JP2021101250A - Image display with fingerprint authentication sensor - Google Patents

Abstract

To provide an image display having a polarizing plate on a visible side of a fingerprint authentication sensor, in which a fingerprint authentication system operates normally even in a case where an orientation film exists on the visible side of the polarizing plate.SOLUTION: An image display device has a polarizing plate on a visual side of a fingerprint authentication sensor, and an orientation film on the visual side of the polarizing plate, where an angle formed by a main orientation direction of the orientation film and a quenching axis direction of a polarizing element of the polarizing plate is equal to or less than 0 degrees±6 degrees, or equal to or less than 90 degrees±6 degrees. (In the above, "equal to or less than" shall be applied only to the numerical value next to "±".)SELECTED DRAWING: None

Description

The present invention relates to an image display device having a fingerprint authentication sensor and an alignment film on the visual side thereof.

Conventionally, a surface protection film has been attached to an image display device to protect the surface. The surface protective film has the purpose of preventing not only scratches on the surface but also scattering when the image cell or the surface glass plate is broken, and an oriented film such as biaxially stretched polyester having excellent impact resistance has been used. It was. Further, in the image display device, a biaxially stretched polyester film has been used as a shatterproof film for a touch sensor member and a glass member.

On the other hand, in mobile terminals and the like, face recognition systems and fingerprint recognition systems have come to be adopted in order to ensure a high degree of security (Patent Documents 1 and 2).
In order to increase the screen size of such mobile terminals due to the size limitation of mobile, the entire main body is used as a display screen, and an authentication system is installed in the screen (the image display area when viewed from the visual side and behind it). It has been proposed to incorporate the sensor of. In particular, in an organic electroluminescence (organic EL) image display device, a fingerprint authentication sensor can be operated through a gap between pixels of an image display cell, and such a method is becoming widespread.

In an image display device provided with a fingerprint authentication system in the screen, a polarizing plate is provided on the visual side of the sensor for authentication. In such an image display device, an alignment film is provided on the visual side of the polarizing plate. If present, especially when a biaxially stretched polyester film is used as the alignment film, the fingerprint authentication system may not operate (recognize) or malfunction (misidentified value).

Japanese Unexamined Patent Publication No. 2016-006648 Special Table 2018-515820

The present invention has been made against the background of the problems of the prior art. That is, an object of the present invention is to provide an image display device having a fingerprint authentication system and further having an alignment film in which the fingerprint authentication system operates normally.

The present inventor has completed the present invention as a result of diligent studies to achieve such an object. That is, a typical invention is as follows.
Item 1.
An image display device having a polarizing plate on the visual side of the fingerprint authentication sensor and an alignment film on the visual side of the polarizing plate.
An image display device in which the angle formed by the main orientation direction of the alignment film and the quenching axis direction of the polarizing element of the polarizing plate is 0 degrees ± 6 degrees or less, or 90 degrees ± 6 degrees or less.
(In addition, in the above, "less than or equal to" shall be applied only to the numerical value next to "±".)

In an image display device having a polarizing plate on the visual side of the fingerprint authentication sensor, it is possible to provide an image display device in which the fingerprint authentication system operates normally even when an alignment film is present on the visual side of the polarizing plate. ..

This is an example in which the fingerprint authentication sensor unit is installed outside the display screen (image display unit). This is an example in which the fingerprint authentication sensor unit is installed in the display screen (image display unit). It is sectional drawing of an example of the case where the fingerprint authentication sensor unit is installed in the display screen (image display unit).

(Image display device)
The present invention is an image display device having a polarizing plate on the visible side of the fingerprint authentication sensor and an alignment film on the visible side thereof. The fingerprint authentication sensor (fingerprint authentication sensor unit) may be installed outside the display screen or inside the display screen (the image display area when viewed from the visual side and behind it). For example, the outside of the display screen referred to here is the state of FIG. 1, and the inside of the display screen (the image display area and the back thereof when viewed from the visual side) is the state of FIG. The type installed inside the display screen is also called a screen-embedded type. For example, as shown in FIG. 3, the outside of the fingerprint authentication sensor is installed at the back of the screen when viewed from the visual side. In FIG. 3, an image display cell (for example, an organic EL cell) is arranged on the visual side of the fingerprint authentication sensor main body. A polarizing plate (preferably a circular polarizing plate is preferable when the image display cell is an organic EL cell) is arranged on the visual side of the image display cell. An alignment film is arranged on the visible side of the polarizing plate via an adhesive layer.

