JP7191542B2 - OPTICAL LAMINATED BODY WITH COVER GLASS AND IMAGE DISPLAY DEVICE WITH COVER GLASS - Google Patents

Description

The present invention relates to an optical layered body, an optical layered body with a cover glass, production methods thereof, and an image display device with a cover glass including the optical layered body or the optical layered body with the cover glass.

Various optical laminates (e.g., polarizing plates) are used in image display devices such as mobile phones and notebook personal computers to realize image display and/or improve the performance of the image display. . After the optical layered body is cut into a predetermined shape, the cut surface may be subjected to finishing by cutting. Furthermore, in recent years, there are cases where it is desired to process the optical layered body into a shape other than a rectangular shape (deformed shape processing). In such cutting, cutting with an end mill may be performed. However, cracks may occur in the optical layered body cut with an end mill.

Japanese Patent Application Laid-Open No. 2007-187781 JP 2018-022140 A

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide an optical layered body in which cracks are suppressed even though it is machined, and a cover including such an optical layered body. An object of the present invention is to provide an optical layered body with glass, a method for producing the same, and an image display device with a cover glass including the optical layered body or the optical layered body with a cover glass.

The optical laminate of the present invention has a cut optical film and an adhesive layer, and the ratio RR/DR between the regular reflectance RR and the diffuse reflectance DR at the cut end face is 0.15 or more.
In one embodiment, the optical film contains a polarizer.
In one embodiment, the optical film further has a protective film on the opposite side of the polarizer to the pressure-sensitive adhesive layer.
In one embodiment, the optical film further has another protective film between the polarizer and the adhesive layer.
In one embodiment, the another protective film serves also as a retardation layer.
According to another aspect of the present invention, an optical laminate with a cover glass is provided. This optical layered body with a cover glass has the above optical layered body and a cover glass laminated via another pressure-sensitive adhesive layer disposed on the side opposite to the pressure-sensitive adhesive layer of the optical layered body.
According to still another aspect of the present invention, an image display device with a cover glass is provided. This image display device with a cover glass has a display cell, the above optical layered body arranged on the viewing side of the display cell, and a cover glass arranged on the viewing side of the optical layered body. Another image display device with a cover glass of the present invention has a display cell and the above-described optical laminate with a cover glass arranged on the viewing side of the display cell.

According to the present invention, cracks (especially after a heat cycle test cracks) can be suppressed. Such an optical layered body can be suitably laminated with a cover glass, and can be suitably applied to an image display device with a cover glass.

It is a schematic sectional drawing explaining the optical laminated body by one Embodiment of this invention. 4 is a photograph of observing the state of transmitted light on a cut end face in a state in which optical laminates according to one embodiment of the present invention are laminated to a predetermined thickness. It is the photograph which observed the state of the transmitted light of the cut end surface in the state which laminated|stacked the optical laminated body which is out of the range of embodiment of this invention by predetermined thickness. FIG. 2 is a schematic plan view showing an example of the shape of the cut optical layered body of the present invention. It is a schematic perspective view for demonstrating an example of cutting of the optical laminated body of this invention. It is a schematic perspective view for explaining an example of the cutting means used for cutting in the manufacturing method of the optical laminated body of this invention. FIG. 7(a) is a schematic sectional view seen from the axial direction for explaining another example of cutting means used for cutting in the method for manufacturing an optical layered body of the present invention; 7(b) is a schematic perspective view of the cutting means of FIG. 7(a); FIG. 1 is a schematic cross-sectional view illustrating an optical laminate with a cover glass according to one embodiment of the present invention; FIG.

Specific embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The drawings are shown schematically for the sake of clarity, and the ratios of length, width, thickness, etc., and angles, etc. in the drawings are different from the actual ones.

