JP5545329B2 - Die coating method using a die coater - Google Patents

Description

  The present invention relates to a die coating method using a die coater.

  For example, a plastic substrate for an optical filter, a glass substrate for a liquid crystal display device, a glass substrate for a color filter, a predetermined layer such as a glass substrate for a color filter, or an ultraviolet absorbing layer for various substrates such as the substrate itself. As a method for obtaining an optical element by forming a layer structure, a coating method is used. The coating method uses a substrate as a material to be coated, and forms a coating film on the surface by applying paints made of various substances constituting the layer structure to be formed. Is carried out by forming a layer structure.

  In the field of optical filters and liquid crystal display devices, products are becoming highly functional and thin, and as a result, the layer structure formed in the optical filter and liquid crystal display device has a thickness while retaining the function of the layer structure. Thin, uniform and high dimensional accuracy is required, and when forming a coating film with a layer structure, it is strongly required to apply the coating material thinly and uniformly on the surface of the material to be coated. Has been.

  As a method of industrially forming such a coating film, a single-wafer coating is performed by supplying a material to be coated one by one to a coater (coating machine), applying a paint, and transporting it to the next process such as drying. Construction method is adopted. In forming a coating film on a material to be coated by the single-wafer coating method, spin coaters, bar coaters, and roll coaters have been widely used as coaters.

  Spin coaters are widely used in the semiconductor manufacturing field when forming a resist film to obtain a semiconductor wafer, or when applying a photoresist to a color filter or the like. The coating film is formed by the spin coater by setting the coating material on the spin coater, rotating the coating material, and dropping the paint on the center (center) of the rotating surface of the rotating coating material. Done. That is, the paint spreads on the surface of the material to be coated by the centrifugal force due to rotation, and a coating film can be formed on the material to be coated. The coating film obtained by the method using a spin coater can make the thickness of the coating film uniform over the entire range of the material to be coated by appropriately setting the composition of the coating. However, in order to form a coating film having a predetermined thickness, it is necessary to use a remarkably large amount of paint, and since it is required to prepare a large amount of paint, the manufacturing cost is likely to increase. In addition, in the method using spin coating, the paint may adhere to the corners and the back surface of the material to be coated, and the paint may scatter and adhere to the inner wall of the spin coater. The paint may be gelled or solidified and remain. As described above, in the method using spin coating, there is a problem that it is difficult to stably obtain a material to be coated having a certain quality in which the coating material does not adhere to the back surface. There is also a problem that it is difficult to maintain in a state.

  A roll coater is a method of transferring paint to a material to be coated through a roller such as a pick-up roll or an application roll. For a long strip-shaped material to be coated or a material to be wound in a roll shape, Thus, it becomes easy to apply a paint to form a coating film. However, in the method using a roll coater, the paint is sequentially sent from the paint pan (paint reservoir) to the pick-up roll and application roll, and after that stage, it is transferred to the material to be coated. The time during which the paint is exposed to the surrounding environment becomes longer. Usually, since the roll coater is disposed in an air atmosphere, the paint is affected by moisture and oxygen in the atmosphere, that is, the paint absorbs and oxidizes, and the quality of the paint is liable to deteriorate. In addition to this, there is a high possibility that foreign matter will be mixed into the paint from the outside, and this also deteriorates the quality of the paint. As a result, in the method using a roll coater, there is a problem that there is a greater possibility that the quality of the coating film is deteriorated.

  The method using a bar coater is a method in which a coating material is applied to a material to be coated using a bar in which a thin wire is wound around a rod. This method has a problem that since the wire wound around the rod is in contact with the material to be coated, streaks tend to enter the coating film, and it is difficult to obtain a thin and uniform coating film.

  In view of the problems in the conventional methods as described above, in recent years, a method using a die coater (die coating method) has been proposed in forming the coating film as described above. Specifically, the die coater is a color filter. It has been proposed to be applied to the manufacture of (for example, Patent Documents 1, 2, and 3). A method for manufacturing an optical compensation element using a die coater has also been proposed (Patent Document 4).

  By the way, the method of forming a layer or a film using a die coater has been widely adopted as an application for forming a thick coating film or a application for continuously applying a high-viscosity coating material to a material to be coated. Is the way.

  As a die coating method for forming a coating film on a material to be coated using a die coater, methods such as a curtain flow method, an extrusion method, and a bead method are known (Patent Documents 5, 6, and 7). Among these methods, the bead method is a state in which a paint reservoir called a paint bead is formed between the material to be coated by discharging the paint from the slit of the die provided on the die body of the die coater. In this method, the coating film is formed by pulling out the paint from the slit along with the traveling of the material to be coated that travels relatively with respect to the die body while maintaining a certain distance from the position of the slit. In the bead method, the coating film is continuously formed by discharging and supplying the same amount of paint that is consumed to form the coating film from the slit, so there is almost no waste of paint and the die head die Since the distance between the slit and the surface of the material to be coated is controlled to be constant, the thickness of the formed coating film can be made uniform with high accuracy (Patent Document 8).

  However, when a thin coating film such as a retardation layer formed on an optical element is continuously formed by a die coating method using a die coater, the paint is dried at the slit portion of the die. As a result, the solidified product of the component constituting the coating deposits, which causes coating unevenness on the coating film in a direction parallel to the direction of travel relative to the coating material of the die. .

  For such a problem that occurs when using a die coater, a method for suppressing the precipitation of solid matter by using a paint to which a drying inhibitor is added has been proposed (Patent Document 9).

JP-A-5-11105 JP-A-5-142407 JP-A-6-339656 JP-A-8-43625 U.S. Pat. No. 4,230,793 US Pat. No. 4,696,885 US Pat. No. 2,761,791 JP 2000-157907 A JP 2005-156739 A

  However, the invention described in Patent Document 9 has a problem that it cannot be applied when a material having poor solubility in a drying inhibitor is contained in the paint, and is inferior in versatility, and an optical element is continuously formed using a die coater. The problem of coating unevenness in the case of producing by the method has not been solved yet.

  The object of the present invention is to solve the problem in producing an optical element using a die coater as described above, and to form a thinner coating film over a wide range and with high accuracy while suppressing thickness unevenness. An object is to provide a die coating method.

The present invention relates to (1) a die coating method for forming a coating film on a surface of a substrate provided with a light-transmitting substrate by discharging a paint composed of a liquid crystal composition containing a polymerizable liquid crystal compound. Because
A die body configured to be able to move a base formed with a slot formed so as to be able to discharge paint and from a manifold extending toward the slit to form a passage for the paint. will be provided, and, a heating mechanism for heating the spinneret provided with a heat generating component, at a predetermined position around the slot being arranged heat-generating components in a predetermined portion including the periphery of the inner and manifolds and slots of the base using a die coater comprising comprises, from the position of the slit while heating the spinneret polymerizable liquid crystal compound and the heating temperature of the base is in a heating mechanism so as to make the phase transition temperature above the temperature at which the liquid crystal phase, on a substrate surface A die coating method characterized by discharging a paint to form a coating film ;
(2) A color filter having a light-transmitting base material and a colored layer that allows visible light having a predetermined wavelength to pass through is used as a base, and the color filter surface from the position of the slit while heating the base with a heating mechanism. The die coating method according to (1) above, characterized in that a coating film is formed by discharging a paint on the surface,
(3) A coating film is formed by discharging paint on the surface of the substrate while maintaining the temperature of the die at a predetermined temperature within a temperature range in which the polymerizable liquid crystal compound exhibits a liquid crystal phase. The die coating method according to (1) or (2) above,
(4) The die coater is provided with a temperature measuring mechanism for measuring the temperature of the die or paint at the slit position, and adjusting the heating of the die by the heating mechanism according to the temperature measured by the temperature measuring mechanism. A gist of the die coating method according to any one of the above (1) to (3), which is characterized.

  That is, in the die coating method of the present invention, an optical element is formed by forming a layer structure (retardation layer) in which a liquid crystal compound is aligned and fixed on a substrate provided with a light-transmitting substrate. can get. In this case, a liquid crystal material composition containing a liquid crystal compound is used as a coating material, and a coating film is formed by discharging the coating material onto the surface of the substrate while heating the die with a heating mechanism of a die coater. An optical element is formed by aligning and fixing the liquid crystal compound contained in to form a retardation layer.

  By the way, the liquid crystal material composition is usually constituted by dissolving a liquid crystal compound in a solvent. When such a liquid crystal material composition is used as a paint and an attempt is made to form a coating film on a substrate with a conventional die coater, the paint flows from the slot of the die coater to the slit at the tip of the lip portion to form the coating film. At the same time, the solvent volatilizes at the tip of the lip, and as the solvent volatilizes, a solid substance of the liquid crystal compound may precipitate at the tip of the lip and adhere to the die. In such a case, in a conventional die coater, the solid matter of the liquid crystal compound deposited on the tip of the lip part may cause streaks on the surface of the coating film when the coating film is formed by the die coater. There is a problem.

  In this respect, in the die coating method of the present invention, it has been clarified that by heating the die of the die body, the precipitation of the liquid crystal compound is suppressed, and the solid matter of the liquid crystal compound with respect to the die can be suppressed. In the present invention, the heating temperature of the die is desirably equal to or higher than the phase transition temperature at which a liquid crystal compound such as a crosslinkable liquid crystal compound contained in the liquid crystal material composition becomes a liquid crystal phase.

  If the die is heated, the volatilization rate of the solvent may increase. However, the volatilization of the solvent does not proceed completely instantaneously but gradually (progresses slowly), and the solvent is heated with the heating of the die. Since the compatibility of the liquid crystal compound and the liquid crystal compound is also increasing, it is assumed that the progress of volatilization of the solvent and the improvement of the compatibility of the solvent and the liquid crystal compound occur simultaneously in the vicinity of the lip portion of the die. When the coating film is formed by the die coater, the paint is discharged intermittently from the slit toward the substrate, so that the paint is solidified from the liquid crystal material composition by the progress of the volatilization of the solvent. It is thought that the object reaches the substrate from the slit before the object is deposited on the lip portion.

  Therefore, in the die coating method of the present invention, when heating the die body die, it is more preferable to control the heating temperature within a range in which the volatilization rate of the solvent does not become excessively high (so as not to be extremely high). . Considering this point, the base is heated to a predetermined temperature in the temperature range indicating the temperature at which the liquid crystal compound forms a liquid crystal phase, and the temperature of the base does not deviate from the temperature range. Is preferably maintained within the "temperature range in which the liquid crystal compound forms a liquid crystal phase", since it is possible to effectively suppress the precipitation of the solid material of the liquid crystal compound while suppressing the volatilization of the solvent. .

