CN116235101A - Polarizing plate, polarizing plate with cover glass, and image display device - Google Patents
Polarizing plate, polarizing plate with cover glass, and image display device Download PDFInfo
- Publication number
- CN116235101A CN116235101A CN202180065707.9A CN202180065707A CN116235101A CN 116235101 A CN116235101 A CN 116235101A CN 202180065707 A CN202180065707 A CN 202180065707A CN 116235101 A CN116235101 A CN 116235101A
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- China
- Prior art keywords
- polarizing plate
- adhesive
- hole
- adhesive layer
- layer
- Prior art date
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133528—Polarisers
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/02—Details
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/80—Constructional details
- H10K59/8793—Arrangements for polarized light emission
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/80—Constructional details
- H10K59/8791—Arrangements for improving contrast, e.g. preventing reflection of ambient light
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- Physics & Mathematics (AREA)
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- General Physics & Mathematics (AREA)
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- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Polarising Elements (AREA)
- Liquid Crystal (AREA)
Abstract
The present invention provides a polarizing plate, which has small deflection in a through hole part even under a high-temperature environment, and in an image display device, when the through hole is filled with an adhesive for covering glass lamination, bubbles in the through hole part can be remarkably restrained. The polarizing plate of the present invention comprises: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; and has a through hole formed therein, the thickness of the polarizing plate is 15 μm or less, |b 1 －b 2 The I is below 45 mm. Here, b 1 B is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing plate 2 Is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing plate.
Description
Technical Field
The present invention relates to a polarizing plate, a polarizing plate with cover glass, and an image display device. More specifically, the present invention relates to a polarizing plate having an adhesive layer and formed with a through hole, a polarizing plate with cover glass, and an image display device including such a polarizing plate.
Background
In image display devices such as mobile phones and notebook-sized personal computers, polarizing plates are widely used to realize image display and/or to improve the performance of the image display. In recent years, polarizing plates are also expected to be used in image display devices, smart watches, instrument panels of automobiles, and the like, in which cameras are mounted, and in which through holes are formed in the polarizing plates. However, in the polarizing plate having the through-holes, there is a problem that the polarizing plate is displaced (substantially, the adhesive layer is displaced) in the through-holes under a high-temperature environment.
However, in order to impart surface hardness and impact resistance to an image display device, there are cases where the outermost surface area layer of the image display device is covered with glass. When a cover glass is laminated on an image display device including a polarizing plate having a through hole, the through hole is typically filled with an adhesive for laminating the cover glass. However, in an image display device in which a through hole is filled with an adhesive, there are cases in which bubbles are generated in a filled portion (through hole portion) due to heat treatment or the like in a manufacturing step.
Prior art literature
Patent literature
Patent document 1: international publication No. 2017/047510
Patent document 2: japanese patent laid-open publication 2016-094569
Disclosure of Invention
The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a polarizing plate in which a displacement in a through hole portion is small even in a high-temperature environment, and in which bubbles in the through hole portion can be significantly suppressed when the through hole is filled with an adhesive for covering a glass laminate in an image display device.
The polarizing plate of the present invention comprises: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; and has a through hole formed therein, the thickness of the polarizing plate is 15 μm or less, |b 1 －b 2 The I is below 45 mm. Here, b 1 B is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing plate 2 Is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing plate.
In one embodiment, the polarizing plate has a rectangular shape, and the absorption axis direction of the polarizing plate is a direction of 135 ° from the long side direction in the clockwise direction when viewed from the viewing side, and the through hole is formed in the upper right corner. In another embodiment, the polarizing plate has a rectangular shape, the absorption axis direction of the polarizing plate is 45 ° from the longitudinal direction in the clockwise direction when viewed from the viewing side, and the through hole is formed in the upper left corner. In still another embodiment, the polarizing plate has a rectangular shape, the absorption axis direction of the polarizing plate is a short side direction, and the through hole is formed at an end portion in the long side direction and at a center portion in the short side direction in a plan view.
In one embodiment, the polarizer has a thickness of 8 μm or less.
In one embodiment, the adhesive layer has a creep value of 140 μm/hr or less.
According to another aspect of the present invention, an image display apparatus is provided. The image display device comprises an image display unit and the polarizing plate, wherein the polarizing plate is attached to the image display unit through the adhesive layer.
According to still another embodiment of the present invention, there is provided a polarizing plate with cover glass attached. The polarizing plate with cover glass comprises: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; another adhesive layer provided on the opposite side of the polarizer from the adhesive layer; and a cover glass adhered via the other adhesive layerCombining; and a through hole is formed, the through hole is filled with an adhesive constituting the other adhesive layer, the thickness of the polarizer is 15 μm or less, |b 1 －b 2 The I is below 45 mm.
According to the embodiment of the present invention, a polarizing plate having a through hole and in which the offset in the through hole portion is small even in a high temperature environment can be realized, and in an image display device, when the through hole is filled with an adhesive for laminating a cover glass, bubbles in the through hole portion can be significantly suppressed.
Drawings
Fig. 1A is a schematic plan view illustrating a position of formation of a through hole in a polarizing plate according to an embodiment of the present invention.
Fig. 1B is a schematic plan view illustrating a position of formation of a through hole in a polarizing plate according to another embodiment of the present invention.
Fig. 1C is a schematic plan view illustrating a position of formation of a through hole in a polarizing plate according to still another embodiment of the present invention.
Fig. 2 is a schematic cross-sectional view of a through hole portion of a polarizing plate according to an embodiment of the present invention.
Fig. 3 is an enlarged cross-sectional view of a main part illustrating the offset in the through hole portion in the polarizing plate according to the embodiment of the present invention.
Detailed Description
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. Further, the drawings are schematically shown for the sake of convenience of observation, and further, ratios of length, width, thickness, etc., and angles, etc., in the drawings are different from those in practice.
A. Integral structure of polarizing plate
Fig. 1A is a schematic plan view illustrating a position of formation of a through hole in a polarizing plate according to an embodiment of the present invention; fig. 1B is a schematic plan view illustrating a position of formation of a through hole in a polarizing plate according to another embodiment of the present invention; fig. 1C is a schematic plan view illustrating a position of formation of a through hole in a polarizing plate according to still another embodiment of the present invention; fig. 2 is a schematic cross-sectional view of a through hole portion of the polarizing plate. The polarizing plate (polarizing plates 100, 101, 102 in the illustrated example) according to the embodiment of the present invention includes: a polarizing plate 11; a protective layer (hereinafter, sometimes referred to as an outer protective layer) 12 disposed on one side of the polarizing plate 11; a protective layer (hereinafter, sometimes referred to as an inner protective layer) 13 disposed on the other side of the polarizing plate 11; and an adhesive layer 20. The adhesive layer 20 is used to attach the polarizing plate 100 to the image display unit. Either the outer protective layer 12 or the inner protective layer 13 may be omitted depending on the purpose, the desired constitution, and the like.
The polarizer is formed with a through hole 30. By forming the through hole, for example, in the case of incorporating a camera in the image display device, adverse effects on the performance of the camera can be prevented. The through-hole may be formed by various methods, such as laser processing, cutting processing with an end mill, punching processing with a Thomson knife or Pinnacle (registered trademark) knife, and the like. The polarizing plate typically has a rectangular shape. In the present specification, when referring to "rectangular shape", it also includes a shape including a deformed portion, for example, an R shape in which each vertex is chamfered as shown in fig. 1A to 1C. Although not shown, a plurality of through holes may be provided. The shape of the through hole in plan view may be any suitable shape according to the purpose. Specific examples of the planar shape include a circle, an ellipse, a square, a rectangle, and a combination thereof (for example, an end of a rectangle is arc-shaped) as shown in the example of the figure. Further, the through hole may be provided and a special-shaped processing portion (for example, a U-shaped recess or a V-shaped recess) may be provided. The present inventors have found the following new problems: when the through-hole is formed in the polarizing plate, the polarizing plate may be offset (substantially, offset of the adhesive layer: hereinafter, sometimes referred to as paste offset) at the through-hole portion in a high-temperature environment, and as a result, there is a concern that light leakage may occur at the through-hole portion; the above problems are solved by adopting a specific configuration (described later) according to the embodiment of the present invention. That is, the present invention solves a hitherto unknown new problem, and the effect obtained thereby is unexpectedly excellent. Further, the present inventors have found that by adopting a specific configuration (described later) of the embodiment of the present invention, bubbles called delay bubbles can be significantly suppressed. Details of the delay bubble are as follows. In order to impart surface hardness and impact resistance to an image display device, there is a case where an outermost surface area layer of the image display device covers glass. In the case of laminating a cover glass in an image display device including a polarizing plate having a through hole, the through hole is typically filled with an adhesive for laminating the cover glass. Such filling is typically performed by bonding a laminate of cover glass and an adhesive sheet to a polarizing plate by vacuum lamination. In many cases, immediately after vacuum lamination, there are no recognizable bubbles in the filled portion, but in the subsequent heat durability test of the image display device, bubbles may be generated. Such bubbles may be typically generated due to shrinkage stress of the polarizing plate applied to the filling portion. Such bubbles are referred to as delay bubbles. The delay bubble is larger than a certain ratio of the planar area of the through hole, and is not fine, and is not allowed to exist from the viewpoint of appearance or from the viewpoint of camera performance of a camera unit provided at a position corresponding to the through hole. Therefore, by suppressing the delay bubble, the commodity value of the image display device can be significantly improved.