A. Optical Laminate The optical laminate of the present invention has a cut optical film and an adhesive layer. FIG. 1 is a schematic cross-sectional view illustrating an optical laminate according to one embodiment of the invention. The optical laminate 100 of the illustrated example has an optical film 110 and an adhesive layer 120 . Practically, the separator 130 is temporarily adhered to the surface of the pressure-sensitive adhesive layer 120 in a releasable manner. The optical layered body of the present invention can be suitably laminated with a cover glass and can be suitably applied to an image display device with a cover glass.

Optical films include any suitable optical films that can be used in applications that require cutting. The optical film may be a film composed of a single layer, or may be a laminate. Specific examples of the optical film include a polarizer, a retardation film, a polarizing plate (typically, a laminate of a polarizer and a protective film), a conductive film for a touch panel, a surface treatment film, and for these purposes Appropriately laminated laminates (for example, antireflection circularly polarizing plate, polarizing plate with conductive layer for touch panel) may be mentioned. According to the embodiment of the present invention, cracks can be remarkably suppressed particularly in an optical layered body including a shrinkable optical film such as a polarizer.

For example, if the optical film 110 is a polarizing plate, the polarizing plate may have a protective film only on the side opposite the adhesive layer 120 of the polarizer, and only between the polarizer and the adhesive layer 120. You may have a film, and you may have a protective film on both. The protective film provided on the opposite side of the adhesive layer may be subjected to surface treatment such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, anti-glare treatment, etc., if necessary. The protective film provided between the polarizer and the pressure-sensitive adhesive layer is preferably optically isotropic in one embodiment. As used herein, “optically isotropic” means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is −10 nm to +10 nm. say. The protective film may also serve as a retardation layer in another embodiment. Any appropriate configuration can be adopted for the configuration of the protective film as the retardation layer depending on the purpose. For example, the protective film may be a λ/2 plate, a λ/4 plate, or a laminate thereof. A λ/2 plate and a λ/4 plate typically have a refractive index characteristic of nx>ny≧nz. The λ/2 plate preferably has an in-plane retardation Re (550) of 180 nm to 320 nm, and the λ/4 plate preferably has an in-plane retardation Re (550) of 100 nm to 200 nm. Further, for example, the protective film may be a laminate of a negative B plate (nx>ny>nz) and a positive C plate (nz>nx=ny). In this specification, "Re(λ)" is an in-plane retardation measured with light having a wavelength of λnm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film). “Rth(λ)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of λ nm. For example, “Rth(550)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film). "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and "ny" is the in-plane direction orthogonal to the slow axis (i.e., fast axis direction) and "nz" is the refractive index in the thickness direction.

The pressure-sensitive adhesive layer 120 is mainly used for bonding the finally obtained optical layered body to the display cell. According to the embodiment of the present invention, cracks (especially cracks after a heat cycle test) can be suppressed even when an optical layered body including an adhesive layer is cut. The adhesive layer 120 can typically be composed of an acrylic adhesive (acrylic adhesive composition). An acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a main component. The (meth)acrylic polymer can be contained in the PSA composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, based on the solid content of the PSA composition. A (meth)acrylic polymer contains alkyl (meth)acrylate as a main component as a monomer unit. (Meth)acrylate refers to acrylate and/or methacrylate. Alkyl groups of alkyl (meth)acrylates include, for example, linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3-9. Monomers constituting the (meth)acrylic polymer include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, etc., in addition to alkyl (meth)acrylates. The acrylic pressure-sensitive adhesive composition can preferably contain a silane coupling agent and/or a cross-linking agent. Silane coupling agents include, for example, epoxy group-containing silane coupling agents. Examples of cross-linking agents include isocyanate-based cross-linking agents and peroxide-based cross-linking agents. The thickness of the adhesive layer can be, for example, 10 μm to 50 μm. Details of the pressure-sensitive adhesive layer or the acrylic pressure-sensitive adhesive composition are described, for example, in JP-A-2016-190996, and the description of the publication is incorporated herein by reference.