  In the die coater used in the die coating method of the present invention, a temperature measuring mechanism may be provided. In this case, the coating film is discharged onto the substrate to form a coating film while keeping the temperature of the coating within a predetermined temperature range. It becomes easy.

  According to the die coating method of the present invention, the coating film can be formed by discharging the coating material onto the surface of the substrate while heating the die with the heating mechanism of the die coater while heating the coating material to a predetermined temperature. According to this die coating method, solid matter that tends to occur at the slit position is suppressed, and unevenness (such as streak) is suppressed in a direction parallel to the direction of travel relative to the base of the die. It is possible to form a coating film having a smooth surface with good yield.

(A) It is a schematic plan view explaining the example of the nozzle | cap | die for die-coaters used for the die-coating method of this invention. (B) It is II sectional drawing of FIG. 1 (A). It is the schematic explaining one Example of the die coater used for the die coating method of this invention. It is the schematic explaining one Example of the die coater used for the die coating method of this invention. It is a top view for demonstrating formation of the coating film using the die coater used for the die coating method of this invention. (A) It is sectional drawing in order to demonstrate the other Example of a nozzle | cap | die used for the die coating method of this invention. (B) It is sectional drawing for demonstrating the other Example of a nozzle | cap | die used for the die coating method of this invention. (C) It is sectional drawing for demonstrating the other Example of a nozzle | cap | die used for the die-coating method of this invention. (D) It is sectional drawing for demonstrating the other Example of the nozzle | cap | die used for the die coating method of this invention. It is a schematic sectional drawing for demonstrating the optical element (1st form) obtained using the die-coater used for the die coating method of this invention. It is a schematic sectional drawing for demonstrating the optical element (2nd form) obtained using the die coater used for the die coating method of this invention. It is a schematic plan view for demonstrating the optical element (2nd form) obtained using the die coater used for the die coating method of this invention. It is a schematic exploded perspective view for demonstrating the liquid crystal display incorporating the optical element obtained using the die coater used for the die coating method of this invention.

<Die coater and die coater base>
A die coater 1 used in the die coating method of the present invention includes a die body 2 provided with a base 4 and a heating mechanism 3 (FIGS. 1A, 1B, 2, and 4). .

  As shown in FIGS. 1 (A) and 1 (B), the die 4 of the die body 2 is integrally configured by combining the die constituting members 5 and 6. Inside the base 4, a space part is formed in the gap between the facing base constituent members 5, 6 that opens to the outside to form a manifold 7. The base 4 is a portion that is narrowly opened from the manifold 7 to the outside, and a portion extending in the longitudinal direction of the base 4 is formed as a slit 8, and further, a space extending from the manifold 7 toward the slit 8 is formed. Slot 9. The outer shape of the base 4 is narrow in the direction from the manifold 7 toward the slit 8, and its tip is a lip portion 20, and the slit 8 is formed at the position of the lip portion 20. The base 4 has a paint supply hole 10 communicating with the manifold 7 at a predetermined position (for example, the center) in the width direction (longitudinal direction) of the base component member 5.

  The paint supply hole 10 is connected to the coating liquid reservoir 11 by a pipe 12. The pipe 12 is provided with a pump 13, and this pump 13 feeds the paint 14 stored in the paint reservoir 11 into the manifold 7 through the paint supply hole 10 of the die body 2. As the pump 13, a commonly used pump such as a gear pump, a diaphragm pump, or a piston pump can be appropriately used. Further, the flow rate of the paint 14 by the pump 13 (the supply speed from the paint reservoir 11 to the manifold 7) may be appropriately controlled. For example, a valve (not shown) is connected to the pipe 12, and the paint by the pump 13 by the valve is used. You may be comprised so that 14 flow volume may be controlled.

  As the base components 5 and 6, stainless steel is usually employed from the viewpoints of rigidity, accuracy, and heat transfer. Since the base components 5 and 6 are made of stainless steel, the clearance (D in FIG. 4) between the tip of the lip 20 and the surface of the base body 30 can be uniformly held in the longitudinal direction of the base 4. It becomes easy to keep the temperature distribution of the entire base 4 constant.

  In the base 4, the width of the slit 8 (K (the distance between the base constituent members 5 and 6 at the tip position of the lip portion 20) in FIG. 1B) is adjusted to a predetermined value in the range of 10 μm to 500 μm. When the width (slit interval) K of the slit 8 is less than 10 μm, the pressure loss of the paint 14 discharge is large, the pump 13 is overloaded, or the response of the paint 14 discharge is delayed with respect to the movement of the pump 13. It is not preferable as work. If the slit interval K exceeds 500 μm, it is difficult to ensure the uniformity of the discharge amount of the paint 14 in the longitudinal direction of the base 4. The clearance, which is the distance between the base 30 and the tip surface of the lip 20, is equal to or less than 100 times the thickness of the coating film 21 in order to obtain the coating film 21 having a uniform thickness by applying the coating 14 as uniformly as possible. Preferably, it is set to a predetermined value in the range of 10 μm to 500 μm. If the clearance is less than 10 μm, it may be difficult to avoid contact between the base body 30 and the tip of the lip 20 due to the undulation of the base body 30 and the accuracy of the mechanism that causes the base body 30 and the base 4 to travel relatively.

  The heating mechanism 3 includes a heat generating component 15 and a control device 16 that controls the heat generation state of the heat generating component 15. Specifically, as the heating mechanism 3, a heater such as an infrared heater can be specifically mentioned.

  In the die coater 1, the heat generating component 15 is provided at a predetermined position around the slot 9 in the base component members 5 and 6 constituting the base 4 of the die body 2. In the example of FIG. 1, the heat generating component 15 is installed in a portion of the periphery of the slot 9 closer to the lip portion 20 than the manifold 7.

  In the example of the die coater 1 shown in FIG. 1, the lip portion 20 of the base 4 is efficiently heated by the heating mechanism 20, and the viscosity and the surface of the paint 14 immediately before being applied to the substrate 30. The tension can be adjusted, and a uniform coating film 21 can be formed.

  In addition, if the heating mechanism 3 is configured by disposing the heat generating component 15 only around the lip portion 20, the temperature of the paint 14 can be adjusted (FIG. 5A). Further, the heating mechanism 3 may be configured such that the heat generating component 15 faces the slot 9 of the base 4 (FIG. 5C) or is arranged on the outer surface of the base 4 (FIG. 5). 5 (D)). However, in consideration of the discharge stability of the paint 14, it is preferable that the heating mechanism 3 is provided with the heat generating component 15 so that the entire periphery of the slot 8 forming a passage through which the paint 14 is sent is heated. It is preferable to arrange the heat generating component 15 not only in the periphery of the slot 8 but also in the entire portion including the periphery of the manifold 7 because the entire base 4 can be easily heated.

  The heating of the entire base 4 by the heating mechanism 3 can be specifically realized by providing the heat generating component 15 around the manifold 7 and the slot 8 of the base 4 (FIG. 5B). In this case, the paint 14 has a more uniform viscosity and surface tension within the manifold 7 inside the base 4, moves inside the slot 8 while maintaining the state, and is discharged from the slit 8 onto the substrate surface. Thus, the paint can be more stably applied to the substrate.

  The heat generating component 15 of the heating mechanism 3 with respect to the base 4 is arranged, for example, by forming a hole in a portion where the heat generating component 15 is to be disposed in the base 4 or by cutting to form a space portion. This can be implemented by securing a space portion in which the heat generating component 15 is disposed and inserting the heat generating component 15 into the space portion.

  The die coater 1 is usually provided with a drive mechanism (not shown). The drive mechanism is a mechanism that moves the die body 2 relative to the surface of the base body 30, and a conventionally known mechanism can be appropriately used. For example, as a drive mechanism, the movement of the die body 2 with respect to the base body is a mechanism configured to move the die body 2 while fixing the position of the base body, and the position of the base body is moved while fixing the die body 2. Examples of such a mechanism include a mechanism configured to move both the die body 2 and the substrate relative to each other.

  The mechanism for fixing the position of the base body 30 while moving the die body 2 is provided with a mounting table, a rail is installed above the mounting table at a predetermined distance from the surface of the mounting table, and slides with respect to the rail. It can be realized by a mechanism formed by arranging a slider (sliding device) so as to be movable and fixing the die body 2 to the slider.

  The mechanism for moving the position of the base body 30 while fixing the die body 2 is arranged such that the base body is arranged on the conveyor, the die body is fixed at a predetermined position above the base body, and the base body is moved as the conveyor is driven. A mechanism configured, or a mechanism configured such that a die body is opposed to a predetermined roller and a surface of the roller, and the base is rotated and moved around the axis of the roller through the predetermined roller. , Etc., can be specifically realized.

  In the example of the die coater 1 shown in FIG. 1, the case where a mechanism including the pump 13 and the pipe 12 is provided as means for supplying the paint 14 toward the die body 2 (paint supply means) is described. The present invention is not limited to this example, and may be a so-called compressed air means such as a means configured to push the paint 14 from the coating liquid reservoir 11 through the pipe 12 toward the paint supply hole 10 with compressed air.

  The die coater 1 is preferably provided with a temperature measuring mechanism 17 having a sensor 18 for detecting temperature, as shown in FIG. In the example of FIG. 3, the temperature measuring mechanism 17 is provided in the die coater 1 with the sensor 18 facing the slit 8 of the base 4 with a gap between the sensor 18 and the base 4. In this case, the sensor 18 measures the temperature of the base or the paint at the position of the slit 8, and an infrared temperature sensor can be specifically mentioned.

  The temperature measuring mechanism 17 is not limited to the case where the sensor 18 is provided outside the base 4 as described above, and the sensor 18 is disposed inside the base 4, a portion facing the slot 9 formed inside the base 4, the base 4. The die coater 1 may be disposed in contact with at least one of the outer surfaces of the lip portion 20. In that case, the sensor 18 can include a sensor that measures the temperature of the slit 8 by directly measuring the temperature of the base 4, and specifically includes a thermocouple. A type in which a thermocouple is attached on the interface with the space formed inside the base 4 is desirable because the temperature of the paint 14 flowing toward the slit 9 in the manifold 7 inside the base 4 can be accurately measured.