In the embodiment of the present invention, the thickness of the polarizing plate is 15 μm or less, preferably 10 μm or less, more preferably 8 μm or less, further preferably 7 μm or less, particularly preferably 6 μm or less, and particularly preferably 5 μm or less. The thickness of the polarizing plate may be, for example, 1 μm or more, or may be, for example, 2 μm or more. By setting the thickness of the polarizing plate to such a range, thermal shrinkage of the polarizing plate itself can be suppressed. As a result, deformation of the adhesive layer (as a result of paste displacement) which may be caused following thermal shrinkage of the polarizing plate can be suppressed.
Further, in the embodiment of the present invention, |b 1 －b 2 The value of I is 45mm or less, preferably 30mm or less, more preferably 20mm or less, still more preferably 10mm or less, particularly preferably 5mm or less. B 1 －b 2 The smaller the i, the better, optimally 0 (zero). If |b 1 －b 2 If the ratio is within such a range, the number of through-hole portions in a high-temperature environment can be reducedAnd delay bubbles can be suppressed. On the other hand, |a 1 －a 2 Substantially no contribution is made to either suppression of paste displacement in the through-hole portion or suppression of delay bubbles. That is, even if |a is changed 1 －a 2 Paste displacement and delay bubbles are not suppressed. Here, b 1 B is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing plate 2 A is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing plate 1 A is a distance from the center of the through hole to one end of the polarizing plate in a direction perpendicular to the absorption axis direction of the polarizing plate 2 Is the distance from the center of the through hole to the other end of the polarizing plate in the direction orthogonal to the absorption axis direction of the polarizing plate. That is, by optimizing the orientation of the position of the absorption axis of the polarizer with respect to the through-hole, both paste displacement and retardation bubbles can be suppressed.
Reference is made to FIGS. 1A-1C for a 1 、a 2 、b 1 B 2 The relationship with the formation position of the through hole will be specifically described. In fig. 1A, the following is shown: the polarizing plate has a rectangular shape, and the absorption axis direction a of the polarizing plate is 135 ° clockwise with respect to the longitudinal direction when viewed from the viewing side (the side opposite to the adhesive layer) of the image display device. In this embodiment, |b 1 －b 2 When the through-hole 30 is formed in a straight line extending from the upper right corner in a direction perpendicular to the absorption axis direction a when the polarizing plate is viewed from the viewer side in the optimization (in fig. 1A, the distance a is shown 1 A 2 On a straight line) of the paste, paste displacement and delay bubble can be suppressed. On the other hand, if |a is adjusted 1 －a 2 The through hole 30 may be preferably formed in the upper right corner while minimizing the influence on the image display. In fig. 1B, the following is shown: the polarizing plate has a rectangular shape, and the absorption axis direction a of the polarizing plate is 45 ° clockwise with respect to the longitudinal direction when viewed from the viewing side of the image display apparatus. In this form, the method can also be carried out by reacting |b 1 －b 2 Optimizing to suppress both paste offset and delay bubbles, and adjusting a 1 －a 2 I minimizes the impact on the image display. As a result, in this form, the through-hole 30 can be preferably formed in the upper left corner. In fig. 1C, the following is shown: the polarizing plate has a rectangular shape, and the absorption axis direction a of the polarizing plate is the short side direction (orthogonal to the long side direction). In this form, the method can also be carried out by reacting |b 1 －b 2 Optimizing to suppress both paste offset and delay bubbles, and adjusting a 1 －a 2 I minimizes the impact on the image display. As a result, in this embodiment, the through-hole 30 can be preferably formed at the end in the longitudinal direction and at the center in the short direction. As can be seen from the above, according to the embodiment of the present invention, regardless of the planar shape of the polarizing plate (for example, even in the case of having a special planar shape), the retardation of the retardation film can be improved by the retardation film b 1 －b 2 Optimizing to determine the relationship between the position of the through hole and the absorption axis direction, which can suppress paste displacement and delay bubbles. Further, by adjusting |a 1 －a 2 And minimizes the effect of the through-hole on the image display.
In one embodiment, as shown in fig. 3, in a state where the polarizing plate 100 is bonded to a glass plate (substrate that can correspond to an image display unit) 120 via an adhesive layer 20, the polarizing plate 100 is subjected to a heating test at 85 ℃ for 120 hours, and then the offset (paste offset) D in the through hole 30 portion is preferably 150 μm or less, more preferably 120 μm or less, still more preferably 100 μm or less, particularly preferably 80 μm or less, and particularly preferably 50 μm or less. The lower limit of the paste offset D is, for example, 10 μm, and may be, for example, 20 μm as the offset D is smaller. The paste offset D is the largest portion of the polarizer that is away from the through-hole when viewed in cross section. Typically, the reference of the through hole portion may be a lower end portion of the adhesive layer. That is, when the polarizing plate is shifted mainly by shrinkage of the polarizing plate 11 (rightward in the illustrated example), the adhesive layer 20 stays on the bonded glass plate 120, and thus the shift is observed in the through hole portion. As shown in fig. 3, the polarizing plate is typically offset from the through hole portion to the side away from the through hole (right side in fig. 3), and the portion opposite thereto is offset so as to protrude to the through hole (left side in fig. 3). As described above, according to the embodiment of the present invention, the newly found problem of paste displacement occurring in the through-hole portion under a high-temperature environment can be solved, and specifically, the paste displacement amount D after a specific heating test can be set to the above-described range.
In one embodiment, the polarizing plate may form an adhesive void portion in the through hole 30 such that the end surface of the adhesive layer 20 is located inward in the plane direction than the end surface of the polarizing plate (substantially the polarizing plate 11 or the inner protective layer 13 (if present)). The size of the adhesive void is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 150 μm or less, particularly preferably 100 μm or less, and particularly preferably 80 μm or less. The lower limit of the size of the adhesive void may be, for example, 10 μm. In the present specification, the "size of the adhesive void portion" refers to the maximum length from the end face of the polarizing plate (substantially the polarizing plate 11 or the inner protective layer 13 (where present)) to the end face of the adhesive layer 20.
In the embodiment of the present invention, the dimensional shrinkage of the polarizing plate after the heating test is preferably 1.0% or less, more preferably 0.6% or less, and still more preferably 0.3% or less. The smaller the dimensional shrinkage, the better, and the lower limit of the dimensional shrinkage may be, for example, 0.01%. The dimensional shrinkage is determined by the following formula. The dimensional shrinkage is the dimensional shrinkage of the entire polarizing plate attached to the glass plate, and when the polarizing plate further has an optical functional layer (for example, a retardation layer or a reflective polarizer) as described below, the dimensional shrinkage of the entire polarizing plate including the optical functional layer is referred to. The "dimension" in the following formula is the dimension in the absorption axis direction of the polarizing plate (substantially the polarizing plate).
Dimensional shrinkage (%) = { (dimension before heat test-dimension after heat test)/dimension before heat test } ×100
The diameter R of the through hole 30 is preferably 10mm or less, more preferably 8mm or less, and further preferably 5mm or less. The lower limit of the diameter of the through hole is, for example, 1.5mm, or may be, for example, 2mm. The ratio D/R of the paste offset D to the diameter R of the through hole is preferably 15% or less, more preferably 10% or less, still more preferably 6% or less, and particularly preferably 5% or less. On the other hand, the smaller the lower limit of D/R, the better. According to the embodiment of the present invention, since the paste offset amount D is extremely small as described above, D/R can be set to such a range even if the diameter of the through hole is reduced. Therefore, even if the diameter of the through hole is reduced, adverse effects on the camera performance can be substantially prevented. As a result, the polarizing plate according to the embodiment of the present invention can be applied to an image display device and/or a borderless image display device in which only the camera portion is a non-display area.
The polarizing plate according to the embodiment of the present invention can be used as a viewing-side polarizing plate or a back-side polarizing plate. The polarizing plate according to the embodiment of the present invention may further have any appropriate optical functional layer depending on the purpose. Examples of the optical functional layer include a retardation layer, a conductive layer for a touch panel, and a reflective polarizer.
In one embodiment, a retardation layer may be provided between the inner protective layer 13 and the adhesive layer 20. The retardation layer may be formed of a single layer or may have a laminated structure. When the retardation layer is formed of a single layer, the retardation layer typically functions as a λ/4 plate. In this case, the in-plane retardation Re (550) of the retardation layer is preferably 100nm to 200nm, more preferably 120nm to 170nm, and further preferably 130nm to 150nm. The angle formed by the absorption axis of the polarizing plate and the retardation axis of the retardation layer is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably 44 ° to 46 °. The phase difference layer preferably exhibits an inverse wavelength dispersion characteristic in which the phase difference value becomes large according to the wavelength of the measurement light. In this case, re (450)/Re (550) of the retardation layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. The retardation layer may be an extended film of a resin film or an alignment cured layer of a liquid crystal compound. In the case where the retardation layer is formed of a resin film, the retardation layer may also serve as an inner protective layer. The retardation layer formed of an elongated film of a resin film is described in, for example, japanese patent application laid-open No. 2017-54093 and Japanese patent application laid-open No. 2018-60014. Specific examples of the liquid crystal compound and details of the method for forming the alignment cured layer are described in, for example, japanese patent application laid-open No. 2006-163343. The description of this publication and the like is incorporated by reference into the present specification. In the present specification, "Re (λ)" is an in-plane retardation measured at 23℃with light having a wavelength of λ nm. For example, "Re (550)" is the in-plane retardation measured at 23℃with light having a wavelength of 550 nm. As for Re (λ), when the thickness of the layer (film) is set to d (nm), the formula: re (λ) = (nx-ny) ×d. nx is a refractive index in a direction in which the refractive index in the plane reaches the maximum (i.e., in the slow axis direction), and ny is a refractive index in a direction in which the refractive index in the plane is orthogonal to the slow axis (i.e., in the slow axis direction).
