JP2009258425A - Method for manufacturing liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of luminance irregularity due to dispersion of pretilt angles in a PSA type liquid crystal display device. <P>SOLUTION: A method for manufacturing a liquid crystal display device includes: a step of binding a pair of substrates to each other with a predetermined interval through a seal material; a step of injecting a liquid crystal material containing a photopolymerizable compound into a space surrounded by the pair of substrates and the seal material by a vacuum injection method; and a step of polymerizing the photopolymerizable compound by irradiating the liquid crystal material with light to form an alignment maintaining layer. The step of injecting the liquid crystal material includes a first injection step of injecting a liquid crystal material containing the photopolymerizable compound at a first concentration C<SB>1</SB>and a second injection step of injecting a liquid crystal material containing the photopolymerizable compound at a second concentration C<SB>2</SB>higher than the first concentration C<SB>1</SB>after the first injection process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly to a method for manufacturing a PSA type liquid crystal display device.

  A liquid crystal display device performs display by utilizing the change in the orientation direction of liquid crystal molecules in accordance with the magnitude of a voltage applied to a liquid crystal layer. The alignment direction (referred to as “pretilt direction”) of liquid crystal molecules in a state where no voltage is applied to the liquid crystal layer has been conventionally defined by the alignment film. For example, in a TN (twisted nematic) mode liquid crystal display device, the pretilt direction of liquid crystal molecules is defined by a horizontal alignment film that has been subjected to rubbing treatment.

  The pretilt direction is represented by a pretilt azimuth and a pretilt angle. The pretilt azimuth refers to a component in the liquid crystal layer plane (in the substrate plane) among vectors indicating the alignment direction of liquid crystal molecules in the liquid crystal layer to which no voltage is applied. The pretilt angle is an angle formed by the alignment film and the liquid crystal molecules, and is determined mainly by a combination of the alignment film material and the liquid crystal material. In the TN mode liquid crystal display device, the pretilt azimuths defined by the pair of alignment films facing each other through the liquid crystal layer are set to be orthogonal to each other, and the pretilt angle is about 1 ° to 5 °.

  In recent years, a PSA (Polymer Sustained Alignment) system has been developed as a technique for controlling the pretilt direction of liquid crystal molecules. The PSA method is disclosed in Patent Documents 1 and 2, for example. In the PSA method, a small amount of a photopolymerizable compound (for example, a photopolymerizable monomer) is mixed in a liquid crystal material, and after assembling a liquid crystal cell, a predetermined voltage is applied to the liquid crystal layer. Light (typically ultraviolet rays) is irradiated, and the pretilt direction of the liquid crystal molecules is controlled by the produced polymer. The alignment state of the liquid crystal molecules when the polymer is generated is maintained (stored) even after the voltage is removed (a state where no voltage is applied). Therefore, the PSA method has an advantage that the pretilt azimuth and pretilt angle of the liquid crystal molecules can be adjusted by controlling the electric field formed in the liquid crystal layer. In addition, since the PSA method does not require rubbing, it is particularly suitable for forming a vertical alignment type liquid crystal layer in which it is difficult to control the pretilt direction by rubbing.

  When manufacturing a PSA liquid crystal display device, it is necessary to fill a liquid crystal cell with a liquid crystal material containing a photopolymerizable compound. A liquid crystal cell (also referred to as “empty cell”) before being filled with a liquid crystal material is formed by bonding a pair of substrates at a predetermined interval with a sealant interposed therebetween. The sealing material is formed in a substantially rectangular shape around the display area, and a liquid crystal material is injected into a space surrounded by the sealing material and a pair of substrates. An injection port (opening) for injecting the liquid crystal material is formed on one side of the sealing material.

The liquid crystal material is typically injected in a state where the space in the empty cell is reduced to a vacuum state. Such a method of injecting a liquid crystal material under vacuum is called a vacuum injection method. After the liquid crystal material is injected, a sealing material (for example, an ultraviolet curable resin) is applied to the inlet of the sealing material, and the liquid crystal material is sealed by curing the sealing material.
JP 2002-357830 A JP 2003-307720 A

  However, when the liquid crystal material is injected by the vacuum injection method, the pretilt angle is different from that of the other region in one side of the sealing material, specifically, in the vicinity of the side facing the side where the injection port is formed. Such variations in the pretilt angle within the display area cause uneven brightness, resulting in a deterioration in display quality. FIG. 6 shows a halftone display state of a liquid crystal cell into which a liquid crystal material is injected using a vacuum injection method.