  By providing the temperature measuring mechanism 17 in this way, the die coater 1 can detect the temperature of the base 4 and the paint 14 and can adjust the heating of the base 4 by the heating mechanism 3 according to the temperature. The temperature of the paint 14 can be adjusted.

  The die coater 1 has an upstream side (left side in the drawing of FIG. 4) or a downstream side with respect to the direction of movement of the base 4 relative to the base body 30 with respect to the paint 14 held between the tip surface of the lip 20 and the base body 30. A mechanism (not shown) for applying pressure or reduced pressure from the right side of the sheet of FIG. 4 is appropriately allowed to be added. This mechanism facilitates adjustment (extrusion suction adjustment) between when the paint is pushed out of the die coater 1 from the tip of the lip portion 20 of the die coater 1 and when the paint is sucked into the die coater 1. . In die coating, in order to prevent coating unevenness and to obtain a coating film with a uniform film thickness, a liquid pool (meniscus) of paint is created at the tip of the lip immediately before coating, and after the coating film is formed, The liquid reservoir is pulled back into the die coater. Therefore, according to the mechanism for facilitating the adjustment of the extrusion suction as described above, a coating liquid reservoir (meniscus) is formed from the tip of the lip portion 20 of the die coater 1 immediately before the coating film is formed on the substrate 30. The paint constituting the meniscus can be easily pulled back into the die coater 1 after the coating film is formed.

<Die coating method>
Next, a method for forming a coating film by applying a coating on the surface of the substrate 30 by the die coater 1 provided with the die coater base 4 (die coating method) will be described in detail with reference to FIG. FIG. 4 is an explanatory diagram for explaining a state in which the die coating method is performed. The case where the die coater 1 is a slit die coater will be described as an example.

  First, as shown in FIG. 4, the die coater 1 and the substrate 30 are arranged facing each other. At this time, in the die coater 1, the slit 8 formed at the tip of the lip portion 20 of the base 4 is directed to the surface of the base body 30 on which the coating film 21 is to be formed.

  Next, the die coater 1 sends the paint 14 stored in the paint storage unit 11 to the manifold 7 through the pipe 12 and the paint supply hole 10 of the die body 2 by the pump 13. In the die coater 1, the paint 14 fed into the manifold 7 is discharged onto the surface of the substrate 30 from the slit 8 of the lip portion 20 via the slot 8.

  Here, in the die coater 1, the control device 16 constituting the heating mechanism 3 appropriately operates the heat generating component 15 provided in the base 4, and the base 4 of the die body 2 is heated. Here, since the heat generating component 15 is disposed around the slot 9 and the slit 8 in the base 4, the temperature of the base 4 heated by the heating mechanism 3 and the temperature of the paint 14 flowing through the slot 8 and the slit 9 are They are the same or roughly the same. Accordingly, in the die coater 1, when the die 4 is heated, the paint moving through the slot 9 toward the slit 8 is heated, so that the paint 14 is heated and discharged from the slit 8 onto the surface of the substrate 30. Is done. The operation timing of the heating mechanism 3 can be appropriately set according to various conditions such as the temperature atmosphere around the die coater 1 as well as the material and properties of the paint and the substrate.

  On the other hand, the die coater 1 appropriately moves the die body 2 relative to the substrate surface in accordance with the discharge of the paint 14 onto the substrate 30 surface. The movement of the die body 2 relative to the base body is not only by moving the die body 2 while fixing the position of the base body 30, but also by moving the position of the base body 30 while fixing the die body 2. It can be realized by both. In addition, moving the position of the base body 30 while fixing the die body 2 is performed by moving the base body 30 in parallel with a predetermined plane or by rotating the base body 30 around a predetermined axis. , Etc., can be specifically realized.

  In this way, the paint 14 is discharged onto the surface of the base 30 from the position of the slit 8 of the die 4 of the die coater 1, and the die body 2 and the surface of the base 30 move relative to each other. A coating film 21 is formed. At this time, the discharge speed of the paint 14 and the relative moving speed between the die body 2 and the surface of the base body 30 are appropriately set according to conditions such as the properties of the paint 14 and the thickness of the coating film 21.

  In forming the coating film 21 using the coating material 14 in the die coater 1, after the coating material 14 is first ejected from the slit 8, the coating material 14 is deposited on the surface of the substrate 1 and the deposited coating material 14. Time (Tr) until the amount (Ws) of the coating reaches the amount (Wr) (amount of coating material 14 constituting the meniscus (amount of meniscus)) required to obtain the first desired thickness of the coating film 21 Is preferably as short as possible (time until a meniscus is formed), and then the amount of meniscus (Wr) is preferably maintained constant. In consideration of such points, the discharge amount (discharge speed) per unit time of the paint 14 depends on the meniscus amount (Wr) corresponding to the thickness of the coating film 21 to be formed on the surface of the substrate 31. Is set as appropriate. That is, the discharge speed is increased (time Tr is made as small as possible) from the start of coating until the discharged amount (Ws) of the paint 14 reaches Wr, and after the discharge amount of the paint 14 exceeds Ws (time Tr) After the elapse of time, it is preferable that the paint 14 is discharged onto the substrate 1 while maintaining the value of Wr. When the relative movement between the die body 2 and the surface of the base body 30 progresses in a state where Ws does not reach Wr, it is several centimeters in the moving direction of the die body 2 from the coating start position at which the paint starts to be applied to the base body. The film thickness of the coating film is insufficient in the range up to the position. Further, if the time Tr is too long, there is a possibility that uneven application occurs.

  The die coating method may be performed using the die coater 1 including the temperature measuring mechanism 17 as described above. In this case, the die coating method detects the temperature of the base 4 by the temperature measuring mechanism 17. The coating film 21 may be formed while adjusting the heating of the base 4 by the heating mechanism 3 according to the temperature. Specifically, in the die coater 1, the temperature measuring mechanism 17 detects the temperature at the position of the slit 8 of the base 4 at a predetermined time interval, and when the detected temperature is out of the predetermined temperature range, the heating mechanism 3 controls the heat generation by the heat generating component 15, and when the detected temperature falls within a predetermined temperature range, the control unit 16 of the heating mechanism 3 causes the heat generating component 15 to generate heat. As a result, the die coater 1 can maintain the temperature of the paint at the position of the slit 8 within a predetermined temperature range.

  The die coating method of the present invention can be suitably used when it is necessary to form a precise coating film by applying a paint to a substrate. In this regard, regarding the optical element, it is necessary to form a precise coating film on the substrate because the optical element needs to exhibit an optical function. In particular, when a liquid crystal composition containing a liquid crystal compound is applied to a substrate to form a coating film, and the coating film is used as a retardation layer to obtain an optical element, the coating film Very precise dimensional accuracy is required, and it is also necessary to suppress the precipitation of the liquid crystal compound to a high degree during the production of the coating film. Therefore, the die coating method of the present invention exhibits a particularly remarkable effect when producing an optical element having such a retardation layer.

  Accordingly, the case where the die coater 1 is used and the coating film 21 is formed on the substrate 30 using the liquid crystal composition containing the liquid crystal compound as the coating material 14 to form an optical element will be described in detail below.

<Optical element obtained using a die coater (first embodiment)>
The optical element 32 formed using the die coater 1 is formed by forming the retardation layer 33 directly or indirectly on the surface of the substrate 30 (first-type optical element) (FIG. 6). In FIG. 6, the optical element 32 is shown only when the retardation layer 33 is formed directly on the substrate 30.

  A base material 31 having optical transparency is used for the base body 30. This base material 31 is comprised from a base material forming material.

  The base material forming material is preferably configured to be optically isotropic. As the substrate forming material, plate-like bodies made of various materials can be selected as appropriate in addition to a glass material such as a glass substrate. Specifically, it may be a plastic substrate made of polycarbonate, polymethyl methacrylate, polyethylene terephthalate, triacetyl cellulose or the like, and further, such as polyethersulfone, polysulfone, polypropylene, polyimide, polyamideimide, polyetherketone, etc. A film can also be used. However, particularly when the retardation control member is used for a liquid crystal display, the substrate forming material is preferably alkali-free glass.

  The retardation layer 33 travels through the retardation layer 33 in the thickness direction, and enters the retardation layer 33 with respect to light that is incident from one surface and emitted from the other surface. This is a layer having a function of birefringent light.

  The phase difference layer 33 has a refractive index nx, ny, nz that satisfies nx <nz and ny <nz, and nx and ny are equal or almost equal to each other, so-called “+ C plate” (positive A layer functioning as a C plate), satisfying nz <nx and nz <ny, and nx and ny are equal or almost equal, and a layer functioning as a so-called “−C plate” (negative C plate), ny = nz <nx or nx = nz <ny, and a layer that functions as a so-called “+ A plate” (positive A plate) can be given. However, with respect to the refractive index of the retardation layer 33, the z-axis is taken in the thickness direction of the retardation layer 4 (normal direction of the retardation layer 4), and the in-plane direction of the retardation layer 4 (thickness direction of the retardation layer 4). When the xyz space is assumed so that the x axis and the y axis are orthogonal to each other in the in-plane direction (the direction parallel to the plane) of a plane (plane) having a normal line to the x axis, the y axis The refractive indexes of light in the z-axis direction are defined as nx, ny, and nz, respectively.

  The retardation layer 33 forms a polymer structure formed by polymerizing liquid crystal molecules having a polymerizable functional group in the molecular structure (referred to as polymerizable liquid crystal molecules).

  The retardation layer 33 is formed in a state where liquid crystal molecules forming a liquid crystal compound are aligned in a predetermined direction. Liquid crystal molecules have an optical axis according to their molecular structure, and have birefringence characteristics that are determined according to the state of the optical axis. By aligning and fixing liquid crystal molecules in a specific direction, the orientation of the liquid crystal molecules The retardation layer 33 is formed as a layer having birefringence characteristics according to the state (for example, a layer having a function of a positive C plate, a layer having a function of a negative C plate, a layer having a function of a positive A plate). The

<When the retardation layer 33 is a layer having a function of a positive C plate>
The liquid crystal compound constituting the retardation layer 33 can be appropriately selected from those capable of making the retardation layer 33 a layer having a function of a positive C plate. As such a liquid crystal compound, a liquid crystal compound capable of forming a nematic liquid crystal phase or a liquid crystal compound capable of forming a smectic liquid crystal phase can be used.