When the retardation layer has a laminated structure, the retardation layer typically has an H layer and a Q layer in this order from the polarizing plate side. The H layer typically functions as a lambda/2 plate and the Q layer typically functions as a lambda/4 plate. Re (550) of the H layer is preferably 200nm to 300nm, more preferably 230nm to 290nm, and still more preferably 260nm to 280nm. The angle formed by the absorption axis of the polarizer and the slow phase axis of the H layer is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and still more preferably 14 ° to 16 °. Re (550) of the Q layer is preferably 100nm to 200nm, more preferably 120nm to 170nm, and still more preferably 130nm to 150nm. The angle formed by the absorption axis of the polarizer and the slow phase axis of the Q layer is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and still more preferably 74 ° to 76 °. The arrangement order of the H layer and the Q layer may be reversed, and the angle formed by the slow axis of the H layer and the absorption axis of the polarizer and the angle formed by the slow axis of the Q layer and the absorption axis of the polarizer may be reversed. The H layer and the Q layer may be an extension film of a resin film, or may be an alignment cured layer of a liquid crystal compound.
In one embodiment, a conductive layer for a touch panel may be provided on the side of the inner protective layer 13 (phase difference layer, if any) opposite to the polarizing plate. With such a configuration, the polarizing plate can be applied to a so-called internal touch panel type input display device in which a touch sensor is incorporated between an image display unit and the polarizing plate. The polarizing plate of this embodiment is typically a visual recognition-side polarizing plate.
In one embodiment, a reflective polarizer may be disposed on the opposite side of the outer protective layer 12 from the polarizer. The reflective polarizer may also serve as an outer protective layer. The polarizing plate of this embodiment is typically a back-side polarizing plate. Details of the reflective polarizer are described in, for example, JP-A-9-507308 and JP-A-2013-235259. The disclosures of these publications are incorporated by reference into this specification.
When the polarizing plate according to the embodiment of the present invention is rectangular, the aspect ratio is preferably 1.3 to 2.5. In this case, the polarizing plate has a size of, for example, 145 to 155mm long and 65 to 75mm wide, or 230 to 240mm long and 140 to 150mm wide. That is, the polarizing plate according to the embodiment of the present invention is suitably used for a smart phone or a tablet PC (Personal Computer ). The smart phone may have a length of 120mm to 200mm and a width of 30mm to 120mm, for example.
Hereinafter, a polarizing plate, a protective layer, and an adhesive layer constituting a polarizing plate will be described in detail.
B. Polarizing plate
B-1 polarizing plate
The polarizing plate is typically composed of a resin film containing a dichroic substance. As the resin film, any suitable resin film that can be used as a polarizing plate can be used. The resin film is typically a polyvinyl alcohol resin (hereinafter, referred to as "PVA-based resin") film. The resin film may be a single-layer resin film or a laminate of two or more layers.
Specific examples of the polarizing plate formed of a single-layer resin film include a PVA-based resin film subjected to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The dyeing with iodine is performed, for example, by immersing the PVA-based resin film in an aqueous iodine solution. The stretching magnification of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. Further, dyeing may be performed after stretching. If necessary, the PVA-based resin film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based resin film in water before dyeing and washing with water, not only stains or an anti-blocking agent on the surface of the PVA-based resin film can be washed, but also the PVA-based resin film can be swelled to prevent uneven dyeing and the like.
Specific examples of the polarizing plate obtained by using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, and a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate. The polarizing plate obtained by using a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate can be produced, for example, by the steps of: coating a PVA resin solution on a resin base material, drying the resin base material, and forming a PVA resin layer on the resin base material to obtain a laminate of the resin base material and the PVA resin layer; the laminate is stretched and dyed to form a polarizing plate from the PVA resin layer. In the present embodiment, the stretching typically includes immersing the laminate in an aqueous boric acid solution to stretch the laminate. Further, the extension may further include, as needed: before the stretching in the aqueous boric acid solution, the laminate is stretched in the air at a high temperature (for example, 95 ℃ or higher). The obtained laminate of the resin substrate and the polarizing plate may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizing plate), or the resin substrate may be peeled off from the laminate of the resin substrate and the polarizing plate, and any appropriate protective layer may be used depending on the purpose of the peeled surface. Details of such a method for producing a polarizing plate are described in, for example, japanese patent laid-open publication No. 2012-73580 and japanese patent No. 6470455. The disclosures of these patent documents are incorporated by reference into the present specification.
The thickness of the polarizer is as described in item A.
The polarizer preferably exhibits absorption dichroism at any one of wavelengths 380nm to 780 nm. The monomer transmittance of the polarizing plate is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The polarization degree of the polarizing plate is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.
B-2. Protective layer
The protective layer is formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that becomes the main component of the film include: triacetyl fiberCellulose resins such as cellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, and polynorbornenes
Transparent resins such as olefins, polyolefins, (meth) acrylic acid, and acetates. Also, it is possible to exemplify: thermosetting resins such as (meth) acrylic, urethane (meth) acrylate, epoxy, and silicone resins, ultraviolet curable resins, and the like. Further, for example, a glass polymer such as a siloxane polymer may be mentioned. Further, a polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007) may be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imino group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain, for example, a resin composition having an alternating copolymer containing isobutylene and N-methyl maleimide and an acrylonitrile-styrene copolymer can be used. The polymer film may be, for example, an extrusion molded product of the resin composition.
If necessary, the outer protective layer 12 (especially, in the case where the polarizing plate is a visual-side polarizing plate) may be subjected to surface treatments such as a hard coat treatment, an antireflection treatment, an anti-sticking treatment, and an antiglare treatment. Further, the external protective layer 12 may be treated to improve visibility when viewed through polarized sunglasses (typically, to impart (elliptical) polarization function and to impart an ultra-high retardation), if necessary. By performing such a process, even when a display screen is visually recognized through a polarized lens such as polarized sunglasses, excellent visibility can be achieved. Therefore, the polarizing plate can be suitably used for an outdoor image display device.
The inner protective layer is preferably optically isotropic. In the present specification, the term "optical isotropy" means that the in-plane retardation Re (550) is from 0nm to 10nm, and the retardation Rth (550) in the thickness direction is from-10 nm to +10nm. Here, "Rth (λ)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of λ nm. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23 ℃ with light having a wavelength of 550 nm. As for Rth (λ), when the thickness of the layer (film) is set to d (nm), the formula: rth (λ) = (nx-nz) ×d. nz is the refractive index in the thickness direction.
The thickness of the protective layer may be any suitable thickness. The thickness of the protective layer is, for example, 10 μm to 50. Mu.m, preferably 20 μm to 40. Mu.m. Further, in the case of performing the surface treatment, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer.
C. Adhesive layer
The adhesive layer 20 is used to attach the polarizing plate to the image display unit as described above. The adhesive layer may be typically composed of an acrylic adhesive (acrylic adhesive composition). The acrylic adhesive composition typically contains a (meth) acrylic polymer as a main component. The (meth) acrylic polymer may be contained in the adhesive composition at a ratio of, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, in the solid content of the adhesive composition. The (meth) acrylic polymer contains an alkyl (meth) acrylate as a monomer unit as a main component. Furthermore, (meth) acrylic esters refer to acrylic esters and/or methacrylic esters. The alkyl (meth) acrylate is preferably contained in the monomer component forming the (meth) acrylic polymer at a ratio of 80% by weight or more, more preferably 90% by weight or more. Examples of the "alkyl" of the "alkyl (meth) acrylate may include straight-chain or branched alkyl having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. The preferred alkyl (meth) acrylate is butyl acrylate. Examples of the monomer (comonomer) constituting the (meth) acrylic polymer include, in addition to alkyl (meth) acrylate: carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth) acrylates, heterocyclic ring-containing vinyl monomers, and the like. Typical examples of the comonomer include: acrylic acid, 4-hydroxybutyl acrylate, phenoxyethyl acrylate, N-vinyl-2-pyrrolidone. The acrylic adhesive composition may preferably contain a silane coupling agent and/or a crosslinking agent. Examples of the silane coupling agent include epoxy group-containing silane coupling agents. Examples of the crosslinking agent include isocyanate crosslinking agents and peroxide crosslinking agents. The acrylic adhesive composition may further contain an antioxidant and/or a conductive agent. The thickness of the adhesive layer is, for example, 50 μm or less, and as described above, preferably 22 μm or less, more preferably 10 μm to 22 μm. Details of the adhesive layer or the acrylic adhesive composition are described in, for example, japanese patent application laid-open No. 2006-183022, japanese patent application laid-open No. 2015-199942, japanese patent application laid-open No. 2018-053114, japanese patent application laid-open No. 2016-190996, and International publication No. 2018/008712, the disclosures of which are incorporated herein by reference.