Generally, since a polarizing plate is provided in the image display area on the image display cell, an image display device of a type in which a fingerprint authentication sensor is installed in the display screen is the subject of the present invention. Even in an image display device of a type in which a fingerprint authentication sensor is installed outside the display screen, a device in which a polarizing plate is provided so as to cover the fingerprint authentication sensor is an object of the present invention.

The image display device is preferably a smart phone, a mobile PC, a PDA, a mobile phone, a game machine, a camera, an electronic dictionary, or the like.

(Image display cell)
The image display cell used in the image display device of the present invention is not particularly limited, but a liquid crystal display cell or an organic EL (OLED) cell can be mentioned as a preferable example in that it can be made smaller and thinner. Among them, the organic EL cell is a preferable example because the fingerprint authentication sensor can be operated through the gap between the pixels of the cell.

(Fingerprint authentication sensor)
Examples of the fingerprint authentication sensor include an optical type, an ultrasonic type, a capacitance type, an electric field strength measurement type, a pressure sensitive type, and a heat sensitive type. The type or ultrasonic type is preferable, and the optical type is particularly preferable.
As an optical fingerprint authentication sensor, for example, it is commercially available from Synaptics under the trade name "Clear ID".
As an ultrasonic fingerprint approval sensor, for example, it is commercially available from Qualcomm Technologies under the trade name "Qualcomm Fingerprint Sensors".

(Polarizer)
As described above, the image display device is in a state where a polarizing plate is provided on the visual side of the fingerprint authentication sensor. The polarizing plate generally includes a polarizer having a function of generating polarized light and a polarizer protective film for protecting the polarizer, but the polarizer protective film is laminated only on one side of the polarizer. It may be a thing, or it may be only a polarizer. Examples of the polarizer include a thin film in which iodine or an organic dichroic dye is adsorbed on uniaxially oriented polyvinyl alcohol, and an alignment film composed of a liquid crystal compound and an organic dichroic dye, but are particularly limited. Can be used without.

The polarizer protective film is not particularly limited, but unstretched or stretched films such as cellulose-based, polyester-based, cyclic polyolefin-based, acrylic-based, and polycarbonate-based films can be used. However, in the case of a stretched film such as polyester, it is preferable that the quenching axis of the polarizer and the main orientation direction of the stretched film are parallel or perpendicular. Here, parallel or vertical means that the angle formed by the quenching axis of the polarizer and the main orientation direction of the stretched film does not have to be exactly 0 degrees or 90 degrees, and the allowable width is ± 6 degrees, which is more preferable. The permissible width is ± 5 degrees, the more preferable permissible width is ± 4 degrees, the particularly preferable permissible width is ± 3 degrees, and the most preferable permissible width is ± 2 degrees.

The quenching axis of the polarizing element of the polarizing plate may be parallel to the long side of the screen, perpendicular to it, or in the direction of 45 degrees. These directions are determined by the type and purpose of the image display cell, and are not particularly limited in the present invention. For example, in the case of an organic EL display cell, it is often arranged at 45 degrees.

A retardation layer may be provided between the polarizer and the image display cell. The retardation layer may be a retardation film in which a resin is stretched, or may be an alignment film of a liquid crystal compound coated and oriented with a liquid crystal compound.
In the case of an organic EL cell, a circular polarizing plate provided with a 1/4 wavelength layer as a retardation layer is used in order to suppress reflection of the metal wiring of the cell. The retardation layer of the circularly polarizing plate is arranged on the organic EL cell side.

(Orientation film)
The image display device of the present invention has a polarizing plate on the viewing side of the fingerprint authentication sensor, and has an alignment film on the viewing side of the polarizing plate. The alignment film is located on the surface of the image display device to prevent scratches on the image display surface and prevent the glass from scattering when the glass members such as the image display cell, touch sensor, and surface cover glass are broken due to impact. It is used as a surface protective film for this purpose, a transparent conductive film that is also used as an electrode of a touch sensor, and a shatterproof film that is located inside a display device and is attached to a glass member to prevent the glass from scattering. , It is a preferable form to be used as a surface protective film.
When the film itself is damaged, the surface protective film is preferably peeled off and replaced. The surface protective film is preferably a base-less adhesive sheet for optics and is attached to an image display device.