  The liquid crystal compound constituting the retardation layer 33 is preferably a polymerizable liquid crystal compound having an unsaturated double bond as a polymerizable functional group in the molecular structure of the liquid crystal molecules forming the liquid crystal compound. In addition, as the polymerizable liquid crystal compound, a polymerizable liquid crystal compound (referred to as a crosslinkable liquid crystal compound or a crosslinkable liquid crystal compound) capable of undergoing a crosslink polymerization reaction in a liquid crystal phase is more preferably used from the viewpoint of heat resistance. As the liquid crystal compound, those having an unsaturated double bond at both ends of the molecular structure (having two or more unsaturated double bonds) are preferable. When the retardation layer 33 is formed using a crosslinked polymerizable liquid crystal compound, a crosslinked polymer structure is formed in the retardation layer 33 by cross-linking liquid crystal molecules forming the crosslinked polymerizable liquid crystal compound. Will be.

  Examples of the crosslinkable liquid crystal compound used for obtaining the retardation layer 33 include a nematic liquid crystal compound having a crosslinkability (crosslinkable nematic liquid crystal compound). Examples of the crosslinkable nematic liquid crystal compound include monomers, oligomers and polymers having at least one polymerizable group such as a (meth) acryloyl group, an epoxy group, an octacene group and an isocyanate group in one molecule. As such a crosslinkable liquid crystal compound, more specifically, one compound (compound (I)) or two or more compounds represented by the following general formula (1) Mixture, one compound (compound (II)) or a mixture of two or more compounds represented by general formula (2) shown in the following chemical formula 2 (compound (III)) 1) or a mixture of two or more thereof, or a combination thereof.

In the general formula (1) shown in Chemical formula 1, each of R ¹ and R ² represents hydrogen or a methyl group, but at least R ¹ is required to broaden the temperature range in which the crosslinkable liquid crystal compound exhibits a liquid crystal phase. And R ² is preferably hydrogen, more preferably both. X in the general formula (1) and Y in the general formula (2) may be any of hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group. Is preferably a chlorine or methyl group. Moreover, a and b which show the chain length of the alkylene group between the (meth) acryloyloxy group and aromatic ring of the both ends of the molecular chain of General formula (1), and d and e in General formula (2) are respectively 1 Although an arbitrary integer can be taken in the range of -12, it is preferable that it is the range of 4-10, and it is further more preferable that it is the range of 6-9. The compound (I) of the general formula (1) in which a = b = 0 or the compound (II) of the general formula (2) in which d = e = 0 has poor stability and is easily hydrolyzed, and the compound (I) or (II) itself has high crystallinity. Further, the compound (I) of the general formula (1) or the compound (II) of the general formula (2) in which a and b, or d and e are each 13 or more, has a low isotropic phase transition temperature (TI). For these reasons, both of these compounds have a narrow temperature range in which the liquid crystal compound stably exhibits liquid crystallinity (temperature range for maintaining the liquid crystal phase), and are not preferable for use in the retardation layer 33.

  As the crosslinkable liquid crystal compound, in the above-mentioned chemical formula 1, chemical formula 2, chemical formula 3, and chemical formula 4, the monomer of the liquid crystal (polymerizable liquid crystal) having polymerizability is exemplified, but the oligomer of the polymerizable liquid crystal, the polymer of the polymerizable liquid crystal, etc. These may also be used, and for these, well-known ones such as the above-mentioned oligomers, chemicals 2, chemicals 3, chemicals 4 and the like can be appropriately selected and used.

  In the retardation layer 33, the degree of polymerization of liquid crystal molecules (in the case of crosslinkable liquid crystal molecules, the degree of crosslink polymerization) is preferably about 80 or more, and more preferably about 90 or more. If the degree of polymerization of the liquid crystal molecules constituting the retardation layer 4 is less than 80, there is a possibility that the uniform orientation cannot be sufficiently maintained. The degree of polymerization and the degree of cross-linking polymerization indicate the proportion of the polymerizable functional group of the liquid crystal molecule consumed in the polymerization reaction of the liquid crystal molecule.

  Using the coating material using the liquid crystal compound as described above and the die coater 1, the retardation layer 33 is positively birefringent anisotropic so that its optical axis faces the z-axis direction in the xyz space assumed above. The liquid crystal molecules are aligned and fixed to form a layer having an optical compensation function as a positive C plate and formed on the substrate 31.

  Using the die coater 1, the retardation layer 33 can be specifically formed as follows.

<Adjustment of paint>
First, as the coating material 14, a composition liquid (liquid crystal material composition liquid) containing a liquid crystal compound constituting the retardation layer 33 is adjusted. That is, a liquid crystal material composition liquid is prepared by blending a liquid crystal compound such as the above-described compound (I), compound (II), and compound (III) constituting the retardation layer 33 with a solvent. If necessary, the liquid crystal material composition liquid may be appropriately added with an additive including an alignment aid for aligning the liquid crystal molecules constituting the liquid crystal compound vertically (sometimes referred to as a vertical alignment aid).

  When an additive is added in the liquid crystal material composition liquid, the liquid crystal compound should be contained so as to be 70% by weight (compared to the compound equivalent) or more, preferably 75% by weight (compared to the compound equivalent). Is preferred. The liquid crystal property of the liquid crystal compound is improved by setting the addition amount to 70% by weight (compared to the equivalent of the compound), and the occurrence of misalignment of the crosslinkable liquid crystal molecules forming the liquid crystal compound in the retardation layer 33 can be ignored. Can be reduced. When the blending amount of the liquid crystal compound in the liquid crystal material composition liquid is 70% by weight (vs. the compound equivalent value) or more, there is little possibility of causing a problem from the viewpoint of the orientation of liquid crystal molecules. The addition amount of the liquid crystal compound can be appropriately determined based on the balance with the amount of additives other than the liquid crystal compound to be added. In addition, the value in terms of the compound is 100, which is the total weight of the liquid crystal material composition liquid minus the weight of the solvent (that is, the total weight of the mixture of liquid crystal compounds and additives before being dissolved or suspended in the solvent). In this case, the weight percentage of each compound (solid material) to be compounded as a component (compound component) constituting the liquid crystal material composition liquid is shown.

  The solvent used for adjusting the liquid crystal material composition liquid is not particularly limited as long as it can dissolve the liquid crystal compound constituting the retardation layer 33, and specifically, benzene, toluene, xylene, n-butyl. Hydrocarbons such as benzene, diethylbenzene and tetralin, ethers such as methoxybenzene, 1,2-dimethoxybenzene and diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and 2,4-pentanedione, acetic acid Esters such as ethyl, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone, 2-pyrrolidone, N-methyl-2-pi Amide solvents such as lidone, dimethylformamide, dimethylacetamide, halogen solvents such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, tritrichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, t-butyl alcohol, diacetone alcohol, One or more of alcohols such as glycerin, monoacetin, ethylene glycol, triethylene glycol, hexylene glycol, ethylene glycol monomethyl ether, ethyl cellosolve, butyl cellosolve, phenols such as phenol, parachlorophenol, etc. It can be used. If only one type of solvent is used, the solubility of compound components such as crosslinkable liquid crystal compounds will be insufficient, or the material that will be the counterpart of application when applying liquid crystal material composition liquid In the case where there is a risk of the material being attacked, these disadvantages can be avoided by using a mixture of two or more solvents. Among the above-mentioned solvents, hydrocarbon solvents and glycol monoether acetate solvents are preferable as the sole solvent, and preferable solvents are ethers or ketones and glycols mixed. It is a mixed solvent. The concentration of the compound component of the liquid crystal material composition solution varies depending on the solubility of the compound component used in the liquid crystal material composition in the solvent and the layer thickness desired for the retardation layer, but is usually 1 to 60% by weight, Preferably it is the range of 3 to 40 weight%.

  Specific examples of the vertical alignment aid contained in the liquid crystal material composition liquid include polyimide, surfactants, and coupling agents.

  When polyimide is used as the vertical alignment aid, the polyimide has a long-chain alkyl group, and the thickness of the retardation layer 4 formed on the retardation control member can be selected within a wide range. preferable. When the vertical alignment aid is polyimide, specific examples of the polyimide include SE-7511 and SE-1211 manufactured by Nissan Chemical Industries, and JALS-2021-R2 manufactured by JSR.

  When a surfactant is used as the vertical alignment aid, the surfactant may be any as long as it can vertically align the polymerizable liquid crystal molecules, but the liquid crystal compound is converted into a liquid crystal phase when the retardation layer is formed. Since it is necessary to heat to the transition temperature, it is required to have heat resistance to such an extent that it is not decomposed even at the transition temperature to the liquid crystal phase. In addition, since the liquid crystal molecules may be dissolved in an organic solvent when the retardation layer 4 is formed, in such a case, it is required that the affinity with the organic solvent for dissolving the liquid crystal molecules is good. Is done. As long as these requirements are met, the surfactant is not limited to nonionic, cationic, anionic, etc., and only one type of surfactant may be used, or a plurality of types of surfactants may be used. An agent may be used in combination.

  When a coupling agent is used as the vertical alignment aid, specific examples of the coupling agent include n-octyltrimethoxysilane, n-octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, and n-dodecyl. Silane coupling agents obtained by hydrolyzing silane compounds such as trimethoxysilane, n-dodecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, amino group-containing silane coupling agents, fluorine group-containing silane cups A ring agent etc. can be illustrated. A plurality of these coupling agents may be selected and added to the liquid crystal material composition.

  Moreover, a photoinitiator and a sensitizer are added to a liquid-crystal material composition as needed.

  Examples of the photopolymerization initiator include benzyl (or bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-benzoyl-4′methyldiphenyl sulfide, benzylmethyl ketal, dimethylamino Methylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl-1- (4 -(Methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4-dodecylphenyl) 2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy- 2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythiosantone, etc. be able to.

  When a photoinitiator is mix | blended with a liquid-crystal material composition, the compounding quantity of a photoinitiator is 0.01 to 10 weight%. In addition, it is preferable that the compounding quantity of a photoinitiator is a grade which does not impair the orientation of a polymerizable liquid crystal molecule as much as possible, and it is preferable that it is 0.1 to 7 weight% in consideration of this point. More preferably, it is 5 to 5% by weight.