The creep value of the adhesive layer is preferably 140 μm/hr or less, more preferably 100 μm/hr or less, still more preferably 75 μm/hr or less, particularly preferably 50 μm/hr or less. The lower limit of the creep value may be, for example, 20 μm/hr. In the present specification, the term "creep value" means a creep value at 85 ℃. The creep value can be determined, for example, by the following sequence: bonding an adhesive constituting the adhesive layer to the support plate; the support plate to which the adhesive was attached was fixed, and in this state, a load of 500g was applied downward in the vertical direction. The amount of offset of the adhesive from the support plate after 1 hour of load application was measured, and the amount of offset was taken as the creep value (μm/hr).
Storage modulus G at-40 ℃ of adhesive layer 2 ' preferably 1.0X10 5 (Pa) or more, more preferably 1.0X10 6 (Pa) or more, and more preferably 1.0X10 7 (Pa) or more, particularly preferably 1.0X10 8 (Pa) or more. Storage modulus G 2 ' may be, for example, 1.0X10 9 (Pa) below. Storage modulus G at 85℃of adhesive layer 3 ' preferably 1.0X10 5 (Pa) or more, more preferably 3.0X10 5 (Pa) or more, more preferably 5.0X10 5 (Pa) or more. Storage modulus G 3 ' may be, for example, 1.0X10 6 (Pa) below.
D. Image display device
The polarizing plate according to the embodiment of the invention is applicable to an image display device. Therefore, the image display device is also included in the embodiment of the present invention. The image display device includes an image display unit and a polarizing plate. The polarizing plate according to the embodiment of the present invention described in any one of items A to C. The polarizing plate is bonded to the image display unit via an adhesive layer. Examples of the image display device include a liquid crystal display device, an organic Electroluminescence (EL) display device, and a quantum dot display device.
E. Polarizing plate with cover glass
When the polarizing plate according to the embodiment of the present invention is applied to the visual side of an image display device, the cover glass may be bonded to the polarizing plate via another adhesive layer (hereinafter, may be referred to as the 2 nd adhesive layer). Accordingly, embodiments of the present invention include a polarizing plate with a cover glass layer. The polarizing plate according to the embodiment of the present invention may be provided in a form in which a spacer is temporarily stuck instead of the cover glass. In this case, when the image display device is manufactured, the spacer is peeled off and the cover glass is bonded via the exposed 2 nd adhesive layer. In any case, the through-holes are typically filled with an adhesive constituting the 2 nd adhesive layer. Hereinafter, the adhesive constituting the 2 nd adhesive layer will be described.
When the 2 nd adhesive layer is laminated on the polarizing plate, the storage modulus at 60℃is typically 1.0X10 4 Pa～1.0×10 5 Pa. Any suitable adhesive may be used for the adhesive constituting the 2 nd adhesive layer, as long as the adhesive has such a storage modulus at the time of lamination. Specifically, the adhesive may be a photo-curable adhesive or a non-curable adhesive. In the present specification, the term "photocurable adhesive" refers to an adhesive in which a crosslinking reaction is performed by irradiation with light. Therefore, the photocurable adhesive is soft and excellent in deformability when laminated, and can impart desired properties (e.g., storage modulus) to the adhesive layer by light irradiation after lamination. Thereby, the filling of the deformed portion of the photo-curable adhesive The adhesive layer 2 (as a result of which the image display device) can be made thin in thickness. Further, even when a thick frame printing layer is formed on the cover glass, good adhesion can be ensured. The term "non-curable adhesive" means an adhesive in which the crosslinking reaction is substantially completed and the crosslinking reaction does not substantially proceed after lamination. In other words, the non-curable adhesive may be a so-called conventional adhesive. The non-curable adhesive does not require light irradiation (photo curing), and therefore has excellent productivity, and further can prevent occurrence of dents, overflow of the adhesive from the end of the die-cut processed product, and defective handling.
The storage modulus at 60 ℃ before curing of the photocurable adhesive may substantially correspond to the storage modulus at the time of lamination. The storage modulus before hardening is 1.0X10 as described above 5 Pa or less, preferably 1.0X10 3 Pa～1.0×10 5 Pa. The storage modulus at 60℃of the photo-curable adhesive after curing is preferably 5.0X10 3 Pa～5.0×10 5 Pa. The gel fraction of the photo-curing adhesive before curing is 0-60%, and the gel fraction after curing is 50-95%. When the 2 nd adhesive layer is made of a photo-curable adhesive, the thickness of the 2 nd adhesive layer is preferably 50 μm to 500. Mu.m, more preferably 75 μm to 475. Mu.m, still more preferably 100 μm to 450. Mu.m.
The storage modulus at 60℃in laminating the non-curable adhesive is preferably 1.0X10 3 Pa～8.0×10 4 Pa, more preferably 5.0X10 3 Pa～6.0×10 4 Pa. When the 2 nd adhesive layer is made of a non-curable adhesive, the thickness of the 2 nd adhesive layer is preferably 50 μm to 1000 μm, more preferably 75 μm to 900 μm, still more preferably 100 μm to 800 μm.
Hereinafter, the characteristics of the 2 nd adhesive layer and the photo-curable adhesive constituting the 2 nd adhesive layer will be described, and then, the non-curable adhesive will be briefly described.
E-1. Property of the 2 nd adhesive layer
The glass transition temperature of the 2 nd adhesive layer is preferably-3 ℃ or lower, more preferably-5 ℃ or lower, and still more preferably-6 ℃ or lower. On the other hand, the glass transition temperature is preferably-20℃or higher, more preferably-15℃or higher, and still more preferably-13℃or higher. When the glass transition temperature is within such a range, the 2 nd adhesive layer having excellent impact resistance can be realized.
The peak top value of the loss tangent tan δ of the 2 nd adhesive layer (i.e., tan δ at glass transition temperature) is preferably 1.5 or more, more preferably 1.6 or more, still more preferably 1.7 or more, particularly preferably 1.75 or more. On the other hand, the upper limit of the peak top value of tan δ is preferably 3.0 or less, more preferably 2.5 or less, and further preferably 2.3 or less. When the peak top value of tan δ is within such a range, the 2 nd adhesive layer exhibits an appropriate deformation behavior (viscoelastic behavior), and therefore a gap is less likely to form in the shaped processed portion, and the delayed bubble can be suppressed.
The total light transmittance of the 2 nd adhesive layer is preferably 85% or more, more preferably 90% or more. The haze value of the 2 nd adhesive layer is preferably 1.5% or less, more preferably 1.0% or less.
E-2 photo-curable adhesive
E-2-1 Properties of Photocurable adhesive
The storage modulus at 60℃of the photocurable adhesive before curing was 1.0X10 as described above 5 Pa or less, preferably 1.0X10 3 Pa～1.0×10 5 Pa, more preferably 5.0X10 3 Pa～8.0×10 4 Pa, and more preferably 7.5X10 3 Pa～6.0×10 4 Pa. When the storage modulus of the photo-curable adhesive before curing falls within such a range, the photo-curable adhesive exhibits an appropriate deformation behavior (viscoelastic behavior) and can flow well into each corner of the shaped processed portion. As a result, gaps are less likely to form in the deformed portion, and the delay bubble can be suppressed. The storage modulus at 60℃of the photo-curable adhesive after curing is preferably 5.0X10 3 Pa～5.0×10 5 Pa, more preferably 7.5X10 3 Pa～4.0×10 5 Pa, and more preferably 8.0X10 3 Pa～3.0×10 5 Pa. If the storage modulus of the photo-curable adhesive after curing falls within this range, the gel elasticity of the 2 nd adhesive decreases and the residual stress becomes smaller. As a result, the bubbles are retardedCan be suppressed.
The gel fraction of the photo-curable adhesive before curing is preferably 0% to 60%, more preferably 0% to 55%, and even more preferably 0% to 50%. If the gel fraction of the photo-curable adhesive before curing falls within such a range, the desired storage modulus can be easily achieved. Therefore, the photocurable adhesive exhibits an appropriate deformation behavior (viscoelastic behavior) and can flow well into each corner of the shaped processed portion. As a result, gaps are less likely to form in the deformed portion, and the delay bubble can be suppressed. The gel fraction of the photo-curable adhesive after curing is preferably 50% to 95%, more preferably 55% to 93%, and still more preferably 60% to 90%. When the gel fraction of the photo-curable adhesive after curing falls within such a range, the cover glass, the 1 st polarizing plate and the image display unit can be firmly fixed. As a result, the delay bubble can be suppressed. Gel fraction can be determined as insoluble in a solvent such as ethyl acetate. Specifically, the gel fraction was determined as the weight fraction (unit: wt%) of the insoluble component of the adhesive constituting the adhesive layer after immersing the adhesive layer in ethyl acetate at 23℃for 7 days, relative to the sample before immersing. The gel fraction can be adjusted by appropriately setting the kind, combination and amount of the monomer components of the base polymer constituting the adhesive, the kind and amount of the crosslinking agent, and the like.