As the resin constituting the alignment film, any resin such as polyester, polyamide, polypropylene, polycarbonate, polystyrene, acrylic resin, cyclic polyolefin, and cellulose is used, but as a protective film such as heat resistance, mechanical strength, and dimensional stability. From the viewpoint of characteristics, polyester, particularly polyethylene terephthalate, is preferable.

The oriented film is oriented by stretching to improve the mechanical strength. The alignment film may be a uniaxially oriented film (uniaxially stretched film) or a biaxially oriented film (biaxially stretched film). From the viewpoint of excellent mechanical strength in all directions, a biaxially oriented film (biaxially stretched film) is preferable. On the other hand, a uniaxially stretched film is preferable from the viewpoint of excellent orientation uniformity. When the film is industrially biaxially stretched with a tenter, the main orientation direction is distorted in an arch shape in the width direction of the film (Boeing phenomenon), but in the uniaxially oriented film stretched uniaxially in the width direction, this distortion is reduced and in the width direction. It is possible to secure a film having a broadly intended orientation direction and excellent orientation uniformity, and it is possible to perform bonding and punching under the same conditions, which is advantageous in terms of improving productivity. However, in a perfect uniaxially stretched film, the mechanical strength against a force orthogonal to the orientation direction may be weakened. In such a case, in order to increase the mechanical strength in the direction orthogonal to the main orientation direction, the film is weakly stretched in the direction orthogonal to the main stretching direction (the film thus obtained is subsequently weakly biaxially stretched). A film or a weak biaxially oriented film) is also preferable. This weak stretching may be performed after the main stretching, but it is preferably performed before the main stretching or at the same time. Of course, it may be a complete uniaxial extension.
As for stretching, roll stretching using continuous rolls is generally used in the flow direction (longitudinal direction) of the film, and stretching using a tenter is used for simultaneous stretching in the width direction (horizontal direction) and vertical and horizontal directions. Is used.
In the present invention, the main orientation direction (main stretching direction) may be the flow direction or the width direction.

Here, (elastic modulus in the direction orthogonal to the main orientation direction) / (elastic modulus in the main orientation direction) is 0.5 or less, or (breaking strength in the direction orthogonal to the main orientation direction) / ( It can be said that a uniaxially oriented film or a weakly biaxially oriented film has a breaking strength) of 0.5 or less in the main orientation direction.
Stretching may be performed at an appropriate temperature, magnification, and speed according to each material. Further, the biaxial stretching and the weak biaxial stretching can be adjusted mainly by the respective stretching ratios.
Further, in the case of a polyethylene terephthalate film, if the difference (ΔNxy) between the refractive index in the main orientation direction and the refractive index in the direction orthogonal to the refractive index is 0.055 or more, preferably 0.06 or more, it can be said to be a weak biaxially stretched film. .. Further, if the refractive index of the slow axis is 1.68 or more, preferably 1.685 or more, and ΔNxy is 0.095 or less, preferably 0.093 or less, it can be said that weak biaxial stretching is applied. ..
As described above, in order to secure the mechanical strength from each direction, a biaxially oriented film (biaxially stretched film) is preferable, ΔNxy is preferably less than 0.06, and more preferably less than 0.055. However, not only is it difficult to achieve uniform and uniform biaxial orientation, but also the orientation direction tends to change in films of the same production due to slight fluctuations in production conditions. In manufacturing, ΔNxy is preferably 0.01 or more, more preferably 0.015 or more, and particularly preferably 0.02 or more, in order to have a uniform orientation direction over a wide area of the film.

Further, in order to strengthen the uniaxiality and stabilize the orientation direction in the entire width of the film, ΔNxy is preferably 0.065 or more, more preferably 0.070 or more, still more preferably 0.75 or more, and particularly. It is preferably 0.80 or more, and most preferably 0.85 or more. ΔNxy is preferably 0.16 or less, more preferably 0.15 or less, particularly preferably 0.14 or less, and most preferably 0.13 or less. If it exceeds the above, it becomes too easy to melt, and the function when used as a surface protective film may not be maintained.

