TWI816846B - Polarizing plate manufacturing system, marking method, polarizing plate manufacturing method and polarizing plate - Google Patents

Abstract

The present invention irradiates visible light laser to the polarizing plate (100), and causes the polarizer film (10) to absorb the visible light laser, thereby degrading the part of the polarizer film (10) that is irradiated with the visible light laser, and causing the deterioration of the polarizer film (10). Marking occurs by changes in the optical properties of the part. Thereby, defects are marked in a polarizing plate including a polarizer film that polarizes visible light.

Description

Polarizing plate manufacturing system, marking method, polarizing plate manufacturing method and polarizing plate

The present invention relates to defect marking for polarizing plates used in liquid crystal devices and the like.

The polarizing plate used in liquid crystal display devices, etc. is generally made by stretching a polyvinyl alcohol (PVA) resin containing iodine or a dye (dichroic dye) to obtain a polarizing film (polarizing original sheet), and then transporting the polarizing film The film is manufactured by laminating support films made of visible light-transmissive resin from both sides.

Such a polarizing plate manufacturing line is generally equipped with a defect detection device that detects defects caused by flaws that occur during manufacturing or foreign matter that is mixed in, or the like. The defect detection device is composed of a light source part, a photography system and a computer. The light source part is usually an LED (light emitting diode). The photography system has a light receiving part such as a CCD (charge coupled device) camera and uses light transmission or Working through reflection, the computer processes the data it obtains.

A marking device is provided on the downstream side of the manufacturing line. The marking device marks the defective portion based on the data of the defect detected by the defect detection device. By adding a mark to the defect of the polarizing plate, the part containing the defect can be removed during the inspection step of the product, or the mark can be confirmed by the user's visual inspection and the part containing the defect can be removed when using the polarizing plate. And use.

Here, examples of marking methods include a method of applying ink with an inkjet or a marker pen, a method of marking with a tape on an end of a film (thin film), and a method of laser irradiation. wait.

In the case of marking using ink, drying time is required because the ink contains a diluting solvent or the like, or the ink may peel off or be transferred to a roller in a subsequent production step. Therefore, there is a risk that peeling ink will contaminate the manufacturing line and the location of the defective part will become unrecognizable. In addition, in the marking method using tape for the end portion, the marking position may be removed due to subsequent production steps, such as slit processing, and the position of the defective part may become unrecognizable. Therefore, although these labeling methods are easy to perform, they cannot be said to be good enough.

On the other hand, the marking method by laser irradiation can eliminate the above-mentioned problems because a thin film such as resin can be directly heated for marking. Typical laser light sources for marking include those using infrared lasers, lasers with a wavelength of 10.6 μm using CO ₂ (carbon dioxide), or lasers with a wavelength of 1064 nm using YAG (yttrium aluminum garnet) crystals. of laser, etc.

For example, Patent Document 1 discloses burning aluminum on a wire grid polarizing plate using a YAG laser. Furthermore, it is described that if a CO ₂ laser is used, holes will be punched in the resin that is the base material of the polarizing plate 100 .

[Prior technical literature] (patent document) Patent Document 1: Japanese Patent Application Publication No. 2011-257343.

(The problem that the invention aims to solve) Here, Patent Document 1 describes using a dust collector or the like to capture dust generated by marking on a film. That is, the marking by laser irradiation will cause damage to the marked portion.

In addition, when laser irradiation is used for marking, it is generally required to increase the output of the laser irradiation in order to improve the visibility of the mark and shorten the laser irradiation time. Therefore, it is considered that local thickness changes accompanied by deformation such as unevenness or distortion occur in the marked portion and its surroundings due to thermal energy generated during marking. Therefore, when product films with such markings are stacked one by one or are continuously wound into a roll, the uneven or distorted shapes are transferred between the overlapping films and become secondary defects such as indentation defects. The reason is that there is a problem of reducing product yield. In addition, smoke or dust is emitted from the marking portion due to the heat irradiated by the laser, which may pollute the environment of the manufacturing line.

An object of the present invention is to provide a marking device and a marking method that can suppress the occurrence of surface irregularities and improve production quality when marking defects by laser irradiation.

(means used to solve problems) As a result of in-depth review, the inventor found that by using visible light laser in laser irradiation for defect marking, the visible light laser can be absorbed by the polarizer film in the polarizing plate, thereby suppressing the When deformation such as unevenness or distortion occurs around the marking portion, the present invention was completed by modifying the polarizing film to perform marking.

The present invention is a marking device that marks defects in a polarizing plate. The polarizing plate includes a polarizer film that polarizes visible light. The marking device includes a laser source that emits a visible light laser; and the marking device makes the aforementioned marking device The polarizer film absorbs the visible light laser from the laser source, so that the polarizer film is modified and the optical properties of the modified part are changed, thereby marking.

In addition, the polarizing plate may include a visible light-transmissive support film sandwiching the polarizer film from both sides, and the visible light laser transmits through the support film and is absorbed by the polarizer film.