E-2-2 constituent Material of Photocurable adhesive
As the photocurable adhesive, any appropriate photocurable adhesive (hereinafter, may be referred to simply as an adhesive composition) may be used as long as it has the above-described characteristics. Examples of the base polymer of the adhesive composition include rubber-based polymers such as (meth) acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate/vinyl chloride polymers, modified polyolefins, epoxy-based polymers, fluorine-based polymers, natural rubber, and synthetic rubber. Preferred are (meth) acrylic adhesive compositions comprising a (meth) acrylic polymer as a base polymer. This is because the optical transparency is excellent, and the adhesive properties such as wettability, cohesiveness and adhesiveness are suitably exhibited, and the weather resistance and heat resistance are also excellent. In the present specification, the term "(meth) acrylic acid" refers to acrylic acid and/or methacrylic acid.
The (meth) acrylic base polymer (hereinafter, may be simply referred to as base polymer) preferably has a crosslinked structure.
E-2-2-1 (meth) acrylic base polymer
The (meth) acrylic base polymer contains an alkyl (meth) acrylate as a main monomer component. As the alkyl (meth) acrylate, an alkyl (meth) acrylate having an alkyl group with 1 to 20 carbon atoms is suitably used. The alkyl group of the alkyl (meth) acrylate may have a branched or cyclic alkyl group. The amount of the alkyl (meth) acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 60% by weight or more, based on the total amount of monomer components constituting the (meth) acrylic base polymer. In terms of setting the glass transition temperature (Tg) of the polymer chain to an appropriate range, the amount of the alkyl (meth) acrylate having a chain alkyl group having 4 to 10 carbon atoms is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 45% by weight or more, relative to the total amount of monomer components constituting the (meth) acrylic base polymer.
The (meth) acrylic base polymer preferably contains a monomer component having a crosslinkable functional group. With this configuration, the gel fraction of the adhesive can be adjusted to a desired range. Examples of the monomer component having a crosslinkable functional group include a hydroxyl group-containing monomer and a carboxyl group-containing monomer. When the crosslinking structure is introduced by the isocyanate crosslinking agent, the hydroxyl group becomes a reaction point for reaction with the isocyanate group, and when the crosslinking structure is introduced by the epoxy crosslinking agent, the carboxyl group becomes a reaction point for reaction with the epoxy group. It is preferable to use a hydroxyl group-containing monomer as a monomer component having a crosslinkable functional group, so that a crosslinked structure can be introduced by an isocyanate-based crosslinking agent. With such a constitution, the crosslinking property of the base polymer can be improved, and the 2 nd adhesive layer having high transparency can be obtained. Further, with such a constitution, a so-called acid-free adhesive can be realized.
The amount of the hydroxyl group-containing monomer is preferably 5 to 30% by weight, more preferably 8 to 25% by weight, and still more preferably 10 to 20% by weight, relative to the total amount of the monomer components constituting the (meth) acrylic base polymer. When the amount of the hydroxyl group-containing monomer is within such a range, the crosslinking degree (gel fraction) can be improved with a smaller amount of the crosslinking agent, and as a result, the filling property and the workability of the deformed portion of the photocurable adhesive before curing can be improved. Furthermore, since unreacted hydroxyl groups after crosslinking can form intermolecular hydrogen bonds, a desired storage modulus can be achieved even if the gel fraction is small.
In the case where the 2 nd adhesive layer may be in contact with the touch panel sensor, for example, the content of the acid in the 2 nd adhesive layer is preferably small in order to prevent corrosion of the electrode by the acid component. In this case, the amount of the carboxyl group-containing monomer is preferably 0.5% by weight or less, more preferably 0.1% by weight or less, still more preferably 0.05% by weight or less, and most preferably 0 (zero), based on the total amount of the monomer components constituting the (meth) acrylic base polymer. With such a configuration, the acid content in the photocurable adhesive is preferably 100ppm or less, more preferably 70ppm or less, and still more preferably 50ppm or less.
The (meth) acrylic base polymer may also contain a nitrogen-containing monomer as a monomer component. By properly containing a hydroxyl group-containing monomer, a carboxyl group-containing monomer, a nitrogen-containing monomer, and other highly polar monomers as monomer components, the (meth) acrylic base polymer can form a 2 nd adhesive layer excellent in the balance of storage modulus, adhesion retention and impact resistance. The amount of the high-polarity monomer (the total of the hydroxyl group-containing monomer, the carboxyl group-containing monomer, and the nitrogen-containing monomer) is preferably 10 to 45% by weight, more preferably 15 to 40% by weight, and still more preferably 18 to 35% by weight, relative to the total amount of the monomer components constituting the (meth) acrylic base polymer. It is particularly preferable that the total of the hydroxyl group-containing monomer and the nitrogen-containing monomer falls within the above range. The amount of the nitrogen-containing monomer is preferably 3 to 25% by weight, more preferably 5 to 20% by weight, and still more preferably 7 to 15% by weight, relative to the total amount of the monomer components constituting the (meth) acrylic base polymer.
The (meth) acrylic polymer may further contain any suitable monomer component according to the purpose. Specific examples of such monomer components include: vinyl monomers such as acid anhydride group-containing monomers, (meth) acrylic acid caprolactone adducts, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, vinyl acetate, vinyl propionate, styrene, and α -methylstyrene; cyano group-containing acrylic monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing monomers such as glycidyl (meth) acrylate; glycol acrylate monomers such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate; acrylic monomers such as tetrahydrofurfuryl (meth) acrylate, fluoro (meth) acrylate, silicone (meth) acrylate, and 2-methoxyethyl (meth) acrylate.
The (meth) acrylic base polymer preferably contains, as a monomer component, the most alkyl (meth) acrylate, more preferably the most alkyl (meth) acrylate having a chain alkyl group of 6 or less carbon atoms. With this configuration, the peak top value of tan δ becomes large, and impact resistance can be improved. The amount of the alkyl (meth) acrylate having a chain alkyl group having 6 or less carbon atoms is preferably 30 to 80% by weight, more preferably 35 to 75% by weight, still more preferably 40 to 70% by weight, based on the total amount of monomer components constituting the (meth) acrylic base polymer. It is particularly preferable that the content of butyl acrylate as the monomer component is within the above range.
The glass transition temperature (Tg) of the (meth) acrylic base polymer is preferably-50℃or higher. On the other hand, the Tg of the (meth) acrylic base polymer is preferably-5℃or lower, more preferably-10℃or lower, and still more preferably-15℃or lower.
E-2-2-2. Cross-Linked Structure
The polymer having a crosslinked structure introduced into the (meth) acrylic base polymer can be obtained, for example, by the following method: (1) A method in which a (meth) acrylic polymer having a functional group reactive with a crosslinking agent is polymerized, and then the crosslinking agent is added to react the (meth) acrylic polymer with the crosslinking agent; and (2) a method of introducing a branched structure (crosslinked structure) into a polymer chain by incorporating a polyfunctional compound into a polymerization component of a polymer. They may be used in combination.
As concrete examples of the crosslinking agent in the method of reacting the base polymer with the crosslinking agent of the above (1), isocyanate-based crosslinking agents, epoxy-based crosslinking agents,
An oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a carbodiimide-based crosslinking agent, a metal chelate-based crosslinking agent, and the like. Among them, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferable in that they have high reactivity with hydroxyl groups or carboxyl groups of the base polymer and are easy to introduce into the crosslinked structure. These crosslinking agents react with functional groups such as hydroxyl groups or carboxyl groups introduced into the base polymer to form a crosslinked structure. As described above, in the case of using an acid-free adhesive in which the base polymer does not contain a carboxyl group, it is preferable to introduce a crosslinked structure by the hydroxyl group in the base polymer and the isocyanate-based crosslinking agent.
The crosslinking agent may be used in a ratio of preferably 0.03 to 0.5 parts by weight, more preferably 0.05 to 0.3 parts by weight, still more preferably 0.06 to 0.25 parts by weight, particularly preferably 0.07 to 0.2 parts by weight, based on 100 parts by weight of the base polymer. By setting the amount of the crosslinking agent to such a range, the gel fraction can be brought within the desired range.
E-2-2-3. Polyfunctional Compounds
In the method of containing a polyfunctional compound in the polymerization component of the base polymer of (2), the monomer component constituting the (meth) acrylic base polymer may be reacted with the entire amount of the polyfunctional compound for introducing a crosslinked structure at one time, or the polymerization may be carried out in multiple stages. As a method for conducting the polymerization in multiple stages, the following method is preferable: a monofunctional monomer constituting a (meth) acrylic base polymer is polymerized (prepolymerized) to prepare a partial polymer (prepolymer composition), and a polyfunctional compound such as a polyfunctional (meth) acrylate is added to the prepolymer composition to polymerize (main-polymerize) the prepolymer composition with the polyfunctional monomer. The prepolymer composition is a partial polymer comprising a polymer of low degree of polymerization and unreacted monomer.
By performing the prepolymerization of the constituent components of the (meth) acrylic base polymer, the branch points (crosslinking points) of the polyfunctional compound can be uniformly introduced into the (meth) acrylic base polymer. Alternatively, a mixture of a low molecular weight polymer or a part of the polymer and an unpolymerized monomer component (adhesive composition) may be applied to a substrate and then subjected to main polymerization on the substrate to form an adhesive layer. Since the low-polymer composition such as the prepolymer composition is low in viscosity and excellent in coatability, the adhesive layer can be produced with improved productivity and uniform thickness by the method of applying the adhesive composition, which is a mixture of the prepolymer composition and the polyfunctional compound, to the substrate and then subjecting the substrate to main polymerization.