In an embodiment of the present invention, the ratio RR/DR between the regular reflectance RR and the diffuse reflectance DR at the cut end face of the optical laminate is 0.15 or more, preferably 0.16 or more, more preferably It is 0.22 or more, more preferably 0.24 or more. The upper limit of the ratio RR/DR is, for example, 0.37, preferably 0.30. If the ratio RR/DR is within such a range, cracks (especially cracks after a heat cycle test) can be suppressed in the optical layered body that has been machined (for example, end milled). In particular, cracks can be suppressed when the cut optical laminate is laminated with a cover glass.

The regular reflectance RR of the cut end surface of the optical layered body is preferably 0.30% or more, more preferably 0.40% or more, and still more preferably 0.50% or more. The upper limit of the regular reflectance RR is, for example, 0.75%, preferably 0.65%. The diffuse reflectance DR of the cut end surface of the optical layered body is preferably 2.40% to 5.00%, more preferably 2.50% to 3.50%.

The regular reflectance RR and the diffuse reflectance DR are obtained, for example, as follows, and the ratio RR/DR is calculated from the obtained RR and DR. The cut optical laminates are randomly selected, and the selected optical laminates are laminated to form a bundle having a thickness of about 15 mm. More specifically, the optical laminate is randomly selected from a plurality of different works (works will be described later). With the measurement surface of the bundle made flush with each other, the bundle is restrained by wrapping rubber bands at predetermined distances (two locations) from both ends of the bundle in the direction of the measurement surface. SCI (Specular Component Include) and SCE (Specular Component Exclude) are measured using a spectrophotometer (for example, "CM-2600d" manufactured by Konica Minolta Co., Ltd.) on the measurement surface of the constrained bundle, and are calculated using the following formula. Determine reflectance RR and diffuse reflectance DR.
Regular reflectance RR=SCI-SCE
Diffuse reflectance DR = SCE

RR/DR will be described in more detail below. FIG. 2 is a photograph of observation of the state of transmitted light on a cut end face in a state in which optical laminates satisfying the above range of RR/DR are laminated with a predetermined thickness, and FIG. It is the photograph which observed the state of the transmitted light of the cut end surface in the state which laminated|stacked the optical laminated body which deviates from such a range by predetermined thickness. As is clear from a comparison of FIG. 2 and FIG. 3, the optical layered body that satisfies the above range of RR/DR has a clear outline of light (there is so-called shine), while the RR/DR is above The outline of the light is unclear (no shine) in the optical layered body outside the range. The inventors of the present invention repeated trial and error regarding the problem of cracks in an optical layered body that has been cut (typically, end milled) and found that cracks are suppressed in an optical layered body that has a shiny cut end surface. discovered. In particular, such a laminate has been found to suppress cracking when laminated with a cover glass. Thus, the present invention solves a new problem in cutting (typically, end milling) of an optical layered body, and optimizes the shine (or RR/DR) of the cut end face. The effect of is an unexpectedly excellent effect. Although FIGS. 2 and 3 show the state of transmitted light in order to clarify the difference, the shininess of reflected light also corresponds to this.

As an example, each step in the method for manufacturing a planar optical layered body as shown in FIG. 4 will be described below.

B. Formation of Work FIG. 4 is a schematic perspective view for explaining the cutting process, in which a work 1 is shown. As shown in FIG. 4, a workpiece 1 is formed by stacking a plurality of optical laminates. The optical laminate is typically cut into any suitable shape when forming a workpiece. Specifically, the optical layered body may be cut into a rectangular shape, may be cut into a shape similar to the rectangular shape, or may be cut into an appropriate shape (for example, a circle) according to the purpose. good too. In the illustrated example, the optical layered body is cut into a rectangular shape, and the workpiece 1 has outer peripheral surfaces (cutting surfaces) 1a and 1b facing each other and outer peripheral surfaces (cutting surfaces) 1c and 1d perpendicular to them. there is The workpiece 1 is preferably clamped from above and below by clamping means (not shown). The total thickness of the work is preferably 8 mm to 20 mm, more preferably 9 mm to 15 mm, still more preferably about 10 mm. With such a thickness, it is possible to prevent damage due to pressure from the clamping means or impact during cutting. The optical laminate is stacked so that the work has such a total thickness. The number of optical laminates constituting the work may be, for example, 10 to 50. The clamping means (e.g., jig) may be composed of a soft material or a hard material. When composed of a soft material, its hardness (JIS A) is preferably 60° to 80°. If the hardness is too high, there may be impressions left by the clamping means. If the hardness is too low, the deformation of the jig may cause misalignment, resulting in insufficient cutting accuracy.