In addition, the aforementioned polarizing film can be modified by absorbing visible light laser, and can be marked by any one or more of the following methods: (i) color sense change, (ii) polarization characteristic change.

In addition, the aforementioned visible light laser may be green light.

Furthermore, the polarizer film may contain a dichroic dye of iodine or dye.

In addition, the visible light laser may be linearly polarized light; and the polarization direction of the visible light laser may be changed in the range of 0 to 90° with respect to the absorption axis direction of the polarizing plate.

Furthermore, the present invention can be a marking method corresponding to the above-mentioned device.

Furthermore, the present invention may be a polarizing plate manufacturing method including the above marking method, or a polarizing plate manufactured by the polarizing plate manufacturing method.

In addition, the modified portion may not have polarization, and the maximum depth and maximum ridge height based on the surface of the base material may be 5 μm or less respectively.

(The effect of the invention) According to the present invention, the polarizer film inside the polarizing plate can be modified to perform marking. Thereby, it is possible to suppress deformation of the marking portion and its periphery caused by laser irradiation. Therefore, it is possible to prevent the occurrence of secondary defects such as transfer of deformed parts or impressions, thereby improving production quality.

Furthermore, because it is a visible light laser, even if the support film of the polarizing plate contains an ultraviolet absorber, the laser light will not be absorbed by the support film and can reach the polarizer film and deteriorate the polarizer film.

The embodiments of the present invention will be described below based on the drawings. In addition, this invention is not limited to the embodiment described here.

(overall composition) FIG. 1 is a diagram showing the overall structure of a polarizing plate manufacturing system, which includes a marking device according to an embodiment.

The polarizing film 10 formed into a long strip-shaped member is pulled out (unwinded) from a roller or the like and transported. Here, as the polarizing film 10, for example, a film (film) made of a polyvinyl alcohol-based resin dyed with a dichroic dye can be used. Typical examples of dichroic dyes include dyes such as iodine and azo compounds, which have polarizing properties in the visible light range. For example, in a liquid crystal display device, it is arranged on the incident side or the emitting side of liquid crystal. Here, the dichroic dye is preferably one that can fully absorb visible light laser used for marking described later.

The thickness of the polarizing film 10 is not particularly limited, but is, for example, about 1 μm to 100 μm. Taking into consideration the ease of stretching, marking properties with laser, visibility of markings, etc., the film thickness is preferably 5 μm or more.

In this example, both sides of the polarizing film 10 are sandwiched between visible light-transmitting support films 12a and 12b. That is, the support films 12a and 12b are overlapped on the upper and lower sides of the transported polarizer film 10, and are pressed from the up and down directions by the rollers 14a and 14b, thereby sandwiching the polarizer between the support films 12a and 12b. Both sides of the film 10 form the polarizing plate 100 .

The support films 12a and 12b are colorless and transparent in optical properties, and are generally used to protect the polarizer film 10, which is fragile to heat or moisture. As an example of other functions of the support film 12, it also has a compensation function for improving the display performance such as viewing angle in the liquid crystal display device. When the polarizing film 10 and the supporting films 12a and 12b are laminated, the polarizing film 10 and the supporting films 12a and 12b are not particularly limited. For example, the polarizing film 10 and the supporting films 12a and 12b may be laminated through an adhesive such as an adhesive made of vinyl alcohol resin. 12b build-up. Examples of the material of the support films 12a and 12b include cellulose acetate resin, norbornene resin, polycarbonate resin, acrylic resin, and the like. In addition, for the support films 12a and 12b, films with a thickness of 100 μm or less are usually used, and generally the thickness is 80 μm or less. However, from the viewpoint of thinning the polarizing plate 100, the thickness can be 60 μm or less. Appropriate surface functional layers such as an anti-glare layer, a hard coating layer, an anti-reflection layer, and an anti-static layer can be formed on the surface opposite to the adhesive surface (outer surface) of the support films 12a and 12b. In addition, the surface functional layer is not suitable for use with films that absorb visible light, but is colorless and transparent.

In addition, in the case of this embodiment, since visible light laser is used for marking, the support films 12a and 12b or the surface functional layer may also have an ultraviolet absorbing function. This ultraviolet absorbing function can be provided, for example, by adding an ultraviolet absorber to the film or surface functional layer. As the ultraviolet absorber, well-known materials such as benzotriazole-based, benzophenone-based, salicylic acid-based, cyanoacrylate-based, and cyclic imide-based materials can be used. In addition, TAC (triacetyl cellulose) is a representative example of the commercially available support film 12 for polarizing plates, and this TAC generally contains an ultraviolet absorber. On the other hand, support films having the aforementioned compensating function containing TAC, acrylic resin, etc. as components generally do not contain ultraviolet absorbers. Therefore, the location of the layer with an ultraviolet absorbing function in the polarizing plate 100 is determined for the purpose of suppressing deterioration caused by ultraviolet rays such as sunlight, and therefore must be determined according to the type of final product in which the polarizing plate 100 is used. design.