The polyfunctional compound for introducing a crosslinked structure may be a compound having 2 or more polymerizable functional groups having an unsaturated double bond (ethylenically unsaturated groups) in 1 molecule. The polyfunctional compound is typically a photopolymerizable polyfunctional compound. The polyfunctional compound is preferably a polyfunctional (meth) acrylate in view of easy copolymerization with the monomer component of the (meth) acrylic polymer. In the case of introducing a branched (crosslinked) structure by active energy ray polymerization (photopolymerization), a polyfunctional (meth) acrylate is preferable.
The molecular weight of the polyfunctional compound is preferably 1500 or less, more preferably 1000 or less. The lower limit of the molecular weight may be, for example, 500. The functional group equivalent (g/eq) of the polyfunctional compound is preferably 50 to 500, more preferably 70 to 300, still more preferably 80 to 200. With this configuration, the viscoelasticity of the photocurable adhesive can be appropriately adjusted.
The polyfunctional compound may be used in a ratio of preferably 1 to 6 parts by weight, more preferably 2 to 5 parts by weight, still more preferably 2.5 to 4 parts by weight, based on 100 parts by weight of the base polymer. If the amount is too small, the adhesion retention of the photocurable adhesive (the 2 nd adhesive layer as a result) may be insufficient. If the amount is too large, the 2 nd adhesive layer formed may be too hard and may have insufficient impact resistance. Further, the photocurable adhesive may have insufficient workability and/or dimensional stability.
In one embodiment, the polyfunctional compound may be a compound having 3 or more photopolymerizable functional groups in 1 molecule, and more preferably may be a (meth) acrylate having 3 or more photopolymerizable functional groups in 1 molecule. By using a photopolymerizable compound having 3 or more functions, the adhesive retention of the photocurable adhesive (resulting in the 2 nd adhesive layer) can be further improved. The 2-functional photopolymerizable compound may be used in combination with the 3-functional or more photopolymerizable compound. The photopolymerizable compound having 3 or more functions may be used in a ratio of preferably 0.5 to 5 parts by weight, more preferably 1 to 4.5 parts by weight, still more preferably 2 to 4 parts by weight, based on 100 parts by weight of the base polymer.
E-2-2-4 adhesive composition
The adhesive composition (photocurable adhesive) may contain, in addition to the base polymer, the crosslinking agent and the polyfunctional compound, a photopolymerization initiator, an oligomer and a silane coupling agent, and may contain any appropriate additive according to the purpose.
Examples of the photopolymerization initiator include: benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, alpha-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzil photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, 9-oxysulfide photopolymerization initiator 
Photopolymerization initiator and acylphosphine oxide photopolymerization initiator. Light sourceThe polymerization initiator may be used alone or in combination of 2 or more. The content of the photopolymerization initiator in the adhesive composition is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the base polymer.
As the oligomer, any suitable oligomer may be used. By using an oligomer, the viscoelasticity (thus, filling property and workability of the deformed portion) and adhesion of the photocurable adhesive can be adjusted. The oligomer is preferably a (meth) acrylic oligomer. The (meth) acrylic oligomer may have excellent compatibility with the base polymer.
The weight average molecular weight of the oligomer is preferably about 1000 to 30000, more preferably 1500 to 10000, and still more preferably 2000 to 8000. When the weight average molecular weight of the oligomer is within such a range, excellent adhesion and adhesion retention can be achieved.
The Tg of the oligomer is preferably 20℃or higher, more preferably 50℃or higher, still more preferably 80℃or higher, particularly preferably 100℃or higher. On the other hand, the Tg of the oligomer is preferably 200℃or lower, more preferably 180℃or lower, and still more preferably 160℃or lower. If the Tg of the oligomer is within such a range, a 2 nd adhesive layer having excellent adhesion can be formed.
The content of the oligomer in the adhesive composition is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the base polymer. When the content of the oligomer is within such a range, the workability and the dimensional stability of the photocurable adhesive can be well maintained, and a 2 nd adhesive layer having excellent adhesion can be formed.
As the silane coupling agent, any suitable silane coupling agent can be used. By using a silane coupling agent, the adhesion of the photocurable adhesive can be adjusted. The content of the silane coupling agent in the adhesive composition is preferably 0.01 to 5 parts by weight, more preferably 0.03 to 2 parts by weight, based on 100 parts by weight of the base polymer.
As the additive, any appropriate additive may be used according to purposes.
In one embodiment, the adhesive composition (photo-curable adhesive) may be provided as an adhesive sheet having a thickness corresponding to the thickness of the 2 nd adhesive layer and having release films temporarily adhered to both sides.
More detailed matters of the adhesive composition (photo-curable adhesive) are described in Japanese patent application No. 2018-218422 filed by the applicant of the present invention. The disclosure of this application is incorporated by reference into the present specification.
E-3 non-hardening adhesive
Any suitable non-curable adhesive may be used as long as it has the above-described properties. By appropriately adjusting the kind, combination, amount, etc. of the monomer components, and the kind, amount, combination, amount, etc. of the crosslinking agent, the silane coupling agent, and the additive, etc., a non-curable adhesive having the desired storage modulus (as a result, the 2 nd adhesive layer) can be obtained. Examples of the non-curable adhesive include: the adhesive described in the above item C is the adhesive described in the 1 st and 2 nd adhesive layers, the adhesive described in japanese patent application laid-open No. 2019-196942 filed by the present applicant, and the adhesive described in japanese patent application laid-open No. 2016-94569. The descriptions of the application and publication are incorporated by reference into the present specification.
E-4 Assembly of optical Components
As described above, the adhesive (adhesive composition) constituting the 2 nd adhesive layer may be provided as an adhesive sheet. In the production of the image display device, the adhesive sheet may be provided as an assembly of optical members together with the polarizing plate according to the embodiment of the present invention. Therefore, the assembly of such optical components is also included in embodiments of the present invention. In one embodiment, the assembly of the optical member may further include another polarizing plate (back-side polarizing plate). That is, in the production of the image display device, the adhesive sheet, the polarizing plate (viewing side polarizing plate) and the 2 nd polarizing plate (back side polarizing plate) of the embodiment of the present invention may be provided as an assembly of optical members.
Examples (example)
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Evaluation items in the examples are as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.
(1) Size of adhesive void
The state of the cross section of the adhesive layer in the through holes of the polarizing plates used in examples and comparative examples was observed by an optical microscope, and the length of the portion where the defect of the adhesive layer from the outer edge to the inner side in the plane direction was maximized was measured and set as the size L (μm) of the adhesive void portion.
(2) Paste offset
The polarizing plates used in examples and comparative examples were bonded to glass, and subjected to autoclave treatment (50 ℃ C./0.5 MPa/15 min), followed by heating test (85 ℃ C., 120 h). The through-hole of the sample after the test was observed with an optical microscope, and the deformed portion of the through-hole, which was located at the end of the polarizing plate, was measured as the displacement amount of the through-hole. The deformed portion was measured using an optical microscope (MX 61L) manufactured by OLYMPUS corporation. Further, 3 test samples were measured, and the maximum value among the 3 measured values was used as the offset.
(3) Bubble assessment
The image display device counterparts obtained in examples and comparative examples were vacuum laminated, then autoclave-treated (50 ℃ C./0.5 MPa/15 min), and UV (Ultraviolet) cured (illuminance 150 mW/cm) 2 An irradiation amount of 3000 mJ). Then, the sample was subjected to a heating test (85 ℃ C., 24 hours), and the state of the bubbles was observed by visual observation or an optical microscope at the time of taking out. The measurement was performed under the condition of n=6, and evaluated according to the following criteria.
4: no bubbles were seen in all samples
3: less than half of the samples were seen as small bubbles, but there were no problems in use
2: half or more of the samples were slightly bubble-visible, but there was no problem in use
1: all samples had bubbles
Production example 1: production of adhesive layer (1)
A four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler was charged with a monomer mixture containing 99 parts of Butyl Acrylate (BA) and 1 part of 4-hydroxybutyl acrylate. Further, 0.1 part by weight of 2,2' -azobisisobutyronitrile and 100 parts by weight of ethyl acetate as polymerization initiators were added to 100 parts by weight of the monomer mixture (solid content), nitrogen was introduced while stirring slowly to replace the mixture with nitrogen, and then the temperature of the liquid in the flask was kept at about 55℃for polymerization for 8 hours to prepare a solution of an acrylic polymer. To 100 parts of the solid content of the obtained acrylic polymer solution, 0.3 parts of benzoyl peroxide (trade name: nyper BMT 40SV, manufactured by Japanese fat and oil (stock)) as a crosslinking agent, 0.1 parts of an isocyanate-based crosslinking agent (trade name: takenate D110N, manufactured by Mitsui chemical (stock)) and 0.2 parts of a silane coupling agent (trade name: KBM-403, manufactured by Xin Yue chemical industry (stock)) were blended to obtain an adhesive composition.