  In the liquid crystal cell shown in the photograph of FIG. 6, two injection ports are provided on the right side of the sealing material (formed so as to surround the display region). As shown in FIG. 6, an area with higher luminance (luminance floating) than the other areas is observed at the left end of the display area, and it can be seen that uneven luminance occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to suppress occurrence of luminance unevenness due to variations in pretilt angles in a PSA liquid crystal display device.

A method of manufacturing a liquid crystal display device according to the present invention includes a pair of substrates facing each other, a liquid crystal layer provided between the pair of substrates, a pair of electrodes facing each other through the liquid crystal layer, and the pair of electrodes A pair of alignment films provided between the liquid crystal layer and a photopolymer formed on each of the liquid crystal layer side surfaces of the pair of alignment films, An alignment maintaining layer that defines a pretilt azimuth of liquid crystal molecules in the liquid crystal layer when no voltage is applied to the liquid crystal layer, wherein the pair of substrates are interposed via a sealing material. A step of laminating at a predetermined interval, a step of injecting a liquid crystal material containing a photopolymerizable compound into the space surrounded by the pair of substrates and the sealing material by a vacuum injection method, and light to the liquid crystal material. Irradiating Therefore, by polymerizing the photopolymerizable compound includes a step of forming the alignment sustaining layer, the step of injecting the liquid crystal material, said liquid crystal comprising the photopolymerizable compound at a first concentration C ₁ A first injection step of injecting a material, and a second injection of the liquid crystal material containing the photopolymerizable compound at a second concentration C ₂ higher than the first concentration C ₁ after the first injection step. And an injection step.

In a preferred embodiment, the first concentration C ₁ and the second concentration C ₂ satisfy a relationship of C ₂ ≧ 1.2C ₁ .

In a preferred embodiment, the first concentration C ₁ and the second concentration C ₂ satisfy a relationship of C ₂ ≦ 6C ₁ .

  In a preferred embodiment, the photopolymerizable compound is a photopolymerizable monomer.

  In a preferred embodiment, each of the pair of alignment films is a vertical alignment film, and the liquid crystal layer includes liquid crystal molecules having negative dielectric anisotropy.

  In the method for manufacturing a liquid crystal display device according to the present invention, the step of injecting the liquid crystal material includes a first injection step of injecting a liquid crystal material having a relatively low concentration of the photopolymerizable compound, and photopolymerization after the first injection step. And a second injection step of injecting a liquid crystal material having a relatively high compound concentration. Therefore, the difference in polymerization due to the difference in injection timing (that is, the difference in oxygen concentration) can be offset by the difference in concentration of the photopolymerizable compound. Therefore, the pretilt angle in the display area can be made uniform, and the occurrence of uneven brightness can be suppressed.

  The inventor of the present application has investigated the cause of the variation in the pretilt angle described above. As a result, it was found that the cause of the variation in the pretilt angle was the variation in polymerizability resulting from the vacuum injection process.

  In the vacuum injection method, of the liquid crystal material injected into the empty cell, the first injected portion has a longer contact time with the vacuum portion in the cell than the later injected portion. Further, the polymerization of the photopolymerizable compound is inhibited by the presence of oxygen. That is, the polymerizability of the photopolymerizable compound is lower as the oxygen concentration is higher and higher as the oxygen concentration is lower. Therefore, the photopolymerizable compound contained in the first liquid crystal material injected into the empty cell is more easily polymerized than the photopolymerizable compound contained in the later injected liquid crystal material. It can be said. Therefore, the pretilt angle is small in the region where the liquid crystal material that is initially injected is finally located (that is, in the vicinity of the side of the sealing material that faces the side where the injection port is formed), that is, no voltage is applied. The tilt angle from the vertical direction (display surface normal direction) of the liquid crystal molecules in the state becomes large.