The polarizing plate 100 to be inspected is preferably in the form of the above-mentioned polarizing plate 100 or the polarizing plate 100 having a surface functional layer. However, as long as the laser light reaches the polarizing film and is absorbed, it can also be a protective film. Films and layers such as films (protective films), retardation films, viewing angle compensation films, adhesive layers, release films (separation films), etc. are formed by laminating one or more layers.

In addition, in this embodiment, the pattern in which the support films 12a and 12b are arranged on both sides of the polarizer film 10 is targeted for marking. However, the polarizer film 10 alone may be marked as described below. In addition, the support film 12 may be provided only on one side of the polarizer film 10 in some cases. These structures are designed to suit the use of the final product, such as a liquid crystal display device or a lens for polarized sunglasses. In the case of the latter configuration, it is preferable to irradiate the self-supporting film side with laser light, thereby achieving the effects of the present invention. In addition, among the defects of the polarizing plate 100 , there are defects that become conspicuous by laminating or sandwiching support films as described later, or defects that disappear by being filled with an adhesive layer, so there is a problem with the efficiency of defect detection. From this point of view, it is more preferable to provide the support film 12 to the polarizer film 10 .

The polarizing plate 100 in which the supporting films 12a and 12b are stacked on both sides of the polarizing film 10 is inspected by the detection device 16. In this example, the detection device 16 is composed of a light irradiation device 16b and a photographing device 16a. The light from the light irradiation device 16b is transmitted through the polarizing plate 100, and the transmitted image is captured by the photographing device 16a. The light irradiation device 16b can be a laser light source or various LEDs (Light Emitting Diodes). The photography device 16a can be a CCD (Charge-Coupled Device) or C-MOS (Complementary Metal Oxide Semiconductor) camera. .

The image signal from the photography device 16a is supplied to the control device 18. The control device 18 has an image processing function, analyzes the image signal, and detects defects such as scratches and foreign matters. The defect can be detected by well-known techniques, such as comparing the photographed image with a pre-memorized normal image to detect abnormalities.

In addition, defects in the polarizing plate manufacturing process called scratches and foreign matter include indentations or friction marks on the film due to unevenness on the surface of the roller when the film is transported, inherent defects in the raw materials, and differences between the films. Dust generated by friction or cutting, optical distortion (knick, crack point) caused by the support film clamping tiny dust attached to the polarizer film, etc., are defects in the final product, that is, liquid crystal Determine whether the quality will be affected when used in display devices or sunglasses. These defects have a size of 1 to 100 μm or more, and are observed in shapes such as dots and lines.

Furthermore, the marking device 20 is arranged on the downstream side of the detection device 16 . The marking device is equipped with a visible light laser source, which irradiates the visible light laser onto the polarizing plate 100 . That is, when a defect is detected in the control device 18, the defect is marked by irradiating visible light laser to the defect position (right above the defect) or its vicinity, etc., at a position where the defect position can be recognized later.

Here, the range of visible light is generally 380 to 780nm. On the other hand, there are cases where the above-mentioned ultraviolet absorber is contained in the support films 12a and 12b. In this case, it is considered that most of the light below 380 nm is absorbed by the support films 12a and 12b, and that light in the vicinity of 390 nm is also absorbed by the support film. The influence of ultraviolet absorbers in 12a and 12b. Therefore, considering the practical range of visible light laser, it is considered that the wavelength is suitable to be 400~780nm.

Typical examples of marking devices equipped with visible light laser include devices that irradiate red light (635 to 690 nm) and green light (532 nm), and commercially available devices can be obtained and used. In particular, a polarizing plate with polarizing properties in the visible light range is generally set to have high optical properties at 550 nm, which has a high visual sensitivity. Therefore, it is preferable to use a green visible light laser with such a polarizing plate. Thereby, the present invention can be widely applied to various optical properties of dye-based and iodine-based polarizing plates.

Furthermore, as mentioned above, the presence or absence of the ultraviolet absorber in the support film 12 of the polarizing plate varies depending on the type of final product using the polarizing plate 100 . Therefore, by using a visible light laser, the mark produced according to the present invention can be applied universally without worrying about whether there is an ultraviolet absorber in the support film 12 .

The so-called "deterioration" of the polarizer film 10 inside the polarizer 100 caused by the irradiation of visible light laser in the present invention refers to the situation where the polarizer film undergoes chemical or physical changes due to the absorption of the thermal effect of the laser light. Specifically, it is considered that the softening of stretched PVA may cause the alignment of the dichroic dye to be relaxed, the dichroic dye contained may be changed or decomposed, and the PVA layer may be damaged. Therefore, the mark mark is visually observed as a change in color perception, and optically, it is observed as a disappearance or deterioration of polarization characteristics.