C. Cutting Next, the outer peripheral surface of the workpiece 1 is cut by the cutting means 20 . Cutting is performed by bringing a cutting blade of a cutting means into contact with the outer peripheral surface of the workpiece 1 . Cutting may be performed over the entire circumference of the outer peripheral surface of the work, or may be performed only at predetermined positions. When manufacturing a planar optical layered body as shown in FIG. 4, cutting is typically performed over the entire circumference of the outer peripheral surface of the work. Cutting is typically so-called end milling, as shown in FIGS. That is, the side surface of the cutting means (end mill) 20 is used to cut the outer peripheral surface of the workpiece 1 . A straight end mill can typically be used as the cutting means (end mill) 20 .

As shown in FIGS. 6 and 7, the end mill 20 has a rotating shaft 21 extending in the stacking direction (vertical direction) of the workpieces 1 and a cutting blade 22 having the outermost diameter of a main body that rotates about the rotating shaft 21. and have The cutting edge 22 may be configured as an outermost diameter twisted along the axis of rotation 21 as shown in FIG. 21 may be configured to extend in a direction substantially parallel (the twist angle may be 0°). It should be noted that "0°" means substantially 0°, and includes the case where there is a slight angle twist due to processing error or the like. When the cutting edge has a predetermined helix angle, the helix angle is preferably 70° or less, more preferably 65° or less, and even more preferably 45° or less. The cutting blade 22 includes a cutting edge 22a, a rake face 22b, and a relief face 22c. The number of blades of the cutting blade 22 can be appropriately set as long as a desired number of contacts, which will be described later, can be obtained. Although the number of blades is three in FIG. 6 and two in FIG. 7, the number of blades may be one, four, or five or more. Preferably, the number of blades is two. With such a configuration, the rigidity of the blade is ensured, and the pocket is ensured, so that the shavings can be discharged satisfactorily.

In one embodiment, the HV hardness of the cutting blade 22 is typically 1500 or higher, preferably 1700 or higher, more preferably 2000 or higher. The upper limit of HV hardness can be 2350, for example. In this case, the cutting edge is typically made of cemented carbide. Cemented carbide is typically obtained by sintering metal carbide powder. Specific examples of cemented carbide include WC--Co alloys, WC--TiC--Co alloys, WC--TaC--Co alloys, and WC--TiC--TaC--Co alloys. HV hardness is also called Vickers hardness and can be measured according to JIS Z 2244.

In another embodiment, the HV hardness of the cutting blade 22 is typically 7000 or higher, preferably 8000 or higher, more preferably 9000 or higher, and even more preferably 10000 or higher. The upper limit of HV hardness can be 15,000, for example. In this case, the cutting blade typically contains sintered diamond. More specifically, the cutting edge has a sintered diamond layer formed on a base made of cemented carbide. Sintered diamond (PCD: Polycrystalline diamond) refers to polycrystalline diamond obtained by sintering small grains of diamond together with metal and/or ceramic powder at high temperature and high pressure.

Cutting conditions can be appropriately set according to the purpose. For example, by appropriately adjusting the feed speed, number of revolutions, number of blades, etc. of the end mill, it is possible to obtain a machined optical laminate having a predetermined RR/DR. As used herein, "feed rate" means the relative speed between the cutting means (end mill) and the work. Therefore, in cutting, only the end mill may be moved, only the work may be moved, or both the end mill and the work may be moved. The number of cuts can be one cut, two cuts, three cuts or more. In one embodiment, the diameter of end mill 20 is preferably between 3 mm and 20 mm.