  Further, when a sensitizer is blended in the liquid crystal material composition, the blending amount of the sensitizer can be appropriately selected within a range that does not significantly impair the orientation of the polymerizable liquid crystal molecules, specifically 0.01 to 1 weight. % Is selected. Only one type of photopolymerization initiator and sensitizer may be used, or two or more types may be used in combination.

  When the liquid crystal material composition that forms the coating material 14 is thus adjusted, the liquid crystal material composition is then applied onto the base material 31 as the base body 30.

<Coating of liquid crystal material composition liquid>
In coating, the liquid crystal material composition forming the coating material 14 is charged into the coating material storage unit 11 of the die coater 1. At this time, it is preferable that the coating material storage unit 11 is sealed so that dust does not enter from the outside.

  Furthermore, a base material 31 as the base body 30 is disposed at a position facing the slit 8 of the die coater 1. At this time, the slit 8 of the die coater 1 faces a predetermined position in the surface where the retardation layer 33 is to be formed on the base material 31. Here, the predetermined position is a position (coating start position) determined as a position where the coating of the retardation layer 33 should be started on the base material 31.

  Thus, when the base material 31 is set on the die coater 1, the die coater 1 operates the pump 13 to move the liquid crystal material composition as the paint 14 from the paint reservoir 11 in the same manner as the die coating method using the die coat 1 described above. It sends out toward the base 4 of the die body 2 (FIG. 4). Then, the paint 14 is discharged onto the surface of the base material 31 through the base 4 through the manifold 7, the slot 9 and the slit 8 in this order. At that time, in the die coater 1, the base 4 is heated by the operation of the heating mechanism 3, and the heat is transmitted to the liquid crystal material composition to heat the liquid crystal material composition to a predetermined temperature. That is, the liquid crystal material composition is discharged to the surface of the base material 31 from the slit 8 while being heated to a predetermined temperature.

  In addition, about the heating of a liquid-crystal material composition, the die-coater 1 can maintain the temperature while heating the nozzle | cap | die 4 to the predetermined temperature in the temperature range in which a liquid crystal compound shows a liquid crystal phase with the heating mechanism 3. preferable. Thereby, the heating temperature of the liquid crystal material composition is heated to a predetermined temperature similar to that of the base 4, that is, a predetermined temperature within a temperature range showing a liquid crystal phase, and can maintain that state.

  Further, when the die coater 1 including the temperature measuring mechanism 17 is used, the temperature of the base 4 is detected, and the heating of the base 4 by the heating mechanism 3 is adjusted according to the temperature. Thereby, the die coater 1 maintains the temperature of the liquid crystal material composition at the position of the slit 8 within a predetermined temperature range.

  The die coater 1 appropriately moves the die body 2 relative to the surface of the base material 31 according to the discharge of the liquid crystal material composition forming the coating material 14. Along with this, a coating film is formed on the surface of the substrate 31. That is, the liquid crystal material composition is applied onto the base material 31 through the slits 8 of the base 4 while the base material 31 is sent relative to the base 4 to form a coating film. Then, the base material 31 is moved relative to the base 4 until the slit 8 of the base 4 faces a position (position where the coating is scheduled to be finished) determined as a position where the formation of the coating film on the surface of the base material 31 is finished. When sent, the operation of the pump 13 stops and the die coater 1 finishes discharging the liquid crystal material composition. At this time, a coating film (liquid crystal coating film) is formed in a predetermined region of the base material 31 (a region from the coating start position to the coating end planned position in the relative movement direction of the base 4 and the base material 31). A state is formed.

  When the liquid crystal coating film is formed on the surface of the base substrate 31, the laminate of the base material 31 and the liquid crystal coating film is dried (drying process), and the solvent in the liquid crystal coating film is distilled off. The drying step may be performed under reduced pressure by reduced pressure drying or under atmospheric pressure, but may be performed under atmospheric pressure, but may be naturally dried under atmospheric pressure to uniformly impart orientation to liquid crystal molecules. This is preferable.

  The polymerizable liquid crystal compound contained in the coating film obtained by applying the liquid crystal material composition liquid to the surface of the base material 31 is aligned as shown below, for example. When the retardation layer 33 has a layer structure having an optical compensation function as a positive C plate, the liquid crystal molecules forming the polymerizable liquid crystal compound are vertically aligned, and the retardation layer 33 having homeotropic alignment is formed. . For imparting orientation to the liquid crystal molecules, the liquid crystal coating film is heated, and the temperature of the liquid crystal coating film is higher than the temperature at which the liquid crystal molecules contained in the liquid crystal coating film become a liquid crystal phase (liquid crystal phase temperature). It is carried out by setting the temperature below the temperature at which the liquid crystal molecules contained in the isotropic phase (liquid phase). At this time, the heating means for the liquid crystal coating film is not particularly limited, and may be a means for placing the substrate on which the liquid crystal coating film is formed in a heating atmosphere, or a means for heating the liquid crystal coating film by irradiating infrared rays.

  In addition to the above method, the method of aligning the polymerizable liquid crystal molecules is to heat the liquid crystal coating film to an isotropic phase temperature according to the polymerizable liquid crystal molecules contained in the liquid crystal coating film and the state of the liquid crystal coating film, Thereafter, the liquid crystal coating film can be cooled, and a method of spontaneously inducing alignment in liquid crystal molecules during the cooling process, or a method of applying an electric field or a magnetic field from a predetermined direction to the liquid crystal coating film can be realized.

  Further, even when polymerizable liquid crystal molecules that have a liquid crystal phase higher than room temperature and usually do not exhibit a liquid crystal phase at room temperature are used as the liquid crystal molecules contained in the liquid crystal material composition, If it is a liquid crystal material composition containing a liquid crystal molecule exhibiting a liquid crystal phase in a cooled state, the liquid crystal material composition is a liquid crystal that has been given orientation even at room temperature within the time range in which the liquid crystal molecule exhibits a liquid crystal phase. It can be used to form a liquid crystal coating film containing molecules.

  Thus, when the state in which the liquid crystal molecules contained in the liquid crystal coating film are aligned is formed, the liquid crystal molecules are subjected to a polymerization reaction (in the case where the liquid crystal molecules are crosslinkable liquid crystal molecules), a crosslink polymerization reaction is performed.

  This polymerization reaction contains liquid crystal molecules that are in a liquid crystal phase with actinic radiation such as light having a photosensitive wavelength (specifically, for example, ultraviolet rays) of a photopolymerization initiator added to the liquid crystal material composition. It progresses by irradiating the entire liquid crystal coating film toward the liquid crystal coating film. At this time, the wavelength of light applied to the liquid crystal coating film is appropriately selected according to the type of photopolymerization initiator contained in the coating film. The light applied to the liquid crystal coating film is not limited to monochromatic light, and may be light having a certain wavelength range including the photosensitive wavelength of the photopolymerization initiator.

  In addition, the polymerization reaction of the liquid crystal molecules is performed by irradiating the liquid crystal coating film with actinic radiation such as light having a photosensitive wavelength of the photopolymerization initiator through a photomask having a light shielding pattern in a state where the liquid crystal coating film exhibits a liquid crystal phase. (Exposure) to partially advance the polymerization reaction (referred to as a partial polymerization step), and after the partial polymerization step, the liquid crystal coating film is heated to a temperature (Ti) at which the liquid crystal molecules become isotropic, In this state, the liquid crystal coating film is further irradiated with actinic radiation such as light having a photosensitive wavelength to advance the polymerization reaction, or after the partial polymerization step, the liquid crystal coating film is heated to a temperature Ti or higher to thermally polymerize liquid crystal molecules. It may be carried out by a method in which the polymerization reaction of the liquid crystal molecules contained in the liquid crystal coating film is advanced to a predetermined degree of polymerization by performing the treatment. The temperature Ti described above is a temperature at which the liquid crystal molecules become isotropic in the liquid crystal coating film before the polymerization reaction proceeds.

  In addition, when the polymerization reaction of liquid crystal molecules is performed through a partial polymerization process using a photomask, after the partial polymerization process is performed on the substrate on which the liquid crystal coating film is formed, By immersing the liquid crystal material composition in an uncured state where the polymerization reaction of the liquid crystal molecules is insufficient, the portion of the liquid crystal coating film where the polymerization reaction of the liquid crystal molecules did not proceed is removed from the substrate surface. It is also possible to form (pattern) a layer structure including liquid crystal molecules in a liquid crystal phase on the substrate in a predetermined pattern.

  The curing of the liquid crystal coating film by irradiating actinic radiation to polymerize the liquid crystal molecules forming the liquid crystal compound in the liquid crystal coating film can be performed not only in an air atmosphere but also in an inert gas atmosphere.

  In forming the retardation layer 33, a vertical alignment film is interposed in advance between the base material 31 and the retardation layer 33, and the retardation layer 33 is laminated directly on the surface of the vertical alignment film. This is preferable because the optical axis of the retardation layer 33 can be oriented in the z-axis direction while making it more uniform.

  The vertical alignment film is formed by applying a vertical alignment film composition liquid containing a component constituting the vertical alignment film on the substrate 31 by a method such as flexographic printing or spin coating to form a vertical alignment film-forming coating film. It can be formed by curing the coating film. Examples of the vertical alignment film composition liquid include a solution containing polyimide. Specific examples of such a vertical alignment film composition liquid containing polyimide include SE-7511 and SE-1211 manufactured by Nissan Chemical Industries, and JALS-2021-R2 manufactured by JSR.

  The vertical alignment film preferably has a thickness of about 100 to 1000 mm. If the thickness of the vertical alignment film is smaller than 0.01 μm, there is a high possibility that it is difficult to exert the effect of vertically aligning the liquid crystal molecules. Further, if the thickness of the vertical alignment film is larger than 1 μm, the degree of light scattering by the vertical alignment film is increased, and there is a high possibility that the light transmittance of the optical element 1 is lowered.

  In the case where the vertical alignment film has high water repellency or oil repellency, before the phase difference layer 33 is formed by applying the liquid crystal material composition on the vertical alignment film by the die coater 1, The wettability of the surface of the vertical alignment film to which the liquid crystal composition liquid is to be applied may be increased in advance by performing UV cleaning or plasma treatment within a range where vertical alignment is possible.