The polarizing plate 100 with the mark completed is affixed with a protective film, wound up by the winding roller 22, and shipped as a product. As an example of another type of product shipment, the polarizing plate 100 described above is affixed with a protective film and continuously cut into a thin plate or sheet shape while being kept in this state. As a further example, there are the following types: the polarizing plate 100 is rolled up, a protective film is affixed, an adhesive layer or a retardation film is laminated, and the polarizing plate 100 is cut into thin plates or sheets and shipped as products. . In the case of thin plate or sheet-like products, the polarizing plate with the mark is rejected by the inspection step as a defective product. In addition, the above-mentioned thin plate refers to a relatively large-shaped product, for example, one side of the product is about 0.5 to 1 m, and the so-called sheet shape refers to a smaller-shaped product, for example, the diagonal of the product is about 0.1 to 10 inches. size.

For example, in a manufacturing line of a liquid crystal display device, the polarizing plate 100 is rolled out of a roll-shaped polarizing plate and cut as needed for use. At this time, by detecting marks indicating defects visually or with a sensor and discarding the corresponding parts, the polarizing plate 100 can be used in a manner that avoids using the parts where the defects exist.

"Specific examples of marking" The following describes the marking device of this embodiment based on the embodiment.

(Example 1) The following test was conducted: using a laser irradiation device (second harmonic of YAG laser, wavelength 532nm) capable of emitting green light as a visible light laser, the dye-based polarizing plate 100SHC-125U (manufactured by Polatechno Co., Ltd.) was irradiated. The polarizing plate 100 is marked.

The dye-based polarizing plate 100SHC-125U is composed of the following elements: a dye-based polarizing film using PVA as a base material as a polarizing film, TAC films as supporting films placed on both sides of the polarizing film, and A PET (polyethylene terephthalate) protective film on one of the TAC layers, and a release film placed on the other TAC layer via an adhesive layer.

In addition, the optical properties of the polarizing plate 100 are a visual sensitivity-corrected transmittance of 39.5% and a visual sensitivity-corrected polarization degree of 99.5%. After peeling off the PET protective film from the polarizing plate 100, laser light is irradiated to the surface of the polarizing plate 100 (TAC layer). At this time, the relationship between the polarization direction of the laser light and the absorption axis of the polarizing plate 100 is 0°, and the laser irradiation output is 51% (the energy density at 100% is 4.8×10 ³ W/mm ² ). The irradiation time is 0.1 seconds per mark, the irradiation distance to the polarizing plate 100 is 30 cm, and the mark size applied thereby is about 2 mm in diameter.

Here, FIG. 2 shows an example of the shape of the marking mark produced by the marking device (the shape is not limited to these shapes). From the left: (i) circle: 4×4 grid, (ii) circle: 9×9 grid, (iii) circle: dots with edges, (iv) circle: concentric circles (contour lines), (v) square: horizontal stripes.

Here, although the larger the printing amount, the easier it is to see, but the printing time also becomes longer and the damage to the substrate increases. The optimal shape can be selected from the viewpoint of line speed in the production step and visibility in subsequent steps. Furthermore, the mark does not need to be formed into a specific shape, and the mark can be irradiated uniformly throughout.

Table 1 shows the results of the appearance of the portion marked by the laser irradiation based on visual observation. The evaluation of the observed marking portion is based on the following factors: (1) visibility of the marking, (2) distortion of the marking portion and the periphery of the marking portion, (3) color sense of the visible marking, among which ( The determination of 1) and (2) is as follows. In addition, regarding (1), identification and judgment were performed by six product inspectors who were actually manufacturing the polarizing plate 100 .

(1) Visibility of marking marks A: All 6 inspectors identified it; B: The number of inspectors who recognized the mark is less than 5; C: The number of inspectors who recognized the mark is less than 2.

(2) Marking marks and distortion around marking marks, etc. ○: Almost no unevenness or distortion; ╳: There are bumps or distortions.

(Example 2) The output of the laser irradiation was set to 30%, and the content was the same as that of Example 1 except that it was set to 30%.

(Example 3) The contents were the same as those described in Example 1 except that iodine-based polarizing plate 100JET-12PU (manufactured by Polatechno Co., Ltd.) was used and the output of laser irradiation was set to 51%. The polarizing plate 100 is composed of a PET protective film, the polarizing plate 100, an adhesive layer and a release film. The optical properties are a visual sensitivity corrected transmittance of 40.4% and a visual sensitivity corrected polarization degree of 99.99%.

(Example 4) The contents were the same as those described in Example 1 except that iodine-based polarizing plate 100JET-12PU (manufactured by Polatechno Co., Ltd.) was used and the output of laser irradiation was set to 30%.

(Comparative Example 1) A laser irradiation device (wavelength 10.6 μm) equipped with CO ₂ laser light irradiation was used, and the output of laser irradiation was set to 70% (energy density at 100% is 1.9×10 ³ W/mm ² ) , otherwise it is the same as described in Example 1.

(Comparative example 2) The content described in Comparative Example 1 was the same except that the output of the laser irradiation was set to 15%. Table 1 shows the results of observation of the appearance of the laser-marked portion.

(Comparative Example 3) A laser irradiation device (wavelength 355nm) equipped with UV laser light irradiation was used, and the output of laser irradiation was set to 70% (energy density at 100% is 3.5×10 ³ W/mm ² ), except Otherwise, it is the same as the description of Example 1.