  Accordingly, the inventors of the present application focused on the fact that the pretilt angle becomes smaller as the concentration of the photopolymerizable compound contained in the liquid crystal material becomes higher, and as a result, the present inventors have come up with the present invention. In the manufacturing method of the liquid crystal display device according to the present invention, the occurrence of variation in the pretilt angle is suppressed by utilizing this characteristic of the photopolymerizable compound. Specifically, in the manufacturing method of the present invention, the step of injecting the liquid crystal material is performed by the step of injecting the liquid crystal material having a relatively low concentration of the photopolymerizable compound and the concentration of the photopolymerizable compound thereafter. And a step of injecting a high liquid crystal material into a plurality of stages. Therefore, the difference in polymerization due to the difference in injection timing (difference in oxygen concentration) can be offset by the difference in concentration of the photopolymerizable compound. Therefore, the pretilt angle in the display area can be made uniform, and the occurrence of uneven brightness can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to the following embodiment.

[Basic configuration and operation principle of PSA liquid crystal display]
First, a basic configuration and operation principle of a PSA liquid crystal display device will be described with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the structure of one pixel included in the liquid crystal display device 100 according to the present embodiment. FIG. 1A is a black display state (when no voltage is applied), and FIG. Indicates the alignment state of the liquid crystal molecules in the white display state (when voltage is applied). Note that, here, a vertical alignment (VA) mode liquid crystal display device 100 that performs display in a normally black mode is exemplified, but the present invention is not limited thereto.

  The liquid crystal display device 100 includes a pair of substrates (for example, glass substrates) 11 and 21 that face each other, and a pair of polarizing plates (not shown) that are provided outside these and disposed in crossed Nicols, and are normally black. It is a liquid crystal display device that performs display by a method. Each pixel of the liquid crystal display device 100 includes a liquid crystal layer 42 provided between the pair of substrates 11 and 21, and a pixel electrode 12 and a counter electrode 22 that face each other with the liquid crystal layer 42 interposed therebetween. The liquid crystal layer 42 includes liquid crystal molecules 42a having negative dielectric anisotropy.

  A pair of vertical alignment films (not shown) are provided between the pixel electrode 12 and the liquid crystal layer 42 and between the counter electrode 22 and the liquid crystal layer 42. A pair of alignment maintaining layers 34a and 34b made of a photopolymer is formed on each surface of the vertical alignment film on the liquid crystal layer 42 side. The alignment maintaining layers 34a and 34b are formed by polymerizing a photopolymerizable compound previously mixed with a liquid crystal material in a state where a voltage is applied to the liquid crystal layer 42 after a liquid crystal cell is produced. .

  The liquid crystal molecules 42a are regulated by a vertical alignment film (not shown) until the photopolymerizable compound is polymerized, and are aligned perpendicular to the substrate surface. When a white display voltage is applied, as shown in FIG. 1 (b), the orientation is inclined in a predetermined direction according to the oblique electric field generated at the edge portion of the pixel electrode 12 and the oblique electric field generated near the opening 22a of the counter electrode 22. Take a state. As shown in FIG. 1A, the alignment maintaining layers 34a and 34b formed in a state where a white display voltage is applied are aligned with the liquid crystal molecules 42a in a state where a white display voltage is applied to the liquid crystal layer 42. It works to maintain (memorize) even after removal (a state where no voltage is applied).

  Since the liquid crystal molecules 42a closest to the vertical alignment film are subjected to a strong anchoring action, they are aligned substantially perpendicular to the surface of the vertical alignment film even when a voltage is applied. Accordingly, the liquid crystal molecules 42a fixed by the alignment maintaining layers 34a and 34b formed on the vertical alignment film are slightly (1 ° to 5 °) from the vertical direction as schematically shown in FIG. Liquid crystal molecules fixed by the alignment maintaining layers 34a and 34b, as shown in FIG. 1 (a) and FIG. 1 (b). The orientation of 42a hardly changes even when a voltage is applied.

  Since the liquid crystal display device 100 in this embodiment includes the alignment maintaining layers 34a and 34b, as shown in FIG. 1A, the liquid crystal display device 100 exhibits an alignment state pretilted in a predetermined direction even when no voltage is applied. The alignment state at this time is consistent with the alignment state of the liquid crystal molecules 42a in the white display state (when voltage is applied) shown in FIG. As a result, alignment stability and response characteristics are improved.

