formula (1) is 25% or more,

formula (1):

nIT (%) = { elastic deformation work amount/(elastic deformation work amount+plastic deformation work amount) } ×100.

3. The optical laminate according to claim 2, wherein the normalized DMT elastic modulus of the 1 st retardation layer is 0.65 or more.

4. The optical laminate according to claim 1 or 2, wherein the 1 st optical layer is a linear polarizing plate or a 2 nd phase difference plate.

5. The optical laminate according to claim 1 or 2, wherein the 1 st optical layer is bonded to the 1 st phase difference plate via a 1 st adhesive layer,

the 1 st adhesive layer has a thickness of 4 μm or less.

6. The optical stack of claim 5 wherein the 1 st adhesive layer comprises an adhesive.

7. The optical laminate according to claim 1 or 2, further comprising a 2 nd optical layer bonded to the other surface of the 1 st phase difference plate,

8. The optical laminate according to claim 7, wherein the 2 nd optical layer is bonded to the 1 st retardation plate via a 2 nd adhesive layer,

the thickness of the 2 nd adhesive layer is 4 μm or less.

9. The optical stack of claim 8 wherein the 2 nd adhesive layer comprises an adhesive.

10. The optical laminate according to claim 1 or 2, wherein the 1 st retardation plate satisfies the following formula (2),

100nm＜Re(550)＜160nm (2)

re (550) represents the in-plane phase difference value at a wavelength of 550 nm.

11. The optical laminate according to claim 1 or 2, which comprises a 2 nd retardation plate,

the ratio nIT of the elastic deformation work amount of the 2 nd retardation layer calculated by the above formula (1) is 10% or more.

12. The optical laminate according to claim 1 or 2, further comprising at least one of a front panel and a touch sensor panel laminated on a viewing side of the 1 st phase difference plate.

13. An image display device comprising the optical laminate of claim 1 or 2.