(Comparative example 4) The content described in Comparative Example 3 was the same except that the output of the laser irradiation was set to 15%.

[Table 1]

[Microscopic observation of laser markers] In order to observe the layer that has been marked by laser irradiation in detail, a microtome method is used to make a slice of the marked portion of the polarizing plate 100 that has been marked by laser irradiation. The section was observed using an optical microscope (APS-004 manufactured by Micro Support). Images of this section are shown in Figures 3 to 5. Figure 3 shows the marking part of Example 1, Figure 4 shows the marking part of Comparative Example 1, and Figure 5 shows the marking part of Comparative Example 3.

[Observation of concave and convex shapes of marking marks] In Table 1, Examples 1 to 4 are the results of marking using green visible light laser. In the case of Examples 1 and 2 in which a dye-based polarizing plate is used as the polarizing plate 100, when the laser output is 51%, both (1) and (2) are good results. The cross section of the polarizing plate 100 in Example 1 is shown in FIG. 3 . Compared to the white color of the comparative example, the outline of the marking mark in Example 1 appears black. From this, it can also be confirmed that only the polarizing film inside the polarizing plate 100 is deteriorated by the laser light. In addition, the marked polarizing plates of Examples 1 and 2 were placed on the white LED backlight module, and the same type of unmarked polarizing plate was placed orthogonally to the polarizing axis from the polarizing plate and observed. In either case where the marked surface is placed toward the viewing side, or the marked surface is placed toward the backlight module side, the marking marks appear as bright spots. From this, it can be confirmed that the marked position is translucent and does not have polarization.

In addition, in the cases of Examples 3 and 4 in which an iodine-based polarizing plate was used as the polarizing plate 100, both (1) and (2) were judged to be good results. However, when the laser output is 51%, although the shape of the support film surface does not change, the film thickness of the polarizing plate 100 around the mark mark increases. This is presumed based on the observation of the cross section of the mark mark because the heat generated rapidly by absorbing the laser light inside the polarizing plate 100 vaporizes moisture and the like, causing the polarizing film to expand. Under any condition, the outline of the marking mark has a reddish-brown color. Therefore, it is presumed that the iodine in the polarizer film is deteriorated by absorbing the heat of the laser light. In addition, similarly to Examples 1 and 2, the marked polarizing plates 100 of Examples 3 and 4 were placed on the white LED backlight module and observed. In either case where the marked surface is placed toward the viewing side, or the marked surface is placed toward the backlight module side, the marking marks appear as bright spots. From this, it can be confirmed that the marked position is translucent and does not have polarization.

From these results, it can be seen that by optimally setting the laser light output according to the transmittance of the polarizing plate 100 or the type of dichroic dye contained in the polarizing plate 100, both the dye-based and iodine-based polarizing plates 100 can be used. The inside of the polarizing plate 100 can be laser marked without distortion or deformation. In addition, since the mark mark is visible, the polarizing plate 100 can be processed without slowing down production efficiency in subsequent processing steps such as defect inspection by an inspector or a detection device.

Comparative Examples 1 and 2 are the results of marking the polarizing plate 100 using CO ₂ laser light. Figure 4 is the result of cross-sectional observation of the mark mark in Comparative Example 1. The deformation caused by the large deformation of the surface of the support film of the polarizing plate 100 due to laser light not only causes unevenness of the mark mark, but also generates polarized light at the center. Due to the distortion of the plate 100, it is difficult to stack it into a roll shape or a thin plate shape as a product. Although the amount of deformation can be reduced by reducing the laser output from 70% to 15%, it is difficult to maintain the visibility of the mark marks.

In addition, similarly to Examples 1 and 2, the marked polarizing plates 100 of Comparative Examples 1 and 2 were placed on the white LED backlight module and observed. When the marked surface is placed toward the viewing side, the marking marks appear as bright spots. However, when the marked surface is placed toward the backlight module side, the marking marks cannot be observed. From this, it was confirmed that the marking by the laser light deformed the surface of the support film of the polarizing plate 100 and could not reach the polarizing film 10 as shown in the cross-sectional observation results. Therefore, the polarizing film 10 did not deteriorate.

Comparative Examples 3 and 4 are the results of marking the polarizing plate 100 using UV laser light. Figure 5 is the result of cross-sectional observation of the mark mark in Comparative Example 3. The deformation of the surface of the support film of the polarizing plate 100 is smaller than that of Comparative Examples 1 and 2. Although the amount of deformation can be further reduced by reducing the laser output from 70% to 15%, it is difficult to maintain the visibility of the mark marks.

In addition, similarly to Examples 1 and 2, the marked polarizing plates 100 of Comparative Examples 3 and 4 were placed on the white LED backlight module and observed. When the marked surface is placed toward the viewing side, the marking marks appear as bright spots. However, when the marked surface is placed toward the backlight module side, the marking marks cannot be observed. From this, it was confirmed that the marking by the laser light deformed the surface of the support film of the polarizing plate 100 and could not reach the polarizing film 10 as shown in the cross-sectional observation results. Therefore, the polarizing film 10 did not deteriorate. Furthermore, in this case, since the support film 12 contains an ultraviolet absorber, the laser light is absorbed by the support film 12 .