  Here, an example is shown in which the opening 22a (portion where no conductive layer is present) 22a is formed in the counter electrode 22 in order to control the alignment direction of the liquid crystal molecules 42a. However, the liquid crystal when forming the alignment maintaining layers 34a and 34b is shown. The method for controlling the orientation direction of the molecules 42a is not limited to this. For example, a protrusion may be provided on the counter electrode 22 instead of the opening 22a. By using a combination of the alignment regulation force due to the oblique electric field formed at the edge portion of the pixel electrode 12 and the alignment regulation force due to the projections provided on the opening 22a or the counter electrode 22 formed in the counter electrode 22, For example, a liquid crystal domain exhibiting an axially symmetric alignment (radially inclined alignment) can be formed. A vertical alignment mode in which liquid crystal domains with axial symmetry alignment are formed is called a CPA (Continuous Pinwheel Alignment) mode. The CPA mode is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-202511. Further, as the vertical alignment mode, an MVA (Multi-domain Vertical Alignment) mode as described in Patent Document 1 is also known, and an alignment regulation structure (projections and electrodes provided on the electrodes) used in the MVA mode is known. Or a slit formed on the substrate may be used. In the MVA mode, four liquid crystal domains having different orientation directions of the liquid crystal molecules 42a are formed.

[Method for manufacturing liquid crystal display device]
Next, a method for manufacturing the liquid crystal display device 100 according to the present embodiment will be described with reference to FIGS.

  First, the substrate 11 provided with the pixel electrode 12 and the vertical alignment film and the substrate 21 provided with the counter electrode 22 and the vertical alignment film are prepared. These substrates 11 and 21 can be produced by various known methods.

  Next, as shown in FIG. 2A, the pair of substrates 11 and 21 are bonded to each other at a predetermined interval via the sealing material 50, thereby producing an empty cell 70 '. The sealing material 50 is typically formed from a thermosetting resin or a photocurable resin. The sealing material 50 is applied on one of the substrates 11 and 21 before bonding, and is cured after bonding. Moreover, as shown in FIG. 3, the sealing material 50 is formed in a substantially rectangular shape, and includes a plurality of inlets 51 for injecting a liquid crystal material on one side thereof. In addition, although the two inlets 51 are illustrated here, the number of the inlets 51 is not limited to this.

  Subsequently, as shown in FIG. 2 (b), a space (space S shown in FIG. 2 (a) and FIG. 3) surrounded by the pair of substrates 11 and 21 and the sealing material 50 is vacuum-injected. By injecting the liquid crystal material, the liquid crystal cell 70 including the liquid crystal layer 42 is obtained. The liquid crystal material injected in this step contains a photopolymerizable compound. As the photopolymerizable compound, it is preferable to use a monomer or oligomer having a functional group capable of radical polymerization such as an acrylate group, a methacrylate group or a vinyl group. From the viewpoint of reactivity, those having an acrylate group or a methacrylate group are more preferable, and among them, a polyfunctional one is preferable. Further, by using a photopolymerizable compound having a liquid crystal skeleton, the alignment of the liquid crystal molecules 42a can be maintained more stably. In particular, those in which an acrylate group or a methacrylate group is directly bonded to the ring structure or condensed ring structure described in Patent Document 2 are preferable. Moreover, this injection | pouring process is performed in multiple steps (two steps) so that it may explain in full detail later. Although not shown here, the injection port 51 of the sealing material 50 is sealed with a sealing material (for example, a photocurable resin) after the liquid crystal material is injected.

  Next, as shown in FIG. 2C, the liquid crystal material (liquid crystal layer 42) is irradiated with light (typically ultraviolet rays), thereby polymerizing the photopolymerizable compound to form alignment maintaining layers 34a and 34b. Form. Light irradiation to the liquid crystal layer 42 is performed in a state where a predetermined voltage (typically a voltage equal to or higher than the white display voltage) is applied to the liquid crystal layer 42. The liquid crystal molecules 42a take a predetermined alignment state by an electric field generated between the counter electrode 22 and the pixel electrode 12 by voltage application. In this state, the photopolymerizable compound is polymerized by light irradiation, whereby the alignment maintaining layers 34a and 34b for fixing the alignment state of the liquid crystal molecules 42a are formed on the vertical alignment film. The above-described series of steps for forming the alignment sustaining layers 34a and 34b may be referred to as “PSA treatment”.

  Then, a liquid crystal display device 100 is completed by attaching a pair of polarizing plates and, if necessary, a retardation plate to the liquid crystal cell 70.

[Liquid crystal material injection process]
Next, the liquid crystal material injection process will be described more specifically.