The method for producing the oriented film is not particularly limited. For example, taking the case of a polyethylene terephthalate film as an alignment film as an example, it can be produced by the following method.
Generally, the stretching is performed by a continuous roll in the vertical direction (film flow direction) as the first-stage stretching, and then in the width direction (direction orthogonal to the film flow direction) as the second-stage stretching. ), Both ends of the width of the film are gripped with clips and stretched in the tenter. The stretching method of the first step and the stretching method of the second step may be reversed. The draw ratio of the first stage is preferably 1.0 to 3.5 times, particularly preferably 1.0 to 3.0 times. The draw ratio of the second stage is preferably 2.5 to 6.0 times, particularly preferably 3.0 to 5.5 times. In the case of uniaxial stretching only, it is preferable to adopt the stretching ratio of the second stage as the stretching ratio. In any of the stretching, the stretching temperature is preferably 80 to 130 ° C, particularly preferably 90 to 120 ° C. Alternatively, both ends of the width of the unstretched film may be gripped by clips and biaxially stretched simultaneously in the vertical direction and the width direction. Subsequently, it is preferable to heat-treat at 100 to 250 ° C., more preferably 180 to 245 ° C. Further, although the tenter stretching described above was in the width direction, stretching may be performed in an oblique direction with respect to the longitudinal direction.

(Angle between the quencher axis (absorption axis) of the polarizer and the main orientation direction of the alignment film)
In the present invention, the quenching axis (absorption axis) of the polarizer and the main orientation direction (direction parallel to the main alignment axis) of the alignment film are preferably parallel or perpendicular. Here, parallel or vertical means that the angle formed by the extinguishing axis of the polarizer and the main orientation direction of the alignment film does not have to be exactly 0 degrees or 90 degrees, and is 0 degrees ± 6 degrees or less or 90 degrees. ± 6 degrees or less is preferable, 0 degrees ± 5 degrees or less or 90 degrees ± 5 degrees or less is more preferable, 0 degrees ± 4 degrees or less or 90 degrees ± 4 degrees or less is further preferable, and 0 degrees ± 3 degrees or less or 90 degrees. ± 3 degrees or less is particularly preferable, and 0 degrees ± 2 degrees or less or 90 degrees ± 2 degrees or less is particularly preferable. In addition, the term "less than or equal to" means that it applies only to the numerical value next to "±". Therefore, for example, the above-mentioned "0 degree ± 6 degrees or less" means that a fluctuation in a range of 6 degrees up and down around 0 degrees is allowed. Similarly, "90 degrees ± 6 degrees or less" means that fluctuations in the range of 6 degrees up and down around 90 degrees are allowed.
When there are a plurality of oriented films, it is preferable that all the oriented films have the above relationship.

If the angle between the quenching axis of the polarizer and the main orientation direction of the alignment film deviates from the preferable range, problems such as the sensor not operating or malfunctioning may occur. This is because the optical fingerprint sensor irradiates light from the bottom toward the surface of the display device and reads the fingerprint with the reflected light, but if there is a polarizing element on the sensor (visual side), it is a polarizing element. Since the linearly polarized light travels in the alignment film with a phase difference at an angle deviated from the optical axis, it becomes elliptically polarized light, and when this is reflected and passes through the polarizer again, the effect of the alignment film with the phase difference In response to this, the amount of light in the image received by the sensor decreases in a specific wavelength range, and it is thought that it becomes difficult to detect the exact pattern of the fingerprint when the light receiving wavelength of the sensor is fixed. Further, it is considered that even when the sensor receives a wide wavelength region, the total amount of light decreases, and the accuracy of the sensor and the subsequent processing cannot be maintained. It should be noted that these reasons are beyond speculation and do not limit the present technology.
As for the main orientation direction, the slow-phase axis and the phase-advance axis are measured with a molecular orientation meter (for example, MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.), and the slow-phase axis is set as the main orientation axis. For styrene-based resins with a negative photoelastic modulus, the phase-advancing axis is the main orientation direction.