Then, the solution of the acrylic adhesive composition was applied to one surface of a silicone-based release agent-treated polyethylene terephthalate film (release film: mitsubishi chemical polyester film (strand) manufactured, MRF 38) so that the thickness of the dried adhesive layer became 20 μm, and dried at 155℃for 1 minute, thereby forming an adhesive layer (1) on the surface of the release film. The creep value of the adhesive layer (1) was 120 μm/hr.
Production example 2: production of adhesive layer (2)
A four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a cooler was charged with a monomer mixture containing 94.9 parts of Butyl Acrylate (BA), 5 parts of acrylic acid, and 0.1 part of 4-hydroxybutyl acrylate. Further, 0.1 part by weight of 2,2' -azobisisobutyronitrile and 100 parts by weight of ethyl acetate as polymerization initiators were added to 100 parts by weight of the monomer mixture (solid content), nitrogen was introduced while stirring slowly to replace the mixture with nitrogen, and then the temperature of the liquid in the flask was kept at about 55℃for polymerization for 8 hours to prepare a solution of an acrylic polymer. To 100 parts of the solid content of the obtained acrylic polymer solution, 0.1 part of benzoyl peroxide (trade name: nyper BMT 40SV, manufactured by Japanese fat and oil (stock)) as a crosslinking agent, 8 parts of an isocyanate-based crosslinking agent (trade name: coronate L, manufactured by Tosoh (stock)) and 0.2 part of a silane coupling agent (trade name: KBM-403, manufactured by Xinyue chemical industry (stock)) were blended to obtain an adhesive composition.
Then, the solution of the acrylic adhesive composition was applied to one surface of a silicone-based release agent-treated polyethylene terephthalate film (release film: mitsubishi chemical polyester film (strand) manufactured, MRF 38) so that the thickness of the dried adhesive layer became 20 μm, and dried at 155℃for 1 minute, thereby forming an adhesive layer (2) on the surface of the release film. The creep value of the adhesive layer (2) was 35 μm/hr.
Production example 3: preparation of Photocurable adhesive constituting the 2 nd adhesive layer
A monomer mixture containing 65 parts of Butyl Acrylate (BA), 5 parts of cyclohexyl acrylate (CHA), 10 parts of N-vinyl-2-pyrrolidone (NVP), 15 parts of 4-hydroxybutyl acrylate (4 HBA) and 5 parts of isostearyl acrylate (ISTA) was added. Further, 0.2 part of 2,2' -azobisisobutyronitrile as a polymerization initiator, 0.065 part of α -Thioglycerol (TGR) as a chain transfer agent, and 233 parts by weight of ethyl acetate were added to 100 parts of the monomer mixture (solid content), and the mixture was stirred under a nitrogen atmosphere at 23 ℃ for 1 hour to perform nitrogen substitution. Then, the reaction was carried out at 56℃for 5 hours, followed by 70℃for 3 hours to prepare a solution of the acrylic base polymer. To the obtained acrylic base polymer solution, the following post-addition components were added to 100 parts of the base polymer and uniformly mixed to prepare a photocurable adhesive b. The storage modulus of the photo-curable adhesive b at 60℃before curing was 4.7X10 4 Pa, storage modulus at 60℃after hardening of 1.0X10 5 Pa. The gel fraction before curing was 40%, and the gel fraction after curing was 80%.
(post-addition component)
Dipentaerythritol hexaacrylate as a polyfunctional compound (photo hardener): 2 parts of
Polypropylene glycol diacrylate (trade name: APG400, manufactured by new middle village chemical industry company, polypropylene glycol #400 (n=7) diacrylate, functional group equivalent 268 g/eq) as a polyfunctional compound (photo hardener): 3 parts of
Photopolymerization initiator (trade name: irgacure184", manufactured by BASF corporation): 0.2 part
(production of adhesive sheet)
The photocurable adhesive b was applied to a polyethylene terephthalate (PET) film (diafil MRF75 "manufactured by mitsubishi chemical company) having a thickness of 75 μm and a silicone release layer provided on the surface, and after heating at 100 ℃ for 3 minutes to remove the solvent, the same release PET film was attached to the surface. The laminate obtained in this manner was aged at 25℃for 3 days to obtain an adhesive sheet I having release films temporarily adhered to both sides.
Production example 4: manufacturing of polarizing plate
Polyvinyl alcohol films having a thickness of 30 μm were dyed in an iodine solution of 0.3% concentration between rolls having different speed ratios at 30℃for 1 minute while being stretched to 3 times. Then, the resulting mixture was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60℃for 0.5 minutes and then stretched until the total stretching ratio became 6 times. Then, the resultant was immersed in an aqueous solution containing 1.5% potassium iodide at 30℃for 10 seconds, and then dried at 50℃for 4 minutes, whereby a polarizing plate having a thickness of 12 μm was obtained. Triacetyl cellulose (TAC) film with a hard coat layer (hard coat layer thickness of 2 μm, TAC thickness of 25 μm) as an outer protective layer was attached to both sides of the polarizing plate, respectively. The liquid crystal alignment cured layer H and the liquid crystal alignment cured layer Q are sequentially transferred to the inner protective layer side of the polarizing plate. Thus, a polarizing plate (1) was produced. Further, the liquid crystal alignment cured layer H and the liquid crystal alignment cured layer Q were fabricated as follows.
A liquid crystal composition (coating liquid) was prepared by dissolving 10g of a polymerizable liquid crystal (product name: paliocolorce LC242, manufactured by BASF corporation, represented by the following formula) exhibiting a nematic liquid crystal phase and 3g of a photopolymerization initiator (product name: irgacure 907, manufactured by BASF corporation) relative to the polymerizable liquid crystal compound in 40g of toluene.
[ chemical 1]
The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed with a rubbing cloth to carry out alignment treatment. The alignment direction was set to be 15 ° with respect to the direction of the absorption axis of the polarizing plate when the polarizing plate was attached to the polarizing plate. The liquid crystal coating liquid was coated on the alignment treatment surface by a bar coater, and dried by heating at 90 ℃ for 2 minutes, thereby aligning the liquid crystal compound. The liquid crystal layer formed in this manner was irradiated with 1mJ/cm using a metal halide lamp 2 The liquid crystal layer is cured, thereby forming a liquid crystal alignment cured layer H on the PET film. The thickness of the liquid crystal alignment cured layer H was 2.5 μm, and the in-plane retardation Re (550) was 270nm. Further, the liquid crystal alignment cured layer H has a refractive index distribution of nx > ny=nz. A liquid crystal alignment cured layer Q was formed on the PET film in the same manner as described above except that the coating thickness was changed and the alignment treatment direction was set to be 75 ° with respect to the direction of the absorption axis of the polarizing plate as viewed from the visual side. The thickness of the liquid crystal alignment cured layer Q was 1.5 μm, and the in-plane retardation Re (550) was 140nm. Further, the liquid crystal alignment cured layer Q has a refractive index distribution of nx > ny=nz.
Production example 5: manufacturing of polarizing plate
Polyvinyl alcohol films having a thickness of 30 μm were dyed in an iodine solution of 0.3% concentration between rolls having different speed ratios at 30℃for 1 minute while being stretched to 3 times. Then, the resulting mixture was immersed in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60℃for 0.5 minutes and then stretched until the total stretching ratio became 6 times. Then, the resultant was immersed in an aqueous solution containing 1.5% potassium iodide at 30℃for 10 seconds, and then dried at 50℃for 4 minutes, whereby a polarizing plate having a thickness of 12 μm was obtained. A triacetyl cellulose (TAC) film with a hard coat layer (the thickness of the hard coat layer is 2 μm, the thickness of the TAC is 25 μm) as an outer protective layer and an acrylic resin film (the thickness of the acrylic resin film is 20 μm) as an inner protective layer are respectively attached to both sides of the polarizing plate, thereby producing a polarizing plate (2).
Production example 6: manufacturing of polarizing plate
1. Manufacture of polarizer
As the thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption of 0.75% and a Tg of about 75℃was used. Corona treatment is performed on one side of the resin base material.
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (trade name "GOHSEFIMER Z410" manufactured by Nippon chemical industry Co., ltd.) were mixed in a ratio of 9:1 to 100 parts by weight of the PVA-based resin mixed in the above step, 13 parts by weight of potassium iodide was added, and the mixture was dissolved in water to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona treated surface of the resin substrate, and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The resulting laminate was subjected to free-end uniaxial stretching treatment in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds until it was stretched to 2.4 times in an oven at 130 ℃.
Subsequently, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insolubilization treatment).
Then, the polarizing film was immersed in a dyeing bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30℃for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the finally obtained polarizing film became a specific value (dyeing treatment).
Then, the resultant was immersed in a crosslinking bath (aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40℃for 30 seconds (crosslinking treatment).
Then, while immersing the laminate in an aqueous boric acid solution (boric acid concentration: 4.0 wt%, potassium iodide: 5.0 wt%) having a liquid temperature of 70 ℃, uniaxial stretching (in-water stretching treatment) was performed between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times in the longitudinal direction (longitudinal direction).
Then, the laminate was immersed in a washing bath (an aqueous solution obtained by mixing 100 parts by weight of water with 4 parts by weight of potassium iodide) at a liquid temperature of 20 ℃ (washing treatment).