  In the manufacturing method according to this embodiment, the liquid crystal material injection step includes a first injection step of injecting a liquid crystal material containing a photopolymerizable compound at a predetermined concentration (hereinafter referred to as a first concentration), and a first injection. After the step, a second injection step of injecting a liquid crystal material containing the photopolymerizable compound at a concentration higher than the first concentration (hereinafter referred to as a second concentration) is included.

  Specific examples of the first injection process and the second injection process will be described with reference to FIGS.

  Prior to the injection of the liquid crystal material, as shown in FIG. 4 (a), two liquid crystal dishes 81A and 81B for accommodating the liquid crystal materials 41A and 41B, respectively, and an empty cell 70 ′ are arranged in the chamber 80, and the chamber The inside of 80 is evacuated to a vacuum state. The liquid crystal material 41A accommodated in one liquid crystal dish 81A contains a photopolymerizable monomer at a relatively low first concentration, and the liquid crystal material 41B accommodated in the other liquid crystal dish 81B is relatively high. It contains a photopolymerizable monomer at a second concentration. Here, a 12.1 type WXGA size cell is used as the empty cell 70 '. Although not shown, a mechanism for moving the empty cell 70 ′ and / or the liquid crystal dishes 81 </ b> A and 81 </ b> B is provided in the chamber 80.

  First, as shown in FIG. 4B, the end of the empty cell 70 ′ is immersed in a liquid crystal material 41A having a low monomer concentration (a liquid crystal material accommodated in the left liquid crystal dish 81A), and the sealing material 50 is poured. The liquid crystal material 41A is injected from the inlet 51. Here, the monomer concentration (first concentration) is 0.1% by weight.

  Next, after the chamber 80 is returned to the atmospheric pressure state (required time is about 3 minutes), as shown in FIG. 5A, the liquid crystal material 41B having a high monomer concentration (contained in the right liquid crystal plate 81B). The end of the empty cell 70 ′ is immersed in the liquid crystal material), and the liquid crystal material 41 B is injected from the injection port 51 of the sealing material 50. Here, the monomer concentration (second concentration) is 0.3% by weight.

  Subsequently, as shown in FIG. 5B, the liquid crystal material 41B is continuously injected until the entire surface of the empty cell 70 'is filled with the liquid crystal material. In this way, the two-stage liquid crystal material injection is completed.

  As described above, in the manufacturing method according to the present embodiment, the step of injecting the liquid crystal material includes the first injection step of injecting the liquid crystal material 41A containing the photopolymerizable compound at the first concentration, and the first injection step. And a second injection step of injecting a liquid crystal material 41B containing a photopolymerizable compound at a second concentration higher than the first concentration. As shown in FIG. 5B, the liquid crystal material 41A initially injected into the empty cell 70 ′ has a relatively low concentration of the photopolymerizable compound (monomer concentration), and the vacuum in the empty cell 70 ′. The oxygen concentration is relatively low due to the long contact time with the part. On the other hand, the liquid crystal material 41B injected subsequently has a relatively high concentration (monomer concentration) of the photopolymerizable compound, and also hardly contacts the vacuum part in the empty cell 70 '. Relatively high. Therefore, the difference in polymerization due to the difference in injection timing (oxygen concentration difference) is offset by the difference in concentration of the photopolymerizable compound. Therefore, the pretilt angle in the display area can be made uniform, and the occurrence of uneven brightness can be suppressed.

In addition, the density | concentration (1st density | concentration) of the photopolymerizable compound in a 1st injection | pouring process and the density | concentration (2nd density | concentration) of a photopolymerizable compound in a 2nd injection | pouring process are not limited to the numerical value illustrated here. However, it is sufficient that the second concentration is higher than the first concentration. However, in order to sufficiently suppress the variation in the pretilt angle, it is preferable that the difference between the first density and the second density be large to some extent. Specifically, assuming that the first concentration is C ₁ (wt%) and the second concentration is C ₂ (wt%), the first concentration C ₁ and the second concentration C ₂ are C ₂ ≧ 1. it is preferable to satisfy the relationship of .2C _1. In other words, the second concentration C ₂ is preferably 1.2 times or more the first concentration C ₁ . However, from the viewpoint of avoiding the influence of the concentration difference of the photopolymerizable compound on the pretilt angle from exceeding the influence of the oxygen concentration difference on the pretilt angle, the first concentration C ₁ and the second concentration C _{2 are used.} It is preferable that the difference is not too large. Specifically, it is preferable that the first concentration C ₁ and the second concentration C ₂ satisfy the relationship of C ₂ ≦ 6C ₁ . That is, the second concentration C ₂ is preferably 6 times or less of the first concentration C ₁ .