As described above, a machined optical layered body having a predetermined RR/DR can be obtained. Note that the cut optical layered body (substantially the optical film and the pressure-sensitive adhesive layer) may typically have cutting marks.

D. Optical Layered Body with Cover Glass The optical layered body according to the embodiment of the present invention (for example, the optical layered body described in the above sections A to C) can be suitably laminated with a cover glass as described above. Therefore, an optical laminate with a cover glass is also included in the embodiments of the present invention. FIG. 8 is a schematic cross-sectional view illustrating an optical laminate with a cover glass according to one embodiment of the invention. The cover glass-attached optical laminate 101 of the illustrated example is laminated via a polarizer 110, an adhesive layer 120, and another adhesive layer 140 arranged on the opposite side of the polarizer 110 to the adhesive layer 120. and a cover glass 150 . A separator 130 is temporarily adhered to the surface of the pressure-sensitive adhesive layer 120 in a releasable manner. That is, the optical layered body 101 with a cover glass is the optical layered body of FIG. and have

The adhesive (adhesive composition) constituting the separate adhesive layer 140 preferably has a storage modulus of 1.0×10 ⁸ (Pa) or more at -40°C. By adopting such an adhesive layer, a synergistic effect with the effect of optimizing the RR/DR of the cut end surface of the optical layered body can be obtained even when a cover glass is attached to the cut optical layered body. Even if there is, cracks (especially cracks after a heat cycle test) can be suppressed. Examples of such adhesives (adhesive compositions) include rubber-based adhesives. A rubber-based pressure-sensitive adhesive may typically contain a butadiene polymer and/or a polyisoprene polymer (or a modified product thereof) and a photopolymerization initiator. The rubber-based adhesive may further contain polyurethane acrylate, polyisoprene-based acrylate or its esterified product, terpene-based hydrogenated resin, dicyclopentenyloxyethyl methacrylate, 2-hydroxybutyl methacrylate, and the like.

Since the cover glass 150 may employ a well-known configuration in the industry, detailed description thereof will be omitted.

The optical layered body with a cover glass is obtained by bonding a cover glass to a cut optical layered body (for example, the optical layered body described in the above sections A to C) via the separate adhesive layer 140. can be obtained.

E. Image Display Device with Cover Glass As described above, the optical layered body according to the embodiment of the present invention (for example, the optical layered body described in the above paragraphs A to C) can be suitably applied to an image display device with a cover glass. Therefore, an image display device with a cover glass is also included in the embodiments of the present invention. An image display device with a cover glass has a display cell, an optical layered body according to an embodiment of the present invention arranged on the viewing side of the display cell, and a cover glass arranged on the viewing side of the optical layered body.

The optical layered body with cover glass according to the embodiment of the present invention (for example, the optical layered body with cover glass described in section D above) can also be applied to an image display device to constitute an image display device with cover glass. In this case, the image display device with cover glass has a display cell and the optical laminate with cover glass according to the embodiment of the present invention arranged on the viewing side of the display cell.

Examples of image display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, and quantum dot display devices.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. Evaluation items in the examples are as follows.

(1) RR/DR
Polarizing plates were randomly selected from a plurality of different works obtained in Examples and Comparative Examples, and the selected polarizing plates were laminated to prepare a bundle having a thickness of about 15 mm. With the measurement surface of the bundle made flush with each other, rubber bands (manufactured by IGO Co., Ltd., #7) were wound at positions (two places) 10 mm from both ends of the bundle in the direction of the measurement surface, and the bundle was formed. restrained. SCI and SCE were measured on the measurement surface of the constrained bundle using a spectrophotometer ("CM-2600d" manufactured by Konica Minolta Co., Ltd.), and regular reflectance RR and diffuse reflectance DR were obtained from the following equations.
Regular reflectance RR=SCI-SCE
Diffuse reflectance DR = SCE
(2) Cracks Glass plates were attached to both sides of the polarizing plates obtained in Examples and Comparative Examples, and a heat cycle (heat shock) test was performed at -40°C to 85°C for 200 cycles. After the test, the state of crack generation was evaluated according to the following criteria by conducting a transmitted light inspection with the polarizing filter arranged so as to be in cross Nicols with the absorption axis of the polarizer of the polarizing plate.
Yes: Light leakage is visible No: Light leakage is not visible