Then, drying was performed in an oven maintained at a temperature of 90 ℃ while being brought into contact with a heated roller made of SUS (Steel Use Stainless, japanese stainless steel standard) maintained at a surface temperature of 75 ℃ for about 2 seconds (drying shrinkage treatment). The shrinkage in the width direction of the laminate after the drying shrinkage treatment was 5.2%.
Thus, a polarizing plate having a thickness of 5 μm was formed on the resin substrate.
2. Manufacture of polarizing plate
The HC-TAC film was bonded to the polarizer surface of the obtained laminate of resin substrate/polarizer via an ultraviolet curing adhesive. Specifically, the cured adhesive was applied so that the thickness of the adhesive became 1.0 μm, and the cured adhesive was bonded by a roller press. Then, UV light was irradiated from the HC-TAC film side to harden the adhesive. Further, HC-TAC films are formed by forming a Hard Coat (HC) layer (thickness 7 μm) on a triacetyl cellulose (TAC) film (thickness 25 μm) and are bonded so that the TAC film is located on the polarizer side. Then, the resin substrate was peeled off, and a TAC film (thickness 20 μm) was attached to the peeled surface in the same manner as described above. Thus, a polarizing plate (3) was produced.
Example 1 >
1. Formation of through-holes
The adhesive layer (1) obtained in production example 1 was formed on the surface of the liquid crystal alignment cured layer Q of the polarizing plate (1) obtained in production example 4 as a polarizing plate with an adhesive layer. The polarizing plate with the adhesive layer was punched out to have a length of 145mm and a width of 68 mm. At this time, punching was performed such that the absorption axis direction of the polarizing plate was 135 ° clockwise with respect to the longitudinal direction. Further, the upper right corner of the punched polarizing plate with the adhesive layer is passed through the endMilling cutter processing forms the through hole with the diameter of 3.9 mm. Thus, a polarizing plate (polarizing plate with an adhesive layer) as shown in fig. 1A was produced. B of the obtained polarizing plate 1 －b 2 The I is 0mm. The size L of the adhesive void was 90. Mu.m. The polarizing plate was subjected to the evaluation of (2). The results are shown in Table 1.
2. Manufacture of image display device correspondence
The polarizing plate with an adhesive layer obtained in the above 1 was bonded to one surface of a glass plate (corresponding to an image display unit) via an adhesive layer. Then, a release film of the adhesive sheet I obtained in production example 3 was peeled off and bonded to cover glass (manufactured by Song Nitro Corp., thickness: 0.8 mm) by a roll laminator. Then, the other release film of the adhesive sheet I was peeled off, and the release film was brought into close contact with the surface of the polarizing plate having the adhesive layer using a vacuum laminator, and the through-hole was filled with the adhesive sheet. The conditions of vacuum lamination are as follows: the heating and press-bonding were performed at 0.2MPa and 60 ℃ (standby time 90 seconds), followed by vacuum lamination at 100Pa for 10 seconds. Further, a metal halide lamp (300 mW/cm 2 ) The cumulative light quantity of irradiation is 3000mJ/cm 2 The photo-curable adhesive is cured by ultraviolet rays of (a). Then, autoclave treatment (50 ℃ C./0.5 MPa/15 min) was performed. Thus, an image display device counterpart was fabricated. The obtained image display device counterpart is supplied to the bubble evaluation of (3). The results are shown in Table 1.
Example 2 >
A polarizing plate (adhesive layer-attached polarizing plate) and an image display device corresponding product were produced in the same manner as in example 1, except that the through-holes were formed at the ends in the longitudinal direction and at the center in the short direction. B of the obtained polarizing plate 1 －b 2 The I is 41mm. The size L of the adhesive void was 90. Mu.m. The obtained polarizing plate and the image display device counterpart were respectively subjected to the same evaluations as in example 1. The results are shown in Table 1. In table 1, the end portions in the longitudinal direction and the central portion in the short direction are simply referred to as "center".
Examples 3 to 7 and comparative examples 1 to 4 >, respectively
A polarizing plate (polarizing plate with an adhesive layer) and an image display device counterpart were produced in the same manner as in example 1, except that the types and sizes of the polarizing plates, the types of adhesive layers, and the formation positions of the through holes were as shown in table 1. The size L of the adhesive void is adjusted by changing the feed speed or rotation speed of the drill during the machining of the end mill for forming the through hole. Here, examples 4 and 6 correspond to the configuration shown in fig. 1A, example 7 corresponds to the configuration shown in fig. 1B, and examples 3 and 5 correspond to the configuration shown in fig. 1C. The obtained polarizing plate and the image display device counterpart were respectively subjected to the same evaluations as in example 1. The results are shown in Table 1.
TABLE 1
As is clear from table 1, the paste offset in the through hole portion after the heating test of the polarizing plate of the example of the present invention was significantly smaller than that of the comparative example, and the retardation bubble was suppressed.
[ Industrial applicability ]
The polarizing plate of the present invention is suitably used for an image display device, and particularly, can be suitably used for an image display device having a camera section typified by a smart phone, a tablet PC, or a smart watch.
Description of the reference numerals
11 polarizing plate
12 outer protective layer
13 inner protective layer
20 adhesive layer
30 through hole
100 polarizing plate
Claims (8)
1. A polarizing plate is provided with: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; and is also provided with
A through-hole is formed in the hollow body,
the thickness of the polarizer is 15 μm or less,
|b 1 －b 2 the I is less than 45mm,
here, b 1 B is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing plate 2 Is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing plate.
2. The polarizing plate according to claim 1, which has a rectangular shape, wherein an absorption axis direction of the polarizing plate is a direction of 135 ° from a long side direction in a clockwise direction when viewed from a viewing side, and the through hole is formed in an upper right corner.
3. The polarizing plate according to claim 1, which has a rectangular shape, wherein an absorption axis direction of the polarizing plate is 45 ° from a long side direction in a clockwise direction when viewed from a viewing side, and the through hole is formed in an upper left corner.
4. The polarizing plate according to claim 1, wherein the polarizing plate has a rectangular shape, the absorption axis direction of the polarizing plate is a short side direction, and the through hole is formed at an end portion in the long side direction and at a center portion in the short side direction in a plan view.
5. The polarizing plate according to any one of claims 1 to 4, wherein the thickness of the polarizing plate is 8 μm or less.
6. The polarizing plate according to any one of claims 1 to 5, wherein the adhesive layer has a creep value of 140 μm/hr or less.
7. An image display device, comprising: an image display unit and the polarizing plate according to any one of claims 1 to 6; and is also provided with
The polarizing plate is bonded to the image display unit via the adhesive layer.
8. A polarizing plate with cover glass, comprising: a polarizing plate; a protective layer disposed on at least one side of the polarizing plate; an adhesive layer; another adhesive layer provided on the opposite side of the polarizer from the adhesive layer; and a cover glass bonded via the other adhesive layer; and is also provided with
A through hole is formed, the through hole is filled with an adhesive constituting the other adhesive layer,
the thickness of the polarizer is 15 μm or less,
|b 1 －b 2 the I is less than 45mm,
here, b 1 B is the distance from the center of the through hole to one end of the polarizing plate in the absorption axis direction of the polarizing plate 2 Is the distance from the center of the through hole to the other end of the polarizing plate in the absorption axis direction of the polarizing plate.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2020160528A JP2022053732A (en) | 2020-09-25 | 2020-09-25 | Polarizing plate and picture display unit |
| JP2020-160528 | 2020-09-25 | ||
| PCT/JP2021/034279 WO2022065224A1 (en) | 2020-09-25 | 2021-09-17 | Polarizing plate, cover glass-equipped polarizing plate, and image display device |
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| CN116235101A true CN116235101A (en) | 2023-06-06 |
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| CN202180065707.9A Pending CN116235101A (en) | 2020-09-25 | 2021-09-17 | Polarizing plate, polarizing plate with cover glass, and image display device |
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| Country | Link |
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| JP (1) | JP2022053732A (en) |
| KR (1) | KR20230071141A (en) |
| CN (1) | CN116235101A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP6538332B2 (en) | 2014-11-17 | 2019-07-03 | 日東電工株式会社 | Optical double-sided adhesive sheet |
| WO2017047510A1 (en) | 2015-09-16 | 2017-03-23 | シャープ株式会社 | Method for producing differently shaped polarizing plate |
| JP6684630B2 (en) * | 2016-03-31 | 2020-04-22 | 住友化学株式会社 | Polarizing plate and method of manufacturing polarizing plate |
| JP2018025630A (en) * | 2016-08-09 | 2018-02-15 | 日東電工株式会社 | Polarizing plate |
| CN106843389B (en) * | 2017-01-09 | 2022-08-05 | Oppo广东移动通信有限公司 | Electronic device |
| CN109407198B (en) * | 2018-12-19 | 2020-09-01 | 武汉华星光电技术有限公司 | Polaroid and display panel |
| CN111510520B (en) * | 2019-01-31 | 2021-06-29 | 北京小米移动软件有限公司 | Display panel, manufacturing method thereof and display device |
| WO2020188872A1 (en) * | 2019-03-20 | 2020-09-24 | 日東電工株式会社 | Adhesive-layer-containing polarizing film, image display panel, and image display device |
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2021
- 2021-09-17 WO PCT/JP2021/034279 patent/WO2022065224A1/en active Application Filing
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| WO2022065224A1 (en) | 2022-03-31 |
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