<In case of negative C plate>
When the retardation layer 33 is a layer having an optical compensation function as a “-C plate”, the retardation layer 33 is a liquid crystal compound having a negative dielectric anisotropy so that its optical axis is directed in the z-axis direction. Can be formed by aligning and fixing liquid crystal molecules constituting the liquid crystal compound. In addition, the retardation layer 33 having an optical compensation function as the “−C plate” is used for the crosslinkable nematic liquid crystal (for example, the compounds (I), (II), and (III)) used for forming the “+ C plate”. A liquid crystal composition comprising a liquid crystal material composition containing a liquid crystal compound and adding a chiral agent thereto to impart cholesteric regularity to polymerizable liquid crystal molecules to form a chiral nematic liquid crystal (chiral agent-containing liquid crystal composition) And may be formed using the chiral agent-containing liquid crystal composition.

  In forming the retardation layer 33 using the chiral agent-containing liquid crystal composition with the die coater 1, specifically, first, the liquid crystal compound as described above, the chiral agent, the photoinitiator, and the solvent are mixed. To prepare a liquid crystal material composition liquid. The liquid crystal material composition liquid is used as the coating material 14 to create a “+ C plate” on the surface of the substrate 31 with the die coater 1 to create a coating film, which is included in the coating film. The retardation layer 33 having an optical function as a “-C plate” is formed by polymerizing and firing the liquid crystal compound. The polymerization of the liquid crystal compound can be carried out by irradiating the coating film with actinic radiation as in the case of the “+ C plate”.

  The chiral agent is preferably a low molecular weight compound having an optically active site in the molecule and having a molecular weight of 1500 or less. As the chiral agent, the compound (I) shown in Chemical formula 1, the compound (II) shown in Chemical formula 2, the compound (III) shown in Chemical formula 3, and the chemical formula (III) shown in Chemical formula 4 are compatible with each other in a solution state or a molten state, and are crosslinkable nematics. Any material that can induce the helical pitch without impairing the liquid crystal properties of the liquid crystal molecules may be used. However, as the chiral agent, those having polymerizable functional groups at both terminal sites in the molecular structure are preferable for obtaining the retardation layer 33 having good heat resistance, and the chiral agent is optically active in the molecular structure. It is important that the compound has a different site.

  Such a chiral agent is blended in a liquid crystal material composition containing the compound (I) shown in Chemical formula 1, the compound (II) shown in Chemical formula 2, the compound (III) shown in Chemical formula 3, and the chemical formula (III) shown in Chemical formula 4 as polymerizable liquid crystal compounds. Then, in forming the retardation layer 33 using the liquid crystal material composition, a helical pitch can be induced with positive uniaxial nematic regularity with respect to the polymerizable liquid crystal compound contained in the retardation layer 33.

  The chiral agent is added to align the liquid crystal molecules forming the liquid crystal compound in a spiral shape, but when the liquid crystal molecules take a helical pitch in the near-ultraviolet region, a reflection color of a specific color is produced by a selective opposite phenomenon. The blending amount of the agent is preferably such that a spiral pitch is obtained such that the selective opposite phenomenon is in the ultraviolet region.

  The chiral agent includes, for example, a compound having one or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine or chiral sulfoxide, or a shaft such as cumulene or binaphthol. Examples include compounds with asymmetry, but depending on the properties of the selected chiral agent, nematic regularity may be destroyed and the orientation may be deteriorated. A chiral agent having not only a situation in which the curing performance by polymerization is lowered but also a situation in which the electrical reliability of the retardation layer formed using the liquid crystal material composition liquid is lowered, and having an optically active site. The use of a large amount of increases the cost. Accordingly, as the chiral agent, it is preferable to select a chiral agent that has a large effect of inducing a helical pitch in the alignment of liquid crystal molecules even in a small amount, and more specifically, a commercially available product such as S-811 manufactured by Merck is used. be able to.

<In case of positive A plate>
When the retardation layer 33 is a layer having an optical compensation function as a “+ A plate”, the retardation layer 33 includes liquid crystal molecules having a positive dielectric anisotropy that form a liquid crystal compound, the optical axes of which are the x axis and the y axis. It is formed by being oriented and fixed so as to be parallel to the xy plane including the axis.

  More specifically, a resin material constituting a resin film (horizontal alignment film) capable of horizontally aligning liquid crystal molecules is adjusted, and the resin material is applied on the surface of the base material 31 to form a horizontal alignment film. A coating film is formed, and the surface of the coating film for forming a horizontal alignment film is subjected to a rubbing process or a photo-alignment process to obtain a horizontal alignment film, and the substrate forming material and the horizontal alignment film form the substrate 30. On the other hand, a liquid crystal material composition solution in which a liquid crystal compound is dissolved in a solvent is prepared. Then, the liquid crystal material composition liquid is used as the coating material 14, and the liquid crystal as the coating material 14 is formed on the horizontal alignment film of the substrate 30 previously formed by the die coater 1 in the same manner as in the case of creating the “+ C plate”. The material composition liquid is applied to form a coating film, and the liquid crystal compound in the horizontally aligned state is obtained by horizontally aligning (polymerizing) the liquid crystal molecules forming the liquid crystal compound contained in the coating film. Then, the coating film is made the retardation layer 33. Thus, the retardation layer 33 as a “+ A plate” can be obtained. The polymerization of the liquid crystal molecules can be carried out by irradiating the coating film with actinic radiation such as light having a photosensitive wavelength of the liquid crystal compound or ultraviolet rays, as in the case of preparing the “+ C plate”.

<Optical element obtained using a die coater (second embodiment)>
In the above description, the optical element of the first embodiment has been described with respect to the case where the substrate 30 is made of the substrate 31. However, the present invention is not limited to this, and a predetermined layer structure is laminated on the substrate 31 surface as the substrate 30. The optical element 1 may be formed by using the above (optical element of the second form). In this case, the layer structure laminated on the base material 31 includes a black matrix that forms a light shielding layer that blocks light traveling in the thickness direction, a layer that transmits visible light having a predetermined range of such light, A layer structure such as a colored layer formed by appropriately combining the above can be given.

  Regarding the optical element 32 using the die coater 1, the optical element 32 includes a base body 31 having a light transmitting property and a structure (color filter) including a colored layer that transmits visible light having a predetermined wavelength as a base 30. The retardation layer 33 may be provided on the surface of the substrate 30 (on the color filter surface) by the die coater 1.

  Therefore, the optical element 32 will be described as an example in which the base 30 is a structure formed by forming a colored layer having a color pattern and a black matrix on the surface of the base 31 (FIGS. 7 and 8). FIGS. 7 and 8 are a schematic cross-sectional view and a schematic plan view, respectively, showing a cross-section for explaining one example of the optical element 32. In FIG. 8, the retardation layer 33 is omitted for convenience of explanation.

  In the optical element 32, a light-shielding black matrix 45 is applied to one surface of the base material 31 in a grid pattern (lattice striped pattern) in the vertical and horizontal directions. Many are formed in a shape. At this time, the formation region of the black matrix 45 corresponds to a light shielding portion, and the opening 50 corresponds to a transmission portion.

  The black matrix 45 can be formed by patterning a metal thin film having a light-shielding property or a light-absorbing property such as a metal chromium thin film or a tungsten thin film on the surface of the substrate 31. The black matrix 45 can also be formed by printing an organic material such as a resin containing a black pigment in a predetermined shape.

  On the base material 31 on which the black matrix 45 is arranged, three color patterns 46, 47, 48 are arranged in a strip shape so as to cover the opening 50, and these color patterns 46, 47, 48 and the black matrix are arranged. 45, a colored layer 43 is formed (FIGS. 7 and 8). The color patterns 46, 47, and 48 are light transmissive, and the visible light that is transmitted is split into red (R), green (G), and blue (B) light, respectively. Therefore, as shown by a two-dot chain line in FIG. 3, each of the three RGB color patterns (red (R) color pattern 46, green (G) color pattern 47, blue (B) color pattern 48) is covered. Each of the openings 50 is formed to form a pixel, and the three openings 50 covered by the three color patterns 46, 47, and 48 are combined to form one picture element 51.

  The color patterns 46, 47, 48 are formed by applying, to the base material 31, a coloring material dispersion in which a coloring material obtained by blending a pigment corresponding to each color type and a resin is dispersed in a solvent for each color type. In addition to being formed by patterning the coating film to be formed into a predetermined shape such as a strip shape, for example, by photolithography, it can also be formed by applying the coloring material dispersion liquid to the base material 31 in a predetermined shape.

  When the black matrix 45 is formed in the colored layer 43, the black matrix 45 has a function of preventing color mixture of the color patterns 46, 47, and 48 applied in a roughly strip shape as a light shielding portion, and an opening. The function of partitioning the portion 50 in plan view to sharpen the outline of the picture element 51. Furthermore, when the optical element 32 is incorporated in a liquid crystal display, a TFT that is normally disposed on the substrate and used to drive the liquid crystal It also has a function of concealing drive circuits and the like from transmitted light.

  In this optical element 32, the arrangement shape of the black matrix 45 is not limited to a rectangular lattice shape, and may be formed in a stripe shape or a triangular lattice shape. Further, the color pattern constituting the colored layer 43 can also be a CMY system that is a complementary color system in addition to the RGB system of three colors, and further, in the case of a single color or two colors, or more than four colors. Cases can also be taken. In addition to the case where the color pattern is formed in a strip shape, a variety of patterns may be adopted depending on the purpose, such as a pattern in which a large number of fine patterns such as a rectangular shape or a triangular shape are dispersedly arranged on the substrate 2. sell.

  In the optical element 32, only the black matrix 45 may be formed between the base material 31 and the retardation layer 33, or the color patterns 46 and 47 may be formed without forming the black matrix 45. 48, only two types, or two types or three types may be formed.

  Note that both the optical element of the first form and the optical element of the second form described above are included in the coating film produced by applying the liquid crystal material composition liquid onto the substrate 30 using the die coater 1. After the liquid crystal molecules forming the liquid crystal compound are polymerized to form the coating film as the retardation layer 33, the retardation layer 33 containing the polymerized liquid crystal molecules is further heated (sometimes referred to as post-polymerization heating treatment). ) Is preferable because the hardness of the retardation layer 33 can be improved. However, when the post-polymerization heat treatment is performed, the base material 31 is required to have heat resistance, and therefore, a glass substrate having heat resistance is preferably used as the base material forming material constituting the base material 31.