Further, the ratio Q ₁ / Q of the amount Q ₁ of the liquid crystal material 41A injected in the first injection step to the total amount Q of the liquid crystal material injected into the empty cell 70 ′ is not particularly limited. However, it is preferable that Q ₁ /Q≧0.01 in order to sufficiently suppress the brightness floating at the edge of the display area. However, if Q ₁ / Q is too large, there is a region where the concentration of the photopolymerizable compound is low even though it is hardly in contact with the vacuum part, and the pretilt angle becomes too large in that region (that is, Since the tilt angle of the liquid crystal molecules 42a with respect to the vertical direction may not be sufficiently large), it is preferable that Q ₁ /Q≦0.05.

  According to the present invention, in a PSA liquid crystal display device, it is possible to suppress the occurrence of luminance unevenness due to variations in pretilt angles. The present invention is preferably used for manufacturing liquid crystal display devices of various display modes, and particularly preferably for manufacturing liquid crystal display devices of vertical alignment modes such as CPA mode and MVA mode.

2 is a cross-sectional view schematically showing the structure of one pixel of the liquid crystal display device 100 according to a preferred embodiment of the present invention, where (a) is a black display state (when no voltage is applied), and (b) is a white display state ( It is a figure which shows the orientation state of a liquid crystal molecule in the time of voltage application. (A), (b) and (c) are sectional drawings which show typically the manufacturing process of the liquid crystal display device 100. FIG. 4 is a plan view schematically showing an empty cell used for manufacturing the liquid crystal display device 100. FIG. (A) And (b) is a figure which shows typically the injection | pouring process of the liquid-crystal material in an empty cell. (A) And (b) is a figure which shows typically the injection | pouring process of the liquid-crystal material in an empty cell. It is a photograph which shows the liquid crystal cell which the brightness nonuniformity has generate | occur | produced.

Explanation of symbols

11, 21 Substrate 12 Pixel electrode 22 Counter electrode 22a Opening 34a, 34b Orientation maintaining layer 41A, 41B Liquid crystal material 42 Liquid crystal layer 42a Liquid crystal molecule 50 Sealing material 51 Inlet 70 Liquid crystal cell 70 'Empty cell 80 Chamber 81A, 81B Liquid crystal dish 100 Liquid crystal display device

Claims (5)

A pair of substrates facing each other;
A liquid crystal layer provided between the pair of substrates;
A pair of electrodes facing each other through the liquid crystal layer;
A pair of alignment films respectively provided between the pair of electrodes and the liquid crystal layer;
An alignment maintaining layer composed of a photopolymer formed on each of the liquid crystal layer side surfaces of the pair of alignment films, and when no voltage is applied to the liquid crystal layer, the liquid crystal molecules of the liquid crystal layer An alignment maintaining layer that defines the pretilt azimuth of the liquid crystal display device,
Bonding the pair of substrates at a predetermined interval via a sealing material;
Injecting a liquid crystal material containing a photopolymerizable compound into the space surrounded by the pair of substrates and the sealing material by a vacuum injection method;
Irradiating the liquid crystal material with light to polymerize the photopolymerizable compound to form the alignment maintaining layer; and
Including
The step of injecting the liquid crystal material includes
A first injection step of injecting the liquid crystal material containing the photopolymerizable compound at a first concentration C ₁ ;
And a second injection step of injecting the liquid crystal material containing the photopolymerizable compound at a second concentration C ₂ higher than the first concentration C ₁ after the first injection step. Production method. 2. The method of manufacturing a liquid crystal display device according to claim 1, wherein the first concentration C ₁ and the second concentration C ₂ satisfy a relationship of C ₂ ≧ 1.2C ₁ . 3. The method of manufacturing a liquid crystal display device according to claim 1, wherein the first concentration C ₁ and the second concentration C ₂ satisfy a relationship of C ₂ ≦ 6C ₁ .   The method for producing a liquid crystal display device according to claim 1, wherein the photopolymerizable compound is a photopolymerizable monomer.   5. The liquid crystal display device according to claim 1, wherein each of the pair of alignment films is a vertical alignment film, and the liquid crystal layer includes liquid crystal molecules having negative dielectric anisotropy. Method.