The thickness of the alignment film can be appropriately set according to each purpose, but is preferably 5 to 200 μm. It is more preferably 10 to 150 μm, and particularly preferably 20 to 100 μm. If it is less than 5 μm, not only may it be too thin to be handled poorly, but also when it is used as a surface protective film or the like, sufficient mechanical strength suitable for the purpose may not be secured. If it exceeds 200 μm, not only the rigidity may become too high and the handleability may deteriorate, but also the display device may not be suitable for thinning.

The in-plane retardation of the alignment film is not particularly limited as long as a clear state is observed as the orientation direction of the molecules, but it is preferably 1000 nm or more. In addition, smartphones and the like are often operated outdoors with polarized sunglasses worn, and when polarized sunglasses are worn, coloring or rainbow unevenness may occur when viewed from an oblique direction. In order to reduce rainbow unevenness that occurs when the image display device is viewed from an oblique direction, the in-plane retardation of the alignment film is preferably 3000 nm or more. It is more preferably 4500 nm or more, and particularly preferably 6000 nm or more. The in-plane retardation is preferably 30,000 nm or less, more preferably 10,000 nm or less, and even more preferably 9000 nm or less. Even if the in-plane retardation exceeds 30,000 nm, it is difficult to expect a significant improvement in the effect of improving rainbow unevenness, and a thickness is required. In order to make it thinner, it is necessary to significantly increase the uniaxial orientation, which is orthogonal to the orientation direction. Mechanical strength may decrease.

(Surface processing, etc.)
The oriented film may be surface-processed according to each purpose. For example, in the case of a surface protective film, a hard coat, an antireflection coat, a low reflection coat, an antistatic coat and the like. Further, an easy-adhesion coat may be provided.

When the fingerprint is pressed against the surface of the alignment film to detect its reflection, it is preferable that the visible side of the surface protective film is smooth enough to recognize the fingerprint. The surface roughness SRa of the surface on the viewing side is preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 30 nm or less.

The total light transmittance of the alignment film is preferably 80% or more, more preferably 85% or more, and particularly preferably 88% or more. The haze of the alignment film is preferably 3% or less, more preferably 2.5% or less, and particularly preferably 2% or less.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

(1) Breaking strength Measured according to JIS C-2318.

(2) Elastic modulus The elastic modulus was measured according to JIS C-2318.

(3) Reference, ΔNxy
The retardation is a parameter defined by the product (ΔNxy × d) of the anisotropy of the refractive indexes of the two orthogonal axes on the film (ΔNxy = | nx−ny |) and the film thickness d (nm). Yes, it is a scale showing optical isotropic and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.), determine the slow-phase axial direction of the film, and make the slow-phase axial direction parallel to the long side of the measurement sample, 4 cm. A rectangle of × 2 cm was cut out and used as a measurement sample. For this sample, the refractive index of two orthogonal axes (refractive index in the slow axis direction: nx, refractive index in the direction orthogonal to the slow axis direction in the plane (that is, refractive index in the phase advance axis direction): ny), And the refractive index (nz) in the thickness direction is determined by an Abbe refractive index meter (manufactured by Atago, NAR-4T, measurement wavelength 589 nm), and the absolute value (| nx-ny |) of the refractive index difference between the two axes is refracted. The index was an index (ΔNxy). The film thickness d (nm) was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf), and the unit was converted to nm. The retardation (Re) was determined from the product (ΔNxy × d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.

(4) Quenching axis of the polarizer The image display device is turned on so that linearly polarized light is emitted by peeling off the surface protective film, etc., and a polarizing filter with a known quenching axis is placed on it to make it the darkest. The direction of the quenching axis of the polarizing filter was determined, and the direction of 90 degrees was defined as the quenching axis direction.

(5) Main Orientation Direction The measurement was performed with a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Measuring Instruments Co., Ltd.).

(6) Light transmittance Measured according to JIS K-7105.

(7) Haze Measured according to JIS K-7105.

(8) Three-dimensional central surface average surface roughness (SRa):
A film having an area of 50 mm × 50 mm is cut out and used on a film surface using a three-dimensional surface shape measuring device (Micromap 550N (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10 times) manufactured by Ryoka System Co., Ltd.). On the other hand, it was measured from the vertical direction, a CCD camera image capture area of 400 μm × 400 μm was specified, and SRa given by the following equation was obtained. The number of measurements was set to 16 on both sides of the film, and the average value thereof was calculated. Fractions after the decimal point were rounded off.