<Example 1>
Surface protective film (48 μm) / hard coat layer (5 μm) / cycloolefin protective film (47 μm) / polarizer (5 μm) / cycloolefin protective film (24 μm) / adhesive layer ( 20 μm)/separator to prepare a polarizing plate with an adhesive layer. The pressure-sensitive adhesive layer was produced according to [0121] and [0124] of JP-A-2016-190996. The pressure-sensitive adhesive layer-attached polarizing plate thus obtained was punched into a shape similar to that shown in FIG. (total thickness of about 10 mm). The obtained workpiece was held between clamps (jig), and the periphery was cut by end milling to obtain a cut polarizing plate with an adhesive layer as shown in FIG. A sintered diamond was used for the cutting edge of the end mill, and the HV hardness was 10,000. The end mill had two blades and the helix angle was 0°. In addition, the feed speed of the end mill (feed speed when cutting a straight portion) is 1000 mm / min, the number of revolutions is 25000 rpm, and the number of times of cutting is 2 times (1st 0.1 mm, 2nd 0.2 mm cutting margin of 0.3 mm). The RR/DR of the obtained cut polarizing plate with an adhesive layer was 0.17.

The surface protective film of the pressure-sensitive adhesive layer-attached polarizing plate was peeled off, and another pressure-sensitive adhesive layer was formed on the peeled surface. Another pressure-sensitive adhesive layer was produced according to [0053] of JP-A-2016-103030. Furthermore, the separator temporarily attached to the adhesive layer on the side of the cycloolefin-based protective film is peeled off, and a glass plate is attached to both sides of the polarizing plate having adhesive layers on both sides thus obtained. It was used for evaluation of cracks. Table 1 shows the results.

<Example 2 and Comparative Examples 1 and 2>
A polarizing plate with a pressure-sensitive adhesive layer cut as shown in FIG. 4 was obtained in the same manner as in Example 1, except that the cutting conditions were changed as shown in Table 1. Table 1 shows the RR/DR of the obtained cut polarizing plate with an adhesive layer. Furthermore, cracks were evaluated in the same manner as in Example 1. Table 1 shows the results.

The cut optical layered body of the present invention is suitably used when a cover glass is laminated on an image display portion, and in particular, a rectangular image display portion typified by a personal computer (PC) or a tablet terminal, and/or Alternatively, it can be suitably used for an irregular-shaped image display unit typified by an automobile instrument panel and a smart watch.

Reference Signs List 1 work 20 cutting means 100 optical laminate 101 optical laminate with cover glass 110 optical film 120 adhesive layer 140 another adhesive layer 150 cover glass

Claims (6)

an optical laminate having a cut optical film and an adhesive layer, wherein the ratio RR/DR between the regular reflectance RR and the diffuse reflectance DR at the cut end face is 0.15 or more ;
and a cover glass laminated via another pressure-sensitive adhesive layer arranged on the opposite side of the pressure-sensitive adhesive layer of the optical layered body. The optical laminate with a cover glass according to claim 1, wherein the optical film contains a polarizer. The optical laminate with a cover glass according to claim 2, wherein the optical film further has a protective film on the side of the polarizer opposite to the pressure-sensitive adhesive layer. The optical laminate with a cover glass according to claim 2 or 3, wherein the optical film further has another protective film between the polarizer and the pressure-sensitive adhesive layer. 5. The optical laminate with a cover glass according to claim 4, wherein said another protective film also serves as a retardation layer. An image display device with a cover glass, comprising a display cell and the optical laminate with a cover glass according to any one of claims 1 to 5 arranged on the viewing side of the display cell.

Images