[Table 2]

Table 2 shows the results of detailed analysis of the shape and state of the mark marks obtained in the tests of Example 1 and Comparative Examples 2 and 3 using an optical microscope (digital microscope VHX-6000 manufactured by Keyence Corporation). . The recess in Table 2 is the maximum depth (μm) of the recess of the mark on the support film of the polarizing plate obtained by the three-dimensional measurement function of the aforementioned device, and represents the portion directly under the laser light. Similarly, the convex portion is the maximum height (μm) of the mark bulge, which represents the peripheral portion irradiated with laser light. The values of the recessed portions and the convex portions were calculated using the surface of the normal portion (surface of the base material) without marking marks on the side of the support film irradiated with laser as a reference (0 μm).

In Example 1, the marking mark was not formed on the surface of the support film, and was distorted on the surface of the support film due to the deterioration of the polarizing film that absorbs laser light. The values of the concave portions and the convex portions accompanying this situation are 0.1 and 1.0 μm, which means that there is almost no deformation of the polarizing plate due to the mark, as in visual observation. Here, according to verification experiments, if the depth and height of the concave portion and the convex portion exceed 5 μm relative to the reference, the deformation becomes conspicuous, which is undesirable. Therefore, it is preferable that the maximum depth (concave portion) and the maximum ridge (convex portion) based on the surface of the base material are each 5 μm or less.

On the other hand, in the cases of Comparative Examples 1 and 3, the values of the concave portions and the convex portions were 5 to 20 μm larger than in Example 1. More specifically, the mark marks contained heat due to laser irradiation. Traces of melting on the surface of the support film, or components of the melted support film becoming scattered. From these results, it can be seen that in the laser marking of the polarizing plate using green light in Example 1, almost no unevenness caused by the marking marks occurs, and the polarizing plate products are stored in rolls or stacked layer by layer. , can suppress the occurrence of indentation defects caused by marking marks. Furthermore, in the case of the present invention, since there are almost no unevenness of marking marks, even when a protective film or the like is laminated on a polarizing plate that has been marked, the films can still be tightly bonded, so that the occurrence of marking marks can be suppressed. Bubble defects caused by unevenness (a state in which the film floats and an air layer exists).

[Modification 1] The structure of variation 1 is shown in FIG. 6 . In this example, the detection device 16 is arranged on the upstream side of the laminated support films 12a and 12b. Therefore, the polarizing film 10 is observed at the detection device 16 . Thereby, defects in the polarizing film 10 can be detected, and the defects can be marked in the marking device 20 .

[Modification 2] The structure of variation 2 is shown in FIG. 7 . In this example, after the support films 12a and 12b are laminated on the polarizing film 10, the polarizing plate 100 is meandered by three rollers 24. That is, the first roller changes the traveling direction by nearly 90°, and then the second roller changes the traveling direction by 180° to turn back the traveling direction. Furthermore, in the third roller 24, the traveling direction is changed by nearly 90°, thereby returning to the original traveling direction. Then, the polarizing plate 100 in the folded state on the second roller 24 is inspected by the reflection detection device 16 . That is, the light irradiation device 16 b irradiates the polarizing plate 100 in the folded state with light, and the photographing device 16 a captures the reflected light.

In this way, by folding back the polarizing plate 100 , a predetermined tension can be applied to the polarizing plate 100 , and since both ends of the polarizing plate 100 are supported by the rollers, distortion is eliminated in the width direction of the polarizing plate 100 . Able to perform inspections with high accuracy. In addition, when inspection is performed by the reflection method, the distortion caused by curling (bending) of the polarizing plate 100 or the like may become a major factor that makes the reference line of the inspection light source unstable. In addition, by applying blackening or matte processing to the surface of the second roller to achieve low reflectivity with respect to the inspection light source, the reference line can be stabilized and detection accuracy can be improved.

[mark] Here, in this embodiment, marking is performed by absorbing visible light in the polarizing film 10 . The polarizing film 10 originally has an absorption axis and a transmission axis for visible light. Therefore, it is preferable to linearly polarize the visible light emitted from the marking device 20 and to set the polarization direction in the direction of the absorption axis of the polarizer film 10 . Thereby, the absorption efficiency of visible light from the marking device 20 can be increased, and marking can be performed efficiently.

Furthermore, as shown in Figure 8, if the polarization axis of the irradiated visible light laser is changed, the amount of absorption can be changed. Therefore, when marking the polarizing plate 100, by changing the angle of the polarized light emitted from the irradiation device with respect to the absorption axis of the polarizing plate 100, the amount of laser light absorbed can be changed. Thereby, not only the density of the mark can be adjusted by adjusting the laser output, but also the density of the mark can be adjusted by controlling the irradiation angle of the polarized light. That is, for visible light laser with linear polarization, the absorption axis of the polarizing plate 100 can be changed in the range of 0 to 90°. By adjusting the polarization direction of the laser light for irradiation, the polarizing film can be used to adjust the amount of light absorbed, thereby adjusting the irradiation intensity of the mark.