_Here, an S M = Lx × Ly, Lx , Ly are x, y-direction range, f (x, y) is the height from the average surface of the measurement point (x, y).

(9) Number of successful authentications The number of successful activations was expressed by 10 attempts to activate by fingerprint authentication. After wiping off the dirt on the fingertips with a wet towel, the water was removed with a dry towel, and after about 3 seconds, the fingertips were placed on the sensor unit.

(10) Surface protection characteristics Using an optical adhesive, an alignment film was attached to a commercially available surface protection glass for smartphones to prepare a test sample. The sample was placed on a table (the film surface was on the top) via a spacer having a thickness of 5 mm on each side of the sample, and a steel ball was dropped from above. Tested with 5 samples. If the glass did not break, the rope was dropped again.
◯: The glass was broken, but there was no sample in which the film was torn.
Δ: There was a sample in which a slight tear of the film was observed at the collision portion of the steel ball.
X: There was a sample in which the film was severely torn.

(11) Observation of rainbow unevenness The image display device for the fingerprint authentication test was observed from an oblique direction while wearing polarized sunglasses.
◯: No rainbow unevenness was observed Δ: Weak rainbow unevenness was observed ×: Clear rainbow unevenness was observed.

(Preparation of alignment film)
The following alignment films A, B, and C were prepared. The characteristics of each are shown in Table 1.

Orientation film A:
A film having a film thickness of 75 μm of Cosmo Shine (registered trademark) A4300 manufactured by Toyobo Co., Ltd. was used. Since the main orientation direction differs depending on the slit position of the film roll, a portion whose main orientation direction is 90 degrees ± 6 degrees or less with respect to the length direction of the film roll was cut out and used.

Orientation film B:
Polyethylene terephthalate chip containing 0.7% by mass of porous silica having an average particle size of 0.9 μm (intrinsic viscosity 0.60 dl / g (phenol: 1,1,2,2-tetrachloroethane = 6: 4 dissolved in a mixed solvent) After drying (measured at 30 ° C.) and hereinafter abbreviated as PET), the mixture was melted at 280 ° C. by a melt extruder and extruded into a sheet on a cooling roll to obtain an unstretched polyethylene terephthalate sheet. Next, a coating agent for an easy-adhesion layer composed of a water-dispersible polyester resin and a blocked isocyanate-modified polyurethane aqueous dispersion was applied to one side of this unstretched sheet, and subsequently led to a tenter-type simultaneous biaxial stretching machine to form a film. While grasping the end with a clip, the film was guided to a hot air zone having a temperature of 125 ° C. and stretched 1.8 times in the vertical direction and 4 times in the width direction. While maintaining the state, the treatment was carried out at a temperature of 225 ° C. for 10 seconds, and further, a relaxation treatment of 2.5% was carried out in each of the vertical and horizontal directions. Since the produced film roll showed some distortion of orientation due to Boeing at the end position, a portion whose main orientation direction was 90 degrees ± 6 degrees or less with respect to the length direction of the film roll was cut out and used.

Orientation film C:
A film of Cosmo Shine (registered trademark) super birefringence type (SRF) manufactured by Toyobo Co., Ltd. with a thickness of 80 μm was used. Since the main orientation direction is almost stable in the width direction of the film roll, it was arbitrarily selected and it was confirmed that the main orientation direction was 90 degrees ± 6 degrees or less with respect to the length direction of the film roll.

(Creation of an oriented film in which a hard coat layer and an adhesive layer are laminated)
Alignment films A, B, which have a hard coat layer on one side, are coated with a UV-curable hard coating agent on the easily adhesive-coated surfaces of the alignment films A, B, and C, dried, and then irradiated with ultraviolet rays with a high-pressure mercury lamp. C was obtained. Further, a commercially available optical adhesive (base material-less type) was applied to the surface of each alignment film opposite to the surface on which the hard coat layer was laminated by peeling off the light release sheet and laminating in a roll-to-roll manner. Table 2 shows the measurement results of the three-dimensional center plane average surface roughness SRa on the hard coat layer side for each oriented film.