  In performing the post-polymerization heat treatment, the heating temperature of the retardation layer 33 is 150 to 260 ° C., but 200 to 250 ° C. indicates that the post-polymerization heat treatment is performed on the retardation layer 33 after the polymerization. From the viewpoint that it can be hardened more effectively than before. The time for performing the post-polymerization heat treatment is 5 to 90 minutes, but is preferably about 15 to 30 minutes from the same viewpoint as the above-mentioned viewpoint for the heating temperature when performing the post-polymerization heat treatment. When the heating temperature is 260 ° C. or the heating time exceeds 90 minutes, the hardness and strength of the retardation layer 33 are increased, but there is a greater possibility that the retardation layer 33 itself is strongly yellowed, while the heating temperature is 150 When the temperature is less than 5 minutes, the possibility that sufficient hardness and strength cannot be obtained increases.

  The phase difference layer 33 is heated and then cooled.

  The post-polymerization heat treatment can be specifically carried out by introducing the structure in which the retardation layer 33 is formed on the substrate 30 into a baking apparatus such as an oven apparatus, and baking under a pressure of atmospheric pressure and an air atmosphere. . In addition, it can implement also by the method by infrared irradiation.

  Further, in performing the post-polymerization heat treatment step, it is preferable that the temperature increase during the heating of the retardation layer 33 and the temperature decrease after the heating are performed gradually.

<Liquid crystal display device obtained using a die coater>
By incorporating the optical element 32 obtained using the die coater 1 into the liquid crystal display device, a liquid crystal display device using the die coater 1 can be formed.

  Therefore, a liquid crystal display incorporating the optical element 32 obtained by using the die coater 1 will be described. In addition, as a liquid crystal display, it is an IPS mode, and demonstrates the case where the optical element 32 (optical element of a 2nd form) provided with the colored layer 43 is integrated (FIG. 9) as an example. FIG. 9 is a diagram for explaining the liquid crystal display 81.

  As shown in FIG. 5, the liquid crystal display 81 can be driven according to a change in the electric field while being placed in an electric field between a pair of opposing substrates 55 (the counter substrate 52 and the TFT array substrate 53). The liquid crystal composition for driving the liquid crystal display (the liquid crystal composition for driving 54) is sealed in the driving liquid crystal layer 58. The liquid crystal display 81 includes a backlight (not shown) that emits light from the outer position of the TFT array substrate 53 toward the TFT array substrate 53 in the thickness direction of the TFT array substrate 53. Yes.

  In the counter substrate 52, a colored layer 43 having a black matrix 45 and color patterns 46, 47, and 48 is laminated on a base material 31, and the retardation layer 33 is formed by covering the surface of the colored layer 43. ing. The retardation layer 33 is produced using the die coater 1 in the same manner as when producing the optical element of the second embodiment.

  Further, on the retardation layer 33, a column body 73 has a base portion (an upper portion in FIG. 5) placed at a predetermined position on the surface of the retardation layer 33 (a column body formation planned position) by a photolithography method or the like. Dispersed using a known method. The columnar formation planned position is appropriately determined in a portion (non-pixel portion) excluding a portion to be a pixel in the counter substrate 52.

  The column 73 is made of a resin material having photocurability, such as acrylic and amide or ester polymers containing polyfunctional acrylate.

  On the counter substrate 52, a linearly polarizing plate 63 is disposed on the surface of the base material 31 in the thickness direction on the surface where the colored layer 43 is not formed.

  The TFT array substrate 53 is for driving for switching driving whether or not a voltage is applied to the liquid crystal 74 of the driving liquid crystal layer 58 on the in-cell side (side where the driving liquid crystal composition 54 is sealed) of the transparent base material 71. A TFT that forms a circuit and a liquid crystal driving electrode that controls the amount of voltage applied to the driving liquid crystal layer 58 are provided (not shown). The liquid crystal driving electrode generates an electric field in the in-plane direction of the driving liquid crystal layer 58 and changes the orientation of the liquid crystal 74 in the in-plane direction of the driving liquid crystal layer 58.

  Further, the TFT array substrate 53 is in contact with the tip portions (downward in the figure) of a large number of column bodies 73 on the outermost surface on the in-cell side. The backlight substrate 53 is provided with a linearly polarizing plate 72 on the out-cell side (opposite side of the in-cell side).

  In the liquid crystal display 81, the linearly polarizing plate 63 of the counter substrate 52 and the linearly polarizing plate 72 of the TFT array substrate 53 are arranged so that their transmission axes are orthogonal to each other. In the figure, the transmission axes of the linear polarizing plates 63 and 72 are indicated by arrows.

  In the liquid crystal display 81, the counter substrate 52 is provided with a layer structure in which the base material 31, the colored layer 43, and the retardation layer 33 are laminated, and this layer structure constitutes the optical element 1. That is, the liquid crystal display 81 is configured by incorporating the optical element 1.

  In the liquid crystal display 81, a retardation film 60 may be disposed inside the linearly polarizing plate 63 in the counter substrate 52 as necessary. In the example shown in FIG. 9, as the liquid crystal display 81, the optical element 32 in which the retardation layer 33 is formed as a layer having an optical compensation function of a positive C plate is incorporated, and the retardation film 60 is used as a positive A plate. An optical compensation function is shown. In FIG. 9, the birefringence characteristics defining the optical compensation functions of the retardation layer 33 and the retardation film 60 are indicated by refractive index ellipsoids 100 and 101, respectively.

  In the liquid crystal display 81, a plurality of retardation films 60 may be interposed as needed. Therefore, for example, the liquid crystal display 81 incorporates the retardation control member 1 in which the retardation layer 33 is formed as a layer having an optical compensation function of a positive C plate, and the retardation film 60 serves as a positive A plate. It may be configured by laminating two or more of those having an optical compensation function and those having other functions.

  In the present specification, the case where the liquid crystal display in which the retardation layer 33 is incorporated is in the IPS mode. This is because the retardation control member 1 is, for example, in the MVA mode or the OCB mode (Optically Compensated Birefringence mode). It is not denied that it is used for liquid crystal displays in other modes.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, it is not limited to these.

<Production of die coater>
A stainless steel (JIS standard SUS304) is used to create a pair of base material components with a width of 29 cm, and the base material components are combined and integrated, and a heating mechanism with a heat generating component and a temperature measurement mechanism with a sensor are provided. A base was prepared and a die coater as shown in FIG. 3 was prepared. Regarding the die coater die, as a heating mechanism, there is a heating mechanism including a component having a thin film surface heater (film heater) in which a heating material made of a nickel alloy is sandwiched by an insulating material made of a polyimide sheet. Used. This heating component was installed in the die by making a hole in the die component material to form a space, and inserting the heating component into the formed space. As the temperature measurement mechanism, a sensor equipped with an infrared thermometer was used as a temperature detection sensor (temperature sensor), and the temperature sensor of the infrared thermometer was arranged toward the slit of the base. In this die coater 1, the heating mechanism and the temperature measuring mechanism are connected by a regulator. This regulator is a control device provided with a mechanism for controlling adjustment of the heating amount by the heating mechanism and holding of the temperature of the base so that heating by the heating mechanism is performed while maintaining the temperature of the base in a predetermined temperature range. . Similarly to the example shown in FIG. 4, the manufactured die coater is provided with a paint reservoir, and a pump is installed so that the paint can be sent from the paint reservoir to the paint supply hole of the die body through the pipe. It was. This die coater was designated as die coater 1.

  Further, a die coater (die coater 2) was manufactured in the same manner as the die coater 1 except that the heating mechanism and the temperature measuring mechanism were not installed.

Example 1
A glass substrate (NA Techno Glass, NA35, dimensions: 300 mm × 400 mm × thickness 0.7 mm) was prepared as a base, and the above-described die coater 1 was used to adjust the paint as follows. Then, the paint was applied to a substrate to form a coating film, and the coating film was used as a retardation layer to produce an optical element.

<Adjustment of paint>
A liquid crystal material composition liquid was employed as a paint used when the die coater 1 was applied to the glass substrate surface. The liquid crystal material composition liquid was prepared as follows.

  First, compounds (a) to (d) shown in the following chemical formula 5, photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 907), silane coupling agent (amine group-containing silane coupling agent (GE Toshiba Silicone) Manufactured by TSL-8331), a surfactant (dodecanol), and a polymerization inhibitor (BHT ((2,6-di-tert-butyl-4-hydroxytoluene)), and a liquid crystal composition having the following composition: The weight ratio of each substance in the liquid crystal composition A shown below is the weight ratio of each substance to the total weight of the liquid crystal composition A.

Liquid crystal composition A
Compound (a) 32.67% by weight
Compound (b) 18.67% by weight
Compound (c) 21.00% by weight
Compound (d) 21.00% by weight
Dodecanol 1.02% by weight
BHT 0.04% by weight
Irgacure 907 5.60% by weight

  Next, the liquid crystal composition A was dissolved in a solvent (propylene glycol monomethyl ether acetate (PGMEA)) to obtain a liquid crystal material composition liquid having a concentration of 20% (weight ratio of the liquid crystal composition A to the solvent). The liquid crystal temperature of the liquid crystal material composition liquid is 80 ° C. to 100 ° C.

  The prepared liquid crystal material composition liquid is charged into the paint reservoir of the produced die coater 1, first applied to 10 substrates to form a liquid crystal coating film, and the liquid crystal material composition adheres to the die coater 1 die. The die coater 1 was left at room temperature for 2 hours in the state. The liquid crystal coating film applied on the substrate was dried. The film thickness of the liquid crystal coating film after drying was 2 μm.

  In applying the liquid crystal material composition liquid by the die coater 1, the heating mechanism heated until the temperature of the die coater 1 die (the temperature from the slot to the lip) reached 80 ° C., and reached 80 ° C. Later, application of the liquid crystal material composition liquid was started (application gap: 60 μm, discharge amount: 1300 μl / s, relative movement speed: 45 mm / s). Further, during the application of the liquid crystal material composition liquid, the temperature measurement mechanism was adjusted so that the temperature of the die did not exceed the range of 80 to 100 ° C. In this adjustment, the heating by the heating mechanism is interrupted when the temperature of the base exceeds 96 ° C., and the regulator is monitored so that the temperature of the base does not exceed 100 ° C. due to the residual heat of the heat generating parts of the heating mechanism. Made by.