For example, the direction of linear polarization can be controlled by enabling the marking device 20 to rotate in a horizontal plane, or using a liquid crystal polarization rotator or the like to control the polarization direction.

In addition, since the extending direction of the polarizing film 10 becomes the absorption axis direction, the light absorption is maximum in the direction parallel to the polarization direction of the laser light (0°) and orthogonal to the direction of the polarizing plate 100 (90°). The direction in which light absorption is minimal. Therefore, from the viewpoint of the visibility of the mark mark and the efficiency of mark formation, the polarizing film 10 absorbs the laser light. Therefore, the relationship between the above-mentioned angles is preferably between 0 and 0. 45°, preferably 0~5°.

Furthermore, if the intensity (energy density) in marking by visible light laser is increased, the time required for marking can be reduced. However, if the strength is increased, the support film, etc. will also be affected. On the other hand, if the intensity is reduced, the time required for marking becomes longer and is affected by the movement (transportation speed) of the polarizing plate 100 .

Therefore, the movement of the polarizing plate 100 may be temporarily slowed down or stopped during marking. Furthermore, the marking device can also be moved in accordance with the movement of the polarizing plate 100 . Generally speaking, the use of a defective polarizing plate 100 is prohibited at certain lengths. Therefore, marking only needs to be performed at predetermined length intervals. It is also suitable to make the moving distance of the marking device correspond to the certain length. Other suitable methods, as adjustment by the marking device, can be to match the scanning speed of the laser irradiation (irradiation speed per unit time) and follow the movement of the polarizing plate 100 to obtain an appropriate mark mark density (printing density) , or use the function of marking a certain area by scanning the laser light in one go (area marking).

[Detection of markers] In this embodiment, the polarizing film 10 absorbs visible light laser and generates heat. As a result, the polarizing film 10 will be deteriorated, but in this case, the polarizing function will be hindered. Therefore, when detecting marks, whether the polarizing film 10 has a polarizing function can be utilized.

FIG. 9 shows an example in which unpolarized light is irradiated onto a polarizing plate 100 with a transmission axis direction of 90° on which a mark is formed, and the transmitted light is detected after passing through a polarizing plate with a transmission axis direction of 0°. In this way, the light from the light source becomes linearly polarized light at 90° in the transmission axis direction by passing through the polarizing plate 100. However, the marked portion loses the polarizing function and remains unpolarized light. Then, if the light that has passed through the polarizing plate 100 passes through the polarizing plate with a transmission axis direction of 0°, polarized light with a transmission axis direction of 0° will pass through the marked portion. Therefore, the mark can be detected as a bright spot.

In FIG. 10 , unpolarized light is irradiated to a polarizing plate 100 with a transmission axis direction of 90° on which a mark is formed, and the transmitted light is detected after passing through the polarizing plate with a transmission axis direction of 90°. Similar to Figure 9, the light from the light source becomes linearly polarized light at 90° in the transmission axis direction by passing through the polarizing plate 100. However, the marked portion loses the polarizing function and remains unpolarized light. Then, if the transmitted light passes through a polarizing plate with a transmission axis direction of 90°, the parts other than the mark will pass through with the original linearly polarized light of 90°, but for the part of the mark, only unpolarized light with a transmission axis direction of 90° will pass through. polarized light passes through. Therefore, the mark can be detected as a dark spot.

In particular, among the above-mentioned detection methods, a method of detecting the mark as a bright point is preferable because it has good visibility and can be easily detected visually or mechanically.

Alternatively, the polarizing film 10 may be irradiated with linearly polarized light and the transmitted light may be detected. That is, if the polarizing film 10 is irradiated with linearly polarized light whose polarization direction is the transmission axis direction, almost all the light will be transmitted. On the other hand, the polarizing function is lost in the marked position, so linearly polarized light is transmitted less. Therefore, the mark can be detected by means of dark spot representation. On the contrary, linearly polarized light may be irradiated in the absorption axis direction of the polarizer film 10 and the transmitted light may be detected. Thereby, the mark can be detected by means of bright point representation. In addition, mark detection is usually performed in a state where the support films 12a and 12b are stacked (polarizing plate 100). However, since the support films 12a and 12b can transmit visible light, there is no problem.

Here, regarding the disappearance of the polarizing function, it is considered that since the polarizing film 10 is stretched PVA, it will soften if heat is applied around 150°C or higher, and the alignment regulation caused by the stretching will be lost. force. In the case of a dye-based polarizing plate modulated to gray, the aligned pigments exist in a random state, so the aligned portions appear darker to the naked eye.

Furthermore, in the case of the iodine-based polarizing plate, it is estimated that the color feeling changes (changes) due to sublimation due to heat and decomposition of the I ₅ ^-complex in the film (the presence ratio of the I ₃ ^-complex increases). into reddish brown). Also, when it changes to red, it is possible that the PVA itself changes and is colored. That is to say, it is possible that along with high heat, the acid produced by hydrolysis of the contained water may act as a catalyst with iodine, causing PVA to react into polyene.