(Assembly of an image display device having a surface protective film)
Examples 1 to 15, Comparative Examples 1 and 2
The alignment film in which the above-mentioned hard coat layer and adhesive layer were laminated was cut to the size of the entire screen of the organic EL display device VIVO X20 Plus UD in which an optical fingerprint authentication sensor was incorporated in the display screen. This was used as a surface protective film and was attached onto the screen of the organic EL display device via the adhesive surface. The surface protective film attached at the time of purchase was peeled off. Tables 3 to 5 show the angles at the time of bonding and the evaluation results thereof. The angle was confirmed by an alignment film in which each of the cut hard coat layers and the adhesive layer was laminated, and then bonded.

Example 16
Imitation of the case where a transparent conductive film of a polyester film is used as a touch sensor, alignment films A and C in which a hard coat layer and an adhesive layer are laminated are laminated and bonded in the same manner as described above.

In Tables 3 to 5, positive values indicate a clockwise direction when the main orientation axis is viewed from the visual side with respect to the light transmitting axis of the polarizer, and negative values indicate a counterclockwise direction.

1 Image display device 2 Image display unit 3 Fingerprint authentication sensor unit 21 Image display cell 22 Polarizing plate 23 Adhesive layer 24 Alignment film (surface protection film)
31 Fingerprint authentication sensor body

In an image display device provided with a fingerprint authentication system in the screen, a polarizing plate is provided on the visual side of the sensor for authentication. In such an image display device, an alignment film is provided on the visual side of the polarizing plate. when present, especially using the biaxially oriented polyester film as an alignment film, the fingerprint authentication system may not operate (cognitive), there or to malfunction (false knowledge).

(Image display device)
The present invention is an image display device having a polarizing plate on the visible side of the fingerprint authentication sensor and an alignment film on the visible side thereof. The fingerprint authentication sensor (fingerprint authentication sensor unit) may be installed outside the display screen or inside the display screen (the image display area when viewed from the visual side and behind it). For example, the outside of the display screen referred to here is the state of FIG. 1, and the inside of the display screen (the image display area and the back thereof when viewed from the visual side) is the state of FIG. Type installed within the display screen are said to display embedded, for example, fingerprint sensor Body as in FIG. 3 is installed in the back of the screen as viewed from the viewing side. In FIG. 3, an image display cell (for example, an organic EL cell) is arranged on the visual side of the fingerprint authentication sensor main body. A polarizing plate (preferably a circular polarizing plate is preferable when the image display cell is an organic EL cell) is arranged on the visual side of the image display cell. An alignment film is arranged on the visible side of the polarizing plate via an adhesive layer.

Further, in order to enhance the uniaxiality and stabilize the orientation direction in the entire width of the film, ΔNxy is preferably 0.065 or more, more preferably 0.070 or more, and further preferably 0. 0 75 or more, particularly preferably 0. 0 80 or more, and most preferably 0. It is 0 85 or more. ΔNxy is preferably 0.16 or less, more preferably 0.15 or less, particularly preferably 0.14 or less, and most preferably 0.13 or less. Too Crack only easily exceeds the, feature might not be maintained when used as a surface protective film.

(10) Surface protection characteristics Using an optical adhesive, an alignment film was attached to a commercially available surface protection glass for smartphones to prepare a test sample. The sample was placed on a table (the film surface was on the top) via a spacer having a thickness of 5 mm on each side of the sample, and a steel ball was dropped from above. Tested with 5 samples. If the glass did not break, the steel ball was dropped again.
◯: The glass was broken, but there was no sample in which the film was torn.
Δ: There was a sample in which a slight tear of the film was observed at the collision portion of the steel ball.
X: There was a sample in which the film was severely torn.

Claims (3)

An image display device having a polarizing plate on the visible side of the sensor of the authentication system and an alignment film on the visible side of the polarizing plate.
An image display device in which the angle formed by the main orientation direction of the alignment film and the quenching axis direction of the polarizing element of the polarizing plate is 0 degrees ± 6 degrees or less, or 90 degrees ± 6 degrees or less.
(In addition, in the above, "less than or equal to" shall be applied only to the numerical value next to "±".) The image display device according to claim 1, wherein the authentication system irradiates light from the lower part toward the surface of the display device and reads the reflected light with a sensor. The image display device according to claim 1 or 2, which includes an organic EL cell.

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