Next, using the die coater 1 after being left at room temperature for 2 hours as it is, a liquid crystal material composition liquid is further coated on the substrate under the same conditions as in the previous application of the liquid crystal material composition to the 10 substrates. And a liquid crystal coating film was formed. Finally, the substrate on which the liquid crystal material composition was applied and the liquid crystal coating film was formed was dried under reduced pressure (pressure: 1.5 × 10 ⁻¹ Torr) and further pre-baked on a hot plate (90 ° C., 3 minutes). In addition, the solvent in the liquid crystal coating film is removed and the liquid crystal molecules contained in the liquid crystal coating film are transferred to the liquid crystal phase (the liquid crystal molecules are vertically aligned), and then the ultraviolet irradiation device (Harrison Toshiba) toward the liquid crystal coating film. Irradiation with ultraviolet rays (365 nm) (100 mJ / cm ² ) using “trade name TOSCURE 751” manufactured by Lighting Co., Ltd.), the liquid crystal coating film is cured to form a retardation layer, and a retardation layer is formed on a substrate. An optical element was obtained. Using this optical element as a test substrate, the quality of the obtained liquid crystal coating film (coating film) was evaluated with respect to the film thickness unevenness based on the evaluation of the film thickness unevenness of the retardation layer.

[Measurement and evaluation method of characteristics]
<About the method for evaluating the occurrence of uneven stripes on the coating surface>
The film thickness unevenness of the coating film that occurs during the coating becomes a problem when the film thickness unevenness remains in the retardation layer of the optical element. Therefore, the evaluation of the coating film thickness unevenness generated during the coating was performed on the retardation layer of the optical element based on the evaluation of the film thickness unevenness. The evaluation method disclosed in Japanese Patent Laid-Open No. 8-173878 was used for evaluating the film thickness unevenness in the retardation layer of the academic element. That is, the thickness of the retardation layer was measured at a pitch of 10 mm from the center of the retardation layer in two directions, the coating direction (the relative movement direction of the die coater with respect to the base) and the direction perpendicular to the coating direction. However, the region from the edge of the retardation layer to the inside of 10 mm was removed from the region of the retardation layer to be measured for film thickness. Using the measured thickness data of the retardation layer, an average value for all data is calculated, ((maximum value of measured data) / average value) × 100 (%) (referred to as Fh), And ((minimum value of measured data) / average value) × 100 (%) (referred to as Fl). The film thickness unevenness of the retardation layer was evaluated based on the values of Fh and Fl thus obtained. Regarding the evaluation, the closer the values of Fh and Fl were to 100%, the less the variation in the thickness of the retardation layer, and the less the film thickness unevenness, and the retardation layer was evaluated to be better in terms of film thickness unevenness. Specifically, the evaluation was performed according to the following evaluation criteria for film thickness unevenness.

<Evaluation criteria for film thickness unevenness>
The values of Fh and Fl are in the range of 95% to 105%. ... The phase difference layer is in a state of small film thickness unevenness, and the phase difference layer is good in terms of film thickness unevenness.
Fh exceeds 105% or Fl is less than 95%. .... The phase difference layer is in a state of large film thickness unevenness, and the phase difference layer is defective in terms of film thickness unevenness.

  When the retardation layer is evaluated as “good” in terms of film thickness unevenness, the coating film formed during coating is also evaluated as “good” in terms of film thickness unevenness. When the evaluation of “unsatisfactory” is made as the evaluation of the film thickness unevenness of the retardation layer, the evaluation of “not good” in terms of film thickness unevenness is also applied to the coating film formed at the time of coating. Was made.

  As a result of evaluating the film thickness unevenness of the retardation layer with respect to the optical element obtained using the die coater 1, Fh was 102% and Fl was 99%, and the film thickness unevenness was small. It was good in terms of thickness unevenness. " Therefore, the evaluation of “good” was also made for the evaluation of the film thickness unevenness of the coating film generated during coating.

Comparative Example 1
A structure (Comparative Element 1) having a retardation layer formed on a glass substrate was produced in the same manner as in Example 1 except that the die coater 2 was used as the die coater. When the film thickness unevenness of the retardation layer was evaluated in the same manner as in Example 1 using the obtained comparative element 1, Fh was 145%, Fl was 65%, and the film thickness unevenness was confirmed. The optical element was evaluated as defective in terms of small film thickness unevenness. Therefore, the evaluation of “unsatisfactory” was also made for the evaluation of the film thickness unevenness of the coating film generated during coating.

Example 2
As the substrate, except that a glass substrate (NH Techno Glass, NA35, dimensions: 300 mm × 400 mm × thickness 0.7 mm) on which a red color pattern was formed as a colored layer as described below was used, In the same manner as in Example 1, an optical element was obtained using the die coater 1. As a result of evaluating the film thickness unevenness of the coating film for the optical element obtained by using the die coater 1, Fh is 103% and Fl is 98%, the film thickness unevenness is small, and the optical element is small in film thickness unevenness. It evaluated that it was favorable at the point. Therefore, the evaluation of “good” was also made for the evaluation of the film thickness unevenness of the coating film generated during coating.

<Adjustment of coloring material dispersion used for forming color pattern>
A coloring material dispersion having a red (R) color pattern was prepared. A pigment-dispersed photoresist was used as the coloring material dispersion with a red color pattern.

  Adjustment of the color pattern pigment dispersion type photoresist is performed by adding beads to the dispersion composition (containing pigment, dispersant and solvent) and dispersing with a disperser (paint shaker (manufactured by Asada Tekko Co., Ltd.)) for 3 hours. Thereafter, a dispersion liquid from which the beads were removed and a clear resist composition (containing a polymer, a monomer, an additive, an initiator and a solvent) were mixed to obtain a pigment-dispersed photoresist. For each color pattern, a pigment-dispersed photoresist having the following composition was used.

(Pigment-dispersed photoresist for red (R) color pattern)
・ Red pigment: 4.8 parts by weight (CIPR254 (manufactured by Ciba Specialty Chemicals, Chromophthal DPP Red BP))
・ Yellow pigment: 1.2 parts by weight (CI PY139 (manufactured by BASF, Paliotor Yellow D1819))
・ Dispersant: 3.0 parts by weight (manufactured by Zeneca Corporation, Solsperse 24000)
・ Monomer: 4.0 parts by weight (Sartomer Co., Ltd., SR399)
-Polymer 1-5.0 parts by weight-Initiator-1.4 parts by weight (Ciba Geigy, Irgacure 907)
・ Initiator: 0.6 parts by weight (2,2′-bis (o-chlorophenyl) -4,5,4 ′, 5′-tetraphenyl-1,2′-biimidazole)
・ Solvent: 80.0 parts by weight (propylene glycol monomethyl ether acetate)

  The polymer 1 is based on 100 mol% of a copolymer of benzyl methacrylate: styrene: acrylic acid: 2-hydroxyethyl methacrylate = 15.6: 37.0: 30.5: 16.9 (molar ratio). 2-methacryloyloxyethyl isocyanate was added at 16.9 mol%, and the weight average molecular weight was 42500.

<Formation of colored layer>
A red (R) pigment-dispersed photoresist adjusted to correspond to the position corresponding to the red color pattern is applied on the BM forming substrate by spin coating, and prebaked at 80 ° C. for 3 minutes. Furthermore, ultraviolet exposure (300 mJ / cm ² ) was performed. Further, spray development using a 0.1% KOH aqueous solution was performed for 60 seconds, followed by post-baking (baking) at 200 ° C. for 60 minutes to form a red (R) color pattern with a film thickness of 1.3 μm on one side. . Thus, a colored layer composed of a red color pattern was formed on the glass substrate.

Comparative Example 2
A structure (comparative element 2) in which a retardation layer was formed on a substrate was manufactured in the same manner as in Example 2 except that the die coater 2 was used as the die coater. When the film thickness unevenness of the retardation layer was evaluated in the same manner as in Example 1 using the obtained comparative element 2, Fh was 148%, Fl was 65%, and the film thickness unevenness was confirmed. The optical element was evaluated as defective in terms of small film thickness unevenness. Therefore, the evaluation of “unsatisfactory” was also made for the evaluation of the film thickness unevenness of the coating film generated during coating.

  In Examples 1 and 2, after the liquid crystal coating film was applied to 10 substrates, the liquid crystal coating film was further formed on the substrate. As a result, an optical element in which a retardation layer with less film thickness unevenness is formed is obtained. Therefore, in the conventional die coater 2 that is not provided with a heating mechanism or the like, there is a risk of causing unevenness in the coating film during coating, and even if the coating film is cured, the unevenness remains in the retardation layer. It is confirmed that the film thickness unevenness is effectively improved in the retardation layer manufactured using a die coater having a heating mechanism such as the die coater 1. It was done.

DESCRIPTION OF SYMBOLS 1 Die coater 2 Die main body 3 Heating mechanism 4 Base 5, 6 Base component 7 Manifold 8 Slit 9 Slot 10 Paint supply hole 11 Paint storage part 21 Coating film 30 Base 32 Optical element 33 Phase difference layer 81 Liquid crystal display

Claims (4)

A die coating method for forming a coating film by discharging a paint composed of a liquid crystal composition containing a polymerizable liquid crystal compound on the surface of a substrate provided with a substrate having light permeability,
A die body configured to be able to move a base formed with a slot formed so as to be able to discharge paint and from a manifold extending toward the slit to form a passage for the paint. will be provided, and, a heating mechanism for heating the spinneret provided with a heat generating component, at a predetermined position around the slot being arranged heat-generating components in a predetermined portion including the periphery of the inner and manifolds and slots of the base using a die coater comprising comprises, from the position of the slit while heating the spinneret polymerizable liquid crystal compound and the heating temperature of the base is in a heating mechanism so as to make the phase transition temperature above the temperature at which the liquid crystal phase, on a substrate surface A die coating method characterized in that a coating film is formed by discharging paint .   A color filter having a light-transmitting base material and a colored layer that transmits visible light having a predetermined wavelength is used as a base, and a paint is applied on the color filter surface from the position of the slit while heating the base with a heating mechanism. The die coating method according to claim 1, wherein a coating film is formed by discharging the slag. The coating film is formed by discharging paint on the surface of the substrate while maintaining the temperature of the die at a predetermined temperature within a temperature range in which the polymerizable liquid crystal compound exhibits a liquid crystal phase. 3. The die coating method according to 1 or 2.   The die coater is provided with a temperature measuring mechanism for measuring the temperature of the die or paint at the slit position, and the heating of the die by the heating mechanism is adjusted according to the temperature measured by the temperature measuring mechanism. The die coating method according to any one of claims 1 to 3.

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