In either case, the polarizing film 10 can be modified by irradiation with visible light and detected optically.

In addition, the detection of the mark can be carried out by human vision or mechanically by using a detection device.

[type of mark] Marks can be of the type shown in Figure 2, or can be formed simply by irradiating visible light lasers of the same intensity to a predetermined area.

Here, since various marks as shown in FIG. 2 can be used, a barcode, a QR code (two-dimensional barcode), etc. can be used as the mark. Such codes can contain information about defect locations. Therefore, a code can be written to any position on the polarizing plate 100, and the defect location can be grasped by reading the code. In this case, it is appropriate to specify the defective position in relation to the recording position of the code (mark).

10:Polarizing film 12a, 12b: Support film 14a, 14b: roller 16:Detection device 16a: Photographic installation 16b:Light irradiation device 18:Control device 20: Marking device 22, 24: Roller 100:Polarizing plate

FIG. 1 is a diagram showing the overall structure of a polarizing plate manufacturing system, which includes a marking device according to an embodiment. Figure 2 shows an example of the shape of marking marks produced by the marking device. Fig. 3 is a photograph showing the cross-section of the marking portion of Example 1 using visible light laser. Fig. 4 is a photograph showing the cross-section of the marking portion of Comparative Example 1 using infrared laser. Fig. 5 is a photograph showing the cross section of the marking portion of Comparative Example 3 using ultraviolet laser. FIG. 6 is a diagram showing the overall structure of a polarizing plate manufacturing system including the marking device of Modification 1. FIG. FIG. 7 is a diagram showing the overall structure of a polarizing plate manufacturing system including the marking device of Modification 2. FIG. FIG. 8 is a diagram illustrating changing the absorption amount by changing the polarization axis of the irradiated visible light laser. Fig. 9 is a diagram showing mark detection (bright spot detection) corresponding to changes in polarization characteristics. Fig. 10 is a diagram showing mark detection (dark spot detection) corresponding to changes in polarization characteristics.

Domestic storage information (please note in order of storage institution, date and number) without

Overseas storage information (please note in order of storage country, institution, date, and number) without

10:Polarizing film

12a, 12b: Support film

14a, 14b: roller

16:Detection device

16a: Photographic installation

16b:Light irradiation device

18:Control device

20: Marking device

22:Roller

100:Polarizing plate

Claims (9)

A polarizing plate manufacturing system that manufactures polarizing plates. The polarizing plate includes a polarizer film that polarizes visible light. The polarizing plate manufacturing system is provided with: a detection device that obtains an image signal of the polarizing plate; a control device that processes the image signal. , and detect defects in the polarizing plate; and, a marking device, which includes a laser source that emits visible light laser, and marks the defects in the polarizing plate; and, the marking device causes the polarizing film to absorb light from The visible light laser of the laser source changes the quality of the polarizer film and changes the optical characteristics of the changed part, thereby marking. The polarizing plate manufacturing system according to claim 1, wherein the polarizing plate includes a visible light-transmitting supporting film on at least one surface of the polarizing film, and the visible light laser transmits through the supporting film and is emitted by the supporting film. Absorbed by the polarizing film. The polarizing plate manufacturing system according to claim 2, wherein the polarizing film is modified by absorbing the visible light laser, and is marked by any one or more of the following methods: (i) color sense change, ( ii) Changes in polarization characteristics. The polarizing plate manufacturing system according to any one of claims 1 to 3, wherein the visible light laser is green light. The polarizing plate manufacturing system according to any one of claims 1 to 3, wherein the polarizing film contains a dichroic pigment of iodine or dye. The polarizing plate manufacturing system according to any one of claims 1 to 3, wherein the visible light laser is linearly polarized; the polarizing direction of the visible light laser can be set to be 0 to 0 with respect to the absorption axis direction of the polarizing plate. Change within the range of 90°. A marking method, which has the following steps: obtaining an image signal from a polarizing plate, the polarizing plate including a polarizer film that polarizes visible light; processing the image signal, and detecting defects in the polarizing plate; by including a device that emits a visible light laser A laser source marking device is used to mark the aforementioned defects in the polarizing plate; wherein the aforementioned marking device causes the aforementioned polarizer film to absorb the aforementioned visible light laser from the aforementioned laser source, so as to cause the aforementioned polarizer film to deteriorate and deteriorate the Changes in the optical properties of parts are used to mark them. A method for manufacturing a polarizing plate, which has the following steps: laminating a supporting film on at least one surface of the polarizing film to form a polarizing plate; using the marking method described in claim 7 to correct the aforementioned defects in the polarizing plate. Mark; and affix a protective film to the polarizing plate that has been marked. A polarizing plate, which is made of polarized light according to claim 8 The plate is manufactured by a method of manufacturing a plate, wherein the modified portion does not have polarizing properties, and the maximum depth and maximum ridge height based on the surface of the base material are each 5 μm or less.

Images